WO2008020134A1

WO2008020134A1 - Sealed connection between a metta0ic pipe and a flexible pipe and method for producing the same

Info

Publication number: WO2008020134A1
Application number: PCT/FR2007/001382
Authority: WO
Inventors: Michel Brachet
Original assignee: Maflow France, Sa
Priority date: 2006-08-18
Filing date: 2007-08-17
Publication date: 2008-02-21
Also published as: FR2904994A1; FR2904994B1

Abstract

The invention relates to a connection (3) and a method of producing a sealed connection (1) between a rigid metallic pipe (2) and the fitting (3) of an elastomer flexible pipe (4) comprising a core (5) of corrugated steel with parallel threads (6), previously exposed at one end and with a backup cylindrical metallic mesh (7). The connection comprises a cylindrical fitting (11) made of steel and having the same outer diameter as the core on the end (12) of which it is welded (14), a sleeve-shaped insert (13) whose inner bore cooperates with said fitting (11) and comprising on one side an end portion (16) for attachment to or forming the rigid pipe (2), and on the other side, an end portion (13) ending in the shape of a bevel (19) and force fitted between the upper portion of the steel core (5) and the metallic mesh (7), and a crimping dowel (20).

Description

SEALED CONNECTION BETWEEN A METAL TUBE AND A FLEXIBLE PIPE, AND METHOD FOR MANUFACTURING SUCH A FITTING

The present invention relates to a sealing connection between a rigid metal tube and a flexible or semi-rigid elastomer hose end provided with a parallel threaded corrugated steel core and a cylindrical reinforcing metal braid.

It also relates to a flexible hose provided on each side of such a tight fitting with a corresponding metal tube and a method of manufacturing this type of tight fitting.

The invention finds a particularly important, although not exclusive, application in the field of sealed connections for refrigerant gas circuits, for example used in air conditioning circuits for motor vehicles, or in the field of systems for power steering. of a motor vehicle. Watertight connections are already known between a rigid pipe end and a flexible pipe provided with a convoluted metallic central core, that is to say corrugated with parallel threads.

The rigid tube end can firstly be force-fitted inside the inner metal core having a cross-section.

Such a type of connection, however, and in particular the disadvantage of reducing the internal diameter of the fluid passage, thereby creating an additional pressure drop.

A connection is also known in which, after removal of the core at the end of the end flexible pipe, it is brought into contact with the end piece by inserting said endpiece into force in the part of the hollowed-out pipe of its core, then crimped.

Such a system, however, has sealing problems. It is also known (EP 1 298 376) a structure and a method for manufacturing a connection between an elastomeric flexible pipe provided with a cored steel core with parallel threads previously stripped at its end, comprising a sleeve for fastening with the tube. by screwing, thereby provided with an inner portion arranged to be screwed onto the stripped portion of the core.

Such a structure, as is moreover the general case with the known devices mentioned above, however always has the disadvantage of not guaranteeing a sufficient seal especially when using certain refrigerants such as with of the liquid known as 134A + PAG oil and this in view of the demands of automakers who are constantly growing.

It is indeed now necessary to demonstrate to vehicle manufacturers the preservation of a sufficient seal during endurance tests comprising more than 150,000 operating cycles at temperatures ranging from -35 ° C to +150 ^° C.

The present invention thus aims to provide a tight fitting, a flexible hose with two sealed connections at each end and a method of manufacturing such a watertight fitting better than those previously known to the requirements of the practice, in particular in that it allows to obtain a better tightness with excellent resistance to vibrations and for an optimized cost, thanks to a fast and simple manufacturing, guaranteeing an optimum crushing of the flexible material pipe without damaging it. With the invention it will be possible to overcome the crimping variables, while avoiding the use of a metal insert inside the convoluted steel tube pressure drop generator. To this end, the invention is based on the principle of producing without welding a metal-to-metal seal, even between heterogeneous metals.

For this purpose, the present invention proposes in particular a sealing connection between a rigid metal tube and an elastomer hose end provided with a cored steel core with parallel threads previously stripped at its end and a cylindrical reinforcing metal braid , characterized in that it comprises a cylindrical end of steel of the same external diameter as the core on the end of which it is welded, a sleeve-shaped insert whose inner bore cooperates with said end piece and comprising one side a part ^~ fixing end on or forming the rigid tube and the other side a end portion ending in bevel, inserted in force between the upper part of the steel core and the braid metal, and a crimp ring on the pipe end of said end portion ending in bevel.

The metal-to-metal contact between the cylindrical steel end of the same internal diameter as the core, thus avoiding any loss of load The internal bore of the sleeve - shaped insert makes it possible to obtain a secure and tight connection, without the risk of damaging the pipe itself during crimping. In advantageous embodiments, one and / or the other of the following provisions is also used:

- The end portion of the beveling insert comprises a stop flange of the elastomeric pipe end also serving as a hooking tooth of the ring;

- The end portion of the bevel terminating insert further comprises a notch extending radially outwardly protruding from the insert, additional hooking inside the pipe during crimping; the cylindrical steel end has a tubular end portion for guiding inserted frictionally into the rigid core; - the insert is made of steel, it is welded in transparency to the steel end piece;

- Since the insert is made of aluminum, the steel end has teeth forming axially distributed longitudinal locking abutments. Such a device makes it possible, during crimping, for the aluminum of the insert, which is more ductile, to partially penetrate, due to compression, into the interior of the harder steel teeth, to further improve the seal; - The tip is provided with sealing means with the inner bore of the O-ring insert; the ring has internal circular ribs hooking. The invention also provides an elastomeric pipe characterized in that it comprises on either side a connection with a rigid tube of the type described above. The invention also provides a method of manufacturing a seal between a metal tube and an elastomeric hose tip as described above.

It also proposes a method for manufacturing a tight fitting between a rigid metal tube and an elastomer hose end provided with a parallel threaded corrugated steel core and a cylindrical metallic braid of structural strength or reinforcement, characterized in that exposed to the end of the rigid core of the pipe over a length of between 5 mm and 20 mm advantageously between 8 and 15 mm, is fixed by welding a metal tip of the same outer diameter on said end, inserts in force by rotation and thrust, a sleeve-shaped insert whose internal bore cooperates frictionally with said tip and having on one side a fixing end portion on or forming the rigid metal tube and on the other side an end portion ending in a bevel whose cutting edge acts as a punch, between the braid and the core of the pipe so that the end of the tube abuts a flange of the insert, then crimped a ring or sleeve so as to pinch the braid between the internal ribs of the sleeve and the insert, to obtain a metal-to-metal seal between tip and insert. Advantageously, the insert being made of steel, the insert is furthermore made transparent by means of the metal endpiece.

In another advantageous embodiment, the insert being aluminum ^', is carried out between the sealing insert and sleeve by O-ring and / or ductile crushing of the insert on the teeth of the steel cap, the latter in being then provided.

The invention will be better understood on reading the following description of embodiments given below by way of non-limiting examples.

The invention refers to the accompanying drawings in which:

Figure 1 shows in section a first embodiment of a seal according to the invention before crimping.

FIG. 2 is an enlarged view showing a second embodiment of a sealing connection according to the invention, showing two half-sections, crimped and not crimped.

Figure 3 shows a flexible hose with sealed connections respectively at each of its ends according to the invention.

FIG. 1 shows a tight fitting 1 between a rigid metal tube 2 and a flexible elastomeric hose tip 3 provided with a parallel threaded stainless steel cylindrical core 6 and a cylindrical metallic braid 7 of structural strength of the pipe. In this example, the elastomer material consists of two elastomer layers separated from one another by the metallic braid, namely, a first outer layer or dress 8 and a second one. inner layer 9, penetrating into the grooves formed outside the core by the parallel threads 6, this second layer being located between the metal braid and the inner corrugated steel core. The hose has a stripped core portion 10 at its end, for example 8 to 15 mm. The stripping is carried out for example by jets of water at very high pressure.

The braid 7 of the pipe may also be exposed or be left covered by the outer dress 8.

According to the invention there is provided a cylindrical tip 11 of steel, for example stainless steel, of the same internal diameter as the core, or substantially of the same internal diameter, and of the same external diameter as the parallel threads, 6, and for example 8 to 15 mm high.

The tip 11 is fixed on the outer periphery 12 of the core 5 by edge-to-edge welding, TIG type or laser welding. The coupling 1 also comprises a metal insert 13 in the form of a sleeve whose internal cylindrical bore 14 cooperates with the external face 15 of the nozzle 11.

The insert 13 has on one side a cylindrical end portion 16 for fixing on the rigid tube 2, for example by welding 17 and on the other side an end portion 18 ending in a bevel 19 inserted in force between the upper part of the metal core 5 and the metal braid 7. A ring or crimping sleeve 20 previously slid on the pipe in the direction suitable for attachment is also provided. The end portion 18 of the insert ending in bevel 19 further comprises a stop flange

21 of the end 22 of the elastomeric pipe, also serving as a hooking tooth of the ring 20 (see Figure 2).

The end portion 18 also has a notch 23 extending radially outwardly protruding from the insert, additional hooking inside the pipe during crimping. In the embodiment more particularly described here, the end piece comprises a small portion of leading end 24, for example cylindrical, of very small thickness, for example l / ^10th of mm and of height less than or equal to 1 or 2 mm, inserted by friction in the rigid core, which allows an excellent positioning of the tip on the end of the core before welding.

The very small thickness of this part which is only used for guidance and positioning is not a problem at the level of pressure drop.

The insert, for example machined by bar turning, also has a flanged edge 25 for abutting the end of the crimping sleeve.

In the embodiment of Figure 1, the insert 3 is fixed in its end portion 16 on the outer cylindrical portion of the tip 11 by welding 26, by stitching or transparency.

The beveled end 19 is, after centering and positioning in front of the convoluted metallic core 5, introduced in force by simultaneous thrust movement and rotation movement 28 between the braid and said core until the end 22 of flexible hose comes into abutment on the flange 21 of the insert.

Thus, under the double action of rotating the insert whose end has a cutting edge and the thrust effect on the pipe, itself being immobilized in clamping means, the body of the insert acts as a punch and cuts the inner layer 9 intermediate between the metal core and the braid, between which it inserts.

The reinforcing braid 7 is made of metal film in known manner, the pipe being for example elastomer EPDM (English initials for Ethylene Propylene Diene Monomer) or HNBR (English initials for Hydrogenated Nitrile Butadiene Rubber).

In the remainder of the description, the same reference numbers will be used to designate the same elements. Figure 2 shows another embodiment of a connector 29 according to the invention, in crimped mode (upper half cut) and not crimped (lower half cut).

The insert 30 is made of aluminum, the tube 31 on which it is connected by welding or brazing cord 32, also being made of aluminum.

In this case, the tip 33 of stainless steel or zinc-plated steel, welded at 34 to the core 5 of steel (stainless steel or galvanized) has on its outer portion 35 directed towards the tube 31, grooves δu teeth 36 machined for example at 60 °.

The outer edges 37 of these grooves forming teeth whose number is for example between five and ten, are dimensioned to be in frictional contact with the inner wall of the bore of the insert 31 before crimping.

In an advantageous embodiment an O-ring 38, of suitable material, is provided and inserted in a groove 39 formed for this purpose between the teeth 36 of the nozzle.

The assembly formed of the pipe 4 with convoluted core 5 and the tip 33 with groove is then introduced into the insert 30 of aluminum, as described above.

The crimping is performed by conventional means on the crimped area, so as to penetrate the ductile aluminum material of the insert in the grooves of the tip. The thickness of the aluminum wall is then calculated in a manner known per se to maintain a permanent elastic stress, so as to ensure the metal-to-metal seal between the two components, while achieving good resistance to mechanical stress and pressure.

Figure 3 shows a flexible hose 40 respectively comprising at each of its ends 41 and 42, connectors 43, 44 crimped to the rigid tubes 45, 46, 'according to the invention.

The tubes themselves are connectable to other parts of pipes in a manner known per se by hexagonal screws 47 for example.

We will now describe with reference to Figure 2 the method of manufacturing a connection according to the invention with aluminum insert.

The metal body of the aluminum insert is first machined by bar turning and its end. is dimensioned according to the concerned flexible hose previously fixed on a workstation. The end of the pipe is denuded from its two elastomeric envelopes 8 and 9 over a length of 10 mm and the metal braid separating them.

Then, on the end of the bare core portion 10, the endpiece 11 is welded in the known manner, the end 24 inserted into the core allowing exact centering and positioning with respect thereto. before welding.

After centering of the insert with respect to the pipe 4 and to the endpiece 11, on which the O-ring 38 has been threaded, one comes by simultaneous thrust movement and rotation movement 28 between the braid 7 and the convoluted soul 5 until the end of the hose 22 comes into abutment on the collar 21 of

1 'insert, leaving the tip 33 to the right of the cylindrical end portion of the insert 13. In the case where the insert and the tip are of the same metal, here is carried out a transparency welding for example TIG .

Otherwise, in the case of an aluminum insert as more particularly described here, and after this insertion operation of the insert in the pipe between the braid and the metal core, is brought the sleeve 20 in position on the fitting so that the end of the sleeve abuts the collar 25 of the body of the insert 13. The crimping and the final assembly are then carried out.

To do this, conventional crimping means make it possible to configure the ring or sleeve 20 and crimped to reduce the diameter so as to pinch the reinforcement braid 7 between the inner teeth 50 of the sleeve and the insert in the area 51. The tooth 23 of the insert is also used to complete the attachment.

During hardening, the aluminum of the insert penetrates the teeth of the nozzle in the zone 52 thus achieving the metal-to-metal seal. All the axial force generated by the pressurization of the product in use is itself directly contained by the braid 7 hooked on the tooth of the insert, metal against metal, and regardless of the thickness of the rubber. In addition, convoluted stainless steel tube of small thickness, for example 0.25 mm, is protected and does not risk deformation during crimping.

In different embodiments, the rigid metal tube is formed in one piece with its tip which thus avoids an end weld.

In this case a suitable ring will be directly crimped onto the tube by anchoring the ring in the tube after having as before, introduced the insert between the braid and the convoluted core. The rings can be of different types, namely long rings, comprising a compression point behind the insert so as to directly contain the pipe inside the insert, which causes less fatigue for the braid or short rings, usable with less severe constraints. These then ensure only crimping the right of the insert by marrying the profile of the latter.

Claims

1. Watertight connection (1) between a rigid metal tube (2) and a tip (3) of flexible elastomer pipe (4) provided with a core (5) corrugated steel with parallel threads (6) previously stripped to its end and a cylindrical metal braid (7) of reinforcement, characterized in that it comprises a cylindrical end piece (11) made of steel of the same external diameter as the core on the end (12) of which it is welded, an insert (13) in the form of a sleeve whose internal bore (14) cooperates with said tip (11) and having on one side an end portion (16) for attachment to, or forming, the rigid tube (2 ) and on the other side an end portion (13) ending in bevel (19) inserted in force between the upper part of the steel core (5) and the metal braid (7) and a ring (20). ) crimping on the pipe end of said end portion ending in bevel.

2. A coupling according to claim 1, characterized in that the end portion (18) of the insert ending in bevel comprises a stop flange

(21) the elastomeric pipe end also serving as hooking tooth of the ring (20).

3. A coupling according to any one of the preceding claims, characterized in that the end portion of the insert ending in bevel further comprises a notch (23) extending radially projecting outwardly of the insert, additional hooking of the ring during crimping.

4. Connection according to any one of the preceding claims, characterized in that the cylindrical end has an end portion (24) frictionally inserted into the rigid core.

5. A coupling according to any one of the preceding claims, characterized in that 1 'insert being steel, it is welded in transparency to the cylindrical tip.

6. A coupling according to any one of the preceding claims 1 to 4, characterized in that, the insert being made of aluminum, the steel endpiece has teeth (36) forming axially distributed longitudinal locking abutments.

,

7. A coupling according to any one of the preceding claims, characterized in that the tip is provided with means (38) for sealing with the internal bore of the insert by O-ring.

8. A coupling according to any one of the preceding claims, characterized in that the ring (20) has internal circular ribs hooking.

9. Elastomer pipe, characterized in that it comprises on either side a connection with a rigid tube according to any one of the preceding claims.

10. A method of manufacturing a tight fitting (1) between a rigid metal tube (2) and an elastomeric hose end (4) provided with a parallel threaded corrugated steel core (5) (6). and a cylindrical metal braid (7) of structural strength, characterized in that exposes the end of the rigid core of the pipe over a length of between 5 mm and 20 mm, is fixed by welding a cylindrical tip (11) steel of the same external diameter on said end, forcibly insert by rotation (28) and thrust (27), a sleeve-shaped insert (13) whose internal bore cooperates frictionally with said end-piece and having on one side a fixing end portion (16) on or forming , the rigid tube (2) and on the other side a beveled end portion (18) whose cutting edge acts as a punch, between the braid (7) and the core (5). ) of the pipe, so that the end of the tube abuts a flange (21) of the insert, then crimps a ring (20) so as to pinch the braid between the internal ribs of the sleeve and the insert, to achieve a metal-to-metal seal between tip and insert.

11. The method of claim 10, characterized in that, the insert being steel, is further welded by transparency the insert with the steel tip.

12. The method of claim 10, characterized in that, the insert being aluminum, one carries out a seal between insert and tip by ductile crushing of the insert on the teeth of the steel tip.

13. Method according to any one of claims 10 to 12, characterized in that, complete the seal by O-ring (38) threaded on the tip.