Abstract: A multi-tube hydraulic cylinder includes annular seal assemblies joining adjacent tubes. Each assembly includes an annular primary seal member and an annular base seal member. The primary seal member is formed from relatively soft elastomer and includes inner and outer seal ribs which engage the bottom of a seal groove and the surface of an adjacent tube. The primary seal member is mounted on the base seal member, is formed from an elastomer harder than the material in the primary seal member, and includes inner and outer seal ribs and a heel facing outwardly of the seal groove on the end of the base member away from the seal ribs. The base member has an axial length greater than its radial thickness. When the seal assembly is compressed between the two tubes the seal ribs of the two members provide low pressure and high pressure seals for confining hydraulic fluid in the chamber.

Abstract: A variable speed controller for an alternating current induction motor reestablishes the start time for firing pulses and clock pulses in a circuit having a uniform frequency generator generating firing and clock pulses. Feedback from the stator terminals sets an oscillator with a sawtooth type ramp output. Subsequent feedback from the stator terminals are compared with the output of the oscillator in a comparator that establishes a time or phase shift in the generated output having the same frequency, for resetting the firing pulses so that the frequency of current to the stator winding is a function of the relationship between the stator and rotor positions, and of the current amplitude in the stator windings. Adjustment of the circuit parameters reduces the difference between the rotor and stator positions and optimizes stator current to maintain flux balance.