Pressure balanced dual seat three-way hydraulic valve
An electrohydraulic valve has a body with a pair of valve seats spaced apart in a bore. A valve element slides within the bore and has first and second end surfaces that selectively engage each valve seat to control fluid flow between a workport and each of an inlet port and an outlet port. The engagement of the valve element with the two valve seats is such that pressure from the workport is applied to substantially identical areas of the first and second end surfaces regardless of the position of the valve element in the bore. Thus the pressure forces exerted on both ends of the valve element balance each other, so that the only net forces producing movement of the valve element are from a spring and a solenoid.
1 . An electrohydraulic valve comprising:
a body with a bore into which a first port, a second port and a workport open, a first valve seat in a flow path between the first port and the workport, and a second valve seat in another flow path between the second port and the workport;
a valve element moveably received within the bore, the valve element having a first surface that engages and disengages the first valve seat and having a second surface that engages and disengages the second valve seat, wherein pressure at the workport exerts substantially equal forces on both the first and second surfaces regardless of a position of the valve element within the bore; and
an electrically operated actuator that causes motion of the valve element between the first and second valve seats.
2 . The electrohydraulic valve as recited in claim 1 wherein pressure from the workport is applied to a substantially identical amount of the first surface whether the first surface is engaging or disengaging the first valve seat, and pressure from the workport is applied to a substantially identical amount of the second surface whether the second surface is engaging or disengaging the second valve seat.
3 . The electrohydraulic valve as recited in claim 1 wherein the electrically operated actuator produces a magnetic field that induces the motion of the valve element.
4 . The electrohydraulic valve as recited in claim 1 further comprising a spring biasing the valve element toward one of the first and second valve seats.
5 . The electrohydraulic valve as recited in claim 1 wherein the first valve seat is engaged by the valve element along substantially only an outer perimeter of the first surface.
6 . The electrohydraulic valve as recited in claim 1 wherein the second valve seat is engaged by the valve element along substantially only an outer perimeter of the second surface.
7 . The electrohydraulic valve as recited in claim 1 wherein the workport opens into a first end of the bore and both the first port and the second port open into the bore between the first end and an opposite second end.
8 . The electrohydraulic valve as recited in claim 7 wherein the second valve seat is between the second port and the second end of the bore.
9 . The electrohydraulic valve as recited in claim 7 wherein the valve element has an aperture extending between the first surface and the second surface.
10 . An electrohydraulic valve comprising:
a body with a bore that has a first end and a second end, a workport opening into the first end, a first port opening into the bore with a first valve seat between the first port and the first end, a second port opening into the bore with a second valve seat between the second port and the second end;
a valve element moveably received within the bore, the valve element having a first surface that engages and disengages the first valve seat wherein pressure from the workport is applied to a substantially identical amount of the first surface whether the first surface is engaging or disengaging the first valve seat, and the valve element having a second surface that engages and disengages the second valve seat wherein pressure from the workport is applied to a substantially identical amount of the second surface whether the second surface is engaging or disengaging the second valve seat; and
an electrically operated actuator that causes motion of the valve element between the first and second valve seats.
11 . The electrohydraulic valve as recited in claim 10 wherein pressure at the workport simultaneously acts on areas of the first and second surfaces which areas are of substantially equal size.
12 . The electrohydraulic valve as recited in claim 10 wherein the valve element has an aperture extending between the first and second surfaces.
13 . The electrohydraulic valve as recited in claim 10 wherein the electrically operated actuator produces a magnetic field that induces the motion of the valve element.
14 . The electrohydraulic valve as recited in claim 10 further comprising a spring biasing the valve element toward one of the first and second valve seats.
15 . The electrohydraulic valve as recited in claim 10 further comprising a spring biasing the valve element toward the first valve seat.
16 . The electrohydraulic valve as recited in claim 10 wherein the first valve seat is engaged by the valve element along substantially only an outer perimeter of the first surface; and the second valve seat is engaged by the valve element along substantially only an outer perimeter of the second surface.
17 . An electrohydraulic valve comprising:
a body with a bore having a first end and a second end, a workport opening into the first end, a first port opening into the bore with a first valve seat between the first port and the first end, a second port opening into the bore with a second valve seat between the second port and the second end;
a valve element moveable into different positions within the bore, the valve element having a first surface that engages and disengages the first valve seat and having a second surface that engages and disengages the second valve seat, wherein pressure at the workport exerts substantially equal forces on both the first and second surfaces regardless of the position of the valve element within the bore;
a spring biasing the valve element toward the first valve seat; and
an electrically operated actuator that produces a magnetic field which induces motion of the valve element between the first and second valve seats.
18 . The electrohydraulic valve as recited in claim 17 wherein the first valve seat is engaged by the valve element along substantially only an outer perimeter of the first surface.
19 . The electrohydraulic valve as recited in claim 17 wherein the second valve seat is engaged by the valve element along substantially only an outer perimeter of the second surface.
20 . The electrohydraulic valve as recited in claim 17 wherein pressure from the workport is applied to a substantially identical amount of the first surface whether the first surface is engaging or disengaging the first valve seat, and pressure from the workport is applied to a substantially identical amount of the second surface whether the second surface is engaging or disengaging the second valve seat.