Patent ID: 7234490

Claim:
A hydraulic accumulator, comprising: a cylindrical housing tube of non-magnetizable material defining a longitudinal axis and having first and second working chambers; a separating piston of a non-magnetizable material mounted in said housing tube for movement axially along said longitudinal axis over a piston stroke path and separating said working chambers from one another; an annular carrier of a non-magnetizable material fixedly mounted on one end of said piston and having a diameter smaller than an interior diameter of said housing tube, said carrier having a circumferential surface concentric with said housing tube; a plurality of permanent piston magnets mounted on and distributed about said circumferential surface, axially aligned with one another relative to said longitudinal axis and arranged with polar axes thereof extending in radial directions relative to said longitudinal axis; and a row of magnetic field sensors mounted on an exterior of said housing tube substantially along all of said piston stroke path, said magnetic field sensors being responsive to said piston magnets to indicate positions of said piston magnets along said row.