FLEXIBLE COUPLING FOR THE DRIVE UNIT SHAFT OF AN INFUSION PUMP

A drive connector for elastomerically coupling a drive shaft to a driven shaft. An elastomeric coupling includes openings on opposite ends that are generally "D"-shaped forming an interference fit with correspondingly shaped ends of the drive shaft and the driven shaft. A web extends transversely within the interior of the elastomeric coupling, limiting the distance that the drive shaft and driven shaft are inserted within the openings of the coupling. The coupling includes a rib that runs longitudinally along its outer length. A sleeve having a groove corresponding in size and shape to the rib is slipped over the coupling and is connected to the driven shaft. The sleeve includes a rigid interior element that is overmolded with an elastomeric material. A cam bearing is fitted over a cam surface on the sleeve and provides a force in one direction, urging a plunger to displace an elastomeric membrane in a pumping cassette, forcing medicinal fluid to flow through the pumping cassette. The elastomeric membrane provides the restoring force to the plunger, so that a loop formed on the upper portion of the plunger and disposed around the cam bearing does not receive any force from the cam bearing to move the plunger away from the pump cassette. The elastomeric coupling and sleeve form a relatively compact assembly for coupling the drive shaft to the driven shaft and accommodate minor misalignment between the center lines of the drive shaft and the driven shaft.