INTERNAL/EXTERNAL PRESSURE DIFFERENCE CONTROL FILTER WITH AUTOMATIC OPEN/CLOSE VALVE FOR FILTER PROTECTING FILM

摘要

PURPOSE: To prevent the clogging or the breakage of a filter film which controls the internal/external pressure difference of a waterproof case of an electronic equipment used outdoor that is caused by an environmental change or a temperature change due to the internal heating. ;CONSTITUTION: A filter film 3 made of a continous porous polytetrafluoroethylene material having both air permeability and waterproof properties is stuck to a packing 4 by an adhesive. Then the packing 4 is attached to the inside of a venthole 10 of a filter 2 attached to a partition plate 1 and tightened by a nut 6 via a spacer 5. When an internal/external pressure difference of the plate 1 is caused, an automatic open/close valve 7 is pulled toward the negative pressure side. Thus the venthole 10 opens to circulate the air while the mixture of rainwater, etc., is prevented by the film 3. So that the internal/external pressure difference of the plate 1 is reduced. When no pressure difference is caused any more, the valve 7 is pulled by the restoring force of a spring 8 and the venthole 10 is closed. Thus the film 3 is shielded from the outside and therefore its clogging and breakage are prevented.;COPYRIGHT: (C)1994,JPO