GB2393709A

GB2393709A - Worm drive for overhead crab

Info

Publication number: GB2393709A
Application number: GB0323034A
Authority: GB
Inventors: Ole Boegh Soerensen
Original assignee: V Guldmann AS
Current assignee: V Guldmann AS
Priority date: 2002-10-01
Filing date: 2003-10-01
Publication date: 2004-04-07
Anticipated expiration: 2023-10-01
Also published as: GB2393709B; GB0323034D0

Abstract

The invention concerns a drive, preferably for an overhead crab, including at least one set of drive wheels (2), at least one shaft member (8), at least one bearing (7), a drive arrangement (10) and a plate part (3), where the drive wheels (2) are mounted around the at least one bearing (7), which is connected to the plate part (3) with the at least one shaft member (8), where the drive wheel set is disposed with at least one drive wheel (2) at each their side of the plate part (3), where each drive wheel (2) has a front side and a rear side that is connected to a contact surface, and where the drive arrangement (10) is provided for transmitting power from a motor (not shown) to the drive wheels (2), where the drive arrangement (10) includes a rotatable worm wheel (1) disposed in a cutout (14) in the plate part (3), the worm wheel (1) being adapted and arranged to engage the set of drive wheels (2) that are provided with worm gear teeth. Preferably, the device forms part of an invalid lifting apparatus.

Description

CRAB DRIVE AND DEVICE FOR TRANSPORTING A PERSON

The present invention concerns a drive, preferably tor an overhead crab, including at least one set of drive wheels, at least one shaft member, at least one bearing, a drive arrangement and a plate part, where the drive wheels are mounted around the at least 5 one bearing, which is connected to the plate part with the at least one shaft member, where the drive wheel set is disposed with at least one drive wheel at each their side of the plate part, where each drive wheel has a front side and a rear side that is connected to a contact surface, and where the drive arrangement is provided for transmitting power from a motor to the drive wheels.

In connection with work place evaluation, much attention is given to heavy and awk ward lifting not to be done in connection with one's work. In the hospital and care sector, heavy lifting may be when e.g. a nurse is to lift a patient or a disabled person from one position to another position, as e.g. when transporting a patient from a bed to 15 a chair/wheelchair.

In order to facilitate the work for the nursing staff, several types of hoisting systems have been developed which can assist with heavy lifts, preferably of persons, from one position to another position.

A type of hoisting system is e.g. designed with a pivotable arm. The patient is placed m a lifting canvas or on a seat while the patient is placed in the bed, after which the nurse/carer by means of a hoisting arrangement lifts the person up from the bed and swings the person away from the bed and across a chair/wheelchair into which the 25 patient is lowered. The drawback of having a hoisting system of this type is that it is stationary and that the work area is limited to the radius of the circle formed by the movement of the pivoting arm.

Another type of hoisting system is designed with an overhead hoisting arrangement.

30 There are different types of overhead hoisting arrangements: The hoisting system is movably attached to a beam running on rails which are

disposed along the outer limits of the desired work area. E.g. the rails may be disposed under the ceiling along two preferably parallel walls, or the rails may be a part of the frame built up around a bed.

The hoisting arrangement is connected via a crab-arrangement to one or more 5 rails where the crab may either can have drive wheels that grip around a rail or run within a rail.

The disadvantages of using a hoisting arrangement movably attached to a beam run-

ning on rails are that: lO. Rails are to be placed with spacing below the ceiling in order that there is space for the crossbar with the hoisting arrangement, causing the lifting height of the hoisting arrangement to be reduced.

Rails are to be supported, either by means of a number of posts, or by using wall/ceiling fittings and/or a frame, whereby the space for moving patients is 15 substantially reduced, and such structures may not always be adapted for spaces for sick and disabled people. E.g. on hospitals it may be a drawback if around a bed there is a stand with a hoisting arrangement that blocks against access for equipment for the patient.

20 The hoisting arrangement connected via a crab arrangement is e.g. known from US 4,125,908 and US 6,006,377, both describing hoisting systems where a stretcher/canvas for carrying is suspended in a hoisting arrangement that via a crab may lift and move a person from one position to another position.

25 A drawback of these hoisting systems is that the crab arrangements shown in these two patent publications are mechanically complicated and impractical to manufacture.

Another drawback of the crab arrangements is that power transmission to the wheel shaft from a motor disposed underneath is effected by a chain.

30 In US 4,125,908 is shown how power from the motor is transmitted to the shaft and out to a gear wheel disposed at the side of one of the crab wheels and engaging a rack disposed within at one side of the overhead rail. This implies that the rail is to be spe

cially made so that there is a rack in the rail, which increases to the costs for the rail, and simultaneously a rack will make it difficult to produce a curving rail. Furthermore, there is risk that skew pulling will arise on the wheels of the crab so that the wheels are worn differently, causing the crab to run skew, and there is risk that it may wedge 5 in the rail.

In US 6,O06,377 there is shown a hoisting arrangement suspended in a crab arrange ment where power from a motor is transmitted to the shaft of a centrally placed wheel set of the crab by means of a chain. By transmitting power from a motor to the wheels 10 via a gear wheel/chain transmission, the gear wheels of the motor are to be placed right under the gear wheel of the crab shaft, implying that flexibility in the power transmission is minimal.

It is therefore the purpose of the invention to provide a crab with a drive which is me 15 chanically simple, easy and cheap to produce, and where direct and uniform power transmission to the drive wheels is effected.

This is achieved with a crab including a drive of the kind described in the introduction,

and where the drive arrangement includes a rotatable worm wheel disposed in a cutout 20 in the plate part, the worm wheel being adapted and arranged to engage the set of drive wheels that are provided with worm gear teeth.

In the following, the invention is described as applied to a hoisting system for trans porting a patient, a sick/elderly/disabled person in a hospital or a nursing institution, 25 but the invention may find application in other places, as e.g.: - in moving people about in their own home, - in transporting bags, pallets and materials m a plane storage, - in transporting slaughtered animals in a slaughterhouse, - in assembly line transport of products in a producing plant.

The drive according to the invention is a very simple mechanical construction, since the bearings are mounted directly on the shaft member in a preferred embodiment of

the invention, after which the drive wheels are mounted on the bearings so that a drive wheel is disposed at each their side on the plate section. This means that the weight suspended in the plate part is distributed to both drive wheels whereby the drive wheels are worn evenly, and the risk of the crab beginning to wobble after long time 5 of use, implying inconvenience for the person transported in the hoisting arrangement, is reduced.

In order to achieve possibility of flexible power transmission from motor to the drive wheels, the plate part is provided with a cutout in which there is mounted a worm 10 wheel. This worm wheel engages the worm gear teeth of the drive wheels so that power transmission may occur directly from the motor to the drive wheels via a flexi ble power transmission unit.

By transmitting power directly to the drive wheels via a worm wheel it is possible to 15 simplify the making of the mechanical parts of the crab, as e.g. it is possible to pro duce one type of drive wheels, where the wheel and worm gear teeth are made in one, simultaneously with this drive wheel can be used irrespectively whether it is placed on one or the other side of the plate part of the crab.

20 In order to ensure that the crab has drive wheels with a contact surface providing even driving of the crab in the overhead rail, each drive wheel has been provided with womm gear teeth on the part of the drive wheel facing the plate part. This worm gear toothing may be disposed at the edge between the contact surface and the rear side of the drive wheel. This means that the worm wheel is to have a dimension correspond 25 ing to half of the womm gear teeth.

Alternatively, the drive wheels may have so large diameter so that it is possible to pro vide the drive wheels with womm gear teeth that are only disposed recessed at the rear side, so that the rear side of the drive wheel surrounds a part of the worm wheel. How 30 ever, this implies that the overhead rail is to have larger dimension.

In order to get optimal transmission of power from the drive unit to the drive wheel,

the rotatable worm wheel is provided at an approximately perpendicular position rela tive to the shaft member. This implies that the worm wheel is disposed so that it is preferably tangential relative to the circumference of the inwards facing rear sides, and thereby is achieved the best and longest possible contact between worm wheel and 5 worm gear teeth.

In a preferred embodiment of the invention, during use of the crab, the worm wheel is disposed in approximately vertical position and mounted on the plate part by means of a top bearing and a bottom bearing. These bearings provide for the worm wheel being 10 secured in the same position irrespectively of the direction the worm wheel is turned.

The alternative to this may be a worm wheel disposed in the plate part so that during use it has a preferably horizontal position, however still tangential to the circumfer ence of the drive wheel. This disposition enables different types of power transmission from motor to worm wheel, but requires that the worm wheel is fixed to the plate part 15 by means of end bearings.

In order for the crab to run in the overhead rail, the drive wheels are mounted with bearings on the shaft member. This shaft member, which connects a set of drive wheels to the plate part, is either one throughgoing shaft or two journals.

In a preferred embodiment of the invention, the shaft member is two journals that may be made of the same material and together with the plate part, simplifying the produc tion process for the crab, causing the two drive wheels about the journal not to be me chanically interconnected.

In a second embodiment of the invention, the shaft member is a throughgoing shaft requiring either that the plate part is provided with a hole through which this shaft may be mounted, or that a bearing is fastened to the plate part of the crab, and that there is a device for providing that the through-going shaft stays in place so that it is not running 30 towards one side.

In order to transmit a force for moving the crab, the rotatable worm wheel is con

nected to a motor with a power transmission unit.

In a preferred embodiment of the invention, the power transmission unit is a cardan shaft which Is connected to the worm wheel at one end and to the motor at the other 5 end. By using a cardan shaft tor power transmission, there will be achieved a flexibil ty in the possibilities for using the crab, since a cardan shaft allows power transmis sion even if the motor is not disposed directly below the axial direction of the worm wheel. This implies that the crab can be made with a motor that may be disposed most suitably in the crab arrangement and thereby possibly reduce the size of the crab ar 10 rangement. Furthermore, a crab with a motor transmitting power via a cardan shaft may be used in connection with overhead rails that curve or change direction.

Altematively, instead of a cardan shaft there may be used flex-wire having the same properties as the cardan shaft.

When the worm wheel is disposed so that it has a preferably horizontal position during use of the crab, a chain drive or a toothed belt may be used, besides using of a cardan shaft and/or a flex wire.

20 The motor may be any of the following types: an electrically driven motor, pneumati cally driven motor, a hydraulically driven motor and/or a crank handle. The choice of motor depends on the weight expected to be moved, and whether there is possibility of connection to electric network, hydraulic pumps or air compressors.

25 In a preferred embodiment of the invention, for hospitals and nursing institutions there will be an electrically driven motor which will be used as power source tor the crab in a hoisting system. The electric motors in the hoisting system will all preferably be connected to the same control, so that the nurse/caretaker possess a panel and/or a re mote control *om where they can control both the crab and the hoisting arrangement.

In order to suspend equipment in the crab, as e.g. a hoisting arrangement and a carry ing canvas, the plate part is provided with at least one cutout and/or a hole for sus

pending the equipment for transporting preferably one person. The cutout or hole im plies, that by means of a bracket/strap/brace/hook connection or similar, it is possible to suspend equipment, such as a hoisting arrangement with a carrying canvas/ stretcher/seat on the crab. In order to achieve best possible weight distribution of the 5 weight of equipment/person on the crab drive wheels, the cutout/hole is preferably provided approximately vertically under the shaft member of the crab. If more than one set of wheels is used in a crab arrangement, the hole/cutout is placed in the plate part approximately at the point where the suspended weight is evenly distributed on the drive wheels of the wheel sets.

In order to reduce the wear on different mechanical parts of the crab, they are made of different material. The womm wheel is made of e.g. a material like aluminium, steel or I similar metallic material. The drive wheels are made of a hard and wear-resistant ma terial as e.g. Nylon, PDM plastic or similar plastic material.

If the crab is to be loaded with a very large weight, as alternative to plastic material for making drive wheels metal materials may be used, as e.g. steel, brass, and similar metal materials. Alternatively, the wheels may be built up of a mixture of the above so that the drive wheels themselves may be made of a plastic material, while the teeth 20 may be made of a metal material.

Since the wheels are made in a hard plastic material, the wear on both womm wheel and worm gear teeth is considerably reduced since the hard and smooth plastic surface reduces the friction between the womm wheel and the worm gear teeth on the drive 25 wheels. A drawback in making the drive wheels of a hard plastic material is that the contact surfaces will be hard and smooth, and therefore there will be no great friction between the contact surface and the inner side of the overhead conveyor, and the contact sur 30 face of the drive wheels will not grip well. Therefore, the drive wheels are provided with one or more grooves in their contact surface.

If the groove is an annular groove, it may be provided with a rubber packing/rubber ring that provides the drive wheels with a better grip at the inner side of the overhead rail. Alternatively, the groove may be a annular groove winding from side to side on the contact surface, and in this groove a rubber ring is placed. By the groove winding 5 from side to side on the contact surface, there will be achieved increased contact be tween rubber ring and the inner side of the rail.

The groove in the contact surface may be a row of oblique grooves and/or transverse grooves in which there are mounted rubber mouldings, implying that a better grip is 10 achieved between drive wheel and down onto the surface of the rail. However, it is to be provided that these laid-in rubber mouldings do not have a size causing the crab to jump up and down while running.

Alternatively, the drive wheels may be surrounded by a broad rubber ring having a 15 width corresponding to the contact surface. However, it is to be provided that the rub ber ring is fastened to the drive wheels.

A further alternative is that the drive wheels are made without grooves, but with the overhead rail being provided at the inner side with a rubber coating so that the drive 20 wheels are running on the rubber coating. The wear on the rubber coating will only occur when the crab is running running on the particular area, while the wear on a rub ber ring mounted on the drive wheels will occur all the time.

By increasing the grip of the drive wheels on the inner side of the rail, the precision of 25 the crab during operation is increased, so that the initiation is effected immediately at an even rate, and braking may be effected in a safe way without the crab continuing further, which may be an advantage when transporting e.g. a patient, who cannot en dure jerks and is to be disposed precisely in a bed.

30 A way of using a crab with a drive according to the invention is to provide a device for transporting preferably one person, where the device includes a preferably overhead rail, a crab with a drive according to the invention, a motor, a hoist arrangement and a

bracket with a canvas for carrying.

This structure of the device for transporting a person provides that the entire hoisting system may be made mechanically simple and with dimensions, which are not unnec 5 essarily space demanding, and simultaneously reduce the energy consumption for driving the crab.

The preferred embodiment is described by way of example with reference to the drawings, where: Fig. I shows a perspective view of a drive embodying the invention, and Fig. 2 shows a perspective view of a worm wheel engaging a drive wheel set. I In the embodiment of the invention on Fig. I appears a drive arrangement 10 for a crab 15 (not shown), including a worm wheel I which is mounted in a cutout 14 in plate part 3 with a top bearing 6 and a bottom bearing 5. Worrn wheel I is disposed so that it engages the worm gear teeth 11 shaped in drive wheel 2. The worm gear teeth 11 on drive wheel 2 are disposed so that they face the plate part 3, enabling that worm wheel 1, which is disposed at the ccntre of plate part 3, to engage both worm gear teeth 1 1 on 20 the drive wheels 2.

Drive wheels 2 are mounted on bearings 7 fastened to shaft member 8, where the shaft member 8 is fastened to plate part 3.

25 On contact surface of drive wheel 2 is provided an annular groove 15 in which there may be mounted a rubber ring/rubber sealing (not shown) in order to increase the drive wheel 2 engagement at the inner side of a rail (not shown).

Cardan shaft 4 Is connected to lower part of worm wheel 1, and at the other end it is 30 provided with a ball 12 for coupling to a motor (not shown). This power transmission with a cardan shaft 4 implies that the crab 10 has possibility of a relatively free move ment relative to the motor (not shown), and therefore it is possible for the crab to in

interact with overhead rails (not shown) that curve or change their direction.

In plate part 3 is provided a hole 13 which is placed approximately directly vertically under the shaft part 8.

On Fig. 2 is seen the drive wheels 2 that each are provided with a half worm gear toothing 11 engaging the worm wheel 1. It is seen here that the drive wheels 2 are Identical, reducing the costs of making drive wheels 2 since only one type of drive wheel 2 is to be made. At the bottom of worm wheel I is placed a cutout 16 used when I 0 coupling a cardan shaft 4 (not shown).

Claims

1. Drive, preferably for an overhead crab, including at least one set of drive wheels (2), at least one shaft member (8), at least one bearing (7), a drive arrangement (10) 5 and a plate part (3), where the drive wheels (2) are mounted around the at least one bearing (7), which is connected to the plate part (3) with the at least one shaft member (8), where the drive wheel set Is disposed with at least one drive wheel (2) at each their side of the plate part (3), where each drive wheel (2) has a front side and a rear side that is connected to a contact surface, and where the drive arrangement (10) is 10 provided for transmitting power from a motor to the drive wheels (2), characterized in that the drive arrangement (10) includes a rotatable worm wheel (1) disposed in a cutout (14) in the plate part (3), the womn wheel (1) being adapted and arranged to engage the set of drive wheels (2) that are provided with worm gear teeth ( 1 1).

15

2. Drive according to claim 1, characterized in that each drive wheel (2) is provided with womm gear teeth ( I 1) on the part of the drive wheel (2) facing the plate part (3).

3. Drive according to any of claims I - 2, characterized in that the rotatable worm wheel (1) is disposed at an approximately perpendicular position relative to the shaft 20 member (8).

4.. Drive according to any of claims I - 3, characterized in that the shaft part (8) connecting one set of drive wheels (2) to the plate part (3) is either one through-going shaft or two joumals.

5. Drive according to any of claims I - 4, characterized in that the drive wheels (2) are provided with one or more grooves ( 15) in their contact surface.

6. Drive according to any of claims I - 5, characterized in that the rotatable worm 30 wheel (1) is connected to the motor via a power transmission unit.

7. Drive according to claim 6, charactcrised in that the power transmission unit is a

cardan shaft (4)

8. Drive according to any of claims I - 7, characterized in that the plate part (3) is l provided with at least one cutout (14) and/or hole (13) for suspending equipment for l 5 transporting e.g. a person.

9. Drive according to any of claims I - 8, characterized in that the drive wheels (2) are made of a hard and wear-resistant material, e.g. nylon, PDM-plastie or similar plastic material.

10. Device for transporting e.g. a person, characterized in that the device includes an overhead rail, a crab with a drive according to any of claims I - 9, a motor, a hoist and a bracket with a canvas for carrying.

15

11. A device for transporting a person substantially as herein described with reference to Figs. I and 2 of the drawings.