WO1994010000A1

WO1994010000A1 - Wheel assemblies

Info

Publication number: WO1994010000A1
Application number: PCT/GB1993/001088
Authority: WO
Inventors: Stanley John Dibben
Original assignee: Stanley John Dibben
Priority date: 1992-10-23
Filing date: 1993-05-26
Publication date: 1994-05-11
Also published as: GB9222283D0; AU4085393A

Abstract

A wheel assembly comprises a wheel (4), a wheel support (6) for rotatably supporting the wheel (4) so as to allow the wheel (4) to travel along a surface, mounting means (8, 10) adapted to pivotally mount the wheel support (6) to an article, such as a trolley, about a pivot axis (7) lying generally perpendicular to the axis of rotation of the wheel (4) so as to allow the direction of travel of the wheel (4) to vary relative to the article, and releasable locking means (12) for locking the wheel (4) in a particular direction of travel relative to the article, said releasable locking means (12) being adapted to automatically release the wheel (4) when a torque greater than a predetermined value is applied to the wheel (4) about said pivot axis (7), and to automatically lock the weel (4) in said particular direction when the wheel is placed in said particular direction.

Description

" heel Assemblies" Most supermarket trolleys are fitted with four castors, each castor comprising a wheel and a wheel support for connecting the wheel to the trolley. The wheel support is pivotable through 360° about a vertical pivot axis which lies substantially perpendicular to the horizontal axis of rotation of the wheel. The axis of rotation of the wheel is offset from the pivot axis so that the wheel automatically swivels around and trails along behind the pivot axis as the trolley is pushed along by the user. The castors allow the trolley to be pushed in any direction, and also allow the trolley to negotiate tight bends.

However, it is now well recognised that trolleys fitted with such castors present a serious safety hazard, and are the cause of thousands of accidents and injuries each year. Supermarket trolleys often do not naturally travel in a straight line even when they are new. The trolleys are particularly dangerous when they are heavily laden, since they can gather a considerable momentum when they are pushed along supermarket floors. The trolleys are also particularly dangerous on sloping surfaces, and can cause serious injuries if the user loses control and the trolley is allowed to run freely down the slope. The British Government is aware of the problem and a British Standard trolley is being developed. It is also thought that a "Euro-Trolley" may follow. However, there is still a need for a trolley which is both safe and convenient to use .

The invention seeks to overcome the disadvantages of the prior art.

According to the invention there is provided a wheel assembly comprising a wheel, a wheel support for rotatably supporting the wheel so as to allow the wheel to travel along a surface, mounting means adapted to pivotally mount the wheel support to an article, such as a trolley, about a pivot axis lying generally perpendicular to the axis of rotation of the wheel so as to allow the direction of travel of the wheel to vary relative to the article, and releasable locking means for locking the wheel in a particular direction of travel relative to the article, said releasable locking means being adapted to automatically release the wheel when a torque greater than a predetermined value is applied to the wheel about said pivot axis, and to automatically lock the wheel in said particular direction when the wheel is placed in said particular direction. Preferably, the mounting means allows the wheel to rotate through an angle of 360 degrees about the pivot axis.

Conveniently, the axis of rotation of the wheel lies to one side of, and does not intersect with, the pivot axis so that, in use, the wheel automatically trails along behind the pivot axis.

The releasable locking means may comprise a locking member, a recess adapted to receive said locking member, and first biasing means for urging the locking member and the recess together when the wheel is in said particular direction so as to releasably lock the wheel in said particular direction. Either the locking member or the recess may be provided on the wheel support.

The recess or the locking member may be formed in or on an annular guide surface which extends around, and is centred upon, said pivot axis, said guide surface being adapted to prevent movement of the biasing means when the wheel is not in said particular direction.

The locking member and recess may be shaped in such a way that, when the locking member is located in the recess, the application of said torque to the wheel causes the locking member to move away from the recess against the action of the first biasing means, so as to release the wheel.

The locking member may be rotatable.

This would, for example, allow the locking member to move freely along the annular guide surface, if such a surface is provided.

Preferably, the first biasing means is of adjustable biasing strength.

The mounting means may be adapted to allow movement of the wheel support towards and away from said article, and may comprise second biasing means for biasing the wheel support away from said article.

It will be appreciated that if the wheel assembly is attached to the bottom of an article, such as a shopping trolley, in order to allow the article to travel along a surface, the second biasing means will provide the article with a degree of suspension, thus providing the article with a smoother ride as it travels along the surface.

Conveniently the second biasing means is of adjustable biasing strength.

Preferably, if the wheel assembly comprises said second biasing means, the wheel assembly is arranged so that movement of the wheel support towards the article against the action of the second biasing means causes an increase in the biasing strength of the first biasing means. This has the advantage that, if the wheel assembly is attached below the article as described above, a heavier article or a more heavily laden article will result in a larger torque being required to release the locking means. The invention also provides an adaption device for enabling an existing castor, comprising a wheel and a wheel support pivotally mounted about a pivot axis, to be adapted so as to enable the castor to be releasably locked in a particular direction of travel, the adaption device comprising an engagement member, biasing means for biasing the engagement member, and attachment means for attaching the engagement member at a location adjacent the wheel support, the biasing means being adapted to urge the engagement member into releasable locking engagement with the wheel support when the wheel is arranged in a particular direction of travel, and to automatically release the wheel support when a torque greater than a predetermined value is applied to the castor about said pivot axis.

The biasing means may be of adjustable biasing strength.

The attachment means may be adapted to engage just above the bearings allowing rotation of the wheel support of a typical castor.

Conveniently, the attachment means is provided with a recess for receiving a bolt used to attach the castor to a trolley or other article. The invention also provides a trolley, the rear but not the front wheels of which, or alternatively all of the wheels of which, are releasably lockable in a particular direction of travel relative to the trolley by any of the means described above. The invention will now be more particularly described, by way of example only, with reference to the accompanying drawings in which:

Figure 1 is a schematic plan view of a castor fitted with an adaption device; Figure 2 is a schematic side view of the castor shown in Figure 1;

Figure 3 is a schematic side view, partly in section, of a castor provided with a releasable locking mechanis ;

Figure 4 is a schematic plan view of a castor provided with a further releasable locking mechanism; and Figure 5 is a schematic side view of the castor shown in Figure .

The castor 2 shown in Figures 1 and 2 comprises a wheel 4 and a wheel support 6. The castor is typical of castors used for supermarket shopping trolleys, and is pivotally connected about a vertical pivot axis 7 to a vertical member 8 forming part of a shopping trolley by means of a bearing assembly 10.

An adaption device 12 is fitted to the castor in order to releasably lock the castor in a given direction of travel. The adaption device comprises a locking member 14 which engages within a small recess 16 formed in an upper part 18 of the wheel support 6. The locking member 14 is provided at the bottom end of a vertical rod 20 which is slidable within a vertical sleeve 22. The sleeve 22 is fixed to the vertical member 8 by means of an angled metal plate 24. The lower end 26 of the plate 24 is clamped between the vertical member 8 and the bearing assembly 10, and is formed with a circular aperture (not shown) for receiving a vertical bolt (not shown) which passes through the centre of the bearing assembly 10 and threadably engages within the vertical member 8 in order to attach the wheel support 6 to the vertical member 8. The upper end 28 of the plate 24 is also formed with a circular aperture for receiving the sleeve 22. The sleeve 22 is either welded to the plate 24, or fixed to the plate 24 by means of an interference fit. A spring 30 extends between the upper end 28 of the plate 24 and a washer 32 which is held in position around the rod 20 by means of a nut 34. The nut 34 is threadably connected to the rod 20, and is used to adjust the compression of the spring 30. It will be seen that the adaption device 12 can be used to convert an existing castor into a releasably locking castor. All that is required is to clamp the plate 24 between the vertical member 8 and the bearing assembly 10, to drill a small recess in the upper part 18 of the wheel support 6, and to adjust the compression of the spring 30 to a suitable value by means of the nut 34.

Usually the adaption device 12 would be fitted only to the rear wheels of a trolley, and would be arranged to releasably lock the wheels of the trolley in a position corresponding to forward travel of the trolley. If the user should require the rear wheels to be pivoted about the vertical axis, for example in order to allow the trolley to negotiate a particularly tight bend, the user can release the wheels from their locked position by simply pulling the trolley backwards by a small amount. When the trolley is pulled backwards, the wheels tend to swivel around, so that the locking member 14 is forced upwards and out of the recess 16 against the biasing action of the spring 30. The locking member 14 will again automatically engage within the recess 16 as soon as the wheels return to their forward travel position.

As an alternative to the rigid plate 24, sleeve 22, rod 20, and spring 30, the adaption device 12 could simply comprise the locking member 14 supported at one end of a horizontal leaf spring (not shown) , the other end of the leaf spring being clamped between the vertical member 8 and the bearing assembly 10. The leaf spring would then bias the locking member 14 towards the recess in the upper part 18 of the wheel support 6.

Figure 3 shows a castor provided with a releasable locking mechanism which ensures that a greε.ter torque is required to release the locking mechanism when the trolley carries a greater load. Similar parts to parts shown in Figures 1 and 2 are denoted by the same reference numerals. The castor 2 is connected to the trolley by means of a vertical shaft 40 which is vertically slidable within a vertical sleeve 42 forming part of the trolley. A first spring 44 is provided for biasing the castor away from the trolley, so as to provide the wheel 4 with a degree of suspension.

A releasable locking device 46 is attached to the vertical sleeve 42 by means of two horizontal support members 48. The releasable locking device 46 comprises a locking member 14 mounted on the bottom of a vertical rod 50 which is vertically slidable within an outer sleeve 52. A spring 54 is provided within the vertical sleeve 52 for biasing the locking member 14 towards the upper part 18 of the wheel support 6. At its lower end, the spring 54 abuts against a cylindrical member 56 which is threadably mounted on the rod 50 in order to allow the compression of the spring 54 to be adjusted.

It will be appreciated that the greater the load carried by the trolley the greater the compression of the spring 44, and hence the greater the compression of the spring 54. This ensures that the locking member 14 engages more firmly within the recess 16 when the trolley is carrying a heavier load. This ensures that when a heavily laden trolley is travelling along a sloping surface, the extra weight in the trolley does not cause accidental release of the locking mechanism.

The releasable locking mechanism shown in Figures 4 and 5 is the same as that shown in Figures 1 and 2, except that it further comprises a circular disc 60, for example of nylon or metal. The circular disc 60 is rigidly fixed to the wheel support 6, resting on the upper part 18 thereof, so as to be pivotable together with the wheel support 6 about the vertical pivot axis 7 of the castor.

The disc 60 is formed with a recess 62 on its upper side, adapted to releasably engage with the locking member 14. When the locking member 14 disengages from the recess 62 the locking member 14 simply slides around the upper surface of the disc 60. The disc 60 therefore supports the locking member 14 at a constant height and avoids the need for the locking member 14 to be raised by the side edges 64 (see Figure 4) of the upper part 18 of the wheel support 6 when the wheel support 6 passes beneath the locking member 14..

As an alternative to the circular disc 60, the side edges 64 may be provided with ramped surfaces for gradually raising the locking member 14 when the wheel support 6 passes beneath the locking member 14. In any of the above embodiments, the locking member 14 could be replaced by a roller ball or wheel. Alternatively, the locking member 14 and its corresponding recess could be replaced by a pair of magnets or electromagnets (not shown) , adapted to retain the castor in a particular direction.

It will be appreciated that the invention has a wide range of applications. For example, the invention may be used with supermarket trolleys, airport luggage trolleys, wheeled hospital stretchers and beds, domestic and industrial food trolleys, warehouse trolleys, and any vehicle or other piece of apparatus using castors.

Claims

1. A wheel assembly comprising a wheel, a wheel support for rotatably supporting the wheel so as to allow the wheel to travel along a surface, mounting means adapted to pivotally mount the wheel support to an article, such as a trolley, about a pivot axis lying generally perpendicular to the axis of rotation of the wheel so as to allow the direction of travel of the wheel to vary relative to the article, and releasable locking means for locking the wheel in a particular direction of travel relative to the article, said releasable locking means being adapted to automatically release the wheel when a torque greater than a predetermined value is applied to the wheel about said pivot axis, and to automatically lock the wheel in said particular direction when the wheel is placed in said particular direction.

2. A wheel assembly as claimed in claim 1, wherein the mounting means allows the wheel to rotate through an angle of 360 degrees about the pivot axis.

3. A wheel assembly as claimed in claim 1 or 2, wherein the axis of rotation of the wheel lies to one side of, and does not intersect with, the pivot axis so that, in use, the wheel automatically trails along behind the pivot axis.

4. A wheel assembly as claimed in any preceding claim, wherein the releasable locking means comprises a locking member, a recess adapted to receive said locking member, and first biasing means for urging the locking member and the recess together when the wheel is in said particular direction so as to releasably lock the wheel in said particular direction.

5. A wheel assembly as claimed in claim 4, wherein the recess is provided on the wheel support.

6. A wheel assembly as claimed in claim 4 or 5 , wherein the recess or the locking member is formed in or on an annular guide surface which extends around, and is centred upon, said pivot axis, said guide surface being adapted to prevent movement of the biasing means when the wheel is not in said particular direction.

7. A wheel assembly as claimed in any of claims 4 to 6, wherein the locking member and recess are shaped in such a way that, when the locking member is located in the recess, the application of said torque to the wheel causes the locking member to move away from the recess against the action of the first biasing means, so as to release the wheel.

8. A wheel assembly as claimed in any of claims 4 to 7, wherein the locking member is rotatable.

9. A wheel assembly as claimed in any of claims 4 to 8, wherein the first biasing means is of adjustable biasing strength.

10. A wheel assembly as claimed in any preceding claim, wherein the mounting means is adapted to allow movement of the wheel support towards and away from said article, and comprises second biasing means for biasing the wheel support away from said article.

11. A wheel assembly as claimed in claim 10 wherein the second biasing means is of adjustable biasing strength.

12. A wheel assembly as claimed in claim 10 or 11, when dependent directly or indirectly on any of claims 4 to 9, wherein the wheel assembly is arranged so that movement of the wheel support towards the article against the action of the second biasing means causes an increase in the biasing strength of the first biasing means.

13. An adaption device for enabling an existing castor, comprising a wheel and a wheel support pivotally mounted about a pivot axis, to be adapted so as to enable the castor to be releasably locked in a particular direction of travel, the adaption device comprising an engagement member, biasing means for biasing the engagement member, and attachment means for attaching the engagement member at a location adjacent the wheel support, the biasing means being adapted to urge the engagement member into releasable locking engagement with the wheel support when the wheel is arranged in a particular direction of travel, and to automatically release the wheel support when a torque greater than a predetermined value is applied to the castor about said pivot axis.

14. An adaption device as claimed in claim 13, wherein the biasing means is of adjustable biasing strength.

15. An adaption device as claimed in claim 13 or 14, wherein the attachment means is adapted to engage just above the bearings which allow rotation of the wheel support of a typical castor.

16. An adaption device as claimed in any of claims 13 to 15, wherein the attachment means is provided with a recess for receiving a bolt used to attach the castor to a trolley or other article.