Patent GB-983744-A (GB)
Title: Method and apparatus for repetitive internal grinding
IPC: B24B49/18
Filed: 1961-03-28
Abstract: 983,744. Internal grinding; dressing grinding wheels. BRYANT CHUCKING GRINDER CO. March 28, 1961 [April 4, 1960], No. 11262/61. Heading B3D. The internal grinding of a workpiece 35, Fig. 1, is effected by (i) providing a dressing position for a diamond 37 which is a predetermined radial distance from the final internal surface of the workpiece, (ii) dressing the grinding wheel 11 by feeding its spindle 12 towards the iamond, traversing the grinding wheel past the diamond and repeating the feed and traverse steps until the axis of the spindle has moved to within a first predetermined distance from the diamond, and (iii) traversing the wheel 11 into grinding position within the workpiece and applying feed until a second predetermined distance of the spindle from the diamond is reached. The grinding wheel spindle is carried in a slide 12 which is axially movable in a crossslide 16 laterally movable in guides 18 against a spring 38 under the action of a feed screw 21 rotatable by a motor-and-belt drive 32, a fluidpressure actuator 44, 45 providing for the axial movement of the spindle 12 through the slide 16 against a return spring 46. A nut 22 on the feed-screw 21, disposed within a housing 19, is held against axial movement and is rotatable by an arm 25 within limits imposed by stops 26, 27, Fig. 2, the arm being movable by a fluid-pressure actuator 23, 24 against a returnspring 28. A " free-wheel " device permits movement of the arm 25 against the stop 26 without rotating the nut so that upward movement of the arm rotates the nut 22 and advances the screw 21 in the direction of feed, 29, Fig. 1, until the arm 25 contacts the stop 27; such increments of unilateral movement of the slide 16 in a fixed housing 17 represent the extent to which material is removed from the wheel 11 at each dressing pass. Rotation of the feedscrew 21 in the direction of the arrow 36, Fig. 1, advances the wheel 11 into the bore surface 34 of the workpiece 35 and oppositely, arrow 37, in the back-off direction; stops 41, 42 engage a collar 43 on the feed screw 21 at the limits of these radial feed and back-off movements. Extending members 47, 51 and 52 attached to the slide 12 operate limit switches LS1, LS2 and LS8 respectively to control operation of the machine. The member 47 moves the switch LS to position A when the wheel 11 is at position 48, and to B when the slide has traversed the wheel to a position 49, these positions 48, 49 being short of the extreme positions 14, 15 or full traverse distance 13, which corresponds to the A and B positions of the switch LS2 as actuated by the member 51. The member 52 carries a cam which moves the switch LS8 from the A to B positions during the period of movement of the wheel past the dressing station, i.e. between positions 53 and 54. The means for automatically controlling the wheel and diamond movements are such that a new wheel is first traversed past the position 53 clear of the retracted diamond and reversed at position 54, the wheel being fed towards the diamond by the nut 22 a predetermined amount at this stage and the diamond moved to its dressing position just before the wheel reaches or traverses past the diamond. After this pass (i.e. to the position 53), the diamond is retracted and the cycle is automatically repeated until the wheel is so positioned that one further pass will dress the wheel to a predetermined size. At this stage, a sensing switch 57 is actuated by the cross-slide 16 as it is advanced by the nut 22 to provide for a dress-finish traverse of the slide past the diamond followed by retraction of the latter, leftward movement of the slide to position 15 where the wheel is in grinding position in the workpiece and rotation of the feed screw 21 by the drive 32 so as to feed the wheel into the work until a feed stop switch 62 on the crossslide housing 17 is actuated to reverse the feedscrew; the resultant backing-off movement of the wheel is accompanied by operation of the nut 22 to advance the wheel to dressing position. As the slide then moves rightwards the switch LS8 causes at the position 54 the advance of the diamond to dressing position so that the wheel is again dressed. The diamond is returned to its retracted position and the slide continues its traverse past the position 53 until at position 48 the actuation of the switch LS1 results in the operation of a loader 66 which discharges the finished workpiece and feeds a new one into grinding position. The slide continues to the position 14 where the combined grinding and dressing cycle is repeated until the supply of workpieces runs out or the repeated dressing has reduced the wheel to a minimum useable size. A worn-wheel dressing switch may be used to stop the grinding operation and signal the need for a new wheel.