Hydrostatic bearing gyroscopes (gyros) include a float (gyro motor and inner cylinder) that is supported radially and axially within a sleeve housing and end plate assembly by pressurized liquid such as a silicone lubricant. The liquid is recirculated within a sealed enclosure by means of a pump. The pressurized liquid flows from the pump through a filtered port to a sleeve inlet orifice. The liquid is circulated from the sleeve inlet orifice around the sleeve annuli through a series of restrictor outlets which act to radially support the cylinder. The liquid is also directed across two step bearing end plates located at each end of the cylinder for axial support. The exhaust liquid is then channeled back to an outlet port and returned to the pump for recirculation. A gyro of the type described is disclosed in U.S. Pat. No. 3,803,924 issued to Howard E. Schulien, William H. Ficken and Robert J. Sgambati on Apr. 16, 1974.
Single degree of freedom gyros so configured are used in gyrocompassing (north seeking) applications. Performance requirements for gyrocompassing, particularly in missile guidance applications, require accurate means for directly determining the level reference of the north seeking gyro.
Prior to the present invention level sensors such as electrolytic switches or accelerometers mounted externally on either the gyro housing or the support ring to which the gyro is mounted have been used to establish the level reference. The present invention provides more accurate results than the prior art arrangements by featuring a hydrostatically suspended pendulum integral with the gyro housing, and utilizing a portion of the liquid already used to suspend the gyro float for suspending the pendulum.