US 3606326 A
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Sept. 20, 197.1 w. J. SPARKS ETAL GRIP FOR HAND POWERED IMPLEMENTS Filed Sept. 25, 1968 INVBNTORS w/LL/fl/VI 6/. snqRKs CHHRLES E. SPARKS W KM HTIZDR/UE).
, w 1 mvAlllllllluJ United States Patent Oifice 3,606,326 Patented Sept. 20, 1971 3,606,326 GRIP FOR HAND POWERED IMPLEMENTS William J. Sparks, Westfield, NJ. (5129 Granada Blvd., Coral Gables, Fla. 33146), and Charles E. Sparks, xvestfield, NJ. (102 Evans Lane, Cherry Hill, NJ.
Filed Sept. 25, 1968, Ser. No. 773,689 Int. Cl. A63b 53/14 US. Cl. 273-81R 9 Claims ABSTRACT OF THE DISCLOSURE The shaft portion of a hand operated and hand powered tool or club is covered by a superimposed layer of a foamed sponge elastomer to form an improved grip. The grip is especially useful for golf clubs. On swinging the club the grip improves precision, prevents slippage, and reduces shock at the time of impact. The elastomer has a Shore A durometer hardness ranging from about 5 to 40, and a thickness from about .5 mm. to 25 mm. In one embodiment, the elastomer is a foamed filled neoprene.
This invention relates to a novel improved grip for the shaft portion of a hand operated and hand powered tool or club. More particularly, this invention relates to a grip in which the shaft portion is covered by a superimposed layer of a foamed sponge elastomer. An especially preferred application of the grip is for a golf club.
Hand powered and hand operated tools are often controlled by direct manual contact with an operating shaft. The hand powered area of the shaft is many times a portion of the shaft itself. For many purposes the manual control area of the shaft is covered by a superimposed layer of a different composition. The contact layer may be serrated, roughened, drilled, wrapped or perforated to provide friction so as to avoid slippage. In the alternative, the shaft may be separated from the hand by a non-adhering insulating layer positioned between the hand and shaft, thus acting like a glove. The use of such devices is important in order to improve precision, to prevent slippage, shifting or turning, and to reduce shock at the time of impact. Of course, this must be done with a minimum of energy loss and with a maximum of energy transfer through the shaft to the manipulated object.
The material of the superimposed layer attached to the shaft has been widely varied. All of the compositions, however, have one common property. Although they may or may not be softer than the shaft material, they are all relatively hard. Hardness is commonly expressed in Shore A durometer hardness units. Shore A hardness is determined with the Shore A durometer in which a pointer is forced into the test specimen. A score from to 100 units reflects the hardness, the higher readings indicating harder compounds, as set forth in the ASTM Standards on Rubber Products D31439 (1944). A metal or wood composition, resin impregnated cloth, or hard rubber would all have a Shore A durometer hardness approaching 100. Rubber compositions vary from a Shore A durometer hardness of almost 100 down to about 40. The usual leather products are in the same range.
We have discovered that foamed sponge elastomers, and particularly such elastomers which have certain physical properties within a carefully selected range, are highly desirable materials for forming the grip covering the shaft of a hand operated and hand powered club or tool. The foamed elastomer compositions especially useful in our invention have a Shore A durometer hardness from about to 40. This degree of hardness may be defined more fundamentally as capable of noticeable deformation at the pressure of the grip at impact. During operation of a hand powered tool or club the muscles of the upper extremities cause the carpel, metacarpel, and phalanges bones of the wrist and fingers to apply force through the soft tissues and skin causing a deformity of the compressible foamed elastomer at the point of the applied force. This deformity of the sponge elastomer prevents slippage and loss of force.
Thickness of the elastomer is also important. In order to obtain the advantages of grip non-slippage and low hand abrasion, the thickness should exceed 0.5 millimeter. In order to minimize gripping zone hysteresis, the thickness should not greatly exceed 25 millimeters. The preferred thickness will vary according to the particular use, as will be more fully explained below.
Another limitation in the use of these softer materials is a loss in certain needed physical properties when the apparent density of the foamed elastomer is too low. In the case of neoprene, for example, we have found that at an apparent density of the foamed elastomer below 40% of that of the original stock, the composition loses abrasion resistance to an undesirable degree. Again in the case of neoprene, the upper range of apparent density should be less than about the density of water at room temperature. The term apparent density is used in this application to mean the density of the sponge elastomer which is measured, as distinguished from the real density of the elastomer before foaming. The lower apparent density results from the substantially uniform generation of gas throughout the structure during or as a part of the vulcanization operation. The foamed sponge elastomer is a vulcanized article having an apparent density less than the density of the original unvulcanized compound. As a rough measure applicable to all elastomers the apparent density of the foamed elastomer may be defined as between 20% and of the density of the unvulcanized stock.
In summary, the sponge elastomer used for our invention will have a Shore A durometer hardness below 40, a thickness from 0.5 mm. to about 25 mm. and an apparent density within the range of about 20% to 95% of the density of the unvulcanized elastomer stock.
The hand grips of this invention are particularly useful for clubs, racquets and the like used in various sports and games, such as field hockey, ice hockey, lacrosse, squash, and the like. An especially preferred embodiment of our invention is in grips for golf clubs. The grip is particularly useful for sporting implements whenever it is desirable that a hand grip be securely grasped and held, and when the impact of the ball with a club or racquet is with suflicient force that it may cause blisters or callouses on the hand. The grip of our invention also makes unnecessary the use of gloves.
The novel grip is also useful for incorporation in hand tools such as a hatchet, hammer, or the like, which are similarly used to transmit power through a shaft to a head that is used to strike an object. The novel grip results in greater precision, less energy loss, and reduced shock at the time of impact.
Our invention also includes within its scope a process for installing the novel grip on the shaft of a club or tool, as well as the novel grip in combination with an anchoring cap adapted to hold the grip in place on the shaft.
A fuller understanding of the invention may be had by referring to the following description and claims, taken in conjunction with the accompanying drawings. Hereinafter the discussion will be for illustrative purposes with reference to a golf club. However, it will be understood that the device of the invention finds application in many fields.
FIG. 1 is a perspective view of a conventional golf club in which the invention may be incorporated.
FIG. 2 is a cross-sectional view of the shaft of a golf club and illustrates the invention being incorporated therein.
FIG. 3 is a cross-sectional view of the shaft of a club or tool with a foamed sponge elastomer grip covered by a solid elastomer outer layer.
FIG. 4 is a cross-sectional view of a cap for holding the grip of a golf club in place.
FIG. 5 is a cross-sectional view of a cap with a thickened lower rim for holding the grip of a golf club in place.
FIG. 6 is a cross-sectional view of a cap with a plurality of downwardly projecting tines for holding the grip of a golf club in place.
As shown in FIG. 1 a conventional golf club has a head 5 for hitting the ball. The head is connected to a shaft 1 which is generally a hollow metal tube or wooden rod with a slight downward taper from the top of the shaft to the neck of the club. A grip 2 encircles the shaft 1 at the uppermost portion for a distance of about to 13 inches. The top of the shaft and grip is protected by cap 3.
In FIG. 2 the shaft 1 of a golf club is enveloped with a foamed sponge elastomer grip 6, the upper end of which folds over the top of the shaft at 7. The folded part of the grip is held in place by cap 3. Optionally a bonding film 8 glues the sponge elastomer grip 2 to shaft 1.
In FIG. 3 the shaft 1 of the tool or club is surrounded with a foamed sponge elastomer grip 9 which is covered with a solid elastomer outer layer 10.
In FIG. 4, cap 3 is an anchoring cap, the top of which may have any desired shape such as fiat, rounded, cupped, and the like. The sides 11 of cap 3 have substantially the same thickness throughout.
In FIG. 5, cap 3 is an anchoring cap, the top of which may have any desired shape such as flat, rounded, cupped, and the like. The lower rim 12 of the sides is thickened for causing greater compression in the sponge elastomer grip.
In FIG. 6, cap 3 has a plurality of tines 13 projecting downwardly between the foamed sponge grip 2 and shaft 1.
Several methods can be used to install the grip an the shaft. For example, the shaft may be coated with a lubricant such as water, an alcohol, gasoline, or an oil which is relatively inert toward the elastomer. The tubing is then forced on the shaft.
In a preferred embodiment of our invention the grip is installed on the shaft by attaching one end of a tubing made of the foamed sponge elastomer to a fluid outlet under pressure, the bore of the tubing having a diameter less than the diameter of the shaft on which it is to be installed. If needed, one or more clamps may be used to secure the end of the tubing at the fluid outlet during the operation. The other end of the shaft is pulled over the end of the shaft of the club on which the grip is to be installed. The fluid is allowed to flow into the tubing under pressure, thus expanding the tubing so that it slips easily over the end of the shaft to the desired position. The pressure is then trned off so as to allow the tubing to contact to fit the contours of the shaft.
The fluid used may be a gas such as air, natural gas, carbon dioxide, hydrogen or helium; or the fluid may be a liquid such as water. A preferred method utilizes water from a faucet under the usual household pressure.
After the pressure is released, the tubing at the upper end of the shaft is held under tension and then cut off at a distance from the end such that on release of the tension the elastomer tubing will curl over the end of the shaft for a distance of about one-half inch. The rubber tubing or sheath overlapping the end of the shaft is referably held in place by a cap positioned over the end of the shaft. The cap extends downwardly over the outside of the shaft for a distance of about one-fourth inch 4 to one inch. The cap has dimensions approximating the contours of the end of the shaft with the elastomer superimposed. The cap is forced onto the end of the shaft, and the compressive tension of the elastomer on the inside of the cap holds the cap on sheath. Thus the cap holds the overlapping end of the sheath in place and the compressive tension of the elastomer against the lateral walls of the cap holds the cap in place. The cap can be quickly put in place, and will hold firmly. The sides of the cap may have substantially the same thickness throughout as in FIG. 4, or the rim may be thickened as in FIG. 5 to cause greater compression in the grip at the rim. Alternately, the cap may have a plurality of tines projecting downwardly as in FIG. 6 for inserting between the elastomer sheath and the shaft of the club, to define a seat for the end of the shaft. The tension of the elastomer on the tines will hold the cap in place. It is evident that caps of the types described are particularly useful when the shaft is covered with a compressible material such as described in our invention.
Although the conventional center screw caps ordinarily used for golf clubs can also be used with an elastomer grip, it is an advantage of our invention that screws and other auxiliary fastening means, which tend to work loose in the course of time, are unnecessary. A grip made of a foamed sponge elastomer will be held securely in place over a long period of time using only the thin molded or malleable caps described above.
In the case of a golf club the elastomer at the lower end of the shaft ordinarily requires no method of securing it because of the taper of the shaft. The compressive forces at the bottom will hold the sheath in place. However, the lower end of the grip may be wound with thread, tape,
.or plastic, etc., if desired. For other types of clubs or tools where the shaft is not tapered, it may be preferable to secure the grip at the lower end.
The cap is made of a thin, tough moldable or malleable material such as plastic, metal, and the like. The cap may be of any color, and insignia may be present on thetop. A plastic cap, for example, may be dyed a bright color and imprinted with a number or symbol to designate a particular club, or with a monogram to be applied at the point of sale to personalize the device.
It is an advantage of this invention that it is unnecessary in most instances to remove a conventional grip already in place on the shaft of a golf club in cases where one desires to equip a present club with this improvement, since the sponge elastomer grip will readily expand to fit over the grip already in place and adhere to it due to elastomeric tension. Thus the sponge elastomer grip of our invention can be used not only to replace .the grip customarily used on the golf club, but can be used as a protective sheath or sleeve for a grip which is already present on the shaft.
For a replacement grip the thickness of the wall of the tubing will generally be thicker than for a protective grip. The thickness of the wall of the tubing (Which can be measured by the difference between the bore diameter and the outside diameter) varies for about 0.5 mm. to about 25.0 mm. The thickness of a protective grip is usually less in an amount sufficient to compensate for the thickness of the grip which is being covered.
The grip may extend completely over the usual length of the grip area, or may cover only a portion of the length thereof. For example, the grip may be positioned only on the part normally held with one hand, thus making it unnecessary to wear a glove on that hand to ensure a tight grip on the club without slippage during the swing of the club. Thus the shaft may be jacketed only intermediate the shaft length. i
The outside of the sponge elastomer grip can be covered, if desired, with a protective or decorative layer of any suitable material, as shown in FIG. 3, such as a nonfoamed solid elastomer, cloth, fiber, plastic, a paint coating, etc. The preferred coating is an unfoamed elastomer which has essentially the same composition as the sponge elastomer and is homogeneously adhered thereto.
The grip may be secured to the shaft with a bonding film as indicated in FIG. 2 by the dotted area. Any suit able adhesive may beused, such, as. a resin or epoxy adhesive, as is well known in the art.
The type of elastomer useful for this invention can be varied widely. Density values for hydrocarbon elastomers other than those containing large amounts of buond Various fillers may be added to the neoprene base. In the following basic formula the addition of fillers give results shown:
Parts by weight styrene are found to be near 0.93 gram per cubic centi- O Cure: 35 minutes at 153 C.
meter as shown in the following Table I.
TABLE I Polymeriza- Density at tion temper- 25 0., Material ature, C. g. per (:0.
Natural rubber 5 0. 911 Polybutadiene emulsio 5 0.892 bound styrene 0. 892 7.9% bound styrene 5 0. 9045 22.6% bound styrene 5 O. 9288 36.3% bound styrene 5 0.9526 53.1% bound styrene. 5 0. 9837 0% bound styrene 50 0. 8936 8.6% bound styrene 50 O. 9065 23.9% bound styren 50 0.9326 43.0% bound styrene. 50 0. 9667 55.7% bound styrene 50 0. 9929 Polystyrene 1. 053 Butadieneacrylonitrile copolymers:
27% bound acrylonitrile 0. 968 33% bound acrylonitrile 0. 978 40% bound acrylonitril 0.999 Polyisobutylene 0. 913 Isobutylene-isoprene copolymer (butyl rubber) 0.92 Silicone rubber 0. 974 Polysulfide rubber (Thiokol FA) 1. 330 Polyehloroprene (neoprene GN) 1. 229
Foamed latex sponge elastomer, both natural and synthetic, is prepared in several ways, as is known in the art. The process in general use consists of beating the thickened latex into a foam. The proper coagulation of the latex so as to give a suitable foam is the key to the successful application. An alternative process calls for the use of a vacuum to cause the generation of gas in the latex. The resulting foam is stabilized by the presence of certain chemicals or by other means.
Various flowing agents and blowing promoters are also used for adding to typical rubber formulas in a quantity necessary to give the desired density. Examples are organic compounds such as N,N-ditrosopentamethyltetramine, biuret, urea, dimethylsiloxane, p,p' oxybis(benzenesulfonyl hydrazide), 1,3-diphenyltriazene, azodicarbonamide, 4,4-diphenyldisulfonyl azide and N,N'-dimethyl-N,N'- dinitrosoterephthalamide; inorganic compounds include ammonium bicarbonate, ammonium carbonate, sodium bicarbonate, and the like.
The agent is added directly to the rubber. It may require the use of a good plasticizer and thorough breakdown and mixing of rubber for uniform blowing.
A preferred material for use in this invention is neoprene foam rubber. The term neoprene is a generic one which denotes a synthetic rubberlike polymer made by polymerizing chloroprene (2-chloro-l,3-butadiene), or by polymerizing a mixture of polymerizable monomers, the major component of which is chloroprene. B y common usage the term has been broadened to include commercial rubberlike compunds of which the major elastomeric constituent is neoprene.
To typical formulas such as the one above are added blowing agents, particularly N,N-dinitrosopentamethylenetetramine in the quantity necessary to give the required density.
Other kinds of elastomers may likewise be used, for example, natural rubber, Butyl rubber, polybutadienestyrene elastomers, silicone rubbers and the like.
Various modifications and variations of the present invention may be made without departing from the spirit of the discovery or the scope of the appended claims.
1. In a hand powered implement comprising the combination of a head used to engage an object, a shaft connected to said head, said shaft having a handle portion, and a jacket encircling said handle portion: the improvement wherein said jacket comprises a superimposed layer of a foamed vulcanized elastomer having a Shore A durometer hardness from about 5 to less than 40, a thickness from about 0.5 mm. to 25 mm., and an apparent density between 20% and of the real density of an unfoamed elastomer of essentially the same composition, said jacket layer being the outermost layer on said handle portion.
2. The combination as in claim 1 wherein said implement is a golf club.
3. The combination as in claim 1 wherein said elastomer is made from a filled neoprene.
4. The combination as in claim 1 wherein said elastomer is made from a filled natural rubber.
5. The. combination as in claim 1 wherein said elastomer is made from a filled butyl rubber.
6. The combination as in claim 1 wherein said elastomer is selected from the group consisting of a filled polybutadiene and a butadiene copolymer.
7. The combination as in claim 1 wherein said implement is a hand tool.
8. The combination as in claim 1 wherein said imple-' ment is a racquet used in sports and games.
9. The combination as in claim 1 wherein said implement is a club used in sports and games.
References Cited UNITED STATES PATENTS 2,327,931 8/1943 Ratner 74558UX 2,872,539 2/1959 Berner 74558.5UX 3,083,124 3/1963 Rahmes 260-2.5X 3,269,400 8/1966 Smith et al. 52 3,500,572 3/1970 Johnson 273-81X (Other references on following page)