Patent GB-1395566-A (GB)
Title: Mating and sizing control for thread grinding machine
IPC: B24B49/04
Filed: 1972-09-29
Abstract: 1395566 Grinding threads REISHAUER AG 29 Sept 1972 [1 Oct 1971] 45137/72 Heading B3D A sizing control for mating grinding on thread grinding machines comprises a first sensor system 128, Fig. 2, for measuring the actual dimension of the reference diameter of a finished internal thread 123, and a second sensor system 156, 157 for measuring a reference diameter of the mating workpiece 153, the whole being adapted for use in a working process having at least two working steps and wherein the first and second systems act on the wheel carriage feed mechanism. The first sensor system determines, by means of a shiftable abutment surface A and in the light of the measurement of the reference diameter of the finished internal thread, a first estimate of the amount of material to be removed from the workpiece, while the second sensor system alters the position, relatively to the abutment surface, of a measuring element 174, 175 determining the magnitude of the feed step to be performed before the start of the final working step. The alteration in such position depends upon evaluation of the measurement of the ground external thread and serves to correct the amount determined by the first sensor system. The workpiece 153 is mounted between a headstock 53 and tailstock 57 on a workslide 52 reciprocatable on a body 51 by rotation of a leadscrew 84 engaging a nut 85, the leadscrew being rotated by gearing including a feed clutch 67 and return clutch 68 driven from a motor 64. The gearing is also connected by change gears 72, ... 75 to a shaft 78 connected by gearing 79, 80 to the headstock spindle 81. The reciprocation of the workslide is controlled by end stops 89, 90 which co-operate with a lever 91 actuating a limit switch 93 to control the clutches 67, 68. The workpiece is ground by a grinding wheel to which is driven by a motor 61 and is adjustable to the helix angle α of the thread on a saddle 59 on a carriage 58 reciprocatable towards and away from the workpiece by rotation of a lead screw 96, either by a handwheel 98 or motor 62, engaging a nut 97. The return position of the carriage 58 is determined by a limit switch 99. A measuring rig 63 is mounted on the body 51. The first sensor system measures the internal diameter of the finished thread 123 of a part 121 of the machine and consists of a part 126 which is clamped by a screw 130 in adjusted position on the rig 63 according to the internal diameter of the part 121 and has balls 131 which are located in a cage 132 and engage the threads of the part 121. The part 126 co-operates with a movable detector 127 which has a ball 133 for engaging the diametrically opposite part of the thread 123 the detector is mounted for vertical movement by spring pivots 134, 135 and is engaged by an element 139 on a rod 138 which, at its lower end, is engaged by a bent lever 136 urged by a spring 137 about a pivot 136a against the rod. The upper end of the rod is joined by a spring plate 140 to a double lever 141 movable about a pivot 141a. When the detector has engaged the thread, the position of the rod 139, and hence the bent lever 136, is retained or stored by operation of an hydraulic device 142 which acts to clamp the double lever 141. The part 121 can then be removed and replaced while maintaining the position of the levers 136, 141. The second sensor system consists of a barrel 144 which can be advanced to an operative position in the rig 63 by a piston 148 in a cylinder 147 which is adjustable by a screw 149, the barrel being urged towards the piston by springs 145, 146. The barrel supports, by way of a spring 197, a pair of feelers 156, 157 on arms 158, 159 connected by spring plates 160, 161 to respective pins 162, 163 movable in barrel 144. Thepin 162 is adjustable by a screw 172 and pin 163 is adjusted by the double lever 141 according to the dimension of the internal thread 123 sensed by the first sensor system. A spring 198 urges the arms 158, 159 into engagement with a measuring element 164 comprising an inductive distance detector 165, Fig. 4, disposed within telescoped parts 167, 168 urged by a spring 171 into engagement with respective ones of the arms 158, 159. With a specimen part 121 on the first sensor system and engaged by the detector 127 and a specimen workpiece 153 engaged by the feelers 156, 157, the arm 158 is adjusted by the screw 172 until the detector element 164 is in a central position and its output voltage equals a reference voltage of a similar detector 165, Fig. 8, the voltages being compared by an instrument 223. The feed system of the wheel carriage is associated with a feed step limiting system having a number, for example, three, measuring elements 173, 174, 175, Fig. 7, according to the number of working steps. The elements are carried by a plate 180 on a rod 178 which is slidable in a fixed tube 176 and pressed by a spring 179 against a nut 177 or a spindle 184 axially shiftable by rotation of a gear 183 driven from a sliding rotor brake motor 181. The elements 173, 174, 175 are arranged to engage the abutment surface A of the bent lever 136 adjusted by the first sensor system and determine the forward feed positions of the wheel carriage 59 in each of the working steps. Each element consists of an inductive distance detector 165, such as shown in Fig. 4, in a chuck which is axially adjustable by a micrometer thread. The machine is equipped with a hydraulic system 281, Fig. 8, for supplying hydraulic fluid to the clamp 142 for the double lever 141 of the first sensor system and the cylinder 147 for advancing the barrel 144 of the second sensor system, and the hydraulic system, the movement of the workslide 52 and wheel carriage 59, and the sequential actuation of the elements 173, 174, 175 are under the control of an electrical system 221 having a programmer 222 which is triggered to operate in steps by a limit switch 227 actuated by a cam 229 on the workslide 52. As described, the machine is set to have three working steps and the elements 173, 174, 175 are set to determine the advance position of the wheel carriage for each step, respectively. The probe arms 158, 159 are also set to the diameter of the workpiece by adjustment of screw 172. In operation, the part 121 with the finished internal thread is placed on the first sensor system and the detector 128 engages the thread to position the abutment surface A. When a start button is pressed, the hydraulic clamp 142 secures the double lever 141 in position so that, if desired, the part 121 can be removed and replaced, and the motor 62 is energized to advance the wheel carriage 58 from point 11, Fig. 9, to a position (point 12) determined by element 173 engaging abutment surface A whereupon the motor 64 is started to move the workslide from left to right and to rotate the workpiece 153, the cam 229 stepping the programmer from step 1 to step 2. At the end of the movement of the workslide (point 14) the lever 91 is actuated to effect a return movement of the wheel carriage 58 (point 15) to actuate limit switch 99 which stops motor 62 and changes over clutches 67, 68 so that both the rotation of the workpiece and movement of the workslide 52 are reversed back to their normal position through point 16 in which the programmer 222 steps to positions 3 to connect element 174 to the instrument 223. At the end of the return movement of the workslide (point 17), the lever 91 actuates switch 92 to disengage clutch 68 and motor 62 advances the wheel carriage to a position (point 18) determined by element 174. The workslide is again moved from left to right and the workpiece rotated as before. At point 19 the cam 229 actuates the programmer to step 4 and hydraulic fluid is supplied to cylinder 147 to advance the second sensor system so that the arms engage the ground thread (point 20) and the output from elements 164 is compared with the set value by the instrument 223. The deviation detected acts as a correction. A cam 230 on the workslide operates a switch to effect both energization of the motor 181, to move rod 176 so that the output from element 174 equals that from element 164, and operation of a valve 288 to cause return movement of the barrel of the second sensor system. At the end of the second working step of the workslide 52 (point 21) the motor 62 returns the wheel carriage 58 to its rear position (point 22) and the workslide 52 is then returned to its initial position (point 24), cam 229 acting to step the programmer to step 5 at point 23. The final feed of the wheel carriage 58 is effected to point 25 which is determined by engagement of element 175 with the abutment surface A, the position being determined by the final set feed plus correction determined from the preceding grinding. The workslide makes its final feed from left to right stepping the programmer at point 26. At point 27 the wheel carriage is returned to point 28 whereat the workslide is returned to its normal position (point 11) stepping the programmer to position 1 at point 29 in preparation for the grinding of the next workpiece. Compensation for dressing of the grinding wheel may be effected by operation of motor 181 to move the rod 178 and plate 180 carrying the elements 173, 174, 175 relative to the abutment surface A.