AUTOMATIC WATER SHUT-OFF SYSTEM

• US 3,770,002 A
• Filed: 11/01/1971
• Issued: 11/06/1973
• Est. Priority Date: 11/01/1971
• Status: Expired due to Term

• Current Assignee: Lawrence C. Brown
• Original Assignee: Lawrence C. Brown
• Inventors: Brown, Lawrence C.
• Primary Examiner(s): Schwadron, Martin P.
• Assistant Examiner(s): Gerard, Richard
• Application Number:
  US05/194,219
• Time in Patent Office: 736 Days
• Field of Search: 137/78,312,314 340/235 165/70 431/119 200/61.05 307/118
• US Class Current: 137/312
• CPC Class Codes: D06F 33/47 Responding to irregular working conditions, e.g. malfunctioning of pumps safety arrangements D06F37/42
• CPC Class Codes: D06F 39/081 Safety arrangements for preventing water damage
• CPC Class Codes: G01M 3/045 with electrical detection means
• CPC Class Codes: G01M 3/16 using electric detection means G01M3/045, G01M3/06, G01M3/12, G01M3/20, G01M3/24, G01M3/26 take precedence
• CPC Class Codes: H01H 35/42 Switches operated by change of humidity
• CPC Class Codes: Y10T 137/5762 With leakage or drip collecting

Abstract

An automatic water shut-off system for an appliance such as an automatic washing machine, water heater or the like, for cutting off the water supply to the appliance in the event of a malfunction such as a leak or overflow which may cause flooding. A solenoid shut-off valve is connected in each appliance water inlet and controlled by a leak detection system including an electrical water sensor located adjacent the appliance so as to be wetted by water leaking or overflowing from the appliance. The valve is automatically closed in response to a change which occurs in an electrical characteristic of the sensor when wetted. In the disclosed embodiment, the sensor is a capacitor having porous wick material between the capacitor plates for inducing wetting of the plates by water contacting the capacitor. The detection system embodies an oscillator which controls a switch for closing the shut-off valve in response to the change in the sensor leakage resistance which occurs when the detector is wetted.

Claims

1. In combination:

an appliance including a water receptacle and at least one inlet to said receptacle for connection to a source of water under pressure from which said receptacle is adapted to be filled with water in use, and an automatic electrical water shut-off system for said appliance including an electrical water sensor adapted to be placed adjacent said appliance externally of said receptacle so as to be wetted in the event of a water leak in said appliance and having an electrical characteristic which has a normal value when the sensor is dry and varies from said normal value when the sensor is wet, an electrical detection circuit responsive to said variation in said electrical characteristic, and a solenoid valve controlled by said detection circuit for blocking water flow to said receptacle through said inlet in response to departure of said characteristic value from said normal value.

2. The combination according to claim 1 wherein:

said sensor is a capacitor and said electrical characteristic is the leakage resistance of said capacitor.

3. The combination according to claim 2 wherein:

said capacitor comprises a pair of spaced capacitor elements, and capillary means for inducing wetting of said elements.

4. The combination according to claim 3 wherein:

said capacitor elements comprise capacitor plates, and said capillary means comprise wick-like dielectric means between said plates.

5. The combination according to claim 4 including:

additional wick-like means about the outside of said plates and joined to said dielectric means between the plates.

6. The combination according to claim 5 wherein:

said detection circuit comprises a relaxatIon oscillator including said capacitor which oscillates at a given frequency when said capacitor is dry, and electrical switch means controlled by said oscillator and connected to said valve for energizing said valve to retain the valve open when said oscillator is oscillating at said given frequency.

7. The combination according to claim 6 wherein:

said appliance is an electrical appliance such as an automatic washing machine having an electrical inlet for connection to an eletrical power source and a switch for turning said appliance on and off, and said water shut-off system includes an electrical connection to said appliance for powering said system from said appliance, whereby said valve closes when said appliance is shut off by said appliance switch.

8. The combination according to claim 1 wherein:

said sensor is a capacitor and said electrical characteristic is the leakage resistance of said capacitor, and said detection circuit comprises a relaxation oscillator including said capacitor which oscillates at a given frequency when said capacitor is dry, and electrical switch means controlled by said oscillator and connected to said valve for energizing said valve to retain the valve open when said oscillator is oscillating at said given frequency.

9. The combination according to claim 8 wherein:

said appliance is an electrical appliance such as an automatic washing machine having an electrical inlet for connection to an electrical power source and a switch for turning said appliance on and off, and said water shut-off system includes an electrical connection to said appliance for powering said system from said appliance, whereby said valve closes when said appliance is shut off by said appliance switch.