Patent GB-650900-A (GB)
Title: Improvements in or relating to control apparatus for fuel burners
IPC: F24C3/12
Filed: 1948-06-21
Abstract: 650,900. Controlling gas burners. ROBERTSHAW-FULTON CONTROLS CO. June 21, 1948, No. 16663. [Class 75(i)] Control apparatus for a fluid fuel (gas) burner 24 comprises a supply valve means 10 biassed to its closed position, a lever device 136 urged by spring means 148 to move the valve means 10 to its open position, safety means 14 responsive to the presence or absence of a flame at a pilot burner 22 to permit or prevent respectively the opening of the valve means 10 by said spring means 148 and lever device 136, means 72 for setting or resetting said safety means 14 after ignition or re-ignition of the pilot burner 22 and arranged to prevent opening of the valve means 10 during the setting or resetting operation, and actuating means 12 (gas cut off timer device) which in its operative position moves said lever device 136 against the spring means 148 to permit closing of the valve means 10 and in its inoperative position allows operation of the lever device 136 by the spring means 148 to open the valve means 10 unless such operation is prevented by the safety means 14 or the resetting means 72. As shown, applied to a gas cooker, the supply valve means 10 comprises a valve 40 which is. urged by a spring 42 to its closed position and has a stem 46 bearing on the underside of a diaphragm 50, the other side of which is engaged by one end of an operating stem 52 in turn engaged by an adjustable screw abutment 146 at one end of a lever 138 of the lever device 136. The lever device 136 consists of two lever members 138, 140, the latter 140 being pivoted at one end to a fixed support 154 depending from a support platform 74, and the former 138 being pivoted on a pin 144 carried by the lever 140. The free end of the lever 138 is urged upwards about the pivot 144 by a spring 148 so that the valve 40 is held open against its spring 42 via the screw 146 and stem 52. The central part of the lever 138 bears against one end 128 of a push-rod 124 (actuating means 12) actuated by an electric clock 132 (not shown), mounted on the platform 74. The safety means 14 comprises an electromagnet connected to a thermocouple 96 exposed to the pilot burner 22. An armature 58 having a stem 64 is biassed away from the magnet 56 by a spring 60. When the pilot burner is alight the current is sufficient to hold the armature in the attracted position against the spring 60 but insufficient to attract the armature to such position. A collar 62 on the stem 64 has a groove 66 engaged by a forked end of the lever 140; a reduced axial portion 68 slides within a bore 70 of a thrust button 72 of the resetting means 98, 72, the bore 70 being deeper than the length of the portion 68. The thrust button 72 has a shoulder 112 for engagement with a bearing surface 152 on the lever 138 and is operable through a bell-crank lever 114, Fig. 4, by a push-button 98. A casing 90 encloses the safety means 14, the resetting means 72 and the lever device 136. A second casing 174 encloses the push-button mechanism 98, 114 and also means which indicates the condition of the safety means 14 and comprises an arcuate plate 168 carrying the words "ON" and "OFF." The plate 168 is mounted on the end of a pivoted arm 164 operated from an upwardly projecting extension 160 of the lever arm 140. Limit stops 170 are provided to allow one or other of the indicia to show through an aperture 179 in the casing 174. In operation, at the end of a cooking period the electric clock 132 depresses the push rod 124 causing the lever 138 to pivot about the pin 144 against the spring 148 and allow the valve 40 to close. If the pilot burner 22 is extinguished the armature 58 is then moved away from the magnet by the spring 60 until the collar 62 engages the thrust button 72. The lever 140 is thereby rotated counter-clockwise about its pivot 155 causing the pivot pin 144 to be raised and the lever 138 to pivot about the fulcrum formed by the end 128 of the push rod 124 thus allowing the valve 40 to close. The extension 160 of the lever 140 causes the pivoted arm 164 to show the words '' OFF " through the casing aperture 179. If the valve 40 is already closed due to the depression of the push rod 124, the abutment 146 is raised still further and when the push rod is allowed to return to its upper position the valve 40 still will not be opened. To reset the safety device, the pilot burner is relit and the button 98 is then pressed causing depression of the thrust button 72 which in turn depresses the armature 58 against the spring 60 to bring it to the attracted position and rotate the lever 140 clockwise about the pivot 155, the word " ON" then appearing in the aperture 179. If the push rod 124 is in its retracted position the shoulder 112 of the button 72 engages the lever 138 and rotates it clockwise against the spring 148 and ensures that the valve 40 remains closed during the resetting operation. When the button 98 is released the lever 138 will be rotated counter-clockwise by the spring 148 until it abuts against the end 128 of the push rod 124, the valve 40 being then opened only if the push rod 124 is in its retracted position. The safety device operates independently of the clock 132 which may be additional equipment installed when desired. Heat responsive timing mechanism may be installed in place of the clock 132.