Patent GB-394595-A (GB)
Title: Method of and means for moulding tennis balls and like hollow articles
IPC: B29C65/02
Filed: 1932-12-28
Abstract: 394,595. Moulding and vulcanizing gas-filled hollow articles of rubber and the like, such as tennis balls. DUNLOP RUBBER CO., Ltd., 32, Osnaburgh Street, London. Dec. 28, 1932, No. 36654. Convention date, Dec. 29, 1931. [Classes 70 and 87 (ii).] In the method of moulding balls or the like in which two semi-circular halves are vulcanized together and the inflating gas supplied in a single operation, means are provided for returning excess gas to the reservoir by the operation of finally bringing the mould parts together. In the illustrated form a lower mould shell 10 fixed on a standard 11 is adapted to receive an upper mould shell 12 movable about the pivot 16 by the hydraulic ram apparatus 19 into the open position shown in dotted lines. A link 21 pivoted to the fixed bracket 17 swings the shell 12 about the pivot 14 during this operation. A catch 63 engaging a pin 66 may be used to lock the member 12 in raised position until released by a sliding rod 66<1>. Each of the shells carries mould parts with semicircular mould recesses, the upper part 31 being fixed in the shell 12 while the lower part 26 has a sliding engagement with the shell 10. In operation, the mould parts are charged with the pre-formed rubber halves while in the open position, beads 68, 69, Fig. 6, on the rubber engaging corresponding recesses in the mould walls to position and retain them in the moulds. The mould shells are then closed and looked by sliding the keys 41 through registering lugs on the two shells by means of the cylinder 49. In this position the mould halves are still slightly separated as shown in Fig. 6. Fluid pressure is then admitted by the duct 35 to the packing rings 34, 36 in order to effect a seal between the mould part 26 and shell 10 and between the upper and lower shells 12, 10. The filling- gas is next admitted by pipe 52 to the interior of the articles, following which higher fluid pressure is admitted to the space between the base of member 26 and the shell 10 to force the mould member 26 upwards in the shell 10 and finally close the mould halves. During this operation, the excess filling-gas is forced back into the supply-pipe. Steam is then admitted through the pipes 56, 59 to the jackets of the moulds to perform the vulcanizing operation. The pipes 59 have a stuffing-box connection with the shell 10 to permit them to slide with the mould member 26. After vulcanizing, cooling-water is admitted to the jackets, and then the gas-supply pipe 52 is utilized to supply compressed air to force the member 26 downwards in its shell and thus effect an initial separation of the mould halves before the shells are opened. The joint between the two rubber halves is made preferably as shown in Fig. 7. One half is bevelled inwardly as shown at 73 and the other half is bevelled to a different angle, the arrangement being such that as the mould section 26 moves upwards, the edge 72 strikes the edge 73 intermediate its ends and thereafter slides along the surface of the edge 73 so that the two edges are pressed together. The edge 74 is preferably rounded off to assist the sliding movement. Several modifications are referred to, including the use of two movable mould shells co-operating with a central double-sided fixed shell, and the sliding of both mould parts in their respective shells instead of one being slidable and the other fixed. The moulding cavities may also be formed integral with the shell in cases where they are not required to slide therein.