A device for forming circumferential grooves in pipe elements uses multiple geared cam bodies mounted on a carriage which rotates about a fixed pinion. The gears engage with the pinion which causes the geared cam bodies to rotate relative to the carriage. Traction surfaces and cam surfaces on the cam bodies traverse the outer surface of the pipe element and impress a circumferential groove therein. Each cam surface has a region of increasing radius and may have a region of constant radius. Second cam surfaces, positioned in spaced relation axially to the first cam surfaces, may also extend around the cam bodies. The second cam surfaces have a constant radius and limit flare of the pipe element.

A device for cold working pipe elements has two or more cams, each having a gear. The gears turn synchronously with one another. Each cam has a cam surface with a region of increasing radius and may have a region of constant radius extending around a cam body. Each cam also has a traction surface extending around a cam body. A discontinuity in each cam surface is aligned with a gap in the traction surface of each cam. The discontinuities and gaps provide clearance for insertion and removal of the pipe element between the cams to form a circumferential groove when the cams are rotated.

A device for cold working pipe elements has two or more cams, each having a gear. The gears turn synchronously with one another. Each cam has a cam surface with a region of increasing radius and may have a region of constant radius extending around a cam body. Each cam also has a traction surface extending around a cam body. A discontinuity in each cam surface is aligned with a gap in the traction surface of each cam. The discontinuities and gaps provide clearance for insertion and removal of the pipe element between the cams to form a circumferential groove when the cams are rotated.

Forming methods of one-piece weldless wheels made of metal sheets including the steps of rolling, forming a primary wheel rim and a primary wheel disc, roll forming, compressing and shaping, in order to obtain one-piece weldless wheels. The methods can form weldless wheels by rolling, cold roll forming and cold extruding, which can reduce energy consumption by 45-55% and cut down material cost by 5-15% while improving strength of the wheel by 20-30%. A wheel with different thicknesses can be formed by the methods and can meet the requirements on mechanical strength. The methods can improve the precision of the wheel and minimize the swing value and jerk value. The wheel produced is safer, and the regular air tight test on the wheel is not necessary.

Forming methods of one-piece weldless wheels made of metal sheets including the steps of rolling, forming a primary wheel rim and a primary wheel disc, roll forming, compressing and shaping, in order to obtain one-piece weldless wheels. The methods can form weldless wheels by rolling, cold roll forming and cold extruding, which can reduce energy consumption by 45-55% and cut down material cost by 5-15% while improving strength of the wheel by 20-30%. A wheel with different thicknesses can be formed by the methods and can meet the requirements on mechanical strength. The methods can improve the precision of the wheel and minimize the swing value and jerk value. The wheel produced is safer, and the regular air tight test on the wheel is not necessary.

A variable thickness process and system for processing steel strips to obtain a profile with at least two different thicknesses along its width which includes at least one heating step, and at least one stretching step and one straightening step.

A plate-shaped workpiece forming method of post-machining a pocket (3) on a curved inner surface of a plate-shaped workpiece (2) in a state where the plate-shaped workpiece (2) curved by a curving machine (10) is spread flat. The method includes a curving step (A) of setting a net curve radius (R.sub.0) obtained by adding a curve radius contraction amount (R.sub.1) due to spring-in to a finished curve radius (R) of a plate-shaped workpiece (2), taking into account an amount of contraction of the curve radius of the plate-shaped workpiece (2) between before and after machining of a pocket (3) due to spring-in, and curving the plate-shaped workpiece (2) so as to achieve the net curve radius (R.sub.0); and a pocket machining step of post-machining the pocket (3) by flatly spreading the curved plate-shaped workpiece (2).

A plate-shaped workpiece forming method of post-machining a pocket (3) on a curved inner surface of a plate-shaped workpiece (2) in a state where the plate-shaped workpiece (2) curved by a curving machine (10) is spread flat. The method includes a curving step (A) of setting a net curve radius (R.sub.0) obtained by adding a curve radius contraction amount (R.sub.1) due to spring-in to a finished curve radius (R) of a plate-shaped workpiece (2), taking into account an amount of contraction of the curve radius of the plate-shaped workpiece (2) between before and after machining of a pocket (3) due to spring-in, and curving the plate-shaped workpiece (2) so as to achieve the net curve radius (R.sub.0); and a pocket machining step of post-machining the pocket (3) by flatly spreading the curved plate-shaped workpiece (2).

A roll body for a hydrostatic rolling tool includes a center, an axis of rotation running through the center, and a machining zone for rolling a workpiece. The roll body is rotatable about the axis of rotation and the machining zone has a working profile line formed in a cross-section of the roll body. The working profile line has a first working arc extending around a first machining center and a second working arc extending around a second machining center. The first machining center is arranged offset to the center, and the second machining center is arranged offset to the center and offset to the first machining center. In an example embodiment, the roll body has a parallel to the axis of rotation, the first machining center lies in the cross-section on the parallel, and the second machining center lies in the cross-section on the parallel.

A roll body for a hydrostatic rolling tool includes a center, an axis of rotation running through the center, and a machining zone for rolling a workpiece. The roll body is rotatable about the axis of rotation and the machining zone has a working profile line formed in a cross-section of the roll body. The working profile line has a first working arc extending around a first machining center and a second working arc extending around a second machining center. The first machining center is arranged offset to the center, and the second machining center is arranged offset to the center and offset to the first machining center. In an example embodiment, the roll body has a parallel to the axis of rotation, the first machining center lies in the cross-section on the parallel, and the second machining center lies in the cross-section on the parallel.