FIELD OF THE INVENTION The invention relates to a hand trolley which has particular, but not exclusive, utility in the field of nesting shopping trolleys.

BACKGROUND OF THE INVENTION It is known to design a hand trolley with swivelling wheels at the front of the trolley and with non-swivelling wheels at the rear of the trolley. It is also known to reverse this arrangement and have the swivelling wheels at the rear of the trolley and the non-swivelling wheels at the front of the trolley. In both of these arrangements the non-swivelling wheels provide a fulcrum to assist the operator to turn the trolley. When the non-swivelling wheels are at the front, the effort required to turn the trolley is low, but the turning circle relative to the operator is large. When the non-swivelling wheels are at the rear, the effort required to turn the trolley is higher, but the turning circle relative to the operator is small.

Such trolleys having non-swivelling wheels at either the front or rear of the trolley are not easy to manoeuvre in a lateral direction due to the presence of the non-swivelling wheels. This lack of ability to manoeuvre in the lateral direction can be even more problematic when multiple trolleys are nested together, as is the common practice in the field of shopping trolleys.

It is also known to design a hand trolley having swivelling wheels at both the front and rear of the trolley. Whilst these swivelling-wheel trolleys permit lateral movement and are much easier to manoeuvre in the lateral direction, particularly when they are nested together as mentioned above, they provide no fulcrum to assist the operator to turn the trolley. Therefore the operator must act as the fulcrum, which dramatically increases the effort required to

manoeuvre the trolley.

There are also other handling problems associated with these swivelling-wheel trolleys. One problem with these swivelling-wheel trolleys is the tendency for them to run in undesired lateral directions due to the influence of gravity when they are moving across an inclined surface. Of course, this undesirable tendency is increased when the swivelling-wheel trolley is heavily loaded with, for example, groceries or the like.

In the same inclined-surface situation with a trolley with front non-swivelling wheels, the lateral force is resisted approximately equally by the front wheels, and by the operator through the rear mounted handle. When the rear wheels are non-swivelling the operator must resist the lateral force at the front of the trolley, but indirectly through the rear mounted handle, and therefore the effort required is high. Changing the direction of travel of swivelling-wheel trolleys can be difficult due to the inertial tendency of the trolley to keep moving in the original direction of travel, in part because there is no fulcrum to work against. Again, this undesirable inertial tendency is increased when the trolley is heavily loaded with, for example, groceries or the like.

It is known to modify a hand trolley having swivelling wheels by adding a non- swivelling wheel in an intermediate position between the front and rear swivelling wheels. The addition of a non-swivelling intermediate wheel reduces the handling problems mentioned above by resisting undesired lateral motion. The intermediate non-swivelling wheel also acts as a convenient fulcrum when changing the direction of travel of the trolley. This reduces the turning circle of the trolley to almost zero and provides a good bending moment between the intermediate non-swivelling wheel and the rear mounted handle to minimise turning effort. When traversing an inclined plane, the lateral load of the trolley is largely resisted by the intermediate non-swivelling wheel, with little lateral force transmitted through the handle by the operator.

The addition of an intermediate non-swivelling wheel to a swivelling-wheel hand trolley is exemplified by:

(i) US Patent 4,826,186 assigned to Ostosvaunuhuolto Oy, and

(ii) European Patent 0 352 647 assigned to Wanzl Metallwarenfabrik KG. Each of these patents is hereby incorporated in its entirety by cross reference. US Patent 4,826,186 teaches the addition of a pair of non-swivelling

intermediate wheels (6a, 6b) which are fixedly mounted at a level slightly lower than the plane containing the swivelling front wheels (5a, 5b) and the swivelling rear wheels (7a, 7b) . As a consequence, either the front swivelling wheels (5a, 5b) or the rear swivelling wheels (7a, 7b) are lifted clear of the supporting surface, depending on how the load is distributed on the trolley. Put differently, the trolley is able to "rock" back and forth on the intermediate non-swivelling wheels (6a, 6b). This would make the trolley particularly unpleasant to use, and the fact that the non-swivelling intermediate wheels are always in contact with the support surface means that the trolley cannot be manoeuvred in a lateral direction, either when in isolation or when nested with other like trolleys.

European Patent 0 352 647 teaches the addition of a single non-swivelling intermediate wheel (16) which depends from a pivotally mounted carrier arm (11) which is spring biased such that the intermediate wheel (16) is resiliently urged into engagement with the underlying support surface. A compression spring (17) extends between a pivotally mounted load-bearing platform (9) and the pivotally mounted carrier arm (11) such that the spring is compressed when a load is placed on platform (9). When unloaded, platform (9) is raised by the spring such that nesting of like trolleys may occur. When like trolleys are nested together, a lifting device (18) on the front of the rear trolley engages a projection (15) on the carrier arm (11 ) of the front trolley and thereby lifts the carrier arm (11) and compresses the compression spring (17), or at least raises the platform (9). The ability to move nested trolleys in a lateral direction is made possible when the non-swivelling intermediate wheel (16) is disengaged from the support surface.

In use, as the load on the platform (9) increases, the platform will pivot downwardly relative to the frame to a substantially horizontal position at which it will engage the frame of the trolley. At this point, the load transferred to the non-swivelling intermediate wheel (16) cannot increase any further as the platform (9) has reached the limit of its downward travel and the compression spring (17) is maximally compressed. Thus, the load transferred to the intermediate wheel (16) is proportional to the load on the platform (9) up to a point, but thereafter the load on the intermediate wheel (16) cannot increase any further. Therefore, any extra load added to the trolley is carried in a lesser and lesser proportion by the intermediate wheel. This limitation is problematic as the handling disadvantages associated with swivelling wheel trolleys are proportional to the load on the trolley as discussed earlier. Whilst this

shortcoming may be addressed to some extent by adopting a stronger compression spring, by delaying the point where contact is made with the fixed frame, this will also delay the point where the platform is horizontal, and an inclined load carrying surface is undesirable.

It is also noted that the act of nesting these trolleys requires the lifting of the carrier arm (11) and, to some degree depending on the ability of the platform (9) to be raised by a corresponding amount, the compression of the compression spring (17). Therefore, if a stronger compression spring is adopted, greater manual force may be required to nest the trolleys together and the trolleys also may have a greater tendency to push themselves apart after they have been nested.

A further problem with this compression spring design resides in the fact that it is generally unsuitable for nesting shopping trolleys, of the type having a raised shopping basket, due to the need for there to be some mechanism for transferring the load on the trolley (i.e. the weight of the groceries located in a raised shopping basket) to the compression spring and hence to the

intermediate non-swivelling wheel. Any such hypothetical mechanism would need to extend downwardly from the raised shopping basket towards the bottom frame and would interfere with the nesting of the shopping trolleys.

SUMMARY OF INVENTION The present invention provides a hand trolley according to the following claims.

In a preferred embodiment, the hand trolley is a nesting shopping trolley with a grocery basket. In a preferred embodiment, the act of nesting hand trolleys together results in the disengagement of the non-swivelling wheel(s) from the support surface.

Other preferred features of the hand trolley will be apparent from the dependant claims and from the following description of the preferred embodiment. BRIEF DESCRIPTION OF DRAWINGS

The invention will now be described in a non-limiting manner with respect to a preferred embodiment in which:-

FIG 1 is a perspective view of a hand trolley according to the present invention;

FIG 2 is an exploded perspective view of the hand trolley; FIGS 3A to 3C are a series of three views with the elevated shopping basket removed from the articulated bottom frame for greater clarity;

FIGS 4A to 4C are a series of three side elevation views (with some hidden detail visible) showing the nesting of a pair of articulated bottom frames; and

FIGS 5A to 5C are a series of three side elevation views (with some hidden detail visible) showing the nesting of a pair of shopping trolleys.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

With reference to FIG 1 , there is shown a shopping trolley 10. The shopping trolley 10 comprises an elevated shopping basket 12, a transversely-extending handle 14, and an articulated bottom frame 16. As is usual, the rear wall of the elevated shopping basket 12 can pivot forwardly about its upper edge to allow nesting of the shopping basket 12 with another following shopping basket. As is usual, the bottom frame 16 is generally U-shaped in plan, and is open to the rear in order to receive the bottom frame of another following trolley during nesting. Referring now to FIG 2, the articulated bottom frame 16 comprises a first or rear sub-frame 18 and a second or front sub-frame 20 which are mounted together in an articulated manner which will be described in more detail below.

First or rear sub-frame 18 comprises of a pair of side members 22 which converge together in the forward direction to facilitate nesting with other like trolleys. The side members 22 may be joined by a transversely extending strut which is not illustrated. Each side member 22 has a swivelling wheel 24 depending downwardly adjacent the rear end of the side member 22 and a basket-mounting bracket 26 extending upwardly from the side member 22. The forward end of each side member 22 terminates in an apertured flange 28 which receives a bolt 30, as will be described in more detail below.

Second or front sub-frame 20 comprises a frame 32 which is generally D- shaped in plan. A pair of swivelling wheels 34 depend downwardly from the forward end of the D-shaped frame 32, and a non-swivelling wheel 36 is mounted on a carrier arm 38 which extends downwardly and rearwardly from the rear of the D-shaped frame 32.

Carrier arm 38 is comprised of a pair of transversely-spaced sub-arms which straddle and mount the axle of the non-swivelling wheel 36 between the spaced sub-arms. Each sub-arm is generally L-shaped in side elevation, as best seen in FIG 3C.

Still referring to FIG 2, an articulation lever 40 extends upwardly and rearwardly from the rear of the D-shaped frame 32. Carrier arm 38 and articulation lever 40 are fixedly mounted to the D-shaped frame 32 by welding or the like.

A contact pad 42 is mounted at the forward end of the D-shaped frame 32. Contact pad 42 is manufactured from a durable, low-friction material such as polyethylene, and is adapted to engage the articulation lever 40 of another leading trolley as will be discussed in more detail below.

Referring now to FlG 3, rear sub-frame 18 and front sub-frame 20 are shown assembled together to form an articulated bottom frame 16. The assembly is achieved via bolts 30 which pass through the apertured flanges 28 and are engaged with threaded bores provided in the lateral sides of the D-shaped frame 32. In the preferred embodiment, a transversely-extending axle is rotatably mounted within the D-shaped frame 32. Each end of the transverse axle includes a threaded bore which receives bolt 30. Of course, washers and the like are used to ensure smooth and reliable articulation of the front sub- frame 20 relative to the rear sub-frame 18.

It will be readily understood that a transversely-extending articulation axis is defined by the transverse axle which extends through the D-shaped frame 32, and the articulation axis is co-axially aligned with the bolts 30 and the aperture in the apertured flange 28.

Articulation of the front sub-frame 20 relative to the rear sub-frame 18 is illustrated in FIGS 3B and 3C. It will be observed that the swivelling wheels 34 of the front sub-frame are located forwardly of the articulation axis, whereas the non-swivelling wheel of the front sub-frame is located rearwardly of the articulation axis. This means that both the swivelling wheels 34 and the non- swivelling wheel 36 are normally urged into engagement with the underlying support surface under the effect of gravity as shown in FIG 3A.

As can be seen from FIG 3C, articulation of the front sub-frame relative to the rear sub-frame is possible in both directions, such that contours in the surface being traversed can be accommodated and all three wheels of the front sub- frame usually remain in contact with the surface.

When articulated in the direction shown in FIG 3B, the non-swivelling wheel 36 is disengaged from the underlying supporting surface. The act of articulating the front sub-frame relative to the rear sub-frame has the effect of lifting the articulation axis and the front of the trolley against the influence of gravity. As a practical matter, the articulation of the front sub-frame relative to the rear sub- frame is limited, in order to ensure that the front sub-frame does not "jack-knife" under the rear-sub-frame when the front swivelling wheels 34 strike. a gutter or the like. In the illustrated embodiment, the articulation axis is about 160mm behind front swivelling wheels' 34 vertical axes, about 230mm in front of the non-swivelling wheel 36, and about 620mm in front of the rear swivelling wheels' 24 vertical axes. This means that the wheelbase of the trolley is about 780mm and the non-swivelling wheel 36 is located at the mid-point of the wheelbase.

In a less preferred embodiment, it is conceivable that both the swivelling wheels and the non-swivelling wheel could be located on the same side of the articulation axis with the act of articulation disengaging the non-swivelling wheel from the underlying support surface. However, in this less preferred

embodiment, there would need to be means to limit the articulation of the front sub-frame relative to the rear sub-frame in both directions, and the ability of the front sub-frame to follow contours would be significantly less. With reference to FIGS 4A to 4C, the nesting of a pair of articulated bottom frames is shown in sequential fashion.

In FIG 4A, the contact pad 42 of the rear trolley has not yet engaged the rearwardly inclined articulation lever 40 of the front trolley.

In FIG 4B, the contact pad 42 has engaged the articulation lever 40 and has begun to articulate the front sub-frame of the front trolley relative to the rear sub-frame of the front trolley. This means that the articulation axis and the front of the front trolley are beginning to be lifted against the effect of gravity and the non-swivelling wheel 36 of the front trolley is beginning to disengage from the underlying support surface.

In FIG 4C, the nesting action has been completed, the front sub-frame of the front trolley has been fully articulated relative to the rear sub-frame of the front trolley, and the non-swivelling wheel 36 of the front trolley has been fully disengaged from the support surface.

It will be noted that articulation lever 40 is formed from a rectangular strip of material which is bent at a point along its length. This allows the articulation lever 40 to present a 2-stage camming profile to the contact pad 42 of the following trolley which ensures that the front sub-frame is firstly articulated to the correct orientation relative to the rear sub-frame and, in a second stage, is securely retained in the correct orientation in a manner which tends to resist separation of the two nested trolleys.

FIGS 5A to 5C show the same nesting sequence, and also illustrate the nesting of the elevated shopping baskets 12. The pivoting rear wall of the elevated shopping basket has been omitted for clarity.

With reference to FIG 5A, it will be noted that the underside of the basket 12 includes a second contact block 43. When the basket 12 of the following trolley is fully nested, the second contact block 43 contacts the upwardly inclined bottom of the basket of the leading trolley and this lifts the front of the following trolley. As the front of the following trolley is lifted, the front sub-frame of the following trolley is articulated. This mechanism ensures that the non-swivelling wheel of the rearmost trolley in a stack of nested trolley is also lifted clear of the supporting surface. Of course, this ensures that the stack of nested trolleys can be manoeuvred in the lateral direction.

It will be appreciated that the preferred embodiment of the present invention provides a swivelling wheel shopping trolley in which a non-swivelling wheel is provided intermediate the front and rear pairs of swivelling wheels in order to provide superior lateral stability relative to other swivelling wheel shopping trolleys. The non-swivelling wheel is selectively disengaged from the support surface during nesting. The rearmost trolley in the stack articulates in response to a different mechanism than that used to articulate the front-most trolley.

The preferred embodiment is greatly simplified relative to the embodiment taught by EP 0 352 647. For example, the preferred embodiment does not require the use of compression springs or the like. Further, the load on the non- swivelling wheel is proportional to the load on the trolley, without limitation.

Whilst the preferred embodiment shows the articulation axis extending transversely of the trolley, it is conceivable that the articulation axis might extend longitudinally of the trolley such that left and right sub-frames are defined, as opposed to front and rear sub-frames.

Whilst the preferred embodiment shows a single non-swivelling wheel, it is conceivable that multiple co-axial non-swivelling wheels might be employed. Whilst the preferred embodiment shows a pair of front swivelling wheels and a pair of rear swivelling wheels, some other number or combination of swivelling wheels (e.g. tricycle) might be employed.

Whilst the preferred embodiment shows conventional wheels with an axle and hub, the term "wheel" is used herein in a generic sense and encompasses other types of rolling elements. Whilst the preferred embodiment shows the front sub-frame being articulated as a consequence of being nested, the front sub-frame may also be associated with other articulation mechanisms, for example a foot pedal or similar. This would be particularly applicable to other types of hand trolleys, e.g. flat bed trolleys designed to transport heavy items. In even heavier applications, the articulation may be driven by a hydraulic ram or the like.

Throughout this specification and the claims, unless the context requires otherwise, the word "comprise" and its variations, such as "comprises" and "comprising," will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

The reference to any prior art in this specification is not, and should not be taken as an acknowledgement or any form of suggestion that such art forms part of the common general knowledge in the art.