CN215965650U

CN215965650U - Large-tonnage metal bending transmission mechanism

Info

Publication number: CN215965650U
Application number: CN202122407535.9U
Authority: CN
Inventors: 徐丰羽; 杨森; 范保杰; 申景金
Original assignee: Nanjing University of Posts and Telecommunications
Current assignee: Nanjing University of Posts and Telecommunications
Priority date: 2021-09-30
Filing date: 2021-09-30
Publication date: 2022-03-08
Anticipated expiration: 2031-09-30

Abstract

The utility model discloses a large-tonnage metal bending transmission mechanism which comprises a pressure arm, a connecting rod, a hinged support, a pressure rod, a moving piece, a lead screw, a nut and a nut rotation driving device, wherein the pressure arm is connected with the connecting rod through a connecting rod; the two pressing arms are symmetrically arranged at the upper parts of two sides of the frame of the metal plate bending equipment; the front end part of each pressure arm facing the upper cross beam is hinged with the top end of a connecting rod, and the bottom end of each connecting rod is hinged with the upper cross beam; the middle part of each pressure arm is hinged on a hinged support which is fixedly arranged on the frame or integrally arranged on the frame; the rear end part of each pressure arm is hinged with the top end of a pressure rod, and the bottom end of the pressure rod is hinged with a moving part; the moving piece is arranged at the front end of the screw rod; the nut is sleeved on the screw rod in a threaded manner and forms screw rod thread pair matching with the screw rod; the nut is also arranged on the frame through a bearing seat and can rotate under the drive of the nut rotation driving device. This application can realize the lift drive of the entablature of 80 tons of heavy loads and above, and the drive noise is little.

Description

Large-tonnage metal bending transmission mechanism

Technical Field

The utility model relates to the field of numerical control bending, in particular to a large-tonnage metal bending transmission mechanism.

Background

At present, numerical control plate bending equipment is mainly divided into a numerical control bending machine and a numerical control bending center according to process characteristics, application range and different automation degrees. The numerical control bending machine and the numerical control bending center respectively comprise an upper beam, an upper beam lifting driving device and an upper die arranged at the bottom of the upper beam.

At present, the domestic and foreign markets mainly adopt hydraulic drive for an upper crossbeam lifting drive device of numerical control bending equipment with the weight of more than 80 tons. The mechanical full-electric servo is still blank at present due to the influence of factors in manufacturing cost, transmission technology, numerical control system, whole machine structure and the like. The hydraulic drive has the advantages that the hydraulic drive can be suitable for large tonnage of more than 80 tons, and the bending processing of large-breadth thick plates is easy to realize. However, there are also disadvantages as follows:

1. large noise, high energy consumption, hydraulic oil leakage and environmental pollution.

2. The cost is higher, because high-precision parts such as hydraulic cylinder, valves, hydraulic pump are with higher costs, and wherein the valves, the high-end market almost relies on the import completely in the hydraulic pump part, and is with high costs.

3. The precision is not high, the position precision control of the hydraulic system has inherent disadvantages, and the position controllability is poor.

4. The service life is short, the components are worn, and the hydraulic oil circuit is polluted, so that the stability of the hydraulic system is easily influenced.

5. The action impact of the slide block is large and not gentle.

6. Is greatly influenced by factors such as the temperature, the humidity and the dust of the environment.

7. The motion control is complicated.

8. The control system relies on the inlet.

9. The processing efficiency is low.

In order to overcome the defects of the hydraulic driving mode, the technology developed in recent years is mainly applied to a small-tonnage full-electric servo bending machine (30-40 tons of the main stream), and generally does not exceed 50 tons. At present, the mechanical full-electric servo bending machine with small tonnage mostly adopts a heavy-load ball screw (direct drive, no link mechanism) driving mode. The driving mode has the following advantages: simple structure, high mechanical transmission efficiency, high speed and high precision, and simultaneously perfectly overcomes a plurality of problems of hydraulic transmission. However, there are also disadvantages in the following respects:

1. the machine tool has high machining and manufacturing precision.

2. The force is increased without a connecting rod mechanism, so that the bending machine is only suitable for a small-tonnage bending machine below 50 tons.

3. The power utilization rate is low, the required driving motor power is large, and the cost is increased.

4. Because the screw rod, the upper cross beam and the frame are all in rigid connection, the drives on the two sides can not be synchronously adjusted. Therefore, the adjustment of the parallelism of the two sides of the ball screw is asynchronous, which can lead to the bending of the screw rod and damage the screw rod.

5. The noise is large.

However, currently, 80 tons and more of market share reaches more than 80%. Therefore, how to replace the traditional hydraulic transmission with the mechanical full-electric servo to realize the energy-saving, environment-friendly, heavy-load and high-precision transmission mechanism becomes a new direction for the development of the metal plate processing industry. The heavy load is 80 tons or more, the high precision is the forming angle precision of the plate bending, the precision is within 0.5 degree, and the positioning precision of the corresponding upper die reaches 0.025mm (for example, the angle error of the plate bending is 0.5 degree, and the positioning precision of the corresponding upper die, namely the upper cross beam is 0.025 mm).

SUMMERY OF THE UTILITY MODEL

The present invention is directed to overcome the above-mentioned shortcomings of the prior art, and an object of the present invention is to provide a large-tonnage metal bending transmission mechanism, which can realize the lifting driving of an upper beam with a heavy load of 80 tons or more, and has low driving noise.

In order to solve the technical problems, the utility model adopts the technical scheme that:

a large-tonnage metal bending transmission mechanism comprises a pressure arm, a connecting rod, a hinged support, a pressure rod, a moving piece, a screw rod, a nut and a nut rotation driving device.

The metal bending transmission mechanism is used for driving the height of an upper beam in the metal plate bending equipment to rise and fall.

The number of the pressing arms is two, and the pressing arms are symmetrically arranged on the upper parts of two sides of the frame of the metal plate bending equipment.

The front end part of each pressure arm facing the upper cross beam is hinged with the top end of the connecting rod, and the bottom end of the connecting rod is hinged with the upper cross beam.

The middle part of each pressure arm is hinged on a hinged support, and the hinged support is fixedly arranged on the frame or integrally arranged on the frame.

The rear end part of each pressure arm, which deviates from the upper cross beam, is hinged with the top end of the pressure rod, and the bottom end of the pressure rod is hinged with the moving piece.

The moving member is installed at the front end of lead screw.

The nut is sleeved on the screw rod in a threaded manner and forms screw rod thread pair matching with the screw rod; the nut is also installed on the frame through the bearing frame to can rotate under the drive of nut rotary driving device, nut rotary driving device includes servo motor.

The moving member is a sliding block, and the sliding block is hinged or fixedly connected with the front end of the screw rod.

The sliding block is arranged on the rack in a sliding manner and is connected with the rack in a sliding pair manner; the sliding block is horizontally arranged or obliquely arranged.

The length of each pressing rod can be extended and retracted.

The moving piece is a support rod, the bottom end of the pressure rod is hinged with the upper part of the support rod, and the lower part of the support rod is hinged on the rack; the front end of the screw rod is hinged with at least one of the pressure lever and the support rod.

The front end of the screw rod is hinged with the bottom end of the pressing rod and the top end of the supporting rod at the same time.

The bracing piece has three pin joint, and the three pin joint of bracing piece is articulated mutually with depression bar bottom, lead screw front end and frame respectively.

The depression bar has three pin joint, and the three pin joint of depression bar is articulated mutually with pressure arm, lead screw front end and bracing piece respectively.

The screw rod is provided with a groove, and the bearing seat is internally provided with a guide key matched with the groove.

The screw is a ball screw.

The utility model has the following beneficial effects:

1. the full-electric servo motor replaces the traditional hydraulic pressure, and is energy-saving and environment-friendly.

2. Due to the non-linear motion characteristic of the mechanism, the mechanism is suitable for large tonnage.

3. The screw rod is low in noise, and the nut rotates and does not rotate, so that relative noise is reduced, generally by 5-10dB, and noise pollution is avoided.

4. Because the stress point of frame is more reasonable, this application passes through the pressure arm with the stress point transfer of frame to the fuselage lean on the position in the middle, no additional moment of flexure, consequently the structure atress is reasonable, and no stress concentration point, rigidity is reliable.

5. The screw rod is convenient to process, manufacture and install, and is not required to rotate, so that the screw rod is simple and easy to connect with parts such as a pressure rod, a support rod, a sliding block and the like.

Drawings

Fig. 1 is a perspective view showing an embodiment 1 of a large-tonnage metal bending transmission mechanism according to the present application, where fig. 1(a) is a first perspective view and fig. 1(b) is a second perspective view.

Fig. 2 shows a schematic diagram of the embodiment 1 of the present application when the sliding block is disposed obliquely and fixedly connected to the front end of the screw rod.

Fig. 3 shows a schematic diagram of the embodiment 1 of the present application when the sliding block is disposed obliquely and the sliding block is hinged to the front end of the screw rod.

Fig. 4 shows a schematic diagram of the embodiment 1 of the present application when the sliding block is horizontally disposed and the sliding block is hinged to the front end of the screw rod.

Fig. 5 is a perspective view showing embodiment 2 of a large-tonnage metal bending transmission mechanism according to the present application, in which fig. 5(a) is a first perspective view and fig. 5(b) is a second perspective view.

Fig. 6 shows a schematic diagram of the moving member as a support rod in embodiment 2 of the present application.

Fig. 7 is a schematic diagram showing a moving member as a support block in embodiment 2 of the present application.

Fig. 8 shows a perspective view of a first embodiment of the nut rotation drive device according to the present application.

Fig. 9 shows a cross-sectional view of a first embodiment of the nut rotation drive of the present application.

Fig. 10 shows a perspective view of a second embodiment of the nut rotation drive device of the present application.

Fig. 11 shows a cross-sectional view of a second embodiment of the nut rotation drive of the present application.

Fig. 12 shows a schematic diagram of a strut with three hinge points in the present application.

FIG. 13 is a schematic view showing a structure of a connecting rod according to the present invention; fig. 13(a) is a three-dimensional view of the link, fig. 13(b) is a second front view of the link, and fig. 13(c) is a sectional view taken along line a-a of fig. 13 (b).

FIG. 14 shows a schematic diagram of the telescoping of the connecting rod of the present invention; fig. 14(a) is a schematic diagram of a normal state of the link, fig. 14(b) is a schematic diagram of an extended state of the link, and fig. 14(c) is a schematic diagram of a contracted state of the link.

Fig. 15 shows a speed characteristic curve and a force characteristic curve when the link length is adjustable in the present invention.

Fig. 16 shows a schematic structure of the pressing arm of the present invention welded by two steel plates.

Among them are:

10. a frame; 11. a side plate; 12. an upper cross beam;

20. a connecting rod; 21. a screw; 22. connecting lugs;

30. pressing the arm; 31. a hinged support;

40. a pressure lever;

51. a slider; 52. a support bar; 53. a support block;

60. a screw rod; 61. a trench;

70. a nut; 71. a bearing seat; 72. a bearing; 73. a guide key;

80. a servo motor; 81. a small belt pulley; 82. a large belt pulley; 83. and (4) a synchronous belt.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and specific preferred embodiments.

In the description of the present invention, it is to be understood that the terms "left side", "right side", "upper part", "lower part", etc., indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of describing the present invention and simplifying the description, but do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and that "first", "second", etc., do not represent an important degree of the component parts, and thus are not to be construed as limiting the present invention. The specific dimensions used in the present example are only for illustrating the technical solution and do not limit the scope of protection of the present invention.

Example 1

As shown in fig. 1, the metal plate bending apparatus includes a frame 10 and an upper beam 12, wherein the frame includes two symmetrical side plates 11, the upper beam is located right in front of the two side plates and can be lifted up and down along the two side plates, and the metal bending transmission mechanism of the present invention is used for driving the upper beam to be lifted up and down.

As shown in fig. 1 and 5, the large-tonnage metal bending transmission mechanism comprises a connecting rod 20, a pressure arm 30, a hinged support 31, a pressure rod 40, a moving part, a screw rod 60, a nut 70 and a nut rotation driving device.

The number of the pressing arms is two, the pressing arms are symmetrically arranged on the upper portions of two sides of the frame of the metal plate bending equipment, and the pressing arms are preferably located above the tops of the two side plates.

The pressing arm is equivalent to a lever, the hinge support is used as a pivot, and the combination of the moving member, the screw rod 60, the nut 70 and the nut rotation driving device can enable the pressing arm to rotate up and down or swing to drive the connecting rod to move, so that the upper cross beam is driven to move up and down. Meanwhile, the stress point of the machine body can be transferred to the position of the hinged support, so that the rigidity and the strength of the rack are greatly improved, and the large-tonnage full-electric servo drive is very important.

In order to improve strength and rigidity, each pressure arm is set to be in a shape with a high middle part and low two sides, and a triangle is preferably selected in the embodiment and is provided with a top angle, a first bottom angle and a second bottom angle. The top angle faces upwards, the first bottom angle faces towards the upper cross beam, and the top angle is located above the two bottom angle connecting lines.

Each press arm can be made of a single steel plate as shown in fig. 1 by welding or casting. Of course, alternatively, two steel plates arranged in parallel as shown in fig. 16 may be connected by a hinge shaft. In addition, each pressing arm can also adopt other known shapes, and if the action principle of the present application can be realized, the equivalent is considered to be within the protection scope of the present application.

The front end part of each pressure arm facing the upper crossbeam is hinged with the top end of the connecting rod, and the bottom end of the connecting rod is hinged with the upper crossbeam.

The length of each connecting rod is preferably adjustable, and as shown in fig. 13, each connecting rod comprises a screw 21 and two connecting lugs 22 which are in threaded connection with the upper end and the lower end of the screw. Wherein, the upper and lower both ends screw thread of screw rod is reverse, and rotatory screw thread can adjust the size between the both ends engaging lug. The connecting lug at the top end of the screw rod is used for being hinged with the pressure arm, and the connecting lug at the bottom end of the screw rod is used for being hinged with the upper cross beam.

Fig. 15 is a speed characteristic curve and a force characteristic curve when the link length is adjustable in the present application. If the length of the connecting rod is different, the positions of the upper die contacting the plate are different, such as points A and B. For example, when the connecting rod is long, the contact plate is at point a; when the connecting rod is shorter, the contact plate is a point B. And A, B the speed and force characteristics of the two points are different. Where the velocity of A is higher than B, but the force output is smaller; the speed at point B is lower than point a, but the force output is higher than point B. The length of the connecting rod can be adjusted to adapt to different working conditions.

In addition, in fig. 14, since the distance between the hinge point a of the pressure arm (the hinge point of the pressure arm and the hinge support) and the hinge point b of the pressure arm (the hinge point of the pressure arm and the connecting rod) is large, when the pressure arm swings and presses down, the swing angle of the corresponding connecting rod is small, and the bending angle is preferably 12.5 ° (which may be deviated due to the actual mechanism operation). Therefore, the change of the length of the connecting rod has less influence on the characteristics of the whole mechanism, so that the connecting rod of the mechanism is suitable for being designed into a part with adjustable length and is suitable for small-angle bending.

The middle part of each pressure arm is hinged on the hinged support, and the hinged support can be fixedly arranged on the rack and also can be used as one part of the rack, namely is integrally arranged with the rack.

The shape of the hinged support is not limited to the shape shown in the figure, and any specific structure capable of realizing the basic action principle based on the technical scheme of the scheme is considered to be equivalent within the protection scope of the scheme.

The screw is preferably a ball screw, the moving member is mounted at the front end of the screw, and the moving member is a sliding block.

As shown in fig. 2, the sliding block may be fixedly connected with the front end of the screw rod. Alternatively, the sliding block may be hinged to the front end of the screw rod, as shown in fig. 3.

As shown in fig. 8 and 9, the nut is sleeved on the screw rod in a threaded manner and forms screw rod thread pair matching with the screw rod; the nut is also mounted on the frame by means of a bearing block 71 and can be rotated by a nut rotation drive.

The bearing seat is hinged (or fixedly installed) on the frame, a bearing 72 is embedded in the inner wall surface of the bearing seat, and the bearing is sleeved on the periphery of the nut. The bearing seat can enable the axial position of the nut to be kept unchanged, and the outer wall surface can rotate freely without friction.

The nut and the screw rod are considered to be equivalent by adopting the nut rotating screw rod in the prior art and are within the protection scope of the claims.

The structural details of the screw rod, the nut and the bearing seat are adjusted on the basis of the technical principle of the scheme, and the changes are considered as equivalent and are within the protection scope of the right of the scheme.

The nut rotation driving device is a conventional device, and may be directly driven by a servo motor or may be driven by a known rotation driving method such as a timing belt or a gear reduction. In this embodiment, a servo motor and a timing belt drive are preferably used. The specific arrangement is as shown in fig. 8 and 9, a large belt wheel 82 is coaxially sleeved on the periphery of the screw rod on one side of the nut, a pinion 81 is mounted at the front end of an output shaft of a servo motor 80 mounted at the top of the frame or the bearing seat, and the small belt wheel and the large belt wheel realize synchronous rotation through a synchronous belt.

Further, as shown in fig. 10 and 11, a groove 61 is provided on the screw rod, and a guide key 73 matched with the groove is provided in the bearing seat, so that the axial displacement of the screw rod can be limited, that is, the screw rod can only axially extend and retract but cannot rotate. Alternatively, the number of the grooves can be two or more along the circumferential direction of the screw rod, and the number of the guide keys can also be two or more along the circumferential direction of the inner wall of the bearing seat. The guide key and groove form a sliding pair fit, and the remaining spline type and face fits and other known guide means are considered equivalent.

Furthermore, the sliding block is slidably mounted on the frame and is connected with the frame in a sliding pair mode. The slider may be disposed horizontally as shown in fig. 4, or may be disposed obliquely as shown in fig. 2 and 3.

In addition, the integral nut rotating type screw rod has the technical effect which is equal to that of the scheme, and is also within the protection scope of the scheme.

Example 2

As shown in fig. 5 to 7, the large-tonnage metal bending transmission mechanism comprises a connecting rod 20, a pressing arm 30, a hinged support 31, a pressing rod 40, a moving part, a screw rod 60, a nut 70 and a nut rotation driving device.

The structure of the pressure arm 20, the connecting rod 30, the hinge support 31, the lead screw 60, the nut 70 and the nut rotation driving device is basically the same as that of embodiment 1, and the description thereof is omitted.

The structure of the pressing rod and the moving part is different, the moving part is a supporting rod 52, the bottom end of the pressing rod is hinged with the upper part of the supporting rod, and the lower part of the supporting rod is hinged on the rack; the front end of the screw rod is hinged with at least one of the pressure lever and the support rod.

The pressure bar and the support bar preferably have the following three embodiments.

First embodiment

As shown in fig. 6, the front end of the screw rod is hinged to the bottom end of the pressing rod and the top end of the supporting rod at the same time, that is, the screw rod, the pressing rod and the supporting rod are hinged to one point.

Second embodiment

As shown in fig. 7, the support rod has three hinge points, and the three hinge points of the support rod are respectively hinged with the bottom end of the pressure rod, the front end of the screw rod and the frame. The three hinge points of the supporting rod can be positioned on the same straight line and also can be arranged in a triangular shape.

Further, the supporting rod is a triangular supporting block 53, three angles of the supporting block are respectively a top angle, a side angle and a bottom angle, the top angle of the supporting block is hinged with the bottom end of the pressing rod, the side angle of the supporting block is hinged with the front end of the screw rod, and the bottom angle of the supporting block is hinged with the rack.

Third embodiment

As shown in fig. 12, the pressing rod is also preferably triangular and has three hinge points, and the three hinge points of the pressing rod are respectively hinged with the pressing arm, the front end of the screw rod and the supporting rod. Three pin joints of the pressure lever can be positioned on the same straight line and also can be arranged in a triangular shape.

The application also has the following special beneficial effects:

1. full electric servo motor replaces traditional hydraulic pressure, and is energy-saving and environment-friendly:

calculated as 50000 market holdings:

the power generation is 3333 degrees per ton of coal, which is equivalent to coal saving in one year:

the national coal consumption is 8.7 million tons, which accounts for about 3.3 ten-thousandths of the national coal consumption. It is also considerable.

And hydraulic oil is saved. Hydraulically driven hydraulic oil is replaced once a year, and the replacement amount is about 300L each time

2. Due to the non-linear motion characteristic of the mechanism, the mechanism is suitable for large tonnage:

the same 2 7.5kw driving motors are adopted, and a common ball screw is directly driven and can only reach 30-40 tons. By adopting the mechanism, the tonnage can reach 80-120 tons under the condition of the same processing efficiency due to the nonlinear characteristic of the mechanism.

3. Because the stress point of the frame is more reasonable:

the strength and the rigidity of the frame are better. Particularly, when the transmission component is arranged symmetrically (preferably, but not limited to) with respect to the center of the two side plates of the frame, the two side plates of the frame are not subjected to bending load (the plate-shaped member is easily unstable due to the bending load, and the strength of the structure is seriously affected). The mechanism has a plurality of mechanisms, the mechanism cannot be arranged about the centers of the two side plates due to structural space limitation, the side plates of the rack bear twisting load, the instability of the rack is easily caused, and the rigidity and the strength cannot be ensured.

This application shifts the stress point of frame to the position that the fuselage leaned on the centre through the pressure arm, does not have additional moment of flexure, therefore the structure atress is reasonable, and no stress concentration point. The rigidity is reliable;

the frame and the press arm are the most critical parts. The pressure arm is transversely arranged at the upper part of the frame, so the space layout is reasonable, the pressure arm can be designed into a shape (such as a triangle) with a high middle part and low two ends, the requirements on the rigidity and the strength of the structure can be easily met, and the structural design of a large-tonnage machine tool can be more easily realized.

4. The inverse kinematics solution is simpler and is easy to control:

the inverse kinematics solution is easier to realize, an explicit analytic solution can be obtained, the motion process can be accurately controlled, and multiple iterations of numerical value solution are not needed. The kinematic inverse solution of the transmission mechanism is that the rotation angle of the driving motor is obtained by an analytical method according to the position required by the upper cross beam, which is the premise of realizing high dynamic characteristic and high-precision control. However, the existing mechanism has no way to solve the analytical solution of the inverse kinematics solution due to the characteristics of the mechanism itself, and can only solve the analytical solution by a numerical iteration mode, so that the control system has a large calculation amount, large control system resources are consumed, the real-time performance and accuracy of the trajectory control of the control system are difficult to ensure, and the speed is seriously influenced, so that the high-dynamic characteristic and high-precision control cannot be realized.

5. Low noise and no noise pollution.

6. Compact appearance, it is more pleasing to the eye: the structure layout is reasonable, the transmission parts can be arranged in the two side plates of the rack and do not protrude out of the rack, so that the appearance of the whole machine is more attractive, and the product competitiveness is improved.

7. The length of the connecting rod is set to be adjustable, and the length of the connecting rod can be manually or automatically adjusted. The positions where the upper die contacts the plate material are different when the link lengths are different, as shown by points a and B in fig. 15. For example, when the connecting rod is long, the contact plate is at point a; when the connecting rod is shorter, the contact plate is a point B. And A, B the speed and force characteristics of the two points are different. Where the velocity of A is higher than B, but the force output is smaller; the speed at point B is lower than point a, but the force output is higher than point B. When the small-size light-load metal plate is bent, the connecting rod can be properly lengthened, and higher speed is realized; conversely, if the connecting rod is heavy, the connecting rod can be properly shortened.

8. The mechanism layout is more reasonable, and the connecting rod, the outstanding crossbeam the place ahead of pressure arm are few, consequently can realize bending of the big breadth panel of small-angle, and be unlikely to take place panel and drive mechanism's collision interference, can realize 12 x 2 ═ 24 degrees, bending of less angle even.

Although the preferred embodiments of the present invention have been described in detail, the present invention is not limited to the details of the embodiments, and various equivalent modifications can be made within the technical spirit of the present invention, and the scope of the present invention is also within the scope of the present invention.

Claims

1. The utility model provides a metal of large-tonnage drive mechanism that bends which characterized in that: the device comprises a pressure arm, a connecting rod, a hinged support, a pressure rod, a moving piece, a screw rod, a nut and a nut rotation driving device;

the metal bending transmission mechanism is used for driving the height of an upper beam in the metal plate bending equipment to rise and fall;

the two pressing arms are symmetrically arranged at the upper parts of two sides of the frame of the metal plate bending equipment;

the front end part of each pressure arm facing the upper cross beam is hinged with the top end of the connecting rod, and the bottom end of the connecting rod is hinged with the upper cross beam;

the middle part of each pressure arm is hinged on a hinged support, and the hinged support is fixedly arranged on the frame or integrally arranged on the frame;

the rear end part of each pressure arm, which is far away from the upper cross beam, is hinged with the top end of a pressure rod, and the bottom end of the pressure rod is hinged with a moving part;

the moving piece is arranged at the front end of the screw rod;

2. A large-tonnage metal bending actuator according to claim 1, wherein: the moving member is a sliding block, and the sliding block is hinged or fixedly connected with the front end of the screw rod.

3. A large-tonnage metal bending actuator according to claim 2, wherein: the sliding block is arranged on the rack in a sliding manner and is connected with the rack in a sliding pair manner; the sliding block is horizontally arranged or obliquely arranged.

4. A large-tonnage metal bending actuator according to claim 1, wherein: the length of each connecting rod can stretch out and draw back.

5. A large-tonnage metal bending actuator according to claim 1, wherein: the moving piece is a support rod, the bottom end of the pressure rod is hinged with the upper part of the support rod, and the lower part of the support rod is hinged on the rack; the front end of the screw rod is hinged with at least one of the pressure lever and the support rod.

6. A large-tonnage metal bending actuator according to claim 5, wherein: the front end of the screw rod is hinged with the bottom end of the pressing rod and the top end of the supporting rod at the same time.

7. A large-tonnage metal bending actuator according to claim 5, wherein: the bracing piece has three pin joint, and the three pin joint of bracing piece is articulated mutually with depression bar bottom, lead screw front end and frame respectively.

8. A large-tonnage metal bending actuator according to claim 5, wherein: the depression bar has three pin joint, and the three pin joint of depression bar is articulated mutually with pressure arm, lead screw front end and bracing piece respectively.

9. A large-tonnage metal bending actuator according to claim 1, wherein: the screw rod is provided with a groove, and the bearing seat is internally provided with a guide key matched with the groove.

10. A large-tonnage metal bending actuator according to claim 1 or 9, wherein: the screw is a ball screw.