Self-locking ejection mechanism and method applicable to oil pan machining fixtures

Abstract

This invention relates to a self-locking ejection mechanism and method for oil pan machining fixtures, belonging to the field of fixture technology. It includes a self-locking mechanism and an ejection mechanism. The self-locking mechanism comprises a drive pin, a lever, and a self-locking pin. The ejection mechanism comprises a push rod, a swing rod, a rotating shaft, a connecting rod, a handle, and a buckle. One end of the handle is connected to the lower shaft of the connecting rod, and the other end is connected to the buckle. One end of the rotating shaft is connected to the upper end of the connecting rod, and the other end is connected to the fixture. The drive pin passes through a slot on the push rod and is fixed therethrough. The waist hole end of the lever passes through the slot and is sleeved with the drive pin. One end of the swing rod is bolted to the rotating shaft, and the other end is connected to the push rod. When the swing rod rotates, the push rod moves back and forth, driving the drive pin and the lever to move, thereby pushing the self-locking pin inward, achieving automatic ejection of the workpiece. The overall structure of this invention is interconnected, and the oil pan can be quickly ejected by operating the handle alone. The operation is simple and the ejection speed is fast.

Description

Technical Field

[0001] This invention belongs to the field of fixture technology, specifically, it relates to a self-locking ejection mechanism and self-locking ejection method suitable for oil pan processing fixtures. Background Technology

[0002] The oil pan is the lower part of the crankcase, also known as the lower crankcase. Its function is to seal the crankcase, acting as an outer shell for the oil reservoir, preventing impurities from entering, collecting and storing the lubricating oil flowing back from the various friction surfaces of the diesel engine, dissipating some heat, and preventing oil oxidation. Currently, the oil pan is machined using a manual clamp. This clamp uses two locating pin holes on the back for positioning and two threaded holes for tightening. The front of the oil pan, including the through holes, locating holes, and dipstick hole, is machined. Figure 1 As shown. Because the front side is a rough surface, the cutting force required during machining is relatively large. Therefore, four threaded locking devices were added to the clamps on both sides of the oil pan to increase rigidity and ensure the stability of machining quality. The clamp structure is as follows. Figure 2 As shown.

[0003] The existing fixture design's operation process is as follows: ① During loading, the overhead crane lifts the workpiece onto the manual fixture and pushes it horizontally into the positioning pin; ② Tighten the tensioning screws with a pneumatic tightening gun; ③ Tighten the four side locking devices manually; ④ During unloading, loosen the tensioning screws with a pneumatic tightening gun; ⑤ Loosen the four side locking devices manually; ⑥ Pull the workpiece horizontally to release it from the pins, and then use the overhead crane to lift the workpiece away from the fixture. This cycle is repeated to achieve the loading and unloading of the oil pan.

[0004] In actual on-site processing, the fixture design requires two operators to complete the operation. One operator is responsible for holding the workpiece in place and lifting / moving it from outside the machine tool, while the other operator enters the machine tool's processing area to tighten / loosen the tension screws with a pneumatic wrench, and finally tighten or loosen the locking device. The operator entering the machine tool places one foot on the side of the fixture and the other on the chip removal surface of the machine tool. Because the sides of the horizontal machining area are generally designed with large slopes to prevent chip accumulation, it is difficult to find a suitable foothold, requiring time to adjust posture and posing a significant safety hazard due to the risk of slipping. To reduce loading and unloading time, the operator also tried tightening the four side locking devices first, rotating the worktable 180°, and then tightening the tension screws to avoid spending too much time entering the processing area to tighten and loosen the tension screws. Since the four locking devices on the side are on the surface of the blank, when the locking screws are tightened first, the locking screws contact the blank surface and generate a radial force, causing the workpiece to pull outward. The workpiece positioning surface and the fixture positioning surface are not tightly fitted. When the tension screws are tightened, the workpiece is deformed by force, rather than having the effect of increasing rigidity as an auxiliary support.

[0005] Meanwhile, difficulty often arises in detaching the fixture locating pin from the workpiece locating pin hole, requiring the operator to use a very long pry bar to remove the workpiece from the fixture locating pin. Since the pry bar's force application point is often not at the workpiece's center of gravity, it is prone to unilateral force, causing the locating pin to bend and deform under stress, further exacerbating the difficulty in detaching the workpiece from the fixture locating pin. Summary of the Invention

[0006] To address the problems existing in the background art, the present invention provides a self-locking ejection mechanism suitable for oil pan processing fixtures, which can greatly simplify the ejection process and reduce the difficulty of ejection.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0008] The self-locking ejection mechanism for oil pan processing fixtures includes a self-locking mechanism and an ejection mechanism;

[0009] The self-locking mechanism includes a drive pin, a lever, a lever support, a self-locking support, a screw plug, a spring, and a self-locking pin;

[0010] The unloading mechanism includes a push rod, a swing rod, a rotating shaft, a bushing, a connecting rod, a handle pin, a handle, a buckle, and a buckle support;

[0011] The self-locking support has a pin channel, in which the self-locking pin, spring, and screw plug are arranged sequentially from the inside to the outside; the self-locking pin has a clearance groove. The lever is an obtuse-angled L-shaped lever, which is connected to the lever support shaft at the corner via a spindle. One end of the lever has a waist hole, and the other end is inserted into the clearance groove of the self-locking pin to prevent the lever from contacting the self-locking pin during loading self-locking. When releasing the self-locking, the outer side of the bottom end of the lever contacts the self-locking pin, driving the self-locking pin to retract and release the self-locking.

[0012] The buckle is fixed on the buckle support. One end of the handle is connected to the lower shaft of the connecting rod through a handle pin, and the other end is engaged with the buckle. One end of the rotating shaft is connected to the upper end of the connecting rod through a bushing, and the other end is connected to the clamp. The push rod is set perpendicular to the rotating shaft, and the push rod has a through groove and a recess. The waist hole end of the lever passes through the through groove on the push rod, and the driving pin passes through the through groove and the waist hole on the lever and is fixed to the push rod. The recess is located behind the through groove. One end of the swing rod is bolted to the rotating shaft, and the other end is inserted into the recess and connected to the push rod. When the swing rod rotates, the push rod moves back and forth.

[0013] Furthermore, the push rod is also provided with a push block, a front end limiting flange of the push rod, and a rear end limiting flange of the push rod;

[0014] The front limiting flange and the rear limiting flange of the push rod are respectively set at the front and rear ends of the push rod. The front limiting flange of the push rod is slidably sleeved with the push rod, and the rear end of the sleeved section is provided with an upper stepped surface that limits the front limiting flange.

[0015] The front and rear limiting flanges of the push rod are fixed to the supplementary machining holes on the fixture base, and the push block is fixed to the top front side of the push rod with bolts.

[0016] The other end of the shaft is fixed to the fixture base with bolts via a shaft fixing flange; the shaft fixing flange end has an elastic retaining ring mounting groove, and a flange retaining ring is installed in the elastic retaining ring mounting groove.

[0017] Furthermore, the feed surface at the outer end of the self-locking pin is an inclined surface.

[0018] Furthermore, the lever support is fixed to the reinforcing rib of the clamp base, and the snap-on support is fixed to the clamp base.

[0019] The self-locking unloading method for oil pan machining fixtures described above uses the aforementioned self-locking unloading mechanism for automatic unloading. The automatic unloading includes the following steps:

[0020] S1. Rotate the handle 90° clockwise to disengage it from the latch and make it flush with the connecting rod.

[0021] S2, press the handle down to make the rotating shaft rotate clockwise, and the rotating shaft drives the rocker arm to rotate clockwise at the same time; because the cylindrical head of the rocker arm is tangent to the side of the groove of the push rod, the push rod is forced to move towards the workpiece, the drive pin fixed on the push rod moves towards the workpiece, the waist hole of the lever moves with the drive pin, and rotates counterclockwise around the spindle at the same time, the lower end of the lever extends outward, pushing the self-locking pin to retract into the pin channel, and releasing the workpiece self-locking.

[0022] S3, continue pressing down the handle, the push rod continues to move forward until the upper step surface of the push rod contacts the front limit flange of the push rod and stops moving. At this time, the push block reaches the farthest end; the workpiece is completely separated from the positioning pin due to the pushing force of the push block, and the workpiece is removed from the pin.

[0023] The self-locking ejection method for oil pan machining fixtures uses the aforementioned self-locking ejection mechanism for self-locking. The self-locking process is as follows:

[0024] S1, the workpiece moves upward along the self-locking support. During the upward movement, the self-locking pin is subjected to axial force due to its contact with the edge of the workpiece and moves outward to both sides of the workpiece to avoid it, so that the workpiece can continue to enter and be contacted to the positioning surface of the fixture.

[0025] S2, as the workpiece flange continues to advance, the flange disengages from the self-locking pin guide surface. The spring force acts on the self-locking pin, causing the self-locking pin to spring back to the contact point with the workpiece flange, thus achieving workpiece self-locking.

[0026] The beneficial effects of this invention are:

[0027] This invention utilizes a transmission connection of a handle, connecting rod, swing arm, push rod, drive pin, lever, and self-locking pin. The workpiece can be disengaged by operating the handle. During workpiece processing, the entire transmission mechanism is locked by engaging the handle with a latch, preventing disengagement. The self-locking pin's design ensures that it does not affect the disengagement mechanism during locking and can be pushed to release the pin during disengagement. The connection between the drive pin and the lever, along with the lever's mandrel-fixed structure, converts the linear movement of the drive pin into the rotation of the lever, thereby pushing the self-locking pin.

[0028] The overall structure of this invention is interconnected, and the oil pan can be quickly unlocked by operating the handle alone. It is simple to operate and the pin release speed is fast. Compared with the prior art, it reduces the probability of bending and deformation of the positioning pin on the oil pan. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the oil pan structure;

[0030] Figure 2 It is an existing technology oil pan clamp

[0031] Figure 3 This is a schematic diagram of the material removal mechanism of the present invention;

[0032] Figure 4 This is a schematic diagram of the self-locking mechanism of the present invention;

[0033] Figure 5 This is a diagram showing the overall structure of the invention in use.

[0034] Figure 6 This is a diagram showing the overall structure of the present invention in use (omitting parts of the fixture structure);

[0035] Figure 7 This is a schematic diagram of the structure of the self-locking pin of the present invention;

[0036] In the figure, 1-oil pan, 2-existing clamp, 3-self-locking ejection mechanism of the present invention, 11-tensioning bolt, 12-diaphragm pin, 13-locking device, 14-round pin, 15-drive round pin, 16-lever, 17-lever support, 18-spindle, 19-self-locking support, 20-plug, 21-spring, 22-self-locking pin, 23-push block, 24-push rod front end limiting flange, 25-push rod, 26-rotor fixing flange retaining ring, 27-rotor fixing flange, 28-push rod rear end limiting flange, 29-swing rod, 30-rotor, 31-shoulder sleeve, 32-connecting rod, 33-handle pin, 34-handle, 35-buckle, 36-buckle support, 37-avoidance groove, 38-upper step surface. Detailed Implementation

[0037] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are all within the scope of protection of this invention.

[0038] In the description of this invention, unless otherwise stated, the terms "left," "right," "front," "rear," "upper," "lower," etc., indicate the orientation or state relationship based on the orientation or state relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0039] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "equipped with" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art will understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0040] To illustrate the present invention more clearly, the following embodiments will be described in detail. Example 1

[0041] like Figure 3-7 As shown, the self-locking ejection mechanism for the oil pan processing fixture includes a self-locking mechanism and an ejection mechanism. The self-locking mechanism is used to lock the oil pan. The self-locking mechanism and the ejection mechanism work together to remove the oil pan from the pin.

[0042] The self-locking mechanism includes a drive pin 15, a lever 16, a lever support 17, a self-locking support 19, a screw plug 20, a spring 21, and a self-locking pin 22.

[0043] The self-locking support 19 adopts a closed design to prevent iron filings generated during processing from entering the moving parts of the self-locking mechanism, causing jamming and wear of moving parts. A pin channel is provided inside the self-locking support 19, with the plug 20, spring 21, and self-locking pin 22 arranged sequentially from the inside to the outside within the pin channel 19. The self-locking pin 22 has a clearance groove 37. The lever 16 is an obtuse-angled L-shaped lever, connected to the lever support 17 shaft at the corner via a spindle 18. One end of the lever 16 has a slotted hole, and the other end is inserted into the clearance groove 37 of the self-locking pin 22. The drive pin 15 passes through the slotted hole of the lever 16. When the drive pin 15 moves back and forth, the lever 16 rotates around the spindle 18, and the connection end between the lever 16 and the self-locking pin 22 moves left and right, pushing the self-locking pin back into the pin channel or releasing it. The clearance groove 37 is designed to prevent the lever 16 from contacting the self-locking pin 22 during loading. When the self-locking is released, the outer side of the bottom end of the lever 16 contacts the self-locking pin 22, driving the self-locking pin 22 to retract and release the self-locking.

[0044] Because the structure of the two sides of the oil pan (hereinafter referred to as workpiece 1) is not completely symmetrical (e.g. Figure 1 As shown), considering that when the pin is removed, the push rod 25 should be as close as possible to the center of gravity of the workpiece 1 so that the workpiece 1 can be removed from the positioning pin more smoothly, the lever 16 is designed with a waist hole structure, and the two levers 16 pass through the through groove of the push rod 25. At the same time, a drive pin 15 passes through the waist hole to drive the two levers 16 to rotate around the spindle 18.

[0045] The unloading mechanism includes a push rod 25, a swing rod 29, a rotating shaft 30, a bushing 31, a connecting rod 32, a handle pin 33, a handle 34, a buckle 35, and a buckle support 36. The push rod 25 is also equipped with a push block 23, a front limiting flange 24, and a rear limiting flange 28. The buckle 35 is fixed to the buckle support 36. One end of the handle 34 is connected to the lower shaft of the connecting rod 32 via the handle pin 33, and the other end can be engaged with the buckle 35. A cotter pin is installed on the handle pin 33 to prevent it from falling off. The handle 34 can rotate 180°. When rotated 90° counterclockwise, it is fixed in the buckle 35, achieving self-locking of the connecting rod 32 and preventing the connecting rod 32 from rotating due to gravity during processing, which would cause workpiece vibration. The handle buckle 35 is fixed on the buckle support 36, and the buckle support 36 is fixed on the clamp base 2. Both are fixed with bolts.

[0046] One end of the rotating shaft 30 is connected to the connecting rod 32 via the bushing 31, and the other end is fixed to the base of the clamp 2 with bolts via the rotating shaft fixing flange 27. The rotating shaft fixing flange 27 has an elastic retaining ring mounting groove at its end, and a flange retaining ring 26 is installed in the elastic retaining ring mounting groove. The flange retaining ring 26 and the rocker arm 29 together restrict the axial displacement of the rotating shaft 30. The rotating shaft fixing flange 27 is fixed to the base of the clamp 2 with bolts.

[0047] The push rod 25 is perpendicular to the rotating shaft 30. The push rod 25 has a through slot and a groove. The end of the lever 16 with its waist hole passes through the through slot, and the drive pin 15 passes through the through slot and the waist hole on the lever 16, fixing it to the push rod 15. The groove is located behind the through slot. One end of the swing rod 29 is bolted to the rotating shaft 30. The swing rod 29 is inserted into the groove and connected to the push rod 15. The head plane of the swing rod 29 is flush with the bottom of the groove, and the arc of the head is tangent to the side of the groove. When the swing rod 29 rotates, the push rod 25 moves back and forth. The movement of the push rod 25 drives the drive pin 15 to move, which in turn drives the lever 16 to rotate and pushes the self-locking pin 22 outward.

[0048] The front end limiting flange 24 and the rear end limiting flange 28 of the push rod are respectively set at the front and rear ends of the push rod 25. The front end limiting flange 24 of the push rod is slidably sleeved with the push rod 25, and the sleeved section is provided with an upper stepped surface 38 for limiting the front end limiting flange 24 of the push rod. The front end limiting flange 24 and the rear end limiting flange 28 of the push rod are respectively fixed on the supplementary machining hole of the base of the fixture 2. The push block 23 is fixed to the front top of the push rod 25 by bolts.

[0049] With the addition of a self-locking ejection mechanism, operators no longer need to enter the processing area to tighten or loosen the tension screws, avoiding the risk of slipping or injury and improving the safety of workpiece loading and unloading. Since operators no longer need to enter the operating area, clamping time is reduced, increasing processing efficiency. Furthermore, loading, which previously required two people, can now be completed by one person after the modification.

[0050] Example 2

[0051] The mechanism of Example 1 is used for workpiece self-locking and pin release.

[0052] Self-locking:

[0053] S1, the overhead crane lifts the workpiece onto the manual clamp 2. The workpiece 1 moves upward along the self-locking support 19. During the upward movement, the self-locking pin 22 is subjected to axial force due to its contact with the edge of the workpiece and moves outward to both sides of the workpiece to avoid it. The workpiece 1 can continue to enter and contact the clamp positioning surface.

[0054] S2, after the workpiece flange continues to advance, the flange disengages from the guide surface of the self-locking pin 22, and the elastic force of the spring 21 acts on the self-locking pin 22, causing the self-locking pin 22 to spring back to the contact point with the workpiece flange, thereby realizing the self-locking of the workpiece.

[0055] S3, after self-locking, tighten the two tension screws 11 on the back of the fixture, and then tighten the four locking devices 13 on both sides of the fixture. Their function is similar to that of auxiliary support, used to enhance the rigidity of the workpiece.

[0056] As a preferred option, the lower end face of the outer end of the self-locking pin 22 is a bevel, which can reduce the loading resistance of the workpiece 1, and the self-locking pin 22 is less prone to deformation due to the reduced resistance.

[0057] Out of stock:

[0058] After workpiece 1 is machined, remove the pins: first loosen the tension screws and the four side locking devices, then perform the following operations:

[0059] S1. Rotate handle 34 clockwise 90° to disengage from buckle 35 and make it flush with connecting rod 32;

[0060] S2, press down on handle 34 to make the rotating shaft 30 rotate clockwise. The rotating shaft 30 drives the swing rod 29 to rotate clockwise at the same time. Because the cylindrical head of the swing rod 29 is tangent to the side of the groove of the push rod 25, the push rod 25 is forced to move towards the workpiece. The drive pin 15 fixed on the push rod 25 moves towards the workpiece. The waist hole of the lever 16 moves with the drive pin 15 and rotates clockwise around the spindle 18 at the same time. The lower end of the lever 16 extends outward, pushing the self-locking pin 22 to retract into the pin channel of the self-locking support 19, thus releasing the workpiece self-locking.

[0061] S3, continue pressing down the handle 34, the push rod 25 continues to move forward until the upper step surface 38 of the push rod 25 contacts the front end limit flange 24 of the push rod and stops moving. At this time, the push block 23 reaches the farthest end; the workpiece 1 is completely disengaged from the positioning pin due to the pushing force of the push block 23, and the workpiece is disengaged from the pin.

[0062] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made to it in form and detail without departing from the scope defined by the claims of the present invention.

Claims

1. A self-locking unloading mechanism suitable for oil pan machining fixtures, characterized in that, Includes a self-locking mechanism and a material unloading mechanism; The self-locking mechanism includes a drive pin (15), a lever (16), a lever support (17), a self-locking support (19), a screw plug (20), a spring (21), and a self-locking pin (22). The unloading mechanism includes a push rod (25), a swing rod (29), a rotating shaft (30), a bushing (31), a connecting rod (32), a handle pin (33), a handle (34), a buckle (35), and a buckle support (36). The self-locking support (19) has a pin channel, and the self-locking pin (22), spring (21) and screw plug (20) are arranged in the pin channel of the self-locking support (19) from the inside to the outside; the self-locking pin (22) has a relief groove (37). The lever (16) is an obtuse-angled L-shaped lever. The lever (16) is connected to the lever support (17) shaft at the corner through the spindle (18). One end of the lever (16) is provided with a waist hole, and the other end is inserted into the clearance groove (37) of the self-locking pin (22) to avoid contact between the lever (16) and the self-locking pin (22) when the material is self-locked. When the self-locking is released, the outer side of the bottom end of the lever (16) contacts the self-locking pin (22), driving the self-locking pin (22) to retract and release the self-locking. The buckle (35) is fixed on the buckle support (36). One end of the handle (34) is connected to the lower shaft of the connecting rod (32) through the handle through pin (33), and the other end is engaged with the buckle (35). One end of the rotating shaft (30) is connected to the upper end of the connecting rod (32) through the bushing (31), and the other end is connected to the clamp (2). The push rod (25) is set perpendicular to the rotating shaft (30). The push rod (25) has a through groove and a recess. The waist hole end of the lever (16) passes through the through groove on the push rod (25), and the driving pin (15) passes through the through groove and the waist hole on the lever (16) and is fixed on the push rod (25). The recess is located behind the through groove. One end of the swing rod (29) is bolted to the rotating shaft (30), and the other end is inserted into the recess and connected to the push rod (25). When the swing rod (29) rotates, the push rod (25) moves back and forth.

2. The self-locking ejection mechanism for oil pan processing fixtures according to claim 1, characterized in that, The push rod (25) is also provided with a push block (23), a front end limiting flange (24) of the push rod and a rear end limiting flange (28); The front end limiting flange (24) and the rear end limiting flange (28) of the push rod are respectively provided at the front and rear ends of the push rod (25). The front end limiting flange (24) of the push rod is slidably connected to the push rod (25), and the rear end of the connecting section is provided with an upper step surface (38) that limits the front end limiting flange (24) of the push rod. The front limiting flange (24) and the rear limiting flange (28) of the push rod are respectively fixed on the supplementary machining holes of the fixture (2) base. The push block (23) is fixed to the front top of the push rod (25) by bolts. The other end of the shaft (30) is fixed to the base of the clamp (2) by bolts through the shaft fixing flange (27); the shaft fixing flange (27) has an elastic retaining ring mounting groove at the end, and a flange retaining ring (26) is installed in the elastic retaining ring mounting groove.

3. The self-locking ejection mechanism for oil pan processing fixtures according to claim 1, characterized in that, The feed surface of the outer end of the self-locking pin (22) is inclined.

4. The self-locking ejection mechanism for oil pan machining fixtures according to claim 1, characterized in that, The lever support (17) is fixed on the reinforcing rib of the clamp base, and the buckle support (36) is fixed on the clamp (2) base.

5. A self-locking stripping method suitable for oil pan machining fixtures, characterized in that, Automatic unloading is performed using the self-locking unloading mechanism as described in any one of claims 2 to 4, wherein the automatic unloading includes the following steps: S1, rotate the handle (34) 90° clockwise to disengage it from the buckle (35) and make it flush with the connecting rod (32); S2, press down the handle (34) to make the rotating shaft (30) rotate clockwise. The rotating shaft (30) drives the swing rod (29) to rotate clockwise at the same time. Because the cylindrical head of the swing rod (29) is tangent to the side of the groove of the push rod (25), the push rod (25) is forced to move towards the workpiece. The drive pin (15) fixed on the push rod (25) moves towards the workpiece. The waist hole of the lever (16) moves with the drive pin (15) and rotates counterclockwise around the spindle (18). The lower end of the lever (16) extends outward, pushing the self-locking pin (22) back into the pin channel, releasing the workpiece self-locking. S3, continue to press down the handle (34), the push rod (25) continues to move forward until the upper step surface (38) of the push rod (25) contacts the front end limit flange (24) of the push rod and stops moving. At this time, the push block (23) reaches the farthest end; the workpiece is completely separated from the positioning pin due to the pushing force of the push block (23), and the workpiece (1) is removed from the pin.

6. A self-locking stripping method suitable for oil pan machining fixtures, characterized in that, The self-locking mechanism as described in any one of claims 1 to 4 is used for self-locking, wherein the self-locking includes the following steps: S1, the workpiece (1) moves upward along the self-locking support (19). During the upward movement, the self-locking pin (22) is subjected to axial force due to its contact with the edge of the workpiece (1) and moves outward to both sides of the workpiece to avoid it. The workpiece (1) can continue to enter and contact with the fixture positioning surface. S2, after the flange of workpiece (1) continues to advance, the flange separates from the guide surface of the self-locking pin (22), and the elastic force of the spring (21) acts on the self-locking pin (22), causing the self-locking pin (22) to spring back to the flange of workpiece (1), thus realizing the self-locking of workpiece (1).

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