An automatic assembly machine and assembly method for tactile switches

Abstract

This invention discloses an automatic assembly machine and method for tactile switches. The technical solution includes: a feeding mechanism comprising a horizontally arranged main feed channel, a side feed channel located at the front end of the main feed channel, a material pulling belt mechanism located at the rear end of the main feed channel, and a vibrator providing a vibration source for the side feed channel. The end face of the main feed channel is provided with a material belt positioning groove for the material feeding belt to pass through. The side feed channel includes a horizontal section connected to the outlet of the vibrating plate and an inclined section connected to the horizontal section. The advantages are as follows: the side feed channel can arrange the metal springs in a uniform direction (convex surface upwards), effectively preventing the problem of reversed installation of the metal springs. Simultaneously, the pressing mechanism, through negative pressure detection and impact, can effectively prevent leakage and over-suction, thereby greatly improving the assembly qualification rate.

Description

Technical Field

[0001] This invention belongs to the field of automation equipment, and in particular relates to an automatic assembly machine for tactile switches. Background Technology

[0002] The structure of a traditional miniature tactile switch, such as Figure 10 and Figure 11 As shown, the assembly includes a switch base 51 and a metal spring 50 (commonly known as a dome switch). During assembly: first, the metal spring 50 is inserted into the switch base 51, then an insulating film is applied, and finally the button is attached. Because miniature tactile switches are very small, to achieve rapid production and assembly, the switch base 51 is typically integrally formed onto a material strip 52 for easy conveying on an automatic machine. Then, the automatic machine sequentially inserts the metal spring 50 and insulating film into the switch base 51 before proceeding to the next assembly step. Finally, the material strip 52 is cut, completing the assembly. A drawback of traditional automatic assembly machines is that metal springs are often missing, over-installed, or installed in the wrong direction, resulting in a low finished product qualification rate. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide an automatic assembly machine and assembly method for tactile switches that prevents metal springs from being missed, over-installed, or reversed.

[0004] To solve the above problems, the technical solution adopted by the present invention includes:

[0005] The feeding mechanism includes a horizontally arranged main feed channel, a side feed channel located at one side of the front end of the main feed channel, a material pulling belt mechanism located at the rear end of the main feed channel, and a straight vibrator that provides a vibration source for the side feed channel. The end face of the main feed channel is provided with a material belt positioning groove through which the feeding belt passes. The side feed channel includes a horizontal section connected to the outlet of the vibrating plate and an inclined section connected to the horizontal section. The surfaces of the horizontal section and the inclined section are provided with a set of smoothly transitioning spring sliding grooves. The spring sliding groove on the inclined section is provided with a spring positioning groove, and the spring positioning groove is provided with a raised arc-shaped surface.

[0006] The pressing mechanism is located above the feeding mechanism and includes a negative pressure pressing mold, a set of hollow negative pressure pressing rods located at the bottom of the negative pressure pressing mold, a first X-axis slide rail that drives the negative pressure pressing mold to move horizontally, a first Y-axis slide rail that drives the negative pressure pressing mold to move up and down, and a first cylinder that drives the negative pressure pressing mold to rotate. The negative pressure pressing mold is connected to the negative pressure equipment through an air pipe.

[0007] The pressing mechanism also includes a film pressing mechanism located behind the negative pressure pressing mold. The film pressing mechanism includes an upper film pressing template and a lower film pressing template that are slidably mounted on a straight rail, a second cylinder that drives the upper film pressing template and the lower film pressing template to move up and down, and a tensioning wheel assembly located on both sides of the upper film pressing template and the lower film pressing template. The upper film pressing template is provided with a film punching rod that punches against the lower film pressing template. The bottom of the lower film pressing template is provided with a film positioning groove for the film to pass through, and the bottom of the film positioning groove is provided with a film perforated plate that cooperates with the film punching rod.

[0008] A set of mold-connecting guide posts is provided between the upper mold-pressing template and the lower mold-pressing template, and a buffer spring is provided outside the mold-connecting guide posts. The lower mold-pressing template is fixed to the lower end of the mold-connecting guide posts, and the upper mold-pressing template is slidably mounted on the mold-connecting guide posts.

[0009] The first Y-axis slide rail is mounted on the first X-axis slide rail via a rotary seat. The upper end of the rotary seat has a protruding first impact part on at least one side. The first X-axis slide rail has a second impact part that cooperates with the first impact part. The first cylinder output shaft is connected to the lower end of the rotary seat.

[0010] The material pulling mechanism includes a second X-axis slide rail and a second Y-axis slide rail that drive the material pulling rod to move horizontally and vertically, and the upper end of the material pulling rod is provided with a needle tip.

[0011] The front end of the main material channel is provided with a first positioning plate that cooperates with the negative pressure pressing mold. The first positioning plate is provided with a set of first positioning holes, including a first conical hole and a first straight hole at the lower end of the first conical hole.

[0012] A second positioning plate is provided between the side material channel and the first positioning plate. The second positioning plate is provided with a set of second positioning holes with a diameter larger than that of the first positioning hole. The second positioning hole includes a second conical hole and a second straight hole at the lower end of the second conical hole.

[0013] The first positioning plate is located at the front end of the main material channel via a lifting cylinder at the bottom.

[0014] The negative pressure pressing mold includes a lower negative pressure template and an upper negative pressure template disposed on the lower negative pressure template. The lower negative pressure template is provided with a set of pressing rod mounting holes, and the upper negative pressure template is provided with a negative pressure cavity communicating with the pressing rod mounting holes. The air pipe is connected to the negative pressure cavity.

[0015] A method for assembling a tactile switch, implemented using the aforementioned automatic tactile switch assembly machine, includes the following steps:

[0016] The negative pressure pressing rod of the pressing mechanism is brought close to the surface of the metal spring in the spring positioning groove. The negative pressure is used to suck up the metal spring and transport it to the feeding mechanism. During the transport process, the current negative pressure value needs to be detected in real time. When the negative pressure value is detected to be less than the preset value, it is determined that the negative pressure pressing rod has a leakage phenomenon. At this time, the negative pressure pressing rod is brought close to the surface of the metal spring in the spring positioning groove again to suck up the spring again.

[0017] The advantages of the automatic assembly machine and assembly method for tactile switches of the present invention are as follows: the side channel can arrange the metal springs in a uniform direction (convex surface facing up), which can effectively prevent the problem of reversed installation of the metal springs. At the same time, the pressing mechanism can effectively prevent leakage and over-suction through negative pressure detection and impact, thereby greatly improving the assembly qualification rate.

[0018] The present invention will now be further described with reference to the accompanying drawings. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the automatic assembly machine for tactile switches according to the present invention;

[0020] Figure 2 This is a schematic diagram of the feeding mechanism of the present invention;

[0021] Figure 3 This is a schematic diagram of the front end structure of the pressing mechanism of the present invention;

[0022] Figure 4 This is a schematic diagram of the rear structure of the pressing mechanism of the present invention;

[0023] Figure 5 This is a cross-sectional view of the pressing mechanism of the present invention;

[0024] Figure 6 This is a schematic diagram of the material pulling mechanism of the present invention;

[0025] Figure 7 This is a cross-sectional view of the side feed channel of the present invention;

[0026] Figure 8 This is a schematic diagram of the structure of the first positioning plate of the present invention;

[0027] Figure 9 This is a schematic diagram of the structure of the second positioning plate of the present invention;

[0028] Figure 10 This is a schematic diagram of the structure of the switch base of the present invention;

[0029] Figure 11 This is a schematic diagram of the structure of the metal spring sheet of the present invention;

[0030] Figure 12 This is a schematic diagram illustrating the working principle between the metal spring sheet and the side feed channel of the present invention.

[0031] The components include: 1. Feeding mechanism; 2. Pressing mechanism; 3. Main material channel; 4. Side material channel; 5. Material pulling belt mechanism; 6. Straight vibrator; 7. Material belt positioning groove; 8. Vibratory feeder; 9. Horizontal section; 10. Inclined section; 11. Spring sliding groove; 12. Spring positioning groove; 13. Arc-shaped surface; 14. Negative pressure pressing mold; 15. Negative pressure 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 punching rod; 26. Film positioning groove; 27. Film perforated plate; 28. Mold guide. 29. Column; 30. Buffer spring; 31. Rotating seat; 32. First impact part; 33. Second impact part; 34. Pull rod; 35. Second X-axis slide rail; 36. Second Y-axis slide rail; 37. Needle tip; 38. First positioning plate; 39. First positioning hole; 40. First conical hole; 41. First straight hole; 42. Second positioning plate; 43. Second conical hole; 44. Second straight hole; 45. Lifting cylinder; 46. Negative pressure lower template; 47. Negative pressure upper template; 48. Pressure rod mounting hole; 49. Negative pressure chamber; 50. Metal spring; 51. Switch base; 52. Material strip; 53. Tensioning wheel assembly; 54. Unwinding wheel. Detailed Implementation Example 1:

[0032] Reference Figure 1-12As shown, the automatic assembly machine for tactile switches of the present invention includes: a feeding mechanism 1 and a pressing mechanism 2. The feeding mechanism 1 and the pressing mechanism 2 can be configured as a single station or a double station as needed; 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 material pulling belt mechanism 5 arranged at the rear end of the main material channel 3, and a direct vibrator 6 providing a vibration source for the side material channels 4. The end face of the main material channel 3 is provided with a material belt positioning groove 7 through which the feeding belt 52 passes. The side material channel 4 includes a horizontal section 9 connected to the outlet of the vibrating plate 8 and an inclined section 10 connected to the horizontal section 9. The surfaces of the horizontal section 9 and the inclined section 10 are provided with a set of smoothly transitioning spring sliding grooves 11. The spring sliding grooves 11 on the inclined section 10 are provided with spring positioning grooves 12, and the spring positioning grooves 12 are provided with a raised arc-shaped surface 13. The pressing mechanism 2, located above the feeding mechanism 1, includes a negative pressure pressing mold 14, a set of hollow negative pressure pressing rods 15 located at the bottom of the negative pressure pressing mold 14, a first X-axis slide rail 16 that drives the negative pressure pressing mold 14 to move horizontally, a first Y-axis slide rail 17 that drives the negative pressure pressing mold 14 to move vertically, and a first cylinder 18 that drives the negative pressure pressing mold 14 to rotate. The negative pressure pressing mold 14 is connected to a negative pressure device via an air pipe 19. The negative pressure device is typically a vacuum pump. During operation: Several metal spring pieces 50 are poured into the vibratory plate 8. The vibration of the vibratory plate 8 causes the metal spring pieces 50 to be randomly conveyed to the spring piece sliding groove 11 of the side material channel 4. Under the vibration of the straight vibrator 6, the several random spring piece sliding grooves 11 continue to advance. When the spring piece sliding groove 11 with the convex surface facing upward slides past the spring piece positioning groove 12, it will be embedded in the groove. When the spring piece sliding groove 11 with the convex surface facing downward slides past the spring piece positioning groove 12, it will slide out of the groove under the action of the arc surface 13 and flow back into the vibratory plate 8. This achieves the orderly arrangement of the metal spring pieces 50 in the inclined section 10. Then the vibratory plate 8 and the straight vibrator 6 stop vibrating. (Note: Since a large number of metal spring pieces 50 pass through each vibration cycle, all spring piece positioning grooves 12 will basically be embedded with metal spring pieces 50.) Next, the negative pressure pressing rod 15 of the pressing mechanism 2 approaches the surface of the metal spring 50 in the spring positioning groove 12, using the negative pressure generated by the negative pressure equipment to draw in the metal spring 50 and transport it towards the feeding mechanism 1, pressing the metal spring 50 into the switch base 51, and then resetting it. Finally, the material belt mechanism 5 pulls the material belt 52 along with the switch base 51 forward to the next process. This process is repeated until the processing is completed.

[0033] Preferably, the pressing mechanism 2 further includes a film pressing mechanism 20 located behind the negative pressure pressing mold 14. The film pressing mechanism 20 includes an upper film pressing template 22 and a lower film pressing template 23 slidably mounted on a straight rail 21, a second cylinder 24 that drives the upper film pressing template 22 and the lower film pressing template 23 to move up and down, and tensioning wheel sets 53 located on both sides of the upper film pressing template 22 and the lower film pressing template 23. On the other side of the unwinding wheel 54, a winding wheel is usually also provided. The upper film pressing template 22 is provided with a film pressing rod 25 that presses against the lower film pressing template 23. The bottom of the lower film pressing template 23 is provided with a film positioning groove 26 for the film to pass through, and the bottom of the film positioning groove 26 is provided with a film perforation plate 27 that cooperates with the film pressing rod 25. The film perforation plate 27 is provided with film holes. The shape of the film pressing rod 25 and the film holes is adapted to the film shape required by the switch base 51. Before operation, the film roll (the lower end is usually the adhesive layer) is placed on the unwinding roller 54 and tensioned by the tensioning roller group 53. When the switch base 51 is conveyed to the area below the film pressing mechanism 20, the second cylinder 24 drives the upper film pressing template 22 and the lower film pressing template 23 to press down. At the same time, the film punching rod 25 punches the film, and under the constraint of the film perforation plate 27, punches the film into the required shape and adheres it to the surface of the switch base 51. This allows for the assembly of the film on the same equipment.

[0034] Preferably, a set of mold-connecting guide posts 28 is provided between the upper mold-pressing template 22 and the lower mold-pressing template 23, and a buffer spring 29 is provided on the outside of the mold-connecting guide posts 28. The lower mold-pressing template 23 is fixed to the lower end of the mold-connecting guide posts 28, and the upper mold-pressing template 22 is slidably disposed on the mold-connecting guide posts 28. By setting the mold-connecting guide posts 28, the second cylinder 24 can simultaneously drive the upper mold-pressing template 22 and the lower mold-pressing template 23 to move up and down, and the buffer spring 29 realizes the buffering and resetting of the upper mold-pressing template 22. When the lower mold-pressing template 23 is pressed down and abuts against the main material channel 3, the upper mold-pressing template 22 can continue to be pressed down, and the buffer spring 29 forms a buffer to reduce the impact force brought by the stamping.

[0035] Preferably, the first Y-axis slide rail 17 is mounted on the first X-axis slide rail 16 via a rotating seat 30. The rotating seat 30 has protruding first impact portions 31 on both sides of its upper end, and the first X-axis slide rail 16 has second impact portions 32 that cooperate with the first impact portions 31. The output shaft of the first cylinder 18 is connected to the lower end of the rotating seat 30. Because the metal spring pieces 50 are very thin and may become magnetic after vibration and friction, multiple metal spring pieces 50 can easily overlap and be sucked up by the negative pressure pressing rod 15. With the above structure, after the negative pressure pressing rod 15 has finished sucking up the metal spring pieces, the first impact portion 31 and the second impact portion 32 continuously collide with each other through the continuous extension and retraction of the first cylinder 18, thereby shaking off the excess metal spring pieces 50 and effectively solving the problem of excessive suction.

[0036] Preferably, the material pulling 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. The upper end of the material pulling rod 33 is provided with a needle tip 36. Needle holes adapted to the needle tip 36 are provided on both sides of the material strip 52 to realize the conveying of the material strip 52.

[0037] Preferably, the front end of the main material channel 3 is provided with a first positioning plate 37 that cooperates with the negative pressure pressing mold 14. The first positioning plate 37 is provided with a set of first positioning holes 38, the first positioning holes 38 including a first conical hole 39 and a first straight hole 40 located at the lower end of the first conical hole 39. After the position of the metal spring sheet 50 is corrected by the first conical hole 39 and the first straight hole 40, it is installed into the switch base 51 to ensure assembly accuracy.

[0038] Preferably, a second positioning plate 41 is provided between the side material channel 4 and the first positioning plate 37. The second positioning plate 41 has a set of second positioning holes 42 with a diameter larger than that of the first positioning hole 38. The second positioning hole 42 includes a second conical hole 43 and a second straight hole 44 at the lower end of the second conical hole 43. Since the positions of some of the metal spring pieces 50 may be significantly offset, they cannot be directly accessed into the first positioning hole 38 for correction. Therefore, initial repair can be performed through the larger diameter second positioning hole 42, and then fine repair can be performed through the first positioning hole 38 to further improve the assembly qualification rate.

[0039] Preferably, the first positioning plate 37 is positioned at the front end of the main material channel 3 via a bottom lifting cylinder 45. When assembling the metal spring 50, the first positioning plate 37 is first lowered using the lifting cylinder 45 to fit against the surface of the switch base 51, thus enabling more precise assembly. After assembly, the first positioning plate 37 is raised using the lifting cylinder 45, allowing the switch base 51 to be conveyed normally.

[0040] Preferably, the negative pressure pressing mold 14 includes a lower negative pressure template 46 and an upper negative pressure template 47 disposed on the lower negative pressure template 46. The lower negative pressure template 46 is provided with a set of pressing rod mounting holes 48, and the upper negative pressure template 47 is provided with a negative pressure cavity 49 communicating with the pressing rod mounting holes 48. The air pipe 19 communicates with the negative pressure cavity 49. The negative pressure pressing rod 15 is disposed in the pressing rod mounting hole 48, thereby realizing the negative pressure function of the negative pressure pressing mold 14. Example 2:

[0041] Reference Figure 1-12 As shown, an assembly method for a tactile switch according to the present invention, implemented using the automatic tactile switch assembly machine described in Embodiment 1, includes the following steps:

[0042] The negative pressure rod 15 of the pressing mechanism 2 is brought close to the surface of the metal spring 50 in the spring positioning groove 12. The negative pressure is used to draw in the metal spring 50 and transport it towards the feeding mechanism 1. During the transport process, the current negative pressure value needs to be monitored in real time. When the detected negative pressure value is less than a preset value, it is determined that the negative pressure rod 15 is leaking suction. At this time, the negative pressure rod 15 is brought close to the surface of the metal spring 50 in the spring positioning groove 12 again for re-suction. The preset value is usually -50 Pa. When each negative pressure rod 15 has drawn in the metal spring 50, the negative pressure value is usually -70 Pa. If one or more negative pressure rods 15 leak suction, the negative pressure value is usually much less than -50 Pa. This method effectively solves the problem of leakage by the negative pressure rod 15.

[0043] The foregoing is not intended to limit the present invention in any way. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed structure and technical content to create equivalent embodiments without departing from the scope of the present invention. However, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A machine for automatic assembly of a tactile switch, characterized in that, The application relates to a feeding mechanism (1) which comprises a horizontally arranged main material channel (3), a side material channel (4) arranged on the front end side of the main material channel (3), a material pulling belt mechanism (5) arranged on the rear end of the main material channel (3) and a straight vibrator (6) which provides vibration source for the side material channel (4), the end surface of the main material channel (3) is provided with a material belt positioning groove (7) through which a material belt (52) passes, the side material channel (4) comprises a horizontal section (9) which is connected with the material outlet of a vibrating disc (8) and an inclined section (10) which is connected with the horizontal section (9), the surfaces of the horizontal section (9) and the inclined section (10) are provided with a group of smooth elastic sheet sliding grooves (11), the elastic sheet sliding groove (11) on the inclined section (10) is provided with an elastic sheet positioning groove (12), and the elastic sheet positioning groove (12) is provided with a convex arc surface (13); a plurality of metal elastic sheets (50) are transmitted in disorder to the elastic sheet sliding groove (11) of the side material channel (4) through the vibration of the vibrating disc (8), then the plurality of disordered metal elastic sheets (50) continue to advance under the vibration of the straight vibrator (6), when the metal elastic sheet (50) with the upward convex surface slides through the elastic sheet positioning groove (12), the metal elastic sheet (50) is embedded in the groove, and when the metal elastic sheet (50) with the downward convex surface slides through the elastic sheet positioning groove (12), the metal elastic sheet (50) slides out of the groove under the action of the arc surface (13) and returns to the vibrating disc (8) to realize the ordered arrangement of the metal elastic sheets (50) in the inclined section (10). The application further relates to a material pressing mechanism (2) which is arranged above the feeding mechanism (1) and comprises a negative pressure material pressing die (14), a group of hollow negative pressure material pressing rods (15) arranged on the bottom of the negative pressure material pressing die (14), a first X-axis sliding rail (16) which drives the negative pressure material pressing die (14) to horizontally move, a first Y-axis sliding rail (17) which drives the negative pressure material pressing die (14) to vertically move and a first air cylinder (18) which drives the negative pressure material pressing die (14) to rotate, and the negative pressure material pressing die (14) is connected with a negative pressure device through an air pipe (19). During assembly, the negative pressure material pressing rod (15) of the material pressing mechanism (2) is close to the surface of the metal elastic sheet (50) in the elastic sheet positioning groove (12), the metal elastic sheet (50) is sucked and carried to the side of the feeding mechanism (1) by using negative pressure; during the carrying process, the current negative pressure value is detected in real time, when the detected negative pressure value is smaller than a preset value, it is determined that the negative pressure material pressing rod (15) has a leakage suction phenomenon, at this time, the negative pressure material pressing rod (15) is close to the surface of the metal elastic sheet (50) in the elastic sheet positioning groove (12) again to perform re-suction. ​ 2. The machine of claim 1, wherein: The pressing mechanism (2) further comprises a film pressing mechanism (20) arranged behind the negative pressure pressing die (14), the film pressing mechanism (20) comprising a film pressing upper die plate (22) and a film pressing lower die plate (23) slidably mounted on a straight rail (21), a second air cylinder (24) driving the film pressing upper die plate (22) and the film pressing lower die plate (23) to move up and down, and a tension wheel set (53) arranged on both sides of the film pressing upper die plate (22) and the film pressing lower die plate (23), the film pressing upper die plate (22) being provided with a film punching rod (25) punched on the film pressing lower die plate (23), the film pressing lower die plate (23) being provided with a film positioning groove (26) at the bottom for the film to pass through, and the film positioning groove (26) being provided with a film hole plate (27) at the bottom matched with the film punching rod (25).

3. The machine of claim 2, wherein: A set of die linking guide columns (28) are arranged between the film pressing upper die plate (22) and the film pressing lower die plate (23), and a buffer spring (29) is arranged outside the die linking guide columns (28), the film pressing lower die plate (23) being fixed to the lower end of the die linking guide columns (28), and the film pressing upper die plate (22) being slidably arranged on the die linking guide columns (28).

4. The machine of claim 1, wherein: The first Y-axis slide rail (17) is mounted 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) being provided with a protruding first impact part (31), the first X-axis slide rail (16) being provided with a second impact part (32) matched with the first impact part (31), and the output shaft of the first air cylinder (18) being connected to the lower end of the rotating seat (30).

5. The machine of claim 1, wherein: The material pulling belt mechanism (5) comprises a material pulling rod (33), a second X-axis slide rail (34) and a second Y-axis slide rail (35) driving the material pulling rod (33) to move horizontally and up and down, and the upper end of the material pulling rod (33) being provided with a needle tip part (36).

6. The machine of claim 1, wherein: The front end of the main material channel (3) is provided with a first positioning plate (37) matched with the negative pressure pressing die (14), the first positioning plate (37) being provided with a set of first positioning holes (38), the first positioning holes (38) comprising a first tapered hole (39) and a first straight hole (40) arranged at the lower end of the first tapered hole (39).

7. The machine of claim 6, wherein: A second positioning plate (41) is arranged between the side material channel (4) and the first positioning plate (37), the second positioning plate (41) being provided with a set of second positioning holes (42) with a larger hole diameter than the first positioning holes (38), the second positioning holes (42) comprising a second tapered hole (43) and a second straight hole (44) arranged at the lower end of the second tapered hole (43).

8. The machine of claim 6, wherein: 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.

9. The machine of claim 1, wherein: The negative pressure pressure-die (14) comprises a negative pressure lower die plate (46) and a negative pressure upper die plate (47) arranged on the negative pressure lower die plate (46), a group of pressure-die rod mounting holes (48) are arranged on the negative pressure lower die plate (46), and a negative pressure cavity (49) in communication with the pressure-die rod mounting holes (48) is arranged on the negative pressure upper die plate (47); the air pipe (19) is in communication with the negative pressure cavity (49).

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