Abstract:
A quick connect coupling for removably joining two pipes includes an upstream element and a downstream element adapted to be fitted axially with the upstream element thereby opening a valve movable between a position of opening and a position of closure. The upstream element is provided with at least one O-ring disposed to surround the valve and is adapted for connection to an upstream pipe for inlet of pressurized gas, particularly oxygen. A primary sealing zone is provided upstream of the O-ring which is dimensioned to induce a significant reduction in a flowrate of gas flowing in the direction of the O-ring in order to limit overheating of the O-ring.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a quick connection for removably joining two pipes, and more particularly to such a connection enabling an upstream tank of oxygen to be placed in fluidic communication with a downstream pipe for distributing this gas. 
     2. Description of the Related Art 
     Such a connection conventionally comprises an upstream element, usually constituting the female part of this connection, which is connected to the tank of the gas, as well as a downstream element, usually constituting the male part of the connection, which is connected to the distribution pipe. These two upstream and downstream elements are adapted to be fitted axially, which then provokes opening of a valve slidably mounted in the body of the upstream element so as to ensure free passage of the fluid. 
     The female part of the quick connection is equipped with a spring-loaded lock, mounted to slide in the body of this female part, transversely to the direction of displacement of the valve. This body is pierced with a central part intended for the male element to fit therein, and at least one O-ring made of elastomer or plastics material is further provided, disposed in the vicinity of the valve. 
     However, this known quick connection, described in particular in EP-A-0 077 743, presents a drawback. 
     In effect, when the gas conveyed is subjected to sudden rises in pressure, the O-rings disposed in the vicinity of the valve of the upstream element become inflamed, which is prejudicial to the mechanical soundness of the connection and is therefore detrimental to its correct use. Moreover, the inflammation of the O-rings sometimes provokes combustion of the connection assembly, which may be at the origin of serious accidents in view of the presence of oxygen. 
     It is an object of the present invention to overcome this drawback by producing a quick connection or coupling which, while ensuring a reliable connection between the two pipes which are connected thereto, is particularly robust, in particular in terms of resistance to overheating, whatever the operating conditions to which the coupling is subjected. 
     SUMMARY OF THE INVENTION 
     To that end, this invention relates to a quick connection or coupling for removably joining two pipes though which oxygen flows, comprising an upstream element, particularly a female element, comprising means for connection to an upstream, pressurized gas inlet pipe, and a downstream element, particularly a male element, adapted to be fitted in each other axially thereby provoking the opening of a valve mounted in a body of the upstream element. The valve is moveable between a position of opening in which the upstream and downstream elements are coupled, and a position of closure in which the upstream and downstream elements are disconnected. The upstream element is provided with at least one O-ring, made of elastomer or plastic material, disposed in the vicinity of the valve, characterized in that this coupling comprises means for forming, both in the positions of opening and of closure, primary sealing zones which extend upstream of the at least one O-ring. The sealing zones have dimensions adapted to induce a significant reduction of the flowrate of gas flowing in the direction of the the at least one O-ring, in order to limit the overheating of the O-ring. 
     The invention also relates to the use of the connection as defined hereinabove for transporting oxygen. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be more readily understood on reading the following description given by way of non-limiting example, with reference to the accompanying drawings, in which: 
     FIG. 1 is a view in longitudinal section, illustrating the upstream and downstream elements of a quick connect coupling according to the invention, mutually disconnected. 
     FIG. 2 is a view similar to FIG. 1, illustrating the elements of the connection of FIG. 1, once they have been connected together. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENT 
     Referring now to the drawings, the quick connection shown in FIGS. 1 and 2 comprises an upstream element generally designated by reference  2 , which constitutes the female part of this connection. This upstream element is conventionally connected to an installation (not shown), delivering oxygen at high pressure, for example close to 200 bars. 
     This upstream element  2  comprises a tubular body  4  which defines an enclosure  6  intended to be placed in communication with the afore-mentioned oxygen installation. This upstream enclosure  6  receives a separate sheath  8  within which a valve is capable of sliding, as will be described hereinafter in greater detail. 
     This sheath  8  forms a peripheral flange  10 , beyond which a chamber  12  extends. The latter is placed in communication, via a re-entrant shoulder  14 , with a cylindrical housing  16  whose diameter, or transverse dimension, is less than that of the afore-mentioned chamber  12 . Grooves are hollowed out in the walls of this housing  16 , which receive two O-rings  18 , disposed one behind the other in the direction of flow of the gas. 
     Furthermore, the body  4  is provided, in its downstream part, with a lock  20  mounted to slide against a spring  22 . This lock allows the removable fixation of a downstream element of the connection, as will be described hereinbelow. 
     A valve  24  is slidably mounted in the interior volume of the upstream element  2 . It comprises a cylindrical body  26  extended, at a first end, by a plurality of axial fingers  28  defining passages. A shank  30 , which extends from the body  26 , opposite to the fingers  28 , is free to slide in the interior volume of the sheath  8 . 
     Furthermore, this valve  24  is provided with a radial ring  32  having bores  34  made therein. A spring  36 , coming into abutment at one of its ends against the flange  10 , makes it possible to return this ring  32  against the shoulder  14  of the upstream element  2 . 
     The quick connect coupling shown in FIGS. 1 and 2 also comprises a downstream element, forming the male part of the coupling. The arrangement of this downstream element  38 , as well as its mode of fixation to the upstream element  2 , via the lock  20 , are of conventional type. The annular free end of this downstream element  38  is given reference  40 . 
     In the position illustrated in FIG. 1, the upstream ( 2 ) and downstream ( 38 ) elements are disconnected. Consequently, the valve is pushed by the spring  22  in downstream direction, with respect to the flow of the gas. In this arrangement, the ring  32  abuts against the shoulder  14 . 
     The body  26  of the valve  24 , received in the housing  16 , is placed opposite an intermediate region R, which borders this housing  16  and lies between the upstream O-ring  18  and the shoulder  14 . This intermediate region is made in massive form, in that its transverse dimensions are sufficient for it to guarantee, due to its metallic nature, an efficient dissipation of heat. This region R presents a significant longitudinal dimension, or length L. 
     The transverse sections of the intermediate region R and of the body  26 , which correspond to the respectively inner and outer diameters of these elements, are such that the latter form an annular gap of reduced section, ensuring a primary seal. 
     This gap, designated by reference I, presents a small transverse section, corresponding to the clearance between the body  26  and the region R opposite. This clearance corresponds to conventional machining tolerances and allows the valve to slide easily in its housing. 
     In service, the rise in pressure in the chamber  12  creates a sudden rise in temperature. However, this sudden rise does not exist in the vicinity of the O-rings, thanks to the primary seal ensured by the gap I. In effect, the quantity of gas flowing in this gap I is small and undergoes a rapid cooling, the intermediate region R as well as the body  26  of the valve opposite, constituting massive metal parts which allow an efficient dispersion of heat. 
     Consequently, the O-rings  18  are only slightly heated and do not risk igniting. 
     In the position illustrated in FIG. 2, the upstream ( 2 ) and downstream ( 38 ) elements are connected to each other. In this arrangement, the fingers  28  of the valve  24  are in abutment against the frontal wall of the annular end  40  of the downstream element  38 . These fingers  28  are arranged upstream of the shoulder  14 , with the result that the gas is free to flow in the direction of the housing  16 , via the bores  34  and the passages formed between these fingers  28 . 
     In the position of opening of FIG. 2, the intermediate region R is opposite the annular end  40  of the downstream element  38 . Their transverse sections, which respectively correspond to the inner diameter of this region R and outer diameter of this end  40 , are such that these latter form an annular gap I′ for passage of the gas. This gap I′ presents a transverse dimension similar to that of the gap I described previously, formed by cooperation of the valve  24  and the region R. 
     When the pressure of the gas suddenly rises in the chamber  12 , in this position of opening of the valve, the resulting sudden rise in temperature is non-existent in the vicinity of the O-rings, thanks to the gap I′ which ensures a primary seal. 
     Consequently, similarly to what happens in the position of closure of the valve, the O-rings  18  are substantially not subject to a rise in temperature, with the result that they do not risk igniting. 
     The length L of the intermediate region R is advantageously greater than the length  1  of the fingers  28 . In effect, this makes it possible to maintain, opposite the region R, either a part of the annular end  40 , or a part of the body  26 , whatever the axial positions of the downstream element and of the valve  24 . Consequently, during translation of the valve  24 , under the action of the downstream element  38 , a portion of annular gap, of small section, permanently exists, which protects the O-rings  18  from the sudden rise in pressure of the oxygen. 
     The invention has been described with reference to upstream and downstream elements, respectively forming female and male parts of the connection. It is also applicable to a connection whose upstream and downstream elements respectively form male and female parts. 
     The invention enables the objects set forth hereinabove to be attained. In effect, Applicants have observed that the phenomena of inflammation, to which the O-rings are subjected, are principally due to sudden rises in the pressure of the oxygen flowing in the vicinity of these O-rings, inducing a considerable temperature rise. 
     The existence of the primary sealing zones I and I′ makes it possible to dissipate the energy that the gas possesses, once it arrives in contact with the O-rings. The latter are thus subjected only to a slight temperature rise, with the result that their mechanical soundness is not affected.