Extendable and Retractable Tennis Racquet

Abstract

One embodiment of an extendable and retractable tennis racquet contains a stringed area 01, throat 02, and shank 03 as one integral member. The handle is comprised of a shank inside of a hollow handle 05. A spring or flexible means 07 connects the shank to the hollow handle. When the racquet is swung, the centrifugal force generated pulls on the head assembly. The shank slides outward telescopically, thereby increasing the length of the racquet. At the end of the racquet swing, the restoring force of the spring overcomes the diminishing centrifugal force, which pulls the shank back to its retracted position. Other embodiments are described and shown.

Claims

1. A tennis racquet having the means to extend and retract, comprising: a stringed frame head with a throat; a shank connected to said throat; a handle; means for joining said shank and said handle telescopically, allowing only a relative sliding motion in the longitudinal direction; and a spring or flexible means to connect both said shank and said handle to prevent said shank to detach from said handle longitudinally.

2. The tennis racquet of claim 1, wherein said stringed frame head, throat and shank are one integral member.

3. The tennis racquet of claim 1, wherein said shank and said handle are comprised of complex cross-sections to increase stiffness.

4. The tennis racquet of claim 1, wherein said handle has a cavity means to accept a portion of said shank.

5. The tennis racquet of claim 4, wherein said spring or flexible means connects to the inside bottom of the cavity of said handle and base of said shank.

6. A tennis racquet having the means to extend and retract, comprising: a stringed frame head with a throat; a shank connected to said throat; a handle; means for joining said shank and said handle telescopically, allowing only a relative sliding motion in the longitudinal direction; a spring or flexible means to connect both said shank and said handle to prevent said shank to detach from said handle longitudinally; and a mechanical stop means between the said shank and said handle.

7. The tennis racquet of claim 6, wherein said stringed frame head, throat and shank are one integral member.

8. The tennis racquet of claim 6, wherein said shank and said handle are comprised of complex cross-sections to increase stiffness.

9. The tennis racquet of claim 6, wherein said handle has a cavity means to accept a portion of said shank.

10. The tennis racquet of claim 9, wherein said spring or flexible means connects to the inside bottom of the cavity of said handle and base of said shank.

11. A tennis racquet having the means to extend and retract, comprising: a stringed frame head with a throat; a shank connected to said throat; a handle; means for joining said shank and said handle telescopically, allowing only a relative sliding motion in the longitudinal direction; a pinion gear mounted to said handle; a rack gear mounted to said shank; and a torsion spring connecting to both said pinion gear and said handle; and said pinion gear is engaged to said rack gear.

12. The tennis racquet of claim 11, wherein said stringed frame head, throat and shank are one integral member.

13. The tennis racquet of claim 11, wherein said shank and said hollow handle are comprised of complex cross-sections to increase stiffness.

14. The tennis racquet of claim 11, wherein said handle has a cavity means to accept a portion of said shank.

15. The tennis racquet of claim 11, wherein said pinion gear is mounted to the shank; said rack gear is mounted to said handle; and said torsion spring connecting to both pinion gear and said shank.

16. The tennis racquet of claim 1 further including a mechanical stop means between the said shank and the said handle.

17. The tennis racquet of claim 1, wherein the said spring or flexible means is a torsional spring; and the said torsional spring connecting to the said handle via a pinion gear and a rack gear.

Description

DRAWING FIGURES

[0022] For a better understanding of the present invention, reference is made to the accompanying drawings in which

[0023] FIG. 1A depicts a standard tennis racquet.

[0024] FIG. 1B shows a sectional view of the preferred embodiment of the present invention with the shank shown in the nominal retracted position.

[0025] FIG. 1C shows a sectional view of the preferred embodiment of the present invention with the shank shown in the extended position.

[0026] FIG. 2 shows various stages of the serve motion with specific identification of each stage.

[0027] FIG. 3 shows a perspective view of the present invention being deployed during various shots.

[0028] FIG. 4A shows a perspective view of a tennis court with the shaded area representing the serviceable area with a linear flat serve.

[0029] FIG. 4B shows a perspective view of a tennis court with a larger serviceable area due to additional vertical reach.

[0030] FIG. 5A shows a sectional view of a second embodiment of the present invention with a mechanical stop feature.

[0031] FIG. 5B shows a sectional view of a second embodiment of the present invention with the mechanical stop feature engaged.

[0032] FIG. 6 shows a sectional view of a third embodiment of the present invention with a torsion spring, pinion gear, and rack gear.

REFERENCE NUMERALS IN DRAWINGS

[0033] 01 Stringed frame head

02 Throat

03 Shank

04 Handle

[0034] 05 Hollow handle
06 Retracted shank

07 Spring

[0035] 08 Extended shank
09 Stretched spring
11 Start of serve motion

12 Take-back

[0036] 13 Trophy position
14 Back-scratch position
15 Contact point

16 Follow-through

[0037] 17 Back swing
18 Forward swing
19 Locus of racquet tip

21 Serve

[0038] 22 Forehand groundstroke
23 Forehand volley
24 Extended racquet head position
25 Standard racquet head position
26 Additional reach
27 Retracted racquet head position
28 Forward racquet motion
31 Flat serve down the middle
32 Angled flat serve
33 Serviceable area
34 Vertical reach
35 Larger serviceable area due to additional vertical reach
41 Mechanical stop feature on shank
42 Mechanical stop feature on handle
51 Torsion spring
52 Pinion gear
53 Rack gear

Summary

[0039] The present invention relates to the field of tennis, especially extendable and retractable tennis racquets. In its broadest aspect, the invention is an extendable and retractable tennis racquet that provides added advantages to players. The racquet design is biomechanical, meaning that the advantages derived from the racquet come as a result of the natural movements of playing tennis. The centrifugal force generated by the natural swing pulls on the head assembly, which extends the racquet. Towards the end of the swing, the player decelerates the racquet, resulting in a diminishing of centrifugal force. As the centrifugal force is overcome by the restoring force in the spring, the head assembly is pulled back to its retracted position. The aforementioned invention described is only one embodiment.

Description of the Preferred Embodiment

[0040] Referring now to FIG. 1A, a tennis racquet is shown to comprise of a stringed frame head 01, throat 02, shank 03, and handle 04. The stringed frame head, the throat and the shank together make up the head assembly. For the present invention, as shown in FIG. 1B, the hollow handle 05 is open at one end; part of the retracted shank 06 is positioned inside the cavity of the hollow handle. The shank and the hollow handle are fitted together telescopically, only allowing relative movement in the longitudinal direction. A spring or flexible member 07 connects the base of the shank to the base of the hollow handle. In this nominal position, the shank is retracted far inside the hollow handle. The spring is also in a free state, neither in tension nor compression. FIG. 1C shows an extended positon 08 where the shank is displaced out of the handle cavity, while the spring is being stretched 09.

[0041] FIG. 2 shows the various stages of a typical serve motion. At the start 11, the player holds the ball in one hand and racquet in the other. Next, the player takes the racquet back as the ball is tossed upward in the take-back 12. After the ball is tossed, the racquet arm swings backward 17 and then up above the head. This brings the player into the trophy-position 13. Immediately after, the racquet is dropped behind the head into the back-scratch position 14 where the forward swing 18 begins. The tossed ball is struck at the contact point 15 with the arm fully extended. After impact, the racquet decelerates throughout the follow-through 16.

[0042] FIG. 3 shows a schematic display of the advantage of the present invention. For the serve motion 21, the ball is struck during the forward swing 18. At the extended position 24, the racquet has a longer vertical reach 26 than a standard racquet 25. For the forehand groundstroke 22, the ball is also struck during the forward swing. The extended racquet has a longer reach than a normal racquet. For the forehand volley 23, the correct technique calls for a short forward motion 28 of the forearm and the racquet. At impact, the racquet remains in the retracted position 27. These principles also apply to the backhand groundstroke and backhand volley.

[0043] FIG. 4A shows the prospective view of a flat serve into the opposite service box. The player can serve down the middle of the court 31, angled diagonally across 32, or anywhere in between. The size of this serviceable area 33 by a flat serve is defined by the player's vertical reach 34.

[0044] FIG. 4B shows the same prospective view of a flat serve into the opposite service box. An additional vertical reach 26 affords a larger serviceable area 35.

Operation of Invention

[0045] The racquet design of the present invention is biomechanical, meaning that the advantages derived from the racquet come as a result of the natural movements of playing tennis. The spring mechanism to extend the racquet is actuated by the centrifugal force generated during the swing. Extension of the racquet allows for longer reach, resulting in more powerful shots. After the ball is struck, the swing motion during the follow-through moderates and the deployment force diminishes. Consequently, the restoring force in the spring retracts the racquet back to its nominal length. Thus, racquet extension and retraction automatically becomes part of the swing. This synchronization does not require conscious decision or physical adjustment, resulting in minimal change for a player to adopt this new racquet. Due to the simplistic design, the weight of the extendable and retractable racquet is comparable to that of a standard tennis racquet.

[0046] There is minimum clearance between the shank 03 and hollow handle 05 so that the shank can slide longitudinally in and out of the cavity of the hollow handle without any lateral free play. This tight fit must be maintained throughout the telescopic deployment range to ensure the overall racquet stiffness necessary to hit the ball effectively. Detailed design of both the shank and hollow handle can include complex structural cross-sections to increase the cross-sectional area and moment of inertia, and a mating feature to ensure a tight fit between the parts.

[0047] Unlike multiple prior art inventions, racquet deployment does not affect the exterior surface of the hollow handle 05. As such, the removal or reapplication of the grip material is unnecessary. Thus, the grip material can remain on the exterior surface of the hollow handle throughout the racquet extension and retraction.

[0048] In the first embodiment of the present invention, FIG. 1B, the spring 07 is in a free state when the shank is retracted 06. During a serve or a groundstroke, the player swings the racquet, imparting motion on the racquet. In doing so, the centrifugal force generated pulls the weight of the racquet head assembly outward, therefore stretching the spring 09 and extending the shank 08 out of the cavity of the hollow handle 05, as shown in FIG. 1C. Towards the end of swing motion, the racquet decelerates. The corresponding centrifugal force is reduced and overcome by the restoring spring force. As a result, the shank retracts back into the cavity of the hollow handle. The advantage is a total lack of conscious decision or physical action required from the player. It is well known that conscious decision-making requires cognitive resources. Increasingly complex decisions place more strain on these resources, so the quality of decision declines as the complexity of decisions increases. This present invention removes conscious decision-making and preserves cognitive resources for gameplay.

[0049] On the serve motion, a longer or extended racquet will increase the vertical reach of the player. Refer to the serve motion 21 and additional vertical reach 26 in FIG. 3. The greater reach will equate to the advantage of a taller player. For a flat serve, which tennis players typically use as a first serve, success depends on speed and placement. The latter is a function of the serviceable area within the service box. A taller player has the distinct advantage of accessing a larger serviceable area due to a higher vertical contact point. This is shown in FIG. 4A where the serviceable area 33 is highlighted. With additional reach, the serviceable area 35 is shown to be increased in FIG. 4B. The larger serviceable area allows for a larger margin of error on serve. The extended racquet will also provide a longer moment arm between the gripping hand and the center of the stringed frame head where the ball is struck. This longer moment arm will result in a more powerful shot. Furthermore, the additional vertical reach will allow the player to hit the serve in a more downward manner.

[0050] In reality, there is a limitation on the racquet length as can be seen in FIG. 2. In the early part of the serve motion, the player takes back 12 his racquet in the form of a back swing 17. The tip of the racquet clears the ground only by a small margin. The locus of the racquet tip is displayed as item 19. As the racquet lengthens, the propensity for the racquet tip to hit the ground during this part of the serve motion is greatly increased. The present invention alleviates this concern since the slower backward motion does not deploy the racquet mechanism that extends the racquet. It is only during the latter stages of the serve motion that the forward swing 18 develops enough centrifugal force to extend the racquet. This inherent delayed deployment is key to allow for more vertical reach and to prevent the racquet from hitting the ground as well.

[0051] The advantages of this invention can be seen in various shots of the game in FIG. 3. During a groundstroke, a longer racquet will afford the advantages of a longer reach 26 during a groundstroke 22. In addition, the longer reach can also generate more force on the ball than that of a standard racquet. This higher force directly translates into a more powerful shot. The player can also hit the ball harder with more spin. While the groundstroke 22 in FIG. 3 shows a forehand shot, the same advantage can be gained in a similar manner for the backhand.

[0052] For volleys, the best racquet position is the retracted position where control is of prime importance. The present invention allows the player to maintain the retracted racquet position. In a typical volley shot, there are no large swing motions. Instead, the racquet is moved forward 28 slightly, shown in volley play 23 in FIG. 3. This translation of the racquet does not induce any centrifugal force to deploy the racquet mechanism to extend. Thus, the racquet remains in the preferred retracted nominal position providing better control.

[0053] This invention combines the advantages of a head-light racquet and the advantages of a head-heavy racquet in one racquet. The head-light characteristics of increased control, maneuverability, and less arm shock are most beneficial during volleys. On the other hand, the head-heavy characteristics of increased power and faster racquet acceleration are most beneficial during a serve or groundstroke. The invention allows the player to achieve all virtues without having to play differently. The player will have all the advantages based on which shot he or she hits.

[0054] In addition to more vertical reach on serves, longer reach on groundstrokes, and the removal of unnecessary conscious decisions, this invention can also generate a time advantage by reducing the overall duration of a serve or groundstroke. At the start of a swing, the racquet is in the retracted position. This more compact racquet configuration will accelerate faster due to the decreased drag, which consequently shortens the duration for the starting portion of the swing motion. In the next part of the swing, the racquet is now fully extended prior to contact. The drag on the racquet is comparable to that of a longer racquet. There are no time advantages to be gained during this small part of the entire swing. In the last part of the swing, the racquet is retracting due to the diminishing centrifugal force. Once again, there will be a time advantage due to the more compact racquet configuration. The overall duration is reduced, giving the player more time to prepare for the next shot.

[0055] Since the amount of extension is related to the centrifugal force derived by the racquet on a swing, a player can select the amount of desired extension by choosing a spring with a specific stiffness. In other words, this invention can be customized to the particular preference of the player.

Description and Operation of Alternate Embodiments

[0056] FIG. 5A shows the second embodiment of the present invention. The difference between the preferred embodiment and this alternate embodiment is the presence of a mechanical stop. The mechanical stop feature, 41 and 42, is located on the outside of the retracted shank 06 and inside of hollow handle 05 respectively. In the nominal retracted racquet position, the spring 07 is in a free state, and the mechanical stop feature is not engaged.

[0057] FIG. 5B shows the same alternate embodiment when the racquet is extended. Similar to the preferred embodiment, the extension of the racquet is actuated by the swing motion. In this case, the spring 09 is stretched and the racquet is extended until the mechanical stop feature, 41 and 42, is engaged. The amount of extension is fixed and pre-determined by the placement of the mechanical stop feature. Any extension force that pulls on the shank 08 will stretch the spring 09 until it has been reacted out at the mechanical stop feature. Therefore, any swing motion will consistently produce the same amount of racquet extension. In practical terms, a player can decide how much racquet extension would be needed to enhance his or her game. A spring of specific stiffness can be installed in the racquet with the mechanical stop feature placed at a specific location. Thus, a normal swing could always produce the same amount of extension.

[0058] FIG. 6 shows the third embodiment of the present invention. The retracted shank 06 is connected to the hollow handle 05 via a torsion spring 51, a pinion gear 52, and a rack gear 53. The torsion spring is attached to the pinion gear at one end and the hollow handle at the other end. The pinion gear is attached independently to the inside of the hollow handle. The rack gear is attached to the shank. The pinion gear teeth are engaged to the opposite teeth in the rack gear. During a swing, the centrifugal force generated pulls on the racquet head assembly thus, pulling the retracted shank out of the hollow handle. The rack gear turns against the pinion gear and winds up the torsion spring. Towards the end of gameplay, the swing motion slows and the corresponding centrifugal force diminishes. As the restoring force in the torsion spring overcomes the centrifugal force, the torsion spring unwinds, turning the rack gear in the opposite direction to drive the shank back inward. As a result, the shank is retracted back into the hollow handle. The rack gear design includes a built-in mechanical stop. As the pinion gear rotates, its teeth continue to engage opposite teeth in the rack gear. This dynamic engagement stops when the pinion teeth run into the end of the toothed portion of the rack gear. The pinion gear can no longer turn thus, stopping any more displacement of the shank. Therefore, a mechanical stop is already built into the rack and pinion arrangement.

Conclusion, Ramifications, and Scope

[0059] This invention relates to an extendable and retractable tennis racquet that can be used to optimize gameplay on the court. The biomechanical design frees the player from having to make a conscious decision of whether to extend the racket. The longer reach results in a lengthened moment arm and therefore, a more powerful shot.

[0060] The spring mechanism used in the current invention can be replaced with a two-way ratchet mechanism with an enabling toggle mechanism and a return mechanism. Once the toggle mechanism is set in place, the racquet can be extended during gameplay. A different setting on the toggle mechanism will enable the return mechanism to retract the racquet to its original length. While this design is still biomechanical in nature, it does require some physical adjustments on the player's part. In addition, the higher complexity of the design will require more elements and may warrant an increase in weight.

[0061] As much as this invention was specifically described for tennis gameplay, it can be applied to a variety of racquet sports. An extendable and retractable racquet may be beneficial in squash and badminton. The more compact and retracted position on the racquet will allow for a faster swing and head-light characteristics. This invention is equally advantageous to the golf game. An extendable and retractable shaft will also allow a faster swing and a more powerful drive.

[0062] Although the description above contains many specificities, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the presently preferred embodiments. It will be apparent to those skilled in the art that various modifications and improvements may be made without departing from the scope and spirit of the invention. Thus, the scope of the invention should be determined by the appended claims and their legal equivalents, rather than by the examples given.