U.S. patent application number 15/275377 was filed with the patent office on 2018-03-29 for extendable and retractable tennis racquet.
The applicant listed for this patent is Nicholas Lo, Patrick Lo. Invention is credited to Nicholas Lo, Patrick Lo.
Application Number | 20180085648 15/275377 |
Document ID | / |
Family ID | 61687466 |
Filed Date | 2018-03-29 |
United States Patent
Application |
20180085648 |
Kind Code |
A1 |
Lo; Nicholas ; et
al. |
March 29, 2018 |
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.
Inventors: |
Lo; Nicholas; (Irvine,
CA) ; Lo; Patrick; (Irvine, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Lo; Nicholas
Lo; Patrick |
Irvine
Irvine |
CA
CA |
US
US |
|
|
Family ID: |
61687466 |
Appl. No.: |
15/275377 |
Filed: |
September 24, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A63B 49/08 20130101;
A63B 60/0085 20200801; A63B 2102/02 20151001; A63B 60/28
20151001 |
International
Class: |
A63B 60/28 20060101
A63B060/28; A63B 49/00 20060101 A63B049/00 |
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
BACKGROUND
1. Field of Invention
[0001] This invention relates to tennis racquets, and more
particularly, to tennis racquets having a mechanism to change its
length during gameplay.
2. Discussion of the Prior Art
[0002] Many adjustable length racquets have been proposed in the
past. Despite having some of the same common goals, the
applications are significantly different. One main area of focus
was the interchangeability of the racquet. Many previous inventions
tried to address a means to exchange a handle or a portion of the
handle in order to suit the individual needs of a particular
player. Another area of focus was a means to adjust the racquet
length using either common, everyday tools or specific tools. Very
few prior art inventions allowed for a quick adjustment that could
be achieved during gameplay.
[0003] In U.S. Pat. No. 4,746,119 to Jeanrot dated May 24, 1988, a
retractable racquet is shown in FIG. 4. The purpose of retraction
is to provide an easier mode of transportation for the racquet.
This racquet is not meant to be changed during gameplay.
[0004] Many of the past inventions were focused on providing an
adjustable length racquet. Many of the noted efforts include U.S.
Pat. No. 5,169,145 to Jang, U.S. Pat. No. 4,641,838 to Gabrielidis,
U.S. Pat. No. 4,671,511 to Trysinksy, U.S. Pat. No. 6,030,302 to
Chojnacki, U.S. Pat. No. 6,033,325 to Hong, U.S. Pat. No. 4,545,584
and 4,691,926 to Adam, and U.S. Pat. No. 3,833,219 to Dean. All of
these prior art inventions have a way to adjust the racquet length
by means of grooved sockets, pins, screws, or bolts. However, none
of these means can be used to quickly change the length of the
racquet. Tools are often required to make the necessary
adjustments. Another drawback to these inventions is that with the
racquet extended, many players would hit the ground with the
racquet on the take-back during the serve.
[0005] A rapidly adjustable racquet is shown in U.S. Pat. No.
3,931,968 to Hedberg dated Jan. 13, 1976. This invention requires
the player to use both hands in order to slide the shank to the
preferred length. The racquet remains at the specified length as
long as the grip is held tightly. It also requires the player to
decide when and to what degree to extend the racquet. This takes
away focus from the game and distracts the player. Lastly, it would
be very challenging to use this invention on the serve because the
player would have to make the adjustment mid-swing. If the
adjustment was made at the onset of the swing, the extended racquet
would hit the ground on the takeback.
[0006] In yet another known prior art, U.S. Pat. No. 5,524,879 to
Lyle dated Jun. 11, 1996, a locking sleeve is used in conjunction
with a spring loaded roller to easily adjust the length of a
racquet. This invention also requires both hands to operate, thus
making it a distraction to the player. This mechanism is also not
suitable to be used during a serve because of the propensity to hit
the ground.
[0007] The last prior art worth mentioning is Chinese Pat. CN
205084346 U, to Wang et al. dated Mar. 16, 2016. The invention
refers to a telescopic badminton racket. With this barrel cam
design, the invention is comprised of radial and longitudinal
grooves, detents, and a provision. More specifically, the outer
handle has multiple radial grooves and a single longitudinal groove
on the inside wall. Detents are embedded at various locations in
the radial grooves. The shaft also has a provision at its base to
accept a detent to lock it in place. To extend, the shaft must
first be rotated along a radial groove and disengaged from its
detent. After this, the shaft must be pulled out telescopically
along the longitudinal groove and rotated into a different radial
groove until another detent is engaged. Apart from the same two
drawbacks prevalent in both Hedberg and Lyle, it is questionable
whether this arrangement in the badminton racket can be adopted
into a tennis racquet. The latter will require a substantial
stiffening of the mechanism and a major resizing. These changes are
crucial because the tennis ball and the hitting forces are greatly
increased from those of badminton.
Objects and Advantages
[0008] It is a principal object of the invention to provide a new
extendable and retractable tennis racquet which overcomes the
disadvantages of the prior art in a simple but effective manner.
This biomechanically designed tennis racquet requires no conscious
decision from the player or physical adjustment on the racquet. The
extension and retraction of the racquet are both done
automatically, as a byproduct of the natural swing. This eliminates
the distractions that were required in all previous adjustable
length racquets.
[0009] It is a major object of the invention to afford a height
advantage during the serve. The inherent delayed deployment of the
mechanism allows the racquet to be swung through the take-back
without hitting the ground.
[0010] It is another object of the invention to provide an
extendable and retractable tennis racquet which affords a longer
reach on groundstrokes.
[0011] It is yet another object of the invention to provide a more
compact racquet configuration at the onset of the swing, resulting
in a shortened duration for the complete swing motion. The racquet
will accelerate faster due to the decreased drag, similar to a
shorter racquet; this translates to a time advantage for the player
to move the racquet or to get it into position for the next
shot.
[0012] It is a further object of the invention to provide a racquet
with a varying weight distribution or balance during gameplay. At
the start of a swing or a volley, the racquet is at the retracted
and compact position. These handling characteristics are comparable
to a head-light racquet. When the ball is struck during a serve or
a groundstroke, the racquet is fully extended; thus, its handling
characteristics are similar to a head-heavy racquet.
[0013] It is an additional object of the invention to provide an
extendable and retractable tennis racquet which is comparable in
weight to a standard racquet. No significant weight penalty is
incurred due to its simplistic design.
Accordingly, several advantages of our invention are:
[0014] a) The racquet mechanism is based on biomechanics, meaning
that the advantages derived from the racquet come as a result of
the forces created during the natural movement of playing tennis.
As a result, the player does not have to play differently in order
to utilize the advantages afforded by our invention. The player can
stay more focused on gameplay because the extension and retraction
are done automatically.
[0015] b) The extendable racquet offers a height advantage during
the serve. The contact point of a player with an additional height
advantage is higher up from the ground. Thus, the player can hit
the ball more downwards. The serviceable area, or maximum area the
player can hit into on the serve as a result of his or her vertical
reach, is also significantly increased, which allows for a larger
margin of error on the serve.
[0016] c) On the serve, the inherent delayed deployment of the
mechanism allows the racquet to be swung through the take-back
without hitting the ground.
[0017] d) On the serve and groundstrokes, the racquet is extended
at contact. It affords the player a larger moment arm and
therefore, better leverage. Thus, the player can hit the ball
harder with more spin. The extended racquet also gives the player a
longer reach.
[0018] e) For two of the three parts of the swing, the invention
will afford a time advantage for the player. The retracted racquet
at the onset of the swing will accelerate faster due to the
decreased drag, similar to that of a compact racquet. This also
applies at the end of the swing. The invention decreases the
overall duration of any typical shot, giving the player more time
to prepare for the next shot.
[0019] f) The invention has a varying balance during gameplay. The
retracted racquet has the advantages of a head-light racquet:
increased control, maneuverability and less shock on the arm. These
characteristics are most beneficial during volleys at the net. On
the other hand, the extended racquet has the advantages of a
head-heavy racquet: increased power and the ability to swing the
racquet faster. These characteristics are most beneficial during a
groundstroke or on the serve. The extendable and retractable
racquet combines all of the aforementioned virtues.
[0020] g) Since the racquet mechanism is simplistic in design with
few added elements, the increase in weight over a standard racquet
is minimal. No specific change in terms of technique is needed to
take advantage of the current invention. Therefore, it would be a
smooth and easy transition for any player to adopt this new
racquet.
[0021] Further objects and advantages of our invention will become
apparent from a consideration of the drawings and ensuing
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.
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