Liquid purification or separation – Filter – With central pervious tubular receiver
Reexamination Certificate
2000-10-13
2003-09-09
Savage, Matthew O. (Department: 1723)
Liquid purification or separation
Filter
With central pervious tubular receiver
C210S493100, C210S493200, C210S497010, C210S450000
Reexamination Certificate
active
06615990
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a filter cartridge, especially for filtering fluids, which comprises an annularly closed filter medium having end plates at its end faces, a center tube comprised of upper and lower parts held together by a snap fastener with a seal formed between each of the end plates and the center tube, and a gasket for sealing the filter cartridge in a housing.
A fluid-filtering cartridge of this type with a center tube is disclosed in Bruss et al., U.S. Pat. No. 5,814,215 (=EP 835 158). The center tube is inserted into the pleated filter paper provided with end plates, and a seal is formed between the end plates and the center tube. To facilitate installation of the center tube and avoid damage to the filter paper, the center tube is composed of two parts, so that it can be inserted from both ends into the pleated filter paper. The inwardly extending ends of the center tube parts abut against one another, so that a snap fastener is closed which secures the center tube in the filter paper.
The assembly of the center tube is simplified by the described snap fastener, but due to the configuration of the snap fastener care must be taken during installation to see that the two center tube parts are at the correct angle relative to one another. This is because snap catches on the upper part of the center tube enter into openings in the lower part of the center tube so as to achieve an interlock. There are angular positions between the two center tube parts in which the snap catches come to rest on the bridges between the openings so that a reliable connection between the two parts is not achieved.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide a filter cartridge which can be easily assembled, contains few components, and is reliable in both assembly and operation.
These and other objects of the invention are achieved by providing a filter cartridge comprising an annularly closed filter medium having an end plate at each of its axial end faces, a center tube comprised of an upper tube part and a lower tube part held together by a snap fastener whereby a seal is formed between each of the end plates and the center tube, and a gasket for sealing the filter cartridge in a filter housing, wherein the snap fastener is comprised of an annular groove in the outer periphery of the upper tube part and a resilient catch on the bottom tube part, the catch being able to snap into the annular groove regardless of the angular position between upper part and lower part.
The filter cartridge according to the invention has a center tube which is comprised of an upper part and a lower part. These two parts are held together by snap fastener. The center tube is installed in the interior of a filter cartridge, and the end plates belonging to the filter paper achieve a sealing action on the outer circumference of the center tube.
The snap fastener is configured such that, on the upper part of the supporting body or center tube, at the place where it is attached to the bottom part, an annular groove is provided, which is at the outer circumference of the upper part. This means that access to the annular groove from the outside thereof is possible. This has the advantage that it is possible to manufacture of the center tube by injection molding without any difficulty. The mold for such components consists normally of three parts: a core to form the interior and two external shells which can form the openings in the supporting tube as well as the groove without any undercutting.
In contrast to the snap fasteners known in the state of the art, the annular groove has no bridges to which attention must be paid when snapping the parts together. The elastic catches on the bottom part can snap into the annular groove regardless of the angular position of the two center tube parts with respect to one another. To do this the elastic catches yield, so that the upper and lower parts can be fastened together.
The resilience of the catches also simplifies the manufacture of the lower part. It can be made like the upper part in a three-part injection mold. When it is stripped from the mold the resilience of the catches serves to enable the core to be withdrawn from the workpiece in spite of the undercuts formed.
The junction between the center tube and the end plates of the filter paper is sealed. The seal, however, need not be a separate component. The inherent resilience of the end plates can also be used to provide a seal with the center tube. It is preferred to use a radial seal. Especially when the end plates are made of a film this principle can be utilized. The film end plates then are comprised of a nitrile rubber which is bonded by the curing process to the ends of the filter paper, providing a certain residual elasticity to seal against the center tube.
In another embodiment of the invention the resilient catch on the circumference of the lower part can have at least one, but—to be more practical—at least two or more gaps. The result is that the catch is not of an annular configuration but is composed of sectors of a circle. These sectors are substantially more resilient than a continuous ring, so that unrestricted functionality of the snap fastener is assured. Alternatively, the catch could also be made annular, in which case, however, a sufficiently resilient material must be chosen. This can be achieved, for example, by the choice of an elastomer which can be bonded to the bottom part by a multi-component injection molding process.
If the gaps on the circumference are of such dimensions that they occupy a greater angular section than the segments forming the catch, or at least an equal one, the result is an especially advantageous variant of the invention. The core needed for the injection molding can then be stripped out without any elastic deformation of the catch, if the latter is rotated by the angular amount which the sectors occupy. In this manner a greater reliability and speed of the process can be achieved. The parts of the center tube can be stripped even though they have not fully cooled, since partial plasticity of the catch cannot result in any permanent deformation.
Furthermore, in accordance with one specific embodiment of the invention, a recess can be provided on the center tube for a gasket which is necessary for the leak-proof installation of the filter cartridge in the housing. The gasket must assure a reliable separation between the clean side and the raw side of the filter.
The recess can be provided, for example, by an axial groove into which an annular gasket is placed. Another possibility is to provide an annular projection which is suitable for the accommodation of a molded gasket. It is also possible to configure the recess such that both molded gaskets and sealing rings can be installed.
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 individually 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.
REFERENCES:
patent: 3259248 (1966-07-01), Wiegand
patent: 3592766 (1971-07-01), Kudlaty
patent: 4559138 (1985-12-01), Harms, II
patent: 5102541 (1992-04-01), Breitbach
patent: 5141637 (1992-08-01), Reed et al.
patent: 5413712 (1995-05-01), Gewiss et al.
patent: 5589060 (1996-12-01), Gerbert et al.
patent: 5603829 (1997-02-01), Baumann
patent: 5783067 (1998-07-01), Belden
patent: 5814215 (1998-09-01), Bruss et al.
patent: 5906737 (1999-05-01), Hoeppner
patent: 6016923 (2000-01-01), Baumann
patent: 6110365 (2000-08-01), Bartels et al.
patent: 0 835 158 (1998-09-01), None
Huber Matthaeus
Jokschas Guenter
Sommer Bruno
Crowell & Moring LLP
Filterwerk Mann & Hummel GmbH
Ocampo Marianne S.
Savage Matthew O.
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