GB2281062A - Hoist - Google Patents

Abstract

A hoist (10 for lifting patients, for example, comprises a base (11), an upright mast (15) attached at one end to the base (11), a boom (16) pivotally attached to the mast (15) towards the upper end of the mast (15), means (19) for suspending a load, attached towards the end of the boom (16) remote from the mast, and an actuator (20) for moving the boom (16) with respect to the mast (15), wherein the actuator (20) is pivotally attached to the mast (15) at a position (24) towards the upper end of the mast (15) and above the pivotal mounting (22) of the boom (16) to the mast (15), and is also pivotally attached to the boom (16) at a position (25) laterally remote from the mast. Preferably the actuator is an electrically driven, linear screw actuator. <IMAGE>

Description

HOIST This invention concerns a hoist, especially a hoist for lifting patients from, for example a hospital bed or wheelchair or a bath.

The known types of hoist, which have been available since the mid 1960's for this purpose, have an upright mast extending from a base; a lateral boom pivotally attached to the mast towards its upper end; a sling for carrying the patient, which sling is attached to the boom towards the end of the boom remote from the mast; and, an actuator for raising and lowering the boom. Commonly the actuator is pivotally attached to the mast at a position below where the boom is attached with the other end of the actuator being pivotally attached to the boom at a position between where the boom is attached to the mast and where the sling is attached to the boom.

The above described type of hoist suffers from a number of disadvantages, most of which have a common root cause. The basic root cause of the problems primarily relates to the requirement that any person being lifted in the hoist needs to be free in space to enable adequate manoeuvrability without fouling on any part of the hoist.

Therefore, clearly with the known hoist designs there is a chance that the actuator impinges on the space under the hoist boom which the patient may require.

In an attempt to overcome this disadvantage the actuator is attached to the mast at a relatively high position and close to the pivotal attachment of the boom to the mast. As a result of this the geometry of the system has required the use of more powerful actuators than is strictly necessary, a pushing force of 635kg will be required to lift a heavier patient of around 127kg and, having regard to safety factors, the actuator must be able to withstand a substantially greater force than that. The use of such powerful actuators requires that the components of the hoist be strengthened and, consequently, the weight of the hoist be increased.

In addition to the requirement that components be strengthened, in some cases the components employed have to be more exotic and therefore costly. For example the actuator at higher loads has to be connected using ball screws rather than a simple screw and nut arrangement, thereby greatly increasing costs.

Cranked and offset masts have also been used in attempts to overcome problems arising from the position of the actuator but these attempts have given rise to problems of their own, for example causing the hoist to overhang and making it more difficult to negotiate the hoist through doorways.

Even though this problem has been well appreciated for a large number of years unfortunately no one as yet has been able to provide a solution which is both light weight and affordably priced. The present invention is concerned with providing a solution to the problems such that substantial advantages may be achieved.

According to the invention a hoist includes: - a base; - an upright mast attached at one end (its lower end) to the base, and having its other end (its upper end) in free space; - a boom which is pivotally attached to the mast towards the upper end of the mast; - means for suspending a load, which means is attached towards the end of the boom which is remote from the mast; and - an actuator for moving the boom with respect to the mast; wherein the actuator is pivotally attached to the mast at a position towards the upper end of the mast and above the pivotal mounting of the boom to the mast, and is also pivotally attached to the boom at a position laterally remote from the mast.

Now, as will be well appreciated by those skilled in the art, there is a relationship between the geometry of the mast, boom and actuator which directly affects the force which the actuator has to exert to lift a given load. This relationship can be broadly summed up using the following ratio Distance between the mountings for the actuator on the boom and the boom to the mast.

Distance between mountings for the actuator on the mast and the boom to the mast.

where as this ratio is increased so the power required to lift a given load is increased.

Now with the trend in the industry to move the mounting of the actuator to the mast towards the mounting of the boom to the mast, this ratio has been rising significantly and is commonly in the order of 5:1. Although this does have the benefit of increasing the space under the hoist for the patient being lifted it does carry the drawback that it does increase the force which the actuator is required to exert leading to the problems outlined.

Now the invention in accordance with the present invention completely alleviates this problem by positioning the actuator above the boom and therefore not- in the area where it could foul the patient.

Consequently the hoist of the invention is particularly suitable for lifting patients e.g. as already indicated and one advantage arising from the position of the actuator is that the actuator does not form an obstruction to the patient e.g. the patient's knees or feet, irrespective of the particular position of the boom at any time.

Moreover, the actuator does not form an obstacle to bringing the hoist right up to a bed for ease of lifting a patient from the bed or lowering a patient onto the bed.

In hoists made in accordance with the present invention because the actuator is located in a position, above the boom, where it does not constitute an obstruction, there is considerable freedom regarding the geometry of the system, namely the triangle defined by boom to mast, actuator to mast and actuator to boom. In particular, the actuator may be relatively long compared with the spacing between the two pivot points on the mast and this means that very powerful actuators are not essential nor are associated components required to be exceptionally strong and therefore heavy.

As a consequence of the above mentioned advantage, the ratio mentioned above can be lowered without any loss of operational performance. The force required to be exerted by the actuator is correspondingly reduced so overcoming the problem.

A hoist made in accordance with the present invention, preferably, has a ratio of Distance between mountings for the actuator to the boom and the boom to the mast Distance between mountings for the actuator to the mast and the boom to the mast in order of 2:1 to 3:1 and, most preferably in the order 2.25:1 to 2.75:1.

Any suitable actuator means may be used in an invention made in accordance with the present invention. However, preferably the actuator used is a screw actuator, most preferably an electrically driven linear screw actuator.

Clearly, the hoist should be provided with means to prevent it from tipping over when a load is being lifted. Any suitable means may be employed but in a preferred embodiment the length of the base is controlled to effect the necessary control.

In a particular arrangement the base length is 2/3 that of the height of the hoist.

Alternatively the base may be provided with means to fixedly attach the hoist to a bed frame or the like. Instead means may be provided to fixedly attach the hoist to the floor.

In one embodiment the hoist may be free standing and the base thereby comprises a pair of legs interconnected by means of a crossbar located towards one end of the legs, the mast extending upwardly from said crossbar.

The crossbar may be hinged so that the legs can be deployed at any suitable angle to each other to assist in positioning the hoist with respect to a bed, chair and bath or the like. Means may be provided to lock the legs in any predetermined position.

The base is preferably provided with castors to assist movement.

At least one handle but preferably two may be provided on the hoist to further assist movement of the hoist, which handles may be mounted one to each side of the mast.

The operations of the hoist may be controlled by a simple switch mounted on the mast the boom or the actuator or by means of a remote control handset.

The invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a side elevation of a hoist in accordance with the invention; and Figure 2 is a plan view of the hoist of Figure 1.

In the Figures the hoist 10 comprises a base 11 having two parallel legs 12 and 13, interconnected by means of a crossbar 14 located towards one end of the legs, a mast 15 fixed at one of it's ends towards the centre of the crossbar 14, a boom 16 having a first portion 17, a second portion 18 and load suspension means 19, an electrically driven actuator 20 which interconnects the mast 15 and the boom 16, and handles 21 suspended from the suspension means 19 to the mast 15.

One end of portion 17 of boom 16 is pivotally mounted to the mast 15 at point 22, the other end of portion 17 is fixedly welded at 23 to one end of the second portion 18 and suspension means 19 pivotally mounted to the other end of the second portion 18.

One end of actuator 20 is pivotally mounted to the mast 15 at point 24 the other end of the actuator is pivotally connected to the boom 16 at point 25 on portion 18.

Controls are provided on panel 26 connected to the actuator and conveniently detachably mounted on the boom 16.

Castors 27 are provided on the base 11 for ease of movement, together with handles 28 mounted on the mast to further assist movement of hoist.

In this embodiment the crossbar 14 is hinged so that the legs 12 and 13 can be deployed at any suitable angle to each other to assist in positioning the hoist with respect to a bed, chair or bath for example.

A lever 29 is provided to lock the legs in any predetermined position.

In use it can be seen that extending the actuator causes the boom to be lowered whilst reducing its length causes the boom to be raised.

To assist in further understanding the inventions the relevant distance defined in the ratio are as follows: D = Distance between the mountings for the actuator to the boom and the booms to the mast; and d = Distance between the mountings for the actuator to the mast and the boom to the mast.

Any suitable sling or other device may be employed for lifting a patient, an example 30 of which is shown in Figure 1.

Claims (20)

1. A hoist including - a base; - an upright mast attached at one end (its lower end) to the base, and having its other end (its upper end) in free space; - a boom which is pivotally attached to the mast towards the upper end of the mast; - means for suspending a load, which means is attached towards the end of the boom which is remote from the mast; and - an actuator for moving the boom with respect to the mast; wherein the actuator is pivotally attached to the mast at a position towards the upper end of the mast and above the pivotal mounting of the boom to the mast, and is also pivotally attached to the boom at a position laterally remote from the mast.

2. A hoist as claimed in Claim 1 wherein the ratio between the distance between the mountings for the actuator on the boom and the boom to the mast, and the distance between the mountings for the actuator on the mast and the boom to the mast is in the range 2:1 to 3:1.

3. A hoist as claimed in Claim 2 wherein the ratio is in the range

2.25: 1(9:4) to 2.75:1. (11:4).

4. A hoist as claimed in any one of Claims 1 to 3 wherein the actuator is a screw actuator.

5. A hoist as claimed in Claim 4 wherein the actuator is an electrically driven linear screw actuator.

6. A hoist as claimed in any one of Claims 1 to 5 wherein the base length is two thirds that of the height of the hoist.

7. A hoist as claimed in any one of Claims 1 to 6 wherein the operations of the hoist are controlled by a switch mounted on the mast.

8. A hoist as claimed in any one of Claims 1 to 6 wherein the operations of the hoist are controlled by a switch mounted on the boom.

9. A hoist as claimed in any one of Claims 1 to 6 wherein the operations of the hoist are controlled by a switch mounted on the actuator.

9. A hoist as claimed in any one of Claims 1 to 6 wherein the operations of the hoist are controlled by a switch mounted on the mast.

10. A hoist as claimed in any one of Claims 1 to 6 wherein the operations of the hoist are controlled by means of a remote control unit.

11. A hoist as claimed in any one of Claims 1 to 10 wherein the base is provided with means to fixedly attach the hoist to a bed frame or the like.

12. A hoist as claimed in any one of Claims 1 to 10 wherein the base is provided with means to fixedly attach the hoist to the floor.

13. A hoist as claimed in any one of Claims 1 to 10 wherein the base comprises a pair of legs interconnected by means of a crossbar located towards one end of the legs.

14. A hoist as claimed in Claim 13 wherein the mast extends from the crossbar.

15. A hoist as claimed in either of Claims 13 or 14 wherein the crossbar is hinged to enable the legs to be deployed at any suitable angle to each other.

16. A hoist as claimed in Claim 15 wherein means is provided to lock the legs in any predetermined position.

17. A hoist as claimed in any one of Claims 1 to 16 wherein the base is provided with castors.

18. A hoist as claimed in any one of Claims 1 to 17 wherein there is provided at least one handle.

19. A hoist as claimed in Claim 18 wherein a pair of handles are provided one to each side of the mast.

20. A hoist substantially as hereinfore described with reference to the accompanying drawings.