| 摘要 |
An improved valve assembly is utilized to divide a flow of fluid between a priority flow utilization device, such as a power steering system, and an excess flow utilization device, such as an auxiliary mechanism. The valve assembly is operable to maintain either one of two predetermined flow rates to the power steering system. The valve assembly includes a housing which defines a chamber in which a valve spool or piston is moved in response to variations in the demand for fluid by the power steering system. The valve spool is provided with two sets of orifices or aperatures which are connected in series with a priority flow outlet through a variable size intermediate opening formed between the end of the valve spool and the housing. During operation of the power steering system, a parallel flow of fluid is conducted at a relatively high rate from the two sets of orifices to the priority flow outlet through the intermediate opening. The rate of fluid flow through the two sets of orifices to the power steering system is maintained constant by shifting the valve spool slightly in response to variations in the pressure differential across the two sets of orifices. When the auxiliary mechanism is being operated, the valve spool is shifted to block one of the two sets of orifices so thaat only a minimum flow of fluid is ported to the power steering system through the other set of orifices. This minimum flow of fluid is maintained substantially constant by varying the size of the intermediate opening in response to variations in the fluid pressure at the priority flow outlet.
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