GB1572440A - Working platform for cranes - Google Patents

Description

(54) WORKING PLATFORM FOR CRANES (71) We, HONGISTO OY, a Company incorporated under the laws of Finland, of Kansipojantie 7, 90520 Oulu 52, Finland, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to working platforms and in particular concerns a working platform suitable for attachment to the jib or oom of a crane.

Various types of hydraulically operated inspection platforms are known in which a cradle or cage is carried by an elevating boom system which is operated hydraulically. In such equipment the cradle or cage is pivotally supported at the end of a boom which is specifically adapted to support the cage or cradle. Such elevating boom systems cannot in practice be employed as cranes, since it is not practical to utilise the supporting booms for the cables and sheeves necessary for suspension of a crane hook.

Although it is known to suspend a working cradle or cage from the hook of a crane, no system is currently known which enables a working platform or cage to be supported rigidly by the jib or boom of a crane, without interfering with the operation of the crane hook.

The present invention provides a working platform which can be attached to a crane jib or boom. A working platform according to the invention comprises support structure having releasable attachment means for attachment to a hook-supporting end of a crane jib or boom, and a cradle or cage device pivotally supported on opposite sides by the support structure for pivotal movement about a horizontal axis, and so arranged that when the platform is fitted to a crane jib or boom the cradle or cage device does not interfere with the operation of the crane hook.

Preferably the support structure comprises a base frame attachable rigidly to a crane jib or boom and a suspension fork fixed to the frame. The base frame may be rectangular, with four points of attachment to a crane jib or boom. Thus in a preferred embodiment of the invention the rectangular base frame has four legs adapted to be releasably attached to the crane jib or boom. The four legs hold the suspension fork away from the end of the crane jib or boom, allowing free passage of the hook suspended from the jib or boom so that the crane hook can be used in a conventional way while the working platform is in use.

The cradle or cage device may be suspended freely in the suspension fork. In a preferred embodiment of the invention, however, hydraulic actuator means are interposed between the cradle or cage device and the suspension fork for controlling the angular position of the cradle or cage device relative to the support structure. Preferably the hydraulic actuator means are connected to a source of hydraulic fluid under pressure and to a discharge reservoir through valve means controlled automatically in response to changes in elevation of the crane jib or boom so as to keep the floor of the cradle or cage device substantially horizontal through the hydraulic actuator means.When the crane jib or boom is in a desired position the valve means may be closed so as to prevent fluid flow into or from the hydraulic actuator means, thereby effectively locking the cradle or cage device rigidly relative to the suspension fork.

The present invention also comprehends a crane having a jib or boom supporting a hook and provided with a working platform as herein defined attached to the free end of the jib or boom without interfering with the operation of the crane.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying purely diagrammatic drawings, in which: Figure 1 is a perspective view of part of a crane jib fitted with a working platform according to the invention; Figure 2 is a side elevation, on a larger scale than Figure 1, of a working platform according to an embodiment of the invention; and Figure 3 is an end elevation in the direction of arrow III of the working platform shown in Figure 2.

Figure 1 of the drawings illustrates part of a crane jib 1 which may be of any conventional type, for example a jib of a vehicle mounted crane. The jib 1 has sheeves 2 at its free end from which a hook 3 is suspended conventionally by four wires. The free end of the crane jib 1, which may comprise an extending part of a telescopic boom, has four attachment lugs 4, two only of which are visible in Figure 1, by means of which a working platform 5 according to the invention is supported from the jib 1. These lugs 4 would in practice normally be provided on the end of a boom for the purpose of attaching an extension jib.

The working platform 5 comprises a support structure 6 from which a cradle or cage device 7 is pivotally suspended. As shown in greater detail in Figures 2 and 3, the support structure 6 has a rectangular base frame 8 having four legs 9 formed integrally with or attached rigidly to the frame 8 and extending parallel to each other, and perpendicular to the plane of the frame 8. The legs 9 extend from the frame 8 towards the free end of the crane jib 1 and are releasably attached to the lugs 4 at the free end of the jib 1 by means of four releasable pin couplings. The four legs 9 serve to hold the base frame 8 of the support structure clear of the free end of the crane jib 1, so that normal operation of the crane hook 3 is not interfered with by the working platform support structure 5.

A suspension fork is fixed to the base frame 9 and comprises two suspension fork arms 10 attached to opposite sides of the base frame 8 and projecting forwardly, that is, in a direction opposite to the support legs 9, in parallel vertical planes. Each fork arm 10 comprises a pair of struts 11 attached to upper and lower parts of the support frame 8 and converging towards each, being interconnected at their free ends by an angle plate 12 (Figure 2). The struts 11 and the lateral members of the base frame 8 form triangular sub-frames which constitute the suspension fork arms on opposite sides of the base frame 8.

The free ends of the respective suspension fork arms 10 are provided with respective bearings in which respective coaxial hinge pins 14 are supported, the hinge pins 14 being fixed to opposite sides of the frame structure of the cradle of cage device 7 so that the latter is pivotally supported by the suspension fork arms 10 for pivotal movement about a horizontal axis coinciding with the common axis of the hinge pins 14.

The support structure, including the base frame 8, the support legs 9, and the struts of the suspension fork arms 10 are preferably constructed from square-section tubular steel members joined together by welding and sealed at their ends with welded joints to render each tubular section water-tight.

The cradle or cage device 7 has a rigid metal framework and a rigid floor, the sides of the cradle or cage device being provided with removable panels of mesh or netting.

The frame of the cradle or cage device 7 is provided with safety harness attachment points (not shown) on opposite sides.

Two hydraulic double acting actuators 16 extend between respective attachment lugs 17, 18 respectively on each suspension fork arm 10 and a part of the frame structure of the cradle or cage device 7. The hydraulic actuators 16 are connected in parallel through respective hydraulic supply pipes 18, 19, shown in broken outline, to a hydraulic distribution valve (not shown) connected to a source of hydraulic fluid under pressure and to a discharge reservoir (not shown). The distribution valve controls the distribution of hydraulic fluid under pressure to opposite sides of the cylinders of the two actuators 16 for controlling the extension and retraction of the actuators and, theefore, the angular position of the cradle or cage device 7 relative to the support structure 5.

The hydraulic distributor valve is itself controlled by means responsive to the angle of elevation of the crane boom 1, so that the operation of the actuators 16 is controlled automatically in a sense to maintain the floor of the cradle or cage device 7 substantially horizontal in all positions of the jib 1. Shutoff valves 20, 21 (Figure 2) are provided in each of the hydraulic pipes 19, 19A leading to each actuator 16. These valves are closed manually when the crane jib 1 reaches a stationary position, thereby hydraulically locking each actuator 16 and effectively anchoring the cradle or cage device 7 rigidly relative to the support structure 5 and crane jib 1. The cradle or cage device therefore provides a rigid working platform for inspection or repair work at a position which may be reached by the crane jib 1.

The working platform as described and illustrated, may be used at any level above the horizontal by suitable positioning of the crane jib 1, while the crane hook 3 remains available for use in all such positions of the jib 1. For use of the working platform below the horizontal, for example in inspection of pit shafts, the support structure 5 of the platform may be disconnected from the end of the crane jib 1 and attached directly to the four suspension wires of the crane hook 3, so that the cradle or cage device 7 is then suspended freely from the crane jib, in a manner similar to the known use of suspended working platforms or cradles.

WHAT WE CLAIM IS: 1. A working platform comprising support structure having releasable attachment means for attachment to a hook-supporting end of a crane jib or boom, and a cradle or cage device pivotally supported on opposite sides by the support structure for pivotal movement about a horizontal axis, and so arranged that when the platform is fitted to a crane jib or boom the cradle or cage device does not interfere with the operation of the crane hook.

2. A working platform according to Claim 1, in which the support structure comprises a base frame attachable rigidly to a crane jib or boom and a suspension fork fixed to the base frame.

3. A working platform according to Claim 2, in which the base frame is rectangular and has four points of attachment to a crane jib or boom.

4. A working platform according to Claim 3, in which the rectangular base frame has four legs adapted to be releasably attached to the crane jib or boom.

5. A working platform according to Claim 2, in which hydraulic actuator means are interposed between the cradle or cage device and the suspension fork for controlling the angular position of the cradle or cage device relative to the support structure.

6. A working platform according to Claim 5, in which the hydraulic actuator means are connected to a source of hydraulic fluid under pressure and to a discharge reservoir through valve means controlled automatically in response to changes in elevation of the crane jib or boom so as to keep the floor of the cradle or cage device substantially horizontal through the hydraulic actuator means.

7. A working platform according to Claim 1 for attachment to a crane jib or boom substantially as herein described with reference to and as shown in the accompanying drawings.

8. A crane having a jib or boom supporting a hook, and a working platform according to any of Claims 1 to 7 attached to the free end of the jib or boom without interfering with the operation of the crane hook.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (8)

**WARNING** start of CLMS field may overlap end of DESC **. the crane jib 1 and attached directly to the four suspension wires of the crane hook 3, so that the cradle or cage device 7 is then suspended freely from the crane jib, in a manner similar to the known use of suspended working platforms or cradles. WHAT WE CLAIM IS:

1. A working platform comprising support structure having releasable attachment means for attachment to a hook-supporting end of a crane jib or boom, and a cradle or cage device pivotally supported on opposite sides by the support structure for pivotal movement about a horizontal axis, and so arranged that when the platform is fitted to a crane jib or boom the cradle or cage device does not interfere with the operation of the crane hook.

2. A working platform according to Claim 1, in which the support structure comprises a base frame attachable rigidly to a crane jib or boom and a suspension fork fixed to the base frame.

3. A working platform according to Claim 2, in which the base frame is rectangular and has four points of attachment to a crane jib or boom.

4. A working platform according to Claim 3, in which the rectangular base frame has four legs adapted to be releasably attached to the crane jib or boom.

5. A working platform according to Claim 2, in which hydraulic actuator means are interposed between the cradle or cage device and the suspension fork for controlling the angular position of the cradle or cage device relative to the support structure.

6. A working platform according to Claim 5, in which the hydraulic actuator means are connected to a source of hydraulic fluid under pressure and to a discharge reservoir through valve means controlled automatically in response to changes in elevation of the crane jib or boom so as to keep the floor of the cradle or cage device substantially horizontal through the hydraulic actuator means.

7. A working platform according to Claim 1 for attachment to a crane jib or boom substantially as herein described with reference to and as shown in the accompanying drawings.

8. A crane having a jib or boom supporting a hook, and a working platform according to any of Claims 1 to 7 attached to the free end of the jib or boom without interfering with the operation of the crane hook.