Flexible couplings with angular limiters

A flexible coupling includes a flexure, a first drive member defining an axis and connected to the flexure, and a second drive member. The second drive member defines an axis and is connected to the flexure on a side of the flexure opposite the first drive member. An angular stop is fixed within the first drive member, extends through a portion of the second drive member, and is arranged to limit angular misalignment of the first drive member axis relative to the second drive member axis while transmitting torque between the first and second drive members.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present disclosure relates to flexible couplings, and more particularly to diaphragm couplings with features designed to limit angular bending.

2. Description of Related Art

Flexible couplings are commonly used to transmit torque while accommodating axial and/or angular misalignment between driving and driven shaft components along a load path. The flexible couplings generally have stiffness that opposes the angular misalignment accommodated by the flexible coupling. In some flexible couplings, such as flexible couplings with relatively low spring rates, it can be possible to overstress the flexible coupling, either during installation or removal of the flexible coupling. Some flexible couplings can also be overstressed while transmitting torque between rotation shafts when the angular misalignment between the interconnected shafts exceeds a predetermined angular misalignment.

Such conventional methods and systems have generally been considered satisfactory for their intended purpose. However, there is still a need in the art for improved flexible couplings for transmitting torque between rotating members while accommodating misalignment between the members. The present disclosure provides a solution for this need.

SUMMARY OF THE INVENTION

A flexible coupling includes a flexure, a first drive member defining an axis and connected to the flexure, and a second drive member defining an axis and connected to the flexure on a side of the flexure opposite the first drive member. An angular stop is fixed within the first drive member, extends through at least a portion of the second drive member, and is arrange to limit angular misalignment of the first drive member axis relative to the second drive member axis while transmitting torque between the first and second drive members. For purposes of illustration, the first drive member will be considered the end with the splined shaft and the second drive member will be considered the end with the bolted flange. Those skilled in the art will readily understand that either end could be considered the first and second member and that the ends of the coupling could include other types of input or output devices.

The first drive member is connected to the first end of a diaphragm coupling and includes a body, a seat, and an angular stop. The seat extends from the body and is connected to the diaphragm coupling. The angular stop extends from the body and is axially overlapped by the seat and the second member to limit bending of the diaphragm coupling.

In certain embodiments, a bore can extend through the second member. The bore provides for lower mass of the overall coupling system and may be larger, smaller, or non-existent depending on the requirements of the application.

The first member includes a body and seat. The body includes a bore which extends through the first member and provides for an annular gap between the angular stop and the output body. In accordance with certain embodiments, the annular gap can be defined within the flexible coupling. The radial width of the annular gap bounded by the output body and the angular stop allows for a limited amount of angular motion between the first and second members.

A drive train system includes mechanical rotation source, a driving shaft, a driven shaft, driven element, and a flexible coupling as described above. The driving shaft is connected to the first drive member. The mechanical rotation source is connected to the first drive member by the driving shaft. The driven shaft is connected to the second drive member. The driven element is connected to the second drive member by the driven shaft. In certain embodiments the driven element is a rotor assembly for a rotorcraft.

Those skilled in the art will readily understand that first and second members may be constructed as one-piece structures having respective flexible diaphragms, a single weld connecting outer rims of the flexible diaphragms connect the first member to the second member. Either or both of the first and second members, or the entire coupling, can be fabricated using a subtractive manufacturing technique, such as by removing material from an interior of a piece of stock material and machining material from the exterior of the piece of stock material. Either or both of the first and second members can be fabricated using an additive manufacturing technique, such as powder bed fusion by way of non-limiting example.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made to the drawings wherein like reference numerals identify similar structural features or aspects of the subject disclosure. For purposes of explanation and illustration, and not limitation, a partial view of an exemplary embodiment of a flexible coupling in accordance with the disclosure is shown inFIG. 1and is designated generally by reference character100. Other embodiments of flexible couplings, drive train systems, and methods of installing, removing, and transmitting torque while accommodating misalignment between driving and driven members in accordance with the disclosure, or aspects thereof, are provided inFIGS. 2-6, as will be described. The systems and methods described herein can be used for drive train systems such as in rotorcraft, though the present disclosure is not limited to rotorcraft or to aircraft in general.

Referring toFIG. 1, a vehicle10, e.g., a rotorcraft, is shown. Vehicle10includes a mechanical rotation source12operably connected to a driven element14by a drive train system16. Drive train system16includes a driving member18, a flexible coupling100with a first drive member102and a second drive member104, and a driven member20. First drive member102defines an axis26. Second drive member104defines an axis28. Drive train system16transmits torque T via flexible coupling100between mechanical rotation source12and driven element14while accommodating one or more axial misalignment22(shown with dotted-dashed line and indicated by offset dimension D) between first drive member102and second drive member104and angular misalignment24(shown in dashed line and indicated by angle indicator alpha) between axes defined by first drive member102and second drive member104. As used herein, the term misalignment can refer to either or both of axial misalignment and angular misalignment.

Mechanical rotation source12may include a motor or an engine, such as a gas turbine engine, and is connected to driving member18. Driving member18is connected to first drive member102of flexible coupling100. Driven member20is connected to second drive member104. Driven element14is connected to driven member20may include, by way of non-limiting example, a rotor assembly. Although flexible coupling100is described herein as transmitting torque T from first drive member102to second drive member104, it is to be understood and appreciated that torque can also be transmitted from second drive member104to first drive member102, as suitable for an intended application.

With reference toFIG. 2, flexible coupling100is shown. Flexible coupling100includes first drive member102, second drive member104, and a flexure108. First drive member102is connected to flexure108. First drive member102defines an internal bore110and includes a body112, a seat114, and an angular stop116. Seat114extends axially from body112and is connected to flexure108opposite second drive member104. Seat114axially overlaps angular stop116and is radially separated from angular stop116by annular gap107.

Bore110tapers from a first width A defined within body112to a second width B defined within angular stop116. Second drive member104defines a bore106which, in conjunction with bore110of first drive member, defines an open through-bore extending through flexible coupling100. As will be appreciated by those of skill in the art in view of the present disclosure, the open through-bore collectively formed by bore110and bore106has no internal contacting surfaces, which potentially could wear against one another.

Angular stop116extends axially from body112and is axially overlapped by at least a portion of second drive member104. A radial gap107separates angular stop116from seat114, flexure108, and a portion of second drive member104to constrain bending of flexure108associated by angular misalignment of first drive member102relative to second drive member104. As will be appreciated by those of skill in the art in view of the present disclosure, angular misalignment can result from manipulation of flexible coupling100during installation and/or removal as well as from misalignment within elements of drive train system16(shown inFIG. 1) accommodated while transmitting torque T (shown inFIG. 1).

Flexure108includes a plurality of diaphragm elements extending between inner hub and outer rims and interposed between first drive member102and second drive member104. While shown in the illustrated exemplary embodiments as having diaphragm elements, it is to be understood and appreciated that flexure108can include other types of flexure structures such as a bellows coupling, a helical coupling, or any other flexible coupling where one of either the input shaft or the output may overlap in this type of geometry, as suitable for an intended application. As shown inFIG. 2, flexure108includes a first diaphragm element126and a second diaphragm element128. This is for illustration purposes only and is non-limiting as flexure108can include a single diaphragm element or more than two diaphragm elements, as suitable for an intended application. Although flexure108is illustrated in the exemplary embodiment as a diaphragm element, it is to be understood and appreciated that other types of flexures, such as disks, gears, flex frames, universal joints, and elastomeric joints by way of non-limiting example can also benefit from the present disclosure.

First diaphragm element126has flexible diaphragm portion130extending radially between an inner hub132and an outer rim134. Second diaphragm element128is similar to first diaphragm element126and includes a flexible diaphragm portion136extending between an inner hub138and an outer rim140. Either or both of flexible diaphragm portion130and136may be arranged to taper in axial thickness to a radial location of minimum thickness between the respective inner hub and outer hub. In this respect either or both of first diaphragm element126and second diaphragm element128may be, for example, as described in U.S. Pat. No. 8,591,345 to Stocco et al., the contents of which are incorporated herein by reference in it is entirety.

Referring toFIGS. 2 and 3, first diaphragm element inner hub132is coupled to first drive member seat114. The coupling may be, for example, through a first weld142. First diaphragm element126couples to outer rim140of second diaphragm element128at outer rim134. The coupling between first diaphragm element126and second diaphragm element128may be, for example, through an intermediate weld143. Second diaphragm element128couples at inner hub138to second drive member104. The coupling between inner hub138and second drive member104may be, for example, through a second weld144.

As will be appreciated by those of skill in the art, connecting elements of flexible coupling100using welds eliminates contacting surfaces at element interfaces, removing potential sources of wear that such contacting surfaces could otherwise pose in flexible coupling100. Either or both of first weld142and second weld144may include a 90 degree weld extending about an axial collar first drive member102and/or second drive member104, the axial collar facilitating assembly of flexible coupling100by providing registration of flexure108relative first drive member102and/or second drive member104during assembly. Such welds can also facilitate the transfer of bending loads while transmitting torque and accommodating misalignment between first drive member102and second drive member104.

With continuing reference toFIG. 2, first drive member102includes a spline118. Spline118is defined on a radially outer surface of first drive member102, and is arranged for rotatably fixing flexible coupling100to driving member18(shown inFIG. 1) such that flexible coupling100is axially free relative to driving member18. Although illustrated as an external spline, it is contemplated that spline118can be an internal spline or any other suitable mechanical input device.

Second drive member104includes a flange122. Flange122has a fastener pattern124configured connecting flexible coupling100to a driven member20(shown inFIG. 1) such that flexible coupling100is fixed both axially and in rotation relative to driven member20. It is contemplated that fastener pattern124of flange122cooperate with spline118to allow flexible coupling100to be installed and/or removed from drive train system16(shown inFIG. 1), installation and/or removal generally being facilitated by the ability of flexure108to accommodate angular misalignment between first drive member102and second drive member104. Although described herein with a splined first drive member and a flanged second drive member, it is to be understood and appreciated that either or both of first drive member102and second drive member104can have splines and/or flanges, as suitable for an intended application. It is also to be understood and appreciated that other connection arrangements can be employed to fasten second drive member104to driving member18and first drive member102to driven member20, including connections like welds that connect directly to a connecting shaft, as suitable for an intended application.

Referring toFIGS. 4 and 5, angular stop has a first position I and a second position II relative to second drive member104. In the first position, shown inFIG. 4, an outer surface146of angular stop116is separated from an interior surface148of second drive member104by radial gap107, a width defined by radial gap107being substantially uniform circumferentially about angular stop116. In the second position II, shown inFIG. 5, outer surface146of angular stop116contacts interior surface148of second drive member104, radial gap107being circumferentially interrupted at the contact location disposed between angular stop116and interior surface148of second drive member104.

When angular mismatch between first drive member102and second drive member104is such that angular stop116is between first position I and second position II, no contact occurs between angular stop116and second drive member104. This prevents wear that would otherwise occur between the contacting surfaces within flexible coupling100. When angular mismatch between first drive member102and second drive member104is such that angular stop116assumes position II, flexible coupling100is axially limited, and further angular mismatch is discouraged (or prevented entirely) by angular stop116. This prevents deformation of flexure108beyond that imposed when angular stop116is in position II. This allows limiting the maximum deformation imposed on flexure108by the sizing selected for radial gap107while minimizing the contact necessitated by the angular misalignment limiting feature of flexible coupling100to only instances where the misalignment is such that angular stop116is in position II.

With reference toFIG. 6, a flexible coupling200is shown. Flexible coupling200is similar to flexible coupling100and additionally includes a two-piece construction. In this respect flexible coupling200includes a first drive member202and second drive member204integrally formed with a portion of a flexure208. In this respect first drive member202extends axially between a spline218and an end of collar216, and includes a first diaphragm element226. First diaphragm element226is integrally connected to a seat214of first drive member202axially opposite spline218, and extends circumferentially about collar216. Second drive member204extends axially between a flange222and a second diaphragm element228. Second diaphragm element228is integrally connected to second drive member204on an end thereof axially opposite flange222. A single weld243couples first diaphragm member226with second diaphragm member228, second drive member204being couple therethrough to first drive member202.

It is contemplated that first drive member202and first diaphragm element226be integral with one another, integral as used herein meaning being jointless or weldless. Jointless and/or weldless arrangements can be formed by removing material from the interior and exterior of single piece of stock material using subtractive machining operations. Jointless and/or weldless arrangements can be formed using additive manufacturing techniques, such as power bed fusion techniques. Such integral construction has the advantage that the structure can be relatively light weight, there being no need to add material to compensate for reduced load carrying capability in the heat-affected zones generally formed in the vicinity of welds.

Diaphragm couplings, e.g., first diaphragm element226(shown inFIG. 2) and second diaphragm element228(shown inFIG. 2), can be used to reliably transmit torque, e.g., torque T (shown inFIG. 1) along a load path while accommodating axial and/or angular misalignment between driving and driven shafts, e.g., driving member18(shown inFIG. 1) and driven member20(shown inFIG. 1). The diaphragm coupling can be arranged to rotate through a bend angle defined between the driving member and the driven member, the diaphragm coupling having geometry arranged to distribute the stress associated with the transmitted torque according to predetermined amount of bending.

In some drive train systems, e.g., drive train system16(shown inFIG. 1), it can be necessary to limit the amount of angular misalignment accommodated by the diaphragm coupling. In embodiments of flexible couplings described herein, angular misalignment is limited by an angular stop fixed within the interior of one of the drive members and extending through the diaphragm coupling and into the other of the drive members. In certain embodiments, the angular stop is separated from an interior surface of the drive member within which it is seated by a radial gap such a seat of the drive member axially overlaps and is radially separated from the angular stop.

In the certain embodiments, the angular stop can have a first position wherein the angular stop is separated from the first member by an annular gap defined between the angular stop and the first member, the separation allowing the flexible coupling to accommodate angular misalignment while bending without mechanical contact (and associated wear) between the angular stop and the first member.

In accordance with certain embodiments, the angular stop can have first and second position within the interior of the second drive member. In the first position the angular stop can be separated from the second drive member, and the flexible coupling can be angularly unlimited. In the second position the angular stop can contact an interior surface of the second drive member, the flexible coupling being angularly limited by the contact between the angular stop and the interior of the second drive member. The contact limits the angular misalignment (and bending) of imposed on the diaphragm coupling, limiting stress while transmitting torque between the driving member and the second member. It is also contemplated that the contact prevent overstress of the flexible coupling during installation and removal, error-proofing the assembly process used to interconnect the flexible coupling between the driving and driven members of the drive train systems.

The methods and systems of the present disclosure, as described above and shown in the drawings, provide for flexible couplings with superior properties including structures for limiting coupling bending during coupling installation, coupling removal, and while transmitting torque between the coupling input and first members. While the apparatus and methods of the subject disclosure have been shown and described with reference to preferred embodiments, those skilled in the art will readily appreciate that changes and/or modifications may be made thereto without departing from the scope of the subject disclosure.