Abstract: The principal of total internal reflection is utilized in sounding an alarm in a medical fluid infusion system when a downstream blockage occurs. A miniature prism is mounted in a cavity in a rigid exterior tube. The infusing fluid flows in a plastic tubing along the central channel of the rigid tube. The plastic tubing in the interior of this exterior rigid tube is diametrically expansive with an unpressurized outside diameter which is less than the inside diameter of said rigid exterior tube. A light source and light detector is positioned adjacent to the equilateral planes of the prism mounted in the rigid tube.

Abstract: A chamber of a peristaltic pump is described wherein a segment of the stator is removed so that said chamber containing the rotor and resilient tube may be stored with the resilient tube not pinched by the eccentric rotor. When the chamber is to be used, a cap is snapped over the chamber which completes the missing segment of the stator and the rotor is engaged to the motor shaft. When the rotor turns in the stator with all segments snapped together, liquid is conducted from inlet to outlet ports.