CUVETTE SYSTEM FOR AUTOMATED CHEMICAL ANALYZER

Abstract: A flexible and disposable cuvette belt (10) which comprises a matching pair of elongated webs (20) joined together along corresponding faces thereof to form integral belt (10). A series of regularly spaced chamber halves (26, 27) are formed laterally in each of the corresponding web faces which define open top cuvette receptacles (16) when the web halves (26, 27) are joined.

Description: -1- CϋVETTE SYSTEM FOR AUTOMATED CHEMICAL ANALYZER Introduction The present invention relates to a cuvette system for use in the chemical analysis of fluid samples in an automated instrument and, more particularly, to a flexible cuvette - belt consisting of a plurality of integrally intercon- 5 nected cuvettes which is designed to be transported through the instrument. Background of the Invention 0 A variety of automated or semi-automated chemical analyzers are known which utilize cuvettes for the chemical testing of samples placed therein. Generally, a predetermined amount of liquid sample, such as a bio¬ logical fluid, is placed in the cuvette which is then transported through the instrument. As the cuvette is being transported, the instrument dispenses 5 a quantity of reagent into the sample and monitors the resulting chemical reaction. Such monitoring is generally accomplished through use of an optical means which views the fluid sample through optically transparent portions of the cuvette. 0 In order to simplify the loading of the cuvettes into the instrument and facilitate their handling by the instrument once so loaded, proposals have been made to provide the cuvettes in the form of a continuous integral strip. The individual cuvettes of the strip are designed to be relatively rigid, but the strip itself is provided with sufficient flexibility to ease its transport 5 through the instrument. Furthermore, by making the cuvettes in a continuous strip form, they can be manufactured relatively inexpensively from suitable - ** plastic material, thereby permitting their disposal after use. This is an im¬ portant feature since it avoids the requirement for washing the cuvettes after use and avoids any possibility of cross-contamination of fluid samples which could cause erroneous test results. A proposed cuvette system designed to meet these requirements is disclosed in U_S. Patent 4,263,256. -2- However, certain drawbacks have been observed in the design of such known cuvette systems which limit their use in automated chemical analyzers. The drawbacks have generally involved the optical characteristics, dimensional tolerances and handling requirements of the integrally ormed cuvette belts. Brief Description of the Invention The cuvette system of the present invention overcomes the drawbacks found with known integrally formed cuvette belts by providing a practical, simplified design that is relatively inexpensive to manuf cture to exacting optical tolerances and which is easily transported and aligned within the analyzer. The cuvette belt of the present invention comprises a matching pair of elongated webs which are joined together along corresponding faces thereof to form an integral belt. A series of regularly spaced chamber halves are formed laterally in each of the corresponding web faces which define open top cuvette receptacles when the web halves are joined. An indexing means is also disclosed for aligning the optical portion of the chamber halves when the webs are joined together, thereby defining a precise optical path through the cuvette. This indexing means may further serve to align the cuvette optical path with respect to the optical examining mechanism of the instrument as the cuvette belt is transported therethrough. The two-piece structure of the present invention also permits novel manufacturing techniques to be employed which greatly simplify the pro- duetion process and reduce the overall cost of the cuvette system. Such production advantages are achieved through the use of low cost thin plastic sheet stock material, with no resulting loss in optical precision or dimensional accuracy in the cuvette. In fact, it has been found that cuvettes may be produced in accordance with the present invention that possess optical char- acteristics and dimensional accuracy heretofore obtainable only through use of injection molding techniques. " v ?δ ~ - - Therefore, an inexpensive disposable cuvette belt may be produced in accordance with the present invention which meets in all respects the precision optical requirements of modern chemical analyzers. The individual cuvettes of the present invention provide a precisely defined optical path through th-e cuvette that is extremely transparent at the wave lengths utilized in such analyzers and which avoids any significant birefringence of the light beam passing therethrough. In addition, such cuvettes may be easily manufactured with an elongated shape of small cross sectional area which is particularly suited for testing micro sample sizes of biological fluids. Furthermore, the indexing means of cuvette belts designed in accord¬ ance with the present invention permits the precise and repeatable positioning of the cuvette optical path with respect to the optical system of the analyzer. Hence, a simplified transport mechanism may be utilized in the analyzer which allows a limited number of optical stations to view a relatively large number of different cuvettes during the period of time that the cuvettes are passed through the analyzer. Accordingly, the cuvette belt design of the present invention also permits an overall reduction in the complexity and cost of the automated chemical analyzer in which it is used. Description of the Drawings Figure 1 is a partial top plan view of an elongated thin plastic sheet stock material which may be utilized to form an embodiment of the present invention; Figure 2 is an end view of the material shown in Figure 1; Figure 3 is a top plan view of the material shown in Figure 1 having chambers formed thereon in accordance with an embodiment of the present invention; Figure 4 is an end view of the formed material shown in Figure 3; Figure 5 is a partial side view of a cuvette belt formed in accordance with an embodiment of the present invention; Figure 6 is an end view of the cuvette belt shown in Figure 5; Figure 7 is a perspective view of a portion of the cuvette belt shown in Figure 5; Figure 8 is an enlarged side view of a portion of the cuvette belt shown in Figure 5; Figure 9 is a sectional top view of the cuvette belt shown in Figure 8 taken along line 9-9 thereof; and Figure 10 is a sectional end view of the cuvette belt shown in Figure 8 taken along the line 10-10 thereof. Description of the Preferred Embodiment Figures 1 through 4 of the drawings illustrate the forming steps of a method by which a cuvette belt constructed in accordance with an embodi¬ ment of the present invention may be produced. This assembled cuvette belt 10 is illustrated in detail in Figures 5 through 10 of the drawings. As shown in Figures 1 and 2, cuvette belt 10 is formed from a thin plastic web of sheet stock material 20 which is cut into elongated strips prior to the forming operation. These strips should be of sufficient length to provide a roll of cuvettes after forming as required for the continuous operation of the analyzing instrument. It has been found that copolyester or vinyl plastic sheet stock in thickness of .003 to .010 inch provide satis¬ factory optical results when formed according to the present invention. An example of such a material is KODAR brand thermoplastic polyester resin material manu actured by Eastman Kodak Co. In addition, in order to facilitate the fabrication and assembly of the cuvette belt, this sheet stock may be a laminate, having a layer of an easily sealable and biologically inert material such as SURLYN brand ionomer resin material manufactured by E.I. Dupont DeNemours & Co., Inc. - - Figures 3 and 4 illustrate sheet stock material 20 having a series of regularly spaced chambers 12 formed laterally across its surface. In the preferred embodiment, these chambers are formed as narrow, shallow indenta¬ tions having a generally rectangular shape. Since chambers 12 are shallow indentations, it is possible to form them utilizing cold molding techniques, thereby avoiding any optical degradation of the material due to heat. In addition, an optical portion 22 of the material may be restrained by clamping or other molding techniques during the chamber forming operation to avoid stretching or other deformation of it which would be detrimental to its optical performance. In this manner, essentially all stretching of the material during the forming process is limited to side walls 14 of the chambers, and optical portions 22 thereof are maintained stress-free and with a uniform thickness. A further advantage of the present invention is that a series of indexing perforations 30 may be formed along opposite longitudinal edges 21 of web material 20 during the chamber-forming operation. These edges of the web may also be clamped during the forming process so as to insure that a precise relationship is maintained between indexing perforations 30 and the cuvette optical window 24 utilized by the analyzing instrument. In the preferred embodiment, these optical windows 24 are located at opposite ends of chamber 12 adjacent to indexing perforations 30 in order to insure that precise align¬ ment of them is repeatedly maintained during transport of the cuvette belt through the instrument. After chambers 12 and indexing per orations 30 are formed, web 20 is longitudinally slit along its center line A-A. In this manner, two corres¬ ponding web halves 26, 27 are obtained which are identical in their configura¬ tion. Indexing perforations 30 are then utilized to precisely align the web halves with respect to each other as illustrated in Figures 5 and 6, so that optical windows 24 will form a precise optical path through the resulting cuvette or receptical 16 when web halves 26, 27 are joined along their cor¬ responding faces. The slitting step may be performed either before or after the web halves are joined. As is best shown in Figure 7, when joined together the chamber halves formed in web halves 26, 27 will define receptacles 16 having an open top 17 adapted to receive and retain fluid sample (not shown). The body of these OMPI -6- receptacles is elongated along central axis B-B extending through their open tops. It has been found that web halves 26, 27 may be joined together about their periphery by a low heat sealing process if a laminate material having a low melting point layer such as SURLYN is utilized, or by impulse bonding techniques if higher melting point materials are utilized. It is also possible to choose other joining methods, such as adhesive bonding, as long as the optical characteristics and dimensional tolerances of the cuvettes are not adversely affected thereby. In the particular embodiment of the cuvette belt 10 shown in Figure 8 through 10, receptacles 16 are substantially rectangular in cross section. Optical portions 22 of the chamber halves 14 are opposite parallel walls of the rectangular receptacles, thereby providing an optical path of precise length through the cuvette. As discussed above, after the cuvette belt is formed, indexing perfora¬ tions 30 may be utilized as a means for aligning the optical path through receptacles 16 with respect to the optical examining system of the instrument (not shown). Furthermore, the spatial relationship between indexing perfora- tions 30 and optical windows 24 will be precisely maintained even though the cuvette belt is laterally flexed or twisted about its longitudinal edge 12 as transported from station to station in the instrument. In this connection, it is important that the transport area 28 along longitudinal edge 21 not permit vertical flexing of the cuvette belt which could interfere with main- taining the proper vertical alignment of the cuvettes in the instrument. Although a specific embodiment of the present invention has been described above andfihown in the drawings, it is to be understood that obvious variations and modifications thereof falling within the scope and spirit of the present invention may be made as required by those skilled in the art. It is therefore intended that the following claims be construed as including such variations and modifications of the present invention.

Claims: - - What is claimed is: 1. An integrally formed, flexible cuvette belt for transporting fluid samples through an instrument having an optical means for examining the fluid samples while disposed within the cuvettes, said cuvette belt com¬ prising: a pair of elongated webs joined together along corresponding faces thereof to form an integral belt, and a series of regularly spaced chamber halves formed laterally in said corresponding web faces, said chamber halves defining open top receptacles for receiving and retaining fluid sample. 2. The cuvette belt of Claim 1 wherein said chamber halves are formed adjacent to a longitudinal edge of said webs. 3. The cuvette belt of Claim 2 wherein the open tops of said recep¬ tacles are located along said web longitudinal edge. 4. The cuvette belt of Claim 3 wherein the central axis of said receptacles extending through their open tops is perpendicular to said web longitudinal edge. 5. The cuvette belt of Claim 4 wherein said receptacles are elon¬ gated along said central axes. 6. The cuvette belt of Claim 5 wherein said chamber halves are relatively shallow in relation to the length of said receptacles. 7. The cuvette belt of Claim 1 wherein said chamber halves have an optical portion therein which forms an optical path through said receptacle. 8. The cuvette belt of Claim 7 further comprising an indexing means for aligning the optical portions of said chamber halves when said webs are joined together. -8- 9. The cuvette belt of Claim 8 wherein said indexing means further serves as a means for aligning the optical path through said receptacle with respect to the optical examining means of the instrument. 5 10. - - The cuvette belt of Claim 9 wherein said indexing means is a series of perforations formed in said webs which are precisely aligned in relation to the optical portions of said chamber halves. 11. The cuvette belt of Claims 3 and 10 wherein said perforations 10 are formed along the web longitudinal edge opposite the open tops of said receptacles. 12. The cuvette belt of Claim 11 wherein the optical portions of said chamber halves are located at the bottom of said receptacle away from 15 its open top. 13. The cuvette belt of Claim 11 wherein said integral belt is sup- ported along said perforated web longitudinal edge as it is transported through the instrument. 20 14. The cuvette belt of Claim 1 wherein said receptacles are sub¬ stantially rectangular in cross section. 15. The cuvette belt of Claims 7 and 14 wherein the optical portions 25 of said chamber halves are opposite parallel walls of said rectangular recep¬ tacles. 16. The cuvette belt of Claim 1 wherein said web pair are formed as mirror images of each other. 30 17. The cuvette belt of Claim 1 wherein said web pair are formed identically to each other. 18. The cuvette belt of Claim 1 wherein said web are made of 35 thin plastic sheet stock. -9- 19. The cuvette belt of Claim 7 and 18 wherein said plastic sheet stock is optically transparent at the wave length utilized by the instrument optical means. 20. " The cuvette belt of Claim 19 wherein said plastic sheet stock may be cold ormed. 21. The cuvette belt of Claim 20 wherein said plastic sheet stock is a laminate, the inner sur ace of which facilitates the joining together of said webs. 22. A method of constructing an integrally formed, flexible cuvette belt having receptacles thereon for retaining and transporting fluid samples through an instrument having an optical means for examining the fluid samples disposed in the receptacles, said method comprising: forming a series of regularly spaced chambers laterally across an elongated web of plastic sheet stock, - slitting said elongated web longitudinally along its center, and joining said web halves together so that said chambers form said receptacles. 23. The method according to Claim 22 wherein said chambers are laterally formed in the center of said web and are slit into corresponding halves of said receptacles when said web is longitudinally slit along its center. 24. The method to Claim 23 further comprising restraining a portion of each chamber so that it does not stretch or otherwise deform when said chambers are formed, thereby preserving the optical uniformity of said por¬ tion. 25. The method according to Claim 24 wherein said chambers are clamped at opposite corresponding portions thereof so that an optical path through said receptical is created when said web halves are joined. -10- 26. The method according to Claim 25 wherein said chambers are formed by a cold forming process. 27. The method according to Claim 26 wherein said chambers are formed as " shallow indentations in said web. 28. The method according to Claim 27 wherein said chambers are formed as narrow indentations extending laterally across said web. 29. The method according to Claim 25 further comprising forming corresponding indexing perforations along the opposite longitudinal edges of said web which are positioned in precise relationship to said chamber optical portions. 30. The method according to Claim 29 further comprising aligning said indexing perforations as said web halves are joined, thereby forming a precise optical path through said resulting receptical. 31. The method according to Claim 22 wherein said web is slit after said web halves are joined together.

Inventors: HSEI PAUL K, LISTON MAX D, SOLBERG ARNE L, HSEI, PAUL, K., LISTON, MAX, D., SOLBERG, ARNE, L.
Applicants: AMERICAN HOSPITAL SUPPLY CORP, AMERICAN HOSPITAL SUPPLY CORPORATION
Application year: 1982
Main classification: B01L3
IPC codes: B01L3, G01N21, G01N35