Fluid controller with load sensing priority flow control capability

Reference Number: N 02-03

Inventors: Stephenson, Dwight B.; Marks, Dennis R.

Owner: NISTAC

USPTO Link: 5065793

Invention Summary

Accordingly, it is an object of the present invention to provide an improved load sensing priority flow control system in which the need for a separate load sensing priority flow control valve, and some of its associated plumbing, is substantially eliminated.

It is a more specific object of the present invention to provide such an improved priority flow control system, in which the priority load circuit comprises a hydrostatic power steering unit (fluid controller), and the load sensing priority flow control valve is integral with the power steering unit.

It is an even more specific object of the present invention to provide an improved load sensing priority flow control system which accomplishes the above-stated objects, and in which the function of the load sensing priority flow control valve is accomplished within and by the valving in the hydrostatic power steering unit.

The above and other objects of the present invention are accomplished by the provision of an improved system including a source of pressurized fluid, a priority fluid pressure operated device, an auxiliary fluid pressure operated device, a controller means operable to control the flow of fluid to the priority fluid pressure operated device, and load sensing priority flow control valve means operable to control the flow of fluid from the source of fluid to the controller means, and to the auxiliary device. The controller means includes housing means defining first and second control fluid ports for connection to the priority fluid pressure operated device, and valve means disposed in the housing means, and comprising a generally cylindrical spool valve member and a hollow, generally cylindrical sleeve valve member disposed radially between the housing means and the spool valve member. The spool and sleeve valve members define a neutral position relative to each other and a first operating position relative to each other, and the housing means and the sleeve valve member define a first position relative to each other. The controller means further defines a controller inlet, a first variable flow control orifice in fluid communication with the fluid inlet, and a second variable flow control orifice in fluid communication with the first control fluid port. The first and second variable flow control orifices are defined at the interface of the spool and sleeve valve members, when the valve members are in the first operating position. The housing means and the valve members cooperate to define a main fluid path providing fluid communication between the first and second variable flow control orifices when the valve members are in the first operating position. The load sensing priority flow control valve means includes means defining a priority flow control orifice operable to control the flow of fluid from the source to the controller means, and an auxiliary flow control orifice operable to control the flow of fluid from the source to the auxiliary device, in response to the demand for fluid by the priority device.

The improved system is characterized by the sleeve valve member and the housing means defining a second position relative to each other. The controller means includes means operable to bias the sleeve valve member toward the first position relative to the housing means, and means operable to bias the sleeve valve member toward the second position, relative to the housing means. The sleeve valve member and the housing means cooperate to define the priority flow control orifice when the sleeve valve member is in the first position relative to the housing means, and the sleeve valve member and the housing means cooperate to define the auxiliary flow control orifice, when the sleeve valve member is in the second position relative to the housing means.