A ladder-type cable tray and its preparation method

Abstract

A ladder-type cable tray includes a first ladder side, a second ladder side, and a number of crossbars. The first ladder side and the second ladder side are arranged in parallel and have an interval space. The upper sides of the first ladder side and the second ladder side are folded towards each other to form a first folded edge, and the lower sides of the first ladder side and the second ladder side are folded towards each other to form a second folded edge, and the width of the second folded edge is greater than the width of the first folded edge. The cross-section of the crossbar is a U-shaped structure with an opening facing upwards. A plurality of groups of connection holes are arranged at intervals along the length direction of the bottom surface of the crossbar. The number of connection holes in each group is two and there is an interval distance between them. A number of crossbars are arranged at intervals between the first ladder side and the second ladder side, and both ends of each crossbar are in tight contact with the first ladder side and the second ladder side respectively. Both ends of the bottom surface of each crossbar are fixedly connected to the second folded edge of the corresponding ladder side, and they are combined to form a ladder-type cable tray. The cable tray of the present invention has a small mass per unit length, high structural strength, and can effectively organize and fix the laid cables, facilitating installation and subsequent maintenance.

Description

Technical Field

[0001] The invention relates to the field of cable bridges, and in particular to a ladder-type cable bridge and a preparation method thereof. Background Art

[0002] Cable trays are devices for centralized installation and layout of cables, and are widely used in industrial and mining enterprises, transportation equipment and other fields. Common cable trays on the market include trough-type cable trays and ladder-type cable trays. Ladder-type cable trays have high structural strength and large load capacity, and are particularly suitable for industrial and mining enterprises and transportation hubs with large cable layouts.

[0003] However, in order to ensure the structural strength, the ladder bridges widely used at present usually use integral rectangular tubes or even solid structures for the ladder sides and cross arms, which results in a large specific weight per unit length of the ladder bridge and high labor intensity when installing the ladder bridge. In addition, the cables installed and laid out are prone to entanglement during long-term use, which is not conducive to later maintenance operations.

[0004] Therefore, how to design a ladder-type bridge that is lightweight and easy to maintain is an urgent problem to be solved by technical personnel in this field. Summary of the invention

[0005] The object of the present invention is to provide a ladder-type bridge frame in view of the deficiencies in the prior art, which has a small mass per unit length, a high structural strength, and can effectively organize and fix the laid cables, facilitating installation and subsequent maintenance.

[0006] The second object of the present invention is to provide a method for preparing the above-mentioned ladder-type bridge, which has high preparation efficiency and low manual labor intensity and meets the actual needs of enterprises.

[0007] The technical solution for achieving one of the purposes of the present invention is: a ladder bridge frame, comprising a first ladder side, a second ladder side, and a plurality of cross arms, the first ladder side and the second ladder side are arranged in parallel and have a spacing space, the upper sides of the first ladder side and the second ladder side are folded toward each other to form a first folded edge, the lower sides of the first ladder side and the second ladder side are folded toward each other to form a second folded edge, and the width of the second folded edge is greater than the width of the first folded edge, the cross section of the cross arm is a U-shaped structure with an opening facing upward, a plurality of groups of connecting holes are arranged at intervals along the length direction on the bottom surface of the cross arm, the number of connecting holes in each group is two, and there is a spacing distance, a plurality of cross arms are arranged at intervals between the first ladder side and the second ladder side, and the two ends of each cross arm are respectively pressed against the first ladder side and the second ladder side, the two ends of the bottom surface of each cross arm are respectively fixedly connected to the second folded edge of the corresponding ladder side, and the combination constitutes a ladder bridge frame.

[0008] The first folded edge and the second folded edge at one end of the first step side are both cut to form a first clearance gap, and the first folded edge and the second folded edge at the other end of the second step side are both cut to form a second clearance gap.

[0009] The two upper sides of the cross arm are bent towards each other to form reinforcing ribs.

[0010] A number of cross arms are evenly spaced between the first ladder side and the second ladder side.

[0011] One end of the cross arm is fixedly connected to the second folded edge of the corresponding ladder side through at least two bolts.

[0012] The technical solution for achieving the second object of the present invention is: The preparation method of any of the above-mentioned ladder-type cable trays is prepared by using a tooling and includes the following steps:

[0013] The tooling includes a base frame, a first installation beam, and a second installation beam.

[0014] The first installation beam is arranged on the base frame and extends in the horizontal direction. The second installation beam is arranged parallel to the first installation beam above it and its height is adjustable.

[0015] A first support plate is arranged at the lower part of the side wall of the first installation beam, and a plurality of first positioning forks are arranged at intervals along the length direction of the top surface of the first installation beam.

[0016] A second support plate is arranged at the upper part of the side wall of the second installation beam. A strip-shaped relief groove extending along the length direction is provided on one side of the second support plate close to the second installation beam. A plurality of second positioning forks are arranged at intervals along the length direction of the bottom surface of the second installation beam.

[0017] 1) Take the first ladder side or the second ladder side, place it with the opening facing up on the first support plate, and make the first folded edge fit against the side wall of the first installation beam.

[0018] 2) Adjust the horizontal positions of the first positioning forks and the second positioning forks so that the first positioning forks are aligned with the corresponding second positioning forks, and the fork openings of each positioning fork correspond to the second folded edge of the first ladder side or the second ladder side.

[0019] 3) Place the cross arm vertically in the fork openings of the corresponding first positioning forks and second positioning forks, so that the opening of the cross arm faces the side wall of the first installation beam, and the bottom surface of the lower part of the cross arm fits against the second folded edge of the first ladder side or the second ladder side.

[0020] 4) Take the second ladder side or the first ladder side, place it with the opening facing down on the second support plate, and make the first folded edge pass through the strip-shaped relief groove and fit against the side wall of the second installation beam.

[0021] 5) Adjust the height of the second installation beam so that the bottom surfaces of the upper parts of the cross arms fit against the second folded edge of the second ladder side or the first ladder side.

[0022] 6) Manually fix the cross arm to the first ladder side and the second ladder side with bolts to obtain a ladder bridge, and manually lift the ladder bridge to move the first folded edge of the second ladder side or the first ladder side out of the strip-shaped clearance groove, and the preparation is completed.

[0023] Furthermore, it also includes a clamping claw, wherein the first claw head of the clamping claw is located on the top surface of the second step edge or the first step edge, and the second claw head of the clamping claw is located on the bottom surface of the second supporting plate, pressing the second step edge or the first step edge onto the second supporting plate.

[0024] Furthermore, two screw rods extending vertically upward are arranged on the first mounting beam, and two ends of the second mounting beam are sleeved on the corresponding screw rods, and are positioned by means of threads on the screw rods and nuts cooperating therewith.

[0025] Furthermore, the first mounting beam and the second mounting beam are respectively provided with a first strip hole extending along the length direction, and the fork handles of the first positioning fork and the second positioning fork are provided with a second strip hole extending along the length direction. Bolts are passed through the first strip hole and the second strip hole, and the threads are matched with nuts to lock the horizontal positions of the first positioning fork and the second positioning fork.

[0026] The above technical solution has the following beneficial effects:

[0027] 1. The ladder bridge includes a first ladder side, a second ladder side, and a plurality of cross arms. The first ladder side and the second ladder side are arranged in parallel and have a spacing space. The upper edges of the first ladder side and the second ladder side are folded toward each other to form a first folded edge, and the lower edges of the first ladder side and the second ladder side are folded toward each other to form a second folded edge. The width of the second folded edge is greater than the width of the first folded edge, which can effectively improve the tensile, compressive, and torsional structural strength of the first ladder side and the second ladder side, and reduce the material consumption and the unit length mass of the first ladder side and the second ladder side. The cross section of the cross arm is a U-shaped structure with an opening facing upward, which can effectively improve the tensile, compressive, and torsional structural strength of the cross arm, and reduce the material consumption and the unit length mass of the cross arm. The bottom surface of the cross arm is provided with a plurality of groups of connection holes spaced apart along the length direction, and the number of each group of connection holes is two and has a spacing distance. A plurality of cross arms are arranged at intervals between the first ladder side and the second ladder side, and the two ends of each cross arm are respectively pressed against the first ladder side and the second ladder side, and the two ends of the bottom surface of each cross arm are respectively fixedly connected to the second folded edge of the corresponding ladder side, and the combination forms a ladder-type bridge. The space between the first ladder side, the second ladder side and the plurality of cross arms of the ladder bridge with this structure forms a space for arranging cables, and the arranged cables can be grouped and fixed by passing materials such as cable ties and ropes through the corresponding group of connection holes on the bottom surface of the cross arms to avoid cable knotting or scattering, which is also beneficial for subsequent maintenance work.

[0028] 2. At one end of the first ladder side, both the first folded edge and the second folded edge are cut out to form a first relief notch, so that the extended length of one end of the first ladder side exceeds the corresponding first folded edge and second folded edge, forming an extended end. At the other end of the second ladder side, both the first folded edge and the second folded edge are cut out to form a second relief notch, so that the extended length of the other end of the second ladder side exceeds the corresponding first folded edge and second folded edge, forming an extended end. When installing and laying two adjacent ladder-type cable trays, one end (extended end) of the first ladder side of the first ladder-type cable tray is inserted into the other end of the first ladder side of the second ladder-type cable tray and is limited by the first ladder side and the corresponding first folded edge and second folded edge. At the same time, the other end (extended end) of the second ladder side of the second ladder-type cable tray is inserted into one end of the second ladder side of the first ladder-type cable tray and is limited by the second ladder side and the corresponding first folded edge and second folded edge. Then, bolts are passed through the butt joint part to form a connection, which can effectively improve the stability of the entire cable tray system (formed by connecting at least two ladder-type cable trays).

[0029] 3. The two upper sides of the cross arm are bent towards each other to form a reinforcing rib. On the basis of reducing the material consumption of the cross arm, the structural strength of the cross arm can be effectively improved, ensuring the stability of the combined ladder-type cable tray.

[0030] 4. One end of the cross arm is fixedly connected to the second folded edge of the corresponding ladder side through at least two bolts, improving the connection stability between the cross arm and the first ladder side and the second ladder side.

[0031] 5. In the preparation method of the present invention, a specific tooling is used to prepare the ladder-type cable tray. First, the first ladder side or the second ladder side is supported and positioned by the first installation beam and the first support plate of the tooling. Then, the corresponding cross arm is supported and positioned by the first positioning fork and the second positioning fork, and the position of the cross arm and the second folded edge of the first ladder side or the second ladder side is determined. Then, the second ladder side or the first ladder side is supported and positioned by the second installation beam and the second support plate, and by adjusting the height of the second installation beam, the position of the cross arm and the second folded edge of the second ladder side or the first ladder side is determined. Finally, the cross arm is manually fixed to the corresponding second folded edges of the first ladder side and the second ladder side with bolts to obtain the finished product of the ladder-type cable tray. The entire preparation process is precise and stable, and the ladder-type cable tray after determining the size can be prepared in a templated manner (the positions of the first positioning fork and the second positioning fork are determined, and the height of the second connecting beam is determined, omitting the processes of adjusting the position of the positioning fork and adjusting the height of the second installation beam), greatly improving the preparation efficiency of the ladder-type cable tray and meeting the actual needs of enterprises.

[0032] The following is a further description in conjunction with the drawings and specific embodiments. Description of the Drawings

[0033] Figure 1 It is a structural schematic diagram of the present invention;

[0034] Figure 2 is Figure 1 View A of

[0035] Figure 3 is Figure 2 a sectional view of;

[0036] Figure 4 is a schematic connection diagram of two adjacent ladder-type bridge frames of the present invention;

[0037] Figure 5 is a schematic structural diagram of the supporting tooling of the present invention;

[0038] Figure 6 is Figure 5 view B of;

[0039] Figure 7 is a schematic cooperation diagram of the first positioning fork and the first mounting beam of the present invention;

[0040] Figure 8 is a sectional view of the second support plate of the present invention.

[0041] In the drawings, 1 is the first ladder side, 2 is the second ladder side, 3 is the cross arm, 4 is the first folded edge, 5 is the second folded edge, 7 is the connecting hole, 8 is the first relief notch, 9 is the second relief notch, 10 is the reinforcing rib, 11 is the first mounting beam, 12 is the second mounting beam, 13 is the base frame, 14 is the first support plate, 15 is the first positioning fork, 16 is the second support plate, 17 is the strip-shaped relief groove, 19 is the second positioning fork, 20 is the screw, 21 is the first strip-shaped hole, and 22 is the second strip-shaped hole. Detailed implementation manners

[0042] Example 1

[0043] Refer to Figures 1 to 3, is a specific embodiment of a ladder bridge. The ladder bridge comprises a first ladder side 1, a second ladder side 2, and a plurality of cross arms 3. The first ladder side 1 and the second ladder side 2 are arranged in parallel and have a spacing space. Specifically, the plane where the first ladder side and the second ladder side are located is located on a vertical plane and extends in the horizontal direction. The upper edges of the first ladder side 1 and the second ladder side 2 are folded toward each other to form a first folded edge 4, that is, the upper edge of the first ladder side is folded 90° to the left, and the upper edge of the second ladder side is folded 90° to the right. The lower edges of the first ladder side 1 and the second ladder side 2 are folded toward each other to form a second folded edge 5, that is, the lower edge of the first ladder side is folded 90° to the left, and the lower edge of the second ladder side is folded 90° to the right. The width of the second folded edge 5 is greater than the width of the first folded edge 4. The cross section of the cross arm 3 is a U-shaped structure with the opening facing upward. In this embodiment, in order to strengthen the structural strength of the cross arm, the two upper edges of the cross arm 3 are bent toward each other to form a reinforcing rib 10. Four groups of connection holes 7 are arranged at intervals along the length direction on the bottom surface of the cross arm 3, and each group of connection holes has two holes and has an interval distance. Several cross arms 3 are arranged at intervals between the first ladder side 1 and the second ladder side 2, and the two ends of each cross arm 3 are respectively pressed against the inner side wall of the first ladder side 1 and the inner side wall of the second ladder side 2. Usually, several cross arms are evenly spaced and distributed between the first ladder side and the second ladder side. The two ends of the bottom surface of each cross arm 3 are respectively fixedly connected to the second folded edge 5 of the corresponding ladder side, and the combination forms a ladder bridge. In this embodiment, the two ends of the cross arm 3 are respectively fixedly connected to the second folded edge 5 of the corresponding ladder side by at least two bolts.

[0044] Furthermore, in order to facilitate the connection with the adjacent ladder bridge to form an integral bridge structure, the first folded edge and the second folded edge at one end of the first ladder side 1 (specifically, in this embodiment, the lower end of the first ladder side) are cut to form a first clearance gap 8, so that the lower end of the first ladder side extends downward and outward to form an extended end. The first folded edge and the second folded edge at the other end of the second ladder side 2 (specifically, in this embodiment, the upper end of the second ladder side) are cut to form a second clearance gap 9, so that the upper end of the second ladder side extends upward and outward to form an extended end.

[0045] Example 2

[0046] The above ladder type bridge is prepared by using tooling and includes the following steps:

[0047] See also Figures 5 to 8The tooling includes a base frame 13, a first mounting beam 11, and a second mounting beam 12. In this embodiment, the base frame is a rectangular parallelepiped frame, and the number of the first mounting beam and the second mounting beam are both two, and the first mounting beam and the second mounting beam are both rectangular tubes. The two first mounting beams are respectively welded and fixed on the two long sides of the top of the rectangular parallelepiped frame, and extend in the horizontal direction. The two second mounting beams 12 are respectively arranged in parallel above the corresponding first mounting beams 11, and the height is adjustable. In this embodiment, each first mounting beam 11 is provided with two screw rods 20 extending vertically upward, and the two ends of the corresponding second mounting beam 12 are sleeved on the corresponding screw rod 20, and two nuts are threadedly matched on the screw rod, one of which is located at the bottom of the second mounting beam, and the other nut is located at the top of the second mounting beam. By adjusting the positions of the two nuts, the height of the second mounting beam is limited to form positioning. The lower part of the outer wall of the two first mounting beams 11 is respectively provided with a first supporting plate 14. Usually, in order to ensure the structural strength, the first supporting plate can be made of angle steel, whose vertical edge is welded on the outer wall of the first mounting beam, and whose horizontal edge corresponds to the bottom of the first mounting beam, as the first supporting plate. The top surface of the first mounting beam 11 is provided with a plurality of first positioning forks 15 at intervals along the length direction. The upper part of the outer wall of the two second mounting beams 12 is provided with a second supporting plate 16. In order to ensure the structural strength, the second supporting plate can be made of angle steel, whose vertical edge is welded on the outer wall of the second mounting beam, and whose horizontal plate corresponds to the top of the second mounting beam. As the second supporting plate, the second supporting plate 16 is provided with a strip-shaped clearance groove 17 extending along the length direction on one side close to the second mounting beam 12, that is, the strip-shaped clearance groove is provided on the horizontal edge of the angle steel and fits with the vertical edge. Obviously, in order to ensure the assembly accuracy, the specifications and dimensions of the angle steel as the first supporting plate and the angle steel as the second supporting plate should be consistent. The bottom surface of the second mounting beam 12 is provided with a plurality of second positioning forks 19 at intervals along the length direction. Generally, in order to improve the practicability of the tooling and meet the preparation requirements of ladder-type bridges of different specifications and sizes, the positions of the first positioning fork and the second positioning fork along the horizontal plane need to be adjustable, and the specific design structure is as follows: the top surface of the first mounting beam 11 and the bottom surface of the second mounting beam 12 are respectively provided with first strip holes 21 extending along the length direction, and the fork handles of the first positioning fork 15 and the second positioning fork 19 are provided with second strip holes 22 extending along the length direction, and the horizontal positions of the first positioning fork 15 and the second positioning fork 19 can be locked by passing bolts through the first strip holes 21 and the second strip holes 22, and the threads are matched with nuts.

[0048] 1) Take the first ladder edge or the second ladder edge, place it on the first supporting plate with the opening facing upward, and the first folded edge is in contact with the vertical edge of the angle steel;

[0049] 2) adjusting the horizontal position of each first positioning fork and the second positioning fork so that the first positioning fork is aligned with the corresponding second positioning fork, and the fork opening of each positioning fork corresponds to the second folded edge of the first ladder side or the second ladder side;

[0050] 3) placing the cross arm in the corresponding fork openings of the first positioning fork and the second positioning fork in the vertical direction, so that the opening of the cross arm faces the outer wall of the first mounting beam, and the bottom surface of the lower part of the cross arm is in contact with the second folded edge of the first ladder edge or the second ladder edge;

[0051] 4) Take the second ladder edge or the first ladder edge, place it on the second supporting plate with the opening facing downward, and the first folded edge passes through the strip-shaped clearance groove and fits with the vertical edge of the angle steel;

[0052] 5) Adjust the height of the second mounting beam so that the bottom surface of the upper portion of each cross arm fits with the second stair edge or the second folded edge of the first stair edge;

[0053] 6) Manually fix the cross arm to the first ladder side and the second ladder side with bolts to obtain a ladder bridge, and the number of bolts is usually multiple. Manually lift the ladder bridge so that the first folded edge of the second ladder side or the first ladder side moves out of the strip-shaped clearance groove, and the preparation is completed.

[0054] Usually, in order to avoid the position change of the second step edge or the first step edge resting on the second supporting plate, a clamping claw is also included, wherein the first claw head of the clamping claw is located on the top surface of the second step edge or the first step edge, and the second claw head of the clamping claw is located on the bottom surface of the second supporting plate, so as to press the second step edge or the first step edge tightly on the second supporting plate.

[0055] The obtained ladder-type bridge frame is further processed into a first clearance gap and a second clearance gap according to actual needs.

[0056] Example 3

[0057] See also Figure 4 , a bridge system is formed by connecting the ladder-type bridge frames recorded in two embodiments 1, specifically, the lower end (extending end) of the first ladder side of the upper ladder-type bridge frame is inserted into the upper end of the first ladder side of the lower ladder-type bridge frame, and is limited by the first ladder side of the lower ladder-type bridge frame and the corresponding first folded edge and second folded edge. At the same time, the upper end (extending end) of the second ladder side of the lower ladder-type bridge frame is inserted into the lower end of the second ladder side of the upper ladder-type bridge frame, and is limited by the second ladder side of the upper ladder-type bridge frame and the corresponding first folded edge and second folded edge. Bolts are then used to pass through the docking parts to form a connection, forming a bridge system (composed of at least two ladder-type bridge frames), and ensuring its stability.

Claims

1. A preparation method of a ladder-type bridge frame, characterized in that: The ladder-type bridge includes a first ladder side (1), a second ladder side (2), and a number of crossbars (3). The first ladder side (1) and the second ladder side (2) are arranged in parallel and have an interval space. The upper sides of the first ladder side (1) and the second ladder side (2) are folded towards each other to form a first folded edge (4). The lower sides of the first ladder side (1) and the second ladder side (2) are folded towards each other to form a second folded edge (5), and the width of the second folded edge (5) is greater than the width of the first folded edge (4). The cross-section of the crossbar (3) is a U-shaped structure with an upward opening. Multiple groups of connection holes (7) are arranged at intervals along the length direction of the bottom surface of the crossbar (3). The number of connection holes in each group is two, and there is an interval distance. A number of crossbars (3) are arranged at intervals between the first ladder side (1) and the second ladder side (2). The two ends of each crossbar (3) are respectively abutted against the first ladder side (1) and the second ladder side (2). The two ends of the bottom surface of each crossbar (3) are respectively fixedly connected to the second folded edge (5) of the corresponding ladder side, and they are combined to form a ladder-type bridge. The preparation using a tooling includes the following steps: The tooling includes a base frame (13), a first installation beam (11), and a second installation beam (12). The first installation beam (11) is arranged on the base frame (13) and extends in the horizontal direction. The second installation beam (12) is arranged in parallel above the first installation beam (11), and its height is adjustable. A first support plate (14) is arranged at the lower part of the side wall of the first installation beam (11). A plurality of first positioning forks (15) are arranged at intervals along the length direction of the top surface of the first installation beam (11). A second support plate (16) is arranged at the upper part of the side wall of the second installation beam (12). A strip-shaped relief groove (17) extending along the length direction is arranged on one side of the second support plate (16) close to the second installation beam (12). A plurality of second positioning forks (19) are arranged at intervals along the length direction of the bottom surface of the second installation beam (12). 1) Take the first ladder side or the second ladder side, place it with the opening facing up on the first support plate, and make the first folded edge fit against the side wall of the first installation beam. 2) Adjust the horizontal positions of the first positioning forks and the second positioning forks so that the first positioning forks are aligned with the corresponding second positioning forks, and the fork openings of each positioning fork correspond to the second folded edge of the first ladder side or the second ladder side. 3) Place the crossbar vertically in the fork openings of the corresponding first positioning forks and second positioning forks, so that the opening of the crossbar faces the side wall of the first installation beam, and the lower bottom surface of the crossbar fits against the second folded edge of the first ladder side or the second ladder side. 4) Take the second ladder side or the first ladder side, place it with the opening facing down on the second support plate, and make the first folded edge pass through the strip-shaped relief groove and fit against the side wall of the second installation beam. 5) Adjust the height of the second installation beam so that the upper bottom surface of each crossbar fits against the second folded edge of the second ladder side or the first ladder side. 6) Manually use bolts to fix the crossbar on the first ladder side and the second ladder side to obtain a ladder-type bridge. Manually lift the ladder-type bridge to move the first folded edge of the second ladder side or the first ladder side out of the strip-shaped relief groove, and the preparation is completed.

2. The preparation method according to claim 1, wherein: The first folding edges and the second folding edges at one end of the first ladder side (1) are both cut to form a first relief notch (8), and the first folding edges and the second folding edges at the other end of the second ladder side (2) are both cut to form a second relief notch (9).

3. The preparation method according to claim 1, wherein: The two upper edges of the cross arm (3) are bent towards each other to form a reinforcing rib (10).

4. The preparation method according to claim 1, wherein: A plurality of cross arms (3) are evenly spaced between the first ladder side (1) and the second ladder side (2).

5. The preparation method according to claim 1, characterized in that: One end of the cross arm (3) is fixedly connected to the second folding edge (5) of the corresponding ladder side by at least two bolts.

6. The preparation method according to claim 1, characterized in that, It further includes a clamping claw. The first claw head of the clamping claw is located on the top surface of the second ladder side or the first ladder side, and the second claw head of the clamping claw is located on the bottom surface of the second support plate, pressing the second ladder side or the first ladder side against the second support plate.

7. The preparation method according to claim 1, wherein Two vertically upward extending screw rods (20) are provided on the first mounting beam (11). The two ends of the second mounting beam (12) are sleeved on the corresponding screw rods (20), and positioning is formed by threadedly mating nuts on the screw rods.

8. The preparation method according to claim 1, characterized in that, First elongated holes (21) extending along the length direction are respectively provided on the first mounting beam (11) and the second mounting beam (12). Second elongated holes (22) extending along the length direction are provided on the fork handles of the first positioning fork (15) and the second positioning fork (19). The first positioning fork (15) and the second positioning fork (19) are locked in the horizontal position by bolts passing through the first elongated holes (21) and the second elongated holes (22) and threadedly mating nuts.

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