Automatic assembly machine and assembly method for touch switch

Abstract

The invention discloses an automatic assembly machine and an assembly method for a touch switch. According to the technical scheme, the feeding mechanism comprises a horizontally-arranged main material channel, a side material channel arranged on one side of the front end of the main material channel, a material belt pulling mechanism arranged at the rear end of the main material channel and a straight vibrator providing a vibration source for the side material channel, and a material belt positioning groove allowing a material belt to pass through is formed in the end face of the main material channel; the side material channel comprises a horizontal section connected with the discharging port of the vibration disc and an inclined section connected with the horizontal section. The invention has the advantages that the side material channel can arrange the metal elastic sheets in a unified direction (convex surfaces face upwards), the problem of reverse installation of the metal elastic sheets can be effectively prevented, and meanwhile, the material pressing mechanism can effectively prevent the phenomena of suction leakage and excessive suction through negative pressure detection and impact, so that the assembly qualification rate is greatly improved.

Description

Technical Field

[0001] The present invention belongs to the field of automation equipment, and particularly relates to a tactile switch automatic assembly machine. Background Art

[0002] The structure of a traditional micro tactile switch, as Figure 10 and Figure 11 shown, includes a switch base 51 and a metal shrapnel 50 (commonly known as a dome sheet). During assembly: first, the metal shrapnel 50 is loaded into the switch base 51, then an insulating film is pasted, and finally a button is installed. Since the volume of the micro tactile switch is very small, in order to achieve the rapid production and assembly of the micro tactile switch, usually the switch base 51 is integrally formed on a strip 52 to facilitate the transfer of the switch base 51 on an automatic machine, and then the metal shrapnel 50 and the insulating film are successively loaded into the switch base 51 through the automatic machine, and then enter the next process for assembly. Finally, the strip 52 is cut to complete the assembly. The disadvantages of traditional automatic assembly machines are that the metal shrapnel often has problems such as missing installation, over-installation, or reverse installation, resulting in a low qualified rate of finished products. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a tactile switch automatic assembly machine and an assembly method in which the metal shrapnel is not easily missing, over-installed, or reversely installed.

[0004] To solve the above problems, the technical solutions adopted by the present invention include: A feeding mechanism, which includes a main material channel arranged horizontally, a side material channel arranged on one side of the front end of the main material channel, a strip pulling mechanism arranged at the rear end of the main material channel, and a linear vibrator providing a vibration source for the side material channel. The end face of the main material channel is provided with a strip positioning groove for the strip to pass through. The side material channel includes a horizontal section connected to the discharge port of the vibrating bowl and an inclined section connected to the horizontal section. The surfaces of the horizontal section and the inclined section are provided with a group of smoothly transitioning shrapnel sliding grooves. The shrapnel sliding groove on the inclined section is provided with a shrapnel positioning groove, and a convex arc surface is provided in the shrapnel positioning groove; A pressing mechanism, arranged above the feeding mechanism, which includes a negative pressure pressing die, a group of hollow negative pressure pressing rods arranged at the bottom of the negative pressure pressing die, a first X-axis slide rail driving the negative pressure pressing die to move horizontally, a first Y-axis slide rail driving the negative pressure pressing die to move up and down, and a first cylinder driving the negative pressure pressing die to rotate. The negative pressure pressing die is connected to a negative pressure device through an air pipe.

[0005] The blanking mechanism further includes a film pressing mechanism arranged behind the negative pressure blanking die. The film pressing mechanism includes a film pressing upper template and a film pressing lower template slidably mounted on a straight rail, a second air cylinder for driving the film pressing upper template and the film pressing lower template to move up and down, and a tension pulley group arranged on both sides of the film pressing upper template and the film pressing lower template. A film punching rod for punching on the film pressing lower template is arranged inside the film pressing upper template. A film positioning groove for the film to pass through is arranged at the bottom of the film pressing lower template, and a film hole plate matching with the film punching rod is arranged at the bottom of the film positioning groove.

[0006] A set of die connecting guide posts is arranged between the film pressing upper template and the film pressing lower template, and a buffer spring is arranged outside the die connecting guide posts. The film pressing lower template is fixed at the lower end of the die connecting guide posts, and the film pressing upper template is slidably arranged on the die connecting guide posts.

[0007] The first Y-axis slide rail is installed on the first X-axis slide rail through a rotating seat. At least one side of the upper end of the rotating seat is provided with a protruding first impact part, and a second impact part matching with the first impact part is arranged on the first X-axis slide rail. The output shaft of the first air cylinder is connected to the lower end of the rotating seat.

[0008] The material pulling belt mechanism includes a second X-axis slide rail and a second Y-axis slide rail for driving the material pulling rod to move horizontally and up and down. A needle tip part is arranged at the upper end of the material pulling rod.

[0009] A first positioning plate matching with the negative pressure blanking die is arranged at the front end of the main material channel. A set of first positioning holes is arranged on the first positioning plate. The first positioning holes include a first tapered hole and a first straight hole arranged at the lower end of the first tapered hole.

[0010] A second positioning plate is arranged between the side material channel and the first positioning plate. A set of second positioning holes with a diameter larger than that of the first positioning holes is arranged on the second positioning plate. The second positioning holes include a second tapered hole and a second straight hole arranged at the lower end of the second tapered hole.

[0011] The first positioning plate is arranged at the front end of the main material channel through a lifting air cylinder at the bottom.

[0012] The negative pressure blanking die includes a negative pressure lower template and a negative pressure upper template arranged on the negative pressure lower template. A set of blanking rod mounting holes is arranged on the negative pressure lower template, a negative pressure cavity communicating with the blanking rod mounting holes is arranged on the negative pressure upper template, and the air pipe is communicated with the negative pressure cavity.

[0013] An assembly method of a tactile switch is realized according to the above-mentioned tactile switch automatic assembly machine, and includes the following steps: Bring the negative pressure pressing rod of the material pressing mechanism close to the surface of the metal elastic piece in the elastic piece positioning groove, suck the metal elastic piece by negative pressure, and transport it toward the feeding mechanism side; during the transportation process, it is necessary to detect the current negative pressure value in real time. When it is detected that the negative pressure value is less than the preset value, it is determined that there is a phenomenon of missed suction in the negative pressure pressing rod. At this time, the negative pressure pressing rod approaches the surface of the metal elastic piece in the elastic piece positioning groove again for re-suction.

[0014] The advantages of the tactile switch automatic assembly machine and the assembly method of the present invention are as follows: The side material channel can arrange the metal elastic pieces in a unified direction (convex side up), which can effectively prevent the problem of incorrect installation direction of the metal elastic pieces. At the same time, the material pressing mechanism can effectively prevent the phenomena of missed suction and multiple suction through negative pressure detection and impact, thereby greatly improving the assembly qualification rate.

[0015] The following further describes the present invention with reference to the accompanying drawings of the specification. Description of the Drawings

[0016] Figure 1 is a schematic structural diagram of the tactile switch automatic assembly machine of the present invention; Figure 2 is a schematic structural diagram of the feeding mechanism of the present invention; Figure 3 is a schematic front-end structural diagram of the material pressing mechanism of the present invention; Figure 4 is a schematic rear-end structural diagram of the material pressing mechanism of the present invention; Figure 5 is a cross-sectional view of the material pressing mechanism of the present invention; Figure 6 is a schematic structural diagram of the pulling tape mechanism of the present invention; Figure 7 is a cross-sectional view of the side material channel of the present invention; Figure 8 is a schematic structural diagram of the first positioning plate of the present invention; Figure 9 is a schematic structural diagram of the second positioning plate of the present invention; Figure 10 is a schematic structural diagram of the switch base of the present invention; Figure 11 is a schematic structural diagram of the metal elastic piece of the present invention; Figure 12 is a schematic diagram of the working principle between the metal elastic piece and the side material channel of the present invention.

[0017] Among them: 1. Feeding mechanism; 2. Material pressing mechanism; 3. Main material channel; 4. Side material channel; 5. Material belt pulling mechanism; 6. Linear vibrator; 7. Material belt positioning groove; 8. Vibration bowl; 9. Horizontal section; 10. Inclined section; 11. Shrapnel sliding groove; 12. Shrapnel positioning groove; 13. Arc surface; 14. Negative pressure material pressing die; 15. Negative pressure material pressing rod; 16. First X-axis slide rail; 17. First Y-axis slide rail; 18. First cylinder; 19. Air pipe; 20. Film pressing mechanism; 21. Straight rail; 22. Upper film pressing template; 23. Lower film pressing template; 24. Second cylinder; 25. Film stamping rod; 26. Film positioning groove; 27. Film hole plate; 28. Die coupling guide pillar; 29. Buffer spring; 30. Rotating seat; 31. First impact part; 32. Second impact part; 33. Material pulling rod; 34. Second X-axis slide rail; 35. Second Y-axis slide rail; 36. Tip part; 37. First positioning plate; 38. First positioning hole; 39. First conical hole; 40. First straight hole; 41. Second positioning plate; 42. Second positioning hole; 43. Second conical hole; 44. Second straight hole; 45. Lifting cylinder; 46. Lower negative pressure template; 47. Upper negative pressure template; 48. Material pressing rod mounting hole; 49. Negative pressure cavity; 50. Metal shrapnel; 51. Switch base; 52. Material belt; 53. Tension pulley set; 54. Unwinding wheel. Detailed implementation mode Example 1:

[0018] Refer to Figure 1-12As shown in the figure, the tactile switch automatic assembly machine of the present invention includes a feeding mechanism 1 and a material pressing mechanism 2. The feeding mechanism 1 and the material pressing mechanism 2 can be set as a single-station or double-station according to needs. In this example, it is a double-station. The feeding mechanism 1 includes a horizontally arranged main material channel 3, side material channels 4 arranged on both sides of the front end of the main material channel 3, a pulling belt mechanism 5 arranged at the rear end of the main material channel 3, and a linear vibrator 6 that provides a vibration source for the side material channels 4. A material belt positioning groove 7 for the passing of the material belt 52 is provided at the end face of the main material channel 3. The side material channel 4 includes a horizontal section 9 connected to the discharge port of the vibrating bowl 8 and an inclined section 10 connected to the horizontal section 9. A set of elastically sliding grooves 11 with smooth transitions are provided on the surfaces of the horizontal section 9 and the inclined section 10. An elastic piece positioning groove 12 is provided in the elastically sliding groove 11 on the inclined section 10, and a convex arc surface 13 is provided in the elastic piece positioning groove 12. The material pressing mechanism 2 is arranged above the feeding mechanism 1, and it includes a negative pressure material pressing die 14, a set of hollow negative pressure material pressing rods 15 arranged at the bottom of the negative pressure material pressing die 14, a first X-axis slide rail 16 that drives the negative pressure material pressing die 14 to move horizontally, a first Y-axis slide rail 17 that drives the negative pressure material pressing die 14 to move up and down, and a first air cylinder 18 that drives the negative pressure material pressing die 14 to rotate. The negative pressure material pressing die 14 is connected to a negative pressure device through an air pipe 19. The negative pressure device is usually a vacuum pump. During operation: A number of metal elastic pieces 50 are poured into the vibrating bowl 8. Through the vibration of the vibrating bowl 8, a number of metal elastic pieces 50 are conveyed disorderly into the elastically sliding grooves 11 of the side material channels 4. Then, under the vibration of the linear vibrator 6, a number of disorderly elastic pieces continue to move forward in the sliding grooves 11. When the elastic piece sliding groove 11 with the convex surface facing up slides past the elastic piece positioning groove 12, it will be embedded in the groove. When the elastic piece sliding groove 11 with the convex surface facing down slides past the elastic piece positioning groove 12, it will slide out of the groove under the action of the arc surface 13 and flow back into the vibrating bowl 8 again, so as to realize the orderly arrangement of the metal elastic pieces 50 in the inclined section 10. Then, the vibrating bowl 8 and the linear vibrator 6 stop vibrating (note: Since the number of metal elastic pieces 50 passing through each vibration cycle is large, basically all the elastic piece positioning grooves 12 are embedded with metal elastic pieces 50). Immediately afterwards, the negative pressure material pressing rod 15 of the material pressing mechanism 2 approaches the surface of the metal elastic piece 50 in the elastic piece positioning groove 12, sucks the metal elastic piece 50 by using the negative pressure generated by the negative pressure device, transports it towards the feeding mechanism 1 side, presses the metal elastic piece 50 into the switch base 51, and then resets. Finally, through the pulling belt mechanism 5, the material belt 52 together with the switch base 51 is pulled forward to the next process. This process is repeated until the processing is completed.

[0019] Preferably, the material pressing mechanism 2 further includes a film pressing mechanism 20 disposed behind the negative pressure material pressing die 14. The film pressing mechanism 20 includes a film pressing upper template 22 and a film pressing lower template 23 slidably mounted on a straight rail 21, a second cylinder 24 for driving the film pressing upper template 22 and the film pressing lower template 23 to move up and down, and a tension pulley group 53 disposed on both sides of the film pressing upper template 22 and the film pressing lower template 23. On the other side of the unwinding wheel 54, a winding wheel is usually further provided. A film punching rod 25 punching on the film pressing lower template 23 is provided inside the film pressing upper template 22. A film positioning groove 26 for the film to pass through is provided at the bottom of the film pressing lower template 23, and a film hole plate 27 matching with the film punching rod 25 is provided at the bottom of the film positioning groove 26. Film holes are provided on the film hole plate 27. The shapes of the film punching rod 25 and the film holes are adapted to the shape of the film required for the switch base 51. Before work, a film roll (the lower end surface is usually an adhesive layer) is placed on the unwinding wheel 54 and tensioned by the tension pulley group 53. When the switch base 51 is conveyed below the film pressing mechanism 20, the second cylinder 24 drives the film pressing upper template 22 and the film pressing lower template 23 to press down. At the same time, the film punching rod 25 punches the film, and under the limitation of the film hole plate 27, the film is punched into the required shape and pasted on the surface of the switch base 51. To achieve the assembly of the film on the same device.

[0020] Preferably, a set of die connecting guide columns 28 are provided between the film pressing upper template 22 and the film pressing lower template 23, and a buffer spring 29 is provided outside the die connecting guide columns 28. The film pressing lower template 23 is fixed to the lower end of the die connecting guide columns 28, and the film pressing upper template 22 is slidably arranged on the die connecting guide columns 28. By providing the die connecting guide columns 28, the second cylinder 24 can drive the film pressing upper template 22 and the film pressing lower template 23 to move up and down simultaneously, and the buffer spring 29 is used to buffer and reset the film pressing upper template 22. When the film pressing lower template 23 presses down and abuts against the main material channel 3, at this time, the film pressing upper template 22 can continue to press down and form a buffer through the buffer spring 29 to reduce the impact force caused by punching.

[0021] Preferably, the first Y-axis slide rail 17 is mounted on the first X-axis slide rail 16 through a rotating seat 30. On both sides of the upper end of the rotating seat 30, there are protruding first impact parts 31. On the first X-axis slide rail 16, there are second impact parts 32 that cooperate with the first impact parts 31. The output shaft of the first air cylinder 18 is connected to the lower end of the rotating seat 30. Since the metal elastic sheet 50 is very thin and may be magnetic after vibration friction, it is easy to cause multiple metal elastic sheets 50 to be sucked by the negative pressure material pressing rod 15 after overlapping. After adopting the above structure, after the negative pressure material pressing rod 15 finishes sucking, the first impact part 31 and the second impact part 32 are continuously impacted against each other through the continuous telescoping of the first air cylinder 18, so that the redundant metal elastic sheets 50 can be vibrated off, effectively solving the problem of multiple suction.

[0022] Preferably, the material pulling belt mechanism 5 includes a second X-axis slide rail 34 and a second Y-axis slide rail 35 that drive the material pulling rod 33 to move horizontally and vertically. At the upper end of the material pulling rod 33, there is a needle tip part 36. On both sides of the material belt 52, there are needle holes adapted to the needle tip part 36 to realize the transmission of the material belt 52.

[0023] Preferably, at the front end of the main material channel 3, there is a first positioning plate 37 that cooperates with the negative pressure material pressing die 14. On the first positioning plate 37, there is a group of first positioning holes 38. The first positioning holes 38 include a first tapered hole 39 and a first straight hole 40 provided at the lower end of the first tapered hole 39. After the position of the metal elastic sheet 50 is corrected by the first tapered hole 39 and the first straight hole 40, it is installed into the switch base 51 to ensure the accuracy of assembly.

[0024] Preferably, between the side material channel 4 and the first positioning plate 37, there is a second positioning plate 41. On the second positioning plate 41, there is a group of second positioning holes 42 with a diameter larger than that of the first positioning holes 38. The second positioning holes 42 include a second tapered hole 43 and a second straight hole 44 provided at the lower end of the second tapered hole 43. Since the positions of some of the metal elastic sheets 50 may deviate greatly and cannot directly enter the first positioning holes 38 for correction. Therefore, preliminary correction can be carried out through the second positioning holes 42 with a larger diameter, and then fine correction can be carried out in the first positioning holes 38 to further improve the assembly qualification rate.

[0025] Preferably, the first positioning plate 37 is arranged at the front end of the main material channel 3 through a lifting air cylinder 45 at the bottom. When assembling the metal elastic sheet 50, first, the first positioning plate 37 is lowered through the lifting air cylinder 45 to make it fit the surface of the switch base 51, so as to achieve more accurate assembly; after the assembly is completed, the first positioning plate 37 is lifted through the lifting air cylinder 45 to enable the normal transmission of the switch base 51.

[0026] Preferably, the negative-pressure material pressing die 14 includes a negative-pressure lower template 46 and a negative-pressure upper template 47 disposed on the negative-pressure lower template 46. A set of material pressing rod mounting holes 48 are provided on the negative-pressure lower template 46, and a negative-pressure cavity 49 communicating with the material pressing rod mounting holes 48 is provided on the negative-pressure upper template 47. The air pipe 19 communicates with the negative-pressure cavity 49. The negative-pressure material pressing rod 15 is disposed in the material pressing rod mounting holes 48 to realize the negative-pressure function of the negative-pressure material pressing die 14. Embodiment 2:

[0027] Refer to Figure 1-12 As shown, an assembly method of a tact switch according to the present invention is realized according to the tact switch automatic assembly machine described in Embodiment 1, and includes the following steps: The negative-pressure material pressing rod 15 of the material pressing mechanism 2 is brought close to the surface of the metal elastic piece 50 in the elastic piece positioning groove 12, and the metal elastic piece 50 is sucked by negative pressure and transported toward the feeding mechanism 1 side. During the transportation process, the current negative-pressure value needs to be detected in real time. When it is detected that the negative-pressure value is less than the preset value, it is determined that the negative-pressure material pressing rod 15 has a phenomenon of missed suction. At this time, the negative-pressure material pressing rod 15 approaches the surface of the metal elastic piece 50 in the elastic piece positioning groove 12 again for re-suction. Usually, the preset value is -50 Pa. When each negative-pressure material pressing rod 15 sucks the metal elastic piece 50, the negative-pressure value is usually -70 Pa. When one or more of the negative-pressure material pressing rods 15 have missed suction, the negative-pressure value is usually much less than -50 Pa. By the above method, the phenomenon of missed suction of the negative-pressure material pressing rod 15 can be effectively solved.

[0028] As described above, it does not impose any formal restrictions on the present invention. Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to the above-disclosed structure and technical content within the scope of the technical solution of the present invention to be equivalent change equivalent embodiments. However, as long as it does not depart from the content of the technical solution of the present invention, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. An automatic assembling machine for a tactile switch, characterized in that Comprising: A feeding mechanism (1), which includes a horizontally arranged main material channel (3), a side material channel (4) arranged on the front side of the front end of the main material channel (3), a pulling belt mechanism (5) arranged at the rear end of the main material channel (3), and a linear vibrator (6) providing a vibration source for the side material channel (4). A material belt positioning groove (7) for the feeding belt (52) to pass through is arranged on the end face of the main material channel (3). The side material channel (4) includes a horizontal section (9) connected to the discharge port of the vibrating bowl (8) and an inclined section (10) connected to the horizontal section (9). A group of elastically sliding grooves with smooth transitions are arranged on the surfaces of the horizontal section (9) and the inclined section (10). An elastic sheet positioning groove (12) is arranged in the elastically sliding groove (11) on the inclined section (10), and a convex arc surface (13) is arranged in the elastic sheet positioning groove (12). A material pressing mechanism (2) is arranged above the feeding mechanism (1), which includes a negative pressure material pressing die (14), a group of hollow negative pressure material pressing rods (15) arranged at the bottom of the negative pressure material pressing die (14), a first X-axis slide rail (16) driving the negative pressure material pressing die (14) to move horizontally, a first Y-axis slide rail (17) driving the negative pressure material pressing die (14) to move up and down, and a first air cylinder (18) driving the negative pressure material pressing die (14) to rotate. The negative pressure material pressing die (14) is connected to a negative pressure device through an air pipe (19).

2. The tactile switch automatic assembly machine according to claim 1, wherein: The material pressing mechanism (2) further includes a film pressing mechanism (20) arranged behind the negative pressure material pressing die (14). The film pressing mechanism (20) includes a film pressing upper template (22) and a film pressing lower template (23) slidably installed on a straight rail (21), a second air cylinder (24) driving the film pressing upper template (22) and the film pressing lower template (23) to move up and down, and a tensioning wheel group (53) arranged on both sides of the film pressing upper template (22) and the film pressing lower template (23). A film punching rod (25) punching on the film pressing lower template (23) is arranged in the film pressing upper template (22). A film positioning groove (26) for the film to pass through is arranged at the bottom of the film pressing lower template (23), and a film hole plate (27) matching with the film punching rod (25) is arranged at the bottom of the film positioning groove (26).

3. The tactile switch automatic assembly machine according to claim 2, characterized in that: A group of die connecting guide columns (28) are arranged between the film pressing upper template (22) and the film pressing lower template (23), and a buffer spring (29) is arranged outside the die connecting guide columns (28). The film pressing lower template (23) is fixed at the lower end of the die connecting guide columns (28), and the film pressing upper template (22) is slidably arranged on the die connecting guide columns (28).

4. The tactile switch automatic assembly machine according to claim 1, characterized in that: The first Y-axis slide rail (17) is installed on the first X-axis slide rail (16) through a rotating seat (30). At least one side of the upper end of the rotating seat (30) is provided with a convex first impact part (31). A second impact part (32) matching with the first impact part (31) is arranged on the first X-axis slide rail (16). The output shaft of the first air cylinder (18) is connected to the lower end of the rotating seat (30).

5. The tactile switch automatic assembly machine according to claim 1, wherein: The material pulling belt mechanism (5) includes a second X-axis slide rail (34) and a second Y-axis slide rail (35) that drive the material pulling rod (33) to move horizontally and vertically, and a tip part (36) is provided at the upper end of the material pulling rod (33).

6. The tactile switch automatic assembly machine according to claim 1, wherein: A first positioning plate (37) that cooperates with the negative pressure material pressing die (14) is provided at the front end of the main material channel (3). A set of first positioning holes (38) are provided on the first positioning plate (37). The first positioning holes (38) include a first tapered hole (39) and a first straight hole (40) provided at the lower end of the first tapered hole (39).

7. The tactile switch automatic assembly machine according to claim 6, characterized in that: A second positioning plate (41) is provided between the side material channel (4) and the first positioning plate (37). A set of second positioning holes (42) with a diameter larger than that of the first positioning holes (38) are provided on the second positioning plate (41). The second positioning holes (42) include a second tapered hole (43) and a second straight hole (44) provided at the lower end of the second tapered hole (43).

8. The tactile switch automatic assembly machine according to claim 6, characterized in that: The first positioning plate (37) is provided at the front end of the main material channel (3) through a lifting cylinder (45) at the bottom.

9. The tactile switch automatic assembly machine according to claim 1, characterized in that: The negative pressure material pressing die (14) includes a negative pressure lower template (46) and a negative pressure upper template (47) provided on the negative pressure lower template (46). A set of material pressing rod mounting holes (48) are provided on the negative pressure lower template (46). A negative pressure cavity (49) communicated with the material pressing rod mounting holes (48) is provided on the negative pressure upper template (47). The air pipe (19) is communicated with the negative pressure cavity (49).

10. An assembly method of a tactile switch, implemented by the automatic assembly machine for the tactile switch according to any one of claims 1-9, characterized in that, Including the following steps: Move the negative pressure material pressing rod (15) of the material pressing mechanism (2) close to the surface of the metal elastic piece (50) in the elastic piece positioning groove (12), suck the metal elastic piece (50) by negative pressure, and carry it towards the feeding mechanism (1) side; during the carrying process, it is necessary to detect the current negative pressure value in real time. When it is detected that the negative pressure value is less than the preset value, it is determined that there is a phenomenon of missed suction in the negative pressure material pressing rod (15). At this time, the negative pressure material pressing rod (15) moves close to the surface of the metal elastic piece (50) in the elastic piece positioning groove (12) again for re-suction.

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