Control of relative humidity in machine enclosures

Claim 1

A machine having a substantially sealed enclosure, operation of the machine creating a rise in temperature within the enclosure, the machine comprising: a rechargeable desiccant within the enclosure for absorbing water vapor therein when said machine is not operating, a shallow tray for containing the desiccant, a retaining cover through which air may pass freely for retaining the desiccant in the tray, two breather orifices communicating between the interior and exterior of the enclosure, a breather filter associated with both the breather orifices which lie on substantially the same radial line, through which filter air must pass when entering the enclosure via the breather orifices, the filter comprising two chambers both divided by a common filter sheet, each chamber being associated with a respective breather orifice, and rotating mechanical elements in said enclosure for creating a pressure differential between the breather orifices during machine operation to produce a circulatory exchange of air between the enclosure and its surrounding atmosphere through the breather orifices, said exchange of air driving off moisture from said desiccant after the start of operation of said machine as a result of said temperature rise.