Airflow coordinated clogging clearing method for ultrasonic screening machine screen

Abstract

The application discloses an airflow coordinated clogging cleaning method for a screen of an ultrasonic screening machine. A detachable and sealed casing is arranged above the screen, and an inner cavity of the casing is divided into an upper space connected with a negative pressure pump and a lower space facing the screen by a controllable communication assembly. A composite elastic net is arranged in the lower space and has assembly gaps and confluence gaps between the screen and the controllable communication assembly. Two steps are alternately executed during cleaning. In the closed blowing step, the controllable communication assembly is in an isolated state, the fine powder wedged in the screen holes is pushed away by the pulse airflow below the screen, and the screen is driven to impact the composite elastic net, the composite elastic net absorbs energy and intercepts the temporarily stored fine powder, and the maximum arching height of the screen becomes a constant value after the fine powder floats against the rigid limiting surface. In the negative pressure suction step, the blowing is stopped, the upper and lower spaces are communicated, the suspended fine powder passes through the composite elastic net and is sucked out through a discharge pipeline for recycling. The two steps are alternately circulated in time, and the clogging cleaning and fine powder recycling can be completed without dismounting the screen.

Description

Technical Field

[0001] This invention relates to the field of screening equipment technology, and in particular to a method for airflow-assisted unclogging of the screen of an ultrasonic screening machine. Background Technology

[0002] Ultrasonic sieving machines are typically used to classify the particle size of superhard materials such as diamond powder, with the sieving particle size generally in the micrometer range. During dry sieving, some particles, whose size is close to the screen mesh size, easily become embedded and clog the mesh. Simultaneously, the powder is prone to generating static electricity under high-frequency vibration and friction, causing particles to agglomerate and adhere to the screen surface. These factors collectively reduce the effective opening rate of the screen, leading to decreased sieving efficiency and classification accuracy, and in severe cases, even affecting the continuous operation of the equipment.

[0003] To address the problem of screen clogging, existing cleaning methods mainly include ultrasonic vibration self-cleaning, mechanically assisted cleaning, and offline cleaning after disassembly. Among these, the ultrasonic vibration of the equipment itself has limited effectiveness in removing particles embedded in the mesh; mechanical cleaning methods such as bouncing balls, cleaning blocks, or brushes are prone to generating impurities and may exacerbate screen wear; while stopping the machine to disassemble and clean the screen will interrupt the production process and affect processing efficiency.

[0004] For example, Chinese patent document CN210098205U (publication date February 21, 2020) discloses an automatic cleaning and recycling device for a ternary material vibrating filter screen. This device removes the clogging material by disassembling the screen and placing it in a dust removal chamber, and uses pulsed airflow to remove the clogging material, while simultaneously collecting the material using a collection device. However, this solution is still an offline cleaning method, requiring disassembly of the screen before implementation; furthermore, it mainly relies on unidirectional airflow for clogging, which has limited removal capabilities for particles tightly fitted to the mesh and agglomerated micropowders, and does not take effective measures to address the electrostatic adsorption problem of micropowders. In addition, this solution does not limit the deformation of the screen caused by the airflow impact during the cleaning process, which may lead to screen fatigue damage. Summary of the Invention

[0005] This invention provides a method for airflow-coordinated unblocking of ultrasonic sieving machine screens, which is used to solve the clogging problem caused by particle jamming, electrostatic adsorption, and agglomeration during the micro powder sieving process of ultrasonic sieving machines.

[0006] The present invention adopts the following technical solution: a method for airflow-coordinated unblocking of the screen of an ultrasonic sieve, characterized in that the method is implemented by means of a detachable and sealed housing above the screen of the ultrasonic sieve; the housing has an inner cavity, and a controllable communication component for switching between an isolation state and a communication state is provided in the inner cavity. The controllable communication component divides the inner cavity into an upper space for an external negative pressure pump and a lower space located above the screen; a composite elastic mesh is provided in the lower space between the controllable communication component and the screen. The composite elastic mesh is used to bear the impact load of the screen and transmit it to the controllable communication component, and an assembly gap is formed between the composite elastic mesh and the screen, and a confluence gap is formed between the composite elastic mesh and the controllable communication component. The aperture of the composite elastic mesh is larger than the aperture of the screen and the particle size of the powder being cleaned. The method includes: a closed purging step: isolating the upper space from the lower space, and outputting pulsed airflow from below the screen to the upper space, causing the screen to arch upward and impact the composite elastic net. The composite elastic net floats upward upon impact and abuts against the rigid limiting surface of the controllable connecting component facing the lower space, thereby limiting the arching deformation of the screen; a negative pressure suction step: stopping the output of the pulsed airflow and switching the controllable connecting component to the connecting state, so that the upper space is connected to the lower space. The peeled micro powder passes through the composite elastic net and enters the upper space under negative pressure, and is extracted and recycled through the discharge pipe connected to the upper space. The closed purging step and the negative pressure suction step are performed alternately in a time-sharing cycle to achieve the synergistic effect of pulse disturbance, elastic limit and negative pressure transfer.

[0007] Preferably, a conductive layer is provided on the surface of the composite elastic mesh. The conductive layer is electrically connected to the shell and grounded, so as to release the static electricity carried by the micro powder and the screen during the process of the screen hitting the composite elastic mesh, thereby reducing the re-clogging caused by static electricity agglomeration.

[0008] Preferably, the composite elastic mesh includes a flexible elastic mesh fabric disposed near the screen and a supporting mesh fabric stacked on top of the flexible elastic mesh fabric. Along the negative pressure suction direction, the apertures of the screen, the flexible elastic mesh fabric, and the supporting mesh fabric increase sequentially to achieve temporary storage and smooth conveying of micro powder.

[0009] Compared with existing technologies, this invention achieves online screen cleaning without disassembling the screen by alternating between two steps: closed-loop purging and negative pressure suction. In the closed-loop purging stage, pulsed airflow generated below the screen dislodges microparticles stuck in the screen holes and drives the screen to arch upwards in a controlled manner. A composite elastic mesh buffers the impact on the screen, while a conductive structure discharges static electricity from the microparticles. In the negative pressure suction stage, the dislodged microparticles are guided through the composite elastic mesh into a recovery channel and recycled through a secondary sorting structure. Through this synergistic effect, the efficiency of removing clogged microparticles is improved while reducing the risk of screen fatigue damage, achieving integrated processing of screen cleaning, static electricity suppression, and microparticle recovery. Attached Figure Description

[0010] Figure 1 A schematic diagram of the cleaning device installed on a screening machine for implementing the method of the present invention; Figure 2 A cross-sectional view of the cleaning device used to implement the method of the present invention in the closed purging step (isolation state). Figure 3 A partially enlarged structural diagram of the cleaning device used to implement the method of the present invention when it is in the negative pressure suction step (connected state); Figure 4 This is a schematic diagram of the structure when the composite elastic mesh is combined with the screen. Figure 5 This is a flowchart of the cleaning method of the present invention; Figure 6 A schematic diagram showing the impact of the screen mesh against the composite elastic mesh during the closed purging process, which causes the diamond powder to be stuck and pushed away from the mesh openings. Figure 7 This is a schematic diagram showing the diamond micropowder being extracted through the composite elastic mesh during the negative pressure suction process. Figure 8 This is a control timing diagram for one cleaning cycle in Example 2; Figure 9 This is a cross-sectional view of the controllable interconnection component with translational misalignment in Example 2 when it is in a misaligned state (isolated state). Figure 10 This is a cross-sectional view of the controllable interconnected component with translational misalignment in Example 2 when it is in the aligned state (connected state).

[0011] Figure label: Screening machine 01, screen 02, diamond micro powder 03, shell 10, controllable connecting component 20, upper space 201, lower space 202, fixed plate 21, movable plate 22, fan-shaped through hole 23, strip-shaped through hole 25, operating swing rod 241, limiting slide 242, composite elastic net 30, flexible elastic net cloth 31, supporting net cloth 32, discharge pipe 40, secondary screening structure 50, pressure relief valve 60. Detailed Implementation

[0012] All references are attached. Figures 1 to 10 .

[0013] Example 1: This embodiment addresses the aforementioned screen clogging problem in ultrasonic sieving machines 01 used for screening ultrahard material particles such as diamond micron powder 03. It provides an airflow-coordinated unclogging method for the ultrasonic sieving machine screen, enabling rapid and continuous effective cleaning of the screen 02 when it becomes clogged. (Reference) Figure 5 The method includes an installation and preparation step S1, a sealed purging step S2, a negative pressure suction step S3, a judgment step S4, and a reset step S5, wherein steps S2 and S3 are performed alternately in a time-sharing cycle. The following is in conjunction with... Figures 1 to 4 Each step is described in detail.

[0014] Step S1: Install the cleaning device and complete the preparations before cleaning.

[0015] refer to Figure 1 , Figure 2 In this step, the cleaning device is detachably mounted above the screen 02. The cleaning device includes a housing 10 that can be fitted and installed with the outer casing of the screening machine 01. The housing 10 contains a controllable communication component 20 and is divided into an upper space 201 and a lower space 202 that can be isolated from or connected to each other (the connection state is as follows). Figure 3 As shown in the figure, the upper space 201 is externally connected to a negative pressure pump (not shown in the figure) and is connected to a discharge pipe 40. The lower space 202 is fitted with a composite elastic net 30. The surface of the composite elastic net 30 is provided with a conductive layer, which has the functions of conductivity and static discharge. The composite elastic net 30 is not used as a micro powder screening and filtration structure, but is used to receive the impact of the screen 02 during the purging stage, transmit the impact load, and provide temporary impediment and bearing for the stripped micro powder. The conductive layer is electrically connected to the housing 10 and led out to ground through the housing 10 (the grounding structure is detailed later). During installation, an assembly gap is left between the composite elastic net 30 and the screen 02, and a flow junction gap is left between the composite elastic net 30 and the controllable communication component 20. At the same time, a pulse valve with an external compressed air source (neither of which is shown in the figure) is matched below the screen 02 to generate an upward pulse airflow.

[0016] Preferably, the assembly gap between the composite elastic mesh 30 and the screen 02 is designed to meet both of the following requirements: Firstly, it avoids an excessively small gap, which would cause the screen 02 to remain in continuous contact with the composite elastic mesh 30 during static deflection under rotational load and installation tolerances, resulting in high-frequency friction under ultrasonic excitation and subsequent wear and damage to the screen 02. Secondly, it avoids an excessively large gap, which would increase the upward arching stroke of the screen 02, weakening the constraint effect of the composite elastic mesh 30 on its maximum deformation amplitude, and causing lateral dispersion of the pulsed airflow, preventing effective suspension and negative pressure suction of the micropowder. The assembly gap can be adjusted using the adjustable mounting flange described later.

[0017] The size of the pre-reserved flow-combining gap between the composite elastic mesh 30 and the controllable communication component 20 is determined to meet the following three requirements. Firstly, it reduces the amount of micropowder that can penetrate the composite elastic mesh 30 and enter the flow-combining dead zone during the closed-loop purging process. Secondly, it balances the airflow distribution during negative pressure suction, preventing excessively high local flow velocities that could cause uneven wear on the composite elastic mesh 30. Furthermore, this flow-combining gap is also the maximum upward stroke of the composite elastic mesh 30 under airflow. Its sum with the aforementioned assembly gap constitutes the maximum upward arch height achievable by the screen 02. Therefore, this gap should not be too large; otherwise, the rigid limiting action of the fixing plate 21 will not be able to intervene in time, and the upward arch amplitude of the screen 02 will lose its definite constraint.

[0018] refer to Figure 4 The composite elastic net 30 adopts a double-layer composite mesh structure. The lower layer near the screen 02 is a flexible elastic mesh 31, which can be made of nylon elastic mesh or polyurethane elastic mesh, to absorb the upward impact of the screen 02 and buffer the energy. The upper layer is a support mesh 32, which can be made of polyester high-strength mesh or fiberglass mesh, with high tensile strength and low elongation. It can collect, distribute and transfer the impact load borne by the flexible elastic mesh 31 upward to the fixed plate 21 described later. The edges of the two meshes are bonded to each other, leaving a gap in the middle and allowing relative movement. Both surfaces are provided with conductive layers. The two conductive layers are bonded to each other at the edge bonding point and maintain electrical conductivity to form a continuous electrostatic discharge layer.

[0019] In another embodiment, the composite elastic mesh 30 may also take the following forms: First, a single layer of flexible elastic mesh 31 is used to receive the impact of the screen 02 and buffer and absorb energy, and a metal woven mesh with a larger aperture is set above it as an independent support and load transfer layer. The two are only pressed and fixed together at the outer periphery, and the impact load is also transferred upward to the fixing plate 21 described later through the support layer; Second, a three-layer structure is adopted, that is, an intermediate transition mesh with an aperture between the flexible elastic mesh 31 and the support mesh 32 is added to form a gentler aperture gradient channel, further reducing the risk of diamond micro powder 03 being trapped between the layers. The conductive layer is not limited to being woven from silver-plated nylon fibers, but can also be made of stainless steel wire or carbon fiber mixed with synthetic fibers, as long as its surface resistance is sufficient to conduct the charge carried by the micro powder at the moment of impact and maintain a continuous electrical path with the pressure ring and the shell 10.

[0020] refer to Figure 4 The pore size of the flexible elastic mesh 31 is much larger than that of the sieve 02 and also much larger than the particle size of the diamond micro powder 03 being cleaned, so that the suspended micro powder in the negative pressure suction step can pass smoothly through the composite elastic mesh 30. If its pore size is only slightly larger than that of the sieve 02, the composite elastic mesh 30 itself constitutes a high flow resistance filter medium. At the same time, the pore size of the supporting mesh 32 is larger than that of the flexible elastic mesh 31, so as to form a smooth micro powder conveying gradient channel and reduce the risk of micro powder getting stuck between the two meshes. Thus, along the airflow direction of the negative pressure suction, the pore sizes of the sieve 02, the flexible elastic mesh 31, and the supporting mesh 32 increase sequentially.

[0021] Furthermore, to ensure that both the closed purging and negative pressure suction steps have clear and controlled airflow channels, this embodiment also provides an air passage interface on the side wall of the lower space 202 of the housing 10. The inner side of the air passage interface is equipped with a filter element, and the outer side is connected to a one- or two-position three-way valve via a pipeline. One path of the three-way valve is connected to the discharge pipe 40, and the other path is connected to the atmosphere via a make-up air pipe. The specific forms of the above-mentioned air passage interface, filter element, pipeline and three-way valve can be selected according to the site layout, so they are not shown in the figure.

[0022] Furthermore, the controllable communication component 20 adopts a rotating or staggered on / off structure with a perforated plate, as shown in the reference. Figure 3It includes a fixed plate 21 and a movable plate 22 that are coaxially fitted and rotatable relative to each other. Both plates have fan-shaped through holes 23 evenly distributed along the circumference. The fan-shaped through holes 23 on the fixed plate 21 and the movable plate 22 are identical in shape, size, and number. Furthermore, the central angle of each fan-shaped through hole 23 is equal to the central angle of the solid sector between two adjacent fan-shaped through holes 23, meaning the through hole and the solid sector each occupy half along the circumference, ensuring that the fan-shaped through hole 23 can be completely covered by the solid plate surface when misaligned. By slightly rotating the movable plate 22, with a rotation angle equal to the central angle corresponding to a single fan-shaped through hole 23, the fan-shaped through holes 23 on it can be aligned one-to-one with the fan-shaped through holes 23 on the fixed plate 21 or completely misaligned (the completely misaligned state is as follows). Figure 2 As shown in the figure, this enables the lower space 202 to be connected to or isolated from the upper space 201.

[0023] In another embodiment, a plurality of circular through holes can be evenly distributed on the plate body of each sector section. Similarly, by rotating the central angle corresponding to the sector area of ​​the movable plate 22, the circular through holes on the movable plate 22 and the circular through holes on the fixed plate 21 can be aligned and connected one by one, or completely blocked by the solid plate surface. Compared with the method of using integral sector through holes 23, the plate of this structure has better rigidity and stronger sealing fault tolerance under closed partition conditions, but the flow resistance of airflow and micro powder will also increase accordingly.

[0024] In another embodiment, the controllable communication component 20 may also adopt a butterfly valve or flap-type on / off structure, that is, a valve plate that can rotate around the axis is provided at each through hole of the fixed plate 21, and the switching between communication and isolation is achieved by the rotation of the valve plate; when this form is adopted, a rigid support grid with a hole diameter larger than that of the composite elastic net 30 should be laid on the lower plate surface of the fixed plate 21 facing the lower space 202, so as to provide a continuous and complete rigid limiting surface for the composite elastic net 30 in the isolation state.

[0025] Both the fixed plate 21 and the movable plate 22 have a chamfer on the side away from their contact surface (the chamfer structure is not shown in the figure), while the contact surface side remains right angled. The chamfer gradually expands from the contact surface side to the side away from the contact surface, i.e., it is set to be wider on the outside and narrower on the inside. This can guide the powder upward when the negative pressure is suctioned, and guide the powder falling back downward when the negative pressure stops. At the same time, it can also prevent the contact surface from accumulating powder and ensure the sealing performance under closed working conditions.

[0026] refer to Figure 1 and Figure 3The movable plate 22 is equipped with an operating swing rod 241 for easy manual rotation. The operating swing rod 241 passes through the housing 10 and can slide within a limiting slide 242 provided on its outer peripheral wall. The central angle of the limiting slide 242 is consistent with the central angle of the fan-shaped through hole 23. Positioning slots are also provided at both ends of the limiting slide 242. After the operating swing rod 241 swings to its designated position, it engages with the corresponding positioning slot to prevent the movable plate 22 from rotating on its own due to vibration of the screening machine 01 and ultrasonic excitation, thus preventing the isolation state from failing. Accordingly, the movable plate 22 is positioned above the fixed plate 21 to reduce the impact of the operating swing rod 241's insertion structure on the lower space 202, avoid minor air leakage in the lower space 202, and ensure the airtightness of the closed purging step.

[0027] In another embodiment, the operating lever 241 can also be driven by an electric actuator or a swing cylinder, and connected to the controller along with the pulse valve and the three-way valve for unified timing control. Since the suspended time of the stripped diamond micro powder 03 in the assembly gap is extremely short, the use of power drive can significantly shorten the switching time between the two steps of closed purging and negative pressure suction, allowing more micro powder to be extracted before it falls back.

[0028] Further, refer to Figure 1 The upper space 201 is connected to a discharge pipe 40, the outlet of which is connected to a negative pressure pump. A secondary screening structure 50 is arranged in the middle section for secondary sorting of the recovered diamond micron powder 03. The secondary screening structure 50 includes a gas-solid separation chamber and a vibrating screen surface disposed within the gas-solid separation chamber. After entering the gas-solid separation chamber, the dust-laden airflow slows down and changes direction. Qualified diamond micron powder 03 settles and is retained on the vibrating screen surface, falling into the finished product collection bucket through the discharge pipe below. Ultrafine dust passes through the screen surface and flows with the airflow to the negative pressure pump, where it is collected by the dust collector at its front end, thus completing the recovery and sorting of the micron powder. The negative pressure pump can be a vacuum pump, a Roots vacuum pump, a water ring vacuum pump, or an induced draft fan. The secondary screening structure 50 can also be replaced by a combination of a cyclone separator and a vibrating screen surface disposed below it. The dust-laden airflow first passes through the cyclone separator to separate coarser particles, and then the vibrating screen surface completes the secondary sorting.

[0029] After completing the above installation, prepare for cleaning: If it is a multi-layer screen structure, it needs to be removed to leave only one layer in a single treatment; turn off the feed of the screening machine 01, keep the rotary vibrating motor and ultrasonic transducer of the screening machine 01 running, and keep the negative pressure pump running throughout the cleaning process.

[0030] Step S2, closed-loop purging.

[0031] refer to Figure 2In this step, the controllable connecting component 20 remains isolated, and the lower space 202 remains sealed, but it is not an absolutely closed dead cavity. The pulsed airflow is sprayed upward from below the screen 02. After passing through the mesh of the screen 02 and entering the lower space 202, it must have a corresponding exhaust path; otherwise, the lower space 202 will be rapidly pressurized, and the pressure difference on both sides of the screen 02 will disappear. Therefore, in this step, the three-way valve is switched to one of the paths connected to the discharge pipe 40, forming an exhaust branch path where the lower space 202 enters the discharge pipe 40 through the filter, air interface, and pipeline, and then flows through the secondary screening structure 50 before being drawn away by the negative pressure pump. The filter is used to intercept the micro powder that escapes with the exhaust, so that the stripped micro powder is retained in the lower space 202 and does not flow away with the exhaust. The effective flow area of ​​the air passage interface is much smaller than the effective screening area of ​​the screen 02, so that the static pressure rise in the lower space 202 during pulse jet blowing is small enough to ensure that an effective pressure difference can be established on both sides of the screen 02, and to prevent the suspended micro powder from being prematurely carried away from the lower space 202 due to excessive exhaust.

[0032] refer to Figure 6 Then, the pulse valve is opened, and the compressed air source is used to intermittently output upward pulse airflow with a short pulse width of 50 to 200 ms. The airflow impulse at the moment of blowing acts directly on the diamond micro powder 03 wedged in the mesh from bottom to top, pushing it upward away from the mesh. This is the main force for peeling off the stuck micro powder. On the other hand, it drives the screen 02 to arch and deform and impact the composite elastic mesh 30 to supplement the mechanical disturbance and electrostatic discharge (see the electrostatic discharge path for details below). The two further work together to drive away the stuck micro powder, so that the micro powder is removed from the screen 02 and suspended inside the assembly gap.

[0033] For diamond micro powder 03 with different particle sizes, the blowing parameters in this step can be adjusted accordingly: for diamond micro powder 03 with coarser particle size and larger single particle mass, it is advisable to increase the blowing pressure of the pulse airflow and set the single blowing time to around 200ms to increase the impulse on stuck particles; for diamond micro powder 03 with finer particle size and stronger tendency to electrostatic agglomeration, it is advisable to shorten the blowing interval and increase the number of single-round blowing, so as to fully agitate the micro powder with high frequency and small impulse while avoiding excessive stretching of the screen 02.

[0034] refer to Figure 2 , Figure 3It should be noted that both the flexible elastic mesh 31 and the supporting mesh 32 are flexible mesh components that deform under stress. Their upward stroke does not have a definite endpoint and can only serve as a buffer and unloading mechanism. They cannot rely on their own stiffness to constrain the deformation of the screen 02. This limiting function must be borne by a rigid plate with sufficient bending stiffness. Therefore, in this embodiment, the fixed plate 21 in the controllable connecting component 20 also serves as the rigid limiting backing of the composite elastic mesh 30: the fixed plate 21 is located below the movable plate 22 and directly faces the lower space 202. The gap between the lower plate surface facing the lower space 202 and the composite elastic mesh 30 is the aforementioned confluence gap. When the pulsed airflow drives the screen 02 to arch upwards and impact the flexible elastic mesh 31, the impact load is transmitted upwards layer by layer through the flexible elastic mesh 31 and the supporting mesh 32, causing both meshes to float upwards synchronously. Once the confluence gap is almost completely compressed, the supporting mesh 32 abuts against the lower surface of the fixed plate 21, where the fixed plate 21 provides a rigid support force that no longer yields. The airflow impulse exceeding this stroke is transmitted to the housing 10 via the fixed plate 21, which is fixedly connected to the inner wall of the housing 10, and is no longer converted into further tensile deformation of the screen 02. Since the rigid plate's own flexural deformation under the aforementioned impact load is negligible, its lower surface is always a definite limiting surface, and the maximum upward arch height of the screen 02 is limited to the sum of the assembly gap and the confluence gap. Thus, this step constitutes a stepwise bearing and limiting chain from the screen 02 to the flexible elastic mesh 31 to the supporting mesh 32 to the fixed plate 21.

[0035] Correspondingly, when the fixed plate 21 serves as the rigid limiting surface of the composite elastic net 30, its cooperation with the movable plate 22 in this step also has the following functions: In this step, the controllable connecting component 20 is in an isolated state, and each fan-shaped through hole 23 on the fixed plate 21 is completely blocked by the solid sector of the movable plate 22. Therefore, when the supporting net 32 ​​floats up and abuts against it, each fan-shaped through hole 23 is backed by the plate surface of the movable plate 22. The net is supported by the backing by inserting at most one plate thickness into the through hole wall. It will not pass through the through hole, nor will it be suspended at the through hole and bear concentrated tension. The limiting surface provided by the fixed plate 21 is thus continuous and complete on the entire plate surface. At the same time, the aforementioned chamfer on the side of the fixed plate 21 away from the bonding surface (i.e., the lower plate surface facing the lower space 202) prevents the lower edge of each fan-shaped through hole 23 from forming a cutting edge, thus avoiding the net from cutting the fibers when it repeatedly abuts against it.

[0036] It should be noted that the composite elastic mesh 30 is not used for sieving, filtering, or permanently retaining the micro powder. Instead, during the intermittent blowing phase, the double-layer mesh structure temporarily impedes and supports the blown micro powder, preventing it from falling directly back to the screen 02 and causing secondary blockage. The reasons are as follows: First, the mesh openings of the flexible elastic mesh 31 and the supporting mesh 32 are not aligned, so the micro powder must pass through both layers of mesh before falling back along the direction of gravity, increasing the probability of it encountering the fiber. Second, the diamond micro powder 03 is a micron-sized particle; after contacting the fiber surface, it is subjected to van der Waals forces and electrostatic mirror forces, allowing it to temporarily adhere to the fiber surface or the space between the two mesh layers.

[0037] refer to Figure 7 The aforementioned adhesion is reversible and temporary, and will not cause permanent blockage of the composite elastic mesh 30. On the one hand, the continuous reciprocating impact of the screen 02 on the flexible elastic mesh 31 in this step will drive the two layers of mesh to vibrate at high frequency, causing the attached diamond micro powder 03 to continuously desorb and resuspend; on the other hand, in the negative pressure suction step described later, the rotary vibrating motor and ultrasonic transducer of the screening machine 01 itself continue to operate, and their vibration is transmitted to the composite elastic mesh 30 through the housing 10, causing the diamond micro powder 03 attached to the fibers to desorb, and then be carried away by the negative pressure airflow from bottom to top. The composite elastic mesh 30 is cleaned after each round of cleaning.

[0038] Step S3: Negative pressure suction.

[0039] refer to Figure 3 In this step, the pulse valve is closed, and the three-way valve is switched to the path leading to the atmosphere. Then, the operating lever 241 is rotated, causing the movable plate 22 to rotate so that its fan-shaped through-hole 23 aligns with the fan-shaped through-hole 23 on the fixed plate 21, thereby opening the communication channel between the lower space 202 and the upper space 201. Since the negative pressure pump is already running, the opening of the channel immediately initiates suction. The switching time between this step and the previous step should be minimized to complete the suction before a large amount of suspended microparticles fall back to the surface.

[0040] In this step, the corresponding replenishment airflow must also be provided for the suction volume of the negative pressure pump; otherwise, the lower space 202 and the screening machine 01 cavity will together form a closed dead cavity. Although negative pressure can be established, there will be no continuous flow, and the suspended micro powder cannot be transported. Therefore, in this step, after switching the three-way valve to the one leading to the atmosphere, two parallel replenishment air channels are formed: First, outside air enters the lower space 202 tangentially through the replenishment air pipe, air interface and filter, forming a transverse sweeping airflow above the screen 02, which re-entrains the micro powder suspended in the gaps and that has fallen back to the screen surface and sends it to the composite elastic net 30. At the same time, this reverse airflow also forms a back-blowing cleaning of the filter; Second, air is replenished into the screening machine 01 cavity through its feed port or a dedicated replenishment air valve. This airflow passes through the screen 02 from bottom to top and enters the lower space 202, forming an airflow to drag away the micro powder that is still partially stuck in the mesh of the screen 02 after the previous disturbance. The total effective flow area of ​​the two air supply channels is greater than that of the discharge pipe 40. The flow ratio of the two airflows is distributed by the opening of the air supply valve, so that the pressure difference between the lower space 202 and the screening machine 01 cavity is limited to a small level. This ensures the dragging and extraction effect while preventing the screen 02 from being sucked upwards to the composite elastic net 30 due to excessive pressure difference on both sides, thus avoiding overload damage. Among them, the screening machine 01 cavity bears the main air supply volume. Therefore, although the effective flow area of ​​the aforementioned air interface is much smaller than the effective screening area of ​​the screen 02 due to the need to establish an effective pressure difference on both sides of the screen 02 in the closed purging step, it still does not affect the satisfaction of the total air supply volume in this step: the two area requirements belong to two different steps, purging and suction, and do not conflict with each other.

[0041] refer to Figure 7 The diamond micro powder 03 being drawn in passes through the composite elastic mesh 30 into the upper space 201 from the assembly gap under negative pressure, and then enters the discharge pipe 40. It then flows through the secondary screening structure 50 for gas-solid separation and secondary sorting. The ultrafine dust is collected by the dust collector at the front end of the negative pressure pump along with the airflow, while the qualified micro powder is trapped on the vibrating screen surface and falls into the finished product collection bucket through the discharge pipe, completing the non-destructive recycling of the micro powder.

[0042] Steps S4 and S5 involve judgment and reset.

[0043] refer to Figure 5The aforementioned closed-loop purging step S2 and negative pressure suction step S3 can be performed alternately in several rounds. After each round, it is determined whether the effective opening area of ​​the screen 02 has recovered to the set level. If it has not recovered, the process returns to step S2 to continue the next round of purging and suction. If it has recovered, the process proceeds to the reset step S5: the pulse valve and negative pressure pump are closed, the controllable communication component 20 is reset to the isolation state, and the feeding is restarted to resume the screening operation. Whether the effective opening area of ​​the screen 02 has recovered to the set level can be determined based on on-site observable parameters such as screening output, thickness of the material layer on the screen, or operating current of the screening machine 01.

[0044] It should also be noted that in this embodiment, the closed purging and negative pressure suction are strictly carried out in separate steps, rather than in a simultaneous purging and suction manner. The reasons are as follows: First, the closed purging relies on the short pulse width airflow to establish an instantaneous pressure difference on both sides of the screen 02 to drive the screen 02 to arch upward and deform and impact the composite elastic net 30. If the controllable connecting component 20 is opened for suction at the same time as purging, the lower space 202 will be fully connected to the upper space 201 through the composite elastic net 30, and the pulse airflow will be directly drawn away, forming an airflow short circuit. It is impossible to establish a sufficient instantaneous pressure difference on both sides of the screen 02, and the upward arching amplitude and impact intensity of the screen 02 will be significantly weakened (the flow area of ​​the aforementioned exhaust branch is much smaller than the effective screening area of ​​the screen 02, and only plays a pressure relief role, and does not constitute the aforementioned short circuit). Second, when purging and suction are carried out simultaneously, the screen 02 is under positive pressure below and negative pressure above. The pressure difference on both sides is the superposition of the two and changes from pulse to continuous action. The screen 02 will bear a load far exceeding the design conditions for a long time, and is prone to fatigue and damage.

[0045] To further improve the implementation conditions of this method, this embodiment also includes several supporting optimization designs for the cleaning device used: The outer periphery of the composite elastic mesh 30 is pressed by a stainless steel pressure ring and sealed and fixed to the housing 10 using high-strength epoxy structural adhesive or weather-resistant silicone sealant. This fixing method keeps the composite elastic mesh 30 under tension and allows it to undergo slight elastic deformation under airflow impact. The conductive layer of the two mesh fabrics is preferably formed by direct weaving of silver-plated nylon fibers, so that the conductive layer is attached to the fiber body, avoiding the cracking and peeling of the metal layer formed by overall chemical plating after the fabric is formed under repeated elastic stretching. Among them, the conductive layer on the surface of the two mesh fabrics of the composite elastic mesh 30 is in direct metal contact with the stainless steel pressure ring at the pressing point; the stainless steel pressure ring is then electrically connected to the housing 10 by metal fastening bolts or braided copper strips, and the outer wall of the housing 10 is provided with a grounding terminal and connected to the equipment protective ground. During the closed purging process, at the moment of contact between the upward arch of the screen 02 and the flexible elastic mesh 31, the charge carried by the diamond micro powder 03 stuck in the mesh of the screen 02 and attached to the screen surface is transferred to the conductive layer through contact, and then discharged to the ground along the continuous path of conductive layer → stainless steel pressure ring → shell 10 → ground. This is the realization method of "electrostatic conduction" mentioned above.

[0046] The shell 10, the fixed plate 21, and the movable plate 22 are all made of stainless steel 304. The fixed plate 21 also serves as a rigid limiting plate for the composite elastic net 30.

[0047] The housing 10 is detachably installed with the screening machine 01 via an adjustable mounting flange at its lower end. The axial installation position of the housing 10 can be adjusted by adjusting the adjustable mounting flange, thereby adjusting the assembly gap between the composite elastic mesh 30 and the screen 02. An elastic sealing skirt is provided on the lower edge of the outer wall of the housing 10, and is externally secured to the screening machine 01 by a stainless steel locking clamp. When the clamp is tightened, the sealing skirt is compressed to form an interference seal.

[0048] The top of the housing 10 is equipped with a pressure relief valve 60 (e.g., Figure 1 , Figure 2 As shown, when residual negative pressure inside the device causes the cleaning device to be tightly adhered to the screening machine 01 and difficult to disassemble, the pressure relief valve 60 can be opened to balance the air pressure inside and outside the cavity, thereby facilitating normal disassembly and assembly of the device. The pressure relief valve 60 is connected to the upper space 201 and is only opened when disassembling and assembling the device during shutdown. It should be kept closed during both the closed purging and negative pressure suction steps to avoid disrupting the negative pressure in the upper space 201.

[0049] The operating lever 241 is fitted with a dustproof lip seal at the junction with the housing 10 as a dynamic sealing component to prevent fine diamond powder 03 from escaping through the installation gap.

[0050] The pulsed airflow is supplied by a compressed air source via an air reservoir and a pulse valve. Its jetting pressure is the same as the pressure inside the air reservoir. A certain distance is maintained between the nozzle outlet and the lower surface of the screen 02 to ensure the jet fully diffuses before reaching the screen, avoiding concentrated impact that could cause localized tearing of the screen 02. The vacuum level of the negative pressure pump is designed to create a sufficient conveying velocity within the discharge pipe 40 for pneumatically conveying the diamond micron powder 03, and to meet the gas-solid separation requirements within the secondary screening structure 50.

[0051] Example 2: The difference between this embodiment and Embodiment 1 is that the cleaning method described herein is adapted to a straight-line ultrasonic screening machine with a square or rectangular screen surface, and each step is automatically executed by the controller according to a set timing sequence. (Reference) Figure 5 The cleaning process in this embodiment is the same as in embodiment 1, and all other aspects not mentioned are also the same as in embodiment 1.

[0052] For a straight-flow ultrasonic sieve with a square or rectangular screen surface, the housing 10 and the composite elastic mesh 30 are respectively made into rectangles that fit the contour of the screen surface. The composite elastic mesh 30 is also pressed and sealed to the housing 10 by pressure rings on all four sides. Assembly gaps and flow gaps are still left between it and the screen 02 and the controllable communication component 20, respectively. The pulse jet blowing device below the screen 02 consists of several sets of jet pipes arranged sequentially along the length of the screen surface. Each set of jet pipes divides the screen surface into several cleaning zones along the length direction, and each is independently controlled by its own pulse valve. In the closed purging step S2, the pulse valves corresponding to each zone blow in turn instead of simultaneously. This ensures that a sufficient instantaneous pressure difference can still be established on both sides of the screen 02 when each zone is blown, even under the condition that the compressed air supply is limited. On the other hand, the screen 02 of the un-blowed zone can also serve as one of the exhaust paths for the airflow of this blow, further slowing down the pressurization speed of the lower space 202.

[0053] refer to Figure 9 and Figure 10 To adapt to the rectangular shell 10, the controllable communication component 20 in this embodiment is changed from the rotational alignment type of Embodiment 1 to a translational misalignment type. Specifically, it consists of a fixed plate 21 whose outer periphery is fixedly connected to the inner wall of the shell 10, and a movable plate 22 attached above it and capable of translational movement along the plate surface. Both have alternating strip-shaped through holes 25 arranged along the translational direction. The width of each strip-shaped through hole 25 is equal to the width of the solid strip area between two adjacent strip-shaped through holes 25. By driving the movable plate 22 with a cylinder to translate by the width of one strip-shaped through hole 25, the strip-shaped through holes 25 of the two components can be completely misaligned (e.g., ...). Figure 9 (as shown) or one-to-one pairing (such as) Figure 10 As shown), this allows for the switching between isolated and connected states. In the aligned state, the stripped diamond micropowder 03 is carried by the negative pressure airflow from the lower space 202 through the aligned strip-shaped through holes 25 into the upper space 201. Similar to the rotational alignment type, in the staggered state, each strip-shaped through hole 25 of the fixed plate 21 is completely blocked by the solid strip area of ​​the movable plate 22, with its plate surface as a backing. The lower plate surface of the fixed plate 21 facing the lower space 202 thus still forms a continuous and complete rigid limiting surface. When the composite elastic net 30 floats and abuts against it, it will not be suspended at the through holes and subjected to concentrated tension.

[0054] refer to Figure 8 In this embodiment, the pulse valves of each cleaning zone ( Figure 8The two-position three-way valves (shown as pulse valves I, II, and III) that switch the air supply path, along with the cylinder or electric actuator that drives the movable plate 22, are connected to the controller. The controller automatically and cyclically executes steps S2 and S3 according to the following sequence: First, the three-way valves are switched to the path connected to the discharge pipe 40, and the movable plate 22 is kept in a staggered position to isolate the controllable communication component 20. Then, the pulse valves of each zone sequentially spray air with short pulse widths of 50 to 200 ms. The dry wheel (e.g., the blowing interval of the same zone is 0.5 to 2 seconds, and each zone blows 3 to 10 times in a single cycle) constitutes the closed purging step S2 in one cycle. After the last blowing, the three-way valve is switched to the one leading to the atmosphere, and the movable plate 22 is driven to move to the alignment position, entering the negative pressure suction step S3, which lasts for, for example, 3 to 15 seconds. After the suction ends, the movable plate 22 returns to the staggered position, and the three-way valve returns to the one leading to the discharge pipe, thus entering the closed purging step S2 of the next cycle. Since the switching between the two steps is completed by power drive, the switching time can be shortened to less than 1 second, which is much shorter than the suspension time of the peeled micro powder in the assembly gap, so that more micro powder is extracted before falling back to the screen, and the number of cleaning cycles that can be completed per unit time is also increased accordingly.

[0055] Accordingly, in this embodiment, the judgment in step S4 is also automatically completed by the detection element and the controller, and can be performed in any of the following ways: First, pressure detection elements are set above and below the screen 02 respectively, and the peak value of the pressure difference between the two sides of the screen 02 at the moment of pulse jet is used to characterize the permeability of the screen 02. When the peak value of the pressure difference drops below the set threshold, it is determined that the effective opening area has been restored to the set level; Second, a dust concentration detection element is set in the discharge pipe 40. When the concentration integral value of the diamond micro powder 03 discharged in a single cycle of negative pressure suction is lower than the set threshold, it is determined that the stuck micro powder has been basically cleared; Third, the set number of cleaning cycles (e.g., 5 to 20 cycles) is directly used as the termination condition. After the judgment is completed, the controller executes the reset step S5. The specific forms of the above detection elements and controller are conventional choices in the art, and therefore are not shown in the figure.

[0056] Furthermore, for the screening machine 01 with multiple screens, in addition to the method of removing only one layer in a single process as described in Example 1, this embodiment can also clean layer by layer: first, install the cleaning device on the top screen frame to complete steps S2 to S5, then remove the cleaning device and remove the screen frame of that layer, and then install the cleaning device on the next uppermost screen frame and repeat the above steps until all screens 02 are cleaned. Since the housing 10 is detachably connected to the screen frame via the adjustable mounting flange at its lower end, and the elastic sealing skirt and stainless steel locking clamp at its lower edge can be adapted to screen frames of the same specification, layer by layer cleaning does not require replacing the cleaning device; only the assembly gap needs to be readjusted via the adjustable mounting flange after each installation.

[0057] It should be noted that the technical features in the two embodiments described above can be combined or substituted for each other without contradicting each other. For example, the rotary alignment controllable communication component 20 in Embodiment 1 can be combined with the controller timing control and automatic judgment method in Embodiment 2. The partitioned sequential blowing method in Embodiment 2 can also be used for the circular screen surface in Embodiment 1. All the combined schemes obtained therefrom are within the scope of protection claimed by this invention.

[0058] The above descriptions are merely two specific examples of the present invention and do not constitute any limitation on the present invention. Obviously, those skilled in the art, after understanding the content and principles of the present invention, may make various modifications and changes in form and detail without departing from the principles and structure of the present invention; however, these modifications and changes based on the spirit of the present invention are still within the scope of protection of the claims of the present invention.

Claims

1. A method for airflow-assisted unclogging of the screen in an ultrasonic screening machine, characterized in that, The method is implemented using a housing (10) that is detachable and sealed above the screen (02) of the ultrasonic sieve (01); the housing (10) has an inner cavity in which a controllable communication component (20) for switching between an isolated state and a connected state is provided; the controllable communication component (20) divides the inner cavity into an upper space (201) for connecting an external negative pressure pump and a lower space (202) located above the screen (02); a composite elastic mesh (30) is provided in the lower space (202) between the controllable communication component (20) and the screen (02); the composite elastic mesh (30) is used to bear the impact load of the screen (02) and transmit it to the controllable communication component (20); and an assembly gap is formed between the composite elastic mesh (30) and the screen (02), and a confluence gap is formed between the composite elastic mesh (30) and the controllable communication component (20); the aperture of the composite elastic mesh (30) is larger than the aperture of the screen (02) and the particle size of the cleaned powder; The method includes: a closed purging step: isolating the upper space (201) and the lower space (202) from each other, and outputting pulse airflow from the lower part of the screen (02) to cause the screen (02) to arch upward and impact the composite elastic net (30). The composite elastic net (30) floats upward and abuts against the rigid limiting surface of the controllable connecting component (20) on the side facing the lower space (202) to limit the arching deformation of the screen (02); a negative pressure suction step: stopping the output of the pulse airflow and switching the controllable connecting component (20) to the connecting state to connect the upper space (201) and the lower space (202). The peeled micro powder passes through the composite elastic net (30) and enters the upper space (201) under the action of negative pressure, and is extracted and recycled through the discharge pipe (40) connected to the upper space (201); The closed purging step and the negative pressure suction step are performed alternately in a time-sharing cycle to achieve the synergistic effect of pulse disturbance, elastic limit and negative pressure transfer.

2. The method according to claim 1, characterized in that, The surface of the composite elastic net (30) is provided with a conductive layer, which is electrically connected to the housing (10) and grounded through the housing (10); in the closed purging step, when the screen (02) impacts the composite elastic net (30), the static electricity carried by the screen (02) and the micro powder is discharged through the conductive layer to achieve static suppression of the micro powder.

3. The method according to claim 1, characterized in that, The pulsed airflow is output by a pulse valve located below the screen (02) and connected to a compressed air source; the pulse valve adopts a short pulse width intermittent blowing mode, and the single blowing time is 50 to 200 ms.

4. The method according to claim 1, characterized in that, The housing (10) is provided with an air passage interface on the side wall corresponding to the lower space (202). The air passage interface is connected to the discharge pipe (40) through a filter and a two-position three-way valve. In the closed purging step, the two-position three-way valve is switched to the position connected to the discharge pipe (40), so that the lower space (202) forms a controlled exhaust channel.

5. The method according to claim 4, characterized in that, In the negative pressure suction step, the two-position three-way valve is switched to the position of being connected to the outside, so that outside air enters the lower space (202) through the air supply pipe to form a replenishing airflow; at the same time, the sieve (01) cavity replenishes air into the lower space (202) to assist in the extraction of micro powder.

6. The method according to claim 1, characterized in that, The composite elastic net (30) includes: a flexible elastic net fabric (31) disposed near the screen (02) for buffering impact loads; and a support net fabric (32) stacked on top of the flexible elastic net fabric (31) for transmitting impact loads; the edges of the flexible elastic net fabric (31) and the support net fabric (32) are fixedly connected, and the middle part is movable relative to each other.

7. The method according to claim 6, characterized in that, Along the negative pressure suction direction, the apertures of the screen (02), the flexible elastic mesh (31), and the support mesh (32) increase sequentially; the composite elastic mesh (30) is used to temporarily impede and support the stripped micro powder during the purging stage, and to allow the micro powder to pass through the composite elastic mesh (30) and be transported during the negative pressure suction stage.

8. The method according to claim 1, characterized in that, The controllable communication component (20) includes: a fixed plate (21) fixedly connected to the housing (10) and forming a rigid limiting surface on the plate surface facing the lower space (202); and a movable plate (22) fitted onto the fixed plate (21); the fixed plate (21) and the movable plate (22) are respectively provided with corresponding through holes, and the switching between the isolation state and the communication state is realized by the movement of the movable plate (22).

9. The method according to claim 8, characterized in that, The movable plate (22) is connected to an operating lever (241), which passes through the housing (10) and moves along the limiting slide (242); or, the movable plate (22) is driven by an electric actuator or a swing cylinder and is linked to the pulse valve for control.

10. The method according to claim 1, characterized in that, The discharge pipe (40) is connected to a secondary screening structure (50); the secondary screening structure (50) is used to perform gas-solid separation and secondary sorting on the extracted micro powder in order to realize micro powder recovery.

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