Water feed control system for concrete mixers

Claim 1

A WATER FEED CONTROL SYSTEM FOR FEEDING ALL BUT A FINAL SMALL PERCENTAGE OF THE REQUIRED AMOUNT OF WATER INTO A BATCH OF DRY AGGREGATES IN A CONCRETE MIXER, AT A FAST FLOW RATE, FEEDING THE REMAINDER OF THE REQUIRED WATER INTO THE BATCH AT A SLOW FLOW RATE; AND ACCURATELY TERMINATING THE FLOW OF WATER INTO THE MIXER WHEN THE CORRECT AMOUNT HAS BEEN FED TO THE BATCH, SAID SYSTEM COMPRISING: MEANS FEED WATER FROM A SOURCE THEREOF INTO THE MIXER INCLUDING VALVE MEANS BY WHICH WATER MAY BE ADMITTED INTO THE MIXER AT EITHER A PRE-SELECTED FAST OR SLOW FLOW RATE; A SINGLE PAIR OF CONTACTS POSITIONED TO BE ELECTRICALLY BRIDGED BY THE CONTENTS OF THE MIXER WITH A RESISTANCE WHICH DECREASES AS THE MIXER CONTENTS BECOME WETTER; A BRIDGE CIRCUIT HAVING TWO FIXED LEGS, A VARIABLE LEG WHICH HAS SAID PAIR OF CONTACTS CONNECTED IN IT SO THAT THE CONDUCTIVITY OF THE MIXER CONTENTS BETWEEN SAID CONTACTS DETERMINES THE RESISTANCE OF SAID VARIABLE LEG, AND A FOURTH LEG WHICH COMPRISES ONE OR THE OTHER OF TWO ADJUSTABLE RESISTORS BY ONE OF WHICH THE BRIDGE CIRCUIT MAY BE ADJUSTED TO BALANCE WHEN THE ADMISSION OF WATER AT THE FAST FLOW RATE SHOULD BE STOPPED, AND BY THE OTHER OF WHICH THE BRIDGE CIRCUIT MAY BE ADJUSTED TO BALANCE WHEN THE AMOUNT OF WATER IN THE BATCH IS CORRECT; MEANS OPERATIVELY CONNECTED WITH THE BRIDGE CIRCUIT AND RESPONSIVE TO THE ATTAINMENT OF A BALANCED CONDITION THEREIN WHEN ITS FOURTH LEG COMPRISES THE FIRST OF SAID ADJUSTABLE RESISTORS TO EFFECT ACTUATION OF THE VALVE MEANS TO STOP FAST FLOW OF WATER INTO THE MIXER AND TO SUBSTITUTE THE SECOND RESISTOR FOR SAID FIRST RESISTOR IN THE FOURTH LEG OF THE BRIDGE CIRCUIT; AND MEANS CONNECTED WITH SAID BRIDGE CIRCUIT AND RESPONSIVE TO THE ATTAINMENT OF A BALANCED CONDITION THEREIN WHEN ITS FOURTH LEG COMPRISES THE SECOND ADJUSTABLE RESISTOR, TO EFFECT CLOSURE OF THE VALVE MEANS AND TERMINATION OF ALL FLOW OF WATER INTO THE MIXER.