CA2231908A1

CA2231908A1 - Thermoplastic polymer shaft having an integrally formed reinforcing member for use in golf clubs and the like

Info

Publication number: CA2231908A1
Application number: CA 2231908
Authority: CA
Inventors: Scott S. Campbell
Original assignee: Individual
Current assignee: Individual
Priority date: 1998-03-12
Filing date: 1998-03-12
Publication date: 1999-09-12

Abstract

A shaft of the present invention is formed as an axially elongated member for use in sports equipment, such as golf clubs, fishing rods or the like. The shaft is made from composite polymers, such as a graphite composite and includes an outer sidewall which extends radially about an axis to define a substantially hollow or resin filled core. At least part of the core is divided into two or more longitudinally extending cavities by a reinforcing web or member which spans radially separate points along the shaft sidewall. The reinforcing member is preferably axially elongated anti extends at least part way along the portion of the shaft. The position of the reinforcing member is oriented in the shaft to increase the shaft rigidity against bending in the direction of bending, load and/or impact forces.

Description

THERMOPLASTIC POLYMER SHAFT HAVING AN
INTEGRALLY FORMED REINFORCING MEMBER
FOR USE IN GOLF CLUBS AND THE LIKE
SCOPE OF THE INVENTION
The present invention relates to an improved thermoplastic shaft for use in sports equipment such as a golf club or fishing rod, and more particularly, a composite polymer shaft having an integrally formed reinforcing member for increased rigidity.
BACKGROUND OF THE INVENTION
The use of graphite composites and other carbon polymer fibers to reinfor~;,e shafts used in sports equipment such as golf clubs and fishing rods is well known.. Graphite or carbon polymer shafts (hereinafter collectively also referred to as graphite shafts) are being increasingly used in various different types of sporting goods ;is they possess both the properties of increased strength and light weight.
Typically, conventional graphite shafts are formed as an elongated hollow tube which often is characterized by a marginally tapering construction.
In the case of golf clubs, the graphite shafts are lighter than conventional steel golf club shafts. Graphite golf club shafts have been found, however, to suffer the disadvantage of a loss in rigidity, particularly where the shaft diameter narrows below 1.5 centimeters. Fishing rods which incorporate graphite shafts ,also suffer a loss in rigiadity where narrower diameter shafts are used. To provide: graphite fishing rods with the desired rigidity near the grip or handle, it is known to form the fishing rod shaft so as to have an enlarged diameter of 2.5 centimeters or more at the grip end. In addition to being unsightly and making the mounting of the fishing rod grip more complex, the larger diameter of the shaft necessitates the use of additional graphite material, increasing the overall manufacturing costs of the rod.
SUMMfARY OF THE INVENTION
Accordingly, the: present invention overcomes at least some of the disadvantages of the prior art by providing a light weight thermoplastic polymer shaft which may be used in sports equipment, such as a golf club or fishing rod, and which includes an axially positioned reinforcing member to provide at least part of the shaft with increased rigidity and structural integrity.
Another object of the invention is to provide an elongated graphite shaft which, for example, is suitable for use as a golf club shaft or fishing rod shaft, and which is reinforced structurally i.n the direction of bend, impact and/or loading forces.
Another object of the invention is to provide an improved method of manufacturing a marginally tapering cylindrical graphite shaft, so as to incorporate an inte;~rally formed elongate rE~inforcing member.
Another object o1~ the invention is to provide a light weight reinforced shaft which is made from a thermoplastic material and is suitable for use as part of a golf club or fishing rod, and 'which may be formed from a single integral casting.
The shaft of the present invention is formed as an axially elongated member for use in sports equipment. The shaft is made from a composite polymer, and preferably a thermoplastic carbon polymer such as a graphite composite.
The shaft is characterized by an outer sidewall having a preferred diameter of less than about 2 cm and which extends radially about the axis to define a shaft core.
At least part of the core is divided into t:wo or more longitudinally extending hollow or resin filled cavities by a reinforcing web or member which spans between radially separate points along the shaft sidewall.

The reinforcing member is preferably elongated and extends longitudinally along the axis at least part way along part of the shaft core.
Most preferably, the reinforcing member has an I-beam type construction and includes a flat web which is joined along each of its longitudinal edge to the sidewall.
The reinforcing member divides the: core of the shaft most preferably through its axial center, although other configurations of reinforcing webs are also possible.
The I-beam is preferably oriented in the shaft so as to increase the shaft rigidity against bending in the direction of bending, load and/or impact forces. As such, in the case of a golf shaft, where an I-beam type reinforcing member is used, the reinforcing member is oriented with its lateral width aligned parallel to the direction along which the club is swung. The reinforcing member is therefore preferably aligned perpendicular to the club face and parallel to the club swing direction, so as to provide maximum rigidity on ball impact. Similarly, where the shaft is to be used on a fishing rod, the lateral width of the reinforcing member is oriented in alignment with the direction at which the rod eyelets project from the periphery of the ~ shing rod .shaft, thereby providing maximum rigidity in the direction of load forces.
Preferably, the shaft sidewall has an overall cylindrical exterior profile, although other configurations such as a hexagonal, octagonal or other polygonal profiles are also possible. Although not essential, where the shaft is to be used as a golf club or fishing rod shaft, the shaft may taper marginally from one enlarged diameter end at the club or rod grip or handle, towards a smaller diameter remote end. The reinforcing member need not extend along the entire axial length of the shaft. if material costs are to be reduced, the reinforcing member could extend only along the part of the shaft which is to be provided with increased rigidity.
For example, in the case of a fishing rod or golf club, only the twenty to sixty centimeter portion of the fishing rod which is adjacent the rod or club handle may be provided with the reinforcing member for increased rigidity.

Accordingly, in cme aspect the present invention resides in an elongated thermoplastic shaft member for use in sports equipment, the shaft member including, a radially extending sidewall defining a substantially open interior core, and a reinforcing web having a pair of spaced longitudinally extending edges, said web spanning said open interior core and being joined along each of its edges to said sidewall.
BRIEF DESCRIPTION OF TH:E DRAWINGS
Further objects and advantages of the invention will now appear from the following description taken together with the accompanying drawings in which:
Figure 1 is a perspective view of a golf club incorporating a reinforced shaft in accordance with a preff:rred embodiment of the invention;
Figure 2 is a schematic side view of the golf club shaft shown in Figure 1;
Figure 3 is an enlarged cross-sectional view of the shaft shown in Figure 2 taken along lines 3-3';, Figure 4 shows an enlarged cross-sectional view of the shaft shown in Figure 1 taken along line 4-4';
Figure 5 shows a perspective view of an inner mold used in the casting of a shaft in accordance with a preferred embodiment of the invention;
Figure 6 shows a schematic side view of an outer mold casing for use in conjunction with the inner mold shown in Figure 5; and Figure 7 shows a schematic view of the positioning of the inner mold of Figure 5 positioned within the mold casing of Figure 6 during t he formation of a molded shaft in accordance with a second embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
Figure 1 shows an assembled golf club 4 having a handle or grip 6 and club head 8 mounted at each end of a golf club shaft 10 in accordance with a preferred embodiment of the invention. Figures 2 and 3 show best the construction of the golf club shaft 10. The shaft 10 consists of a carbon or graphite fiber reinforced thermoplastic, which as will be described permits its manufacture by moldin ~. When the shaft 10 is to be used in the assembled golf club 4 (Figure 1), the shaFt 10 has a generally cylindrical construction and preferably tapers at an angle of between about 3 to 15 ° from an enlarged diameter end 12 having a preferred diameter of between about 1.5 to 2 cm to a smaller reduced diameter end 14, having a diameter of about 3/4 to 1-114 cm. The shaft is elongated along its longitudinal axis A-A, (Figure 2), and depending on the particular golf club 4, will have a length of between about 1 to 1.4 meters. In assembly of the completed golf club 4 of Figure l, the golf club grip 6 is fitted over the portion of the shaft 10 adjacent the enlarged diametf:r end 12, and the club head 8 is mounted to the reduced diameter end 14.
Figure 3 shows best the shaft 10 as including an outer sidewall 20 which extends radially about thc: club axis A-A,. The outer sidewall 20 is generally cylindrical in shape and defines a substantially hollow core 22. A reinforcing web 24 is integrally formed with the sidewall 20. The reinforcing web 24 is provided in an I-beam type configuration and consists of a thin planar member 28 extending laterall_~ from a first longitudinal edge 30a joined along a first portion of the sidewall 20 to longitudinal edge 30b joined along a second radially opposite portion of the sidewall 22. The web 24 has a lateral width W from edge 30a to edge 30b which is selected equal to the inner diarr~eter of the sidewall 22 so that the member 28 spans across the shaft core 22. FigurE~ 2 shows the web 24 as extending longitudinally the entire length of the shaft 10 from end 12 to end 14 with the planar member 28 extending through the axial center A, of the shaft 10. The web 24 thus divides the interior core 22 of the shaft 10 into two symmetrically disposed semi-circular cavities 26a,26b.
To provide the shaft 10 with sufficient strength, the sidewall 20 and planar member 28 preferably each have a thickness selected at between about 1 to 2 mm. It: is to be appreciated, however, that the sidewall 20 and/or web 24 thicknesses may vary along their longitudinal length, or other thicknesses could be used depending upon the intended function of the shaft 10.
Figure 4 shows best the cutaway end view of the golf club 4 shown in Figure 1 taken through the shaft: 10. Figure 4 shows the golf club head 8 mounted to the end 14 of the shaft 10. Thf~ shaft 10 is oriented so that the lateral width of the planar member 28 is parallel to the path along which the club 4 is swung, as represented by arrow 32, and which is also perpendicular to the leading edge 34 of the club head 8. It is to be appreciated, that with this orientation, the reinforcing web 24 provides the shaft 10 with .enhanced rigidity in the direction of impact forces.
Further, because the core 22 is substantially hollow, except for the reinforcing web 24, the reinforcing web 24 does not add any appreciable increased weight or material cost to the finished golf club 4.
Figures 5 to 7 show a preferred mold assembly 36 (Figure 7) used in the production of a thermoplastic shaft, having a construction to that shown in Figure 1. The mold assembly 36 shown in Figure 7 would produce a shaft having a more pronounced taper than that shown in Figure 1, and which, for example, could be used as the handle or stock portion of a fishing rod.
The mold assembly 36 consists of an inner mold 38 shown in Figure 5 and an outer mold casing 40 shown in Figure 6. The inner mold 38 is characterized by a pair of projecting fins 42a,42b, each having a complementary shape a.nd spacing to corresponding cavities 26a,26b to be formed in the resulting shaft, and a base 44. The fins 42a,42b are fixedly mounted to the base 44 so as to taper upwardly therefrom to a respective endmost tip 45a,45b.
Figure 6 shows the outer mold casing 40 as including a right casing member 46 and a left casing member 48 which are adapted for movement into and out of abutting contact. It is to be appreciated that the inner wall 49 of each casing member 46,48 is configured to provide the desired overall exterior shape and taper to the finished shaft. A pair of mating guide elements 50a,50b are provided in the top peripheral edge of each casing member 46,48. The guide elements 50a,50b are configured to move between the endmost tips 45a,45b of the fins 42a,42b to assist in the alignment of the casing members 46,48 as they are brought together.
Figure 7 shows the mold assembly 36 with the outer mold casing 40 assembled over the fins 42a,42b. The casing members 46,48 are preferably coupled to the mounting base 44 by a respective hinge 52a, 52b enabling their pivoting movement together and apart in the direction of arrows 53.
With the outer casing members 46,48 joined together over the inner mold fins 42a,42b in the position shown in Figure 7, the thermoplastic melt is injected into the mold cavity 54 which is defined by the spacing between each of the fins 42a,42b, and that between the fins 42a,42b and the inner walls 49 of the adjacent casing members 46,48. After the thermoplastic has been injected and then permitted to cool in the mold 36, the casing halves 46,48 are swung apart on their respective hinges 52a,52b, and the cooled shaft is then lifted axially off of the inner mold fins 42a,42b. A knock-out plug 56 ;Figure 7) may be fitted in a bore formed through the base 44~ between the fins 42a,42b. The knock-out plug 56 may be used to apply an axial force on the cooled shaft: to assist in its removal from the inner mold fins 42a,42b.
While Figure 2 shows the reinforcing web 24 as extending along the _ g _ entire length of the shaft 10, the invention is not so limited. If desired, the golf club shaft 10 could be formed so that the reinforcing web 24 extends only partway along its length. For example, the reinforcing web 24 could be provided only along the part of the shaft 10 immediately adjacent the grip 6. In this configuration, the web 24 is provided where maximum shaft rigidity is required, and omitted from the lower part of the shaft 10 where increased flexibility may be desired.
Figure 1 shows the shaft 10 as tapering towards the shaft end 14. It is to be appreciated that although preferred, it is not necessary that the shaft 10 taper at the approximate angle shown, or for that matter at all.
Although the preferred embodiment of the invention discloses a reinforcing web 24 having a generally I-beam type configuration, the invention is not so limil:ed. If desired, the reinforcing web could be of an open diamond, V, X, Y
or W shaped construction without departing from the scope and spirit of the invention.
While Figures 1 to 4 disclose the use of the shaft 10 as part of a golf club 4, the invention is not so limited. The shaft could equally be used in other sports equipment where an elongated lightweight member is required, including by way of non-limiting examples, as part of a fishing rod or in the handle portion of a tennis or squash racquet.
Although Figures 2 and 3 show the shaft 10 as having a pair of symmevtrical open cavities 26a, 26b, the invention is not so limited. If desired, the cavities could be infilled with a resin to provide the shaft 10 with still increased rigidity.
Although the detailed description of the invention describes and illustrates various preferred embodiments, the invention is not so limited.
Many modifications and variations will now appear to those skilled in the art. For a more precise definition of the invention, reference may be had to the appended claims.

Claims

1. An elongated thermoplastic shaft member for use in sports equipment, the shaft member including, a radially extending sidewall defining a substantially open interior core, and a reinforcing web having a pair of spaced longitudinally extending edges, said web spanning said open interior core and being joined along each of its edges to said sidewall.

2. A shaft member as claimed in claim 1 wherein the said reinforcing web and said sidewall are integrally formed.

3. A shaft member as claimed in claim 1 or claim 2 wherein said sports equipment comprises a golf club.

4. A shaft member as claimed in any one of claims 1 to 3 wherein said shaft member includes a longitudinally extending central axis, said sidewall extending radially about said axis as a generally cylindrical body.

5. A shaft member as claimed in claim 4 wherein said cylindrical body tapers from an enlarged end towards a reduced diameter end.

6. A shaft member as claimed in claim 4 wherein the reinforcing web extends substantially the entire length of said cylindrical body.

7. A shaft member as claimed in any one of claims 1 to 6 wherein the reinforcing web extends substantially the entire length of said cylindrical body.

8. A shaft member as claimed in any one of claims 1 to 7 wherein the thermoplastic comprises a graphite composite reinforced thermoplastic.

9. A shaft member as claimed in claim 3 wherein said golf club includes a club head mounted to said shaft, and the reinforcing web is oriented generally parallel to the direction of club head movement as said golf club is swung.

10. A shaft member as claimed in claim 1 or claim 2 wherein said sports equipment comprises a fishing rod.