Method of making a poppet valve

Details Method of making a poppet valve Method of making a poppet valve

1999-10-07

2001-02-06

Hughes, S. Thomas (Department: 3726)

Metal working

Method of mechanical manufacture

Prime mover or fluid pump making

C029S446000

Reexamination Certificate

active

06182363

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to a poppet valve for controlling pressure in a fluid power assist steering system. In particular, the present invention relates to a method of making such a poppet valve.
2. Description of the Prior Art
A known fluid power assist steering system includes a pump for pumping hydraulic fluid under pressure to a fluid power assist steering gear. The output pressure demands on the pump can vary with the pump flow and system load restriction. This pressure must be limited to a predetermined maximum in order to protect the pump and other system components from damage. To this end, the pump contains a relief valve assembly.
The relief valve assembly includes a movable spring biased spool that contains an internal poppet valve assembly. The spool normally covers a fluid exhaust port. The spool is exposed to the output pressure of the pump. Output pressure is also communicated through an orifice to the opposite side of the spool, which contains a venting passage normally blocked by the poppet valve assembly. When the output pressure of the pump exceeds the predetermined maximum amount, the poppet valve assembly opens to exhaust fluid through the vent passage. The reduced pressure on this side of the spool allows the spool to move, opening the exhaust port, and thereby relieving the output pressure.
The prior art poppet valve assembly includes a poppet spring that biases a poppet against a poppet seat. The force applied by the poppet spring determines the pressure at which the poppet valve assembly opens. This force is determined by assembling the poppet valve assembly using shims to set the initial position of the poppet valve seat and, thus, the force applied by the poppet valve spring. Determining the correct number of shims to use in a particular poppet valve assembly is a time-consuming and labor-intensive process.
SUMMARY OF THE INVENTION
The present invention is a method of making a valve having a poppet valve member that is biased by a spring toward a closed position against a poppet valve seat, the spring acting between the poppet valve member and a spring seat and applying a predetermined force to the poppet valve member. The method comprises the steps of providing a valve housing having a chamber; inserting into the chamber in sequential order the poppet valve seat, the poppet valve member, the spring, and the spring seat; applying a force to the spring seat to compress the spring a predetermined amount; and securing the poppet valve seat and the spring seat to the housing while maintaining the spring compressed the predetermined amount.


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