Abstract:
A filter holder assembly includes at least one frame having a peripheral wall and an inwardly directed peripheral edge substantially perpendicular to said peripheral wall and adapted to support a filter. At least one cam lock lever is secured to the peripheral wall at a first predetermined distance from the inwardly directed peripheral edge for compressing the filter in the frame and against said inwardly directed peripheral edge. The cam lock lever has a handle portion at one end thereof and a cam head provided with a cam foot at an opposite end thereof. The cam lock lever is rotatable to cause the cam foot to move between an open position and clamping position where the cam foot exerts a compressive force on the filter.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This invention relates to turbine inlet air filtration systems and, more specifically, to a filter holding frame assembly that incorporates devices for holding one or more filters in a surrounding frame. 
         [0002]    Gas turbines used for power generation are frequently located in industrial areas close to other combustion sources where the local atmosphere can contain high levels of small particulates such as carbon. Power plants may also be located in deserts and other arid environments where high levels of particulates such as sand can also significantly impair the performance of the turbine. It is therefore essential that inlet air filtration systems be optimized to minimize negative impact on turbine performance due to particulate-laden air. 
         [0003]    In the past, filters have been retained in their respective holding frames by various methods. For example, a lift and drop method has been used where a holding frame is comprised of horizontal channels, the top channel being deeper than the bottom channel. This allows a filter to be inserted into the top channel and then dropped into the bottom channel. The advantage of this method is simplicity and lack of clips and/or clamps. However, the sealing of the filter and its frame relies on the airflow through the filter creating a force that compresses the filter gasket. As a result, the sealing is not 100 percent effective. Moreover, due to the weight of typical V-cell filters, this method is not suitable for front panel filters. A spring clip method has also been used where four (4) spring clips are located in the respective corners of each filter to provide a more positive compression of the filter gasket. This method is more complex and costly, however, and the spring clips are not robust. Another technique employs a screw-clamp located in each corner of the filter for compressing the filter gasket. Effective compression of the gasket is achievable, but difficult to confirm. With this technique, removal and replacement of filters is a time-consuming process, due to the length of the screws employed. The screws also pose a potential health and safety risk to the extent they protrude from the holding frame. Moreover, None of the above methods are suitable for both retention and sealing of back-to-back V-cell filters in a single frame assembly. 
       BRIEF SUMMARY OF THE INVENTION 
       [0004]    In accordance with a first exemplary but non-limiting embodiment, there is provided a filter holder assembly comprising at least one frame having a peripheral wall and an inwardly directed peripheral edge substantially perpendicular to the peripheral wall and adapted to support a filter; at least one cam lock lever secured to the peripheral wall at a first predetermined distance from the inwardly directed peripheral edge for compressing the filter in the frame and against the inwardly directed peripheral edge, the cam lock lever having a handle portion at one end thereof and a cam head provided with a cam foot at an opposite end thereof, wherein the cam lock lever is rotatable to cause the cam foot to move between an open position and a clamping position wherein, in the clamping position, the cam foot exerts a compressive force on the filter. 
         [0005]    In another aspect, the invention relates to a filter holder assembly comprising a plurality of frames in a substantially planar grid, each of the plurality of frames defined by a peripheral wall including two pair of substantially parallel side walls and an inwardly directed peripheral edge adapted to support a filter, the grid including at least one group of four mutually adjacent frames wherein four converging side walls of the four mutually adjacent frames, respectively, intersect to define four corner quadrants, and wherein each of the four converging side walls is common to two of the four mutually adjacent frames; the peripheral wall having a height sufficient to support two filters in stacked relationship; each of the four corner quadrants having a first cam-lock lever secured by a pivot pin to one of the four converging side walls at a first predetermined distance from the inwardly directed peripheral edge for clamping one of the two filters against the inwardly directed peripheral edge, and a second cam lock lever secured by a pivot pin to an adjacent one of the four side walls at a second predetermined distance from the inwardly directed peripheral edge for clamping the other of the two filters against the first of the two filters; each of the cam lock levers comprising a handle portion at one end thereof and a cam head at an opposite end thereof, the lever rotatable to cause the cam foot to move between an open position and a clamping position wherein the cam head exerts compressive force on a respective one of the filters. 
         [0006]    In still another aspect, the invention relates to A cam lock lever for holding a filter in a filter frame comprising an elongated handle portion at one end and a substantially circular cam head at an opposite end; and a cam foot extending laterally away from the substantially circular cam head. 
         [0007]    The invention will now be described in connection with the drawings identified below. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a front elevation view of a single filter frame in accordance with an exemplary but nonlimiting embodiment of the invention; 
           [0009]      FIG. 2  is a bottom plan view of the filter frame shown in  FIG. 1 ; 
           [0010]      FIG. 3  is a cross section taken along the line  3 - 3  of  FIG. 1 ; 
           [0011]      FIG. 4  is a side elevation of the frame shown in  FIG. 1 ; 
           [0012]      FIG. 5  is a cross section taken along the line  5 - 5  of  FIG. 1 , but with a filter in place and a cam lock lever installed; 
           [0013]      FIG. 6  is a partial section with the filter frame of  FIG. 5  turned ninety degrees and showing the cam lock lever in locked and unlocked (in phantom) positions; 
           [0014]      FIG. 7  is a side view of a cam lock lever in accordance with an exemplary but nonlimiting embodiment of the invention; 
           [0015]      FIG. 8  is an edge view of the cam lock lever shown in  FIG. 7 ; 
           [0016]      FIG. 9  is a cross section similar to  FIG. 5  but showing a further exemplary embodiment where back-to-back cam lock levers are used to clamp adjacent filters within a multi-filter frame assembly; 
           [0017]      FIG. 10  is a cross section similar to  FIG. 5  but showing a further exemplary embodiment where two filters are stacked in tandem within frame, and clamped by a pair of cam lock levers oriented at ninety degrees relative to each other; 
           [0018]      FIG. 11  is a partial perspective view of the stacked filter arrangement shown in  FIG. 10 ; 
           [0019]      FIG. 12  is a partial cross section showing an alternative pivot mount arrangement for a cam lock lever; 
           [0020]      FIG. 13  is a side elevation showing a tool used to swage the pivot pin shown in  FIG. 12 ; and 
           [0021]      FIGS. 14A and 14B  are section and side elevation views, respectively, showing an operating handle or tool for use with the cam lock lever shown in the various Figs. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0022]    With reference initially to  FIG. 1-4 , a filter holding frame  10  in an exemplary but non-limiting embodiment is substantially square in shape with two pair of substantially parallel side walls  12 ,  14 ,  16  and  18 . At the respective lower edges of the walls, horizontal support flanges  20 ,  22 ,  24  and  26  are provided for supporting a substantially planar and substantially square filter as described further herein. Opposed side walls  14  and  18  are each provided with a pair of holes  28 , while side walls  12  and  16  are each provided with a pair of holes or apertures  30 . In the exemplary embodiment, holes  28  are located approximately 73 mm from the lower edge of the walls while holes  30  are located at approximately 43 mm above the lower edge of the walls. The frame as shown is designed to hold a single filter, or a pair of filters stacked in tandem. In the latter instance, in holes  28  and  30  support cam-locking devices at different elevations relative to the support flanges  20 ,  22 ,  24  and  26  as described further herein. The locations of the holes may vary, of course, depending on specific applications. 
         [0023]      FIG. 5  illustrates a portion of a substantially-square filter  32  having a resilient gasket  34  applied about the lower peripheral edge of the filter. The filter is supported on the lower horizontal support flanges  20 ,  22 ,  24  and  26  of the filter holding frame  10 .  FIG. 5  also illustrates a cam lock lever  36  mounted by way of a pivot pin  35  in one of the holes  30  of the filter holding frame  10 . With reference to  FIGS. 7 and 8 , the cam lock lever  36  comprises an elongated handle portion  38  at one end and a substantially-circular cam head  40  at an opposite end. The cam head  40  mounts (or is formed with) a laterally-extending cam foot  42  that is generally aligned along the longitudinal axis of the lever  36 . The cam foot  42  is formed to include a lateral extension  44  which is located axially beyond the radiused surface of the cam head  40  via tab  45 , and is provided on one or both ends with a chamfered or upturned edge  46 , the purpose for which will be described later herein. Centrally-located within the cam head  40 , there is a mounting hole or aperture  50  also aligned along the longitudinal axis of the lever. The aperture  50  is adapted to receive the pivot pin  35  illustrated in  FIG. 5  by which the cam lock lever  36  is rotatably mounted to the frame  10  via hole  30 . 
         [0024]    With specific reference to  FIGS. 5 and 6 , it will be appreciated that the location of the holes  30  in the holding frame side walls  12  and  16  is selected such that the cam lock levers  36  can move between open and clamped positions where, in the open position, the cam foot  42  may lightly engage, for example, the holding frame side wall  16  as shown in  FIG. 6 , and when rotated 90 degrees to the clamped position, the cam foot  42  will engage the upper surface  52  of the filter  32  with the chamfered or upturned edge  46  providing a smooth engagement with the filter in the direction of rotation of the lever  38 , and then compress the filter  32  and the gasket  34  against the horizontal support flange  20  to thereby clamp and seal one corner of the filter  32  in place within the holding frame. Note also that the cam lock lever  36  is formed with an offset  48  which, at best appreciated from  FIG. 5 , provides space between the holding frame side wall  12  and the handle portion  38  to reduce friction and to facilitate gripping and rotation of the handle portion  38 . It will be understood that cam-lock levers  36  may be installed in each of the four corners of the filter, utilizing the four mounting holes  30  as arranged in  FIG. 1-4 . 
         [0025]    In an alternative arrangement in  FIG. 9 , a filter-holding frame assembly includes adjacent filter-holding frames  10 ,  110 , formed in part by a double-thickness, common side wall  112 . In this embodiment, a second cam lock lever  136  may be installed with the first lever  36  but on the opposite side of the side wall  112 . An extended pivot pin  35  enables assembly of the double cam lock lever. In this way, one double-cam lock device can be used to independently clamp two adjacent filters  32 ,  132  and their respective gaskets  34 ,  134  on adjacent support surfaces  20 ,  120  in the adjacent holding frames  10 ,  110 . 
         [0026]    It will be appreciated that the filter-holding frame assembly may be enlarged to include, for example, a planar grid that includes one or more groups of four mutually adjacent filter frames where four side walls converge at an intersection defining four corner quadrants, respectively, of four mutually adjacent frames. Each of the four intersecting side walls is common to two of the four mutually adjacent frames. If desired, one, two or all four of the side walls may be provided with a double-cam lock lever device as described above, proximate the intersection. This arrangement may be repeated throughout the grid as desired. 
         [0027]    It will be appreciated, however, that the present invention is not limited to any particular holding frame arrangement. 
         [0028]    An alternative pivot pin construction particularly useful in the multi-cam lock lever arrangement of  FIG. 9  is shown in  FIG. 12 . The pivot pin  52  includes a first pin component  54  that is received within a second pin component  56 . When mounting the cam lock levers  36 ,  136  to a frame-holding wall  112 , the pivot pin assembly is installed from opposite sides of the holding frame wall, and a tool  60  is then used to swage the hollow end of the first pin component  54  radially outwardly into locking engagement with a beveled edge  62  of the second pin component  56  to thereby permanently secure the cam lock lever  36  to the holding-frame wall. 
         [0029]    In another exemplary embodiment, as best seen in  FIGS. 10 and 11 , a pair of filters  32 ,  232  may be stacked in tandem when a single holding frame  10  in which case, additional cam lock levers  64 ,  164  may be secured by means of the vertically-spaced holes  28  on the holding frame side walls  14 ,  18  and utilized to clamp the second or stacked filter  232  in substantially the same manner as described above. It will be appreciated that the cam lock levers mounted in the holes  30  extend substantially 90 degrees relative to the cam lock levers mounted in the holes  28 . Thus, for a stacked arrangement, four cam lock levers may be used to clamp the corners of the lower or downstream filter  32  and four cam lock devices may be used to clamp the corners of the upper or upstream filter  232  but arranged at a 90 degree angle relative to the cam lock levers clamping the lower filter. 
         [0030]    This arrangement allows the upper or upstream filters  232  to be removed from the filter holding frame while the underlying lower or downstream filter  32  remains clamped and sealed within the holding frame. This is important in that any particles dislodged due to removal/replacement of the upstream filter will not pass the downstream filter and, by keeping the downstream filter clamped and sealed, no dislodgement of any particles occurs at the downstream filter. 
         [0031]    As apparent from  FIG. 11 , the stacked filters  32 ,  132  are shown in one of four partially shown mutually perpendicular filter frames. It will be appreciated that double-cam lock lever devices may be employed here as well to conveniently lock the filters in the respective adjacent frames, with a double-cam lock lever secured to each of the four intersecting holding frame side walls as described above. 
         [0032]    It is another feature of the invention that the cam lock levers and the holding frame side walls be provided with cooperating projections and detents to prevent accidental movement of the cam lock levers from either the open or closed (i.e., clamped) position. More specifically, detents  66  ( FIG. 11 ) are provided in the holding frame side walls where they are engaged by projections  68  stamped or otherwise formed in the cam lock levers  32 ,  232  in both the open and closed (or clamped) positions. Other substantially equivalent means for providing the retention or locking function may be employed as well. 
         [0033]      FIG. 13  illustrates a tool stand assembly  70  employed to support the tool  60  used to deform the pivot pin assembly  52  shown in  FIG. 12 . The tool  60  may be adjusted along vertical and horizontal shafts  72 ,  74  to locate the tool  60  as needed. At the same time, the frame  112  is held in a U-shaped support frame  76 . Note that in this view, the individual cam-lock levers are only partially shown. 
         [0034]    Turning now to  FIG. 14 , a cam lock lever operating handle or tool  78  may be slidably attached to the distal end of the elongated handle portion  38  cam lock lever  36  to facilitate rotation. The tool  78  is comprised of a hollow sleeve that includes a first portion  80  that is substantially coaxial with the handle portion  38  and an angled portion  82  that extends angularly away from the first portion  80 . The angled portion  82  provides a more convenient gripping surface for the user as the cam lock lever is rotated between its open and closed (or clamped) positions. 
         [0035]    While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.