(57) A valve unit for regulating the flow-rate of a fuel gas delivered through a delivery
duct (3) is described and comprises a servo-valve (4) having a closure element (5)
controlled by a diaphragm (8), the diaphragm being subjected to the gas-delivery pressure
on one side and to a reference pressure established in a control chamber (9) of the
servo-valve on the other side, a pressure-regulator device associated with the servo-valve
(4) and comprising a regulation valve (10; 51) for controlling the reference pressure
in the control chamber (9), additional regulator means for modulating the delivery
pressure and/or the output flow-rate of gas through the delivery duct (3) in dependence
on an external control, the additional regulator means acting alternatively on the
pressure-regulator device or on means (53) for choking the delivery duct in order
to modulate the delivery pressure, or to modulate the flow-rate delivered through
the delivery duct (3), respectively, and actuator means for the additional regulator
means, comprising a reversible motor (32) having a rotor (31) connected to a male-and-female
screw coupling (28, 29; 58, 57) acting on the pressure-regulator device or on the
choking means, for the operative control thereof.
|
|
