Abstract:
A filter system for a fluid, particularly a liquid filter, especially an oil filter for an internal combustion engine, having a receiving head, a cup-shaped housing releasably connectable to the receiving head, and a replaceable filter element disposed the cup-shaped housing, in which the filter element has a liquid-tight casing which is received in the interior of the cup-shaped housing.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to a fluid filter, particularly a liquid filter, especially an oil filter for an internal combustion engine, comprising a receiving head, a cup-shaped housing releasably connectable to the receiving head, and a replaceable filter element disposed in the cup-shaped housing.  
         [0002]     Two major types of fluid filters, particularly oil filters for internal combustion engines, are known in the art. The first major type comprises so-called spin-on filters. A spin-on filter has a cup-shaped housing, a filter element non-releasably disposed therein, and a threaded end plate. The cup-shaped housing is made of metal, so that it can withstand the pressure pulsation which occurs in the interior of the filter during operation of the internal combustion engine. The spin-on filter is screwed onto a receiving flange, or directly onto the engine block of the internal combustion engine, and during servicing is completely replaced with a new spin-on filter. This has drawbacks, however, resulting from the material mix of the filter because a mixture of plastics, paper, and metal must be disposed of, and material separation for disposal is problematic.  
         [0003]     The second major filter type comprises so-called oil modules in which a filter element is releasably disposed in a preferably cup-shaped housing and with the aid of this housing is likewise screwed onto a receiving head located within the oil circuit. For servicing, only the metal-free filter cartridge needs to be replaced, while the cup-shaped housing is a lifetime component.  
         [0004]     German Utility Model No. DE 200 04 31 U1 discloses a liquid filter with a bypass valve. A hollow cylindrical filter element is releasably disposed within a cup-shaped housing, and the cup-shaped housing is screwed onto a connection head. A support tube, which receives the bypass valve, is disposed concentrically within the interior of the filter element. The drawback of this arrangement lies in the changing of the filter element. First, there is a risk of contamination of the direct surroundings of the oil filter element because the oil-soaked filter medium still contains a residual amount of oil, which may drip as the filter element is replaced. In addition, the hands of the service personnel may become soiled because they come into direct contact with the oil-soaked filter element.  
       SUMMARY OF THE INVENTION  
       [0005]     Accordingly, it is the object of the present invention to provide an improved fluid filter, especially one which is suitable for internal combustion engine applications.  
         [0006]     Another object of the invention is to provide a fluid filter that can be disposed of without requiring separation of different materials.  
         [0007]     A further object of the invention is to provide a fluid filter which is simple and clean to use.  
         [0008]     It is also an object of the invention to provide a fluid filter which offers protection against pressure pulsations.  
         [0009]     These and other objects are achieved in accordance with the present invention by providing a filter system for filtering a fluid comprising a receiving head, a cup-shaped housing releasably connectable to said receiving head, and a replaceable filter element disposed in said housing, in which the filter element is provided with a liquid-tight casing which is received in the interior of the cup-shaped housing.  
         [0010]     The fluid filter system according to the invention, particularly a liquid filter, especially an oil filter for an internal combustion engine, has a cup-shaped housing, a replaceable filter element disposed therein, and a receiving head, such that the cup-shaped housing is releasably connectable to the receiving head. The filter element further has a liquid-tight casing within the cup-shaped housing. The liquid-tight casing is preferably made of a plastic material, which may be blow molded or injection molded. The exterior shape resembles the interior shape of the cup-shaped housing, i.e., here too, a cup shape is preferred. This shape may be designed to fully contact the cup-shaped housing, contact it only at a few points, or not contact it at all, but the distance between the inner wall of the cup-shaped housing and the outer wall of the liquid-tight casing should be as small as possible. This has the positive effect that when the filter element is replaced, the liquid present within the filter element cannot escape, and contamination of the environment is prevented. Soiling of the hands of the service personnel is also avoided because the outer shell of the liquid-tight casing is dry and clean. A further advantage compared to the conventional oil modules is that soiling of the inner wall of the cup-shaped housing is also avoided because the inner wall of the cup-shaped housing does not come into contact with the circulating oil.  
         [0011]     In accordance with one advantageous embodiment of the invention, the cup-shaped housing is capable of absorbing and counteracting operational diameter fluctuations of the liquid-tight casing. These operational diameter fluctuations may, for example, comprise a diameter increase as a result of temperature fluctuations. By matching the liquid-tight casing to the cup-shaped housing it is possible to produce the liquid-tight casing with a thin wall thickness and to use an inexpensive plastic, so that the manufacture of the filter element becomes more cost-effective, and the desired functions can nevertheless be fulfilled. The cup-shaped housing, on the other hand, can be made more robust using a metal or plastic, so that it can absorb the diameter increase of the liquid-tight casing. The liquid-tight casing is supported against the robust cup-shaped housing, which as a lifetime component can have a greater wall thickness than the liquid-tight casing.  
         [0012]     It is advantageous if the filter element comprises at least one hollow cylindrical filter bellows, which sealingly separates a liquid inlet from a liquid outlet. To this end, the liquid-tight casing includes a support for the radial outer contour of the filter bellows. The filter bellows may be constructed from a zigzag folded or wound filter medium, which may be made of filter paper or a synthetic nonwoven material. Because of the pressure pulsation during operation there is a risk that the filter bellows will collapse under certain circumstances. To counteract this, many hollow cylindrical filter elements have a support member within their interior diameter, but this does not eliminate the risk of an outward collapse. With this configuration, a radial expansion of the filter bellows as a result of pressure pulsations can be absorbed by the support within the liquid-tight casing. In combination with the absorption of the diameter fluctuations of the liquid-tight casing by the cup-shaped housing, the forces that occur can be transmitted directly to the cup-shaped housing via the liquid-tight casing. The result is a combination of ease of maintenance through clean servicing of the filter element, integration of the function of an external support member for the filter bellows, and cost-effective design of the liquid-tight casing because certain functions influencing stability can be assumed by the cup-shaped housing.  
         [0013]     It is advantageous if the outer support is constructed as circumferentially distributed support contours in the liquid-tight casing. On the one hand, the support contours support the outer contour of the filter bellows against radially outwardly acting forces and, on the other hand, the support contours transmit the absorbed forces to the cup-shaped housing.  
         [0014]     In accordance with another embodiment of the invention, the support contours form discharge volumes between the filter bellows and the inside of the liquid-tight casing, such that the discharge volumes communicate with the floor of the liquid-tight casing. As a result, the liquid cleaned by the filter bellows can flow through the discharge volumes to the floor of the liquid-tight casing. Apart from these advantages, i.e., greater ease of maintenance and the function of an external support member, a third advantage is achieved, i.e., the possibility of using the support member to receive and transfer a liquid.  
         [0015]     In accordance with yet another advantageous embodiment of the invention, the liquid-tight casing has at least one active contour in the region of one of the end faces, extending radially beyond the circumferential diameter. This active contour enables, for example, a precise radial and axial association or positioning relative to the cup-shaped housing. The active contour also makes it possible to check whether a filter element is inserted and whether the inserted filter element is suitable for the filter system.  
         [0016]     Advantageously, the active contour is designed to communicate with a recess in the cup-shaped housing. Because no liquid is present outside the filter element, the filter element can be easily inserted into the cup-shaped housing and axially and radially fixed without a special seal being required.  
         [0017]     According to another advantageous embodiment of the inventive concept, an integral anti-drain membrane or back-flow check membrane is disposed in the region of the liquid inlet and outlet. This integral anti-drain membrane functions as a normal anti-drain membrane in the inlet region and, in addition, as an anti-drain valve in the outlet region. During operation of the internal combustion engine the inlet and outlet are open if the filter element is inserted. If the filter element is removed, however, the integral anti-drain membrane prevents the content of the filter element from flowing out of the inlet and/or outlet. This again has a substantial advantage during servicing because the filter element can be removed from the cup-shaped housing and disposed of at an angle to the horizontal without any leakage of the liquid contents which remain in the filter element.  
         [0018]     According to yet another embodiment of the invention, two hollow cylindrical filter bellows are arranged concentrically within the interior of the liquid-tight casing. The filter bellows have a common end disk on one end face, and each bellows has a separate end disk on the other end face. The end disk is preferably made of a thermoplastic material, and the filter bellows are connected to the end disk by adhesive bonding or fusion welding. The common end disk is preferably annular in shape, so that a flow-through opening for the filtered liquid is formed concentrically in the interior of the inner filter bellows. The separate configuration of the two end disks on the opposite end face of the two filter bellows makes it possible to realize filter bellows having differing axial lengths.  
         [0019]     It is advantageous if the common end disk has spring member on the side opposite the filter bellows to support the filter bellows against the inside of the floor of the liquid-tight casing. This makes it possible to axially support and fix the filter bellows relative to the liquid-tight casing.  
         [0020]     According to yet another advantageous embodiment of the invention, the separate end disk of the outer filter bellows simultaneously forms a tight seal for the liquid-tight casing, so that the radially outer rim of the end disk is tightly and non-releasably connected to the liquid-tight casing. This connection may, for example, be provided by welding, bonding or some other conventional process for permanently connecting two plastic parts.  
         [0021]     In addition, the separate end disk may advantageously have an annular collar that extends axially away from the filter element. A seal member to seal the filter element relative to the connection head is disposed within the annular collar. This seal member may, for example, be an O-ring or a sealing ring, which is disposed in a groove formed in the outer or inner circumference of the annular collar. Thus, the end disk of the outer filter bellows on the one hand secures the filter element and on the other hand seals the filter element and provides a connection to a connection head.  
         [0022]     The liquid is filtered as follows. The unfiltered liquid flows through at least one inlet into a gap between the two filter bellows. To filter the liquid, it then passes through the two filter bellows—radially inwardly on the one hand and radially outwardly on the other. The filtered portion of the liquid stream that flowed inwardly into the interior of the inner filter bellows then flows back into the liquid circuit through the outlet. The filtered portion of the liquid that flowed radially outwardly into the outer filter bellows is conducted to the floor of the liquid-tight casing by the active contours of the liquid-tight casing, from where it flows through the opening in the separate end disk to reach the interior of the inner filter bellows. From there it is likewise transferred back into the liquid system through the outlet.  
         [0023]     These and other features of preferred embodiments of the invention, in addition to being set forth in the claims, are also disclosed in the specification and/or the drawings, and the individual features each may be implemented in embodiments of the invention either alone or in the form of subcombinations of two or more features and can be applied to other fields of use and may constitute advantageous, separately protectable constructions for which protection is also claimed. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]     The invention will be described in further detail hereinafter with reference to illustrative preferred embodiments shown in the accompanying drawing figures, in which:  
         [0025]      FIG. 1  is a sectional view of a liquid filter according to the invention;  
         [0026]      FIG. 2  is a sectional view of the filter element and the cup-shaped housing;  
         [0027]      FIG. 3  is a perspective view of the filter element and the cup-shaped housing;  
         [0028]      FIG. 4  is a separate perspective view of the cup-shaped housing;  
         [0029]      FIG. 5  is a sectional view of an outer shell of a filter element according to the invention;  
         [0030]      FIG. 6  is a perspective view of the anti-drain membrane;  
         [0031]      FIG. 7  is a top view of a section in the region of the blocking member;  
         [0032]      FIG. 8  is a sectional view of an alternative anti-drain membrane, and  
         [0033]      FIG. 9  is a sectional view of a portion of an alternative filter element.  
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0034]      FIG. 1  is a sectional view of a liquid filter system  10  in which a cup-shaped housing  11  is connected to a connection head by a bayonet connection. The connection head  12  may be a separate connecting flange, or it may be formed directly from an internal combustion engine component. The filter system is suitable for liquids of any kind used in an internal combustion engine, such as oils, fuels, hydraulic fluids, or coolants. An inlet  13  and an outlet  14  are disposed in the connection head  12  of the filter system  10 . The outlet  14  is arranged concentrically in the center of the connection between the cup-shaped housing  11  and the connection head  12 . The inlet  13  is distributed concentrically around the outlet  14 , also in the interior of the connection between the cup-shaped housing  11  and the connection head  12 .  
         [0035]     Inside the cup-shaped housing  11  is a filter element  15 . The filter element  15  comprises a canister  16  which holds the filter medium or media. The circumference of the canister  16  is radially outwardly supported against an inside wall  17  of the cup-shaped housing  11 . At the same time the canister supports an outer wall  18  of a first filter bellows  19  via grooves formed in the canister  16 . The canister  16  is liquid-tight and additionally functions as an outer support tube for the first filter bellows  19  and a support against pressure pulsations at the cup-shaped housing  11 . As a result, the canister  16  can be constructed relatively thin with regard to its material thickness because the actual support against each pressure pulsation is provided by the cup-shaped housing  11 .  
         [0036]     Disposed concentrically within the interior of the filter element is a support tube  20  around which extends a second filter bellows  21 . The first and second filter bellows may be a zigzag folded filter medium, a wound filter medium, a combination thereof, or some other conventional filter bellows. In the region of a housing floor  22  of the canister  16 , the two filter bellows are held by an end disk  23 , which is ring-shaped with a concentrically disposed opening  24 . A spring element  25  is integrally formed on the end disk  23 . Spring element  25  supports the filter bellows against the housing floor  22  and axially locates and fixes the filter bellows by applying an axial spring force in an upward direction. Radial location and fixation is achieved by the inner contour of the canister  16 .  
         [0037]     At the opposite end of the filter bellows, the first filter bellows  19  has an end disk seal  26 . The second filter bellows  21 , which is disposed in the interior of the first filter bellows  19 , extends slightly higher in the axial direction than the first filter bellows  19 . The end face seal of the second filter bellows  21  is provided by an end disk  27 , which is annular in shape and has a concentric passage for the outlet  14 . The end disk  27  has a coupling contour  28  extending axially toward the connection head  12  for an anti-drain membrane  29 . This coupling contour  28  is distributed across the end disk  27  and comprises a plurality of pins or mushroom-shaped contours protruding axially toward the connection head  12 . The anti-drain membrane  29  is tightly coupled to the end disk  27  by the coupling contour  28 . It seals the liquid inlet  13  when the internal combustion engine is stopped and the liquid outlet  14  during servicing. The anti-drain membrane  29  is preferably made of a soft thermoplastic material, such as a thermoplastic elastomer (TPE).  
         [0038]     The end disk  26  comprises a concentric, axially protruding annular collar  30  with a groove in its outer circumference to accommodate a sealing ring  31 . When the cup-shaped housing  11  is connected to the connection head  12 , the annular collar  30  is inserted into a collar seat  32  of the connection head, so that the sealing ring  31  provides a seal between the annular collar  30  and the collar seat  32 . Disposed concentrically in the interior of the collar seat  32  is an outlet tube  33 , which extends into the opening of the end disk  27  and thereby opens the anti-drain element of the anti-drain membrane  29  on the outlet side. To seal the unfiltered side from the filtered side, sealing is effected radially between the anti-drain membrane  29  and the outlet tube  33 , which is disposed in the connection head  12 . To seal the filter element  15  liquid tight, the canister  16  and the end disk  26  are non-releasably and sealingly interconnected by a connecting contour  34 , e.g., by fusion welding or adhesive bonding.  
         [0039]     To release the filter element for servicing and to connect it, the cup-shaped housing  11  has a tool-holding fixture  35  having, for example, a hexagon socket or a hexagon head. For servicing, a tool is applied at this point to separate the cup-shaped housing  11  from the connection head  12 , or to reconnect the two parts. The plurality of circumferentially spaced locking element parts  36  in the form of a radially outwardly protruding lug is shaped from the one axial end of the canister  16 . These parts engage in recesses of the cup-shaped housing and recesses within a locking contour of the cup-shaped housing  11 , which will be described with reference to the following figures. The part  36  of the locking elements of the canister  16  simultaneously serves as a connecting contour  34  relative to the end disk  26 . The connection head  12  has guides  37  into which locking contours formed from the part  36  of the locking elements of the canister  16  and from the cup-shaped housing  11  can be inserted and in which they are guided.  
         [0040]     Disposed in the outer region of the connection head  12  is at least one blocking member  38 , which prevents a connection between the cup-shaped housing and the connection head  12  when no filter element  15  or a wrong filter element is inserted. The blocking member  38  then engages in a recess  44  of the cup-shaped housing  11  and thereby prevents the bayonet connection from closing. The function of the blocking member  38  is illustrated in  FIG. 7 .  
         [0041]     The liquid to be filtered flows through the inlet  13  of the connection head  12  into a space  39  between the two filter bellows  19 ,  21 , then flows through the second or inner filter bellows  21  into a discharge chamber  40  located on the filtered side within the support tube  20 . From the discharge chamber  40  the filtered liquid flows back into the system through the anti-drain membrane  29 , which is opened by the outlet tube  33 , and through the outlet  14  located on the filtered side. Another portion of the unfiltered liquid flows radially outwardly from the space  39  through the first or outer filter bellows  19  into a space on the canister side, from whence it flows downwardly to the canister floor  22 . From the canister floor the liquid can again be returned to the system through the outlet  14  on the filtered side.  
         [0042]      FIG. 2  illustrates the combination of the filter element  15  and the cup-shaped housing  11  in a sectional view. Components corresponding to those depicted in  FIG. 1  are identified by the same reference numerals.  FIG. 2  shows that when the cup-shaped housing  11  and the filter element  15  are released from the connection head  12 , the anti-drain membrane  29  returns to its original shape in the region of the outlet  14  on the filtered side because the outlet tube  33  is no longer present, so that the anti-drain membrane prevents the liquid stored in the filter element  15  from leaking out. Since the anti-drain membrane  29  is made of a thermoplastic elastomer, the contour can generate a return force within the blocking membrane, which return force has the effect of producing a tightly closed seal at the outlet.  
         [0043]      FIG. 3  is a perspective view of the cup-shaped housing  11  and the filter element  15  disposed therein. Parts corresponding to those depicted in the previous figures are identified by the same reference numerals. This figure clearly shows the plurality of coupling contours  28  of the end disk  27  for the anti-drain membrane  29 . The open axial end of the cup-shaped housing  11  further has a plurality of regularly spaced locking contours  42  around the circumference to produce the bayonet connection within the filter system  10 .  
         [0044]     When the filter element  15  is correctly installed, the locking element part  36  on the filter element side is disposed in a recess  43  of the locking contour  42  to complete the locking contour  42 . If the filter element  15  is not inserted, or if the filter element does not match, the recess  43  within the locking contour  42  remains free, so that the blocking member  38  prevents a bayonet-type connection between the cup-shaped housing  11  and the connection head  12 . The blocking member  38  then engages in the recess  43  and prevents the cup-shaped housing  11  from being twisted relative to the connection head  12 .  
         [0045]      FIG. 4  shows a perspective view of the cup-shaped housing  11 . To insert the filter element  15 , the cup-shaped housing  11  has circumferentially spaced recesses  44  extending axially from the open end of the cup-shaped housing  11  and ending in the recesses  43  for the locking contour. The filter element  15  with the parts  36  of the locking elements is inserted into the recesses  44  until it reaches the end of the recess  43  of the locking contour so as to complete the locking contour  42 . Only this completes the locking contours  42  to establish the connection to the connection head  12 .  
         [0046]      FIG. 5  is a sectional view of the canister  16 , which represents the outer shell of the filter element  15 . A plurality of grooves  45  are distributed across the lateral face of the canister  16  and form a support face  46  within the interior of the canister  16  for the first filter bellows  19 . Because the grooves,  45  in the inner circumference of the canister  16  are not continuous, the filtered liquid flowing through the first filter bellows  19  can be easily fed to the discharge space  40  on the filtered side via the canister floor  22 .  
         [0047]     The rest of the above-described filter element is then inserted into the canister  16  and is connected to the canister  16  at the connecting contour  34 . This creates a liquid-tight system that prevents contamination of the surroundings and the environment and eliminates the handling of dirty filters by the maintenance personnel during servicing. The axial seal of the canister  16  in the region of the open end is again formed by the locking element part  36 , which engages in the recess . 43  of the locking contour  42  of the cup-shaped housing  11 .  
         [0048]      FIG. 6  is a perspective view of the anti-drain membrane  29 . Components corresponding to those shown in the preceding figures are again identified by the same reference numerals. The anti-drain membrane  29  is substantially plate-shaped and is preferably made from a thermoplastic elastomer. Anti-drain membrane  29  has a plurality of openings  47  in the plate-shaped part to create the coupling with the end disk  27  via the coupling contour  28 . In its outer region, the anti-drain membrane  29  has a sealing face  48  angled relative to the plate-shaped region for the inlet area of the filter system  10 . Because of the flexibility of the material, the inlet area lifts from a sealing face in the end disk seal  26  as the liquid to be filtered streams in and thereby ensures the inflow of the liquid. When the internal combustion engine is stopped, i.e., when there is no liquid pressure against the anti-drain membrane, the sealing face  48  seals the inlet  13  because of its elasticity.  
         [0049]     Concentrically disposed in the interior of the anti-drain membrane  29  is a type of sealing valve  49  to seal the outlet when the filter element is removed from the liquid circuit. The outlet seal  49  has a kind of duckbill, which in the inserted state is opened from the connection head  12  by the outlet tube  33  and which closes again because of its inherent elasticity when the outlet tube  33  is removed. Here, the anti-drain membrane and the anti-drain valve are integrated in a single component.  
         [0050]      FIG. 7  illustrates one possibility of using the blocking member  38 . Once again, parts corresponding to those shown in the previous figures are identified by the same reference numerals.  FIG. 7  shows a top view of a cutaway section in the area of the blocking member  38 . The blocking member  38  is disposed in the connection head  12 . A locking pin  50  and a spring member  51  are disposed in the connection head  12  such that the locking pin  50  is axially displaceable against the force of the spring member  51 .  
         [0051]     When the cup-shaped housing  11  and the locking head  12  are brought together and no filter element  15  is present or provided, the force of the spring  51  causes the locking pin  50  to engage in the recess of the locking contour  43 , thereby preventing the twisting necessary to create the bayonet connection. If the filter element  15  is inserted correctly, the recesses  43  and  44  are filled by the locking element part  36  of the filter element  15  and thereby complete the locking contour  42 . As a result, the locking pin  50  is pushed into the locking head  12  against the force of the spring member  51 , so that the cup-shaped housing  11  can be twisted relative to the connection head  12 , allowing the bayonet connection to be created.  
         [0052]      FIG. 8  shows a sectional view of an alternative anti-drain membrane  29 . Again, pars corresponding to those shown in the preceding figures are identified by the same reference numerals. In this embodiment, the connection to the filter element is realized in an alternative manner through a circumferential annular groove  52  disposed concentrically to the inlet sealing face  48 . This annular groove receives an end disk (not shown). This connection is discussed further below with reference to  FIG. 9 .  
         [0053]      FIG. 9  shows a sectional view of a portion of an alternative filter element using the anti-drain membrane  29 . Again, parts corresponding to those shown in the preceding figures are identified by the same reference numerals. In this case, the inner filter bellows  21  is sealingly connected by hot plate welding to the lower end disk  23  and the upper end disk  27 . A securing ring  53  holding the anti-drain membrane  29  is concentrically disposed within the end disk seal  26 . The securing ring  53  is preferably integrally connected to the end disk seal  26  via connecting webs  55 , such that the connecting webs  55  are circumferentially disposed around the outlet  14 . The end disk seal  26  and the end disk  23  each have sealing faces  54  for the outer filter bellows  19  and in addition fix the outer filter bellows. The canister  16  (not shown) may be configured analogously to the preceding embodiments and thus connects the two end disks  23  and  26 .  
         [0054]     The foregoing description and examples have been set forth merely to illustrate the invention and are not intended to be limiting. Since modifications of the described embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed broadly to include all variations within the scope of the appended claims and equivalents thereof.