GB2467956A

GB2467956A - Tyres

Info

Publication number: GB2467956A
Application number: GB0902976A
Authority: GB
Inventors: Balbinder Singh Sehmi
Original assignee: EVA PLAS INJECTION MOULDING LT
Current assignee: EVA PLAS INJECTION MOULDING LT
Priority date: 2009-02-21
Filing date: 2009-02-21
Publication date: 2010-08-25
Anticipated expiration: 2029-02-21
Also published as: GB2467956B; GB0902976D0

Abstract

A studded tyre 3 for a trolley, cart, buggy or the like is made of expanded foam with studs 25 of generally frusto-conical shape arranged in two circumferentially extending rows. Each row contains the same number of studs 25 uniformly spaced apart in the circumferential direction with the studs 25 in one row transversely aligned with the studs 25 of the other row. The tyre 3 is formed with integral studs 25 by injection moulding. The tyre 3 is mounted on a rim 5 of a wheel 7 for attaching to the trolley, cart, buggy or the like and the tyre 3 and rim 5 are configured to resist relative rotation. The tyre 3 may be fitted onto the wheel 7 while hot and allowed to cool on the wheel 7 so that the tyre 3 contracts to grip the wheel 7.

Description

TYRES

This invention relates to tyres. The invention has particular, but not exclusive, application to tyres for a wheel of a trolley, cart, buggy or the like. The invention is especially suitable for tyre and wheel assemblies for trolleys used to transport equipment such as a golf trolley for golf clubs or a fishing trolley for fishing tackle.

Golf trolleys are commonly used by golfers to transport a golf bag containing their clubs. The golfer may push or pull the trolley around the course. The known golf trolleys may employ solid rubber tyres or pneumatic tyres. In dry conditions, such tyres cause little or no damage to the course. However, in wet conditions when the ground may become soft or muddy the tyres can cause ruts or furrows in the ground producing uneven lies for golf balls and may result in the grass dying. It has already been proposed to alleviate these problems by employing tyres having a wide tread that spreads the weight of the trolley and golf clubs in order to reduce damage to the course. This solution is not entirely satisfactory, however as increasing the width of the tyre increases the contact surface between the tyre and the ground which in turn increases the drag making it harder to manoeuvre the trolley over the ground.

Manoeuvring the trolley can also be made harder due to the weight of mud and dirt picked up by the tyre which is increased with increased width of the tyre.

The present invention has been made from a consideration of the foregoing and seeks to provide a tyre for a wheel of a trolley, cart, buggy or the like that overcomes or at least mitigates one or more of the problems and disadvantages of existing tyres.

According to a first aspect of the invention, we provide a tyre for attachment to a wheel of a trolley, cart, buggy or the like wherein the tyre has a plurality of studs extending generally radially from an outer surface of the tyre, the studs being arranged in a plurality of rows extending in a circumferential direction around the outer surface of the tyre, and wherein the studs in at least two rows are aligned.

The studs reduce the contact area between the tyre and the ground so that drag and damage to the ground may be reduced, especially in wet conditions and, a trolley to which the tyres are fitted may be easier to manoeuvre.

The alignment of the studs distributes loads evenly between the tyre and the ground so that the tyre can run smoothly over the ground and damage to the ground and to the wheel, especially wheel bearings, may be reduced.

Preferably, the studs are arranged symmetrically about a centre line of the outer surface. This may further assist in distributing loads evenly.

Preferably, studs are resilient. For example, the studs may comprise a foam plastics that imparts a degree of resilience to the studs. Preferably the studs comprise an expanded foam plastics where expansion of the foam plastics is controlled to provide a desired resilience.

Preferably, the studs are formed integrally with the tyre. For example, the tyre and tyre studs may be formed by injection moulding a foam plastics and allowing the foam plastics to expand to form the tyre and tyre studs.

Preferably, the foam plastics is ethylene vinyl acetate (EVA) although other polymers and/or copolymers may be employed. Preferably, the EVA is mixed with a blowing agent and peroxide to achieve the desired expansion. The mix may be varied to control expansion according to the size and/or density of the finished tyre.

Preferably, the tyre is initially produced in an unexpanded form and heated so that the material expands to the required size and shape of the finished tyre. For example, the mixture may be heated to around 170°C to 180°C Preferably, the tyre is fitted to the wheel while still hot. We have found that the foam material contracts slightly on cooling and this contraction can contribute to obtain a tight fit of the tyre on the wheel.

Preferably, the studs in each row are uniformly spaced apart in the circumferential direction. Preferably, there are at least eight studs, more preferably at least twelve studs and most preferably at least sixteen studs in each row.

With sixteen studs, the spacing between successive studs in the circumferential direction subtends an arc of 22.5°. We have found this spacing together with the resilience of the studs can produce a smooth "cushion" ride over surfaces of different type and/or different hardness such as may be encountered in different areas, for example tarmac often used for car parks and paths and grass used for the tees, fairways and greens of a golf course.

Preferably, the studs are of frusto-conical shape with a convexly rounded tip. We have found this shape does not dig into the ground so that the trolley may be easier to pull and damage to the ground and wear of the studs may be reduced.

According to a second aspect of the invention, we provide a tyre for attachment to a wheel of a trolley, cart, buggy or the like wherein the tyre has a plurality of studs extending generally radially from an outer surface of the tyre, the studs being arranged in a plurality of rows extending in a circumferential direction around the outer surface of the tyre, and wherein the studs are resilient.

Other features of the studs and the tyre may be as described for the first aspect of the invention.

According to a third aspect of the invention, we provide a tyre for attachment to a wheel of a trolley, cart, buggy or the like wherein the tyre has a plurality of studs extending generally radially from an outer surface of the tyre, the studs being arranged in a plurality of rows extending in a circumferential direction around the outer surface of the tyre, and wherein the studs are of frusto-conical shape with a convexly rounded tip.

According to a fourth aspect of the invention, we provide a tyre for attachment to a wheel of a trolley, cart, buggy or the like wherein the tyre has a plurality of studs extending generally radially from an outer surface of the tyre, the studs being arranged in a plurality of rows extending in a circumferential direction around the outer surface of the tyre, and wherein the studs comprise a foam plastics.

According to a fifth aspect of the invention, we provide a tyre and wheel assembly for a trolley, cart, buggy or the like employing a tyre according to any of the preceding aspects of the invention.

Preferably the wheel has an annular wheel rim and the tyre is mounted in the wheel rim. Preferably, a radially outer surface of the tyre is wider than the wheel rim. Preferably, the radially outer surface of the tyre extends laterally to either side of the wheel rim. Preferably, the wheel rim is radially aligned with a centre line of the tyre.

Preferably the tyre and wheel rim are co-operable to resist relative rotation between the tyre and wheel. For example, the wheel rim may have one or more notches or recesses to receive a lug on the inner surface of the tyre. Alternatively or additionally, the wheel rim may have one or more spikes arranged to embed in the tyre. Preferably, the or each spike is inclined in the circumferential direction.

Preferably, the wheel is rotatable about an axis of rotation defined by a wheel hub. Preferably, the wheel hub includes a bearing for rotatably supporting the wheel on a shaft or axle.

According to a sixth aspect of the invention, we provide a method of manufacturing a tyre according to any of the preceding aspects of the invention, the method including the steps of forming the tyre using an expandable foam.

Preferably, the method includes the step of forming an unexpanded pre-form and allowing the pre-form to expand to the required shape of the tyre at an elevated temperature.

Preferably, the method includes the step of fitting the tyre to a wheel while hot and allowing the tyre to cool on the wheel such that the tyre contracts to grip the wheel.

Other features, benefits and advantages of the invention will be apparent from the following description of exemplary embodiments.

The invention will now be described in more detail by way of example only with reference to the accompanying drawings wherein Figure 1 is a side view of a tyre and wheel assembly embodying the invention; and Figure 2 is a section on the line 2-2 of Figure 1.

Referring to the drawings, a tyre and wheel assembly 1 embodying the invention is shown and comprises a microcellular solid foam tyre 3 mounted on a rim 5 of a rigid wheel 7 having a central hub 9 containing a bearing (not shown) for rotatably mounting the wheel 7 on an axle (not shown) of a golf trolley (not shown).

The tyre 3 is an injection moulded foam plastics material such as ethylene vinyl acetate (EVA) mixed with a blowing agent and peroxide to obtain the desired expansion. The wheel 7 is an injection moulded rigid plastics material such as polypropylene (PP). Foam plastics is preferred for the tyre 3 for lightness and EVA is the preferred foam material for toughness, hard wearing and abrasion resistance. Rigid plastics is preferred for the wheel 7 for combined strength and lightness and PP is the preferred material for cleaning and resistance to extremes of heat and cold. It will be understood however that other plastics materials and composites thereof may be used for the tyre 3 and/or wheel 7.

Alternatively or additionally, the tyre 3 and/or wheel 7 may be made of any other suitable materials. For example, the tyre may be made of elastomeric foam and the wheel may be made of metal.

The rim 5 comprises an annular groove 11 of generally U-shape having a base ha and sidewalls llb,llc. The tyre 3 comprises an annular body 13 of generally triangular shape having a generally flat, radially outer surface 13a and sidewalls 13b,13c convergent to a base 13d that is located in the groove 11. As shown in Figure 2, the outer surface 13a of the body 13 of the tyre 3 is wider than the groove 11 of the rim 5 of the wheel 7.

The rim 5 and tyre 3 are provided with co-operating formations to resist rotation of the tyre 3 relative to the wheel. The co-operating formations include a plurality of radially inwardly extending lugs 15 uniformly spaced apart around the circumference of the base 13d of the tyre body and two sets of diametrically opposed notches or recesses 17 in the groove 11. In this embodiment there are three recesses 17 in each set and eight lugs 15 spaced apart at intervals of 450 so that a pair of lugs spaced apart 180° are located in the recesses 17 to locate the tyre in the circumferential direction. One set of recesses 17 may be indicated by a witness mark 27 on the rim to assist alignment of the lugs 15 with the recesses 17 when fitting the tyre 3 to the rim 5.

The groove 11 is also provided with spikes 19 that project from the base ha of the groove and embed in the base 13d of the tyre 3 to further resist rotation of the tyre 3 relative to the wheel 7. In this embodiment there are four spikes 19 arranged in two pairs with one pair in the area 21 between the recesses 17 on one side of the wheel and the other pair in the areas 23 between the recesses 17 on the other side of the wheel. The spikes 19 extend in the circumferential direction with each pair of spikes extending in opposite directions to one another. In this way, one spike of each pair tends to become more embedded in the base 13d of the tyre 3 in response to any force tending to rotate the tyre relative to the wheel in one direction and the other spike tends to become more embedded in the base 13d of the tyre 3 in response to any force tending to rotate the tyre relative to the wheel in the opposite direction. The number, spacing and arrangement of the spikes may vary according to requirements. One spike may be provided but generally there will be at least two spikes circumferentiafly inclined in opposite directions.

The tyre 3 is further provided with a plurality of studs 25 formed integrally with the body 13 to extend radially from the outer surface 13a.

the studs 25 are arranged in two sets 25a, 25b of studs uniformly spaced apart in the circumferential direction. The studs in each set are aligned in the circumferential direction and are also aligned in a transverse direction with the studs of the other set. The studs are also arranged symmetrically with respect to a centre line of the outer surface 13a of the tyre 3. In this embodiment there are 16 studs in each set spaced apart at intervals of 22.5°. With this number and spacing of the studs, a minimum of two studs -one from each set -engage the surface over which the tyre is travelling at any time and the four studs -two from each set -engage the surface as the tyre rotates to transfer the contact from stud to stud in the circumferential direction.

The symmetrical arrangement of the aligned studs may allow the wheel to rotate smoothly in a balanced manner without rocking from side to side.

In this way, loads can be distributed evenly and out of balance forces that may cause increased wear and failure of the bearings can be reduced or may even be avoided. The number and spacing of the studs may vary according to the dimensions of the wheel and tyre assembly and is preferably chosen so that successive studs in the circumferential direction come into contact the surface after a relatively small amount of angular movement and so that four studs contact the surface at rest thereby further increasing stability. Eight studs may be provided in each row but generally there will be at least twelve studs per row and more usually sixteen or more studs per row.

The studs are of frusto-conical shape with a convex or rounded tip so that any tendency for the studs to dig into a soft surface such as when traversing grass can be reduced thereby reducing damage to the surface.

Furthermore, the resilience of the foam material from which the tyre is constructed can have a cushioning effect when traversing different surfaces potentially resulting in increased comfort for the user and reduced damage to the surface, especially harder surfaces such as tarmac or block paving used for car parks, paths and other areas of high density usage.

Furthermore, the resilience of the foam material can reduce damage to the tyre from impact with objects such as stones and may prevent pick-up of stones while the use of a tough, abrasion resistant material can reduce wear to the tyre from contact with rough surfaces or materials such as grit.

We prefer to form the tyre by injection moulding an unexpanded pre-form using a mix of EVA or other polymer, blowing agent and peroxide at an elevated temperature in the region of 170°C to 180°C for EVA and allowing the pre-form to expand to the required shape of the tyre. The mix may include a colouring agent to produce a coloured tyre according to customer requirements. We may mount the tyre on the wheel rim before it has cooled whereby contraction of the tyre that occurs on cooling may be used to ensure a tight fit of the tyre on the wheel.

Typically a hand pulled golf trolley will have a pair of tyre and wheel assemblies 1 as above-described rotatable about a common axis. An electric golf trolley may have in addition, a third tyre and wheel assembly which may be steerable for controlling the direction in which the trolley moves. A remote control unit may be provided to operate an electric golf trolley. The tyre and wheel assemblies of an electric golf trolley may have wider tyres to accommodate the extra weight and this may require the tyre to have more than two sets of circumferentially extending studs.

For example a set of studs may be provided on the centre line of the tyre with a further set of studs symmetrically arranged on either side of the centre set. All three sets may contain the same number of studs with the studs circumferentially aligned. Alternatively, the two outer sets may contain the same number of studs with the studs circumferentially aligned and the centre set may contain the same or a different number of studs that are circumferentially offset relative to the studs in the outer sets while maintaining an arrangement that is symmetrical about the centre line. Other arrangements of the studs will be apparent to those skilled in the art.

While the invention has been described with particular reference to a tyre and a tyre and wheel assembly for a golf cart, it will be understood that we do not intend to be limited to such application and that the invention may be used for any type of trolley, cart, or buggy, for example a fishing trolley as well as other articles having one or more ground engaging wheels, for example a wheelbarrow.

Claims

CLAIMS1. A tyre for attachment to a wheel of a trolley, cart, buggy or the like wherein the tyre has a plurality of studs extending generally radially from an outer surface of the tyre, the studs being arranged in a plurality of rows extending in a circumferential direction around the outer surface of the tyre, and wherein the studs in at least two rows are aligned.
2. A tyre according to claim 1 wherein, the studs are arranged symmetrically about a centre line of the outer surface of the tyre.
3. A tyre according to claim 1 or claim 2 wherein, the studs are formed integrally with the tyre.
4. A tyre according to any preceding claim wherein, the studs are resilient. * *
5. A lyre according to claim 4 wherein, the studs comprise foam * plastics that imparts a degree of resilience to the studs. S.

: 20
6. A tyre according to claim 5 wherein, the studs comprise expanded **S S.* * foam plastics.
7. A tyre according to claim 6 wherein expansion of the foam plastics is controlled to provide a desired resilience.
8. A tyre according to any of claims 5 to 7 wherein, the tyre and studs are formed by injection moulding a foam plastics and allowing the foam plastics to expand to form the tyre and studs.
9. A tyre according to any of claims 5 to 8 wherein, the foam plastics is ethylene vinyl acetate (EVA).
10. A tyre according to claim 9 wherein, the EVA is mixed with a blowing agent and peroxide to achieve the desired expansion.
11. A tyre according to any of claims 8 to 10 wherein, the tyre is initially produced in an unexpanded form and heated so that the material expands to the required size and shape of the finished tyre.
12. A tyre according to any of the preceding claims wherein, the studs in each row are uniformly spaced apart in the circumferential direction.
13. A tyre according to any of the preceding claims wherein, there are at least eight studs in each row. * *
14. A tyre according to claim 13 wherein, there are at least twelve studs in each row. **
15. A tyre according to claim 14 wherein, there are at least sixteen *..*..* studs in each row.
16. A tyre according to any of the preceding claims wherein, the studs are of frusto-conical shape with a convexly rounded tip.
17. A tyre according any of the preceding claims wherein, the studs in each row are aligned in the circumferential direction and are aligned in a transverse direction with studs of another row.
18. A tyre according to any of the preceding claims wherein, four studs contact the surface at rest.
19. A tyre for attachment to a wheel of a trolley, cart, buggy or the like substantially as hereinbefore described with reference to Figures 1 and 2 of the accompanying drawings.
20. A tyre and wheel assembly for a trolley, cart, buggy or the like provided with a tyre according to any of the preceding claims.
21. A tyre and wheel assembly according to claim 20 wherein, the tyre is mounted on a rim of the wheel.
22. A tyre and wheel assembly according to claim 21 wherein, a radially outer surface of the tyre is wider than the wheel rim.* ** S.. * I
23. A tyre and wheel assembly according to claim 22 wherein, the radially outer surface of the tyre extends laterally to either side of the wheel rim. *5* *. 20IS.....

*
24. A tyre and wheel assembly according to claim 23 wherein, the wheel rim is radially aligned with a centre line of the tyre.
25. A tyre and wheel assembly according to any of claims 21 to 24 wherein, the tyre and wheel rim are co-operable to resist relative rotation between the tyre and wheel.
26. A tyre and wheel assembly according to claim 25 wherein, the wheel rim has one or more notches or recesses to receive a lug on the inner surface of the tyre.
27. A tyre and wheel assembly according to claim 25 or claim 26 wherein, the wheel rim has one or more spikes arranged to embed in the tyre.
28. A tyre and wheel assembly according to claim 27 wherein, the or each spike is inclined in the circumferential direction.
29. A tyre and wheel assembly according to any of claims 20 to 28 wherein, the wheel is rotatable about an axis of rotation defined by a wheel hub.
30. A tyre and wheel assembly according to claim 29 wherein, the wheel hub includes a bearing for rotatably supporting the wheel on a shaft **I* or axle.* S.... * *
31. A method of manufacturing a tyre according to any of claims 1 to 19, the method including the steps of forming the tyre using an :. expandable foam. * 20

* *. S., *
32. A method according to claim 31 wherein, the method includes the step of forming an unexpanded pre-form and allowing the pre-form to expand to the required shape of the tyre at an elevated temperature.
33. A method according to claim 32 wherein, the method includes the step of fitting the tyre to a wheel while hot and allowing the tyre to cool on the wheel such that the tyre contracts to grip the wheel.