Airflow controller for ducting

Abstract

A control unit is provided for monitoring the efficacy of an air filter in the ducting of an operating HVAC system. Specifically, the control unit monitors airflow velocity in the ducting to evaluate and control the power requirements that are necessary for the HVAC system to maintain a constant airflow velocity in the ducting of the system. In accordance with the present invention, the power requirements are measured and evaluated during the duty cycle of an air filter, to thereby determine when the air filter needs to be removed or replaced.

Claims

1. A control unit for monitoring and evaluating the efficacy of an air filter which comprises: an air duct, wherein the air duct defines an airflow channel extending between an upstream end and a downstream end; a fastener mounted on the air duct for holding the air filter at a location in the airflow channel; an impeller positioned at the downstream end of the air duct for drawing air through the airflow channel from the upstream end to the downstream end, wherein a power P for operating the impeller is variable; an airflow velocity sensor positioned at the upstream end of the airflow channel to measure an airflow velocity v entering the airflow channel; and a controller connected to the impeller for varying the P requirements of the impeller, wherein the controller is connected to the airflow velocity sensor for detecting changes in v (v) and for varying P to minimize v, to maintain a constant velocity v for airflow into the air channel, and wherein a power P.sub.base is the power P required for the impeller to establish the velocity v for air entering the airflow channel when a fresh, unused air filter is being held in the airflow channel, and wherein a power P.sub.max is a predetermined maximum power limit for an operation of the impeller needed to maintain the constant airflow velocity v when the air filter is held in the airflow channel.

2. The control unit recited in claim 1 wherein the air duct has a cross-section area at the location of the fastener, and the air filter comprises: a supply roll, wherein the supply roll includes an n number of contiguous panels of filter material, and each panel is dimensioned to cover the cross-section area of the air duct at the location of the fastener; a take-up roll; and a motor connected to the take-up roll for periodically rotating the take-up roll to recover a panel of used filter material from the air duct onto the take-up roll, and to replace therewith an unused panel of filter material from the supply roll.

3. The control unit recited in claim 2 wherein the controller activates the motor of the air filter to replace filter material across the air duct whenever P equals P.sub.max.

4. The control unit recited in claim 3 wherein the controller provides a signal for changing the air filter material in the air filter whenever the P required for operating the impeller satisfies a predefined value P.sub.signal equal to P.sub.max(n).

5. The control unit recited in claim 1 wherein the airflow velocity sensor is positioned in the airflow channel between the fastener and the upstream end of the air duct.

6. The control unit recited in claim 5 wherein the airflow velocity sensor is a pitot-static tube.

7. The control unit recited in claim 1 wherein the control unit is incorporated into a Heating-Ventilating-Air-Conditioning (HVAC) system.

8. A control unit for monitoring and evaluating the efficacy of an air filter located in an air duct of a Heating-Ventilating-Air-Conditioning (HVAC) system, wherein the air duct defines an airflow channel and has an upstream end and a downstream end, the control unit comprising: an impeller positioned at the downstream end of the air duct for drawing air into and through the airflow channel; an airflow velocity sensor positioned at the upstream end of the airflow channel to measure an airflow velocity v in the airflow channel; and a controller connected to the impeller for varying power requirements P of the impeller, and wherein the controller is connected to the airflow velocity sensor for detecting changes in airflow velocity v (v), and further wherein the controller increases P for the impeller to minimize v and maintain a constant velocity v for airflow into the air channel, and wherein a power P.sub.base is the power P required for the impeller to establish the velocity v for air entering the airflow channel when a fresh, unused air filter is being held in the airflow channel, and wherein a power P.sub.max is a predetermined maximum power limit for an operation of the impeller needed to maintain the constant airflow velocity v when the air filter is held in the airflow channel.

9. The control unit recited in claim 8 wherein the controller varies P between P.sub.base and P.sub.max as needed to maintain the constant airflow velocity v when the air filter is held in the airflow channel.

10. The control unit recited in claim 8 wherein the airflow velocity sensor is positioned in the airflow channel adjacent the upstream end of the air duct.

11. The control unit recited in claim 8 wherein the airflow velocity sensor is a pitot-static tube.

12. The control unit recited in claim 8 wherein the air duct has a cross-section area at the location of the fastener, and the air filter comprises: a supply roll, wherein the supply roll includes an n number of contiguous panels of filter material, and each panel is dimensioned to cover the cross-section area of the air duct at the location of the fastener; a take-up roll; and a motor connected to the take-up roll for periodically rotating the take-up roll to recover a panel of used filter material from the air duct onto the take-up roll, and to replace therewith an unused panel of filter material from the supply roll.

13. The control unit recited in claim 12 wherein the controller activates the motor of the air filter to replace filter material across the air duct whenever P equals P.sub.max.

14. The control unit recited in claim 13 wherein the controller provides a signal for changing the air filter material in the air filter whenever the P required for operating the impeller satisfies a predefined value P.sub.signal equal to P.sub.max(n).

15. A method for monitoring and evaluating the efficacy of an air filter when the air filter is located in an air duct of a Heating-Ventilating-Air-Conditioning (HVAC) system, wherein the air duct defines an airflow channel and has an upstream end and a downstream end, the method comprising the steps of: positioning an impeller at the downstream end of the air duct to draw air into and through the airflow channel; positioning an airflow velocity sensor at the upstream end of the airflow channel to measure an airflow velocity v in the airflow channel; detecting changes in airflow velocity v (v); and increasing power requirements P for the impeller based on the detecting step to minimize v and maintain a constant velocity v for airflow through the air filter in the air channel, and wherein a power P.sub.base is the power P required for the impeller to establish the velocity v for air entering the airflow channel when a fresh, unused air filter is being held in the airflow channel, and wherein a power P.sub.max is a predetermined maximum power limit for an operation of the impeller needed to maintain the constant airflow velocity v when the air filter is held in the airflow channel.

16. The method recited in claim 15 wherein a power P.sub.base is a minimum power P required for the impeller to establish a desired velocity v for air in the airflow channel, and wherein a maximum power P.sub.max is a predetermined maximum power limit for an operation of the impeller.

17. The method recited in claim 16 wherein the increasing step varies P between P.sub.base and P.sub.max as needed to maintain the constant airflow velocity v when the air filter is held in the airflow channel.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The novel features of this invention, as well as the invention itself, both as to its structure and its operation, will be best understood from the accompanying drawings, taken in conjunction with the accompanying description, in which similar reference characters refer to similar parts, and in which:

(2) FIG. 1 is a perspective view of components, in combination, for an air filter control unit in accordance with the present invention, wherein the control unit is shown incorporated into the air ducting of an HVAC system with portions shown in phantom for clarity; and

(3) FIG. 2 is a composite time graph of airflow velocity v in the ducting of an HVAC system, and the power requirements P of the HVAC system that are necessary to maintain a constant airflow velocity v during sequential duty cycles of respective air filters.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(4) Referring initially to FIG. 1, a control unit for an airflow velocity v is shown and is generally designated 10. As shown, the control unit 10 includes an air duct 12 from a Heating-Ventilating-Air-Conditioning (HVAC) system which defines an airflow channel 14. In detail, the airflow channel 14 extends through the air duct 12 from an upstream end 16 to a downstream end 18.

(5) Further, as seen in FIG. 1, the control unit 10 includes an impeller 20 which is intended to draw air into the air duct 12, and through the air channel 14 in an airflow direction indicated by the arrow 22. FIG. 1 also shows that an airflow sensor 24 is positioned at the upstream end 16 of the air duct 12 to measure the velocity v of air entering the air duct 12. As intended for the present invention, the airflow sensor 24 is preferably of a type well known in the pertinent art as a pitot-static tube.

(6) Still referring to FIG. 1, it will be seen that an air filter 26 is positioned and held in the airflow channel 14 by a fastener 28. As shown, the filtering material of the air filter 26 is initially provided on a supply roll 30. When used for the present invention, the filtering material is sequentially drawn across the airflow channel 14 and onto a take-up roll 32 by a motor 34 in a predetermined manner. The filtering material collected on the take-up roll 32 is then, eventually, discarded. In particular, an air filter 26 for use with the present invention is preferably of a type that is disclosed and claimed in U.S. application Ser. No. 15/332,901 for an invention entitled Automatic Air Filter with Enhanced Air Flow Filtering Area, which is assigned to the same assignee as the present invention.

(7) A controller 36 is shown in FIG. 1 to be connected with the impeller 20. In particular, this connection is provided to control the power requirement P of the impeller 20. Also, the controller 36 is shown to be connected with the airflow velocity sensor 24. Specifically, with this connection, the controller 36 is used to monitor the velocity v of air flowing through the air duct 12. With these connections between the controller 36, the airflow sensor 24 and the impeller 20, the control unit 10 is able to monitor v in the airflow channel 14 and determine changes in the velocity v that will occur as material in the air filter 26 gets dirty. At the same time, based on v, the control unit 10 will increase the power P that is required by the impeller 20 to counter any diminution in v. As indicated above, increases in P can continue until a value P.sub.max is reached. At that time, the panel (section) or filter material in the air filter 26 is replaced.

(8) For the operation of a control unit 10 in accordance with the present invention, consider the power requirements P for impeller 20, and the airflow velocity v through the airflow channel 14 in their relationship to each other. In particular, consider these values when an air filter 26 has an n number of panels of filter material. In this case, each panel includes sufficient filter material to extend completely across the airflow channel 14 when it is positioned on the air filter 26 as shown in FIG. 1. The power requirements P and airflow velocity v considerations for such an operation are shown in FIG. 2.

(9) Referring to FIG. 2, it will be appreciated that an n number of panels of filter material can be sequentially used by an air filter 26 between a start time t.sub.0 and a finish time t.sub.n (Note: the time between t.sub.0 and t.sub.n will typically be several months, and could possibly be longer than a year). In detail, one panel will be used during a first time interval t.sub.0-t.sub.1, and another panel will then be used during a subsequent second time interval t.sub.1-t.sub.2, and so on until the n.sup.th time interval t.sub.(n-1)-t.sub.n has been completed. As intended for the present invention the airflow velocity v will be determined by the operational capabilities of the HVAC system, and will remain substantially constant from t.sub.0 to t.sub.n.

(10) Although airflow velocity v is to remain substantially constant from t.sub.0 to t.sub.n, the power requirements P of the impeller 20 that are necessary to maintain a constant airflow velocity v do not. Instead, the power requirements P of the impeller 20 must vary. In particular, as shown in FIG. 2, for each time interval (e.g. t.sub.0-t.sub.1) the power requirement P for impeller 20 begins with a value P.sub.base at t.sub.0 and is thereafter gradually increased until a value P.sub.max is reached at t.sub.1. As noted above, the increasing power requirement for impeller 20 is caused by the accumulation of dirt and particulates in air filter material of the air filter 26, and the consequent resistance to airflow in the airflow channel 14. In the event, whenever the power requirement for the impeller 20 that is necessary to maintain a constant airflow velocity v reaches P.sub.max, the used panel of air filter material is removed and/or is replaced. A consequence here is that changes of air filter panels are determined by power requirements and not by time considerations. As indicated in FIG. 2, this process continues until all n panels have been used by the air filter 26.

(11) While the particular Airflow Controller for Ducting as herein shown and disclosed in detail is fully capable of obtaining the objects and providing the advantages herein before stated, it is to be understood that it is merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended to the details of construction or design herein shown other than as described in the appended claims.