Abstract: The present invention relates to an automatic gear box and a control therefor of a motor vehicle, including two pulleys connected by a transmission belt (driving belt), each of which is formed by a couple of disks, of which one is movable in regard to the other one, in order to vary the winding radius of the belt. The control for the automatic gear box includes an hydraulic circuit which incorporates a number of actuating cylinders, a couple of delaying valves and a valve for issuing a fluid gradually and under increasing pressure only if the inlet pressure is above a preestablished value.

Abstract: The valve is arranged to control the pressure of a hydraulic fluid by discharging a proportion of its flow, and comprises a mobile valve element arranged to control the opening of a discharge port of a first chamber and kept normally closed by the action of a spring, a piston element rigid with said valve element and arranged to define a second chamber which is in hydraulic communication with the first by way of a first bore of predetermined size, and a third chamber in hydraulic communication both with the preceding by way of a second bore also of predetermined size, and with the discharge outlet by way of a discharge port the opening of which is controlled by an interception member operated by an electromagnet; the pressure of said fluid is controlled by varying the discharge port controlled by said interception member and consequently the rate of a flow of control fluid passing through said first bore, second chamber, second bore and third chamber.

Abstract: The distributor is designed to control the supply of a fluid under pressure into a chamber of a hydraulic actuator and the outlet of fluid from another chamber of said actuator, and comprises a first chamber and a second chamber, which are designed to be communicated with one of said chambers of the actuator, and a slide valve movable in the direction of its axis in a corresponding seat of the distributor; the distributor comprises means which respond to the pressure prevailing inside said first and second chambers of the distributor and means for choking the cross-section of the outlet for the fluid from said first and second chambers of the distributor, said pressure-responsive means being connected to said choking means so that, as a result of a movement of the movable member of said actuator at a velocity higher than a predetermined velocity, said choking means bring about a reduction in the velocity of said movable body.

Abstract: The regulator is designed to control the flow of a pressurized fluid between a source of said fluid which feeds it at a feed pressure, and a user device in which the fluid is at a utilization pressure which depends on the operating conditions of the device; the regulator also comprises a valve element mobile in the direction of its axis and arranged to vary the degree of closure of an orifice between a feed chamber and a utilization chamber, and a first and second cavity in which there is housed a first and second active surface respectively, on one of which there acts the utilization pressure and on the other of which there acts a control pressure arranged to control the movement of the valve element.