Patent GB-218086-A (GB)
Title: Electrical means for automatically controlling the temperature in pasteurising, evaporating, drying and such like operations
IPC: G05D23/275
Filed: 1923-06-11
Abstract: 218,086. Jones, T. L. June 11, 1923. Thermostats. - In pasteurizing, drying and like operations in which the material treated is heated by a fluid medium, the temperature of the material is maintained between predetermined maximum and minimum limits by thermostatic means operating in conjunction with two relays 5, 7, Figs. 1 and 4, one, 5, of which is associated with a solenoid 15 adapted tc move in the closing direction the valve 13, Fig. 2, controlling the supply of heating-fluid and a solenoid 30 for moving in the opening direction the valve 14, Fig. 3, controlling the supply of the material, while the other relay 7 is associated with a solenoid 16 for opening the valve 13 and a solenoid 25 for closing the valve 14. The cores of the solenoids 15, 16 and 25, 30 actuates the valves 13, 14 respectively through the intermediary of levers 22, 20 and 31, 26 and pawl-and-ratchet mechanism. When any one of these solenoids is energized the corresponding core is moved outwardly to operate one of the valves 13, 14 and also to close one of four pairs of contacts 34, 40, 44, 48 and is locked in the outward position by the engagement of a detent 39 with one of four catches 34, 41, 45, 49 controlled by unlocking solenoids 37, 43, 47, 51 respectively. In the arrangement shown which is applied to a pasteurizing operation for maintaining the temperature between 195‹ F. and 205‹ F., a maximum thermometer 1 is associated with the relav 5 and a minimum thermometer 2 with the relay 7, the current being derived from a low voltage transformer 3. The switch 6 controlled by the relay 5 is normally open and is associated with the solenoids 15, 30 and with one solenoid' 60 controlling a rocking-switch 64, while the switch 8 controlled by the relav 7 is normally closed and is associated with the solenoids 16, 25 and the other solenoid' 61 controlling the rocking-switch 64. The pairs of contacts 34, 48 are associated with a solenoid 52 actuating a normally closed switch 4 in the thermometric circuit and a normally open switch 55 arranged in unlocking circuits with the solenoids 37, 51, while the pairs of contacts 40, 44 are associated with a solenoid 56 actuating a normally open switch 9 in the thermometric circuit and a normally open switch 59 arranged in unlocking circuits with the solenoids 43, 47. One terminal of a relatively high voltage transformer 74 is connected to the main arm of the switch 64 which has four mercury contact-cups 66, 67, 68, 69, while the other terminal is connected to the solenoids 52, 56. An additional solenoid 72 for closing a switch 12 in a local circuit including an electric warning- bell 11 is associated with the solenoid 25. The cores of the solenoid's 52, 56, 60, 61, 72 are adapted to fall by gravity to their lower or normal positions and operate in combination with adjustable dash-pots 43, 57, 62, 63, 73 which retard the movements in one direction to a required degree. The action of the apparatus is as follows. In normal circumstances when the temperature is between 195‹ F. and 205‹ F. the relay 7 is energized and the relay 5 non- energized, both switch 8, 6 therefore being open, while the rocking-switch 64 makes contact at 68, 69. Should the temperature rise to 205‹ F. or above the relay 5 is energized and the switch 6 closed completing the circuit 6, 15, 68, thus moving the core of the solenoid 15 to close the valve 13 by one step and simultaneously closing the pair of contacts 34. The circuit 68, 34, 52 is thus established, and the solenoid 52 opens the switch 4 and closes the switch 55, the former operation de-energizing the relay 5 and opening the switch 6, while the latter operation establishes the unlocking circuit 37, 55, 68 and thus releases the core of the solenoid 15. If at the end of this cycle of operations the temperature is still above 205‹ F., the cycle will be repeated and the valve 13 is closed still further, the repetition occurring until the temperature falls below 205‹ F. On the other hand, should the temperature fall below 195‹ F., the relay 7 is de-enargized and the switch 8 closes establishing the circuit 8, 61, 16, 69, and causing the core of the solenoid 16 to open the valve 13 by one step and closing the contact 40, whereby the circuit 40, 56, 69 is established. The solenoid 56 being thus energized allows the contacts 9 to close and re-energize the relay 7, and also closes the switch 59 whereby the circuit 43, 59, 69 for unlocking the core of the solenoid 16 is established. Meanwhile the solenoid 61 is also energized, but its action upon the rocking-switch 64 is delayed by the dash-pot 63 so that the cycle of operations detailed may take place the requisite number of times before the switch 64 is rocked over to make contact at 66, 67. In this latter position of the switch 64, if the temperature still continues below 195‹ F. the solenoid 25 is energized anl causes the supply through the valve 14 of the material treated to be reduced, or if the temperature rises above 205‹ F. the solenoid 30 is energized and the supply of material treated increased, the series of steps involved being simlar to those described with reference to the valve 13. Owing to the delay action of the dash-pot 73, the solenoid 72 operates the switch 12 only after the valve 14 has been closed to the limit allowed and atfer the solenoid 25 has made an abortive attempt to move its core, a warning thus being given to the attendant that the temperature has fallen permanently below the required level.