Environmentally friendly filter cartridge

A filter cartridge which is environmentally friendly in that it is made up of components which are all incinerateable. The ends of a filter element are sealed using potting compound and plastic endcaps. The upper endcap, which is closed, has a pressure relief aperture associated therewith to prevent bowing. In a plugged filter condition the high-downward pressure introduced on the upper endcap is compensated by providing the cartridge with centering ribs which bottom on an associated ledge in the housing to provide a positive stop for the top endcap, preventing it from being driven down into and through the filter element. Rubber gaskets are associated with the respective endcaps, and are reliably secured to the endcaps by being snap fit into grooves molded into the plastic of the endcaps. The lower endcap utilizes a simple radial seal gasket which is both highly effective and also positioned to avoid structural crushing forces on the cartridge. A keying system prevents the installation of improper filters.

FIELD OF THE INVENTION

This invention pertains to filters, and more particularly to an environmentally friendly filter cartridge.

BACKGROUND OF THE INVENTION

Most conventional filters and filter cartridges present a disposal problem. Driven by ease of installation, many applications have gone to self-contained spin-on cartridges. These have a metal outer case, a metal base plate, and other metal components within the filter. Replaceable cartridges also have significant metal components, often in the form of centertubes or support grids for supporting the filter element, and metal endcaps. Thus, significant elements of a filter will not burn thus preventing the use of incineration for relatively complete disposal of the spent filters or filter cartridges.

BRIEF SUMMARY OF THE INVENTION

In view of the foregoing, it is a general aim of the present invention to provide an environmentally friendly filter cartridge, capable of being incinerated, and which is economical to manufacture and provides for simple and reliable installation. The cartridge is environmentally friendly in that it contains no metallic parts.

In practicing the invention, the cartridge can be made from a limited class of materials, preferably all incinerateable. The materials include the media (normally cellulose or perhaps polyester with plastic backing), two plastic endcaps, two rubber gaskets, and potting compound (epoxy, plastisol, hot melt or urethane), all of which are incinerateable. The cartridge itself has no centertube; to the extent internal support is required, it is built into the housing, which is compatible with the cartridge. The fact that the cartridge will burn and it is lightweight (due to no metal parts) simplifies disposal.

It is a feature of the invention that pre-molded plastic endcaps are utilized in the filter along with structures which compensate for the reduction in strength of plastic endcaps over conventional metal endcaps.

In a particular embodiment, the invention provides an environmentally friendly filter cartridge containing no metal parts. The cartridge includes a cylindrical filter element having an internal bore, which has no integral supporting centertube. A pre-molded plastic endcap, having an open center corresponding to the internal bore of the filter, it is ealed to the filter element at a first end thereof. An annular groove formed near the outer periphery of the first endcap has a radial seal gasket fitted therein. The radial seal gasket has a peripheral mounting bead sized to be stretched and snap fit into the annular groove. The radial seal gasket has a depending skirt coaxial with the filter element and positioned at about the outer periphery of the filter element. A second pre-molded plastic endcap is provided having a closed end. The second end of the filter element is sealed to the second endcap. The second endcap also has an annular groove at the outer periphery thereof. In this case a disc-like axial seal is stretch fit into the groove to project from the outer periphery of the second endcap to provide an axial seal. A pressure equalizing aperture is formed in the second endcap for equalizing the pressure differential across the second endcap during filter operation. Support shoulders associated with the lower portion of the second endcap serve to resist crushing forces applied to the second endcap during filter operation.

Subsidiary features of the invention include a handle also formed in the second endcap for facilitating user manipulation of the filter cartridge.

The filter cartridge, according to the invention, is used in a housing, which receives the filter cartridge. The housing has a centertube fixed therein for supporting the inner bore of a cartridge when inserted in the housing. A cover is threaded onto the housing in such a way as to compress the axial seal gasket between the cover and the housing. The pressure equalization apertures serves to equalize the pressures between the upper endcap and the cover to prevent bowing of the plastic of the second endcap under operating pressure.

In certain applications, the upper endcap has a plurality of tapered ribs positioned near the periphery thereof and oriented to assist in centering the cartridge in the housing. Shoulders formed on the tapered ribs interfit with an annular ridge in the housing for supporting the shoulders to resist crushing pressures on the filters under operating conditions.

In certain instances, the filter also has a plurality of keys associated with the second endcap. The key positions are on the underside of the endcap facing toward the centertube. The housing centertube has a top surface having a plurality of keyed positions. A slot is formed in a selected one of the keyed positions to correspond with the position of the key on the inside of the second endcap.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Turning then toFIG. 1, there is shown, in elevation, a cartridge20constructed in accordance with the present invention. This disclosure of the cartridge20is intended to be general, since the cartridge20can be configured for different applications. More particularly the cartridge can have elements configured such that it will be used as a fuel filter, a full flow oil filter, a hydraulic filter, or a bypass oil filter. The cartridge features, which will be described in detail herein, will be common to any of the foregoing applications. The universal housing, which will also be described below, is readily reconfigureable for the foregoing applications, without the necessity for change of the characteristics of the filter cartridge. Referring back toFIG. 1, it will be seen that the filter cartridge20includes a filter element21having a lower endcap22, which carries a radial seal gasket23. An upper endcap24, also secured to the filter element21, provides a number of features, including a mechanism for supporting an axial seal gasket26, an integrally molded handle27on the top of the endcap24, and centering beveled projections28, which both serve to center the cartridge20as it is inserted into the housing and which also have lower shoulders29bthereon which tend to support the plastic endcap24on the housing to resist crushing forces in filter operation. Also of note is a pressure equalization aperture30formed in the upper endcap24, which serves to equalize the differential pressure across the endcap24to prevent bowing and possible fracture of the endcap24.

The cross-sectional view ofFIG. 2reveals additional constructional details of the filter ofFIG. 1. There it will be seen that the lower endcap22, which is made of pre-molded plastic, provides an upstanding annular channel31into, which a first end of the filter element21is fit and potted. Potting can be accomplished with any conventional potting material used in this art, which includes epoxy, plastisol, hot melt or urethane. The particular potting material used may depend upon the nature of the application to which the filter is put. The potting tends to seal the lower portions of all of the pleats into a unitary endcap. The lower endcap22has a central opening35for passing fluid which is passed through the filter to the central bore thereof to a housing outlet (not shown inFIG. 2).

The filter element20has an outer circumference and an open inner bore21a.Normally flow through the filter is from the outside in, making the internal bore21athe area which receives and passes to an external conduit the filtered fluid. It is possible, of course, to operate the filter in the opposite direction in which the internal bore21awould be the filter inlet, and clean filtered fluid would be obtained at the outside periphery of the filter.

The lower endcap22also has an annular groove32formed therein near the periphery of the filter. The radial seal gasket23has an enlarged in-turned annular bead34which is sized to be stretched and snap fit into the groove32. In that way the gasket23is positively and reliably locked in place on the endcap22. The gasket23has a depending skirt23awhich depends from the endcap22and has a radius very near the outside radius of the filter element21, so that the axial seal performs its sealing function near the outside of the filter cartridge20for reasons to be explained below.

FIG. 2also shows the upper endcap24which, like the endcap22, is a pre-molded plastic element. In the case of the upper endcap24, the endcap has a closed end. An internal annular channel36is provided for receiving the second end of the filter element21. Like the first end, the second end is also potted into the associated channel in the endcap.

The upper endcap24has an annular groove38preferably located at the outer periphery thereof. A disc-like rubber annular gasket26, which serves as an axial seal gasket, is sized so that it can be stretched and snap fit into the groove38. In this way, the gasket is reliably and securely positioned for automatic installation with the cartridge20.

FIG. 2also illustrates the centering ribs28(see alsoFIG. 6for an enlarged view). It will be seen that the ribs28each have an angled face29which, as suggested inFIG. 7, causes the filter cartridge to self center as it is slid into the housing. The housing has a circular ridge29a(see alsoFIG. 7) over which the angled projections29ride to ultimately seat the lower shoulders29bon a ledge29cformed in the housing. The dimensions are such that the upper endcap24firmly seats the shoulders29bon the ledge29cso that additional downward force on the endcap24created by pressures during operation of the filter will not drive the endcap24into the housing and crush the filter. These ribs28, in conjunction with the pressure relief port30in the upper endcap24, are significant features in allowing the use of a plastic endcap in an application which heretofore had required the structural stability of a metal endcap.

Also of note inFIG. 2is the integrally molded handle27formed on the upper surface of the upper endcap24. Also, as a subsidiary feature, the inside surface of the upper endcap24is provided with a key feature generally indicated at62, which will be described in greater detail below.

FIG. 7shows an exemplary housing into which the filter ofFIG. 1can be fit. In the illustrated housing, inlet fluid is provided through an inlet port42. The housing also has an outlet port44, which is connected by an internal passage44a in the housing to the center lower portion of the filter, in fluid communication with the bore21a.The housing has a removable cap45which is threaded onto the housing to compress the axial seal gasket26set in the annular groove38on the periphery of the upper endcap24. Also of note is the bottom49of the housing, which may be removably secured in place by fasteners such as bolts. This allows the installation of different housing bottoms for different applications, such as a bottom including a sump for a fuel filter application, or a concave bottom for high pressure lubrication applications.

The lower portion of the housing has an annular flange46which provides a sealing surface acted upon by the skirt23aof the radial seal gasket23which, it is recalled, is carried in the groove32of the lower endcap22. The seating of the radial seal gasket23into the groove32is better illustrated in the enlarged partial view ofFIG. 5, while the interaction between the radial seal23and the housing flange46is best shown inFIG. 7. Use of a radial seal in this position is significant in that the gasket is positioned near the outer periphery of the filter so that the pressure differential serves to enhance the sealing action. The gasket23seals radially between itself, the endcap22that supports it, and the housing flange46. This seal separates the filtered and unfiltered fluid. Use of a radial seal for this component utilizes the pressure differential across the filter to assist the sealing function by forcing the radial seal gasket23against both the endcap22, which supports it and the housing flange46of the filter housing. In addition, placing the seal at the external periphery tends to put a pressure differential across the lower endcap which is positive at the outside of the filter (and therefore the inside of the endcap) and negative at the bottom of the endcap. This pressure differential tends to put the pleated paper filter in tension, which the media is capable of resisting. Moving the skirt23aof the gasket inboard would tend to put at least part of the media in compression, which is not so readily resisted by pleated paper media. Keeping the media in tension is particularly important in resisting what would otherwise be crushing forces encountered in a plugged filter condition.

Returning to the upper endcap24, it will be seen that at least one pressure relief port30is formed in the upper endcap24. The purpose of this port is to equalize the pressure across the upper endcap24to prevent bowing or possible fracture of the endcap24. This is accomplished by, in effect, allowing a small portion of the unfiltered fluid on the outside of the cartridge to move through the pressure relief aperture30to the top of the endcap24. The purpose is to allow the pressure to equalize across the gasket at the top and to avoid putting undue stresses on the endcap24or the axial seal gasket26.

The pressure downstream of the media is always less than the upstream pressure (when the filter is flowing fluid). This differential pressure can be quite high in cases where the filter is plugged, the velocity is high, or the fluid is cold and viscous. When a pressure relief aperture30is provided, this pressure is carried to the top of the upper endcap24and causes an unbalanced force to be placed on the upper endcap24, tending to force it into the housing. In practicing this aspect of the invention, this force is counterbalanced in the housing. The unbalanced force is due mainly to the center of the endcap24which has the upstream pressure on one side, and downstream pressure on the bottom side. The unbalanced force is in the downward direction and tries to push the cartridge into the housing and crush the element. The cartridge has the aforementioned shoulders29bon the bottoms of the ribs29, and these seat against a stop29cto provide a positive stop for the top endcap and thus seat the overall filter in the housing.

FIGS. 3 and 4illustrates a keying feature which can be used in the practice of the present invention. The inside24aof the upper endcap24is provided with a plurality of key positions, best illustrated inFIG. 4. It will be seen that at a given radius from the center of the endcap24, a plurality of key positions60are provided. The illustrated embodiment includes eight key positions in a single ring. More or fewer key positions per ring, as well as additional rings can also be provided, but it is believed that the eight key positions, which can provide the sixteen possibilities illustrated inFIG. 4, is adequate for most applications.

Referring primarily toFIG. 3, it will be seen that a single key62is provided on the underside of the illustrated endcap in a given position. While only a single key is shown, as contrasted with the three keys ofFIG. 4it is believed that the single key will adequately illustrate the invention without overcomplicating the drawings. The key is in a fixed angular position with respect to the key circle63(the circle in which the keys are located). The key62projects into the internal bore21aof the filter element21.FIG. 3shows a portion of the housing centertube64having a top surface65which is substantially solid except for a key opening66. The upper surface65of the centertube has a plurality of key positions in a key circle67in the same pattern as illustrated inFIG. 4. However, instead of projections62, the keys in the upper surface65are apertures to receive the projections.FIG. 3shows a single aperture66positioned in the key circle67to engage the single projection62positioned in the key circle63. Thus, when the filter is installed in the housing, the keys will align and allow the filter to reach the seated position, allowing the cover to be placed on the housing and operation to continue. If the wrong filter inserted, the filter will not seat, and the user will be incapable of completing assembly.

This feature is particularly significant when using a universal housing as illustrated in this application. For example, two housings might be used side-by-side to provide a primary and a secondary fuel filter system. Both housings would be of the same diameter and height, but would require different filter cartridges. The keys will prevent the cartridges for one of the housings from being installed incorrectly in the other housing. It would be a simple matter to have several different key configurations to suit various applications and indeed various customers.

The assembly of the filter will now be briefly described, primarily with reference toFIG. 2. Basically the endcaps22,24are potted onto the filter element21in whichever sequence the manufacture desires. Using conventional techniques, an end of the filter element is placed, for example, in the channel31of the lower endcap, and potting material (epoxy, plastisol, hot melt or urethane) is introduced into the channel31to seal the ends of all the pleats and join them to the endcap22. A similar operation is performed on the other end in connection with endcap24. The gaskets26,23can be preinstalled before potting, or are preferably installed after potting by simply stretching the gaskets and snapping them into place. The filter is then ready for packaging and ready for use by the ultimate consumer. The fact that the gaskets are so reliably joined to the filter makes changing a cartridge filter constructed in accordance with this invention about as simple as changing a spin-on filter. The result, however, is that the spent filter can be disposed of by incineration, rather than contributing to landfill waste.