Patent GB-527545-A (GB)
Title: Improvements in or relating to feed mechanism for use in machine tools such as grinders and the like
IPC: B24B47/20
Filed: 1939-04-14
Abstract: 527,545. Hydraulic feed mechanisms for machine-tools. CINCINNATI MILLING MACHINE CO. April 14, 1939, No. 11364. Convention date, July 25, 1938. [Class 69 (ii)] A feed mechanism for machine tools comprises a manually controlled fluidpressure power transmission mechanism for effecting relative movement of the work and tool through a cycle, and an auxiliary fluid-pressure actuated driving and timing mechanism operably connected to, and initially actuated by, the first' power transmission mechanism, and thereafter to automatically drive said power transmission mechanism, to effect a cycle of said relative movement. As applied to apparatus for producing an automatic feed for a grinding machine which will achieve a rapid advance, dwell, and rapid return and stop, the support for the grinding wheel is pivoted and has formed integrally therewith a cylinder 18 in which moves a piston 17, the rod of which rests on a cam 86 mounted on a shaft 33 operated by a servomotor 50. Operation of a handle 23 moves a ported sleeve 29 to admit pressure fluid to one end of the cylinder 50 which in turn rotates the shaft 33 having a portion 34 integral therewith tending during its movement to close the ports in the sleeve 29 so that the servomotor only acts while the handle 23 is being operated. A friction clutch on the shaft 33 actuates a rod 72 and crosshead 71 which, after some lost motion, operate two valves 69, 70. The valve 69, together with a pressure-reducing valve 89, controls the flow of pressure fluid to a motor 83 actuating a work chuck, and the valve 70 controls the flow of pressure fluid to the cylinder 80 to cause a rapid movement of the wheel support towards the work and to a motor 196 to operate a switch for a headstock motor. Subsequently the wheel will continue to be fed by the cam 86. By reversing the movement of the handle 23, the action is reversed and a rapid'retraction of the tool from the work is obtained. The pressure fluid is supplied from a pump 55 connected to a pressure relief valve 97, and a low-pressure relief valve 58 is fitted in the return pipe to the reservoir 151. In order that an automatic operation of the handle 23 may be obtained, the handle is connected to a servomotor 104 by a linkage 107 ... 110, Fig. 10, the shaft 108 of which carries cams 152, 163. Movement of the handle 23 through a small angle turns the cam 152 sufficiently to move a pilot valve 121 to the right, Fig. 10, against spring action, so as to admit pressure fluid through a conduit to the left hand end of a piston valve 123 so as to move it to the right and allow fluid pressure to pass through a conduit 127 and passages 128, 117 of a piston valve 118 when in the position shown, to the right-hand end of the servomotor 104 so as to continue the operation of the handle 23. The other end of the motor is connected by a conduit 114 to passages 116, 132 in valve 118, conduit 133, passages 134, 135 in valve 123 and conduit 136 to the low pressure conduit 150, an adjustable valve 138 being provided between the 'conduits 136, 150 to control the flow and thus provide means for varying the speed of the motor 104. The cam 163 is set so as to start moving the valve 118 to the right against the action of a spring 164' when the motor 51 has completed its stroke and the tool is in contact with the work. This allows pressure fluid from the conduit 127 to pass through a port 129 and act on differential areas 167, 168 of the valve 118 and move the valve rapidly to the right. For the initial part of this movement, and until a passage 170 is closed, fluid can escape from the right-hand of the piston through the passage 170 to the low pressure conduit 150. Subsequently, the trapped fluid has to pass through a conduit 171 and adjustable valve 173 to the conduit 150, the setting of the valve 173 thus determining the time taken for the valve 118 to complete its movement to reverse the movement of the motor 104 and therefore the duration of the dwell of the tool on the work. At the completion of the movement of the valve 118, the pressure port 128 is connected to the port 116 and the exhaust port 170 to the port 117 so as to reverse the movement of the motor 104 and therefore of the handle 23 and shaft 108. The valve 118 is retained in its new position by the fluid pressure on the areas 167, 168 until the cam 152 allows the valve 121 to move sufficiently to connect ports 120, 156.to admit pressure fluid to port 158 and move valve 123 to the left to connect the conduit 127 to the exhaust conduit 150. Movement of the valve 121 is retarded by a choke coil 159<SP>1</SP> so as to allow the lever 23 to be returned to its initial position before the valve 118 is released. The speed of the grinding wheel towards the work may be increased at will, by pressing on the handle 23 so as to increase the back pressure in the motor 104 which causes a piston 184 in the exhaust line to be moved back against the action of a spring 187 to provide, through ports 139, an additional passage to exhaust in parallel with the valve 138. The automatic mechanism shown in Fig. 10 may be rendered inoperative by means of a cut-out valve 192.