Patent Application
20220268320
This application claims priority to European patent application No. EP 21400004.4 filed on Feb. 25, 2021, and European patent application No. EP 21167598.4 filed on Apr. 9, 2021, the disclosures of which are incorporated in their entirety by reference herein.
The present embodiments relate to an overload coupling, and, more particularly, to an overload coupling for coupling a driving device to a driven device. The present embodiments also relate to a rotating drive system with such an overload coupling, to a rotor system with such a rotating drive system, and to a rotary-wing aircraft with such a rotor system.
Rotating drive systems usually require connecting parts that are able to reliably transfer high torques, moments, and/or rotational speeds in the nominal driving direction. Moreover, the entire rotating drive system generally needs to exhibit a high rigidity in order to avoid vibrations or oscillations. Furthermore, the rotating drive system is usually required to transfer a certain decelerating moment in the direction that is opposite the nominal driving direction.
However, due to the high inertia of the rotating parts, very high forces and/or moments may be generated in case of a failure. As an example, a failure may involve the blocking of an engine or a bearing. Sometimes, such a failure may involve a sudden stoppage of at least a portion of the rotating drive system. Such a sudden stoppage may cause serious damage not only to the rotating drive system itself, but also to the parts that are connected to the rotating drive system and sometimes even to people in the vicinity of such rotating drive systems.
For example, a sudden stoppage of a helicopter engine may cause a complete rupture of the drive train between the helicopter engine and the rotor blades.
Overload couplings may prevent such catastrophic failures of rotating drive systems. However, conventionally, such overload couplings are complex, heavy, and fatigue sensitive, which is an issue especially in aircraft applications.
Document WO 2008/149732 A1 describes a power transmission device having a coupling portion of a driven body and a drive body constituted by combining a positive torque transmission member for transmitting torque in forward rotational direction but interrupting transmission of torque from the drive body by breaking itself when the drive load of the driven body exceeds a predetermined level, with a separate negative torque transmission member for transmitting torque in reverse rotational direction is further provided with a means for generating pretension in the positive torque transmission member in the pulling direction and simultaneously generating a pretension in the negative torque transmission member in the compressing direction after both torque transmission members are combined. A highly reliable power transmission device which can impart a desired pretension precisely and conveniently, and can interrupt torque properly by suppressing fatigue of material at the coupling portion can be provided.
Document EP 2 060 814 A1 describes a power transmission device in which a driven body and a driving body for driving the driven body are rotated in the same direction and are connected to each other by a connection section to transmit torque of the driving body to the driven body and in which the transmission of the torque from the driving body is interrupted when a drive load on the driven body exceeds a predetermined level. The connection section is constructed by combining separate elements that are a positive torque transmission member, and a negative torque transmission mechanism or a negative torque transmission member. The positive torque transmission member transmits torque in the normal rotational direction and interrupts transmission of torque from the driving body by breaking itself when a drive load on the driven body exceeds the predetermined level. The negative torque transmission mechanism or the negative torque transmission member can transmit torque in the reverse rotational direction. In the power transmission device, fatigue of materials of the connection section is suppressed and torque is accurately interrupted at a target interruption torque value.
These prior art solutions both require complex assemblies with multiple different parts in the load path. However, an increase in the number of parts is usually more cost intensive in the production, in the quality management, and in the part inventory management.
Document EP 3 730 920 A1 describes an automotive air-conditioning damper-limiter pulley testing machine. The testing machine is for testing of the pulley endurance, in particular the damper and the limiter without connection to an air-conditioning system. The limiter is a mainly shear/bending driven design of a shear plate with arms. The individual arms are curved and intended to break in case of reverse overload.
Document WO 2013/168889 A1 describes a compressor pulley assembly in which a pulley forming the pulley assembly is formed of a magnesium alloy and which prevents damage that can occur during processing and is suitable for high-temperature environments, and to a method for manufacturing same. The compressor pulley assembly according to the present disclosure is configured to include: a pulley having a hollow cylindrical shape and formed of a magnesium alloy; a cylindrical inner ring that is integrated in the pulley by insert injection molding, is fixed to an inner circumferential surface of the pulley, and is formed of a material that is different from the material of the pulley; and a bearing that is press-fitted and fixed to an inner circumferential surface of the inner ring.
However, the latter two solutions are based on curved arms that are neither fail-safe nor damage tolerant. The fatigue sensitivity is high, and the arrangement requires additional items or parts respectively.
Document EP 1 279 849 A2 describes a torque limiter which operatively couples a rotor of an engine to a driving shaft of a compressor. The torque limiter is configured so as to be able to cut off transmission of an excessive torque from the engine to the compressor. More specifically, the torque limiter is formed by a main body and a cylindrical portion. The main body is constituted by an outer peripheral portion, an inner peripheral portion disposed at the inside of the outer peripheral portion, and coupling portions coupling the outer peripheral portion and the inner peripheral portion so as to bridge them. The cylindrical portion is protrusively provided at the center position of the inner peripheral portion. The torque limiter is made of sintered metal such as JIS (Japanese Industrial Standard), 12EPC etc. and configured by integrally forming the outer peripheral portion, the inner peripheral portion, the coupling portions and the cylindrical portion. Three coupling portions are provided with the same interval around the axial line of the driving shaft. Each of the coupling portions is slanted on the clockwise side toward the outer peripheral portion from the inner peripheral portion. Thus, at the time of power transmission, tensile stress acts on the coupling portions between the outer peripheral portion and the inner peripheral portion by the torque limiter rotating clockwise. Each of the coupling portions is configured to be thinner in its width gradually toward the inner peripheral portion from the outer peripheral portion. A broken portion is provided around a boundary between the inner peripheral portion and each of the coupling portions.
Based on the limitations and drawbacks of the prior art, an objective is to provide an overload coupling that overcomes the above-described limitations and drawbacks of prior art solutions. Furthermore, the overload coupling should be lightweight, simple, robust, fail-safe, fatigue-insensitive, sturdy in the nominal rotation direction and reliably protect the rotating drive system from overloading in the reverse rotation direction. This objective is solved by an overload coupling comprising the features of claim 1.
More specifically, an overload coupling for coupling a driving device to a driven device comprises an inner connecting element and an outer connecting element that are concentrically arranged and rotate in normal operation around a common rotation axis in a section of rotation, wherein the inner connecting element is coupled to the driving device and the outer connecting element is coupled to the driven device. The overload coupling further comprises at least a first and a second arm that connect the inner connecting element with the outer connecting element, wherein the first arm is attached to the inner connecting element at a first attachment point and to the outer connecting element at a second attachment point, wherein the second attachment point is angularly displaced relative to the first attachment point by a first angle such that the first attachment point is ahead of the second attachment point in the first direction of rotation, wherein the second arm is attached to the inner connecting element at a third attachment point and to the outer connecting element at a fourth attachment point, wherein the fourth attachment point is angularly displaced by a second angle relative to the third attachment point such that the third attachment point is ahead of the fourth attachment point in the first direction of rotation, wherein the first and second angles have first and second initial values, respectively, when no force is acting on the first and second arms, wherein the first and second initial values are smaller than 175 degrees, and wherein each one of the at least first and second arms comprises an arrangement of at least one plate, wherein the at least one plate is loaded in tension when a first torque acts on the inner connecting element in the first direction of rotation or on the outer connecting element in a second direction of rotation that is opposite the first direction of rotation, and wherein the at least one plate is loaded with a compression force when a second torque acts on the inner connecting element in the second direction of rotation or on the outer connecting element in the first direction of rotation, wherein the first and second arms are formed with predefined geometries to enable buckling of the first and second arms when the second torque exceeds a predetermined threshold, and wherein the second torque causes the first and second angles to decrease below the respective first and second initial values. The arrangement of the at least one plate comprises a staggered arrangement of at least two separate plates.
It should be noted that above the inner connecting element is coupled to the driving device and the outer connecting element is coupled to the driven device. However, if desired, the inner connecting element may be coupled to the driven device and the outer connecting element may be coupled to the driving device. In this case, an overload coupling for coupling a driving device to a driven device comprises an inner connecting element and an outer connecting element that are concentrically arranged and rotate in normal operation around a common rotation axis in a section of rotation, wherein the outer connecting element is coupled to the driving device and the inner connecting element is coupled to the driven device. The overload coupling further comprises at least a first and a second arm that connect the inner connecting element with the outer connecting element, wherein the first arm is attached to the inner connecting element at a first attachment point and to the outer connecting element at a second attachment point, wherein the second attachment point is angularly displaced relative to the first attachment point by a first angle such that the first attachment point is ahead of the second attachment point in the first direction of rotation, wherein the second arm is attached to the inner connecting element at a third attachment point and to the outer connecting element at a fourth attachment point, wherein the fourth attachment point is angularly displaced by a second angle relative to the third attachment point such that the third attachment point is ahead of the fourth attachment point in the first direction of rotation, wherein the first and second angles have first and second initial values, respectively, when no force is acting on the first and second arms, wherein the first and second initial values are smaller than 175 degrees, and wherein each one of the at least first and second arms comprises an arrangement of at least one plate, wherein the at least one plate is loaded in tension when a first torque acts on the inner connecting element in the first direction of rotation or on the outer connecting element in a second direction of rotation that is opposite the first direction of rotation, and wherein the at least one plate is loaded with a compression force when a second torque acts on the inner connecting element in the second direction of rotation or on the outer connecting element in the first direction of rotation, wherein the first and second arms are formed with predefined geometries to enable buckling of the first and second arm when the second torque exceeds a predetermined threshold, and wherein the second torque causes the first and second angles to decrease below the respective first and second initial values. The arrangement of the at least one plate comprises a staggered arrangement of at least two separate plates.
Each plate may have an individual thickness, material, adapted shape, etc.
If desired, the at least first and second arms may have an out-of-plane curvature or other features that would facilitate the decrease of first and second angles below the respective first and second initial values when the second torque is applied.
Preferably, the overload coupling comprises a staggered arrangement of several plates. Illustratively, the inner connecting element may be an inner ring and the outer connecting element a concentric outer ring. The inner and outer ring may be connected by at least two arms. If desired, the inner and outer ring may be connected by more than two arms.
Illustratively, the arms should be almost tangential to the inner ring's outer diameter. If desired, the arms may be tilted relative to a purely tangential orientation in case this is beneficial for the individual application. The tangential or almost tangential orientation of the arms leads to a direction-dependent stiffness and failure behavior.
The inner ring may be connected to a driving device such as an engine or a drive shaft. Illustratively, the outer ring may be connected to a driven device such as a rotor, a rotor shaft, a wheel, or any other driven device.
The behavior under load is dependent on the sense of rotation of the overload coupling. In other words, the overload coupling exhibits a separation between the two opposing torque directions. A torque that is transferred during a normal operation of the driving device is sometimes also referred to as a positive torque. A torque in a direction that is in an opposite direction to the positive torque is sometimes also referred to as negative torque.
Positive torque loads the individual arms in tension. The coupling between the inner and outer rings is extremely stiff under positive torque. The coupling, and in particular the individual arms, may only fail when the ultimate strength of the material is exceeded.
Negative torque loads the individual arms with compression. At comparatively small negative torque, the individual arms are still able to transfer the load with high stiffness. However, when the negative torque exceeds a first predefined threshold, the individual arms start to buckle. A further increase of negative torque may lead to a stepwise collapse of the coupling. It should be noted that the first predefined threshold and any other threshold at which the coupling collapses may be realized by selecting the number of arms, the geometries of the individual arms, and/or the geometries and number of separate plates, accordingly.
This first predefined threshold is also known as Euler's critical load and the corresponding buckling as Euler's buckling, Euler buckling, or Eulerian buckling. As Euler's buckling occurs on all individual arms, the transferrable moment decreases suddenly, and the rotational stiffness of the overload coupling is extremely low.
Between the first predefined threshold and a second predefined threshold, an almost free relative movement of the inner and outer rings is possible. When the negative torque reaches the second predefined threshold, the arms may be ripped off the inner or outer ring. This characteristic is beneficial in a highly dynamic environment as the forces for ripping off the arms is comparatively low and don't lead to an overload in any other region of the rotating parts.
After ripping off the arms, a free rotation of the outer ring is possible, and a blocking of the driven device is avoided. Thus, in a failure case, a smooth overload behavior is generated without sudden or arbitrary load peaks.
The abovementioned overload coupling offers several advantages compared to conventional overload couplings. For example, when positive torque is applied (i.e., in the main driving direction), the overload coupling is extremely rigid and stiff, has an excellent dynamic behavior, and big radial forces may be transferred.
However, when negative torque is applied, the characteristics of the overload coupling may be tuned to almost any desired static and dynamic characteristic (e.g., by selecting the number of arms, the geometries of the individual arms, and/or the geometries and number of separate plates). These characteristics may include the determination of thresholds at which the arms start to buckle and rip off. Furthermore, a free rotation can take place after the arms have been ripped off. The free rotation avoids high accelerations and thus stress peaks in the parts to be protected. Moreover, in case the arms are made of a material with a certain yielding behavior, debris can be avoided as the arms stay connected to at least one end.
Furthermore, the abovementioned overload coupling is simple to manufacture as it requires merely a sheet or a few identical sheets in case of a staggered arrangement of plates, is cheap as it may be made of sheet parts and standard parts only, has a high robustness as even some of the individual arms can fail without a notable detrimental impact on the load transfer, can be adapted in diameter and size to any environment, can consist of any material (e.g., metal, fiber reinforced materials, plastics, etc.), and requires no other parts (e.g., screws, connectors, etc.).
The above-mentioned overload coupling may be joined easily with adjacent structures such as driving device and driven device. For example, the overload coupling may be joined with the driving device and/or the driven device through moulding, welding, riveting, simple form fit, etc. or any combination thereof. It may be simple to install and to replace. If desired, the overload coupling may be combined in any arbitrary way with bearings and other functional items.
Moreover, a fail-safe and damage tolerant design may be achieved with several staggered sheets and multiple arms in the load path. The design may further be non-sensitive to fatigue due to smooth transitions without notches between the inner ring, the arms, and the outer ring. The design may also be in-sensitive to centrifugal forces and can be used for extremely fast rotating applications such as drive shafts for turbines.
Additionally, Euler's buckling is very predictive. Thus, it is easy to predict the point of failure in a very reliable manner and precisely. The buckling is barely dependent on fatigue and environmental conditions such as temperature or moisture. For example, the buckling may be dependent on the number of sheets and the dimensions.
According to one aspect, at least two of the at least two separate plates are separated by a gap.
According to one aspect, at least two of the at least two separate plates have a different thickness.
According to one aspect, at least two of the at least two separate plates are made of different materials.
According to one aspect, the second attachment point comprises a plurality of attachments, each attachment of the plurality of attachments being located at a different location on the outer connecting element, wherein at least two adjacent plates of the at least two separate plates connect the first attachment point with different attachments of the plurality of attachments, and wherein the at least two adjacent plates are located immediately next to each other in the staggered arrangement.
According to one aspect, the at least two adjacent plates overlap each other partially at the second attachment point.
According to one aspect, the at least two adjacent plates overlap each other at the second attachment point with an increasing overlap in the second direction of rotation.
According to one aspect, the at least two adjacent plates connect the first attachment point with two attachments of the plurality of attachments that are separated by at least one other attachment of the plurality of attachments.
According to one aspect, the inner connecting element is ring-shaped and has an outer diameter.
According to one aspect, the at least first and second arms are arranged tangential to the outer diameter of the inner connecting element.
According to one aspect, the outer connecting element is ring-shaped.
According to one aspect, the overload coupling further comprises fasteners that fasten the at least first and second arms to at least one of the inner connecting element or the outer connecting element.
According to one aspect, the at least first and second arms are integrally formed with at least one of the inner connecting element or the outer connecting element.
According to one aspect, the at least first and second arms comprise at least one of a fillet or a recess at the transition with the at least one of the inner connecting element or the outer connecting element.
According to one aspect, the at least first and second arms further comprise at least one of an out-of-plane pre-deformation or a narrowing section.
According to one aspect, the first and third attachment points are equally spaced around the common rotation axis.
Moreover, a rotating drive system may include a driving device, a driven device, and the overload coupling as described above.
Furthermore, a rotor system for a rotary-wing aircraft may include the abovementioned rotating drive system, wherein the driving device comprises at least an engine, and wherein the driven device comprises at least a plurality of rotor blades.
Moreover, a rotary-wing aircraft may include the rotor system as described above.
Embodiments are outlined by way of example in the following description with reference to the attached drawings.
In these attached drawings, identical or identically functioning components and elements are labeled with identical reference numbers and characters and are, consequently, only described once in the following description.
Exemplary embodiments may be used with any devices or vehicles with a rotating drive system that includes a driving device and a driven device that are connected by a rotating drive shaft with an overload coupling in which the drive shaft rotates around an associated rotation axis and transmits thereby mechanical torque from the driving device to the driven device. Examples for such devices may include wind turbines, transmission of forces from an engine, transmissions of forces from/to rotors, dynamometers, etc. Examples for vehicles may include aircraft such as airplanes, quadcopters, helicopters, and drones, land-based vehicles including cars, buses, trucks, and motorcycles, or vessels such as ships and boats, etc.
Illustratively, helicopter 100 may have a fuselage 120 that forms an airframe of the helicopter 100. The fuselage 120 is connected to a suitable landing gear and exemplarily forms a cabin 123 and a rear fuselage 127. The rear fuselage 127 is connected to a tail boom 130.
By way of example, helicopter 100 may include at least one counter-torque device 140 configured to provide counter-torque during operation, i.e., to counter the torque created by rotation of the at least one rotor system 110 for purposes of balancing the helicopter 100 in terms of yaw. If desired, counter-torque device 140 may be shrouded.
The at least one counter-torque device 140 is illustratively provided at an aft section of the tail boom 130 and may have a tail rotor 145. The aft section of the tail boom 130 may include a fin 150. Illustratively, the tail boom 130 may be provided with a suitable horizontal stabilizer 135.
Illustratively, helicopter 100 may have at least one rotor system 110, which is illustratively provided as a multi-blade rotor system 110, for providing lift and forward or backward thrust during operation. The at least one rotor system 110 comprises an engine 111 coupled to a plurality of rotor blades 112, 113. By way of example, the plurality of rotor blades 112, 113 may be mounted at an associated rotor head 114 to a rotor shaft 115, which rotates in operation of the helicopter 100 around an associated rotation axis 117 in a rotor plane 119.
The rotor shaft 115 may have first and second ends. Rotor head 114 with rotor blades 112, 113 may be attached to the first end of the rotor shaft 115. The second end of the rotor shaft 115 may be installed within a gearbox, which may be driven by the engine 111.
If desired, an overload coupling may couple the engine 111 with the rotor blades 112, 113 of the multi-blade rotor system 110. For example, one of the illustrative overload couplings 200 shown in
The driving device 280 may transmit a torque via a drive shaft 285 to the overload coupling 200. For example, the overload coupling 200 may have an inner connecting element, and drive shaft 285 may be coupled to the inner connecting element.
By way of example, the overload coupling may have an outer connecting element. Illustratively, overload coupling 200 may include at least a first and a second arm that connect the inner connecting element with the outer connecting element. The at least first and second arms may transmit the torque from the inner to the outer connecting element.
If desired, drive shaft 295 may be coupled to the outer connecting element. Drive shaft 295 may couple the outer connecting element with the driven device 290.
As an example, consider the scenario in which rotating drive system 270 represents at least a portion of rotor system 110 of rotary-wing aircraft 100 of
The driving device 280 may transmit a torque via a drive shaft 285 to the overload coupling 200. For example, the overload coupling 200 may have an inner connecting element 210, and drive shaft 285 may be coupled to the inner connecting element 210.
By way of example, the overload coupling may have an outer connecting element 220. Illustratively, overload coupling 200 may include at least a first and a second arm 230, 240 that connect the inner connecting element 210 with the outer connecting element 220. The at least first and second arms 230, 240 may transmit the torque from the inner connecting element 210 to the outer connecting element 220.
Drive shaft 295 may be coupled to the outer connecting element 220. Any suitable means may couple the outer connecting element 220 to the drive shaft 295.
As an example, a chain or a belt may couple the outer connecting element 220 to a wheel that is coupled to the drive shaft 295. As shown in
If desired, the outer rim of the outer connecting element 220 may be notched with teeth, and a cogwheel may be mounted to drive shaft 295 such that the cogwheel meshes with the teeth of the outer connecting element 220, thereby transmitting the rotation from drive shaft 285 to drive shaft 295.
Illustratively, the transmission of the rotation between drive shaft 285 and drive shaft 295 may occur inside a gearbox with the overload coupling 200 being placed inside the gearbox.
By way of example, overload coupling 200 may include an inner connecting element 210 and an outer connecting element 220 that rotate in normal operation around a common rotation axis 275 in a first direction of rotation 277. For example, the inner connecting element 210 may be coupled via drive shaft 285 to the driving device and the outer connecting element 220 to the driven device.
Illustratively, inner connecting element 210 and outer connecting element 220 may be concentrically arranged around the common rotation axis 275. By way of example, inner connecting element 210 and outer connecting element 220 may be arranged in a same plane. If desired, inner connecting element 210 and outer connecting element 220 may be arranged in different planes that are parallel to each other.
The overload coupling 200 may include at least a first and a second arm 230, 240. The at least first and second arms 230, 240 may connect the inner connecting element 210 with the outer connecting element 220.
Illustratively, the first arm 230 may be attached to the inner connecting element 210 at a first attachment point 232 and to the outer connecting element 220 at a second attachment point 233. As shown in
Similarly, the second arm 240 may be attached to the inner connecting element 210 at a third attachment point 242 and to the outer connecting element 220 at a fourth attachment point 243. As shown in
Illustratively, the first and second angles have first and second initial values, respectively, when no force is acting on the first and second arms 230, 240. The first and second initial values are smaller than 175 degrees.
If desired, each one of the at least first and second arms 230, 240 may include an arrangement of at least one plate. As shown in
Illustratively, the inner connecting element 210 and/or the outer connecting element 220 may include an arrangement of at least one plate. As shown in
By way of example, the at least first and second arms 230, 240 may be integrally formed with at least one of the inner connecting element 210 or the outer connecting element 220. As shown in
The at least two separate plates of each one of the at least first and second arms 230, 240 may be adapted to be loaded in tension when a first torque 272 acts on the inner connecting element 210 in the first direction of rotation 277 or on the outer connecting element 220 in a second direction of rotation 278 that is opposite the first direction of rotation 277.
Similarly, the at least two separate plates of each one of the at least first and second arms 230, 240 may be adapted to be loaded with a compression force and buckle (e.g., as shown in the detail representation of arm 230 of
The illustrative overload coupling 200 may include three arms 230, 240, 246. The three arms 230, 240, 246 may be arranged tangential to the outer diameter 215 of the inner connecting element 210. For example, the three arms 230, 240, 246 may be attached to the inner connecting element 210 at attachment points 232, 242, 247, respectively and to the outer connecting element 220 at attachment points 233, 243, 248, respectively, such that one edge of the respective arm 230, 240, 246 forms a tangent to the outer diameter 215 of the inner connecting element 210.
Illustratively, the attachment points 232, 242, and 247 may be equally spaced around the common rotation axis 275. For example, the attachment points 232, 242, and 247 may be spaced at an angle of 120° from each other on the inner connecting element 210. Similarly, the attachment points 233, 243, and 248 may be equally spaced around the common rotation axis 275. For example, the attachment points 233, 243, and 248 may be spaced at an angle of 120° from each other on the outer connecting element 220.
Illustratively, attachment point 233 may be angularly displaced relative to attachment point 232 by a first angle 235 such that attachment point 232 is ahead of attachment point 233 in the first direction of rotation 277. Similarly, attachment point 243 may be angularly displaced relative to attachment point 242 by a second angle 245 such that attachment point 242 is ahead of attachment point 243 in the first direction of rotation 277. First and second angles 235, 245 may be equal. If desired, first and second angles 235, 245 may be different.
As shown in
Each arm 230, 240 in each one of the four illustrative overload couplings 200 may be attached to the inner connecting element 210 at respective attachment points 232, 242. Illustratively, the attachment points 232, 242 may be equally spaced around the common rotation axis 275.
For example, the three attachment points of the overload coupling 200 with three arms may be spaced at an angle of 120° from each other on the inner connecting element 210, the four attachment points of the overload coupling 200 with four arms may be spaced at an angle of 90° from each other on the inner connecting element 210, the five attachment points of the overload coupling 200 with five arms may be spaced at an angle of 72° from each other on the inner connecting element 210, and the six attachment points of the overload coupling 200 with six arms may be spaced at an angle of 60° from each other on the inner connecting element 210.
Similarly, each arm 230, 240 in each of the four illustrative overload couplings 200 may be attached to the outer connecting element 220 at respective attachment points 233, 243. Illustratively, the attachment points 233, 243 may be equally spaced around the common rotation axis 275.
For example, the three attachment points of the overload coupling 200 with three arms may be spaced at an angle of 120° from each other on the outer connecting element 220, the four attachment points of the overload coupling 200 with four arms may be spaced at an angle of 90° from each other on the outer connecting element 220, the five attachment points of the overload coupling 200 with five arms may be spaced at an angle of 72° from each other on the outer connecting element 220, and the six attachment points of the overload coupling 200 with six arms may be spaced at an angle of 60° from each other on the outer connecting element 220.
Inner connecting element 210 and outer connecting element 220 may both be ring-shaped. The four arms 230, 240 may be attached to the inner connecting element 210 at attachment points 232, 242, respectively, and to the outer connecting element 220 at attachment points 233, 243, respectively.
Illustratively, the four arms may be tangential to the inner connecting element's 210 outer diameter 215. In other words, an imaginary line between inner and outer attachment points 232 and 233 or 242 and 243 may be parallel to a tangent to ring-shaped inner connecting element 210, whereby one edge of the arm 230 coincides with the tangent.
As shown in
By way of example, the four arms 230, 240 may have a same thickness and/or a same width between attachment points 232, 242 at the inner connecting element 210 and attachment points 233, 243 at the outer connecting element 220, as illustratively shown in
The narrowing section 258 may have any arbitrary shape. As an example, the narrowing section 258 may have an hourglass shape. As another example, the narrowing section 258 may have a concave shape.
Illustratively, the four arms 230, 240 may be integrally formed with at least one of the inner connecting element 210 or the outer connecting element 220. As shown in
If desired, fasteners may fasten at least one of the four arms 230, 240 to at least one of the inner connecting element 210 or the outer connecting element 220. Fasteners may include nuts and bolts, rivets, screws, pins, or any combination thereof. Alternatively, or in addition, the at least one of the four arms 230, 240 may be bonded to the at least one of the inner connecting element 210 or the outer connecting element 220.
As an example, fasteners 260 may fasten all four arms 230, 240 to the outer connecting element 220. As another example, fasteners 260 may fasten all four arms 230, 240 to the inner connecting element 210. As yet another example, fasteners 260 may fasten all four arms 230, 240 to inner and outer connecting elements 210, 220.
The transition between arms 230, 240 and inner and/or outer connecting elements 210, 220 may be sensitive to fatigue, static strength, buckling, and/or rip-off characteristics. Thus, the transition between arms 230, 240 and inner and/or outer connecting elements 210, 220 may be altered. If desired, arms 230, 240 may include at least one of a fillet or a recess at the transition with the at least one of the inner connecting element 210 or the outer connecting element 220.
As an example, arms 230, 240 may include a fillet at the transition with the inner connecting element 210.
Illustratively, arms 230, 240 may include a recess at the transition with the inner connecting element 210.
Overload coupling 200 of
The at least two separate plates 255 may be loosely arranged (i.e., without being fixed to each other). If desired, at least two of the at least two separate plates 255 may be fixed together. As an example, the at least two of the at least two separate plates 255 may be bonded together. As another example, a fastener may fasten the at least two of the at least two separate plates 255 together. If desired, all plates of the at least two plates 255 may be fixed together.
Illustratively, inner connecting element 210 and/or outer connecting element 220 may include a staggered arrangement 250 of at least two separate plates 255. As shown in
Illustratively, the separate plates 255 may all have the same thickness. For example,
If desired, at least two of the separate plates 255 may have a different thickness. For example,
By way of example, the separate plates 255 may all be tightly packed together. If desired, at least two of the separate plates 255 may be separated by a gap 257. For example,
Illustratively, the separate plates 255 may all be made of the same material. If desired, at least two of the separate plates 255 may be made of different materials. The materials may be selected based on predetermined criteria. The predetermined criteria may include elasticity, plasticity, stiffness, strength, etc.
As an example, the upper and lower plates 255 may be made of a first material, and the plates 255 between the upper and lower plates 255 may be made of a second material. Illustratively, the first and second materials may be selected according to a predetermined criterion. As an example, the first and second materials may be selected such that the first material has a higher elasticity than the second material. As another example, the first material may be selected such that the first material has a protective function.
By way of example, the arms 230, 240 may have variations in their geometry. As an example, the arms 230, 240 may have an out-of-plane pre-deformation 259. As another example, the arms 230, 240 may have sections that are thicker and/or wider than other sections.
The out-of-plane pre-deformation 259 may have any arbitrary shape. As an example, the out-of-plane pre-deformation 259 may have an arc shape. As another example, the out-of-plane pre-deformation 259 may have an S-shape.
As shown in
Illustratively, inner connecting element 210 and/or outer connecting element 220 may include a staggered arrangement 250 of at least two separate plates 255. As shown in
By way of example, overload coupling 200 may include at least a first and a second arm 230, 240 that connect the inner connecting element 210 with the outer connecting element 220. As shown in
Two plates 852, 853, 854, 855 of the staggered arrangement 250 of separate plates 255 are hereinafter considered to be adjacent if these two plates are located immediately next to each other in the staggered arrangement 250. For example, plates 852 and 853, plates 853 and 854, or plates 854 and 855 are considered to be two adjacent plates.
The first arm 230 may be attached to the inner connecting element 210 at a first attachment point 232 and to the outer connecting element 220 at a second attachment point 233. The second attachment point 233 may be angularly displaced relative to the first attachment point 232 by a first angle 235 such that the first attachment point 232 is ahead of the second attachment point 233 in the first direction of rotation 277.
By way of example, the second attachment point 233 may include a plurality of attachments 833. Each attachment 833 of the plurality of attachments 833 may be located at a different location 820 on the outer connecting element 220.
Illustratively, at least two adjacent plates 852, 853 of the at least two separate plates 255 may connect the first attachment point 232 with different attachments 833 of the plurality of attachments 833.
For example, at least two adjacent plates 852, 853 of the at least two separate plates 255 may overlap each other only partially at the first attachment point 232. As shown in
Illustratively, at least two adjacent plates 852, 853 of the at least two separate plates 255 may overlap each other partially at the second attachment point 233.
As shown in
As shown in
As an example, the at least two adjacent plates 852, 853, 854, 855 may overlap each other at the second attachment point 233 with an increasing overlap 865 in the second direction of rotation 278. Thus, the non-overlapping portion 860 of the separate plates 255 may decrease in the second direction of rotation 278.
As another example, the at least two adjacent plates 852, 853, 854, 855 may overlap each other at the second attachment point 233 with a decreasing overlap 865 in the second direction of rotation 278. Thus, the non-overlapping portion 860 of the separate plates 255 may increase in the second direction of rotation 278.
In this example, the arms 230, 240 may approximate the shape of an airfoil. Thus, the arms 230, 240 that rotate in normal operation around rotation axis 275 in direction 277 may experience an airflow 870 such that the overload coupling 200 may act as a fan that produces an air stream. The air stream may have a predetermined delivery direction. If desired, the increasing overlap 865 in the second direction of rotation 278 of the at least two adjacent plates 852, 853, 854, 855 at the second attachment point 233 may be selected to determine the strength and/or the quantity and/or the delivery direction of the air stream.
Illustratively, the air stream produced by the overlap coupling 200 may be used to actively cool a device such as for example a bearing, an engine, a transmission, etc. The device may be located in the proximity of the overload coupling 200. If desired, an air duct may transport the air stream from the overload coupling 200 to a device that is located further apart from the overload coupling 200.
As shown in
As shown in
Illustratively, the at least two adjacent plates 853, 854 may connect the first attachment point 232 with two attachments 833 of the plurality of attachments 833 that are separated by at least one other attachment 833 of the plurality of attachments 833. For example, as shown in
In this example, the at least two adjacent plates 853, 854 may experience at least a reduced friction against each other when the at least two adjacent plates 853, 854 are loaded with a compression force and buckle when a torque acts on the inner connecting element 210 in direction of rotation 278 or on the outer connecting element 220 in direction of rotation 277 compared to the plates 255 of the overload coupling 200 of
If desired, the at least two adjacent plates 853, 854 may connect the first attachment point 232 with two attachments 833 of the plurality of attachments 833 that are next to each other on the outer connecting element 220.
The overload couplings 200 of
The second arm 240 is attached to the inner connecting element 210 at a third attachment point 242 and to the outer connecting element 220 at a fourth attachment point 243 such that the fourth attachment point 243 is angularly displaced by a second angle (e.g., angle 245 of
Illustratively, the first and second angles have first and second initial values, respectively, when no force is acting on the first and second arms 230, 240. As an example, the first and second initial values are smaller than 175 degrees.
By way of example, each one of the at least first and second arms 230, 240 includes an arrangement of at least one plate (e.g., arrangement 250 of plates 255 of
The abscissa 310 of diagram 300 shows the change in angle between the inner and outer connecting elements. Thus, abscissa 310 of diagram 300 depicts the relative change of the angles between the attachment points of the arms at the inner connecting element and the attachment points of the arms at the outer connecting element (i.e., of angles 235, 245 of
In other words, a zero on the abscissa 310 means that angles 235, 245 of
For example, consider the scenario in which angle 235 of
It should be noted that the diagram 300 may not be to scale. In particular, the angles 235, 245 may only increase slightly (e.g., less than 2°) during normal operation on the linear elastic working curve 350 between failure onsets 360 and 365.
The ordinate 320 of diagram 300 shows the load in the respective arms 230, 240. A positive value on the ordinate 320 means that the respective arms 230, 240 are loaded in tension 330. A negative value on the ordinate 320 means that the respective arms 230, 240 are loaded with a compression force 340.
Thus, the relationship between the change in angle between the inner and outer connecting elements and the load in the respective arms 230, 240 passes from the first quadrant 330 through the origin into the third quadrant 340.
As an example, consider the scenario in which the overload coupling 200 of
Moreover, consider that the arms 230, 240 are attached at attachment points 232, 242 to the inner connecting element 210 and at attachment points 233, 243 to an outer connecting element, that the attachment points 233, 243 are angularly displaced relative to attachment points 232, 242 by angles 235, 245, respectively, and that each one of the arms 230, 240 includes an arrangement of at least one plate that is adapted to be loaded in tension 330 when a first torque 272 acts on the inner connecting element 210 in the first direction of rotation 277 or on the outer connecting element in a second direction of rotation 278 that is opposite the first direction of rotation 277.
Consider further that the at least one plate is adapted to be loaded with a compression force 340 and buckle when a second torque 273 acts on the inner connecting element 210 in the second direction of rotation 278 or on the outer connecting element in the first direction of rotation 277 such that the second torque 273 causes the first and second angles 235, 245 to decrease below the respective first and second initial values.
As a first example in this scenario, engine 111 of
In this first example, a very high stiffness in the arms 230, 240 may be observed. The angles 235, 245 may only increase slightly during normal operation and remain on the linear elastic working curve 350 within range 345 of
If for any reason (e.g., due to an increased resistance from the rotor blades 112, 113) the angles 235, 245 increase by more than a value of 314 and less than a value shown with reference value 315 (i.e., as long the angles 235, 245 increase by a value within range 346), the arms 230, 240 may experience an onset of plasticization 360. Thus, even after an elimination of the torque 272, the angles 235, 245 may not return to their initial values.
Any further increase of the angles 235, 245 beyond value 315 (i.e., by a value selected from range 347), may cause a sudden rupture 370 of the arms 230, 240. Thereby, the tension in the arms returns to zero.
As a second example in this scenario, engine 111 of
The behavior of the overload coupling 200 in this second example is illustrated with reference to
In this second example, the angles 235, 245 are allowed to decrease slightly during normal operation (e.g., when the throttle of the engine is reduced while the rotor blades are turning) and remain on the linear elastic working curve 350 within range 341 of
A further increase in torque 273 may lead to an increase in compression force in arms 230, 240 and in turn to a further decrease of angles 235, 245 by a value that is greater than the value shown with reference number 311 and less than the value shown with reference number 312 (i.e., a decrease by a value from within range 342). Such a further increase in torque 273 may represent a hazard for the stability of the overload coupling 200, which is depicted in
As a result, the arms 230, 240 may experience an onset of failure 365 caused by an initial buckling, which is illustratively shown in
The forming of the bulge and the folding and/or twisting of the arms has the effect that the compression force in the arms 230, 240 remains nearly constant even though the angles 235, 245 further decrease as shown in
The reference value 311 at which onset of failure 365 is observed may be preselected based on the number of arms 230, 240, the material of the arms 230, 240, the number of staggered plates, the thickness of the individual plates, the presence or absence of fillets, the presence or absence of recesses, etc.
When the decrease of angles 235, 245 reaches value 312, the arms 230, 240 begin to be torn from either the inner or the outer connecting element as illustratively shown in FIG. 12E. As a result, the compression force in the arms 230, 240 further decreases while the change of angles 230, 240 is within range 343 of
When the decrease of angles 235, 245 becomes greater than the value shown with reference number 313 (i.e., the decrease is in range 344), the arms 230, 240 are ripped off the inner or outer connecting element as illustratively shown in
Thus, the characteristic of the overload coupling 200 is a smooth rupture with high deformation capability. If desired, at least portions of the arms 230, 240 may remain connected to the inner and/or outer connecting element.
Diagram 300 of
It should be noted that the abovementioned embodiments are merely described for illustration purposes, but not in order to restrict the present disclosure thereto. Instead, multiple modifications and variations of the presented embodiments are possible and should, therefore, also be considered as being part of the disclosure.
For example, overload couplings 200 of
Furthermore, the arms 230, 240 of
| Number | Date | Country | Kind |
|---|---|---|---|
| 21400004.4 | Feb 2021 | EP | regional |
| 21167598.8 | Apr 2021 | EP | regional |
