MATERIAL LAYER AND METHODS

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application relates to and claims priority to U.S. Provisional Patent Application Serial No.62/172,482, filed on June 8, 2015, and U.S. Provisional Patent Application Serial No. 62/222,895, filed on September 24, 2015, the disclosures of which are incorporated by reference herein in their entirety.

TECHNICAL FIELD

[0002] The subject matter herein generally relates to the design and construction of rollers and wheels for friction drive systems and methods. The subject matter herein more particularly relates to the construction of a body and/or outer contact portion of a friction roller.

BACKGROUND

[0003] In conventional configurations for aircraft landing gear systems, the main landing gear wheels are driven by elastomeric rollers that apply torque by friction on a crown track attached to the wheels. Because of this arrangement, it is desirable to have a flexible (i.e., soft) contact between the rollers and the crown track in order to accommodate the relative displacements of the wheel with the landing gear structure (e.g., about 5 degrees of freedom).

[0004] Because of the high forces on the wheel, however, the elastomer needs to be relatively stiff, but a stiff elastomer at the surface lowers the coefficient of friction and results in a high heat build-up in the body of the roller. Furthermore, low hysteresis compounds tend to be poor in abrasion resistance.

[0005] As a result, it would be desirable for a friction roller to be able to carry the high loads but to give low heat build-up. In addition, it would be further desirable for at least an outer portion of such a roller to provide both high abrasion resistance for wear and a high coefficient of friction.

SUMMARY

[0006] In accordance with this disclosure, improvements in the design and construction of rollers and wheels for friction drive systems and methods are provided. In one aspect, a drive roller is provided in which a coupling element is configured to be driven by a rotary force input, a body portion surrounds the coupling element, and an outer contact portion surrounds the body portion and is configured for transferring torque from the rotary force input to a driven element. In some embodiments, the body portion comprises one or more layers of elastomer-reinforced fabric including at least one fabric layer arranged between at least two of a plurality of elastomeric layers, the at least one fabric layer and the elastomeric layers being bonded together to form the body portion.

[0007] In another aspect, roller drive system is provided. A crown track is configured to be rotationally coupled to a driven element, a coupling element is configured to be driven by a rotary force input, a body portion surrounds the coupling element, and an outer contact portion surrounding the body portion is configured for engaging the crown track for transferring torque from the rotary force input to the driven element. In some embodiments, the body portion comprises one or more layers of elastomer-reinforced fabric including at least one fabric layer arranged between at least two of a plurality of elastomeric layers, the at least one fabric layer and the elastomeric layers being bonded together to form the body portion.

[0008] In yet another aspect, a method for making a drive roller is provided. The method includes positioning one or more layers of elastomer-reinforced fabric about a coupling element that is configured to be driven by a rotary force input, the one or more layers of elastomer-reinforced fabric comprising at least one fabric layer positioned between at least two of a plurality of elastomeric layers. The method further includes bonding the at least one fabric layer and the elastomeric layers together to form a body portion and positioning an outer contact portion about the body portion.

[0009] Although some of the aspects of the subject matter disclosed herein have been stated hereinabove, and which are achieved in whole or in part by the presently disclosed subject matter, other aspects will become evident as the description proceeds when taken in connection with the accompanying drawings as best described hereinbelow.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 is a perspective side view of an aircraft landing gear assembly including a friction drive roller assembly.

[0011] Figure 2 is a side view of elements of a friction drive roller assembly associated with a crown track of an aircraft landing gear assembly.

[0012] Figure 3 is a perspective side view of a friction drive roller. [0013] Figures 4-5 are side sectional views illustrating friction drive rollers.

[0014] Figure 6 is a side view illustrating a body portion of a friction drive roller including a fiber-reinforced laminated material.

[0015] Figure 7 is a perspective side view of a method of forming a fiber-reinforced laminated material for use as a body portion of a friction drive roller.

[0016] Figure 8 is a side view of a method of forming a fiber-reinforced laminated material for use as a body portion of a friction drive roller.

[0017] Figures 9A-9C are side views of various embodiments of a fiber-reinforced laminated material for use as a body portion of a friction drive roller .

[0018] Figure 10 is a side sectional view illustrating a lobed drive roller of an alternate embodiment of the invention.

[0019] Figure 11 is a side view of a lobed drive roller engaged with a contoured crown track of an alternate embodiment of the invention.

[0020] Figure 12 is a detail view of the lobed drive roller engaged with a contoured crown track according to the embodiment illustrated in Figure 11.

DETAILED DESCRIPTION

[0021] Figures, (also "FIGS.") 1-12 illustrate various aspects, views, and/or features associated with improvements in the design and construction of rollers and wheels for friction drive systems and methods. In one aspect, the present subject matter comprises a friction drive system for use in the main landing gears of aircraft. Referring to the embodiment illustrated in FIGS. 1-2, a landing gear system comprises a landing gear wheel 100 that is connected to a crown track 110 for rotation together. To drive the motion of landing gear wheel 100, one or more rotary force inputs 120 are configured to drive the rotation of a corresponding one or more friction drive rollers 130, which are sized and positioned to frictionally engage crown track 110. In some embodiments, friction drive rollers 130 are movable into and out of contact with crown track 110 (See, e.g., arrows in FIG. 2) to selectively engage or disengage rotary force input 120 from driving the motion of landing gear wheel 100. [0022] In contrast to conventional configurations in which stiff elastomer rollers (e.g., rubber) are used to couple rotary force input 120 to crown track 110, at least a portion of the body of friction drive rollers 130 disclosed herein comprise a fabric-reinforced elastomer. Fabric reinforcement of the elastomer adds stiffness to the elastomeric material in addition to conferring durability and/or fatigue resistance. In particular, in some embodiments, the use of woven fabric serves to increase both stiffness and mechanical properties to a level not attainable through filler addition alone.

[0023] In the non-limiting example illustrated in FIGS. 3-5, friction drive roller 130 includes a coupling element 131 at is core configured to be driven by rotary force input 120. Coupling element 131 in the illustrated examples is a substantially ring-shaped hub having an internal gear configuration in which teeth are cut into the inside diameter of the ring for engagement with a complementary gear element on rotary force input 120. Those having ordinary skill in the art will recognize that any of a variety of other known mechanisms for connecting rotary force input 120 and coupling element 131 for rotation together (e.g., a keyed joint, adhesive bonding) are also contemplated for use with the present subject matter.

[0024] Surrounding this coupling element 131, a body portion 133 comprises one or more layers of elastomer-reinforced fabric. In some embodiments, the body portion 133 includes at least one fabric layer 134 and a plurality of elastomeric layers 135, where each fabric layer 134 is arranged between two elastomeric layers 135. The fabric layers 134 and the elastomeric layers 135 are bonded together to form body portion 133. In some embodiments, fiber materials that are known for use in composite structures are also appropriate for use in the construction of at least one fabric layer 134. In some representative examples the at least one fabric layer 134 is composed include a woven or non-woven fabric made from carbon fibers, carbon nanofibers, cellulose, graphite, glass, aramid, nylon, rayon, polyester, and/or combinations thereof. In some particular embodiments, the at least one fabric layer 134 are comprised of an epoxy-carbon or epoxy-graphite prepreg. Further, where each fabric layer 134 comprises single-direction fibers, it is advantageous to use at least two layers together, with the fiber directions being aligned in different directions (e.g., the fiber direction of one layer being oriented 90° from that of another layer). Regardless of the particular composition or form, at least one fabric layer 134 is arranged between at least two of elastomeric layers 135 as indicated above. In some embodiments, elastomeric layers 135 are comprised of rubber stock that is calendered to be as thin as possible, but on the order of five (5) to ten (10) times the thickness of the fabric layer 134.

[0025] Regardless of the particular compositions of fabric layer 134 and elastomeric layers 135, in some embodiments, fabric layer 134 and elastomeric layers 135 are separate elements that are layered together to form the desired shape of body portion 133, and the layers are subsequently bonded together. (See, e.g., FIG. 4) Alternatively, in other embodiments, one or more of fabric layer 134 and one or more elastomeric layers 135 are integrated together into a corresponding one or more composite fabric-elastomer layers 136 that are employed as discrete "sheets" of substantially two-dimensional, elastomer-coated fabric. (See, e.g., FIG. 5) In some embodiments, for example, composite fabric-elastomer layers 136 comprise elastomeric material that is reinforced with up to 10 parts per hundred rubber (phr) fiber selected from the group consisting of carbon fibers, carbon nanofibers, cellulose, graphite, glass, aramid, nylon, rayon, polyester, and combinations thereof. Specifically, for example, in some embodiments, each fabric layer 134 is bonded to elastomeric layers 135 using commercially available resorcinol formaldehyde latex (RFL) treatments, adhesives such as CHEMLOK®, and/or combinations thereof to form composite fabric-elastomer layers 136. Alternatively or in addition, in some embodiments, each fabric layer 134 is calendered (e.g., by frictioning and/or skimming) or otherwise sandwiched within elastomeric layers 135 prior to assembling the layers for bonding. In yet further alternative embodiments, each fabric layer 134 is coated with the elastomer (e.g., by frictioning and/or skimming via calendering) on only one side of each fabric layer 134 prior to assembling the layers for bonding.

[0026] In any form, composite fabric -elastomer layers 136 are arranged in radial layers (e.g., around coupling element 131) to form body portion 133. In some embodiments, a further bonding process is performed to bond successive strata of composite fabric -elastomer layers 136 together. Furthermore, one or more process steps in this formation of body portion

133 results in each fabric layer 134 being substantially encapsulated by one or more surrounding elastomeric layers 135. In such embodiments, elastomeric layers 135 are configured to substantially fill the interstices of fabric layer 134 such that the individual layers of elastomer and fabric are virtually indiscernible.

[0027] Regardless of the form of fabric layer 134 and elastomeric layers 135, one method of achieving a radial configuration of these elements is shown in FIG. 6, wherein fabric layer

134 and elastomeric layers 135 are arranged in a radial array in which multiple discrete sheets of fabric layer 134 and elastomeric layers 135 are arranged in substantially concentric annular shells around coupling element 131. In this configuration, successive layers of fabric layer 134 and elastomeric layers 135 are laid up and molded about coupling element 131.

[0028] In other embodiments, fabric layer 134 and elastomeric layers 135 are spirally rolled around a central core (i.e., around coupling element 131) to define alternating layers of material as illustrated in FIGS. 7-8. Additionally, fabric layer 134 and elastomeric layers 135 are each single sheets of material that are wound in a substantially continuous spiral configuration, such as is illustrated in FIG. 8. In alternative embodiments, multiple composite fabric -elastomer layers 136 are wound in a discontinuous spiral about the center as shown in FIGS. 9A-9C. In these alternate embodiments, composite fabric-elastomer layers 136 comprise a plurality of panels (e.g., a first composite fabric-elastomer panel 136a, a second composite fabric- elastomer panel 136b, a third composite fabric-elastomer panel 136c) that are wound sequentially in a substantially end-to-end arrangement around coupling element 131 to together form body portion 133.

[0029] Referring to FIGS. 9A-9C, the sequential panels of composite fabric -elastomer layers 136 are sized such that they wrap distances around coupling element 131 that are designed such that seams 139 between the individual panels of composite fabric-elastomer layers 136 (e.g., between a first panel 136a and a second panel 136b) are not radially aligned. The lengths of composite fabric-elastomer layers 136 are selected such that they wrap distances that do not divide evenly into the circumference of body portion 133 at that layer. Since seams 139 are essentially discontinuities in the fabric reinforcement, alignment of these discontinuities between adjacent panels of composite fabric-elastomer layers 136 result in weak spots forming in body portion 133. By designing the location of seams 139 to not align with one another in any particular region or regions of body portion 133, the ability of body portion 133 to effectively transfer forces (e.g., from rotary force input 120 to crown track 110) is improved. In the embodiments illustrated in FIGS. 9A-9C, the panels can be sized to wrap an arc of about 375° (See, e.g., FIG. 9A), about 190° (See, e.g., FIG. 9B), or about 40° (See, e.g., FIG. 9A) around coupling element 131. Those having ordinary skill in the art will recognize that these embodiments are only provided as representative examples, and other configurations and panel sizes can be used to achieve a desired form for body portion 133.

[0030] In any configuration, the design of at least a portion of body portion 133 of friction drive roller 130 focuses on carrying the high loads without causing undesirable heat build-up. Where body portion 133 is formed by a spiral roll of elastomer-reinforced fabric, shear forces that develop as a result of the torques applied to friction drive roller 130 are taken up in tension within the layers of the elastomer-reinforced fabric of body portion 133. As a result, this configuration of body portion 133 of friction drive roller 130 is configured to provide better resistance to the high shear forces and heat build-up over conventional rollers. In addition, the specific composition and/or construction of body portion 133 is selected to produce a desired stiffness.

[0031] In some embodiments, friction drive roller 130 is provided with an outer roller surface. Referring to the embodiments illustrated in FIGS. 3-5, friction drive roller 133 comprises an outer contact portion 140 that surrounds body portion 133 and is configured for transferring torque from rotary force input 120 to a driven element (e.g., crown track 110 associated with landing gear wheel 100). Outer contact portion 140 comprises a plurality of outer material layers 141 (e.g., further elastomeric material layers having the same or different composition from elastomeric layers 135) arranged about body portion 133. For example illustrated in FIG. 4, outer material layers 141 are arranged in a spiral winding. In some alternative embodiments, outer material layers 141 are arranged in concentric radial shells similar to the construction of body portion 133 discussed above with respect to the embodiment of FIG. 8. In other embodiments, outer contact portion 140 is composed of a single, comparatively thicker layer of substantially solid rubber material as shown in FIG. 5. In any form, the material of outer contact portion 140 is selected to have a high coefficient of friction to more efficiently transfer the torque from rotary force input 120 to the driven element. In this case, the term high coefficient of friction means equal to or greater than 1.0. In typical operating conditions for existing rollers, the range of the coefficient of friction is between 0.5 and 1.0 for dry conditions. Also, wet, fouled or extremely cold conditions lower the coefficient of friction is lower. Furthermore, a high abrasion resistance extends the life of the material of outer contact portion 140.

[0032] Those skilled in the art understand that the coefficient of friction drops with increasing pressure and velocity. For tire grip, with increasing pressure and velocity the coefficient of friction initially increases until the material fills the nooks and crannies of the mating surface when the coefficient of friction remains constant. Then the coefficient of friction begins to decrease with increased pressure and velocity as more pressure does not cause an increase in the fill. [0033] In some embodiments, body portion 133 and outer contact portion 140 are co- formed and in some cases co-cured in the desired shape. Furthermore, this assembly of body portion 133 and outer contact portion 140 can be post-vulcanization bonded to coupling element 131, one or more mechanical fasteners can be used (not shown), or a combination of bonding mechanisms can be used to couple all of the elements of friction drive roller 130 together. Referring to FIG. 4, the illustrative embodiment shows that body portion 133 is constructed to have an innermost elastomeric layer 135a bonded to an outer surface of coupling element 131, either over the entire outer surface of coupling element 131 or at one or more discrete joints. In some embodiments, innermost elastomeric layer 135a is simply the first of one or more elastomeric layers 135 that are integrated with the at least one fabric layer 134. Alternatively, in other embodiments, innermost elastomeric layer 135a is a separate layer that is not associated with a fabric layer 134.

[0034] In any of the above-described arrangements, outer contact portion 140 of friction drive roller 130 provides a high coefficient of friction (e.g., a coefficient of friction that equal to or greater than 1.0) for engaging a driven element. Additionally, outer contact portion 140 of friction drive roller 130 provides a high abrasion resistance for wear. Referring to FIGS. 1 and 2, outer contact portion 140 is configured to transfer torque to a driven element, such as crown track 110 in the case of a frictional drive system for landing gear wheel 100. In common configurations in which crown track 110 is a substantially smooth, circular element, the ability of friction drive roller 130 to transfer torque from rotary force input 120 to crown track 110, and thus to landing gear wheel 100, depends primarily on the frictional engagement of outer contact portion 140 with crown track 110. Accordingly, the material composition of outer contact portion 140 discussed above directly impacts the ability of friction drive roller 130 to provide an efficient transfer of torque.

[0035] Alternatively, the crown track and friction roller of such a system is configured to exhibit improved coupling that does not rely on frictional engagement alone. The crown track and friction roller allows the lobed drive roller 150 to maintain or increase the coefficient of friction with increasing pressure by working around the limitation of a decreasing coefficient of friction. In the embodiment illustrated in FIGS. 1 and 2, the pressures are greater than 1,000 pounds per square inch (6,895 kilopascals) and approaching 2,000 pounds per square inch (13,790 kilopascals). As illustrated in FIGS. 10-12, a lobed drive roller 150 is configured for use with a contoured crown track 115. Similar to the construction of friction drive roller 130 discussed above, in these embodiments, lobed drive roller 150 comprises a coupling element 151 at its core that is configured to be driven by rotary force input 120. Although not shown in FIGS. 10-12, those having ordinary skill in the art will recognize that coupling element 151 can have some form of engagement element (e.g., an internal gear configuration as discussed above with respect to coupling element 131) configured for engagement with rotary force input 120. In addition, lobed drive roller 150 also comprises a body portion 153 surrounding coupling element 151 and an outer contact portion 160 configured for transferring torque to an associated driven element (e.g., provided either as an outermost region of body portion 153 as shown in FIGS. 11-12 or as a separate element that surrounds body portion 153). In some embodiments, body portion 153 again comprises one or more layers of elastomer-reinforced fabric. In this regard, body portion 153 can be constructed in any of a variety of configurations substantially similar to those discussed above with respect to the construction of body portion 133 of friction drive roller 130. Alternatively, body portion 153 need not be composed of a fabric -reinforced elastomer material. In some particular embodiments, for example, body portion 153 is composed of a stiff elastomer material substantially similar to conventional rollers.

[0036] In any configuration, in contrast to the construction of friction drive roller 130, lobed drive roller 150 comprises one or more lobes 162 that extend outwardly from outer contact portion 160. Any of a variety of methods can be used to form lobes 162. In the embodiment shown in FIG. 10, coupling element 151 has a contoured, sprocket-like outer surface having one or more protrusions 152 that correspond to the one or more lobes 162 to be formed. With this structure, as body portion 153 is formed about, adhered to, or otherwise positioned about coupling element 151, the shape of body portion 153 substantially mimics the contour of the outer surface of coupling element 151 (e.g., as defined by the one or more protrusions 152) to correspondingly define lobes 162 at outer contact portion 160.

[0037] In the embodiment illustrated in FIG. 10, body portion 153 is formed from a layup 157 of elastomer-reinforced fabric (e.g., a plurality of spiral windings of fabric and elastomer layers), which is positioned about coupling element 151 and bonded thereto. In some embodiments, one or more mold elements are sized and/or configured to apply substantially uniform pressure to the outer surface of layup 157 to bend or otherwise form it into a shape that conforms to the contour of coupling element 151. In this way, lobes 162 are formed as the elastomer-reinforced fabric is layered over protrusions 152 of coupling element 151. Accordingly, the particular shape and configuration of lobes 162 is influenced by a combination of the shape and/or configuration of coupling element 151 (e.g., the size, shape, and positions of protrusions 152) and the way in which body portion 153 is formed, coupled, and/or molded onto coupling element 151. Alternatively, element 151 and body portion 153 are shaped and configured to be substantially ring-shaped (i.e., similar to coupling element 131 and body portion 133 discussed above), and lobes 162 are build-up independently during the formation of outer contact portion 160.

[0038] However lobes 162 are formed, improved coupling with the associated driven element is achieved where lobes 162 of lobed drive roller 150 are configured to positively engage with one or more surface features on a complementary driven element. FIGS. 11-12 illustrate engagement of lobed drive roller 150 with a contoured crown track 115. In such a configuration, contoured crown track 115 comprises one or more protuberances 116 that are configured to engage with lobes 162 of lobed drive roller 150. In some embodiments, the shape and arrangement of protuberances 116 on contoured crown track 115 are designed such that a substantially sinusoidal surface contour is defined. Lobes 162 extending from lobed drive roller 150 are correspondingly shaped and arranged to be substantially enmeshed between adjacent ones of protuberances 116.

[0039] In this arrangement, in addition to lobed drive roller 150 being able to transfer torque to contoured crown track 115 by pure frictional contact, this coupling is enhanced by the positive engagement of lobes 162 with protuberances 116. Referring to FIG. 12, with lobes 162 being enmeshed between adjacent protuberances 116, rotation of lobed drive roller 150 causes a given one of lobes 162 to impose a force having a compressive component on an associated "upstream" protuberance 116a of contoured crown track 115. Thus, lobed drive roller 150 and contoured crown track 115 are operable in a manner substantially similar to a geared connection for the transmission of torque. As a result, whereas the coupling of friction drive roller 130 with crown track 110 can slip in situations where the experienced load exceeds the frictional coupling, greater loads can be transferred by lobed drive roller 150. In some embodiments, this increased load transfer capacity compared to the substantially purely frictional load transfer of friction drive roller 130 is achieved even where the design of outer contact portion 160 defines a pressure angle having a value that is greater than standard values used in the design of gears (e.g., pressure angle shown in FIG. 12 is about 42° compared to standard values associated with gears being about 14.5°, 20°, or 25°). [0040] Furthermore, the design of lobed drive roller 150 helps to minimize wear of outer contact portion 160 compared to conventional friction drive rollers. In some embodiments where the engagement of lobed drive roller 150 and contoured crown track 115 is designed such that each of lobes 162 is configured to be at least partially nested between "upstream" protuberance 116a and a "downstream" protuberance 116b, the increased stiffness of body portion 153 (e.g., compared to conventional friction drive rollers) helps to minimize the "upstream" and "downstream" bulge slip wear. In addition, "downstream" protuberance 116b is functional to prevent substantial deformation of the enmeshed one of lobes 162 as a result of its interaction with "upstream" protuberance 116a. (See, e.g., FIG. 12)

[0041] In any configuration, the friction drive rollers discussed herein are adapted to be used in place of conventional designs as part of a frictional drive system for use in aircraft landing gear systems such as those shown in FIGS. 1-2. In addition to these exemplary implementations of fabric-reinforced friction drive roller described herein, those having skill in the art should recognize that fabric -reinforced friction drive roller can be implemented in any of a variety of other applications in which it is desired for such an element to be able to carry high loads, provide high abrasion resistance, and a high coefficient of friction but to give low heat build-up.

[0042] Other embodiments of the current invention will be apparent to those skilled in the art from a consideration of this specification or practice of the invention disclosed herein. Thus, the foregoing specification is considered merely exemplary of the current invention with the true scope thereof being defined by the following claims.