Patent GB-895381-A (GB)
Title: Grinding machine feed mechanism
IPC: B24B47/20
Filed: 1960-10-05
Abstract: 895,381. Grinding. CINCINNATI MILLING MACHINE CO. Ltd. Oct. 5, 1960 [Oct. 13, 1959], No. 34198/60. Class 60 [Also in Group XXIV] A grinding machine comprises a wheelhead 20, Figs. 1 and 2, which rotatably supports a grinding wheel 21 and has a member 23 located between first and second abutment surfaces 32, 120 relatively movably mounted on a base 15, power means 25, 28 for urging the first abutment surface towards the second abutment surface, and additional means 143, 145 for moving the second abutment surface towards a workpiece support 17. The power means and additional means are controlled so that the grinding wheel is first rapidly moved towards the grinding wheel and then moved with coarse, fine and micro feeds, the grinding wheel then being permitted to spark-out before being rapidly returned to its initial position. The first abutment surface is located on a thrust vice 32 on the end of a shaft 22 carrying the piston 28 in the cylinder 25 of the power means. The thrust race, when the shaft 22 is moved by fluid pressure supplied to a chamber 193 in the cylinder 25, engages the member 23 which consists of a shaft supported in a nut 39 depending from the wheelhead 20. The forward end of the shaft 23 is provided with a member 122 which is transversely movable relative to the axis of the shaft and engages the second abutment surface in the form of a ball 120 on a non-rotatable shaft mounted in a nut 129 connected by gearing 138, 139 to a rack 144 on a piston 145 which is movable by fluid pressure supplied to a cylinder 143. The gear 139 is secured to a shaft 140 connected by gearing 141, 146 to a shaft 147, Fig. 6, having a cam 155, which, when rotated as the piston 143 moves to rotate the nut 129, actuates control valves CA, CB in a block 150, the control valves actuating rate valves RA, RB, RC to control the rate of flow of fluid from the cylinder 143 to provide the coarse, fine and micro feeds of the grinding wheel effected by the nut 129 on the shaft 24. Springs 137 bearing against a thrust race 135 prevent backlash between the nut and shaft. The shaft 23 which, during the feed of the grinding wheel, does not rotate and generate heat in the nut 39 and wheelhead, is provided with a gear 62 engaging a gear 59 integral with a gear 60 engaging a further gear 69, Fig. 3, formed on its side faces with teeth 95. The teeth 95 can be engaged by complementary teeth 96 on the pistons 73 of clutch mechanisms 68, 70 operated by fluid pressure supplied to chambers 75, the teeth on the piston of clutch 68 being engaged when the position of the grinding wheel is to be manually adjusted by a handwheel connected by gearing to a bevel gear 97 during the setting up of the machine, and the teeth on the piston of the clutch 70 being engaged after a number of grinding operations determined by a counter so that when fluid pressure is supplied to one end of a piston 105 connected to the clutch by a rack-and-quadrant mechanism 103 and a ratchet mechanism 98, the position of the grinding wheel is adjusted to compensate for wear thereof. The fluid supply to the cylinders 25, 143 is controlled by limit switches actuating relays in a circuit which also includes a timer operative at the end of the feeding movements of the grinding wheel to permit spark-out. When a start button is depressed, a hydraulic pump is operated which is in permanent communication with a piston-and-cylinder device 42, Fig. 2, to urge the wheelhead away from the workpiece support so that backlash between the shafts 22, 23 is eliminated. The output of the pump is also connected by a solenoid-operated valve to the chamber 193 of the cylinder 25 to move the shafts 22, 23 and the wheelhead rapidly towards the workpiece, the connections to the cylinders being arranged so that towards the end of the rapid movement, the flow from the cylinder is restricted to reduce the speed of the wheelhead. During the forward movement, the member 122 on the shaft 23 abuts the fall 120 and a limit switch actuates a solenoid-operated pilot valve 218, Fig. 10, controlling a reversing valve 219 which connects a line 182 from the pump to a port 239a in the cylinder 143 to move the piston 145 and hence rotate the nut 129 on the shaft 24, the axial movement of which permits axial movement of the shaft 23 and movement of wheelhead towards the workpiece. The movement of the piston 145 is also transmitted by the shaft 140 and gears 141, 146 to the cam 155. During the initial movement of the cam, the operating surfaces 270A, 270B, thereof are spaced from the plungers 241A, 241B of the control valves CA, CB and the flow of fluid from the cylinder 143 is controlled by the rate valve RA which is adjusted to provide a coarse feed of the wheelhead. After a predetermined travel of the wheelhead, the cam surface 270A engages the plunger 241A of valve CA which is then moved rapidly by hydraulic fluid admitted through a port 293A to by-pass the flow of fluid from the cylinder 143 through the valve RA and direct it through the rate valve RB which is adjusted for fine feed of the grinding wheel. After further movement of the wheelhead, the cam surface 270B operates the control valve CB to direct the flow from the cylinder 143 through the rate valve RC which is set to control the flow from the cylinder for a micro feed of the wheelhead. The control valves are axially adjustable to determine the position of the wheelhead in which they are operated and may be adjusted so that one or more of the coarse, fine or micro feeds may be omitted. The forward movement of the wheelhead is terminated when the piston 143 abuts an axially-adjustable member 177 of a valve 166, the wheelhead remaining in its forward position for spark-out of the grinding wheel, after which the pilot valve 218 is operated by a timer to actuate the reversing valve 219 and direct the supply from the pump through line 282, control valve CC and line 280 to a port 239b in the cylinder 143. At the same time the supply to the cylinder 25 is disconnected so that the pressure in cylinder 42 returns the wheelhead and shafts 22, 23 to their initial position, the flow from the cylinder 25 being restricted to reduce the speed of the wheelhead as it approaches its rearward position. With the reverse movement of the piston 145, the cam 155 rotates in the opposite direction until a surface 270c of the cam engages the plunger 241c of the control valve CC to actuate the valve and disconnect the supply line 182 from the cylinder 143, the position of the valve CC being axially adjustable to determine the retracted position of the cylinder. Specification 895,382 is referred to.