Device for separating a surface layer of a liquid

A device for separating a surface layer of a liquid, including a container (6), which is intended to be submerged in the liquid and which includes:

• a bottom (7);
• a wall member (8), which has a centre axis (x) extending substantially vertically when the container (6) is submerged in the liquid, which wall member (8) is connected to the bottom (7) at a lower end of the wall member and has a variable length along the centre axis (x);
• and
• a separating member (9) connected to an upper end of the wall member (8), which separating member has an opening, communicating with a space (10) formed in the container (6), and an overflow portion (11), arranged, during separation of liquid from the surface layer having a free liquid surface, to be located at least below and adjacent to this liquid surface and to permit the flowing of liquid from the surface layer over the overflow portion (11) through the opening into the space (10), in which a volume of separated liquid is collected,
• wherein the device also includes a discharge conduit (4), which extends from a part of the space (10), said part being filled with liquid during separation, and is arranged to discharge liquid from the space (10), and a floating member (15), which is connected to the separating member (9) and which is arranged to float on the liquid located outside the container (6) and to exert a lifting force upon the separating member (9) in a direction prolonging the wall member (8),
• characterised in that the device also includes a submerging member (16) provided in the space (10), which submerging member is connected to the separating member (9) and located at a certain vertical distance from and below the overflow portion (11), wherein the submerging member (16) has a certain mass and is arranged to exert a downwardly directed force upon the separating member (9), which is of such an order that it is able to press the separating member (9) so far down into the liquid surrounding the container (6) against the action of the lifting force from the floating member (15) that the overflow portion (11) becomes located below the free liquid surface, and wherein the submerging member (16) also is arranged in such way that the submerging member (16) and the separating member (9) are influenced by a force in a lifting direction by the liquid pressure acting upon the submerging member (16) from the liquid, which is located above the lowest point of the submerging member (16) when the space (10) has been filled with such a quantity of liquid that a part of the submerging member (16) is located in this liquid.