Abstract: The conical disc spring column has a central shaft with retention shields at both ends thereof and with aligned superposed conical discs positioned about the shaft, the shaft being formed of two coaxial telescopic sections having a sliding connection therebetween for controlled retraction and extension of the shaft.

Abstract: One or a plurality of valve-operated branch pieces can be attached to any point of any pipe. To this end, two opposite openings (16, 18) are made in the pipe (10), and a branch valve body is clamped about the pipe in bracket-like manner at the prepared site.

Abstract: An oxygen sensor based on a metal-air cell, typically a commercially available zinc-air battery of the type used in hearing aids. The cell, which admits oxygen to generate electric current at its cathode is disposed in a mechanical housing which restricts the flow of oxygen to the cell, and is connected to an electrical circuit which provides a variable resistance load, the load increasing as current flow through the circuit decreases, to prevent hydrogen evolution at the cathode. Current flow through the cell is measured, and is proportional to oxygen concentration.

Abstract: One or a plurality of machined timber elements of complimentary first and second configuration wherein each element is characterized by having at least one face surface (1,2) and one abutment surface (3,4) wherein said abutment surface incorporates in said first configuration an elongate undercut slot or female dovetail (5) and in said second configuration incorporates a correspondingly shaped, undercut elongate protuberance or male dovetail (8) and said abutment surface is not orthogonal in relation to said face surface such that said first timber element configuration and said second timber element configuration are adapted for co-operative engagement to effect the joining together of a first timber element incorporating said first timber element configuration with a second timber element incorporating said second timber element configuration whereby the undercut slot of said first timber element interengages with the protuberance of said second timber element to form a self locking joint.