Abstract:
A liquid filter suitable for motor vehicles which includes a filter head ( 11 ), a vessel ( 12 ) and a filter element ( 16 ) disposed within the vessel ( 12 ) sealingly separating an inlet ( 14 ) from an outlet ( 15 ) such that liquid from the inlet must flow through the filter element to reach the outlet. The filter element ( 16 ) has guide projections ( 27, 28 ) positioning the filter element ( 16 ) within the vessel ( 12 ). Prior to installation, the filter element ( 16 ) is preassembled into the vessel ( 12 ) and fixed in position by pushing the filter element ( 16 ) into an element guide ( 29 ), after which the preassembly is screwed onto the filter head ( 11 ). When the vessel ( 12 ) is unscrewed from the filter head ( 11 ), the filter element ( 16 ) slides out of the element guide ( 29 ) and moves axially upwardly to free a volume V. Liquid flowing into the vessel ( 12 ) from the higher regions of the liquid filter ( 10 ) can flow into this volume, thus enabling drip-free replacement of the filter element.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of international patent application no. PCT/EP2007/051631, filed Feb. 21, 2007 designating the United States of America, the entire disclosure of which is incorporated herein by reference. Priority is claimed based on Federal Republic of Germany utility model application no. DE 20 2006 013 088.8, filed Aug. 25, 2006. 
     
     BACKGROUND OF THE INVENTION 
       [0002]    The invention relates to a liquid filter especially suitable for use with motor vehicles. 
         [0003]    Liquid filters comprising a filter head, a vessel screwed to the filter head, and a filter element disposed inside the vessel are known in the art. When the vessel is unscrewed from the filter head, liquid fuel oil spills over the rim of the vessel because fuel or oil from parts of the liquid circuit above the vessel flows into the vessel and causes the vessel to overflow. 
       SUMMARY OF THE INVENTION 
       [0004]    It is therefore an object of the invention to provide an improved liquid filter construction. 
         [0005]    Another object of the invention is to provide a liquid filter which minimizes or eliminates liquid spillage when the vessel is detached from the filter head. 
         [0006]    A further object of the invention is to provide a liquid filer which enables a filter vessel to accommodate an influx of liquid when the vessel is detached from a filter head. 
         [0007]    It is also an object of the invention to provide a liquid filter that has a simple design and can be manufactured at reasonable cost. 
         [0008]    These and other objects are achieved in accordance with the present invention by providing a liquid filter comprising a filter head, a vessel detachably mounted on said filter head, and a filter element sealingly positioned inside the vessel separating a filter inlet from a filter outlet so that liquid from the inlet must flow through the filter element to reach the outlet, wherein the filter element is provided with guide projections which position the filter element inside the vessel, and the axial position of the filter element inside the vessel is shifted when the vessel is detached from the filter head. 
         [0009]    The liquid filter according to the invention thus comprises a filter head, a vessel and a filter element arranged within the vessel. The filter element is disposed in such a way that it separates an inlet from an outlet in a sealed manner. Liquid filters of this kind are suitable for filtering fuel or oil, particularly for internal combustion engines in vehicles and the like. The filter element has guide projections to position the filter element within the vessel. Prior to installation, the filter element is preassembled into the vessel. To this end, the filter element is pushed into element guide and fixed in position. This preassembled unit is then screwed onto the filter head. When the vessel is unscrewed from the filter head, the filter element slides out of the element guide and moves axially upwardly, thereby freeing a volume V. Liquid that flows into the vessel from the higher regions of the liquid filter can flow into this volume. Thus the filter can be replaced without dripping. To make it easier for the liquid to flow out of the higher regions, closeable ventilation holes may be provided, which are opened prior to unscrewing the filter so as to allow air to flow into this higher region. This prevents a negative pressure from forming within the filter. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The invention will be described in further detail hereinafter with reference to illustrative preferred embodiments shown in the accompanying drawing figures, in which: 
           [0011]      FIG. 1  is a sectional view of a liquid filter constructed in accordance with the present invention; 
           [0012]      FIG. 2  is a perspective view of the filter element of  FIG. 1 ; 
           [0013]      FIG. 3  is a perspective view of an alternative filter element embodiment in accordance with the present invention; 
           [0014]      FIG. 4  depicts the liquid filter of  FIG. 1  a partially detached state; 
           [0015]      FIG. 5  is a detail view of the filter element guide of the vessel; 
           [0016]      FIG. 6  is a depiction of an alternative embodiment of the guide, and 
           [0017]      FIG. 7  is a view of yet another alternative embodiment of the guide. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0018]      FIG. 1  is a sectional view of a liquid filter  10 . The liquid filter  10  has a filter head  11  and a vessel  12 . The vessel  12  can be connected to the filter head  11  via a threaded joint  13  using an O-ring  17   a  to form a tight seal. As an alternative, other kinds of connections may be used, e.g., a bayonet joint. Inlets and outlets  14 ,  15  for the liquid to be filtered and the filtered liquid, for example fuel or oil, are provided within the filter head  11 . In other embodiments, these inlets and outlets  14 ,  15  may also be arranged on the vessel  12 . The inlet  14  is separated from the outlet  15  by a filter element  16  so as to form a seal. An O-ring  17  is provided to seal the filter element  16  on the filter head  11 . This O-ring  17  is mounted to a seal shoulder  18  of the filter element  16  and is compressed when the filter element  16  is mounted to a fitting  19  of the filter head  11 . 
         [0019]    The filter element  16  has an annularly closed filter medium  20  and a support tube  21  arranged within the filter medium  20 . This support tube has a lattice structure which allows the liquid to flow through it without appreciable pressure loss. The support tube  21  has a concentrically disposed pin geometry  22 , which opens a valve  23  when the filter element  16  is inserted correctly enabling the liquid to flow out of the filter arrangement. The valve  23  is spring loaded by a coil spring  24 , so that the valve  23  is closed when no filter element  16  is installed or when the filter element is installed incorrectly. The valve  23  is also closed when the filter element is replaced. 
         [0020]    The filter element  16  further has an upper end disk  25  and a lower end disk  26 . The end disks  25 ,  26  are connected to the filter medium  20  so as to form a seal. This connection can, for example, be produced by adhesive bonding, welding or in some other manner. The seal shoulder  18  is disposed on the upper end disk  25 . The upper end disk  25  also has a plurality of outwardly protruding guide projections  27  distributed around its circumference, which position the filter element  16  during axial movement within the vessel  12 . 
         [0021]    The lower end disk  26  also has a plurality of guide projections  28  distributed around its periphery. These guide projections  28  fix the filter element  16  within the vessel  12 . To this end, the vessel  12  has axial and radial element guide  29 , which will be described in greater detail below with reference to  FIG. 5 . 
         [0022]    In its bottom area, the vessel  12  has axially extending detent hooks  30  enclosed by a spring  31 . The spring  31  communicates with the lower end disk  26 . In the preassembled state of the filter element  16  within the vessel  12 , the filter element  16  is axially fixed inside the vessel  12  by the lower guide projections  28 , thereby compressing the spring  31 . When the vessel  12  is unscrewed from the filter head  11 , the O-ring  17  radially fixes the filter element  16  on the fitting  19 , such that no analogous radial movement of the filter element  16  together with the vessel  12  occurs. 
         [0023]    By rotating the vessel  12  by e.g., 5 to 10°, the guide projections  28  can therefore disengage from the element guide  29 . In other embodiments a rotation of up to approximately 45° may be required for the guide projections  28  to disengage from the element guide  29 . The spring force of the spring  31  pushes the filter element upwardly by approximately 2 to 3 cm. Depending on the overall size of the liquid filter, the filter element  16  may have to travel a greater axial distance in large-volume liquid filters or a smaller distance in very small liquid filters. The lower end disk  26  can rebound up to the detent hooks  30 . 
         [0024]    The detent hooks  30  prevent any further axial movement of the filter element  16  so that during removal the filter element  16  cannot remain on the fitting  19  of the filter head  11  but is removed together with the vessel  12 . This axial rebound of the filter element  16  from its fixed position frees a volume in the vessel  12  into which fuel can flow. This free volume can therefore receive incoming liquids so as to prevent any overflow of the vessel  12 . This geometric configuration of the components enables a clean replacement of the filter element. 
         [0025]      FIG. 2  is a perspective view of a filter element  16 . Components corresponding to those of  FIG. 1  are identified by the same reference numerals. The filter element  16  has four guide projections  27  distributed uniformly around the circumference of the upper end disk  25 . The number of guide projections  27  is arbitrary, but three to five guide projections  27  are preferred. Preferably, the guide projections  27  are uniformly distributed along the periphery of the end disk. The guide projections  27  extend from the periphery of the end disk  25  in such a way that a gap  32  is formed between the guide projections  27  in relation to the geometry of the vessel  12  (indicated by the broken line). The liquid can flow through this gap  32 . The guide projections  27  contact the geometry of the vessel  12  so that wedging of the filter element  16  is prevented. 
         [0026]      FIG. 3  shows an alternative filter element  16 ′. Components corresponding to those of  FIG. 2  are again identified by the same reference numerals. In contrast to  FIG. 2 , the guide projections  27  form a peripheral margin  33 , with elongated slots  34  provided to allow the liquid to flow through. Thus, the filter element  16  conforms to the vessel geometry over the entire periphery, such that an adequate flow cross-section is provided for the liquid. 
         [0027]      FIG. 4  shows the liquid filter depicted in  FIG. 1  in a partially disassembled state. Components corresponding to those of  FIG. 1  are identified by the same reference numerals. The threaded joint  13  between the filter head  11  and the vessel  12  is shown in the unscrewed state. The filter element  16  is disengaged from the element guide  29  and has been pushed upwardly by the spring  31  so as to free a volume V in the lower vessel region. 
         [0028]    Because the filter element  16  has been displaced in axially downward direction, the pin geometry  22  no longer contacts the valve  23 . The spring  24  presses the valve  23  against the valve seat, so that the valve  23  is closed and the outlet  15  can no longer communicate with the environment. Only when a correct filter element  16  is inserted and mounted is the valve  23  lifted from its valve seat so that the interior of the filter  10  can again communicate with the outlet  15 . 
         [0029]      FIG. 5  shows a detail of the element guide  29  of the vessel  12 . The element guide  29  has an axial region  35  and a horizontal region  36 . These geometries  35 ,  36  protrude into the interior of the vessel  12 . To preassemble the filter element  16  in the vessel  12 , the guide projections  28  are inserted into the axial region  35  and are pushed up to the horizontal region  36 . A subsequent 5 to 10° rotation of the filter element  16  within the vessel  12  axially fixes the filter element  16  within the vessel  12 . The horizontal region  36  has a stop  37  to prevent the filter element  16  from being rotated too far within the vessel. In alternative embodiments of the horizontal region  36 , this area may also be inclined. 
         [0030]      FIG. 6  illustrates an alternative embodiment of the element guide  29  to that shown in  FIG. 5 . This element guide  29 ′ has an axial region  35  and a horizontal region  36  similar to that shown in  FIG. 5 . The axial region  35  has a shoulder  38  disposed at a distance from the horizontal region  36 . This shoulder  38  is positioned axially offset from the horizontal region  36  and in opposition to the direction of rotation in relation to the horizontal region. The axial distance between the horizontal region  36  and the shoulder  38  is approximately 20 mm. This distance must be such that when the filter element is removed it travels a sufficient axial distance so that a sufficiently large volume is freed. 
         [0031]    The shoulder  38  serves to fix the filter element  16  within the vessel  12  when the device is opened so as to prevent the element from “getting caught” on the filter head  11 . In the preassembled state of the filter element  16  inside the vessel  12 , the guide projections  28  are guided in the horizontal region  36  so that the element  16  is held in axial direction. To remove it, the filter element  16  is rotated out of the horizontal region  36  until the guide projections  28  slide axially along the axial region  35  out of the vessel  12 . 
         [0032]    The shoulder  28  prevents the filter element from sliding completely out of the vessel  12  because the guide projections  38  strike the shoulder  38  and thus limit the axial path of the filter element  16  after approximately 2 cm. Instead of this tongue and groove configuration of the element guide  29 , the guide projections  28  may also be formed as detent projections communicating with corresponding geometries on the vessel  12 . To this end, the vessel  12  can have polygon-shaped geometries distributed over its circumference. 
         [0033]      FIG. 7  shows yet another alternative of the inventive fixation of the filter element  16  inside the vessel  12 . In this embodiment, the support tube  21  has projections  39  which fix the position of the filter element  16  inside the vessel  12 . To this end, the vessel  12  has detent hooks  30  on which the projections  39  are fixed in position. 
         [0034]    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.