US Patent 7022228 Filter device

A filter device includes a pot-shaped filter housing (1) that defines a longitudinal axis along which a filter element (13) can be inserted into and removed form the filter housing (1). A retaining device detachably retains the filter element (13) in the filter housing (1) and has first and second retaining elements on the inner side of the filter housing (1) and on the filter element (13) and interacting with one another. At least one set of the retaining elements has a shape coaxial to the longitudinal axis of the filter housing (1) and forms at least a part of a thread. When the filter element (13) is rotated about its longitudinal axis, it is locked in a form-fit.