Pilger rolling mill with a crank drive

Abstract

A pilger rolling mill with a roll stand moves linearly back and forth along a movement direction and includes a crank mechanism having a rotatably supported crankshaft with a crank pin and push rod. A first end of the push rod is pivotably fastened to the crank pin and a second end is pivotably fastened to the roll stand, so that during operation of the pilger rolling mill a rotary movement of the crankshaft is converted into an oscillating movement of the roll stand along the movement direction. A compensation shaft is rotatably supported about an axis of rotation and includes a distribution of mass that is not rotationally symmetrical relative to its axis of rotation and a counter-mass. The crankshaft and the compensation shaft are connected to one another by a transmission so that a rotation of the crankshaft leads to a rotation of the compensation shaft.

Claims

1. A pilger rolling mill with a roll stand linearly moveable back and forth along a movement direction, the pilger rolling mill comprising: a crank mechanism including a crankshaft rotatably supported about an axis of rotation, the crankshaft having a crank pin spaced at a radial distance from the axis of rotation, wherein the crankshaft is a crank wheel, the crank pin being spaced on the crank wheel at a radial distance from the axis of rotation of the crankshaft, the crank wheel having a width in a direction parallel to the axis of rotation of the crankshaft, wherein a compensation mass is arranged inside the width of the crank wheel; a push rod having a first end and a second end, whereby the first end of the push rod is pivotably fastened to the crank pin, and whereby the second end of the push rod is pivotably fastened to the roll stand, such that during operation of the pilger rolling mill a rotary movement of the crankshaft is converted into a linearly oscillating movement of the roll stand; and a compensation shaft rotatably supported about an axis of, the compensation shaft including a distribution of mass that is not rotationally symmetrical relative to its axis of rotation and a counter-mass, whereby the crankshaft and the compensation shaft are connected to one another by a transmission so that a rotation of the crankshaft leads to a rotation of the compensation shaft, the axis of rotation of the crankshaft and the axis of rotation of the compensation shaft being spaced at a distance from each other in a direction vertical to the direction of movement of the roll stand.

2. The pilger rolling mill according to claim 1, wherein the axis of rotation of the crankshaft and the axis of rotation of the compensation shaft lie in a plane vertical to the direction of movement of the roll stand.

3. The pilger rolling mill according to claim 1, wherein the axis of rotation of the crankshaft is arranged in a direction vertical to the direction of movement of the roll stand under the axis of rotation of the compensation shaft.

4. The pilger rolling mill according to claim 1, wherein the roll stand includes two rolls, whereby the rolls fix a central pipe axis of a pipe to be rolled, whereby the axis of rotation of the crankshaft is arranged underneath the central pipe axis and the axis of rotation of the compensation shaft is arranged above the central pipe axis.

5. The pilger rolling mill according to claim 1, the compensation mass and the crank pin with the push rod are arranged at a distance from each other in the direction of the axis of rotation.

6. The pilger rolling mill according to claim 1, wherein the compensation shaft is a compensation wheel that has a width in the direction of the axis of rotation of the compensation shaft, whereby the counter-mass is arranged at least in sections outside of the width of the compensation wheel.

7. The pilger rolling mill according to claim 6, wherein the crank wheel and the compensation wheel are tooth wheels that mesh with one another and form the transmission connecting the crankshaft and the compensation shaft to one another.

8. The pilger rolling mill according to claim 1, wherein the crank mechanism includes two crank pins rotatable about a common axis of rotation and distanced radially from the common axis of rotation and two push rods, each having a first and a second end, whereby the first end of each push rod is pivotably fastened on a crank pin and whereby the second end of each push rod is pivotably fastened on the roll stand so that during the operation of the pilger rolling mill a rotary motion of the crankshaft is converted into a linearly oscillating movement of the roll stand, and whereby the compensation shaft includes two compensation masses that can rotate about the same axis of rotation.

9. The pilger rolling mill according to claim 1, further comprising a drive motor with a motor shaft, whereby the motor shaft is directly connected to the crankshaft or to the compensation shaft such that a rotation of the motor shaft results in exactly one rotation of the crankshaft or of the compensation shaft.

10. The pilger rolling mill according to claim 1, further comprising a drive motor arranged to drive the compensation shaft and via the latter drives the crankshaft.

Description

(1) Other advantages, features and application possibilities of the present invention become clear using the following description of embodiments and of the associated figures.

(2) FIG. 1 shows a schematic lateral view of a first embodiment of a pilger rolling mill in accordance with the invention.

(3) FIG. 2 shows a top view of the embodiment in FIG. 1.

(4) FIG. 3 shows a partially broken away schematic view from the front onto a crank drive with compensation shaft in another embodiment of the invention.

(5) In the figures the same elements are designated with the same reference numerals.

(6) FIGS. 1 and 2 show a first embodiment of the pilger rolling mill in accordance with the invention and a drive unit for the roll stand of such a pilger rolling mill in schematic views.

(7) A roll stand 2 of the pilger rolling mill 1 is driven in such a manner with the aid of the drive discussed here that it moves back and forth oscillating in a linear manner in a direction of movement 3. In order to generate this linearly oscillating movement of the roll stand 2, a crank drive is used comprising a crankshaft 4 and a connecting rod 5. The crankshaft 4 can rotate about an axis of rotation 13.

(8) The crankshaft 4 consists in the embodiment shown of a crank wheel 4 with a crank pin 6 eccentrically fastened on it on which the connecting rod 5 is pivotably arranged with the aid of a bearing. While the first end 7 of the connecting rod 5 is fixed on the crank wheel or its crank pin 6, the second end 8 of the connecting rod 5 is pivotably fastened on the roll stand 2 with the aid of a bearing. In this manner a rotation of the crank wheel 4 results in a linearly oscillating motion of the roll stand 2 in the direction of movement 3. The crank wheel 4 additionally comprises a non-rotationally symmetric distribution of mass that is made available in that a compensation mass 9 is eccentrically fastened on the crank wheel 4.

(9) The crank wheel 4 is constructed as a toothed wheel in the embodiment shown. This crank wheel meshes with a drive wheel 10 that for its part is driven by a torque motor and thus puts the crank wheel 4 in rotation.

(10) Moreover, the crank wheel 4 meshes with a compensation wheel 11 as a compensation shaft in the sense of the present application. The compensation wheel 11 serves to compensate free forces and moments of the first order on account of the oscillating motion of the roll stand 2 and to thus contribute to a quieter and more uniform course of the roll stand 2.

(11) To this end the compensation wheel 11 comprises a counter-mass 12 that is eccentrically fastened on the compensation wheel 11. Since the crank wheel 4 and the compensation wheel 11 have the same diameter, a revolution of the crank wheel 4 also results in exactly one revolution of the compensation wheel 11 and of the counter-mass 12 fastened on it. Compared to the compensation mass 9 of the crank wheel 4, the counter-mass 12 of the compensation wheel 11 is arranged offset by approximately 180 relative to the direction of translation 3 of the roll stand 2. That is, the compensation mass 9 and the counter-mass 12 are located in opposing halves of the crank wheel 4 and of the compensation wheel 11 at the reversal points of the roll stand 2 (upon a change of direction).

(12) It can be clearly recognized from FIG. 1 that the axis of rotation 13 of the crank wheel 4 and the axis of rotation 14 of the compensation wheel 11 lie in a plane 15 that is vertical to the direction of movement 3 of the roll stand 2, i.e., they are arranged vertically above one another. This makes possible a space-saving arrangement relative to the construction length of the rolling mill.

(13) The rolls received in the roll stand 2 (not shown in FIG. 1) define the position of the central axis 16 of the tube to be rolled. It can be clearly gathered from the representation of FIG. 1 that on account of the arrangement of the axes of rotation 13, 14 of the crank wheel 4 and of the compensation wheel 11 above one another, the central axis 16 runs between these axes of rotation 13, 14.

(14) The selected construction has two general advantages. On the one hand the closeness of the axis of rotation 13 of the crank wheel 4 to the central axis 16 of the tube allows a comparatively flat angle between the connecting rod 5 and the direction of translation 3 of the roll stand 2. This results in a more uniform course of the roll stand 2 and therefore in less wear on its guide elements. Given the simultaneous desire for a short construction length of the pilger rolling mill with the resulting consequence of the vertical arrangement of the axes of rotation 13, 14 above one another, there is either a solution at which the compensation wheel 11 is arranged deep below in a pit in the machine hall with all the associated difficulties, or, as is optimally solved in the embodiment presented, with an arrangement of the compensation wheel 11 vertically above the crank wheel 4.

(15) Whereas the vertical arrangement of the wheels 4, 11 and their axes of rotation 13, 14 above one another, here the compensation wheel 11 above the crank wheel 4, can be clearly gathered from FIG. 1, FIG. 2 shows in a top view onto the pilger rolling mill 1 in FIG. 1 that the selected arrangement concerns an arrangement that is symmetrical to a plane vertical to the axes of rotation 13, 14 and through the central axis 16 of the tube to be rolled.

(16) It is clear from FIG. 2 that the arrangement comprises two crank wheels 4, 4 (they are actually not shown in FIG. 2 since they are located in the shown view from above under the compensation wheels 11, 11 and covered by them) that drive two connecting rods 5, 5 via two crank pins 6. 6. Furthermore, both two ends 8, 8 of the connecting rods 5, 5 are pivotably attached to the roll stand 2. Even the drive wheel 10, 10 is present twice and each one meshes with a crank wheel 4, 4. The symmetric arrangement relative to a plane of symmetry through the central axis 16 of the tube to be rolled helps to compensate bending moments acting on the arrangement.

(17) FIG. 2 also shows that the drive of the drive wheels 10, 10 is made available by an electric direct drive with a motor 17 that acts, without an intermediate transmission, via a coupling on the shaft 18 of the drive wheels 10, 10.

(18) The embodiment of FIG. 3 differs from the embodiment of FIGS. 1 and 2 substantially in that the drive motor 17 here does not act first on the shaft of two drive wheels but rather that the hollow shaft of the motor 17 is pushed directly onto a projecting section 19 of the shaft 20 of the compensating wheels 11, 11 and is connected to it. In this manner the motor 17 directly drives the shaft 20 of the compensation wheels 11, 11. The compensation wheels 11, 11 therefore replace the drive wheels 10, 10 of the embodiment in FIGS. 1 and 2. Since the compensation wheels 11, 11 are designed as previously as gears that mesh with the crank wheels 4, 4, the crank wheels are directly driven by the motor, i.e., without a step-up or step-down, since the compensation wheels 11, 11 as well as the crank wheels 4, 4 have the same diameter. The high torque required for this is made available by a so-called torque motor. Torque motor in the sense of the present application is in particular a high-polar, electrical direct drive from the group of slow-speed engines. Torque motors have very high torques at relatively low rotational speeds.

(19) In addition, the representation of the embodiment in FIG. 3 allows a preferred symmetrical arrangement of the masses on the wheels 4, 4, 11, 11 to be clearly recognized. As shown, the compensation wheels 11, 11 as well as the crank wheels 4, 4 have a finite width. The crank pins 6, 6 on the crank wheels 4, 4 extend axially outward from the wheels, i.e., they are located outside of their width so that the connecting rods 5, 5 can pivot freely on the crank pins 6, 6. The compensation masses 9, 9 (cannot be recognized in the view of FIG. 3) are located opposite them inside the width of the crank wheels 4, 4. In other words, the crank pins and the first ends 7, 7 of the connecting rods 5, 5 received on them lie in a first plane vertical to the axes of rotation 13, 14 and the compensation masses 9, 9 lie in a second plane offset to the first plane in the axial direction.

(20) The counter-masses 12, 12 of the compensation wheels 11, 11 are arranged oppositely in the same planes as the crank pins 6, 6 and the connecting rods 5, 5 fastened to them.

(21) It is pointed out for purposes of the original disclosure that all features that result for a person skilled in the art from the present specification, the drawings and the claims, even if they were described concretely only in conjunction with certain other features, can be combined individually as well as in any combinations, in as far as this was not expressly excluded or technical features render such combinations impossible or meaningless. For the sake of brevity and the readability of the specification, a comprehensive, explicit presentation of all conceivable combinations of features is not made here.

(22) Whereas the invention was presented and described in detail in the drawings and the preceding specification, this presentation and this description are only meant to be by way of example and not as a limitation of the protective scope as it is defined by the claims. The invention is not limited to the disclosed embodiments.

(23) Modifications of the disclosed embodiments are obvious to the person skilled in the art from the drawings, the specification and the attached claims. In the claims the word comprise does not exclude other elements or steps and the indefinite article a does not exclude a plurality. 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.

LIST OF REFERENCE NUMERALS

(24) 1 pilger rolling mill 2 roll stand 3 direction of movement 4, 4 crank wheel 5, 5 connecting rod 6,6 crank pin 7,7 first end of the connecting rod 8,8 second end of the connecting rod 9,9 compensation mass 10, 10 drive wheel 11, 11 compensation wheel 12, 12 counter-mass 13 axis of rotation of the crank wheel 14 axis of rotation of the compensation wheel 15 plane 16 central axis of the tube to be rolled 17 motor 18 shaft of the drive wheels 19 drive shaft 20 shaft of the compensation wheels