Patent GB-658285-A (GB)
Title: Improvements in or relating to grinding machines
IPC: B24B3/42
Filed: 1948-07-27
Abstract: 658,285. Grinding. JERSEY, E. W. R. DE. July 27, 1949, No. 19993. [Class 60] [Also in Group XXV] In a grinding machine the object to be ground is mounted and rotated in bearing members and the grinding wheel is slidably mounted upon and rotated by a shaft carried in bearings arranged so that the shaft lies alongside the axis of the object to be ground, the bearing members for the latter being mounted in longitudinal alignment on a carriage' or base plate and means being provided to effect sliding movement of said carriage or base plate towards and away from the grinding wheel shaft in order to vary the distance between the object to be ground and the grinding wheel shaft and to ensure true parallelism of said axis and said shaft. The grinding wheel shaft 10 and bearing members 11, 12 for the cylindrical knife 13 of a lawn mower are mounted above a rectangular table 14 supported by a pedestal at each end; pulleys 15, 16 belt driven from a cross shaft, disposed in the space between the pedestals and driven by an electric motor, drive the grinding wheel shaft and the cylindrical knife. The grinding wheel shaft 10 is mounted by ball bearings in pillars 17, 18 upstanding from the table 14. The bearing members 11, 12 for the cylindrical knife are mounted on a sliding carriage 20 the ends of which are slidably mounted in slots 21 in end members 22 extending rearwardly from the bearing pillars 17, 18. Sliding adjustment of the carriage 20 towards and away from the grinding wheel shaft 10 is effected by two spaced screwed rods 23 having unthreaded ends rotatably mounted in bearing housings 24, 25 at the front and rear edges of the table 14; each screwed rod 23 co-operates with a tapped central box 26a in a cylindrical block 26 beneath the carriage 20, lateral movement of the cylindrical block 26 relative to the carriage 20 being prevented by rectangular blocks 27 abutting the ends of the cylindrical blocks 26, the upper edges 27a of the rectangular blocks 27 being secured to the undersurface of the carriage 20 and the rectangular blocks 27 having substantially central bores 27b which are a clearance fit on the screwed rod; rotation of the cylindrical blocks 26 is prevented by two radial projections 28 thereon which bear on the upper surface of the table 14. The construction permits replacement of the cylindrical blocks 26 when the threads are worn. The screwed rods 23 carry handwheels 29; each rod 23 carries a graduated thimble 30 co-operating with an index mark on the front of the housing, whereby parallelism of the cylindrical knife axis and the grinding wheel shaft can be maintained. The exposed portions of the screwed rods 23, may be enclosed by expanding rubber bellows 74. To accommodate cylindrical knives of different lengths, the bearing blocks 11, 12 are slidably mounted on guide bars 31 secured at their ends to blocks 32 on the carriage 20; the blocks 11, 12 are secured in adjusted position by clamp screws 33. Each end of the shaft 19 of the cylindrical knife 13 is supported by V-blocks 34, 34a carried in a recess 35 in the upper end of a bearing block; a detachable bridge piece 36, secured by bolts 37, has a screw 38, provided with a lock nut, for tightening the upper V-block down on to the shaft 19. Dowels 39 anchored at their lower ends in the bearing blocks 11, 12 pass upwardly through holes drilled in the V-blocks to locate them. The .cylindrical knife 13 is driven from a co-axial shaft 40, mounted in bearing blocks 41 on the carriage 20 and carrying the pulley 16, by a laterally projecting finger 42 engaging a dog 43 detachably secured to the end of the shaft 19 of the cylindrical knife. The grinding wheel shaft 10. has one or more longitudinal grooves 44 engaged by a feather or tongue projecting inwardly from the central bore of the grinding wheel 45. A member 46 has side limbs 47, spaced apart by a block 49, the inner ends if which extend one at each side of the grinding wheel and have apertures 48 through which the shaft 10 passes ; the outer portions of the side limbs 47 have apertures 50 through which passes a horizontal bar 51 adjustably carried on horizontal threaded shafts 52 secured to the upper ends of the bearing pillars 17. 18. The member '46 has a'handle 46a by which it, and the grinding wheel, can be traversed; the member 46 also carries a sheet metal shield 53 for the grinding wheel. To grind the required clearance angle on the rear edges of the blades of the cylindrical knife 13, a cradle 54 is hung from the member 46 by side members 56 and an end member 57 and has a horizontal. member 55 projecting inwardly immediately below the grinding wheel; a detachable angle piece 58 longitudinally slotted to allow for adjustment, is secured by screw and wing nut 59 to the underside of the horizontal member 55, and the vertical limbs 58a of the angle piece 58 carries a T-shaped block-supporting member 60 secured by a bolt 61 passing through a slot 62 for adjustment purposes. When the edges of the blades 63 of the cylindrical knife 13 have been ground truly cylindrical the dog 43 is removed from the shaft 19 so that the cylindrical knife is no longer driven; the angle piece 58 and blade-supporting member 60 are adjusted to bring the upper bevelled edge 60a of the latter above the horizontal centre line of the grinding wheel. To enable the stationary blade or sole plate of the lawn mower to be ground a holder 66 is mounted in the bearing blocks 11, 12 in place of the cylindrical knife 13; the holder comprises a rectangular metal bar 67 having a rectangular slot 68 in the upper face extending the whole length of the bar. The bar is adjustably mounted between the outer ends of two side plates 69 by means of bolts 70; the inner ends of the side plates are secured to a shaft 71 the ends of which are mounted in the V-blocks 34, 34a. The stationary blade or sole plate is clamped in the slot 68 by screws 72.