moving the piston 30 against the wall 20 whilst clamping the friction disc 32 and the unlocking also referred to as unclamping of this clutch 28 are achieved in a fashion known per se by varying the pressure between the control chamber 58 and the turbine chamber 59 a second embodiment of the hydrokinetic coupling appliance according to the invention will now be described with reference to fig3 in this figure the elements similar to those depicted in fig1 and 2 are designated by identical references in this embodiment the friction stop 68 is carried by the piston 30 is arranged radially beyond the external periphery 100 of the plate 24 and is produced in a single piece in this case the friction stop 68 also consists of the obturation means here metallic plugs preferably produced from pressed sheet metal and which are for example force fitted in the corresponding passage orifices 30 t each plug 68 has the general form of a bowl and comprises a re entrant rolled edge 68 r here constituting the active part 68 a of the friction stop 68 the edge 68 r being in abutment against the damper plate 36 naturally the metallic plugs in particular the active part 68 a can be given treatment with a view to improving the properties for example their coefficients of friction the passive part 68 p comprising the means.