GB2339266A

GB2339266A - A tubular shaft

Info

Publication number: GB2339266A
Application number: GB9814825A
Authority: GB
Inventors: Ian Anthony Simmons
Original assignee: Flight Refuelling Ltd
Current assignee: Cobham Mission Systems Wimborne Ltd
Priority date: 1998-07-08
Filing date: 1998-07-08
Publication date: 2000-01-19
Also published as: GB9814825D0

Description

2339266 A Rotary Power Transmission Arrangement This invention relates to

a rotary power transmission arrangement comprising a rotary power transmission shaft which is adapted to be coupled to a universal joint at either end.

In certain installations there is a need to transmit rotary along a path which is not straight. This requires the use of rotary power transmission shafts which are journalled for rotation about their axes which are oblique one to another and which are coupled together at their adjacent ends by a universal joint by which rotary power is transmitted from one shaft to another. In the simplest form of such an installation, which comprises just two such rotary power transmission shafts, there would be three universal joints, one between the two shafts and one at the other end of each of the shafts, as well as a number of structural mounting arrangements for supporting the shafts and the universal joints. If the need for so many universal joints and structural mounting arrangements could be reduced, there would be a gain in both weight, which is of particular benefit in an aircraft installation, and cost.

An object of this invention is to provide an 2 arrangement for transmitting rotary power along a path which is not straight and which requires fewer universal joints and structural mounting points than must be provided when the power is transmitted by shafts which are journalled for rotation about axes which are obliaue one to another.

According to this invention there is provided a rotary power transmission arrangement comprising a rotary power transmission shaft which is adapted to be coupled to a universal joint at either end, and which is Journalled in a bearing race between those ends, the shaft being formed so that, when it is coupled to the respective universal joint at either end, it can be bent to allow the bearing race to be mounted on support structure offset from the notional straight line that extends between the centre of the shaft at either end and so that it will transmit rotary power between the two universal joints to which it is connected by those ends along the curved path through the offset bearing race that it follows.

Preferably the rotary power transmission shaft comprises a tube which is formed as a one piece moulded fibre reinforced plastics structure, wherein the one piece tube of fibre reinforced plastics material is lined internally by an integral tubular 3 mandrel.

In a preferred embodiment, the rotary power transmission shaft is a shaft which embodies the invention that forms the subject of our International Patent Publication No W098/20263, wherein the fibre reinforcement is a continuous tape of fibre, preferably carbon fibre, which is helically wound along the tube. The shaft may have an integrant flange at either end for coupling to the respective universal joint, and the helically wound continuous tape preferably follows a similar path into the flanges.

Conveniently the edges of juxtaposed turns of the helically wound tape are contiguous and the tape is formed with continuous lengths of fibre running substantially parallel to the edges of the tape. Each flange may include additional material in annular form, such as a moulded fibre reinforced plastics material, which reinforces the respective flange portion of the one piece reinforced plastics structure, the fibre reinforcement of which is helically wound. Conveniently the fibre reinforcement comprises a stack of annular layers thereof.

One embodiment of this invention is described now by way of example, with reference to the accompanying drawings, of which:

Figure I is a half-sectioned elevation of one form of power transmission shaft journailed in a tubular bearing, with an illustration in dotted lines of an installation of that tubular shaft which embodies this invention; and Figure 2 is an exploded view illustrating assembly of one end of the shaft shown in Figure 1.

Figure 1 shows a rotary power transmission shaft 10 comprising a tubular mandrel 11 of a carbon fibre reinforced plastics material which lines the inner surface of a tube 12 which has an integrant annular flange 13, 14 at either end. Each integrant annular flange 13, 14 is reinforced by annular composite structure. Figure 2 illustrates the elements which comprise such an annular composite structure. Each reinforced annular flange 13, 14 has four holes formed through it parallel to the axis of its central aperture at equi-angularly spaced locations on a common pitch circle diameter.

To form the rotary power transmission shaft 10, the mandrel 11 is formed from carbon fibre reinforced plastics material by moulding and is cut to length. When so formed, it is supported between centres in a CNC tape winding machine as is described in International Patent Publication W098/20263. Each centre is spigotted into the mandrel 11 and has a larger diameter body portion which comprises a medial right cylindrical portion. The latter is between a pair of frusto-conical portions which each taper away from it. The diameter of the smaller end of the frusto-conical portion that is adjacent to the mandrel 11 is the same as the outside diameter of the mandrel 11. A step is formed between that smaller end and the respective spigot portion, that step being abutted by the end of the mandrel 11 into which that spigot portion is spigotted. The mandrel 11 is then rotated with the centres by the machine whilst carbon fibre tape impregnated with thermo-setting resin is helically wound, firstly over the centre at one end of the mandrel 11, then along the whole length of the mandrel 11, onto and over the other centre whereupon it is turned around and helically wound back over that centre and back along the whole length of the mandrel 11 to the centre of the first mentioned end of the mandrel 11. The spiral path of the tape is substantially 45' to the axis of the mandrel 11. This is repeated for the required number of layers of preimpregnated tape of carbon fibre material that are to be laid to form the tube, each alternate layer being 6 wound in the opposite direction to its juxtaposed layer. The tape is arranged with continuous lengths of carbon fibre running along its length substantially parallel to its sides. Also the edges of the tape 5 abut one another as the tape is wound helically.

The mandrel 11, with the centres at its ends and the helically wound tape thereon is then removed from the tape winding machine. The end portions of helically wound tape are cut away to an edge which extends circumferentially around the centre of the medial right cylindrical portion of each centre. The centres are then withdrawn from the mandrel 11 so as to leave the mandrel 11 with helically wound tape projecting therefrom at either end by an amount which is sufficient to form the integrant flanges 13 and 14 at either end. The flared ends of helically wound tape that project from the mandrel 11 at either end are then deformed into substantially radial flanges. The centres with the larger diameter medial body portions having spaced frusto-conical portions which taper away from one another are used so that the helically wound tape follows the required geodetic path into these flanges.

Once the flared ends of helically wound tape at either end of the mandrel 11 have been deformed into 7 substantially radial flanges, a suitable number of stacks 15 of contiguous annular layers 16 of thin sheet material which comprises carbon fibre impregnated with uncured resin are assembled substantially coaxially with each other and with the mandrel 11 at either end of the mandrel 11. The inside and outside diameters of each of the annular layers 16 are respectively substantially the same as the inside diameter of the mandrel 11 and of the outside diameter of the radial flanges 13 and 14. Each layer 16 has carbon fibres which extend parallel to each other and to a diameter of the respective layer, as shown at 17 in Figure 2. The carbon fibres 17 of each layer 16 of a stack 15 are oriented at 450 to the carbon fibres 17 of each of the juxtaposed layers 16 so that the carbon fibres 17 of each alternate layer 16 of a stack 15 are oriented at 90' to each other. Each annular layer 16 was formed by stamping from stock material in sheet form which conveniently is 0. 005 inches (0. 13 nun) thick. The number of stacks 15 and of layers 16 in each stack is a matter of design choice governed by the thickness required for the resultant end flange of the shaft.

The radially inner edges of each of the layers 16 may be deformed so as to flare axially to a small extent, 9 those flared deformations being arranged to extend into the bore of the mandrel 11 to provide a tidy finish and improve material density to either end of the bore of the resultant shaft.

The radial flanges 13, 14 formed at either end of the mandrel 11 by the flared ends of helically wound tape taper radially outwardly because the material of the tape has a substantially constant volume. To compensate for the consequent relative thinness of the radially outer portions of the flanges 13 and 14, an additional stack 18 of contiguous annular layers 19 of resin impregnated carbon fibre material is assembled coaxially with and in juxtaposition with the stacks 15. The inside diameter of each annular layer 19 is somewhat greater than that of each of the layers 16.

A mould is then assembled around the assembly of the stacks 15 and 18 and the radial flanges 13 and 14 formed by the helically wound tape at either end of the mandrel 11, and moulding of the integrant flanges is carried in an autoclave as described in International Patent Application No W098/20263.

The shaft 10 comprises a small diameter tube with a high aspect ratio (that is to say the ratio of tube diameter to wall thickness). The dimensions of the small diameter tube are within the ranges of between 9 about 23 mm and 30 mm for the outside diameter and about 17 mm. to about 23 mm for the bore. A prefe--red embodiment has an outside diameter of 26 mm and a bore of 22 mm.

This invention enables the shaft 10 to transmit rotary power between two universal joints (not shown) where there is structure or some other obstacle located between those two joints so that it is physically impossible for the shaft to extend between those two points in its normal straight form.

In carrying out this invention, a bearing race 21 is assembled around the tube 12 substantially midway between the two flanges 13 and 14. The bearing race 21 is secured by straps 22 and 23 to structure 24 of the aircraft and the length of the straps 22 and 23 is such that the bearing race 21 is displaced laterally with respect to the location it would have were the shaft 10 to extend between the two universal joints in its normal straight form. The mid portion of the shaft 10 is located by being journalled within the bearing race 21. The end portions of the shafts, including the flanges 13 and 14, are bent and the flanges 13 and 14 are coupled to the respective universal joints so that the shaft 10 is curved as shown dotted in Figure 1.

Rotary power is transmitted between the two universal joints by the shaft 10 in its curved form and the obstacle between those two universal joints is bypassed by the shaft 10. The fatigue performance of the shaft is good due to the use of carbon fibre in its structure. This is beneficial, not only in installations in which the shaft transmits power over long periods of time, but also when the shaft is required to idle for considerable periods.

11

Claims

1. A rotary power transmission arrangement comprising a rotary power transmission shaft which is adapted to be coupled to a universal joint at either end, and which is journalled in a bearing race between those ends, the shaft being formed so that, when it is coupled to the respective universal joint at either end, it can be bent to allow the bearing race to be mounted on support structure offset from the notional straight line that extends between the centre of the shaft at either end and so that it will transmit rotary power between the two universal joints to which it is connected by those ends along the curved path through the offset bearing race that it follows.

2. A rotary power transmission arrangement according to claim 1 wherein the rotary power transmission shaft comprises a tube which is formed as a one piece moulded fibre reinforced plastics structure, wherein the one piece tube of fibraz reinforced plastics material is lined internally by an integral tubular mandrel.

3. A rotary power transmission arrangement according to claim 2 wherein the fibre reinforcement is a continuous tape of fibre.

4. A rotary power transmission arrangement according to claim 3 wherein the tape is of carbon fibre and is helically wound along the tube.

5. A rotary power transmission arrangement according 12 to claim 4 wherein the rotary power transmission shaft includes an integral flange at either end for coupling to a universal joint.

6. A rotary power transmission arrangement according to claim 5 wherein the helically wound continuous tape follows a similar path into the flanges.

7. A rotary power transmission arrangement according to claim 6 wherein the continuous tape is formed with contiguous lengths of fibre running substantially parallel to the edges of the tape.

8. A rotary power transmission arrangement according to any one of claims 5 to 7 wherein one or both flanges include an additional material in annular form which reinforces a respective flange portion of the said one-piece reinforced plastics structure.

9. A rotary power transmission arrangement according to claim 8 wherein the additional material in annular form comprises a coaxial stack of annular layers.

10. A rotary power transmission arrangement according to claim 8 or claim 9 wherein the additional material is a moulded fibre reinforced plastics material.

11. A rotary power transmission arrangement substantially as described hereinbefore with reference to and as illustrated in the accompanying drawings.