US3874818A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Bifilar vibration dampers
Assignee: Westland Group PLC
•
Filing: 1973-10-01
•
Granted: 1975-04-01
•
Expires: 1993-10-01
Abstract
Abstract In bifilar vibration dampers adapted for cancelling vibrations in helicopter rotor systems a mass is connected by two pins to a support so that the mass is capable of pendulous movements relative the support. The pins are located in opposed arcuate slots in the mass and the support, so that the washers for the pin have only to be of slightly larger diameter than the width of the slots in order to retain the pins, thereby minimising inertia effects to significantly increase the operational efficiency of the damper.
Inventors
- 👤 James Edwin Saunders
- 👤 Alan Henry Vincent
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 21:15
CPC Classifications
F; F16; F16F; F16F15/00; F16F15/10; F16F15/14; F16F15/1407; F16F15/145; B; B64; B64C; B64C27/00; B64C27/001; B64C2027/005; Y; Y10; Y10S; Y10S416/00; Y10S416/50
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
281 words
A bifilar vibration damper indlucing in combination: a support arm adapted to extend radially from and to be rotated in a plane about an axis of rotation and having two arcuate slots extending therethrough, the slots being concentric about parallel axes which are parellel to and equidistant from the axis of rotation and located with their concave surfaces closest the axis of rotation, a pendulous member of U-shaped cross section having substantially parallel side plate members positioned on opposite sides of said support member and spaced therefrom so as to define a spacing distance from said support member when said pendulous member is centered laterally with respect to the support member, each side plate member having two arcuate slots extending therethrough, the slots being concentric about parallel axes which are substantially parallel to the axis of rotation and being of substantially the same dimensions as the support member slots, the slots in each side plate member being sligned respectively with the slots of the other side plate member and located with their convex surfaces closest the axis of rotation, a pin member extending through each of the slots of the support member and the aligned slots of the side plate members to connect the pendulous member to the support member, the pin member being of substantially circular cross section and concentric about a straight line axis and having a diameter less than the width of the slots, an annular washer positioned between the support member and each of the side plate members and connected at its inner diameter to the pin member and having an outer diameter greater than the width of the slots in the support and side plate members.
Claim 2
Dependent Claim
281 words
A bifilar vibration damper indlucing in combination: a support arm adapted to extend radially from and to be rotated in a plane about an axis of rotation and having two arcuate slots extending therethrough, the slots being concentric about parallel axes which are parellel to and equidistant from the axis of rotation and located with their concave surfaces closest the axis of rotation, a pendulous member of U-shaped cross section having substantially parallel side plate members positioned on opposite sides of said support member and spaced therefrom so as to define a spacing distance from said support member when said pendulous member is centered laterally with respect to the support member, each side plate member having two arcuate slots extending therethrough, the slots being concentric about parallel axes which are substantially parallel to the axis of rotation and being of substantially the same dimensions as the support member slots, the slots in each side plate member being sligned respectively with the slots of the other side plate member and located with their convex surfaces closest the axis of rotation, a pin member extending through each of the slots of the support member and the aligned slots of the side plate members to connect the pendulous member to the support member, the pin member being of substantially circular cross section and concentric about a straight line axis and having a diameter less than the width of the slots, an annular washer positioned between the support member and each of the side plate members and connected at its inner diameter to the pin member and having an outer diameter greater than the width of the slots in the support and side plate members.
Claim 3
Dependent Claim
23 words
A damper as claimed in claim 1, the said washers having an outer diameter slightly greater than the width of the arcuate slots.
Claim 4
Dependent Claim
41 words
A damper as claimed in claim 2, wherein the washers are fixed longitudinally on the pins by annular spacer membeers clamped by a nut, the outer surface of the spacer members forming the rolling surfaces of the pins in the slots.
Claim 5
Dependent Claim
19 words
A damper as claimed in claim 1, wherein a liner is located on the concave surface of each slot.
Claim 6
Dependent Claim
22 words
A damper as claimed in claim 4, wherein the liners are of a different material than the support arm and pendulous member.
Claim 7
Dependent Claim
27 words
A damper as claimed in claim 1, wherein the support arm and pendulous member are supported centrally of the slots by spacer members secured within the apertures.
Claim 8
Dependent Claim
25 words
A damper as claimed in claim 1, wherein the opposed arcuate slots are machined through the side portions of the support arm and pendulous member.
Claim 9
Dependent Claim
18 words
A damper as claimed in claim 1, wherein the arcuate slots extend through an arc of approximately 180*.
Claim 10
Dependent Claim
58 words
At least three bifilar vibration dampers as claimed in claim 1, the said axis of rotation being the axis of rotation of a helicopter main rotor system, each bifilar being secured at the end of an arm extending radially from a rotor hub for rotation with the rotor system in a plane perpendicular to the axis of rotation.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-03-31 | 1978-09-30 | 1979-04-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-03-31 | 1982-09-30 | 1983-04-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-03-31 | 1986-09-30 | 1987-04-01 | $7700.00 | Window Closed / Lapsed |