This invention relates to a liquid filter. Existing liquid filters used for filtering, for example, the lubricating oil of an automotive vehicle, are usually of the so-called "spin-on" type in which the filter housing is provided with a threaded outlet opening which is engaged with a mounting stud extending from a mounting surface of the vehicle engine. The filter housing also carries a gasket which circumscribes the threaded opening and which is tightened against the mounting surface on the engine to provide a seal which prevents leakage of the lubricating oil. Such filters commonly include a relief valve, which opens to permit the lubricating oil to bypass around the filtering element when the pressure differential across the filter element becomes too high. Of course, the relief valve is then thrown away with the filter when the oil filter is changed.

The present invention provides a mounting base which can either be installed as a component of the engine when the engine is manufactured or spun on to the existing oil filter mounting surface on existing engines. The base supports a filter assembly which is held in place by a quick connect/disconnect quarter turn bayonet connection. The necessary relief valve if required is installed into the mounting base and, accordingly, is not discarded every time that the filter element is changed. The filter element may be easily separated from the housing and disposed of in an environmentally safe manner. Existing filters are normally discarded, and are very difficult to recycle since it is difficult to separate the paper filter element, the liquid oil remaining in the filter, and the metal housing. Furthermore, the housing itself may be made to be either reused or thrown away. Even if the housing itself is thrown away, the heavy steel tapping plate necessary in spin-on filters is eliminated. Furthermore, a simple O-ring pressure seal is effected between the base and the housing, instead of the lock-seam seal used between the tapping plate and the housing on

spin-on filters, so that a more positive seal is attained which may permit higher oil pressures to be maintained. Furthermore, the quick connect/disconnect mechanism allows faster changing of the filter than the existing spin-on filters.

These and other advantages of the present invention will become apparent from the following description, with reference to the accompanying drawings, in which: Figure 1 is a longitudinal cross-sectional view of a filter base and removable cartridge assembly made pursuant to the teachings of the present invention;

Figure 2 is a view of the filter base taken substantially along lines 2-2 of Figure 1; Figure 3 is a cross-sectional view of the mounting base, omitting the removable adapter, and which is taken substantially along lines 3-3 of Figure 2; Figure 4 is a side elevational view taken substantially along lines 4-4 of Figure 3; and Figure 5 is a view similar to Figure 1 but illustrating an alternate embodiment of the present invention.

Referring now to the drawings, a filter assembly generally indicated by the numeral 10 includes a housing 12 consisting of cup-shaped portion terminating in an opened end 14 circumscribed by a radially outwardly pro¬ jecting flange 16. A filter element generally indicated by the numeral 18 is received within the housing 12 through the open end 14 and consists of a substantially conventional circumferentially extending array of pleated paper 20, the upper and lower edges of which are sealed by closed end caps 22, 24 and an open end cap. A perforated metallic centertube 26 having a closed upper end (viewing Figure 1) extends between the end caps 22, 24 and is circumscribed by the array 20 and resists radially inward collapse of the pleats. A spring 28 is disposed between the closed end of the end cap 22 and the dome shaped end 30 of the housing 12 and yieldably urges the filter

element 18 toward the open end 16 of the housing 12.

The filter element 18 and the housing 12 comprise a filter cartridge which is mounted on a filter base generally indicated by the numeral 32. An adapter 34 is secured to one end of the base 32 by bolts (not shown) received in registering apertures 36 in the base 32 and the adapter 34. Adapter 34 is provided with a threaded opening 38 which may be "spun-on" a threaded mounting boss (not shown) which extends from the filter mounting surface of a conventional internal combustion engine (not shown) . A circumferentially extending gasket or O-ring seal 40 circumscribes the threaded opening 38. Conventionally, the base 32 and adapter 34 are spun onto the aforementioned mounting stud until the gasket 40 is brought into sealing engagement with the mounting surface. According to the invention, the base 32 and adapter 34 are only mounted on the engine once, and the filter cartridge may be changed periodically without removal of the base 32 from the engine. Of course, the mounting filter base 32 may be permanently installed on the engine when the engine is manufactured, in which case the adapter 34 is not required.

A gasket or O-ring seal 44 is clamped between the adapter 34 and base 32 when the latter are assembled by installing bolts in the apertures 36. Gasket or O-ring seal 44 has appropriate openings which register with a pair of inlet openings 42 to permit communication from the inlet openings 42 through the gasket into inlet passages 46 in base 32. Similarly, communication is permitted from outlet passage 48 which is defined in a boss 50 carried by base 32 through the gasket 44 and into the threaded opening 38. The boss 50 projects axially from the upper surface 52 of base 32 and defines a circumferentially extending support surface 54, against which the filter element 18 is urged by the spring 28 when the filter cartridge is installed upon the base. Lubricating oil is communicated through inlet openings 42 and the inlet passages 46 across the surface 52 and into an inlet

chamber 56 defined between circumferentially extending wall 58 of the housing 12 and the outer tips of the pleats comprising the array 20. Liquid is then filtered through the array 20 and is received within the outlet chamber defined within the centertube 26. Liquid then communicates through the outlet passage 48 and threaded opening 38 back into the engine.

The base 32 defines a circumferentially extending surface 60 which is received in the open end 14 of the housing 12 and which slidably engages the circumferen¬ tially extending wall 58. A circumferentially extending O-ring seal 62 is carried by the circumferentially exten¬ ding surface 60 and sealingly engages the circumferen¬ tially extending wall 58. Circumferentially spaced, radially projecting bayonet lugs 64 project outwardly from the surface 60 and are separated by recesses 66. A collar 68 circumscribes the housing 12 and carries radially inwardly projecting, circumferentially extending bayonet lugs 69. The bayonet lugs 69 cooperate with the body of the collar to define a recess 70 therebetween having a shoulder 72 which engages the flange 16. Accordingly, when a new cartridge is to be installed on the base 32, the collar 68 is slipped over the housing 12 until the shoulder 72 is engaged with the flange 16. The bayonet lugs 69 are then introduced into the recesses 66, and the collar 68 is then rotated one quarter turn to engage the lugs 69 with the lugs 64. Axially extending portion 70 of the lugs 64 acts as a stop against which the lugs 69 engage when the collar is rotated to the fully engaged position. Axially extending detent 72 locks against the opposite end of the lugs 69 from the end engaging the portion 70, and acts as a safety catch to force the serviceman to move the collar 68 a small distance axially before it is rotated counterclockwise to disengage the lugs 69 from the lugs 64, again permitting the lugs 69 to be removed through the recesses 66. The spring 28 then urges the housing 12 away from the base 32, permitting whatever pressure exists within the housing to leak past

the seal 62 before the housing is finally removed from the base. The housing 12 may either be permanent or discardable each time the filter is changed. If the housing 12 is permanent, the element 18 can be easily removed from the housing and disposed of and a new element installed within the housing 12 before the latter is reinstalled on the base 32.

Conventional spin-on filter elements many times include a relief valve within the housing that is discarded each time the filter is changed. This relief valve opens to permit flow directly from the inlet to the outlet, bypassing the filter element, to thereby prevent engine damage in the event of a clogged filter. According to the present invention, a permanent relief valve generally indicated by the numeral 74 is provided in the base 32 when required. According to the invention, a bore 76 is provided in the base 32 that communicates with the inlet chamber 56 through an aperture 78 in the surface 52. A valve seat 80 circumscribes lower portion of the bore 76. A valve member 82 is urged against the valve seat 80 by a spring 84 which bears against a retainer 86 which is snapped into a recess 88 on the wall of the bore 76. The spring 84 is sufficiently strong that the valve member 82 normally is sealingly engaged with the valve seat 80 when the filter is used, so that the lubricating oil communicated into inlet chamber 56 communicates through the filter element 18 and out through the outlet passage 48. However, when the pressure differential between the passage 48 and the inlet chamber 56 attains a predetermined level, the valve element 82 opens, thereby communicating lubricating oil directly from the inlet chamber 56 into the outlet passage 48, which shares an open wall with the bore 76. Accordingly, lubricating oil bypasses the filter element 18, and passes directly from inlet chamber 56 to outlet passage 48.

Referring now to the alternate embodiment of Figure 5, elements substantially the same as those in the preferred embodiment retain the same reference numerals,

but are increase by 100. In the embodiment of Figure 5, the housing 12 and collar 68 are incorporated within as a single housing member generally indicated by the numeral 190. The bayonet lugs 69 on the collar 68 of the preferred embodiment are incorporated as at 169 in radial outwardly extending portion 192 of the housing 190. The lugs 169 are engaged with the lugs 164 of the base 132 in exactly the same manner as the lugs of the collar 68 are engaged with the lugs 64 of the base 32 of the preferred embodiment. Similarly, the housing 190 defines a circumferentially extending wall 158 which sealingly engages seal 162 carried in circumferentially extending surface 160 of the base 132.