Patent GB-563221-A (GB)
Title: Improved shock-absorbing means especially suitable for use with typewheels in printing apparatus
IPC: B41J1/32
Filed: 1943-01-29
Abstract: 563,221. Type - printing telegraphy. CREED & CO., Ltd., and SALMON, R. D. Jan. 29, 1943, No. 1537. [Class 100 (iv)] [Also in Groups XXXII, XXXIV and XL] In a printing-telegraph receiver of the kind in which a type-wheel shaft 3 is arrested by the engagement of an arm 24 with one of a number of selectively-positioned stops 25, the stop arm is driven by a clutch 75 and is resiliently connected to the type-wheel, damping means, such as a friction bearing 28, being provided to dissipate the energy of the type-wheel &c. latch means 26 prevents rebound of the stop arm from the stop. The type-wheel shaft 3 is driven through gearing 14, 15, 20, 21, 22 from the rotating shaft 55 through a friction clutch 75 and resilient connection which couples the shaft 23 to the gear 22. The resilient connection comprises a spring 32, Figs. 1 and 2, arranged in a radial hole in the shaft 23 and held under stress by a transverse member 31 pressed down by two pairs of pins, one pair 29, 30 fixed to the stop arm 24 and the other pair 33, 34 to the gear 22, so that the spring 32, member 31 and pins form a resilient connection between the friction clutch 75 and gear 22. The part of the shaft 23 within the gear 22 is split in a plane passing through the axis, the two parts being urged outwards by springs 27 so that frictional pressure is exerted on the inside of the gear which is lined with a self-lubricating bearing 28. When the stop arm is arrested by a stop 25, the type-wheel continues its rotation for a short period, compressing the shockabsorber spring 32, which causes the gear 22 and type-wheel to rotate in the reverse direction. The type-wheel thus oscillates but quickly comes to rest in a period determined by the torque of spring 32 and the torque exerted on the gear 22 by the friction bearing 27, 28 which dissipates the energy. In a modification, Figs. 4 to 6 (not shown), a frictionally-driven ratchet clutch replaces the clutch 75, Fig. 2. The type-wheel carriage is traversed for letter spacing by pawls 8a, 8b and racks 7a, 7b, one of which is reciprocated by cam 52. The type-wheel is normally clear of the platen 1 but can be raised into one or other of two printing positions by a lever 12 moved by bail 62 which is engaged by two levers 65, 68 pivoted at 64, 69 respectively. The movement of lever 68 is limited by a catch 71 controlled by the case shift signal, the arrangement being such that if catch 71 engages lever 68, as shown in Fig. 1, when cam 67 moves the lever 65 anti-clockwise, the lever pivots about 64 to move bail 62 an amount sufficient to raise the upper row of type into printing position. If, however, catch 71 releases lever 68, the latter is free to follow lever 65 and rotates about pivot 69 and, because of the difference in the lever ratio, it imparts a greater movement to bail 62 sufficient to raise the lower row of type into printing position. The Provisional Specification describes an alternative arrangement utilizing a vibration damper of the piston and cylinder dashpot type. An apertured plate, fixed to a sleeve sliding on the piston-rod, is so arranged that it may occupy any angular position relative to the piston so as to more or less uncover holes in the end wall of the piston. The position of the sleeve and plate is controlled by a bi-metallic strip responsive to the temperature of the oil in the cylinder. Specifications 228,842, [Class 100 (iv)], and 350,044., 381,218 and 524,342 are referred to.