Patent Document

BACKGROUND OF THE INVENTION 
     The present invention relates to a filter element, in particular for filtering liquids or gases, e.g., for filtering oil for an internal combustion engine, having a bypass valve for the fluid to be filtered. Furthermore, the invention relates to a filter device suitable for containing the filter element of the invention, and to a method for maintaining a filter device of the invention. 
     It is known that in fluid filters having cylindrical filter inserts the bypass valve can be accommodated in the area of an end disk. The bypass valve is provided on the filter element to ensure fluid flow in the case of an unacceptable increase in flow resistance such as a clogged filter. By opening the bypass valve, the supply of fluid or gases to the system is ensured in this case. 
     A fluid filter with a bypass valve is disclosed, for example, in U.S. Pat. No. 5,770,054 (=DE 196 05 425).  FIG. 2  in that document shows a fluid filter in a disassembled state. A supporting dome is provided in the housing, to which is attached a valve body biased by a spring. This valve body finds a valve seat in the end disk belonging to the filter element when the filter element is installed. This provides an inexpensive design of the bypass valve. When the filter element is changed, however, only the valve seat together with the filter element is replaced. The valve body remains in the supporting dome, which is designed to be permanently attached to the housing. Therefore in the course of use of the filter, the valve body is subject to wear and soiling. With modern diesel engines in particular, the valve body may lose its tightness due to deposits of particles, so that an unwanted and unfiltered side stream of the lubricating oil is formed at the bypass valve. This worsens the quality of the lubricating oil, so that either the function of the internal combustion engine is endangered or more frequent oil change intervals are required. To avoid a malfunction, the valve body could also be replaced each time the filter is changed, but this creates increased installation costs and creates possible sources of error because the mechanic might forget to replace the valve body. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide an improved filter element especially for filtering a liquid or a gas. 
     A further object of the invention is to provide an improved filter device which can use the filter element of the invention. 
     Another object of the invention is to provide a filter element and filter device especially for filtering a liquid or a gas, which are highly reliable. 
     These and other objects have been achieved in accordance with the present invention by providing a filter element for filtering a liquid or a gas, the filter element comprising a concentrically arranged filter medium folded in zigzag pleats and being provided with end disks at the axial end faces of the filter medium, each end disk having an inner side that is connected to the filter medium and an outer side that faces away from the filter element; wherein at least a first end disk carries a valve element which is arranged concentrically inside the filter medium, the valve element comprising a valve seat which bulges outward above the plane of the outer side of the end disk and a valve body or valve disk which cooperates with the valve seat and which is mounted on the first end disk in an axially movable manner inside and surrounded by the filter medium. 
     The filter element according to the invention comprises a filter medium, for example, a nonwoven filter web or a paper, that is arranged concentrically and is provided with end disks on it axial end faces, in which one of the end disks carries a valve element which comprises a valve seat and an axially displaceable valve element, the axial movement of which is limited by a guide. In replacing the filter element, this valve is also replaced, so that it is possible to ensure that the filter will function reliably. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described in further detail hereinafter with reference to illustrative preferred embodiments shown in the accompanying drawing figures, in which: 
         FIG. 1  is a half section of a filter element according to the present invention; 
         FIG. 2  is a perspective view of a first end disk for the filter element of the invention viewed from above; 
         FIG. 3  is a perspective view of the end disk of  FIG. 2  viewed from below, and 
         FIG. 4  is shows a sectional diagram of a fluid filter with a filter element according to the invention arranged therein. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The half-sectional view in  FIG. 1  shows a filter element  10  that comprises a filter medium  11  which is folded in zigzag pleats and is arranged concentrically around the central axis  12 . The filter medium is bounded at its axial end faces by a first end disk  13  and a second end disk  14 . The end disks ensure a tight seal and are secured to the filter medium  11  by adhesive bonding or, if the end disks are thermoplastic end disks and the filter medium is a thermoplastic material, by a welding operation. The end disks each have an outer flange  15 ,  16  for concentric positioning of the filter medium  11 . Whereas the end disk  14  has an essentially flat construction and an opening  17  to accommodate a connection in its inner area, the first end disk  13  is designed as a functional part and serves at the same time as a carrier for a valve  18 . 
     Valve  18  comprises the following components: first the first end disk  13  is provided with a bulge  19 . This bulge  19  forms a valve seat  20  in its inner area. Within the valve seat there is a valve opening  21  through which liquid or gas can flow into to filter as long as the valve is open. The valve  18  is also provided with guide webs  22 , only one of which can be seen in this Figure. In the area of the guide web  22  a contact pin  23  is provided, as explained in greater detail below. 
     Inside of the first end disk  13  is a valve body part or sliding valve  24  which is held by the guide webs and is bordered axially at the top by the valve seat  20 . This sliding valve  24  has a valve body surface  25  which cooperates with the valve seat  20  and in the position shown here ensures a seal of the interior space  26  within the filter medium  11 . The valve body part  24  has a cylindrical surface  27  and can move axially downward. The axial movement of the valve body  24  is guided by the guide webs  22  along the surface  27 . 
     The open position of the valve is shown in  FIG. 4 . Furthermore in FIG. 1, snap-in elements  28 ,  29  are also provided on the first end disk  13  and may cooperate with a housing cover 111, as cover shown in FIG.  4  1. 
       FIG. 2  shows a perspective view of the first end disk  13  without the filter medium  11 . Corresponding parts are identified by the same reference numerals. The valve body part  24  is shown in the axially lower end position, so the valve is opened. It can be seen here that the guide webs  22  and  22 a are opposite one another and other guide webs are provided, offset by 90.degree. in relation to the guide webs shown here, so the valve body part  24  is reliably guided. A supporting edge  30  is provided in the area of the valve body surface and also ensures that the valve body part  24  is supported. As shown in  FIG. 1 , the sliding valve or valve body part  24  has an axially extending outer cylindrical surface  27 . As shown in  FIG. 2  with further reference to  FIG. 1 , the axially extending outer cylindrical surface  27  of the valve body part  24  is without gaps or grooves, (i.e. a circumferentially continuous cylindrical surface  27 , also see  FIG. 1 ). 
       FIG. 3  shows the guide webs  22 ,  22 a and  32 ,  32 a. Furthermore, this drawing figure shows the contact pins  23 ,  23 a,  33 ,  33 a that are arranged in the area of the guide webs and whose mechanism of action is described in greater detail below. The end disk  13  and the valve body part  24  are both made of a thermoplastic synthetic resin material. The valve body part  24  is simply engaged in the end disk at the time of assembly. As shown in  FIG. 3 , the guide webs  22 ,  22 a and  32 ,  32 a are formed by a radially inwardly leg and the respective contact pins  23 ,  23 a,  33 ,  33 a are formed by a radially outwardly leg of the a plurality of V-shaped members (for example V-shaped member having legs  22 a+ 23 a). As shown in  FIG. 3 , the V-shaped members are secured to said inner side of said first end disk ( 13 ) and spaced apart radially around the exterior of the axially extending outer cylindrical surface  27  of the sliding valve or valve body part  24  (see also  FIGS. 1 and 2 ). 
     The fluid filter shown in  FIG. 4  contains a filter element like that shown in  FIG. 1  and is explained in greater detail below. First, a base  110  is provided as well as a screw-on cover  111 . In the area of the base there is an outlet  113  and an inlet  115 . The fluid to be filtered flows through the inlet  115  into a raw or unfiltered fluid side  116  of the filter, passing from there through the filter medium  117  of a filter insert  118 , and then going into an interior space  119  of the filter insert, which represents the clean side of the filter. The filtered fluid then flows out of the filter through the outlet  113 . 
     When a certain pressure difference on the filter element is exceeded, a bypass valve, which comprises a valve body  120  and a valve seat  121  opens so that the fluid flows through the bypass openings  123  and thus passes directly from the raw fluid side  116  to the interior space  119  of the filter insert  118 . In the illustrated embodiment, the end of the valve body  120  which faces away from the valve seat  121  engages an axially moveable intermediate member  135  which is mounted on the support tube or support dome  124  (which also serves as a support tube) fixedly mounted in the base  110 . A spring  122  mounted in the support tube dome  124  urges the intermediate member axially upwardly and thus presses the valve body  120  against the valve seat  121 . Retainers  38  with catches  37  on the intermediate member  135  limit the axial movement of the intermediate member  135  and prevent it from disengaging from the support tube dome  124 . 
     The centrally disposed support tube  124  also serves to support the filter medium  117 . During installation, the filter insert  118 , into which the valve body  120  and the valve seat  121  are integrated, can be pushed onto this supporting dome. Then the screw-on cover  111  is screwed into the base  110 . A seal is achieved by a molded gasket  126  between the base and the screw-on cover. 
     The compression spring  122  exerts an axially directed closing force through the intermediate member  135  on the ribs  140  of the valve body  120  and normally holds the valve closed. In this figure, however, the valve body  120  is shown in the position in which its valve body surface  124  125 is spaced a distance from the valve seat  121 . Thus, as depicted in  FIG. 2 , fluid can pass between the holding webs  22  from the raw fluid side to the clean fluid side. This open position of the valve body surface  124  125 is assumed only when the fluid pressure on the raw fluid side is significantly above the fluid pressure on the clean fluid side. 
     The filter insert  118  is sealed at the end faces with end disks  139 a,  139 b. A radial gasket  142  that is provided on the end disk  139 a ensures a seal in this area between the raw fluid side and the clean fluid side. A snap-in connection  141  is provided on the end disk  139 b for securing the filter insert  118  in the screw-on cover  111  when the filter is screwed on. 
     Furthermore, contact pins  143 ,  144  are arranged on the end disk  139 b and are engaged with the supporting dome  124  or functional elements on the supporting dome  124 . Thus through these contact pins the supporting dome or parts of the supporting dome are held in a predefined axial position relative to the end disk 139b. Furthermore these contact pins may actuate functional components on the supporting dome such as locking systems. The crucial function of these contact pins is that they achieve a functionally reliable cooperation between the supporting dome  124 , the filter insert  118 , the screw-on cover  111  and the base  110 . 
     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.

Technology Category: 7