Abstract:
A device for stopping a leak in a pipe having at least one crack, including an elastomer sheet applied against the crack with a force applicator and a clamping mechanism arranged around the pipe for applying a force on the force applicator. The force applicator includes shearing elements preferably consisting of a first group of rigid parallel partitions and a second group of parallel partitions arranged perpendicularly to the partitions of the first group, the partitions being arranged perpendicularly to the pipe and applying shearing efforts on the elastomer sheet on the site of the crack, forcing the elastomer to be deformed so as to match the shape of the crack, thereby stopping it.

Description:
TECHNICAL FIELD  
         [0001]    The present invention relates to the repair of pipes used to transport water, gas and other fluids, and particularly a device for stopping a leak in a pipe.  
         BACKGROUND ART  
         [0002]    A leak in a water or gas pipe may be repaired by different techniques. One of these techniques consists in stopping the leak by applying an elastomer on the cracks present on the pipe by means of a sleeve. Such a sleeve is comprised of two half-shells, the interior wall of which is made of elastomer and adapted to surround the pipe at the area where the cracks are located. The half-shells are secured together and clamped to the pipe by threaded rods or other means.  
           [0003]    Unfortunately, stopping leaks with this type of sleeve presents numerous inconveniences. The sleeve must be clamped with considerable force so that the elastomer applies a force greater than the pressure of the fluid inside the pipe, which can sometimes reach 100 bar. The two half-shells which form the sleeve are generally made of steel and thus quite heavy and expensive. Implementation is delicate and painstaking, and may take 7 to 8 hours. Furthermore, new cracks may occur under the clamping force if the operation is not performed properly. Finally, the half-shells used to form the sleeve are adapted to a specific diameter of pipe, requiring as many diameters of shells as there are pipe diameters.  
         SUMMARY OF THE INVENTION  
         [0004]    This is why the object of the invention is to provide a device for stopping a leak in a pipe which can be quickly installed and does not require considerable clamping force.  
           [0005]    Another object of the invention is to provide a device for stopping a leak in a pipe that is light-weight, inexpensive and which can be adapted to pipes of different diameters.  
           [0006]    The invention relates therefore to a device for stopping a leak in a pipe having at least one crack, comprising an elastomer sheet applied against the crack with a force applicator and a clamping mechanism arranged around the pipe for applying a force to the force applicator. The invention is characterized in that the force applicator includes shearing elements arranged radially in relation to the pipe and applying shearing forces on the elastomer on the location of the crack, forcing the elastomer to be deformed so as to match the shape of the crack, thereby stopping the leak.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    The objects, features and advantages of the invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which:  
         [0008]    [0008]FIG. 1 represents a pipe having cracks on which the leak stopping device according to the invention is installed,  
         [0009]    [0009]FIG. 2A represents a bottom view of the force applicator forming part of the leak stopping device according to the invention,  
         [0010]    [0010]FIG. 2B represents a sectional view of the force applicator represented in FIG. 2A,  
         [0011]    [0011]FIG. 3 represents a sectional view of a first force distributor which could be used in the leak stopping device according to the invention, and  
         [0012]    [0012]FIG. 4 represents a sectional view of a second force distributor which could be used in the leak stopping device according to the invention.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0013]    [0013]FIG. 1 shows a cross-sectional view of a pipe  10  designed to transport a fluid such as a liquid or a gas, and presenting cracks  12  and  12 ′ in its upper section. On these cracks is placed an incompressible elastomer sheet  14  having good creep strength, such as rubber or neoprene, and having a thickness between 0.3 and 3 cm, designed to stop the leak by penetrating into the upper part of the cracks by pressure. Above the elastomer sheet  14  is a force applicator  16  of approximately the same size as the elastomer sheet  14  and designed to apply shear forces on the elastomer sheet. A force distributor  18 , placed on top of the force applicator  16 , is designed to distribute the clamping forces caused by the tightening of a clamping strap which is comprised, in this case, of two strap portions  20  and  22 . Each strap portion is stretched between two end rods. In this manner, the strap portion  20  features the two end rods  24  and  26  while the strap portion  22  features the two end rods  28  and  30 . The end rods  24  and  28  are connected by a threaded rod  32  and the end rods  26  and  30  are connected by a threaded rod  34 . When rotated, the threaded rods are progressively introduced into the bores of the end rods of the strap portions and tighten the strap formed by the two portions around the pipe  10 . As tightening continues, shear forces are applied to the elastomer sheet  14  thereby filling the cracks  12  and  12 ′.  
         [0014]    The force applicator  16  is shown in FIGS. 2A and 2B, and represents a bottom view of the applicator and a sectional view along A-A of said applicator, respectively. In the preferred embodiment of the invention, this applicator  16  is presented in the form of a lattice consisting of a first group of parallel partitions  40  arranged horizontally on the figure and a second group of parallel partitions  42  arranged vertically on the figure, the partitions of both groups being perpendicular to one another and integral with a support or backing  44 .  
         [0015]    In the preferred embodiment of the invention, the applicator  16  is in the shape of a rectangular sheet measuring 100 mm×50 mm with partitions 2 mm in depth and a thickness less than 1 mm. The material preferably used is rigid yet deformable plastic such as polyamide, polypropylene or polycarbonate, or made of metal having the same deformability characteristics, namely aluminum. In this manner, the deformability of the force applicator  16  allows the same applicator to be used regardless of the diameter of the pipe to be repaired.  
         [0016]    It should be noted that, according to variants of the preferred embodiment of the invention, the applicator  16  may not be provided with a support or backing  44  and the partitions  40  and  42  could be presented differently, that is not necessarily arranged parallel and/or perpendicular to one another. Furthermore, the applicator may be in any shape whatsoever, triangular, rectangular or hexagonal.  
         [0017]    Whatever the arrangement of the partitions  40  and  42  may be, one essential characteristic is that they be perpendicular to the surface of the pipe when the applicator  16  is placed on the elastomer  14 , as shown in FIG. 1, that is in such a manner as to apply shear forces to the elastomer.  
         [0018]    The force distributor  18 , illustrated in FIG. 3, is a sheet of approximately the same dimensions as that of the applicator  16  although slightly thicker, between 0.5 cm and 4 cm, the thickness being relatively thin for a pipe of small diameter and thick (4 cm, for example) for a pipe of large diameter. In the embodiment shown in FIG. 3, the thickness is constant and features grooves  50 . The fact that the grooves open during the clamping operation allow the force distributor  18  to be adapted to pipes of different diameters. The distributor  18  is preferably made of a plastic material such as polyamide, polypropylene or polycarbonate. The purpose of the distributor is to correctly distribute the clamping forces onto the force applicator  16 .  
         [0019]    According to a variant, the force distributor may have the shape shown in FIG. 4. In this variant, it has a variable thickness which becomes thinner from the center toward the ends, for example from 2 cm to 1 cm.  
         [0020]    Although it is not indispensable, the force distributor  18  greatly improves the efficiency of the leak stopping device according to the invention, mainly when it takes the form as shown in FIG. 4. The distributor converts the orthoradial forces into radial compression forces, the curvature of the distributor adding together with that of the pipe. In this case, the tension is no longer tangent to the surface of the system as can be seen in FIG. 1. The larger curvature allows the radial component of the tension force to be transmitted. The distributor thus allows these forces to be recovered along the entire length of the force applicator and not only at the ends. Moreover, in this manner, a force gradient increasing from the center to the ends is obtained, thereby concentrating a maximum amount of force on the leak.  
         [0021]    In this manner, for the same clamping force enabling a pressure of 20 bar to be applied, if only the force applicator  16  is used without the force distributor  18 , this pressure exceeds 35 bar when a distributor of constant thickness according to FIG. 3 is used, and to more than 50 bar when a distributor of variable thickness as shown in FIG. 4 is used. Furthermore, whether the force distributor is of constant or variable thickness, it was noted that an increase in thickness, particularly in the center in the case of variable thickness and thus a greater distance from the clamping belt in relation to the pipe, allows a greater clamping pressure to be obtained capable of reaching 100 bar.  
         [0022]    Generally speaking, the principle of the invention consists in applying a relatively weak clamping force owing to a characteristic mode of compression of an incompressible elastomer and having good creep strength. To this end, the elastomer is stressed according to its most flexible mode, that is shearing, by means of the force applicator and its partitions perpendicular to the surface of the pipe.  
         [0023]    Although the above description presents a preferred embodiment of the invention, it is clear that changes can be made without departing from the framework of the invention. As such, any clamping mechanism may be used to implement the invention, such as a flexible steel cable of small diameter, for example. However, the use of straps (illustrated in FIG. 1) and in a general manner, several portions of straps which are inter-connected by appropriate clamping means that bring the strap portions ends closer to each other during the clamping operation (in particular, these clamping means may be threaded rods as described in the preferred embodiment of the invention), is a system which can be adapted to all pipe diameters, each pipe requiring possibly the use of 1, 2, 3 . . . portions of identical straps connected together. Moreover, is judicious to ensure that the portions which comprise the strap be placed in a sleeve so that part of the clamping force will not be absorbed by friction forces as it is the case when the strap rubs directly on the pipe during the clamping operation.  
       APPENDIX  
     Version with Markings to Show Changes Made  
       [0024]    IN THE SPECIFICATION  
         [0025]    The paragraph on page 1 between the title and the first heading is new.