PRESSURE DEVICES, SYSTEMS AND METHODS FOR SCREENING MATERIALS

Abstract

A vibrating screen comprises replaceable screen assemblies. Compression mechanisms are used to attach the replaceable screen assemblies to the vibrating screen. Each compression mechanism exerts a force on a replaceable screen assembly that includes both a horizontal and a downward vertical component. Each replaceable screen assembly is typically substantially flat prior to installation in a vibrating screen. The force exerted on the screen assembly by one or more compression mechanisms causes the screen assembly to be forced into engagement with underlying concave support members, causing the screen assembly itself to assume a concave shape with the center of the screen assembly lower than the side edges. The downward vertical force component contributes to the attachment of the screen assembly to the screen.

Description

This application claims the benefit of U.S. Provisional Patent Application Serial No. 63 / 464,982, filed May 9, 2023, the entire contents of which are hereby incorporated by reference and the priority of which is hereby claimed.REGIONThe present disclosure relates generally to screening materials. More particularly, the present disclosure relates to apparatus and methods for compressing screen assemblies for screen machines.BACKGROUNDScreening of materials involves the use of vibratory screening machines. Vibrating screen machines provide the ability to move an installed screen so that materials laid on the screen can be separated to a desired extent. Oversized materials are separated from oversized materials. Screens wear over time and must be replaced. Thus, screens are designed to be replaceable.BRIEF DESCRIPTION OF THE DRAWINGSFigure 1A shows a perspective view of a twin trough vibratory screening machine with replaceable screen assemblies installed, in one embodiment. FIG. 1B shows a perspective view of the twin trough vibratory screening machine of FIG. 1A with one of the replaceable screen assemblies removed, in one embodiment. FIG. 1C shows a side view of the vibrating screen machine of FIG. 1A, in one embodiment. FIG. 1D shows a perspective view of a single trough vibrating screen machine with a replaceable screen assembly installed, in one embodiment. FIG. 2A shows an end view of a portion of an example twin trough shaker machine, in one embodiment. FIG. 2B shows an end view of an example single trough shaker machine, in one embodiment. FIG. 2C shows a close-up view of a portion of the vibratory screening machine of FIG. 2B, in one embodiment. FIG. 3A shows a first embodiment of a carrier plate of a screen assembly. FIG. 3B shows a second embodiment of a carrier plate of a screen assembly. FIG. 3C shows a screen assembly including a support plate as depicted in FIG. 3B. FIG. 4A is a top perspective view of a single trough vibrating screen machine that includes a side pressure mounting mechanism for mounting screen assemblies within the machine. FIG. 4B is another perspective view of the vibratory screening machine depicted in FIG. 4A. FIG. 4C is a top view of the vibratory screening machine depicted in FIG. 4A. FIG. 4D is an enlarged perspective view of a portion of the vibratory screening machine depicted in FIG. 4A. Figure 4E is a perspective view of a portion of a single trough vibrating screen machine such as that depicted in Figure 4A, with a screen assembly support plate resting therein. Figure 4F is an enlarged perspective view of a portion of a single trough vibrating screen machine such as that depicted in Figure 4A, with a screen assembly support plate resting therein. FIGS. 5A-5C illustrate steps of a process for mounting the support plate of a screen assembly to a single trough shaker screen machine, in one embodiment. FIG. 6A is a perspective view of an embodiment of a pressure assembly. FIG. 6B is a top perspective view of an embodiment of a plunger of the pressure assembly depicted in FIG. 6A. FIG. 6C is a bottom perspective view of the plunger depicted in FIG. 6A. FIG. 7A is a perspective view illustrating how a support plate of a screen assembly rests in a bed of a vibratory screening machine while the rams of the mounting assembly are in a retracted position. FIG. 7B is a perspective view illustrating how a support plate of a screen assembly rests in a bed of a vibratory screening machine while the rams of the mounting assembly are in an extended position. FIG. 8A is a top perspective view illustrating another embodiment of a plunger and a corresponding mounting aperture of a backing plate. FIG. 8B is a bottom view of the plunger and mounting aperture shown in FIG. 8A. FIG. 8C is a top perspective view of another embodiment of a plunger and a corresponding mounting aperture of a backing plate. FIG. 8D is a bottom view of the plunger and mounting aperture shown in FIG. 8C. FIG. 8E is a top perspective view of another embodiment of a plunger, a corresponding mounting aperture, and an access aperture of a backing plate. FIG. 8F is a side perspective view of the plunger and the mounting hole shown in FIG. 8E. FIG. 8G is a perspective view of the end of a plunger similar to that shown in FIGS. 8E and 8F, and further including an alignment finger at its distal end. FIG. 8H is a perspective view illustrating a portion of a support plate of a screen assembly resting in a bed of a vibratory screening machine when using rams similar to those shown in FIG. 8G to mount the support plate to the vibratory screening machine. FIG. 9A is a perspective view of a stationary plunger assembly. FIG. 9B is a cross-sectional view of the stationary pressurizing piston assembly shown in FIG. 9A. FIGS. 10A-10C illustrate how a pressurizing assembly with a pressurizing piston may be used to mount an injection molded screen assembly in a vibratory screening machine. FIG. 11A shows an end view of the shaker screen machine, in one embodiment. FIG. 11B shows a partial end view of the shaker screen machine of FIG. 11A, in one embodiment. FIG. 12A shows a perspective view of a screen assembly, in one embodiment. FIG. 12B shows the perspective of the screen assembly of FIG. 12A with a portion of the screen surface removed, in one embodiment. FIG. 12C shows a top view of a support plate of a screen assembly, in one embodiment. FIG. 12D shows a close-up view of a portion of the carrier plate of FIG. 12C, in one embodiment. FIG. 12E shows a perspective view of a portion of the carrier plate of FIG. 12C engaged by hooks of an actuation assembly, in one embodiment. FIGS. 13A and 13B illustrate first and second perspective views of a printing assembly, in one embodiment. FIGS. 13C and 13D illustrate first and second side views of the printing assembly of FIGS. 13A and 13B in retracted and extended configurations, respectively, in one embodiment. FIG. 13E illustrates a cross-sectional view of the printing assembly of FIGS. 13A and 13B, in one embodiment. FIG. 13F illustrates an exploded view of the printing assembly of FIGS. 13A and 13B, in one embodiment. FIG. 14A illustrates three views of a pawl including: (a) a rear perspective view; (b) a front perspective view; and (c) a side view, in one embodiment. FIG. 14B illustrates three views of an internal press-fit clamp comprising: (a) a cross-sectional side view; (b) a front perspective view; and (c) a top view, in one embodiment. FIG. 14C illustrates three views of an exterior press-fit clip comprising: (a) a side view; (b) a perspective view; and (c) a bottom view, in one embodiment. FIG. 14D illustrates three views of an eccentric nut comprising: (a) a first perspective view; (b) a second perspective view; and (c) a rear view, in one embodiment. FIG. 14E illustrates four views of an actuation bracket comprising: (a) a first side view; (b) a second side view; (c) a perspective view; and (d) a top view, in one embodiment. FIGS. 14F and 14G illustrate perspective and exploded views, respectively, of a stationary hook assembly, in one embodiment. FIG. 15A illustrates a pressure assembly, stationary hook assembly, and plate assembly of a shaker screen machine in an embodiment in which the plate assembly is not compressed; FIG. 15B illustrates the pressure assembly, stationary hook assembly, and plate assembly of FIG. 15A in an embodiment in which the plate assembly is not compressed. FIG. 15C illustrates a partial close-up view of the push assembly and stationary hook assembly of FIGS. 15A and 15B in an embodiment in which the plate assembly is not compressed. FIG. 15D illustrates a partial close-up view of the compression assembly and stationary hook assembly of FIGS. 15A and 15B compressing a plate assembly of a screen assembly, in one embodiment. FIG. 15E illustrates an alternative pawl for use with the push assembly and / or stationary hook assembly, in one embodiment. FIGS. 15F and 15G illustrate radius of curvature of a pressurized screen assembly and a prior art screen assembly, respectively, in one embodiment. FIG. 15H illustrates an end view of the screen assembly of FIG. 15F compressed against a bed of a pressurized screening machine, in one embodiment. FIG. 15 l illustrates an end view of the screen assembly of FIG. 15G compressed against the bed of a prior art screening machine, in one embodiment. FIG. 16A shows a perspective view of a portion of a shaker machine, in one embodiment. FIG. 16B shows the portion of the shaker of FIG. 16A with a screen surface removed, in one embodiment. FIG. 16C shows the portion of the shaker of FIG. 16A with a screen surface removed, in one embodiment. FIG. 17A shows a perspective view of a portion of the shaker of FIG. 16A, in one embodiment. FIG. 17B shows a cross-sectional view of the portion of the shaker shown in FIG. 17A, in one embodiment. FIG. 17C shows a pawl and hook of the part of the shaker shown in FIG. 17A prior to compression, in one embodiment. FIG. 17D shows a pawl and hook of the part of the shaker shown in FIG. 17A after compression, in one embodiment. FIGS. 17E and 17F show a pawl in an uncompressed position, in one embodiment. FIG. 17G shows another pawl and carrier plate, in one embodiment. Figure 18 illustrates a support plate of a screen assembly that could be used with two different types of mounting assemblies. FIG. 19A shows a perspective view of a screen assembly, in one embodiment. FIG. 19B shows the perspective of the screen assembly of FIG. 19A with a portion of the screen surface removed, in one embodiment. FIG. 19C shows a top view of a support plate of a screen assembly, in one embodiment. FIG. 20 shows a partial perspective view of a portion of a shaker machine, in one embodiment. FIG. 21A illustrates a removable handle that can be used to actuate the printing assembly, in one embodiment. FIG. 21B illustrates how the removable handle shown in FIG. 21A interacts with a printing assembly to actuate the printing assembly, in one embodiment. FIG. 21C illustrates a removable handle that can be used to simultaneously actuate two adjacent print assemblies, in one embodiment. FIG. 21D illustrates how the removable handle shown in FIG. 21C interacts with two adjacent print assemblies to actuate both print assemblies, in one embodiment. Figure 21E illustrates how two adjacent print assemblies may be connected to allow dual actuation with a single handle, in one embodiment. FIG. 21F illustrates a pneumatic pressure assembly, in one embodiment. FIG. 21G illustrates a cross-sectional view of the pneumatic pressure assembly of FIG. 21F, in one embodiment. FIGS. 22A and 22B illustrate top and bottom perspective views, respectively, of another embodiment of a pressurized screen assembly, in one embodiment. FIG. 22C illustrates a pressing assembly and a stationary hook assembly compressing a screen assembly of FIGS. 22A and 22B, in one embodiment. FIG. 23A illustrates a plurality of sectional bed supports forming a support rail along a wall of a screening machine, in one embodiment. FIG. 23B illustrates a sectional bed support, in one embodiment. FIGS. 24A and 24B illustrate the installation of a bed rubber or seal in a bed support, in one embodiment. FIG. 24C illustrates two bed supports forming a corner connection; FIG. 24D illustrates two pieces of bed rubber or gaskets forming a corner seal, in one embodiment. FIG. 25A illustrates a screen assembly, in one embodiment. FIG. 25B illustrates a screen assembly with a portion of the screen surface removed, in one embodiment. FIG. 25C shows a top view of a support plate of a screen assembly, in one embodiment. FIG. 25D shows a cross-sectional side view of a portion of a screen assembly having a multi-layered screen surface, in one embodiment. FIG. 25E shows how parts of a screen surface are connected to or contact a support plate, in one embodiment. Figure 26 is a perspective view of a first embodiment of a synthetic screen assembly having an end rod with continuous compression points. Figure 27 is a perspective view of the synthetic screen assembly of Figure 17 showing how the end bar is attached to the screen units. Figure 28 is a perspective view of the synthetic screen assembly shown in Figures 17 and 18 after the end bar has been coupled to the screen units. Figures 29A-29D illustrate a twin trough shaker screen machine that includes several different types of screen assemblies. Figures 30A-30C illustrate how combinations of different types of screen assemblies may be mounted together on a vibratory screening machine.DETAILED DESCRIPTIONScreening of materials involves the use of vibratory screening machines. Vibrating screen machines provide the ability to move an installed screen so that materials laid on the screen can be separated to a desired extent. Oversized materials are separated from oversized materials. Screens wear over time and must be replaced. Thus, screens are designed to be replaceable.Vibrating screen machines are used in various industries and are generally subjected to substantial vibrating forces and transmit the vibrating forces to screens and screen assemblies to shake them. One industrial application is oil and gas drilling, in which screens mounted on shakers are subjected to compressive forces of 2-4k psi to keep the screens stationary on the shakers. Cuttings, rock and mud are then poured onto the screens at hot temperatures and the screens are shaken with forces of 3-9G.Embodiments of the present disclosure may be used for various applications, including wet and dry applications, and may be used in various industries. The present disclosure is not limited to the oil and gas industry and mining industry. Disclosed embodiments may also be used in any other industry where separation of materials by vibrating screen machines is required, including the pulp and paper industry, chemical and pharmaceutical industry, and other industries. In various embodiments, screen assemblies according to the present disclosure are configured to withstand high jarring forces (e.g., accelerations in the range of 3-9 G), abrasive materials (e.g., liquids having a few percent up to 65 percent abrasive solids), and high stress requirements (e.g., liquids having a specific gravity of up to 4). The disclosed screen assemblies are also designed to withstand a compressive load of up to 2000-4000 pounds at the edges of the screen assemblies, as described, for example, in U.S. Pat. Nos. 7,578,394 and 9,027,760, the entire disclosure of which is hereby incorporated by reference.Vibrating screen machines are generally subjected to substantial vibrating forces and transmit the vibrating forces to screens and screen assemblies to shake them. Screens and / or screen assemblies must be securely attached to the vibrating screen machines to ensure that the vibrating forces are transferred to the screens or screen assemblies and that the screen or screen assembly does not become detached from the vibrating screen machine. Efficient transfer of the jarring forces from the machine to the attached screen assemblies is crucial to screen performance. Screen assemblies that are not securely attached to the screening machine cannot effectively perform the screening and / or dewatering function. In addition, if screen assemblies are not securely attached to the screening machine, the screen assemblies and the screening machine itself are subject to increased wear and breakage.Various approaches may be used to attach a screen or assembly to a vibratory screening machine, including clamps, clamp assembly, etc. The disclosed printing apparatus, systems and methods are designed to securely attach screen assemblies to screening machines under operating conditions including the aforementioned compressive load, high vibratory forces, and in the presence of heavy liquids.One approach to mounting a screen assembly on a screening machine is to pressurize the screen or assembly to hold the screen or screen assembly in position. The screen or screen assembly may be inserted into the vibrating screen machine such that one side abuts a portion of the vibrating screen machine and the opposite side faces a pressure assembly. The pressure assembly can then be used to apply compressive forces to the screen or assembly. Print assemblies may be powered by motor or manually.Embodiments of the present disclosure relate to systems, apparatus, and methods for attaching screen assemblies to a vibratory screening machine. More particularly, the disclosure relates to systems, apparatus, and methods for attaching a screen assembly to a vibratory screening machine using a pressure assembly that deflects a screen into a concave shape, though these are not limiting embodiments.Embodiments of the present disclosure provide a printing assembly that can be used for printing screens and / or screen assemblies on a vibratory screening machine. In some embodiments, the press-mounting mechanism may include plungers that abut a side edge or face of a screen assembly and apply both a horizontal and a vertical compressive force. In other embodiments, the press-fit mechanism may comprise an arrangement in which one or more hook elements pass through a screen assembly and exert both a horizontal force on a side or edge surface of the screen assembly and a downward force on an upper surface of the screen assembly. Such an embodiment may increase the vertical downward component of a compressive force applied to the screen compared to known pressure assemblies, which may result in improved attachment of the screen assembly to the screening machine and / or in improved sealing between the screen assembly and the screening machine.In one embodiment under pressure, a set of stationary hooks attached to the screening machine (e.g., a wall member or a central member) extends through a corresponding set of passage pressure points (e.g., openings) extending through a screen assembly in an interior of the screen assembly (e.g., within a perimeter of a support plate of a screen assembly and spaced from a first edge of the support plate). Such stationary hooks may extend through a screen assembly from a bottom surface to a top surface.A set of movable or actuated hooks of one or more printing assemblies disposed along an opposing wall member of the screening machine extend through a corresponding set of pass-through printing points within the screen assembly (e.g., spaced from a second edge of the screen assembly). Actuation of the push assemblies moves the hooks from a first position (e.g., retracted) to a second position (extended) to apply a horizontal push force to the screen assembly (e.g., an inner edge of the pass-through push point). Actuation of the pusher assemblies may also apply a downward force to an upper surface of the screen assembly. The combined horizontal and downward vertical forces may bend the screen assembly into a concave shape and attach the screen assembly to the screening machine.Embodiments of the present disclosure may provide a separate pressure assembly for each movable or actuated hook of the shaker screen machine. Separate assemblies for each movable or actuated hook may allow the energy required to apply the compression to be distributed among multiple assemblies. In other embodiments, a single printing assembly may actuate two or more movable or actuated hooks.The pressure assembly may have a removable handle. A single handle may be used to actuate multiple print assemblies. Printing assemblies may be mounted along a first and / or second wall of a vibrating screen machine. Printing assemblies may be mounted on a vibrating screen machine such that multiple (e.g., two, three, four, or more) printing assemblies are configured to engage each screen installed in the vibrating screen machine and / or each screen assembly. By using multiple pressure assemblies for a single screen or screen assembly, the combined clamping force applied to the screen assembly by the multiple pressure assemblies is increased while the energy required to activate a single pressure assembly remains the same.Figures 1A, 1B and 1C illustrate a non-limiting embodiment of a vibratory screening machine 300 having replaceable screen assemblies installed. More specifically, FIG. 1A illustrates the fully assembled screening machine 300 having two parallel rows of replaceable screen assemblies 320 a, 320 b, FIG. 1B illustrates the screening machine 300 with one screen assembly removed to illustrate the underlying components of the screening machine, and FIG. 1C illustrates a side view of the screening machine. In the illustrated embodiment, the screening machine 300 uses two sets of replaceable screen assemblies 320a, 320b arranged in parallel along the length of the screening machine 300. Each set of screen assemblies 320a and 320b comprises four longitudinally aligned screen assemblies.Material is loaded into a feed hopper (not shown) and then directed onto the top surface 8 of the two parallel screen assemblies 320a, 320b. The material flows in the flow direction 6 to the outlet end 4 of the vibrating screen machine 300. The material flowing in direction 6 is retained in the parallel concave troughs of the parallel screen assemblies 320 and prevented from leaving the sides of the screen assemblies 320. Sub-sized and / or liquid material passes through the parallel screen assemblies 320 a, 320 b(hereafter 320, unless expressly referred to) on a separate discharge material flow path for further processing. Oversized materials exit the outlet end 4. The screen material may be dry, slurry, etc. The screen assemblies 320 may be downwardly inclined from the hopper toward the opposite end in direction 6 to assist in feeding the material. Alternatively, the screen assembly may be inclined upwardly to increase a basin depth and thereby improve contact between the screen and the sieved materials.The vibratory screening machine 300 includes wall members 312 a, 312 b(hereinafter 312 unless expressly referred to), concave support surfaces 314 (e.g., bulkhead or cheek), a central member 316, an accelerator assembly 18 (e.g., one or more vibration motors), a plurality of screen assemblies 320, and pressure assemblies 322. A central element 316 divides the vibrating screen machine 300 into two concave screen regions (e.g., double trough).The print assemblies 322 are secured to an outer surface of each of the wall members 312. However, vibrating screen machines may also have a concave screen region (e.g., single trough) sized to receive a set of screen assemblies, with the printing assemblies disposed on a wall member. Such a single tray machine 300A is illustrated in Figure 1D, in which like reference numerals are used to identify like elements. Such an arrangement may be desirable when space is limited and maintenance and operating personnel have access only to one side of the shaker screen machine. A single trough machine may also be advantageous if it is advantageous for the assembly of the screen assemblies if pressure assemblies 322 are located on both sides of the machine. While the vibratory screening machine 300 is illustrated in Figures 1A-1C as having a plurality of longitudinally oriented screen assemblies forming two parallel concave webs of material (e.g., dual trough), the screen assemblies are not limited to such a configuration and may be oriented differently.In the screening machine 300 shown in Figures 1A-1C, the central member 316 is disposed between the wall members 312 such that the screening machine has two parallel flow paths (e.g., a double trough construction). As shown, each screen assembly 320 includes a first edge disposed proximate the first or second wall member 312a or 312b and a second edge disposed proximate the central member 316 which forms a stop surface for the screen assemblies. In a single trough embodiment using a single screen assembly, the central member is eliminated so that a single set of screen assemblies extends between the first and second walls of the screening machine 300A. In such an arrangement, one wall may include printing assemblies and the other wall may form a stop surface. In an alternative embodiment, printing assemblies are provided on both walls. In either arrangement, the pressing assemblies 322 press the screen assemblies 320 against the concave supports 314 to bend the screen assemblies 320 into a concave profile.FIG. 1B illustrates the screening machine 300 with one screen assembly removed and one screen surface removed from another screen assembly to expose an underlying perforated support plate 324. The configuration of the screen assemblies 320 and their support plates 324 will be explained in more detail in the following description. As shown in FIG. 1B, a plurality of concave support surfaces 314 extend between the first wall 312 aand the central support 316. Although not shown, a plurality of concave support surfaces also extend between the second wall 312b and the central support 316. Single tray machines (e.g., FIG. 1D ) may use similar concave supports extending between the first and second walls. As shown, the concave supports 314 each have a first end secured to the wall member and a second end secured to the central support 316. As shown, the concave supports 314 are equally spaced and parallel. However, a different spacing may be used.Vibrating screen machine pressure assemblies are typically mounted to an outer surface of wall members and include a retractable member that extends and contracts to apply pressure to screen assemblies that rest on a bed of the screen machine. The retractable members may extend and contract in response to manually applied forces, pneumatic, hydraulic, electrically generated, and spring forces. Figure 2A shows a partial end view of a prior art double trough screening machine 10 wherein a pressure assembly 22 mounted on a first wall 12 of the machine 10 compresses a screen assembly 20 disposed between the first wall 12 and a central member 16 of the machine. The compression assembly 20 uses a retractable member 32, shown as a pin, to apply a compressive force against a vertical flange 28 that extends across an upper surface of the screen assembly 20. The pressure on the vertical flange 28 near a first edge of the screen assembly forces a second edge of the screen assembly against the central member 16 (or a second wall of a single trough screening machine) and deforms the screen assembly 20 into a concave profile against one or more underlying concave support surfaces 14.Figures 2B and 2C show an end view of the single trough screening machine 10A of the prior art. As shown, a pressure assembly 22a attached to a first wall 12a presses a screen assembly 20a against a stop surface 26 located on a second wall 12b of the machine 10A. Although illustrated as a generally flat surface, the stop surface 26 may also have other configurations, such as, without limitation, a groove. The compressive force applied by the compression assembly 22 ato the screen assembly 20 abends the screen assembly 20 ainto a concave profile against one or more underlying concave support surfaces 14 a. Screen machines and printing assemblies shown in Figures 2A-2C are described in U.S. Patent No. 9,027,760, the entire contents of which are incorporated herein by reference.Aspects of the present disclosure are based in part on the recognition that compressive forces acting on a vertical flange extending across the rim of the screen assembly do not provide an ideal hold-down force for the screen assembly. That is, a moment about such a vertical flange and / or deflection of the vertical flange when compressed exerts only a limited downward force (i.e., a vertical component of a hold down force) on the screen assembly. Moreover, the compressive force exerted by the compression assembly 22a on the vertical flange causes the side edge of the support plate to deflect upwardly, away from the wall member and away from the underlying support surfaces 14a. As a result, liquid and aggregate material often accumulates at the screen edges behind the flange, leading to maintenance and contamination problems.The low downward vertical component of the hold-down force may also result in poor sealing between the peripheral edges of the screen assemblies and the screening machine, which may result in contamination of the screened materials. That is, unscreened oversized material can exit the peripheral edges of the screen assembly and fall within the area intended for capture of oversized material. Additionally, the low downward vertical component of the hold-down force may allow some movement (e.g., flutter) of the screen assembly relative to the screening machine, which increases wear of the screen assemblies and / or the underlying rubber seal beds (e.g., seals) and reduces screen efficiency and / or performance.The problems described above, as well as additional advantages, are addressed by the hold-down printing assemblies, screen assemblies, and associated methods disclosed herein. Generally speaking, the disclosed press-mount assemblies and screen assemblies allow for the increase of a vertical component of a hold-down force applied to the screen assembly in conjunction with the bending of the screen into a concave profile. This results in, among other advantages, improved sealing of the screen assemblies and / or less movement of the screen assemblies relative to the underlying support members and seals of the screening machine.As mentioned above, a screen assembly mounted on a vibrating screen machine typically includes a support plate and a screen surface secured to the top surface of the support plate. Each of the screen assemblies shown in Figure 1A includes a corrugated screen surface secured to the top surface of the support plate. Figure 1B shows one of the screen assemblies with the corrugated screen surface removed to expose the underlying support plate 324. As shown in Figure 1B, the support plate has a plurality of apertures through which materials that have passed the screen surface can easily fall through the support plate 324. Figures 2A-2C show that in prior art screen assemblies, a vertical flange 28 extends upwardly from the side edges of the support plate. As discussed above, the prior art screening machine compression mechanism rests on the upwardly extending vertical flange 28 to apply a compressive force by which the screen assembly is secured to the screening machine.The following description discloses several different embodiments of a new type of screen assemblies and corresponding mounting mechanisms used for mounting screen assemblies on a vibratory screening machine. In one embodiment of the novel mounting mechanisms, a compressive force is applied directly to a side edge of the carrier plate that lies below a screen surface of a screen system. Since the compressive force is applied to the side edges of the carrier plate, the compressive force does not tend to rotate the side edges of the carrier plate upwardly and away from the underlying support members of the screening machine.In addition, the plungers abutting the side edges of the backing plate may do so to apply a greater downward vertical force to the edges of the backing plate. Namely, the pressing surfaces of the plungers abut on the side edges of the supporting plate of a screen assembly so that the plungers exert a vertical constraint which prevents the side edge of the supporting plate from moving upward even under high vibration acceleration forces. All of these factors contribute to keeping the screen assembly firmly attached to the support members of the vibrating screen machine and contribute to the bottom surface of the support plate forming a good seal with the underlying seals or flanges on the screen machine to prevent material from bypassing the screen surface and contaminating the already screened materials.FIG. 3A illustrates a support plate 202 of a new screen assembly. A screen surface would be mounted on the support plate 202 to form a screen assembly. The support plate 202 includes a plurality of flow apertures 210. As a result, any material passing through a screen surface mounted on top of the support plate 202 may fall down through the flow apertures 210.The carrier plate includes a leading edge 202, a trailing edge 204, a first side edge 206, and a second side edge 208. A plurality of mounting apertures 220 are formed on the first and second side edges 206, 208. Each mounting aperture 220 includes pressure surfaces 222 located on opposite sides of an alignment slot 224.FIG. 3B shows an alternative embodiment of a carrier plate 202 that includes upwardly directed flanges 230 on the sides of the carrier plate 202. Access openings 232 are formed in the upwardly extending flanges 230 to allow plungers to move inwardly and engage the mounting openings 220. The upwardly extending flanges 230 may provide advantages that are discussed below.FIG. 3C shows a screen assembly including a screen surface 326 mounted on the top surface of a support 202, as shown in FIG. 3B. In this embodiment, the screen surface 326 has a corrugated configuration. However, in alternative embodiments, the screen surface could be substantially flat or have other configurations.The number and distribution of the mounting apertures 220 may be varied to achieve various objectives. The mounting apertures 220 are typically provided at regular intervals along the side edges 206, 208, and the positions of the mounting apertures 220 correspond to the positions of the printing assemblies of a shaker screen machine.Figures 4A-4D show a single trough vibratory screening machine that includes a first embodiment of a pressure mounting mechanism that serves to attach screen assemblies to the screening machine. FIG. 4A shows a first perspective view showing a plurality of concave support surfaces 314 each extending from a first side member 312 ato a second side member 312 b. The concave support surfaces are arranged from an input end 311 to an output end 313. One or more vibration motors 18 are mounted on the machine to apply vibrational forces to the machine and ultimately to the screen assemblies mounted on the machine.Along the length of the shaker screen machine, a plurality of screen assemblies would be mounted. Each screen assembly would extend across the width of the screening machine and cover most of the distance between the first side member 312a and the second side member 312b. A plurality of print assemblies 322 for mounting the screens of the screening machine are mounted along the length of the screening machine. In some embodiments, the print assemblies 322 are mounted on the exterior of both the first and second side members 312 a, 312 b. In other embodiments, the print assemblies 322 may be mounted on the exterior of only one of the first and second side members 312 a, 312 b. Aspects of these two different configurations are discussed below.Each printing assembly includes a plunger 240 extending through the side member 312a / 312b to which the printing assembly is attached. A pusher assembly 322 is capable of extending pusher 240 inwardly toward the center of the screening machine and retracting it rearwardly away from the center of the screening machine.Figs. 4E and 4F show only a portion of the larger vibratory screening machine shown in Figs. 4A-4D. FIGS. 4E and 4F help illustrate how a screen assembly is mounted to the shaker screen machine. In Figure 4E, a support plate 202 of a screen assembly is shown after it has been lowered onto the concave support surfaces. Note that a complete screen assembly would include a screen surface attached to the top surface of the support plate 202. The screen surface has been removed so that only the support plate 202 remains to illustrate how the screen assembly is attached to the vibrating screen machine. Furthermore, no flow openings 210 are shown in the carrier plate 202.As seen in Figure 4E, the side edges of the platen 202 are aligned with four print assemblies 322 on the side walls 312a, 312b of the screening machine. As a result, each of the four printing assemblies on each side wall causes plungers to extend inwardly toward the center of the screening machine to mount and secure the screen assembly support plate 202 to the screening machine. The four plungers cooperate with the corresponding mounting apertures 220 of the backing plate (as shown in FIG. 3).FIG. 4F is an enlarged view showing more details of the support plate 202. As seen in FIG. 4F, in this embodiment, upwardly extending flanges 230 are provided at the side edges of the support plate 202. However, access openings 232 that are coincident with the mounting apertures 220 of the support plate 202 are provided in the upwardly extending flanges 230. The access openings 232 allow the rams of the thrust assemblies 322 to extend inwardly so as to abut directly against the thrust surfaces 222 of the mounting apertures 220, as will be explained in more detail below. As a result, the plungers of the pusher assemblies 322 do not abut the upwardly extending flange 230 as in the mechanism shown in Figures 2A-C. FIG. 4F illustrates the backing plate 202 in an intermediate position before being pressed down during an assembly operation to engage the plungers of the printing assemblies 322.FIGS. 5A-5C illustrate the assembly operation of the screen assembly. To aid in illustrating the assembly operation, only the support plate 202 of a screen assembly is shown in FIGS. 5A-5B. It should be appreciated that an actual screen assembly would include a screen surface mounted on top of the support plate 202.Triangularly shaped mounting ramps 343 seen in Figures 4E and 5A-5C are provided on the side walls 312a, 312b of the shaker screen machine. When a screen assembly is mounted to the vibrating screen machine, the mounting ramps 343 on the exterior of the upwardly extending flanges 230 abut the side edges of the support plate 220 when such upwardly extending flanges 230 are present. If no upwardly extending flanges 230 are provided on the support plate 202, then the mounting ramps 343 simply abut the side edges 206, 208 of the support plate 202. The mounting ramps 343 serve to urge the sides 206, 208 of the backing plate inward so that the mounting apertures 220 are inward from the ends of the plungers of the pusher assemblies 322. The inward movement of the side edges of the carrier plate 202 caused by the mounting ramps 343 also causes the carrier plate 202 to flex into a concave shape. Once the carrier plate 202 has assumed a concave shape, it may be easier for the plungers to cause further bending of the carrier plate 202 to urge the carrier plate 202 into the assembled position. Prebending the backing plate 202 also ensures that when the plungers engage the side edges of the backing plate, the backing plate will bend further in the concave direction. In other words, prebending the backing plate 202 into a concave shape eliminates the possibility that the rams can bend the backing plate into a convex shape where the center of the backing plate moves away from the shaker screen machine.The assembly operation begins, as illustrated in Figure 5A, where the right side edge of the platen 202 has been lowered over the rams of the pusher assemblies 322 located in the first side wall 312a of the shaker screen machine. FIG. 7A is a partial perspective view of how a corner of the right side of the carrier plate 202 would look when the carrier plate 202 is positioned as shown in FIG. 5A. As shown in FIG. 7A, the mounting ramps 343 abut the outer surface of an upwardly extending flange 230 on the side of the backing plate 202 and have pushed the side edge of the backing plate 202 inward so that the backing plate 202 can be lowered to a position where the mounting apertures 220 are aligned with and engaged by the plungers 240 of the printing assemblies 322.As illustrated in FIG. 5B, the left side of the screen assembly is then pushed down so that the left edge of the carrier plate 202 also lowers so that the mounting apertures 220 on the left side of the carrier plate 202 are aligned with and engaged by the rams 240 of the pusher assemblies 322 on the left side wall 312 bof the shaker screen machine. This includes letting the upwardly extending flange 230 on the left side edge of the carrier plate 202 down the mounting ramps 343 on the left side wall 312 bof the shaker screen machine. As a result, the support plate 202 changes from a substantially flat shape as illustrated in FIG. 5A to a curved shape as illustrated in FIG. 5B.FIGS. 5A and 5B show how the right side of the carrier plate 202 is lowered into position as illustrated in FIG. 5A, followed by lowering the left side of the carrier plate 202 as illustrated in FIG. 5B. However, the order in which the two sides are lowered could be interchanged. Therefore, the above description should not be considered as limiting.In the final assembly step, the plungers 240 of the pusher assemblies 322 are moved inwardly. Inward movement of the rams 240 brings the thrust surfaces 246 of the rams 240 into contact with the thrust surfaces 222 of the mounting apertures 220 on the backing plate 202. Further inward movement of the rams 240 exerts a force on the thrust surfaces 222 of the mounting apertures 220 causing the support plate 202 to deflect further and be forced into contact with the underlying concave support surface 314 of the shaker screen machine, as illustrated in Figure 5C. FIG. 7B illustrates the rams 240 after they have moved inward and have been brought into contact with the thrust surfaces 222 of the mounting apertures 220 on the backing plate 202. FIG. 7B also shows that an alignment finger 244 at the end of each plunger 240 moves into the alignment slot 224 of a corresponding mounting aperture 220 on the backing plate 202.FIG. 6A shows a perspective view of some elements of an embodiment of a pressure assembly 322 that is used to attach a screen assembly to a shaker screen machine. Figure 6A also shows portions of the underlying support structure of the shaker screen machine supporting the side edges of a screen assembly.The pressure assembly 322 includes a plunger 240 slidably mounted in a housing 351. A swing arm 352 fixed to a sleeve 341 is pivotally mounted to the housing 351 via a pivot 353. A spring 345 surrounds the rear of the plunger 240 and is captured between the pivot arm 352 and a shoulder 245 on the plunger 240.The housing 351 includes a mounting bracket 328 that is attachable to a side wall of a shaker machine as shown in Figures 4A-4D. The side wall of the shaker screen machine is not shown in Figure 6 to clearly illustrate the elements of the printing assembly 322.The end of the ram projects through the side wall (not shown) of the shaker machine and extends over a seal 670 mounted on a bed support 380. As a result, the end of the pressure piston 240 abuts an assembly opening on the side edge of a carrier plate of a screen assembly. The side edge of the screen assembly support plate would rest on the seal 670. One of the functions of the pressing assembly 322 is to press the screen assembly support plate against the upper surface of the seal 670, forming a seal between the support plate lower surface and the seal 670 upper surface.To actuate the thrust assembly 322, one would insert a rod into the sleeve 341 and allow the sleeve 341 and attached pivot arm 352 to pivot about the pivot pin 353. This causes the rear end of spring 245 to move inwardly, which in turn causes the front end of spring 245 to exert a force on shoulder 245 of plunger 240 and urge the plunger inwardly. As a result, the end of the plunger 240 abuts an assembly opening of a support plate of a screen assembly, as described in more detail below, and exerts a compressive force on the support plate. Once the pivot arm 352 and sleeve 341 have been rotated sufficiently far about the pivot pin 353, a locking lever 334 may be rotated downwardly to engage a detent groove on the pivot arm 352 to prevent rearward rotation of the pivot arm 352 and relief of pressure on the plunger 240. This arrangement results in the end of the plunger 240 exerting a compressive force on the backing plate. However, the end of the plunger 240 may come to a standstill in various positions relative to the housing 351 and the side wall to which the housing 351 is fixed.The swing arm 352 exerts a force on the rear end of the spring 345. The forward end of spring 345 exerts a force on collar 245 of plunger 240.FIG. 6B is a top perspective view of an embodiment of a plunger 240. FIG. 6C is a bottom perspective view of the plunger 240. As shown in these figures, an inclined upper surface 243 on the upper surface of the pressurizing piston 240 leads to a flat upper surface 241. The flat top surface 241 terminates at the end surface 242 of the plunger 240 which is angled with respect to the longitudinal centerline of the plunger 240.On the lower surface of the plunger 240, there is a flat bottom surface 248 as illustrated in FIG. 6C. Two portions of material are removed from the bottom of the end face 242 to form a central alignment finger 244. Each of the removed portions on either side of the alignment finger 244 includes a side pressure surface 246 and an upper pressure surface 247 meeting at a pressure corner 250. In some embodiments, the side thrust surfaces 246 do not form a right angle to the central longitudinal axis of the thrust piston 240 but tilt downward and forward toward one end of the thrust piston. Likewise, in some embodiments, the upper pressure surfaces 247 are not parallel to the longitudinal centerline of the pressure piston 240. Therefore, the angle formed at the pressure corner 250 may be an obtuse angle.When the end of a plunger 240 is engaged with a mounting aperture 220 on a side edge of a screen assembly support plate 202, the alignment finger 244 extends into the alignment slot 224 of the mounting aperture 220. The pressure surfaces 222 of the mounting opening 240 may initially contact the side pressure surfaces 246 or the top pressure surfaces 247. As the plunger 240 moves further inward, the pushing surfaces 222 of the mounting apertures 220 slide along the surface with which they first come into contact until the pushing surfaces 222 rest in the pushing corner 250. Further inward movement of the ram 240 then causes the support plate to flex into a concave shape and to be forced into engagement with the underlying support structures on the shaker screen machine.By clamping the pressure surfaces of the mounting apertures 220 of the support plate 202 in the pressure corners 250 at the ends of the plunger 240, a pressure force may be applied to the mounting aperture 220 having both a horizontal, inboard and a vertical, downward component. When the ram 240 is mounted to the side wall 312 of the shaker screen machine such that its central longitudinal axis is inclined downwardly and inwardly relative to the support plate 202, inward movement of the ram 240 produces a downwardly directed component of the compressive force. However, even if the plunger were mounted to move horizontally inward, the angled top pressure surfaces 247 at the end of the plunger would still produce a downward component of the compressive force. As mentioned above, this vertical downward force forces the carrier plate 202 into engagement with the underlying seal 670 of the shaker screen machine. This vertical downward force also serves to firmly secure the screen assembly to the vibratory screening machine during screening operations when the screen assembly is subjected to substantial acceleration forces.Moreover, the upper pressure surfaces 247 of the pressure piston 240 acting on the upper edges of the pressure surfaces 222 of the mounting holes 220 prevent the side edges of the support plate 202 from moving upward relative to the vibrating screen machine. This ensures that the side edges 206, 208 of the carrier plate remain in engagement with the seals 670 of the vibrating screen machine lying below, regardless of the strength of the vibrational or acceleration forces acting on the carrier plate 202.The inward movement of the plunger 240 also exerts a compressive force on the compression surfaces 222 of a mounting aperture 220 having a significant horizontal inward component. This inward pressing force causes the support plate 202 to be concavely bent. This forces the lower surface of the support plate 202 into engagement with the concave support members of the shaker screen machine. Also, because the inward compressive force is substantially aligned in the plane of the backing plate 202 at the side edges, it does not result in the side edges 206, 208 of the backing plate 202 turning upwardly away from the underlying seals 270. This is one of the problems with known pressure mounting mechanisms in which the compressive force is applied to an upwardly projecting flange on the side of the backing plate 202.In the prior art pressure mounting systems wherein a compressive force is applied to an upwardly projecting flange, the upwardly projecting flanges have no openings at the side edges of the support plate of the screen assembly. As a result, when material to be screened landed behind the flange--substantially between the outer surface of the flange and the side wall of the screening machine--it could not re-enter the screening area. In contrast, with the construction described above having access openings 232 in the flanges 230, any material which has landed between the outside of the flange and the side wall of the screening machine can pass through the access openings 232 and re-enter the screening area. Moreover, in some embodiments, the upwardly projecting flange 230 does not extend the entire length of the support plate or screen assembly. This means that at the front and rear edges of the upwardly projecting flange 230 there are locations at which material which has caught behind the upwardly projecting flange 230 can pass again into the screening region. An example of this can be seen in FIG. 7A, where the upwardly projecting flange 230 does not extend over the entire length of the lateral edge of the carrier plate 202 and ends shortly before the front edge of the carrier plate 202. These design features help screen almost all of the material deposited on the screen assemblies and prevent material buildup between flange 230 and the side wall of the screening machine.Figures 7A and 7B show a side edge of a screen assembly support plate 202 abutting a seal 670 which, in turn, is mounted to the side wall of a shaker screen machine via a seal mount 270. As discussed above, rams 240 exert compressive forces on the mounting apertures at the side edges of the backing plate 202. The compressive forces may include both a horizontal, inboard and a vertical, downward component. The vertical downward component forces the bottom surface of the support plate 202 into engagement with the top surfaces of the seals 670. This helps prevent material to be screened from running around the side edges of the screen assembly and contaminating the materials that have passed through the screen assembly.FIG. 7A illustrates a state in which the rams 240 are in a retracted state such that the carrier plate 202 can be lowered into place on the shaker screen machine with the side edges of the carrier plate 202 resting on the seal 670. Note that triangular mounting ramps 343 on the side wall of the shaker screen machine press the side edge of the support plate 202 inward as the support plate 202 is lowered into position.FIG. 7B illustrates a state in which the plungers 240 have moved inward to apply a pressing force to the mounting holes on the side edge of the base plate 202. Alignment fingers 244 at the ends of the plungers 240 project into corresponding alignment grooves 224 at the mounting apertures.FIGS. 8A and 8B illustrate an alternative embodiment of a plunger 440 and the associated mounting aperture of a backing plate. In this embodiment, the plunger 440 includes a triangular-shaped alignment finger that includes a first angled side surface 444 aand a second angled side surface 444 bextending from the end surface 445. The mounting aperture in the carrier plate includes a triangular shaped alignment slot formed by first and second angled side edges 424a, 424b. As the plunger 440 moves inward, the triangular-shaped alignment finger is received in the triangular-shaped alignment slot.The remaining construction of the plunger 440 and the mounting opening are substantially similar to the previous examples. The mounting aperture on the support plate has two pressure surfaces 421 on opposite sides of the triangularly shaped alignment slot. Pressure surfaces at the end of the pressure piston 440 abut the pressure surfaces 421 of the mounting opening to secure the screen assembly to the vibrating screen machine. The access opening 432 on the upwardly projecting side flange 230 is similar to the access openings of the preceding embodiments.FIGS. 8C and 8D illustrate another embodiment of a plunger 460 and a corresponding mounting aperture on a support plate of a screen assembly. In this embodiment, the plunger 460 has a rounded alignment finger 463 at the distal end of the plunger 460. A rounded engagement surface 464 on the rounded alignment finger 463 is received in and abuts a rounded alignment slot 465 of the mounting aperture.The remaining construction of the plunger 460 and the mounting aperture are substantially similar to the previous examples. The mounting aperture on the backing plate has two pressure surfaces 466 on opposite sides of the rounded alignment slot 465. Pressure surfaces at the end of the pressure piston 460 abut the pressure surfaces 466 at the mounting opening to secure the screen assembly to the shaker screen machine. The access opening 462 on the upwardly projecting side flange 230 is similar to the access openings of the preceding embodiments.FIGS. 8E and 8F illustrate another embodiment of a plunger 470 and a mounting aperture of a support plate of a screen assembly. In this embodiment, the access opening in the upwardly projecting side flange 230 is formed by two angled side surfaces 473 a, 473 b. The portion of the plunger that passes through the access opening in the upwardly projecting side flange 230 has a substantially triangular cross-section. Angled side surfaces 472a, 472b at the end of the plunger 470 generally mirror the shape and angles of the two angled side surfaces 473a, 473b of the access opening in the upwardly projecting flange 230. Interaction between the angled side surfaces 473a, 473b of the access opening and the angled sides 472a, 472b of the plunger 470 may provide an alignment function that results in the screen assembly being properly positioned on the shaker screen machine.Because the alignment function can be provided as described above, the mounting aperture on the support plate of the screen assembly can include a single, straight pressure surface 475. In other words, in some embodiments, it is not necessary to form a separate alignment slot 224 in the mounting apertures 220 of the carrier plate 202. Corresponding pressure surfaces 476, 477 at the end of the plunger 470 abut the single pressure surface 475 of the mounting aperture to secure the screen assembly to a vibratory screening machine.Figure 8G shows the end of an alternative embodiment of a plunger 480 having a triangularly shaped profile similar to that shown in Figures 8E and 8F. In this embodiment, however, the end of the plunger 480 includes an alignment finger 474. Pressure surfaces 476, 477 are formed on both sides of the alignment finger 474. The alignment finger 474 is configured to be received in an alignment slot 224 of a mounting aperture 220 of a carrier plate 202 such as that shown in FIG. 3.Figure 8H shows how a ram 480 as shown in Figure 8G would interact with a platen to attach a screen assembly to a vibrating screen machine. As shown in FIG. 8H, each of the access openings on the upwardly projecting side flange 230 comprises two angled side surfaces. The pressure pistons 480 with the angled sides project through the access openings. The alignment fingers 474 at the ends of the plungers 480 are recessed into the alignment slots 224 of the mounting apertures on the backing plate. The two pressure surfaces on opposite sides of the alignment finger 474 abut the pressure surfaces of the mounting apertures to secure the carrier plate and screen assembly to the shaker screen machine.In the embodiment shown in FIG. 8H, the alignment function could be performed in unison by: (1) the interaction of the angled sides 472 a, 472 bof the plunger 480 with the angled side surfaces 473 a, 473 bof the access openings; and (2) the engagement between the alignment finger 474 on the plunger 480 and the alignment slot 224 of the mounting opening on the support plate of the screen assembly.In some embodiments, the access ports on the upwardly projecting side flange 230 could be large enough to provide some clearance between the angled side surfaces 473a, 473b of the access ports and the angled sides 472a, 472b of the plunger 480. Even with considerable clearance, the interaction between the rams 480 and the access ports would provide a coarse alignment function which ensures that the screen assembly has been mounted in nearly the proper position on the shaker screen machine. Then, as the rams 480 travel inwardly, the engagement between the alignment fingers 474 on the rams 480 and the alignment slots 224 on the platen would allow fine adjustment of the position of the screen assembly on the shaker screen machine.In prior art machines, such as that shown in Figures 2A-2C, wherein a plunger abuts an upwardly projecting flange on a side edge of a support plate of a screen assembly, the screen assemblies could be mounted in incorrect positions on the vibrating screen machine with respect to the longitudinal direction or the material feed direction. Screens could also be rotated obliquely or slightly incorrectly, which could lead to some pressure pistons exerting little or no pressure force on the upwardly projecting flange, which weakened the holding force. Moreover, when a screen assembly was mounted obliquely or slightly rotated, the screen assembly did not assume the proper concave shape and the bottom of the screen assembly was likely not to form an effective seal with the underlying seals of the shaker screen machine.In contrast, in the mounting mechanisms described above and illustrated in Figures 3-8H, the manner in which the ends of the rams engage the mounting apertures on the side edges of the carrier plate ensures that the carrier plate and thus the screen assembly is correctly positioned on the vibrating screen machine in the longitudinal or material feed direction. The engagement between the ends of the rams and the mounting apertures also prevents oblique or slightly twisted mounting of a screen assembly and ensures that each ram exerts the correct compressive forces on the support plate. All of these factors help ensure that the screen assembly is correctly positioned on the shaker screen machine and the screen assembly support plate is securely forced into engagement with the underlying seals of the shaker screen machine.In prior art machines, as illustrated in FIGS. 2A-2C, the engagement between the rams and the upstanding flange could permanently deform the flange of a screen assembly. This can lead to the holding force exerted by the pressure piston being lower than provided. If a permanently deformed screen assembly is removed and later mounted again on a vibrating screen machine, it would be difficult for maintenance personnel to recognize the deformation. As a result, the re-installed screen assembly is likely to be held with less force than is provided. In contrast, the above-described print assemblies and shown in FIGS. 3-8H are unlikely to exhibit such permanent deformation.Moreover, a screen assembly having the mounting mechanisms described above and illustrated in Figs. 3-8H does not require an upwardly projecting flange, such as conventional mounting systems such as those illustrated in Figs. 2A-2C. This reduces manufacturing costs, speeds up the assembly process, and results in lighter screen assembly, which can reduce shipping costs. Moreover, the lack of side flanges prevents problems with material becoming caught behind the side flanges, making the screening operation more effective.The embodiment of a vibratory screening machine illustrated in Figures 4A-4D has the screening machine having a single trough with pressure assemblies 322 located on both side walls of the screening machine. In this type of screening machine, a single screen assembly extends across the entire width of the screen area, and a single row of screen assemblies is arranged along the entire length of the screening machine. This configuration may be advantageous because it allows the mounting of a screen assembly to such a screen machine by means of the printing assemblies 322 on only one side of the screen machine.For example, the printing assemblies on a first side of the screening machine may be left in the locked position with the rams extended. The pusher assemblies on the second side of the screening machine are opened so that the pusher pistons on the second side of the screening machine are in the retracted position. A new screen assembly can then be mounted to the machine by forcing the first side of the screen assembly down into the bed of the screen machine so that the mounting apertures on the first side edge of the support plate of the screen assembly are forced into engagement with the extended rams on the first side of the screen machine. The second side of the screening assembly is then forced down into the bed of the screening machine. Then, the pusher assemblies on the second side of the screening machine are actuated so that the pusher pistons on the second side of the screening machine extend inwardly, pushing the screening assembly into engagement with the concave support surfaces of the screening machine and securing the screening assembly to the screening machine.In this type of screening machine configuration, operators need only access to one side of the screening machine to mount screen assemblies. And since printing assemblies are located on both sides of the screening machine, operators can mount screen assemblies to the screening machine from both sides of the screening machine. On the other hand, this screen machine configuration means that printing assemblies must be provided on both sides of the screen machine, which increases the cost and complexity of the machine.Instead of mounting printing assemblies 322 on both side walls of the screening machine, the printing assemblies could also be provided on only a first side wall of the screening machine. The second side wall could include stationary stop members, the configuration of which matches the end of the rams of the printing assemblies installed on the first side wall. In this configuration, operators would mount screen assemblies from the first side of the screen machine where print assemblies are provided.To mount a screen assembly on such a machine, the screen assembly would be initially placed on the machine and the second side of the screen assembly would be pressed down such that the stationary stop members on a second side wall of the screen machine are aligned with the mounting apertures 220 on a second side edge of the support plate 202 of the screen assembly. Then, the first side of the screen assembly is pressed down so that the mounting apertures 220 on the first side of the screen assembly support plate 202 are aligned with the ends of the movable rams 240 of the press assemblies 322 on the first side wall of the screening machine. Then, the printing assemblies 322 on the first side wall of the screening machine are actuated. By actuation of the pushing assemblies on the first side of the screening machine, the pushing pistons are pushed into engagement with the pushing surfaces 222 of the mounting apertures 220 on the first side of the carrier plate 202. Further inward movement of the plungers also causes the pushing surfaces 222 of the mounting apertures 220 on the second side of the backing plate 202 to be urged into engagement with the stationary stop surfaces. Further advancement of the rams causes the support plate 202 to flex and be forced into engagement with the support surfaces of the screening machine.The stationary stop surfaces could be rigidly mounted on a side wall of a screening machine. Alternatively, the stationary stop surfaces could be configured to have some compliance. If a stationary stop surface has some resiliency, the member that mimics the end of a movable plunger can move resiliently relative to the side wall of the shaker screen machine. An example of a stationary stop member having compliance is illustrated in FIGS. 9A and 9B.FIG. 9A illustrates a stationary ram assembly 239 that may be mounted externally to a sidewall of a vibratory screening machine. Bolt holes 269 in the housing 268 of the stationary ram assembly 239 may be used to attach the assembly to a side wall of a vibratory screening machine. The stationary plunger assembly 239 includes an elastically mounted plunger 260 that extends through a circular bore of the housing 268. Upon mounting the stationary ram assembly 239 externally to the side wall of a shaker screen machine, the end of the ram 260 would extend into the interior of the shaker screen machine through an opening in the side wall.As shown in FIG. 9B, a compression spring 261 is mounted around the rear part of the pressurizing piston 260. A first end of the spring 261 abuts a collar 262 of the plunger. The second, opposite end of the spring abuts a flange assembly 267. The flange assembly 267 includes external threads 269 that engage internal threads in an internal bore of a cylindrical portion 265 of the housing 268. This holds compression spring 261 in the cylindrical portion 265 of the housing.The plunger 260 may slide inwardly into the housing 268, compressing the spring 261. Depending on the setting of the stationary plunger assembly 239, when no force is acting on the end of the plunger 260, the compression spring 261 acting on the collar 262 may urge the plunger 260 outward until the collar 262 abuts the end of the cylindrical portion 265 of the housing 268.A nut 266 is threaded onto a threaded rear end of the plunger 260. The nut 266 may be rotated to adjust the position of the plunger 260 within the housing 268. Thus, when no forces are applied to the end of the plunger 260, the collar 262 may be spaced from the end of the cylindrical portion 265 of the housing.A single trough vibratory screen machine, such as that shown in Figures 4A-4D, may include a plurality of pressure assemblies 322 on a first side wall and a plurality of stationary pressure piston assemblies, such as that shown in Figures 9A and 9B, on a second, opposite side wall. A twin trough vibratory screening machine such as that shown in Figures 1A and 1B could include a plurality of pressure assemblies mounted on the first and second outer side walls of the screening machine, with stationary pressure piston assemblies mounted on either side of a central abutment 316.In the foregoing examples, pusher piston pusher assemblies 322 are used to mount screen assemblies that include a backing plate and screen elements mounted thereon. The same basic print assemblies could also be used to mount different types of screen assemblies to a vibratory screening machine.An alternative type of screen assembly is one which consists of several individual screen units which are interconnected to form a complete screen assembly. Each individual screen unit may comprise a support structure and one or more screen elements attached thereto. Each support structure may comprise fasteners used for coupling to other support structures such that multiple screen units may be interconnected to form a complete screen assembly. Both the support structure and the screen elements can be produced from a plastic or synthetic material by injection molding. Examples of such screen assemblies are disclosed in U.S. Patent Nos. 9409209, 9884344, 10046363, 10259013, 10576502, 10835926, 10843230, 10981197, 10994306, 10960438, 10974281, 10933444, 10967401, 11413656, 111611150, 11000882, 11426766, 11638933, 11417913, 11446704, and 11471914, the contents of which are hereby incorporated by reference.Figures 10A-10C illustrate how an alternative screen assembly formed by assembling screen units from injection molded support structures and injection molded screen elements can be mounted to a vibratory screening machine using a pressurizing assembly 322 with pressurizing pistons 240. Figures 10A-10C show only a portion of a complete screen assembly for clarity and to aid in describing the assembly process. In Figures 10A-10C, only the support members of a portion of a complete screen assembly are shown. Screen members would be mounted on the support members shown in Figures 10A-10C.Figure 10B shows that a portion of an entire screen assembly is formed by the joining together of a plurality of flat support members 281 and a plurality of pyramidal support members 280. As may be best seen in FIG. 10B, each support member 280 / 281 includes fasteners that attach the individual support members together. The fasteners include protruding clips 284 and clip openings 283. The clip apertures 283 of a first support member receive the clips 284 of a second adjacent support member to connect the support members together. FIGS. 10A-10C illustrate a plurality of flat support members 282 joined end-to-end to form two elongated strips of flat support members 282. A plurality of pyramidal support members 280 are joined together to form an elongated strip of pyramidal support members 280. The sides of the elongated strip of pyramidal support members 280 are then joined to the sides of the two elongated strips of flat support members 281 to form part of a complete screen assembly. As mentioned above, screen elements (not shown) would be mounted on the support elements.Figures 10A-10C also illustrate that the left side edge of the screen assembly has a connector strip 282. Like the support elements 280 and 281, this connecting strip 282 has protruding clips and clip openings. As a result, the clips and clip openings of the connector bar 282 can be connected to the corresponding clips and clip openings of the elongated strip of flat support members 281 that form the left side of the screen assembly. A complete screen assembly would include another connector bar along the opposite side edge of the screen assembly.A plurality of support members attached to each other may form a "support member" of a screen assembly. In some embodiments, the support member may also include connecting ledges attached to the sides of the assembled support members. As discussed above, screen members are secured to the upper surfaces of the interconnected support members to form the complete screen assembly.A plurality of interconnected support elements and optionally also connecting strips correspond approximately to the support plate of a screen assembly in the preceding examples. In the following description, the terms "support plate" and "support member" are used interchangeably and refer to the portion of a screen assembly that cooperates with a mounting mechanism to attach the screen assembly to a vibratory screening machine.As shown in FIG. 10C, mounting holes 284 are formed on the outside of the connecting strip 282. The mounting apertures 284 are configured to define the end of the rams 240 of the ram assemblies 322 of the shaker screen machine. To mount such a screen assembly on a vibrating screen machine, a complete screen assembly with connecting strips on opposite side edges is placed on the machine in such a way that the mounting openings 284 on the connecting strips are aligned with the pressure pistons 240 of the pressure assemblies. The pressure pistons are then pushed into the mounting openings 284 of the connecting strips 282. The end members of the rams engage the surfaces within the mounting apertures, similar to that described above in connection with the first type of screen assembly. This may include an alignment finger 244 on the plunger 240 being received in an alignment slot 285 of the mounting aperture 284. End surfaces of the plunger may abut one or both of a lower pressure surface 286 or an upper pressure surface 287 of the mounting apertures 284. This allows the plunger 240 to exert both a horizontal inward force and a vertical downward force on the connector bar 282 and the remainder of the screen assembly. These forces urge the bottom surface of the screen assembly into engagement with the support structures of the shaker screen machine below the screen assembly.Of course, rams 322 could be provided with movable rams 240 on opposite sides of the shaker screen machine so that the movable rams 240 engage the connector ledges on both opposite sides of the screen assembly. Alternatively, such a screen assembly could be used on a vibrating screen machine using stationary ram assemblies as shown in Figures 9A and 9B on one side of the screen assembly.In some embodiments, the connector bar 282 could also be made of a synthetic or plastic material by injection molding or other manufacturing methods. In alternative embodiments, the connector bar could be a composite structure comprising injection molded plastic or synthetic elements as well as metal or glass fiber stiffener elements. The stiffener members would be configured to help distribute the compressive forces exerted by the rams across the entire side of a screen assembly. Further, the connecting strip could be formed from a metal material.In some embodiments, the mounting apertures 284 could be configured to receive the same pressurizing pistons as used with other screen assemblies, such as those described above with a metallic backing plate. In alternative embodiments, the mounting apertures 284 could be configured to receive different sized and / or shaped ends of rams. For example, the mounting apertures 284 of a connector strip 282 could have larger pressure surfaces 286, 287 to distribute a particular pressure force over a larger surface. This could require the use of rams with other larger areas to mount such screen assemblies to a vibrating screen machine. Alternatively, it could be possible to mount an end cap with larger pressure areas on the end of a plunger designed for the first type of screen assembly described above. Again, the end caps mounted on the ends of the rams would be configured to distribute a certain compressive force over a larger area than do the first embodiments described above.In some embodiments, the connector strips 282 may be constructed such that the mounting apertures 284 are made of a material having higher strength than other portions of the connector strip 282. This could be accomplished by mounting inserts of hard plastic or metal into openings on the connector bars to form the mounting apertures 284, or the entire connector bar 282 could be made of metal.A second type of screen assembly and pressure mounting mechanism utilizes pressure mechanisms that extend from the bottom surface of the screen member through the mounting apertures of a support plate. Figures 11A and 11B illustrate an end view and a partial end view of a double trough screening machine 300 incorporating this second type of press mounting mechanism. As previously mentioned, a double trough screening machine 300 includes two parallel screen assemblies 320a, 320b (hereinafter 320 unless specifically referred to) disposed between the inner surfaces of the spaced apart wall members 312a, 312b (hereinafter 312 unless specifically referred to). A central element 316 divides the screening machine 300 into two parallel screening areas. Each screen assembly 320 includes a first edge proximate a wall member 312 and a second edge proximate the center member 316. Pressing assemblies 322 press each of the screen assemblies against the underlying concave supports 314. A seal 317 (e.g., of rubberized or otherwise compressible materials) may be mounted on the concave top surface of each support 314. When the pressing assemblies 322 press the screen assemblies 320 into a concave profile, the bottom surface of the screen assembly (e.g., the bottom surface of the support plate 324) may be pressed against the seal 317 on the top surface of the concave supports 314 to form a seal between the screen assembly and the screening machine. The seals may have a width that allows sealing of an interface between two longitudinally arranged screen assemblies.As illustrated in Figure 11A, one of the screen assemblies 320b is shown with one screen surface 326 above an underlying perforated support plate 324, while the other screen assembly 320a is shown without the screen surface. In operation, each screen assembly will be surrounded over a screen surface. Although illustrated as a corrugated or corrugated surface, it should be appreciated that the screen surface may have other configurations (e.g., substantially flat). The screen surface may be comprised of, without limitation, woven mesh materials, metals, and / or synthetic materials such as polyurethane, thermoplastic polymers (e.g., polyurethane), and thermoset polymers. Each screen assembly also has an underlying perforated support plate 324.The embodiment of the screening machine 300 of Figures 1A-1C, 11A and 11B utilizes a so-called "pressurized" arrangement to press each screen assembly horizontally (e.g., against the central support or a second wall) and vertically downwardly against the concave supports. In the illustrated embodiment of the pressurized assembly, the printing assemblies 322 on the wall member 312 ainclude movable / actuated latches 336 that extend through corresponding pass-through printing points 350 a(see, e.g., FIGS. 12B-12C ) near a first edge 340 of the support plate 324. Each pawl 336 will typically include one or more hooks for engaging the support plate 324 of the screen assembly. More specifically, the latches 336 and their hooks engage through pressure points 350a located within the perimeter of the underlying support plate 324 of the screen assembly. The passage pressure points 350a are spaced from a first edge 340 of the support plate 324. When the screen assembly is installed on the screening machine, the pawls 336 extend through the passage pressure points 350a of the support plate 324 from the lower surface of the support plate 324 to the upper surface thereof. Actuation of the print assemblies 322 moves the pawls 336 between a first position (e.g., retracted) and a second position (e.g., extended). In the extended position, the hooks carried by the latches 336 exert a compressive force having both a horizontal component on the edge surface of the passage compression points 350a and a vertical, downward component on the top surface of the support plate 324. See also FIGS. 15A and 15B. These forces can bend the screen assembly into a concave shape while securing it to the screening machine.It should be noted that the pawls 336 exert the downward component of the compressive force on the upper surface of the support plate 324, which is supported between its side edges 340 and 342 prior to compression (see, e.g., FIG. 15A ). The application of this force between the supported side edges of the plate causes a multiplying effect on the downward force as compared to prior systems which applied a compressive force to the edges of such a screen assembly and required the plate to "buckle" to bend into the concave profile. That is, a distance between the plate edges 340 and 342 and the location at which the pawls 336 engage the plate 324 provides a lever arm for the downward force.Referring again to Figures 11A and 11B, a set of stationary hook assemblies 330 (only one shown) are secured to the central member 316, and each has one or more hooks on the stationary pawl 336 that extend through respective passage pressure points 350b proximate an opposing edge 342 of the support plate 324. See also FIG. 4C. The stationary pawls 336 extend through the passage pressing points 350b of the support plate 324 from the lower surface to the upper surface of the support plate 324. Although the use of the stationary pawls on the central member 316 (or the second wall in other embodiments) is discussed herein, it should be appreciated that in various embodiments, the second edge 342 of the carrier plate 324 may engage a stop or abutment surface (e.g., a channel) on the central member / the second wall and the screening machine, thereby eliminating the stationary pawls and / or hooks.FIGS. 12A, 12B, and 12C illustrate a screen assembly 320, a screen assembly 320 with a portion of the screen surface 326 removed, and a top view of a support plate 324, respectively, in one embodiment. In one embodiment, the upper surface of the screen assembly 320 may include an optional handle 305 for installing the screen assembly in a screening machine. As shown, the support plate 324 of the screen assembly 320 is generally rectangular and has a first edge 340, a second edge 342, a first end 344, and a second end 346. These edges and ends together define the periphery of the panel. The plate 324 is typically made of sheet metal, but other materials are possible. The support plate 324 has a plurality of flow apertures 348 extending through a body of the plate in its interior (e.g., within its perimeter), as defined by the edges and ends. The flow apertures 348 are configured to allow oversized materials passing through a supported screen surface to pass through the support plate 324. Although shown as having rectangular flow apertures 348, it should be appreciated that the size, shape, and distribution of the flow apertures across the support plate 324 may be varied. A plurality of passage pressure points 350a, 350b (hereafter 350 unless specifically referred to) are disposed along and spaced from the first and second edges 340, 342 of the backing plate 324. As discussed above and herein, the passage pressure points 350 are used to attach the screen assembly to a screening machine. More specifically, an inner edge of each passage pressure point 350 (e.g., relative to the centerline A-A' of the support plate 324) forms a contact or pressure surface against which a horizontal and / or vertical force may be applied to the plate inside. This contact or pressure surface may be substantially vertical (e.g., perpendicular to the top surface of the backing plate 324) or at a predetermined angle. See, e.g., FIG. 17G.As shown in FIGS. 12A and 12B, the screen surface 326 is illustrated as a wavy or wavy surface. However, it should be appreciated that the screen surface 326 may also have other configurations (e.g., substantially flat). Screen surface 326 may be made of, without limitation, woven mesh materials, metals, and / or synthetic materials such as polyurethane, thermoplastic polymers (e.g., polyurethane), and thermoset polymers. When using a woven mesh material, the screen surface 326 may comprise one or more layers of woven mesh material. Such woven mesh material may be secured to the backing plate 324 by bonding, welding, or mechanical attachment. Such a multilayer woven mesh screen is discussed below in connection with a discussion of Figures 25A-25E. Molded polyurethane screens are described, for example, in U.S. Pat. Nos. 8,584,866; 9,010,539; 9,375,756; 9,403,192 and 9,908,150; the disclosures of which are hereby incorporated by reference in their entirety. Screens of thermoset and thermoplastic polymers are described, for example, in U.S. Patent Nos. 9,884,344; 9,409,209; 10,046,363; 10,259,013 and 10,576,502; and in U.S. Patent Applications Nos. 15 / 965,363; 16 / 269,646; 16 / 269,656; 16 / 359,773; 16 / 359,830; 16 / 743,516; 16 / 743,581, 16 / 743,609, 16 / 743,626; 16 / 743,662; 16 / 837,716 and 16 / 904,819; the disclosure of which is hereby incorporated by reference in its entirety.In the illustrated embodiment, the passage pressure points 350 are generally T-shaped and each have a generally rectangular opening (e.g., first opening portion) with an alignment slot 354 (e.g., second opening portion) extending from a center of the inner edge (e.g., relative to the centerline A-A of the backing plate 324). See FIGS. 12B, 12C, and 12D. The alignment slot 354 is configured to receive an alignment member or bump of the latches 336 of the printing assemblies or the stationary hook assemblies.The engagement of the passage pressure points 350 with respect to a movable pawl 336 of a printing assembly is illustrated in FIG. 12E, in one embodiment. The operation of the stationary hook assemblies is substantially identical and is omitted for brevity. Referring to FIGS. 11B and 12B-12E, the alignment slot 354 receives an alignment bump 338 disposed between two hooks 332 a, 332 bof the pawl 336. As shown, the support plate 324 may include a plurality of through-print dots 350, each including an alignment slot 354. In the illustrated embodiment, each side of the support plate 324 includes four passage print dots 350, each including an alignment slot 354. When the carrier plate 324 is positioned in the screening machine, the alignment bumps 338 of the pawls 336 of the print assemblies 322 are in the alignment slots 354 of the pass print dots 350 along the first edge 340 of the carrier plate 324, while the alignment bumps 338 of the pawls 336 of the stationary hook assemblies 330 are in the alignment slots 354 of the pass print dots 350 disposed along the second edge 342 of the carrier plate 324.The bump alignment slots 354 and the alignment bumps 338 form a positive positioning system for the screen assembly 320. That is, once the bumps 338 are positioned in a screen assembly through the alignment slots 354, the position of the screen assembly 320 along the length of the screen machine (i.e., along the walls) is necessarily correct, thereby eliminating the need to manually position screen assemblies along the screen machine as previously required. The proper positioning of the screen assemblies by the alignment prevents adjacent screen assemblies from jamming or becoming dislodged from each other during use and leaving a gap. The correct positioning also ensures that the screen assemblies are not properly compressed, which could lead to damage. Moreover, proper positioning better aligns the screen assemblies to the underlying seals, providing improved sealing. In addition, reducing the need to fully manually position the screen assemblies as provided by the alignment assembly reduces the time required for installing a set of screen assemblies.The T-shaped passage pressure points 350 also form first and second contact or pressure surfaces 356a, 356b disposed on either side of the alignment slot 354. In operation, this allows the dual hook 332a, 332b of the movable pawl 336 of the print assemblies or the dual hook of a stationary pawl of a stationary hook assembly to engage both sides of the alignment slot. Such an arrangement ensures good contact between the screen assembly and the hooks / latches, thus permitting the exertion of high hold-down forces.Although each pass-through pressure point 350 is illustrated as having an alignment slot 354, it should be appreciated that a first subset of the pass-through pressure points 350 may include an alignment slot 354 while a second subset of pass-through pressure points 350 is clear of an alignment slot. The alignment slots 354 are shown extending inward from the inner edge of the passage pressure points 350. Further, although shown as being disposed in the center of the passage pressure points 350, it should be understood that the position of the alignment slot 354 may be varied along the length of the passage pressure points 350. Moreover, it should be appreciated that the alignment slots 354 may extend from the outer edges of the passage pressure points 350 and / or from the upper and lower ends of the passage pressure points 350. Here, the passage pressure points 350 may have different shapes (e.g., other than T-shape). In any configuration, a first portion of the passage pressure point 350 will have a first portion (e.g., first opening portion) with one or more inner edges (e.g., relative to the centerline A-A of the support plate 324) that enables application of a horizontal and / or vertical compressive force to the support plate 324, and a second portion (e.g., second opening portion) that enables receipt of an alignment member. The second portion of the passage pressure point (e.g., second opening portion) will typically have one or more side walls that are transverse to the inner edge of the first opening portion. In this sense, other shapes such as L-shaped or cross-shaped through points, to name a few, may also be used.Figures 13A-13F illustrate an embodiment of a pressurized assembly 322 in which an engagement member (e.g., pawl and / or hook) and an alignment member (bump) pass through the bottom of a screen assembly to align the screen assembly on a screen machine and apply both a horizontal force to a side or edge surface of the screen assembly and a downward force to the top surface of the screen assembly. More specifically, FIGS. 13A and 13B illustrate first and second perspective views of the printing assembly 322 in one embodiment; FIGS. 13C and 13D illustrate first and second side views of the printing assembly 322 in retracted and extended configurations, respectively, in one embodiment; FIG. 13E illustrates a cross-sectional view of the printing assembly 322 in one embodiment; and FIG. 13F illustrates an exploded view of the printing assembly 322 in one embodiment.As variously shown in Figs. 13A-13F, the printing assembly 322 has an outer press mounting bracket 370 for attachment to the outer surface of a wall member of a shaker screen machine. The printing assembly 322 also includes an inner press mounting bracket 372 for attachment to the inner surface of the wall member of the shaker screen machine. The brackets 370, 372 are constructed so that they can be mounted flush with the intermediate wall element (not shown). The brackets 370, 372 may be bolted together through the wall member. As discussed further below, the press-mounting brackets 370, 372 collectively define an inner actuating rod pin that houses an actuating pin or rod 374 that extends through an opening in the wall member (not shown). The pawl 336 is fixed to a front and distal end of the operating rod 374, respectively. As shown, the actuation rod 374 is disposed at a downward angle "α" to the horizontal (e.g., angle of inclination) when the assembly 322 is mounted on a vibratory screening machine (see, e.g., FIG. 13E ). This angle of inclination facilitates the application of a downward force to the screen assembly upon extension of the pawl 336 of the pusher assembly. In some embodiments, the angle of inclination α is between about 0° and 20°. In some embodiments, the angle of inclination α is between about 1° and about 10°.The actuating pin or rod 374 is shown in Figures 13A-13F as a cylindrical pin or rod. However, in alternative embodiments, the actuating pin or rod may have other cross-sectional shapes. For example, the actuation pin or rod may have a square, rectangular, or hexagonal cross-section, as well as various other cross-sectional shapes. Also, the diameter of the actuating pin or rod 374 may vary along its length. Therefore, the illustration of the actuating pin or rod shown here is in no way to be understood as restrictive.An actuation bracket 376 is attached to the outer wall press-mount bracket 370. The attachment of the actuation bracket 376 may be via a screw, pin, or other axle (not shown) passing through aligned openings in the actuation bracket 376 and the outer press-fit bracket 370. Accordingly, the actuating bracket 376 can rotate relative to the outer press-fit bracket 370 about the axis formed by the screw connection. The actuating bracket 376 is attached via extension arms 378 to a rear end of the actuating rod 374, which is pivotally connected to the rod 374 via first and second pins 371 that fit into lateral notches 375 in the rod 374. A compression spring 384 is disposed in the pin defined by the press mounting bracket and around the actuating rod 374. More specifically, spring 384 is configured to extend between extension arms 378 of actuation bracket 376 and a collar 377 disposed about actuation rod 374. The spring 384 is configured to maintain the actuation rod and the pawl attached thereto in a retracted position in an uncompressed state.The actuation bracket 376 further includes a sleeve 379 configured to receive a first end of a handle (see, e.g., FIG. 21A ). A downward and rotational force may be applied to this handle to compress the compression spring 384 via the extension arms 378 and move the actuation rod 374 inward, thereby moving the pawl 336, which may be fixedly connected to a front end of the actuation rod 374, from a retracted to a compressed position or extended position (see FIG. 13D ). Printing assembly 322 may be locked in the printing position by engaging a locking tab 392 of a locking pawl 390 with a locking stop 394 of the actuation bracket 376. See also Fig. 14E. That is, when the actuation bracket 376 is in a push configuration, the locking pawl 390 may be rotated downwardly to engage the locking tab 392 with the locking stop 394 of the actuation bracket 376. The push assembly 322 may be released or unlocked by applying a downward force to the handle (not shown) until the locking tab 392 of the pawl 390 is free to rotate away from the locking stop 394 of the actuation bracket 376, thereby allowing retraction of the push pawl 336.FIG. 14A illustrates three views of the pawl 336 including: (a) a rear perspective view; (b) a front perspective view; and (c) a side view, in one embodiment. The pawl 336 is configured for use with the screen assembly of FIGS. 12A-12C and has passage push points 350 with an alignment slot 354 configured to receive an alignment bump. The latch 336 includes first and second hooks 332 a, 332 band an alignment bump 338. In the illustrated embodiment, the alignment bump 338 is integrally formed with and disposed between the first and second hooks 332 a, 332 b.A contact surface (e.g., hook surface) 337 of each hook 332 a, 332 bis disposed at an acute opening angle θ to the generally planar top surface of the screen assembly (e.g., prior to compression). The contact surface 337 could comprise two or more planar surfaces, each oriented at a different angle to the planar top surface of the screen assembly. The contact surface 337 could also be curved or arched. In one embodiment, the opening angle θ is between about 5° and 85°. In a further embodiment, the opening angle θ is between approximately 15° and 75°. In a further embodiment, the opening angle θ is between approximately 50° and 60°. The acute angle of the contact surfaces 337 of the pawls 336 facilitates the application of a downward force to the screen assembly as the pawls 336 are advanced.The first and second hooks 332 a, 332 band the boss 338 are mounted to a first leg of an L-shaped bracket 502, the second end of which is secured to a mounting member 504, in the illustrated embodiment. The shape of the clip 502 allows the contact surface(s) 337 of the hooks 332 a, 332 bto protrude beyond the printing assembly and extend through and engage an overlying support plate. The clip 502 also allows engagement with passage pressure points 350 that are closer to the edges of the support plate 324. Although advantageous for engaging the interior of the carrier plate 324, it has been found that too much distance of the passage pressure points 350 from the edges 340, 342 of the carrier plate 324 may result in reduced pressure forces along the edges 340, 342 of the carrier plate 324.The mounting member 504 includes an opening 506 that serves to attach the latch 336 to the distal end of the actuation rod 374 via a fastener 381, such as a bolt. See, e.g., FIG. 13E. Such attachment enables easy replacement of the pawl 336, which is a component that wears during machine operation. Moreover, because the pressure assembly and pawl 336 are below the screen assembly, these components are removed from the liquid pool on the top of the screen assembly, further reducing wear on these components.In the illustrated embodiment, the protuberance 338 extends vertically over the dual hook 332a, 332b. The upper inner edge of the boss 338 also defines an angled or inclined surface 362. As previously mentioned, the bumps 338, when engaged in the alignment slots 354 of a screen assembly, assure proper longitudinal position of the screen assembly along the side wall of the screen machine. The use of the inclined surface 362 on the print assembly bumps 338 and the corresponding inclined surfaces on the bumps 338 of the opposing stationary hook assemblies ensures proper lateral positioning between the side walls (or a side wall and a center member) of a screening machine. More specifically, the support plate 324 may seat on the bumps 338 of the printing assembly and slide down the inclined surface 362. The same operation is performed upon engaging the bumps 338 of the stationary hooks 336. Accordingly, the positioning of the carrier plate 324 between the wall elements or between a side wall and a central element is necessarily correct. This may allow the correct positioning of the edges 340, 342 of the support plate 324 on the seals 319, 329 covering the support surfaces that support the edge surfaces 340, 342 of the support plate 324. See FIGS. 15A and 15B. Such positioning may provide improved sealing between the screen assembly and the screening machine. Moreover, the positioning of the screen assemblies made possible by the alignment assembly reduces the time required for installing a set of screen assemblies.FIG. 14B illustrates three views of the inner press-fit clip 372 including: (a) a side cross-sectional view; (b) a front perspective view; and (c) a top view, in one embodiment. The inner press-mount bracket 372 includes a base plate 516 configured for attachment to an inner wall of the screening machine. A hollow pin housing 518 extends from the base plate 516. The cavity 510 of the pin housing 518 is sized to receive the actuating rod 374 and the surrounding spring 384. See also FIG. 13E. The cavity 510 of the pin housing 518 includes a step 512 of reduced diameter. When the actuator assembly is assembled, collar 377 disposed about actuator rod 374 abuts step 512.In one embodiment, the inner press-mount bracket 372 includes first and second alignment guides 514a, 514b that are secured to the top surface of the pin housing 518. These guides 514a, 514b are on opposite sides of the L-shaped bracket 502 of the pawl 336 (see, e.g., Fig. 14A) when the printing assembly is assembled (see, e.g., Figs. 13A and 13B). The guides 514a, 514b provide stability to the pawl 336 as it moves between retracted and extended positions. It is also noted that the use of the L-shaped bracket 502 and guides 514a, 514b allows the pawl 336 to engage a screen assembly closer to its edge, while the inner portion of the pusher assembly is positioned below the pawl 336 and the screen assembly.FIG. 14C illustrates three views of the outer press-fit bracket 370 including: (a) a side view, (b) a perspective view; and (c) a bottom view, in one embodiment. The outer press-fit bracket 370 includes a base plate 520 configured to be attached to an outer wall of the screening machine and, in one embodiment, to the inner press-fit bracket 372. The base plate 520 includes a base plate opening 522 through which the actuating rod 374 and the surrounding spring 384 may pass. A pin or rear bearing 524 receives the rear end of the actuating rod 374 when the printing assembly is assembled. See also FIG. 5E. The outer bracket 370 also includes a mounting aperture 526 that extends transversely to the base aperture 522 and the rear bearing 524. The mounting aperture 526 provides a location to pivotally attach the actuation bracket 376 to the outer press mounting bracket 370. Additionally, the outer press-fit bracket 370 includes a bolt 528 for mounting the latch 390 to the outer bracket 376. The bolt 528 includes a round base portion 530 and a hexagonal portion 532. The bolt 528 engages an eccentric nut to which the locking pawl 390 is secured, as discussed below. It should be noted that the addition of the rear bearing 524 provides additional support for the actuating rod 374 in assembly of the printing assembly. That is, a front end of the operation rod 374 is supported inside the inner press-mounting bracket 372, while the rear end of the operation rod 374 is supported by the rear bearing 524. This reduces the non-linear movement of the actuating rod 374 and thus reduces wear and extends the life of the actuating rod 374.FIG. 14D illustrates three views of an eccentric nut 540, including: (a) a first perspective view; (b) a second perspective view; and (c) a rear view, in one embodiment. The eccentric nut 540 is configured to attach the latch pawl 390 to the bolt 528 of the outer press mounting bracket 370. The eccentric nut 540 includes a first cylindrical outer surface 542 sized for receipt in a corresponding opening 396 of the locking pawl. See also FIG. 13F. The locking pawl 390 rotates about this outer surface in the assembled state. The eccentric nut 540 also includes a second cylindrical outer surface 544 that forms a retaining lip about the first cylindrical surface 542. This retaining lip holds the locking pawl 390 in place when the eccentric nut 540 is secured to the bolt 528 of the outer bracket. The eccentric nut 540 includes two hollow interior portions, a round portion 546 and a hexagonal portion 548. The round portion 546 of the nut 540 is configured to fit over and around the round portion 530 of the outer bracket bolt 528, and the hexagonal portion 548 of the eccentric nut 540 is configured to fit over and around the hexagonal portion 532 of the outer bracket bolt 528. The hollow inner portions of the eccentric nut 540 are offset from the central axis of the outer cylindrical surfaces of the nut 540. When the eccentric nut 540 is engaged with the bolt 528 (see also FIG. 14C ), the mating hexagonal portions prevent rotation of the eccentric nut 540. By selecting the orientation of the eccentric nut 540 relative to the bolt 528, the position of the outer surface 542 on which the locking pawl 390 rotates may be adjusted. Such an adjustment enables fine tuning of the pawl and / or spring tension.FIG. 14E illustrates four views of the actuation bracket 376 including: (a) a first side view; (b) a second side view; (c) a perspective view; and (d) a top view, in one embodiment. The actuating bracket 376 is connected to the outer press mounting bracket 370 via a bolt or pin passing through an opening 383 passing through the first and second extension arms 378 a, 378 b. As mentioned above, the inner surfaces of the extension arms 378 a, 378 bcomprise first and second pins 371 a, 371 b, respectively, configured to pivotally engage the lateral notches 375 of the actuation rod 374. See also FIGS. 13E and 13F. The distal tips 385 a, 385 bof the bifurcated extension arms 378 a, 378 bare configured to engage a rear end of the spring 384 when the printing assembly is assembled.FIGS. 14F and 14G illustrate perspective and exploded views of a stationary hook assembly 330 for attachment to a wall member or center member of a screening machine, in one embodiment. The stationary hook assembly 330 uses the same pawl 336 as used by the printing assembly discussed with reference to FIG. 14A, including a protuberance 338 between the two hooks 332 aand 332 b. Further explanation of the pawl 336 is omitted for brevity. In use with the stationary hook assembly 330, the pawl mounting member 504 is bolted to a mounting bracket 560 having a plate 562 configured for attachment (e.g., bolted or welded) to a wall or central member of the screening machine.In some embodiments, the stationary hook assembly 330 could include a biasing member, such as a spring, similar to the stationary plunger assemblies shown in FIGS. 9A and 9B. This would allow for easy movement of the stationary hooks 332a, 332b during assembly of a screen assembly. This could also allow the rest positions of the stationary hooks 332 a, 332 bto be easily adjusted.FIGS. 15A and 15B illustrate the movable pawl 336 of the pusher assembly 322 in conjunction with the stationary pawl 336 of the stationary hook assembly 330 as they compress a screen assembly support plate 324 from a substantially planar profile (FIG. 15A ) to a substantially concave profile (FIG. 15B ). Once the screen assembly is properly positioned with the hooks of the latches 336 extending through the passage push points 350 and the alignment bumps 338 guided through the corresponding alignment slots 354, the push assemblies 322 may be actuated to move the movable latches 336 from a retracted position to an extended position. As shown in FIG. 15A, the support plate 324 may be substantially planar prior to actuation. Upon actuation, the movable pawl 336 of the push assembly 322 may be advanced to apply a compressive force having a horizontal component applied to an edge of the passage point of pressure 350 and a vertical, downward component applied to the top surface of the support plate 324 (see FIG. 15B ). This presses the carrier plate 324 against the stationary pawls 336 of the stationary hook assemblies 330 that extend through the passage pressure points 350 near the second edge 342 of the carrier plate 324. Further advancement of the movable latches 336 results in the bending of the support plate 324 into a concave shape against the concave support surfaces (see FIG. 15B ).FIGS. 15C and 15D show partial close-up views of the pawls 336 aand 336 bof the printing assembly 322 and the stationary hook assembly 330 engaging the support plate 324 of a screen assembly. The movable or actuated pawl of the push assembly is referred to as pawl 336a, while the stationary pawl of the stationary hook assembly 330 is referred to as pawl 336b. First, the movable pawl 336 aof the printing assembly 322 is advanced so far that the hook contact surface 337 aof the movable pawl 336 aengages the inner edge (e.g., measured from the centerline of the support plate 324) of the passage printing point 350 a. See also FIG. 12E. Advancement of the movable pawl 336a pushes the support plate 324 until the inner edge of the opposing passage push point 350b engages the contact surface 337b of the fixed pawl 336b. At this time, the support plate 324 is not yet bent and fixed between the opposing pawls 336 a, 336 b(see FIG. 15C ). After the plate is fixed between the pawls 336a, 336b, further advancement of the movable pawl 336a, represented by the force vector "F", causes the carrier plate 324 to slide down the angled contact surfaces 337a, 337b of the pawls 336a, 336b, as shown by the motion arrow down the face of the pawl. Further inward movement of the movable pawl 336a exerts an increasingly greater force on the carrier plate. Movement down these opposing angled contact surfaces 337 a, 337 bcauses the vertical component of the force vector "V" to increase more than the horizontal component of the force vector "H" applied to the backing plate 324. This results in the carrier plate 324 being pressed with a large vertical, downward force component into a concave profile against underlying supports (not shown).It should be noted that the carrier plate 324 should not adhere to the contact surfaces 337a, 337b of the pawls when the inner edges of the passage pressure points 540 engage and slide down the contact surfaces 337a, 337b. Accordingly, it has been found that an increase in the hardness of the hooks / pawls 336 and / or the contact surfaces 337 a, 337 bin relation to the hardness of the carrier plate 324 may prevent such adhesion. That is, if at least the contact surfaces 337 a, 337 bhave a hardness greater than the hardness of the backing plate 324, the backing plate 324 will not scratch the contact surfaces 337 a, 337 b, which may result in the backing plate 324 hanging on the contact surfaces 337 a, 337 band not sliding down on the contact surfaces 337 a, 337 b. In one embodiment, the contact surfaces 337 a, 337 bhave a hardness of Rockwell C45. In another embodiment, the contact surfaces 337 a, 337 bhave a hardness of greater than Rockwell B 100 (HRB 100) or Rockwell C 20 (HRC 20).In some cases, it may be advantageous to adjust the strength of the downward vertical component V to the force applied to the support plate 324. See Fig. 15D. That is, if the carrier plate 324 slides too far down the contact surfaces 337 of the pawls 336, the vertical force V may multiply while the horizontal force H is excessively reduced. This could possibly result in too little horizontal force being applied to the plate, thereby reducing the concave curvature of the plate and reducing the engagement of the support plate with underlying supports and / or gaskets in their inner areas (e.g., near its centerline axis).Figure 15E shows a partial view of a latch 336 having two contact surfaces that alter or limit the movement of a carrier plate 324 down the contact surfaces 337, 339 of the hook 332. As shown, a first contact surface 337 has an opening angle between about 5° and about 85° (see also FIG. 14A ). In addition, the pawl 336 has a second contact surface 339 disposed at a different angle than the first contact surface 337. The different angles of the first and second contact surfaces may allow for changing, limiting, or preventing further movement of the panel along the pawl 336. In an embodiment, the first contact surface 337 may have a first angle that initially exerts a primary downward vertical force component on the carrier plate. Once the carrier plate reaches the intersection between the first and second contact surfaces 337, 339, the additional downward vertical force may be reduced while more horizontal force is applied to the plate. In another embodiment, the second contact surface 339 may be substantially vertical (e.g., perpendicular to a horizontal reference plane defined by an overlying non-bent support plate 324; see, e.g., FIG. 15A ). Alternatively, the second contact surface 339 may form a lip or step (e.g., a surface substantially parallel to a horizontal reference plane defined by an overlying non-deflected support plate 324). In such an embodiment, the second contact surface 339 limits or prevents movement of a carrier plate 324 beyond the first contact surface 337. After the carrier plate 324 moves downwards along the contact surface 337 and has reached the substantially vertical second contact surface 339, a further sliding of the carrier plate 324 is largely or completely prevented. Accordingly, any further movement of the pawl 336 will result primarily in the application of additional horizontal force to the support plate 324. It should be appreciated that the angles, lengths, and / or positions of the first contact surface 337 and the second contact surface 339 may be selected to apply horizontal and vertical forces of desired magnitudes to the support plate 324. Further, it should be appreciated that a contact surface may be an arcuate surface where the vertically and horizontally applied forces vary over the length of the arcuate or otherwise irregular surface.Referring again to FIGS. 15A and 15B, the movable pawls 322 of multiple print assemblies adjacent the first side edge 340 of the carrier plate 324 are configured to engage the corresponding through print points 350 aalong the first side edge 340 of the carrier plate 324. Similarly, a plurality of stationary pawls 330 mounted on a central abutment or an opposing side wall of a shaker screen machine are configured to engage the corresponding passage pressure points 350b on the second side edge 342 of the support plate 324. Ideally, the movable pawls 322 would all be aligned with each other and the stationary pawls 330 would all be aligned with each other. However, if the side wall on which the pusher assemblies are mounted is not exactly parallel to the opposite side wall or abutment on which the stationary pawls are mounted, the spacing between each pair of movable and stationary pawls may be different. As the printing assemblies or stationary pawls change or flex over time, the distance between each pair of movable and stationary pawls may also be different. These differences in the distance between each pair of movable and stationary latches can result in undesirable warping or bending of the platen when the printing assemblies are actuated to secure a screen assembly to the vibratory screening machine.One way to accommodate small differences in the spacing between each pair of movable and stationary latches is to incorporate some compliance into the print assemblies. For example, each thrust assembly could be configured such that the plunger or movable pawl in each thrust assembly does not need to be advanced inwardly just the same distance before the thrust assembly snaps into place. This could be achieved by spring mounting of the plunger or movable pawls so that their final locking positions could vary slightly.Another way to accommodate small differences in the distance between each pair of movable and stationary pawls is to incorporate some compliance into the stationary pawls 330. For example, the stationary pawl mounting bracket 560 (see Figs. 14F and 14G) could include a spring member that allows for easy inward / outward movement of the stationary pawls relative to the side wall or the stop to which the stationary pawls are attached. This will allow for easy inward / outward movement of the stationary pawls when a screen assembly is mounted on a shaker screen machine to accommodate small differences in spacing between pairs of movable and stationary pawls.Another advantage of the pressurized arrangement is that the screen assemblies 320 may be installed in a flatter (e.g., less concave) configuration. That is, the ability to grasp the panels through the carrier plate between their edges and apply an increased downward force to the carrier plate 324 allows for sufficient fixation of the screen assemblies 320 relative to a screening machine while maintaining the screen assemblies 320 flatter. FIG. 15F illustrates a radius of curvature R 1 of a screen assembly 320 configured for engagement by a pressurized assembly according to one or more embodiments of the present disclosure. FIG. 157G illustrates a radius of curvature R2 of a prior art screen assembly 20 configured for engagement over an edge surface, such as an upwardly directed flange 25 projecting over an upper surface of the support plate 24. In the prior art screen assembly 20, a radius of curvature R2 (e.g., in inches) was in a range between about 40 and 60, with Figure 15G illustrating a screen assembly 20 having a radius of curvature of 50 inches. That is, a high degree of concavity was required to allow the screen assembly 20 to sufficiently bulge and seal with the underlying gaskets.In contrast, screen assemblies 320 configured for use with the pressurized assembly described herein can be manufactured with larger radii of curvature and yet sufficiently seal with underlying seals. As illustrated in FIG. 15F, the screen assembly 320 has a 100 inch radius of curvature, resulting in a significantly flatter screen assembly compared to prior art screen assemblies. Moreover, screen assemblies 320 used with the pressurized assemblies described herein could have radii of curvature R1in the range of about 60 inches to about 140 inches. The ability to provide flatter screen assemblies provides a significant advantage to a screening machine. In particular, as material (e.g., liquid pool) runs the length of the screen assemblies, the liquid pool distributes over a greater portion of the width of the concave screen assembly (between its opposing edge surfaces). This results in the liquid accumulation coming into contact with a larger part of the screen surface, thereby increasing the screen capacity of each screen assembly.FIG. 15H illustrates an end view of the screen assembly of FIG. 15F pressed against a bed of a pressurized screening machine 300A in accordance with the present disclosure (see also FIG. 1D ). FIG. 151 illustrates an end view of the prior art screen assembly 20 of FIG. 15G pressed against the bed of a prior art screen machine 10A (see also FIG. 2B ). As shown in FIG. 15H, the pressure assembly 322 and the stationary hook assembly 330 each have a pawl 336 that extends through the passage pressure points in the support plate 324 of the screen assembly 320 disposed between the first and second side walls 312 a, 312 bof the single tray screen machine 300A illustrated.In contrast, as shown in Figure 15l, the screening machine employs a pushing assembly 22 disposed on a first wall 12a of the machine which engages a vertical flange 28 which projects beyond the edge surface of a plate 24 of a screening assembly to push a second edge surface of the screening assembly 20 against a second wall 12b (e.g., abutment surface) of the machine. In the pressurized machine 300A of FIG. 15H, the pawls 336 engage the screen assembly 320 at locations within the support plate 324 (e.g., between the edges of the plate) and spaced from the side walls 312 a, 312 b. As discussed above, the position of the latches inside the screen assembly and / or the shape of the hooks of the latches (e.g., the contact surface or hook surface) of the assembly under pressure allows a greater downward force to be applied to the screen assembly compared to the pressure assembly 22 shown in FIG. 15 l. In the screen machine in FIG. 15 l, the pressure assembly 22 applies a force to the edge of the screen assembly, thereby using a majority of the downward force to bulge the plate 24 of the screen assembly 20. Moreover, the machine in Figure 15l does not take advantage of the shape of the plate contacting latches / hooks which act as a force multiplier.The ability to engage the screen assembly 320 through a lower surface on an upper surface of the support plate 320 also allows lowering the position of each printing assembly 322 on the outer surface of the wall member(s) of the screening machine 300A. That is, the printing assemblies 322 of the screening machine of FIGS. 1D and 15H may be positioned lower than the printing assemblies 22 of the screening machine 10A of FIGS. 2B and 15L engaging an upper surface or vertical flange protruding above the screening assembly. The lowering of the pressure assemblies can avoid interference between the pressure assemblies and braces on the outer walls of the screening machine. This may also allow for more even distribution of the printing assemblies along the length of the screening machine, providing for more even compression of the screening assemblies. Although discussed as lowering the print assemblies in a single tray machine of Figs. 1D and 15H, it should be understood that the use of a pressurized assembly in the dual tray machine 300 of Figs. 1A-1C may also allow lowering of the print assemblies on the outer wall of the machine.In use, the screen assembly 320 may be mounted on a screening machine 300. More specifically, the screen assembly 320 may be disposed between the first wall 312 aand the central member 316 of the screening machine 300 (e.g., in a double trough screening machine). Alternatively, such a screen assembly 320 may be disposed between the first and second walls of a single trough screening machine. Once disposed between the wall 312a and the central member, the screen assembly may be moved along the length of the screening machine 300 until the pawl(s) 336 and protuberance 338 are disposed on a first wall 312a through the passage pressure points 350a proximate a first edge 340 of the support plate 324, and the pawl(s) 336 and protuberance 338 are disposed on the central member 316 (or the second wall of a single tray machine) through the passage pressure points 350b proximate a second edge 342 of the support plate 324. More specifically, the bumps 338 will be disposed through the alignment slots 354 of the various passage pressure points 350, thereby properly positioning the screen assembly relative to the screen machine. At this time, the actuator(s) may be activated to move the movable latches 336 between a retracted position and an extended position. In the extended position, the pawls 336 apply a compressive force having a horizontal component and a vertical downward component to the passage compression points 350 atoward the first edge 340 of the support plate 324. The horizontal component of the force presses the carrier plate 324 against the stationary pawls 336 of the stationary hook assemblies 330 that extend through the passage pressure points 350b near the second edge of the carrier plate 324. Further advancement results in the vertical component of the force exerted by the movable pawls 336 and stationary pawls 336 urging the panel into a concave shape (e.g., against the underlying stringers 314). See Fig. 11A.FIGS. 11B, 15A, and 15B also illustrate the compression of the plate 324 of the screen assembly 320 against various seals extending around the perimeter of the support plate 324. That is, a first seal 319 may be disposed between the first edge 340 of the support plate 324 and an underlying support surface, a second seal 329 may be disposed between the second edge 342 of the support plate 324 and an underlying support surface, and third and fourth seals 317 (only one shown) may be disposed on the upper surfaces of the concave support surfaces 314 below the first and second ends 344, 346 of the support plate 324 (see also FIG. 12C ). Due to the increased hold-down force achieved by the higher vertical component provided by the pressure assembly (i.e., downward force component), the pressure force applied to the screen assembly against all underlying seals of the screen machine may be increased. The increased force / pressure against the seals not only provides better sealing between the screen assembly and the screening machine, but also extends the life of the seals as the screen assemblies move less (e.g., flutter) relative to the seals. Accordingly, less material can pass between the carrier plate and the seals. Reduced movement of the screen assembly relative to the screening machine also results in improved screening. That is, as each screen assembly more tightly abuts the screen machine, the vibration generated by the screen machine is better transferred to the material on the screen assemblies.Another advantage of the disclosed embodiments is that the screen assemblies may dispense with an upwardly directed flange near one or both edges that has been previously used to apply a compressive force to the screen assemblies. The omission of this flange avoids the risk of material being caught behind such a flange. The elimination of such flanges or channels in conjunction with the increased hold-down forces reduces or prevents material leakage at the edges of the screen assemblies.The pressurized arrangement of Figs. 1A-15B also enables the manufacture of support plates and screen assemblies which are free of grooves and / or flanges at their edges. That is, the support plates may be formed of a flat plate. Since no special edge grooves need to be attached to the edges of the carrier plates, the plates can be punched or laser cut. In addition, the screen assemblies can be thinner because they do not have grooves at the edges. This may allow more screen assemblies to be accommodated in a package of a particular size. The omission of the grooves or flanges at the edges of the carrier plate also offers an additional usable surface compared to a carrier plate of the same width with flanges or grooves for fastening the carrier plate to a screening machine. This additional usable surface makes it possible to cover the upper surface of the carrier plate with additional screen surface and thus to increase the capacity of each screen assembly. Referring to FIG. 12A, it is noted that the screen surface 326 has eleven peaks across its width. Previous screen assemblies of the same width with fastening grooves and / or flanges have used screen surfaces with ten wave peaks of the same size. Adding an additional crest to the screen surface on the top surface of the support plate increases the screen surface by about 5% to 12%. Accordingly, the capacity of each screen assembly increases by a similar percentage. In other words, the use of the arrangement described herein under pressure to attach screen plates to a screening machine results in an increase in screen area and screen capacity of the screening machine.Another advantage of the pressurized systems described herein is that the components of the printing assembly, except for a small portion of the pawl 336, are positioned below the screen assembly. Moreover, all the internal components of the pressure assembly are located below the screen assembly. This reduces the wear of these components (e.g. of the actuating rod) and reduces the maintenance effort of the screening machine. In other words, by displacing these components below the screen surface, these components are not exposed to the materials and liquids (e.g., the aggregate) above the screen surface.FIGS. 16A-16C illustrate an embodiment of a portion of a screening machine, referred to herein as a screening machine 100. The cut-out portion may be a portion of a screening machine similar to the screening machine 300 of FIGS. 1A-1C, with variations being possible. As shown, screening machine 100 includes two screen assemblies 120a, 120b (hereafter 120, unless specifically referred to) disposed between the inner surfaces of spaced apart wall members 112a, 112b (hereafter 112, unless specifically referred to). A central element 116 divides the screening machine 100 into two screening areas. That is, each screen assembly 120 includes a first edge proximate to a wall member 112 and a second edge proximate to the central member 116. While the screening machine 100 is shown having two screen assemblies engaging a central member 116 and defining two concave screen areas when the screens are compressed, the screening machine may also include a screen assembly defining a single concave screen area between the first and second walls 312. See, e.g., FIG. 1D.Print assemblies 122 are secured to the outer surfaces of wall members 112a and 112b. The print assemblies 122 each include a retractable member that expands and contracts. The print assemblies may be similar to the print assemblies described above with respect to FIGS. 13A and 13B. However, the configuration of the pawl may vary. In operation, the pusher assemblies 122 engage a first side of the adjacent screen assembly 120 and urge a second side of the screen assembly 120 against the central member 116 (or a second wall of a single trough screening machine) while deforming the screen assembly 120 into a concave profile against one or more underlying concave support surfaces 114 (e.g., stringers). As discussed below, in one embodiment, the central member 116 or the second wall may include hooks that engage the second side of the screen assembly 120.FIG. 16A illustrates the screen assembly 120 having a screen surface 126, while FIG. 16B illustrates the screening machine 100, with the screen surfaces 126 removed from the screen assemblies 126 to expose an underlying perforated support plate 124 of the screen assemblies 120. The configuration of the screen assembly 120 and the support plate 124 is discussed in more detail in the description of Figures 19A-19C. FIG. 16C illustrates the screening machine 100 with one of the screen assemblies 120 removed to expose the concave support surfaces 114 extending between the first wall 112 aand the central support 116. Single tray machines (e.g., FIG. 1D ) may use similar concave supports extending between the first and second walls. As shown, each of the concave supports 114 is attached at a first end to the wall member and at a second end to the central support 116. As shown, the concave supports 114 are arranged evenly and in parallel. However, other distances are possible. Each post 114 has a concave top surface 115. A seal 117 (e.g., of rubberized or otherwise compressible materials) may be disposed on the concave top surface 115 of each support 114. Accordingly, when the pressing assemblies 122 press the screen assemblies 120 into a concave profile, the bottom of the screen assembly (e.g., the bottom of the support plate 124) may be pressed against the seal 117 on the upper side of the concave supports 114 to form a seal between the screen assembly and the screening machine. The seals may be so wide that an interface between two longitudinally arranged screen assemblies (not shown) may be sealed.The embodiment of the screening machine 100 in Figures 16A-16C shows an "under pressure" arrangement that presses the screen assembly horizontally (e.g., against the central support or the second wall) and vertically downward against the concave supports. In the pressurized embodiment, the printing assemblies 122 on the wall member 112 include movable / actuated hooks or latches 136 that extend through a series of hold-down or pass-through printing points 152 along an edge 142 of the support plate 124. See FIGS. 19B and 19C. The latches 136, each defining a hook in one embodiment, extend through the carrier plate 124 from the bottom side of the plate to the top side of the plate. Actuation of the print assemblies 122 moves the pawls 136 between a first position (e.g., retracted) and a second position (e.g., extended) in which the pawls engage a print surface of the carrier plate 124.In one embodiment, a set of stationary fingers or hooks 130 are attached to the central support 116 (or the second wall member in a single tray machine 10A) and pass through a corresponding set of hold down / pass pressure points 150 along an opposing edge 140 of the support plate 124. See FIGS. 17A, 17B, and 19C. The stationary hooks 130 extend through the support plate 124 from the lower side of the plate to the upper side of the plate. The stationary hooks could be attached to the central support 116 with a mounting mechanism that includes a biasing member, such as a spring, similar to the stationary plunger assemblies shown in FIGS. 9A and 9B. This would allow for easy movement of the stationary fingers or hooks 130 during assembly of a screen assembly. This may also allow for easy adjustment of the rest positions of the stationary fingers or hooks 130.When moved to the extended position, the pawls 136 exert a compressive force "F" having both a horizontal component "H" and a vertical, downward component "V". See, e.g., FIG. 17D. The pressing force is applied to a pressing surface 162 of the support plate 124. The vertical component V of force F exerts a downward force on the support plate 124, while the horizontal component H of force F forces the plate 124 away from the wall member and against the stationary hooks attached to the central member (or the second wall member in a single tray machine). The applied compressive force may bend the screen assembly into a concave shape and simultaneously attach it to the screening machine. Although described herein as the use of stationary hooks on the central wall (or second wall element in a single tray machine), it should be appreciated that in various embodiments, the opposing edge 140 of the panel may abut an abutment or abutment surface 26 (e.g., a channel) on the central element / second wall and the stationary hooks may be omitted. Each of these components will be further explained herein.In the embodiments described above, the support plate of the screen assembly is configured to cooperate with either a movable piston contacting a mounting aperture on a side edge of the support plate as shown in FIGS. 3-8B or latches extending through passage pressure points of the support plate as shown in FIGS. 11-17G. In alternative embodiments, a support plate of a screen assembly could be configured to cooperate with both types of mounting arrangements.FIG. 18 illustrates a support plate 324 that includes mounting apertures 220 on the first side edge 340 configured to receive a movable piston of the mounting assembly depicted in FIGS. 3-8B. The support plate 324 also includes a plurality of passage pressure points 350b that are located inward from the second side edge 342 and that are configured to receive movable or stationary latches of a mounting arrangement depicted in FIGS. 11-17G. The support plate shown in Figure 18 could be used for a vibratory screen machine comprising movable piston thrust assemblies as shown in Figures 3-8B on one side wall and stationary pawls 330 as shown in Figures 6F and 6G mounted on a second side wall or central abutment of a twin trough machine. Conversely, the same backing plate could also be used in conjunction with a vibratory screening machine that includes movable piston thrust assemblies as depicted in Figures 11-17G and stationary thrust pistons as depicted in Figures 3-8B on an opposing side wall or central abutment of the screening machine.FIGS. 19A, 19B, and 19C illustrate the screen assembly 120, the screen assembly 120 with a portion of the screen surface 126 removed, and a top view of a support plate 124, respectively, in one embodiment. As shown, the screen surface 126 is secured to the upper surface of the support plate 124. The support plate 124 is generally rectangular and has a first edge 140, a second edge 142, and a first end 144 and a second end 146. The support plate 124 is typically formed of a sheet metal, although other materials are also possible. The support plate 124 includes a plurality of flow apertures 148 extending through the body of the support plate 124 in its interior defined by the edges and ends. As mentioned above, the support plate 124 carries a screen surface on its upper surface. Such a screen surface may be secured to the support plate 124 in any suitable manner. The flow apertures 148 are configured to allow materials passing through a supported screen surface to pass through the support plate 124. Although shown as having rectangular flow apertures 148, it should be understood that the size, shape, and distribution of the flow apertures across the support plate 124 may be varied. As mentioned above, along the first and second edges 140, 142 of the backing plate 124, there are a plurality of hold-down or pass-through pressure points 150, 152. In one embodiment, the passage pressure points 150, 152 may be located outside of the flow apertures 148 (e.g., relative to a centerline of the plate). In the illustrated embodiment, the passage pressure points 150, 152 each include a ledge 160 as discussed further below.As illustrated in Figures 17A and 17B, where half of the screening machine is removed for clarity, the stationary hooks 130 are attached to the central member 116 below a support surface 118 located at the top of the central member 116. The support surface 118 supports the first edge 140 of the support plate 124. A seal 119 or other compressible seal may be disposed between the first edge 140 of the support plate 124 and the support surface 118. A first end of the stationary hook 130 is attached to the central member 116 and protrudes (e.g., cantilevered) away from the support surface 118. A free end of each hook 130 projects upwardly so that it can extend through the passage pressure points near the first edge 140 of the screen assembly 120 when the first edge of the support plate 124 rests on the support surface 118. Upon installation, the screen assembly may be placed on the machine such that the stationary hooks 130 of the central member 116 (or the second wall) penetrate the passage pressure points 150 at the first edge 140 of the support plate 124. Alternatively, if the central member / second wall does not have stationary hooks, the first edge 140 of the support plate 124 may be placed on an abutment or abutment surface. The screen assembly 120 may then be lowered so that the movable hooks / latches 136 proximate the wall member 112 may penetrate the passage pressure points 152 at the second edge 142 of the carrier plate 124. It should be noted that the use of the passage pressure points in conjunction with the latches on at least the wall member and / or the stationary hooks on the central member (or the second wall member in a single trough machine) enables improved positioning of the screen assembly along the length of a screen machine. That is, once the hooks 130, 136 are positioned through the screen assembly, the position of the screen assembly along the length of the screening machine is necessarily correct, thereby eliminating the need to manually position screen plates along the length of the machine as previously required.Once the screen assembly 120 is properly positioned and the hooks and pawls pass through the passage pressure points, the pressure assemblies 122 may be actuated to move the movable pawls 136 from a retracted position to an extended position. This is illustrated in FIGS. 17C and 17D. As illustrated in FIG. 17C, each stationary hook 130 may be guided by a passage pressure point 150 (shown in phantom) on a first edge 140 of the carrier plate 124, while each movable pawl 136 may be first guided by a passage pressure point 152 (shown in phantom) on a second edge 142 of the carrier plate 124. At this time, the support plate 124 may be substantially planar. Upon actuation, the movable pawl 136 may be advanced and / or rotated to apply a horizontal force to the support plate 124 (e.g., a side edge of the passage pressure point 152) and a downward force to the top surface of the support plate 124. See Fig. 17D. This results in the inner edges of the passage pressure points 150 being pressed along the first edge 140 of the carrier plate 124 against the stationary hooks 130 extending through the passage pressure points 150. Further advancement and / or rotation of the hooks / pawls 136 results in the carrier plate 124 bending into a concave shape against the concave support surfaces. See FIGS. 17B and 19B. The bending of the support plate 124 into a concave profile is facilitated by a downward angle of the push rod of the push assembly 122 in conjunction with the angled surface of the latches 136 and hooks 130.To improve the engagement of the hooks 130 and latches 136 with the upper surface of the carrier plate 124, each of these elements may have a recessed contact surface. That is, a contact surface of the hooks 130 and pawls 136 may be recessed from the free tip of these members (e.g., as measured from the central axis A-A' of the plate 124). See, e.g., FIG. 17C. More specifically, the free tip 132 of the hook 130 protrudes beyond a contact surface 134 of the hook 130 (i.e., relative to the central axis A-A'). Likewise, a free tip 137 of the pawl 136 protrudes beyond a contact surface 138 of the pawl 136 (i.e., relative to the central axis A-A'). The resulting undercut of the hooks 130 and latches 136 (e.g., hook surface) allows each of these elements to better engage a top surface of the carrier plate 124.In the embodiment shown in Figures 17A-17D and 19A-19C, the backing plate 124 also includes ledges 160 that are attached near an inner edge (e.g., measured from the central axis A-A') of each of the passage pressure points 150, 152. In this embodiment, the ledges 160 protrude beyond the upper surface of the carrier plate 124 and are shaped to matingly engage the latches 136 and / or hooks 130. The ledges 160 may be secured (e.g., adhered, screwed, riveted, welded, etc.) to the carrier plate 124 in any suitable manner. Alternatively, the ledges 160 may be integrally formed with the carrier plate 124 (e.g., by bending and forming sheet metal or by compression molding). As shown in FIGS. 17C and 17D, the contact surfaces 132, 138 of the hooks 130, and latches 136, respectively, are angled and configured to contact a correspondingly angled contact or pressure surface 162 of the respective ledge 160 (i.e., as the latch 136 is advanced to contact its ledge 160). The use of the mating angled surfaces on the hooks 130 and latches 130 with the ledges 160 allows for an increase in the compressive force transmitted to the plate 124.In one embodiment, the contact surfaces 132 and / or 138 are disposed at an acute angle of opening θ to the generally planar top surface (i.e., prior to compression) of the backing plate 124. In one embodiment, the opening angle θ is between about 5° and 85°. In a further embodiment, the opening angle θ is between approximately 15° and 75°.Although the various figures illustrate the use of the ledge 160 to improve contact between the hooks 130 and the latches 136, it should be appreciated that the ledges 160 may be omitted in other embodiments. In such embodiments, hooks 130 and latches 136 may directly contact an upper surface of the carrier plate 124. Figures 17E and 17F show an alternative embodiment of the movable pawl 136 where the pawl 136 has a contact surface 138 formed as an inner corner below the free tip 137. In such an embodiment, the inner corner contact surface 138 may directly engage the inner edge of the hold-down aperture 152. The hooks (not shown) may be formed similarly. It should be appreciated that several variations of the contact surface 138 may be used while still applying a horizontal force to a side surface of the screen assembly and a downward force to the top surface of the screen assembly and / or support plate.FIG. 17G illustrates another alternative embodiment in which the movable pawl 136 engages a matingly angled contact or pressure surface 153 formed on the support plate 124. More specifically, an inner edge of the carrier plate 124 (e.g., the inner edge of the passage pressure point 152 as measured from the centerline of the plate) may be formed at an angle θ 2 that corresponds to the angle θ 1 of the contact surface 138 of the pawl 136. In one embodiment, these angles are the same. In other embodiments, these angles may be different.FIG. 20 illustrates the second edge 142 of a support plate 124 proximate the wall member 112 of a screening machine. As shown, the second edge 142 of the support plate 124 is supported on a support surface 128 that is secured to the inner surface of the wall member 112. In the illustrated embodiment, the support surface 128 is a horizontal flange of an angle bracket having a vertical member attached to the inner surface of the wall member 112. Other support surface configurations are possible. A seal or other compressible seal 129 may be disposed between the second edge 142 of the support plate 124 and the horizontal support surface 128. In this regard, seals / compressible seals (hereafter seals) may be disposed around the entire perimeter of the screen assembly support plate 124. That is, a first seal 119 may be attached between the first edge 140 of the support plate 124 and the support surface 118 (see, e.g., FIG. 17A ), a second seal 129 may be attached between the second edge 142 of the support plate 124 and the wall member support surface 128, and third and fourth seals 117 may be attached on the upper surfaces of the concave support surfaces 114 below the first and second ends 144, 146 of the support plate 124 (see, e.g., FIGS. 16C and 17A ). The increased hold-down force exerted on the support plate 124 allows the pressure against all seals to be increased. The increased pressure against the seals not only provides better sealing but also extends the life of the seals since the screen assemblies move less relative to the seals and less material can enter between the support plate 124 and the seals.Another advantage of the presented embodiments is that the screen assemblies can dispense with the upwardly directed flange which was previously used for applying pressure to the screen assembly. Accordingly, removal of this flange eliminates the possibility of material inclusions behind this flange. Another advantage of the present embodiment provided by the engagement of the screen assemblies is that the screen area on the upper surface of the screen assembly can be increased. Moreover, by laying the hooks and latches under the plate and under the screen surface, these elements are not exposed to the materials and liquids above the screen surface. This arrangement reduces the wear of these components of the printing system.As mentioned above, the print assemblies may be operated in various ways, including, but not limited to, manual, hydraulic, and pneumatic. Various means for manually operating the print assemblies are shown. More specifically, Figures 21A and 21B illustrate one embodiment of a printing assembly that uses a single removable handle to actuate individual printing assemblies, Figures 21C and 21D illustrate one embodiment of a printing assembly that uses a single removable handle to actuate two adjacent printing assemblies, and Figure 21E illustrates the connection of adjacent printing assemblies for dual actuation with a single handle. Figures 21A and 21E use reference numerals that correspond to the components of the screening machine of Figures 1A and 1C. It will be understood, however, that these means for operating the printing assemblies may be used with any of the screen machines described.As shown in FIGS. 21A and 21B, a removable handle 400 may be formed with a first engagement end 402 configured to engage (e.g., be received in) the sleeve 379 of the actuation bracket of the print assemblies 322 and an elongated second end 404. A user may grasp the elongated second end 404 of the handle once the first end 402 is inserted into the sleeve 379 of the actuation bracket, and use the handle 400 having a bend between its first and second ends to rotate the actuation bracket and thereby activate or deactivate a single printing assembly 322. The single handle 400 may be used to activate and / or deactivate multiple print assemblies.FIGS. 21C and 21D illustrate a dual handle 410 that may be used to enable or disable adjacent print assemblies 322 a, 322 bon the outer wall 312 of a screening machine 300. As already mentioned, it has been found that by lowering under the screen assemblies, the printing assemblies can be distributed more evenly along the outer wall of the screening machine. Thanks to this even arrangement, a single handle can be configured to engage two (or more) adjacent print assemblies for activating or deactivating these adjacent print assemblies. As shown, the handle 410 has two engaging ends 402a, 402b that each engage the sleeve 379a or 379b of one of the two adjacent print assemblies 322a, 322b. A user may grasp a second end 406 of the handle, which in turn may be bent along its length to rotate the adjacent actuating brackets and thereby activate or deactivate two adjacent print assemblies 322 a, 322 b.FIG. 21E illustrates the connection of two adjacent print assemblies 322a, 322b via a connecting rod 412. In this embodiment, the connecting rod 412 extends between and physically connects the actuating brackets 376a, 376b of two adjacent print assemblies 322a, 322b. Accordingly, rotation of one of the brackets 376a or 376b will result in rotation of the other bracket. Thus, two print assemblies may be actuated with a single handle (see, e.g., FIG. 21D ). Although FIG. 21E shows the use of a single connecting rod 412 to secure two adjacent brackets, it should be understood that two connecting rods could be used to connect three brackets. In addition, other ways of connecting the print assemblies for joint actuation are possible and are within the scope of the present disclosure.Figures 21F and 21G illustrate another embodiment of a printing assembly 422 that can be used with all screening machines described herein. The pressure assembly 422 is a fluid operated (pneumatic or hydraulic) pressure assembly. The assembly has the same inner wall components as the printing assembly described with reference to Figures 13A-13D. Similarly, a pawl 336 is secured to the end of an actuating rod 374 which extends through an inner housing bracket 372 which is secured to the inner surface of a wall 312 of a screening machine. Instead of a manually operated clamp on the outer surface of the wall, the pressure assembly 422 includes a pneumatic / hydraulic actuator 450 (hereinafter pneumatic actuator) that engages the rear end of the actuating rod 374 and selectively advances and retracts it. The pneumatic actuator 450 includes a housing 452 that abuts the outer surface of the wall 312. The pneumatic actuator housing 452 may be bolted to the inner housing bracket 372 through wall 312. The housing 452 may include various seals (e.g., O-rings) to seal the interface between the actuation rod and a pin in the housing through which the actuation rod passes. The housing 452 includes an inner cylinder bore that houses a piston 454 that engages the rear end of the actuation rod 374. The piston 454 is configured to move along the cylinder bore to advance or retract the actuating rod 374 and the pawl 336 attached thereto. More specifically, a valve 456 may selectively pressurize a portion of the cylinder bore forward of the piston 454 to retract the piston, the actuation rod 374, and the pawl 336. Technicians can then place the panels in a screening machine. The valve 456 (e.g., a three-way valve) may then exhaust the pressure in the cylinder bore. In the present embodiment, a plurality of biasing springs 458 are clamped between a rear surface of the piston and an end cap of the cylinder bore. The biasing springs maintain the actuation rod 374 and the pawl 336 in an extended position (e.g., to lock a screen assembly to the bed of a screening machine) when no pneumatic pressure is applied, retracting the actuation assembly 422. That is, in the extended position, the spring force alone may maintain the actuating rod 374 and the pawl 336 in the extended position without pneumatic pressure. The size and number of springs 458 may be selected to maintain the desired compressive force on a screen assembly. However, it is understood that variations are possible. For example, a similar pneumatic or hydraulic pressure assembly may utilize pneumatic or hydraulic pressure to extend the actuation rod 374 and the pawl 336. In such arrangements, pressure may be continuously maintained or a mechanical latch may latch the actuation rod 374 and the pawl 336 in the actuated position.Figures 22A and 22B illustrate another embodiment of a pressurized screen assembly 620. More specifically, FIG. 22A illustrates a top perspective view of the screen assembly 620, and FIG. 22B illustrates a bottom perspective view of the screen assembly 620, with a portion of the screen surface 626 removed for illustration purposes. As shown, the screen assembly includes a substantially rectangular support plate 624 having a first edge 640, a second edge 642, a first end 644, and a second end 646. The support plate 624 includes a plurality of flow apertures 648 extending through a body of the support plate 624 within. However, unlike the pressurized backing plates described above with reference to Figures 12A-12C and 19A-19C, the screen assembly 620 does not require pass-through pressure points, although these may be present. Rather, the screen assembly 620 includes a plurality of brackets 650 that engage the support plate 624 of the screen assembly 620 and facilitate attachment to an underlying printing assembly. In one embodiment, each bracket 650 includes a flat portion 652 that may be attached (e.g., bonded, welded, etc.) to the bottom surface of the support plate 624. The brackets 650 also include a downwardly projecting tab 654 having an opening 656 configured to engage a hook member of a movable or stationary latch. In one embodiment, each clip 650 may optionally include an upwardly directed tab 658 that can engage an edge surface (e.g., 640 or 642) of the support plate 624. In one embodiment, the upwardly directed tabs 658 may have a length that allows these tabs to engage upwardly directed flanges formed along the length of the carrier plate edges 640, 642.FIG. 22C illustrates the screen assembly 620 disposed and compressed between a pressure assembly 322 and a stationary hook assembly 330. The printing assembly 322 and the stationary hook assembly 330 are substantially similar to the printing assemblies described above with reference to FIGS. 13A-13F, except that these components may utilize a modified pawl 636. As shown, the modified latches 636 do not extend as far beyond the assemblies 322 and 330. That is, since the modified pawls 636 do not need to be passed through the support plate 624, the modified pawls 636 may have a different upward dimension. However, each modified pawl 636 may include a hook 632 and an angled contact surface 637. As shown, the tip of each hook 632 penetrates the opening 656 of the associated clip 650. Advancement of the movable pawl 636 of the pusher assembly 322 moves the screen assembly 620 until an edge of the staple apertures 656 contact the contact surfaces 637 of the opposing pawls 636. The continued advancement of the movable pawl 636 of the pusher assembly 322 results in deformation of the screen assembly 620, substantially similar to the screen assembly discussed in FIGS. 15A and 15B. It should be noted that the use of the brackets 650 and the modified pawls 636 may enable the use of existing screen assemblies (e.g., with edge flanges) with the pressurized systems of the present disclosure.FIGS. 234A and 23B illustrate another component that can be incorporated into any of the screening machines described in this disclosure. More specifically, these figures illustrate sectional bed supports 380 that support bed rubbers / gaskets along the edges of the screen assemblies as well as the edges of the screen assemblies themselves. Referring briefly to FIGS. 15A and 15B, in one embodiment, the edges 340, 342 of the support plate 324 are supported over first and second seals 319, 329 which in turn are supported by the sectional bed supports 380. In conventional screening machines, the edges of the screen assemblies and the intermediate rubbers / seals are typically supported by a single ledge or rail (e.g., angle iron) extending the entire length of the screening machine along its side walls and / or central member. Such conventional rail-like supports are usually welded to the machine. Accordingly, if a portion of the rail is damaged (e.g., bent or otherwise worn), the entire rail must be replaced.As illustrated in FIG. 23A, a plurality of sectional bed supports 380 may be attached to the inside of a side wall 312 of a screening machine. Likewise, a plurality of bed supports 380 may be attached to the central member (e.g., in a dual tray machine) or to a second wall of the screening machine (e.g., in a single tray machine). In the present embodiment, the sectional bed supports 380 are each disposed over one of the print assemblies 322. It should be understood, however, that the sectional bed supports 380 may have other dimensions. For example, a single bed support 380 could span multiple print assemblies 332 or stationary hook assemblies on an opposing wall / center member.As illustrated in FIG. 23B, the sectional bed support 380 includes a top surface 660 that, when aligned with adjacent sectional bed supports 380, may form a continuous ledge or rail along a sidewall and / or a center member of a screening machine when secured thereto. A body of the bed support 380 may include one or more openings 668, with which the bed support 380 may be bolted to a sidewall or center member of a screening machine. Due to the sectional nature of the bed supports 380, when one of a plurality of bed supports 380 forming a rail is damaged, the damaged bed support 380 may be individually removed and replaced.In the illustrated embodiment, the upper surface 660 of the bed support 380 includes an optional recessed press-fit channel 662 for receiving a correspondingly shaped tab 672 that is secured to the lower surface of a seal 670 supported on the upper surface 660 of the bed support. See, e.g., FIGS. 24A and 24B. In such an arrangement, the top surface is divided by the recessed channel 662 and includes a rear surface / ledge 661 that will abut a wall surface of a screening machine and a front surface / ledge 663 that extends toward and within the screening machine. The interference fit channel 662 may include first and second opposing retaining ridges 664 that engage the side edges of the tab on the underside of the seal. Once the seal is press fit into the channel 662, the resulting press fit provides improved sealing to the walls / center member of the screening machine.Figures 24A and 24B illustrate the engagement of a piece of bed rubber or seal 670 to the bed support 380 bolted to a wall 312 of a screening machine. A single or multiple bed supports may extend along the entire wall of the machine. The seal 670 has a generally flat top surface for engaging the bottom surface of an overlying support plate when a screen assembly is pressed onto the machine. See also the seals 319 and 329 and the overlying plate 324 in Figures 15A and 15B. In the illustrated embodiment, the seal 670 also includes the tab 672 formed on its bottom surface that is configured to be received in the recessed press-fit channel 662 of the bed support 380. A rear edge 674 of the seal is configured to engage the wall 312 of the screening machine. First, the gasket 670 is inserted end first (Fig. 24A) and tilted to engage the rear edge and press against the side wall 312. The seal 670 is then snapped in place by placing a recess 676 in the underside of the seal over the front ledge 663 of the bed support such that a front lip 678 of the seal covers the front edge / lip of the bed support.FIGS. 24C and 24D illustrate the use of the first and second bed supports 380 a, 380 bto form a corner seal that enhances previous designs. More specifically, the first bed support 380a may be continuously bolted to the side wall 312 of the machine to a corner where the side wall 312 meets an end wall 306. A first bed rubber or seal 670a may be press fit into the first bed support 380a. The second bed support 380 bmay be attached to the end wall 306. A bed rubber or seal 670b may be disposed in this support and terminate at the first seal 670a. In either case, the corner between side wall 312 and end wall 306 may be completely sealed, which has been problematic in prior designs.FIGS. 25A-25E further illustrate an embodiment of the screen assembly 320. As shown, the screen assembly 320 includes a screen surface 326 attached to a perforated metal support plate 324, such as steel or any other suitable metal, having a first pair of opposing side edges 340 and 342 and a second pair of edges / ends 344 and 346 and an upper surface and a lower surface. The support plate 324 includes apertures 348 defined by elongated metal strip-like members or members 347 extending between edges 340 and 342 and shorter strip-like members 349 extending longitudinally between ends 344 and 346. The apertures 348 may be formed by a stamping operation and are squares of approximately 1 square inch with rounded corners, but may be any other desired shape and size. Strip-shaped portions 347 and 349 are about 1 / 10 inch wide, but they may be any width. The length of the support plate 324 may have a width of about 2.5 feet and a length of about 3.5 feet, and may have a thickness of about 1 / 16 inch. It should be understood, however, that the size of the support plate 324 may vary to accommodate different screening machines. The width of each opening 348 is a small fraction of the width of the support plate 324 between the edges 340 and 342. The same applies to the relationship between the height of the openings and the length of the plate between ends 346 and 348. Although not shown, channel shaped members may be formed or attached to one or both edges 340, 342 for use in attaching the support plate 324 to a screening machine. However, embodiments in which such channel-shaped elements are omitted may provide a larger screen area on the support plate 324, as an area that would otherwise be covered by a channel element may be covered with additional screen area.As illustrated in FIG. 25D, the screen surface 326 is composed of a plurality of screens connected to one another in a planar manner. Screen surface 326 therefore includes a coarse screen 323 that performs a support function and may be between 6 and 20 mesh or any other suitable size. A fine screen 325 is connected to the supporting coarse screen 323 and may have a mesh size between 30 and 325 mesh, or any other suitable size. An even finer screen 327 is connected to the fine screen 325 and may have a mesh size between 40 and 400 mesh, or any other suitable size. Preferably, the center fine screen 325 should be two U.S. screen sizes coarser than the finer uppermost screen 327. The three screens 323, 325 and 327 are interconnected by a fused plastic mesh 321 which penetrates all three screens. The screen surface 326 is formed in a wave-like curved shape as shown in Fig. 25D, and has ribs 331 and dimples 333. The undersides of wells 333 are bonded to the backing plate 324 at 335 with a suitable adhesive such as epoxy. This connection at 335 is made wherever the undersides of the troughs 333 contact the strips 347 and 349 as shown in Figure 25E. The open ends of the ribs 331 may be closed or blocked by insert molded caps. The caps could be made of polyurethane or other plastic or synthetic materials.In the foregoing descriptions, the screen assemblies included a screen surface that is attached to the top surface of a support plate. The support plate includes passage pressure points engaged by the pawls of pressure mechanisms to secure the screen assembly to a vibratory screening machine. In many cases, the screen surface is formed from metal wire braid assemblies which may comprise multiple layers of wire braid and / or synthetic braid as well as adhesives or binders.In alternative embodiments, the screen assemblies could be configured quite differently. Instead of attaching a screen surface to the top of a support plate, a screen assembly could be formed by assembling multiple screen units of synthetic or plastic materials into a screen plate. End rods are then attached to the opposite ends of the screen plate and have similar passage pressure points to the support plate of the previously described embodiments.Various embodiments of synthetic or plastic screen units joined together to form a screen plate are described in U.S. Patent Nos. 9,409,209; 9,884,344; 10,046,363; 10,259,013; 10,576,502; 10,835,926; 10,843,230; 10,933,444; 10,960,438; 10,967,401; 10,974,281; 10,981,197; 10,994,306; 11,000,882; 11,161,150; 11,198,155; 11,413,656; 11,426,766; 11,446,704; 11,471,913 and 11,471,914, the entire contents of which are hereby incorporated by reference.The above-identified patents describe screen assemblies formed by the connection of a plurality of individual screen units. Each screening unit may comprise a screen element having a screen surface attached to a supporting subgrid. The sub-grids of each screen unit may comprise fasteners configured to connect the sub-grids together. By connecting the sub-grids of several screen units, a larger screen plate can be formed. End bars are then secured to the ends of the screen plate to form a screen assembly.In some embodiments, the screen members are formed by injection molding a plastic or synthetic material, such as a thermoplastic. Each screen element includes a plurality of elongated openings formed between adjacent elongated screen surface elements. The sub-grids may also be made by injection molding a plastic or synthetic material such as a thermoplastic. However, the sub-grids may be made of a different material or materials than the screen elements.As already mentioned, each screen unit is formed by the fastening of a screen element to a sub-grid. Fasteners on the screen members and sub-grids may be used to secure a screen member to a sub-grid. For example, openings on the screen elements may receive corresponding protrusions on the sub-grids, or vice versa. A screen element can then be attached to a subgrid by fusing the protrusions and recesses together. This may be done by laser welding or other similar means. Screen elements may of course also be secured to sub-grids in other ways, such as by adhesives or a mechanical attachment mechanism. In some embodiments, multiple screen elements may be mounted on a single subgrid to form a screen unit.The fasteners on the sub-grids configured to connect sub-grids together may include clips and clip openings. A clip on one subgrid is received in a clip opening of an adjacent subgrid to connect two screen units together. Of course, various other means of securing the screen units may be used to assemble a larger screen assembly from multiple screen units.The screen units could take a variety of different forms. In some cases, each screen unit could have a flat, planar shape. In other cases, the screen elements could be attached to pyramidal subgrids to form pyramidal screen units. A multiple screen unit screen assembly could be formed entirely from the same type of screen unit. Alternatively, a screen assembly could be formed from combinations of flat screen units and pyramidal screen units.Figure 26 illustrates a screen assembly 700 formed from a combination of flat screen units 702 and pyramidal screen units 704. Figure 26 shows only one corner of the screen assembly 700. The larger screen assembly 700 would include multiple rows of flat screen units 702 disposed between rows of pyramidal screen units 704. Each row of flat screen units is formed by a plurality of flat screen units 702 arranged in a row. Likewise, the row of pyramidal screen units is formed from a plurality of pyramidal screen units 704 arranged in a row. The sub-grids of the individual screen units 702, 704 are interconnected by attachment mechanisms such as clips and clip openings to form the larger screen assembly.End bars 710 are attached to opposite ends of the composite flat and pyramidal screen units 72, 704. Each end rod includes a plurality of passage pressure points 712 similar to the passage pressure points of the backing plates of the previously described embodiments.In the embodiment shown in Figure 26, the last row of flat screen units 702 and the last row of pyramidal screen units 704 are mounted on the top surface 714 of a receiving base 711 of the end bar 710. The end bar 710 has attachment mechanisms configured to mate with the corresponding attachment mechanisms of the flat screen units 702 and the pyramidal screen units 704. For example, mounting protrusions 716 at a distal end of the receiving base 711 are configured to mate with corresponding openings in the flat screen units 702 and / or the pyramidal screen units 704. Likewise, clip apertures 718 are formed in the inner surface 712 of the end rail 713 of the end bar 710. The clip openings 718 resemble the clip openings on the subgrids of the flat screen units 702 and the pyramidal screen units 704. Thus, the clip openings 718 are configured to mate with the existing protrusions already present on the screen units 702 / 704.Figure 27 shows the end bar 710 being brought up to the side edge of an assembly of flat screen units 702 and pyramidal screen units 704. Figure 28 shows the screen assembly after the end bar 710 has been attached to the screen units 702, 704. A similar end bar 710 would be mounted on the opposite side of the assembly of screen units 702, 704. The resulting screen assembly 700 may then be mounted on a vibrating screen machine with the above described printing mechanisms, in substantially the same manner as a screen assembly comprised of a support plate and a screen surface would.The compression mechanisms apply compressive forces to the inner edges of the end rod passage compression points 722. These compressive forces compress the end rods 710 at opposite ends of the screen assembly 700. Thus, the same compressive forces used to attach the screen assembly 700 to the shaker screen machine also serve to compress the individual screen units 702, 704 and thus help the screen assembly 700 maintain structural integrity.The end rods 710 could be formed of metal or synthetic materials. Each end bar 710 could also have a composite structure comprising reinforcing elements such as carbon or glass fibers.In the above embodiment, the end rods 710 are attached to the screen units 702, 704 using at least some of the attachment mechanisms that also serve to attach the screen units 702, 704 to each other. However, alternative or additional fasteners may be used to attach the end rods 710 to an assembly of screen units 702, 704. For example, the end rods 710 could be secured to the screen units 702, 704 by adhesives, welding, fusion, various fasteners, or combinations of these fasteners.A vibratory screening machine typically has an elongated screen section with an inlet and an outlet end. A plurality of screen assemblies are mounted along the length of the screen area. In a single trough embodiment, each screen assembly extends across the entire width of the interior of the screening machine, and the plurality of screen assemblies are arranged along the length of the screen area. In a double trough embodiment, each screen assembly extends over a portion of the width (e.g., half) of the screening machine. In such an embodiment, parallel screen assemblies are arranged along the length of the screen region.Material to be screened is deposited at the entrance end of the screen section and the screen assemblies are vibrated to transport the material along the length of the screen section to the exit end. The screen assemblies mounted to the screen area may be mounted to form a continuous screen surface oriented at an angle to the horizontal, for example, with a higher input end than output end. An inclined screen surface may help the material to be transported from the input to the output end by gravity. Other configurations are possible.The screen assemblies may be made from a number of different types of materials. These different materials may provide different properties to the screen assemblies. Typically, screen assemblies made of plastic or synthetic materials can better resist screen wear than screen assemblies made of woven metal wire mesh. On the other hand, screen assemblies made of woven metal wire mesh can have better screen and dewatering properties than screen assemblies made of plastic or synthetic materials.The conditions present in the screen section of a vibrating screen machine vary along the screen section. The entire quantity and weight of the material to be screened is deposited at the entrance end of the screening zone. As a result, the screen assembly(s) at the input end, which are exposed to the total weight of the entire input material to be screened, are subject to the greatest wear. During material transport along the length of the screen area, liquid and smaller particles fall through the screen assemblies. As a result, the amount and weight of material transported in a downstream region (e.g., the second half) of the screen region is not as great as the amount and weight of material transported in the upstream region (e.g., the first half) of the screen region. For this reason, the screen assemblies mounted in the downstream region of the screen region are subject to less wear than the screen assemblies mounted in the upstream region of the screen region.Embodiments of the present disclosure relate to systems, apparatus, and methods for minimizing overall wear of screen assemblies mounted along the length of a vibratory screening machine while maintaining the desired screening and dewatering characteristics of the vibratory screening machine. In one embodiment, a screening system, a screening machine, and a screening method are provided where various types of screen assemblies are mounted along the length of the screen surface of a screening machine. In one embodiment, a plastic or synthetic screen assembly is mounted at the inlet end of the screen surface and along an initial portion (e.g., the first half) of the length of the screen surface. Such plastic or synthetic screen assemblies are better able to withstand the higher load imposed by the screen assemblies mounted along the initial or inlet portion of the screen region than screen assemblies made of metallic wire mesh. Additionally, metal wire mesh screen assemblies are mounted along a rear portion (e.g., the second half) of the length of the screen surface. As mentioned above, the screen assemblies mounted in the outlet portion of the screen section are not subject to wear as much as the screen assemblies mounted in the inlet portion of the screen section. Therefore, wear of the metal wire mesh screen assemblies is a less severe factor when in the outlet portion of the screen area.FIGS. 29A and 29B illustrate front and rear perspective views of a screening machine 300 in which various screen assemblies are mounted along a length of the screen area of the screening machine. In the illustrated embodiment, the screening machine has two parallel sets of screen assemblies arranged along the length of the screening machine. For purposes of explanation, only one set of screen assemblies will be described. The parallel set may be substantially identical. This description also applies to a single trough screening machine (e.g., Fig. 1D) in which a single set of screen assemblies extends along the screen region of the machine.As shown in FIGS. 29A and 29B, the screening machine 800 uses first and second plastic or synthetic screen assemblies 810 a, 810 b(hereafter 810 unless specifically referred to) mounted on the machine, between the inlet end 801 of the screen region and extending over the first half of the screen region. Additionally, the screening machine 800 employs first and second wire mesh screen assemblies 812a, 812b (hereinafter 812 unless specifically referred to) disposed between the outlet end 4 of the screen section and the center of the screen section. In this embodiment, the four screen assemblies 810a, 810b, 812a, 812b collectively cover the screen area of each trough of the screening machine. In use, materials to be screened are fed into the inlet end 801 of the machine onto the upper surface of the first plastic / synthetic screen assembly 812a. By vibration of the machine 800, the material passes the surface of the first plastic / synthetic screen assembly 810a, the surface of the second plastic / synthetic screen assembly 810b, the surface of the first wire mesh screen 812a, the surface of the second wire mesh screen assembly 812b, and exits the outlet end 804 of the machine 800. As mentioned above, the plastic / synthetic screen assemblies 810 are better able to resist wear experienced at the inlet end of the screen region than the wire mesh screen assemblies 812. Also, as the material to be screened passes through the screen area, a first portion of the liquid in the material passes through the plastic / synthetic screen assemblies 810 as the material to be screened travels along the plastic / synthetic screen assemblies 810. A second portion of the liquid in the material passes through the wire mesh screen assemblies 812 as the material passes over the wire mesh screen assemblies 812.A screening machine 800 using a combination of plastic / synthetic screen assemblies 810 and wire mesh screen assemblies 812 (e.g., hybrid machine 800) achieves at least as efficient screening and dewatering as a screening machine using a full set of wire mesh screen assemblies. Additionally, the wear of the wire mesh screen assemblies 812 of the hybrid screen machine 800 is less compared to a screen machine that uses a full set of wire mesh screen assemblies. Accordingly, the hybrid machine wire mesh screen assemblies 812 need to be less frequently replaced, further reducing engine downtime and increasing overall efficiency. The average screen life also increases.FIGS. 29C and 29D show an end view and a partial end view, respectively, of the screening machine 800 of FIGS. 29A and 29B. As illustrated in these figures, the plastic / synthetic screen assemblies 810 and the wire mesh screen assemblies 812 may also have different physical configurations. As shown, in one embodiment, the plastic / synthetic screen assemblies 810 and the wire mesh screen assemblies 812 may each use a corrugated or corrugated screen surface, the screen surface having alternating peaks and valleys. In the illustrated embodiment, the height of the peaks of the plastic / synthetic screen assemblies 810 is higher than the peaks of the wire mesh screen assemblies 812. It should be understood, however, that the screen assemblies may also be configured the same. Additionally, although the screen surfaces of the screen assemblies 810, 812 are each shown as corrugated or corrugated surfaces, it should be appreciated that the screen surface may have other configurations (e.g., substantially flat).The plastic / synthetic screen assemblies 810 may have screen surfaces made of, without limitation, synthetic materials such as polyurethane, thermoplastic polymers (e.g., polyurethane), and thermosetting polymers. Molded polyurethane screens are described, for example, in U.S. Pat. No. 9,908,150, the disclosure of which is hereby incorporated by reference. Screens of thermoset and thermoplastic polymers are described, for example, in U.S. Patent Publication No. US-20210354173, the disclosure of which is hereby incorporated by reference.The wire mesh screen assemblies 812 may comprise one or more layers of woven mesh material. This woven mesh material may be secured to an underlying backing plate by adhesive, welding or mechanical attachment. Exemplary wire mesh screen assemblies are described, for example, in U.S. Pat. No. 7,228,971, the disclosure of which is hereby incorporated by reference.FIG. 30A graphically illustrates an arrangement of the plastic / synthetic screen assemblies 820 and the wire mesh screen assemblies 830 on a two-screen-section screening machine and the arrangement of a single-screen-section screening machine. In this arrangement, the machines each include a first synthetic screen assembly 820a at the inlet / inlet end and a second synthetic screen assembly 820b immediately behind the first synthetic screen assembly 820a. A first wire mesh screen assembly 830a is disposed behind the second synthetic screen assembly 820b. Finally, a second wire mesh screen assembly 830b is disposed behind the first wire mesh screen assembly 830a and adjacent the outlet end / outflow. In this arrangement, the two screen section machines use two sets of parallel synthetic screen assemblies 820a, 820b and two sets of parallel wire mesh screen assemblies 830a, 830b, while the one screen section machine uses two synthetic screen assemblies 820a, 820b and two wire mesh screen assemblies 830a, 830b. One half (i.e., inlet / upstream half) of the screen region is covered by synthetic screen assemblies and one half (i.e., outlet / downstream half) of the screen region is covered by wire mesh screen assemblies.Figures 30B and 30C illustrate alternative screen assembly arrangements. More specifically, Figure 30B illustrates an arrangement in which the screening machines use three synthetic screen assemblies 820a, 820b, and 820c and a single wire mesh screen assembly 830a positioned at the outlet end. FIG. 30C illustrates an arrangement where the screening machines include a synthetic screen assembly 820a at the inlet end and three wire mesh screen assemblies 830a, 830b, and 830c. For machines with different numbers of screen assemblies, further variants are possible.Although described above primarily in connection with screen machines having concave support surfaces (e.g., stringers or bulkheaders) in which a screen assembly is pressed into a concave shape, it should be appreciated that aspects of the various printing devices may also be used with screen machines of different configuration. For example, the printing devices can be used in screen machines with a flatter bed section (e.g., less concave or even flat).All directional references (e.g., plus, minus, upper, lower, upward, downward, left, right, leftward, rightward, upward, downward, above, below, below, vertical, horizontal, clockwise, and counterclockwise) are for purposes of identification only to facilitate the reader's understanding of the present disclosure, and do not present limitations, particularly with respect to the position, orientation, or use of any aspect of the disclosure. As used herein, the terms "configured to," "configured to," and similar terms indicate that the subject device, device, or system is designed and / or constructed (e.g., by appropriate hardware, software, and / or components) for satisfying one or more particular object purposes, but not that the subject device, device, or system is only capable of satisfying the object purpose. Connection designations (e.g., attached, coupled, connected, etc.) are to be broadly construed and may include intermediate members between a connection of members and the relative movement between members. Connecting covers do not necessarily mean that two elements are directly connected to one another and are in a fixed relationship to one another. It is intended that all matter in the above description or the accompanying drawings be interpreted as illustrative only and not as restrictive. Changes to details or structure are possible without departing from the scope of the disclosure as defined in the appended claims.Any patent, publication, or other disclosure material, in whole or in part, that is said to be incorporated herein by reference is incorporated herein only insofar as the incorporated materials do not conflict with existing definitions, statements, or other disclosure material of this disclosure. As required, the disclosure expressly set forth herein replaces all conflicting material incorporated herein by reference. Any material, or part thereof, that is said to be incorporated herein by reference, but that conflicts with existing definitions, statements, or other disclosure material set forth herein is only incorporated insofar as no conflict arises between the incorporated material and the existing disclosure material.References included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedUS 63 / 464,982

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[0205]

Claims

A method of attaching a screen assembly to a vibratory screening machine, comprising: placing a screen assembly on a screen receiving portion of a vibratory screening machine, the screen assembly comprising a support member and a screen surface, the support member having leading and trailing edges, first and second side edges, an upper surface, a lower surface, and a first plurality of mounting apertures on the first side of the support member, each mounting aperture comprising at least one pressure surface, the screen surface being attached to the upper surface of the support member, wherein placing the screen assembly on the screen receiving portion of the vibratory screening machine comprises positioning the screen assembly such that a first plurality of pressure pistons of pressure mechanisms on the vibratory screening machine are aligned with corresponding ones of the first plurality of mounting apertures; and causing the screen assembly to move toward the screen assembly to the screen receiving portion of the vibratory screening machine, wherein the first plurality of rams move from a retracted position to an extended position closer to a centerline of the support member than the retracted position, wherein each of the rams comprises first and second thrust surfaces meeting at a thrust corner, and wherein when each of the first plurality of rams move from the retracted position to the extended position, the at least one thrust surface of a mounting aperture slides along one of the first and second thrust surfaces of the ram until the at least one thrust surface of the mounting aperture abuts the thrust corner, and wherein the resulting thrust forces applied to the first plurality of mounting apertures by the first plurality of rams cause the screen assembly to take a concave shape and be forced into engagement with underlying concave support surfaces of the shaker screen machine.The method of claim 1, wherein the resulting compressive forces applied to the first plurality of mounting apertures by the first plurality of rams comprise a first component directed horizontally toward a centerline of the support member and a second component directed vertically downward.The method of claim 1, wherein each of the first plurality of mounting apertures comprises an alignment slot, wherein an end portion of each of the first plurality of plungers comprises an alignment finger, and wherein when the first plurality of plungers move from the retracted position to the extended position, the alignment finger of each of the first plurality of plungers is received in an alignment slot of a corresponding one of the first plurality of mounting apertures.The method of claim 1, wherein a plurality of mounting ramps are provided on at least one sidewall of the shaker screen machine, and wherein placing the screen assembly on the screen receiving portion of the shaker screen machine comprises sliding a side of the support member along the plurality of mounting ramps, and wherein when the side of the support member slides along the plurality of mounting ramps, the side of the support member is pushed inward toward a center of the screen receiving portion of the shaker screen machine.A method of attaching a screen assembly to a vibratory screening machine, comprising: placing a screen assembly on a screen receiving portion of a vibratory screening machine, the screen assembly comprising a support member and a screen surface, the support member having front and rear sides, first and second sides, an upper surface, a lower surface, a plurality of flow apertures, and a first plurality of mounting apertures along the first side, each mounting aperture comprising at least one pressure surface located on an inner side of the mounting aperture relative to a centerline of the support member, the screen surface being attached to the upper surface of the support member, wherein placing the screen assembly on the screen receiving portion of the vibratory screening machine comprises positioning the screen assembly so, a first plurality of rams of pressure mechanisms on the shaker screen machine are aligned on the first plurality of mounting apertures; and causing the first plurality of rams to advance toward a centerline of the support member, each of the first plurality of rams having at least one pressure surface configured to abut a pressure surface of a mounting aperture such that as the first plurality of rams advance toward the centerline of the support member, resulting compressive forces applied to the pressure surfaces of the first plurality of mounting apertures comprise a first component directed horizontally toward the centerline of the support member and a second component directed vertically downward, the resulting compressive forces causing the screen assembly to flex into a concave shape, wherein a center of the support member is lower than the sides of the support member, and wherein the resulting compressive forces cause the support member to be forced into engagement with underlying concave support surfaces of the vibratory screening machine.The method of claim 5, wherein the compressive forces applied to the compressive surfaces of the first plurality of mounting apertures together apply a holding force to the screen assembly urging the screen assembly into engagement with the concave support surfaces of the shaker screen machine, the holding force being between about 2,000 psi and about 4,000 psi.The method of claim 5, wherein causing the first plurality of rams to move towards the centerline of the support member comprises causing the first plurality of rams to move both inwardly towards the centerline of the support member and vertically downwardly.The method of claim 5, wherein each of the first plurality of mounting apertures comprises an alignment slot, wherein an end portion of each of the first plurality of plungers comprises an alignment finger, and wherein as the first plurality of plungers advances toward a centerline of the support member, the alignment finger of each of the first plurality of plungers is received in an alignment slot of a corresponding one of the first plurality of mounting apertures.The method of claim 5, wherein a second plurality of mounting apertures is provided on the second side of the support member, wherein a second plurality of rams are provided on the vibratory screening machine, wherein each of the second plurality of rams is configured not to move inwardly toward the centerline of the support member, and wherein advancing the first plurality of rams toward the centerline of the support member results in pressure surfaces of the second plurality of mounting apertures being forced into engagement with pressure surfaces of the second plurality of rams such that resultant pressure forces are applied to the pressure surfaces of the second plurality of mounting apertures, wherein the resultant pressure forces applied to the second plurality of mounting apertures cause a first component directed horizontally toward the centerline of the support member, and a second component directed vertically downward.The method of claim 9, wherein each of the second plurality of rams is movably mounted to the vibratory screening machine, and wherein when the thrust surfaces of the second plurality of mounting apertures are urged into engagement with the thrust surfaces of the second plurality of rams, the second plurality of rams move relative to the vibratory screening machine.The method of claim 10, wherein when the pressure surfaces of the second plurality of mounting apertures are forced into engagement with the pressure surfaces of the second plurality of rams, the second plurality of rams move relative to the shaker screen machine in a direction away from a center of the screen receiving portion of the shaker screen machine.A screen assembly configured to be mounted on a receiving portion of a vibratory screening machine comprising a plurality of pressure mechanisms, each of the pressure mechanisms comprising a ram, the screen assembly comprising: a support member having front and rear sides, first and second sides, an upper surface, a lower surface, a plurality of flow apertures, and a first plurality of mounting apertures located along the first side, each mounting aperture comprising: at least one pressure surface located on an inner side of the mounting aperture relative to a centerline of the support member, the at least one pressure surface configured to contact a corresponding pressure surface of a ram as the ram is advanced toward the centerline of the support member such that a resultant one of the pressure surfaces is engaged by a corresponding pressure surface of a ram, A pressing force applied to the at least one pressing surface of the mounting hole comprises a first component horizontally directed toward a center line of the support member and a second component vertically directed downward, and an alignment slot configured to receive an alignment finger of a pressing piston; and a screen surface mounted on the upper surface of the support member.The screen assembly of claim 12, wherein the at least one pressure surface of each mounting aperture comprises first and second pressure surfaces located on opposite sides of the alignment slot.The screen assembly of claim 12, wherein the support member comprises a metal plate and wherein the first plurality of mounting apertures extend through the entire thickness of the metal plate.The screen assembly of claim 12, wherein the support member comprises a plurality of support members joined together, the support members being made of plastic or synthetic material.The screen assembly of claim 15, wherein the first plurality of mounting apertures comprise apertures located along the first side of the support member do not extend an entire height of the support member such that as rams of thrust mechanisms advance towards the centerline of the support member, end faces of the rams are received in the first plurality of mounting apertures.The screen assembly of claim 16, wherein the support member comprises a connecting strip connected to the plurality of support members and forming the first side of the support member, the first plurality of mounting apertures being formed in the connecting strip.A method of attaching a screen assembly to a vibratory screening machine, comprising: placing a screen assembly on a screen receiving portion of a vibratory screening machine, the screen assembly comprising a support member and a screen surface, the support member having front and rear sides, first and second sides, an upper surface, a lower surface, a plurality of flow apertures, and a first plurality of mounting apertures along the first side, each mounting aperture comprising a pressure surface located on an inner side of the mounting aperture relative to a centerline of the support member, the screen surface being attached to the upper side of the support member, wherein placing the screen assembly on the screen receiving portion of the vibratory screening machine comprises positioning the screen assembly so, a first plurality of rams of pressure mechanisms on the shaker screen machine are aligned on the first plurality of mounting apertures; and causing the first plurality of rams to advance toward the centerline of the support member, each of the first plurality of rams having at least one pressure surface configured to abut a pressure surface of a mounting aperture, the at least one pressure surface of the rams being configured such that when the first plurality of rams are advanced toward the centerline of the support member and abut the pressure surfaces of the first plurality of mounting apertures, resultant compressive forces applied to the pressure surfaces of the first plurality of mounting apertures comprise a first component directed horizontally toward a centerline of the support member and a second component directed vertically downwardly, wherein the resulting compressive forces cause the screen assembly to flex into a concave shape with a center of the support member lower than the sides of the support member, wherein the resulting compressive forces cause the support member to be forced into engagement with underlying concave support surfaces of the shaker screen machine, and wherein the resulting compressive forces are sufficient to hold the screen assembly to the support surfaces of the shaker screen machine while the screen assembly is subjected to vibrational forces exerting an acceleration between 3G and 9G on the screen assembly.The method of claim 18, wherein the pusher mechanisms are configured such that end surfaces of the first plurality of pusher pistons move downward as the pusher pistons move inward toward the centerline of the support member.The method of claim 18, wherein the at least one pressure surface on each pressure piston comprises a side pressure surface and an upper pressure surface that meet at a pressure corner.The method of claim 20, wherein as the first plurality of rams advance toward the centerline of the support member, the pressure surface of each of the first plurality of mounting apertures slides along either the top pressure surface or the side pressure surface of a corresponding ram until the pressure surface of the mounting aperture abuts the pressure corner of the ram.The method of claim 18, wherein the screen assembly support member comprises a second plurality of mounting apertures along the second side of the support member, and wherein placing the screen assembly on the shaker screen machine further comprises positioning the screen assembly such that a second plurality of rams are aligned with the second plurality of mounting apertures, and wherein the second plurality of rams are not configured to move inwardly toward the centerline of the support member while the causing step is performed.The method of claim 22, wherein advancing the first plurality of rams toward the centerline of the support member causes thrust surfaces of the second plurality of mounting apertures to be urged into engagement with thrust surfaces of the second plurality of rams so that resultant thrust forces are applied to the thrust surfaces of the second plurality of mounting apertures, wherein the resultant thrust forces applied to the second plurality of mounting apertures comprise a first component directed horizontally toward the centerline of the support member and a second component directed vertically downward.The method of claim 18, wherein each of the first plurality of rams comprises an alignment finger, wherein the first plurality of mounting apertures comprise alignment slots, and wherein placing the screen assembly on shaker screen machine comprises positioning the screen assembly such that the alignment slots of the first plurality of mounting apertures are aligned with the alignment fingers of the corresponding one of the first plurality of rams.The method of claim 24, wherein each of the first plurality of plungers comprises pushing surfaces on opposite sides of the alignment finger, wherein each of the first plurality of mounting apertures comprises pushing surfaces on opposite sides of the alignment slot, and wherein as the first plurality of plungers advances toward the centerline of the support member, the pushing surfaces on opposite sides of the alignment finger of each of the first plurality of plungers engage corresponding pushing surfaces on opposite sides of the alignment slot of a corresponding each of the first plurality of mounting apertures.The method of claim 18, wherein the screen assembly does not comprise a pressure flange located on or adjacent a side of the support member.The method of claim 18, wherein when the support member of the screen assembly is forced into engagement with underlying concave support surfaces of the shaker screen machine, the support member is bent into an arcuate shape having a radius of curvature between about 70 inches and about 140 inches.The method of claim 18, wherein the support member of the screen assembly comprises a metallic support plate.The method of claim 18, wherein the support member of the screen assembly comprises a plurality of support members connected together, the support members being made of a plastic or synthetic material.The method of claim 29, wherein the first plurality of mounting apertures comprise apertures formed in the first side of the support member and do not extend the entire height or thickness of the support member such that as the first plurality of rams advance toward the centerline of the support member, end faces of the first plurality of rams are received in corresponding ones of the first plurality of mounting apertures.

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