Heat treated rapid response pressure gauge spring

摘要

In general, the invention features a spring assembly for a gauge with a hollow metal tube that changes in volume in response to differential pressures applied across the walls. The tube has a neck connected to a fitting of the gauge, a body connected at one end to the neck with its other end sealed, and at least a portion of the walls of the body being flattened and cold worked to a reduced thickness to thereby increase their yield point to a spring temper. The body is coiled into a spiral or helix. The coiled tube is heat treated to increase its elasticity. The interior of the neck is in pressure communication with the fitting, and the interior of the body is in pressure communication through its unsealed end with the interior of the neck, whereby a change in the pressure applied to the fitting is communicated along the interior of the body changing the differential pressure across the walls of the body to cause a corresponding change in the volume.