Patent GB-1248309-A (GB)
Title: Improvements in flat bed type casting machines
IPC: B29C43/00
Filed: 1969-03-19
Abstract: 1,248,309. Casting press. WOOD INDUSTRIES Inc. 19 March, 1969 [29 March, 1968], No. 14379/69. Heading B5A. [Also in Division B6] General operation.-In a press for casting thin plastics printing plates from a liquid thermosetting material having exothermic characteristics during curing, an upper platen 3 carried by a frame 5 is closed on to a matrix M, clamped on a lower platen 2, by initial pivoting movement of the frame 5 with a shaft 7, which is located in the machine frame 9, until brackets 15 on either side of the frame 5 abut stops 17, whereafter the closing movement of the upper platen 3 occurs about a shaft 16, journalled in the brackets 15, and at a progressively decreasing rate so that the liquid material initially poured on to the matrix M at the end thereof adjacent the shaft 16 flows across the matrix M at a lower rate as the cure thereof progresses to avoid the entrappment of air bubbles. The platens 2 and 3 are of heavy gauge steel to provide a heat sink for the curing resin and are maintained at a desired temperature by heating fluid circulated therein. Press actuating mechanisms.-The pivoting movement of the frame 5 with the shaft 7 is obtained by an arm 6, which also carries the shaft 16, and is fixed to the shaft 7 which is rotated by an hydraulic cylinder 10, via a pistonrod 12 connected to the shaft by an arm 12<SP>1</SP>. The pivoting movement of the frame 5 about shaft 16 is obtained from an hydraulic cylinder 21 pivotally mounted to the arm 6, at a shaft 23, and a piston-rod 22 whereof is connected to one end 24 of a bell crank lever 25 which is fixed to a rotatable shaft 26, carried by the arm 6, and connected at the other end 27 thereof to the frame 5 by a link 28, the shaft 26 carrying a cam 30 which engages a follower 32 connected to actuate a fluid control valve 33 whereby the flow of hydraulic fluid from the rod end of the cylinder 21 is progressively decreased as shaft 26 is rotated by the cylinder 21 to decrease the rate of closing movement of the platen 3 about the shaft 16. The actuation of hydraulic cylinders 21 and 10 is controlled from limit switches and, after closing of the press, pressure is maintained in the upper platen 3 by the cylinder 21. Platen spacing adjustment.-In the Fig. 1 embodiment the spacing of the upper platen 3 above the lower platen 2 is obtained by vertical adjustment of the stops 17 by screws 18 and of similar stops engaging frame brackets at the other end of the frame 5. In an alternative embodiment, Fig. 6 (not shown), the adjustment is obtained by bracket stops which are provided on a member (51), the lower surface of which is inclined to the horizontal and which is displaceable over rollers (52) by a screw mechanism rotated from a hand wheel by bevel gears. Matrix clamping mechanism.-The matrix M is clamped to the lower platen 2 by the knife edge 40 of a frame 4 which is pivotally mounted, midway along the platen 2 between a pair of arms 42 which are vertically displaceable from a handle 52, through an operating connection comprising bell crank leverages about a shaft 44 and links 46 to leverages about a shaft 48 which is rotatable by a pinion drive 49, 50 from a shaft 51 rotated by the handle 52. The pivotal mounting of frame 4 permits the accommodation of matrices M which are thicker at one end than the other, and of a tilting of the lower platen if employed to facilitate resin flow over the matrix M: