Metal deforming – By use of tool acting during relative rotation between tool... – During rotation of work
Reexamination Certificate
2000-04-19
2001-10-02
Tolan, Ed (Department: 3725)
Metal deforming
By use of tool acting during relative rotation between tool...
During rotation of work
C072S083000, C072S085000
Reexamination Certificate
active
06295854
ABSTRACT:
The invention relates to a pressing roller device and a method for moulding a grooved structure, for example a thread or a toothing, into the inner surface of a tubular workpiece.
Devices are known for the manufacture of pipes with internal toothing or internal threads, which have a round shaping tool with an external toothing, on to which a tubular workpiece is pushed. Pressure is exerted on to the attached pipe from the outside with a pressing tool, with the result that an internal thread corresponding to the shaping tool is formed in its interior. The pressing tool is moved in the longitudinal direction of the pipe with an advancing movement, with the result that the same pressure is exerted on to each point of the outer surface.
In the so-called cylindrical pressing methods, smooth cylindrical pipes of relatively small wall thickness are made from a relatively short workpiece with a thick wall thickness. In this procedure the workpiece is subjected to a rotating extrusion moulding procedure. The workpiece is attached to a cylindrical shaping tool provided with a thread or a toothing, while, on the outside, several press rollers rotate about the shaping tool and the workpiece and in this way press the workpiece into the contouring of the shaping tool and in the process extend it with an advancing movement. An extrusion-deformation of the metal takes place between the shaping tool and the press rollers, with the original wall thickness of the workpiece decreasing and the length increasing as a result.
In DE-OS 24 20 014 a so-called flow turning process is described. A workpiece located on a tool mandrel is pressed by at least three pressing rollers rotating about the workpiece and subject to an axial advancing movement, against the shaping tool which has an external thread or a toothing, with the result that an internal thread or a toothing is formed in the workpiece. The driven pressing rollers are located in a radial plane of the shaping tool, i.e. the three identical pressing rollers engage the same circumferential region of the workpiece. Because the shaping tool is rotated relative to the pressing rollers, a relatively large torsional force acts on the workpiece, this force leading to a twisting of the workpiece during the plastic deformation by way of the pressing rollers. The torsion of the workpiece leads to a strain on the shaping structure of the tool, with the result that the service life of the shaping tool is considerably reduced. Shearing of the shaped structure can even possibly result.
The object of the invention is to improve the manufacture of tubular workpieces with an inner grooved structure to the extent that the torsion of the workpiece and therefore the strain on the shaping tool is considerably reduced.
In tests it has been found that the torsion of the workpiece can be almost completely prevented if the entry angle of the pressing roller which has engaged last is greater than the entry angle of the forward pressing rollers.
The entry angle of the last pressing roller is preferably at least 30°, the entry angle being, in particular, approximately 50% larger than that of the first pressing roller.
REFERENCES:
patent: 3149512 (1964-09-01), Leinbach
patent: 5115656 (1992-05-01), Kummerling et al.
patent: 5428980 (1995-07-01), Iidaka
patent: 61-27109 (1986-02-01), None
patent: 893361 (1981-12-01), None
patent: 1294444 (1987-03-01), None
Putz Karl-Heinz
Stein Bernd
Steinhauer Heinz
Zimmermann Wilhelm
Antonelli Terry Stout & Kraus LLP
Dynamit Nobel GmbH Explosivstoff-und Systemtechnik
Tolan Ed
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