A method for producing a valve body of a hollow valve includes providing a workpiece blank or semi-finished product, spin extruding the workpiece to produce a preform having a cup with a hollow shape formed by the cup wall. A hollow valve produced by this method is also provided.

The invention relates to a method for producing a connecting element comprising at least two ball-like sections, wherein two ball-like sections are directly adjacent to each other, or wherein two ball-like sections are connected to each other by means of a connecting section, wherein the rolling of a single-piece blank, which is cylindrical at least in sections, between at least two rolling tools and the shaping of the at least two ball-like sections and optionally of the connecting section during the rolling are provided.

The invention relates to a method for producing a connecting element comprising at least two ball-like sections, wherein two ball-like sections are directly adjacent to each other, or wherein two ball-like sections are connected to each other by means of a connecting section, wherein the rolling of a single-piece blank, which is cylindrical at least in sections, between at least two rolling tools and the shaping of the at least two ball-like sections and optionally of the connecting section during the rolling are provided.

A method for producing a valve body of a hollow valve includes providing a workpiece blank or semi-finished product, spin extruding the workpiece to produce a preform having a cup with a hollow shape formed by the cup wall. A hollow valve produced by this method is also provided.

Provided are a hollow drive shaft using an upsetting method and a method of manufacturing the same, in which hot forging and upsetting processes are applied to both ends of a workpiece so that an outer diameter at both ends of the workpiece is greater than an outer diameter of a middle part of the workpiece, thereby reducing a weight of the drive shaft and enabling the drive shaft to transmit higher driving power. According to the present invention, the upsetting process is applied during the hot forging process to manufacture the hollow drive shaft, portions to be substantially processed are limited to portions at both ends of the workpiece, and the number of upsetting processes is limited to a minimum number (2 or the like), such that initial investment costs and manufacturing costs are low because the number of processes is small.

A method for producing a hollow shaft from a tubular preform by pressure rolling shapes each end of the preform using at least one forming roller. A tubular preform with a round or polygonal cross-section is used, and the preform is held on a workpiece holder in the central tube region during the entire production process until the hollow shaft is completed.

A method for producing a hollow shaft from a tubular preform by pressure rolling shapes each end of the preform using at least one forming roller. A tubular preform with a round or polygonal cross-section is used, and the preform is held on a workpiece holder in the central tube region during the entire production process until the hollow shaft is completed.

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. To substantially prevent rotation of the pipe element the pitch circle diameter of the pinion equals the outer diameter of the pipe element and the pitch circle diameters of the traction surfaces equal the pitch circle diameters of the gears.

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. To substantially prevent rotation of the pipe element the pitch circle diameter of the pinion equals the outer diameter of the pipe element and the pitch circle diameters of the traction surfaces equal the pitch circle diameters of the gears.

Provided are a hollow drive shaft using an upsetting method and a method of manufacturing the same, in which hot forging and upsetting processes are applied to both ends of a workpiece so that an outer diameter at both ends of the workpiece is greater than an outer diameter of a middle part of the workpiece, thereby reducing a weight of the drive shaft and enabling the drive shaft to transmit higher driving power. According to the present invention, the upsetting process is applied during the hot forging process to manufacture the hollow drive shaft, portions to be substantially processed are limited to portions at both ends of the workpiece, and the number of upsetting processes is limited to a minimum number (2 or the like), such that initial investment costs and manufacturing costs are low because the number of processes is small.