Pressure equalisation device

Abstract

A pressure equalisation device adapted to be operatively connected to an enclosure, the device including an air passage which, when the device is so connected to the enclosure, provides a fluid communication between the interior of the enclosure and atmosphere, the air passage containing a barrier wall comprising an air permeable membrane forming a micro-particulate filter.

1 . A pressure equalization device adapted to be operatively connected to an enclosure, the device including a first air passage which, when the device is so connected to the enclosure, provides a fluid communication between the interior of the enclosure and atmosphere, the first air passage containing a barrier wall comprising an air permeable membrane forming a particulate filter.  
   
   
       2 . A device according to  claim 1 , wherein the barrier wall extends across the first air passage and a predetermined distance along the passage so as to have an area subjected to the air flow which is greater than the cross-sectional area of the passage.  
   
   
       3 . A device according to  claim 1 , including a carrier for the barrier wall, the carrier being sealingly insertable in a bore in a wall of the enclosure, the first air passage being formed in part by said bore.  
   
   
       4 . A device according to  claim 3 , wherein the permeable membrane forms a micro-particulate filter.  
   
   
       5 . A device according to  claim 4 , wherein the filter is formed of a polymer material.  
   
   
       6 . A device according to  claim 1 , wherein the barrier wall also forms a water barrier preventing the ingress of water into the enclosure.  
   
   
       7 . A device according to  claim 3 , further including baffle means to inhibit water entering the air passage.  
   
   
       8 . A device according to  claim 7 , wherein the baffle means serves to clamp the carrier to the enclosure.  
   
   
       9 . A device according to  claim 1 , including a second air passage in parallel with the first air passage for venting the enclosure, the second air passage including a one-way vent valve adapted to permit air flow out of the enclosure through said second air passage but to prevent air flowing into the enclosure through said second air passage.  
   
   
       10 . A device according to  claim 9 , wherein the second air passage is formed in said carrier, the one-way vent valve comprising a resilient diaphragm biased to close said second air passage and additionally being urged to a closed position by air flowing in a direction towards the enclosure and being opened against the resilient bias by air flowing out of the enclosure.  
   
   
       11 . A device according to  claim 1 , further including baffle means to inhibit water entering the air passage.