Patent GB-512194-A (GB)
Title: Improvements in or relating to grinding or abrading machines
IPC: B24B47/06
Filed: 1938-08-03
Abstract: 512,194. Grinding machines; hydraulic transmission of power; valves. NORTON CO. Aug. 3, 1938; No. 22947. Convention date, Aug. 16, 1937. [Class 60] [Also in Group XXIX] In a grinding-machine a work table is reciprocated by a fluid pressure piston and cylinder, the admission of the fluid being controlled by a valve moved by dogs on the table, the arrangement being such that at the end of a stroke, the valve is moved to a central neutral position to stop the table for a period determined by an electrical time delay relay, the valve then being moved so as to start movement of the table in the reverse direction. The table 10 is reciprocated on a base 9 by a cylinder 11 secured to the table and movable over two spaced pistons 12, 13 secured by hollow rods 14, 15 to the base 9, and fluid is supplied to the cylinder through a control valve 25 from a reservoir 20 by means of a pump 22. The valve 25 has a stem 29 on which are pistons 30 - - - 34, fluid being supplied by pipes 23, 24 to either of the chambers 37, 38 between pistons 31, 32, and 32, 33 so as to pass through a pipe 39 or a pipe 44 to the hollow rods 14 or 15; exhaust fluid passes through a pipe 45 and speed controlling throttle valve 50 to a pipe 46 leading to the reservoir 20. The valve 50, which may be integral with the valve 25, comprises a stem 51 having thereon spaced pistons 52, 53, and in the valve casing is a port 54 of V-shape communicating with the pipe 45. The valve stem 51 is rotatable by a knob 59 so as to bring the inclined end of piston 53 to cover, more or less, the port 54, and the stem is held in adjusted position by a spring pawl 61, which engages notches in a part 60 on the stem; this arrangement allows the valve to be moved axially by a lever 70 so as to stop or start the table movement without altering the angular'setting of the valve. When the valve is moved to stop the table, by closing the port 54, the chamber 82 between the pistons 52, 53 communicates with pipes 80, 81 so as to connect the pipes 39, 44, thereby allowing of free manual adjustment of'the table. The movements of the table are reversed by movement of the valve 25, this being achieved by means of a lever 93, moved by dogs 90, 91 adjustably mounted on the table, and carried by a stud 94 pivoted in the base 9. The stud has fixed thereon a lever 95, and rotatable thereon a lever 96, the levers being formed at their ends with recesses 101, 102 respectively to house a spring 105, and the lever 96 engaging,- by a pin 97 thereon, a slot in the valve stem 29; the lever 96 carries a pin 100 lying in an aperture 99 in lever 95 so as to permit relative movements of the levers to compress the spring 105. The operation of reversing is carried out in two stages, so as to obtain the desired dwell at the end of each stroke, the first stage being movement of the valve to central or neutral position by the levers 93, 95, 96, when the table stops, and further movement of the valve is resisted, as described below. The second stage is brought about by the spring 105, which, when the valve is free to move, gives it a slight movement so as to uncover either of the ports 110, 111 allowing fluid to enter chamber 112 or 113 and, on account of the difference of the areas of the pistons 33, 34 or 31, 30 respectively, to move the valve rapidly to reversing position. The resistance to the movement of the valve is brought about by auxiliary valves 130, 140, one for each chamber 112, 113, the valves 130, 140, when closed, preventing flow of fluid through pipes 124, 125 to a reservoir 123 or through pipes 126, 127 to a reservoir 122. The valves 130, 140 are moved respectively in one direction by solenoids 132, 142 supplied with current through time delay relays 133, 143, the circuits being closed by switches 135, 145 actuated respectively by the dogs 90, 91; adjustment of the relays allows of the provision of a dwell of any desired duration at either end of the strokes of the table. Specification 463,334 is referred to.