Electro hydraulic servo valve

Claim 2

An electro hydraulic servo valve including a pilot member, means operably associated with the pilot member for moving the pilot member in proportion to an electric signal applied to the valve, a metering member operably associated with the pilot member and at least initially responsive to movement thereof to move in accordance with the movement of the pilot member and means operably associated with the pilot member for changing the relative movement of the metering member and pilot member at some point in the movement of the pilot member to provide a variable gain servo valve.

Claim 3

Structure as set forth in claim 1 wherein the means for changing the relative movement to provide a variable gain comprises an abutment engageable with the pilot member during movement thereof.

Claim 4

Structure as set forth in claim 2 and further including means operably associated with the abutment for adjusting the position of the abutment relative to the pilot member.

Claim 5

Structure as set forth in claim 3 wherein the abutment is a solid abutment.

Claim 6

Structure as set forth in claim 3 wherein the abutment is a resilient abutment.

Claim 7

Structure as set forth in claim 1 wherein the pilot member is a nozzle tube.

Claim 8

Structure as set forth in claim 6 wherein the metering member is a spool surrounding the nozzle tube.

Claim 9

Structure as set forth in claim 7 and further including resilient means connected between the nozzle tube and a relatively fixed abutment and between the nozzle tube and spool.

Claim 10

Structure as set forth in claim 8 wherein the resilient means have different spring rates.

Claim 11

Structure as set forth in claim 8 wherein the position of the abutment is adjustable.

Claim 12

In electro hydraulic servo valve structure including a body member, a spool reciprocably mounted in the body member, a nozzle tube reciprocably mounted in the spool, a force motor mounted on the body member having a metering member operably associated with and movable relative to the nozzle tube and hydraulic fluid means operably associated with the body member, spool and nozzle tube for moving the spool in response to movement of the nozzle tube in accordance with movement of the force motor metering member relative thereto to meter hydraulic fluid through said valve, an abutment secured to the body member and engageable with the nozzle tube for varying the movement thereof in response to movement of the force motor metering member to provide a variable gain servo valve.

Claim 13

In electro hydraulic servo valve structure including a body member, a spool reciprocably mounted in the body member, a nozzle tube reciprocably mounted in the spool, a force motor mounted on the body member having a metering member operably associated with and movable relative to the nozzle tube and hydraulic fluid means operably associated with the body member, spool and nozzle tube for moving the spool in response to movement of the nozzle tube in accordance with movement of the force motor metering member relative thereto to meter hydraulic fluid through said valve, an abutment secured to the body member and engageable with the nozzle tube for varying the movement thereof in response to movement of the force motor metering member to provide a variable gain servo valve.

Claim 14

Structure as set forth in claim 11 and further including means operably associated with the abutment for adjusting the abutment.

Claim 15

Structure as set forth in claim 11 wherein the abutment is resilient.

Claim 16

Structure as set forth in claim 11 and further including resilient means operable between the body member and nozzle tube and between the body member and nozzle tube and between the nozzle tube and spool.

Claim 17

Structure as set forth in claim 14, wherein the resilient means are springs and the spring rates of the springs are different.

Claim 18

An electro hydraulic servo valve comprising a body member having an extending opening therethrough, a spool reciprocably mounted within the opening in the body member, a nozzle tube mounted in the spool for reciprocal movement relative thereto axially thereof, an annular abutment in each end of the opening through the body member limiting the movement of the spool therein, a source of hydraulic fluid, fluid passages extending from the source of hydraulic fluid through the body member, through an outer portion of one end of the nozzle tube, between the spool and the annular abutment adjacEnt the one end of the nozzle tube, through an inner portion of the other end of the nozzle tube, between the spool and the annular abutment adjacent the other end of the nozzle tube, through an inner portion of the other end of the nozzle tube and through nozzles at the inner end of the inner portion of both ends of the nozzle tube into a hydraulic return to the source of hydraulic fluid, a force motor having a flapper valve operably associated with the nozzles of the nozzle tube for metering the flow of hydraulic fluid through the nozzles in accordance with the position of the force motor flapper valve and providing a differential pressure between the abutments and spool to provide movement of the spool in accordance with movement of the nozzle tube, end caps secured over the opposite ends of the opening through the body member and abutment means adjustably secured to at least one of the end caps for restricting movement of the nozzle tube after an initial movement thereof thereby varying the relative movement of the spool relative to the nozzle tube in response to movement of the flapper and providing a servo valve variable gain characteristic.

Claim 19

An electro hydraulic servo valve comprising a body member having an extending opening therethrough, a spool reciprocably mounted within the opening in the body member, a nozzle tube mounted in the spool for reciprocal movement relative thereto axially thereof, an annular abutment in each end of the opening through the body member limiting the movement of the spool therein, a source of hydraulic fluid, fluid passages extending from the source of hydraulic fluid through the body member, through an outer portion of one end of the nozzle tube, between the spool and the annular abutment adjacEnt the one end of the nozzle tube, through an inner portion of the other end of the nozzle tube, between the spool and the annular abutment adjacent the other end of the nozzle tube, through an inner portion of the other end of the nozzle tube and through nozzles at the inner end of the inner portion of both ends of the nozzle tube into a hydraulic return to the source of hydraulic fluid, a force motor having a flapper valve operably associated with the nozzles of the nozzle tube for metering the flow of hydraulic fluid through the nozzles in accordance with the position of the force motor flapper valve and providing a differential pressure between the abutments and spool to provide movement of the spool in accordance with movement of the nozzle tube, end caps secured over the opposite ends of the opening through the body member and abutment means adjustably secured to at least one of the end caps for restricting movement of the nozzle tube after an initial movement thereof thereby varying the relative movement of the spool relative to the nozzle tube in response to movement of the flapper and providing a servo valve variable gain characteristic.