GB1254171A - Improvements in and relating to processing arrangements - Google Patents

Abstract

1,254,171. Grain dryers. LITOVSKY NAUCHNO - ISSLEDOVATELSKY INSTITUT MEKHANIZATSII I ELEKTROFIKATSII SELSKOGO KHOZYAISTVA. 7 Jan., 1969, No. 905/69. Heading F4G. An apparatus for forced air grain drying comprises a number of heating elements which are switched successively in dependence on temperature difference between inlet and outlet air, the temperature sensors being connected in a bridge circuit controlling a reversible stepping switch connecting the heating elements on unbalance of the bridge circuit. When the drying has reached the required value, the drying is discontinued. Inlet and outlet air temperature sensors 4, 5 and a switchable ambient temperature sensor 11 are connected into a bridge circuit 13. The circuit is put into operation by moving a switch 34 into position B and momentarily closing a manual switch 29 also switches 32 which energize heaters (not shown) through relay coils 10. When the air temperature has stabilized, as indicated by a micro ammeter (not shown) switch 34 is moved manually to the reverse position A. The bridge is connected to an amplifier 35 which closes contacts 36 energizing a relay 37, 38 causing stepping switch 16 to move to the left thus energizing contact 20 and consequently making one heater operative. A time delay relay 9 is also actuated concurrently which temporarily prevents further operation of the stepping switch 16. At the end of the delay if the bridge still has an output a further heater is energized. When the moisture absorbing capacity of the arrangement reaches 1À1 g./kg., unbalance of the bridge causes contacts 39 to close energizing a relay 40, 41 moving the bridge 16 successively to the right hence disconnecting contacts 18, 19, 20 in turn thus de-energizing the heating elements successively, and at the same time making on contacts 24, 25 thus operating relay 28 which opens contacts 42 thus preventing further movement of bridge 16 and stopping the drying procedure. Relay 27 is also deenergized through contacts 22, which opens contacts 43. Contact 21 may energize a fan motor (not shown) through a relay 26.