Liquid filter for the lubricating oil of an internal combustion engine

A liquid filter for cleaning the lubricating oil of an internal combustion engine, said filter comprising:

• a filter housing defining a filter chamber, a dirty liquid inlet leading to said filter chamber, a filtrate outlet leading from said filter chamber, a drain passageway, and a shut-off valve chamber interposed between said filter chamber and said drain passageway such that said drain passageway communicates with said filter chamber through said shut-off valve chamber;
• a removable cover for closing said filter chamber;
• a replaceable annular filter insert through which liquid to be filtered flows radially, said filter insert being disposed in said filter chamber and dividing said filter chamber into a dirty liquid chamber into which said dirty liquid inlet leads and a filtrate chamber from which said filtrate outlet leads;
• and
• a shut-off valve assembly comprising:
• a cylindrical valve housing received in said shut-off valve chamber,
• a first valve body axially movable within said valve housing between a closed position in which said valve body engages a valve seat at one end of said valve housing and an open position in which said valve body is spaced from said valve seat,
• a plunger axially displaceable within said valve housing having a projection extending through the other end of said valve housing toward said filter chamber and engaging said filter insert disposed in said filter chamber,
• an equalizing spring interposed between said first valve body and said plunger, and
• a valve spring interposed between said valve housing and said first valve body for urging said first valve body toward said open position, said valve spring
• having a lower spring constant than said equalizing spring;
• whereby, when said filter insert is positioned in said filter chamber, said plunger will be displaced by said filter insert and the displacement will be transmitted through said equalizing spring to said first valve body to urge said first valve body into said closed position, and when said filter insert is removed, said valve spring will urge said first valve body toward said open position to open said drain passageway.