US3758230A — Rotor system having viscoelastic lead-lag damper

Claim 1

Independent Claim 340 words

In a rotor system for a helicopter or the like including a rotor hub rotatable about a central axis, a sustaining blade, means connecting said blade to said rotor hub with said blade normally extending generally radially from said hub for rotation with said hub about said central axis, said blade being subject to lead-lag motion relative to said hub generally within the plane of rotor hub rotation, the improvement therewith of a leadlag elastomeric damper comprising an elongate body of viscoelastic material disposed adjacent and apart from said connecting means and extending longitudinally along an axis generally parallel to the plane of rotation of said blade, elongate inner plate means embedded centrally within and bonded to said body of viscoelastic material and extending longitudinally thereof substantially the entire length thereof, separate elongate outer plate means bonded to opposite sides of said body of viscoelastic material substantially throughout the length thereof in spaced apart substantially parallel relation to said inner plate means and the plane of rotation of said blade, means interconnecting said separate outer plate means to each other and precompressing said body of viscoelastic material between said inner and outer plate means, rigid spacer means disposed between said outer plate means at longitudinally spaced locations and cooperating with said outer plate interconnecting means for limiting the precompression of said body of viscoelastic material and insuring uniform precompression, pivot means carried by and connecting said outer plate means to one of said rotor hub and blade for pivotal movement about an axis parallel to the axis of said lead-lag movement and pivot means carried by and connecting said inner plate means to the other of said rotor hub and blade for pivotal movement about an axis parallel to the axis of said lead-lag movement and spaced from said outer plate pivot means so that said plate means move relative to each other in response to lead-lag movement of siad blade relative to said rotor hub for subjecting said body of viscoelastic material to predominately shear along its longitudinal axis.

Claim 2

Dependent Claim 340 words

In a rotor system for a helicopter or the like including a rotor hub rotatable about a central axis, a sustaining blade, means connecting said blade to said rotor hub with said blade normally extending generally radially from said hub for rotation with said hub about said central axis, said blade being subject to lead-lag motion relative to said hub generally within the plane of rotor hub rotation, the improvement therewith of a leadlag elastomeric damper comprising an elongate body of viscoelastic material disposed adjacent and apart from said connecting means and extending longitudinally along an axis generally parallel to the plane of rotation of said blade, elongate inner plate means embedded centrally within and bonded to said body of viscoelastic material and extending longitudinally thereof substantially the entire length thereof, separate elongate outer plate means bonded to opposite sides of said body of viscoelastic material substantially throughout the length thereof in spaced apart substantially parallel relation to said inner plate means and the plane of rotation of said blade, means interconnecting said separate outer plate means to each other and precompressing said body of viscoelastic material between said inner and outer plate means, rigid spacer means disposed between said outer plate means at longitudinally spaced locations and cooperating with said outer plate interconnecting means for limiting the precompression of said body of viscoelastic material and insuring uniform precompression, pivot means carried by and connecting said outer plate means to one of said rotor hub and blade for pivotal movement about an axis parallel to the axis of said lead-lag movement and pivot means carried by and connecting said inner plate means to the other of said rotor hub and blade for pivotal movement about an axis parallel to the axis of said lead-lag movement and spaced from said outer plate pivot means so that said plate means move relative to each other in response to lead-lag movement of siad blade relative to said rotor hub for subjecting said body of viscoelastic material to predominately shear along its longitudinal axis.

Claim 3

Dependent Claim 32 words

In a rotor system, as set forth in claim 1, wherein the pivot axis of one of said pivot connecting means passes through the elastic center of the body of viscoelastic material.

Claim 4

Dependent Claim 40 words

In a rotor system, as set forth in claim 2, wherein the pivot axis of said other pivot connecting means is spaced from the one of said pivot connecting means along the longitudinal axis of said body of viscoelastic material.

Claim 5

Dependent Claim 52 words

In a rotor system, as set forth in claim 1, wherein said inner plate means and at least one of said outer plate means have proximate mating convex and concave surfaces extending transversely thereof to resist relative transverse movement between said inner plate means and said at least one outer plate means.

Claim 6

Dependent Claim 26 words

In rotor system, as set forth in claim 4, wherein said pivot connecting means are disposed at remote ends of said inner and outer plate means.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1976-09-10	1977-03-12	1977-09-11	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1980-09-10	1981-03-12	1981-09-11	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1984-09-10	1985-03-12	1985-09-11	$7700.00	Window Closed / Lapsed

Rotor system having viscoelastic lead-lag damper

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