GB2244926A - Raquets - Google Patents

Abstract

A racquet frame (24) comprises a head frame (27) having a plurality of spaced apart string holes (37) in its inner face, and string support structures affording string passages (36) are provided within the cross-section of the head frame (27) so as to extend between said string holes (37), such that a string of the racquet may be passed through such a hole into the head frame and remain inside the head frame until it emerges from another such hole in the head frame. Many other embodiments are described. <IMAGE>

Description

Title:Racquets Description of Invention This invention relates to racquets suitable for use in the playing of games such as tennis, squash, badminton or the like.

Typically such a racquet comprises a handle or "grip" by which a user may take hold of the racquet, and a head across which a plurality of strings are disposed, the strings being arranged in a generally planar array known as the "string web".

The term "string" is used herein in a generalised sense which includes any suitable elongate flexible element, whether single stranded, multistranded, non-metallic or metallic.

The underlying structure of the racquet is herein referred to as the "racquet frame" and typically comprises a head portion (herein referred to as the "head frame"), which at least substantially bounds and defines an opening across which the strings extend, and a shaft which affords or carries said handle or grip.

In some racquets the shaft is connected directly, at one of its ends, to the head, while in other racquets the shaft is connected to the head through the intermediary of a "throat", which throat may comprise a pair of elongate members which diverge from the end of the shaft and meet the head frame at spaced apart locations, known as "shoulders", on the head frame.

In some racquets the head frame is in the form of a closed loop including a bridge portion/section which extends between said shoulders. The extremity of the head frame furthest from the shaft is know as the "crown".

Racquets having moulded frames, for example moulded in fibre reinforced plastics, have become widely accepted due to their combination of mechanical properties, the possibility of producing a wide variety of aesthetically appealing shapes, and the fact that they iend themselves to automated production methods.

However, the full benefits of moulded racquet frames have not been realised because most frame designs are merely adaptations of earlier wooden or metal designs. That is, they have strings passing through an array of spaced apart holes extending approximately radially through the frame of the head of the racquet into a peripheral groove on the outside of the head.

From the groove they return back through the frame, usually through an adjacent hole, to pass across the head and through the frame again, usually on the opposite side of the head.

This arrangement has a number of disadvantages, including low torsional stiffness of the frame, poor aerodynamics. exposed strings, and poor aesthetics. An additional problem is that any shock loads or vibrations developed in the strings are transmitted directly into the frame. and hence to the player.

It is an object of this invention to provide new and improved racquet frames which overcome some or all of the above mentioned disadvantages.

According to the present invention, there is provided a racquet frame wherein the head frame has a plurality of spaced apart string holes in its inner face, and string support structures are provided within the cross-section of the head frame so as to extend between said string holes, such that a string of the racquet may be passed through such a hole into the head frame, and remain inside the head frame, until it emerges from another such hole in the head frame.

In certain preferred embodiments of the invention, at least the head frame is of moulded construction.

In preferred embodiments of the invention, the cross-section of the head frame has a wholly convex profile to the exterior.

A shaft of the racquet frame, including any "throat" where present, may be integrally moulded with the head frame.

Preferably the racquet frame or the moulded portion or portions thereof, is or are moulded from plastics materials, and preferably from reinforced plastics materials.

Several embodiments of this invention will now be described by way of example only, with reference to the accompanying drawings in which: Figure 1 is a plan view of one type of racquet frame to which the present invention is applicable; Figure 2 is a detailed sectional view of part of the head frame of a racquet of one embodiment of the invention, which includes an internal wall across the cross section of the head frame and string passages produced using extractable or expendable cores.

Figure 3 is a cross-section through part of the head frame of a racquet showing how the frame illustrated in Figure 2 could be produced using resin impregnated material wrapped around expanding foam cores.

Figure 4 shows a cross section through a typical mould tool to produce the frame as illustrated in figures 2 and 3.

Figure 5 shows a detailed sectional view of part of the head frame of a racquet of another embodiment of the.

invention, which includes an internal wall with pre-formed flanged tubes to form the string passages.

Figures 6a and 6b show two views of part of the head frame of a racquet of another embodiment of the invention, whereby pre-formed tubes are used to provide string passages linking non-adjacent string holes.

Figure 7 is a cross-section through part of the head frame of a racquet showing how the frame illustrated in Figure 5 could be produced using resin impregnated material wrapped around expanding foam cores.

Figures 8a, 8b, and 8c show various views of a part of a racquet head frame of another embodiment of the invention, whereby string passages are formed by bonding undersize blocks into recesses in the inside edge of the frame.

Figures 9a, 9b and 9c are detailed sectional views of part of the head frame of a racquet of another embodiment of the invention, whereby the string support is a flexible arched structure inside the frame, showing three possible cross sections of the string support.

Figure 10 is a part sectioned view on the head frame of a racquet of another embodiment of the invention, in which the arched string supports are joined together to form a convoluted band which is joined to the frame between alternate pairs of string holes.

Figures lia, lib and lic show various views of a part of a racquet head frame similar to that shown in Figures 8a, 8b and 8c, this embodiment including an elastomeric material in the string support.

Figures 12a and 12b show two sectional views of part of a racquet head frame similar to that shown in Figures 9 and 10, but in which the string supports are in the form of solid curved blocks.

Figure 13 shows a part sectioned view on the head frame of a racquet similar to that shown in Figure 12b, but in which the string support blocks are joined together at their ends.

The racquet frame 24 illustrated by way of example in Figure 1 is a moulded racquet frame, in this example being moulded from reinforced plastics material, and comprises a head portion 27, in the form of a head frame of closed loop form, and a shaft 26 which carries a grip 25. The.

shaft 26 joins the head frame via shoulders 29 of a throat 28, the portion 30 of the head frame between the shoulders 29 being the bridge, and the opposite extremity of the head frame being the crown.

In one embodiment of the invention, a typical section through the head frame, as shown in Figure 2, includes an internal wall 35 which incorporates a string passage 36, completely enclosed within the head frame, linking advantageously adjacent holes 37 in the inner face of the head frame, and through which the strings 38 of the racquet are threaded.

In this way the outside surface of the racquet can be designed to provide the desired mechanical performance wthout any compromise associated with the need to locate, directly support, or protect the strings.

The head frame cross-section forms a wholly convex profile to the exterior, and although in this example the cross-section of the head frame is elliptical, it could alternatively be circular or of rounded square profile.

The string passages may be formed during the moulding of the racquet by accurately positioning in the moulding either rigid pre-formed loops or blocks, or flexible rods or tubes of advantageously circular cross section, and of the desired size and shape, advantageously semi-circular or other gradually changing shape.

If rigid pre-formed loops are used they could be of some expendable material, for example, a low melting point alloy, or soluble plaster or salt.

If flexible loops were used they could be for example, of PTFE or similar material to which the resin used in the moulding would not become bonded, and could, therefore, be removed from the moulding after the resin had solidified.

It is understood that many different methods of moulding racquet frames are now widely known, and that the methods of producing the string passages described above could be included in many of them. However, some methods of producing the string passages may be more appropriate to one moulding technique than to others. For example, using a flexible PTFE rod or similar may be most appropriate in a moulding technique that was least likely to move or distort the loop. Therefore, press moulding the frame using pre-impregnated woven fibres around two expanding foam cores would be a particularly suitable technique, ie referring to Figures 3 and 4.

The foam cores 45 are wrapped with the resin impregnated material 46, or advantageously placed inside braided tubes of resin impregnated material. The two cores wrapped in the desired quantity of material are placed together trapping the loops of PTFE rod 47 or similar between them in approximately the correct positions. Finally, if required, further resin impregnated material 48 can be wrapped around the whole section binding it together, however, the projecting less of the PTFE loops must be pushed through the material in the appropriate positions.The completed layup is then placed in the lower tool half 55 as shown in Figure 4, and the projecting legs of the PTFE loops 47 positioned in slots 56 on the inside edge of the tool, the slots being of appropriate size and section, such that when the clamping plate 57 of the tool is positioned and screwed down, it clamps the loops in place. Finally, the upper tool half 58 is positioned and the complete tool may be placed between the platens of a press and cured in the conventional manner. After removing the frame from the tool, the PTFE loops 47 are removed from the moulding.

In a second embodiment, a typical section through the head frame of the racquet, as shown in Figure 5, includes an internal wall 35 as in the previous embodiment, the string passage 36 in this embodiment being provided by a pre-formed tube 60 which is positioned in the moulding in a similar way to the PTFE loops 47 in the previous embodiment, but which becomes permanently embedded in the moulding when the plastic material solidifies.

Advantageously, the pre-formed tube may be rigid, possibly light alloy, of adequate section to withstand the loads applied during moulding, and have flanged ends 61.

An advantase of a rigid tube is that the string passage it provides can be of more complicated form than would be possible to produce using a simple flexible loop, for example see Figures 6a and 6b, which show tubes 60 connecting non-adjacent holes in the frame. Depending on the method of manufacturing the frame, and by careful forming of the tubes, careful shaping of any lightweight cores, and placement of reinforcing materials, it is possible to route the strings through the frame in many different ways.

Once again it is understood that this method of providing string passages could be incorporated in many of the different racquet moulding techniques. Figure 7 describes its use in the same manufacturing method as that described in the previous embodiment.

In this case, the two cores 45 trap the tubes 60 which are to become part of the moulding and through which are threaded flexible tensioning/locating members 65, which, in addition to fitting into slots in the tool similar to the previous embodiment, also enable the tubes 60 to be pulled towards the inner tool surface, and therefore, exert pressure on the outer layers of material 48 if desired, and also if of suitable size, prevent resin from entering the string passages themselves.

Advantageously, the tensioning/locating members 65 should be of PTFE or similar material for the same reasons as before, and are treated similarly to the loops of the previous embodiment for the remaining steps in the manufacturing process.

A further embodiment of the invention is shown in figures 8a, 8b and 8c. In this case the head frame of the racquet 27 is moulded with a series of semi-circular or similarly shaped recesses 80 around its inside edge. The recesses define part of the string passage 36, their length being slightly greater than the required string spacing and their width approximately that of the diameter of the strings. The string passages 36 are formed by bonding blocks of appropriate material 81 into the recesses, the blocks 81 being smaller than the recesses 80, such that a passage remains in the racquet head frame.

In the previous embodiments of the invention, the string passages provided rigid support for the strings within the actual frame itself, which allows several of the disadvantages of conventional racquet frames to be overcome. It is envisaged that this relatively straightforward design of frame could be used in the manufacture of many good quality racquets. However, better quality racquets aimed at the more expensive end of the market can be obtained by taking the concept of internal string supports a stage further. In the following embodiments of the invention, the fact that the string supports can be considered as separate structures in their own right, housed inside the actual frame, is used to provide further important advantages over other racquet designs. That is, rather than it simply being a dividing wall across the cross section of the racquet head frame, the string support can be a structure in itself, performing a totally different role to that of the frame, and having particular mechanical properties, which, when combined with the mechanical properties of the strings and frame, results in a racquet with much improved playing characteristics.

For example, the string supports can be designed to provide a flexible connection between the strings and the frame, thereby introducing some shock absorbing qualities to the racquet.

Furthermore, the stiffness of the string supports may vary with different loadings in the same way as a variable rate spring. That is, at low loadings when a ball is hit gently, the string supports could be very flexible, resulting in a racquet having characteristics as if it were loosely strung. However, when a ball is hit more firmly, the string supports could rapidly become more rigid, resulting in the racquet exhibiting the characteristics of being more tightly strung.

If this concept of flexible string supports is applied to the support for each pair of strings individually, then a further important advantage over conventional racquets can be achieved. For example, the stiffness of each string support can be individually tailored to provide, in addition to the features described above, some control of the tension, and more importantly, the change in tension of the strings when a ball is struck, thus: A major problem with most racquets arises as a result of the differing string lengths, and the fact that when a ball is struck, this gives rise to different changes in tension in the strings. The result is, whatever tension the racquet was originally strung at, the actual string tensions when a ball is struck, vary considerably string to string, and playing characteristics like feel and control are impaired.Some proposals have been put forward to overcome this, for example, employing different tensions in particular strings when the racquet is initially strung. However, the number of variations in how a ball can be struck - how hard, and from where on the string mesh - means that such a solution is only satisfactory in a limited number of cases.

Flexible string supports provide a variable element in the racquet/string assembly, and provide a means to attain a far more equal distribution of string tension throughout the racquet, with consequent improvement in playing characteristics.

Therefore, two further embodiments of the invention will be described by way of additional examples, as illustrated in Figures 9a, 9b, 9c, 10, lia, 11b and lic.

A string support 70 is contained inside the head frame of a racquet, and in this case is in the form of a simple arch, which may have a variety of cross sections, three of which are shown in Figures 9a, 9b and 9c. The string support 70 incorporates a string passage 36 advantageously produced by one of the means described in earlier embodiments, and which advantageously joins adjacent holes 37 in the inner face of the head frame 27.

The string supports 70 may be joined together at the point at which they join the head frame itself as shown in Figure 10, so that they may be formed as a single continuous convoluted band, the construction and shape of each individual arch being designed to give the desired degree of rigidity or flexibility. In addition, it is possible to include an elastomeric material or other material with the desired properties into region 75 to contribute to the final mechanical properties of the string support.

Once again it is understood that the racquet described above could be made by any one of a number of widely known techniques, however, the added complexity of this embodiment may mean that whereas the earlier embodiments could easily be made in one single moulding, it may be advantageous to manufacture this embodiment in two or more separate pieces, with an assembly operation being required to form the finished racquet.

A further embodiment of the invention is shown in figures lla, llb and 11c which is basically a further development of that shown in figures 8a, 8b and Sc to include flexible supports for the strings. Once again recesses 80 are formed in the inside edge of the moulding, In this case the undersize blocks 81 which are bonded into the recesses to form the string passages 36 include an elastomeric material 82 around at least part of their periphery that supports the string, the properties of which provide the desired degree of flexibility in the string support.

It is understood that although the invention has been described as applying to an entire racquet, it may also be applied to just part of a racquet, for example, the bridge section.

It is also understood that although most of the foregoing is described as for a ball and racquet game, the principles also apply to all racquet games, including badminton and the like.

Where the string passages are afforded by internal walls, they may alternatively be afforded by a multitude of curved internal walls at least substantially perpendicular to the plane of the string web, the walls being curved about an axis at least substantially orthogonal to the plane of the string web.

The string passages described and illustrated herein are in the form of arches, which turn the string through an angle of essentially 1800, but in alternative constructions the string passages may be in the form of arches which turn the string through other angles, for example through angles in excess of 1800 The string passages could alternatively be defined by a series of blocks disposed within the head frame.

The blocks 81 could themselves incorporate pre-formed string passages.

Any of the aforesaid blocks could be joined together at their ends, to facilitate handling and insertion of the blocks.

Further embodiments of the invention are shown in Figures 12a, 12b and 13. These embodiments are variations on those shown in Figures 9a to 9c and 10, in which the arched string supports are replaced by solid curved blocks 85.

Once again the blocks 85, or at least part of them could be made from an elastomeric material, or other material which gives the string support its appropriate mechanical properties.

Also, as before, the blocks could be joined together at their ends as shown in Figure 13.

In Figure 12a the blocks 85 are of semi-circular, elliptical, parabolic or other curved profile, connected to the inside of the head frame between pairs of string holes. In Figure 12b, alternative blocks 85, similaraly connected to the inside of the head frame, each incorporate a respective semi-circular, elliptic, parabolic or other curved shape string passage, ends of which passage at least substantially coincide with the string holes in the head frame.

It will be appreciated that the invention, in its broadest terms, is not limited to moulded racquet frames, but is also aplicable to other types of racquet frames, such as hollow metal racquet frames for example.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in there specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, or a class or- group of substances or compositions, as appropriate, may, separately or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims (36)

CLP.TMn

1. A racquet frame wherein the head frame has a plurality of spaced apart string holes in its inner face, and string support structures are provided within the cross-section of the head frame so as to extend between said string holies, such that a string of the racquet may be passed through sL.h a hole into the head frame, and remain inside the head frame, until it emerges from another such hole in the head frame.

2 A racquet frame as clai ;: lain 1 nereit the cioss sectar or the head is of circular elliptical or rounde - square p -c, n e

3. A racquet frame as claimed in Claim 1 or Claim 2, wherein the string support structure is an internal wall which divides the cross section of the head frame in the plane of the string web, the wall incorporating string passages.

4. A racquet frame as claimed in Claim 1 or Claim 2, wherein the string support structure is an internal wall which divides the cross section of the head frame in a plane other than that of the string web, the wall incorporating string passages.

5. A racquet frame 2S claimed in Claim I or Claim 2 wherein the string support structure comprises a multitude of curved internal walls at least substantially perpendicular to the plane of the string web, the walls being curved about an axis at least substantially orthogonal to the plane of the string web, arranged such that ends of the internal walls join the outside wall of the head frame adjacent to respective string holes, so as to extend between said string holes, and in use a string is passed through such a string hole, into the frame, around the curved wall of a string support and out of the frame through another of the holes.

ó. A racquet frame as claimed in Claim I or Claim 2, wherein the string support structure comprises a multitude of curved internal walls at least substantially perpendicular to the plane of the string web, the walls being curved about an axis at least substantially orthogonal to the plane of the string web, arranged such that the opposite ends of the internal walls join the outside wall of the head frame at the positions of respective string holes, so as to extend between the string holes, the internal wall incorporating a string passage which links the string holes.

7. A racquet frame as claimed in Claim I or Claim 2, wherein the string support structures are discrete structures within the cross-section of the head frame, independent of the frame itself apart from being connected to it at or in the vicinity of the string holes.

8. A racquet frame as claimed in Claim 7 wherein the string support structure includes a series of blocks of semi-circular, elliptical, parabolic or other curved profile connected to the inside of the head frame between pairs of string holes, such that in use a string is passed through such a string hole into the frame, where it passes over such a string support block and out of the frame through another of the string holes.

9. A racquet frame as claimed in Claim 7 wherein the string support structure comprises a series of blocks, each incorporating a string passage, connected to the inside of the head frame between pairs of string holes, the ends of the string passages at least substantially coinciding with the string holes, such that in use a string is passed through such a string hole, around such a string passage inside the frame, and out of the frame though another of the string holes.

10 A racquet frame as claimed in Claim 8 or Claim 9, wherein the blocks are joined together at their ends.

11. A racquet frame as claimed in any one of Claims 8, 9 or 10 wherein the blocks are made entirely or in part from an elastomeric or other flexible material.

12. A racquet frame as claimed in Claim 7 wherein the string support structures-are in the form of arches with their bases joined to the inside surface of the head frame, such that the arches extend between pairs of string holes, such that in use a string is passed through a string hole into the frame, where it passes over such a string support and out of the frame through another of the string holes.

13. A racquet frame as claimed in Claim 12, wherein the string support structures are-in the form of arches joined together at their bases to form a convoluted band, the profile of the section which joins the arches being that of the inside of the head frame to which they are joined.

14. A racquet frame as claimed in Claim 7, wherein the string support structures are in the form of arches, each arch incorporating a string passage, the base of the arches join the inside surface of the head frame such that they span alternate pairs of string holes and the string holes coincide with the string passages, such that in use a string is passed through a string hole around the string passage in the arch and out of the frame through an adjacent string hole.

15. A racquet frame as claimed in Claim 14, wherein the string support arches are joined together at their bases to form a convoluted band, the profile of the section which joins the arches being that of the inside of the head frame to which they are joined.

16. A racquet frame as ciaimed in any one of Claims 12. 13, 14 or 15, wherein the arches are rigid.

17. A racquet frame as clairned in any one of Claims 12. 13, 14, or 15.

wherein the arches are flexible.

18. A racquet frame as claimed in any one of Claims 12, 13, 14 or 15.

wherein the arches have a variable flexibility such that a unit defiection at high loads produces a greater change in stiffness than a unit deflection at low loads.

19. A racquet frame as claimed in any one of Claims 12. 13, 14 or 15, wherein the arches have differing flexibilities depending on their position around the racquet head.

20. A racquet frame as claimed in any one of Claims 12. 13, 14, or 15, wherein the flexibility of each arch is related to the properties and/or lengths of the strings it supports.

21. A racquet frame as claimed in any one of Claims 17 to 20, wherein an elastomeric or other flexible material is included in the region under the arch and which connects the arch to the inside of the frame.

22. A racquet frame as claimed in any one of Claims 1 or 2, wherein the string passage is produced by moulding curved slots or recesses in the inside surface of the head frame corresponding to the string positions, spacings, and diameter, and bonding into the slots blocks to form the string supports, which fill the slots width, but whose profile is different from that of the slots such that a curved passage is formed in the frame.

23 A racer frame as claimed in Claim 22, wherein the blocj'-:s which are :tonaea into the slots are at lee partly fleXiQiC.

24. A racquet frame as claimed in any one of Claims 3, 4. 6, 9 to 11 or 14 to 2 1, wherein the string passages are manufactured by the use of flexible loops of PTFE, or PTFE coated material. which are removed from the moulding after it has become rigid.

25. A racquet frame as claimed in any one of Claims 3, 4, 6, 9 to 11. or 14 to 21! wherein the string passages are manufactured by the use of flexible loops of suitable material such that the loops can be removed from the moulding after it has become rigid.

26. A racquet frame as claimed in any one of Claims 3, 4. 6, 9 to I l,or 14 to 21. wherein the string passages are manufactured by the use of loops of soluble plaster which are washed out of the moulding after it has become rigid.

27. A racquet frame as claimed in any one of Claims 3, 4. 6, 9 to 11 or 14 to 21. wherein the string passages are manufactured by the use of loops formed from a low temperature melting point alloy, which are melted out of the moulding after it has become rigid.

28. A racquet frame as claimed in any one of Claims 3, 4. 6, 9 to II or 14 to 21, wherein the string passages are manufactured by the use of loops formed from any suitable expendable material which is removed from the moulding after it has become rigid.

29. A racquet frame as claimed in any one of Claims 3, 4, 6, 9 to 11, or 14 to 21, wherein the string passages are formed by the inclusion of pre-formed tubes.

30. A racquet frame as claimed in Claim 29, wherein the pre-formed tubes are metallic.

31. A racquet frame as claimed in any one of Claims 29 and 30, wherein the pre-formed tubes have flanged ends which become joined to the inside of the outer wall of the moulding.

32. A racquet frame according to any one of the preceding claims wherein at least the head frame is of moulded construction.

33. A racquet frame substantially as described herein with reference to the accompanying drawings.

34. A racquet comprising a racquet frame according to any one of Claims 1 to 33.

35. A racquet substantially as hereinbefore described with reference to the accompanying drawings.

36. Any novel feature or novel combination of features described herein and/or illustrated in the accompanying drawings.