Weighing apparatus

Claim 1

WEIGHING APPARATUS OF THE KIND ARRANGED TO GIVE AN INDICATION WHEN THE WEIGHT OF AN ARTICLE IS BELOW A FIRST PREDETERMINED VALVE OR ABOVE A SECOND PREDETERMINED VALVE, SAID APPARATUS INCLUDING IN COMBINATION AN A.C. SOURCE, A LOAD CELL CONNECTED TO SAID A.C. SOURCE, SAID LOAD CELL PRODUCING AN A.C. SIGNAL OF AMPLITUDE DEPENDENT UPON THE WEIGHT OF AN ARTICLE BEING MEASURED, MEANS DERIVING FROM SAID A.C. SOURCE FIRST AND SECOND A.C. SIGNALS OF THE SAME POLARITY AS OPPOSIBLE HALF-CYCLES RESPECTIVELY OF THE OUTPUT FROM SAID LOAD CELL, BUT OF AMPLITUDES CORRESPONDING TO THE MAXIMUM AND MINIMUM PREDETERMINED WEIGHT OF AN ARTICLE, MEANS IN CIRCUIT WITH SAID LOAD CELL FOR SUBSTRACTING SAID FIRST AND SECOND SIGNALS FROM SAID OPPOSITE HALF-CYCLES OF THE OUTPUT FROM SAID LOAD CELL, SO PRODUCING A RESULANT SIGNAL WHICH CONSISTS OF HALF-CYCLES OF ONE POLARITY ONLY WHEN THE WEIGHT OF SAID ARTICLE LIES BETWEEN SAID PREDETERMINED WEIGHTS, A DIODE THROUGH WHICH THE RESULANT SIGNAL IS FED, SAID DIODE PREVENTING PASSAGE THERETHROUGH OF SIGNALS OF SAID ONE POLARITY, AND A PHASE-SENSITIVE DETECTOR FOR DETECTING THE PHASE OF ANY SIGNALS OF THE OPPOSITE POLARITY PASSING THROUGH THE DIODE, AND PRODUCING ONE OF TWO SIGNALS DEPENDING ON WHETHER AN ARTICLE IS OVERWEIGHT OR UNDERWEIGHT.