Abstract:
A filter cartridge for use in a filter apparatus having a tube sheet is provided. The filter cartridge has a tubular filter with opposite ends, a mounting cap and a mounting plate. The mounting cap is secured to one end of the tubular filter and has a first surface and a ledge extending from the tubular filter. The mounting plate has an opening sized for receipt of the tubular filter. The ledge of the mounting cap overlies the mounting plate when the tubular filter is received within the opening, and, the mounting cap is supported by the mounting plate to enable the first surface to engage the tube sheet when the filter apparatus in operation.

Description:
CROSS-REFERENCE 
     “Not Applicable” 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT 
     “Not Applicable” 
     BACKGROUND OF THE INVENTION 
     The present invention generally relates to filters within a baghouse or dust collector and more particularly to an air filter cartridge having a reusable mounting plate for securing the filter within the baghouse. 
     Filter apparatus, such as baghouses, are commonly used for removing particulates and aerosols from the air in industrial environments. Baghouses typically include two large chambers, or plenums, that are divided by a tube sheet. The filter cartridges, preferably containing fabric filtration elements, are secured to the tube sheet at one end to suspend the cartridge within the lower plenum. Fabric filter media having longitudinal pleatings are particularly effective for removing particulates. One such air filter cartridge is disclosed in U.S. Pat. No. 5,632,791. 
     Air containing particulates is forced into the first plenum by a forced air means such as a fan. The air passes from the first plenum to the second plenum via the air filter cartridges held by the tube (or pan) sheet. The particulates are retained on the outer surface of the fabric filter element of the cartridge filter, and the clean air is directed into the second plenum and exits the baghouse through an exhaust passageway. 
     Oftentimes, the baghouses are operated continuously for relatively long periods of time. As with most physical filtration media, the effectiveness of the filter media diminishes as particulates collect on the outer surfaces of the filter elements and restrict the airflow through the filters. To remove accumulation of particulate on the baghouse filters, air may be pulsed through the baghouse cartridge filters from the second plenum to the first plenum. The air pulses dislodge the particulates embedded on the exterior surface of the filter, and the loose particulates are removed from the first plenum. Accordingly, the effectiveness of the baghouse is greatly increased without having to frequently remove and replace the cartridges. One such apparatus for cleaning baghouse filters is disclosed in U.S. Pat. No. 5,837,017. 
     While the cleaning process significantly increases the life span of the filter elements, the filter cartridges must be replaced periodically. Accordingly, a number of systems have been used to releasably secure the filter cartridges in sealing engagement with the tube sheet. One such mechanism, disclosed in U.S. Pat. No. 4,322,231, utilizes a pair of longitudinal bars underlying the tube sheet. A metal mounting plate is integrally formed with the upper end of each filter cartridge. The mounting plate is slid along the bars and suspended therefrom. When the filter cartridges are in the proper position on the longitudinal bars, the bars are rotated so that a curvilinear surface on each bar forces the mounting plates into sealing engagement with the pan sheet. A gasket on each filter cartridge seals the cartridges to the pan sheet when the cartridges are locked in the operational position within the baghouse. 
     However, the cartridge filters used within this mounting system are costly to manufacture, in part, due to the costs of the raw materials that are discarded when the cartridges no longer effectively remove particulates from the air. Moreover, it is difficult and costly to form the mounting plate integrally with the filter cartridge, and is particularly difficult to manufacture an integral mounting plate sized to fit between the locking mechanism and tube sheet. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an air filter cartridge having a mounting plate to removably mount a filter cartridge in a baghouse. 
     In accordance with the foregoing and other objects evident from the following description of a preferred embodiment of the invention, a filter cartridge for use in a baghouse having a tube sheet is provided. The filter cartridge includes a tubular filter having opposite ends, a mounting cap and a reusable mounting plate. The mounting cap is secured to one end of the tubular filter and has a first surface and a ledge extending from the tubular filter. The mounting plate has an opening sized for receipt of the tubular filter. The ledge of the mounting cap overlies the mounting plate when the tubular filter is received within the opening, and the mounting cap is supported by the mounting plate to enable the first surface to engage the tube sheet when the baghouse is in operation. 
     In another aspect, a filter cartridge for use in a baghouse having a tube sheet and a locking mechanism is provided. The filter cartridge has a tubular filter with opposite ends, a mounting cap and a mounting plate. The mounting cap is secured to one end of the tubular filter and has a first surface and a ledge extending from the tubular filter. The mounting plate has an opening sized for receipt of the tubular filter. The ledge of the mounting cap overlies the mounting plate when the tubular filter is received within the opening. Thus, the mounting cap is supported by the mounting to enable the first surface to engage the tube sheet when the locking mechanism moves the mounting plate in a direction towards the tube sheet and the baghouse is in operation. 
     In yet another aspect of the present invention, a method for securing a filter cartridge in a filter apparatus (such as a baghouse) is provided. The method includes providing a reusable mounting plate having an opening, placing the filter cartridge within the opening of the plate and releasably securing the mounting plate to a tube sheet within the baghouse. 
     By providing an air filter cartridge in accordance with the present invention, numerous advantages are achieved. For instance, the mounting plate may be re-used with the replacement filter cartridges as the prior cartridges lose their utility. Also, the unique filter cartridge provides a compact and effective design wherein the combined height of the mounting cap and mounting plate is relatively thin. Moreover, the cost of production of the device of the present invention is significantly lower than filter cartridges having integral mounting plates of the prior art. 
    
    
     BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS 
     FIG. 1 is a perspective view of the interior of a portion of a filter apparatus utilizing cartridge filters according to the present invention; 
     FIG. 2 is an exploded perspective view of a filter cartridge according to the invention; 
     FIG. 3 is a top plan view of a portion of the filter apparatus of FIG. 1 and a filter cartridge with portions removed to better illustrate the relationship between the air filter cartridge and filter apparatus; 
     FIG. 4 is a cross sectional view of the filter apparatus taken generally along line  4 — 4  of FIG. 3; 
     FIG. 5 is an enlarged fragmentary view of a portion of the filter apparatus generally denoted by numeral  5  in FIG. 4; and 
     FIG. 6 is a partial bottom perspective view of the filter cartridge of FIG.  2 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With initial reference to FIG. 1, a portion of a filter apparatus (or baghouse) utilizing filter cartridges made in accordance with the present invention is designated generally by the reference numeral  10 . The filter apparatus  10  includes a tube sheet  12  and a plurality of filter cartridges  14 . Typically, tube sheet  12  separates a clean air plenum above the tube sheet from a dirty air plenum located below the sheet. Tube sheet  12  includes a plurality of openings  16  typically arranged in an array. The filter cartridges  14  are held on the underside of tube sheet  12  in communication with openings  16 . When the filter apparatus  10  is in operation, air is forced through the filter cartridges  14  to remove particulate material previously suspended in the air flowing from the dirty air plenum to the clean air plenum. 
     With reference to FIG. 2, each filter cartridge  14  includes a unitary filter element  18  and a reusable mounting plate  20 . Filter element  18  includes a tubular filter  22  secured between a mounting cap  30  and an end cap  31 . Tubular filter  22  (also referred to as a pleat pack, filter media, or filter sheet) is formed of a pleated filtration media arranged in a generally cylindrical shape defining a central chamber  24 . The surface of tubular filter  22  may include dimples (not shown) to prevent engagement of one pleat to the adjacent pleat. The tubular filter  22  is formed about, and abuts against, a tubular support screen  26 . Preferably, screen  26  is made from of a light metal, but may also be manufactured from a group of other materials typically used for screens such as plastic. A plurality of straps  28  are secured about the outer circumference of the filter sheet  22 . These straps  28  are preferably formed from a woven synthetic material such as plastic or a similar material having a relatively high tensile strength. The straps  28  are permanently positioned about the circumference of tubular filter  22  by securing the ends of each strap to one another and adhering the straps to the filtration media with a hot melted adhesive. The straps  28  ensure the dimensional stability of the tubular filter  22 , particularly when air is pulsed from the central chamber  24  through the tubular filter and outwardly into the dirty air plenum during the filter cartridge cleaning process. 
     With reference to FIGS. 2 and 3, mounting cap  30  is located at one end of tubular filter  22 . The annular mounting cap  30  has an inner edge  33  (FIG. 3) and an outer edge  35 . The diameter D 1  at inner edge  33  is somewhat smaller than the inner diameter of tubular filter  22 . In the preferred embodiment, the mounting cap  30  extends radially outwardly from the circumference of the tubular filter  22  and includes a downwardly facing ledge  32  (as viewed in FIGS.  4  and  5 ). Ledge  32  and the opposing, uppermost surface  36  of mounting cap  30  are generally planar. An arcuate surface  37  (FIG. 5) extends between ledge  32  and surface  36 . Preferably, mounting cap  30  is made from a potting compound such as a cast, molded or extruded polymer. As is well understood in the art, the potting compound is heated within a mold defining the shape of the mounting cap  30 . The edge of tubular filter  22  and the upper edge of support screen  26  are placed in the mold in the potting compound. The potting compound cures to shape and encases the tubular filter  22  and support screen  26 . 
     A gasket  38  is located in an annular channel  40  formed in the surface  36  of mounting cap  30 . Preferably, as best shown in FIG. 5, an annular channel  40  has a generally rectangular cross-section in upper surface  36 . In the preferred embodiment, the channel  40  locates and supports the gasket  38  so it extends axially away from surface  36  of the mounting cap  30 . An adhesive such as a high strength glue is placed within channel  40  and the prefabricated gasket  38  is placed therein. In the preferred embodiment, the gasket  38  is made of a foam material. 
     Alternatively, if a channel is not utilized to locate the gasket  38 , the gasket may be applied by foaming the gasket in place onto surface  36 . In another alternative, the upper surface  36  would include a male protrusion that is matingly received in a groove formed within a prefabricated gasket  38  to secure the gasket to upper surface  36 . In these alternative embodiments, a urethane gasket is secured to mounting cap  30  by a contact cement or similar adhesive and treated by a sulfur or peroxide curing process. 
     With reference to FIGS. 2 and 6, end cap  31  has an annular ring  42  and a steel dome  44  that enclose the bottom of tubular filter  22 . The steel dome  44  has a generally cylindrical portion  46  and a dome section  48 . Like the mounting cap  30 , the annular ring  42  is preferably made from a suitable potting compound such as a cast, molded or extruded polymer. The tubular filter  22  and steel dome  44  are placed within a mold and secured to end cap  31  by casting the potting compound around the components. Specifically, the steel dome  44  is embedded near the inner diameter of the annular ring  42  by placing the cylindrical portion  46  into the mold for forming the annular ring. The dome  44  may include a flange (not shown) formed normally to the cylindrical portion  46  to facilitate a firm connection between dome and bottom cap  31 . 
     With reference to FIG. 2, reusable mounting plate  20  is generally rectangular and has an opening  50 . The mounting plate  20  is preferably made from a sheet metal, such as steel. In the preferred embodiment, the comers of the mounting plate are removed and the sides of the plate (FIG. 2 and 3) turned upwardly at right angles to form a plurality of upstanding flanges  52 . The diameter D 2  of opening  50  (FIG. 2) is somewhat greater than the diameter of the openings  16  of the tube sheet  12  and less than the diameter D 3  of upper ledge  32  at outer edge  35  (FIG.  3 ). Opposite flanges  52  of the mounting plate  20  are spaced apart a distance greater than the diameter D 3  of the ledge  32  of mounting cap  30 . The combined height H of the mounting plate  20  and mounting cap  30  is less than the space between a known support structure in a “closed” position and the tube sheet  12  of the filter apparatus  10 . 
     In the preferred embodiment shown in FIGS. 3 and 4, a support structure is shown as a pair of longitudinal locking bars  54 . Generally, the locking bars  54  underlie tube sheet  12  and are movable from a first position at a distance from the tube sheet and a second position relatively closer to the tube sheet. For example, the filter element locking mechanism disclosed in U.S. Pat. No. 4,322,231 to Hilzendeger and Masuda includes such a support structure and locking bars. 
     In operation, to mount and secure the unitary filter element  18  in the filter apparatus  10 , end cap  31  of filter element  18  is placed within opening  50  of the reusable mounting plate  20 . 
     Next, tubular filter  22  is slidingly received within opening  50  and the mounting plate  20  is moved upwardly, as viewed in FIG. 2, relative to the unitary filter element  18 . As best shown in FIGS. 4 and 5, the mounting plate  20  contacts and abuts ledge  32 . Next, the mounting plate  20  is placed on the locking bars  54  and slid so that the central filter chamber  24  is in communication with an opening  16  on tube sheet  12 . The process is repeated until each of the openings  16  in the tube sheet  12  has a respective filter element  18  disposed below it. 
     In the preferred embodiment, as shown in FIG. 3, a flange  52   a  of a mounting plate  20   a  may contact a flange  52   b  of an adjacent mounting plate  20   b  when placed on the locking bars  54 . During this initial loading process, the support structure, specifically the locking bars  54 , are in the first position at a distance away from tube sheet  12  (if used in a system with locking structure as disclosed in U.S. Pat. No.  4,322,231).  When all of the filter cartridges  14  are in the appropriate position, the locking bars  54  are moved to the second position relatively closer to tube sheet  12 . In this position, the gasket  38  engages the underside of tube sheet  12  to form a seal between the unitary filter element  18  and the tube sheet  12 . Thus, when the filter apparatus  10  is in operation, the air within the dirty air plenum passes through tubular filter  22  and is forced upwardly through central filtering chamber  24  and ultimately opening  16  of the tube sheet  12  without escaping at the connection between the filter element  18  and the tube sheet  12 . 
     After extensive use and cleaning through conventional techniques, the filter elements  18  eventually lose their effectiveness. When this occurs, a support structure (such as the mechanism taught by U.S. Pat. No. 4,322,231) may be manipulated so that the locking bars  54  are in their first position at a distance from the tube sheet  12  and the filter cartridges  14  may be slidingly removed. Once the cartridges  14  are removed from the filter apparatus  10 , the mounting plates  20  are removed from the filter elements  18 . After the filter elements  18  are discarded, new filter elements may be placed in the filter apparatus using the reusable mounting plates  20  as described above. 
     From the foregoing it will be seen that this invention is one well adapted to attain all the ends and objects hereinabove set forth, together with the other advantages which are obvious and which are inherent to the invention. It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims. Since many possible embodiments may be made of the invention without departing from the scope thereof, it is understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.