Games using tangible projectile – Golf – Club or club support
Reexamination Certificate
1998-06-25
2001-10-23
Chapman, Jeanette (Department: 3711)
Games using tangible projectile
Golf
Club or club support
C428S036300
Reexamination Certificate
active
06306047
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a golf club shaft.
2. Description of the Related Art
Generally, a shaft, used in a golf club, is produced by a method in which so-called prepreg sheets, each formed by arranging or orienting reinforcing fibers in one direction and then by impregnating these fibers with a synthetic resin, are wound in a superposed manner on a metal core, and then a cellophane tape is wound on this layer structure, and then the synthetic resin is thermally set or cured in a heating furnace, and then this product is cooled, and then the metal core and the cellophane tape are removed from this product, and then this product is subjected to other steps such as grinding and coating, thereby producing the golf club shaft.
Generally, the laminate structure, formed by the prepreg sheets wound on the metal core, comprises a body layer which comprises an oblique fiber layer formed by the prepreg sheets (that is, the oblique prepreg sheets having the reinforcing fibers oriented (that is, arranged to extend) in a direction oblique relative to the axis of the metal core (usually, at an angle of 45° relative to the axial direction) ) wound in such a superposed manner that the direction of orientation of the fibers of the these prepreg sheets cross each other (usually at angles of ±45° relative to the axial direction), and an axial fiber layer formed by the prepreg sheet (that is, the axial prepreg sheet having the reinforcing fibers oriented in the direction of the axis of the metal core). Further, reinforcing layers, formed respectively by an axial prepreg sheet and a peripheral prepreg sheet (having the reinforcing fibers oriented in a peripheral or circumferential direction), are provided at necessary portions of the body layer.
In the above construction, the oblique sheets and the axial sheet, used in the body layer, usually have a thickness of about 0.1 mm to about 0.2 mm.
However, as described above, the oblique sheets are wound on the metal core in such a superposed manner that the directions of orientation of the fibers of these sheets cross or intersect each other, and therefore the combined thickness of the oblique sheets are about twice larger than the thickness of the axial sheet. Namely, for example, if the oblique sheets and the axial sheet have a thickness of 0.1 mm, the combined thickness of the oblique sheets are 0.2 mm since the two oblique sheets are superposed together, and this thickness is twice larger than the thickness of the axial sheet. Therefore, when such thick sheet is wound, an uneven thickness condition due to this thickness develops at an overlapping portion at a winding-end region.
Particularly recently, shafts have been required to have a lightweight, high-elasticity design, and the number of winding of oblique sheets and axial sheets has been reduced. Therefore, if an uneven thickness condition due to the above-mentioned thickness difference develops at the end region of the wound sheets, there is encountered a problem that this causes the reduction of the strength, or the unevenness of the strength increases.
Usually, the shaft has a larger diameter at a grip side, and has a smaller diameter at a head side, and therefore a torsional rigidity is larger at the grip side, and is smaller at the head side. Therefore, the number of winding of the oblique sheets at the head side is different from that at the grip side so that the oblique fiber layer can have a larger thickness at the head side, and can have a smaller thickness at the grip side.
With this construction, however, there is encountered a problem that the strength is liable to be reduced at a generally-central portion of the shaft by a torsion and a load of the head, so that the shaft is liable to be broken or damaged.
SUMMARY OF THE INVENTION
It is an object of this invention to provide a golf club shaft which is prevented from being reduced in strength and also from having an uneven strength.
In order to achieve the above object, according to the invention, there is provided a golf club shaft formed by winding prepreg sheets one on another, each of the prepreg sheets having reinforcing fibers oriented in one direction and impregnated with synthetic resin, the golf club shaft including:
an oblique fiber layer formed from at least two adjacent ones of the prepreg sheets, wherein the two adjacent prepreg sheets are mutually arranged so that the reinforcing fibers in one of the two adjacent prepreg sheets intersect the reinforcing fibers in the other of the two adjacent prepreg sheets, wherein the two adjacent prepreg sheets are wound about an axis so that the reinforcing fibers in the two adjacent prepreg sheets are obliquely arranged with respect to the axis, and wherein each of the two adjacent prepreg sheets has a thickness equal to or less than 0.06 mm.
The thickness of conventional prepreg sheets, wound on the shaft, was about 0.1 mm to about 0.2 mm, and in this invention, the thickness of each of the prepreg sheets of the oblique fiber layer is not more than 0.06 mm, and therefore the thickness of the oblique fiber layer, formed by superposing these prepreg sheets, is about 0.1 mm to about 0.2 mm, and the thickness difference at an overlapping portion at a winding-end region can be reduced, and the reduction of the strength and the unevenness of the strength are suppressed.
According to the invention, there is provided a golf club shaft formed by winding prepreg sheets one on another, each of the prepreg sheets having reinforcing fibers oriented in one direction and impregnated with synthetic resin, the golf club shaft including:
an oblique fiber layer formed from at least two adjacent ones of the prepreg sheets, wherein the two adjacent prepreg sheets are mutually arranged so that the reinforcing fibers in one of the two adjacent prepreg sheets intersect the reinforcing fibers in the other of the two adjacent prepreg sheets, wherein the two adjacent prepreg sheets are wound about an axis so that the reinforcing fibers in the two adjacent prepreg sheets are obliquely arranged with respect to the axis, wherein the number of winding of the oblique prepreg sheets at a distal end portion of the shaft is different from that at a proximal end portion of the shaft, and wherein the each of prepreg sheets is wound in not less than 2 plies (i.e., two superimposed layers) in the arranged direction of the fibers at that region of the shaft ranging between 40% and 60% of an overall shaft length from the distal end thereof.
Usually, the shaft is liable to be broken by torsion and a load of a head at that region ranging between 40% and 60% of the overall shaft length from the distal end thereof. The thickness of the oblique fiber layer is increased at this region, thereby enhancing the strength, and also suppressing such breakage.
According to the invention, there is provided a golf club shaft formed by winding prepreg sheets one on another, each of the prepreg sheets having reinforcing fibers oriented in one direction and impregnated with synthetic resin, the golf club shaft including:
an oblique fiber layer formed from at least two superposed prepreg sheets, wherein the superposed prepreg sheets are formed by the two adjacent prepreg sheets so that one of the adjacent prepreg sheets superposes on another, wherein the superposed prepreg sheets are arranged so that the reinforcing fibers in one of the two adjacent prepreg sheets and the reinforcing fibers in the other of the two adjacent prepreg sheets almost cross at right angles, wherein the superposed prepreg sheets are wound about an axis so that the reinforcing fibers in the two adjacent prepreg sheets are obliquely arranged with respect to the axis, and wherein the superposed prepreg sheets are wound in such a manner that winding-initial positions of prepreg sheets are displaced with respect to each other in a peripheral or circumstantial direction.
When the oblique fiber layer is formed by at least two superposition prepreg sheets, their winding-starting positions are displaced with re
Blau Stephen L.
Chapman Jeanette
Daiwa Seiko Inc.
Liniak Berenato Longacre & White
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