Abstract:
An analytical instrument and associated method for ascertaining gas transmission rates of a target-analyte through a capped mouth of a bottle. The instrument employs a unique fixture that includes (1) a selectively openable and closeable enclosure defining a chamber, and (2) a mounting post extending into the chamber. The post is configured and arranged to sealingly engage an inner surface of a capped bottle neck, wherein mounting of a capped bottle neck onto the post sealingly separates the chamber into a first compartment inside the mounted capped bottle neck and a second compartment outside the mounted capped bottle neck. The fixture is configured and arranged with passageways for introducing a pressurized target-analyte-containing fluid into the first compartment of the chamber and flushing the second compartment of the chamber with a target-analyte-free fluid.

Description:
BACKGROUND 
     Carbonated beverages are ubiquitous in modern society. As the name indicates, such beverages are infused with carbon dioxide and maintained under pressure. Loss of carbonation causes a carbonated beverage to become stale or “flat”. Bottlers of carbonated beverages desire to know the rate of carbonation loss for its various bottled products as such information allows the bottler to determine the shelf-life of its products and test various bottle types and designs for their ability to retain carbonation. 
     Carbonated beverage bottles typically include a body portion, a neck portion that is narrower than the body, and a mouth atop the neck. The mouth of the bottle is closed with a twist-off or pry-off cap or closure after the bottle has been filled. 
     Carbonated beverages tend to lose carbonation through both the walls of the bottle body and neck, and through the cap or closure area of the bottle. Loss of carbonation through the bottle walls occurs by permeation of carbon dioxide through the walls. Loss of carbonation through the cap or closure area tends to occur by both permeation of carbon dioxide through the cap and leakage of carbon dioxide through the seal formed between the cap and the bottle. 
     Testing equipment has been developed for measuring a total rate of carbonation loss from a bottle, such as described in U.S. Pat. Nos. 6,964,191 and 7,624,622, and for ascertaining the rate of carbonation loss from permeation through the cap or closure area as a component of total carbonation loss from a bottle, such as described in U.S. Pat. No. 6,018,987. However, none of the testing equipment developed to date is capable of providing an accurate measurement of the effectiveness of a cap or closure to prevent loss of carbonation as the testing equipment measures the rate of carbonation loss through the cap or closure area while allowing a contemporaneous unmeasured lose of carbonation through the sidewalls of the bottle. By allowing a contemporaneous loss of carbonation through the bottle sidewall, a second variable is introduced (e.g., ΔP and ΔP CO2  across the bottle may vary from test to test), preventing the test data from serving as a true and accurate indication of transmission of carbon dioxide through the cap or closure area, and destroys the ability to directly compare test results. 
     Accordingly, a substantial need exists for testing equipment capable of accurately and reliably measuring the carbon dioxide transmission rate through the cap or closure area of a carbonated beverage bottle. 
     SUMMARY OF THE INVENTION 
     A first aspect of the invention is a fixture for use in testing gas transmission rates through a capped mouth of a bottle. The fixture includes (1) a selectively openable and closeable enclosure defining a chamber, (2) a mounting post extending into the chamber, and (3) a passageway through the post for introducing a pressurized fluid into the chamber. The post is configured and arranged to sealingly engage an inner surface of a capped bottle neck, wherein mounting of a capped bottle neck onto the post sealingly separates the chamber into a first compartment inside the mounted capped bottle neck and a second compartment outside the mounted capped bottle neck. The passageway is configured and arranged for introducing pressurized fluid into the first compartment of the chamber. 
     A second aspect of the invention is an analytical instrument for measuring gas transmission rate of a target-analyte through a capped mouth of a bottle. The instrument includes (i) a fixture in accordance with the first aspect of the invention, (ii) a source of pressurized gas containing a target-analyte in fluid communication with the first compartment via the passage through the post, and (iii) a target-analyte sensor in communication with the second compartment for detecting target-analyte in the second compartment. 
     A third aspect of the invention is a method of measuring gas transmission rate of a target-analyte through a capped mouth of a bottle. The method includes the steps of (A) obtaining an instrument in accordance with the second aspect of the invention, (B) obtaining a capped neck portion of a bottle, (C) mounting the capped bottle neck onto the post so as to form the first compartment, (D) closing the enclosure so as to seal the entire mounted capped bottle neck within the chamber and form the second compartment, (E) flushing the second compartment to remove target-anlayte from the second compartment, (F) introducing pressurized gas containing target-analyte into the first compartment via the passage through the post, and (G) detecting and measuring target-analyte passing from the first compartment into the second compartment through the mounted capped bottle neck. 
     The capped neck portion of a bottle can be obtained by severing the neck portion of a bottle from a majority of the body portion of the bottle. Enhanced accuracy is achieved by testing a capped bottle neck rather than the cap alone as testing of the cap alone (i.e., mounting just the cap sans the entire bottle onto a mounting post) ignores “leakage” through the seal between the cap and the bottle. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of a standard plastic carbonated beverage bottle. 
         FIG. 2  is a schematic flow-diagram of one embodiment of the invention. 
         FIG. 3  is an exploded perspective view of one embodiment of the fixture depicted in  FIG. 2  with a capped bottle neck severed from the bottle body. 
         FIG. 4   a  is a top view of the tray component of the fixture depicted in  FIG. 3  with the clips slid outward for allowing mounting and release of a capped bottle neck on the mounting post. 
         FIG. 4   b  is a top view of the tray component of the fixture depicted in  FIG. 3  with the clips positioned inward for clamping a capped bottle neck onto the mounting post. 
         FIG. 5  is a cross-sectional side view of the fixture depicted in  FIG. 3  taken along line  5 - 5  with a capped bottle neck clamped onto the mounting post. 
         FIG. 6  is a cross-sectional side view of the fixture depicted in  FIG. 3  taken along line  6 - 6  with a capped bottle neck clamped onto the mounting post. 
         FIG. 7  is a cross-sectional side view of the fixture depicted in  FIG. 3  taken along line  7 - 7  with a capped bottle neck clamped onto the mounting post. 
         FIG. 8  is an enlarged cross-sectional side view of the mounting post and mounted capped bottle neck depicted in  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
     Definitions 
     As used herein, including the claims, the phrases “flushing gas” and “target-analyte free gas” mean a gas having less than 0.1%, preferably less than 0.01% target-analyte. 
     As used herein, including the claims, the phrase “target analyte” means a molecule whose presence-absence within the second compartment is detected and measured. Typical target-analytes are oxygen O 2  and carbon dioxide CO 2 . 
     As used herein, including the claims, the phrase “essentially 100%” means containing only trace amounts of contaminants. 
     Nomenclature 
     
         
           10  Analytical Instrument 
           110  Source of Pressurized Target-Analyte-Containing Test Gas 
           111  Control Valve for Test Gas 
           112  Test Gas Supply Line from Source of Test Gas to Fixture 
           113  Venting Valve for Test Gas 
           120  Source of Pressurized Target-Analyte-Free Carrier Gas 
           121  Control Valve for Carrier Gas 
           122   a  Carrier Gas Supply Line from Source of Carrier Gas to Fixture 
           122   b  Carrier Gas Exhaust Line from Fixture to Sensor 
           123  Venting Valve for Carrier Gas 
           130  Source of Target-Analyte-Free Flushing Gas 
           131  Control Valve for Flushing Gas 
           132  Flushing Gas Supply Line from Source of Flushing Gas to Fixture 
           133  Venting Valve for Flushing Gas 
           200  Fixture or Enclosure 
           209  Chamber 
           209   1  First Compartment of Chamber 
           209   2  Second Compartment of Chamber 
           210  Tray 
           211  Mounting Post 
           211   d  Distal End of Mounting Post 
           212   a  First Stanchion 
           212   b  Second Stanchion
         215  Annular Channel on Exterior of Mounting Post     
           216  First or Test Gas Passageway 
           216   i  Test Gas Inlet 
           216   o  Test Gas Outlet 
           216   v  Test Gas Vents 
           217  Second or Carrier Gas Passageway 
           217   i  Carrier Gas Inlet 
           217   o  Carrier Gas Outlet 
           218  Third or Flushing Gas Passageway 
           218   i  Flushing Gas Inlet 
           218   o  Flushing Gas Outlet 
           219  Well in Tray 
           220  Cover 
           221  Ring Fitting on Cover 
           228  Dimple in Top of Cover 
           229  Cavity Defined by Cover 
           231  Chamber O-Ring 
           232  Vent O-Ring 
           233  Proximal O-Ring on Post 
           234  Distal O-Ring on Post 
           240  Compression Beam 
           249  Threaded Orifice Through Compression Beam 
           250  Knob 
           251  Handle 
           252  Shaft 
           252   t  Tip of Shaft 
           260  Slide Clips 
           269  Slot in Slide Clips 
           270  Machine Screw 
           300  Target-Analyte Sensor 
         B Bottle 
         C Bottle Cap 
         F Annular Flange on Bottle Neck 
         M Mouth 
         N Bottle Neck 
         N i  Inner Surface of Bottle Neck 
         Z Capped Bottle Neck 
       
    
     DESCRIPTION 
     Construction 
     Referring generally to  FIGS. 1 and 2 , the invention is directed to an analytical instrument  10  with a unique mounting fixture  200  effective for accurately measuring gas transmission rate of a target-analyte through the capped mouth M of a bottle B. 
     Referring to  FIGS. 5 and 6 , the fixture  200  has a base or tray  210  that defines a well  219 , and a cover  220  that defines a cavity  229 . The well  219  and cavity  229  form a test chamber  209  when the cover  220  is secured atop the tray  210 . 
     Referring to  FIGS. 5 ,  6 ,  7  and  8 , a mounting post  211  extends upward from the well  219 . The mounting post  211  is configured and arranged to fit within and be crowned by a capped bottle neck Z so as to form a first compartment  209   1  within the capped bottle neck Z between the distal end  211   d  of the mounting post  211  and the cap C on the capped bottle neck Z. A pair of axially spaced o-rings  233  and  234  are provided on the mounting post  211  for sealingly engaging the inner surface N i  of the bottle neck N on the capped bottle neck Z. The o-rings  233  and  234  seal the first compartment  209   1  off from the surrounding environment. 
     Referring to  FIG. 6 , the tray  210  includes a passageway  216  through which test gas—containing a known concentration of target-analyte—can be introduced into the first compartment  209   1  from a pressurized source of the test gas  110  during testing. 
     Referring to  FIG. 7 , an annular channel  215  is preferably provided on the exterior surface (unnumbered) of the mounting post  211  intermediate the upper o-ring  233  and the lower o-ring  234  on the mounting post  211  for capturing and venting any test gas that may leak from the first compartment  209   1  through the upper o-ring  233 . The annular channel  215  is preferably in fluid communication with a source of target-analyte-free gas  130  for flushing the annular channel  215  during testing. 
     Referring to  FIG. 6 , the cover  220  is configured and arranged to cooperatively engage the tray  210  so as to form a test chamber  209  that sealingly surrounds the mounting post  211 , whereby mounting of a capped bottle neck Z onto the mounting post  211  divides the test chamber  209  into the previously described first sealed compartment  209   1  within the capped bottle neck Z and a second sealed compartment  209   2  surrounding the capped bottle neck Z. An o-ring  231  encircling the test chamber  209  is provided between the interface of the tray  210  and the cover  220  for sealing the test chamber  209  from the surrounding environment. 
     Referring to  FIGS. 3 and 5 , the cover  220  may be secured to the tray  210  by any number of suitable attachment mechanisms or systems known to those of routine skill in the art. One such mechanism, depicted in  FIGS. 3 and 5 , includes a pair of mushroom head stanchions  212   a  and  212   b  that extend upward from diametric corners of the tray  210 , a beam  240  for selectively engaging the stanchions  212   a  and  212   b  below the mushroom head on each stanchion  212   a  and  212   b  such that the beam  240  can slide along the length of the stanchions  212   a  and  212   b  but is trapped below the mushroom heads on the stanchions  212   a  and  212   b , and a knob  250  with a handle  251  and a shaft  252  for threadably engaging and extend through an orifice  249  in the beam  240  and pressing against the top of the cover  220 . Referring to  FIG. 6 , the tip  252   t  of the shaft  252  on the knob  250  is preferably captured by a dimple  228  in the top of the cover  220  so that the shaft  252  does not slide across the top of the cover  220  as the knob  250  is rotated relative to the joist  240  to press the cover  220  down onto the tray  210 . 
     Carbonated beverages are typically bottled at a pressure of between 4 and 6 atmospheres. Hence, in order to accurately emulate real-world conditions, the first compartment  209   1  should be pressurized to approximately 4-6 atmospheres with test gas when testing capped bottle necks Z from bottles B intended for use with carbonated beverages. Accordingly, the fixture  200  preferably includes a mechanism for clamping a capped bottle neck Z down onto the mounting post  211  in order to prevent the mounted capped bottle neck from being “shot” off the mounting post  211  during testing by the pressure within the first compartment  209   1 . A capped bottle neck Z may be secured to the mounting post  211  by any number of suitable attachment mechanisms or systems known to those of routine skill in the art. One such mechanism, depicted in  FIGS. 4   a ,  4   b  and  8 , includes a pair of clips  260  slidably secured to the tray  210  on opposite sides of the mounting post  211  by a machine screw  270  extending through a slot  269  in the clip  260 . The clips  260  can be selectively moved away from one another for allowing mounting and release of a capped bottle neck Z on the mounting post  211  as depicted in  FIG. 4   a , and moved towards one another for engaging the top of an annular flange F on the bottle neck N—thereby clamping the capped bottle neck Z onto the mounting post  211 , as depicted in  FIG. 4   b.    
     The fixture  200  preferably includes a safety feature that prevents pressurization of the first compartment  209   1  unless a capped bottle neck Z mounted onto the mounting post  211  is clamped down, and prevents unclamping of a capped bottle neck Z clamped onto the mounting post  211  when the first compartment  209   1  is pressurized. An elegant system for reliably providing this safety feature is depicted in  FIG. 6 . The depicted system prevents pressurization of and releases pressure from the first compartment  209   1  any time the cover  220  is not sealingly engaging the tray  210  by providing venting channels  216   v  in the tray  210  that are in fluid communication with the test gas passageway  216  for venting test gas into the atmosphere and are sealed off by the cover  220  that sealingly engages o-rings  232  that encircle the outlet (unnumbered) of the venting channels  216   v  between the tray  210  and the cover  220  when the cover  220  is fitted and compressed onto the tray  210 . The depicted system also prevents the cover  220  from sealingly engaging the tray  210  unless and until a capped bottle neck Z mounted onto the mounting post  211  is clamped down onto the mounting post  211  by providing an axially extending ring fitting  221  on the lower end of the cover  220  that is configured and arranged to extend into the well  219  in the tray  210 , such that fitted engagement of the cover  220  onto the tray  210  is obstructed by contact between the fitting  221  and the clips  260  when the clips are in the open position (i.e., moved away from one another), but is unhindered when the clips  260  are in the closed or clamping position (i.e., moved towards each other). 
     Referring to  FIGS. 3 and 6 , a first passageway  216  with diametrically opposed inlet  216   i  and outlet  216   o  orifices is provided in the tray  210  for allowing target-analyte-containing test gas from a source of test gas  110  to be introduced under pressure via a supply line  112  into the first compartment  209   1  during testing. 
     Referring to  FIGS. 3 and 5 , a second passageway  217  with diametrically opposed inlet  217   i  and outlet  217   o  orifices is provided in the tray  210  for allowing target-analyte-free carrier gas from a source of carrier gas  120  to flow into the second compartment  209   2  via a supply line  122   a  and out from the second compartment  209   2  via an exhaust line  122   b  for purposes of flushing the second compartment  209   2  prior to commencement of testing, and conveying the contents of the second compartment  209   2  into sensing contact with a target-analyte sensor  300  during testing. 
     Referring to  FIGS. 3 and 7 , a third passageway  218  with diametrically opposed inlet  218   i  and outlet  218   o  orifices is provided in the tray  210  for allowing target-analyte-free flushing gas—preferably from a source of flushing gas  130 —to flow into the annular channel  215  in the mounting post  211  via a supply line  132  and vent the contents of the channel  215  into the atmosphere during testing. For some applications, the source of carrier gas  120  and the source of flushing gas  130  can be the same source. Alternatively, for some applications air can be used as the flushing gas so long as air contains only trace quantities of the target-analyte. 
     The fixture  200  should be constructed from a material that is essentially impervious to target-analyte and does not appreciably absorb, adsorb or emit target-analyte. A preferred material of construction is stainless steel. 
     Use 
     The instrument  10  can quickly, accurately and reliably measure the gas transmission rate of a target-analyte (typically CO 2 ) through a capped mouth M of a bottle B. 
     First, a capped bottle neck Z, sans bottle body, must be obtained. Typically, this can be achieved by simply removing a filled and sealed bottle B from the production line, and severing the capped bottle neck Z from the body of the bottle B. The bottle body and bottle contents can be discarded. 
     With the control valve  111  for the source of test gas  110 , the control valve  121  for the source of carrier gas  120 , and the control valve  131  for the source of flushing gas  130  closed, the cover  220  is separated from the base  210 , the clips  260  slid outward—away from one another—and the severed capped bottle neck Z press fitted by hand onto the mounting post  211 . 
     The clips  260  are slid inward—towards one another—into clamping engagement with the upper surface of the annular flange F on the mounted bottle neck N. The cover  220  is then fitted onto the base  210  and sealingly compressed against the base  210  by placing the compression beam  240  over the cover  220 , securing the ends of the compression beam  240  to the stanchions  212   a  and  212   b  below the head of each stanchion  212   a  and  212   b , and then rotating the knob  250  within the threaded orifice  249  in the compression beam  240  until the tip  252   t  of the shaft  252  engages and compresses the cover  220  down onto the base  210 . 
     Prior to placing the sensor  300  into fluid communication with the fixture  200 , the first compartment  209   1  is flushed with target-analyte-containing test gas (such as 100% CO 2 ) from the source of test gas  110  by opening both the test gas control valve  111  and the test gas venting valve  113 , and the second compartment  209   2  is flushed with target-analyte-free carrier gas (such as 100% N 2 ) from the source of carrier gas  121  by opening both the carrier gas control valve  121  and the carrier gas venting valve  123 . When fully flushed, testing can be commenced by closing the test gas venting valve  113  so as to pressurize the first compartment  209   1  with target-analyte-containing test gas (such as 100% CO 2 ), and closing the carrier gas venting valve  123  so as to direct the flow of carrier gas and thereby the contents of the second compartment  209   2  into sensing engagement with the target-analyte sensor  300 . Optionally, the annular channel  215  in the mounting post  211  can be flushed with target-analyte-free flushing gas from the source of flushing gas  130  by opening flushing gas control valve  131  as desired. 
     Timed detection of target-analyte in the second compartment  209   2  correlates to the transmission rate of target-analyte through the capped bottle neck Z as the only statistically significant paths available for introducing target-analyte into the second compartment  209   2  is via permeation through the cap C on the capped bottle neck Z or leakage through the seal formed between the cap C and the bottle neck N on the capped bottle neck Z. 
     When testing is completed, the control valve  111  for the source of test gas  110 , the control valve  121  for the source of carrier gas  120 , and the control valve  131  for the source of flushing gas  130  are closed, followed by opening of the venting valve  113  for the source of test gas  110 , the venting valve  123  for the source of carrier gas  120 , and the venting valve  133  for the source of flushing gas  130  to release any pressure from within the fixture  200 . The knob  250  can then be rotated to release clamping pressure on the cover  220 , the cover  220  separated from the base  210 , the clips  260  slid outward—away from one another—and the mounted capped bottle neck Z removed from the mounting post  211 .