Abstract:
A racket and method of making same structured with a wide throat spanned with a structural member and the racket having a multi-thickness honeycomb core joined together with and encased in reinforced plastic. A plastic strip with a plurality of integral grommets inserted in the head of the racket has a reduced area between grommets.

Description:
BACKGROUND OF THE INVENTION 
     Rackets such as a tennis racket require characteristics of longitudinal bending rigidity and torsional rigidity to stand up under loads imparted when in use. In addition, the head of the racket must not give or warp due to the tension imparted by stringing. Historically wood has been used for racket structure, however, more recently metals and combinations of metal and reinforced plastics are being used. U.S. Pat. No. 3,702,701 utilizes an extruded metal frame with a molded plastic throat. U.S. Pat. No. 3,690,658 utilizes shaped metal face sheets covering layers of elastomeric material and a syntactic foam core. 
     It was discovered a racket utilizing honeycomb core material covered with a resin impregnated reinforcement gives excellent racket characteristics. 
     SUMMARY OF THE INVENTION 
     A tennis racket with a wide throat formed by arms extending from the handle to a head or essentially oval shaped frame. A reinforcing member extends between the arms across the throat. All of the structure areas of the racket have an integral honeycomb core with open cells of the core extending between the faces of the racket, and a reinforced plastic edge closure cover. Preferably, the honeycomb core is made up with two or more thicknesses or layers of honeycomb with a bonding layer of a plastic between the layers of honeycomb. All bonding layers or encasement of plastic are firmly bond to the honeycomb, but do not fill the cells. A thermosetting resin advanced to the B-stage may be used to assure a good bond without flowing into and filling the cells. 
     A strip of plastic with a plurality of grommets extending normal thereto has reduced areas between grommets. The grommets extend through the head of the racket and the reduced area in the strip prevents the build up of stresses. 
     An object of this invention is to provide a lightweight racket with outstanding torsional rigidity, longitudinal bending characteristics and dimensional stability. 
     Another object of this invention is to provide a racket with an integral honeycomb core. 
     It is yet another object to provide a strip with grommets for use in a racket without building up stresses in the strip. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a plan view of the racket of this invention. 
     FIG. 2 is a cross sectional view of the handle area of the racket taken along lines 2--2 of FIG. 1. 
     FIG. 3 is a fragmented plan view of the handle partially cut away. 
     FIG. 4 is a cross sectional view of the head area of the racket taken along lines 4--4 of FIG. 1. 
     FIG. 5 is a fragmented plan view of the head partially cut away as viewed from 5--5 of FIG. 4. 
     FIG. 6 shows a section of a throat reinforcing member taken along lines 6--6 of FIG. 1. 
     FIG. 7 shows a plan view of a different embodiment of the racket of FIG. 1. 
     FIG. 8 is a sectional view taken along lines 8--8 of FIG. 7. 
     FIG. 9 is a sectional view as in FIG. 8 but of another embodiment. 
     FIG. 10 shows a plan view of yet another embodiment of the racket of FIG. 1 without showing the handle cover. 
     FIG. 11 is a sectional view taken along lines 11--11 of FIG. 10. 
     FIG. 12 shows a sectional view taken along lines 12--12 of FIG. 10. 
     FIG. 13 shows a plan view of a plastic strip with integral grommets prior to placing the strip in the racket of FIG. 10. 
     FIG. 14 shows a side elevational view of the strip with grommets of FIG. 13. 
     FIG. 15 shows a side elevational view of a cover for the handle area of FIG. 10. 
     FIG. 16 is a sectional view taken along line 16--16 of FIG. 15. 
    
    
     DETAILED DESCRIPTION 
     Racket 10, has handle 12, throat section 14 and head or oval frame 16. The throat 18 is defined by a pair of arms 20a and 20b which extend from the handle to opposite sides of the head. A reinforcing member 22 extends across the throat from arm to arm. The spacing of the arms provides a wide throat and the stabilizing cross member combines with the arms to yield extreme torsional resistance to off-center hits and provide accuracy in hitting an object where the racket is aimed. The arms preferably extend essentially straight to merge on a tangent with the outside periphery of the oval frame and the depth 24 of the throat preferably extends at least a third of the distance from the end of the handle 26 to the closest part 28 of the oval frame. 
     The entire structure of the racket 10 has an integral core 30 of honeycomb material, preferably of a metal such as aluminum. This may be a single thickness of honeycomb or may be in two or more layers of honeycomb with three layers preferred as shown at 30a, 30b, and 30c in FIGS. 2 through 6. The layers of honeycomb are bonded together with a layer of an adhesive, preferably a structurally reinforced resin or plastic at 32a and 32b, and the core is entirely encased in reinforced plastics made up of face sheets 34a and 34b and side covering sheets 36a and 36b. The encasing material is integral throughout the racket. In FIG. 4 the face sheets extend past side covering sheet 36a at 38a and 38b. A plastic material 40 preferably a high wear resistant plastic material such as polyethylene, polyurethane, or acrylo nitrile butadiene styrene is integrally bonded into the recess formed around the exposed outer periphery 42 of the head which essentially extends from arm 20a to 20b. In the handle, see FIG. 2, the encased honeycomb core is covered first with a foamed plastic 44 which in turn is bonded to a cover material 46 to form the grip for the handle. The outer dimensions may be varied to fit the requirements for various sized persons and bonded to the encased honeycomb core. The head 16 has netting 48 stretched across to form the contact surface for a ball being hit. This netting or strings may be of stretched gut, nylon, etc. In FIGS. 4 and 5 grommets 50 protect the strings when passing through the sides of the racket and the strings are recessed at 52 to prevent damage from abrasion. 
     In FIGS. 7 through 9 is shown a different embodiment of the invention. The racket 54 varies by having a recess 56 which extends around the outer periphery 58 of the head 60 of the racket in the exposed part of the head. This recess protects the strings 62 from abrasion. Grommets may be used but are not shown in this embodiment. In these figures a preferred embodiment is shown with the honeycomb core made up of three layers 64a, 64b and 64c wherein the middle layer 64b is narrower than the two outside layers. The honeycomb layers are bonded with reinforced plastic layers 66a and 66b. Face sheets 68a and 68b extend at 70a and 70b to form the recess 56 around the outer periphery of the head. Sides 72a and 72b in conjunction with the face sheets encase the honeycomb core. An additional layer of cover material 74 is bonded into but does not fill the recess. FIG. 9 shows yet another preferred embodiment with a recess 56a formed with a channel or U-shaped member 76 bonded around the outside of the exposed part of the head at 78. This U-shaped member is preferably of a resilient material such as polyurethane, but it is not intended to be limited to that material. The honeycomb core in layers 80a, 80b, and 80c is bonded to layers 82a and 82b, and also bonded to and encased in reinforced plastic 84. The bonding layers and the covering layers in all the figures are shown as a single thickness, however, this finished single layer may be made up of several layers of reinforcement such as but not limited to fiber glass with unidirectional, bi-directional or random layers of fiber integrally bonded with a resin such as but not limited to a epoxy resin. 
     FIGS. 10 through 16 show yet another embodiment of this invention. Racket 86 with head 88, throat area 90 and handle area 92 shows the outside periphery of the head to be recessed at 94 around the exposed outer periphery. The racket has an integral honeycomb core in three layers 96a, 96b and 96c with the middle layer 96b preferably thinner than the other two layers. The honeycomb may be conventional with cell openings as shown here at 90° to the face or may extend with openings at 45° to each other, however, with either type the cell openings in the honeycomb extend toward the faces of the racket. The layers of honeycomb are bonded together with structurally reinforced resin at 98a and 98b. These layers bond the honeycomb together without filling the cells of the honeycomb. Side enclosing layers 100a and 100b and face enclosing layers 102a and 102b all of reinforced plastic combine to completely encase the core. In the exposed part of the head area, as best shown in FIGS. 10 and 12 the face sheets 102a and 102b extend outward at 104a and 104b, respectively, to form a side reinforcement for a filler 106 of a thermoplastic resin such as but not limited to acrylo nitrile butadiene styrene or polyethylene. The filler does not completely fill the space, but instead leaves the recess 94. A plastic strip 108 with a plurality of integral grommets 110 is placed in the recess. The grommets extend inwardly and normal to the outer periphery of the racket head. The plastic strip has an S-shaped area 112 between each grommet to provide a reduced area to allow bending of the strip while inserting the grommets without setting up stresses. The S-shape made up with a thin transverse member joined at opposite ends to alternate grommet sections provides complete flexibility between grommets. 
     The handle area 92 of the racket 86 is shown in FIG. 11 with the honeycomb encased core having additional side reinforcing members 114a and 114b. All four corners 116 of the encased core are preferably bevelled at 45° as shown. In this embodiment the handle cover 118 is a sectionalized or an integral cover that is slipped over the handle end of the racket and bonded thereto. The cover comprises outside layer 120 with integral inwardly extending ribs 122a and 122b, and 124a and 124b. 
     The honeycomb being arranged with the longitudinal axis of the cells extending toward the faces of the racket provides longitudinal bending resistance while at the same time imparting a dampening effect to prevent shock with attendant arm fatigue in a person using the racket. The layers of resin between thicknesses of honeycomb assist in the dampening, by breaking up the honeycomb cell walls into smaller shear panels and impart side compression capability to the core to resist forces set up in the head due to tension in the strings.