An arm assembly includes an outer stem (52) and an inner stem (50) slidable in the outer stem and including a number of recesses (107) along its length. A biased locking device (117) engages one or more of the recesses (107) to lock the position of the inner stem (50) relative to the outer stem (52)....http://www.google.sh/patents/US6840582?utm_source=gb-gplus-sharePatent US6840582 - Height adjustable arm assembly
