GB722125A - Improvements in and relating to circular saw machines - Google Patents

Abstract

722,125. Sawing. CUNDEY, J. E., and CUNDEY, W. B. Aug. 5, 1953 [May 5, 1952; Sept. 16, 1952]. Nos. 11267/52 and 23185/52. Class 145. A circular saw machine has a circular saw blade 15a, Fig. 1, which is raised and lowered in synchronism with a gripper device 30 to hold the timber in place before the cutting action begins and an end stop 40 to locate the timber at the beginning of the cutting operation, the end stop being automatically withdrawn to allow the timber to drop at the end of the cutting operation. The saw is moved about a pivot 16 by a hydraulic ram 25 and is belt-driven from a shaft 11 which also drives a pump for the hydraulic apparatus through a belt 21. The shaft 11 is mounted on a frame 10, which may be on wheels for towing, and is driven by an internal combustion engine or other motor, the gripper 30 is operated by a spring-loaded hydraulic ram 31 and holds the timber in a rest formed by an inclined pair of rollers (not shown) while the stop 40 is adjustably secured to a sub-frame 53 pivotally connected by links 54 to the frame 10 and operated by a spring-loaded hydraulic ram 41. With the saw in its raised position, the pressure in the ram 25 is communicated through pipes 86, Fig. 2, and a pilot valve 87 to a cylinder 75 to hold a valve 85 against a pawl 88 held by a catch 91. Oil or other fluid under pressure from a pump 77 is thus able to traverse a closed circuit including pipes 76, 81, 83 and a tank 82. When the timber is brought into contact with the stop 40 the sub-frame 53 is displaced slightly in relation to the ram 41 to displace the catch 91 and allow the valve 85 to push the pawl into contact with a cam 93 the setting of which controls the speed of descent of the saw. The catch 91 may alternatively be released manually by a push rod 92, Fig. 1, and a lever 90. The valve in its new position allows fluid to exhaust from the ram 25 through a pipe 80, a port 85b and the pipe 81 while simultaneously pressure fluid flows from the pump 77 through lines 76, 95 to the rams 31 and 41. The ram 31 is loaded by a weaker spring than the ram 41 so that the gripper 30 engages the timber before the stop 40. When the saw has completed its descent under gravity it operates the pilot valve 87 to connect the pipe 86 to the pipe 81 so that a spring 99 displaces the valve 85 to the left in which position it connects the pipes 76 and 80 to liftthe saw and the pipes 95 and 81 to return the gripper and end stop to their original positions. A relief valve 98 prevents excessive pressure in the line 95 if the operation of the pilot valve 87 is delayed, and a valve 96, which allows oil to flow freely into the ram 41 but only slowly out of it again, ensures that the stop 40 is not restored to its original position until the cut timber has fallen from the saw. A number of end stops spaced at different distances from the saw may be provided, the required stop being released for displacement by a spring 63 to an operative position either by a hydraulic control mechanism or by a cable 61 and lever 60.