Method and device for producing press-rolled pipes with inner wa

Details Method and device for producing press-rolled pipes with inner wa Method and device for producing press-rolled pipes with inner wa

1998-09-01

2000-03-21

Larson, Lowell A.

Metal deforming

By use of tool acting during relative rotation between tool...

During rotation of work

7237002, 7237025, B21D 2216

Patent

active

06038901&

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The invention relates to a method and a device for producing press-rolled pipes.
Rotationally symmetrical parts (for example tubes) are required in the structural design of loaded parts in the construction of vehicles (for example bicycle/motorcycle construction) which should be as light as possible, but must have the necessary resistance torques at the loaded positions. For this purpose, with tubular structural parts, for example, the ends are reinforced on the inside, the wall thicknesses in the middle are reinforced on the inside, longitudinal ribs are applied to the inside or combinations of these measures are carried out. Because the outer dimensions of these tubular structural parts cannot be changed for structural reasons, these even being standardized in part (for example in the case of bicycles), these measures are basically applied advantageously to the inside of the tubular workpieces.
These measures for modification of the inner region of the rotationally symmetrical parts have already been known for a long time and are prior art. However, the measures necessary for this purpose are very costly and even today to some extent cannot represent, in practice, justifiable costs. In this way, a tubular structural part for bicycles with inner thickening of the tube ends on both sides can already be produced today. However, for this purpose several costly pulling procedures are required, and on every individual structural part. Because of the method-dependent tolerances dependent upon the method in the conventional production of these parts, any advantage in terms of weight cannot be used in full because of the large tolerance zone of, for example, the uneven walls (differences in wall thickness), because the smallest wall thickness must be considered in the structural calculation.
The generic DE-P 44 46 919 describes a method for flow turning internally geared parts, wherein a workpiece is arranged on a press mandrel, which workpiece is plastically deformed by means of the force loading of pressure rollers. The co-pressing method and the counter-pressing method are described in detail.
In this respect, press-rolling technology allows maximized use of weight advantages as a result of the very small wall thicknesses due to the very high highest levels of hardening of the materials used (steel, steel alloys, aluminium and aluminium alloys, titanium and titanium alloys, copper and copper alloys, special steels etc.) which are attainable and the extremely even thickness of the parts produced. In particular the method allows excellent surfaces to be obtained in the interior of the workpieces, i.e. there is very little roughness. This low surface roughness guarantees special protection against cracks which can start from internal notches in the event of, for example, overstressing. In addition, the method allows high reproducible levels of accuracy. Fluctuations within the workpieces are minimal.


SUMMARY OF THE INVENTION

The object of the invention is to create a method and an associated device with which it is possible to produce tubes which are press-rolled in a cost-favourable manner and with accurate tolerance and which have inner wall thickenings at the ends.
In accordance with the invention the object is achieved by using, in a first working operation, a first press mandrel with a tailstock-end shoulder, by the pressure rollers beginning their transforming work at the tailstock-end shoulder and working in the direction of the machine spindle, by the half-finished tube subsequently being taken from the first press mandrel, by the half-finished tube at the end with the wall thickening which has already been produced being clamped in a second working operation into a lathe chuck (tensioning spindle or similar) mounted in the press-rolling machine, and a second press mandrel, fastened on the tailstock end and having an outer diameter which corresponds to the inner diameter of the wall thickening, being pushed into the half-finished tube, and by the pressure rollers subsequent

REFERENCES:
patent: 4036044 (1977-07-01), Yoshimura

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