A DEVICE FOR CONTROLLING THE SUPPLY OF A COMBUSTIBLE GAS TO A BURNER, PARTICULARLY FOR WATER HEATERS

What is described is a device for controlling the supply of a combustible gas to a burner, particularly a water heater having a draught shut-off device in the exhaust pipe for the combustion fumes, comprising a main gas supply pipe in which are positioned a first and a second servovalve, in series with each other, with respect to the direction of flow of the gas, the servovalves including respective valve seats associated with corresponding shut-off members with diaphragm control for the opening of the seats in opposition to respective resilient return means. A pilot pipe is branched from the main pipe, upstream of the servovalves, to supply a pilot burner, a thermoelectric magnetic safety unit with a manual activating knob being provided on the main pipe, this unit acting on the pilot pipe so as to allow gas to flow towards the pilot burner when the unit is activated. The draught shut-off device comprises a corresponding shut-off member which is movable from and towards a position in which the fume exhaust pipe is shut off, and diaphragm-controlled pneumatic actuating means of the shut-off member, the diaphragm forming, at least partially, a corresponding control chamber of the shut-off member which is connected to and in fluid communication with a section of an auxiliary pipe branched from the main pipe, a first portion upstream of this section being provided for the supply of gas to the control chamber and a second portion, which is an extension of the first portion, being provided downstream of the section for the discharge of the gas from the chamber in the proximity of the pilot burner. A corresponding valve is provided on the discharge portion of the auxiliary pipe, downstream of the section, for the selective control of the opening or shut-off of the discharge portion.