Patent Publication Number: US-2021162326-A1

Title: Gas filtration apparatus

Description:
This application claims priority to U.S. Provisional No. 62/942,342, filed Dec. 2, 2019, the complete disclosure of which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     This application relates generally to an improvement in gas filtration products and methodologies. More specifically, it relates to a customizable, modular assembly of parts used to secure a large surface area of a media substrate into a limited space without limitations on the size or configuration of the media “capsule”. 
     Gas filtration is extremely important in microelectronic industries, medical industries, and other numerous industries. Gas filters come in a few different arrangements, mainly surface mount filters, in-line filters, and point-of-use filters. Surface mounted filtration devices are often used in applications where floor space is restricted. An arrangement of valves, flow controllers, and other elements can be implemented as needed using a surface mount fitting. 
       FIG. 1  illustrates a simple, exemplary surface mount fixture  10  that is intended for use with a filtration device having filter media positioned within a surrounding housing. The mount  10  provides a gas inlet port  18  and a center-line aligned port  16 . The port  16  is typically an outlet port, but in some cases could be used as an inlet port. As shown in  FIGS. 2A and 2B , a filtration device  20  with a cylindrical casing  22  may be secured to the mount&#39;s attachment fixture  14  so that the cylindrical base  12  of the mount  10  acts to close off the bottom of the device&#39;s casing  22 . Typically, the filtration device  20  has an annular cylindrical filter medium  24  with a central passage  26  that may be closed off at its upper end by the top of the casing  22  and that is aligned with the exit port  16 . The filter medium  24  is sized and positioned so that when the device  20  is installed on the surface mount  10 , gas entering through the a second port  18  flows into the interior of the casing  22  surrounding the filter media  24 . By establishing a pressure differential between the inlet port  14  and the first port  16 , particle laden gas is drawn radially through the filter medium  24  into the central passage  26 . The filter medium  24  is configured to prevent passage of particles exceeding a predetermined size, thereby removing them from the gas flow. 
     The standard for surface mounts and other vertically configured filters is to have the filtration media be of a sintered porous metal design. Companies often develop this technology in-house. The development task is cumbersome and entails numerous months or years of development cycling. The resulting media tend to be expensive and may have a relatively short life-span. 
     SUMMARY OF THE INVENTION 
     An illustrative aspect of the invention provides a filtration element assembly for use in conjunction with a cylindrical filter casing having a casing diameter. The filtration element assembly comprises a prismatic support body having top and bottom base walls and a plurality of rectangular side walls connecting the top and bottom base walls. The top, bottom and side walls define a support body interior space. The side walls collectively form a polygonal outer cross-sectional shape defining a circumscribed circle having a circumscribed circle diameter less than or equal to the casing diameter. The base wall has an outlet flow passage formed there-through. At least one of the side walls has an inlet flow passage formed-there-through with a filtration element receiving channel surrounding the inlet flow passage. The filtration element assembly further comprises a porous filtration structure disposed within the filtration element receiving channel of each of the at least one of the side walls so as to cover the inlet flow passage. The filtration structure is configured for removing particulate matter from a gas flow passing there-through. The filtration element assembly also comprises; a clamping member attached to each of the at least one side wall. Each clamping member has a framing portion and a flange portion. The framing portion extends along a full length and a full width of said at least one side wall and has a flow window formed there-through in registration with the inlet flow passage. The flange portion extends from the framing portion and is sized and configured for reception into the receiving channel to engage and retain the filtration element within the receiving channel. 
     Another illustrative aspect of the invention provides a filtration apparatus comprising a cylindrical casing, having a longitudinal casing centerline, a cylindrical wall having an inside diameter, and first and second end caps. The cylindrical wall and first and second end caps define a casing interior space. The casing has a first flow port formed through the first cap along the casing centerline and a second flow port formed through one of the first and second end caps. The filtration apparatus further comprises a prismatic support body disposed within the cylindrical casing along the longitudinal casing centerline. The support body has top and bottom base walls and a plurality of side walls connecting the top and bottom base walls. The top, bottom and side walls define a support body interior space and the base wall has an outlet flow passage formed there-through. At least one of the side walls has an inlet flow passage formed-there-through and a filtration element receiving channel surrounding the inlet flow passage. The support body is secured to the first end cap so that the outlet flow passage is in registration and fluid communication with the first flow passage. The filtration apparatus still further comprises a porous filtration structure disposed within the filtration element receiving channel of each of the at least one of the side walls so as to cover the inlet flow passage. The filtration structure is configured for removing particulate matter from a gas flow passing there-through. The filtration apparatus also comprises a clamping member attached to each of the at least one side wall. Each clamping member has a framing portion and a flange portion. The framing portion extends along a full length and a full width of said at least one side wall and has a flow window formed there-through in registration with the inlet flow passage. The flange portion extends from the framing portion and is sized and configured for reception into the receiving channel to engage and retain the filtration element within the receiving channel. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention can be more fully understood by reading the following detailed description together with the accompanying drawings, in which like reference indicators are used to designate like elements, and in which: 
         FIG. 1  is a perspective view of a prior art filtration apparatus surface mount; 
         FIG. 2A  is a perspective view of a prior art filtration apparatus mounted to the surface mount of  FIG. 1 ; 
         FIG. 2B  is a perspective view of the apparatus of  FIG. 2A  with its cylindrical cover removed; 
         FIG. 3  is a perspective view of a filtration apparatus according to an embodiment of the invention mounted to the surface mount of  FIG. 1 ; 
         FIG. 4  is a front view of the filtration apparatus of  FIG. 3 ; 
         FIG. 5  is a side view of the filtration apparatus of  FIG. 3 ; 
         FIG. 6  is a longitudinal section view of the filtration apparatus of  FIG. 3 ; 
         FIG. 7  is a longitudinal section view of the filtration apparatus of  FIG. 3 ; 
         FIGS. 8A, 8B and 8C  illustrate top, front and side views respectively of a filtration apparatus support body according to an embodiment of the invention; 
         FIG. 9  is a lateral section view of the filtration apparatus of  FIG. 3 ; 
         FIG. 10  is a lateral section view of the filtration apparatus of  FIG. 3 ; 
         FIG. 11  is a perspective view of the filtration apparatus of  FIG. 3  with the cylindrical cover removed; 
         FIG. 12  is a exploded perspective view of a filtration element assembly according to an embodiment of the invention; 
         FIG. 13  is a front view of a filtration apparatus according to an embodiment of the invention; and 
         FIG. 14  is a longitudinal section view of the filtration apparatus of  FIG. 13 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     While the invention will be described in connection with particular embodiments, it will be understood that the invention is not limited to these embodiments. On the contrary, it is contemplated that various alternatives, modifications and equivalents are included within the spirit and scope of the invention as described. In the description of the invention, the majority of references are to an example used as a surface mount. If otherwise, it will be stated. 
     While surface mounted filters have significant advantages, they are often restricted to a small surface footprint. Accordingly, their main scalable feature is height. Although it is possible to increase the filtration area of sintered porous metal media by extending the height of the cylindrical filter element, the cost may be prohibitive. Embodiments of the present invention provide planar filter media elements and media retention mechanisms that may be less costly and allow the use of media materials that may not be usable in cylindrical media configurations. The height of such media elements is virtually unlimited, and filtration performance can meet or exceed that of comparable sintered metal media. 
     Filtration devices of the invention may use a cylindrical casing similar to (but typically longer than) the casing  22  of  FIG. 2A  and may be adapted for use with standard surface mounts like the mount  10  of  FIG. 1 . These devices use an annular center body to support planar, vertically mounted filter media elements that are held in place by clamping members. The combined media retention assembly is configured to fit within the cylindrical casing while maximizing the challenge area of the filter media. The center body is typically formed as a prism-shaped body with a polygonal cross-section. This provides flat faces on one, some, or all of the sides through which flow windows are formed. The planar filtration media elements are positioned so as to span these windows. Frame-like clamping members are attached to the center body so as to hold the media elements in place. 
       FIGS. 1-12  illustrate an exemplary filtration apparatus  1000  according to an embodiment of the invention. While the filtration apparatus  1000  is illustrated in conjunction with the surface mount  10  of  FIG. 1 , it will be understood that it is usable with or may be adapted for use with other surface mount configurations. The filtration apparatus  1000  has a cylindrical casing  1050  with that has a closed upper end  1054  and an open base end that, upon installation of the apparatus  1000  on the surface mount  10 , is sealed by the base  12  of the mount  10 . The casing  1050  has an interior space  1052  and an inside diameter C D . 
     The filtration apparatus  1000  may incorporate a filtration element assembly  100  according to a particular embodiment of the invention. The assembly  100  has a prismatic center support body  110  that has a constant, polygonal outside cross-section along its longitudinal axis  118 . In the illustrated embodiment, the polygonal cross-section is rectangular, but other shapes may also be used. Regardless of the number of sides, the polygonal cross-section defines a circumscribed circle C I  that is centered on the longitudinal axis  118  and has a diameter that is less than (or, in some embodiments, equal to) the inside diameter C D  of the casing  1050 . This allows the support body  110  to be received into the interior space  1052  of the casing  150 . The support body  110  has top and bottom walls  117 ,  119  and a number of rectangular side walls  111  equaling the number of sides in the polygonal cross-section. The top, bottom and side walls  117 ,  119 ,  111  collectively define a support body interior space  112 . The bottom wall  119  has a centerline-aligned support body exit port  114  formed there-through. An annular attachment flow fitting  115  may be attached to the bottom wall  119  at the exit port  114  to provide for aligned attachment of the support body  110  to the surface mount  10  and to provide for fluid communication between the support body exit port  114  and the surface mount exit port  16 . 
     In the rectangular support body  110 , two opposing sides  111   b ,  111   d  of the support body  110  have flow windows  116  formed there-through to provide communication between the interior space  112  and the exterior of the support body  110 . The remaining two side walls  111   a ,  111   c  are closed. It will be understood that, while the illustrated embodiment has two walls  111  with flow windows  116 , any number of side walls  111  may have a flow window  116 . Each wall  111  having a flow window  116  also has a recessed receiving channel  113  surrounding the flow window  116 . The receiving channel  113  is sized and configured to receive a filter medium structure  150  that fits within the recessed channel  113  so that the medium structure  150  spans across the flow window  116 . 
     The filter medium structure  150  includes one or more filtration media elements. These media elements are each substantially self-sustaining planar members that are configured to screen particulate matter from gas flowing through the elements. The filter medium structure  150  may be configured to have desired flow-through, porosity, and filtration characteristics. In some embodiments, the filter medium structure  150  may consist of a single filtration medium layer. In other embodiments, the filter medium structure  150  may have multiple filtration medium layers. In the illustrated embodiment, each flow window  116  has an associated filtration element  150  that has an outer filter medium element  130 A,  130 B and an inner filter medium element  140 A,  140 B. The inner and outer filter medium elements  140 ,  130  may have different materials, structures, flow and/or filtration characteristics. In some embodiments, the inner and outer filter elements  140 ,  130  may be attached to one another to form a single filter element structure. 
     The individual filtration medium layers may be or include any substantially planar screening structure formed from materials suitable to the gas environment and the desired particle removal size. Particularly suitable filtration media are or include self-sustaining fiber structures, particularly those formed from metal fibers. As used herein, “self-sustaining” means that the fiber medium has sufficient structural integrity to withstand the pressure differential across the flow window  116  without additional reinforcement. The integrity of such structures can be established through a high level of entanglement and compression or through bonding (e.g., by sintering) of the fibers at spaced apart points of contact. In some embodiments, a metal fiber filtration medium may be constructed from a single highly convoluted and entangled fiber or from a plurality of entangled fibers. Typical metal fiber diameters may range from 1-100 μm. Suitable materials for the metal fibers used in the above-described filter media may include stainless and other steels as well as other alloys including, but not limited to nickel alloys and Hastelloy® alloys. The specific metal(s) can be selected based on, for example, expected temperature/environment and corrosion resistance. In some embodiments, the filtration media elements may be or include structures that are formed from sintered metal powder or a sintered combination of entangled metal fiber(s) and metal powder. 
     The filter medium structure  150 , generally, and the filter medium elements, in particular, can be tailored to provide desired filtration characteristics. In typical applications, the filter medium structure can be configured to remove particles having an effective diameter greater than 1.000 micron. In particular applications the filter medium structure  150  can be configured to remove particles having an effective diameter greater than 0.100 μm. As noted above, the inner and outer filter medium elements  140 ,  130  may have varying characteristics. In some cases, the outer filter medium element  130  may be configured to screen only particles having a relatively high diameter, while the inner filter medium element  140  may be configured to screen smaller particles. In a particular example, the outer filter medium element  130  could have a porosity in a range of 50-80 percent (more particularly, 60-70 percent) and the inner filter medium element  140  could have a porosity in a range of 30-60 percent (more particularly, 40-50 percent. This form of staged filtration can serve to prevent clogging and consequent increased pressure loss through the life of the filtration apparatus  100 . Any number of media elements can be used to provide the desired filtration gradient. Alternatively, a single media element having a variable porosity gradient may be used. By staging filtration media, efficient filtration of particles down to 0.003 μm can be achieved without producing undesirable pressure losses or reducing the life of the device. 
     The filter medium structure  150  is sized so that it completely covers the flow window  116  and fits into the recessed receiving channel  113  surrounding the flow window  116 . The initial thickness of the filter medium structure  150  may be greater than the depth of the receiving channel  113  so that subsequent placement of the filter retention clamping member results in compression of the portion of the filter medium structure  150  surrounding the flow window  116 . 
     As best seen in  FIG. 12 , the filtration element assembly  100  has two clamping members  120 A,  120 B that serve to hold the filter medium structures  150 A,  150 B in place within the receiving channels  113  of the support body  110 . It will be understood that embodiments having additional flow windows and filter medium structures will also have corresponding clamping members. Each clamping member  120  has a frame portion  122  having a flat, inward facing surface  123  that engages a support body side wall  111   a  or  111   c . A flange portion  124  extends inwardly from the flat surface  123 . A clamp member window  121  extends through the frame portion  122  and the flange portion  124 . When the filtration assembly  100  is assembled, the clamp member windows  121  are in registration with the flow windows  116  of the support body  110 . The perimeter of the flange portion  124  is sized and shaped to correspond to the shape of the receiving channel  113  for reception therein. The frame portion  122  is configured so that the perimeter dimensions of the flat surface  123  matches those of the side walls  111   a ,  111   c . The longitudinal cross-section of the flange portion  124  (best seen in  FIG. 9 ) is configured so that the combined support body  110  and clamping members  120 A,  120 B fit within the cylindrical casing  1050 . In particular embodiments, the flange portion  124  may be configured so that the combined support body  110  and clamping members  120 A,  120 B collectively form a polygonal cross-sectional shape that defines a circumscribed circle, which may be the same circle C I  defined by the cross-section of the support body  110  alone. In such embodiments, the cross-section of the flange portion  124  may be a trapezoid as in the illustrated embodiment. In other embodiments, the outer portion of the frame portion  122  may be curved to fit within the casing  1050 . 
     When the filtration element assembly  100  is assembled, the filter medium structures  150 A,  150 B are disposed or partially disposed within the receiving channels  113 . The clamping members  120 A,  120 B are then mated to the support body  110 . In accomplishing this, the flange portions  124  are inserted into the receiving channels  113  to engage and compress the filter medium structures  150 A,  150 B. When the flange portions  124  are fully inserted, the flat surface  123  of the clamping member  120 A engages the surface of side wall  111   b  and the flat surface  123  of the clamping member  120 B engages the surface of side wall  111   d . The clamping members  120  may be attached to the support body  110  in this configuration by any suitable means such as welding or bonding. 
     The support body  110  and the clamping members  120  may be formed from any materials that provide sufficient rigid support for the filter element structures  150  and that will retain structural integrity under expected environmental conditions. Such materials may include, but are not limited to stainless and other steels as well as other alloys including, but not limited to nickel alloys and Hastelloy® alloys. 
     The filtration element assembly  100  may be received into the cylindrical casing  1050  and the two mounted to the surface mount  10  as shown in  FIGS. 5-7 . In this configuration, particle laden gas may be introduced through the surface mount port  18  into the casing interior space  1052  surrounding the filtration element assembly  100 . The particle laden gas is then drawn through the filter element structures  150 A,  150 B into the support body interior  112 , thereby producing filtered gas, which then passes out through the support body exit port  114  and the surface mount port  16 . 
     It will be understood that in some embodiments, the upstream and downstream flow directions may be reversed. In such embodiments, the in-flow of gas would be through the port  16  and the out-flow through port  18 . This would put the challenge side of the filter medium structure  150  inside the support structure interior  112  with the gas flow outward through the filter media. 
     The filtration element assembly  100  may also be used in “in-line” applications gas flow line applications. With reference to  FIGS. 13 and 14 , a filtration apparatus  2000  has a cylindrical casing  2050  with an upper end  2054  having an inlet port  2055  and a lower end  2056  having an outlet port  2057 . An inlet fitting  2060  having an inlet flow channel  2062  is attached to the upper end  2054  and an outlet fitting  2070  having an outlet flow channel  2072  is attached to the lower end. The fittings  2060 ,  2070  are configured for connection to gas flow lines and to provide fluid communication from such lines into and through the filtration apparatus  2000 . The casing  2050  has an interior space  2052  and an inside diameter C D . 
     While the attachment fitting  115  may be adapted for use in the in-line configuration, the filtration element assembly  100  is substantially unchanged from the configuration described above for use with a surface mount. As before, the filtration element assembly  100  may be sized to maximize filtration flow area within the limits of the diameter of the surrounding casing  2050 . If length is not a limiting factor, the casing  2050  and the filtration element assembly may be lengthened to increase filtration area and efficiency. In the in-line configuration, particle-laden gas is brought into the casing interior  2052  through the inlet fitting  2070  from an upstream gas line. The particle laden gas passes through the filter element structures  150 A,  150 B into the support body interior  112 , thereby producing filtered gas, which then passes out through the exit fitting  2070  to a downstream gas line. 
     It will be understood that in some embodiments the flow direction of particle laden gas may be in the reverse direction so that the port  2057  through the lower end  2056  operates as an inlet and the port  2055  through the upper end  2054  operates as an exit. 
     The filtration apparatus of the present invention provide significant performance advantages over prior art ‘sintered powder media’ apparatus. Exemplary test results have shown that filtration apparatus of the invention having the same challenge surface area as a comparable cylindrical sintered metal apparatus may provide lower pressure loss across the filtration media, higher flow rates, and longer life within the same cross-sectional footprint. These performance advantages may be further enhanced through the use of staged media layers. The planar filtration media used in the apparatus of the invention are also less expensive to manufacture and allow a high degree of flexibility in producing desired filtration efficiencies. The filtration apparatus of the invention are not limited to any particular size, flow rate, or environment. 
     It will be readily understood by those persons skilled in the art that the present invention is susceptible to broad utility and application. Many embodiments and adaptations of the present invention other than those herein described, as well as many variations, modifications and equivalent arrangements, will be apparent from or reasonably suggested by the present invention and foregoing description thereof, without departing from the substance or scope of the invention.