Measuring and testing – Sampler – sample handling – etc. – Capture device
Patent
1991-07-31
1993-03-30
Raevis, Robert
Measuring and testing
Sampler, sample handling, etc.
Capture device
G01N 114
Patent
active
051973405
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a method and to apparatus for sampling liquid. It is particularly concerned with the sampling of waste waters so as to obtain a representative portion of liquid from which its average composition can be determined.
When sampling a flowing liquid, such as waste waters from a drain, a common requirement is to establish its average composition over a specific period (such as twenty four hours). This is normally achieved by aggregating a set of individual sub-samples taken with sufficient frequency to include all the effect of changes in composition of the flow over the period of the sample. Individual sub-samples can either be aggregated in a single container to provide a bulk sample giving a gross average or alternatively each sub-sample can be passed into a separate container in a sequence of such to store samples of the flow from hour to hour.
The more frequent the taking of the samples the more representative the eventual aggregated sample will be. The frequency of sampling may be at regular time intervals or at time intervals whose length are in inverse proportion to a rate of flow of the sampled liquid (such sampling is termed `flow proportional sampling`).
When sampling waste waters it is important to include solid wastes carried by the waters so that the, or each, sample is representative of the material flowing or conveyed at the time of sampling. Consequently an effective sampling system needs to be able to provide for the passage of solid waste components into a sample container.
According to a first aspect of the present invention there is provided a method of liquid sampling by way of a self contained unit comprising the steps of: sub-atmospheric pressure to cause a bulk sample of liquid for sampling to be drawn into the chamber from a body of liquid by way of a first passage; liquid from the bulk sample to drain from the chamber by way of the first passage; and a second passage under the control of a delivery valve characterised in that: sub-atmospheric pressure is undertaken by way of a valve system comprising first and second flexible tubes, the first flexible tube linking a source of air at atmospheric pressure to the chamber and the second tube linking the source of air at sub-atmospheric pressure to the chamber: and a first clamping device in the form of a first cam which can, depending on the disposition of the first cam, alternately: sub-atmospheric source while allowing the chamber to communicate with the atmospheric source by way of the second tube; atmospheric source while allowing the chamber to communicate with the sub-atmospheric source by way of the second tube.
According to a first preferred version of the first aspect of the present invention the step of allowing at least a part of sample volume hitherto retained in the sample chamber to pass out of the chamber by the second passage is characterised by the use of a flexible duct and is undertaken by way of a second clamping device operable between open and closed positions by way of a second cam so that: duct to prevent the passage of sample volume out of the chamber by way of the flexible duct; and sample volume out of the chamber by way of the flexible duct.
Preferably the first and second clamping devices are powered by a common prime mover.
According to a second preferred version of the first aspect of the present invention or the first preferred version thereof the first clamping device is characterised by being in the form of a cam and an anvil, the cam being located eccentrically and rotatable relative to the anvil to leave a sequence of working clearances therebetween, each flexible duct being located in a working clearance.
According to a third preferred version of the first aspect of the present invention or any preceding preferred version thereof the second clamping device takes the form of a pivoted clamp having jaws acting on the outlet duct which jaws are displacable between the open and closed positions by the second cam.
According to a fourth preferred version of the first aspect of the p
REFERENCES:
patent: 3209598 (1965-10-01), Anderson et al.
patent: 3587670 (1971-06-01), Brailsford
patent: 3589197 (1971-06-01), Brooks, Sr.
patent: 3691844 (1972-09-01), Moore
patent: 3901087 (1975-08-01), Hannes Fabritius
patent: 4037472 (1977-07-01), Gates
patent: 4163392 (1979-08-01), Fleenor et al.
patent: 4418581 (1983-12-01), Jones
Patent Abstracts of Japan, vol. 10, No. 327, P513, abstract of JP 61-133835, publ. Jun. 21, 1986 (Fuji Electric Co., Ltd.).
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