Cold pilger rolling mill and method for forming a tube shell to a tube

Abstract

A cold pilger rolling mill for forming a tube shell to a tube includes a feed clamping carriage for receiving the tube shell and with a drive that is arranged to move the feed clamping carriage such that during the operation of the cold pilger rolling mill the tube shell moves step-by-step in the direction of the tool. A control and a sensor detect a measure of a force exerted during the operation of the cold pilger rolling mill by the tool onto the tube shell, and wherein the control is connected to the drive and the sensor. The control is arranged to regulate, during the operation of the cold pilger rolling mill, the step length per advance step with which the drive moves the feed clamping carriage to the tool as a function of the measure for the force, which measure is detected by the sensor.

Claims

1. A cold pilger rolling mill for forming a tube shell to a tube with a pair of rolls that are rotatably attached to a roll stand and with a roll mandrel as a tool, the cold pilger rolling mill comprising: a feed clamping carriage for receiving the tube shell; a drive for the feed clamping carriage arranged to move the feed clamping carriage during operation of the cold pilger rolling mill such that the tube shell moves step-by-step in a direction of the tool; and a control and a sensor for detecting a measure for a force exerted during operation of the cold pilger rolling mill by the tool onto the tube shell, wherein the control is connected to the drive and the sensor, wherein the control is arranged to regulate, during operation of the cold pilger rolling mill, a step length per advance step with which the drive moves the feed clamping carriage onto the tool as a function of the measure for the force, wherein the sensor is a position sensor that detects an actual position of the feed clamping carriage, wherein the control is arranged to compare the actual position of the feed clamping carriage detected by the sensor with a nominal position of the feed clamping carriage, and wherein a difference between the actual position and the nominal position is a measure of the force exerted during operation of the cold pilger rolling mill by the tool onto the tube shell.

2. The cold pilger rolling mill according to claim 1, wherein the control is arranged to regulate the step length per advance step during operation of the cold pilger rolling mill in such a manner that the measure of the force is below a pre-determined threshold value.

3. The cold pilger rolling mill according to claim 2, wherein the control is arranged to control the step length per advance step of the feed clamping carriage during operation of the cold pilger rolling mill in such a manner that maximizes the step length per advance step.

4. The cold pilger rolling mill according to claim 1, wherein the control is arranged to detect the measure for the force exerted by the tool onto the tube shell in a stationary state of the drive and during rolling over with the pair of rolls.

5. The cold pilger rolling mill according to claim 4, wherein the control reduces the step length per advance step if the force exerted during operation of the cold pilger rolling mill by the tool onto the tube shell and derived or derivable from a measurement of the sensor is above a pre-determined threshold value.

6. The cold pilger rolling mill according to claim 1, wherein the control is arranged to control the step length per advance step of the feed clamping carriage during operation of the cold pilger rolling mill in such a manner that the difference between the actual position of the feed clamping carriage and the nominal position of the feed clamping carriage is less than a pre-determined threshold value.

7. The cold pilger rolling mill according to claim 1, wherein the drive is arranged to allow a deviating movement of the feed clamping carriage in a direction opposed to a direction of advance of the tube shell if the measure of the force exerted during operation of the cold pilger rolling mill by the tool onto the tube shell exceeds a holding force of the drive.

8. The cold pilger rolling mill according to claim 1, wherein the drive for the feed clamping carriage includes at least one direct electromechanical linear drive.

9. The cold pilger rolling mill according to claim 8, wherein the at least one direct electromechanical linear drive includes a hydraulic or pneumatic brake.

10. The cold pilger rolling mill according to claim 1, wherein the control reduces the step length per advance step if the force exerted during operation of the cold pilger rolling mill by the tool onto the tube shell and derived or derivable from a measurement of the sensor is above a pre-determined threshold value.

11. A method for forming a tube shell to a tube comprising the steps of: providing a cold pilger rolling mill having a pair of rolls that are rotatably attached to a roll stand and including a roll mandrel as a tool, a feed clamping carriage in which a tube shell is received, and a drive for the feed clamping carriage; moving the feed clamping carriage with the drive such that the tube shell moves step-by-step in a direction of the tool; detecting an actual position of the feed clamping carriage with a position sensor; comparing the actual position of the feed clamping carriage detected by the sensor with a nominal position of the feed clamping carriage, wherein a difference between the actual position and the nominal position is a measure for the force exerted during operation of the cold pilger rolling mill by the tool onto the tube shell; and regulating a step length per advance step with which the drive moves the tube shell to the tool as a function of the measure for the force.

12. The method according to claim 11, wherein the measure for the force exerted during operation of the cold pilger rolling mill by the tool onto the tube shell is below a pre-determined threshold value.

13. The method according to claim 12, wherein regulating the step length per advance step maximizes the step length per advance step.

Description

(1) Further advantages, features and possibilities of using the present invention will become clear using the following description of a preferred embodiment and the associated FIGURE.

(2) FIG. 1 shows a schematic side view of the construction of a cold pilger rolling mill according to an embodiment of the present invention.

(3) The construction of a cold pilger rolling mill is schematically shown in a side view in FIG. 1. The roll mill consists of a roll stand 1 with rolls 2, 3, a calibrated roll mandrel 4 and a feed clamping carriage 5. The rolls 2, 3 form together with the roll mandrel 4 the tool of the cold pilger rolling mill in the sense of the present invention. It should be noted that in FIG. 1 the position of the roll mandrel 4 cannot be seen inside the tube shell 11.

(4) In the embodiment shown the cold pilger rolling mill comprises a linear motor designated by the reference numeral 6 in FIG. 1. The linear motor 6 forms a direct drive for the feed clamping carriage 5 and is constructed by a rotor 7 and a stator 8. During the cold pilgering in the rolling mill shown in FIG. 1 the tube shell 11 experiences a step-by-step advance in the direction of the roll mandrel 4 and beyond it. The rolls 2, 3 are moved horizontally back and forth while rotating over the mandrel 4 and therefore over the tube shell 11. During this time the horizontal movement of the rolls 2, 3 is set by the roll stand 1 in which the rolls 2, 3 are rotatably supported. The roll stand 1 is moved back and forth with the aid of a crank drive 10 in a direction parallel to the roll mandrel. The rolls 2, 3 receive their rotary motion from a toothed rack that is stationary relative to the roll stand and into which toothed gears firmly connected to the roll shafts engage.

(5) The advance of the tube shell 11 is performed at the reversal points of the roll stand 1 with the aid of the feed clamping carriage 5 that, driven by the linear motor 6, makes possible a movement of translation in a direction parallel to the axis of the roll mandrel. The so-called pilger mouth formed by the rolls grasps the tube shell 11 after each advance and the rolls 2, 3 press from the outside a small metal wave away that is extended by the smoothing caliber of the rolls 2, 3 and the roll mandrel 4 to the intended wall thickness until an idle caliber of the rolls 2, 3 frees the finished tube again.

(6) The tube shell 11 is advanced by a further step toward the roll mandrel 4 with the aid of the feed clamping carriage 5 after having reached the idle caliber of the rolls 2, 3. At the same time the tube shell 11 experiences a rotation about its axis in order to achieve a uniform shape of the finished tube. A uniform wall thickness and roundness of the tube as well as a uniform inside and outside diameter are achieved by multiply rolling over each tube section.

(7) A central sequencing control 12 controls the drives 6, 10 of the rolling mill, that are at first independent, so that the previously described course of the rolling process is achieved. The control 12 begins with the release of an advance step of the linear motor 6 for advancing the tube shell 11. Upon reaching the advance position, i.e. the end of the advance step, the linear motor 6 is controlled in such a manner that it statically holds the feed clamping carriage 5 and the velocity of the rotation of the crank drive is controlled in such a manner that after the ending of each advance step the roll stand 1 is pushed horizontally over the tube shell 11, wherein the rolls 2, 3 roll out the tube shell 11.

(8) In order to meet its control tasks the sequencing control 12, for example an industrial PC, is connected via control lines 13, 14 to the drive motor for the crank drive 10 and also to the linear motor 6. In addition, the sequencing control 12 detects with the aid of a measuring line 15 the actual position of the feed clamping carriage 5 mounted on the rotor 7, which position is detected by a position sensor 16 in the linear motor 6.

(9) It has shown that the force exerted by the tool 2, 3, 4 on the tube shell 11 depends in particular on the properties of the tube shell, especially on its dimensions. If this action of the force is below a pre-determined threshold value a sufficient quality of the tube can be ensured and damage to the feed clamping carriage 5 or to the drive 6 can be prevented. However, the force exerted by the tool 2, 3,4 on the tube shell 11 also depends on the step length with which the feed clamping carriage 5, and with it the tube shell 11, is moved per advance step to the tool 2, 3, 4.

(10) If the action of the force of the tool 2, 3, 4 onto the tube shell 11 is very large the feed clamping carriage 5 on the rotor 7 is displaced from the nominal position given to it by the sequencing control 12 via the control line 14 opposite to the direction of advance. I.e., the holding force exerted by the linear motor 6 is less than the force exerted by the tool 2, 3, 4 on the tube shell 11. Due to this fact, a deviation then results between the nominal position of the feed clamping carriage 5 given by the linear motor 6 and the actual position of the carriage 5 detected by the measuring line 15 during the rolling. The deviation or difference between the nominal position and the actual position is then a measure for the force exerted by the tool 2, 3, 4 on the tube shell 11.

(11) If the difference between the nominal position and the actual position of the feed clamping carriage 5 is above a pre-determined threshold value, it is assumed that the action of the force of the tool 2, 3, 4 on the tube shell 11 is too large in order to still ensure a sufficient quality of the tube after the roll stand 1. In order to reduce the force exerted by the tool 2, 3, 4 on the tube shell 11, the sequencing control 12 then reduces the step length with which the feed clamping carriage 5 is moved per advance step onto the tool 2, 3 4. The force exerted by the tool 2, 3, 4 on the tube shell 11 will also decrease as the velocity of the feed clamping carriage 5 becomes less, so that the difference between the nominal position and the actual position of the feed clamping carriage 5 again is below the threshold value that ensures the necessary quality. However, at the same time the control 12 attempts to hold the step length of the feed clamping carriage 5 at a maximum in order to also ensure the necessary productivity of the mill in addition to the necessary quality. For this purpose, the control has not only an upper threshold value for the difference between the actual position and the nominal position of the feed clamping carriage but also a lower threshold value that together define a tolerance window. If the deviation between the actual position and the nominal position of the carriage falls below the lower threshold value then the step length can be increased again in order to retain the productivity of the mill.

(12) It is pointed out for purposes of the original disclosure that all features that are apparent to a person skilled in the art from the present specification, the drawing and the claims, even if they were also concretely described in conjunction with certain other features, can be combined individually as well as in any combinations with other features or groups of features disclosed here in as far as this was not expressly excluded or if technical circumstances render such combinations impossible or illogical. A comprehensive, explicit presentation of all conceivable feature combinations will not be given here for the sake of brevity and the legibility of the specification.

(13) If the invention was presented in detail in the drawings and the previous specification, this presentation and specification are performed solely by way of example and is not meant as a limitation of the protective scope as defined by the claims. The invention is not limited to the disclosed embodiments.

(14) Modifications to the disclosed embodiments are obvious to the person skilled in the art from the drawings and the specification. In the claims the words comprises does not exclude other elements or steps and the indefinite article a or one does not exclude the plural. The mere fact that certain features are claimed in different claims does not exclude their combination. Reference numerals in the claims are not meant to be a limitation of the protective scope.