EP0323456B1

EP0323456B1 - Process and apparatus for the cold shaping of pipes or fittings, and articles thus obtained

Info

Publication number: EP0323456B1
Application number: EP87904388A
Authority: EP
Inventors: Augusto Archi; Enrico Sebastiani
Original assignee: Individual
Current assignee: Individual
Priority date: 1986-06-30
Filing date: 1987-06-29
Publication date: 1993-02-03
Anticipated expiration: 2007-06-29
Also published as: IT8620988A0; WO1988000099A1; AU7644487A; IT8620988A1; DE3784070D1; EP0323456A1; IT1191835B; DE3784070T2

Abstract

A pipe or fitting tubular section (17) is at first deformed so as to obtain at least a radial wall, substantially perpendicular to the pipe axis, and having, as regards the thickness, such a height that its buckling limit load is inferior to its combined bending and compressive limit load; then said pipe is deformed by substantially radial forces acting on a zone adjacent to said radial wall which acts as a support. The radial wall can be supported at its internal base. The radial wall (22, 22a) can be formed by operating shaped radial inserts (40) on the pipe wall or by axially operating one against other two dies that leave the pipe free at a desired point thus creating a collar. A subsequent cold-working can be carried out both by radial inserts and by putting in contact a pipe portion adjacent to said radial wall with a fixed surface which shapes said portion. An axial shaping of the radial wall can be provided axially operating with dies.

Description

The present invention refers to a process and apparatus for the cold shaping or cold forming of pipes or metallic pipe fittings.
Shaped pipes or pipe fittings are normally obtained by casting or through a mechanical process, therefore they are expensive. The attempt to produce these articles made of plastics has resulted in pieces having a mechanical resistance definitely unsuitable for the most common uses.
FR-A-1 393 986 provides for a process, as defined in the pre-characterizing part of the claim 1, consisting of applying a longitudinal pressure on the cylindrical walls of a piece of pipe to obtain a collar with a thickness double compared to the one of the cylindrical walls. The collar, in a second step is radially compressed from the outside on six sides, since the surfaces are simultaneously closed both internally and externally, to form a massive hexagon. FR-A-1 393 986 also discloses an apparatus, as defined in the pre-characterizing part of claim 3, for carrying out the above process.
The aim of the present invention is to produce pipes or metallic pipe-fittings of various shapes which are much more economical than the prior art ones, while still maintaining their sturdiness unaltered.
The above mentioned aim has been achieved by a process as specified in claim 1 and an apparatus as claimed in claim 3.
The process of the invention for cold forming of pipes or pipe-fittings, according to which a pipe or pipe-fitting is inserted into a die and two radially extending, interconnected walls - namely perpendicular to the axis of the pipe or pipe-fitting - are formed, then substantially radially inwardly acting forces are applied on zones adjacent to said radial walls, said zones being adjacent to the radially outermost ends of said radial walls which are internally supported, is characterized in that said radial walls have at least one side not supported and that the reaction forces to said applied radial forces are provided by means of said radial walls, the base of each radial wall being supported by an internal support, said radial walls acting as only means of contrast to these forces, being the ratio height/thickness of said radial walls such that their buckling limit load is lower than their combined bending and compressive stress. In other words, the ratio height/thickness of the walls is such that said walls do not bend, when undergoing a radial compression.
The radially extending walls can be formed by shaped radial die slides or inserts acting on the pipe or pipe-fitting wall.
The obtained articles are preferably, but not limitedly: pipes or pipe-fittings having a same diameter at both ends or different diameters and with a polygonal or circular collar; pipes or pipe-fittings with ring at their ends. These hose fittings can have circular collars capable of being sealed with conical or flat coupling surfaces.
The process essential steps, the apparatus according to a preferred but not limiting embodiment of the invention and the articles thereby obtained, are illustrated in the enclosed drawings, therein:

Fig. 1 is a plan view of an apparatus for the shaping of a pipe or pipe-fitting in two successive operating steps;
Fig. 2 is a sectional view along line 2-2 of Fig. 1;
Fig. 3 shows the first shaping step of a pipe which will have ends of different diameters;
Fig. 4 shows a forming phase of two adjacent radial walls on the pipe illustrated in Fig. 3;
Fig. 5 shows the shaping phase of the connecting zone between the radial walls formed in the phase illustrated in Fig. 4; and
Figs. 6 and 7 show a part-sectional side view of two embodiments of the obtained pipe-fittings.

Figure 1 and 2 show the working phases on a pipe section 17. This pipe section is inserted in the dies 20 and 20a provided with abutments 13 and is compressed axially, thus obtaining first, in a known way, through cone 29, the enlargement of one of its portions, then the forming of radial walls 22 and 22a. These latter are them shaped by inserts 40 acting radially to the pipe section 17. During these working phases, the pipe and particularly the internal base of each radial wall 22 and 22a is supported by a support 30 inside the pipe, preferably a plug. This internal support 30 is provided with at least a cone 29 which carries out the shaping of the pipe and supports the internal base of the radial walls 22 and 22a.
Figures 3, 4 and 5 show more in detail the above mentioned working phases; as shown in Fig. 3 a portion of pipe 17 is first enlarged, then, continuing the compression by moving the dies 20 and 20a, the radial walls 22 and 22a are formed (Fig. 4). During this phase the approach of the two dies 20 and 20a is carried out until the distance between the extreme ends 21 of the dies is equal to twice the thickness of the pipe to be shaped.
Fig. 5 shows the shaping of zone 10 connecting the radial walls 22 and 22a. In this phase, while the insert 40 presses on the radial wall, the two dies 20 and 20a are left free to move away until the distance between the extreme sides 21 is equal to the thickness required for the collar 11. The inserts 40 have front sides 40a having a width equal to the collar thickness.
Embodiments of the obtained articles are shown in Figs. 6 and 7. Fig. 6 shows a pipe-fitting 18 having a polygonal collar 11 and two portions having different diameter and Fig. 7 shows a pipe-fitting 19 similar to the one in Fig. 6, but having equal diameter at both ends.

Claims

A process for cold forming of pipes or pipe-fittings, according to which a pipe or pipe-fitting is inserted into a die and two radially extending, interconnected walls (22,22a) - namely perpendicular to the axis (X-X) of the pipe or pipe-fitting - are formed, then substantially radially inwardly acting forces are applied on zones (10) adjacent to said radial walls (22,22a), said zones being adjacent to the radially outermost ends of said radial walls which are internally supported, characterized in that said radial walls (22,22a) have at least one side not supported and that the reaction forces to said applied radial forces are provided by means of said radial walls (22,22a), the base of each radial wall being supported by an internal support (30), said radial walls acting as only means of contrast to these forces, being the ratio height/thickness of said radial walls such that their buckling limit load is lower than their combined bending and compressive stress.
A process as in claim 1, characterized in that during application of said radial forces the die (20,20a) is free to axially move.
An apparatus for cold forming of a pipe or pipe-fitting, comprising a die (20,20a) capable of forming two radial walls (22,22a) on the pipe or pipe-fitting; a shaping member (40) provided to act in succession, in a substantially radial direction, on a zone (10) adjacent to the radial walls (22,22a); an internal support (30), which can be inserted into the pipe or pipe-fitting to be shaped and which internally supports the base of the radial walls (22,22a), characterized in that the die comprises two opposed portions (20,20a) which are only axially movable and are free to move when the shaping member (40) comes into contact with said zone (10), the shaping member being capable of acting radially inwards to perform the forming action.