Abstract: A fluid pump includes a piston disposed within a compartment and defining therewith a fluid-charging chamber on one side of the piston and a fluid-pumping chamber on the opposite side of the piston. The piston is formed with an opening therethrough establishing communication between the chambers. A one-way valve carried by the piston is effective to close the opening through the piston during the forward-pumping strokes and to open the opening during the return strokes. Further valve means are provided effective: to open the inlet with respect to the fluid-charging chamber during the forward-pumping strokes, to close the inlet with respect to the fluid-charging chamber during the return strokes, to open the outlet with respect to the fluid-pumping chamber during the forward-pumping strokes, and to close the outlet with respect to the fluid-pumping chamber during the return strokes.

Abstract: An electromagnetic device includes a core and a coil in the space between a central section and an outer section of the core and spaced inwardly of an open side of the core such that the coil is completely recessed within the core. An armature, facing and aligned with the recess in the core is being movable towards and away from the coil. A pair of springs on the opposite ends of the core, and coaxial with the longitudinal axis of the core, mount the armature for straight-line reciprocatory movements parallel to the longitudinal axis of the core such that during the movement of the armature: (a) a recess in the armature receives the central section of the core; (b) the outer surface of the armature defines a first working gap with the inner surface of the core outer section; (c) and the inner surface of the armature at the recess defines a second working gap with the outer surface of the core central section.

Abstract: An electromagnetic device includes a core and a coil in the space between a central section and an outer section of the core and spaced inwardly of an open side of the core such that the coil is completely recessed within the core. An armature, facing and aligned with the recess in the core is being movable towards and away from the coil. A pair of springs on the opposite ends of the core, and coaxial with the longitudinal axis of the core, mount the armature for straight-line reciprocatory movements parallel to the longitudinal axis of the core such that during the movement of the armature: (a) a recess in the armature receives the central section of the core; (b) the outer surface of the armature defines a first working gap with the inner surface of the core outer section; (c) and the inner surface of the armature at the recess defines a second working gap with the outer surface of the core central section.

Abstract: An electromagnetic vibrator, includes a pair of electromagnets each having a core of E-configuration to define three parallel legs joined together at one side by a bridge, and a coil on the middle leg. The electromagnets are secured together with their bridges facing outwardly and with their legs aligned with, but spaced from, each other. A plunger carrying magnetisable material is disposed within the space between the legs of the electromagnets such as to be movable along the longitudinal axis of the plunger upon the energization of the coils of the electromagnets. A pair of springs yieldingly mount the opposite ends of the plunger to the electromagnets, each spring being yieldable in the direction of the longitudinal axis of the plunger and stiff in the direction of the transverse axis of the plunger.