GB706877A - Rebound dampening devices for printing hammers - Google Patents

Abstract

706,877. Typewriters &c. NATIONAL CASH REGISTER CO. Jan. 7, 1952 [Jan. 12, 1951], No. 445/52. Class 100 (4) Hammer-impression arrangements.-The rebound of a printing hammer is prevented by absorbing the return energy by the displacement of one or more elements, e.g. cam plate 70, Fig. 1, or balls 86, Fig. 5, disposed within a bracket 72 or a chamber 87, respectively. The cam plate 70 is pivotally mounted on a stud 71 in the bracket 72 and has a stud 73 projecting into an aperture 74. When a cam edge 76 on the hammer engages the cam plate 70 the energy is absorbed by a weighted end 75 until the stud 73 strikes the side of the aperture 74. In a modifi - cation, a further surface pivoted on the cam 70 is first engaged by the hammer and pushed against a spring until this further surface engages the cam 70 which then functions as before. In the embodiment shown in Fig. 5, the hammer energy is absorbed by a series of balls 86 which are pushed up the sloping sides 89 of the chamber 87. The hammer is actuated three times in each cycle or revolution of a shaft 49, by the studs 47 engaging a three-armed lever 37. The right arm 39 of this lever has a stud 40 which engages a finger 41 of a pawl 24 and pivots it counterclockwise as the studs 47 engage and pivot the lever 37. A pin. 22 on a hammer arm 17 is thus unlatched from a notch 23 on the pawl 24 and is drawn into contact with a ledge 38 of the arm 39 by a spring 30. When the nose 46 passes each stud 47, a spring 50 drives the arm 39 counterclockwise and ledge 38 effects an impression stroke to the hammer through the pin 22. The movement of the arm 39 is limited by a lower arm 36 of the three arm lever 37 engaging a resilient adjustable stop assembly 34, 53, 54, 55, and the hammer completes its stroke by momentum. The hammer drops back to its normal position and the pawl 24 having been released by the stud 40 and pivoted by a spring 26, re-engages the stud 22 to prevent the hammer rebounding and causing a second impression. With the rapid repeated impressions in each cycle the rebound, without the energy absorbing devices described would be too rapid for the pawl 24 to prevent a second hammer stroke.