GB789764A - Improvements relating to the regulation and control of saw cutting machinery and the like - Google Patents

Abstract

789,764. Sawing. QUALTERS & SMITH BROS., Ltd. Sept. 25, 1956 [Sept. 26, 1955], No. 27361/55. Class 145. [Also in Group XXXII] Means for controlling the operation of a saw comprises a hydraulic cylinder-and-piston assembly C, Fig. 2, a valve 16 controlling the flow of fluid through a port 17, Fig. 3, in the piston 14, a pump 24 which has a plunger P actuated by the reciprocation of the saw and is connected through valves 25, 27 to the cylinder spaces below and above the piston 14, a knockoff control for closing the valve 16 in a pre-set lowered position of the piston, and means for releasing the pressure, which is built up beneath the piston as a consequence of the closure of the piston valve, when the piston is fully raised. As shown in Fig. 1, a hack-saw bow slide 10 is reciprocated by crank mechanism 11 which also incorporates an eccentric strap 13 operating upon the plunger P of the pump 24. The rod 15 of the piston 14 is connected at its upper end to the bow slide so as to move vertically therewith. The piston valve 16 is in the form of a disc which is positioned below the piston 14 and tilted to control the port 17 by the action of a rod 18 in adjustable screwed connection at its upper end with a boss 20 engaging a rotary cam 22 on the rod 15; when the piston 14 reaches a pre-determined lower position, a lever 23 contacts a knock-off pin 29 whereby the cam is rotated to position a nick 22a therein to permit the upward movement of the rod 18 under the action of a spring 19 and thereby close the valve 16. In operation, as the saw is reciprocated, the inward stroke of the plunger P forces fluid through the valve 25 into the space below the piston 14 so as to lift the latter slightly and its outward stroke draws fluid into the pump cylinder through the valve 27. The weight of the saw assembly acting on the rod 15 forces fluid through the port 17 at a rate which is set by the valve 16 so that the drop of the piston is slightly faster than its rise whereby the saw progressively cuts through the work. When the pre-determined cut has been made, the lever 23 rotates the cam 22 to permit the rod 18 to rise and close the valve 16. The continued action of the plunger P in pumping fluid to the underside of the piston 14 forces the latter up until it rises above an orifice 30 ; the piston remains in this position until the device is re-set by pressing down the lever 23.