Cap seal for lubricant injector

A gasket for releasably holding a cup-shaped cap on an end structure of a lubricant metering device and for forming a seal between the cap and the end structure to prevent moisture or dirt contamination, said lubricant metering device having a generally cylindric body with said end structure projecting endwise from the body, the gasket comprising:

• a washer of a flexibly resilient material having an annular shape with a top surface and a bottom surface, an inner edge and an outer edge, the washer being sized for placement on the end structure of the device so that the washer surrounds the end structure and the inner edge forms a fluid-tight seal thereon, the top surface facing generally away from the body and the bottom surface facing generally toward the body, the washer further being sized so that the outer edge engages an inner surface of the cap when the cap is received on the end structure to form a fluid-tight seal against the inner surface and hold the cap in generally fixed position relative to the washer, the washer being resiliently flexible between an undeflected position wherein the washer has a generally flat profile and said outer edge is generally aligned with the inner surface of the cap when the cap is mounted on the end structure, and a deflected position wherein the washer has a curved profile and said outer edge is not aligned with the inner surface of the cap;
• and
• a first notch on said outer edge of the washer, the notch being a beveled notch extending between said outer edge and said top surface, the notch being positioned so that the washer in the deflected position is unsealed and permits passage of air through the notch to prevent build-up of air pressure in the cap as the cap is mounted on the end structure.