AU2002210271B2

AU2002210271B2 - Variable height folding undercarriage for a stretcher

Info

Publication number: AU2002210271B2
Application number: AU2002210271A
Authority: AU
Inventors: Adrian Douglas; John Grant-Thomson; John Hilton
Original assignee: Individual
Current assignee: WATT NORMAN
Priority date: 2000-10-23
Filing date: 2001-10-23
Publication date: 2005-11-10
Anticipated expiration: 2021-10-23

Description

WO 02/34191 PCT/AU01/01356 "Variable Height Folding Undercarriage for a Stretcher" BACKGROUND OF THE INVENTION This invention relates to a variable height folding undercarriage which is particularly suitable for transporting a patient on a stretcher. The invention will be described hereinafter as a stretcher transporting undercarriage however it is to be understood that the undercarriage has much wider application as a means for transporting a diverse variety of goods and materials besides people on stretchers.

Stretcher undercarriages have a number of practical disadvantages associated with the means by which the height of their patient carrying platform is raised and lowered, and also their maneuverability at different heights. Various designs have been proposed to enable patients to be loaded at one level and transported or carried at another level, or to enable the entire stretcher undercarriage to be folded and loaded into an ambulance or other transporting means while the patent remains in place. However, since such stretcher undercarriage designs typically involve manual exertion by the attendant in adjusting the undercarriage heights, and maneuvering the undercarriage at different heights, strain is placed upon the attendant which over a period of time can give rise to adverse medical conditions such as back strain.

OBJECT OF THE INVENTION It is therefore the main object of the present invention to provide a variable height, folding stretcher undercarriage which does not place as much strain upon the attendant as conventional designs typically do.

WO 02/34191 PCT/AU01/01356 2 SUMMARY OF THE INVENTION Accordingly, in its broadest aspect, the present invention provides an undercarriage comprising a support platform with two foldable frames thereunder, each of said frames having a pair of spaced wheels at one end thereof and being hinged at the other end and slidable on rails carried by the support platform, wherein the slidable ends of the frames are also journalled to respective worms lying in the plane of the framework which are powered by a servomotor, there being fixed linkages between the respective ends of the support platform and a region on the frames so that when the servomotor is activated to rotate a worm, the end of the frame journalled to the worm moves along the rails and the wheeled end of the frame moves either toward or away from the respective end of the support platform, thereby lowering or raising that end of the platform framework.

According to a second aspect of the present invention there is provided a wheeled undercarriage comprising at least one pair of castor wheels fitted to a frame which is foldable beneath the undercarriage, said castor wheels being located on a common member of the frame which is maintained in a horizontal position during folding of the frame by means of a pair of pivotal arm members of the frame, one of which arm members is cranked at its lower end and provides the main support.

DETAILED DESCRIPTION OF THE INVENTION By providing a stretcher undercarriage with a motor driven power source, the major problems associated with existing manual operable folding designs is effectively alleviated. The problem of maneuverability is addressed by re-designing the arrangement in which the castor wheels are supported for effective castoring. In a common stretcher undercarriage arrangement, there is WO 02/34191 PCT/AU01/01356 typically a fixed pair of wheels on the ends of the forwardly located frame and a castored pair of wheels on the ends of the rearwardly or trailing located frame to facilitate steering. However, steering is only effectively possible with the wheeled frames fully extended since as the frames are retracted, the castoring angle between the frame and the castor wheel support changes, and the directional force through the frame to the castor wheel becomes increasingly greater to pivot the wheel. It therefore becomes more difficult for the attendant to pivot the wheel in the direction in which the undercarriage is to be moved. The above defined arrangement according to the present invention overcomes these problems.

Raising or lowering of the stretcher undercarriage is effected by hand operable controls on one end of the support platform framework, associated with the handles used to move the undercarriage in a forward or reverse direction. The servomotors will normally be powered by a self-contained battery pack, such as a 12V battery, however powering from external dc.

sources, such as the power source of an ambulance, is also possible. In addition a gearbox may be provided to ensure adequate torque for rotating the respective worms.

Each servomotor will preferably be independently operable so as to enable one or other of the ends of the stretcher undercarriage to be raised or lowered, for instance where it is necessary to maintain the patient level on an uneven surface or where it is necessary to elevate either the head or legs of the patient. Generally, however, the controls will be synchronised so that the stretcher undercarriage can be raised or lowered at a uniform rate which maintains the support platform in a level condition.

The support platform will have the necessary WO 02/34191 PCT/AU01/01356 4 attachments to enable a stretcher or other patient carrying means to be fitted thereto either permanently or, more usually, in a detachable manner. In addition, provision for life-support equipment to be fixed to the undercarriage may be provided.

Preferably, the support platform will be substantially rectangular and will incorporate a set of four fixed wheels located, respectively, at the leading corners and mid-region of the support platform. These wheels are designed to support the platform when the frames are in a fully folded position, such as when the undercarriage has been placed in an ambulance.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a side elevational view of a fully extended stretcher undercarriage according to one aspect of the invention, Figure 2 is a side elevational view of the stretcher undercarriage shown in Figure 1, with one wheeled support frame fully folded, and Figure 3 is a top/side perspective view of the stretcher undercarriage shown in Figure 1, with both wheeled support frames fully folded.

DESCRIPTION OF PREFERRED EMBODIMENT A preferred embodiment of the invention will now be described with reference to the accompanying drawings, in all of which like reference numerals refer to like parts.

Referring to all of the drawings simultaneously, the undercarriage comprises a support WO 02/34191 PCT/AU01/01356 platform 10 having two foldable wheeled frames 11, 12 fitted to its undersurface.

The support platform 10 has a rectangular configuration of box section aluminium or galvanized steel with bracing members 13, 14.

Fixed brackets 16, 17 are located on the trailing corners of the support platform for housing freely rotatable wheels 20, 21. Similar brackets 23, 24 are located at intermediate positions between the ends of the support platform also for housing freely rotatable wheels 25, 26.

A housing 27 for a battery, which drives an associated servomotor and reduction gearbox, both of which are also located within the housing, is fitted to bracing member 13. The reduction gearbox connects to two worm drives 30, 31 extending between the bracing members 13, 14.

Wheeled frame 12 comprises a substantially rectangular array of aluminium or galvanized steel profiled supports and linkages which are pivotally interconnected to enable folding as described below. The lower section of the frame includes a pair of castor wheels 32, 33 having castor housings supported by a common linkage 34. The common linkage 34 is, in turn pivotally connected at each end to respective support members 35, 38 which are cranked at their lower ends.

(This cranking can be seen for support member 35 in Figure 1 where a cranked end is referenced by numeral 36). An arm (see for instance arm 37 in Figure 1) also pivotally connects each end of the common linkage 34 to the undercarriage and further arms (see for instance arm 39 in Figure 1) extend from the end of the undercarriage to a mid region of the respective support members 35, 38.

The upper ends of the support members 34, 35 are WO 02/34191 PCT/AU01/01356 6 pivotally connected to a cross-member 50 (see Figure 3) which is adapted to move in the plane of the platform framework in rail housings 51, 52. Worm drive 30 is journalled to this cross-member.

The geometry of all these supports and linkages is such that upon folding of the frames up under the support platform, the free-castoring of the wheels 32, 33 remains unhindered, as described below.

Wheeled frame 11 also comprises a substantially rectangular array of aluminium or galvanized steel profiled supports and linkages which are pivotally connected in such a manner as to enable folding. The frame includes a pair of freely rotatable wheels 40, 41 supported on the end of member 46. Support struts 45, 46 extend for connection to the undercarriage platform and pivotal links 47, 48 extend between the end of the undercarriage platform and mid-regions of the support struts. The upper end of the frame is pivotally connected to a cross member 49 which also slides within the rail housings 51, 52 but on the bottom side thereof.

Worm drive 31 is journalled to this housing.

Control of the servomotor, and thus the folding of the frames, is effected by switches 53, 54 on one end of the platform framework.

The undercarriage can be folded from the fully extended arrangement depicted in Figure 1 to the fully collapsed arrangement depicted in Figure 3, or to any intermediate position, and vice-versa by operation of the switches 53, 54 at one end of the platform framework. In addition, operation of only one switch at a time enables one end of the undercarriage to be raised or lowered.

In operation, upon activating the switches on the end of the support platform when, for instance, in an WO 02/34191 PCT/AU01/01356 7 extended state as shown in Figure 1, the servomotor and gearbox are activated and the drive screws 30, 31 rotate.

This causes the cross members 50, 60 to move along the rail housings 51, 52 in opposite directions and to rotate the support members 35, 38 and 45, 46 in, respectively, clockwise and anti-clockwise directions as indicated by the heavy arrows, until the required reduction in height of the support platform is reached.

Claims

2. An undercarriage as claimed in claim 1, wherein at least one of the pairs of spaced ground wheels comprises caster wheels and wherein the caster wheels are located on a respective common member of the frame which is maintained in a horizontal position during folding of the frame by means of a pair of pivotal arm members of the frame, one of which arm members is cranked at its lower end and provides a main support member of the frame.
3. An undercarriage as claimed in claim I. or claim 2, wherein raising or lower-ing of the undercarriage is effected by hand operable control switches on one end of the support platform.
4. An undercarriage as claimed in claim i- or claim 2, wherein the serv oml-otor is powered by a self-contained .battery pack, An undercarriage as claimed in claim I or claim 2, and including a gearbox between the servometer and the WO 02/34191 PCT/AU01/01356 9 worms.
6. An undercarriage as claimed in claim 1 or claim 2, wherein there is a separate servomotor associated with each worm and wherein each servomotor is independently operable.
7. An undercarriage as claimed in claim 1 or claim 2, wherein the support platform is substantially rectangular and wherein there is a set of four fixed wheels located at the leading corners and the mid-region of the support platform.
8. An undercarriage as claimed in claim 1 or claim 2, wherein the support platform comprises a substantially rectangular array of aluminium or galvanized steel profiled elements with traverse bracing elements.
9. An undercarriage as claimed in claim 1 or claim 2, wherein the foldable frames each comprise a pair of elongate members with freely rotatable wheels on one end, cross-braces between the elongate members, and pivotal links which extend between the end of the support platform and the mid regions of the elongate members. An undercarriage substantially as herein described with reference to the accompanying drawings.