# US 4,391,092 A · Multiple position digital actuator > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 4,391,092 A - Document ID: US4391092A - Status: Granted - Kind: A - Application number: 06/173,531 - Filed: 1980-07-30 - Granted: 1983-07-05 - Earliest claimed: 1980-07-30 - Assignees: The Bendix Corporation - Inventors: Samuel E. Arnett - Web page: https://patentgrep.com/patent/US4391092A ## CPC - F15B 11/125: {by means of digital actuators, i.e. actuators in which the total stroke is the sum of individual strokes} - F05B 2200/22: Power - F15B: SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR - F05B: INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G ## Abstract An actuator particularly adapted to control a plurality of bleed air valves of a gas turbine engine is disclosed. The actuator comprises n solenoid pilot valves where 2.sup.n is the number of actuation positions and 2.sup.n -1 is the number of bleed air valves to be actuated. The actuator receives as n bit digital signal corresponding to the number of bleed air valves to be actuated for a particular operating condition of the engine and the actuator converts this number into a correct mechanical position. The conversion is accomplished by a series of telescoping cylinder and piston assemblies each having an expandable chamber. Each chamber is independently contracted or expanded by an associated pilot valve controlling a pressure source in response to the presence or absence of a particular bit in the digital word. The size of the expandable chamber of each assembly is related to the others by ascending powerts of two and correspond to a bit position in the digital input signal. ## Claims ### Claim 1 A multiposition actuator for changing a N-bit digital word into N physical positions of an actuator element comprising: N-1 telescoped open ended cylinders mounted in an open ended bore with the open ends of said cylinders disposed toward the closed end of said bore and an end cap closing the open end of said bore; said actuator element including an elongated body passing through an aperture in the closed end of said bore and having a flange being a double acting piston disposed within the innermost cylinder; said actuator element, cylinders and end cap forming N piston cylinder combinations wherein the piston area of each successive piston increases from the innermost combination to the outermost combination, and wherein the flange piston area disposed toward the closed end of the bore is less than the flange piston area for the innermost cylinder; each of said combinations operable to move said actuator element independently of the other combinations through a distance controlled by an expandable chamber disposed between the cylinder and piston of each combination, each distance being related to the other distances by powers of the numeral 2; N pilot solenoids, each associated with an expandable chamber and operable to control means for communicating a source pressure to a corresponding chamber and the source pressure from a corresponding chamber to a reference pressure and each associated with one of the bits of said digital input and actuated by one of the states of said bit; a bias chamber defined by the open ends of said cylinders and the closed end of said bore; means for communicating said source pressure to said bias chamber such that movement of the expandable chambers is accomplished by the force difference between the pistons because of the source and reference pressures acting over the differing piston areas. ### Claim 2 (depends on 1) A multiposition actuator as defined in claim 1, wherein said n piston cylinder combinations are telescoped within each other such that the distances moved by the actuation element for adjacent combination is in ascending powers of two. ### Claim 3 (depends on 2) A multiposition actuator as defined in claim 2, wherein: said n piston cylinder combinations are telescoped within each other such that the distance moved by the actuation element for adjacent combinations is in descending powers of two. ### Claim 4 (depends on 1) A multiposition actuator as defined in claim 1, further including: n pressure ports, each associated with and controlled by one of said n pilot valves for pressurizing said expandable chambers. ### Claim 5 (depends on 4) A multiposition actuator is defined in claim 4, wherein: each pressure port communicates with an associated expandable chamber by a series of auxiliary chambers. ### Claim 6 (depends on 5) A multiposition actuator as defined in claim 5, wherein: the number of auxiliary chambers between a pressure port and an expandable chamber is the power of two represented by the chamber minus one. ### Claim 7 (depends on 6) A multiposition actuator as defined in claim 6, wherein: said pressure source is a compresssed air source. ### Claim 8 (depends on 7) A multiposition actuator as defined in claim 7, wherein: said pressure source is a vacuum air source. ### Claim 9 (depends on 8) An air bleed control system as disclosed in claim 8, wherein: said digital number is an n bit digital number. ### Claim 10 An air bleed control system for a gas turbine engine including a compressor having more than one stage and a plurality N of air bleed valves controllable by an actuator, said system comprising: an electronic controller means for generating a digital number indicative of the number of air bleed valves which are to be actuated, wherein said digital number is generated by said controller means as a function of at least one operating parameter of the engine; an actuator, for receiving said digital number and transforming the number into a plurality of physical positions of an actuator element indicative of the number of air bleed valves which are to be actuated; and means for actuating the air bleed valves in response to the positioning of the actuator element. ### Claim 11 (depends on 10) An air bleed control system as disclosed in claim 10, wherein: said actuator is operable to move said actuator element to n positions.