GB2056288A - Long string racket - Google Patents

Abstract

Tennis and racquetball rackets having a conventional grip 11, shank 12, and head 13 supporting a string network including transverse strings 24 are given significantly longer longitudinal strings 25. This is made possible by extending long strings 25 from the distal boundary 17 of frame 15 across ball-hitting region 20, through shank region 12, to a proximal end support for the strung lengths of strings 25 located in grip 11. The long strings 25 are guided or fanned across ball-hitting region 20 and are preferably passed through a suspended shank guide holding them clear of the frame. They offer substantially longer strung lengths for tensioning and deformation to give shots higher velocity and increased accuracy without increasing the overall size of the frame or racket. The longer strings are also strung at higher tensions than the transverse strings so that both long and transverse strings vibrate at about the same frequency to cooperate with each other in simultaneously returning stored impact energy to a ball being hit. <IMAGE>

Description

SPECIFICATION Long string racket The invention involves tennis rackets, racquetball rackets, and other sport rackets having a string network. As applied to tennis rackets, the oversized Prince racket according to Head U.S.

Patent No. 3,999,756 has demonstrated advantages in a larger head providing longer strings and a larger ball-hitting region. This is confirmed in a paper entitled "Physics of the Tennis Racket" by H. Brody in the June 1979 issue of the "American Journal of Physics" 47(6) at page 482 reporting on kinematics investigations of tennis balls, tennis rackets, and string networks and showing generally that a large head with a rigid frame supporting a large string network can increase the velocity and accuracy of shots.

There are practical limits to how large the head of a tennis racket can be made, and the present oversized Prince racket at least approaches those limits. The shank region of this racket between the grip and the head flares enough to make a second hand hold on the shank of the racket difficult for some people, and much larger rackets would be unwieldly and impractical.

Many players still prefer the advantages of small or medium sized racket heads to the string network improvements obtainable with the large size Prince racket. Improving the performance of the string network benefits all sizes of rackets and is accomplished by my invention.

I have discovered a way of substantially lengthening strings of a racket's string network without enlarging frame dimensions so that a racket can be handled in the customary way and yet achieve significant advantages in having much longer strings in its network. My invention also recognizes a requirement for different stringing tension between long longitudinal strings and short transverse strings so that both strings vibrate at about the same frequency and cooperate in simultaneously returning stored impact energy to a ball being hit. These changes reduce vibration and shock transmitted to the hand and improve substantially over conventional rackets in increasing velocity and accuracy of shots from an increased efficiency in long strings transmitting hitting power to the ball being hit.

The invention applies to sports rackets having a hand grip joined to a frame supporting a string network that extends throughout a ball-hitting region spaced from the grip. The frame has a hand-holdable shank region extending from the grip and flaring outward to the ball-hitting region and the frame extends outward from the shank region along lateral sides of the bal-hitting region and around a distal boundary of the ball-hitting region opposite the grip. The string network has transverse strings strung between lateral sides of the frame, and longitudinal strings that converge in the shank region and fan outward across the ball-hitting region.

My improvement provides longitudinal strings having a strung length that extends from the distal boundary across the ball-hitting region through the shank region and reaches to the region of the grip. This makes the strung length of the long strings substantially longer than the distance across the ball-hitting region. The long strings are strung at substantially higher tensions than the transverse strings, and the difference in tensions is predetermined so both strings will vibrate at aboul the same frequency to simultaneously return stored impact energy to a ball as it is hit.

In the accompanying drawings:- Figure 1 is a partially schematic, partially cutaway, plan view of preferred features for a tennis racket having long strings arranged according to my invention: Figures 2-4 are cross-sectional views taken respectively along the lines 2-2, 3-3, and 4-4 of FIG. 1 showing string supports inside the grip; Figure 5 is a fragmentary plan view of a string guide device located between the frame sides of the throat of a racket where the shank flares into the head; Figure 6 is a fragmentary view of an alternative string support device arranged near the grip of a tennis racket; Figure 7 is a cross-sectional view of the string support devices of FIG. 6 taken along the line 7-7 thereof; Figure 8 is a cross-sectional view of a stiffener and guide taken along the line 8-8 of FIG. 1;; Figure 9 is a partially cutaway, fragmentary view of the grip and shank region of an alternative long string guiding and supporting system according to my invention; Figures 10 and 11 are fragmentary elevational views of alternative string guides according to my invention; Figure 12 is a cross-sectional view of a frame support and string guide bushing of the racket of FIG. 9, taken along the line 12-12 thereof; Figure 1 3 is a fragmentary cross-sectional view of a long string proximal anchorage pin taken along the line 1 3-1 3 thereof; Figure 14 is a fragmentary, partially schematic, plan view of additional preferred features usable in my long string racket;; Figures 1 5-1 8 are cross-sectional views of the racket of FIG. 1 4 taken respectively along the lines 15-15, 16-16, 17-17, and 18-18 thereof; Figure 1 9 is a cutaway elevational view of an alternative preferred string guide according to my invention; and Figure 20 is a partially schematic, fragmentary view of a preferred string network arrangement in a ball-hitting region according to my invenion.

Tennis racket 10 as shown in FIG. 1 preferably has a conventional size and shape for a grip 11, a shank 12, and a head 13. Its frame 15 can be made of wood, metal, fiber glass, or other material, as is generally known; and the preferred frame 1 5 as illustrated is formed of a long strip of material having a generally constant crosssectional shape and arranged with its opposite ends located within grip 11 so that it extends outward along opposite sides of shank region 12, flares into head region 13, and extends around ball-hitting region 20. Frame 1 5 extends along lateral sides 1 6 of ball-hitting region 20 and around a distal boundary 17 of ball-hitting region 20 opposite grip 11. Transverse strings 24 are strung between lateral sides 16 of frame 15 across ball-hitting region 20.

Longitudinal strings 25, at least in the longitudinal central region of ball-hitting region 20, are arranged according to my invention to have a strung length that extends from distal boundary 1 7 of frame 1 5 across ball-hitting region 20 through shank region 12, and reaches to the region of grip 11. Such a long strung length for longitudinal strings 25 substantially exceeds the distance across ball-hitting region 20, which is the conventional limit for the strung length of strings.

By extending longitudinal strings 25 into the space available in the region of shank 12 and grip 11, strings 25 can have a strung length much longer than the conventional distance across ball-hitting network 20 to achieve significant advantages that are explained below.

The distal ends 26 of the strung length of longitudinal strings 25 are supported on the distal boundary 17 of frame 15 in the usual way, and supports for the proximal ends of the strung lengths of strings 25 are arranged within or near grip 11 so that strings 25 reach through shank region 12. As shown in FIG. 1, one convenient way of accomplishing this is to arrange longitudinal strings 25 to diverge outward across ball-hitting region 20 so that although they are relatively closely spaced and crowded together in shank region 12, they fan outward across ballhitting region 20.

The throat region of the racket at the distal end of shank region 12 and the proximal end of head region 1 3 preferably includes a stiffener 1 8 that stiffens frame 1 5 and straddles the longitudinal strings 25 in their fanned out orientation across ball-hitting region 20. Stiffener 1 8 is a simple cross brace that can have many other forms. It preferably does not restrict vibrational motion of the strings, and it is preferably relatively wide for this purpose. It also can be made in more than one piece and have many different shapes.

Guides for the long strings 25 as they pass from the shank region into the throat region are also possible, the several different anchorages for the proximal ends of the long strings can be used.

Many of the possible alternatives are described below, and these can be combined in various ways in any particular racket.

As shown in FIG. 5, a guide 19 at the throat of the racket can have string-guiding pins 21 around which longitudinal strings 25 bend so that pins 21 guide strings 25 along a direction more nearly perpendicular to transverse strings 24. It is also possible according to the invention to anchor longitudinal strings toward the lateral sides of ballhitting network 20 to frame 1 5 in the conventional way and make only the strings 25 in the longitudinally central region of ball-hitting region 20 extend into the shank and to the region of grip 11. Also, instead of fixed pins 21 on throat piece 19, several suspended harnesses tied to frame 1 5 can locate individual strings or groups of strings along the throat region without adding substantial mass to the strings or impairing their vibrational motion.

I prefer keeping at least some of the long strings out of direct contact with frame 1 5 in the shank region 12 to avoid shock transmission from the strings to the frame through frictional contact.

As best shown in FIGS. 9-11, I prefer a suspended bushing or guide 40 to accomplish this. Guide 40 is positioned longitudinally of the racket at the proximal end of the throat region where the shank begins to flare. It has curved sides 41 that guide the strings to fan outward through the shank and across the ball-hitting region and also hold the strings clear of the frame.

Although guide 40 or a similar guide keeping at least the centra! long strings out of contact with the frame has advantages in insuring free vibration of the strings, any such guide should not add much mass to the vibrating strings and works better if it is freely suspended within the frame rather than rigidly joined between frame members.

One way to do this is with a support strand 42 that ties guide 40 to throat stiffener 1 8 to prevent longitudinal movement of guide 40 toward grip 11 as shown in FIG. 9. The long strings in tension as they pass through guide 40 tend to center guide 40 between frame members 15, so that guide 40 is self-centering. However, the fanning outward of strings across the ball-hitting region tends to force guide 40 toward grip 11; and strand 42 effectively prevents this, keeping guide 40 suspended and shock free within the racket shank.

An alternative suspension of guide 40 by a pair of support strands 42 connected to frame members 1 5 is shown in FIG 1 0 to illustrate that other possibilities for suspending guide 40 exist.

Another alternative shown in FIG. 11 is a pair of pins 44 and 45 mounted on guide 40 so that a pair of central strings 25 can pass in a zigzag path around pins 44 and 45 to anchor guide 40 against longitudinal movement. The remaining strings can pass through guide 40 in the usual way, and a string guide can have shapes other than the one illustrated to support strings clear of frame 15.

Another variation as shown in FIG. 1 9 is a single pin 91 in a similar suspension guide 90 arranged so that a pair of central strands can wrap around a single pin 91 in a U-turn that anchors guide 90 longitudinally of the string direction.

Another alternative shown in FIGS. 14 and 1 7 is a lightweight loop or harness 70 secured between frame elements 1 5 in the shank region of the racket by a string 71 extending transversely between the racket sides. Harness 70 surrounds the central region long strings 25 and tends to be centered between frame elements 1 5 by the tension on these strings. Transverse string 71 prevents longitudinal movement of harness 70, and strings 25 vibrate freely to absorb shock and prevent its transmission to the racket grip. Instead of anchoring string 71, harness 70 can be held longitudinally by a support strand 42 as shown in FIG. 9 or by racket strings wrapped around a pin such as shown in FIGS. 11 or 19.

Although not necessarily combined as illustrated in FIG. 14, side guides 72 secured to frame elements 15 in the shank region of the racket guide the outer long strings 25 along the sides of the racket, leaving the central region clear for free vibration of the mid-region long strings.

Side guides 72 can also be combined with a cross piece or brace stiffening the frame members and can be formed in many ways to harness the outermost strings to the frame sides and leave the central strings vibrationally free.

Stiffener 78 illustrated in FIG. 14 has another possible feature. It is made relatively wide from one side of the racket to the other to allow plenty of vibration room for strings 25. Stiffener 78 can be as wide as frame elements 1 5 so that strings 25 rarely touch stiffener 78 during play.

FIGS. 1-4 show a convenient way of anchoring proximal end supports for the strung lengths of strings 25 within grip 11. Support spools 30,31, and 32 each have cylindrical flanges located in opposed recesses in frame sides 1 5 within grip 11 and have string support spindles 33-35 that preferably increase in diameter proceeding toward the proximal end of grip 11.

Each of the spindles 33-35 provides a successively larger diameter anchorage for long strings 25, with a few strings wrapped around each spindle so that the strings are slightly spaced from each other and do not interfere with each other's tensioning and deformation. Grip 11 is removed as strings 25 are strung around spindles 33-35 and is replaced after the racket is fully strung.

An even better way of anchoring the proximal ends of the strung lengths of strings 25 is shown in FIGS. 9 and 13 as a single cross pin 50 connected between the ends of frame members 1 5 at the proximal end of grip 11. This has several advantages. It gives long strings 25 a maximum possible length with the proximal support for their strung lengths being located at the proximal end of the racket. This takes fullest advantage of the improvement to be gained from long strings.

Furthermore, a single cross pin 50 oriented as illustrated allows strings 25 to be simply wrapped around pin 50 without requiring any time consuming threading of strings through openings or spaces around spindles. Rivets or other simple fasteners can anchor cross pin 50 in place at the ends of frame members 15; and with grip 11 removed, stringing over pin 50 is' fast and efficient.

Long strings 25 according to my invention are substantially longer than conventional strings and require more time in pulling greater lengths through holes in the process of stringing the racket. To reduce this time, it is possible to cut the strings into shorter lengths that thread faster and rejoin the cut lengths with knots positioned within grip 11 to be concealed when the grip is replaced.

Another possible improvement shown in FIGS.

9 and 12 is a support bushing 60 having an axial hole 61 for guiding strings 25 into the region of grip 11 and providing a transverse support between frame elements 1 5. Screws 62 or other simple fasteners connect bushing 60 between frame elements 1 5 for stiffening and support, while central opening 61 provides ample clearance for strings 25 to pass. Since strings 25 are parallel with the racket axis as they pass through bushing 60, they have insufficient frictional contact with opening 61 to transmit shock. Bushing 60 is also preferably enclosed by grip 11 for concealment.A preferred alternative for bushing 60 is bushing 80 of FIGS. 14 and 15 serving the same general purpose but having a central pin 81 and side recesses 82 adjacent frame elements 1 5. This guides the strings in two groups that are partially recessed into frame elements 15, leaving the space between the frame sides clear of strings. Bushing 80 strengthens the frame and improves the racket appearance by neatly guiding the strings along the frame elements in the shank region.

An alternative anchorage for the proximal ends of the strung length of strings 25 is shown in FIGS. 6 and 7. A support plate 37 having string support pins 36 is anchored between frame sides 15 where shank 12 joins grip 11. The proximal ends of strings 25 are supported on pins 36 adjacent grip 11 which does not have to be removed for stringing the racket.

For racquetball rackets lacking a shank region, the proximal end string supports should be within grip 11 to have a length substantially longer than the distance across ball-hitting region 20. The preferred anchorage for proximal end string support for racquetball rackets is cross pin 50 at the proximal end of the racket as shown in FIGS. 9 and 13. Cross pin 50 can also be moved longitudinally to locations within grip 11 spaced from the proximal end of the racket if desired.

To facilitate fanning longitudinal strings 25 outward across ball-hitting region 20, it is preferable to make shank 12 flare outward at the throat region where shank 12 joins head 1 3 by as much of a flare as can be comfortably accommodated by the users. To make the racket usable in the customary way, it is preferred that shank region 12 be narrow enough to be gripped by the free hand of the player above grip 11.

As long strings 25 fan out across the ballhitting region of the string network, they diverge at the distal end 1 7 of the racket. This spaces long strings 25 further apart at the distal portion of the ball-hitting region and produces a soft spot in the string network. To counteract this, I prefer spacing transverse strings 24 more closely together in the distal portion of the ball-hitting region than in the promimal portion as schematically shown in FIG.

20. This increases the density of the transverse strings 24a where the fanned out strings 25 are furthest apart and reduces the density of the transverse strings 24b where the fanned out strings 25 are closest together. Such an arrangement makes the string network lively and responsive throughout the ball-hitting region.

Long strings 25 having a length substantially exceeding the distance across the ball-hitting region have a substantial advantage in being able to store the same amount of elastic strain energy derived from the impact of a ball with much less impact force than would be required to store the same amount of elastic strain energy in a conventionally short string. Reducing the impact force that is required to store strain energy in a long string reduces shock to the user and deformation of the ball so that more of the energy is stored in the string network and returned to the ball for a higher velocity rebound and a stronger return shot A network strung with long strings according to my invention is thus responsive and resilient, subjects the player to less shock, and returns balls more efficiently at higher velocities.

Giving longitudinal strings 25 a substantially greater length compared to conventionally short transverse strings 24 requires cooperative interaction between strings having significantly different strung lengths. I have found that successful cooperation between long strings 25 and transverse strings 24 requires that these strings be strung at substantially different tensions. I have also found that the difference in tensions between long strings and short strings should be established so that both strings vibrate at about the same frequency. This allows both long and short strings to return simultaneously from an impact deformation storing and returning elastic strain energy to the ball being hit.A tension differential that tunes the long and short strings to the same frequency allows them to react together on impact with the ball so that their cooperative and simultaneous response returns stored elastic energy to the ball at the same instant for greater efficiency and effectiveness. If the long and short strings are strung at the same tension as is conventional with prior art string networks, the short strings vibrate at a much higher frequency than the long strings and return their stored energy more quickly to the ball. By the time the more slowly responding long strings return from their deformation to add their stored energy to the ball being hit, it is already rebounding from the string network. This greatly reduces efficiency.

Proper tensions and tension differences between long and transverse strings can vary considerably, not only with different lengths of strings, but with different string and racket frame materials. For example, wooden rackets are generally strung with less tension; and steel and composite racket frames can be strung with higher tensions that these materials can withstand. Of course, the strings must also be formed of materials than can withstand the desired tensions.

It is also possible to use several different string tensions, rather than merely two tensions.

Longitudinal strings running through the center of the string network are longer than the longitudinal strings that fan out toward the sides of the string network, and tension differences are possible and appropriate to tune these different length strings to approximately the same frequency. Length differences in transverse strings vary less, but the same principle applied. Differences in capacity and style of players also require higher and lower string tensions as generally known; but regardless of tension level desired, longer and shorter strings are preferably tensioned differently to vibrate at about the same frequency.

I have found that transverse strings 24 having about a 10 inch length are preferably tensioned at about 35-75 pounds in a conventional manner and that long strings 25 having a substantially greater length of about 26 inches should be tensioned at about 80-1 50 pounds to vibrate at about the same frequency as the transverse strings. This tunes the long and short strings to about the same frequency so that they cooperate efficiently and simultaneously in returning stored energy to the ball. This arrangement has the additional advantage of requiring much less impact force to store the same amount of energy in the long strings so that less energy is wasted in deforming the ball and more energy is returned to the ball in a higher velocity rebound from the string network. Linear vibration theory confirms these findings.

I prefer especially strong and unyielding strings for long strings 25 and have achieved excellent results with strings having a minimum 260 pound breaking stress at a 3% yield, strung at 80 to 1 50 pound tensions for long strings 25. These strings cooperate well with transverse nylon strings 24 having a breaking stress at 1 60 pounds and a yield at 17% and strung at tensions of 35-75 pounds. Experience may suggest different optimum string tensions to take advantage of the longer string tension capacity of rackets according to my invention.

Claims (8)

1. A racket having a hand grip joined to a frame supporting a string network that extends throughout a ball-hitting region spaced from said grip, said frame having a shank region extending from said grip and flaring outward across said ballhitting region, said frame extending outward from said shank region along lateral sides of said ballhitting region and around a distal boundary of said ball-hitting region opposite said grip, said racket comprising:: a. transverse strings extending between said lateral sides of said frame and longitudinal strings converging in said shank region and fanning outward across said ball-hitting region; b. said longitudinal strings having a strung length that extends from said distal boundary across said ball-hitting region through said shank region and reaches to the region of said grip so that said strung length of said long strings substantially exceeds the distance across said ball-hitting region; c. said long strings being strung at substantially higher tensions than said transverse strings; and d. the tension differences between said long strings and said transverse strings being predetermined so both strings vibrate at about the same frequency and cooperate with each other in simultaneously returning stored impact energy to a ball being hit.

2. The racket of claim 1 wherein said transverse strings are arranged closer together in a distal portion of said ball-hitting region than in a proximal portion of said ball-hitting region.

3. The racket of claim 1 including means extending between lateral sides of said frame at a proximal edge of said ball-hitting region for stiffening said frame and locating said long strings at said proximal edge of said ball-hitting region.

4. The racket of claim 3 wherein said transverse strings are arranged closer together in a distal portion of said ball-hitting region than in a proximal portion of said ball-hitting region.

5. The racket of claim 1 including a guide for holding at least some of said long strings away from said frame in said shank region.

6. The racket of claim 5 including means for suspending said guide against longitudinal movement in said shank region.

7. The racket of claim 5 including a bushing for said long strings, said bushing being connected between regions of said frame at the distal end of said grip.

8. A racket substantially as hereinbefore described with reference to and as illustrated by any one of the embodiments shown in the accompanying drawings.