Patent GB-665246-A (GB)
Title: Improvements in grinding machines, more particularly for grinding impeller bucket shanks
IPC: B24B19/14
Filed: 1949-08-05
Abstract: 665,246. Grinding turbine blades. JONES & LAMSON MACHINE CO. Aug. 5, 1949 [Aug. 14, 1948], No. 20423/49. Class 60 A grinding-machine, more particularly for grinding the shanks of turbine blades, comprises a pair of grinding-wheels 12, Fig. 1, mounted on reciprocatable carriages 150 which are themselves mounted on reciprocatable carriages, a work holder located between the wheels 12 on a work support 11, means for reciprocating the wheels 12 simultaneously towards and away from each other and for reciprocating the work carried by the work holder in a plane perpendicular to the axes of the wheels and at right-angles to the line joining the centres of the wheels, and trueing devices 156 movable towards and away from the wheels. The work holder is mounted upon a carriage 11, Fig. 4, which is bored vertically so as to be movable on two bars 16, 17 carried by a bracket 20 adapted for slight angular adjustment about a vertical axis; the bearings for the two bars are protected by collapsable bellows 28, 29. Movement of the carriage 11 is effected from a hydraulic cylinder 37 which is mounted on the bracket 20 and has its piston rod 36 connected with the carriage. The supply of fluid alternately to opposite ends of the cylinder 37 to cause reciprocation of the carriage is under the control of a rotary valve 111, Fig. 10, automatically operated by the energisation of two solenoids 109, 115 by switches 105, 106; these switches are closed alternately as the carriage reaches the ends of its stroke by adjustable dogs 103, 104, Fig. 4, on a drum 100 rotated by a pinion 96 meshing with a vertical rack 95 on the carriage. The work holder, which has a slot 40, Fig. 5, for the reception of the turbine blade, is supported on an L-shaped bracket 42 secured to the carriage, being clamped against the horizontal and vertical faces of the bracket and the rear face of a retaining strip by two clamps 60, 72. The clamp 60 is pivoted at 61 on the bracket 42, has an inclined face 63 engaging diagonally of the work holder, and is operated by rods 65, 67 controlled by a piston 68 moving in a hydraulic cylinder in a casing 69. The clamp 72 is in the form of a plunger operated from a piston 75 in a second hydraulic cylinder in the casing 69. Clamping is effected by setting a hand-operated valve 80, Fig. 10, so that pressure fluid passes to the two cylinders to cause downward movement of the pistons 68, 75, check valves 87, 88 preventing operation of the piston 75 and clamp 72 until the piston 68 has closed the clamp 60. When the work holder is clamped, a switch 90, Fig. 10, is closed so as to open a solenoid-actuated valve 112 in the supply to the valve 111 and thereby actuate the carriage; when the clamps are released by operating the valve 80, the switch 90 acts to close the valve 112 and stop the carriage. Each grinding-wheel 12 is mounted on a carriage 150, Fig. 1, which is movable to.and from the bracket 20 in ways on a bed and carries a motor 151 for driving the wheel. Each carriage 150 is mounted on a second carriage 170, Fig. 19, which directly contacts the bed and is fed to and from the bracket 20 by a shaft 176 journalled in the carriage 170; this carriage is constantly urged to retracted positions by a chain 171 passing over a sprocket wheel 172 and connected to a spring 174. The outer end of the shaft 176 is in screw-threaded engagement with a sleeve 178, Fig. 12, slidable in a fixed casing 184 and carrying at its outer end a cam drum 180. The sleeve 178 is slidably keyed in a sleeve 188 carrying a gear 187 meshing with a gear 186 on a shaft 185, and the cam drum 180 is engaged by a ball contact 182 on one end of a pivoted lever 181. Feed of the carriage is effected intermittently by driving the shaft 185 through gearing 190, 191 from a hollow shaft 192 which is driven through further gearing by intermittent ratchet mechanism 201 (not shown), including a verticallymovable link 202, Fig. 1. The links 202 of the two carriages are connected by crank-and-link mechanism 204, 205 and actuated by an hydraulic cylinder 230. A second shaft 196, Fig. 12, passing through the hollow shaft 192 has a screwthreaded extension 197 engaging a fixed nut 198 and contacting the outer end of the lever 181; rotation of the shaft 196 by a hand-wheel 203, Fig. 1, causes the lever 181 to adjust the sleeve 178 axially and the position of the carriage independent of its movement by rotation of the sleeve 178. When the work has been reduced to the desired size, each wheel is automatically retracted through the closure of a switch 245, Fig. 20, by a lug 240 on the cam drum 180. A solenoid 246 is thereby energised to actuate a valve 248 whereby pressure fluid raises a piston 238 in a cylinder 237 so that a rack 236 on the piston rod acts through a pinion 230 to rotate the shaft 192 for retracting the carriage. The pinion 230 is coupled to the shaft 192 so that it is driven thereby only when the latter rotates in the direction to withdraw the carriage. A stop which is normally in position to engage the lug 240 is withdrawn by exerting a pull on a cable 259, Fig. 1, through a hand-lever 260. An additional feed to compensate for wear of the wheels is provided by a further motion of each carriage 150 under the action of a shaft 210, Fig. 19, which is journalled in the carriage 170 and has a screw-threaded connection with a bracket 213 on the carriage 150. This shaft has a splined connection with a shaft 214 which is journalled in the casing 184 and, through further gearing and shafting, is rotated by ratchet mechanism 224, Fig. 1; a hydraulic cylinder 231 actuates the mechanism 224 of both carriages through a lever 227 and links 226. Each carriage 150 is provided; as described in Specification 548,551, [Group XXII], with wheel-trueing mechanism 156, Fig. 1, which is housed in a cylindrical opening in the carriage. A table 50, Fig. 4, is arranged adjacent the bracket 42 for facilitating the transfer of the work holder, with the work, to and from operative position, the table being vertically adjustable by jacks 51, 52.