# US 2021/0277920 A1 · System that maintains the last commanded position of device controlled by a two-stage, four-way electrohydraulic servo valve upon power interruption > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2021/0277920 A1 - Document ID: US20210277920A1 - Status: Published application - Kind: A1 - Application number: 16/810,068 - Filed: 2020-03-05 - Published: 2021-09-09 - Earliest claimed: 2020-03-05 - Assignees: Honeywell International Inc. - Applicants: Honeywell International Inc. - Inventors: Paul W. Futa; Matthew Arend; Charles Walejewski; Calin Bondariu - Web page: https://patentgrep.com/patent/US20210277920A1 ## CPC - F15B 13/0436: {the pilot valves being of the steerable jet type} - F15B 20/002: {Electrical failure} - F15B 13/0438: {the pilot valves being of the nozzle-flapper type} - F15B 15/1485: {Special measures for cooling or heating} - F15B 21/0423: Cooling - F15B 2211/30565: having multiple valves for a single output member, e.g. for creating higher valve function by use of multiple valves like two 2/2-valves replacing a 5/3-valve - F15B 2211/8623: Electric supply failure - F15B 2211/8752: Emergency operation mode, e.g. fail-safe operation mode - F15B: SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR ## Abstract A system uses a two-stage, four-way electrohydraulic servo valve that includes an additional control port that commands a fail-fixed valve to lock the position of a device in the last commanded position. The additional port is modulated by an existing land on the EHSV valve element, adding little to no complexity. Major technical benefits of the disclosed system are that it adds little to no cost, complexity, size, or weight the device being controlled. The disclosed configuration allows for the use of a relatively small and simple fail-fixed valve, and the control ports on the controlled device keep “drift” to a minimum, when transitioning between normal operating mode and fail-fixed operating mode. ## Claims ### Claim 1 A system, comprising: a fail-fixed valve body including a first inlet port, a second inlet port, a third inlet port, a first outlet port, and a second outlet port; a fail-fixed valve element disposed within the fail-fixed valve body and moveable therein between a first position, in which the first inlet port is in fluid communication with the first outlet port and the second inlet port is in fluid communication with the second outlet port, and a second position, in which the first inlet port is not in fluid communication with the first outlet port and the second inlet port is not in fluid communication with the second outlet port; and a two-stage, four-way electrohydraulic servo valve (EHSV) including: a servo valve body including a supply pressure port, a return pressure port, a head pressure port, a rod pressure port, and a fail-fixed control pressure port, the head pressure port in fluid communication with the first inlet port, the rod pressure port in fluid communication with the second inlet port, the fail-fixed control pressure port in fluid communication with the third inlet port, and a servo valve element disposed within the servo valve body and moveable therein between a centered control position and a plurality of non-centered control positions, and further moveable to an electrical null bias fail-fixed position, wherein: in the centered control position, the supply pressure port and the return pressure port are both fluidly isolated from the head pressure port, the rod pressure port, and the fail-fixed control pressure port, in the plurality of non-centered control positions, the supply pressure port and the return pressure port are both fluidly isolated from the fail-fixed control pressure port, and either (i) the supply pressure port is in fluid communication with the head pressure port and the return pressure port is in fluid communication with the rod pressure port or (ii) the supply pressure port is in fluid communication with the rod pressure port and the return pressure port is in fluid communication with the head pressure port, and in the electrical null bias fail-fixed position, the supply pressure port is in fluid communication with the fail-fixed control pressure port and the head pressure port, and the return pressure port is in fluid communication with the rod pressure port, whereby the fail-fixed valve element is moved from the first position to the second position. ### Claim 2 (depends on 1) The system of claim 1, further comprising: a bias spring disposed within the fail-fixed valve body and engaging the fail-fixed valve element, the bias spring supplying a bias force to the fail-fixed valve element that urges the fail-fixed valve element toward the first position. ### Claim 3 (depends on 1) The system of claim 1, wherein the fail-fixed valve element comprises: a first end portion; a second end portion; and an intermediate portion, wherein: the first end portion and the second end portion have a first diameter, the intermediate portion has a second diameter, and the second diameter is less than the first diameter. ### Claim 4 (depends on 1) The system of claim 1, further comprising: a first plurality of dynamic seals mounted on the first end portion of the fail-fixed valve element; and a second plurality of dynamic seals mounted on the second end portion of the fail-fixed valve element. ### Claim 5 (depends on 1) The system of claim 1, further comprising: a first flow restriction formed in the head pressure port; and a second flow restriction formed in the rod pressure port. ### Claim 6 (canceled) ### Claim 7 (depends on 1) The system of claim 1, wherein the two-stage, four-way EHSV further comprises a torque motor, the torque motor coupled to the servo valve body. ### Claim 8 (depends on 7) The system of claim 7, wherein the torque motor is a dual-channel torque motor. ### Claim 9 (depends on 1) The system of claim 1, wherein the rod pressure port is in fluid communication with the fail-fixed control pressure port via a flow path. ### Claim 10 (depends on 9) The system of claim 9, further comprising: a bleed orifice disposed within the flow path. ### Claim 11 (depends on 1) The system of claim 1, further comprising: an actuator housing having an inner surface, an outer surface, a first actuator pressure port, and a second actuator pressure port, the inner surface defining an actuator cavity, the first and second actuator pressure ports spaced apart from each other and extending between the inner and outer surfaces; and an actuator disposed at least partially in, and movable within, the actuator cavity, the actuator including a piston that divides the actuator cavity into a variable head pressure cavity and a variable rod pressure cavity, wherein: the first actuator pressure port is in fluid communication with the variable head pressure cavity and the first outlet port, and the second actuator pressure port is in fluid communication with the variable rod pressure cavity and the second outlet port. ### Claim 12 (depends on 11) The system of claim 11, wherein the piston includes: a first side, a second side, and an orifice that extends between the first side and the second side and provides fluid communication between the variable head pressure cavity and the variable rod pressure cavity. ### Claim 13 A system, comprising: a fail-fixed valve body including a first inlet port, a second inlet port, a third inlet port, a first outlet port, and a second outlet port; a fail-fixed valve element disposed within the fail-fixed valve body and moveable therein between a first position, in which the first inlet port is in fluid communication with the first outlet port and the second inlet port is in fluid communication with the second outlet port, and a second position, in which the first inlet port is not in fluid communication with the first outlet port and the second inlet port is not in fluid communication with the second outlet port; and a two-stage, four-way electrohydraulic servo valve (EHSV) including: a servo valve body including a supply pressure port, a return pressure port, a head pressure port, a rod pressure port, and a fail-fixed control pressure port, the head pressure port in fluid communication with the first inlet port, the rod pressure port in fluid communication with the second inlet port, the fail-fixed control pressure port in fluid communication with the third inlet port and in fluid communication with the rod pressure port via a flow path, the flow path having a bleed orifice disposed therein, a first flow restriction formed in the head pressure port, a second flow restriction formed in the rod pressure port, a servo valve element disposed within the servo valve body and moveable therein between a centered control position and a plurality of non-centered control positions, and further moveable to an electrical null bias fail-fixed position, and a dual-channel torque motor coupled to the servo valve body, wherein: in the centered control position, the supply pressure port and the return pressure port are both fluidly isolated from the head pressure port, the rod pressure port, and the fail-fixed control pressure port, in the plurality of non-centered control positions, the supply pressure port and the return pressure port are both fluidly isolated from the fail-fixed control pressure port, and either (i) the supply pressure port is in fluid communication with the head pressure port and the return pressure port is in fluid communication with the rod pressure port or (ii) the supply pressure port is in fluid communication with the rod pressure port and the return pressure port is in fluid communication with the head pressure port, and in the electrical null bias fail-fixed position, the supply pressure port is in fluid communication with the fail-fixed control pressure port and the head pressure port, and the return pressure port is in fluid communication with the rod pressure port, whereby the fail-fixed valve element is moved from the first position to the second position. ### Claim 14 (depends on 13) The system of claim 13, further comprising: a bias spring disposed within the fail-fixed valve body and engaging the fail-fixed valve element, the bias spring supplying a bias force to the fail-fixed valve element that urges the fail-fixed valve element toward the first position. ### Claim 15 (depends on 13) The system of claim 13, wherein the fail-fixed valve element comprises: a first end portion; a second end portion; and an intermediate portion, wherein: the first end portion and the second end portion have a first diameter, the intermediate portion has a second diameter, and the second diameter is less than the first diameter. ### Claim 16 (depends on 13) The system of claim 13, further comprising: a first plurality of dynamic seals mounted on the first end portion of the fail-fixed valve element; and a second plurality of dynamic seals mounted on the second end portion of the fail-fixed valve element. ### Claim 17 (canceled) ### Claim 18 (depends on 13) The system of claim 13, further comprising: an actuator housing having an inner surface, an outer surface, a first actuator pressure port, and a second actuator pressure port, the inner surface defining an actuator cavity, the first and second actuator pressure ports spaced apart from each other and extending between the inner and outer surfaces; and an actuator disposed at least partially in, and movable within, the actuator cavity, the actuator including a piston that divides the actuator cavity into a variable head pressure cavity and a variable rod pressure cavity, wherein: the first actuator pressure port is in fluid communication with the variable head pressure cavity and the first outlet port, and the second actuator pressure port is in fluid communication with the variable rod pressure cavity and the second outlet port. ### Claim 19 (depends on 18) The system of claim 18, wherein the piston includes: a first side, a second side, and an orifice that extends between the first side and the second side and provides fluid communication between the variable head pressure cavity and the variable rod pressure cavity. ### Claim 20 (canceled)