Importance

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Abstract

A system for delivering a drug to a patient according to the preferred embodiment of the present invention is shown as including a plunger assembly reciprocally received in a reservoir for forcing the drug therefrom for delivery to the patient. The plunger assembly is axially advanced by the rotation of a lead screw rotatably mounted and axially movable with respect to the chassis. In a first axial position, the end of the lead screw deflects contacts of a switch member into electrical engagement which interrupts operation of the motor which rotates the lead screw. The lead screw is biased out of its first axial position such that the first end of the lead screw does not actuate the switch member and rotation of the lead screw is not interrupted. An increase in the force necessary to advance the plunger assembly into the reservoir due to excessive reservoir back pressure caused by occlusion, plunger assembly friction, a depleted reservoir, and like conditions will cause the lead screw to move into its first axial position against its bias and to actuate the switch member.

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First Claim