This invention relates generally to actuation systems, and more particularly, to a compact linear hydraulic actuator.
A rotorcraft may include one or more rotor systems. One example of a rotorcraft rotor system is a main rotor system. A main rotor system may generate aerodynamic lift to support the weight of the rotorcraft in flight and thrust to counteract aerodynamic drag and move the rotorcraft in forward flight. Another example of a rotorcraft rotor system is a tail rotor system. A tail rotor system may generate thrust in the same direction as the main rotor system's rotation to counter the torque effect created by the main rotor system.
Particular embodiments of the present disclosure may provide one or more technical advantages. A technical advantage of one embodiment may include the capability to provide a linear hydraulic actuator that is both compact and provides a long stroke. A technical advantage of one embodiment may also include the capability to utilize triplex cylinders with inverted unbalanced-area pistons. A technical advantage of one embodiment may include the capability to provide forty percent more stroke length for a given actuator envelope length and provide increased failure tolerance over conventional dual parallel or dual tandem actuator configurations.
Certain embodiments of the present disclosure may include some, all, or none of the above advantages. One or more other technical advantages may be readily apparent to those skilled in the art from the figures, descriptions, and claims included herein.
To provide a more complete understanding of the present invention and the features and advantages thereof, reference is made to the following description taken in conjunction with the accompanying drawings, in which:
Rotor system 110 may rotate blades 120. Rotor system 110 may include a control system for selectively controlling the pitch of each blade 120 in order to selectively control direction, thrust, and lift of rotorcraft 100. In the example of
Fuselage 130 represents the main body of rotorcraft 100 and may be coupled to rotor system 110 (e.g., via wing 150) such that rotor system 110 and blades 120 may move fuselage 130 through the air. Landing gear 140 supports rotorcraft 100 when rotorcraft 100 is landing and/or when rotorcraft 100 is at rest on the ground.
Teachings of certain embodiments relating to rotor systems described herein may apply to rotor system 110 and/or other rotor systems, such as non-tilting rotor and helicopter rotor systems. It should also be appreciated that teachings from rotorcraft 100 may apply to aircraft other than rotorcraft, such as airplanes and unmanned aircraft, to name a few examples.
In the example of
Rotorcraft 100 also features at least one empennage 160. Empennage 160 represents a flight control surface coupled to the tail portion of fuselage 130. In the example of
In operation, according to one example embodiment, the control system of rotor system 110 may include a swashplate 112 in mechanical communication with blades 120.
Repositioning the swashplate 112 may change the pitch of each blade 120 collectively or cyclically so as to selectively control the direction, thrust, and lift of rotorcraft 100.
In some embodiments, one or more linear hydraulic actuators may be provided to reposition swashplate 112 during operation of the aircraft. In some tiltrotor aircraft, the swashplate actuators may have three times the stroke length of a conventional helicopter's swashplate actuator. In addition, the installation envelope for a tiltrotor swashplate actuator may be significantly more constrained as compared to the installation envelope for a conventional helicopter's swashplate actuator. Furthermore, such an actuator should be capable preventing small, uncontrolled actuator motions in the event of a flight control system failure.
Linear hydraulic actuators may have two primary types of piston/cylinder configurations: balanced and unbalanced.
Balanced hydraulic actuator 200 features a chamber 210, a piston 220, a piston rod 230, and a balance rod 240. Piston 220 is positioned within chamber 210 so as to divide chamber 210 into a retract chamber portion 210a and an extend chamber portion 210b. In operation, increasing hydraulic pressure in retract chamber portion 210a causes hydraulic fluid to apply a pressure against a retract piston surface 220a of piston 220, which causes piston 220 to move piston rod 230 in a retract direction. Likewise, increasing hydraulic pressure in extend chamber portion 210b causes hydraulic fluid to apply a pressure against an extend piston surface 220b of piston 220, which causes piston 220 to move piston rod 230 in an extend direction.
In the example balanced-piston configuration of
To minimize a linear hydraulic actuator's length, an “unbalanced piston” piston/cylinder configuration may be used. In the example of
In the example unbalanced-piston configuration of
For tiltrotor swashplate applications, the predominant load direction may place the actuator in tension, requiring the retract piston area to be under almost continuous pressure to control rotor loading. For piston-area sizing of a tiltrotor actuator, teachings of certain embodiments recognize that the retract area for the piston should be larger than the extend area to react the predominant load direction and minimize uncontrolled actuator motion in the event of a system failure. Using a balanced piston configuration, however, may result in an excessively long actuator, and using an unbalanced piston configuration may not provide the desired larger retract piston area or the necessary column stability.
Accordingly, teachings of certain embodiments recognize the capability to provide an improved piston area sizing for tiltrotor swashplate actuators by venting the conventional extend piston area to atmosphere.
In operation, increasing hydraulic pressure in retract chamber portion 410a causes hydraulic fluid to apply a pressure against a retract piston surface 420a of piston 420, which causes piston 420 to move piston rod 430 in a retract direction. Likewise, increasing hydraulic pressure in extend chamber portion 410b causes hydraulic fluid to apply a pressure against an extend piston surface 420c of piston 420, which causes piston 420 to move piston rod 430 in an extend direction. Piston rod 430 comprises an elongated conduit extending between and coupling surfaces 420a and 420c. Chamber 410 includes two ports 450a, 450b, separated by retract piston surface 420a. The port 450b is vented to atmosphere. Balance tube 440 includes two ports 450c, 450d. Port 450c is disposed within the elongated conduit of piston rod 430 and port 450d is disposed outside the elongated conduit of piston rod 430.
In this example embodiment, hydraulic pressure applied inside the balanced tube and piston rod may create an “inverted unbalanced” cylinder configuration where the extend piston area is smaller than the retract area, as seen in the example of
To improve the column stability of the actuator and provide system redundancy to manage flight control system failures, three inverted, unbalanced hydraulic actuators 400 may be jointed together in a triangular configuration, such as seen in the example of
For fly-by-wire applications, an electronic transducer may communicate the stroke position of the actuator to the flight control computers. Although transducers could be installed in the center of the balance rod or balance tube to provide protection from damage and minimize envelope, teachings of certain embodiments recognize that, because this internal volume may be used for the extend piston area, the transducers may be moved to the protected and unused envelope created at the center of the three joined cylinders.
Modifications, additions, or omissions may be made to the systems and apparatuses described herein without departing from the scope of the invention. The components of the systems and apparatuses may be integrated or separated. Moreover, the operations of the systems and apparatuses may be performed by more, fewer, or other components. The methods may include more, fewer, or other steps. Additionally, steps may be performed in any suitable order.
Although several embodiments have been illustrated and described in detail, it will be recognized that substitutions and alterations are possible without departing from the spirit and scope of the present invention, as defined by the appended claims.
To aid the Patent Office, and any readers of any patent issued on this application in interpreting the claims appended hereto, applicants wish to note that they do not intend any of the appended claims to invoke paragraph 6 of 35 U.S.C. § 112 as it exists on the date of filing hereof unless the words “means for” or “step for” are explicitly used in the particular claim.
Pursuant to 35 U.S.C. § 119 (e), this application claims priority to U.S. Provisional Patent Application Ser. No. 62/131,014, entitled COMPACT LINEAR HYDRAULIC ACTUATOR, filed Mar. 10, 2015. U.S. Provisional Patent Application Ser. No. 62/131,014 is hereby incorporated by reference.
Number | Name | Date | Kind |
---|---|---|---|
5400696 | Weber | Mar 1995 | A |
20060054016 | Davies | Mar 2006 | A1 |
20080015796 | Dlugosch | Jan 2008 | A1 |
20080168897 | Guay | Jul 2008 | A1 |
20090308243 | Tillaart | Dec 2009 | A1 |
20100084517 | Benson | Apr 2010 | A1 |
20120199699 | Isaac | Aug 2012 | A1 |
20120292456 | Hollimon | Nov 2012 | A1 |
20130119196 | Lindahl | May 2013 | A1 |
20130209252 | Dickman | Aug 2013 | A1 |
20130276516 | Tabor | Oct 2013 | A1 |
20140034779 | Fenny | Feb 2014 | A1 |
20140263854 | Ross | Sep 2014 | A1 |
20140263855 | Ross | Sep 2014 | A1 |
20150175259 | Foskey | Jun 2015 | A1 |
20150300908 | Laramee | Oct 2015 | A1 |
Number | Date | Country | |
---|---|---|---|
20160264239 A1 | Sep 2016 | US |
Number | Date | Country | |
---|---|---|---|
62131014 | Mar 2015 | US |