GB968496A - Anti-rebound device for a printing hammer - Google Patents

Abstract

968,496. Typewriters. NATIONAL CASH REGISTER CO. Aug. 22, 1963 [Oct. 11, 1962], No. 33204/63. Heading B6F. An anti-rebound device for a type character printer comprises a printing hammer 10, Fig. 1, urged into printing position by a spring 30 and an anti-rebound pawl 32 mounted adjacent the hammer and having a non-locking portion 34a and a looking portion 34c so formed and cooperating with projection 38 on the hammer that when the hammer is urged by the spring the projection co-operates with the non-locking surface 34a to permit the hammer to move freely into the printing position, whereas on rebound the projection engages the locking portion 34c to lock the hammer against making a successive impact with a type carrier 13. Type-bar machines; type-bar actions.-The printer comprises a plurality of type bars 13, Fig. 1, each associated with a hammer 10 and pivoted at its lower end to a differential mechanism (not shown) so that a digit value entered into the printer may be represented by a particular type member 17. The type bars are movable vertically in slotted guides 14, 15 with respect to a platen 16. Hammer-impression arrangements.-In operation the hammer 10, Fig. 1, is released by a hammer latch 18 via an interponent 20 rocked into engagement with a step 18a on the latch, whereupon the spring 30 urges the hammer into printing position and the projection 38 is driven along the non-locking portion 34a of the antirebound pawl 32, jumps the recess of the locking portion 34c separating the non-locking portion 34a from a second portion 34b and positions itself above the said portion 34b (Fig. 2, not shown). When the hammer 10 recoils from its impact with the selected type member 17, Fig. 3, the projection 38 on the hammer will move backward with the hammer and off the second portion 34b into alignment with the recess in the locking portion 34c in turn permitting the pawl 32 to rock anti-clockwise under the influence of the spring 35 to engage the projection 38. To permit the projection 38 to clear the locking portion 34c when the hammer moves initially into printing position, the spring 30 is made much stronger than the spring 35 of the pawl 32, which is relatively weak and also the curvature of the portion 34b is of a smaller radius than that of the non-looking portion 34a. The hammer 10 is reset by a bail 28 mounted on pivotal restoring arms 29, Fig. 1, oscillated by operating arms 23 which in turn are rocked by a cam lever 25 secured on a drive shaft 24. In another embodiment (not shown) the antirebound pawl may be mounted above the projection 38 and the pawl urged into engagement with the projection under gravity. Specification 693,659 is referred to.