Patent Publication Number: US-3874667-A

Title: Die-cast light-metal racket and stringing means therefor

Description:
United States Patent [191 Gallagher et al.  
 [451 Apr. 1, 1975 DIE-CAST LIGHT-METAL RACKET AND STRINGING MEANS THEREFOR [75] Inventors: Peter Christopher John Gallagher;  
 Gerald R. Kotler, both of l-lightstown, NJ.  
 [73] Assignee: N L Industries, lnc., New York,  
  22 Filed: Dec. 26, 1973 21 Appl. No.2 427,515  
  Related U.S. Application Data [62] Division of Ser. No. 279,166, Aug. 9, 1972, Pat. No.  
 [52] U.S. Cl. 273/73 D, 273/73 H [51] Int. Cl. A63b 51/00, A63b 49/12 [58] Field of Search 273/73 R, 73 C, 73 D, 73 F, I 273/73 G, 73 H, 73 K [56] References Cited UNITED STATES PATENTS 1,548,134 8/1925 Gallaudet 273/73 H 1,954,327 4/1934 Panker 273/73 D 2,610,056 9/1952 Lovell 273/73 D 3.582.073 6/1971 Melnick et al.....  
 Wilkens 3,642,283 Latham et a1 273/73 H X Primary Examiner-Richard J. Apley [57] ABSTRACT A metal tennis racquet is die cast so as to incorporate independent stringing means within the frame head. The stringing means may comprise a multiplicity of spaced eyelets partially cast into the frame head, or a sinuous wire annulus of spaced and alternating crests and troughs, the troughs being cast into the frame head and the crests receiving the racquet string. Either form of stringing means may be connected to a metal band of the same general size and shape as the frame head, which band is cast into the frame.  
 3 Claims, 6 Drawing Figures DIE-CAST LIGHT-METAL RACKET AND STRINGING MEANS THEREFOR BACKGROUND Metal racquets, particularly for tennis, but also for similar games such as badminton and squash, have be come quite popular. Many players find them easier to handle than conventional wooden racquets and capable of providing a greater thrust to a ball, for a given stroke, than does a wooden racquet.  
  The variety of shapes, sizes and compositions now on the market is almost endless. Generally, metal racquets are formed by an extrusion process although recently some manufacturers have turned to casting. In either method, the formation of the stringing apertures has proved to be the most difficult and perhaps most expensive step. In some racq uets, holes are simply drilled into the frame head. These holes must be either machined to a fine finish, or filled with grommets, as an unmachined or roughly drilled hole will abrade the strings causing them to break long before their expected life span. The present invention completely eliminates the need for machining or filling the holes inasmuch as the stringing means are, at least initially, not part of the frame head.  
  Most prior art metal racquets are strung in the conventional manner; similar to threading a shoelace in a shoe. Racquets strung thusly rely completely on the racquet frame to supply the stroking force. The present invention provides an additional power factor in that the stringing means acts essentially independently of the frame. It is capable of elastically flexing producing a trampoline&#34; effect.  
  A further aspect of the prior art metal racquets merits discussion. Most racquets presently in production are fabricated from a steel or aluminum alloy. Steel racquets provide sufficient flexibility but tend to vibrate greatly. Aluminum racquets are rather stiff under most playing conditions in spite of their relative lightness. The tennis racquet of the present invention, comprises die cast magnesium which provides a very vibration-resistant racquet with adequate flexibility for power, and acceptable control.  
 SUMMARY A primary object of the present invention is the provision of a metal tennis racquet having independent stringing means.  
  Another object of the present invention is the provision ofa metal tennis racquet which is produced by die casting and requires little or no machining.  
  Yet another object of the present invention is to provide a metal tennis racquet of superior playing characteristics by means of a simple and inexpensive process.  
  A metal tennis racquet of conventional shape and weight is produced by a die casting process, the metal used being preferably magnesium. The stringing means of the racquet is produced independently of the racquet frame.  
  The stringing means may be any one of four different embodiments. Thus a series of spaced eyelets may be castdirectly into the frame or the eyelets may first be secured to a metal band which is then cast into the frame. Alternatively, a sinuous wire annulus having crests and troughs may have its trough portions cast directly into the frame or first secured to a metal band which is then cast into the frame. The racquet is then conventionally strung through either the eyelets or the crests of the sinuous wire annulus.  
 DESCRIPTION OF THE DRAWINGS FIG. 1 shows a completed cast tennis racquet incorporating the stringing technique of the present invention.  
  FIG. 2 illustrates a perspective view of a fragment of a preferred embodiment stringing means.  
  FIG. 3 illustrates a perspective view of a fragment of an alternative stringing means.  
  FIG. 4 is a schematic transverse sectional view of the die showing the casting of the preferred stringing means into the racquet frame.  
  FIG. 5 is a schematic perspective view of the die showing the alternative embodiment stringing means as it protrudes from the die during the casting procedure.  
  FIG. 6 is a cross sectional view of the completed racquet frame taken along the line 66 of FIG. 1.  
 PREFERRED EMBODIMENT OF THE INVENTION FIG. 1 illustrates a conventional type tennis racquet 10, characterized by handle 12, neck 14 and head 16 sections. There is virtually no limitation on the acceptable shapes of the preceding sections other than those limitations which assure adequate structural characteristics for demanding playing conditions. Specifically, the head 16 can be the standard oval shape, or the very contemporary and popular round shape. The neck 14 may be a solid bar, similar to conventional wooden racquets, or may be fabricated as two parallel rails with a substantial space therebetween.  
  The metal racquet of the instant invention is produced by a die casting process, the preferred metal used being magnesium. Magnesium has been little used for tennis racquets heretofore but possesses favorable characteristics for such use. As a particularly light metal, a metal racquet can now be designed with a substantial frame (similar to wood racquet frames) without proving to be too heavy for most players. Another characteristic of magnesium is its vibration absorbtive ability. None of the metals currently popular for use as tennis racquets are as absorbtive of vibrations as magnesium. This would permit a player to powerfully stroke a ball without the undesirable vibrations attendant with most contemporary metal racquets. 7  
  FIG. 2 is illustrative of the preferred stringing means employed by the instant invention. The preferred stringing means 18 comprises a metal base or band 20 with a multiplicity of spaced eyelets 22 attached thereto. The preferential manner of attaching the eyelets 22 to the metal band is by spot welding. The eyelets 22 are characterized by elongated stems 24 and eyes 26 unitarily connected to said stems, said eyes 26 being adapted to receive the strings of the racquet.  
  FIG. 3 illustrates alternative stringing means 28. This embodiment is characterized by a metal band 30 and a sinuous stringing wire 32 connected thereto. The sinuous stringing wire comprises a series of crests 34 and troughs 36, the crests being adapted to receive the tennis racquet strings. The troughs are adapted to be connected to the band 30 preferably by spot welding.  
 Referring now to FIGS. 4 and 5, the manner of connecting the stringing means 18 and 28 respectively to the racquet frame head 16 is shown. A conventional two part die 38 is shown in diagrammatic form with numeral 40 indicating the parting line. The die has a casting interior 41 shaped to define the racquet frame head 16. Prior to pouring the molten magnesium into the die cavity 41, the metal band of the stringing means 18 or 28, as the case may be, is bent to generally conform to the shape of the frame head 16 and placed within the die cavity. When using the metal band with eyelets 22, the die is provided with a series of spaced holes 42 at the parting line of the die which permit relatively short portions of the stems 24 of the said eyelet 22 to protrude therefrom inwardly toward the center of the racquet head 16. The band is arranged with the plane of its major axis substantially perpendicular to the plane of the stringing area. The molten magnesium is then die cast into the die cavity and upon solidification, the metal band 20 and most of the stem portions 24 of said eyelets are irremovably cast into the racquet frame head 16. It should be noted that it is possible to proportion the lengths of the stems 24 of the eyelets such that the portions protruding from the die are short or relatively long, as the case may be. The longer the stem portions, the greater will be the flexing of the stems 24 during play with an attendant increase in power. Worth indicating at this point, is the fact that in lieu of the metal band 20, the individual eyelets 22 may be located in the die by placing the stems of the individual eyelets 22 in the holes 42 at the parting line of the die. Upon casting, the eyelets will be individually captured within the metal frame head and provide a tennis racquet hav- .;ing similar playing characteristics.  
  Another aspect of the use of the eyelets 24 is worthy of note. As shown in FIG. 2, the stems of the eyelets are all assembled substantially perpendicular to the metal band. Hence, upon casting and then stringing the racquet, the racquet strings 44 will not all be linear with the stems 24. This will produce a bending moment about the point 46 ofjoinder between each stem 24 and the metal band 20. This moment is not sufficient to alter the superior playing characteristics of the racquet. However, it is possible to avoid this situation by initially securing the eyelets 22 to the metal band 20 at preselected angles, such that when the band is bent into the oval or circular shape of the frame head, all strings are linear with respect to the eyelet stems 24. Where it is decided not to use the metal band 20, the holes 42 at the parting line of the die may be formed at the preselected angles which will permit substantial alignment of the stems 24 of the eyelets 22 with the racquet strings 44.  
  Turning now to the embodiment shown in FIG. 5, the wire 32 is shown assembled in the die cavity 41 just prior to casting the molten magnesium. As seen, the troughs 36 are completely within the die cavity 41 whereas the crests 34 are completely outside the die. A  
 plurality of properly spaced holes 48.are formed at the parting line of the die to accomodate the sections of wire joining the troughs and crests. The sinuous wire 32 may also be combined with the metal band 30. In either case, the molten magnesium is then introduced into the die 38 capturing the troughs 36 of the wire therewithin.  
  In all the various embodiments previously described, little or no machining is required in the production of the finished product. Specifically, the most critical part of the racquet as far as machining is concerned, the stringing means, needs no machining at all. There are no burrs or rough edges to abrade the string inasmuch as the stringing means is not a part of the casting process. The stringing means, as initially provided, is capable of immediate stringing, and no drilling or other finishing steps need be done in the manufacture of a playable racquet. The playing characteristics of the embodiments described herein are superior to those of contemporary racquets which have stringing holes formed in the frame head. The stringing means of the instant invention extends inwardly of the inner periphery of the frame head. It is therefore capable of flexing upon the impact of a ball on the strings. The elastic reaction of the stringing means imparts an additional thrust to the ball as it leaves the strings. As heretofore stated, the absorbtive capabilities of magnesium permit a player to produce powerful strokes with minimal aftershock.  
  While the above description and appended claims have been limited to tennis racquets, it should be understood that this invention is equally applicable for other similar racquets for games such as squash and badminton. Additionally, various changes may be made in the details of the instant invention without departing from the spirit and scope of the appended claims.  
 We claim:  
  1. A die-cast, light-metal playing racquet comprising: a curvalinear head portion having a solid metal cross section and constructed and arranged to enclose a stringing area; a handle integral with said head portion; and stringing means comprising a separate implant encapsulated by said solid metal head portion, said implant consisting of a metal band conforming substantially to said curvalinear head portion and arranged with the plane of its major axis substantially perpendicular to the plane of said stringing area, and a plurality of individual string receiving members fastened to said metal band in spaced relationship therearound, said string receiving members comprising wire loops arranged to protrude from said head portion inwardly into said stringing area and in the plane thereof.  
  2. A die-cast, light-metal playing racquet according to claim 1 wherein said wire loops comprise the crests of a sinuous wire the troughs of which are fastened to said metal band.  
  3. A die-cast, light-metal playing racquet according to claim 1 wherein said wire loops comprise eyelets having stems fastened to said metal band.