WO1996014177A1

WO1996014177A1 - Shrinking method

Info

Publication number: WO1996014177A1
Application number: PCT/FR1995/001438
Authority: WO
Inventors: Richard Chene; Pascal Detable; Michel Andre
Original assignee: Etablissements Caillau
Priority date: 1994-11-02
Filing date: 1995-11-02
Publication date: 1996-05-17
Also published as: DE69526065T2; EP0737114A1; TW305783B; PL178959B1; KR100264241B1; FR2726208B1; HU9601811D0; KR960706379A; HUT75563A; ES2173984T3; HU214856B; FR2726208A1; CA2178740C; RU2113929C1; CN1138302A; JPH09507795A; BR9506434A; CZ189196A3; JP3179499B2; MX9602541A

Abstract

A method for shrinking a ring (14) fitted over the free end (10a) of a flexible tube (10) on a rigid tubular member (12). The method uses a shrinking die (16) with an axial cavity (18) including a splayed section (18a) and a broad open end (20) whereat the diameter of the cavity is substantially the same as the greatest diameter (d) of said section. The shrinking die (16) is positioned so that at least the broad end (20) of the cavity is located around the portion (14) to be shrunk while its narrow end is in front of the tube, and, while axially supporting one of the ring (14) and the shrinking die (16), both are mutually axially moved in a direction (F) extending from the free end (10a) of the tube (10) towards the other end thereof.

Description

SHRINKING PROCESS

We know, for example to make a connection device to a rigid tubular end piece, the possibility of enclosing the free end of a flexible pipe between a ring and a rigid tubular element arranged coaxially, respectively outside and at the inside the pipe.

To do this, a shrinking operation aimed at reducing the diameter of the ring is necessary.

The present invention relates, in general, to a method for shrinking a ring fitted on the free end of a flexible pipe fitted on a rigid tubular element, said ring having at least one portion called "to shrink" whose diameter is greater to that of the pipe.

The method implements a constriction matrix provided with an axial cavity comprising a flared section widening between a first and a second end, the cavity having a wide open end at which the diameter of said cavity is substantially equal to diameter of said flared section at the second end of the latter.

Axial necking is commonly used for custom work of rigid tubes. The patent issued in the UNITED STATES under number 2314002 describes a method which attempts to use axial constriction to constrict a ring fitted on the free end of a flexible pipe.

According to this method, the necking die is first of all placed around the pipe and is then moved, on the ring, towards the free end of the pipe.

Due to the need to arrange the necking die around the pipe, the smallest diameter of the axial cavity is at least equal to the outside diameter of the pipe. The ring itself being arranged around the pipe, its internal diameter is also at least equal to the external diameter of the pipe. Consequently, the effective reduction in diameter during the constriction is at most equal to the thickness of the ring.

As a result, the reduction in diameter may not be sufficient to ensure the reliability of the holding of the pipe, ring, tubular element assembly. The only way to increase the amplitude of the necking, that is to say to make the reduction in diameter greater, is to increasing the thickness of the ring, which inevitably leads to an increase in the material cost and to an increase in the required shrinking power.

We also know the possibility of carrying out a radial constriction using a constriction tool comprising a plurality of angular sectors movable with respect to each other. This process is not satisfactory insofar as it causes appearance defects on the constricted portion, which can go as far as the appearance of longitudinal folds due to the radial intervals separating the angular sectors. These defects can cause, on the pipe, the appearance of damaging beads vis-à-vis the seal. The invention aims to remedy these drawbacks. This object is achieved thanks to the fact that the shrinkage matrix is put in place so that at least the wide end of the cavity is around the portion to be shrunk and that the first end of the flared section of said cavity is located beyond the pipe, in front of the free end of the latter, and to the fact that, while maintaining axially one of the two elements constituted by the ring and the shrinking die, an axial displacement is carried out relative of these two elements in the rearward direction (F), going from the free end, called "front end" of the pipe to the other end, called "rear end" of the latter.

Thanks to these provisions, the constriction is not limited to the thickness of the ring. In addition, the fact of moving backwards significantly improves the mechanical strength of the pipe, ring, tubular element assembly due to the behavior of the pipe material, which generally comprises rubber, during the shrinking operation.

Indeed, part of the material constituting the pipe is repressed during the necking, that is to say that it undergoes creep and is pushed back in the direction of movement of the necking matrix relative to the pipe. If this movement were towards the free end of the pipe, the material pushed back would tend to accumulate towards this free end. When no empty zone is provided inside the ring, this surplus material undergoes reverse creep so that, overall, the creep is a creep towards the rear, that is to say in the direction contrary to the relative movement of the necking die and the ring. It turns out that the thickness of a flexible hose, made of rubber-like material, varies relatively considerably depending on the manufacturing parameters, the tolerance interval may even be of the order of a millimeter. Due to local variations in thickness, the volume of the excess material, that is to say the volume of the material that the creep tends locally to repel, is also very variable. Consequently, the pressure of the material constituting the pipe inside the ring undergoes very significant local variations. In order for the ring to be able to withstand these variations without deforming and for the tensile strength of the connection between the pipe, the ring and the tubular element to be ensured, the thickness of the ring must be relatively large. In addition, in the case of a displacement towards the free end of the pipe, the material constituting this pipe is subjected both to creep and to an intense pressure variation, which affects its mechanical qualities.

When constricted by a rearward displacement, in accordance with the invention, the compression forces exerted on the free end of the pipe are continuously distributed over the entire circumference of the latter, so that no Pipe area is not suddenly crushed or pinched. In addition, the constriction taking place progressively in the axial direction from the free end of the pipe, the material constituting the latter undergoes progressive creep which does not damage the pipe and in particular ensures compliance with the qualities required in sealing material of the assembly.

The necking is therefore carried out in a manner that is both homogeneous and progressive, so that the assembly of the ring and the pipe is solid and reliable, the latter having no bead or any accumulation of material at its end clamped between the ring and the rigid tubular element and no zone of weakness in particular in the region of the end of the ring remote from the free end of the pipe. The connection is ensured reliably even with rings whose thickness is relatively small. Advantageously, the relative axial movement of the ring and the necked die is stopped before the first end of the flared section reaches the end of the portion to be shrunk most distant from the free end of the pipe.

Thus, the rear portion of the ring can be slightly flared and does not risk injuring the pipe. To ensure the reliability and durability of the connection devices, they are subjected to endurance tests. more and more severe. One of these tests is to oscillate the pipe relative to the ring. The fact that the rear portion of the ring is flared makes it possible to prevent the pipe from being damaged, or even cut, during such a test. The invention will be well understood and its advantages will appear better on reading the detailed description which follows, of embodiments shown by way of nonlimiting examples. The description refers to the accompanying drawings in which:

- Figure 1 is a longitudinal section showing a ring fitted on the free end of a flexible pipe, itself fitted on a rigid tubular element, as well as a shrinking matrix, using which prepares to implement the method according to a first embodiment.

- Figures 2 and 3 respectively illustrate the start and end of the process of the invention;

- Figure 4 is a view similar to that of Figure 1, on which we are about to implement the method according to an alternative embodiment;

- Figure 5 shows the implementation of this method.

FIG. 1 shows a flexible pipe 10, the free end 10a of which is fitted onto a rigid tubular element 12, while a ring 14, of cylindrical shape, is fitted onto the free end 10a.

In the following, to simplify the description, it will be considered that the end 10a is the front end of the flexible pipe 10. The figures being truncated, its other end, located at the rear, is not shown. In FIG. 1, the ring 14 is shown before it is shrunk, and its diameter D is greater than that of the pipe 10.

We also see in FIG. 1 a constriction matrix 16 provided with an axial cavity 18. This cavity comprises a flared section lδa which widens between a first end 19a of diameter d 'and a second end 19b of diameter d . The diameter d is greater than the diameter D, itself greater than the diameter of. On the side of the first end 19a of the flared section, the cavity has a cylindrical section 18b of diameter d 'which opens onto a narrow open end 17. On the other side, the cavity has a wide open end which, in the example shown, coincides with the second end 19b of the flared section, which is frustoconical. Figure 1 shows these various elements just before the start of the necking process, in a position in which the axis of the cavity is aligned with the longitudinal axis A of the flexible pipe and the wide open end 20 is directed towards the 'back. We still see in Figure 1 a tool 22 for axially holding the ring 14, with which the rear end 14b of this ring cooperates with a stop. This tool is only shown diagrammatically in FIG. 1. It can comprise two jaws which are placed around the pipe so as to cooperate with the rear end 14b of the ring 14 to maintain the latter during the constriction.

To initiate the necking process, the necking die is placed so that at least the wide end 20 of the cavity is around the ring to be shrunk, while the first end 19a is towards the front, beyond the front end of the pipe. In other words, the matrix is moved relative to the neck ring in the direction of arrow F, that is to say in the direction from the front end 10a of the pipe to its rear end, less until the end 20 of the cavity is at the front end 14a of the ring.

The actual constriction begins when the wall of the cavity begins to cooperate with the outer periphery of the ring.

To make the necking, as shown in FIGS. 2 and 3, the necking matrix 16 is moved axially on the ring 14 in the direction of the arrow F, that is to say backwards.

It is understood that as this movement progresses, the ring being held by the holding tool 22, its external diameter will be progressively reduced to the small diameter d 'of the cavity 18. In doing so, a gradual creep of the end 10a of the flexible pipe.

At the end of the constriction, one arrives at the configuration of FIG. 3, in which the ring 14 is crimped on the end 10a of the pipe, which is firmly clamped between the rigid tubular element 12 and this ring 14.

As can be seen in this figure, which illustrates the end of the constriction, the relative axial displacement of the constriction matrix 16 and of the ring 14 is preferably stopped before the end of smaller diameter of the flared section 18a of the cavity does not reach the rear end 14b, the furthest from the free end 10a of the pipe 10, of this ring 14. The terminal portion -

back of the ring is thus slightly flared and does not risk injuring the pipe.

Furthermore, it can be seen in the figures that the tubular element 12 has, in the vicinity of its rear end, a radial bulge 13. Preferably, the constriction is stopped without completely restricting the ring on the bulge. This ensures a reliable connection between the elements of the connection device, while avoiding local crushing of the pipe on the bulge, which could harm its mechanical qualities.

The necking being completed, it will suffice to disengage the ring from the necking matrix by moving the latter in the direction opposite to the direction of the arrow F, and to remove the holding tool 22.

In Figures 1 to 3, the cylindrical ring 14 is constricted over almost its entire length.

In some cases, as shown in Figures 4 and 5, it is desirable to shrink only a portion of the ring. In these figures, elements similar to those in Figures 1 to 3 are designated by the same references increased by 100.

The ring 114 has a first portion 115a which must not be constricted. This portion 115a which, in the example shown, extends forwardly beyond the front end 110a of the flexible pipe 110, can serve as a housing for an annular seal 117 or be provided with a fastening member to a rigid tubular end piece to which the pipe is to be connected

110.

It is therefore only the rear portion 115b of the ring 114 that one wishes to restrict. The portion 115a constitutes an axial obstacle which makes it impossible to use, under the conditions previously mentioned in relation to FIGS. 1 to 3, the shrinking matrix 16 in one piece.

A shrinking matrix 116 is therefore used, comprising two shells 116a and 116b. To set up this matrix around the ring, the shells 116a and 116b are first moved away from one another to define a sufficient passage for the ring or, more precisely, for the front portion 115a of the latter. The axial shrinkage proper, during which the matrix is moved in the direction of arrow F, begins after bringing these two shells close to the ring until this passage is removed. When the two shells are thus assembled, a cavity 118 of the matrix is defined, having a flared section 118a and a cylindrical section of small diameter 118b.

The small end 121 of the cavity located opposite the wide end 120 of the latter, is open. This makes it possible, as seen in FIG. 5, to arrange the matrix 116 around the portion 115b to be constricted, while leaving the first portion 115a of the ring 114 to protrude forwards beyond the matrix.

The shrinking of the portion 115b is carried out by moving the matrix 116 in the direction of the arrow F, that is to say by making it pass from its start position of the shrinkage, represented in broken dashed lines, to its position of end of the constriction, shown in solid lines. Throughout the axial displacement of the necking die, the ring is held axially using a necking tool 122. In the example of FIGS. 4 and 5, the tool 122 comprises jaws which cooperate with the front part of the ring 114. More specifically, the jaws of the tool 122 are placed around the ring, immediately behind the first portion 115a of the latter, and cooperate in abutment with a shoulder 114 'to hold the ring and prevent it from moving backwards during the shrinking. It can be seen in FIG. 4 that the whole of the second portion 115b, located behind the first portion 115a of the ring, has before shrunk a diameter greater than the diameter to which it is desired to bring it by the shrinkage operation. This is particularly the case of the region of the front end 115c of the portion 115b, directly located behind the first portion 115a. Therefore, when the shells are brought together around the ring 114, prior to the axial displacement of the matrix, a preliminary step of radial constriction is carried out in this region 115c, over a small part of the length of the portion to be constricted.

Preferably, as seen in FIGS. 4 and 5, the region 115c in which the preliminary step of radial constriction is carried out extends forwardly beyond the front end 110a of the flexible pipe, so that the possible drawbacks linked to this radial necking operation do not affect the pipe.

It is also conceivable that the diameter of the intermediate portion 115c is immediately less than or equal to the necking diameter, in which case no preliminary step of radial necking is necessary. It should also be noted that although in the examples illustrated by the figures, the ring is maintained axially and the matrix is displaced in the direction of arrow F, it would also be possible to carry out the constriction by axially holding the matrix and by moving the ring in the opposite direction to that of arrow F. The important thing is that the two elements which constitute the ring and the matrix are moved relative to each other in the direction of arrow F, that is to say say backwards, along the portion to shrink.

Claims

1. Method for shrinking a ring (14, 114) fitted on the free end (10a, 110a) of a flexible pipe (10, 110) fitted on a rigid tubular element (12, 112), said ring having at least a portion (14, 115b) called "to shrink" whose diameter (D) is greater than that of the pipe, the method using a shrinking matrix (16, 116) provided with an axial cavity (18, 118) , comprising a flared section (18a, 118a) widening between a first and a second end (19a, 19b), the cavity having a wide open end (20, 120), to which the diameter (d) of said cavity is substantially equal to the diameter of said flared section, at the second end of the latter, characterized in that the shrinking matrix (16, 116) is put in place so that at least the wide end (20 , 120) of the cavity (18, 118) is around the portion to be constricted (14, 115b), and that the first ex end of the flared section (18a, 118a) of said cavity is beyond the pipe (10, 110), in front of the free end (10a, 110a) of the latter, in that, while maintaining axially the 'one of the two elements constituted by the ring (14, 114) and the shrinking matrix (16, 116), a relative axial displacement of these two elements is carried out in the direction (F) towards the rear, going from the free end (10a, 110a), called the "front end" of the pipe (10, 110) at the other end, called the "rear end" of the latter.

2. Method according to claim 1, characterized in that one stops the relative axial movement of the ring (14, 114) and of the necked die (16, 116) before the first end (19a) of the flared section (18a, 118a) does not reach the end (14b, 114b) of the portion to be constricted (14, 115b) furthest from the free end (10a, 110a) of the pipe (10, 110).

3. Method according to one of claims 1 and 2, characterized in that the ring (14, 114) is kept axially and the shrinkage matrix (16, 116) is moved axially over the portion to be shrunk ( 14, 115b).

4. Method according to any one of claims 1 to 3, characterized in that one uses a shrinking matrix (116) comprising two shells (116a, 116b) and in that, to set up the matrix (116 ) around the ring, the shells (116a, 116b) are moved away from one another to define a sufficient passage for the ring (114), and said shells are brought closer around said ring, until that this passage be deleted.

5. Method according to claim 4, characterized in that during the bringing together of the shells (116a, 116b) around the ring (114), a preliminary step of radial constriction is carried out in the region (115c) of the end of the portion to be constricted (115b) closest to the free end (110a) of the pipe (110), over a short length of said portion (115b).