BILLIARD CUE SHAFT FOR REDUCING DEFLECTION

Abstract

A billiard cue shaft includes a shaft body having first and second ends, a longitudinal axis and a first length. The shaft body includes a wooden rod and an outer layer of fiber reinforced plastic (FRP) wrapped around the surface of the wooden rod. The shaft body further includes a straight section with a first outer diameter and a second length, and a tapered section. The wooden rod has a bore with a predetermined inner diameter and a predetermined depth. The predetermined depth of the bore of the wooden rod is about 15% to 55% of the first length of the shaft body. The predetermined inner diameter of the bore of the wooden rod is about 51% to 81% of the first outer diameter of the straight section of the shaft body. The billiard cue shaft thereby has the advantage of natural wood and can decrease the deflection.

Claims

1. A billiard cue shaft comprising: a shaft body having a first end, a second end, a longitudinal axis and a first length extending from the first end along the longitudinal axis to the second end; the shaft body including a wooden rod and an outer layer of fiber reinforced plastic (FRP) wrapped around the surface of the wooden rod; the shaft body further including a straight section with a first outer diameter and a second length extending from the first end thereof toward the second end, and a tapered section extending from an end of the straight section to the second end of the shaft body; the wooden rod having a bore with a predetermined inner diameter and a predetermined depth extending from the first end along the longitudinal axis to the second end; the predetermined depth of the bore of the wooden rod being about 15% to 55% of the first length of the shaft body; and the predetermined inner diameter of the bore of the wooden rod being about 51% to 81% of the first outer diameter of the straight section of the shaft body.

2. The billiard cue shaft of claim 1, wherein the outer layer comprises fiberglass impregnated with epoxy resin.

3. The billiard cue shaft of claim 1, wherein the predetermined depth of the bore is equal to or less than the second length of the straight section of the shaft body.

4. The billiard cue shaft of claim 1, wherein the second length of the straight section of the shaft body is about 31% to 54% of the first length of the shaft body.

5. The billiard cue shaft of claim 4, wherein the first length of the shaft body is about 711 mm to 813 mm.

6. The billiard cue shaft of claim 5, wherein the first length of the shaft body is about 737 mm.

7. The billiard cue shaft of claim 6, wherein the second length of the straight section of the shaft body is about 394 mm.

8. The billiard cue shaft of claim 7, wherein the predetermined depth of the bore of the wooden rod is about 370 mm.

9. The billiard cue shaft of claim 5, wherein the first outer diameter of the straight section of the shaft body is about 10.5 mm to 13.5 mm.

10. The billiard cue shaft of claim 9, wherein the inner diameter of the bore 32 is about 5.36 mm to 10.94 mm.

11. The billiard cue shaft of claim 9, wherein the first outer diameter of the straight section of the shaft body is about 12.75 mm.

12. The billiard cue shaft of claim 11, wherein the predetermined inner diameter of the bore of the wooden rod is about 8.50 mm.

13. The billiard cue shaft of claim 9, wherein the thickness of the outer layer is about 3.6% to 5.8% of the first outer diameter of the straight section of the shaft body.

14. The billiard cue shaft of claim 13, wherein the thickness of the outer layer is about 0.74 mm.

15. The billiard cue shaft of claim 5, wherein the weight of the shaft is about 96 grams to 120 grams.

16. The billiard cue shaft of claim 15, wherein the weight of the shaft is about 106 grams.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The various features, advantages and other uses of the present invention will become more apparent by referring to the following detailed description and drawing in which:

[0018] FIG. 1 is a side view of a billiard cue with a shaft embodied according to the present invention;

[0019] FIG. 2 is a cross sectional view of a shaft body of the shaft taken along line 2-2 in FIG. 1;

[0020] FIG. 3 is a cross sectional view taken along line 3-3 in FIG. 2;

[0021] FIG. 4 is a cross sectional view taken along line 4-4 in FIG. 2;

[0022] FIG. 5 is a schematic drawing showing a testing for measuring the flexibility of the billiard cue shaft shown in FIG. 1; and

[0023] FIGS. 6 and 7 are vector diagrams depicting the impact of a conventional cue shaft and the cue shaft of the present invention with a cue ball.

DETAILED DESCRIPTION OF THE INVENTION

[0024] Referring firstly FIGS. 1-4, there is shown a billiard cue 100 with a shaft 10 constructed in accordance with the teachings of the present invention. The billiard cue 100 includes a shaft 10 and a butt 12 connected to the shaft 10 by a connector 13. The shaft 10 has a top end on which a ferrule 14 and a tip 15 are mounted. The butt 12 has a bottom end on which a rear pad 16 is mounted.

[0025] The billiard cue shaft 10 comprises a shaft body 20 having a first end 22, a second end 24, a longitudinal axis X-X′ and a first length L.sub.1 extending from the first end 22 along the longitudinal axis X-X′ to the second end 24. The first length L.sub.1 of the shaft body 20 is exemplary about 711 mm to 813 mm. Preferably, the first length L.sub.1 is about 737 mm.

[0026] According to the present invention, the shaft body 20 is constructed to have a straight section 26 and a tapered section 28. The straight section mentioned here means that it has a constant outer diameter. In more detail, the straight section 26 has, as shown in FIGS. 2 and 3, a first outer diameter D.sub.1 and extends from the first end 22 to the line a-a′ by a second length L.sub.2. The tapered section 28 extends from the line a-a′ to the second end 24 with an outer diameter continuously increasing from the line a-a′ to the second end 24. Preferably, the second length L.sub.2 of the straight section 26 is about 31% to 54% of the first length L.sub.1. Preferably, the second length L.sub.2 of the straight section 26 is about 394 mm. The first outer diameter D.sub.1 of the straight section 26 is exemplary about 10.5 mm to 13.5 mm. Preferably, the first outer diameter D.sub.1 of the straight section 26 is about 12.75 mm.

[0027] The shaft body 20 includes a wooden rod 30 usually made of hard maple or ash and an outer layer 40 of fiber reinforced plastic (FRP) wrapped around the surface of the wooden rod 30.

[0028] In the present invention, the wooden rod 30 further includes a bore 32 having an inner diameter D.sub.2 and a depth H.sub.1 extending from the first end 22 along the longitudinal axis X-X′ to the second end 24. The depth H.sub.1 and the inner diameter D.sub.2 should be properly matched with each other so that the front portion of the shaft body 20 has appropriate flexibility and significantly reduced mass. The depth H.sub.1 of the bore 32 of the wooden rod 20 is preferably about 15% to 55% of the first length L.sub.1 of the shaft body 20. More preferably, the depth H.sub.1 of the bore 32 of the wooden rod 30 is about 370 mm. It is noted that the depth H.sub.1 of the bore 32 preferably is equal to or less than the second length L.sub.2 of the shaft body 20 such that the front portion of the shaft body 20 has a constant flexibility. The inner diameter D.sub.2 of the bore 32 of the wooden rod 30 is about 51% to 81%, preferably 51% to 70%, of the first outer diameter D.sub.1 of the straight section 26 of the shaft body 20. The inner diameter D.sub.2 of the bore 32 is exemplary about 5.36 mm to 10.94 mm. Preferably, the inner diameter D.sub.2 of the bore 32 is about 8.50 mm.

[0029] In addition, in the present invention, the outer layer 40 is completely wrapped around the surface of the wooden rod 30. The outer layer 40 is formed of fiber reinforced plastic (FRP), for example, fiberglass impregnated with epoxy resin, and has a predetermined thickness T.sub.1. The thickness T.sub.1 of the outer layer 40 is preferably about 3.6% to 5.8% of the first outer diameter D.sub.1 of the straight section 26 of the shaft body 20. More preferably, the thickness T.sub.1 of the outer layer 40 is about 0.74 mm. It must be mentioned that the weight of the billiard cue shaft 10 can be controlled in a certain value for having the specific size of the shaft body 20. The weight of the billiard cue shaft 10 is generally kept at about 96 grams to 120 grams, preferably, at about 106 grams.

[0030] The advantages of the billiard cue shaft 10 of the present invention may be more clearly understood by reference to FIGS. 5-7. FIG. 5 shows a testing for measuring the flexibility of a billiard cue shaft. Firstly, the first end of a tested billiard cue shaft is placed on a first support device S.sub.1 of a supporting means S and the second end of the tested billiard cue shaft is placed on a second support S.sub.2 of the supporting means S. The distance herein between support S.sub.1 and support S.sub.2 is 500 mm. Then, a pressure means M applies a pressure of 22 pounds (lb) at a speed of 10 mm/min to the pressure point P of the tested billiard cue shaft for getting a bending amount of the tested billiard cue shaft at point P. The bending amount of a prior art cue shaft 80 without a bore is 0.313 inches. The bending amount of a billiard cue shaft of the present invention with a straight section of 394 mm length, and a bore of 280 mm depth and of 8.50 mm inner diameter is 0.338 inches. The bending amount of a billiard cue shaft of the present invention with a straight section of 394 mm length and a bore of 370 mm depth and of 8.50 mm inner diameter is 0.361 inches.

[0031] The performance of a prior art cue shaft and the billiard cue shaft provided by the present invention when hitting a cue ball off center is shown in FIGS. 6 and 7. Firstly, referring to FIG. 6, when hitting a cue ball 90 with a prior art cue shaft 80, if the hitting point 82 is off the center 92 of the cue ball 90 by a distance d, a deflection usually occurs. In more detail, when being lined up with an intended path P.sub.0 of movement of the cue ball to strike the hitting point 82 of the cue ball 90, the prior art cue shaft 80 would apply a side force F.sub.0 to the cue ball 90. The side force F.sub.0 is a resultant of a vertical component force F.sub.01 and a horizontal component force F.sub.02. Due to the effect of the horizontal component force F.sub.02, the actual path P.sub.1 of the cue ball 80 will deflect from the intended path P.sub.0 by an angle θ.sub.0.

[0032] Referring now to FIG. 7, when being lined up with the intended path P0 of movement of the cue ball 90 to strike the hitting point 82, the billiard cue shaft 10 provided by the present invention would also apply a side force F.sub.0 to the cue ball 90. However, because the front section of the billiard cue shaft 10 has appropriate flexibility and significantly reduced mass, especially in the straight section 26, will produce an allowable buckling, as shown by the dotted line in FIG. 7. The allowable buckling will apply another side force Fr on the cue ball 90. This side force F.sub.r is a resultant of a vertical component force F.sub.r1 and a horizontal component force F.sub.r2. As shown in FIG. 7, the horizontal component force F.sub.r2 can just offset the horizontal component force F.sub.02. Therefore, the actual path P.sub.2 of the cue ball 90 will deflect from the intended path P.sub.0 by an angle θ.sub.1 being less than θ.sub.0.