AU642484B2 - Patient hoists - Google Patents

Description

1- 642484 COMMONWEALTH OF AUSTRALIA Patents Act 1952 0* OS

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Name of Applicant J. NESBIT EVANS CO. LTD.

Address of Applicant: Unit 8, Woodsbank Trading Estate, Woden Road, West, Wednesbury, West Midlands, 7BL, England Actual Inventor JOHN MERVYN CROXTON Address for Service GRANT ADAMS COMPANY, Patent Trade Mark Attorneys, Level 9, National Mutual Centre, 144 Edward Street, BRISBANE. QUEENSLAND. 4000

AUSTRALIA.

COMPLETE SPECIFICATION FOR THE INVENTION ENTITLED: "PATIENT HOISTS" The following statement is a full description of the invention including the best method of performing it known to us.

so 0 PATIENT HOISTS THIS INVENTION relates to mobile patient hoists of the kind described in prior Australian Patent No. 288887 in which a chair or other patient support can be lifted and lowered relative to a wheeled chassis.

The hoisting mechanism comprises a crank handle on a first fixed axis which turns a sprocket to displace a roller chain. The chain is coupled to a second sprocket freely hanging in a bight, and the limb of the bight opposite to that engaged by the crank driven sprocket is fixed. So the handle, which may have a mechanical advantage of for example 8:1 gains a further 2:1 by the chain system which can raise or lower the second sprocket carrying the load.

The crank is connected to the first sprocket by a screw and nut mechanism via a clutch annulus of friction material and a free-wheel which in a commercially available construction under the patent has been a ratchet device.

Raising involves crank movement in the appropriate direction to cause tightening of the screw to grip the friction annulus against the free-wheel to S.turn it in the permanently free direction and thus turn S•the sprockets correspondingly.

"i 0 25 Lowering involves the opposite direction crank movement to loosen the screw and free the friction disc which allows the sprocket to turn the free-wheel in the controlled movement direction, but this latter movement tightens up the nut on the screw, reclamps the friction 0 disc and brings the movement to a halt. However, continued movement of the crank handle in the :appropriate direction keeps tho screw turning in the loosening direction as fast as the nut moves in the tightening direction caused by the load displacing the 35 chain and sprockets, and allows lowering to be continuous.

One disadvantage of this mechanism is that it calls for care by the nurse or orderly particularly in the apparently simple task of lowering a patient. If the patient is to be lowered into a bath, for example, and the seat comes to rest on the edge of the bath because of misalignment, continued turning of the handle in the same direction can result in the seat becoming unbalanced, and the patient is then at risk.

The object of the invention is to provide improvements.

According to one aspect of the invention a mobile patient hoist device comprising: a seat support which can be raised and lowered; an endless loop of chain which extends vertically between an upper drive sprocket and a lower idle sprocket, each journalled on fixed axes, the seat support being connected thereto to be raised and lowered on rotation of the drive sprocket; and a crank handle operatively connected to the drive sprocket via a connection including a screw and S nut mechanism, said nut turning on said screw to engage, via a friction means, a one way free wheel on rotation 25 of the crank to rotate thereby the drive sprocket and raise the seat support, rotation oppositely lowering the seat support.

Preferably -the loop is driven by a second endless loop of chain which can provide a gear reduction between the driving crank handle and the load which is then is not fixed at 2:1. It can easily be of the order of 3:1 or 4:1 for example and without limitation; enabling the same size of crank handle as in the prior art to give e.g. a 50% or 100% increase in mechanical kLjA 35 advantage, or the same mechanical advantage with substantial reduction in handle length or any other desired compromise or variation. The higher mechanical advantage is preferred not only for nurse fatigue reasons but because more gentle movements result if the **ee *ee o e*

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handle is turned at uniform rate.

Some embodiments of the invention together with certain variations and modifications therein are now more particularly described with reference to the accompanying diagrammatic drawings, wherein:- FIG. 1 is a part-exploded perspective view of a first form of patient hoists; FIG. 2 is a diagrammatic side elevation thereof; FIG. 3 is a diagrammatic plan view thereof; FIG. 4 is diagram of jacking mechanism of said hoist; FIG. 5 is a sectional view of a manual drive of said mechanism; and FIG. 6 is a sectional view of an alternative form of said manual drive.

Referring firstly to FIGS. 1, 2 and 3, a patient hoist includes a chassis 10 of generally conventional construction comprising a pair of parallel spaced side members 12 at near ground level connected by a cross member 14 adjacent one end. A vertical mast 16 is mounted rigidly at the centre of cross member 14 and the side members 12 are provided with ground o: engaging castor action wheels 18 so that the entire 25 hoist, with or without a patient thereof, can be manually propelled to the required location. Brakes (not shown) will be provided acting on one or more of the wheels 18. The cross member 14 may be telescopic or otherwise adjustable in effective length for varying the 30 track to provide added stability if the hoist is ••.operable to raise a patient to a high level or off- 06.° centre, but allowing the track to be reduced to a minimum for manoeuvering through narrow doors or into and out of restricted locations such as a toilet .i 35 cubicle.

Handlebars 19 are provided near the top of mast 16 for propelling and manoeuvering the hoist.

A patient support element in the form of a rigid cantilever jib seat support arm 20 is guided for vertical movement up and down mast 16. As best seen in FIG. 1 arm 20 is generally of inverted V-shape with a shorter proximal limb 21 cranked downwardly parallel to a side face of mast 16 and the end of that limb engaged in a socket of a slider formation 22 running in a vertical slot in the side of mast 16 for guidance and for operation by jacking mechanism of the hoist referred to hereafter. A median portion of arm 20 thus extends forward of mast 16 and to one side thereof angled as best seen in FIG. 1 with a longer distal limb 24 extending downwardly and somewhat away from the centre line of the hoist.

An annular seat support ring 26 is rigidly attached to the lower end of the limb 24 to lie in a horizontal plane somewhat below the level of formation 22 and substantially centered in the horizontal plane with respect to the hoist as a whole. A seat 28 is mounted on support ring 26 by means of a large diameter ring bearing 30 (shown in exploded relationship in FIG.

S.1) so that the seat is captive thereon but can rotate 25 about the axis of ring 26 with respect to the remainder of the hoist.

The seat may be provided with fixed, 5*O adjustable and/or removable arms and backrest and/or :...various forms and shapes of seat may be provided which can be interchangeably mounted on the ring 26.

The form of seat shown in the drawings has a .central through aperture so that it can itself serve as :a toilet seat. In the form shown in FIGS. 1 to 4 the seat has an integral backrest 29 and a pair of seat arms 0 35 31 whose inner ends are pivotal to the backrest. Arms 4 31 are cranked so that they extend round towards the front of a patient's waist as shown in full lines in FIG. 1 for added security, but can be swung clear upwardly and outwardly to the positions shown in broken lines to facilitate manoeuvre of the patient onto or off the seat.

The facility for rotating the seat with a patient thereon and the cranked and offset shaping of the jib arm 20 renders the hoist particularly adaptable and convenient in use.

The hoist can be positioned at the side or end of a bed or bath. Seat 28 can be angularly positioned by rotation for the most convenient transfer of the patient from or to a bed e.g. either from a sideways sitting position on the bed or from a position sitting or lying longitudinally of the bed; the patient can be lowered into a bath, again from the side or end by rotating the seat to the appropriate alignment, the shape of arm 20 allowing the seat to be fully lowered into the bath by spanning its side indicated in broken lines at 32 in FIG. 2. A particular advantage of the above arrangement is that a patient may be taken to the S.toilet and may use it while remaining seated on the hoist, the rotation of seat 28 enabling him or her to be positioned facing mast 16 so that the hoist can be positioned in even a narrow toilet cubicle, i.e.

sideways access to the toilet itself is not necessary.

Preferably an indexing catch or detent is provided enabling the rotating seat to be selectively 30 locked against rotation at predetermined angular

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S. locations. Typically said locations will include the forward and rearward facing positions and positions facing to either side, i.e. at intervals of 900 about *0 the axis of rotation.

35 I 35 If other forms of patient support element are needed jib arm 20 with the seat thereon is simply freed from the socket of formation 22 by releasing a safety catch (not shown) and lifting it clear. Other elements and associated lifting or carrying tackle can then be mounted to formation 22. Thus a longer and taller sling jib arm 20 as shown in broken lines in FIG. 1 may be substituted, having hooks for a hammock type seat or other sling.

The hoist further includes jacking mechanism for the controlled raising and lowering of the patient support, a preferred arrangement being shown diagrammatically in FIG. 4. An endless loop of sprocket chain 34 extends within mast 16 passing round a drive sprocket 36 at the top of the mast and an idler sprocket 38 near the bottom of the mast, one flight of the chain being coupled to the slider formation 22. Thus, by rotation of sprocket 36 in the appropriate direction the load is positively raised and lowered in a controlled manner, in particular, there can be no accumulation of slack if the descent is obstructed which would give the risk of sudden uncontrolled dropping or movement of the load if the hoist is moved away from the obstruction.

To provide mechanical advantage for reducing the effort needed to raise the patient the drive input 25 to sprocket 36 will preferably be by way of a step-down sprocket and chain or epicyclic or other geared transmission 40 mounted at the top of the mast, operation being a crank handle 42 to the rear of the mast.

To ensure positive and controlled raising and .0o lowering the drive transmission will preferably include a self-braking device whereby the load is automatically held at the selected height and will not drop unless and until the crank handle 42 is turned in the appropriate 35 direction, and then only in a manner under positive 5drcin control by operation of the handle. It is preferred that the mechanism does not include conventional clicktype ratchet devices as silent operation is desirable e.g. if the hoist should need to be used at night while other patients are asleep.

Two forms of self-braking device are shown in FIGS. 5 and 6 both operating on the same general principles.

Referring firstly to FIG. 5 a shaft journalled in a cylindrical housing 52 has an output sprocket 54 fixed thereon, said sprocket forming part of the transmission 40 referred to above.

The crank handle 42 includes a hub in the form of a nut 56 in screw engagement with a threaded outer end portion of shaft Sandwiched between an inner radial face of nut 56 and an opposing radial face of sprocket 54 is a free-wheel device 58 between a pair of annular clutch discs 60 of high friction material.

Free-wheel device 58 is a silent sprag-type one way drive device having radially outer and inner members including ramp formations coacting with balls or 0* .rollers to provide a wedging action which will transmit drive in one direction of rotation but allow the members 25 to rotate freely relative to each other in the opposite direction. The radially outer member of the device 58 is secured within housing 52 so that it cannot rotate while the inner member is free to rotate relative to shaft 50 but is acted on axially by the clutch discs 30 Turning handle clockwise will tighten nut 56 on shaft 50 so clamping the inner member of device 58 :between disc 60 to rotate along with the shaft and sprocket 54, the free-wheel device permitting free rotation in this direction which will be for raising the 35 hoist seat. As soon as the winding ceases the loading 8 on sprocket 54 exerted by gravity is transmitted fron sprocket 54 to the remainder of the mechanism to maintain the braking as the screw remains tightened and the free-wheel device prevents anti-clockwise rotation.

However, if controlled lowering is to be effect. handle 42 will be turned in the opposite direction tending to unscrew the nut 56 so allowing rotation of the shaft and sprocket independently of the free-wheel device, though the lowering will be controlled in that any tendency of sprocket 54 to overtake the speed of rotation of handle 42 will re-apply the brake, thus raising and lowering is always achieved in a smooth aid positively controlled manner.

FIG. 6 shows an alternative construction of the above mechanism. In this case nut 56a to which handle 42 is attached is fast with shaft 50a and the sprocket 54a is in screw threaded engagement with an inner end part of shaft 50a. The free-wheel device 58 and clutch disc 60 are sandwiched between hub 56a and sprocket 54a to act as described aboe.

Other forms of free-wheel device may be used.

A form having the desirable property of smooth and silent operation as above utilises a wound helical spring which is tightened onto a drum or shaft in one 25 drive direction but is slackened to allow free rotation in the opposite drive direction.

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Claims (4)

1. A mobile patient hoist device comprising: a seat support which can be raised and lowered; an endless loop of chain which extends vertically between an upper drive sprocket and a lower idle sprocket, each journalled on fixed axes, the seat support being connected thereto to be raised and lowered on rotation of the drive sprocket; and a crank handle operatively, connected to the drive sprocket via a connection including a screw and nut m~echanism, said nut turning on said screw to engage, via -i friction means, a one way free wheel on rotation of the crank to rotate thereby the drive sprocket and raise the seat support, rotation oppositely lowering the seat support.

2. A device as claimed in c'laim 1 wherei.n: said endlesq loop of chain runs on sprockets journalled on fixed axes as aforesaid and a stepdown sprocket and chain, system operatively connects rotation of the crank handle to the drive sprocket.

A device as claimed in claim 1 wheroin: the crank handle drives the nut of said ***:screw and nut mechanism so that in one direction of rotation of the handle the rnut tightens the friction *disk onto the free-wheel to turn the latter in a permanently free direction and a second friction disk 9 9also tightened by the nut drives the sprocket.

4. A device as claimed in Claim 3 wherein: 30 turnin~g the handle in the opposite direction loosens the friction disks whereas rotaticsi of the screw by gravity acting on the seat tightens the friction disks. A mobile patient hoist substantially as >.hereinbefore described with reference to and as shown in hereinbefore described with reference to and as shown in FIGS. 1 to 4; or FIGS. 1 to 4 with the addition of FIG. or FIG. 6 of the accompanying drawings. DATED this seventeenth day of August 1993. J. NESBIT EVANS CO. LTD., by its Patent Attorneys, GRANT ADAMS COMPANY. e: ABSTRACT PATIENT HOISTS Mobile hoist for lifting, transporting and lowering patients or other subjects with impaired mobility includes a wheeled chassis (10) mounting a rigid vertical mast (16) at one end having a slider formation (22) guided for vertical movement thereof in a controlled self-braking manner by jacking mechanism actuated by a crank handle A cantilever arm or jib (20) extends from said formation cranked both in the vertical aspect so that it can reach over the side of e.g.a bath and in plan somewhat to one side of the centre line of the hoist, its outer end carrying a seat support ring A seat (28) having an open centre so that it can be used for toilet purposes is rotatable on the ring relative to the remainder of the hoist so that a subject seated thereon can be turned to face at least to the front or rear of the hoist. oft *t ft ft f