Seal arrangement for spin-on filters

A seal arrangement for fluid filters is provided. The seal arrangement generally concerns compressing a gasket between selected portions of the filter base and filter cartridge. A preferred frusto-conical configuration is provided, to advantage. Methods of assembly and use are described, as well as preferred filter base configurations and preferred filter cartridge configurations.

FIELD OF THE INVENTION 
The present invention relates generally to fluid filters. In certain 
particular embodiments shown it relates to fluid filters of the spin-on 
type. More particularly, the invention relates to a seal formed between 
spin-on filter cartridges and a filter base, when the filter cartridge is 
mounted on the base. Methods of accomplishing a preferred seal are 
provided. 
BACKGROUND OF THE INVENTION 
Spin-on filter arrangements have been employed in a variety of applications 
including, for example, hydraulic systems, fuel systems and lubrication 
systems. Such filter arrangements generally include a filter element 
positioned within a can, casing or housing having a cover or top plate at 
one end thereof, by which the filter can be mounted on a filter head or 
filter base. A central opening and several surrounding openings in the 
cover are usually provided to direct flow through the filter and filter 
element therein, which flow can be in either an inside/out (reverse flow) 
or an outside/in (forward flow) pattern. A circular gasket on the outside 
of the cover serves as an external seal between the filter and the filter 
head. A gasket (or combination of gaskets) on the inside of the cover 
functions as an internal seal between portions of the filter element and 
the cover. Spin-on filters are typically intended to be used for a limited 
period, with follow-up removal and replacement during servicing. 
Herein the combination of can, element and other components which are 
"spun" or otherwise mounted onto the filter base will sometimes be 
referred to as the removable and replaceable filter cartridge or cartridge 
assembly. 
A variety of conventional arrangements have been used to provide for 
sealing engagement with respect to fluid flow outwardly from between the 
filter base and the cartridge. Many of these have concerned positioning an 
o-ring, compressed, axially, between the two as the filter cartridge is 
spun onto the filter base. Examples of these are shown: in U.S. Pat. No. 
4,969,994, FIG. 1 at 7 and FIG. 3 at 134; in U.S. Pat. No. 4,369,113 in 
FIG. 2 at 44; and, in U.S. Pat. No. 4,743,374 in FIGS. 2 and 5, at 46. The 
complete disclosures of the previously mentioned '994, '113 and '374 
patents are incorporated herein by reference. 
Reliability and durability of the seal between the liquid filter and the 
filter head is important. Significant leakage of the fluid being filtered 
during operation can result in catastrophic damage to the engine, vehicle 
component, or other equipment and component involved. 
SUMMARY OF THE INVENTION 
According to certain aspects of the present invention, a filter assembly is 
provided. The filter assembly comprises: a filter base; a removable and 
replaceable filter cartridge mounted on the filter base; and, a sealing 
gasket pressed between the filter base and the filter cartridge. The 
filter base generally includes an inwardly directed (typically radially 
inwardly directed) sealing surface, preferably frusto-conical in 
configuration. By the term "radially" inwardly directed inches in this 
context, it is meant that: the sealing surface is circular in 
configuration; and the sealing surface circumscribes and is directed 
toward a central axis. By the term "frusto-conical" in this context, it is 
meant that the sealing surface has a flat portion in cross-section (viewed 
in a plane having the central axis therein), and thus defines a 
frusto-conical surface. In general, the preferred arrangement is 
constructed and arranged such that the sealing gasket is compressed 
between the frusto-conical sealing surface and a gasket seat on the filter 
cartridge. 
Preferably the frusto-conical sealing surface has a flat portion, in 
cross-section, having a width within a range of 0.100 inches to 0.750 
inches. Also preferably this flat portion of the frusto-conical sealing 
surface extends at an angle of about 85.degree. to about 45.degree., 
relative to a plane perpendicular to a center line (center axis) of the 
frusto-conical sealing surface. 
In the preferred assembly, the gasket has a generally circular 
cross-section. Thus, the gasket is preferably an o-ring with a circular 
cross-section. 
In the typical embodiment shown, the filter cartridge includes an end wall 
piece having: a center recess or recess portion; an outer wall; and, an 
inner wall, with the center recess and inner wall defining the gasket seat 
against which the o-ring is compressed. Generally the center recess 
extends between the inner and outer walls, with the inner and outer walls 
being generally axially directed in extension from the recess, i.e., the 
inner and outer wall project generally toward the filter base, during 
assembly. 
Preferably the filter base includes a center post, of circular 
cross-section (viewed in a plane perpendicular to the center line), with 
external threads thereon and the filter cartridge includes an internally 
threaded bore sized and configured to be threadibly received on the center 
post. Thus, in preferred embodiments, the filter cartridge is a spin-on 
filter, which is mounted onto the filter base by being threaded thereon. 
The compression of the gasket, then, to form the seal occurs as a result 
of the act of threading (or mounting); i.e., drawing of the cartridge 
toward the filter base. 
Preferably the filter base includes a skirt structure or wall structure, 
constructed and arranged to directly contact a portion of the center 
recess in the cartridge end wall piece, when the filter cartridge is 
mounted on the filter base. Thus, preferably when a spin-on filter is 
involved, the spinning is conducted until a selected rigid portion of the 
filter base comes into direct contact with a selected rigid portion of the 
filter cartridge, providing a "hard stop" to the mounting. This helps 
avoid guesswork of appropriate levels of compression of the gasket. In the 
immediate location of the arrangement where the "stop" takes place, the 
gasket is not positioned between the two contacting pieces. Of course, the 
gasket is compressed between the frusto-conical sealing surface and the 
filter cartridge. However where the "hard stop" occurs, preferably the 
filter base wall structure directly contacts or abuts the filter 
cartridge. 
In a preferred embodiment, the filter base wall structure includes an outer 
rim with a plurality of protrusions or projections thereon, each one of 
the plurality of protrusions projecting in a direction toward and into 
direct contact with a center recess in the filter cartridge end wall 
piece, when the filter cartridge is operably mounted on the filter base. 
By "operably mounted" in this context, it is meant that the assembly is 
configured for use. Of course, when protrusions of the type described in 
this paragraph are used, it is the protrusions which provide the hard stop 
against the filter cartridge. 
In preferred embodiments, the base wall structure includes an inner wall 
portion, and the frusto-conical sealing portion comprises a portion of the 
base wall structure inner wall portion. That is, both the protrusions 
providing for the hard stop and the frusto-conical sealing surface are 
positioned on the same base wall structure, but in different locations, in 
certain preferred embodiments. 
Preferably, the filter base comprises a metal casting, for example 
aluminum, magnesium, zinc; sand cast or die-cast. The filter cartridge is 
preferably a liquid filter. The filter cartridge may be either a forward 
flow filter or a reverse flow filter. Typical applications of the assembly 
are as a hydraulic, engine lube, fuel, or coolant filter on internal 
combustion engines. 
Also according to the present invention, a filter base is provided. The 
filter base is generally one which is usable to form an assembly of the 
type described previously. The filter base, then, would generally comprise 
a center post having a threaded outer surface; and, a base wall 
circumscribing the center post and spaced therefrom. The base wall 
preferably has, on an inner portion thereof and directed toward the center 
post, a frusto-conical sealing surface. The frusto-conical sealing surface 
preferably has a flat portion, in cross-section, of the type described 
above. Also, the base wall preferably includes a plurality of protrusions 
of the type described above, for use to form the hard contact as 
described. 
Also according to the present invention, a preferred filter cartridge is 
provided. The filter cartridge preferably has an end piece including a 
center recess positioned between an axially directed outer wall and an 
axially directed inner wall. Also, preferably a seal gasket is positioned 
on the filter cartridge, circumscribing the axially directed inner wall 
and nested against the center recess and axially directed inner wall. In 
such arrangements, preferably the axially directed inner wall includes a 
flange extending over at least a portion of the seal gasket. This flange, 
in conjunction with the axially directed wall and recess, will form a nest 
for the gasket, and will protect the gasket during shipment, handling and 
assembly. 
According to the present invention, a method of sealing a filter cartridge 
to a filter base is provided. Generally, the method concerns mounting a 
filter cartridge onto a portion of a filter base while compressing a seal 
gasket therebetween. Preferably constructions as described hereinabove are 
used.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
I. Some Problems with Conventional Arrangements. 
In many instances, fluid filter arrangements are engine mounted, or are 
otherwise mounted on moving, vibrating machinery, and as such are exposed 
to significant vibration and shock during normal machine operation. Many 
of the seal systems designed for conventional spin-on filters are designed 
in a fashion that relies on a face sealing gasket to provide sealing of 
the contained fluid. The gasket may also serve as a vital structural 
component in the assembly to the filter base, providing a bearing surface 
to the filter base that provides rigidity to the assembly. 
Reliance on an elastomer for a rigid interface can be problematic. For 
example, when exposed to vibration and shock, the gasket flexes and can 
suffer pinching or other damage and material fatigue due to excessive 
stress in the material. This can result in significant leakage that can 
lead to catastrophic failure in the system. 
Another related problem concerns the installation method generally 
associated with a face sealing type gaskets. Typically, proper 
installation is specified as turning the filter until the gasket contacts 
the seal surface, and then further tightening a specified fraction of a 
turn. In some instances, during servicing, the filter is not tightened 
adequately because there is no fixed point of reference for consistently 
determining the proper fraction of a turn. Evenly spaced marks around the 
circumference are usually provided as a visual reference, but are an 
unreliable means of ensuring proper installation. 
II. FIGS. 1-5. 
The reference numeral 1, FIG. 1, generally designates an assembly according 
to the present invention comprising a filter base 4 (sometimes referred to 
as the filter head); a removable and replaceable filter or filter 
cartridge 5; and, a seal ring, not shown in FIG. 1, appropriately 
positioned between the filter cartridge 5 and filter base 4 to cause a 
seal therebetween. The filter ring is shown in FIG. 2 at reference numeral 
10. 
Still referring to FIG. 1, in general, assembly 1 is installed for use to 
filter a fluid in a mechanical system, for example, a hydraulic fluid 
system on construction equipment or a lubricating fluid system on a 
vehicle (truck, wheel loader) or associated with an engine or some other 
form of equipment (for example engine-powered stationary). The filter base 
4 in such assemblies 1 is generally mounted semi-permanently to the 
equipment. Filter cartridge 5, on the other hand, is an item designed to 
be regularly serviced, typically by replacement. In general, the filter 
cartridge 5 is of a limited lifetime and is removed and replaced, during 
routine servicing of the equipment. 
Attention is now directed to FIG. 2. FIG. 2 is a cross-sectional view taken 
generally along line 2--2, FIG. 1. FIG. 2 is somewhat schematic in its 
presentation, for simplicity and clarity. 
Referring to FIG. 2, filter base 4 generally comprises a seamless casting, 
typically metal, for example an aluminum casting, machined for appropriate 
features. Referring to FIG. 2, filter base 4 includes fluid flow inlet 
aperture 15 and internal fluid inlet conduit 16, terminating in outlet 17. 
In addition, filter base 4 includes fluid flow outlet conduit 20 defined 
as extending between inlet aperture 21 and outlet aperture 23. Filter base 
4 includes central mounting post 25 thereon, typically circular in 
horizontal cross-section relative to FIG. 2, defining a portion 26 of 
conduit 20 extending therebetween; and, having, on an exterior surface 27 
thereof, mounting threads 28 for filter cartridge 5. 
Referring still to FIG. 2, attention is now directed to filter cartridge 5. 
Filter cartridge 5 includes: outer can or housing 35 defined by wall 36 
and cover flange (or end flange) 37; internally received filter 
construction 40, generally defined by filter media 41 extending between 
upper and lower end caps 42 and 43, respectively, and positioned between 
outer and inner liners 45 and 46, respectively; internal gasket 50; cover 
piece 51; and, internal spring 52. In the housing 35, wall 36 and flange 
37 are secured to one another along roll seam or peripheral seam 38. 
In operation, fluid to filtered is directed into region 60 by passage 
through aperture 61 in cover 51. That is, fluid flow through inlet conduit 
16 is directed into space 70 between cartridge 5 and filter base 4, and 
then either under pressure applied in the direction of arrow 75 or under 
suction draw in the direction of arrow 76, the fluid is directed into 
region 70, through aperture 61, and into region 60. Fluid flow is then 
directed through filter construction 40, in the direction generally 
indicated by arrows 78, into internal volume 79 defined by inner liner 46. 
After having been thus filtered, the fluid flow is then directed into 
conduit section 26 in central post 25, in the general direction indicated 
by arrow 79, through conduit 20 and outwardly from the filter base 4 in 
the direction indicated generally by arrow 76. Selected specific conduit 
sizes and shapes in filter base 4 are used to accommodate couplings and to 
facilitate fluid flow. 
An arrangement constructed with fluid flow as shown in FIG. 2, i.e., from 
an exterior or outer liner 45 through to inner liner 46, during filtering, 
is generally referred to as a "forward flow" arrangement. It is noted that 
seal arrangements as defined herein can also be used in association with 
various "reverse flow" arrangements, in which fluid flow moves in an 
opposite direction through filter arrangement 40; i.e., from an interior 
to an exterior of the filter media. 
Within the volume 77 defined by outer side wall construction 35 is included 
a spring 52 which biases filter arrangement 40 against gasket 50, and, as 
a result, gasket 50 against cover 51. As a result of this biasing, and 
configuration of gasket 50, a seal to inhibit filter flow between both of: 
gasket 50 and post 25; and, gasket 50 and end cap 42, is provided. 
As thus far defined, filter cartridge 5 and filter base 4 are generally 
conventional. Arrangements and features such as those described in U.S. 
Pat. Nos. 4,369,113 and 4,743,374, incorporated by reference, can be used, 
for example, in analogous manners. 
The present disclosure concerns unique features provided in association 
with a specific seal between base 4 and filter cartridge 5, as will be 
best understood by reference to FIG. 3, an enlarged view of a portion of 
FIG. 2. 
Referring to FIG. 3, filter base 4 includes a depending or projecting wall 
structure (or skirt structure) 80 thereon. In the embodiment shown, 
structure 80 is a ring-shaped wall structure 81 which depends (projects) 
from filter base 4 in direction toward filter cartridge 5. Structure 81 
circumscribes, and is spaced from, post 25. 
Ring-shaped wall structure 81 includes radially, inwardly directed sealing 
surface 83. By the terms "radially" and "inwardly" in this context, it is 
meant that sealing surface 83 as it circumscribes post 25, is directed 
toward (i.e., faces) post 25 and/or center line or axis 87; center axis 87 
being generally a central axis of circular symmetry for sealing surface 
83. 
In the preferred embodiment, sealing surface 83 possesses the following 
features: it is machined to be generally flat in cross-section, FIG. 3 
over an extension of width; and, it is frusto-conical in configuration, 
with a line such as line 85 tangential to the surface 83 extending at an 
angle of about 85.degree. to 45.degree. relative to a plane (or line) such 
as a plane including line 86 perpendicular to central axis 87, FIG. 2, of 
central post 25. 
Still referring to FIG. 3, filter gasket 10 is nested within a circular or 
annular recess 90 defined by a portion of can end 37. In particular, can 
end 37 includes a segment or end wall piece 92 defining a recess between 
outer wall 93 and inner wall 94. Seal ring 10 is configured to nest 
against inner wall 94. That is, seal ring 10 abuts, and circumscribes, 
inner wall 94. Note that inner wall 94 includes upper flange 95. Upper 
flange 95 is preferably of a sufficient size to extend partially, but not 
completely, typically no more than about 95% and usually about 75 to 90%, 
over seal ring 10. 
For the preferred construction shown, sealing surface 83 is configured and 
directed to engage ring 10 compressing same against portions of wall 94 
and a base surface 91, FIG. 3, as filter cartridge 5 is mounted on base 4, 
for example by being spun onto threads 28, FIG. 2. The directions of 
compression are indicated generally by arrows 98, 99, FIG. 3, and include 
both a radial and axial character (or component). That is, the compressive 
forces are partly axial and partly radial. Note, however, that in the 
preferred embodiment shown no portion of seal gasket 10 is compressed 
between and against end surface 100 of structure 80 and cartridge 5, 
during sealing. In addition, during sealing, structure 80 is positioned 
between seal gasket 10 and outer wall 93. This is a preferred 
configuration, for reasons stated hereinbelow. 
Referring to FIGS. 4 and 5, end surface 120 of wall 80 includes a plurality 
of spaced projections or protrusions 101 depending downwardly therefrom. 
In the specific embodiment shown, three radially evenly spaced (i.e., 
spaced 120.degree. apart) protrusions 101 are shown. Each protrusion 
preferably projects a distance of about 0.010 inches to 0.100 inches from 
surface 120 in a direction toward cartridge 5 (when assembled). The 
protrusions 101 are preferably also a part of the cast of filter base 4. 
Referring to FIG. 3, the protrusions 101 are sized and configured to 
provide a "hard" stop to movement of the filter cartridge 5 toward filter 
base 4, during mounting. Preferably the total surface area of the 
protrusions 101 which engages filter cartridge 5 is no greater than about 
0.03 to 0.10 sq. inches for each protrusion; and, preferably the total 
number of protrusions is between 3 and 6. This will ensure that the 
surface area of contact will be relatively small, and thus will be 
relatively easy to obtain and to dislocate. 
As a result of the configuration shown, a good control over mounting is 
obtained. The filter cartridge 5 is spun (mounted) onto base 4 until the 
stop (preferably a hard stop as described) is encountered. That is, 
preferably a rigid engagement between the cartridge 5 and the filter base 
4 is obtained, when filter can end 37 engages protrusions 101. If the 
appropriate combinations of sizes of protrusions, gasket and seal surfaces 
is chosen, a good seal is obtained. This is because sealing surface 83 is 
directed toward ring 10 in such a manner that as the protrusions 101 are 
brought into contact with a surface, for example, a bottom surface of the 
annular recess 90, seal 83 compresses ring 10 in the direction indicated 
by arrows 98, 99, FIG. 3. A fluid tight seal is thus attained by simply 
choosing appropriate dimensions for the various portions. In sections 
presented hereinbelow, sample dimensions are provided. From these, a wide 
variety of alternate sizes and configurations can be readily developed. 
Sample Specifications 
In this section, an example is provided of a set of operating materials and 
specifications. These are intended as an example. A wide variety of 
alternate materials and sizes can be used. 
The specific example is for use as a fuel filter. The filter base 4 would 
be cast from aluminum in the configuration shown in FIGS. 1-5. The 
dimensions would be generally as follows: 
The housing 5 is constructed from steel. The housing 5 has an outer 
diameter of about 4.25 inches, and a length of about 7.00 inches. The 
outlet tube of the filter base 4 has an average inner diameter of about 
1.00 inches. 
The filter media includes a media made from cellulose or synthetic fiber. 
This media has an efficiency of about 50% or 5 micron particles and a 
typical life of about 250-500 service hours. Installed in the arrangement 
of FIG. 1, the media has an outside diameter of about 3.75 inches, and an 
inside diameter of about 1.75 inches. 
End caps on the filter element are constructed from steel. End cap 42 has 
an outer diameter of about 3.80 inches, and an inner diameter of about 
1.70 inches. End cap 43 has an outer diameter of about 3.75 inches. 
Spring 52 is a coil spring with about 4 coils. In an uncompressed state, 
spring 52 has a length of about 1.50 inches, a diameter of about 1.50 
inches, and is constructed from spring steel. Spring 52 has an installed 
force of about 30 pounds. 
Wall structure 81 has an inner diameter of about 3.30 inches and an outer 
diameter of about 3.84 inches. It has a length of about 0.45 inches. 
Surface 83 is at an angle from surface 86 of about 70.degree.. The seal 
member includes a hardness measurement of about 70 durometer. 
Upper flange 95 has a width of about 0.08 inches. Inner wall 94 has a 
length of about 0.300 inches. 
Protrusions 101 project a distance of about 0.04 inches from surface 120.