Patent Description:
Hydraulic actuators find many applications, particularly in controlling movement of a moveable component. In aircraft, many moveable components and surfaces are moved by means of a hydraulic actuator. In general terms, a hydraulic actuator comprises a cylindrical housing in which is mounted an axially moveable piston rod. A head of the rod, inside the housing, divides the housing into two chambers each having a fluid port via which pressurized fluid can be injected into the chamber or low-pressure fluid exits the chamber, so as to change the relative pressure in the two chambers either side of the piston head, thus causing movement of the piston relative to the housing. A free end of the piston rod that extends out of the housing is attached to a component or surface to be moved.

Hydraulic fluid is provided to the actuator, from a hydraulic fluid supply in fluid communication with the interior of the actuator housing via the ports in the housing, to cause the piston rod to extend out of the housing, or hydraulic fluid is withdrawn from the housing to cause the piston rod to retract back into the housing. The movement of the piston rod is determined by the direction or and pressure of the fluid applied to the actuator, which is in response to a control signal. As the piston rod moves relative to the housing, the moveable component or surface to which it is attached will move accordingly.

To allow both extension of the rod and retraction of the rod, a valve is provided to set the movement to extension or retraction. This may be a servovalve, more specifically an electrohydraulic servovalve (EHSV). The valve is positioned between the hydraulic fluid supply and the actuator and is moveable, in response to an electric control signal, between a first position in which high pressure fluid flows from the supply into one chamber of the actuator housing and low pressure fluid exits from the other chamber, and a second position in which high pressure fluid is injected into the other chamber and withdrawn from the first chamber of the actuator housing. The valve may also have a neutral or closed position in which fluid is neither supplied to nor withdrawn from the actuator housing. Hydraulic actuators are disclosed in <CIT>.

According to one aspect of the present invention, a hydraulic actuator system for an aircraft is provided as defined by claim <NUM>.

In embodiments, the system can also include an extend line fluidly connected to the second region and a retract line fluidly connected to the third region.

In embodiments, when in the second mode the second volume is fluidly connected to the extend line and the third volume is fluidly connected to the retract line.

In embodiments, the system can also include: a control element connectable to a high pressure source and a low pressure source. The control elemen is configured to selectively couple the high pressure source to the extend line to extend the piston and to the retract line to retract the piston.

In embodiments, the control element is configured to selectively couple the low pressure source to the extend line to retract the piston and to the retract line to extend the piston.

In embodiments, the control element is an electro-hydraulic servovalve.

In embodiments, further comprising an aircraft system, wherein the piston is configured to actuate a component of the aircraft system.

Also provided is a method of operating a actuator system onboard an aircraft as defined by claim <NUM>.

In embodiments, wherein when in the second mode, the piston moves at a second speed that is slower than the first speed.

The method can include connecting the piston to actuate a component of an aircraft system.

It should be understood, however, the following description and drawings are intended to be illustrative and explanatory in nature and non-limiting, and that the scope of the invention is defined by the claims.

The subject matter, which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:.

When designing an actuator and EHSV for a system the performance sizing factors are typically required slew rate, and load capabilities. Greater loads will require a piston diameter larger, and larger piston diameter require larger EHSVs to meet slew rate requirements, which typically come with high leakages, stability issues across large ranges of pressures, and increased envelope size.

If the max load conditions do not coincide with the fastest slew rate requirements there is an opportunity to tune the design for both faster slews where needed and greater loads where needed.

As will be described below, provided herein is an actuator that includes three piston heads. The heads include a large head and at least two smaller heads that are disposed on opposite sides of the large head. The small diameter heads allow for fast slew rates at lower force outputs with low flow and the larger diameter head allows for greater force output at a reduced slew rate with the same flow. With the inclusion of a mode selection element (e.g., a switching solenoid or EHSV) the actuator can operate thus operate in two different modes, a high speed mode and high power output mode.

Referring to <FIG> is a schematic illustration of an actuator system <NUM> in accordance with an embodiment of the present invention are shown. The actuator system <NUM> may be used onboard aircraft to perform an actuating operation of through actuation or movement of a piston <NUM> within a housing <NUM>. The combination of the housing and piston may be referred to as actuating element <NUM> that in combination with the mode selection device <NUM> can define an actuator herein.

The piston <NUM> includes multiple piston heads as more fully explained below. Regardless of the operation mode of the system, the piston <NUM> is configured to move either in the positive or negative direction (see arrows +/-) based on pressure on different sides of the piston heads. Based on configuration, force provided by the piston can be either direction A or direction B. The amount of force provided will depend at least in part on the mode of operation that the system is operating in.

The piston <NUM> includes a first piston head <NUM> that has a first diameter. The piston <NUM> also includes two smaller piston heads <NUM>, <NUM> that are disposed on opposing sides of the first piston head <NUM>. The smaller piston heads can be referred to as second and third piston heads <NUM>, <NUM> herein from time to time. The diameter of the first (or larger) piston head <NUM> is greater than both the diameter of the second and third piston heads <NUM>, <NUM>. The second and third piston heads <NUM>, <NUM> can have the same or substantially the same dimensions in one embodiment.

All piston heads <NUM>, <NUM>, <NUM> are shown as being connected to single shaft <NUM>. The shaft <NUM> can be connected to a movable element (not shown) such a flap or other aerodynamic surface of an aircraft and can cause it to move. It shall be understood that the shaft could be segmented one embodiment.

With additional reference now to <FIG>, the housing <NUM> is arranged and configured such that it defines three regions, R1, R2, R3. The regions R1, R2, R3 is cylindrical in shape. The R1, R2, R3 have respective diameters D1, D2 and D3. Of course, in other cases not encompassed by the claimed invention, the regions could be, for example, square/rectangular and D1, D2 and D3 could refer a side length or major axis. In such a case, rather than being round in shape, the piston heads could match the shape of the region. As illustrated, D1 is greater than D2 and D3. In one embodiment, D2 and D3 are the same or similar.

In operation, each region R1, R2 and R3 will have respective piston heads <NUM>, <NUM>, <NUM> disposed within them. As such, the piston heads <NUM>, <NUM>, <NUM> will also be sized such that are the same or approximately the same (to allow for some sliding) as the region in which it is located. Thus, piston heads <NUM>, <NUM>, <NUM> will have diameters of D1, D2 and D3, respectively, in the case according to the claimed invention where each region is cylindrical. The skilled artisan should understand the relationship between D1, D2 and D3 as applied to the regions R1, R2, R3 and the piston heads <NUM>, <NUM>, <NUM> and may apply flanges or other elements around the piston heads so the actuating element <NUM> operates as intended and fluid cannot easily pass around each piston head <NUM>, <NUM>, <NUM>.

The housing <NUM> has a first end <NUM> and a second end <NUM>. As shown in <FIG> and <FIG>, the second piston head <NUM> defines a movable volume V1 between it and the first end <NUM>. A second volume V2 is defined within housing <NUM> and is between the second piston head <NUM> and the first piston head <NUM>. A third volume V3 is defined within housing <NUM> and is between the third piston head <NUM> and the first piston head <NUM>. As the piston <NUM> moves, V2 can be formed within both R1 and R2 and V3 can be formed within in both R2 and R3 to varying degrees. The third piston head <NUM> similar defines a movable volume V4 between it and the second end <NUM>.

The housing <NUM> also includes multiple input/output ports. These ports allow for fluid to be provided into the housing from, for example, high and low pressure lines. Herein, the second region R2 and the third region R3 include, respectively, ports PR2 and PR3. The housing <NUM> also includes two additional ports that are arranged such they can be in fluid communication with the first region R1. As shown, these ports PR1-<NUM> and PR1-<NUM> are directly connected to the first region R1. However, the exact location can be moved as long as the ports PR1-<NUM> and PR1-<NUM> provide fluid on opposing sides of the first piston head <NUM> and between the second and third piston heads <NUM>, <NUM>. Thus, the ports PR1-<NUM> and PR1-<NUM> could alternatively be, for example, located where the X's are shown in <FIG>.

In a typical actuator system, the piston would have a single piston head that divides the housing into a retract chamber and an extend chamber on opposite sides of a piston head. These chambers are connected to high and low pressure fluid sources by an EHSV.

As shown in <FIG>, the system <NUM> includes a control element <NUM> (e.g. EHSV) that is operably connected to a high pressure line <NUM> and a low pressure line <NUM> for the purpose of controlling the amount or level of pressure in the chambers/volumes defined in the housing <NUM> by the piston heads <NUM>, <NUM> and <NUM>. The control element <NUM> is connected to extend supply line <NUM> and retract supply line <NUM> and can selectively connect high pressure line <NUM> and low pressure line <NUM> to them.

To move the piston <NUM> to right in the example of <FIG>, high pressure line <NUM> is connected to extend supply line <NUM> and low pressure line <NUM> is connected to retract pressure line <NUM>. To move the piston to the left in the example of <FIG>, high pressure line <NUM> is connected to retract supply line <NUM> and low pressure line <NUM> is connected to the extend supply line <NUM>. In this manner, the control element <NUM> can cause translational movement of the piston <NUM> relative to the housing <NUM> and thus control an extension or retraction of the shaft <NUM>.

As shown in <FIG>, the system <NUM> is configured in a first mode. In the first mode, the mode selection device <NUM> is in a first position. In this position, the mode selection device fluidly connects the ports PR1-<NUM> and PR1-<NUM>. As such, as the piston <NUM> moves fluid from V3 can move into V2 and vice versa. In general, the connection via the mode selection device <NUM> results balanced pressure on opposing sides of the first piston head <NUM>, and, in essence, removes the first piston head <NUM> from having an appreciable affect on the operation of the actuating element.

Herein, each mode will have different retract and extend chambers. For example, in a first mode shown in <FIG>, the extend chamber is the movable volume V1 between defined between the first head <NUM> and the first end <NUM>. In this mode, the retract chamber is movable volume V4 defined between the third piston head <NUM> and the second end <NUM>. In such a case, to move in the positive direction (+) the extend chamber (V1) is fluidly connected via the extend supply line <NUM> to the high pressure line <NUM> and the retract chamber V4 is fluidly connected by the retract supply line <NUM> to the low pressure line <NUM>. Alternatively, to move in the retract direction, the extend chamber (V1) is fluidly connected via the extend supply line <NUM> to the low pressure line <NUM> and the retract chamber V4 is fluidly connected by the retract supply line <NUM> to the high pressure line <NUM>. This selection can be done by the control element <NUM> in a known manner. For example, the control element <NUM> is configured to control the amount of pressure in each of the retract chamber V4 and the extend chamber V1 to cause translational movement of the piston heads <NUM>, <NUM> relative to the housing <NUM> and thus control an extension or retraction of the piston <NUM>.

Relative to the second mode discussed below, the first mode can be low load - high speed mode. In the following discussion, certain shorthand notations are made. First, the second and third pistons <NUM>, <NUM> can have equal areas and that area can be referred to as A. Further, in the below certain forces are described. Those magnitude of that force will be equal to a pressure within a certain volume multiplied by a piston head area exposed to that pressure. Thus, the pressure move in the + positive direction created by the first piston head is equal to the pressure in V1 times area A. The third piston <NUM> (and the opposite side of the first piston <NUM>) even if D2=D3, does not, however, present and area A. Rather, it presents a smaller area (B) that is A minus the size of the shaft <NUM>. Similarly, the first piston <NUM> presents area C which is D1 minus the size of the shaft <NUM>.

Consider the case where an extension (e.g., motion in the positive direction is desired). In the first mode, the pressure in V1 is equal to the pressure in the high pressure line <NUM> (denoted as PC1 below) and the pressure in V4 is equal the pressure in the low pressure line <NUM> (denoted PC2) below. In the below, the pressure in volumes V2 and V3 are indicated as PV2 and PV3, respectively.

The force produced by the piston in such a state is: <MAT>.

In the above: A*PC1 is the force in the + direction due to pressure in V1 times area A (the positive contribution due to the second piston <NUM>); C*PV2 is the force in the + direction due to pressure in V2 times area C (the positive contribution due to the first piston <NUM>); B*PV3 is the force in the + direction due to pressure in V3 times area B acting (the positive contribution due to the third piston <NUM>). Similarly, - B*V2 is the force in the - direction due to pressure in V2 times area B (the negative contribution due to the second piston <NUM> acting again pressure P2); -C*PV3 is the force in the - direction due to pressure in V3 times area C (the negative contribution due to the first piston <NUM>); and -B*PC2 is the force in the - direction due to pressure in V4 (PC2) times area B acting (the negative contribution due to the third piston <NUM> compressing V4).

Given that PV2= PV3, certain terms can be eliminated as indicated below: <MAT> such that force reduces t:o <MAT>.

Such a force is in-line with single piston solenoid where the piston has area A.

The system <NUM> can also operate in a second mode. In this mode, the mode selector <NUM> is set so that it joins V2 to extend line <NUM> and V3 to retract line <NUM> as shown in <FIG>. This, in effect, "joins" V1 with V2 and V3 with V4. In this configuration, the force produced is basically due to the difference in pressure between the high and low pressure lines <NUM>, <NUM>. In more detail, and with the same nomenclature as above.

Noting that as configured, PV2= PC1 and PV3=PC2, equation <NUM> can be reduced to: <MAT>.

As C is larger that A/B it shall be understood that in this configuration more force can be generated than in the first mode.

Based on the above description it shall be understood that a single system can be provided that have two different operational characteristics. In particular, by proving the position <NUM> with multiple (<NUM>, <NUM>, <NUM>) of different sizes the mode switching element <NUM> configured to switch pressures sources between the heads/volumes allows for the system to control the force output and slew rate capabilities of the system. In particular, in the first mode the small diameter heads on the outside (heads <NUM>, <NUM>) control and allow for fast slew rates at lower force outputs with low flow. Conversely, when in the second mode the larger diameter head (<NUM>) controls and allows for greater force output at a reduced slew rate with the same flow. Further, adding a second diameter inside allows for effective gearing of the hydraulic system.

Based on the above, it shall be understood that also disclosed is method. The method can include operating the above system in both the first and second modes. When in the first mode, the piston moves at a first speed and first force and when in the second mode, the piston with a second force that is greater than the first force. In the second mode, the piston can move at a second speed that is slower than the first speed.

<FIG> illustrates an example of an aircraft <NUM> on which various embodiments can be implemented. The illustrated aircraft includes aircraft engines surrounded by (or otherwise carried in) nacelles <NUM>. The aircraft <NUM> includes wings <NUM> that extend from an aircraft fuselage <NUM>. Each wing <NUM> may include one or more slats <NUM> on a forward edge or leading edge and one or more flaps <NUM> on an aft, rear, or trailing edge thereof. The wings <NUM> may also include ailerons <NUM> on the trailing edges, as will be appreciated by those of skill in the art. The aircraft <NUM>, as shown, includes a tail structure <NUM> which can include various flaps, ailerons, slats, and the like, as will be appreciated by those of skill in the art. The flaps, slats, ailerons, and the like are generally referred to herein as "aerostructures" or "aerodynamic structures" as they are movable under aircraft power systems and are configured to control flight and motion of the aircraft <NUM>. An actuator system <NUM> disclosed herein may be connected to one or more of the aerostructures and is illustrated by way of example, by reference numeral <NUM>. For example, each wing <NUM> and the tail structure <NUM> may include one or more aerostructure actuator systems <NUM>. The aerostructure actuator systems <NUM> may be operably connected to the various aerostructures and configured control the operation/position of the aerostructures to control flight of the aircraft <NUM>.

Further, the engines of the aircraft <NUM> may include various actuators and control mechanisms that can incorporate one or more actuator systems such as shown and described above with respect to <FIG>. As such, the described actuator systems of the present invention may be incorporated into aircraft engine systems and/or aircraft flight systems. It will be appreciated that such actuator systems as described herein may be used for other purposes onboard aircraft, such as for actuating doors, landing gear, or the like.

The terms "about" and "substantially" are intended to include the degree of error associated with measurement of the particular quantity based upon the equipment available at the time of filing the application.

Additionally, the term "exemplary" is used herein to mean "serving as an example, instance or illustration. " Any embodiment or design described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments or designs. The terms "at least one" and "one or more" are understood to include any integer number greater than or equal to one, i.e., one, two, three, four, etc. The term "a plurality" is understood to include any integer number greater than or equal to two, i.e., two, three, four, five, etc. The term "connection" can include an indirect "connection" and a direct "connection".

Claim 1:
A hydraulic actuator system for an aircraft, the actuator system comprising:
a hydraulic actuator having a housing (<NUM>) with a piston (<NUM>) having a piston shaft (<NUM>) arranged within the housing,
wherein the housing is formed to have first, second and third regions (R1, R2, R3), wherein the first, second and third regions are cylindrical, wherein the first region has a first diameter and second region and third regions have a second diameter that is smaller than the first diameter, wherein the first region is between the second and third regions and has a larger diameter than the second and third regions;
first, second, and third piston heads (<NUM>, <NUM>, <NUM>) connected to the piston shaft with the first piston head being between the second and third piston heads, wherein the first piston head is within the first region and divides the first region into a second (V2) and third (V3) volumes, the second piston head is in the second region and defines a first volume (V1) and the third piston head is in the third region and defines a fourth volume (V4); and
a mode selection device (<NUM>) operably connected to the first, second, third and fourth volume;
wherein in a first mode the mode selection device connects the second volume to the third volume and characterised in that in a second mode the mode selection device connects the first volume to the second volume and connects the third volume to the fourth volume.