WO1997039806A1

WO1997039806A1 - Golf ball

Info

Publication number: WO1997039806A1
Application number: PCT/EP1997/001971
Authority: WO
Inventors: Gernot Herrmann; Uwe Weinzierl; Michael Weinholdt
Original assignee: Pts Gesellschaft Für Physikalisch-Technische Studien Jena Mbh
Priority date: 1996-04-23
Filing date: 1997-04-18
Publication date: 1997-10-30
Also published as: EP0855930A1; AU2388397A; DE19616111C1; JPH11508176A; CA2224328A1; AU734770B2; KR19990022894A

Abstract

The invention relates to a golf ball, designed in several parts, which has a core (1), a case (2) and a shell (3) and also fulfils the requirements for long distance and provides sufficient spin when the core (1) cannot be deformed or only extremely slightly. Said core (1) of the golf ball therefore consists of an extremely energy-resilient material which can only be deformed slightly and has a modulus of elasticity of ≥ 3 GPa at room temperature. An extremely entropy-resilient elastomer which can be deformed to a high extent, has a modulus of elasticity of ≤ 50 MPa at room temperature, a glass transition temperature of ≤ 0° Celsius and a mechanical loss factor tan δ ≤ 0.2 in a frequency range of up to 1 kHz at room temperature is provided for the case (2) which is ≥ 2 mm thick.

Description

Golf ball

Field of the Invention

The invention relates to a golf ball in a multi-part constructive design with a core, a casing and a shell.

State of the art

Golf balls are manufactured worldwide in large quantities and in different designs. The differences in the designs result from different structural designs and the materials used for each. All balls, regardless of their design, must comply with the golf rules (e.g. rule book of the German Golf Association, Appendix III).

However, the golfer has expectations of the golf balls that go beyond the properties specified in the rules (e.g. minimum size, maximum weight). He expects a golf ball to have a wide range, the ability to take a spin (what players call "feeling") and a long durability.

This sets narrow limits for golf ball manufacturers. Because all requirements and desires cannot be combined in one ball, a large number of different balls are now available on the market, each with one or more properties preferred. Two basic constructive designs have prevailed:

The so-called "three-piece ball" CThree-Piece-Ball ") has a core made of rubber or a bladder, which can be filled with various liquids. Around this core are

Wrapped rubber threads that represent the second of the three parts. The outer shell (the third Part) consists of either a balata rubber (a natural product) or a synthetic,

® thermoplastic (e.g. SURLYN from Du Pont).

The "two-piece ball", on the other hand, consists of a rubber core, which is preferably made from a polybutadiene rubber or from an elastic, thermoplastic material. This core again receives an outer ball shell, which in this case preferably consists of a synthetic, thermoplastic material. Common to all materials used is that they have more or less good elastic properties, i.e. that they are able to be deformed to a large extent at the moment of impact. They all have a Shore A hardness of over 100.

The difference between these two types of ball is that a two-piece ball tends to take up less spinning than a three-piece ball, but on the other hand it reaches a greater distance under otherwise identical conditions. In addition, three-piece balls have the disadvantage that they require a much higher manufacturing effort than two-piece balls.

Another way to influence the properties of the balls is to use materials with different hardness. This affects the resistance of the ball at the moment of impact. The hardness of the ball is called compression and usually fluctuates between 90 and 100. A ball with a compression 90 is softer than a ball with a compression 100, takes up more spin, but does not reach the same distance under otherwise identical conditions. In general, however, a balata crate (which itself is softer than a plastic shell) can result in the ball absorbing more spin. On the other hand, the balata shell is much more susceptible to mechanical wear than a plastic shell, which is expressed in a significantly shorter service life.

DE 294 64 40 A1 describes a ball, for example a mini golf ball, which has such a hard core that there is no deformation of the core during a rolling movement on a hard surface. This is intended to achieve more precise playing on hard documents. With the core designed in this way, the rolling behavior of the ball is improved, particularly at low speeds. Although this core, which does not deform when rolling on a hard surface, can be described as relatively hard, under the conditions of golf, especially with hard shots, a quite strong deformation nevertheless occurs. The reason is that the struck golf ball, in contrast to the rolling ball, accelerates from a standstill (0 m / s) to a speed of up to 70 m / s when the golf club hits it, which in known golf balls leads to a Compression up to 50%, ie the conventional golf ball can be deformed up to half its diameter at the moment of the stroke. DE 293 87 52 C2 describes a golf ball with a "fixed" golf ball center piece or a "fixed" golf ball core. Here, too, the phrase "firm" does not preclude the deformability of the core, because the description of the invention points out that golf ball centerpieces with high rebound and different indentation depths can be produced according to the invention. In this case, the rebound properties are due to the styrene and butadiene content In the modern golf game, among other things, golf balls are desirable which on the one hand meet the expectations of the golf ball player and also meet the rules of the game of golf, but on the other hand have a much more energy-elastic and only slightly deformable core Golf balls are provided with integrated electronic or other assemblies, which are intended to make it possible to locate and find lost or lost golf balls. However, the technical implementation of such systems presupposes that a golf ball with the appropriate type ignored constructive features is available.

Description of the invention

The object of the present invention is to develop a golf ball of the type mentioned at the outset in such a way that it meets the requirements for a great distance and sufficient effect even with a core which is not or extremely slightly deformable.

According to the invention, this object is achieved in that the core consists of an extremely energy-elastic and only slightly deformable material, namely a material with a modulus of elasticity at room temperature of> 3 GPa, and for the sheathing an extremely entropy-elastic and highly deformable elastomer with an elastic modulus that at room temperature is <50 MPa, with a glass transition temperature ≤ 0 ° C and with a mechanical loss factor tan δ ≤ 0.2 in a frequency range up to 1 kHz at room temperature, whereby the sheathing is made in a layer thickness of ≥ 2 mm.

This core, for example made of a thermoset or thermoplastic material, has the advantage that it does not deform, or deforms only very little at the moment of impact, and therefore does not convert the energy transferred to the ball at the moment of impact, or converts it to heat only to a small extent through internal friction. So it has a high energy elasticity.

The core is preferably 32 mm or less in diameter; if plastic is used, it should be provided with a glass transition temperature of ≥ 50 ° Celsius. The extremely soft sheath, however, according to the invention consists of a material with a high entropy elasticity, that is, that even small forces lead to large deformations. The elastic modulus of this material is less than 50 MPa. The material ensures that the energy transferred from the club to the ball is transferred to the inner core with almost no loss, but the golf ball as a whole receives sufficient deformation to be able to take on a lot of hitting moment. The very low mechanical loss factor tan δ ≤ 0.2 at load frequencies of up to 1 kHz at room temperature is essential for this function, which must also be ensured at high deformation speeds (such as occur when teeing off), as is the glass transition temperature must be equal to or less than 0 ° C and, depending on the design, can be as low as -80 ° C. Compliance with the specified layer thickness for the sheathing is also of essential function. The material of the sheathing should have a Shore hardness of A ≤ 90.

A core with sheathing consisting of such a material combination, which has not previously been used for golf balls, can now be provided with an outer, resistant and wear-resistant shell using known methods.

Such a golf ball preferably has a compression of 80 or less and, under otherwise identical conditions, reaches the same or a similarly high initial speed (and thus a width) as is known from balls with a compression of 100 or higher. The relatively low compression, on the other hand, ensures that the ball takes up a lot of spin, which is expressed in a good "feeling" for the golfer.

This relatively low compression is also achieved, for example, when using a thermoplastic material for the shell, which has a favorable effect on a long service life.

In addition, the golf ball according to the invention has the advantage that, in spite of its three-part construction, it causes much less manufacturing effort than a known three-piece ball "and the manufacturing effort is only insignificantly higher than in the production of" two-piece balls " .

In addition to the advantageous properties already mentioned, the golf ball according to the invention offers the possibility of integrating components into the interior of the core which are very sensitive to impact but which give the golf ball further properties. These can be, for example, electronic assemblies, which make it easier to find lost golf balls. Brief description of the drawings

The present invention is explained in more detail below using an exemplary embodiment. The drawing illustrates the basic construction of a golf ball according to the invention.

Detailed description of the drawings

As shown in FIG. 1, the golf ball according to the invention consists of a core 1, a casing 2 and an outer shell 3.

The core 1 is made of an extremely energy-elastic 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 70 ° C. Materials with such properties are e.g. Epoxy resin casting compounds known from the electronics industry.

A highly entropy-elastic and highly deformable elastomer is provided for the sheathing, which has a modulus of elasticity of 46 MPa at room temperature. The glass transition temperature of this elastomer is -50 ° Celsius, the mechanical loss factor tan δ is 0.16 in a frequency range up to 1 kHz at room temperature. The elastomer has a Shore A hardness of 50 at room temperature. Elastomers with such properties typically come from the class of thermoplastics and are e.g. thermoplastic polyurethanes, thermoplastic polyesters or thermoplastic polyether esters.

The core 1 is designed with a diameter of 32 mm, the layer thickness of the sheathing being 2 mm.

The outer shell 3 consists of a resistant, wear-resistant thermoplastic material, as is also conventionally used for golf balls.

Claims

claims

1. Golf ball in a multi-part design with a core (1), a casing (2) and a shell (3), characterized in that the core (1) consists of a material with a modulus of elasticity at room temperature of ≥ 3 GPa and for the sheathing (2) is an elastomer with a modulus of elasticity, which is ≤ 50 MPa at room temperature, with a glass transition temperature <0 ° C and with a mechanical loss factor tan δ ≤ 0.2 in a frequency range up to 1 kHz at room temperature, the Sheath (2) is executed in a layer thickness of ≥ 2 mm.

2. Golf ball according to claim 1, characterized in that a plastic with a glass transition temperature> 50 ° Celsius is provided for the core (1).

3. Golf ball according to one of the preceding claims, characterized in that the core (1) has a diameter of ≤ 32 mm.

4. Golf ball according to one of the preceding claims, characterized in that the material of the casing (2) is an elastomer with a Shore A hardness of ≤ 90 at room temperature.