GB2162072A

GB2162072A - Three-piece solid golf balls

Info

Publication number: GB2162072A
Application number: GB08515676A
Authority: GB
Inventors: Gary West Slater
Original assignee: Dunlop Ltd
Current assignee: Dunlop Ltd
Priority date: 1984-07-04
Filing date: 1985-06-20
Publication date: 1986-01-29
Also published as: GB2162072B; GB8515676D0

Abstract

An inner core member for a three- piece solid golf ball is of generally cubic, tetrahedral or octahedral configuration and includes a plurality of with the inner core member and support members which are integral symmetrically disposed relative to its centre. The inner core member may comprise a plurality of struts diverging from a common centre (40) for example four struts (30, 31, 32, 33), each directed towards one apex of a notional tetrahedron. The support members serve to locate the inner core member symmetrically within a moulding cavity so that in turn the weight of the inner core member is uniformly distributed within the finished golf ball. <IMAGE>

Description

SPECIFICATION Three-piece solid golf balls This invention relates to a method of making three-piece solid golf balls and to golf balls obtained thereby.

As is well known to those skilled in the art, a threepiece solid golf ball consists essentially of: (a) an inner core member (b) an outer core member and (c) a cover member.

The inner and outer core members may be made of identical or similar materials. The cover member may be made of a material different from that of the two core members.

The inner and outer core members are formed into a unitary assembly, suitably by compression or injection moulding. This unitary assembly may then be placed between a pair of preformed "halfshells", the "half-shells" being united under suitable temperature and pressure to form the cover member and thus to complete the golf ball.

Alternatively, the cover material may be injectionmoulded around the unitary core assembly.

The playing properties of a golf ball when struck with a club are directly related to its spin properties.

The spin properties are, in turn, a function of the weight-distribution of the ball itself. It is well established that, for optimum playing properties, the weight of a ball should be symmetrically distributed about its centre of mass.

In manufacturing terms, this means that the unitary assembly of inner and outer core members must be symmetrically located within the cover member. Consequently, the inner core member must be symmetrically located within the outer core member.

This symmetrical location has hitherto been achieved by providing, in a mould of which the mould cavity defines the periphery of the outer core member, retractable pins or similar supports which serve initially to locate the inner core member symmetrically within the mould cavity.

These pins or supports are withdrawn from the mould cavity during the moulding process. Moulds provided with such retractable pins are complicated to make, expensive to produce and not consistent in operation.

The present invention aims to minimise these disadvantages by eliminating the retractable pins from the mould and instead providing the inner core member itself with integral supports, whereby the inner core member can be placed symmetrically into a mould cavity and maintained in the correct position relative to the cavity throughout the moulding process.

Accordingly, the present invention provides a method of making a three-piece solid golf ball by moulding an outer core member around an inner core member and applying a cover member thereto, in which the inner core member is of generally cubic, tetrahedral or octahedral configuration and includes support members, said support members being integral with, and symmetrically disposed relative to the centre of, said inner core member.

The present invention also provides a three-piece solid golf ball made by the method described in the immediately-preceding paragraph.

The present invention further provides an inner core member for a three-piece solid golf-ball, said inner core member being of generally cubic, tetrahedral or octahedral configuration and including a plurality of support members, said support members being integral with, and symmetrically disposed relative to the centre of, said inner core member.

In one embodiment of the present invention, the inner core member including integral support members may be made by means of a forming operation (e.g. by moulding).

Alternatively, the inner core member can be formed by taking an "oversized" spherical core and machining the surface to produce the integral support members.

In a second embodiment, the support members may be made separately and attached to an alreadyproduced core member, e.g. by screwing, pegging or by means of an adhesive.

In a further embodiment of the present invention, the inner core member may comprise a plurality of struts diverging from a common centre. A particularly preferred example of such an inner core member comprises four diverging struts having a common centre, the struts each extending towards one apex of a notional tetrahedron.

The inner and outer core members may be made from a formulation including polybutadiene and a metal salt of an unsaturated organic acid, e.g. zinc methacrylate or zinc dimethacrylate, together with fillers and other ingredients well known to those skilled in the art.

Aiternatively, the inner and/or outer core members may be made from an injectionmouldable thermoplastics material.

The inner core member is most conveniently formed by compression moulding in a suitablyshaped mould. The inner core member obtained according to the present invention is then placed in the cavity of a mould which is to form the outer core member (the support members on the inner core member ensuring its symmetrical positioning within the mould cavity) and the outer core formed by injection-moulding, compression moulding or transfer moulding. The integral assembly of inner and outer core members so obtained is then provided, by means known per se, with a cover member.

The present invention will be illustrated, merely by way of example, in the following description and with reference to the accompanying drawing, the single figure of which shows: a schematic perspective view of an inner core member according to one embodiment of the present invention.

The inner core member comprises four struts 30, 31,32 and 33 diverging from a common centre 40.

Each strut extends from the common centre towards one apex of a notional tetrahedron (shown by dotted lines).

Claims

1. A method of making a three-piece solid golf ball by moulding an outer core member around an inner core member and applying a cover member thereto, in which the inner core member is of generally cubic, tetrahedral or octahedral configuration and includes a plurality of support members, said support members being integral with, and symmetrically disposed relative to the centre of, the inner core member.

2. A method according to Claim 1, in which the inner core member with integral support members is made by means of a forming operation.

3. A method according to Claim 2, in which the forming operation comprises moulding.

4. A method according to Claim 2, in which the forming operation comprises machining of an "oversized" core member.

5. A method according to Claim 1, in which the support members are made separately and attached to an already-produced core member.

6. A method according to any one of Claims 1 to 5, in which the inner core member comprises a plurality of struts diverging from a common centre.

7. A method according to Claim 6, in which the inner core member comprises four struts diverging from a common centre, each said strut being directed towards one apex of a notional tetrahdreon.

8. A method according to Claim 1, substantially as hereinbefore described.

9.An inner core member for a three-piece solid golf ball, said inner core member being of generally cubic, tetrahedral or octahedral configuration and including a plurality of support members, said support members being integral with, and symmetrically disposed relative to the centre of, the inner core member.

10. An inner core memberfor a three-piece solid golf ball, substantially as hereinbefore described, with reference to and as illustrated in the accompanying drawing.

11. A three-piece solid golf ball made by the method of any one of Claims 1 to 8.