Abstract: A height-adjustable support arm with a parallelogram linkage has a stationary first articulated head and a second articulated head which is movable relative thereto, the second articulated head having a support bar connected thereto for mounting a device such as a hanging lamp. In order to avoid gaps in the exterior portion of the second articulated head, the movable parts thereof are surrounded by a flexible covering mounted on a tubular parallelogram leg at one end and at the free end of the support bar at its other end. The exterior dimensions of the covering correspond substantially to the tubular parallelogram leg and the interior dimensions are selected such that the second articulated head can move freely therein within an adjustment range.

Abstract: A hydraulic-pneumatic control device characterized by a narrow elongated supply strip having a plurality of channels extending parallel to a longitudinal axis of the strip, a plurality of separate groups of openings spaced along the strip with each group having an opening in communication with each channel, a connecting block having a plurality of separate passages mounted on the strip with the passages in communication with the channels and a control block for each of the dental apparatuses whose agents are being regulated. Each of the control blocks is mounted on the separate group of openings of the supply strip for receiving agents from the channels therein and each block has pneumatically actuated valves for regulating the flow of the agent therethrough.