Lifting arm and mandrel gripping device

Abstract

The present application relates to a kind of lifting arm and mandrel clamping device, including swing arm and the drive mechanism for pushing the upper end of swing arm in horizontal direction reciprocating swing, the movement track of the upper end of swing arm includes first track section and second track section with height difference, the first track section and second track section constitute a closed swing track.The technical scheme, swing arm is continuously transported by swing form between production line and waiting roller bed mandrel, can effectively reduce the movement space of swing arm, to reduce the space occupied by device equipment, simultaneously, mandrel can be reduced in the lifting height of a certain extent in the process of transport, improve stability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of transfer equipment, in particular to a lifting arm and mandrel clamping device. BACKGROUND

[0002] The mandrel is a mechanical transmission device, usually composed of a cylinder or a cone, used to transmit torque and withstand shear force. It is the core component in mechanical devices, carrying and controlling the center axis of the element (such as sliding structure or rotating structure).

[0003] In the prior art, when the mandrel to be processed is clamped and transferred from the production line to the waiting roller, a clamping device is needed for transfer. However, the mandrel to be processed is usually more than 15 meters long and weighs more than 3 tons. The transfer method is roughly divided into hoisting and lifting, wherein:

[0004] The hoisting method needs to set up lifting points, and multiple lifting points need to move simultaneously, so the structure of the transfer device is relatively complex;

[0005] The lifting method sets up multiple parallel support arms, one end of the support arm is rotatably connected as a support point, and the other end is provided with a clamping seat for fixing the mandrel. When the support arm rotates around the support point, the clamping seat will move in a circular motion with the support arm, i.e. its trajectory is a circle. On one side of the trajectory, the clamping seat moves upward, and on the opposite side, it moves downward. The upward moving side can be used as the side intersecting the production line, and the downward moving side can be used as the side intersecting the waiting roller. When the clamping seat rotates along the trajectory, it can lift the mandrel on the production line from bottom to top, and then place the lifted mandrel on the waiting roller from top to bottom. Compared with the hoisting method, the production continuity is good, and the device structure is relatively simple;

[0006] However, the movement trajectory of the support arm is a complete circle, which has a large swing operation space, and the overall device needs to occupy a large space. SUMMARY

[0007] Therefore, the purpose of the present application is to provide a lifting arm and mandrel clamping device to solve the problem of the prior art that the movement trajectory of the support arm is a complete circle, which has a large swing operation space and the overall device needs to occupy a large space.

[0008] The present application is achieved by the following technical solutions:

[0009] A reciprocating swing mechanism, comprising a swing arm and a driving mechanism for pushing the upper end of the swing arm to reciprocate horizontally, the movement trajectory of the upper end of the swing arm comprises a first trajectory segment and a second trajectory segment with a height difference, and the first trajectory segment and the second trajectory segment form a closed swing trajectory.

[0010] Further limited, the driving mechanism comprises a first rocker arm and a second rocker arm, one end of the first rocker arm is fixedly connected with a driving shaft perpendicular to the movement track plane of the upper end of the swing arm, the other end is rotationally matched with the middle part of the swing arm, when the driving shaft rotates, it can drive the first rocker arm to rotate around the axis of the driving shaft away from one end of the driving shaft, and simultaneously drive the swing arm to reciprocatingly lift and lower;

[0011] One end of the second rocker arm is rotationally matched with the lower end of the swing arm, the other end is connected with a support shaft, and a rotation fulcrum is formed through the support shaft, when the swing arm moves with the first rocker arm, the lower end of the swing arm is restricted by the second rocker arm to reciprocatingly swing around the support shaft as the center, so as to push the upper end of the swing arm to reciprocatingly swing in the horizontal direction along the first track segment and the second track segment alternately;

[0012] The length of the first rocker arm is less than the length of the second rocker arm.

[0013] A lifting arm comprises a rack and two reciprocating swing mechanisms symmetrically installed in the rack;

[0014] The driving shaft and the support shaft are both rotationally installed on the rack;

[0015] Two clamping jaws for jacking mandrels are installed between the upper ends of the two swing arms.

[0016] Further limited, a connecting shaft is arranged in the middle part of the clamping jaw, and the connecting shaft is rotationally installed between the upper ends of the two swing arms;

[0017] A limiting mechanism clamped on both sides of the lower end of the clamping jaw is further included, and the clamping jaw keeps vertical during the swinging of the upper end of the swing arm through the limiting mechanism.

[0018] Further limited, the limiting mechanism comprises a support frame fixedly installed in the rack, a sliding groove extending in the vertical direction is arranged on the support frame, a sliding rod is slidingly matched in the sliding groove, and the sliding rod can reciprocate along the length direction of the sliding groove;

[0019] An extension plate is arranged at the lower end of the clamping jaw, the extension plate is arranged in parallel with the sliding rod, support rods are arranged between both ends of the extension plate and the sliding rod, and both ends of the extension plate and the sliding rod are rotationally connected with both ends of the two support rods respectively, forming a parallelogram structure.

[0020] Further limited, a plurality of rollers are arranged on both sides of the sliding rod along the length direction.

[0021] Further limited, a limiting groove is arranged on the wheel surface of the roller, and the limiting groove is clamped with the side edge of the sliding groove.

[0022] Further limited, the limiting mechanism comprises a first gear and a second gear meshing between the two swing arms, the first gear and the second gear are coaxially fixedly connected with a first special-shaped wheel and a second special-shaped wheel respectively;

[0023] The first special-shaped wheel and the second special-shaped wheel are located on both sides of the lower end of the claw respectively, the first gear is further coaxially fixedly connected with a first sprocket, the first swing arm is provided with a second sprocket at one end of the swing arm, the second sprocket is coaxially arranged with the rotation point of the first swing arm and the swing arm, and a transmission chain is arranged between the first sprocket and the second sprocket.

[0024] The first special-shaped wheel and the second special-shaped wheel are respectively tangent to the two sides of the lower end of the claw during the swing of the swing arm, and the midpoint of the two tangent points is located directly below the rotation fulcrum of the claw.

[0025] Further limited, the lower end of the claw is rotatably installed with a supporting wheel, and the wheel surfaces of the two special-shaped wheels are respectively abutted on both sides of the supporting wheel.

[0026] A mandrel clamping device, comprising at least two parallel arranged lifting arms, and two drive shafts are coaxially connected.

[0027] The beneficial effects of the present application are:

[0028] The lifting arm and the mandrel clamping device, the swing arm continuously transfers the mandrel between the production line and the waiting roller way in the form of swing, which can effectively reduce the movement space of the swing arm, reduce the space occupied by the device equipment, and at the same time, can reduce the lifting height of the mandrel during the transfer process to a certain extent, and improve the stability.

[0029] Other advantages, objects and features of the present application will be explained in the following description, and to some extent, it will be obvious to those skilled in the art based on the following study, or can be taught from the practice of the present application. The objects and other advantages of the present application can be achieved and obtained by the following description. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 It is a structure schematic view of the reciprocating swing mechanism;

[0031] Figure 2 It is a structure schematic view of the lifting arm;

[0032] Figure 3 It is a structure schematic view of the first embodiment of the limiting mechanism;

[0033] Figure 4 It is a structure schematic view of the sliding rod;

[0034] Figure 5Schematic diagram of the matching structure of the first sprocket and the second sprocket in the second embodiment of the limiting mechanism;

[0035] Figure 6 Schematic diagram of the cooperation structure of the first special-shaped wheel, the second special-shaped wheel and the claw in the second embodiment of the limiting mechanism;

[0036] Figure 7 It is a structural schematic diagram of the mandrel clamping device;

[0037] In the figure: 1. Swing arm; 2. First rocker arm; 3. Second rocker arm; 4. Drive shaft; 5. Support shaft; 6. Frame; 7. Clamping claw; 8. Connecting shaft; 9. Support frame; 10. Slide groove; 11. Sliding rod; 12. Extension plate; 13. Support rod; 14. Roller; 15. First gear; 16. Second gear; 17. First special-shaped wheel; 18. Second special-shaped wheel; 19. First sprocket; 20. Second sprocket; 21. Transmission chain; 22. Support wheel; 23. Production line; 24. Waiting roller; 25. Core shaft. DETAILED DESCRIPTION

[0038] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0039] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort shall fall within the scope of protection of the present invention.

[0040] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0041] In the above description of the present invention, it should be noted that the terms "one side," "the other side," and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, or the orientations or positional relationships in which the inventive product is typically placed when in use. These terms are intended solely to facilitate the description of the present invention and simplify the description, and are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and the like are used solely for distinction and should not be construed as indicating or implying relative importance.

[0042] In addition, the term "same" and the like do not mean that the components are absolutely the same, but there can be slight differences. The term "vertical" only means that the positional relationship between the components is more vertical than "parallel", and does not mean that the structure must be completely vertical, but can be slightly inclined.

[0043] Please refer to Figure 1 The present application provides a technical solution: a reciprocating swing mechanism, comprising a swing arm 1 and a driving mechanism for pushing the upper end of the swing arm 1 to reciprocate horizontally, the movement trajectory of the upper end of the swing arm 1 comprises a first trajectory segment and a second trajectory segment with a height difference, and the first trajectory segment and the second trajectory segment constitute a closed swing trajectory.

[0044] The upper end of the swing arm 1 serves as a support point for lifting the mandrel 25, the driving mechanism is used to drive the upper end of the swing arm 1 to swing, and the swing trajectory is a closed swing trajectory composed of a first trajectory segment and a second trajectory segment with a height difference;

[0045] The first trajectory segment is located above the second trajectory segment, when the upper end of the swing arm 1 moves from the second trajectory segment to the first trajectory segment, the upper end of the swing arm 1 will move upward, and when the lower end of the swing arm 1 moves from the first trajectory segment to the second trajectory segment, the upper end of the swing arm 1 will move downward;

[0046] In the closed swing trajectory, the upper end of the swing arm 1 will move alternately along the first trajectory and the second trajectory in one direction;

[0047] The position where the upper end of the swing arm 1 moves from the second trajectory segment to the first trajectory segment can intersect the production line 23, and during the movement of the upper end of the swing arm 1, the mandrel 25 on the production line 23 can be lifted upward, and then the mandrel 25 is lifted along the first trajectory segment;

[0048] The position where the upper end of the swing arm 1 moves from the first trajectory segment to the second trajectory segment can intersect the waiting roller 24, and during the movement of the upper end of the swing arm 1, the mandrel 25 can be lifted from the top to the bottom through the waiting roller 24, and then the mandrel 25 is placed on the waiting roller 24, and then moves along the second trajectory segment, and the above transfer process is repeated;

[0049] The swing arm 1 continuously transfers the mandrel 25 between the production line 23 and the waiting roller 24 in the form of swinging, which can effectively reduce the movement space of the swing arm 1, reduce the space occupied by the device equipment, and at the same time, can reduce the lifting height of the mandrel 25 during the transfer process to some extent, and improve the stability.

[0050] In the embodiment, the driving mechanism comprises a first rocker arm 2 and a second rocker arm 3, one end of the first rocker arm 2 is fixedly connected with a driving shaft 4 perpendicular to the plane of the movement track of the upper end of the swing arm 1, the other end is rotationally connected with the middle part of the swing arm 1, and the driving shaft 4 can drive the first rocker arm 2 to rotate around the axis of the driving shaft 4 when the driving shaft 4 rotates, and simultaneously drive the swing arm 1 to reciprocatingly lift and lower;

[0051] One end of the second rocker arm 3 is rotationally connected with the lower end of the swing arm 1, the other end is connected with a supporting shaft 5, and the supporting shaft 5 forms the rotation fulcrum of the second rocker arm 3, when the swing arm 1 moves with the first rocker arm 2, the lower end of the swing arm 1 is restricted by the second rocker arm 3 to reciprocatingly swing around the supporting shaft 5, so as to push the upper end of the swing arm 1 to reciprocatingly swing in the horizontal direction along the first track segment and the second track segment;

[0052] The length of the first rocker arm 2 is less than the length of the second rocker arm 3.

[0053] The driving shaft 4 is a power input part, which can be drivingly connected with the output shaft of the motor, and is driven by the motor, and the driving shaft 4 drives the first rocker arm 2 to rotate around the driving shaft 4 during the rotation of the driving shaft 4, and the first rocker arm 2 drives the swing arm 1 to rotate around the driving shaft 4 during the rotation of the first rocker arm 2;

[0054] One end of the second rocker arm 3 is rotationally connected with the lower end of the swing arm 1, the other end is connected with a supporting shaft 5, and the supporting shaft 5 forms the rotation fulcrum of the second rocker arm 3, when the swing arm 1 moves with the first rocker arm 2, the lower end of the swing arm 1 is restricted by the second rocker arm 3 to reciprocatingly swing around the supporting shaft 5, so as to push the upper end of the swing arm 1 to reciprocatingly swing in the horizontal direction along the first track segment and the second track segment;

[0055] The length of the first rocker arm 2 is less than the length of the second rocker arm 3.

[0056] When the length of the first rocker arm 2 is equal to the length of the second rocker arm 3, and the driving shaft 4 is located directly above the rotation connecting point between the second rocker arm 3 and the swing arm 1, the first rocker arm 2, the second rocker arm 3 and the swing arm 1 form a parallelogram structure, and when the first rocker arm 2 rotates, the upper end of the swing arm 1 moves, and the movement track is a circular structure;

[0057] In the technical solution, the second rocker arm 3 is a movement restricting structure of the swing arm 1, and the length of the second rocker arm 3 is greater than the length of the first rocker arm 2, the length of the first rocker arm 2 determines the vertical lifting height of the swing arm 1, that is, the lowest position of the upper end of the swing arm 1 is when the rotation connecting point between the first rocker arm 2 and the swing arm 1 is at the lowest position, and the highest position of the upper end of the swing arm 1 is when the rotation connecting point between the first rocker arm 2 and the swing arm 1 is at the highest position;

[0058] When the rotating connection point of the first rocker arm 2 is above the drive shaft 4, and the rotating connection point of the first rocker arm 2 and the rotating connection point of the second rocker arm 3 and the swing arm 1 are on the same straight line, the rotating connection point of the second rocker arm 3 and the swing arm will be at the highest position of operation, and the point position of the upper end of the swing arm 1 at this point is set as point a;

[0059] When the rotating connection point of the first rocker arm 2 and the swing arm 1 is between the drive shaft 4 and the rotating connection point of the second rocker arm 3, and the three are on the same straight line, the rotating connection point of the second rocker arm 3 and the swing arm 1 is at the lowest position, and the point position of the upper end of the swing arm at this point is set as point b;

[0060] When the upper end of the swing arm 1 moves from point a to point b, the swing arm 1 as a whole is in a descending state, and during the descending process, it will rotate with the rotating connection point of the first rocker arm 2 as the fulcrum. The rotating connection point of the swing arm 1 and the first rocker arm 2 passes from below the drive shaft 4, and the rotating connection point of the second rocker arm 3 and the swing arm 1 will also be pushed down synchronously;

[0061] When the upper end of the swing arm 1 moves from point b to point a, the swing arm 1 as a whole will be lifted, and during the lifting process, it will rotate with the rotating connection point of the first rocker arm 2 as the fulcrum. The rotating connection point of the swing arm 1 and the first rocker arm 2 will pass from above the drive shaft 4, and the rotating connection point of the second rocker arm 3 and the swing arm 1 will also be lifted synchronously;

[0062] Moreover, when the upper end of the swing arm 1 approaches point a or moves away from point a, the lower end of the swing arm 1 will be restrained by the second rocker arm 3, so that the lateral movement distance of the upper end of the swing arm 1 is greater than the longitudinal movement distance, and the first trajectory segment is formed on both sides of point a;

[0063] When the upper end of the swing arm 1 approaches point b or moves away from point b, the lower end of the swing arm 1 will be restrained by the second rocker arm 3, so that the lateral movement distance of the upper end of the swing arm 1 is greater than the longitudinal movement distance, and the second trajectory segment is formed on both sides of point b;

[0064] By driving the upper end of the swing arm 1 to swing to form the first trajectory segment and the second trajectory segment with a lateral movement distance greater than a longitudinal movement distance, the movement space of the swing arm 1 can be effectively reduced to reduce the space occupied by the device, and at the same time, the lifting height of the mandrel 25 during the transfer process can be reduced to a certain extent, and the stability is improved.

[0065] Please refer to Figure 2 A lifting arm, comprising a rack 6 and two reciprocating swing mechanisms symmetrically installed in the rack 6;

[0066] The drive shaft 4 and the support shaft 5 are both rotatably installed on the rack 6;

[0067] The upper ends of the two swing arms 1 are provided with a claw 7 for jacking the mandrel 25.

[0068] The rack 6 can be a hollow structure, and the two reciprocating swing mechanisms are installed in the rack 6. The rack 6 can also be a plate structure, and the two reciprocating swing mechanisms are installed on both sides of the rack 6, that is, the rack 6 is used as a mounting base of the driving shaft 4 and the supporting column, so that a space for mounting the clamping jaw 7 is formed between the upper ends of the two swing arms 1. The clamping jaw 7 is moved by the swing arms 1 under the action of the driving mechanism to transfer the mandrel 25.

[0069] In this embodiment, the clamping jaw 7 is provided with a connecting shaft 8, and the connecting shaft 8 is rotatably installed between the upper ends of the two swing arms 1.

[0070] The limiting mechanism is further clamped on both sides of the lower end of the clamping jaw 7, and the clamping jaw 7 is kept in a vertical state through the limiting mechanism during the swinging process of the upper end of the swing arm 1.

[0071] Since the inclination angle of the swing arm 1 changes continuously during the movement process, the angle of the clamping jaw 7 also changes continuously during the movement of the upper end of the swing arm 1. The clamping jaw 7 is kept in a vertical state through the limiting mechanism, which is beneficial to lifting the mandrel 25 from the production line 23, lifting the mandrel 25, and separating the mandrel 25 after being transferred to the waiting roller 24.

[0072] Please refer to Figure 3 In this embodiment, the limiting mechanism includes a supporting frame 9 fixedly installed in the rack 6, and a sliding groove 10 extending in the vertical direction is formed in the supporting frame 9. A sliding rod 11 is slidably connected in the sliding groove 10, and the sliding rod 11 can reciprocate along the length direction of the sliding groove 10.

[0073] The lower end of the clamping jaw 7 is provided with an extension plate 12, and the extension plate 12 is arranged in parallel with the sliding rod 11. The extension plate 12 and the sliding rod 11 are both provided with a supporting rod 13 at both ends, and the extension plate 12 and the sliding rod 11 are rotatably connected with both ends of the two supporting rods 13, respectively, to form a parallelogram structure.

[0074] The extension plate 12 is integrally formed with the clamping jaw 7, and is an extension of the structure of the clamping jaw 7. The extension plate 12 is parallel to the sliding rod 11, and the two are connected by the two supporting rods 13 to form a parallelogram structure. The sliding rod 11 is slidably connected in the sliding groove 10 of the supporting frame 9 fixed on the rack 6. The sliding groove 10 can be a strip structure extending in the vertical direction.

[0075] When the clamping jaw 7 moves along with the upper end of the swing arm 1, the clamping jaw 7 will rotate relative to the swing arm 1 with the connecting shaft 8 as the fulcrum, and can rotate through the two supporting rods 13 or drag the sliding rod 11 to move along the sliding groove 10 in the process of rotation of the two supporting rods 13. In this process, due to the principle of parallelogram structure, the extension plate 12 and the sliding rod 11 always maintain a parallel state, that is, the extension plate 12 maintains a vertical state, thereby achieving the purpose of keeping the clamping jaw 7 in a vertical state.

[0076] Please refer to Figure 4 In the embodiment, a plurality of rollers 14 are arranged on the length direction of the two side edges of the sliding rod 11.

[0077] The sliding rod 11 is a moving component, and the two sides thereof are provided with a plurality of rollers 14, which are used as contact positions with the two sides of the sliding groove 10. In the sliding process, rolling friction is used to replace sliding friction, thereby reducing the friction resistance of the sliding rod 11 moving in the sliding groove 10.

[0078] In the embodiment, the wheel surface of the roller 14 is provided with a limiting groove, and the limiting groove is clamped with the side edge of the sliding groove 10.

[0079] The cooperation structure of the roller 14 and the sliding groove 10 is improved, and the stability of the overall structure is improved.

[0080] Please refer to Figures 5-6 In the embodiment, the limiting mechanism includes a first gear 15 and a second gear 16 rotatably installed between the two swing arms 1 and engaged with each other, and the first gear 15 and the second gear 16 are coaxially and fixedly connected with a first special-shaped wheel 17 and a second special-shaped wheel 18, respectively.

[0081] The first special-shaped wheel 17 and the second special-shaped wheel 18 are located on the two sides of the lower end of the clamping jaw 7, the first gear 15 is also coaxially and fixedly connected with a first sprocket 19, the first swing arm 2 is installed with a second sprocket 20 at one end of the swing arm 1, the second sprocket 20 is coaxially arranged with the rotation point of the first swing arm 2 and the swing arm 1, and the first sprocket 19 and the second sprocket 20 are provided with a transmission chain 21 therebetween.

[0082] The first special-shaped wheel 17 and the second special-shaped wheel 18 are respectively tangent to the two side edges of the lower end of the clamping jaw 7 in the swing process of the swing arm 1, and the midpoint of the two tangent points is located directly below the rotation fulcrum of the clamping jaw 7.

[0083] The first swing arm 2 is a power input point for driving the swing arm 1 to swing, and the first swing arm 2 will constantly rotate relative to the swing arm 1 during the movement of the swing arm 1. The second sprocket 20 is installed at the end of the swing arm 1, so the second sprocket 20 will also be in a constant rotating state. During the rotation, the first sprocket 19 will be driven to rotate through the transmission chain 21, and then the first gear 15 and the first profiled wheel 17 will rotate synchronously, and finally the second gear 16 and the second profiled wheel 18 will rotate, and the rotation directions of the first gear 15 and the first profiled wheel 17 are opposite to those of the second gear 16 and the second profiled wheel 18.

[0084] The profile edge lines of the first profiled wheel 17 and the second profiled wheel 18 can be designed according to the movement trajectory of the upper end of the swing arm 1. During the constant rotation with the movement of the upper end of the swing arm 1, the two profiled wheels remain in a tangent state, and the tangent point is located directly below the connecting shaft 8, that is, the lower end of the claw 7 is pressed directly below the connecting shaft 8, so that the claw 7 always maintains a vertical state during the movement of the upper end of the swing arm 1.

[0085] In the embodiment, the lower end of the claw 7 is rotatably installed with a supporting wheel 22, and the wheel surfaces of the two profiled wheels abut against the two sides of the supporting wheel 22, respectively.

[0086] The supporting wheel 22 is a contact point with the first profiled wheel 17 and the second profiled wheel 18, and when it is in contact with the first profiled wheel 17 and the second profiled wheel 18 which are in a constant rotating state, it can effectively reduce the contact friction.

[0087] Please refer to Figure 7 A mandrel clamping device includes at least two parallel arranged lifting arms, and the two driving shafts 4 are coaxially connected in transmission.

[0088] One lifting arm can only lift one point, and the mandrel 25 is in a long strip shape, so at least two points need to be lifted during the carrying process. In the specific implementation process, the number of lifting arms is set according to the diameter and length of the mandrel 25, and multiple lifting arms are coaxially driven to achieve synchronous movement.

[0089] Finally, it should be pointed out that the above embodiments are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application 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 application can be modified or replaced equivalently without departing from the purpose and scope of the technical solutions of the present application, and they should be covered in the scope of the claims of the present application.

Claims

1. A lifting arm, comprising a frame and two symmetrical reciprocating swing mechanisms mounted in the frame; the reciprocating swing mechanism comprises a swing arm and a driving mechanism for pushing the upper end of the swing arm to reciprocate horizontally, the movement track of the upper end of the swing arm comprises a first track segment and a second track segment with a height difference, and the first track segment and the second track segment constitute a closed swing track; the driving mechanism comprises a first rocker arm and a second rocker arm, one end of the first rocker arm is fixedly connected with a driving shaft perpendicular to the plane of the movement track of the upper end of the swing arm, the other end is rotationally connected with the middle part of the swing arm, and when the driving shaft rotates, the first rocker arm can be driven to rotate around the axis of the driving shaft away from one end of the driving shaft, and simultaneously drive the swing arm to reciprocate vertically; one end of the second rocker arm is rotationally connected with the lower end of the swing arm, the other end is connected with a supporting shaft, and a rotation fulcrum is formed through the supporting shaft, when the swing arm moves with the first rocker arm, the lower end of the swing arm is restricted by the second rocker arm to reciprocate around the supporting shaft as the center, so as to push the upper end of the swing arm to reciprocate horizontally along the first track segment and the second track segment alternately; the length of the first rocker arm is less than the length of the second rocker arm; the driving shaft and the supporting shaft are rotationally mounted on the frame; a clamping jaw for jacking a mandrel is mounted between the upper ends of the two swing arms; a connecting shaft is arranged in the middle of the clamping jaw, and the clamping jaw is rotationally mounted between the upper ends of the two swing arms through the connecting shaft; a limiting mechanism clamped on both sides of the lower end of the clamping jaw is further arranged, and the clamping jaw remains vertical during the swing of the upper end of the swing arm through the limiting mechanism; characterized in that the limiting mechanism comprises a first gear and a second gear rotationally mounted between the two swing arms and engaged with each other, and the first gear and the second gear are coaxially fixedly connected with a first special-shaped wheel and a second special-shaped wheel respectively; the first special-shaped wheel and the second special-shaped wheel are respectively arranged on both sides of the lower end of the clamping jaw, the first gear is further coaxially fixedly connected with a first sprocket, and the first rocker arm is provided with a second sprocket at the end close to the swing arm, the second sprocket is coaxially arranged with the rotation point of the first rocker arm and the swing arm, and a transmission chain is arranged between the first sprocket and the second sprocket; the first special-shaped wheel and the second special-shaped wheel respectively maintain tangential state with both sides of the lower end of the clamping jaw during the swing of the swing arm, and the midpoint of the two tangent points is located directly below the rotation fulcrum of the clamping jaw.

2. A lifting arm according to claim 1, characterised in that: a supporting wheel is rotationally mounted on the lower end of the clamping jaw, and the wheel surfaces of the two special-shaped wheels abut against both sides of the supporting wheel respectively.

3. A mandrel gripping device characterized by: at least two lifting arms as claimed in claim 1 or 2 are arranged side by side, and the two driving shafts are coaxially transmissionally connected.

Images