Patent Application
20090246883
The invention pertains to tapes which carry gas responsive materials usable in monitoring ambient gases in a region. More particularly, the invention pertains to such tapes which carry axially extending tracks of materials that can simultaneously respond to different gases.
Known processes of producing toxic gas sensitive paper tapes results in a roll with a chemical reagent (many chemicals that combine to form toxic gas sensitive material) impregnated across the entire width of the paper tape. One example of how to produce this tape is a method which submerges the tapes in a bath of chemical reagent prior to drying the reagent and re-winding the roll. Two examples of known production schemes and resulting tapes are illustrated in
In known systems, the tape is sampled at multiple locations at once. The tape is about 1″ wide. In an example of prior art sensing, illustrated in
The gas being sampled is pulled through the paper tape and if a toxic gas to which the chemical reagent is sensitive is present a color change occurs. That color change can be monitored via any number of optical measurements, and calibrated to correspond to a concentration of the toxic gas.
In all of these instruments each sampling location pulls a unique air sample. The example above would be capable of monitoring the concentration of one gas family at eight different locations at once. Other configurations can pull a gas being monitored through different numbers of reagent samples.
Since known tapes carry only a single gas sensitive material, multiple tapes must be exposed at a site to monitor the concentrations of different gases. These do not represent as efficient or cost effective approaches as would be desired.
There is thus a continuing need to monitor a variety of different toxic gases simultaneously in a more cost effective fashion than has heretofor been possible. It would also be desirable to be able to reduce the number of required sampling sites while still monitoring multiple gases simultaneously.
While embodiments of this invention can take many different forms, specific embodiments thereof are shown in the drawings and will be described herein in detail with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention, as well as the best mode of practicing same, and is not intended to limit the invention to the specific embodiment illustrated.
In embodiments of the invention, multiple lines or tracks of chemicals are formed on a substrate such as a roll of paper or plastic tape. The tracks could extend continuously along the tape, or be discontinuously formed by pluralities of circles, squares, or other shapes of deposited material which extend axially along the tape.
The chosen chemical tracks could include the same chemical reagent or multiple chemical reagents with multiple gas sensitivities. As such, one paper tape could detect multiple chemical families. For example one embodiment would be able to detect four different chemical families.
If used with an eight-point reader or sampling manifold, the paper tape could be used to monitor the concentration of four chemical species at two locations. This however is widely variable depending on the sampling manifold and is not be a limitation of the invention.
In one aspect of the invention, various exemplary methods can be used to deposit the reagents. In one process in accordance with the invention, drop formation devices such as micro solenoid valves, inkjet printers, piezoelectric, acoustic, or thermal could be used. Another type of dispenser could be an aerosol or spray-based dispensing head. A third could be to pump a small volume of reagent out of a small orifice or tube.
Both the first and second options could include a liquid pump, if desired, associated with them to deliver the reagent. The third type of dispensing could use an applied force (peristaltic, syringe, capillary) to deliver the reagent to the print head and onto the paper tape. It will be understood that various deposition methods come within the spirit and scope of the invention.
The various materials can be deposited onto substrate 14, see enlargement 20, in the form of spaced apart, continuously extending axial tracks 20-1, 20-2 and 20-3. Each of the deposited tracks 20-i can be sensitive to a different gas. None of the number of deposited tracks, nor their width nor their spacing represent limitations of the invention. Alternately, instead of a continuously extending track, such as 20-1, a discontinuous, axially extending series of axially spaced apart areas, or dots can be deposited onto substrate 14. In yet another embodiment, continuous tracks can be used in combination with discontinuously formed tracks or sequences of dots or areas.
Pairs of sensors such as 36-1 and 38-1 are associated with and respond to color changes on a common track such as 20-4. Sensors 36-4 and 38-4 respond to color changes on track 20-1. It will be understood that neither the numbers of sensors associated with a track, nor their configuration are limitations of the present invention.
Output signals from sensors 36, 38 are coupled to control circuits 44. Control circuits 44 which might be implemented with one or more programmable processors 44a and executable control software 44b, respond to the signals S1 . . . S8.
Control circuits 44 evaluate signals such as S1 and S5, associated with a common track 20-4 and establish a gas concentration in response thereto. Control circuits 44 can actuate the transport mechanism 32 to advance tape 10, in direction 40a to provide an on going sequence of sampled locations on tape 10 to the sensors 36, 38.
By configuring unit 30 such that circuits 44 track signals such as Si, Sj associated with a common track, as the tape 10 is advanced by mechanism 32, a sequence of signals from sensors such as 36-1 and 38-1, relative to a common track, such as 20-4 can be analyzed to establish a concentration C1 for the gas to which the material on track 20-4 responds. Similarly, concentration C2 can be established for the gas to which the material on track 20-3 responds using signals S2 and S6, and incorporating as many samples thereof as desired. Similar comments apply to sensor pairs 36-3, 38-3 and 36-4, 38-4.
Signals, from sensor pairs, for a common gas, such as 36-1, 38-1 can be sensed substantially simultaneously. Further signals indicative of concentrations of different gases can also be detected by circuits 44 substantially simultaneously if desired. Hence, concentrations for up to four gases in the embodiment of
In yet another embodiment of the invention, a multi-track, or multi-strip tape can be used to measure a common species of gas in different concentration ranges. In such embodiments, sampling times or flow rates need not be altered to take into account different concentration ranges since formulations of different tracks can be adjusted to respond to respective ranges of gas concentrations.
From the foregoing, it will be observed that numerous variations and modifications may be effected without departing from the spirit and scope of the invention. It is to be understood that no limitation with respect to the specific apparatus illustrated herein is intended or should be inferred. It is, of course, intended to cover by the appended claims all such modifications as fall within the scope of the claims.
