| 摘要 |
A metering apparatus for measuring out a volume of reagent consists of a basic appliance and a plurality of interchangeable piston pump units. A reversing valve is to be created which, as a result of its special design of the rotary vane, is capable of accelerated implementation of the preparatory and concluding working stages during a metering operation, in addition to the conventional function. The reversing valve consists of the valve piston, made from cold-formed polytetrafluoroethylene alloyed with molybdenum disulphide, with the conical part and the packing, and of the bonnet with the coupling device and the valve housing. The valve housing is provided with two conical holes, the cylinder with two ducts and the packing with three perforations. The two conical holes, viewed in clockwise direction, enclose an angle of preferably 150 DEG , the two ducts an equal angle of preferably 150 DEG , the first and second perforations an angle of preferably 75 DEG , and the first and third perforations an angle of preferably 210 DEG .
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