GB684863A - Machine and method for making hollow articles - Google Patents

Abstract

684,863. Moulding hollow plastic articles. MILLS, E. E. May 19, 1950 [Oct. 3, 1949], No. 12645/50. Class 87 (ii). In making plastic hollow ware a tube of softened organic plastic material is introduced in a mould, the tube is sealed at each end of the mould against leakage of a fluid confined in the tube and is pierced within the mould and a fluid is introduced in the tube within the mould through the pierced opening under a positive pressure sufficient to expand the plastic material to the shape of the mould. Pairs of mould halves, upper 16 and lower 15, are disposed around the periphery of a circular continuously rotatable table 11. The upper half of each mould is attached to a piston rod 17 which is actuated by fluid pressure in a cylinder 18 supported from the table. A hollow needle 28 passes through the upper half of each mould. The actuating cylinder 18 is connected by piping to a valve 38 and the needle 28 is similarly connected to a valve 39, the valves 38, 39 being connected by piping to a source of fluid pressure. The ends of the mould halves have sharp edges 33, 34 which may or may not just meet when the mould is closed. Coolant can pass from a tank 47 through chambers 36 in the mould halves and thence to a drain-pan 53, from which it may be pumped back to the tank. Softened plastic tubing 55 is extruded from a machine 54 and, as the open moulds on the table 11 are brought near the tubing, moving in the same direction as it is being extruded, it lies in the lower halves of successive moulds. As the table continues to move, a rocker arm 40 meets a cam 42 and thereby operates the valve 38 to allow fluid pressure in the cylinder 18 to actuate the piston rod 17 and close the upper mould half. The edges 33, 34 compress the tubing 55 and seal off a portion of it in the mould and the needle 28 pierces the material and enters the sealed-off portion. A rocker arm 40a meets a cam 42a and thereby operates the valve 39 to cause fluid to be forced through the needle 28 and expand the sealed-off portion of the tubing against the inside of the mould. Before the fluid pressure is released coolant is circulated through the chambers 36 to cause the material of the moulded article to set. As the table 11 continues its rotation the fluid pressure within the article is released and the upper mould half 16 raised, when the moulded article may be removed. The needle 28 is arranged to pierce an extension of the moulded article (e.g. the neck of a bottle) which is afterwards removed. If the sharp edges 33, 34 are slightly short of the meeting surfaces of the mould halves successive moulded articles will be connected by short lengths of the tubing 55, thus facilitating manual removal of the articles from the moulds.