GB2124735A

GB2124735A - Drive shaft

Info

Publication number: GB2124735A
Application number: GB08320262A
Authority: GB
Inventors: Karl-Wilhelm Kalk; Jurgen Klug
Original assignee: MAN Maschinenfabrik Augsburg Nuernberg AG
Current assignee: MAN AG
Priority date: 1982-07-28
Filing date: 1983-07-27
Publication date: 1984-02-22
Also published as: FR2531158A1; DE3228110A1; GB8320262D0; DE3228110C2; FR2531158B1; GB2124735B

Abstract

A drive shaft 10 of fibre reinforced plastics material and having a cylindrical tubular shaft portion 11 which in one embodiment expands at least one end to a hollow elliptical connecting portion 13 via an approximately conical transition piece 12. Bonded into the cavity 15 of the elliptical connecting portion is a connecting member 14 serving to enable connection of the shaft to other driving or driven elements such as cardan joints or splined connections. The transfer of power from the shaft to the joints is by positive connection in the elliptical portion of the connection. The hollow connecting portion may be of any other non-circular shape. <IMAGE>

Description

SPECIFICATION Torque shaft This invention relates to a torque shaft, particularly though not exclusively, a drive shaft suitable for use in aerospace technology.

D.E.-05 29 46.530 discloses a torque shaft of this kind and formed as a composite fibre tube at each end of which the fibres are wound around a metal connecting piece, the fibres being bonded together and to the connecting piece by an adhesive. Torque is transmitted at the joint by virtue of the adhesive and friction acting between the fibre reinforced tube and the metal connecting piece. Due to differential thermal expansion and contraction and also to alternating loads, however, there is a tendency for the joint to loosen. For reasons of safety it has been proposed to improve the security of the joint by forming a threaded portion or the like around the outer circumference of the connecting piece. If this is to be of advantage however, the thread must be wound or wrapped with extreme care, where the thread in no way affects the strictly non-positive frictional connection.

One object of the present invention is to facilitate manufacture of a torque shaft affording secure and durable connection for coupling to driven and/or driving elements in a torque transmission.

According to the present invention we propose forming a torque shaft in one piece, having a cylindrical shaft portion at least one end of which merges or extends into a hollow connection portion, the internal cross-section of which is of a noncircular preferably regular shape, for example generally oval or elliptical or polygonal.

When the connection portion and the cylindrical shaft portion, are required to be of different sizes, the intervening transition portion preferably tapers and may vary in cross-section so as to merge between the exterior of the cylindrical portion and the connection portion.

The non-circular internal cross-section of the connecting portion, enables a positive driving connection with a coupling element having a connecting portion of complementary shape. Alternatively, a separate connecting piece or flange having an external surface complementary with the noncircular internal cross-section may be inserted and, if required, bonded in the hollow connecting portion as described below. This can then be coupled to driving or driven element in any convenient manner.

A shaft according to the present invention is also very simple to manufacture from any desired material, where the cylindrical portion can be made either tubular or solid. Owing to the simple coupling requiring only few components, and to the free choice of materials, the shaft of the present invention is particularly suitable for aerospace applications.

In a preferred embodiment of the present invention, the cylindrical portion expands to the size of the hollow connecting piece via an approximately conical transition piece.

The expanded cross-section assists the design and manufacture of the torque transfer region having regard to mechanical (static, dynamic) strength and/or adequate flexural rigidity to avoid shaft vibrations.

The expansion also allows space for access through the transition portion to the interior of the connecting piece so as to facilitate assembly and coupling to driving or driven elements.

Although, in general, the shaft may be made from any suitable material we prefer to wind the shaft in one piece, using fibre reinforced, preferably carbon fibre reinforced plastics material. Strips of fabric or webbing may be inserted between fibre windings or layers to provide additional reinforcement where required, for example, at the end portions of the shaft.

If desired, both the interior and the exterior of the hollow connecting portions may be of the said non-circular shape.

According to another aspect of this invention therefore, we propose a method of forming a torque shaft, by winding fibres around a mandrel to form an integral structure having a cylindrical portion and on at least one end thereof a hollow connecting portion the internal cross-section of which is of a noncircular shape.

To protect against external mechanical impact or load, a thin layer of glass or aramide fibre may be applied to the outside and conceivably also the inside of the shaft. In practice the internal protective layer of fibre is formed before the structural tube is wound, and the outer layers after winding the tube.

This will produce controlled compaction of the tube laminate.

In an arrangement greatly facilitating manufacture a connecting flange which may be nade of any suitable material such as metal or plastics material, is bonded into the hollow connecting portion. Where shafts are made of fibre-reinforced material, the connecting flange can be wrapped over for direct connection to the shaft.

The bond between the connecting flange and the tubular shaft also permits the transmission of limited axial forces.

We have found a shaft in which both the interior and the exterior of the connecting portion are of generally oval or elliptical shape, to be particularly advantageous. Such a shaft is easier to form by winding in one piece using composite fibres as described above, than a shaft having a polygonal connecting portion. Also irrespective of the method of manufacture, less material is required by virtue of the preferred geometry and since the optional connecting flange may be formed of plastics material, it is possible to produce a lightweight (minimum mass) shaft having the requisite torsional rigidity.

Embodiments of the invention will now be described by way of example with reference to the accompanying drawing of which: Figure 1 is a perspective view of a drive shaft according to the invention; and Figure 2 is a fragmentary perspective view of another drive shaft according to the invention.

Figure 1 illustrates a drive shaft 10 having a central cylindrical portion 11, each end of which terminates in a hollow elliptical connecting piece 13 via a conical transition piece 12. The cross-section of the connecting piece can be any desired, non-circular symmetrical or regular shape, such as rectangle, square or polygon. Figure 2 shows a connecting piece 13' which is octagonal in inner cross-section and which connects directly to the cylindrical portion 11'.

The shaft 10 is made in one piece of a composite fibre material, by winding over a collapsible mandrel (not shown on the drawing). Fibre matting or fabric can be inserted for reinforcement in the end areas 12 and 13. Suitable fibres would be carbon, aramide and glass.

After the shaft 10 has been wound and the mandrel withdrawn by first dismantling and removing the ends thereof and subsequently withdrawing the cylindrical core, a connecting flange 14 of metal or plastic is bonded into the cavity 15 of the elliptical end portion 13. The elliptical or polygonal crosssection of the connecting pieces 13 or 13' permits the installation of fittings to accommodate any desired shaft connections, such as cardan joints or splined connections permitting limited relative axial displacement e.g. to compensate for inaccuracies or mismatch in the length of the mating parts.

On the fibre-reinforced shafts 10 the connecting flange 14 can be wound directly on the outer circumference, eliminating the need for additional bonding.

In some applications, as perhaps for aircraft, the connecting flange 14 may be of plastics material to minimise the weight of the drive shaft 10. The connecting flange can be formed to suit a particular application and different forms may be used at opposite ends of the shaft 10. Depending on the application the drive shaft may also be fitted with a hollow connecting piece 13 only. Slots 16 in the conical transition portion permit the introduction of tools for assembling the shaft to a driving or driven element.

Claims

1. Atorque shaft comprising a cylindrical shaft portion having at one end thereof and integral therewith a hollow connecting portion the internal cross-section of which is non-circular in shape.

2. A shaft according to claim 1 wherein the internal cross-section shape of the connecting portion is oval, elliptical or polygonal.

3. A shaft according to claim 1 or claim 2 wherein a transition portion intervening between the cylindrical shaft portion and the connection portion varies in cross-section so as to merge between the exterior of the cylindrical portion and the connecting portion.

4. A shaft according to claim 3 wherein the transition region is generally conical in shape.

5. A shaft according to any one of the preceding claims and formed of a composite fibre material.

6. A shaft according to claim 5, wherein the cylinder shaft portion, the connecting portion or portions and the optional transition portion or portions comprise several layers of fibre wound in one operation.

7. A shaft according to any one of the preceding claims, and comprising an external and/or internal protective layer of glass or aramide fibre.

8. A shaft according to claim 5, wherein end portions of the shaft include fibre matting or fabric between wound fibre layers.

9. A shaft according to any one of the preceding claims, wherein a connecting flange is bonded or wound within the connecting portion.

10. A shaft according to any one of the preceding claims, wherein both the exterior and the interior of the hollow connecting portions are generally oral or elliptical in cross-section.

11. A method of forming a torque shaft substantially as hereinbefore described.

11. A method of forming a torque shaft comprising winding fibres around a mandrel to form an integral structure having a cylindrical shaft portion and, on at least one end thereof a hollow connecting portion the internal cross-section of which is of a non-circular shape.

12. A torque shaft constructed and arranged substantially as hereinbefore described with reference to and as illustrated in the accompanying drawing.

13. A method of forming a torque shaft substantially as hereinbefore described.

New claims or amendments to claims filed on 27 Oct 1983 Superseded claims 1-13 New or amended claims:- 1-11 attached CLAIMS

1. A torque shaft comprising a cylindrical shaft portion having at one end thereof and integral therewith a hollow connecting portion the internal cross-section of which is oval or elliptical in shape and wherein a transition portion intervening between the cylindrical shaft portion and the connecting portion varies in cross-section so as to merge between the exterior of the cylindrical portion and the connecting portion.

2. A shaft according to claim 1 wherein the transition region is generally conical in shape.

3. A shaft according to any one of the preceding claims and formed of a composite fibre material.

4. A shaft according to claim 3, wherein the cylinder shaft portion, the connecting portion or portions and the optional transition portion or portions comprise several layers of fibre wound in one operation.

5. A shaft according to any one of the preceding claims, and comprising an external and/or internal protective layer of glass or aramide fibre.

6. A shaft according to claim 3, wherein end portions of the shaft include fibre matting or fabric between wound fibre layers.

7. A shaft according to any one of the preceding claims, wherein a connecting flange is bonded or wound within the connecting portion.

8. A shaft according to any one of the preceding claims, wherein both the exterior and the interior of the hollow connecting portions are generally oval or elliptical in cross-section.

9. A method for forming a torque shaft comprising winding fibres around a mandrel to form an integral structure having a cylindrical shaft portion and, on at least one end thereof a hollow connecting portion the internal cross-section of which is oval or elliptical in shape.

10. A torque shaft constructed and arranged substantially as hereinbefore described with reference to and as illustrated in the accompanying drawing.