Membrane retainer assembly for physiological sensing units

Abstract

Disclosed herein is a retainer assembly for applying a membrane to a physiological sensing unit for the transcutaneous determination of the magnitude of physiological quantities, particularly for measuring the partial pressure of gases in blood or the like. The assembly constitutes a preassembly of a membrane, with a clamping ring accommodating the membrane and having an annular recess receiving the rim of the membrane. The clamping ring has a lip in the form of an inwardly protruding annular edge for removably securing the clamping ring together with the membrane to the sensing unit by virtue of the lip resiliently snapping into a peripheral groove of the sensing unit, the lip defining the periphery of the annular recess. A retainer element is provided for temporarily and removably assembling the membrane with the clamping ring prior to assembly with the sensing unit. The retainer element includes a retaining ring fitted loosely into the annular recess of the clamping ring, to maintain the outer rim of the membrane within the annular recess. In accordance with a preferred embodiment of the invention, the retaining ring is provided with at least one radially inwardly extending tongue-like tab formed integrally with and of the same material as the retaining ring. When the assembly is secured to the sensing unit, the tongue-like tab functions so as to provide a capillary connection between the atmosphere and the electrolyte film disposed between the membrane and the measuring surface of the sensing unit to eliminate fluctuations in electrolyte film thickness caused by water vapor diffusing through the membrane and into the electrolyte.