Patent Application
20200307304
The present disclosure relates to bolted joints, and more specifically, to bolted joints for wheel assemblies.
Aircraft typically include landing gear for supporting the aircraft above a ground surface and for allowing the aircraft to move relative to the ground surface while remaining supported by the ground surface. The landing gear may include one or more wheel assemblies. The wheel assemblies may be split wheel assemblies, for example, and may have an inboard wheel portion and an outboard wheel portion. Such wheel portions of a split wheel are often held together using a plurality of tie bolts. Such tie bolt configurations may have a limited useful life in view of the repetitive and extreme operating conditions of aircraft wheel assemblies. For example, tie bolts of aircraft wheel assemblies may experience tensile and bending stresses in response to static internal loads (such as tie bolt preload and tire inflation pressure) and/or dynamic external radial and side loads during operation (e.g., wheel rolling, aircraft taxi maneuvers, etc.). While conventional solutions for mitigating tensile and bending stresses and improving fatigue life involve using more robust materials and/or using more material (e.g., bolt length, bolt diameter, wheel half dimension, etc.), such solutions generally involve increased costs and/or increased volume and weight, which adversely affects operating efficiencies.
In various embodiments, the present disclosure provides a wheel assembly that includes a split wheel, a nut, and bolt. More specifically, the split wheel comprises a first wheel portion and a second wheel portion, and the nut comprises a first portion and a second portion. The first portion of the nut comprises a thrust face engaging the split wheel, the nut defines a bore extending through both the first portion and the second portion, the bore in the first portion is nonthreaded, and the bore in the second portion is threaded, according to various embodiments. Further, the bolt extends through the first wheel portion and the second wheel portion, with a threaded end of the bolt extending through the first portion of the nut and being coupled to the second portion of the nut, according to various embodiments.
In various embodiments, a clamped length of the bolt is defined as a first distance between a head of the bolt and the thrust face of the nut and an effective bending length of the bolt is defined as a second distance between the head of the bolt and the second portion of the nut. In various embodiments, the effective bending length of the bolt is greater than the clamped length. In various embodiments, the second portion of the nut comprises a thread count of between 3 and 7 threads.
In various embodiments, the first portion of the nut comprises a first axial length, the second portion of the nut comprises a second axial length, the first axial length plus the second axial length is a third axial length, and the first axial length is between 10% and 75% of the third axial length. In various embodiments, the first axial length is between 15% and 50% of the third axial length. In various embodiments, the first axial length is between 15% and 30% of the third axial length. In various embodiments, the bore in the first portion of the nut has a first diameter, the bore in the second portion of the nut has a maximum second diameter, and the first diameter is substantially equal to the maximum second diameter.
Also disclosed herein, according to various embodiments, is a wheel assembly comprising a first wheel portion having a first web, wherein the first web comprises a first mating surface and a first outer surface opposite the first mating surface. The wheel assembly further includes a second wheel portion comprising a second web, wherein the second web comprises a second mating surface and a second outer surface opposite the second mating surface, according to various embodiments. Still further, the wheel assembly may include a bolt comprising a head and a threaded end and a nut comprising a first portion and a second portion. The first portion comprises a thrust face, the nut defines a bore extending through both the first portion and the second portion, the bore in the first portion is nonthreaded, and the bore in the second portion is threaded, according to various embodiments. In various embodiments, the first mating surface of the first wheel portion engages the second mating surface of the second wheel portion, the bolt extends through the first web and the second web, the head of the bolt engages the first outer surface of the first wheel portion, the threaded end of the bolt extends into the bore of the nut and is coupled to the second portion of the nut, and the thrust face of the nut engages the second outer surface of the second wheel portion.
In various embodiments, the wheel assembly further includes a first washer and a second washer. The first washer may be disposed between the head of the bolt and the first outer surface of the first wheel portion such that the head of the bolt engages the first outer surface via the first washer. The second washer may be disposed between the thrust face of the nut and the second outer surface of the second wheel portion such that the thrust face of the nut engages the second outer surface of the second wheel portion via the second washer. In various embodiments, the bolt is preloaded such that the bolt is in tension and the first wheel portion and the second wheel portion are compressed together. In various embodiments, the threaded end of the bolt is directly adjacent the bore in the first portion of the nut such that no intervening elements are disposed between the threaded end of the bolt and the first portion of the nut within the bore.
Also disclosed herein, according to various embodiments, is a method of assembling a wheel assembly. The method may include inserting a threaded end of a bolt through a first wheel portion and a second wheel portion of a split wheel, through a bore opening defined in a thrust face of a nut, and into a bore of the nut. A first portion of the nut may include the thrust face, the first portion of the bore may be nonthreaded, and a second portion of the bore is threaded. The method may further include torquing or preloading the bolt relative to the nut such that the threaded end of the bolt is coupled to the second portion of the nut, wherein torquing or preloading the bolt relative to the nut compresses the first wheel portion and the second wheel portion together.
In various embodiments, the method further includes, before inserting the threaded end of the bolt through the bore opening and into the bore of the nut, removing a first section of threads from the bore of the first portion of the nut, thereby leaving a second section of threads in the bore of the second portion of the nut. In such embodiments, torquing (e.g., preloading) the bolt relative to the nut comprises engaging the threaded end of the bolt to the second section of threads. Removing the first section of threads from the bore of the first portion of the nut may include machining away the first section of threads.
The forgoing features and elements may be combined in various combinations without exclusivity, unless expressly indicated herein otherwise. These features and elements as well as the operation of the disclosed embodiments will become more apparent in light of the following description and accompanying drawings.
The subject matter of the present disclosure is particularly pointed out and distinctly claimed in the concluding portion of the specification. A more complete understanding of the present disclosure, however, may best be obtained by referring to the detailed description and claims when considered in connection with the drawing figures.
The detailed description of exemplary embodiments herein makes reference to the accompanying drawings, which show exemplary embodiments by way of illustration. While these exemplary embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosure, it should be understood that other embodiments may be realized and that logical changes and adaptations in design and construction may be made in accordance with this disclosure and the teachings herein without departing from the spirit and scope of the disclosure. Thus, the detailed description herein is presented for purposes of illustration only and not of limitation.
As used herein, a first component that is “radially outward” of a second component means that the first component is positioned at a greater distance away from a common axis than the second component. A first component that is “radially inward” of a second component means that the first component is positioned closer to the common axis than the second component. In the case of components that rotate circumferentially about a common axis, a first component that is radially inward of a second component rotates through a circumferentially shorter path than the second component. As used herein, “distal” refers to the direction outward, or generally, away from a reference component. As used herein, “proximal” and/or “proximate” refer to a direction inward, or generally, towards the reference component.
With reference to
Turning to
In various embodiments, wheel assembly 200 also defines a tube-well 204. Tube-well 204 may be defined by respective flange sections of the first wheel portion 201 and the second wheel portion 202. Tube-well 204 may be configured to receive a tire and may form a seal with tire to allow pressurized air to inflate the tire. In various embodiments, the first wheel portion 201 also includes a radially outward extending lip or rim 208 located at an inboard end of the first wheel portion 201, and the second wheel portion 202 may also include a similar radially outward extending lip or rim 209 located at an outboard end of the second wheel portion 202.
In various embodiments, and with reference to
In various embodiments, and with reference to
In various embodiments, and with reference to
The nut 260, however, is not a conventional nut that has threads disposed along an entire length of the inner cylindrical wall that defines the bore 265. Instead, the nut 260 has a first portion 261 and a second portion 262, with the bore 265 in the first portion 261 of the nut 260 being nonthreaded and the bore in the second portion 262 of the nut 260 being threaded. As used herein, the term nonthreaded refers to a section of the bore 265 of the nut 260 that does not have mechanical threads. For example, the section of the bore 265 disposed in the first portion 261 of the nut 260 may be defined by a smooth cylindrical inner wall. Said differently, although the bore 265 extends through both the first portion 261 and the second portion 262 of the nut 260, only a section of the nut 260 (e.g., the second portion 262) has internal threads.
In various embodiments, and with continued reference to
With the nut 260 being configured in this manner, the bolt 250 has a clamped length 281 and an effective bending length 282. The clamped length 281 is generally defined herein as the distance between the head 251 of the bolt 250 and the thrust face 263 of the nut 260, and thus refers to the region clamped/compressed by the bolt/nut system. The effective bending length 282 is generally defined herein as the distance between the head 251 of the bolt 250 and the second portion 262 of the nut 260, and thus refers to the length of the bolt 250 deflected by the bending moment. That is, because the threaded end 252 of the bolt 250 is not directly nor threadably engaged to the first portion 261 of the nut 260, the effective bending length 282 of the bolt 250, at least for purposes of calculating bending stress (as described in more detail below), is greater than it would otherwise be if the nut had threads on the first portion. Accordingly, by using a nut 260 having this configuration (first portion 261 nonthreaded, second portion 262 threaded), the effective bending length of the bolt 250 is increased (i.e., the effective bending length 282 is greater than the clamped length 281) without having to actually increase the length of the bolt 250. Therefore, as further articulated below, the bending stress is decreased and the fatigue/useful life is increased without adding extra material (i.e., weight) to the assembly.
In various embodiments, and as shown in the following equations, bending stress of a bolt is dependent on the effective bending length 282 of the bolt 250.
σ=M*c/I Equation 1
dx/dy=M*L/E*I Equation 2
M=dx/dy*E*I/L Equation 3
σ=dx/dy*E*c/L Equation 4
Equation 1 shows bolt bending stress as a function of various parameters (defined above). Equation 2 shows how the slope (e.g., joint opening angle) of the bolt is dependent on the bending moment, and Equation 3 is merely Equation 2 after solving for the bending moment. Combining Equations 1 and 3 produces Equation 4 (more specifically, the bending moment variable (“M”) in Equation 1 is replaced with Equation 3, thereby resulting in Equation 4. As is apparent from Equation 4, increase the effective bending length (“L”) of the bolt means an increase in the denominator, which decreases the calculated stress.
In various embodiments, the second portion 262 of the nut 260 has a thread count sufficient to maintain strength/integrity of the bolted joint. As used herein, the term “thread count” refers to the number of complete thread/raceway rotations around the inner surface of the nut 260. For example, the second portion 262 of the nut 260 comprises a thread count of between 3 and 10 threads. In various embodiments, the thread count of the second portion 262 of the nut 260 is between 3 and 7 threads. In various embodiments, the first portion 261 of the nut 260 has a first axial length 286 and the second portion 262 of the nut 260 has a second axial length 287. The sum of the first axial length 286 and the second axial length 287 is referred to herein as the third axial length, which may be the total/overall axial length of the nut 260. In various embodiments, the first axial length 286 is between 10% and 75% of the third axial length. In various embodiments, the first axial length 286 is between 15% and 50% of the third axial length. In various embodiments, the first axial length 286 is between 15% and 30% of the third axial length. In various embodiments, bore 265 in the first portion 261 of the nut 260 has a first diameter, the bore 265 in the second portion 262 of the nut 260 has a maximum second diameter, and the first diameter is equal to or greater than the maximum second diameter. In various embodiments, the first diameter is substantially equal to the maximum second diameter. As used in this context only, the term “substantially equal” means the first diameter is equal to or up to 10% greater than the maximum second diameter. Thus, the threaded end 252 of the bolt 250 may be directly adjacent to the cylindrical wall defining the bore 265 in the first portion 261 of the nut 260 such that no intervening elements are disposed between the threaded end 252 of the bolt 250 and the first portion 261 of the nut 260 within the bore 265.
In various embodiments, and with reference to
In various embodiments, and with reference to
In various embodiments, and with reference to
Benefits, other advantages, and solutions to problems have been described herein with regard to specific embodiments. Furthermore, the connecting lines shown in the various figures contained herein are intended to represent exemplary functional relationships and/or physical couplings between the various elements. It should be noted that many alternative or additional functional relationships or physical connections may be present in a practical system. However, the benefits, advantages, solutions to problems, and any elements that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as critical, required, or essential features or elements of the disclosure.
The scope of the disclosure is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more.” It is to be understood that unless specifically stated otherwise, references to “a,” “an,” and/or “the” may include one or more than one and that reference to an item in the singular may also include the item in the plural. All ranges and ratio limits disclosed herein may be combined.
Moreover, where a phrase similar to “at least one of A, B, and C” is used in the claims, it is intended that the phrase be interpreted to mean that A alone may be present in an embodiment, B alone may be present in an embodiment, C alone may be present in an embodiment, or that any combination of the elements A, B and C may be present in a single embodiment; for example, A and B, A and C, B and C, or A and B and C.
Also, any reference to attached, fixed, connected, coupled or the like may include permanent (e.g., integral), removable, temporary, partial, full, and/or any other possible attachment option. Different cross-hatching is used throughout the figures to denote different parts but not necessarily to denote the same or different materials.
The steps recited in any of the method or process descriptions may be executed in any order and are not necessarily limited to the order presented. Furthermore, any reference to singular includes plural embodiments, and any reference to more than one component or step may include a singular embodiment or step. Elements and steps in the figures are illustrated for simplicity and clarity and have not necessarily been rendered according to any particular sequence. For example, steps that may be performed concurrently or in different order are illustrated in the figures to help to improve understanding of embodiments of the present disclosure.
Any reference to attached, fixed, connected or the like may include permanent, removable, temporary, partial, full and/or any other possible attachment option. Additionally, any reference to without contact (or similar phrases) may also include reduced contact or minimal contact. Surface shading lines may be used throughout the figures to denote different parts or areas but not necessarily to denote the same or different materials. In some cases, reference coordinates may be specific to each figure.
Systems, methods and apparatus are provided herein. In the detailed description herein, references to “one embodiment”, “an embodiment”, “various embodiments”, etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described. After reading the description, it will be apparent to one skilled in the relevant art(s) how to implement the disclosure in alternative embodiments.
Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. No claim element is intended to invoke 35 U.S.C. 112(f) unless the element is expressly recited using the phrase “means for.” As used herein, the terms “comprises”, “comprising”, or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
