AU734770B2 - Golf ball - Google Patents

Description

GK-GEY-1009 GOLF BALL Field of the Invention The invention is directed to a golf ball in a multiple-part construction with a core, a covering, and a shell.

Prior Art Golf balls are manufactured the world over in large quantities and in different constructions. The differences in construction result from various construction designs and from the different materials used for these designs. In this respect, all balls, regardless of construction, must conform to golfing regulations German Golf Association Rules, Appendix Ill).

Nevertheless, the golfer has certain expectations for the golf balls which go beyond the characteristics set down in the regulations minimum size, maximum weight). The golfer expects the golf ball to achieve long distances and to have the ability to receive spin when struck (what is referred to by the golfer as "feel") and to have long-term durability.

These expectations set strict limits for the golf ball manufacturer.

Since all requirements and preferences cannot be united in one ball, a large number of different balls are commercially available which possess one or more preferred characteristics. In this regard, two fundamental designs have gained acceptance.

The three-piece ball, as it is called, has a rubber core or a bubble core which can be filled with a wide variety of liquids. Rubber threads are wound about this core forming the second of the three parts. The outer shell (the third part) is made of either a Balata rubber (natural product) or a synthetic thermoplastic Surlyn® by DuPont).

The two-piece ball, on the other hand, comprises a rubber core which is preferably manufactured from a polybutadiene rubber or an elastic thermoplastic.

This core, in turn, is given an outer ball shell which, in this case, is preferably made of a synthetic thermoplastic. All of the materials used have in common that they possess good elastic or resilient characteristics to varying extent, they are

'A

-2capable of deforming to a great extent in the instant of impact or at the instant when struck. They all have a Shore A hardness of greater than 100.

The difference between these two types of balls is that a two-piece ball tends to take on less spin than a three-piece ball, but, all other conditions remaining the same, achieve greater distance. In addition, three-piece balls have the disadvantage that they require a substantially greater manufacturing effort than twopiece balls.

A further possibility of influencing ball characteristics consists in using materials of different hardness. This affects the resistance of the ball in the instant S when struck. The hardness of the ball is referred to as compression and generally varies between 90 and 100. A ball with a compression of 90 is softer than a ball with a compression of 100 and takes on more spin, but does not achieve equal distance, other conditions remaining the same. In general, however, a balata shell (which is even softer than a plastic shell) can also result in higher spin in the ball.

On the other hand, the balata shell is substantially more susceptible to mechanical wear than a plastic shell, which manifests itself in a substantially shorter useful life.

In DE 294 64 40 A1, a ball or sphere is described, for example, a minigolf ball, whose core is so hard that there is no deformation of the core during a rolling movement on a hard surface. A more accurate play on hard ground is supposed to be achieved in this way. A core constructed in this way improves the roll behavior of the sphere, especially at low velocities. Although this core which does not deform during a rolling movement on a hard surface can be called relatively hard, a quite extensive deformation takes place under playing conditions, especially when the ball is struck hard. The reason for this is that the struck golf ball, in contrast to the rolling sphere, is accelerated from a standstill (0 m/s) to a velocity of up to 70 m/s within a fraction of a second when struck by the golf club. In known golf balls, this can result in a compression set of up to 50%, the conventional golf ball can be deformed by up to half its diameter in the instant of being struck.

A golf ball with a "fixed" golf ball center piece or a "fixed" golf ball core is described in DE 293 87 52 C2. In this case also, the expression "fixed" does not 1- 5-01;12:28PM;DAVIES COLLISON CAVE 6/ 14 -3exclude deformability of the core, because it is noted in the description of this invention that golf ball center pieces according to this invention can be produced with high rebound depths and different impression depths. The rebound characteristics are influenced in this case by the styrene content and butadiene content in the golf ball center piece. In modern golf, desirable characteristics of golf balls are, among other things, that they meet the expectations of the golfer and conform to golfing regulations on the one hand and, on the other hand, that they have a core which has a far greater energy resiliency and which is deformable only to a small degree. Such requirements are imposed, for example, on golf balls with 3 integrated electronic components or other components which make it possible to search for and find mishit or lost golf balls. However, the technical realization of such systems presupposes the availability of a golf ball having design features suited to this purpose Description of the Invention ""15 Advantageously the present invention provides a golf ball of the type mentioned above developed in such a way that it meets the requirements for long distance and sufficient spin and has a core which is not deformable or is deformable only to an extremely small degree.

According to the invention there is provided a golf ball in a multiple-part construction with a core, a covering, and a shell, wherein the core is made of a material with a modulus of elasticity greater than or equal to 3 GPa at room -i temperature and the covering is an elastomer with a modulus of elasticity less than or equal to 50 MPa at room temperature, with a glass transition temperature less than or equal to 0°C and with a mechanical dissipation factor tan 5 0.2 in a frequency range of up to 1 kHz at room temperature, wherein the covering is constructed with a layer thickness greater than or equal to 2 mm.

This core which is manufactured, for example, from a duromer plastic or thermoplastic has the advantage that it deforms only to a very small degree, if at all, in the instant when struck and, accordingly, the energy transferred to the ball in 01/05 '01 TUE 12:27 [TX/RX NO 9368] -4the instant when struck is converted by internal friction into heat not at all or only to a very small extent. It is also highly energy-resilient.

The core preferably has a diameter of 32 mm or less; when plastic is used, this plastic should have a glass transition temperature greater than or equal to 50 0

C.

On the other hand, the extremely soft covering, according to the invention, is made from a highly entropy-resilient material, even small forces lead to high deformations. The modulus of elasticity of this material is less than MPa. The material ensures that the energy transferred to the ball by the club is *0 transmitted to the inner core virtually without losses, but the golf ball as a whole retains sufficient deformability to be able to take on substantial spin in the instant when struck. For this function, which must also be ensured at high deformation rates such as those occurring when teeing off or driving), the very low mechanical dissipation factor of tan 6 0.2 at load frequencies of up to 1 kHz at room temperature is essential, as is the glass transition temperature which must be less than or equal to 0 0 C and can be as low as -80o C, depending upon design. It is also essential with respect to function that the indicated layer thickness of the covering be maintained. The material of the covering should have a Shore A hardness A 0 A core having a covering and comprising a combination of materials of this kind which has not previously been employed for golf balls can now be provided with a resistant and abrasion-proof outer shell by means of known methods.

A golf ball of this kind preferably has a compression of 80 or less and, all other conditions remaining the same, achieves the same or similar high initial velocity (and accordingly distance) as balls with a compression of 100 or greater.

On the other hand, the relatively low compression ensures high spin in the ball which manifests itself for the golfer in good "feel".

This relatively low compression is also achieved, for example, when a thermoplastic material is used for the shell, which benefits long life.

In addition, the golf ball according to the invention has the advantage that, in spite of its three-piece construction, substantially less effort is expended in its manufacture than in the manufacture of two-piece balls.

In addition to the advantageous characteristics already mentioned, the golf ball according to the invention offers the possibility that components which are very sensitive to shock but which impart further characteristics to the golf ball can be integrated in the interior of the core. For example, these components can be electronic component assemblies which facilitate the finding of mishit golf balls.

Brief Description of the Drawings The present invention is explained more fully hereinafter with reference to an embodiment example. The drawing shows the basic construction design of a golf ball according to the invention.

Detailed Description of the Drawings As is shown in Fig. 1, the golf ball according to the invention comprises a core 1, a covering 2, and an outer shell 3.

The core 1 is made of an extremely energy-resilient and only slightly deformable plastic with a modulus of elasticity at room temperature of 2.8 GPa. The glass transition temperature of this plastic is 700 C. Materials with such 0 characteristics are, for example, epoxy-resin casting or sealing compounds known from the electronics industry.

A highly entropy-resilient and highly deformable elastomer having a modulus of elasticity of 46 MPa at room temperature is provided for the covering.

The glass transition temperature of this elastomer is -500 C and the mechanical dissipation factor tan 6 is 0.16 at a frequency range of up to 1 kHz at room temperature. The elastomer has a Shore A hardness of 50 at room temperature.

Elastomers with such characteristics typically come from the class of thermoplastics and are, for example, thermoplastic polyurethane, thermoplastic polyester or thermoplastic polyetherester.

1- 5-01;12:28PM;DAVIES COLLISON CAVE 7/ 14 -6- The core 1 is constructed with a diameter of 32 mm, wherein the layer thickness of the covering is 2mm.

The outer shell 3 comprises a resistant, abrasion-proof thermoplastic material such as is also conventionally used for golf balls.

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

e **e 01/05 '01 TUE 12:27 [TX/RX NO 9368]

Claims (5)

1- 5-01 12:28PM;DAVIES COLLISON CAVE 8/ 14 PIPER%~A lt&dW4231347 S tb 1W I -7- THE CLAIMS DEFINING THE INVENTION AREAS FOLLOWS: 1. Golf ball in a multiple-part construction with a core, a covering, and a shell, wherein the core is made of a material with a modulus of elasticity greater than or equal to 3 GPa at room temperature and the covering is an elastomer with a modulus of elasticity less than or equal to 50 MPa at room temperature, with a glass transition temperature less than or equal to 0 0 C and with a mechanical dissipation factor tan 65 0.2 in a frequency range of up to 1 kHz at room temperature, wherein the covering is constructed with a layer thickness greater than or equal to 2 mm.

2. Golf ball according to claim 1, wherein a plastic with a glass transition temperature greater than or equal to 50 0 C is provided for the core. 15

3. Golf ball according to one of the preceding claims, wherein the core has a diameter less than or equal to 32 mm.

4. Golf ball according to one of the preceding claims, wherein the material of the covering is an elastomer with a Shore A hardness less than or equal to 90 at 20 room temperature.

5. Golf ball substantially as hereinbefore described with reference to the accompanying drawings. DATED this 30 t h day of April, 2001 PTS Gesselschaft fur Physikalisch-Technische Studien Jena mbH by DAVIES COLLISON CAVE Patent Attorneys for the Applicant(s) 01/05 '01 TUE 12:27 [TX/RX NO 9368]