Replaceable filter cartridge with support element and liquid filter with such a filter cartridge

#The invention relates to a exchangeable filter cartridge for a liquid filter with an annularly constructed filter medium arranged on a support element. The invention further relates to a liquid filter in which such a filter cartridge is installed.

#Filter cartridges of the initially described type are known, for instance, from U.S. Pat. No. 5,413,712. This document describes a filter cartridge comprising a support tube holding the filter medium whose end faces are provided with end disks. This filter cartridge can be replaced by removing a cover from the filter housing. A spring in the cover pushes the installed filter cartridge axially against a centrally arranged outlet port. A sealing membrane provides an axial seal between the outlet port and the end disk of the filter cartridge. The sealing membrane is simultaneously configured as a return flow barrier or check valve.

#The disadvantage of the described prior art is the use of a spring to produce an axial force to act against the seal. This spring is an additional component in the filter unit and thus reduces the economic efficiency of the solution. Moreover, the axial force that can be applied by the spring to provide a seal is limited. Increasing the axial force by making the spring stiffer has the disadvantage of increasing the closing forces that have to be applied to the cover, which makes it more difficult to replace the filter element.

#The invention will be described in further detail hereinafter with reference to illustrative preferred embodiments shown in the accompanying drawings in which:

#FIG. 1 is a cross section through the center of a liquid filter according to the invention; and

#FIG. 2 is an enlarged detail X according to FIG. 1 showing an alternative embodiment of the sealing membrane.

#The liquid filter according to FIG. 1 comprises a filter cartridge 10 disposed inside a housing 11 comprising a base plate 12 and a screw-on cover 13, which is screwed together with the base plate with an interposed O-ring 14 to form a seal. The filter assembly comprises a support element 15 onto which is slipped a star-folded filter paper that is provided with end disks 16 in such a way that a radial seal is obtained between the support element 15 and the end disks 16. Further, in an end area 18 of the support element, a sealing membrane 19 is mounted in a seat 20. The sealing membrane has a sealing edge 21 which is supported against the base plate 12 and thus provides a seal with respect to the inlets 22 which are also located in the base plate. Further, the sealing membrane has a sealing surface 23 to ensure a radial seal between seat 20 on support element 15 and an outlet port or nipple 24 which is accommodated in the base plate.

#The support element further comprises a stop or abutment 25 for one of the end faces 26 of the filter cartridge 10. The filter cartridge is pushed onto the support element prior to mounting the sealing membrane 19 on the support tube 15. The entire filter cartridge/support tube assembly is fixed by means of a snap connection 27 whose interacting elements are accommodated on the support element 15 and in the screw-on cover 13. As a result, when the screw-on cover 13 is removed, the filter cartridge 10 remains inside the cover.

#When the filter is in operation, the fluid flows in the direction of the arrows through inlet 22 to an unfiltered side 28. It then flows radially inwardly through filter paper 17 and reaches a filtered side 29, which communicates with the interior 31 of the support tube 15 via openings 30 made in support element 15. From there, the filtered fluid leaves housing 11 through an outlet 32 located in the outlet nipple 24.