Abstract:
A sample analysis cup, sample cup assembly, and method is provided including a cell body with an open top end including an outer top wall and an inner top wall, each extending axially and positioned in concentric relationship; a bottom wall extending from the outer top wall to the inner top wall, the bottom wall and the inner and outer top walls defining an internal reservoir therebetween; a transverse wall extending a selected distance from the inner top wall, the transverse wall partially closing the open top end; an open bottom end including an outer bottom wall and an inner bottom wall, each extending axially and positioned in concentric relationship, the outer and inner bottom walls defining an internal channel therebetween; and a hollow chamber defined between the open top end and the open bottom end.

Description:
RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Patent Application No. 61/606,578, filed on Mar. 5, 2012, the entire disclosure of which is hereby incorporated by reference herein. 
    
    
     FIELD OF THE INVENTION 
     The invention relates generally to sample analysis cups, and more particularly, to sample analysis cups used in spectrochemical analysis. 
     BACKGROUND OF THE INVENTION 
     Spectroscopy is an analytical science where the characteristics or properties of a sample substance are determined based on the spectra of energy that the sample absorbs or emits. Technological advancements in both wavelength-dispersive (WD-XRF) and energy-dispersive (ED-XRF) X-ray fluorescence instrumentation enable the spectroscopic analysis of many types of sample materials, including liquid, solid, and powdered specimens. 
     Sample analysis cups are used with spectroscopic instrumentation to retain the sample substances during analysis. The sample substances may be disposed in a central chamber of a sample cup. A thin film of material may be disposed across an open end of a cup to retain a sample substance within the chamber and to provide a sample surface plane which is exposed to an excitation source, such as an X-ray beam, laser diode or other energy sources. The sample substance contained in the cup is subjected to analysis when energy beams impinge upon the sample surface plane. It is essential for the surface of the thin film of material, which covers an open end of the cell body, to remain planar and taut during analysis in order to produce reliable, accurate, and precise data. 
     With the spectrochemical analysis of specimens that exhibit high abrogation in air, a sample cup containing a specimen may be placed within a vacuum or pressurized inert gas environment. Under vacuum conditions where pressure equalization is not implemented, the thin film of material will distend outwardly due to the differential in pressures between the area within the sample cup and the environment surrounding the sample cup, which places portions of the thin film of material closer to the source of excitation. The variation and decrease in distance from the sample surface plane to the source of excitation alters the absorption and emission of radiation from the sample specimen and the intensity of radiation impinging upon the specimen. Consequently, erroneous qualitative and quantitative data may be produced. 
     In applications requiring a pressurized inert gaseous environment, where pressure is greater on the outside of the sample cup than inside the sample cup, the thin film of material distends into the hollow of the sample cup providing a concave sample surface, thereby increasing the distance between the sample surface plane and the excitation source, also resulting in erroneous analytical data. 
     To equalize the pressure between the inside and outside of the sample cups, and to eliminate distension of the sample surface plane, some sample cups are provided with a venting means, or may include a vent hole in the top or cap of an assembled cup. The venting means may be activated or punctured to provide pressure equalization between the inside and outside of the cup. Other sample cups may include a main cell body with a double open-ended cup, which, upon assembly with a thin film, allows for continuous venting during analysis. 
     In addition to the problem of distention, the sample substance contained in a sample cup may escape or exude from the central chamber during analysis onto the analysis chamber, an X-ray tube, an X-ray detector, or other delicate electronic components of the instrumentation, causing damage thereto. In addition, the exuded sample substance may cause contamination issues, costly cleanups, and non-productive down time. 
     There remains a need for sample cups that provide a planar sample surface plane while substantially eliminating the possibility of any sample exuding from the cup during analysis, and the subsequent damage and contamination to the instrumentation. 
     SUMMARY OF THE INVENTION 
     According to an aspect of the invention, a sample analysis cup includes a a cell body, including: an open top end including an outer top wall and an inner top wall, each of the walls extending axially and positioned in concentric relationship; a bottom wall extending from the outer top wall to the inner top wall, the bottom wall and the inner and outer top walls defining an internal reservoir therebetween; a transverse wall extending a selected distance from the inner top wall, the transverse wall partially closing the open top end; an open bottom end including an outer bottom wall and an inner bottom wall, each of the walls extending axially and positioned in concentric relationship, the outer and inner bottom walls defining an internal channel therebetween; and a hollow chamber defined between the open top end and the open bottom end is provided. 
     According to an aspect of the invention, a sample cup assembly including a cell body, including: an open top end including an outer top wall with and an inner top wall, each of the walls extending axially and positioned in concentric relationship; a bottom wall extending from the outer top wall to the inner top wall, the bottom wall and the inner and outer walls defining an internal reservoir therebetween; a transverse wall extending a selected distance from the inner top wall, the transverse wall partially closing the open top end; an open bottom end including an outer bottom wall and an inner bottom wall, each of the walls extending axially and positioned in concentric relationship, the outer and inner bottom walls defining an internal channel therebetween; and a hollow analysis chamber defined between the open top end and the open bottom end; a thin film of material; an annular ring member configured for insertion into the internal channel for retaining the thin film of material; and a rotatable cap configured for placement on the open top end is also provided. 
     According to another aspect of the invention, a method for mounting a thin film of material across an open end of a sample cup includes the steps of: providing a cell body including: an open top end including an outer top wall and an inner top wall, each of the walls extending axially and positioned in concentric relationship; a bottom wall extending from the outer top wall to the inner top wall, the bottom wall and the outer and inner top walls defining an internal reservoir therebetween; a transverse wall extending a selected distance from the inner top wall, the transverse wall partially closing the open top end; an open bottom end including an outer bottom wall and an inner bottom wall, each of the walls extending axially and positioned in concentric relationship, the outer and inner bottom walls defining an internal channel therebetween; and a hollow chamber defined between the open top end and the open bottom end; disposing a thin film of material across the open bottom end; inserting an annular ring member into the internal channel; and disposing a rotatable cap on the partially closed open top end is also provided. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Throughout the drawings, like reference numerals are used to indicate common features of the described devices. 
         FIG. 1  is an exploded view of the sample cup and a sample cup assembly according to an aspect of the invention; 
         FIG. 2  is a cross-sectional view illustrating the sample cup according to an aspect of the invention; 
         FIG. 3  is a cross-sectional view illustrating the sample cup according to an aspect of the invention; 
         FIG. 4  is a top plan view of a cell body according to an aspect of the invention; 
         FIG. 5  is an exploded view of a sample cup according to an aspect of the invention; 
         FIG. 6  is a cross-sectional view of a sample cup illustrating the vent hole in a closed position; and 
         FIG. 7  is a cross-sectional view of a sample cup illustrating the vent hole in an open, vented position. 
     
    
    
     The above-identified drawing figures set forth several of the embodiments of the invention. Other embodiments are also contemplated, as disclosed herein. The disclosure represents the invention, but is not limited thereby, as it should be understood that numerous other modifications and embodiments may be devised by those skilled in the art which fall within the scope and spirit of the invention as claimed. 
     DETAILED DESCRIPTION OF THE INVENTION 
     As used herein, the terms “comprises”, “comprising”, “includes”, “including”, “has”, “having”, or any other variation thereof, are intended to cover non-exclusive inclusions. For example, a process, method, article or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. In addition, unless expressly stated to the contrary, the term “of” refers to an inclusive “or” and not to an exclusive “or”. For example, a condition A or B is satisfied by any one of the following: A is true (or present) and B is false (or not present); A is false (or not present) and B is true (or present); and both A and B are true (or present). 
     The terms “a” or “an” as used herein are to describe elements and components of the invention. This is done for convenience to the reader and to provide a general sense of the invention. The use of these terms in the description herein should be read and understood to include one or at least one. In addition, the singular also includes the plural unless indicated to the contrary. For example, reference to a device containing “an element” includes one or more elements. As used in this specification and the appended claims, the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise. 
     All numeric values are herein assumed to be modified by the term “about,” whether or not explicitly indicated. The term “about” generally refers to a range of numbers that one of skill in the art would consider equivalent to the recited value (i.e., having the same function or result). In any instances, the terms “about” may include numbers that are rounded to the nearest significant figure. 
     Referring to  FIG. 1 , according to an aspect of the invention, a sample cup assembly  100  includes a generally open-ended and cylindrical tiered cell body  10 . As illustrated in  FIG. 1 , toward the upper portion of the cell body  10 , adjacent the open top end  12  is an annular outer top wall  14  with an outer top planar edge  16  and an annular inner top wall  18  with an inner top edge  20 . The inner top edge  20  of annular inner top wall  18  includes a planar portion  50  disposed thereon. Inner top edge  20  also includes a series of semi-spherical channels  21  disposed along a portion of the inner edge  20  that extend from the inner surface  17  of wall  18  through to the outer surface  19 . Parallel outer top and inner top walls  14  and  18  extend axially and are positioned in concentric relationship about central axis Y. 
     An annular internal overflow reservoir  22  is defined in the space between the inner surface  15  of outer top wall  14 , the outer surface  19  of inner top wall  18 , and the rounded, concave upper surface  25  of transverse horizontal wall  24 . As illustrated in  FIG. 1 , the overflow reservoir has a U-shaped cross-section. It should be understood that the upper surface of transverse horizontal wall  24  may also be flat or planar, with the resulting cross-section being hem i-rectangular. 
     During analysis, thermally-sensitive sample materials may expand in volume due to excitation from the energy beam. Internal overflow reservoir  22  is configured for receiving the overflow of a thermally-sensitive liquid sample  72  from the analysis chamber  27  ( FIG. 3 ). According to an aspect of the invention, the inner top edge  20  of the inner top wall  18  is positioned a selected distance below the outer top edge  16  of outer top wall  14 . According to another aspect of the invention, the inner top edge  20  is at the same level and planar with the outer top edge  16 . Regardless of the height of the inner top edge  20 , any expanded sample overflows from the analysis chamber through the series of channels  21  and into the internal reservoir  22 , and is retained in the internal reservoir  22  to prevent the expanded sample from escaping from the cell assembly and causing possible damage to the instrumentation and the concomitant and time-consuming decontamination clean-ups associated therewith. 
     Still referring to  FIG. 1 , the lower portion of cell body  10  includes an open bottom end  26  with an outer bottom wall  28  and an inner bottom wall  30 . Parallel outer and inner bottom walls  28  and  30  extend axially and are positioned in concentric relationship about central axis Y. The inner bottom wall  30  adjoins the outer top wall  14 . An internal receiving channel  32  is defined in the annular space between the inner surface  29  of outer bottom wall  28 , the outer surface  31  of inner bottom wall  28 , and the lower surface  33  of outer transverse horizontal wall  34 . 
     Still referring to  FIG. 1 , a substantially cylindrical, and two-tiered hollow analysis chamber  27 , defined in the space between the annular inner top wall  18 , from the inner top edge  20  to the open bottom end  26 , is configured for receiving a sample material  72  and retaining the sample material before, during, and after spectrochemical analysis. 
     As further illustrated in  FIG. 1 , an annular collar  36 , configured for insertion into the internal receiving channel  32 , includes an open top end  38 , an open bottom end  40 , and a substantially cylindrical wall  42 . Annular collar  36  may include an external peripheral flange  44  disposed about the outer periphery of the open bottom end  40 . The edge  39  of the open top end  38  may be rounded to avoid tearing a thin film of material upon assembly, as will be described hereinafter. 
     When external peripheral flange  44  is present on the annular collar  36 , the inner surface  29  of the outer bottom wall  28  of cell body  10  includes an internal peripheral recess  46  having a shape complementary to the external peripheral flange  44 . According to an aspect of the invention, the external peripheral flange  44  and the internal peripheral recess  46  may be rectangular or square in cross-section as illustrated in  FIGS. 1 and 2 , or external peripheral flange  44 ′ may be configured with an indent  70  and the internal peripheral recess  46 ′ with a bead  68  as illustrated in  FIG. 3 . 
     Referring still to  FIG. 1 , a cap  52  configured for assembling with the cell body  10  includes a top surface  54 , a bottom surface  56 , and a peripheral sidewall  58  that extends downwardly from the top surface  54  of the cap  52 . The cap  52  includes a vent or through-hole  60  that extends from the top surface  54  through to the bottom surface  56 . The vent hole  60  is off-centered, as illustrated in FIG.  1 . The cap  52  may also include an internal annular bead or projection  64  disposed on the inner surface  65  of the peripheral sidewall  58 . A top plan view of the cap  52  illustrating the planar member  50  and the series of channels  21  is illustrated in  FIG. 4 . 
     The diameter of vent hole  60  is a factor to consider with respect to the rate of withdrawal of any contained air or gases to be evacuated when attempting to reach equilibrium of pressure from within an assembled sample cup  100  and the sample analysis chamber of the instrumentation. Attaining equilibrium of pressure is necessary, for example, when a sample substance is in a fine, powdered form, and having a low density. The powdered sample tends to become airborne during the initial evacuation surge. With the advantage of independent user control of the vent, this condition is eliminated, since a greater volume of any entrapped air or gas is evacuated with no or minimum disruptive effect to the sample substance particles. 
     When an assembled sample cup is used in a positive pressure environment, for example, an inert gas including helium being introduced into the sample chamber, the vent hole  60  serves as a point of entry for the inert gas into the sample chamber. By controlling the vent size, the rate of entry is also advantageously controlled by the user to maintain a planar sample plane and avert distension. Liquid samples behave in a similar manner, in that the initial surge of evacuation tends to agitate the liquid, which problem is avoided with the adjustable and moveable vent hole  60 . A suitable vent hole diameter may range between about 0.175″ (4.45 mm), although other suitable diameters may also be employed. 
     When a bead  64  is present on the cap  52 , as further illustrated in  FIGS. 2 and 3 , the outer surface  23  of outer top wall  14  of cell body  10  includes a corresponding recess  62  configured for receiving the cap  52  in a snap-fit and rotational engagement. When a cap  52  with a bead  64  is disposed on the cell body  10  with a corresponding recess  62 , the cap  52  may be rotated about the periphery of the cell body  10 . In addition, the upper surface  35  of outer transverse horizontal wall  34  acts as a stop for the cap  52 . 
     As further illustrated in  FIG. 5 , the cell body  10  includes a semi-circular disk-shaped planar member  50  that covers about one-half of the open top end  12 . Rotation of cap  52  allows one to position the vent hole  60  directly over the open half A of the open top end  12 , as illustrated in  FIG. 6 , to achieve maximum pressure equilibrium between the interior of the cup and the sample analysis chamber  27 . The rate of equilibrium may also be controlled to maintain the thin film material  66  in a flat plane by rotating the cap  52  and positioning the vent hole  60  over the closed half B of the open top end  12 , as illustrated in  FIG. 7 . Although a semi-circular member  50  is illustrated, it should be understood that alternative geometric shapes for member  50  may also be suitable. 
     As an additional advantage, after analysis is complete, the vent hole  60  may be repositioned over the semi-circular member  50  and sent to storage, which avoids contamination issues during the storage thereof, and maintains the specimen for future referral. 
     Assembling the sample cup and mounting a thin film of material across the open bottom end  26  according to an aspect of the invention includes providing a cell body  10 , disposing a thin film of material  66  across the open bottom end  26 , and inserting the annular collar  36  into the internal receiving channel  32 . The annular collar  36  initially grasps the thin film of material  66  and is progressively advanced while drawing the thin film across the open bottom end  26  of the cell body  10 , until the film material  66  is completely encased within the internal receiving channel  32 , resulting in a taut, flat sample plane. A sample intended for analysis is disposed in the cell body  10  through the open top end  12 . Thereafter, a rotatable cap may be disposed onto the top end  12  of the cell body, and placed in an analysis chamber of suitable instrumentation. 
     Referring to  FIGS. 2 and 3 , assembled sample cups according to various aspects of the invention are illustrated. Advantageously, upon assembly of the sample cup  100 , the flanges  44  ( FIG. 2 ) and  44 ′ ( FIG. 3 ), which assist in handling the cup upon assembly, are embedded within the corresponding recesses  46  and  46 ′ of the cell body  10  to help maintain a taut, flat plane for precise and accurate analysis. 
     The cell body  10 , the annular collar  36  and cap  52  may be formed of an appropriate polymer, for example, polyethylene. The thin film of material  66  may be formed from polyethylene, polyester, polyethylene terephthalate, polypropylene, polyimide, polycarbonate, ETNOM, or other materials exhibiting minimal and comparative absorption that are suitable for spectroscopic analysis. The ETNOM brand of thin film material, along with the others described above, are available from Chemplex Industries, Inc. 
     Advantageously, by using a suitably-sized thin film of material  66 , the thin film of material  66  will be completely encased within the internal receiving channel  32  of the cell body  10 , thus avoiding the need to trim or contend with clippings that tend to cling to surfaces. As an additional advantage, the assembled sample cup includes smooth outer surfaces, without any potentially interfering projections that can impede introduction, retention or removal from an analysis chamber. 
     The invention has been described with reference to specific embodiments. One of ordinary skill in the art, however, appreciates that various modifications and changes can be made without departing from the scope of the invention as set forth in the claims. For example, although the cell body and annular collar are illustrated as being flush, the annular collar may protrude or extend outwardly from the cell body, as in  FIG. 6 . Accordingly, the specification is to be regarded in an illustrative manner, rather than with a restrictive view, and all such modifications are intended to be included within the scope of the invention. 
     It should be understood that the aforementioned descriptions with respect to the upper and lower, and inner and outer elements of the cell, for example, are merely for convenience, and are not intended to be limiting. 
     Benefits, other advantages, and solutions to problems have been described above with regard to specific embodiments. The benefits, advantages, and solutions to problems, and any element(s) that may cause any benefits, advantages, or solutions to occur or become more pronounced, are not to be construed as a critical, required, or an essential feature or element of any or all of the claims.