Patent GB-306623-A (GB)
Title: Improvements in or relating to control mechanism for refrigerating apparatus
IPC: F25B49/02
Filed: 1927-12-01
Abstract: 306, 623. White, A. E., (Delco-Light Co.). Dec. 1, 1927. Refrigerating, compression machines and processes for.-The adjustable mechanism normally controlling the circulation of the refrigerant to maintain a predetermined mean temperature is adapted to have its operation temporarily modified by an auxiliary control device to obtain a different temperature without affecting the adjusted setting of the normal control mechanism. After a predetermined period of abnormal operation the apparatus may be automatically restored to normal action. Fig. 1 shows a simple form in which a thermostat responsive to the temperature within the cooling unit rocks a lever a carrying a weight b 'and operating the electric switch (not shown) of the compressor motor. The auxiliary control device comprises a spring c connected to the lever a by a rod d which passes freely through a hole e in the lever and is provided with nuts at its lower end. The spring c is attached to an arm on a shaft g journaled in the front wall h of the refrigerator and provided with a handle i working over a quadrant j. In the position shown the spring c supports part of the weight b and the motor switch will be opened and closed by the thermostat at a lower limit of temperature than normal, e.g. for ice making. By rotating the handle i through 180‹ to the stop k the spring c is lowered so that it has no action on the lever a and the normal temperature limits will be resumed. For different temperatures the handle i may be held in intermediate positions. Fig. 9 shows a form in which the pressure of the refrigerant in the low pressure pipes or the pressure in a thermostatic tube located in the expansion unit is transmitted by a tube 136 to bellows 137 acting on a switch-operating lever 151. The switch is opened or closed by a snap action after a certain movement of the lever. Adjustment of a counterweight 155 on the lever determines the normal temperature limits at which the switch operates, and to alter the temperature a U-shaped snap spring lever 161 is interposed in the path of the lever 151. Normally the lever 161 pivoted at 162 is urged upwards as shown, out of the path of the switch-operating lever, by a spring 167. To defrost, a wire 170 is pulled by an exterior handle, rocking a spring lever 169 which snaps the lever 161 into the interposed position in which it is urged downwardly by its spring 167, delaying the closing of the switch. By placing the lever 161 below the lever 151 to delay the opening of the switch a temperature lower than normal would be obtained). Apparatus automatically restored to normal action after a predetermined number of operations of the switch is shown in Fig. 2, in which the bellows 41 connected by a pipe 42 with the evaporator carries a cover plate 43 pivoted by a link 45 to the framework 46. Notches 66 on the cover plate engage a knife edge 65 on a lever 64 which operates the switch 50 through a rod 62. A further knife edge 67 on the lever 64 is adapted to engage fixed notches 68, and the lever carries an adjustable weight 69 which determines the lower limit of temperature, at which the switch will be opened. As the weight 69 rises it picks up weights 71, 76 adjustable on pivoted rods 72, 77, these weights determining the upper limit of temperature, at which the switch will be closed. To obtain closure of the switch at a lower temperature, for ice making, a cam 97 having a flat part 98 is turned by an external handle so that its round part lifts the lever 77 and weight 76 out of the path of the weights 69, 71. Fixed to the cam 97 is a ratchet wheel 102 and each time the weight 71 rises and falls a pawl 98a pivoted to the rod 72 at 99 turns the ratchet wheel through one tooth until the flat part 98 of the cam has been brought adjacent to the rod 77, returning the weight 76, the pawl then reaching a smooth part of the ratchet. Thus the extent to which the cam 97 has been turned determines approximately the duration of the lower mean temperature in the refrigerator and the external handle can move over a scale indicating the number of ice cubes &c. to be frozen. Stops 80, 82 limit the movements of the weights.