| 摘要 |
PROBLEM TO BE SOLVED: To make it possible to cut off water reliably by obtaining a sufficient compression stress by laminating a non-water expansible rubber member having a generally U-shaped cross section and a water expansible rubber member circumscribed thereto and providing a specified thickness and cross sectional area ratio. SOLUTION: The composite water cutoff member 1 is structured by laminating a water expansible rubber member 2 whose both sides project triangularly from the external surface of a non-water expansible rubber member 3 having a generally U-shaped cross section. The thickness of the non-water expansible rubber member 3 is 2 mm or higher or K×Nmm (K is 0.33×10<-2> to 1.8×10<-2> and N is the sectional area of the composite cut-off member 1 in mm<2> ), and the minimum thickness Tmin of the non-wafer expansible rubber member and the maximum thickness Tmax thereof must satisfy Tmax=h×Tmin (h is a number between 1.0 and 2.6). The thickness of the water expansible rubber member 2 is 3 mm or greater, and the ratio of the sectional area of the non-water expansible rubber member 3 to that of the water expansible rubber member 2 is 9:1 to 2:8. In addition, the ratio of the sectional area of the composite water cutoff member to the apparent sectional area of a concave part is 1:0.1 to 0.5. Such composition helps avoid an extreme difference in the thickness of the non-water expansible rubber member 3, uniformize water cutoff, obtain uniform compression stress and execute reliable water cutoff.
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