Patent GB-797510-A (GB)
Title: Improvements in or relating to means for automatically controlling the supply of gas to gas heated appliances
IPC: G05D23/12
Filed: 1952-01-17
Abstract: 797,510. Fluid-pressure servomotor-control systems. SOUTH EASTERN GAS BOARD, PAINTER, F. E., and COLLINS, P. July 12, 1954 [Jan. 17, 1952], No. 1421/52. Class 135. Apparatus for automatically controlling the supply of gas to a gas-heated appliance comprises a main gas valve 11, a weight-loaded diaphragm 14 arranged below and operatively connected to the valve so as to close the valve under the action of gravity, a control conduit 1 communicating the gas pressure on the inlet side of the valve to the underside of the diaphragm so as to maintain the latter raised with the valve open and at least one detector device B, C, D connected in the control conduit and having valve means which either cuts off communication between the two ends of the control conduit and releases the gas pressure on the underside of the diaphragm to permit the main valve to close when a change occurs in the operation of the appliance or, when the gas supply pressure falls below a predetermined value, permits the fall in pressure to be communicated to the underside of the diaphragm and then cuts off communication between the ends of the conduit. The device B is responsive to the gas supply pressure and comprises a casing formed into two compartments by a weighted diaphragm 38, the upper compartment 39 being vented to atmosphere at 40 and the lower compartment being divided into a gas-inlet chamber 41 and an outlet chamber 42 communicating through an opening 43 closed by the diaphragm 38. The latter diaphragm is less heavily weighted than the diaphragm 14 of the main valve and therefore descends more slowly when the supply pressure drops. The pressure in the inlet chamber 41 alone is insufficient to raise the diaphragm 38 and consequently at starting the outlet chamber 42 is also supplied with gas by connecting both chambers through two manually and simultaneously-operated valves 44, 45 and a housing 46 which is connected to the gas supply pipe 5 leading to the burner 6 between the main valve 11 and a gas cock 7. If the gas cock 7 is open at starting gas bleeds from the chambers 41, 42 and prevents the pressure therein from raising the diaphragm 38. The device C is responsive to the flame of a pilot burner 21 and comprises a casing divided into a gas inlet compartment and a gas outlet compartment by a partition 26 having a gas passage 27 the upper inlet end of which is closable by a valve 28 secured to an armature 29, and the lower outlet end of which is closable by an auxiliary valve 33 connected to a spring- returned press button 34. A pipe 31 opens into the passage 27 and supplies gas to the pilot burner 21. The pilot burner heats a thermocouple 22 which energizes an electromagnet 30 for holding the upper valve 28 open. At starting the press button is actuated to close the auxiliary valve 33 and a projection on the upper side thereof lifts the upper valve 28 to admit gas to the pilot burner supply pipe 31 and to bring the armature into the field of the electromagnet 30. The press button is then released to open the auxiliary valve 33. At failure of the pilot burner the armature is released by the electromagnet so that the upper valve 28 closes and the gas in the part of the control conduit 1 leading to the weighted diaphragm 14 of the main valve leaks away through the pilot burner supply pipe 31. The device D operates to close the main valve when a predetermined temperature is exceeded in the gas appliance and comprises a casing divided by a weighted diaphragm 53 into an upper compartment 54 and a lower compartment divided into an inlet chamber 55 and an outlet chamber 56 communicating by an opening 57 closable by the diaphragm. The upper compartment 54 is connected by a pipe 58 to the inlet side of a thermostaticallycontrolled valve 50, the outlet side of which communicates with a vent pipe 59. The diaphragm has a weep' orifice 60 small enough to enable the gas pressure in the inlet chamber 55 to maintain the diaphragm in its open position so long as the thermostatic valve remains open but when the thermostatic valve closes on the predetermined temperature in the appliance having been attained, the pressure on both sides of the diaphragm becomes equalized and the opening 57 is closed. At the same time an auxiliary valve 61 connected to the diaphragm opens a vent 62 in the outlet chamber 56 to allow gas in the part of the control conduit 1 leading to the weighted diaphragm 14 of the main valve 11 to escape to atmosphere. Specification 417,712 is referred to,