Eight-rope anti-swing crane carriage

Abstract

The utility model discloses an eight-rope anti-swing crane carriage, which belongs to the technical field of lifting devices and comprises a chassis and a balance plate, the upper end face of the chassis is rotatably connected with a winch drum, eight lifting ropes are wound on the winch drum, four anchor blocks for fixing the lifting ropes are symmetrically arranged on the upper end face of the balance plate, and two fixing points are arranged on each anchor block. A guide device is arranged between the winch cylinder and the balance plate, and the free end of each hoisting rope is fixedly connected with the corresponding fixing point through the guide device. When the hoisting device is used, materials to be hoisted are fixed through the balance plate, then the twisting barrels are rotated, so that the eight hoisting ropes are wound by the two twisting barrels at the same time, the free ends of the eight hoisting ropes move upwards and pull up the balance plate at the same time, and the eight hoisting ropes balance the tension of the balance plate through the arrangement of the guide device and the anchor block; and therefore, the balance plate does not swing when the balance plate ascends or the chassis moves in parallel, so that stable transfer of the hoisted materials is ensured, and the occurrence rate of safety accidents is reduced.

Description

Technical Field

[0001] This utility model relates to the technical field of lifting devices, and in particular to an eight-rope anti-sway lifting trolley. Background Technology

[0002] A crane is a multi-action lifting machine that vertically lifts and horizontally moves heavy objects within a certain range. It is also called an overhead crane, gantry crane, or hoist. A bridge crane is a lifting device that spans across workshops, warehouses, and material yards for material handling. Because its two ends rest on tall concrete pillars or metal supports, it resembles a bridge. The bridge frame of a bridge crane runs longitudinally along tracks laid on elevated structures on both sides, making full use of the space beneath the bridge frame for material handling without being obstructed by ground equipment. It is the most widely used and numerous type of lifting machinery.

[0003] The vertical lifting function of a crane is generally achieved through a wire rope and a fixed pulley. First, a winding drum is set up to wind up or release the wire rope by driving the drum to rotate. The end of the wire rope is used to lift or lower the material. When existing cranes lift goods for longitudinal movement, the material hanging at the end of the wire rope is in a free state. Due to inertia, it often swings, causing the material hanging at the end of the wire rope to perform a pendulum motion after the crane moves longitudinally to the designated position. As a result, it cannot be accurately placed in the predetermined position, which causes inconvenience to safe production. Utility Model Content

[0004] The purpose of this utility model is to provide an eight-rope anti-sway lifting trolley, which can achieve the effect of no material swaying when the crane lifts goods for longitudinal movement. It effectively solves the problem in the prior art where the material hanging at the end of the wire rope moves like a pendulum, making it impossible to accurately place it in the predetermined position, which brings inconvenience to safe production.

[0005] This utility model adopts the following technical solution: an eight-rope anti-sway lifting trolley, including a chassis and a balance plate, a winch is rotatably connected to the upper end face of the chassis, eight lifting ropes are wound on the winch, four anchor blocks for fixing the lifting ropes are symmetrically arranged on the upper end face of the balance plate, each anchor block is provided with two fixing points, a guide device is provided between the winch and the balance plate, and the free end of each lifting rope is fixedly connected to the corresponding fixing point through the guide device; when the winch rotates, it drives the eight lifting ropes to be wound or released synchronously; a fixing device is provided on the lower end face of the balance plate.

[0006] Furthermore, the guiding device includes a plurality of fixed pulleys rotatably connected to the chassis. The fixed pulleys include a first fixed pulley, a second fixed pulley, a third fixed pulley, a fourth fixed pulley, a fifth fixed pulley, a sixth fixed pulley, a seventh fixed pulley, an eighth fixed pulley, a ninth fixed pulley, a tenth fixed pulley, an eleventh fixed pulley, and a twelfth fixed pulley. The first and sixth fixed pulleys rotate horizontally; the second, fifth, eighth, and eleventh fixed pulleys rotate forward and backward; the third, fourth, ninth, and tenth fixed pulleys rotate left and right; and the seventh and twelfth fixed pulleys are inclined.

[0007] Furthermore, the anchor points include points P1, P2, P3, P4, P5, P6, P7, and P8; one end of each lifting rope is fixedly connected to the corresponding winch, and the lifting ropes include a first lifting rope, a second lifting rope, a third lifting rope, a fourth lifting rope, a fifth lifting rope, a sixth lifting rope, a seventh lifting rope, and an eighth lifting rope; the first lifting rope 25 is wound around the twelfth and eleventh fixed pulleys, and its other end is fixedly connected to point P1; the second lifting rope is wound around the first and second fixed pulleys, and its other end is fixedly connected to point P6; the third lifting rope is wound around the... The third lifting rope is wound around the tenth fixed pulley, and the other end of the fourth lifting rope is fixedly connected to point P7; the fifth lifting rope is wound around the ninth fixed pulley, and the other end of the fifth lifting rope is fixedly connected to point P3; the sixth lifting rope is wound around the fourth fixed pulley, and the other end of the sixth lifting rope is fixedly connected to point P4; the seventh lifting rope is wound around the fifth and sixth fixed pulleys, and the other end of the seventh lifting rope is fixedly connected to point P5; the eighth lifting rope is wound around the seventh and eighth fixed pulleys, and the other end of the eighth lifting rope is fixedly connected to point P2.

[0008] Furthermore, the chassis includes a bottom frame and a mounting base fixedly mounted on the upper surface of the bottom frame via support columns. Several fixing blocks are fixedly mounted on both the bottom frame and the mounting base. The bottom frame is rotatably connected to the first, second, fifth, sixth, eighth, and eleventh fixed pulleys through the corresponding fixing blocks. The mounting base is rotatably connected to the third, fourth, seventh, ninth, tenth, and twelfth fixed pulleys through the corresponding fixing blocks.

[0009] Furthermore, there are two winches, each wound with four lifting ropes.

[0010] Furthermore, the upper end face of the mounting base is fixedly provided with two side plates, and the winch is rotatably mounted on the corresponding side plates. Each winch has a pin fixedly mounted on one of its adjacent sides.

[0011] Furthermore, a gearbox is fixedly mounted on the mounting base, and the two output shafts of the gearbox are respectively fixedly mounted to corresponding pins; the front side of the lower end face of the gearbox is fixedly mounted to the front crossbeam; a power motor is fixedly mounted on the front crossbeam, and the output shaft of the power motor is fixedly mounted to the input shaft of the gearbox.

[0012] Furthermore, the fixing device is an electromagnet.

[0013] Furthermore, crossbeams are fixedly installed on both the left and right sides of the chassis, and rollers are rotatably connected to both ends of the crossbeams. A servo motor is fixedly installed at both ends of each crossbeam, and the output shaft of each servo motor is fixedly installed with the corresponding roller.

[0014] Furthermore, four fixed columns are provided. Two tracks are provided above the columns along the front-to-back direction. The lower end of the right track is fixed to the two right columns, and the lower end of the left track is fixed to the two left columns. Each track has a track groove on its upper end along the front-to-back direction. The roller at the right end of each crossbeam is located in the track groove of the right track, and the roller at the left end of each crossbeam is located in the track groove of the left track.

[0015] I. This utility model, by setting up winches, balance plates, lifting ropes, and anchor blocks, allows the material to be lifted to be fixed by the balance plate during use. Then, by rotating the winches, two winches simultaneously wind up eight lifting ropes. The free ends of all eight lifting ropes move upwards, simultaneously pulling up the balance plate. The tension of the eight lifting ropes on the balance plate is balanced by the guide device and anchor blocks, thus preventing the balance plate from swaying when it rises or when the chassis moves horizontally. This ensures the smooth transfer of the lifted material and reduces the incidence of safety accidents.

[0016] II. This utility model, by setting up a chassis, crossbeam, track, rollers and servo motor, allows the servo motor to drive the rollers to roll in the track groove during use, so that the chassis can move back and forth, thereby achieving the purpose of moving back and forth after the balance plate lifts the material. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall three-dimensional structure of this utility model;

[0018] Figure 2 This is a front view structural diagram of the present utility model;

[0019] Figure 3 This is a top view of the structure of this utility model;

[0020] Figure 4 This is a three-dimensional structural diagram of the crossbeam in this utility model;

[0021] Figure 5 This is a three-dimensional structural diagram of the mounting base in this utility model;

[0022] Figure 6 This is a three-dimensional structural diagram of the bottom frame in this utility model;

[0023] Figure 7 This is a schematic diagram of the lifting rope winding method in this utility model.

[0024] In the diagram, 1. Chassis; 2. Balance plate; 3. Winch; 4. Lifting rope; 5. Anchor block; 6. Fixing device; 7. Crossbeam; 8. Roller; 9. Servo motor; 10. Column; 11. Track; 12. Track groove; 13. First fixed pulley; 14. Second fixed pulley; 15. Third fixed pulley; 16. Fourth fixed pulley; 17. Fifth fixed pulley; 18. Sixth fixed pulley; 19. Seventh fixed pulley; 20. Eighth fixed pulley; 21. Ninth fixed pulley. 22. Tenth fixed pulley; 23. Eleventh fixed pulley; 24. Twelfth fixed pulley; 25. First lifting rope; 26. Second lifting rope; 27. Third lifting rope; 28. Fourth lifting rope; 29. ​​Fifth lifting rope; 30. Sixth lifting rope; 31. Seventh lifting rope; 32. Eighth lifting rope; 33. Base frame; 34. Support column; 35. Mounting base; 36. Fixing block; 37. Side plate; 38. Pin shaft; 39. Gearbox; 40. Power motor. Detailed Implementation

[0025] Please see Figure 1-7 The present invention will now be described in detail with reference to the accompanying drawings and embodiments:

[0026] The eight-rope anti-sway lifting trolley of this utility model includes a chassis 1 and a balance plate 2. A winch 3 is rotatably connected to the upper end of the chassis 1, and eight lifting ropes 4 are wound on the winch 3. Four anchor blocks 5 for fixing the lifting ropes 4 are symmetrically arranged on the upper end of the balance plate 2. Each anchor block 5 has two fixing points. A guide device is provided between the winch 3 and the balance plate 2. The free end of each lifting rope 4 is fixedly connected to the corresponding fixing point through the guide device. When the winch 3 rotates, it drives the eight lifting ropes 4 to be wound or released synchronously. A fixing device 6 is provided on the lower end of the balance plate 2 for fixing the material to be lifted.

[0027] In use, the material to be hoisted is fixed by the balance plate 2, and then the two winches 3 are rotated so that they simultaneously wind up the eight lifting ropes 4. The free ends of the eight lifting ropes 4 move upward and pull up the balance plate 2. The tension of the eight lifting ropes 4 is balanced by the guide device and the anchor block 5, so that the balance plate 2 does not sway when it rises or when the chassis 1 moves in parallel, thus ensuring the smooth transfer of the hoisted material and reducing the accident rate.

[0028] In this embodiment, crossbeams 7 are fixedly installed on both the left and right sides of the chassis 1. Rollers 8 are rotatably connected to both ends of each crossbeam 7. A servo motor 9 is fixedly installed at both ends of each crossbeam 7. The output shaft of each servo motor 9 is fixedly installed with the corresponding roller 8. Four fixed columns 10 are also provided. Two tracks 11 are provided above the columns 10 along the front-back direction. The lower end face of the right track 11 is fixedly installed with the two right columns 10, and the lower end face of the left track 11 is fixedly installed with the two left columns 10. The upper end face of each track 11 is provided with a track groove 12 along the front-back direction. The roller 8 at the right end of each crossbeam 7 is located in the track groove 12 of the right track 11, and the roller 8 at the left end of each crossbeam 7 is located in the track groove 12 of the left track 11.

[0029] In use, four columns 10 are fixedly set according to the site conditions. The servo motor 9 drives the rollers 8 to roll in the track groove 12, so that the chassis 1 moves back and forth. This achieves the purpose of moving back and forth when the balance plate 2 lifts the material. When the balance plate 2 lifts the material and moves back and forth, the eight lifting ropes 4 provide balanced tension on the balance plate 2, so the balance plate 2 does not sway when moving back and forth, which facilitates the transfer of materials.

[0030] In this embodiment, the directional terms appearing are... Figure 6For reference, the guiding device includes several fixed pulleys rotatably connected to the chassis 1. The fixed pulleys include a first fixed pulley 13, a second fixed pulley 14, a third fixed pulley 15, a fourth fixed pulley 16, a fifth fixed pulley 17, a sixth fixed pulley 18, a seventh fixed pulley 19, an eighth fixed pulley 20, a ninth fixed pulley 21, a tenth fixed pulley 22, an eleventh fixed pulley 23, and a twelfth fixed pulley 24. The first fixed pulley 13 and the sixth fixed pulley 18 rotate horizontally; the second fixed pulley 14, the fifth fixed pulley 17, the eighth fixed pulley 20, and the eleventh fixed pulley 23 rotate forward and backward. The third fixed pulley 15, the fourth fixed pulley 16, the ninth fixed pulley 21, and the tenth fixed pulley 22 rotate in the left and right directions; the seventh fixed pulley 19 and the twelfth fixed pulley 24 are inclined; the anchor block 5 is fixed at points P1, P2, P3, P4, P5, P6, P7, and P8; one end of each lifting rope 4 is fixed to the corresponding winch 3, and the lifting rope 4 includes the first lifting rope 25, the second lifting rope 26, the third lifting rope 27, the fourth lifting rope 28, the fifth lifting rope 29, the sixth lifting rope 30, and the seventh lifting rope 30. 31 and the eighth lifting rope 32; the first lifting rope 25 is wound around the twelfth fixed pulley 24 and the eleventh fixed pulley 23, and the other end of the first lifting rope 25 is fixedly connected to point P1; the second lifting rope 26 is wound around the first fixed pulley 13 and the second fixed pulley 14, and the other end of the second lifting rope 26 is fixedly connected to point P6; the third lifting rope 27 is wound around the third fixed pulley 15, and the other end of the third lifting rope 27 is fixedly connected to point P7; the fourth lifting rope 28 is wound around the tenth fixed pulley 22, and the other end of the fourth lifting rope 28 is fixedly connected to point P7. P8 is fixedly connected; the fifth lifting rope 29 is wound around the ninth fixed pulley 21, and the other end of the fifth lifting rope 29 is fixedly connected to point P3; the sixth lifting rope 30 is wound around the fourth fixed pulley 16, and the other end of the sixth lifting rope 30 is fixedly connected to point P4; the seventh lifting rope 31 is wound around the fifth fixed pulley 17 and the sixth fixed pulley 18, and the other end of the seventh lifting rope 31 is fixedly connected to point P5; the eighth lifting rope 32 is wound around the seventh fixed pulley 19 and the eighth fixed pulley 20, and the other end of the eighth lifting rope 32 is fixedly connected to point P2.

[0031] In operation, rotating the winch 3 releases each lifting rope 4, causing the balance plate 2 to fall downwards under gravity. At this time, each fixed pulley rotates under the drive of the lifting rope 4. After securing the material below the balance plate 2 using the fixing device 6, rotating the winch 3 in the opposite direction causes each lifting rope 4 to wind up. Each lifting rope 4 pulls the balance plate 2 upwards through its free end, thereby lifting the material. The lifting ropes 4 simultaneously apply pressure to points P1, P2, P3, P4, P5, P6, P7, and P8. The same force ensures that the balance plate 2 rises smoothly without swaying. After the material is lifted to the set height, the servo motor 9 drives the roller 8 to roll in the track groove 12, causing the chassis 1 to move back and forth on the track 11. This, in turn, drives the material to move back and forth horizontally via the lifting rope 4 and the balance plate 2. Since the lifting rope 4 applies the same force to points P1, P2, P3, P4, P5, P6, P7, and P8 simultaneously, the balance plate 2 will not sway during its horizontal movement, facilitating the transfer of materials and reducing the incidence of safety accidents.

[0032] In this embodiment, the chassis 1 includes a bottom frame 33 and a mounting base 35 fixedly mounted on the upper surface of the bottom frame 33 via a support column 34. A plurality of fixing blocks 36 are fixedly mounted on both the bottom frame 33 and the mounting base 35. The bottom frame 33 is rotatably connected to the first fixed pulley 13, the second fixed pulley 14, the fifth fixed pulley 17, the sixth fixed pulley 18, the eighth fixed pulley 20, and the eleventh fixed pulley 23 through the corresponding fixing blocks 36. The mounting base 35 is rotatably connected to the third fixed pulley 15, the fourth fixed pulley 16, the seventh fixed pulley 19, the ninth fixed pulley 21, the tenth fixed pulley 22, and the twelfth fixed pulley 24 through the corresponding fixing blocks 36.

[0033] In this embodiment, there are two winches 3, and each winch 3 is wound with four lifting ropes 4.

[0034] In this embodiment, two side plates 37 are fixedly provided on the upper end face of the mounting base 35, and the winches 3 are rotatably mounted on the corresponding side plates 37. Each winch 3 has a pin 38 fixedly provided on one side of the adjacent side. A gearbox 39 is fixedly provided on the mounting base 35, and the two output shafts of the gearbox 39 are fixedly provided with the corresponding pins 38 respectively. The front side of the lower end face of the gearbox 39 is fixedly provided with the front crossbeam 7. A power motor 40 is fixedly provided on the front crossbeam 7, and the output shaft of the power motor 40 is fixedly provided with the input shaft of the gearbox 39. In use, the power motor 40 starts and drives the two winches 3 to rotate synchronously and in the same direction through the gearbox 39, so as to achieve the purpose of driving the two winches 3 to rotate synchronously and in the same direction.

[0035] In this embodiment, the fixing device 6 can be an electromagnet, which uses the attraction force of the electromagnet to attract the material to be hoisted.

[0036] The working principle of this utility model is as follows: In use, four columns 10 are set according to the site conditions. The servo motor 9 drives the rollers 8 to rotate, causing the chassis 1 to move back and forth. Then, the power motor 40 drives the two winches 3 to rotate synchronously in the same direction, so that the two winches 3 release each lifting rope 4. The balance plate 2 falls back down under the action of gravity. At this time, each fixed pulley rotates under the transmission of the lifting rope 4. After the material is fixed under the balance plate 2 by the fixing device 6, the winches 3 rotate synchronously in the opposite direction, so that the two winches 3 wind up each lifting rope 4. Each lifting rope 4 pulls the balance plate 2 upward through its free end, thereby driving the material to rise. Since the tension of the eight lifting ropes 4 on the balance plate 2 is balanced, the balance plate 2 does not sway when moving back and forth, which facilitates the transfer of materials.

Claims

1. An eight-rope anti-sway hoist trolley comprising a chassis (1) and a balance plate (2), characterized in that: The upper end surface of the chassis (1) is rotationally connected with a winding drum (3), eight hoisting ropes (4) are wound on the winding drum (3), the upper end surface of the balance plate (2) is symmetrically provided with four anchor blocks (5) for fixing the hoisting ropes (4), two fixing points are arranged on each anchor block (5), a guide device is arranged between the winding drum (3) and the balance plate (2), and the free end of each hoisting rope (4) is fixedly connected with the corresponding fixing point through the guide device; when the winding drum (3) rotates, eight hoisting ropes (4) are synchronously wound or released; and the lower end surface of the balance plate (2) is provided with a fixing device (6).

2. The eight-rope anti-sway hoist trolley according to claim 1, characterized in that: The guide device comprises a plurality of fixed pulleys rotationally connected with the chassis (1), the fixed pulleys comprise a first fixed pulley (13), a second fixed pulley (14), a third fixed pulley (15), a fourth fixed pulley (16), a fifth fixed pulley (17), a sixth fixed pulley (18), a seventh fixed pulley (19), an eighth fixed pulley (20), a ninth fixed pulley (21), a tenth fixed pulley (22), an eleventh fixed pulley (23) and a twelfth fixed pulley (24); the first fixed pulley (13) and the sixth fixed pulley (18) rotate in the horizontal direction; the second fixed pulley (14), the fifth fixed pulley (17), the eighth fixed pulley (20) and the tenth fixed pulley (23) rotate in the front-rear direction; the third fixed pulley (15), the fourth fixed pulley (16), the ninth fixed pulley (21) and the tenth fixed pulley (22) rotate in the left-right direction; and the seventh fixed pulley (19) and the twelfth fixed pulley (24) are arranged in an inclined manner.

3. The eight-rope anti-sway hoist trolley according to claim 2, characterized in that: The fixed points of the anchor block (5) include points P1, P2, P3, P4, P5, P6, P7, P8; one end of the hoisting rope (4) is fixedly arranged with the corresponding winding drum (3), the hoisting rope (4) includes first hoisting rope (25), second hoisting rope (26), third hoisting rope (27), fourth hoisting rope (28), fifth hoisting rope (29), sixth hoisting rope (30), seventh hoisting rope (31) and eighth hoisting rope (32); the first hoisting rope (25) is wound on the twelfth fixed pulley (24) and the tenth fixed pulley (23), and the other end of the first hoisting rope (25) is fixedly connected with the point P1; the second hoisting rope (26) is wound on the first fixed pulley (13) and the second fixed pulley (14), and the other end of the second hoisting rope (26) is fixedly connected with the point P6; the third hoisting rope (27) is wound on the third fixed pulley (15), and the other end of the third hoisting rope (27) is fixedly connected with the point P7; the fourth hoisting rope (28) is wound on the tenth fixed pulley (22), and the other end of the fourth hoisting rope (28) is fixedly connected with the point P8; the fifth hoisting rope (29) is wound on the ninth fixed pulley (21), and the other end of the fifth hoisting rope (29) is fixedly connected with the point P3; the sixth hoisting rope (30) is wound on the fourth fixed pulley (16), and the other end of the sixth hoisting rope (30) is fixedly connected with the point P4; the seventh hoisting rope (31) is wound on the fifth fixed pulley (17) and the sixth fixed pulley (18), and the other end of the seventh hoisting rope (31) is fixedly connected with the point P5; the eighth hoisting rope (32) is wound on the seventh fixed pulley (19) and the eighth fixed pulley (20), and the other end of the eighth hoisting rope (32) is fixedly connected with the point P2.

4. The eight-rope anti-sway hoist and trolley according to claim 2, characterized in that: The bottom plate (1) includes a bottom frame (33) and a mounting seat (35) fixedly arranged on the upper end face of the bottom frame (33) through a support column (34), a plurality of fixed blocks (36) are fixedly arranged on the bottom frame (33) and the mounting seat (35), and the bottom frame (33) is rotatably connected with the first fixed pulley (13), the second fixed pulley (14), the fifth fixed pulley (17), the sixth fixed pulley (18), the eighth fixed pulley (20) and the tenth fixed pulley (23) through the corresponding fixed blocks (36); and the mounting seat (35) is rotatably connected with the third fixed pulley (15), the fourth fixed pulley (16), the seventh fixed pulley (19), the ninth fixed pulley (21), the tenth fixed pulley (22) and the twelfth fixed pulley (24) through the corresponding fixed blocks (36).

5. The eight-rope anti-sway hoist trolley according to claim 4, characterized in that: The winding drum (3) is two, and each winding drum (3) winds four hoisting ropes (4).

6. The eight-rope anti-sway hoist trolley according to claim 5, characterized in that: The upper end face of the mounting seat (35) is fixedly provided with two side plates (37), and the winding drum (3) is rotatably arranged on the corresponding side plate (37); and each winding drum (3) is coaxially fixedly provided with a pin shaft (38) on the side surface close to each other.

7. The eight-rope anti-sway hoist trolley according to claim 6, characterized in that: The mounting base (35) is fixedly provided with a gear box (39), two output shafts of the gear box (39) are fixedly provided with corresponding pin shafts (38) respectively, the front side of the lower end surface of the gear box (39) is fixedly provided with the front cross beam (7), the front cross beam (7) is fixedly provided with a power motor (40), and the output shaft of the power motor (40) is fixedly provided with an input shaft of the gear box (39).

8. The eight-rope anti-sway hoist and trolley as claimed in claim 1, characterized in that: The fixing device (6) is an electromagnet.

9. The eight-rope anti-sway hoist and trolley as claimed in claim 1, characterized in that: The bottom plate (1) is fixedly provided with cross beams (7) on the left and right sides, the two ends of the cross beam (7) are rotatably connected with rollers (8), the two ends of each cross beam (7) are fixedly provided with servo motors (9), and the output shafts of the servo motors (9) are fixedly provided with corresponding rollers (8).

10. The eight-rope anti-sway hoist trolley according to claim 9, characterized in that: Four fixed columns (10) are further arranged, two tracks (11) are arranged on the upper portion of the column (10) in the front-rear direction, the lower end surfaces of the right track (11) are fixedly provided with the right two columns (10), the lower end surfaces of the left track (11) are fixedly provided with the left two columns (10), the upper end surfaces of each track (11) are provided with track grooves (12) in the front-rear direction, the rollers (8) at the right end of each cross beam (7) are located in the track grooves (12) of the right track (11), and the rollers (8) at the left end of each cross beam (7) are located in the track grooves (12) of the left track (11).

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