Patent ID: 7204268

Claim:
An internal pressure equilibrium device comprising: a pipe 8 mounted on a wall 9 of an airtight space and in communication with the airtight space, the pipe having a plurality of holes 81 at a periphery of the pipe, a cap 1 sealing an upper portion of the pipe 8 located away from the wall 9 , a case 7 surrounding an external periphery of the pipe 8 and having a plurality of holes 71 on a side wall thereof, and a first port 3 on an inner end of the case 7 , a partition wall 12 disposed between the case 7 and the pipe 8 to separate the holes 81 of the pipe 8 and the holes 71 of the case 7 , the partition having second port 5 , a first ring 4 slidably inserted on an external periphery of the pipe 8 between the partition wall 12 and an outer end of the case 7 , and a second ring 6 slidably inserted on the external periphery of the pipe 8 between the partition wall 12 and an outer end of the case 7 .