Bayonet plunger rod

Abstract

This "plunger rod" is used in an "infusion pump system". (1) As shown in the reference diagram, the "infusion pump system" consists of a reusable "drive unit" and a disposable "reservoir". Although not shown in the diagram, a drug vial is connected to the right side of the "reservoir" via an adapter. The "release member" is fixed immovably to the base end of the "reservoir", and initially, the "engaging member" is bayonet-coupled to this "release member". The right side of the "engaging member" in the diagram functions as a "plunger head" when connected to the "plunger rod". (2) As shown by arrow A, after the "reservoir" is connected to the "drive unit", the "plunger rod" is extended from the "drive unit" side by the motor and gear train. The "fins" on the head of the "plunger rod" pass between the "ribs" of the "engaging member", and the "flange" of the "plunger rod" presses the "engaging member" to the right in the diagram. As a result, the cooperative action of the bayonet pin of the release member and the bayonet slot of the engagement member causes the engagement member to rotate within the reservoir, locking the fins of the plunger rod and the ribs of the engagement member (at the same time, the connection between the engagement member and the release member is released, and the engagement member, together with the plunger rod, becomes able to move to the right in the reservoir in the diagram). (3) When the plunger rod is pulled into the drive unit by the motor and gear train and the engagement member reaches the release member, the bayonet pin of the release member and the bayonet slot of the engagement member engage again, causing the engagement member to rotate within the reservoir and releasing the lock between the fins of the plunger rod and the ribs of the engagement member. The fins of the plunger rod then become able to pass between the ribs, and the plunger rod is housed within the drive unit.

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