GB416153A - Electrically-operated chucks for machine tools - Google Patents

Abstract

416,153. Chucks. HERBERT, SIR A., LLOYD, A. H., and JINMAN, C. H., c/o Herbert, Ltd., Canal Road, Edgwick, Coventry. June 14, 1933, No. 16955. [Class 83 (iii).] In an electrically operated chuck the jaws are actuated through bell-crank levers or other means, (not shown), controlled by a push rod 31 secured to a nut 28 splined at 30 within a lathe &c. spindle 12. The nut 28 is engaged by a screwed spindle 29 rotatably mounted within the spindle 12 by means of roller thrust bearings 26 located between roller journal bearings 27 and carrying an annular gear 24 meshing with floating pinions 22 which also engage an annular gear 23 secured to the spindle 12 through a casing 13. The stator casing 15 of an electric motor is secured to the casing 13 to rotate with the spindle 12 whilst the rotor 19 is mounted in bearings 20 in the casing and carries a pinion 21 engaging the pinions 22. The annular gears 23, 24 have slightly different numbers of teeth so as to provide a reduction ratio of about 70 to 1. The spindle 29 has a quick-pitch screw thread of about three threads per inch and is non- reversible so as to maintain the clamping pressure on the jaws. To provide a yielding telescopic connection between the push-rod 31 and the jaws, a sleeve 37, Fig. 2, may be attached to the rod 31 and provided with a collar 38 engaging springs 39, 41. These springs act on a push-rod 36 rigidly connected to the jaws, through a collar 40 on the rod and a sleeve 42 secured to the rod by a pin 43 slidable in a slot 44 in the rod 31. When applied to a small lathe, the bearings 27 are replaced by a plain journal bearing and the bearings 26 by two ball thrust bearings acting on opposite sides of a collar on the spindle 29 located at one end of the plain bearing, and within the bearing for the lathe spindle 12. Current may be supplied to the motor through brushes 32 and slip-rings 33, arranged either as shown or on the periphery of the stator, control being effected by a switch on the lathe headstock connected with electromagnetic contactors on an auto-transformer arranged away from the lathe. The tappings of the transformer maybe used to vary the engagement pressure of the jaws on the work. Alternatively, a polyphase resistance in series with the stator winding may be used, or the motor might be a series-wound direct current motor controlled through a variable resistance. The motor is controlled by a double-acting switch which is biassed to the " off " position so that it may be held by the operator in either position until the jaws have either opened or closed and the motor has stalled, whereupon on release of the switch it returns to the " off " position.