US1792362A - Rubber ball - Google Patents

Description

Feb. 10, 1931. M. J DE FRANCE; 1,792,362 1 RUBBER BALL Filed Feb. 29. 1928 WITNESS Patented Feb. 10, 1931 ATENT orrlcs MUBRELL J. DE FRANCE, 01 JEANNETTE, PENNSYLVANIA, ASSIGNOR '10 PENNSYL- VANIA RUBBER COMPANY, OF- JEANNETTE, PENNSYLVANIA, A CORPORATION OF PENNSYLVANIA RUBBER BALL Application filed February as, 192a Serial no. 257,932.

My invention relates to improvements in the method of making inflated rubber shells and. "ecifically rubber playing balls. I employ tlhe term rubber in its popular and nontechnic al sense. Rubber balls in the common meaning of the term are hollow and ordinarily thin-walled spheres of a composition which includes caoutchouc and certain min eral substances, into which composition a quantity of sulphur is introduced. The ball when shaped is vulcanized, and the wall of the finished ball has qualities of softness, elasticity, and durability, to the attainment. of

which the composition of materials and the dimensions and proportions of the ball have been carefully worked out. While not limited in its application to rubber playing balls of any particular sort, my invention finds practical application in the making of tennis balls, and in such particular application I shall show and describe it.

In the accompanying drawin Fig. I is a view incentral section of one of t e two hemi- 1 spherical shells which go to make u a tennis ball. It may be understood that e shell as it is here shown is a shell of semi-cured i'ubber, as it. comes from the mold. Fig. II is a diagrammatic view in vertical section, illusag erated thickness.

tennis ball is, it W111 be understood, a

' thoroughly standardized article; It is a hollow, thin-walled, rubber ball, inflated, and covered externally with felt. Its dimensions, its wall thickness, its degree of inflation. its weight, and the characteristics which adapt it to its intended use, are most minutely dcfined. Problems arise, to produce economically the standard article, and to give durability in largest measure to the ball which initially comes up to the standard.

A thin wall of rubber such as that of. a

tennis ball is byno means impervious to gas, particularly when, as is the case with a tennis ball, the pneumatic pressures u on its opposite surfaces are unequal. An because the rubber wall is permeable, it has long since been the practice, in order to prolong the life of the tennis ball, to coat the wall interiorly with-a preparation of gelatin. Such an inner coating, without undue'prejudice to the qual-- ity and character of the all in other res ects, renders it tighter'to resist theescape 0 gas. And, since the ball is inflated; that is to say, since it contains gas under super-atmospheric pressure, the life of the ball is by this expedient prolonged. i

In themaking of tennis balls, it is the universal practice to shape hemispherical shells of green rubber and,-',after partial and incomplete vulcanization, to unite two shellsedge to edge, and to complete vulcanization after the ball itself has so .been completely shaped. I

And in making balls with interior coatings of gelatin, it is the universal practice to apply the gelatin to the hemispherical and incompletely cured shells. The gelatin is ordinarily prepared in the form of an aqueous solution, and it may then be applied in various ways, as by painting or spraying the solution uponthe surface of the rubber, or by dipping therubber article in a bath of elatin solu 'tion. The hemispherical shell 0 semi-cured rubber, as it comes from the mold, is shown in Fig. I of the drawings. My preferred way of applying gelatin to the rubber shell, is illustrated n Fig. II. 'A reservoir 4 is provided, adapted to contain a suitable quantity of gelatin solution. The reservoir is jac eted, so that hot water may circulate around the body of gelatin solution within the reservoir. From the;bottom of the reservoir a valved and open-ended tube 5 extends downward.

The reservoirotherwise closed, is provided through its top with two valve-controlled connections 6 and 7, one to a source of air under pressure, the other to pressure-reducing means. In operation the semi-cured shell 1 is placed beneath the reservoir, its rim carefully leveled, and tube 5 at its lower end closgly adjacent to the mid-point ofthe con- IOU -cavity of the shell. The valves in tubes 5 and 6 then are opened, whereupon hot gelatin solution flows through the tube and fills the shell. When the flood of gelatin solution rising within-the shell reaches the edge, the valve in tube 6 is closed and the valve in tube 7 is ,opened. Thereupon the flood of gelatin is drawn back from the shell into the cylinder 4 again, leaving however a thin film, coating peditiously and with PIGCiSlOXl, and the edge v tin Wit the shell interiorly. It is of great importance that the very edge 12 be not coated with gelatin, and by enploying the apparatus which in the course of ball manufacture, a step of "drying; and, since an aqueous solution of gelatin is ve slow to dry, a very serious delay is so in]ected into the progress of the operation of ball making. My invention ini cludes a subjecting of the shell when coated with gelatin solution to ultra-violet rays emanating from a suitable light source. I have discovered that, according to what principle I know not, ultra-violet rays have the remarkable effect of causing the gelatin coating spread upon the rubber to dry in a relatively brief interval of time. In consequence,- the procedure of makingtennis balls is very considerably hastened and that with economy in reduction as'a whole.; I

e solution which I preferably employ.

for coatin the inner. surface of the ball contains in a dition to gelatin-a substance which is a coagulant of gelatin, acting upon the gelaan effect akin to tanning. Various substances possess this property or quality,

- efiect of the ultra-violet rays acting in thetypical among which is formaldehyde. If formaldehyde be resent in the solution, not only will-the coating dry, but it will become tough and leathery'to a degree which the gela- -'tin alone never would attain, an

being so modlfied in its character and qua i'ty, it is even more serviceable to the intended end.

I have found that if one or another of certam substances be used as the coagulant, the

manner described will bemore immediate and more pronounced, and among the substances which I have so foundto be effective, I enumerate the following: formaldehyde, potas- 'sium dichromate, sodium dichromate, alcohol, potassium iodide, ferrous sulphate, and

tannic acid.- I do not consider this to bean exhaustive catalogue, but merely indicative of substancessrhich have the e'fiect described.

flccordingifomy' preferred mode of procedure, Ishapethe hollow he heres of rubber and semi-cure them in usua manner,

coat them interiorly with gelatin solution, and deposit them on a travelling support.

This support may conveniently be an endless belt, and I cause it as it travels to bear the hemispheres directly beneath a dome-like reflector, within which is arranged a light source which emanates ultra-violet rays. Passing "at moderate rate beneath the 1nfluence of such a light sourceso situated, the hemispheres pass on with their gelatin coatings in effectively dried condition.

Various expedients are resorted to for effecting proper inflation of the tennis ball. One expedient is to enclose within the ball when the component hemispherical shells are brought together, chemical substances which reacting shall generate gas, and, the quantities being accurately measured, the quantity of gas so generated ispredetermined, and it is sufiicient both to --give the desired tension from within while the ball is undergoing its ultimate vulcanization, and also to afford for the finished ball'the desired degree of inflation. Specifically, in the procedure in which I have developed this invention, separate ellets of predetermined content one of so 'um nitrite and the other of ammonium chloride, are closed within the ball and with them a small and measured quantityof water. Reaction occurs under the heat ofthe 'vulcanizing operation, nitrogen is generated, and the-desired efiect is gained. In followingsuch procedure, if the hemspheres -be'interiorly faced with gelatin, the inflation creating materials so introduced will V have a localized deteriorating effect upon the gelatinous coating, and this will tend to imptair the quality of the finished ball. y further invention lies in adding to the interiorly coated hemisphere one interior coating more, a coating protective of the latin'against deterioration by introduce inflation-creating materials, and preferably this second coating is a coating of rubber.

"The rubber is preferably applied in fluid condition,,and this is attained by dissolving it ina suitable solvent, benzene, for example.

I. conveniently syray the rubber solution upon the gelatin-coated inner surface of the hemisphere, by bringing the hemisphere to place above a nozzle and projecting the solution in a spray from the nozzle. The solvent quickly evaporates and the rubber coating remains, of controlled thickness, effecting no impairment of the article for its intended purpom, and rendering the hemispherical shell better adapted forthe further steps of manufacture.

Incidentally, I preferably so coat, not the interior surface only ofthe hemisphere, but the edge 12 as well, so that when two hemisheres are brought together'their edges'are with' n rubber-- bber cement,

it is terme andin consequence an improved weld or union of the edges is effected. The rubber in solution may have sulphur mingled with it, so that it too is susceptible to vulcanization, but it will not itself ordinarily pletely vulcanized rubber, coating the shells mteriorly with gelatin, coating the shells over the gelatin coating and over their edges as well with rubber cement, bringing the two shells together edge to edge within a mold and with quantities of gas-generating substance and of water in the interior space, and ralsing the mold enclosed article to vulcanizing temperature.

In testimony whereof I have hereunto set my hand.

' MURRELL J. DE FRANCE. 7

facture, this product of the vulcanizing mold will be covered in usual manner with felt.

Fig. I of the drawings shows the molded and semi-cured hemispherical shell of rubber. Fig. II illustrates the step of coating with gelatin. Fig. III shows the hemispherical shell coated interiorly with rubber. The shell itself is indicated at 1, and from it, as will be perceived, the flash or fin 11, incident to the initial molding operation, has been trimmed away.- The coating of gelatin is indicated at 2, and the inner coating of rubber is indicated at 3. It will be observed that this inner coating of rubber faces not only the interior hemispherical surface, but at 33 it faces the edges of the shells as well.

Fig. IV illustrates the meeting of the two hemispherical shells edge to edge, and it will be seenthat the meeting of the two edge coatings 33 of the two shells facilitates and assures the integration of the shells to form the complete ball when the assembled blank is brought within the mold and vulcanized.

During vulcanization the gas generated within the hollow attains a pressure adequate to vulcanization, and when the finished ball returns to atmospheric temperature the con tained pressure is adequate to the ends in view.

I claim as my invention:

1. As a step in the manufacture of an inflated rubber article the method herein described, which consists in spreading upon a wall of rubber a coating of a solution of gelatin. drying the applied coating under, ultraviolet rays, and applying over the dried coatmg a second coating of rubber.

2. In the manufacture of an inflated rubher article the method herein described, which consists in forming a hollowblank of incom pletely vulcanized rubber,- coated interiorly with successive layers of gelatin and of rubber, inclosing within the blank water and chemically reactive gas generative substances, and subjecting the blank withina mold to vulcanizing temperature.

3. In the manufacture of atennis ball the method herein described which consists in forming two hemispherical shells of i'ncom--

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