GB2086830A

GB2086830A - Lifting blocks for cranes and similar lifting machines

Info

Publication number: GB2086830A
Application number: GB8132807A
Authority: GB
Original assignee: John Mowlem and Co Ltd
Current assignee: John Mowlem and Co Ltd
Priority date: 1980-11-03
Filing date: 1981-10-30
Publication date: 1982-05-19
Also published as: GB2086830B

Abstract

The block of a crane which has a fluid pressure operated device carried by the block is provided with a reel (19) for taking up and paying out the fluid pressure supply hose as the block is raised and lowered. The hose reel (19) is coupled to the block pulley (16) so that when the pulley is driven by the hoist rope (7) as it is winched in to raise the block, the reel is driven by the pulley to wind on the hose at substantially the same speed as the block is raised. The coupling is also arranged so that the reel is able to rotate independently of the pulley when the pulley is driven by the rope in the opposite direction. The coupling between the reel (19) and the pulley (16) includes a friction clutch (13, 21) which permits the reel to slip when being driven by the pulley. <IMAGE>

Description

SPECIFICATION Improvements relating to lifting blocks for cranes and similar lifting machines This invention relates to cranes and other lifting machines which have a fluid pressure operated device, such as a grab, carried by a block which is suspended by a rope or cable (hereinafter referred to as a rope) extending around the block pulley and which is raised or lowered by respectively winching in or out the rope at one of its ends.

The fluid under pressure for operating the device carried by the block is supplied via one or more, usually two, hoses which run between the device and the part of the lifting machine from which the block is suspended. Each hose will have a length sufficient to accommodate the maximum drop of the block, and in order to avoid the hose becoming slack and forming a loop at the side of the block when the block is raised, it is common to provide the lifting machine with means for taking up and paying out the hose as the block is raised and lowered. This means may comprise a hose reel which is driven either by a spring or by a motor.In the first case the tension in the hose varies according to the length of hose which is off the reel, and in the second case it is necessary to use a high torque stallable motor because of the variation in load according to the length of hose which is off the reel. Also, it is difficult to vary the speed at which the hose is wound or unwound from the reel to match any variations in the speed at which the block moves, which is of course related to the speed at which the hoist rope travels.

According to the present invention, the hose reel is mounted on the block and is coupled to the block pulley so that the reel is driven by the pulley to wind on the hose when the pulley is driven by the rope as it is winched in to raise the block, the arrangement being such that the hose is wound on the reel at substantially the same speed as the block is raised, and the coupling allowing the reel to rotate independently of the pulley when the pulley is driven by the rope in the opposite direction so that the hose is pulled from the reel on demand when the block is lowered.

One way of arranging that the hose is wound on the reel at substantially the same speed as the block is raised during winching in of the rope is by suitable selection of the ratio of the diameters of the hose reel and the pulley. For example, where the block has a single pulley, the rope will move twice as fast as the block, and the diameter of the hose reel must be substantially twice that of the pulley in order to wind on the hose at the same speed as the block rises.

Preferably however, the arrangement is such that the hose reel is driven by the pulley slightly faster than is necessary to wind on the hose at the desired rate, the coupling between the pulley and the reel permitting slip as necessary. This means that the hose will always be maintained under tension (which will be substantially constant and determined by the load at which the slip will occur) and that it is not important if the ratio of the rope speed to the hose wind-on speed varies slightly during operation.

In a preferred form of the coupling between the pulley and the hose reel, the pulley and the reel are rotatably mounted on a shaft which is free to rotate in one direction only, the pulley being couplied to the shaft so that it drives the shaft when the pulley is driven in the said one direction by the rope, i.e. when the rope is winched in to raise the block, and so that the pulley rotates freely on the shaft when the pulley is driven by the rope in the opposite direction, and the reel being coupled to the shaft by a friction clutch so that the reel is driven by the shaft when the shaft is rotated in the said one direction and so that the reel is able to rotate on the shaft against the braking effect of the clutch in the opposite direction.This braking effect of the clutch is exhibited when the block is lowered and the hose is being pulled from the reel, the braking serving to maintain the hose in tension and to prevent overrun of the reel when the block stops.

The friction clutch preferably comprises an annular clutch plate fixed concentrically on the shaft, and at least one friction pad which is mounted on one side of the hose reel and which is spring biassed against the clutch plate. In this case the load which must be exerted on the clutch before slip will occur is determined, amongst other things, by the spring force which presses the friction pad or pads against the clutch plate.

Preferably this force is adjustable, for example, by adjusting the axial position of the reel on the shaft relative to the clutch plate.

As mentioned earlier, there will usually be two fluid pressure hoses for supplying the operating fluid to the device carried by the block, and in this case it will be usual to provide two substantially identical hose reels, one for each hose, which will conveniently be mounted on the block on opposite sides of the pulley.

An example of a block for a lifting machine in accordance with the invention is illustrated in the accompanying drawings in which: Figure 1 is a side elevation of the block; and, Figure 2 is a part axial section through the block taken on the line Il-Il in Figure 1.

The block comprises a shaft 1 rotatably mounted by bearings 2 through one end of a pair of fixed sheave side plates 3 which pivotally carry at their other end a link 4 and shackle 5 for the connection of a fluid pressure operated device such as a grab. A pulley 6 for guiding a hoist rope 7 is rotatably mounted by bearings 8 centrally on the shaft 1 between the two sheave side plates 3.

Attached to each side of the hub 9 of the pulley 6 is the outer ring 10 of a sprag clutch of which the inner ring 11 is keyed at 12 to the shaft 1, these sprag clutches drivingly connecting the pulley 6 to the shaft 1 when the pulley rotates in one direction, but allowing the pulley 6 to freewheel on the shaft 1 when the pulley rotates in the opposite direction.

Surrounding the shaft 1 axially outwards of each sheave side plate 3 is an annular, radially extending friction clutch plate 13 having an axially projecting hub portion 14 which is keyed to the shaft 1 at 15 and which forms the inner ring of a sprag clutch 16, the outer ring 1 7 of the sprag clutch 1 6 being fixed to the sheave side plate 3.

These sprag clutches 1 6 lock the shaft 1 and the friction clutch plates 13 relative to the sheave side plates 3 when the pulley freewheels on the shaft 1, but allow the shaft, and with it the clutch plates 13, to rotate when the pulley 6 is drivingly coupled to the shaft.

At each end of the shaft 1 axially outwards of the friction clutch plate 13, the hub 1 8 of a hose reel 19 is rotatably mounted on the shaft by bearings 20. On the side of each hose reel 1 9 facing the adjacent friction clutch plate 13 is an annular friction pad 21 which is keyed to the reel 1 9 by locating pins 22 projecting axially through holes in the side of the reel 19, and which is pressed into frictional engagement with the plate 13 by springs 23 located in housings 24 carried by the reel 1 9 at evenly spaced intervals around the pad 21.Consequently, when the pulley 6 drives the shaft 1 and the clutch plates 13, the two hose reels 19 are driven therewith through the frictional engagement of the plates 13 and the pads 21, although slippage will occur if the load exerted on the reel 1 9 exceeds a predetermined limit. On the other hand, when the shaft 1 and the clutch plates 13 are locked relative to the sheave side plates 3, the frictional engagement of the plates 13 and the pads 21 act as a brake on the hose reels 19 which will nevertheless rotate provided sufficient torque is exerted to overcome the friction brake. This limit can be adjusted by adjusting the axial position of the hose reels 1 9 on the shaft so that the springs 23 are further compressed or relaxed.Axial adjustment of the hose reels 1 9 is carried out by means of an adjusting nut 25 at each end of the shaft 1.

The diameter of the peripheral surface 26 of each hose reel 1 9 on which, in use, a hose will be wound is a little less than twice the groove diameter of the pulley 6. At opposite ends of the surface 26 of each hose reel 19, the reel has a pair of hose retaining side walls each formed by a number of radially projecting spokes 27 connected by an outer circumferentially extending member 28. In addition the block includes a hose guard 29 which is fixed to the sheave side plates 3 at 30 (Figure 1) and which surrounds both hose reels 1 9 in the upper region of the block for guiding the hoses onto and off the reels during operation.

Similarly the two sheave side plates 3 are provided with spacers 31 carrying rollers which act not only as rope guards but also as stops for limiting any counter rotary movement of the sheave side plates 3 which may occur during hose reeling operations.

Mounted on the outside of each hose reel 19 is a rotary coupling 32 by which the inner end of the hose which is wound on the reel, and therefore rotates with the reel, is coupled to a hose 33 for conducting the fluid under pressure to the device carried by the block, the coupling 32 having a hose connector 34 which rotates with the reel 1 9 for connection to the reel hose, and a connector 35 which remains stationary for connection to the hose 33.

Claims

1. A lifting machine having a block which is suspended by a rope extending around the block pulley and which is raised or lowered by respectively winching in or out the rope at one of its ends, and a reel for a hose for supplying fluid under pressure to a fluid pressure operated device which, in use, may be carried by the block, the reel being arranged to take up and pay out the hose as the block is raised and lowered, characterised in that the hose reel is mounted on the block and is coupled to the block pulley so that the reel is driven by the pulley to wind on the hose when the pulley is driven by the rope as it is winched in to raise the block, the arrangement being such that the hose is wound on the reel at substantially the same speed as the block is raised, and the coupling allowing the reel to rotate independently of the pulley when the pulley is driven by the rope in the opposite direction so that the hose is pulled from the reel on demand when the block is lowered.

2. A lifting machine according to Claim I, in which, when the rope is winched in to raise the block, the hose reel is driven by the pulley slightly faster than is necessary to wind on the hose at the rate at which the block is raised, the coupling between the pulley and the reel permitting slip as necessary.

3. A lifting machine according to Claim 1 or Claim 2, in which the pulley and the reel are rotatably mounted on a shaft which is free to rotate in one direction only, the pulley being coupled to the shaft so that it drives the shaft when the pulley is driven in the said one direction by the rope, i.e. when the rope is winched in to raise the block, and so that the pulley rotates freely on the shaft when the pulley is driven by the rope in the opposite direction, and the reel being coupled to the shaft by a friction clutch so that the reel is driven by the shaft when the shaft is rotated in the said one direction and so that the reel is able to rotate on the shaft against the braking effect of the clutch in the opposite direction.

4. A lifting machine according to Claim 3, in which the friction clutch comprises an annular clutch plate fixed concentrically on the shaft, and at least one friction pad which is mounted on one side of the hose reel and which is spring biassed against the clutch plate.

5. A lifting machine according to Claim 4, in which there is a single annular friction pad mounted on the side of the hose reel by means of locating pins projecting axially through holes in the side of the hose reel, and the pad is pressed towards the clutch plate by means of a number of springs acting between the hose reel and the pad at evenly spaced intervals around the pad.

6. A lifting machine according to Claim 4 or Claim 5, in which the spring force pressing the friction pad or pads against the clutch plate is adjustable.

7. A lifting machine according to Claim 6, in which the spring force is adjusted by adjusting the axial position of the hose reel on the shaft relative to the clutch plate.

8. A lifting machine according to any one of the preceding claims, in which there are two substantially identical hose reels mounted on the lifting block on opposite sides of the pulley for taking up and paying out two fluid pressure supply hoses as the block is raised and lowered.

9. A lifting machine according to Claim 1, having a block substantially as described with reference to the accompanying drawings.