GB2101558A - Mobile lifting device - Google Patents

Abstract

A mobile lifting device for use in lifting and transporting heavy objects manually, comprises a frame made up of an operating arm (1) and a load- carrying arm carried on wheels which provide both mobility and the centre about which the frame moves as a lever for the manual movement of a load, the whole being preferably fitted with an additional wheel (9) carried on a movable member (10) attached to the frame so that it is movable by the operator between a retracted position in which it does not interfere with the lifting operation and an extended position which provides a stable configuration for maintaining the load clear of the ground and allowing the device with its load to be moved about. A spring (16) or its equivalent, and a latch (17), to lock the additional wheel in the load-carrying position may be provided. <IMAGE>

Description

SPECIFICATION Lifting device This invention relates to a lifting device and especially to a self-contained mobile device for lifting and moving heavy objects without the need for overhead installations.

In engineering workshops it is frequently necessary to lift objects which are too heavy for any single man to lift and to move them about the workshop or outside it. This is commonly the case when objects weighing several hundred pounds in weight (e.g. electrical motors, pumps and the like) have to be taken out of an installation for repair or servicing, and when these have to be re-installed after service or repair.

As these objects are so heavy, it is usual to lift them by either a block and tackle attached to an overhead gantry or trolley system, or to use a transportable crane. Both these methods have disadvantages however, the gantry needs to be fixed and stable, and the crane needs to have adequate provision for counter weighting (to avoid over-balancing) and to have adequate room for its jib above the object to be lifted.

I have now devised a very convenient form of lifting device which requires no fixed overhead gear and can easily lift objects where there is little headroom, and also enables the lifted object to be moved easily, even across open areas. Moreover, this device is easily operated by one or two men, and greatly facilitates maintenance work in confined spaces in a workshop or industrial plant.

Thus according to my invention I provide a mobile lifting device which comprises a frame made up of two arms connected rigidly together at an angle to each other and carried on wheels, one arm being adapted for manual movement by the operator and the other being adapted to be attached to an object to be lifted, and the relationship between the two arms being such that they function as the two arms of a lever about a fulcrum and a force applied to the first arm produces a suitably amplified upward force by the second arm.

The angle between the two arms is not critical, but is preferably less than 90 degrees so as to achieve most effective operation. Either or both of the arms may be straight or may be cranked, curved or shaped in any way which aids their use; preferably both are cranked so as to be reduce the overall height of the device.

The arms may be made of any convenient material and found together in any convenient way, as the maker and/or the user may require.

Commonly they will be of metal (which may be, for example, rod or tubular in form) and may be of iron or steel, and these may be joined together by welding, boits or other conventional means.

Either or both of the arms may be single members or composite in construction the preferred form being a pair of members which extend from the axis of the fulcrum about which the arms are movable, these two members coming together (for example by convergence or by a return loop bend) to provide better stability and rigidity. This is especially desirable for the arm adapted to be attached to the object to be lifted.

It is usually desirable also to provide one or more bracing members between the first and second arms to reduce the strain at the junction point and to improve safety of operation.

Opportunity can be taken by a designer to modify the form of construction from its simplest form, using known design techniques, to improve the distribution of forces around the structure so as to achieve adequate safety margins and to make optimum use of the various members while minimising the strain put upon the joints in use.

The first arm is adapted for manual movement by the operator by having a section towards its outer end suitably shaped to assist the operator to grasp it, or by having an attachment which serves as a handle and can give the operator an improved grip.

The second arm is adapted to be attached to the object to be lifted, by having a hook, grip, or other conventional attachment device at or near its outer end. This device may be a composite one, incorporating the hook or grip itself and a second part engaging with it, which may be adjustable to take up or let out slack between the arm and object being lifted. The choice of this means for attachment will usually be made on the basis of convenience of operation in any particular instance, and will also be subject to any precautions or rules which may be appropriate for safety of operation or for compliance with any governmental or other regulations which may apply to the construction or use of equipment.

Examples of such devices include slings (e.g. of canvas or the like), lashings, and chain fastenings, which can secure the object to be lifted. These may be around or through the object to be lifted (where this is practicable or permissible) or otherwise arranged to secure it. Alternatively, a co-operating means (for example an eye-bolt or the like) may be attached to the object to be lifted or made part of its construction, to facilitate the attachment to the lifting device when required.

If the device has one part moving within or through another part (for example a chain moving through an eye or hole in the arm or some part of the attachment device) then it is prudent for this to be provided with some "fail-safe" fitment (e.g.

a stop, catch or the like) which limits any accidental slippage in use which could cause injury or damage.

The ratio between the lengths of the two arms, or their effective lengths as measured from the fulcrum to the points at which the load and the operator respectively act, will depend upon the weight intended to be lifted. Commonly this will give the first arm (the operator's arm) an effective length three to eight times that of the second arm (the load arm), as this will enable one or two men to lift loads up to six hundredweights or so without difficulty. The ratio may be outside this range if desired, however, and may even be made variable by having means for adjusting the lengths of the arms or the prints at which the load or the operator's force is effective.

The whole is carried on wheels, which most conveniently may be a simple pair of wheels carried upon an axle. The type of wheel is not critical, but is conveniently a small pneumatic tyred wheel of a size and shape which will maintain an adequate grip on the ground over which the device is used. Pneumatic tyres are preferred as they are better at taking up shocks which could affect the device or operators.

Most advantageously, the axle of the wheels substantially coincides with the junction of the two arms of the fulcrum about which the lower action of the device acts. The axle and the junction of fulcrum need not coincide exactly, as the form of construction used may enable them to be separate, but they should be close together to make operation easy.

The form of construction may vary considerably, for example by use of more than two wheels, more than one axle, or even by carrying the wheels on suitable bearings or stub axles instead of a full axle. Thus, if desired, there may be used a four-wheel bogie as the means for allowing the whole device to be moved about, possibly with a transfer roller to aid movement of the arm assembly between the positions for lifting and for transporting an object.

To aid safety in operation, additional items may be included, for example brakes secure the wheels. Such brakes most conveniently may have their operation controlled from the operator's hand grip at the end of the first arm.

Another desirable and strongly preferred attachment is an additional wheel carried on a movable member (for example a sliding or swinging arm) which allows it to be kept out of contact with the ground while the device is being used to lift a load but allows it to be moved into contact with the ground when the load has been lifted sufficiently clear of the ground and the load is ready to be moved.The simplest form of this is a third wheel carried on a movable arm which is attached to the frame near to the axle or member carrying the two wheels, and which can be swung close to (and conveniently, substantially parallel to) the axle or said member, during lifting operation and can then be swung forward, underneath the load, when the load has been lifted and so stabilise the device as a whole with the load in the "lifted" position ready for the stage of moving the lifting device and its load. For safety reasons, this additional wheel arm may need to have a safety catch and/or release to ensure that when it is in use it cannot allow any sudden movement or rotation of the frame and cause injury to the operator.It may also have a spring or other impeller, situated in any convenient place in the construction, to move it out into the "fail safe" position, and possibly also a latch or similar safety locking device to keep it in the "fail-safe" position.

The release of this latch can be by means fitted to the operating handle or arm.

My invention is illustrated in the attached drawings, which are schematic and not to scale, and in which Figures 1, 2 and 3 represent views (in perspective, side view and plan view respectively) of a simple form of my invention.

Figures 4 and 5 represent views of the included movable third wheel, to provide stability under load conditions.

In Figures 1, 2 and 3, a frame is made up of a cranked bar or arm (1) and two bars (2) attached to a cross member (3) so as to form, the two arms of a lever system, set at an angle to each other.

The far ends of the two bars (2) are joined together to form, with the cross member (3), a triangular structure. A strengthening tie-bar (4) is arranged to link the apex of the triangular structure to the cranked arm (1). The tie bar (4) carried an extension (7) which carries a hook or other means (8) for gripping or attachment of a load.

The whole is carried on two wheels (6) mounted at the ends of the cross member (3). The wheels may be fitted with brakes (not shown) if so desired.

In Figure 4, the parts have the same numbering and function as specified above for Figures 1,? and 3 but additionally there is provision for a third wheel (9), carried upon a cranked arm (10) which is in turn connected to the cross member (3) by a pivot (11) on a bracket (12).This arm (10), at the opposite end from the wheel (9), has an operating wire or rod (1 3) attached which is supported on the arm (1 ) by guides (14 and 1 5).The arm (10) is also connected to a spring (16) and an operating handle with a grip or release device (17), which allows the wheel (9) and its supporting arm (10) to move between the position as shown, close to cross-member (3) and another position (shown as (9A) and (1 OA)) in which the wheel (9A) can act as a support by engaging the ground. The spring (16) and the grip or release (17) are arranged to act together so that the wheel (9) on its arm (10) can be moved, and appropriately forced as the operator desires between the normal and the "A" positions. Preferably, the spring (16) forces the wheel (9) towards the "safe" position indicated by "A".

In operation, the device can be wheeled up to the load to be lifted (e.g. an electric motor or pump) and positioned so that the extension arm (7) and hook (8) are over the load. Then, the operator can lower the hook (8) by raising the arm (1) until it is in a convenient position to attach the load. Then, after securing the load to the hook (8), the load can be lifted by downward pressure on the arm (1) until the load is clear of the ground or its mounting.

The whole device, with load attached, can then be moved about on the wheels.

For safer operation, however, the third wheel (9) can be swung away from the cross-member (3) into the position (9a) which allows it to engage the ground. This movement may be by operation of the grip or release (1 7) and with assistance from the spring (16). When in the "engaged" position, i.e. with the third wheel on the ground, it is advantageous to provide means (not shown) which enable the arm (10) to be locked into position (1 0A), for example by suitable engagement with a receiving slot in bracket plate (12). With the wheel (9) in the position (9A), the load is then supported so that the arm (1) cannot fly upwards and injure the operator.When the load has been moved to its new site, the operator can release the load by depressing arm (1) sufficiently to take the weight off the third wheel (9), then retracting the third wheel (9) by operating the grip or release (17), and lowering the load by raising arm (1) and finally disconnecting the load from the hook (8).

In Figure 5, there is shown an alternative arrangement for attaching the movable third wheel, in this case using a pivot which is at the side of the lifting device, and adapted so that it lies in a retracted position adjacent to the axle (3) or in an extended position forward of the axle (3).

The parts have the numbers and functions as for Figure 4. For simplicity of showing this variant, the actuating means, safety locks, and springs are not shown, but can be arranged in a manner very similar to that shown in Figure 4. Also in this arrangement the angle through which the arm moves is much less than 90 degrees (commonly about 45 degrees) so the wheel (9) at its end requires to be set at a corresponding angle to the direction of the arm so that when it swings forward into the "support load" position the wheel (9) in the position (9A) can be substantially in line with the two main wheels.

Claims (7)

1. A mobile lifting device which comprises a frame made up of two arms connected rigidly together at an angle to each other and carried on wheels, one arm being adapted for manual movement by the operator and the other being adapted to be attached to an object to be lifted, and the relationship between the two arms being such that they function as the two arms of a lever about a fulcrum and a force applied to the first arm produces a suitably amplified upward force by the second arm.

2. A mobile lifting device as claimed in claim 1 wherein there is provided an additional wheel carried on a movable member which allows it to be kept out of contact with the ground while the device is being used to lift a load but allows it to be moved into contact with the ground when the load has been lifted and is to be moved.

3. A mobile lifting device as claimed in claim2 wherein the movable member is a swinging arm which can be swung close to the wheels of the frame during use for a lifting operation and also swing forward, underneath the load when that has been lifted, and so stabilise the device as a whole with the load in the lifted position ready for the stage of moving the lifting device and its load.

4. A mobile lifting device as claimed in claim2 or claim 3 wherein there is provided an impeller adapted to urge the movable wheel-bearing member into the "fail-safe" position required for the support of a raised load.

5. A mobile lifting device as claimed in any one of claims2 to 4 wherein the movable wheelbearing member is provided with a locking device to secure it in the extended position.

6. A mobile lifting device as claimed in any one of claims 1 to 5 wherein the frame is provided with one or more bracing members to add strength to the construction.

7. A mobile lifting device substantially as described with reference to the attached drawings.