Patent Application
20150078909
1. Technical Field
The present application relates to a rotor blade, as well as a structural system for coupling the rotor blade to a rotor hub.
2. Description of Related Art
Conventionally, rotor blades have been coupled to the rotor hub in a variety of ways. One conventional rotor blade attachment system involves attaching the rotor blade with two bolts oriented along a chordwise axis at the root end of the rotor blade. Another conventional rotor blade attachment system involves attaching the rotor blade with two bolts oriented along a spanwise axis at the root end of the rotor blade. Though significant improvements in rotor blade attachments have been made, significant room for improvement remains.
There is a need for an improved rotor blade, as well as an improved structural system for coupling the rotor blade to a rotor hub.
The novel features believed characteristic of the embodiments of the present application are set forth in the appended claims. However, the embodiments themselves, as well as a preferred mode of use, and further objectives and advantages thereof, will best be understood by reference to the following detailed description when read in conjunction with the accompanying drawings, wherein:
Illustrative embodiments of the apparatus and method are described below. In the interest of clarity, all features of an actual implementation may not be described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developer's specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.
In the specification, reference may be made to the spatial relationships between various components and to the spatial orientation of various aspects of components as the devices are depicted in the attached drawings. However, as will be recognized by those skilled in the art after a complete reading of the present application, the devices, members, apparatuses, etc. described herein may be positioned in any desired orientation. Thus, the use of terms such as “above,” “below,” “upper,” “lower,” or other like terms to describe a spatial relationship between various components or to describe the spatial orientation of aspects of such components should be understood to describe a relative relationship between the components or a spatial orientation of aspects of such components, respectively, as the device described herein may be oriented in any desired direction.
Referring now to
Referring to
During operation, dynamic forces act upon rotor blade 105 and associated components of rotor system 103. Primary dynamic forces include a combination of centrifugal force loading in a centrifugal force direction 145, a chordwise bending in a bending direction 147, and a beamwise bending in a bending direction 149. Such loading must be reacted by the attachment mechanism used to attach the rotor blade 105 to the grip 119. Further, torsional loading about pitch change axis 143 can be experienced from aerodynamic loading as well as pitch change inputs from pitch horn 123. Conventional two-bolt attachment arrangements have several shortcomings. For example, when the two bolts are arranged approximately spanwise, the torsional loading about pitch change axis 143 can induce bending along an axis formed by the two spanwise located bolts. In the conventional two-bolt arrangement wherein the two bolts are arrange approximately chordwise, the beam bending in direction 149 can induce bending along an axis formed by the two chordwise located bolts. In these conventional two-bolt arrangements, the two bolts must be sized in order to react the bending loads, which can add weight since a larger diameter bolt can increase edge distance requirements, bolt weight, and rotor blade structure at the root end.
In contrast to conventional two-bolt arrangements, the embodiments of the present disclosure include a three-bolt triangular pattern that collectively react the operation loads in such a manner so as to reduce the size of the bolts and corresponding attachment lugs in both the rotor blade 105 and grip 119, thereby reducing the overall weight of rotor system 103 and increasing the useful load of the rotorcraft 101. Further, the aerodynamic drag of the three-bolt pattern is actually less than two-bolt chordwise arrangement. Furthermore, utilizing more than three bolts can add unnecessary weight, and further add complexity to the manual rotor blade folding procedure.
The three rotor blade attachment bolt arrangement includes the first bolt 129, which is the most inboard of the three bolts, and lies upon a center spanwise plane of rotor blade 105. The three rotor blade attachment bolt arrangement also includes the second bolt 131 and the third bolt 133 that are aligned along a chordwise plane, and offset from the first bolt 129 in an outboard spanwise direction by a distance D1. The second bolt 131 and the third bolt 133 are offset from the center spanwise plane by chordwise distances C1 and C2, respectively. In the example embodiment, C1 is equal to C2.
The combination and arrangement of the first bolt 129, the second bolt 131, and the third bolt 133 for attachment of the rotor blade 105 to grip 137 has unique advantages. First regarding the beam bending in direction 149, if first bolt 129 weren't present, then second bolt 131 and third bolt 133 would be subject to relatively large bending forces from the beam bending in direction 149 due to the second bolt 131 and third bolt 133 being aligned in a chordwise direction. However, the presence of first bolt 129 acts to greatly reduce the bending forces on second bolt 131 and third bolt 133 by creating a heel/toe effect. Secondly regarding torsionally forces approximately about pitch change axis 143, if either of second bolt 131 or third bolt 133 weren't present, then an input from pitch horn 123 or aerodynamic force, for example, would act to create relatively large bending forces about an axis formed between the first bolt 129 and either of the second bolt 131 or the third bold 133. However, the presence of both second bolt 131 and third bolt 133, in addition to first bolt 129, acts to greatly reduce the bending forces by creating a heel/toe effect.
Further, by locating first bolt 129 inboard to the chordwise oriented second bolt 131 and third bolt 133, the rotor blade 105 can taper down or become more narrow at the root end. The tapering of rotor blade 105 at the root end allows for clearance between the root end of rotor blade 105 and the damper attachment portion 141 of pitch horn.
Referring now also to
Rotor blade 105 can include a forward taper 715 and an aft taper 717 that each taper toward a centerline axis of the rotor blade until joining at a rounded portion 719. Rounded portion 719 can have a radius that is a function of a desired edge distance from hole 709.
In
The embodiments herein are illustrated with regard to a main rotor assembly on a rotorcraft; however, it should be appreciated that the embodiments may be adaptable to a tail rotor assembly.
The particular embodiments disclosed above are illustrative only, as the apparatus may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Modifications, additions, or omissions may be made to the apparatuses described herein without departing from the scope of the invention. The components of the apparatus may be integrated or separated. Moreover, the operations of the apparatus may be performed by more, fewer, or other components.
Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the application. Accordingly, the protection sought herein is as set forth in the claims below.
To aid the Patent Office, and any readers of any patent issued on this application in interpreting the claims appended hereto, applicants wish to note that they do not intend any of the appended claims to invoke paragraph 6 of 35 U.S.C. §112 as it exists on the date of filing hereof unless the words “means for” or “step for” are explicitly used in the particular claim.
