Patent ID: 7475537

Claim:
A fail-fixed valve for maintaining the position of a device controlled by an electrohydraulic servo-valve (EHSV) upon loss of an input position command, the device having a first control port and a second control port for moving the device, the EHSV having a first and second control pressure line for controlling the flow of a source pressure and a drain pressure to the first control port and the second control port to position the device, the valve comprising: a first end in fluidic communication with the first control pressure line; a second end in fluidic communication with the second control pressure line; a first port in fluidic communication with, via a second port, the first control port of the device during normal operation of the electro-hydraulic servo-valve and one of the source pressure and the drain pressure for moving the device during normal operation, the fail-fixed valve adapted to move as a result of the pressure differential between the first and second ends created after the loss of the input position command to a position such that the first port is disconnected from the first control port and the device is kept within a tolerance window of a last commanded position; a third port in fluidic communication with, via a fourth port, the second control port of the device during normal operation and wherein the second port is disconnected from the second control port after the loss of the input position command by movement of the fail-fixed valve; and a fifth port and a sixth port, the second port and the fifth port connecting the first control port to one of source pressure and drain pressure and the sixth port and the fourth port connecting the second control port to the other of source pressure and drain pressure after the first end initially hits a stop.