GB2100683A - Mounting structure for engine accessories - Google Patents

Abstract

A mounting for an accessory equipment 14 of a gas turbine powerplant 10 on a fan duct 13 of the powerplant comprises pivoted links 23,24,25 supporting a housing 15 of the equipment 14 on the duct 13 in a position to one side of the vertical centre line 21 of the duct. The links are tangential to the duct 13 and lie in a plane including the centre of gravity of the equipment. The housing is also connected to the duct by a pivot 29 spaced axally from side plane and situated close to a radial shaft 16 connecting the engine 11 of the powerplant to the accessory equipment. The links 23,24,25 are so arranged that differential thermal expansion of the duct and the housing do not significantly change the angular position of the housing in the sense of placing a bending load on the shaft. <IMAGE>

Description

SPECIFICATION Mounting structure This invention relates to a mounting structure or mounting and is concerned with mounting a supported on a supporting member in a case where the supporting member is annular and the supported member has a position to one side of the vertical centre line of the annular member and where the position of the supported relative to the supporting member has to be maintained within certain limits of accuracy notwithstanding thermal expansion and contraction of the members.

The invention is applicable to the mounting of an accessory equipment on the fan duct of a gas turbine engine powerplant for aircraft propulsion.

According to this invention there is provided an assembly of an annular supporting member, a supported member having a centre of gravity situated to one side of the vertical centre line of the supporting member, and a mounting comprising a first, a second, and a third pivoted link connected between the supported member and circumferentially spaced apart mounting points on the supporting member, the links extending substantially in a plane including said centre of gravity and in directions tangential to the annulus of the supporting member, and a pivot directly connecting the members at a position axially spaced from said plane.

The arrangement of the three links enables the mounting to control the angular position of the supported member about said pivot notwithstanding thermal changes in the members.

An example of an assembly according to this invention will now be described with reference to the accompanying drawings wherein: Figure 1 is a front elevation of the assembly essentially comprising a gas turbine engine powerplant, an accessory equipment therefor, and a mounting connecting the equipment to the engine.

Figure 2 is a section on the line ll-ll in Fig.

1.

Figure 3 is a developed view on the line Ill-Ill in Fig. 1.

The powerplant, denoted 10, comprises a core engine 11 adapted to drive a fan enclosed by an annular fan duct 1 3 having an axis 1 3A. The accessory equipment, denoted 14, is arranged at the outside of the duct 1 3 and comprises a housing 1 5 connected to the core engine by a shaft 1 6 extending radially in respect of the fan duct through a vane 1 7 connecting the fan duct to the core engine.

The equipment 14 further includes a starter motor 1 8 and a generator 1 9 mounted on the housing 1 5 and connected to the shaft 1 6 through gearing within the housing 1 5. The duct 1 3 and equipment 1 4 constitute a supporting and supported member respectively.

The powerplant 10 is provided on an aircraft (not shown) and the arrangement is such that when the aircraft stands on the ground the clearance between the fan duct 1 3 and the ground surface, denoted 20, is relatively small. It would ordinarily be desirable to mount the equipment at the underside of the duct 1 3 but in order to avoid a ground clearance problem the equipment 14 is located at one side of the vertical line 21 of the duct 1 3 and such that the shaft 1 6 extend at an angle a of approximately 45 to the vertical.

The equipment 1 4 is connected to the duct 1 3 by a mounting 22 comprising an upper link 23, an intermediate link 24, and a lower link 25, all arranged in a common plane 27 which lies transverse to the axis 1 3A and passes approximately through the centre of gravity 26 of the equipment (Fig. 2). For reasons of general layout the shaft 1 6 is situated a significant distance to the rear (i.e.

axially toward the exhaust end of the powerplant) of the plane 27.

The mounting includes a pivot 29 connected between the duct 1 3 and the housing 1 5 in a position as closely as possible to the shaft 16. The pivot 29 has a pivot axis 29A perpendicular to the axis 13A, i.e. parallel to the plane 27 and comprises a pivot pin 30 directly connected between lugs secured to the duct 1 3 and housing 1 5 respectively. The pivot 29 may include a spherical joint such that the housing 1 5 can tilt by a limited amount about an axis 29B perpendicular to the axis 29A. However, essentially the pivot 29 locates the housing 1 5 in such a way that, at the position of the shaft 16, any relative motion between the housing 1 5 and the duct 1 3 is minimized.Ideally the intersection of the axes 29A, 29B should lie on the axis 1 6A of the shaft 1 6 but a small spacing can be tolerated. Relative or joint thermal expansion of the housing 1 5 and duct 1 3 in the direction of the axis 1 6A shaft is transmitted directly through the pivot 29 and is accommodated by axial sliding of the shaft in splined connections 30,31 to gears 32,33 provided respectively in the housing 1 5 and duct 1 3 for the purpose of transmitting drive between the engine and the equipment 1 4. The gears 32,33 are supported for rotation in bearings 34,35 respectively provided in the engine 11 and the housing 1 5 and, as will be explained, the mounting operates to support the housing 1 5 against angular displacement such as would tend to bend the shaft or misalign the bearings 34,35. It will be understood that the shaft transmits drive between the engine 11 and the equipment 1 4 for the purpose of starting the engine by the starter motor or driving the generator when the engine is running.

The links 23,24,25 have spherical joints 23A,24A,25A connecting the links to the duct 1 3 and respective spherical joints 23B,24B,25B connecting the links to the housing 1 5. The joints 23B,24A,24B and 25B lie approximately on a line 28 tangential to the duct 1 3 so that the mounting can readily accommodate differential thermal ex pansion of the duct 1 3 and the housing 1 5 in the direction of the axis 13A. Insofar as the latter differential expansion results in pivoting of the housing 1 5 about the pivot 29, such pivoting is so small that it can be absorbed by working clearances between the shaft and the gears at the splines 30,31.

The links 23,24,25 each lie substantially tangential to the periphery of the duct 1 3 and are each subject to tension under the load of the housing 1 5 as applied at the centre of gravity 26 as seen in Fig. 1. It will be noted that the joint 24B lies below the joint 24A and the centre of gravity 26 is offset from the joint 24B towards the side thereof remote from the duct 1 3 so that the load tends to turn the link 24 in the clockwise direction with the result that the link 25 is in tension under the weight of the equipment 1 4. It will also be clear that the weight of the equipment 14 tends to turn the housing 1 5 in the anticlockwise direction about the pivot 24B so that the link 23 is in tension also.The tension in the links 23,25, which can be approximately equal, is small compared to that in the link 24, the latter taking the majority of the load. However, since the link 24 is tangential to the duct 1 3 the latter is in the most favourable condition to absorb the load.

The links 23,25 are mutually convergent in the direction away from the duct 1 3 as a corallory of their respective tangential relationship to the duct 1 3. The tangential position is of course of importance to minimize distortion of the duct but there is also an advantage, regarding differential thermal expansion, arising from the convergent relationship. In particular, if the duct 1 3 expands the pivot 29 tends to move the housing 1 5 away from the axis 13A. This tends to swing the links 23,25 towards one another about the joints 23A,25A and, therefore, tends to shorten the radial spacing of the housing 1 5 and duct 1 3 in the plane 27. The radial expansion of the duct 1 3 at the joints 23A,25A will have the same effect. However, the housing 15, being subject to the same ambient temperature, will expand in the direction of the line 28 away to either side of the link 24. In as much as the housing 1 5 is made of a light alloy having a higher coefficient of expansion than the duct 13, the expansion of the housing 1 5 is sufficient to swing the links 23.25 in the opposite sense and this tends to maintain the radial spacing of the housing 1 5 and the duct 1 3 at the plane 27 the same as at the pivot 29 so that movement about this pivot and consequent strain in the splines 30,31 is substantially avoided.

Claims (8)

1. An assembly of an annular supporting member, a supported member having a centre of gravity is situated to one side of the vertical centre line of the supporting member, and a mounting comprising a first, a second, and a third pivoted link connected between the supported member and circumferentially spaced apart mounting points on the supporting member, the links extending substantially in a plane including said centre of gravity and in directions tangential to the annulus of the supporting member, and a pivot directly connecting the members at a position axially spaced from said plane.

2. An assembly according to Claim 1, wherein the links are arranged approximately in a lower quarter of the annulus of the supporting member, the first link is situated at the upper end of said quarter, the third link is situated at the lower end of said quarter, and the second link is situated intermediate between the first and third links.

3. An assembly according to Claim 1 or Claim 2, wherein the first and third links are mutually convergent in a direction away from the supporting member.

4. An assembly according to Claim 3 as dependent on Claim 2, wherein the centre of gravity of the supported member is situated adjacent the second link in a position offset from the second link to the side thereof remote from the supporting member.

5. An assembly according to any one of Claims 2, 3 or 4, wherein the second link depends from the supporting member so as to define an upper and a lower end connected respectively to the supporting and supported member.

6. An assembly according to any one of Claims 2 to 5 wherein said pivot is substantially in line with the second link in the direction of the annulas axis of the supporting member.

7. An assembly according to any one of the preceding claims including a shaft supported in bearings provided respectively on the supporting and supported members and extending radially in respect of the supporting member and adjacent the said pivot.

8. An assembly substantially as described herein with reference to the accompanying drawings.