Patent Description:
Rotors are usually provided for producing thrust in a predetermined direction during operation. The thrust produced by the rotor blades of a rotor can be controlled in two different ways: either by controlling the rotation speed of the rotor blades around the rotor axis, or by controlling an aerodynamic lift coefficient of the rotor blades. The aerodynamic lift coefficient is usually controlled by adjusting an underlying pitch angle of the rotor blades.

Pitch angle adjustment is also desirable to compensate for asymmetries in air velocity, for example during operation in non-axial inflow fields i.e., when the air flow has a component that is perpendicular to the rotor plane and at the same time a component that is lateral to the rotor plane. In non-axial inflow fields, some rotor blades are rotating against the lateral air flow while others are rotating with the lateral air flow, which leads to unbalanced lift at the different rotor blades, depending on their current position. Unbalanced lift often leads to vibratory stresses on the rotor blades. Controlling the pitch angle of each rotor blade separately according to its rotation position, which is sometimes also referred to as "cyclic pitch control" or "cyclic pitch actuation", may lead to an evenly distributed lift on all rotor blades.

Controlling the pitch angle of rotor blades requires the active or passive control of flexible joints in rotor assemblies. In actively controlled rotor assemblies, each associated rotor blade is articulated and controlled individually over its azimuth angle of rotation, which often requires complex, heavy, and cost intensive pitch adjustment devices that require active control means with external energy supplies to adjust the pitch angle of each rotor blade individually.

Actively controlled rotor assemblies are usually not only provided with cyclic, but also with collective pitch adjustment devices in order to be effective regarding lift and drag. Examples for actively controlled rotor assemblies with pitch adjustment devices are described in documents <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, and <CIT>.

However, the cyclic and collective pitch adjustment devices are generally embodied with a comparatively great complexity and weight and require the implementation of cost-intensive, complex controlling mechanisms and surveillance means. More specifically, the cyclic and collective pitch adjustment devices usually comprise pitch control rods that are moved by a swashplate, or by an axially moveable ring around a respective rotor mast.

The document <CIT> describes a rotor or propeller with rotor blades and a passive pitch angle adjustment apparatus. The passive pitch angle adjustment apparatus includes levers, rods, and a central rod. The levers are connected to the rotor blades and rotate them around a respective pitch axis. The rods are connected to the levers and mechanically link the levers with each other via a central point that is located outside the rotor plane. The central rod connects the central point with a base point that is located in a longitudinal direction of the rotor axis. The passive pitch angle adjustment apparatus enables a cyclic pitch adjustment of the rotor blades.

Document <CIT> describes a stabilizing system for adjusting simultaneously (a) collectively the pitch of the blades of a helicopter rotor, and (b) the cyclic pitch variation of the blade or several blades thereof. The stabilizing system comprises a simple arrangement of an inner and an outer annular member. The inner annular member can rotate around a fixed eccentric axis. The outer annular member is rotatably disposed about the inner annular member and connected by articulated linking members to the blades of a helicopter rotor for variation of the pitch of the latter. The rotor further comprises rod means for indicating the inclination of the blade cone and for automatically converting that inclination into a simultaneous interdependent adjustment of the collective pitch and the individual pitch variation of the rotor blades. In other words, the tilting of the whole blade cone is used as an input for balancing lift forces, and the stabilizing system is working in one flight direction only due to the fixed position of the eccentric axis. Therefore, the effects of sidewinds or a sideward flight cannot be recovered by this stabilizing system.

Document <CIT> describes a hub for a rigid rotor of a rotary winged aircraft that includes means for varying the blade angle of attack of each blade of a rotor as each blade rotates around the path traced out by the rotor to bring about a non-sinusoidal cyclic pitch change whilst independently allowing a sinusoidal cyclic pitch control to be superimposed thereon through the medium of a spider, the means being associated with each of the blade roots and includes a spindle for each blade, the spindles being equidistantly mounted for rotational movement in a rotatable component of the hub, and at their inner ends are each in spiral-splined engagement with a plunger whose inner end bears on a fixed cam and whose outer periphery has a predetermined peripheral profile to enable, for each blade, the blade angle of attack in relation to its azimuth position to be varied to suit the speed of the rotary winged aircraft.

Document <CIT> describes a collective and cyclic pitch control arrangement for jet-driven wings of a rotary wing aircraft that comprises rotor hub means rotatable with the wings of the aircraft, conduit means formed in said hub means for conducting operating gas to said wings, a stationary member including means rotatably supporting said hub means, said stationary member including a hollow cylinder means, a hollow piston means axially movable in said cylinder means, means operatively connected to said wings and to said piston means for increasing the wing angle upon movement of said piston means in one direction, restoring means operatively connected to said wings for decreasing the wing angle and moving said piston means in the opposite direction, conduit means formed in said stationary member and communicating with said conduit means in said hub means for conducting operating gas thereto.

Document <CIT> describes an aircraft that comprises a body, a driven member mounted upon said body for rotation about a generally vertical axis, a lifting rotor having blades pivotally mounted upon said member for blade pitch adjustment about a transverse axis, said rotor also being pivotally mounted upon said member for tilting adjustment about the inter section of said vertical and transverse axes, control means including a ball-and-socket assembly supported from said body, and operating mechanism cooperatively, connecting said assembly with said rotor for adjusting said rotor blades about said transverse axis for collective pitch control of said rotor blades and cyclic pitch control mechanism including vertically translatable push-pull means operatively connected to said control means for tilting adjustment of said assembly for the cyclic pitch control of the blades of said rotor.

Some of the cited prior art documents describe passive pitch angle adjustment apparatuses. Others need complex arrangements of actuators, which create extra costs including recurring costs for maintenance.

Based on the limitations and drawbacks of the prior art, an objective is to provide a cyclic pitch angle adjustment apparatus for a rotor with a rotor head and rotor blades. The cyclic pitch angle adjustment apparatus should be relatively simple, lightweight, and have low purchase and maintenance costs. Furthermore, the cyclic pitch angle adjustment apparatus should provide an increased efficiency of the rotor system in case of lateral air flow with reduced bending moments and vibration on the rotor head and rotor axis due to balanced lift forces.

These objectives are solved by a cyclic pitch angle adjustment apparatus comprising the features of claim <NUM>.

More specifically, according to the presently claimed invention, a cyclic pitch angle adjustment apparatus for a rotor with a rotor head and rotor blades that rotate around a rotor axis in a rotor plane comprises a base point, a bearing that is located in a central point outside the rotor plane, a first lever that is connected to a first rotor blade of the rotor blades and rotates the first rotor blade around a first pitch axis, a second lever that is connected to a second rotor blade of the rotor blades and rotates the second rotor blade around a second pitch axis, first and second rods that mechanically link the first and second levers with the bearing in the central point such that the first and second rods are movable relative to the central point, a central rod that connects the bearing with the base point, wherein the central rod is movable from a first position in which the central rod forms a fixed angle with the rotor axis to a second position in which the central rod forms the same fixed angle with the rotor axis, and wherein the first and second positions differ, and a motor that is coupled to the central rod and adapted for moving the central rod from the first position to the second position, wherein the central rod is adapted for adjusting the cyclic pitch angle of the first and second rotor blades in the first position to a first pitch angle and in the second position to a second pitch angle that is different than the first pitch angle. Furthermore, according to the presently claimed invention, the cyclic pitch angle adjustment apparatus comprises an adjustment device coupled between the motor and the central rod which is adapted for adjusting a distance of the bearing from the rotor axis.

Illustratively, a rotor may include a rotor hub and a rotor head, whereby the rotor hub is adapted for rotating around the rotor head. The rotor blades may be rotatably mounted on the rotor hub to allow for a change in the angle of attack (i.e., a change in pitch angle) of the rotor blades. An eccentric bearing journal may be attached to the rotor head, preferably apart from the rotor axis.

A lever is preferably firmly connected to the rotor blades. A rod may connect the eccentric bearing journal with the lever. A balance weight may be necessary on the opposite side of the connection between the rod and the lever. Depending on the position of the rotor blade, the distance between the connection of the rod and the lever to the eccentric bearing journal changes, so that a deflection of the rotor blade results to compensate this offset. The rotor blades change the angle of attack cyclically over the circumference, whereby the advancing rotor blade has a small angle of attack, and the retreating rotor blade has a comparatively larger angle of attack.

The presented cyclic pitch arrangement apparatus requires a slight increase in the complexity of the rotor system, while at the same time significantly improving aerodynamic behavior.

The cyclical pitch angle adjustment improves the distribution of the induced airspeed and the generation of lift over the rotor blade surface. Due to the improved aerodynamics, the cruising speed of the associated rotorcraft can be increased. In addition to the advantage of increased cruising speed, there is also an increase in efficiency due to improved aerodynamics.

Furthermore, a more even generation of lift has a positive effect on the loads and service life of the rotorcraft. Load fluctuations that occur due to high speeds on the advancing rotor blade and lower flow velocities on the returning rotor blade can be reduced in this way.

With an adjustable eccentricity, an optimization for the two flight states hovering and cruising is possible.

According to one aspect, a first move of the central rod with the bearing relative to the rotor axis causes a second move of the first and second rods that causes first and second rotational moves of the first and second levers and thereby first and second rotations of the first and second rotor blades around the first and second pitch axes, respectively.

According to one aspect, the cyclic pitch angle adjustment apparatus further comprises a third lever that is connected to a third rotor blade of the rotor blades and rotates the third rotor blade around a third pitch axis, and a third rod that mechanically links the third lever with the bearing in the central point such that the third rod is movable relative to the central point.

According to one aspect, the adjustment device further comprises a guiding groove that encompasses the central rod and guides the central rod from the first position to the second position.

According to one aspect, the adjustment device further comprises a control lever that is connected to the motor, wherein the motor moves the control lever such that the control lever moves the central rod in the guiding groove from the first position to the second position.

According to one aspect, the central rod is located inside the rotor head.

Moreover, a rotor may include the cyclic pitch angle adjustment apparatus as described above and rotor blades that rotate around a rotor axis in a rotor plane.

Furthermore, a rotorcraft may have the rotor 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 or elements are labeled with identical reference numbers and characters and are, consequently, only described once in the following description.

Exemplary embodiments may be included with any rotor or propeller having at least two rotor blades. For example, embodiments may be included in a rotor or a propeller of a transportation vehicle, if desired.

<FIG> shows an example of a transportation vehicle. A transportation vehicle may be an airplane, a quadcopter, a helicopter, or any other rotary wing transportation vehicle. As shown in <FIG>, the transportation vehicle may be a rotorcraft <NUM> that is exemplarily illustrated as a helicopter. Thus, for purposes of simplicity and clarity, the rotorcraft <NUM> is hereinafter referred to as the "helicopter" <NUM>.

Illustratively, helicopter <NUM> has a fuselage <NUM> that forms an airframe of the helicopter <NUM>. The fuselage <NUM> is connected to a suitable landing gear and exemplarily forms a cabin <NUM> and a rear fuselage <NUM>. The rear fuselage <NUM> is connected to a tail boom <NUM>.

Illustratively, helicopter <NUM> may have at least one multi-blade rotor <NUM> for providing lift and forward or backward thrust during operation. The at least one multi-blade rotor <NUM> comprises at least two rotor blades <NUM> that are mounted at an associated rotor head <NUM> with a rotor hub <NUM> to a rotor shaft <NUM>, which rotates in operation of the helicopter <NUM> around an associated rotor axis <NUM> in a rotor plane <NUM>.

By way of example, helicopter <NUM> may include at least one counter-torque device <NUM> configured to provide counter-torque during operation, i.e. to counter the torque created by rotation of the at least one rotor <NUM> for purposes of balancing the helicopter <NUM> in terms of yaw. If desired, counter-torque device <NUM> may be shrouded.

The at least one counter-torque device <NUM> is illustratively provided at an aft section of the tail boom <NUM> and may have a tail rotor <NUM>. The aft section of the tail boom <NUM> may include a fin <NUM>. Illustratively, the tail boom <NUM> may be provided with a suitable horizontal stabilizer <NUM>.

If desired, the at least one multi-blade rotor <NUM> and/or the tail rotor <NUM> may include a cyclic pitch angle adjustment apparatus for adjusting the cyclic pitch angle of the respective rotor blades <NUM>.

<FIG> shows an illustrative rotor <NUM> with an example cyclic pitch angle adjustment apparatus <NUM> not forming part of the presently claimed invention, and <FIG> shows a cross-sectional view of the illustrative rotor <NUM> with the example cyclic pitch angle adjustment apparatus <NUM> of <FIG>.

According to the presently claimed invention, the rotor <NUM> includes rotor blades <NUM>. The rotor blades <NUM> rotate around a rotor axis <NUM> in a rotor plane <NUM>. Illustratively, the rotor blades <NUM> may be mounted to a rotor hub <NUM> that rotates with the rotor blades <NUM> around a rotor head <NUM> and thereby around the rotor axis <NUM>. Preferably, the rotor blades <NUM> are rotatably mounted to the rotor hub <NUM> to enable a pitch angle change through a rotation around a pitch axis 235a, 235b.

Cyclic pitch angle adjustment apparatus <NUM> may be adapted for adjusting the cyclic pitch angle of the rotor blades <NUM>. As shown in <FIG>, the cyclic pitch angle adjustment apparatus <NUM> includes a base point <NUM> and a bearing <NUM> that is located in a central point <NUM> outside the rotor plane <NUM>.

The cyclic pitch angle adjustment apparatus <NUM> includes a first lever 230a that is connected to a first rotor blade 212a of the rotor blades <NUM> and a second lever 230b that is connected to a second rotor blade 212b of the rotor blades <NUM>.

The first lever 230a rotates the first rotor blade 212a around a first pitch axis 235a, and the second lever 230b rotates the second rotor blade 212b around a second pitch axis 235b.

The cyclic pitch angle adjustment apparatus <NUM> includes first and second rods 240a, 240b. The first and second rods 240a, 240b mechanically link the first and second levers 230a, 230b with the bearing <NUM> in the central point <NUM> such that the first and second rods 240a, 240b are movable relative to the central point <NUM>.

If desired, the first and second rods 240a, 240b of <FIG> may be integrally formed as a single rod <NUM>. Optionally, the cyclic pitch angle adjustment apparatus <NUM> may include a connection <NUM>. The connection <NUM> may connect the first lever 230a, the second lever 230b, and the single rod <NUM> with each other in a first location <NUM>.

The cyclic pitch angle adjustment apparatus <NUM> includes a central rod <NUM> that connects the bearing <NUM> with the base point <NUM>. The central rod <NUM> is movable from a first position in which the central rod <NUM> forms a fixed angle with the rotor axis <NUM> to a second position in which the central rod <NUM> forms the same fixed angle with the rotor axis <NUM>, whereby the first and second positions differ.

The fixed angle between the central rod <NUM> and the rotor axis <NUM> may be any angle. For example, the fixed angle may be <NUM>°. In other words, the central rod <NUM> may be parallel to the rotor axis <NUM>.

According to the presently claimed invention, the bearing <NUM> has a first distance from the rotor axis <NUM> in the first position and a second distance from the rotor axis <NUM> in the second position, wherein the first and second distances from the rotor axis <NUM> differ. As an example, the bearing <NUM> may have a first distance from the rotor plane <NUM> in the first position and a second distance from the rotor plane <NUM> in the second position, wherein the first and second distances from the rotor plane <NUM> differ.

If desired, bearing <NUM> may be implemented as a pivot bearing with only one degree of freedom, and the central rod <NUM> may be rotatably mounted at the base point <NUM>.

Through a move of the central rod <NUM> from the first to the second position, the central rod <NUM> is adapted for adjusting the cyclic pitch angle of the first and second rotor blades 212a, 212b in the first position to a first pitch angle and in the second position to a second pitch angle that is different than the first pitch angle.

For example, a first move of the central rod <NUM> with the bearing <NUM> relative to the rotor axis <NUM> causes a second move of the first and second rods 240a, 240b that causes first and second rotational moves of the first and second levers 230a, 230b and thereby first and second rotations of the first and second rotor blades 212a, 212b around the first and second pitch axes 235a, 235b, respectively.

Illustratively, the cyclic pitch angle adjustment apparatus <NUM> changes the angle of attack of the rotor blades <NUM> over the course of rotation around the rotor axis <NUM>. Over the course of a rotation of the rotor blades <NUM> around the rotor axis <NUM>, the rotor blades <NUM> that move forward in the relative airflow, (i.e., in the same direction as the rotorcraft) (e.g., rotor blade 212a of <FIG>) are sometimes also referred to as advancing rotor blades, and the rotor blades <NUM> that move backward in the relative airflow (i.e., in the opposite direction as the rotorcraft) (e.g., rotor blade 212b of <FIG>) are sometimes also referred to as retreating rotor blades.

For example, consider the scenario in which a rotorcraft with rotor <NUM> flies in flight direction <NUM> and that the rotor blades <NUM> rotate around rotor axis <NUM> in direction of rotation <NUM>.

In this scenario, the cyclic pitch angle adjustment apparatus <NUM> may adjust the cyclic pitch angle of the first and second rotor blades 212a, 212b by reducing the angle of attack of the advancing rotor blade (i.e., the first rotor blade 212a in the position shown in <FIG>) and increasing the angle of attack of the retreating rotor blade (i.e., the second rotor blade 212b in the position shown in <FIG>). Illustratively, the cyclic pitch angle (i.e., the angle of attack) may be adjusted depending on the flight speed.

As an example, an increase in flight speed from a first flight speed to a second flight speed may result in a reduction of the angle of attack of the advancing rotor blade (i.e., the first rotor blade 212a in the position shown in <FIG>) from a first to a second angle of attack and an increase of the angle of attack of the retreating rotor blade (i.e., the second rotor blade 212b in the position shown in <FIG>) from a third to a fourth angle of attack.

As another example, a decrease in flight speed from the second flight speed to the first flight speed may result in an increase of the angle of attack of the advancing rotor blade 212a from the second to the first angle of attack and a decrease of the angle of attack of the retreating rotor blade 212b from the fourth to the third angle of attack.

By way of example, the cyclic pitch angle adjustment apparatus <NUM> may include a balance weight <NUM>. The balance weight <NUM> may prevent imbalances during rotation of the rotor <NUM> around rotor axis <NUM>. These imbalances could cause severe damage to the rotor <NUM>.

The balance weight <NUM> may be arranged in a second location <NUM>. The first and second locations <NUM>, <NUM> rotate around the rotor axis <NUM> with the rotor blades <NUM>. Preferably, the first and second locations <NUM>, <NUM> are on opposite sides of the rotor axis <NUM>.

<FIG> is a diagram of an illustrative rotor <NUM> with a cyclic pitch angle adjustment apparatus <NUM> according to an example not forming part of the presently claimed invention, having levers 230a, 230b that extend around the rotor hub <NUM>, and <FIG> is a cross-sectional view of the illustrative rotor <NUM> with the illustrative cyclic pitch angle adjustment apparatus <NUM> of <FIG>.

The cyclic pitch angle adjustment apparatus <NUM> of <FIG> differs from the cyclic pitch angle adjustment apparatus <NUM> of <FIG> in that the levers 230a, 230b are elongated and connect in the second location <NUM>. Thus, the levers 230a, 230b are identical and therefore interchangeable, which reduces the number of different parts in rotor <NUM>.

Moreover, the balance weight <NUM> may be arranged in the second location <NUM> in which the elongated levers 230a, 230b connect. As a result of the elongated and connected levers 230a, 230b and the position of the balance weight <NUM>, the cyclic pitch angle adjustment apparatus <NUM> of <FIG> may have an improved centripetal force distribution compared to the cyclic pitch angle adjustment apparatus <NUM> of <FIG>.

<FIG> is a diagram of an illustrative rotor <NUM> having a cyclic pitch angle adjustment apparatus <NUM> according to an example not forming part of the presently claimed invention, and four rotor blades <NUM> that rotate around a rotor axis <NUM> in a rotor plane. The illustrative cyclic pitch angle adjustment apparatus <NUM> includes a bearing <NUM> that is located in a central point <NUM> outside the rotor plane.

Levers 230a, 230b, 230c, 230d are connected to respective rotor blades <NUM> and rotate the respective rotor blades <NUM> around a respective pitch axis 235a, 235b, 235c, 235d.

Illustratively, rods 240a, 240b, 240c, 240d mechanically link the respective levers 230a, 230b, 230c, 230d with the bearing <NUM> in the central point <NUM> such that the rods 240a, 240b, 240c, 240d are movable relative to the central point <NUM>.

If desired, the cyclic pitch angle adjustment apparatus <NUM> may include a distribution element. The distribution element may establish a connection between the bearing <NUM> and the rods 240a, 240b, 240c, 240d.

As an example, the distribution element may include first, second, third, and fourth ball joints. The first, second, third, and fourth ball joints may connect the first, second, third, and fourth rods 240a, 240b, 240c, 240d with the bearing <NUM> in the central point <NUM>, respectively. If desired, four additional ball joints may connect the first, second, third, and fourth rods 240a, 240b, 240c, 240d with the first, second, third, and fourth levers 230a, 230b, 230c, 230d, respectively.

According to the presently claimed invention, cyclic pitch adjustment apparatus <NUM> includes a central rod <NUM> that connects the bearing <NUM> with a base point. As an example, the base point may be located on the rotor head <NUM>.

The central rod <NUM> is movable from a first position in which the central rod <NUM> forms a fixed angle with the rotor axis <NUM> to a second position in which the central rod <NUM> forms the same fixed angle with the rotor axis <NUM>.

Thereby, the central rod <NUM> is adapted for adjusting the cyclic pitch angle of the rotor blades <NUM> in the first position to a first pitch angle and in the second position to a second pitch angle that is different than the first pitch angle.

For example, a first move of the central rod <NUM> with the bearing <NUM> relative to the rotor axis <NUM> may cause a second move of the rods 240a, 240b, 240c, 240d that cause rotational moves of the levers 230a, 230b, 230c, 230d and thereby rotations of the rotor blades <NUM> around the pitch axes 235a, 235b, 235c, 235d, respectively.

According to examples not forming part of the presently claimed invention, a motor and/or an adjustment device may move the central rod <NUM> with the bearing <NUM> from the e-first position to the second position. However, according to the presently claimed invention, a motor and an adjustment device coupled between the motor and the central rod move the central rod <NUM> and the bearing <NUM> from the first position to the second position.

<FIG> show cyclic pitch angle adjustment apparatuses according to the presently claimed invention, with a motor and an adjustment device that are adapted for moving the central rod <NUM> with the bearing <NUM>. For purposes of simplicity and clarity, some features have been omitted from the illustrative cyclic pitch angle adjustment apparatuses of <FIG>. For example, rods <NUM> and levers <NUM> and the connections with the rotor blades <NUM> are not explicitly shown. However, the cyclic pitch angle adjustment apparatuses of <FIG> may be integrated with any cyclic pitch angle adjustment apparatus <NUM> and any rotor <NUM> of <FIG>, if desired.

<FIG> is a diagram of a cyclic pitch angle adjustment apparatus according to the presently claimed invention, with a motor <NUM> and an adjustment device <NUM>. As shown in <FIG>, the motor <NUM> is coupled to the central rod <NUM> and adapted for moving the central rod <NUM> from the first position to the second position.

According to the presently claimed invention, the motor <NUM> is coupled to the central rod <NUM> via the adjustment device <NUM>.

The adjustment device <NUM> that is coupled between the motor <NUM> and the central rod <NUM> is adapted for adjusting a distance of the bearing <NUM> from the rotor axis <NUM>, preferably also a distance of the bearing <NUM> from the rotor plane <NUM>.

Illustratively, the motor <NUM> may be any actuator that is able to move the central rod <NUM> via the adjustment device <NUM> from the first position to the second position. For example, the motor <NUM> may be any rotary actuator or linear actuator that allows for precise control of angular or linear position. If desired, the motor <NUM> may be a servomotor. Such a servomotor may include an electric motor and a sensor for position feedback.

As an example, the bearing <NUM> may have a first distance from the rotor axis <NUM> in the first position and a second distance from the rotor axis <NUM> in the second position, whereby the first and second distances from the rotor axis <NUM> differ. As another example, the bearing <NUM> may have a first distance from the rotor plane <NUM> in the first position and a second distance from the rotor plane <NUM> in the second position, whereby the first and second distances from the rotor plane <NUM> differ.

Illustratively, the adjustment device <NUM> may include a platform <NUM>. The base point <NUM> of the cyclic pitch angle adjustment apparatus <NUM> may be located on the platform <NUM>. For example, the central rod <NUM> may be fixedly attached to the platform <NUM> at the base point <NUM>.

By way of example, the adjustment device <NUM> may include legs 530a, 530b. Legs 530a, 530b may be rotatably attached to platform <NUM>. Furthermore, leg 530a may be rotatably attached to rotor head <NUM>, while leg 530b may be fixedly attached to motor <NUM>.

Thus, as shown in <FIG>, the adjustment device <NUM> may be adapted for adjusting both, the distance of the bearing <NUM> from the rotor axis <NUM> and the distance of the bearing <NUM> from the rotor plane <NUM> simultaneously.

As an example, consider the scenario in which the motor <NUM> is a rotary actuator that rotates around axis <NUM>. In this scenario, the motor <NUM> may move the platform <NUM> and thereby the bearing <NUM> such that the distance of the bearing <NUM> from the rotor axis <NUM> and the rotor plane <NUM> changes.

When the bearing <NUM> is located on the rotor axis <NUM> and furthest away from the rotor plane <NUM>, the cyclic pitch adjustment apparatus <NUM> may adjust the pitch angle of all rotor blades to be the same. Thus, the rotor is optimized for hover flight.

When the bearing <NUM> is located furthest away from the rotor axis <NUM> and closest to the rotor plane <NUM>, the cyclic pitch adjustment apparatus <NUM> may adjust the cyclic pitch angle of the advancing and retreating rotor blades to have the greatest pitch angle difference. Thus, the rotor is optimized for fast forward flight.

<FIG> is a diagram of an illustrative cyclic pitch angle adjustment apparatus <NUM> according to the presently claimed invention, with an adjustment device <NUM> that includes a guiding groove <NUM>.

The cyclic pitch angle adjustment apparatus <NUM> includes a central rod <NUM>. The central rod <NUM> connects a base point with a bearing <NUM> that is located in a central point <NUM>.

The central rod <NUM> is movable from a first position <NUM> to a second position <NUM> that is different than the first position <NUM>, thereby adjusting the cyclic pitch angle of rotor blades <NUM> from a first pitch angle in the first position <NUM> to a second pitch angle in the second position <NUM>.

Illustratively, a guiding groove <NUM> may encompass the central rod <NUM>. If desired, the guiding groove <NUM> may guide the central rod <NUM> from the first position <NUM> to the second position <NUM>. For example, the guiding groove <NUM> may turn relative to the rotor axis <NUM>, thereby changing the eccentricity of the bearing <NUM> (i.e., the distance from the rotor axis <NUM> from the first distance <NUM> to the second distance <NUM>) by moving the central rod <NUM> from the first to the second position <NUM>, <NUM>.

Thus, as shown in <FIG>, the bearing <NUM> has a first distance <NUM> from the rotor axis <NUM> in the first position <NUM> and a second distance <NUM> from the rotor axis <NUM> in the second position <NUM>, whereby the first and second distances <NUM>, <NUM> from the rotor axis <NUM> differ. If desired, the bearing <NUM> may have a first distance from the rotor plane <NUM> in the first position <NUM> and a second distance from the rotor plane <NUM> in the second position <NUM>, whereby the first and second distances from the rotor plane <NUM> differ.

By way of example, the guiding groove <NUM> may be formed as part of the rotor head <NUM>. For example, the guiding groove <NUM> may be a groove in the cover of the rotor head <NUM>.

<FIG> is a diagram of a cyclic pitch angle adjustment apparatus <NUM> according to the presently claimed invention, with a motor <NUM> and an adjustment device <NUM> that includes a control lever <NUM>. As shown in <FIG>, the motor <NUM> may be located on the rotor head <NUM> apart from the rotor axis <NUM>. Illustratively, the motor <NUM> may rotate around an axis that is parallel to the rotor axis <NUM>. If desired, the motor <NUM> may rotate around an axis that is inclined by an angle relative to the rotor axis <NUM>.

The control lever <NUM> may be connected to the motor <NUM> such that a rotation of the motor <NUM> causes a rotation of the control lever <NUM>. Illustratively, the control lever <NUM> may encompass the central rod <NUM>. For example, the control lever <NUM> may have a fork shape that encompasses the central rod <NUM> such that a rotation of the control lever <NUM> moves the central rod <NUM>.

If desired, the central rod <NUM> may move in a guiding groove <NUM>. For example, the motor <NUM> may move the control lever <NUM> such that the control lever <NUM> moves the central rod <NUM> in the guiding groove <NUM> from the first position <NUM> to the second position <NUM>.

<FIG> is a diagram of a cyclic pitch angle adjustment apparatus according to the presently claimed invention, with a motor <NUM> and an adjustment device <NUM> that includes a guiding groove <NUM> and a control lever <NUM>, and <FIG> is a cross-sectional view of the illustrative cyclic pitch angle adjustment apparatus <NUM> of <FIG>.

Illustratively, the motor <NUM> may be located on the rotor axis <NUM>. For example, the motor <NUM> may be embedded in the rotor head <NUM> as shown in <FIG>. If desired, the motor <NUM> may rotate around the rotor axis <NUM> in a first direction of rotation <NUM> or in a second direction of rotation <NUM>.

The control lever <NUM> of the adjustment device <NUM> may be connected to the motor <NUM> such that the motor <NUM> moves the control lever <NUM>. For example, the control lever <NUM> may rotate around the rotor axis <NUM> in response to a rotation of the motor <NUM> around the rotor axis <NUM>.

The guiding groove <NUM> of the adjustment device <NUM> may encompass the central rod <NUM> and guide any movement of the central rod <NUM>. As shown in <FIG>, the guiding groove <NUM> may have a gradient that is furthest away from the rotor plane <NUM> at the rotor axis and that approaches the rotor plane <NUM> with an increased distance from the rotor axis <NUM>. The gradient may be constant.

If desired, the gradient may be non-constant. Thus, the gradient may change with the distance from the rotor axis <NUM>. As an example, the gradient may increase with an increased distance from the rotor axis <NUM>. As another example, the gradient may decrease with the distance from the rotor axis <NUM>. As yet another example, the gradient may increase or decrease first and then decrease or increase with an increased distance from the rotor axis <NUM>.

The control lever <NUM> may be bow-shaped and encompass the central rod <NUM>. For example, the control lever <NUM> may have a fork or a loop at the end that is opposite the motor <NUM> with which the control lever <NUM> may move the central rod <NUM> in the guiding groove <NUM>. Illustratively, the motor <NUM> and the control lever <NUM> may move the central rod <NUM> in the guiding groove <NUM> from the first position <NUM> to the second position <NUM>.

As an example, consider the scenario in which the motor <NUM> rotates counterclockwise when seen from above (i.e., in direction of rotation <NUM> as shown in <FIG>). In this scenario, the bow-shaped control lever <NUM> may move in direction of rotation <NUM>, thereby moving the central rod <NUM> from the first position <NUM> to the second position <NUM>.

With the move of the central rod <NUM> from the first position <NUM> to the second position <NUM>, the bearing <NUM> that is connected to the central rod <NUM> also changes positions. As shown in <FIG>, the bearing <NUM> has a first distance <NUM> from the rotor axis <NUM> in the first position <NUM> and a second, different distance <NUM> from the rotor axis <NUM> in the second position <NUM>. Simultaneously, the bearing <NUM> has a first distance <NUM> from the rotor plane <NUM> in the first position <NUM> and a second, different distance <NUM> from the rotor plane <NUM> in the second position <NUM>.

As another example, consider the scenario in which the motor <NUM> rotates clockwise when seen from above (i.e., in direction of rotation <NUM> as shown in <FIG>). In this scenario, the bow-shaped control lever <NUM> may move in direction of rotation <NUM>, thereby moving the central rod <NUM> from the second position <NUM> to the first position <NUM>.

With the move of the central rod <NUM> from the second position <NUM> to the first position <NUM>, the bearing <NUM> that is connected to the central rod <NUM> also changes positions. As shown in <FIG>, the bearing <NUM> has a second distance <NUM> from the rotor axis <NUM> in the second position <NUM> and a first, different distance <NUM> from the rotor axis <NUM> in the first position <NUM>. Simultaneously, the bearing <NUM> has a second distance <NUM> from the rotor plane <NUM> in the second position <NUM> and a first, different distance <NUM> from the rotor plane <NUM> in the first position <NUM>.

Thus, as shown in <FIG>, the motor <NUM> and the adjustment apparatus <NUM> are adapted for adjusting both, the distance from the rotor axis <NUM> and the distance from the rotor plane <NUM>, at the same time.

<FIG> is a diagram of a cyclic pitch angle adjustment apparatus <NUM> according to the presently claimed invention, with an adjustment device <NUM> that adjusts a distance from the rotor plane <NUM> and a distance from the rotor axis <NUM>, and <FIG> is a cross-sectional view of the illustrative cyclic pitch angle adjustment apparatus of <FIG>.

As shown in <FIG>, the top of the rotor head <NUM> may be inclined relative to the rotor plane <NUM>. In particular, the distance between the top of the rotor head <NUM> and the rotor plane <NUM> may be greatest at the rotor axis <NUM> and decrease with an increased distance from the rotor axis <NUM>.

Illustratively, a motor <NUM> may be mounted on the top of the rotor head <NUM>. The motor <NUM> may be located away from the rotor axis <NUM> on the inclination of the top of the rotor head <NUM> as shown in <FIG>.

By way of example, the control lever <NUM> of the adjustment device <NUM> may be connected to the motor <NUM> such that the motor <NUM> moves the control lever <NUM>. If desired, a guiding groove may encompass the central rod <NUM> and guide any movement of the central rod <NUM>.

The control lever <NUM> may encompass the central rod <NUM>. For example, the control lever <NUM> may have a fork or a loop at the end that is opposite the motor <NUM> with which the control lever <NUM> may move the central rod <NUM> in the guiding groove.

Illustratively, the motor <NUM> and the control lever <NUM> may move the central rod <NUM> in the guiding groove over the top of the rotor head <NUM> between different positions.

The central rod <NUM> is movable from a first position in which the central rod <NUM> forms a fixed angle <NUM> with the rotor axis <NUM> to a second position in which the central rod <NUM> forms the same fixed angle <NUM> with the rotor axis <NUM>, wherein the first and second positions differ.

The fixed angle <NUM> between the central rod <NUM> and the rotor axis <NUM> may be any angle. For example, the fixed angle <NUM> may be <NUM>°. In other words, the central rod <NUM> may be parallel to the rotor axis <NUM> (e.g., as shown in <FIG>, <FIG>, and <FIG>). As shown in <FIG>, the fixed angle <NUM> may be different than <NUM>°.

With the move of the central rod <NUM> between different positions, the bearing <NUM> that is connected to the central rod <NUM> also changes positions. For example, the bearing <NUM> may change a distance from the rotor axis <NUM> and a distance from the rotor plane <NUM> simultaneously.

During a change in distance from the rotor axis <NUM> and/or from the rotor plane <NUM>, the bearing <NUM> may adjust the pitch angle of the rotor blades that are attached via rods and levers to the bearing <NUM> (e.g., as described with reference to <FIG>).

<FIG> is a diagram of a cyclic pitch angle adjustment apparatus <NUM> according to the presently claimed invention, with an adjustment device <NUM> that includes a control lever <NUM> that guides a central rod <NUM> in a guiding groove <NUM>, and <FIG> is a cross-sectional view of the illustrative cyclic pitch angle adjustment apparatus <NUM> of <FIG>.

As shown in <FIG>, the top of the rotor head <NUM> may be parallel to the rotor plane <NUM>, and a motor <NUM> may be mounted on the top of the rotor head <NUM>. Illustratively, the motor <NUM> may be located on the top of the rotor head <NUM> at a predetermined distance from the rotor axis <NUM> as shown in <FIG>.

By way of example, the control lever <NUM> of the adjustment device <NUM> may be connected to the motor <NUM> such that the motor <NUM> moves the control lever <NUM>. Illustratively, the guiding groove <NUM> may be adapted for adjusting a distance of the bearing <NUM> from the rotor axis <NUM> and a distance of the bearing <NUM> from the rotor plane <NUM> simultaneously. If desired, the guiding groove <NUM> may have the shape of a spiral.

As an example, the guiding groove <NUM> may encompass the central rod <NUM> and guide any movement of the central rod <NUM>. Thus, a move of the central rod <NUM> in the guiding groove <NUM> by means of the motor <NUM> and the control lever <NUM>, and thus a move of the bearing <NUM>, may change the distance of the bearing <NUM> from the rotor axis <NUM> and the distance of the bearing <NUM> from the rotor plane <NUM>.

As another example, the control lever <NUM> may be attached to the central rod <NUM> and guided in a spiral-shaped guiding groove <NUM>. Thus, a move of the central rod <NUM> by means of the motor <NUM> and a move of the control lever <NUM> in the guiding groove <NUM> may adjust the distance of the bearing <NUM> from the rotor axis <NUM> and the distance of the bearing <NUM> from the rotor plane <NUM>.

During a change in distance from the rotor axis <NUM> and/or from the rotor plane <NUM>, the bearing <NUM> may adjust the pitch angle of the rotor blades that are attached via rods and levers to the bearing <NUM>.

<FIG> is a diagram of an illustrative rotor <NUM> with a cyclic pitch angle adjustment apparatus <NUM> according to the presently claimed invention, inside a rotor head <NUM>, and <FIG> is a cross-sectional view of the illustrative rotor of <FIG>.

For purposes of simplicity and clarity, the rotor head cover <NUM> has been removed in <FIG>. In particular, the central rod <NUM> of the cyclic pitch angle adjustment apparatus <NUM> may be located inside the rotor head <NUM>.

Placing the cyclic pitch angle adjustment apparatus <NUM> inside the rotor head <NUM> may improve the aerodynamics of the rotor <NUM> and shield the cyclic pitch angle adjustment apparatus <NUM> from weather and soiling, which may increase the robustness, reduce deterioration, and decrease maintenance costs.

The cyclic pitch angle adjustment apparatus <NUM> includes a base point <NUM> and a bearing <NUM> that is located in a central point <NUM> outside the rotor plane <NUM>. As an example, the rotor plane <NUM> may be located between the central point <NUM> and the rotor head cover <NUM>.

As shown in <FIG>, first and second levers may be integrally formed as a single lever <NUM>. The single lever <NUM> may be connected to the rotor blades <NUM>. The single lever <NUM> may rotate a first rotor blade <NUM> around a first pitch axis 235a and a second rotor blade <NUM> around a second pitch axis 235b.

Illustratively, first and second rods may be integrally formed as a single rod <NUM>. A connection <NUM> may connect the single lever <NUM> and the single rod <NUM> with each other in a first location <NUM>. The single rod <NUM> may mechanically link the single lever <NUM> with the bearing <NUM> in the central point <NUM> such that the single rod <NUM> is movable relative to the central point <NUM>.

The cyclic pitch adjustment apparatus <NUM> includes a central rod <NUM> that connects the bearing <NUM> with the base point <NUM>. The central rod <NUM> is movable from a first position in which the central rod <NUM> forms a fixed angle with the rotor axis <NUM> to a second position <NUM> in which the central rod <NUM> forms the same fixed angle with the rotor axis <NUM>. For example, the central rod <NUM> may be movably mounted at rod <NUM>.

Thereby, the central rod <NUM> is adapted for adjusting the cyclic pitch angle of the first and second rotor blades <NUM> in the first position to a first pitch angle and in the second position to a second pitch angle that is different than the first pitch angle.

If desired, the cyclic pitch angle adjustment apparatus <NUM> may include a balance weight. The balance weight may be arranged in a second location. The first location <NUM> and the second location may be on opposite sides of the rotor axis <NUM>. As an example, the single lever <NUM> may be extended on the side of the rotor axis <NUM> that is opposite the first location <NUM>.

It should be noted that the above described embodiments are merely described to illustrate possible embodiments of the present invention, but not in order to restrict the present invention thereto. Instead, multiple modifications and variations of the above described embodiments are possible.

For instance, the first and second levers 230a, 230b of <FIG> that are connected to the first and second rotor blades and rotate the first and second rotor blades <NUM> around the first and second pitch axes 235a, 235b, respectively are shown as separate levers. However, the first and second levers 230a, 230b may be integrally formed as a single lever, if desired.

Claim 1:
A cyclic pitch angle adjustment apparatus (<NUM>) for a rotor (<NUM>) with a rotor head (<NUM>) and rotor blades (<NUM>) that rotate around a rotor axis (<NUM>) in a rotor plane (<NUM>), comprising:
a base point (<NUM>);
a bearing (<NUM>) that is located in a central point (<NUM>) outside the rotor plane (<NUM>);
a first lever (230a) that is connected to a first rotor blade (212a) of the rotor blades (<NUM>) and rotates the first rotor blade (212a) around a first pitch axis (235a);
a second lever (230b) that is connected to a second rotor blade (212b) of the rotor blades (<NUM>) and rotates the second rotor blade (212b) around a second pitch axis (235b);
first and second rods (240a, 240b) that mechanically link the first and second levers (230a, 230b) with the bearing (<NUM>) in the central point (<NUM>) such that the first and second rods (240a, 240b) are movable relative to the central point (<NUM>);
a central rod (<NUM>) that connects the bearing (<NUM>) with the base point (<NUM>), wherein the central rod (<NUM>) is movable from a first position (<NUM>) in which the central rod (<NUM>) forms a fixed angle (<NUM>) with the rotor axis (<NUM>) to a second position (<NUM>) in which the central rod (<NUM>) forms the same fixed angle (<NUM>) with the rotor axis (<NUM>), and wherein the first and second positions (<NUM>, <NUM>) differ; and
a motor (<NUM>) that is coupled to the central rod (<NUM>) and adapted for moving the central rod (<NUM>) from the first position (<NUM>) to the second position (<NUM>), wherein the central rod (<NUM>) is adapted for adjusting the cyclic pitch angle of the first and second rotor blades (212a, 212b) in the first position (<NUM>) to a first pitch angle and in the second position (<NUM>) to a second pitch angle that is different than the first pitch angle; characterized in that an adjustment device (<NUM>) coupled between the motor (<NUM>) and the central rod (<NUM>) is adapted for adjusting a distance of the bearing (<NUM>) from the rotor axis (<NUM>).