Bubble detecting infusion apparatus

An infusion apparatus having liquid flow path means for conducting a flowing infusion liquid from a source thereof to a patient, the improvement comprising a light transmissive conduit member in said flow path means and adapted for flow therethrough of infusion liquid, said conduit member having external shoulder means and having a lumen which is generally semicircular in tranverse cross section to provide a flat generally diametrical lumen wall surface portion therein;

• a yoke in which said conduit member is removably disposed in operative position, said yoke having positioning shoulder means cooperable with the external shoulder means on said conduit member when the latter is in said operative position to prevent rotation of said conduit member relative to said yoke, said yoke also having a light source for directing a light beam through said conduit member wall toward said flat lumen wall surface portion when said conduit member is in said operative position, said yoke also having a light sensor positioned to receive light from said source reflected by said flat lumen wall surface portion through said conduit member wall when said conduit member is in said operative position, said yoke, when said conduit member is in said operative position therein, positioning said light source and light sensor with respect to said flat lumen wall surface portion at an angularity such that when liquid flowing through the conduit member is bubble-free, said surface is not substantially reflective, whereas when a bubble is entrained in the liquid flowing through said conduit member and contacts said flat lumen wall surface portion, substantially all of the light from said source incident upon said flat lumen wall surface portion is reflected by said wall surface portion through said conduit member wall toward said sensor, wherefore sensing of substantial light by the sensor indicates the presence of a bubble in the infusion liquid flowing through said conduit member.