| 摘要 |
PCT No. PCT/AT91/00114 Sec. 371 Date May 19, 1993 Sec. 102(e) Date May 19, 1993 PCT Filed Oct. 23, 1991 PCT Pub. No. WO92/09753 PCT Pub. Date Jun. 11, 1992.In order to prevent the penetration of surface water into a shaft or manhole, the latter is fitted with an insert (5) consisting of a dish-shaped section (9) of impermeable material and the interior space of this dish is connected via connecting ducts (11) with the portion of the shaft or manhole located below the dish (9). The connecting ducts (11) are provided with shut-off devices (12) in the form of spherical floats which act in conjunction with a valve seat (13) to seal off the connecting ducts (11) when the level of liquid in the dish rises (FIG. 1). |
