GB2116129A

GB2116129A - Anti-rotation lock

Info

Publication number: GB2116129A
Application number: GB08206665A
Authority: GB
Inventors: Horace Poole
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 1982-03-06
Filing date: 1982-03-06
Publication date: 1983-09-21

Abstract

In a gas turbine engine thrust reverser of the kind where one cowl portion separates axially from another to create a gap it is possible for air loads in the cowl inner and outer surfaces, to move the cowl portion to open the gap, at times other than those when the gap is required. The most likely time for this to happen is if connection is lost between the actuation motor and ballscrew (24). The pull of the cowl portion on the ball screw (24) is sufficient to rotate it. Three gears (36, 38, 40) are arranged, one to be driven by the ball screw (24) the other two freely rotatable and all engageable to create opposing loads and so lock the ballscrew (24) against rotation. Locking engagement may be brought about by a solenoid actuator (46). <IMAGE>

Description

SPECIFICATION Anti-rotation leck This invention relates to a device whereby apparratus which is required to rotate whilst operating, is prevented from rotating when inoperative.

The invention has wide application, and is particu larly useful when used on a gas turbine jet propulsion engine which is provided with thrust reversing apparatus which has rotating parts.

According to the present invention, a gas turbine engine includes a thrust reversing apparatus comprising fixed and movable cowl portions, a screw mechanism in one cowl portion, a nut mechanism in and fixed to the other cowl portion, and in which the screw mechanism engages, drive means connected to rotate the screw mechanism in the nut mechanism and so bring about relative movement of the cowl portions towards and away from each other, a first toothed wheel connected for co-rotating with the screw mechanism and second and third freely rotatable toothed wheels which are meshablewith thefirsttoothedwheel and with each other and means for moving at least one of the second and third toothed wheels to cause interengagement between all the said wheels, the arrangement being such that when all three toothed wheels are in mesh, rotating of any is prevented by their interengagement.

Preferably, either the second orthird toothed wheel is in permanent mesh with the firsttoothed wheel and the other of the second orthird toothed wheels is rollable around one toothed wheel into and out of mesh with the first toothed wheel.

Alternatively, both second and third toothed wheels are in permanent mesh with thefirsttoothed wheel, and are rollable around the firsttoothed wheel into and out of mesh with each other.

The invention will now be described, by way of example and with reference to the accompanying drawings in which: Fig. lisa diagrammatic partview of a gas turbine engine including a thrust reverser which incorporates and embodiment of the invention.

Fig. 2 is an enlarged partviewon line 2-2 offig. 1.

Fig. 3 is an alternative embodiment of the invention.

Fig. 4 is afurther embodiment ofthe invention.

Referring to fig. 1. Agas turbine engine 10 includes aductedfan 12. The duct 13 is defined by a core engine 14 and a cowl 16.

Cowl 16 informed from an upstream fixed portion 18 and a downstream movable portion 20.

A motor 22 which may be operated electrically, hydraulically or pneumatically, is fixed within cowl portion 16 and a ball screw 24 is connected to motor 22 for rotation. Ball screw 24 projectsfrom motor22 into the movable downstream cowl portion 20, and through a ball nut26which is fixed in cowl portion 20.

Actuation of motor 22 rotates ball screw 24 and the resulting reaction between the ball screw 24 and ball nut 26, causes cowl portion 20 to move eithertowards or away from cowl portion 18. A gap 30 is thus opened or closed, which in turn enables or prevents a reversal of flow of fluid from duct 13.

Duringtalceoffand cruiseof an aircraftwhich normally is propelled by a gas turbine engine 10, itis of vital importance, that cowl portions 18 and 20 should not separate. In orderto ensure that such an event does not occur, an array 32 oftoothed wheels is provided and will now be described with reference to fig. 2.

In fig. 2 a bulkhead 34 supports the walls of cowl portion 18. The ball screw 24 protrudes through the bulkhead 34 and a first toothed wheel 36 is affixed to ball screw 24 for co-rotating.

Asecond toothed wheel 38 is mounted on bulkhead 34, and permanently in mesh with first wheel 36 so as to be rotated by wheel 36. Athird toothed wheels 40 is supported in meshing engagement with second wheel 38, by a yoke 42, one end ofwhich is pivotable aboutthe axis of rotation of second wheel 38.

A rod 44 is connected via one end to that end of yoke 42 which supports third wheel 40. The other end of rod 44 is connected to the core of a solenoid 46, which in turn is fixed to bulkhead 34.

In operation, when thrust reversal is required, solenoid 46 is activated so as to pivot yoke 42 in a clockwise direction as viewed in figure 2. The third toothed wheel 40 isthus rolled out of engagement with thefirsttoothed wheel 36, around the second toothed wheel 38, to the position shown in chain dotted lines. First toothed wheel 36 can then be rotated by the action of motor 22 (fig. 1) rotating ball screw 24, and so bring about translation of cowl portion 20 in a downstream direction,to open gap 30.

When thurst reversal is no longer required, motor 22 is actuated so as to rotate ball screw 24 in a reverse direction and thus cause cowl portion 20to translate in an upstream direction. On total closure of gap 30, rotation ceases and solenoid 46 is activated so as to roll third toothed wheel 40 into mesh with first toothed wheel 36so as to lock it against further, undesirable rotation. The locking effect is achieved by the teeth of toothed wheels 38 and 40 being moved in opposite directions and so forced against each other, in the eventthatfor any reason beyond the control of the operator, toothed wheel 36 is rotated at the wrong time.

It is important that the first toothed wheel 36 has stopped rotating, before the third toothed wheel 40 mesheswith it. Although no means are shown by which this may be achieved, one example of how to achieve the object would be to use a limit switch, which is situated for engagement by cowl portion 20 and would be actuated byfinal closure of gap 30 and electrically connected to activate solenoid 46. A limit switch override device would also be needed and could be connected between the limit switch and reverse thrust selection apparatus, for operation by the latter. When reverse thrust is selected, the effects of the limit switch would be cancelled and solenoid 46 would be activated so that its would pull third toothed wheel 40 out of mesh with first toothed wheel 36.

Referring now to figure 3. In this embodiment of the invention, second and third toothed wheels 38 and 40 are maintained in mesh with first toothed wheel 36, but spaced from each other. When toothed wheel 36 is required to be locked against rotation, solenoid 46 is activated so asto roll both second and third toothed wheels 38 and 40 around first toothed wheel 36, into engagement with each other.

In the embodiment depicted in figure 3, second and third toothed wheels 38 and 40 are maintained in mesh with each other and are displaceable bodily, in a direction axially of ball screw 24, into and out of mesh with first toothed gear 36.

Referring to fig. 4. Screw 24 is driven via a gearbox 50, and a flexible cable 52. In this arrangement, the toothed wheel 36 is fixed to a shaft 54 along with input gear 56. Toothed wheel 38 is in mesh with toothed wheel 36 and is mounted for rotation on wall 58.

Toothed wheel 40 is rollable around toothed wheel 36, into mesh with toothed wheel 38.

Claims

1. A gas turbine engine including thrust reversing apparatus comprising fixed and movable cowl portions, a screw mechanism in one cowl portion, a nut mechanism in and fixed to the other cowl portion and in which the screw mechanism engages. drive means connected to rotate the screw mechanism in the nut mechanism and so bring about relative movement of the cowl portions towards and away from each other, a firsttoothed wheel connected for co-rotating with the screw mechanism and second and third freely rotatable toothed wheels which are meshable with theflrsttoothed wheel and with each other and meansformoving afleastone ofthe second and third toothed wheels to cause interengagement between all the said wheels, the arrangement being such that when all three toothed wheels are in mesh, rotation is prevented by their interengagement.

2. A gas turbine engine as claimed in claim 1 wherein said drive means comprises a motor driven flexible cable connected to an input gear, an output gear in mesh with said input gearand fixed to said screw mechanism and a shaft on which said input gear and first toothed wheel are fixed for co-rotation.

3. A gas turbine engine as claimed in claims 1 wherein said drive means comprises a motor directly connected to an end of said screw mechanism and said first toothed wheel is fixed to said screw mechanism for co-axial, co-rotation.

4. Agasturbine engine asclaimed in claim 1 or claim 2 wherein eitherthe second or third toothed wheel is in permanent mesh with the first toothed wheel and the remaining toothed wheel is in mesh with and rollable around the second orthird toothed wheel, into mesh with thefirsttoothed wheel.

5. A gas turbine engine as claimed in claim 1 or claim 2wherein the second and third toothed wheels are permanent mesh with the firsttoothed wheel and rollable around thefirsttoothed wheel, into and out of mesh with each other.

6. Agasturbineengineincludingthrustreversing apparatus substantially as described in this specifica tion with reference to figs. 1 and 2 of the drawings.

7. A gas turbine engine including thrust reversing apparatus substantially as described in this specification with reference to fig. 3 ofthe drawings.

8. A gas turbine engine including thrust reversing apparatus substantially as described in this specification with reference to fig. of the drawings.