Internal roller tool for bending a strip into a tube

An internal tool for bending a strip passing in a strip-travel direction into a tube has a support juxtaposable with a face of the passing strip, at least two roller holders pivotal on the support about respective offset holder pivot axes generally parallel to the strip-travel direction, and respective rollers carried in the holders and rotatable about respective roller axes generally perpendicular to the respective holder axes.

FIELD OF THE INVENTION

The present invention relates to the manufacture of tubing from strip. More particularly this invention concerns an internal roller tool for bending a strip into a tube.

BACKGROUND OF THE INVENTION

The invention relates to an internal shaping tool for deforming a metal sheet or strip into a pipe. The tool has at least two rollers that are pivotable about swivel axes and that start on one side of the metal sheet for shaping same.

In pipe manufacturing, according to one common technology first a flat metal strip, generally wound from a coil, is shaped into a tubular element and in a subsequent operation is welded at the joint that is formed on the edges of the strip. For the shaping of the metal strip into the tubular element, devices are known in practice that have the above-described internal shaping tools, typically acting with outer tools that engage the outer face of the strip to press its inner face against the internal tool.

The known internal shaping tools employ rollers that are either fixedly or rigidly provided in a defined position on a hearing element, or are each positioned in a pivotal holder.

The shape of the body to be manufactured depends on the final dimensions to be achieved, as well as the material properties of the metal strip, i.e. its tensile strength, yield point, and also its thickness. For the known internal shaping tool having fixed rollers, response to a change in characteristics for the pipe or shaped body to be shaped can be made only with great effort. In particular, a modification using a different or rebuilt internal shaping tool is necessary.

However, for the known rollers that are pivotal via their holders it is also not possible to achieve a desired configuration of the pipe geometry via adjustment of their angular positions. Namely, the pivot point is arbitrarily selected and has no relation to the shape to be produced, and thus also cannot be compensated for by the contoured shape of the rollers.

In practice, therefore, it has been shown that due to the inadequate adaptability of the internal shaping tool the rollers often do not bear on the workpiece over their full width, resulting these roller running on their edges. This results in surface damage to the metal strip being shaped.

OBJECTS OF THE INVENTION

It is therefore an object of the present invention to provide an improved internal roller tool for bending a strip into a tube.

Another object is the provision of such an improved internal roller tool for bending a strip into a tube that overcomes the above-given disadvantages, in particular that avoids the above-given disadvantages.

A particular objective is to easily, quickly, and thus economically ensure optimal full-width bearing of the rollers, even if the shape of the workpiece changes.

SUMMARY OF THE INVENTION

An internal tool for bending a strip passing in a strip-travel direction into a tube. The tool has according to the invention a support juxtaposable with a face of the passing strip, at least two roller holders pivotal on the support about respective offset holder pivot axes generally parallel to the strip-travel direction, and respective rollers carried in the holders and rotatable about respective roller axes generally perpendicular to the respective holder axes.

Since according to the invention the pivot axes are provided where the work is done, specifically, at the midpoint or in the vicinity of the midpoint of the rollers themselves, the rollers may be easily adapted or adjusted precisely to the shape desired, since the rollers are in the optimal position for shaping a specific metal strip. The rollers may thus be pivoted such that they always contact the metal strip along their full width, and edge bearing may be reliably avoided.

The two pivot axes are preferably symmetrically positioned with respect to a center plane of a common holder, and both rollers can be symmetrically pivoted.

According to one advantageous embodiment, means are provided for synchronizing the pivoting of the rollers that are pivotally positioned in or on the support. These means allow mirror-image pivoting of the rollers pivotally positioned in or on the holder, relative to the central piano of the holder. Thus they are pivoted synchronously toward and away from each other.

According to the invention, the means are formed by toothed sector gears that are respectively connected in a fixed manner to the roller holder and that mesh with one another. Furthermore, at least one extensible actuator is provided that engages between the support and the roller holder in order to pivot the roller holder together with the roller about the pivot axis. In one preferred embodiment, only a single extensible actuator is provided for this purpose.

In addition to the pivotal rollers, a nonpivoting center roller may be provided on the support or on an additional holder adjoining the holders of the side rollers. In this case, the nonpivoting center roller may be mounted on the support or on an additional holder in such a way that the center roller lies in the center plane of the support. The center roller may also be positioned so as to be adjustable in a direction lying in the center plane, for example in the vertical direction. In this case the adjustability may be achieved by means of a spacer. In one alternative, the adjustability is achieved by a threaded adjuster, a screw-nut element. Alternatively, an eccentric or a rocker may be provided for adjusting and setting the center roller.

By use of the proposed embodiment of an internal shaping tool, the position of the side rollers may be easily and economically adapted to the desired geometric proportions, thus providing an optimal start on the metal strip to be shaped. A response may thus be easily made to a change in the shape of the shaped body.

SPECIFIC DESCRIPTION

FIGS. 13show an internal shaping tool1. The metal strip2to be shaped being shown only inFIG. 1. The metal strip2is displaced in a strip-travel direction R and is pressed inward against the tool1by unillustrated outer tools as illustrated schematically at7inFIG. 1.

To impart the desired shape to the metal strip2, the internal shaping tool1has a support3on which in the present case a total of three rollers4,5, and6, namely two side rollers4and5and a center roller6, are mounted, pivotal about respective center axes4A,5A, and6A. All three rollers4,5, and6contact one face7of the metal strip2, here shown already bent into a U- or C-section. Not illustrated on the other side of the metal strip are starter rollers, that are provided on side roller beams in a known manner, and that exert the inward bending force F.

The two side rollers4and5are not rigidly mounted on the support3, as is the center roller6, but instead are pivotal about respective pivot axes8and9that extend perpendicularly through the axes4A and5A and parallel to the strip-travel direction R. As illustrated most clearly inFIG. 1, the two side rollers4and5are supported in respective roller holders14and15that pivot symmetrically with respect to a center plane10of the common support3, the axes8and9symmetrically also flanking this plane10. Means11are provided for synchronizing the pivoting of the side rollers4end5. In the illustrated embodiment, according to one preferred embodiment these means11are composed of sector gears12and13fixed and even formed on the holders14and15. The sector gear12and13are centered on the respective axes8and9and mesh with each other.

The means11for synchronization ensure symmetrical positioning of the rollers4and5, thereby facilitating a stable shaping process. In particular, twisting of the shaped body, i.e. the metal strip2to be shaped, is prevented.

To enable the two side rollers4and5to be quickly and easily adjusted to a desired pivot angle, a single extensible actuator16is present that, for example, is designed as a screw-nut adjusting system. One end of the extensible actuator16connected at a pivot20to the support3. The other end of the extensible actuator16is likewise connected at a pivot21to one of the two roller holders, here to roller holder14. Actuation of the extensible actuator16results in a change in the distance between the pivots20and21, causing the desired pivoting of the roller holder14, and therefore the side roller4, about the pivot axis6. Engagement of the two toothed sector gears12and13causes this pivot motion to be simultaneously transmitted to the other roller holder15, and thus to the other side roller5, so that both side rollers4and5are symmetrically pivoted with respect to the center plane10.

The additional roller6designed as a center roller is bisected by the center plane10and the axis6A is perpendicular to this plane10, which here is parallel to the direction R. The roller6may be mounted directly on the support3or, as shown inFIGS. 2 and 3, may be mounted on a separate, holder17. The holder17may be vertically shiftable on the support3by means or a vertical dovetail guide22.

The center roller6is adjustable vertically perpendicular to the shaping direction R. In the case of the illustrated embodiment according toFIG. 2, the adjustment in this direction is made by an appropriately selected spacers18. The approach according toFIG. 3instead provides an adjusting element19, designed as a screw-nut system, that easily allows the center roller6to be adjusted.

By use of the proposed embodiment of the internal shaping tool the rollers may be easily and quickly adapted to a change in the geometry of a shaped body, ensuring precise adjustment to the geometric requirements of the shaped body.

Depending on the application, it is also possible to set only a starting position with the pivot adjustment. The rollers then have a certain degree of freedom for optimal free adjustment, that is achievable in particular by gearing as a transmission means that produces a symmetrical adjustment. In other words the rollers4and5are set at a certain position to begin the tube-forming operation, but once it has started they are allowed to pivot freely, the sector gears12and13ensuring that they move synchronously.