DK153305B - PROCEDURE FOR MAKING A SPORT BALL - Google Patents

Description

in

DK 153305B

The invention relates to a method of producing a sports ball of the kind set forth in the preamble of claim 1.

For the most important properties of balls produced by an adhesive method, when looking at their appearance, one can count the rubber ribs which clearly show a network and which very precisely limit fields for the individual tire segments which Most are made of natural or synthetic leather. The rubber ribs must not be too high or too low. If they are higher than the cover parts, poor grip and poor kickback properties are obtained at the ball. If they are too low, the rim of the tire parts will be slightly damaged by the use of the ball.

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In order to form said rubber ribs on the surface of adhesive balls, several manufacturing methods have been proposed. According to a manufacturing process described in the description of Czechoslovakian Patent No. 135,824, a ball bag, i.e.

to an inflated inner rubber bladder coated with a textile garment, by adhesive fastening rubber bands of the ribs in selected positions, the final shape and distribution of the bands being determined by placing the bag in a mold and pressing it under heating, under which the rubber material in the ribs become vulcanized. In this way, the ribs formed will confine single fields to an attachment of tire segments by adhesion.

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A substantially analogous method of manufacture can also be found in a study of the disclosure of French Patent No. 1,488,920, although the exact process for making the rubber ribs is not discussed in more detail in this patent.

In U.S. Patent No. 3,887,416, a ribbon fastening is also disclosed which is made of rubber and has been pre-vulcanized. From United States Patent Nos. 3,653,818 and 2,219,078, there are also known methods of manufacture in which rubber ribs are formed, the height of which exceeds the height of the tire segments. However, it is also admitted by the manufacturers of such balls that these balls, whose rubber ribs are of the said type, have been found to be unsatisfactory because a small excessive height of the ribs has not provided a reliable grip of the ball in the hands of the player 20 , while a large superior height adversely affects the ball's jumping properties.

US Patent No. 3,887,416 discloses a method of applying a malleable and vulcanizable rubber sheet to a base member, after which a network is adhered to retain the cover members so that they do not contact each other. The procedure is complicated and the internal height of the ribs between the tire segments is not secured.

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For all these known modes of production, it is a disadvantage that the manufacture is relatively complicated, thereby becoming unnecessarily expensive, which means a disadvantage, even for the subsequent 3

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manufacturing steps in the manufacture of such balls if the inner height of the ribs is to be secured and kept uniform.

The present invention aims to simplify and improve the manufacture of sports balls so as to achieve a high quality and durability.

This is accomplished by proceeding as specified in Claims · 10 l's Characteristic Part.

By proceeding in this way, first and foremost, a considerable simplification of the production of the ball is achieved, which in turn results in a reduction of 15 production costs. The network of rubber ribs adhered between the leather-cover segments can flow precisely into the gaps between them without being too high or too low. The ribs can also be cured below. At the same time, you get a cheap manufacture and a very durable and precise design.

Also, the use properties of rubber rib balls made by the method of the present invention are greatly improved, particularly as regards the bounce power and flight control of the balls when impacted on the floor of sports halls.

For a reliable manufacture of the rubber rib network between the individual tire segments on the shaped ball surface by the method of the present invention, it is important that the plate made of the rubber mixture be used as an intermediate layer to join the winding on the molded surface. 4

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inflated rubber bladder, the so-called sack, and the surface tire segments. Essentially, this plate is made of a mixture of natural rubber and of synthetic rubber, optionally also mixtures of these rubber, with the addition of accelerators, fillers, antioxidants, lubricants, dyes and other necessary components.

In order to carry out the method according to the invention, the mixture must have a built-in vulcanization system suitable for ensuring a sufficient flow or creep of the mixture into the spaces between the adhesive surface covering elements during the vulcanization. Therefore, the viscosity of the rubber blend must be sufficient, also for this preparation step, which is of crucial importance for carrying out the process of the invention. Finally, by varying the properties of the rubber plate and the amount thereof, one can positively influence not only the weight of the ball but also its final use properties, in particular the elasticity of the ball.

The rubber blend plate for making the rubber ribs or, rather, the network of the rubber ribs between the individual tire segments on the surface of the shaped ball by the method of the present invention contains a vulcanization system which sustains 2.7 to 3.6 weight percent of a mixture. 30 of vulcanization accelerators, namely a mixture of mercaptobenzthiazoles, tetramethylthiuram disulfide and Ν, Ν-diphenylguanidine, and of 0.2 to 0.4% by weight of isobutylidene-bis-4,6-dimethyl phenol. The thickness of the sheet varies by the method of the invention

DK 153305B

between 0.4 and 1.5 mm.

A typical example of a blend for making the rubber ribs using the process of the invention is a blend which, by weight of 1000 parts by weight, contains 185 parts by weight of natural rubber, 185 parts by weight of butadiene styrene rubber, 7 parts by weight of sulfur, 8 parts by weight of zinc oxide, 5.5 parts by weight mercap-tobenzthiazole, 7.2 parts by weight tetramethylthiuram disulphide, 15 parts by weight Ν, Ν-diphenyl guanidine, 2 parts by weight isobutylidene-bis-4,6-dimethyl phenol, 4 parts by weight stearin, 1.8 parts by weight rosin, 50 parts by weight carbon -black and 429 parts by weight of calcium carbonate.

The rubber compound for use in the method of the invention can be manufactured in many modifications and in various shades of color. Thermoplastic rubber and suitable plastic materials can be used.

In the preparation of the rubber mixture, 20 does not proceed in the usual manner. Special preparation steps and temperatures are used which have proven to be suitable for the preparation of the rubber blend. The same goes for the plate made from the mixture. Rubber sheets are conventionally prepared in a 25 two-roll calender, whereupon accelerators and sulfur are added to the mixture in precisely selected quantities while maintaining the temperatures during treatment at minimum values. After the rubber mixture containing the vulcanizing agents has been prepared in the 30-roll calender, it is immediately transferred to a four-roll or five-roll calender in several successive doses, the mixture then calendered to a plate of the desired thickness.

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The temperature of the mixture in the calender must not exceed 60 ° C. The plate thus prepared is then cut into desired segments. The placement of the plate on the ball sack to produce the 5 rubber ribs by the method according to the invention takes place as follows: The prepared segments, i.e. circular pieces of a desired diameter are retained by a specially designed equipment, after which a coating of dissolved adhesive is applied to the segments. The plate may also be activated by a suitable organic solvent, e.g. petrol.

The ball's suitably inflated bag, which is provided with a reinforcing layer of wire or rope winding and then calibrated by a prior pressing, is secured along the circumference of a dividing plane, after which one of the rubber plate segments or both of these segments is simultaneously applied to the ball bag which has been coated with a thin layer of an adhesive of the same composition as the adhesive used to apply the plate segments.

Due to the elasticity of the rubber plate segments, these can be shaped to correspond substantially to the shape of a hemisphere of the ball as a result of holding circular rings pressed down to cover the ball on the surface of the bag, the rubber plate only reaching one the desired distance from the ball's dividing plane, without any folds forming during the application of the 30 plate. Since the rubber plate segments are provided with an adhesive coating on the back, the plate is attached to the ball segments from both sides in exact positions determined by the retaining circular rings. Then both plate segment caps are off 7

DK 153305B

cut along the perimeter of them, after which an uncoated strip is formed at the central portion of the ball sack along the large circle about the perimeter. On it is then placed a segment of the rubber sheet, which is already formed into a strip of suitable width. The circumference of the rubber pad strip must be precisely positioned between the perimeter of both previously placed cap segments, since the perimeter of the rubber segments must not overlap at any point.

In this way, a uniform arrangement of the rubber plate is obtained along the entire surface of the ball ball. Then, the profile of the ball is marked with the marking of exact positions of the surface covers to be applied to the prepared sack of the ball, provided with a coating of the rubber plate.

This is done by pressing the ball sack into a mold provided with grooves of the desired depth and shape, which ensures a characteristic shape of the final 20 surface of the ball. The pressing is carried out using not too high temperatures. Due to the viscosity of the rubber piace mixture, the softened mixture will flow into the grooves in the mold, resulting in an accurate marking of the fields for later placement of the surface tire segments. The ball bag thus prepared is then further processed by attaching the surface cover segments by adhesive and by pressing, optionally by vulcanizing the rubber plate to form 30 rubber ribs by the method of the invention.

First, surface cover segments of the desired shape are cut out of natural leather, possibly of synthetic> 8

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materials, using a cutting machine. The circumference of these segments is cut or split at the back of a slot machine about 6 mm wide, the gap width depending on the nature of the cover material and the type of the ball. As mentioned earlier, the cutting occurs from the back of the segments. Then, an adhesive coating is applied to the back of the segments and also to the surface of the ball bag. The adhesive used is a solution of natural rubber, vulcanizing agents and dyes with fillers dissolved in an organic solvent, e.g. petrol.

When the adhesive coating is applied to the back of the 15 tire segments, a solution is used whose solids content is between 18 and 20%. To apply adhesive to the ball bag, a thinner solution containing a solids content of between 10 and 15% can be used.

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The adhesive coating on the back of the tire segments can be done manually, but an appropriate coating machine can also be used, as the adhesive, as already mentioned, is applied to the back of the segments. For the 25 ball bag, the adhesive can also be applied manually, but in this case also a suitable machine can be used for coating with adhesive.

After the adhesive has been applied to both surfaces to be joined by adhesive, the tire segments are placed on the ball sack after a space of 5 to 45 minutes in such a way that they fit exactly into the predetermined fields marked by the grooves in the brand form which

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g written above.

The shape of the fields on the ball and also the shape of the tire segments is special for each type of ball. When the surface tire segments are placed using the method of the invention, no substantial physical effort is required to compress the segment peripheries to achieve tight joints.

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A perfect bonding between the ball bag, the rubber plate and the cover material is achieved by a sufficient slip of the rubber plate mixture and by the vulcanization of this mixture using elevated temperatures during pressing. During this operation, the exact position of the surface cover segments is sufficiently stabilized because the adhesive used has sufficient stability. After the tire segments have been placed, residues of the 20 adhesive, and possibly other impurities, are removed from the surface of the ball, which is then ready for pressing. The subsequent pressing and vulcanization of the balls is carried out in spherical molds consisting of two spherically lockable hemispheres. The size-25 travel of the mold is determined by the ball type. The temperatures used and the pressing time of the ball as well as the vulcanization of the rubber blend plate depend on the type of cover material and the temperature resistance of this material, using temperatures between 90 30 and 130 ° C. If synthetic materials with high resistance to elevated temperatures are used, substantially higher temperatures may be used than those mentioned. The pressing time and the curing time depend on the temperatures used. Sperm 10

DK 153305B

usually the time used is between 2 and 7 minutes. In the case of higher temperatures used, the time may also be shorter. The purpose of pressing the ball is to achieve a smooth and uniform surface of the 5 ball, while maintaining its round shape.

During vulcanization of the mixture, the rubber rib network is formed by the method according to the invention, because the softened mixture 10 flows completely into the spaces between the circumferences of the tire segments. In a first phase, where the mixture is plasticized under heat, and in a second phase where a perfect joint between the tire segments and the plate is obtained, a good joint is achieved between the plate and the ball, as a result of the vulcanization of the mixture. and the adhesive in the given condition. There is also a significantly higher degree of strength against peeling between the tire segments and the ball as well as a greater reliability 20 of the joint itself. There is virtually no scaling of the tire segments at the periphery, as has usually been the case with balls made by the known methods.

In order to preserve the characteristic shape of the ball's surface, namely the division of the surface resulting from the plastic composition of the tire segments with delayed circumferences, it is important to cut or split the tire segments. The sealing or splitting of the circumferences of the tire segments and the relatively high overpressure on the inside of the ball during pressing and vulcanization ensures perfect sealing of the split or sloped circumferences in the sheet material, resulting in

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n in a very close connection. After the steps of vulcanizing the plate and pressing the ball are completed, the pressure in the ball is substantially reduced. The overpressure used during the vulcanization and pressing of the ball will never be used again during the practical use of the ball.

At substantially lower inflation pressure in the ball, the surface of the ball will practically never be smoothed again, so that the ball surface, due to the split or beveled circumferences of the tire segments, will retain its typically articulated appearance. If certain ball types should require a completely round surface, excluding a visible joint division as the result of the varying thickness of the tire segments, the above-mentioned splitting or beveling of the peripheries of the tire segments is omitted. The ball surface then becomes completely round in shape and appearance, without plastic projections of the individual segments. The segments then appear only in the optical appearance, while an equally close connection is obtained between the surface tire segments and the ball sack.

When the pressing is completed, the balls are placed for cooling and then inflated to the required pressure to test the air tightness. Then the balls can be shipped in inflated or emptied condition.

The process of the invention is explained in more detail by the following example.

Example 12

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On a pressed ball bag made by wrapping a mixture of synthetic and natural yarn on an inflated rubber bladder, a layer of an adhesive is applied in the form of a 20% solution of natural rubber in gasoline. The same adhesive coating is applied simultaneously to one of the surfaces of a rubber plate having a thickness between 0.5 and 0.6 mm, which plate is then retained in a special tool adapted to place the plate on the round , inflated ball bag. The plate is placed after 20 to 30 minutes after the adhesive has been applied.

The successive individual steps of applying the rubber blend plate include the centering of two plate hemispheres, which are then formed during the application, and an application of a central strip of the plate which offsets any irregularities that may have occurred during the application of the hemispheres. . The placement of the central plate strip between said hemispheres is carried out with care to prevent overlap of individual plate segments, as otherwise the surface of the finished ball would show irregular projections at such points.

After the plate is placed on the ball sack, the ball is pressed into a profiled cold form to ensure the boundary between the plate and the ball sack during the pressing and possibly to mark orientation points and grooves on the sack surface to facilitate later on. position the tire segments.

The pressed ball bag is provided with a coating 13

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of an adhesive of a type of 20% natural rubber solution in gasoline. At the same time, the back of the tire segments are coated with the same type of adhesive as two coatings follow one after the other. After at least 30 minutes have elapsed after application of the adhesive coating, the adhesive has become dry and the tire segments made of natural leather are applied by adhesive to the fabricated ball sack. After the tire segments have been placed, the ball sack is conditioned for at least one hour by subsequent pressing and vulcanization thereof. The purpose of the pressing and vulcanization is to correct for or smooth out any irregularities along the surface of the ball which may have occurred during the attachment of the tire segments and during the vulcanization of the rubber mixture. The pressing and vulcanization takes place in a smooth, round, 20 cm diameter mold at temperatures in the range of 100 to 110 ° C for three minutes. After the balls have been pressed, the inflated or pressureless are cooled, and after inflating to the required pressure in the inner rubber bladder, they are taken for technical testing and shipment after 24 hours.

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Claims (3)

A method of producing a sports ball, in which, by winding a thread or by applying a tissue to an air-filled rubber bladder, a workpiece is applied to which is applied a deformable, vulcanizable rubber layer on which a net is made, the rubber suture layer is cured and adhesive non-contact tire areas are adhered to the fields, characterized in that the sealing layer is applied by applying a 0.4 to 1.5 mm thick film and The net is made by cold embossing this foil, and after the covering of the tire parts, the sports ball is pressed into a smooth hollow sphere shape 1.5 to 10 minutes at 90 to 150 ° C. Method according to claim 1, characterized in that, for the application of the foil first, two spherically aligned ball caps are applied to the blank first, leaving a free equatorial center strip, on which a corresponding foil strip is subsequently applied. Method according to claim 1 or 2, characterized in that the edges of the back of the tire parts are sharpened before the adhesive on the fields. 30