GB2329351A

GB2329351A - Joining by means of rolling elements

Info

Publication number: GB2329351A
Application number: GB9720082A
Authority: GB
Inventors: Masoud Mobaraki
Original assignee: Rolls Royce Power Engineering PLC
Current assignee: Rolls Royce Power Engineering PLC
Priority date: 1997-09-23
Filing date: 1997-09-23
Publication date: 1999-03-24
Also published as: GB9720082D0

Abstract

A method of joining components (12,14) involves an apparatus with a rotating head (24), including rolling elements (22), and a thrust bearing (26) through which a load is transmitted. In operation the components (12, 14) are inserted between the rotating head (24) and the thrust bearing (26). The rolling elements (22) rotate under pressure to join the interface between the components (12, 14). As the rolling elements (22) rotate small deformations take place in the component (12) which causes gradual dispersion of the metal away from the rolling elements (22) and a joint is provided between the components (12,14).

Description

METHOD OF JOINING AND APPARATUS FOR USE IN THE SAME The present invention relates to a method of joining components and to apparatus for use in such a method. In particular it relates to a method of joining a plate to a cylindrical member such as a boss or shaft.

There are certain manufactured parts in which thin plates are fabricated to thick bosses. If these components are fitted with bearings and used for running shafts then high tolerances are required. In particular the centre of the hole in the plate through which the boss is inserted must align with the centre of the boss and the sides of the boss and the plate must be at 90 degrees.

To attain the accuracy and high tolerances required the components go through an extensive number of manufacturing activities, including milling and drilling operations consequently affecting component and final product costs.

The present invention seeks to provide a simplified manufacturing technique which eliminates expensive and time consuming milling and drilling operations whilst attaining the accuracy of alignment and the high tolerances required.

According to the present invention a method of joining components comprises the steps of rotating rolling elements under pressure at the interface between the components so that metal is dispersed away from the rolling elements and a joint is formed at the interface between the components.

In the preferred embodiment of the present invention the components are a cylindrical member and a metal plate. The cylindrical member is inserted through an aperture in the metal plate and the metal in the plate disperses away from the rolling elements to form a joint between the cylindrical member and the metal plate.

The cylindrical member may have an aperture therein and the metal in the plate is dispersed away from the rolling elements so that the centre of the aperture in the cylindrical member is aligned with the centre of the aperture in the metal plate.

Preferably the pressure at the interface between the cylindrical member and the metal plate is sufficient to maintain the sides of the cylindrical member and the plate at 90 degrees.

The pressure at the interface between the cylindrical member and the metal plate may be sufficient to form an air tight seal therebetween.

In a further aspect of the present invention apparatus for joining components comprises a rotating head which includes at least one rolling element and a thrust means through which a load is transmitted, whereby in operation the components to be joined are inserted and by rotation of the head and the application of a load through the thrust means material is dispersed from the rolling elements to form a joint between the components.

Rolling elements may be provided on either or both sides of the joint.

Preferably a central spline is provided on which the components are located. The thrust means is preferably a trust bearing and the load is applied through a compression spring acting on the thrust bearing.

A plurality of rolling elements may be used which rotate in a circular path. The circular path may reduce in diameter as the rolling elements rotate.

The head is adapted for rotation by attachment to a power tool and the head is preferably hexagonal.

The present invention will now be described with reference to the accompanying drawings in which; Figure 1 shows the components to be joined.

Figure 2 shows the final assembly incorporating the joined components.

Figure 3 is a cross-sectional view of a forming tool in accordance with the present invention.

In certain manufactured parts 10 a thin plate 12 is fabricated to a thick boss 14, figure 1. The plate 12 and boss 14 are joined together by forming metal from around a hole 13 in the thin plate 12 to the outside of the boss 14.

Once fabricated two of the manufactured parts 10 are fitted with bearings 16 and used for running shafts 18, figure 2.

Cold forming of the metal to join the plate 12 and boss 14 is achieved by rotating rolling elements 22, such as ball bearings, under pressure against the interface between the plate 12 and the boss 14. As the ball bearings 22 are rotated against the plate 12 it causes small deformations to take place. This causes gradual dispersion of the metal away from the ball bearings 22 which in turn causes the metal to be pushed into the gap C in figure 1.

The gradual metal movement around three of more ball bearings 22 causes the hole 13 in the plate 12 to close up evenly. In this way the centre of the hole 13 in the plate 12 and the centre of the boss 14 are aligned perfectly whilst the downward forces ensure that the plate 12 and boss 14 remain at 90 degrees with respect to one another.

The strength of the joint is determined from the variables B, C, D, d, T shown in figure 1 and the material properties used. For example for D=45, T=4, B=1, d=37 and a material choice of mild steel a joint capable of withstanding a torque of 240 NM and a pull force of 3000Kg may be achieved. However the natural age annealing process in certain materials such as mild steel causes a drop in the grip and consequently affects the strength of the joint. A drop in torque of up to 50% may be experienced.

Figure 3 shows a forming tool 20 designed to facilitate joining of the plate 12 and boss 14. The tool 20 splits into an two halves. One half includes a housing 25, thrust bearing 26, compression spring 27, compression collar 28 and a nut 29. The other half includes a central spline 21, rotating head 24 which includes the ball bearings 22 and a circular bearing race 23.

The tool 20 is split into two halves and the plate 12 and boss 14 are inserted. The boss 14 is located on the housing 25 and the plate 12 on the boss 14. The tool is then reassembled by the insertion of the central spline 21 through the boss 14. The nut 29 is fastened and holds the two halves of the tool 20 together.

In figure 3 the tool 20 is shown assembled with the plate 12 and boss 14 in situ.

Pressure is applied to the interface between the plate 12 and the boss 14 via the nut 29 and compression collar 28 which compresses the spring 27 and applies a load through the thrust bearing 26.

A power tool (not shown) is attached to the rotating head 24 which is hexagonal. The power tool drives the head 24 to rotate the ball bearings 22 around the circular bearing race 23. Rotation of the ball bearings 22 and the pressure applied through the thrust bearing 26 causes cold forming of the metal at the interface between the plate 12 and the boss 14.

It will be appreciated by one skilled in the art that any number of ball bearings 22 may be used in each bearing race 23. Alternatively a multiple number of bearing races 23 may also be used for example one may be used on each side of the interface between the plate 12 and the boss 14.

A further facility may also be provided where the ball bearings 22 move radially inward as they rotate ie. the diameter of the bearing race 23 would reduce over the race cycle.

Claims

Claims:

1. A method of joining components comprising the steps of rotating rolling elements under pressure at the interface between the components so that metal is dispersed away from the rolling elements and a joint is formed at the interface between the components.

2. A method as claimed in claim 1 in which the components are a cylindrical member and a metal plate.

3. A method as claimed in claim 2 in which the cylindrical member is inserted through an aperture in the metal plate and the metal in the plate disperses away from the rolling elements to form a joint between the cylindrical member and the metal plate.

4. A method as claimed in claim 2 or claim 3 in which the cylindrical member have an aperture therein and the metal in the plate is dispersed away from the rolling elements so that the centre of the aperture in the cylindrical member is aligned with the centre of the aperture in the metal plate.

5. A method as claimed in any of claims 2-4 in which the pressure at the interface between the cylindrical member and the metal plate is sufficient to maintain the sides of the cylindrical member and the plate at 90 degrees.

6. A method as claimed in any preceding claim in which the pressure at the interface between the components is sufficient to form an air tight seal therebetween.

7. Apparatus for joining components comprising a rotating head which includes at least one rolling element and a thrust means through which a load is transmitted to the components to be joined, whereby in operation the components to be joined are inserted and rotation of the head and the application of a load through the thrust means causes material to be dispersed away from the rolling elements to form a joint between the components.

8. Apparatus as claimed in claim 7 in which rolling elements are provided on both sides of the joint.

9. Apparatus as claimed in claim 7 or claim 8 in which a central spline is provided on which the components are located.

10. Apparatus as claimed in claim 9 in which the thrust means is preferably a trust bearing and the load is applied through a compression spring acting on the thrust bearing.

11. Apparatus as claimed in claims 7-9 in which a plurality of rolling elements are used which rotate in a circular path.

12. Apparatus as claimed in claim 11 in which the circular path reduces in diameter as the rolling elements rotate.

13. Apparatus as claimed in claim 12 in which the head is adapted for rotation by attachment to a power tool.

14. Apparatus as claimed in claim 13 in which the head is hexagonal.

15. A method of joining components as hereinbefore described with reference to and as shown in figure 1 and 2.

16. Apparatus for joining components as hereinbefore described with reference to and as shown in figure 3.