Patent ID: 8272402
Filing Date: 2012-09-25
Classification: F16K,Y10T

Abstract:
1. A sequential stepped directional control valve having at least three operating positions, in which one of the operating positions is a neutral position, comprising: (A) a hollow cage having an axial direction and a radial direction, the cage being pierced by a cage pressure port, by a cage first stage port, by a cage second stage port, and by a cage pump port, and the cage having a hollow cage central passage; (B) a spool adapted to fit snugly within the cage in which location the spool is moveable relative to the cage in a direction substantially parallel to the axial direction of the cage; (C) a solenoid coil substantially annularly surrounding a pole piece adapted to produce a magnetic force in response to an electrical current applied to the solenoid coil; (D) a magnetically responsive plunger attached to the spool, the plunger being magnetically responsive to the magnetic force produced by the pole piece; (E) one or more springs within the sequential stepped directional control valve directly or indirectly biasing the spool; (F) wherein (1) when no electrical current is applied to the solenoid coil, the springs within the sequential stepped directional control valve directly or indirectly bias the spool such that the spool is located in the neutral position; (2) when a first predetermined electrical current is applied to the solenoid coil, the magnetic force produced in the pole piece acts upon the plunger to counteract the biasing caused by the springs directly or indirectly upon the spool so as to cause the plunger to move to a position within the sequential stepped directional control valve such that the spool attached to the plunger is located in a first stage operating position different from the neutral position; and (3) when a second predetermined electrical current is applied to the solenoid coil, the magnetic force produced in the pole piece acts upon the plunger to counteract the biasing caused by the springs directly or indirectly upon the spool so as to cause the plunger to move to a position within the sequential stepped directional control valve such that the spool attached to the plunger is located in a second stage operating position different from the neutral position and different from the first stage operating position; and (G) wherein (1) when the spool is in the neutral position, the spool acts to block hydraulic fluid under pressure from entering the cage central passage of the sequential stepped directional control valve through the cage pressure port, the spool allows hydraulic fluid to flow through the cage first stage port into the sequential stepped directional control valve and the spool directs the hydraulic fluid entering the cage first stage port into the sequential stepped directional control valve to flow out of the sequential stepped directional control valve through the tank port, and the spool allows hydraulic fluid to flow through the cage second stage port into the sequential stepped directional control valve and the spool directs hydraulic fluid entering the second stage port into the sequential stepped directional control valve to flow out of the sequential stepped directional control valve through the tank port; (2) when the spool is in the first stage operating position, the spool allows hydraulic fluid under pressure to flow through the cage pressure port into the sequential stepped directional control valve and the spool directs the hydraulic fluid under pressure entering the cage pressure port to flow out of the sequential stepped directional control valve through the cage first stage port, the spool allows hydraulic fluid to flow through the cage second stage port into the sequential stepped directional control valve and the spool directs hydraulic fluid entering the second stage port into the sequential stepped directional control valve to flow out of the sequential stepped directional control valve through the tank port, and the spool blocks hydraulic fluid from the cage first stage port from flowing out of the sequential stepped directional control valve through the tank port; and (3) when the spool is in the second stage operating position, the spool allows hydraulic fluid under pressure to flow through the cage pressure port into the sequential stepped directional control valve and the spool directs the hydraulic fluid under pressure entering the cage pressure port to flow out of the sequential stepped directional control valve through the cage first stage port and through the cage second stage port, and the spool blocks hydraulic fluid from the cage first stage port and from the cage second stage port from flowing out of the sequential stepped directional control valve through the tank port.