AU732100B2

AU732100B2 - A castor wheel assembly

Info

Publication number: AU732100B2
Application number: AU92461/98A
Authority: AU
Inventors: Ronald Barry Morris
Original assignee: Individual
Current assignee: Individual
Priority date: 1997-09-23
Filing date: 1998-09-23
Publication date: 2001-04-12
Anticipated expiration: 2018-09-23
Also published as: AU9246198A

Description

WO 99/15346 PCT/AU98/00800 1 A CASTOR WHEEL ASSEMBLY Field of the Invention The present invention relates to a castor wheel assembly as well as apparatus having such an assembly.

There is also provided a method of stabilising movement of a castor wheel to assist in the steering of apparatus fitted with an existing castor wheel assembly. The castor wheel assembly of the invention may be attached to any apparatus commonly provided with castor wheels.

Background of the Invention Castor wheels are commonly used where it is desirable to be able to push along and manoeuvre apparatus. However, apparatus fitted with castor wheels can be difficult to steer and castor wheels have a tendency to deflect from the path of travel, particularly on rough or uneven surfaces which can exacerbate steering problems. Most people have experienced this problem with shopping trolleys.

The use of castor wheels on shopping trolleys also presents another problem. More particularly, when shopping trolleys are swung around or steered sharply around a corner, the front castor wheels swing outwardly to allow for the change in direction of travel. Accordingly, the support provided by the front castor wheels shifts toward the outward side of the trolley at this time and the trolley becomes more susceptible to tipping over on its opposite side in the event excessive weight is exerted on the opposite side as can occur when an unrestrained child is carried in the trolley. It has been reported that a frightening number of children are injured each year due to shopping trolley accidents, a substantial number of which resulted in head and facial injuries.

There is, therefore, a need to improve the steerability of apparatus provided with castor wheels like shopping trolleys, and to reduce the possibility of shopping trolleys or other such apparatus tipping over in F PCT/AU98/00800 Received 06 August 1999 -2use.

There is also a need to improve stability, handling, and steerability of apparatus provided with castor wheels such as, for example, hospital bed trolleys and industrial trolleys which is often used in locations of restricted space whereby manuverability is so restricted that the apparatus generally needs to be reversed out of position.

In these cases, the castor wheel assemblies must undergo an abrupt change in direction without causing the apparatus undue loss of stability.

Summary of the Invention It is an aim of the present invention to address one or more problems of the prior art.

In a first aspect of the invention there is provided an apparatus having at least one castor wheel assembly comprising a castor wheel and a castor pin about which the castor wheel is rotatable, the castor pin being inclined at an angle to the vertical, a support bracket secured to a retaining pin and on which a support wheel and the castor pin are mounted so that the castor wheel and the support wheel are rotatable about the retaining pin, and the castor wheel leads the support wheel when the castor wheel assembly is rolled along a surface on the castor wheel and the support wheel.

In accordance with a second aspect the invention provides a castor wheel assembly for affixture to apparatus to be moved on said castor wheel assembly, having a castor pin having a longitudinal axis, a rotary yoke rotatably supported on the castor pin for rotation about said longitudinal axis and a castor wheel supported on the rotary yoke by a wheel axle, wherein said castor pin is affixed to said apparatus so as to be inclined to the vertical.

It is preferred that the castor pin is provided with N3 at least one wedge-shaped element having an opening Sprovided between convergent faces through which the pin

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AMENDED SHEET (Article 34) (IPEA/AU) PCT/AU98/00800 Received 06 August 1999 3 extends thereby to effect said inclined affixture to the apparatus.

Preferably also the wheel axle is a horizontal wheel axle.

The invention extends to a wedge-shaped element for inclining a castor pin of a castor wheel assembly, said element having a body provided with a pair of outwardly directed convergent faces and an opening extending from one face to the other, and at least one of said convergent faces is provided with one or more upstanding protrusions adapted to be ensconced within a recess or recesses of the apparatus.

The provision of the protrusion(s) facilitate orientation of the element with respect to the apparatus and/or enhance the strength of the joint formed by the castor pin, wedge-shaped element and apparatus.

Preferably the apparatus is a shopping trolley having a frame provided with a pair of convergent elongate side beams to which castor assemblies are affixed wherein each side beam is formed of a pair of coextensive substantially parallel spaced apart tubular members extending in a AMENDED SHEET (Article 34) (IPEA/AU) WO 99/15346 PCTIAU98/00800 4 substantially horizontal plane.

Preferably the castor pin is inclined to the vertical at a negative castor angle. More preferably the angle is in the range of 1 to 250.

It is preferred that the negative castor angle is in the range 50 to 150, and more preferably 7*.

The present invention also provides a castor wheel assembly for affixture to apparatus to be moved on said castor wheel assembly, having a castor wheel, wherein the assembly is affixed to the apparatus so that the castor wheel swivels about on axis inclined to the vertical.

In another aspect of the invention there is provided apparatus having at least one castor wheel assembly comprising a castor wheel and a castor pin about which the castor wheel is rotatable, the castor pin being inclined at an angle to the vertical.

The castor wheel assembly may also comprise a support bracket secured to a retaining pin and on which a support wheel and the castor pin are mounted. The castor wheel and the support wheel are rotatable about the retaining pin, and the castor wheel leads the support wheel when the castor wheel assembly is rolled along a surface on the castor wheel and the support wheel. The support wheel is also located to be unable to come into contact with the castor wheel when the castor wheel is rotated about the castor pin.

Hence, in an additional aspect of the invention there is provided a castor wheel assembly comprising: a retaining pin and a castor pin; a castor wheel that is rotatable about the castor pin; and a support bracket secured to the retaining pin and on which a support wheel and the castor pin are mounted, the support wheel being positioned to be unable to contact the castor wheel in use; WO 99/15346 PCT/AU98/00800 5 wherein the castor wheel and the support wheel are rotatable about the retaining pin, and the castor wheel leads the support wheel when the castor wheel assembly is rolled along a surface on the castor wheel and the support wheel.

Generally, the castor wheel will be offset in the primary direction of travel relative to the retaining pin when the assembly is rolled along the surface. Usually, the castor wheel and the support wheel will be in alignment, one behind the other, when the apparatus is rolled along a straight path. Either or both the retaining pin and the castor pin may be inclined at an angle to the vertical to produce castor action to stabilise the movement of the or each wheel in use as the case may be. Normally, the retaining pin will have an opposite inclination to that of the castor pin. Typically, the castor pin of a castor wheel assembly embodied by the invention will be inclined in an upright plane extending in the primary direction of travel and usually, will be inclined at a negative castor angle relative to the vertical.

The provision of the support wheel enables the castor wheel assembly to have a longer wheel base and so enhances the support of the apparatus when being manoeuvred on the castor wheel assembly.

In accordance with another aspect the invention provides a castor wheel assembly having a bracket for affixture to apparatus to be moved on said castor wheel assembly, a castor pin having a longitudinal axis supported on said bracket, a rotary yoke rotatably supported on the castor pin for rotation about said longitudinal axis and a castor wheel supported on the rotary yoke by a wheel axle, wherein said castor pin is hingedly supported on said bracket by a pivot axle for rotation thereabout thereby enabling the castor pin to be inclined to the vertical.

It is preferred that the castor pin is hingedly supported by the pivot axle to enable the castor pin to WO 99/15346 PCT/AU98/00800 6 swing about a longitudinal axis of the pin from a first disposition defining a first inclined castor angle to a second disposition defining a second inclined castor angle.

Preferably said pivot axle is a horizontal pivot axle.

Preferably also the wheel axle is a horizontal wheel axle.

It is preferred that the castor pin can swing from said first inclined angle to said second inclined angle in response to a change in direction of movement of the apparatus on the castor wheel assembly from a first direction to a second direction, wherein the first and second directions are opposite directions.

Preferably the bracket is provided with a pair of downwardly projecting arms hingedly supporting the horizontal pivot axle.

Preferably further the castor pin is fixed to the bracket pivot axle for rotation about a horizontal axis.

It is preferred that the pivot axle is provided with a pair of divergent upwardly projecting abutments in the form of legs adapted in use to selectively and discretely abut the underside of the bracket thereby to limit respective clockwise and anti-clockwise rotation of the pivot axle and thus the angle of inclination from the vertical of the castor pin when the apparatus is moved in respective forward or reverse directions.

Preferably the rotary yoke is rotatably supported on the castor pin for rotation about the longitudinal axis of the pin and the castor wheel is rotatably supported on the rotary yoke by a horizontal wheel axle.

It is preferred that the pin is mounted for movement about a horizontal axis from a first position in which the castor pin extends at a first negative castor angle from the vertical in response to movement of the apparatus in a first direction to a second position in which the castor pin extends at a second negative castor angle from the vertical in response to movement of the apparatus in a WO 99/15346 PCT/AU98/00800 7 second direction wherein the said second direction is the reverse of the said first direction.

Preferably the yoke rotates 1800 about the longitudinal axis of the pin in response to said change in direction of movement from said first direction to said second direction.

Preferably, in use, the pin projects downwardly from the pivot axle at an inclined angle and in changing direction of movement of the apparatus from said forward direction to said reverse direction the yoke swivels 1800 and the pivot axle rotates about its horizontal axis so that the castor pin is swung over centre from a first negative castor angle to a second negative castor angle.

Preferably the first negative castor angle is an angle in the range of 10 to 250 and the second negative castor angle is in the range of 10 to 250.

Preferably the first negative angle is in the range of to 15 and more preferably 100.

Preferably the second negative castor angle is in the range 50 to 150, and more preferably Preferably a pair of divergent abutment means extend upwardly and outwardly from the horizontal pivot axle to selectively abut an underside of said bracket thereby to limit rotation of the axle in response to said changes in direction of movement of said apparatus.

Castor wheel assemblies of the invention may be utilised on any apparatus commonly fitted with castor wheels such as beds and other furniture, wheelchairs, support stands, scaffolding and trolleys, including shopping trolleys and hospital bed trolleys.

The present invention will now be described hereinafter with reference to preferred embodiments shown in the accompanying drawings which are not to scale.

WO 99/15346 PCT/AU98/00800 8 Brief Description of the Accompanying Drawings Figure 1 is a partial side view of apparatus provided with a castor wheel assembly embodied by the invention; Figure 2 is an important component of the castor wheel assembly shown in figure 1; Figure 3 is a partial top view of apparatus provided with a further castor wheel assembly embodied by the invention illustrating important components of the invention; Figure 4 is an enlarged detail of area 4 of Figure 3 but with the upper wedge shaped element deleted to show how protrusions fit between tubular members; Figure 5 is an enlarged detail of area 5 of Figure 3; Figure 6 is a cross-sectional side view of components illustrated in Figure 5 taken along the line 6-6; Figure 7 is a perspective view of the wedge shaped elements of embodiment illustrated in Figures 3 to 6.

Figure 8 is a partial side view of apparatus provided with a further castor wheel assembly embodied by the invention; Figure 9 is a wedge of the castor wheel assembly shown in Figure 8; and Figures 10, 11 and 12 are plan views of the castor wheel assembly shown in Figure 3 during manoeuvring of the apparatus.

Figure 13 is a partial side view of apparatus provided with a further castor wheel assembly embodied by the invention illustrating important components during movement of the apparatus in one direction.

Figure 14 is a partial side view of the apparatus and the further castor wheel assembly shown in figure 3 during movement in an opposite direction; Figure 15 is an end view of the castor wheel assembly shown in Figures 13 and 14, and Figure 16 is a perspective view of an alternative mount to that shown in Figure 14 for use with heavier WO 99/15346 PCT/AU98/00800 9 loads.

Detailed Description of Preferred Embodiments of the Invention.

The castor wheel assembly 10 shown in Figure 1 comprises a castor wheel 12 mounted to a rotary yoke 14 having a recess 16 in which is held a bearing 18 (shown in phantom outline) received on a castor pin The rotary yoke 14 is rotatably supported on the castor pin 20 for rotation about the longitudinal axis of the pin 20. A castor wheel 12 is rotatably supported on the rotary yoke 14 by ahorizontal wheel axle 11.

Accordingly, castor wheel 12 is readily rotatable about the castor pin Castor pin 20 is secured to a beam 22 of a rear end region of a shopping trolley 24 by a nut 26 and extends through an aperture 28 of a wedge-shaped element 30 causing the castor pin 20 to be inclined at a negative castor angle a from the vertical. When retrofitting this preferred embodiment of the invention to apparatus such as a shopping trolley, an additional wedge-shaped element 31 is provided above the beam 20 so that the nut 26 bears on a substantially flat surface extending in a plane generally perpendicular to longitudinal axis of the pin In the preferred embodiment shown, the castor pin is inclined at an angle of 70 to the vertical although embodiments may be provided wherein a is in a range of from about 10 to about 250. By inclining the castor pin 20 to the vertical, bearing 18 is also tilted with respect to the horizontal plane. The inclination of the bearing 18 results in a tendency for castor yoke 14 of the castor wheel assembly to be maintained in its resting trailing position as shown in figure 1 providing the castor wheel with fore-and-aft directional stability and a self-centring action following angular deflection when the shopping WO 99/15346 PCT/AU98/00800 10 trolley is pushed along.

Another castor wheel assembly 10 is arranged toward an opposite side of the shopping trolley 24 such that both castor wheel assemblies are in alignment as is commonly known. The castor pin of that castor wheel assembly is also held at the same negative castor angle a by wedgeshaped elements 30, 31 as illustrated. The wedge-shaped element 30 is more clearly shown in figure 2. To inhibit displacement of the wedge-shaped elements in use, at least the lower element 30 is provided with recesses 32 and 34 that receive studs (not shown) located on beam 22. In this embodiment the upper element 31 is substantially identical to the lower element 30. Provision of substantially identical elements may inhibit production costs and/or minimise errors in retro-fitting.

As is commonly known castor wheel assemblies are also provided on opposite sides of the trolley towards the front end region of the trolley. Instead of or in addition to the castor wheel assemblies 10 according to the preferred embodiment of the invention being provided to the rear end region of the shopping trolley, a pair of castor wheel assemblies according to the invention can be provided to the front end region of the trolley so as to provide and/or to enhance fore-and-aft directional stability.

It will be understood from the above that existing castor wheel assemblies fitted to apparatus such as shopping trolleys can be readily modified to stabilise castor wheel movement by simply inserting a wedge-shaped element into the assembly to cause the castor pin to be inclined at an angle to the vertical. Rather than using a wedge-shaped element, the apparatus can also be modified by, for example, angling the frame or support to which the castor wheel assembly is attached to cause the castor pin to be so inclined. Alternatively, an angled castor pin may be Used.

WO 99/15346 PCT/AU98/00800 11 Important components of a further preferred embodiment of a castor wheel assembly is depicted in figures 3 to 9.

This embodiment is also provided with a castor wheel arrangement having a castor pin inclined to the vertical but in this instance at least one of the wedge-shaped elements 40, 41 is provided with at least one protrusion projecting from a face thereof.

The lowermost frame member of conventional shopping trolleys typically comprises a pair of convergent elongate side beams 42, 44 and a pair of substantially parallel end braces 43 welded end to end to form a trapezium having a narrow end and a wide end, the narrow end forming the front end region of the trolley.

Two castor wheel assemblies 50, 51 are generally secured to each side beam 42, 44 one at or towards the front of the trolley and another pair 52, 53 at or towards the rear.

Each side beam 42, 44 is generally in the form of a pair of substantially parallel, spaced apart tubular members 45 extending in a substantially horizontal plane.

The castor pin typically extends through the gap 46 between the tubular members 45 and is bolted to the side beam by means of a nut thereby to extend in a generally upright or vertical direction.

In accordance with the further preferred embodiment of the present invention, the castor pin (not shown) is supported to extend in a direction inclined to the vertical at a negative castor angle.

This is achieved by providing a wedge-shaped element 40 having an opening 48 through which the castor pin may extend disposed below the side beam 42, 44 intermediate the lower end of the castor pin and the side beam 42, 44 and an additional wedge-shaped element 41, having an opening 58 through which the castor pin may extend, disposed above the side beam 42, 44 intermediate the upper end of the castor pin and the beam 42, 44 as hereinbefore described with WO 99/15346 PCT/AU98/00800 12 reference to figures 1 and 2.

It is desirable that the wedge-shaped elements 40, 41 of each castor wheel assembly be provided with means to facilitate accurate alignment and/or quick affixture of the assembly to the trolley.

To facilitate said desiderata at least one of each pair of wedge-shaped elements 40, 41 is provided with one or more protrusions projecting from a convergent face of the element, adapted to project into and be ensconced within the gap 46 between the tubular members 45. The protrusions may be of a shape and configuration and/or sufficient width to enable the element to be temporarily self-held in position during assembly prior to the nut being tightened on the castor pin. For example, the protrusion or protrusions may project into the gap 46 between adjacent tubular members 45 forming the respective side beams and be held in snap fit engagement therewith.

It is desirable that in embodiments in which one of the wedge-shaped elements only is provided with protrusions the protrusions have a height marginally less than or at most equal to the diameter of the tubular members to facilitate accurate spacing between the upper and lower wedge-shaped elements and to strengthen the joint formed thereby.

In embodiments in which both wedge-shaped elements are provided with protrusions it is desirable that the sum of the heights of oppositely disposed protrusions is less than or at most equal to the diameter of the tubular members The further castor wheel assembly is rigidly attached to a shopping trolley to be moved on said castor wheel assembly, by means of a threaded castor pin and nut as hereinbefore described with reference to figures 1 and 2.

As illustrated in figures 3 to 9, the lower wedge-shaped element 40 is provided with a pair of upwardly projecting protrusions 47. The protrusions 47 are provided on the convergent face 48 adapted to engage the underside of the WO 99/15346 PCT/AU98/00800 13 side beam 42.

It is desirable that the wedge-shaped element or elements 40, 41 of each castor wheel assembly be disposed to longitudinally extend substantially parallel to one another and substantially parallel to the longitudinal axis of the trolley.

To address this desiderata the protrusions 47 are axially offset so that upon insertion into the gap 46 between the tubular members 45 the longitudinal axis of the wedge-shaped element 40 is oriented to extend substantially parallel to the longitudinal axis of the trolley. Hence, wedge-shaped elements 40 adapted for one side of a trolley (viz figure 5) differ from those for the other side (viz figure 9) in that the protrusions 47 are axially offset at respective positive and negative angles to attend to differences in the direction of the longitudinal axis of respective convergent side beams 42 with respect to the longitudinal axis of the trolley.

The upper wedge-shaped element 41 is devoid of protrusions. The height of the protrusions corresponds essentially to but generally marginally shorter than the diameter of the tubular members 45 of the side beams 42, 44 so that the tip of the protrusions 47 can engage the underside of the upper wedge-shaped element 41 upon the nut (not shown) being tightened on the castor pin (not shown) so as to strengthen the joint formed thereby.

The protrusion(s) may be of a shape, size and configuration to a snap-fit engagement with the tubular members, or at least temporary engagement in anticipation of emplacement of the pin through the opening of the wedge shaped element and affixture of the castor wheel assembly to the frame by tightening the nut on the castor pin.

This temporary engagement facilitates substantially "hands free" retrofitting of the assembly, according to the invention, to a shopping trolley.

WO 99/15346 PCT/AU98/00800 14 Surprisingly the provision of a castor angle inclined to the vertical provides substantial enhancement of the steering capabilities of the trolley being moved on the castor wheel assembly.

A further castor wheel assembly 36 embodied by the invention is depicted in figure 8. This embodiment is also provided with a castor wheel arrangement as described above but in this instance the castor pin 20 is secured to a leading end region of a support arm 38 which in turn is secured to a retaining pin 60 about which both the castor wheel 12 and a support wheel 62 mounted on a trailing and of the support arm are rotatable. The support wheel 62 is spaced from the castor wheel rearwardly of the retaining pin to enable rotation of the castor wheel about castor pin 20 without contact of the two wheels.

The retaining pin 60 is secured to beam 64 of a front end region of shopping trolley 24 by a nut 66 and is inclined at a positive castor angle 0 of 70 to the vertical as a result of the presence of a wedge-shaped element Usually, angle will be the same as angle a and accordingly, may also be in a range of from about 10 to about 100 or more.

Bearing 68 held in recess 70 of support arm 38 which enables the castor wheel 12 and the support wheel 62 to rotate about the retaining pin is also tilted due to the inclination of the retaining pin. As a result, there is also a tendency for support arm 38 to be maintained in its resting trailing position as shown and for movement of the support wheel in use to be stabilised.

The wedge-shaped element 72 through which castor pin extends is the same as wedge-shaped element 30 except that it is not provided with recesses 32 and 34 as indicated in figure 9. If desired, however, support arm 38 may be provided with studs to inhibit displacement of the wedge-shaped element in use in which case wedge-shaped WO 99/15346 PCT/AU98/00800 15 element 72 can be replaced with a wedge-shaped element Support wheel 62 is able to pivot a restricted distance about pivot pin 76 in response to bumps on the ground surface along which the shopping trolley is pushed.

This avoids castor wheel 12 from being lifted from the ground surface when the support wheel travels over such bumps. Generally, the pivotation of the support wheel about pivot pin 76 will be restricted such that the support wheel is only able to be lifted about 12mm from its resting position on the ground surface. A spring located within support arm 38 about pivot pin 76 exerts a downwardly directed force on the support wheel 62 to thereby return the support wheel to its resting position following pivotation about the pivot pin.

An additional castor wheel assembly 36 is secured on an opposite side of the front region of the shopping trolley to the one as shown in figure 8. The retaining pin of the additional castor wheel assembly 36 is also inclined at a positive castor angle P of The relative movement of the castor wheel 12 and the support wheel 62 when the shopping trolley is being manoeuvred in use is illustrated in figures 10, 11, 12.

As indicated in figure 10, support wheels 62 of castor wheel assemblies 36 are in alignment with and trail the respective castor wheels 12 when the shopping trolley is pushed in a forward direction. When turning as shown in figure 11, in this instance to the right, castor wheel 12 and support wheel 62 rotate about retaining pin 60 causing support arm 38 to swing around and orientate in the direction of travel. As the support arm swings, castor wheels 12 are drawn toward side 78 of shopping trolley 24 so that the support provided by the castor wheels is offset relative to the longitudinal axis of the shopping trolley.

At the same time, support wheels 62 swing outwardly toward trolley side 80 until each aligns with the corresponding castor wheel upon further manoeuvring of the trolley as WO 99/15346 PCT/AU98/00800 16 indicated in figure 12. Since pivoting of each support wheel about the corresponding pivot pin is limited, the support wheels act to support side 80 of the trolley and indeed, widen the front wheel base of trolley 24 compared to that if conventional castor wheel assemblies were used.

The realignment of the castor wheel 12 and the support wheel 62 is assisted by the tendency for castor bracket 14 and support arm 38 to return to their resting trailing positions due to the inclination of castor pin 20 and retaining pin A further castor wheel assembly 1 embodied by the invention is depicted in figures 13, 14 and 15. This embodiment is also provided with a castor wheel arrangement having a castor pin 8 inclined to the vertical but in this instance the castor pin 8 is secured to the apparatus by means of a hinge joint.

The illustrated castor wheel assembly 1 of figures 13, 14 and 15 has a bracket 2 rigidly attached to a shopping trolley 3 to be moved on said castor wheel assembly 1 by means of a threaded mounting shank 4 and a nut 5. The bracket 2 is provided with a pair of downwardly projecting arms 6, hingedly supporting a horizontal pivot axle 7. A castor pin 8 is rigidly fixed to said horizontal pivot axle 7 for rotation about a horizontal axis.

The pivot axle 7 is also provided with a pair of divergent upwardly projecting abutments in the form of legs 13 and 15 adapted in use to selectively and discretely abut the underside of the bracket 2 thereby to limit respective clockwise and anti-clockwise rotation of the pivot axle 7 direction and thus the angle of inclination from the vertical of the castor pin 8 when the trolley 3 is moved in the respective forward or reverse directions.

A rotary yoke 9 is rotatably supported on the castor pin 8 for rotation about the longitudinal axis of the pin 8. A castor wheel 12 is rotatably supported on the rotary yoke 9 by a horizontal wheel axle 11.

WO 99/15346 PCT/AU98/00800 17 The castor pin 8 is mounted for movement about a horizontal axis from a first position in which the castor pin extends at a first castor angle a from the vertical in response to movement of the trolley 3 in a first direction as, for example, illustrated in Figure 13, to a second position in which the castor pin 8 extends at a second castor angle a' from the vertical in response to movement of the trolley 3 in a second direction as, for example, illustrated in Figure 14 wherein the said second direction is the reverse of the said first direction. As best illustrated in Figures 13 and 14, the yoke 9 generally rotates 1800 about the longitudinal axis of the castor pin 8 in response to a change in direction of movement from said first direction to said second direction.

In use, the castor pin 8 projects downwardly from the pivot axle 7 at an inclined angle. In changing direction of movement from a forward direction as illustrated in figure 13 to a reverse direction as illustrated in figure 14, the yoke has swivelled 1800 and the pivot axle 7 has rotated about its horizontal axis so that the castor pin has swung over centre from a negative castor angle a of 100 to a negative castor angle a' of Less dramatic changes in direction of movement of the trolley are accommodated by swivel motion of the rotary yoke 9. Surprisingly the provision of a castor angle inclined to the vertical provides substantial enhancement of the steering capabilities of the trolley being moved on the castor wheel assembly.

Although the present invention has been described with reference to the specific embodiments shown in the accompanying drawings, it will be understood that numerous modifications and variations are possible without departing from the spirit and scope of the invention. For example, the illustrated horizontal pivot axle is hingedly supported by the bracket, however in other embodiments the pivot axle WO 99/15346 PCT/AU98/00800 18 may be fixed to the bracket and the castor pin may be hingedly supported thereby. In these embodiments the castor pin is provided with abutments to limit rotation about the horizontal axis of the pivot axle.

Claims

2. A castor wheel assembly comprising: a retaining pin and a castor pin; a castor wheel that is rotatable about the castor pin; and a support bracket secured to the retaining pin and on which a support wheel and the castor pin are mounted, the support wheel being positioned to be unable to contact the castor wheel in use; wherein the castor wheel and the support wheel are rotatable about the retaining pin, and the castor wheel leads the support wheel when the castor wheel assembly is rolled along a surface on the castor wheel. and the support wheel and at least one of the retaining pin and the castor pin is inclined at an angle to the vertical to produce castor action to stabilise the movement of the or each wheel in use as the case may be.
3. A castor wheel assembly according to claim 2 wherein the castor wheel is offset in the primary direction of travel relative to the retaining pin when the assembly is rolled along the surface. AMENDED SHEET (Article 34) (IPEA/AU) PCT/AU98/00800 *Received 06 August 1999 20
4. A castor wheel assembly according to claim 2 or claim 3 wherein the castor wheel and the support wheel will be in alignment, one behind the other, when the apparatus is rolled along a straight path. A castor wheel assembly according to any one of claims 2 to 4 wherein the retaining pin has an opposite inclination to that of the castor pin.
6. A castor wheel assembly according to any one of claims 2 to 5 wherein the castor pin of a castor wheel assembly is inclined in an upright plane extending in a primary direction of travel and at a negative castor angle relative to the vertical.
7. A castor wheel assembly for affixture to apparatus to be moved on said castor wheel assembly, having a castor pin having a longitudinal axis, a rotary yoke rotatably supported on the castor pin for rotation about said longitudinal axis and a castor wheel supported on the rotary yoke by a wheel axle, wherein said castor pin is affixed to said apparatus so as to be inclined to the vertical, wherein the castor pin is provided with at least one wedge-shaped element having an opening provided between convergent faces of the wedge shaped element through which the pin extends thereby to effect said inclined affixture to the apparatus and wherein the wedge shaped element is provided with one or more upstanding protrusions adapted to be ensconced within a recess or recesses of the apparatus.
8. A castor wheel assembly according to claim 7 wherein the wheel axle is a horizontal wheel axle.
9. A castor wheel assembly according to claim 7 or claim 8 wherein the apparatus is a shopping trolley having a AMENDED SHEET (Article 34) (IPEAAU) PCT/AU98/00800 Received 06 August 1999 21 frame provided with a pair of converging elongate side beams to which castor assemblies are affixed wherein each side beam is formed of a pair of coextensive substantially parallel spaced apart tubular members extending in a substantially horizontal plane. A wedge-shaped element for inclining to the vertical a castor pin of a castor wheel assembly, said element having a body provided with a pair of outwardly directed convergent faces and an opening extending from one face to the other and at least one of the convergent faces is provided with at least one upstanding protrusion projecting from one of said pair of convergent faces adapted to be ensconced within a recess or respective recesses disposed in apparatus to which a castor wheel assembly is affixed.
11. A wedge-shaped element as defined in claim 10 wherein the at least one upstanding protrusion is so shaped and/or disposed as to provide a predetermined orientation of the element upon engagement with the apparatus.
12. A castor wheel assembly having a bracket for affixture to apparatus to be moved on said castor wheel assembly, a castor pin having a longitudinal axis supported on said bracket, a rotary yoke rotatably supported on the castor pin for rotation about said longitudinal axis and a castor wheel supported on the rotary yoke by a wheel axle, wherein said castor pin is hingedly supported on said bracket by a pivot axle for rotation thereabout thereby enabling the castor pin to be inclined to the vertical, and wherein the castor pin is hingedly supported by the pivot axle to enable the castor pin to swing about a longitudinal axis of the pin from a first disposition defining a first inclined castor angle to a second disposition defining a second S inclined castor angle in response to a change in direction of movement of the apparatus on the castor wheel assembly AMENDED SHEET (Article 34) (IPEA/AU) PCT/AU98/00800 Received 06 August 1999 22 from a first direction to a second direction.
13. A castor wheel assembly according to claim 12 wherein the pivot axle is a horizontal pivot axle and the wheel axle is a horizontal wheel axle.
14. A castor wheel assembly according to claim 12 or claim 13 wherein the first and second directions are opposite directions. A castor wheel assembly according to any one of claims 12 to 14 wherein the bracket is provided with a pair of downwardly projecting arms hingedly supporting a horizontal pivot axle.
16. A castor wheel assembly according to claim 15 wherein the castor pin is fixed to the bracket pivot axle for rotation about a horizontal axis.
17. A castor wheel assembly according to any one of claims 12 to 16 wherein the pivot axle is provided with a pair of divergent upwardly projecting abutments in the form of legs adapted in use to selectively and discretely abut the underside of the bracket thereby to limit respective clockwise and anti-clockwise rotation of the pivot axle and thus the angle of inclination from the vertical of the castor pin when the apparatus is moved in respective forward or reverse directions.
18. A castor wheel assembly according to claim 17 wherein the yoke rotates 1800 about the longitudinal axis of the pin in response to said change in direction of movement from said first direction to said second direction and in use, the pin projects downwardly from the pivot axle at an inclined angle and in changing direction of movement of the apparatus from said forward direction to said reverse AMENDED SHEET (Article 34) (IPEA/AU) PCT/AU98/00800 SReceived 06 August 1999 23 direction the yoke swivels 1800 and the pivot axle rotates about its horizontal axis so that the castor pin is swung over centre from a first negative castor angle to a second negative castor angle. AMENDED SHEET (Article 34) (IPEA/AU)