Patent GB-1040201-A (GB)
Title: A gauging unit
IPC: B24B49/04
Filed: 1965-01-07
Abstract: 1,040,201. Grinding. CINCINNATI MILLING MACHINE CO. Jan. 7, 1965 [Jan. 28, 1964], No. 822/65. Heading B3D. A gauging unit automatically adjustable over a range of sizes to measure an object sized within the range comprises a housing, a pair of calipers received in the housing and operable to measure the object when the object is embraced therebetween, the calipers being movable in the housing toward and away from one another, a motor connected to the pair of calipers and operable when energized to move the calipers relatively, means to indicate the instantaneous relative position of the calipers, means to produce a signal representative of a predetermined measureable size, and control means responsive to the position-indicating means and predetermined size signal to energize the motor to adjust the calipers for measurement of the predetermined size. A grinding wheel 17 is carried by a wheelhead 12 movable on a bed 11 by a rapid advance motor 19 and a screw 20, backlash being prevented by a biasing motor 22. A workpiece 16 having portions 24, 25, 26 of different diameter is rotatably supported by head and tail stocks on a table 13 movable on ways 14, 15 on the bed. An automatic gauge unit 23 for measurement of the workpiece as it is ground is mounted on the front of the bed 11, the unit being supported in a housing 30 having front and rear sheet metal covers 31, 32. The unit comprises calipers 27, 28 spanning the workpiece diameter and attached to rods 33, 34, Fig. 2 (not shown), extending from carriages 35, 36. Guide rails 39, 40, Fig. 3 (not shown), fixed in the housing 30 pass respectively through the carriages 35, 36 and extensions 41, 42 thereof; the extensions enclose preloaded ball bearing bushings 43. The carriages 35, 36 have fixed nuts 44, 45, Fig. 4 (not shown), of preloaded recirculating ball bearing type respectively meshing with ball bearing screws 37, 38. The carriages 35, 36 are equally and oppositely adjusted by a motor 29 which drives the screw 37 directly and the screw 38 through reversing gearing 49, 50; the gear 50 has upper and lower relatively rotatable halves biased to eliminate backlash. The rods 33, 34 are movable axially in the carriages 35, 36 from a retracted position to an advanced position in which the calipers 27, 28 engage the workpiece. To effect this, the rod 33 has a piston 54, Fig. 6 (not shown), in a pneumatic cylinder 53 formed in the carriage 35. The rear end of the rod 33 carries a bracket 57 in which is fixed a connecting rod 58 axially movable, by a ball bearing bushing, through a bracket 59 carried by the rear end of the rod 34 so that the rods 33, 34 move in unison. A bracket 62 extending rearwardly from the carriage 36 mounts limit switches 63, 64, Fig. 5 (not shown), actuated by a dog 65 on the bracket 59, the switches producing signals used in the circuits controlling the operating cycle of the grinding machine. The rod 33 passes through preloaded ball bearing bushings 55, 56 at the ends of the carriage 35; the rod 34 is similarly mounted in the carriage 36. The caliper 27, which has a work-contacting anvil 86, Fig. 7 (not shown), is secured to the forward end of a lever 67 pivotally mounted in a head 68 secured to the forward end of the rod 33. A spring 79 urges the rear end of the lever 67 towards an orifice 78 supplied with pressure air from a conduit 83 extending through the rod 33; air escaping through the orifice passes through the rod 33 and escapes freely from its rear end. As the size of the workpieee is reduced, back-pressure in the conduit 83 increases. The caliper 28 is identical. The calipers are supplied from a common air supply like the back pressure in which, contributed by the combined effect of the calipers 27, 28, operates penumatic relay to control the grinding cycle as a predetermined size is reached. A safety device preventing the calipers from being forced over a diameter too large for measurement with the particular spacing of the carriages 35, 36 comprises a lever 92, Fig. 9 (not shown), pivoted in a member 91 attached to a bracket extending forwardly from the carriage 36. A spring-loaded plunger 93 biases the lever 92 so that its rear end closes an orifice 95 supplied with pressure air through a tube 96 connected to a pneumatic relay 97, Fig. 10, which provides a signal if the lever 92 is swung by contact with the workpiece to release air from the orifice 95 thus reducing the pressure in the tube 96. The signal is used to prevent operation of the piston 54 and cylinder 53 which advance the rods 33, 34. While the workpiece is being positioned prior to the application of the calipers to it, the carriages 35, 36 are spaced to their maximum spacing and when the workpieee is positioned the carriages are closed to the appropriate spacing. To correct for repeatable errors in the carriage adjusting means due to errors e.g. in the screws 37, 38 and gears 49, 50, a cam 98, Fig. 2 (not shown), fixed to the carriage 36 cooperates with a follower 100 of a differential 1 transformer 99 fixed to the carriage 35. The cam is shaped in accordance with the repeatable errors so that the transformer produces a correction signal. Gauge size setting information is stored in a permanent record, e.g. a punched tape 101, Fig. 10, portions of which are scanned periodically by a reader 102 producing corresponding electrical signals which determines the voltages in the stator windings of a position analogue unit 111. The output of the rotor winding of the unit 111, to which is added the correction signal from the transformer 99, actuates a servovalve 121 which distributes fluid to the motor 29. The motor rotates the rotor of the unit through a mechanical connection 124.