Patent Application
20080110562
Industrial processes often require maintenance of an atmospheric analyte within a workspace above or below a given concentration range. Analytes of interest or concern are typically reactive analytes such as O2, CO or VOCs. One such example is the modified atmosphere packaging (MAP) of foods where the workspace in which the foods are packaged is flushed with an inert gas, such as nitrogen, to reduce the oxygen concentration within the resultant packaging and thereby increase the shelf life of the packaged product.
Analyte concentration within a workspace is typically measured by pumping atmospheric samples from the workspace to a remotely located on-line analyte reading analyzer. While generally effective, such systems are relatively expensive, prone to frequent failures, and have a short life-span. While repair and replacement of these systems is problematic, the greater business concern is the time and cost involved in preventing potentially defective product, produced while the analyte sensing system was not functioning, from reaching consumers. Of even greater concern is that defective product will reach consumers, resulting in a tarnishing of the business' reputation.
Accordingly, a need exists for an inexpensive yet reliable atmosphere analyte sensing system possessing an extended useful life.
A first aspect of the invention is a system for sensing and reporting atmospheric analyte levels in a workspace. The system includes (i) a remotely located gas analyte sensor, (ii) a tube attached to the sensor and defining a lumen through which the sensor is placed in fluid communication with a workspace, and (iii) a fan in fluid communication with the lumen of the tube for continuously moving gaseous content from the workspace through the lumen and into operative engagement with the sensor.
A specific embodiment of the first aspect of the invention is a system for sensing and reporting O2 levels in the workspace of a form, fill, and seal machine. The system includes (i) a form, fill, and seal machine defining a workspace open to the atmosphere wherein packaging is filled with a product and sealed, (ii) a flush system for flushing the workspace with an inert gas to reduce oxygen levels in the workspace, (iii) an oxygen sensor remotely located relative to the workspace, (iv) a tube attached to the oxygen sensor and defining a lumen through which the oxygen sensor is placed in fluid communication with the workspace, and (v) a fan in sealed fluid communication with the lumen of the tube for continuously moving gaseous content from the workspace into operative engagement with the oxygen sensor.
A second aspect of the invention is a method for sensing and reporting analyte levels in a workspace. The method includes the steps of (i) placing a distal end of a tube attached to an analyte sensor within a workspace, (ii) activating a fan in sealed fluid communication with the lumen of the tube so as to continuously move gaseous content from the workspace through the tube and into operative engagement with the sensor, and (iii) sensing and reporting analyte levels in the workspace with the sensor.
A specific embodiment of the second aspect of the invention is a method for controlling inert gas flushing of a form, fill, and seal machine workspace. The method includes the steps of (i) placing the distal end of a tube attached to an oxygen sensor within the workspace of a form, fill, and seal machine, (ii) activating a fan in sealed fluid communication with the lumen of the tube so as to continuously move gaseous content from the workspace through the tube and into operative engagement with the oxygen sensor, (iii) sensing and reporting O2 levels in the workspace with the oxygen sensor, and (iv) adjusting a flow rate of inert gas into the workspace based upon the reported level of O2 in the workspace.
As utilized herein, including the claims, the term “fan” means a machine including at least a rotor, blades and a housing for moving gases at relatively low pressure differentials wherein the blades do NOT sealingly engage the housing.
The gas analyte system 10 of the present invention is effective for measuring the concentration of a gaseous analyte in a workspace 50. Common analytes of interest include specifically, but not exclusively, carbon dioxide, carbon monoxide, oxygen, ozone, water vapor, and volatile organ compounds such as propane, benzene, toluene, methanol, etc.
Referring to
An inert gas 61, typically N2, CO2 or a combination thereof, is pumped into the workspace 50 through a gas introduction system 60 for purposes of reducing O2 levels in the workspace 50. By way of example, snack food such as potato chips are typically packaged with an O2 concentration of less than about 3% in the headspace (not shown) of the bag. By reducing O2 levels in the workspace 50, the O2 levels in the headspace of the sealed bags formed by the form, fill, and seal machine will contain reduced O2 levels corresponding to the O2 concentration within the workspace 50 as the headspace is filled with air from the workspace 50.
Referring to
The gas introduction system 60 is equipped with a flow-control valve 70 for allowing manual or automatic control of gas flow through the gas introduction system 60 based upon the sensed and reported concentration of analyte within the workspace 50. The gas introduction system 60 can be used to introduce an inert gas within the workspace 50 in order to maintain a reduced concentration of an analyte within the workspace 50 (i.e., a flushing system), or alternatively can be used to introduce a reactive gas within the workspace 50 in order to maintain a desired reactive environment within the workspace 50 (i.e., reactant supply system). An exemplary use of the gas introduction system 60 as a flushing system places the flow-control valve 70 and the analyte sensor 20 into electrical communication with a microcontroller 100 programmed to open valve 70 in order to increase the flow of inert gas into the workspace 50 when the analyte sensor 20 senses an analyte level above a defined upper threshold value (e.g., 4%) to prevent contamination of product processed within the workspace 50, and close valve 70 in order to decrease the flow of inert gas into the workspace 50 when the analyte sensor 20 senses an analyte level below a defined lower threshold value (e.g., 2%) to prevent overuse of inert gas.
An exemplary use of the gas introduction system 60 as a reactant supply system places the flow-control valve 70 and the analyte sensor 20 into electrical communication with a microcontroller 100 programmed to open valve 70 in order to increase the flow of analyte into the workspace 50 when the analyte sensor 20 senses an analyte level below a defined lower threshold value (e.g., 40%) to ensure the presence of sufficient analyte within the workspace 50, and close valve 70 in order to decrease the flow of the gaseous analyte into the workspace 50 when the analyte sensor 20 senses an analyte level above a defined upper threshold value (e.g., 50%) to prevent overuse of analyte.
Gas samples for testing by the analyte sensor 20 are withdrawn from the workspace 50 through tubing 40 on a continuous basis by a fan 30 in sealed fluid communication with the lumen 49 of the tube 40. The fan 30 includes a housing 31, rotor 32 and blades 33 for continuously pulling gases at relatively low pressure differentials through the tube 40. I have surprisingly discovered that suitable samples may be pulled from a workspace 50 and passed by an analyte sensor 20 utilizing a fan 30 (i.e., a machine for moving gases at relatively low pressure differentials wherein the blades do not sealingly engage the housing) rather than a pump (i.e., a machine for moving fluids at relatively high pressure differentials wherein the blades sealingly engage the housing), resulting in a significant cost savings and substantial increase in the useful life of the gas analyte sensing system 10.
A wide range of fans 30 may suitably be used in the gas analyte sensing system 10. Preferred fans 30 are the small fans (i.e., typically about 1-10 inches wide by about 1-10 inches tall and about ½-2 inches thick) with an RPM of between about 1,500 and about 15,000 widely used on CPUs and in similar applications.
The sensing system 10 should be constructed, configured and arranged to provide a gas flow rate from the workspace 50 through the sensor 20 of at least 0.1 liters/minute as a flow rate of less than 0.1 liters/minute can significantly delay detection of a change in analyte concentration within the workspace 50. For most applications, the flow rate should be kept below about 5 liters/minute, preferably well below 5 liters/minute as a flow rate of greater than about 5 liters/minute depletes the concentration of desired gases from the workspace 50 without a corresponding benefit. The primary variables affecting flow rate are the performance rating of the fan 30 employed and the size of the lumen 49 in the tube 40.
The gas analyte system 10 may be effectively deployed and used to sense and report analyte levels in a workspace 50 by simply (i) placing the distal end 40b of the tube 40 into fluid communication with the workspace 50, (ii) activating the fan 30 so as to continuously move gaseous content from the workspace 50 through the tube 40 and into operative engagement with the sensor 20, and (iii) sensing and reporting analyte levels in the gaseous samples pulled from the workspace 50 with the sensor 20.
