Automatic device for the detection and shutoff of unwanted liquid flow in pipes

• US 4,736,763 A
• Filed: 02/26/1987
• Issued: 04/12/1988
• Est. Priority Date: 02/26/1987
• Status: Expired due to Fees

• Current Assignee: The United States of America As Represented By The Secretary of Agriculture
• Original Assignee: The United States of America As Represented By The Secretary of Agriculture
• Inventors: Britton, George L., Ratino, David A., Peterman, Alfred W.
• Primary Examiner(s): Cohan, Alan
• Application Number:
  US07/019,265
• Time in Patent Office: 411 Days
• Field of Search: 137/487.5, 137/460, 137/486, 137/1, 137/2, 73/3, 73/592, 73/861.18, 73/40.5 R, 73/40.5 A
• US Class Current: 137/10
• CPC Class Codes: D06F 2105/58 Indications or alarms to the control system or to the user
• 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 3/243 for pipes
• CPC Class Codes: G08B 21/18 Status alarms G08B21/02 takes precedence
• CPC Class Codes: Y10T 137/0368 By speed of fluid
• CPC Class Codes: Y10T 137/7727 Excessive flow cut-off
• CPC Class Codes: Y10T 137/7761 Electrically actuated valve

Abstract

A pipe flow detector for activating a solenoid to automatically close a pipe shutoff valve in the event of a leak. The detector comprises a piezoelectric film transducer attached to the pipe, the transducer producing a fluctuating electrical signal in response to pipe vibration. An amplifier amplifies the signal, which is then passed to a tunable low-pass filter. The output from the filter is passed to an averaging circuit to produce an electrical signal representative of the total voltage changes of the fluctuating electrical signals. An LED is connected to the output of the averaging circuit to provide a means to tune the filter. The filter may be tuned by: (a) providing a pipe flow substantially equal to the pipe flow that would occur in the presence of a leak and tuning the filter to provide the brightest output of the LED; (b) starting and stopping pipe flow and tuning the filter to a point where an output of the LED is generally present only in the presence of a flow; or, (c) externally causing a starting and stopping pipe vibration and tuning the filter to a point where the LED generally does not become brighter in response to the externally caused pipe vibration. During unattended operation, the averaging circuit output is passed through an RC timing circuit that passes the averaging circuit output after a preselected period of time. A latchable level detector receives the timing means output and, when a high enough signal level is received, sends a signal to a solenoid driver which drives the solenoid.

Claims

1. A method of detecting unwanted fluid flow in a pipe to automatically trigger means for shutting off the flow, comprising:

(a) attaching a piezoelectric transducer to the pipe to produce a first fluctuating electrical signal in response to pipe vibration;

(b) amplifying the first fluctuating electrical signal to produce a second fluctuating electrical signal;

(c) passing the second fluctuating electrical signal through a tunable low-pass filter to produce a third fluctuating electrical signal comprising a selectable portion of the frequency bandwidth of the second fluctuating electrical signal;

(d) substantially averaging the total voltage changes of the third fluctuating electrical signal to produce a fourth electrical signal, wherein the frequency bandwidth of the third fluctuating electrical signal has been previously selected by;

(i) causing a fluid flow in the pipe substantially equal to the flow that would occur in the event of a leaking pipe;

(ii) measuring the level of the fourth electrical signal and tuning the tunable low-pass filter to produce the highest level of the fourth electrical signal; and

,

(iii) ceasing the fluid flow in the pipe;

(e) measuring the length of time the fourth electrical signal is present and producing a fifth electrical signal when the fourth electrical signal is present for a preselected period of time; and

,

(f) detecting for the presence of a preselected level of the fifth electrical signal and, when detected, triggering the means for shutting off the flow.

2. A method of detecting unwanted fluid flow in a pipe to automatically trigger means for shutting off the flow, comprising:

(a) attaching a piezoelectric transducer to the pipe to produce a first fluctuating electrical signal in response to pipe vibration;

(b) amplifying the first fluctuating electrical signal to produce a second fluctuating electrical signal;

(c) passing the second fluctuating electrical signal through a tunable low-pass filter to produce a third fluctuating electrical signal comprising a selectable portion of the frequency bandwidth of the second fluctuating electrical signal;

(d) substantially averaging the total voltage changes of the third fluctuating electrical signal to produce a fourth electrical signal, wherein the frequency bandwidth of the third fluctuating electrical signal has been previously selected by;

(i) alternatively starting and stopping a fluid flow in the pipe;

(ii) measuring the level of the fourth electrical signal as the tunable low-pass filter is tuned across its range;

(iii) selecting a tuned frequency bandwidth wherein the level of the fourth electrical signal is substantially zero when the flow is stopped, and above zero when the flow is started; and

,

(iii) ceasing the fluid flow in the pipe;

(e) measuring the length of time the fourth electrical signal is present and producing a fifth electrical signal when the fourth electrical signal is present for a preselected period of time; and

,

(f) detecting for the presence of a preselected level of the fifth electrical signal and, when detected, triggering the means for shutting off the flow.

3. A method of detecting unwanted fluid flow in a pipe to automatically trigger means for shutting off the flow, comprising:

(a) attaching a piezoelectric transducer to the pipe to produce a first fluctuating electrical signal in response to pipe vibration;

(b) amplifying the first fluctuating electrical signal to produce a second fluctuating electrical signal;

(c) passing the second fluctuating electrical signal through a tunable low-pass filter to produce a third fluctuating electrical signal comprising a selectable portion of the frequency bandwidth of the second fluctuating electrical signal;

(d) substantially averaging the total voltage changes of the third fluctuating electrical signal to produce a fourth electrical signal, wherein the frequency bandwidth of the third fluctuating electrical signal has been previously selected by;

(i) starting and stopping an externally caused vibration in the pipe;

(ii) measuring the level of the fourth electrical signal as the tunable low-pass filter is tuned across its range;

(iii) selecting a tuned frequency bandwidth wherein the level of the fourth electrical signal generally does not increase in response to the externally caused pipe vibration; and

.

(iii) ceasing the externally caused pipe vibration;

(e) measuring the length of time the fourth electrical signal is present and producing a fifth electrical signal when the fourth electrical signal is present for a preselected period of time; and

,

(f) detecting for the presence of a preselected level of the fifth electrical signal and, when detected, triggering the means for shutting off the flow.