Abstract:
A system for providing gas to a container includes a source of gas under pressure, a container, and a pressure regulating device. The pressure-regulating device includes an inlet intended to be connected to a source of the gas under pressure, an outlet, connected by a duct to the inlet and intended to be placed in communication with the container, a first valve for limiting the pressure at the outlet to a predetermined maximum value Ps, which valve is a delivery valve placed in a first passage which connects the duct to an orifice for discharging inert gas. The device also includes a second valve for keeping the pressure at the outlet above a predetermined minimum value Pi, which valve is an intake valve placed in a second passage which connects the duct to an orifice that lets fluid into this duct.

Description:
This application is a continuation of application Ser. No. 09/354,575, filed Jul. 16, 1999, now U.S. Pat. No. 6,209,568, which is incorporated by reference herein. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a pressure-regulating device for supplying a gas to a container, comprising an inlet intended to be connected to a source of the said gas under pressure, an outlet, connected by a duct to the said inlet and intended to be placed in communication with the container, a first valve for limiting the pressure at the said outlet to a predetermined maximum value Ps, which valve is a delivery valve placed in a first passage which connects the said duct to an orifice for discharging inert gas. 
     The invention applies in particular to the supply of working liquids in the electronics industry. 
     2. Description of the Related Art 
     The electronics industry, particularly the microelectronics industry, involves the use of ultrapure working liquids such as H 2 O 2 , HCl, H 2 S, etc., for example. 
     Such liquids are generally held in storage containers, the structure of which makes it possible to prevent these liquids from becoming contaminated, especially through the presence of particularly expensive and delicate internal coatings, for example perfluoroalkoxy coatings (PFA). 
     The delicate nature of these internal coatings considerably limits, inside these containers, the permissible variations in pressure about atmospheric pressure to which these containers are subjected externally. 
     Thus, the gauge pressure inside these containers must, for example, be between −20 and +150 mbars. 
     In order to observe this constraint and avoid the contamination of the working liquids that are to be dispensed, the vacuum created in such a container when working liquid is drawn off is filled by the supply of corresponding amounts of an ultrapure inert gas, typically nitrogen. 
     Nitrogen is generally supplied to a container for the storage of working liquid by a supply system which comprises a pressure-regulating device, means of connecting an inlet of the device to a source of inert gas under pressure, these means being equipped with means of expanding the gas to a datum pressure Pc that lies in the range of pressures which are permissible inside the container, and a pipe for placing an outlet of the device in communication with the storage container. The pressure-regulating device is intended to prevent damage to the storage container in the event of an operating incident. 
     Until now, there have been two types of pressure-regulating device. 
     In the first type, the device comprises a permanent communication with the ambient atmosphere of the duct connecting the inlet and the outlet of the regulating device, through a calibrated vent. Although this type of device provides the storage containers with good protection against variations in internal gauge pressure, it does, however, entail constant consumption of ultrapure nitrogen, whether or not working liquid is being dispensed, and this leads to high running costs. 
     In the second type, the pressure-regulating device comprises a delivery valve with a valve element balanced by a spring, to place the duct of the regulating device in communication with the ambient atmosphere. A device of this kind exhibits numerous drawbacks. Specifically, it does not safeguard the containers, on the one hand, against any depression and, on the other hand, in case of substantial overpressure upstream of the regulating device, because of the low delivery rates allowed by these clack-type valves. Furthermore, this type of device entails regular checks on the settings of the clack valve and of the expansion means, which are dependent on one another. Finally, as the use of metal components in such regulating devices is forbidden in order to maintain the purity of the inert gases, this type of device is complex and expensive to produce. 
     The object of the invention is to solve these problems by providing a simple pressure-regulating device of low manufacturing and running costs and which is able to safeguard storage containers when dispensing ultrapure working liquids. 
     SUMMARY OF THE INVENTION 
     To this end, the subject of the invention is a pressure-regulating device for supplying a gas to a container, comprising an inlet intended to be connected to a source of the said gas under pressure, an outlet, connected by a duct to the said inlet and intended to be placed in communication with the container, a first valve for limiting the pressure at the said outlet to a predetermined maximum value Ps, which valve is a delivery valve placed in a first passage which connects the said duct to an orifice for discharging inert gas, characterized in that the device also comprises a second valve for keeping the pressure at the said outlet above a predetermined minimum value Pi, which valve is an intake valve placed in a second passage which connects the said duct to an orifice that lets fluid into this duct. 
     According to particular embodiments, the device may have one or more of the following features, taken in isolation or in any technically feasible combination: 
     the first valve comprises a first shutter which can move between a lower shut-off position and an upper flow, position, under the action of a positive difference P + between the pressures in part of the duct and at the said discharge orifice, acting against the action of the self weight of the first shutter, the said shutter being of a mass carefully determined to balance the action of a predetermined pressure difference P + c; 
     the first shutter is placed on a seat intended to be substantially horizontal; 
     the discharge orifice is an orifice for communicating with the ambient atmosphere at pressure Pa, and P + c=Ps−Pa; 
     the second valve comprises a second shutter which can move between a lower shut-off position and an upper flow position under the action of a negative difference P − between the pressures in part of the duct and at the intake orifice, acting against the action of the self weight of the second shutter, the shutter being of a mass carefully determined to balance the action of a predetermined negative pressure difference P − c; 
     the second shutter is placed on a seat intended to be substantially horizontal; 
     the intake orifice is an orifice for communicating with the ambient atmosphere at pressure Pa, and P − c=Pi−Pa. 
     Another subject of the invention is a system for supplying inert gas to a container, comprising a pressure-regulating device, means of connecting an inlet of the device to a source of the gas under pressure, and a pipe for placing an outlet of the device in communication with the container, characterized in that the pressure-regulating device is a device as defined hereinabove. 
     In an alternative form, the connecting means comprise means of expanding the inert gas to a datum pressure Pc which lies approximately between Pi and Ps, and preferably close to Ps. 
     A final subject of the invention is an installation for dispensing a working liquid, comprising a container for storing the working liquid, means of dispensing the working liquid which are connected to the container, a system for supplying gas, especially inert gas, to the container ( 4 ), and a source of the gas under pressure, the supply system being connected to the source and to the container so as to fill in the latter a vacuum produced as a result of the withdrawing of the liquid, characterized in that the gas-supply system is a system as defined hereinabove. 
    
    
     BRIEF DESCRIPTION OF THE FIGURES OF THE DRAWING 
     The invention will be better understood from reading the description which will follow, given merely by way of example and made with reference to the appended drawings, in which: 
     FIG. 1 is a diagrammatic side view in part section of an installation for dispensing working liquid according to the invention, and 
     FIGS. 2 to  4  are sectioned and enlarged side views of the pressure-regulating device of the installation of FIG. 1, each illustrating the operation of this regulating device under different conditions. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 depicts an installation  1  for dispensing an ultrapure working liquid  2  to a consumer unit  3  of an industrial site, for example a microelectronics site. 
     This installation  1  essentially comprises a container  4  for storing the liquid  2 , means  5  for dispensing the liquid  2 , a system  6  for delivering inert gas to the container  4  and a source  7  of gaseous ultrapure nitrogen at 10 bar absolute. 
     The container  4  is internally coated with a layer of PFA (not depicted) which means that the gauge pressure inside this container  4  must lie between −20 mbar and +150 mbar. 
     The dispensing means  5  comprise a pipe  8  immersed in the liquid  2  contained in the container  4  and equipped with a pump  9  placed between two manual shut-off valves  11 . 
     The system  6  for supplying ultrapure nitrogen essentially comprises a pressure-regulating device  12 , means  13  of connecting an inlet  14  of the device  12  to the source  7 , and a pipe  15  for placing an outlet  16  of the device  12  in communication with the upper part of the container  4 . 
     The connecting means  13  comprise, in succession, in the direction in which the nitrogen flows, an expansion valve  170  and a stop and non-return valve  17 . 
     The pump  9  is rated to be able to supply an appropriate maximum flow rate of working liquid  2 . 
     The expansion valve  170  is rated and adjusted to expand the nitrogen from the source  7  as far as a datum pressure Pc corresponding to a gauge pressure of close to 40 mbar, and to supply a sufficient flow rate of nitrogen to compensate for the flow rate of the pump  9  irrespective of its speed. 
     The pressure-regulating device  12  comprises (FIG. 2) a first substantially parallelepipedal external box  18  placed with its lower  19  and upper  20  faces substantially horizontal. 
     The inlet  14  and the outlet  16  of the device  12  are calibrated orifices of appropriate cross section, each formed facing the other in lower parts of opposite side faces  22  and  23  of the box  18 . 
     The device  12  also comprises walls placed inside the box  18 . These walls form, on the one hand, a second substantially parallelepipedal box  24 , one side face of which is formed by part of the wall  23  of the first box  18 , and the other faces of which are placed some distance away from and substantially parallel to the other faces of the box  18 . The walls form, on the other hand, a third substantially parallelepipedal box  25 , smaller in size than the second box  24 . The lower face of this third box is formed by part of the upper face  26  of the second box  24 , and its other faces are arranged some distance away from and substantially parallel to the corresponding faces of the first box  18 . 
     The side face  23  of the first box  18  is also pierced, in an upper part, with a calibrated orifice  27  of appropriate cross section, placing the inside of the second box  24  in communication with the ambient atmosphere. 
     The lower face  28  of the second box  24  is pierced with a calibrated orifice  29  placing the inside of the second box  24  in communication with the rest of the first box  18 . 
     The upper face  26  of the second box  24  is pierced with a calibrated orifice  30  placing the inside of the third box  25  in communication with the inside of the second box  24 . 
     The lower faces  19  of the box  18  and  28  of the box  24  delimit between them a duct  31  connecting the inlet  14  to the outlet  16  of the device  12 . 
     Side faces of the third box  25  are pierced with orifices  32  placing the inside of the third box  25 , and therefore the inside of the second box  24  via the orifice  30 , in communication with the rest of the inside of the first box  18 . 
     The three boxes  18 ,  24  and  25  delimit, on the one hand, a first passage  34  connecting the orifice  27  to the duct  31  via the orifice  29  and, on the other hand, a second passage  35 , delimited in part between the side face  22  of the second box  24  and the adjacent side face of the first box  18 , which connects the orifice  30  to the duct  31  via orifices  32  pierced in the side faces of the third box  35 . 
     The first passage  34  is equipped with a clack-type delivery valve  36 , that is to say a valve with a shutter that can move substantially at right-angles to the seat. The seat consists of the lower face  28  of the second box  24 , and the shutter, that is to say the clack-valve element, is a substantially parallelepipedal block  34  capable of moving in the box  24 . This block  37  is of carefully determined mass and is placed on the face  28 . 
     The mass of the block  37  is carefully determined to balance the action thereon of a gauge pressure P + c of about 40 mbar (corresponding to a maximum absolute pressure Ps) at the orifice  29  of the duct  31 . 
     The block  37  is guided by the side walls of the box  24  and can move vertically between a lower position in which it shuts off the orifice  29  (FIG.  2 ), in which position the block  37  rests on the face  28 , and an upper position in which there is flow through the orifice  29  (FIG.  3 ), in which position the block  37  is raised off the face  28 . 
     The second passage  35  is equipped with a clack-type intake valve  39 , the seat of which consists of part of the upper face  26  of the second box  24  and the shutter, that is to say the clack-type valve element, of which is a substantially rectangular plate  41  able to move in the third box  25 . This plate  41  is of carefully determined mass and placed on the face  26 . 
     The mass of the plate  41  is carefully determined to balance the action thereon of a gauge pressure P − c of about −5 mbar (corresponding to a minimum absolute pressure Pi) in part of the duct  31 . 
     This plate  41  is guided by the side walls of the box  25  and can move vertically between a lower position in which it shuts off the orifice  30  (FIG.  2 ), in which position the plate  41  rests on the face  26 , and an upper position for flow through the orifice  30 , in which position the plate  41  is raised off the face  26  of the second box  24  (FIG.  4 ). 
     The pressure-regulating device  12  is made of plastic such as polypropylene and/or polyethylene. 
     The dispensing means  5  allow liquid  2  to be pumped from the container  4  to be dispensed to the consumer installation  3 . The supply system  6  allows ultrapure nitrogen to be supplied to the container  4  to fill the vacuum created therein as a result of the dispensing of the liquid  2 . 
     FIG. 2 illustrates the way in which the pressure-regulating device  12  operates when the gauge pressure at the inlet  14 , the outlet  16  and therefore in the container  4  is between P − c and P + c. 
     The shutters  37  and  41  are in the shut-off position and thus form an almost perfect seal between the inlet  14  and the outlet  16 . Only a nitrogen leakage flow rate, depicted by the arrow  43 , flows through the orifice  29  between the walls of the box  24  and the block  37 , and thus makes it possible to prevent any vapour of the liquid  2  from returning towards the expansion means  170  when the pump  9  is not running. 
     FIG. 3 illustrates the way in which the device  12  operates when the pressure at the inlet  14  is above P + c, for example in the event of defective operation of the expansion means  170 . 
     The shutter  37  is then in the raised, flow, position, and the shutter  41  is in the shut-off position. The overpressure with respect to P + c at the inlet  14  of the device  12  is then discharged, via the first conduit  34 , to the ambient atmosphere, as depicted diagrammatically by the arrow  44 . The pressure at the outlet  16 , and therefore inside the container  4 , is thus kept below its maximum permissible value, even when the pressure at the inlet  14  is 10 bar absolute, because of the delivery through the orifice  27 . 
     FIG. 4 illustrates the operation of the device  12  when the gauge pressure in part of the duct  31  is below P − c, for example when the flow rate of nitrogen supplied by the device  12  is not high enough to compensate for the flow rate at which liquid  2  is drawn off. The shutter  37  is then in the shut-off position and the shutter  41  is then in the raised, flow, position. Air is therefore taken in from the ambient atmosphere towards the outlet  16  and therefore towards the container  4  via the second passage  35 , as depicted diagrammatically by the arrow  45 . Thus, the pressure inside the container  4  remains above its minimum permissible value even with zero pressure at the inlet  14 . The liquid  2  therefore becomes contaminated, but the integrity of the container is preserved. 
     The pressure-regulating device  12  according to the invention therefore makes it possible, in complete safety, to supply inert gas to a storage container  4  of an installation  1  for supplying working liquid. The consumption of nitrogen, or more generally of inert gas, is, in practice, minimal and automatically tailored to the speed of the pump  9 . 
     Furthermore, the particularly simple structure of this device means that it can be made entirely out of materials which are well suited to preserving the purity of the inert gas used and of the working liquids dispensed. 
     Finally, this device has no adjustment controls, which makes it simple to use, and the limited number of moving parts means that it suffers practically no wear over time.