Differential switch for detecting leaks

• US 4,252,088 A
• Filed: 09/26/1975
• Issued: 02/24/1981
• Est. Priority Date: 09/26/1975
• Status: Expired due to Term

• Current Assignee: Gerald R. Frisby
• Original Assignee: Gerald R. Frisby
• Inventors: Frisby, Gerald R.
• Primary Examiner(s): Weakley, Harold W.
• Application Number:
  US05/617,106
• Time in Patent Office: 1,978 Days
• Field of Search: 200/81.9 M, 122/504, 122/507, 340/242, 335/207, 137/460
• US Class Current: 122/507
• CPC Class Codes: F24D 3/10 Feed-line arrangements, e.g. providing for heat-accumulator tanks, expansion tanks ; Hydraulic components of a central heating system
• CPC Class Codes: G01M 3/2807 for pipes G01M3/2892, G01M3/30 take precedence
• CPC Class Codes: Y10T 137/7727 Excessive flow cut-off

Abstract

A flapper is provided in the inlet and outlet lines to a domestic hot water heater or the like and a permanent magnet is affixed to the bottom portion of each of the flappers. Immediately adjacent each flapper and outside of the pipe, a magnetically operated switch is placed. The magnetically operated switches are connected in circuit with a relay which in turn controls a solenoid valve for cutting off or permitting the entry of water from the source into the inlet pipe. Under normal operating conditions when there is a flow of water in the inlet pipe and the outlet pipe the connection of the magnetically operated switches is such that the relay will not operate and the solenoid actuated valve will be open permitting the entry of water from the source. When a leak occurs, the ensuing movement of the flappers caused by the change in liquid flow will operate their associated magnetic switches, causing the relay to be actuated and closing the solenoid actuated valve, thus cutting off the supply of water. A thermal time delay switch is incorporated in the circuit to prevent the actuation of the magnetic switches in response to "water hammer" or the like.

Claims

1. In a hot water heating system comprising a hot water heater having an inlet pipe and an outlet pipe, apparatus for cutting off the water supply to the system in response to a leak in said system, comprising:

(a) valve means disposed in said inlet pipe for selectively admitting or cutting off water flow to said inlet pipe;

(b) first magnetically responsive switch means disposed outside and adjacent said inlet pipe;

(c) second magnetically responsive switch means disposed outside and adjacent said outlet pipe;

(d) first water flow responsive switch activating means disposed within said inlet pipe comprising a freely pivotable flapper valve having a permanent magnet attached thereto and disposed in the path of said water flow, said flapper valve being seatable so that it may be moved from its seat only in the direction of water flow;

(e) second fluid responsive switch activating means disposed within said outlet pipe comprising a freely pivotable flapper valve having a permanent magnet attached thereto and disposed in the path of said water flow, said flapper valve being seatable so that it may be moved from its seat only in the direction of water flow; and

(f) means for closing said valve means in response to any movement of said first flapper valve away from its seated position in response to any water flow in said inlet pipe, with no movement of said second flapper valve away from its seated position corresponding to no fluid flow in said outlet pipe.

2. The apparatus set forth in claim 1 wherein said means for closing said valve means comprises a voltage source;

voltage responsive switching means connected between said voltage source and said valve means, said valve means being voltage responsive; and

means interconnecting said first and second switch means, said voltage source and said switching means so that said switching means applies voltage from said voltage source to said valve means to close the same.

3. The apparatus set forth in claim 2 further including means for delaying the application of voltage to said valve means for a predetermined period of time after said first flapper valve moves away from its seated position in response to water flow in said inlet pipe and no movement of said second flapper valve away from its seated position occurs, corresponding to no fluid flow in said outlet pipe.

4. The apparatus set forth in claim 3 wherein both said first and second switch means close in order to apply voltage to said valve means after said predetermined period of time and wherein under equilibrium conditions one of said switch means is open and the other of said switch means is closed and under conditons of normal fluid flow in said system the open and closed conditions of said first and second switch means reverse from their positions during equilibrium conditions.

5. The apparatus set forth in claim 3, wherein said means for delaying comprises time delay switching means connected in circuit with said first switch means, said voltage source and said voltage responsive switching means.

6. The apparatus set forth in claim 3, further including means for resetting said voltage responsive switching means to its initial condition and means for maintaining said voltage responsive switching means in its switched condition until said resetting means is actuated.

7. The apparatus set forth in claim 6, further including manually operable switch means connected between said voltage responsive switching means and said valve means for permitting said valve means to be opened to refill said system, after the condition causing said leak has been remedied.

8. A hot water heating system having means for cutting off the water supply in response to a leak, which comprises:

tank means for heating water contained therein;

an inlet pipe for delivering cold water to said tank means to be heated;

an outlet pipe for receiving hot water from said tank means;

valve means for selectively admitting or cutting off cold water flow through said inlet pipe;

a first flapper valve having a permanent magnet attached thereto and being disposed within said inlet pipe so as to be freely pivotable between a fully seated position during periods of no water flow through said inlet pipe to an unseated position during periods of water flow through said inlet pipe;

a second flapper valve having a permanent magnet attached thereto and being disposed within said outlet pipe so as to be freely pivotable between a fully seated position during periods of no water flow through said outlet pipe to an unseated position during periods of water flow through said outlet pipe;

a first switch having a permanent magnet attached thereto and disposed outside said inlet pipe adjacent said first flapper valve so as to be responsive to pivotal movements thereof;

a second switch having a permanent magnet attached thereto and disposed outside said outlet pipe adjacent said second flapper valve so as to be responsive to pivotal movements thereof; and

electric circuit means connected to said first and second switches for actuating said value means to cut off cold water flow through said inlet pipe in response to the concomitant unseated position of said first flapper valve and seated position of said second flapper valve.

9. The system as set forth in claim 8, wherein one of said first and second switches is open during periods of no water flow through its associated pipe and the other of said switches is closed during periods of no water flow through its associated pipe, the positions of said switches being reversed during periods of water flow through their respective pipes.

10. The system as set forth in claim 9, wherein said electric circuit means is responsive to the concomitant closure of said first and second switches for actuating said valve means to cut off cold water flow through said inlet pipe.

11. The system as set forth in claim 10, wherein said first and second switches each include a moveable contact and a stationary contact, the stationary contact of one of said switches being electrically connected to the moveable contact of the other, the permanent magnets of each of said switches being connected to their respective moveable contacts.

12. The system as set forth in claim 9, wherein the contacts of said first switch are normally open during periods of no water flow through said inlet pipe, and the contacts of said second switch are normally closed during periods of no water flow in said outlet pipe, and first and second swtiches being responsive to water flow through their associated pipes to close and open respectively.