GB2223545A

GB2223545A - Positive clutch arrangement

Info

Publication number: GB2223545A
Application number: GB8823021A
Authority: GB
Inventors: Charles Ian Broom
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 1988-09-30
Filing date: 1988-09-30
Publication date: 1990-04-11
Anticipated expiration: 2008-09-30
Also published as: GB8823021D0; GB2223545B

Abstract

The setting of a variable guide vane 1 for a gas turbine engine is controlled by a mechanical input member 8 coupled to an output member 7 and the guide vane 1 by an arrangement of interengaging splined members. The said members are biased by a spring 26 into an engaged position in which the input drive is connected. Splined intermediate members 12, 14 are arranged concentrically with the members 7 and may be moved relatively axially so that the splines 22 of member 14 are disengaged from splines 20 of member 12. The uppermost end of member 14 may then be engaged by a key and the member 14 depressed and rotated to effect vane adjustment. <IMAGE>

Description

CLUTCH ARRANGEMENT The invention relates to a clutch arrangement and especially to an arrangement for selectively disengaging air flow guide vanes in a variable geometry jet engine to permit the basic setting of the said air flow guide vanes to be altered.

Variable angle guide vanes are installed in engine intakes and between compressor stages to give a degree of swirl to air entering the front of the compressor and between stages. The degree of swirl, ie the tangential velocity components, imparted to the air is determined by the angle of the vanes with respect to the longitudinal axis of the engine. The vane angle is adjusted automatically to minimise stall conditions at the compressor front face under "off-design" engine operating conditions.

A plurality of guide vanes of the type referred to may be disposed in a radial array in front of the first compressor stage and between compressor stages. In each ring the vanes are connected with a circumferential operating ring so that they may all be operated in unison and turned through the same angle simultaneously.

Where there are several such stages of guide vanes these are usually connected together so that a constant angular relationship is retained between the various sets of the vanes as they are operated. However, it is sometimes necessary to vary this relative angular relationship, so that at any given engine operating condition different rings of vanes are presented at different angles of incidence. With such known arrangements the angular relationship between sets of the vanes can only be changed by partially stripping down an engine. The present invention seeks to provide a clutch arrangement by which this angular relationship can be varied almost at will and certainly without the penalty of major engine work.

According to the invention a clutch arrangement comprises a plurality of concentric members including a rotary input member, a rotary output member and first and second intermediate members positively engaged respectively with the input and output members and with each other through a coupling which may be selectively disengaged to permit the relative angular orientation input and output members to be altered.

In its application to a jet engine the rotary input member is connected with one of the said guide vanes and is driven by a unison ring in an arrangement as referred to above.

The intermediate members of the clutch arrangement are arranged for telescopic movement to disengage one from the other. Preferably they are biased towards the engaged position.

In a preferred form of the invention the intermediate members are provided with splines which in the engaged position mutually engage to couple the input and output members and permit the relative angular alignment of the input and output members to be altered in a stepwise manner.

The invention will now be described in greater detail with reference, by way of example only, to an arrangement illustrated in the accompanying drawings, in which: Figure 1 shows a section view through a guide vane clutch arrangement in the disengaged position, and Figure 2 shows a similar view of the clutch arrangement in the engaged position.

Referring now to the drawings a variable guide vane 1 is shown mounted in a boss 2 carried in the outer skin of a compressor casing 3. The vane 1 is formed with an axial spindle 4 which has at its distil'end a tapered shoulder 5 and a locknut 6. An output member 7 comprising a cylindrical portion 7a and extending radially outwards from the base of the cylinder an operating arm 7b. The base of the cylinder 7a is formed with a right conical hole which mates with the conical shoulder 5 of the spindle 4. The locknut 6 holds the output arm fast on the spindle.

An input member 8 comprising a cylindrical portion 8a and extended range of the outwards from one end thereof and operating arm 8b is arranged concentrically the cylindrical portion 7a of the output member.

The lower end of the cylindrical portion 7a of the output member is flanged to form a shoulder against which the lower edge of the cylindrical portion 8a of the input member rests. The cylinder 7a as shown is longer than the cylindrical portion 8a and towards its upper end a ring groove is formed in the outer surface to receive a circlip 9 which retains the input member in position.

A set of splines 10 are formed on the inner surface of the cylinder 7a and a second set of axial splines 11 are formed on the outer surface of the cylinder 8a. The input and output members are coupled together by means of a pair of intermediate members 12 and 14 which are disposed concentrically with the output members and the axis of the guide vanes.

Coupling member 12 in the form of a stepped cylinder has a wider lower end which is formed with splines 16 which engage with the external splines 11 on the outside of the cylindrical portion 8a. However diameter portion of member 12 is also provided with internal axial splines 20. The second coupling member 14 comprises an axial rod or tubular member which has elongate splines 22 formed towards its lower end. These intermediate coupling members are arranged concentrically with the input and output members -7 and 8 and the guide vane 1 and its spindle 3.

The outer coupling member 12 has a lower section of larger diameter which has on its inner surface axial splines 16 which mesh with complementary axial splines 11 formed on the outer surface of the cylindrical portion 18 of the input member. The smaller diameter section of member 12 is also provided towards its lower end with a further set of axial splines 20. These splines 20 may be selectively engaged with further elongate axial splines 22 formed towards the lower end of the second intermediate member 14 which also engage with splines 10 formed on the internal surface of the upper part of the cylindrical member 7a.

The upper portion of the first intermediate member 12 has the same internal diameter as the cylindrical portion 7a of the output member. Thus the splines 22 carried on the intermediate member 14 can be engaged with either or both the splines 20 on the coupling member 12 or the splines 22 on the output member 7 simply by moving the member 14 axially.

Normally the member 14 is biased towards an axial position in which its splines 22 engage both sets of splines 20 and 10. A compression spring 26 trapped under the lower end of the member 14 urges the member into the position which engages both sets of the said splines. Sufficient axial improvement is provided so that the coupling members 12 and 14 may be telescoped in order that the splines 22 of member 14 may be disengaged from the splines 20 on member 12. Thus, the members 12 and 14 may be uncoupled thereby. also uncoupling the input and output members. The uppermost end of member 14 is shaped to receive a key (not shown) which may be used to depress the member against spring 26 and to turn it for adjustment.

When uncoupled the member 14 may be rotated relative to the member 12, and therefore the input and output member may be rotated relatively so that the angular disposition of guide vane 1 with respect to the position of the arm 8b of the input member may be altered at will through the uncoupling of the member 12 and 14. With their respective splines disengaged the member 14 will be free to rotate relative to the other coupling member 12 but will carry with it the guide vane 1 since splines 10 and 20 remain meshed.

If desired means may be provided for capturing member 14 so that it can be held in the uncoupled position. Also, a protractor head 28 may be provided towards the upper end of the coupling member 12 and a pointer provided carried by the member 14 so that the relative angular positions with respect to a predetermined datum may be inspected visually.

Claims

1. A clutch arrangement comprises a plurality of concentric members including a rotary input member, a rotary output member and first and second intermediate members positively engaged respectively with the input and output members~ and with ~each other through a coupling which may be selectively disengaged to permit the relative angular orientation of the input and output members to be altered.

2. A clutch arrangement according to claim 1 wherein the intermediate members are arranged for telescopic movement to disengage one from another.

3. A clutch arrangement according to claim 1 or claim 2 wherein the intermediate members are biased towards the engaged position.

4. A clutch arrangement according to any preceding claim wherein the intermediate members are provided with splines which in the engaged position mutually engage to couple the input and output members.

5. A clutch arrangement according to claim 4 wherein the splines provided on the intermediate members permit the relative angular alignment of the input and output members to be altered in a stepwise manner.

6. A clutch arrangement according to any preceding claim wherein the intermediate members carry a protractor arrangement to indicated the relative angular orientation of the input and output members.

7. A clutch arrangement according to any preceding claim wherein the first and second intermediate members are engaged respectively with the input and output members by means of splined formations.

8. An arrangement for a variable geometry jet engine comprising airflow guide vanes connected to a control system operative to control angular setting of the guide vanes and a clute vanes and a clutch arrangement according to any preceding claim by means of which a basic orientation of the vanes may be selectively altered.

9. An arrangement according to claim 8 wherein the clutch arrangement in externally accessible for selective disengagement to alter the basic setting of the vanes.

10. An arrangement substantially as hereinbefore described with reference to the accompanying drawings.