Nested extension/retraction structure and method of fabrication

A telescoping, axially extensible and retractable structure comprising:

• a) a first, hollow, tube-like member having internal and external walls and elongated on a central axis between first and second ends;
• b) first stop means extending inwardly from said internal wall of said first member adjacent said first end;
• c) means defining a first, helical thread on said internal wall of said first member extending substantially from said second end to said first stop means;
• d) a second, hollow, tube-like member, positioned at least partially within said first member, having internal and external walls and elongated on said central axis between third and fourth ends;
• e) means defining a second, helical thread on said external wall of said second member extending substantially from said fourth end to a predetermined position less than half the distance to said third end, said first and second threads being mutually engaged for relative axial movement of said first and second members in response to relative rotation thereof;
• f) second stop means extending inwardly from said external wall of said second member adjacent said predetermined position;
• and
• g) means for effecting relative rotation of said first and second members to produce said relative axial movement thereof between a relatively retracted position, wherein said second and fourth ends are substantially adjacent one another, and a relatively extended position, wherein said first and second stop means are in mutual contact, whereby both said first and second threads remain externally unexposed throughout the range of said relative axial movement of said first and second members.