Sample cell

#The present invention relates to an improved sample cell for use with X-ray fluorescence analytical devices.

#Sample cells that are used for positioning a sample within an X-ray fluorescence analyzer typically employ a telescopically interfitting cup and ring combination for capturing there between and thereby supporting a radiation-permeable membrane through which the sample is analyzed. After a sample is placed in the cup and the radiation-permeable membrane is positioned across the mouth of the cup, the ring is forced down over the membrane and down along the exterior surface of the cup. The interfitting components serve to capture the membrane there between and pull it taut across the mouth of the cup. Upon inversion of the cup, the sample becomes supported on the flat, wrinkle-free membrane surface on which it is positioned over the X-ray source for analysis. Such sample cells are intended for a single use and are disposed of after the analysis is completed. The cup and ring components are therefore typically molded from a synthetic plastic such as nylon, polyethylene, polypropylene or polyester.

#In order to cause the membrane to be tightly and uniformly stretched across the mouth of the cup and to then be maintained in such condition, it had been found to be necessary for the cup and the ring to be very tightly interfitting. The use of such tight tolerances were, however, found to be problematic in that the membrane was thereby prone to bind over the lip of the cup and to then tear or pucker as the ring was pushed into place. While the application of a lubricant reduced the risk of damaging the membrane, considerable time and effort were required in order to properly apply the lubricant so as to avoid contact with the interior of the cup and to thereby avoid contaminating the sample.

#These and other features and advantages of the present invention will become apparent from the following detailed description of the preferred embodiment which, taken in conjunction with the accompanying drawings, illustrate by way of example the principles of the invention.

#FIG. 1 is a vertically exploded perspective view of the sample cell of the present invention;

#FIG. 2 is a perspective view showing the components of FIG. 1 in their fully assembled state;

#The drawings illustrate a preferred embodiment of the sample cell of the present invention. The sample cell is specially configured to (a) space the cell membrane off of a flat supporting surface, (b) allow the cell membrane to directly engage the aperture surface of an analyzer device during the actual analysis step and (c) more readily allow the sample cell to be properly positioned with respect to the analyzer aperture. The latter capability facilitates the automated handling of the sample cell and reduces the need for operator intervention.

#Referring now to the drawings, FIG. 1 is an exploded view of the components of the sample cell 10 prior to assembly. The cell includes a cup component 12 and a ring component 16 which, upon assembly, cooperate to support a radiation-permeable membrane 14 across the mouth of the cup. After introduction of a sample into the cup, the membrane is positioned over the mouth of the cup and the ring is pushed down over the membrane into telescoping engagement with the cup. This serves to pull the membrane taut across the mouth of the cup to provide the assembly shown in FIG. 2. For analysis, the cell is inverted and placed over the analyzer aperture so as to be exposed to the X-ray source located within the fluorescence analyzer.

#FIG. 3 is an enlarged cross-sectional view of the assembled sample cell 10 shown in FIG. 2. The cup component 12 is of integral molded construction and includes a circular sidewall 20 as well as bottom wall 22 so as to define a cavity 24 for receiving sample 18 therein. A puncturable dimple 26 is formed in the bottom wall to allow the sample cell to readily be vented while in its inverted state. The ring component 16 is also of integral molded construction and includes a circular sidewall 28 that is dimensioned to fit about the exterior of the cup's sidewall. The proximal end of the ring includes a radially extending flange 30 that extends about the cup's entire circumference. The distal end of the ring terminates in a specially shaped lip 32 that extends beyond the surface defined by the membrane 14 that is stretched across the mouth of the cup component 12.