Patent GB-727157-A (GB)
Title: An improved apparatus for compensating grinding disc wear in internal grinding machines
IPC: B24B49/18
Filed: 1952-05-12
Abstract: 727,157. Internal grinding. MESSERSOHMIDT, S. May 12, 1952, No. 11948/52. Class 60. In an internal grinding machine, compensation for grinding disc wear is effected by gauging the work-piece after grinding, the response of the gauge causing automatic adjustment of the grinding disc by an amount corresponding to the deviation of the gauged size from the desired size. A grinding disc 2 is driven by a motor by means of a hollow shaft 3 arranged in a slide 4. Adjustment of the slide is effected by a threaded spindle 6, having hand wheel 5, engaging a nut 7; a pin 8 prevents rotation of the nut 7 but permits it to move relatively to the casing 1. The nut 7 is engaged by one end of a lever 9 pivotally mounted on shaft 10, the other end of the lever 9 engaging a cam 11 driven through bevel wheels 12, 14 by a shaft 15. A spring 18 is interposed between the slide 4 and a plate 19. The spindle 6 is mounted at 50 in the slide 4 and carries a hollow shaft 22 mounted on ball-bearings 21; the shaft 22 .has a toothed rim 23 meshing with spur gear 24 driven by gear 51 on the shaft 15. The spindle 6 and hollow shaft 22 can be coupled together by a clutch 25 operated by an electromagnet 52, whereby the shaft 15 drives the spindle 6 and adjusts the slide 4 to compensate for wear of the grinding disc. A measuring and adjusting device 26 mounted on the slide 4 comprises feelers 27, 28 which receive a ground work-piece 20<SP>1</SP>. The feeler 28 is pivotally mounted on a shaft 30 and is provided at its other end with a lever 32 co-operating with an adjustable abutment 33 and a further abutment 34. The abutment 34 is mounted by ball bearings 35 on the spindle 6; the abutment 34 and spindle 6 can be coupled together by a clutch 36 operated by the electromagnet 52. When the clutch is engaged, the abutment 34 rotates with the spindle 6; when the clutch is disengaged, a spring 37 rotates the abutment 34 until the lever 32 is again in contact with the abutment 33. The feeler 27 is pivotally mounted on a shaft 39 and its opposite end acts, through adjusting screw 40 on an indicating device 41. This comprises a dropping loop 44 formed as a conductor and two rails 45, 46; when a mark 49 on scale 48 is reached by an indicator 47 the loop 44 falls from rail 46 on to rail 45. The electromagnet 52, feeler 28, work-piece 201, feeler 27, rail 46 and the dropping loop 44 are electrically connected in series; if the work-piece 201 is electrically non-conducting, a separate switch is provided for closing the circuit after the work-piece has been placed around the feelers. When no workpiece is present, indicator 47 is in its extreme right-hand position beyond mark 49, and dropping loop 44 rests on rail 45. When gauging is to be performed, feeler 27 is lowered, causing indicator 47 to move to its extreme lefthand position. A ground work-piece 20<SP>1</SP> is then placed over the feelers, and the feeler 27 allowed to rise until it contacts the work-piece, the indicator moving in the direction of the mark 49, the dropping loop 44 being moved off the rail 45 on to rail 46. If, due to grinding-wheel wear, the internal diameter of the work-piece is less than the desired value the indicator 47 will not reach mark 49 and dropping loop 44 remains on conducting rail 46; the circuit is thus closed, energizing electromagnet 52 to operate clutches 25, 36. Spindle 6 is rotated to adjust the grinding wheel; simultaneously, the abutment 34 is rotated, lever 32 moves away from the stationary abutment 33 and feeler 28 moves upwards whereby feeler 27 may move in the same direction; this causes indicator 47 to be deflected in the direction of the mark 49. When indicator 47 reaches mark 49, dropping loop 44 falls off rail 46, thus breaking the circuit and deenergizing the electromagnet 52. Spring 37 acts through the abutment 34 to return the lever 32 and therefore the feeler 28 to its original position.