Patent GB-827716-A (GB)
Title: Surface grinding machine
IPC: B24B47/06
Filed: 1957-04-16
Abstract: 827,716. Grinding. CINCINNATI MILLING MACHINE CO. April 16, 1957 [April 27, 1956], No. 12387/57. Class 60. [Also in Group XXIX] In a surface grinder having a table 14, Fig. 1 reciprocatably mounted on a saddle 11 on a bed 10, an adjustable pick-feed mechanism for the saddle comprises a hydraulic motor 150, Fig. 12, a reversing valve 322 for the motor, and a metering cylinder 376 which receives exhaust fluid from the motor to determine the length of the operation thereof and has a reversing valve 373 operated at each end of the stroke of the table for alternately connecting the exhaust to opposite ends of the cylinder. The table 14, Fig .1, is longitudinally reciprocatable on guideways on the saddle which is transversely adjustable on guideways 12, 13 on the bed 10. An extension at the rear of the bed has vertical ways for guiding a carrier 19 on which is mounted a spindle 20 carrying a grinding wheel 21, the prime mover for the wheel also being mounted on the carrier. A depending bracket 81, Fig. 4, from the saddle carries a nut 82 engaging a lead screw 83 mounted for axial movement in a sleeve 84 which is rotatably mounted in bearings 87, 88 in the bed 11 and is integrally formed with a gear 86. The screw has a rod 91 formed at its end on which is a piston 92 normally urged by fluid pressure against a cap 96 in the end of a cylinder 95 ; pressure is supplied alternately to the ends of the cylinder to reciprocate the screw 83 and saddle when it is desired to dress the grinding wheel by means of a diamond mounted on the table 14. The gear 86 is connected by gears 99, 101 and 102, Fig. 8, to a gear 104 which is formed integrally with a bevel gear 105 and secured to a tubular shaft 107 mounted in the bed 10. The gear 105 is rotatable in opposite directions to adjust the saddle 11 by a bevel gear 111, Fig. 12, on the hydraulic motor 150 which is controlled by the reversing valve 322 actuated by a pilot valve 323 operated automatically by alternate engagement of a forked lever 352 with adjustable abutments 356, 357 on the saddle, the movement of the plunger 343, which has an enlarged centre portion to enable the valve to be selfactuating to finish its stroke, of the valve 323 then being limited by shoulders thereon engaging washers 359, 360 spring urged apart in an enlargement in the valve housing. Further movement of the plunger is possible by manual operation of lever 350 to provide a continuous rapid movement of the saddle. The motor 150 is actuated to provide an incremental- or pickfeed of the saddle at each end of the stroke of the table by control dogs 368, 369, Fig. 13, on the pilot valve 45, controlling the reciprocation of the table, contacting switches 370, 371 to energise one or other of solenoids 371<SP>1</SP>, 374, Fig. 12, to actuate the reversing valve 373 to alternately connect one or other of the ends of the cylinder 376 to the motor 150, the piston 375 then moving towards the other end to expel fluid from the cylinder until it reaches the end of its travel and blocks the flow of fluid from the motor. The movement of the piston can be adjusted to determine the amount of fluid pasing through the motor, and hence the time it operates and how far the saddle moves, by adjustment of a nut 404 which is engaged in a thread in the piston and keyed to a shaft 403 axially located in the bed 10 ; the piston is therefore movable from the position shown to a position wherein the nut abuts the shoulder 408 of the shaft 403. The shaft is rotated by a knob 409. Fig. 14 and the position of the nut indicated on a graduated drum 431. Each revolution of the drum is indicated by the action of an eccentric 410 which radially displaces a disc 412, prevented from rotating by a pin 413, to cause a tooth 415 to be moved to engage and rotate an internal gear 416 an amount sufficient to present a number on the gear to an orifice in a cover 419 secured to the machine. Accurate positioning of the gear is effected by a ratchet wheel 422 secured to the cover and a spring urged detent 430 attached to the gear. The reciprocation of the table 14 is delayed during the pick-feed operation by a delay valve 396, Fig. 12, which, when fluid is flowing through the metering cylinder 376 and hence lowering the pressure in the supply line, has its plunger 398 axially moved by a spring 403<SP>1</SP> to disconnect the reversing valve 227, Fig. 13, of the table. When the piston 375, Fig. 12, reaches the end of its stroke, the fluid flow is blocked, the plunger 396 moved against the spring and reciprocation of the table recommenced. In order to permit manual adjustment of the saddle, a by-pass valve 385 is provided which connects the supply lines to the motor 150 together when fluid is not flowing through the cylinder 376 so that during rotation of the gears 99-105 by a handwheel 110, Fig. 8, the bevel gear 111 on the motor can rotate and fluid flow from one side of the motor to the other. The handwheel is disconnected from the shaft 107 when fluid pressure is applied to the motor 150 to rotate the gear 111 by pressure axially moving a plunger 139, Figs. 8 and 12, to displace a rod 134 in the shaft 107. The end of the rod engages a cross pin 135 in a sleeve 137 to disengage clutch teeth 116 on the handwheel from similar teeth 117 on a sleeve 118 secured to the shaft 107 ; manual operation of the handwheel is necessary to re-engage the teeth. The sleeve 118 has additional teeth 125 engaging teeth 124 on a graduated drum 120 which can be moved against spring pressed pins 122 for adjustment of the drum relative to the shaft 107. In an alternative hydraulic circuit for controlling the pick-feed operation of the saddle, the connecting of the lines to the motor 150 together for manual operation or the exhaust of the motor to the metering cylinder 376 for power operation is controlled by a valve disposed between the rod 134 and the plunger 139. The table 14, Fig. 1, has depending brackets 27 connected by rods 25, 26 to pistons 23, 24, Fig. 13, in a cylinder 22 connected to the reversing valve 227 which is actuated by the pilot valve 45. Actuation of the pilot valve at the end of each stroke of the table momentarily stops the flow of fluid from the cylinder 22. To provide a cushioning effect to the table and to prevent too high a pressure occurring in the fluid, a relief 306 is provided in the lines from the cylinder to permit fluid to displace a spring urged plunger 308. A dynamic resistor 307 is included in parallel with the relief valve and comprises a plurality of discs 312 having one side concave and a small central hole through which the fluid flows to the other side of the plunger 308. In a modified circuit for dissipating the pressure surges, the lines from the cylinder 22 are led to individual check valves before being led to the relief valve and the pilot valve is arranged to control the exhaust connection from the cylinder while the reversing valve controls the pressure connection. When the valves are operated, a pressure surge exists in the exhaust line from the motor which passes through the check valve to the relief valve: The dynamic resistor is inserted between the pilot and reverse valves and a further check valve is included in the return line to prevent the pressure surge passing too far back into the system. The speed of the table is controlled by a rate valve 257 having a plunger 269 which can be rotated an amount determined by a graduated drum 272 to adjust the flow of fluid to the cylinder 22. The reciprocation of the table can be stopped by a valve 256 controlled by a lever 264d, Fig. 1, on the front of the machine. The valve inter-connects the ends of the cylinder 22 and also removes pressure from a piston-and-cylinder device 35, 39, Fig. 13, to permit a spring 40 to re-engage a gear 29 with the rack 28 of the table and with a gear 30 connected to a handwheel 34 so that the table can be manually adjusted. With the table stationary, a hand operated reversing valve 281 can be actuated to supply fluid pressure to the cylinder 95 to traverse the saddle during the trueing operation, an adjustable rate valve 297 controlling the speed of traverse ; actuation of the valve 281 is prevented during reciprocation of the table by fluid pressure supplied to a chamber 286 of the valve. The plunger 44 of the pilot valve 45, which has an enlarged centre portion to enable the valve to be self actuating to complete its stroke, is axially moved to operate the reversing valve of the table at the end of each stroke by the rocking of a rod 42, Fig. 9, having at one end a lever 43 on which is a pin 43a engaging a recess in the plunger 44 and, at the other end a member 47, the rod being rotatably mounted in a sleeve 61, in turn, rotatably mounted in the saddle 11 ; the recess is wider than the pin to provide lost motion there between and enable the valve 45 to fire without interference from the pin. A lever 51, Fig. 10, is pivoted to the member 47 and is urged by a flat spring 55 against cams 56, 57 which are formed on members 66, 67 keyed to shafts 20 and longitudinally move the lever at the end of each stroke to rock the member 47 and rod 42. The members 66, 67 are rotated by gearing 64, 65 driven from a gear 63, Fig. 9, on the end of the sleeve 61, the other end of the sleeve carrying a gear 60 engaging the rack of the table. The gears 64, 65 have radial teeth 77 engaging similar teeth on clutch members 71 secured to the shafts 70. The position of the cams relative to the gears can thus be adjusted by axially moving the rods carrying the clutch members against springs 74 and rotating the shafts by means of knobs 73, 78. The table can overrun the limit positions determined by the cams 56, 57 by laterally moving the member 47 by means of a lever on the rod 42 to displace the lever 51 out of the plane of the cams and rocking the rod 42 in the desired direction to actuate the valve 45, screws 47a, 47b limit the m