News Column

Patent Issued for Method for Filtering Fluid Using a Filter Vial

June 4, 2014



By a News Reporter-Staff News Editor at Journal of Engineering -- A patent by the inventors Ellis, Samuel A. (Oceanside, CA); Hingorani, Kishan G. (Oceanside, CA), filed on November 6, 2012, was published online on May 20, 2014, according to news reporting originating from Alexandria, Virginia, by VerticalNews correspondents.

Patent number 8728329 is assigned to Scientific Plastic Products, Inc. (Oceanside, CA).

The following quote was obtained by the news editors from the background information supplied by the inventors: "Filter vials have a tubular plunger with a filter at the bottom end of the plunger. The plunger fits into a mating vial containing a fluid and things suspended in the fluid. When the plunger is inserted into the vial fluid passes through the filter and into the plunger in order to separate the fluid from particles or molecules too large to pass through the filter in the bottom of the plunger. The filtered fluid can be extracted from the plunger for further use.

"The diameter and thickness of the filters can vary greatly from filter to filter and the thickness of the filter can vary greatly even across one filter. These variations make it difficult to seal the filters so all the fluid being filtered passes through the filter, and so that fluid does not wick around the peripheral edge of the filter to contaminate the filtered fluid in the plunger. Further, as fluid is forced through the filters the filters can bow or otherwise deform and allow fluid to bypass the filter as it enters the body of the plunger. Many current assemblies use ultrasonically welded assemblies. Even if the filters are ultrasonically welded to the adjacent walls of the assemblies that still leaves plasticizers that may contaminate the fluids placed in the vials during use.

"Moreover, current filter vials leave a slight gap between the bottom of the plunger and the bottom of the vial, leaving a portion of the sample unfiltered and unusable for future testing or processing. While the volume of this unfiltered sample may be small in absolute terms, it may represent a sufficiently large portion of the sample that its absence can be important. There is thus a need for a filter vial that avoids the loss of fluid samples and processes more of those samples."

In addition to the background information obtained for this patent, VerticalNews journalists also obtained the inventors' summary information for this patent: "A filter vial for separating biological, chemical or other fluids has a cylindrical sidewall with an open top and a closed bottom. A frustoconical protrusion extends upwards from the middle of the bottom to form an annular recess in the bottom of the vial. A tubular plunger has an open bottom end to which is fastened an annular cup having an outer sidewall that is sized to fit into and seal against the vial's sidewall. The annular cap has an inner sidewall that holds a filter over an opening in the bottom of the plunger and forms a shaped cavity leading to that filter. The space between the cap's inner and outer sidewalls mates with a tubular end of the plunger. The annular cup on the end of the plunger fits snugly into the annular recess in the vial as the protrusion fits into the shaped recess so as to force fluid from the vial past the protrusion, through the filter and into the plunger.

"In more detail, there is provided a filter vial and plunger assembly for filtering fluids in which the plunger is a tubular plunger having sidewalls defining an internal fluid cavity. The plunger has a top and bottom ends with a plunger opening in the bottom end of the plunger. An annular cap is connected to the bottom end of the plunger. The annular cap has concentric inner and outer sidewalls with the outer sidewall connected to an outer sidewall of the plunger and the inner sidewall defining a shaped cavity in fluid communication with the plunger opening. The cap's outer sidewall has an outwardly extending first sealing surface at or by its bottom. A filter is interposed between the cap's inner sidewall and the plunger opening to filter fluid passing through the opening. The plunger fits into a vial that has an open top and closed bottom joined by cylindrical sidewalls of sufficient diameter to form a fluid tight seal with the first sealing surface. The vial has a protrusion extending from the center of its bottom toward the top. The annular the bottom of the cap and the bottom of the vial having complementary shapes, including complementary shapes of the protrusion and shaped cavity, to direct fluid from the vial through the shaped cavity during use. Optionally, shallow channels may be formed in the bottom of the vial and in an exterior surface of the protrusion with the channels orientated to carry fluid toward the top of the protrusion. Preferably, but optionally, the protrusion is frustoconical.

"There is also provided a filter vial apparatus having a tubular vial with a closed bottom, an open top and a sidewall defining a cylindrical interior with a diameter D located along a longitudinal axis of the vial. The closed bottom has a protrusion extending toward the open top and the vial bottom and protrusion define an annular recess about the vial's longitudinal axis of the vial with the protrusion at the center of the annular recess. The apparatus also includes a tubular plunger assembly having a longitudinal axis. The plunger assembly includes a plunger with opposing top and bottom ends joined by a sidewall to define a fluid holding cavity in the plunger. The plunger's bottom end has an outer annular surface and an inner annular surface axially offset toward the top end from the outer annular surface. The inner annular surface is generally orthogonal to the assembly longitudinal axis and is joined to the first annular surface by a recess sidewall to form a recess that encircles the assembly's longitudinal axis. The second annular surface defines a recess opening that is in fluid communication with the fluid holding cavity of the plunger. The assembly also has an annular cap with inner and outer concentric sidewalls defining an annular recess into which the outer annular surface on the bottom of the plunger is placed. The cap's outer sidewall extends over the outer surface of the bottom of the plunger while the cap's inner sidewall is placed adjacent the sidewall of the recess in the end of the plunger. The inner sidewall of the cap defines a shaped cavity configured to snugly receive the protrusion on the vial's bottom. The shaped cavity has an upper end in fluid communication with the recess opening in the plunger. Further, an outer surface of the outer sidewall of the cap has a diameter sufficiently larger than diameter D to form a fluid tight seal when the plunger assembly is inserted into the vial yet allowing movement of the annular cap to the bottom of the vial. The assembly also includes a filter interposed between the inner annular surface in the plunger and the inner wall of the annular cap. Further, the annular cap on the bottom of the plunger assembly is configured to fit into the annular recess at the bottom of the vial.

"In further variations of this filter vial apparatus, the annular cap on the bottom of the plunger conforms in size and shape to the annular recess in the bottom of the vial and forms a snug fit with the bottom and protrusion and a snug fit or a slight interference fit with the vial sidewall. Further, the protrusion and shaped cavity may both be frustoconical with substantially the same dimensions and larger at the bottom than toward the top. Still further, shallow channels may optionally be formed in the bottom of the vial and the sides of the protrusion in order to channel fluid through the channels to the filter. Also, the filter vial assembly may have a releasable end cap on the top end of the plunger, with the end cap configured to provide a fluid seal to the fluid holding cavity of the plunger. Still further, the above filter vial apparatus may optionally have a cap flange on the upper end of the outer sidewall of the cap with the cap flange extending outward from the cap sidewall to provide the outer surface of the outer sidewall of the cap that forms the fluid tight seal with the sidewall of the vial.

"The apparatus may also include an outward facing recess in the outer surface of the tubular plunger with that recess located adjacent the bottom end of the plunger and with the cap flange located in that outward facing recess. The plunger may have an outwardly extending plunger flange at or adjacent to the bottom end of the outward facing recess. The outer sidewall of the cap and outward facing recess may be located so the outer sidewall of the cap extends over the plunger flange and into that outward facing recess, with the outer diameter of the outer wall of the cap at the location of the flange having a diameter larger than diameter D to form a fluid tight fit with the sidewall of the vial during use.

"The filter vial apparatus may advantageously have the recess sidewall in a convex shape and curved toward the longitudinal axis of the plunger, with the inner sidewall of the annular cap having an outer surface is concave and conforms to the shape of the recess sidewall to nest with the convex surface on the recess sidewall. Further, the vial may advantageously be configured to hold about 10 or fewer micro liters of fluid to be forced through the filter. Advantageously, the bottom of the annular cap may abut the bottom of the vial and less than about 10 micro liters of fluid has passed through the filter into the fluid holding cavity of the plunger. Also, the apparatus may include a frit or filter support on the upper side of the filter and abutting the filter. Preferably, the inner and outer sidewalls of the annular cap each engage a portion of the plunger to hold the annular cap onto the bottom end of the plunger.

"In another embodiment, there is provided a filter vial apparatus having a longitudinal axis that includes a vial, a tubular plunger and an annular cap. The vial comprises a cylindrical walled vial with a closed bottom and an open top. The vial has a centrally located protrusion on the bottom that extends toward the top to form an annular recess at the bottom of the vial. The plunger comprises a hollow, tubular plunger that extends into the vial. The plunger has an annular bottom with an axially facing recess therein ending at an annular wall encircling and defining a recess opening in fluid communication with a cavity inside of the tubular plunger. The annular cap has inner and outer sidewalls placed over the annular bottom of the plunger with the outer sidewall on an outer sidewall of the plunger. The outer sidewall has an outer surface a first portion of which extends outward from the longitudinal axis a distance sufficient to form a first sealing surface that forms a fluid tight seal with the cylindrical wall of the vial when the plunger is advanced into the vial a distance sufficient to engage the first portion with the vial's wall during use of the assembly. The inner sidewall of the cap fits into the axially facing recess and extends a distance sufficient to hold a filter against the annular wall of the recess and to also place the filter in fluid communication with the shaped cavity formed by the inner sidewall of the annular cap. The annular cap is configured to fit into the annular recess of the vial with the vial's protrusion snuggly fitting into the shaped cavity.

"In further variations of this filter vial assembly, the first sealing surface comprises a flange at the bottom end of the plunger forcing the outer sidewall of the annular cap outward against the vial's sidewall. Preferably, the sealing surface is located at a bottom end of the plunger and annular cap. Further, the assembly may have a second sealing surface on the outer sidewall of the annular cap located upward of the first sealing surface. Advantageously the protrusion is frusto-conical in shape and the inner wall of the cap has an inward facing surface that is frusto-conical in shape. Further, the axial facing recess in the end of the plunger may have a sidewall that is convex in shape and the cap may have an outward facing surface on the inner sidewall that is configured to mate with the convex sidewall. Still further, channels in the bottom of the vial may be placed in fluid communication with channels in the surface of the protrusion in order to carry fluid from the container bottom toward the filter during use of the filter vial assembly.

"There is also provided a tubular plunger assembly for filtering fluids, for use with various vials. The tubular plunger has at least an open bottom with a fluid holding cavity in the plunger. The plunger has a bottom end with an inner and an outer annular surface which not only encircle and are orthogonal to a longitudinal axis of the plunger but are separated a distance along that by a recess sidewall that encircles and faces the longitudinal axis to define a plunger recess in the bottom end of the plunger. The inner annular surface encircles and defines an opening to the recess which opening is in fluid communication with the fluid holding cavity of the plunger. The plunger assembly has an annular cap with a cap bottom from which extends inner and outer concentric sidewalls configured to fit over the bottom end of the plunger. The outer sidewall fits over an outer surface of the bottom end of the plunger. The inner and outer sidewalls receive the outer annular surface therebetween. The inner sidewall has an outer surface abutting the sidewall of the plunger recess. The inner surface of the inner sidewall defines a shaped cavity in fluid communication with the opening to the recess. The inner sidewall has a top end. A filter is clamped between that top end of the inner sidewall and the inner annular surface.

"In further variations, the tubular plunger assembly has a portion of the outer surface of the outer sidewall of the annular cap, at or by the bottom of the annular cap, extending outwardly a distance sufficient to form a first sealing surface that provides a fluid tight seal against a filter vial when the cap is inserted into the vial during use of the plunger assembly. The first sealing surface is advantageously formed by a flange on the end of the plunger which forces a portion of the cap's sidewall outward. The plunger assembly may also include a frit or support interposed between the filter and the first annular surface. Further, the assembly may have a sealing surface facing along and encircling the longitudinal axis and formed on at least one of the first and second annular surfaces. Also, the recess sidewall may have a convexly curved shape in which case the outer surface of the inner sidewall of the cap preferably has a mating concave shape. The shaped cavity is preferably frustoconical in shape. Advantageously, the tubular plunger has a sidewall that is thicker at the location of the second annular surface. Preferably, the plunger assembly may have a removable closure configured to releasably form a fluid tight seal at the top end of the plunger.

"There is also provided a filter vial kit that includes any of the above described plunger assemblies as well as a filter vial. The filter vial may have an open top and a closed bottom with a protrusion on the center of the bottom. The protrusion extends toward the top a distance about the same as a height of the inner sidewall of the annular cap measured along the longitudinal axis. The protrusion conforms in shape to the shaped cavity in the cap. The filter vial may also have an internal diameter slightly smaller than the outer diameter of at least a portion of the outer sidewall of the cap on the bottom of the plunger to form the fluid tight seal with the first sealing surface.

"In further variations the filter vial kit may include a removable cap and a volume of less than about 30 micro liters. Also, the interior bottom of the vial and protrusion may be configured to conform to the exterior shape of the bottom of the cap and shaped recess. Advantageously, but optionally, the bottom of the filter vial may have shallow channels formed therein which channels are in fluid communication with shallow channels in the surface of the protrusion. The channels are orientated to carry fluid to the top of the protrusion during use.

"Another filter vial kit is also provided in which includes a plunger, a filter, an annular cap and a vial. The plunger comprises a hollow tubular plunger having top and bottom ends with an opening at a bottom end of the plunger. The filter extends across the opening in the bottom end of the plunger. The annular cap is fastened to the bottom end of the plunger. An outer sidewall of the cap extends along an outer surface of the bottom end of the plunger with a portion of that outer sidewall extending outward a predetermined diameter to form a first sealing surface. The annular cap has an inner sidewall forming a shaped cavity in fluid communication with the opening in the bottom end of the plunger. The vial has an open top and a closed bottom with the bottom having a central protrusion extending toward the open top of the vial. The vial also has a cylindrical sidewall that is sufficiently smaller in diameter than the predetermined diameter to form a fluid tight seal between the vial and annular cap. The bottom of the annular cap and the shaped recess are configured to mate with the shape of the vial's bottom and the protrusion so as to force fluid in the vial through the shaped cavity and filter.

"In further variations of this filter vial kit the bottom of the vial has shallow channels in fluid communication with shallow channels in the surface of the protrusion so fluid is forced through the channels toward the filter as the annular cap fits snuggly against the vial's bottom and its protrusion. Further, the inner sidewall of the cap may push the filter against a portion of the plunger to hold the filter in place. Preferably, the shaped cavity is frustoconical and the protrusion has a mating frustoconical shape with shallow channels in the surface of the protrusion to carry fluid to the top of the protrusion.

"An improved filter vial is also provided. The improved vial includes a plastic filter vial having an open top and a closed bottom connected by a cylindrical sidewall. The bottom has a protrusion extending a short distance along a longitudinal axis of the vial toward the top. The filter vial has a volume of about 30 micro liters or less and a sidewall thickness of about 0.050 inches or less. Optionally, the protrusion is frustoconical and extends for a distance of less than about 0.2 inches. Optionally, the bottom of the vial has shallow channels therein that are in fluid communication with shallow channels in an outer surface of the protrusion and orientated to carry fluid through the channels toward the top of the protrusion. The channels are preferably radially orientated."

URL and more information on this patent, see: Ellis, Samuel A.; Hingorani, Kishan G.. Method for Filtering Fluid Using a Filter Vial. U.S. Patent Number 8728329, filed November 6, 2012, and published online on May 20, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=103&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=5146&f=G&l=50&co1=AND&d=PTXT&s1=20140520.PD.&OS=ISD/20140520&RS=ISD/20140520

Keywords for this news article include: Scientific Plastic Products Inc.

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Source: Journal of Engineering


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