Mechanical barometer

Abstract

An analog pressure indicator assembly, particularly useful as a barometer, accurately indicates pressure or pressure changes using the fewest number of and/or least expensive components possible. The assembly is typically gearless, and includes a pressure sensitive element [e.g. aneroid chamber] having a first portion that moves in a path in response to pressure. A cam has a first curved surface and a second surface, and is mounted for rotation about a first axis, and the curved first surface operatively engages the pressure sensitive element. A force transmitting element, and a shaft mounted for rotation about a second axis spaced from the first axis, and a pointer operatively connected to the shaft, are also provided. The force transmitting element may be a strand, or a strand in combination with a bar or rod, and operatively connects the cam second surface to the shaft in order to cause the shaft to rotate about the second axis in response to the pressure sensitive element rotating the cam about the first axis. Preferably a torsion spring or the like biases the cam into operative engagement with the pressure sensitive element. The cam may comprise a roller, ball bearing, or section of a ball bearing, or it may comprise a curved surface and lever (forming the second surface of the cam) that are integrally formed. A scale and housing are also typically provided, the pointer mounted within the housing to move with respect to the scale. The movement of the pressure sensing element may be linear, but if non-linear the cam curved surface is shaped to transform the non-linear movement into substantially precisely accurate arcuate movement of the pointer with respect to the scale.