Patent GB-723099-A (GB)
Title: Improvements in or relating to printing telegraph apparatus
Inventor: SALMON REGINALD DENNIS
IPC: H04L13/04
Filed: 1952-02-22
Abstract: 723,099. Friction clutches. gearing for stopping and starting machinery; shaft couplings. CREED &. CO., Ltd. Feb. 22, 1952 [Feb. 26, 1951], No. 4643/51. Class 80 (2) [Also in Group XL (b) ]. Printing telegraph apparatus is driven through a friction clutch provided with means for automatically reducing the pressure of the clutch engaging spring when the torque transmitted by the clutch tends to exceed a predetermined amount. In the printing telegraph apparatus shown, drive is transmitted through a pinion 20 and sleeve member 19 to a lined friction drum 18, comprised by a plurality of segments each secured to a backplate whereby the diameter of the housing can be adjusted to compensate for wear in the lining, which is internally gripped by a clutch band 11, of the form shown in Fig. 8, engaged at one end 14 in' a slot in an arm 6 rotatable on a driven spindle 8 and at its other driving end 10 engaging through a spring loop 12 with a driving arm 9 adjustable in a lever assembly 5, 7 clamped to the driven spindle 8, The clutch band is pressed into engagement with the surrounding hub by a spring 15, Fig. 3, between a stop 16 on the assembly 5, 7, on the spindle 8, and the rotatable arm 6, the arrangement being such that on overload the driving end 10 of the clutch band presses the ears of the spring loop 12 somewhat together and the arm 6 turns relatively to the assembly 5, 7 to engage the stop 16; at further deflection of the spring ears the separation of the two ends of the clutch band is reduced and the clutch is allowed to slip. On removal of the overload the clutch band is re-engaged with drum by the spring 15. The driving arm 9 is provided with an eccentric portion engaging the spring ears 12 to drive the end 10 of the clutch band so that by rotating it on its own axis the angular distance between the spring loop 12 and stop 16 can be varied and hence the degree of deflection of the spring loop 12, which must take place before the torque transmitted is limited, can be controlled. The clutch is disengaged by one of twenty-six stop members such as 3, which is allowed to move inwardly under the action of a spring 4, when notched permutation discs 1 are set by a selector mechanism (not described) to allow rollers 2 to move into the notches, so that the stop-member is struck by the rotatable arm 6, and the trailing end 14 of the clutch band 11 is thus held to withdraw the band out of' frictional contact with the surrounding drum. The arm 7 is, e.g., of spring steel, and is cammed at its end so that it can slide under the stop 3 which then lies between the arms 5, 7, whereby the spindle 8 to which it is clamped is restrained from rotation. A friction damping device is provided between the spindle 8 and the final shaft 23 driving.the type wheel (not shown) and comprises a cam member 24, Figs. 1, 4, 5, integral with the spindle 8, engaged by a plastic etc. bobbin 25 having corresponding cam faces and axially slidable on the arms of a fork piece 26 splined on the shaft 23 and secured for rotation with a cylindrical casing 27, engagement between the cam faces being produced by a compression spring 28 and a damping block 29 being situated between the member 24 and the end of the cylinder 27. When the friction clutch is disengaged and the rotation of the spindle 8 suddently arrested, the inertia of the shaft 23 &c. causes the cams 24, 25 to turn relatively to each other, whereby the casing 27 is urged towards the member 24 as the spring 28 is compressed and the block 29 therebetween is gripped to dampen the rotation. The shaft 23 &c. is then rotated in the reverse direction by the energy stored in the spring 28, the shaft 23 &c. oscillating until all the kinetic energy is dispersed by friction damping. Grease is fed into the casing 27 through a hole 32 and the bobbin is provided with a hole 33 so that, as it oscillates, the grease can pass to and fro through it, a seal 34 being provided at the far end. Specification 668,921 is referred to.