GB2089219A - Wooden racket frames - Google Patents

Abstract

A wooden racket frame comprises a head-portion (10), a handle-portion (11) integrally formed therewith, reinforcing members (12,13,14) and a throat-piece (15). At least the throat- piece (15) is made of a cellular plastics material, which may comprise a polyurethane foam or a polymethacrylimide foam. The use of a plastics material for the throat-piece results in an overall decrease in weight of up to 12 g when compared with an "all-wood" frame. <IMAGE>

Description

SPECIFICATION Wooden racket frames This invention relates to wooden racket frames.

Whilst the present invention will be described herein with particular reference to wooden racket frames comprising a head portion and a handle portion integrally formed therewith, it is not to be construed as being limited thereto.

Wooden racket frames are conventionally made by laying-up a plurality of laminae of one or more woods (e.g. ash, beech and maple), applying an adhesive to the adjacent surfaces of the laminae, forming the assembly into a "keyhole" configuration with the aid of additional wooden components including a throat piece and applying pressure thereto to form an integral structure.

Subsequently, other wooden components are bonded to the structure to complete the frame, such inserts including handle-reinforcements and framereinforcements. The frame may then be further strengthened by the application of reinforcing laminae which are bonded to the frame by means of thermosettable adhesives.

With the recent increase in popularity of games involving the use of wooden-framed rackets (especially tennis and squash) the supply of suitable woods of sufficiently low density has decreased, whilst the demand for lighter-weight frames has increased.

We have found that the weight of a wooden racket frame may be considerably reduced, without adverse effect on the physical dynamic and playing properties of the rackets, if the conventional wooden throat-piece is replaced by a throat-piece made of a cellular plastics material.

Accordingly, the present invention provides a wooden racket frame comprising a head-portion and a handle-portion integrally formed therewith, together with a throat-piece and other reinforcing members, in which at least the throat-piece is made of a cellular plastics material.

The cellular plastics material should have a density of less than 350 Kg/m3, a Young's Modulus in the range 30 to 110 N/mm2 (preferably about 70 N/mm2) and a flexural strength in the range 0.5 to 2.7 N/mm2 (preferably about 1.6 N/mm2).

Suitable cellular plastics material include polyurethane foams and polymethacrylimide foams.

The present invention will be illustrated, merely by way of example, in the following description and with reference to the accompanying drawing.

The drawing shows schematically a side elevation of a racket frame comprising a head-portion 10, a handle-portion 11, reinforcing members for the head-portion (12, 13 and 14 respectively) and a throat-piece 15.

Example 1 A polyurethane foam having a free-height density of 200 to 220 Kg/m3 was moulded to a shape suitable for use as a throat-piece and bonded into position in a wooden tennis racket frame. The frame was subsequently faced with five laminae 0.8 mm thick of vulcanised fibre in the region between X and Z on each side of the frame. The frame was about 6 g lighter than a comparable frame with a mahogany throat-piece. The durability and impact-resistance was acceptable, as was the performance of the frame in play.

Example 2 A polymethacrylimide foam, available from Roehm GmbH as ROHACELL 51 was machined to a shape suitable for use as a throat-piece and bonded in position in a wooden tennis racket frame. The frame was subsequently faced with glass-fibrereinforced laminae 0.4 mm thick in the region between X and Z on each side of the frame and further laminae 0.8 mm thick in the region between X and Y on each side of the frame.

The throat-piece of ROHACELL 51 weighed approximately 1.65 g (compared to one of mahogany which weighed about 13 g). The overall reduction in weight for the racket when compared with an "all-wood" racket was lotto 12 g.

1. Awooden racket frame comprising a head portion and a handle-portion integrally formed therewith, together with a throat-piece and one or more reinforcing members, in which at least the throat-piece is made of a cellular plastics material.

2. A frame according to Claim 1, in which the cellular plastics material has a density of less than 350 kg/m3.

3. A frame according to Claim 1 or 2, in which the cellular plastics material has a Young's Modulus in the range 30 to 110 N/mm2.

4. A frame according to Claim 3, in which the cellular plastics material has Young's Modulus of 70 N/mm2.

5. A frame according to any one of Claims 1 to 4, in which the cellular plastics material has a flexural strength in the range 0.5 to 2.7 N/mm2.

6. Aframe according to Claim 5, in which the cellular plastics material has a flexural strength of 1.6 N/mm2.

7. Aframe according to any of Claims 1 to 6, in which the cellular plastics material comprises a polyurethane foam.

8. A frame according to any one of Claims 1 to 6, in which the cellular plastics material comprises a polymethacrylimide foam.

9. Awooden racket frame, substantially as hereinbefore described with reference to either of the Examples.

10. A racket having a wooden frame according to any one of the preceding claims.

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

Claims (10)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Wooden racket frames This invention relates to wooden racket frames. Whilst the present invention will be described herein with particular reference to wooden racket frames comprising a head portion and a handle portion integrally formed therewith, it is not to be construed as being limited thereto. Wooden racket frames are conventionally made by laying-up a plurality of laminae of one or more woods (e.g. ash, beech and maple), applying an adhesive to the adjacent surfaces of the laminae, forming the assembly into a "keyhole" configuration with the aid of additional wooden components including a throat piece and applying pressure thereto to form an integral structure. Subsequently, other wooden components are bonded to the structure to complete the frame, such inserts including handle-reinforcements and framereinforcements. The frame may then be further strengthened by the application of reinforcing laminae which are bonded to the frame by means of thermosettable adhesives. With the recent increase in popularity of games involving the use of wooden-framed rackets (especially tennis and squash) the supply of suitable woods of sufficiently low density has decreased, whilst the demand for lighter-weight frames has increased. We have found that the weight of a wooden racket frame may be considerably reduced, without adverse effect on the physical dynamic and playing properties of the rackets, if the conventional wooden throat-piece is replaced by a throat-piece made of a cellular plastics material. Accordingly, the present invention provides a wooden racket frame comprising a head-portion and a handle-portion integrally formed therewith, together with a throat-piece and other reinforcing members, in which at least the throat-piece is made of a cellular plastics material. The cellular plastics material should have a density of less than 350 Kg/m3, a Young's Modulus in the range 30 to 110 N/mm2 (preferably about 70 N/mm2) and a flexural strength in the range 0.5 to 2.7 N/mm2 (preferably about 1.6 N/mm2). Suitable cellular plastics material include polyurethane foams and polymethacrylimide foams. The present invention will be illustrated, merely by way of example, in the following description and with reference to the accompanying drawing. The drawing shows schematically a side elevation of a racket frame comprising a head-portion 10, a handle-portion 11, reinforcing members for the head-portion (12, 13 and 14 respectively) and a throat-piece 15. Example 1 A polyurethane foam having a free-height density of 200 to 220 Kg/m3 was moulded to a shape suitable for use as a throat-piece and bonded into position in a wooden tennis racket frame. The frame was subsequently faced with five laminae 0.8 mm thick of vulcanised fibre in the region between X and Z on each side of the frame. The frame was about 6 g lighter than a comparable frame with a mahogany throat-piece. The durability and impact-resistance was acceptable, as was the performance of the frame in play. Example 2 A polymethacrylimide foam, available from Roehm GmbH as ROHACELL 51 was machined to a shape suitable for use as a throat-piece and bonded in position in a wooden tennis racket frame. The frame was subsequently faced with glass-fibrereinforced laminae 0.4 mm thick in the region between X and Z on each side of the frame and further laminae 0.8 mm thick in the region between X and Y on each side of the frame. The throat-piece of ROHACELL 51 weighed approximately 1.65 g (compared to one of mahogany which weighed about 13 g). The overall reduction in weight for the racket when compared with an "all-wood" racket was lotto 12 g. CLAIMS

1. Awooden racket frame comprising a head portion and a handle-portion integrally formed therewith, together with a throat-piece and one or more reinforcing members, in which at least the throat-piece is made of a cellular plastics material.

2. A frame according to Claim 1, in which the cellular plastics material has a density of less than 350 kg/m3.

3. A frame according to Claim 1 or 2, in which the cellular plastics material has a Young's Modulus in the range 30 to 110 N/mm2.

4. A frame according to Claim 3, in which the cellular plastics material has Young's Modulus of 70 N/mm2.

5. A frame according to any one of Claims 1 to 4, in which the cellular plastics material has a flexural strength in the range 0.5 to 2.7 N/mm2.

6. Aframe according to Claim 5, in which the cellular plastics material has a flexural strength of 1.6 N/mm2.

7. Aframe according to any of Claims 1 to 6, in which the cellular plastics material comprises a polyurethane foam.

8. A frame according to any one of Claims 1 to 6, in which the cellular plastics material comprises a polymethacrylimide foam.

9. Awooden racket frame, substantially as hereinbefore described with reference to either of the Examples.

10. A racket having a wooden frame according to any one of the preceding claims.