Refrigerated case drain blockage warning structure

Claim 1

IN A REFRIGERATED CASE HAVING A DRAIN FOR CONDUCTING WATER THEREFROM TO PREVENT ICE FORMATION THEREIN, MEANS FOR PROVIDING REFRIGERATING AIR THEREFOR, AND MEANS FOR CIRCULATING REFRIGERATING AIR THEREFOR, AND MEANS FOR FOR MAINTAINING A PREDETERMINED LOW TEMPERATURE, SAID CIRCULATING MEANS INCLUDING A GENERALLY HORIZONTAL PASSAGE FROM THE BOTTOM OF WHICH SAID DRAIN OPENS, THE IMPROVEMENT COMPRISING BAFFLE MEANS EXTENDING PARTIALLY ACROSS SAID PASSAGE TOWARD THE BOTTOM THEREOF ADJACENT SAID DRAIN AND DEFINING WITH SAID PASSAGE BOTTOM AN APERTURE OF AREA SUBSTANTIALLY ONLY SUFFICIENT FOR CIRCULATION OF AIR IN SAID SUFFICIENT VOLUME, SAID APERTUTE UPON BLOCKAGE OF THE DRAIN BEING RAPIDLY RESTRICTED BY RESULTANT FREEZING OF UNDRAINED WATER PREVENT CIRCULATION OF SAID SUFFICIENT VOLUME AND CAUSE NONMAINTENANCE OF SAID PREDETERMINED TEMPERATURE, WHEREBY TO GIVE AN INDICATION OF ICE FORMATION BEFORE GREAT ACCUMULATION THEREOF, MEANS RESPONSIVE TO SAID NONMAINTENANCE OF TEMPERATURE FOR GIVING ADDITIONAL INDICATION THEREOF.