Patent GB-363020-A (GB)
Title: Improvement in hydraulically operated cylindrical grinding machine
IPC: B24B47/06
Filed: 1930-09-30
Abstract: 363,020. Hydraulically operated grinding and polishing machines. NORTON CO., New Bond Street, Worcester, Massachusetts, U.S.A. Sept. 30, 1930, No. 29270. Convention date, Sept. 30, 1929. [Class 60.] Rollers, spindles, and the like, heating; trueing rotating tools.-In a cylindrical grinding machine wherein the rotating work is traversed axially past a grinding wheel which is fed radially inwards at the end of each traverse, the work is traversed by a fluidpressure piston which is so controlled as to cause a dwell at the end of each traverse during which the wheel is fed in, the work performing at least one complete revolution after stoppage and before the next feed and at least another revolution after the feed and before the traverse commences in the opposite direction. The work is mounted between centres on a table 20, Figs. 1 and 2, traversed along guides 22 by a piston 36 within a cylinder 35, and the grinding wheel 16 is supported by a carriage 17 fed along transverse guides 18 by a feed screw 26 which is rotated intermittently through gearing 28, a ratchet wheel 30 and a pawl 31. Fluid pressure is supplied by a pump 43, Fig. 3, drawing from a sump 42 and delivering through a pipe 44 to a reversing valve 40. To traverse the table 20 in the direction of the arrow in Fig. 3 the plunger 49 of the reversing valve is in its extreme left-hand position, the piston 47 then uncovering the port 50, and the plunger 55 of a pilot valve 41 is in a central position, closing both ports 64, 65. Towards the end of the traverse a dog 59 on the table strikes a pin 58 on a lever 56, pivoted at 57, and causes the lower end to push the plunger 55 of the pilot valve 41 to the left, thereby causing the plunger to be displaced from its normal central position and allowing the port 64 to be opened. Fluid then passes from the reversing valve, through pipe 67, port 64, and a pipe 70 to the chamber 71 of the reversing valve to move the valve to the right. After a predetermined travel of the lever 56, the pin 58 strikes an adjustable screw 85 on a lever 80, whereupon the two levers oscillate together and the latter moves the reversing valve to the right through a link 81, lever 82, and link 84, thus closing the port 50 and bringing the table to rest. Fluid passing through the pilot valve and pipe 70 then moves the reversing valve further to the right until a port 52 is uncovered by a piston 48 to traverse the table in the opposite direction, an adjustable valve 90 being provided in the pipe 70 to vary the rate of flow through this pipe and consequently the speed at which the reversing valve is moved, thereby causing the table to remain stationary for a variable time before commencing its return traverse. A spring 93 situated between collars on the plunger 55 restores the pilot valve and lever 56 to a central position as soon as the dog 59 recedes from the pin 58, the pilot valve then confining the flow from the reversing valve and through the pipe 67 to the closed chamber 66. A similar sequence of events occurs at the opposite end of the traverse by means of a second dog 60 on the table encountering the pin 58 and a second valve 116 provides for varying the duration of the dwell at this end. Exhaust from the cylinder 35 takes place through the pipes 51 or 53, reversing valve 40, ports 101 or 111, pipe 102, cylinder 103, and pipe 113 to the sump 42. The outlet port 106 in the cylinder 103 is elongated and is adapted to be covered to a greater or less extent by means of a balanced piston 105 to throttle the exhaust and so vary the speed of travel of the table 20. A lever 107 pivoted at 108 is connected to the piston 105 to control the traverse speed by hand and also to stop the traverse by closing the port 106. A rotatable cam 160, Fig. 2, is adjustable by a turnbutton 163 and a scale to determine the rearward position to which the piston may be returned, thereby ensuring that the table will be traversed at the same speed after a stoppage. A pin 128, Fig. 1,' is movable into the path of an adjustable screw 130 on the lever 107 to give a setting of the lever suitable for a slow traverse of the table for trueing the grinding wheel. Two handles 120, 121 co-operate with scales 124 for setting each of the valves 90, 116 to vary the period of dwell. The pilot valve 41 exhausts into a pipe 144 connected to the return pipe 113, an adjustable plug 95, Fig. 3, being provided for varying the rate of exhaust at one end and hence delaying the speed of movement of the plunger 55 to ensure the port 50 or 52 being fully open before the pilot valve returns to its central position. A pipe 155 or a passage connects the chamber 156 of the speed control valve 103 to the exhaust line 113 to relieve pressure above the piston 105. The pawl 31, Fig. 2, for giving the grinding wheel its transverse feed is actuated by a connecting-rod and crank disc 132 on a shaft 133 which carries a pinion 134. A toothed sector 135 engages the pinion and is oscillated at each end of the table traverse by an adjustable screw 137, 138 on the lever 82 connected by the link 84 to the reversing valve 40, the lost motion between the sector arm 136 and the screws 137, 138 ensuring that the work will rotate after the traverse has stopped and before the in-feed of the wheel takes place. The pawl rotates the ratchet 30 whilst the crank rotates from 33 to 33a, but from 33a to 33b the pawl rides idly over the ratchet teeth to ensure that the work will rotate after the feed of the wheel and before the return traverse commences. Variation of the amount of feed is effected by radial adjustment of the crank pin on the disc 132.