GB2463668A

GB2463668A - A powered drive assembly for use with a trolley

Info

Publication number: GB2463668A
Application number: GB0817157A
Authority: GB
Inventors: Carl Fothergill
Original assignee: Leec Ltd
Current assignee: Leec Ltd
Priority date: 2008-09-19
Filing date: 2008-09-19
Publication date: 2010-03-24
Anticipated expiration: 2028-09-19
Also published as: GB2463668B; GB0817157D0

Abstract

A powered drive assembly 30 for a wheeled trolley having a frame 12 on which are mounted a plurality of wheels 14 which enable the trolley to move across the ground. The drive assembly 30 includes a wheel 32 which is drivingly rotated by power means (34, figure 4). The drive wheel 32 is rotably carried by a linkage assembly which is adapted for connection to the main frame 12 of the trolley 10. The linkage assembly is movable between first and second configurations in each of which the rotation of the wheel 32 when in contact with the ground urges the linkage assembly 50 to press the wheel 32 into contact with the ground. The linkage assembly 50 may be provided as a rocking link capable of moving in a rotary direction about the axis of the wheel 32.

Description

A POWERED DRIVE ASSEMBLY

The present invention relates to a powered drive assembly for driving a wheeled trolley across a floor and to a wheeled trolley including such a drive assembly.

In particular but not exclusively the invention is concerned with a wheeled trolley of the type used in hospitals or mortuaries for moving patients or bodies from one location to another. This type of trolley typically includes a frame having four ground engaging wheels. The wheels are usually castor wheels to enable the trolley to be easily moved in any direction particularly when negotiating tight corners or positioning the trolley next to a location for transfer of a patient or body to/from the trolley.

Usually the ground engaging wheels of the trolley are free running and so movement of the trolley is effected by an operative pushing or pulling the trolley in the desired direction. Over a working day it will be appreciated that this activity can be extremely tiring for the operative particularly bearing in mind that these trolleys will be heavy when loaded with a patient or body.

A general aim of the present invention is to provide a powered drive assembly for a trolley which enables the trolley to be driven across a floor under the control of an operative.

A particular aim of the invention is to provide a powered drive assembly for a trolley which enables the trolley to be driven across a floor without detracting from the manoeuvrability of the trolley.

According to a first aspect of the invention there is provided a powered drive assembly for a wheeled trolley having a main frame on which are mounted a plurality of ground engaging wheels which enable the trolley to move across the ground, the drive assembly including a ground engaging drive wheel which is drivingly rotated by rotary power means, the drive wheel being rotably carried by a linkage assembly which is adapted for connection to the main frame of the trolley, the linkage assembly being moveable between first and second configurations in each of which the rotation of the wheel when in contact with the ground urges the linkage assembly to press the wheel into contact with the ground irrespective of the direction of rotation of the wheel, the linkage assembly being rotatable in respectively opposite directions in order to attain the respective first and second configurations.

Various aspects of the present invention are hereinafter described with reference to the accompanying drawings, in which: Figure 1 is a schematic perspective view of a trolley according to a first embodiment of the invention; Figure 2 is a schematic side view of the drive assembly of Figure 1 when arranged to drive the trolley in a rearwards direction; Figure 3 is a schematic side view of the drive assembly of Figure 1 when arranged to drive the trolley in a forwards direction; Figure 4 is a more detailed side view of the drive assembly of Figure 1; Figure 5 is a plan view of the drive assembly as shown in Figure 4; Figure 6 is a perspective view, partly exploded, of the drive assembly shown in Figure 4; and Figure 7 is a part perspective view of a second embodiment according to the present invention.

In Figure 1 there is shown a typical trolley 10 with which the present invention is concerned. The trolley 10 includes a main frame 12 having four ground engaging castor wheels 14. The trolley 10 further includes a body tray or mattress supporting frame 16 upon which a body or patient may be supported for conveyance by the trolley 10.

The supporting frame 16 is connected to the main frame 12 by a conventional scissor frame assembly 18 to enable the height of the supporting frame to be adjusted relative to the ground. Raising and lowering of the supporting frame 16 is preferably conventionally achieved by a hydraulic ran unit connected between the main frame 12 and the scissor frame assembly 18.

In accordance with a first embodiment of the present invention the trolley 10 is provided with a powered drive assembly 30 which is operable to drive the trolley 10 in a forwards or rearwards direction across the ground.

The drive assembly 30 includes a ground engaging drive wheel 32 which preferably is formed from a high friction material such as, for example, a rubber tyre 33 to provide good ground engaging traction. The drive wheel 32 is preferably fixedly mounted on a drive shaft 38 which is rotably mounted in a housing 36 having a pair of opposed side walls 37 joined together and spaced apart by a top wall 40.

The drive wheel 32 is located in between the side walls 37 with the lower portion of the drive wheel projecting below the side walls 37. The axis of rotation of the wheel 32 defined by the drive shaft 38 is fixed and is arranged to extend perpendicularly to the side walls 37.

The housing 36 is mounted on the main frame 12 such that the axis of rotation of the wheel 32 is generally perpendicular to the longitudinal axis of the main frame 12.

Accordingly rotation of the wheel 32 in one direction drives the trolley 10 in one longitudinal direction (i.e. a forwards direction) and rotation of the wheel 32 in the opposite direction drives the trolley 10 in the opposite longitudinal direction (i.e. a rearwards direction).

The drive wheel 32 is movably mounted on the main frame 12 by a linkage assembly 50 of which the housing 36 forms part. In this respect the housing 36 defines a terminal rocking link of the linkage assembly 50.

The linkage assembly 50 is arranged to respond to the rotation of the wheel 32 in either direction when in engagement with the ground so as to urge the wheel 32 toward the ground and so in effect press the wheel 32 in a groundwards direction and so maintain traction with the ground regardless of the direction of rotation of the wheel 32. In principle this is achieved by using the rotational reaction force of the wheel 32 to press the wheel 32 into engagement with the ground.

An embodiment of a suitable linkage assembly 50 will now be described in combination with Figures 1 to 6.

In the illustrated embodiment the linkage assembly 50 further includes a first link member 52 and a second link member 54.

The first link member 52 is pivotally connected by pivotal connection 60 at one end to the rocking link 36 (i.e. the housing 36) at a location on the forwards side of the rotational axis of the wheel 32 and is pivotally connected by pivotal connection 61 at its opposite end to the main frame 12 at a location on the rearwards side of the rotational axis of the wheel 32.

The second link member 54 is pivotally connected by pivotal connection 64 at one end to the rocking link 36 at a location on the rearwards side of the rotational axis of the wheel 32 and is pivotally connected by pivotal connection 65 at its opposite end to the main frame 12 ata location on the forwards side of the rotational axis of the wheel 32.

At least one of the pivotal connections between the rocking link 36, first and second link members 52, 54 and the main frame 12 is arranged to be displaceable in order to provide sufficient movement in the linkage assembly 50 to enable the rocking link 36 to rotate about an axis defined by the rotational axis of the wheel 32, as will be explained in greater detail below.

In the embodiment shown in Figures 1 to 6, the pivotal connection 65 is defined by a pivot shaft fixedly mounted on a reciprocal thrust shaft 70. The thrust shaft 70 is mounted for limited reciprocal movement in a thrust bearing 72 which is mounted on the main frame 12, the reciprocal movement of the thrust shaft 70 being in the longitudinal direction of the main frame 12.

In this embodiment the range of reciprocal movement of the thrust shaft 70 permits rotation of the rocking link 36 between a first configuration, as shown in Figure 1, and a second configuration, as shown in Figure 2.

In the embodiment of Figure 7 the thrust shaft 70 arrangement is dispensed with. Instead there is built into the pivotal connections 61, 65 sufficient lateral play to provide the desired rotation of the rocking link 36 between the first and second configurations.

The pivotal connections 61, 65 between the link members 52, 54 and the main frame 12 are defined by pivot rods 67 which are rotably mounted at opposite ends in rotatable bushings 68 mounted on the frame 12. The rotatable bushings 68 additionally permit linear movement.

I Preferably the amount by which the rocking link 36 is permitted to rotate in each direction about the rotary axis of the wheel 32 is limited by co-operating stop formations 90 on the rocking link 36 and first and second link members 52, 54 respectively. In the illustrated embodiment the co-operating stop formations 90 are in the form of a projecting stop arms 91, 92 which project outwardly from respective side walls 37 to abuttingly engage the underside of a respective link member 52, 54.

In use the linkage assembly 50 of each of the aforementioned embodiments acts to maintain wheel 32 in driving contact with the ground in the following manner.

In Figure 2 the wheel 32 is shown rotating in an anti-clockwise direction in order to drive the trolley in, say, a rearwards direction.

The rotational effect of the wheel 32 causes the rocking link 36 (i.e. housing 36) to rotate in a clockwise direction, in the direction indicated by arrow F, about the axis of the wheel 32. Such movement of the link 36 continues until the stop 92 engages beneath link member 52. Accordingly the linkage assembly 50 adopts a first configuration.

The rotational force imparted by the wheel 32 now tends to cause the link member 52 to rotate in a clockwise direction about pivotal connection 61 and so tends to press the wheel 32 further into contact with the ground. The wheel 32 is therefore positively urged to engage the ground when driving the trolley in the rearwards direction.

Similarly the linkage assembly 50 acts to cause the wheel 32 to positively engage the ground when driving the trolley in the opposite, forwards, direction.

In Figure 3, the wheel 32 is shown rotating in a clockwise direction for driving the trolley forwardly.

Such rotational movement of the wheel 32 causes the rocking link 36 to rotate anti-clockwise in the direction of arrow R about the rotational axis of the wheel 32.

Such movement causes the stop 91 to engage beneath link member 54 so as to cause the linkage assembly to adopt a second configuration. Continued rotational force imparted by the wheel 32 then tends to cause the link member 54 to rotate anti-clockwise about pivotal connection 65 and so press the wheel 32 into contact with the ground.

I Accordingly the interaction of link member 54 and rocking link 36 tends to urge the wheel 32 into contact with the ground.

Preferably drive wheel lifting means 80 are provided which are selectively operable by an operator to raise the drive wheel 32 clear of the ground to an inoperative stowed position.

This is desirable as it enables the drive wheel 32 to be positioned clear of the ground and enable free movement of the trolley 10 in any direction using the castor wheels 14 only.

Preferably the lifting means 80 is in the form of a sheathed Bowden (RTM) cable 81 wherein one end of the cable 81 is attached to the top wall 40 of the housing 36 and the other end is attached to an operating mechanism, such as an electrically operated linear actuator 83 operated by a switch on a handle 17 of the trolley.

Alternatively the operating mechanism may be a mechanically operated mechanism such as a lever on the handle 17.

The sheath 84 of the cable 81 is attached to a reaction plate 88 fixedly located with respect to the main frame 12.

Preferably the operating mechanism moves the cable 81 between two positions; a first position corresponding to the raised, stowed, position of the drive wheel 32 whereat the effective length of the cable 81 is shortened by it being retracted into its sheath and a second position corresponding to a lowered operative position of the drive wheel 32 whereat the effective length of the cable 81 is lengthened by it being extended from its sheath.

Preferably the amount by which the effective length of the cable is lengthened is sufficient to permit the wheel 32 to fall below the running level of the trolley as defined by the castor wheels 14 by a desired amount, e.g. by about 40 mm. This in effect enables the wheel 32 to rise above and fall below the running level of the trolley (as defined by the castor wheels) whilst it drives the trolley along the ground and so maintains driving contact with the ground when travelling across uneven surfaces.

It also provides a limit to the permitted drop of the wheel 32 and so permits the trolley 10 to pass over deep indentations in the ground (eg steps, gulleys) without the wheel 32 falling an excessive distance into these indentations.

S Preferably the wheel 32 is driven by an electric motor 34 drivingly connected to one end of the drive shaft 38. The motor 34 is mounted on one of the side walls 37 of housing 36 and so moves in unison with the housing 36 during operation of the drive assembly 30.

Conveniently the electric motor 34 is powered by a battery (not shown) stored on the main frame 12 of the trolley 10.

It will be appreciated that the drive assembly may be fitted retrospectively to standard body or patient trolleys.

Claims

CLAIMS: 1. A powered drive assembly for a wheeled trolley having a main frame on which are mounted a plurality of ground engaging wheels which enable the trolley to move across the ground, the drive assembly including a ground engaging drive wheel which is drivingly rotated by rotary power means, the drive wheel being rotably carried by a linkage assembly which is adapted for connection to the main frame of the trolley, the linkage assembly being moveable between first and second configurations in each of which the rotation of the wheel when in contact with the ground urges the linkage assembly to press the wheel into contact with the ground irrespective of the direction of rotation of the wheel, the linkage assembly being rotatable in respectively opposite directions in order to attain the respective first and second configurations.
2. An assembly according to claim 1 wherein the linkage assembly includes a rocking link on which the drive wheel is rotably mounted, the rocking link being capable of moving in a first rotary direction about the axis of the wheel when the wheel is rotated in one direction and being capable of moving in a second rotary direction about the axis of the wheel when the wheel is rotated in the opposite direction, the rocking link being pivotally carried by at least a pair of link members which are pivotalty movable relative to the main frame and arranged such that movement of the rocking link in either the first or second rotary directions causes the link members and rocking link to move the linkage assembly between the first and second configurations.
3. An assembly according to claim 2 wherein the rocking link has a forward end and a rearward end, the wheel being mounted on the rocking link such that its axis of rotation is located between said forward and rearward ends, and wherein one end of a first of said link members is pivotally connected to the rocking link at a location on the forward side of the axis of rotation of the wheel and the opposite end of the first link member is pivotally connected to the main frame at a location on the rearward side of the axis of rotation of the wheel and wherein one end of a second of said link members is pivotally connected to the rocking link at a location on the rearward side of the axis of rotation of the wheel and the opposite end of the second link member is pivotally connected to the main frame at a location on the forward side of the axis of rotation of the wheel.
4. An assembly according to claim 3 wherein at least one of the pivotal connections between the main frame, first and second link members and rocking link is movable in S the forward/rearward direction to determine the maximum movement of the linkage assembly.
5. An assembly according to any preceding claim wherein the linkage assembly includes one or more attachment members for securing the linkage assembly to the frame by way of at least one connection that permits linear motion so as to accommodate arcuate movement of at least one link member.
6. An assembly according to Claim 5 wherein the said connection is or includes a linear thrust bearing.
7. An assembly according to Claim 5 wherein the said connection is or includes a rotatable bushing that additionally permits linear movement.
8. An assembly according to any of Claims 3 to 7 wherein the rocking link and the first and second link members are provided with co-operating stop formations to limit the extent of rocking rotary movement of the rocking link about the axis of rotation of the wheel.
9. An assembly according to any preceding claim including lifting means operable on the linkage assembly to selectively raise the wheel to an inoperative stowed position whereat the wheel is clear of the ground and to selectively lower the linkage assembly so that the wheel lies in a ground engaging position to drive the trolley.
10. An assembly according to any preceding claim wherein the wheel is driven by an electrical motor mounted on the linkage assembly.
11. A powered drive assembly for a wheeled trolley substantially as herein described with reference to and as illustrated in the accompanying drawings.
12. A patient or body trolley incorporating a powered drive assembly according to any preceding claim.