A gravity-type shell column blank clamping device

Abstract

The present application relates to the technical field of load hanging devices for lifting and lowering cranes, and discloses a gravity-type shell column blank clamping device, including a clamp, an upper crossbeam and a lower crossbeam, wherein the clamp is movably arranged on the upper crossbeam and the lower crossbeam, and is characterized in that a trigger clamping mechanism is arranged between the upper crossbeam and the lower crossbeam to automatically lock or unlock the lower crossbeam, self-locking: after the trigger clamping mechanism is pushed upward by the blank, the lower crossbeam is locked; unlocking: after the trigger clamping mechanism is pushed upward for a second time by the blank, the lower crossbeam is released, and the locking and unlocking are cyclical changes, which is suitable for transporting shell column blanks that are not easy to fall, and realizes the function of automatically clamping and releasing the reciprocating blank transportation.

Description

Technical Field

[0001] The invention relates to the technical field of load hanging devices for lifting and lowering cranes, in particular to a gravity-type shell column blank clamping device. Background Art

[0002] Cranes are equipment responsible for transporting billets in today's production workshops. They are used to transport billets such as slabs and column billets. Billet clamping equipment is an important component of cranes for lifting and lowering. It clamps the billets when lifting heavy objects. In the existing technology, gravity-type billet clamps are one of the commonly used clamping equipment that does not require external power. It can clamp, lift and release conveniently and quickly. When the clamp is lifted, a clamping force is formed between the billet and the clamp under the action of its own gravity. At the same time, the friction between the jaws and the side of the billet is increased to drive the clamping and movement of the billet. Under the influence of the gravity of the billet, the purpose of billet transportation is achieved.

[0003] For example, document CN2787627 discloses a gravity-driven automatic opening and closing slab clamp, which specifically includes a lifting platform, a pin shaft, a hanging beam, a clamp, a hinge shaft and an automatic opening and closing device, wherein the clamp consists of a jaw, a clamp arm and a lifting arm, the clamp arm and the lifting arm are hinged by a hinge shaft, and two sets of clamps are arranged in parallel between the hanging beam and the bottom beam. The automatic opening and closing device is fixed on the hanging beam and fixed to the corresponding position of the bottom beam through a base connection, and uses its own gravity to push the opening and closing of the automatic opening and closing device to realize the cyclic process of clamping and placing the slab.

[0004] During actual production, the jaws can easily slip on the column blank due to factors such as wear on the jaw surface and irregularities in the surface of the clamped blank. This can lead to inability to clamp and transport the column blank, or even the blank falling. Furthermore, the clamped column blank is heavy and has an irregular shape, making it more prone to slipping. If the column blank slips or falls during suspended handling, it can seriously impact worker safety and normal factory production. Summary of the Invention

[0005] The purpose of the present invention is to provide a gravity-type housing column blank clamping device to solve the problem that the column blank is easy to fall.

[0006] In order to achieve the above-mentioned purpose, the present invention provides a gravity-type shell column blank clamping device, including a clamp, an upper crossbeam and a lower crossbeam, and the clamp is movably arranged on the upper crossbeam and the lower crossbeam, and is characterized in that: a trigger clamping mechanism is arranged between the upper crossbeam and the lower crossbeam to automatically lock or unlock the lower crossbeam, self-locking: after the trigger clamping mechanism is pushed upward by the blank, the lower crossbeam is locked; unlocking: after the trigger clamping mechanism is pushed upward by the blank for a second time, the lower crossbeam is unlocked.

[0007] In order to enable the clamping and releasing of the clamp to be fully automatic, the trigger clamping mechanism is pushed by the blank and triggers self-locking and unlocking in a periodic change, and the self-locking and unlocking constitute one cycle.

[0008] Preferably, the trigger clamping mechanism includes a lead push rod, a cylindrical guide rail, a trigger push rod and a compression spring, the lead push rod is movably connected to the upper crossbeam through a connecting block, the compression spring is sleeved on the lead push rod, the cylindrical guide rail is fixed on the lower crossbeam, the lower end portion of the lead push rod is provided with double serrations with equal gaps, and is connected to the single serrations provided with equal gaps on the cylindrical guide rail, the trigger push rod is inserted in the cylindrical guide rail and is located below the lead push rod, the upper end portion of the trigger push rod has double serrations with the same gap as the cylindrical guide rail, and the trigger push rod moves up and down at the gap of the cylindrical guide rail to push the lead push rod to move upward.

[0009] In order to realize the reciprocating conveyance of clamping and releasing the blank, an annular double serration is provided at the lower end of the lead push rod, an annular single serration is provided on the inner side of the cylindrical guide rail, and an annular double serration is provided at the upper end of the trigger push rod.

[0010] In order to adapt to the sizes of different blanks and enhance the clamping force, an upper lead scale is provided between the connecting block and the upper crossbeam. The upper end face of the upper lead scale is fixedly connected to the lower end face of the upper crossbeam. A plurality of rows of holes are provided on the upper lead scale. The connecting block is connected to the rows of holes through a limit lock A to adjust the distance between the upper crossbeam and the lower crossbeam and change the elastic potential energy of the compression spring.

[0011] In order to avoid damage to the equipment, a buffer spring is sleeved on the trigger push rod, and a contact plate is provided at the bottom of the trigger push rod.

[0012] In order to adapt to the triggering distance of different blanks and determine the opening and closing timing of the clamp, a lower lead scale is set on the lower end surface of the lower crossbeam and is mounted on the trigger push rod. A plurality of rows of holes are set on the lower lead scale, and the rows of holes are connected by a limit lock B to limit the position of the buffer spring.

[0013] In order to maintain overall balance, the trigger clamping mechanism is located in the middle of the upper beam and the lower beam.

[0014] Preferably, in order to enhance the self-locking strength, a plurality of the trigger clamping mechanisms are arranged on the upper beam and the lower beam. For an even number of the trigger clamping mechanisms, all the trigger clamping mechanisms are symmetrically distributed on both sides of the central axis; for an odd number of the trigger clamping mechanisms, one trigger clamping mechanism is arranged on the central axis of the upper beam and the lower beam, and the remaining trigger clamping mechanisms are symmetrically distributed on both sides of the central axis.

[0015] In order to facilitate the flexible extension and retraction of the clamp, the clamp includes a lower clamp arm, a connecting plate and an upper clamp arm. The middle part of the lower clamp arm is rotatably connected to the connecting plate, the connecting plate is rotatably connected to the lower crossbeam, the upper end of the lower clamp arm is rotatably connected to the lower end of the upper clamp arm, and the upper end of the upper clamp arm is rotatably connected to the upper crossbeam.

[0016] The present invention provides a gravity-type shell column blank clamping device, which has the following advantages: by lowering the gravity-type shell column blank clamping device, the column blank is brought into contact with the triggering clamping mechanism, so that no external power is generated from locking the lower crossbeam, and then the position of the clamp is locked, ensuring that the clamp firmly clamps the column blank to prevent the column blank from falling, and the gravity-type shell column blank clamping device is lowered twice to achieve power-free unlocking, which is convenient and quick to operate; it has the function of automatically clamping and releasing the reciprocating blank transportation; the equipment has a simple structure and low cost, can be modularly manufactured and installed, and is easy to replace and repair; the distance between the upper crossbeam and the lower crossbeam can be adjusted at will, and automatic opening and closing, clamping and self-locking can be achieved at a specific position, which is suitable for transporting blanks of different shapes; it is suitable for most gravity-type blank clamping equipment in use today, and can also be used for the transformation and upgrading of old equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 3D isometric diagram of the gravity-type housing column blank clamping device in Example 1;

[0018] Figure 2 Schematic diagram of the overall assembly of the gravity-type housing column blank clamping device in Example 1;

[0019] Figure 3 for Figure 1 Schematic diagram of the installation position of the trigger clamping device;

[0020] Figure 4 for Figure 1 A schematic diagram of the structure of the trigger clamping device;

[0021] Figure 5 Schematic cross-section of the trigger clamping device in Examples 1 and 2;

[0022] Figure 6 Schematic side view of the clamps in Examples 1 and 2;

[0023] Figure 7 This is a schematic diagram of the internal trajectory of the lead push rod;

[0024] Figure 8 This is a schematic diagram of the internal trajectory of the cylindrical guide rail;

[0025] Figure 9 This is a schematic diagram of the internal trajectory of the trigger push rod;

[0026] Figure 10A schematic diagram showing the comparison of the motion trajectory of the trigger clamping device;

[0027] Figure 11 This is a schematic diagram of the Max motion trajectory of the trigger clamping device;

[0028] Figure 12 A schematic diagram of the motion trajectory for triggering the clamping device to reset;

[0029] Figure 13 Schematic diagram of the motion trajectory of the triggering clamping device Min.

[0030] Figure markings: 1. lower clamp arm; 2. pin A; 3. connecting plate; 4. pin B; 5. pin C; 6. upper clamp arm; 7. pin D; 8. upper crossbeam; 9. pin E; 10. pulley assembly; 11. trigger clamping mechanism; 12. lower crossbeam; 13. clamp; 14. center axis; 1101. upper lead scale; 1102. limit lock A; 1103. connecting block; 1104. compression spring; 1105. lead push rod; 1106. cylindrical guide rail; 1107. trigger push rod; 1108. lower lead scale; 1109. support column; 1110. limit lock B; 1111. buffer spring; 1112. contact plate. DETAILED DESCRIPTION

[0031] The specific embodiments of the present invention are further described in detail below with reference to the accompanying drawings, but the present invention is not limited to these embodiments. Without departing from the principles of the present invention, improvements made to the present invention also fall within the scope of protection of the claims of the present invention.

[0032] Example 1

[0033] like Figure 1-6As shown, a gravity-type shell column blank clamping device includes a pair of clamps 13, an upper crossbeam 8, a lower crossbeam 12 and two trigger clamping mechanisms 11. The two clamps 13 are rotatably connected to the two end portions of the upper crossbeam 8 and the lower crossbeam 12 respectively, and the two trigger clamping mechanisms 11 are symmetrically distributed on the upper crossbeam 8 and the lower crossbeam 12. The upper end of the trigger clamping mechanism 11 is fixed on the upper crossbeam 8, and the middle part passes through the lower crossbeam 12. The trigger clamping mechanism 11 includes a lead push rod 1105, a cylindrical guide rail 1106, a trigger push rod 1107 and a compression spring 1104. The lower part of the lower crossbeam 12 is screwed to a hollow connecting block 1103. The connecting block 1103 is conical. The connecting block 1103 is movably connected to the upper end of the cylindrical guide rail 1106. The lead push rod 1105 is fixed at the upper crossbeam 8, and the middle part passes through the lower crossbeam 12. The connecting block 1103 is free to move axially, and the lower end of the lead push rod 1105 is provided with double serrations at equal gaps and in a ring shape. The compression spring 1104 is sleeved on the lead push rod 1105, and the cylindrical guide rail 1106 is screwed to the upper end surface of the lower crossbeam 12. The inner wall of the cylindrical guide rail 1106 is provided with double serrations at equal gaps and in a ring shape, and is connected to the double serrations of the lead push rod 1105. The trigger push rod 1107 is inserted into the cylindrical guide rail 1106 and is located below the lead push rod 1105. The upper end of the trigger push rod 1107 has double serrations with the same gap as the cylindrical guide rail 1106 and in a ring shape. The trigger push rod 1107 moves up and down in the gap of the cylindrical guide rail 1106 to push the lead push rod 1105 to move upward.

[0034] like Figure 7-10 As shown, the double serrations at the lower end of the lead push rod 1105 are respectively A stroke and B stroke, each double serration is spaced apart by π / 4 of idle stroke, π / 2 is a period, the single serration of the cylindrical guide rail 1106 is part C, the end of the single serration is sloped, each single serration is spaced apart by π / 4 of idle stroke, the double serrations of the trigger push rod 1107 are divided into A stroke and B stroke, are located in the idle stroke of the cylindrical guide rail 1106, and are cross-connected with the single serration of the cylindrical guide rail 1106.

[0035] An upper lead scale 1101 is provided between the connecting block 1103 and the upper crossbeam 8. The upper end face of the upper lead scale 1101 is fixedly connected to the lower end face of the upper crossbeam 8 by screws. A plurality of rows of holes are provided on the upper lead scale 1101. The connecting block 1103 is provided with rows of holes of the same specification. The connecting block 1103 is connected to the rows of holes through a limit lock A1102 to adjust the distance between the upper crossbeam 8 and the lower crossbeam 12 and limit it.

[0036] The trigger push rod 1107 passes through the lower cross beam 12 , and a contact plate 1112 is provided at the lower end of the trigger push rod 1107 , and a buffer spring 1111 is sleeved in the middle, and a contact plate 1112 is provided at the bottom of the trigger push rod 1107 .

[0037] The clamp 13 includes a lower clamp arm 1, a connecting plate 3, an upper clamp arm 6, and a lifting pulley group 10. The middle part of the lower clamp arm 1 is rotatably connected to the connecting plate 3 through a pin A2 to realize a rotatable hole-axis connection. The connecting plate 3 is rotatably connected to the lower crossbeam 12 through a pin B4. The upper end of the lower clamp arm 1 is rotatably connected to the lower end of the upper clamp arm 6 through a pin C5. The upper end of the upper clamp arm 6 is rotatably connected to the upper crossbeam 8 through a pin D7. The two clamps 13 are symmetrically distributed along the central axis 14, and their installation and connection are completely consistent.

[0038] The two pulley assemblies 10 are symmetrically arranged on the upper end surface of the upper cross beam 8 along the central axis 14 and are respectively connected by a pin E9.

[0039] The middle portion of the lower clamp arm 1 is rotatably connected to the connecting plate 3 , the connecting plate 3 is rotatably connected to the lower crossbeam 12 , the upper end portion of the lower clamp arm 1 is rotatably connected to the lower end portion of the upper clamp arm 6 , and the upper end portion of the upper clamp arm 6 is rotatably connected to the upper crossbeam 8 .

[0040] The lower end face of the lower cross beam 12 is screwed with a lower lead scale 1108, and the lower lead scale 1108 is sleeved on the trigger push rod 1107, and the trigger push rod 1107 is longer than the lower lead scale 1108. A plurality of rows of holes are provided on the lower lead scale 1108, and the rows of holes are connected by a limit lock B1110, and the limit lock B1110 limits the position of the upper end of the buffer spring 1111 to adjust the compression state of the buffer spring 1111, which is suitable for contacting column blanks of different weights.

[0041] The lower end of the trigger push rod 1107 is connected to two support columns 1109, and the support columns 1109 are respectively provided with buffer springs 1111. The bottom of the support column 1109 is connected to the contact plate 1112 to enhance the buffering capacity and avoid equipment damage.

[0042] Example 2

[0043] Referring to the gravity-type shell column blank clamping device of Example 1, the difference is that: three trigger clamping mechanisms 11 are set on the upper crossbeam 8 and the lower crossbeam 12, one of the trigger clamping mechanisms 11 is located on the central axis 14, and the remaining two are parallel and symmetrically located on both sides of the central axis.

[0044] Working principle:

[0045] Descending stage: Figure 11As shown, after the trigger clamping mechanism 11 is installed on the gravity-type shell column blank clamping device according to the designed position, as the gravity-type shell column blank clamping device falls, under the action of the gravity of the gravity-type shell column blank clamping device, the buffer spring 1111 is first compressed to alleviate the reverse impact from the column blank, and then the vertical position of the trigger push rod 1107 in the cylindrical guide rail 1106 is changed, and the lower cross beam 12 and the cylindrical guide rail 1106 move downward relative to the trigger push rod 1107. At the same time, the vertical position of the lead push rod 1105 is pushed upward by the trigger push rod 1107 for the first time and stops at the top of the single serration slope inside the cylindrical guide rail 1106. It should be noted that in the process of the lead push rod 1105 being pushed upward, the lead push rod 1105 does not rotate in the cylindrical guide rail 1106; while the lead push rod 1105 is pushed, it is sleeved on the The compression spring 1104 outside the lead push rod 1105 is compressed for the first time under the joint action of the lead push rod 1105 and the connecting block 1103. When the serrated end of the lead push rod 1105A stroke reaches the top of the single serrated slope of the cylindrical guide rail 1106, driven by the unbalanced force of the compressed compression spring 1104, the double serrated A stroke of the lead push rod 1105 is connected with the A stroke of the trigger push rod 1107. After the contact point slides and rotates around the axis of the cylindrical guide rail 1106 along the slope surface of the cylindrical guide rail 1106, the trigger push rod 1107 falls back. When the lead push rod 1105 rotates to a certain angle, the single serrated head of the cylindrical guide rail 1106 supports the stroke of the lead push rod 1105B. At this time, the lead push rod 1105 and the cylindrical guide rail 1106 achieve the first position locking, reaching the Max movement point of the trigger clamping device. It can be foreseen that at this time, the distance between the upper crossbeam 8 and the lower crossbeam 12 is the largest, and under the action of the compression spring, a repulsive force is generated to increase the distance between the upper crossbeam 8 and the lower crossbeam 12. Specifically, the angles of the upper clamp arm 6 and the lower clamp arm 1 connected to the upper crossbeam 8 and the lower crossbeam 12 relative to the middle vertical plane are reduced, and the jaw distance of the lower clamp arm 1 becomes smaller, thereby achieving clamping of the column blank. At the same time, the repulsive force generated by the compression spring increases the holding force pressure of the lower clamp arm 1 on the side of the column blank, thereby increasing the pre-clamping force of the column blank and forming a self-locking.

[0046] Lifting stage: As the gravity-type shell column blank clamping device is lifted by the crane, the column blank is clamped and transported to the predetermined location;

[0047] Second descent stage: Figure 12As shown, after reaching the predetermined position, the gravity-type shell column blank clamping device falls again, and the process is as follows: the column blank first contacts the ground, and the gravity-type shell column blank clamping device continues to fall. At this time, as the upper and lower beams 12 fall, the gravity of the gravity-type shell column blank clamping device is converted by the crane into the power to trigger the clamping. At this time, the buffer spring 1111 is compressed again, and then the relative vertical position of the trigger push rod 1107 and the cylindrical guide rail 1106 changes, and the lower crossbeam 12 and the cylindrical guide rail 1106 move downward again relative to the trigger push rod 1107. Relatively speaking, the trigger push rod 1107 moves upward again relative to the cylindrical guide rail 1106, and at the same time, the vertical position of the lead push rod 1105 in the cylindrical guide rail 1106 is pushed upward for the second time by the trigger push rod 1107. It should be noted that at this time, during the process of the lead push rod 1105 being pushed upward, no rotation in the cylindrical guide rail 1106 occurs; similarly, while the lead push rod 1105 is being pushed, The compression spring 1104 is compressed for the second time under the combined action of the lead push rod 1105 and the tapered connection. At the moment when the apex of the lead push rod 1105B stroke reaches the single serration head of the cylindrical guide rail 1106, driven by the unbalanced force of the compressed compression spring 1104, the apex of the lead push rod 1105B stroke slides at the contact point of the B stroke of the trigger push rod 1107 and rotates around the axis of the cylindrical guide rail 1106 for the second time along the slope surface of the cylindrical guide rail 1106. At this time, the trigger push rod 1107 falls back for the second time. After the lead push rod 1105 rotates a certain angle, the lead push rod 1105 disengages from the locking of the single serration of the cylindrical guide rail 1106 and is contact locked.

[0048] Reciprocating stage: Figure 13As shown, the B stroke vertex of the lead push rod 1105 cannot be mechanically self-locked on the slope of the cylindrical guide rail 1106, and the B stroke vertex of the lead push rod 1105 slides at the contact point with the B stroke of the trigger push rod 1107, and rotates around the axis of the cylindrical guide rail 1106 for the third time along the inclined slope of the cylindrical guide rail 1106; after the rotation angle π / 4, the limited stroke A+B of the cylindrical guide rail 1106 slides into the idle stroke of the cylindrical guide rail 1106 and falls, contacting the trigger push rod 1107. 7 stops after contacting the end, thus completing the reset movement and also reaching the 11Min movement point of the trigger clamping mechanism. It can be foreseen that at this time, the distance between the upper crossbeam 8 and the lower crossbeam 12 is the smallest. At this time, the repulsive force of the compression spring begins to release, and the angle of the upper clamp arm 6 and the lower clamp arm 1 connected to the upper crossbeam 8 and the lower crossbeam 12 relative to the middle vertical plane increases. The jaw distance of the lower clamp arm 1 becomes larger, realizing the release of the column blank and releasing the contact pressure applied to the side surface of the column blank. Thus, the release of the clamped column blank and the reset of the trigger clamping device are completed. Under the lifting and movement of the crane, the gravity-type shell column blank clamping device returns to the initial column blank clamping position, completing a cycle of movement and starting the next cycle of column blank clamping operation.

Claims

1. A gravity-type housing column blank clamping device, comprising a clamp (13), an upper crossbeam (8) and a lower crossbeam (12), wherein the clamp (13) is movably arranged on the upper crossbeam (8) and the lower crossbeam (12), characterized in that: A trigger clamping mechanism (11) is provided between the upper crossbeam (8) and the lower crossbeam (12) to automatically lock or unlock the lower crossbeam (12), self-locking: after the trigger clamping mechanism (11) is pushed upward by the blank, the lower crossbeam (12) is locked; unlocking: after the trigger clamping mechanism (11) is pushed upward by the blank for a second time, the lower crossbeam (12) is unlocked; after the trigger clamping mechanism (11) is pushed by the blank, the self-locking and unlocking are triggered in a periodic change, and the self-locking and unlocking are one cycle; the trigger clamping mechanism (11) comprises a lead push rod (1105), a cylindrical guide rail (1106), a trigger push rod (1107) and The compression spring (1104) is connected to the upper crossbeam (8) through the connecting block (1103). The compression spring (1104) is sleeved on the lead push rod (1105). The cylindrical guide rail (1106) is fixed on the lower crossbeam (12). The lower end of the lead push rod (1105) is provided with double serrations at equal intervals and is connected to the single serrations provided at equal intervals on the cylindrical guide rail (1106). The trigger push rod (1107) is inserted into the cylindrical guide rail (1106) and is located below the lead push rod (1105). The upper end of the trigger push rod (1107) has a The cylindrical guide rail (1106) has double-toothed saw teeth with the same gap, and the trigger push rod (1107) moves up and down at the gap of the cylindrical guide rail (1106) to push the lead push rod (1105) to move upward; the lower end of the lead push rod (1105) is provided with an annular double saw tooth, the inner side of the cylindrical guide rail (1106) is provided with an annular single saw tooth, and the upper end of the trigger push rod (1107) is provided with an annular double saw tooth; an upper lead scale (1101) is provided between the connecting block (1103) and the upper crossbeam (8), the upper end face of the upper lead scale (1101) is fixedly connected to the lower end face of the upper crossbeam (8), and the upper lead scale (1101) is fixedly connected to the lower end face of the upper crossbeam (8). 101) is provided with a plurality of rows of holes, and the connecting block (1103) is connected to the rows of holes through a limit lock A (1102) to adjust the distance between the upper crossbeam (8) and the lower crossbeam (12); a buffer spring (1111) is sleeved on the trigger push rod (1107), and a contact plate (1113) is provided at the bottom of the trigger push rod (1107); a lower lead scale (1108) is provided on the lower end surface of the lower crossbeam (12) and sleeved on the trigger push rod (1107), and a plurality of rows of holes are provided on the lower lead scale (1108), and the rows of holes are connected through a limit lock B (1110) to limit the position of the buffer spring (1111);The double serrations at the lower end of the lead push rod (1105) are divided into an A stroke and a B stroke, each double serration is separated by an idle stroke of π / 4, and π / 2 is a cycle. The single serration of the cylindrical guide rail (1106) is part C, and the end of the single serration is sloped, and each single serration is separated by an idle stroke of π / 4. The double serrations of the trigger push rod (1107) are divided into an A stroke and a B stroke, and are located in the idle stroke of the cylindrical guide rail (1106) and cross-connected with the single serration of the cylindrical guide rail (1106).

2. The gravity-type housing column blank clamping device according to claim 1, characterized in that: The trigger clamping mechanism (11) is located in the middle of the upper crossbeam (8) and the lower crossbeam (12).

3. The gravity-type housing column blank clamping device according to claim 2, characterized in that: A plurality of trigger clamping mechanisms (11) are provided on the upper crossbeam (8) and the lower crossbeam (12). For an even number of the trigger clamping mechanisms (11), all the trigger clamping mechanisms (11) are symmetrically distributed on both sides of the central axis (14); for an odd number of the trigger clamping mechanisms (11), one trigger clamping mechanism (11) is provided on the central axis (14) of the upper crossbeam (8) and the lower crossbeam (12), and the remaining trigger clamping mechanisms (11) are symmetrically distributed on both sides of the central axis (14).

4. The gravity-type housing column blank clamping device according to claim 3, characterized in that: The clamp (13) comprises a lower clamp arm (1), a connecting plate (3) and an upper clamp arm (6); the middle portion of the lower clamp arm (1) is rotatably connected to the connecting plate (3); the connecting plate (3) is rotatably connected to the lower crossbeam (12); the upper end portion of the lower clamp arm (1) is rotatably connected to the lower end portion of the upper clamp arm (6); and the upper end portion of the upper clamp arm (6) is rotatably connected to the upper crossbeam (8).

Images