On Feb 9, 7:31*pm, DerbyDad03 wrote:
I've got a snow brush that can be set to various lengths by turning it in
one direction to loosen the inside tube, setting to the length you want and
then turning it in the other direction to lock it down. There are no
pre-determined lengths, like indents or anything like that. It can be set
to any length within it's upper and lower limits.

On rare occasions, it doesn't lock and just continues to turn regardless of
what length I set it to. If I keep fiddling with it, it eventually locks
and then it's good for quite awhile.

This morning while I was cleaning the Nor'easter off of a couple of cars, I
loosened it to extend it and no matter what I tried I couldn't get it to
lock down again. Assuming it was finally really broken, I brought it into
the house with the plan to see what I could do to fix it. A few hours later
I picked it up to have a look and when I turned it, it locked right down. I
played around with it and it locked down at every position I tried.

So what is inside the tube that allows the tubes to loosen and slide and
then tighten back down and lock? Could the cold affect whatever the locking
mechanism is?

I believe that most of these "infinitely" adjustable telescoping poles
have an eccentric element that tightens / "jams" against the tube ID.

Patents are not the easiest way to understand a mechanism
check this out & click on the "drawing" selection

http://www.google.com/patents/US4076437

cheers
Bob