Manufacture of tubular components

Abstract

 A method and apparatus for push-pointing a tube so as to produce a smaller diameter end portion includes means for sizing and finishing the reduced diameter portion utilizing a headed mandrel located in the tube and withdrawn through the reduced diameter portion whilst the latter is engaged in the push-pointing die. Figure 5 shows the push-pointing step completed, and the mandrel engaged with the die ready to begin the internal sizing operation.

Description

[0001] This invention relates to the manufacture of tubular components by an axial swageing or reduction/extrusion process involving forcing an extrusion die over an end portion of a tube, or "push-pointing" as such process is usually called. The die has a conical entry portion of larger diameter than the untreated tube and a smallest diameter portion corresponding to the required diameter of the finished tube. The tube needs to be clamped, or alternatively, particularly where a component requires both ends to be similarly formed, both ends can be treated at the same time thus reducing or even obviating the need for clamping of the tube.

[0002] The object of the present invention is to provide an improved method and apparatus for carrying such operations where the reduced diameter portion has a finite length (as distinct from the situation where it is merely a frusto-conical or like shaping at each end).

[0003] The expressions "diameter", "conical" and "frusto-conical" used herein are strictly correct in the case of circular cross section tube, but the invention can be applied to non-circular tube in which case these expressions are to include the frusto-pyramidal and other forms which are produced by analogous operations in their scope.

[0004] The invention offers particular advantages where the tube has a welded seam, as distinct from a seamless drawn tube, although the invention is also applicable (with less advantage) in the seamless tube situation.

[0005] According to the present invention a method of making a stepped diameter tubular component comprises firstly introducing a headed mandrel into the interior of the untreated tube, secondly push-pointing the end of the tube to form a portion of reduced diameter, and then withdrawing the mandrel through the reduced diameter portion to size the interior.

[0006] By the cooperation of the push-pointing die used to form the exterior dimension of the stepped (reduced) portion with the mandrel head, both the interior and the exterior of the stepped portion can be drawn to finished size, and any, for example, weld bead on the inside of the reduced diameter portion can be cleaned off and removed.

[0007] It will be appreciated by those skilled in the art that the push-pointing die has a parallel portion of finite length, and the sizing of the internal diameter of the component is effected whilst the mandrel is within that portion. It is conventional to provide a push-pointing die with a wide angle mouth of frusto-conical formation having a large end which is of greater diameter than the untreated component so as to receive that end and guide it into the working portion of the tapered throat so afforded; followed by a relatively short axial length which is of uniform diameter, and then a relatively narrow angle frusto - conical portion behind that, so as to reduce frictional drag on the reduced diameter portion if a substantial length of the same - greater than the length of the uniform diameter portion of the die - is formed. For the purposes of the present invention however, at least in order to obtain maximum advantage and best sizing of internal and external surfaces, it is preferred that the parallel portion is either to be made of greater length than usual, or alternative equivalent means may be used as explained below.

[0008] According to a feature of the invention, the alternative means comprise arrangements for axially displacing the push-pointing die and the mandrel substantially synchronously whilst the mandrel head is located within the uniform diameter portion of the die. Hence there is no risk of the internal diameter being perfected to the detriment of the external diameter as might be the case if the mandrel head were to be moved relative to the push-pointing die through the back tapered portion of the same.

[0009] According to another feature of the invention, a component has both ends formed successively or simultaneously by like means.

[0010] The invention is now more particularly described with reference to the accompanying drawings wherein:

Figure 1 is a diagrammatic elevation of an apparatus:

Figures 2 to 6 are fragmentary sectional elevations on an enlarged scale to illustrate the method of the invention;

Figure 7 is a further enlarged view like Figure 5; and Figures 8 and 9 are respectively an elevation and a plan view of a practical embodiment.

[0011] Turning first to Figure 1, the apparatus comprises a clamp 10 to hold a tube 12 in position for treatment. If one end only of the tube is to be treated a fixed abutment may lie at the other end of the tube and the clamp is only a steady. The illustrations assume that both ends of a tube are to be treated, although not necessarily simultaneously, as hereinafter discussed. The apparatus shown is adapted for treatment at both ends by the provision of duplicated sets of displacement rams 14 and dies 16.

[0012] Figures 2 to 7 show only a single end of the machine for clarity, but as mentioned both ends will be the same. Referring now to Figure 2, each die comprises a major frusto-conical portion 18 with its larger end adjacent to the tube, a parallel portion 20 opening from the small end of the portion 18, and a tapered portion 22 which increases in diameter from the parallel portion to the opposite end of the die. The die is mounted on a ram 24 of hydraulic cylinder 26.

[0013] The die structure further includes mandrel 28 which may be somewhat barrel-shaped as shown preferably but not essentially having a uniform diameter portion of finite length generally mid-way along its axial length, the uniform diameter being the maximum diameter of the mandrel. The mandrel is mounted on a second ram 30 powered by a hydraulic cylinder 32. Ram 30 extends through ram 24. In accordance with a feature of the invention the two rams 24, 28 can be coupled by a lock 34. Appropriate hydraulic fluid flow control valves are provided to enable the rams to be displaced in either direction.

[0014] The method ot the invention can now be described. Assuming that a suitable tube, die and mandrel are positioned in the apparatus and appropriately attached and clamped, ram 30 is first extended to the maximum travel so as to locate mandrel 28 in the tube 12 and beyond the zone to be treated. Ram 24 is then, or simultaneously, extended so as to force the die onto the tube and push-point the end of the tube into a frusto-conical shape 40 as shown in Figure 3. Ram 24 continues to extend to displace the whole die structure along the tube so as to produce a reduced diameter tube portion 44 (Figure 4) and effectively move the frusto-conical portion 40 along the tube length. This extension of ram 24 to the desired extent may accompany or follow the extension of ram 30: Figures 3 and 4 show the ram 30 movement as being completed before ram 24 movement is completed.

[0015] When the desired external shape of the tube is produced (Figures 4 to 6) the next step is to begin the return movement of ram 30 so as to position mandrel 28 in alignment with the parallel portion (or minimum diameter portion) of the die as shown in Figures 5 and 7, whilst the die structure is in contact with the frusto-conical push-pointed portion of the tube. Lock 34 is then operated and both rams are returned together, thus drawing the die and mandrel over and through (respectively) the reduced diameter portion of the tube. This cleans, trues and sizes the portion 44 internally and externally.

[0016] When both ends of the tube are to be treated, it is a preferred feature of the invention that the push-pointing rams 24 are displaced towards one another alternately: this reduces the maximum power required. The power requirement for the . sizing operation is usually less, dependent to some extent upon the nature of the tube and the permissible tolerances so that usually both sets of locked rams can be withdrawn together to size both ends simultaneously: but again alternate operation is possible if required.

[0017] The drawings illustrate a die with a parallel portion substantially equal in length to the uniform diameter portion mandrel to suit the simultaneous withdrawal technique described. However, one or other of the mandrel or die may have a uniform portion of infinite length. That is to say the mandrel may be wholly barrel-shaped or the two tapered portions in the die may meet without a parallel diameter portion.

[0018] Alternatively, the parallel diameter portion may be longer than illustrated in which event it may be possible for there to be relative movement between die and mandrel during the external/internal sizing operation. The simultaneous movement of the two over the tube is preferred to obtain maximum quality of finished tube sized both internally ana externally.

[0019] Moreover, it is intended to be within the scope of the invention to size and finish the interior of the reduced diameter portion only, for which purpose relative movement of the mandrel and tube is required but not of the die.

[0020] Turning now to Figures 9 and 10, it will be seen that in the practical embodiment the dies and rams are arranged on a table 50 with ram cylinders 52 (for the ram 30) and 54 (for the ram 24) mounted on brackets 56 running on slideways to facilitate adjustment to set up for particular dimensions. The workpiece mount or clamp 20 is here shown as comprising a pair of aligned hydraulic cylinders 58 having their axes transverse to those of the push-pointed dies and sizing mandrel. Cylinders 58 are likewise mounted on slideways to enable adjustment to suit the workpiece. The machine structure includes a hydraulic reservoir 60, a pump and motor set 62, and the associated fluid control valves 64.

Claims

1. A method of making a stepped diameter tubular component comprises firstly introducing a headed mandrel in the interior of the untreated tube, secondly push-pointing the end of the tube to form a portion of reduced diameter, and then withdrawing the mandrel through the reduced diameter portion to size its interior.

2. A method as claimed in Claim 1 which further comprises simultaneously sizing the interior and exterior of the reduced diameter portion, by withdrawing the push-pointing die simultaneously with the aligned mandrel to draw them through and over the tube.

3. A method as claimed in Claim 2 wherein the die and mandrel are locked together with the minimum diameter portion of the die and maximum diameter portion of the mandrel coincident, prior to the sizing operation.

4. A method as claimed in Claim 1 wherein both ends of the tube are treated and the push-pointing steps effective on the two ends take place alternately.

5. Apparatus for carrying out the method of Claim 1 comprising a push-pointing die having a frusto-conical push-pointing portion, and a headed mandrel, ram means for displacing the said die in a first direction to effect push-pointing, and ram means for displacing the mandrel in the opposite direction to effect sizing.

6. Apparatus as claimed in Claim 5 wherein the die has a minimum diameter portion of finite length and the mandrel has a maximum diameter portion of finite length, and means are provided for locking the mandrel and die together with the said portions coincident.

7. Apparatus as claimed in Claim 5 comprising a pair of push-pointing dies and mandrels arranged to operate on opposite ends of a tube and means for effecting alternate displacement of at least a push-pointing ram.

Drawing