of a fabric 1 in the form of an endless rope formed by a storage chamber 2 of curved tubular semicircular construction in the vertical plane by an upper chamber 3 corresponding to one end of the chamber 2 and by a substantially horizontal transport duct 4 arranged between the upper chamber 3 and the other end of the chamber 2 a circuit for the treatment liquor 5 comprises a duct 6 having a discharge valve 7 associating the bottom of the chamber 2 with the upper chamber 3 through a vertically extending filter 8 a means comprising a motor 9 and a pump 10 and a heat exchanger 11 the treatment liquor 5 is held at a level n in the chamber 2 said level being adjustable by the liquor circuit the filter 8 comprises a vertical chamber having a cover 8a wherein the filter medium is contained said filter 8 is disposed vertically its upper edge being at a higher level than level n so that the filter may be cleaned without having to drain the treatment liquor circuit the upper chamber 3 is provided with a side cover 12 and houses a winch 13 wrapped by the fabric 1 the winch 13 may rotate freely or have its shaft 14 coupled to a group formed by a motor 15 variator 16 and a speed reducer 17 without excluding other variable speed units such as d c motors and hydraulic motors within said upper chamber 3 there is an overflow chamber 18 provided with an annular chamber 19 illustrated in the drawings.