A quick-acting telescopic tube has a stationary tube, a detent lining, an extension tube, a lock activating assembly, a bottom plug, an activating rod, a spring and a ball. The detent lining is mounted securely in the stationary tube and has multiple detents. The extension tube is mounted movably in the detent lining and has a top and a bottom. The lock activating assembly is mounted around the top of the extension tube and has a lever extending into the extension tube. The bottom plug is mounted securely in the bottom of the extension tube and has a transverse through hole. The activating rod is mounted in the extension tube, connects to the lever and has a locking piston with an annular recess. The ball is mounted in the transverse through hole and selectively in either one of the detents or the annular recess.
A foot for optical or photographic supports includes a telescopic rod having several telescopic members and, for each pair of adjacent telescopic members, an expanding stop mechanism mounted on one telescopic member of the pair and acting on the other telescopic member of the pair in order to block their relative sliding motion. The stop mechanism includes a radially expandable ring and an expander body for the ring for pressing the elements of the ring radially against an inner shell of the other telescopic member. The ring includes a plurality of barrel rollers having an outer shell with a curvature coinciding substantially with the curvature of the inner shell of the other telescopic member.
Disclosed is an apparatus for regulating a height of a music rack capable of improving convenience and operability of a use by allowing a strut length of the music rack to be regulated conveniently and easily while simplifying its structure to improve manufacturability and assemblability.
