Patent GB-349448-A (GB)
Title: Arrangement for reducing oscillations in the working of automatic regulators, for example the temperature regulators for furnaces
IPC: G05D23/20
Filed: 1930-02-14
Abstract: 349,448. Thermostats. SIEMENS & H'ALSKE AKT.- GES., Siemensstadt, Berlin. Feb. 14,1930, No. 5050. Convention date, Feb. 27, 1929. [Class 64 (ii).] An automatic regulator, e.g. a temperature regulator for furnaces, which operates in intermittent impulses on the control of an electric motor, is provided with means, independent of the controlling instrument and of the electric motor, to interrupt the regulating circuit for a predetermined period to enable the controlling impulse to work itself out before a subsequent controlling impulse can be applied. In Fig. 1, the temperature of a furnace 1 is measured continuously by a thermal element 2 and pointer 4. A pivoted stirrup 5 is actuated at intervals by a bimetal switch 7 and electromagnet 6 to depress the pointer 4, which moves over maximum and minimum contacts 11, 12 and a normal contact 13. The latter is closed whenever the pointer 4 is between the contacts 11, 12, by means of an extension 14. Bimetallic time switches 19, 20 are arranged in series with relay switches 21, 22 in the circuits of the motor windings 15<11>, 151. When the contact 11 or 12 is closed, the corresponding winding 15<11> or 15<1> is energized, the motor runs to right or left, and the fuel supply valve 16 is adjusted. Assuming that the contact 11 is closed, the relay switch 21 is also closed and the motor 15 rotates to close the valve 16. At the same time the heating coil of the switch 19 is energized, and after a predetermined interval which is adjusted by the resistance 23, the switch 19 opens and the motor 15 stops. After a further predetermined interval, which is adjustable by any known means, the switch 19 closes again, but until this happens any further closing of the contact 11 by the reciprocating member 5 is ineffective. If during the open period of the switch 19 the pointer 4 moves over the maximum contact 12, the motor 15 is similarly operated to run in the opposite direction. In another form, Fig. 2, the contacts 11, 12, 13 are operated as before, but the time switch is modified. The contacts 11, 12 are in series with electromagnets 32, 33 acting through a lever 34 to move an escapement wheel 35 provided with a locking member 41. The shaft 36 is provided with a restoring spring 39 and carries a contact arm 37 moving over contacts 38. Assuming that the maximum contact 11 is closed, the winding 15<11> is energized through line 44, and the motor 15 runs to close the valve 16. At the same time the electromagnet 32 is energized, the lever 34 is attracted, and the wheel 35 and arm 37 are moved one step. The arm 37 then stands on a dead contact and if the contact 11 is again closed the motor circuit is not completed, but the arm 37 is moved another step. The motor circuit is not again completed until the arm 37 reaches another live contact, the location of which may be selected, or until the normal contact 13 is completed, when the electromagnet 40 is energized, and the locking member 41 releases the wheel 35 to return to its initial position.