External automatic lifting reflux condensation pipe rack for water bath kettle

Abstract

The utility model discloses an external automatic lifting reflux condensation pipe frame of a water bath kettle. The external automatic lifting reflux condensation pipe frame comprises a base, a lifting frame, a lifting driving mechanism, a plurality of guide rails and a plurality of condensation pipe clamping mechanisms, a water bath kettle placing platform is arranged on the base; the guide rails are distributed on the peripheral side of the base and fixedly connected to the base in the vertical direction; the lifting frame is arranged above the water bath kettle placing platform and is connected with each guide rail in a lifting and sliding manner; the lifting driving mechanism is mounted between the base and the lifting frame and used for driving the lifting frame to lift and slide along the guide rails; an empty window is formed in the middle of the lifting frame, each condensation pipe clamping mechanism is provided with a clamp, the condensation pipe clamping mechanisms are fixedly installed on the top of the lifting frame, and each movable clamp extends into the empty window. The device can automatically lift the reflux condensers in batches, is compatible with water bath kettles with different sizes and specifications, and improves the experiment efficiency.

Description

Technical Field

[0001] This utility model relates to the technical field of drug and food testing devices, and in particular to an external automatic lifting and lowering reflux condenser tube rack for a water bath. Background Technology

[0002] In experiments involving the extraction of traditional Chinese medicinal materials, the extraction of prepared Chinese medicines, and the determination of fatty acids in food, water bath reflux is widely used. Currently, pharmaceutical and food testing laboratories typically employ reflux devices built on an electrically heated constant-temperature water bath (hereinafter referred to as a water bath). The reflux device includes basic equipment such as the water bath, condenser tubes, flasks, and inlet / outlet hoses, as well as equipment for fixation such as iron stands, crossbars, tube clamps, and flask clamps. During use, each sample requires manual raising and lowering of the reflux device twice (three times for fatty acid determination), which is cumbersome and affects the parallelism of the measurements. For example, when measuring four samples, it is necessary to first loosen the clamps on one set of condenser tubes, connect the flasks, adjust their position, tighten the clamps, and then process the second, third, and fourth samples. After the measurements are completed, the clamps are loosened for each sample, the condenser tubes are raised, the sample is cooled, and the reflux device is removed for the reflux experiment. When there are many samples in the same batch, it may be necessary to use a larger water bath to measure 6 or even 8 samples at the same time. The existing reflux device cannot meet the current testing needs. In order to improve the efficiency of the experiment and be compatible with water baths of various sizes, this application proposes an external automatic lifting reflux condenser tube rack for water baths. Utility Model Content

[0003] This invention provides an external automatic lifting and lowering reflux condenser tube rack for water baths, which can realize batch automatic lifting and lowering of reflux condensers and is compatible with water baths of different sizes and specifications, thereby improving experimental efficiency.

[0004] To achieve the above objectives, the technical solution adopted by this utility model is as follows:

[0005] An external automatic lifting and reflux condenser tube rack for a water bath includes a base, a lifting frame, a lifting drive mechanism, several guide rails, and several condenser tube clamping mechanisms. A water bath placement platform is provided on the base. The guide rails are distributed around the base and fixedly connected to the base vertically. The lifting frame is arranged above the water bath placement platform and is slidably connected to each guide rail. The lifting drive mechanism is installed between the base and the lifting frame to drive the lifting frame to slide up and down along the guide rails. A window is provided in the middle of the lifting frame. Each condenser tube clamping mechanism is equipped with a clamp, and the condenser tube clamping mechanisms are fixedly installed on the top of the lifting frame, with each movable clamp extending into the window.

[0006] Furthermore, the condenser pipe clamping mechanism includes clamps, a push-pull rod, a fixed guide rail, and a locking spring; the clamps include movable clamps and fixed clamps; the movable clamps have a U-shaped structure, with both ends of the U-shape of the movable clamps connected to one end of the push-pull rod; the fixed guide rail is fixedly connected to the lifting frame; the push-pull rod is slidably connected to the fixed guide rail; the horizontal end of the U-shape of the movable clamps is located inside the window; the fixed clamps are fixedly connected to the edge of the window and are positioned opposite to the horizontal end of the U-shape of the movable clamps; one side of the push-pull rod is provided with several spaced slots; the locking spring is fixedly installed on the lifting frame and located on one side of the slots; one end of the locking spring is provided with an elastically retractable pin, which abuts against one of the slots.

[0007] Furthermore, the push-pull rod is designed with an I-shaped structure, and the two ends of the U-shaped movable clamp are provided with external threads. A connecting through hole is provided on one horizontal end of the push-pull rod corresponding to the two ends of the U-shaped movable clamp. Both ends of the U-shaped movable clamp are connected to the push-pull rod through an adjusting nut, and a soft rubber pad is provided between the two ends of the U-shaped movable clamp and the push-pull rod.

[0008] Furthermore, both the movable clamp and the fixed clamp are provided with rubber pads on opposite sides, and the opposite sides of the two rubber pads are arc-shaped.

[0009] Furthermore, the lifting frame includes two fixed plates arranged parallel to each other at an upper and lower interval; each of the two fixed plates has a window in the middle, and each of the two fixed plates is equipped with a plurality of condenser pipe clamping mechanisms that correspond one-to-one.

[0010] Furthermore, the number of guide rails is set to four, distributed at the four corners of the base; each guide rail has two oppositely arranged and axially extended arc-shaped grooves on its outer periphery; the two fixing plates are slidably connected to the four guide rails; each fixing plate is provided with a threaded ball screw at each position of each arc-shaped groove of each guide rail; the ball end of each ball screw abuts against the corresponding arc-shaped groove.

[0011] Furthermore, the lifting drive mechanism includes two lifting drive rods, two return springs, two reduction gearboxes, a transmission shaft, and a drive motor. The two reduction gearboxes are respectively fixedly connected to both sides of the base in the width direction. The bottom of each lifting drive rod slides vertically into one of the reduction gearboxes. Each reduction gearbox is provided with a coaxially linked transmission gear and a cam. The bottom of each lifting drive rod abuts against a corresponding cam. The bottom of each lifting drive rod extends outward with a flange. Each return spring is sleeved on one of the lifting drive rods. The top of the return spring abuts against the top inner wall of the reduction gearbox, and the bottom of the return spring abuts against the flange. The drive motor is fixedly installed on one of the reduction gearboxes and is connected to the transmission gear in the corresponding reduction gearbox. The two reduction gearboxes are connected by the transmission shaft and rotate at the same angular velocity. The top of each lifting drive rod is fixedly connected to two fixed plates.

[0012] Furthermore, the base includes a flat plate, four support columns, and two crossbeams; the four support columns are fixedly connected to the four corners of the bottom of the flat plate, the flat plate is set as a platform for placing the water bath, the two crossbeams are distributed on both sides of the width direction of the flat plate, and each crossbeam is fixedly connected between two corresponding support columns; each gearbox is fixedly connected to one of the crossbeams.

[0013] Furthermore, each of the fixed plates is provided with a bushing at the position corresponding to the two lifting drive rods. Each bushing is slidably connected to a corresponding lifting drive rod. Each bushing is provided with at least two fixing bolts, and one end of each fixing bolt abuts against the corresponding lifting drive rod.

[0014] The beneficial effects of this utility model are:

[0015] 1) The movable clamp can hold and fix the condenser tubes, allowing them to extend into the open area. The water bath is placed on the platform, with several condenser tubes positioned directly above it. A lifting mechanism drives the lifting frame to move up and down along the base, causing the condenser tubes in the open area to repeatedly enter and exit the water bath. The process of lowering for heating and raising for cooling is repeated according to the number of times required for the experiment, automatically completing the integrated water bath reflux operation. This invention is an external application based on existing conventional water baths, compatible with water bath products of various sizes. It can simultaneously measure multiple samples according to experimental needs, improving experimental efficiency and solving the problem of inconvenient operation of existing reflux condensation equipment at a low cost.

[0016] 2) The distance between the movable clamp and the fixed clamp is adjusted by using the elastic telescopic pin on the locking spring, thereby adjusting the tightness of the clamp holding the condenser tube; rotating the adjusting nut can finely adjust the position of the movable clamp, thereby finely adjusting the tightness of the clamp holding the condenser tube and improving the clamping effect.

[0017] 3) The lifting frame is guided to move vertically relative to the base using guide rails; the end of the glass ball screw has a rolling steel ball, which changes the motion friction between the fixed plate and the guide rail to rolling friction, thereby improving the durability of the equipment; rotating the glass ball screw can adjust the damping of the fixed plate sliding on the guide rail and provide a certain support for the fixed plate.

[0018] 4) The distance between the two fixed plates can be adjusted by the bushing, and with the condenser tube clamping mechanism, condenser tubes of various lengths can be clamped; the drive motor drives the transmission gear in the reduction gearbox to rotate, which in turn drives the cam to rotate. The eccentric action of the cam, combined with the elastic force of the return spring, drives the lifting drive rod and the lifting frame to move back and forth. Attached Figure Description

[0019] The specific embodiments of this utility model will be further described in detail below with reference to the accompanying drawings, wherein:

[0020] Figure 1 This is a perspective view of the overall structure of this utility model;

[0021] Figure 2 A top view of the present invention with a six-condenser tube clamping mechanism installed;

[0022] Figure 3 A top view of the present invention with an eight-condenser tube clamping mechanism installed;

[0023] Figure 4 This is a perspective view of the present invention from a side view.

[0024] Figure 5 for Figure 1 A magnified view of a section at point A in the middle;

[0025] Attached image labels:

[0026] 1-Base, 2-Lifting frame, 3-Lifting drive mechanism, 4-Guide rail, 5-Condensate pipe clamping mechanism, 21-Open window, 22-Fixing part, 23-Ball screw, 24-Busset, 25-Allowing notch, 51-Clamping clamp, 52-Push-pull rod, 53-Fixing guide rail, 54-Locking snap ring, 55-Adjusting nut, 511-Moving clamp, 512-Fixing clamp, 513-Rubber pad, 31-Lifting drive rod, 32-Reset spring, 33-Reduction gearbox, 34-Drive shaft, 35-Drive motor, 41-Arc groove, 331-Drive gear, 332-Cam, 11-Plate, 12-Support column, 13-Crossbeam. Detailed Implementation

[0027] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0028] It should be noted that when a component is described as "fixed to" another component, it can be directly on the other component or may have a central component. When a component is described as "connected to" another component, it can be directly connected to the other component or may have a central component. When a component is described as "set on" another component, it can be directly set on the other component or may have a central component. When a component is described as "set in the middle," it is not simply set in the exact center, as long as it is not set within the area defined by both ends being in the middle. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0030] Reference Figures 1 to 5As shown, an external automatic lifting and reflux condenser tube rack for a water bath includes a base 1, a lifting frame 2, a lifting drive mechanism 3, several guide rails 4, and several condenser tube clamping mechanisms 5. A water bath placement platform is provided on the base 1. The several guide rails 4 are distributed around the base 1 and fixedly connected to the base 1 in a vertical direction. The lifting frame 2 is arranged above the water bath placement platform and is slidably connected to each of the guide rails 4. The lifting drive mechanism 3 is installed between the base 1 and the lifting frame 2 to drive the lifting frame 2 to slide up and down along the several guide rails 4. A window 21 is provided in the middle of the lifting frame 2. Each condenser tube clamping mechanism 5 is provided with a clamp 51. The several condenser tube clamping mechanisms 5 are fixedly installed on the top of the lifting frame 2, and each clamp 51 extends into the window 21. Specifically, clamp 51 is used to clamp and fix the condenser tubes, allowing the condenser tubes to extend into the area of ​​the window 21. The water bath is placed on the water bath platform, with several condenser tubes positioned directly above the water bath. The lifting mechanism 3 drives the lifting frame 2 to move up and down along the base 1, thereby causing several condenser tubes in the area of ​​the window 21 of the lifting frame 2 to repeatedly enter and exit the water bath. The condenser tubes are lowered for heating and raised for cooling according to the number of times required for the experiment, automatically completing the integrated water bath reflux operation. This utility model is an external application based on the existing conventional water bath, compatible with water bath products of various sizes. It can simultaneously measure multiple samples according to experimental needs, improving experimental efficiency and solving the problem of inconvenient operation of existing reflux condensation equipment at low cost.

[0031] The condenser pipe clamping mechanism 5 includes a clamp 51, a push-pull rod 52, a fixed guide rail 53, and a locking spring 54. The clamp 51 includes a movable clamp 511 and a fixed clamp 512. The movable clamp 511 has a U-shaped structure, and the two ends of the U-shape of the movable clamp 511 are connected to one end of the push-pull rod 52. The fixed guide rail 53 is fixedly connected to the lifting frame 2 by bolts. The push-pull rod 52 is slidably connected to the fixed guide rail 53. The horizontal end of the U-shape of the movable clamp 511 is located inside the window 21. The fixed clamp 512 is fixedly connected to the edge of the window 21 and is arranged opposite to the horizontal end of the U-shape of the movable clamp 511. The push-pull rod 52 has several spaced slots on one side. The locking spring 54 is fixedly installed on the lifting frame 2 and located on one side of the slot. One end of the locking spring 54 has an elastically extendable pin, and one end of the pin abuts in one of the slots. The elastic extension and retraction function of the pin is similar to that of the elastic latch in the prior art. The distance between the movable clamp 511 and the fixed clamp 512 is adjusted by using the elastic extension and retraction pin on the locking spring 54, thereby adjusting the tightness of the clamp 51 in holding the condenser tube.

[0032] The push-pull rod 52 is designed with an I-shaped structure. The U-shaped ends of the movable clamp 511 are threaded externally. A connecting through hole is provided on one horizontal end of the push-pull rod 52 corresponding to the U-shaped ends of the movable clamp 511. Both U-shaped ends of the movable clamp 511 are connected to the push-pull rod 52 via an adjusting nut 55. A soft rubber gasket is provided between both U-shaped ends of the movable clamp 511 and the push-pull rod 52. Rotating the adjusting nut 55 allows for fine adjustment of the position of the movable clamp 511, thereby precisely adjusting the tightness of the clamp 51 in holding the condenser tube and improving the clamping effect.

[0033] Both the movable clamp 511 and the fixed clamp 512 are provided with rubber pads 513 on opposite sides. The rubber pads 513 are fixed by bolts. The opposite sides of the two rubber pads 513 are arc-shaped. The arc-shaped rubber pads 513 not only have an anti-slip effect, but also prevent the condenser tube from tilting or shifting, thus improving the clamping effect.

[0034] Since condenser tubes on the market come in different lengths, to improve the clamping effect, as a preferred solution in this embodiment, the lifting frame 2 is designed as two parallel fixed plates 22 spaced vertically. Each fixed plate 22 has a window 21 in the middle, and each fixed plate 22 is equipped with several condenser tube clamping mechanisms 5 that correspond one-to-one. By clamping the condenser tube at two points (one above and one below), displacement, tilting, or detachment of the condenser tube from the clamps 51 during lifting is prevented. As shown in the figure, each fixed plate 22 is equipped with six condenser tube clamping mechanisms 5. Depending on the number of samples to be measured, each fixed plate can be equipped with up to eight condenser tube clamping mechanisms 5. Of course, if the number of samples to be measured is large, the fixed plate 22 needs to be lengthened as needed, and multiple mounting holes should be pre-set to allow users to install more condenser tube clamping mechanisms 5 as required.

[0035] To guide the lifting frame 2 to move vertically relative to the base 1, this invention designs four guide rails 4 on the base 1, with each guide rail 4 corresponding to one of the four corners of the base 1. Each guide rail 42 has two opposing, axially extending arc-shaped grooves 41 on its outer periphery. Two fixing plates 22 are slidably connected to the four guide rails 4. Each fixing plate 22 has a threaded ball screw 23 at each arc-shaped groove 41 of each guide rail 4, with the ball end of each ball screw 23 abutting against the corresponding arc-shaped groove 41. In this embodiment, the arc-shaped grooves 41 of the four guide rails 4 all face the length direction of the fixing plate 22. Each fixing plate 22 has a threaded hole at the outer arc-shaped groove 41 position corresponding to each guide rail 4, and a clearance notch 25 at the inner arc-shaped groove position corresponding to each guide rail 4. The clearance notch 25 has a threaded hole on the side corresponding to the arc-shaped groove 41 position. The end of the ball screw 23 has a rolling steel ball, which changes the motion friction between the fixed plate 22 and the guide rail 4 into rolling friction, thereby improving the durability of the equipment. Rotating the ball screw 23 can adjust the damping of the sliding motion of the fixed plate 22 on the guide rail 4 and provide a certain support for the fixed plate 22.

[0036] The lifting drive mechanism 3 includes two lifting drive rods 31, two return springs 32, two reduction gearboxes 33, a transmission shaft 34, and a drive motor 35. The two reduction gearboxes 33 are respectively fixedly connected to both sides of the base 1 in the width direction. The bottom of each lifting drive rod 31 slides vertically into one of the reduction gearboxes 33. Each reduction gearbox 33 is provided with a coaxially linked transmission gear 331 and a cam 332. The bottom of each lifting drive rod 31 abuts against a corresponding cam 332, and the bottom of each lifting drive rod 31 faces outward. The gearbox 31 has a flange extending laterally. Each of the aforementioned return springs 32 is sleeved on one of the lifting drive rods 31. The top of the return spring 32 abuts against the top inner wall of the gearbox 33, and the bottom of the return spring 32 abuts against the flange. The drive motor 35 is fixedly installed on one of the gearboxes 33 and is connected to the transmission gear 331 in the corresponding gearbox 33 via gears. The two gearboxes 33 are connected by the transmission shaft 34 and rotate at the same angular velocity. The top of each lifting drive rod 31 is fixedly connected to two fixed plates 22. Each fixed plate 22 is provided with a bushing at the position corresponding to the two lifting drive rods 31. Each bushing 24 is slidably connected to the corresponding lifting drive rod 31. Each bushing 24 is provided with at least two fixing bolts, and one end of each fixing bolt abuts against the corresponding lifting drive rod 31. The distance between the two fixed plates 22 can be adjusted by the bushing 24. Combined with the condenser tube clamping mechanism 5, it can clamp condenser tubes of various lengths. The bushing 24 enables a detachable connection between the fixed plates 22 and the lifting drive rod 31. The fixed plates 22 can be replaced according to the style of the water bath to install a matching number of condenser tube clamping mechanisms 5, achieving modular assembly and better overall compatibility. The drive motor 35 drives the transmission gear 331 in the reduction gearbox 33 to rotate, which in turn drives the cam 332 to rotate. The eccentric action of the cam 332, combined with the elastic force of the return spring 32, drives the lifting drive rod 31 and the lifting frame 2 to reciprocate up and down. Of course, the drive motor 35 can also be replaced with different power sources according to actual needs, such as a manual ratchet. If precise control of the number and duration of entry and exit from the water bath is required, the drive motor 35 can also be a servo motor.

[0037] The base 1 includes a flat plate 11, four support columns 12, and two crossbeams 13; the four support columns 12 are fixedly connected to the four corners of the bottom of the flat plate 11, which is the platform for placing the water bath, and the water bath is placed on the flat plate 11; the two crossbeams 13 are distributed on both sides of the width direction of the flat plate 11, and each crossbeam 13 is fixedly connected between two corresponding support columns 12; each gearbox 33 is fixedly connected to one of the crossbeams 13.

[0038] The above embodiments are only used to illustrate the technical solution of this utility model and are not intended to limit it. Any modifications or equivalent substitutions that do not depart from the spirit and scope of this utility model should be covered within the scope of the technical solution of this utility model.

Claims

1. A water bath external automatic lifting reflux condenser tube rack, characterized in that, The device includes a base, a lifting frame, a lifting drive mechanism, several guide rails, and several condenser pipe clamping mechanisms. A water bath placement platform is provided on the base. Several guide rails are distributed around the base and fixedly connected to the base in a vertical direction. The lifting frame is arranged above the water bath placement platform and is slidably connected to each of the guide rails. The lifting drive mechanism is installed between the base and the lifting frame to drive the lifting frame to slide up and down along the guide rails. A window is provided in the middle of the lifting frame. Each condenser pipe clamping mechanism is provided with a clamp. Several condenser pipe clamping mechanisms are fixedly installed on the top of the lifting frame, and each clamp extends into the window.

2. The external automatic lifting reflux condenser pipe rack of a water bath kettle according to claim 1, characterized in that, The condenser pipe clamping mechanism includes clamps, a push-pull rod, a fixed guide rail, and a locking spring. The clamps include movable clamps and fixed clamps. The movable clamps have a U-shaped structure, with both ends of the U-shape connected to one end of the push-pull rod. The fixed guide rail is fixedly connected to the lifting frame, and the push-pull rod is slidably connected to the fixed guide rail. The horizontal end of the U-shape of the movable clamp is located inside the window, and the fixed clamp is fixedly connected to the edge of the window, opposite to the horizontal end of the U-shape of the movable clamp. One side of the push-pull rod has several spaced slots. The locking spring is fixedly installed on the lifting frame and located on one side of the slots. One end of the locking spring has an elastically retractable pin, which abuts against one of the slots.

3. The external automatic lifting reflux condenser pipe rack of a water bath kettle according to claim 2, characterized in that, The push-pull rod is designed with an I-shaped structure. The two ends of the U-shaped movable clamp are provided with external threads. A connecting through hole is provided on one horizontal end of the push-pull rod corresponding to the two ends of the U-shaped movable clamp. Both ends of the U-shaped movable clamp are connected to the push-pull rod through an adjusting nut. A soft rubber pad is provided between both ends of the U-shaped movable clamp and the push-pull rod.

4. The external automatic lifting reflux condenser pipe rack of a water bath according to claim 2, characterized in that, Both the movable clamp and the fixed clamp have rubber pads on opposite sides, and the opposite sides of the two rubber pads are arc-shaped.

5. The external automatic lifting reflux condenser tube rack of a water bath according to claim 2, characterized in that, The lifting frame includes two parallel fixed plates arranged at an upper and lower interval; each of the two fixed plates has a window in the middle, and each of the two fixed plates is equipped with a plurality of condenser pipe clamping mechanisms that correspond one-to-one.

6. The external automatic lifting reflux condenser tube rack of a water bath according to claim 5, characterized in that, The number of guide rails is set to four, distributed at the four corners of the base; each guide rail has two opposite arc-shaped grooves extending axially on its outer periphery; the two fixing plates are slidably connected to the four guide rails; each fixing plate is provided with a threaded ball screw at each arc-shaped groove position relative to each guide rail; the ball end of each ball screw abuts against the corresponding arc-shaped groove.

7. The external automatic lifting reflux condenser tube rack of a water bath according to claim 5, characterized in that, The lifting drive mechanism includes two lifting drive rods, two return springs, two reduction gearboxes, a transmission shaft, and a drive motor. The two reduction gearboxes are fixedly connected to opposite sides of the base in the width direction. The bottom of each lifting drive rod slides vertically into one of the reduction gearboxes. Each reduction gearbox contains a coaxially linked transmission gear and a cam. The bottom of each lifting drive rod abuts against a corresponding cam. A flange extends outward from the bottom of each lifting drive rod. Each return spring is sleeved on one of the lifting drive rods, with its top abutting against the inner top wall of the reduction gearbox and its bottom abutting against the flange. The drive motor is fixedly mounted on one of the reduction gearboxes and is connected to the transmission gear in the corresponding reduction gearbox. The two reduction gearboxes are connected via the transmission shaft and rotate at the same angular velocity. The top of each lifting drive rod is fixedly connected to two fixed plates.

8. The external automatic lifting reflux condenser tube rack of a water bath according to claim 7, characterized in that, The base includes a flat plate, four support columns, and two crossbeams; the four support columns are fixedly connected to the four corners of the bottom of the flat plate, the flat plate is set as a platform for placing the water bath, the two crossbeams are distributed on both sides of the width direction of the flat plate, and each crossbeam is fixedly connected between two corresponding support columns; each gearbox is fixedly connected to one of the crossbeams.

9. The external automatic lifting reflux condenser tube rack of a water bath according to claim 7, characterized in that, Each of the fixed plates is provided with a bushing at the position corresponding to the two lifting drive rods. Each bushing is slidably connected to a corresponding lifting drive rod. Each bushing is provided with at least two fixing bolts, and one end of each fixing bolt abuts against the corresponding lifting drive rod.

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