Yoke for helicopter rotor systems

• US 5,358,381 A
• Filed: 03/19/1993
• Issued: 10/25/1994
• Est. Priority Date: 03/19/1993
• Status: Expired due to Term

• Current Assignee: Bell Helicopter Michigan Inc (Textron Inc)
• Original Assignee: Bell Helicopter Textron Incorporated (Textron Inc)
• Inventors: Robinson, Madison K., Powell, Ernest A., Tisdale, Patrick R., Ledbetter, Timothy K., Sehgal, Ajay, Covington, Cecil E.
• Primary Examiner(s): Look, Edward K.
• Assistant Examiner(s): Sgantzos, Mark
• Application Number:
  US08/034,345
• Time in Patent Office: 585 Days
• Field of Search: 416/134 A, 416/136 A, 416/140 A
• US Class Current: 416/134.00A
• CPC Class Codes: B29C 70/86 Incorporated in coherent impregnated reinforcing layers, e.g. by winding
• CPC Class Codes: B29K 2105/101 Oriented
• CPC Class Codes: B29L 2031/08 Blades for rotors, stators, fans, turbines or the like, e.g. screw propellers
• CPC Class Codes: B64C 27/33 having flexing arms

Abstract

An improved feathering flexure for a helicopter rotor system yoke includes, in transverse cross section, a relatively thin central web and six relatively thin flanges. Three flanges extend from each of the web'"'"'s two edges, and the flanges lie in planes which are approximately radial relative to the neutral feathering axis of the feathering flexure. The feathering flexure is constructed of fiberglass material embedded in a polymer matrix. The web'"'"'s fiberglass material in the web is bias material, that is, material whose glass fibers are oriented at plus or minus 45 degrees relative to the yoke'"'"'s spanwise axis. In transverse cross section, each of the flanges includes two unidirectional belts disposed on either side of a bias pack. The glass fibers in the unidirectional belts are oriented parallel to the yoke'"'"'s spanwise axis. The fiberglass material in the bias packs is bias material. Each flange'"'"'s unidirectional belts taper inwardly toward its bias pack adjacent to web, thereby decreasing the thickness of the flange adjacent to the web. In addition, the portion of each flange adjacent to the web is configured to minimize torsional rigidity and shear stress resulting from twisting the feathering flexure.

Claims

1. In a helicopter rotor blade system yoke, a feathering flexure comprising, in transverse cross section:

a thin central web;

at least two flanges extending from each of at least two separated points on said web, said flanges lying substantially in planes which are approximately radial relative to a neutral feathering axis of said feathering flexure; and

each said flange comprising two belts constructed of unidirectional composite material and a bias pack constructed of bias composite material, said belts being disposed on opposite sides of said bias pack and tapering inwardly toward said bias pack adjacent to an intersection of said flange and said web.

2. An integral yoke for a helicopter rotor blade system comprising:

a hub, a flapping flexure, an inboard transition section, a feathering flexure, an outboard transition section, and an outboard joint;

said flapping flexure extending from said hub and having a substantially rectangular transverse cross section;

said inboard transition section extending from said flapping flexure, having an inboard end whose transverse cross section is substantially identical to that of an outboard end of said flapping flexure, and having an outboard end whose transverse cross section is substantially identical to that of an inboard end of said feathering flexure;

said feathering flexure extending from said inboard transition section and having a transverse cross section characterized by a thin central web and at least two flanges extending from each of a least two separated points on said web, said flanges lying substantially in planes which are approximately radial relative to a neutral feathering axis of said feathering flexure;

each said flange comprising two belts constructed of unidirectional composite material and a bias pack constructed of bias composite material, said belts being disposed on opposite sides of said bias pack and tapering inwardly toward said bias pack adjacent to an intersection of said flange and said web; and

said outboard transition section extending from said feathering flexure, having an inboard end whose transverse cross section is substantially identical to that of an outboard end of said feathering flexure, and having an outboard end whose transverse cross section is substantially identical to that of an inboard end of said outboard joint.

3. In a helicopter rotor blade system yoke, a feathering flexure comprising, in transverse cross section:

a thin central web;

at least two flanges extending from each of at least two separated points on said web, said flanges lying substantially in planes which are approximately radial relative to a neutral feathering axis of said feathering flexure; and

a portion of at least one flange adjacent to each of said points on said web being oriented substantially at 90 degrees relative to said web.