is associated with a rigid plate 40 which extends at least over part of the length of the filtering medium in fig7 and 8 the rigid plates 40 are fixed in pockets 42 formed in a bag filter 9a when this bag filter 9a is fitted into the perforated basket 6 it is angularly positioned in such a way that each of its leaves 40 is made to coincide with a deformable leaf 20 during the clearing the deformation of each leaf 20 acts on the rigid plate 40 in the manner of a piston so that the radial force of breaking up the cake is spread approximately uniformly over the length of the plate 40 and improves the fragmentation of this cake the pockets 42 may be replaced by rigid runners or any other means providing their connection with the bag 9a each plate 40 which is inserted between the clearing member 20 and the filtering medium 9a may also as shown in fig1 be fixed to the member and in this as shown in fig1 be fixed to the member and in this case to a leaf 20c or to the fabric backing 10 if there is one in another embodiment depicted in fig1 and 12 each clearing member 49 consists of several rigid elements 50 joined together in the manner of a chain and of articulations 51a and 51b the end element 50a is connected by its articulation 51a to the wall 6b of the basket while the other end element 50b is secured to a control means such as a radial peg 29 sliding in a slot 30 in the basket 6 there is an even number of elements and.