GB2283687A

GB2283687A - Shuttlecock

Info

Publication number: GB2283687A
Application number: GB9422617A
Authority: GB
Inventors: Robert Christopher Haines
Original assignee: Dunlop Ltd
Current assignee: Dunlop Ltd
Priority date: 1993-11-10
Filing date: 1994-11-09
Publication date: 1995-05-17
Anticipated expiration: 2014-11-09
Also published as: GB9422617D0; TW245645B; CN1107376A; GB9323203D0; GB2283687B

Abstract

A shuttlecock, and particularly the skirt portion of a shuttlecock, is provided to have properties, especially the sound emitted when struck by a racket, closely resembling those of a goose feather shuttlecock. The shuttlecock skirt 20 is formed of sheet material and has the shape of a frustum of a cone with a corrugated outline in sections transverse to the longitudinal axis of the cone, the corrugations 21 being secured at their internal or external extremities to at least one reinforcing band 23 of corresponding frusto-conical shape whose longitudinal axis is coincident with the longitudinal axis of the skirt, whereby the band and corrugations define a series of tubular structures. The skirt may be formed into the desired shape by cutting and folding from a flat sheet, or by moulding of plastics material, or by extruding plastics material into tubular form and moulding the tube to the desired corrugated frusto-conical form, and then attaching at least one reinforcing band to extremities of the corrugations such as by adhesive or welding. <IMAGE>

Description

SHUTTLECOCK This invention relates to a shuttlecock and particularly to the skirt portion of a shuttlecock.

The invention is particularly concerned to provide a shuttlecock of a quaiity sufficient for the playing of the game of badminton and will therefore be more specifically described below with reference to badminton shuttlecocks. Nevertheless, it will be appreciated that the invention is not to be so limited and may be applicable to a wider variety of uses including toy shuttlecocks.

Top quality badminton shuttlecocks traditionally have been made from goose feathers. An array of, usually sixteen, suitably trimmed goose feathers have their stems inserted into a cork such that adjacent feathers overlap and their flights lie on the notional surface of the frustum of a cone, the smallest diameter of the frustum coinciding with the cork or end cap of the shuttlecock. The stems of the feathers are then tied together with a cord, and the cord is then lacquered to provide stiffening whereby a relatively rigid skirt is formed. The structure so obtained provides the desired aerodynamic properties of a shuttlecock including speed and spin and is light in weight, stiff in flexure and reasonably resistant to damage by impact from a racket.

Goose feather shuttlecocks, however, are expensive and for many years a variety of moulded plastics shuttlecock skirts have been made to provide a cheaper and more durable alternative. Such plastics skirts normally are made in a lace-like structure by injection moulding a thermoplastics material into the form of a frustum of a cone. The smaller diameter end of the frustum is then attached to a suitable cork or alternative end cap.

While injection-moulded badminton shuttlecocks have been successful commercially, they suffer from certain shortcomings, notably in that the sound they emit when struck by a racket is not the sharp "crack" emitted by a feather shuttlecock and this diminishes the satisfaction experienced by the player. This difference in sound is due in part to the lower stiffness of the injection-moulded skirt compared with the goose feather skirt, i.e. the "lace-like" skirt is a less effective soundbox.

The invention aims, therefore, to provide a shuttlecock skirt of lightweight structure but of greater stiffness than that of conventional plastics skirts, whereby the "crack" of a feather shuttlecock striking a racket can be more nearly emulated.

Accordingly, in one aspect, the invention provides a shuttlecock skirt of frusto-conical shape, which comprises a frusto-cone of corrugated sheet material having a corrugated outline in sections transverse to the longitudinal axis of the frusto-cone, and a reinforcing band secured to transverse extremities of the corrugations, said reinforcing band having a frusto-conical shape corresponding to that of the sheet material frusto-cone and being oriented such that the longitudinal axes of the band and sheet material frusto-cone are coincident, whereby the band and corrugations define a series of tubular structures.

In another aspect of the invention, there is provided a shuttlecock having a frusto-conical skirt described in the immediately-preceding paragraph attached at its narrow end to a shuttlecock end cap.

By 'sheet material' there is meant material in sheet form, i e laminar or film-like form. For manufacture of the skirt, the sheet material initially may be in either flat sheet form or in tubular form, which may be produced by, for example, extrusion from granular material.

According to a further aspect of the invention, there is provided a method of making a shuttlecock skirt of frusto-conical shape, which comprises: forming corrugations in a sheet material and shaping the sheet material to form a frusto-cone corresponding to the frusto-conical shape of the skirt, whereby the frusto-cone is provided with a corrugated outline in sections transverse to the longitudinal axis of the frusto-cone; locating a reinforcing band at a position on the frusto-cone for conferring radial stiffness, said band having a frusto-conical shape corresponding to that of the frusto-cone at that position and being oriented such that the longitudinal axis of the band is coincident with the longitudinal axis of the frusto-cone; and attaching the reinforcing band to transverse extremities of the corrugations at that position to provide a series of tubular structures.

The reinforcing band may be secured to the inner or outer transverse extremities of the corrugations. The skirt may have one or more than one such band, e g two bands. When more than one band is present, they may all be secured to corrugation extremities at the inside of the skirt or all be secured to corrugation extremities at the outside of the skirt, or one or more bands may be secured to corrugation extremities at the inside of the skirt and one or more bands may be secured to corrugation extremities at the outside of the skirt.

The, or each, band may be located around the frusto-cone of corrugated sheet material at a position, or positions, to confer desired stiffness in the radial (transverse) direction of the skirt.

In one preferred embodiment a reinforcing band is positioned adjacent the wide end of the frusto-cone and is secured to the internal extremities of the corrugations.

In another preferred embodiment a reinforcing band is positioned at the narrow end of the frusto-cone and is secured to the internal or external extremities of the corrugations.

The, or each, band has a frusto-conical shape corresponding to that of the frusto-cone of corrugated sheet material at the position of securement, i e the conical surface of the band is parallel to the conical surface of the sheet material frusto-cone as defined by the corrugation extremities at the securement interface.

The, or each, band provides a link between extremities of the corrugations to produce a series of tubular structures (hollow tubes or openended boxes), each of which is defined by the corrugation surface between adjacent extremities and the band surface linking those extremities.

The, or each, band suitably is secured to the internal or external extremities of a majority of the corrugations and preferably is secured to the internal or external extremities of all of the corrugations.

The bands may be attached to the internal or external extremities of the corrugations by any suitable means, e.g. by adhesive or, if both band and corrugated sheet material are of thermoplastics material, by welding.

The corrugations should be of sufficient depth to produce the desired degree of stiffness in the conical surface of the skirt along lines formed by the intersection with that surface of planes through the longitudinal axis of the cone. Preferably the corrugations are of a depth "d" such that the ratio d:r is from 1:4 to 1:2 at any section transverse to the longitudinal axis of the cone, where "r" is the internal radius of the frusto-cone, i.e. the radius of the notional surface defined by the internal extremities of the corrugations.

In a preferred embodiment the number of complete corrugations extending around the frusto-conical surface is sixteen, i.e. to correspond to the number of feathers in a feather shuttlecock, as specified by the rules of the game of badminton. Thus each corrugation can then be regarded as approximating the exposed edge of an overlapped feather.

Preferably the corrugations extend along substantially the whole length of the skirt. However, if desired, the corrugations may extend along only a proportion of the skirt length, but preferably along at least 30% of the skirt length, for instance from the narrow end of the skirt. When the corrugations extend along only a proportion of the skirt length, the remainder of the skirt may be, for instance, of smooth configuration.

The, or each, reinforcing band may have a band width such as in the range 30% to 100% of the length of the corrugations.

The corrugations may be aligned so that their longitudinal axes each lies in a plane passing through the longitudinal axis of the notional frusto-cone of the skirt. Alternatively, the longitudinal axes of the corrugations may lie at an angle to this plane or may spiral about the longitudinal axis of the frusto-cone. In this latter embodiment the overall appearance of the skirt resembles that of a tapering threaded screw.

The corrugations may be of angular or curved outline. They may follow, for example, a castellated outline, i.e. a wave form based on repeating angular elements, e.g. of square or triangular shape, or a wave form based on repeating curvatures, e.g. a sinusoidal curve of the type y = sin x. However, although they may be regarded in some embodiments as repeating geometrical elements as in a wave form, they may comprise other repeating elements which cannot properly be described in terms of a continuous wave form, e.g. a truncated wave form to give a fluted appearance to the skirt.

The skirt of the invention may be provided with holes to reduce weight and holes may be positioned to promote spin of the shuttlecock in flight. The holes may be provided in the sheet material from which the skirt is to be formed or may be produced after the skirt has been formed.

Any materials suitable for shuttlecocks may be used for the sheet material and reinforcing band(s). Thus, stiff paper, thermosetting plastics material or thermoplastic plastics material may be used. The material used will also govern the method of manufacture to be employed.

The skirt may be made by any convenient means but is preferably made by one of the two following basic methods.

The first preferred method is applicable to thermosetting or thermoplastic plastics materials. The corrugations are induced by heat-setting a thin film of the material while it is constrained in the appropriate profile. The desired profile shape of the skirt may be obtained by, for example, blow-moulding, vacuum-forming or matched-die-forming, all techniques well known by the skilled man in the plastics forming art.

Moreover, more than one such operation may be used sequentially.

In this first method, the corrugations may, if desired, be formed in stages such that the amplitude of the corrugations is increased progressively so that the effective angle of the frusto-conical formation changes progressively until the desired cone angle is achieved.

The second preferred method comprises first cutting out a suitably sized disc of the desired sheet material and then removing a smaller co-axial disc from the central region of the first disc to form a skirt blank.

Corrugations are then formed by inserting creases along the radii of the skirt blank corresponding to the vertices of the chosen wave form. The amplitude of the corrugations is increased uniformly towards the outer periphery of the blank so that, when all the corrugations have been made, the disc is transposed into the desired frusto-conical shape. The relationship between the relative amplitude of the corrugations at the inner and outer peripheries and the circumference of the circles defining these peripheries will control the "angle" of the cone from which the frusto-cone is derived. The dimensions of the original disc and corrugations preferably are chosen to produce a frusto-conical structure which approximates closely to the accepted dimensions of a badminton shuttlecock.It will be appreciated that in converting a disc of sheet material into the frusto-conical structure by corrugating it in the manner described, no change is made in the thickness of the sheet by stretching. The frusto-cone is formed simply by geometrical changes effected by the corrugations.

Whichever method of manufacture is used, it will be appreciated that the shuttlecock skirt is formed as a unitary shaped construction from sheet material and then has the reinforcing band(s) applied, as required. Hence an advantageous construction can be made by convenient means and shuttlecocks of the invention have been found in play to have excellent flight characteristics and durability together with a more satisfactory "crack" on impact with a racket than have conventional plastics shuttlecocks.

As an example of the above-described first method, a shuttlecock skirt of sine-wave transverse section can be made from a heated tubular film of polypropylene emanating from an extruder die. The hot tubular film is passed into a blow-moulding die of shape such that, on pressuring, the tube is transposed into the form of a frustum of a cone with a part-circular corrugated transverse section in the form of an endless sine wave consisting of sixteen complete cycles.

It will be appreciated that the thickness of the material will change as stretching occurs during this forming operation. Thus, for example, from a starting thickness of about 1.0 mm, the skirt corrugation may have a thickness of about 0.8 mm at the narrow end and about 0.3 mm at the wide end of the frustum.

The wide and narrow ends of the frustum are then trimmed and holes are punched through it to reduce its weight and confer desirable aerodynamic qualities such as spin, for instance by providing holes on one side only of each corrugation profile.

The skirt is then completed by positioning a frusto-conical band of polypropylene on its exterior and welding it to the extremities of the corrugations at the wide end of the skirt by applying localised heating.

Alternatively or additionally, a frusto-conical band may be secured to the interior extremities of the corrugations.

Further examples and specific embodiments of the invention will be described by way of example only with reference to the accompanying drawings in which: Figure 1 is a plan view of a sheet material blank to form a corrugated frusto-cone of a shuttlecock skirt of the invention; Figure 2 is a perspective view of a shuttlecock of the invention having a skirt formed from the blank of Figure 1; Figure 3 is an exploded diagrammatic illustration of various parts of a shuttlecock of the invention; Figure 4 is a graph of a truncated sinusoidal wave form on which an alternative corrugated frusto-cone for a skirt of the invention can be based; Figure 5 is a graph of a "sawtooth" configuration on which a further alternative corrugated frusto-cone for a skirt of the invention can be based; and Figure 6 is a transverse section through a skirt of the invention with a number of the corrugations removed for clarity.

As shown in Figure 1, a disc 10 of sheet material such as of poly(ethylene terephthalate) 0.006 inch (0.15 mm) thick, has a central co-axial disc 11 removed from it to form shuttlecock skirt blank 12.

The blank 12 is marked with a series of crease lines Al C1, A2 C2, B1 D1 and B2 D2 extending from its outer periphery 12B to its inner periphery 12A to define sixteen "inner" 13, "outer" 14 and "side" 15 portions of a square wave profile.

The blank is then creased through an angle of 90 in one direction along lines Al C1 and A2 C2 and then through 900 in the opposite direction along lines B1 D1 and B2 D2 to form the corrugations and the frusto-conical skirt structure shown in Figure 2.

In Figure 2, shuttlecock skirt 20 has sixteen corrugations 21 each defined by an inner portion 13, outer portion 14 and two side portions 15 formed from the blank of Figure 1. A frusto-conical reinforcing band 23 such as of poly(ethylene terephthalate) has been attached by adhesive to the inside faces of inner portions 13 adjacent the wide end of the skirt to define a series of hollow tubes conferring stiffness to the skirt. A similar reinforcing band (not shown) can be present at the narrow end of the skirt.

The narrow end of the skirt has been fitted into a 'cork' end cap 24 to form the desired shuttlecock.

In Figure 3, a shuttlecock of the invention has a corrugated skirt 30, a series of holes 31 having been made on one side 32A only of each corrugation 32.

An internal stiffening member or reinforcing band 33 of frusto-conical shape is of a size to fit inside the lower or narrower portion of skirt 30. The narrow end 34 of skirt 30 can be fitted into a correspondingly tapered recess 35 in a 'cork' end cap 36 and bonded in place.

Figure 4 illustrates an alternative form of corrugated shape that can be used in a skirt of the invention. Those portions 40 of the wave form shown dotted are removed to provide a fluted configuration having curved portions 41 separated by straight portions 42.

In Figure 5, the corrugations are provided by "sawtooth" portions defined by edges 50 and 51 separated by straight portions 52.

Figure 6 shows a section through a skirt 60 of the invention transverse to its longitudinal axis and taken in the region of a reinforcing band 61. Only five of the sixteen corrugations 62 are shown for clarity.

The depth "d" of each corrugation and the internal radius "r" of the skirt are such that d:r, as indicated above, preferably lies in the range 1:4 to 1:2.

Claims

1. A shuttlecock skirt of frusto-conical shape comprising a frusto-cone of corrugated sheet material having a corrugated outline in sections transverse to the longitudinal axis of the frusto-cone, and a reinforcing band secured to transverse extremities of the corrugations, said reinforcing band having a frusto-conical shape corresponding to that of the sheet material frusto-cone and being oriented such that the longitudinal axes of the band and sheet material frusto-cone are coincident, whereby the band and corrugations define a series of tubular structures.

2. A shuttlecock skirt according to Claim 1, wherein the corrugations extend along substantially the whole length of the skirt.

3. A shuttlecock skirt according to Claim 1 or 2, wherein the skirt has more than one reinforcing band, each at a different position on the frustocone.

4. A shuttlecock skirt according to any of the preceding Claims, wherein the or each reinforcing band is secured to the internal or external extremities of all of the corrugations.

5. A shuttlecock skirt according to any of the preceding Claims, wherein a reinforcing band is positioned adjacent the wide end of the frusto-cone and is secured to internal extremities of the corrugations.

6. A shuttlecock skirt according to any of the preceding Claims, wherein a reinforcing band is positioned at the narrow end of the frusto-cone and is secured to internal extremities of the corrugations.

7. A shuttlecock skirt according to any of the preceding Claims, wherein the or each reinforcing band is secured to the corrugation extremities by adhesive or by welding.

8. A shuttlecock skirt according to any of the preceding Claims, wherein the corrugations are of a depth "d" such that the ratio d:r is from 1:4 to 1:2 at any section transverse to the longitudinal axis of the frusto-cone, where "r" is the internal radius of the frusto-cone.

9. A shuttlecock skirt according to any of the preceding Claims, wherein there are sixteen corrugations extending around the frusto-conical surface.

10. A shuttlecock skirt according to any of the preceding Claims, wherein the corrugations are aligned so that their longitudinal axes each lies in a plane passing through the longitudinal axis of the frusto-cone.

11. A shuttlecock skirt according to any of Claims 1 to 9, wherein the corrugations are aligned so that their longitudinal axes lie at an angle to or spiral about the longitudinal axis of the frusto-cone.

12. A shuttlecock skirt according to any of the preceding Claims, wherein the corrugations are of square or triangular shape.

13. A shuttlecock skirt according to any of Claims 1 to 11, wherein the corrugations have a wave form shape based on repeating curvatures.

14. A shuttlecock skirt according to any of the preceding Claims, wherein the corrugated sheet material is provided with holes positioned to promote spin.

15. A shuttlecock skirt according to any of the preceding Claims, wherein the sheet material and reinforcing band(s) are made of material selected from stiff paper, thermosetting plastics material and thermoplastic plastics material.

16. A shuttlecock skirt according to any of the preceding Claims, wherein the reinforcing band width is 30% to 100% of the length of the corrugations.

17. A method of making a shuttlecock skirt of frusto-conical shape, which comprises: forming corrugations in a sheet material and shaping the sheet material to form a frusto-cone corresponding to the frusto-conical shape of the skirt, whereby the frusto-cone is provided with a corrugated outline in sections transverse to the longitudinal axis of the frusto-cone; locating a reinforcing band at a position on the frusto-cone for conferring radial stiffness, said band having a frusto-conical shape corresponding to that of the frusto-cone at that position and being oriented such that the longitudinal axis of the band is coincident with the longitudinal axis of the frusto-cone; and attaching the reinforcing band to transverse extremities of the corrugations at that position to provide a series of tubular structures.

18. A method according to Claim 17, wherein the corrugations are formed in stages whereby the amplitude of the corrugations is increased progressively so that the effective angle of the frusto-conical formation changes progressively until the desired cone angle is achieved.

19. A method according to Claim 17 or 18, wherein the frusto-cone is shaped from a thin film of thermosetting or thermoplastic plastics material and the corrugations are induced by heat setting.

20. A method according to any of Claims 17 to 19, wherein the desired shape of the frusto-cone is obtained by blow-moulding, vacuum-forming or matched-die-forming.

21. A method according to any of Claims 17 to 20, wherein the frustocone is made by extruding a tubular film from an extruder die and passing the extruded tube into a blow-moulding die where the tube is pressurised to the desired frustum of a cone with corrugated outline.

22. A method according to Claim 17, 18 or 19, wherein the frusto-cone is formed by cutting a suitably sized first disc from sheet material, removing a smaller co-axial disc from the central region of the first disc to leave a skirt blank, forming corrugations in the blank by inserting creases along the radii of the blank corresponding to the vertices of the desired corrugations with the amplitude of the corrugations increasing uniformly to the outer periphery of the blank, and transposing the creased blank into the desired frustum of a cone with the desired corrugated outline in sections transverse to the longitudinal axis of the frusto-cone.

23. A method according to any of Claims 17 to 22 wherein the reinforcing band is attached to the corrugation extremities by adhesivebonding or by heat-welding.

24. A method of making a shuttlecock skirt substantially as hereinbefore described with reference to and as shown in any of the accompanying drawings.

25. A shuttlecock skirt made by the method of any one of Claims 17 to 24.

26. A shuttlecock skirt substantially as hereinbefore described with reference to and as shown in any of the accompanying drawings.

27. A shuttlecock having a frusto-conical skirt attached to an end cap, wherein the skirt is as defined in any of Claims 1 to 16, 25 or 26.