Patent attributes
A height adjustment device used on furniture includes an inner tube having multiple clamp portions and multiple contact portions extending from the inner periphery thereof. Multiple grooves are defined in the outer periphery of the inner tube. A pneumatic tube is inserted into the inner tube and clamped by the contact portions. The inner tube is located in an outer tube that has a bottom cap and a top cap. Multiple ridges extend from the inner periphery of the outer tube. Each reduced opening accommodates the ridge corresponding thereto. The pneumatic tube has a piston rod and is connected to the bottom cap of the outer tube. The piston rod drives the inner tube to move relative to the outer tube. Multiple roller units are connected to ridges and roll the grooves of the inner tube to reduce friction between the inner tube and the outer tube.
