Patent GB-1085942-A (GB)
Title: Improvements in and relating to surface grinding machines
Inventor: LUMSDEN THOMAS HAROLD
IPC: B24B49/18
Filed: 1963-04-26
Abstract: 1,085,942. Surface grinding. LUMSDEN MACHINE CO. Ltd. April 27, 1964 [April 26, 1963], No. 16525/63. Heading B3D. Means for terminating the feed of a grinding wheel of a surface grinding machine when the working surface of said wheel is at a predetermined distance from the work-table and so as to compensate automatically for wear of said working surface comprises (a) A wheelhead wherein said grinding wheel is mounted; (b) A carrier displaceable relative to the wheelhead in the directionof movement thereof; (c) A probe mounted on said carrier and projecting towards the work-table; (d) Means engaged with said probe and displaceable when the probe being in advance of said working surface engages a workpiece to actuate a control switch; (e) Means for displacing said carrier with respect to the wheelhead; (f) A motor operable by said control switch when actuated to move said displacing means to displace said carrier away from the work-table; and (g) A trip device mounted on said carrier to be displaceable therewith, said trip device serving to actuate a feed stop switch for the wheelhead. Workpieces A mounted on a rotary table B are ground by a grinding wheel C carried by a wheelhead D fed by a motor M. A slide 1 is vertically displaceable, on a slideway 2 secured to the wheelhead D, by screw and nut means 5, 6 and differential reduction gearing 4 operated selectively by a unidirectional motor 3 and a hand wheel 19. The slide 1 carries a pivotally mounted probe 7 projecting from its lower end. The upper arm 8 of the probe engages a lower shorter arm 9 of a magnifying lever 10 adapted to actuate a switch 11 controlling the motor 3. A post 12 is mounted on a bracket 13 secured to the slide 1 and a body coarsely adjustable on the post carries micrometer screw adjusting means 15 for a trip cam 16 disposed to engage an actuator 17 for a switch 18 which when actuated controls the wheelhead feed motor M to terminate the feed. A hemi-cylindrical guard door is displaceable around its axis to cover the front of a cavity in the machine within which the table B and grinding wheel C are located. Closure of the door automatically starts the table B rotating at fast working speed and starts downfeed of the wheelhead D at an " approach rate". When the probe 7, which is initially adjusted by the hand wheel 19 to be slightly in advance of the working surface of the grinding wheel, first touches a workpiece the deflection of the probe 7 results in actuation of a switch 20 on the slide 1 whereby the downfeed of the wheelhead D is changed to normal grinding feed rate; deflection of the probe 7 also results in actuation of the switch 11 whereby the motor 3 runs to retract the slide 1 on the wheelhead D until the tip of the probe 7 in its undeflected position is level with the working surface of the grinding wheel. The latter adjustment accompanies wear of the wheel, and the resultant retraction of the slide 1 maintains the trip cam 16 at a constant distance from the working surface of the wheel. When eventually the trip cam 16 actuates the switch 18, the wheelhead feed motor is stopped, the rate of rotation of the table B is changed from fast to slow, there is a timed pause for " spark-out ", the wheelhead is raised by a distance determined by a trip cam 26 and switch 21, and the table is stopped for unloading and reloading.