SPRING CONSTANT OF PRESSURIZED DIAPHRAGM MADE OF FABRICS REINFORCED RUBBER SHEET

Abstract

The flat diaphragm made of plain fabrics reinforced rubber sheet has been used for a transducer element of pressure to displacement. This diaphragm is furnished usually in a circular ring plate having orthotropic elasticity, of which outer periphery is firmly fixed to the inside wall of a metal cylinder and inner periphery is connected to a concentric circular metal plate of the piston.
In this paper, we analyzed the deformation shape of the diaphragm equilibrated with the air pressure, p, under an arbitrary stroke, δ, of the piston. The effective pressurized area, D, of the membrane-like diaphragm is defined as the enclosed area by a locus curve of the position where the deflection in each radial direction takes the peak value. Then, the balanced external force, F, can be evaluated by the product of p and D, and further the equivalent spring constant, K₁, is obtained as the derivative F with respect to δ′. In this analysis, we used the energy method, because it is convenient for evaluating approximatelythe large deflection of a flat diaphragm under the inflation pressure. The predicted relationship between the external force, F, and the piston stroke, δ′, is confirmed to have a reasonable agreement with the experimental results for a diaphragm specimen with Nylon fabrics.