Field of the Invention This invention relates generally to apparatus and a method for extending the length of conventional sports rackets, and more particularly, to a handle extender for conventional tennis rackets.

Background of the Invention

Current tennis rackets are typically only 27 to 28 inches in length, well within the International Tennis Federation (ITF) and the United States Tennis Association

(USTA) regulation maximum length of 32 inches. With these current standard racket lengths, a player must be approximately six feet, one inch tall to hit a flat serve (i.e., straight-line trajectory from the racket head to within the service-box bounds). The head velocity of the racket in the serve and in play is also lower for a shorter person playing with a standard-length racket. Players who are taller thus have an advantage over shorter players, especially with the serve. Another problem with conventional rackets is the handle vibration that occurs upon impact of the racket head with the ball. This vibration is known to contribute to tennis elbow and reduces the energy transferred to the ball.

Longer rackets have been manufactured to provide added reach, but the average player does not initially have the arm or elbow strength to aggressively play with a longer racket without incurring elbow injuries. These longer rackets immediately increase the length beyond what the player is prepared to handle. They do not allow the player to increase racket length in small increments. Additionally, such rackets have not corrected the vibration problem.

Rackets have also been developed that have adjustable-length handles. For instance, a racket with an adjustable handle sleeve is disclosed in European Patent No. 0130623 A 1 (Puma). The patent describes an adjustable-length racket wherein the handle slides on the outside of the shank and is adjustable by means of a screw protruding into the core of the shank (see FIG. 1). An adjustable length racket would be desirable, since it would allow a player to slowly progress to longer racket lengths, thus possibly avoiding elbow and control problems. However, the adjustable-length racket disclosed in the Puma patent has several drawbacks. For example, the entire non-conventional racket must be used if the length adjustment features are desired; the system is not adapted for use with conventional rackets. Also, vibration absorption problems are not alleviated with the Puma handle system. The length is not extendible more than a short distance. Extending the length any further would contribute to increased losses in handle strength. Furthermore, the Puma system does not provide any means to rebalance the racket at the length to which it is adjusted. Another attempt at providing an adjustable length tennis racket handle is disclosed in U.S. Patent No. 3,931,968 (Hedberg). However, besides suffering from all of the same disadvantages of the Puma system, this racket violates the USTA rule that the "frame, including the handle, shall be free of attached objects and devices other than those utilized solely and specifically to limit or prevent wear and tear or vibration, or to distribute weight. Any objects and devices must be reasonable in size and placement for such purposes. " USTA Rule 4(c), USTA Official's- Handbook (January 1, 1990).

An adjustable racket is also disclosed in German Patent No. 2030998 (Kranz). The Kranz racket shaft and handle consist of detachably connected sections. The handle itself is not adjustable to change the overall racket length; removal or addition of shaft segments is employed. This racket is so unconventional that many of the dynamic advantages of an integral shaft have been lost. The racket's strength is seriously diminished and no vibration-absorption qualities are apparent.

Several other patents have issued on racket extenders of one sort or another, but they all suffer from many of the disadvantages discussed above, particularly in that they have not been designed or disclosed for use with conventional, widely available rackets so that a player may gradually lengthen an off-the-shelf conventional racket handle. In addition, design requires the movable portion of many of these adjustable- length handles to be hollow. As a result, the distal movable portion cannot contain vibration dampening material when it is in its extended position. As above, the design of these adjustable handles does not allow for rebalancing of the extended racket

either. See, for example, the handles disclosed in U.S. Patent Nos. 3,674,267 (Hollis) and 4,641,838 (Gabrielidis).

In consideration of the limitations and disadvantages of the devices and methods currently in use, it should be apparent that an effective solution to the problem of properly lengthening a conventional sports racket is not provided in the known prior art. Accordingly, the present invention was developed, and it provides significant advantages over previous devices or methods to lengthen tennis racket handles.

Summary of the Invention In accordance with this invention, a racket handle extender for use with a conventional sports racket is provided. The extender comprises a bar having a cross- sectional shape that substantially matches the cross-sectional shape of the racket handle and a stem protruding from one end of the bar. The stem has a cross section smaller than that of the bar that is shaped to be placed within the end of the shaft of a conventional sports racket after the shaft has been properly hollowed out.

In accordance with a particular aspect of this invention, the bar is partially hollow and has an opening at the end opposite the stem for inserting balancing weights and a cap.

In accordance with another aspect of this invention, supports are disposed along at least one side of the bar and the shaft for strengthening the attachment of the extender to the racket.

In accordance with another aspect of this invention, the bar is made of a vibration absorbent, lightweight, strong material.

In accordance with another aspect of this invention, vibration dampening material is attached to the handle extender.

This invention is also directed to a method for lengthening conventional sports rackets. The steps include removing the grip from the handle, inserting a handle extender made to fit within a hollow portion of the shaft to form an extended portion of the handle, and wrapping the handle and extended portion with a grip. In accordance with another aspect of the method of this invention, a portion of the inside of the shaft is hollowed out before inserting the handle extender.

In accordance with another aspect of the method of this invention, a step of placing balancing weights within the handle extender is included.

In accordance with further aspects of this invention, the method further comprises adding a support along at least one side of the handle extender and

attaching vibration absorbent material to the handle extender to reduce vibrations and add structural strength.

In accordance with another aspect of this invention, the method further comprises the step of placing textured material on the grip at the end of the handle. The textured material is characterized by its ability to be felt by the player for proper hand positioning without having to look at the grip.

In accordance with an additional aspect of this invention, the method further includes the step of building up the grip size of the handle and handle extender to larger than is normally used by a player before wrapping the handle with the grip, to increase the leverage the player has against the ball.

In accordance with an alternate embodiment of this invention, a handle extender is provided for use with a conventional sports racket. The extender comprises a hollow tube having a cross-sectional shape similar to that of the racket shaft, such that the tube may be secured' to an end portion of the shaft. Means to absorb vibrations and braces to provide structural support are disposed within the tube. The tube is made of lightweight strong material that itself absorbs vibrations. A cap is placed over an end of the tube opposite the end secured to the shaft.

In accordance with another aspect of the alternate embodiment of this invention, the extender further comprises weights removably secured within the tube for balancing the racket.

In accordance with another aspect of the alternate embodiment of this invention, the extender further comprises a means to removably secure the tube to the shaft. The securing means includes at least one notch disposed within an outer surface of the tube and engagement means that may be coupled to the shaft and may be moved into engagement with the notch such that the tube may be removably secured to the shaft.

In accordance with another alternate embodiment of this invention, the cross- sectional shape of at least a portion of the extender tube is larger than that of the shaft, such that the tube is adopted to slide over the end portion and be secured in place.

In accordance with another embodiment of this invention, a handle extender is provided for use with a conventional sports racket having a recess in the end of its shaft. The extender comprises a bar and attachment means. The bar has a cross- sectional shape matching that of the shaft. The attachment means are coupled to the bar to secure the bar to the racket shaft. Preferably, the attachment means comprise a rod having one end shaped to fit within the end portion recess of the shaft. The end

of the bar includes an opening shaped to receive another end of the rod such that the rod may be disposed partially within the bar and partially within the shaft for attachment of the bar to the shaft to extend the racket.

Brief Description of the Drawings The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:

FIGURE 1A is a perspective view of the preferred embodiment of the invention, illustrating the use of the invention as attached to the end of a tennis racket; FIGURE IB is a perspective view of a portion of the invention, illustrating placement of a textured material;

FIGURE 2 is a cross-sectional plan view of the invention including weights and side supports installed on the end of a tennis racket shaft; FIGURE 3 is a cross-sectional plan view of the invention, illustrating an alternate embodiment of the supports disposed partially within the shaft;

FIGURE 4 A is a perspective view of the invention, illustrating a stem having a circular cross-sectional shape;

FIGURE 4B is a perspective view of the invention, illustrating a stem having an octagonal cross-sectional shape;

FIGURE 5 A is a perspective view of an alternate embodiment of the invention and a tennis racket prepared for use with the alternate embodiment;

FIGURE 5B is a cross-sectional view of the alternate embodiment of the invention as installed within the end of a racket; FIGURE 5C is a cross-sectional view of an alternate embodiment of the invention as installed on the end of a racket;

FIGURE 6 is a cross-sectional view of another alternate embodiment of the invention, illustrating a means to removably secure the extender to a racket shaft; and FIGURE 7 is a cross-sectional view of an alternate embodiment of the invention, showing a stem that can be inserted into recesses in both the shaft and the extender bar to make the attachment between the two.

Detailed Description of the Preferred Embodiment

A preferred embodiment of the present invention is illustrated in FIGURE 1 A.

A tennis racket 20 is shown with an extender 22 installed. Racket 20 is a conventional, "off-the-shelf model. Extender 22 of this invention is designed to modify the length of existing rackets. Racket 20 includes a head 24, a shaft 26. a

handle 28, and a grip 30. In a preferred embodiment, extender 22 includes a stem 32, a bar 34 including a flare 36 at one end and a bore 37, weights 38, supports 40, and a cap 42.

Racket 20 is prepared for installation of extender 22 by removing grip 30 from handle 28 and boring a cavity 43 in the end of shaft 26. A titanium drill bit is preferably used to drill out the end of shaft 26 due to its ability to cleanly and easily cut a straight path into most conventional racket materials. It may not be necessary to bore cavity 43, however, depending on the configuration of the particular racket into which extender 22 will be installed. Many conventional rackets already have a hollow core, in which case, the end cap of the racket is removed to expose the cavity in the shaft. Handle 28 may also be removed, depending on its configuration. If handle 28 completely encircles shaft 26 it may be necessary to remove it before securing supports 40 to the shaft, as explained below.

At this point, extender 22 is inserted within the end of shaft 26 by inserting stem 32 until bar 34 is flush with the end of handle 28 and shaft 26. A longer bar 34 requires a longer stem 32 to secure it to shaft 26 to ensure that the extension is strong and secure. It may be desirable to apply an adhesive or glue to the stem before insertion depending upon the permanence of the installation desired. Many players will wish to start with a short extension of their racket and eventually increase the length of the extension by small increments when they have developed adequate strength and skill. In this case, it would be inappropriate to permanently glue extender 22 into place. Even with a short extension, it is important for the player to swing the racket easily at first to build up the arm and prevent elbow (or other) injuries. Several months of regular play should go by before a longer extension is used. Eventually, significant increases in both a player's reach and racket head velocity can be achieved.

Supports 40 are then preferably placed on two opposite sides of bar 34 so that the supports extend onto the sides of shaft 26 or handle 28, depending on the configuration of the particular racket 20. These supports add structural strength to the connection between extender 22 and racket 20. Supports 40 also contribute to vibration reduction.

After adding supports 40 to the sides of bar 34 and shaft 26, the extended racket handle is preferably built up to a larger size by wrapping the bar and shaft with a foam tape (not shown). The foam tape functions not only to create the desired grip size (which may be larger than usual so as to increase leverage on the ball) but also to absorb vibrations and increase the strength of extender 22.

Grip 30 is wrapped tightly around handle 28 and extender 22 including supports 40 and the foam tape (if used). One or more weights 38 may be placed within bore 37 of bar 34 to balance racket 20 with its new longer length. More weights 38 are placed within bore 37 to make head 24 feel comparatively lighter. Fewer weights make for a "heavier" head 24. Finally, cap 42 is placed over the end of bar 34.

As shown in FIGURE IB, a textured material 44 may be placed around extender 22 on the outside of grip 30 near the intersection of extender 22 with shaft 26. This may be desirable since with a longer racket 20 and a longer handle 28 as a result of installing extender 22, a player may frequently wish to "choke-up" on the handle. With a material, which has a different texture than that of grip 30 so that it can be felt by the player, disposed around a portion of extender 22, proper hand positioning can be achieved without requiring the player to look at the grip. Flare 36, disposed at the end of extender 22, also helps in this regard. Textured material 44 is preferably disposed close to and over flare 36. This allows one to "choke-up" above textured material 44 and provides a larger grip at the end of the racquet when the full length is used during play. That larger grip provides the player with more leverage and thus reduces stress on the elbow.

Alternatively, extender 22 may have its own textured grip separate from grip 30 disposed on the original racket handle. The extender grip would be pre-sized to match the size of the grip on the original handle. In this manner, not only would at least a portion of extender 22 preferably have a different feel to the player but installation of extender 22 would be simplified since the original grip would not even need to be removed before installation of extender 22. One could insert stem 32 into a hollow shaft of racket 20 after simply removing the original cap at the end of handle 28.

FIGURE 2 illustrates the details of construction and placement of extender 22 in greater detail. Weights 38 are disposed within bore 37 along the longitudinal axis of bar 34. Three weights 38 are shown in FIGURE 2, but clearly a different number could be used depending on the length of the bore and the length (or mass) of the weights required. A racket that is "light in the head" (for decreased stress on the elbow and for better ball control) may be produced by adding weights 38 within bore 37. If a "head heavy" racket is desired (for increased power), some or all of weights 38 may be removed. Smaller weights, having less mass, provide the advantage of allowing more precise balancing of the racket. If fewer than a full load of weights is used, lightweight (e.g., foam) plugs (not shown) may be inserted in their

place so that weights 38 do not slide within bore 37 when racket 20 is in use. Preferably, weights 38 are made of lead due to its high density. Weights 38 may be omitted to produce a hollow handle, or to allow for the insertion of additional vibration dampening material. Bore 37 may also be extended up into shaft 26 past the end of stem 32 to make the overall racket lighter. As an alternate embodiment, flat weights (not shown) may be disposed along the outside of the more distal portion of bar 34.

Supports 40 are shown disposed along two sides of bar 34 and shaft 26. Clearly, the number of supports 40 used is optional. Preferably, supports 40 are constructed of carbon-fiber reinforced polymers (CFRP, with a density of 1.5- 1.6 Mg/m ³ and tensile strength of 670 MPa), but many different rigid, lightweight, strong materials could be used in the alternative. Supports 40 with substantial vibration absorbing characteristics may also be employed. Supports 40 may be secured into place (such as with an adhesive) or held in place by simply wrapping grip 30 around them.

Bar 34 and stem 32 are integrally constructed of balsa wood in the preferred embodiment. Balsa wood is easily (and inexpensively) formed into a shape to match that of the handle and shaft and has the added advantage of providing substantial vibration absorption. The vibration absorption qualities of extender 22 help to avoid causing tennis elbow. Balsa wood is lightweight and strong enough not to break with the considerable forces generated while playing tennis. Balsa wood is quickly and easily drilled out to form bore 37. Additionally, balsa wood remains in place inside shaft 26, without requiring additional means of attachment once it has been properly fitted inside that shaft, and can be easily removed and replaced. Other materials could also be used with or in place of balsa wood to form bar 34 and stem 32. For example, balsa wood and carbon-fiber reinforced polymers could be combined (either by layering a CFRP material over the balsa wood or inserting rods made of CFRP material into the balsa wood) to form a lightweight, strong, vibration absorbent material that could be utilized in this as well as other embodiments of the invention. The use of sufficient lightweight, strong, vibration absorbent materials with this and other embodiments of the invention renders a racket, whose length has been extended, playable. Various vibration absorbent materials can be used with the invention. Preferably, those with a density less than 2.3 Mg/m ³ are employed. For example, glass fiber reinforced polymers may be used, which have a range of densities from 1.4- 2.2 Mg/m ³ .

The density of a material used in constructing the bar or the stem of the extender is preferably less than or equal to that of titanium (i.e., 4.6 Mg/m ³ ). The preferable tensile strength of such material is greater than 5 MPa, which is that of a rigid foam polymer. Some rigid foam polymers have a tensile strength as low as 0.2 MPa and may alternatively be used to construct a very short extender (e.g., less than one inch). In the preferred embodiment, balsa wood is used, which has a tensile strength of 23 MPa.

The length of bar 34 is selected to extend racket 20 to a length desired by a player based on his or her skill and strength. Generally, racket 20 will be extended from one-quarter inch to five inches, since the length of most conventional rackets is about 27 inches and the USTA Rules specify a maximum racket length of 32 inches. When a player has developed sufficient strength and ability, a slightly longer extender can be inserted in place of the first, thus allowing a player to extend his/her racket in short increments. The cross-sectional shape and size of bar 34 is selected to match that of handle 28 to provide a smooth transition between the two after grip 30 is wrapped around the handle.

FIGURE 3 illustrates an alternate embodiment of extender 22'. In this embodiment, supports 40' are disposed within the end of shaft 26 and fit within a portion of bar 34'. Other elements of this embodiment are generally consistent with the embodiment shown in FIGURES 1 and 2. The purpose of supports 40' is simply to strengthen the connection between racket 20 and extender 22'. Supports 40" could, alternatively, be constructed to run outside of shaft 26 and then inside bar 34' or vice- versa (not shown).

FIGURES 4 A and 4B illustrate different stem 32 configurations. The shape of stem 32 depends on the racket to which it will be attached. Some racket shafts have an existing hollow octagonal shape cavity that would match stem 32' shown in FIGURE 4B. Other racket shafts may need to be hollowed out with a drill to form an appropriate cavity 43 to receive the stem shown in FIGURE 4A. Drill bits made of titanium are preferably used in this process since they are harder than conventional bits and consequently allow this procedure to be done quickly and accurately. Alternatively, bar 34 may be glued (e.g., epoxy) or otherwise attached directly to shaft 26 by omitting both stem 32 and cavity 43.

FIGURES 5 A and 5B illustrate an alternate embodiment of extender 22". In a preferred form of this embodiment, an elongate, octagonal tube 46 (made of lightweight, strong material such as a CFRP material) with sides 48 that are sized to match the inner cross-sectional shape of the cavity in racket shaft 26 is provided.

Tube 46 is secured within shaft 26. Glue, rivets, screws, or other means of attachment (e.g., supports 40 previously described) may be employed to secure tube 46 within shaft 26 while still maintaining a smooth outer surface of both shaft 26 and tube 46. Next, grip 30 is wrapped around handle 28 and tube 46 to build up tube 46 to the proper handle size and provide a secure place for a player to hold the assembly. A build-up material (not shown), such as vibration absorbing foam tape or other suitable material, may be wrapped around shaft 26 and tube 46 prior to applying grip 30. This material helps secure the two parts together and reduces vibration. The build-up material may also be used to increase the handle size. Tube 46 is preferably injected with a filler material 50 characterized by its ability to absorb vibrations. Tube 46 preferably has bore 37 in which to insert balancing weights 38 through an opening covered by cap 42. Tube 46 may itself be made of vibration absorbing materials (e.g., Kevlar, which has a density of 1.44 Mg/m ³ and a tensile strength of 3620 MPa). Structural braces 51 (see FIGURE 5B) may also be placed inside tube 46 for the purpose of strengthening tube 46 and to reduce vibration. Braces 51 are preferably made of hard rubber or another lightweight, strong, vibration dampening material. Such braces are preferably oriented perpendicular to the longitudinal axis of tube 46 and are preferably shaped as discs (with sides flattened to allow them to be fit into an octagonal tube). Three such braces are preferably placed within tube 46 at spaced-apart locations having filler material 50 disposed between them. Braces 51 are preferably thin (three-sixteenth inch width octagonal discs) and have an outer shape matching that of the inner shape of tube 46, so they fit tightly inside. Such braces 51 may be made as an integral part of handle extender 22" rather than being slid into it. Clearly, other means of internal bracing of tube 46 can be devised. A larger grip size than that normally used by a player is preferably employed with this (FIGURES 5 A and 5B), as well as any other embodiments of extender 22. The purpose of the larger grip size is to increase the player's leverage against the ball and, consequently, to reduce stress on the elbow while using the extended racket. As discussed above, a larger grip may be made by using a build-up material. FIGURE 5C illustrates an embodiment of extender 22"' similar to that of

FIGURES 5A and 5B. In this embodiment the cross-sectional size of tube 46 is slightly larger than that of shaft 26 so as to be able to slide over the end of shaft 26 before being secured in place. Other aspects of this embodiment are similar to the embodiment illustrated in FIGURES 5 A and 5B. FIGURE 6 illustrates another embodiment of extender 22"" also similar to that of FIGURES 5 A and 5B. The tube 46' of this embodiment, however, only has one

open end, onto which cap 42' is secured. The other end of tube 46' includes a head 56 defined by a groove 54 around the perimeter of the outer portion of tube 46'. Screws 52, or other retaining means, are inserted through shaft 26 and into groove 54 to removably secure extender 22"" in place. Obviously, the screws 52 can be removed and tube 46" slid out of cavity 43 at a later time once a player's arm is built up and he/she is desirous of a longer extension. Racket 20 would not have to be modified further to accept another (preferably longer) handle extender. Extender 22"" also includes a step 58 that allows for a smooth transition to shaft 26. The length of tube 46' from step 58 to cap 42' is the length racket 20 is extended. This entire region has an outer cross-sectional shape matching that of shaft 26. The portion of tube 46' disposed within shaft 26 has an outer cross-sectional shape matching the inside of shaft 26. Other aspects of this embodiment are similar to those shown in FIGURES 5A and 5B.

FIGURE 7 shows another alternate embodiment of the invention. In this embodiment a rod 60 is used to make an interconnection between the racket shaft 26 and the bar 34'". Successive lengthening of the racket may be accomplished by simply replacing bar 34'" with a longer bar installed on rod 60. Thus a conventional racket is effectively modified to accept extenders by securing rod 60 within the end of shaft 26. Thereafter, a player may change the length of his or her racket simply by securing the desired bar 34'" of a desired length over rod 60. This is preferably accomplished without removal of any grip or handle material from shaft 26. Bar 34'" preferably already has its own textured grip material (not shown in FIGURE 7).

While the preferred embodiment of the invention has been illustrated and described, along with alternate embodiments, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the invention. For example, other means of attaching an extender to a racket could be devised, such as a locking mechanism similar to that on the shaft of an umbrella which would allow removal of the extender at a later time. Extender 22 could, alternatively, slide into and then "snap" in place inside cavity 43. In contrast to a locking mechanism (such as the one described in conjunction with FIGURE 6) located on the inside of cavity 43, one could be devised to lock an extender bar 34, a tube 46, or other embodiment to the outside of handle 28 (or shaft 26).