GB2446441A

GB2446441A - Dual cylinder Actuator Arrangement for aeroengine nozzle and reverser

Info

Publication number: GB2446441A
Application number: GB0702195A
Authority: GB
Inventors: Tony Jones; Neil Davies; John Herbert Harvey; Mark Hubberstey; Mark Anthony Guy; Brett Wharton; Peter Bacon
Original assignee: Goodrich Actuation Systems Ltd
Current assignee: Goodrich Actuation Systems Ltd
Priority date: 2007-02-06
Filing date: 2007-02-06
Publication date: 2008-08-13
Also published as: GB0702195D0

Abstract

An actuator arrangement comprises a first piston 12 reciprocable within first cylinder 10 and includes a first rod 14 protruding from the first cylinder 10. A second piston 24 is reciprocable within a second cylinder 22 and includes a second rod 34 protruding from the second cylinder 22. The second cylinder 22 is carried by the first piston 12. Also described is an arrangement including a failsafe port in the second cylinder for exposure to return pressure which is obscurable by the second piston 24 whereby the actuator can be held in a failsafe condition when supply pressure is applied to second piston control ports 30. An arrangement for locking the first and second rods together when the second is extended comprises a ramped plunger 80 forcing balls 90 into recesses 94 under first piston extension pressure. The second piston drives a variable air fan nozzle (VAFN) and the first piston drives a thrust reversing cowl in an aircraft engine.

Description

I

Actuator Arrangement This invention relates to an actuator arrangement, and in particular to an arrangement suitable for use in controlling the variable air fan nozzle (VAFN) cowls and thrust reverser cowls of an aircraft engine.

It is known to provide an aircraft engine with a series of movable cowls, the positions of which can be adjusted, using appropriate actuators, to vary the nozzle dimension of the engine to suit the operating conditions of the engine. The nozzle dimension is the size of the exit throat defined between the exit end of the fan cowl and the core engine housing. It has been found to be advantageous for the nozzle dimension to be relatively large during the take-off and climb phases of the engine operation, and to be of reduced dimensions during cruise conditions. During descent, the nozzle dimension is often increased in case it is necessary to abort landing, and so enter another climb phase.

The thrust reverser system may also include a series of cowls movable between a stowed position and a deployed, operative position.

Typically, separate actuators are provided to drive the VAFN cowls and the thrust reverser cowls. The actuators may comprise, for example hydraulic actuators or electrically driven ball-screw type linear actuators. US 5806302 describes a system in which the actuators used to driye the VAFN cowls are anchored to the actuators used to operate the thrust reverser system so that, upon extension of the thrust reverser actuators to deploy the thrust reverser system, the VAFN cowls are automatically moved to increase the nozzle dimension. Controlling the operation of the VAFN actuator in such an arrangement is difficult as the control arrangement has to be able to accommodate movement of the thrust reverser cowls. US 5778659 describes an arrangement in which separate actuators for the two sets of cowls are provided, both actuators being grounded to the airframe structure. Such an arrangement results in the VAFN actuator having to be of very large stroke which has significant cost, power and weight implications.

US 5655360 uses a single actuator to control both the nozzle dimension and the thrust reverser. A first part of the actuator's stroke adjusts the nozzle dimension, further movement driving the thrust reverser to its deployed position. As this arrangement would require the thrust reverser actuator locks to be released when the thrust reverser is not to be deployed, this arrangement may be unsuitable for use in some applications.

It is an object of the invention to provide an actuator arrangement for use in such applications of simple and convenient form.

According to a first aspect of the invention there is provided an actuator arrangement comprising a first piston reciprocable within a first cylinder, the first piston including a first drive rod protruding from the first cylinder, a second piston reciprocable within a second cylinder, the second piston including a second drive rod protruding from the second cylinder, wherein the second cylinder is carried by the first piston.

The second cylinder conveniently encircles part of the first drive rod and is preferably located within the first cylinder.

Preferably the first cylinder defines flow ports which register with control ports provided in the second cylinder when the first piston occupies a predetermined position.

The second cylinder is preferably provided with first and second control ports and a failsafe port In a failsafe operating mode, the first and second control ports are conveniently supplied with fluid at high pressure, and the failsafe port is connected to low pressure. In this operating mode, the second piston is urged towards a position in which it closes the failsafe port, thus a failsafe mode position of the second piston is defined by the location of the failsafe port.

Preferably, the first drive rod is connected to the thrust reverser cowl of an aircraft engine, and the second drive rod is connected to the VAFN cowl of the engine.

Alternatively, the second drive rod may be located within or partially within the first drive rod. A synchronising arrangement may be provided having an output arranged to rotate in the event of movement at least one of the drive rods. A lock mechanism may be provided to permit locking together of the drive rods. The lock mechanism may include a locking piston having a ramped surfce cooperable with one or more balls or other lock components such that movement of the locking piston drives the balls or other lock components from a retracted, unlocked position to a radially extended, locked position.

According to another aspect of the invention there is provided a VAFN actuator arrangement comprising a piston movable within a cylinder, the cylinder being provided with first and second control ports and a failsafe port obscurable by the piston in a failsafe operating mode whereby a VAFN cowl moved, in use, by the actuator arrangement is held in a failsafe position in the failsafe operating mode.

The invention will further be described, by way of example, with reference to the accompanying drawings, in which: Figures 1 and 2 are sectional views illustrating an actuator arrangement in accordance with an embodiment of the invention; Figure 3 is an enlargement of part of Figure 1; Figure 4 illustrates a control arrangement for the actuator arrangement; and Figure 5 illustrates an alternative embodiment of the invention.

Referring firstly to Figures 1 to 3 there is illustrated an actuator arrangement comprising a first, outer, cylinder 10 in which a first piston 12 is reciprocable.

Connected to the first piston 12 is a first drive rod 14 which projects from an end of the first cylinder 10. The first piston 12 divides the interior of the first cylinder 10 into first and second chambers 16, 18 which can be connected to sources of fluid under supply or return pressure by a control valve arrangement 20 which will be described subsequently with reference to Figure 4. In use, the first chamber 16 is connected, constantly, to the supply pressure, and the control valve arrangement 20 controls whether the second chamber 18 is connected to return pressure or supply pressure. When the second chamber is connected to return pressure, the first piston 12 and drive rod 14 are held in a stowed position, the drive rod 14 being moved to a deployed position upon the application of supply pressure to the second chamber 18, due to the differential areas of the first piston 12 exposed to supply pressure within the first and second chambers 16, 18.

The first piston 12 carries a second cylinder housing 22 which encircles the first drive rod 14. Within the second cylinder housing 22 is located a second piston 24, dividing the second cylinder housing 22 into first and second chambers 26, 28 which communicate with respective control ports 30. With the first piston 12 in the stowed position, the control ports 30 register with respective flow ports 32 provided in the first cylinder 10.

The second piston 24 is connected to a second drive rod 34 which projects from the second cylinder housing 22, through the first cylinder 10 and from an end thereof, the second drive rod 34 encircling the first drive rod 14.

In use, the actuator arrangement is mounted with the first cylinder 10 secured to the aircraft's airframe, with the first drive rod 14 connected to the thrust reverser cowl and with the second drive rod 34 connected to the VAFN cowl to be moved using the actuator arrangement The actuator arrangement includes a conventional Acme screw synchronisation arrangement 36 so that operation of the actuator arrangement to deploy a thrust reverser cowl is synchronised to the operation of other actuator arrangements to synchronise the movement of all of the thrust reverser cowls.

When it is desired to move the VAFN cowl, supply pressure is applied to the second chamber 28 of the second cylinder whilst return pressure is applied to the first chamber 26 thereof; resulting in the second piston 24 and second drive rod 34 moving from their retracted positions, as shown, to their extended posilions moving the associated VAFN cowl to modify the nozzle dimension to a desired size. Return movement is achieved by reversing the pressure connections to the chambers 26,28.

Movement of the second drive rods 34 and/or the VAFN cowls may be sensed by appropriate sensors, for example linear variable differential transformers (LVDTs) and the position information used by the control unit of the system in controlling the operation thereof.

To deploy the thrust reverser, as discussed hereinbefore, supply pressure is applied to both of the first and second chambers 16, 18. As movement of the first piston 12 commences, the control ports 30 of the second cylinder housing 22 move out of communication with the respective flow ports 32, thus locking the second piston 24 against movement relative to the second cylinder. Return movement is achieved by connecting the second chamber 18 to return pressure During deployment of the thrust reverser, supply pressure is applied to the flow ports 32 so as to ensure that the movement of the second cylinder 22 and consequent movement of the control ports 30 out of register with the flow ports 32 and into communication with the first and second chambers 16, 18 does not interfere with the deployment of the thrust reverser.

Appropriate sensors, for example linear variable differential transformers (LVDTs) may be used to sense the positions of the drive rod 14 and/or components of the thrust reverser system to allow monitoring of the operation thereof. Alternatively, the operation of the synchronisation arrangement 36 may be used to provide this information. !n either case, the position information may be fed back to the control unit used to control the operation of the system.

The actuator arrangement includes a failsafe arrangement whereby, in the event of a loss of control of the second piston, the VAFN cowl will be moved to an intermediate, failsafe position which, although not optimum, gives an adequate nozzle dimension for all engine operating conditions. The failsafe arrangement is provided by a failsafe port 38 provided in the second cylinder 22 which communicates with a failsafe feed port 40 provided in the first cylinder 10. In the event that a fault is sensed, and the hydraulic system is still operating, then supply pressure is applied to both control ports 30, and the failsafe port 38 is connected to return pressure. As a consequence, the second piston 24 is urged towards a position in which it obscures the failsafe port 38 as, if the second piston 24 is to the left of the failsafe port 38, the first chamber 26 will be at lower pressure whilst the second chamber 28 is at supply pressure, urging the second piston 24 to the right, and vice versa.

Figure 4, illustrates, diagrammatically, a control valve arrangement 20 suitable for use with the actuator arrangement of Figures 1 to 3. The control valve arrangement comprises a series of VAFN control units 50 (one per actuator) and a single thrust reverser control unit 52, all operable under the control of the full authority digital engine controller (FADEC) 53. The VAFN control units 50 each comprise a servo valve 54 which controls whether feed lines 56, 58 are isolated or connected to supply or return pressure, and a mode valve 60 operable to control whether the second piston 24 operates in its failsafe mode (as shown) or in its normal operating mode. With the mode valve 60 in its normal operating position, it will be appreciated that the servo valve 54 controls which of the first and second chambers 26,28 is exposed to supply pressure and which is at return pressure, thus the servo valve 54 controls the VAFN nozzle dimension. In this position of the mode valve 60, the failsafe port 38 is not connected to either supply or return pressure but rather is closed.

The thrust reverser control unit 52 comprises a VAFN mode valve 62 operable to control the position of the mode valve 60, a thrust reverser isolation valve 64 and a thrust reverser control valve 66. In normal use, the VAFN mode valve 62 is energised and so occupies the opposite position to that shown. This results in return pressure being applied to one end of the mode valve 60 and as a consequence the mode valve 60 occupies its normal operating position (opposite to that shown) and VAFN actuation control is as outlined above with control of the VAFN actuator position being achieved through operation of the servo valve 54. To deploy the thrust reverser, the isolation valve 64 is energised and moves to its opposite position from that shown. The control valve 66 is then used to control deployment of the thrust reverser. The operation of the isolation valve 64 also results in supply pressure being applied to an end of the mode valve 60, moving it to the position illustrated. In this position, supply pressure is applied to both feed ports 32 and the failsafe feed port 40 which is advantageous for the reasons set out hereinbefore.

If it is desired to move the VAFN actuator into its failsafe mode, then the VAFN mode valve 62 is de-energised and moves to the position shown which, in turn, drives the mode valve 60 to the position illustrated. In this position, supply pressure is applied tobothfeedports32whilstthefhilsafe feedport40isconnected,viathethrustreverser isolation valve 64, to return pressure. As described hereinbefore, this results in the second piston 24 moving towards a position in which it obscures the failsafe port 38, and hence in the VAFN cowl being moved to its failsafe position.

In the event of a power failure, the various valves move to the positions illustrated. External forces will tend to extend the VAFN cowl, causing movement of the second piston. A non-return valve 70 serves to ensure that, once the second piston has reached a position in which it obscures the thilsafe port 38, further movement of the second piston 24, and the VAFN cowl, is prevented by a hydraulic lock being fonned.

It will be appreciated that Figure 4 simply illustrates one convenient control valve arrangement and that other valve arrangements could be used. Further, a wide range of modifications and alterations may be made to the actuator arrangement without departing from the scope of the invention.

Figure 5 shows an actuator arrangement which, in many respects, is similar to that of Figures 1 to 3, and like reference numerals will be used to denote like or similar parts. One significant difference between the arrangement of Figure 5 and that of Figures 1 to 3 is that in Figure 5 the first drive rod 14 encircles the second drive rod 34, thus the synchronisation arrangement 36 directly mechanically synchronises the second drive rods 34 which, in use, drive the VAFN cowls, and indirectly synchronizes the first drive rods 14 (as described below) which, in use, drive the thrust reverser cowls of the system.

Mother significant difference is that, within the second drive rod 34 is located a locking piston 80 having a first end of diameter A' exposed to the fluid pressure within the control chamber 18 and a second end of a smaller diameter a' exposed to the pressure within a vented chamber 82. A spring 84 urges the piston 80 to the left in the orientation illustrated. The piston 80, intermediate its ends, includes a reduced diameter region defined, in part, by a ramped surface 86 and by a detent groove 88. The second drive rod 34 is formed with openings 90 within which are located balls 92. With the piston 80 in the position illustrated, the balls 92 do not protrude from the openings 90 externally of the second drive rod 34. However, when the second drive rod 34 occupies its right hand most extreme position relative to the first drive rod 14, movement of the piston 80 causes the balls 92 to ride up the ramped surface 86 to project into pockets 94 provided in the first drive rod 14, pushing components 96 further into the pockets 94 against the action of detent springs 98. Once the piston 80 readies its right hand most position, the balls 92 sit in the detent groove 88, resisting return movement of the piston

FL

80. It will be appreciated that in this condition, the first and second drive rods 14, 34 are locked to one another.

In normal use, to adjust the positions of the VAFN cowls, the pressures applied to the control ports 30 are controlled to move the second piston 24, and hence the second drive rod 34 and VAFN cowls to the desired position. Movement of the second dnve rod 34 is transmitted to the synchronisation arrangement 36 thereby synchronising the operation of several actuators and, if desired, permitting sensing of movement During this mode of operation, the first drive rod 14 is held against movement by having high pressure applied to the control chamber 16 and low pressure applied to the control chamber 18, and also by a conventional line lock arrangement 100.

As with the arrangement described hereinbefore with reference to Figures 1 to 3, the VAFN cowls can be moved to an intermediate, failsafe position by applying high pressure to both control ports 30 whilst failsafe port 38 is connected to low pressure.

To deploy the thrust reverser, the VAFN cowls are first moved to their extended positions, thus aligning openin 90 with pockets 94. High pressure is applied to the control chamber 18, and the tine lock arrangement 100 is released. As described hereinbefore with reference to Figures 1 to 3, the differential area of the first piston 12 results in the first piston 12, fIrst drive rod 14, and hence the thrust reverser cowls moving towards their deployed positions. The applied pressure will also simultaneously, drive the locking piston 80 to its right band most position, forcing the balls 92 outwards thereby locking the first and second drive rods 14, 34 to one another with the result that movement of the first drive rod 14 causes movement of the second drive rod 34 which is transmitted to the synchronisation arrangement 36.

Thrust reverser actuation is thus synchronised and, if desired, can be sensed.

The thrust reverser cowls can be stowed by applying low pressure to the control chamber 18, thus driving the first drive rod 14 to the position shown. Once this position has been reached, the lock piston 80 can be returned to the position shown by applying high pressure to the control chamber 26 which communicates via a passage 102 (shown in exaggerated form in FigureS) between the first and second drive rods 14, 34 and the openings 90, with the reduced diameter part of the piston 80. The differential area of the piston 80 due to the difference in diameters (A-a), in combination with the action of the spring 84, is sufficient to lift the balls 92 out of the detent groove 88 against the action of the springs 98, thereby allowing the piston 80 to return to the position shown and, subsequently, allowing the second drive rod 34 to return to the position shown.

It will be appreciated that there are a number of possible other arrangements which also fall within the scope of the invention.

Claims

1. An actuator arrangement comprising a first piston reciprocable within a first cylinder, the first piston including a first drive rod protruding from the first cylinder, a second piston reciprocable within a second cylinder, the second piston including a second drive rod protruding from the second cylinder, wherein the second cylinder is carried by the first piston.

2. A VAFN actuator arrangement comprising a piston movable within a cylinder, the cylinder being provided with first and second control ports and a failsafe port obscurable by the piston in a failsafe operating mode whereby a VAFN cowl moved, in use, by the actuator arrangement is held in a failsafe position in the failsafe operating mode.

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3. An actuator arrangement substantially as hereinbefore described with reference *. 15 totheaccompanyingdrawings