Patent GB-121068-A (GB)
Title: Improvements in and connected with Letter-spacing and Back-spacing Mechanism for Typewriting Machines.
Inventor: FAIRWEATHER WALLACE CRANSTON
IPC: B41J19/74
Filed: 1917-11-28
Abstract: 121,068. Fairweather, W. C., (Underwood Typewriter Co.). Nov. 28, 1917. Letter-spacing and backspacing mechanisms. - Relates to machines in which the letterspacing and back-spacing mechanisms are mounted on the carriage-shift frame. (1) The escapement-wheel 54 is mounted on a spindle 56 secured to plates 25, 26 on the shift-frame, the carriage 31 being mounted on the plates by means of balls 34, 35 arranged between rails 32, 33 on the carriage and offset parts 27, 28 of the plates. A pinion 39 secured to the hub 55 of the escapement-wheel engages a rack 38 on the carriage. A rocker 61, Figs. 6 and 7, trunnioned at 62 in ears 63 on the plate 25, is formed with a fast dog 97 and carries a loose dog 59 which is pivoted at 60, and is connected to springs 98, 99. The loose dog is normally in engagement with the escapement-wheel and abuts on a stop 101 on the rocker. The rocker is operated by a draw-link 69 which passes through a slot 67 in the rocker and carries a nut 68 for engaging the rocker. The draw-link is pivoted at the rear to a lever 71 and has a pin-and-slot connexion 90 at the front with a lever 88, the levers 71, 88 being pivoted on brackets on the main frame 15. A universal bar 82, pivoted at 83 on the main frame and operated by the key-levers 76, is connected by a link 85 and an arm 86 to the lever 88. At each operation of the key-levers, the loose dog is released and the fast dog is caused to engage the escapement-wheel, the loose dog being moved upwards by the spring 98, and the movement being limited by the spring 99. On release of the keylever, the rocker is returned by a spring 64, and the loose dog re-engages the escapement-wheel, which can then move until the loose dog engages the stop 101. The slot 67 in the rocker enables the rocker to be operated in all shift positions of the platen. To cause the draw-link 69 to impart a uniform movement to the rocker in all shift positions, the part of the rocker in which the slot is formed is, as shown in Fig. 7, inclined in the direction of movement of the shift-frame. (2). The back-spacing. mechanism comprises a pawl 114, Fig. 6, pivoted on an arm 113 which is pivoted on the spindle 56 of the escapement-wheel 54 and is connected to a back-spacing-key lever 103 carried by the main frame 15. The pawl 114 is normally held out of engagement with the escapement-wheel by a spring 115 which holds the tail of the pawl against a fixed stop 116. The arm 113 is connected by a link 112 to a bell-crank 111 which is pivoted on a bracket on the main frame and engages the key-lever 103. When the backspacing key is depressed, the arm 113 moves the pawl idly until the tail rides off the stop 116; the pawl then engages the escapement-wheel and backspaces the carriage, the movement being limited by the engagement of the pawl with a stop 118. The bell-crank 111 is connected to a returning- spring. When the platen is shifted, the link 112 moves idly. (3) The spring drum 44, Fig. 3, for driving the carriage is mounted on the plates 25, 26 of the shift frame, the spring 45 being connected to the casing 44 and to a sleeve 46 which is mounted on a stud 47 on the plate 26 and in a sleeve 48 on the plate 25. A ratchet-wheel 49, secured by a nut 50 to the sleeve 46, is engaged by a holding-dog which is pivoted on a bar 51 secured to the plate 25. Carriage-releasing arrangements.-The feed-rack 38, Fig. 6. is mounted on trunnions 40 in the carriage and is provided with a release-lever 41. Space-key actions.-The space-key lever 92, Fig. 7, is connected by a link 95 to the lever 71 of the escapement-operating mechanism, a slot 96 permitting the space-key lever to remain at rest when the printing-key levers 76 are operated.