Patent GB-672633-A (GB)
Title: Improvements in and relating to typewriters
IPC: B41J19/64
Filed: 1945-06-25
Abstract: 672,633. Typewriters. TRIGGS, W. W. (Coxhead Corporation, R. C.). June 25, 1945, No. 16184/45. [A Specification was laid open to inspection under Sect. 91 of the Acts, Jan. 9, 1946.] Class 100 (iv). Type-wheel machines; letter-spacing mechanism. In a rear-strike typewriter wherein a hammer hits the paper against the type mounted on a shuttle and the shuttle is interchangeable for using fonts of various styles, the letter spacing varies according to the letter being typed and control means are provided which can be set according to the font and to the case in that font which is in use so that the spacing is appropriate thereto. Means are also provided whereby the unit of spacing can be varied. The machine described is adapted for printing in three different styles, e.g. Gothic, Roman or Italic. Its carriage 16 is driven by a spring drum 19, Fig. 2, which through an escapement rotates a shaft 41 carrying gears 32-35 one of which engages a rack 31 mounted on the carriage. By means of a spindle 24 with a setting knob 25, the rack 31 can be lifted clear of the gears, and the gears moved axially on the shaft 41 so as to bring into mesh with the rack the gear which gives the desired unit spacing. Each type-key 5 is associated with one to three depending rods Ia, IIa, IVa, Figs. 3, 5, which pass through holes in an arcuate plate 47 having restricted endwise movement on pins 48. The plate 47 is held in its normal central position by spring jaws 52, 54, Fig. 5, engaging a pin 51 thereon and is moved to the left or to the right by the depression of capital and figure shift-keys 22, 21 respectively, carrying the lower ends of the rods Ia, IIa, IVa with it. The shift keys act on a cam plate 64, Fig. 4 (not shown), having a pin-and-slot connection with a bracket 60 on the plate 47. Beneath the rods are three universal bars Ib, IIb, IVb respectively, one or more of which are depressed by the rods when a key is actuated. The number of and the particular bar or bars depressed. are determined by slots suitably disposed in their upper faces. When a slot in a bar is situated beneath a rod, that bar is not depressed when the corresponding key is actuated. Depression of a shift key causes the disposition of the rods relatively to the bars to be altered, and thus the bar or bars depressed are varied. Movement of a bar Ib, IIb or IVb depresses one end of a corresponding lever Ic, IIc or IVc and raises the far end to which is pivoted an escapementoperating link Id, IId, or IVd. Each link, e.g. link Id, passes through a hole h in a plate i, Fig. 6, and has a cam-surface Ida engaging the edge of the hole so as to be moved to the left and to pivot a latch 106a into the path of a trip-lever 12f associated with the hammer-escapement mechanism. Simultaneously with the operation of the link Id by a key, release of the hammer and raising of the lever 12f and therefore the latch 106a takes place. Pivoted on the.latch and on a fixed pivot 85 is a dog 106 which now engages a toothed disc If of the escapement and at the same time disengages a retaining dog 105 by means of its extension 109, so that a very slight movement of the disc can take place under the action of the escapement spring. Lever 12f, and therefore the latch 106a, do not return to normal positions until the hammer-escapement member makes the return movement, whereupon the disc If can rotate one tooth space and be reengaged by dog 105. The links IId, IVd operate similar toothed discs IIf, IVf. It is arranged that the space-bar 70 actuates the link IVd only, and since depression of the bar is not accompanied by an operation of the lever 12f, the upward movement of the dog 106a is caused by the engagement of the end of the link IVd with a projection g thereon. The discs If, IIf, IVf and the shaft 41 are coupled together by an epicyclic gearing 88, 89, 90, 91, 92, 99, 101, 104, Fig. 11. The arrangement is such that actuation of a link Id, IId or IVd causes a spacing movement of one, two or four units respectively, and operation of two or more links causes a spacing corresponding to the sum of the separate movements. Thus according to the key depressed and whether a shift-key is operated, one or more of the universal bars Ib, IIb and IVb are depressed and one or more of the escapement discs If, IIf, IVf are released to give the required spacing. In order to provide for use of type fonts of different styles, e.g. Gothic, Roman or Italic, each universal bar comprises a set of three bars riveted together. The bars are connected by links I, II, IV, Fig. 5, to a spindle n connected by a link o to an eccentric p on a spindle r. By setting the spindle r according to the style to be used, one bar of each set is moved into position to be engaged by the depending rods Ia, IIa, IVa and thus the spacing is determired by the operative set of bars. Back-spacing mechanism. A back-spacing key 3, Figs. 29; 32, is provided whereby the carriage can be returned selectively a distance of one or four units. For this purpose, the toothed disc If is employed, detent pawls being provided to prevent backward movement of the other discs IIf, IVf. The key 3 has two integral fingerpieces 3a, 3b pivoted thereon. Depression of the piece 3a causes a full stroke of the key 3, but when the piece 3b is operated its end 3c swings inwardly to engage the frame 1 so that only a quarter stroke of the key 3 occurs. Movement of the key 3 is transmitted by a shaft 13 and links 13b, 13c to a spring-pressed pawl 23 which operates the toothed disc If to back space the carriage either one or four units according to the finger-piece depressed. At the end of the return movement, the pawl 23 is lifted by a pin 43a engaging a cain slot 43 therein. At the end of a full stroke of the key 3, a pin 105b on link 13c engages a pin 105a on the dog 105 to prevent further backward movement of the disc If, and a tail 13i on the pawl 23 engages a fixed pin 63 to take the shock of the stroke: The back-spacing mechanism forms the subjectmatter of Specification 672,641. Sound-deadening. The dog 105 of the disc If is lifted during carriage return so as to lessen the noise and friction by a spring wire 73a wound on a grooved wheel 73 fixed on the shaft 41 and which engages the pin 105a during such movement. When letter-spacing is taking place, the spring 73a engages a fixed stop 105c and tends to unwind so that it exerts little frictional resistance to the carriage movement. Justifying mechanism as described in Specification 672,642 may be incorporated in the machine. Specifications 657,892 and 672,638 also are referred to.