text: as can be seen more particularly in fig1 the device constituting this embodiment comprises , in conventional manner : a rigid base 1 comprising a central head 1a that is extended upwards by a threaded shank 1b ; a rigid ring 2 having a vertical axis x and constituted by two superposed annular plates 2a and 2b , each shaped on the inside to have a folded - back rim given a respective reference 2a 1 or 2b 2 , said two plates extending outwardly so as to form two diametrically opposite tabs 2c for the ring 2 , each of the tabs 2c being pierced by a fixing hole 2c 1 ; a thick elastomer wall 3 that is frustoconical about the axis x and that provides good resistance to axial compression , so as to act as a &# 34 ; support &# 34 ;, said wall 3 connecting the base 1 in sealed manner to the ring 2 and flaring from said base towards the plate 2a ; a thin flexible bellows 4 connected in sealed manner to the ring 2 , and co - operating with the ring , the wall 3 , and the base 1 to define a housing ; a rigid cap 5 for protecting the bellows 4 , the periphery of said cap 5 being fixed to the ring 2 ; a rigid intermediate partition 6 subdividing the housing into two chambers , namely a working chamber a adjacent to the wall 3 , and a compensation chamber b adjacent to the bellows 4 ; a constricted passage 7 interconnecting the two chambers a and b and formed in the periphery of the intermediate partition 6 ; a mass of liquid l filling the two chambers and the constricted passage ; and a valve member 8 mounted between two grids 9 and 10 forming portions of the intermediate partition 6 such that the amplitude of axial displacements of the various points of the valve member is limited to a value of less than 1 mm , and preferably of the order of 0 . 5 mm , said valve member 8 being in the form of a circular - outline disk of elastomer . the edge 2b 1 surrounds the peripheral edges of the partition 6 , the bellows 4 , and the cap 5 . the flexible bellows 4 is secured relative to the ring 2 by its periphery being clamped between the peripheral edge of the cap 5 and a peripheral zone of the partition 6 . the partition 6 , the bellows 4 , and the cap 5 are secured for this purpose between the large base of the frustoconical wall 3 and the edge 2b 1 by crimping the end periphery of the edge 2b 1 onto the periphery of the cap 5 . the edge 2a 1 of the plate 2a defines a truncated cone that flares towards its base that is furthest from the main portion of the plate . this edge 2a 1 is embedded in the large base of the thick frustoconical wall 3 . the grids 9 and 10 , and also the membrane 8 are all circular in outline and centered on the axis x . with reference more particularly to fig2 to 4 , it can be seen that the intermediate partition 6 is mainly constituted by two complementary pieces 11 and 12 which are superposed and whose walls co - operate to define a housing 8a for the valve member 8 , and also to define the constricted passage 7 . the piece 11 is constituted by the grid 9 whose outline is circular and by an annular groove 13 surrounding said grid 9 . the groove 13 is delimited by an inside skirt 15 which surrounds the grid 9 in cylindrical manner , by a flat annular end wall 17 , and by a skirt 19 surrounding the outer periphery of the end wall 17 . the inner skirt 15 extends from the grid 9 and the end wall 17 over a height that corresponds substantially to the height of the housing 8a of the valve member 8 . the height of the skirt 19 corresponds to half the height of the passage 7 . an inlet / outlet opening 21 is formed through the end wall 17 for enabling the damping liquid to enter and escape from the constricted passage 7 . in similar manner , the piece 12 comprises a grid 10 and a groove 14 delimited by an end wall 18 and two skirts : an inner skirt 16 and an outer skirt 20 . the end wall 18 has an inlet / outlet opening 22 passing therethrough . the outer wall of the skirt 16 and the inner wall of the skirt 15 are both substantially frustoconical and of complementary outline . they engage one on the other , thereby providing sealed clamping when the pieces 11 and 12 are assembled together . the skirts 19 and 20 have the same diameter , with their free edges being held against each other in sealed manner by the above - mentioned clamping performed by the crimping of the edge 2b 1 . the constricted passage 7 extends substantially all the way round the grids 9 and 10 . the groove 13 is terminated at its end that is angularly furthest from the opening 21 by means of a wall 23 that is disposed substantially level with the opening 22 , and that forms a sealed division between the ends of the passage 7 . the skirt 22 is interrupted level with this division 23 and the opening 22 . the opening 20a formed in this way through the skirt 20 is of dimensions that are complementary to the dimensions of the division 23 , such that when the pieces 11 and 12 are assembled together , the opening 20a engages in sealed manner on the division 23 . slots given respective references 11a and 12a are formed through the walls of the grids 9 and 10 . these slots are uniformly distributed over the grids 9 and 10 around two main circumferences . rings 27 and radial arms 24 of solid matter extend between the slots 11a and 12a , these rings and arms constituting the bearing surfaces against which the faces of the valve member 8 come to bear . each of the grids 9 and 10 has a central projection 26 with the valve member 8 being pinched between them . the invention relates more particularly to the grids 9 and 10 and to the valve member 8 . radial ribs 25 are distributed over the surfaces of the radial arms 24 of the grid 9 against which the valve member 8 is to bear , which ribs 25 extend towards the center of the grid 9 from the peripheral zone of the grid that receives the edge of the skirt 16 . the arm 24 that is closest to the opening 21 carries a rib 25 that extends substantially all the way to the pinching projection 26 of the grid 9 . the three arms 24 following it angularly in a given direction are provided with ribs 25 of length that decreases with increasing angle . the other two radial arms 24 of the grid , and in particular the arm which is closest to the opening 22 have no such ribs 25 . the grid 10 does not carry any ribs . thus , the ribs 25 are distributed in non - uniform manner and in non - repetitive manner around the axis . the angular thickness of the ribs is about one millimeter , with the closest - together points of two successive ribs 25 being spaced apart by a distance of more than 10 millimeters . the angle between the outlines of two successive ribs 25 is thus greater than ten times the angle over which one such rib 25 extends . during deformation of the valve member 8 this valve member is compressed progressively angularly about the ribs 25 . the disposition of these ribs breaks the symmetries with which the valve member 8 moves . the phenomena of unwanted noise and banging due to discontinuities in the reciprocating displacement of the valve member , and in particular to the shocks of said valve member against the radial and annular bearing surfaces are considerably diminished . this reduction in the unwanted phenomena is accentuated by positioning the largest rib 25 close to an inlet / outlet ( opening 21 ) of the constricted passage 7 , and also by the fact that the grid 10 does not have any ribs . other variant embodiments are also possible . the ribs may be replaced by any other relief that is not repetitive relative to the axis of the grids and of the valve member , and in particular by studs . the studs which may be implemented by stamping the grids are advantageously in the form of spherical caps . the non - uniform relief may also be carried by the valve member , with greater attenuation being obtained with relief that is carried by the grids , relief carried by a grid acting in the same way as a projection 26 to pinch the valve member . attenuation of banging and unwanted noise phenomena is also obtained when the surfaces in contact have no relief and present a general profile that is angularly non - uniform and non - repetitive all the way around the axis of the grids and of the valve member . such a general profile is advantageously associated with relief that is angularly non - uniform and non - repetitive . progressive angular application of the valve member against said grids can also be achieved by having a valve member of non - uniform stiffness , with the non - uniformity in stiffness being non - repetitive relative to the above - mentioned axis . to this end , the valve member may be made of a material that is angularly uniform but that is of a thickness that varies angularly in a non - repetitive manner . alternatively , it may be made of a material that is not uniform , with one or more inserts being distributed through the thickness of the valve member so that non - uniform stiffness is imparted thereto . experience shows that it is also particularly advantageous to provide set - back areas 11b , 12b or &# 34 ; spot faces &# 34 ; along at least some of the slots 11a , 12a in the grids , in their faces that face the valve member 8 , which spot faces can be formed by milling or can be integrally molded with the corresponding grids : the surface discontinuities that result from such set - back zones reinforce the favorable bang - reducing effect of the asymmetrical relief . naturally , and as can be seen from the above , the invention is not limited in any way to the particular applications and embodiments that have been described more particularly . on the contrary , the invention extends to any variants thereof , and in particular to : variants in which the valve member has an outline that is not circular , but that defines an axis analogous to an axis of revolution , e . g . a repetition axis ( i . e . the outline of the valve member repeats after the valve member has been rotated through 2π / n about said axis , where n is an integer ), and in particular variants in which the valve member is elliptical or rectangular in outline ; variants in which two damping devices are connected in parallel , a two - part valve member controlling communication between the chambers of said two devices ; variants in which the valve member between its two grids is not provided on the intermediate partition 6 , but at a different location on the inside face of the working chamber a , and in particular in the vicinity of the base 1 , in which case the valve member controls communication between the chamber a and a third chamber ( not shown ), said third chamber being likewise deformable and being defined for this purpose in particular by a sealed flexible membrane whose face outside the chamber in question defines an air chamber that may optionally be lined with foam or that may connect directly to the atmosphere ; variants in which the anti - vibration device in question is in the form of a sleeve that operates essentially along a diameter and in which the two rigid frame members are tubular , one inside the other , and are preferably circularly symmetrical and coaxial , at least under load ; variants in which one of the frame members constituting the damping device is in the form of a tube passing through the device , in which case the valve member is an annular plate surrounding said frame member ; and variants in which the constricted passage is formed in portions of the device other than the periphery of the intermediate partition , and in particular through the central zone of the valve member itself .