CN219362928U - Lifting machine - Google Patents

Abstract

The utility model provides a lifting machine, and relates to the technical field of lifting equipment. The elevator comprises a frame, a lifting table and a falling prevention mechanism; the lifting platform is arranged on the frame; the anti-falling mechanism comprises a first rack, a second rack and a driving mechanism. The first rack is vertically and fixedly arranged on the frame, and the teeth of the first rack are provided with supporting surfaces deviating from the falling direction of the lifting table; the second rack is arranged on the lifting table opposite to the first rack, the second rack is suitable for being meshed with the first rack, and the second rack is provided with a compression surface matched with the supporting surface; the driving mechanism is connected with the second rack and is suitable for driving the second rack to be close to or far away from the first rack so as to enable the first rack and the second rack to be meshed with each other or separated from each other, and when the second rack is meshed with the first rack, the pressing surface is abutted with the supporting surface. The utility model can solve the problems of falling risk and poor safety performance of the elevator in the prior art, and has the effects of falling prevention and safety performance improvement.

Description

Lifting machine

Technical Field

The utility model relates to the technical field of lifting equipment, in particular to a lifting machine.

Background

The Elevator (well elevating conveyor/elementer) is a large mechanical device that is transported by changing potential energy, such as a mine hoist, a dam passing hoist, etc. Broadly, elevators, crown blocks, hoists, car stables, cranes, hoist, etc. may be referred to as hoists. The hoist typically moves the transported goods up and down by driving the flexible member wire rope/sprocket chain through the power machine.

In the process of lifting the heavy object, the falling risk caused by power failure of a motor, breakage of a steel wire rope/chain and the like exists, and a large potential safety hazard exists.

Disclosure of Invention

The utility model aims to overcome the defects of falling risk and poor safety performance of a lifting machine in the prior art, thereby providing the lifting machine.

In order to solve the problems, one aspect of the utility model provides a lifter, which comprises a frame, a lifting table and a falling prevention mechanism; the lifting platform is arranged on the frame; the anti-falling mechanism comprises a first rack, a second rack and a driving mechanism. The first rack is vertically and fixedly arranged on the frame, and the teeth of the first rack are provided with supporting surfaces deviating from the falling direction of the lifting table; the second rack is arranged on the lifting table opposite to the first rack, the second rack is suitable for being meshed with the first rack, and the second rack is provided with a compression surface matched with the supporting surface; the driving mechanism is connected with the second rack and is suitable for driving the second rack to be close to or far away from the first rack so as to enable the first rack and the second rack to be meshed with each other or separated from each other, and when the second rack is meshed with the first rack, the pressing surface is abutted with the supporting surface.

Optionally, the included angle between the supporting surface and the falling direction of the lifting platform is greater than or equal to 90 degrees.

Optionally, the teeth of the first rack have a first extrusion surface opposite to the supporting surface, the teeth of the second rack have a second extrusion surface matched with the first extrusion surface, and the first extrusion surface and the supporting surface are arranged at an acute angle.

Optionally, the driving mechanism comprises a cylinder, and the end part of a piston rod of the cylinder is fixedly connected with the second rack.

Optionally, the first end of the lifting platform is connected with the frame, and the second end of the lifting platform extends towards a direction away from the frame to form a cantilever.

Optionally, the anti-falling mechanism is connected in the middle part of elevating platform, and the top of the tooth of second rack sets up in the direction of extension of cantilever dorsad.

Optionally, the lifting platform further comprises a guide mechanism, and the lifting platform is in sliding connection with the frame through the guide mechanism.

Optionally, the guiding mechanism comprises a sliding rail fixedly arranged on the frame and a sliding block fixedly arranged on the lifting platform, the sliding block is provided with a sliding groove matched with the sliding rail, and the sliding block is slidingly arranged on the sliding rail.

Optionally, the chute is a rectangular chute.

Optionally, the sliding rail includes a first sliding surface protruding in the middle and second sliding surfaces disposed on two sides of the first sliding surface; the bottom wall of the sliding groove is provided with a strip-shaped mounting hole, one side of the sliding block, which is opposite to the sliding groove, is provided with a first pulley, the outer circumferential surface of the first pulley protrudes out of the bottom wall of the sliding groove through the mounting hole, and the outer circumferential surface of the first pulley is suitable for sliding along a first sliding surface of the sliding rail;

and/or the number of the groups of groups,

the two side walls of the chute are provided with notches, the two sides of the slide block, which are positioned on the chute, are respectively provided with a second pulley, the second pulleys are correspondingly arranged with the notches, and the part of the outer circumferential surface of each second pulley protrudes out of the side wall of the chute through the notches; the outer circumferential surface of the second pulley is suitable for sliding along the second sliding surface of the sliding rail.

The utility model has the following advantages:

1. according to the technical scheme, the first rack is fixedly arranged and provided with the supporting surface, the second rack is arranged on the lifting platform and can lift along with the lifting platform, and the second rack is provided with the pressing surface, so that when the first rack is meshed with the second rack, the pressing surface of the second rack is in butt fit with the supporting surface of the first rack, and when power failure or other faults occur, the lifting platform and a heavy object on the lifting platform can be prevented from falling, and the safety performance is improved; through setting up actuating mechanism for the second rack is when rising along with the elevating platform, and the second rack can stagger with first rack, and can mesh with first rack again, thereby realizes the function of preventing falling. When the lifting platform descends, the second rack can be separated from the first rack through the driving mechanism, so that the lifting platform descends. The anti-falling device is simple in structure, and can realize the anti-falling function of the elevator, so that the safety performance of the elevator is greatly improved.

2. The guide mechanism adopts the structure of slide rail and slider, and the spout is the rectangle groove, to the lifting machine of cantilever type, the assembly precision between slider and the slide rail of being convenient for to can improve slide rail and slider's sliding fit's precision, and be the fitting surface of rectangle between slide rail and the slider, can reduce the load deflection that receives of the installation end of cantilever type elevating platform, improve life.

3. The slider sets up first pulley, and the bottom wall of the part protrusion spout of first pulley and/or the slider sets up the second pulley, and the part protrusion spout of second pulley lateral wall can improve the slip precision between slider and the slide rail.

Drawings

In order to more clearly illustrate the embodiments of the present utility model or the technical solutions in the prior art, the drawings that are needed in the description of the embodiments or the prior art will be briefly described, and it is obvious that the drawings in the description below are some embodiments of the present utility model, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.

Fig. 1 shows a schematic structural diagram of a hoist according to an embodiment of the present utility model;

FIG. 2 shows an enlarged view of a partial structure at the fall arrest mechanism of FIG. 1;

FIG. 3 shows a side view of the fall arrest mechanism;

FIG. 4 shows a schematic structural view of an embodiment of a first rack;

FIG. 5 shows a schematic structural view of another embodiment of a first rack;

FIG. 6 shows an enlarged view of a partial structure at the guide mechanism in FIG. 1;

fig. 7 shows a schematic view of the structure of the slider in fig. 6.

Reference numerals illustrate:

1. a first rack; 11. a support surface; 12. a first pressing surface; 2. a second rack; 21. a compression surface; 22. a second pressing surface; 3. a driving mechanism; 31. a cylinder; 10. a fall prevention mechanism; 20. a hoist; 4. a frame; 41. a column; 5. a lifting table; 6. a lifting mechanism; 7. a guide mechanism; 71. a slide rail; 72. a slide block; 721. a chute; 722. a second pulley; 723. a first pulley; 8. reinforcing ribs.

Detailed Description

The following description of the embodiments of the present utility model will be made apparent and fully in view of the accompanying drawings, in which some, but not all embodiments of the utility model are shown. All other embodiments, which can be made by those skilled in the art based on the embodiments of the utility model without making any inventive effort, are intended to be within the scope of the utility model.

In the description of the present utility model, it should be noted that the directions or positional relationships indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. are based on the directions or positional relationships shown in the drawings, are merely for convenience of describing the present utility model and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present utility model. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

In the description of the present utility model, it should be noted that, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be either fixedly connected, detachably connected, or integrally connected, for example; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present utility model can be understood by those of ordinary skill in the art according to the specific circumstances.

In addition, the technical features of the different embodiments of the present utility model described below may be combined with each other as long as they do not collide with each other.

For the purpose of illustrating the concepts of the utility model, the drawings and detailed description are to be regarded as illustrative in nature and not as restrictive.

Example 1

A lifter 20, referring to fig. 1-7, comprises a frame 4, a lifting table 5 and a fall protection mechanism 10; the lifting platform 5 is arranged on the frame 4; the fall protection mechanism 10 includes a first rack 1, a second rack 2, and a drive mechanism 3. The first rack 1 is vertically and fixedly arranged on the frame 4, and the teeth of the first rack 1 are provided with a supporting surface 11 deviating from the falling direction of the lifting table 5; the second rack 2 is arranged on the lifting platform 5 opposite to the first rack 1, the second rack 2 is suitable for being meshed with the first rack 1, and the second rack 2 is provided with a pressing surface 21 matched with the supporting surface 11; the driving mechanism 3 is connected with the second rack 2 and is suitable for driving the second rack 2 to be close to or far away from the first rack 1 so as to enable the first rack 1 and the second rack 2 to be meshed with each other or separated, and when the second rack 2 is meshed with the first rack 1, the pressing surface 21 is abutted with the supporting surface 11.

According to the technical scheme, as the first rack 1 is fixedly arranged and is provided with the supporting surface 11, the second rack 2 is arranged on the lifting table 5 and can lift along with the lifting table 5, the second rack 2 is provided with the pressing surface 21, and when the first rack 1 and the second rack 2 are meshed, the pressing surface 21 of the second rack 2 is in abutting fit with the supporting surface 11 of the first rack 1, so that when power failure or other faults occur, the lifting table 5 and a weight on the lifting table can be prevented from falling, and the safety performance is improved; through setting up actuating mechanism 3 for second rack 2 is when rising along with elevating platform 5, and second rack 2 can stagger with first rack 1, later can mesh with first rack 1 again, thereby realizes the function of preventing falling. When the lifting platform 5 descends, the second rack 2 can be separated from the first rack 1 through the driving mechanism 3, and dislocation avoidance is achieved, so that the lifting platform 5 descends. The utility model has simple structure, can realize the anti-falling function of the elevator 20, and greatly improves the safety performance of the elevator 20.

Specifically, referring to fig. 1, the frame 4 includes a column 41, and the lifting table 5 is connected to the column 41, and the lifting table 5 can perform lifting movement along the column 41. The first rack 1 is fixedly arranged on the upright 41.

Optionally, the angle between the supporting surface 11 and the falling direction of the lifting platform 5 is greater than or equal to 90 °.

Optionally, the angle between the supporting surface 11 and the falling direction of the lifting platform 5 is 90 °. Referring to fig. 2-4, the support surface 11 faces away from the falling direction of the lifting platform 5, in particular, the support surface 11 is capable of providing an upward supporting force, and thus the support surface 11 may be inclined, as shown in fig. 4, or the support surface 11 may be horizontal, as shown in fig. 5.

Alternatively, referring to fig. 3 to 5, the teeth of the first rack 1 have a first pressing surface 12 disposed opposite to the supporting surface 11, and the teeth of the second rack 2 have a second pressing surface 22 engaged with the first pressing surface 12, the first pressing surface 12 being disposed at an acute angle to the supporting surface 11. The arrangement is such that when the second rack 2 is lifted along with the lifting platform 5, the second pressing surface 22 of the second rack 2 abuts against the first pressing surface 12, the second pressing surface 22 presses the first pressing surface 12 upwards, accordingly, the first pressing surface 12 applies a reverse acting force to the second pressing surface 22, the second rack 2 moves towards a direction away from the first rack 1 due to the driving mechanism 3, the second rack 2 moves towards the direction away from the first rack 1, the second rack 2 and the first rack 1 are switched from the engaged state to the separated state, and when the second rack 2 continues to lift, the second pressing surface 22 of the second rack 2 passes over the first pressing surface 12, the second rack 2 moves in the opposite direction under the action of the driving mechanism 3, the teeth of the second rack 2 are meshed with the teeth of the first rack 1 again, and the supporting surface 11 of the first rack 1 abuts against the pressing surface 21 of the second rack 2 due to the plurality of teeth of the second rack 2, so that the plurality of pressing surfaces 21 of the second rack 2 and the plurality of supporting surfaces of the first rack 1 abut against each other at the same time, and the falling resistance can be improved.

Optionally, the driving mechanism 3 includes a cylinder 31, and the end of a piston rod of the cylinder 31 is fixedly connected with the second rack 2.

Specifically, the axial direction of the cylinder 31 is horizontally arranged, the end part of the piston rod of the cylinder 31 is fixedly connected with the second rack 2, when the second rack 2 ascends, the first extrusion surface 12 is abutted against the second extrusion surface 22, the pressure applied by the first extrusion surface 12 to the second extrusion surface 22 has a component force along the horizontal direction to push the second rack 2 to be away from the first rack 1 along the horizontal direction, the second rack 2 compresses the piston rod, and the piston rod is retracted, so that the second rack 2 can be separated from the first rack 1, misplacement avoidance is realized, the second rack 2 can be ensured to ascend, and when the second extrusion surface 22 passes over the first extrusion surface 12, the piston rod of the cylinder 31 automatically extends under the action of air pressure in the cylinder 31, so that the second rack 2 is close to the first rack 1, the second rack 2 is meshed with the first rack 1, and the supporting surface 11 is abutted against the pressing surface 21, thereby preventing the lifting platform 5 from falling. Therefore, during the ascent of the elevating platform 5, the relationship between the second rack 2 and the first rack 1 is: engagement, disengagement, engagement, disengagement … …. When the lift platform is lowered, the piston rod is retracted by controlling the cylinder 31, so that the second rack 2 and the first rack 1 are separated, and the lift platform 5 can be lowered smoothly.

To improve connection reliability, the hoist 20 includes two or more fall arrest mechanisms 10.

Alternatively, the first end of the lifting platform 5 is connected to the frame 4, and the second end of the lifting platform 5 extends away from the frame 4 to form a cantilever.

Referring to fig. 1, in the present embodiment, the frame 4 includes two columns 41. One side of the lifting platform 5 is an installation side, and two ends of the installation side are correspondingly connected with the two upright posts 41. A reinforcing column is further provided between the two upright posts 41, and the fall prevention mechanism 10 is provided on the reinforcing column. When two or more fall protection mechanisms 10 are provided, as one example, the fall protection mechanisms 10 are provided at intervals on the installation side of the elevating platform 5. In the utility model, two anti-falling mechanisms 10 are arranged, correspondingly, two reinforcing columns are also arranged, and first racks 1 in the two anti-falling mechanisms 10 are respectively and correspondingly arranged on the two reinforcing columns. The two fall protection mechanisms 10 can be operated simultaneously, or one can be operated and the other can be standby, according to the situation.

Optionally, the anti-falling device is arranged in the middle of the lifting platform 5, and the tooth top surface of the second rack 2 is arranged back to the extending direction of the cantilever. When the fall prevention mechanism 10 is provided in one, it is connected to the middle of the installation side of the elevating platform 5.

Optionally, the elevator further comprises a guiding mechanism 7, and the lifting platform 5 is slidably connected with the frame 4 through the guiding mechanism 7.

Alternatively, referring to fig. 6 and 7, the guide mechanism 7 includes a slide rail 71 fixedly disposed on the frame 4 and a slide block 72 fixedly disposed on the lifting platform 5, the slide block 72 is provided with a slide groove 721 engaged with the slide rail 71, and the slide block 72 is slidably disposed on the slide rail 71. The cantilever type elevator 20, the cantilever and the frame 4 are connected with one side receiving great load deflection, and the guiding mechanism 7 adopts the cooperation of slider 72 and slide rail 71, compares in adopting slide rail and gyro wheel complex mode, can improve the bending moment of slide rail 71, reduces the load deflection of the installation side of elevating platform 5 to the life-span of elevator 20 is prolonged.

Optionally, the chute 721 is a rectangular slot. Of course, the cross section of the chute 721 may be other shapes, for example, the chute 721 is a dovetail.

The guide mechanism 7 adopts the structure of the slide rail 71 and the slide block 72, the slide groove 721 is a rectangular groove, and the assembly precision between the slide rail 71 and the slide block 72 is improved for the cantilever type lifter 20, so that the precision of the sliding fit between the slide rail 71 and the slide block 72 is improved, and the rectangular matching surface between the slide rail 71 and the slide block 72 can reduce the load deflection of the cantilever, namely the mounting side of the lifting platform 5, and prolong the service life.

Optionally, the sliding rail 71 includes a first sliding surface protruding in the middle and second sliding surfaces disposed on two sides of the first sliding surface; the bottom wall of the chute 721 is provided with a strip-shaped mounting hole, one side of the slider 72 facing away from the chute 721 is provided with a first pulley 723, a part of the outer circumferential surface of the first pulley 723 protrudes from the bottom wall of the chute 721 through the mounting hole, and the outer circumferential surface of the first pulley 723 is adapted to slide along the first sliding surface of the slide rail 71.

Optionally, two side walls of the chute 721 are provided with notches, two sides of the slide block 72, which are positioned on the chute 721, are provided with second pulleys 722, the second pulleys 722 are correspondingly arranged with the notches, and part of the outer circumferential surface of the second pulleys 722 protrudes out of the side walls of the chute 721 through the notches; the outer circumferential surface of the second pulley 722 is adapted to slide along the second sliding surface of the slide rail 71.

Specifically, referring to fig. 7, both the portion of the first pulley 723 protruding from the bottom wall of the chute 721 and the portion of the second pulley 722 protruding from the side wall of the chute 721 are inferior arcs. As one example, the height of the first pulley 723 protruding from the bottom of the chute 721 and the height of the second pulley 722 protruding from the side wall of the chute 721 are controlled to be between 0.5mm and 1 mm.

In this embodiment, the two first pulleys 723 on the slide block 72 are in sliding fit with the first sliding surfaces of the slide rail 71, and the two second pulleys 722 are in matching with the two second sliding surfaces of the slide rail 71, so that the accuracy of sliding fit between the slide rail 71 and the slide rail 72 can be improved, the bending resistance of the slide rail 71 can be improved, and the load deflection of the lifting platform 5 can be reduced.

Referring to fig. 1, two guide mechanisms 7 are provided, the slide rails 71 in the two guide mechanisms 7 are respectively and correspondingly arranged on the two upright posts 41, the slide blocks 72 are slidably sleeved on the slide rails 71, and meanwhile, the slide blocks 72 are provided with mounting holes and are fixedly connected to the lifting platform 5 through fasteners.

In order to further improve the bending resistance of the slide rail 71 and reduce the load deflection of the mounting side of the lift table 5, a reinforcing rib 8 is connected between the lift table 5 and the slider 72. Referring to fig. 6, the reinforcing rib 8 has a plate-like structure, and further, the reinforcing rib 8 has a rectangular triangle-like structure, and two right-angle sides of the reinforcing rib 8 are fixedly connected with the slider 72 and the lifting table 5, respectively.

Specifically, referring to fig. 1, the elevator 20 includes a lifting mechanism 6, where the lifting mechanism 6 includes a motor and a transmission assembly, and the transmission assembly may be driven by a sprocket chain, or may be driven by a drum and a wire rope. Specifically, the tops of the two uprights 41 of the frame 4 are connected by a cross beam, on which the motor is mounted.

According to the above description, the present patent application has the following advantages:

1. by arranging the anti-falling mechanism 10, the first rack 1 is provided with the supporting surface 11, the supporting surface 11 deviates from the falling direction of the lifting table 5, and by arranging the second rack 2, the second rack can be meshed with the first rack 1 in the lifting process, and the pressing surface 21 of the second rack 2 is abutted with the supporting surface 11, so that the anti-falling effect is achieved, and the safety performance of the lifting machine 20 is improved;

2. a guide mechanism 7 is arranged between the lifting platform 5 and the frame 4, the guide mechanism 7 adopts a sliding rail 71 and a sliding block 72, the matching surface of the sliding rail 71 and the sliding block 72 is rectangular, the bending moment of the sliding rail 71 can be improved for the cantilever type lifting machine 20, the load deflection of the installation side of the cantilever type lifting platform 5 is reduced, and the service life of the lifting machine 20 is prolonged;

3. in the slide groove 721 of the slider 72, the first pulley 723 is provided at the bottom wall of the slide groove 721 and/or the second pulleys 722 are provided at the side walls of the two side wall slide grooves 721, so that the sliding engagement accuracy of the guide mechanism 7 can be improved.

It is apparent that the above examples are given by way of illustration only and are not limiting of the embodiments. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. While still being apparent from variations or modifications that may be made by those skilled in the art are within the scope of the utility model.

Claims (8)

1. The elevator is characterized by comprising a frame (4), a lifting table (5) and a falling prevention mechanism (10); the lifting table (5) is arranged on the frame (4); the fall arrest mechanism (10) comprises:

the first rack (1) is vertically and fixedly arranged on the frame (4), and teeth of the first rack (1) are provided with supporting surfaces (11) deviating from the falling direction of the lifting table (5);

a second rack (2) arranged on the lifting platform (5) opposite to the first rack (1), wherein the second rack (2) is suitable for being meshed with the first rack (1), and the second rack (2) is provided with a pressing surface (21) matched with the supporting surface (11);

the driving mechanism (3) is connected with the second rack (2) and is suitable for driving the second rack (2) to be close to or far away from the first rack (1) so as to enable the first rack (1) and the second rack (2) to be meshed with each other or separated from each other, and when the second rack (2) is meshed with the first rack (1), the pressing surface (21) is abutted with the supporting surface (11);

the driving mechanism (3) comprises an air cylinder (31), and the end part of a piston rod of the air cylinder (31) is fixedly connected with the second rack (2);

the teeth of the first rack (1) are provided with first extrusion surfaces (12) which are arranged opposite to the supporting surfaces (11), the teeth of the second rack (2) are provided with second extrusion surfaces (22) which are matched with the first extrusion surfaces (12), and the first extrusion surfaces (12) are arranged at an acute angle with the supporting surfaces (11).

2. Hoisting machine according to claim 1, characterized in that the angle between the supporting surface (11) and the falling direction of the hoisting table (5) is greater than or equal to 90 °.

3. Hoisting machine according to claim 1 or 2, characterized in that the first end of the hoisting table (5) is connected to the frame (4), and that the second end of the hoisting table (5) extends in a direction away from the frame (4) forming a cantilever.

4. A hoisting machine as claimed in claim 3, characterized in that the fall protection mechanism (10) is connected to the middle part of the hoisting table (5), the tooth top surface of the second rack (2) being arranged facing away from the extension direction of the cantilever.

5. Hoisting machine according to claim 1 or 2, characterized in that it further comprises a guiding mechanism (7), by means of which guiding mechanism (7) the hoisting platform (5) is slidingly connected to the frame (4).

6. The hoisting machine according to claim 5, characterized in that the guiding mechanism (7) comprises a sliding rail (71) fixedly arranged on the frame (4) and a sliding block (72) fixedly arranged on the hoisting table (5), wherein the sliding block (72) is provided with a sliding groove (721) matched with the sliding rail (71), and the sliding block (72) is slidingly arranged on the sliding rail (71).

7. The hoisting machine as claimed in claim 6, characterized in that the chute (721) is a rectangular chute.

8. Hoisting machine according to claim 6 or 7, characterized in that the slide rail (71) comprises a first sliding surface protruding in the middle and second sliding surfaces provided on both sides of the first sliding surface;

a strip-shaped mounting hole is formed in the bottom wall of the sliding groove (721), a first pulley (723) is arranged on one side, facing away from the sliding groove (721), of the sliding block (72), the outer circumferential surface of the first pulley (723) protrudes out of the bottom wall of the sliding groove (721) through the mounting hole, and the outer circumferential surface of the first pulley (723) is suitable for sliding along a first sliding surface of the sliding rail (71);

and/or the number of the groups of groups,

two side walls of the sliding groove (721) are provided with notches, two sides of the sliding block (72) positioned on the sliding groove (721) are respectively provided with a second pulley (722), the second pulleys (722) are arranged corresponding to the notches, and part of the outer circumferential surface of each second pulley (722) protrudes out of the side wall of the sliding groove (721) through the notches; the outer circumferential surface of the second pulley (722) is adapted to slide along the second sliding surface of the slide rail (71).