Patent GB-960887-A (GB)
Title: Grinding machine
IPC: B24B47/14
Filed: 1961-03-21
Abstract: 960,887. Grinding. HEALD MACHINE CO. March 21, 1961 [March 22, 1960], No. 10307/61. Heading B3D. [Also in Divisions F1 and F2] A grinding machine comprises a wheelhead including an axially reciprocable rotating spindle, carrying a grinding wheel, a resilient member biasing the spindle in one direction, a source of static pressure associated with the spindle to move it in the other direction against the said bias, and means for imposing on the said static pressure a series of pressure pulsations to bring about axial reciprocation of the spindle. A workhead 12 is mounted on a base 13 for transverse movement by a feeding mechanism 14, the workpiece 11 being rotated by a motor 18. The bore of the workpiece is ground by a grinding wheel 21 on a spindle 26 carried by a wheelhead 16 mounted on a table 15 mounted on the base 13. A diamond dresser 20 for the grinding wheel is mounted on the base 13. The wheelhead comprises a housing 22 having a broad flat base for attachment to the table 15 and having a through bore 23. Mounted in the housing at the ends of the bore are bearing assemblies 24, 25 through which extends the spindle 26 having at one end a threaded bore 27 for a holding screw for the grinding wheel 21 and at the other end a threaded bore 28 for a holding screw for a pulley belt driven from the wheelhead motor 17. A piston 31 slidable in the bore 23 has a keyway 39 engaging a key 41 fastened in the wall of the bore 23. The spindle 26 passes through a bore 33 in the piston head and has a flange 29 located in a bore 32 in the piston. The bearing assembly 25 has a boss 34 extending into the bore 32. Around the boss is a coil spring 35 bearing at one end against the assembly 25 and at the other end against a sleeve 37 fitting loosely within the bore 32 and loosely around the flange 29. The inner end of the bearing assembly entirely fills the bore 23 to form a fluid chamber 38. The bearing assembly 24 has a bore receiving the spindle 26 and having shallow annular recesses 44, 45. Recess 44 is connected through passage 46 and orifice member 47 with an annular groove 48 on the outer surface of the bearing assembly. Recess 45 is connected through passage 51 and orifice member 52 with the groove 48. High pressure fluid is supplied to the groove 48 through a passage 49 in the housing 22. Fluid collection grooves 53, 54, 55 are connected to a collection manifold 56. A seal 57 prevents leakage around the spindle 26. The bearing assembly 25 has shallow recesses 58, 59, each comprising three pockets separated by lands which lie close to the surface of the spindle. High pressure fluid supplied to an annular groove 63 on the outer surface of the bearing assembly passes through orifice members 62, 65 and passages 61, 64 to the recesses 58, 59. Collection grooves 66, 67 connect with the collection manifold 56. Pressure fluid supplied through pressure regulating valve 74 and check-valve 73 to the chamber 38 moves the piston 31 against the resistance of the spring 35 to a position in which the grinding wheel is within the bore of the workpiece. Reciprocation of the grinding wheel axially of the bore is effected by a piston 77 reciprocated through a Scotch-yoke mechanism 78 by a motor. The reciprocation of the spindle 26 can be stopped by moving a valve 75 to connect the line 76 to an exhaust line 79. The grinding wheel is withdrawn from the bore by moving a valve 71 to connect the line 69 to a line 81. By means of a valve 82 the line 81 can be connected to an exhaust line 83 giving rapid withdrawal or to an exhaust line 84 containing a restriction 85 giving slow withdrawal for trueing the wheel.