Abstract:
A filter device includes a filter element ( 9 ) received in a housing ( 1 ). The housing can be closed by a cover part ( 3 ) having fluid ducts ( 35, 41 ). A connecting unit is provided to create a fluid-conducting connection between the filter element ( 9 ) and an associated fluid duct ( 35 ) of the cover part ( 3 ). The connecting unit is in the form of a coupling having a movable coupling part ( 33 ) creating the fluid connection in the functional state.

Description:
FIELD OF THE INVENTION 
     The invention relates to a filter device with a filter element received in a housing closed by a cover part having fluid ducts. A connecting unit forms a fluid-conducting connection between the filter element and an associated fluid duct of the cover part. The invention furthermore relates to a filter element for the filter device. 
     BACKGROUND OF THE INVENTION 
     Filter devices for receiving filter elements are readily available on the market in a plurality of embodiments, for example as disclosed in EP 1 287 871 A1 and EP 0 891 214 B1. A not insignificant portion of the production costs in these filter devices originates from the formation of the connecting unit which, in the operating state in which the filtration process can take place, establishes a suitable connection between the filter element and the respective fluid duct in the cover part. The connecting unit must be designed such that the installation processes for changing the filter elements are simple and uncomplicated, but that reliable sealing occurs, even at high pressure levels. Moreover, the connecting unit, as much as possible, should be made such that in the operation of the filter device “replacement reliability” is provided. In other words, a construction is desirable in which in view of the plurality of designs of filter elements on the market, only those filter elements specially adapted to the housing and the cover part can achieve an operating state. The risk that filter elements of an unintended type with unsuitable filter properties will then be inadvertently operated is avoided. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to provide an improved filter device with a connecting unit meeting the requirements imposed to a significant extent. 
     According to the invention, this object is basically achieved by a filter device having a connecting unit formed by a coupling with a movable coupling part. In the operating state of the device, the coupling part establishes the fluid-conducting connection between the filter element and the associated fluid duct of the cover part, i.e., assumes a coupling position in the operating state. In this way a fluid connection can be implemented forming perfect sealing. Also, corresponding construction of the filter housing, especially its cover part, ensures that the device can only be put into the operating state when the filter element installation in the housing causes the movable coupling part of the connecting unit to assume its operating or coupling position. 
     Preferably, a movable coupling part can be axially moved and adjoins a stationary coupling part of the connecting unit in the operating state by spring pretensioning of the movable coupling part to form a seal. This arrangement is especially advantageous in that the connecting unit is “self-controlling”. Specifically the attachment of the cover part to the housing then leads directly to elastic contact of the axially movable coupling part with the associated stationary coupling part. 
     Especially advantageously, the movable coupling part is on the filter element, and the stationary coupling part is on the cover part and is formed by the mouth edge of the associated fluid duct. The direct interaction between the movable coupling part and mouth edge of the fluid duct leads to an especially simple and compact construction. 
     The element-side movable coupling part can be advantageously formed by a sleeve body forming a fluid passage from the filter cavity coaxial to the longitudinal axis and surrounded by a filter medium to the associated fluid duct of the cover part. 
     In this respect, the sleeve body on the outer peripheral side can be displaceably guided with the formation of a seal in a duct connected to the end cap of the filter element. The sleeve body then performs a coupling function and establishes a direct fluid passage between the fluid duct of the cover part and the inner filter cavity of the filter element conventionally bordered by a tubular, fluid-permeable support body that is in turn surrounded by a filter medium. The duct of the sleeve body can form an extension of the end of the support body adjacent to the end cap so that the sleeve body forms a coaxial extension of the filter cavity. 
     Advantageously, the coupling can be made such that the mouth edge of the associated fluid duct forming the stationary, cover-side coupling part defines a seal plane against which the sleeve end edge of the sleeve body forming the movable coupling part can be pressed to form an axial seal by spring pretensioning. As a result, an especially compact construction of the coupling arises. 
     In this configuration, on the mouth edge of the cover-side fluid duct and on the sleeve end edge of the sleeve body, sealing edges and/or sealing surfaces interact with one another and can form the axial seal. 
     In especially advantageous embodiments, the axial seal can be made such that the sleeve end edge and the mouth edge each form a ring surface. One ring surface is made as a continuous radial plane. The respective other ring surface is made as a radial plane with a sealing edge projecting slightly out of it. This arrangement results in especially good sealing so that operating reliability is ensured even at high pressure levels. 
     Especially advantageously, the sealing edge can be located annularly on the outer periphery of a ring surface such that it encloses the outer periphery of the other ring surface as a centering element. This arrangement ensures that when the cover part is attached, an extremely precise, flush alignment of the coupling parts occurs, even if components on the side of the filter element, such as the end cap, support body, and the like, as injection moldings of plastic material are subject to tolerances, since the centering formed on the sealing surfaces also ensures in this case exact alignment and thus the desired seal properties. 
     The subject matter of the invention is also a filter element for a filter device. 
     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, discloses 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 a side elevational view in section of a filter device according to a first exemplary embodiment of the invention, drawn schematically simplified and on a slightly reduced scale compared to a practical embodiment; 
         FIG. 2  is a front elevational view in section of the filter device of  FIG. 1 , taken along line II-II in  FIG. 1 ; 
         FIG. 3  is an enlarged partial section front elevational view in section of only the head part of the filter device of  FIG. 2 ; and 
         FIG. 4  is a partial perspective view in section of only the upper region of a filter device according to a second exemplary embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A cup-shaped filter housing  1  is largely circularly cylindrical and is closed on the bottom. The housing upper end can be closed by a cover part  3  detachably joined to the housing  1  via a screw connection  5 . The cover part  3  in the head region has pockets  7  as encapsulated bore shoulders for a fouling display (not shown). The housing  1  can receive a filter element  9  having a conventional design with a hollow cylindrical filter medium  11 , for example in the form of layers of filter mat or a multilayer, folded, or pleated filter body, surrounding a tubular support body  13  injection molded from plastic material. The support body, as is most apparent in  FIG. 4 , has a succession of peripheral circular rings  15  spaced apart from one another, of which only a few are numbered in the figures. As conventional for these support bodies  13 , rings  15  are connected to a carrier located inside and made as a star that is three-pointed in cross section, with three points  17 . On the end associated with the bottom of the cup of the housing  1 , the filter element  9  is closed by a bottom cap  19  of plastic material forming an enclosure  21  for the filter medium  11 . On the opposite end, an end cap  23  formed from plastic material forms the termination of the filter element  9  facing the cover part  3 . The end cap  23 , in a similar manner to the bottom cap  19 , forms an enclosure  25  for the pertinent end of the filter medium  11 . 
     As shown most clearly from  FIGS. 3 and 4 , on the radially inside region of the enclosure  25 , a hollow body  27  with an extension  29  projects axially on the radially inside end of the end cap  23  in the direction to the cover part  3  and forms a circularly cylindrical guide or guide duct  31  in which a sleeve body  33  is guided to be axially displaceable. Between the hollow body  27  and the extension  29 , a seat is formed for a sealing element  32  sealing the sleeve body  33  relative to the duct  31 . The sleeve body  33  is used as a movable coupling part of a connecting unit for producing a fluid connection between the filter element  9  and the fluid duct  35  in the cover part  3 . 
     As shown in  FIG. 1 , the first fluid duct  35  in the cover part  3  is connected to the fluid outlet  37  for the cleaned fluid. A fluid inlet  39  located in the cover part  3 , opposite outlet  37 , for the fluid to be cleaned is connected in the cover part  3  to a second fluid duct  41 . From duct  41 , the fluid to be cleaned can flow via inflow openings  43  in the end cap  23  into the annulus  45  on the outside of the filter medium  11  forming the contaminated side of the filter device. From the outside of the filter medium, the fluid to be cleaned passes through the filter medium  11  from the outside to the inside and reaches the inner filter cavity  47  forming the clean side. From the inner filter cavity  47 , the cleaned fluid travels through the sleeve body  33  forming the coupling part of the connecting unit to the fluid duct  35  of the cover part  3  and then to the fluid outlet  37 . 
     The end cap  23  is in a sealed connection both to the cup-shaped housing  1  and to the cover part  3  by a seal arrangement  49  on the outer peripheral part of end cap  23 . Seal arrangement  49  is pressed against the housing  1  when the cover part is screwed onto the housing  1  by an inner collar  51  of the cover part  3 . The seal arrangement is formed in the embodiment of  FIGS. 1 to 3  by a ring seal in the form of an O-ring  53 . In the example shown in  FIG. 4 , on the outer periphery of the end cap  23 , a dovetail-shaped flange ring  55  is formed on which a profile seal  57  is secured and has two lips  59  opposite one another in the axial direction. Each lip forms their own sealing region relative to the cover part  3  and relative to the housing  1 . Otherwise, the embodiment from  FIG. 4  corresponds to the embodiment as shown in  FIGS. 1 to 3 . For a description of the details of the connecting unit, reference can be made both to  FIGS. 1 to 3  and also to  FIG. 4 . 
     As already mentioned, as the movable coupling part a sleeve body  33  is guided to be axially displaceable within guide duct  31 . The hollow body  27  connected to the end cap  23  and forming a part of the duct  31 , on its inner end region, has a shape projecting radially inward and forming a stop shoulder  61  on which one end of a helical compression spring  63  is supported. The spring is supported within the sleeve body  33 , adjoining its inside ribs  65  (only a few being numbered in  FIG. 3 ). The spring other end is supported on the inner ring shoulder  67  of the sleeve body  33 . The sleeve body  33  pretensioned by the spring  63  for axial motion in the direction to the cover part  3 . To limit this motion in an end position, on the extension  29  forming part of the guide duct  31 , a step  69  is formed, constricts the duct and interacts with a step  70  on the outer periphery of the sleeve body  33  for limiting the pretensioned sleeve body end position. All drawing figures show the operating state of the filter device when the cover part  3  has been screwed on, with the sleeve body  33  pushed out of its end position against the pretensioning of the compression spring  63  axially into the filter element  9 . This movement is due to the mouth edge  71  of the cover-side fluid duct  35 , as the stationary coupling part of the connecting unit for forming the coupling connection when the cover part  3  is screwed tight, pressing on the sleeve end edge  73  of the sleeve body  33  and pushing it out of the end position. The pretensioning of the compression spring  63  is then active as a sealing force between the mouth edge  71  of the fluid duct  35  and the sleeve end edge  73  of the sleeve body  33 . In other words, the coupling connection of the connecting unit is automatically established when the device is shifted into the operating state by screwing the cover part  3  onto the housing  1  containing the pertinent filter element  9 . 
     The interacting regions of the sleeve body  33  and the fluid duct  35 , which in the coupling state form the seal arrangement, are designed such that one of the annular surfaces, which are pressed against one another by the pretensioning of the spring, forms a continuous radial plane. The other ring surface forms a radial plane with a sealing edge projecting out of it. In these embodiments, the ring surface  75  on the fluid duct  35  is continuously level. The ring surface  77  along its peripheral edge forms a slightly projecting sealing edge  79 . The sealing edge  79 , with the radially outer edge of the ring surface  75 , forms a seal in interaction with its surface edge. Additionally the edge enclosure of the mouth edge  71  of the fluid duct  35  also forms centering ensure that extremely precise alignment of the coupling connection of the connecting unit necessarily takes place when the cover part  3  is screwed on. Since the filter element  9 , aside from the compression spring  63 , can be made without metal, mechanical or thermal effects could lead to slight deformations. This centering constitutes an extremely advantageous contribution to the operating reliability of the device. 
     While various embodiments have 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.