Abstract:
A filter medium, which is resiliently expandable in an axial direction and is able to deform the filtration gaps in size in accordance with its expansion, including a compression limiting member for providing required filtration gaps by limiting the amount of compression applied to the filter medium. The filter medium is held by a holder in such a manner that the amount of compression may be adjustable.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a filter element to be used in a filtering apparatus for filtering a fluid. 
     DESCRIPTION OF THE RELATED ART 
     Conventionally, as a filter element to be attached to the filtering apparatus for filtering a fluid, various kinds of filter elements having various structures are known. 
     Filter elements as described above are, however, generally disposable type, and even though they are reusable by cleaning, much time and effort is required to recover them because it is hard to remove foreign materials deposited thereon, or sometimes they have to be soaked into a specific chemical agent for a long time to remove the same. 
     Therefore, it would be desirable if foreign materials deposited on a filter element can be easily removed and thus the filter element is easily recovered for reuse. 
     DISCLOSURE OF THE INVENTION 
     An object of the present invention is to provide filter elements with enhanced ease-of-handle features and excellent usability which can filter out foreign materials to be removed from a fluid satisfactorily and from which deposited foreign materials blocking the filtration gaps can be easily washed out in a short period of time. 
     In order to achieve above described challenge, according to the present invention, a filter element comprising a cylindrical filter medium and a holder for holding the filter medium is provided. The filter medium is constructed to be resiliently expandable in the direction of axis and to be subject to deformation of the filtration gaps in varying sizes in accordance with the expansion thereof. The filter medium includes a compression limiting means for providing required filtering gaps by limiting the amount of compression applied to the filter medium, and is held by the holder in such a manner that the amount of compression can be adjusted. 
     According to the present invention, the filter medium is made of a hard resilient material having no compressibility in itself. 
     According to a detailed embodiment of the present invention, the filter medium is formed by winding a resilient wire rod in a helical fashion including filtration gaps between adjacent wound portions and a plurality of notches for providing the filtration gaps between adjacent wound portions. The notches may be formed by bending parts of the resilient wire rod. 
     According to another detailed embodiment of the present invention, the filter medium is formed by stacking a plurality of annular resilient plates, and each plate has a plurality of spring portions for resiliently widening the space between adjacent plates and a plurality of projections for providing filtering gaps between adjacent plates when the filter medium is under compression. The spring portions and projections may be formed by making incisions on the plate and raising them up. 
     According to still another detailed embodiment of the present invention, the filter medium is formed by stacking a plurality of annular spring members and a plurality of annular gap forming members alternately in layers. The spring members are corrugated in the direction of their thickness to be resiliently deformed into the shape of flat plates when the filter medium is under compression. The gap forming members is provided with a plurality of radially extending filtration channels thereon. The filtration channels may be formed on both front and back surfaces of the gap forming members. 
     The filter element according to the present invention, having structure described so far, is provided with required filtration gaps in the state that the filter medium is compressed to ensure that a fluid is filtered through these filtration gaps. In order to release the compressed state of the filter medium for cleaning, the filtration gaps can be expanded sufficiently by manual operation, by means such as an actuator, or by resilience of a resilient wire rod and/or resilient plates which constitute the filter medium, so that foreign materials deposited on the filter element may be removed easily and satisfactory. 
     In other words, in the case where the filter medium is configured in the form of coil by a resilient wire rod, when it is under compression, the filtration gaps are provided by notches formed on the resilient wire rod, and when it is removed from the filtering apparatus, the resilient wire rod is expanded because the filter medium is released from compressed state and thus the filtration gaps widen more or less uniformly. 
     In the case where the filter medium is configured by annular resilient plates, when it is under compression, the filtration gaps in constant widths are provided by means of projections formed on the respective plates, and when it is released from the compressed state, the filtration gaps provided between adjacent plates is widened by spring portions formed on the respective plates. 
     In addition, in the case where the filter medium is configured by stacking spring members and gap forming members alternately, when the filter medium is under compression, the spring members are flattened into the shape of plates respectively and then filtration gaps of uniform width are provided by the filtration channels formed on the gap forming members. When compression is released, the filtration gaps are widened by restoration of spring members corrugated in the direction of the thickness. 
     Since the filtration gaps of the filter element can be easily widened as described above, foreign materials filtered out may easily be removed by cleaning. Especially when the filter medium is formed of separate resilient plates or spring members, or of the gap forming members etc., easier cleaning is ensured because they may be disassembled into pieces for cleaning. In addition, the above mentioned disassembled members may be reassembled with relative ease and thus foreign materials may be removed more easily. With such a structure, the filter element itself is readily recoverable and reusable. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1 is a sectional side elevation view of a filter element according to the first embodiment of the present invention; 
     FIG. 2 is a horizontal sectional view of the same filter element; 
     FIG. 3 is a side elevational view of a resilient wire rod under compression; 
     FIG. 4 is a side elevational view of the same resilient wire rod in the state where compression is released; 
     FIG. 5 is a sectional side elevational of a laminated body of plates according to the second embodiment illustrating the compressed state; 
     FIG. 6 is a plan view of the same laminated body of plates; 
     FIG. 7 is a sectional side elevational of the same laminated body of plates illustrating the state where compression is released; 
     FIG. 8 is a sectional side elevational view of a filter element according to the third embodiment; 
     FIG. 9 is a plan view of the same; 
     FIG. 10 is a side elevational view of the third embodiment illustrating the state where compression of the laminated body formed of spring members and gap forming members is released; 
     FIG. 11 is a plan view of the same gap forming member; 
     FIG. 12 is an enlarged end view of the gap forming member taken on line A—A of FIG. 11; and 
     FIG. 13 is a plan view of a spring member according to the third embodiment. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings, there are shown some preferred embodiments of a filter element according to the present invention in detail. FIGS. 1-4 show the first embodiment of a filter element of this invention. 
     A filter element  1  is to be mounted in the filtering apparatus for filtering a fluid, comprising, as shown in FIGS. 1 and 2, a cylindrical filter medium  3  which is resiliently expandable in the direction of axis, and a holder  5  for holding the filter medium  3  in the compressed state. 
     The filter medium  3  is, as shown in FIG. 2-4, formed by winding a hard resilient wire rod  3   a  made of material having no compressibility in itself such as metal or ceramics in a helical fashion, and is provided with a designated number of notches  7  per unit turn formed by locally bending parts of the resilient wire rod  3   a  nearly equidistantly. As clearly shown in FIG. 3, the formation of such notches  7  provides filtration gaps corresponding to the height of the notches  7  between adjacent parts of winding when the filter medium  3  is compressed. Therefore, the notches  7  constitute a compression limiting means for providing required filtration gaps by limiting the amount of compression applied to the filter medium  3 . The filter medium  3  is held by the holder  5  with its ends caught between an end plate  13  and a movable plate  15  of the holder  5 . 
     The holder  5  comprises, as shown in FIGS. 1 and 2, a plurality of guide bars  17  surrounding the filter medium  3  equidistantly, end plates  11 ,  13  secured to the both ends of these guide bars, and a movable plate  15  mounted to the guide bars between these end plates  11 ,  13  in inserted state and movable only in directions along these guide bars. 
     The end plate  11  is provided with a cylindrical guide cylinder portion  11 A extending through the center portion of the holder  5  toward the other end plate  13 , and within the guide cylinder portion  11 A, a rotating body  19  having a threaded portion  19   a  on its periphery is rotatably received and retained by a C-frame retaining ring. The movable plate  15  is slidably fitted around the outer surface of the guide cylinder portion  11 A of the end plate  11  via a O-ring  23  and has a cylindrical portion  15 A extending toward the same direction as the guide cylinder portion  11 A, and on the inner surface of the end portion of the cylindrical portion  15 A, there is provided a threaded portion  15   a  for screwing in the threaded portion  19   a  prepared on the outer surface of the rotating body  19 . In this arrangement, by rotating the rotating body  19 , the movable plate  15  may be reciprocated along the guide bars  17 . 
     By placing the filter medium  3  between the end plate  13  and a movable plate  15  and moving the movable plate  15  toward end plate  13  while rotating the rotating body  19 , the filter medium  3  is compressed until the position where respective notches  7  come into pressing contact with adjacent wound portions, and thereby the filter medium  3  is held by a holder under compression with filtration gaps provided between adjacent wound portions by notches  7 . 
     Reference numbers  25  and  27  in FIG. 1 denote packings mounted on the outer surfaces of the end plates  11  and  13 , respectively. 
     In the filter element  1  of the first embodiment having above described structure, filtration gaps of the predetermined widths are provided on its side wall by means of notches  7  formed on a resilient wire rod  3   a  (FIG.  3 ), and thereby a fluid flowing between the inside and the outside of a cylindrical filter medium  3  is filtered. When the filter medium  3  is resiliently expanded (FIG. 4) by moving the movable plate  15  away from the end plate  13  along the guide bar  17  while rotating the rotating body  19  in the holder, the filtration gaps may be sufficiently widened. 
     Therefore, when cleaning the filter element, foreign materials filtered out by the filter element  1  may be removed easily and satisfactory, and thereby the filter element  1  itself may be recovered and reused. 
     Referring now to FIGS. 5-7, there are shown the second embodiment of the filter element of the present invention. In the filter element of the second embodiment, a filter medium  33  to be held under compression by the holder  5  is formed by stacking a plurality of annular resilient plates  33 A in a cylindrical shape. 
     Respective plates  33 A are made of a hard material such as metal or ceramics as in the case of the resilient wire rod  3   a,  and comprise a plurality of spring portions  33   a  for resiliently widening gaps between adjacent plates  33 A and a plurality of projection  33   b  as compression limiting means for providing required filtration gaps between adjacent plates  33 A when the filter medium  33  is compressed. These spring portions  33   a  and projections  33   b  are formed by making evenly spaced incisions on the plate  33 A in the same direction and raising them up. Respective plates  33 A are then stacked on top of each other with the positions of spring portion  33   a  of adjacent plates  33 A staggered alternately by half a pitch to form the laminated body  33 . 
     Since the holder used in the second embodiment may employ the same structure as the first embodiment, FIGS. 1 and 2 may be referred to know the structure of the holder and thus it is not specifically shown in a figure here. 
     In the filter element of the second embodiment with the structure described above, the filter medium  33  formed by stacking annular plates  33 A is held by the holder  5  under compression as shown in FIG.  5 . At this time, the spring portions  33   a  of respective plates  33 A are deformed to the extent where the projections  33   b  come into contact with adjacent plates  33 A, and thereby between adjacent plates  33 A,  33 A, there are formed filtration gaps of a width provided by the height of the projections  33   b.    
     On the other hand, when compression applied to the filter medium  33  is released, as shown in FIG. 7, the filter medium  33  is expanded by resilient restoring force of the spring portions  33   a  of respective plates  33 A, and consequently the filtration gaps between adjacent plates  33 A,  33 A are widened almost uniformly. 
     Accordingly, since the filtration gaps of the filter medium  33  in the filter element may be widened easily, foreign materials filtered out may be removed easily by cleaning. 
     Especially, the filter medium  33  of the second embodiment is formed of a plurality of plates  33 A which can be disassemble, cleaning may be performed for each individual plate  33 A after disassembling them into pieces, which makes removal of foreign materials by cleaning easier. Moreover, restacking of plates in this case is also easy. 
     Referring now to FIGS. 8-13, there are shown the third embodiment of the present invention. The filter element  61  of the third embodiment is configured in such a manner that the filter medium  63  to be held by the holder  65  under compression is formed in generally cylindrical shape by stacking a plurality of annular spring members  63 A and a plurality of annular gap forming members  63 B as compression limiting means alternately in layers. 
     The spring members  63 A are, as seen in FIG.  10  and FIG. 13, corrugated in the direction of thickness so that they may resiliently widen the gaps between adjacent gap forming members  63 B when the filter medium  63  is not compressed, and they may be resiliently deformed into flat plates to come into intimate contact with the gap forming members  63 B when the filter medium  63  is compressed. In FIG. 13, parts  63   c  designate upwardly raising convex surfaces, and parts  63   d  designates downwardly depressed concave surfaces. 
     The gap forming members  63 B are, as shown in FIGS. 11 and  12 , have a plurality of radially extending filtration channels  63   b  on both front and back surfaces, and the filtration channels on the upper surface  63   b  are displaced from the filtration channels on the lower surface  63   b  by half a pitch. 
     On the other hand, the holder  65  is, as shown in FIGS. 8 and 9, comprises two end plates  71 ,  73  for catching the filter medium  63  from both sides, a tension bolt  75  for adjusting the distance between these end plates  71 ,  73 , and a plurality of guide bars  77 ,  78  for supporting the filter medium  63  from inside. 
     On the inner surfaces of the end plates  71 ,  73 , there are provided supporting members  71 A,  73 A. On one supporting member  71 A, one end of the tension bolt  75  is secured by means of nuts  74   a,    74   b,  and on the other supporting member  73 A, the other end of the tension bolt  75  is secured by a butterfly nut  74   c,  and the tension bolt  75  may be expanded and contracted by rotating the butterfly nut  74   c  to adjust the distance between the end plates  71  and  73 . 
     The guide bars  77 ,  78  have a length shorter than the axial length of the holder  65  but longer than a half the axial length thereof, and are mounted to respective end plates  71 ,  73 . In other words, the end plate  71  located at the bottom of the holder is provided with guide bars  77  mounted in the direction of the axis of the holder  65  at equiangular intervals, and the upper end plate  73  is provided with other guide bars  78  mounted at equiangular intervals so as not to cause interference with the guide bars  77 . These guide bars  77 ,  78  support spring members  63 A and gap forming members  63 B which constitute the filter medium  63  from the inside to maintain their stacked shape. 
     The filter medium  63  is disposed between the end plates  71 ,  73  with the guide bars  77 ,  78  inserted into the end plates  71 ,  73 , and held between the end plates  71 ,  73  under compression by tightening the butterfly nut  74   c  and thereby contracting the tension bolt  75 . 
     In the filter element  61  of the third embodiment having above described structure, when the filter medium  63  formed by stacking annular spring members  63 A and annular gap forming members  63 B alternately is compressed by the holder  65 , the spring members  63 A are flattened and brought into intimate contact with the gap forming members  63 B so that a constant filtration gaps are formed by the filtration channels  63   b  provided on both front and back surfaces of the gap forming members  63 B. 
     On the other hand, when compression applied by the holder  65  is released, the filtration gaps between adjacent gap forming members  63 B are expanded due to restoration of the spring members  63 A into corrugated shape. 
     The holder  5  of the first and second embodiments and the holder  65  of the third embodiment described above may be used respectively for holding filter medium of other embodiments as well. In other words, the holder  5  may be used also for holding the filter medium  63  of the third embodiment comprising spring members  63 A and gap forming members  63 B, while the holder  65  may be used for holding the filter medium  3  and  33  of the first and second embodiments as well. 
     Especially when the holder  65  of the third embodiment is used for holding the filter medium  33  of the second embodiment, as shown in FIG. 6, a plurality of recesses  33   c  may be provided radially on the inner radius of the plate  33 A so that the guide bars  77 ,  78  mounted on the holder  65  may be fitted into these recesses  33   c.  In this case, the recesses  33   c  are to be formed as many as the number of the guide bars  77 ,  78 . 
     The structure of the holder is not limited to ones illustrated in respective embodiments, and other appropriate structures may be employed as far as they can hold the filter medium under compression. 
     As described so far, according to the present invention, the filter element which may filter out foreign materials to be removed contained in a fluid satisfactory, and may be cleaned easily in a short period of time for reuse is provided.