US3815660A

US3815660A - Improved method for casting metal tennis racquet

Info

Publication number: US3815660A
Application number: US00279166A
Authority: US
Inventors: P Gallagher; G Kotter
Original assignee: NL Industries Inc
Current assignee: Farley Inc; NL Industries Inc
Priority date: 1972-08-09
Filing date: 1972-08-09
Publication date: 1974-06-11
Anticipated expiration: 1991-06-11

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.

Description

United States Patent [191 Gallagher et al.

[ June 11, 1974 IMPROVED METHOD FOR CASTING METAL TENNIS RACQUET [75] Inventors: Peter Christopher John Gallagher;

Gerald R. Kotter, both of l-lightstown, NJ.

[73] Assignee: N L Industries, Inc., New York,

[22] Filed: Aug. 9, 1972 211 Appl. No.: 279,166

[52] US. Cl 164/112, 164/332, 273/73 D, 273/73 H [51] Int. Cl. B22d 19/02, A63b 49/12 [58] Field of Search 164/98, 108, 111, 112, 164/332; 273/73 D, 73 H [56] References Cited UNITED STATES PATENTS,

678,997 7/1901 Gorton 164/111 X Duncan 164/108 X 3,664,669 5/1972 Latham et a1 273/73 D 3,731,726 5/1973 Eberle 164/112 X FOREIGN PATENTS OR APPLICATIONS 800,262 4/1936 France 273/73 H 414,345 10/1932 Great Britain 339,330 4/1959 Switzerland 164/1 1 1 Primary Examiner-R. Spencer Annear 5 7 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.

4 Claims,'6 Drawing Figures IMPROVED METHOD FOR CASTING METAL TENNIS RACQUET BACKGROUND Metal racquets, particularly for tennis, but also for similar games such as badminton and squash, have become 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 racquets, holes are simply drilled into the frame head. These holes must be either machined to a fine finish, or filled with gromets, 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 arefat least initially, not part of the frame head. I

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 act essentially independently of the frame. It is capable of elastically flexing producing a trampoline 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 spiteof 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. v I I 1 Another object of the'present invention is the provision of a 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 racquetof conventional shape and weight is produced by a die casting process, themetal used being preferablymagnesium. 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 cast directly 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 -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 6-6 of FIG 1.

PREFERRED EMBODIMENT OF THE INVENTION FIG. 1 illustrates a conventional type tennis racquet 10, characterizedby 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 structuralcharacter; istics 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 attendantfwith most contemporary metal racquets."

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 headl6. 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. Thelo'nger'the stem portions, the greater will be the flexing of the stems 24 during play with an attendantincrease 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 having 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 eachstem 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 tothe 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 joiningthe troughsand 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 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 ofa 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 after-shock.

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 maybe made in the details of the instant invention without departing from the spirit and scope of the'appended claims.

We claim: I

1. In a-method for forming a die case light-metal racquet the improvement which comprises: providing a die having a cavity corresponding in configuration to the frame head of said racquet, providing independent stringing means to be mounted in said, die cavity, said independent stringing means comprisinga substantially flat metal band having integral string receiving ele* ments extending from one flat side thereof at substantially right angles thereto, positioning saidflat metal band throughout the length of said die cavity with those portions of said string receiving elementsthat receive racquet strings extending exteriorly of said die cavity in a substantially horizontal plane and inwardly of said frame head, introducing a molten light-metal into said die cavity to fill said cavity and envelop the metal band and the portions of said string receiving elements that lie within said die cavity, and cooling said molten metal a to solidify said metal both to form a die cast light-metal frame head and simultaneously capture said independent stringing means therein.

2. In a method for forming a die cast light-metal racquet according to the improvementof claim 1 wherein the light-metal is magnesium.

3. In a method for forming a die cast light-metal racquet according to the improvement of claim 1 wherein the string receiving elements comprise eyelets having integral stems, said stems being secured to saidmetal band with the string receiving eyelets extending exterisaid die cavity with the crests of said sinuous wire extendingexteriorly of said die cavity in a substantially the finished product. Specifically, the most critical part 7 of the racquet as far as machining is concerned, the

horizontal plane and inwardly of said frame head, said frame headbeing die cast about, said metal band andv the troughs of said sinuous wire.

UNITED STATES PATENT OFFICE (:ERTWIcATE oF CORRECTION P tent 3815600 Dnted Q l llM Invent0r(s) Peter C. J. Gallagher, Gerald R. Kotler It is certified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

In (75) Inventors: of the issued patent Kotter has been changed to Kotler.

Signed and sealed this 12th day of November 1.974.

(SEAL) Attest:

McCOY M. GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents FORM PO-105O (10-69) USCOMM-DC 603704 69 u s GOVENNMEN! Pnmnur. on'lts 93 o

Claims

1. In a method for forming a die case light-metal racquet the improvement which comprises: providing a die having a cavity corresponding in configuration to the frame head of said racquet, providing independent stringing means to be mounted in said die cavity, said independent stringing means comprising a substantially flat metal band having integral string receiving elements extending from one flat side thereof at substantially right angles thereto, positioning said flat metal band throughout the length of said die cavity with those portions of said string receiving elements that receive racquet strings extending exteriorly of said die cavity in a substantially horizontal plane and inwardly of said frame head, introducing a molten light-metal into said die cavity to fill said cavity and envelop the metal band and the portions of said string receiving elements that lie within said die cavity, and cooling said molten metal to solidify said metal both to form a die cast light-metal frame head and simultaneously capture said independent stringing means therein.

2. In a method for forming a die cast light-metal racquet according to the improvement of claim 1 wherein the light-metal is magnesium.

3. In a method for forming a die cast light-metal racquet according to the improvement of claim 1 wherein the string receiving elements comprise eyelets having integral stems, said stems being secured to said metal band with the string receiving eyelets extending exteriorly of said die cavity in a substantially horizontal plane and inwardly of said frame head, said frame head being die cast about the metal band and the stems of said eyelets.

4. In a method for forming a die cast light-metal racquet according to the improvement of claim 1 wherein said string receiving elements comprise the crests of a sinuous wire having alternate crests and troughs said troughs being fastened to said metal band mounted in said die cavity with the crests of said sinuous wire extending exteriorly of said die cavity in a substantially horizontal plane and inwardly of said frame head, said frame head being die cast about said metal band and the troughs of said sinuous wire.