EP1052042A1

EP1052042A1 - Process for manufacturing a hollow central body for the connection of pipe fittings

Info

Publication number: EP1052042A1
Application number: EP00830341A
Authority: EP
Inventors: Pierluigi Raccorderie Metalliche S.p.A. Ceccardi
Original assignee: Raccorderie Metalliche SpA
Current assignee: Raccorderie Metalliche SpA
Priority date: 1999-05-13
Filing date: 2000-05-10
Publication date: 2000-11-15

Abstract

The present invention relates to a process for the manufacture of a hollow central body (1,10), provided with openings (3,4,11,12,13) suitable for the application of pipe fittings (7,8,9) comprising an operation of precision casting.

Description

The present invention relates to a process for manufacturing a hollow central body which allows press-fittings or other types of pipe fittings to be connected according to various angles, and particularly to a process which comprises a precision casting operation.
It is known that press-fittings are used for connecting pipes in a definitive way. In order to obtain a deviation or a branching of the pipes to be connected, said press-fittings are applied to the openings of hollow central bodies having suitable configurations: particularly, a simple deviation is obtained by means of an elbow-shaped central body with two openings. In the case of three pipes to be connected, said body has the shape of a T, with three openings.
According to the prior art said central bodies are manufactured starting from a tube segment which is subjected to different workings according to whether an elbow-shaped or a T-shaped central body is being made. In the first case, the first step of the manufacture consists in bending the tube segment until the desired angle is formed, for instance of 90° or 135°.
In the case of manufacture of a T-shaped central body, an elliptical hole is first made in the central zone of the tube segment. Then, said bore is subjected to a mechanical deforming operation, carried out by a machine that, by means of a spherical-headed piston coupled to a fixed matrix, exerts an outward directed pressure on the hole. The third round opening is thus formed, whose edges must be regulated and made even.
Finally, in both cases the openings are profiled and the pipe fittings are welded thereto.
However, the above described processes for the manufacture of central bodies imply many subsequent steps and therefore request a long production time and corresponding high costs.
A second drawback of the above described process according to the prior art for the manufacture of elbow-shaped central bodies consists in that mechanical deformation of the tube segment results in flattening of the tube at the bending point, so that the tube cross-section in that point is not round any more, but elliptical. If the bending point is very close to the open ends of the tube segment, these also become flattened and take on a more or less elliptical shape.
Further, said bending of the tube segment can lead to the undesired formation of wrinkles, again at the bending point, or even to breakage of the welding of the tube segment itself. In this case, the broken piece must be discarded and working must start again with a new segment.
Object of the present invention is therefore to provide a process for the manufacture of a central body which is free from the above mentioned drawbacks. Said object is achieved by a process whose main features are specified in the first claim. The features of the central bodies obtained by the process according to the present invention are specified in claim 2 and following claims.
The manufacture of the central body by precision casting enables shorter production times and therefore lower costs to be obtained. Moreover, it offers the advantage of allowing central bodies to be mass-produced for the different needs of the users. Particularly, T-shaped central bodies wherein one of the three openings is reduced and elbow-shaped central bodies providing the desired connection angle can be mass-produced with a suitable precision.
Another advantage of the process according to the present invention consists in that the walls of the central bodies obtained by precision casting have a uniform thickness and are stronger than those obtained by mechanical deformation.
A further advantage of the process according to the present invention consists in that, by avoiding mechanical deformation steps, it prevents wastes of starting material due to breakage of the tube segment at the welding point.
Further advantages and features of the process according to the present invention will appear to those which are skilled in the art from the following detailed description of some embodiments thereof with reference to the accompanying drawings, wherein:

figure 1 is a perspective view of an elbow-shaped central body obtained by the process according to the present invention;
figure 2 is a sectional view of the same central body taken along line II-II of figure 1;
figure 3 shows an elbow central body seen in a section similar to that of figure 2 whereto press-fittings have been applied;
figure 4 shows a perspective view of a second embodiment of an elbow central body obtained by the process according to the present invention;
figure 5 is a perspective view of a T-shaped central body obtained by the process according to the present invention;
figure 6 is a cross-sectioned view of the same central body taken along line VI-VI of figure 5;
figure 7 is a cross-sectioned view of the same central body taken along line VII-VII of figure 5;
figure 8 shows a T-shaped central body seen in a cross-section similar to that of figure 6, whereto press-fittings have been applied.

With reference to figure 1 there is shown that central body 1 is internally hollow and forms an elbow 2 of about 90°. Said central body 1 is provided with two round openings 3 and 4, arranged at the ends thereof and mutually perpendicular.
In the process according to the present invention, a central body is obtained by means of a precision casting operation, wherein into a first wax model is poured a coating material which hardens after evaporation of the solvent. In the subsequent baking the wax melts, and the refractory liquid solidifies, thus forming the ceramic mould which has a perfectly smooth surface. The molten metal is poured in the still hot ceramic mould. Precision casting is greatly used industrially for producing small objects or pieces having particularly smooth surfaces and limited dimensional tolerances, and therefore does not request a detailed description.
Any kind of suitable metal can be used for the precision casting operation; for instance, stainless steel, carbon steel, brass or aluminum. Stainless steel is used in a preferred embodiment of the present invention.
Once central body 1 has been obtained by precision casting, the edges of openings 3 and 4 are turned in order to suit their thickness to that of the pipe fittings which have to be applied thereon.
With reference to figure 2, there can be seen that each one of openings 3 and 4 has been internally turned in order to obtain a boring 5. The figure also shows that the wall of central body 1 at the internal side of elbow 2 has no wrinkles, on the contrary it forms a solid corner 6 which confers a higher resistance to the piece obtained by the process according to the present invention. Particularly, the wall of central body 1 has a uniform thickness in all the portions thereof. In facts, by the process according to the present invention it is possible to obtain walls whose strength is suitable for the particular needs of the users.
Figure 3 shows central body 1 whereto two pipe fittings 7 and 8 of the press-type have been applied by head welding. The press-fittings to be welded to central body 1 are advantageously those described in Italian patent n. 1290534 in the name of the same applicant.
With reference to figure 4, there is shown that in a second embodiment of the process according to the present invention the obtained central body 1 has an elbow of 135°. The process according to the present invention enables central bodies having elbows of any desired angle, according to the particular users' needs, to be obtained.
In another embodiment of the process according to the present invention central bodies provided with more than two openings can also be obtained. Figure 5 shows T-shaped central body 10 which is provided with three round openings 11, 12 and 13 positioned at the ends of the arms of the T.
With reference to figure 6 there is shown that the three openings 11, 12 and 13 have been turned on a lathe. Borings 15 as well as the relevant bevelings 14 can be seen on each one of the three openings. The figure also shows that the walls of the central opening 13 form, together with the adjacent walls of the openings 11 and 12, solid corners 16 which confer a greater strength to the piece obtained by the process according to the present invention.
Figure 7 better shows that the walls of central opening 13, here seen in a cross-section, have the same thickness as the rest of central body 10.
Figure 8 shows central body 10 whereto three press- fittings 7, 8 and 9 have been applied by head welding. In particular cases one of the three fittings 7, 8 and 9, normally 7, can be threaded instead of the press-type.
In another particular embodiment of the present invention, the diameter of one of the openings 11, 12 and 13 is smaller than the diameter of the other two, and therefore it is possible to obtain any desired flow reduction. The opening having smaller dimension is preferably central opening 13.
Other variants and additions to the embodiments herewith described and illustrated are available to those which are skilled in the art while remaining within the scope of the present invention. For example, cross-shaped central bodies having four openings can be obtained by the process of the present invention.

Claims

A process for the manufacture of a hollow central body (1, 10), provided with openings (3, 4, 11, 12, 13) suitable for the application of pipe fittings (7, 8, 9), characterized in that it comprises an operation of precision casting.
A central body according to claim 1 characterized in that it is produced by precision casting.
A central body according to claim 2, characterized in that it is elbow-shaped and provided with two end openings (3, 4).
A central body according to claim 3, characterized in that the longitudinal axes of the pipe fittings applied thereto reciprocally form an angle of about 90°.
A central body according to claim 3, characterized in that the longitudinal axes of the pipe fittings applied thereto reciprocally form an angle of about 135°.
A central body according to claim 2, characterized in that it is T-shaped and provided with three end openings (11, 12, 13) at the ends of the T arms.
A central body according to claim 6, characterized in that said three openings (11, 12, 13) have all the same diameter.
A central body according to claim 6, characterized in that one of the openings (11, 12, 13) has a different diameter with respect to the other two.
A central body according to claim 8, characterized in that the diameter of the central opening (13) is smaller than the diameters of the other two openings.
A central body according to one of the claims 2 to 9, characterized in that it is made of stainless steel.