WO2008089583A1 - Improved diaphragm-sealed valve, actuating means therefor and method using the same - Google Patents

Abstract

There is provided a diaphragm-sealed valve having an improved design to limit fluid velocity into the port while allowing a pressure built-up in the space defined between the seal member and the circular flow recess, thereby reducing the sucking effect of the diaphragm into the port. An improved diaphragm having preformed elevated portions is also provided for further enhancing the performances of the valve. Improved actuating means having a plurality of adjusting devices, each being mounted with a corresponding plunger for independently adjusting an operating pressure thereof is also provided. A method of operating the improved valve as well as an analytical chromatographic method using the same are also provided.

Description

IMPROVED DIAPHRAGM-SEALED VALVE, ACTUATING MEANS THEREFOR

AND METHOD USING THE SAME

FIELD OF THE INVENTION

The present invention generally relates to a diaphragm-sealed valve for fluid analytical systems, and more particularly concerns a diaphragm-sealed valve having improved characteristics. The present invention also concerns a method of operating such a valve as well as an analytical chromatographic method using such a diaphragm-sealed valve.

BACKGROUND OF THE INVENTION

As well known from people involved in the art, chromatographic systems rely on the use of valves to allow reproducible sample introduction and various column switching schemes.

Today, in the chromatographic field, there are mainly two types of valves used: the rotary valves and the diaphragm-sealed valves. The rotary type, as the name suggests, uses a rotary movement to switch or divert various flow paths required for a particular application. Description of such valves may be found in US patent application by the same Applicant published under No. 2006/0042686, whose disclosure is incorporated by reference therein.

The rotary chromatographic valves are well suited for liquid applications, even if they are also suitable for gas applications. Their design allows the use of various materials to provide inertness or very long lifetime, and relatively high working pressure and temperature which can be required in various liquid chromatography applications. The actuating means used to actuate a rotary valve is generally a pneumatic rotary one or an electrical motor equipped with some gear to increase the torque needed to rotate the valve. In both cases, these assemblies, i.e. actuating means and valve, require a relatively large amount of room in a system. Furthermore, in cases where a pneumatic actuator is used, extra 3-way solenoid valves must be used to allow pneumatic gas to be switched.

In the bulk gas analysis like He, H2, 02, N2, Ar₁ Kr, Xe₁ Ne, CO, CO2, CH4, THC, H2O and some other gases, the working pressure and temperature of the chromatographic system is relatively low compared to liquid chromatography. A diaphragm-sealed chromatographic valve could therefore be used since it is generally well suited for gas chromatography. It would so be advisable and beneficial to use diaphragm-sealed valves instead of rotary valves for gas chromatography wherein the design of a rotary valve may probably be overkilled for low pressure and temperature application in gas chromatography.

A diaphragm-sealed chromatographic valve that would take much less room than a rotary system and that could be built at a lower cost, mainly when compared to rotary valves using ceramic material, while providing a long working lifetime would therefore be very desirable.

For the last forty years, many people have designed diaphragm valves for chromatography. Such diaphragm valves have been used in many commercially available gas chromatographs. They are able to be integrated more easily in a gas chromatograph due to their physical size and since the actuator is embedded in the valve itself. These characteristics make them attractive for gas chromatograph manufacturers. However, their performances are poor. For example, the leak rate from port to port is too high and thus limits the system performance. Moreover, the pressure drop on the valve's ports differs from port to port, causing pressure and flow variation in the system. This causes detrimental effect on column performance and detector baseline. Furthermore, many of them have too much inboard contamination. Such valve designs are shown in US patents Nos. 3,111 ,849; 3,140,615; 3,198,018; 3,376,894; 3,387,496; 3,417,605; 3,439,542; 3,492,873; 3,545,491 ; 3,633,426; 4,112,766; 4,276,907; 4,333,500; 5,601 ,115 and 6,202,698. The general concept of these valves is shown in Figure 1.

As illustrated in Figure 1 , the valve 1 is provided with a top block 2 having an interface 4 and a plurality of ports 6. Each of the ports 6 opens at the interface 4 and has an inclined thread passage 8 to connect various analytical fitting and tubing (not shown). At the bottom of the inclined thread passage 8, there is a conduit 10 extending in the top block 2 and opening at the interface 4. The ports 6 are arranged on a circular line on the interface 4 of the top block 2. The interface 4 is advantageously flat and polished to minimize leaks between port and from ambient atmosphere. The valve 1 is also provided with a bottom block 12 and a diaphragm 14, which is generally made of polyimide, Teflon™ or other polymer material. The diaphragm 14 is positioned between the top block interface 4 and the bottom block 12. The valve 1 is also provided with a plurality of plungers 16, each being respectively arranged to be able to compress the diaphragm 14 against the top block 2 at a position located between two of the ports 6. Preferably, as illustrated, when the valve is at rest, three plungers 16 are up while the three others are down. When the plungers are up, they compress the diaphragm 14 against the top block 2 for closing the conduits made by diaphragm recess 18, so that fluid circulation is blocked. Alternatively, there is fluid flowing between the ports where the corresponding plungers are down. The recess 18 in the diaphragm 14 sits down in the recess 20 made in the bottom block 12, thereby allowing some clearance for fluid circulation. The bottom block 12 keeps the plungers 16 and the actuating mechanism in position.

Referring now to Figure 2A, there is shown a typical chromatographic application wherein a sample is injected on a separation column to separate the impurities and then to measure them by the integration of successive signal peaks by the detector, as well known in the art. In Figure 2A, the sample loop SL is swept by the sample gas, while the separation column and the detector are swept by the carrier gas, coming from the valve port #2. To allow this flow path through the valve, the plungers B, D and F are down while the plungers A, C and E are up. The mechanical equivalent of this valve position is shown in Figure 2B. To do a sample injection, all valve ports must first be isolated from each other to avoid cross port leaks that invariably lead to inaccurate measurements. This is done by setting plungers B, D and F in the up position. The valve analytical flow path and mechanical equivalent of this valve position is shown in Figure 3A and 3B. This step is only a temporary intermediate one. Its time duration depends on the actuating mechanism used and the required actuating pneumatic pressure. Then, the sample loop is put in the carrier circuit. This step is generally known as the sampling loop injection position. This is done by moving down plungers A, C and E while keeping plungers B, D and F in the up position. This position is shown on Figure 4A and the mechanical one in Figure 4B. In a similar way, to come back in the sampling position which is illustrated in Figure 2A, the plungers A, C and E are first brought back in the up position. This leads to the intermediate position shown in Figure 3A, i.e. all plungers up. Finally, the plungers B, D and F are brought back down. So, the valve is now in the position shown in Figure 2A, i.e. sampling loop filling position. All the patents that we previously referred use this general concept or some slight variation thereof.

Referring again to Figure 1 , the main aspect of this concept is to interrupt the flow between two adjacent ports. For that, the corresponding plunger presses the diaphragm 14, which is then pressed on the interface 4 of the top block 2. Thus, the sealing relies simply on the surface of the plunger defining the area that presses the diaphragm recess 18 on the interface 4. This technique imposes tight tolerances on the surface finish, surface flatness and the plungers' length. Any scratch on the interface 4 or imperfection of the diaphragm 14 will generate leaks. Moreover, the length of all plungers must be the same. Any difference in their lengths will result in leaks, since a shorter plunger will not properly compress the diaphragm against the interface 4. In the prior art, there are some variations of this general concept. The main one relates to the location of the bottom block recess 20. In the past, this recess 20 or its equivalent was located internally in the top block 2, or on its interface 4. US patents Nos. 3,111 ,849; 3,198,018; 3,545,491 ; 3,633,426 and 4,112,766, which were granted to the same group of people, illustrate this concept. However, as they reported in a more recent valve brochure specification entitled "Applied Automation Company, series 11 diaphragm valve", this method has been dropped because of a too high cold flow. Cold flow is also often referred to as cross port flow leak. Their latest design, which was commercialized, uses a flat and polished interface 4 on the top block 2 and a recess 20 in the bottom block 12. In this design, the diaphragm 14 has no recess. Moreover, in order to reduce the cold flow, it was also envisaged to use two diaphragms. In fact, as disclosed in US patent No. 3,111 ,849, the use of a "cushion" diaphragm helps to compensate for any slight non-parallelism or length difference of plungers. Other attempts have also been made to correct the non- parallelism, as disclosed in US patents Nos. 3,376,894; 3,545,491 and 3,633,426, wherein the use of solid plungers has been replaced with the use of small steel balls.

The concern about plunger length has also been taken into consideration in US patent No. 6,202,698, granted to Valco Company, which suggests the use of plungers made of softer material. This allows tolerance reduction for the length of such plungers.

However, such designs still result into too much leak rate between ports since the sealing done by the plungers' pressure is not equal on diaphragm.

Other attempts have been made in the past to eliminate problems caused by plunger tolerance variations. US patent No. 3,139,755 discloses a valve wherein no plunger is used. Instead, a hydraulic pressure is used. However, an auxiliary source of pressure must be used since the pneumatic amplification of pneumatic actuating mechanism does not exist. The system, as far as we know, wasn't commercialized. Cross port leaks are still an important problem. Another design is disclosed in US patent No. 3,085,440. In this valve, the diaphragm has been replaced by an O-ring. Nevertheless, cross port leaks are still too high for modern high sensitivity detector.

In brief, in view of the previously mentioned patents, it can be seen that many attempts have been made to try fixing cross port leaks problems and outboard or inboard contamination. All of the proposed designs are quite similar in regard to sealing mechanisms and have the same drawbacks. For example, US patent No. 3,140,615, granted in 1964, and US patent No. 6,202,698, granted in 2001 , do use the same sealing concept in regard to flow switching between ports.

Valco Company did release the DV series valve wherein the diaphragm 14 has an additional recess 18 as illustrated in Figure 1. The recess 18 sits down in the recess 20 of the bottom block 12. So, when a plunger 16 is in down position, the diaphragm recess 18 sits in the bottom block recess 20, thereby clearing the passage between two adjacent ports, reducing the pressure drop and helping to operate with a low pressure sample.

Finally, it can be seen from the various brochures used to market these valves that the lifetime of these valves is mostly stated in terms of actuations. Most of the time, the number of actuations stated is between 500,000 and 1 ,000,000. However, it appears that this specification is related to the actuating mechanism and not to the leak rate of the valve. In this aspect, the diaphragm type valve's specifications are not as well defined as the rotary type valve, wherein it is clear that the lifetime of the valve is expressed in terms of leaks.

Besides, a brand new diaphragm valve will often have too many leaks between ports for low level applications. Moreover, it appears that when the valve is at rest for a long period of time, it doesn't perform well when put back in service. This is caused by the diaphragm getting compressed and marked where the plungers press it. It is even worst for valves having fine edge plungers defining a ring type sealing surface.

Thus, the diaphragm type gas chromatography valves of the prior art have several disadvantages: they present too much cross port leaks and too much pressure drop on selected adjacent ports. Moreover, they are difficult to operate when sample pressure is low and they cannot conveniently work with sub- atmospheric sample pressure. Furthermore, they rely on tight tolerance of plungers' length, to minimize cross port leaks.

In order to overcome most of the above-mentioned drawbacks, the Applicant of the present invention proposed an inexpensive improved diaphragm- sealed valve, as disclosed in US patent No. 7,216,528.

More particularly, as shown in Figures 5A and 5B, the proposed diaphragm-sealed valve 22, which can be referred to as a three way switching cell, is provided with a first body 24 having a first interface 26 provided with a recessed fluid communication channel 28 extending therein. The first body 24 has a first, a second and a common fluid port, respectively 32, 34 and 36. Each of the ports is provided with a fluid passage 38 connected to a threaded hole 40 providing tubing connections. Each of the ports 32, 34, 36 opens into the recessed fluid communication channel 28 for interconnecting each of the ports together through the fluid communication channel 28, which acts as a fluid conduct. Each of the first and second ports 32, 34 is provided with a seat 42 disposed so as to allow fluid communication therearound within the communication channel 28.

The diaphragm-sealed valve 22 is also provided with a second body 44 interconnected with the first body 24 and having a second interface 46 facing the first interface 26. The second body 44 also has a first and a second passage 48, 50. Each of the passages 48, 50 faces one of the first and second ports 32, 34 respectively. The valve 22 is also provided with a seal member 52 compressibly positioned between the first and second interfaces 26, 46. The seal member 52 has a shape adapted to cover the first and second ports 32, 34, and advantageously the entire fluid communication channel 28 to act as a seal for inboard or outboard contaminations. This seal member 52 allows to provide a flow interruption through the corresponding port 32 or 34, when it is pressed against the seat 42 of the port. In a preferred embodiment, the seal member 52 has a Teflon spacer 51, a metallic diaphragm 53 which is advantageously a stainless diaphragm, and a polymer diaphragm 55. Each of these elements is advantageously arranged in a stacked relationship, the polymer diaphragm 55 being pressable against the seat 42 of each of the first and second ports 32, 34. The valve 22 is also provided with a first and a second plunger 54, 56, each being respectively slidably disposed in one of the passages 48, 50 of the second body 44. Each of the plungers 54, 56 has a closed position wherein the corresponding plunger presses down the seal member 52 against the seat 42 of the corresponding port 32, 34 for closing the corresponding port, and an open position wherein the plunger extends away from the seat 42 of the corresponding port 32, 34 for allowing a fluid communication between the corresponding port and the channel 28.

The valve 22 also has actuating means 58 for actuating each of the plungers 54, 56 between the closed and open positions thereof. Advantageously, the actuating means 58 independently actuate each of the plungers 54, 56. Preferably, and as illustrated, the actuating means 58 advantageously have first and second resilient means, preferably a first and a second spring 64, 66, each being respectively mounted on a corresponding plunger 54, 56 for biasing the corresponding plunger. Each of the spring 64, 66 can advantageously be mounted in two different positions, thereby providing a predetermined resting position for each of the plungers 54, 56. Thus, different valve configurations can advantageously be obtained at power off. In the illustrated embodiment, the spring 64 associated with the solenoid 60 is mounted to force the plunger 54 down while the spring 66 associated to the solenoid 62 is mounted to force the plunger 56 up. This results in a configuration normally closed (NC) between port 32 and 36, and normally open (NO) between port 34 and 36, when there is no power on the solenoids 60 and 62.

Figures 6A to 6D illustrate the working principle of one of the first and second ports 32, 34. In Figures 6A and 6B the port 32 is open, so the fluid is allowed to flow through port 32 and then in each direction away from the seat 42. Of course, according to a particular application, the fluid could flow from or to the port 32. In Figures 6C and 6D, the port 32 is shown in the closed position. The fluid from the other ports is allowed to flow around the seat 42 in the fluid communication channel 28.

Figures 7A to 7H illustrate the different fluid flow paths and the schematic equivalents which can be obtained with the valve presently described. Figures 7A and 7B show the port 32 in the open position while port 34 is in the closed position. Figures 7C and 7D show the port 32 closed while the port 34 is opened. Figures 7E and 7F show both ports 32, 34 open while Figures 7G and 7H show both ports 32, 34 closed.

As can be deducted from Figures 6A to 6D and also 7A to 7H, in anyone valve positions, there is no dead volume since there is always fluid flowing around the seat 42 and in the loop shaped portion 30 of the fluid communication channel 28. So there is no dead volume effect generated by the valve since the channel 28 always appears like a fluid conduit or tubing.

It can also be understood that another important aspect of this proposed valve is the independent control of the ports 32 and 34. This allows the different valve positions shown in Figures 7A to 7H.

The fact of sealing the ports 32 and 34 by pressing the diaphragm 52 thereon results in a positive sealing effect. Indeed, it seals completely the port 32 or 34 and totally blocks the fluid flow therefrom or thereinto. So, relatively high pressure could be applied to the ports 32, 34 without generating any leak nor any detrimental impact on the analytical results.

It is also important to understand that the valve presently described advantageously allows sub atmospheric pressure operation. Indeed, as illustrated in Figure 8, the valve 22 may further have a purge circulation line 68. The purge circulation line 68 is provided with an annular recess 70 extending in the first interface 26 and surrounding the fluid communication channel 28. The purge circulation 68 line also has a fluid inlet 72 and a fluid outlet 74, each having an opening lying in the annular recess 70 for providing a continuous fluid flow in the annular recess 70. The fluid inlet and outlet 72, 74 are each provided with a fluid passage 76 and an associated threaded hole 78 for allowing tubing connections. Thus, a clean purging fluid can advantageously be allowed to flow through the purge circulation line 68, thereby evacuating any inboard and outboard contamination and any fluid process leak. This concept is well detailed in US application of the same Applicant published under No. 2006/0042686.

Still referring to Figure 8, the presently described valve can also advantageously be used in an analytical chromatographic system 80 to provide a system having improved characteristics. Indeed, such an analytical chromatographic system 80 is advantageously provided with a diaphragm-sealed valve 22 as defined above and provided with a purge circulation line 68. The analytical system 80 is also advantageously provided with monitoring means 82 operatively connected to the fluid outlet 74 for monitoring a fluid passing therethrough. In a preferred embodiment, the monitoring means 82 have a purity detector for detecting contamination of said fluid. Preferably, the monitoring means 82 are adapted to monitor the fluid passing through the purge circulation line 68 continuously.

In a further embodiment, a plurality of elementary switching cells as previously described are advantageously embedded in a single valve 84, as shown in Figure 1OA.

Referring again to Figure 2A, there is shown a typical chromatographic application known in the art, which uses a six port traditional gas chromatographic valve. When the valve is actuated, the sample is injected or put into the carrier circuit as shown in figure 4A. Figures 9A to 9C show schematic representations of the different steps which could be realized with the application illustrated in Figure 2A but realized with the valve 84 of US patent No 7,216,528. In this preferred embodiment illustrated in Figure 1OA, the valve 84 is provided with three elementary switching cells 22. Each switching cell 22 is represented by a rectangular box with three small circles identifying the ports. The letter c in the rectangular box identifies the common port 36. Figure 9A shows the valve at power off. This position is the sampling one like shown in figure 2A. Figure 9B shows the intermediate position wherein all ports 32, 34 are closed to prevent port flow mixing, like in Figure 3A. Finally, Figure 9C shows the sample injection position, like in Figure 4A.

Even if the above-described valve well improves over the prior art in overcoming most of the drawbacks of the other existing valves, there still remains a need for an improved diaphragm-sealed valve that would offer an enhanced reliability. It would also be desirable to provide an improved diaphragm-sealed valve that would be easier to operate while being inexpensive to produce.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a diaphragm-sealed valve that satisfies the above-mentioned needs.

Accordingly, the present invention provides a diaphragm-sealed valve comprising a first body having a first interface. The first interface is provided with a recessed fluid communication channel extending therein. The first body has a first, a second and a common fluid port. Each of the ports has a fluid conduct of a predetermined diameter and an open end connected thereto and opening into the recessed fluid communication channel for interconnecting each of the ports together through the fluid communication channel. Each of the first and second ports is provided with a seat disposed so as to allow fluid communication therearound within the communication channel. The open end of each of the first and second ports has a predetermined diameter smaller than the diameter of the corresponding fluid conduct to limit fluid velocity therein.

The diaphragm-sealed valve is also provided with a second body interconnected with the first body and having a second interface facing the first interface. The second body has a first and a second passage, each of the passages facing one of the first and second ports respectively. The diaphragm- sealed valve is also provided with a seal member compressibly positioned between the first and second interfaces. The seal member has a shape adapted to cover the first and second ports. The diaphragm-sealed valve is also provided with a first and a second plunger, each being respectively slidably disposed in one of the passages of the second body. Each of the plungers has a closed position wherein the corresponding plunger presses down the seal member against the seat of the corresponding port for closing the corresponding port, and an open position wherein the plunger extends away from the seat of the corresponding port for allowing a fluid communication between the corresponding port and the channel. The diaphragm-sealed valve is also provided with actuating means for actuating each of the plungers between the closed and open positions thereof.

The particular design of the first and second ports that are provided with an open end of a reduced diameter advantageously allow to limit fluid velocity into the port while allowing a pressure built-up in the space defined between the seal member and the circular flow recess. This design is also particularly advantageous since it prevents the sucking effect of the diaphragm into the open end of the port.

In a preferred embodiment of the present invention, the seal member has a metallic diaphragm and a polymer diaphragm arranged in a stacked relationship, the polymer diaphragm having first and second preformed flat elevated portions, each extending above and being pressable against the seat of one of the corresponding first and second ports.

In a further preferred embodiment, the actuating means have first and second adjusting devices, each being mounted with a corresponding one of the plungers for independently adjusting an operating pressure thereof, the valve being operated with a single pneumatic control varying pressure.

In a further preferred embodiment of the present invention, there is also provided another diaphragm-sealed valve comprising a first body having a first interface. The first interface is provided with a plurality of distinct recessed fluid communication channels extending therein. The first body has a plurality of port sets, each comprising a first, a second and a common fluid port. Each port of a corresponding set having a fluid conduct of a predetermined diameter and an open end connected thereto opening into a corresponding one of the recessed fluid communication channels respectively for interconnecting each port of the corresponding set together through the corresponding fluid communication channel respectively. Each of the first and second ports of each of the sets is provided with a seat disposed so as to allow fluid communication therearound within the corresponding communication channel. The open end of each of the first and second ports of each port set has a predetermined diameter smaller than the diameter of the corresponding fluid conduct to limit fluid velocity therein.

The diaphragm-sealed valve is also provided with a second body interconnected with the first body and having a second interface facing the first interface. The second body has a plurality of passage pairs, each comprising a first and a second passage. Each passage of a corresponding pair respectively faces one of the first and second ports of a corresponding set. The diaphragm- sealed valve is also provided with a seal member compressibly positioned between the first and second interfaces. The seal member has a shape adapted to cover each of the first and second ports of all of the port sets. The diaphragm- sealed valve is also provided with a plurality of pairs of first and second plungers, each plunger of a corresponding pair being respectively slidably disposed in one of the passages of a corresponding pair. Each of the plungers has a closed position wherein the corresponding plunger presses down the seal member against the seat of the corresponding port for closing the corresponding port, and an open position wherein the plunger extends away from the seat of the corresponding port for allowing a fluid communication between the corresponding port and a corresponding channel. The diaphragm-sealed valve also has actuating means for actuating each of the plungers between the closed and open positions thereof.

In a further preferred embodiment, the actuating means advantageously have a plurality of adjusting devices, each being mounted with a corresponding one of the plungers for independently adjusting an operating pressure thereof, the valve being operatable with a single pneumatic control pressure increasing progressively from a lower level to an upper level, thereby allowing a controlled timing sequence of the valve.

According to another aspect of the invention, there is also provided a method of operating a diaphragm-sealed valve comprising steps of: a) providing a diaphragm-sealed valve having a plurality of normally open and normally closed ports and corresponding plungers having a closed position closing the corresponding port and an open position opening the corresponding port, each of the plungers being provided with an adjusting device for independently adjusting an operating pressure thereof; b) adjusting each adjusting device for adjusting each operating pressure; and c) providing the valve with a pneumatic actuating pressure, the actuating pressure increasing progressively from an initial value to each of the operating pressures until reaching a maximum value, thereby actuating each of the plungers according to a predetermined timing sequence.

According to a further aspect of the invention, there is also provided an analytical chromatographic method using the method of operating a diaphragm- sealed valve as described above. The chromatographic method comprises steps of: a) providing a fluid sampling system having a sample inlet, a carrier inlet, a sampling loop having an inlet and an outlet, a sample vent line and analytical means provided with an inlet, each being operatively interconnected to the valve through a corresponding one of the ports; b) providing fluid communication from the sample inlet to the inlet of the sampling loop by actuating the corresponding ports, thereby providing a fluid sample in the sampling loop; c) closing the outlet of the sampling loop by actuating the corresponding port to isolate the sampling loop; d) providing fluid communication from the carrier inlet to the inlet of the sampling loop by actuating the corresponding port to pressurize the sampling loop; e) preventing fluid communication from each of the ports to the remaining ports by actuating the corresponding ports; and f) providing fluid communication from the outlet of the sampling loop to the inlet of the analytical means by actuating the corresponding port, thereby injecting the sample in the analytical means. BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and advantages of the invention will become apparent upon reading the detailed description and upon referring to the drawings in which :

Figure 1 (PRIOR ART) is an exploded perspective view of a typical diaphragm-sealed valve known in the art.

Figure 2A (PRIOR ART) is a schematic representation of a prior typical chromatographic application using a six-port valve, the valve being in a sampling position.

Figure 2B (PRIOR ART) is an exploded perspective view of the diaphragm- sealed valve shown in Figure 2A.

Figure 3A (PRIOR ART) is a schematic representation of the valve shown in Figure 2A₁ the valve being in an intermediate position.

Figure 3B (PRIOR ART) is an exploded perspective view of the valve shown in Figure 3A.

Figure 4A (PRIOR ART) is a schematic representation of the valve of Figure 2A, the valve being in a sample injection position.

Figure 4B (PRIOR ART) is an exploded perspective view of the valve shown in Figure 4A.

Figure 5A (PRIOR ART) is a top view of the first body of the prior art diaphragm-sealed valve proposed by the present Applicant. Figure 5B (PRIOR ART) is a cross-sectional side view taken along line A-A of the diaphragm-sealed valve shown in Figure 5A.

Figure 6A (PRIOR ART) is a top view of a port of the valve shown in Figure 5B, the port being in an open position.

Figure 6B (PRIOR ART) is a cross-sectional side view of the port shown in Figure 6A.

Figure 6C (PRIOR ART) is a top view of the port shown in Figure 6A, the port being in a closed position.

Figure 6D (PRIOR ART) is a cross-sectional view of the port shown in Figure 6C.

Figure 7A (PRIOR ART) is a top view of the first body shown in Figure 5A, the ports being in a predetermined position.

Figure 7B (PRIOR ART) is a schematic representation of the ports shown in Figure 7A.

Figure 7C (PRIOR ART) is a top view of the first body shown in Figure 5A, the ports being in another position.

Figure 7D (PRIOR ART) is a schematic representation of the ports shown in Figure 7C.

Figure 7E (PRIOR ART) is a top view of the first body shown in Figure 5A, the ports being in another position.

Figure 7F (PRIOR ART) is a schematic representation of the ports shown in Figure 7E.

Figure 7G (PRIOR ART) is a top view of the first body shown in Figure 5A, the ports being in another position.

Figure 7H (PRIOR ART) is a schematic representation of the ports shown in Figure 7G.

Figure 8 (PRIOR ART) is a top view of another preferred embodiment of the first body of the prior art diaphragm-sealed valve proposed by the present Applicant.

Figure 9A is a schematic representation of a typical chromatographic application using a diaphragm-sealed valve according to the present invention, the valve being in the sampling position.

Figure 9B is a schematic representation of the chromatographic application illustrated in Figure 9A, the valve being in the intermediate position.

Figure 9C is a schematic representation of the chromatographic application illustrated in Figure 9A₁ the valve being in the sample injection position.

Figure 1OA (PRIOR ART) is an exploded perspective view of a prior art diaphragm-sealed valve proposed by the present Applicant.

Figure 1OB is a schematic representation of a diaphragm-sealed valve according to a preferred embodiment to the present invention, the valve being in the sampling position.

Figure 10C is another schematic representation of the valve shown in Figure 10B, the valve being in the intermediate position. Figure 1OD is another schematic representation of the valve shown in Figure 1OB, the valve being in the sample injection position.

Figure 11 is a schematic representation of a particular step of an analytical chromatographic method, according to a preferred embodiment of the present invention.

Figure 12A illustrates a conventional baseline generated by a prior art valve.

Figure 12B illustrates a baseline generated by a preferred embodiment of the valve of the present invention.

Figure 13 (PRIOR ART) is a schematic representation of another typical chromatographic application known in the art, the configuration using two six-port valves of the prior art.

Figure 14A is a schematic representation of the chromatographic application shown in Figure 13, the configuration using a diaphragm-sealed valve of the present invention, the valve being in the sampling position.

Figure 14B is another schematic representation of the chromatographic application shown in Figure 14A, the valve being in the sample injection position.

Figure 14C is another schematic representation of the chromatographic application shown in Figure 14A, the valve being in the heartcut position.

Figure 15A is another schematic representation of the chromatographic application shown in Figure 14A. Figure 15B is another schematic representation of the chromatographic application shown in Figure 14B.

Figure 15C is another schematic representation of the chromatographic application shown in Figure 14C.

Figure 16A is a schematic representation of another preferred embodiment of the diaphragm-sealed valve of the present invention, the valve being in the sampling position.

Figure 16B is another schematic representation of the valve shown in Figure 16A, the valve being in the intermediate position.

Figure 16C is another schematic representation of the valve shown in Figure 16A, the valve being in the sample injection position.

Figure 16D is a schematic representation of another preferred embodiment of the diaphragm-sealed valve of the present invention.

Figure 17A (PRIOR ART) is an exploded perspective view of a prior art diaphragm-sealed valve.

Figure 17B (PRIOR ART) is a cross sectional view of the valve actuator shown in FIGURE 17A.

Figures 18A and 18B are partial cross sectional views of a diaphragm- sealed valve, showing a port and its associated plunger.

Figure 19 is a partial cross sectional view of an improved diaphragm-sealed valve showing an improved seat and an improved diaphragm, according to a preferred embodiment of the present invention. Figure 20 is a cross-sectional view of an improved diaphragm-sealed 6-way valve showing an improved seat and an improved diaphragm, according to a further preferred embodiment of the present invention.

Figure 21 is a cross-sectional view of an improved diaphragm-sealed 3-way valve showing an improved seat and an improved diaphragm, according to a further preferred embodiment of the present invention.

Figures 22A to 22C are partial cross-sectional views showing details of a valve of the present invention.

Figure 23 is a graph showing a timing valve actuation sequence, according to a preferred embodiment of the present invention.

While the invention will be described in conjunction with example embodiments, it will be understood that it is not intended to limit the scope of the invention to such embodiments. On the contrary, it is intended to cover all alternatives, modifications and equivalents as may be included as defined by the present description and the appended claims.

DESCRIPTION OF PREFERRED EMBODIMENTS

In the following description, similar features in the drawings have been given similar reference numerals and, in order to weight down the figures, some elements are not referred to in some figures if they were already identified in a precedent figure.

The present invention concerns a diaphragm-sealed valve, also referred to as a diaphragm based tight shut off valve, mostly dedicated for analytical equipments, and more particularly chromatographic equipments or on line analyzers.

The present invention also concerns a particular method of operating such a valve as well as chromatographic methods based on the use of such a diaphragm-sealed valve. As it will be greater detailed herein below, the chromatographic methods are based on the use of at least one diaphragm-sealed valve, which, in a first preferred embodiment can be referred to as a three way switching cell. According to the general concept of the valve of the present Applicant disclosed in US patent 7,216,528, this switching cell has one common port and two actuated ports, these actuated ports being advantageously independently actuated. Thus, each of the independently actuated ports is preferably independently controlled in a way that both could be open or closed at the same time or one could be open while the other is closed and vice versa. Moreover, it is worth mentioning that the fluid flowing through the common port could be allowed to flow to or from any one of the independently actuated ports at the same time or in a predetermined sequence.

In preferred embodiments of the present invention which will be described below, a plurality of three-way switching cells are advantageously used to allow more complex flow path switching schemes. As described in US patent 7,216,528, which is hereby incorporated by reference, by interconnecting together various switching cells, a typical chromatographic diaphragm valve could be done. In the case an elementary cell is used, the switching steps could be: make before break, break before make, all ports opened or all ports closed. These switching steps are not available with standard three way valves.

As previously mentioned, the different embodiments of the valve described in US patent No. 7,216,528 and illustrated in Figures 5A to 5B have been deeply tested and various problems were noted. 1) Problems

a) Venturi effect causing diaphragm extrusion

The main problem that was noted is the diaphragm extrusion into the seat of the ports of the valve. When this happens, there is no more flow through the valve. It has also been shown that this situation is more commonly to happen when there is a sudden system depressurisation through the port, leading to a very high gas flow velocity, which generates a localised venturi effect.

To refer to a practical application, reference is made to Figures 9A to 9C. In Figure 9A, the port 6 of the valve 22 is working at the atmospheric pressure, since the sample gas is simply vented. When, as shown in Figure 9C, the sample is injected into the column 1, the valve 22 internal pressure is set at the carrier pressure that could be 100 PSI and much higher (>1000 PSIG). When the valve 22 is returned to the position shown in Figure 9A, the sample loop volume SL is depressurised through the port 6 of the valve 22. Suddenly, there is a very high gas flow through the port, violently sucking down the diaphragm against the seat of the port. There are many configurations where this situation could happen.

For example a very popular configuration in chromatography is the heart cut one like shown in Figures 14A to 14C. When the column 1 is switch to vent through port 11, the same situation arises. The above cited problems can have a dramatic impact, since the system may simply stops working and this after a relatively short period of time.

b) Mechanical problem causing diaphragm extrusion

The tests conducted also showed that the force exerted by a plunger on the multilayer diaphragm assembly may cause the diaphragm to extrude in the valve seat's orifice. This phenomenon was more pronounced for the normally open ports that are closed when the actuator of the valve is operated by allowing pneumatic gas to flow in it. In US patent No. 7,216,528, the seal member is advantageously provided with a polymer diaphragm backed by a metallic one. The reason for this is to avoid the deformation of the polymer diaphragm when operating at high pressure. Moreover, the metallic diaphragm advantageously eliminates the risk of sample diffusion out of the system, or the diffusion of ambient air into the system by making a barrier through which gases can not permeate. Since H₂ and He gases have a strong tendency to permeate through polymer or plastic, this point becomes an important factor when working at ppt or sub ppb levels. It should however be noted that this point is not a problem with liquid sample.

As shown in Figures 5B, 6B and 6D, when the plunger 54 is forced down, it sets up a pressure against its surface and the metallic diaphragm 53. So there is also a force or a pressure applied on the polymer diaphragm 55 by the circular surface defined by the plunger cross sectional area. This force is counter balanced by the valve metal seat 42. However, the valve seat surface has an annular form, like a donut form, since there is an opened orifice in the middle thereof to allow fluid flow.

This means that the polymer diaphragm 55, and the metallic one 53 too, are not supported in the area defined by the seat orifice. So, when the plunger 54 is down, the polymer and the metallic diaphragms 53, 55 are deformed or extruded into the orifice opening, resulting in valve malfunction. This problem is well illustrated in Figure 18B. It should however be noted that this phenomenon does not appear on the normally closed port, as it will be more clearly explained thereinafter.

The diaphragm-sealed valve of the present invention advantageously allows to overcome the above-mentioned drawbacks. 2) Solutions

a) Venturi effect problem

In order to prevent the "sucking" effect of the diaphragm into the orifice of the seat as shown in Figure 18B, an improved seat design is proposed. More particularly, a seat particularly adapted to specifically limit the gas velocity and to allow a pressure build up in the space defined between the diaphragm and the circular flow recess around the seat is provided.

Reference is now made to Figure 19 which shows a preferred embodiment of a valve 200 having an improved seat design as previously mentioned, according to the present invention, and also to Figures 5A to 5B. Similarly to the valve disclosed in US patent No. 7,216,528, the illustrated diaphragm-sealed valve 200 according to a preferred embodiment of the present invention is provided with a first body 24 having a first interface 26 provided with a recessed fluid communication channel 28 extending therein. The recessed fluid communication channel 28 preferably has a loop shaped portion 30. The first body 24 has a first, a second and a common fluid port, respectively 32, 34 and 36. As known in the art, each of the ports is preferably provided with a fluid passage 38 connected to a threaded hole 40 providing tubing connections. Each of the ports 32, 34, 36 has a fluid conduct 202 of a predetermined diameter and an open end 204 opening into the recessed fluid communication channel 28 for interconnecting each of the ports together through the fluid communication channel 28, which acts as a fluid conduct. Each of the first and second ports 32, 34 is provided with a seat 42 disposed so as to allow fluid communication therearound within the communication channel 28. The present valve improves over the prior art valve of the same Applicant in that the open end 204 of each of the first and second ports has a predetermined diameter smaller than the diameter of the corresponding fluid conduct 202 to limit fluid velocity therein. As a non-limitative example, instead of providing an open end of .040 or .030 inch diameter, a smaller open end is built through the seat for a depth of .020 inch. Open end diameters of .015 and .010 inches were successfully tested and efficiently prevent the sucking of the seal member in the port.

As for the prior art valve of the same Applicant, the present diaphragm- sealed valve 200 is also provided with a second body 44 interconnected with the first body 24, preferably by any convenient attaching means known in the art such as a set of screws (not shown). The second body 44 has a second interface 46 facing the first interface 26. The second body 44 also has a first and a second passage 48, 50. Each of the passages 48, 50 faces one of the first and second ports 32, 34 respectively.

The valve 200 is also provided with a seal member 52 compressibly positioned between the first and second interfaces 26, 46. The seal member 52 has a shape adapted to cover the first and second ports 32, 34, and advantageously the entire fluid communication channel 28 to act as a seal for inboard or outboard contaminations. This seal member 52 allows to provide a flow interruption through the corresponding port 32 or 34, when it is pressed against the seat 42 of the port. Preferably, the seal member 52 has a polymer diaphragm 55 and each of the first and second interfaces 26, 46 has a planar and circular shape. More preferably, the seal member 52 has a metallic diaphragm 53 which is advantageously a stainless diaphragm, and a polymer diaphragm 55 arranged in a stacked relationship, the polymer diaphragm 55 being pressable against the seat 42 of each of the first and second ports 32, 34.

The valve 200 is also provided with a first and a second plunger 54, 56, each being respectively slidably disposed in one of the passages 48, 50 of the second body 44. Each of the plungers 54, 56 has a closed position wherein the corresponding plunger presses down the seal member 52 against the seat 42 of the corresponding port 32, 34 for closing the corresponding port, and an open position wherein the plunger extends away from the seat 42 of the corresponding port 32, 34 for allowing a fluid communication between the corresponding port and the channel 28. The valve 200 also has actuating means 58 for actuating each of the plungers 54, 56 between the closed and open positions thereof.

It should be mentioned that the above described valve of the present invention relies on the same general working principle of the valve of US patent 7,216,528, as illustrated in Figures 6A to 7H. Thus, as it can be deducted from Figures 6A and 7H, in anyone valve positions, there is no dead volume since there is always fluid flowing around the seat 42 and in the loop shaped portion 30 of the fluid communication channel 28. So there is no dead volume effect generated by the valve since the channel 28 always appears like a fluid conduit or tubing.

It should also be understood that the sealing the ports 32 and 34 by pressing the diaphragm 52 thereon results in a positive sealing effect. Indeed, it seals completely the port 32 or 34 and totally blocks the fluid flow therefrom or thereinto. So, relatively high pressure could be applied to the ports 32, 34 without generating any leak nor any detrimental impact on the analytical results.

As already explained, as a first application, the valve could be used as a simple three way type switching valve used to switch between two streams. However, an interesting aspect of the present invention is revealed when we combine together a plurality of elementary switching cells 200 as previously described with reference to Figure 19. Such a valve, which embodied the improved seat design shown in Figure 19, is illustrated in Figure 20. This valve 220 was also successfully tested, even with an internal pressure exceeding 1000 PSI. Sudden depressurisation from the top of the seat through the seat orifice and then to atmosphere does not affect the polymer diaphragm, even after many thousands of actuations. Therefore, the flow orifice effect described above is very effective to solve the problem. It advantageously eliminates the venturi effect that extrudes the polymer diaphragm into the seat orifice. Referring to Figure 20, the illustrated diaphragm-sealed valve 220 is provided with a first body 24 having a first interface 26 provided with a plurality of distinct recessed fluid communication channels 28 extending therein. The first body 24 has a plurality of port sets, each comprising a first, a second and a common fluid port 32, 34, 36. Each port of a corresponding set having a fluid conduct 202 of a predetermined diameter and an open end 204 connected thereto opening into a corresponding one of the recessed fluid communication channels 28 respectively for interconnecting each port 32, 34, 36 of the corresponding set together through the corresponding fluid communication channel 28 respectively. Each of the first and second ports 32, 34 of each of the sets is provided with a seat 42 disposed so as to allow fluid communication therearound within the corresponding communication channel 28. As for the valve of Figure 19, the open end 204 of each of the first and second port of each port set has a predetermined diameter smaller than the diameter of the corresponding fluid conduct 202 to limit fluid velocity therein. Preferably, each of the first and second ports 32, 34 is advantageously circularly arranged in a port circle 96 concentrical with the first interface 26.

The diaphragm sealed valve 220 is also provided with a second body 44 interconnected with the first body 24 and having a second interface 46 facing the first interface 26. The second body 44 has a plurality of passage pairs, each comprising a first and a second passage 48, 50. Each passage 48, 50 of a corresponding pair respectively faces one of the first and second ports 32, 34 of a corresponding set. The diaphragm sealed valve 220 is also provided with a seal member 52 compressibly positioned between the first and second interfaces 26, 46. The seal member 52 has a shape adapted to cover each of the first and second ports 32, 34 of all of the port sets. Preferably, as previously described with reference to Figure 19, the seal member 52 has a metallic diaphragm 53 which is advantageously a stainless diaphragm, and a polymer diaphragm 55. Each of these elements is advantageously arranged in a stacked relationship, the polymer diaphragm 55 being pressable against the seat 42 of each of the first and second ports 32, 34.

The diaphragm sealed valve 220 is also provided with a plurality of pairs of first and second plungers 54, 56. Each plunger 54, 56 of a corresponding pair is respectively slidably disposed in one of the passages 48, 50 of a corresponding pair. Each of the plungers 54, 56 has a closed position wherein the corresponding plunger presses down the seal member 52 against the seat 42 of the corresponding port 32, 34 for closing the corresponding port, and an open position wherein the plunger extends away from the seat 42 of the corresponding port 32, 34 for allowing a fluid communication between the corresponding port and a corresponding channel 28. The diaphragm sealed valve 220 also has actuating means 58 for actuating each of the plungers 54, 56 between the closed and open positions thereof.

As shown in Figures 6B and 6D, in the primary design of the valve described in US patent No. 7,216,528, the seat of the first and second ports is preferably lower than the first interface of the first body for giving sufficient room for the seal member vertical movement. However, in the improvement presently described and illustrated in Figures 19 and 20, the seat advantageously has a raised portion extending at the same level as the first interface of the first body.

This modification of the seat design advantageously allows to propose an improved seal member. Indeed, as shown in Figure 19, the proposed improved seal member is advantageously provided with a polymer diaphragm backed with a metallic diaphragm. The polymer diaphragm is advantageously pre-formed to allow more vertical deflection. More particularly, the diaphragm advantageously has at least first and second preformed flat elevated portion 230, each extending above and being pressable against the seat of one of the corresponding first and second ports. Of course, since the valve of the present invention has a plurality of ports, a plurality of such elevated portions 230 is provided, each extending above a corresponding port. More room is also advantageously provided under and over the diaphragm preformed elevated portions 230 to allow these portions to "pop up" when the corresponding plunger is in the upper position. In other words, the particular shape of the diaphragm allows to ensure that the corresponding elevated portion of the diaphragm is still in the up position when required, thereby preventing the "sucking" of the diaphragm into the orifice of the seat. In a further embodiment, each of the first and second plungers is advantageously attached to the corresponding flat elevated portion of the polymer diaphragm. Thus, when the plunger 54 or 56 is in the open position, it pulls up the diaphragm 52 from the port 32 or 34.

In all related prior art documentation previously referred to, there is no reference to this problem, except in the valve design shown in US patent No. 4,112,766. In US patent No. 4,276,907, the authors reported diaphragm extrusion into the recess provided in the base of the cap. However their concept is different than the one of the present invention since they interrupt the flow between the ports, not sealing the port like in the present valve. Their problem is different and could not be fixed by the design provided by the present invention. In this particular case, this is the fluid pressure action that force the diaphragm into the recess provided in the valve base, not fluid velocity.

There is two main reasons why these problems were not reported in the prior art. First, many of the related prior art valves are designed for liquid application where fluid velocity is very low compare to gas application. So there could be no venturi effect. Second, in some prior art documentation like in US patent No. 5,765,591 , the fluid flow is liquid and, additionally, the fluid flows out of the port, thereby lifting the diaphragm, and never flows in, as shown by the arrows in Figures 6 and 7 of this previously mentioned patent.

4b) Solution to mechanical problem

It appears that in process Gas Chromatograph, it is particularly advantageous to use a pneumatic actuating means for actuating each of the plungers between the closed and open positions. Indeed, it costs less to manufacture and there is always some pneumatic gas available on site. Furthermore, it is easier to interface with the control system, since it requires only one inexpensive solenoid valve to actuate the diaphragm-sealed valve. So, in the preferred embodiment of the valve which will be described below, a pneumatic actuator is preferred over the electrical solenoid based actuating means, even if other convenient actuating means could nevertheless be considered for a particular application.

In the embodiment of US patent No. 7,216,528 which is illustrated in Figures 17A and 17B of the present disclosure, the normally closed ports are maintained in the closed position by the action of the Belleville washer 174 that applies pressure on the piston 168 and then on the piston shaft 170. When comes the time to operate the valve, the normally closed ports must open while the open ones must close. There is also an intermediate step when all ports must advantageously be closed to avoid cross ports flows. To do so, the actuating pressure is applied to both pistons 168, 172 at the same time through port 178 and 184, as better shown in Figure 17B. At that time, the normally open piston 172 is force down, thereby pushing his corresponding plunger against the diaphragm assembly. During that portion of pneumatic pressure rise, all plungers are down since there is not yet enough actuating pressure to lift up the piston 168. A higher pressure is required to compress the Belleville washer assembly 174. This is at this particular step that the problem arrives.

Indeed, the extra pressure required to open the normally closed ports, i.e. move the piston 168 up, over stresses the already closed and sealed normally open ports. In fact, both pistons 168, 172 are supplied with the same operating pressure. The tests conducted showed that there is too much stress applied on the diaphragm assembly during this step and this is why the polymer and metallic diaphragms are mechanically extruded into the seat's orifice. The tests also showed that similar problems arise with the actuator described in US patent No. 6,202,698 granted to Stearns. However, in this case, the diaphragm is not extruded in a seat's orifice since the flow is interrupted between the ports. However, after a certain period of use, an inspection of the diaphragm clearly shows much more wearing on the normally open ports than for the normally closed ones. In some cases, this is the reason of the valve failure, since the diaphragm gets «punched» and breaks, thereby causing a major leak. It is also important to note that the above problem is even worse if there is a slight difference in the length of the plungers.

In order to overcome the above mentioned problem, an improved pneumatic actuator that requires only one solenoid valve to actuate has been developed and successfully tested. In fact, the idea is to make sure that only the required force necessary to properly close the normally open ports is used, and, at the same time, that the normally closed ports are properly open. Figure 20 shows a valve using such an improved actuator which is provided with six independent pistons (only two pistons are shown). As it can be seen, in a preferred embodiment, the diameter of the normally open piston is advantageously smaller than the one of the normally closed piston.

According to the concept of the invention, the system can advantageously be tuned in order to have the normally closed ports fully open, while having the normally open ports properly closed and sealed under the system operating condition, without applying to much force on the normally open ports. Since the normally open piston's diameter is smaller, there is less "weight" or force applied on the diaphragm.

In a further embodiment, referring again to Figures 19 and 20, in order to allow a convenient tuning of the valve, the actuating means is advantageously provided with first and second adjusting devices 240, 242, each being mounted with a corresponding one of the plungers for independently adjusting the operating pressure thereof. Preferably, each of the adjusting devices respectively has resilient means, more preferably a first and a second spring 64, each being respectively mounted on a corresponding plunger 54, 56 for biasing the corresponding plunger. In the illustrated embodiment, the first plunger is a normally open plunger while the second plunger is a normally closed plunger. More preferably, the adjusting device 240 mounted with the normally closed plunger comprises a Belleville washer assembly 244 and a set up screw 246 pressing against the plunger.

An additional beneficial aspect of the previously described design is that each port has its own independent piston. Thus, the problem related to the tight tolerance for the plunger length is eliminated. Each port has therefore the right closure force. This even for the normally closed ports, since each normally closed piston has its own set up screw to adjust the required pressure to seal them.

The above described improved design of the internal ports of the valve and of the actuator advantageously allows to fix the problem of diaphragm extrusion into valve seat's orifice. Many tests were conducted and get excellent results. Of course, the new concept described above could be adapted to the 3-way type valve also described herewith.

Here, it is important to recall that a simple 3-way cell embedded into a circular substrate is advantageously used to realize the equivalent of a standard six ports diaphragm valve. For the applications using a six ports diaphragm valve, the improved pneumatic actuators previously described are advantageously used. For a simple 3-way valve as illustrated in Figure 21 , the actuator has only two pistons of different size.

It should be noted that the improved actuator design also advantageously has the flexibility to limit the piston travelling distance or the stroke. Like previously mentioned, it is very beneficial to have a minimum of hardware to control a process G-C valve. In a process plant, there is "instrument air" available to control various process valves. Generally, the instrument air pressure is around 125 to 150 PSIG. This is well above the gas pressure required to operate the diaphragm G-C valve proposed herewith.

Generally, a pressure of about 60 PSIG will be sufficient to operate the valve of the present invention in most G-C applications. An instrument air pressure of 150 PSIG will be more than twice the required pressure. In this case an internal pressure regulator has to be added to the process G-C to turn down the pressure. Extra hardware, like fittings, tubing, pressure regulator, mounting brackets, etc. is required. It consumes available space inside the process G-C cabinet. Therefore, it would be beneficial to operate the valve directly from the instrument air line without adding any hardware to regulate down the pneumatic pressure.

However, over pressurising the actuator will also damage the diaphragm assembly by extruding it into the valve seat's orifice or by breaking it as previously explained. The valve seat could also be damage by scratching it. Should this happen, the valve body must be replaced.

Referring now to Figures 22A to 22C, which illustrate enlarged views of the pistons of the actuator of the valve of the present invention, to avoid this situation while using higher pneumatic actuation pressure, the actuator cylinders are advantageously provided with some room therearound to add shim elements 248, 250 of various thicknesses. These shim elements stop the piston travelling, since the piston will seat thereon. The idea is to use the right shim thickness for a particular application. These shims are advantageously used on normally open piston ports and also on the normally closed ones. However, it is important to note that the use of such shims on the normally closed piston ports is not intended to avoid damage when using a higher operating pressure to actuate the valve, since pressure is used to lift the pistons to open the corresponding ports.

Indeed, as it can be seen on Figures 20 and 21 , when adjusting the set screw on the top of the normally closed pistons, it sets a compressive force or a pressure on the Belleville washer assembly. Depending on how much pressure is applied on the Belleville washer assembly by the corresponding set screw, a different pneumatic pressure will be required to open the corresponding port. These features advantageously allow the following interesting possibilities.

First, if the set screws are adjusted in order to require a high pressure to open their corresponding port, the result is that the time that all ports are closed upon valve actuation will advantageously be longer, then eliminating even more the risk of cross port flow or the so called "mixing". This higher pressure operation will not damage the normally open ports since the corresponding piston strokes are limited by the shims elements. This provides a convenient way to adjust or to "time" the valve sequence operation by setting the step of "all ports closed" more or less longer.

Second, as previously said, in the valve illustrated in Figure 20, there are 3 independent set screws and 3 independent Belleville washers stacks (only one of each is shown on the cross-sectional view). So, the required opening pneumatic pressure for each normally closed piston could be set at a different level, just by adjusting differently the associate set screw.

These features advantageously allow to provide an improved method of operating a diaphragm-sealed valve comprising the steps of: a) providing a diaphragm-sealed valve having a plurality of normally open and normally closed ports and corresponding plungers having a closed position closing the corresponding port and an open position opening the corresponding port, each of the plungers being provided with an adjusting device for independently adjusting an operating pressure thereof; b) adjusting each adjusting device for adjusting each operating pressure; and c) providing the valve with a pneumatic actuating pressure, the actuating pressure increasing progressively from an initial value to each of the operating pressures until reaching a maximum value, thereby actuating each of said plungers according to a predetermined timing sequence.

For example, let's say that in Figure 9A, all three-way valves shown are mounted on the same substrate and controlled by the above described pneumatic actuator. In this case, the ports # 2, 4, and 7 of valves 22 will be the normally closed ports, associated to their corresponding pistons forced down by their corresponding Belleville washer assembly, and associated set screw. In such arrangement it is possible to adjust each set screw in a way that their corresponding port will open at a different moment in time.

To more clearly understand this latter point, reference is now made to Figure 23 which illustrates an exemplary timing valve actuation sequence that can advantageously be implemented with the preferred pneumatic actuator described above. As illustrated, when the pneumatic actuating pressure is applied, the pressure will ramp up to 100 PSIG after a certain amount of time. This time can be simply controlled by adding the appropriate flow restrictor in series with the actuating port of the actuator in order to decrease gas velocity.

When actuating pressure is reaching 20 PSIG, all normally open ports are properly closed. Then, between 20 to 30 PSIG, all valve ports are closed to avoid cross port flow or "mixing." This is valve's port position shown in Figure 9B. So, the raise of the actuating pressure allow to move from the sampling position shown in FIGURE 9A to the all ports closed position shown in Figure 9B. Then, the actuating pressure still ramps up at a predetermined rate, to eventually reach 35 PSIG. At this point in time, the port # 4 opens, thereby connecting the vent side of the sampling loop to port # 7, that still is in closed position. Then, the actuating pressure reaches 50 PSIG. At this moment, port # 2 opens. This has for result to pressurise the sampling loop at the same pressure as the carrier gas, as shown in Figure 11. Finally, the actuating pressure reaches 65 PSIG, opening port # 7. This final configuration of valve port position is the one shown by Figure 9C, i.e. sample loop injection into separation column.

The improvements described above are particularly advantageous since they allow to implement a pressurisation of the sample before injection, as shown in Figure 11 and as it will be described thereafter. These improvements provide the unique feature that only one valve system is required with one control line, instead of 3 independent three-way valves and their corresponding solenoid valve and control system digital output. Of course, other valve's port sequence could be done by adjusting corresponding set screw differently.

As previously noted, the diameter of the pistons for the open ports can advantageously be reduced in order to also reduce the force applied on the diaphragm. However, pistons having the same diameter could also be used if shim elements are used to limit the stroke of the pistons and therefore, the force applied on the diaphragm. Of course, pistons of a smaller diameter for the open ports could also be implemented in a valve provided with shim elements.

As mentioned in US patent 7,216,528, the valve of the present invention advantageously allows sub atmospheric pressure operation. Indeed, Figure 8 shows another preferred embodiment of the present invention, wherein the valve further has a purge circulation line 68. The purge circulation line 68 is provided with an annular recess 70 extending in the first interface 26 and surrounding the fluid communication channel 28. The purge circulation 68 line also has a fluid inlet 72 and a fluid outlet 74, each having an opening lying in the annular recess 70 for providing a continuous fluid flow in the annular recess 70. Preferably, the fluid inlet and outlet 72, 74 are each provided with a fluid passage 76 and an associated threaded hole 78 for allowing tubing connections. Thus, a clean purging fluid can advantageously be allowed to flow through the purge circulation line 68, thereby evacuating any inboard and outboard contamination and any fluid process leak. This concept is detailed in US patent application published under No. 2006/0042686, whose disclosure is incorporated herein by reference.

Referring again to Figure 19 and also to Figure 8, the valve of the present invention can also advantageously be used in an analytical chromatographic system 80 to provide a system having improved characteristics. Indeed, such an analytical chromatographic system 80 is advantageously provided with a diaphragm-sealed valve as defined above and provided with a purge circulation line 68. The analytical system 80 is also advantageously provided with monitoring means 82 operatively connected to the fluid outlet 74 for monitoring a fluid passing therethrough. In a preferred embodiment, the monitoring means 82 have a purity detector for detecting contamination of said fluid. Preferably, the monitoring means 82 are adapted to monitor the fluid passing through the purge circulation line 68 continuously.

The further embodiment of the valve shown in Figure 20 can also be further provided with a purge circulation line 68, as illustrated in Figure 10B The purge circulation line 68 has a looped recessed fluid circuit 86 extending in the first interface 26. The looped fluid circuit 86 has an outer annular recess 88 and an inner recess 90, each extending in the first interface 26. The fluid circuit 86 further has a plurality of separation recesses 92 radially extending in the first interface 26. Each of the separation recesses 92 is connected to each of the outer and inner recesses 88, 90 for defining a plurality of first interface portions 94 isolated from each others. Each of the first interface portions 94 encloses one of the fluid communication channels 28. The fluid circuit 86 is also provided with a fluid inlet 72 and a fluid outlet 74, each having an opening lying at the first interface 26. Each of the inlet and outlet 72, 74 is in continuous fluid communication with a respective one of the outer and inner recesses 88, 90 for providing a continuous fluid flow in the looped recessed fluid circuit 86. This preferred embodiment is particularly advantageous since it allows to continuously monitor the working of the valve for detecting any undesirable contamination and/or leaks.

As described in US patent No. 7,216,528, with the different valve configurations described above, different applications can be envisaged.

Figures 1OB to 1OD illustrate the valve of the present invention in different positions. Figure 10B shows the sampling mode position, Figure 10C shows the intermediate position wherein all ports 32, 34 are closed, while Figure 10D shows the sample injection position. So, one can see that the three elementary switching cells 22 are simply embedded in the same substrate. As described above, in this illustrated preferred embodiment, there is an outer annular recess 88 surrounding all of the cells 22, and separation recesses 92 for isolating each of the cells 22. Thus, a purging fluid can advantageously be introduced into the fluid inlet 72, preferably extending in the inner recess 90, where the separation recesses 92 join together. This purging fluid can thus flow through the separation recesses 92 between the cells 22, and then to the outer annular recess 88 and then exit by the fluid outlet 74, preferably extending therein. Of course, the fluid inlet 72 could extend in the outer recess 88 while the fluid outlet 74 could extend in the inner recess 90. So any leak that may occur over the time from anyone of the cells 22 will reach the purge circulation line 68 first, avoiding contaminating the other cells. Indeed, with reference to Figure 10B, the valve 84 can advantageously be used in an analytical chromatographic system 126 to provide a system having improved characteristics. Such an analytical chromatographic system 126 is advantageously provided with a diaphragm-sealed valve 84 having a purge circulation line 68 as described above. The analytical system 126 is also advantageously provided with monitoring means 82 operatively connected to the fluid outlet 74 for monitoring a fluid passing therethrough. In a preferred embodiment, the monitoring means 82 have a purity detector for detecting contamination of said fluid. Preferably, the monitoring means 82 are adapted to monitor the fluid passing through the purge circulation line 68 continuously. Again, this feature is well explained in the previously mentioned US application. In this illustrated valve configuration, one of the switchable ports 32, 34 is preferably closed while the other switchable port 32 or 34 is opened when the valve is at rest or not actuated. Again, the springs 64, 66 associated to the plungers 54, 56 are advantageously particularly arranged to push down one plunger and move up the other one. Each of the three cells 22 is configured this way. It is an advantageous convenient way to provide all the switching cells 22 on the same substrate, since it eliminates tubing connections. The ports connected together are preferably linked by an internal conduct drilled in the substrate. It is also possible to use three elementary separate cells 22 and connect them together with tubing. The result would be the same and there would be no difference on performance.

The valve design provided by the present invention resolves another problem inherent to the design of the prior art valves. Indeed, in the prior art, when a valve is operated to inject a sample, the cycle is generally done in three steps: sampling, isolating (all ports closed) and finally the sample injection. In gas chromatography, most of the time the sample is at ambient or sub atmospheric pressure and the carrier is at much higher pressure. Since the sample is at low pressure, the sample volume of the sample loop is made bigger to have more sample, and then more impurities, in order to increase the sensitivity of the gas chromatographic system. Mostly, in the prior art, the sample loop is generally made of tubing having a diameter bigger than the tubing of the gas chromatographic carrier circuit. For example, it is not uncommon to have a sampling loop having an outer diameter of 1/8", while the carrier distribution network is made of tubing having an outer diameter of 1/16". So, when suddenly the sample volume is introduced into the carrier circuit, there is a system flow and pressure perturbation. When the system sensitivity is high, this perturbation generally generates a dramatic detector's baseline shift that interferes with the impurities to be measured, thereby reducing the overall system repeatability and sensitivity. The impact is even more dramatic in a system wherein a permeation tube or a dopant gas are added to the detector, since flow variation results in change of dilution ratio, thereby changing the level of dopant into the detector. Moreover, the pressure or flow variation can also change the separation column operating conditions. Indeed, since the sample loop must be pressurized before the flow comes back to its operating point, the column inlet pressure decreases and there is a reverse flow from the column. In gas solid chromatography, the column packing may eventually release some molecules that are normally trapped into the column. When the flow starts back, a part of these molecules will reach the detector, thereby generating a false peak or baseline shift.

However, with the diaphragm sealed valve provided by the present invention, most of these prior art drawbacks can be overcame. Indeed, with the valve of the present invention, another step may be added to a conventional injection cycle. The cycle is then: sampling, sample loop isolation and pressurization, all ports closed and sample injection. The sample loop isolation and pressurization step is shown in Figure 11. In this step, the vent side 98 of the sampling loop 102 is closed by actuating the corresponding plunger. The inlet 100 of the sampling loop 102 is then connected to the carrier inlet 104, as shown by the valve flow path. In this position, the sampling loop 102 is pressurized at a pressure equal to the column head pressure. At this moment, the sampling loop 102 is put into the carrier circuit. There is no perturbation generated. Figure 12A shows a conventional baseline where a sample is injected with a conventional valve. One can see there is a strong upset. In Figure 12B, the conventional valve has been replaced with the valve of the present invention. One can see that no upset occurs, even when enlarging the baseline. This method has a beneficial impact on hardware used to regulate carrier flow and pressure since there is no more column head pressure variation. Thus, a simpler regulation method can be used instead of those of the prior art, thereby allowing to reduce the overall system cost and complexity.

Accordingly, still with reference to Figure 11 , the present invention thus provides an improved analytical chromatographic method relying on the method of operating the diaphragm-sealed valve described above. This improved method comprises the steps of: a) providing a fluid sampling system 106 comprising a diaphragm-sealed valve 200 as described above, a sample inlet 108, a carrier inlet 104, a sampling loop 102 having an inlet 100 and an outlet 110, a sample vent line 98 and analytical means 112 provided with an inlet 114, each being operatively interconnected to the valve 200 through a corresponding one of the ports; b) providing fluid communication from the sample inlet 108 to the inlet 100 of the sampling loop 102 by actuating the corresponding ports 32, 34, thereby providing a fluid sample in the sampling loop 102; c) closing the outlet 110 of the sampling loop 102 by actuating the corresponding port 32, 34 to isolate the sampling loop 102; d) providing fluid communication from the carrier inlet 104 to the inlet 100 of the sampling loop 102 by actuating the corresponding port 32, 34 to pressurize the sampling loop 102; e) preventing fluid communication from each of the ports 32, 34, 36 to the remaining ports by actuating the corresponding ports; and f) providing fluid communication from the outlet 110 of the sampling loop 102 to the inlet 114 of the analytical means 112 by actuating the corresponding port, thereby injecting the sample in the analytical means 112.

In the past, many have designed complex flow or pressure regulation subsystems in the attempt of reducing baseline upset at sample injection. For example, US Patents Nos. 4,976,750 and 5,952,556 illustrate such regulation subsystems. This goal is easily achieved with the present valve design because of the particular port actuation and positive sealing action making a leak tight system when in closed position. Moreover, with the present design, no dead volume effect occurs where part of sample can be trapped and slowly diffused back on injection and cause tailing peak.

According to the present invention, the principle of the present valve could also be used in other typical columns, complex valves and detector configurations commonly used in the field. For example, common conventional configurations like heartcut, back flush, column selection, series-across the detector (SAD), series by-pass, trap selection, etc can be realized. So, the invention is not limited to sample loop injection. For example, a common application is the heartcut one as shown in Figure 13. This application can be done with a 10 port valve or two six port valves. The application shown in Figure 13 uses two six port valves of the prior art. In Figures 14A to 14C, this application, which is functionally equivalent to the one shown in Figure 13, is illustrated with a plurality of three way elementary cells 22 of the present invention, in the different valve positions. Figures 15A to 15C show another preferred embodiment of this application using the valve 84 of the present invention, in different valve positions. The extra switching cells 22 are added to the common substrate. The switching cell ports that are common together are internally connected by flow passage machined into the first body 24 of the valve 84, thereby reducing the number of external fittings.

Thereinbelow, there will be described a plurality of preferred embodiments of the present invention, each using a combination of at least one elementary cell 22 having independently controlled ports 32, 34. For example, with reference to Figures 16A to 16D, as a first preferred variation, a real flow path equivalent like typical gas chromatographic six port valve could be realized. In this configuration, there still is sample flowing through the valve on injection position. In this application, six elementary cells 22 are used, preferably extending on a circle 96 concentrical with the first interface 26. One of the controlled ports 32, 34 of a cell 22 is closed while the other is opened when the valve is not actuated. The chromatographic community is more familiar with this preferred valve embodiment and the resulting flow path. This preferred embodiment however introduces some dead volume. The fluid does not sweep the connecting conduits tied to common ports 36 when the corresponding ports are closed. Nevertheless, tests have been performed and show that this dead volume does not change the analytical results because of its small size. This assumption is correct for gaseous applications but may not be correct if the fluid is a liquid.

Figures 16A to 16C show different valve positions of a conventional injection cycle. It is obvious for people involved in the art that any number of elementary cells 22 can be embedded on the same substrate, which is preferably circularly or rectangularly shaped to provide the appropriate number of ports required for a particular application. It is also evident that even a four port valve could be realized. Presently, there are no four port gas chromatographic diaphragm valves available on the market. There are only four port rotary gas chromatographic valves. It is also evident that the valves may also be installed in a system that monitors the quality of the purging gas flowing in the circulation line 68 for diagnostic purposes, as shown in Figure 16D and as already explained. With the valve of the present invention, when the ports 32, 34 are actuated, the purging circulation line 68 is never in contact with the fluid carrier or sample fluid. So, no synchronization of the purity detector is required and continuous measurements can be done, resulting in a continuous monitoring of valve performance. This characteristic is an important one of the present invention since it can not be obtained with the valves of the prior art.

Although preferred embodiments of the present invention have been described in detail herein and illustrated in the accompanying drawings, it is to be understood that the invention is not limited to these precise embodiments and that various changes and modifications may be effected therein without departing from the scope or spirit of the present invention.

Claims

WHAT IS CLAIMED IS:

1. A diaphragm-sealed valve comprising: a first body having a first interface provided with a recessed fluid communication channel extending therein, said first body having a first, a second and a common fluid port, each of said ports having a fluid conduct of a predetermined diameter and an open end connected thereto opening into said recessed fluid communication channel for interconnecting each of said ports together through said fluid communication channel, each of said first and second ports having a seat disposed so as to allow fluid communication therearound within said communication channel, the open end of each of said first and second ports having a predetermined diameter smaller than the diameter of the corresponding fluid conduct to limit fluid velocity therein; a second body interconnected with said first body and having a second interface facing said first interface, said second body having a first and a second passage, each of said passages facing one of said first and second ports respectively; a seal member compressibly positioned between said first and second interfaces, said seal member having a shape adapted to cover said first and second ports; a first and a second plunger, each being respectively slidably disposed in one of said passages of said second body, each of said plungers having a closed position wherein the corresponding plunger presses down the seal member against the seat of the corresponding port for closing said corresponding port, and an open position wherein said plunger extends away from the seat of the corresponding port for allowing a fluid communication between the corresponding port and said channel; and actuating means for actuating each of said plungers between said closed and open positions thereof.

2. The diaphragm-sealed valve according to claim 1 , wherein the seat of each of said first and second ports comprises a raised portion extending at a level of the first interface.

3. The diaphragm-sealed valve according to claim 1 , wherein the seal member comprises a metallic diaphragm and a polymer diaphragm arranged in a stacked relationship, said polymer diaphragm having first and second preformed flat elevated portions, each extending above and being pressable against the seat of one of the corresponding first and second ports.

4. The diaphragm-sealed valve according to claim 3, wherein each of said plungers is attached to the corresponding flat elevated portion of the polymer diaphragm.

5. The diaphragm-sealed valve according to claim 1 , wherein the valve is operated with a single pneumatic control pressure.

6. The diaphragm-sealed valve according to claim 5, wherein said actuating means comprise first and second adjusting devices, each being mounted with a corresponding one of the plungers for independently adjusting an operating pressure thereof.

7. The diaphragm-sealed valve according to claim 6, wherein each of said adjusting devices respectively comprises resilient means, each being respectively mounted with a corresponding plunger for biaising said plunger, the first plunger being a normally open plunger while the second plunger is a normally closed plunger.

8. The diaphragm-sealed valve according to claim 7, wherein the adjusting device mounted with the normally closed plunger comprises a Belleville washer assembly and a set up screw pressing against the plunger.

9. The diaphragm-sealed valve according to claim 8, wherein each of said adjusting devices comprises shim elements, each being respectfully mounted with the corresponding plunger for reducing a stroke thereof.

10. The diaphragm-sealed valve according to claim 9, wherein said actuating means comprise a single control valve mounted with a flow restrictor so that said pneumatic control pressure increases progressively from a lower level to an upper level.

11. The diaphragm-sealed valve according to claim 1 , wherein the first plunger is a normally open plunger and the second plunger is a normally closed plunger diametrically larger than the normally open plunger.

12. A diaphragm-sealed valve comprising: a first body having a first interface provided with a plurality of distinct recessed fluid communication channels extending therein, said first body having a plurality of port sets, each comprising a first, a second and a common fluid port, each port of a corresponding set having a fluid conduct of a predetermined diameter and an open end connected thereto opening into a corresponding one of said recessed fluid communication channels respectively for interconnecting each port of said corresponding set together through said corresponding fluid communication channel respectively, each of said first and second ports of each of said sets having a seat disposed so as to allow fluid communication therearound within said corresponding communication channel, the open end of each of the first and second ports of each port set having a predetermined diameter smaller than the diameter of the corresponding fluid conduct to limit fluid velocity therein; a second body interconnected with said first body and having a second interface facing said first interface, said second body having a plurality of passage pairs, each comprising a first and a second passage, each passage of a corresponding pair respectively facing one of said first and second ports of a corresponding set; a seal member compressibly positioned between said first and second interfaces, said seal member having a shape adapted to cover each of said first and second ports of all of said port sets; a plurality of pairs of first and second plungers, each plunger of a corresponding pair being respectively slidably disposed in one of said passages of a corresponding pair, each of said plungers having a closed position wherein the corresponding plunger presses down the seal member against the seat of the corresponding port for closing said corresponding port, and an open position wherein said plunger extends away from the seat of the corresponding port for allowing a fluid communication between the corresponding port and a corresponding channel; and actuating means for actuating each of said plungers between said closed and open positions thereof.

13. The diaphragm-sealed valve according to claim 12, wherein each of said first and second ports are circularly arranged in a port circle concentrical with said first interface.

14. The diaphragm-sealed valve according to claim 12, wherein the seal member comprises a metallic diaphragm and a polymer diaphragm arranged in a stacked relationship, said polymer diaphragm having a plurality of sets of first and second preformed flat elevated portions, each extending above and being pressable against the seat of a corresponding one of the first and second ports.

15. The diaphragm-sealed valve according to claim 1 , wherein the actuating means comprise a plurality of adjusting devices, each being mounted with a corresponding one of the plungers for independently adjusting an operating pressure thereof, the valve being operatable with a single pneumatic control pressure increasing progressively from a lower level to an upper level, thereby allowing a controlled timing sequence of the valve.

16. A method of operating a diaphragm-sealed valve comprising steps of : a) providing a diaphragm-sealed valve having a plurality of normally open and normally closed ports and corresponding plungers having a closed position closing the corresponding port and an open position opening the corresponding port, each of said plungers being provided with an adjusting device for independently adjusting an operating pressure thereof; b) adjusting each adjusting device for adjusting each operating pressure; and c) providing said valve with a pneumatic actuating pressure, the actuating pressure increasing progressively from an initial value to each of the operating pressures until reaching a maximum value, thereby actuating each of said plungers according to a predetermined timing sequence.

17. The method of operating a diaphragm-sealed valve according to claim 16, wherein the operating pressure of each of the normally open ports is smaller than the operating pressures of the normally closed ports for allowing an all-ports- closed position.

18.An analytical chromatographic method using the method of operating a diaphragm-sealed valve as defined in claim 16, the chromatographic method comprising steps of: a) providing a fluid sampling system having a sample inlet, a carrier inlet, a sampling loop having an inlet and an outlet, a sample vent line and analytical means provided with an inlet, each being operatively interconnected to said valve through a corresponding one of said ports; b) providing fluid communication from said sample inlet to the inlet of the sampling loop by actuating the corresponding ports, thereby providing a fluid sample in said sampling loop; c) closing the outlet of said sampling loop by actuating the corresponding port to isolate said sampling loop; d) providing fluid communication from the carrier inlet to the inlet of the sampling loop by actuating the corresponding port to pressurize said sampling loop; e) preventing fluid communication from each of said ports to the remaining ports by actuating the corresponding ports; and f) providing fluid communication from the outlet of the sampling loop to the inlet of the analytical means by actuating the corresponding port, thereby injecting said sample in said analytical means.