Patent GB-484231-A (GB)
Title: Improvements in or relating to a regulator for the automatic control of a variable condition by the production of electrical variations in accordance with changes in the condition
IPC: G05B11/01
Filed: 1937-01-12
Abstract: 484,231. Hunting- switches, SMOOT, K. E. Jan. 12, 1937, No. 940. Convention date, Jan. 17, 1936. [Class 38 (v)] [Also in Group XXXV] Means for the automatic control of a variable condition comprises a pair of feeler members co-operating with a sensitive member, moving in accordance with the condition, to close selectively electrical circuits for control purposes. The feeler members are periodically operated towards the sensitive member. Auxiliary means shift the feeler members upon closure of a control circuit so that they move about a new mean position which is gradually returned to the normal position as the condition is restored. A constantly running motor 108 drives a disc 166 and a pawl 168 operating a timing mechanism 174 (adjustable to determine the length of its cycle) which eventually releases a latch 182 and resets itself to commence another period. The latch 182 when released permits a pawl 192 to couple the disc 166 to a shaft 194 for one revolution. The shaft 194 carries a cam 80 and a disc 196 with pins 198 and a stop 216. The cam 80, moves a rod 76 slowly in one direction, a spring 78 returns the rod rapidly. At this moment the pawl 192 is freed from the disc 166 and a latch 208 is released by the stop 216. The rod 76 carries an equalizer bar 74 on a friction pivot, and the bar 74 actuates through curved racks 62, 64 and shafts 58, 60 feelers 54, 56 which move together towards a control part 46 the position of which corresponds to the state of the condition to be controlled. This part carries an electric contact co-operating with contacts on the feelers 54, 56, As soon as contact is made with one of the feelers an electromagnet 104 or 106 is energized through the contacts 116. The electromagnet releases a latch 132 or 134 permitting one of two springs 144, 154, which normally centralize a switch arm 148 between contact pairs 150, 160, to actuate a shaft 98. The shaft 98 actuates through a rod 94 two locking pawls 66, 68 one of which engages the curved rack 62 or 64 associated with the feeler which is in engagement with the control part 46 to prevent its further movement. During the remainder of the stroke of the rod 76 the equalizer bar 74 turns on its pivot and causes the other feeler to move beyond its normal range. The effect of this is to cause the centre line toward which the feelers move to coincide with the control part 46. On the return of the rod 76 one of two pawls 82, 84, pivoted on the ends of the equalizer bar and urged outward against stops thereon by a spring 86, engages a rack 88 or 90 near the end of the movement and successive return strokes cause this pawl to " wall " and gradually move the equalizer bar back to its balanced position on the rod 76. The feeler centre line thus follows the movement of the control part 46 as it responds to the adjustment effected in the condition. Eccentric stops 92 provide adjustment of the racks 88, 90 to control the rate of " walking " in accordance with the permitted time lag in the action of the control.