Patent GB-656782-A (GB)
Title: Improvements in or relating to centreless grinding machines
IPC: B24B5/18
Filed: 1947-12-31
Abstract: 656,782. Centreless grinder. HATEBUR, F. B. Dec. 31, 1947, No. 35222. Convention date, Oct. 17, 1942. [Class 60] A centreless grinding machine, of the type in which the control wheel is advanced towards the grinding wheel to bring the work into contact with the grinding wheel and thereafter to feed the work into the grinding wheel, comprises a first pneumatic or hydraulic jack to move the control wheel with a highspeed approach movement, a second pneumatic or hydraulic jack the end load of which is less than the end load of the first jack and means automatically applying the end load of the second jack to the first jack to act in opposition thereto at, or immediately prior to, commencement of the grinding operation whereby the control wheel performs a slow-speed grinding feed movement. The grinding wheel 1 and control wheel 3 are arranged in conventional manner, the workpiece 2 in the grinding throat being supported by a work rest 8. The control wheel carriage 7 is mounted on a frame 4 for reciprocation relatively thereto; the frame 4 is pivotally mounted at 5 on the machine bed and is vertically adjustable by handwheel 4a. The control wheel 3 is driven by shaft 11 through bevel gearing 9, 10, the shaft being driven through bevel gearing 90, 100, the bevel gear 100 being mounted on shaft 11 by splines permitting relative axial movement of shaft and gear. The carriage 7 is rockable about the shaft 11 by means of worm gearing 11b to vary the inclination of the axis of the control wheel relatively to the axis of the grinding wheel to suit the shape of the workpiece. The shaft 11 is held against axial movement relatively to carriage 7 by throat bearing 11a; shaft 11 carries the ram 12 of a hydraulic or pneumatic jack 12a by which the carriage 7 is moved. The work rest 8 is adjustably connected with the carriage 7 so as to move with the control wheel. A stop 14 is carried by a rod 13 in two parts screwthreaded one into the other, one part being rotatable by handwheel 26, while the other part is held against rotation, thereby axially adjusting the stop. The ram 17 of a hydraulic or pneumatic jack 18 is mounted on a rod 16a, the free end of which carries a stop 16b passing through an abutment 15 on sleeve 16 axially adjustable by handwheel 24; pressure in the jack 18 is regulated by control valve 18a. When jack 12a is rendered operative, the carriage 7 and control wheel approach the grinding wheel at a high speed; when the workpiece engages the grinding wheel, or immediately prior thereto, stop 14 engages stop 16b, and the carriage 7 continues its movement towards the grinding wheel at a slow grinding-feed speed. When a desired depth of cut has been made, stop 14 engages abutment 15 and further advance of the carriage 7 is prevented. The pressures in jacks 12a, 18 may be separately indicated. When stop 14 engages abutment 15, jack 12a automatically withdraws carriage 7; the withdrawal may be delayed to provide sparking-out. A sensitive indicator, e.g. a clock indicator graduated in thousandths of an inch, is operated by a feeler 25; stop 14 carries member 14b to engage feeler 25 and it is arranged that when stop 14 engages abutment 15, member 14b will have returned the pointer to its zero position, whereupon the withdrawal motion is initiated. By means of handle 19, mechanism 20, actuated by handwheel 23 for feeding diamond 21 into the grinding wheel 1, can be coupled through gear 22 to the mechanism for longitudinally adjusting stop sleeve 16, so that abutment 15 is moved back a distance equal to the reduction in radius of the grinding wheel due to trueing. The projection of the stop 16b beyond the abutment 15 is limited by screw 36.