GB2229499A

GB2229499A - Blade-base fastening for a fibre rotor blade

Info

Publication number: GB2229499A
Application number: GB8929278A
Authority: GB
Inventors: Wilhelm Hoffmuller; Axel Rossmann; Seigfried Sikorski
Original assignee: MTU Motoren und Turbinen Union Muenchen GmbH
Current assignee: MTU Aero Engines GmbH
Priority date: 1988-12-29
Filing date: 1989-12-28
Publication date: 1990-09-26
Anticipated expiration: 2009-12-28
Also published as: DE3844191C2; FR2641324B1; DE3844191A1; FR2641324A1; GB2229499B; GB8929278D0

Description

1 M&C FOLIO: 230P59799 WANGDOC: 1015k "Blade-base fastening for a fibre

rotor blade,' The present invention relates to a blade-base fastening for a fibre rotor blade connected to a metal blade base detachably mountable in a rotor.

Various solutions have been disclosed for solving the problem of fastening a fibre rotor blade to a metal rotor disc. An arrangement is known, for example. from US 3,737.250 in which the blade base is constructed as a dovetail and is fixed in a blade carrier. which in turn is mounted in the rotor by way of roller bearings. This arrangement permits a simple removal of the propeller fan blades in a direction along the axis of the driving mechanism. which is advantageous particularly in the case of driving mechanisfns with a propeller fan casing. A disadvantage of this arrangement is the considerable space requirement of the blade-base fastening in the rotor.

An object of the invention is therefore to provide a structurally simple blade-base fastening which requires little space and which is also constructed so as to be acceptable in terms of the fibres. In addition. it should be possible to fit and dismantle the blade in a 2 simple manner.

The invention provides blade-base fastening as claimed in Claim 1.

This arrangement has the advantage that the rotor blade can be fitted and dismantled in a simple manner. This is carried out by inserting the blade base into the blade-base carrier and turning it so that the toothed segments engage with the internal flange segments of the blade-base carrier. The design of the fibre shaft allows the centrifugal forces arising during operation to be transmitted to the blade base from the blade itself in a favourable manner. In order to permit as low a weight as possible the blade base is advantageous produced from a titanium-based alloy.

In a preferred embodiment of the invention the shaft is glued to the blade base. as a result of which a substantial transmission of force can be achieved with favourable stressing of the fibres.

Alternatively or additionally thereto the fibre shaft may be riveted or screwed to the blade base transversely to the shaft axis through an opening.

The toothed segments are preferably 1/8 of the 1 3 circumference of the blade, and preferably three rows of toothed segments are arranged one behind the other. In this way a favourable transfer of forces arising during operation. in particular centrifugal forces. can take place from the blade base to the rotor. The toothed segments are advantageously shaped like a fir tree in cross-section. as a result of which a loading of the toothed segments favourable to the material is achieved. The toothed segments may be made without a pitch or can be arranged with a pitch not equal to zero. The latter case is particularly advantageous for producing a simultaneous stressing of the blade base with the blade carrier and so preventing vibration during operation.

In a further advantageous embodiment of the invention the end region of the fibre shaft is shaped like a bell. on the one hand this prevents the shaft from springing out of the blade base and on the other hand it results in a reduction in weight. since the material portion of the blade base. which consists of metal. is reduced at the expense of the shaft portion. Alternatively. the rectangular fibre shaft may be surrounded in the manner of a bell by a short-fibre moulded mass in the vicinity of the end region. In this way, a reduction in weight is likewise achieved.

4 In a further embodiment of the invention the fibre shaft of the blade terminates in the region of the cross-sectional plane of a blade-base flange integrally formed on the blade base. In this connection the shaft is glued to the blade base andlor secured by means of a rivet or a screw. This simpler design is only possible, however. when the permissible material stresses in the neck of the blade base and the blade shaft are not exceeded.

A plurality of regularly spaced bores. which are orientated radially with respect to the rotor axis. are preferably arranged between the centrally arranged opening and the toothed segments distributed over the periphery. This arrangement likewise permits a saving in weight.

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings. in which.

Fig. 1 is a longitudinal section through a blade-base in accordance with the invention.

Fig. 2 is a longitudinal section thr.ough a modified embodiment of Fig. 1, Fig. 3 is a longitudinal section through a further embodiment of the invention, Fig. 4 is a cross-section through the embodiment of Fig. 3.

Fig. 5 is a longitudinal section through a further embodiment of the invention. and Fig. 6 is a longitudinal section through an embodiment with a short shaft.

In Fig. 1 a blade base 1 connects a fibre blade 5. preferably a propellerfan blade. to a blade-base carrier 9 of a rotor. The blade 5 has a shaft 4 extending radially of the rotor and fitting in a corresponding opening 2. The connection between the shaft 4 and the wall of the opening 2 is by adhesion.

The blade base 1 has a plurality of toothed segments 6 distributed over the inner periphery of the base 1 and provided in two superposed rows. The toothed segments 6 engage by way of radially outer flanks 17 with correspondingly matching flanks 18 of inner flange segments 8 mounted-in the blade-base carrier 9. In addition, the blade base 1 has a blade-base flange 15 which, in order to brace bending forces. cooperates with 6 an appropriately formed flange 16 of the blade-base carrier 9. A rivet 22 further secures the shaft 4 to the blade base 1.

The embodiment according to Fig. 2 is provided in the radially inner end region 3 of the shaft 4 with a dovetail-like enlargement. by means of which the shaft 4 can be prevented from springing out of the opening 2. In addition. a plurality of radial (relative to the rotor) bores 14 are provided, which are closed by plugs 20 adapted to their shape. The bores reduce the weight of the blade base 1.

The embodiment of Fig. 3 has a.bell-shaped opening 2. The space between the shaft 4 and the outer wall of the opening 2 is filled with shortfibre moulded mass 12. In this case the connection surfaces between the shaft 4 and the short-fibre moulded mass 12 are glued to the blade base 1.

Fig. 4 shows a cross-section along the line W-W of Fig. 3. The blade base 1 comprises two half shells 10a, 10b, connected to each other along abutment faces 19. The shaft 4 is substantially rectangular in crosssection. while the opening 2 is round in cross-section. The space between the shaft 4 and the blade base 1 is filled by short-fibre moulded mass 12.

1 7 The toothed segments 6 are distributed over the outer periphery of the blade base 1. and they extend over approximately 118 of the periphery. Gaps 7 of approximately equal length. which are used for the. insertion or removal of the blade base 1. are provided between the inner flange segments 8. To this end. the blade base 1 is turned by approximately 118 of a revolution. until the toothed segments 6 are located completely inside the gaps 7. The blade base 1 is then withdrawn radially (of the rotor) from the blade-base carrier 9.

A further embodiment of the invention is shown in Fig. 5, in which the shaft 4 is adapted to the bell-shaped design of the opening 2.

Another preferred embodiment of the invention is shown in Fig. 6. In this embodiment the shaft 4 is secured by adhesion to the blade base 1, and is fastened in the region of the neck 21 of the blade base by a rivet or a_ plurality of rivets 22. The end 23 of the shaft 4 is situated approximately in a cross-sectional plane with the flange 15 of the blade base 1. Although a smaller transmission of force can be achieved with this embodiment than with the embodiments illustrated above. there is a saving in weight. In addition. the blade base can be replaced without the blade base having to be 8 separable, which leads to an advantageous simplification.

9

Claims

Claims:

1. A blade-base fastening for a fibre rotor blade connected to a metal blade base detachably mountable in a rotor, wherein the metal blade base has an opening arranged radially to the rotor axis, a shaft of the fibre blade base is machined and secured in the opening. and toothed segments extending in the peripheral direction are provided on the outer periphery of the blade base with gaps arranged therebetween, to allow detachable bayonet mounting of the blade base in a pot-shaped blade-base carrier of the rotor having correspondingly-formed internal flange segments.

2. A blade-base fastening according Claim 1. wherein the blade base comprises two half shells which are welded to each other.

3. A blade-base fastening according to Claim 1. wherein the blade base is in one piece.

4. A blade-base fastening according to any one of the preceding Claims. wherein the blade base is connected to the fibre shaft by means of adhesive.

5. A blade-base fastening according to any one of the preceding Claims, wherein the blade base is riveted or screwed to the fibre shaft.

6. A blade-base fastening according to any one of the preceding Claims. wherein the toothed segments are 1/12 to 1/4, and preferably 1/8, of the circumference of the blade base.

7. A blade-base fastening according to any one of the preceding Claims. wherein one to five. and preferablythree. rows of toothed segments are arranged radially to the axis of the rotor blade one behind the other.

8. A blade-base fastening according to any one of the preceding Claims. wherein the toothed segments are shaped like a fir tree in cross-section.

9. A blade-base fastening according to Claim 1. wherein the material of the blade base is a titanium-based alloy.

10. A blade-base fastening according to any one of the preceding Claims. wherein the toothed segments are arranged helically with a pitch not equal to zero.

11. A blade-base fastening according to any one of the preceding Claims. wherein the fibre-shaft is shaped like a bell in the end region.

1 11

12. A blade-base fastening according to any one of the preceding Claims. wherein the fibre shaft is surrounded in the manner of a bell by a short- fibre moulded mass in the vicinity of the end region.

13. A blade-base fastening according to any one of Claims 1 to 10, wherein a plurality of regularly spaced bores extending radially with respect to the rotor axis are arranged between the centrally arranged opening and the toothed segments distributed over the outer periphery.

14. A blade-base fastening according to Claim 5 or 6. characterized in that the fibre shaft terminates in the region of the cross-sectional plane of a blade-base flange integrally formed on the blade base.

15. A blade-base fastening substantially as herein described with reference to any one of the embodiments shown in the accompanying drawings.

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