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Abstract

A heart pacemaker including a captive sealing setscrew for securing and preventing leakage of body fluids to the catheter. The setscrew has a head of a material of high tensile strength, stiffness, resiliency, toughness and fatigue endurance, typically Delrin. The head is cylindrical but has a circumferential projection at its inner end. The pacemaker includes an internally threaded receptacle which is engaged by the setscrew as the setscrew is advanced to secure the catheter. Externally of this receptacle there is a sleeve of silicone rubber. At the outer end of the rubber sleeve there is a recess. Inwardly of the recess the rubber sleeve is of smaller internal diameter than the projection so that when the screw is screwed into the receptacle, a tight seal to prevent penetration of body fluids is formed by the projection and sleeve. The recess has a greater diameter than the projection but has an outwardly extending lip of smaller diameter than the maximum diameter of the projection but of greater diameter than the remainder of the head. The screw can be disengaged from the threaded sleeve but its ready release from the rubber sleeve is prevented. The setscrew is screwed in by a screwdriver also of Delrin which has a substantially lower torque resistance than the head of the setscrew so that the setscrewdriver twists out of shape before enough torque can be applied to the head to damage it.

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First Claim