Patent GB-153324-A (GB)
Title: Typewriting machines
IPC: B41J1/32
Filed: 1920-11-01
Abstract: 153,324. Block, A. Nov. 5, 1919, [Convention date]. Hammer-impression arrangements; letter-spacing mechanism.-In a visible-writing typelever, type-wheel, or other machine, an impression bar operating with a dwelling pressure to reduce noise of impact is mounted on the paper carriage and controlled by universal-bar mechanism from the keyboard but actuated by power, which may be derived from the spring drum of the letter-spacing mechanism. Means is provided for adjusting the throw of the impression bar as required for varying thicknesses of paper and for manifolding. A type-lever machine is shown in Fig. 2, the impression bar 4 being mounted on the paper-carriage 2 behind a striking-strip 6 serving for further reduction of the noise of impact. The impression bar 4 forms part of a frame 3 pivoted at 5 on the carriage and having a rear bar 12, Figs. 5 and 11, in sliding connexion with a yoke 7 on a vertically movable bar 7<a>, which is actuated through a lever 7<c> from a spring 7<d>. The lever 7<c> is normally held up against the pull of the spring by a pivoted detent 7t controlled from the keyboard, and is restored into engagement with the detent by an arm 23<b> on a rock-shaft 23 actuated by the escapement letter-spacing mechanism described below. The universal bar 18a, Figs. 2 and 10, actuates a slide B in loose operative connexion with a second slide C terminating in a cam surface C<2> for successive operation of a rock-shaft 32 for releasing the detent 7t of the impression bar and a rock-shaft 33 controlling the escapement mechanism. The escapement mechanism comprises a detent ratchet D, Figs. 10 and 11, controlled from the rock-shaft 32, and a movable member consisting of a frame 21, Figs. 5 and 11, pivoted on a fixed support 21g and rocked by connexions 24, 25 from the rock-shaft 33, and an upper member 21r slidable on the frame 21 under the action of a spring 21j and provided with ratchet projections 21a, 21b for alternate engagement with the carriage rack 20 and with a pinion 22 on the rock-shaft 23 for restoring the impression bar, and stops 21e, 21f for limiting the movement in either direction. In order of operation, the ratchet detent D is engaged with the rack 20, the movable escapement member 21r is withdrawn from the rack 20 and engaged with the pinion 22 on the rock-shaft 23, restoring the impression bar, the member 21r is returned into engagement with the rack, allowing return of the rock-shaft 23 by a spring 23<x>, and the detent D is withdrawn from the rack, allowing displacement of the member 21r with the rack for letterspacing, the spring 21f being tensioned by this movement. The member 21r is engaged in normal position by a spring-pressed detent 21v, which prevents the sliding movement of the member until the member has been swung clear of the detent. The detent 7t of the lever 7c is projected into operative position by a spring 7P, and is released from the rock-shaft 32 by means of a sliding bar D<5> carrying an overhanging bellcrank D<8>, which in the downward stroke of the bar first engages the tail of the detent to release it, and then passes out of engagement to allow return of the detent by its spring, and in the upward stroke yields to pass beyond the detent, which is prevented by a stop 7<x> from further movement in that direction. When the spacekey is operated, the impression bar is locked against movement by means of a detent 85, Figs. 2 and 10, which is swung over the lever 7<c> by loose cam connexions 85b, 83b at the end of the space-key lever 83, and returned by a spring 86. The throw of the impression bar is adjusted by means of a stop 77, Fig. 11, in the path of the outer end of the lever 7<c>, carried by a screw shaft 78 which is geared to a shaft 75 extending to the front of the machine and provided with a crank-handle. Carriaye-releasing arrangements.-The carriage rack 20, Fig. 11, can be released by means of a thumb-lever 2h or by the line-spacing lever 2a through a rocker-arm 2d, connected to an arm 2n of the lever. Type-lever actions; alining for impression.- The type-lever 14, Fig. 2, has loose operative connexion by means of a cam slot 14a with a stud at one end of a sub-lever 15, which is pivoted at the other end and connected at an intermediate point by a link 16 to the key-lever 19. The alining-guide 13 serves also as an anvil for abutment of the selected type-head 14<e> during impression.