Cold pilger rolling mill and method for forming a hollow shell into a tube

Abstract

A cold pilger rolling mill includes a pair of rolls rotatably attached to a roll stand, a crank drive on a driveshaft, which is rotatably mounted around a rotation axis, with a counterweight attached to the crank drive at a radial distance from the rotation axis, and a push rod with a first and a second end. The first end of the push rod is rotatably attached on the crank drive wherein, during the operation of the mill, a rotation of the crank drive is converted into a translation movement of the roll stand between a first and a second reversal position. The radial distance of the first end of the push rod from the rotation axis is adjustable, so that the distance between the two reversal positions of the translation movement of the roll stand is adjustable.

Claims

1. A cold pilger rolling mill for forming a hollow shell into a tube, the cold pilger rolling mill comprising: a pair of rolls rotatably attached to a roll stand; a rolling mandrel tool; a feeding clamping carriage for receiving the hollow shell, wherein during the operation of the mill, the feeding clamping carriage moves between a first and a second extreme position in such a manner that the hollow shell moves stepwise in a direction toward the tool; a crank drive disposed on a driveshaft and rotatably mounted around a rotation axis; a counterweight attached to the crank drive at a radial distance from the rotation axis; and a push rod having a first and a second end, the first end of the push rod being rotatably attached on the crank drive around a crank pin at a radial distance from the rotation axis, and wherein the second end of the push rod is attached to the roll stand, so that, during the operation of the mill, a rotation of the crank drive is converted into a translation movement of the roll stand between a first reversal point and a second reversal position, the radial distance of the first end of the push rod from the rotation axis being adjustable, so that a distance between the two reversal positions of the translation movement of the roll stand is adjustable, wherein the crank drive includes a through hole having a cross-section which is at least in some sections radially symmetric, but not rotationally symmetric, for receiving the crank pin, a base body with a front side and a back side, a pin section arranged on the front side and a securing section arranged on the back side, wherein the base body has a cross section, which at least in some sections is complementary to the cross-section of the through hole, so that the base body is received in a twist-proof manner and with positive lock in the through hole.

2. The cold pilger rolling mill according to claim 1, wherein the radial distance of the first end of the push rod from the rotation axis is adjustable in discrete steps or continuously.

3. The cold pilger rolling mill according to claim 2, wherein the crank drive includes a plurality of sockets for the crank pin for the attachment of the first end of the push rod, wherein the sockets are arranged at mutually different radial distances from the rotation axis.

4. The cold pilger rolling mill according to claim 1, wherein the through hole and the base body of the crank pin have at least in some sections an elliptical cross section.

5. The cold pilger rolling mill according to claim 4, wherein a major axis of the elliptical cross section of the through hole is oriented in radial direction of the crank drive.

6. The cold pilger rolling mill according to claim 4, wherein the pin section is arranged on the major axis at a distance from a minor axis of the elliptical cross section.

7. The cold pilger rolling mill according to claim 1, wherein the through hole is tapered in an axial direction and the base body has a tapering that is complementary to the taper of the through hole.

8. The cold pilger rolling mill according to claim 1, further comprising an attachment device for the detachable attachment of the counterweight.

9. The cold pilger rolling mill according to claim 8, wherein the crank drive includes a plurality of attachment devices for the detachable attachment of the counterweight, the attachment devices being arranged at mutually different radial distances from the rotation axis.

10. The cold pilger rolling mill according to, claim 1, wherein the radial distance of the counterweight from the rotation axis is adjustable, in discrete steps or continuously.

11. The cold pilger rolling mill according to claim 1, wherein a shortest distance between an extreme position of the feeding clamping carriage and a reversal position of the rolling stand is adjustable by adjusting the extreme position.

12. The cold pilger rolling mill according to claim 1, wherein the pin section is arranged eccentrically on the base body, so that the pin section can be arranged, by rotating the base body before the introduction into the through hole, at different radial distances from the rotation axis of the crank drive, wherein, on the pin section, the first end of the push rod is attached so that the push rod can be rotated around the longitudinal axis of the pin section, and wherein, on the securing section, a securing element is arranged, so that the crank pin is secured against being pulled out of the through hole.

13. A method for forming a hollow shell into a tube, comprising the steps of: providing a cold pilger rolling mill having a pair of rolls rotatably attached to a roll stand, a rolling mandrel tool, and a feeding clamping carriage with the hollow shell received therein; moving the feeding clamping carriage between a first extreme position and a second extreme position, such that the hollow shell moves stepwise in a direction toward the tool; forming the hollow shell into the tube using the tool, wherein a rotation of a crank drive is converted into a translation movement of the roll stand between a first reversal position and a second reversal position, wherein the crank drive is rotatably mounted around a rotation axis on a driveshaft, a counterweight is attached at a radial distance from the rotation axis on the crank drive, and a push rod is arranged with a first and a second end so that the first end of the push rod is rotatably attached at a radial distance from the rotation axis around a crank pin on the crank drive and the second end of the push rod is attached to the roll stand; and adjusting the distance between the two reversal positions of the translation movement of the roll stand by adjusting the radial distance of the first end of the push rod from the rotation axis, wherein the crank drive has a through hole with a cross section that is at least in some sections radially symmetric but not rotationally symmetric for receiving the crank pin, the crank pin having a base body with a front side and a back side, a pin section being arranged on the front side and a securing section being arranged on the back side, wherein the base body has a cross section at least in some sections to be complementary to the cross section of the through hole, so that the base body can be received in a twist-proof manner and with positive lock in the through hole.

14. The method according to claim 13, wherein the pin section is arranged eccentrically on the base body, wherein, on the pin section, the first end of the push rod is attached so that the push rod can be rotated around the longitudinal axis of the pin section, wherein, on the securing section a securing element is arranged, so that the crank pin is secured against being pulled out, and wherein the step of the adjustment of the radial distance of the first end of the push rod from the rotation axis includes detaching the securing element, pulling the crank pin out of the through hole, rotating the crank pin around a longitudinal axis of the crank pin, reintroducing the crank pin into the through hole, and attaching the securing element.

Description

(1) Additional advantages, features and application possibilities of the present invention become clear in reference to the following description of preferred embodiments and the associated figures.

(2) FIG. 1 shows a diagrammatic representation of a cold pilger rolling mill in a side view,

(3) FIG. 2 shows a diagrammatic representation of a crank drive according to the invention with drivetrain, push rod and roll stand in a side view,

(4) FIG. 3 shows a diagrammatic representation of a flywheel according to the invention in a view in the direction of the rotation axis, and

(5) FIGS. 4a and 4b show diagrammatic representations of a flywheel with elliptical crank pin in a view in direction of the rotation axis and as a cross-sectional view.

(6) FIG. 1 diagrammatically shows the structure of the cold pilger rolling mill in a side view. The rolling mill comprises a roll stand 1 with two rolls 2, 3, a calibrated rolling mandrel 4 as well as, in the embodiment depicted, two clamping devices 31, 32 each with a chuck 41, 42, wherein the clamping jaw means of the chuck in each case are formed in the shape of a wedge. The rolls 2, 3 together with the rolling mandrel 4 form the tool of the cold pilger rolling mill in the sense of the present application. It should be noted that, in FIG. 1, reference numeral 4 marks the position of the rolling mandrel, which in fact cannot be seen, within the hollow shell 11.

(7) The chucks 41, 42 are substantially identical and they differ only in the dimensioning of their clamping jaw supports, which are dimensioned so that they can clamp different nominal diameters.

(8) The chuck 42 mounted on the feeding clamping carriage 52 clamps the hollow shell 11 in front of the roll stand 1 as an inlet chuck and ensures the feeding of the hollow shell 11 over the rolling mandrel 4. The feeding device 51 with chuck 41 as outlet chuck receives the tube 60 that has been completely reduced and pushes it out of the mill.

(9) During the cold pilger rolling on the rolling mill shown in FIG. 1, the hollow shell 11, driven by the feeding clamping carriage 52, undergoes a stepwise feeding in the direction toward the rolling mandrel 4 and over and past the latter. The rolls 2, 3 are moved horizontally back and forth over the mandrel 4 and thus over the hollow shell 11. Here, the horizontal movement of the rolls 2, 3 in a direction parallel to the axis of the rolling mandrel 4 is predetermined by the roll stand 1 on which the rolls 2, 3 are rotatably mounted. The roll stand 1 is moved back and forth by means of a crank drive 10 via a push rod 6 in a direction parallel to the axis of the rolling mandrel 4. The rolls 2, 3 themselves are set in rotation here by a rack (not shown) which is stationary relative to the roll stand 1, and with which toothed wheels (not shown) firmly connected to the roll axles engage. The push rod 6 has a first end 16 rotatably arranged on the crank drive 10 and a second end 17 rotatably arranged on the roll stand 1. The crank drive 10, more precisely the crankshaft, is in the form of a flywheel in the embodiment depicted. On the flywheel 10, a driving wheel 29 is arranged, which in turn is driven by a torque motor (not shown) and thus sets the flywheel 10 in rotation.

(10) The crank pin 19 is detachably attached to the flywheel 10 in a socket 14. The flywheel 10 has a plurality of such sockets 14 arranged on a straight line. Thus, the distance 8 of the crank pins 19, and thereby of the first end 16 of the push rod 6, from the rotation axis 18 of the flywheel 10 can be freely selected in discrete steps. In addition, the flywheel also has a plurality of sockets arranged radially on a straight line and used as attachment devices 15. By means of these attachment devices 15, one or more counterweights 9 can be detachably attached to the flywheel 10. Thus, in the embodiment depicted, the distance 7 of the counterweight 9 from the rotation axis 18 of the flywheel 10 can also be freely selected in discrete steps.

(11) The feeding of the hollow shell 11 over the mandrel 4 occurs in each case at the reversal points U.sub.1, U.sub.2 of the roll stand 1 by means of the feeding clamping carriage 52, which grips the hollow shell 11 by means of the chuck 42 and allows a translation movement in a direction parallel to the axis of the rolling mandrel 4. Here, the feeding carriage moves back and forth between two extreme positions E.sub.1, E.sub.2. The roll stand 1 has two rolls 2, 3, wherein the two rolls 2, 3 arranged one above the other form the so-called pilgering mouth and they firmly secure the tube central axis of the tube 60 to be rolled between themselves. The rotation axis 18 of the flywheel 10 is arranged under the tube central axis. The two calibrated rolls 2, 3 in the roll stand 1 rotate against the feeding direction of the feeding clamping carriage 52. The pilgering mouth formed by the rolls grips the hollow shell 11, and the rolls 2, 3 push off a small wave of material from the outside, which is stretched out by a smoothing pass of the rolls 2, 3 and by the rolling mandrel 4 to the intended wall thickness, until an idle pass of the rolls 2, 3 releases the finished tube 60 again. During the rolling, the roll stand 1 moves with the rolls 2, 3 attached thereto against the feeding direction of the hollow shell 11.

(12) By means of the feeding clamping carriage 52, the hollow shell 11 is pushed forward, after achievement of the idle pass of the rolls 2, 3, by an additional step onto the rolling mandrel 4. The rolls 2, 3 return with the roll stand 1 into their horizontal starting position. At the same time, the hollow shell 11 undergoes a rotation about its axis, in order to achieve a uniform shape of the finished tube 60. By rolling each tube section several times, a uniform wall thickness and roundness of the tube 60 as well as uniform inner and outer diameters are achieved.

(13) FIG. 2 shows an embodiment of a drive unit (6, 10, 29) according to the invention for the roll stand 1 of a cold pilger rolling mill in a diagrammatic detailed view from the side.

(14) The roll stand 1 of the cold pilger rolling mill is driven in such a manner that it moves back and forth oscillating linearly in a movement direction parallel to the axis of the rolling mandrel 4. For the generation of such a linearly oscillating movement of the rolling stand 1, a crank drive 10 is used, which consists of a crankshaft to which a push rod 6 is attached. The push rod 6 has a first and second end 16, 17. In the represented embodiment, the crankshaft is formed as flywheel 10, which can be rotated around a rotation axis 18.

(15) On the flywheel 10, a crank pin 19 is attached eccentrically, on which, in turn, a push rod 6 is pivotably arranged by means of a bearing. While the first end 16 of the push rod 6 is thereby fixed to the flywheel 10 or the crank pin 19 thereof, the second end 17 of the push rod 6 is pivotably attached to the roll stand 1 by means of a bearing. In this manner, a rotation of the flywheel 10 leads to a linearly oscillating movement of the roll stand 1 in the movement direction 3 parallel to the axis of the rolling mandrel. The flywheel 10 in addition has a rotationally symmetric weight distribution, which is the result of the eccentric attachment of a counterweight 9 to the flywheel 10.

(16) The crank pin 19 is detachably attached in a socket 14 to the flywheel 10. Here, the flywheel 10 has a plurality of sockets 14 arranged radially on a straight line, so that the distance 8 of the crank pins 19 and thereby of the first end 16 of the push rod 6 from the rotation axis 18 of the flywheel 10 can be freely selected in discrete steps. Similarly, the flywheel comprises a plurality of attachment devices 15, in the form of sockets, which are arranged radially on a straight line, and by means of which one or more counterweights 9 can be detachably attached to the fly 10. In this way, in the represented embodiment, the distance 7 of the counterweight 9 from the rotation axis 18 of the flywheel 10 can be freely selected in discrete steps.

(17) The flywheel 10 is designed as a toothed wheel in the represented embodiment. This toothed wheel engages with a driving wheel 29, which in turn is driven by a torque motor (not shown) and in this way sets the flywheel 10 in rotation.

(18) The rolls received in the roll stand 1 define the position of the central axis 30 of the tube 60 to be rolled. The selected construction has the general advantage that the closeness of the rotation axis 18 of the flywheel 4 to the central axis 16 of the tube 60 makes it possible to implement a comparatively obtuse angle between the push rod 6 and the translation direction 3 of the roll stand 1. This leads to a more uniform running of the roll stand 1 and thereby to less wear of its guide elements.

(19) FIG. 3 shows a diagrammatic view of a flywheel 10 as crank drive from the front, i.e., in the direction of the rotation axis 18, which comprises a plurality of sockets 14 for the detachable attachment of the crank pin 19 to the flywheel 10. The flywheel 10 is rotationally symmetric relative to its rotation axis 18. The sockets 14 for the crank pin 19 are arranged in discrete steps with identical step lengths radially along a straight line. Offset by 180° relative to the rotation axis 18, an additional plurality of attachment devices 15 in the form of sockets are arranged. These attachment devices 15 are used for the attachment of a counterweight 9 to the flywheel. In general, it would also be conceivable to attach several counterweights 9 to different attachment devices 15. The attachment devices 15 are arranged in a distribution radially along a straight line in discrete steps with identical step widths.

(20) By means of the represented embodiment of a flywheel 10 according to the invention, the distance 8 of the crank pin 19 and thus of the first end of the push rod 6 from the rotation axis 18 of the crank drive 10 can be varied in a simple and cost effective manner in discrete steps with identical step width. Thus, the stroke of the roll stand 1 is also varied in a corresponding manner in discrete steps with identical step width. If the position change is not transferred directly to the roll stand 1, as is the case in the embodiments of the cold pilger rolling mill according to the invention shown in FIGS. 1 and 2, then, depending on the design of the transmission mechanics, a variation of the crank pin position with identical step widths can also result in a variation of the roll stand stroke with non-identical step widths.

(21) In FIG. 4a, the embodiment according to the invention of a flywheel 10 in a view in the direction of the rotation axis 18 can be seen. The flywheel 10 comprises a socket 14 for a crank pin 19, which has an elliptical cross section. The socket 14 is formed as a through hole 24 with a front and a back side 25, 26. The crank pin 19 arranged in the through hole 24 has a corresponding elliptical cross section. The pin section 21 of the crank pin 19 is arranged with distance from the minor axis of the elliptical cross section. The longitudinal axis of the elliptical through hole 24 and thus also of the elliptical crank pin 19, when the latter is introduced into the through hole 24, are oriented in radial direction of the flywheel 10.

(22) The crank pin 19 can be introduced in two possible positions or orientations into the through hole 24. These two positions differ by 180° rotation around the central point of the elliptical cross section. Thus the distance 27 of the pin section 21 from the rotation axis 18 of the flywheel 10 varies as a function of whether the first or second position is selected. As a result of this design of the through hole 24 and the crank pin 19, it is possible, in one form, to produce two distances 27 of the pin section 21 and thus of the first end 16 of the push rod 6 from the rotation axis 18 of the flywheel 10.

(23) As a result of the longitudinal extent of the crank pin 19 in the direction of the longitudinal axis of the elliptical cross section, a high twist-proofness of the crank pin 19 in the through hole 24 is guaranteed. This is particularly advantageous since, by means of the crank drive 10 and of the flywheel 6 attached thereto by means of the crank pin 19, large torque moments in general have to be converted into a linear force in translation direction of the roll stand, which leads to high stresses on the corresponding connecting elements and in particular on the crank pin 19.

(24) FIG. 4b is a cross-sectional view of an embodiment according to the invention of a flywheel 10 with the crank pin 19 as shown in FIG. 4a. One can see the shape of the through hole 24 which is tapered backward in the direction of the rotation axis 18 of the flywheel 10 as well as the corresponding shape of the base body 20 of the crank pin 19. The central base body 20 here has a front and a back side 25, 26. A securing section 22 protrudes on the back side 26 out of the socket 14 of the flywheel 10 and it is secured with a securing element 23. As a result, the crank pin 19 is prevented from being pulled out of the through hole 24. The crank pin 19 is prevented from being pushed into the flywheel 10, over and beyond the position represented, by the tapering of the through hole 24 and the crank pin 19. In this way, the crank pin 19 is secured against shifting in all spatial directions, as well as against a twisting. In the represented embodiment, the securing element 23 is represented, for example, as a securing cotter, which is introduced into the crank pin through a through hole through the securing section 22 of the crank pin 19 perpendicular to the longitudinal axis of the crank pin 19 and is secured detachably against pulling out. However, other designs of corresponding securing elements 23 known from the prior art also conceivable as well, for example, a securing nut or securing screw, which can be connected via a corresponding thread connection to the crank pin 19, more precisely to its securing section 22.

(25) For the purposes of the original disclosure, it is pointed out that all the features as they become apparent from the present description, the drawings and the dependent claims, to a person skilled in the art, even if they were described concretely only in connection with certain further features, can be combined both individually and also in any combination with other features or feature groups disclosed here, to the extent that this is not explicitly ruled out or technical circumstances make such combinations impossible or senseless. It is only for the sake of the brevity and readability of the description, that the summarized explicit representation of all the conceivable feature combinations and the stressing of the independence of the individual features from one another are omitted here.

LIST OF REFERENCE NUMERALS

(26) 1 Roll stand 2, 3 Rolls 4 Rolling mandrel 51, 52 Feeding clamping carriage 6 Push rod 7 Radial distance of the counterweight 8 Radial distance of the push rod 9 Counterweight 10 Crank drive 11 Hollow shell 14 Socket 15 Attachment device 16 First end of the push rod 17 Second end of the push rod 18 Rotation axis 19 Crank pin 20 Base body 21 Pin section 22 Securing section 23 Securing element 24 Through hole 25 Front side 26 Back side 27 Radial distance of the pin section 29 Driving wheel 38 Shortest distance between extreme position and reversal position 30 Central axis 31, 32 Clamping devices 41, 42 Chuck 60 Stainless steel tube E.sub.1 First extreme position E.sub.2 Second extreme position U.sub.1 First reversal position U.sub.2 Second reversal position