FAILURE TOLERANT ROTOR BLADE PITCH ANGLE CONTROLLING DEVICE

Abstract

A mechanically simple rotor system is a novel mechanism that collectively drives the pitch of the rotor blades by combining the input from three separate servos. Each servo can be controlled by redundant control systems. This configuration reduces total error caused by any one system and allows the continuation of rotor pitch control in the event of one or more servo or system failures.

Claims

1. A rotor blade pitch angle controlling device, comprising: a. a plurality of actuators; b. a swivel plate of rigid material connecting said plurality of actuators; c. a slider of rigid material; d. a swiveling joint connecting said swivel plate to said slider; e. a collective fitting of rigid material; f. a rotational bearing connecting but allowing rotation between said slider to said collective fitting; g. a plurality of rotor blades; h. a plurality of rotor blade control arms rigidly attached to said rotor blades as means of converting translation of said collective fitting to rotation of said plurality of rotor blades; i. means of collectively controlling pitch angle of said plurality of rotor blades by averaging the translational input of said plurality of actuators.

2. The blade pitch angle controlling device of claim 1, wherein said structure connects three irreversible actuators to said swivel plate.

3. The blade pitch angle controlling device of claim 1, wherein said structure connects more than three reversible actuators to said swivel plate.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] FIG. 1 is a side view of the voting rotor pitch control systemtwo-bladed rotor shown.

[0020] The preferred embodiment of the present invention is a mechanical voting pitch control system that allows averaging from three irreversible servo 89 or actuator inputs to drive the rotor blade 41 pitch positions (FIG. 28). In the event one or more servos 89 or control systems stop functioning, the other servo or servos can drive the pitch system. FIG. 28 depicts a side view of the present invention's rotor system, showing only two of the six blades and associated linkages for clarity. Rotor blades 41 and control arms 103 have pitch positions controlled by movement of three irreversible servos 89. The servos 89 are connected to a swivel plate 93 that pivots around a spherical bearing that is part of the slider 101. The three servo connections define a plane that determines the position of the slider 101 along the rotor shaft 85. The swivel plate 93 and the slider 101 do not rotate with the rotor shaft. Bearings 107 allow rotational isolation of the rotor shaft 85 and the slider 101 while still maintaining lateral continuity. The slider 101 is connected to a rotating collective fitting 91 through a rotational bearing 105 that is captured by a retaining clip 97 that resides in a machined groove. The rotational bearing 105 isolates the rotational movement of the collective fitting 91 to that of the slider 101 while still maintaining lateral and axial positioning. The collective fitting 91 translates along the rotor shaft and moves each rotor link 87 the same axial distance the slider 101 moves. Each rotor link 87 is attached to a blade pitch arm 103, which is rigidly attached to a blade. The rotor pitch arms 103 convert linear motion of the links 87 to rotation of the blade 41 about the blade pitch axis. A set of links 99 is attached between the collective fitting 91 and the rotor hub 43. These maintain rotational position between the rotor head 43 and collective fitting 91 without impeding relative axial movement. Similarly, another set of links 109 attaches the swivel plate 93 to a rigid component on a vehicle or other machine. These links 109 keep the swivel plate 93 from rotating with the rotor shaft 85 while still allowing the swivel plate to pivot freely about the its spherical bearing center. A spherical bearing is required to attach the link 109 to the swivel plate 93 to allow independent rotation.

[0021] Other embodiments of the present invention may control the rotors pitch in a similar manner using different geometry and components but maintaining the ability to mechanically vote using a swivel plate 93 and multiple servos or actuators. The preferred embodiment uses three irreversible actuators to determine the swivel plate 93 orientation and position. Other embodiments of the present invention may use more than three reversible servos or actuators to vote and provide control redundancy to the rotor pitch system. A reversible servo or actuator is one that does not maintain position when power or commanded signal is lost. Still another embodiment of this invention is a system that contains multiple parallel pitch mechanisms that controls pairs of rotor blades attached opposite to each other on the rotor hub 43. Each system is driven by a servo 89, actuator or sets of either to independently control the pitch of pairs of rotor blades. For instants, a rotor hub containing six rotor blades could be controlled by three independent pitch mechanisms. Loads from the paired blades would be balanced across the rotor hub 43 even if they were commanded at different pitch angles from the other blade sets, or if they were inoperative.

[0022] The forgoing is considered as illustrative only to the principal of the invention. Further, since numerous changes and modification will occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described above, and accordingly, all suitable modifications and equivalents may be resorted to falling within the scope of the invention.