Resilient return strut of the elastic-hydraulic type with incorporated linear damping by throttling a high-viscosity fluid

Resilient return strut of the elastic-hydraulic type with incorporated linear damping, by throttling a hydraulic fluid, intended in particular for a blade of an aerodyne rotor of a rotary-wing aircraft, and comprising:

• (a) first and second rigid elements (25, 29), each provided with articulation means (26, 32) for connecting one of said rigid elements to a first part, as a blade or a part-joining said blade to a rotor hub, and the other of said rigid elements to a second part, such as said rotor hub;
• (b) a hydraulic damper (1) comprising two damper chambers (34, 35), of inversely variable capacities, said damper chambers being delimited within a tubular body (12) which is unitary with one of said rigid elements (29) and being separated from one another by a transverse partition (10), constituting a piston, said partition being mounted in said tubular body (12) and being unitary with one of said rigid elements (29), and which are filled with a hydraulic fluid intended to flow from one to the other of the damper chambers (34, 35) through at least one narrow connecting passage (39) between these chambers (34, 35) when the rigid elements (25, 29) are displaced one in relation to the other substantially along the general axis (A--A) of the strut, so as to produce a linear damping effect on the relative displacement of the rigid elements (25, 29);
• (c) a device (52) for compensation of thermal expansion of the hydraulic fluid, comprising an auxiliary chamber (58) containing a volume of hydraulic fluid, said auxiliary chamber being permanently connected with at least one of the damper chambers (34) through a damper base (19) which partially delimits the auxiliary chamber (58) and is adjacent to a damper chamber (34);
• (d) at least one resilient return device (2 or 3) comprising a sleeve (17 or 18) made of an elastically-deformable material and attached so as to be water-tight by its internal and external lateral surfaces, respectively, between two rigid tubular sections, internal (15 or 16) and external (13 or 14) respectively, each of said tubular sections being substantially coaxial with said general axis (A--A) of the strut and unitary with one of said first and second rigid elements (25, 29), respectively, such that the sleeve (17 or 18) is deformed by shearing when said first and second rigid elements (25, 29) are displaced relative to one another substantially along said general axis (A--A) of the strut, and such that the sleeve (17 or 18) exerts on said rigid elements a resilient return effect tending to return them to an initial relative position, in which arrangement said sleeve (17 or 18) also forms a fluid-tight closure seal sealing the hydraulic damper (1);
• (e) wherein the damper chambers (34, 35) are delimited axially between first and second resilient return devices (2, 3) having external rigid tubular sections (13, 14) arranged longitudinally on either side of said tubular damper body (12), said external rigid tubular sections (13, 14) being substantially coaxial one with the other and with said tubular body (12) and being unitary with said tubular body (12) while constituting a single external tubular armature (4) which is unitary with one (29) of said two rigid elements, and in which arrangement the internal rigid tubular sections (15, 16) of the resilient return devices (2, 3) are substantially coaxial one with the other, are arranged longitudinally while leaving clearance on either side of said transverse partition (10) of the damper (1), and are unitary with one another and with the other rigid device (15), with which said external tubular armature (4) does not form a single piece, while forming a single internal armature (28) comprising a central part (23) which passes axially through the two damper chambers (34, 35) and secures the two internal tubular sections to one another, while being enclosed by the transverse partition (10) which is annular in shape and unitary with one of the armatures (4), and in such a way that said sleeves (17, 18) made of an elastically-deformable material each provide the fluid-tight sealing of one of the two damper chambers (34, 35) respectively, on opposite sides of the transverse partition (10), said narrow connecting passage being a narrow annular passage (39) delimited by radial throttling play between said transverse partition (10) and that one (28) of the armatures with which said transverse partition (10) does not form one piece, and through which the highviscosity hydraulic fluid, which is contained in the damper chambers (34, 35) and in the auxiliary chamber (58), is throttled;
• and
• (f) wherein each of the two damper chambers (34, 35) delimited on either side of said transverse partition (10) in the tubular damper body (12) is subdivided by a rigid transverse wall (68, 69) unitary with that one of the two armatures with which said transverse partition (10) is not unitary, into two chambers of which one, in an internal axial position and adjacent to said transverse partition (10), is a working chamber (70, 72) operating under dynamic pressure, and of which the other, in an external axial position and directly adjacent to the elastically-deformable sleeve (17, 18) on the corresponding side, is a compensation chamber (71, 73) which controls variations in volume resulting from deformations in the elastically-deformable material, and which is permanently connected with the other chamber of the same kind and in the external axial position by means of at least one conduit (74).