Abstract:
A filter with a multi-piece filter body has a filter head connected to a filter pot and has at least one filter element. The filter element has a support tube surrounded by a filter mat. The filter mat free ends have element mountings. One of the element mounting is rigidly connected to the support tube and can be placed in contact with the filter head. An intermediate member is arranged, at least at that end of the filter element mounting connected to the filter head, between that element mounting and that end of the filter mat, and can be removed along with the filter mat from the support tube which remains connected to the filter head. Axial support of the end caps of the cylindrical filter element is achieved in that a possible fluid passage point, in particular a gap which can be closed after the start of operation by the resulting fluid differential pressure, is provided in the axial mounting direction at least between one part of the intermediate members and the associated filter element mounting, when a filter mat is mounted on the support tube, providing reliable control also of high differential pressures.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a filter with a filter housing formed of multiple parts, including a filter head connectable with a filtering pot. The housing receives at least one filter element including a support tube surrounded by a filter mat provided at its free ends with filter element mountings. At least one of the filter element mountings is connected securely with the support tube and can be brought into contact with the filter head. At least at the end of the filter mat which has the filter element mounting connected with the filter head, an intermediate spacing member is arranged between this filter element mounting and this end of the filter mat. The intermediate spacing member can be removed together with the filter mat from the support tube, which remains connected with the filter head. 
     BACKGROUND OF THE INVENTION 
     Filters, as disclosed EP 0 547 291 A, serve mainly to decontaminate contaminated fluid, especially hydraulic oil, by removing the contaminants. For this purpose, the contaminated fluid passes through an inlet opening into the filter arrangement and flows through the filter from the exterior to the interior. The filter mat is supported on the support tube constructed in the form of a hollow cylinder with apertures. The contaminants remain in the filter mat, and the fluid cleansed of its contaminants is discharged from the filter arrangement through a discharge opening. If the filter mat is obstructed by the contaminants, which can be determined generally by a rise of the differential pressure, then, with the conventional arrangements, the filter must be exchanged for a new filter. 
     For the exchange of the filter element, the filtering pot is unscrewed from the filter head and the filter mat obstructed with contaminants is exchanged for a new one. The contaminated filter mat is removed from the support tube along with its intermediate spacing member, while the support tube remains on the filter head, together with the associated filter element mounting. The costs involved in a filter mat exchange are thus reduced and the environment is less contaminated in the process, since the filter mats in question are recyclable without further treatment. 
     With very high fluid differential pressures, however, problems arise in these conventional arrangements in the area of the filter element mounting, because of the low support forces present at that point. The low support forces can lead to failure of the entire filter arrangement. The effectiveness of the sealing in the vicinity of the mounting can be reduced and leakage cannot be avoided. Furthermore, there is the possibility of impacting or buckling of the filter assembly with the drawbacks which that entails. 
     SUMMARY OF THE INVENTION 
     Objects of the present invention are to provide a filter arrangement that avoids the aforementioned drawbacks in conventional filter arrangements. 
     The foregoing objects are basically attained by a filter arrangement having a multi-part filter housing, a filter element, first and second filter element mountings, a first intermediate spacing member, and a first axial gap extending between the first intermediate spacing member and the first filter element mounting. The filter housing includes a filter head detachably coupled to a filter pot. The filter element includes a support tube surrounded by a filter mat, with the mat being open at opposite first and second ends. The filter element mountings are mounted on the respective ends of the filter mats. The first filter element mounting is securely connected with the support tube and contacts the filter head. The intermediate spacing member is coupled to filter mat first end, is removable with the filter mat from the support tube when the support tube remains connected with the filter head, and is mounted between the filter mat first end and the first filter element mounting. The axial gap forms a first possible fluid passage point at the first filter element mounting, which gap is closed by fluid differential pressure generated after operation start-up of the filter arrangement. 
     Closing the gap by the resulting fluid differential pressure following the start-up of operation provides axial support of the end caps of the cylindrical filter element and guarantees that the high differential pressures are overcome. Furthermore, following closing off of this possible fluid passage point by means of the prebiasing or preloading caused by the fluid differential pressure, higher quality sealing occurs in the vicinity of the filter mounting, so that leakage is avoided. With sufficient prebiasing of the filter assembly, the gap can be deleted, while a theoretical passage point nonetheless remains. 
     The filter mats which are used can be produced either with or without supporting meshing made of simple paper elements. Higher quality support elements incorporate a multi-layer mat construction made up of a variety of materials. The filter mat can also be designed to be pleated. 
     In one preferred embodiment of the filter arrangement according to the present invention, the prebiased filter element mounting connected with the filter head is an integral component part of the filter housing or with radial prebiasing can be moved forward onto an interior support of the filter head. With the integrated arrangement, the filter element mounting turned toward the filter head together with the support remains in any case on this member. With forward movement of the filter element mounting on an associated interior support of the filter head, the filter element mounting is detachably connected with the filter head and can be removed together with the support tube. An O-ring, which is prebiased between interior supports of the filter head and the filter element mounting, can serve to produce the raidal prebiasing. 
     In another preferred embodiment of the filter arrangement according to the present invention, the intermediate spacing member, arranged between the end of the filter mat and the filter element mounting connected with the filter housing, overlaps this filter mat end in a cap-like manner. The intermediate spacing member is detachably connected with the filter element mounting, preferably by means of a clamp ring. In this manner, the intermediate spacing member, either additionally or alternately in an axial mounting arrangement, has an elastically flexible sealing, which can be brought into contact with the filter element mounting. In this configuration, after release of the clamping ring, the filter mat together with the intermediate spacing member can be removed from the filter element mounting and the support tube. 
     In another preferred embodiment of the filter arrangement according to the present invention, the filter element mounting connectable with the filter head incorporates cam drive elements, which can be brought into contact with the filtering pot under the effect of an outside power source. With smaller relative movement of the filter element relative to the filtering pot, and with simultaneous screwing up and down of the filtering pot, the filter element can be removed from the filter housing or inserted therein. Insofar as the aforementioned cam drive elements are part of at least one intermediate spacing member, the filter element mounting in turn can remain with the support tube in the housing. Only the filter mat is removed with the intermediate spacing members connected with it. 
     Preferably, in this manner, the end of the filter element remote from the filter head is closed off by a filter element mounting constructed of a plurality of parts. The associated intermediate spacing member then surrounds it in a cap-like arrangement. Preferably, the intermediate spacing members can in turn be caught and held together with the associated filter element mounting by means of a catch connection. 
     In one further preferred embodiment of the filter arrangement according to the present invention, a power source is inserted between support tube and filter head of the filter housing, usually in the form of a tension or compression spring. Another power source is located, preferably between the filter pot and the filter element, and is usually a compression spring, working on the filter element mounting remote from the filter head. In this manner, even during increasing compression or impacting stress on the filter element, impacting or thrust-driving of the exchangeable filter element to be inserted in axial alignment can be prevented, which if necessary for the exchange would lead to damage. 
     The present invention furthermore relates to a filter element for use in a filter arrangement as described above, wherein the filter mat is configured as a hollow cylinder with an intermediate spacing member mounted on at least one end. Together with the filter mat, the intermediate spacing member can be removed or can be moved forwardly by sliding onto a support tube. The filter, designed and constructed as a modular element, can thus be used again together with the support tube and the filter element mounting. When the filter material becomes obstructed by contaminants, the depleted hollow cylindrical filter need simply be exchanged for a new one in a manner which is low cost and environmentally safe. 
     As a result of the arrangement having the support tube closed off at the bottom end in connection with an elastic end cap or in connection with a catch arrangement or limiting boss arrangement for the end cap, a rigid support in axial alignment is obtained. Especially at high pressures, it guarantees reliable function of the filter arrangement. 
    
    
     Other objects, advantages and salient features of the present invention will become apparent from the following detailed description, which, taken in conjunction with the annexed drawings, disclose preferred embodiments of the present invention. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Referring to the drawings which form a part of this disclosure: 
     FIG. 1 is side elevational view in section of a filter arrangement according to a first embodiment of the present invention; 
     FIG. 2 is an enlarged, partial side elevational view in section of the part of filter arrangement, indicated with “X” in FIG. 1; 
     FIG. 3 is an enlarged side elevational view in section of the part of the filter arrangement indicated with “Y” in FIG. 1; 
     FIG.  4 . is a side elevational view in section of a filter arrangement according to a second embodiment of the present invention; and 
     FIG. 5 is a side elevational view in section of a filter arrangement according to a third embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The filter arrangement shown in FIG. 1 has a two-part filter housing  10  with a filter head  12  arranged at the top and a filter pot  14  thereunder. Filter pot  14  can be screwed or threaded into filter head  12  by means of its exterior threading. Within filter pot  14  and in coaxial alignment with the longitudinal axis  16  of filter housing  10 , a filter element  18  is arranged. Filter element  18 , constructed in this case is essentially a hollow cylinder, which for example can be made up of a pleated filter mat, and has a plastic or metal support tube  20  in its interior with apertures  22 . Support tube  20  is surrounded by a filter mat  24 , provided on its free ends with filter element mountings  26  and  28 . 
     An inlet and an outlet  32  in filter head  12  serve for the intake of the contaminated liquid and the discharge of the decontaminated liquid from the filter arrangement, respectively. The flowthrough direction within filter housing  10  is shown by the arrows in FIG.  1 . The liquid to be decontaminated consequently passes through filter element  18  from the outside to the inside, through filter mat  24  and apertures  22  of support tube  20 . Thus, filter mat  24  retains the contaminants in the filter element made of woven material. Support tube  20  is open at its end closer to or adjacent to filter head  12 , and is closed off at its other end by a base  34 . 
     The filter element mounting  26  shown at the top in FIG. 1 is connected securely with the open end of support tube  20  in the vicinity of its opening, and contacts internal support  36  of filter head  12 . To the right and left of longitudinal axis  16 , two different constructions for filter element mounting  26 , as well as associated internal support  36  are illustrated and are more fully described hereinafter. Between the end of filter mat  24  and annular filter element mounting  26  an annular intermediate spacing member  38 , shown in detailed in larger scare in FIG. 2, is illustrated. Spacing member  38 , in a cap-like manner overlaps and surrounds the top open end of filter mat  24  around its top edge. 
     This intermediate spacing member  38  engages on the working surface at the open end in the top area of filter mat  24  and is connected securely with the filter mat, for example by means of an adhesive connection or the like. Filter element mounting  26 , in the form shown to the right in FIG. 1, has an internal sealing ring or gasket  40  extending in a groove in filter element mounting  26 . In this form, filter element  18  is held by radial clamping onto the associated internal support  36  of filter head  12 . 
     In the form of top filter element mounting  26  shown to the left in FIG. 1, a flange-like central fillet  42  is connected in an associated groove of filter head  12 , engaging and being an integrated component part of filter head  12 . Since the radial sealing gasket of the left side form can be deleted in this construction, the flow parameters indicated with “A” can be enlarged. For the purpose of flow-favorable guiding, the flow parameters indicated with “B” can be made identical to the flow parameters “A”. 
     As shown in the larger scale illustration of FIG. 2, representing the section “X” in FIG. 1, intermediate spacing member  38  forms a seal by means of an annular foamed or embedded sealing ring  44  (FIG.  2 ). Ring  44  projects outwardly on the top and on the exterior of the periphery of intermediate spacing member  38 . This sealing ring  44  can be prebiased by means of a clamping ring or the like, which engages a ring contact surface extending parallel to the longitudinal axis  16  on the interior periphery both in intermediate spacing member  38  and also through an associated groove in filter element mounting  26 , which in turn can be mounted securely by means of its central fillet  42  on filter head  12 . The top of filter mat  24  is secured to the bottom of intermediate spacing member  38  by an adhesive layer  54 , as shown in FIG.  2 . 
     With the construction of a filter element mounting of FIG. 2, rigid axial support is realized to withstand high differential pressures. The axial support is undertaken through end cap  26  and not as in the state of the art, where the insertion of the filter element normally also undertakes the support of axial forces. Therefore, a prebiased axial sealing is provided over the gap  52 . The pressure ratios on the filter element generated during filter operation are shown graphically in FIG. 2 with Pi and Pa, whereby Pi represents the internal pressure within the filter element and Pa represents the external fluid pressure. Enhancement of the prebiasing and a tighter sealing by closing gap  52  with rising differential pressure, ΔP=Pa−Pi, is attained solely by means of the fluid pressure from the fluid medium impacting on intermediate spacing member  38  and filter element mounting  26 . As a result of the arrangement of flexible sealing ring  44  on the external edge of the filter unit, intermediate spacing member  38  can be pressed by external pressure against filter element mounting  26  upon closing off of gap  52 . Increased sealing effect is obtained as a result of this prebiaising. As a result of the axial support of filter element mounting  26 , no axial forces are transmitted onto the filter unit. 
     As shown in FIGS. 2 and 3, a resulting radial gap  52   a  can also be arranged on the opposite end of filter  18 . As a result of this arrangement, the relevant intermediate spacing members  38  surround support tube  20  around its external periphery in the vicinity of its open ends. Furthermore, a projecting click-catch  60  is arranged on the open end of each one of the filter element mountings  26  and  28 . Each catch  60  engages by catching on an associated catch notch  62  on both of the intermediate spacing members  38  and  39  to produce a catch connection between these structural parts. Insofar as filter element mountings  26 ,  28  are formed of an elastic, flexible synthetic resin or the like, the resulting click-catch or other catch connection can be released manually without any other action. As especially shown in FIG. 3, bottom filter element mounting  28  is configured of two parts. A cover part  56  forms base  34  and is in contact through another sealing ring  64  adjacent to filter element mounting  66  and in sealed connection therewith. 
     For the exchange of filter elements, first of all filter pot  14  is screwed off of filter head  12 . After detachment of the security or clamping ring, filter mat  24  with bottom filter element mounting  28  and intermediate spacing member  38  are all manually withdrawn from the outside of support tube  20 . Support tube  20  extends over the top filter element mounting  26 , and remains connected with filter head  12  as another component part of filter housing  10 . A newly inserted filter mat  24  can then be slipped over support tube  20  and over the clamping ring connected with top filter element mounting  26 . Following screwing of filtering pot  14  into filter head  12 , the filter is ready for a new filtering procedure. 
     In the embodiment of FIG. 1, intermediate spacing members  38  and  39  are mounted at the two open ends of filter mat  24 , and the rings arranged on filter mat  24  can be of foamed material. Intermediate spacing members  38  and  39  particularly can be of polyurethane or silicon foam, but a rubber elastic material would likewise be conceivable. In FIG. 1, top and bottom, the two annular intermediate spacing members  38  and  39  are surrounded by cap-like filter element mountings  26  and  28 . Especially as seen in FIGS. 2 and 3, a certain degree of play is present in the form of annular gaps  52  and  52   a , on the working side between the surfaces of intermediate spacing members  38  and  39  and filter element mountings  26  and  28  which are turned toward one another, insofar as the filter is not in operation. Gap  52  or  52   a  is not closed by the fluid differential pressure being generated until operation is assumed, whereby the total pressure ranges is obtained, as seen in FIG. 2, by the differential pressures Pi and Pa impacting on the bottom of intermediate spacing member  38  and running in wedge configuration on the other side. 
     When filter element  18  is constructed with its shortest length, bottom filter element mounting  28  contacts a flange-like limiting boss  53  which is part of the overturned and thrust-forward cover part  56 . Cover part  56  closes off support tube  20  at the bottom and in this case is part of the multi-part bottom filter element mounting  28 . Bottom annular gap  52   a  is retained. When the filter reaches its greatest length, a gap  58  occurs between limiting boss  53  and bottom filter element mounting  28 . The gap does not exceed double the axial length of bottom annular gap  52   a . If filter element  18  in turn is acted upon with external excess pressure upon start-up of the filter operation, which corresponds for example to the pressure differential ΔP with a contaminated filter mat  24 , then, with a filter mat  24  having the smallest dimensions, as aforementioned, the axial force of bottom filter element mounting  28  is introduced directly through limiting boss  53  in cover part  56  of bottom filter element mounting  28  and finally further through this cover part into support tube  20 . With use of a filter mat  24  having the largest dimensions, the axial force of bottom filter element mounting will further deform the two sealing beads or rings  44  of the filter mat  24 , until annular gaps  52 ,  52   a  are closed top and bottom, and bottom filter element mounting  28  contacts the limiting boss  53 . Therefore, excess axial forces are in turn carried off through support tube  20 . The loads or charges on filter mat  24  can then be minimized in the axial direction. With an element exchange, all of the parts of the element exchange unit could be reused. 
     The following embodiments of the filter arrangement are explained only insofar as they differ notably from the embodiment of FIG. 1 in this description. Identical structural parts are indicated with the same references, but increased by 100 for the second embodiment and by 200 for the third embodiment. The above descriptions of component parts then also suffice for the following second and third embodiments. 
     In the second embodiment of FIG. 4, the base  134  closing off filter  118  at the bottom is formed of dished-end plate construction. The flexibly constructed bottom filter element mounting  128  facing and contacting dished-end plate base  134  is bevelled to fit with the dished-end plate base, and thus prevents transfer of damaging axial forces to the filter unit. 
     In the third embodiment, now to be described relative to FIG. 5, the filter element mounting  226  connectable with filter head  212  incorporates cam drive elements  268 . Under the effect of power sources, here in the form of spring elements, the cam drive elements can be brought into force-locking contact with filter pot  214  along its interior periphery. Because cam drive elements  268  form a sort of holding clamp arrangement, with only very slight relative movement between filter element  218  and filter pot  214 , they can be removed from filter housing  210  together with the filter. Furthermore, cam drive elements  268  center filter element unit  218  within filtering pot  214 . 
     Between support tube  220  and filter head  212 , a power source  270  in the form of a compression spring is supported with its one end of the bottom of support  236  of filter head  212  and with its other end on an annular flange  272 . Flange  272  is arranged in the interior of support tube  220  in its top third, and is securely connected with the support tube. Between filter pot  214  and filter element  218  another power source  274  is arranged. Power source  274  is in the form of a compression spring, and acts on the filter element mounting  228  remote from filter head  212  and particularly on its cover part  256 . Cover part  256  is hollowed out in the third embodiment on its surface facing away from the interior of support tube  220 . In the middle of the other power source  274 , a holding rod  276  is screwed into cover part  256  and is arranged to be movable with its screw head with formation of a limiting boss in a housing part  278 . Compression spring  274  is supported with its one end on cover part  256  and its other end on an annular flange of housing part  278 . The maximum length of extension of compression spring  274  is limited by the screw head stop arrangement of holding rod  276 . 
     For the mounting of the exchangeable filter element  218 , this unit is first placed in filter pot  214 , whereby the holding clamps or cam drive elements  268  center the unit in the middle of filter pot  214 . The exchangeable filter element unit is supported on the base of filter pot  214  by means of housing part  278 . Finally, filter pot  214  is screwed into filter head  212 . As soon as exchangeable filter element  218  has reached the interior support  236  of filter head  212 , this interior support will prebias the compression spring  270  by means of a guide ring  280 , whereby the filter element mounting  226 , seen at the top in FIG. 5, slides over supports  236  on the exterior periphery. A sealing is accomplished by means of O-ring  240 . After the exchangeable filter element on filter head  211  has reached and is stopped by its limiting boss, compression spring  274  is prebiased by stretching over housing part  278  until filter pot  214  has reached the limiting boss in filter head  212 . 
     In this cited position, the prebias force of compression spring  274  is greater than the prebias force of compression spring  270 . Therefore, during operation, the filter element is prevented from being pressed away from filter head  212  by compression spring  270 . Especially at times of increasing pressure load on filter  218  generated by the fluid to be filtered, the resulting compacting of the entire exchangeable filter element in axial direction would lead to damages to the filter assembly. The exchangeable filter element is disassembled in the reversed procedure, whereby first of all compression spring  274  is slackened. Instead of the multi-part bottom filter element mounting  228 , this mounting can also be constructed of one single piece. After detachment of top and bottom filter element mountings  226  and  228  from the aforementioned catch connection  260  and  262 , filter mat  224  in turn can be exchanged together with annular intermediate spacing members  238  and  239  of the support tube  220  for an exchange of the filter mat. 
     As a result of the increase of sealing in the vicinity of the filter element mountings by means of the prebiasing producible as described as well as with the axial support of the filter element mountings, no damaging axial forces are transferred onto the filter unit as compared with the conventional filters and leakage in the high pressure area is also certainly avoided. 
     While various embodiments has been chosen to illustrate the invention, it will be understood by those skilled in the art that various changes and modifications can be made therein without departing from the scope of the invention as defined in the appended claims.