A priority valve is disclosed for controlling fluid flow between a power source and a secondary hydraulic function operated by the power source. The priority valve includes a housing having first and second bores formed therein. An inlet passage connects the power source to the first bore while an outlet passage connects the first bore to the hydraulic function. A priority function is also fluidly connected to the power source upstream of the priority valve. A valve spool is positioned in the first bore. The valve spool is movable between a first position blocking fluid flow from the first passage to the outlet passage and a second position permitting fluid flow therebetween. A pin is movably positioned in the second bore and has an enlarged end which extends into the first bore. Springs are present for urging the valve spool toward the first position and the pin toward the spool valve. A load signal passage connecting the priority function to the second end of the first bore. When full fluid is demanded by the priority function the valve spool moves toward its first position. When the priority valve demands less than full flow the spool valve moves toward its second position. If the priority function demands pressure approaching a maximum pressure which can be delivered by the power source the enlarged end of the pin contacts the valve spool and forces it toward its second position.
A hydraulic pressure-control device, specially for powershift transmissions of motor vehicles, comprises a fluid pump (1) and a main valve for regulating the pressure in at least one high-pressure consumer device (6), which is attached to a pressure pipe (3) between the fluid pump (1) and the main pressure valve. The main pressure valve is designed as pressure-relief valve. In the main pressure valve is integrated the operation of a second pressure-relief valve. Two different pressure limits can be adjusted in the pressure pipe (3) by a valve piston (21) through two compression springs (17, 18) connected in parallel of which one compression spring (18) is bound.
A hydraulic system suited for use with a backhoe apparatus and which is configured to automatically direct a priority flow of actuating fluid from an actuating fluid source to hydraulic motors used to swing the backhoe apparatus into a desired swing position independently of other backhoe operations and the corresponding loads thereof. The hydraulic system of the present invention includes a priority valve which is connected to the fluid source and has priority and secondary hydraulic circuitry extending therefrom. The priority valve is positioned under the influence of fluid pressure differentials applied against it. In response to operator desires to swing the backhoe apparatus from one position to another, the priority valve automatically directs a dedicated flow of actuating fluid through the priority circuit to the swing motors used to swing the backhoe apparatus into the desired swing position. The flow to the swing motors is independent of other backhoe functions concurrently operated therewith thereby allowing a substantially constant swing speed for the backhoe apparatus. When the backhoe apparatus is held in a static position, the priority valve automatically directs actuating fluid from the fluid source through the secondary circuit to other hydraulic motors in the hydraulic system.
Fluid-dynamic circuit for supplying primary and auxiliary uses with preset priorities comprises a pressurised fluid source, at least one first use with primary priority, at least one second use with secondary priority, at least one third use with low priority; said first use is directly connected to said source by a relative first pipe and said second use and third use are connectable to said source with respective second and third pipes by interposing a valve equipped with an internal distributor member to control said second and third pipes and movable according to at least three connection configurations, in a first configuration said second use and third use being shut, in a second configuration said second use being open and said third use being shut, in a third configuration said second use being open and said being open.
A priority valve (10) useful in, for example, an aircraft constant speed drive system controls sump oil level and prioritizes oil flow to several critical components during periods of oil supply interruption. The priority valve (10) includes a movable spool (17) which has a reduced portion (19) surrounded by a spring (18) to urge the spool (17) toward a closing position in which oil is supplied directly from an accumulator (80) to a deaerator (20). The spool (17) is caused to move against the bias of the spring (18) by output oil pressure of the deaerator (20) which is input into the valve (10). The member (17) has an axial passageway (101) with branch radial passageways (103, 104, 105, and 106) for selectively prioritizing the flow of oil to critical system components such as a generator rotor (52), a generator stator (53), and a hydraulic case (90) so that whatever oil is available in the system is made available to the most critical system components.
