CN113336084A

CN113336084A - Hoisting equipment

Info

Publication number: CN113336084A
Application number: CN202110725943.0A
Authority: CN
Inventors: 刘世显; 李盼盼; 高旭; 孙冬冬; 孙卓
Original assignee: China 22MCC Group Corp Ltd; Beijing Tianrun Construction Co Ltd
Current assignee: China 22MCC Group Corp Ltd; Beijing Tianrun Construction Co Ltd
Priority date: 2021-06-29
Filing date: 2021-06-29
Publication date: 2021-09-03

Abstract

The invention belongs to the technical field of building construction, and discloses hoisting equipment which comprises a support bracket, a first rotating shaft, a pulley assembly and a traction rope, wherein the support bracket comprises a first support rod and a second support rod which are arranged at intervals, the pulley assembly is arranged on the support bracket and comprises a fixed pulley, the first rotating shaft can rotate relative to the first support rod and the second support rod, the traction rope can be wound on the first rotating shaft by rotating the first rotating shaft or the traction rope is gradually led out from the first rotating shaft, and the leading-out end of the traction rope bypasses the fixed pulley and is connected with a hook assembly. When the main exhaust pipe is installed, the hoisting equipment is placed on the upper floor of the floor where the main exhaust pipe to be installed is located, the supporting bracket and the wall surface are triangular, the first rotating shaft is rotated, the hook component is placed below the supporting bracket, the hook component is hung on the main exhaust pipe to be installed and then lifted, the problem that the main exhaust pipe is difficult to lift in a limited space is effectively solved, and construction materials are prevented from being damaged.

Description

Hoisting equipment

Technical Field

The invention relates to the technical field of building construction, in particular to hoisting equipment.

Background

In the construction of building projects, the installation of a plurality of devices and materials needs to be carried out in a limited space, and the construction difficulty is greatly increased. Especially, equipment installation in the vertical direction, such as the installation of building exhaust pipe, the installation of on-vehicle pump pipe in concrete placement construction stage, the installation of riser in the fire hose etc. because the space of operatable is comparatively narrow when installing, has brought very big inconvenience for constructor, and the efficiency of construction is low, and often the installation quality is relatively poor after the equipment installation of these positions.

Taking the installation of a building exhaust pipeline as an example, a reserved hole for penetrating the exhaust pipeline is formed in a floor slab, the main structure of the exhaust pipeline, namely the reserved hole of a main exhaust pipe, is generally located at the internal corner of a kitchen, the edge of the reserved hole is close to a wall body, the pipe wall of the main exhaust pipe is close to the wall body during installation, the traditional exhaust pipeline installation method is manual layer-by-layer installation, time and labor are wasted, an object striking collision accident is easy to happen, and serious damage is caused to finished materials.

Disclosure of Invention

The invention aims to provide hoisting equipment which can solve the problem that a main exhaust pipe is difficult to lift in a limited space, prevent construction materials from being damaged and improve the installation efficiency.

In order to achieve the purpose, the invention adopts the following technical scheme:

a lifting apparatus, comprising:

the supporting bracket comprises a first supporting rod and a second supporting rod which are arranged at intervals;

the two ends of the first rotating shaft are respectively and rotatably connected to the first supporting rod and the second supporting rod;

the pulley assembly is arranged on the supporting bracket and comprises a fixed pulley;

the traction rope is wound on the first rotating shaft, one end of the traction rope bypasses the fixed pulley and is connected with a lifting hook component, and the lifting hook component is used for hooking an object to be lifted.

The preferable scheme of the hoisting equipment provided by the invention further comprises a second rotating shaft, wherein a first gear is sleeved on the first rotating shaft, a second gear matched with the first gear is sleeved on the second rotating shaft, a driving handle is connected to the second rotating shaft, and the first rotating shaft is rotated under the action of the meshing force of the first gear and the second gear by rotating the driving handle.

As a preferable aspect of the hoisting apparatus provided by the present invention, the number of teeth of the first gear is greater than the number of teeth of the second gear.

As a preferable scheme of the hoisting device provided by the invention, a stop plate is further sleeved on the first rotating shaft, and the traction rope wound on the first rotating shaft is limited between the first gear and the stop plate.

As a preferred scheme of the hoisting equipment provided by the invention, the hoisting equipment further comprises a first bearing and a second bearing, wherein a first mounting plate is arranged on the first supporting rod, and a second mounting plate is arranged on the second supporting rod;

the first mounting plate and the second mounting plate are respectively provided with a first bearing seat, and two ends of the first rotating shaft are respectively connected to the corresponding first bearing seats in a rotating manner through the first bearings;

the first mounting plate faces away from one side of the first bearing seat and the second mounting plate faces away from one side of the first bearing seat, second bearing seats are arranged on one sides of the second mounting plate faces away from the first bearing seat, and two ends of the second rotating shaft are connected to the corresponding second bearing seats in a rotating mode through the second bearings.

As a preferable scheme of the hoisting apparatus provided by the present invention, the driving handle includes a connecting rod and a holding portion that are vertically connected, the holding portion is disposed in parallel with the second rotating shaft, and one end of the connecting rod, which is far away from the holding portion, is connected to the second rotating shaft.

As a preferable scheme of the hoisting equipment provided by the invention, a hanging rod is arranged between the first support rod and the second support rod, the pulley assembly further comprises a hook and an installation frame, the fixed pulley is rotatably connected to the installation frame, and the installation frame is located between the hanging rod and the first rotating shaft and is hung on the hanging rod through the hook.

As a preferable scheme of the hoisting equipment provided by the invention, the hook comprises a hook body and a first stopping portion, and the first stopping portion is rotatably connected to the hook body to block an opening of the hook body.

As a preferable aspect of the hoisting apparatus provided by the present invention, the hook assembly includes a hook body and a second stopper portion, and the second stopper portion is rotatably connected to the hook body to close the opening of the hook body.

As a preferable scheme of the hoisting apparatus provided by the present invention, the support bracket further includes a plurality of reinforcing rods disposed at intervals, one end of each of the reinforcing rods is connected to the first support rod, and the other end is connected to the second support rod.

The invention has the beneficial effects that:

the invention provides a hoisting device which comprises a supporting bracket, a first rotating shaft, a pulley assembly and a traction rope, wherein the supporting bracket comprises a first supporting rod and a second supporting rod which are arranged at intervals, two ends of the first rotating shaft are respectively connected to the first supporting rod and the second supporting rod to form a stable supporting structure, the pulley assembly is arranged on the supporting bracket and comprises a fixed pulley, the first rotating shaft can rotate relative to the first supporting rod and the second supporting rod, the traction rope can be wound on the first rotating shaft by rotating the first rotating shaft or can be gradually led out from the first rotating shaft, and the leading-out end of the traction rope bypasses the fixed pulley and is connected with a hook assembly. When the main exhaust pipe is installed, the hoisting equipment needs to be placed on the upper floor of the floor where the main exhaust pipe is to be installed, the support bracket is inclined and placed on the floor on the upper floor, namely, one ends of the first support rod and the second support rod are abutted to the wall surface, the other ends of the first support rod and the second support rod are supported on the floor surface, so that a stable triangular structure is formed between the first support rod and the wall surface and between the second support rod and the wall surface, the stability of the hoisting equipment during working is improved, and great shaking is avoided during lifting operation. Then, the first rotating shaft is rotated to lead out a traction rope on the first rotating shaft, the hook component is made to be aligned to a reserved hole in a floor slab to be placed, a constructor located on the lower layer (namely the floor where the main exhaust pipe to be installed is located) hooks the placed hook component on the main exhaust pipe to be installed, then, the first rotating shaft is rotated reversely, the traction rope is enabled to be reeled on the first rotating shaft again, the hook component rises under the driving of the traction rope to lift the main exhaust pipe connected with the hook component until the main exhaust pipe is lifted to the position to be installed, and finally, the installation and the fixation are carried out. In the lifting process, the traction rope drives the fixed pulley to roll, so that the lifting resistance is effectively reduced, and the working strength is reduced. When the lifting device is used, lifting installation of the main exhaust pipe can be achieved only by rotating the first rotating shaft, construction efficiency is high, constructors on the upper layer and the lower layer are matched with each other, the problem that the main exhaust pipe is difficult to lift in a limited space is effectively solved, and construction materials are prevented from being damaged.

Drawings

FIG. 1 is a top view of a lifting apparatus according to an embodiment of the present invention;

FIG. 2 is a front view of a lifting apparatus provided in accordance with an embodiment of the present invention;

FIG. 3 is an enlarged view of a portion of FIG. 2;

fig. 4 is a side view of a lifting device according to an embodiment of the present invention.

In the figure:

1-a support bracket; 2-a first rotating shaft; 3-a pulley assembly; 4-a hauling rope; 5-a hook component; 6-a second rotating shaft; 7-a driving handle; 8-a first bearing seat; 9-a second bearing block; 10-fastening bolts;

11-a first support bar; 12-a second support bar; 13-a first mounting plate; 14-a second mounting plate; 15-hanging the rod; 16-a reinforcing rod;

21-a first gear; 22-a stop plate;

31-a fixed pulley; 32-hanging hooks; 33-a mounting frame; 321-a hook body; 322-a first stop;

51-a hook body; 52-a second stop;

61-a second gear;

71-a connecting rod; 72-a grip portion; 73-anti-slip sleeve.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.

In the description of the present invention, unless expressly stated or limited otherwise, the terms "connected," "connected," and "fixed" are to be construed broadly, e.g., as meaning permanently connected, removably connected, or integral to one another; can be mechanically or electrically connected; either directly or indirectly through intervening media, either internally or in any other relationship. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

In the present invention, unless otherwise expressly stated or limited, "above" or "below" a first feature means that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact with each other via another feature therebetween. Also, the first feature being "on," "above" and "over" the second feature includes the first feature being directly on and obliquely above the second feature, or merely indicating that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature includes the first feature being directly under and obliquely below the second feature, or simply meaning that the first feature is at a lesser elevation than the second feature.

In the description of the present embodiment, the terms "upper", "lower", "left", "right", and the like are used based on the orientations and positional relationships shown in the drawings only for convenience of description and simplification of operation, and do not indicate or imply that the referred device or element must have a specific orientation, be configured and operated in a specific orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first" and "second" are used only for descriptive purposes and are not intended to have a special meaning.

As shown in fig. 1 to 4, the present embodiment provides a hoisting apparatus including a support bracket 1, a first rotating shaft 2, a pulley assembly 3, and a traction rope 4.

The support bracket 1 includes a first support bar 11 and a second support bar 12 which are spaced apart. Both ends of the first rotating shaft 2 are connected to the first support bar 11 and the second support bar 12, respectively, to form a stable support structure. The pulley assembly 3 is disposed on the support bracket 1 and includes a fixed pulley 31. The first rotating shaft 2 can rotate relative to the first supporting rod 11 and the second supporting rod 12, and the traction rope 4 can be wound on the first rotating shaft 2 by rotating the first rotating shaft 2 or the traction rope 4 is gradually led out from the first rotating shaft 2. The leading end of the traction rope 4 passes around the fixed pulley 31 and is connected with the hook component 5. When installing the main exhaust pipe, need place this hoisting equipment in the last floor of waiting to install the floor that the main exhaust pipe is located, and make support bracket 1 slope place in the floor on upper strata, the equal butt in wall of the one end of first bracing piece 11 and second bracing piece 12 promptly, the other end all supports in floor ground, so that form stable triangular structure between first bracing piece 11 and second bracing piece 12 and the wall, improve the steadiness of hoisting equipment during operation, produce great the rocking when avoiding promoting the operation. The first rotating shaft 2 is then rotated to lead out the hauling cable 4 on the first rotating shaft 2 and to put down the hook assembly 5 aiming at the reserved hole on the floor. The constructor located at the lower floor (i.e., the floor where the main exhaust pipe to be installed is located) hooks the lowered hook assembly 5 to the main exhaust pipe to be installed. And then, reversely rotating the first rotating shaft 2 to enable the traction rope 4 to be reeled on the first rotating shaft 2 again, and lifting the hook component 5 under the driving of the traction rope 4 to lift the main exhaust pipe connected with the hook component until the main exhaust pipe is lifted to a position to be installed, and finally, installing and fixing. In the lifting process, the traction rope 4 drives the fixed pulley 31 to roll, so that the lifting resistance is effectively reduced, and the working strength is reduced. When the lifting device is used, lifting installation of the main exhaust pipe can be achieved only by rotating the first rotating shaft 2, construction efficiency is high, constructors on the upper layer and the lower layer are matched with each other, the problem that the main exhaust pipe is difficult to lift in a limited space is effectively solved, and construction materials are prevented from being damaged.

Alternatively, referring to fig. 1, 2 and 4, the first rotating shaft 2 is driven to rotate by the driving handle 7 in the present embodiment. Specifically, the driving handle 7 is connected with a second rotating shaft 6, and the second rotating shaft 6 is arranged in parallel with the first rotating shaft 2. The first rotating shaft 2 is sleeved with a first gear 21, and the second rotating shaft 6 is sleeved with a second gear 61 matched with the first gear 21. When the installation main exhaust pipe was treated in the promotion, it is rotatory in order to drive second pivot 6 to rotate drive handle 7, and first pivot 2 and then rotatory under the engaging force effect of first gear 21 and second gear 61 to make first pivot 2 book establish haulage rope 4 or draw forth haulage rope 4, convenient operation is laborsaving.

Alternatively, the driving handle 7 includes a link 71 and a grip 72 that are vertically connected. The holding portion 72 is parallel to the second shaft 6, and one end of the connecting rod 71 away from the holding portion 72 is connected to the second shaft 6. The moment arm when the rotation driving handle 7 is rotated can be increased by arranging the connecting rod 71, and the moment required for rotating the first rotating shaft 2 is a fixed value because the rotation moment is the product of the applied action force and the moment arm, so that the applied action force when the rotation driving handle 7 is rotated can be reduced by increasing the moment arm, thereby achieving the labor-saving effect and reducing the working strength.

Optionally, a slip-proof sleeve 73 is sleeved on the holding portion 72. The friction between the hand of the operator and the grip portion 72 can be increased by providing the slip-preventing sleeve 73, thereby preventing slipping. The antiskid sleeve 73 is preferably a PVC pipe, has a large friction coefficient, does not rust, and avoids scratching hands of construction personnel.

Preferably, the number of teeth of the first gear 21 is greater than that of the second gear 61. The ratio of the number of teeth in gear transmission is equal to the ratio of the torque, i.e. the ratio of the number of teeth of the first gear 21 to the number of teeth of the second gear 61 is equal to the ratio of the torque of the first rotating shaft 2 to the torque of the second rotating shaft 6. Therefore, set up the number of teeth of first gear 21 to be greater than the number of teeth of second gear 61, when the effort that rotates first pivot 2 and applys is certain, can reduce the torque value in the second pivot 6, also reduced and rotated the required effort of second pivot 6 promptly, combine above-mentioned connecting rod 71 that increases the arm of force, can effectively reduce constructor and rotate the required effort of drive handle 7, the operation of being convenient for.

Of course, in other embodiments of the present invention, the first rotating shaft 2 may also be driven to rotate by an electric drive. Specifically, set up driving motor on support bracket 1, driving motor's output and 6 transmission connections of second pivot to drive second pivot 6 rotatory, first gear 21 is rotatory under the drive of second gear 61 simultaneously, thereby drives first pivot 2 rotatory, need not manual operation, only needs start driving motor can transfer lifting hook subassembly 5 or promote the main exhaust pipe.

In this embodiment, the first rotating shaft 2 and the first gear 21, and the second rotating shaft 6 and the second gear 61 are all connected by keys, and may be connected by flat keys or spline connections.

Optionally, referring to fig. 3 and 4, both ends of the first rotating shaft 2 are respectively sleeved with a first bearing, both ends of the second rotating shaft 6 are respectively sleeved with a second bearing, and friction resistance when the first rotating shaft 2 and the second rotating shaft 6 rotate can be reduced by arranging the first bearing and the second bearing, so that transmission efficiency is improved.

Referring to fig. 4, a first mounting plate 13 is provided on the first support bar 11, and a second mounting plate 14 is provided on the second support bar 12. First bearing seats 8 are arranged on the first mounting plate 13 and the second mounting plate 14, and two ends of the first rotating shaft 2 are rotatably connected to the corresponding first bearing seats 8 through first bearings. The side of the first mounting plate 13 facing away from the first bearing seat 8 and the side of the second mounting plate 14 facing away from the first bearing seat 8 are both provided with a second bearing seat 9, and both ends of the second rotating shaft 6 are rotatably connected to the corresponding second bearing seats 9 through the second bearings. First bearing frame 8 and second bearing frame 9 can support first pivot 2 and second pivot 6 respectively, and intensity is great, can bear the comprehensive load of rotation in-process, guarantee first pivot 2 and the gyration precision of second pivot 6.

Optionally, the first bearing seat 8 and the second bearing seat 9 are fixedly connected through a fastening bolt 10. The fastening bolt 10 sequentially passes through the seat body of the first bearing seat 8, the first mounting plate 13 (the second mounting plate 14), and the seat body of the second bearing seat 9, and is in threaded connection with the stopper nut, so as to firmly fix the first bearing seat 8 and the second bearing seat 9 on the first mounting plate 13 (the second mounting plate 14). Further, the first mounting plate 13 is welded on the first supporting rod 11, the second mounting plate 14 is welded on the second supporting rod 12, the welding mode is firm and reliable, the deformation is not easy, and the phenomenon that the joint is cracked too fast or even broken is avoided.

Optionally, referring to fig. 4, a stop plate 22 is further sleeved on the first rotating shaft 2, and the pulling rope 4 wound on the first rotating shaft 2 is limited between the first gear 21 and the stop plate 22 to prevent the pulling rope 4 from being separated from the first rotating shaft 2 to cause disorder of the pulling rope 4.

Optionally, referring to fig. 1 and 3, a hanging bar 15 is disposed between the first support bar 11 and the second support bar 12. Pulley assembly 3 further comprises a hook 32 and a mounting bracket 33, fixed pulley 31 is rotatably connected to mounting bracket 33, and mounting bracket 33 is located between peg 15 and first rotating shaft 2 and is hooked on peg 15 through hook 32. When the hoisting equipment is used, a stable triangular structure is formed between the first support rod 11 and the second support rod 12 and the wall body and between the first support rod 11 and the floor slab ground, and a smaller acute angle is formed between the second support rod 12 and the wall body. Wherein, peg 15 and 2 top-down settings of first pivot, when mounting bracket 33 hung on peg 15 through couple 32 hook, mounting bracket 33 and fixed pulley 31 are towards first pivot 2 under the action of gravity, at this moment, can transfer hook component 5 after driving haulage rope 4 around fixed pulley 31 with hook component 5. That is to say, based on the service environment of the hoisting equipment in this embodiment, the mounting rack 33 mounted with the fixed pulley 31 can be normally used only by hooking the hook 32 on the hanging rod 15, and the mounting and dismounting are very convenient. The distance between the hanging rod 15 and the first rotating shaft 2 can be set according to specific construction requirements, a plurality of hanging rods 15 can be arranged along the axial direction of the first supporting rod 11 at intervals, and during construction, the mounting rack 33 is hooked on the proper hanging rods 15 through the hooks 32 according to the specific mounting environment of the main exhaust pipe.

Referring to fig. 3, the hook 32 includes a hook body 321 and a first stopper 322, the first stopper 322 is rotatably connected to the hook body 321 to block the opening of the hook body 321, so as to prevent the hook body 321 from separating from the hanging rod 15 when the traction rope 4 drives the fixed pulley 31 to roll, and the installation performance is high.

Similarly, the lifting hook assembly 5 includes a lifting hook body 51 and a second stopping portion 52, and the second stopping portion 52 is rotatably connected to the lifting hook body 51 to block the opening of the lifting hook body 51, so as to prevent the lifted main exhaust pipe from being separated from the lifting hook body 51, and prevent the main exhaust pipe from falling on the ground in the lifting process to injure constructors or damage the main exhaust pipe.

Optionally, the support bracket 1 further includes a plurality of reinforcing rods 16 arranged at intervals, one end of each reinforcing rod 16 is connected to the first support rod 11, and the other end of each reinforcing rod 16 is connected to the second support rod 12, so as to improve the connection strength between the first support rod 11 and the second support rod 12, avoid serious deformation after the construction of the first support rod 11 and the second support rod 12, and prolong the service life of the support bracket. The number of the reinforcing bars 16 can be specifically selected according to construction requirements, and is not limited herein. The reinforcing bar 16 may be a first bar and a second bar which are cross-connected so that the first bar, the second bar, the first support bar 11 and the second support bar 12 form a plurality of stable triangular structures therebetween to stabilize the support bracket 1.

It should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Numerous obvious variations, adaptations and substitutions will occur to those skilled in the art without departing from the scope of the invention. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A hoisting device, comprising:

the support bracket (1) comprises a first support rod (11) and a second support rod (12) which are arranged at intervals;

the two ends of the first rotating shaft (2) are respectively and rotatably connected to the first supporting rod (11) and the second supporting rod (12);

the pulley assembly (3) is arranged on the supporting bracket (1), and the pulley assembly (3) comprises a fixed pulley (31);

the traction rope (4) is arranged on the first rotating shaft (2) in a winding mode, one end of the traction rope (4) bypasses the fixed pulley (31) and is connected with the lifting hook component (5), and the lifting hook component (5) is used for hooking an object to be lifted.

2. The hoisting device as recited in claim 1, further comprising a second rotating shaft (6), wherein the first rotating shaft (2) is sleeved with a first gear (21), the second rotating shaft (6) is sleeved with a second gear (61) matched with the first gear (21), the second rotating shaft (6) is connected with a driving handle (7), and the first rotating shaft (2) is rotated under the meshing force action of the first gear (21) and the second gear (61) by rotating the driving handle (7).

3. Hoisting device as claimed in claim 2, characterized in that the number of teeth of the first gear wheel (21) is greater than the number of teeth of the second gear wheel (61).

4. Hoisting device as claimed in claim 2, characterized in that a stop plate (22) is further provided on the first shaft (2), and the traction rope (4) wound on the first shaft (2) is confined between the first gear (21) and the stop plate (22).

5. The hoisting device of claim 2, further comprising a first bearing and a second bearing, wherein the first support bar (11) is provided with a first mounting plate (13) and the second support bar (12) is provided with a second mounting plate (14);

the first mounting plate (13) and the second mounting plate (14) are respectively provided with a first bearing seat (8), and two ends of the first rotating shaft (2) are respectively connected to the corresponding first bearing seats (8) in a rotating manner through the first bearings;

the first mounting plate (13) is back to one side of the first bearing seat (8) and the second mounting plate (14) is back to one side of the first bearing seat (8) and is provided with a second bearing seat (9), and two ends of the second rotating shaft (6) are connected to the corresponding second bearing seats (9) in a rotating mode through the second bearings.

6. Hoisting device as claimed in claim 2, characterized in that the driving handle (7) comprises a vertically connected connecting rod (71) and a grip (72), the grip (72) being arranged parallel to the second axis of rotation (6), the end of the connecting rod (71) remote from the grip (72) being connected to the second axis of rotation (6).

7. Hoisting device as claimed in claim 1, characterized in that a peg (15) is arranged between said first support bar (11) and said second support bar (12), said pulley assembly (3) further comprising a hook (32) and a mounting frame (33), said fixed pulley (31) being rotatably connected to said mounting frame (33), said mounting frame (33) being positioned between said peg (15) and said first shaft (2) and being hooked to said peg (15) by said hook (32).

8. Hoisting device as claimed in claim 7, characterized in that the hook (32) comprises a hook body (321) and a first stop (322), the first stop (322) being rotatably connected to the hook body (321) for blocking the opening of the hook body (321).

9. Hoisting device as claimed in claim 1, characterized in that the hook assembly (5) comprises a hook body (51) and a second stop (52), the second stop (52) being rotatably connected to the hook body (51) for blocking an opening of the hook body (51).

10. Hoisting device as claimed in claim 1, characterized in that said support bracket (1) further comprises a plurality of reinforcement bars (16) arranged at intervals, each reinforcement bar (16) being connected at one end to said first support bar (11) and at the other end to said second support bar (12).