GB944390A - Temperature control system - Google Patents

Abstract

944,390. Controlling gas burners. ROBERTSHAW-FULTON CONTROLS CO. April 10, 1962, No. 13838/62. Heading F4T. [Also in Division F2] A control device for a main gas burner 16 of an oven comprises a thermostatic valve 50 actuated by a bulb 54 sensitive to the temperature of the oven and a cycling valve 12 for cycling the flow of gas to the main burner when the thermostatic valve 50 is set to maintain the temperature of the oven at the low end of the temperature range. The cycling valve 12 prevents the flow of gas to the main burner when a flame at a heater pilot burner 132 is extinguished and comprises a valve member 90 biased by a spring 92 to closed position and adapted to be opened by a lever 112 pivoted at 110 to a bracket 106. The heater pilot burner 132 heats a mercury bulb 96 connected by a capillary tube 98 to a power element 100 which abuts an adjusting screw 102 passing through an aperture in the lever 112 and threaded into an aperture in a further lever 104 pivoted at 108 to the bracket 106. A coil spring 114 is compressed between the two levers. The heater pilot burner 132 causes the power element 100 to rotate the two levers in a clockwise direction to open the valve member 90. The gas flow to the heater pilot burner 132 is controlled by the thermostatic valve 50 co-operating with the ends of two passages 42, 43 in a seat member 32 screwed into the casing of the thermostatic valve and connected by a hollow connector 30 to a manually-operated gas cock in the form of a hollow tapered plug 26 having an arcuate port 36 for the passage of gas from an inlet 20 to the hollow connector 30 and the seat member 32. Rotation of the plug 26 also causes axial movement of the seat member 32 to determine the temperature to be maintained in the oven. The thermostatic valve 50 is by-passed by an aperture 68 in the hollow connector 30 and an adjustable passage 72 in the valve casing. When the oven temperature reaches the value set by rotating the plug 26 the thermostatic valve 50 closes and shuts-off the gas supply through the two passages 42, 43 to the heater pilot burner 132, but the main burner continues to be supplied through the by-pass 72. The mercury bulb 96 cools and closes the cycling valve 12 to shut down the main burner. When the oven cools the thermostatic valve 50 opens again and the heater pilot burner is ignited by a constantly burning pilot 126. The mercury bulb 96 then opens the cycling valve 12 and the main burner is then fed with gas through the by-pass 72 and through the thermostatic valve 50. When the plug 26 is rotated to set the oven temperature to a high value the arcuate port 36 therein also supplies gas to an adjustable passage 81 which bypasses the heater pilot passages 42, 43 controlled by the thermostatic valve 50. The heater pilot burner 132 therefore remains burning when the thermostatic valve 50 closes and consequently the cycling valve remains open and the main burner is supplied through the by-pass 72.