FIELD OF INVENTION The present invention relates to grommet strips for tennis racquets and other types of sports racquets.

BACKGROUND OF THE INVENTION

Conventionally, tennis racquets have a head portion which, either alone or together with a throat bridge piece, defines a strung hitting surface. A plurality of string holes are formed in the head portion, and an elongated string is threaded sequentially through the string holes to form a plurality of main (longitudinal) string segments and interwoven cross string segments. The frame is normally formed with a stringing groove along the outer periphery of the head portion of the racquet, so that the connecting portions of the string, i.e., the portions that connect one string segment with the next, and which lie on the outer side of the stringing holes, are disposed in the stringing groove. This acts to protect the strings from abrasion in the event that the racquet frame hits against the ground or another object. It is also conventional in present day tennis racquets to utilize plastic grommet strips as seats for the strings in the string grooves. Grommet strips include grommet pegs that extend through the string holes, and connecting strips that lie along the bottom of the stringing groove. The grommet strips act to protect the string and also, in the case of composite racquets, prevent the string from biting into the frame material.

In the case of frames made of composite materials, i.e., fiber-reinforced resins, a pair of grommet strips are provided along the opposite sides of

the frame with a thin connecting strip disposed within the stringing groove. At the outer tip region of the frame, the grommet strip, in addition to having the connecting strip lying within the stringing groove, also has a pair of flanges that extend to either side of the stringing groove and overlie the outer surfaces of the frame. These parts, which are usually referred to as bumper strips, not only act as a seat for the connecting segments of the strings, but also protect the outer surface of the frame from damage from accidental impact with the ground or other surfaces. For purposes of the present application, bumper strips and grommet strips shall generically be referred to as grommet strips.

In conventional stringing systems, the string holes lie within the stringing plane and extend generally perpendicular to the outer surface of the racquet. It is thus possible to mold grommet strips flat, with the grommet pegs oriented perpendicular to the connecting strip. When the grommet strip is bent to conform to the curved shape of the racquet head, the grommet pegs will be angled so as to extend inwardly toward the center of the strung surface, and thus will align themselves with the string holes in the frame.

Commonly owned application Serial No. 989,267, filed concurrently herewith [Docket No. 1135928-385], discloses a double strung sports racquet in which the string holes, rather than lying within the stringing plane, extend from the stringing groove through the frame at an angle, e.g., of 45°, relative to the central stringing plane. The two angled surfaces of the stringing groove are arranged at about a 45° angle relative to the central plane, and a series of stringing holes extends generally perpendicular to each of the angled side wall surfaces through the frame. The holes exit the opposite

frame surface to define holes for two, generally parallel stringing surfaces.

Because of the angle of the string holes, it would not be possible to utilize a conventional grommet strip. Assuming even that the grommet pegs could be forced through the angled holes, the connecting grommet strip would not lie flush against the angled stringing groove surface.

The double strung racquet disclosed in application Serial No. 989,267 [Docket No. 1135928-385] includes a throat bridge, which has two corresponding series of holes that diverge at an angle from the center plane. The inner openings of the holes, and the outer openings of the holes, are aligned across the throat bridge, and the holes extend in planes parallel to the racquet axis. However, not only is the outer surface of the throat bridge curved, but due to the differing lengths of the string holes, the diverging angle of the string holes varies. For these reasons, conventional throat grommet strips cannot be used in such a racquet. It would thus be desirable to provide grommet strips that can accommodate varying string hole angles, such as in the racquet disclosed in application Serial No. 989,267 [Docket No. 1135928-385], but also in other racquets where the string holes extend from angled surfaces.

SUMMARY OF THE INVENTION

The present invention relates to grommet strips for a sports racquet. In one preferred embodiment, a grommet strip has a flat, bendable connecting strip and a plurality of grommet pegs extending from the lower surface of the strip perpendicular thereto. The axis of the connecting strip is curved, and the grommet pegs are disposed along the curve, such that the axes of the

grommet pegs are parallel but do not lie in the same plane as one another. In this manner, the connecting strip may be bent to lie flat against a conical surface defined by two parallel planes perpendicular to the axis of the cone, and the grommet pegs will project inwardly at an angle relative to said planes. The grommet strip may be used where the string holes are disposed at an angle relative to the center plane of the stringing surface, such as in a double strung racquet where the stringing holes extend from the angled surfaces of the stringing groove.

The conical surface may have a radius which varies therealong. If such is the case, the curve defining the connecting strip has a radius of curvature which varies as a function of the conical surface radius. In an alternate embodiment, a flange extends from one of the edges of the connecting strip, so as to act as a bumper guard on one side of the frame.

The grommet strips according to the invention are preferably utilized in combination with a sports racquet, preferably a tennis racquet, of the type in which the frame head portion has an outwardly facing frame surface disposed at an angle other than 90° to said central plane, such that the frame surface constitutes part of a conical surface defined by two parallel planes perpendicular to the axis of the cone. The head portion includes a plurality of stringing holes extending inwardly from the frame surface in a direction generally perpendicular to said frame surface. Thus, when the connecting strip is bent to lie flat against the frame surface, the grommet pegs project through the stringing holes.

A grommet strip according to the invention is most preferably intended for use with a double strung racquet which includes a stringing groove including a

pair of angled side wall surfaces disposed on opposite sides of the central plane at an angle of less than 180° relative to one another. A first series of string holes extends from one of the side wall surfaces and a second series of string holes extend from the other side wall surface. The first and second series of string holes diverge from said central plane at opposite angles.

Preferably, a pair of grommet strips are disposed along each of the opposed sides of the head portion, one for each series of holes, and a pair of additional grommet strips are disposed along the outer tip region, one for each series of holes. The grommet strips for the outer tip region each have a flange extending outwardly from one edge of the connecting strip, which acts as a bumper guard to cover one side of the outer frame surface.

Another embodiment of a grommet strip is designed especially for a curved throat bridge of a sports racquet having string holes which lie in planes parallel to the racquet axis, but extend at an angle to the center plane of the stringing area, and in which the inner ends of the holes are located in the same plane. The grommet strip comprises a connecting strip and a plurality of parallel grommet pegs extending from the upper surface of the strip. The upper surface of the strip, in the longitudinal direction, is in the shape of a convex curve to follow the curvature of the throat bridge and in cross section is bevelled at an angle relative to the grommet pegs corresponding to the angle of the stringing holes. In addition, the connecting strip axis is curved, and the grommet pegs are disposed along the curve, such that, as in the case of the prior embodiments, the grommet pegs are parallel but do not lie in the same plane as one another.

Preferably the ends of the strings are tied off in the stringing groove, rather than on the inside of the strung surface 14, as is customary. In order to do so, the grommet strips are provided with a tie-off system located in the stringing groove. More particularly, the tie-off system includes one or more raised portions on the grommet strip, which allow a string to pass over the raised portion and leaves an interstitial area below the string which can be used to tie off another string. In the exemplary racquet employing the grommet strips of the invention, the angle of the string holes in the lower corners of the racquet differs from adjacent string holes, due to the additional thickness of the throat joint between the head portion and throat bridge. In order to accommodate the holes in the corners, a joint is formed between the main portion of the connecting strip and the end of the connecting strip supporting the corner grommets. The joint allows the end portion of connecting strip to rotate and pivot as necessary to orient the corner grommet pegs at the correct angle. For a better understanding of the invention, reference is made to the following detailed description of a preferred embodiment, taken in conjunction with the drawings accompanying the application.

BRIEF DESCRIPTION OF THE DRAWINGS

Figs. 1 and 2 are front and side views, respectively, of a tennis racquet in which the present invention may be utilized; Fig. 3 is a front view of the head portion of the racquet, showing the location of string holes;

Fig. 4 an enlarged sectional view of the throat piece of the racquet, taken through lines 4-4 of Fig. 3;

Fig. 5 is an enlarged sectional view of the throat potion of the racquet, taken through lines 5-5 of Fig. 1;

Fig. 6 is an enlarged sectional view of the shaft of the racquet, taken through lines 6-6 of Fig. 1;

Fig. 7 is an enlarged sectional view of the racquet handle, taken through lines 7-7 of Fig. 1;

Fig. 8 is an enlarged sectional view of the joinder region between the head portion and throat piece, taken through lines 8-8 of Fig. 3;

Fig. 9 is an enlarged sectional view of the head portion of the racquet, taken through lines 9-9 of Fig. 3;

Fig. 10 is an enlarged, front view of the junction of the throat bridge and head portion of the racquet of Fig. 1;

Fig. 11 is a sectional view, taken through lines 11-11 of Fig. 10;

Figs. 12-14 are bottom, side and top views, respectively, of a grommet strip in accordance with the invention;

Figs. 15-17 are bottom, side, and end views, respectively, of a grommet strip including a bumper guard in accordance with the invention; Fig. 18 is an axial end view of the grommet strip of Fig. 15;

Fig. 19 is a cross-sectional view of the bumper strip of Fig. 15, taken through lines 19-19 of Fig. 15;

Fig. 20 is an enlarged, sectional view of the racquet head, taken through lines 20-20 of Fig. 3, and further showing the grommet strip of Figs. 12-14 and stringing;

Fig. 21 is an enlarged view, taken in the direction of lines 21-21 of Fig. 3, showing a string tie- off location;

Fig. 22 is an enlarged view, taken in the direction of lines 22-22 of Fig. 3, showing another string tie-off location;

Figs. 23-26 are front, side, top and bottom views, respectively, of a throat grommet strip according to the invention; and

Fig. 27 is an enlarged sectional view, taken through lines 27-27 of Fig. 23.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Exemplary embodiments of grommet strips according to the invention will be described in connection with the double strung tennis racquet shown in the drawings.

Figures 1 and 2 illustrate a tennis racquet which includes a frame 10 having a frame head portion 12 defining a stringing area 14. A throat bridge 18 spans the throat area to enclose the lower end of the stringing area 14. A pair of opposed frame throat portions 16 extend from the head portion 12 and converge to extend side-by-side and form a shaft 20, as shown in Figure 6. A portion of the shaft 20 is molded into the shape of a handle 22. The olded-in handle 22 is shown in cross section in Fig. 7.

Fig. 9 shows the general configuration of the cross section of the head portion 12. As shown, the head portion 12 has a generally convex surface 24 which faces inwardly toward the stringing area 14, and an outwardly facing stringing groove 26. The stringing groove 26 includes a pair of angled side wall surfaces 28 disposed on opposite sides of the central plane 30 of the stringing area. The side wall surfaces 28 are preferably disposed at an angle of less than 180° relative to one another, as shown.

The head portion 12 includes a plurality of string holes therethrough, including a first series of

string holes 32 lying on one side of the central plane 30, and a second series of string holes 34 lying on the opposite side of the central plane 30. As shown in Fig. 9, each string hole, 32,34 extends from its respective side wall surface 28 through the opposed convex surface 24. The two sets of string holes diverge from the central plane 30 at opposite angles, which are preferably 45° (i.e., such that the string holes 32, 34 extend at a 90° angle relative to one another) . Moreover, the wall surfaces 28 and 24 are formed at an angle such that the string holes 32, 34 are generally perpendicular to the respective surfaces. Thus, the surfaces 24, 28, in the region where the string holes are formed, are generally parallel to one another. Fig. 4 illustrates the throat piece 18 and it ^' s hole configuration. The throat piece has a generally convex surface 38 which faces inwardly toward the stringing area 14. Surface 38 preferably has the same configuration as surface 24, so that the border of the stringing area is a uniform shape. Unlike head portion 12, however, the outwardly facing surface 40 of the throat piece 18, in cross section, is preferably flat. A first series of string holes 42, corresponding to string holes 32 in the frame portion 12, lies on one side of the central plane 30, and a second series of string holes 44, corresponding to holes 34, lies on the opposite side of the central plane 30. As shown in Fig. 4, each string hole, 42, 44 extends from the convex surface 38 through the opposed outer surface 40. The two sets of string holes diverge from the central plane 30 at opposite angles, which are preferably 35°.

As can be seen in Figs. 3, 8, 10, and 11, the lower corners of the head portion 12, in the region of the throat joint 46, have a specially shaped profile. The outwardly facing stringing groove 26 continues down into

the throat joint 46. However, the inwardly facing surface 48 comprises, in cross section, a pair of shoulders 50 on opposite sides of the central plane 30 and a central boss section 50 disposed between the shoulders and extending inwardly toward the strung surface 14. As shown in Fig. 8, string holes 32a, 34a extend from each angled side wall to each of the shoulders 52.

String holes 32a, 34a diverge from the central plane 30 at an angle of approximately 35°. The shoulder sections 50 are angled so as to be generally perpendicular to the direction of the string holes. In addition to providing surfaces which are generally perpendicular to the holes 32a, 34a, the shoulders reduce the length that the string holes need to travel through the frame profile. Also, the shoulders act to space the strings in the lower corners of the racquet so as to avoid contact with the central boss section 52.

Fig. 3 shows an exemplary arrangement of string holes for one series of holes, e.g., 32, 32a, and 42, which are labelled as a ¹ through a ³⁴ . The string holes for the opposite side of the racquet are a mirror image. In the stringing arrangement shown, holes a ¹ through a ⁶ , a ⁸ , a ¹⁰ , a ²⁵ , a ²⁷ , and a ²⁹ through a ³⁴ are used for the main strings, whereas the remaining string holes are used for the cross strings, as described further below.

The racquet frame 10 may be molded utilizing known techniques. For example, if the frame is to be made of a fiber reinforced thermoset resin, a tubular profile member of, e.g., uncured fiber-reinforced resin, is placed in a mold having the shape of a racquet. A throat member is also positioned in the mold, and the throa joint is wrapped with additional fiber-reinforced resin material as needed. The mold is then closed and the profile member is internally pressurized and heated to conform to the mold and cure. Thereafter, the now formed

frame is removed from the mold and string holes are drilled. Alternatively, the frame may be formed with a fiber-reinforced thermoplastic material, as disclosed in commonly owned, co-pending U.S. application No. 07/645,255.

In the frame of Fig. 1, the holes in the head portion extend at a 45° angle relative to the central stringing plane yet are generally perpendicular to the angled surfaces 28 in the stringing groove 26. Similarly, while the string holes in the throat are parallel to one another, they are angled relative to the string plane and extend through a curving surface. Thus, conventional bumper and grommet strips could not accommodate such hole angles and at the same time remain flat against the angled surfaces 28.

A preferred embodiment of a plastic grommet strip 60 according to the invention is shown in Figs. 12-14. A preferred embodiment of a grommet strip 70 having a bumper guard is shown in Figs. 15-19. A preferred embodiment of a throat grommet strip is shown in Figs. 23-27.

A grommet strip 60 according to the invention includes a plurality of grommet pegs 62, which fit in the string holes 32, 34, and a thin, connecting strip 64. Each grommet peg 62 extends perpendicular to the connecting strip 64 and has a central longitudinal bore 66 through which a string can pass.

It is not practical to mold a plastic grommet piece on a 45° angle with all grommets pointing toward the center of curvature as required on a racquet frame. However, it is possible, by flattening out the curved portion of the cone representing surface 28, to create a two dimensional piece, in which the connecting strip 64 is flat, and the grommet pegs 62 extend normal to the connecting strip 64.

In order to make a flat, moldable piece, the shape of the connecting strip 64 is determined by considering each surface 28 of the bevelled 45° string groove 26 to represent a portion of a cone having a vertex angle of 90°. The section of the cone represented by the surface 28 is thus defined by parallel planes perpendicular to the cone axis. If this conical surface, together with the projecting grommet pegs, is flattened out, the result is a part in which, as shown in Figs 12 and 14, the axis of the connecting strip 64 is curved. As can be seen, the grommet pegs lie along the same curve, rather than in a straight line. However, all of the grommet pegs extend normal to the connecting strip surface. Such a part can be readily molded and yet, when bent to lie flat against the stringing groove surface 28, will resume the shape of the cone section and cause the grommet pegs 62 to extend inwardly at the desired angle.

If the head portion 12 of the racquet were circular, the connecting strip 64 would follow a constant curve. However, .in most tennis racquets, including the racquet shown in Fig. 1, the head is generally elliptical in shape, rather than circular. As a result, the stringing groove 26 extends about an elliptical curve. Thus, while the 45° string hole angle remains constant (except as discussed below) , the radius of curvature of the stringing groove varies at different locations of the head portion of the racquet. In order to conform the bumper strip to the stringing groove at various locations on the head, the radius of curvature of the connecting strip is varied as a function of the radius of curvature of the stringing groove so that the connecting strip 64 lies flat against the surface 28 and the grommet pegs 62 project at the desired angle.

Referring again to Figure 3, in order for string hole a ³⁰ to emerge at the desired position on the interior

side of the frame surface, due to the increased thickness of the frame at the joinder region 46, the string hole a ³⁰ extends at a different angle, in the stringing plane, than the adjoining holes, e.g. a ²⁹ and a ²⁸ . To accommodate the angle of string hole a ³⁰ , a joint 65 is provided between the main section of the connecting strip 64 and the end strip 67 holding the end grommet peg 68. This allows the end strip 67 to be rotated and pivoted as needed about the centerline 69 of the grommet strip 60 to accommodate the angle of hole a ³⁰ .

Grommet strip 70 is formed in a similar manner to grommet strip 60, using the theory of cones to define the radius of curvature of the connecting strip 72. As shown, grommet strip 70 includes grommet pegs 74, along with a bumper guard 76 that fits over the outer surface of the racquet frame. As shown in Fig. 16, the bumper guard 76 may be formed with rectangular depressions 78 or holes (which are omitted in Fig. 17 for clarity) , which can be used to reduce weight and provide an ornamental appearance. In addition, the connecting strip 72 includes a plurality of cutouts 80 adjacent to selected grommet pegs 74a. The upper surfaces 82 of the selected grommet pegs 74a are raised, as described further in connection with Figure 22. Throat grommet strips 110, one of which is shown in Figs. 23-26, are utilized in the bridge piece 18. Referring to Figs. 23, 24, and 27, the grommet strip 110 includes four grommet pegs 112 and a connecting strip 114. The grommet pegs 112 are parallel to one another but, as shown in Fig. 24, do not lie within the same plane. Also, as can be seen in Fig. 23, the connecting strip 114 is curved so that its upper surface 116 follows the curvature of the throat piece 18. Moreover, as shown in Fig. 27, the upper surface 116, in cross section, is bevelled at an angle α relative to the grommet pegs 112,

which angle α is 35° in the exemplary embodiment, such that the upper surface can be flat against the throat piece surface and such that the grommet pegs extend at a 35° angle up into the throat piece holes. Because the holes in the bridge piece, a ³¹ - a ³⁴ , are drilled in planes which are parallel to the racquet axis, the distance through the string holes 42, 44, i.e., the distance from the outer surface 40 to the inner surfaces 38, varies, being slightly greater for string hole a ³¹ than for string hole a ³⁴ . In order to accomodate the different lengths, but to allow the grommet strips to be molded parallel to one another, the connecting strip 114 is curved, as shown in Figs. 25 and 26, such that the longitudinal axis of the grommet pegs 112 also are disposed along a curve rather than a straight line.

Racquet assembly and stringing, utilizing the grommet strips of the present invention, will be described with reference to Figs. 20-22. Referring to Figs. 20 and 21, in order to string the racquet frame 10, a pair of grommet strips 60 and 60a are positioned in the stringing groove 26 along each side of the frame 10, starting above the throat. Grommet strip 60a is a mirror image of grommet strip 60, so that it is molded with opposite curvature. As discussed above, when the grommet strips 60, 60a are bent to follow the curvature of the head portion 12 of the frame, the connecting strips 64, 64a will lie flat against the surfaces 28, and the grommet pegs 62 will extend through the 45° stringing holes at the proper angle. A pair of grommet strips 70 (see Fig. 22) are then positioned in the remaining portion of the stringing groove 26, in the outer tip region of the frame, so as to extend between the grommet strips 60, 60a. Separate bumper strips do not need to be molded for the opposite sides of the stringing groove, in that the two bumper

strips 70 are merely oriented in opposite directions so as to fit the respective surfaces 28. When the bumper strips 70 are positioned in the stringing groove 26, the bumper guards 72 overlie the outer surfaces of the frame to either side of the stringing groove, thus protecting the outside of the racquet frame.

Finally, four throat grommet strips are positioned so that grommet pegs project through the holes in the throat piece 18. Two of the grommet strips are grommet strips 110, whereas the other two grommet strips are mirror images of strip 110, with an opposite curvature.

Once the grommet strips and bumper strips are in place, each strung surface 90 and 90a is strung with a plurality of interwoven main strings 92, 92a and cross strings 94, 94a (one cross string for each surface is shown in Fig. 20) .

Although the specification refers to a plurality of main and cross strings, normally a racquet is strung with only one or two long strings, which are directed from hole-to-hole and extend along the grommet or bumper strip between holes. As used herein, the terminology main strings and cross strings includes the use of an elongated string where each cross string or main string is only a segment of a longer string.

Stringing may be done with any desirable stringing pattern. As shown in Fig. 21 and 22, however, the ends of the strings are tied off in the stringing groove, rather than on the inside of the strung surface 14, as is customary. In this connection, the grommet strips and bumper strips are provided with a tie-off system located in the stringing groove. More particularly, the tie-off system includes a raised portion on the bumper strip or grommet strip that allows a string to pass over the raised portion and leaves an

interstitial area below the string which can be used to tie off another string.

An exemplary tie-off system is shown in Figs. 21 and 22. In the case of the grommet strip 60 or 60a, a raised portion 120 is formed on the connecting strip 64, 64a, in this case on the end strip portion 67. In addition, the joint 65 is disposed to the side of the strip 64, 67 so as to leave a recessed area 113 directly adjacent the raised portion 110. As shown, string portion 124, which passes between holes a ²⁹ and a ³⁰ , extends over the recessed area 113 and is supported above the frame by raised portion 120. As a result, loose string end 126 exiting from the string hole a ²⁸ can readily be tied around the string portion 124, utilizing the recessed area 113. Moreover, the raised portion 110 is provided with a groove 130. After tying the string end 126, the string end 126 is trimmed, and the remaining end inserted into the groove 130.

The grommet strip 70 similarly includes raised areas 82, over which a string portion 132 extends, which cooperate with adjacent recesses 80 formed in the connecting strip 72, to provide a tie-off area for a loose string end 134.

The foregoing represents a preferred embodiment of the invention. Variations and modifications will be apparent to persons skilled in the art, without departing from the inventive concepts disclosed herein. All such modifications and variations are intended to be within the skill of the art, as defined in the following claims.