Patent GB-432083-A (GB)
Title: Improvements relating to platens for typewriting machines
IPC: B41J3/28
Filed: 1935-01-28
Abstract: 432,083. Typewriters. TRIGGS, W. W., 57, Lincoln's Inn Fields, London.-(Underwood Elliott Fisher Co. ; 342, Madison Avenue, New York, U.S.A.) Jan. 28, 1935, No. 2739. [Class 100 (iv)] Paper-supports; sheet-clamping arrangements.-In machines comprising a type-carriage movable for letter-spacing and line-spacing relatively to a flat platen which is automatically depressible to release the work, the platendepressing means is operated when the typecarriage arrives at selected line-space positions. In the machine shown in Figs. 2, 3, and 4, a line-spacing carriage 9 supporting a typecarriage 7 runs on a frame 1 within which is mounted a flat platen 4. The line-spacing carriage is associated with the traversing- mechanism described in Specification 312,136, [Class 100 (iv)], and comprising a motor 20 and a longitudinally movable control-shaft 21 provided with a grooved wheel 27 engaging a bail 25 which can be moved in either direction by the operator, or automatically by co-operation of cams 32 thereon with a lug 33 on the linespacing carriage. The platen is now mounted at each side on a pair of toggles 41 connected to strong springs 54, and is counterbalanced by means of a pair of bell-cranks 38 connected by a spring 40. The platen is constrained at the front by two pivoted arms 34. Each toggle 41 consists of a double plate 42 and a link 44, the plate being mounted on ball-bearings 43 on the frame, and the links being connected to the plate and platen by pivots 46, 45 respectively. The pivots 45, 46, 43 are in alignment when the platen is raised into contact with sheet-clamping strips 5. The toggles are connected by links 58 and arms 60 to a shaft 56 which is connected bv an arm and link 62 to a bell-crank 63 pivoted in a bracket 64 at the rear of the frame 1. Attached to the rear of the line-spacing carriage is a frame 67 comprising sides 68 and cross-rods 69, 70, a rod 73 provided with a forked head 75 being secured to a pintle 74 mounted in the cross-rods. When, as shown in Fig. 3, the rod 73 projects rearwardly, the head 75 can co-operate with a roller 66 on the bell-crank 63. When, as shown in Fig. 2, the head is out of use, the rod is folded within the frame, and the head is turned upwards to prevent obstruction if it is desired to tilt the line-spacing carriage. A dog 76, co-operating with either of a pair of notches in the rod 73, retains the head in normal or disabled position. The rod 73 is held in normal or folded position by an over-centre spring 84 connected by a cranked link 83 to an arm 85 on the pintle. A stop-arm 82 and stops 80, 81 prevent overthrow. When full-length sheets are employed, the rod 73 is folded within the frame 67, and the line-spacing carriage is moved rearward until the cross-bar 70 engages the roller 66. Thereupon the toggles 41 are broken, the platen is depressed to permit of the sheets being placed beneath the clamping-strips, and the rear cam 32 is effective to disconnect the motor. The platen is maintained in depressed position by gravity. When the line-spacing carriage moves forwards, the roller 66 is released, the springs 40, 54 act through the bell-cranks 38 and toggles 41 to raise the platen, and the sheets are clamped. The springs 54 are of such strength that the platen is pressed very firmly into contact with the clamping-strips. When short sheets are employed, the rod 73 is folded outwards to cause the head 75 to engage the roller 66 and thereby effect depression of the platen after a relatively short rearwards movement of the line-spacing carriage. The bail 25 is provided with an intermediate cam 86, Fig. 3, which co-operates with the lug 33 to disconnect the motor. The cam is hinged to the bail and is held in operative or inoperative position by a spring. A finger-lever 91, connected to the shaft 56, is provided for manually depressing the platen.