Abstract:
A rear feed solenoid-operated valve design is particularly suited for micro-fluidic applications. The solenoid valve contains various structures and features that provide for small dispense volumes, small internal volume, and fast operating speed. The valve includes an inlet, outlet, coil housing, magnetic plunger rod and a diaphragm assembly. In a preferred embodiment, the diaphragm assembly ensures zero leakage. The solenoid-operated valve further has features allowing for low power consumption. The valve is placed at a desired location by a positioning mechanism located at the rear end of the valve. The positioning mechanism feeds fluid through the inlet and dispenses the fluid at the outlet located at the front, or bottom of the valve.

Description:
[0001]     PRIORITY CLAIM  
         [0002]     This application relates to U.S. Provisional Patent Application Ser. No. 60/561,777 filed on Apr. 12, 2004 which is incorporated herein by reference and to which priority is claimed pursuant to 35 USC §119. 
     
    
     BACKGROUND OF THE INVENTION  
       [0003]     1. Field of the Invention  
         [0004]     The present invention pertains generally to valves for physical transport and isolation of liquids and gases. More particularly, the present invention pertains to fluidic dispense valves that are designed for low power and quick dispensing applications.  
         [0005]     2. Description of the Prior Art and Related Information  
         [0006]     Solenoid-operated valves for isolation and transport of fluids are well known. An attractive characteristic of all solenoid-operated valves is that they can be remotely operated because electrical power is used to actuate the valve. Also, a solenoid valve is an attractive option when fluid systems require a valve to cycle open and closed, and thereby pass a set dispense volume of fluid. This is because solenoid valves use a generated and collapsing electromagnetic field to engage a valve stem or a plunger rod. Thus, a power supply can be easily cycled on and off to pass a particular amount of fluid.  
         [0007]     Advancements in micro-fluidic arts such as blood chemistry analysis, drug discovery, DNA sequencing, liquid chromatography and other technical arts requiring precision fluid handling have created a need for progress in the components that control and dispense the fluids. Thus, a need exists for a design and method for making and using a solenoid valve that provides for small dispense volumes in close proximity with small fluidic components that can be coupled to a positioning mechanism at the inlet end. In addition, the nature of most micro-fluidic applications places importance on conserving a fluid sample. Therefore, a valve design that allows many valves to be utilized in close proximity resulting in a smaller fluidic platform is desired. Similarly, an isolation valve should be designed for zero leakage.  
       BRIEF SUMMARY OF THE INVENTION  
       [0008]     The present invention, in a preferred embodiment, is particularly but not exclusively, useful as a rear feed micro-mini solenoid-operated valve for positioning mechanisms and has the ability to control and adjust the flow amount, dispense volume and dispense speed. The novel design of the valve provides a quick operating time and full flow with relatively short movement of the plunger rod. This allows for reduced power consumption by the valve and reduces unnecessary use. In one aspect, a solenoid-operated valve comprises external elements that include a coil housing that defines an axis therethrough and an end cap having a sealing apex on a first side and coupled to a needle on a second side.  
         [0009]     The internal elements include a fluid inlet, a fluid outlet and a solenoid coil disposed about the axis and configured to fit inside of the coil housing. Also included within the coil housing is a diaphragm assembly is coupled to a magnetic plunger rod at a proximal end thereof. The solenoid coil generates a magnetic field when energized. The magnetic field causes the plunger rod to traverse axially inside of the coil housing. In an open cycle, the plunger rod moves axially to unseat the valve. In a closed cycle, the plunger rod moves in a reverse axial direction to seat the valve.  
         [0010]     Unlike conventional valves, the coil housing design allows the diaphragm to be pressed into the end cap and form a fluid tight seal with the housing in one simple, time saving assembly procedure. Conventional designs use screws to attach the end cap to the housing which can take up to 20 seconds to screw in. Pressing the end cap into the housing, however, takes approximately 2-3 seconds. This is an important money saving feature when multiplied over by the production of thousands of valves.  
         [0011]     The diaphragm assembly is coupled to the plunger rod using an insert molding process and forms a fluid tight seal against the raised sealing apex when the solenoid-operated valve is in the normally closed position. In a preferred embodiment, the fluid inlet is adapted to be coupled to a positioning mechanism at a top end of the valve. This is a preferable design feature due to the ultimate use of the valve. The valves are ultimately used with XYZ machines that dispense into cuvettes from a top end. Cuvettes are essentially miniature cups or cavities in a plate. The dispense tips of the XYZ machines fit right into the cuvettes and dispense fluid therein. Having an XYZ machine come from the bottom of the cuvettes would be inefficient because of the wiring of the XYZ machine.  
         [0012]     In a second embodiment, the diaphragm assembly comprises a diaphragm sleeve that couples to the diaphragm on one side and to a tip of the plunger rod on the other side.  
         [0013]     The valve further comprises a valve seat about the axis and around an inner diameter of the end cap. When the valve is in the closed position the diaphragm assembly engages with the valve seat and the raised sealing apex and forms a fluid tight seal.  
         [0014]     The internal volume is approximately equal to 17 μl in a preferred embodiment. The inlet has a diameter of approximately 0.020 inches in a preferred embodiment.  
         [0015]     The valve further comprises a bobbin disposed about the axis of the coil housing. The bobbin fits inside of the coil housing and defines an inner hollow section. The bobbin and the coil housing together define an outer hollow section. A solenoid coil is wrapped around the bobbin within the outer hollow section. The valve further comprises a diaphragm assembly coupled to the plunger rod at a proximal end thereof. A spring having a spring force fits in between a protruding rib of the diaphragm assembly and around a circumference of the plunger rod.  
         [0016]     In an open cycle, the solenoid coil is energized and creates a magnetic field. The magnetic field forces the plunger rod to traverse axially against the spring force and move the diaphragm assembly in a direction away from the outlet, allowing fluid to pass. In a closed cycle, the solenoid coil is de-energized and releases the magnetic field. This allows the spring force to move the diaphragm assembly in a reverse direction sealing the inlet and the outlet.  
         [0017]     The valve further comprises a mag pin configured to fit inside of the bobbin, in the inner hollow section and adjacent to the plunger rod. When the solenoid-operated valve is in the closed position the mag pin and plunger rod together define an air gap with a magnitude designed for optimum performance. In a preferred embodiment, the air gap is approximately equal to 0.005 inches. The mag pin is adjustable to control the flow amount, dispense volume, and dispense speed. The mag pin may have threads, which have a pitch length of approximately 0.025 inches. The adjustability of the air gap is crucial for the accuracy of the valve. Without an adjustable air gap there is no way to set the flow of the tolerances. The present invention dispenses at an accuracy of approximately 2-3% from each other and the increase of the gap increases the dispense speed by approximately 10%.  
         [0018]     The valve may further comprise a mag disc configured to fit around the mag pin at an end thereof. The mag disc configuration is selected for optimum strength of the magnetic field and optimum performance of the valve. The valve further comprises one or more electrical leads mechanically coupled to the bobbin and electrically coupled to the solenoid coil.  
         [0019]     In a preferred embodiment, the dead volume, or fluid internal to the valve that is not flushed out during a purge cycle, is approximately equal to zero. This avoids the problem of carryover. The valve is designed for zero leakage past the diaphragm assembly. Thus, the solenoid-operated valve may preferably comprise an isolation valve.  
         [0020]     In a preferred embodiment the coil housing is rectangular in shape and has sides that are approximately 0.250 inches wide. This miniature size is unique and desirable for isolation valves because modernly smaller samples are being used. The small size allows for a smaller internal volume and therefore is easier to flush out. The valves can provide more accurate sample dispenses because there is less fluid inside the valve and the smaller valve is easier to turn on and off. The size of the valve also allows more valves attach to the same platform. This is crucial for upcoming platform technology that allows the platforms to be transported.  
         [0021]     The valve may have a dispense speed designed to be approximately 10 milli-sec in a preferred embodiment. The end cap may be composed of a chemically inert polymer, such as PEEK (Poly Ether Ether Ketone), while the plunger rod and the coil housing may be composed of 400-series stainless steel. Unlike conventional rear feed valves, the valve is designed for low power consumption approximately equal to one (1) Waft.  
         [0022]     The valve may further comprise a seal adjacent to the end cap for providing a fluid tight seal to a valve manifold. The seal has one or more built-in O-rings and may be composed of EPDM (Ethylene Propylene Diene Monomer) rubber material.  
         [0023]     A method of making a solenoid-operated valve is also provided. The method includes the steps of providing a coil housing defining an axis, disposing a solenoid actuated plunger rod within the coil housing and allowing for axial movement of the plunger rod. The method also includes providing an air gap adjacent to the solenoid actuated plunger rod, and setting the dispense volume of the pump by precisely setting the size of the air gap. The method further comprises providing a spring having a spring force configured axially with the plunger rod to assist axial movement of the plunger rod.  
         [0024]     In a preferred embodiment, the method further comprises energizing the solenoid to induce a magnetic field along the axis, the spring force and the magnetic field configured to provide axial movement of the plunger rod when the magnetic field is alternated on and off.  
         [0025]     The invention provides a solenoid-operated valve design and method particularly for small manufacture. The valve design allows for small dispense volumes, a small internal volume, and fast operating speed and is particularly suited for a compact, high-density valve manifold. Unlike conventional rear feed valves, the valve is designed for low power consumption and is easy to manufacture, simple to use, and cost effective.  
         [0026]     The term fluid used herein, means any substance that can flow, liquid or gas.  
         [0027]     These, as well as other advantages of the present invention, will become more apparent from the following description and drawings. It is understood that changes in the specific structure shown and described may be made within the scope of the claims, without departing from the spirit of the invention.  
         [0028]     While the apparatus and method has or will be described for the sake of grammatical fluidity with functional explanations, it is to be expressly understood that the claims, unless expressly formulated under 35 USC 112, are not to be construed as necessarily limited in any way by the construction of “means” or “steps” limitations, but are to be accorded the full scope of the meaning and equivalents of the definition provided by the claims under the judicial doctrine of equivalents, and in the case where the claims are expressly formulated under 35 USC 112 are to be accorded full statutory equivalents under 35 USC 112. The invention can be better visualized by turning now to the following drawings wherein like elements are referenced by like numerals.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0029]     The novel features of this invention, as well as the invention itself, both as to its structure and its operation, will be best understood from the accompanying drawings, taken in conjunction with the accompanying description, in which similar reference characters refer to similar parts, and in which:  
         [0030]      FIG. 1  is an exploded side view of a preferred embodiment of a solenoid-operated valve according to the present invention;  
         [0031]      FIG. 2  is an exploded isometric view of a preferred embodiment of a solenoid-operated valve according to the present invention;  
         [0032]      FIG. 3  is an axial cross-sectional view of the preferred embodiment of a solenoid-operated valve in the closed position according to the present invention;  
         [0033]      FIG. 4  is an axial cross-sectional view of the preferred embodiment of a solenoid-operated valve in the open position according to the present invention;  
         [0034]      FIG. 5  is an exploded isometric view of the diaphragm assembly of a second preferred embodiment according to the present invention; and  
         [0035]      FIG. 6  is an exploded isometric view of the second preferred embodiment of a solenoid-operated valve according to the present invention.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0036]     Referring initially to  FIG. 1 , a first preferred embodiment of a solenoid-operated valve  10  according to the present invention is shown. The valve  10  is a two-way isolation valve in that the valve  10  has two positions: open and closed. In this example, the valve  10  is de-energized in the closed position. The valve  10  comprises external components including a coil housing  11  and an end cap  12 . A top or rear end  23  of the solenoid valve  10  includes electrical leads  13  that provide power to energize a solenoid coil  14 . The valve  10  includes an inlet  15  at the rear end  23  of the valve  10  and an outlet  20  on the bottom, in order to conveniently couple the valve  10  to a positioning mechanism, such as an XYZ machine (not shown). In a preferred embodiment, the valve  10  is an isolated valve that is fed through the top or rear end  23 .  
         [0037]     Unlike conventional valves, the housing  11  is square with four 0.250 inch sides, allowing many valves to be utilized in close proximity so as to provide a smaller fluidic platform. The smaller size is unique and desirable for isolation valves because smaller samples are being requested as different technologies advance. The small size allows for a smaller internal volume and therefore is easier to flush out. The valves can provide more accurate sample dispenses because there is less fluid inside the valve and the smaller valve is easier to turn on and off.  
         [0038]     A plunger rod  16  is configured to reciprocate axially inside of the coil housing  11  when the valve  10  is cycled open and closed. Further, a diaphragm assembly  17  is located on an end of the plunger rod  16 , and seats the inlet and outlet ports  24 ,  25  inside of the end cap  12 . In the preferred embodiment, the diaphragm assembly  17  comprises a diaphragm  29  adapted to be coupled to the plunger rod  16 .  
         [0039]     The diaphragm  29  includes a rib  18  protruding around a circumference thereof. The rib  18  assures the seal between the plunger rod  16  and the inlet and outlet ports  24 ,  25 . Further, a spring  19  is located between the rib  18  and an end of a spool  52 . The solenoid coil  14  is wrapped around the spool  52  as shown. When the coil  14  is deactivated, the spring  19  provides a bias that forces the plunger rod  16  to close the outlet port  25  of the valve  10 . The outlet  20  is coupled to the housing  11  by a stem  31  that is in fluid communication with the outlet port  25  via a stem insert  32 . The stem insert  32  provides a tight connection between the end cap  12  and the outlet  20 .  
         [0040]      FIG. 2  is, an exploded isometric view of individual components of the valve  10 , disposed about center axis  50 .  FIG. 2  shows a rear end view of the valve  10 , wherein a head portion of a mag pin  26  is illustrated. The adjustability of the air gap is crucial for the accuracy of the valve. Without an adjustable air gap there is no way to set the flow of the tolerances. The present invention dispenses at an accuracy of approximately 2-3% from each other and the increase of the gap increases the dispense speed by approximately 10%.  
         [0041]     A mag disc  30  lies adjacent to the solenoid coil  14 . When the coil is energized, the mag disc  30  shapes a magnetic flux field generated by the solenoid coil  14 . The spool  52  defines an inner hollow section  52 A that allows the plunger rod  16  to reciprocate axially.  
         [0042]     A first end  15 A of the inlet  15  attaches to a positioning mechanism (not shown) while the valve  10  hangs there from. Having the inlet  15  located at a tope end of the valve  10  allows the positioning mechanism to feed into cuvettes or cavities for dispensing the fluid into. When assembled, a second end  15 B of the inlet  15  is inserted into a first aperture  21 A of the housing  11  and extends through a second aperture  21 B of the housing  11 . The second aperture  21 B of the housing is aligned with a third aperture  21 C on the end cap  12 . The end cap  12  further includes a plug  27  that the second end  15 B of the inlet  15  feeds into. The plug  27  leads to the inlet port  24  (shown in  FIGS. 1 and 4 ) within the end cap  12 . Additionally, the end cap  12  presses against the coil housing  11 , forming a fluid tight junction in between.  
         [0043]     Unlike conventional valves, the coil housing design allows the diaphragm to be pressed into the end cap and form a fluid tight seal with the housing in one simple, time saving assembly procedure. Conventional designs use screws to attach the end cap to the housing, which can take up to 20 seconds to screw in. However, pressing the end cap into the housing takes approximately 2-3 seconds. This is an important money saving feature when multiplied over by the production of thousands of valves.  
         [0044]     As is best seen in  FIG. 3 , the coil housing  11  and the spool  52  together define an outer hollow section  54  that provides an area for the solenoid coil  14  to be wrapped around the spool  52 . Preferably, the coil  14  is wrapped with coating or tape to prevent shorting. As an example, when operated, the spring  19  exerts a linear spring force on the diaphragm  29  and seals the diaphragm  29  against the end cap  12 . The spring force moves the plunger rod  16  axially to shut the valve  10  when the solenoid coil  14  is de-energized. An air gap  56  determines how far the plunger rod  16  travels during a dispense cycle open and closed operation.  
         [0045]     Unlike conventional valves, the mag pin  26  can be operated by a user to adjust the magnitude of the air gap  56 . In a preferred embodiment, the mag pin  26  further includes threads  28  to adjust the magnitude of the air gap  56 . The air gap  56  controls the flow amount, dispense volume and dispense speed. As those skilled in the art will recognize, a similar design embodied by the present invention can be a valve that is normally open.  
         [0046]     As shown in  FIG. 4 , when the solenoid coil  14  is activated a DC voltage pulse energizes the coil  14  and actuates valve  10 . The coil  14  generates a magnetic flux field that causes the plunger rod  16  and the diaphragm  29  to move against the force of the spring  19  proximate the air gap  56  until the plunger rod  16  contacts the mag pin  26  which is in a fixed position. At this point, the diaphragm  29  pulls away from the sealing apex of the end cap  12  whereby the liquid or gas media flows through the inlet port  24  and out of the outlet port  25 . In this manner, the valve  10  provides quick operation such that the diaphragm assembly  17  need not travel a great distance to provide full flow past the valve  10 .  
         [0047]     In a preferred embodiment, the mag screw  26 , the plunger rod  16 , the coil housing  11 , and the mag disc  30  are made from 400-series stainless steel chosen for its magnetic properties and its ability to resist corrosion. The end cap  12  has channels that form the inlet and outlet ports  24 ,  25 , is preferably composed of a chemically inert material, such as PEEK (Poly Ether Ether Ketone). Significantly, the valve  10  is designed for zero “dead volume” which conserves samples such as in medical applications, and provides ease of cleaning and flushing. It is also important to note that valve  10  can be specifically employed in micro-fluidic applications. In a preferred embodiment, the valve  10  has a dispense volume of approximately five (5) nano-liters or less for one open/closed cycle, and an end cap  12  internal volume of approximately 17 micro-liters.  
         [0048]     Preferably, the magnitude of the air gap  56  is, for example, approximately 0.005 thousandths of an inch and a diameter of the inlet port  24  is, for example, approximately 0.020 thousandths of an inch. Further, the magnitude of the air gap  56  is selected to be, for example, approximately one-quarter (%) the design diameter of the inlet port  24 . Such dimensions, unlike conventional valves, provide quick operating time and full flow with relatively short movement of the plunger rod  16 , reduce power consumption by the valve  10  and reduce unnecessary use of the solenoid coil  14  which can be relatively weak (e.g., one (1) Watt). Such a coil  14  is also beneficial in minimizing the effects of residual magnetism that affect the dispense speed of valve  10 . In a preferred embodiment, the valve  10  has a dispense speed of approximately 10 milli-seconds.  
         [0049]     In a second embodiment illustrated in  FIGS. 5 and 6 , elements of similar structure are designated by the same reference numerals followed by the lower case “d”. In the second preferred embodiment, the diaphragm assembly  17   d  includes a diaphragm  29   d , a diaphragm sleeve  40  and a plunger rod  16   d . The diaphragm sleeve  40  couples the diaphragm  29   d  to the plunger rod  16   d  via a first and second peripheral opening  42 ,  44  located on the sleeve  40 . During de-actuation, the diaphragm  29   d  fills the first peripheral opening  42 . Once actuated, a tip  13  of the plunger rod  16   d  seats into the second opening  44  of the sleeve  40 , thereby filling the second opening  44  and sealing the apex.  
         [0050]     Many alterations and modifications may be made by those having ordinary skill in the art without departing from the spirit and scope of the invention. Therefore, it must be understood that the illustrated embodiments have been set forth only for the purposes of example and that it should not be taken as limiting the invention as defined by the following claims. For example, notwithstanding the fact that the elements of a claim are set forth below in a certain combination, it must be expressly understood that the invention includes other combinations of fewer, more or different elements, which are disclosed in above even when not initially claimed in such combinations.  
         [0051]     While the particular Rear Feed Micro-fluidic Two-Way Isolation Valve as herein shown and disclosed in detail is fully capable of obtaining the objects and providing the advantages herein before stated, it is to be understood that it is merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended to the details of construction or design herein shown other than as described in the appended claims.  
         [0052]     Insubstantial changes from the claimed subject matter as viewed by a person with ordinary skill in the art, now known or later devised, are expressly contemplated as being equivalently within the scope of the claims. Therefore, obvious substitutions now or later known to one with ordinary skill in the art are defined to be within the scope of the defined elements.