This invention relates generally to constant velocity joints, and more particularly, to a constant velocity joint with spring rate control mechanism.
A rotorcraft may include one or more rotor systems. One example of a rotorcraft rotor system is a main rotor system. A main rotor system may generate aerodynamic lift to support the weight of the rotorcraft in flight and thrust to counteract aerodynamic drag and move the rotorcraft in forward flight. Another example of a rotorcraft rotor system is a tail rotor system. A tail rotor system may generate thrust in the same direction as the main rotor system's rotation to counter the torque effect created by the main rotor system.
Particular embodiments of the present disclosure may provide one or more technical advantages. A technical advantage of one embodiment may include the capability to provide a constant velocity joint. A technical advantage of one embodiment may include the capability to reduce friction and wear in a CV joint. A technical advantage of one embodiment may include the capability to reduce the number of bearings in a CV joint.
Certain embodiments of the present disclosure may include some, all, or none of the above advantages. One or more other technical advantages may be readily apparent to those skilled in the art from the figures, descriptions, and claims included herein.
To provide a more complete understanding of the present invention and the features and advantages thereof, reference is made to the following description taken in conjunction with the accompanying drawings, in which:
Power train 112 features a power source 112a and a drive shaft 112b. Power source 112a, drive shaft 112b, and hub 114 are mechanical components for transmitting torque and/or rotation. Power train 112 may include a variety of components, including an engine, a transmission, and differentials. In operation, drive shaft 112b receives torque or rotational energy from power source 112a and rotates hub 114. Rotation of rotor hub 114 causes blades 120 to rotate about drive shaft 112b.
Swashplate 116 translates rotorcraft flight control input into motion of blades 120. Because blades 120 are typically spinning when the rotorcraft is in flight, swashplate 116 may transmit flight control input from the non-rotating fuselage to the hub 114, blades 120, and/or components coupling hub 114 to blades 120 (e.g., grips and pitch horns). References in this description to coupling between a pitch link and a hub may also include, but are not limited to, coupling between a pitch link and a blade or components coupling a hub to a blade.
In some examples, swashplate 116 may include a non-rotating swashplate ring 116a and a rotating swashplate ring 116b. Non-rotating swashplate ring 116a does not rotate with drive shaft 112b, whereas rotating swashplate ring 116b does rotate with drive shaft 112b. In the example of
In operation, according to one example embodiment, translating the non-rotating swashplate ring 116a along the axis of drive shaft 112b causes the pitch links 118 to move up or down. This changes the pitch angle of all blades 120 equally, increasing or decreasing the thrust of the rotor and causing the aircraft to ascend or descend. Tilting the non-rotating swashplate ring 116a causes the rotating swashplate 116b to tilt, moving the pitch links 118 up and down cyclically as they rotate with the drive shaft. This tilts the thrust vector of the rotor, causing rotorcraft 100 to translate horizontally following the direction the swashplate is tilted.
In the example of
In general, a CV joint may refer to a type of mechanism that connects two rotating components making an angle with one another. This angle may vary during service, such as may be the case with the angle between hub 114 and drive shaft 112b. Teachings of certain embodiments recognize that a CV joint may mechanically couple an input shaft to an output shaft in such a way that torque may be transmitted from the input shaft to the output shaft whilst maintaining a substantially CV characteristic. A CV characteristic refers to a characteristic wherein the instantaneous angular velocity of the input shaft is substantially matched to the instantaneous angular velocity of the output shaft throughout a full rotation of the shafts. It is to be understood that the CV characteristic may represent a design goal, and various embodiments may achieve this characteristic to a greater or lesser degree based on parameters, which may include mechanical and structural variations in the assembly. Thus, a joint may maintain a substantially CV characteristic even if the angular velocities do not perfectly match. In some embodiments, a CV joint may maintain a substantially CV characteristic despite variations in angle between the input and output shafts.
CV joint 200 features an inner yoke 210, an outer yoke 220, and elastomeric bearings 230. Teachings of certain embodiments recognize that the torsional spring rates of elastomeric bearings 230, in combination, may provide a control mechanism that maintains a CV characteristic between drive shaft 202 and hub 204.
As shown in
Teachings of certain embodiments recognize that inner yoke 210 may include an opening for receiving drive shaft 202. In this example, the CV control mechanism is positioned away from the opening through inner yoke 210 so as not to interfere with the opening receiving drive shaft 202. Teachings of certain embodiments recognize that such an arrangement may represent an improvement over CV joints that feature control mechanisms that interfere with the ability to receive a drive shaft through its center.
Outer yoke 220 is positioned about inner yoke 210. In this example, yoke coupler 222 couples outer yoke 220 to inner yoke 210 and allows outer yoke 220 to rotate about a second axis relative to inner yoke 210 and yoke coupler 222. In some embodiments, yoke coupler 222 is positioned inside of respective openings of inner yoke 210 and outer yoke 220 so as to maintain inner yoke 210 and outer yoke 222 as substantially coaxial. As shown in
Hub 204 is positioned about drive shaft 202. Hub couplers 224 couple outer yoke 220 to hub 204 and allow outer yoke 220 to rotate about a third axis relative to hub couplers 224 and hub 204. As shown in
In some embodiments, CV joint 200 also features three sets of elastomeric bearings 230 comprised of an elastomeric material. An elastomeric material is a material, such as a polymer, having the property of viscoelasticity (colloquially, “elasticity”). Elastomeric materials generally have a low Young's modulus and a high yield strain when compared to other materials. Elastomeric materials are typically thermosets having long polymer chains that cross-link during curing (i.e., vulcanizing).
For example, in some embodiments, an elastomeric bearing 232 may be disposed between inner trunion 212 and inner yoke 210, an elastomeric bearing 234 may be disposed between yoke coupler 222 and inner yoke 210 and/or outer yoke 220, and an elastomeric bearing 236 may be disposed between yoke coupler 222 and outer yoke 220. As will be explained in greater detail below, the torsional spring rates of elastomeric bearings 232 and 236, in combination, may provide a control mechanism that maintains a CV characteristic between drive shaft 202 and hub 204. Elastomeric bearings 232 and 236 are shown in greater detail with regard to
In
In
Even with yoke coupler 222, however, movement of inner yoke 210 and outer yoke 220 may be relatively unconstrained. For example,
In some embodiments, elastomeric bearings 232 and 236, in combination, may provide a control mechanism that maintains a CV characteristic between drive shaft 202 and hub 204. In particular, the torsional spring rates of elastomeric bearings 232 and 236 may be chosen such that inner yoke 210 is substantially positioned along an angle bisecting the angle between the input and output shafts (e.g., mast 202 and hub 204).
As seen in
Travel arc c represents a travel path of a reference point f. Point f represents a location of inner yoke 210 (along with yoke coupler 222 and outer yoke 220). In some embodiments, point f may be coaxial with the second axis. Because the second axis also intersects point a, line a-f is may also be coaxial with the second axis. This second axis, as stated above, is an axis of rotation of the outer yoke 220. In the example of
Travel arc d represents a travel path of a reference point e. Reference point e indicates a relative position of hub 204. For example, as shown in
Teachings of certain embodiments recognize that elastomeric bearings 232 and 236 may help maintain a CV characteristic during operation of CV joint 200 by positioning the second axis on the angular bisector for the deflection angle between drive shaft 202 and hub 204 (e.g., the angle between lines a-b and lines a-e) for a range of deflection angles. In the example of
When hub 204 is deflected 10 degrees relative to mast 202, hub 204 moves hub couplers 224, which repositions outer yoke 220. In response, outer yoke 220 repositions inner yoke 210. This repositioning may cause the second axis (coaxial with line a-f) to move away from the zero degree reference line a-b. If the repositioning of the second axis is not controlled (e.g., if line a-f moves too far away from line a-b), CV joint 200 can vibrate or suffer from high loads due to kinematic error.
To manage the repositioning of the second axis during operation of CV joint 200, elastomeric bearings 232 and 236 manage rotation of inner yoke 210 and outer yoke 230 about the first and third axes, respectively. For example, the torsional spring rate of the elastomeric bearings 232 and 236 may oppose the forces that attempt to rotate the inner yoke 210 and outer yoke 230 about the first and third axes, respectively. Thus, in one example scenario, when hub 204 is rotated X degrees, the spring rates of bearings 232 and 236 may cause inner yoke 210 to rotate X/2 degrees. In the example of
As reference point e moves along travel arc d (either increasing or decreasing in angle), reference point f likewise moves along travel arc c (likewise either increasing or decreasing in angle based on the angle associated with point e, but such changes in angle being smaller in magnitude). Teachings of certain embodiments recognize that line a-f may bisect the angle between the 0 degree reference line a-b and line a-e for a range of deflection angles. For example, if the deflection angle is reduced to 6 degrees, then the angle between line a-e and line a-f would be approximately 3 degrees. Accordingly, teachings of certain embodiments recognize the capability of elastomeric bearings 232 and 236 to allow inner yoke 210 and outer yoke 220 to move such that their axis of rotation (the second axis) is positioned in the angular bisector of the deflection angle between drive shaft 202 and hub 204.
Teachings of certain embodiments recognize that positioning inner yoke 210 and outer yoke 220 may allow CV joint 200 to achieve a substantially CV characteristic. In particular, teachings of certain embodiments recognize that center inner yoke 210 and outer yoke 220 along the angular bisector of the cocking angle between drive shaft 202 and hub 204 may allow CV joint 200 to achieve a substantially CV characteristic. In addition, teachings of certain embodiments recognize that elastomeric bearings 230 may position inner yoke 210 and outer yoke 220 while CV joint 200 is at zero cocking angle.
Modifications, additions, or omissions may be made to the systems and apparatuses described herein without departing from the scope of the invention. As one example, the embodiments described and contemplated herein may apply to rotorcraft 100 as well as other rotorcraft or other vehicles, including but not limited to tiltrotor aircraft and tandem main-rotor aircraft. As another example, teachings of certain embodiments may apply to a variety of double U-joint style CV joints whose U-joints are coincident by using spring ate to control the positioning of the coupling housing.
The components of the systems and apparatuses may be integrated or separated. Moreover, the operations of the systems and apparatuses may be performed by more, fewer, or other components. The methods may include more, fewer, or other steps. Additionally, steps may be performed in any suitable order.
Although several embodiments have been illustrated and described in detail, it will be recognized that substitutions and alterations are possible without departing from the spirit and scope of the present invention, as defined by the appended claims.
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.
Pursuant to 35 U.S.C. §119 (e), this application claims priority to U.S. Provisional Patent Application Ser. No. 61/906,039, CONSTANT VELOCITY JOINT WITH SPRING RATE CONTROL MECHANISM, filed Nov. 19, 2013. U.S. Provisional Patent Application Ser. No. 61/906,039 is hereby incorporated by reference. Pursuant to 35 U.S.C. §120, this application is a continuation-in-part of and claims priority to U.S. patent application Ser. No. 13/673,475, CONSTANT VELOCITY JOINT WITH CONTROL MECHANISM, filed Nov. 9, 2012. U.S. patent application Ser. No. 13/673,475 is hereby incorporated by reference.
Number | Date | Country | |
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61906039 | Nov 2013 | US |
Number | Date | Country | |
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Parent | 13673475 | Nov 2012 | US |
Child | 14258187 | US |