NO117368B - - Google Patents

Description

Procedure for pressing light metal cable sheaths.

This invention relates to sheathing

of electric cables and especially sheathing with aluminum or other light metals or their alloys which are pressed at a relatively high temperature. One of the purposes of this invention is to provide a process and apparatus which enables such metals to be pressed directly onto the cable core without damaging the cable insulation.

Another object of the invention

is to provide a process which makes it possible to use metal blocks of sufficient size to sheath entire fabrication lengths with cable without filling the press. When desired, filling of the press can also be carried out without risk or difficulty.

A further purpose of the invention is to provide a process and apparatus which can be operated at relatively low pressure and temperature, with which sufficient capacity is obtained for cable sheathing without the mechanical parts in the press being overloaded.

To achieve continuous pressing of

sheaths of light metal, it is previously known to use several recipients that open into a common press head. Furthermore, in connection with plastic presses, it is known to use primary and secondary recipients.

In general, this invention includes

a process where a relatively large metal block is pressed into a smaller metal block which is then pressed through the matrix around the cable core in a second pressing process. In this way, the pressing is carried out in stages and the cable core is exposed

only for the heat from the secondary pressing.

According to the invention, the pressing apparatus comprises one or more main recipients for receiving the metal to be pressed, equipment for pressing the metal from these recipients, one or more secondary recipients in which the metal from the main recipient is pressed, a matrix in connection with the secondary recipient and equipment for pressing the metal from the secondary recipient through the matrix and around the cable.

But in particular the invention relates to a process and apparatus for pressing cable sheaths of aluminum (or light metal alloy) where the aluminum is first pressed from a metal block in the main recipient into the secondary recipient containing the press head and then the sheath is pressed under the influence of another pressure piston for pressing in the secondary recipient.

The secondary recipient's capacity is relatively small compared to the main recipient's capacity, as it normally has a smaller diameter and a relatively short stroke.

The two recipients are placed at an angle to each other (normally right angles) so that the cable core passes through the main recipient.

The rhythm in the press where this process is carried out would be reciprocal because the pressing

into the secondary recipient and the pressing

of the cable jacket is carried out alternately and. in

order. In its simplest form, only two recipients are used, but there are several advantages to using at least two main recipients from which pressing into the secondary recipient occurs simultaneously. The advantage of

this, is that it allows the pressing of cable sheaths carried out in apparatus that is positioned so that the cable core passes through the press at right angles to the direction of pressing from the main recipient without the increase in temperature and pressure that this pressing method normally results in.

Also, the length of cable core passing through the secondary recipient is reduced very much compared to the length of the core, which would be necessary to pass through the center of the recipient when pressing equipment is used where pressure and temperature are kept at a low level by carrying out pressing in a rectilinear manner (ie pressing from a container coaxial with the cable core). This is advantageous because it simplifies the construction of the parts in the press head, and it limits the period of time when the cable core is exposed to high temperatures. It also allows the construction of a press with a very large capacity for filling aluminum without the disadvantages of the cable core being exposed to high temperatures for an extended period of time.

The advantage of this is the provision of a press of suitable dimensions to allow filling blocks of aluminum large enough to cover, if necessary, a full fabrication length of the cable core, so that welding in subsequent fillings can be avoided.

Alternative constructions of presses where this process could be carried out include the use of at least two main recipients arranged radially towards the common center line. Each of these simultaneously presses the metal into the secondary recipient. A number of other embodiments are possible, e.g. use of three or more receivers which press simultaneously and which are arranged in the same plane at right angles to the cable core's direction of passage.

According to a further embodiment, the cable core does not pass through the secondary piston. Two or more secondary recipients can be arranged at an acute angle to the cable core's direction of passage through the press head's central chamber. This method has advantages due to the fact that the pressure pistons for secondary pressing can be massive, while the secondary pressure piston in the previous example is whole and has alternating thickness and where the cable core is supported, as it passes coaxially through the secondary recipient in the press head.

The main process described up to this point may include further advantageous features, and among these the construction of apparatus for carrying out the process with features that are not possible in connection with known presses. These features include the use of hydraulic cylinders to move the main receivers into and out of contact with the press head, so that at the end of a cable sheathing operation, excess aluminum in the main receiver or receiver can be removed by moving the receiver back over the stationary pressure ram which remains in contact with the aluminum block. A cutting device is then affected which cuts away the remaining aluminum from the press head. When the pressing of the next cable core takes place, the sheath's quality is therefore not affected by collected slag and surface defects which are usually deposited on the remaining parts of the old metal block. Also, welding the new metal block to the old one can be done over a limited area of freshly cut aluminum instead of over the entire old metal block area, so that better welds are formed that can be incorporated into the cable jacket if required.

In normal pressing of a light metal alloy into sections and pipes, it has been found to be a great advantage to use a loose pressing block or a "follower" between the aluminum block and the surface of the pressing piston, as this can be removed with the remaining metal and then is put back behind the following metal block. This is not possible by other methods of cable sheathing, and difficulties have been encountered in the use of a solid tapered piston, or a piston with a butt-block attached to it by threads. The aforementioned process allows the use of such a loose pressure block. Moreover, at the end of a cable sheathing operation or series of such operations, this process enables (except for the option where the cable core does not pass through the secondary press punch) to use the secondary press punch for quick removal of the press tool (die and nipple) together with all remaining aluminum in the secondary recipient, and this provides a handy method for protection against the accumulation of impurities in the secondary recipient and a quick method for changing matrices either for cleaning or to change the dimension of the pressed mantle.

The invention will be better understood by reference to the attached drawings where figures 1 to 5 are the same section of part of the press equipment which schematically shows the cycle in the process.

Figure 6 is a simplified vertical section

of a complete press for carrying out a method according to the invention.

Figure 7 is a vertical section of the press in a plane perpendicular to figure 6. Figure 8 is a horizontal section of an alternative embodiment of a press with two diametrically opposite main recipients arranged to simultaneously press metal into the secondary recipient. Figure 9 is a divided vertical section of another alternative embodiment of the press according to the invention, and Figure 10 is a cross-section in the horizontal plane through the line 10—10 in Figure 9.

To illustrate the simplest design of this process and associated apparatus, reference is made below to figures 1 to 7 in the drawing. Figures 1 to 5 show the cycle for the operation of the press in a schematic way, and figures 6 and 7 show a simplified drawing of a press for carrying out the process. Figure 6 shows a section of the press in a plane that passes through the center line of both recipients, and Figure 7 shows the section of such a press in a plane perpendicular to the first plane and through the center line of the main recipient.

In these drawings, 1 denotes the main receiver, 2 the pressure piston in the main receiver, 3 a metal block, (not shown in Figures 6 and 7), 4 a press head, 5 the secondary receiver, 6 nipple and die, 7 a nipple holder, 8 a nipple, 9 a matrix, 10 a punch for secondary pressing and 11 a cutter. The cable core is marked X and the pressed jacket Y.

Figures 6 and 7 are the main hydraulic cylinder acting on a piston 2 shown at 12, and an auxiliary cylinder for moving the piston when filling the press is shown at 13. The reference number 14 indicates an auxiliary cylinder for moving the main recipient 1, and for holding it down on the press head 4 (only one of these is shown, but two or more can be advantageously used).

The reference designation 15 (figure 7) denotes an auxiliary hydraulic cylinder for retraction of the piston 2 (only one is shown, but more than one will normally be used). At 16 is shown a hydraulic cylinder for a secondary piston and 17 shows a hollow cylinder which allows the passage of the cable through the hydraulic cylinder for secondary pressing. A matrix support 18 is included to take up the pressure from matrix 9. Reference designation 19 is a hydraulic cylinder for maneuvering the cutter 11. To simplify the drawing, this does not show the auxiliary hydraulic cylinders for retraction of the piston for secondary pressing and the hydraulic cylinders used to affect the matrix block, as this is unnecessary for understanding the invention.

Figure 1 shows the position of the parts of the press as the press operation begins. The metal block 3 is placed in the main recipient 1 and the piston for secondary pressing 10 is pushed forward in its front position.

This is the position of the press when it is filled with the first aluminum block at the start. The piston 2 is then moved into line with the main recipient 1 under the influence of the hydraulic cylinder 13 (figure 1), and under the influence of the main cylinder 12 acting on the piston 2, pressing takes place from the main recipient 1 into the second row recipient 5 and this forces it secondary piston 10 back to the position shown in figure 2. This piston's travel is limited by the determined stroke length for the press, and when this position is reached, the main cylinder 12's pressure is reduced so that primary pressing ceases. During this part of the process, the pressure in the secondary hydraulic cylinder 16 is kept low, so that the aluminum is forced into the secondary recipient. At this stage, the position of the press and the aluminum in the press head is as shown in figure 2. As soon as the secondary recipient is filled, the pressure is immediately increased in the secondary cylinder 16 until pressing forward takes place through the nipple and the matrix 6, so that the pressing of the cable jacket from the matrix begins. At this stage, as shown in Figure 3, the cable core X is fed through the hollow cylinder 17 and the piston 10, and is carried forward by the pressing of the tube Y. When the secondary piston has reached the limit of its forward movement as shown in Figure 3 , the pressure in the secondary cylinder 16 is reduced, and the pressure in the main cylinder 12 increases until/the secondary piston 10 has again reached the limit of its backward movement as shown in Figure 4. This operation is repeated until the entire length of the cable is sheathed or until the main piston 2 has reached the limit of its movement.

In the first case, another cable core can now be fed into the press, and in the second case, the main recipient 1 is moved by maneuvering an auxiliary cylinder 14, and the cutter 11 is actuated by the hydraulic cylinder 19 to remove the rest of the metal block from the press head surface. This is indicated in figure 5. The main piston which protruded past the main receiver can be brought back under the influence of the heel cylinder 15. The position of the press is then as shown in figure 5.

When a loose "follower" has been used, it can be removed from the waste and reused in a later pressing. However, such a "follower" of this type is not shown in the drawing.

After this stage, the cutter 11 can be withdrawn, the main container 1 moved back into contact with the press head 4, the piston 2 moved out of line with the main recipient under the influence of the hydraulic cylinder 13 and another charge supplied to bring the press back into the supply condition shown in Figure 1 with the exception that the inlet to the secondary recipient 5 and the die opening are filled with aluminium. When the process continues as already described, the new filling in the recipient will be welded to the surface of the aluminum in the opening of the press head where it is cut off with 11, and the pressing process is continued by alternating action of the two pistons.

It is fundamental to this process that the stroke length of the secondary piston 10 is relatively short, so that the passage of the cable core X through the press head 4, which has the necessary high temperature for pressing, is as short as possible.

Means should also be provided before cooling the cable when it passes through the hollow piston 10 into the nipple holder 7, and this can be done by providing a jet of cooled compressed air on the cable core where this goes from the nipple holder 1 to the nipple 8. -correspondingly, water cooling or other methods for cooling the mantle can be used where the mantle leaves the matrix 9.

When the cable sheathing operation is completed and it is necessary to change tools, e.g. the nipple 8 or the die 9 or when it is necessary to clean the sekjm die recipient 5 the support 18 can be removed by hydraulic means or by other means and the secondary piston 10 is advanced past its normal stroke to protrude past the press head to force out all the aluminum in the secondary recipient 5 together with the nipple in the matrix 6. Although the stroke length of the secondary hydraulic cylinder 16 in normal operation is short, for this purpose it will be designed so that it can perform its extended function, and this can be achieved by supplying of low-pressure fluid to cylinder 16.

For simplicity, the drawings only show a martise construction which in general

The hole is known as a "port hole die". This process is equally applicable to other forms of matrix construction and "port hole" device. It can e.g. is replaced with a cross that supports the nipple holder 7 and the nipple 8.

In the construction and operation of the process in simplified form as described, the forces acting on the nipple holder 7 when maneuvering the main piston will become unbalanced. To prevent difficulties caused by this and also to increase the volume capacity of the press, it is possible in a simple way to calculate presses for carrying out this process, so that two or more main recipients are used.

Figure 8 shows such a press construction where the two main recipients 1 and 1 are arranged diametrically and simultaneously press metal into the secondary recipient 5.

The features already described for moving the main receivers, moving the main rams to allow filling of the press and cutting the remaining metal from the press head can be provided on such a press, as is clear from the drawing.

This press works in the same way as already described, except that two aluminum blocks are introduced at the same time, and when pressing takes place into the secondary recipient 5, an equal amount of metal is supplied from both main recipients. Equal pressing from the two recipients 1 and 1 is achieved by the usual means of simultaneous operation of two hydraulic cylinders. The same reference designations refer to the same parts in this figure, so that the construction and operation of the press can be easily understood from the short description above.

In the presses already described, the process is carried out in such a way that the cable core passes through the nipple holder which is coaxial with the piston for secondary pressing.

In a further alternative embodiment shown in Figures 9 and 10, the aluminum is pressed

from a main recipient 1 into two or more

secondary recipients 5 and 5 which are filled through a chamber in the press head 4. To avoid the passing of the secondary pistons over the nipple holder, the secondary recipients 5 and 5' are placed in a plane perpendicular to the main recipient 1 and at an acute angle to the direction of the cable core's passage through the press head.

Figure 10 shows a cross-section of this press through the middle line of the secondary recipients. For the sake of simplicity, these drawings show a press with only two secondary recipients, but more recipients can of course be arranged radially around the direction of movement of the cable core.

The construction of the press with respect to the main recipient is clearly shown in Figure 9, where it is clear that there is complete similarity in construction and operation of the main recipient with the already described press construction and where similar reference designations refer to the same parts. This alternative press construction works in the same way as already described, in that when the pressure is applied to the main recipient 1, the aluminum that is pressed into the chamber in the press head 4 forces the secondary press pistons 10 and 10' back until they reach the limit of their movement , and the pressure in the main cylinder 12 is reduced and the pressure in the secondary cylinders 16 and 16' is increased so that aluminum is pressed from the secondary recipients 5 and 5' through the nipple and die 6 to form a cable sheath in the normal manner. When the pistons 10 and 10' have reached the limit of their forward movement, the pressure in the cylinder 16 and 16' is reduced and the pressure in the main cylinder 12 is increased so that the secondary recipients 5 and 5' are again filled with aluminium. While this alternative method of carrying out the process does not allow the ejection of the tool and aluminum from the secondary recipients in the same way as in the embodiment described earlier, it is an advantage that a hollow piston over the nipple holder has been replaced with solid pistons. The distance that the cable is passed through the press is thus reduced, and the secondary rams are less likely to cause mechanical difficulties. With this process, cutters for removing residues from the main recipient can also be used and two main recipients can be used.

It is clear that with all the constructions described, a large block is pressed in stages from a main recipient into a smaller secondary recipient from which the metal is pressed directly onto the cable core through a matrix. The metal block can thus be of such a size that long cable lengths can be sheathed without filling the press.

With the process according to this invention, it is calculated that it is possible to carry out cable sheathing at an aluminum temperature that does not exceed 350° C with a press calculated for a specific pressure of approx. 8 tons/cm2 compared to 400° C in the normal straight-through method or 500° C in pressing through a right-angled press head at the same pressure. Arrangements for controlling the pressure fluid supplied to the various hydraulic cylinders are not shown, but it is clear that any suitable methods, either manual or automatic, can be used, and those skilled in the art will undoubtedly be aware of this.

Claims (10)

1. Method for pressing cable sheaths made of light metal directly onto a cable core, characterized in that the pressing takes place in four stages, with part of a relatively large primary metal block (3) being pressed in the first step to form one or more smaller metal blocks, with the smaller metal blocks are pressed through a matrix (9) around the cable core (X) in the second step to thus form the cable jacket (Y). 2. Method according to claim 1, characterized in that the main recipient is supplied to a preheated metal block, after which the block is subjected to pressure and a part of this is pressed into a secondary recipient (5), the cable core being passed through the matrix, that the pressure in the main recipient is reduced and the pressure on the part of the block which is in the secondary recipient is increased to press it through the matrix and onto the cable core, that the pressure in the secondary recipient is then reduced and the pressure on the block in the main recipient is increased to fill the secondary recipient, this cycle of operation being continued until the main recipient is substantially empty . 3. Method according to claim 2, characterized in that the main recipient is removed from the press head (4) after the metal block has been pressed out and a cutting device (11) is maneuvered so that the remainder is cut away, after which a new metal block is supplied to the recipient and welded to the cut surface which remains in the press head. 4. Method according to claim 3, characterized by the fact that the metal block in the main recipient is massive and that the part that is pressed into the secondary recipient forms a hollow metal block that surrounds the nipple holder (7). 5. Method according to claim 4, characterized in that the hollow metal block in the secondary recipient is pressed through the matrix by means of a hollow piston which surrounds the nipple holder. 6. Apparatus for sheathing electric cables according to a method as stated in claim 1, characterized by one or more recipients for receiving the metal to be pressed, devices for pressing the metal from said recipients, one or more secondary recipients into which the metal from the main recipient is pressed into, a matrix in connection with the secondary recipients and means for pressing the metal from the secondary recipient through said matrix and around the cable core. 7. Apparatus according to claim 6, characterized in that the secondary recipient's capacity is small compared to the main recipient's (or main recipient's) capacity and that the devices for pressing the metal include one or more pistons with a short stroke. ' 8. Apparatus according to claim 6, characterized in that the axis of the main recipient forms an angle, preferably at a right angle, with the axis of the secondary recipient, the arrangement being such that the cable core only passes through the secondary recipient and not through the primary recipient. 9. Apparatus according to claim 6, characterized by devices for raising the main recipient in relation to the secondary recipient and by a cutting device for removing the remaining metal in the main recipient. 10. Apparatus according to claim 6, characterized in that the devices for pressing the metal from the secondary recipient comprise a hollow piston which surrounds the nipple holder.