| 摘要 |
770,871. Extruding. FIELDING & PLATT, Ltd., and HENLEY'S TELEGRAPH WORKS CO., Ltd., W. T. Nov. 19, 1953 [Oct. 15, 1952], No. 25891/52. Class 83 (4). [Also in Group V] An hydraulically-operated continuous extrusion press for producing solid sections and tubes from metals or synthetic resins, particularly for sheathing cables with aluminium, has at least two billet containers in which billets 21, 22 are extruded in succession through a common die by hydraulic rams 1, 2, respectively, the pressure liquid supply to the rams being so controlled by a change-over valve 20 that during the changeover the feed of one ram decreases at the same rate as the feed of another ram increases, and an auxiliary source of hydraulic pressure is provided for pre-stressing the incoming ram prior to the change-over. The pressure liquid is supplied by a variable delivery pump 7. Near the end of its working stroke the ram 1 closes a limit switch 24 which actuates a solenoid to open a pre-loading valve 11. This allows pressure liquid from an accumulator 8 to pass into the other ram 2 and pre-stress the ram and its cylinder and all the packings associated therewith so that the extrusion of the billet 22 will commence immediately upon the change - over. When the ram 1 has completed its stroke a second limit switch 25 is closed and electrical actuating means, such as a motor, is operated to move the change-over valve 20 to the right, thereby gradually transferring the pressure liquid supply to the ram 2. When the valve 20 has completed its movement a limit switch 26 is operated to close the pre-loading valve 11 and actuate a bypass valve 15 and a drawback control valve 18, whereby pressure liquid from a constant delivery pump 14 passes through a check valve 16 and the valve 18 into a drawback cylinder 12 for retracting the ram 1. Simultaneoulsy, a combined filling and exhaust valve 3 is opened by the pressure liquid from the pump 14 to allow the liquid in the ram cylinder 1 to be returned to a pre-filling tank 6. At the end of its return stroke the ram 1 engages a limit switch 27 to return the valves 15, 18 to their inoperative positions. A new billet 21 is then loaded in front of the die box 23, which houses the two billet containers and the extrusion die, and the drawback control valve 18 is again actuated to exhaust the drawback cylinder 12 and to open the filling valve 3, thereby allowing liquid at pre-filling pressure from the tank 6 to enter the ram cylinder 1 and move the ram forwardly to move the billet into its container and upset it therein. When the ram 2 has nearly completed its stroke a limit switch 28 is operated and the change-over cycle is repeated in the reverse manner. The accumulator 8 is charged by a pump 9. Instead of the accumulator a pump may be used. The pump 7 may be a constant delivery pump or two or more constant delivery pumps may be used singly or collectively to supply the high pressure liquid to two or more ram cylinders. The pre-stressing may be performed by a supplementary variabledelivery pump. Alternatively, all the hydraulic pumps may be replaced by accumulators. The rams 1, 2 may have the same bore and stroke or they may have dissimilar dimensions. The hydraulic control system may be used in extrusion presses of the kind described in Specification 770,872. Reference has been directed by the Comptroller to Specification 695,012.
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