| JP10037419 | DEVICE FOR HANGING ROOF PANEL |
| JP09310501 | AUXILIARY DEVICE FOR PULLING SUSPENDED LOAD |
| JP3275176 | BELT TYPE HOIST |
| 1. | A self levelling device comprising; a lifting shackle including a guide wheel and for use with a length of flexible lifting member, such as a chain, which passes over the guide wheel and of which the ends are for attachment to a load said device including locking means operable by the tension in the said member when the load is lifted from the shackle and member, to lock the wheel from rotation to prevent the member from feeding through the shackle, which locking means disengages when the tension in the member is released permitting the shackle to be displaced relative to said member and the load, characterised by restrictor means operative to prevent the free feeding of the said member through the shackle when the said member is disconnected from the load. |
| 2. | A device according to Claim 1, wherein said guide wheel is movably mounted on said shackle between a raised unloaded position and a lowered loaded position, and said locking means comprises complimentary means on the guide wheel and shackle which interengage in said loaded position. |
| 3. | A device according to Claim 2, wherein said complimentary means comprises a ring of sprocket teeth on the guide wheel and a locking pin or projection on the shackle. |
| 4. | A device according to Claim 2, wherein said restrictor means comprises a restrictor wheel on the shackle and lying with its axis parallel to the axis of rotation of the guide wheel, the periphery of said wheel being adapted to project between adjacent ones of said sprocket teeth in the raised unloaded position such as to prevent free rotation of the guide wheel due to the weight of the flexible member but allowing the guide wheel to be rotated under a manual pulling load on said flexible member. |
| 5. | A device according to Claim 4, wherein said restrictor wheel has a periphery of a material of a semiresilient nature. |
| 6. | A self levelling device substantially as hereinbefore described with reference to the accompanying drawings. |
This invention relates to a self-levelling device for lifting a load, and concerns a device of which an example is set forth in European Patent Specification No. 0307063.
In the said European patent specification, the self-levelling device comprises a shackle which rotatably supports a guide wheel around which an elongated flexible member is trained. Typically the length of flexible member is a chain and the wheel is a chain wheel. The guide wheel is mounted relative to the shackle for at least limited movement against spring action so that the self-levelling device has an unloaded, raised position in which the guide wheel is in a raised position, and a loaded position in which the guide wheel is in a lowered position and when the self-levelling device supports the load.
In the raised position, the guide wheel is free to rotate relative to the shackle, whilst in the loaded lowered position, the guide wheel is locked against rotation.
The reasons for this construction are well explained in the said European patent application, but it has been found that when in particular a chain is used as the length of flexible member which is trained round the guide wheel, when the self- levelling device is in an elevated position, and there is no load connected thereto, the chain, under gravity, tends simply to rotate the guide wheel due to the fact that one portion of the length of chain to one side of the guide wheel will probably be longer and therefore heavier than the other portion of the length of chain to the other side of the guide wheel, with the result that the chain either falls from the device, or a load engaging hook at the appropriate end of the length of chain jams in the shackle. Either event means
inconvenience for the user of the self-levelling device, and the present invention seeks to provide a means for overcoming this disadvantage.
In accordance with the invention, there is provided a self levelling device comprising: a lifting shackle including a guide wheel and for use with a length of flexible lifting member, such as a chain, which passes over the guide wheel and of which the ends are for attachment to a load said device including locking means operable by the tension in the said member when the load is lifted from the shackle and member, to lock the wheel from rotation to prevent the member from feeding through the shackle, which locking means disengages when the tension in the member is released permitting the shackle to be displaced relative to said member and the load, characterised by restrictor means operative to prevent the free feeding of the said member through the shackle when the said member is disconnected from the load. By this arrangement, the disadvantageous effect described above is avoided and even if the length of flexible member is a heavy link chain, and is unevenly draped over and hangs from the guide wheel, there will still be no free running of the chain as the restrictor means will prevent this. The invention also applies when the guide wheel is in the form of a pulley supporting a wire rope or flat belt to serve as the lifting member, but obviously best application arises in the case of a heavy link chain used as the length of flexible member.
The guide wheel, as described in the said European patent application, may be provided with a ring of sprocket teeth, which serve as the means for locking the guide wheel when in the lowered and loaded position in that a locking pin or projection in such lowered position engages between adjacent
ones of said teeth. The sprocket teeth when provided may usefully cooperate with the restrictor means to place the restraint on undesirable turning of the guide wheel when in the unloaded condition and when the chain is not connected to a load, and in this regard the restrictor means may comprise a roller or wheel of semi-resilient material which engages between a pair of the said teeth. Such roller may be of a plastics material such as a polyurethane material. By this arrangement, it is provided that the guide wheel can be turned against the restrictor means, such restrictor being provided simply to prevent the unrestrained running of the chain under no load. Thus it may be possible by manual effort by pulling on the chain to cause the guide wheel to turn against the restrictor, the surface of which will deflect by virtue of the teeth deflecting the polyurethane roller surface.
The restrictor roller is preferably located to the top side of the sprocket wheel so that when the guide wheel moves to the lowered position when under load, engagement between the sprocket teeth and restrictor roller is eliminated, and the restrictor roller plays no part in restraining any turning movement of the guide wheel.
Other forms of restrictor devices may be used, and such restrictors may include friction discs and pads spring loaded into engagement with the guide wheel or another component which turns with the guide wheel.
An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, wherein:-
Fig. 1 is a diagrammatic side elevation to illustrate the utilisation of a self-levelling device;
Fig. 2 is an enlarged side elevation of the device shown in Fig. 1 and according to the embodiment of the invention; and
Fig. 3 is a central sectional elevation of the device shown in Fig. 2.
Referring to the drawings, and firstly to Fig. 1, reference numeral 10 represents an asymmetrical load such as a lathe or a turbine which is to be lifted by means of a length of flexible member 12 coupled to the device 14 of the embodiment of the invention. The chain 12 passes over a guide or chain wheel 16 of the device 14 and is attached to the load 10 at the points 18 and 20. In the full line position the device 14 is located approximately above the centre of gravity of the load 10, and therefore lifting the device as indicated by arrow 22 and hence lifting of load 10 ensures that the load 10 is lifted in a generally level fashion i.e. with its base surface 24 at least approximately horizontal.
Also in the figure, the load 10 and member 12 are shown in dotted lines in a slightly different configuration, although the member 12 is connected to the same load points 18 and 20, but in this case the device 14 is positioned approximately over the mid length point of the load as opposed to over the centre of gravity. One should assume that the device 14 was positioned at the mid length position in the first instance, and when the device 14 was lifted, the load took up or moved towards the tilted attitude shown in dotted lines in Fig. 1. The operator controlling the device 14 upon seeing the load take up or move towards this position would have immediately lowered the load back onto the ground, and then would have moved the device 14 in the direction of arrow 26 until the device 14 is positioned more over the centre of gravity, eventualy reaching the full line position as shown in Fig. 1.
The device 14 as disclosed in European Patent No. 0207418 as referred to herein is designed to operate so that the wheel 16 has a free running unloaded position enabling the movement of the device 14 relative to the member 12 for example as indicated by arrow 26, and a locked or loaded position in which the wheel 16 is locked so that the member 12 will not train round the wheel 16 when lifting is taking place as indicated by arrow 22, but the permitting of the wheel 16 to have a free running position does give rise to a shortcoming which the present invention seeks to overcome, as will be explained hereinafter.
From the information given herein, and from an understanding of the operation of the device shown in Fig. 1, it will be appreciated that a self-levelling device 14 provides a considerable technical advantage compared to the conventional slinging of loads when the attachment points are constantly changed in an effort to reach a position in which the load will be lifted in a level fashion. It should be mentioned that if it is desired to lift the load so that when lifted the load will take up a pre-set angle, for example as indicated in dotted lines in Fig. 1, then the device 14 can be positioned accordingly. It may for example be desirable to hold a load at a particular angle when it has to be moved up a staircase or stairwell of which the steps are arranged on a flight at the particular angle.
The device 14 in accordance with the invention is constructed so that as long as the wheel 16 is urged downardly by virtue of the tension in the member 12, the wheel will be held in the locked position, but when the load is supported on the ground, and the device 14 is lowered, as soon as the member 12 becomes slack the wheel 16 can be rotated, but against a restriction, as opposed to being freely rotatable enabling the controlled adjustment of the device as will be explained
herein. In a modification, there may be an auxilliary locking device, such as a locking pin, which can lock the wheel in the locked position permanently until the auxilliary locking device is removed, which may be effected by hand.
The automatic lock and release of the device 14 may be achieved in any suitable manner, and the lifting member may be a chain.as illustrated in Figs. 2 and 3 or a belt or rope.
Referring to Figs. 2 and 3, the device comprises a pair of steel side plates 30 and 32 which are symmetrically arranged around an axis 34 of symmetry of the device. The plates are secured together by means of shouldered bolts 36 and at the top of the plates by a large hook bolt 38, the bolt 38 being received in collars 40 on the inner surfaces of the plate, and being retained in position by nuts 42. A central section 44 of bolt 38 is of waisted configuration, for engagement with the lifting hook 46 of the hook block of the lifting crane. Instead of a hook bolt 38 the plates 30, 32 may be angled inwards so that the portions thereof come face to face and in such portions are eye holes for receiving securing hook 46.
The plates 32 are provided with elongated reception slots 48 having parallel sides and curved ends to receive the ends 50 of a spindle 52. The said ends 50 have flats 54 (Fig. 2) which face the straight portions of slots 48 whereby the spindle is prevented from turning about its axis, but in fact the spindle 52 can move vertically in the slots 48 between a lower and locked position, and an upper adjustment position, and to this end connected to the spindle ends are tension springs 56 which urge the spindle 52 to the upper position. The springs 56 are connected by bolts 58 to the mounting flanges 60 on the outside of plates 32, and to the ends 50 of the spindle 52 by bolts 61. The springs are concealed and
protected by cover plates 53.
Spindle 52 is provided with a pair of plane bearings 62 which rotatably support a chain wheel 64 (which is in fact wheel 16 in Fig. 1), the periphery of the chain wheel 64 being contoured as shown at 66 to receive the links of the chain 12 in a driving fashion so that a driving connection is established between the chain 12 and the wheel 64.
The wheel 64 is provided on its side faces with grooves receiving locking sprocket plates 68 having teeth 70 equally spaced therearound. The sprocket plates are secured to the wheel by bolts 72.
The spindle 52 is prevented from moving axially relative to the plates 32 by virtue of the shoulders 74 (Fig. 2) formed at the ends of the flats 54 lying adjacent the surfaces of the plates 32.
The operation of the device as described so far will be understood from the previous description, but if reference is made to Fig. 2 it can be explained that as long as the chain 12 is under tension i.e. in a load lifting condition, the net downward thrust by the chain on the wheel 64 displaces the wheel to the lowermost position in slots 48 and the spindle is supported on the slot bottoms 76 which take the weight of the load being lifted, and two of the teeth 70 of each sprocket plate lie to opposite sides of a locking pin 78 extending between the plates 68, so that the sprocket cannot turn about its axis and the chain 12 cannot feed around and rotate the sprocket. The load is therefore held stably and cannot tilt during lifting. When the load is lowered and is supported on the ground however, the continued lowering of the device allows the chain 12 to go slack and the springs 56 therefore commence lifting the wheel 64 and its sprocket
plates 68 until the teeth 70 disengage from the pin 78, at which point wheel 64 can turn on spindle 52 and the device can be moved horizontally allowing the chain to feed round the wheel 64 as it rotates, permitting the device to take up a new position. It should be mentioned that the device is lowered only by an amount sufficient to allow the wheel 64 to turn, the springs taking the weight of the chain, and the chain will, not therefore become uncontrollably slack. When the device has been re-positioned, and is again raised so that the chain 12 takes the load, the wheel will again be moved downwards until the teeth engage the locking pins 78 as shown in Fig. 2.
The extent of the movement of the wheel 64 is indicated by the full and chain dotted-line positions A and B indicated in Fig. 3, position A being the locked position and position B being the free position.
A difficulty which has been experienced with the self- levelling device described in the said European patent is that when the device is unloaded, and the wheel 64 is raised and is freely turnable, if the chain 12 does not have its ends connected to the load, and the device is in elevated position, unless the chain is centred on the device i.e. equal halves of the chain hang from opposite sides of the wheel 64, the chain will in fact run freely and uncontrollably over the wheel 64, so much so that the chain will either drop from the device or the lifting hook at one end of the chain will jam in the device. The present invention seeks to overcome this difficulty, by providing a restricting means which restricts the movement of the wheel 64 when in the unloaded position. In the embodiment of the invention illustrated, the restricting device comprises a roller 80 which is mounted for free rotation on the inside of plate 32, and is positioned so that when the wheel 64 is in
the raised position, a pair of sprocket teeth 70A as shown in Fig. 2 engage the surface of roller 80 preventing free rotation of the wheel 64. As shown in Fig. 2, the pitch circle of the tips of the teeth 70 intersects the periphery of the roller 80 whereby the roller serves to prevent free rotation of the wheel 64. The roller 80 is defined by a sleeve 82 of a deformable material such as a plastics material, typically polyurethane having a suitable hardness so that when force is applied to the chain 12 to turn the wheel 64 when it is in the raised position, the teeth such as teeth 70A can be forced past the roller 80 to permit the device to be adjusted as described herein. As soon as the force tending to turn the wheel 64 is removed, the wheel will again be held by the restricting roller 80.
The roller 80 is positioned to the top side of the device so that when the device is loaded and the wheel 64 is moved to the lower and locked position, the roller 80 and teeth 70 or 70A will be out of contact whereby wear on the roller 80 is minimised.
By the means of the embodiment, a simple and effective restricting device is provided which prevents the chain from running freely over the wheel 64 when the device is in elevated position and is not connected to a load. Such circumstances may in the appropriate environment occur frequently, because when the device is out of use it may well be raised to an elevated position clear of a floor surface on which personnel may be working and over which machinery and components may be from time to time moved.
The device will clearly be designed to meet the working conditions under which the device will be used. Thus it will have a safe working load rating indicating the loads which can safely be lifted by the device.
Modifications of the invention are possible within the scope of the appended claims. For example, in a device according to the invention may be adapted to be used in conjunction with two or more chain or belt slings, there may be two or more of said guide wheels arranged side by side and operating on the principle described herein. Additionally, in a further modification, the device may embody a guard or retaining plate which locates above but not in contact with the guide wheel in order to prevent the chain or belt from jumping clear of the guide wheel pockets, recesses or surfaces. Such guide or retention means could for example be fixed to the guide wheel axle so that it will move with the guide wheel between the various positions thereof, and in all positions will perform the chain retaining function.
The device may embody or be connected to a means for indicating a load which is being lifted. Such means may comprise a strain gauge with associated visual display device carried by the device or located nearby an operators' station so that the weight of the load being lifted at any time can be viewed.
The present invention can be used in conjunction with the invention set forth in co-pending Patent Application No. 8817385.1 of the United Kingdom wherein two self-levelling devices are ganged to enable self-levelling of a load into different vertical planes.
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