IMPROVEMENTS IN SHUTTLECOCKS

Field of the invention

The invention relates to badminton shuttlecocks.

Background of the invention

A shuttlecock, herein also termed a shuttle for short, is a projectile that is used in the sport of badminton having the shape of an open cone with a high aerodynamic drag. The cone is traditionally formed of a number of overlapping goose feathers embedded into a rounded cork base which is covered with thin leather. The shape of a shuttle makes it extremely stable aerodynamically and regardless of its initial orientation, it will turn to fly base first and remain in the base first orientation during flight.

The feathers of a traditional shuttle are brittle and fragile. As a result, shuttles may need to be replaced several times during a single game. For this reason, synthetic shuttles have been developed that replace the feathers with a plastics skirt. The part of the skirt near the base, herein termed the stem portion, consists of a plurality of longitudinal stems emulating the shafts of feathers. These stems are connected to one another at the wider end of the skirt by a web or mesh which emulates the air resistance of the vane portions of feathers, this portion of the skirt remote from the base being herein termed the flight portion.

Plastics shuttles are far more durable, typically lasting many matches without any impairment to their performance. Because they are significantly more economical, many players and clubs prefer to play with plastics shuttles .

However, the playing characteristics of feather shuttles and the existing plastics shuttles are quite different. In particular, the skirt of a plastics shuttle will tend fold if the shuttle is hit very powerfully. Once the skirt has folded, the aerodynamic drag on the shuttle is greatly reduced. Consequently, skilled players can hit plastics shuttles extremely fast with relative ease. This changes the nature of the game because, amongst skilled players, the use of plastics shuttles will favour power players over players who place more reliance on delicate shots, which place the shuttle more accurately in a part of the court which cannot be reached by the opponent.

Most experienced and skilful players greatly prefer feather shuttles, while serious tournaments and leagues are almost invariably played using feather shuttles. In Asia, where feather shuttles are more affordable, plastics shuttles are hardly ever used by serious players, though this may have been affected by the recent outbreak of bird flu, which has pushed up the price of feather shuttles.

The aim of the present invention is therefore to improve plastics shuttles so that their performance may approximate more closely to that of feather shuttles.

In existing one piece plastics shuttles the main stiffening elements of the designs are longitudinal stems which emulate the rigid quill or shaft sections of each feather in a feather shuttlecock. However, because the weight of the stems must be minimised and because they have a solid cross section, they provide far less rigidity than the hollow shafts of feathers.

It is known to mould one or more annular ribs to connect the solid stems in a generally circumferential manner. The skirt is conventionally formed as a one-piece injection moulding, and this places limitations on the shape

these annular ribs if they are not to interfere with the extraction of the skirts from their mould at the completion of the moulding process. This in turn can affect the rigidity of the ribs and their performance in resisting the collapse of the skirt of the shuttle.

Object of the invention

The present invention therefore seeks to provide a shuttle construction which allows the designer considerable freedom in the shape and dimensioning of the annular reinforcing rib

Summary of the invention

According to the present invention, there is provided a shuttlecock having a base and a plastics conical skirt, the skirt comprising, at its narrower end adjacent the base, a stem portion formed of a plurality of longitudinally extending stems and, at its wide end, a flight portion within which a web extends between the individual stems to increase the aerodynamic drag on the shuttle, characterised in that the skirt comprises two separately formed injection moulded frustro-conical components which are subsequently joined to one another, the two components constituting, at least predominantly, the stem portion and the flight portion of the assembled skirt, respectively.

By splitting the skirt into two components joined to one another at the transition between stem portion and the flight portion of the skirt, the invention allows the annular reinforcement ring at this transition to protrude into the interior to the skirt to such an extent as to make it impossible for it to be injection moulded using mould with a simple core. Though neither of the frustoconical components has an undercut that interferes with the moulding process, the assembled skirt has a substantial reinforcement

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rib at the joint where the stems join on to the flight portion .

It has been suggested in GB 1,386,484 to form a shuttle by folding a fan-shaped flat skirt with radiating "feathers" into a cone and to hold it in this position by securing the stems of the plastics feathers to a separately formed ring. In this case, the flight and the stem portion of the skirt is formed as one piece and the ring acts as a means of retaining the feathers in the shape of cone and it is not integrally formed as a part of the skirt.

The forming of the skirt as two frustro-conical components, as proposed by the present invention, offers the additional advantage that the two components may be formed of different plastics materials, each chosen to optimise the performance of the respective part of the skirt.

The plastics materials may also be made of different colours making the shuttles more aesthetically attractive and distinctive.

It is preferred for the annular reinforcement rib which extends between the stems at the junction between the stem and flight portions of the skirt to protrude from the stems into the interior of the skirt and to have a smaller inside diameter at its tip than points on the inner surface of the flight portion nearer to the base.

The annular reinforcement rib is preferably formed of two parts, each integrally formed with a respective one of the two frustro-conical components. The two parts of the annular reinforcement ring, which may be designed to fit into one another or to abut one another face to face, are preferably glued one another. Alternatively be welded or joined by any other suitable bonding process, such as over- moulding.

The primary aim of the invention is to produce a shuttle in which the skirt is formed by moulding but having an annular rib of sufficient substance to provide the needed rigidity. This normally entails a rib that would present an undercut which would interfere with the separation of the moulded skirt from the core about which it is moulded. While the splitting of the skirt into two components circumvents this problem, it would alternatively be possible to use a mould with a collapsible core.

Hence, in accordance with an alternative aspect of the invention, there is provided a shuttlecock having a base and a plastics conical skirt, the skirt comprising, at its end narrower adjacent the base, a stem portion formed of a plurality of longitudinally extending stems and, at its wide end a flight portion within which a web extends between the individual stems to increase the aerodynamic drag on the shuttle, characterised in that an annular reinforcement rib extends between the stems at the junction between the stem and flight portions of the skirt, the reinforcement rib protruding from the stems into the interior of the skirt and having a smaller inside diameter at its tip than points on the inner surface of the flight portion nearer to the base.

Circumferential undercut ribs have previously been formed on a moulded skirt close to the fixing point to the base in order to hold the skirt moulding on the core of the mould during separation. Such a rib can be forcibly stripped off, or "jumped off", the core whilst the moulded skirt is still hot as the moulding has thicker sections at this lower point. It is not however possible to jump off such an undercut rib if formed further up the stems, notably at the junction between the stem portion and the flight portion, as the moulding will distort due to the thinness and lack of integrity.

Collapsible cores formed of several pieces that move relative to one another to allow the core to clear an undercut are well known and have been used for example in the manufacture of tyres and plastics lidded containers, such as paint pots. EP 0 218 345 describes one example of a collapsible core that would be suitable for manufacturing a skirt with an undercut rib at the junction between the stem portion and the flight portion.

It is preferred for the web extending between the individual stems in the flight portion to be a continuous unperforated web.

To maintain the lightness of the skirt, the continuous web should not contain any more plastics material than the conventional mesh. This will necessitate the web being thinner than the mesh in the flight portion of a conventional plastics shuttle. When injection moulding any article, there is a limit placed by the moulding process on the length to thickness ratio. In a conventional one piece skirt, it would be difficult to form an unperforated web of the desired thickness. However, this problem is lessened if the skirt is formed of two separate moulded components as the length of the flight portion would then be reduced sufficiently to enable the desired wall thickness to be achieved using standard injection moulding techniques. The simplified form of the flight section would facilitate the use of compression moulding and other forming techniques.

Brief description of the drawings

The invention will now be described further, by way of example, with reference to the accompanying drawings, in which : - Figure 1 is a perspective exploded view of a skirt of a shuttle of the invention, and

Figure 2 shows a section through a conventional stem reinforcing rib,

Figure 3 shows an undercut reinforcement rib that can be produced using a mould with a collapsible core, Figures 4 and 5 show different configurations of the end flanges of the skirt portion and flight portion of the embodiment shown in Figure 1 that can be adopted to achieve the same effect as the undercut reinforcement rib of Figure 3, and Figure 6 shows the two parts of the embodiment shown in Figure 4 during their assembly.

Detailed description of the preferred embodiment (s)

A typical plastics shuttlecock has two parts, namely the base and the skirt. The base can be a homogeneous unit, typically plastics foam, or a composite of different materials, typically cork and a fabric covering. The skirt is fitted to the base by means of a circular wall pushed into a clearance hole recessed into the base.

Figure 1 shows just the skirt of a shuttle of the invention. The skirt 10 comprises a stem portion 12 and a separately moulded flight portion 14. The stem portion is formed from longitudinally extending stems 16 which emulate the shafts of the feathers of a feather shuttle. The stems 16 are joined to one another at the narrow end by a circumferential wall 18 which together with a spigot 20 is typically used to retain the skirt 10 on the base (not shown) of the shuttle.

The stems 16 are joined to one another by an annular flange 22 at their ends remote from the base and an annular reinforcement rib 24 strengthens the ribs at their mid- points. The rib 24 can be formed with an undercut because at its position it can be jumped off the core of a mould without causing the moulding any damage. It should be noted

that a rib 24 in the illustrated position can only have a slight undercut and it would need to be closer to the base and connected with a solid infill to have a significant undercut. In such a case, the rib would do little to the stiffness of the stem section. The flange 22, on the other hand, is so far removed from the base that it cannot be formed as an undercut.

The flight portion 14 is formed with continuations 26 of the stems 16 and a thin, preferably unperforated, web 28 extending between the stems. At its narrower end, the flight portion 14 is formed with an annular flange 30 designed to mate with and be joined to the flange 22 to form a reinforcement rib at the junction between the flight portion 14 and the stem portion 12.

Figure 2 shows a stem 16 and a conventional reinforcing rib 40 of a shuttle skirt formed in one piece. The line of draw of the core is presented by an arrow in Figure 2 and as is runs parallel to the face 42 of the rib 40, it is seen that there is no undercut to interfere with withdrawing the core from the skirt after it has been moulded. This however restricts the radial width of the rib 40 and the rigidity that it can add to the stem portion.

The rib 50 in Figure 3 uses the same quantity of plastics material as the rib 40 but is considerably more rigid in response to impact from the side of the skirt. However, this rib is undercut and if formed on a one-piece skirt it can only be removed from the mould if the core is collapsed. This is similarly true of any undercut formed on the outside of the skirt which would require the female part of the mould to be split.

Figures 4 and 6 show an annular reinforcing formation with similar or increased rigidity as that of the rib 50 in Figure 3 but in this case the reinforcing formation is

formed in two parts consisting of two flanges 22' and 30' that are joined to one another, and corresponding to the flanges 22 and 30 shown in Figure 1. These flanges, while forming an undercut when the portions of the skirt are assembled to one another, can readily be injection moulded separately without having to resort to a collapsible core.

An alternative configuration of the flanges to that of Figures 4 and 6 is shown in Figure 5 where matching reference numerals (with an additional prime) have been allocated to like elements to avoid repeating their description. In this embodiment the web thickness is varied to provide a better weight to strength ratio. The thickening of the edges of the flanges gives an increased rigidity and resistance to impact fracture. This detail can only be produced using a two part construction.