Filter assembly having an outer filter element and an inner filter element removably installed within the outer filter element

A filter element for a filter assembly, the filter element comprising:

• an end cap having an opening for removably inserting another filter element of the filter assembly within the filter element;
• a coupling member for engaging a corresponding coupling member of the another filter element of the filter assembly, and connecting the filter element with the another filter element when the another filter element is removably installed within the filter element, the coupling member disposed within the opening of the end cap and including one of:
• a continuous thread or a thread segment;
• a continuous groove or a groove segment;
• and
• a lug;
• and
• a detent member for resisting disengagement of the coupling member from the corresponding coupling member of the another filter element when the another filter element is installed within the filter element;
• wherein the coupling member comprises a filter lock insert having an annular circumferential surface, the filter lock insert including one of:
• the continuous thread or the thread segment provided on the circumferential surface of the filter lock insert;
• the continuous groove or the groove segment provided in the circumferential surface of the filter lock insert;
• and
• the lug provided on the circumferential surface of the filter lock insert.

A filter element for a filter assembly, the filter element comprising:

• a handle structure including a handle member, the handle member including an abutment end surface;
• a coupling member for engaging a corresponding coupling member of another filter element of the filter assembly, and connecting the filter element with the another filter element when the filter element is removably installed within the another filter element, the coupling member including one of:
• a continuous thread or a thread segment;
• a continuous groove or a groove segment;
• and
• a lug;
• and
• a detent member for resisting disengagement of the coupling member from the corresponding coupling member of the another filter element when the filter element is installed within the another filter element, the detent member disposed on the abutment end surface of the handle;
• wherein the handle structure further includes a closure member that merges with the abutment end surface of the handle member, the closure member including the coupling member.