GB2087770A - Jointing method - Google Patents

Abstract

A cold forming process for permanently connecting a generally tubular part 17 to an outer or inner part 16 utilizes a high radial pressure to the tubular part by means of press apparatus 4 acting upon an elastically deformable material 18. The tubular part is plastically deformed or compressed into tight engagement with the outer or inner part by the material, the material radially diverting part of an axially applied pressure in a direction towards the tubular part and inner or outer part. <IMAGE>

Description

SPECIFICATION Method and apparatus for connecting parts This invention relates to a method and apparatus for permanently connecting parts such as rotatable shaft components in which a generally tubular part is connected to an outer or inner part by applying a high radial pressure to the tubular part by means of a press apparatus, such that the tubular part is plastically deformed or compressed into tight engagement with the outer or inner part.

Processes are already known, for example as shown in UK Patent Specification 1,264,707, in which a tubular shaft component is connected to a further component part inserted without the shaft tube by cold swaging the metal of the shaft component into tight engagement with the inner component part.

This process is carried out by radial compression of the tubular part within a suitably shaped multi-piece die assembly. However, the process according to this disclosure has the disadvantage in that the die assembly must be accurately dimensioned if unwanted distortion of the tubular part during compression is to be avoided. Furthermore, the parts to be connected must also have correspondingly accurate dimensional tolerances if unwanted distortion or deformation is to be avoided.

It is an object of the present invention to provide a process for connecting a generally tubular part to an outer or inner part in which unwanted distortion or deformation is avoided and the requirement for accurate dimensional tolerances between the parts to be connected is obviated. It is a further object of the present invention to provide apparatus for carrying out this process.

According to theinvention, there is provided a cold forming process for permanently connecting a generally tubular part to an outer or inner part by applying a high radial pressure to the tubular part by means of press apparatus, such that the tubular part is plastically deformed or compressed into tight engagement with the outer or inner part; wherein pressure in the press apparatus is produced in the direction of the longitudinal axis of the apparatus and acts on an elastically deformable material, with said material radially diverting part of the pressure in a direction towards the tubular part and inner or outer part.

The process according to the invention may be used for connecting the outer parts of a rotary constant velocity ratio universal joint to a tubular shaft to form a drive shaft. To facilitate torque transmission, splines may be provided on the outside of the inner part and the tube plastically deformed around the splines to a corresponding shape suitable for torque transmission.

According to a further aspect of the present invention there is provided apparatus for carrying out the process abovedefined, the apparatus comprising, means for supporting the parts to be connected, means defining a cavity adjacent the tubular part, the cavity containing an electromeric material, and means for applying an axial pressure to the material in the cavity so that a radial pressure is exerted on the tubular part. The means defining a cavity may comprise a sleeve and a pressure ring, slidable within the sleeve, and such means may be splittable to allow withdrawal of a work-piece connected according to the process of the present invention.

The apparatus may further comprise plastics seals to seal the elastically deformable material, which material may comprise a plurality of segments. A supporting mandrel may be provided to support the inner or outer part during deformation of the tubular part.

Apparatus for carrying out the process according to the present invention comprises an arrangement in which a pressure ring is slidable within a sleeve filled with an elastically deformable material. The sleeve is placed adjacent the tubular part and, when pressure is applied to the pressure ring, the elastic material exerts a radial pressure to deform the tubular part. The use of an elastomeric material is particularly advantageous in that an axially introduced force is partly diverted into a radial force acting on the parts to be connected with elastic material uniformly adhering to the surface of the tubular part to cause the material in this part to flow uniformly.

The provision of plastics sealing rings to seal the elastically deformable material in the cavity defined by the sleeve and pressure ring has the advantage in that it is relatively easy to cold form tubes of differing diameters with a single apparatus in which the difference in tolerances can be compensated for by using appropriate sized seals. This prevents extrusion of the elastic material past the pressure ring or sleeve if the tubular part is not a tight fit within the sleeve or ring.

The provision of a supporting mandrel to support the inner or outer part has the advantage in that unwanted springing of these parts under the influence of the pressure exerted by the apparatus on the tubular part is avoided.

The process of the invention and apparatus for carrying out such will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 shows an apparatus suitable for connecting parts of a drive shaft by a method according to the invention; Figure 2 is a sectional view of part of the apparatus shown in Figure 1; Figure 3 is an enlarged view of part of the apparatus, and parts to be connected; Figure 4 shows the parts of Figure 3 connected after completion of the process of the invention; Figure 5 shows the connected parts after the pressure in the apparatus has been removed; Figure 6 is a section along the line I - I of Figure 5; Figure 7shows the connected parts being removed from the apparatus; Figure 8 shows plastics sealing rings between the elastomeric material and the sleeve in an unpressurised condition;; Figure 9 shows the sealing rings of Figure 8 while pressure is being applied; Figure 10 shows an alternative embodiment of a plastics sealing ring; Figure 11 shows an alternative apparatus for carrying out the process of the present invention; Figure 12 is a section along the line A-B of the apparatus shown in Figure 11; Figure 13 is a detailed view of the arrangement of the elastomeric material shown in Figure 11; Figure 14 is a section along the line C-D of the apparatus shown in Figure 11.

Referring to Figure 1, apparatus according to the invention comprises a machine bed 1 upon which is fixed a tool head 2 for receiving parts to be connected according to the process of the invention.

Aforming tool 4, operable via hydraulic unit 3 is fixed to the tool head 2 and receives at one end a tube 5 which is one of the parts to be connected and is further supported by support means 6 extending upwardly from and fixed to the machine bed 1.

In Figure 2 is shown a detailed section of the forming tool 4, the tool comprising a rigid tool body 7 within which is fixed an annular sleeve 8 by screws 9. A cylindrical surface 10 within the sleeve 8 defines a cavity within which a complementary shaped part of a pressure ring 11 is slidable. A piston 12 is slidable within a bore in the tool body 7 and is movable to the left in Figure 2 by hydraulic fluid supplied via conduits 13 and 14to urge the ring 11 towards the sleeve 8. The piston 12 is of annular form and is slidable on an ejector 15, itself slidable to eject the assembly of the joined parts after operation of the apparatus. The parts to be joined comprise an annular inner part 16 with a knurled or spliced portion 21 on its external surface, and a tubular shaft 17 corresponding to the tube 5 shown in Figure 1.

The ejector 15 has a flanged end which abuts the end of tubular shaft 17.

Elastomeric material 18 is provided in the space between the tube 17, the sleeve 8 and the pressure ring 11 and is sealed therein by annular plastics sealing rings 19 and 20 of wedge-section. To support the inner part 16 from unwanted distortion during operation of the apparatus, a mandrel 23 of shape corresponding substantially to the inner bore of the inner part 16 and having a flanged end is provided between the ejector 15 and inner part 16.

Release springs 22 are provided between the pressure ring 11 and sleeve 8 to urge the ring 11 and piston 12 back to their initial position after operation of the apparatus.

Referring now to Figures 3, 4 and 5, the sequence of operation of the apparatus is shown. In Figure 3, the inner part 16 has been inserted within the tube 17 and the combined work-piece (16 and 17) is placed within the forming tool 4 such that one end of the tube 17 abuts the ejector mechanism 15 and the supporting mandrel 23 engages in the bore of the inner part 16. In this position, the elastomeric material 18 is in its substantially uncompressed state.

In Figure 4, the pressure ring 11 has been urged towards the material 18 under axial pressure exerted by the hydraulic unit 3 on the piston 12. Compression of the material 18 exerts a radial force on that part of the tube 17 adjacentthe material 18to squeeze the wall of the tube 17 in this region into conformation with the knurled or spliced recess 21 on the inner part 16. The plastics seals 19 and 20 prevent extrusion of the elastomeric material 18 along the length of the tube 17 during compression.

In the position shown in Figure 5, axial pressure on the ring 11 has been relieved and the elastomeric material 18 has returned to its original shape corresponding to that shown in Figure 3. Plastic deformation of the wall of the tube 17 has occurred in the region of the splined recesses 21 in the inner part 16. This condition can be seen clearly with reference to Figure 6 in which it will be noted that the inner part 16 and tube 17 have been forced into tight engagement in the region of the splines 21.

In Figure 7 is shown the final stage in the process, in which the ejector 15 has been advanced along the length of the sleeve 8 to eject the work-piece. The ejector 1 5 then returns to its starting position.

In Figures 8 and 9, are shown details of the seals 19 and 20, the position shown in Figure 8 corresponding to that shown in Figure 3 and the position of Figure 9 corresponding to that shown in Figure 4. In Figure 8, a space 25 exists between the elastic material 18 and the tube 17 which represents the usual material tolerance of the outer diameter of the tube 17. No pressure has been applied to the elastic material 18. In Figure 9, the elastic material is under pressure and, as a result, it first adheres to the sealing ring 19 which, in turn, due to the force PR, is pressed radially against the work-piece 17 and the sealing ring 19 is pressed radially outwards against the sleeve 8. This ensures that even with large tolerances in the material of the shaft 17, the elastic material 18 cannot escape between the sleeve 8 and the tube 17.By using the sealing rings 19 and 20 and their mutually facing inclined surfaces 24, the pressure acting in the direction of the longitudinal axis is divided into the force P which is the axial force and the radial force PR which determines the effectiveness of the seal 20.

In Figure 10, the sealing ring 26 is in the form of a disc and has no inclined surfaces corresponding to those on the seals 19 and 20. This type of seal may be used where it is expected that only relatively small diametrical tolerances are present in the shaft 17.

In Figure 11 is shown an alternative apparatus in which the inner part 16 has at one end an external diameter greater than the diameter of the tube 17.

Consequently, to achieve a satisfactory connection, the sleeve 8 is split along the axis of the apparatus to allow increase of the inner diameter of the sleeve 8 for withdrawal of the connected work-piece. The split sleeve 8 is slidable on an inclined surface 27 and a corresponding guide 28. On each half of the sleeve 8 is slidably fixed one-half of the pressure ring 11, each ring being spring-biased away from each sleeve half 8 by a spring arranged between the ring 11 and sleeve half 8 on a securing bolt. Each sleeve half 8 is provided with a semi-circular portion of the elastomeric material 18, together with semi-circular plastics seals.

In the arrangement shown in Figure 11, it will be apparent that axial pressure from the hydraulic unit pressurises the elastomeric material 18 via the semi-circular rings 11 when the sleeve 8 fully encloses the tube 17. However, because one end of the inner part 16 has a greater diameter than the tube 17 release of the connected work-piece from the tool head is facilitated by sliding each half of the tool head in a direction along the inclined surface 27.

In Figure 12 is shown in detail a sectional view of each half of the tool head in its fully engaged position with the tube 17 and inner part 16. The sliding arrangement of each sleeve 8 along guides 28, protruding from a tool outer ring 29, can be clearly seen.

In Figure 13 is shown the method of retaining each half of the elastomeric material 18 and corresponding plastics seals 30 and 31 within a dove-tailed groove in each sleeve 8.

In Figure 14the divided elastic material 18 is shown arranged around the tube 17 prior to application of pressure for each semi-circular ring part 11.

Claims (10)

1. A cold forming process for permanently connecting a generally tubular part to an outer or inner part by applying a high radial pressure to the tubular part by means of press apparatus, such that the tubular part is plastically deformed or compressed into tight engagement with the outer or inner parts; wherein pressure in the press apparatus is produced in the direction of the longitudinal axis of the parts and acts on an elastically deformable material, with said material radially diverting part of the pressure in a direction towards the tubular part and inner or outer part.

2. Apparatus for carrying out the process of Claim 1, comprising means for supporting said parts to be connected, means defining a cavity adjacent said tubular part, which cavity contains an elastomeric material, and means for applying an axial pressure to said material in said cavity so that a radial pressure is exerted on said tubular part.

3. Apparatus according to Claim 2, comprising a pressure ring slidable within a sleeve, the ring and sleeve together defining said cavity.

4. Apparatus according to Claim 2 or Claim 3 comprising plastics seals to seal the elastically deformable material in said cavity.

5. Apparatus according to Claim 2,3 or 4 in which a supporting mandrel is provided to support the inner or outer part during the formation of the tubular part.

6. Apparatus according to any one of Claims 2 to 5 in which the means defining a cavity is splittable to allow removal of said parts after connection.

7. Apparatus according to any one of claims 2 to 6 in which the elastic material comprises a plurality of segments.

8. Apparatus for carrying out the process according to Claim 1, substantially as herein described with reference to and as shown in Figures 1 to 10 of the accompanying drawings.

9. Apparatus for carrying out the process according to Claim 1, substantially as herein described with reference to and as shown in Figures 11 to 14 of the accompanying drawings.

10. A process substantially as hereinbefore described.