A lithium battery compression molding equipment and process flow

Abstract

The present invention provides a lithium battery compression molding equipment and its process flow, including a cell feeding unit, a hot pressing and cooling unit, a high-voltage testing unit and a detection and discharge unit arranged in sequence, wherein the cells are transferred between the cells by an automatic transplanting and handling unit. The cell feeding unit includes a feeding part and a code reading part in sequence, the hot pressing and cooling unit includes a hot pressing engineering part and a cooling and pressurizing part in sequence, the high-voltage testing unit includes a semi-permeable membrane molding part, a bottom gluing part and a high-voltage testing part in sequence, and the detection and discharge unit includes an image detection part and a discharge part in sequence. The present invention is conducive to the automated completion of the fixing, visual inspection and heating processes on the slide base, and uses visual inspection to accurately locate the position of the lithium battery, thereby improving positioning accuracy, reducing the difficulty of work switching, and improving the qualified rate of finished products.

Description

Technical Field

[0001] The present invention mainly relates to the field of automated production technology equipment, and in particular to a lithium battery compression molding equipment and its process flow. Background Art

[0002] For lithium batteries before they are filled with liquid (hereinafter referred to as "elements"), the compression molding technology involves a series of processes including heating and compression molding, cooling, semi-permeable membrane heating molding, bottom tape application, high voltage testing, and image detection. The traditional method is to manually use a single device for the process, which requires a lot of manpower and is complex to operate. It is inefficient, has a low pass rate, and is difficult to switch and adjust models, which greatly increases costs.

[0003] A published Chinese invention patent, application number CN201710756563.7, title: A Lithium Battery Processing System, filed on August 29, 2017, discloses a lithium battery processing system for processing battery cell skirts. The system comprises a machine platform and a positioning device mounted on the machine platform. The positioning device comprises a left adjustment baseplate and a right adjustment baseplate disposed in opposite directions. The left and right adjustment baseplates are used to mount a battery cell processing mechanism. The left and right adjustment baseplates can slide relative to each other on the machine platform to adjust the position of the battery cell processing mechanism to contact the battery cell. A conveyor device is provided between the left and right adjustment baseplates. The conveyor device comprises a front conveyor device and a rear conveyor device, which are connected front and back to each other. The battery cell is transferred between the front and rear conveyor devices to different workstations. The present invention achieves central positioning of the battery cell during the lithium battery processing process through the interaction of the positioning device and the conveyor device, enabling simultaneous processing of the skirts on both sides of the battery cell and facilitating device adjustment during battery cell replacement. Summary of the Invention

[0004] The present invention provides a lithium battery compression molding equipment and a process flow thereof. In view of the above-mentioned defects of the prior art, a lithium battery compression molding equipment is provided, which includes a cell feeding unit, a hot pressing and cooling unit, a high-voltage testing unit and a detection and discharge unit arranged in sequence, and the cells are transferred between them by an automatic transplanting and handling unit. The cell feeding unit includes an feeding part and a code reading part in sequence, the hot pressing and cooling unit includes a hot pressing engineering part and a cooling and pressurizing part in sequence, the high-voltage testing unit includes a semi-permeable membrane molding part, a bottom gluing part and a high-voltage testing part in sequence, and the detection and discharge unit includes an image detection part and a discharge part in sequence.

[0005] Preferably, the semipermeable membrane forming part includes a positioning platform, a fixing mechanism, a visual inspection mechanism, a thermoforming mechanism and a slide base, the slide base is driven by a driving electric cylinder 1 to drive a positioning platform movably installed on the upper side, and a fixing mechanism and a visual inspection mechanism are respectively provided on both sides of the positioning platform, the fixing mechanism is movably installed on the slide base, the visual inspection mechanism is fixed to the slide base by bolts, the thermoforming mechanism is arranged in the travel direction of the positioning platform, and the thermoforming mechanism is fixedly installed on the slide base.

[0006] Preferably, the positioning platform includes a base 6, a slide cylinder 7, a linear slide 8, a spring mechanism 9 and a vacuum assembly 10. The base 6 is in a "convex" shape, and a fixed seat 11 and a linear slide 8 are respectively provided on both sides of the convex portion of the base 6. A reference plate 13 is fixed on the fixed seat 11, and a spring mechanism 9 and a movable plate 14 are sequentially provided on the linear slide 8. The spring mechanism 9 is driven by the slide cylinder 7, and the gap between the reference plate 13 and the movable plate 14 and the convex portion of the base 6 form a positioning platform. The bottom of the positioning platform is connected to the vacuum assembly 10 through a joint 28.

[0007] Preferably, optical fiber sensors 15 are respectively provided on both sides of the base 6 , and the optical fiber sensors 15 are provided on a side of the base 6 close to the thermoforming mechanism.

[0008] Preferably, the fixing mechanism includes a linear guide rail 12, a slider 16, a U-shaped seat 17, a linear bearing 18, a lifting cylinder 2, a balance rod 19 and a pressure block 20. The linear guide rail 12 is fixed on the slide base, the slider 16 is embedded in the linear slide rail 8, the slider 16 is installed with a U-shaped seat 17, linear bearings 18 are installed on both sides of the U-shaped seat 17, the lifting cylinder 2 is installed in the middle of the U-shaped seat 17, the linear bearing 18 and the top of the lifting cylinder 2 are hinged with a balance rod 19, and a pressure block 20 is vertically provided on the side of the balance rod 19 away from the lifting cylinder 2.

[0009] Preferably, an adjusting cylinder 3 is installed on the lifting cylinder 2, and the pressing block 20 is made of silicone rubber.

[0010] Preferably, the visual detection mechanism includes a camera bracket 21 and a light source bracket 22. The camera bracket 21 is an inverted L-shape, and a CCD4 and a lens 23 are vertically installed on the horizontal part of the camera bracket 21 in sequence. A light source 24 is installed on the top of the light source bracket 22, and the position of the light source 24 corresponds to that of the lens 23.

[0011] Preferably, a vacuum detector 5 is installed on the vertical portion of the camera bracket 21 .

[0012] Preferably, the thermoforming mechanism includes a heating bracket 25, on which a heating device is fixed by bolts, and insulation plates 26 are attached around the four sides of the heating device. The heating device consists of built-in heating rods and thermocouples 27 corresponding to each other, and the thermocouple 27 is connected to a temperature controller.

[0013] A lithium battery compression molding process using the device according to claim 1, characterized in that it includes the following steps: S1: tray input; S2: element retrieval and buffering; S3: element positioning, dust removal and code reading; S4: heating and pressing; S5: cooling and pressing; S6: semi-permeable membrane heating and molding; S7: bottom tape application; S8: high voltage test; S9: CCD image detection; S10: automatic plate collection.

[0014] The beneficial effects of the present invention are: it is conducive to automatically completing the fixing, visual inspection, and heating processes on the slide base, using visual inspection to accurately locate the position of the lithium battery, improving positioning accuracy, reducing the difficulty of work switching, and improving the qualified rate of finished products. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a structural block diagram of the present invention;

[0016] Figure 2 It is a three-dimensional structural diagram of the present invention;

[0017] Figure 3 A top view of the positioning platform in the present invention;

[0018] Figure 4 This is a front view of the positioning platform in the present invention;

[0019] Figure 5 It is a three-dimensional structural diagram of the fixing mechanism in the present invention;

[0020] Figure 6 A three-dimensional structural diagram of the visual detection mechanism of the present invention;

[0021] Figure 7 It is a three-dimensional structural diagram of the thermoforming mechanism in the present invention;

[0022] Figure 8 It is a left side view of the thermoforming mechanism of the present invention;

[0023] Figure 9 is a process flow chart of the present invention;

[0024] In the figure,

[0025] 1. Driving electric cylinder; 2. Lifting cylinder; 3. Adjusting cylinder; 4. CCD; 5. Vacuum detector; 6. Base; 7. Sliding cylinder; 8. Linear slide; 9. Spring mechanism; 10. Vacuum assembly; 11. Fixed seat; 12. Linear guide; 13. Reference plate; 14. Movable plate; 15. Fiber optic sensor; 16. Slider; 17. U-shaped seat; 18. Linear bearing; 19. Balance bar; 20. Pressure block; 21. Camera bracket; 22. Light source bracket; 23. Lens; 24. Light source; 25. Heating bracket; 26. Heat insulation board; 27. Thermocouple; 28. Connector. DETAILED DESCRIPTION

[0026] like Figure 1-9 As shown, the present invention includes: a cell input unit, a hot pressing and cooling unit, a high-voltage testing unit and a detection and discharge unit arranged in sequence, and the cells are transferred between them through an automatic transplanting and handling unit. The cell input unit includes an input part and a code reading part in sequence, the hot pressing and cooling unit includes a hot pressing engineering part and a cooling and pressurizing part in sequence, the high-voltage testing unit includes a semi-permeable membrane molding part, a bottom gluing part and a high-voltage testing part in sequence, and the detection and discharge unit includes an image detection part and a discharge part in sequence.

[0027] In this embodiment, preferably, the semipermeable membrane forming part includes a positioning platform, a fixing mechanism, a visual inspection mechanism, a thermoforming mechanism and a slide base, and the slide base drives the positioning platform movably installed on the upper side by driving the electric cylinder 1, and a fixing mechanism and a visual inspection mechanism are respectively provided on both sides of the positioning platform, the fixing mechanism is movably installed on the slide base, the visual inspection mechanism is fixed to the slide base by bolts, the thermoforming mechanism is arranged in the travel direction of the positioning platform, and the thermoforming mechanism is fixedly installed on the slide base.

[0028] The implementation process of this patent is as follows:

[0029] (1) Place a lithium battery that has not been thermoformed with a semi-permeable membrane on the positioning table. It can be placed manually or connected to the front-end production equipment for full automatic operation. The lithium battery is clamped on the left and right, and the vacuum component opens the vacuum to adsorb the lithium battery;

[0030] (2) The fixing mechanism is adjusted by the lifting cylinder 2 and constrained by the regulating cylinder 3 to slowly and steadily press and fix the lithium battery;

[0031] (3) The electric cylinder 1 drives the positioning platform to the visual inspection mechanism for shooting. The CCD 4 detects the captured image and identifies the position of the detection edge on the lithium battery, and compares it with the reference edge to obtain the difference. The data that needs to be compensated is then transmitted to the electric cylinder 1. The electric cylinder 1 compensates for the upcoming hot forming position to ensure that the length of the semipermeable membrane of each lithium battery after melting is equal.

[0032] (4) Driving the electric cylinder 1 to drive the positioning platform and the lithium battery to the thermoforming mechanism for thermoforming;

[0033] (5) A control and monitoring system was constructed using a Keyence KV7500 PLC, CCD, and PROFACE vacuum detector. The PLC stored the process parameters of different lithium battery models, including CCD reference values, thermoforming temperature, and thermoforming time. The corresponding process data was automatically found by inputting parameters through the vacuum detector or scanning the product name of the lithium battery product with a barcode gun. The CCD controller transmitted the parameters of each lithium battery before and after thermoforming to the PLC via the Ethernet IP protocol. The PLC could store these parameters for easy viewing.

[0034] like Figure 3-4 As shown, in this embodiment, preferably, the positioning platform includes a base 6, a slide cylinder 7, a linear slide 8, a spring mechanism 9 and a vacuum assembly 10. The base 6 is in a "convex" shape, and a fixed seat 11 and a linear slide 8 are respectively provided on both sides of the convex portion of the base 6. A reference plate 13 is fixed on the fixed seat 11, and a spring mechanism 9 and a movable plate 14 are sequentially provided on the linear slide 8. The spring mechanism 9 is driven by the slide cylinder 7, and the gap between the reference plate 13 and the movable plate 14 forms a positioning platform with the convex portion of the base 6. The bottom of the positioning platform is connected to the vacuum assembly 10 through a joint 28.

[0035] With the above structure, during operation, the slide cylinder 7 drives the spring mechanism 9 to open the receiving platform. After the lithium battery is placed on the receiving platform, the slide cylinder 7 resets, and the spring mechanism 9 extends to clamp the lithium battery to form a position. The left and right clamping is maintained by the spring mechanism 9, and the vacuum component 10 opens the vacuum to adsorb the lithium battery.

[0036] like Figure 3-4 As shown, in this embodiment, preferably, optical fiber sensors 15 are respectively provided on both sides of the base 6 , and the optical fiber sensors 15 are provided on a side of the base 6 close to the thermoforming mechanism.

[0037] With the above structure, during operation, the optical fiber sensor 15 is used to detect the position to prevent the positioning platform from being overloaded, ensuring that it can accurately fall into the position below the visual detection mechanism, reducing the error rate and improving work efficiency.

[0038] like Figure 5As shown, in this embodiment, the fixing mechanism preferably includes a linear guide rail 12, a slider 16, a U-shaped seat 17, a linear bearing 18, a lifting cylinder 2, a balance rod 19 and a pressure block 20. The linear guide rail 12 is fixed on the slide base, the slider 16 is embedded in the linear slide rail 8, the slider 16 is equipped with a U-shaped seat 17, linear bearings 18 are installed on both sides of the U-shaped seat 17, the lifting cylinder 2 is installed in the middle of the U-shaped seat 17, the linear bearing 18 and the top of the lifting cylinder 2 are hinged with a balance rod 19, and a pressure block 20 is vertically provided on the side of the balance rod 19 away from the lifting cylinder 2.

[0039] The above structure is set up, and the downward movement of the lifting cylinder 2 is used to drive the downward movement of the balance bar 19, and is stabilized by the linear bearing 18, so that the pressure block 20 presses and fixes the lithium battery. In addition, since the linear slide rail 8 and the slider 16 are provided at the bottom of the balance bar 19, simultaneous displacement can be guaranteed to ensure that the lithium battery does not move during the movement.

[0040] like Figure 5 As shown, in this embodiment, preferably, an adjusting cylinder 3 is installed on the lifting cylinder 2, and the pressing block 20 is made of silicone rubber.

[0041] With the above structure, the pressing force is achieved by adjusting the air intake pressure of the cylinder 3, and the pressing block 20 made of silicone rubber is used to ensure that no damage is caused to the surface of the lithium battery.

[0042] like Figure 6 As shown, in this embodiment, the visual detection mechanism preferably includes a camera bracket 21 and a light source bracket 22. The camera bracket 21 is an inverted L-shape, and the CCD4 and the lens 23 are vertically installed on the horizontal part of the camera bracket 21 in sequence. The top of the light source bracket 22 is installed with a light source 24, and the position of the light source 24 corresponds to that of the lens 23.

[0043] The above-mentioned device has a simple structure and is easy to operate. It can adapt to different devices and can capture and identify the position of the lithium battery. The CCD identifies the position of the detection edge on the lithium battery through image detection. The CCD transmits the captured image to the vacuum detector 5 and compares it with the reference edge to obtain the difference. The data that needs to be compensated is then transmitted to the driving electric cylinder 1, and the electric cylinder compensates for the upcoming hot forming position.

[0044] like Figure 6 As shown, in this embodiment, preferably, a vacuum detector 5 is installed on the vertical portion of the camera bracket 21.

[0045] The above device is set up, and the vacuum degree of the entire device, especially the vacuum degree under the positioning platform, is detected by the vacuum detector 5 to ensure that the lithium battery does not deviate.

[0046] like Figure 7-8As shown, in this embodiment, the thermoforming mechanism preferably includes a heating bracket 25, on which a heating device is fixed by bolts, and insulation plates 26 are attached around the four sides of the heating device. The heating device consists of built-in heating rods and thermocouples 27 corresponding to each other, and the thermocouple 27 is connected to a temperature controller.

[0047] The above structure is set up, and two heating rods and two thermocouples 27 are set to heat the lithium battery in use. The heating temperature can be set by the thermostat. After the lithium battery reaches the thermoforming position, the semipermeable membrane is heated and melted on the heating block.

[0048] A lithium battery compression molding process using the device according to claim 1, characterized in that it includes the following steps:

[0049] S1: Pallet input: Manually place 10 layers of pallets loaded with elements into the equipment input port in the specified direction and start the equipment button; the cylinder transfer mechanism transports the 10 layers of pallets to the material retrieving position; the lower servo motor lifting mechanism lifts the pallets upward to the photoelectric sensor point, which is the material retrieving height;

[0050] S2: Element retrieval and buffering: The three-axis XYZ robot moves to the pallet retrieval position, where sensors detect the elements in the pallet to determine whether they are present. The three-axis robot moves directly above the element, the Z-axis electric cylinder descends, and the vacuum is activated, sucking the element. The XY robot moves to the discharge position above the conveyor line and places the element onto the servo conveyor line. The servo conveyor line drives the element forward one position, and the servo conveyor line can buffer a maximum of 20 elements.

[0051] S3: Element positioning, dust removal, and code reading: The cylinder transfer mechanism adsorbs and moves the element at the end of the servo conveyor line to the positioning platform; the positioning platform consists of a claw-type cylinder, a set of laser displacement sensors, and a photoelectric sensor. The cylinder clamps the element and positions it in the X direction. The Y direction is detected by the laser displacement sensor and data compensation is performed; the XYZ three-axis manipulator adsorbs the positioned element to the dust removal position; the dust removal mechanism consists of ion wind, vacuum adsorption, and filter pipes, which can remove dust adsorbed by electrostatics on the surface of the element; the XYZ three-axis manipulator moves the element to the code reading position, reads the QR code, and uploads the data to the server; after reading, the element is placed on the 6-station buffer receiving station;

[0052] S4: Heating and pressing: The automatic transfer mechanism adsorbs and places the six elements onto the receiving platform of the heating and pressing station; the receiving platform moves to the pressing station; the heating and pressing mechanism uses a heating rod to heat the fixture, and the temperature is precisely controlled by a thermocouple and temperature controller. The pressing cylinder accurately controls the cylinder output pressure through an electric proportional valve and uses a pressure sensor for real-time monitoring to heat and press the elements;

[0053] S5: Cooling and pressing: The automatic transfer mechanism adsorbs and places the six elements onto the receiving platform of the cooling and pressing station; the receiving platform moves to the pressing station; the cooling and pressing mechanism uses a circulating cooler to cool the fixture, and the temperature is precisely controlled by thermocouples and temperature controllers. The pressing cylinder uses an electric proportional valve to precisely control the cylinder output pressure to cool and press the elements;

[0054] S6: Semi-permeable membrane thermoforming: The element is positioned in the X direction using a pneumatic cylinder, and then in the Y direction using a visual system. Distance compensation is then performed using an electric cylinder. The pneumatic cylinder mechanism presses and secures the element. The thermoforming mechanism heats the jig using a heating rod, and the temperature is precisely controlled using a thermocouple and thermostat. The operating distance is controlled to thermoform the semi-permeable membrane, and inspection and judgment are performed after forming.

[0055] S7: Bottom tape application: The tape is unwound by multiple cylinders and rollers and accurately fed by electric cylinders. The tape is precisely positioned using a vision system and then cut with a tool. An XY electric cylinder and gripper cylinder mechanism grips the element, corrects it, and then applies the tape. The tape is then fed into a roller pressing mechanism to adhere evenly to the bottom of the element.

[0056] S8: High voltage test: The element is positioned in the X and Y directions using a pneumatic cylinder. The receiving platform moves to the pressurization and testing station. The pressing cylinder precisely controls the cylinder pressure via an electric proportional valve to pressurize the element. A probe is used to contact the electrode tip of the element, and a high voltage test is performed on the element using a tester.

[0057] S9: CCD image detection: The element is placed on a receiving platform with a blue background and fixed by adsorption; the CCD and light source are installed on the X / Y / Z three-axis robot; the image detection uses a high-performance CCD to detect multiple dimensions of the element and upload them to the database;

[0058] S10: Automatic tray collection: The XYZ three-axis robot collects good and bad products separately; the trays are automatically stacked into 10 layers by multiple cylinders and then discharged.

[0059] The above embodiments are merely illustrative of the principles and effects of this patent application and are not intended to limit this patent application. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of this patent application. Therefore, all equivalent modifications or alterations made by persons of ordinary skill in the art without departing from the spirit and technical concepts disclosed in this patent application shall be covered by the claims of this patent application.

Claims

1. A lithium battery compression molding device, characterized in that: The invention comprises a cell feeding unit, a hot pressing and cooling unit, a high-voltage testing unit and a detection and discharge unit which are sequentially arranged in front and back, and the cells are transferred between them by an automatic transplanting and handling unit. The cell feeding unit comprises a feeding part and a code reading part in sequence, the hot pressing and cooling unit comprises a hot pressing engineering part and a cooling and pressurizing part in sequence, the high-voltage testing unit comprises a semi-permeable membrane forming part, a bottom gluing part and a high-voltage testing part in sequence, and the detection and discharge unit comprises an image detection part and a discharge part in sequence; the semi-permeable membrane forming part comprises a positioning platform, a fixing mechanism, a visual inspection mechanism, a thermoforming mechanism and a slide base, the slide base is driven by a driving electric cylinder (1) to drive a positioning platform which is movably mounted on the upper side, a fixing mechanism and a visual inspection mechanism are respectively arranged on both sides of the positioning platform, the fixing mechanism is movably mounted on the slide base, the visual inspection mechanism is fixed to the slide base by bolts, the thermoforming mechanism is arranged in the direction of the positioning platform, and the thermoforming mechanism is fixedly mounted on the slide base; The positioning platform comprises a base (6), a slide cylinder (7), a linear slide rail (8), a spring mechanism (9) and a vacuum assembly (10). The base (6) is in a "convex" shape. A fixed seat (11) and a linear slide rail (8) are respectively provided on both sides of the convex portion of the base (6). A reference plate (13) is fixedly provided on the fixed seat (11). A spring mechanism (9) and a movable plate (14) are sequentially provided on the linear slide rail (8). The spring mechanism (9) is connected to the slide cylinder (7) and the movable plate (14) is provided. ) is driven, the gap between the reference plate (13) and the movable plate (14) and the raised part of the base (6) form a positioning platform, and the bottom of the positioning platform is connected to the vacuum component (10) through a joint (28). During operation, the slide cylinder 7 drives the spring mechanism 9 to open the positioning platform. After the lithium battery is placed on the positioning platform, the slide cylinder 7 resets, and the spring mechanism 9 extends to clamp the lithium battery to form a positioning position. The left and right clamping is maintained by the spring mechanism 9, and the vacuum component 10 opens the vacuum to adsorb the lithium battery.

2. The lithium battery compression molding equipment according to claim 1, characterized in that: Optical fiber sensors (15) are respectively provided on both sides of the base (6), and the optical fiber sensors (15) are provided on a side of the base (6) close to the thermoforming mechanism.

3. The lithium battery compression molding equipment according to claim 2, characterized in that: The fixing mechanism includes a linear guide rail (12), a slider (16), a U-shaped seat (17), a linear bearing (18), a lifting cylinder (2), a balance rod (19) and a pressure block (20), wherein the linear guide rail (12) is fixed on the slide base, the slider (16) is embedded in the linear guide rail (8), a U-shaped seat (17) is installed on the slider (16), linear bearings (18) are installed on both sides of the U-shaped seat (17), a lifting cylinder (2) is installed in the middle of the U-shaped seat (17), a balance rod (19) is hinged at the top of the linear bearing (18) and the lifting cylinder (2), and a pressure block (20) is vertically arranged on the side of the balance rod (19) away from the lifting cylinder (2).

4. The lithium battery compression molding equipment according to claim 3, characterized in that: An adjusting cylinder (3) is installed on the lifting cylinder (2), and the pressing block (20) is made of silicone rubber.

5. The lithium battery compression molding equipment according to claim 4, characterized in that: The visual detection mechanism comprises a camera bracket (21) and a light source bracket (22); the camera bracket (21) is in an inverted L-shape; a CCD (4) and a lens (23) are vertically mounted on the horizontal portion of the camera bracket (21); a light source (24) is mounted on the top of the light source bracket (22); and the light source (24) and the lens (23) are positioned correspondingly.

6. The lithium battery compression molding equipment according to claim 5, characterized in that: A vacuum detector (5) is installed on the vertical portion of the camera bracket (21).

7. The lithium battery compression molding equipment according to claim 6, characterized in that: The thermoforming mechanism comprises a heating bracket (25), a heating device is fixed to the heating bracket (25) by bolts, and heat insulation plates (26) are attached to the four sides of the heating device. The heating device is composed of built-in heating rods and thermocouples (27) corresponding to each other, and the thermocouples (27) are connected to a temperature controller.

8. A lithium battery compression molding process using the device according to claim 1, characterized in that: The process includes the following steps: S1: tray input; S2: elements are taken into the cache; S3: Element positioning, dust removal and code reading; S4: Heating and pressing; S5: Cooling and pressing; S6: Semi-permeable membrane heating and molding; S7: Bottom tape application; S8: High voltage test; S9: CCD image detection; S10: Automatic plate collection.

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