Measuring and testing – Sampler – sample handling – etc. – With constituent separation
Reexamination Certificate
2000-02-29
2002-11-12
Noland, Thomas P. (Department: 2856)
Measuring and testing
Sampler, sample handling, etc.
With constituent separation
C073S031020, C073S863310, C073S863720, C073S864340
Reexamination Certificate
active
06477906
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to the field of apparatus and methods for gathering and analyzing samples of gas, and, more particularly, to systems for automatically collecting a plurality of air samples for subsequent analysis at a remote location.
BACKGROUND OF THE INVENTION
There are many applications in which it is desirable to collect gas samples from a particular environment, and to subsequently analyze these samples for certain constituents, and in particular for minor or trace constituents. A typical application for this technology is the United States manned space flight program where archival air samples are collected from the interior of a spacecraft, and subsequently analyzed for constituents of the samples at a ground based location. Analysis of these samples has been a key component of the assessment of spacecraft air quality for crew health purposes. Periodic analysis at predetermined time intervals, such as intervals during a flight, is also important in the overall air quality assessment program.
In using air sampling techniques in ground-based applications, sampling is typically linked to eight-hour time intervals to correctly assess an employee's exposure during a typical “work day”. In using air-sampling techniques in space flight applications, the “work day” of a spacecraft crew is typically twenty-four hours. Although experience has shown that spacecraft air quality regarding major constituents such as oxygen and nitrogen is stable over long periods such as months, substantial changes in trace constituents or contaminants can occur over a twenty four hour period as the crew engages in different activities such as exercise and experiments. Therefore, a twenty-four hour integrated sample of spacecraft air would most accurately represent crew exposure to possible air contaminants.
Under normal circumstances, contaminant concentrations during shorter sampling periods might be unduly biased by one or more crew activities during the sample time, and longer sampling time periods would tend to average or “flatten” contaminant fluctuations. A twenty-four hour sample collects a sufficient quantity of certain constituents that are present in very low concentrations so that such constituents might not otherwise be detected. Furthermore, automatic sampling is desirable. Conditions can be encountered, however, when shorter sampling periods are desirable, and when manual initiation of the sampling is required.
In effectively sampling air for human use, means are required which trap volatile organic contaminants, but not major constituents such as nitrogen, oxygen, carbon dioxide, and water. In space flight applications, sampling means which conserve power are also desirable since spacecraft power is limited. Prior art systems employ a solid sorbent air sampler unit (SSAS) to monitor spacecraft cabin air. The SSAS consists of a plurality of tubes containing a sorbent and into which sampled air is directed by mean of a valving system. The SSAS is a manually activated device that requires a crew member to manipulate a valve to collect an air sample in a tube containing sorbent material and then record the time of this sample session.
Manual operation is subject to human error or mechanical and has resulted in samples which are unusable. For example, batteries which operate an SSAS system may be exhausted during a mission, resulting in unusable samples. The sampling acquisition valve may not be switched to the next sample tube in a timely manner resulting in an unusable sample due to a sample “overload” of the sorbent in the tube. Sample collection times may go unrecorded, or be recorded improperly, or recorded illegibly, once again resulting in an unusable sample. The SSAS sample pump used to draw samples into the sample tube may malfunction, but notice of the malfunction may not be provided, resulting in questionable samples in all tubes rendering the samples unusable.
In addition to the sampling problems and lack of automation discussed above, various flow rate orifices are subject to clogging. Changing tube sorbents is extremely difficult because sample tubes must be removed from the sampling device. The overall configuration of the system is not ideally suited for this procedure.
Other air sampling systems have been used on board spacecraft. These systems, like the SSAS, suffer from certain shortcomings. For example, glass-lined sample collection tubes present a breakage hazard. Such tubes require disassembly after sampling so that they can be cleaned in order not to contaminate subsequent sampling cycles. Such systems may also suffer cross contamination of samples due to multi-port valve design, and o-ring contamination of drawn sample gases.
In view of these prior art methods and apparatus, an object of the present invention is to provide a gas sampling system which can be used to collect a number of samples of gas for subsequent analysis.
Another object of the invention is to provide a system which employs sorbents in sample tubes, and the sorbents are sensitive to trace contaminants but not the major constituents of air.
Yet another object of the present invention is to provide sampling tubes which can be adjusted in size to accommodate varying amounts of sorbent, which are silica-lined metal and therefore have inert surfaces, yet do not present a breakage hazard, and from which samples can be drawn for analysis without physically removing the sample tube from the sample apparatus.
Another object of the invention is to provide a fully programmable sampling sequence which can draw samples at predetermined times and for predetermined intervals, with manual override capabilities which can be used to draw a sample at the discretion of an operator.
Still another object of the invention is to provide a system which can be cleaned, perform sampling, and then be desorbed without disassembling the device. This insures sample integrity and prevents any contamination from the analytical processes.
Another object of the present invention is to provide a sampling system which uses minimal electrical power thereby extending the life of batteries operating the system for long sampling periods.
Although the invention is directed toward sampling air in spacecraft, it should be understood that the invention can be used for other applications such as sampling air in the vicinity of hazardous materials manufacturing facilities, sampling air in contained environments, and the like. Other objects and applications of the invention will become apparent in the following disclosure.
SUMMARY OF THE INVENTION
The sampling system of the present invention will be referred herein to as an Automated Multi-Sorbent Tube Air Sample, or “AMTAS”. The apparatus comprises a “multi-port” valve and 16 sorbent tubes. Each tube is connected to the multi-port valve by means of pairs of the valve ports. The multi-port valve is constructed and operated in a predetermined sequence to create a flow path through the multi-port valve. The flow path directs an air sample to only one connected sorbent tube at a given time and for a given time interval.
In operation, a gas sample flows from a sample source, such as air from a spacecraft cabin, through an inlet filter and intake line, into a primary inlet port of the multi-port valve, through the multi-port valve, through the sequentially connected sorbent tube, back through the multi-port valve and out through a primary outlet port, through a pump, and then through a pump exhaust. The action of the pump draws the sample into and through the connected sorbent tube.
The sequencing of the multi-port valve, the time at which flow is initiated through a given sorbent tube, and the duration of the flow through a given sorbent tube, is controlled by a processor such as a computer. The movement of the multi-port valve is controlled by an actuator cooperating with the computer, which moves the valve to one of thirty two positions, for example, under the control of the computer. Sixteen of the valve positions discretely align a given sorbe
Moser, Patterson & Sheridan L.L.P.
Noland Thomas P.
Roger Peterson Family Limited
LandOfFree
Automatic multi-sorbent tube air sampler does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Automatic multi-sorbent tube air sampler, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Automatic multi-sorbent tube air sampler will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2993386