Patent GB-635920-A (GB)
Title: Improvements in typewriting machines
IPC: B41J35/14
Filed: 1947-06-24
Abstract: 635,920. Typewriters &c. UNDERWOOD CORPORATION. June 24, 1947, No. 16695. Convention date, June 4, 1942. [Class 100 (iv)] In a power - operated typewriter having means for normally holding a typewriter ribbon removed from a printing point and adapted to be operated by typing means to present a portion of the ribbon to the printing point, and a device which is settable to predetermine whether or not the ink ribbon is moved into printing position by a typing action, the power means is driven at a constant speed and the setting device is also adapted to predetermine the operating impulse that is imparted to the typing means for each setting of the device. As shown, the ink ribbon 58 is moved into a typing position 56 by a bell-crank 63, link 84 and a crank 82 by the engagement of either of two pins 81 thereon by a bar 76 raised at each typing operation. The bar 76 is positioned to engage during its upper movement either or neither of the pins, by means of a crank 80 rotated from a knob 96 through gearing 93, 94, according to which of the colour strips 61 are to be moved into typing position or whether no movement is to be given to the mechanism 82, 84, 65 in the case of stencils being cut. The type action which comprises a constant speed power shaft 22 adapted on depression of a type key to be engaged by a pawl 21 on a selected actuator 18 to impart printing movement to a type-bar 10 is described in Specification 635,916. In the present instance the ribbon positioning or vibrating mechanism is actuated by tail pieces 66 on levers 14 forming part of the type-bar actuating mechanism, the tail pieces 66 engaging a universal bar 67 attached to a lever 68 thereby to rotate a shaft 77, straighten a toggle 73, 74, depress a lever 75, and raise the bar 76. The impulse imparted to type-bars 10 is controlled by adjustment of the point at which the pawls 21 are disengaged from the shaft 22. Abutment screws 36, which by engaging a lower surface of the actuators 18 release the pawls are 'mounted on a universal bar 35 carried by a pivoted frame 38 adjustably positioned by the rotation of a dial 51 having a cam 45 engaging the frame 38 through an interponent 47. Interponent 47 has three thicknesses 106, 117, 105 which are moved into place between the cam 45 and frame 38 in accordance with the position of the knob 96. With the knob in a middle position, i.e. set for stencil cutting, a cam 115 on a shaft 92 operates a lever 113 which through a coupling 110 and a crank 108 positions the portion 117 between the cam 45 and the frame 38, and with the knob turned to the " Black " or " Red " positions, i.e. for typing through the respective strips 61 of the ribbon,' the parts 105, 106 respectively, are positioned between the cams and frame. Since the power absorbed when the upper ribbon part is moved to the printing line is less than when the lower ribbon part is so moved, and is still less when the ribbon is not employed, the parts 105, 106, 117, corresponding to these three operations, increase in thickness in that order. Thus the position of screws 36 is adjusted so that lesser impulses are imparted to the type bars when the absorbed power is less so that the typing force remains constant Adjustment of the' dial 51 varies equally the impulses imparted to all the type bars.