Mechanism for the relative positioning of chair arm

Claim 1

A positioning mechanism comprising: a shroud including a first opening that passes through said shroud, a second opening that passes through said shroud, said second opening is disposed above said first opening, and a top plate, a supporting member disposed in an interior of said shroud, said supporting member comprises a longitudinal cavity having a plurality of notches on a side of said cavity, a shuttle member disposed in said interior of said shroud, said shuttle member includes a vertical member having a slanted slot provided near a bottom end of said vertical member, a top horizontal member of said shuttle member has a riser protruding from a surface of said top horizontal remember, a spring being disposed on said riser and being biased between said top horizontal member and said top plate, and a lock pin that is inserted through said slanted slot, said first opening, and said cavity, said lock pin being received in one of said notches; wherein raising said top horizontal member of said shuttle member causes said lock pin to slide along said cavity, said first opening, and said slanted slot so that said lock pin moves out of said one of said notches, thereby allowing motion of said shroud relative to said supporting member, and when said horizontal member is released, a biasing force of said spring causes said lock pin to slide in an opposite direction along said cavity, said first opening, and said slanted slot so that said lock pin moves into one of said notches, thereby fixing said shroud in position on said supporting member.