Patent GB-774975-A (GB)
Title: Improvements in or relating to machine tools
IPC: B24B7/07
Filed: 1953-09-15
Abstract: 774,975. Grinding. MID-WEST ABRASIVE CO. Sept. 15, 1953 [March 30, 1953], No. 25465/53. Class 60 [Also in Groups XXIV and XXXVII] A grinding machine comprises a boom 86, Fig. 2, which is pivotally mounted on a support 36 for swinging movement in a vertical plane and is slidable along its 'longitudinal axis relative to the pivotal mounting. a grinding wheel 107 and counterbalancing means mounted on the boom on opposite sides of the pivotal mounting, a reversible electric motor 185 for sliding the boom axially in opposite directions and sliding the counterbalancing means along the boom in a direction opposite to that of movement of the boom and mechanism for reversing the motor at each end of the sliding movement of the boom including means automatically operated at each end of such movement. The support 36 is in the form of a carriage movable on rails 37, 38 in a direction parallel to the length of the workpiece, W, and during grinding the boom reciprocates across the workpiece, the counter-balancing means always moving in opposite direction from that of the boom to maintain uniform grinding pressure. Various control switches, are mounted on a control panel positioned on 'the carriage near a seat on which the operator rides. The carriage 36 has two axles, each of which is formed of two connected tubes 41, 43, Fig. 5, supported by bearings on stub shafts 51, 63 and provided at its ends with a flanged wheel 49 and cylindrical wheel 59 cooperating with the rails 37, 38. A reversible motor 81 on the carriagedrives one of the axles through gearing 83, 78, 74 and clutch teeth 76 on a two-part coupling 66, 67 connecting the tubes 41, 43 of the axle. The boom comprises a tube 87 which is movable axially in a mounting on the carriage arranged to permit vertical swinging movement of the tube. For this purpose. the tube 87 at its carriage end is disposed in a sleeve 227, Fig. 28, supported in a block 228 having transverse trunnions 235 journalled in roller bearings in a housing 229 on the carriage; the tube 87 is guided in its swinging movement by rollers 241, Fig. 22, which engage vertical guide plates and are carried by plates 239 projecting above and below the tubes from the outer end of the sleeve 227. The axial movement of the tube 87 in the sleeve 227 is provided by the motor 185. Figs. 2 and 15,'which is mounted on a casing 186 on the carriage end of the boom. Two parallel screws 193. 198 in the casing are driven from the motor by a belt-drive 190 and gears 192, 200; the screw 198 is disposed in a sleeve 196 coaxial with the tube 87 and by its screw-threaded engagement with a nut 206 coupled to the end of such tube causes the latter to slide through the sleeve 227. A counterbalancing weight 212 has rollers 217 running on tracks on the sleeve 196 and is fitted with a nut 221 in screw-threaded engagement with the screw 193. Since the screws 193, 198 rotate in opposite directions the weight 212 always moves in opposite direction to that of the tube 87. The weight 212 has a substantial portion of its mass below the sleeve 196 and auxiliary weights 223 may be secured to its lower surface by studs 224. The operator actuates a switch to reverse the motor 185 at each end of traverse of the boom and this is effective to reverse the direction of movement of the latter provided the appropriate one of a pair of limit switches LS-1, LS-2, Fig. 15. disposed at opposite ends of the casing 186 has then been closed by a coacting plunger (226 or 225) on the weight. The grind- .ing wheel 107 is mounted in a housing 89 which is apertured at 90, Fig. 31, for fitting over the end of the tube 87 and has a hinged cover 93. A driven pulley 101 and connected sleeve 105 are journalled on a spindle 97 in the housing, the grinding wheel being secured on the sleeve by a nut 109. The belt drive 121 to the pulley 101 is from a pulley 120, Fig. 8, on the output shaft 147 of a speed-changer 119 driven by a motor 111, Fig. 2, which is mounted on rails 114 on the carriage .36 so as to move with the axial movement of the tube 87; the speed- - changer and housing 89 are connected for the latter 'purpose by a tie-rod 122 which is built up of interconnected parts and springs (Fig. 30, not shown), to permit adjustment of its length by worm gearing 136. 137 at the screw-threaded connection of the rod with the housing. The speed-changer 119, Fig. 8 comprises two gears 144, 145 on the motor shaft 143 meshing with two gears 146, 152 which are rotatable on the shaft 147 and spindle thereon so that either the gear 146 may be clutched by teeth 150 to the pulley 120 or the gear 152 may be clutched by teeth 153 to a second pulley 155 secured on the shaft 147 and having a belt drive with a plugging switch arranged in the control circuit of the motor 7 for reducing the speed of the latter before thegearing is changed to a faster drive through the gears 144, 146 and so bring the speed of the motor within a range more suitable for the change (for example, when it is necessary to increase the peripheral speed of the grinding wheel because its diameter has been reduced by wear). The gears 146, 152 are shifted by mechanism (see Group XXIV), including a double-acting solenoid controlled by a switch in the control circuit, and signal lamps are provided on the control panel to show whether the drive is fast or slow. A flexible protective sleeve 268, Fig. 2, encloses the tube 87 from the housing 89 to the outer end of the sleeve 227. The boom may be swung to lift the grinding wheel from the workpiece by energizing a motordriven pump to supply pressure fluid to a cylinder-and-piston device 248, Fig. 2, for operating an arm 246 connected to the inner end of the sleeve 227; when the pump is stopped the return of fluid from the device 248 through a pipe 249 which is caused by the weight of the outer end of the boom assembly assisted by a weight 212<SP>1</SP>, Fig. 22, is regulated by a valve to control the engagement of the grinding wheel with the workpiece. To prevent the surface of the grinding wheel becoming flat or developing sharp edges, the tube 87 is oscillated about its axis during grinding by means of a motor 267, Fig. 2, acting through a speed reducer and crank mechanism upon an arm 256, Fig. 15, having keys 258 engaging longitudinal slots in the tube; two switches provide for the tube to be oscillated either automatically or under the control of the operator. Lubricant - may be conducted to various parts of the - machine through a pipe line from a pump which is immersed in a supply tank (Fig. 26, not shown), and operated by the swing- ing movement of the boom assembly. Specifications 774,976 and 774,977 are referred to.