US3575300A

US3575300A - Device for suspension and placement of the load in a distributive jib tower crane

Info

Publication number: US3575300A
Application number: US778225A
Authority: US
Inventors: Pierre Durand
Original assignee: Individual
Current assignee: Individual
Priority date: 1967-12-11
Filing date: 1968-11-22
Publication date: 1971-04-20
Anticipated expiration: 1988-04-20
Also published as: FR1557820A

Abstract

A tower crane with a horizontal distributive jib is traversed by a carriage bearing hoist cables with terminal swivels from which hangs a crossbar. The crossbar carries a load-bearing hook. The hoist cables pass over guide pulleys on the carriage in opposite directions via a plurality of further pulleys to respective drums synchronized winches. The further pulleys include two mounted on a block which moves horizontally in a direction opposite to that of the carriage so as to compensate for the changes in length of the hoist cables and hence to keep the load at a constant level. The tendency of the hoist cables and crossbar to twist is thereby obviated.

Description

United States Patent DEVICE FOR SUSPENSION AND DISPLACEMENT OF THE LOAD IN A DISTRIBUTIVE JIB TOWER CRANE 7 Claims, 3 Drawing Figs.

US. Cl 212/63, 212/76, 212/81, 212/20, 212/27 Int. Cl B66c 23/02 FieldofSearch, 212/19, 20,

Primary Examiner-Harvey C. l'lomsby Att0rney-Waters, Roditi, Schwartz & Nissen ABSTRACT: A tower crane with a horizontal distributive jib is traversed by a carriage bearing hoist cables with terminal swivels from which hangs a crossbar. The crossbar carries a load-bearing hook. The hoist cables pass over guide pulleys on the carriage in opposite directions via a plurality of further pulleys to respective drums synchronized winches. The further pulleys include two mounted on a block which moves horizontally in a direction opposite to that of the carriage so as to compensate for the changes in length of the hoist cables and hence to keep the load at a constant level. The tendency of the hoist cables and crossbar to twist is thereby obviated.

DEVICE FOR SUSPENSION AND DISPLACEMENT OF THE LOAD IN A DISTRIBUTIVE JIB TOWER CRANE This invention relates to a device for the suspension and displacement of the load, applicable to tower cranes with a horizontal distributive jib, and more particularly to those in which the load-bearing carriage does not bear the hoisting winch and serves only as movable starting point for the vertical cables which support this load.

The invention will be more clearly understood from the following description with reference to the accompanying diagrammatic drawings in which:

FIG. 1 shows the usual arrangement used in the case of these tower cranes with a distributive jib;

FIG. 2 shows a second conventional arrangement based on the same principle as that of FIG. 1; and

FIG. 3 shows an embodiment of the device according to the invention.

In FIG. 1, 1 designates the tower of a crane, 2 its distributive jib, 3 the turning hook from which the load is suspended, and 4 the load-bearing carriage. The cables, respectively 5 for displacement of the load and 6 for displacement of the carriage, are independent and are controlled by two independent winches, respectively 7 and& The cable 6 for displacement of the carriage fonns a closed loop of which the displacement movement draws the carriage 4 on the rolling track generally constituted by the lower member of the jib. During this displacement of the carriage 4, one of the strands of the cable 5 for suspension of the load ascends, while the other descends by the same amount, which enables the load to dwell at a constant height.

In FIG. 2 which shows a system for suspension and for displacement based on the same principle as that of FIG. I, the suspension block 9 comprises five pulleys; the load per strand hence becomes a quarter of the total load, and no longer half, as in the case of FIG. 1.

In the case of the arrangement shown in FIG. 1 or that shown in FIG. 2, the cable 5 being a twisted cable and being subject to a traction through the load suspended at the hook, has a tendency to be untwisted, by the very reason of the dissymmetry of its internal construction. The couple which results therefrom is transmitted to the attachments at the end of the cable and to the block cheeks on which it is wound. This is without effect when the attachments and the pulleys are rigidly fixed; but it is not the same for the hanging part of the equipment. The assembly: block, crossbar and hook being in fact subject to the sum of the untwisting couples of the strands of the cable, pivots around a vertical axis, which has the effect of bringing together the suspension strands into a single twisted bundle. There results a troublesome phenomenon in working, and a source of wear and of risk of accident due to the untwisting of the cable.

To avoid these disadvantages, at least partially, various solutions have been proposed and adopted, especially for example the use of so-called antigyratory cables, of which the structure enables reduction of the tendency to untwist under load. Another solution consists of spreading out or spacing to a maximum the various suspension strands, that is to say to give the maximal dimension to the space a of FIGS. 1 and 2, so as to create a restoring couple which stabilizes the orientation of the crossbar to an angle sufficiently reduced not to be troublesome. Yet another solution consists of attaching the fixed point of the cable 5 on a swivel 10, as shown in FIG. 1, which swivel can turn freely so as to enable the cable to find its equilibrium in being untwisted without restraint. This swivel is however only effective for the part of the cable which separates it from the nearest pulley; beyond this pulley the action of the swivel is very limited, and is not instantaneous on variations of load.

Among the solutions previously proposed to avoid at least partially the twisting of the hoisting cable, there is yet another which is fairly currently used which consists purely and simply of increasing the dead weight of the block, which has however the drawback of reducing in consequence the useful lifting load.

Hence means have not hitherto existed for enabling untwisting of the lifting cable in tower cranes with horizontal distributive jib to be effectively overcome. This absence of means becomes more and more unfavorable in proportion as the height of the crane increases, which renders practically impossible the provision of distributive tower jib cranes having very great heights, for example meters or more. In the case of such heights, it is not in fact particularly possible to spread out the vertical cables, that is to say the space a of FIGS. 1 and 2, proportionately to the hoisting height.

It is an object of the present invention to remedy these conditions.

It is a further object to provide a device for suspension and displacement of the load enabling elimination entirely of any tendency of the load-carrying block to twist.

According to the invention there is provided the following combination of devices: interposition of a swivel, or of a similar turning member, between the hook or the suspension crossbar of the load and the end of the hoisting cables, and association with the hoisting cables of a movable means bearing pulleys over which these cables pass and serving as a relay shifting in the reverse direction from the carriage and compensating the theoretical displacement of ascent or of descent of the hoisting cable, resulting from translatory movement of the carriage, by a theoretical and equal movement of descent or of ascent of the same cable.

FIG. 3 shows, by way of purely of illustration and nonlimiting example, one embodiment of the device for suspension and displacement of the load, according to the invention.

l6a-16b designate the two strands of the hoist cable to which the crossbar 17 is suspended by means of two swivels 18a-18, which suppress all tendency of the cable to twist, but which pose the problem of the horizontal shifting of the hoisting carriage, without using the usual arrangement of cables for carriage shifting and for hoisting, referred to above with reference to FIG. 1, in which arrangement the shifting of the carriage is always accompanied by the descent of one of the strands of the hoist cable and the equal ascent of the other strand of this cable.

This problem is resolved by combining the suspension of the crossbar 17 at swivels l8a-18b, with a system of compensation which forms part of the invention.

22 designates the tower of the crane, 23 its jib; 17 designates the hoist crossbar, 19a and 19b the two guide pulleys borne by the hoist carriage 20. The winch for translation of the carriage is not shown; only the two ends of the cable 38 for translating the carriage are visible, which ends are attached to the carriage.

The system comprises, for the hoisting of the load, two strictly synchronized winch drums, 39a and 3% respectively, from which come two lifting cables l6a-16b. Each of the two cables ,16a-l6b passes successively over two guide pulleys, respectively 41a and 41b and 42a-42b, before passing over the guide pulleys I9a-19b borne by the carriage 20. The two

guide pulleys

42a and 42b are borne at fixed points of the jib 23; but the pulleys 41a-4lb are borne by a movable apparatus 43 which, according to the invention, is specifically essential to enable the hoisting hook to dwell at a constant level when the hoisting carriage is shifted.

To raise or lower a load, it suffices to rotate the two drums 3.9a-39, simultaneously at the same speed, to obtain an equal ascent or equal descent of the two cables 16a-l6b, the mobile apparatus or relay 43 remaining motionless.

When the hoisting carriage 20 is to be shifted on the jib, by displacementof its cable 38 actuated by the winch not shown in the drawing, the relay 43 compensates for the vertical displacement in the level of the hook 17 which would result therefrom.

Assuming in fact that the carriage 20 is shifted in the direction of the arrow 44, there results a displacement ofthe various strands of the cable 16b in the direction of the

arrows

45a and 45b, with displacement of the relay 43 in the direction of the arrow 450, which causes finally a traction on the cable 16a, in the direction of the

arrows

46a and 46b. The crossbar 17 thus dwells at a constant level.

It will be apparent that various changes and modifications may be made in the embodiment described without departing from the essential concept of the invention as defined in scope by the appended claims.

lclaim:

l. A device for the suspension and displacement of the load in a distributive jib tower crane, said jib being transversed linearly by a carriage bearing hoist cables from which hang load-suspending means, said device comprising in combination, turning means interconnecting the loadsuspending means and the ends of the hoist cables, and a movable means bearing pulleys over which said hoist cables pass and serving as a relay for cooperatively shifting linearly in a direction reverse from that of the carriage and compensating for the theoretical displacement of ascent and descent of the hoist cables, resulting from the translatory movement of the carriage, by a theoretical movement equal to the descent and ascent of the hoist cables.

2. A device according to claim 1, wherein said turning means is a swivel.

3. A device according to claim 1, wherein said loadsuspending means comprises a crossbar.

4. A device according to claim 1, wherein said loadsuspending means comprises a hook.

5. A device according to claim 3, wherein said loadsuspending means comprises a hook.

6. A device according to claim 1, wherein said turning means comprise two swivels attached to the ends of two hoist cables which pass over a plurality of guide pulleys including those of said movable means, to the drums of two synchronized winches.

7. A device according to claim 6, wherein said loadsuspending means comprises a hook borne by a crossbar.

Claims

1. A device for the suspension and displacement of the load in a distributive jib tower crane, said jib being transversed linearly by a carriage bearing hoist cables from which hang loadsuspending means, said device comprising in combination, turning means interconnecting the load-suspending means and the ends of the hoist cables, and a movable means bearing pulleys over which said hoist cables pass and serving as a relay for cooperatively shifting linearly in a direction reverse from that of the carriage and compensating for the theoretical displacement of ascent and descent of the hoist cables, resulting from the translatory movement of the carriage, by a theoretical movement equal to the descent and ascent of the hoist cables.

2. A device according to claim 1, wherein said turning means is a swivel.

3. A device according to claim 1, wherein said load-suspending means comprises a crossbar.

4. A device according to claim 1, wherein said load-suspending means comprises a hook.

5. A device according to claim 3, wherein said load-suspending means comprises a hook.

7. A device according to claim 6, wherein said load-suspending means comprises a hook borne by a crossbar.