| 摘要 |
A barrier serving for preventing a rat from entering a sewage pipe in the direction against the flow. The barrier comprises a first pivotal shutter (4) and a second pivotal shutter (5) located upstream of the first shutter (4). Both shutters (4,5) are forming an acute angle with the direction of flow when they are in a first angular position, in which at least the first shutter (4) is barring the aperture of the sewage pipe. From the first angular position, the first shutter (4) can be swung to a second angular position, in which it is clear of the aperture of the sewage pipe. The two shutters (4,5) are detachably locked to each other when they both are in their first angular position. The second shutter (5) is simultaneously detachably locked to a fixed stop (13) on the barrier. The rat can therefore not open the first shutter and thereby force the barrier. When the flow in the sewage pipe gets so strong that the rat cannot struggle its way upstream, the liquid pressure will force the second shutter (5) towards a second angular position in relation to the first shutter (4), whereby the locking engagement between the second shutter (5) and the stop (13) is released. Them, the liquid pressure is allowed to force the first shutter (4) to its second angular position, in which the liquid freely can flow through the sewage pipe but at such a force that the rat is not able to pass the barrier. |
