Abstract:
The present invention relates to a filtering apparatus including a filter element formed by winding thin paper into a rolled state, and a method of manufacturing a filter element roll for the filtering apparatus, and is intended to provide a highly accurate filtering capability irrespective of a single-tier construction.  
     The thin paper unwound from the wide rolled paper material is separated by a slitter, and a corrugation forming roller having a circumferential groove formed for each paper strip of thin paper is disposed downstream of the slitter, so that corrugations is continuously formed at one end of the divided paper strip with respect to the centerline by the circumferential groove. By winding the thin paper having corrugation, a filter element roll having a higher density at one end than the other end is obtained.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a filtering apparatus using a filter element manufactured by winding a thin paper into a rolled state and a method of manufacturing a rolled filter element to be used therefor, and is suitable for removing foreign substances in lubricating oil systems such as a bearing.  
           [0003]    2. Description of the Related Art  
           [0004]    A type of filtering apparatus is well known in which the filtering apparatus is manufactured by the steps of winding a wide piece of thin paper from a rolled paper material, cutting the thin paper into a plurality of narrow pieces by means of a slitter, winding each narrow piece in a rolled state to produce a filter element, press fitting the filter element into a case having a large opening at one end and a center hole at the other end, and further press fitting the case into a housing. The filtering apparatus is used by introducing a fluid to be filtered {such as lubricating oils} into the housing whereby the fluid is flown from the inlet end of the filter element to the other end thereof so that foreign substances in the fluid is colleted.  
           [0005]    In the filtering apparatus of this type, since foreign substances in fluid are captured by paper fibers together constituting the rolled filter element, it is required to increase the filter density of the filter element in order to improve the capturing accuracy to the level in which small foreign substances can surely be captured. However, if the filter density of the filter element is increased, foreign substances of relatively large sizes are likely to be caught at a portion of the surface layer side (entry side) of the filter element and the portion is highly likely to be clogged whereby the flow rate of the filter element may be lowered although the under layer side (exit side) thereof still has enough capturing capability left and consequently, the life of the filer element comes to the end. Accordingly, the filter density of the filter element is generally set relatively large in order to avoid such consequences or in order to ensure a certain prolonged period of life. Further, if a high accuracy is required, a tandem multi-tier construction is employed in which a coarse filter element having a low filter density is disposed on the upper tier, and a fine filter element having a high filter density is disposed on the lower tier. However, such a construction results in increase in costs.  
         SUMMARY OF THE INVENTION  
         [0006]    Accordingly, it is an object of the present invention to provide a single filter element roll (single-tier construction) with highly accurate filtering capability.  
           [0007]    The first aspect of the invention provides a filtering apparatus for capturing foreign substances comprising a rolled filter element produced by winding a thin paper, and a cylindrical case for accommodating the rolled filter element, the case having two openings at both ends thereof with respect to the axis direction of the rolled filter element accommodated, one of which is an entry opening though which a fluid to be filtered is flown into the cylindrical case and the other of which is an exit opening through which the fluid already filtered is flown out therefrom, and the filter density of the rolled filter element being higher on the exit opening side than on the entry opening side.  
           [0008]    According to the first aspect of the invention, since a fluid to be filtered is introduced into the cylindrical case whereby the fluid is flown from one end to the other end in the axis direction of the rolled filter element. The filter density of the filter element is higher on the exit opening side than on the entry opening side. Accordingly, coarse particles are captured at the lower filter density portion on the entry opening side and fine particles are captured at the higher filter density portion on the exit opening side. Therefore, particles of various sizes are captured at the corresponding portions of a single, rolled filter element, whereby manufacturing costs may be reduced. In addition, since the life of the rolled filter element is prolonged, reductions in running costs can be accomplished.  
           [0009]    The second aspect of the invention provides a filtering apparatus for capturing foreign substances comprising a rolled filter element produced by winding a thin paper, and a cylindrical case for accommodating the rolled filter element, the case having two openings at both ends thereof with respect to the axis direction of the rolled filter element, one of which is an entry opening though which a fluid to be filtered is flown into the cylindrical Case and the other of which is an exit opening through which the fluid is flown out therefrom, and each rolled thin paper layer, which together make the rolled filter element, having a circumferentially extending corrugated area on the exit opening side.  
           [0010]    According to the second aspect of the invention, a fluid to be filtered is introduced into the cylindrical case whereby the fluid is flown from one end to the other end in the axis direction of the rolled filter element. Each thin paper layer has a circumferentially extending corrugated area on the exit opening side, whereby the rolled filter element has a portion in which the corrugated areas are overlapped. The portion has a higher filter density than the other portion. Thus, the same operation and effects as in the first aspect of the invention are accomplished. In addition, provision of different filter densities on the single, rolled filter element may be realized simply by providing a corrugated area on a thin paper, which contributes to reductions in costs.  
           [0011]    The third aspect of the invention provides a filtering apparatus for capturing foreign substances comprising a plurality rolled filter elements each produced by winding a thin paper, a plurality of cylindrical cases each for accommodating the rolled filter element, the case having two openings at both ends thereof with respect to the axis direction of the rolled filter element accommodated, one of which is an entry opening though which a fluid to be filtered is flown into the cylindrical case and the other of which is an exit opening through which the fluid already filtered is flown out therefrom, and the filter density of the rolled filter element being higher on the exit opening side than on the entry opening side, and a housing for accommodating the cylindrical cases in a multi-tier construction and allowing a fluid to be filtered to be flown therein in a parallel manner.  
           [0012]    According to the third aspect of the invention, since each thin paper layer has a circumferentially extending corrugated area, and the corrugated area makes a higher filter density portion at the exit opening area in the rolled filter element than the other portion, the same operation and effects as in the first aspect of the invention are accomplished. That is, particles of various sizes can be captured by the single, rolled filer element. In addition, a large volume of flow can be treated by disposing a plurality of such rolled filter elements in the housing so as to allow a fluid to be filtered to be flown in a parallel manner to enter into the rolled filter elements.  
           [0013]    The fourth aspect of the invention provides a method of manufacturing a rolled filter element to be used for the filtering apparatus comprising the step of: winding a thin paper unwound from a rolled paper material, dividing the thin paper into separate pieces, forming a portion of each piece with a continuous corrugation area, and winding each piece with the continuous corrugation area to make a rolled filer element, each continuous corrugation area being positioned aside from the center to the one side with respect to the axis direction of the rolled filter element.  
           [0014]    According to the fourth aspect of the invention, a continuous corrugation area is formed on the thin paper prior to winding. Thus, the resultant rolled filter element has a higher filter density portion at one end in the axis direction thereof than the other end. This characteristic rolled filter element can be manufactured easily and surely.  
           [0015]    The fifth aspect of the invention provides a method of manufacturing a rolled filter element comprising the steps of winding a thin paper unwound from a wide rolled paper material, dividing the thin paper into separate pieces by means of a slitter, forming a portion of each piece with a continuous corrugation area by means of a corrugation forming roller, the corrugation forming roller having a plurality of circumferential grooves, respectively for corresponding to the pieces and being positioned downstream of the slitter with respect to the flow of the pieces, and winding each pieces with the continuous corrugation area to make a rolled filter element, each continuous corrugation area being positioned aside from the center to the one side with respect to the axis direction of the rolled filter element.  
           [0016]    According to the fifth aspect of the invention, since one corrugation forming roller having circumferential grooves is disposed respectively for corresponding to the pieces of the thin paper downstream of the slitter, each piece is formed with a corrugation continuously upon being passed over the circumferential groove and then is wound into a rolled state. Therefore, provision of the corrugation forming roller having circumferential grooves, respectively, for the pieces of the thin paper effectively realizes easy and reliable formation of corrugation. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]    [0017]FIG. 1 is a schematic plan view of a corrugation forming and winding system for a filter element according to the invention;  
         [0018]    [0018]FIG. 2 is a schematic side view of the corrugation forming and winding system for the filter element according to the invention;  
         [0019]    [0019]FIG. 3 is a plan view of a single corrugation forming roller;  
         [0020]    [0020]FIG. 4 is a schematic drawing illustrating in a resulting rolled filter element the state or the corrugation areas;  
         [0021]    [0021]FIG. 5 is a drawing showing the first step (insertion of a mandrel) for assembling the filtering apparatus;  
         [0022]    [0022]FIG. 6 is a drawing showing the second step (fitting of the case) for assembling the filtering apparatus;  
         [0023]    [0023]FIG. 7 is a cross sectional view of the cylindrical case (taken along the line VII-VII shown by the arrow in FIG. 8);  
         [0024]    [0024]FIG. 8 is a detailed cross sectional view of the upper portion of the filtering apparatus in the assembled state; and  
         [0025]    [0025]FIG. 9 is across sectional view of the entire construction of the filtering apparatus in the assembled state. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0026]    Referring now to the drawings, an embodiment of the invention will be described. FIG. 1 and FIG. 2 illustrate a corrugation forming process and a winding step from a rolled paper material  10 . The rolled paper material  10  is attached to a center shaft  12 , and the center shaft  12  is rotatably supported by a bearing, not shown, and connected to a rotational drive unit and the like, not shown. A slitter  16  is disposed downstream with respect to the delivering directionof an unwound paper material  14  from the rolled paper material  10 . The slitter  16  comprises a revolving shaft  18  and a plurality (six in the embodiment shown in the figure) of circular blades  20  disposed farther apart from each other on the revolving shaft  18 . The revolving shaft  12  is supported by a bearing, not shown, and connected to a rotational drive unit for rotation, not shown. Rotation of the center shaft  12 , or in other words, rotation of the circular blades  20  divides the paper material  14  into seven elongated pieces  22 , and each piece is wound on a paper pipe on a spindle  24  to make a rolled filter element  26 . The spindle  24  is also supported by a bearing, not shown, and is connected to a rotational drive unit, not shown.  
         [0027]    A corrugation forming roller  28  is disposed downstream of the slitter  16  and upstream of a winding station for making the rolled filter element  26 . As shown in FIG. 3, a corrugation forming roller  28  includes a revolving shaft  30  and a plurality (eight in the embodiment shown in the figure) of large diameter roller  32  fitted onto the revolving shaft  30 , small diameter rollers  34  disposed between the adjacent large diameter rollers  32 , and securing members  36  disposed at both ends for maintaining the rollers  32 ,  34  in a fixed state. In such a construction having the small diameter rollers  34  each being interposed between the adjacent large diameter rollers  32 , there is provided a plurality (seven in this embodiment) of annular grooves  38 , the number of which is the same as that of the pieces  22 . A shown in FIG. 1, each annular groove  38  is disposed at a position aside from the centerline to one end with respect to the width direction of each piece  22 . As shown in FIG. 2, the corrugation forming roller  28  is positioned in a height so that the running routes of the pieces  22  are bent to form an slightly upwardly projecting angle. The revolving shaft  30  of the corrugation forming roller  28  is supported by a bearing, not shown, and is connected to a rotational drive unit, not shown.  
         [0028]    After the unwound paper material  14  is slit into the pieces  22 , the pieces  22  are passed over the corrugation forming roll  28 . When passing over the corrugation forming roll  28 , each piece is in no contact with the corrugation forming roll  28  at a position facing the annular groove  38 . In addition, the corrugation forming roller  28  is positioned in a height so as to bend the running route of the pieces  22  into a slightly upwardly projecting angle. Therefore, each piece  22  is tensed and pressed against the corrugation forming roller  28 , and the no contact portion of each piece  22  corresponding to each annular groove  38  is forced and guided into each annular groove  38 . As a result, the no contact portion of each piece  22  is formed with a continuous corrugation area  40 . The width of the continuous corrugation area  40  may suitably be adjusted by altering the width of the annular groove  38 . The position of each corrugation area  40  is offset slightly from the centerline of each piece  22 . The corrugation area  40  once formed is not restored and remains as is even when the piece  22  is rolled to make the rolled filter element  26 . Such corrugation extends circumferentially at the position offset from the axial center of the rolled filter element  26 .  
         [0029]    [0029]FIG. 4 schematically illustrates an axial cross piece of the rolled filter element  26  at a portion where the corrugation area  40  is formed. The reference numeral  26 - 1  designates layers produced by winding one piece  22 . Each layer has a corrugated area  40 . In the corrugated area  40 , the piece  22  is felled into a pile. Accordingly, the filter density of the filter element  26  is higher on this portion than on the other (no corrugation) portion. Therefore, the filer density of the filter element  26  may be varied on a single roll  26  by presence or absence of the corrugation.  
         [0030]    [0030]FIG. 5 to FIG. 9 illustrate the construction of a filtering apparatus including the rolled filter element  26  of the construction described above as well as the assembling procedure. FIG. 5A illustrates the first step of assembly, and the rolled filter element  26  is schematically illustrated in a cross piece taken in the axial direction. A reference numeral  42  designates a paper pipe, and vertical lines schematically illustrate layers produced by winding the piece  22 . The corrugated areas  40  of the layers provide the rolled filter element  26  with a higher filter density portion. This higher filter density portion is schematically shown as a portion  50  drawn with increased number of vertical lines. The portion having a higher filter density of the rolled filter element  26  is located at a lower side of the rolled filter element  26  with respect to the center thereof. A reference numeral  52  designates a plastic mandrel. The mandrel  52  has a flange  54  extending outwardly from the outer periphery thereof at the lower end, and an annular projection  56  extending inwardly from the inner periphery thereof at an upper end. The annular projection  56  is provided for attaching an  0 -ring at the inner periphery of the upper end. The mandrel  52  is inserted into the paper pipe  42  until the flange  54  abuts against the paper pipe  42  as shown by an arrow f. FIG. 5B illustrates a state in which the mandrel  52  has been inserted.  
         [0031]    [0031]FIG. 6 illustrates the second step of assembly. The rolled filter element  26 ,into which the mandrel  52  has been inserted, is press fitted into a plastic case  58 , as shown by an arrow g. The case  58  is fully opened at the upper side and has, at the lower side, a bottom wall with an opening  60  formed therein. As shown in FIG. 7, radially extending ribs  62  are formed on the inner surface of the bottom wall, and a space between adjacent ribs  62  form a recess  64 , which extends to the opening  60 . FIG. 6B illustrates a state in which fitting of the rolled filter element  26  into the plastic case  58  has been completed. In this fitted state, the flange  54  of the mandrel  52  abuts against the ribs  62  on the inner surface of the plastic case  58 , and thus a flow passage of a fluid to be filtered is formed from the rolled filter element  26  through the recess  64  between the ribs  62  to the opening  60 . Since the upper end of the rolled filter element  26  is the same with or slightly lower than that of the plastic case  58  and the upper end  52 A of the mandrel  52  is slightly upwardly projected from the plastic case  56 , a gap is formed between the adjacent plastic cases  58  when another plastic case  58  is placed thereon. Accordingly, a fluid to be filtered can surely be flown from the upper side into each rolled filter element  26 .  
         [0032]    [0032]FIG. 8 and FIG. 9 illustrate the third step of assembly. In the third step, a plurality of the cases  58  each with the rolled filter element  26  are accommodated in a metallic housing  66  in a multi-tier construction (four-tier in this embodiment). The housing  66  has a cylindrical shape and integrally fixed to a bottom supporting plate  68  (FIG. 9) so as to stand uprisingly therefrom by a suitable means such as welding. The bottom supporting plate  68  has a boss portion  70  with a central hole  70 - 1  formed therein. The central hole  70 - 1  of the boss portion  70  is threaded. On the other hand, a metallic cylindrical shaft  72  is provided with a handle  74  at the upper end thereof. The cylindrical shaft  72  is inserted into a cover  75  and four-tier of the cases  58  each with the rolled filter element  26  as shown in FIG. 6B. As shown in FIG. 8, the O-ring  76  is attached on the annular projection  56  at the upper end of the mandrel  52  between the plastic cases  58  being adjacent one above the other, and the portion between the plastic cases  58  adjacent one above the other is sealed by the O-ring  76  abutted against the lower end surface of the case  58  of the upper tier, so that an unfiltered fluid (lubricating oils) is avoided to leak directly into the cylindrical shaft (exit piping side)  72 . As shown in FIG. 9, the plastic case  58  of the lowest tier is placed on a metallic stopper ring  80  via a seal  78 , so that the plastic cases  58  of the four-tier construction are positioned with respect to the cylindrical shaft  72 . The stopper ring  80  is engaged to a threaded portion  72 A at the lower end of the cylindrical shaft  72 .  
         [0033]    The cylindrical shaft  72 , to which the four-tier of the plastic cases  58  each with the rolled filter element  26  is attached, is engaged to the threaded portion  72 A of the threaded hole  70 - 1  of the boss portion  70  on the bottom supporting plate  68 , as shown in FIG. 9. The cylindrical shaft  72  is engaged to the boss portion  70  by rotating a handle  74 . The handle  74  is provided at the upper end. The cover  75  has, on the lower surface, an annular groove  82  along the outer peripheral side. In the annular groove  82 a, a O-ring  76 ′ is inserted. The upper end of the housing  66  is abutted against the O-ring  76 ′. The cover  75  has also, on the upper surface, an annular groove. In the annular groove, another O-ring  76 ″ is inserted. When tightening the handle  74 , the lowest case  58  of the four-tier construction is pressed against the stopper ring  80  via the seal  78 . Between the adjacent plastic cases  58 , the lower surface of the upper plastic case  58  is pressed against the O-ring  76  attached on the upper end of the mandrel  52  projecting from the lower plastic case  58 . On the upper side of the uppermost plastic case  58 , the cover  75  is pressed against the O-ring  76  attached on the upper end of the mandrel  52  projecting from the uppermost plastic case  58  in the inner periphery, and the O-ring  76 ′ on the outer periphery seals between the cover  75  and the housing  66 . Therefore, a central cavity in the cylindrical shaft  72  acting as the exit side is completely blocked off from an internal space S acting as the entry side in the housing  66 , so that no unfiltered fluid leaks directly into the exit side.  
         [0034]    In FIG. 8, the cylindrical shaft  72  is formed with a plurality of inlet holes  84  for receiving filtered fluid farther apart from each other in the longitudinal direction. In this embodiment, these inlet holes  84  are disposed so as to face toward the openings  60  of the recesses  64  formed on the lower end of the plastic case  58  between the radially extending ribs  62  for recovering the fluid already filtered through the rolled filter element  26 .  
         [0035]    As shown in FIG. 9, the bottom plate  68  is provided with a union (connecting pipe)  86  for receiving a fluid to be filtered such as lubricating oils. A fluid to be filtered is flown from a feed pump, not shown, into the space S in the housing  66  under pressure as shown by an arrow H. The fluid, which has been flown into the housing  66 , is introduced into the rolled filter element  26  in each case  58  from the upper side thereof in a parallel manner as shown by an arrows J. In this manner, the fluid introduced into rolled filter elements  26  in a parallel manner passes through the rolled filter element  26  from top to bottom, during which foreign substances are captured. The resultant, filtered fluid is flown out from the rolled filter element  26  at the lower end thereof. Then the fluid is flown within the recesses  64  between the ribs  62  radially inwardly, as shown by an arrow L (see FIG. 7), and are guided and captured via the opening  60  and the inlet hole  84  into the central cavity within the cylindrical shaft  72 . The fluid thus recovered is flown downwardly through the central cavity in the cylindrical shaft  72  as shown by an arrow M, and taken out from the central hole  70 - 1  of the boss portion  70  on the bottom plate  68 , as shown by an arrow N in FIG. 9, and then returned back to the lubricating oil system.  
         [0036]    Foreign substances are captured by the paper fibers of the rolled filter element  26  (thin paper) when a fluid to be filtered is passed through each rolled filter element  26  from top to bottom. The upper side of the rolled filter element  26  with no corrugation is a lower filter density portion, and the lower side of the rolled filter element  26  with the corrugation area  40  is the higher filter density portion  50 . Large sized foreign substances are captured at the lower filter density portion  50  and fine foreign substances are captured at the higher filter density portion  50 . Therefore, one single rolled filter element  26  can capture various sizes of particles ranging from coarse particles to fine particles, and an entire area in the vertical direction of the rolled filter element  26  can be effectively used for capturing foreign substances, which contributes to increase the life of the rolled filter element. In contrast to the present invention, the prior art, rolled filter element has a uniform filter density in the vertical direction. Therefore, when the density of the filter element is increased to capture fine foreign substances, lowering of flow rate may be caused once large sized foreign substances are captured on the upper side, and thus the roll may ends its life even when the lower side thereof still has a capturing capability. Accordingly, it is required to provide a plurality of rolled filter elements having different filter densities and disposed in a tandem two-tier construction, which may be led to increase in costs. The invention forms coarse portion and fine portion on one single rolled filter element by forming corrugation during winding step, and thus the manufacturing costs and the running costs may be improved, thereby realizing significant total reduction in costs.