Patent ID: 9062694
Filing Date: 2015-06-23
Classification: F15B,Y10T

Abstract:
1. A hydraulic linear actuator comprising a cylindrical piston and a housing, the piston disposed inside the housing for reciprocal movement along an axis, the housing having a wall made of ferromagnetic material with an internal surface and an external surface, the piston having axially spaced first and second end surfaces, at least a first chamber defined between one of the first and second end surfaces and the internal surface of the wall for receipt of actuating fluid, the piston having at least one magnetic field generator for generating a magnetic field that passes through and out of the wall of the housing, and a magnetic sensor arrangement for determining the axial position of the piston relative to the housing, the sensor arrangement comprising at least a pair of magnetic sensor elements arranged on the opposite side of the wall to the piston at axially spaced locations with respect to the external surface of the wall for sensing the strength of the magnetic field passing through and out of the wall of the housing, wherein the at least one magnetic field generator is disposed in a recess defined in an external surface of the piston, the recess being axially positioned between the first and second end surfaces of the piston the recess having the shape of a segment of the cylindrical form of the piston and wherein there is provided a magnet holder of magnetically insulating material in which the magnetic field generator is supported, the magnet holder disposed in the recess in the piston, wherein the at least one magnetic field generator comprises at least one magnet disposed between axially spaced north and south pole pieces distinct from the piston, and the pole pieces are supported in the holder on each side of the magnet; and wherein the holder has a pair of pockets for supporting the pole pieces.