60/146,849, filed August 3,1999.

Background of the Invention This invention relates to roller assemblies for cold rolling tubes.

During cold rolling, the tube is typically offset angularly from the centerline of grooving roll contact surface so that the tube continuously feeds itself into the grooving machine. It has been known to use a guide roller positioned to the side of the tube to offset the axis of the tube so that the user does not have to manually offset the tube while the tube is being cold rolled.

When cold rolling a groove in a tube, the end of the tube being cold rolled has a tendency to flare. Flaring is increased when the opposite end of the tube angles upward from horizontal. When cold rolling longer tubes, e. g., longer than about 4 or 5 feet, flaring is minimized because the weight of the tube itself prevents it from angling upward.

U. S. Patent No. 5,778,715, to Lippka et al., the complete disclosure of which is hereby incorporated by reference, discloses a tube positioning assembly with a pair of positioning rollers that act to angle the tube slightly, causing the tube to feed in towards the grooving rolls during cold rolling.

Summary of the Invention According to one aspect of the invention, a roller assembly of a cold rolling apparatus for forming an end of a tube includes an inside roll, and an outside roll. An axis of rotation of one of the rolls is angularly offset relative to an axis of rotation of the other roll.

Embodiments of this aspect of the invention may include one or more of the following features. The angular offset is selected to cause the tube to self-feed into the roller assembly during cold rolling. The angular offset is in a range of up to about 1°, and preferably in a range of about 1/4° to l/2°. One of the rolls, e. g., the inside roll, is a driven roll, and the other of the rolls is angularly offset from the driven roll. The driven

roller is configured such that the axis of rotation of the driven roll coincides with an axis of the cold rolling apparatus.

In the illustrated embodiment, the roller assembly is in combination with a positioning roller assembly.

According to another aspect of the invention, a method of cold rolling a tube includes positioning the tube between an inside roll and an outside roll with the axis of rotation of one of the rolls being angular offset relative to the axis of rotation of the other roll.

The angular offset between the inner and outer rolls advantageously provides hands-off feeding of the tube between the groove rolls.

Brief Description of the Drawings Fig. 1 is a diagrammatic perspective view of a cold rolling machine according to the invention; Fig. 2 shows a rolling assembly of the machine of Fig. 1; Fig. 3 is an end view of the rolling assembly of Fig. 2; Fig. 4 is an end view of outside and inside rollers of the rolling assembly of Fig.

2; and Fig. 5 illustrates the angular offset of the rotational axes of the outside and inside rollers.

Detailed Description of the Invention Referring to Figs. 1-3, a cold rolling machine 10 includes a roller assembly 12 for positioning a tube 14 for and during cold rolling of the tube 14. As used throughout this disclosure, the term"tube"includes any tube, pipe, or fitting element which can be cold rolled. Roller assembly 12 includes an outside groove roll 18 and an inside, driven groove roll 20. A hydraulic ram 22 lowers outside groove roll 18 to act against inside groove roll 20 to form a groove in tube 14. A positioning roller assembly 30 is mounted for movement with outside groove roll 18. Positioning roller assembly 30, for example the positioning roller assembly described in U. S. Patent No. 5,778,715, supra, or the positioning roller assembly described in U. S. S. N, filed August 3,2000 (which claims the benefit of U. S. Provisional Application No. 60/146,848 filed August 3,1999), the complete disclosure of which is hereby incorporated by reference, enables hands-off feeding of the tube into the groove rolls.

Referring to Figs. 2 and 3, roller assembly 12 includes a pivot arm 40 to which outside groove roll 18 is rotatably mounted. Hydraulic ram 22 is lowered (arrow 42) to contact a surface 44 of pivot arm 40 to lower outside groove roll 18 and positioning roller assembly 30 by pivoting motion of pivot arm 40 relative to a rolling assembly frame 45 about a pivot point 46. Pivot arm 40 includes an extension 48 with a notched section 47 which runs along a threaded guide rod 49. The position of pivot arm 40 is adjusted by rotation of guide rod 49. A depth stop 50 threadedly connected to guide rod 49 limits the depth to which pivot arm 40 can be lowered.

Positioning roller assembly 30, which is particularly suited for producing a groove in a short length of tubing, e. g., steel piping having a length as short as about 4.5 inches and a diameter in the range of about 2-12 inches, includes first and second positioning rollers 60,62. When pivot arm 40 is lowered, roller 62 contacts tube 14 followed by roller 60 contacting the tube. This produces a relatively greater force between roller 62 and the tube than between roller 60 and the tube. During cold rolling, the differential load causes tube 14 to seek to reposition itself to equalize the loads, thus offsetting tube 14 from a line of contact 63 between outside and inside rollers 18,20, e. g., by about'/4. The offset restricts tube 14 from feeding itself out of the cold rolling machine 10. The rollers 60,62 also provide a downward load on tube 14, which positions tube 14 at a downward angle from line of contact 63 of, e. g., about'/4, to reduce flaring of the tube end 24 during grooving (see Fig. 1). This combination of the tube being offset and the downward load on the tube enables hands-off feeding of the tube between the groove rolls 18,20.

Referring to Figs. 4 and 5, to further insure self-feeding of tube 14 into roller assembly 12, and to inhibit tube 14 from feeding itself out of the cold rolling machine 10, the rotational axes 100 and 102 of outside roll 18 and inside roll 20, respectively, are angularly offset by an angle 8. As shown in the top view of Fig. 5, and referring also to Fig. 1, rotational axis 100 of inside roll 20 coincides with machine axis, Y.

Outside roll 18 is offset clockwise by angle 6. Alternatively, outside roll 18 is offset counterclockwise, or rotational axis 102 of outside roll 18 coincides with machine axis, Y, and inside roll 20 is offset relative to outside roll 18. Angle S, which is greatly exaggerated in Fig. 5, preferably ranges up to about 1 °, and more preferably is in a range of about 1/4° to l/2°.