Abstract

A multi-port valve uses a flexible sample tube to selectively intercept gases flowing from inlet ports into a common manifold space. The manifold space is placed under sufficient vacuum to insure that gas samples will be selectively received by the sample tube when the sample tube is placed in close proximity to the selected inlet port to be sampled. The sample tube is arranged so that gases to be sampled from the selected port wash over the entrance end of the sample tube so that contaminated or mixed gases from the manifold space are prevented from entering the sample tube. The sample tube is mounted to pivot inside a valve body and is moved by a sample tube guide which rotates inside the valve body to selectively align the sample tube with the inlet ports. The valve body may be sealed by a cover through which the valve guide is driven to rotate by a magnetic coupling, or by a bearing seal through which the sample tube guide projects. The sample guide may be rotated in a stepwise fashion by a stepper motor for slow collection rates, or may be rotated quickly by a motor for rapid sampling. Magnetic detectors or a shaft decoder may be used to monitor the position of the sample tube guide. The multi-port valve may be used in a system in which a measuring device such as a mass spectrometer and a data system are used.