Automatic manufacturing equipment for motor punching sheet

Abstract

The invention belongs to the technical field of steel punching, and particularly relates to automatic manufacturing equipment for a motor punching sheet. The invention provides automatic manufacturing equipment for a motor punching sheet, which comprises a punching machine, a placing plate arranged at the lower part of the punching machine, a lifting seat driven by a hydraulic cylinder arranged at the upper part of the punching machine, a fixed column connected to the lower part of the lifting seat, a sliding seat arranged on the fixed column and capable of sliding back and forth, and a punching head arranged on the sliding seat, the left side of the lifting base is rotationally connected with a hinge rod, the lower end of the hinge rod is rotationally connected with a bulldozing cylinder, and an elastic piece is connected between the hinge rod and the lifting base. Steel is intermittently conveyed leftwards, the hydraulic cylinder is controlled to enable the lifting base, the fixing column, the sliding base, the punching head, the bulldozing barrel and the pressing rod to move downwards, the pressing rod presses the steel to avoid displacement of the steel, and under the action of the elastic piece, the bulldozing barrel rolls on the surface of the steel, so that the steel is bulldozed, the punching head punches the steel, and the flatness and the punching effect of the steel are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of steel stamping, and particularly relates to an automatic manufacturing device for motor punching sheets. Background Art

[0002] Stamping is a forming process method that relies on a press to apply an external force to a sheet material to separate the sheet material, thereby obtaining a workpiece with the required shape and size. When stamping a sheet material, specifically, the sheet material is conveyed below the stamping head, and the stamping head is controlled to stamp the sheet material.

[0003] However, the existing stamping equipment lacks effective flattening and positioning structures. During the stamping process of a very long sheet material, uneven parts such as wrinkles may appear on the surface of the sheet material during transportation, and the problem of sheet material displacement may also occur during stamping, making it difficult to ensure the flatness of the sheet material and resulting in poor final stamping effect of the sheet material. Summary of the Invention

[0004] In view of this, the present invention provides an automatic manufacturing device for motor punching sheets.

[0005] The technical implementation solution of the present invention is as follows: an automatic manufacturing device for motor punching sheets, including a stamping machine, a placement plate is installed below the stamping machine, a lifting seat driven by a hydraulic cylinder is installed above the stamping machine, a fixed column is connected to the lower part of the lifting seat, a sliding seat that slides back and forth is provided on the fixed column, a stamping head is installed on the sliding seat, a hinge rod is rotatably connected to the left side of the lifting seat, a flattening cylinder is rotatably connected to the lower end of the hinge rod, and an elastic member is connected between the hinge rod and the lifting seat.

[0006] More preferably, the automatic manufacturing device for motor punching sheets further includes a connecting column and a pressing rod. A connecting column is connected to the lifting seat, a sliding pressing rod is provided on the connecting column, and a compression spring is connected between the pressing rod and the connecting column.

[0007] More preferably, the automatic manufacturing device for motor punching sheets further includes a mounting frame I. A mounting frame I is provided on the left side of the stamping machine. A lifting column is provided on the mounting frame I. A row of positioning pins are connected to the bottom of the lifting column. A rear side plate is connected to the rear of the mounting frame I. A front and rear moving support plate is provided at the front of the mounting frame I. A front side plate is connected to the top of the support plate. A translation block that slides back and forth is provided on the mounting frame I. The support plate is connected to the translation block. A screw rod that is threadedly connected to the translation block is rotatably connected to the mounting frame I.

[0008] More preferably, the automatic manufacturing equipment for motor punching sheets further includes a moving mechanism. The moving mechanism includes a first rack. Inside the fixed column, there is a first rack that slides back and forth and a second rack that slides back and forth. Inside the fixed column, there is a connecting block. On the connecting block, there is a coaxially rotating pinion and a large gear rotatably connected. The first rack meshes with the pinion, and the second rack meshes with the large gear. The sliding seat is connected to the first rack. At the front end of the second rack, there is a connecting rod rotatably connected. At the end of the connecting rod away from the second rack, there is a first rotating rod rotatably connected. On the front side plate, there is a long hole. At the rear end of the first rotating rod, there is a roller located in the long hole.

[0009] More preferably, the automatic manufacturing equipment for motor punching sheets further includes a cutting mechanism. The cutting mechanism includes a second mounting frame. A second mounting frame is connected to the first mounting frame. On the second mounting frame, there is a belt conveyor. At the upper part of the second mounting frame, there is a guide rod. On the guide rod, there are two sliding guide rails sliding in opposite directions. On the sliding guide rails, there are sliding sliders. On the sliders, there are laser cutting heads mounted.

[0010] More preferably, the cutting mechanism further includes an electric push rod. An electric push rod is connected to the second mounting frame. On the telescopic rod of the electric push rod, there is a moving block. Between the moving block and the two sliding guide rails, there are second rotating rods rotatably connected.

[0011] More preferably, the cutting mechanism further includes a material guiding plate. An inclined material guiding plate is connected to the second mounting frame.

[0012] More preferably, the automatic manufacturing equipment for motor punching sheets further includes a lifting rod and a triangular block. At the lower part of the second mounting frame, there is a sliding lifting rod. Between the lifting rod and the second mounting frame, there is a return spring connected. At the front end of the lifting rod, there is a limiting end with an inclined surface. At the rear end of the lifting rod, there is a contact end. A triangular block is connected to one of the sliders. When the triangular block moves backward, the triangular block will contact the contact end to squeeze the lifting rod to descend.

[0013] Compared with the prior art, the present invention has the following advantages: 1. The steel is intermittently conveyed to the left. The control hydraulic cylinder makes the lifting seat, fixed column, sliding seat, punching head, flattening cylinder, and pressing rod move downward. The pressing rod holds the steel to prevent the steel from displacing. Under the action of the elastic member, the flattening cylinder rolls on the surface of the steel, thereby flattening the steel, and the punching head punches the steel, improving the flatness of the steel and the punching effect.

[0014] 2. The steel is continuously conveyed. The rear side plate contacts the rear side of the steel, and the front side plate contacts the front side of the steel. The steel is limited in the front and rear directions by the rear side plate and the front side plate. The control linear motor makes the slider and the laser cutting head move backward. The laser cutting head cuts the steel, and the belt conveyor conveys the steel. The waste generated by cutting falls along the material guiding plate for discharging.

[0015] 3. Control the electric push rod to drive the moving block to translate, drive the two sliding guide rails to move away from or close to each other in the left-right direction through the second rotating rod, and the slider and the laser cutting head move along with the sliding guide rails, so that the distance between the two laser cutting heads in the left-right direction can be adjusted.

[0016] 4. The steel is extruded against the limiting end, causing the lifting rod to descend. When the punching hole of the steel aligns with the limiting end, the reset spring causes the lifting rod to rise, and the limiting end passes through the punching hole of the steel to limit the steel through the limiting end, preventing the steel from shifting during the cutting process and improving the cutting accuracy. After the cutting is completed, the triangular block extrudes the contact end to cause the lifting rod to descend, and the limiting end leaves the punching hole of the steel.

[0017] 5. By rotating the screw rod, the translation block, the support plate, the front side plate, the roller, the connecting rod, the first rotating rod, and the second rack move forward. The distance between the front side plate and the rear side plate adapts to the width of the steel. The second rack causes the large gear and the small gear to rotate, and the first rack, the sliding seat, and the punching head move forward. The forward movement distance of the punching head is half of the forward movement distance of the front side plate, and the punching head synchronously moves to the center of the steel, with high automation and synchronization in adjustment. Description of the Drawings

[0018] Figure 1 It is a schematic diagram of the overall structure of the present invention.

[0019] Figure 2 It is a schematic diagram of the structure of the punching machine, the placing plate, the lifting seat, the fixing column, the first rotating rod, the articulated rod, the pushing cylinder, the connecting column, the pressing rod, and the elastic member of the present invention.

[0020] Figure 3 It is a partial sectional structure schematic diagram of the lifting seat, the fixing column, the sliding seat, the punching head, the articulated rod, the pushing cylinder, the connecting column, the pressing rod, and the elastic member of the present invention.

[0021] Figure 4 It is a schematic diagram of the structure of the first mounting frame, the lifting column, the positioning pin, the rear side plate, the support plate, the front side plate, the translation block, and the screw rod of the present invention.

[0022] Figure 5 It is a partial sectional structure schematic diagram of the fixing column, the sliding seat, the punching head, and the moving mechanism of the present invention.

[0023] Figure 6 It is a schematic diagram of the structure of the first rack, the connecting block, the small gear, the large gear, and the second rack of the present invention.

[0024] Figure 7 It is a schematic diagram of the structure of the support plate, the front side plate, the connecting rod, and the roller of the present invention.

[0025] Figure 8 It is a schematic diagram of the structure of the cutting mechanism of the present invention.

[0026] Figure 9 Schematic diagram of the connection relationship between the lifting rod and the triangular block of the present invention.

[0027] The markings of each component in the attached drawings are as follows: 1, punching machine; 2, placement plate; 3, lifting seat; 4, fixed column; 5, sliding seat; 51, first rack; 52, connecting block; 53, pinion; 54, large gear; 55, second rack; 56, connecting rod; 57, roller; 58, first rotating rod; 59, long hole; 6, punching head; 60, steel; 7, articulated rod; 70, rotating shaft part; 8, flattening cylinder; 81, connecting column; 82, pressing rod; 9, elastic member; 101, first mounting frame; 102, lifting column; 103, positioning pin; 104, rear side plate; 105, support plate; 106, front side plate; 107, translation block; 108, screw rod; 110, material guiding plate; 111, second mounting frame; 112, belt conveyor; 113, guide rod; 114, sliding guide rail; 115, slider; 116, laser cutting head; 117, electric push rod; 118, moving block; 119, second rotating rod; 121, lifting rod; 122, limiting end; 123, contact end; 124, triangular block. Detailed implementation mode

[0028] An automatic manufacturing device for motor laminations, referring to Figures 1-3 , includes a punching machine 1, a placement plate 2, a lifting seat 3, a fixed column 4, a sliding seat 5, a punching head 6, an articulated rod 7, a flattening cylinder 8 and an elastic member 9. The structures and principles of the punching machine 1 and the punching head 6 are prior arts. A placement plate 2 is installed below the punching machine 1, and a lifting seat 3 driven by a hydraulic cylinder is installed above the punching machine 1. A fixed column 4 is fixedly connected to the lower part of the lifting seat 3. A sliding seat 5 that slides back and forth is provided on the fixed column 4. A punching head 6 is installed on the sliding seat 5. An articulated rod 7 is rotatably connected to the left side of the lifting seat 3. The articulated rod 7 includes a rotating shaft part 70 at its upper end. The articulated rod 7 rotates around the rotating shaft part 70. A pair of flattening cylinders 8 are rotatably connected to the lower end of the articulated rod 7. An elastic member 9 is fixedly connected between the middle part of the articulated rod 7 and the lifting seat 3. The elastic member 9 is a tension spring.

[0029] Referring to Figures 1-3 , the automatic manufacturing device for motor laminations further includes a connecting column 81 and a pressing rod 82. A connecting column 81 is fixedly connected to the right side of the lifting seat 3. A pressing rod 82 that slides up and down is provided on the connecting column 81. A compression spring is fixedly connected between the pressing rod 82 and the connecting column 81.

[0030] Referring to Figure 1 and Figure 4, the automatic manufacturing equipment for motor punching sheets further includes a first mounting frame 101, a lifting column 102, positioning pins 103, a rear side plate 104, a support plate 105, a front side plate 106, a translation block 107, and a screw rod 108. There is a first mounting frame 101 on the left side of the punching machine 1. A lifting column 102 driven by a linear actuator is provided on the first mounting frame 101. A row of positioning pins 103 is connected to the bottom of the lifting column 102. The rear part of the first mounting frame 101 is fixedly connected to a rear side plate 104. A support plate 105 that moves back and forth is provided at the front of the first mounting frame 101. The front side of the top of the support plate 105 is fixedly connected to a front side plate 106. A translation block 107 that slides back and forth is provided at the front of the first mounting frame 101. The support plate 105 is fixedly connected to the translation block 107. A screw rod 108 is rotatably connected to the first mounting frame 101, and the screw rod 108 is threadedly connected to the translation block 107.

[0031] Reference Figure 1 , Figure 2 , Figure 5 , Figure 6 and Figure 7 , the automatic manufacturing equipment for motor punching sheets further includes a moving mechanism. The moving mechanism includes a first rack 51, a connecting block 52, a small gear 53, a large gear 54, a second rack 55, a connecting rod 56, a roller 57, and a first rotating rod 58. A first rack 51 that slides back and forth and a second rack 55 that slides back and forth are provided inside the fixed column 4. A connecting block 52 is fixedly connected to the front side inside the fixed column 4. A coaxially rotating small gear 53 and a large gear 54 are rotatably connected to the connecting block 52. The number of teeth of the small gear 53 is half of the number of teeth of the large gear 54. The first rack 51 meshes with the small gear 53, and the second rack 55 meshes with the large gear 54. The sliding seat 5 is connected to the first rack 51. The front end of the second rack 55 extends outside the fixed column 4. A connecting rod 56 is rotatably connected to the front end of the second rack 55. One end of the connecting rod 56 away from the second rack 55 is rotatably connected to a first rotating rod 58. A long hole 59 is opened on the front side plate 106. The rear end of the first rotating rod 58 is connected to a roller 57, and the roller 57 is located inside the long hole 59.

[0032] Reference Figure 1 , Figure 8 and Figure 9, the automated manufacturing equipment for motor punching sheets further includes a cutting mechanism. The cutting mechanism includes a second mounting frame 111, a belt conveyor 112, guide rods 113, sliding guide rails 114, sliders 115, and a laser cutting head 116. The left side of the first mounting frame 101 is fixedly connected to the second mounting frame 111. The belt conveyor 112 is mounted on the second mounting frame 111. The belt conveyor 112 is a prior art and includes two spaced conveyor belts. Two symmetric front and rear guide rods 113 are connected to the upper part of the second mounting frame 111. Two sliding guide rails 114 with opposite sliding directions are slidably connected between the two guide rods 113. The sliding guide rails 114 are each provided with a slider 115 that slides back and forth. Linear motors for driving the sliders 115 to slide are mounted on the sliding guide rails 114. Laser cutting heads 116 are mounted on the sliders 115. The cutting mechanism further includes an electric push rod 117, a moving block 118, and a second rotating rod 119. The electric push rod 117 is bolted to the rear of the second mounting frame 111. A moving block 118 is connected to the telescopic rod of the electric push rod 117. Second rotating rods 119 are rotatably connected between the moving block 118 and the middle parts of the two sliding guide rails 114. The cutting mechanism further includes a material guiding plate 110. An inclined material guiding plate 110 is fixedly connected to the lower left side of the second mounting frame 111.

[0033] Reference Figure 8 and Figure 9 , the automated manufacturing equipment for motor punching sheets further includes a lifting rod 121 and a triangular block 124. A vertically sliding lifting rod 121 is provided at the lower part of the second mounting frame 111. A return spring is connected between the lifting rod 121 and the second mounting frame 111. The front end of the lifting rod 121 has a limiting end 122 with an inclined surface, and the limiting end 122 extends out between the two spaced conveyor belts. The rear end of the lifting rod 121 has a contact end 123. A triangular block 124 is connected to the right slider 115. When the triangular block 124 moves backward, the triangular block 124 will contact the contact end 123 to squeeze the lifting rod 121 to descend.

[0034] In this embodiment, the automated manufacturing equipment for the motor punching sheet can be specifically used to manufacture the motor punching sheet. The steel material 60 is intermittently conveyed to the left by the externally provided conveying equipment. The steel material 60 passes through the placing plate 2, the support plate 105, and the belt conveyor 112 from right to left in sequence. Control the hydraulic cylinder to drive the lifting seat 3 to descend. The lifting seat 3 drives the fixed column 4, the sliding seat 5, the first rack 51, the connecting block 52, the pinion 53, the big gear 54, the second rack 55, the punching head 6, the articulated rod 7, the leveling cylinder 8, the connecting column 81, and the pressing rod 82 to move downward together. Since the second rack 55 descends, the first rotating rod 58 will rotate, and the roller 57 rolls to the left in the long hole 59. When the pressing rod 82 contacts the surface of the steel material 60, the pressing rod 82 stops descending. The pressing rod 82 presses the steel material 60 to prevent the steel material 60 from displacing. When the leveling cylinder 8 contacts the surface of the steel material 60, the leveling cylinder 8 stops descending, while the lifting seat 3, the sliding seat 5, the first rack 51, the connecting block 52, the pinion 53, the big gear 54, the second rack 55, the punching head 6, and the connecting column 81 continue to descend, and the compression spring compresses. The descending lifting seat 3 drives the articulated rod 7 to rotate clockwise around the rotating shaft part 70, and the elastic member 9 deforms. Under the action of the elastic member 9, the leveling cylinder 8 rolls on the surface of the steel material 60, and the leveling cylinder 8 levels the steel material 60. The punching head 6 that continues to descend punches the steel material 60. During the punching process, the flatness of the steel material 60 is improved by the cooperation of the leveling cylinder 8 and the pressing rod 82, thereby improving the punching effect.

[0035] Then control the hydraulic cylinder to drive the lifting seat 3 to rise and reset, driving the fixed column 4, the sliding seat 5, the first rack 51, the connecting block 52, the pinion 53, the big gear 54, the second rack 55, the punching head 6, the articulated rod 7, the leveling cylinder 8, the connecting column 81, and the pressing rod 82 to rise and reset. The pressing rod 82 and the leveling cylinder 8 are separated from the steel material 60, and the compression spring and the elastic member 9 are restored. The articulated rod 7 rotates counterclockwise around the rotating shaft part 70 to reset.

[0036] The steel material 60 is continuously conveyed to the left. The rear side plate 104 contacts the rear side of the steel material 60, and the front side plate 106 contacts the front side of the steel material 60. Thus, the steel material 60 is limited in the front-rear direction by the rear side plate 104 and the front side plate 106. Control the linear actuator to drive the lifting column 102 to descend, driving the positioning pin 103 to descend. The positioning pin 103 presses the steel material 60 to prevent the steel material 60 from moving during the punching process. Control the linear motor to drive the two sliders 115 to move backward, driving the laser cutting head 116 to move backward. At the same time, control the two laser cutting heads 116 to cut the steel material 60. Then control the belt conveyor 112 to convey the cut steel material forward, and the waste generated by the cutting falls along the material guide plate 110 for discharging.

[0037] When it is necessary to adjust the cutting width, the control electric push rod 117 is driven to move the moving block 118 to translate in the front-back direction. Driven by the second rotating rod 119, the two sliding guide rails 114 move away from or close to each other in the left-right direction. The slider 115 and the laser cutting head 116 move in the left-right direction along with the sliding guide rails 114, so that the distance between the two laser cutting heads 116 in the left-right direction can be adjusted.

[0038] When the steel material 60 moving to the left contacts the limiting end 122, under the action of gravity, the steel material 60 presses the limiting end 122, causing the lifting rod 121 to descend and the return spring to deform. After the punching hole of the steel material 60 aligns with the limiting end 122, the return spring restores, causing the lifting rod 121 to rise and reset. The limiting end 122 passes through the punching hole of the steel material 60, thereby limiting the steel material 60 through the limiting end 122 and preventing the steel material 60 from shifting during the cutting process, improving the cutting accuracy; the rearward-moving slider 115 drives the triangular block 124 to move backward. After the cutting is completed, the triangular block 124 will contact the contact end 123. The triangular block 124 presses the contact end 123 through the inclined surface, causing the lifting rod 121 to descend and the return spring to deform. The limiting end 122 leaves the punching hole of the steel material 60, and the belt conveyor 112 can convey the cut steel material forward.

[0039] When it is necessary to punch the steel material 60 with a larger width, the screw rod 108 is manually rotated. Under the action of the threaded connection, the translation block 107 slides forward, driving the support plate 105 and the front side plate 106 to move forward, so that the distance between the front side plate 106 and the rear side plate 104 adapts to the width of the steel material 60. At the same time, the front side plate 106 will drive the roller 57, the connecting rod 56, the first rotating rod 58 and the second rack 55 to move forward. Under the meshing action, the second rack 55 rotates the large gear 54, and the large gear 54 drives the small gear 53 to rotate. The rotating small gear 53 makes the first rack 51 move forward. The sliding seat 5 and the punching head 6 move forward along with the first rack 51. Since the number of teeth of the small gear 53 is half of the number of teeth of the large gear 54, the forward movement distance of the first rack 51 is half of the forward movement distance of the second rack 55, and the forward movement distance of the punching head 6 is half of the forward movement distance of the front side plate 106, so that the position of the punching head 6 can be synchronously moved to the center of the steel material 60. The adjustment is automatic and has high synchronism, and the steel material 60 with a larger width can be punched.

Claims

1. An automated manufacturing device for motor punching sheets, including a punching machine (1), characterized in that: A placing plate (2) is installed at the lower part of the stamping machine (1). An elevating seat (3) driven by a hydraulic cylinder is installed at the upper part of the stamping machine (1). A fixed column (4) is connected to the lower part of the elevating seat (3). A sliding seat (5) that slides back and forth is arranged on the fixed column (4). A stamping head (6) is installed on the sliding seat (5). A hinged rod (7) is rotatably connected to the left side of the elevating seat (3). A pushing and leveling cylinder (8) is rotatably connected to the lower end of the hinged rod (7). An elastic member (9) is connected between the hinged rod (7) and the elevating seat (3).

2. The automated manufacturing equipment for a motor punching sheet according to claim 1, characterized in that: The automatic manufacturing equipment for motor punching sheets further includes a connecting column (81) and a pressing rod (82). The connecting column (81) is connected to the elevating seat (3). A sliding pressing rod (82) is arranged on the connecting column (81). A compression spring is connected between the pressing rod (82) and the connecting column (81).

3. An automated manufacturing device for a motor punching sheet according to claim 2, characterized in that: The automatic manufacturing equipment for motor punching sheets further includes a first mounting frame (101). A first mounting frame (101) is arranged to the left of the stamping machine (1). A lifting column (102) is arranged on the first mounting frame (101). A row of positioning pins (103) are connected to the bottom of the lifting column (102). A rear side plate (104) is connected to the rear part of the first mounting frame (101). A support plate (105) that moves back and forth is arranged at the front part of the first mounting frame (101). A front side plate (106) is connected to the top of the support plate (105). A translation block (107) that slides back and forth is arranged on the first mounting frame (101). The support plate (105) is connected to the translation block (107). A screw rod (108) that is rotatably connected to the first mounting frame (101) and is threadedly connected to the translation block (107) is provided on the first mounting frame (101).

4. An automated manufacturing device for a motor punching sheet according to claim 3, characterized in that: The automatic manufacturing equipment for motor punching sheets further includes a moving mechanism. The moving mechanism includes a first rack (51). A first rack (51) that slides back and forth and a second rack (55) that slides back and forth are arranged inside the fixed column (4). A connecting block (52) is connected inside the fixed column (4). A small gear (53) and a large gear (54) that rotate coaxially are rotatably connected to the connecting block (52). The first rack (51) meshes with the small gear (53). The second rack (55) meshes with the large gear (54). The sliding seat (5) is connected to the first rack (51). A connecting rod (56) is rotatably connected to the front end of the second rack (55). A first rotating rod (58) is rotatably connected to the end of the connecting rod (56) away from the second rack (55). A long hole (59) is formed on the front side plate (106). A roller (57) located inside the long hole (59) is connected to the rear end of the first rotating rod (58).

5. The automated manufacturing equipment for a motor punching sheet according to claim 4, characterized in that: The automated manufacturing equipment for the motor punching sheet further includes a cutting mechanism. The cutting mechanism includes a second mounting frame (111). The second mounting frame (111) is connected to the first mounting frame (101). A belt conveyor (112) is mounted on the second mounting frame (111). A guide rod (113) is connected to the upper part of the second mounting frame (111). Two sliding guide rails (114) with opposite sliding directions are slidably connected to the guide rod (113). Sliders (115) are provided on the sliding guide rails (114). Laser cutting heads (116) are mounted on the sliders (115).

6. An automated manufacturing device for a motor punching sheet according to claim 5, characterized in that: The cutting mechanism further includes an electric push rod (117). The electric push rod (117) is connected to the second mounting frame (111). A moving block (118) is connected to the telescopic rod of the electric push rod (117). A second rotating rod (119) is rotatably connected between the moving block (118) and the two sliding guide rails (114).

7. An automated manufacturing device for a motor punching sheet according to claim 6, characterized in that: The cutting mechanism further includes a guide plate (110). An inclined guide plate (110) is connected to the second mounting frame (111).

8. The automated manufacturing equipment for a motor punching sheet according to claim 7, characterized in that: The automated manufacturing equipment for the motor punching sheet further includes a lifting rod (121) and a triangular block (124). A sliding lifting rod (121) is provided at the lower part of the second mounting frame (111). A return spring is connected between the lifting rod (121) and the second mounting frame (111). The front end of the lifting rod (121) has a limiting end (122) with an inclined surface. The rear end of the lifting rod (121) has a contact end (123). A triangular block (124) is connected to one of the sliders (115). When the triangular block (124) moves backward, the triangular block (124) will contact the contact end (123) to squeeze the lifting rod (121) to descend.

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