Cutting equipment for pressure vessel production

Abstract

The invention relates to the field of disk saw cutting equipment, in particular to cutting equipment for pressure vessel production, which comprises a conveying support, a numerical control circular saw and a workpiece, and further comprises a frame body, the frame body is composed of a pair of rectangular frames and four cross rods connected with the frames, and each frame is composed of an upper channel steel, a lower channel steel and two vertical channel steel; the clamping mechanism comprises two vertically-arranged guide rods, guide rails are horizontally arranged at the top ends and the bottom ends of the guide rods, the two ends of each guide rod are slidably connected with the adjacent guide rails, and the two guide rods are slidably connected with sliding tables. On the basis that the advantage of small occupied space of circular saw cutting equipment is reserved, the device can automatically judge the diameter of the workpiece, select the optimal position to clamp and drive the workpiece to rotate, and achieve cutting of workpieces with different pipe diameters.

Description

Technical Field

[0001] The invention relates to the field of circular sawing equipment, in particular to a cutting equipment for producing pressure vessels. Background Art

[0002] The production of small high-pressure pressure vessels, such as fire extinguisher tanks, compressed gas cylinders, etc., is generally achieved by heating and rolling the ends of the steel pipe, sealing the two ends of the steel pipe, and then processing the interface assembly valve body and other accessories. The production of seamless steel pipes is achieved by extruding steel bars. The length of the seamless steel pipe depends on its production equipment and cannot be flexibly adjusted. Therefore, before the hot pressing of the pressure vessel bottle body, the seamless steel pipe needs to be cut into sections.

[0003] The shape of the steel pipe circular saw cutting equipment is close to a straight line, while the shape of the steel pipe band saw cutting equipment is close to a cross. Therefore, the band saw cutting equipment occupies a larger area than the circular saw cutting equipment. However, the band saw cutting has a wide range of applicability for different pipe diameters, while the cutting range of the circular saw cutting equipment is limited by the radius of the saw blade and can often only be used for small-diameter pipe cutting. Under ideal conditions, it is necessary to reduce the size of the steel pipe cutting equipment and reduce the occupation of the site by the cutting equipment, and the cutting equipment must be compatible with a larger cutting processing range. Therefore, a cutting equipment for pressure vessel production that can perform rotary cutting on steel pipes is proposed. Summary of the invention

[0004] In view of the above or prior art pressure vessel body cutting and processing equipment, the problem that the band saw cutting equipment occupies a large area while the circular saw cutting equipment has a narrow processing range, the present invention is proposed.

[0005] Therefore, an object of the present invention is to provide a cutting device for pressure vessel production.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions: a cutting device for pressure vessel production, comprising a conveying bracket, a CNC circular saw and a workpiece, and also comprising: a frame body, the frame body is composed of a pair of rectangular frames and four cross bars connecting the frames, each of the frames is composed of an upper channel steel, a lower channel steel and two vertical channel steels; a clamping mechanism, which comprises two vertically arranged guide rods, the top and bottom ends of the guide rods are horizontally provided with guide rails, and the two ends of the guide rods are slidably connected to adjacent guide rails, the two guide rods are slidably connected to slides, and the sides of the two slides close to each other are rotatably connected to a pair of rollers, the two guide rods are located on the sides away from each other and are fixedly connected to hydraulic cylinders one, and the piston rods of the two hydraulic cylinders one are vertically upward with the adjacent The slide is fixedly connected, and a cylinder and a bidirectional screw rod are arranged between the bottom ends of the two guide rods, and the cylinder body of the cylinder is fixedly connected to the adjacent lower channel steel, and the piston rod of the cylinder is vertically fixedly connected to the guide rod, and the bidirectional screw rod is threadedly connected to the guide rod, and a group of clamping mechanisms are assembled in each of the frame. In one of the frame, the two guide rails are respectively fixedly connected to the upper channel steel and the lower channel steel, and the two ends of the bidirectional screw rod are respectively rotatably connected to the two vertical channel steels; a measuring mechanism, which includes an angle steel fixedly connected to the top of the frame, and the angle steel is fixedly connected with a slide rail, and the slide rail on the angle steel is slidably connected with a hydraulic cylinder 2, and the piston rod of the hydraulic cylinder 2 is vertically downwardly arranged, and a connecting rod is hinged between the bottom end of the piston rod of the hydraulic cylinder 2 and one end of the angle steel.

[0007] As a preferred embodiment of the cutting equipment for pressure vessel production of the present invention, the CNC circular saw is sleeved in a frame, and the shell of the CNC circular saw is fixedly connected to the frame, the workpiece parallel cross bar passes through the two side frames of the frame, and the conveying bracket slides to support the part of the workpiece located outside the frame, the CNC circular saw is located at the bottom of the workpiece, and the axis of the workpiece and the axis of the cutting blade of the CNC circular saw are parallel to each other.

[0008] As a preferred solution of the cutting equipment for pressure vessel production of the present invention, the conveying bracket is arranged in a concave shape, and bull's eye rollers are arranged on both sides of the conveying bracket, the shell of the bull's eye roller is fixedly connected to the conveying bracket, and the bull's eye roller is in rolling contact with the outer wall of the workpiece.

[0009] As a preferred solution of the cutting equipment for pressure vessel production of the present invention, the two guide rods are both located at the top end of the slide table and sleeved with springs.

[0010] As a preferred solution of the cutting equipment for pressure vessel production of the present invention, the cylinder, the lower channel steel and the bidirectional screw are parallel to each other, and the two sections of threads of the bidirectional screw from the middle to the two ends are symmetrical to each other.

[0011] As a preferred solution of the cutting equipment for pressure vessel production of the present invention, the angle steel is fixedly connected to the bottom edge of the upper channel steel of the two sets of frame frames, and the angle steel is connected to the middle part of the upper channel steel, the angle steel is located at one end of the equipment feeding and extends outside the frame body, and the connecting rod is hinged to the bottom edge of one end of the angle steel extension.

[0012] As a preferred solution of the cutting equipment for pressure vessel production of the present invention, the bottom of the connecting rod away from the hinge axis of the angle steel is connected with a ball, and the ball is in rolling contact with the outer wall of the workpiece.

[0013] As a preferred solution of the cutting equipment for pressure vessel production of the present invention, in which: in a group of clamping mechanisms, the axes of the four rollers are parallel to the axis of the workpiece, and the rollers are rollingly pressed against the outer wall of the workpiece, and one of the slides is fixedly connected to a motor, one end of the rotating shaft of the roller and the output shaft of the motor are connected to pulleys, and a synchronous belt is wound around the three pulleys.

[0014] As a preferred solution of the cutting equipment for pressure vessel production of the present invention, the rotation direction of the motor output shaft is opposite to the rotation direction of the saw blade of the CNC circular saw.

[0015] As a preferred embodiment of the cutting equipment for pressure vessel production of the present invention, the top end of the cylinder body of hydraulic cylinder 2 is connected to the bottom end of the cylinder body of hydraulic cylinder 1 through an oil pipe, and the effective action area ratio of the piston rods of hydraulic cylinder 1 and hydraulic cylinder 2 is one to two.

[0016] The beneficial effects of the cutting equipment for pressure vessel production of the present invention are as follows: while retaining the advantage of the circular saw cutting equipment that it occupies less space, the device can also automatically determine the diameter of the workpiece through a measuring mechanism, and through the hydraulic cylinder 2 of the measuring mechanism linking the hydraulic cylinder 1 of the clamping mechanism, drive the slide to rise to the optimal position to clamp the workpiece, and drive the workpiece to rotate, thereby achieving efficient cutting of workpieces of different diameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0018] Figure 1 This is a schematic diagram of the overall structure of the cutting equipment used in pressure vessel production.

[0019] Figure 2 Cutting equipment for pressure vessel production Figure 1 Schematic diagram of the structure at A in the middle.

[0020] Figure 3 for Figure 1 Schematic diagram of the structure from another perspective.

[0021] Figure 4 Exploded view of the connection frame between the two clamping mechanisms of a cutting device for pressure vessel production.

[0022] Figure 5 A cross-sectional view of the clamping mechanism and frame assembly structure of a cutting device for pressure vessel production.

[0023] Figure 6 Schematic diagram of the measuring mechanism and frame assembly structure of the cutting equipment used in pressure vessel production (oblique upward perspective).

[0024] Figure 7 This is a schematic diagram of the interaction structure between the measuring mechanism of the cutting equipment used in pressure vessel production and the steel pipe.

[0025] In the figure: 100, conveying bracket; 101, CNC circular saw; 100a, bull's eye roller; 200, frame; 201, frame; 202, cross bar; 201a, upper channel steel; 201b, lower channel steel; 201c, vertical channel steel; 300, clamping mechanism; 301, guide rod; 302, guide rail; 303, slide; 304, roller; 305, hydraulic cylinder one; 306, two-way screw rod; 307, cylinder; 308, spring; 309, motor; 310, pulley; 311, synchronous belt; 400, measuring mechanism; 401, angle steel; 402, hydraulic cylinder two; 403, connecting rod; 404, ball bearing; 500, workpiece. DETAILED DESCRIPTION

[0026] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings.

[0027] Example, see Figure 1 to Figure 7 , which is the first embodiment of the present invention, provides a cutting device for pressure vessel production, which can cut steel pipes of different diameters in a large range, and the device has a compact structure and occupies a small area. Figure 1 As shown, it includes a conveying bracket 100, a CNC circular saw 101 and a workpiece 500, and also includes a frame 200, a clamping mechanism 300 and a measuring mechanism 400, as shown in FIG. Figure 4 As shown, the frame 200 is composed of a pair of rectangular frames 201 and four crossbars 202 connecting the frames 201. Each frame 201 is composed of an upper channel steel 201a, a lower channel steel 201b and two vertical channel steels 201c. Figure 5As shown, the clamping mechanism 300 includes two vertically arranged guide rods 301, the top and bottom ends of the guide rods 301 are horizontally provided with guide rails 302, and the two ends of the guide rods 301 are slidably connected to the adjacent guide rails 302, the two guide rods 301 are slidably connected to the slides 303, and the sides of the two slides 303 close to each other are rotatably connected to a pair of rollers 304, the two guide rods 301 are located on the sides away from each other and are fixedly connected to hydraulic cylinders 305, and the piston rods of the two hydraulic cylinders 305 are vertically fixedly connected to the adjacent slides 303 upward, a cylinder 307 and a bidirectional screw rod 306 are arranged between the bottom ends of the two guide rods 301, and the cylinder body of the cylinder 307 is fixedly connected to the adjacent lower channel steel 201b, the piston rod of the cylinder 307 is vertically fixedly connected to the guide rod 301, and the bidirectional screw rod 306 is threadedly connected to the guide rod 301; as shown Figure 4 As shown, each frame 201 is equipped with a set of clamping mechanisms 300. In a frame 201, two guide rails 302 are fixedly connected to the upper channel steel 201a and the lower channel steel 201b respectively, and the two ends of the bidirectional screw rod 306 are rotatably connected to the two vertical channel steels 201c respectively; Figure 6 and Figure 7 As shown, the measuring mechanism 400 includes an angle steel 401 fixedly connected to the top of the frame 200, and the angle steel 401 is fixedly connected to a slide rail, the slide rail on the angle steel 401 is slidably connected to a hydraulic cylinder 2 402, the piston rod of the hydraulic cylinder 2 402 is vertically arranged downward, and a connecting rod 403 is hinged between the bottom end of the piston rod of the hydraulic cylinder 2 402 and one end of the angle steel 401.

[0028] Specifically, Figure 1 and Figure 3 As shown, the CNC circular saw 101 is sleeved in the frame 200, and the shell of the CNC circular saw 101 is fixedly connected to the frame 200, the parallel crossbar 202 of the workpiece 500 passes through the two side frames 201 of the frame 200, and the conveying bracket 100 slidably supports the part of the workpiece 500 located outside the frame 200, the CNC circular saw 101 is located at the bottom of the workpiece 500, and the axis of the workpiece 500 and the axis of the cutting blade of the CNC circular saw 101 are parallel to each other, the conveying bracket 100 is arranged in a concave shape, and bull's eye rollers 100a are arranged on both sides of the conveying bracket 100, the shell of the bull's eye roller 100a is fixedly connected to the conveying bracket 100, and the bull's eye roller 100a is in rolling contact with the outer wall of the workpiece 500; as shown in FIG. Figure 4 As shown, the two guide rods 301 are both located at the top of the slide 303 and are sleeved with a spring 308; the cylinder 307, the lower channel steel 201b, and the bidirectional screw rod 306 are parallel to each other, and the two sections of the thread of the bidirectional screw rod 306 from the middle to the two ends are symmetrical to each other; Figure 6As shown, the angle steel 401 is fixedly connected to the bottom edge of the upper channel steel 201a of the two sets of frame 201, and the angle steel 401 is connected to the middle of the upper channel steel 201a. The angle steel 401 is located at one end of the equipment feed and extends outside the frame 200, and the connecting rod 403 is hinged to the bottom edge of one end of the angle steel 401. Figure 7 As shown, the bottom of the connecting rod 403 away from the hinge axis of the angle steel 401 is connected with a ball 404, and the ball 404 is in rolling contact with the outer wall of the workpiece 500; Figure 2 As shown, in a set of clamping mechanisms 300, the axes of four rollers 304 are parallel to the axis of the workpiece 500, and the rollers 304 are rollingly pressed against the outer wall of the workpiece 500, and one of the slides 303 is fixedly connected to a motor 309, one end of the rotating shaft of the roller 304 and the output shaft of the motor 309 are connected to a pulley 310, and a synchronous belt 311 is wound around the three pulleys 310, and the rotation direction of the output shaft of the motor 309 is opposite to the rotation direction of the saw blade of the CNC circular saw 101.

[0029] The present invention mainly provides a circular saw cutting device that can quickly adapt to different diameters of workpieces 500, and identifies the diameter of the workpiece 500 in a purely mechanical way, vertically lifts the slide 303 in the clamping mechanism 300 to the height of the center axis of the workpiece 500, so that the clamping mechanism 300 clamps the workpiece 500 at symmetrical positions on both sides, and drives the workpiece 500 to rotate. During the process, the CNC circular saw 101 cuts from the bottom of the workpiece 500.

[0030] In the prior art, the saw blade of the numerically controlled circular saw 101 can be raised and lowered, and the present invention operates on this basis.

[0031] To achieve the above functions, the present invention also involves the following technical details: First, the present invention provides a measuring mechanism 400 to Figure 1 Taking the perspective as an example, when a workpiece 500 is fed from the left side to the right side through the measuring mechanism 400, the end of the workpiece 500 will push the connecting rod 403, causing the end of the connecting rod 403 hinged with the hydraulic cylinder 402 to deflect upward, and the hinge axis of the connecting rod 403 and the hydraulic cylinder takes an arc motion path, which can be decomposed into two directions of movement, one is a horizontal linear displacement along the guide rail 302 on the angle steel 401, and the other is a vertical displacement. The horizontal displacement is adaptively adjusted by the hydraulic cylinder 402 sliding along the guide rail 302, and the vertical displacement is used to measure the diameter of the workpiece 500. In the initial state, the ball 404 at the bottom end of the connecting rod 403 is at the (close to) lowest point of the workpiece 500 on the conveying bracket 100. When the workpiece 500 passes through the measuring mechanism 400, as shown in FIG. Figure 3 As shown, the ball 404 will slide as it moves to the top of the workpiece 500. During this process, the ball 404 will be displaced in the vertical direction by the height of the diameter of the workpiece 500 (a small error is allowed); The top of the cylinder body of hydraulic cylinder 2 402 is connected to the bottom of the cylinder body of hydraulic cylinder 1 305 through an oil pipe, and the ratio of the effective action area of ​​the piston rods of hydraulic cylinder 1 305 and hydraulic cylinder 2 402 is one to two. When this condition is established, it can be known from Pascal's law that the sum of the piston areas of the four hydraulic cylinders 1 305 is twice the piston area of ​​hydraulic cylinder 2 402, and assuming that the pistons of the four hydraulic cylinders 1 305 move synchronously, then the stroke of the piston rod of hydraulic cylinder 2 402 moving with the ball 404 is twice the stroke of hydraulic cylinder 1 305. Therefore, when the ball 404 moves a distance of the diameter of a workpiece 500, hydraulic cylinder 1 305 will push the slide 303 to rise vertically along the guide rail 302 to a height of the radius of the workpiece 500. Then, the starting point of the slide 303 is set to be the same as that of the ball 404, and the slide 303 will be lifted to the position on both sides of the workpiece 500 located on the central axis; Second, the clamping mechanism 300 of the present invention, such as Figure 5 As shown, both ends of the bidirectional lead screw 306 are rotatably connected to the frame 201, so the bidirectional lead screw 306 cannot be displaced except for rotation. The bidirectional lead screw 306 is used to allow the two guide rods 301 connected thereto to make synchronous relative movement toward or in the opposite direction relative to the frame 201. Through the transmission of the lead screw, the cylinder 307 only needs to push or pull one of the guide rods 301 to achieve the movement control of the two guide rods 301. When the slide 303 reaches the target height, the two guide rods 301 can be driven by the cylinder 307 to move toward each other, so that the roller 304 on the slide 303 clamps the outer wall of the workpiece 500, and then the motor 309, the pulley 310 and the synchronous belt 311 drive the roller 304 to rotate. The roller 304 drives the workpiece 500 to rotate through friction. At this time, the saw blade of the CNC circular saw 101 only needs to have a cutting depth greater than the wall thickness of the pipe. In order to smoothly achieve the above operation, the ball lead screw 404 and the ball 404 nut should be used.

[0032] Thirdly, to achieve the functional purposes of "one" and "two", the piston rods of the four hydraulic cylinders 305 need to move synchronously. Since there are slight differences in the movement resistance of each piston rod, the movement speed of the piston rods of each hydraulic cylinder 305 is not necessarily the same when the total oil intake remains unchanged. Therefore, in the clamping mechanism 300, each hydraulic cylinder 305 is configured with a spring 308 of the same specification. The elastic force generated by the compression of the spring 308 when the slide 303 moves is much higher than the difference in movement resistance between the piston rods. Therefore, if one of the piston rods has a smaller movement resistance and a faster speed, it means that the piston rod will compress the spring 308 faster, which means This requires an oil inlet pressure higher than that of other hydraulic cylinders 305, and the hydraulic cylinders 305 are connected and feed oil together, and the oil inlet pressures of the hydraulic cylinders 305 are also the same. Therefore, under the same oil inlet pressure, no hydraulic cylinder 305 obtains a greater compression stroke pressure on the spring 308. Therefore, there will be no significant difference in the compression stroke of each spring 308, and the stronger the elasticity of the spring 308, the smaller the compression stroke difference will be, and it can be ignored. Therefore, the elastic force of the spring 308 covers the difference in the resistance to movement of the piston rod, so that the piston rods of each hydraulic cylinder 305 maintain (allowing slight differences) synchronous movement.

[0033] In summary, while retaining the advantage of the circular saw cutting equipment in that it occupies less space, the device can also independently determine the diameter of the workpiece 500, select the best position to clamp, and drive the workpiece 500 to rotate, thereby achieving the cutting of workpieces 500 of different diameters.

[0034] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A cutting device for pressure vessel production, comprising a conveying support (100), a numerically controlled circular saw (101) and a workpiece (500), characterized in that: Also includes, A frame (200), the frame (200) comprising a pair of rectangular frames (201) and four crossbars (202) connecting the frames (201), each of the frames (201) comprising an upper channel steel (201a), a lower channel steel (201b) and two vertical channel steels (201c); The clamping mechanism (300) comprises two vertically arranged guide rods (301), the top and bottom ends of the guide rods (301) are both horizontally provided with guide rails (302), and the two ends of the guide rods (301) are slidably connected to adjacent guide rails (302), the two guide rods (301) are both slidably connected to slideways (303), and the two slideways (303) are rotatably connected to a pair of rollers (304) on the sides close to each other, the two guide rods (301) are both fixedly connected to hydraulic cylinders (305) on the sides away from each other, and the piston rods of the two hydraulic cylinders (305) are vertically upwardly fixedly connected to the adjacent slideways (303), and the two guide rods ( A cylinder (307) and a bidirectional screw rod (306) are arranged between the bottom ends of the upper and lower channel steels (201a and 201b), and the cylinder body of the cylinder (307) is fixedly connected to the adjacent lower channel steel (201b), the piston rod of the cylinder (307) is vertically fixedly connected to the guide rod (301), the bidirectional screw rod (306) is threadedly connected to the guide rod (301), and a group of clamping mechanisms (300) are installed in each frame (201). In one frame (201), the two guide rails (302) are respectively fixedly connected to the upper channel steel (201a) and the lower channel steel (201b), and the two ends of the bidirectional screw rod (306) are respectively rotatably connected to the two vertical channel steels (201c); The measuring mechanism (400) comprises an angle steel (401) fixedly connected to the top of the frame (200), wherein the angle steel (401) is fixedly connected to a slide rail, the slide rail on the angle steel (401) is slidably connected to a second hydraulic cylinder (402), the piston rod of the second hydraulic cylinder (402) is vertically arranged downward, and a connecting rod (403) is hinged between the bottom end of the piston rod of the second hydraulic cylinder (402) and one end of the angle steel (401).

2. The cutting device for pressure vessel production according to claim 1, characterized in that: The numerically controlled circular saw (101) is sleeved in a frame (200), and a shell of the numerically controlled circular saw (101) is fixedly connected to the frame (200); a parallel cross bar (202) of the workpiece (500) passes through two side frames (201) of the frame (200); and the conveying bracket (100) slidably supports a portion of the workpiece (500) located outside the frame (200); the numerically controlled circular saw (101) is located at the bottom of the workpiece (500), and an axis of the workpiece (500) and an axis of a cutting blade of the numerically controlled circular saw (101) are parallel to each other.

3. The cutting device for pressure vessel production according to claim 2, characterized in that: The conveying support (100) is arranged in a concave shape, and bull's eye rollers (100a) are arranged on both sides of the conveying support (100), the shell of the bull's eye roller (100a) is fixedly connected to the conveying support (100), and the bull's eye roller (100a) is in rolling contact with the outer wall of the workpiece (500).

4. The cutting device for pressure vessel production according to claim 3, characterized in that: The two guide rods (301) are both located at the top end of the slide table (303) and are sleeved with springs (308).

5. The cutting device for pressure vessel production according to claim 1, characterized in that: The cylinder (307), the lower channel steel (201b), and the bidirectional screw rod (306) are parallel to each other, and the two sections of threads of the bidirectional screw rod (306) from the middle to the two ends are symmetrical to each other.

6. The cutting device for pressure vessel production according to claim 5, characterized in that: The angle steel (401) is fixedly connected to the bottom edge of the upper channel steel (201a) of the two sets of frame frames (201), and the angle steel (401) is connected to the middle part of the upper channel steel (201a). The angle steel (401) is located at one end of the equipment feeding and extends outside the frame (200), and the connecting rod (403) is hinged to the bottom edge of one end extending outward from the angle steel (401).

7. The cutting device for pressure vessel production according to claim 1, characterized in that: A ball (404) is connected to the bottom of one end of the connecting rod (403) away from the hinge axis of the angle steel (401), and the ball (404) is in rolling contact with the outer wall of the workpiece (500).

8. The cutting device for pressure vessel production according to claim 7, characterized in that: In a clamping mechanism (300), the axes of the four rollers (304) are parallel to the axis of the workpiece (500), and the rollers (304) are rollingly pressed against the outer wall of the workpiece (500), and one of the slides (303) is fixedly connected to a motor (309), one end of the rotating shaft of the roller (304) and the output shaft of the motor (309) are connected to pulleys (310), and a synchronous belt (311) is wound around the three pulleys (310).

9. The cutting device for pressure vessel production according to claim 8, characterized in that: The rotation direction of the output shaft of the motor (309) is opposite to the rotation direction of the saw blade of the numerically controlled circular saw (101).

10. The cutting device for pressure vessel production according to claim 1, characterized in that: The top end of the cylinder body of the second hydraulic cylinder (402) is connected to the bottom end of the cylinder body of the first hydraulic cylinder (305) through an oil pipe, and the ratio of the effective action area of ​​the piston rods of the first hydraulic cylinder (305) and the second hydraulic cylinder (402) is one to two.

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