Liquid purification or separation – Flow – fluid pressure or material level – responsive – Discharge of treated material
Reexamination Certificate
1998-01-22
2001-04-17
Savage, Matthew O. (Department: 1723)
Liquid purification or separation
Flow, fluid pressure or material level, responsive
Discharge of treated material
C210S130000, C210S136000, C210S137000, C210S299000, C210S428000, C210S430000, C210S436000, C210S438000, C210S450000, C210S454000
Reexamination Certificate
active
06217755
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to fluid filters and methods. More particularly, this invention relates to liquid filters. One application described is a hydraulic in-tank filter.
BACKGROUND OF THE INVENTION
Fluid filters have been employed in a variety of applications including hydraulic systems, fuel systems, and engine lubrication systems.
Liquid filters which have sensitive downstream components are of a concern. Particularly, it is of concern to prevent cavitation of pumps downstream from liquid filters. Conditions such as cold starts, flow surges, or occluded elements can result in damaged downstream components. Improvements are desirable.
SUMMARY OF THE INVENTION
The invention is directed to a liquid filter assembly. To achieve the advantages of the invention and in accordance with the purposes of the invention, as embodied and broadly described herein, a liquid filter assembly comprises a filter head and filter housing. The filter head and filter housing define a liquid flow inlet path, a first liquid flow outlet path, and a second liquid flow outlet path. A filter media construction is positioned within the housing. The filter media construction, in combination with the housing, defines an unfiltered liquid volume, and a filtered liquid volume. A liquid flow inlet is provided in the assembly. The first liquid flow inlet path is constructed and arranged to direct liquid from the liquid flow inlet to the unfiltered liquid volume. A first liquid flow outlet is provided in the assembly. The first liquid flow outlet path is constructed and arranged to direct liquid flow from the filtered liquid volume to the first liquid flow outlet. A second liquid flow outlet is provided. The second liquid flow outlet path is constructed and arranged to direct liquid flow from the filtered liquid volume to the second liquid flow outlet. A first valve assembly, or back-flow pressure valve, is constructed and arranged to selectively open the second liquid flow path to passage of liquid therethrough in response to a first selected liquid pressure level within (or differential including) the filtered liquid volume. A second valve assembly comprises a first bypass valve assembly, and is constructed and arranged to selectively direct fluid flow from the unfiltered liquid volume to the second liquid flow outlet, in response to a second selected liquid pressure level within (or differential including) the unfiltered liquid volume.
In one arrangement, the liquid flow inlet and the first liquid flow outlet are positioned within the filter head.
Preferably, the housing comprises an elongate, generally cylindrical wall having first and second opposite ends. The housing first end is secured to the filter head, and the housing second end is positioned remote to the filter head and includes the second liquid flow outlet therein.
In one embodiment, the filter media construction comprises a cylindrical extension of media defining an internal volume. The filter media internal volume comprises at least a portion of the filtered liquid volume. Preferably, the filter media construction includes first and second end caps with the cylindrical extension of media extending therebetween. The first end cap has an open central aperture in fluid flow communication with the media internal volume and the first outlet flow path. The second end cap has an open central aperture with the first valve assembly positioned therein.
In one arrangement, the first valve assembly comprises a tubular outer wall including, positioned therein, a first spring-loaded valve head and a first valve seat having a flow port extending therethrough. Details are later described.
In certain arrangements, the second valve assembly includes a second spring-loaded valve head and a second valve seat having a flow port extending therethrough. Details are later described.
In certain arrangements, the spring of the second valve assembly and the spring of the first valve assembly comprise opposite end portions of the same spring.
Preferably, the filter head includes an air flow channel therethrough, and the assembly includes a breather filter construction mounted on the filter head and oriented in air flow communication with the air flow channel in the filter head.
The arrangement is particularly well constructed to operate as an “in-tank” filter. That is, it is used to filter fluid circulating to a reservoir tank, such as a hydraulic fluid reservoir.
In certain preferred arrangements, the filter media construction is secured to a removable centerpiece or center piece of the filter head. In such arrangements, the removable centerpiece is positioned in a bore in a base member of the filter head of sufficient size so that when the centerpiece is withdrawn from the base member, the filter media construction is withdrawn upwardly through the bore in the base member for servicing. Preferably, the filter media construction is removably secured to the centerpiece so that during servicing, a first filter media construction attached to the centerpiece can be replaced by a second filter media construction.
The filter media construction may include a contaminant collection trap mounted thereon.
The invention also provides a method for changing a filter element in a housing. The method comprises a step of detaching a service cover from a filter head. After the step of detaching the service cover, the filter element is removed from the housing by removing the service cover from the filter head and pulling the filter element through an aperture defined by a bore in the filter head.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate one embodiment of the invention and together with the description, serve to explain the principles of the invention.
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Fobe Johan
Greco Enrico
Schiavon Angelo
Stifelman Jack
Donaldson & Company, Inc.
Merchant & Gould P.C.
Savage Matthew O.
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