Patent GB-1305553-A (GB)
IPC: B29C48/48
Filed: 1969-03-11
Abstract: 1305553 Dual ram extruder BARWELL ENG Ltd and J H BARWELL 5 March 1970 [11 March 1969] 12745/69 Heading B5A [Also in Division F1] Heated flowable material e.g. rubber, is continuously extruded from a die head assembly 31, Fig. 3, to which it is supplied by a horizontal conduit 29, Fig. 4, the supply whereto, through ports 30, from the cylinders, 13 or 14, of alternately advanced rams 59, is maintained constant by a rotary valve member located in the conduit 29 and which simultaneously progressively closes a port 30 from one cylinder as a port 30 from the other cylinder is being opened, the valve being actuated by an hydraulic ram, to which pressurized hydraulic actuating fluid is supplied from a source separate from means supplying pressurized fluid to actuate the rams 59. In the Fig. 4 embodiment, the flow through the ports 30 is valved by a pair of ports 44 in the cylindrical surface of a valve member, the closed end whereof engages at dogs 43 with a tubular shaft 38 which is arcuately reciprocated, to effect the valving action, by an hydraulic power cylinder actuated lever 35. The die head 31 (which is secured closed by a latch 35), may be pivoted at 33 to an open position in which the valve member may be ejected for cleaning purposes by the piston 51 of a power cylinder 50 connected to the shaft 38, the valve member being replaced manually. The valve member may alternatively comprise a disc, Fig. 6 (not printed), which is incrementally unidirectionally indexed by a ratchet and pawl mechanism from the lever 45, to effect the valving action by means of five uniformly circumferentially spaced, axially projecting closure surfaces (47). In a modified valve construction (not shown) the extrusion cylinders may be interconnected by the valve member for passage of material therebetween to effect softening and mixing thereof, prior to the valve switching to discharge material through the die. Each extrusion ram 59 is advanced in its extrusion barrel, 13 or 14, by hydraulic pressure fluid, supplied from a separate pump for each ram, admitted to the upper ends of concentric power cylinders 55, 56, of power cylinder assemblies, 20 or 21, and is retracted by pressure fluid admitted to the lower end of each inner cylinder 56, the fluid pressure supply to advance one ram 59, and then from a separate pump to actuate the valve in conduit 29, being initiated by a device 65 located between the inner and outer cylinders 55, 56, and which senses when the material in the other cylinder is nearly exhausted. The device also senses when a ram 59 has been retracted from its cylinder 13 or 14, to initiate the supply of pressure fluid to actuate a further power cylinder, 22 or 23, which pivots the power cylinder assemblies alternately about posts 18 away from above its extrusion cylinder to enable the loading thereof with further extrusion material. In their position above each extrusion barrel, the cylinder assemblies, 20 and 21, latch into the machine frame 28 which bears the thrust during extrusion. A safety device prevents movement of a ram 59 when not in alignment with an extrusion cylinder. A seal 61 is slidable around each cylinder 57 to seal around the extrusion cylinder open end during advancement therein of the ram 59, when air is evacuated from the extrusion cylinder through ram bores 59, which are closed by a flap 59b, when this contacts the extrusion material. Each barrel, 13 and 14, is lagged and provided with electric heaters. Electrical, steam, gas or other fluid heating elements, melt flow regulating devices and screening devices may be located within the conduit 29. The conduit 29 may contain screens, or devices varying the extrusion pressure over the upstream face of the die.