Double diaphragm pump

Abstract

The invention relates to a double diaphragm pump (10) comprising: - a housing (11) and a piston rod (25) movably mounted therein, - wherein the housing (11) has at least one inlet opening and at least one outlet opening, and - wherein a first diaphragm (16) and a second diaphragm (17) are arranged at one end of the piston rod (25), - wherein the first diaphragm (16) is arranged in a first chamber (19) of the double diaphragm pump (10) and the second diaphragm (17) is arranged in a second chamber (20), - wherein the diaphragms (16, 17) are configured to separate the chambers (19, 20) into a product chamber (21; 22) and an expansion chamber (23; 24), respectively, and - with a drive device (26) for effecting a translational movement of the piston rod (25).The invention proposes a compact double diaphragm pump (10) with a piston rod (25) designed to perform a self-regulating, oscillating movement and thus enables simplified control of the diaphragms (16, 17).

Description

[0001] The invention relates to a double diaphragm pump according to the preamble of claim 1.

[0002] Such double diaphragm pumps, which are used in particular for conveying and dosing liquid media such as chemicals, solvents, paints, varnishes and much more, are generally known.

[0003] The pumping action is achieved by means of a piston rod that is movably mounted within the double diaphragm pump. This piston rod causes an oscillating translational movement of diaphragms located at its ends. Each diaphragm is assigned to a chamber of the double diaphragm pump, with the chamber being divided into two separate chamber sections by the diaphragm. In a pneumatically driven double diaphragm pump, one chamber section contains compressed air, while the other contains the medium to be pumped. In mechanically driven double diaphragm pumps, the diaphragm can be coupled to a reciprocating piston rod, which transmits the reciprocating motion to the diaphragms, thus generating the pumping strokes.Double diaphragm pumps are characterized by the fact that, compared to diaphragm pumps with only one diaphragm, an improved and more uniform volume flow of the medium to be pumped can be achieved.

[0004] A generic double diaphragm pump is known from patent application WO 2021 / 202689 A1. This pump converts the rotary motion of the pump drive into a translational motion of the piston rod by means of a rotatably mounted hollow cylinder that encompasses the piston rod. The piston rod is designed in the form of a spindle. To achieve the oscillating motion of the diaphragms, the end positions are monitored, and a complex control mechanism for reversing the spindle's direction of rotation is employed. This results in the oscillating motion of the piston rod and thus of the diaphragms, generating a defined deceleration and acceleration ramp. A disadvantage of this double diaphragm pump is that the motor must be switched to reverse the spindle's direction of rotation. This results in a considerable energy consumption.

[0005] A piston pump with a camshaft mechanism is known from GB 572 502 A. The reciprocating motion is achieved through the interaction of two elements. The conversion of the rotary motion into a linear motion is accomplished by using a reversing spindle. However, a reversing spindle is unsuitable for a diaphragm pump or double diaphragm pump because it cannot, or at least cannot, achieve the short stroke movements required for a diaphragm pump. Furthermore, the forces required to drive a diaphragm in the axial direction can only be absorbed poorly, and especially not reliably over the long term.

[0006] US Patent 2,508,253 A discloses a compressor in which a compressor cylinder and its piston are axially mounted in an electric drive motor. The motor rotor and the compressor piston are coupled in such a way that when the rotor rotates, the compressor piston moves back and forth. To facilitate this reciprocating motion, the piston has a helical groove on its circumference. A spherical element, mounted in a sleeve of the rotor, engages in this groove. When the rotor rotates, this rotary motion is converted into a linear motion of the piston. However, the sphere guided in the sleeve creates a point load, resulting in a tilting moment and thus an uneven load distribution. This uneven load distribution, in turn, causes additional friction and wear, which negatively impacts the service life of the overall system.Furthermore, a disadvantage is that the compression cylinder and the piston within it have relatively small diameters compared to a diaphragm pump, due to the system design. The pressure achieved by the piston is therefore relatively low and unsuitable for transmitting high axial forces.

[0007] From DE 10 2020 112 114 A1, a mechanism for converting a rotational motion into a translational linear motion is known. This involves the use of a pair of symmetrically arranged ball bearings with curved grooves. These enable the mutual conversion between rotational and linear motion of the two elements relative to each other: when the inner part rotates, the outer part performs a linear motion, and conversely, the inner part performs a linear motion when the outer part rotates. A disadvantage of this mechanism is that the cam of the ball drive can only absorb axial forces in one direction. Therefore, the drive is unsuitable for generating an oscillating motion. Furthermore, due to the small number of balls, the described cam guide is insufficiently suited for transmitting forces acting in the axial direction.Furthermore, the described cam mechanism requires a considerable amount of installation space in the axial direction due to system limitations and prevents a compact design of the drive.

[0008] Further pumps and drive devices for pumps are known from DE 20 2004 020 335 U1, CA 2 009 361 A1, US 3 652 187 A, US 3 914 958 A and EP 1 418 959 B1. The object of the invention is to eliminate the described disadvantages and to provide a double diaphragm pump which is characterized by a compact design and simplified control of its diaphragms.

[0009] This problem is solved by a double diaphragm pump with the features of claim 1.

[0010] An example of a double diaphragm pump includes: a housing and a piston rod movably mounted in the housing along a longitudinal axis of the housing, wherein the housing has at least one inlet opening and at least one outlet opening, and wherein a first diaphragm of the double diaphragm pump is arranged at a first rod end of the piston rod and a second diaphragm of the double diaphragm pump is arranged at a second rod end of the piston rod facing away from the first rod end, wherein the first diaphragm is arranged in a first chamber of the double diaphragm pump formed in the housing and the second diaphragm is arranged in a second chamber formed in the housing, wherein the diaphragms are designed to separate the chambers into a product chamber and an expansion chamber respectively, and with a drive device for bringing about a translational movement of the piston rod.

[0011] A diaphragm pump is characterized by the fact that the fluid is moved over a large area. Alternatively, one can think of the diaphragm in a double diaphragm pump as corresponding to a piston with a disproportionately large piston area, but which only makes short strokes. Since the pressure generated by a pump is derived from the force per unit area, large piston or diaphragm surfaces result in large axial forces.

[0012] For example, the piston rod has features designed to produce a self-regulating, oscillating motion. In other words, the piston rod's movement is a self-regulating, oscillating motion. This means that the oscillating motion is generated by its design and is therefore self-regulating. No additional measure or means are required to produce this oscillating motion, which has so-called inflection points.

[0013] In one embodiment of the double diaphragm pump, the piston rod is divided and the self-regulating, oscillating movement of the piston rod is realized by means of at least two independently designed cams, one cam being designed for the movement of the first diaphragm and the other cam being designed for the movement of the second diaphragm.

[0014] The split piston rod comprises a first and a second piston rod section, each with the same central axis. The first piston rod section is coupled to the first diaphragm, and the second piston rod section to the second diaphragm. Analogous to a continuous piston rod, the two piston rod sections are located between the two diaphragms, but are spaced apart from each other. In simplified terms, the split piston rod corresponds to a continuous piston rod divided into two halves with a gap between the two parts. This gap, preferably located in the middle of the piston rod, forms a space that decouples the stroke movements of the two piston rod sections, making them independent of each other.

[0015] While a continuous piston rod prevents the superposition of pump strokes from the two diaphragms, the cam guides in a split piston rod can be symmetrical or mirror-symmetrical. In this case, the gap, i.e., the distance between the two piston rod sections, is not constant during a pump-suction cycle but varies. For example, while one piston rod section is still moving to the right, the switching point may already have been reached for the other piston rod section, and a reversal of movement may be taking place.

[0016] As a result, a cam guide with superimposed pump strokes can be implemented particularly easily with a piston rod divided into two piston rod sections.

[0017] The advantage lies in the fact that the cam mechanism allows for simple, independent movement of the diaphragms, and thus the suction and pump strokes. The cams in the piston rod are designed in such a way that a complex rotation direction control of the drive mechanism is unnecessary.

[0018] A cam follower is a guide that transmits the movement of one component to another by forcibly changing the direction of movement. In this case, the cam follower serves to transmit the rotary motion of a motor to a rod in the form of a translational back-and-forth motion.

[0019] Therefore, the motor provided in this case comprises a hollow cylinder and a piston rod arranged inside the hollow cylinder. The hollow cylinder and piston rod together form a clearance fit and are coupled to each other via a cam guide in such a way that the rotational movement of the hollow cylinder is converted into a translational reciprocating movement of the piston rod.

[0020] For example, a pin can be provided on the outer surface of the shaft, engaging in a non-linear, groove-like guide track (cam) provided in the inner surface of the hollow cylinder. As the hollow cylinder rotates, the pin, and thus the entire shaft, is displaced linearly. Alternatively, instead of a pin projecting from the shaft into a groove-like guide track of the hollow cylinder, the pin can also be provided on the inner surface of the hollow cylinder and engage in a non-linear, groove-like guide track (cam) provided in the outer surface of the shaft. Depending on the specific application, the pitch and path of the cam guide can also be designed differently. For example, it can be provided that the movements of the two diaphragms are different, preferably even temporarily opposed, during a pump-suction cycle.

[0021] In the diaphragm pump, the piston rod is not designed as a spindle. One advantage of this is that the direction of rotation of the spindle does not need to be reversed, as is the case in prior art designs.

[0022] It should be noted here that the cam track system consists of at least one cam track assigned to the first membrane and another to the second membrane. Likewise, two, three, or more cam tracks could be used to move a single membrane. Ideally, each membrane is assigned the same number of cam tracks.

[0023] To achieve a compact double diaphragm pump, the drive unit for generating the translational movement of the piston rod is designed with a rotor that is coaxial with the piston rod. This allows the required translational movement to be easily achieved using a rotary motion.

[0024] In particular, the drive unit is an electric drive unit. A compact design is important because, for example, when used as a pump for paint supply in a paint shop or in printing presses, installation space is always limited, and bulky designs are then difficult or impossible to accommodate. A compact design is also advantageous for retrofitting, i.e., modernizing and / or upgrading an existing system. For example, the compact design allows for the replacement of less energy-efficient pneumatic pumps, as the pumps can then be replaced without major modifications.

[0025] The electric drive unit is particularly advantageous when designed as a torque motor. A torque motor is understood to be a preferably high-pole, direct-drive electric motor. Torque motors typically exhibit very high torques at relatively low speeds. In simple terms, a torque motor can be considered a hollow-shaft motor optimized for high torque. One advantage of a torque motor is its very low energy consumption.

[0026] In contrast to the state-of-the-art solution according to GB 572502 A, the torque motor allows the conversion of rotary motion into linear motion within the motor itself. This results in a significantly more compact design.

[0027] Due to its design, the torque motor can achieve the high torque required to move the diaphragms without a reduction gearbox. A torque motor's rated operating point is at a freely selectable lower speed. In contrast, an asynchronous motor requires a full magnetizing current even at low speeds to generate a rotor field. Therefore, in the low speed range required for diaphragm pumps, the asynchronous motor cannot be used without a gearbox for double diaphragm pump applications.

[0028] As an alternative to an electric torque motor, a pneumatically driven external rotor motor would also be conceivable.

[0029] Furthermore, the torque motor allows for the simple implementation of a coaxial rotor and piston rod configuration. Regardless of whether a split or undivided piston rod is used, the diaphragms are coupled to the outer ends of the piston rod. The torque motor is thus located in the area between the diaphragms. This results in a particularly compact design and a less bulky form factor compared to, for example, drives arranged perpendicular to the piston rod.

[0030] In contrast to the double diaphragm pump known from WO 2021 / 202 689 A1, the direction of rotation can be changed without switching the motor by using a piston rod with integrated cams instead of a spindle. Guide elements such as cams, balls, or rollers engage with these cams, thus forming a cam control mechanism. Preferably, the guide elements return to their starting position after a full revolution. This cam control eliminates the need to switch the motor's direction of rotation, allowing the motor to operate at a constant speed.

[0031] As an alternative to a control system where the cams are designed so that the guide elements reverse the stroke direction of the piston rod and diaphragm after a full revolution, it is also possible to provide one or more switching points after less than a full revolution, for example, after 0.5 revolutions of the piston rod. Such a control system is particularly well-suited when the installation space available for the piston rod is large enough to allow the piston rod itself to have a relatively large diameter or circumference. A cam guide with switching points during a revolution has the advantage that, for the same diaphragm stroke, the cam pitch can be greater than with a cam guide that switches after every full revolution. Furthermore, the pumping frequency increases at a constant motor speed.

[0032] The use of balls as guide elements is particularly preferred. A piston rod with an integrated guide and guided balls can also be called a ball screw. In simple terms, a ball screw is a screw thread in which inserted balls transmit the force between the screw and nut. Both parts have a helical groove with a semicircular cross-section, which together form a helical tube filled with balls. The balls form the positive-locking connection in the thread perpendicular to the helical path. During rotation between the screw and nut, the balls roll in their tube and convert the rotary motion generated by the motor into a linear motion. This rolling motion reduces frictional resistance and, consequently, wear and the drive requirement.

[0033] The elimination of the rotation direction change, and the associated braking and acceleration losses, results in significant energy savings.

[0034] A further advantage is that the cam control can have not just one cam, but several cams, for example, four cams. In a cam control with four cams, a tilting moment caused by the drive is absorbed by the cam guide or piston rod in four quadrants. Due to the cam tracks being arranged preferably at uniform intervals, for example, four cam tracks arranged at 90° intervals, the start and end points of the cams are evenly distributed around the circumference. This avoids tilting moments, such as those that occur in the prior art known from GB 572 502 A. The piston rod does not tilt, or at least tilts less severely, and the drive runs more smoothly. This reduces wear and saves energy.

[0035] Since a complex rotation direction control is unnecessary, the torque motor can be operated with a standard frequency converter. For the desired flow rate of the double diaphragm pump, only the desired speed needs to be specified in this design.

[0036] To achieve a simple design for the cam guide, the cam is designed in an annular shape. This means it is closed around the circumference of the piston rod. For example, the cam guide can be designed by incorporating groove-like recesses into the piston rod and / or the inner cylinder wall of the torque motor.

[0037] In a further embodiment of the double diaphragm pump, several cams, for example two, associated with each diaphragm are identically designed and arranged parallel to one another. The advantage is a lower surface pressure on the guide elements projecting into the cam. In other words, several, at least two, cams of identical shape are arranged next to each other or one behind the other in the direction of movement, thus reducing the surface pressures.

[0038] Particularly in a design with a split piston rod, at least two cams are provided for the movement of each of the diaphragms, with the two cams arranged one behind the other on the piston rod in the axial direction of the piston rod. One cam thus serves to control the movement of one diaphragm and the other cam to control the movement of the other diaphragm. The two cams preferably have a rotational angular offset from each other. This allows the guide elements designed for guidance in the cam to be arranged spatially offset and provide precise guidance of the piston rod over its entire circumference. If the cam guide has a guide element designed independently of the cam, improved, reliable operation of the double diaphragm pump is achieved in a simple manner, since jamming is significantly reduced, in particular eliminated.An independently designed guide element is understood to be a guide element that can move freely within the guide. The guide elements, which engage with both the rotor and the piston rod and are used to create the oscillating motion of the piston rod, are thus operatively connected to the rotor and the piston rod, but are not rigidly connected to either component; rather, they are movable relative to both.

[0039] The double diaphragm pump according to the invention is preferably reliable in operation if the guide element is designed in the form of a ball, a roller, or a pin. In particular, if the guide element is designed in the form of a ball, the rotational symmetry of the ball prevents tilting or jamming in the guide. To compensate for dynamic loads and / or tolerances, the guide elements can also be spring-loaded.

[0040] In a further advantageous embodiment of the double diaphragm pump according to the invention, the cam guide has a guide sleeve movably arranged on the piston rod and coupled to the torque motor, which is designed to receive the guide elements. Thus, the guide elements are securely held movably within the cam guide.

[0041] In symmetrically operating double diaphragm pumps, the suction stroke and the pumping stroke alternate after equal periods of time. Therefore, when the diaphragms reach their end positions, a reversal of direction is necessary, leading to a brief interruption of the flow. This phenomenon, known as pulsation, is typically minimized using pulsation dampeners. The disadvantage of using pulsation dampeners is that they represent an additional cost and complicate the cleaning of the pumps and delivery lines when changing materials or decommissioning the pumps. It is therefore advantageous to minimize pulsation to such an extent that the use of pulsation dampeners can be dispensed with, allowing the double diaphragm pump to operate as uniformly and continuously as possible.This can be achieved, for example, through a suitable design of the cams, thus with the help of appropriate cam shapes and / or through a suitable design of the piston rod.

[0042] In a further advantageous embodiment of the double diaphragm pump according to the invention, the cams are designed such that the time required for a suction stroke is shorter than the time required for a delivery stroke. This makes it possible to minimize pulsation to such an extent that the use of pulsation dampeners can be dispensed with and the double diaphragm pump exhibits a virtually uniform, uninterrupted delivery.

[0043] In a further advantageous embodiment of the double diaphragm pump according to the invention, the cams are designed such that at a switching point of one diaphragm, the opposite diaphragm is still in a pumping stroke, and vice versa. The pumping strokes of the two diaphragms thus overlap. Therefore, there is no point in time when neither diaphragm is not in pumping mode and the volume flow of the pumped medium drops to zero. Thus, pulsation can be further reduced.

[0044] Pulsation reduction can also be achieved, or supplemented by, the aforementioned configurations, by having the first membrane have a flow profile that differs from that of the second membrane. This can be easily accomplished, for example, by using different membrane materials. The figures show:

[0045] Fig. 1 shows a perspective view of a double diaphragm pump according to a first embodiment, which is not part of the inventive idea; Fig. 2 shows a longitudinal section II-II of the double diaphragm pump according to Fig. 1. Fig. 1 ; Fig. 3 shows in detail view III the double diaphragm pump acc. Fig. 1 Fig. 4 shows in a perspective view a piston rod with a guide sleeve having two diaphragms of the double diaphragm pump according to the first embodiment, which is not part of the inventive idea; Fig. 5 shows in a longitudinal section the piston rod according to Fig. 4 Fig. 6 shows a perspective view of the piston rod of the double diaphragm pump in a second embodiment, which is not part of the inventive idea; Fig. 7 shows a perspective view of the piston rod according to Fig. 6 with the guide sleeve; Fig. 8 shows in a perspective view the piston rod acc. Fig. 6Fig. 9 shows a side view of the piston rod according to... Fig. 6 Fig. 10 shows a perspective view of a piston rod of the double diaphragm pump according to a third embodiment, comprising the two diaphragms; Fig. 11 shows a perspective view of the piston rod according to the third embodiment. Fig. 10 ; Fig. 12 shows a side view of the piston rod according to. Fig. 11 , and Fig. 13 shows in a time-volume flow diagram a volume flow curve of a double diaphragm pump according to the prior art in comparison with a volume flow curve according to the third embodiment.

[0046] Identical or similar elements in the following figures may be designated with the same or similar reference numerals. Furthermore, the figures of the drawing, their description, and the claims contain numerous features in combination. It is clear to a person skilled in the art that these features can also be considered individually or combined into further combinations not described in detail here. The invention expressly extends to embodiments that are not defined by combinations of features from explicit cross-references in the claims, meaning that the disclosed features of the invention can be combined with one another in any way that is technically feasible. The exemplary embodiments shown in the figures are therefore merely descriptive and are not intended to limit the invention in any way.

[0047] A first embodiment of a double diaphragm pump 10 is described in Fig. 1in a perspective representation and in Fig. 2 The double diaphragm pump 10 is shown in section II-II along a longitudinal axis 15. It should be noted that the double diaphragm pump 10 described here is not limited to the illustrated embodiments, but rather can be applied to any conceivable embodiment of a double diaphragm pump.

[0048] The double diaphragm pump 10 essentially comprises a housing 11 with a pump body 14 arranged between a first housing cover 12 and a second housing cover 13. Furthermore, the double diaphragm pump 10 includes two diaphragms as essential elements, namely a first diaphragm 16 and a second diaphragm 17. The diaphragms 16 and 17 are pressed together and held in place between the respective housing covers 12 and 13 and the pump body 14 by means of a peripheral annular bead 18 formed around their circumference.

[0049] Elastomeric composite materials, such as NBR, are preferably used as materials for the membranes 16, 17. The NBR material acts as an elastic base material onto which a chemically resistant, thin PTFE film can be laminated, particularly on the media side.

[0050] The housing covers 12, 13, together with the pump body 14, form two chambers: a first chamber 19 and a second chamber 20. Each chamber is divided by the diaphragms 16, 17 into a product chamber 21, 22 and an expansion chamber 23, 24 with alternating volumes. This means that the first chamber 19 is divided by the first diaphragm 16 into the first product chamber 21 and the first expansion chamber 23, and the second expansion chamber 24 is divided by the second diaphragm 17 into the second product chamber 22 and the second expansion chamber 24. In pneumatically driven double diaphragm pumps, the chambers 23, 24 serve as expansion chambers, which, controlled by valves, are alternately pressurized with compressed air, thus creating a flow rate of the medium to be pumped.

[0051] The diaphragms 16, 17 are connected to a piston rod 25 at its rod ends 37, 38 in such a way that they alternately expand and compress the product chambers 21, 22. As is typical for pumps, each cycle is divided into a pumping stroke and a suction stroke.

[0052] During the pumping stroke, the diaphragms 16, 17 alternately push towards the housing covers 12, 13, displacing the product or medium to be pumped from the product chambers 21, 22. During the suction stroke, the piston rod 25 pulls the diaphragms 16, 17 towards the center of the pump body 14, causing the product chambers 21, 22 to expand and drawing in a further quantity of the medium. To ensure a uniform flow rate of the medium being pumped, the double diaphragm pump 10 is designed so that when one diaphragm 16 is pumping, the other diaphragm 17 is suctioning, and vice versa. Backflow of the medium during the switching of the chambers 19, 20 is prevented by suitable check valves (not shown).

[0053] An electric drive unit 26 in the form of a torque motor 40 is arranged between the diaphragms 16, 17. The drive unit 26, in the form of the torque motor 40, enables a compact coaxial design for its rotor 27 and piston rod 25, which is formed between the diaphragms 16, 17. In other words, a bulky design, i.e., one requiring a large installation space, such as that of drive motors arranged perpendicular to the piston rod 25 and thus perpendicular to a movement axis 28 of the diaphragms 16, 17, is no longer necessary.

[0054] As an example, a self-regulating oscillating movement of the piston rod 25 is realized with the aid of a cam guide 29, which in the illustrated embodiment is formed on the piston rod 25. It should be noted here that the oscillating movement of the piston rod 25 is not a vibrating movement like the oscillating movement of the diaphragms 16, 17, but rather a translational back-and-forth movement of the piston rod.

[0055] For this purpose, guide elements 30 arranged in the rotor 27 of the drive unit 26, or, as in the present embodiment, in a guide sleeve 32 coupled to the rotor 27, engage in groove-like recesses in the piston rod 25. The groove-like recesses in the piston rod 25 thus form cams 31 of the cam guide 29. In this embodiment, two guides are arranged parallel to each other. They are independent of each other in that they do not cross each other.

[0056] In the present embodiment, the guide elements 30 are designed in the form of spherical elements or spheres. The guide sleeve 32 includes recesses for receiving the spheres. In the assembled state, the spheres protrude from the recesses of the guide sleeve 32 and into the cams 31 of the piston rod 25. The positive guidance provided by the cam guide 29 achieves the oscillating movement of the piston rod 25 necessary for driving the diaphragms 16, 17. In other words, the self-regulating, oscillating movement of the piston rod 25 is achieved by means of a cam guide 29 comprising at least two independently designed cams 31.

[0057] The cam track 29 thus has a guide element 30 that is designed independently of the cam track 31. In particular, the guide element 30 is also designed independently of the drive unit 26. It is therefore freely movable within the cam track 31 according to a guide form of the cam track 31.

[0058] Fig. 3 shows one of the Fig. 2Detail III of the double diaphragm pump 10 according to the first embodiment. The guide sleeve 32 forms a clearance fit with the piston rod 25. It can also be seen that two guide elements 30, here: balls, couple the guide sleeve 32 and the piston rod 25 to each other. Since the recesses in the guide sleeve 32 are circular bores for receiving the balls, these can rotate around their center point in the bores with relatively little resistance, but cannot perform any translational movement relative to the guide sleeve 32. In contrast, the cams 31 in the piston rod 25 are channel-like guide tracks. When the guide sleeve 32 is rotated by means of the rotor 29, the rotational movement of the guide sleeve 32 is thus converted into a translational movement of the piston rod 25.The length of the stroke and the time component for the suction stroke and pump stroke depend on the design of the cam 31 or can be structurally determined by the design of the cam 31.

[0059] In the Figures 4 and 5 The piston rod 25 is enclosed by the guide sleeve 32 and shown together with the diaphragms 16 and 17 coupled to the piston rod 25. Figures 4 and 5 show the first embodiment according to the Figures 1 to 3 The double diaphragm pump 10 is shown in a perspective view or in a longitudinal section. The guide sleeve 32 of the cam guide 29 is movably arranged on the piston rod 25.

[0060] The cam guide 29 comprises cams 31, which are designed such that a reversal of the direction of rotation of the drive unit 26 is unnecessary. A complex direction control is therefore superfluous. This means that the double diaphragm pump 10 is self-regulating. The drive unit 26, designed as a torque motor 40, can thus be operated with a commercially available frequency converter (not shown). For a desired flow rate of the double diaphragm pump 10, only a rotational speed corresponding to that flow rate needs to be specified.

[0061] The cams 31 are each annular in shape, meaning they each form a closed annular groove extending over the circumference of the piston rod 25. At least one guide element 30 is arranged in each of these cams 31, which can move completely around the circumference of the cam 31. Or, in other words, each guide element 30 is fully movable around the circumference of the cam 31. This ensures reliable operation of the double diaphragm pump 10.

[0062] The piston rod 25 according to the first embodiment has, in the illustrated embodiment, two identical cams 31 arranged in pairs and parallel to each other. Because the two cams 31 are arranged in pairs in the present embodiment, the surface pressure caused by the cam guide is reduced. Or, in other words, to prevent wear of the piston rod 25 and the guide elements 30 caused by high surface pressure, several cams 31 of identical shape are arranged next to each other, thus reducing the surface pressure. Of course, it is also possible to further reduce the surface pressure by adding one or more additional cams. An angular offset of the cams is also possible. This allows for a distribution of forces around the circumference.

[0063] The paired cams 31 arranged side by side according to the first embodiment enable a higher packing density in order to achieve the lowest possible surface pressure.

[0064] Alternatively, the cams 31 are designed so that all balls realize the same lifting-suction movement on the one hand, but are also evenly distributed over the circumference of the guide sleeve 32 and piston rod 25 (cf. Fig. 7 The load caused by the cam guide 29 is therefore not transferred unilaterally, i.e. along a single straight line parallel to the central axis of the piston rod 25, from the guide sleeve 32 to the piston rod 25, but uniformly, for example by four guide elements 26 or pairs of guide elements at four points or pairs of points at 90°, 180°, 270° and 360° from the guide sleeve 32 to the piston rod 25.

[0065] In the Figures 6 to 9The piston rod 25 is illustrated in different views according to the exemplary double diaphragm pump 10. Figure 6 Figure 1 shows an embodiment in a perspective view with the membranes 16, 17, but without guide sleeve 32. Figure 7 The system shows according to Fig. 6 with mounted guide sleeve 32, in another perspective view. Figures 8 and 9 show the piston rod 25 with the cams 31 inserted into the piston rod 25 in a perspective view, Figure 9 The piston rod 25 shows according to Fig. 8 in a side view. In this second embodiment, the cams 31 are freestanding, thus not arranged in pairs. The cams 31 arranged side by side according to the second embodiment are radially and axially offset from each other, as particularly shown in the Figures 6, 8 and 9 is illustrated.

[0066] The number of cams 31, or cam pairs, is fundamentally dependent on the desired application area of ​​the double diaphragm pump 10 and its corresponding axial extension.

[0067] By means of a selected rotational angular offset of the individual cams 31 or cam pairs relative to each other, the guide elements 30 can be arranged spatially offset and thus also form a precise, preferably ball-bearing, guide for the piston rod 25 over its entire circumference. In other words, at least two cams 31 are provided for the movement of the diaphragm 16, 17, wherein the two cams 31 are arranged side by side on the piston rod 25, and wherein the two cams 31 have a rotational angular offset relative to each other.

[0068] The guide elements 30 are arranged to be movable in receiving openings 34 of the guide sleeve 32 by means of the guide sleeve 32, which encompasses the piston rod 25 around its outer surface 33.

[0069] In a third embodiment of the double diaphragm pump 10 according to the invention, the piston rod 25 is designed in two parts. This split connecting rod 25 is located in the Figures 10 to 12 depicted, whereby they are in the Figures 10 and 11 in a perspective view with membranes 16, 17 and without these membranes 16, 17 and in Fig. 12 a side view is also illustrated without membranes 16, 17.

[0070] In principle, with double diaphragm pumps 10, the flow of the pumped medium or product is briefly interrupted when the diaphragms 16, 17 reach their end positions and the piston rod 25's direction of movement is reversed. This results in a so-called pulsation, which is usually minimized using pulsation dampeners. The disadvantage of using pulsation dampeners is that they represent an additional cost and make cleaning the double diaphragm pumps 10 and the delivery lines (not shown) more difficult when changing materials or taking the double diaphragm pumps 10 out of service.

[0071] The split piston rod 25 thus has a first piston rod section 35 and a second piston rod section 36, wherein the first piston rod section 35 has the first diaphragm 16 at its first rod end 37, which faces away from the second piston rod section 36, and the second piston rod section 36 has the second diaphragm 17 at its second rod end 38, which faces away from the first piston rod section 35. The two piston rod sections 35, 36 are preferably of the same dimensions.

[0072] In other words, the piston rod 25 of the double diaphragm pump 10 according to the second embodiment is preferably interrupted in the middle, thus enabling independent movements of the two diaphragms 16, 17.

[0073] In the formation of at least two independent cams 31 in each piston rod section 35; 36, the movement of the diaphragms 16, 17 is realized such that the time required for a suction stroke of the diaphragms 16, 17 is shorter, preferably minimally shorter, than the time required for a delivery stroke. This results in a forced superposition of the delivery strokes of the two diaphragms 16, 17.

[0074] The movement profiles are preferably designed such that at the switching point of the first diaphragm 16, where there is no flow of the medium, the second diaphragm 17 has just not yet reached its switching point and thus maintains the flow of the double diaphragm pump 10. Conversely, the interruption of the flow at the switching point of the second diaphragm 17 is at least partially compensated for by the flow of the first diaphragm 16.

[0075] This is possible because the suction stroke time, due to the design of the cams 31 in the split piston rod 25, or in other words, in the two piston rod sections 35, 36, is always shorter than the delivery stroke time. Thus, the pulsation phenomenon can be significantly reduced, and the use of pulsation dampers can be eliminated.

[0076] It should be mentioned here that in both double diaphragm pumps 10 with a through piston rod 25 and in double diaphragm pumps 10 with a split piston rod 25, each diaphragm 16, 17 is assigned a support disc 39 so that the pressure exerted by the piston rod 25 on the diaphragm 16, 17 can be transmitted over a large area to the respective diaphragm 16, 17. Without this support disc, the pressure transmission to the diaphragm 16, 17 would be localized or very localized.

[0077] In Fig. 13A time-volume flow diagram shows a first volume flow curve V1 of a double diaphragm pump according to the prior art in comparison with a second volume flow curve V2 of the double diaphragm pump 10 according to the third embodiment of the invention. The second volume flow curve V2 is shown with a dashed line.

[0078] Both flow rate profiles V1 and V2 exhibit essentially identical characteristics before switching at a specific switching time T1. Switching always results in a reduction of the delivered flow rate, which is why the first flow rate profile V1 drops from a first value W1 v1 of the first flow rate profile V1 to a second value W2 v1 of the first flow rate profile V1, and the second flow rate profile V2 drops from a first value W1 v2 to a second value W2 v2 of the second flow rate profile V2. It can be seen that the flow rate V1 (solid line) drops very sharply to the very low value W2 v1 after switching. In contrast, the flow rate V2 (dashed line) of the double diaphragm pump 10 according to the invention drops considerably less sharply, namely only from the value W2 v1 to the value W2 v2.

[0079] After switching, the first volume flow curve V1 rises to a third value W3 v1, likewise the second volume flow curve V2 rises to a third value W3 v2, whereby the two third values ​​W3 v1 , W3 v2 are identical, as are the first values ​​W1 v1 , W1 v2 .

[0080] During the further course of the pump stroke, both flow rate profiles V1 and V2 also decrease from the values ​​W3v1 and W3v2, respectively, to their initial values ​​W1v1 and W1v2. This fundamental behavior of the flow rate profiles V1 and V2 is due to the elasticity of the diaphragms 16 and 17 and the pipes. Pulsation is defined as the difference in the flow rate profile between the second value (the value achieved at the time of switching) and the third value during a pump cycle. Thus, the first flow rate profile V1 exhibits a first pulsation P1, and the second flow rate profile V2 exhibits a second pulsation P2. It is clearly evident that the second pulsation P2 is significantly smaller than the first pulsation P1.

[0081] With the aid of the piston rod 25 according to the third embodiment of the double diaphragm pump 10 according to the invention, that is to say, the split piston rod 25, it is possible to realize a short suction stroke, for example 2 / 5 of the time of a pump cycle, and a longer pump stroke, for example 3 / 5 of the time of a pump stroke, for each diaphragm 16; 17. The different durations are achieved by different slopes of the cams 31 formed in the piston rod sections 35, 36. Due to the duration of a pump stroke being more than 50%, it is possible for the pump strokes of the two diaphragms 16, 17 to overlap. This overlap of the pump strokes makes it possible to significantly reduce pulsation, as shown by the second volume flow curve V2 compared with the first volume flow curve V1. Reference symbol list

[0082] 10 Double diaphragm pump 11 Housing 12 First housing cover 13 Second housing cover 14 Housing body 15 Longitudinal axis 16 First diaphragm 17 Second diaphragm 18 Ring bead 19 First chamber 20 Second chamber 21 First product chamber 22 Second product chamber 23 First expansion chamber 24 Second expansion chamber 25 Piston rod 26 Drive unit 27 Rotor 28 Axis of motion 29 Cam guide 30 Guide element 31 Cam 32 Guide sleeve 33 Shell surface 34 Mounting opening 35 First piston rod section 36 Second piston rod section 37 First rod end 38 Second rod end 39 Support washer 40 Torque motor Section II - II Section (from Fig. 1 ) III excerpt (from Fig. 2) P1 First pulsation P2 Second pulsation T Time T1 Switching time V Volume flow V1 First volume flow V2 Second volume flow W1 V1 First value of the first volume flow profile W1 V2 First value of the second volume flow profile W2 V1 Second value of the first volume flow profile W2 V2 Second value of the second volume flow profile W3 V1 Third value of the first volume flow profile W3 V2 Third value of the second volume flow profile

Claims

1. Double membrane pump (10), comprising: - a casing (11) and a piston rod (25) received in the casing (11) and movable in translation along a longitudinal axis (15) of the casing (11), - wherein the casing (11) has at least one inlet opening and at least one outlet opening, and - wherein a first membrane (16) of the double membrane pump (10) is arranged on a first bar end (37) of the piston rod (25) and a second membrane (17) of the double membrane pump (10) is arranged on a second bar end (38) of the piston rod (25) facing away from the first bar end (37), - the first membrane (16) being arranged in a first chamber (19) of the double membrane pump (10) formed in the casing (11) and the second membrane (17) being arranged in a second chamber (20) formed in the casing (11), - the membranes (16, 17) are formed to separate the chambers (19, 20) into a product chamber (21; 22) and an expansion chamber (23; 24), respectively, and - with a drive device (26) for causing a translational movement of the piston rod (25), characterised in that - the piston rod (25) is divided and a self-regulating, oscillating movement of the piston rod (25) is brought about with the aid of a sliding block guide (29) having at least two sliding blocks (31) formed independently of one another, - one sliding block (31) is formed to move the first membrane (16) and the other sliding block (31) is formed to move the second membrane (17) - at least two sliding blocks (31) are formed to move the membrane (16; 17), the two sliding blocks (31) are arranged next to each other on the piston rod (25), and the two sliding blocks (31) have a rotational angle offset relative to each other so that the pump strokes of the two membranes (16, 17) overlap in such a way that, at a switchover time of one diaphragm at which a reversal of movement occurs, the opposite diaphragm is still in a delivery stroke.

2. Double membrane pump (10) according to claim 1, characterised in that the drive device (26) has a rotor (27) designed coaxially with the piston rod (25).

3. Double membrane pump (10) according to one of the preceding claims, characterised in that the drive device (26) is an electric drive device.

4. Double membrane pump (10) according to claim 3, characterised in that the electric drive device (26) is designed in the form of a torque motor (40).

5. Double membrane pump (10) according to one of claims 1 to 4, characterised in that the sliding block (31) is formed to be ring-shaped.

6. Double membrane pump (10) according to one of claims 1 to 5, characterised in that several sliding blocks (31) are identically formed and arranged parallel to each other.

7. Double membrane pump (10) according to one of claims 1 to 6, characterised in that the sliding block guide (29) has a guide element (30) formed independently of the sliding block (31).

8. Double membrane pump (10) according to claim 7, characterised in that the guide element (30) is formed in the form of a ball, a roller or a pin.

9. Double membrane pump (10) according to one of claims 1 to 8, characterised in that the sliding block guide (29) has a guide sleeve (32) arranged movably on the piston rod (25).

10. Double membrane pump (10) according to one of claims 1 to 9, characterised in that the sliding blocks (31) are formed such that the time span for a suction stroke is shorter than the time span for a delivery stroke.

11. Double membrane pump (10) according to one of claims 1 to 10, characterised in that the sliding blocks (31) are formed such that, at a switching point of one membrane (16; 17), the opposite membrane (17; 16) is still in a delivery stroke.

12. Double membrane pump (10) according to claims 1 to 11, characterised in that the first membrane (16) has a delivery profile which differs from the delivery profile of the second membrane (17).

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