IES58939B2 - A process for manufacturing a tennis ball - Google Patents

Description

A process for manufacturing a tennis ball The invention relates to an improved process for manufacturing a tennis ball and in particular a pressureless seamed.

Various processes have been developed for producing pressureless seamed tennis balls. However, such processes involve a large number of steps and are both time consuming and labour intensive.

To produce good quality tennis balls it is essential that the felt pieces surrounding the cover core are effectively attached to the core. Various methods have been proposed to attach felt pieces to the core however to date none of these methods so far have been entirely satisfactory.

This invention is directed towards providing an improved process for manufacturing a pressureless seamed tennis ball.

According to the invention there is provided a process for manufacturing a pressureless seamed tennis ball comprising the steps ofsmixing up rubber based core forming materials to form a paste; forming the core forming paste into a sheet; cutting the sheet into a ribbon; · It extruding the ribbon to form a pellet of core forming material; cooling the pellet; - 2 loading the pellets into individual core forming moulds ·, «/ forming each pellet into an individual hemispherical half core; trimming off the mating edges of the half cores; grinding the mating edges of the half cores; applying adhesive to the mating edges of the half cores; bonding two half cores together to form a complete core; vulcanising the bonded cores; flexure testing of the cores; roughening the outer surface of the cores; applying a solvent based adhesive to the core; drying the adhesive on the core; forming a stack of covering felt pieces; applying a seam adhesive to the side edges of the ' stack; ' orientating the core to receive felt pieces; applying two felt pieces to the core; kneading the felt pieces to the core by pressing the balls in an annulus between a drum and a kneading member extending around the core, the drum being rotated and simultaneously moved axially to move the balls through the annulus between an inlet and an outlet while kneading them between the drum and the kneading member, and vulcanising the balls thus formed to chemically bond the felt pieces to the core and to form the bonded seam.

In a particularly preferred embodiment of the invention the width of the annulus formed between the drum and the shielding member decreases between the inlet and the outlet.

In an especially preferred embodiment the invention to process includes the step of setting the width of the annulus over the path of the ball between the inlet and outlet.

Preferably the process includes the step of preliminary kneading of the balls by passing them between a rotating disk and an outer kneading member while rotating the disk.

In an especially preferred embodiment of the invention the process includes the step of delivering the kneaded balls to a feed chute extending from the outlet and directing the balls to one of two outlet chutes.

Preferably the process includes the step of automatically counting the balls passing through one outlet chute and closing the chute when a predetermined number of balls pass through the chute and opening the other outlet chute.

In a preferred arrangement the process includes the step of unloading individual felt pieces from the stack to two felt applying heads, delivering the core to the felt applying heads and moving the heads to apply the felt 5 pieces to the core.

In one embodiment of the invention the process includes a step of steam treating the balls after vulcanisation to fluff up the felted surface of the ball.

The invention also provides tennis balls whenever 10 manufactured by a process according to the invention.

The invention will be more clearly understood from the following description thereof given by way of example only with reference to the accompanying drawings in whichs Fig. 1 is a flow diagram illustrating the process of 15 the invention, Figs. 2a and 2b are perspective views of a front and rear side of a felt blank, Fig. 3 is a perspective view of a ball with the felt blanks applied, Fig. 4 is a perspective view illustrating kneading steps in the process of the invention, Fig. 5 is a side view of part of the kneading apparatus used in the process of the invention, and Fig. 6 is a plan view of part of the kneading 25 apparatus.

Referring to the drawings, a tennis ball is manufactured according to the invention by first manufacturing a pressureless rubber core 2 from two core halves 2a and 2b which meet at a seam 2c (see Fig. 3). Two felt blanks 4 are applied to the core 2. As will be apparent from Figs. 4a and 4b, each of the felt blanks 4 has a felted or outer side 4a and inner side 4b to which adhesive is applied to apply the felt pieces to the core 2. Seam adhesive is applied to the side marginal edges 4c of the felt blanks 4. It will be noted that in this case the felt blanks 4 are of generally rectangular shape having rounded shorter edges .

Referring to Fig. 1 the process according to the invention involves first mixing in step 10 of rubber based core forming materials which are formed using conventional technology into a paste 11. The paste 11 is then formed in step 12 into sheets which are cut into narrow ribbon strips 13. The ribbon strips are extruded to form pellets in step 14 which are cooled in step 15 by means of cold water. An anti-tack material such as zinc stearate is added to the cooling water to assist in free flow of the pellets. The pellets are weighed in step 16 and loaded into trays which are stacked in step 17 ready for further processing. In step 18 the pellets are loaded into individual moulds which are used to form a half core 2a or 2b. In step 19 the pellets are moulded into the half cores and in step 20 the excess material is trimmed off and recycled as required. There are two streams of half cores, each of which undergo in step 21 grinding of the seam forming edge and loading in step 22 onto an orientating and mating plate. Adhesive is applied in step 23 to the mating edges of the half cores and the half cores with the adhesive applied to the mating edges are led in step 24 to a bonding station at which, in step 25, the half cores are bonded together.

The bonded cores are vulcanised in step 26. In step 27 the flexibility of the cores is tested and cores which do not meet a predetermined flexibility level are rejected. t The outer surfaces of the cores are then roughened in step 28 and a solvent based adhesive is applied to the cores in step 29 by dipping the cores in an adhesive and mixing the cores around in the adhesive. In step 30 the cores are left to dry until ready to receive the felt blanks 4.

To form the felt blanks, rolls of felt 40 are unwound and an adhesive is applied in step 41 to one side of the felt.

Using die cutters, the felt is then cut in step 42 into the rounded rectangular shapes illustrated. The rounded rectangular shaped felt blanks are gathered together in step 43 to form an elongate stack of blanks. In step 44 a seam adhesive is applied to the side edges of the stack of the felt blanks and again the blanks are left to allow the adhesive to dry in step 45.

It will be appreciated that the cores are randomly arranged and to prepare the cores for receiving the felt blanks 4 they are first orientated in step 50 to receive the felt pieces in such a way that the seam of the core does not correspond with the seam between the cover pieces. In step 55 the felt blanks 4 are applied to the core 2. This is done by unloading individual felt pieces from the stack to two felt applying heads, delivering the core to the felt applying heads and moving the heads to apply the felt pieces to the core. In step 56 a preliminary kneading pressure is applied prior to final • kneading in step 57. The balls are counted in step 58 and vulcanised again in step 59 to bind the felt blanks to the » core and to form the bonded seam between the felt blanks.

In step 60 steam is applied to the felted balls to fluff up the felt. Checks are carried out in step 61 for any visual defects, the balls are orientated in step 62 and in step 63 the manufacturer's mark and other data is applied to the ball.

In more detail, and referring particularly to Figs. 4 to Λ 6, the cores 2 with the felt blanks applied are delivered along a chute 80 which delivers the balls to a prekneading station in which a disk 81 rotates relative to an outer housing 82, the balls being delivered into the space between the disk 81 and the housing 82 to knead the felt blanks 4 to the core as the disk 81 is rotating. The balls are delivered to a further chute 83 to a main kneading station 84.

The kneading station 84 comprises a drum 85 and an outer kneading member 86 which is spaced-apart from the periphery of the drum 85 to define therebetween an annulus through which the balls are led to knead the felt blanks to the cores. It will be noted that the kneading member 86 is adjustably mounted so that the width of the annulus may be varied as required. The drum 85 is also mounted for axial movement by means of a ram 88 which moves the drum axially as it is rotating to ensure that all the surface of the felt blanks are kneaded to the core of the ball. The drum 85 rotates the balls around to an outlet 90 for delivery along a chute 91 to one of two outlet chutes 92, 93. The entry to the chutes 92 and 93 is closed by a hinged valving plate 94 which is movable from a position closing one of the outlet chutes 92 while opening the other 93 to a reverse position of which the other outlet chute 9 3 is open and the first one 92 is closed. The balls delivered out through the chute 92 or 93 are automatically counted and when a desired number of balls have been delivered the plate 95 is automatically moved to the other position to direct the balls to the other chute. In this way the optimum number of balls for vulcanising can be readily collected.

Many variations on the specific embodiments of the invention described will be readily apparent and accordingly the invention is not limited to the embodiments hereinbefore described which may be varied in 5 both construction and detail.

Claims (5)

1. A process for manufacturing a pressureless seamed tennis ball comprising the steps ofsmixing up rubber based core forming materials to form a paste; forming the core forming paste into a sheet; cutting the sheet into a ribbon; extruding the ribbon to form a pellet of core forming material; cooling the pellet; loading the pellets into individual core forming moulds; forming each pellet into an individual hemispherical half core; trimming off the mating edges of the half cores; grinding the mating edges of the half cores; applying adhesive to the mating edges of the half cores; bonding two half cores together to form a complete core; vulcanising the bonded cores; flexure testing of the cores; roughening the outer surface of the cores; applying a solvent based adhesive to the core; drying the adhesive on the core; forming a stack of covering felt pieces; applying a seam adhesive to the side edges of the stack; orientating the core to receive felt pieces; 10 applying two felt pieces to the core; kneading the felt pieces to the core by pressing the balls in an annulus between a drum and a kneading member extending around the core, the drum being rotated and 15 simultaneously moved axially to move the balls through the annulus between an inlet and an outlet while kneading them between the drum and the kneading member, and vulcanising the balls thus formed to 20 chemically bond the felt pieces to the core and to form the bonded seam.

2. A process as claimed in claim 1 wherein the width of the annulus formed between the drum and the shielding member decreases between the inlet and the outlet, preferably the method includes the step of setting the width of the annulus over the path of the ball between the inlet and outlet, preferably the width of the annulus is adjustable.

3. A process as claimed in claim 1 or 2 including the step of preliminary kneading of the balls by passing them between a rotating disk and an outer kneading member while rotating the disk, preferably the kneaded balls are fed to a feed chute extending from the outlet and directing the balls to one of two outlet chutes, preferably the method includes the step of automatically counting the balls passing through one outlet chute and closing the chute when a predetermined number of balls pass through the chute and opening the other outlet chute, preferably the method also includes the step of unloading individual felt pieces from the stack to two felt applying heads, delivering the core to the felt applying heads and moving the heads to apply the felt pieces to the core, preferably the process further includes the step of steam treating the balls after vulcanisation to fluff up the felted surface of the ball.

4. A process substantially as hereinbefore described with reference to the accompanying drawings.

5. Tennis balls whenever manufactured by a process as claimed in any preceding claim.