Patent Grant
6852048
The present invention relates generally to sports racquets, such as racquetball racquets, tennis rackets, squash racquets and badminton racquets used for hitting a projectile such as a ball, and more particularly for string guide structures on sports racquets for easier stringing and dampening vibration of the strings during play.
Sports racquets, such as racquet ball racquets and tennis rackets, have evolved with a number of objectives including the increase of power to hit a projectile, such as a ball or other propellable object such as a shuttlecock. Referring to
Referring to
Due to the lengthening of the long strings 206 and 312 into the handle, even though the string bed in such a racquet is about 15½ inches long (for racquetball and tennis racquets), the effective length of the main, long strings is about 22 inches (for racquetball racquets) or about 27-28 inches long (for tennis racquets). Long string racquets for other racquet sports such as squash and badminton will have commensurate increases in effective length. As a result, the long strings 206 and 312 provide greater deflection and “dwell” time with the ball (not shown), which stores greater energy. This in turn causes a ball to be propelled from a racquet with more power and speed. The long string configurations are disclosed, for example, in U.S. Pat. No. 5,919,104 issued to Mortvedt et al., which is entirely incorporated herein by reference.
The long string configuration, however, is difficult to string since the looping or anchoring pin or bearing 210, 310 is enclosed within the handle 208, 308 of the known racquets. The stringing of these racquets takes more time than is usual, as the stringer has to contend with a string that tends to coil or twine on itself and otherwise behave in an unruly fashion. Threading e.g. monofilament nylon strings through elongated cavities in handles and shafts is time-consuming and frustrating. Further, when inserting the strings 206, 312 into the handle and looping or bending them around the pin 210, 310, it is difficult to maintain a proper alignment of the long strings 206, 312 within the handle and on the pin relative to the alignment of the strings on the string bed. The string tends to end up being routed in an unplanned way.
At the pin 210, 310 itself, the strings 206, 312 may abut against each other while placing the string around the pin, and can become entangled due to crossing or further lateral movement of the strings on the pin. If a string is pulled around the pin and on top of another string, it can later roll off the bottom string and lose a portion of its tensioning.
Yet another problem that occurs while stringing the long string racquets is that once a string 206, 312 is bent around the pin 210, 310, emerges from the handle 208, 308 and is pulled into the string bed 202, 306, it can then be difficult for the stringer to determine where on the racquet head or head frame 214, 304 the string should be attached to next. This is especially true in string bed patterns where the strings are not necessarily strung through adjacent holes on the frame all the way around the frame (i.e. the string is laced through non-adjacent holes such as every other hole or every third hole).
Finally, the long strings 206, 312 are more directly attached to the handle via a pin, at least compared to known racquets that terminate their vertical strings on a head frame separated from the handle by a throat area. This direct contact with the handle transfers undesired forces more easily to the handle, such as vibration formed upon the racquet's impact with an object. Vibration can cause discomfort and tire the muscles of a user's hand and arm holding the racquet more quickly. This vibration is a particularly troublesome issue in long string racquet designs such as those shown in
The problems mentioned above are solved by the invention, which in a first aspect provides a sports racquet for hitting a projectile, and that has a racquet head with a frame and a string bed supported by the frame. A stem is attached to the frame and has inner walls defining a cavity. As used herein, “stem” can mean either a shaft, present in shafted racquets of the sort used in tennis, squash and badminton, or a handle, which in nonshafted racquets such as those used in racquetball are connected directly to the frame. The stem has a longitudinal axis extending the length of the stem and intersecting the string bed. At least one continuous string for forming the string bed includes a plurality of string segments that extend from the string bed and into the cavity of the stem. The string segments are also referred to herein as the main or long strings or sometimes just “strings.” A string guide system is disposed within the stem and guides the continuous string at least through a turn for redirecting the continuous string back out of the cavity and toward the string bed. The redirection defines shared ends of a pair of connected consecutive string segments. The string guide system also defines a width that extends transversely to the longitudinal axis. The string guide system disposes the string segments at predetermined lateral positions along the width at least at the turn.
In a further aspect of the present invention, a number of preselected string segments extend from the string bed and into the cavity, which is preferably elongated. The stem defines an opening to the cavity that opposes the racquet head. The string guiding means guides the preselected string elements to respective predetermined fixed lateral positions within the cavity. It also redirects the strings back out of the cavity toward the string bed.
In a further aspect, elongate tubes reside at least partially within the cavity, and the strings are disposed within the tubes, which dampen vibration of the strings. In yet another aspect of the invention, these tubes have distal ends disposed near a string bearing and proximal ends near the string bed, and are used to string the strings through the cavity from and to the bearing.
In a further aspect of the invention, a sports racquet is provided with a string bed. At least some of the string segments making up the string bed have portions disposed between the string bed and their respective anchor points. Tubes according to the invention may be provided for these non-bed portions as dampening devices, stringing aids or both.
In yet another aspect of the present invention, the string guide system is disposed within the cavity and includes the tubes extending from a vicinity of the opening to a vicinity of the distal (or butt) end for receiving the strings. The string guide system also includes a string bearing assembly within the cavity and spaced away from the near end in a direction toward the distal end. The string bearing assembly has curvilinear channels with two ends, and bores for receiving the tubes. The tubes are disposed so as to communicate with each end of the channels. The tubes are continuous with the channels for receiving the string.
In still another aspect, the invention is directed to a method of stringing a string bed that includes the steps of:
The present invention applies to sports racquets of both shafted and nonshafted varieties.
The above mentioned and other features of the present invention and the manner of obtaining them will be apparent, and the invention itself will be best understood by reference to the following description of the preferred embodiment of the invention in conjunction with the following drawings, in which:
a is a partial front/sectional view of a racquet according to an alternative embodiment of the invention;
a is a graph showing vibration intensity for a racquet with tubes according to the invention, as measured with a piezoelectric shock accelerometer; and
b is a graph similar to
Referring to
The main strings 18 are generally parallel to a longitudinal axis L of the racquet that extends from within the upper end or top 26 of the frame 12, through the bottom 20 of the frame and along the length of stem 16. In the illustrated embodiment, the main strings 18 are not completely parallel to each other but are generally arranged in a fan shaped configuration. In the illustrated embodiment, the racquet 10 also includes twenty-two cross strings 28.
The main strings 18 and cross strings 28 form a tensioned string bed 30 defining a plane which is laterally surrounded by the head frame 14. The string bed 30 is approximately sixteen inches long measured from an upper interior surface 26a of the frame top 26 to a lower interior surface or end 20a of the frame bottom 20 and near stem 16. The length of the string bed 30 is measured along axis or center line L.
It will be appreciated that while a single continuous string may be woven or strung with the frame to form the entire string bed 30, the term “string” as is used in main strings 18 or 22, and in cross strings 28 typically refers to a string segment between its two fixed or anchored ends on the frame or stem of the racquet unless the context of the description indicates otherwise. The present invention has application to sports racquets which are strung with one continuous length of string or two or more such lengths.
The stem 16 has a near end 32 defining the opening 24 to an elongated cavity 34 defined by inner surfaces or sidewalls 36 and front/back walls 96 (shown in FIG. 8). While an integral cavity is preferred for purposes of manufacture and minimal interference with string movement, in other embodiments the cavity can be divided into two or more lumens or divisions, with ones of the main strings routed ISO through one, some or all of them. The long strings or string segments 22 extend into cavity 34 and have fixed ends preferably disposed in the vicinity of a far or distal end 38 of the stem 16 for providing an effective length for the long strings that is significantly longer than the string bed 30. The distal end 38 may have a separate cap or cover plate (not shown).
Referring to
Since the string bearing assembly 44 is positioned at the ends of each long string 22 entering the cavity, it defines each long string or string segment 22 as either an entry segment 46 or an exit string segment 48 that are portions of a single continuous string that is threaded through the string bearing assembly 44. In other words, the segment of one long string 22 that engages a tube 42 before the string bearing assembly 44 is referred to as an entry segment 46 while the segment of the subsequent long string 22 engaging another tube after engaging the string bearing assembly 44 is deemed an exit segment 48.
The string bearing assembly 44 also defines an end 50 of the string segments 22 where the redirection of the string occurs. The bearing accepts at least a large portion of the tensile force placed on it by the strings.
In order to receive the strings 22 and establish the entry and exit segments 46, 48, the tubes 42 have hollow cores 52, with each tube preferably receiving and holding either an entry or an exit segment of each string 22. The tubes 42 have an inner diameter preselected to be larger than the diameter of the string 22 to accommodate the sliding of the string through the tubes, yet small enough so that the tube is sufficiently tight against the string segments 22 to provide a dampening effect described below. The string is typically nylon 16.
a illustrates an alternative embodiment of the invention in which a racquet 600, which in the illustrated embodiment is a racquetball racquet but which could easily be a racquet of a shafted type, has a simpler bearing 602 located at some point within the cavity of the stem 34. In this embodiment, the long strings or string segments 22 are threaded through individual tubes 42, as before. However, the tubes 42 are not affixed to any structure inside the cavity or elsewhere, but are basically free-floating.
a illustrates only one of several alternatives available for providing tubes according to the invention. For example, the tubes may be loosely or firmly attached at their midpoints inside the cavity 34, while their proximal and distal ends remain free-floating. The tubes may be loosely or firmly affixed to any other structure inside the handle cavity or to the side of the frame. While eight tubes, one provided for each long string segment, are shown in the illustrated embodiments, this number could easily vary; only the cross sectional area of the handle cavity 34 poses a physical constraint on the number of the tubes which can be used. Further, there is no absolute requirement that all string segments have such tubes, as the provision of tubes on only some string segments will still have beneficial vibration dampening effects and stringing advantages. Still further, while the illustrated embodiment shows the tubes 42 as extending through all or almost all of the available length of the internal cavity 34, they instead can be shortened to extend through only a portion of this length. While the tubes are presently illustrated as extending somewhat in a proximal or upper direction into the string bed, in other embodiments the tubes may be disposed to be entirely within the cavity 34, or may extend outwardly into the string bed by more than is presently shown. While it is preferred that the tubes 42, or at least groups of them, be connected together as webs, it is nonetheless possible to have the tubes entirely separated from each other. And while the tubes 42 are shown to occupy a single unitary channel or cavity 34, the cavity 34 can easily be subdivided into variously sized longitudinal spaces, and the tubes disposed in one or more of them.
Referring to
The channels 68 (at the bottom thereof) have a turning radius of approximately 3.2 mm to form the curve in the U-shape. This is much larger than the prior art radius of the pin, which reduces the possibility of kinks within the string 22 at the string bearing assembly 44, distributes bending stress over a longer length of the string and therefore prolongs string life. The channels 68 are preferably arcuate (as shown in
While at least one channel 68 should be provided when only one pair of string segments 22 extends into cavity 34, the preferred configuration has multiple pairs of string segments 22 extending into the cavity 34 as shown in FIG. 4. In this case, the channels 68 are spaced apart from each other along a width “w” (shown in
The channels 68 are preferably uncovered so that the strings 22 can extend from the string bearing assembly 44 and out of a hole 100 on the butt end 98 of the racquet (shown on
Referring to
The pin (28 mm long) is preferably longer than the width w of the string bearing assembly (15 mm) for securing to walls 96. However, the pin 74 could just as easily be secured to the inner sidewalls 36, instead of the front/back walls 96, as shown in dashed line 99 on FIG. 8. In this case, the direction of the width w of the string bearing assembly 44, and in turn, the direction of the spacing of the predetermined lateral positions, would be along w2, or parallel to the string bed plane P, rather than perpendicular to P along w1. In alternative embodiments, pin 74 need not extend all the way across the cavity 34, and may be limited to crossing at least one of the junctures of the string bearing assembly aperture 72 and the cavity walls 36 or 96.
Referring to
The string bearing assembly 44 is preferably made by injection molding of nylon 11 and 30% injected fiber glass whiskers (chop-fibers). Of course, any material that can withstand the tensioning of the strings, typically 30 lb. per string segment, will suffice.
Referring to
Referring to
The heat during one tube extrusion process adheres pairs of extruded adjacent tubes 42 to each other. This prevents further slapping and collisions at least between the two adjacent tubes, and reduces vibration against each other. It also provides further rigidity or stiffness to the tubes 42 for maintaining a predetermined alignment of strings at opening 24 for placement into a pre-selected string pattern. Thus, it will be appreciated that any number of the tubes 42 may be adhered together, including in one alternative for racquet 10 where all four tubes extending from a first side 86 of the string bearing assembly are adhered together and all four tubes 42 extending from a second side 90 are separately adhered together (FIG. 9A).
Referring to
Tests were performed that show that the tubes 42 do in fact dampen vibration. In one test, a Koss microphone was placed under the strings of a racquet near the center of its string bed to identify sound waveforms caused by vibration when the racquet was struck with a ball dropped 50 inches from the racquet to simulate a strike during play. The racquet was clamped to a holding structure so the racquet frame would not vibrate. The microphone was connected to a computer that was using a REALAUDIO™ spectrum analyzer and a sound card. A number of trials were performed with varying striking forces. Typical resulting waveform patterns are shown on
In the data for both the racquet with the tubes 42 (graphed on
As can also be seen by comparing
In contrast, the undampened racquet (
To verify the results of the microphone tests shown in
The X axes of the graph of
In the undamped racquet (
The racquet filled with tubes according to the invention (
Thus, the tubes 42, as made preferably with polyurethane of Shore ‘A,’ durometer reading of 65 provide much improved vibration dampening characteristics that will reduce wear on a players hand and arm and provide more comfort during play. However, any other material that provides similar dampening characteristics while having the capabilities for guiding strings 22 can be used. It will also be appreciated that the durometer, dimensions and type of material can be varied for tubes from string to string or along the length of a single tube (or on a line of separate tubes on a single string 22) in order to intentionally vary the dampening characteristics for particular strings or particular sections of strings.
Referring to
As an alternative, not every tube needs to be colored or covered with indicia. The coloring may only be on exit segment tubes or entry segments or specific individual tubes. In addition, the tubes may merely be colored or printed with indicia on a segment or end of the tube rather than the entire length of the tube.
Such an indicium for a tube 42 indicates a specific predetermined routing order to place a long string or string segment 22 at a particular location within string bed 30. This maintains a selected or predetermined string bed pattern while preventing tangling or twisting together of string segments 22 as they emerge from the stem 16.
For the illustrated racquet 10, the interior surface 26a of the top of the frame 26 has hole edges 77 that define a plurality of holes 78. Each hole is encircled with an indicium or color ring 80 printed on the interior surface 26a and that corresponds to the routing order and matches the indicium or different color of a tube 42. The holes 78 receive top ends of the long string segments 22 and connect to a grommet (not shown) disposed within the frame top 26. The running of the string through the holes forms anchor points at edges 77 on the frame 12. The long string or string segments 22 either enter the frame top 26 through holes 78 from the string bed 30 or exit the frame 26 through holes 78 to reenter the string bed 30.
In one example indicia configuration, as shown on
It will be appreciated that while the corresponding hole-tube colors and corresponding exit/entry segments are the same color here, the colors may be off (i.e. different hues, brightness, etc.) or may be completely different colors that correspond based on a color table or chart provided with or on the racquet (not shown) that shows, for instance, that the string from the black tube is to be placed in the white hole, the string from the yellow tube is to be placed in a green hole, as some examples.
The indicia on the frame 14 may be other than colored rings, such as alphanumeric characters, whether of different colors or not, and may be of different objects or shapes, such as arrows either pointing toward certain holes on the frame or indicating the route of the string through the top frame portion 26.
Still referring to
Referring to
While it is preferred that every string segment 22 that enters cavity 34 engage a tube 42 due to the directing, indicia and dampening affects of the tube, it will be appreciated that not all of the entry and exit segments of the string segments 22 in the cavity 34 must be encased in tubes 42 if so desired.
The method of stringing racquet 10 can be broken down into four main steps:
The step of moving the string 94 through the string guide system 40 includes directing the string 94 through the selected tube 42 and to a particular channel 68 for positioning the string at the turning point 44. This positions string 94 at a particular or predetermined lateral position (a-d) relative to the longitudinal axis L at the string bearing assembly 44, which avoids undesired contact between strings 22.
For uncovered channels 68, the string 94 first extends through string hole 66 and continues straight toward the back end 98 of the stem 16. A stringer must then bend the string 94 to insert the end of the string back into the string bearing assembly 44 at the other end 92 of the channel 68. Once the string 94 lies within the channel 68 it is redirected in a direction pointing back toward the string bed 30.
The stringer must then push the string back through the string bearing assembly 44 and through the exit segment tube 42. Once the string emerges from the second end 76 of the exit segment tube 42, the string can be extracted from the second end until the string is taut and lays flush within channel 68. With this process, the string 94 can be strung through stem 16 without entangling or twisting string segments 22 together and while maintaining a configuration in the stem 16 that avoids any direct contact between the strings. The process then continues with the weaving into the string bed 30.
When extracting the string 94 from a tube 42, the stringer looks at the indicia of that tube (i.e. what color it is), and then looks for the hole 78 on the frame top 26 that has the corresponding color or color ring 80 in order to decide which hole to place string 90 into next. The stringer then strings string 90 through the string bed and into that hole 78 with the corresponding color.
The string guide system according to the invention is particularly advantageous when used with a “long string” racquet design like those shown in
Referring to
Referring to
Referring to
String bearing assemblies 400, 500 can be provided in many different configurations as long as the strings and tubes are positioned to avoid a pin 74 if a pin is used at all (i.e., while not preferred, the snug fit of the cavity 34 around the string bearing assembly 400 or 500 may alone create enough friction to secure the assembly, or the cavity 34 may be provided with an internal shoulder or stop longitudinally upward from the bearing assembly 400/500 to prevent upward movement thereof after strings 22 have been tensioned around it).
Also referring to
The advantages of the present racquet are now apparent. The racquet 10 has a string-guide system 40 disposed within a stem 16 of the racquet and has tubes 42 connected to a string bearing assembly 44 for guiding a string through a cavity 34 of the stem 16. This structure permits a string 22 to be guided through the cavity 34 and disposed in a configuration that avoids entanglement or twisting of strings in the cavity. The tubes 42 also dampen vibration of strings 22 and provide indicia for indicating a routing order for a particular string bed pattern.
While various embodiments of the present invention have been described, it should be understood that other modifications and alternatives can be made without departing from the spirit and scope of the invention, which should be determined from the appended claims.
| Number | Name | Date | Kind |
|---|---|---|---|
| 2089118 | Fritsch | Aug 1937 | A |
| 2165701 | Goerke | Jul 1939 | A |
| 4203597 | Reedhead et al. | May 1980 | A |
| 4333650 | Soong | Jun 1982 | A |
| 4437662 | Soong | Mar 1984 | A |
| 4613138 | Haythornthwaite | Sep 1986 | A |
| 4634124 | Yuhas et al. | Jan 1987 | A |
| 4826167 | Lo | May 1989 | A |
| 4828259 | Davis | May 1989 | A |
| 4875679 | Movilliat et al. | Oct 1989 | A |
| 4909511 | DeVille et al. | Mar 1990 | A |
| 4919438 | Yoneeyama | Apr 1990 | A |
| 4983242 | Reed | Jan 1991 | A |
| 5039096 | Chen | Aug 1991 | A |
| 5048830 | Lo | Sep 1991 | A |
| 5054779 | Marrello | Oct 1991 | A |
| 5071125 | Shen | Dec 1991 | A |
| 5096194 | Yong et al. | Mar 1992 | A |
| 5098098 | Petralia | Mar 1992 | A |
| 5100136 | Chen | Mar 1992 | A |
| 5106086 | Acosta | Apr 1992 | A |
| 5133552 | Feeney et al. | Jul 1992 | A |
| 5135223 | You | Aug 1992 | A |
| 5137273 | Jseng | Aug 1992 | A |
| 5141228 | Soong | Aug 1992 | A |
| 5174568 | You | Dec 1992 | A |
| 5197732 | Lanctot | Mar 1993 | A |
| 5211397 | Davis et al. | May 1993 | A |
| 5290031 | Natsume | Mar 1994 | A |
| 5306004 | Soong | Apr 1994 | A |
| 5374057 | Lai et al. | Dec 1994 | A |
| D368749 | Severa et al. | Apr 1996 | S |
| 5919104 | Mortvedt et al. | Jul 1999 | A |
| 6027420 | Soong | Feb 2000 | A |
| 6062994 | Grimes et al. | May 2000 | A |
| 6432005 | Lin | Aug 2002 | B1 |
| Number | Date | Country |
|---|---|---|
| 2056288 | Mar 1981 | GB |
