Patent GB-225715-A (GB)
Title: Improvements in or relating to machines for molding plastic material
IPC: B28B3/00
Filed: 1923-12-19
Abstract: 225,715. Wade, H., (Gates, E.). Dec. 19, 1923. Endless-chain machines ; moulding- machines ; processes.-Plastic material placed within a mould is caused to conform to the mould by suddenly and directly applied gaseous pressure. Two forms of machine are described ; in the first (a) the gaseous pressure is derrived from the explosion of a combustible gaseous mixture, whilst in the second (b) the pressure is derived from a relatively large quantity of gas under high pressure. (a) The mould A, Fig. 10, into which plastic material, e.g. terra-cotta, has been roughly pressed by hand, is placed within a chamber 20 into which the combustible mixture is introduced and exploded. A shaft 60, mounted on a head 54 communicating with air and fuel reservoirs, carries spark contacts and also carries controlling valves for the chamber 20. The shaft 60 is periodically rotated through one revolution by a constantly-running pulley 62 through a spider 63, Fig. 7, which carries a band 64 encircling a brake flange 62<a> on the pulley. One end of the band is secured at 65 to the spider and the other end is attached to an arm 66 associated with a lever 68 and spring 69 tending to tighten the band on the flange 62<a>. The arm 66 is normally held by a pawl 72 on a lever 70 pivoted at 71 and retained by a rod 78 and spring 74. A trip lever 82 secured to a cam-controlled lever 83 depresses the lever 70 through a pivoted trip finger 77 which is subsequently disengaged from the lever 82 by the arm 66. the chamber 20, Fig. 10, is provided with a pair of doors 21 for entrance and exit of the moulds A. The doors 21 are partly balanced and when in closed position are forced against hollow gaskets 27 by end yokes 28 coupled by screwed shafts rotated by racks which are reciprocated by cranks on the main shaft 45. Roller arms on the lower pair of shafts raise the doors 21. The moulds A are supported by trays B which are advanced to the chamber 20 along a runway 88 by a pawl 99 on a carriage 91 connected to a rod 92 reciprocated by cranks 44 on the shaft 45 through levers 97 and links 96. As a tray enters the chamber 20 it pushes the preceding tray on to a chain 102 which is also reciprocated by the rod 92 through a slide 93. Pawls 101, 105 prevent backward movement of the trays. (b). Fig. 20 shows a modified machine in which the mould C is raised by an hydraulic ram 115 into a chamber 110 surmounted by a drum or shell 116 containing air under a pressure of 75 lbs. per square inch or more, the head 118 of the chamber 110 being furnished with a number of passages 120 normally closed by valves 121 adapted to be suddenly released so as suddenly to raise the pressure within the chamber 110 to that of the drum 116. The valves 121 are suspended by hollow stems 122 from a platen 123 slidably fitting a shallow cylinder 124 which communicates by passages 129 with a chamber 128 furnished with an air vent 132 adapted to be closed by a valve 131a carried by a piston 131 in a cylinder 130. A pipe 133 leading to the cylinder 130 is furnished with a three-way valve through which the cylinder can be connected either to the drum 116 or to the atmosphere. Upon opening the cylinder 130 to the atmosphere, the piston 131 falls, opening the vent 132 and causing the platen 123 to rise suddenly under the pressure within the drum 116 thereby raising the valves 21 and permitting the air within the drum to rush through the openings 120 into the chamber 110. The threeway valve is then turned to re-establish connection between the cylinder 130 and chamber 116 causing the valves 121 to close again.