Gradient proportional valve

Abstract

The present invention discloses a gradient proportional valve for liquid chromatography, the gradient proportional valve comprising a plurality of inlet ports configured to receive a plurality of fluids; a manifold connected to each of the plurality of inlet ports, the inlet ports configured to mix the plurality of fluids in a controlled manner to provide a liquid composition, the manifold including a plurality of conduits inside the manifold, the plurality of conduits being configured to receive the plurality of fluids from the plurality of conduits, each conduit of the plurality of conduits receives fluid through a respective inlet port of the plurality of inlet ports; an actuation mechanism having a piston located within a bore structure surrounding the piston, the actuation mechanism configured to open and close at least one conduit of the plurality of conduits in a controlled manner, where the piston and the bore structure have a tight tolerance configured to create a fluid tight seal; and a common outlet port configured to receive the fluid composition.

Description

[0001] Related Applications This application is a non - provisional patent application claiming priority to U.S. Provisional Patent Application No. 62 / 941,236, filed on November 27, 2019, entitled "Gradient Proportioning Valve", which is incorporated herein by reference. Technical Field

[0002] The present invention generally relates to gradient proportioning valves. More specifically, the present invention relates to gradient proportioning valves having damping features and associated systems and methods. Background Art

[0003] In liquid chromatography, a solvent manager is used to deliver mobile - phase solvents to the rest of the instrument stack with very precise flow rates, pressures, and solvent compositions. In one example, a quaternary solvent manager (QSM) is a solvent manager that measures and mixes solvents at low pressure before pressurization and delivers the solvents to the rest of the instrument stack. Metering of solvents at low pressure is typically performed by a gradient proportioning valve (GPV).

[0004] Known GPVs are used in low - pressure mixing liquid chromatography systems (i.e., quaternary systems). U.S. Patent No. 5,862,832 describes an exemplary prior - art GPV. Specifically, the GPV is responsible for setting the desired solvent composition in the system. A typical GPV includes a plurality of solenoid valves mounted on a common manifold that open and close relative to the system pump cycle at precise times. When opening and closing the GPV solenoid valves, pressure pulses are introduced into the system. Pressure pulses are also caused by the start and end of the intake stroke during the pump cycle. Such pressure pulses can cause unwanted oscillations in the composition error of the chromatography system. Thus, these oscillations reduce the composition accuracy and performance of the liquid chromatography system.

[0005] When switching inlet channels open and closed, a typical GPV uses a flexible diaphragm or a lift valve to form a seal. At each actuation, unwanted pressure pulses are generated by the valve and introduced into the solvent. These pressure pulses cause errors in the solvent metering using the GPV and can thus affect the composition accuracy and the user's chromatography method. Some GPV designs utilize accumulator diaphragms upstream of each inlet channel to mitigate the pressure pulses introduced by valve actuation. While these accumulator chambers improve performance, the accumulator chambers are expensive, require a large amount of space in the manifold, and limit the design freedom. There may also be limitations to the effectiveness of the accumulator chambers as the flow rate increases.

[0006] Therefore, improved GPVs that reduce or attenuate unwanted pressure pulses are well received in the art. Summary of the Invention

[0007] In one embodiment, a gradient proportioning valve for liquid chromatography includes: a plurality of inlet ports configured to receive a plurality of fluids; a manifold connected to each of the plurality of inlet ports, the inlet ports being configured to mix the plurality of fluids in a controlled manner to provide a fluid composition, the manifold including a plurality of conduits inside the manifold, each of the plurality of conduits receiving fluid through a corresponding one of the plurality of inlet ports; an actuation mechanism having a piston located within a drilled structure surrounding the piston, the actuation mechanism being configured to open and close at least one of the plurality of conduits in a controlled manner, wherein the piston and the drilled structure have a tight tolerance configured to create a fluid-tight seal when the actuation mechanism closes at least one of the plurality of conduits; and a common outlet port configured to receive the fluid composition.

[0008] Additionally or alternatively, the gradient proportioning valve further includes a separate actuation mechanism for each of the plurality of conduits, each of the separate actuation mechanisms having a piston located within a bore, the bore having a tight tolerance configured to create a fluid-tight seal.

[0009] Additionally or alternatively, the piston and the bore create a fluid-tight seal without a deformable seal element.

[0010] Additionally or alternatively, the actuation mechanism is an electromagnetic valve.

[0011] Additionally or alternatively, the piston is made of ceramic.

[0012] Additionally or alternatively, the actuation mechanism is configured to open and close two or more of the plurality of conduits.

[0013] Additionally or alternatively, the piston is configured to rotate about the drilled structure to open and close at least one of the plurality of conduits in a controlled manner.

[0014] Additionally or alternatively, the piston is configured to rotate less than 90 degrees to open and close at least one of the plurality of conduits in a controlled manner.

[0015] Additionally or alternatively, the piston includes a flat surface in the keyed side.

[0016] Additionally or alternatively, the piston extends axially along its length, wherein the piston includes a bore extending axially within the piston, the bore being configured to receive fluid and discharge fluid from the piston.

[0017] Additionally or alternatively, the tight tolerance creates a gap of 5 microns or less between the piston and the drilled structure.

[0018] Additionally or alternatively, the piston is configured to axially move within the bore structure to open and close at least one of the plurality of conduits in a controlled manner.

[0019] Additionally or alternatively, the piston is configured to axially move and rotate relative to the bore structure.

[0020] In another embodiment, a method of mixing fluids includes providing a gradient proportioning valve including a manifold having a plurality of conduits; receiving a plurality of fluids at a plurality of inlet ports of the gradient proportioning valve; opening and closing each of the plurality of conduits in a controlled manner by an actuating mechanism having a piston located within a bore structure surrounding the piston, maintaining a fluid tight seal between the piston and the bore structure during the opening and closing, wherein the piston and the bore structure have tight tolerances configured to create a fluid tight seal; mixing the plurality of fluids in a controlled manner within the manifold of the gradient proportioning valve; and outputting a fluid composition from a common outlet port of the gradient proportioning valve.

[0021] Additionally or alternatively, the method further includes preventing unwanted fluid pressure pulses in the manifold by the actuating mechanism by minimizing the internal fluid volume within the piston and the bore structure.

[0022] Additionally or alternatively, the actuating mechanism is made of ceramic.

[0023] Additionally or alternatively, the method further includes opening two or more of the plurality of conduits by the actuating mechanism.

[0024] Additionally or alternatively, the method further includes rotating the piston about the bore structure to open and close at least one of the plurality of conduits in a controlled manner.

[0025] Additionally or alternatively, the method further includes axially moving the piston within the bore structure to open and close at least one of the plurality of conduits in a controlled manner.

[0026] Additionally or alternatively, the method further includes moving the piston both axially and rotationally relative to the bore structure.

[0027] In another embodiment, a liquid chromatography system includes: a gradient proportioning valve for liquid chromatography, the gradient proportioning valve including: a plurality of inlet ports configured to receive a plurality of fluids; a manifold connected to each of the plurality of inlet ports, the inlet ports being configured to mix the plurality of fluids in a controlled manner to provide a fluid composition, the manifold including a plurality of conduits inside the manifold, each of the plurality of conduits receiving fluid through a corresponding one of the plurality of inlet ports; an actuating mechanism having a piston located within a drilled structure surrounding the piston, the actuating mechanism being configured to open and close at least one of the plurality of conduits in a controlled manner, wherein the piston and the drilled structure have a tight tolerance configured to create a fluid tight seal when the actuating mechanism closes at least one of the plurality of conduits; and a common outlet port configured to receive the fluid composition; an injector; a separation column; and a detector. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The above and other advantages of the present invention will be better understood by reference to the following description in conjunction with the accompanying drawings, in which like reference numerals refer to the same elements and features in each of the drawings. For clarity, not every element is labeled in each drawing. The drawings are not necessarily to scale, and emphasis is placed on illustrating the principles of the invention.

[0029] Figure 1 A schematic diagram of a liquid chromatography apparatus according to one embodiment is depicted.

[0030] Figure 2 A perspective view of a gradient proportioning valve according to one embodiment is depicted.

[0031] Figure 3 Depicts a side cross-sectional view of a gradient proportioning valve according to one embodiment of Figure 2

[0032] Figure 4 Depicts a schematic diagram of a gradient proportioning valve according to one embodiment of Figures 2 - 3

[0033] Figure 5 A schematic cross-sectional view of an actuating mechanism for a switching valve according to one embodiment is depicted.

[0034] Figure 6 A schematic cross-sectional view of an actuating mechanism for a switching valve according to one embodiment is depicted.

[0035] Figure 7 A schematic cross-sectional view of an actuating mechanism for a switching valve according to one embodiment is depicted.

[0036] Figure 8Depicts a schematic cross-sectional view of an actuating mechanism for a switching valve according to an embodiment.

[0037] Figure 9 Depicts a schematic diagram of a gradient proportioning valve according to an embodiment.

[0038] Figure 10 Depicts a schematic cross-sectional view of an actuating mechanism for a switching valve according to an embodiment.

[0039] Figure 11 Depicts a schematic cross-sectional view of an actuating mechanism for a switching valve according to an embodiment.

[0040] Figure 12 Depicts a schematic cross-sectional view of an actuating mechanism for a switching valve according to an embodiment.

[0041] Figure 13 Depicts a schematic diagram of a gradient proportioning valve according to an embodiment.

[0042] Figure 14 Depicts a schematic cross-sectional view of an actuating mechanism for a switching valve according to an embodiment. Detailed Description

[0043] References to "an embodiment" or "embodiments" in this specification mean that a particular feature, structure, or characteristic described in connection with the embodiments is included in at least one embodiment of the present teachings. References to particular embodiments in this specification are not necessarily all referring to the same embodiment.

[0044] The gradient proportioning valve accommodates a fluid flow from an external reservoir into the valve for mixing in a proper proportion to form a liquid composition in liquid chromatography. The gradient proportioning valve described herein includes an inlet conduit in communication with one or more inlet valves that are normally closed. The actuating mechanism can be switched open in a controlled manner to provide the appropriate amount of fluid required when mixing the liquid composition. The function of the entire valve is to provide a continuous flow of an accurately synthesized mixture of components, such as solvents in a high-performance liquid chromatography (HPLC) embodiment. The mixture can be provided from a common outlet under flowing conditions without disturbing the flow rate of the fluid input system and without altering or otherwise affecting the quality / composition of the fluid inputs used for mixing.

[0045] The embodiments of the gradient proportioning valve described herein can be configured to attenuate or otherwise reduce pressure pulses that occur due to the opening and closing of channels in the valve's fluid system and in the valve itself. Such pressure pulses have been found to cause large sinusoidal oscillations in the composition error. Thus, the gradient proportioning valve described herein can be configured to provide improved composition accuracy across the solvent composition range. This improved composition accuracy can be particularly important at higher flow rates.

[0046] In embodiments of the gradient proportioning valve described herein, each of the one or more actuating mechanisms that open and close the inlet conduit includes a plunger or piston mechanism that operates in conjunction with a drilled structure. By fabricating the plunger and the drilled structure with very tight tolerances, a seal is formed when the plunger is inserted into the drilled structure. Using the plunger and drilled structure with high-precision dimensions as a sealing mechanism, the gradient proportioning valve reduces or minimizes the volume of liquid storage in the gradient proportioning valve and results in little or no pressure pulse downstream of the actuating mechanism. As described herein, tight tolerances describe a situation where the gap between the plunger and the drilled structure can be less than 6 micrometers. For example, in some embodiments, it is contemplated that the gap between the plunger and the drilled structure is between 2 micrometers and 5 micrometers. Such tight tolerances and low gaps can provide a fluid-tight seal without the need to deploy a deformable sealing element or other seals. Additionally, embodiments herein contemplate ceramic materials for the piston and / or the surrounding drilled structure.

[0047] Figure 1 is a block diagram of an exemplary liquid chromatography system 100 suitable for preparative or industrial liquid chromatography according to an embodiment of the present invention. System 100 is an exemplary system and, according to the embodiments described herein, may include a gradient proportioning valve therein. Apparatus 100 includes four solvent reservoirs 1A, 1B, 1C, 1D; a gradient proportioning valve 2; an inlet manifold valve 3; a pump 4; a solvent mixer 5; an injector 8; a separation column 6; a detector 7; and a control unit 9. Gradient proportioning valve 2 represents a valve that includes one or more of the damping features described herein. Thus, gradient proportioning valve 2 can be Figures 2 - 12 any of the gradient proportioning valves shown and described below.

[0048] In operation, the gradient proportioning valve 2 and the pump 4 select and draw one or more solvents from the reservoirs 1A, 1B, 1C, 1D in response to the control of the control unit 9. The gradient proportioning valve 2 can operate in response to the control of the control unit 9 to provide a selected solvent composition, which optionally varies over time, for example to implement gradient mode chromatography. The solvent mixer 5 is any suitable mixer, including known passive and active mixers. The injector is any suitable injector 8, including known injectors, for injecting a sample into the solvent stream. The injector 8 is optionally positioned at an alternative location in the solvent flow path, as will be understood by those of ordinary skill in the field of liquid chromatography. The inlet manifold valve 3 is connected from the gradient proportioning valve 2 to the outlet tube and to two inlet tubes connected to the pump 4 to supply the solvent to the two piston chambers. The inlet manifold valve 3 optionally includes a sample injector to inject the sample into the solvent before the sample enters the pump 4. The control unit 9 (including, for example, a personal computer or a workstation) receives data and / or provides control signals to, for example, the gradient proportioning valve 2, the pump inlet manifold 3, the pump 4, and / or the detector 7 via wired and / or wireless communication. The control unit 9 supports, for example, the automation of sample processing. In various illustrative embodiments, the control unit 9 is implemented in the form of software, firmware, and / or hardware (e.g., as an application specific integrated circuit). The control unit 9 includes a storage component and / or communicates with one or more storage components.

[0049] Suitable implants for the control unit 9 include, for example, one or more integrated circuits, such as a microprocessor. In some alternative embodiments, a single integrated circuit or microprocessor includes the control unit 9 and other electronic parts of the device 100. In some embodiments, one or more microprocessors implement the software enabling the functions of the control unit 9. In some embodiments, the software is designed to run on a general-purpose device and / or a dedicated processor dedicated to the functions described herein.

[0050] In some embodiments of the system 100, the control unit 9 includes a user interface to support interaction with the control unit 9 and / or other parts of the system 100. For example, the interface is configured to accept control information from the user and provide information about the system 100 to the user. The user interface is used, for example, to set system control parameters and / or provide diagnostic and troubleshooting information to the user. In one embodiment, the user interface provides networked communication between the system 100 and a user located locally or remotely from the operating environment. In some embodiments, the user interface is used to modify and update the software. Given the description of the illustrative embodiments provided herein, it will be apparent to those of ordinary skill in the separation field that various other configurations and embodiments of the control unit can be utilized in other embodiments of the present invention to provide automatic control of industrial and preparative chromatography.

[0051] The pump 4 can be configured to provide solvent at a pressure of at least 500 psi, or 1,000 psi, or 5,000 psi, 10,000 psi or greater. The pump includes any suitable piston-based pump, including known pumps such as those available from Waters Corporation, Milford, Mass. The column 6 is any column suitable for industrial and preparative chromatography. The column contains any medium suitable for such purposes, including known media. The adsorbent material is selected from any suitable adsorbent material, including known materials such as silica or a mixture of silica and a copolymer with, for example, an alkyl compound. The solvent is any solvent suitable for the desired separation process, including known solvents.

[0052] Similarly, the system 100 described above is intended to be an exemplary liquid chromatography system in which various embodiments of a gradient proportioning valve can be deployed. However, the gradient proportioning valve described herein can be implemented in any system that performs gradient fluid mixing. For example, in a liquid chromatography quaternary system, after the solvent reservoirs 1A, 1B, 1C, 1D, the next component into which the solvent enters can be a degassing chamber. The solvent can enter the gradient proportioning valve 2 from the degassing chamber. After the gradient proportioning valve 2, the solvent can then pass through a check valve to the pump (i.e., an inlet manifold valve is not required). Any liquid chromatography system configuration in which a gradient proportioning valve is deployed is contemplated for incorporating the principles described herein.

[0053] Now referring Figure 2 , a perspective view of a gradient proportioning valve 2A according to one embodiment is shown. The gradient proportioning valve 2A includes accumulators 19A, 19B positioned directly adjacent to switching valves 17A, 17B, the accumulators being on the side closest to the reservoirs 10A, 10B. It should be understood that embodiments of the gradient proportioning valve 2A can include two additional accumulators and switching valves (not shown) on two open sides of the gradient proportioning valve 2A, thereby connecting the gradient proportioning valve 2 to two additional reservoirs, such as Figure 1 the reservoirs 1C, 1D shown in. Each of the accumulators 19A, 19B can include a soft-walled flexible plastic tube 50 having a generally circular cross-section. As shown, the accumulator 50 can be adapted to be positioned at the end closest to the valve inlet to slide snugly over a rigid plastic connector 52. A connecting tube 54 can be implemented at the opposite end of the accumulator tube to maintain a relatively long length of flow tube 56 connecting the valve to the reservoirs 1A, 1B. The end of the accumulator tube adjacent to the connecting tube can be given a cross-section of a generally flattened ellipse 55, which can allow significant internal volume changes in the accumulator tube with little pressure change, thereby allowing the accumulator to overcome the effects of hydraulic inertia.

[0054] Figure 3Depicts a side cross-sectional view of a gradient proportioning valve 2A according to one embodiment. The gradient proportioning valve 2A includes a valve manifold 10 that houses a fluid flow from an external reservoir (not shown). For the sake of clarity in the following discussion, the illustrative valve described herein has the ability to mix only two input fluid flows. However, the features described herein can be applied to valve mixing, such as four or more input fluid flows. Input fluid flows to be mixed are received from a reservoir and introduced into the valve at an inlet port 12. Fluid (e.g., solvents used in HPLC) from corresponding reservoirs, as is known in the art, flows into the respective inlet ports 12 and then through respective inlet conduits 14 in the manifold 10 into respective accumulator volumes or chambers 16. Although Figure 2 the embodiment shown in Figure 3 includes an accumulator volume or chamber 16, other embodiments contemplated herein may not include an accumulator chamber 16. Such embodiments may include inlet ports that provide fluid directly to switching valves 17A, 17B without first passing through an accumulator chamber.

[0055] As shown, the integrated accumulator chamber 16, as well as the inlet port 12 and inlet conduit 14, are sized appropriately in accordance with the flow rate variations of the valve application. Chamber 16 is conical, having a conical base opposite the inlet conduit 14. The chamber is shaped to maximize the surface area of the diaphragm (for compliance), and the inlet conduit 14 is positioned to allow for an optimal swept volume geometry. Thus, chamber 16 also has a smooth transition from a larger cross-section to a smaller cross-section. The placement of the chamber is such that the fluid resistance between the switching valves 17A, 17B and the accumulator is minimized. The fluid flowing through conduit 14 flows perpendicular to the conical base into chamber 16 to limit the base or back of chamber 16.

[0056] An accumulator diaphragm 18 is disposed at the conical base or back of chamber 16, opposite the inlet conduit 14. The diaphragm 18 in this illustrative embodiment is a 0.002-inch thick film formed of polytetrafluoroethylene (PTFE) with fluorinated ethylene propylene (FEP) laminated on each side. Diaphragm 18 affects the membrane or compliant member at the back of accumulator chamber 16 to allow for internal volume changes in the chamber with very little pressure variation.

[0057] The oversized hole 20 behind the conical base or back side of the liquid reservoir chamber 16 is configured to receive the diaphragm 18 to tightly clamp and seal the diaphragm in the liquid reservoir chamber. The seating surface 22 inside the hole 20 provides an abutment against the diaphragm seat. The sealing groove 24 is disposed in the seating surface 22 and provides part of a single seal implemented in an embodiment according to the present invention. The cylindrical sealing plug 26 formed of stainless steel includes a sealing ridge 28 that tightly fits into the sealing groove 24 to seal the diaphragm in the hole 20 when the plug 26 engages against the seating surface 22, where the diaphragm is clamped between the plug and the seating surface.

[0058] Preferably, the sealing plug 26 is sized to fit tightly but slidably fit within the hole 20. The plug 26 is held in place by a clamping plate 30 that is mechanically attached to the valve manifold by screws 32. Additional mounting holes 33 are provided in the clamping plate 30 to facilitate the mechanical fastening of the clamping plate to the valve manifold 10. In this illustrative embodiment, an elastic member such as a Belleville spring 34 or washer is disposed between the sealing plug 26 and the clamping plate 30 to provide some elasticity.

[0059] The diaphragm can overcome hydraulic inertia while minimizing the volume of fluid in the valve exposed to potential air penetration by restricting the surface area of the diaphragm exposed to ambient air. An atmosphere port 36 is provided in the clamping plate 30 to allow ambient air to be present at the back side of the diaphragm 18. When diaphragm exposure to ambient air is desired, the reduced surface area of the interior of the atmosphere port significantly limits air penetration through the diaphragm.

[0060] Thus, in operation, an input fluid stream to be mixed is received from a reservoir and introduced into the valve manifold 10 at the inlet port 12. Fluids from the respective reservoirs flow into the respective inlet ports 12 and thereafter flow through the respective inlet conduits 14 in the manifold 10 into the respective liquid reservoir volumes or chambers 16. The fluid to be mixed exits the chamber 16 through the chamber port 38, and thus the fluid is available at the switching valves 17A, 17B. The switching valves 17A, 17B operate according to the principles of the present invention described below. The controlled switching of the switching valves 17A, 17B determines the proportion of the respective fluids received in the common port 42 within the valve manifold 10. The respective fluids are mixed in the common port 42 in their respective proportions and are available at the outlet port 44 for downstream processing as known in the art.

[0061] Although in Figure 3Only two input valve embodiments are described herein, but it should be understood that the concepts according to the present invention can be implemented in valves having any number of inlet ports for mixing liquid compositions. Further, while the embodiments described herein include a single switching valve 17A, 17B for each inlet port 12, in other embodiments, the single switching valves 17A, 17B can be operative to open and close a plurality of inlet ports 12, as described below.

[0062] Figure 4 FIG. 4 depicts a schematic view of another gradient proportioning valve 2B according to one embodiment. The gradient proportioning valve 2B is schematically shown and includes four separate inlet ports 12 that provide fluid to a reservoir chamber 16 (such as Figure 3 the chamber 16 shown) via conduits or channels. Figure 3 Different from Figure 4 the embodiment shown in FIG. 5, in the embodiment shown in FIG. 6, there are four separate reservoir chambers 16 to accommodate the four inlet ports 12. Further, separate switching valves 17A, 17B, 17C, 17D are present downstream of each of the reservoir chambers 16. Each of the four switching valves 17A, 17B, 17C, 17D individually outlets fluid to a downstream mixing point 50 where the fluids are combined into a single stream. An outlet 44 is present downstream of the mixing point 50.

[0063] Figure 4 FIG. 7 shows an exemplary schematic view of the gradient proportioning valve 2B where each inlet channel includes its own valve 17A, 17B, 17C, 17D. Further, the schematic view shows one reservoir chamber 16 for each inlet port 12. In other contemplated embodiments, a reservoir chamber 16 may not be required prior to the mixing valves 17A, 17B, 17C, 17D. In still other embodiments (such as those described below), the reservoir chamber and switching valve combination can be configured to receive more than one inlet, e.g., a single reservoir chamber and switching valve for two or more inlets. However, for the embodiment shown in FIG. 7, a single actuation mechanism is shown for each inlet port. Such a schematic view can be used to describe embodiments consistent with the actuation mechanism shown in FIG. 8 and described below. Figure 4 FIG. 7, a situation where a single actuation mechanism can be used for each inlet port is shown. Such a schematic view can be used to describe embodiments consistent with the actuation mechanism shown in Figures 5 - 8 FIG. 8 and described below.

[0064] Several embodiments of an actuation mechanism for a switching valve, such as one of the switching valves 17A, 17B, 17C, 17D described above, are described below. Below, with respect to Figures 5 - 9 , Figure 11 , Figure 12 and Figure 14The described embodiments of the actuating mechanism for the switching valve can be implemented via any switching valve mechanism configured to move a piston relative to a bore structure or cylinder. For example, the rotational movement of the piston relative to the bore structure can be actuated by a stepper motor, a servo motor, or any other rotary actuator. The axial movement can be controlled by a solenoid, a voice coil, a piezoelectric actuator, or any other axial actuator. Additionally, while the embodiments below describe various forms of actuating mechanisms for switching fluid flow, other embodiments consistent with the principles described herein are envisioned.

[0065] Furthermore, the embodiments described below can use ceramic materials for the piston and / or the bore structure. The piston and the bore structure can be manufactured with tight tolerances so as to produce a clearance of less than 6 microns. The tight tolerances can provide a fluid-tight seal between the conduits of the actuating mechanism without the use of additional deformable sealing elements between the components. Depending on the exact requirements of the particular design, the tolerances and material properties of the embodiments described herein can vary. For example, the operating pressure, the piston and / or bore size, the choice of material, etc. can all affect the ability to achieve a seal via precision-machined components without the use of external sealing components (such as deformable seals).

[0066] In the embodiments described herein, ceramic materials can be particularly advantageous due to their ability to be manufactured with extremely tight tolerances. Additionally, the high hardness of ceramics, as well as the wear resistance, corrosion resistance, and oxidation resistance of ceramics, can make ceramic materials particularly advantageous. Ceramics can also prevent the introduction of unwanted temperature effects. However, other chemically inert metals or other materials are envisioned. Examples of other materials can include stainless steels such as Nitronic 60; titanium; nickel-cobalt alloys such as tantalum, etc.

[0067] In the following embodiments, the bore structure is shown with various inlet and outlet conduits that allow fluid flow through the piston occupancy area of the actuating mechanism. While the inlet and outlet conduits are shown in the following Figures 5 - 9 、 Figure 11 、 Figure 12 and Figure 14 as openings in the bore structure in each cross-sectional view, it should be understood that a manifold or housing can be attached to the outside of the bore structure of each embodiment for connecting external fluid conduits thereto. Such a manifold or housing can be made of, for example, a different material such as plastic. The bore structure can be accommodated within the plastic manifold in a variety of ways, including but not limited to being pressed in, heat-shrinking the plastic manifold around the bore, etc. Accommodating the bore structure in this way can provide ease in connecting and aligning the ceramic (or other material) inlets and outlets with the inlet and outlet channels of the solvent lines in a liquid chromatography system.

[0068] Furthermore, while shown below inFigures 5 - 9 , Figure 11 , Figure 12 and Figure 14 describe embodiments in which the piston and the corresponding bore structure are cylindrical in shape and structure, but it is also contemplated that the pistons and bore structures described herein can take the form of various shapes not limited to cylinders. Further, while the pistons are described as moving components in the embodiments described below, it should also be understood that the bore structure can be the moving component rather than the piston. It should be understood that the embodiments contemplated herein require relative movement between the pistons and their corresponding bore structures, but movement of either or both of these components can create the necessary relative movement.

[0069] Although not shown in the cross-sectional views below, the actuation mechanisms described herein can utilize one or more hard stop features to facilitate alignment between the pistons and their corresponding bore structures and to help control and prevent unwanted movement. In embodiments that utilize hard stop features, shock absorbing material can be added to any of these hard stop features to reduce wear.

[0070] Now referring to Figure 5 , a schematic cross-sectional view of an actuation mechanism 200 for a switching valve according to one embodiment is depicted. The actuation mechanism 200 includes a piston 210 located within a bore structure 212. An inlet conduit 214 and an outlet conduit 216 provide fluid through the actuation mechanism 200. The piston 210 includes a key flat surface 220 cut out therefrom, which forms an open space 218 between the piston 210 and the bore structure 212. Although a space is shown between the piston 210 and the bore structure 212, it should be understood that the present invention contemplates using a very tight clearance between the piston 210 and the bore structure 212 such that there is little space between them. Similarly, a clearance of less than 6 microns is contemplated in order to maintain a fluid tight seal when the piston 210 rotates to close one or more of the inlet and outlet conduits 214, 216 without the use of any external sealing components or deformable seals.

[0071] Although only the top cross-sectional view of the actuation mechanism 200 is shown, it should be understood that the actuation mechanism includes an appropriate depth to accommodate the inlet conduit 214 and the outlet conduit 216 and to accommodate the attachment of the piston 210 to the motor to effect rotational movement. Although the depth of the piston 210 and the bore structure 212 can be greater than the amount required to accommodate the inlet conduit 214 and the outlet conduit 216, the key flat surface 220 and the open space 218 can be specifically designed to correspond to the depth required to accommodate the inlet conduit 214 and the outlet conduit 216 to minimize the volume of the open space 218.

[0072] The actuation mechanism 200 can be configured to open and close the inlet conduit 214 and the outlet conduit 216 via rotation of the piston 210 about the bore structure 212. Figure 5 The position in shows the actuation mechanism 200 in an open state, whereby fluid can flow through the inlet 214 into the open space 218 created by the key flat surface 220 of the piston 210. A clockwise rotation from this open position will close the inlet conduit 214, while a counterclockwise rotation will close the outlet. The actuation mechanism 200 can deploy either of these rotations to effect opening and closing of the conduits 214, 216. Additionally, an angle θ is shown, which defines the rotational distance between the inlet conduit 214 and the outlet conduit 216. It may be desirable to include a relatively small angle θ, such as less than 90 degrees, in order to reduce the size of the open space 218 in the system. Reducing the size of this open space 218 and rapidly opening and closing the inlet via the small angle θ can help reduce or eliminate pressure pulses generated by the actuation mechanism 200.

[0073] Figure 6 A schematic cross-sectional view of another actuation mechanism 300 for a switching valve according to one embodiment is depicted. The actuation mechanism 300 includes a piston 310 located within a bore structure 312. The inlet conduit 314 and the outlet conduit 316 are provided with fluid via the actuation mechanism 300. The piston 310 includes a conduit 318 that extends through the piston to connect the inlet conduit 314 with the outlet conduit 316 when the piston 310 is in the opposite position of the shown bore structure 312. As with the previous embodiment, a gap of less than 6 microns is envisioned between the piston 310 and the bore structure 312 in order to maintain a fluid tight seal when the piston 310 rotates to close the inlet conduit 314 and the outlet conduit 316 without the use of any external sealing components or deformable seals.

[0074] Although only the top cross-sectional view of the actuation mechanism 300 is shown, it should be understood that the actuation mechanism includes an appropriate depth to accommodate the inlet conduit 314 and the outlet conduit 316 and to accommodate the attachment of the piston 310 to the motor to effect rotational movement. The actuation mechanism 300 can be configured to open and close the inlet conduit 314 and the outlet conduit 316 via rotation of the piston 310 about the bore structure 312 in either direction relative to the shown position. Figure 6The position in [description] shows the actuating mechanism 300 in an open state, whereby fluid can flow from the inlet conduit 314 through the conduit 318 of the piston 310 and out of the actuating mechanism 300 through the outlet conduit 316. The actuating mechanism 200 can be deployed by rotating clockwise or counterclockwise to achieve opening and closing. In addition, the angle θ between the inlet conduit 314 and the outlet conduit 316 is shown as 180 degrees, and a straight line is generated through the actuating mechanism 300 when the actuating mechanism 300 is open. Such an embodiment can reduce the amount of rotation necessary to open and close the valve. However, including this straight-line method is only feasible when each actuating mechanism 300 has a single inlet and a single outlet.

[0075] Figure 7 Depicts a schematic cross-sectional view of another actuating mechanism 400 for a switching valve according to an embodiment. The actuating mechanism 400 includes a piston 410 located within a bore structure 412. Inlet conduit 414 and outlet conduit 416 provide fluid through the actuating mechanism 400. The piston 410 includes a conduit 418 that extends through the piston to connect the inlet conduit 414 with the outlet conduit 416 when the piston 410 is in the relative position of the bore structure 412 shown. The conduit 418 of the piston 410 can be designed to drill two vertical holes into the piston 410 that are 90 degrees apart and meet in the middle of the piston 410. As in the previous embodiment, a gap of less than 6 microns is envisioned between the piston 410 and the bore structure 412 to maintain a fluid-tight seal when the piston 410 rotates to close the inlet conduit 414 and the outlet conduit 416 without the use of any external sealing components or deformable seals.

[0076] Although only the top cross-sectional view of the actuating mechanism 400 is shown, it should be understood that the actuating mechanism includes an appropriate depth to accommodate the inlet conduit 414 and the outlet conduit 416 and to accommodate the attachment of the piston 410 to the motor to effect rotational movement. The actuating mechanism 400 can be configured to open and close the inlet conduit 414 and the outlet conduit 416 by rotation of the piston 410 around the bore structure 412 in either direction relative to the position shown. Figure 7 The position in [description] shows the actuating mechanism 400 in an open state, whereby fluid can flow from the inlet conduit 414 through the conduit 418 of the piston 410 and out of the actuating mechanism 400 through the outlet conduit 416. The actuating mechanism 400 can be deployed by rotating clockwise or counterclockwise to achieve opening and closing. In addition, the angle θ between the inlet conduit 414 and the outlet conduit 416 is shown as 90 degrees, creating a vertical angle within the piston 410 through which the fluid must flow to exit through the outlet conduit 416 when the actuating mechanism 400 is open. This change in flow direction may be desirable in reducing pressure pulses during opening and closing downstream of the actuating mechanism 400. This embodiment can be similar to Figure 6The embodiments of Figure 5 the embodiment, the amount of rotation required to open and close the valve is reduced. However, including this method is only feasible when there is a single inlet and a single outlet for each actuating mechanism 300.

[0077] Figure 8 FIG. depicts a schematic cross-sectional view of another actuating mechanism 500 for switching a valve according to an embodiment. The actuating mechanism 500 includes a piston 510 located within a bore structure 512. An inlet conduit 514 and an outlet conduit 516 provide fluid through the actuating mechanism 500. The piston 510 includes a conduit 518 that extends through the piston to connect the inlet conduit 514 with the outlet conduit 516 when the piston 510 is in the opposite position of the bore structure 512 shown. As with the previous embodiments, a gap of less than 6 microns is envisioned between the piston 510 and the bore structure 512 so as to maintain a fluid-tight seal when the piston 510 moves to close the inlet conduit 514 and the outlet conduit 516 without the use of any external sealing components or deformable seals. Different from the previous embodiments, the movement of the actuating mechanism 500 for opening and closing the piston 410 relative to the bore structure 512 is axial rather than rotational.

[0078] Although only a side cross-sectional view of the actuating mechanism 500 is shown, it should be understood that the actuating mechanism includes an appropriate depth to accommodate the inlet conduit 514 and the outlet conduit 516 and to accommodate the attachment of the piston 510 to the motor to effect axial movement. The actuating mechanism 500 can be configured to open and close the inlet conduit 514 and the outlet conduit 516 via axial movement of the piston 510 relative to the bore structure 512 in either direction relative to the position shown. Figure 6 The position in shows the actuating mechanism 500 in an open state, whereby fluid can flow from the inlet conduit 514 through the conduit 518 of the piston 510 and out of the actuating mechanism 500 through the outlet conduit 516. While the previous embodiments may deploy rotational movement via a stepper motor, a servo motor, or other rotary actuator, Figure 8 the embodiment shown in can be controlled via a solenoid, a voice coil, a piezoelectric motor, or other axial movement system.

[0079] Figure 9Depicts a schematic view of another gradient proportioning valve 2C according to an embodiment. The gradient proportioning valve 2C is schematically shown, which includes four separate inlet ports 12 that supply fluid to two separate switching valves 17A, 17B via conduits or channels. As shown, each switching valve 17A, 17B is configured to receive fluid from two separate inlet ports 12 and provide a single outlet from the respective switching valve 17A, 17B. The single outlets of the two separate switching valves 17A, 17B each separately outlet the fluid to a downstream mixing point 50. At the mixing point 50, the fluid is combined into a single stream from the two separate streams received from the switching valves 17A, 17B. There is an outlet 44 downstream of the mixing point 50.

[0080] Figure 9 Shows an exemplary schematic view of the gradient proportioning valve 2C, where two inlet channels are connected to one valve 17A, 17B. Additionally, the schematic view does not show the liquid storage chamber 16. In other embodiments, there may be a liquid storage chamber for each inlet port 12 before supplying fluid to the switching valves 17A, 17B. The schematic view with two inlet channels for each valve can be used to describe embodiments consistent with the Figures 10 - 12 actuation mechanism shown and described below.

[0081] Figure 10 Depicts a schematic cross-sectional view of another actuation mechanism 600 for a switching valve according to an embodiment. The actuation mechanism 600 includes a piston 610 located within a bore structure 612. A first inlet conduit 614 and a second inlet conduit 616 supply fluid to the actuation mechanism 600 from different fluid sources. The piston 610 includes a conduit 618 that extends from the exterior of the piston 610 into the middle of the piston 610. An outlet conduit 620 is axially drilled from the piston 610 to allow fluid to flow out of the actuation mechanism 600. As in the previous embodiment, a gap of less than 6 microns is envisioned between the piston 610 and the bore structure 612 to maintain a fluid tight seal when the piston 610 rotates to close the inlet conduit 414 and the outlet conduit 416 without using any external sealing components or deformable seals.

[0082] Although only the top cross-sectional view of the actuation mechanism 600 is shown, it should be understood that the actuation mechanism includes an appropriate depth to accommodate the inlet conduit 614 and the outlet conduit 616, to accommodate the attachment of the piston 610 to the motor for rotational movement, and to accommodate connecting the outlet 620 of the piston 610 to the rest of the downstream liquid chromatography system.

[0083] The actuation mechanism 600 can be configured to open and close the respective first and second inlet conduits 614, 616 by rotation of the piston 610 around the bore structure 612. Figure 10The position in [the figure] shows the actuating mechanism 600 in the following state, where the first inlet conduit 614 is in the open state, whereby fluid can flow from the inlet conduit 614 through the conduit 618 of the piston 610 and out of the axially drilled outlet conduit 620 of the piston 610. The actuating mechanism 600 can be deployed on the piston 610 clockwise or counterclockwise relative to the drilling structure 612 to effect opening and closing. For example, a clockwise rotation can move the piston 610 from opening the first inlet 614 to opening the second inlet 616. Alternatively, from the shown position, a counterclockwise rotation can close both the first and second inlets 614, 616. In the shown embodiment, a closed state can also occur when the piston 610 rotates such that the outlet of the conduit 618 faces the wall of the drilling structure 612 located between the first inlet 614 and the second inlet 616. This embodiment contemplates that the actuating mechanism 600 is capable of switching between two separate inlets 614, 616, with one inlet open at a given time, and whereby the actuating mechanism always includes the same outlet 620.

[0084] In addition, the angle θ between each of the first and second inlet conduits 614, 616 defines the rotational distance between the first inlet conduit 614 and the second inlet conduit 616. It may be desirable to include a relatively small angle θ, such as an angle less than 90 degrees, to allow the actuating mechanism 600 to switch between positions more quickly. This can help reduce or eliminate pressure pulses generated by the actuating mechanism 600.

[0085] Figure 11 A schematic cross-sectional view of another actuating mechanism 700 for a switching valve according to one embodiment is depicted. The actuating mechanism 700 includes a piston 710 located within a drilling structure 712. The first inlet conduit 714 and the second inlet conduit 715 in the drilling structure 712 supply fluid to the actuating mechanism 700 from different fluid sources. The drilling structure 712 also includes an outlet conduit 716 located between the first inlet conduit 714 and the second inlet conduit 715. The piston 710 includes a key flat surface 720 cut out therefrom, which forms an open space 718 between the piston 710 and the drilling structure 712. Although a space is shown between the piston 710 and the drilling structure 712, it should be understood that the present invention contemplates using a very tight clearance between the piston 710 and the drilling structure 712 such that there is little space between them. Similarly, a clearance less than 6 microns is contemplated to maintain a fluid tight seal when the piston 710 rotates to close one or more of the inlet conduits 714 and the outlet conduits 715, 716 without the use of any external sealing components or deformable seals.

[0086] Although only a top cross-sectional view of the actuating mechanism 700 is shown, it should be understood that the actuating mechanism includes a suitable depth to accommodate the inlet conduit 714 and the outlet conduit 716, to accommodate the attachment of the piston 710 to the motor for rotational movement, and to accommodate the connection of the outlet 720 of the piston 710 to the remainder of the downstream liquid chromatography system.

[0087] The actuating mechanism 700 can be configured to open and close the respective first and second inlet conduits 714, 715 by rotation of the piston 710 about the bore structure 712. Figure 10 The position in shows the actuating mechanism 700 in a state where the first inlet conduit 714 is in an open state, whereby fluid can flow through the inlet 714 into the open space 718 created by the key flat surface 720 of the piston 710. A clockwise or counterclockwise rotation from this open position will close the first inlet conduit 714. Similarly, rotating the piston 710 clockwise such that the key flat surface 720 extends between the second inlet conduit 715 and the outlet conduit 716 will open the second inlet conduit 715 and close the first inlet conduit 714.

[0088] The actuating mechanism 700 can deploy any of these rotations in order to effect the opening and closing of the first and second inlet conduits 714, 715. Additionally, the angles θ between each of the first inlet conduit 714 and the outlet conduit 716 and between the second inlet conduit 715 and the outlet conduit 716 are shown. These angles θ define the rotational distance between the respective conduits 714, 715, 716. It may be desirable to include relatively small angles θ, such as angles less than 90 degrees, in order to reduce the size of the open space 718 in the system. Reducing the size of this open space 718 and rapidly opening and closing the inlets with small angles θ can help reduce or eliminate pressure pulses generated by the actuating mechanism 700.

[0089] Figure 12 A schematic cross-sectional view of another actuating mechanism 800 for a switching valve according to one embodiment is depicted. The actuating mechanism 800 includes a piston 810 located within a bore structure 812. A first inlet conduit 814 and a second inlet conduit 816 supply fluid from the bore structure 812 to the piston 810. A combined outlet conduit 818 allows fluid to exit the actuating mechanism 800. The piston 810 includes a conduit 820 that extends through the piston to connect the second inlet conduit 816 to the outlet conduit 818 when the piston 810 is in the relative position within the bore structure 812 shown. The piston 810 can be moved axially to the left to connect the first inlet conduit 814 to the outlet conduit 818. Alternatively, the piston can be moved axially to the right to close each of the first and second inlet conduits 814, 816.

[0090] As in the previous embodiments, a clearance of less than 6 microns is envisioned between the piston 810 and the bore structure 812 to maintain a fluid-tight seal when the piston 810 moves to open or close the inlet conduit 814 and the outlet conduit 816 without the use of any external sealing components or deformable seals. Similarly, different from the Figure 11 embodiment shown in, the movement of the piston 810 relative to the bore structure 512 is axial rather than rotational to open and close the two inlet conduits 814, 816 via the actuation mechanism 800.

[0091] Figure 13 A schematic diagram of another gradient proportional valve 2D according to an embodiment is depicted. The gradient proportional valve 2D is schematically shown and includes four separate inlet ports 12 that supply fluid to a single switching valve 17A via conduits or channels. As shown, the switching valve 17A is configured to receive fluid from each of the four separate inlet ports 12 and provide a single outlet from the switching valve 17A. Downstream of the single switching valve may be a downstream mixing point 50, and downstream may be a larger volume area that aids in mixing the fluid after the switching valve 17A but before the outlet. The mixing point 50 may be incorporated into the actuation mechanism of the switching valve 17A rather than a separate volume chamber. There is an outlet 44 downstream of the mixing point 50.

[0092] Figure 13 An exemplary schematic diagram of the gradient proportional valve 2D is shown, where all four inlet channels are connected to a single switching valve 17A. Additionally, the schematic does not show the liquid storage chamber 16. In other envisioned embodiments, there may be a liquid storage chamber for each inlet port 12 before supplying fluid to the switching valve 17A. A schematic diagram with four inlet channels for each valve can be used to describe embodiments consistent with the actuation mechanism shown in Figure 14 below.

[0093] Figure 14Depicts a schematic cross-sectional view of another actuating mechanism 900 for a switching valve according to an embodiment. The actuating mechanism 900 includes a piston 910 located within a bore structure 912. A first inlet conduit 914, a second inlet conduit 916, a third inlet conduit 918, and a fourth inlet conduit 920 each supply fluid to the actuating mechanism 900 from different fluid sources. The piston 910 includes a conduit 922 that extends from the exterior of the piston 910 into the middle of the piston 910. An outlet conduit 924 is axially drilled out of the piston 910 to allow fluid to flow out of the actuating mechanism 900. As with the previous embodiment, a gap of less than 6 microns is envisioned between the piston 910 and the bore structure 912 so as to maintain a fluid tight seal when the piston 910 rotates to close the inlet and outlet conduits 914, 916, 918, 920 without the use of any external sealing components or deformable seals.

[0094] Although only the top cross-sectional view of the actuating mechanism 900 is shown, it should be understood that the actuating mechanism includes an appropriate depth to accommodate the inlet and outlet conduits 914, 916, 918, 920, to accommodate the attachment of the piston 910 to a motor for rotational movement, and to accommodate connecting the outlet 924 of the piston 910 to the remainder of the downstream liquid chromatography system.

[0095] The actuating mechanism 900 can be configured to open and close the respective first, second, third, and fourth inlet conduits 914, 916, 918, 920 via rotation of the piston 910 about the bore structure 912. Figure 14 The position in shows the actuating mechanism 900 in a state where the second inlet conduit 916 is in an open state, whereby fluid can flow from the second inlet conduit 916 through the conduit 922 of the piston 910 and out of the axially drilled outlet conduit 924 of the piston 910. The actuating mechanism 900 can be deployed in a clockwise or counterclockwise rotation on the piston 910 relative to the bore structure 912 so as to effect the opening and closing of the various inlet conduits 914, 916, 918, 920. For example, a clockwise rotation can move the piston 910 from opening the second inlet conduit 916 to opening the third inlet conduit 918. Alternatively, from the shown position, a counterclockwise rotation can open the first inlet conduit 914. In the shown embodiment, a closed state can also occur when the piston 910 rotates such that the outlet of the conduit 922 faces the wall of the bore structure 612 that is located between one of the inlet conduits 914, 916, 918, 920 or counterclockwise to the first inlet conduit 914 or clockwise to the fourth inlet conduit 920. This embodiment envisions that the actuating mechanism 600 is capable of switching between four separate inlets 914, 916, 918, 920, with one inlet being open at a given time, and whereby the actuating mechanism always includes the same outlet 924.

[0096] In addition, the angle θ between each of the inlet conduits 914, 916, 918, 920 defines the rotational distance between the various inlet conduits 914, 916, 918, 920. It may be desirable to include a relatively small angle θ, such as an angle less than 90 degrees, to allow the actuation mechanism 900 to switch between positions more quickly. This can help reduce or eliminate pressure pulses generated by the actuation mechanism 900.

[0097] While the above embodiments have been described using axial or rotational movement, it is contemplated that other embodiments for the actuation mechanism may use a combination of both axial and rotational movement. For example, it is contemplated that the inlets may actually be positioned axially spaced apart as well as rotationally spaced apart. For example, in Figure 14 the embodiment shown, two inlets (e.g., inlets 916, 920) may be axially spaced apart relative to the other two inlets (e.g., inlets 914, 918), rather than having all four inlets reach the piston 910 at the same depth. Using both axial and rotational spacing can allow for a reduction in the total space between the various inlets. For example, if the inlets 914, 916, 918, 920 are located at the corners of a rhombus or square shape, the movement of the piston from any one inlet to another will be approximately the same. Compared to an embodiment where the inlets 914, 916, 918, 920 reach the piston 910 at a single plane each separated by an angle θ, the movement between inlet 914 and inlet 920 is greater than the movement between inlet 916 and inlet 918. Various embodiments of the above-described actuation mechanism having more than one inlet may use a combination of rotational and axial movement to reduce the space between the various inlets.

[0098] In addition, while the embodiments described above show four inlet ports for each gradient proportioning valve 2D, the actuation mechanism described herein may be incorporated into a gradient proportioning valve having any number of solvent lines and any number of inlets. Further, while embodiments of the actuation mechanism show a single inlet, two inlets, or four inlets, the principles of the actuation mechanism described above may be applied to other numbers of inlets, such as three inlets or more than 4 inlets. Regardless of the embodiment, the actuation mechanism contemplated herein may include a single outlet, regardless of how many inlets the actuation mechanism is configured for.

[0099] Methods for operating a switching valve of a gradient proportioning valve of a liquid chromatography system are also envisioned. For example, methods envisioned herein include providing a gradient proportioning valve, such as one of the valves 17A, 17B, 17C, 17D described herein, including a manifold having a plurality of conduits. The method includes receiving a plurality of fluids at a plurality of inlet ports of the gradient proportioning valve and using an actuating mechanism having a piston to open and close each of the plurality of conduits in a controlled manner, the piston being located within a bore structure surrounding the piston, the actuating mechanism being one of the actuating mechanisms 200, 300, 400, 500, 600, 700, 800, 900, the piston being one of the pistons 210, 310, 410, 510, 610, 710, 810, 910, and the bore structure being one of the bore structures 212, 312, 412, 512, 612, 712, 812, 912. The method includes maintaining a fluid tight seal between the piston and the bore structure during opening and closing, wherein the piston and the bore structure have tight tolerances configured to create a fluid tight seal. The method includes mixing the plurality of fluids in a controlled manner within the manifold of the gradient proportioning valve and outputting a fluid composition from a common outlet port of the gradient proportioning valve.

[0100] Additional methods include preventing unwanted fluid pressure pulses in the manifold by minimizing the internal fluid volume within the piston and bore structure using the actuating mechanism. Additionally, methods envisioned include using the actuating mechanism to open two or more of the plurality of conduits, such as in the Figures 9 - 14 illustrated embodiments.

[0101] The method also includes rotating the piston about the bore structure to open and close at least one of the plurality of conduits in a controlled manner, such as in the Figures 5 - 7 , Figure 10 , Figure 11 and Figure 14 illustrated embodiments. Alternatively, the method includes axially moving the piston within the bore structure to open and close at least one of the plurality of conduits in a controlled manner, such as in the Figure 8 and Figure 12 illustrated embodiments. Alternatively, the method may include moving the piston both axially and rotationally relative to the bore structure as described above.

[0102] Although the invention has been shown and described with reference to particular embodiments, those skilled in the art will understand that various changes in form and detail may be made without departing from the spirit and scope of the invention as recited in the appended claims.

Claims

1. A gradient proportioning valve (2) for liquid chromatography, comprising: a plurality of inlet ports (12) configured to receive a plurality of solvents; a manifold (10) connected to each of the plurality of inlet ports (12), the manifold (10) configured to mix the plurality of solvents in a controlled manner to provide a solvent composition, the manifold (10) including a plurality of conduits (14) inside the manifold (10), each of the plurality of conduits (14) receiving fluid through a corresponding one of the plurality of inlet ports (12); an actuating mechanism (200) having a piston (210) located within a drilled structure (212) surrounding the piston (210), the actuating mechanism (200) configured to open and close at least one of the plurality of conduits (14) in a controlled manner, wherein the piston (210) and the drilled structure (212) have a tight tolerance configured to create a fluid-tight seal when the actuating mechanism (200) closes at least one of the plurality of conduits (14); and a common outlet port (44) configured to receive the solvent composition, wherein the gradient proportioning valve (2) is configured to provide a continuous flow of an accurate mixture of the components of the solvent.

2. The gradient proportioning valve according to claim 1, wherein, the piston (210) and the drilled structure (212) create the fluid-tight seal without a deformable sealing element.

3. The gradient proportioning valve according to claim 1, wherein, the actuating mechanism (200) includes an electromagnetic valve.

4. The gradient proportioning valve according to claim 1, wherein, the piston (210) is made of ceramic.

5. The gradient proportioning valve according to claim 1, wherein, the actuating mechanism (200) is configured to open and close two or more of the plurality of conduits (14).

6. The gradient proportioning valve according to claim 1, wherein, the piston (210) is configured to rotate around the drilled structure (212) to open and close the at least one of the plurality of conduits (14) in the controlled manner.

7. The gradient proportioning valve according to claim 6, wherein, the piston (210) is configured to rotate less than 90 degrees to open and close the at least one of the plurality of conduits (14) in the controlled manner.

8. The gradient proportioning valve according to claim 1, wherein, the tight tolerance creates a gap of less than 6 microns between the piston (210) and the drilled structure (212).

9. The gradient proportioning valve according to claim 1, wherein, the gradient proportioning valve (2) is configured to mix the plurality of solvents upstream of a pump in a liquid chromatography system.

10. The gradient proportioning valve according to claim 1, wherein, The actuating mechanism (600) includes a plurality of inlet conduits (614, 618), each operatively connected to one of the plurality of conduits (14) of the manifold (10), and the actuating mechanism (600) includes a common outlet conduit (620).

11. The gradient proportioning valve according to claim 1, wherein, the gradient proportioning valve (2) does not include an integral liquid storage chamber.

12. The gradient proportioning valve according to claim 1, configured for low-pressure mixing.

13. A method of mixing solvents, comprising: providing a gradient proportioning valve (2) according to any one of claims 1-12; setting an exact solvent composition required for mixing the plurality of solvents; receiving the plurality of solvents at a plurality of inlet ports (12) of the gradient proportioning valve (2); opening and closing each of the plurality of conduits (14) in a controlled manner by an actuating mechanism (200); maintaining a fluid-tight seal between the piston (210) and the bore structure (212) during the opening and closing; mixing the plurality of solvents in a controlled manner within the manifold (10) of the gradient proportioning valve (2); outputting the solvent composition from a common outlet port (44) of the gradient proportioning valve (2); and providing a continuous flow of an accurate mixture of the components of the plurality of solvents.

14. The method according to claim 13, further comprising: utilizing the actuating mechanism (200) to prevent unwanted fluid pressure pulses in the manifold (10) by minimizing the internal fluid volume within the piston (210) and the bore structure (212).

15. A liquid chromatography system, comprising: a gradient proportioning valve (2) according to any one of claims 1-12; a pump (4) located downstream of the gradient proportioning valve (2); an injector (8); a separation column (6); and a detector (7).

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