GB1449919A - Stepping mechanism acting forwards and backwards - Google Patents

Abstract

1449919 Ratchet gearing F HARTMANTN 16 Jan 1974 01981/74 Heading F2Q [Also in Division G4D] A mechanism for stepping a star wheel 2 in either direction by single depressions and releases of appropriate push buttons 3a, 3b, for operating, e.g. coded switches, comprises a slide 3 integrally carrying both push buttons on resilient webs 3e, 3e<SP>1</SP>, and capable of sliding longitudinally and rocking transversely, for stepping and direction selection respectively, in a fixed casing 1, to an extent limited by fixed pins 1c, 1d, 1e, engaging respectively on the slide 3 a wedge cut-out 3g and inclines 3h, 3h<SP>1</SP>, the slide carrying pawls 3c, 3d one or other of which produces a half step of the wheel 2 on button depression, and a wedge-pawl 3f which completes a second half of the step under spring load 4 on button release. Apart from the spring the entire mechanism is made from a plastics material. In operation, depression of a button, say 3a, causes the slide 3 to slide longitudinally over the fixed pin 1c and to be rocked counterclockwise by contact of the inclined surface 3h with the fixed pin 1d. The wedge-pawl 3f is freed from the star wheel and the slide pawl 3c rides over the adjacent star wheel tooth and its face 3cc down the flank of that tooth, producing a half step counterclockwise, which presents the next tooth to the pawl 3f, which latter, on release of the push button 3a, and consequent spring return of the slide 3, rides down the flank of that tooth to produce another half step counterclockwise, finally locking the star wheel with one whole step completed. The casing may carry a printed citcuit and the star wheel 2 may earry digits or other symbols visible through a window.