WO2012153182A1

WO2012153182A1 - Assembly of a tube and of a sheet

Info

Publication number: WO2012153182A1
Application number: PCT/IB2012/000914
Authority: WO
Inventors: Dominique NINFORGE
Original assignee: Arcelormittal Investigacion Y Desarrollo S.L.
Priority date: 2011-05-12
Filing date: 2012-05-10
Publication date: 2012-11-15

Abstract

The invention relates mainly to a method of assembling a tube (7) of inside diameter D_i and a sheet (1) of thickness E_t having at least one substantially planar portion involving steps whereby the tube is positioned level with the substantially planar portion of the sheet, the end section of the tube being at least partially in contact with the sheet, then the sheet is assembled with the tube by flow drilling the sheet using a drill bit (2) of a diameter greater than or equal to D_i - 2 x E_t, the flow drilling being performed from the sheet towards the tube, along the axis of the tube. The invention also relates to the assembly of a tube and of a sheet and to the use of the method for the manufacture of solar absorbers.

Description

ASSEMBLY OF A TUBE AND SHEET

The present invention relates to the assembly of metal elements and more particularly to the assembly of a tube and a sheet.

The fluo-flow consists of a method of drilling a metallic object by local heating of the object. A non-cutting tool, commonly referred to as a drill, rotating at high speed, is pressurized in contact with the object. The local heating generated by the friction of the drill on the object softens the material and represses it. The material returned by the drill gives birth to a small tube of material commonly referred to as the sleeve. This can subsequently be tapped by repression or serve as a landing.

It is known to use fluo-piercing to assemble metal objects. It is known in particular from GB 1 601 951 to use flow-forming to assemble a sheet and a tube. In a first step, a sheet is pierced by flow-forming so as to form a sleeve. In a second step, a tube is introduced into the socket and crimped by widening the diameter of the tube at the height of the sleeve. Such a method has the disadvantage of requiring several successive steps.

It is also known from EP 0 008 135 to use flow-forming to assemble a tube and an object such as a tube or a sheet. The two parts to be assembled are first brought into contact. A drill diameter slightly smaller than the inside diameter of the tube is then introduced into the tube and pierces the second piece. The local heating generated by the friction of the drill on this second part softens it as well as the end of the tube, which leads to the welding of the two parts. Such a method has the disadvantage of being able to be implemented only for rectilinear and short length tubes. In addition, in practice, it is necessary to use a tube plugged at its end to obtain sufficient local heating. The present invention aims to facilitate the assembly by flow of a tube and a sheet. It has been designed and realized to overcome the defects presented previously and to obtain other advantages.

For this purpose, the invention firstly relates to a method of assembling a tube of internal diameter D, and a sheet of thickness E _t having at least a substantially flat portion comprising the steps according to which:

- Positioning the tube at the substantially flat portion of the sheet, the end section of the tube being at least partially in contact with the sheet,

- The sheet is assembled to the tube by perforation of the sheet by means of a drill with a diameter greater than or equal to D, - 2 x E _t , the flow being made from the sheet to the tube, in the axis of the tube.

The method according to the invention may also comprise the following optional characteristics, taken alone or in combination:

- The tube is positioned perpendicular to the substantially flat portion of the sheet;

- The drill is of diameter greater than or equal to D,;

- The drill includes a collar;

- The drill has a chamfer;

- The drill includes a shoulder;

- The tube is positioned in such a way that its end section protrudes from the surface of a support on which the sheet is then deposited;

The assembly method comprises a preliminary step in which the end section of the tube is crushed.

A second object of the invention is constituted by the assembly of a tube and a sheet having at least a substantially flat portion obtainable by the method according to the invention for which the sheet comprises a sleeve lining a part of the inside of the tube.

The assembly according to the invention may also comprise the following optional features, taken separately or in combination: - The part of the tube in contact with the sleeve is crimped;

- The sheet comprises a circular bulge surrounding the outside of the end of the tube;

- The end section of the tube includes a disintegration.

A third object of the invention is the use of the method according to the invention for the manufacture of a solar absorber.

Other characteristics and advantages of the invention will appear on reading the description which follows.

The invention will be better understood on reading the description which follows, given for explanatory but non-limiting purposes, with reference to the appended figures which represent:

- Figure 1 is an illustration of the drilling of a sheet by fluo-piercing according to the prior art;

- Figure 2 is an example of the method of assembling a sheet and a tube according to the invention;

- Figure 3 is a micrographic section of an example of assembly of a sheet and a tube according to the invention, detailing the contact between the wall of the tube and the sheet.

The same reference numbers represent the same elements in each of the figures.

Throughout the text, sheet metal means a metal body of flat shape, that is to say of small thickness compared to its other dimensions. The sheet may be in the form of a plate or sheet made of a single metallic material or a composite assembly. In the latter case, the sheet is a superposition of several layers of the same material or different materials. By way of non-limiting example of metallic materials, mention may be made of steel, aluminum and copper. Preferably the metallic material is a metal alloy such as steel.

Prior to the implementation of the method according to the invention, the sheet may have been shaped by any known method of shaping which will be mentioned by way of non-limiting example folding, profiling, stamping. However, it will be ensured, during this shaping, that the sheet retains at least a local portion substantially flat, that is to say sufficiently flat so that the section of a tube can be supported.

The flow-through method according to the prior art is described with reference to FIG.

In Figure 1a, a sheet 1 is brought into contact with a non-cutting drill 2. The drill 2 comprises a conical portion 3, a cylindrical portion 4 and a flange 5. The rotation of this drill rubbing on the sheet and the pressure exerted by the drill on the sheet causes a very strong local heating of the sheet. The metallic material constituting the sheet is softened and allows the drill to pass through the sheet. During this movement, the softened material is pushed back on both sides of the sheet. Most of this material is forced towards the face opposite to the pierced face and forms a small tube of metallic material, open at both ends, referred to as a sleeve, as illustrated in FIG. This sleeve then has an inside diameter substantially equivalent to the diameter of the cylindrical portion 4 of the drill. The small portion of material discharged towards the pierced face is in turn crushed by the flange 5 of the drill arriving at the end of the stroke.

An example of assembly of a tube and a sheet according to the invention is now described with reference to FIG.

As illustrated in FIG. 2a, a sheet 1 is first at least partly brought into contact with the end section of a tube 7 at one of its substantially flat local portions. The axis of the tube is, in this case, perpendicular to the substantially flat local portion.

As illustrated in Figure 2b, a drill 2 is positioned in contact with the sheet facing the tube, the axis of the drill being in the axis of the tube.

As illustrated in FIGS. 2c to 2e, the sheet 1 is pierced by flow-forming so as to form a hole opening into the tube. The material pushed towards the face opposite to the pierced face forms a sleeve 6 which comes uniformly inside the end of the tube and thus weld the sheet to the tube. The intimate contact of this sleeve and the tube makes it possible to firmly secure the tube and the sheet.

Unlike the previously described prior art for which the tube-sheet contact was limited to the end section of the tube, the contact surface obtained in the context of the present invention substantially corresponds to the developed surface of the socket which reinforces considerably the mechanical strength of the assembly obtained.

Depending on the quality of the desired assembly, it will be possible to use drills of varying diameter, that is to say drills with cylindrical portions of varying diameter. During the tests carried out, the inventors have observed that a drill bit of diameter equal to D - E x _t 2, with D, the inner pipe diameter and _t E thickness of the sheet, was sufficient to obtain a sufficiently strong joining tube and sheet. However, preferably, the drill will have a diameter equal to the inner diameter of the tube, or even slightly higher, so as to crimp the tube at the sleeve. The term "crimping" here means forcing the widening of the end of the tube. The drill with a diameter equal to or slightly greater than the inside diameter of the tube separates the bushing and presses it further in contact with the tube which itself widens. The contact between the tube and the sheet is all the better and the assembly is all the more resistant.

Alternatively, it will be possible to use a drill having a chamfer, that is to say an oblique surface, located between the cylindrical portion 4 and the flange 5 of the drill. In this case, at the end of the drill stroke, the chamfer spreads the bushing and presses it further in contact with the tube which itself widens, thus reinforcing the assembly.

It is understood that the same drill may simultaneously have a diameter slightly greater than the inner diameter of the tube and a chamfer and to crimp the tube with even more efficiency.

During the tests conducted, the inventors were able to observe that, surprisingly, the flange 5 of the drill had an unexpected effect, particularly on sheets of thin thickness. At the end of the flow, this collar comes into contact with the sheet. The pressure exerted by the flange on the sheet and local warming causes the thinning of the sheet at the end section of the tube and the incrustation of this end section in the thickness of the sheet.

Micrographic sections of the assembly obtained, such as that presented in FIG. 3, made it possible to observe that the sheet surrounds the end of the tube, both inside the tube, in the form of a socket, and the outside in the form of a circular bulge 8. This incrustation of the end of the tube in the thickness of the sheet contributes to greatly strengthen the strength of the assembly obtained.

In the case of thick sheets, the effect of the flange of the drill is less sensitive because the sheet then has more resistance to thinning.

The limit between thin and thick was identified at 0.8mm in the context of the tests conducted. However it is allowed to think that this limit is variable and is a function of parameters such as the inside diameter of the tube, the conditions of flow or the thickness of the wall of the tube.

In order to increase the strength of the assembly, it will be possible, during the implementation of the method, to have various alternatives favoring the incrustation of the end of the tube in the thickness of the sheet, and whatever is the thickness of the sheet used.

A first alternative is to provide the collar with a shoulder. This shoulder consists of one or more circular rings added to the flange on the side of the cylindrical portion 4 of the drill. This shoulder contributes to deforming the substantially flat portion of the sheet around the end of the tube before the flange comes into abutment on the sheet. This shoulder thus promotes the formation of the circular bulge and thus the incrustation of the end of the tube in the thickness of the sheet.

A second alternative is to impress the end section of the tube, that is to say to thicken the wall of the tube at its end section. During the incrustation of this section in the thickness of the sheet, the blockage blocks the possible withdrawal of the tube thus contributing to the mechanical strength of assembly. It is possible to envisage doing this in at least two different ways.

A first way consists of a step prior to the positioning of the tube in contact with the sheet during which the end section of the tube is crushed.

A second way is to change the position of the tube before drilling. While it is possible, in certain cases, to fix the tube in a vice so that its end section is flush with the surface of a support on which the sheet is then deposited, the end of support tube. The pressure exerted by the collar during the flow, not only to thin the sheet, contributes to the disintegration of the end section of the tube. As a function of the distance separating the support from the end section of the tube, this end section is more or less more or less flattened. As a result, this distance will be adjusted to obtain the desired mechanical strength.

It is understood that these different alternatives can be implemented individually or in combination.

The method described through the above examples has the following advantages:

- The drilling of the sheet and the fixing of the tube to the sheet are made in a single step, thus significantly reducing the manufacturing time of the assembly,

the tube-sheet contact surface corresponds substantially to the developed surface of the socket, which considerably strengthens the mechanical strength of the assembly obtained,

- The heat released by the fluoperçage solder the sheet and the tube which allows to obtain a much greater mechanical strength than a simple crimping or a weld limited to the end of the tube,

the method makes it possible to use all kinds of tubes without limitation as to their shape or size,

the process has several alternatives significantly enhancing the mechanical strength of the tube-sheet assembly, - The drilling of the sheet resulting in the formation of a hole opening into the tube, this method is particularly advantageous for applications in which a fluid is circulated in the assembly, in particular for the heating circuits, the cooling circuits , heat exchangers, solar absorbers ...

In the case of the above examples, the axis of the tube was perpendicular to the substantially flat local portion. However, it is possible to tilt the axis of the tube and to make the assembly just as easily. In this case, the end section of the tube will preferably be adjusted so that it is in contact with the substantially flat local portion of the sheet.

Claims

1) A method of assembling a tube (7) of internal diameter D, and a sheet (1) of thickness E _t having at least a substantially flat portion comprising the steps according to which:

- Positioning said tube at the substantially flat portion of said sheet, the end section of the tube being at least partially in contact with the sheet,

- said sheet is assembled to said tube by flow drilling of the sheet by means of a drill (2) of diameter greater than or equal to D - E x _t 2, said flow drilling is carried out of the sheet to the tube, in the axis of the tube.

2) A method of assembly according to claim 1 wherein said tube (7) is positioned perpendicular to the substantially planar portion of said sheet (1).

3) A method of assembly according to one of claims 1 or 2 wherein said drill (2) has a diameter greater than or equal to D ,.

4) The assembly method according to one of claims 2 or 3 wherein said drill (2) comprises a flange (5).

5) A method of assembly according to one of claims 2 to 4 wherein said drill (2) comprises a chamfer.

6) A method of assembly according to one of claims 2 to 5 wherein said drill (2) comprises a shoulder.

7) A method of assembly according to one of claims 1 to 6 wherein said tube (7) is positioned in such a way that its end section protrudes from the surface of a support on which is then deposited said sheet ( 1). 8) A method of assembly according to one of claims 1 to 7 comprising a preliminary step of which one crushes the end section of said tube.

9) assembly of a tube (7) and a sheet (1) having at least a substantially flat portion obtainable by the method according to any one of claims 1 to 8 wherein said sheet (1) comprises a sleeve (6) lining a portion of the interior of said tube (7).

10) assembly of a tube and a sheet according to claim 9 wherein the portion of said tube (7) in contact with said sleeve (6) is crimped.

1) Assembly of a tube and a sheet according to one of claims 9 or 10 wherein said sheet (1) comprises a circular bulge (8) surrounding the outside of the end of the tube.

12) assembly of a tube and a sheet according to one of claims 9 to 11 for which the end section of the tube comprises a épatement ..

13) Use of the method according to any one of claims 1 to 8 for the manufacture of a solar absorber.