DE946535C - Working method for reloading in continuous extrusion on a double block press - Google Patents

Description

Working method for reloading in continuous extrusion on a double block press When pressing cable sheaths on hydraulic lead or aluminum presses, it is common to add metal fillings and one after the other to be squeezed out in order to obtain practically endless cable sheath lengths. For refilling the metal inserts, the pressing pressure must be relaxed to remove the ram from the Pull out the metal holder and the latter for refilling the new metal insert to free. This relaxation of the pressure is transferred to the cable sheath forming ends Annular gap, which is more or less strong, depending on the size of the pressure difference, as a so-called bamboo ring on the finished coat. When pressing Cable sheaths made of aluminum, for which very high pressing pressures are necessary, are such Bamboo rings very pronounced. Mechanically and in the case of concentric high-frequency cables, they in which the jacket also performs an electrical conduction function, also electrically a sensitive point of interference.

Such bamboo rings can be avoided when relaxing of the material filling the press chamber is prevented and continuously, d. H. without interruption of work, while loading is continued.

To make this possible, it has already been proposed, so-called double block presses, at them the pressed metal from two opposite sides a cable sheath forming tool is pressed by pressing each one out one by one Side to exploit a continuous working process.

The problem arises during the one-sided pressing when the other side is relaxed to refill the new material insert To prevent the material from flowing back into this metal sensor. It became that the installation of valves and locks proposed, so a special constructive Measure provided, but to be viewed as a pressure-absorbing brake and constructive difficult to achieve.

It has therefore also been proposed that one or more valveless Passages between the exit end of each transducer and the common one Form the extrusion chamber so that an angle of less than go ° between the directions of flow of the plastic metal in the passage and in the chamber at the point of confluence or arises between the passages of different sensors at the union point. Another suggestion is valveless inlet channels leading from the extrusion chamber towards the transducer, tapering towards the transducer at the same angle. Specially trained tools must be used in these solutions.

With the process technology proposed below, it becomes simple type possible, a double block press without the use of special constructive means conventional design by pressing out the metal fillings one after the other to form a continuous Use crimping of cable jackets so that bamboo rings are avoided.

The invention relates to a working method for reloading during continuous Extrusion, for example of cable sheaths, on a double block press which the pressed material from the annular gap temporarily only from one and temporarily only from is fed to the other pick-up, while the one in which there is still a residue is located, is reloaded, and consists in that before reloading a transducer the working pressure in both transducers is gradually reduced until one low extrusion speed sets that then the sensor is maintained the reduced pressure on the opposite side is reloaded, and then continue to work both transducers with full pressure. For the procedure is suitable advantageously a press whose compression chamber is separated from the interior of the receiver by webs is.

The normal working pressure of a double block press is at the same time Pressing from both sides, for example, 26o to 28o kg / cm2 on the punch, with one Pressing speed of 60 m / min or 1 m / sec is maintained. One relaxes the If the pressing pressure is set to zero, the cable sheath exit speed will also be the same Zero and a sharp bamboo ring is created. You relax on the stamp side The pressure, however, does not go down to zero, but a pressure of 60 kg / cm2 is maintained upright, the cable sheath exit speed drops to a few cm / min, but does not come to a standstill, although this pressure is below the one who is required to initiate the flow process. If you press on it again 26o to 28o kg / cm2 further, the strand exit speed increases again to 60 m / min, and you can see that no bamboo ring has been created because that Pressed material was not completely relaxed in the annular gap.

With a very low pressure you can, on the other hand, if the strand once it is flowing, a very small exit velocity of a few cm / min keep going with one-sided pressure. The press residue on the opposite side If it is thick enough, it holds it through its internal toughness and wall friction low back pressure. It acts as a stopper so that the ram can be pulled out without the material being pressed back.

To the pressing, d. H. to enable the start of the work process, becomes a block of lesser, for example, on one side at the start of work half the length of the normal length.

The method according to the invention is explained with reference to the drawing, namely Fig. i shows a press head which can be used to carry out the method, while FIGS. 2 to 8 are a schematic representation of an axial section through the Press head with pick-up and press ram in various operating positions demonstrate.

In the press head according to FIG. I, the tools are in a bore i of the press block z used. The mandrel carrier 3 is over two to six webs 4 connected to the die holder 5. The die 6 is through in the die holder a screw member 7 held while the mandrel carrier 3 receives the mandrel 8. In the direction the arrow g is pressed alternately or simultaneously from both sides. Since the The diameter of the receiving bores is greater than the diameter of the mandrel holder 3, the Preßgutströme meet in the middle and flows Preßgut along the Bars 4 all around 'the mandrel holder 3 evenly in the pressing chamber. The tools can also be designed differently, for example without webs 4, in which case the mandrel carrier is kept for itself alone (in Fig. i above). Also can the tools be pushed up so far that the shell-forming gap between The mandrel 8 and die 6 lies approximately in the axis of the receiving bores, with the material to be pressed then flows exclusively radially to the press nip.

The sequence of the method is explained schematically in FIGS. 2 to 8. For starting, a normal block b is shown on the right and a half block on the left, as shown in FIG. 2 Block a inserted. It will then with a force P equal to normal pressure 1V pressed from both sides with the punches io, which sit on plungers i i, until the state according to FIG. 3 is reached, in which only a pressing residue remains from the block a exists and block b has decreased in size. Now the will be on both sides Compression pressure reduced so much that there is only a low strand speed results. This pressure can be considerably below that required for initiation the flow process is required. Thereupon the left ram is withdrawn io, while the right ram continues to press with little force, so that the flow of the strand does not stop completely. Here acts according to FIG. Q. the press residue a as Plug. The new block c is now introduced on the left-hand side and according to Fig. 5 on both sides with - the normal pressing force P pressed again. this will continued until there is only a pressing residue left of the block b, such as Fig. 6 shows. Then the pressing pressure is again reduced on both sides, so that the outflow velocity decreases. If the right ram is now withdrawn as shown in Fig. 7, so the press residue b acts as a plug, which a slow further pressing with little Pressing pressure of the left ram allows. A new block d appears on top of this introduced on the right side and then, as shown in FIG. 8, again on both sides worked with full pressure.

While the known devices for continuous extrusion, z. B. with throttle devices of any kind, always the same extrusion speed of the strand and while in the usual non-continuous extrusion a complete standstill of the strand to be squeezed out during reloading occurs, which leads to the disadvantageous bamboo rings, is according to the invention normally pressed out of both transducers at full speed, but for the duration of reloading pressed on one side with a low punch speed, so that the Strand speed then drops. Even with the low extrusion speed However, the dreaded bamboo ring occurs when the pressed strand comes to a standstill not on.

The method according to the invention is preferably used with pressing Chamber matrix applied, d. H. in those whose mandrel or mandrel carrier through webs is connected to the die or the die holder. By using such a Tool is namely excluded the risk of being temporarily unilateral on the mandrel acting pressure radial displacements between mandrel and die occur, which would have to lead to an unequal pressed product.

Claims (3)

PATENT CLAIMS: i. Working procedure for reloading in the case of continuous Extrusion, for example of cable sheaths, on a double block press which the pressed material to the annular gap temporarily only from one and temporarily only is fed from the other pickup, while the one in which there is still a Press residue is located, is reloaded, characterized in that 'before reloading of a transducer the working pressure in both transducers is gradually reduced, until a low pressing speed is reached, that then the pick-up under Maintaining the reduced pressure of the counter ram is reloaded, and that then both punches continue to work with full pressure. 2. Procedure according to claim i, characterized in that for pressing on one side for the first time a block of about half the length is used. 3. Application of the procedure according to - Claims i and 2 for presses with a chamber die. Considered publications: Swiss patent specifications No. 201 358, 2o7 756.