Patent GB-764510-A (GB)
Title: Improvements relating to crushing units for truing grinding wheels and grinding machines incorporating such units
IPC: B24B53/07
Filed: 1955-01-03
Abstract: 764,510. Grinding; trueing grinding wheels. CIMATOOL CORPORATION. Jan. 3. 1955 [Jan. 6, 1954], No. 64/65. Class 60 A crusher unit for trueing a grinding wheel 110, Fig. 7, comprises a crusher roll 200 mounted in a carrier 204 which is guided in a housing 111, Fig. 12, for movement to and from the grinding wheel 110, an operating shaft 212 mounted for rotation and bodily-axial movement in the housing, a nut 206 in screwthreaded engagement with the shaft and having a degree of lost motion relative to the carrier, power means driving a screw - threaded connection between the shaft and housing for moving the shaft axially and so rapidly moving the crusher roll relatively to the grinding wheel, and second power means  started by switch means responsive to the taking up of the lost motion between the nut and carrier when the ,crusher roll engages the grinding wheel for rotating the shaft in the nut and sc feeding the crusher roll into the grinding wheel The crusher unit is described as mounted on the grinding head 102, Fig. 1, of a grinding machine, the head 102 being movable to and from a workhead 101. Grinding machine construction and operation. The workhead 101, Fig. 1, has a motor-driven work spindle 104 and auxiliary grinding wheels 106, 107 for operating upon the workpiece 105 after it has been ground by the grinding wheel 110. The grinding wheel is driven by a high-speed motor .1A, Fig. 8, during grinding and low-speed motor 8A during crushing, these motors being connected to the wheel through an over-running clutch 295. The head 102 is slidable to and from the head 101 on rollers (122, 124, Fig. 17, not shown) and guided in a straight path by rollers engaging the side faces of rails. Traverse of the head 102 is by a lead screw 135, Fig. 18, engaging a non- rotatable nut 136 fixed in a two-part housing 134, 138 carried from the head; the lower housing 138 is axially slidable relatively to the upper housing 134, and a screw 146, which is rotatable on the nut 136 but axially fixed in the lower housing 138, engages a nut 147 fixed in the upper housing. Rapid traverse of the head is provided by a drive to the lead screw 135 from a high-speed reversible motor 5A, Fig. 5, through a clutch 13A, and fast and slow feed by a second drive to the screw from a low-speed motor 2A through high and low speed gearing each including a clutch 14A, 15A; the drive from both these sources includes a brake 11A and slip clutch 154. During crush trueing of the grinding wheel (see below) the screw 146 is rotated by gearing 292, 294, Fig. 18, from the means for applying feed to the crusher roll so that the grinding wheel is adjusted forwardly a distance to compensate for the reduction of its diameter by trueing. The control circuit of the machine includes relays and limit switches governing an automatic cycle which follows upon the actuation of a cycle switch. This cycle is as follows:- (a) release of the brake 11A, Fig. 5; (b) energization of the grinding head feed motor 2A (but with the clutches 14A, 15A disengaged) and workhead motor 2B; (c) energization of the grinding head rapid, traverse motor 5A and engagement of the clutch 13A to move the head rapidly to the workhead until a dog 191 moving with the head actuates a switch 34; (d) consequent stopping of the motor 5A, disengagement of the clutch 13A, and engagement of the clutch 15A so that the motor 2A moves the head through a fast feed until a second dog 192 actuates a switch 35; (e) consequent disengagement of the clutch 15A and engagement of the clutch 14A for the slow feed of the head until a plunger 155 moving with the head engages an adjustably-clamped sleeve 156 whereby the clutch 154 slips and a switch 36 is actuated by a stop 157 to disengage the clutch 14A and energize a timer; and (f) energization, after a pre-determined time to allow for "sparking out" of the grinding wheel, of the motor 5A in reverse for the rapid withdrawal of the head until a third dog 195 actuates a switch 37 to stop the motor and re-set the circuit for the next cycle. A pressure switch included in the circuit prevents the start of a cycle until an air-operated work clamp grips the workpiece with a ,prescribed pressure. The dogs 191, 192, 195 and their switches 34, 35, 37, together with a further dog 194 coacting with an overtravel switch 32, are mounted in a panel box 168, Fig. 5, the cover of which must be closed before the automatic cycle can start. The dogs are disposed on a carrier 170 which is detachably connected for movement with the head by a nut 166 on the lead screw 135. For set-up purposes, the screw 135 is operated from a handwheel 181 through a chain-and-sprocket drive which can be set by cams on a handoperated shaft 177 so that the head can be moved manually either forwardly only or both forwardly and rearweardly; during set-up, the head is moved through its proposed path while the dogs 191, 192, 194, 195 and sleeve 156 are positioned for the correct actuation of their switches in the cycle. The various control buttons are mounted on a main panel 112, Fig. 1, and auxiliary panel 114. The main panel includes a lamp which lights up during the grinding cycle; the auxiliary panel, which is of particular use when setting up the machine, has three lamps which are respectively extinguished automatically after the rapid traverse, fast feed, and slow feed stages of the head, and a lamp which lights up should the head overtravel. Construction and operation of crusher unit. The carrier 204, Figs. 12 and 13, for the crusher roll is slidable vertically in the head 111 by means of a screwthreaded shaft 212 engaging the nut 206 which is mounted for relative vertical movement in the carrier; the nut is engaged at its upper face by flanges on side plates 207, 208 of the carrier and is biased from the carrier by springs 210, 211. Axial movement of the shaft to move the unit to and from the grinding wheel is effected by a rack 230, Fig. 10, operated by a cylinder-and-piston device 227 and driving a gear 226 meshing with a gear 225, Fig. 12, formed as a nut in screwthreaded engagement with a sleeve 217 which is non-rotatably mounted in the head 111 for movement axially with the shaft 212. Air is supplied through speedcontrol valves to the opposite ends of the device 227 as determined by a solenoid valve 236, Fig. 7. Rotation of the shaft 212 to feed the crusher roll into the grinding wheel is effected through a gear 249 splined on the upper end of the shaft and driven through a clutch 260, Fig. 12, and variable' gearing from an electric motor 7A, Fig. 7, or from a hand-operated shaft 251, the clutch then being disengaged. The control circuit for the crushing operation forms part of the control circuit for the grinding machine and permits of an automatic cycle upon the actuation of an appropriate switch. This cycle consists first in the operation of the solenoid valve 236 to actuate the rack 230 for the rapid downward movement of the crusher unit. At the end of the lost-motion movement of the nut 206 following the engagement of the crusher roll with the grinding wheel, a plunger 269, Fig. 15, enters a notch in the nut and thereby, through a hinged plate 270 and spring-pressed plunger 271, actuates a switch 40, Fig. 7, to . set into operation a motor-driven timer switch which energizes the slow-speed motor 8A, Fig. 1, to rotate the grinding wheel and the contacting crusher roll. After a preset time, the timer switch brings a second similar switch into operation to energize the crusher feed motor 7A for a prescribed time and then re-set the first time switch so as to stop the motor 8A after a "dwell" interval and cause the rack 230 to restore the unit to its normal position. The crusher unit may be returned to its upper position at any time during the cycle by actuating a manual emergency switch, and an over-travel switch 38, Fig. 7, is arranged to be actuated by a plunger 273, Fig. 15, at a prescribed maximum downfeed of the unit, and therefore minimum size of crushing of the grinding wheel, so as to stop the crushing cycle and light up a warning lamp. The control circuit is capable of being set so that either (a) the automatic crushing cycle continues until either the emergency switch or over-travel switch is actuated, or (b) the automatic cycle continues only so far as to bring the crusher roll into yielding contact with the grinding wheel and start the slowspeed grinding wheel motor 8A, a hand crank then being .employed on the shaft 251, Fig. 12, in order to rotate the shaft 212 to provide the crushing feed. The control buttons for the crushing cycle are mounted on a panel 11.5, Fig. 1, on the head 111.