What is claimed is
1. A valve system comprising a body, open through means formed in one surface of said body, a membrane positioned against said one surface of said body and acting as one wall of said trough means to provide a closed flow path, a plurality of ports extending into said body and terminating at spaced points on said one surface adjacent to said flow path, partition means separating each of said ports from said flow path at said spaced points, said membrane being elastically deformable in response to fluid pressure to move away from said partition means and allow fluid communication between said ports and said flow path, a plurality of movable means for contacting an opposite surface of said membrane and holding it in contact with each said partition means to close each said port from said flow path, actuator means engaging each said movable means for selectively opening and closing each of said ports to permit fluid flow between said flow path and any selected ports, said membrane being clamped between said body and a block, said block including a series of cylinders located in registration with each of said partition means, said movable means for closing said ports constituting plungers which are reciprocatingly mounted in said cylinders, and said plungers containing separate parts which are slidably interconnected with resilient spring means for transferring force to the part which bears against said membrane to force it in contact with said partition means.
2. A valve system in accordance with claim 1 wherein one end of said flow path connects to a reactor, and wherein a separate valve in said valve system which is opened and closed by said membrane connects to said reactor and to a waste.
3. A valve system in accordance with claim 2 wherein s source of carrier gas is connected to the end of said flow path opposite to said one end to supply gas through said flow path to said reactor.
4. A valve system in accordance with claim 3 wherein means for introducing a sample is connected to said opposite end of said flow path through one of said ports.
5. In a valve system for predetermined addition of reactants selectively to a sample in a reactor, said valve system being adapted to be connected to a sample source, a plurality of reactant sources and reactor means, the combination comprising,
6. A valve system as claimed in claim 5 wherein said trough means is formed in one surface of said body and said valve means comprises a membrane positioned against said one surface of the body acting as one wall of said trough means to provide the closed flow path, partition means separating each of said ports from said flow path, said membrane being elastically deformable in response to fluid pressure to move away from said partition means and allow fluid communication between said ports and said flow path, a plurality of movable means for contacting an opposite surface of said membrane and holding it in contact with each of said partition means to close each said ports from said flow path.
7. A valve system as claimed in claim 6 wherein said membrane is clamped between said body and a block, said block including a series of cylinders located in registration with each of said partition means, said movable means for closing said ports constituting plungers which are reciprocatingly mounted in said cylinders, means for biasing said plungers in a direction away from said partition means, and rotatable cam means for moving said plungers to open and close said ports in a predetermined selective manner during rotation of said cam means.
BACKGROUND OF THE INVENTION
The present invention relates to valve systems. More particularly it is directed to a valve system for connecting multiple passages to a main flow path, which system is particularly adapted for use as a part of chemical analysis apparatus.
Chromatographic analysis, for example gas chromatography, is often used to separate and identify the various components of a sample. These samples are often originally in liquid or solid form and not sufficiently volatile to permit direct gas chromatographic analysis. It is therefore necessary that such samples undergo various preliminary chemical reactions to prepare them for the ultimate identification of their components. In such preliminary reactions, the samples may be treated with several different reactants in various sequentially performed steps.
For repetitive laboratory analyses of samples, the treatment for each sample with proper concentrations of reactants in a particular sequence is desirably automated to facilitate standardized operation with a minimum of manual intervention. Accordingly, it is desirable to have an automatic valve system which facilitates the treatment of a sample with the desired reactants in a predetermined sequence preparatory to final analysis of the sample.
It is an object of the invention to provide an improved valve system designed to handle a plurality of fluid components. It is another object of the present invention to provide a valve system adapted for the addition of reactants to a sample in predetermined amounts and in a predetermined sequence. It is a further object of the present invention to provide a valve system which permits the automatic addition of several different solvents and/or reactants to a reactor while maintaining the reagent supplies out of contact with one another.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other objects of the present invention should be apparent from a reading of the following detailed description and in conjunction with the drawings wherein:
FIG. 1 is a perspective view of a valve system embodying various features of the present invention;
FIG. 2 is a top view of the valve system shown in FIG. 1,
FIG. 3 is a sectional view of the valve system taken along the line 3--3 of FIG. 2; and
FIG. 4 is a fragmentary sectional view of a valve of the present invention taken along the line 4--4 of FIG. 3.
DETAILED DESCRIPTION OF THE INVENTION
Briefly, a valve system 10 (FIG. 1) is provided including a head 12 and a block 14, which in the illustrated embodiment are rectangular in cross section and complementary in size. A deformable membrane 16 is clamped between the head 12 and the block 14. The head 12 contains a series of (inlet or outlet) passageways or ports 18a through 18i (FIG. 2) which extend into the valve head 12 to several of which act as inlets for various reagents, and other of which connect as outlets to collectors. As shown in FIG. 3, each of the ports 18 is a continuous passageway extending from the front surface 19 of the head 12 to the bottom surface 20 abutting the deformable membrane 16 which separates the head and the block. Individual valves A to I are formed at the end of each passageway 18 at the bottom surface 20 in cooperation with the deformable membrane 16.
A flow path 22 (FIGS. 2 and 3) in the form of a downwardly open trough extends longitudinally along the bottom surface 20 of the head from valves B to G. The deformable membrane 16 closes the trough to form a generally closed channel serving as the flow path 22. The illustrated flow path 22 is made up of a plurality of straight sections 23 which interconnect annular sections 24 surrounding each of the ports 18 at the spaced locations at which they emerge into the bottom surface 20. Each port 18 is separated by a ring-shaped wall or partition 26 from the annular sections 24 of the flow path. At each end of the flow path 22, (outlet or inlet) passageways 28 are provided which extend rearward from annular sections 24 to a rear surface 29 of the head 12.
The membrane 16 is elastically deformable and is unsupported on its undersurface in the region of the valves as a result of cavities or cylinders 30 which are provided in the block 14 in underlying registration with each of the annular sections 24 of the flow path. Thus, the application of fluid pressure via the respective inlet passageways 18 to the upper surface of the membrane causes it to move downward away from the partition 26 to permit fluid flow between the ports 18 and the annular sections 24 of the flow path.
To maintain the valves A-I closed until it is desired to open them, plungers 32 (FIGS. 3 and 4) are provided for reciprocating movement in the vertical cylinders 30 and extend through the block 14. Each cylinder 30 has an upper portion 31 of a diameter about the same size as the annular section 24 of the flow path. The plunger 32 in each cylinder 30 has a head 34 of a size greater than the ring-shaped partition 26 and a rod 36 which extends downwardly therefrom. The lower end of the rod 36 is received in a guide 38 which extends below the bottom surface of the block through a lower portion 37 of the cylinder 30 of reduced diameter and provides a bearing surface for the outer surface of the guide 38 which slides therein. In the illustrated embodiment, each of the nine independent valves A-I of the system contains such a guide 38, the bottom surface of which rides along the surface of the rotating cam 40. The shape of the individual cam 40 and the speed of its revolution determines whether a valve will be open or whether the plunger head 34 will be held in contact with the deformable membrane 16 in the latter case forcing it against the partition 26 to close the valve by preventing fluid flow between the port 18 and the longitudinal flow path 24.
The head 12 made of a block of suitable material, such as polytrifluoromonochloroethylene (Kel-F), which is not chemically affected by exposure to the reagents employed and which has a low wettability with respect to most liquids (so there is a high angle of liquid contact with respect thereto). The head 12 is suitably formed by machining or by molding or casting.
Each of the nine ports 18a through 18i (FIG. 3) extends horizontally into the head from the front surface 19 of the valve head 12 to approximately its transverse center. At this point, the horizontal passageway ends at a vertical passageway extending downward to the bottom surface 20 where the deformable membrane 16 is located. Each of the ports 18 is of identical construction, and each port contains a tapered entrance section 41a (FIG. 3) of enlarged diameter which is adapted to receive a tapered plug 41b. Couplings 42, which may each be provided with a calibrated orifice, are attached to the outer ends of the plugs 41b.
In the illustrated embodiment, liquid reagents are fed from supply lines 43 through the orifice-holding couplings 42 into individual valves A, C, E, E, F, and I. By the employment of the separate removable orifice-containing couplings 42, careful metering and regulation of the fluid flow through each of the various ports is accomplished. The size of the particular orifice is determined by the properties, e.g. viscosity, surface tension, and/or density of the liquid which passes therethrough. Generally, a uniform pressure, for example, 1-2 p.s.i.g., of dry inert gas, upon the reagent supplies (not shown) is employed to deliver the liquids to the valves at a constant pressure head.
As stated earlier, the flow path 22 is in the form of a groove or trough formed in the bottom surface 20 of the head 12. The deformable membrane 16 is quite thin and may be of any suitable resilient material that is chemically inert to the various reagents intended to be employed with the valve system 10, for example polytetrafluoroethylene or special types of synthetic rubber. The valve system 10 is designed to operate at relatively low pressures, i.e., 1 to 2 p.s.i.g., and the thickness of the membrane 16 should permit deformation at such pressure differentials whenever the plunger head 34 is withdrawn from the underside of the membrane 16. A typical membrane 16 of polytetrafluoroethylene which may be used is of the order of 2 to 5 mils in thickness. When the plunger 32 is withdrawn from the underside of the membrane 16 (as shown in FIG. 3), it will bow downward as shown to connect the inlet port 18 and the flow path 12 in fluid communication. Such bowing occurs so long as the pressure in either the inlet port 18 or the flow path 22 is above atmospheric (discharge) pressure. The valve construction permits flow in either direction therethrough, depending upon where the higher pressure region is located.
The membrane 16 is substantially coextensive with the entire undersurface 20 of the head 12 and the block 14. The membrane has no openings except those which permit the passage of fastening members, such as capscrews 44, (FIG. 3), which are threaded upward into the head and clamp the membrane 16 between the block 14 and the undersurface 20 of the head 12. The block 14 may be made of any suitable material, as all of the fluid flow passageways are in the head 12 located above the membrane.
Because of its thinness, the membrane 16 does not provide a reliable seal, and a separate resilient gasket 45 (FIGS. 3 and 4) is preferably employed, which is substantially thicker than the membrane 16. The resilient gasket 45 cushions and protects the membrane 16 and avoids the creation of stresses at locations adjacent the cylinder openings 30 where it would otherwise be tightly clamped between two rigid surfaces. The gasket 45 has circular openings which register with each of the cylinders 30 and permit the deformation of the membrance thereinto.
As previously indicated, the illustrated block 14 is provided with nine cylinders 30, wherein plungers 32 are located, below each partition. The plunger 32 in each cylinder 30 selectively seals the respective port 18 in a positive manner by forcing the membrane 16 upward against the partition 26. In the illustrated embodiment, each plunger head 34 is circular, having a flat upper surface upon which a resilient pad 52 of rubber or other suitable material is mounted to engage the membrane 16. The resilient pad 52 avoids damage to the thin membrane 16 which might result from repeated cycling of the plunger 32 into and out of contact with the membrane. The guide 38 has a central bore 54 into which the plunger rod 36 is slidingly accepted. The guide 38 in turn is slidingly received in the lower portion 37 of the cylinder 30 and is provided with a circular flange 56 at its upper extremity that prevents its removal downward from the cylinder.
Near the bottom of the guide 38 (FIGS. 3 and 4) (which carries a wheel 57 that rides along the peripheral edge of the cam 40), a groove is provided to receive a retaining or snapring 58. A coil spring 60 is provided between the retaining ring 58 and the undersurface of the block 14 to bias the guide 38 downward. When the location of the cam 40 allows the guide 38 to move downward, the plunger 32 follows as a result of gravity and the sliding friction between the outer surface of the rod 36 and the bore 54 of the guide. To interconnect the plunger 32 and the guide 38, a second coil spring 62 is located surrounding the rod 36 between the upper surface of the flange 56 on the guide and the undersurface of the piston head 34. In order to permit free movement of the rod 36 within the central bore 54 of the guide, a small air vent 64 is located in the bottom of the guide 38. The provision of the spring 62 cushions the closing of each valve and determines the force with which each plunger 32 contacts the thin membrane 16.
As mentioned earlier, the plunger assembly of each of the nine valves is actuated by means of cams 40 which are mounted on a common shaft 66 positioned therebelow. The radius of each cam 40 is sufficient at at least one location about its periphery to force the guide 38 upward a sufficient distance to cause the resilient pad 52 on the piston head 34 to press the membrane 16 against the partition and close the respective valve. Each cam 40 is relieved to provide one or more cutouts 68 which are of varying size and permit the downward displacement of the guide 38 and plunger 32, thus establishing the desired sequence of valve openings. For purpose of illustration, one cutout 68 is shown on the cam 40 in FIG. 3.
When the guide 38 is forced upward by the cam 40, the coil spring 60 surrounding the guide 38 is compressed, and the flange 56 at the upper end of the guide moves upward. The coil spring 62 surrounding the rod 36 in turn elevates the plunger head 34 and the pad 52 until it contacts the membrane 16 and presses it against the partition 26 and closing the valve. Some compression of the coil spring 62 occurs which cushions the closing of the valve. Thus, the strength of the spring 62 determines the force with which the valve is held closed. The valve remains closed until the cam 40 rotates to position a cutout 68 below the cylinder 30, to permit the lower coil spring 60 to withdraw the guide 38 and the plunger 32 which follows the guide downward. The valve then remains open for the desired length of time which is determined by the speed of rotation of the shaft 66 and the cutout area of the cam 40.
The operation of the valve system 10 may be better understood in connection with an illustrative process wherein the valve system may be utilized. In this respect, reference is made to copending U.S. Pat. application Ser. No. 750,235, filed Aug. 5, 1968, in the names of Milton Winitz and Jack Graff, entitled "Amino Acid Analysis," or to Analytical Chemistry, 34, No. 11, 1414 (Oct. 1962). This copending application describes a process for analyzing a biological sample to quantitatively determine the amounts of amino acids therein.
To facilitate treatment of a biological sample according to the teaching of this copending application, a sample holder 72 (FIG. 1) is connected between lines 28a and 28b. A reactor 74 wherein the programmed reaction takes place is connected between lines 28c and 28d. The biological sample, which may for example be human blood (containing a mixture of nonvolatile amino acids), is first pretreated using cationic exchange resins and then eluted from the resins, using a suitable liquid such as acidified n-propanol. The eluted sample which contains the amino acids is then transferred manually to the sample holder.
The automatic programming of the device then takes place with the shaft 66 being driven by a suitable motor (not shown) at the desired rate of rotation, e.g., 1 revolution an hour, causing the cams 40 to actuate the individual valves A to I at the desired sequences. When the process is actuated, a slow constant flow of dry inert gas, for example nitrogen, is fed to the sample holder 72 through the line 76 and carries the sample through the line 28b to the valve B. The cams 40 are arranged so that the valves A and B open generally in unison, and additional solvent for the sample is supplied to the sample holder 72 through the valve A. The carrier gas entering through the line 76 moves the sample and solvent to the valve B. For convenience in making connection, the construction of the valve B is reserved with respect to the valve A (as seen in FIG. 2), and the line 28b connects to the center of the valve B whereas the port 18b connects the annular section 24.
To facilitate movement along the flow path 22 toward the reactor 74, an ancillary flow of dry nitrogen is fed through the port 18b throughout the operation of the device. This nitrogen flow assists travel along the flow path into the reactor 74 during the time allotted.
At the end of the flow path 22, the sample passes out the line 28c and into the reactor 74 for conversion to volatile amino acid derivatives preparatory to gas-liquid chromatography. Here, a liquid gas separation takes place, and the gas flows through the line 28d and out the valve H, which is open throughout most of the process, to a line 78 leading to a waste container 80. While the valves A and B are open, the carrier gas flows through the sample holder 72 to assure that the sample holder is completely cleared of sample and solvent.
After the sample has been transferred to the reactor 74, different reagents are supplied sequentially by systematically opening the valves C, D, E and F. The reagents sequentially: (1) dry the sample by azeotropic distillation, (2) esterify the amino acids, (3) again dry by azeotropic distillation, (4) acetylate to form a volatile derivative, and (5) again dry. In carrying out the process described in the copending patent application, a mixture of n-propanol and benzene (as azeotroping agent) is supplied through valve c, and anhydrous n-propanol-HC1 (esterification agent) is supplied through valve D. Acetic anhydride (acetylating agent) is supplied through valve E, and pyridine (to neutralize the (HC1) is supplied through valve F. It takes the cams 40 about 60 minutes to make one complete revolution, and during this time various of the valves open and close more than once.
As previously indicated, the valve H remains open until the reaction is complete and then closes. When the valve H closes, the valves G and I open. The valve I leads to an open top collector 82. A source of dry nitrogen gas and a suitable solvent, such as ethyl acetate, is connected to valve I. Accordingly, the ethyl acetate is carried in a line 28d into the reactor 74, where it dissolves the sample, and flows out of the bottom of the reactor through line 28c leading to the flow path 22. Because the valve G is open and because the supply of carrier gas continues into the port 18b, preventing flow of the liquid from the reactor along the flow path 22, the liquid leaving the reactor passes out the valve G through the port 18g to the open top collector 82.
In an operation such as this, it is important that metered amounts of liquid be fed to the reactor 74 throughout the individual process steps. Metering of the liquids is carried out by the amount of time the individual valves are open and by the size of the individual orifices disposed in the receptive couplings 42 connected between supply of reagent and the port leading to the valve. A relatively constant gas pressure, for example 1 to 2 p.s.i.g., is maintained on all of the reagent supplies, and it is this gas pressure which causes the flow of liquid whenever the valves A, C, D, E or F are opened. Thus, based upon this constant driving pressure, the desired amount of flow is established by choosing the proper size orifice relative to the amount of time that the valve will be open. For a different reaction or when a liquid of different physical properties is employed, a desired timed flow can be achieved simply by changing the orifice size, within certain limits.
Although the invention has been illustrated with respect to a particular arrangement of a flow path and interconnected valves, it will be understood that many variances are possible using the basic valve system to provide automatic, timed, sequential flow of liquids for use in chemical processes, particularly preliminary to anaylsis.
The arrangement of the individual valves located generally interior of the annular sections 24 of a longitudinal flow path provides an arrangement wherein there is essentially zero dead space at the valves wherein reagents might accumulate and influence subsequent steps, as for example by interreacting with another reagent being supplied for a subsequent step. The constant purge flow of carrier gas throughout the longitudinal flow path 22 during the operation assures the transportation of the liquids injected into the system through the individual valves (particularly when the head 12 is made of a material having the low wettability of Kel-F). This serves as a positive prevention of any undesirable accumulation in the flow path. Likewise, provision of orifices in couplings 42 which can be substituted to change the size thereof affords flexibility in establishing precise metered amounts of liquid being fed to the reactor during any single step, and it also affords adaptation of the overall system to other liquids having different physical properties.
Other modifications as would be apparent to one skilled in the art may be made to the illustrated valve system without departing from the scope of the invention which is defined in the appended claims. Various of the features of the invention are set forth in the following claims.