# US 8,783,291 B2 · Servo valve > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,783,291 B2 - Document ID: US8783291B2 - Status: Granted - Kind: B2 - Application number: 12/894,457 - Filed: 2010-09-30 - Published: 2011-04-07 - Granted: 2014-07-22 - Earliest claimed: 2009-09-30 - Assignees: Liebherr-Aerospace Lindenberg GmbH - Applicants: Franz Weixler; Florian Lau - Inventors: Franz Weixler; Florian Lau - Web page: https://patentgrep.com/patent/US8783291B2 ## CPC - F15B 13/0436: {the pilot valves being of the steerable jet type} - Y10T 137/7761: Electrically actuated valve - Y10T 137/8659: Variable orifice-type modulator - Y10T 137/86606: Common to plural valve motor chambers - F15B: SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR - Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION ## Abstract The present invention relates to a two-stage electrohydraulic servo valve with a first stage, which operates as pilot stage and includes a movable nozzle tube, and a second stage which operates as power stage, wherein the nozzle tube of the pilot stage is guided by means of a torsion element and the oil supply of the movable nozzle tube is integrated in the torsion element. ## Claims ### Claim 1 A two-stage electrohydraulic servo valve with a first stage (1), which operates as pilot stage and includes a movable nozzle tube (10), and a second stage (2) which operates as power stage, wherein the first stage (1) additionally comprises an integral a torsion element (11), with the nozzle tube (10) of the pilot stage (1) mounted upon and guided by the integral torsion element (11) and an oil supply of the movable nozzle tube (10) integrated in the torsion element (11), a base plate (17), with opposite ends of the integral torsion element (11) affixed to the same base plate (17), and the second stage (2) comprises a control piston or slide (3) reciprocally mounted therein and a return spring (6) engaging the control piston or slide (3) and firmly connected with the nozzle tube (10) to generate an increasingly reverse torque on the nozzle tube (10) until the nozzle tube (10) swivels back into vertical neutral position. ### Claim 2 (depends on 1) The two-stage electrohydraulic servo valve according to claim 1, wherein the oil supply is located in the neutral fiber of the torsion element (11). ### Claim 3 (depends on 1) The two-stage electrohydraulic servo valve according to claim 1, wherein the torsion element (11) is a torsion bar spring. ### Claim 4 (depends on 1) The two-stage electrohydraulic servo valve according to claim 1, wherein the torsion element (11) has an oil supply bore on one side and an additional bore is provided on the opposite side. ### Claim 5 (depends on 1) The two-stage electrohydraulic servo valve according to claim 1, wherein the torsion element (11) is made of titanium. ### Claim 6 (depends on 1) The two-stage electrohydraulic servo valve according to claim 1, wherein the torsion element (11) is made of a copper-beryllium alloy. ### Claim 7 (depends on 1) The two-stage electrohydraulic servo valve according to claim 1, wherein the torsion element (11) is made of steel. ### Claim 8 (depends on 1) The two-stage electrohydraulic servo valve according to claim 1, wherein the nozzle tube (10) is connected with the torsion element (11) by press fit. ### Claim 9 (depends on 4) The two-stage electrohydraulic servo valve according to claim 4, wherein the bores in the torsion element (11) are closed by ball bearing balls (16). ### Claim 10 (depends on 4) The two-stage electrohydraulic servo valve according to claim 4, wherein the bores in the torsion element (11) are closed by means of cylindrical plugs. ### Claim 11 (depends on 1) The two-stage electrohydraulic servo valve according to claim 1, wherein the base plate (17) is sealed against the power stage (2) by an axial seal (14). ### Claim 12 (depends on 1) The two-stage electrohydraulic servo valve according to claim 1, wherein an oil supply conduit (20) is guided through the base plate (17) up to the torsion element (11). ### Claim 13 (depends on 1) The two-stage electrohydraulic servo valve according to claim 1, wherein an oil supply conduit (20) is sealed between torsion element (11) and base plate (17) by an axial seal (15). ### Claim 14 (depends on 1) The two-stage electrohydraulic servo valve according to claim 1, additionally comprising an oil supply bore extending through at least part of the torsion element (11) and arranged to communicate an oil supply conduit (20) with an internal channel of the movable nozzle tube (10). ### Claim 15 (depends on 14) The two-stage electrohydraulic servo valve according to claim 14, wherein the torsion element (11) has a step-like configuration, with the nozzle tube (10) being attached to a central step of the nozzle tube (10) by press fit. ### Claim 16 (depends on 15) The two-stage electrohydraulic servo valve according to claim 15, wherein the nozzle tube (10) is arranged with a longitudinal axis thereof extending in a vertical direction from the torsion element (11) through the base plate (17) and into a valve block of the second stage (2), with stationary control lines (5a, 5b) extending to stationary control spaces (4a, 4b) adjacent opposite ends of the control piston or slide (3) at ends of the control lines (5a, 5b) and, at opposite ends of the control lines (5a, 5b), being laterally offset with respect to the vertically-extending nozzle tube (10). ### Claim 17 (depends on 16) The two-stage electrohydraulic servo valve according to claim 16, wherein the control piston or slide (3) has variable diameter or cross-section along a length thereof, and additionally comprising two pressure outlet channels (C1, C2), a pressure inlet opening (PP) and a return channel (RP) opening into a space of the valve block containing the control piston or slide (3). ### Claim 18 (depends on 1) The two-stage electrohydraulic servo valve according to claim 1, wherein the second stage (2) comprises two control lines (5a, 5b) leading to control spaces (4a, 4b) at opposite end faces of the control piston (3), and with the nozzle (10) pivotally mounted to swivel between the two control lines (5a, 5b), and the spring (6) extends, in unbiased condition, along an axis of the nozzle (10) in the vertically neutral position of the nozzle (10) and between the two control lines (5a, 5b).