WO1993022005A2

WO1993022005A2 - Tennis racquet

Info

Publication number: WO1993022005A2
Application number: PCT/CA1993/000175
Authority: WO
Inventors: Willi H. Velke
Original assignee: Velke Willi H
Priority date: 1992-04-29
Filing date: 1993-04-28
Publication date: 1993-11-11
Also published as: AU4257093A; WO1993022005A3; CA2067618A1

Abstract

An improved racquet, such as a tennis racquet, which may be manufactured by way of an injection moulding method rather than by hollow resin casting, using a corrugated skeleton structure for its frame construction, which acts to reduce drag and to modulate racquet frame resonancy, increasing efficiency of such racquet at a more consistent quality level and reduced production cost.

Description

E3MIS RftCQUET

BACKGROUND OF THE INVENTION Tennis racquets have undergone various design improvements over the years, especially with respect to weight reduction and method of construction, and racquets today only weigh a fraction of their former wood laminate counterparts. Racquets are now manufactured of a light-weight carbon fibre and resin combination and are moulded into a shape using a tubular construction to provide the necessary strength and to be able to contain the tightened string webbing «d to withstand constant impact with the ball during the game.

Strength and light weight of construction are therefore two of the main ingredients inherent in a modern day racquet and further desired components are control of resonance, enlargement of the "sweet spot", improved aerodynamics and ease or efficiency of production.

Conventional racquets are constructed in a mould by way of a cold-cast or thermally-hardened resin cast and fibre combination method and as such require the shape of a hollow-tube frame construction to obtain the necessary strength to weight ratio. Hollow cast moulding is a complicated and cost-inefficient manufacturing method and is prone to produce inconsistent resin distribution conditions in frames constructed in this manner, which obviously results in uneven wall strength and hence weaknesses in such frame construction, which will remain undetected until such product is in the marketplace.

It would therefore be most desirous to have available an improved racquet frame design and construction, which would allow for a more efficient method of manufacture to produce a tennis racquet frame of more consistent quality at a reduced labour cost. SUMMARY OF THE INVENTION:

An object of the present invention is to provide an improved general frame configuration for a racquet such as a tennis racquet, so that a more efficient moulding process may be employed for its manufacture.

Another object of the present invention is to provide an improved moulding technique for a racquet such as a tennis racquet, which accommodates a more precise and efficient production method. A racquet frame designed for such a production method may include in its surface certain surface features not reproducible in the moulding method heretofore employed for racquets.

Yet another object of the present invention is to provide an improved style of frame construction for a racquet such as a tennis racquet, with such construction including a choice of variable dimensions especially effective in modulating racquet resonance, in order to increase the racquet's accuracy of delivery of a ball, when striking such ball into a specified direction. These and other objects are part of the present invention comprising a racquet such as a tennis racquet for use with a ball of limited resiliency, incorporating a racquet handle portion, a racquet frame portion provided with string, and a racquet throat region which connects the handle portion with the racquet frame portion.

In accordance with the principles of this invention, there is herewith provided a racquet of substantially the same overall dimensions as any known racquet, but with its frame and throat portion comprising a non-tubular construction, which employs the principle of corrugation to provide the necessary strength to weight ratio required for such racquet frame and throat portions.

A sectional view through such frame of a racquet of the present invention reveals a generally oval outline, the same as appearing in the construction of any known racquet, except that rather than creating a void condition inside the oval outline thereby arriving at a hollow tube configuration, such void, or in other words, such reduction of material within the confines of its oval outline is instead created by a reduction of material from the outer edges of such oval outline towards its centre. It thereby creates a corrugated skeleton of generally oval exterior outline rather than an oval tube, with such corrugated skeleton frame possessing similar or even superior strength qualities than a tube frame. Further in accordance with the present invention there is provided a corrugated skeleton racquet frame with superior aerodynamics, when compared with a tube frame of similar dimensions, as the exterior surface of such corrugated skeleton racquet frame comprises a number of longitudinally located trough-like depressions, arranged in parallel and at more or less ninety degree angle to the direction of swing, and such surface features will reduce base drag and thereby increase swing power and performance of a racquet so equipped. Further in accordance with the present invention there are provided corrugation portions or fins, which comprise part of the construction of the corrugated skeleton frame and throat area of a racquet, whereby such corrugation portions or fins may be varied and adjusted with respect to their thickness, depth and height, so as to add more body and stiffness to the frame area employing such adjusted corrugation portions or fins, and thereby assisting in the modulation of a racquet's oscillation frequency to a most desirable range. This may be achieved by locating such oversize corrugation portions or fins anywhere along an area between the frame, throat area and handle portion of a racquet, in such dimensions and volume as to be most effective in achieving the particularly desired result. The modulation may be adjusted in relation to the general force a racquet is expected to be operated with, varying according to the strength of a player, which could range from that of a young child to that of a powerful male athlete.

Further in accordance with the present invention there is herewith provided a moulding method, which allows a much more efficient racquet production process and a reduction of the number of components which are normally required to assemble a complete racquet as it is known today. The use of such improved moulding method is made possible by replacing the tube configuration, used exclusively in prior art racquet frame construction, with the simplified corrugated skeleton configuration in accordance with the present invention. This skeleton configuration, because of it being of non-tubular construction, and because its basic design concept incorporates corrugation members of generally equal dimensions and thickness, now allows for the use of an injection moulding method, which is a much more quality controllable and less labour intensive production process, resulting in significantly increased production efficiency. Mould parting lines need to be fundamentally relocated and mould components therefore provide differently interrelated functions when such moulding process has changed from a resin casting technique to an injection moulding technique for the purpose of producing tennis racquets. Although injection moulding has been used to produce a vast number of finished and component parts, it has never been successfully employed to produce tennis racquets.

As yet another part of the present invention skeleton type racquet frames produced through the injection moulding method do not require any string support inserts, as they are already moulded right into the corrugated frame structure. Such string support inserts are normally independently manufactured and inserted by hand into holes jig drilled into all tube-type racquet frames as a necessary requirement before adding the high tension string webbing. According to the present invention, this design and moulding simplification therefore represents a major manufacturing improvement, as it reduces cost by reducing parts and labour.

Without being limited in accordance with any particular theory of operation or effect, there is hereby provided, as part of the present invention, a frame configuration and moulding method for a racquet such as a tennis racquet, which results in a much superior racquet, by improving its design to include frame surface features to reduce drag, by including a device to modulate resonance frequencies, by creating a frame structure of increased strength and consistency, by providing the feasibility for use of an injection moulding method to simplify production and to reduce production cost.

INTRODUCTION TO THE DRAWINGS:

Figure 1 of the drawings appended hereto depicts a plan view of a known tennis racquet, comprising a tube- shape construction.

Figure 2 of the drawings depicts a side elevation view of a tennis racquet, such as shown in Figure 1.

Figure 3 of the drawings depicts a view of a section of a typical tubular frame construction of a known tennis racquet.

Figure 4 of the drawings depicts a section view through Section Line 'A-A' in Figure 2.

Figure 5 of the drawings depicts a section view through a section of a known tubular racquet frame, illustrating its corresponding mould parts.

Figure 6 of the drawings depicts a preferred embodiment, illustrating a tennis racquet in side elevation view.

Figure 7 of the drawings depicts a section view through the frame section of a preferred embodiment at Section Line 'B-B' as illustrated in Figure 6. Figure 8 of the drawings depicts a section view through .Section Line 'B-B' as illustrated in Figure 7, this time showing it with its corresponding mould parts. Figure 9 of the drawings depicts an isometric view of a section of racquet frame as illustrated in Figure 6.

Figure 10 of the drawings depicts a preferred embodiment, this time illustrating in side elevation view an alternate surface feature design.

Figure 11 of the drawings depicts an alternate frame shape in section view at Section Line ^•C-C* in Figure 10.

Figure 12 of the drawings depicts an isometric view of a frame portion using a configuration based on a section as illustrated in Figure 10, this time however using discrete depression surface features.

Figure 13 of the drawings depicts a half section of a shape as illustrated in Figure 11, this time with its moulding parts. Figure 14 of the drawings depicts an isometric view of a frame portion using a shape based on a section as illustrated in Figure 11. using trough-like surface depression features.

DETAILED DESCRIPTIONS OF A PREFERRED EMBODIMENT:

Figure 1 of the drawings appended hereto depicts a plan view of a tennis racquet of prior art, of typical one- piece, hollow tube-shape frame construction, comprising an oval frame portion (a), containing the string webbing (b), a throat region (c) which connects the frame portion to the handle portion (d).

Figure 2 of the drawings appended hereto depicts a side elevation view of a tennis racquet of prior art, as shown in Figure 1, illustrating a recessed channel (e) along the exterior of the oval frame section of such racquet, with string holes located within it.

Figure 3 of the drawings appended hereto depicts an isometric view of a typical interior construction detail of a hollow frame section of a tennis racquet of prior art, which illustrates fiber material (f), preshaped into a hollow tube configuration, sometimes re-inforced with additional fiber strands (g), to form an integrated fibrous structure which will then be impregnated with casting resin as part of the moulding process, to harden into a solid hollow tube shape. Figure 4 of the drawings appended hereto depicts a sectional view through a typical moulded racquet frame portion of prior art, as indicated at Section Line 'A-A' in Figure 2. Such section view shows the fiber and resin ormed hollow tube configuration (a), with its recessed ° channel (e), and a sectional view of a string insert part (h), which will seat in a corresponding string hole (i) drilled into such recessed channel through the opposite wall of the racquet frame tube. Such string insert arrangement is necessary to distribute the high tension of ⁵ the string webbing when installed, and to prevent the string from cutting through and crushing the thin fiber and resin formed racquet frame wall of such prior art construction.

Figure 5 of the drawings appended hereto depicts a sectional view of a typical racquet frame portion of prior art, as indicated at Section Line 'A-A* in Figure 2, this time showing such hollow tube section (a) within its mould portions (j), (k) and (1) and their parting lines (m) . The location of parting lines obviously dictates the direction - the mould portions need to be moved in order to release a finished moulded part. In this case, three mould portions are necessary, when viewed in section view, to accommodate the moulding of the required shape for the finished part.

Figure 6 of the drawings appended hereto depicts a 0 si•de elevation view of a preferred embodiment, comprising a racquet frame portion (a) and a throat region (c) which according to the present invention is constructed using a corrugated skeleton structure rather than a hollow tube type shape to form such racquet frame portion and throat 5 region. Channel (e) has become part of the corrugation shape construction with string holes located within it. Figure 7 of the drawings appended hereto depicts a sectional view of a preferred embodiment, comprising a corrugated skeleton shape (a) according to the present invention, as illustrated in Figure 6 at Section Line 'B-B' and showing its fin and groove arrangement with string hole locations as indicated by arrow (n). No string inserts are necessary to be used in this type of construction as the frame centre portion at arrow (n) provides sufficient strength to accommodate string webbing tension. Figure 8 of the drawings appended hereto depicts a sectional view through a corrugated skeleton frame as illustrated in Figure 7, this time showing such section enclosed in its mould parts (j) and (k), with their parting lines (m). Again such parting line locations dictate the directions in which mould sections need to be moved in order to release the finished part. Such parting lines illustrated here are located in a completely opposite location from parting lines used in the prior art moulding process and thereby represent a major departure from such prior art moulding method. Only two mould portions (j) and (k) are necessary, when viewed in section, for this moulding portion, with such mould portions now able to accommodate frame surface features, such as grooves and discrete depressions, not normally reproducible in the prior art moulding process.

Figure 9 of the drawings appended hereto depict an isometric view of a racquet frame portion as illustrated in Figure 6 at Section Line ^•B-B' . Such frame portion view illustrates the fin and groove arrangement (q) which comprises the construction of a corrugated skeleton configuration according to the present invention. Depth of grooves, height of fins and dimension of centre bar may all be adjusted to accomplish desired changes of racquet resonancy. Figure 10 of the drawings appended hereto depicts a side elevation view of a preferred embodiment, this time comprising a racquet frame portion (a) and a corresponding throat region (c), which according to another aspect of the present invention includes in the surface of such racquet portions discrete surface depressions. Such alternate racquet frame surface feature is arranged in a pattern so as to improve swing motion efficiency of a tennis racquet with a frame surface so equipped. Figure 11 of the drawings appended hereto depicts a sectional view of a preferred embodiment as illustrated in Figure 10 at Section Line 'C-C, this time comprising two separate section halves (a) and (al), which when cemented or fused together at their touching centre line areas complete a racquet frame construction of a generally oval exterior outline but with hollow cores (p) to reduce weight and material. This configuration again allows for the use of an improved moulding method, according to the present invention, which enables the accommodation of discrete surface depressions (q) in the surface of a racquet frame as illustrated in Figure 12 and as an alternative surface feature as illustrated in Figure 14 of the appended drawings, with such surface features not normally reproducible in the resin casting method used exclusively in the moulding of prior art racquet frames.

Figure 12 of the drawings appended hereto depicts an isometric view of a portion of racquet frame as illustrated in Figure 11 in section view. Such racquet frame herewith includes discrete surface depressions (q) in a pattern located in the exterior surface of such racquet frame, thereby improving racquet efficiency in accordance with the present invention. Such racquet frame surface features are usually not mouldable in an efficient and quality controllable way using the moulding method heretofore employed to produce prior art tennis racquet frames. Figure 13 of the drawings appended hereto depicts a preferred embodiment as illustrated in Figure 11, this time comprising half of a racquet frame portion, located in its mould parts (j) and (k), and with parting lines (m.) again dictating directions in which mould sections need to be moved in order to release the finished part. Parting lines are located again in opposite directions when compared to parting lines used in the prior art moulding method thereby accommodating a superior moulding technique in accordance with the present invention.

Figure 14 of the drawings appended hereto depicts an alternative surface feature arrangement in accordance with the present invention, as part of a frame construction detailed in section view in Figure 11, this time showing an isometric view of the use of trough-like depressions (q) instead of discrete depressions, to equip a racquet frame with a surface feature using injection moulded frame sections cemented or fused into a finished tennis racquet frame.

Claims

I CLAIM:

I. A tennis racquet using a corrugated skeleton structure for its frame construction. 2. A racquet frame according to Claim 1, which is, when viewed in cross section, of generally oval configuration.

3. A racquet frame according to Claim 2, which uses a mould with its two major parting lines located along the apex of its generally oval-shaped frame configuration, rather than along the flat areas of such generally oval- shaped frame configuration.

4. A corrugated skeleton frame according to Claim 1, which is moulded as a single piece, solid core unit.

5. A corrugated skeleton frame according to Claim 1, which is moulded as a single-piece, hollow core unit.

6. A corrugated skeleton frame according to Claim 1, which is moulded as a multi-piece, hollow core unit.

7. A corrugated skeleton frame according to Claim 1, which uses a combination of trough-like depressions and, or protruding fins to create a corrugation effect.

8. A corrugated skeleton frame according to Claim 1, which uses a pattern of discrete spherical, non-spherical or other geometrically shaped depressions extending below the frame surface to create a corrugation effect. 9. A corrugated skeleton frame according to Claim 1, which uses a pattern of discrete spherical, non-spherical or other geometrically shaped protrusions extending above the frame surface to create a corrugation effect. 10. A corrugated skeleton frame according to Claim 4, which is moulded by way of an injection moulding method.

II. A corrugated skeleton frame according to Claim 5, which is moulded by way of a fibre and resin casting method. 12. A corrugated skeleton frame according to Claim 6, which is moulded by way of an injection moulding method. 13. A corrugated skeleton frame according to Claim 3, which is moulded in a fibre and resin casting method. 14. A corrugated skeleton frame according to Claim 1, which is produced by way of a RIM or reinforced injection moulding method.

15. A corrugated skeleton frame according to Claim 4,

5 which is moulded by way of an extrusion moulding method.

16. A racquet frame according to Claim 3, which is of non-corrugated, hollow-core construction.

17. A racquet frame according to Claim 1, which is a racquet for use in games other than tennis.

10 18. A racquet frame according to Claim 16, which is a racquet for use in games other than tennis. 19. A racquet frame according to Claim 5, which employs a pattern of surface corrugation in only parts of its exterior surface area.