GB816830A - Automatic cut off for electrically operated typewriters - Google Patents

Abstract

816,830. Typewriters. INTERNATIONAL BUSINESS MACHINES CORPORATION. Dec. 23, 1955 [Dec. 30, 1954], No. 36937/55. Class 100(4) A power driven typewriter having driving means controlled by an electrical switch 4 includes an automatic cut off device comprising a bracket 16 pivoted for movement from a rest position to an operative position and linked to the switch so that the latter is shut off when the bracket has been moved to its operative position, and actuating means carried by the bracket for rocking the latter from its rest position to its operative position after a predetermined uninterrupted period and comprising a pair of wheels of different diameters coaxially mounted on the bracket for rotation by the driving means while the bracket is in its rest position, means mounting one of the wheels for lateral movement in response to a predetermined continuous rotation of the wheels, and an actuating cam in response to this lateral movement for rocking the bracket to its operative position. With the bracket in the rest position driving wheel 18 and climbing wheel 22, of smaller diameter, are rotated by contact with power roll 2, and the latter wheel rotating at the faster rate rotates relatively to the threaded shaft 24 and moves along that thread, and after a predetermined time, if the typewriter is not operated, engages cam 20 and rotates it slightly against the pull of spring 49. Cam 20 then engages and is driven by roll 2, until the widest part of the cam leaves the roll, and finally returns to its rest position under its own momentum. As the cam is thus driven it causes bracket 16 to rock clockwise, Fig. 1, about stud 28, and through link 50 operate switch 4 to shut off the motor (not shown). The cutoff mechanism is disabled by operation of certain typewriter function keys which reset the climbing wheel to its rest position. Thus, for example, operation of the case shift key 56 rotates plate 58 counterclockwise, Fig. 1, and via pin 62, yoke 63, and arm 54 rocks the bracket slightly to interrupt the drive between roll 2 and wheel 22, whereupon spring 26 moves wheel 22 axially to its start position. Switch 4 may be operated manually by means of arm 8 acting through link 6. Specifications 655,492 and 773,939 are referred to.