FLUID FLOW SENSOR AND LOW FLOW CUT-OFF DEVICE

The present disclosure provides a fluid flow sensor and low flow cut-off device and an associated method for its operation that is easily integrated into a fluid delivery and/or fluid control system for a variety of appliances, such as boilers and water heaters. The fluid flow sensor and low flow cut-off device can determine a fluid flow rate in or to an appliance and whether that fluid flow rate meets or exceeds a predetermined fluid flow rate threshold for the safe and/or efficient operation of the appliance and, if the threshold is not met, disable the appliance from operating or continuing to operate under such conditions.

Skip to: Description  ·  Claims  · Patent History  ·  Patent History
Description
FIELD

The present disclosure relates to a fluid flow sensor and low flow cut-off device for boiler or water heater systems and an associated method of operation.

BACKGROUND

This section provides background information related to the present disclosure which is not necessarily prior art.

Conventional boilers and water heater systems include a cut-off device that is intended to interrupt the operation of the boiler or water heater to prevent damage to the system in the event that water flow in or to the boiler or water heater falls below a predetermined minimum flow rate required for the safe and/or efficient operation of the appliance. Such conventional low flow cut-off devices have a mechanical design configuration associated with a switch having relay contacts that open or close to disable/enable the operation of a burner for the boiler or water heater. In the event of a low flow condition, the relay contacts open and prevent the burner from turning ON or continuing to run.

Such conventional electro-mechanical low flow cut-off devices, however, exhibit less than desirable operating life spans. Moreover, the devices do not provide a continuous signal indicative of the fluid flow rate as feedback into a system controller for enabling/disabling operation of the burner. Consequently, in certain instances there is a potential for the device to latch in a given state even though the fluid flow rate may have changed. In addition, the device includes multiple separate components and does not comprise an integrated device. As such, there exists a need for an improved low flow cut-off device for a water heater or boiler systems.

SUMMARY

This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.

A fluid flow sensor and low flow cut-off device for an appliance is disclosed as including a probe disposed at a fluid supply to the appliance, a first control unit in electrical communication with the probe, and a second control unit in electrical communication with the first control unit and the appliance.

The probe is operable to generate an output signal indicative of a fluid flow rate to the appliance.

The first control unit monitors the output signal and determines the fluid flow rate over time. The fluid flow rate is compared to a predetermined threshold fluid flow rate at a first time. If the fluid flow rate is greater than or equal to the predetermined threshold fluid flow rate, the first control unit generates a first safety signal output. The first control unit also compares the fluid flow rate to the predetermined threshold fluid flow rate at a second time. If the fluid flow rate at the second is greater than or equal to the predetermined threshold fluid flow rate, the first control unit generates a second safety signal output.

In another aspect of the disclosure, the first control unit monitors the output signal and determines a fluid flow rate over time, and compares the fluid flow rate to a predetermined threshold fluid flow rate and simultaneously generates both a first safety signal output and a second safety signal output if the fluid flow rate is greater than or equal to the predetermined threshold fluid flow rate.

The second control unit includes a switch that is operable to enable operation of the appliance. The switch has a first switch interface and a second switch interface. The first safety signal output is received at the first switch interface and the second safety signal is received at the second switch interface. Only when both the first and second safety signal outputs are received, respectively, at the first and second switch interfaces, however, does the switch enable operation of the appliance.

In another aspect of the disclosure, one of the first and the second safety signal outputs can be a constant signal and the other of the first and the second safety signal outputs can be a pulsed signal. The switch can comprise a relay having a normally-opened condition, the first switch interface can comprise a high-side control for the relay, and the second switch interface can comprise a low-side control for the relay, and one of the first and second switch interfaces can comprise a pulse detector circuit, such as resistor-capacitor (R-C) circuit. Alternatively, both the first and the second safety signal outputs can be a pulsed signal and both the first and second switch interfaces can comprise a pulse detector circuit.

The fluid flow sensor and low flow cut-off device for an appliance of the disclosure can be operable to enable operation of a burner for and appliance like a boiler or a water heater.

In another aspect of the disclosure, a method for controlling the operation of an appliance is provided. The method includes determining a first fluid flow rate at the appliance at a first time, comparing the first fluid flow rate to a threshold fluid flow rate, and generating a first safety signal if the first fluid flow rate is greater than or equal to the threshold fluid flow rate. In addition, the method includes determining a second fluid flow rate at the appliance at a second time, comparing the second fluid flow rate to the threshold fluid flow rate, and generating a second safety signal if the second fluid flow rate is greater than or equal to the threshold fluid flow rate. The first safety signal is communicated to and/or received by a high-side of a switch for enabling operation of the appliance. The second safety signal is communicated to and/or received by a low-side of the switch. The switch is closed only when both the first safety signal and the second safety signal are communicated to the switch, thereby enabling operation of the appliance.

Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.

The present disclosure will become more fully understood from the detailed description and the accompanying drawing, wherein:

FIG. 1 is a schematic block diagram of a fluid flow sensor and low flow cut-off device according to the present disclosure;

FIGS. 2A and 2B show block diagrams of a fluid flow sensor and low flow cut-off device according to the present disclosure having alternative configurations; and

FIG. 3 is a flow chart describing the operation of a fluid flow sensor and low flow cut-off device according to the present disclosure.

 DETAILED DESCRIPTION

Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. The example embodiments will now be described more fully with reference to the accompanying drawings.

The present disclosure provides a fluid flow sensor and low flow cut-off device 1 and an associated method for its operation that is easily integrated into a fluid delivery and/or fluid control system for a variety of appliances, such as boilers and water heaters. The fluid flow sensor and low flow cut-off device 1 of the present disclosure can determine a fluid flow rate F in or to an appliance and whether that fluid flow rate F meets or exceeds a predetermined fluid flow rate threshold Ft for the safe and/or efficient operation of the appliance and, if the threshold is not met, disable the appliance from operating or continuing to operate under such conditions.

FIG. 1 generally depicts the major components of the fluid flow sensor and low flow cut-off device 1 in accordance with the present disclosure. The device 1 includes a fluid flow rate sensor 10 for detecting the flow of a fluid (e.g., water) in or to an appliance 12 (e.g., a boiler or water heater) and an appliance cut-off switch 14 for disabling the operation of the appliance 12 in the event of a low fluid flow condition. When the fluid flow rate in or to the appliance 12 is greater than or equal to a requisite threshold flow rate that is needed for the safe and/or efficient operation of the appliance, e.g., a predetermined threshold fluid flow rate Ft, the fluid flow rate sensor 10 generates and sends redundant (e.g., at least two) digital safety signal outputs, first safety signal output 16 and second safety signal output 18, that are indicative of a positive flow condition. The first and second safety signal outputs 16, 18 are transmitted to the appliance cut-off switch 14 and enable operation of the appliance 12. As described with respect to the exemplary embodiment disclosed herein, operation of the appliance 12 is enabled only when both the first and second safety signal outputs 16, 18 are generated and sent to the cut-off switch 14 to indicate a positive flow condition.

The fluid flow rate sensor 10 is of the thermo-anemometer-type and contains no moving parts. The fluid flow rate sensor 10 includes a probe 20 and a first control unit 22. In use, the probe 20 is disposed at or within the fluid supply of the appliance 12, for example, and is subjected to the flow of fluid leading to the appliance 12. When subjected to fluid flow, the probe 20 experiences a change in condition and can produce an output signal 24 (e.g., a voltage) that is indicative of a fluid flow rate F. The features, functions and methods associated with operating the fluid flow rate sensor 10 and determining a fluid flow rate F and other conditions (e.g., temperature of the fluid) are generally known. For example, such a sensor is shown and described in U.S. Pat. No. 7,685,875, entitled “Fluid Flow Rate Sensor and Method of Operation,” issued Mar. 30, 2010 and in U.S. Pat. No. 7,333,899, entitled “Fluid Flow Rate Sensor and Method of Operation,” issued Feb. 19, 2008, both owned by Therm-O-Disc, Incorporated, the assignee of the present patent application, the disclosures of which are both hereby incorporated in their entirety by reference.

Referring again to FIG. 1, the fluid flow rate sensor 10 includes a first control unit 22 in electrical communication with the probe 20. The first control unit 22 communicates with and controls the operation of the probe 20. The first control unit 22 can determine the fluid flow rate F and the temperature T of the fluid in a well-known manner, for example, and provide one or more outputs representative of those conditions. The fluid flow rate F and other conditions can be continuously or intermittently monitored and determined by the fluid flow rate sensor 10 over time. For example, at time=tn, a fluid flow rate Fn can be determined, thereafter at time=tn+1, a fluid flow rate Fn+1 can be determined, and so on.

In addition, the first control unit 22 can perform comparisons of the determined fluid flow rate F against a predetermined threshold fluid flow rate Ft over time. Based on the comparisons, the first control unit 22 can generate one or more of the digital safety signal outputs 16, 18. For example, the first control unit 22 can compare the fluid flow rate Fn to the predetermined threshold flow rate at time=tn. If the fluid flow rate Fn is greater than or equal to the predetermined threshold Ft, then the first control unit 22 can generate one of the first or second digital safety signal outputs 16, 18. Thereafter, at time=tn+1, the first control unit can compare the fluid flow rate Fn+1 to the predetermined threshold fluid flow rate Ft. Similarly, if the fluid flow rate Fn+1 is greater than or equal to the predetermined threshold Ft, then the first control unit 22 can generate the other of the first or second digital safety signal outputs 16, 18. If the comparisons determine that either fluid flow rate Fn and/or Fn+1 is less than the predetermined threshold Ft, then the first control unit 22 does not generate the first safety signal output 16 and/or the second safety signal output 18. In an alternative example, the first control unit 22 can simultaneously generate (and/or regenerate) both the first safety signal output 16 and the second safety signal output 18 each time (e.g., tn, tn+1, tn+2, etc.) the first control unit 22 conducts a comparison of the fluid flow rate (e.g., Fn, Fn+1, Fn+2, etc.) to the predetermined threshold Ft flow rate and the fluid flow rate F is greater than or equal to the predetermined threshold Ft.

Also as shown in FIG. 1, a second control unit 24 can be included in the fluid flow sensor and low flow cut-off device 1. The second control unit 24 is electrically connected to the first control unit 22. The second control unit 24 can include an electrically-operated switch or relay 36 that is normally open. As shown in FIG. 1, the relay 36 has a first switch interface 32, e.g., a high side control switch for the relay 36, and a second switch interface 34, e.g., a low side control switch for the relay 36 that are electrically in series with the relay 36. The first and second safety signal outputs 16, 18 generated and sent by the first control unit 22 are received in the second control unit 24, respectively at the first and second switch interfaces 32, 34. When both the first switch interface 32 and the second switch interface 34 are closed, the relay 36 switches to a closed condition and the appliance 12 is operable (e.g., the burner is ENABLED). If either of the first switch interface 32 or second switch interface 34 is open, however, the relay 36 switches to or remains in an open condition and the appliance 12 is not operable (e.g., the burner is DISABLED).

In alternative configurations shown in FIGS. 2A and 2B, however, although still electrically in series with the relay 36, both the first switch interface 32 and the second switch interface 34 can together form either a high-side control for the relay 36 (FIG. 2A) or a low-side control for the relay 36 (FIG. 2B). In either alternative configuration, though, if either of the first switch interface 32 or second switch interface 34 is open, however, the relay 36 switches to or remains in an open condition and the appliance 12 is not operable (e.g., the burner is DISABLED).

Operation of an exemplary fluid flow sensor and low flow cut-off device 1 can be understood with reference to FIGS. 1 and 3. The fluid flow rate sensor 10 can determine the fluid flow rate F in or to the appliance 12 continuously or at regular intervals in a manner well-known and described in U.S. Pat. No. 7,685,875, entitled “Fluid Flow Rate Sensor and Method of Operation,” issued Mar. 30, 2010. At time=tn, the fluid flow rate Fn is compared against the predetermined threshold flow rate value Ft. If the fluid flow rate Fn is greater than or equal to the predetermined threshold flow rate value Ft, then the first control unit 22 can generate the first safety signal 16 which is communicated to the first switch interface 32. When received at the first switch interface 32, the first safety signal 16 causes the high side control switch for the relay 36 to close.

Thereafter, at time=tn+1, the fluid flow rate Fn+1 is compared against the predetermined threshold flow rate value Ft. If the fluid flow rate Fn+1 is greater than or equal to the predetermined threshold flow rate value Ft, then the first control unit 22 can generate the second safety signal 18. The second safety signal 18 is communicated to the second switch interface 34. When received at the second switch interface 34, the second safety signal 18 causes the low side control switch for the relay 36 to close.

Consequently, if the first safety signal 16 is not generated by the first control unit 22, then no signal is sent to the high-side control 32 of the relay 36 and the relay 36 remains in its normally open condition. Similarly, if the second safety signal 18 is not generated by the first control unit 22, then no signal is sent the low side control 34 of the relay 36 and the relay 36 remains in its normally open condition. In either situation, the appliance 12 is not operable (e.g., the burner is DISABLED). If both the first switch interface 32 and the second switch interface 34 are closed, however, then the relay 36 is caused to be closed and the appliance 12 is operable (e.g., the burner is ENABLED). The appliance can then safely and/or efficiently be operated and/or continue to operate without the risk of damage to the appliance due to a low fluid flow condition. Moreover, it can be appreciated that the alternative configurations shown in FIGS. 2A and 2B likewise function in a similar manner, necessitating that both the first switch interface 32 and the second switch interface 34 must respectively receive the first and second safety signals 16, 18 in order to cause the relay 36 to close or remain closed.

At least one of the first safety signal 16 and second safety signal 18 can be a pulsed signal (i.e. voltage) delivered to its respective switch interface 32, 34, and the other of the first safety signal 16 and second safety signal 18 can be a constant signal delivered to its respective switch interface 32, 34. In addition, at least one of the first switch interface 32 and second switch interface 34 can be pulse detector circuit, such as a resistor-capacitor (R-C) circuit, that receives the pulsed safety signal. If the pulsed safety signal is not periodically sent to the R-C circuit switch interface, then the R-C circuit no longer stays closed and the relay 36 returns to its normally open condition, thereby disabling the appliance 12. For the purposes of the exemplary embodiment described in this disclosure, the first safety signal 16 is a constant signal received at the first switch interface 32 and the second safety signal 18 is a pulsed signal received at the second switch interface 34. However, it can be understood that both the first and second safety signals 16, 18 can also be pulsed signals.

Because the first control unit 22 can conduct multiple, comparisons between the fluid flow rates Fn and Fn+1 determined over time, such as times tn and tn+1, with the predetermined threshold flow rate value Ft, and because the results of those comparisons must both indicate a positive flow condition (i.e., the fluid flow rate is greater than or equal to the predetermined threshold fluid flow rate) in order for the appliance 12 to be operable, the fluid flow sensor and low flow cut-off device 1 provides a failsafe protection against operation of the appliance 12 under conditions where fluid flow in or to the appliance is below that which is required for the safe and/or efficient operation of the appliance. For example, even if one of the first safety signal 16 and second safety signal 18 represents a false positive regarding sufficient fluid flow, the absence of the other of the first and second safety signals 16, 18 can still prevent operation of the appliance. Therefore, the risk that a hardware and/or software fault could produce an incorrect or false signal regarding the flow of fluid F through the system, and maintain the appliance in an operable state when the appliance should, instead, be disabled, is reduced.

Consequently, even if a hardware fault or the like causes a false indication of a positive flow condition and one of the safety signal outputs 16, 18 is erroneously generated and sent by the fluid flow rate sensor 10 to the cut-off switch 14, the absence of the redundant safety signal output(s) 16, 18 can prevent operation of the appliance 12.

The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.

Claims

1. A fluid flow sensor and low flow cut-off device for an appliance comprising:

a probe disposed at a fluid supply to the appliance;
a first control unit in electrical communication with the probe; and
a second control unit in electrical communication with the first control unit and the appliance;
wherein the probe generates an output signal indicative of a fluid flow rate to the appliance;
wherein the first control unit monitors the output signal and determines the fluid flow rate over time and compares the fluid flow rate to a predetermined threshold fluid flow rate at a first time, and generates a first safety signal output if the fluid flow rate is greater than or equal to the predetermined threshold fluid flow rate, and compares the fluid flow rate to the predetermined threshold fluid flow rate at a second time and generates a second safety signal output if the fluid flow rate is greater than or equal to the predetermined threshold fluid flow rate;
wherein the second control unit comprises a switch operable to enable operation of the appliance, the switch having a first switch interface and a second switch interface, wherein the first safety signal output is received at the first switch interface and the second safety signal is received at the second switch interface; and
wherein only when both the first and second safety signal outputs are received, respectively, at the first and second switch interfaces does the switch enable operation of the appliance.

2. The fluid flow sensor and low flow cut-off device for an appliance of claim 1 wherein at least one of the first and the second safety signal outputs is a pulsed signal; and

wherein at least one of the first and second switch interfaces comprises a pulse detector circuit.

3. The fluid flow sensor and low flow cut-off device for an appliance of claim 2 wherein the at least one of the first and second switch interfaces that comprises a pulse detector circuit is a resistor-capacitor circuit.

4. The fluid flow sensor and low flow cut-off device for an appliance of claim 2 wherein the switch comprises a relay having a normally-opened condition; and

wherein the first switch interface and the second switch interface are electrically in series with the relay.

5. The fluid flow sensor and low flow cut-off device for an appliance of claim 4 wherein the first switch interface comprises a high-side control for the relay, and the second switch interface comprises a low-side control for the relay.

6. The fluid flow sensor and low flow cut-off device for an appliance of claim 4 wherein the first switch interface and the second switch interface are electrically in series with one another and together comprise either a high-side control or a low-side control for the relay.

7. The fluid flow sensor and low flow cut-off device for an appliance of claim 1 wherein the appliance is a boiler or a water heater and the switch is operable to enable operation of a burner for the appliance.

8. A method for controlling the operation of an appliance, the method comprising:

determining a first fluid flow rate at the appliance at a first time;
comparing the first fluid flow rate to a threshold fluid flow rate;
generating a first safety signal if the first fluid flow rate is greater than or equal to the threshold fluid flow rate;
determining a second fluid flow rate at the appliance at a second time;
comparing the second fluid flow rate to the threshold fluid flow rate;
generating a second safety signal if the second fluid flow rate is greater than or equal to the threshold fluid flow rate;
communicating the first safety signal to a high-side of a switch for enabling operation of the appliance;
communicating the second safety signal to a low-side of the switch;
closing the switch only when both the first safety signal and the second safety signal are communicated to the switch; and
enabling operation of the appliance.

9. A fluid flow sensor and low flow cut-off device for an appliance comprising:

a probe disposed at a fluid supply to the appliance;
a first control unit in electrical communication with the probe; and
a second control unit in electrical communication with the first control unit and the appliance;
wherein the probe generates an output signal indicative of a fluid flow rate to the appliance;
wherein the first control unit monitors the output signal and determines a fluid flow rate over time and compares the fluid flow rate to a predetermined threshold fluid flow rate, and simultaneously generates both a first safety signal output and a second safety signal output if the fluid flow rate is greater than or equal to the predetermined threshold fluid flow rate;
wherein the second control unit comprises a switch operable to enable operation of the appliance, the switch having a first switch interface and a second switch interface, wherein the first safety signal output is received at the first switch interface and the second safety signal is received at the second switch interface; and
wherein only when both the first and second safety signal outputs are received, respectively, at the first and second switch interfaces does the switch enable operation of the appliance.

10. The fluid flow sensor and low flow cut-off device for an appliance of claim 9 wherein at least one of the first and the second safety signal outputs is a pulsed signal; and

wherein at least one of the first and second switch interfaces comprises a pulse detector circuit.

11. The fluid flow sensor and low flow cut-off device for an appliance of claim 10 wherein the at least one of the first and second switch interfaces that comprises a pulse detector circuit is a resistor-capacitor circuit.

12. The fluid flow sensor and low flow cut-off device for an appliance of claim 10 wherein the switch comprises a relay having a normally-opened condition; and

wherein the first switch interface and the second switch interface are electrically in series with the relay.

13. The fluid flow sensor and low flow cut-off device for an appliance of claim 12 wherein the first switch interface comprises a high-side control for the relay, and the second switch interface comprises a low-side control for the relay.

14. The fluid flow sensor and low flow cut-off device for an appliance of claim 12 wherein the first switch interface and the second switch interface are electrically in series with one another and together comprise either a high-side control or a low-side control for the relay.

15. The fluid flow sensor and low flow cut-off device for an appliance of claim 9 wherein the appliance is a boiler or a water heater and the switch is operable to enable operation of a burner for the appliance.

Patent History
Publication number: 20150053151
Type: Application
Filed: Aug 22, 2013
Publication Date: Feb 26, 2015
Applicant: Therm-O-Disc, Incorporated (Mansfield, OH)
Inventor: Timothy Graff (Mansfield, OH)
Application Number: 13/973,212
Classifications
Current U.S. Class: By Other Than Temperature Of Water (122/14.21); Automatically Operated (219/509)
International Classification: F24H 9/20 (20060101);