Abstract:
The device comprises a monobloc subassembly ( 1 ) of cast stainless steel comprising a principal portion in the form of a disc ( 4 ) mounted on a collar ( 2 ) of the reservoir ( 3 ) and defining at least two channels ( 8, 9 ) for the passage of fluid, typically for filling, communication with the atmosphere, and withdrawal of liquid and gaseous phases reheated by atmospheric reheaters ( 23; 30 ) for the supply ( 31 ) of a controlled gaseous flow. 
     Application particularly to cryogenic reservoirs for medical oxygen for oxygen therapy.

Description:
FIELD OF THE INVENTION 
     The present invention relates to reservoirs for cryogenic fluid and more particularly devices for closing and connecting to external conduits such reservoirs. 
     BACKGROUND OF THE INVENTION 
     Known devices for closing and connecting reservoirs of cryogenic fluid are constituted by a mechanical-welded assembly of a closure plate and connection pieces machined and fixed, typically by welding, in openings machined in the closure plate. This technique is particularly cumbersome, because of the number of different pieces to be produced, stored and assembled, and the large amount of scrap resulting from problems of machining and welding constitute materials, typically austenitic stainless steels. 
     SUMMARY OF THE INVENTION 
     The present invention has for its object to provide a device of simplified structure permitting overcoming most of these problems and greatly reducing the cost of production and assembly. 
     To do this, the invention provides a device comprising a monobloc subassembly of cast stainless steel, typically produced by lost wax molding, defining at least two, typically at least three channels for the passage of fluid. 
     According to a more particular characteristic of the invention, the monobloc subassembly is made by molding from an austenitic stainless steel alloy comprising at least 16%, typically between 16 and 18.5% chromium, and at least 10%, typically between 10 and 10.13% nickel, and having, in the liquid phase, a ferrite content greater than 2%, preferably not exceeding 6%. 
     The present invention also has for its object a reservoir for cryogenic fluid, particularly liquid oxygen for household oxygen therapy, provided with such a device and typically provided with two atmospheric reheaters connected to outlet passages for the liquid and gas of the device. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other advantages and characteristics of the present invention will become apparent from the following description of one embodiment, given by way of illustration but in no way limiting, with respect to the accompanying drawings, in which: 
     FIG. 1 is a schematic view in vertical cross-section of the upper portion of a cryogenic reservoir for oxygen therapy, provided with a device according to the invention; 
     FIG. 2 is a cross-sectional view of the device of FIG. 1 in a plane perpendicular to the plane of FIG. 1; and 
     FIG. 3 is a left side view of the device of FIG.  2 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In FIG. 1, there is shown a device according to the invention in place on a neck collar  2  mounted in the neck of a cryogenic reservoir  3 . 
     According to one aspect of the invention, the device according to the invention comprises a monobloc subassembly  1  made of cast stainless steel comprising essentially a principal portion in the form of a disc  4  having a lower transverse surface forming a joint plane  5  mounted flat against the collar  2  and provided with an O ring  6 . 
     The subassembly  1  comprises a central chimney  7  orthogonal to the disc  4 , substantially coaxial to this latter, and defining a central passage  8 . In the principal portion  4  are defined, by projections on the surface opposite the joint plane  5 , a first transverse channel  9 , a second transverse channel  10  orthogonal to the preceding one, and a third transverse channel  11  in the plane of channel  10  and diametrically opposite this latter. 
     The channel  10  opens through the lower part of the disc  4  in a cavity  12  whilst the channel  11  itself opens through a portion of channel  13  formed in a portion of the projecting shoulder  14  through which also opens downwardly the central channel  8 . The channel  9  similarly opens downwardly through a portion of a channel formed in a projecting shoulder  15 . 
     As seen in FIG. 1, opposite the channel  9  is an axial channel  16  passing through the disc  4  receiving a piece  17  permitting the electrical connection to a capacitative level gauge  18 . 
     The monobloc subassembly  1  is mounted on the collar  2  by three angularly spaced screws (not shown) and by a column  19  with a screwthreaded lower end also serving, via a support plate  20 , to support a flow rate control valve housing  21 , as will be seen later. 
     As is seen in FIG. 1, in the assembled condition, the channel  9  receives the upstream end  22  of an atmospheric reheating coil  23 , as described in French patent application FR 99 13617, the portion of the channel in the shoulder  15  receiving the end of a dipping tube  24  extending to adjacent the bottom of the interior of the receptacle of the reservoir  3 . Similarly, a dipping tube  25  is mounted in the lower end of the channel  8 . This latter is prolonged upwardly by a recess formed in a head  26  of enlarged diameter comprising an external screwthread  27  and receiving the lower end of a one-way filling connection  28  held in place on the chimney  7  by a nut  29  coacting with the screwthread  27 . 
     To the transverse channel  10  is connected the upstream end of an atmospheric reheating coil  30  whose downstream end is connected to the above-mentioned valve housing  21 . The channel  11  is itself externally connected to a valve communicating with the open air (not shown). 
     The use of the described device is the following: the filling with liquefied fluid, of the reservoir  3 , takes place at a low pressure, about 3 bars, through the one-way connection  28 , the channel  8  and the tube  25 , the internal volume of the reservoir being, during this operation, in communication with the ambient atmosphere via the channels  13  and  11  and the valve connecting with the open air downstream of this latter. Typically an overflow tube (not shown) extending into the reservoir, is brazed into the channel  13  to limit the height of liquid in the reservoir. In use, the removal of cryogenic fluid in liquid phase contained in the reservoir, pressurized by the gaseous overhead in the reservoir, takes place through the tube  24 , the channel  9  and the coil  23  before reaching the flow rate control valve housing  21  supplying, at its outlet  31 , a gaseous flow at a controlled flow rate toward the user. The removal of the gaseous phase in the reservoir  3  takes place through the channel  10  and the coil  30  before rejoining the valve housing  21 , provided with at least one safety overpressure valve  32 . 
     As is seen in FIG. 1, the liquid outlet channel  9  is disposed opposite the passage  16  for mounting the probe  18  such that the withdrawal of the liquid takes place with a minimum of transmission of cold to the crossing  17  of the probe  18 . Similarly, as is seen in FIG. 2, the channel  11  is prolonged beyond the disc  4  by a transverse tubular extension  33  permitting spacing the valve that communicates with the open air, from the disc  4 , and hence avoiding excessive chilling of this valve. 
     In a preferred embodiment, the subassembly  1  is made by lost wax molding, which substantially avoids machining operations, from stainless steel comprising at least 16% of chromium and at least 10% of nickel, typically a stainless steel billet of the 316L type which, after casting, has a ferrite content greater than 2%, typically between 2 and 6%, which is obtained by an addition of chrome to the bath of molten metal.