著者

堀江 陽介 森 高通

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.83, no.849, pp.16-00579-16-00579, 2017 (Released:2017-05-25)

参考文献数

15

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In a biochemical automatic analyzer, generally it is necessary to open the cap of the sample tube before the analysis. Users of the analyzer demand a closed tube sampling (CTS) function to reduce the workload and the infection risk. CTS is a sampling method in which the sharp tip of a nozzle goes through the rubber cap of a sample tube and aspirates a part of the liquid in the tube. One of the main challenges of this method is the development of a nozzle that has high durability (requires low insertion load) and produces few rubber chips when inserted through the rubber cap. This paper describes the study of the shape of the nozzle in order to reduce the insertion load and the production of rubber chips. It was found that the parameter that influences the insertion load most is the angle of the taper. Therefore, to reduce the load, it is necessary to reduce the taper angle. By using a nozzle with a tip diameter of 0.8 mm, base diameter of 1.6 mm, and taper length of 20 mm, it was possible to reduce the load required to insert the nozzle through a rubber cap to 34 N. It was also found that the parameter that most influences the production of chips is the cut angle of the nozzle. Rubber chip production could be avoided with the combination of an angle smaller than 28.5° at the nozzle chip for smooth insertion and an angle larger than 15.0° at the inside edge for preventing cutting rubber off. Finally, to validate the durability and effectiveness of this shape, the nozzle was subjected to a test in which it was inserted through a rubber plate 50,000 times. Results showed that there was almost no nozzle abrasion nor increase of insertion load, which demonstrates the durability and effectiveness of this new shape.