DE1927396C3 - Device for holding the mandrel axially in relation to the die in a pipe extrusion press - Google Patents

Description

The invention relates to a device for maintaining the axial position of the mandrel with respect to the die in a pipe extrusion press with a double-acting hydraulic cylinder-piston drive arranged in the plunger for the mandrel, its advance and retraction chambers via a valve arrangement with a pressure medium source or a collecting container is connectable.

There are known presses (US-PS 29 03 130; US-PS 33 62 208), in which the pressing process with standing Mandrel tip the frictional force is supported by mechanical stops on the stationary press frame to keep the mandrel tip stationary in the die opening. The tensile forces caused by the Friction of the flowing press material on the mandrel surface are caused by the mechanical Transfer the stops and the stationary press frame to the foundation. So part of the Forming force lost. This can be a significant loss because of the mandrel friction force is often a fifth to a quarter of the total pressing force.

In US-PS 33 62 208, in addition to the mechanical mandrel support on the press frame, a hydraulic one Described support of the dome, in which the disadvantage of reducing the pressing force does not occur. In this press, which also has a mandrel drive cylinder arranged in the main press piston, are Supply lines with valves provided for the advance and retraction chambers of the mandrel drive, About the independently each of the two chambers with a pressure medium source or with one Collection container can be connected. For axial adjustment of the mandrel tip in relation to the die the valves are actuated during the stroke of the main ram in such a way that to compensate for the stroke movement of the main ram a certain amount of pressure medium into the retraction chamber of the mandrel drive occurs and at the same time a corresponding amount of pressure medium from the feed chamber of the mandrel drive exit. Due to the oil cushion in the retraction chamber, the friction of the flowing material on the The pulling force caused by the mandrel is transferred to the main plunger and is thus effective as a pressing force.

Due to the pressing conditions that change during the pressing process, such as pressing speed, frictional force on the mandrel etc., an exact compliance with the axial mandrel position is without corresponding Readjustment of the valves is not guaranteed. Provisions for such actuation of the valves for Compliance with the axial mandrel position is not met in this described arrangement.

The object of the invention is to improve this hydraulic position holder for Jen Dorn in such a way that that an automatic compliance with the exact axial position of the dome relative to the die is guaranteed.

This is achieved according to the invention in that the valve arrangement is a sensor valve known per se, whose slide is actuated via a stop that moves with the mandrel.

The hydraulic sensor valve used for the device according to the invention is part of a position or Path control with properties that are particularly important in terms of accuracy and reliability as well as the robust construction just correspond to the intended purpose. The use of such sensing valves for position or path control of machine parts has been known for a long time (Machinery, November 1959, Page 152 ff and the DT-AS 11 69 256). There will be a

ίο double-acting piston cylinder drive for one to moving part or part that can be controlled is acted upon via a sensor-controlled valve. The valve points two control pistons lying in a row, the piston rod of which acts as a sensor for the changes in position of the to controlling part taps. With the appropriate position of the control piston in the valve, there are two terminal ones Holes in the valve body and a central drain hole for the piston of the piston-cylinder drive Position of the sensor moved back and forth. Through the

3υ use of such a known Fühierventils in connection with the mandrel drive cylinder, the axial position retention of the mandrel is achieved with simple means achieved. Also a subsequent installation of such a sensor control in presses with in the main press piston horizontal hydraulic mandrel drive is possible without any special structural or spatial effort and in any case gives the additional advantage of increasing the pressing force of the main press drive.

Furthermore, it is in a pipe extruder (GB-PS 8 37 126) with a arranged in the plunger Drive piston known for the piercer, during the Pressing process into the retraction chamber of the mandrel drive piston to press pressure medium in such an amount, that the mandrel tip remains in the die opening. The retraction chamber of the mandrel drive is mil the working space of a hydraulic cylinder-piston unit, the plunger of which acts as a stop for the mandrel position holding device is used, connected. The main disadvantage of this known device is also in the Loss of active pressing force, as the forces to hold the piercer against that of the Press stand itself frictional force exerted are derived from the main press drive. The accuracy is thereby speed of the positioning of the piercer from Leckverlu costs in the hydraulic system, inaccuracies in de Manufacture of the stop cylinder and the Dornan drive cylinder, which should be of the same volume, VoIu changes in the cylinder through pressure changes in the cylinders through pressure changes as well as de

& ° Adversely affect the compressibility of the pressure medium In addition, this device is determined by the dimensions of the mandrel drive cylinder, spatially proportion moderately expensive.

The drawing illustrates a Ausführungsbe game of the invention. It shows

1 to 4 show a pipe and extrusion press with the device according to the invention for holding the mandrel position in different work phases and

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An ori! Ckle: ti; ··, ;; leads from the pump 16. ^ λ.-il; * ". control valve 19 and /. to sense ennl X>. b" :: * i return line 24 connects valves 19 and 20 iv.is v ^: .ei · -. < _Λ Container 17. Lines 25 lead from the two valves 19 and 20 in several sections; to the left! · Chamber 13a and also from several sections: * Existing lines 26 to the right chamber Ui sies cylinder-piston drive for the mandrel 15. The l .ciuin-> o gen 25 and 26 contain joints to take into account the fact that the Preßkolb ^ n moves and the hydraulic system stands still.

A wire rope 27 is connected to the piston 13, which is wound with its outer end on a drum 28_s5, which is under spring tension and that Keeps rope 27 under tension. The cable 27 is laterally out of the cylinder-piston drive via pulleys 29 for the mandrel 15 led out. On the rope 27, a stop 30 is attached, which with an axial ck> adjustable stop 32 cooperates on a push rod 3t. An arm 33 is connected to the push rod 31 connected, which is in "effective connection with the piston 2t of the sensor valve 20 is. The piston 21 forms the actuating member in the sense of the opening paragraph Executions. The rod 31 runs in a guide 34.

The press described is described as follows:

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Stop 32 the distance between the mandrel tip 15a between the position which it is in its basic position F i g. 1 assumes, and the position it takes when pressing according to FIG. 4 in the die is the same. In this latter position, the mandrel tip projects generally a small distance a over the The die opening is in this position the stop 30 on the end face of the stop 32, as in FIG. 5 is drawn.

If the ram is now acted upon and the mandrel 15 is carried along by the plunger 4, the mandrel tip moves within the die, as seen in FIG. 4, to the right. The same movement, however, is carried out by the stop 30, which thereby moves the stop 32, that is to say the actuating element of the valve 20. The valve, which was initially closed according to FIG. 5, is thereby opened, that is to say in the position according to FIG. 6 brought. A small displacement of the valve slide 21 by a distance x is sufficient for this. By opening the valve 20, the pressure medium source 16 is via the lines 23 and 25 with the chamber 13b and the

Return line 24 connected via line 25 to the container 17, so that the mandrel tip 15a by the distance a is withdrawn again, so that the state according to FIG. 5 is restored.

This process can now be repeated continuously during the entire pressing out of the block 12 by the dome 15 performs an oscillating movement, the amplitude of which is at most equal to χ. This amplitude can but can be kept within narrow limits by suitable design of the characteristics of the sensor valve 20, roughly on the order of a few millimeters. Natural damping and sluggishness are incidentally usually cause that the slide of the valve 20 during the entire pressing in a Intermediate positions, in which the supply and discharge of the pressure medium to and from the chambers 13a and adjusts 13b so that the mandrel is practically at rest. Otherwise a pendulous movement would have been det Dornspitze itself to the full extent no harmful consequences.

For this purpose 4 sheets of drawings

Claims (1)

Claim: Device for maintaining the axial position of the dome opposite to the die in a pipe extrusion press with one arranged in the plunger, double acting hydraulic cylinder-piston drive for the mandrel, its advance and retraction chambers via a valve arrangement with a pressure medium source or a collecting container, characterized in that the valve arrangement is a known sensor valve (20), the slide (21) of which is connected to the mandrel (15) moving stop (30) is oetätigi