Abstract:
A filter wall and method of making the filter is disclosed. The filter includes a filter wall having at least one layer of filter media. A first end cap is disposed at one end of the filter wall and a second end cap is disposed at a second end of the filter wall. An elongated support extends between the first end cap and the second end cap and is fastened to each, for example, by way of a mechanical fastener. In one embodiment, the mechanical fastener may include a rivet. The filter is devoid of adhesive material and avoids the penetration of the filter media by the mechanical fasteners. The use of mechanical fasteners enables the filter to be used in high temperature environments without concern for failure due to degradation of adhesive materials. Additionally, the use of mechanical fasteners enables the simple and efficient refurbishment and reconditioning of a filter after the filter media has become sufficiently spent.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims the benefit of U.S. Provisional Application No. 60/643,293, filed Jan. 12, 2005. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention is generally related to filtration apparatuses and, more particularly, to filtration structures or apparatuses used to filter particulates or other matter from a fluid stream and which are capable of withstanding elevated temperatures without failure or substantial degradation of the filtration structure.  
         [0004]     2. State of the Art  
         [0005]     Filtration apparatuses, referred to herein generally as filters, are utilized in numerous environments and processes. Generally, filters are utilized to separate two or more components from one another as a mixture of such components is passed through the filter. For example, filters are often used to separate or remove particulates from a fluid stream, the fluid being either a liquid or a gas. Removal of the particulates may be to harvest the particulate matter from the fluid stream for further processing, to provide a more purified fluid stream, or for both purposes. In one example, particulates may be filtered from a stream of water for purification purposes of the water. In another example, minerals may be filtered out of a slurry for further processing and refinement.  
         [0006]     Similarly, particulates may be removed from a gaseous stream for purification of the gas. The gas may, for example, be used in a combustion process wherein it is desirable to eliminate particulate matter prior to the combustion process because presence of such particulates might be harmful to the combustion apparatus or otherwise reduce the efficiency of the combustion process. In another example, a gaseous stream produced by a combustion process may be filtered to remove particulates that are potentially dangerous to the surrounding environs, including the air being breathed by individuals in a location where the combustion gas is being exhausted.  
         [0007]     In many industrial environments, filtering of the exhaust gas produced by machinery and equipment is required and is heavily regulated by government institutions. For example, the Mine Health and Safety Administration (MSHA) and the National Institute for Occupational Safety and Health (NIOSH) impose various regulations on the type of emissions that are allowed in various environments including underground mining operations. Such exhaust may include, for example, that of diesel equipment. In one particular example, diesel equipment utilized in underground mining operations is heavily regulated regarding exhaust emissions and, particularly, regarding the emission of diesel particulate matter (DPM).  
         [0008]     Referring to  FIGS. 1 and 2 , a prior art filter  100  is shown which is used to filter diesel particulate matter from an exhaust stream of diesel powered equipment. The filter  100  is shaped generally as a cylindrical or annular member. Generally, the filter  100  may be positioned so that a fluid (exhaust) stream passes into the center area  102  and is forced through a filter wall  104  of the filter, which wall contains a filter media. Of course the fluid stream path could be in the reverse direction such that the fluid travels through the filter wall  104  into the center area  102 . After passing through the filter wall  104  and its associated filter media, the filtered fluid stream may be exhausted from the associated system or it may be further filtered or processed depending on the specific application and associated regulations or other requirements.  
         [0009]     The filter  100  is constructed from a number of individual components. For example, the filter  100  includes a first end cap  106  and a second end cap  108  that are coupled to respective ends of the filter wall  104 . The filter wall  104  contains one or more layers of filter media  110  ( FIG. 2 ) through which the fluid stream is passed. As a part of the filter wall, the filter media  110  may be contained and supported by an inner radial support  112  and an outer radial support  114  which may comprise, for example, mesh or screen. The radial supports  112  and  114  are generally configured to support the filter media  110  while still allowing a fluid stream to pass therethrough.  
         [0010]     The end caps  106  and  108  are generally configured as annular, cup-like structures covering the longitudinal end portions of the filter media  110  and associated supports  112  and  114 . The end caps  106  and  108  are maintained in place relative to the filter media  110  and the supports  112  and  114  by means of an adhesive material  116 .  
         [0011]     A filter  100 , constructed as described with respect to  FIGS. 1 and 2 , should generally provide satisfactory filtering performance assuming that the temperature of the environment in which the filter  100  is placed is not elevated to a level that results in degradation and failure of the adhesive  116 . Unfortunately, many applications or environments in which such filters  100  are required expose the filter  100  to temperatures beyond the performance limit of available adhesive materials. One such application includes the use of filters in what is known as “nonpermissible” equipment.  
         [0012]     In accordance with United States Government standards, mobile, diesel-powered equipment may be classified as “permissible” or “nonpermissible.” The “permissible” classification indicates that the equipment is authorized for service in various environments and applications including various underground mining applications. In order to be classified as “permissible” equipment, certain criteria set forth in 30 Code of Federal Regulations (CFR) Part 36 must be met. While 30 CFR Part 36 provides various technical requirements that define whether a mobile diesel powered machine is to be classified as “permissible” or not, one requirement is that permissible equipment or machines cool the diesel exhaust before releasing it into the atmosphere. Specifically, 30 CFR § 36.25(c) states that permissible equipment must include an exhaust cooling system capable of reducing the temperature of the undiluted exhaust gas to less than 170° F. at the point of discharge from the cooling system.  
         [0013]     Nonpermissible equipment, one the other hand, is not required to have its exhaust cooled. The practical effect is that a filter configured to operate in equipment classified as being permissible, such as a filter  100  utilizing an adhesive material  112 , will likely be inappropriate for use in equipment that is “nonpermissible” due to the elevated temperatures to which the filter will likely be exposed. At best, a filter utilizing adhesive materials will fail at a faster rate when placed in an environment with an elevated temperature and, therefore, require more frequent replacement when used in nonpermissible equipment.  
         [0014]     While filters have recently been produced using “ceramic” type adhesives which provide for exposure to relatively higher temperatures for relatively longer periods of time, such adhesives are more expensive and are still prone to temperature-induced failure. Additionally, even with higher temperature adhesives, an operator of both permissible and nonpermissible equipment will either have to purchase, stock and maintain multiple types of filters (i.e., one type for permissible equipment and another type for nonpermissible equipment) or will have to buy all of its filters with high-temperature adhesive so as to enable the filters to be compatible with both types of equipment.  
         [0015]     One attempt to produce filters without adhesive materials includes that which is disclosed by U.S. Patent Publication No. US 2004/0154977 A1 (hereinafter the “Wells publication”). This publication discloses a filter which avoids the use of “potting compounds” in assembling the filter and, instead, secures the end caps to the filter material by use of mechanical fasteners. However, the fastening of the ends caps directly to the filter material by penetration of the filter material with a mechanical fastener results in a potential fluid stream bypass path which will allow an amount of fluid to pass therethrough without being filtered. In other words, penetration of the filter media by a mechanical fastener creates the extreme likelihood that an opening will be formed through which fluid may travel instead of having to pass directly through the fluid media for removal of particulates or other matter. In essence, penetration of the filter media results in the creation of a “short circuit” in the fluid path relative to the filter media allowing a portion of the fluid to bypass the filtering process.  
         [0016]     In view of the shortcomings in the art, it would be advantageous to provide a filter and method of manufacturing such a filter that enables the use of the filter in high temperature environments, such as with so-called impermissible equipment, without the limitations imposed by adhesive materials and without undesired penetration of the filter media. Additionally, it would be advantageous to provide a filter which is relatively inexpensive to construct such that a single style filter may be stocked and utilized regardless of whether it is expected to be used in high temperature or relatively low temperature applications. It would further be advantageous to provide a method of manufacturing such a filter and a method of refurbishing and reconditioning such a filter.  
       BRIEF SUMMARY OF THE INVENTION  
       [0017]     In accordance with one aspect of the invention a filter is provided. The filter comprises a filter wall comprising at least one layer of filter media. A first end cap is disposed at a first end of the filter wall and a second end cap is disposed at a second end of the filter wall. At least one elongated support is positioned to extend between the first end cap and the second end cap. A first mechanical fastener couples a first end of the at least one elongated support to the first end cap, and a second mechanical fastener couples a second end of the at least one elongated support to the second end cap. The filter wall may be configured as a cylindrical or annular filter wall and may include a material such as fiberglass for the filter media. The filter may include additional components such as, for example, support structures in association with the filter media.  
         [0018]     In accordance with another embodiment of the invention, a method of manufacturing a filter is provided. The method includes providing a filter wall having at least one layer of filter media. A first end cap is disposed at a first end of the filter wall and a second end cap is disposed at a second end of the filter wall. At least one elongated support is disposed between the first end cap and the second end cap and is mechanically fastened to the first end cap and the second end cap.  
         [0019]     In accordance with yet another embodiment of the present invention, another method of manufacturing a filter is provided. The method includes providing a filter wall having at least one layer of filter media, providing a first end cap and a second end cap, and coupling the first end cap to a first longitudinal end of the filter wall and coupling the second end cap to a second longitudinal end of the filter wall without the use of adhesives and without penetration of the at least one layer of filter media.  
         [0020]     In accordance with yet a further aspect of the present invention, a method of refurbishing a filter is provided. The filter being refurbished includes a filter wall with at least one layer of filter media, a first end cap disposed at a first end of the filter wall, a second end cap disposed at a second end of the filter wall, an elongated support extending between the first end cap and second end cap, and at least one mechanical fastener connecting the elongated support and the first end cap. The method of refurbishing the filter comprises removing the at least one mechanical fastener, removing the first end cap and replacing the at least one layer of filter media with at least one other layer of filter media. The first end cap is repositioned at the first end of the filter wall and the elongated support is mechanically refastened to the first end cap.  
         [0021]     In accordance with yet another aspect of the present invention, a filtration system is provided. The filtration system includes equipment including a fluid source configured to produce a fluid stream. A flow path, including a housing, is coupled with the fluid source. A filter is disposed in the housing. The filter may comprising a filter wall comprising at least one layer of filter media, a first end cap disposed over a first longitudinal end of the filter wall, a second end cap disposed over a second longitudinal end of the filter wall, at least one elongated support extending between the first end cap and the second end cap, a first mechanical fastener coupling a first end of the at least one elongated support to the first end cap, and a second mechanical fastener coupling a second end of the at least one elongated support to the second end cap. The flow path is configured to direct the fluid to the filter, through the filter wall and out an exit formed in the housing. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0022]     The foregoing and other advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings in which:  
         [0023]      FIG. 1  is perspective view of a prior art filter;  
         [0024]      FIG. 2  is partial cross-sectional view of the filter shown in  FIG. 1 ;  
         [0025]      FIG. 3  is a perspective view of a filter in accordance with one embodiment of the present invention;  
         [0026]      FIG. 4  is a side plan view of the filter shown in  FIG. 3 ;  
         [0027]      FIG. 5  is a cross-sectional view of the filter shown in  FIG. 3 ;  
         [0028]      FIG. 6  is a partial cross-sectional view of the filter shown in  FIG. 3 ; and  
         [0029]      FIG. 7  is a schematic of a system including a filter in accordance with an embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0030]     Referring to  FIGS. 3 and 4 , a filter  200  is shown that may be used, for example, in filtering particulates or other matter from a fluid stream. The filter  200  is configured as a generally cylindrical or annular shaped structure. Depending on the application and on the specific type of equipment in which the filter is installed, a fluid stream, such as an exhaust stream from a diesel or other combustion type engine, may be directed into the center volume  202  of the filter and then directed through the filter wall  204  of the filter  200  (which defines the center volume  202  or area). The filter wall  204  contains a filter media as shall be discussed in further detail below.  
         [0031]     As the fluid stream passes through the filter media of the filter wall  204 , particulates of a specified type or size may be captured by the filter media to remove them from the gas stream. The filtered gas stream may then be exhausted or further filtered or processed depending on the specific application and environment. Of course, a fluid stream may be directed in the reverse direction such that it passes through the filter wall  204  into the center area  202  of the filter  200  and then subsequently exhausted. The fluid flow path may depend, for example, on the specific equipment or environment in which the filter  200  is disposed.  
         [0032]     It is noted that the filter wall  204 , while depicted as being cylindrical or annular, may exhibit other geometries and configurations. For example, the filter wall  204  may be constructed as a flat panel wherein a fluid flow path simply traverses the filter wall from a first side thereof to a second side thereof. Additionally, rather than cylindrical, the filter wall  204  may exhibit geometries, such as a polygonal cross-sectional geometry, as taken substantially transverse to its longitudinal axis, and may or may not exhibit an enclosed or circumscribed geometry.  
         [0033]     The filter  200  is formed of a number of individual components, including a pair of end caps  206  and  208  which are disposed at the longitudinal ends of the filter wall  204 . In one embodiment, the end caps  206  and  208  may be configured to substantially cover the longitudinal ends of the filter wall  204  such as seen in  FIG. 6 .  
         [0034]     As seen in  FIGS. 5 and 6 , the filter wall  204  is constructed of a number of components including one or more layers of filter media  210 . The filter media  210  may be formed from a number of different materials depending, for example, the type of fluid stream anticipated to flow therethrough as well as the type of particulates or other material being filtered from the fluid stream. In one particular embodiment, the filter media  210  may comprise a fiber glass material formed generally as a sheet. As shown in  FIG. 5 , the filter material may be configured in the form of what is known as a pleated pack. The use of a pleated pack provides a structure which increases the surface area of the exposed filter media  210 . While not expressly shown in the drawings, a light gauge mesh or wire screen may be disposed on one or both sides of the filter media  210  and be conformal therewith such that it too exhibits a pleated configuration to provide a measure of structural support to the filter media  210 .  
         [0035]     Additionally, the filter media  210  may be disposed between a first support structure  212 , located radially inwardly of the filter media  210 , and a second support structure  214  that is disposed radially outwardly of the filter media  210 . The support structures  212  and  214  are configured to allow passage of a fluid stream therethrough and may be formed, for example, of a screen or mesh material that is generally a heavier gauge material than the conformal mesh or screen discussed hereinabove. In one exemplary embodiment, the support structures  212  and  214  may be formed of expanded metal. The support structures  212  and  214  serve to structurally support and contain the filter media  210  disposed therebetween.  
         [0036]     Still referring to  FIGS. 3 and 4 , a plurality of elongated supports  216  are disposed adjacent the cylindrical wall  202  and extends between the end caps  206  and  208 . The elongated supports  216  are coupled with the end caps  206  and  208  so as to couple the various components (e.g., support structures  212  and  214 , filter media  210 , and end caps  206  and  208 ) together as a unified structure. As shown in  FIGS. 5 and 6 , the elongated support structures  216  may be placed adjacent the second support structure  214  and positioned such that the radially outer wall  220  of an end cap  206  covers or conceals the longitudinal end  222  of a given elongated support  216 .  
         [0037]     It is noted that the presently disclosed embodiment shows the elongated supports  216  located only adjacent the second support structure  214  (i.e., along the outer radial side of the filter wall  204 ). However, in other embodiments, the elongated supports may be located adjacent the first support structure  212  (i.e., along the inner radial side of the filter wall  204 ) or adjacent both support structures  212  and  214 . When the filter wall  204  is cylindrically configured, or exhibits another circumscribing geometry, placement of the elongated supports  216  only adjacent the radially outer side of the filter wall  204  provides adequate support to couple the filter  200  together while greatly simplifying the assembly and manufacture of the filter  200 .  
         [0038]     In one embodiment, the elongated support  216  may be fastened to the radial outer wall  220  of the end cap by way of a mechanical fastener  224 . In one particular example, the mechanical fastener may be in the form of a rivet. Use of a rivet to fasten the end caps  206  and  208  with the elongated supports  216  enables simple and efficient assembly and manufacture of the filter  200 . It is specifically noted that the mechanical fastener  224  does not penetrate the filter media  210 , although it may or may not be coupled with a support structure  214 .  
         [0039]     In other embodiments of the present invention, the mechanical fastener  224  may include a screw or some other threaded fastener. In yet other embodiments of the invention, the elongated support members may be joined to the end cap by means of a spot weld or by brazing. However, such thermomechanical means of joining may not provide the same advantages in the assembly and construction of the filter  200  and, further, may not provide the same reliability as a strictly mechanical means of fastening when the filter is intended to be placed in high temperature environments.  
         [0040]     Referring more specifically to  FIG. 6 , in one embodiment, an end layer of filter media  226  is disposed between an end cap  206  and the cylindrical wall  202  to prevent particulates from flowing through such a path without being properly filtered. The end layer of filter media  226  may be stapled or otherwise fixed to the end cap  206 . In another embodiment the end layer of filter material may be held in place by compression effected between the end cap and the cylindrical wall  202 . In either case, the elongated supports  216  may be used to help control the amount of compression between the end caps  206  and  208  and the cylindrical wall  202 .  
         [0041]     For example, the elongated supports  216  may be configured to exhibit a predetermined length relative to a length of the cylindrical wall  202  to provide an abutment against which the end caps  206  and  208  may bear. In other words, the difference in length exhibited by the elongated supports  216  as compared to the cylindrical wall  202  may be used to control the amount of compression experienced by the end layer of filter media  226  when the end caps  206  and  208  are assembled on to the filter  200  and fixed to the elongated supports  216 .  
         [0042]     It may be desirable to control the amount of compression experienced by the end layer of filter media  226 , for example, to prevent the ends of the support structures  212  and  214  from cutting the filter media  226  and thereby provide an unfiltered flow path for any fluid being passed through the filter  200 .  
         [0043]     The elongated supports  216 , therefore, may be configured as members that experience tension between the end caps  206  and  208 , such as a guy or a stay, they may be configured to act in compression, such as a columnar member, or they may be configured to provide support in both tension and compression.  
         [0044]     The configuration of the filter  200  provides various advantages over prior art filters that are constructed using an adhesive to bond the end caps to, for example, the cylindrical wall of the filter. As previously discussed, a filter utilizing adhesive is subject to thermal degradation and failure when the adhesive is exposed to elevated temperatures, such as when they are installed in impermissible equipment. The filter  200  of the present invention does not rely on adhesive materials to join any of its components and, therefore, is substantially more reliable than adhesively joined filters in high temperature environments. Similarly, in certain applications where the filter is exposed to corrosive or caustic environments, an adhesive may be adversely affected while the mechanically joined filter  200  of the present invention provides improved reliability and more predictable performance.  
         [0045]     To further enhance the reliability and performance of the filter  200 , various components may be constructed of materials capable of withstanding high temperatures, corrosive environments, or both. In one embodiment, the end caps  206  and  208 , the support structures  212  and  214 , and the elongated supports  216  may be formed of a material comprising, for example, steel, stainless steel, other metals or metal alloys, or combinations of such materials.  
         [0046]     It is further noted that the configuration of the filter  200  of the present invention enables simple recycling, refurbishing and reconditioning thereof. For example, after the filter media  210  of a given filter has captured a significant amount of particulates or other filtered matter, it becomes “clogged” or “plugged” such that the flow rate of fluid that may pass through the filter media is sufficiently reduced. Thus, with the configuration of the present invention, the mechanical fasteners  224  may be removed and the filter  200  disassembled. The old filter media  214  may be replaced by new filter media and the filter  200  may be reassembled, again using mechanical fasteners  224  (which mechanical fasteners may the same as those removed or they may be new mechanical fasteners replacing the old ones). Prior art filters utilizing adhesive materials do not accommodate the refurbishing and reconditioning of used filters with such simplicity and efficiency.  
         [0047]     Referring now to  FIG. 7 , a system  300  is shown in which a filter  200  constructed in accordance with an embodiment of the present invention is utilized. The system includes equipment  302  that produces a fluid stream from a fluid source  304 . For example, the equipment  302  may include stationary or mobile equipment having a combustion engine wherein the exhaust of the combustion engine is the fluid source  304 . Various examples of such equipment may include underground mining equipment such as scoops and shield haulers and other related equipment, although the present invention is not limited to such equipment.  
         [0048]     The fluid source  304  produces fluid which passes to the filter  200  which is disposed in a an associated housing  306 . The fluid is passed to the center volume  202  ( FIG. 3 ) of the filter  200  and through the filter wall  204  ( FIGS. 3 through 6 ) such as previously discussed and as indicated by directional arrows  308 . The filtered fluid (i.e., the fluid that has passed through the filter wall  204 ) may then be directed from the housing  306  as indicated by directional arrow  310  and exhausted to atmosphere or it may be additionally filtered or processed as desired.  
         [0049]     It is noted that additional layers of filter media  312  and  314  may be strategically placed between the filter  200  and housing  306 , such as adjacent the end caps  206  and  208 , such that any potential fluid path other than that through the filter wall  204  still provides filtering of the fluid stream. Thus, if fluid were to attempt to bypass the filter wall  204  and travel between the end caps  206  and  208  and the adjacent surfaces of the housing  306 , the fluid would still pass through one or more layers of filter media  312  and  314  to capture particulates or other matter.  
         [0050]     While the invention may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. However, it should be understood that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the following appended claims.