HYDRAULIC ACTUATORS

1 . An actuator for moving a valve gate between open and closed valve positions within a valve body, the actuator comprising:

a. an actuator housing having a proximal end oriented toward a gate valve and a distal end oriented away from the gate valve;

b. an operator shaft with a distal end and a proximal end, the proximal end extending through a bore of a packing retainer fitted within an internal bore of a bonnet and into the valve body, the bonnet operatively connected to the proximal end of the actuator housing, and the operator shaft defining a shaft axis;

c. a plurality of hydraulic pressure chambers aligned along the shaft axis and separated by at least one piston;

d. a plurality of pistons, each having a piston head and each having a proximal side and a distal side, aligned along the shaft axis and capable of movement in proximal and distal directions within the actuator housing;

e. a hydraulic fluid path connecting one hydraulic pressure chamber to another hydraulic pressure chamber, the fluid path positioned within at least one piston head; and

wherein a change in hydraulic fluid pressure in one hydraulic pressure chamber operatively connected through the fluid path within a piston to another hydraulic pressure chamber results in movement of another piston in a proximal direction or distal direction, and wherein the pistons and the hydraulic pressure chambers are positioned within a cylinder having a hollow interior.

2 . The actuator of claim 1 , wherein the piston comprising a fluid path further comprises a proximal piston shaft operatively connected to the fluid path, the proximal piston shaft having a proximal end.

3 . The actuator of claim 2 , wherein the fluid path flows continues through the proximal piston shaft and hydraulic fluid exits the proximal end of the piston shaft.

4 . The actuator of claim 2 , further comprising one or more seals surrounding the piston shaft, wherein hydraulic fluid is prevented from providing a distal force against the proximal side of the piston.

5 . The actuator of claim 4 , further comprising a hydraulic fluid separator plate surrounding the piston and positioned between the piston and the cylinder.

6 . The actuator of claim 5 , wherein the hydraulic fluid separator plate is affixed to the hollow interior of the cylinder.

7 . The actuator of claim 1 , wherein a piston not comprising a fluid path comprises a proximal piston shaft with a proximal end affixed to the operator shaft.

8 . The actuator of claim 1 , further comprising a spring having an outer diameter, the spring being capable of producing a biasing force opposing axial movement of the operator shaft toward the valve body.

9 . The actuator of claim 8 , wherein a piston not comprising a fluid path is operatively connected to a downstop.

10 . The actuator of claim 9 , wherein the downstop is operatively connected to the spring.

11 . The actuator of claim 10 , wherein the spring, the operator shaft and the cylinder are enclosed within an unpressurized housing.

12 . The actuator of claim 1 , further comprising a top shaft having a proximal end and a distal end, the distal end extending from the distal end of the cylinder.

13 . The actuator of claim 12 , wherein the top shaft is affixed to a piston having a fluid path.

14 . A method of moving a gate valve between an open and closed valve position by a hydraulic actuator, the method comprising:

a. obtaining a hydraulic actuator having a plurality of hydraulic pressure chambers aligned along an axis and separated by at least one piston; the actuator further comprising a plurality of pistons, each having a piston head and each having a proximal side and a distal side, aligned along the axis and capable of movement in proximal and distal directions within the actuator; the actuator further having an operator shaft with a distal end and a proximal end, the proximal end extending through into the valve body, the operator shaft connected to a piston;

b. applying or removing hydraulic pressure from a hydraulic fluid path, the hydraulic fluid path connecting one hydraulic pressure chamber to another hydraulic pressure chamber, the fluid path positioned within at least one piston head; and

wherein applying or removing pressure moves the pistons and the operator shaft in a proximal or distal direction, and wherein the operator shaft opens or closes a gate valve.

15 . The method of claim 14 , wherein the piston comprising a fluid path further comprises a proximal piston shaft operatively connected to the fluid path, the proximal piston shaft having a proximal end.

16 . The method of claim 15 , wherein the fluid path flows continues through the proximal piston shaft and hydraulic fluid exits the proximal end of the piston shaft.

17 . The method of claim 14 , wherein a piston not comprising a fluid path comprises a proximal piston shaft with a proximal end affixed to the operator shaft.

18 . The method of claim 17 , wherein upon application of hydraulic pressure, the operator shaft opens or closes a gate valve.

19 . The method of claim 17 , wherein upon removal of hydraulic pressure, a spring being capable of producing a biasing force opposing axial movement of the operator shaft toward the valve body moves the operator shaft in a distal direction.

20 . The method of claim 14 , wherein the piston comprising a fluid path remains stationary upon application of hydraulic pressure and a piston not comprising a fluid path moves in a distal direction.