A bi-directional and double-punch balanced high-speed bodymaker

Abstract

A bi-directional and double-punch balanced high-speed bodymaker comprises a punch driving mechanism and a blank pressing mechanism, wherein: the punch driving mechanism is composed of a crankshaft (1), two identical connecting rods (2), two identical slide rails (3), two identical sliders (4) and two identical punches (5). And the crankshaft is rotationally supported by a bearing, and the crankshaft is provided with a first crank (11), a second crank (12), a first blank pressing cam (13) and a second blank pressing cam (14). Compared with the prior art, this scheme has two characteristics: first, the swing lever and the secondary connection are removed from each set of punch driving mechanism, which greatly simplifies the structure, while still maintains all the original functions, constituting the omission of elements. Second, it adopts two blank pressing cams and arranges the first driving point of the first blank pressing cam opposite to the second driving point of the second blank pressing cam, and finally, the directions of the first torque (N1) and the second torque (N2) are opposite and they counteract each other, so as to maintain the balance of overall torque on the plane passing the crankshaft axis during the operation of the bodymaker.

Description

High-speed balanced bidirectional double-impact tank stretching machine Technical Field

[0001] This invention relates to can stretching equipment, and particularly to a bidirectional, double-punch can stretching machine that exhibits good process force and torque balance under high-speed operating conditions (stretching speed 400 times / min). A can refers to a metal component with a can shape, such as the can body of an aluminum can, a battery casing, or other metal objects with a can shape. Background Technology

[0002] Metal cans have a wide range of uses in daily life and industry. Typical examples include aluminum cans and lithium battery casings in power batteries. The annual usage of these cans is enormous, especially aluminum cans, whose demand is increasing as people's living standards continue to improve.

[0003] Aluminum cans are typically made of either aluminum or iron, and their structure consists of two parts: the can body and the easy-open lid. The can body is formed by stretching metal sheets using a stretching machine. Existing can stretching machines generally consist of a cup-feeding mechanism, a pressing mechanism, a punch drive mechanism, a stretching die, and a can-exit mechanism. The cup-feeding mechanism transports the pre-stretched can blank (the pre-stretched cup-shaped component), the pressing mechanism clamps the can blank during stretching, the punch drive mechanism provides the stamping stroke during stretching, the stretching die is used to stretch and form the can, and the can-exit mechanism unloads and outputs the can after stretching. The core technology of can stretching machines lies in the design and layout of the punch drive mechanism and the pressing mechanism. With technological advancements and market demands, can stretching machines are developing towards both high speed and high quality. On the one hand, there is a need to continuously increase the stretching speed (stretching speed 400 times / minute), and on the other hand, to achieve high-quality can stretching. This places very high demands on the balance of process forces and torques during the can stretching machine's idle stroke. Therefore, maintaining the balance of process force and torque in a tank stretching machine under high-speed operating conditions is a technical challenge in this field.

[0004] Chinese patent CN102581107A discloses an invention patent application titled "Bidirectional Double-Punch Tank Stretching Machine," with application number 201210040629.X. This patent arranges two sets of punch drive mechanisms sharing a single crankshaft in a symmetrical layout. This balances the process forces and torques of components such as the swing arm, slider, and punch during movement, as well as the reaction forces generated during tank forming. This significantly reduces the load on the crankshaft support bearings, lowers bearing design and processing requirements, and extends their service life. While this patent achieves significant results in reducing process forces and torques through the symmetrical layout of the two punch mechanisms, it still has the following problems: First, the structure is complex, with many moving parts. This patented solution has two sets of punch drive mechanisms. Each punch drive mechanism consists of a crankshaft, main connecting rod, rocker arm, secondary connecting rod, guide rail, slider, and punch. The rocker arm can amplify the punching stroke and reduce the crank radius. The secondary connecting rod can reduce the pressure angle between the slider and the guide rail, which is beneficial to the accuracy and stability of the sliding mechanism. However, the presence of the rocker arm and secondary connecting rod also increases the overall size of the equipment, makes the mechanism more complex, and increases the number of moving parts. Secondly, the equipment still has shortcomings in terms of overall layout and force distribution. For example, when using the first layout design shown in Figure 5 of the patent, the process force and torque in the horizontal direction can be balanced because the two rocker arms maintain symmetry during movement. However, in the vertical direction, they are not only unbalanced but also superimposed. If the second layout design shown in Figure 9 of the patent is adopted, although the horizontal and vertical directions can basically maintain balance from the perspective of process force and torque, the structure becomes very complex, and there is a large vertical drop between the left and right stretching stations.

[0005] In view of this, the research topic of this invention is how to design a bidirectional double-punch tank stretching machine with a simpler structure that is more conducive to the balance of process forces and torques.

[0006] Summary of the Invention

[0007] This invention provides a high-speed balanced bidirectional double-punch tank stretching machine, the purpose of which is to solve the problems of complex structure and poor balance of process force and torque in existing bidirectional double-punch tank stretching machines.

[0008] To achieve the above objectives, the technical solution adopted by this invention is: a high-speed balanced bidirectional double-punch tank stretching machine, comprising a punch drive mechanism and a pressing mechanism, the innovation of which lies in: the punch drive mechanism is composed of the following connected components:

[0009] A crankshaft, which is rotatably supported by bearings, is provided with a first crank, a second crank, a first pressure cam and a second pressure cam.

[0010] There are two links, namely the first link and the second link.

[0011] There are two slide rails, namely the first slide rail and the second slide rail.

[0012] There are two sliders, namely the first slider and the second slider.

[0013] Two strikers, namely the first striker and the second striker.

[0014] in:

[0015] The first crank is rotatably connected to one end of the first connecting rod, and the other end of the first connecting rod is rotatably connected to the first slider. The first slider is mounted on the first slide rail and is slidably connected to the first slide rail. The first slide rail is fixed relative to the base of the tank stretching machine, and the first slider is fixedly connected to the first punch.

[0016] The second crank is rotatably connected to one end of the second connecting rod, and the other end of the second connecting rod is rotatably connected to the second slider. The second slider is mounted on the second slide rail and is slidably connected to the second slide rail. The second slide rail is fixed relative to the base of the tank stretching machine, and the second slider is fixedly connected to the second punch.

[0017] The first crank, the first connecting rod, the first slider, the first slide rail, the first punch, and the first pressure cam are located on one end of the crankshaft and constitute the first punch drive mechanism; the second crank, the second connecting rod, the second slider, the second slide rail, the second punch, and the second pressure cam are located on the other end of the crankshaft and constitute the second punch drive mechanism.

[0018] The pressing mechanism consists of a first pressing mechanism and a second pressing mechanism. The first pressing mechanism is configured to correspond to the first punch drive mechanism. The first pressing cam is driven to the first pressing mechanism and has a first drive point. The second pressing mechanism is configured to correspond to the second punch drive mechanism. The second pressing cam is driven to the second pressing mechanism and has a second drive point.

[0019] On the plane that crosses the crankshaft axis, the first punch drive mechanism and the second punch drive mechanism are symmetrically arranged with the rotation center point of the crankshaft as the reference, so that the tank stretching machine maintains overall force balance on the plane that crosses the crankshaft axis when it is working.

[0020] On the plane passing through the crankshaft axis, the first crank and the second crank have opposite turning directions. The first and second pressing cams are fixedly connected relative to the crankshaft. Simultaneously, on the plane passing through the crankshaft axis, the first driving point of the first pressing cam and the second driving point of the second pressing cam are opposite in position. In operation, the tensile force applied by the first connecting rod to the first crank is defined as the first tensile force, the tensile force applied by the second connecting rod to the second crank is defined as the second tensile force, the pressing force applied by the first pressing mechanism to the first pressing cam is defined as the first pressing force, and the pressing force applied by the second pressing mechanism to the second pressing cam is defined as the second pressing force. On the plane passing through the crankshaft axis, the first tensile force and the second tensile force are parallel to each other and opposite in direction, forming a first torque. The first pressing force and the second pressing force are parallel to each other and opposite in direction, forming a second torque. The first torque and the second torque are opposite in direction, ensuring that the tank stretching machine maintains overall torque balance on the plane passing through the crankshaft axis during operation.

[0021] The relevant content in the above technical solution is explained as follows:

[0022] 1. In the above-described solution, the can stretching machine, as a complete machine, also includes a housing, two sets of molds, two sets of cup-feeding mechanisms, and two sets of can-discharging mechanisms. Since the innovation of this invention lies in the punch drive mechanism and the edge-pressing mechanism, these mechanisms can utilize existing technologies, and therefore are not described or illustrated in detail in the above solution. This is understandable and acceptable to those skilled in the art.

[0023] 2. In the above scheme, the "edge-pressing mechanism" refers to the mechanism that presses the can blank during can stretching (pressing it at the bottom edge of the can blank). It is an indispensable component of the can stretching machine, but in this invention, the specific structure and form of the edge-pressing mechanism do not affect the expression and embodiment of the innovative content of this invention. Therefore, the above scheme only gives the term "edge-pressing mechanism" without specifying its specific structure and form.

[0024] 3. In the above scheme, "on the plane that intersects the axis of crankshaft 1" corresponds to the plane shown in Figure 1. "on the plane that passes through the axis of crankshaft 1" corresponds to the plane shown in Figure 2.

[0025] 4. In the above scheme, the "blade clamping force" refers to the process force used to clamp the can blank during the can body stretching process, excluding the inertial force during the mechanism's movement. The "stretching force" refers to the process force used to stretch the can blank during the can body stretching process, excluding the inertial force during the mechanism's movement.

[0026] 5. In the above scheme, the first crank and the second crank are arranged adjacent to each other in the axial direction of the crankshaft, the first pressure cam is arranged on the outer side of the first crank in the axial direction, and the second pressure cam is arranged on the outer side of the second crank in the axial direction.

[0027] 6. In the above scheme, the first pressing cam and the second pressing cam are arranged adjacent to each other in the axial direction of the crankshaft, the first crank is arranged on the outer side of the first pressing cam in the axial direction, and the second crank is arranged on the outer side of the second pressing cam in the axial direction.

[0028] The design principle and concept of this invention are as follows: In order to solve the problems of complex structure and poor balance of process force and torque of existing bidirectional double-punch tank stretching machines, this invention has made the following two improvements and breakthroughs in the structural design of the tank stretching machine.

[0029] Firstly, for the existing bidirectional double-punch tank stretching machine (CN102581107A, scheme in Figure 5), the swing arm and secondary connection are eliminated in each punch drive mechanism, and the other end of the main connecting rod is directly rotatably connected to the slider. This simplifies the most important punch drive mechanism in the tank stretching machine structure.

[0030] Secondly, in the crankshaft structure design, a first pressing cam is designed for the first crankshaft, and a second pressing cam is designed for the second crankshaft. Simultaneously, the pressing force of the first pressing mechanism acting on the first pressing cam and the pressing force of the second pressing mechanism acting on the second pressing cam are designed to be parallel and opposite in direction. Ultimately, torque balance can be achieved by using the technical measure of the first torque and the second torque having opposite directions.

[0031] Due to the application of the above technical solution, the present invention has the following advantages and effects compared with the existing bidirectional double-punch tank stretching machine:

[0032] 1. This invention eliminates the rocker arm and secondary connector in each punch drive mechanism. From a practical perspective, this not only greatly simplifies the structure but also retains all original functions. From an innovative standpoint, this constitutes an omission of key elements, thus possessing significant substantive characteristics. For existing bidirectional double-punch tank stretching machines (CN102581107A, Figure 5), the rocker arm amplifies the punching stroke and reduces the crank radius, while the secondary connector reduces the pressure angle between the slider and the guide rail, which is beneficial for the accuracy and stability of the sliding mechanism. However, the presence of the rocker arm and secondary connector also increases the overall size of the equipment, complicates the mechanism, and increases the number of moving parts. From the design of existing bidirectional double-punch tank stretching machines, it seems that the rocker arm and secondary connector cannot be omitted in the punch drive mechanism. However, this invention makes a bold breakthrough in structural design, which is obviously non-obvious to those skilled in the art. As for the force and balance problems that may arise from omitting the rocker arm and secondary connector, this invention also overcomes them through the arrangement of the pressure cam.

[0033] 2. This invention specifically incorporates a first pressure cam and a second pressure cam in the crankshaft structure design. This design plays a crucial role in the force and balance of the punch drive mechanism. Those skilled in the art know that the punch drive mechanism is the core of the tank stretching machine, and it is a motion mechanism with high force and inertia. Especially under high-speed operating conditions (stretching speed 400 times / minute), the balance of process force and torque becomes particularly prominent from the perspective of the entire equipment. This not only affects the service life of the equipment but also directly impacts the stretching quality and effect. For the existing bidirectional double-punch can body stretching machine (CN102581107A), in the first layout design shown in Figure 5, the process force and torque of the equipment can be balanced in the horizontal direction (the horizontal direction shown in Figure 5, relative to the left-right direction "on the plane intersecting the crankshaft axis" as described in this invention) because the two rocker arms maintain symmetry during movement. However, in the horizontal plane (relative to the left-right direction "on the plane passing through the crankshaft axis" as described in this invention), the tension force of the first connecting rod on the first crank and the tension force of the second connecting rod on the second crank are parallel and opposite in direction, forming a first torque, which leads to an imbalance of forces on the crankshaft and the support bearing. In particular, after omitting the rocker arms in this invention, the crank radius is increased to meet the stamping stroke, which makes the torque balance problem particularly prominent, increasing the impact and load on the crankshaft support bearing. To address this problem, the present invention utilizes two pressure cams, with the first driving point of the first pressure cam and the second driving point of the second pressure cam positioned opposite to each other. Ultimately, on the plane passing through the crankshaft axis, the first torque and the second torque are in opposite directions and cancel each other out, maintaining overall torque balance in the plane passing through the crankshaft axis during the operation of the tank stretching machine. Therefore, the present invention not only incorporates the advantage of maintaining overall force balance on the plane intersecting the crankshaft axis of the existing bidirectional double-punch tank stretching machine (CN102581107A), but also overcomes the deficiency of torque imbalance on the plane passing through the crankshaft axis, achieving significant results and maintaining overall torque balance on the plane passing through the crankshaft axis during the operation of the tank stretching machine.

[0034] 3. This invention enables foundation-free installation. Tank stretching machines are large-scale stretching equipment, especially under high-speed operation (stretching speed 400 times / minute). Due to the large process forces, torques, and vibrations, foundation installation is usually required. In this case, a one-meter-deep pit needs to be dug, followed by pouring a large concrete foundation. Finally, the tank stretching machine is fixed to the concrete foundation. Because this invention fully considers the balance of forces and torques in the overall design, the resulting equipment can be installed without a foundation, greatly facilitating installation and construction while also saving installation costs. Attached Figure Description

[0035] Figure 1 is a schematic diagram of the punch drive mechanism of the present invention;

[0036] Figure 2 is a schematic diagram of the crankshaft of the present invention;

[0037] Figure 3 is a perspective view of the punch drive mechanism according to an embodiment of the present invention;

[0038] Figure 4 is a perspective view of the crankshaft according to an embodiment of the present invention.

[0039] In the attached diagrams: 1. Crankshaft; 11. First crankshaft; 12. Second crankshaft; 13. First blanking cam; 14. Second blanking cam; 2. Connecting rod; 21. First connecting rod; 22. Second connecting rod; 3. Slide rail; 31. First slide rail; 32. Second slide rail; 4. Slider; 41. First slider; 42. Second slider; 5. Punch rod; 51. First punch rod; 52. Second punch rod; F1. First tensile force; F2. Second tensile force; F3. First blanking force; F4. Second blanking force; N1. First torque; N2. Second torque. Detailed Implementation

[0040] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0041] Example: A high-speed balanced bidirectional double-impact tank stretching machine

[0042] The can stretching machine consists of a box body, two sets of molds, two sets of edge pressing mechanisms, two sets of cup feeding mechanisms, two sets of punch drive mechanisms, and two can discharging mechanisms. Since the innovation of this invention lies in the punch drive mechanism and the edge pressing mechanism, the other structures or mechanisms can adopt existing technologies. Therefore, they are not described in detail in this embodiment, which is understandable and acceptable to those skilled in the art.

[0043] Referring to Figures 1-4, the punch drive mechanism is composed of the following connected components:

[0044] A crankshaft 1 (see Figures 2 and 4) is rotatably supported by bearings. The crankshaft 1 is provided with a first crank 11, a second crank 12, a first pressure cam 13, and a second pressure cam 14. The first crank 11 and the second crank 12 are arranged adjacent to each other in the axial direction of the crankshaft 1. The first pressure cam 13 is arranged axially outside the first crank 11, and the second pressure cam 14 is arranged axially outside the second crank 12 (see Figure 2).

[0045] Two identical links 2, namely the first link 21 and the second link 22 (see Figures 1 and 3).

[0046] Two identical slide rails 3, namely the first slide rail 31 and the second slide rail 32 (see Figure 1).

[0047] Two identical sliders 4, namely the first slider 41 and the second slider 42 (see Figures 1 and 3).

[0048] Two identical strikers 5, namely the first striker 51 and the second striker 52 (see Figures 1 and 3).

[0049] in:

[0050] The first crank 11 is rotatably connected to one end of the first connecting rod 21, and the other end of the first connecting rod 21 is rotatably connected to the first slider 41. The first slider 41 is mounted on the first slide rail 31 and is slidably connected to the first slide rail 31. The first slide rail 31 is fixed relative to the base of the tank stretching machine. The first slider 31 is fixedly connected to the first punch 51 (see Figures 1 and 3).

[0051] The second crank 12 is rotatably connected to one end of the second connecting rod 22, and the other end of the second connecting rod 22 is rotatably connected to the second slider 42. The second slider 42 is mounted on the second slide rail 32 and is slidably connected to the second slide rail 32. The second slide rail 32 is fixed relative to the base of the tank stretching machine. The second slider 32 is fixedly connected to the second punch 52 (see Figures 1 and 3).

[0052] The first crank 11, first connecting rod 21, first slider 41, first slide rail 31, first punch 51, and first pressure cam 13 are located at one end of the crankshaft 1 and constitute the first punch drive mechanism (see Figures 1 and 3). The second crank 12, second connecting rod 22, second slider 42, second slide rail 32, second punch 52, and second pressure cam 14 are located at the other end of the crankshaft 1 and constitute the second punch drive mechanism (see Figures 1 and 3).

[0053] The edge-pressing mechanism consists of a first edge-pressing mechanism and a second edge-pressing mechanism. The first edge-pressing mechanism is configured to correspond to the first punch drive mechanism, and the first edge-pressing cam 13 is drivenly connected to the first edge-pressing mechanism and has a first drive point. The second edge-pressing mechanism is configured to correspond to the second punch drive mechanism, and the second edge-pressing cam 14 is drivenly connected to the second edge-pressing mechanism and has a second drive point. In this embodiment, the specific structure of the first and second edge-pressing mechanisms is not important; existing technologies can be used, and this does not affect the implementation and effect of the invention. The key is that the first edge-pressing cam 13 can drive the first edge-pressing mechanism to perform the pressing task on the edge of the can blank before the can body is stretched.

[0054] On the plane that crosses the axis of crankshaft 1 (i.e., the plane shown in Figure 1), the first punch drive mechanism and the second punch drive mechanism are symmetrically arranged with the rotation center point of crankshaft 1 as the reference, so that the tank stretching machine maintains overall force balance on the plane that crosses the axis of crankshaft 1 when it is working (see Figure 1).

[0055] On the plane passing through the axis of crankshaft 1 (i.e., the plane shown in Figure 2), the first crank 11 and the second crank 12 have opposite turning directions. The first pressing cam 13 and the second pressing cam 14 are fixedly connected relative to crankshaft 1. Simultaneously, on the plane passing through the axis of crankshaft 1, the first driving point of the first pressing cam 13 and the second driving point of the second pressing cam 14 are opposite in position. In the working state, the tensile force applied by the first connecting rod 21 to the first crank 11 is defined as the first tensile force F1, and the tensile force applied by the second connecting rod 22 to the second crank 12 is defined as the second tensile force F2. The blanking force applied to the first blanking cam 13 by the second blanking mechanism is the first blanking force F3, and the blanking force applied to the second blanking cam 14 by the second blanking mechanism is the second blanking force F4. On the plane passing through the axis of crankshaft 1, the first tensile force F1 and the second tensile force F2 are parallel to each other and opposite in direction, forming the first torque N1. The first blanking force F3 and the second blanking force F4 are parallel to each other and opposite in direction, forming the second torque N2. The first torque N1 and the second torque N2 are opposite in direction, so that the tank stretching machine maintains overall torque balance on the plane passing through the axis of crankshaft 1 when it is working (see Figure 1).

[0056] The following description addresses other embodiments and structural changes of the present invention:

[0057] 1. In the above embodiments, as shown in Figure 2, the first crank 11 and the second crank 12 are arranged adjacent to each other in the axial direction of the crankshaft 1, the first pressing cam 13 is arranged on the outer side of the first crank 11 in the axial direction, and the second pressing cam 14 is arranged on the outer side of the second crank 12 in the axial direction. However, the present invention is not limited to this. It can be modified so that the first pressing cam 13 and the second pressing cam 14 are arranged adjacent to each other in the axial direction of the crankshaft 1, the first crank 11 is arranged on the outer side of the first pressing cam 13 in the axial direction, and the second crank 12 is arranged on the outer side of the second pressing cam 14 in the axial direction. It can even be changed to other arrangements, but essentially it is required that the first torque N1 and the second torque N2 are in opposite directions, so as to play a role in balancing torques in the plane passing through the axis of the crankshaft 1.

[0058] 2. In the above embodiments, two pressure cams are used, and the first driving point of the first pressure cam 13 and the second driving point of the second pressure cam 14 are arranged in opposite positions. This ensures that the first torque N1 and the second torque N2 are in opposite directions and cancel each other out, maintaining overall torque balance in the plane passing through the crankshaft axis during the operation of the tank stretching machine. In practice, while the opposite directions of the first torque N1 and the second torque N2 are necessary in this invention, complete cancellation is not essential and depends on the specific design. Complete cancellation is optimal, but partial cancellation is also permissible, and the final determination can be based on the overall effect.

[0059] 3. In the above embodiments, two identical connecting rods 2 are used, namely the first connecting rod 21 and the second connecting rod 22. Two identical slide rails 3 are used, namely the first slide rail 31 and the second slide rail 32. Two identical sliders 4 are used, namely the first slider 41 and the second slider 42. Two identical punches 5 are used, namely the first punch 51 and the second punch 52. However, the present invention is not limited to this. For example, the first connecting rod 21 and the second connecting rod 22 may have different shapes or some different dimensions. The first slider 41 and the second slider 42 may have different shapes or some different dimensions.

[0060] 4. In the above embodiments, the specific structure and form of the pressing mechanism are not described because the pressing mechanism is an indispensable component for the tank stretching machine. However, in this invention, the specific structure and form of the pressing mechanism do not affect the expression and embodiment of the innovative content of this invention. Therefore, only the term "pressing mechanism" is given in the above schemes, without specifying its specific structure and form. In fact, the type of pressing mechanism used is irrelevant to this invention. As long as the pressing mechanism can cooperate with the first pressing cam 13 and the second pressing cam 14 on the crankshaft 1, the purpose of this invention can be achieved, and the expected effect of this invention can be realized.

[0061] 5. In the above embodiments, the first tensile force F1 corresponds to the first punch drive mechanism, and the first blank-pressing force F3 corresponds to the first blank-pressing mechanism. The first punch drive mechanism and the first blank-pressing mechanism act on the same stretched can blank. The second tensile force F2 corresponds to the second punch drive mechanism, and the second blank-pressing force F4 corresponds to the second blank-pressing mechanism. The second punch drive mechanism and the second blank-pressing mechanism act on another can blank that is stretched. However, the present invention is not limited to this. The first blank-pressing force F3 and the second blank-pressing force F4 shown in Figure 2 can be interchanged. That is, the first blank-pressing mechanism corresponding to the first blank-pressing force F3 can be paired with the second punch drive mechanism, and the second blank-pressing mechanism corresponding to the second blank-pressing force F4 can be paired with the first punch drive mechanism.

[0062] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A high-speed balanced bidirectional double-punch tank stretching machine, comprising a punch drive mechanism and a pressing mechanism, characterized in that: The punch drive mechanism is composed of the following connected components: A crankshaft (1) is rotatably supported by bearings, and the crankshaft (1) is provided with a first crank (11), a second crank (12), a first pressure cam (13) and a second pressure cam (14); Two links (2), namely the first link (21) and the second link (22); Two slide rails (3), namely the first slide rail (31) and the second slide rail (32); Two sliders (4), namely the first slider (41) and the second slider (42); Two strikers (5), namely the first striker (51) and the second striker (52); in: The first crank (11) is rotatably connected to one end of the first connecting rod (21), and the other end of the first connecting rod (21) is rotatably connected to the first slider (41). The first slider (41) is mounted on the first slide rail (31) and slidably connected to the first slide rail (31). The first slide rail (31) is fixed relative to the base of the tank stretching machine. The first slider (31) is fixedly connected to the first punch (51). The second crank (12) is rotatably connected to one end of the second connecting rod (22), and the other end of the second connecting rod (22) is rotatably connected to the second slider (42). The second slider (42) is mounted on the second slide rail (32) and slidably connected to the second slide rail (32). The second slide rail (32) is fixed relative to the base of the tank stretching machine. The second slider (32) is fixedly connected to the second punch (52). The first crank (11), the first connecting rod (21), the first slider (41), the first slide rail (31), the first punch (51), and the first pressure cam (13) are located on one end of the crankshaft (1) and constitute the first punch drive mechanism; the second crank (12), the second connecting rod (22), the second slider (42), the second slide rail (32), the second punch (52), and the second pressure cam (14) are located on the other end of the crankshaft (1) and constitute the second punch drive mechanism; The pressing mechanism consists of a first pressing mechanism and a second pressing mechanism. The first pressing mechanism is configured to correspond to the first punch drive mechanism. The first pressing cam (13) is driven to the first pressing mechanism and has a first drive point. The second pressing mechanism is configured to correspond to the second punch drive mechanism. The second pressing cam (14) is driven to the second pressing mechanism and has a second drive point. On the plane that crosses the axis of the crankshaft (1), the first punch drive mechanism and the second punch drive mechanism are symmetrically arranged with the rotation center point of the crankshaft (1) as the reference. On the plane passing through the crankshaft (1) axis, the first crank (11) and the second crank (12) have opposite turning directions. The first pressure cam (13) and the second pressure cam (14) are fixedly connected relative to the crankshaft (1). Simultaneously, on the plane passing through the crankshaft (1) axis, the first drive point of the first pressure cam (13) and the second drive point of the second pressure cam (14) are opposite in position. In the working state, the tensile force applied by the first connecting rod (21) to the first crank (11) is defined as the first tensile force (F1), and the tensile force applied by the second connecting rod (22) to the second crank (12) is defined as... The first pressing force (F2) is the pressing force applied by the first pressing mechanism to the first pressing cam (13), which is the first pressing force (F3). The second pressing mechanism applies the pressing force to the second pressing cam (14), which is the second pressing force (F4). On the plane passing through the axis of the crankshaft (1), the first pressing force (F1) and the second pressing force (F2) are parallel to each other and opposite in direction, forming the first torque (N1). The first pressing force (F3) and the second pressing force (F4) are parallel to each other and opposite in direction, forming the second torque (N2). The first torque (N1) and the second torque (N2) are opposite in direction.

2. The tank stretching machine according to claim 1, characterized in that: The first crank (11) and the second crank (12) are arranged adjacent to each other in the axial direction of the crankshaft (1). The first pressure cam (13) is arranged on the outer side of the first crank (11) in the axial direction, while the second pressure cam (14) is arranged on the outer side of the second crank (12) in the axial direction.

3. The tank stretching machine according to claim 1, characterized in that: The first pressing cam (13) and the second pressing cam (14) are arranged adjacent to each other in the axial direction of the crankshaft (1). The first crank (11) is arranged on the outer side of the first pressing cam (13) in the axial direction, while the second crank (12) is arranged on the outer side of the second pressing cam (14) in the axial direction.