Patent GB-364975-A (GB)
Title: Improvements in control mechanism for refrigerating systems
IPC: F25D21/00
Filed: 1931-04-21
Abstract: 364,975. Refrigerating ; electric switches. GILL, E. R., 41, Alta Avenue, Yonkers, New York, U.S.A. April 21, 1931, No. 11783. Convention date, May 7, 1930. [Class 29.] Compression machines.-Means are provided in connection with known temperature-responsive control means for the motor or other source of energy of a refiigerating system whereby after a certain time interval or a certain number of cycles of operation and idleness a higher temperature limit is imposed on the control.. to bring about defrosting of the evaporator automatically. The invention is described as applied to the type of control comprising a bellows member 11, Fig. 3, containing fluid at evaporator pressure, engaging an actuating arm 15 of a motor &c. switch 27, 26. The arm 15 is pivoted to the frame 17 and at its free end carries a pair of arms 20 journalled on a pin 19 and united by a wearing block 21 engaging a spring-pressed roller 34. An insulator 24 pivoted at 25 to the inner ends of the arms 20 is adapted to engage the upper spring contact 27. Adjustment to desired limits of temperature is effected by springs 46, 621 on an intermediate rod 47, and in addition a setting arm 53 with a spring bolt 58 may be positioned over one of a series of holes 56 in a dial plate to vary the tension of a spring 59, Fig. 2, engaging the pin 19. When placed in the " off " position the arm 53 interposes a stop arm 62 in the path of the pivot 25 to prevent the switch from being closed.. A toothed wheel 64 frictionally mounted on the pin 19 is carried bodily up and down by the arm 15, and in each descent is advanced one tooth by a spring pawl 68. It is provided with a pin 75 which after a certain number of switch actuations comes against a dog 77 depending from a lever 76, and an additional resistance is imposed on the bellows 11, resulting in the defrosting action. The arm 76 is pivoted at 17 and has secured thereto a block 81 normally resting on the spider frame of the bellows. An arm 79 is pivoted to the block 81 and pivoted at 88 to this arm 79 is a rod 87 slidable through lugs in a plate 85 secured to the arm 76. An adjustable spring 89 mounted on the slidable rod 87 and bearing against the upper lug of the plate 85 constitutes the additional resistance to the rise of the switch arm, the rise of the arm 79 being prevented by the engagement of the stop arm 62 of the setting member with a roller 84 on the arm. The defrosting interval may be varied by widening the dog 77 or the pin 75 or by providing additional pins 751 on the toothed counting wheel. In another arrangement, the switch above described but without the toothed wheel and auxiliary control is employed for the normal control, and defrosting is effected by timing an auxiliary mercury switch 118, Fig. 5. A supplementary bellows 11<1> is adapted to move an actuating arm 104, in the upper end of which slides a pivoted rod 116 with a snap action spring 116<1>. The switch is held latched by a member 120 thereon engaging a pivoted detent 122 during cycles governed by the main control, and the arm 104 moves idly. The detent 122 has a tail 125 engaging an eccentric 126 driven by a clock train, and at determined intervals is moved thereby to release the latch and allow the arm 104 to rock the switch, whereupon the main circuit is held open while defrosting occurs. Alternatively the eccentric 126 may be rotated by a ratchet drive either from the arm 104 or from an electromagnet energized at each actuation of the main control.