AU677884B2 - Locking device for trolley wheels - Google Patents

Description

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Invention Title: ~.NQ pg~~ Q TROLLEY WHE E LS :The following statement is a full description of this invention, including the best *:.:method of performing it known to me:-

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FIELD OF INVENTION The invention relates generally to manually propelled vehicles such as trolleys. Trolleys may take any of a variety of constructions although they usually comprise a carrying portion supported by castors or wheels capable of swivelling movement with respect to the carrying portion. Vehicles of this kind have been in common use for many years for transporting goods in such places as factories, shops, offices, hospitals, schools and so forth. A very common example of this kind of vehicle in use today is a shopping trolley of the type used by shoppers in supermarkets. The invention will be described in relation to a shopping trolley because of its particular application thereto.

S: 10 Shopping trolleys are generally provided with four wheels, each mounted in a forked yoke or similar assembly (hereinafter embraced within the term "yoke") for rotation about a substantially horizontal axis. The yoke is mounted on the trolley to be freely rotatable about a substantially vertical axis. The substantially horizontal axis of the wheel is spaced from the substantially vertical axis of the yoke. When the trolley is pushed, the yoke is 15 supposed to rotate to cause the wheel to adopt a trailing position in the desired direction of .".travel.

BACKGROUND OF INVENTION It has been well-known for a long time that a problem exists with trolleys of the kind described in that trolleys rarely, if ever, move smoothly in the direction required by the user. This problem is prevalent with shopping trolleys, particularly those which have been in use for some time, possibly due to the rather functional nature of the wheel assemblies and certainly due to the rugged treatment that shopping trolleys receive, particularly when they are taken outside a supermarket or shop. When taken outside, shopping trolleys are often propelled by the shopper over rough and corrugated ground, pushed up and down gutters and exposed to other harsh conditions. When abandoned remote from the -3supermarket, shopping trolleys are sometimes maltreated by, for example, being upturned, by being pushed into a ditch or subjected to other improper treatment or to vandalism.

Even when trolleys are collected from disparate locations they may be subject to rough treatment as trolleys are often pushed together to form a train of trolleys and pushed to their storage location either manually or by means of a tractor or like vehicle. Whatever the cause may be, it is well-known that when a shopping trolley is propelled in normal use, the front wheels usually move rapidly from side to side or remain fixed at an inappropriate angle to the desired direction of travel. In an attempt to rectify this situation, some or all of the wheels are often replaced or some other maintenance is carried out on the wheel assembly. However, the problem persists.

9o S• Attempts to alleviate this problem have been proposed. For example, British Patent No.792,374 describes a fully swivelling wheeled castor which includes a fixed component for attachment to the leg of a hand propelled trolley and a swivelling wheel fork carrying 99o.

the castor wheel. The fixed component (or wheel fork) is provided with a spring urged ball .9 9 (or its equivalent) for engagement with a recess in the wheel fork (or fixed component) to locate the castor in a trailing position when the trolley is pushed. When it is desired to move the trolley in other than a straight line, the interengagement of the ball and recess can •be overcome by a lateral force on the trolley. It is mentioned that, when the ball housing is mounted on the wheel fork, a plate attached to the fixed portion may be provided with two diametrically positioned recesses so that the wheeled castor can be located in a fore or aft trailing position with the object of enabling a trolley to be propelled from either end and still retain the advantages of enabling it to be propelled in a straight line without accidental deviation.

A disadvantage with the construction described in British Patent No.792,374 is that the ball housing, irrespective of whether it is mounted on the fixed component or on the wheel fork, is mounted in a rather exposed position and is very liable to be knocked or otherwise damaged. The risk of damage is greater when the wheel is not located in a trailing position. Damage to the ball housing, its mount or other associated parts may cause misalignment of the ball and recess rendering the device ineffective. The construction described in British Patent No.792,374 is not suitable for use on shopping trolleys which experience very rough handling leading to a high damage rate.

Other constructions designed to lessen this problem use a similarly exposed ball housing and suffer the same disadvantage.

In an earlier Australian Application No.17214/92, I proposed a similar construction to overcome this problem wherein the ball housing is mounted in a less exposed position.

However, this earlier proposal was not entirely satisfactory, particularly for shopping trolleys.

o:ooo BRIEF DESCRIPTION OF THE INVENTION It is an object of the invention to provide a device for facilitating the movement of a trolley

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in the direction desired by the person pushing the trolley.

It is also an object of the invention to provide a device for that purpose which can be attached to existing trolleys.

It is another object of the invention to provide a device for that purpose which may be incorporated into new trolleys, It is an additional object of the invention to provide a device for locking a wheel assembly of a trolley to move the trolley in a particular direction and releasing the assembly to move the trolley in a different direction.

It is a further object of the invention to provide such a device which is more rugged that those previously proposed and is suitable for use with shopping trolleys.

Accordingly, the present invention provides a device for releasably locking a wheel assembly of a trolley of the kind described in which a wheel is mounted on a yoke for rotation about a substantially horizontal axis, the yoke being mounted on the trolley for rotation about a substantially vertical axis, the device comprising two members each having an opening surrounding said substantially vertical axis, a first member fixed with respect to the yoke and being rotatable therewith around said substantially vertical axis, a second member adapted to be fixedly mounted with respect to the trolley, the first and second members having adjacent mating surfaces each surrounding the opening in the member, the ;mating surfaces being provided with co-operating locking means to lock the yoke for movement of the trolley in a particular direction and to release the yoke for movement of the trolley in a different direction.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be described in relation to the accompanying drawings in which Fig. 1 is a perspective view of a known wheel assembly of a shopping trolley of the kind currently in use in supermarkets; Fig. 2 is a perspective view of a wheel assembly fitted with a releasable locking device in accordance with one embodiment of the invention; Fig. 3 is an exploded view of the locking device used in Fig, 2; and Fig. 4 is a sectional view of a wheel assembly fitted with a releasable locking device in accordance with a second embodiment of the invention.

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DETAILED DESCRIPTION OF THE DRAWINGS Fig. 1 illustrates a known wheel assembly of a shopping trolley of the kind which has been in use in some supermarkets. The assembly comprises a wheel 1 mounted for rotation about a substantially horizontal axle 2 carried by a forked yoke 3. The forked yoke 3 is integral with or fixedly attached to bearing housing 4. The assembly is mounted on a substantially channel shaped frame member 5 of the trolley (not otherwise shown) by means of a bolt 6 extending from beneath housing 4 through an aperture in frame member and fastened thereto by means of a nut 7. Bearings within housing 4 allow wheel 1, yoke 3 and housing 4 to rotate through 360 degrees about a substantially vertical axis coincident *e S.0 with the cylindrical axis of bolt 6. Axle 3 is spaced from the substantially vertical axis.

When the trolley is pushed, the friction between wheel 1 and the ground should be sufficient to cause yoke 3 to rotate about the substantially vertical axis so that wheel 1 will adopt a trailing position in the direction of travel. However, it is well-known that this seldomly occurs in practice and, as has already been stated, the front wheels of shopping 15 trolleys usually move rapidly from side to side or remain fixed at an inappropriate angle to the desired direction of travel so that forward propulsion of the trolley becomes difficult.

Figs. 2 and 3 illustrate one embodiment of the invention. A wheel assembly of the type illustrated in Fig. 1 is fitted with a releasable locking device comprising two members 11 and 12. Member 11 comprises a ring-like portion 13 with an opening 14 and a skirted portion 15. The bottom edge of skirt 15 may be shaped to engage the limbs of yoke 3.

When assembled, member 11 is positioned over housing 4 and yoke 3 and is firmly held against yoke 3 to lock therewith so that it will rotate with the yoke 3. Of course, member 11 may be fixedly attached to yoke 3 by adhesive, by welding or by any other suitable means. Ring portion 13 is provided with two diametrically opposed spring biased ball capsules 16, equally spaced from the centre of opening 14. Each spring biased ball capsule

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-7may comprise a housing mounted on ring portion 13 and retaining a ball biased outwardly by a compression spring.

Member 12 is in the form of a plate with an opening 17. Member 12 is provided with two diametrically spaced indents 18, equally spaced from the centre of opening 17 at an appropriate distance so that, when the device is assembled, balls 16 are able to co-operate with indents 18 to lock yoke 3 in position. The depth and contour of indents 18 are such as to allow the balls 16 to be released from indents 18 by the application of an appropriate lateral force to yoke 3 or the trolley.

A releasable locking device may be fitted on an existing trolley having a wheel assembly of 10 the type illustrated in Fig. 1 by removing the assembly from frame member 5, passing bolt 6 through openings 16 and 17 and correctly positioning skirt 15 to engage the limbs of yoke 3. Bolt 6 is then passed through the aperture in frame member 5 and nut 7 screwed onto bolt 6. Plate member 12 is held against rotation with respect to the trolley by being retained within the channel of frame member .o 15 Members 11 and 12 have closely adjacent parallel mating surfaces surrounding openings 14 and 17, respectively, and are provided with co-operating locking means in the form of spring biased balls in one member and intents in the other. The locking means are so positioned that, when balls 16 are retained in indents 18, wheel 1 is located and retained in a fore or aft trailing position for forward or backward propulsion of the trolley. By applying a lateral force to the trolley, the locking means are released and the yoke 3 is free to rotate and the trolley may be moved in other than a forward or backward direction.

Furthermore, the use of two diametrically opposed balls 16 and indents 18 provides better balance and control than a device using only one ball 16 and indent 18.

The co-operating locking means being located on the mating surfaces close to openings 14 and 17 and bolt 6 and between plate 12 and ring portion 13 are reliably protected from the -8likelihood of damage. Further protection is aflborded by channel shaped frame member 5 as plate member 12, ring portion 13 and the co-operating locking means are located within the channel. There is thus provided a more reliable and more efficient locking device which has little liability to damage despite the rough treatment shopping trolleys receive.

In the case of new trolleys, parts of the locking device may be formed as integral parts of the wheel assembly or of the trolley frame. For example, member 11 may be formed as an integral part of yoke 3 and/or indents 18 may be formed in the frame member A locking device according to the invention may be fitted to both front, or both back, wheels of a trolley or even fitted to all four wheels. However, somewhat surprisingly, it has been found that a releasable locking device, when fitted to only one wheel, has a more ;positive, single control power than when fitted to two or four wheels. Because each wheel revolves about a substantially vertical axis, they naturally follow a directed lead. By fitting the locking device to only one front wheel, it automatically becomes the masterwheel, encouraging the other wheels to follow. Further, there may be an advantage in fitting a locking device to the front left wheel of a trolley due to a tendency of shoppers keeping left and turning left. This puts the control unit at a pivoting point and presents a disengaging advantage when required.

A second embodiment of the invention is illustrated in Fig. 4 which employs the same reference numerals to indicate the same parts as in the previous embodiment. Members and 21 each comprise a cylindrical shell having an axial opening therethrough mounted coaxially with the substantially vertical axis. In the case of member 20, the cylindrical shell is fixedly attached to the cylindrical surface of bearing housing 4 to rotate therewith about the substantially vertical axis. Member 21 is cup shaped as the cylindrical shell is partially closed at one end to provide protection for the locking means. The external cylindrical surface of member 21 is provided with diametrically opposed flattened portions 19 so that cup shaped member 21 may be retained within frame member 5 so that it is fixed in relation

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-9to the trolley. Mating surfaces are the external cylindrical surface of member 20 and the internal cylindrical surface of member 21. The mating surfaces are provided with cooperating locking means comprising spring biased ball capsules 16 mounted in the cylindrical wall of member 21 and indents 18 provided in member 20. The device functions in the same way as in the first embodiment and the co-operating locking means is similarly protected from damage.

Modifications of the invention will be apparent to persons skilled in the art. For example, the locations of the spring biased ball capsules and indents may be reversed. The compression spring in the capsule could be replaced by other resilient means. Instead of spring biased balls and indents, ol'ier mechanical locking means may be employed. Again, magnetic or electric locking means may be used. Instead of being horizontal as in Figs. 2 and 3, or vertical as in Fig. 4, the mating surfaces could be inclined or frustoconical.

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Claims (5)

1. A device for releasably locking a wheel assembly of a trolley of the kind described in which a wheel is mounted on a yoke for rotation about a substantially horizontal axis, the yoke being mounted on the trolley for rotation about a substantially vertical axis, the device comprising two members each having an opening surrounding said substantially vertical axis, a first member fixed with respect to the yoke and being rotatable therewith around said substantially vertical axis, a second member adapted to be fixedly mounted with respect to the trolley, the first and second members having adjacent mating surfaces each surrounding the opening in the member, the mating surfaces being provided with co- operating locking means to lock the yoke for movement of the trolley in a particular direction and to release the yoke for movement of the trolley in a different direction.

2. A device as claimed in Claim 1, wherein the locking means comprises an indent in S.the mating surface of one member positioned to co-operate selectively with a spring biased ball on the mating surface of the other member.

3. A device as claimed in Claim 1 or Claim 2, wherein the locking means comprises two diametrically opposed indents in the mating surface of one member, the indents being equally spaced from said substantially vertical axis, positioned to co-operate selectively with two spring biased balls on the mating surface of the other member.

4. A device as claimed in Claim 1, 2 or 3, wherein first member comprises a r;.g-like portion on which the mating surface of the first member is located and a skirt depending from the ring-like portion interlocked with the yoke. A device as claimed in Claim 4, wherein said second member is a plate positioned adjacent to the ring-like portion of said first member.

11- 6. A device as claimed in Claim 1, 2 or 3, wherein the first member is in the form of a cylindrical shell mounted coaxially with said substantially vertical axis, the mating surface of the first member being formed on the external cylindrical surface of the shell. 7. A device as claimed in Claim 6, wherein said second member is adapted to be fixedly mounted with respect to the trolley and is cup shaped having a cylindrical portion Siounted coaxially with the substantially vertical axis, the mating surface of the second member being formed on the internal cylindrical surface of the cylinder. S. 8. A device for releasably locking a wheel assembly of a trolley of the kind described substantially as herein described with reference to Figs. 2 and 3 of the accompanying drawings. 9. A device for releasably locking a wheel assembly of a trolley of the kind described substantially as heiein described with reference to Fig. 4 of the accompanying drawings. DATED this 15th. day of FEBRUARY 1995. GEOFFREY ANDREW GRANT By His Patent Attorney PAUL KILDEA.