Patent ID: 8172811
Filing Date: 2012-05-08
Classification: A61M,F03G,Y10T

Abstract:
1. A pump drive used to dispense a liquid drug from a container having a plunger piston, said pump drive comprising: a unidirectional clutch provided about a rotational axis and supporting centrally a wheel, the unidirectional clutch having an inner race operably connected to the plunger piston, wherein the unidirectional clutch is configured to rotate both the inner race about the rotational axis in unison with rotation of the wheel in only a first rotational direction which advances the plunger piston, and to let the wheel rotate relative to the inner race about the rotational axis in a second rotational direction opposite to the first rotational direction without advancing the plunger piston; at least one shape memory alloy wire providing a motor force when excited to rotate the wheel in at least the first rotational direction; a spring to rotate the wheel in the second rotational direction; and a pair of inner and outer concentric tubes with helical slots and bearings therebetween located about the axis of rotation, wherein the shaped memory alloy wire and the spring act on the inner tube in opposition such that the inner tube reciprocates only with linear motion along the axis of rotation, wherein the helical slots and bearings cause the outer tube to reciprocate with only rotary motion about the axis of rotation as the inner tube reciprocates with linear motion along the axis of rotation, and wherein the outer tube is connected to the wheel such that the rotary motion of the outer tube causes the wheel to rotate in the first rotational direction and then in the second rotational direction as the inner tube reciprocates only with linear motion along the axis of rotation.