Abstract:
An apparatus for measuring the concentration of a target substance includes a detection container, a pump, and an integral temperature indicator or integral temperature correction factor indicator. The detection container has or contains a detection material chemically reactive with the target substance to produce an observable indication upon exposure to the target substance and such that the concentration of the target substance detected is readable from the observable indication. The pump is engageable with the detection container and operable to draw a sample of a gaseous environment into the detection container, the drawn sample containing the target substance, such that the detection material is exposed to the target substance. The integral temperature correction factor indicator, is particularly adapted to illuminate or indicate the correction factor applicable to the concentration measurement at specific temperatures.

Description:
[0001]    The present invention claims the benefit of the filing date of U.S. Provisional Application Ser. No. 60/385,416 filed Jun. 3, 2002 and U.S. Non-provisional Application Ser. No. 10/453,802 filed Jun. 3, 2003. These priority documents are hereby incorporated by reference for all purposes and made a part of the present disclosure. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates generally to an apparatus and a method for detecting the presence of a target substance in a gaseous environment. More particularly, the invention relates to such an apparatus and method for measuring the concentration of the target substance that includes an integral temperature factor correction device displaying a plurality of correction factors and an illumination means indicating an appropriate correction factor to be applied to a measured target substance in determining an accurate amount of the target substance present in a local environment. In one aspect of the invention, the apparatus and method employ an integral temperature indicator and correcting device to account for temperature variations that may cause an incorrect reading of the measured target substance. The method includes calculating an accurate reading of a target substance by multiplying a measured amount of the target substance with an indicated correction factor that is displayed on the integral temperature factor correction device. 
       SUMMARY OF THE INVENTION 
       [0003]    The present invention is directed to an apparatus and a method for accurately measuring the concentration of a target substance in a local environment. In one aspect of the invention, the inventive apparatus includes a detection container, a pump, and an integral temperature correction factor indicator arranged on an exterior of the apparatus. Preferably, the detection container has or contains a detection material that is chemically reactive with the target substance to produce an observable indication upon exposure to the target substance and such that an initial measurement of the concentration of the target substance detected is readable from the observable indication. Thereafter, a reading relating to a temperature correction factor is read from the apparatus. The detection material is temperature sensitive such that a reaction time between the target substance and the detection material is directly affected by a temperature at which the target substance is measured. The pump is engageable with the detection container and operable to draw a sample of a gaseous environment into the detection container. The drawn sample contains the target substance, such that the detection material is exposed to the target substance to provide a measured amount of the target substance in a particular environment. More preferably, the temperature correction factor indicator is integrally located about the detection container or the pump at a location where an appropriate correction factor may be easily read from the apparatus, and most preferably, on the outer surface of the pump. 
         [0004]    In one aspect of the invention, an integral temperature correction factor indicator is provided with a plurality of correction factors for indicating the appropriate correction factor applicable to the concentration measurement at a specific temperature. The temperature correction factor indicator may be provided in addition to or in lieu of a temperature indicator for automatically determining an appropriate correction factor. In one embodiment, temperature indications are provided in addition to temperature correction factor indications and are located so as to correspond with a matching temperature correction factor indicator. Preferably, each temperature correction factor indicator (or temperature indicator) is adapted to illuminate an appropriate correction factor in response to a specific temperature. Thus, in a method according to the invention, the user obtains both the measured concentration of the target substance and the appropriate temperature correction factor from the apparatus. By applying or multiplying the correction factor with the measured or indicated concentration, the user obtains the proper or corrected concentration of the detected target substance. Thus, an operator of the instant apparatus is less prone to obtain an incorrect measurement of the target substance. The appropriate correction factor and the measured amount of the target substance are automatically obtained by viewing the apparatus. The illuminated correction factor and measured amount of target substance are multiplied together to yield the accurate measure of target substance present in the local environment. In this manner, there is no need for a temperature measurement to be taken by the operator to determine the accurate measure of target substance, since the temperature correction factor indicator illuminates an appropriate correction factor. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0005]    For a more complete understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawing, in which: 
           [0006]      FIG. 1  is a simplified diagram depicting a gas detection apparatus according to the present invention; 
           [0007]      FIG. 1A  is a simplified diagram depicting a detector tube for use with the apparatus of  FIG. 1 ; 
           [0008]      FIG. 2  is a cross sectional view across line  2 - 2  in  FIG. 1  depicting an integral temperature indicator for use with the apparatus of  FIG. 1 ; 
           [0009]      FIG. 3  is a simplified diagram of an alternative gas detection apparatus according to the invention; and 
           [0010]      FIGS. 4A-4B  are simplified diagrams of an alternative gas detection apparatus according to the present invention; and 
           [0011]      FIG. 5  is an alternative thermostrip with temperature correction factor indications provided thereon, according to the present invention.  FIG. 5A  depicts an integral temperature correction factor indicator having a plurality of correction factors that each correspond to a particular temperature. One of the correction factors is illuminated to indicate a correction factor to be applied to a measured amount of a target substance. The integral correction factor indicator may be used in place of the thermostrip shown in  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0012]      FIGS. 1-2  depict an apparatus for detecting a target substance embodying various aspects of the present invention.  FIG. 3  depicts an alternative embodiment of the inventive apparatus. The inventive apparatus and method are employable to detect the concentration of the target substance in a local gaseous environment, and providing an observable indication of the concentration detected. Further, the inventive apparatus and method provide a means for detecting the concentration of the target substance and providing an indication that is correctable for temperature variations attributed to the local gaseous environment in which the substance is detected. In several embodiments, the temperature correction factor indicator is located integrally with (e.g., incorporated therewith) one of the basic components of the gas detection apparatus. 
         [0013]    As used herein, the term “detected” or “detection” is used to refer to a primary function or result of the inventive method. More specifically, the inventive apparatus is used to “detect” the presence of or an initial measurement of concentration of the target substance. Since the detection material is temperature sensitive, this initial measurement may or may not be an accurate measurement of the amount of the target substance present in the local environment. However, detection of the target substance preferably includes providing a measure of the amount or concentration detected and readily communicating this measurement to the user (e.g., by a color change or other observable indication). Thereafter, an appropriate correction factor may be obtained from the device and used to calculate the accurate measure of the target substance. 
         [0014]    It should first be noted that, upon review of the detailed description of the drawings provided herein, it will become apparent to one ordinarily skilled in the relevant art (e.g., the instrumentation or measurement art) that the various aspects of the present invention may be applicable to other means for detecting a target substance in a local gaseous environment. The focus of the present description is an application to a gas detection system employing a detection tube and a manual piston type pump. It should become apparent, however, that the temperature correction device may be applied to other gas or target substance detection systems. Accordingly, the application of the invention is not limited to a detection system that employs a detection tube and/or utilizes a manual piston type pump. Thus, the present invention is not intended to be limited to the structures and methods specifically described and illustrated herein. 
         [0015]    Referring to  FIG. 1 , the present invention is particularly applicable to a gas detection system or apparatus  9  employing a detection tube  11  with a manual piston sampling pump  13 . Such a system may be, for example, one of several commercially available piston-type designs including those marketed as the Gastec, Kitagawa, and Rae detector tube systems or one of several commercially-available bellows-type designs marketed by or as Draeger or MSA detector tube system. In the present invention, however, this basic system or apparatus  9  is modified to incorporate a temperature correction factor indicator device that allows for correction of field measurements at specific temperatures. As shown in  FIG. 1A , the detector tube  11  is preferably a thin glass tube with calibration scales printed thereon, by which an operator can directly read concentrations of the substances (gases or vapors) to be initially measured. Each tube contains a detection material or reagent  11   a  that is selected because of its sensitivity to the target substance and because it produces a distinct layer of color change upon exposure to the target substance. The reagent  11   a  is temperature sensitive. That is, the reaction time between the reagent  11   a  and the target substance is affected by the temperature of the local environment in which the target substance is present. In one instance, the reaction time is increased at warmer temperatures and decreased at lower temperatures. The detector tube  11  is typically packaged with hermetically sealed ends  11   b,    11   c  that may be broken or severed during operation, or may be provided in a series connection with another detection tube. As will be discussed below, the detection tube  11  may be engaged by a pump  13  so as to provide a field carry-able unit for sampling a local gaseous environment. 
         [0016]    As is known in the art, the detection tube  11  holds or houses a quantity of detection material  11   a.  Upon exposure to the target substance, the detection material  11   a  reacts calorimetrically with the target substance to produce an observable and measurable color change. In alternative embodiments, the detection material may be an electrochemical sensor or other material chemically reactive with the target substance. 
         [0017]    Manual piston-type sampling pumps such as the pump  13  depicted in  FIG. 1  are known to be used with a gas detection apparatus. It should be noted, however, that other types of pumps may be used with the inventive gas detection apparatus including a manual bulb-type pump. The pump  13  includes a cylinder body  15  having a grippable outer surface and a piston handle  17 . The pump includes a first end or detector end  23  for engaging the detector tube  11  and a second end  19  accommodating the travel or stroke of the piston. The handle end  19  of the pump includes a generally radial surface oriented perpendicularly to the longitudinal axis of the pump  13 . Situated centrally on this radial surface is a bore  21  in which the piston travels, as also shown in  FIG. 2   
         [0018]    By operating the manual pump  13 , the user draws gas into the detector tube  11  causing the required colorimetric reaction. As a result, color change occurs in the detection material in the form of an observable stain. The intensity or length of the stain is representative of the concentration of the target substance detected and is measurable using the calibrated scale on the tube  11 . Since the detection material  1  la is temperature sensitive, this intensity or length of stain may vary substantially based on the temperature of the local environment in which the gas is measured. 
         [0019]    Applicants have discovered, however, that such a chemical reaction is particularly sensitive to the temperature of the gas being measured. Due to inherent temperature effects on chemical reactivity (typically slower reactions at lower temperatures), the length or intensity of stain is directly affected by temperature due to more or less material reacting with the target gas, relative to the temperature sensitivity of the chemicals involved. It is for this reason that some detector tubes may have a large difference in the length of stain relative to temperature, while others may have little or no effect. Thus, obtaining accurate measurements often requires correcting for the temperature of the local gaseous environment sampled and then applying or multiplying the measured amount with a correction factor to accurately read or determine the concentration of the target substance. For this purpose, correction charts or sheets are often provided with the gas detection device. These so called correction charts may be specifically generated depending on the target substance and the detector tube design. In any event, the operator must also determine the temperature upon which the sampling or measurement occurs. With prior art systems and methods, it is often difficult to provide this temperature correction because users of the gas detection device often do not to carry a thermometer with them in the field. Accordingly, inaccurate measurements or readings are commonplace. 
         [0020]      FIG. 2  illustrates a temperature indicating strip or label that may be used with the present inventive gas detection apparatus. Temperature indicating strips or thermostrips are available in polyester (Mylar) construction that uses microencapsulated liquid crystal color changing inks to indicate a specific temperature or range. These thermostrips are commercially available but are available only as elongated strips with temperature indications thereon. Typical applications of these strips are found in consumer products, medical laboratory products, and in advertising. 
         [0021]    In the present invention, the thermostrips have been modified to come in an alternate form or configuration and include a plurality of correction factors that are each illuminated at a particular temperature, which are particularly and uniquely advantageous in gas measuring applications. As shown in  FIG. 2 , a preferred design is a circular design wherein the temperature indications are arranged in a circular pattern. The thermostrip  31  has a “doughnut” shape which includes a central hole and a gap in the circular pattern. As a result, the circular thermostrip  31  may be placed conveniently and advantageously at a preferred location on the manual pump  13 . Specifically, the circular thermostrip  31  may be advantageously placed on the handle surface  19  of the pump  13 , as shown in  FIG. 2 . At this location, the temperature indicators may be easily and conveniently read by the user, while the user is operating the handle  21 . Moreover, this surface or area of the pump  13  is less likely to come in contact with the user&#39;s hands or other external surfaces that may influence the temperature of the thermostrip  31 . The temperature correction factor indicator device  51  of  FIG. 5  may be substituted for the one shown in  FIG. 2  and used as described herein. Likewise, a temperature correction factor indicator device may be substituted for the thermostrip  31  that is shown on  FIG. 3 . 
         [0022]    Alternatively, the thermostrip  31  may be placed circumferentially or may be placed around the circumferential surface of the pump body  15 , as is shown in  FIG. 3 . In such an application, the thermostrip is elongated but the temperature indicators are arranged in a linear pattern. In an alternative embodiment of the invention as shown in  FIG. 5 , the temperature correction factor indicator device  51  is modified to include a plurality of correction factor indications  55 . Such correction factors are normally provided on a separate correction charge. The temperature correction factor indicator device  51  provides the correction factor indications  55  in a circular pattern, which correspond to particular temperature indications  53 . Thus, the user can simply take the correction factor from the gas detection device rather than measuring a temperature of the local environment and consulting a correction sheet. This is yet another aspect of the inventive apparatus and method. In yet another alternative embodiment, the temperature correction factor indicator device may be provided with correction factor indications  55 , but not the temperature indications  53 , as shown in  FIG. 5A . In this embodiment, the appropriate correction factor illuminates to prompt the user as to an appropriate correction factor to use when calculating the accurate amount of target substance present in the local environment. Thus, an operator merely reads the measured amount of the target substance as indicated by the graduation marks of the detection container as shown in  FIG. 1A  and thereafter determines the illuminated correction factor provided on the temperature correction factor indicator device  51  that is preferably arranged on the apparatus  9  as shown in  FIGS. 2-3 . Thereafter, the operator multiplies the measured amount indicated on the detection container with the illuminated correction factor to obtain an accurate measurement of the target substance present in the local environment. In the previous embodiment, the temperature indications may illuminate (i.e., to indicate the relevant temperature), so that the user is directed to the correction factor positioned adjacent the illuminated temperature indication. Thus, the user can simply read the correction factor from the gas detection device rather than consulting a correction sheet. This is yet another aspect of the inventive apparatus and method. 
         [0023]      FIGS. 4   a  and  4   b  depict yet another embodiment of the gas detection system or apparatus according to the invention. In this embodiment, a bellows-style pump  113  is used in combination with a detector tube. The manual bellows-style sampling pump  113  performs a similar function as that of the manual piston-type pump of  FIG. 3 , but requires squeezing of the accordian-style bellows  121  to force air to discharge (while simultaneously drawing air through the tube).  FIG. 4  illustrates an alternative placement of a thermostrip  131  on a different location on the pump and on a different style pump. In  FIG. 4   b,  the thermostrip  131  is shown advantageously placed on a top surface of the pump  113 . The temperature correction factor indicator device  51  shown in either  FIG. 5  or  5 A may be substituted for the thermostrip  131  for providing an apparatus that includes a temperature correction factor indicator device. During use, an appropriate correction factor is illuminated such that the background on which the appropriate correction factor is displayed changes in color relative to the background on which the other correction factors are displayed. That is, the temperature sensitive ink of a temperature correction factor indicator device illuminates the appropriate correction factor. 
         [0024]    Various embodiments of the present invention have been described herein. It should be understood by those of ordinary skill in the art, however, that the above-described embodiments, such as an apparatus employing a gas detector tube and a standard detector tube and manual piston pump, are set forth merely by way of example and should not be interpreted as limiting the scope of the invention, which is defined by the appended claims. Other alternative embodiments, variations and modifications of the foregoing embodiments that embrace various aspects of the present invention will also be understood upon a reading of the detailed description in light of the prior art. For instance, it will be understood that application of a thermostrip or the various types and configurations of thermostrips and/or temperature correction factor indicator devices, may be combined with features of other embodiments while many other features may be omitted or replaced (e.g., the manual pump, as being non-essential to the practice of the present invention).