Hydraulic servo valve with pressure feedback

Claim 2

A pressure control valve comprising a housing containing a bore intersected by pressure feed, cylinder, and return passages, a valve spool axially movable within said bore for selectively establishing fluid communication between said cylinder passage and said pressure feed and return passages, a longitudinal opening through said valve spool, and axially fixed support means extending through said longitudinal opening from one end of said bore to the other for providing a central load reaction path for said valve spool.

Claim 3

The pressure control valve of claim 1 wherein there are two of said return passages and two of said cylinder passages intersecting said bore, said valve spool being movable to establish fluid communication between said pressure feed passage and one of said cylinder passages and between the other cylinder passage and one of said return passages, and vice versa.

Claim 4

The pressure control valve of claim 1 further comprising spring means engaging the end of said valve spool for urging said valve spool to a position establishing fluid communication between said cylinder passage and pressure feed passage or return passage.

Claim 5

The pressure control valve of claim 1 wherein said longitudinal opening in said valve spool has a counterbore in one end, and said support means comprises two separate pistons, one of said pistons having close sliding engagement with the wall of said longitudinal opening and extending from the end of said bore adjacent said longitudinal opening into said counterbore, and the other of said pistons having close sliding engagement with the wall of said counterbore and extending from the inner end of said one piston to the other end of said bore, said pistons providing a substantially continuous, axially fixed support for said axially movable valve spool over the full length of said bore, the inner end of said counterbore providing a feedback area in communication with said cylinder passage.

Claim 6

The pressure control valve of claim 4 further comprising valve means for providing variations in the fluid pressure at the ends of said bore for varying the fluid pressure force action on the end areas of said valve spool exposed to fluid pressure in the ends of said bore.

Claim 7

A pressure control valve comprising a housing containing a bore intersected by pressure feed, cylinder, and return passages, a valve spool axially movable within said bore for selectively establishing fluid communication between said cylinder passage and said pressure feed and return passages, a longitudinal opening through said valve spool, and support means extending through said longitudinal opening from one end of said bore to the other for providing a central load reaction path for said valve spool, said longitudinal opening in said valve spool having a counterbore in both ends, and said support means comprising a plunger contained in said longitudinal opening with the ends of said plunger extending into said counterbores, a first piston separate from said plunger having a close sliding fit in one of said counterbores and extending from one end of said bore into engagement with said plunger, and a second piston separate from said plunger having a close sliding fit in the other of said counterbores and extending from the other end of said bore into engagement with said plunger, the inner ends of said counterbores providing feedback areas, and passage means in said valve spool providing fluid communication between said cylinder passage and one of said feedback areas.

Claim 8

A pressure control valve comprising a housing containing a bore intersected by pressure feed, cylinder, and return passages, a valve spool axially movable within said bore for selectively establishing fluid communication between said cylinder passage and said pressure feed and return passages, a longitudinal opening through said valve spool, and support means extending through said longitudinal opening from one end of said bore to the other for providing a central load reaction path for said valve spool, said longitudinal opening in said valve spool having a counterbore in both ends, and said support means comprising a plunger contained in said longitudinal opening with the ends of said plunger extending into said counterbores, a first piston separate from said plunger having a close sliding fit in one of said counterbores and extending from one end of said bore into engagement with said plunger, and a second piston separate from said plunger having a close sliding fit in the other of said counterbores and extending from the other end of said bore into engagement with said plunger, the inner ends of said counterbores providing feedback areas, and passage means in said valve spool providing fluid communication between said cylinder passage and one of said feedback areas.

Claim 9

The pressure control valve of claim 6 wherein said passage means in said valve spool provide communication between said cylinder passage and both of said feedback areas when said valve spool is in a position communicating said cylinder passage with said pressure feed passage.

Claim 10

The pressure control valve of claim 7 further comprIsing a land on said plunger separating said pressure feed areas, said land having a free fit in said longitudinal opening.

Claim 11

The pressure control valve of claim 6 wherein said passage means in said valve spool provide communication between said cylinder passage and one of said feedback areas and between said pressure feed passage and the other of said feedback areas.

Claim 12

The pressure control valve of claim 6 further comprising means for varying the fluid pressure in the ends of said bore for varying the fluid pressure force acting on the end areas of said valve spool exposed to fluid pressure in the ends of said bore.

Claim 13

A pressure control valve comprising a housing containing a bore intersected by pressure feed, cylinder and return passages, a valve spool axially movable within said bore for selectively establishing fluid communication between said cylinder passage and said pressure feed and return passages, a longitudinal opening through said valve spool, and support means extending through said longitudinal opening from one end of said bore to the other for providing a central load reaction path for said valve spool, there being two of said return passages and two of said cylinder passages intersecting said bore, said valve spool being movable to establish fluid communication between said pressure feed passage and one of said cylinder passages and between the other cylinder passage and one of said return passages, and vice versa, said longitudinal opening in said valve spool having a counterbore in both ends, and said support means comprising a plunger contained in said longitudinal opening with the ends of said plunger extending into said counterbore, a first piston having a close sliding fit in one of said counterbores and extending from one end of said bore into engagement with said plunger, and a second piston having a close sliding fit in the other of said counterbores and extending from the other end of said bore into engagement with said plunger, the inner ends of said counterbores providing feedback areas, and passage means in said valve spool providing communication between the cylinder passages and said feedback areas.

Claim 14

A pressure control valve comprising a housing containing a bore intersected by pressure feed, cylinder and return passages, a valve spool axially movable within said bore for selectively establishing fluid communication between said cylinder passage and said pressure feed and return passages, a longitudinal opening through said valve spool, and support means extending through said longitudinal opening from one end of said bore to the other for providing a central load reaction path for said valve spool, there being two of said return passages and two of said cylinder passages intersecting said bore, said valve spool being movable to establish fluid communication between said pressure feed passage and one of said cylinder passages and between the other cylinder passage and one of said return passages, and vice versa, said longitudinal opening in said valve spool having a counterbore in both ends, and said support means comprising a plunger contained in said longitudinal opening with the ends of said plunger extending into said counterbore, a first piston having a close sliding fit in one of said counterbores and extending from one end of said bore into engagement with said plunger, and a second piston having a close sliding fit in the other of said counterbores and extending from the other end of said bore into engagement with said plunger, the inner ends of said counterbores providing feedback areas, and passage means in said valve spool providing communication between the cylinder passages and said feedback areas.

Claim 15

A pressure control valve comprising a housing containing a bore intersected by pressure feed, cylinder, and return passages, a valve spool axially movable within said bore for selectively establishing fluid communication between said cylinder passage and said pressure feed and return passages, a longitudinal opening through said valve spool, and support means extending through said longitudinal opening from one end of said bore to the other for providing a central load reaction path for said valve spool, said longitudinal opening in said valve spool having a counterbore in both ends, and said support means comprising a plunger contained in said longitudinal opening with the ends of said plunger extending into said counterbores, a first piston having a close sliding fit in one of said counterbores and extending the entire distance between one end of said bore and the adjacent end of said plunger, and a second piston having a close sliding fit in the other of said counterbores and extending the entire distance between the other end of said bore and the other adjacent end of said plunger, said piston and plungers providing a substantially continuous, axially fixed support for said axially movable valve spool over the full length of said bore, the inner ends of said counterbores providing feedback areas, and passage means in said valve spool providing fluid communication between said cylinder passage and at least one of said feedback areas.

Claim 16

A pressure control valve comprising a housing containing a bore intersected by pressure feed, cylinder, and return passages, a valve spool axially movable within said bore for selectively establishing fluid communication between said cylinder passage and said pressure feed and return passages, a longitudinal opening through said valve spool, and support means extending through said longitudinal opening from one end of said bore to the other for providing a central load reaction path for said valve spool, said longitudinal opening in said valve spool having a counterbore in both ends, and said support means comprising a plunger contained in said longitudinal opening with the ends of said plunger extending into said counterbores, a first piston having a close sliding fit in one of said counterbores and extending the entire distance between one end of said bore and the adjacent end of said plunger, and a second piston having a close sliding fit in the other of said counterbores and extending the entire distance between the other end of said bore and the other adjacent end of said plunger, said piston and plungers providing a substantially continuous, axially fixed support for said axially movable valve spool over the full length of said bore, the inner ends of said counterbores providing feedback areas, and passage means in said valve spool providing fluid communication between said cylinder passage and at least one of said feedback areas.