AU4084400A - Improved steering wheel geometry for shopping trolleys, shopping carts and the like - Google Patents

Description

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AUSTRALIA

Patents Act 1990 Inventions Development Engineering Answers Pty Ltd

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Invention Title: Improved steering wheel geometry for shopping trolleys, shopping cart and the like The following statement is a full description of this invention including the best method of performing it known to us:- Field of the Invention This invention relates to an improved steering wheel geometry for shopping carts.

Background of the Invention Shopping carts, also referred to as supermarket trolleys or shopping trolleys are notoriously difficult to control. Hereinafter the term "shopping cart" will be used to embrace shopping trolleys, shopping carts, supermarket trolleys and similar carts and trolleys. Shopping carts typically include a chassis comprising a base frame to which four wheels or castors are mounted.

A "basket" or cage for receiving groceries and the like is supported above the chassis. As well as rolling about a horizontal axis, the wheels can also swivel *.*about a vertical axis to enable the cart to change direction easily. This makes the carts very manoeuvrable and able to spin about their centres, which is necessary in order to be able to steer the shopping cart in crowded supermarket aisles, past other customers and past their shopping carts.

However, the swivelling wheel arrangement also means that shopping carts very rarely steer satisfactorily in a straight line.

Many supermarkets are located in shopping malls and customers will often use the shopping cart to push their shopping from the supermarket to their car which will typically be parked in a car park some distance away from the actual supermarket. Car parks tend to have rough, uneven, and often sloping surfaces and such surfaces increase the tendency for the shopping cart to wander and veer to one side in a generally uncontrollable fashion, when pushed. The typical shopping cart's lack of directional stability is also believed to be potentially responsible for back injuries to people pushing trolleys, particularly elderly persons. Yet despite the fact that this problem of steering shopping carts has been known, and indeed joked about, for many years, a shopping cart which steers in a satisfactory manner, has not yet been devised.

Because of their directional instability, shopping carts also have a tendency to tip over. Over a period of three years in the USA, seventy five thousand children were traumatised by being tipped out of shopping trolleys/carts.

The invention seeks to address the problems of the prior art discussed above and provide an improved shopping cart which has sufficient manoeuvrability to be utilised in crowded supermarket aisles, yet also has directional stability, particularly when running on uneven or sloping surfaces.

It is desirable that the improved cart may be provided at an economically viable manufacturing cost.

Summary of the Invention In a first aspect of the present invention, there is provided a shopping cart or the like having a front and back and having a base frame defining a plane from which a plurality of wheels or castors depend, the castors having a rolling axis offset from a swivel axis characterised in that the pivoting or swivel axis of one or more of the castors intersects the plane of the base frame at an angle which is offset from the perpendicular and that the swivel axis also lies in a plane which extends generally along the length of the trolley from back to front.

15 Typically the offset from the perpendicular is 5 to 150.

Most preferably, the offset is about 7 from the perpendicular.

Existing shopping carts may be retrospectively converted to embody the present invention. One method involves the fitting of washers tapered at 7y2 .00 to offset the swivel axis of the cart's existing castors.

.00. 20 In a second aspect of the present invention, there is provided a shopping cart having a base frame, from which depend a plurality of wheels or castors .00 which are mounted so as to be able to swivel about an axis which is generally .perpendicular to the base frame, characterised in that an additional pair of 0 wheels is mounted to the base frame which additional pair are arranged to roll about a fixed axis in a plane parallel to the plane of the base of the base frame, with the ground contacting portion of the fixed axis wheels being spaced from the plane of the frame base of the shopping trolley by a greater distance than the swivelling wheels such that when the trolley rests on a planar horizontal surface, the fixed axis wheels are in contact with that surface.

By fitting the two additional fixed axis wheels to a shopping cart, the cart then becomes steerable and will run in a straight linear direction even on sloping and uneven surfaces, such as is typical in car parks. Yet the cart can still swivel about its own axis.

It is preferred that the floor contacting portion of the pair of fixed axis wheels is about 10mm further below the base frame than the other wheels.

The cart will typically include four swivelling wheels, one at each corner of the base frame.

Shopping carts may be manufactured with the two additional fixed axis wheels already fitted or alternatively the wheels can be retro-fitted to existing shopping carts.

A shopping cart may be provided which encompasses both first and second aspects of the present invention.

In a yet further aspect of the present invention, the present invention encompasses a shopping cart in which either the front or rear pair of a set of swivelling castors on a shopping trolley or cart are fixed so that they cannot swivel. The cart can thus be made easier to steer.

Brief Description of the Drawings A specific embodiment of the present invention will now be described 15 by way of example only and with reference to the accompanying drawings in which: Figure 1 is a schematic drawing of a shopping cart; Figure 2a illustrates an existing castor; Figure 2b illustrates a castor embodying aspects of the present invention; ,Figure 3 illustrates a second embodiment of a shopping cart; Figure 4 illustrates the use of two tapered washers to adjust the swivel axis of an existing trolley; Figure 5 is a perspective view of a tapered washer shown in Figure 4; and Figure 6 is a section through the washer of Figure 5 along lines A-A.

Detailed Description of the Preferred Embodiment Referring to the drawings, Figure 1 shows a schematic representation of a shopping cart 10. The shopping cart includes a basket 12 in which groceries and the like can be placed, which is mounted on a chassis 14 comprising a base frame 16 and a number of supporting wheel or castor assemblies 18.

Figure 2a illustrates a typical existing castor 20 which includes a wheel 22 which rolls about an axle/axis D. The axle is supported by an inverted generally U-shaped frame 24. A post 26 projects vertically upwardly from the frame and defines a pivot or swivel axis V which is substantially perpendicular to the rolling axis D and when the cart rests on the floor, is also substantially perpendicular to the floor 28 and to the plane of the base frame 16 of the shopping cart.

Figure 2b shows a castor 30 embodying the present invention in which the pivot or swivel axis V is offset from the vertical axis V such that the swivel axis V intersects the horizontal plane of the floor or ground 28 and the base frame 16 at a non-perpendicular angle when the cart rests on that floor/ground.

The angle of tilt a is preferably between about 50 and 150 and is most preferably about 7 The tilting of the swivel axis V tends to bias the trolley castor to forward movement along the floor which tends to make the shopping trolley or cart easier to direct and aim over surfaces including uneven surfaces.

:i The axis V lies in a plane extending from the front to the rear of the trolley.

It is sufficient for the shopping cart to have its two front castors having such an offset swivel axis The rear castors may have the standard vertical 15 swivel axis V. It has been found that tilting the front castors and leaving the rear castors with the normal vertical swivel axis, provides substantially improved steering. In tests, with this arrangement it has proved to be possible to move a cart with one hand, up across and diagonally, and in an upslope e*ee curve in a ten degree slope. It will also be appreciated by the reader that the improvement to the shopping cart, steering does not involve any additional components and it should in theory be possible to manufacture improved carts oooo •at the same costs as existing carts. In production, depending on the manufacturing process used, the necessary change may be simply made by altering a welding jig. Existing carts may be converted by fitting tapered washers.

Although it is only necessary to offset the front two castors, all four castors may be offset if desired.

Figures 4 to 6 illustrate the conversion of an existing cart to a cart having offset swivel axes on its two front castors. Arrow A indicates the normal, forward direction of travel of the cart. Two tapered washers 50 are used on each of the two front castors. The washers are shown in more detail in Figures and 6. Each washer tapers from a thick side 54 and a thin side 52 and is about 35mm long and 35mm wide. The angle of the taper is 70 30'. The diameter of the bore 55 through the washer is 13mm.

As shown in the cross sectional view (Figure the sides of the bore are tapered outwards from the centre of the bore at an angle of This allows q, 6 a smaller bore to be provided in the washer than would otherwise be required to cope with the inclined post 26 of the castor. A notch 56 is provided in the narrow (2mm thick) end 52 of the washer. This is provided to indicate to technicians that the washer is correctly installed.

As shown in Figure 4 on the underside of the chassis 16, the thick side 54 of the washer faces the direction of travel A with the notch to the rear.

Above the chassis, the notch faces forward with the thick end 54 of the washer facing away from direction of travel A.

Figure 3 shows a second embodiment of a shopping cart 40. As is the case of the first embodiment, the cart includes a basket 12 mounted on a chassis 14 including a base frame 16, and a handle 19. At each corner of the base frame of the cart, there are four standard swivelling wheels 20 or castors which roll about a generally horizontal axis generally parallel to ground but which are mounted so that they can swivel about a generally vertical axis, as is 15 well known in the art.

In the centre of the base there are two additional wheels 42. Those wheels are mounted on a fixed horizontal axis 44 so that they roll about that fixed horizontal axis 44 but are not capable of swivelling about a vertical axis.

The diameter of the fixed axis wheels 42 is some 10mm greater than that of the swivelling wheels 20 so that when the cart rests on ground, it is supported by the middle wheels 22 and one pair of either the front or the rear castor wheels

S

•g of the cart.

:This particular arrangement maintains the steerability of the trolleys as S" the swivelable wheels are retained at the four corners of the base 16. The trolley can still be swivelled around on its own axis A, as illustrated by arrows C-C. However, when pushing the trolley in a straight line, the fixed axis wheels 42 provide directional stability on uneven and sloping ground.

The wheels 42 can be retro-fitted to existing trolleys as well as incorporated in newly manufactured trolleys.

It will also be possible to utilise both aspects of the present invention in the same shopping trolley or cart with castors having offset swivel axes and additional centre wheel or wheels embodying the second aspect of the present invention.

7 A further method of improving the steerability of a shopping cart involves the fixing of either the front pair or rear pair of the swivel castors on a shopping trolley so the castors can only roll and not swivel. However, although this increases the steerability of the shopping trolley, it has the disadvantage that the shopping trolley can no longer swivel on its central axis.

It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

*ooo*

Claims (12)

1. A shopping cart or the like having a front and rear and having a base frame defining a plane, from which a plurality of wheels or castors depend, the castors having a rolling axis offset from a swivel axis characterised in that the swivel axis of one or more of the castors intersects the plane of the base frame at an angle which is offset from the perpendicular and which lies in a plane which extends generally along the length of the trolley from the rear to the front of the cart.

2. A shopping cart as claimed in claim 1 wherein the offset from the perpendicular is from about 5' to about 15

3. A shopping cart as claimed in claim 1 or claim 2 wherein the offset from the perpendicular is about 7

4. A shopping cart as claimed in any preceding claim wherein the offset is ""."achieved by the use of tapered washers. 00 15

5. A shopping cart having a base frame, from which depend a plurality of 9*99 see* swivelable wheels or castors which are mounted so as to be able to swivel about an axis which is generally perpendicular to the base frame, characterised ooo in that an additional pair of wheels is mounted to the base frame which additional pair are arranged to roll about a fixed axis in a plane parallel to the plane of the base of the base frame, with the ground contacting portion of the fixed axis wheels being spaced from the plane of the frame base of the shopping trolley by a greater distance than the swivelling wheels such that 99 when the trolley rests on a planar horizontal surface, the fixed axis wheels are in contact with that surface.

6. A shopping cart as claimed in claim 5 wherein the floor contacting portion of the pair of fixed axis wheels extends about 10mm further below the base frame than the swivelable wheels.

7. A shopping cart as claimed in claim 5 or claim 6 wherein the trolley includes four swivelling castor wheels, one at each corner of the base frame.

8. A shopping cart comprising a basket or cage for receiving groceries, and having a front and a rear end, said rear end defining a handle for pushing the cart the basket or cage being mounted on a chassis, said chassis comprising a base frame a pair of front castors and a pair of rear castors for supporting the base frame and chassis on a floor surface or the like, the floor contacting portions of the castors defining a plane, wherein at least one pair of castors have a swivel axis oriented in a plane extending generally from the rear to the front of the cart and wherein the swivel axis also makes an angle of between about 50 and about 150 to a vertical axis extending perpendicular to the defined plane.

9. A method of improving the directional stability of a shopping cart having front castors having a rolling axis offset from a vertical swivel axis which vertical swivel axis is substantially perpendicular to a plane along which the cart rolls in normal use, characterised by offsetting the swivel axis by 5° to 150 from the vertical in the direction of normal forward motion of the cart.

10. The method of claim 9 wherein two tapered washers are used to effect the offset. 0

11. A shopping cart substantially as hereinbefore described with reference to and as shown in Figures 1 and 2, or Figure 3.

12. A castor for a shopping cart substantially as hereinbefore described with reference to and as shown in Figures 4, 5 and 6 of the accompanying drawings. Dated this thirteenth day of June 2000 **Of Inventions Development Engineering Answers Pty Ltd Patent Attorneys for the Applicant: F B RICE CO