Abstract:
A fluid filtration system, such as an ambient air cleaner, employs a measurement mechanism to determine the amount of fluid flow through the system. The measurement system provides data or actuates an indicator. The indicator may have a pointer to indicate fluid flow along a gradient display that contains numeric information and/or is color coded. Alternatively, fluid flow may be displayed electronically. The indicator may be protected within a separate housing that projects from a filtration unit housing or may be disposed within a recess of the filtration unit housing.

Description:
FIELD OF THE INVENTION 
     The present invention generally relates to the field of fluid filtration, and, particularly, to an apparatus and method for detecting when a filter used for filtering air or other fluid is to be replaced. 
     BACKGROUND OF THE INVENTION 
     Air filtration systems are used in a variety of applications for filtering particulate matter from air and other fluids. For example, air filtration systems are found in woodshops, kitchens, furnaces, semiconductor clean rooms, mines, elevator shafts, air conditioning systems, submersible vehicles, space vehicles, and other areas where the air may be contaminated by dust and other particles. 
     As air filters extract particulate matter, a build up of residue forms on their surface over time requiring their replacement. Normally, such residue particles are small making it difficult to perform a visual inspection of them. Thus, visual inspection of the air filter is inconvenient and less than fully trustworthy. Accordingly, good filters are often thrown away prematurely, while needed replacements are not provided on a timely basis. Further, equipment operators and other users forget to inspect the provided filters and assign the task of inspecting the filter a low priority. 
     Therefore, it would be desirable to provide an apparatus and method that would clearly indicate to a user that a filter needs to be replaced especially for an ambient air filter. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention is directed to an air filtration indicator for indicating when a filter used for filtering particulate matter from air or other fluid needs to be replaced. 
     In particular, the present invention relates to a fluid filtration system that includes a filter for filtering the fluid received from the fluid intake, a fluid flow measurement mechanism for measuring a fluid flow rate of the filtered fluid from the filter, and an indicator that for displaying a fluid flow rate. The fluid flow measurement mechanism includes a flap and a shaft that rotate in unison. It is the rotational movement of the flap and/or shaft that determines the rate of fluid flow through the apparatus. 
     The present invention offers an easy to implement method for determining if an air (or, fluid) filter needs to be replaced. It is done through an effective arrangement of an indicator display. The display and detection mechanism may be implemented very simply through a purely mechanical system or may also involve electronic components including electronic displays. 
     It is to be understood that both the forgoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed. The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate an embodiment of the invention and together with the general description, serve to explain the principles of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The numerous advantages of the present invention may be better understood by those skilled in the art by reference to the accompanying figures in which: 
     FIG. 1 illustrates the essential features of the present invention in an embodiment; 
     FIG. 2 illustrates an air filtration system that incorporates the elements of FIG. 1 of the present invention; 
     FIG. 3 illustrates a representative process for the present invention; 
     FIGS. 4 and 5 illustrate an indicator scheme of the present invention; 
     FIGS. 6-8 illustrate the placement of a measuring device within an air channel in the present invention; 
     FIG. 9 illustrates a variant indicator gauge of the present invention; 
     FIG. 10 illustrates a measurement device of the present invention that uses the flap support shaft to set a resistance value; 
     FIG. 11 illustrates an exemplary circuit that provides a visual signal for a condition of the air filter in the present invention; 
     FIG. 12 illustrates an alarm mechanism when the airflow reaches a certain level in the present invention; 
     FIG. 13 illustrates a circuit incorporating the alarm mechanism of FIG. 11; and 
     FIG. 14 illustrates an air channel in which the shaft is oriented vertically. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made in detail to the presently preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. 
     FIG. 1 illustrates an exemplary embodiment of the essential features of the present invention. The basic features include a flap  210  suspended or supported in an air channel by a shaft  230 . The flap  210  and shaft  230  rotate in unison according to the pressure placed upon the flap. Another basic feature of the present invention is an indicator indicia  40  that provides information about the air flow as measured by the flap  230 . Variations of the present invention include translating the rotary motion of shaft  230  to provide airflow information that may be either mechanically or electronically displayed. FIG. 1 shows an embodiment in which the rotary motion of the shaft  230  directly drives a pointer  50  that passes over indicator indicia  40 . 
     FIG. 2 illustrates an air filtration system in accordance with the present invention. The air filtration system  10  includes a fluid filtration system housing  12  that provides an entrance  20  for air or other gas or fluid to enter. The housing  12  may have a tight fitting construction so that only channeled fluid passes through it and may be formed of plastic, metal, or other suitable material. In the exemplary embodiment, entrance  20  may include a protective grate  22  formed of mesh, fabric, or other porous material, as the application requires, to keep out material that might immediately damage or clog interior filters. An internal or external pointer  50  indicates the movement of fluid after the fluid has been filtered. The indicator  40  may be color coded, numeric, or otherwise fashioned to provide an easily readable display with pertinent information, such as a gradient, to be displayed for repair or maintenance personnel or other users. Indicators may be disposed on both sides of the housing  12  or may be disposed on top of it. 
     FIG. 3 illustrates an air filtration process of the present invention. A fluid intake  100 , which may correspond to the entrance of the housing  12 , passes a fluid into the housing  12 . In embodiments of the invention, the fluid may be moved through the housing  12  by a pump or blower. The fluid intake  100 , corresponding to entrance  20  and grate  22 , may perform prefiltering or have a blocking effective to protect the more fragile elements within the housing. One or more filters  110  may pass the fluid through and trap particulate matter that is over a certain size. For instance, the air intake may pass objects smaller than 1 centimeter, the first filter may pass particles under 50 microns, and the second filter may pass particles under 5 microns. In the case where several filters are used, the first filter, which may be a prefilter, may be the coarsest filter to remove the largest particles, while the last filter may be the finest filter to remove the smallest particles. Two or more filters, which have the same filtering ability, may be used in tandem to provide a redundant effect to ensure that particulate matter over a certain size is filtered out in case of defects or damage in one of the filters. The filtered fluid flow rate is measured by a measurement detector and indicator  120 , variations of which are presented throughout this disclosure. In essence, the flow rate of a fluid, especially a gas or gas mixture, may be measured by the degree of rotational movement experienced by a flap suspended or support on a rotary shaft within the path of airflow. The degree of rotation may be used to derive a measurement value of the airflow. After passing by the flap, the fluid leaves the unit through an outlet  130 . 
     Other variations of arranging the filters and the measurement detector and indicator are possible. For example, the measurement detector and indicator  120  may be placed after the first filter or may even be placed after the fluid intake  100  and in front of the filters when the fluid intake has some filtering effect. Also, multiple measurement detectors and indicators may be placed between various filters. 
     FIGS. 4 and 5 illustrate an exemplary indicator. In one embodiment, the indicator  40  may be disposed within a recess within the housing  12 . This arrangement affords greater protection to the indicator in the event the housing brushes up against something during transportation or someone or something collides with the housing. In another embodiment, the indicator may be unprotected or may be disposed in its own housing to afford a user easier access to the indicator  40  itself. 
     As shown in FIG. 4, the indicator is divided into multiple zones. Although two are shown here, there may be three, four, or more. The zones  42  and  44  may be color coded to facilitate recognition that the unit is not performing or not performing well. For example, the low fluid flow zone  42  may be color coded red and the high fluid flow zone  44  may be color coded green. More varied color coding schemes may be employed such as green, yellow, and red, or green, chartreuse, yellow, orange, and red. Glow in the dark paint or pigment used to form the indicator may be advantageous to a home owner who checks the furnace filter in the dark or under poor lighting conditions. In general, the color-coding indicator may be applied to the housing by painting, spraying, printing, adhering a label, or the like. Aside from, or in addition to, color-coding, numeric values may be placed on the indicator with or without color-coding to provide calibrated information such as airflow in cubic feet per minute. The arrangement of the numeric values may be linear or may be logarithmic for scaling in making measurements. Furthermore, alphabetic, alphanumeric, or other characters or indicia may be used as part of the indicator, such as providing text that reads “REPLACE FILTER”. The housing  70  in FIG. 5 protects the indicator and may be made of a variety of materials, including metal or plastic. The housing  70 , as an independent structure, may snap onto or be screwed onto housing  12 . A window  60  may be retentively placed within the housing  70 . In exemplary embodiments, the window  60  may be formed of plastic, glass, or any other suitable transparent or translucent material. Preferably, the window  60  and indicator housing  70  may be made as shallow as possible to reduce the risk of collision damage with a person or object. Further, the window  60  may be a liquid crystal window, which is opaque when the fluid filtration unit is turned off and transparent when it is powered up. 
     Alternately, the fluid filtration housing  70  may contain a window that allows direct viewing of the flap. The flap may be of a particularly noticeable color and may be of a luminescent material so as to act as a pointer itself and provide an indicating means with fewer component parts. The flap or indicator may include a material, which changes color in response to temperature. In this manner, the flap may serve as an independent, crude temperature gauge. Markings on the housing itself may show flow rate values or fault conditions. 
     FIGS. 6 through 8 illustrate the placement of the measurement device within the fluid channel of the filtration unit in which FIG. 6 illustrates a state in which there is no airflow, FIG. 7 illustrates an intermediate airflow state, and FIG. 8 illustrates a maximal airflow state. The measurement device  205  includes a flap  210 , which is fixedly attached to a rotatable shaft  230 . Although the rotatable shaft  230  is shown as approximately near the top of the channel with respect to the flap (i.e., opposite the direction of gravitational attraction), it may be located within the top half of the fluid channel. The greater range of movement provided by placing the shaft near the top of the channel may allow finer measurements of the rate of fluid flow if the indicator is coupled to the end of the flap. The size and weight of the flap may be adjusted to measure the applicable fluid flow. The flap  210  may have an upper section  222  and a lower section  224 . In this embodiment, the flap  210  has a normal vertical orientation in which the lower section  224  may rise up to the level of the upper section  222 . The flap  210  may be formed from metal, plastic, or other rigid or at least substantially rigid material that moves the shaft  230  so as to provide an accurate measurement of the airflow. The fit of the flap  210  to the channel walls may allow a gap or space or may be in loose or tight contact. The lower end  224  of the flap  210  may be weighted to facilitate the flap&#39;s return to an initial vertical state when fluid or air flow stops. In an alternative embodiment, flap  210  may consist solely of lower section  224 ; that is, there would be no upper section. The advantage of this alternative embodiment is that it would maximize efficiency of air flow. 
     The flap  210  may pivot about a vertically oriented shaft provided that the flap experiences a difference in pressure between its left and right sides during fluid flow. As fluid enters the channel, the flap  210  rotates under pressure at a certain angle. The rotary movement of the shaft  230  drives the pointer. For a vertically oriented shaft, a spring mechanism, such as a spring  410  and a stationary post  420  for securing the spring, may be used to return the flap to an initial, closed position, as shown in FIG.  14 . The initial, closed position of the flap  210  corresponds to a warning condition to an operator that there is no or substantially limited airflow. The arrangement of a vertically oriented shaft is especially useful when the air intake is on a ceiling or is extended horizontally or at an angle. 
     Alternately, the pointer  50  may be driven by an attachment at the end of a flap. This attachment may be rod shaped and may be guided by a track or slot. For greater accuracy, tracks or slots may be placed on both sides of the end of the flap to guide the movement of the flap. FIG. 9 illustrates another embodiment of the indicator  40  in which the flap itself drives a bar  80  which is rotatable about pivot  82 . The bar  80  may be weighted so that it retains a horizontal orientation as the pointer  50  which carries it rotates about the pivot point  52  that is secured to the shaft  230  of FIGS. 6 through 8. A slot  90  is provided to aid in the travel of the bar  80  such as by placing a guide opposite the pivot point  82  which passes into or through the slot  90 . In this embodiment, the pointer may be located either within or external to the housing of the fluid filtration housing unit. 
     FIG. 10 illustrates a mechanism that relates pressure on the flap to a measurable value. As the shaft rotates, the rotatable portion  320  of the potentiometer  300  turns relative to potentiometer housing  310  to set a resistance value. 
     FIG. 11 illustrates an exemplary indicator circuit that uses a variable resistance such as provided by the mechanism of FIG.  10 . The variable resistance  300  of the potentiometer is connected to a power source  350  and a visual indicator  360 . The visual indicator may be a light emitting diode or some other light source. The light may experience a change of color and/or intensity or may blink in response to a change of current determined by the variable resistance  300 . The indicator  360  may be, instead or additionally, a buzzer or other audible indicator. In this embodiment, the variable resistance  300  is always supplying current to the indicator  360 . As an alternative, the variable resistance may be used to actuate a switch to toggle the indicator  360  completely on or completely off. 
     FIG. 12 illustrates a variation in which an indicator is activated when there is little or no fluid flow. In this embodiment, a mechanism has a pointer  50  that mechanically actuates a switch  370  at the end of its travel. The position of the pointer  50  when it actuates the switch  370  corresponds to a fault zone. The switch  370  has an arm  374  that is pushed by the pointer  50  to electrically close the switch by contacting the contact point  372 . 
     FIG. 13 illustrates an indicator circuit, which uses a switch. When the switch  370  is closed, a light  360  or buzzer may be activated. 
     A gear mechanism may be used to vary the fineness of the calibration of the indicator, to amplify shaft motion to actuate a 360 degree dial, to convert a rotary motion of the shaft to a linear motion of a bar used as part of the indicator in which the bar may have a horizontal, vertical, or angled linear motion, or to mechanically translate the measurement information to another part of the housing. 
     The indicator need not be limited to a static display, but may use a dynamic electronic display such as an electrochromic, liquid crystal, electroluminescent, or plasma display or may be an array of light emitting diodes by translating the rotary motion of shaft  230  into an electrical measurement that may be displayed electronically for an operator. 
     The present invention is primarily directed to an air filtration system in which the collection of dust on the air filter reduces or stops airflow, but may be practiced with any filtration system or detection system in which there is fluid flow. 
     It is believed that the present invention and many of its attendant advantages will be understood by the forgoing description. It is also believed that it will be apparent that various changes may be made in the form, construction and arrangement of the components thereof without departing from the scope and spirit of the invention or without sacrificing all of its material advantages. The form herein before described being merely an explanatory embodiment thereof. It is the intention of the following claims to encompass and include such changes.