Abstract: The invention relates to a viscous coupling particularly suitable as a brake for a firebreak door. Outer plates are non-rotatably associated with a housing by means of teeth. Between each two outer plates there is arranged one of two inner plates, which are non-rotatably connected to a hub rotatably arranged in the housing by teeth. The other inner plate is connectable in the direction of rotation to the first inner plate and to each other by two sets of lugs such that there is a free rotational path. When the lugs of two successive inner plates contact one another in the direction of rotation, a driving action occurs. Consequently, torque increases in a stepwise fashion. Therefore, it is possible for firebreak doors to affect the braking of movement into a closed position because braking is delayed and changes in steps.

Abstract: A rotary actuator device having an annular piston rod, the device comprising at least one piston held provided with sealing means and co-operating with an annular piston rod mounted so as to be capable of moving in an annular chamber, together with means for selectively applying a fluid under pressure in said annular chamber, wherein the piston head co-operates with the piston rod via a hinge having one degree of freedom in rotation and one degree of freedom in translation, said hinge comprising a piece in the form of a knife whose edge co-operates with a V-groove in a female portion of triangular profile, the knife edge and the V-groove being parallel to the axis of rotation of the piston rod. This disposition enables the forces exerted on the sealing means to be brought back into balance, thereby increasing sealing even under high pressures.

Abstract: The present invention relates to a tandem rotary master-cylinder for a vehicle brake circuit comprising a body (10;102) in which a first vane (20;114) is mounted for rotation in response to rotation of an input shaft (12;100) in order to generate pressure in a first working chamber (18;126) formed in the body (10;102) and delimited in part by the first vane (20;114).According to the invention the master-cylinder further comprises a second vane (30;120) rotatably mounted in the body (10;102) and delimiting with the first vane (20;114) the first working chamber (18;126) the second vane being rotatable in response to rotation of the first vane (20;114) to generate pressure in a second working chamber (62;128).A rotary master-cylinder with braking assistance is also described.