Stretching apparatus and method

Abstract

The present application relates to a kind of stretching device and method.It solves the defects such as unreasonable design of prior art.This stretching device includes lower drawing female die and upper drawing male die distributed sequentially from bottom to top, the lower drawing female die includes multiple layers of drawing female die ring distributed from bottom to top at intervals;The upper drawing male die includes multiple layers of combined drawing punch, and upper driving plate and lower driving plate are spaced and parallel from top to bottom, the multiple layers of combined drawing punch include drawing punch rod and at least one first forming sleeve sleeved on the lower end of the drawing punch rod, the upper end of first forming sleeve is fixed to lower driving plate, the upper end of drawing punch rod is fixed to upper driving plate, and the stretching device further includes multiple layers of driving plate linkage release mechanism connected between the upper driving plate and lower driving plate.The advantages of the present application are: coaxial stretching processing is realized, and the machining precision of the stretched part is ensured.

Description

Technical Field

[0001] This invention belongs to the field of metal tubular stretching technology, and particularly relates to a stretching device and a stretching method. Background Technology

[0002] When stretching metal casings (such as cylindrical battery casings) or cylinders, existing stretching devices use multiple sets of independent and continuous stretching dies for stretching. The drawback of this method is that the stretched part needs to be stamped and stretched by different independent stretching die punches. The stretching performed in succession cannot guarantee that the axis of the stretching punch coincides with the axis of the stretched part, which seriously affects the stretching accuracy.

[0003] For example, in the battery cylindrical steel shell forming process and battery assembly process described in 202211226031.X, a continuous punching die is used to punch and form a cylindrical blank. Then, a stamping die is used to stretch the cylindrical blank into a long cylindrical blank. Explosion-proof markings and annular protrusions are stamped onto the closed surface of the long cylindrical blank to form a cylindrical steel shell with these markings and protrusions. The battery cell assembly is then installed into the cylindrical steel shell, and the battery top cover is welded and fixed to the open end of the cylindrical steel shell to form a cylindrical steel shell battery. The closed surface with an explosion-proof valve is combined with the annular shell to form an integrated cylindrical steel shell, improving the explosion-proof valve's burst performance. Elliptical grooves are formed on the battery top cover, and multiple batteries are connected by electrical connectors for restraint and positioning, thereby improving battery life. This solution does not solve the aforementioned technical problems. Summary of the Invention

[0004] The purpose of this invention is to address the above-mentioned problems by providing a stretching device and stretching method that can solve the aforementioned technical problems.

[0005] To achieve the above objectives, the present invention adopts the following technical solutions:

[0006] This stretching device includes a lower stretching die and an upper stretching punch arranged sequentially from bottom to top. The lower stretching die includes a multi-layer stretching die ring spaced apart from bottom to top. The upper stretching punch includes a multi-layer combined stretching punch, and an upper drive plate and a lower drive plate spaced apart and parallel from top to bottom. The multi-layer combined stretching punch includes a stretching punch rod and at least one first forming sleeve sleeved on the lower end of the stretching punch rod. The upper end of the first forming sleeve is fixed to the lower drive plate, and the upper end of the stretching punch rod is fixed to the upper drive plate. The stretching device also includes a multi-layer drive plate linkage release mechanism connected between the upper drive plate and the lower drive plate.

[0007] In the above-mentioned tensioning device, the multi-layer drive plate linkage release mechanism includes at least two parallel locking tongue guides. The lower end of each locking tongue guide is fixed relative to the lower drive plate, and the upper end of each locking tongue guide is slidably connected to the upper drive plate. A guide bar is slidably fitted on the outside of each locking tongue guide. The lower end of the guide bar is fixed to the lower drive plate, and the upper end of the guide bar is slidably fitted to the upper drive plate. A locking block is slidably provided on the upper drive plate.

[0008] When the locking block is locked at the top of the latch guide bar and the top of the guide bar, the upper drive plate and the lower drive plate are relatively fixed; when the locking block is released, the upper drive plate can move relative to the lower drive plate.

[0009] In the above-mentioned tensioning device, the locking block and the locking tongue guide are vertically distributed, the locking block and the guide bar are vertically distributed, and the locking block and the upper drive plate are slidably connected.

[0010] In the above-described tensioning device, a first unlocking inclined surface is provided at the top of the latch guide bar, the top of the guide bar is lower than the top of the latch guide bar, a first horizontal locking plane is provided at the top of the guide bar, and a second inclined surface is connected to the first horizontal locking plane. A second unlocking inclined surface that matches the first unlocking inclined surface is provided at the inner end of the lock block, and a second horizontal locking plane that matches the first horizontal locking plane is provided at the bottom surface of the inner end of the lock block. The second inclined surface and the first unlocking inclined surface have the same inclination angle, and the first unlocking inclined surface is located above the second inclined surface, and the lower side of the first unlocking inclined surface is lower than the upper side of the second inclined surface.

[0011] In the above-described tensioning device, the lower end of each of the latch guide bars extends downward through the lower drive plate and the lower end of the latch guide bar is fixed relative to the lower drive plate. The lower end of each of the latch guide bars has an exposed end exposed below the lower surface of the lower drive plate.

[0012] In the above-mentioned stretching device, the lower stretching die also includes a stretching part demolding structure located below the lowest stretching die ring.

[0013] In the above-mentioned stretching device, the demolding structure of the stretching member includes an annular plate with a through hole for the stretching member. A plurality of demolding claws are hinged to the annular plate and are evenly distributed along the circumferential direction of the through hole for the stretching member. At least a portion of the demolding claws extends into the through hole for the stretching member. A stripping elastic drive is provided between the annular plate and the demolding claws, such that the portion of the demolding claws extending into the through hole for the stretching member converges toward the axis of the through hole for the stretching member.

[0014] In the above-mentioned stretching device, the demolding claw includes a horizontal part and an inclined part connected to the inner side of the horizontal part. The horizontal part and the inclined part form an obtuse angle. The inner inclined surface of the inclined part is provided with an arc concave surface, and all the arc concave surfaces are coaxial.

[0015] In the above-described tensioning device, a rounded tip is provided at the lower end of each of the inclined portions.

[0016] In the above-mentioned stretching device, the highest stretching die ring is fixed to the fixed plate, and a pulling mechanism is provided on the lower drive plate. The pulling mechanism is used to pull the material to the lower surface of the fixed plate.

[0017] In the above-mentioned stretching device, the material pulling mechanism includes at least two material pulling hooks with their upper ends hinged to opposite sides of the lower drive plate. A transverse drive spring is provided between the lower drive plate and the outer side of the material pulling hooks. The transverse drive spring causes the hook portion of the material pulling hook to hook onto the lower surface of the fixed plate. A plurality of pull rods are installed on the lower drive plate. The upper end of the pull rod is slidably engaged with the upper drive plate. An anti-detachment cap is provided at the upper end of the pull rod. The anti-detachment cap is used to prevent the pull rod from detaching downward from the upper drive plate.

[0018] This application also provides a stretching method, wherein the stretching method employs the aforementioned stretching device.

[0019] Compared with existing technologies, the advantages of this application are:

[0020] It can achieve continuous coaxial stretching processing with different stretching depths along the same vertical axis, ensuring the stretching quality of the stretched parts and the coaxiality of the stretching parts during different stretching processing steps, and can adapt to different process requirements.

[0021] The multi-layer drive plate linkage and release mechanism is used for the linkage and release of the upper and lower drive plates, and plays a switching function between linkage and release to achieve coaxial multi-stage stretching processing, such as first-stage stretching and second-stage stretching processing, to ensure stretching quality. Attached Figure Description

[0022] Figure 1 This is a three-dimensional structural diagram of the stretching device provided by the present invention.

[0023] Figure 2 This is a schematic diagram of the tensioning device provided by the present invention.

[0024] Figure 3 yes Figure 2 Schematic diagram of the cross-sectional structure along line AA.

[0025] Figure 4 This is a schematic diagram of the material guiding mechanism for stretched finished parts provided by the present invention.

[0026] Figure 5 This is a top view schematic diagram of the demolding structure for the stretching part provided by the present invention.

[0027] Figure 6 yes Figure 5 Schematic diagram of the cross-sectional structure along the middle BB line.

[0028] Figure 7 This is a schematic diagram of a partial explosion of the demolding structure for the stretching part provided by the present invention.

[0029] Figure 8 This is a three-dimensional structural diagram of the quick-release mechanism provided by the present invention.

[0030] Figure 9 This is a top view schematic diagram of the quick-release mechanism provided by the present invention.

[0031] Figure 10 yes Figure 9 Schematic diagram of the cross-sectional structure along the CC line.

[0032] Figure 11 This is a schematic diagram of the exploded structure of the multi-layer combined stretching punch provided by the present invention.

[0033] Figure 12 This is a schematic diagram of the multi-layer combined stretching punch cooling structure provided by the present invention.

[0034] Figure 13 This is a partial exploded structural diagram of the material pulling mechanism provided by the present invention.

[0035] Figure 14 This is a schematic diagram of the state after the material pulling mechanism provided by the present invention pulls the highest fixed plate.

[0036] Figure 15 This is a partial structural schematic diagram of the multi-layer drive plate linkage release mechanism provided by the present invention.

[0037] Figure 16 This is a top view schematic diagram of the tensioning device provided by the present invention.

[0038] Figure 17 This is a schematic diagram showing the changes in the metal stamped cup part provided by the present invention after multiple stretching processes using the stretching device of this application.

[0039] Figure 18 This is a schematic diagram of the first-stage tension locking state of the multi-layer drive plate linkage loosening mechanism provided by the present invention.

[0040] Figure 19 yes Figure 18 A schematic diagram of the explosion structure.

[0041] Figure 20This is a schematic diagram of the pull rod structure of the material pulling mechanism. Detailed Implementation

[0042] The following are specific embodiments of the invention, which are described in conjunction with the accompanying drawings. The technical solution of the invention will be further described, but the invention is not limited to these embodiments.

[0043] Example 1

[0044] like Figure 17 As shown, this stretching device is used for stretching metal stamping cup parts a, such as battery casing cylinders, etc. After stretching, the metal stamping cup part a is formed into a stretched finished part or a stretched component.

[0045] The function of the stretching device is to stretch a metal stamped cup a multiple times axially, so that the diameter of the stamped cup continuously decreases and the axial length of the stamped cup continuously increases.

[0046] Specifically, such as Figures 1-3 As shown, the stretching device in this embodiment is a vertical stretching device, which includes a lower stretching die 1 and an upper stretching punch 2 arranged sequentially from bottom to top. The metal stamping cup a is pre-placed in the lower stretching die 1, and the upper stretching punch 2 moves relative to the lower stretching die 1 so that the metal stamping cup a is stretched.

[0047] The lower stretching die 1 includes a base plate 10, on which an inverted U-shaped overhead support seat 11 is provided. At the top of the overhead support seat 11, there are multi-layer stretching die rings 12 distributed from bottom to top. The multi-layer stretching die rings 12 are coaxial and their inner diameter gradually decreases from top to bottom.

[0048] like Figure 3 As shown, the overhead support 11 has a drawing blanking through hole 110 that communicates with the internal space of the drawing die ring 12. During each drawing process, the inner diameter of each drawing die ring 12 is different. At this time, two drawing die rings 12 spaced apart vertically can form one drawing stroke. When the drawing process is performed in the last few or one drawing process, the lower end of the drawing drawing cup enters the drawing blanking through hole 110. That is, one drawing die ring 12 can form one drawing process for the drawing cup. Of course, the drawing cup moves downward from the uppermost drawing die ring 12 for multiple drawing processes.

[0049] like Figure 4 As shown, a drawing guide mechanism 3 for drawn finished parts is provided on the base plate 10 or the overhead support 11. The drawing guide mechanism 3 is used to guide the drawn finished parts that fall downward after being demolded from the upper drawing punch 2 at an incline, so as to prevent the drawn finished parts from overlapping each other and remaining on the lower drawing die 1 after falling downward.

[0050] Specifically, the stretching finished part guiding mechanism 3 of this embodiment includes an inclined elastic plate 30 fixed to the upper side of the overhead support 11 and located within the overhead support 11. The upper end of the inclined elastic plate 30 is located outside the lower opening of the stretching unloading through hole 110, and the lower side of the inclined elastic plate 30 is free. A bottom support platform 100 is provided on the upper surface of the base plate 10, located directly below the stretching unloading through hole 110. A stretching motion stroke is formed between the lower opening of the stretching unloading through hole 110 and the bottom support platform 100. Under normal conditions, the lower side of the inclined elastic plate 30 is in the stretching motion stroke. When the last stretching is performed, the stretched finished part is stretched further downward and contacts the inclined elastic plate 30, causing the inclined elastic plate 30 to deform. When the lower end of the stretched finished part contacts the bottom support platform 100, it indicates that the stretching of the stretched finished part is completed, and then it enters the demolding stage.

[0051] A deformation limiting plate 31, which is normally vertically arranged, is connected to the lower side of the inclined elastic plate 30. The inclined elastic plate 30 and the deformation limiting plate 31 form an obtuse angle greater than 90°.

[0052] A transverse plate 32 is connected to the upper side of the inclined elastic plate 30, forming an obtuse angle with the transverse plate 32 and the inclined elastic plate 30. Alternatively, the transverse plate 32 can be directly fixed to the overhead support base 11. Specifically, several fasteners are threaded through the transverse plate 32, and these fasteners are connected to threaded holes on the overhead support base 11. Using fasteners facilitates the assembly and disassembly of the transverse plate 32.

[0053] From a vertical perspective, the length of the inclined elastic plate 30 is longer than the length of the deformation limiting plate 31, so as to play a guiding role with a long contact surface.

[0054] In a preferred embodiment, the inclined elastic ramp 30 is either a flat plate or a U-shaped plate with a contoured groove.

[0055] After the demolding process, when the inclined elastic plate 30 recovers its elasticity, the stretched finished part is pulled downwards and ejected from the die 1. Then the next stretching process is repeated.

[0056] A discharge ramp 101 is provided on the base plate 10, located below the inclined elastic ramp 30 when it is in an inclined state. When the stretched finished part is ejected downward under the elastic force of the inclined elastic ramp 30, the discharge ramp 101 forms the final discharge guide for the stretched finished part.

[0057] In order to prevent the finished product from being damaged by impact when it falls, a flexible block 32 is provided on the base plate 10. The flexible block 32 is such as rubber. A splicing slope 320 with the same inclination angle as the discharge slope 101 is provided on the flexible block 32. The lower side of the splicing slope 320 is spliced ​​to the upper side of the discharge slope 101.

[0058] The flexible block 32 is a triangular block, and its vertical surface abuts against the periphery of the bottom support platform 100. The bottom support platform 100 has a square structure, and the vertical surface of the flexible block 32 abuts against one surface of the bottom support platform 100.

[0059] Of course, the stretching finished part guiding mechanism 3 in this embodiment can be replaced by a swing-type pushing mechanism. For example, the stretching finished part guiding mechanism 3 includes a swing plate hinged to the upper side of the overhead support 11, the swing plate is connected to the swing driver, and the swing driver is hinged to the overhead support 11. The swing driver is, for example, a cylinder or a hydraulic cylinder.

[0060] When the oscillating plate is tilted, it can form a guide for materials.

[0061] like Figure 3 , Figures 5-7 As shown, in order to achieve automatic demolding and protect the outer wall of the stretched finished part, a demolding structure 4 for the stretched part is provided on the overhead support 11. The demolding structure 4 for the stretched part can demold from the upper stretching punch 2, and the demolded stretched finished part is discharged by the stretch finished part guiding mechanism 3.

[0062] Specifically, such as Figure 3 , Figures 5-7 As shown, the demolding structure 4 of the stretching part in this embodiment includes an annular plate 40 fixed on the overhead support 11 and having a through hole for the stretching part. The axis of the through hole for the stretching part coincides with the axis of the stretching blanking through hole 110, and the annular plate 40 is located above the stretching blanking through hole 110. Of course, the annular plate 40 can also be set in the stretching blanking through hole 110 or at the lower opening of the stretching blanking through hole 110.

[0063] The annular plate 40 is fixed to the overhead support 11 using several countersunk bolts. That is, the top surface of the head of the countersunk bolt is flush with the upper surface of the annular plate 40 to prevent interference.

[0064] A plurality of demolding claws 41 are hinged to an annular plate 40, evenly distributed along the circumference of the through hole of the drawing member. At least a portion of the demolding claws 41 extends into the through hole of the drawing member. A stripping elastic drive member 42 is provided between the annular plate 40 and the demolding claws 41, such that the portion of the demolding claws 41 extending into the through hole of the drawing member converges towards the axis of the through hole. During the drawing process, the demolding claws 41 in this embodiment always hold the outer wall of the drawing member. When the lowest drawing process is completed, the portion of the demolding claws 41 extending into the through hole of the drawing member detaches from the outer wall of the drawing member. It can be understood that the demolding claws 41 are now above the upper opening of the drawing member.

[0065] After the ejector claw 41 disengages from the drawn part, it then holds the outer wall of the upper drawing punch 2. As the upper drawing punch 2 continues to descend, the upper end of the drawn part is held in place by the ejector claw 41, so as to achieve the purpose of the drawn part disengaging downward from the upper drawing punch 2.

[0066] Furthermore, a plurality of claw mounting station slots 400 evenly distributed in a circular pattern are provided on the upper surface of the annular plate 40. At least a portion of the demolding claw 41 is hinged to the claw mounting station slot 400 by a hinge shaft 401, and the remaining portion of the demolding claw 41 extends obliquely downward into the through hole of the stretching member.

[0067] like Figures 5-7 As shown, the demolding claw 41 in this embodiment includes a horizontal portion 410 and an inclined portion 411 connected to the inner side of the horizontal portion 410, with the horizontal portion 410 and the inclined portion 411 forming an obtuse angle.

[0068] An arc-shaped concave surface 412 is provided on the inner inclined surface of the inclined portion 411, and all the arc-shaped concave surfaces 412 are coaxial. The arc-shaped concave surface 412 is modeled after the outer cylindrical surface of the drawn part, and the arc-shaped concave surface 412 is modeled after the outer cylindrical surface of the upper drawing punch 2.

[0069] The concave surface 412 of the ejector claw 41 can form a stretching elastic grip on the stretched part, which can improve the downward movement stability of the stretched part during the stretching process. Secondly, the concave surface 412 can prevent the ejector claw 41 from being squeezed or bumped when it comes into contact with the stretched part or the upper stretching punch 2. For example, the stretched part or the upper stretching punch 2 may be squeezed or bumped.

[0070] The stripping elastic drive 42 is a spring. The stripping elastic drive 42 is vertically or inclined. The upper end of the stripping elastic drive 42 abuts against the demolding claw 41, and the lower end of the stripping elastic drive 42 abuts against the bottom of the claw mounting station groove 400. In order to prevent stripping, a spring insertion blind hole is provided at the bottom of the claw mounting station groove 400. The lower part of the stripping elastic drive 42 is inserted into the spring insertion blind hole.

[0071] Each inclined portion 411 has a rounded tip 413 at its lower end. The rounded tip 413 contacts the center position of the upper end face of the drawing part. At this time, the rounded tip 413 can avoid damaging the outer cylindrical surface of the upper drawing punch 2 during demolding.

[0072] In a preferred embodiment, there are 3-N demolding claws 41. The demolding claws 41 forming a circle can effectively exert uniform force on the stretched part in the circumferential direction for demolding, which can prevent the stretched part from being subjected to single-point force during demolding or edge squeezing and rolling, which could lead to stretching or cracking of the inner wall of the stretched part in severe cases.

[0073] The demolding structure 4 of this embodiment not only guides the stretched part during the stretching process, but also provides radial elastic support to improve the stretching quality. Furthermore, after stretching, the demolding structure 4 can also form a demolding ring on the upper stretching punch 2, achieving automatic mechanical demolding and significantly improving production efficiency.

[0074] Meanwhile, the specific structure of the stretching part demolding structure 4 of this application can prevent damage to the upper stretching punch 2 and the stretching part, and extend the service life of the stretching device.

[0075] The inner side of the claw mounting station slot 400 is connected to the through hole of the stretching part. The edge at the connection between the through hole of the stretching part and the claw mounting station slot 400 can limit the movement of the demolding claw 41 when it rotates downward around the hinge axis.

[0076] The multi-layer stretching die ring 12 includes a bottommost stretching die ring and at least one upper stretching die ring located above the bottommost stretching die ring. In this embodiment, there are two upper stretching die rings that are spaced apart vertically. The vertical spacing between the multi-layer stretching die rings 12 is determined by the stretching stroke of the stretching member.

[0077] like Figure 1 , Figures 8-10 As shown, each layer of stretching die ring 12 is fixed by a quick-release mechanism. Specifically, at least one fixing plate 13 is provided on the top of the overhead support 11, spaced apart from or directly fixed to the top of the overhead support 11. In the spaced arrangement: the lowest fixing plate 13 closest to the overhead support 11 is fixed to the top of the overhead support 11 by two pads 14. When there are multiple fixing plates 13 distributed from top to bottom, two adjacent fixing plates 13 are also connected by two pads 14. The two pads 14 are parallel to each other, and the distance between the opposite outer surfaces of the two pads 14 is less than the length or width of the fixing plate 13. This facilitates the installation of the fixing plate 13 and also facilitates the subsequent material pulling mechanism to hook onto the lower surface of the fixing plate 13 for material pulling.

[0078] The fixed plate 13 is provided with a tension clearance hole, and the tension die ring 12 is fixed to the top of the overhead support 11 by a quick-release mechanism. Figure 1 Please refer to the unviewed version. Figures 8-10 ), and the stretching die ring 12 is fixed to the upper surface of the fixed plate 13 by a quick-release mechanism.

[0079] Specifically, the quick-release mechanism of this embodiment includes two guide blocks 18 disposed on the top of the overhead support 11 or on the upper surface of the fixed plate 13. The guide blocks 18 are right-angled and a guide groove is formed between the two guide blocks 18. The stretching die ring 12 is fixed on the insertion slide plate 15. The insertion slide plate 15 is inserted into the guide groove to form a sliding fit. A fixed backing 16 is provided at one end of the guide groove. When one side of the insertion slide plate 15 abuts against the fixed backing 16, it indicates that the insertion slide plate 15 has slid into place. After sliding into place, the insertion slide plate 15 is locked on the side away from the fixed backing 16 by a fastener, that is, the insertion slide plate 15 cannot move relative to the overhead support 11 and the insertion slide plate 15 cannot move relative to the fixed plate 13.

[0080] The fastener body is, for example, a pin. For example, the pin is inserted into a pin blind hole on the top of the plug-in slide plate 15 and the overhead support 11.

[0081] A handle 150 is provided on the circumferential surface of the plug-in slide 15 away from the fixed support 16. The handle 150 facilitates disassembly and assembly operations.

[0082] A die mounting hole is provided in the central area of ​​the insertion / removal slide plate 15, and the stretch die ring 12 is fixed in the die mounting hole. At the same time, a circulating cooling channel 150 is provided inside the insertion / removal slide plate 15. The circulating cooling channel 150 is preferably in the form of a disc-shaped spiral structure. Both ends of the circulating cooling channel 150 are connected to a refrigerant storage tank through external pipelines. The refrigerant can be water, and a power pump is provided on the external pipelines.

[0083] When the power pump is turned on, the refrigerant enters the circulating cooling channel 150, which can then exchange heat with the stretching die ring 12, thereby extending the service life of the stretching die ring 12.

[0084] A protective plate 151 is provided on the upper surface of the insertion and removal slide plate 15. The protective plate 151 is provided with a clearance hole that communicates with the upper end of the forming chamber of the stretching die ring 12. The diameter of the clearance hole is equal to or slightly larger than the inner diameter of the upper end of the forming chamber of the stretching die ring 12.

[0085] The centerline of the clearance hole body coincides with the centerline of the stretching die ring 12, so that the hole wall of the clearance hole body is flush with the upper inner wall of the forming cavity.

[0086] When in the fixed state, the horizontal sub-block of the guide block 18 is restricted to the opposite sides of the upper surface of the plug-in slide plate 15, and the plug-in slide plate 15 is restricted in all four directions under the constraints of the positioning backrest and the pin.

[0087] The above method can realize the sliding withdrawal of the insertion and removal slide plate 15. Withdrawal can make the stretching die ring 12 provided on the insertion and removal slide plate 15 withdraw synchronously, which can improve the replacement efficiency of different stretching die rings 12, shorten the downtime caused by replacing the stretching die ring 12, and thus improve production efficiency.

[0088] Secondly, the methods described above can also meet the usage requirements.

[0089] Of course, the aforementioned pin can be replaced by a detachable positioning backing block 17, that is, the detachable positioning backing block 17 is fixed to the plug-in slide plate 15 by bolts or positioning pins.

[0090] When there are multiple fixed plates 13, the outer diameter of the fixed plates 13 is equal or gradually increases from top to bottom. The material pulling mechanism is installed on the upper stretching punch 2, and the lifting and lowering of the upper stretching punch 2 will drive the material pulling mechanism to move up and down synchronously.

[0091] Specifically, such as Figure 3 and Figure 11 As shown, the upper stretching punch 2 in this embodiment includes a multi-layer combined stretching punch 20, and an upper drive plate 21 and a lower drive plate 22 that are spaced apart from top to bottom and parallel to each other.

[0092] The multi-layer combined stretching punch 20 includes a stretching punch 200 and at least one first forming sleeve 201. The first forming sleeve 201 is sleeved on the lower end of the stretching punch 200 and the stretching punch 200 and the first forming sleeve 201 are slidably fitted.

[0093] The first forming sleeve 201 is subjected to a first-stage stretching process, and the stretching punch 200 is subjected to a second-stage stretching process. Of course, multiple first forming sleeves 201 that slide against each other and whose outer diameter gradually decreases from the outside to the inside can be designed according to the actual stretching depth.

[0094] The upper end of the first forming sleeve 201 is fixed to the lower drive plate 22, and the upper end of the stretching punch 200 is fixed to the upper drive plate 21. The lower drive plate 22 drives the first forming sleeve 201 to rise and fall, and the upper drive plate 21 drives the stretching punch 200 to rise and fall.

[0095] The lower end of the drawing punch 200 is provided with a punch core 202, which is cylindrical. The diameter of the drawing punch 200 is equal to the diameter of the punch core 202. A first forming sleeve 201 is fitted onto the punch core 202. The hardness provided by the punch core 202 is the same as the hardness of the first forming sleeve 201, or the hardness of the first forming sleeve 201 is higher than that of the punch core 202, for example, through heat treatment such as quenching. The length of the punch core 202 is longer than the length of the first forming sleeve 201.

[0096] The lower end of the tension punch 200 is provided with a reduced diameter section 203, and the punch core 202 is provided with a blind hole with an open upper end for the reduced diameter section. That is, the lower end of the punch core 202 is closed, and the reduced diameter section 203 is inserted into the blind hole for the reduced diameter section. The two are fixedly connected by interference fit, or the two are connected by threaded connection.

[0097] The lower drive plate 22 is provided with a molding sleeve mounting hole 220. The upper end of the first molding sleeve 201 extends into the molding sleeve mounting hole 220. A flange 204 is provided on the first molding sleeve 201. The flange 204 is fixed to the lower surface of the lower drive plate 22 by several flange 204 bolts. A cooling circulation system for cooling the first molding sleeve 201 is provided inside the lower drive plate 22. The cooling circulation system refers to the cooling structure of the stretching die ring 12 described above.

[0098] The upper end of the stretching punch 200 passes through the upper drive plate 21, and a fixed seat 23 is provided on the upper surface of the upper drive plate 21, which is fitted onto the upper end of the stretching punch 200.

[0099] The multi-layer combined drawing punch 20 in this embodiment can achieve continuous coaxial drawing processing of different drawing depths along the same vertical axis, which can ensure the drawing quality of the drawn part and the coaxiality of the drawing part during different drawing processing steps. When it is a cylindrical drawing part, it can make the roundness of the drawn part better.

[0100] Secondly, the multi-layer combined drawing punch 20 of this application can be adapted to different process requirements.

[0101] The stretching punch 200 can be either a hollow or solid rod with a closed lower end. The stretching punch 200 can also be either a cylindrical or square punch, and the first forming sleeve 201 can be either a cylindrical or square forming sleeve.

[0102] When selecting a cylindrical punch, a cylindrical forming sleeve should be used.

[0103] When hollow rods are selected, such as Figure 12As shown, a circulating cooling water core 24 for cooling the core 202 of the punch is provided inside the tension punch 200. Specifically, a water core insertion blind hole 200a with an open upper end is provided in the axial direction of the tension punch 200, and an inlet 200b and an outlet 200c are provided at the upper end of the tension punch 200. The circulating cooling water core 24 is cylindrical and the top end of the circulating cooling water core 24 is closed. The circulating cooling water core 24 is a metal tube. At least a portion of the outer diameter of the circulating cooling water core 24 is smaller than the diameter of the water core insertion blind hole 200a. It is inserted into the water core insertion blind hole 200a, with a gap space 200d between the bottom of the water core insertion blind hole 200a and the lower end of the circulating cooling water core 24. A section of the circulating cooling water core 24 with an outer diameter smaller than the diameter of the water core insertion blind hole 200a forms an annular space 200e with the water core insertion blind hole 200a. The inlet 200b communicates with the interior of the circulating cooling water core 24, and the outlet 200c communicates with the annular space 200e. A connecting hole 200f is provided at the upper end of the circulating cooling water core 24, connecting the inlet 200b and the interior of the circulating cooling water core 24.

[0104] The inlet 200b and outlet 200c are connected to the cold water tank via pipelines, and a power circulation pump is installed on the pipelines.

[0105] When the power circulation pump is turned on, the water in the cold water tank passes through the inlet 200b, the connecting hole 200f, the internal space of the circulating cooling water core 24, the spacing space 200d, the annular space 200e, and the outlet 200c in sequence, and finally returns to the cold water tank. The above process forms a cooling cycle. The cooling cycle can cool the punch core 202 and the first forming sleeve 201 to different degrees, so as to extend the service life of the multi-layer combined drawing punch 20.

[0106] Furthermore, the upper end of the circulating cooling water core 24 is sealed to the opening of the water core insertion blind hole 200a. Specifically, a sealing ring 240 is provided at the upper end of the circulating cooling water core 24, and the sealing ring 240 contacts the wall of the water core insertion blind hole 200a to form a seal.

[0107] A removable top cover 200g is provided on the top of the stretching punch 200. The upper end face of the circulating cooling water core 24 contacts the lower surface of the removable top cover 200g, and a locking screw 200h is threaded through the removable top cover 200g and threaded to the upper end of the circulating cooling water core 24.

[0108] The circulating cooling water core 24 includes an upper large outer diameter section and a lower small outer diameter section connected to the lower end of the upper large outer diameter section. The upper large outer diameter section and the water core insertion blind hole 200a are fitted with a very small clearance, and a sealing ring 240 groove is provided on the outer wall of the upper large outer diameter section, with at least a portion of the sealing ring 240 located in the sealing ring 240 groove. The lower small outer diameter section and the water core insertion blind hole 200a form the aforementioned annular space 200e, and the lower end of the lower small outer diameter section and the bottom of the water core insertion blind hole 200a form the aforementioned spacing space 200d.

[0109] Both the inlet 200b and the outlet 200c are located at the upper end of the tension rod 200, allowing the cooling water to have a longer flow path to improve cooling efficiency. Furthermore, the inlet 200b and the outlet 200c are spaced vertically apart to facilitate easier pipe connection.

[0110] like Figure 3 , Figure 13 and Figure 14 As shown, a plurality of fixed plates 13 have a highest fixed plate 13. The material pulling mechanism described above includes at least two material pulling hooks 25 with their upper ends hinged to opposite sides of the lower drive plate 22. When the lower drive plate 22 drives the first forming sleeve 201 to descend and perform the first stretching forming, the material pulling hooks 25 descend synchronously with the lower drive plate 22. Because the material pulling hooks 25 are in a hinged state, they swing outward when they contact the highest fixed plate 13. When the hook part of the material pulling hook 25 descends to the lower surface of the fixed plate 13, the hook part of the material pulling hook 25 hooks onto the lower surface of the fixed plate 13 through the transverse drive spring 250 provided between the lower drive plate 22 and the outer side of the material pulling hook 25. The material pulling hook 25 can connect the lower drive plate 22 and the highest fixed plate 13, playing a stabilizing role. At this time, during the first stretching forming, it can prevent the highest fixed plate 13 from shifting.

[0111] Taking two material hooks 25 as an example, the transverse drive spring 250 always has the tendency to make the hooks of the material hooks 25 move towards each other.

[0112] The upper drive plate 21, the lower drive plate 22, and the fixed plate 13 are connected by a vertical guide mechanism, which includes either a guide rail pair or a guide sleeve / rod pair. The vertical guide mechanism includes a plurality of guide posts 213 provided on the lower surface of the upper drive plate 21, and guide holes or guide sleeves 214 for inserting the guide posts are respectively provided on the lower drive plate 22 and the fixed plate 13 to guide the lifting and lowering movements.

[0113] Specifically, a U-shaped block 26 is provided on the lower surface of the lower drive plate 22, and the upper end of the pull hook 25 is placed in the U-shaped groove of the U-shaped block 26. The upper ends of the U-shaped block 26 and the pull hook 25 are connected by a longitudinal hinge shaft 27 that is relatively perpendicular to the transverse drive spring 250.

[0114] A closing block 28 is provided at the opening of the U-shaped block 26. One end of the horizontally placed drive spring 250 abuts against the outer side of the pull hook 25, and the other end of the horizontally placed drive spring 250 abuts against the closing block 28.

[0115] The transverse drive spring 250 is located on the outside and below the longitudinal hinge shaft.

[0116] In a preferred embodiment, there are four material pulling hooks 25. Two material pulling hooks 25 are distributed on one side of the opposite sides of the lower drive plate 22, and the other two material pulling hooks 25 are distributed on the other side of the opposite sides of the lower drive plate 22.

[0117] When the material hook 25 contacts the bottom of the U-shaped groove, it is in an upright state. At this time, the material hook 25 hooks the lower surface of the highest fixed plate 13. When the material hook 25 swings outward, it disengages from the lower surface of the lower drive plate 22.

[0118] The hook of the material pull hook 25 can be understood as a detour. The upper side of the hook is provided with an upper chamfer 251, and the lower side of the hook is provided with a lower chamfer 252. The upper and lower chamfers serve as guides when contacting the highest fixed plate 13, avoiding jamming and facilitating the cancellation of material pulling and tightening after demolding.

[0119] Secondly, the two opposite sides of the fixed plate 13 are both side facades, and each side facade has a chamfer at the upper and lower corners. When the upper chamfer 251 and the lower corner chamfer match, a wedge-shaped sliding fit is formed. Similarly, when the lower chamfer 252 and the upper corner chamfer match, a wedge-shaped sliding fit is formed, so as to improve the efficiency of material pulling and eliminate material pulling.

[0120] The U-shaped block 26 is fixed to the lower surface of the lower drive plate 22 by several bolts. In a preferred embodiment, there are three bolts arranged in an isosceles triangle.

[0121] like Figure 1 and Figure 20 As shown, several pull rods 215 are installed on the lower drive plate 22. The upper end of the pull rod 215 is slidably engaged with the upper drive plate 21. An anti-detachment cap 216 is provided at the upper end of the pull rod 215. The anti-detachment cap 216 is used to prevent the pull rod 215 from detaching downward from the upper drive plate 21. When the material pulling hook 25 pulls the lower surface of the highest fixed plate 13 and is about to pull out the material, the upper drive plate 21 rises. At this time, the anti-detachment cap 216 at the upper end of the pull rod 215 blocks the upper surface of the upper drive plate 21. The transverse drive spring 250 is forced to stretch under the influence of the continuously rising upper drive plate 21. At this time, the hook of the material pulling hook 25 can be disengaged from the lower surface of the fixed plate 13.

[0122] Of course, the upper drive plate 21 is provided with a pull rod hole 217, the pull rod 215 and the pull rod hole 217 are slidably engaged, the upper opening of the pull rod hole 217 is provided with a countersunk hole 218, the anti-detachment cap 216 and the countersunk hole 218 are slidably engaged, when the anti-detachment cap 216 contacts the bottom of the countersunk hole 218, the lower drive plate 22 and the upper drive plate 21 can rise together in the vertical direction, which can make the hook of the material hook 25 disengage from the lower surface of the fixed plate 13.

[0123] like Figure 1 , Figure 3 and Figure 15 As shown, in order to realize the linkage of the multi-layer drive boards, this embodiment further provides a multi-layer drive board linkage release mechanism 5. The multi-layer drive board linkage release mechanism 5 is used for the linkage and mutual release of the upper drive board 21 and the lower drive board 22, and plays the function of switching between linkage and release.

[0124] Specifically, such as Figure 1 , Figure 3 and Figure 15 As shown, the multi-layer drive plate linkage release mechanism 5 includes at least two parallel locking tongue guides 50. The lower end of each locking tongue guide 50 passes through the lower drive plate 22 downward and is fixed relative to the lower drive plate 22. The lower end of the locking tongue guide 50 has an exposed end 500 exposed below the lower surface of the lower drive plate 22. The upper end of each locking tongue guide 50 is slidably connected to the upper drive plate 21 in the vertical direction.

[0125] In a preferred embodiment, the locking tongue guide bar 50 has roots and is arranged in a cross shape.

[0126] Of course, to ensure stability, such as Figure 1 , Figure 3 and Figure 15 As shown, the top surface of the guide block 18 on the highest fixed plate 13 is provided with a contour groove 140. The contour groove 140 is contoured to the exposed end 500. The exposed end 500 enters the contour groove 140 to form a lifting guide. At the same time, when the exposed end 500 contacts the bottom of the contour groove 140, the lower drive plate 22 drives the first forming sleeve 201 to complete the stretching process.

[0127] During the stretching process of the first forming sleeve 201, the stretching punch 200 is always inserted into the first forming sleeve 201 to ensure that the first forming sleeve 201 has relatively high strength, especially radial strength. If the punch core 202 is not provided, the lower end face of the stretching punch 200 is flush with the lower end face of the first forming sleeve 201. If the punch core 202 is provided, the lower end face of the punch core 202 is flush with the lower end face of the first forming sleeve 201.

[0128] like Figure 1 , Figure 3 and Figure 15 As shown, a guide bar 51 is slidably fitted on the outside of each latch guide bar 50. The lower end of the guide bar 51 is fixed to the lower drive plate 22, and the upper end of the guide bar 51 is slidably fitted with the upper drive plate 21. A locking block 52 is provided on the upper drive plate 21. The locking block 52 and the latch guide bar 50 are vertically distributed, and the locking block 52 and the guide bar 51 are vertically distributed. The locking block 52 and the upper drive plate 21 are slidably connected. A track groove 210 or track hole is provided on the upper drive plate 21 for the locking block 52 to slide. A locking block drive member 54 is installed in the track groove 210. The locking block drive member 54 is a spring. One end of the locking block drive member 54 abuts against the outer end of the locking block 52, and the other end of the locking block drive member 54 abuts against the blocking part 53 at the outer end of the track groove 210.

[0129] The lock block drive 54 causes the lock block 52 to tend to move toward the bolt guide bar 50 and guide bar 51.

[0130] like Figure 15 and Figure 16 As shown, the upper drive plate 21 is provided with a first groove 211 that slides in cooperation with the latch guide bar 50, and a second groove 212 that slides in cooperation with the guide bar 51.

[0131] like Figure 3 , Figure 15 , Figure 18 and Figure 19 As shown, a first unlocking inclined surface 501 is provided at the top of the latch guide bar 50. The top of the guide bar 51 is lower than the top of the latch guide bar 50. A first horizontal locking plane 510 is provided at the top of the guide bar 51, and a second inclined surface 511 is connected to the first horizontal locking plane 510. A second unlocking inclined surface 520 that matches the first unlocking inclined surface 501 is provided at the inner end of the lock block 52. A second horizontal locking plane 521 that matches the first horizontal locking plane 510 is provided at the bottom surface of the inner end of the lock block 52. The second inclined surface 511 and the first unlocking inclined surface 501 have the same inclination angle. The first unlocking inclined surface 501 is located above the side of the second inclined surface 511, and the lower side of the first unlocking inclined surface 501 is lower than the upper side of the second inclined surface 511.

[0132] The second unlocking ramp 520 can match the first unlocking ramp 501, or the second unlocking ramp 520 can match the second ramp 511. If they match, it means that the tilt angles are the same.

[0133] During the first stage of stretching, the second horizontal locking plane 521 and the first horizontal locking plane 510 on the bottom surface of the locking block 52 coincide, and the second unlocking inclined surface 520 and the first unlocking inclined surface 501 at the inner end of the locking block 52 coincide. At this time, the distance between the upper drive plate 21 and the lower drive plate 22 is locked by the locking tongue guide bar 50 and the guide bar 51. When the upper drive plate 21 moves downward, it can drive the first forming sleeve 201 on the lower drive plate 22 to perform the first stage of stretching.

[0134] When the exposed end 500 of the lower end of the locking tongue guide bar 50 contacts the top surface of the guide block 18 on the highest fixed plate 13, the first forming sleeve 201 completes the stretching process, that is, the first forming sleeve 201 can no longer descend, thus completing the first stage of stretching.

[0135] During the secondary stretching, the upper drive plate 21 continues to descend. Since the lower end of the latch guide 50 is held in place by the guide block 18, the latch guide 50 and guide bar 51 are currently fixed. The further descent of the upper drive plate 21 causes the first unlocking inclined surface 501 of the latch guide 50 and the second unlocking inclined surface 520 of the lock block 52 to lose their engagement. When the first unlocking inclined surface 501 and the second unlocking inclined surface 520 of the lock block 52 lose their engagement, the second horizontal locking plane 521 will disengage from the first horizontal locking plane 51. With a translational thrust of 0, the locking block drive 54 is elastically compressed. The second unlocking inclined surface 520, which is detached from the first unlocking inclined surface 501, will match the second inclined surface 511 located at the top of the guide bar 51. At this time, the lower end of the stretching punch 200 extends out from the lower end of the first forming sleeve 201 to perform secondary stretching processing. As the stretching depth increases (i.e., the upper drive plate 21 continues to descend), the first unlocking inclined surface 501 will detach from the lower side of the second inclined surface 511 and the locking block 52 will continue to descend along the guide bar 51 to complete the secondary stretching processing.

[0136] Preferably, in this embodiment, the guide bar 51 has a U-shaped cross-section, and the locking tongue guide bar 50 is inserted into the guide bar 51.

[0137] Secondly, the U-shaped guide bar 51 is divided into two opposite sides and a central part connecting the two opposite sides. A second inclined surface 511 is provided at the top of the central part, and a second horizontal locking plane 521 is provided on the top surface of the two opposite sides.

[0138] After all the stretching processes are completed, the upper drive plate 21 and the lower drive plate 22 are reset. After the reset, the locking block 52 is in the state where the second horizontal locking plane 521 and the first horizontal locking plane 510 on the bottom surface of the locking block 52 during the first stretching are in the state where the second unlocking inclined surface 520 and the first unlocking inclined surface 501 on the inner end of the locking block 52 are in the state where the exposed end 500 is disengaged from the contour groove 140.

[0139] The stretching method in this embodiment includes the following steps:

[0140] S1. The metal stamping cup a is pre-placed in the highest position of the stretching die ring 12.

[0141] S2. The first forming sleeve 201 of the multi-layer combined drawing punch 20 moves downward in a state where the upper drive plate 21 and the lower drive plate 22 are locked relative to each other. That is, it performs a first-stage drawing process on the metal stamping cup a in the highest drawing die ring 12 to obtain a first-stage drawn part. During the first-stage drawing, the drawing mechanism is tightened to the highest fixed plate 13. Of course, during the second-stage drawing, the tightening mechanism is also tightened to the highest fixed plate 13.

[0142] S3. When the exposed end 500 of the locking tongue guide bar 50 abuts against the top surface of the guide block 18 on the highest fixed plate 13, the first forming sleeve 201 is stretched into place.

[0143] S3. If the upper drive plate 21 continues to descend in step S3, the relative locking between the upper drive plate 21 and the lower drive plate 22 will be canceled. At this time, the lower end of the stretching punch 200 extends out of the lower end of the first forming sleeve 201. The primary stretching part is subjected to secondary stretching processing in the stretching die ring 12 below the highest stretching die ring 12 to obtain the secondary stretching part.

[0144] After S4 and S3 are completed, the upper drive plate 21 is reset upward. At this time, the secondary stretching part moves upward with the stretching punch 200. The demolding structure 4 of the stretching part on the lower stretching die 1 has its demolding claw 41 holding the secondary stretching part in an elastic manner. As the upper stretching punch 2 continues to descend, the upper end of the stretching part is blocked by the demolding claw 41. At this time, the upper stretching punch 2 rises again to achieve the purpose of the stretching part moving downward and separating from the upper stretching punch 2.

[0145] S5. During the second-stage stretching, the stretched part will come into contact with the inclined elastic plate 30. After S4 is completed, the inclined elastic plate 30 will cause the stretched part to deviate from the inclined direction of the straight fall and be stripped, that is, the stretched part is obtained.

[0146] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A stretching device, comprising a lower stretching die (1) and an upper stretching punch (2) arranged sequentially from bottom to top, characterized in that, The lower drawing die (1) includes a multi-layer drawing die ring (12) spaced apart from bottom to top; the upper drawing punch (2) includes a multi-layer combined drawing punch (20), and an upper drive plate (21) and a lower drive plate (22) spaced apart and parallel from top to bottom. The multi-layer combined drawing punch (20) includes a drawing punch (200) and at least one first forming sleeve (201) sleeved on the lower end of the drawing punch (200). The upper end of the first forming sleeve (201) is fixed to the lower drive plate (22), and the upper end of the drawing punch (200) is fixed to the upper drive plate (21). The drawing device also includes a multi-layer drive plate linkage release mechanism (5) connected between the upper drive plate (21) and the lower drive plate (22). The multi-layer drive plate linkage release mechanism (5) is used for the linkage and mutual release of the upper drive plate (21) and the lower drive plate (22). When the upper drive plate (21) and the lower drive plate (22) are linked, the stretching punch (200) is axially fixed relative to the first forming sleeve (201), and the stretching punch (200) and the first forming sleeve (201) jointly perform first-stage stretching forming. When the upper drive plate (21) and the lower drive plate (22) are disengaged from each other, the stretching punch (200) moves axially relative to the first forming sleeve (201) and the stretching punch (200) performs secondary stretching forming; The multi-layer drive plate linkage release mechanism (5) includes at least two parallel locking tongue guides (50). The lower end of each locking tongue guide (50) is fixed relative to the lower drive plate (22), and the upper end of each locking tongue guide (50) is slidably connected to the upper drive plate (21). A guide strip (51) is slidably fitted on the outside of each locking tongue guide (50). The lower end of the guide strip (51) is fixed to the lower drive plate (22), and the upper end of the guide strip (51) is slidably fitted to the upper drive plate (21). A locking block (52) is slidably provided on the upper drive plate (21). A lock block drive member (54) is provided on the upper drive plate (21), and the lock block drive member (54) causes the lock block (52) to have a tendency to move toward the lock tongue guide bar (50) and the guide bar (51); When the locking block (52) is locked at the top of the locking tongue guide (50) and the top of the guide bar (51), the upper drive plate (21) and the lower drive plate (22) are relatively fixed; when the locking block (52) is unlocked, the upper drive plate (21) can move relative to the lower drive plate (22).

2. The tensioning device according to claim 1, characterized in that, The locking block (52) and the upper drive plate (21) are slidably connected. The locking block (52) and the locking tongue guide (50) are vertically distributed. The locking block (52) and the guide bar (51) are vertically distributed.

3. The stretching device according to claim 1, characterized in that, A first unlocking inclined surface (501) is provided at the top of the latch guide (50), the top of the guide bar (51) is lower than the top of the latch guide (50), a first horizontal locking plane (510) is provided at the top of the guide bar (51), and a second inclined surface (511) is connected to the first horizontal locking plane (510). A second unlocking inclined surface (520) that matches the first unlocking inclined surface (501) is provided at the inner end of the lock block (52), and a second horizontal locking plane (521) that matches the first horizontal locking plane (510) is provided at the bottom surface of the inner end of the lock block (52). The second inclined surface (511) and the first unlocking inclined surface (501) have the same inclination angle, and the first unlocking inclined surface (501) is located above the second inclined surface (511) on the side, and the lower side of the first unlocking inclined surface (501) is lower than the upper side of the second inclined surface (511).

4. The tensioning device according to claim 1, characterized in that, The lower end of each of the latch guide bars (50) extends downward through the lower drive plate (22) and the lower end of the latch guide bar (50) is fixed relative to the lower drive plate (22), and the lower end of each of the latch guide bars (50) has an exposed end (500) exposed below the lower surface of the lower drive plate (22).

5. The stretching device according to claim 1, characterized in that, The lower stretching die (1) also includes a stretching part release structure located below the lowest stretching die ring (12).

6. The stretching device according to claim 5, characterized in that, The demolding structure of the stretching part includes an annular plate (40) with a through hole for the stretching part. A plurality of demolding claws (41) are hinged on the annular plate (40) and are evenly distributed along the circumferential direction of the through hole for the stretching part. At least a portion of the demolding claws (41) extends into the through hole for the stretching part. A stripping elastic drive (42) is provided between the annular plate (40) and the demolding claws (41) such that the portion of the demolding claws (41) extending into the through hole for the stretching part converges toward the axis of the through hole for the stretching part.

7. The stretching device according to claim 6, characterized in that, The demolding claw (41) includes a horizontal part (410) and an inclined part (411) connected to the inside of the horizontal part (410). The horizontal part (410) and the inclined part (411) form an obtuse angle. The inner inclined surface of the inclined part (411) is provided with an arc concave surface (412), and all the arc concave surfaces (412) are coaxial.

8. The stretching device according to claim 7, characterized in that, Each of the inclined portions (411) has a rounded tip (413) at its lower end.

9. The stretching device according to claim 1, characterized in that, The highest position of the stretching die ring 12 is fixed on the fixed plate (13), and a pulling mechanism is provided on the lower drive plate (22). The pulling mechanism is used to pull the material to the lower surface of the fixed plate (13).

10. The stretching device according to claim 9, characterized in that, The material pulling mechanism includes at least two material pulling hooks (25) with their upper ends hinged to opposite sides of the lower drive plate (22). A transverse drive spring (250) is provided between the lower drive plate (22) and the outer side of the material pulling hooks (25). The transverse drive spring (250) causes the hook of the material pulling hook (25) to hook onto the lower surface of the fixed plate (13). A plurality of pull rods (215) are installed on the lower drive plate (22). The upper end of the pull rod (215) is slidably engaged with the upper drive plate (21). An anti-detachment cap (216) is provided at the upper end of the pull rod (215). The anti-detachment cap (216) is used to prevent the pull rod (215) from detaching downward from the upper drive plate (21).

11. A stretching method, characterized in that, The stretching method employs the stretching apparatus according to any one of claims 1-10, and the stretching method includes the following steps: S1. The metal stamping cup (a) is pre-placed in the highest position of the stretching die ring (12); S2. The first forming sleeve (201) of the multi-layer combined stretching punch (20) moves downward in the state of relative locking of the upper drive plate (21) and the lower drive plate (22) to perform first-level stretching processing on the metal stamping cup (a) in the highest stretching die ring (12). S3. When the exposed end (500) of the locking tongue guide (50) abuts against the top surface of the highest fixed plate (13), the first forming sleeve (201) is stretched into place to obtain a first-level stretched part. S3. If the upper drive plate (21) continues to descend in step S3, the relative locking between the upper drive plate (21) and the lower drive plate (22) will be canceled. At this time, the lower end of the stretching punch (200) extends out of the lower end of the first forming sleeve (201). The first-stage stretching part is subjected to second-stage stretching processing in the stretching die ring (12) below the highest stretching die ring (12) to obtain the second-stage stretching part. After S4 and S3 are completed, the upper drive plate (21) is reset upward. At this time, the secondary stretching part moves upward with the stretching punch (200). The demolding claw (41) of the demolding structure (4) on the lower stretching die (1) holds the secondary stretching part in an elastic manner. As the upper stretching punch (2) continues to descend, the upper end of the stretching part is blocked by the demolding claw (41). At this time, the upper stretching punch (2) rises again to achieve the purpose of the stretching part moving downward away from the upper stretching punch (2).

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