Operation safety protection device for assembly type protection platform

Abstract

The invention discloses an operation safety protection device for an assembly type protection platform, and relates to the technical field of protection platforms, the operation safety protection device comprises a mounting fence and two climbing rods, and the outer side of each climbing rod is provided with a self-locking assembly; wherein the self-locking assembly comprises square frames, through openings are formed in the tops and the bottoms of the square frames, the climbing rods are sleeved with the square frames in a sliding mode through the through openings, and the two square frames located on the top are fixed to the mounting fence; a connecting plate is fixed between the two square frames located at the top and a connecting plate is fixed between the two square frames located at the bottom. According to the anti-falling protection platform, in the falling process of the protection platform, the arc-shaped plates on the two sides of the climbing rod rotate towards the climbing rod by means of friction force between the arc-shaped plates and the climbing rod, the arc-shaped plates on the two sides clamp the climbing rod, and therefore falling prevention is achieved; and the arc-shaped plate and the climbing rod cannot slide, so that the anti-falling function is further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of protective platforms, and in particular to an operation safety protection device for an assembled protective platform. Background Art

[0002] Construction workers usually suspend a protective platform close to the building's facade from a rope on the top of the building for entry, and use a drive device on the top of the building to pull or release the rope to lift the protective platform vertically to the working position.

[0003] After searching, the Chinese patent with the authorization announcement number CN214785853U discloses the technical field related to the construction lifting platform, especially a safety protection device for the integrated lifting platform of the assembled building facade, which includes a hanger for hanging on the building facade, a safety enclosure component is arranged on the hanger, and a safety hanging component for connecting the building facade is arranged inside the hanger. This patent has the effect of forming a fence protection for the construction personnel inside the hanger and enhancing the safety during the hanger suspension process.

[0004] However, the above invention has the following shortcomings: the construction lifting platform uses a lifting rope for lifting and lowering movements, and generally a steel rope winder is used as a drive to wind up the lifting rope. However, if the steel rope winder fails and the construction lifting platform has no anti-fall mechanism, it is difficult to further improve the construction environment of the construction platform. Summary of the invention

[0005] The object of the present invention is to provide an operation safety protection device for an assembled protection platform to solve the problems raised in the above-mentioned background technology.

[0006] The technical solution of the present invention is: an operation safety protection device for an assembled protection platform, comprising a mounting fence and two climbing poles, each of the climbing poles being provided with a self-locking assembly on its outer side;

[0007] The self-locking assembly comprises a square frame, the top and bottom of the square frame are provided with through openings, and the square frame is slidably mounted on the climbing pole through the through openings, the two square frames at the top are fixed to the mounting bar, a connecting plate is fixed between the two square frames at the top and between the two square frames at the bottom, concave blocks are fixed on both sides of the square frame, and arc plates are rotatably mounted in the notches of the concave blocks, and a centering mechanism for bringing the two arc plates closer to each other is arranged in the square frame;

[0008] The mounting bar and the outer side of the connecting plate at the top are both provided with through holes, a transmission shaft is rotatably mounted in the through holes, a second connecting rod is fixed to one end of the transmission shaft, a first connecting rod is rotatably mounted to one end of the second connecting rod, and one end of the first connecting rod is rotatably mounted on the connecting plate at the bottom;

[0009] Wherein, a driving assembly for causing the transmission shaft to perform axial rotation is arranged on the outer side of the installation fence.

[0010] Furthermore, a mounting plate is fixed to one side of the climbing pole, and positioning holes are provided at four corners of the outer side of the mounting plate.

[0011] Furthermore, rollers are rotatably mounted on both sides of the through opening, and the rollers are in contact with the climbing poles.

[0012] Furthermore, the centering mechanism includes an electric push rod, the bottom of the outer shell of the electric push rod is fixed to the bottom of the square frame, the telescopic end of the electric push rod is fixed with a circular plate, the outer side of the telescopic end of the electric push rod is fixed with a limiting ring, the telescopic end sliding sleeve of the electric push rod is provided with a slide plate, and the slide plate is located between the limiting ring and the circular plate, the telescopic end sleeve of the electric push rod is provided with a second spring, and the two ends of the second spring are respectively in contact with the limiting ring and the slide plate, both ends of the slide plate are rotatably installed with a third connecting rod, and one end of the third connecting rod is rotatably installed with a connecting rod, and one end of the connecting rod on the two third connecting rods is rotatably installed on the two arc plates respectively.

[0013] Furthermore, ratchet grooves are provided on both sides of the climbing pole, and ratchet blocks are provided on the outer arc surfaces of the arc plates as an integral structure therewith.

[0014] Furthermore, the driving assembly includes a worm, a worm wheel and two fixed plates, the fixed plates are fixed to the mounting bar, the outer sides of the fixed plates are provided with rotating holes, the two ends of the worm are respectively rotatably mounted in the two rotating holes, the worm wheel is coaxially fixed to the transmission shaft, and the worm is meshed with the worm wheel.

[0015] Furthermore, the drive assembly also includes a servo motor, the casing of the servo motor is fixed on the mounting bar, the output shaft of the servo motor is fixed with a double-section telescopic cylinder coaxially arranged therewith, a limiting plate is fixed to the outer side of one end of the double-section telescopic cylinder, a second friction disk is fixed to the other end of the double-section telescopic cylinder, a first spring is sleeved on the outer side of the double-section telescopic cylinder, and the two ends of the first spring are respectively in contact with the limiting plate and the second friction disk, and one end of the worm is fixed with a first friction disk coaxially arranged therewith.

[0016] Furthermore, a fixing frame is fixed to the bottom of the connecting plate located at the top, and recesses are provided on the outer side of the connecting plate and the fixing frame, a first photoelectric sensor is fixed to the recess on the fixing frame, a second photoelectric sensor is fixed to the recess on the top connecting plate, a reference frame is fixed between the two square frames located at the top, a first photoelectric receiver and a second photoelectric receiver are fixed to the outer side of the reference frame, and the first photoelectric receiver and the second photoelectric receiver are aligned with the first photoelectric sensor and the second photoelectric sensor, respectively.

[0017] The present invention provides an operation safety protection device for an assembled protection platform by improving the present invention, which has the following improvements and advantages compared with the prior art:

[0018] First, in the present invention, when the protection platform falls, the arc plates on both sides of the climbing pole rotate toward the climbing pole by means of the friction between the arc plates and the climbing pole, and the arc plates on both sides clamp the climbing pole, thereby preventing the climbing pole from falling. Since the arc plates are provided with thorn blocks, the thorn blocks are stuck in the thorn grooves on the climbing pole, so that no sliding occurs between the arc plates and the climbing pole, thereby further improving the anti-falling function.

[0019] Secondly, the present invention can provide climbing power for the protection platform without the aid of a crane. The hoisting rope of the crane is relatively soft, and the protection platform is prone to shaking during the rising process. However, the square frame and the climbing rod are interconnected in the present invention, making the rising process of the protection platform more stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 It is a schematic diagram of the overall three-dimensional structure of the present invention;

[0022] Figure 2 It is a schematic diagram of the three-dimensional structure of the driving component of the present invention;

[0023] Figure 3 This is a schematic diagram of the overall first-view stereoscopic structure of the present invention (without the installation bar);

[0024] Figure 4 It is a schematic diagram of the overall second viewing angle stereoscopic structure of the present invention (without the installation column);

[0025] Figure 5 This is a schematic diagram of the three-dimensional structure of the self-locking assembly of the present invention from a first viewing angle;

[0026] Figure 6 It is a schematic diagram of the three-dimensional structure of the self-locking assembly of the present invention from a second viewing angle;

[0027] Figure 7 It is a structural schematic diagram of the self-locking component of the present invention in a non-self-locking state;

[0028] Figure 8 It is a schematic diagram of the partial three-dimensional structure of the climbing pole of the present invention.

[0029] Reference numerals:

[0030] 1. Mounting bar; 2. Driving assembly; 3. Connecting plate; 4. Climbing rod; 5. Self-locking assembly; 6. Worm gear; 7. Transmission shaft; 8. Fixed plate; 9. Worm; 10. First friction disc; 11. Second friction disc; 12. First spring; 13. Double-section telescopic cylinder; 14. Limiting plate; 15. Servo motor; 16. First connecting rod; 17. Second connecting rod; 18. Fixed frame; 19. First photoelectric sensor; 20. Second photoelectric sensor; 21. Mounting plate; 22. Reference frame; 23. Square frame; 24. Electric push rod; 25. Limiting ring; 26. Second spring; 27. Round plate; 28. Slide plate; 29. ​​Third connecting rod; 30. Arc plate; 31. Through port; 32. Roller; 33. Connecting rod; 34. Ratchet block; 35. Concave block; 36. Ratchet groove. DETAILED DESCRIPTION

[0031] The present invention is described in detail below, and the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] The present invention provides an operation safety protection device for an assembled protection platform through improvement. The technical solution of the present invention is:

[0033] like Figures 1 to 8 As shown, an embodiment of the present invention provides a work safety protection device for an assembled protection platform, comprising a mounting fence 1 and two climbing poles 4. The mounting fence 1 is fixed to the outside of the protection platform by fixing bolts, and a self-locking component 5 is provided on the outside of each climbing pole 4.

[0034] Among them, combined with Figure 6 The self-locking assembly 5 includes a square frame 23, the top and bottom of the square frame 23 are provided with through openings 31, and the square frame 23 is slidably mounted on the climbing rod 4 through the through openings 31, the two square frames 23 at the top are fixed to the mounting bar 1 by fixing bolts, and a connecting plate 3 is fixed (this fixing method is welding) between the two square frames 23 at the top and the two square frames 23 at the bottom, and concave blocks 35 are fixed on both sides of the square frame 23, and arc plates 30 are rotatably installed in the recesses of the concave blocks 35, and a centering mechanism for bringing the two arc plates 30 closer to each other is provided in the square frame 23. When the protective platform falls, the arc plates 30 at both sides of the climbing rod 4 rotate toward the climbing rod 4 by means of the friction between the arc plates 30 and the climbing rod 4, and the arc plates 30 on both sides clamp the climbing rod 4, thereby preventing the climbing rod from falling;

[0035] Among them, combined with Figure 3-4 , the mounting bar 1 and the outer side of the connecting plate 3 at the top are both provided with through holes, in which a transmission shaft 7 is rotatably mounted, a second connecting rod 17 is fixed to one end of the transmission shaft 7, a first connecting rod 16 is rotatably mounted to one end of the second connecting rod 17, and one end of the first connecting rod 16 is rotatably mounted on the connecting plate 3 at the bottom. Here, the first connecting rod 16 and the second connecting rod 17 are supplemented. In order to prevent the square frame 23 at the top position from colliding with the square frame 23 at the bottom position, the first connecting rod 16 is longer than the second connecting rod 17;

[0036] A driving assembly 2 for causing the transmission shaft 7 to perform axial rotation is arranged on the outer side of the mounting fence 1 .

[0037] Specifically, combined with Figure 3-4 A mounting plate 21 is fixed to one side of the climbing pole 4 by welding, and positioning holes are provided at the four corners of the outer side of the mounting plate 21, and fixing bolts pass through the positioning holes to fix the mounting plate 21 on the building.

[0038] Specifically, combined with Figure 5-7 Rollers 32 are rotatably mounted on both sides of the through opening 31, and the rollers 32 are in contact with the climbing rod 4. The setting of the rollers 32 changes the contact form between the square frame 23 and the climbing rod 4 into rolling contact, thereby reducing friction damage.

[0039] Specifically, combined with Figure 5-7The centering mechanism includes an electric push rod 24, the bottom of the shell of the electric push rod 24 is fixed to the bottom of the square frame 23, a circular plate 27 is fixed to the telescopic end of the electric push rod 24, a limiting ring 25 is fixed to the outer side of the telescopic end of the electric push rod 24, a sliding plate 28 is provided on the telescopic end sliding sleeve of the electric push rod 24, and the sliding plate 28 is located between the limiting ring 25 and the circular plate 27, a second spring 26 is provided on the telescopic end sleeve of the electric push rod 24, and the two ends of the second spring 26 are respectively in contact with the limiting ring 25 and the sliding plate 28, and the two ends of the sliding plate 28 are rotatably installed with a third connecting rod 29, and one end of the third connecting rod 29 is rotatably installed with a connecting rod 33, and one end of the connecting rod 33 on the two third connecting rods 29 is rotatably installed on the two arc plates 30 respectively; when the electric push rod 24 remains in the extended state, the second spring 26 The slide plate 28 is lifted up, and the second spring 26 makes the slide plate 28 contact with the circular plate 27. The slide plate 28 makes the curved plates 30 on both sides of the climbing rod 4 contact with the climbing rod 4 through the two third connecting rods 29. During the upward movement of the entire square frame 23 along the climbing rod 4, the curved plates 30 cannot clamp the climbing rod 4. When the square frame 23 moves downward, the curved plates 30 on both sides of the climbing rod 4 rotate toward the climbing rod 4 with the help of the friction between the curved plates 30 and the climbing rod 4, and the curved plates 30 on both sides clamp the climbing rod 4; when the electric push rod 24 is shortened, the electric push rod 24 pulls the slide plate 28 down through the circular plate 27, and the slide plate 28 separates the curved plates 30 on both sides of the climbing rod 4 from the climbing rod 4 through the two third connecting rods 29. At this time, the square frame 23 can slide freely on the climbing rod 4.

[0040] Specifically, combined with Figure 5-7 Ratchet grooves 36 are provided on both sides of the climbing rod 4, and the outer arc surface of the arc plate 30 is provided with a ratchet block 34 with an integral structure therewith. The arc plate 30 is provided with a ratchet block 34, and the ratchet block 34 is inserted into the ratchet groove 36 on the climbing rod 4, so that there is no sliding between the arc plate 30 and the climbing rod 4, further improving the anti-fall function.

[0041] Specifically, combined with Figure 2 The driving assembly 2 includes a worm 9, a worm wheel 6 and two fixed plates 8. The fixed plate 8 is fixed to the mounting fence 1. The outer side of the fixed plate 8 is provided with a rotating hole. The two ends of the worm 9 are rotatably installed in the two rotating holes respectively. The worm wheel 6 is coaxially fixed with the transmission shaft 7, and the worm 9 is meshed with the worm wheel 6. When the worm 9 rotates, the worm 9 rotates the transmission shaft 7 through the worm wheel 6 meshed with it.

[0042] Specifically, combined with Figure 2The drive assembly 2 also includes a servo motor 15, the housing of the servo motor 15 is fixed on the mounting column 1, the output shaft of the servo motor 15 is fixed with a double-section telescopic cylinder 13 coaxially arranged therewith, a limit plate 14 is fixed on the outer side of one end of the double-section telescopic cylinder 13, and a second friction disk 11 is fixed on the other end of the double-section telescopic cylinder 13, a first spring 12 is sleeved on the outer side of the double-section telescopic cylinder 13, and the two ends of the first spring 12 are respectively in contact with the limit plate 14 and the second friction disk 11, and a first friction disk 10 coaxially arranged therewith is fixed at one end of the worm 9, the servo motor 15 rotates the double-section telescopic cylinder 13 coaxially fixed therewith through the output shaft, the first spring 12 on the double-section telescopic cylinder 13 applies an outward thrust to the second friction disk 11, so that the second friction disk 11 contacts the first friction disk 10 on the worm 9, and the second friction disk 11 on the double-section telescopic cylinder 13 rotates the first friction disk 10 through friction, and the first friction disk 10 drives the worm 9 to rotate.

[0043] Specifically, a fixing frame 18 is fixed to the bottom of the connecting plate 3 at the top, and recesses are provided on the outer side of the connecting plate 3 and the fixing frame 18. A first photoelectric sensor 19 is fixed to the recess on the fixing frame 18, and a second photoelectric sensor 20 is fixed to the recess on the top connecting plate 3. A reference frame 22 is fixed between the two square frames 23 at the top, and a first photoelectric receiver and a second photoelectric receiver are fixed to the outer side of the reference frame 22. The first photoelectric receiver and the second photoelectric receiver are aligned with the first photoelectric sensor 19 and the second photoelectric sensor 20, respectively.

[0044] To supplement the above, a controller is fixedly installed on the mounting bar 1, and all the electrical components described above are electrically connected to the controller. Assuming that the second connecting rod 17 rotates clockwise, and assuming that the servo motor 15 is in forward rotation at this time, when the second connecting rod 17 blocks the light source of the first photoelectric sensor 19, the first photoelectric receiver cannot receive the light source of the first photoelectric sensor 19, and the electric push rod 24 at the top position is first extended, and then the electric push rod 24 at the bottom position is shortened. When the second connecting rod 17 rotates to the top, the first connecting rod 16 and the second connecting rod 17 block the light source of the first photoelectric sensor 19 and the light source of the first photoelectric sensor 19, and the first photoelectric receiver and the first photoelectric receiver cannot receive the light source. At this time, the electric push rod 24 at the bottom position is first extended, and then the electric push rod 24 at the top position is shortened; when the servo motor 15 is reversed, the working order of the above-mentioned electric push rods is reversed.

[0045] Working principle: Assuming that the second connecting rod 17 rotates clockwise to climb upward, and assuming that the servo motor 15 rotates forward, the electric push rod 24 in the bottom square frame 23 is in an extended state, and the electric push rod 24 in the square frame 23 at the top position is in a shortened rotation;

[0046] The servo motor 15 rotates the double-section telescopic cylinder 13 coaxially fixed therewith through the output shaft. The first spring 12 on the double-section telescopic cylinder 13 makes the second friction disc 11 contact with the first friction disc 10 on the worm 9. The second friction disc 11 on the double-section telescopic cylinder 13 rotates the first friction disc 10 through friction force. The first friction disc 10 drives the worm 9 to rotate. When the worm 9 rotates, the worm 9 rotates the transmission shaft 7 through the worm wheel 6 meshing therewith.

[0047] During the downward rotation of the second connecting rod 17, the electric push rod 24 in the bottom square frame 23 keeps extending and rotating, and the arc plates 30 on both sides of the climbing rod 4 rotate toward the climbing rod 4 by means of the friction between the arc plates 30 and the climbing rod 4. The arc plates 30 on both sides clamp the climbing rod 4, and the square frame 23 at the bottom position cannot move. The first connecting rod 16 and the second connecting rod 17 push the connection at the top position upward;

[0048] When the second connecting rod 17 blocks the light source of the first photoelectric sensor 19, the first photoelectric receiver cannot receive the light source of the first photoelectric sensor 19, and the electric push rod 24 at the top position first extends, and the square frame 23 at the top position is fixed on the climbing rod 4, and then the electric push rod 24 at the bottom position shortens again, and the square frame 23 at the bottom position is pulled up;

[0049] When the second connecting rod 17 rotates to the uppermost position, the first connecting rod 16 and the second connecting rod 17 block the light source of the first photoelectric sensor 19 and the light source of the first photoelectric sensor 19, and the first photoelectric receiver and the first photoelectric receiver cannot receive the light source. At this time, the electric push rod 24 at the bottom position first extends, and then the electric push rod 24 at the top position shortens;

[0050] When the servo motor 15 is reversed, i.e. climbing downward, the working order of the electric push rods is reversed;

[0051] Since the electric push rods 24 at the top and bottom positions do not work synchronously, there must be a moment when the arc plates 30 in the square frame 23 are in contact with the climbing rod 4. At this time, the top and bottom square frames 23 are fixed on the climbing rod 4, and the first friction plate 10 and the second friction plate 11 rotate relative to each other.

[0052] The above description enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A work safety protection device for an assembled protection platform, comprising a mounting fence (1) and two climbing poles (4), characterized in that: A self-locking component (5) is provided on the outer side of each climbing pole (4); The self-locking component (5) comprises a square frame (23), the top and bottom of the square frame (23) are provided with through openings (31), and the square frame (23) is slidably mounted on the climbing pole (4) through the through openings (31), the two square frames (23) at the top are fixed to the mounting bar (1), a connecting plate (3) is fixed between the two square frames (23) at the top and between the two square frames (23) at the bottom, concave blocks (35) are fixed on both sides of the square frame (23), and arc plates (30) are rotatably mounted in the recesses of the concave blocks (35), and a centering mechanism for bringing the two arc plates (30) closer to each other is provided in the square frame (23); The installation bar (1) and the connecting plate (3) at the top are both provided with through holes on their outer sides, a transmission shaft (7) is rotatably mounted in the through holes, a second connecting rod (17) is fixed to one end of the transmission shaft (7), a first connecting rod (16) is rotatably mounted to one end of the second connecting rod (17), and one end of the first connecting rod (16) is rotatably mounted on the connecting plate (3) at the bottom; Wherein, a driving assembly (2) for causing the transmission shaft (7) to rotate axially is arranged on the outer side of the installation fence (1).

2. The operation safety protection device for an assembled protection platform according to claim 1, characterized in that: A mounting plate (21) is fixed to one side of the climbing pole (4), and positioning holes are provided at four corners on the outside of the mounting plate (21).

3. The operation safety protection device for an assembled protection platform according to claim 1 is characterized in that: Rollers (32) are rotatably mounted on both sides of the through opening (31), and the rollers (32) are in contact with the climbing pole (4).

4. The operation safety protection device for an assembled protection platform according to claim 1, characterized in that: The centering mechanism comprises an electric push rod (24), the bottom of the shell of the electric push rod (24) is fixed to the bottom of the square frame (23), a circular plate (27) is fixed to the telescopic end of the electric push rod (24), a limiting ring (25) is fixed to the outer side of the telescopic end of the electric push rod (24), a sliding plate (28) is provided on the sliding sleeve of the telescopic end of the electric push rod (24), and the sliding plate (28) is located between the limiting ring (25) and the circular plate (27), the telescopic end of the electric push rod (24) is provided with a second spring (26), and the two ends of the second spring (26) are respectively in contact with the limiting ring (25) and the sliding plate (28), and the two ends of the sliding plate (28) are rotatably mounted with a third connecting rod (29), and one end of the third connecting rod (29) is rotatably mounted with a connecting rod (33), and one end of the connecting rod (33) on the two third connecting rods (29) is rotatably mounted on the two arc plates (30).

5. The operation safety protection device for an assembled protection platform according to claim 1, characterized in that: Both sides of the climbing pole (4) are provided with ratchet grooves (36), and the outer arc surface of the arc-shaped plate (30) is provided with a ratchet block (34) which is an integral structure therewith.

6. The operation safety protection device for an assembled protection platform according to claim 1, characterized in that: The driving assembly (2) comprises a worm (9), a worm wheel (6) and two fixing plates (8); the fixing plates (8) are fixed to the mounting bar (1); the outer sides of the fixing plates (8) are provided with rotation holes; the two ends of the worm (9) are respectively rotatably mounted in the two rotation holes; the worm wheel (6) is coaxially fixed to the transmission shaft (7), and the worm (9) is meshed with the worm wheel (6).

7. The operation safety protection device for an assembled protection platform according to claim 6, characterized in that: The drive assembly (2) further comprises a servo motor (15), the housing of the servo motor (15) being fixed on the mounting bar (1), the output shaft of the servo motor (15) being fixed with a double-section telescopic cylinder (13) coaxially arranged therewith, a limit plate (14) being fixed on the outer side of one end of the double-section telescopic cylinder (13), a second friction disc (11) being fixed on the other end of the double-section telescopic cylinder (13), a first spring (12) being sleeved on the outer side of the double-section telescopic cylinder (13), and the two ends of the first spring (12) being in contact with the limit plate (14) and the second friction disc (11) respectively, and one end of the worm (9) being fixed with a first friction disc (10) coaxially arranged therewith.

8. The operation safety protection device for an assembled protection platform according to claim 7, characterized in that: A fixing frame (18) is fixed to the bottom of the connecting plate (3) located at the top, and notches are provided on the outer side of the connecting plate (3) and the fixing frame (18), a first photoelectric sensor (19) is fixed to the notch on the fixing frame (18), a second photoelectric sensor (20) is fixed to the notch on the top connecting plate (3), a reference frame (22) is fixed between the two square frames (23) located at the top, a first photoelectric receiver and a second photoelectric receiver are fixed to the outer side of the reference frame (22), and the first photoelectric receiver and the second photoelectric receiver are aligned with the first photoelectric sensor (19) and the second photoelectric sensor (20) respectively.

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