Abstract:
In various embodiments a fluid control device suitable for high pressure analytical instruments includes a housing having an interior surface with an end wall. The interior surface defines a chamber. A valve assembly disposed in the chamber controls the flow of fluid through the chamber. An end cap is disposed in the housing opposite the end wall to enclose the chamber. The end wall and end cap each have an opening to pass a fluid to the chamber or to remove a fluid from the chamber. The housing and end cap each has an abutment surface to receive the other abutment surface. At least one of the abutment surfaces has a plastic seal coating. A means of compression, such as a compression housing and compression sleeve, is included to engage the end cap to deform the plastic seal coating between the abutment surfaces and thereby seal the chamber.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority from U.S. Provisional Patent Application No. 60/550,972, filed Mar. 5, 2004 and Application Ser. No. 60/577,405, filed Jun. 4, 2004. The contents of these applications are incorporated herein by reference. 
    
    
     STATEMENT ON FEDERALLY SPONSORED RESEARCH 
     N/A 
     Embodiments of the present invention are directed to devices and method for coupling, or joining components for receiving and discharging fluids. Devices made in accordance with the present invention have special application to fittings, valves and check valves. 
     BACKGROUND OF THE INVENTION 
     The present invention is directed to devices for receiving and discharging fluids. Devices embodying features of the present invention include, by way of example, without limitation, tees, unions, fittings, valves and check valves. These devices are sometimes placed in line between two or more conduits that are joined in the form of a union, or tee, or valve. The term “union” is used in the sense of joining or bringing together. A “tee” is a form of fitting in which fluid flow is split or combined. The devices are sometimes part of a larger structure in which the device communicates through ports or openings. This application will use the term “fluid path means” to mean all conduits, tubing, pipes, openings or ports which convey or transport fluids. 
     In this application, the term fitting will be used in the broadest sense to refer to a device that may be placed in a larger structure, for example, a pump assembly, or in line. 
     The term “valve” is used in a conventional manner to denote a device that can stop fluid flow in a conduit or pipe. A check valve is a special valve that allows fluid to flow in one direction only. 
     Fitting and valves of the prior art typically have gaskets and seals that are separate and discrete parts. These gaskets and seals exhibit material creep, cold flow and relaxation. That is, as the fluid pressure fluctuates, the gaskets move. This movement can lead to the gasket slipping from an original position, leading to gasket or seal failure. 
     This movement also creates a rebound of the gasket as the pressure is released, creating a potential pressure ripple. Analytical instruments, in particular, are sensitive to the rebound and pressure ripple effect. 
     These problems are amplified as the pressure contained by such devices increases. Analytical instruments, such as chromatography pumps and detectors typically operate at pressures of up to 3,000 to 4,000 pounds per square inch (psi). It is desirable to have analytical instruments operate at higher pressures, however, fittings, valves and check valves have a high failure rate at pressures greater than 3,000 psi. 
     SUMMARY OF THE INVENTION 
     Embodiments of the present invention feature devices and methods for holding fluids at high pressures. One embodiment of the present invention features a device for receiving and discharging fluids. The device comprises a first housing having at least one side wall. The side wall has an interior surface defining at least one chamber and has at least one end cap abutment surface for receiving an end cap. The device has at least one end cap having at least one first housing abutment surface. The first housing abutment surface receives the end cap abutment surface positioning the end cap on the first housing for enclosing the chamber. At least one of the first housing abutment surface and the end cap abutment surface has first seal coating. The first seal coating comprises a deformable plastic adhering to the abutment surface. The device further comprises a fluid path means for receiving and removing fluid from the chamber. And, the device comprises compression means to compress the end cap, with the end cap abutment surface received on said first housing abutment surface, towards said first housing to deform said first seal coating and seal said chamber. 
     Preferably, the seal coating is selected from one or more of the polymeric coatings consisting of polytrifluoroethylene (PTFE), polyetheretherketone (PEEK), polychlorotrifluoroethylene (PCTFE), perfluoroalkoxy (PFA) and fluorinatedethylenepropylene (FEP). 
     As used herein, the term “fluid path means” refers to openings, ports, conduits and pipes that provide fluid. Thus, embodiments of the present invention can be placed in line, with fluid path means comprising conduits and pipes or incorporated within the housing of a larger structure, for example, without limitation, a pump head or pump housing. 
     Preferably, the end cap abutment surface and/or the housing abutment surface is a ridge to localize compression forces on said seal coating. The ridge is a relatively narrow protrusion capable of contact with an opposing abutment surface. 
     Embodiments of the present invention are ideally suited for fittings and valves. Where the device is in the form of a valve, the chamber contains a valve assembly. The valve assembly may comprise rotary-type valves, gated valves or check valves. 
     In the case where the device is in the form of a check valve, the first housing has at least one end wall opposite the end cap. The fluid path means comprises at least one opening in said end cap and at least one opening in said end wall. And, the chamber holds a valve assembly comprises a ball seat and a ball. 
     Preferably, the interior wall and/or the end cap has a ball seat abutment surface. And, the ball seat comprises a cylinder having a two rims, and a fluid passage. At least one of the rims has a ball receiving surface for engaging the ball and closing the fluid passage. And, at least one of the rims has a rim abutment surface for engaging the ball seat abutment surface and sealing the ball seat and the housing and/or end cap. 
     Preferably, the ball seat abutment surface and/or rim abutment surface has a ball seat seal coating. Preferably, the ball seat coating is made and formed as described above with respect to the seal coating. 
     Preferably the first housing end wall has an interior surface and an exterior surface, and one or more end wall openings. And, the exterior surface has an end wall abutment surface encircling the one or more end wall openings. Preferably, the end wall abutment surface has an end wall seal coating, the end wall seal coating comprising a deformable plastic to sealably engage an adjoining wall. Preferably, the end wall seal coating is made and formed as described above with respect to the seal coating. Devices of this type are well suited to be mounted in a further major housing structure having the adjoining wall. For example, without limitation, the end wall seal coating would engage the adjoining wall of a pump head housing. In this embodiment, preferably, the adjoining wall has an adjoining wall opening for the passage of fluid into the end wall opening. In this embodiment, the compression means comprises such adjoining wall for receiving the end wall and compressing the end wall seal coating in sealing engagement. 
     For inline application, preferably, the compression means comprises a compression housing assembly comprising a compression housing and compression sleeve. The compression housing has a compression chamber for receiving the housing. The compression sleeve engages the end cap for placing the end cap, and first housing under compression. 
     Preferably, the compression housing assembly has a compression nut. The compression nut and compression housing have cooperating threads which engage upon relative rotation of the compression nut and compression housing. The compression nut engage the compression sleeve to compress the compression sleeve, end cap and first housing within the compression housing chamber. 
     A further embodiment of the present invention comprises a method of joining fluid passages. One embodiment of the present method comprises the steps of providing a device having a first housing having a at least one side wall. The side wall has an interior surface defining at least one chamber, and has at least one end cap abutment surface for receiving an end cap. The device has at least one end cap. The end cap has at least one first housing abutment surface and is capable of being received on the first housing abutment surface for enclosing said chamber. The device has a first seal coating on at least one of the first housing abutment surface and the end cap abutment surface. The first seal coating comprises a deformable plastic adhering to the abutment surface. The device has a fluid path means for receiving and removing fluid from the chamber; and compression means to compress the end cap, with said end cap abutment surface received on said first housing abutment surface, towards said first housing to deform said first seal coating and seal said chamber. The method further comprises the step of placing the receiving conduit and discharge conduits in communication with the fluid passages. 
     Embodiments of the present method can be practiced with any of the devices of the present invention described above. The devices and methods of the present invention are ideally suited for high pressure applications. These high pressure applications include pressures of 4000 psi and greater. 
     The devices made in accordance of the present invention do not have seals that exhibit material creep, cold flow and relaxation. That is, as the fluid pressure fluctuates, the seal coating do not move. The seal coatings are adhered to or fixed to one of the abutment surfaces. As such the seal coating can not move or slip from an original position. Thus, embodiments of the present invention provide devices that do not have gasket failure. 
     Nor do devices of the present invention exhibit rebound pressure ripple due to gasket movement as the pressure is released. Analytical instruments, in particular, having devices made in accordance with the present invention are less sensitive to pressure fluctuations. These features and advantages will be apparent to those skilled in the art to which this invention relates upon viewing the Figures and reading the detailed description that follows. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  depicts, in cross section, a side view of a device made in accordance with the present invention; 
         FIG. 2  depicts, in slight elevation, a view of an end cap of a device made in accordance with the present invention; 
         FIG. 3  depicts, in slight elevation a view of an end cap of a device made in accordance with the present invention; 
         FIG. 4  depicts, in cross section, a side view of an end cap of a device made in accordance with the present invention; and, 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Embodiments of the present invention will now be described with respect to the Figures, with the understanding that the Figures and description are directed to the preferred embodiments of the present invention. For example, the present invention will be described in detail with respect to a check valve. Individuals skilled in the art will recognize that features of the present invention have application in many devices which hold or transport fluids under pressure. 
     Turning now to  FIG. 1 , a device, for holding fluids at high pressures, generally designated by the numeral  11 , is depicted. The device  11 , for receiving and discharging fluids, is in the nature of a check valve. Device  11  comprises a first housing  13 , an end cap  15 , at least one seal coating  17  and compression means  19 . 
     Turning now to  FIG. 2 , the first housing  13  has at least one side wall  25 . Side wall  25  has an interior surface  27   a  and an exterior surface  27   b . The interior surface  27   a  defines at least one chamber  29 , preferably, cylindrical in shape. Interior surface  27   a  has at least one end cap abutment surface  31  for receiving the end cap  15 . Preferably, the end cap abutment surface  31  is recessed into chamber  29  to facilitate positioning of the end cap  15 . As depicted, interior surface  27  has a recess section  33  forming the recess for receiving end cap  15 . 
     The housing  13  has an end wall  35  having an interior surface  37   a  and an exterior surface  37   b . The end wall  35  closes the chamber  29  defined by the interior surface  27   a  of the side wall  25 . 
     End cap  15  is cylindrical in shape to cooperate with the recess section  33  of the interior surface  27   a  of the first housing  13 . End cap  15  has at least one first housing abutment surface  39 . Turning now to  FIGS. 3 and 4 , alternative embodiments of end cap  15  are disclosed. The end cap  15  of  FIG. 2  is illustrated in greater detail in  FIG. 3 . End cap abutment surface  39  is a ridge  39   a  to localize compression forces on said seal coating  17 . The ridge  39   a  is a protrusion jutting upward from a planar surface  39   b . The ridge  39   a  is capable of contact with an opposing abutment surface such as end cap abutment surface  31  of the first housing  13 . The ridge  39   a  localizes or focuses compression forces in a small area. 
     Turning now to  FIG. 4 , a further embodiment of the end cap  15  is illustrated, generally designated by the numeral  15 ′. End cap  15 ′ is cylindrical in shape to cooperate with the recess section  33  of the interior surface  27   a  of the first housing  13 . End cap  15 ′ has at least one first housing abutment surface  39 ′. In this embodiment, the first housing abutment surface  39 ′ is planar, without any protruding surface features. The abutment surface  39 ′ is capable of contact with an opposing abutment surface such as end cap abutment surface  31  of first housing  13 . 
     The first housing abutment surface  31  receives the end cap abutment surface  39  and  39 ″ positioning the end cap  15  and/or  15 ′ on the first housing  13  for enclosing the chamber  29 . The end cap  15  and/or  15 ′ and first housing are typically made of stainless steel; however, other materials can readily be substituted. In the case where, the first housing  13  and end cap  15  and/or  15 ′ are parts of a check valve, the first housing  13  is approximately 0.25 to 0.75 mm in length and diameter. The end cap  15  and or  15 ′ are approximately 0.1 to 0.70 in diameter and 0.1 to 0.2 mm in thickness. 
     At least one of the first housing abutment surface  39  and/or  39 ′ and the end cap abutment surface  31  has first seal coating  17 . The first seal coating  17  comprises a deformable plastic adhering to first housing abutment surface  31  and/or  31 ′ or the end cap abutment surface  39 . Seal coating  17  is selected from one or more of the polymeric coatings consisting of polytrifluoroethylene (PTFE), polyetheretherketone (PEEK), polychlorotrifluoroethylene (PCTFE), perfluoroalkoxy (PFA) and fluorinatedethylenepropylene (FEP). The polymeric coating is applied to the entire end cap  15  and/or  15 ′ or the first housing abutment surface  31  and/or  31 ′ to a thickness of 0.0005-0.0025 inches, and most preferably, approximately 0.0010 to 0.0015 inches. Methods of placing a polymeric coating on a metal substrate are well known in the art. 
     The device  11  further comprises fluid path means for receiving and removing fluid from the chamber. Referring now to  FIGS. 3 and 4 , the end cap  15  and  15 ′ have an end cap opening  45 . And, returning now to  FIG. 1 , the first housing has a first housing opening or more preferably a pair of first housing openings  47   a  and  47   b  for introducing fluids into the chamber  29 . Preferably, the pair of openings are set off axis for check valve applications in end wall  35 . 
     The end cap opening  45  and first housing openings  47   a  and  47   b  may comprise any ports, conduits and pipes that provide fluid. Thus, embodiments of the present invention can be placed inline, with fluid path means comprising conduits and pipes or incorporated within the housing of a larger structure, for example, without limitation, as depicted in  FIG. 1 , a pump head or pump housing  49 . 
     The device  11  comprises compression means  19  to compress the end cap  15  and/or  15 ′, with the end cap abutment surface  31  and/or  31 ′ received on said first housing abutment surface  39 , towards said first housing  13 . The compression deforms the first seal coating  17  and seals the chamber. As illustrated in  FIG. 1 , the compression means  19  comprises pump housing  49 , compression housing  51  and screw fitting  53 . 
     It will be recognized by those skilled in the art that pump housing  49  may be substituted with a further fitting that cooperates with compression housing  51  and screw fitting  53 , to allow the device  11  to be placed in a fluid line. 
     Embodiments of the present invention are ideally suited for fittings and valves. Where the device is in the form of a valve, referring to  FIG. 2 , the chamber  29  contains a valve assembly  61 . The valve assembly  61  may comprise rotary-type valves (not shown), gated valves (not shown) or check valves, to described in further detail. 
     In the case where the device is in the form of a check valve, the first housing  13  has at least one end wall  65  opposite the end cap  15  or  15 ′. The fluid path means comprises at least one opening  45  in said end cap  15  or  15 ′ and at least one opening, and preferably two,  47   a  and  47   b , in said end wall  65 . Chamber  29  holds a valve assembly  61  comprising a ball seat  71  and a ball  73 . 
     Preferably, the interior wall  27   a  has a first ball seat abutment surface  77 . And, the end cap  15  and/or  15 ′ has a ball seat abutment surface  79 . The ball seat  71  comprises a cylinder section  81  having a first rim  83 , a second rim  85  and a fluid passage  87 . The first rim  83  has a ball receiving surface  89  for engaging the ball  73  and closing the fluid passage  87 . Second rim  85  has a rim abutment surface  91  and end cap  15  and/or  15 ′ has a ball seat abutment surface  79 . Preferably, at least one of the rim abutment surface  91  and ball seat abutment surface  79  has a ball seat seal coating  95 . The ball seat seal coating  95  engages the abutment surface opposite to that it is placed and seals the ball seat and the housing  13  and/or end cap  15  and/or  15 ′. The ball seat coating  95  may comprise a portion of the seal coating  17  on the end cap  15  and/or  15 ′. Preferably, the ball seat coating is made and formed as described above with respect to the seal coating  17 . 
     The exterior surface  37   b  of end wall  35  has an end wall abutment surface  99  encircling the one or more end wall openings  47   a  and  47   b . Preferably, the end wall abutment surface  99  has an end wall seal coating  101 . The end wall seal coating  101  is a deformable plastic made and formed as described above with respect to the seal coating  17 . The end wall seal coating  101  sealably engages an adjoining wall to which it is compressed. 
     Devices of this type are well suited to be mounted in a further major housing structure having the adjoining wall. For example, turning now to  FIG. 1 , the end wall seal coating  101  engages the adjoining wall  105  of a pump head housing  49 . In this embodiment, preferably, the adjoining wall  105  has an opening  103  for the passage of fluid into the end wall opening (not shown). In this embodiment, the compression means  19  comprises such adjoining wall  105  and a cylindrical wall  107  for receiving the end wall abutment surface  99  and compressing the end wall seal coating  101  in sealing engagement. The compression means  19  comprises a compression assembly comprising a compression housing  51  and compression sleeve  53 . The compression housing  51  has a compression chamber  113  for receiving the first housing  13  and the end cap  15  and/or  15 ′. The compression sleeve  53  engages the compression housing  51  for placing said end cap  15  and/or  15 ′, and first housing  13  under compression. 
     Preferably, the compression sleeve  53  and compression nut (not shown) or the pump head  49  or other apparatus to which it is placed has cooperating threads  115  as depicted in  FIG. 1 . The cooperating threads  115  engage upon relative rotation of the compression sleeve and pump housing  49  or compression nut (not shown). 
     Turning now to  FIG. 2 , the compression housing  51  has an second end cap abutment surface  117 . At least one of the end cap  15  and/or  15 ′ has a compression assembly seal coating  121 . The compression assembly seal coating  121  is a deformable plastic made and formed as described above with respect to the seal coating  17 . The compression assembly seal coating  121  sealably engages an adjoining wall to which it is compressed. 
     In operation, a method of using the present invention to joining fluid passages comprises the steps of providing a device  11  having a first housing  13 , an end cap  15  and or  15 ′, a seal coating  17  and compression means  19 . The device has a fluid path means for receiving and removing fluid from the chamber  29 . The method further comprises the step of placing the receiving conduit and discharge conduits in communication with the fluid passages and compressing the seal coating  17  to seal the chamber  29 . 
     The devices and methods of the present invention are ideally suited for high pressure applications. The devices made in accordance of the present invention do not have seals that exhibit material creep, cold flow and relaxation. That is, as the fluid pressure fluctuates, the seal coating do not move. The seal coatings are adhered to or fixed to one of the abutment surfaces. As such the seal coasting can not move or slip from an original position. Thus, embodiments of the present invention provide devices which do not have gasket failure. 
     These and other advantages and features will be apparent to those skilled in the art to which this invention relates and therefore the present invention should not be limited to the precise details disclosed herein but should encompass the subject matter of the claims that follow.