Patent ID: 7963751

Claim:
An electromagnetic reciprocating fluid device comprising: a piston having a piston rod and a magnetic armature secured to the piston rod, the piston reciprocating along a longitudinal axis of the piston rod; a single magnetic circuit having a pair of magnetic pole members spaced from each other in a direction perpendicularly intersecting the axis, the single magnetic circuit being intermittently excited to generate magnetic force between the magnetic pole members, thereby intermittently magnetically attracting the armature to drive the piston a predetermined direction along the axis; and a coil spring that urges the piston in a direction opposite to the direction in which the piston is magnetically attracted and driven by the single magnetic circuit; wherein the armature has a circular arc surface part centered around and extending in parallel with the axis and having opposite edges in parallel with the axis and a flat surface part extending between the opposite edges of the circular arc surface part and in parallel with the axis; wherein the pair of magnetic pole members have circular arc surfaces that are centered around and extend in parallel with the axis and are opposite to each other; further wherein the armature is arranged such that the flat surface part is positioned outside a space between the opposing circular arc surfaces of the pair of the magnetic pole members and, as the flat surface part enters the space due a rotational movement of the armature in response to the reciprocation of the piston in the predetermined direction, permeance between the magnetic pole members decreases and the magnetic force generates a torque that drives the armature in a direction opposite to the rotational movement of the armature to prevent the armature from being further rotated in the predetermined direction.