FI100865B - Sealing piece for single or multi-strand composite blank - Google Patents

Description

100865

Single or multi-strand composite blank closure piece -

The present invention relates to a closure body for a single or multi-strand composite blank.

The method of making single or multi-stranded wires (superconducting conductors or the like) involves the step of assembling several hundred or thousands of rods (e.g., an alloy of niobium and titanium in a matrix of copper or nickel-copper alloy) inside a machined cylindrical body. The body is closed at both ends by lids or closure pieces of varying shape. These closure pieces are usually fitted to and welded to the bore of the cylinder body. This gives a blank suitable for wire drawing.

In order to improve the cohesion of the product after extrusion, the blank thus formed must be subjected to isostatic hot or cold pressing after the lids have been attached by welding. Due to the radial stiffness of the closure bodies, the compression of the cylinder body does not take place in a completely uniform manner. Those parts of the cylinder which are adjacent to the closure pieces are compressed less than other parts of the blank, and the cylindricality can change considerably. The cohesion of the product obtained after extrusion may thus be deficient at these points.

With the present invention, this drawback can be remedied. To this end, the lids are provided with inner and outer grooves which allow radial deformation of the lids during isostatic pressing.

The invention thus relates to a closure body of a single or multi-strand composite blank, the blank consisting of a tubular body filled with one or more cylindrical components, each end of the tubular body being closed by said closure body having two main surfaces, the inner part of the tubular body and the second main surface are on opposite sides of the first surface, the body being characterized in that each of the two main surfaces is provided with a continuous groove so that one groove surrounds the other and the depth of the grooves is such that they partially overlap.

The grooves may be concentric circumferential grooves with respect to the axis of the tubular body when the closure body closes the tubular body. This facilitates their manufacture.

15

The grooves are preferably straight grooves.

The width of the grooves and their mutual spacing are preferably such that they are completely or partially filled by the material of the closure body after the isostatic pressing of the blank. This provides the most homogeneous compression possible on the preform structure.

The closure piece can be equipped with a suction pipe.

25

The invention will now be described in detail by means of an embodiment, which, however, is not intended to limit the invention in any way, with reference to the accompanying drawings, in which:

Fig. 1 is a half-sectional view showing a multi-stranded blank according to the prior art prior to the isostatic pressing step; Figures 2, 3 and 4 show the blank of Figure 1 after the isostatic pressing step; 3 100865

Figures 5 and 6 show closure pieces according to the invention; and

Figures 7, 8 and 9 show a blank provided with closure caps-5 pieces according to the invention after an isostatic pressing step.

Figure 1 shows a blank conventionally used in the manufacture of multifilament yarn. It consists of hexagonal bars 10 formed of NbTi or other alloy strands embedded in a matrix of copper or other alloys or conductive metals. The rods 1 are assembled, for example, in a copper tubular body 2. Each end of the tubular body 2 is closed by a lit-15 closure body 3, 4. The bodies 3 and 4 fit into the bore of the tubular body. The closure body 3 is provided with a suction tube 5, by means of which a vacuum can be formed inside the blank. The closure pieces are welded from their joints to the tubular body so that the blank 20 becomes airtight.

When the preform is closed, it is subjected to an isostatic pressing step.

25 When such a blank is used, the tubular body is not pressed evenly onto the rods at the ends of the blank. This error is due to the stiffness of the closure pieces. It is shown in Figures 2-4.

30 Isostatic compression has deformed some parts of the blank, as shown in Figure 2. The outer diameter of the tubular body has been somewhat reduced except for its ends which have not been able to be compressed due to the bodies 3 and 4. Likewise, the center portion of each closure body, with the exception of the circumferential portion 35, is slightly depressed.

Figure 3, which is an enlarged view of the circumferential corners of the blank, shows well the inhomogeneity of the compression at this point. The rods 1 are bent, and an empty space 6 is left between the rods and the tubular body 2.

5 Figure 4 shows the blank seen from the side of the closure body 4. The circles marked with dashed lines show the inner circumference of the tubular body 2 at the center of the blank, circle 7, and at its ends, circle 8.

According to Figure 5, the closure body 11 according to the invention has two main surfaces 12 and 13. In this embodiment, the body 11 is flat and round. It is shown in half section. The body 11 has a collar 14 which facilitates its fitting into the tube body 15 of the blank. When the blank is closed, the surface 13 thus comes against the ends of the rods. The surface 13 is provided with a circular groove 15 of concentric and straight cross-section. The surface 12 is provided with a groove 16 of the same shape as the groove 15 so that the groove 15 surrounds it. The depth of each of the 20 grooves is such that the grooves partially overlap. There is a spacer 17 between them.

According to Figure 6, the second closure body 21 according to the invention comprises two main surfaces 22 and 23. In this exemplary embodiment, the body 21 is flat and round. It is shown in half section. The body 21 has a collar 24 which facilitates its insertion into the blank body piece. When the blank is closed, the surface 23 thus comes against the ends of the rods. The surface 23 is provided with a circular groove 25 of a sa-30 and straight cross-section. The depth of both grooves is such that the grooves partially overlap. Between them there is a spacer 27. The Kap-35 piece 21 is provided with an axial suction tube 28, by means of which a vacuum can be formed in the blank.

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The closure pieces may be the same or a different metal or alloy as the pipe piece.

The blank provided with closure pieces corresponding to bodies 11 and 21 allows the tubular body to be evenly deformed both at the center and at the ends. This deformation provides a homogeneous compression along the entire length of the body. It allows a more even flow of products during the next extrusion step. Figures 7-9 10 show this case.

The isostatic compression has uniformly deformed the pipe body 2, as shown in Fig. 7. Its inside diameter has decreased steadily. This is illustrated in bold lines 15 as a circle 31 in Figure 9, which shows the blank as seen from the side of the closure body 11.

Figure 8, which is an enlarged view of the circumferential corner of the blank, clearly shows the homogeneity of the compression at this point.

20 The rods 1 are straight and there is no empty space between the rods and the tubular body 2.

By appropriately dimensioning the grooves, i.e. their width and the thickness of their intermediate circumference 17 or 27, the best compression effect is obtained. In order to achieve the best result, it is then required that the closure pieces can be compressed radially to the desired amount. On the other hand, the deformation of the closure pieces must be sufficient to achieve uniform compression of the rods. On the other hand, the tightness of the blank must not deteriorate. This is shown in Figure 7, which shows that the grooves 15, 16 of the closure body 11 and the grooves 25, 26 of the closure body 21 are practically closed. The slight axial depression of the closure members due to isostatic compression has caused the grooves 16 and 35 26 to close at the outer major surfaces 12 and 22 of the closure members. Thus, in Figure 9, the groove 16 has become a single line.

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By means of the invention, a better quality blank can thus be obtained after compression. This increases the overall efficiency of further processing of the blank. Another advantage is that the machining of the tubular body no longer needs to be repaired after the compression step for extrusion. Since the tubular body is practically uniformly compressed, it can be placed in the extrusion tank without any problems.

Flat closure bodies have been described above, but the invention is equally suitable for other shaped closure bodies, e.g. those which may include an inner or outer cone.

Claims (5)

100865 A closure body of a single or multi-strand composite preform, the preform consisting of a tubular body (2) filled with one or more cylindrical components 5, each end of the tubular body being closed by said closure body (11, 21) having two main surfaces, the main surface (13, 23) encloses the interior of the tubular body and the second main surface (12, 22) is on the opposite side 10 of the first surface, characterized in that each of the two main surfaces is provided with a continuous groove (15, 16, 25, 26) such that one groove surrounds the other, and the depth of the grooves is such that they partially overlap. Closure body according to Claim 1, characterized in that the grooves (15, 16, 25, 26) are circumferential grooves concentric with the axis of the tubular body (2) when the closure body closes the tubular body. Closure body according to Claim 1, characterized in that the grooves (15, 16, 25, 26) are straight grooves. Closure body according to one of Claims 1 to 3, characterized in that the width of the grooves and the distance between them are such that, after isostatic pressing of the blank, the material of the closure body fills them in whole or in part. Closure body according to one of Claims 1 to 4, characterized in that it is provided with a suction pipe (28). 100865