Moisture-governed automatic control for irrigation system

Claim 1

IN A CONTROL FOR THE TYPE OF IRRIGATING SYSTEM IN WHICH IRRIGATING WATER IS SUPPLIED FROM A PRESSURE SOURCE OF SUPPLY UPON THE ENERGIZING OF A NORMALLY DE-ENERGIZED CYCLING ELECTRIC TIMER, THE COMBINATION WITH SAID TIMER, A NORMALLY OPEN HOLDING SWITCH ACTING WHEN CLOSED TO ENERGIZE THE TIMER FOR A PERIOD SUFFICIENT FOR THE LATTER TO COMPLETE A CYCLE OF OPERATION, TWO SWITCHES CONNECTED IN SERIES ONE A NORMALLY OPEN SWITCH AND OPERATIVELY INTERCONOTHER A NORMALLY OPEN SWITCH AND OPERATIVELY INTERCONNECTED WITH THE HOLDING SWITCH SO THAT THE LATTER IS CAUSED TO CLOSE WHEN BOTH SWITCHES ARE CLOSED, MEANS FOR CLOSING THE NORMALLY OPEN SWITCH OF SAID IN-SERIES SWITCHES FOR ONLY A MOMENTARY PERIOD AT GIVEN INTERVALS OF TIME, A RESISTOR ADAPTED TO BE EMBEDDED IN THE SOIL IN THE AREA BEING IRRIGATED AND EMPLOYING THE MOISTURE IN THE SOIL AS A RESISTANCE MEDIUM, A TRANSFORMER HAVING ITS INPUT SIDE CONNECTED IN PARALLEL WITH THE MOMENTARY SWITCH TO BE EXCITED EITHER BY A CLOSING OF THE HOLDING SWITCH OR BY THE MOMENTARY SWITCH WHEN THE MAGNETIC SWITCH IS ALSO CLOSED, A RECTIFIER RECEIVING FOR ITS INPUT CIRCUIT LOW-VOLTAGE A.C. OUTPUT OF THE TRANSFORMER AND INCLUDING IN SAID INPUT CIRCUIT A FIXED RESISTOR TOGETHER WITH SAID SOIL-EMBEDDED RESISTOR, A COIL FOR THE MAGNETIC SWITCH INCLUDED IN THE D.C. OUTPUT CIRCUIT OF THE RESISTOR AND SO ASSOCIATED WITH SAID MAGNETIC SWITCH THAT THE LATTER IS OPENED ONLY WHEN THE MAGNETIC FIELD OF THE COIL IS ABOVE A GIVEN VALUE, AND A VARIABLE RESISTOR ALSO INCLUDED IN THE RECTIFIER''S OUTPUT CIRCUIT CAPABLE OF BEING PRES-SET TO A SELECTED VARIABLE RESISTANCE AND ACTING AS A COMPLEMENT TO THE SOIL-EMBEDDED RESISTOR AND THE FIXED RESISTOR TO ESTABLISH FOR THE COIL A FIELD POTENTIAL, SUFFICIENT TO OPEN SAID MAGNETIC SWITCH, ONLY WHEN THE MOISTURE CONDITION OF THE GROUND IS AT A PREDETERMINED HIGH LEVEL.