GB1188199A - Improvements in or relating to Programme Controllers - Google Patents

Abstract

1,188,199. Thermal switches. J. B. G. ALFORD. 3 Feb., 1969 [8 Nov., 1967], No 50688/67. Heading H1N. [Also in Division F2] In a programme timer for making sudden changes in the setting of a variable by sudden adjustment of a control arm 4, Fig. 1, a follower arm 15, yieldingly mounted on the control arm 4 continuously follows a plurality of setting members 12, 13 on a timer disc 10 while the control arm 4 is held stationary at its previously set position by a brake, the timer releasing the brake at the preset times whereby the control arm 4 moves suddenly under the action of the yielding mounting. In the particular example applied to the adjustment of a temperature setting screw 3, Fig. 2, of a bimetal 1 in a thermostat, the control arm 4 is threaded at 5 in a fixed nut 6 and carries a manually adjustable screw threaded spindle 3. The control arm 4 is normally held stationary by a brake pad 24 on a spring-loaded arm 25 which is moved by adjustable tappets 12, 13 on a timer disc 10 which engage a roller 28 on the arm 25. The follower arm 15 is slotted to engage a pair of pins 16, 17 on the control arm 4 and is yieldingly held in position by a spring 18. A further spring 22 urges the follower arm 15 into engagement with one of the pins 12, 13 on the timer disc whereby the follower arm 15 pivots on one or other of the pins 16, 17 against the action of the spring 18. At each of the timer positions requiring a change of setting, the pins 12, 13 engage a flat 21 on the follower arm 15 and simultaneously engage roller 28 to release the brake 24 whereby the main arm 4 moves suddenly to its new position. Arm 29 provides for an overriding manual setting against the action of the brake 24. In a modification the main arm 4 may move a rheostat which varies the heating of a bimetal to control the thermostat temperature setting.