GB2053004A

GB2053004A - Golf club shafts

Info

Publication number: GB2053004A
Application number: GB8020543A
Authority: GB
Original assignee: Accles and Pollock Ltd
Current assignee: Accles and Pollock Ltd
Priority date: 1979-06-21
Filing date: 1980-06-23
Publication date: 1981-02-04

Abstract

A golf club shaft has a portion intermediate of the extremities of the shaft which is of increased mass per unit length, when compared with the immediately adjacent portions of shaft on either side. By this means the position of the dynamic "kick" or "flex" point, below which dynamic flexing of the shaft occurs, may be accurately controlled to give a shaft with the desired dynamic characteristics. <IMAGE>

Description

SPECIFICATION Golf club shafts This invention relates to golf club shafts.

During the downswing of a golf club, the club head and part of the shaft spring or accelerate forward from a position along the shaft. The golfer tries to time this springing or acceleration forward of the head, so that the club face at impact is at maximum speed and square with the ball. The position along the shaft from which the shaft and clubhead spring forward is called the dynamic "kick" or "flex" point. For conventional golf club shafts, this kick point is illdefined and will vary from shaft to shaft within a set.

According to one aspect the present invention provides a golf club shaft in which a portion intermediate of the extremities of the shaft is of increased mass per unit length, when compared with the immediately adjacent portions of shaft on either side. By this means the position of the dynamic kick or flex point, below which dynamic flexing of the shaft occurs, may be accurately controlled to give a shaft with the desired dynamic characteristics.

The flexibility of the lengths of shaft on either side of the portion of increased mass per unit length may be the same or one length may be made more or less flexible than the other, depending on the overall characteristics required for the shaft. These portions may be plain, stepped or tapered or a combination of these configurations and may have additional design or cosmetic features on them, for example flutes, hexagonal or octagonal sections.

One method of producing a golf club shaft according to the present invention comprises telescoping together two lengths of tubular shaft so that portions of the lengths of shaft overlap and securing the lengths of shaft together by, for example, bonding with an adhesive, brazing or silver soldering. The overlapped portions of the lengths of tubular shaft provide the portion of increased mass per unit length. The position of the overlapped portion and the length of overlap may be selected to give the required characteristics for the shaft.

Conveniently the telescoped lengths of shaft are tapered, thus providing for mechanical location of one length of shaft within the other. Lengths of parallel tube may alternatively be used, a stepped portion at the appropriate point in each length of shaft providing for location of one length of shaft with respect to the other.

Alternative methods of producing the portion of increased mass per unit length include the use of a butt drawn tubular shaft, in which a portion of thicker wall section is produced at the appropriate point in the tubular shaft when it is drawn; or alternatively, a short length of tube may be secured to a one piece shaft at the appropriate position. In the latter case the length of the tube may be secured to the shaft by bonding with adhesive, brazing or silver soldering and may be positioned either internally or externally of the one piece shaft.

The various parameters; position of portion of increased mass per unit length, the mass of this portion and flexibility, wall thickness and diameter etc. of the portions of the shaft above and below the portion of increased mass per unit length, may be varied as desired to produce shafts of various standard ratings of flexibility and also to give the required characteristics within a set of shafts.

For example, for a set of shafts, formed from overlapped lengths of tapered tube, the overlapped portion could be 1 OOmm and the length of tube above and below the overlap being 660mm and 304mm respectively for a "2" iron, both lengths progressively decreasing for shorter irons. The typical characteristics for such a shaft are illustrated in the accompanying drawings in which: Figure 1 is a plot showing the mass distribution of the shaft; and Figure 2 is a plot showing the sectional modulus variation of the shaft.

Fig. 1 shows the increase in mass in the overlap portion of the shaft (section 10 of the plot), in comparison with the uniform mass per unit length portions of the shaft, above and below the overlap portion (sections 11 and 1 2 of the plot respectively). Fig. 2 shows how the portion of increased mass per unit length increases the resistance to flexing of the portion of shaft above the overlap portion, ie the grip end portion (section 1 5 of the plot) and thus gives greater control of the "flex" or "kick" point 14.

While in the above example the portion of shaft above the overlap portion and the portion below the overlap portion are of constant mass per unit length, this need not be the case.

1. A golf club shaft in which a portion, intermediate of the extremities of the shaft, is of increased mass per unit length, when compared with the immediately adjacent portions of shaft on either side.

2. A golf club shaft according to Claim 1 in which two lengths of tubular shaft are telescoped together so that the lengths of the shaft overlap to give an intermediate portion of increased mass per unit length.

3. A golf club shaft according to Claim 2 in which the lengths of shaft are secured together by bonding with an adhesive, brazing or silver soldering.

4. A golf club shaft according to Claim 2 or 3 in which the lengths of shaft are tapered thereby providing for mechanical location of

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Golf club shafts This invention relates to golf club shafts. During the downswing of a golf club, the club head and part of the shaft spring or accelerate forward from a position along the shaft. The golfer tries to time this springing or acceleration forward of the head, so that the club face at impact is at maximum speed and square with the ball. The position along the shaft from which the shaft and clubhead spring forward is called the dynamic "kick" or "flex" point. For conventional golf club shafts, this kick point is illdefined and will vary from shaft to shaft within a set. According to one aspect the present invention provides a golf club shaft in which a portion intermediate of the extremities of the shaft is of increased mass per unit length, when compared with the immediately adjacent portions of shaft on either side. By this means the position of the dynamic kick or flex point, below which dynamic flexing of the shaft occurs, may be accurately controlled to give a shaft with the desired dynamic characteristics. The flexibility of the lengths of shaft on either side of the portion of increased mass per unit length may be the same or one length may be made more or less flexible than the other, depending on the overall characteristics required for the shaft. These portions may be plain, stepped or tapered or a combination of these configurations and may have additional design or cosmetic features on them, for example flutes, hexagonal or octagonal sections. One method of producing a golf club shaft according to the present invention comprises telescoping together two lengths of tubular shaft so that portions of the lengths of shaft overlap and securing the lengths of shaft together by, for example, bonding with an adhesive, brazing or silver soldering. The overlapped portions of the lengths of tubular shaft provide the portion of increased mass per unit length. The position of the overlapped portion and the length of overlap may be selected to give the required characteristics for the shaft. Conveniently the telescoped lengths of shaft are tapered, thus providing for mechanical location of one length of shaft within the other. Lengths of parallel tube may alternatively be used, a stepped portion at the appropriate point in each length of shaft providing for location of one length of shaft with respect to the other. Alternative methods of producing the portion of increased mass per unit length include the use of a butt drawn tubular shaft, in which a portion of thicker wall section is produced at the appropriate point in the tubular shaft when it is drawn; or alternatively, a short length of tube may be secured to a one piece shaft at the appropriate position. In the latter case the length of the tube may be secured to the shaft by bonding with adhesive, brazing or silver soldering and may be positioned either internally or externally of the one piece shaft. The various parameters; position of portion of increased mass per unit length, the mass of this portion and flexibility, wall thickness and diameter etc. of the portions of the shaft above and below the portion of increased mass per unit length, may be varied as desired to produce shafts of various standard ratings of flexibility and also to give the required characteristics within a set of shafts. For example, for a set of shafts, formed from overlapped lengths of tapered tube, the overlapped portion could be 1 OOmm and the length of tube above and below the overlap being 660mm and 304mm respectively for a "2" iron, both lengths progressively decreasing for shorter irons. The typical characteristics for such a shaft are illustrated in the accompanying drawings in which: Figure 1 is a plot showing the mass distribution of the shaft; and Figure 2 is a plot showing the sectional modulus variation of the shaft. Fig. 1 shows the increase in mass in the overlap portion of the shaft (section 10 of the plot), in comparison with the uniform mass per unit length portions of the shaft, above and below the overlap portion (sections 11 and 1 2 of the plot respectively). Fig. 2 shows how the portion of increased mass per unit length increases the resistance to flexing of the portion of shaft above the overlap portion, ie the grip end portion (section 1 5 of the plot) and thus gives greater control of the "flex" or "kick" point 14. While in the above example the portion of shaft above the overlap portion and the portion below the overlap portion are of constant mass per unit length, this need not be the case. CLAIMS

4. A golf club shaft according to Claim 2 or 3 in which the lengths of shaft are tapered thereby providing for mechanical location of one length of shaft within the other, when they are telescoped together.

5. A golf club shaft according to Claim 2 or 3 in which the lengths of shaft are parallel, step portions being provided at appropriate points in each length of shaft to provide for location of one length of shaft with respect to the other.

6. A golf club shaft according to Claim 1 in which a short length of tube is secured to a one piece shaft to give the portion of increased mass per unit length.

7. A golf club shaft according to Claim 6 in which the length of tube is positioned either internally or externally of the one piece shaft.

8. A golf club shaft according to Claim 6 or 7 in which the length of tube is secured to the one piece shaft by bonding with adhesive, brazing or silver soldering.

9. A golf club shaft according to Claim 1 formed from a length of butt-drawn tube, in which a portion of thicker wall section is produced during the drawing of the tube, to provide the portion of increased mass per unit length.

10. A golf club shaft substantially as described herein.