Liquid filter for vehicle internal combustion engines

1. A filter for vehicle internal combustion engines, comprising an outer casing ( 11 ) and an upper closure cover ( 12 ) which enclose an inner chamber ( 13 ) having an inlet for the liquid to be filtered and an outlet for the filtered liquid, a filter cartridge ( 20 ) having a tubular filter medium ( 21 ) positioned inside the inner chamber ( 13 ), to separate the filter inner chamber ( 13 ) into a first region communicating with the inlet and a second region communicating with the outlet, and an upper disc ( 22 ) joined to the upper end of the filter medium ( 21 ),

first coupling elements ( 31 ) and second coupling elements ( 41 ) acting together to achieve mutual snap-coupling, the first coupling elements ( 31 ) or the second coupling elements ( 41 ) being joined to the cover ( 12 ) and projecting axially towards the interior of the chamber ( 13 ) and, vice versa, the second coupling elements ( 41 ) or the first coupling elements ( 31 ) formed as a unit with the upper disc ( 22 ) and projecting axially towards the upper cover ( 12 ),

wherein said first coupling elements ( 31 ) comprise axially extending coupling teeth with elastic action in a radial direction, said second coupling elements ( 41 ) comprising an overall cylindrical surface divided into a number of identical sectors equal to the number of coupling teeth ( 31 ), each sector comprising a coupling region ( 43 ) for snap-engaging the coupling teeth ( 31 ) axially, and a disengagement region ( 44 ), positioned adjacent to the side of the coupling region ( 43 ), for sliding the coupling teeth ( 31 ) from their engagement position on the coupling region ( 43 ) by rotating the cartridge ( 20 ) through a small angle relative to the upper cover ( 12 ), and

wherein said disengagement region ( 44 ) comprises a smooth cylindrical surface portion ( 44 a ) extending over a height thereof, and an arc-shaped surface strip ( 44 b ) forming a connection ramp in a plane transverse to the axis of the filter cartridge beginning in the coupling region and extending to the smooth cylindrical surface position to transfer the coupling teeth ( 31 ) from a toothed groove ( 43 b ) in the coupling region to the smooth cylindrical surface portion ( 44 a ), the ramp radially decreasing in a circumferential direction.

2. A filter as claimed in claim 1 , characterised in that each said coupling region ( 43 ) defines a second coupling tooth complementary to the first coupling teeth ( 31 ) and arranged to snap-receive the first coupling teeth ( 31 ) by mutual approach in an axial direction, and engage them.

3. A filter as claimed in claim 1 , characterised by comprising axial abutment elements ( 32 ) projecting from the upper cover ( 12 ) and arranged to abut against the upper surface of the upper disc ( 22 ) when said coupling elements ( 31 and 41 ) are mutually engaged, to exactly define the distance between the cover ( 12 ) and the disc ( 22 ) and render the connection between said coupling elements ( 31 , 42 ) free of slack.

4. A filter as claimed in claim 3 , wherein said abutment element ( 32 ) are conical tube segments.

5. A filter as claimed in claim 4 , wherein the tube segments are external of the coupling elements.

6. A filter as claimed in claim 1 , characterised by comprising axial abutment elements ( 32 ) projecting from the upper disc ( 22 ) and arranged to abut against the lower surface of the upper cover ( 12 ) when said coupling elements ( 31 and 41 ) are mutually engaged, to exactly define the distance between the cover ( 12 ) and the disc ( 22 ) and render the connection between said coupling elements ( 31 , 42 ) free of slack.

7. A filter as claimed in claim 6 , wherein said abutment element ( 32 ) are conical tube segments.

8. A filter as claimed in claim 7 , wherein the tube segments are external of the coupling elements.