Patent GB-676221-A (GB)
Title: Improvements in typewriters
IPC: B41J19/32
Filed: 1949-04-13
Abstract: 676,221. Typewriters &c. TRIGGS, W. W. (Coxhead Corporation, R. C.). April 13, 1949, No. 10007/49. [A Specification was laid open to inspection under Sect. 91 of the Acts, Oct. 17, 1949.] Class 100 (iv). Variable letter spacing in a typewriter is effected by an escapement mechanism the spacing action of which is determined by the interaction of one or more universal bars 114, 115, Fig. 5, and a series of push rods 129, one operated by each key lever and having heads 131 extending perpendicular to the universal bars, the rod heads 131 having operative and inoperative zones for selectively operating the universal bar or bars to effect varying degrees of letter spacing, the bars 114, 115 being shifted relatively to the heads 131 so that the spacing system is regulated to (a) accommodate the different width of characters necessary due to capital shift (b) accommodate different width due to Figure shift and (c) to effect a uniform spacing for all characters if desired. The machine described is of the kind in which the type characters are embossed upon a shuttle 25 mounted for character selection movement about the cylindrical surface of an anvil 26. A hammer 29 coacts with the shuttle at the printing position 27 to drive the paper and an ink ribbon 30 against the type. The forward or operating stroke of the hammer 29, raises a roller 106, Fig. 3, permitting a lever pawl 107 to rotate anticlockwise, thus permitting rotation of an escapement shaft 70 and an escapement actuating lever 109 under tension of spring 110. An adjustable screw 111 on the lever 109 engages an extension 89 of a movable dog lever 52 having a fixed dog 51 shaped with a knife edge 72 which engages in peripheral teeth 49 of an escapement wheel 47. The dog 52 has also an extension 71 which during this forward movement of the hammer engages a concentric surface 62 of an arcuately moving dog 50 having a knife edge 66 on a depending arm 64 which is thus disengaged from the escapement wheel 47 and which slides and rotates on a collar 57 against the influence of a spring 69 The amount of anticlockwise rotation of the dog 50 is limited by settable stops 75B-D and limit stop 75E which determine the amount of movement of the escapement wheel and hence the amount of letter spacing to be effected. As the hammer 29 returns to normal position the roller 106 moves the lever pawl 107 clockwise and so releases the dog 52 from the escapement wheel and edge 66 of dog 50 engages wheel 47 which is thereby allowed to rotate clockwise under pull of the usual carriage movement spring until the dog 50 engages a limit stop 74. Rotation of the escapement wheel 47 is transmitted through a pair of pawls 55 mounted on the forward side of the wheel 47 and which forms part of a free-wheel drive to a shaft carrying a number of pinions forming a variable gear connection to a carriage rack. The gear mechanism is described in Specification 672,633. The amount of rotation determined by the stops 75B, C, D, E corresponds to 1, 2, 3 and 4 units of space respectively. Stop 75B is operated only by a special key 90 for purposes of aligning the commencement of'a line or tabulating. The key 90, by a plunger and cam action rotates a spindle 96, Fig. 2, moving the stop 75B, against the action of a torsion spring 100, into the path of the extension 68 of the arcuate dog 50. Stops 75C and 75D are moved into position by the character keys according to the width of the type. Each character key 22, Fig. 5, has its own push rod 129 and the zoned heads 131 are individually shaped to engage either of the two universal bars 114, 115 operatively connected by linkages 116, 117, 119, 120 and 124, 125, 126, 127 to stops 75C, 75D respectively. The heads 131 may be shaped so that neither universal bar is engaged in which case the dog 50 travels to the anticlockwise limit stop 75E to effect 4 units of space. When a space bar 32 is operated its associated push rod 129 engages the bar 114 to effect 2 units of space and the escapement mechanism is operated by a link 84, Fig. 2, connected to a lever 87 fixed to the escapement shaft 70. If 4 units of space is required the push rod 129 may be oscillated against the bias of a spring, Fig. 9 (not shown), so that it enters a slot in the bar 114 which is thus not operated. To accommodate a difference in spacing between the upper and lower case of one size type the bars 114, 115 are arranged to be moved bodily in relation to the zoned heads 131 e.g. for normal capital letter a key 34 is depressed, Fig. 11, pivoting a lever 150 and allowing a fork 137 to pivot clockwise under the pull of a spring 152 and so move a link 139 to the right carrying the pivots 134 of bars 114-115 along slots 135 in the casing. The bars are thus moved into zones 2 and 6, Fig. 13, of the head 131. When " Fig." key 35 is depressed a greater rotation is given to lever 150 and the bars 114, 115 are moved into zones 3 and 7 of the heads. The machine can also be set to type uniform spacing by disconnecting the variable space mechanism, effected by moving the bars 114, 115 forwardly one zone so that bar 115 is cammed upwardly by a hump 140 in the slots 135 so that the stop 75D is permanently operated and so that bar 114 is positioned above a gap in the head 131. The movement of the bars forwardly is arranged by rotating by hand, a knob on a shaft 155, Fig. 11, which turns a cam 154 engaging an arm 158 of the forked lever 137. Specifications 657,892 and 676,195 also are referred to.