| 摘要 |
1,133,229. Compensating for temperature fluctuations in machine tools. PRATT & WHITNEY Inc. 22 Feb., 1966 [23 Feb., 1965], No. 7614/66. Heading B3B. [Also in Division G3] Pneumatic or electrical means are used to measure the thermal expansion of a feed screw of a machine tool carriage or table and to compensate therefor by applying suitable rotation to the feed nut associated with the carriage. In a first embodiment the thermal expansion of a feed screw 28 is measured by means of an air pressure nozzle 45 positioned adjacent -the free end of the screw, any rise in pressure being employed to adjust the position of a pivoted linear cam 48 which through a follower 47 and lever arm 46 attached to the feed nut 35 imparts compensating rotation thereto. Compensating movement of the linear cam 28 causes a fall in pressure at a second air nozzle 51 positioned adjacent a part of the cam, the two nozzles being connected to a common amplifier, Fig. 6, so that a null or balanced pressure point is reached when compensating movement is is complete. A reversible motor 50 is arranged to raise or lower the cam in accordance with the pressure signals. The cam is pivoted adjacent the fixed end of the feed screw and extends generally parallel thereto. The cam surface is preferably ground to compensate for any manufacturing errors in the screw. The system is described as applied to two feed screws (Fig. 1, not shown), one for the carriage of a boring or drilling machine and the other for a table mounted thereon. In a second embodiment (Fig. 7, not shown), thermal expansion of the feed screw (28) adjusts the position of a movable core (153) associated with a first transformer (150); the latter has two windings (151, 152) connected in a bridge circuit with a second similar transformer, (155) having a core (198) movable with the cam member (48). Electrical imbalance in the circuit is caused by expansion of the feed screw and is utilized to operate a motor (163) which adjusts the position of the cam till electrical balance is restored and the thermal expansion of the screw compensated for. |
