Two-stage pressure regulator for feeding internal combustion engines with gaseous fuel at constant pressure

The two-stage pressure regulator (10) feeds an internal combustion engine of injection type with gaseous fuel taken from a relative tank. The first stage comprises a first chamber (52) communicating with the tank via a first valve (22), a part of the inner surface of the first chamber (52) being formed by a first elastic membrane (38) the outer side of which is at atmospheric pressure. On the first membrane (38) there acts a first preset elastic means (40), means (36, 32, 28, 30, 46, 48, 50) being provided to control the first valve (22) by the deformation of the first membrane (38). The second stage comprises a second chamber (58) which communicates with the first chamber (52) via a second valve (54), a part of the inner surface of the second chamber (58) being formed by a second elastic membrane (74) on which a second preset elastic means (76) acts. The second chamber is divided into two parts, of which the first part (62) communicates directly with the exit (68) and also, via the second valve (54), with the first chamber (52), the second part (64) being partly bounded by the second membrane (74). The two parts (62, 64) are connected together by a tube (66) which extends from the wall (63) dividing the two parts (62, 64) to a position corresponding with the exit (68), so contracting it in such a manner as to obtain a venturi effect. The first valve (22) opens in the fuel flow direction, the second valve (54) opening in the opposite direction.