Hydraulic priority valve

In a hydraulic priority valve for preferential feeding of a low consumption primary loop in fluid communication with a hydraulic accumulator which is chargeable from a pressure medium source via a flow control means, against a non-preferential secondary loop which can be switched in with the aid of said priority valve when said primary loop is sufficiently pressurized, said hydraulic priority valve having protecting means for protecting both loops from excess pressure comprising a pressure-limiting valve which functions to make an outlet flow path available when pressure is excessive;

• the improvement wherein the priority valve is a sequence valve in a structural module with the pressure-limiting valve, having a valve element means with a hydraulic fluid interface surface which valve element means acts against the force of a resistance means, said valve element means being permanently pressurized from the pressure medium source,
• whereby when a first given pressure is attained a first pressure medium flow path is opened from a pressure connection which is upstream of the flow control means to a first consuming device connection which is linked to the secondary loop, said first pressure medium flow path being activated by the movement of the valve element means,
• whereby when a second higher given pressure is attained a second pressure medium flow path is opened by a valve member acted upon by the pressure medium, to direct the pressure medium to an outlet connection and back to the tank, said second pressure medium flow path being activated by a further movement of the valve element means in the same direction, and
• whereby after at least the first given pressure is attained, the valve element has been moved sufficiently to permit a permanent link between the pressure medium source and the first consuming device connection so that when the second given pressure is attained the secondary loop is linked to said outlet connection in addition to being linked to the primary loop;
• and
• wherein the flow control means is a check valve, the valve element means is a slideable control piston having an end face opposite to the resistance means which is a return spring, the hydraulic interface surface comprising at least said end face in the control piston, and the pressure medium is hydraulic fluid;
• whereby when the first given pressure is attained, the end face passes a first control edge and as a result opens up a flow path from a second bore hole which accommodates the control piston and a third bore hole which is connected to the pressure medium source, to a ring-shaped groove located in the second bore hole which is linked to a first consuming-device connection;
• whereby an inner blind hole extending inwardly from the end face into the control piston is linked via transverse hole means to the outer surface of the control piston at the bottom of the inner blind hole, so that when the second given pressure is attained, the transverse hole means moves into fluid communication with a first bore hole which is linked to the outlet connection.