Patent Publication Number: US-2004045096-A1

Title: Chemical-specific sensor for monitoring amounts of volatile solvent during a drying cycle of a dry cleaning process

Description:
[0001] This application is a continuation-in-part of co-pending and commonly assigned U.S. patent application Ser. No. 10/127,001 filed Apr. 22, 2002. 
    
    
     
       BACKGROUND OF THE INVENTION  
       [0002] The present invention is generally related to a laundering appliance, and, more particularly, to a dry cleaning appliance that uses a volatile solvent for cleansing the articles and, even more particularly, to sensing devices for monitoring amounts of the volatile solvent present during a drying cycle of a dry cleaning process.  
       [0003] Conventional household clothing washers use anywhere from about 60 liters to about 190 liters of water to wash a typical load of clothing articles. The spent water and cleaning agents are then dumped into sewage. Furthermore, the water is frequently heated to improve wash effectiveness and usually requires a large amount of energy to be put into the articles as heat in order to vaporize the retained water and dry the articles. The combination of high water usage, high-energy usage and disposal of cleaning additives in the detergent can put a large strain on the environment.  
       [0004] Conventional professional dry cleaning perchloroethylene (PERC) solvent has been shown to be hazardous to human health as well as to the environment. Use of a cyclic siloxane composition, more specifically decamethylcyclopentasiloxane (or simply siloxane, also commercially referred to as D5), as a replacement for PERC is known. The use of a siloxane solvent in laundering has been shown to result in reduced wrinkling, superior article care, and better finish than water washing. Furthermore, the siloxane solvent has a lower heat of vaporization than water. Compared to water, the siloxane solvent can be more easily dried out of the article. If a washing machine contained a solvent based cleaning cycle, the solvent cycle could replace some or all of the washing currently being done in water, which would result in a significant reduction in energy and water use.  
       [0005] There are currently commercial dry cleaning machines, which use a cyclic siloxane dry cleaning process, but these machines present several barriers to in-home use. Known commercial dry cleaning machines are generally much larger than typical home washing machines, and would not fit within typical washrooms. These commercial dry cleaning machines typically require high voltage power (&gt;250V) and often require separate steam systems, compressed air systems, and chilling systems to be attached externally. The solvent amount generally stored in the commercial dry cleaning machines is usually more than about 190 liters, even for the smallest capacity commercial machines. The typical dry cleaning facility has both solvent cleaning and water cleaning machines on the premises and uses each machine for their separate functions. Known commercial dry cleaning machines are typically designed to be operated by a skilled employee and do not contain appropriate safety systems for either in-home locations or for general use. In many states, the use of commercial dry cleaning machines by the general public is forbidden.  
       [0006] U.S. patent application Ser. No. 10/127,001, titled “Apparatus and Method for Article Cleaning”, filed on Apr. 22, 2002, (Attorney Docket No. RD-29557), commonly assigned to the same assignee of the present invention, and herein incorporated by reference in its entirety, represents one innovative implementation of an appliance that provides solvent, or water-based cleaning (or combination thereof). As set forth in the foregoing patent application, this appliance may be advantageously accommodated either in an in-home or in a coin-operable laundry setting. That is, an appliance that may be used not just for commercial dry cleaning applications, but also having the appropriate small size, cost, and user-interface considerations for a home-based laundry system.  
       [0007] In order to reduce usage costs and improve safety of commercial coin-operable versions and in-home versions of waterless or very low water washers employing a solvent, such as volatile cyclic siloxane, as the primary wash fluid, it is desirable to provide a “dry-to-dry” cleansing operation and be able to sense the state of dryness of the clothes during a drying cycle. To that end, a relatively low-cost chemical-specific sensor that accurately and reliably senses amounts of the volatile siloxane solvent is desirable.  
       BRIEF DESCRIPTION OF THE INVENTION  
       [0008] Generally, the present invention fulfills the foregoing needs by providing in one aspect thereof, a solvent vapor sensor for determining amounts of solvent vapor flowing during a solvent dry cleaning process, e.g., during a drying cycle of the dry cleaning process. The solvent cleaning process utilizes a solvent based cleaning fluid comprising cyclic siloxane solvent.  
       [0009] In another aspect thereof, the present invention further fulfills the foregoing needs by providing an article cleaning apparatus including an air management mechanism, a cleaning basket assembly, and a fluid regeneration device. A working fluid device is coupled to the fluid regeneration device, the cleaning basket assembly, and the air management mechanism. A clean fluid device is coupled to the cleaning basket assembly and the fluid regeneration device. A controller is coupled to the air management mechanism, the cleaning basket assembly, the working fluid device, the regeneration device, and the clean fluid device. The controller may be configured to control a cleaning process including at least a solvent cleaning process that utilizes a solvent based cleaning fluid comprising cyclic siloxane solvent. A solvent vapor sensor is coupled to the controller to determine amounts of solvent vapor flowing during the solvent cleaning process, e.g., during a drying cycle of the dry cleaning process.  
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0010] The features and advantages of the present invention will become apparent from the following detailed description of the invention when read with the accompanying drawings in which:  
     [0011]FIG. 1 is a block diagram of the article cleaning apparatus in accordance with one embodiment of the present invention;  
     [0012]FIG. 2 is a schematic diagram of the fluid processing mechanism in accordance with one embodiment of the present invention;  
     [0013]FIG. 3 is a schematic diagram of a filter arrangement in accordance with one embodiment of the present invention;  
     [0014]FIG. 4 is a schematic diagram of a filter arrangement in accordance with another embodiment of the present invention;  
     [0015]FIG. 5 is a schematic diagram of the air management mechanism and the cleaning basket assembly in accordance with one embodiment of the present invention;  
     [0016]FIG. 6 is a schematic diagram of the air management mechanism and the cleaning basket assembly in accordance with another embodiment of the present invention;  
     [0017]FIG. 7 is a schematic diagram of the devices coupled to the controller in accordance with one embodiment of the present invention;  
     [0018]FIG. 8 is a schematic cross sectional view of the cleaning basket assembly in accordance with one embodiment of the present invention;  
     [0019]FIG. 9 is a three-dimensional partial cross sectional view of the article cleaning apparatus in accordance with one embodiment of the present invention;  
     [0020]FIG. 10 is a plot of retained moisture content as a percentage of an article&#39;s weight versus the relative humidity;  
     [0021]FIG. 11 is a block diagram of the process selection in accordance with one embodiment of the present invention;  
     [0022]FIG. 12 is a flow diagram of a humidity sensing process in accordance with one embodiment of the present invention;  
     [0023]FIG. 13 is a flow diagram of a solvent cleaning process in accordance with one embodiment of the present invention;  
     [0024]FIG. 14 is a flow diagram of a water cleaning process in accordance with one embodiment of the present invention;  
     [0025]FIG. 15 is a flow diagram of a basket drying process in accordance with one embodiment of the present invention;  
     [0026]FIG. 16 is a flow diagram of a cycle interruption recovery process in accordance with one embodiment of the present invention;  
     [0027]FIG. 17 plots exemplary phase spectra of siloxane and water vapor in the near IR region;  
     [0028]FIG. 18 plots exemplary phase spectra of siloxane and water vapor in the mid IR region;  
     [0029]FIG. 19 shows a block diagram of an exemplary embodiment of an spectral sensor for infrared detection of siloxane vapor;  
     [0030]FIG. 20 shows a block diagram of another exemplary embodiment of an spectral sensor for infrared detection of both siloxane and water vapor;  
     [0031]FIG. 21 shows a plot of an exemplary mid-IR sensor response to saturated siloxane vapor;  
     [0032]FIG. 22 shows a plot of an exemplary mid-IR sensor response saturated siloxane and water vapor;  
     [0033]FIG. 23 shows a schematic of an exemplary resonator, e.g., a QCM resonator, including a transducer film for detecting volatile siloxane; and  
     [0034]FIG. 24 shows a plot of an exemplary QCM resonator coated with an exemplary transducer film, e.g., RTV-615 in the presence of siloxane and water vapor. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     [0035] The present invention includes an apparatus and method for the cleaning of articles at home or in a coin-op laundry setting. As used herein, the term, “articles” is defined, for illustrative purposes and without limitation, as fabrics, textiles, garments, and linens and any combination thereof. As used herein, the term, “solvent based cleaning fluid” is defined for illustrative purposes and without limitation, as comprising a cyclic siloxane solvent and, optionally, a cleaning agent. If water is present in a solvent based cleaning fluid, the water is present in an amount in a range from about 0.25 percent to about 10 percent of the total weight of the solvent based cleaning fluid. In another embodiment of the present invention, if water is present in the solvent based cleaning fluid, the water is present in an amount in a range from about 0.25 percent to about 2 percent of the total weight of the solvent based cleaning fluid. As used herein, the term, “cleaning agent” is defined for illustrative purposes and without limitation, as being selected from the group consisting of sanitizing agents, emulsifiers, surfactants, detergents, bleaches, softeners, and combinations thereof. As used herein, the term, “water based cleaning fluid” is defined for illustrative purposes and without limitation, as comprising water and, optionally, a cleaning agent. In the present invention, the article cleaning apparatus  1000  of FIG. 1 is configured to perform a cleaning process  350  of FIG. 11. As used herein, the term, “cleaning process” is defined, for illustrative purposes and without limitation, as utilizing a solvent cleaning process  375 , a water cleaning process  600 , and any combination thereof. The solvent cleaning process  375  and the water cleaning process  600  are presented in more detail after the article description of the cleaning apparatus  1000  of FIG. 1. It is recognized that alternative configurations of the article cleaning apparatus  1000  are possible.  
     [0036] The article cleaning apparatus  1000  comprises the air management mechanism  1 , the cleaning basket assembly  2 , and a fluid regeneration device  7 . The article cleaning apparatus  1000  further comprises a working fluid device  6  that is coupled to the fluid regeneration device  7 , the cleaning basket assembly  2 , and the air management mechanism  1 . The article cleaning apparatus  1000  further comprises a clean fluid device  8  that is coupled to the cleaning basket assembly  2  and the fluid regeneration device  7 . The article cleaning apparatus  1000  further comprises a controller  5  which is coupled to the air management mechanism  1 , the cleaning basket assembly  2 , the working fluid device  6 , the regeneration device  7 , and the clean fluid device  8 . The controller  5  is configured to perform the cleaning process  350 .  
     [0037] The cleaning basket assembly  2  of FIG. 1 typically comprises a rotating basket  14  coupled to a motor  3 . The rotating basket  14  has a plurality of holes  17 . The motor  3  rotates the rotating basket  14 . Suitable drive system alternatives, presented for illustration and without limitation include, direct drive, pulley-belt drive, transmissions, and any combination thereof. The direct drive orientation of the rotating basket  14  and the motor  3  is provided for illustrative purposes and it is not intended to imply a restriction to the present invention. In one embodiment of the present invention (not shown in FIG. 1), the motor  3  has a different major longitudinal axis than the longitudinal axis  220  of the rotating basket  14 , and the motor  3  is coupled to the rotating basket  14  by a pulley and a belt.  
     [0038] As shown in FIG. 2, the working fluid device  6 , the fluid regeneration device  7 , and the clean fluid device  8  comprise a fluid processing mechanism  4 .  
     [0039] In one embodiment of the present invention, the working fluid device  6  comprises a check valve  40  in a drain conduit line  70  that couples the cleaning basket assembly  2  to a working tank  45 . Fluid from the cleaning basket assembly  2  passes through the check valve  40  and is collected in the working tank  45 . The fluid in the working tank  45  is defined as a working fluid  165 . A drain tray  73  is disposed in the air management mechanism  1  to collect condensate. An additional drain conduit  71  couples the working tank  45  to the drain tray  73 . Condensate in the drain tray  73  is typically gravity drained to the working tank  45 , where it is collected as part of the working fluid  165 . A regeneration pump  115  is coupled to the working tank  45  and to a conductivity sensor  151 . A waste water drain valve  155  is disposed between the conductivity sensor  151  and the fluid regeneration device  7 . The waste water drain valve  155  is coupled to waste water discharge piping  154 .  
     [0040] In one embodiment of the present invention, the controller  5  of FIG. 7 is configured to direct the working fluid  165  of FIG. 2 through to the fluid regeneration device  7  when the conductivity sensor  151  indicates that the working fluid  165  comprises less than about 10% water by weight. The controller  5  of FIG. 7 is further configured to divert the working fluid  165  of FIG. 2 through the waste water drain valve  155  and the waste water discharge piping  154  when the working fluid  165  flowing through the conductivity sensor  151  comprises a minimum of at least about 10% by weight of water to avoid overwhelming the water adsorption capability of the fluid regeneration device  7 .  
     [0041] In another embodiment of the present invention, a water separator  152  is disposed in the working tank  45 . In another embodiment of the present invention, the water separator  152  is disposed between the waste water drain valve  155  and the fluid regeneration device  7 . In another embodiment of the present invention, a bypass line  145  of FIG. 2 is disposed between the discharge of the water separator  152  and the inlet of the clean fluid device  8  to reduce the possibility of overwhelming the water removal capability in the fluid regeneration device  7 . In another embodiment of the present invention (not shown in FIG. 2), the bypass line  145  is disposed between the waste water drain valve  155  and the clean fluid device  8 . The bypass line  145  is typically sized to bypass a range from about one-quarter to about three-quarter of the total flow of the working fluid  165  around the fluid regeneration device  7 .  
     [0042] In one embodiment of the present invention, the water separator  152  is fabricated from materials selected form the group consisting of calcined clay, water adsorbing polymers, sodium sulfate, paper, cotton fiber, lint, and any combination thereof. In another embodiment of the present invention, the water separator  152  comprises a distillination device that utilizes heat to remove water.  
     [0043] The fluid regeneration device  7  comprises a regeneration cartridge  141 . The inlet side of the regeneration cartridge  141  is typically coupled to the working fluid device  6 . The regeneration cartridge  141  typically comprises at least a water absorption media  130  coupled to a cleaning fluid regeneration absorption media  135 . In one embodiment of the present invention, the regeneration cartridge  141  further comprises a mechanical filter  120  and a particulate filter  125 . In one embodiment of the present invention, the working fluid  165  passes sequentially through the mechanical filter  120 , particulate filter  125 , water absorption media  130 , and cleaning fluid regeneration absorption media  135 . The cleaning fluid regeneration adsorption media  135  contains a portion of the solvent based cleaning fluid  30  in order to replenish the solvent based cleaning fluid  30  that is consumed during the solvent wash/dry process  500  of FIG. 13. The cleaning fluid regeneration adsorption media  135  also contains a replacement amount of solvent based cleaning fluid  30  which is disposed of when changing out the regeneration cartridge  141 .  
     [0044] In one embodiment of the present invention, the cleaning fluid regeneration adsorption media  135  is selected from a group consisting of a packed bed column, a flat plate bed, a tortuous path bed, a membrane separator, a column with packed trays, and combinations thereof.  
     [0045] In one embodiment of the present invention, the materials to fabricate the cleaning fluid regeneration adsorption media  135  are selected from the group consisting of activated charcoal, carbon, calcined clay, Kaolinite, adsorption resins, carbonaceous type resins, silica gels, alumina in acid form, alumina in base form, alumina in neutral form, zeolites, molecular sieves, and any combination thereof. Both the amount of solvent based cleaning fluid regeneration and the speed of solvent based cleaning fluid regeneration depend on the volume of the cleaning fluid regeneration adsorption media  135 .  
     [0046] In one embodiment of the present invention, the regeneration cartridge  141  containing the cleaning fluid regeneration adsorption media  135  in the packed bed column form is disposed in a single packed bed column cartridge form. In another embodiment of the present invention, the regeneration cartridge  141  comprising the cleaning fluid regeneration adsorption media  135  in the packed bed column form is disposed in a plurality of packed bed column cartridges. In an alternative embodiment of the present invention, the regeneration cartridge  141  comprises the cleaning fluid regeneration adsorption media  135  in a plurality of packed bed column cartridges, which are disposed in series with respect to one another. In yet another embodiment of the present invention, the regeneration cartridge  141  further comprises the cleaning fluid regeneration adsorption media  135  in the plurality of packed bed column cartridges, which are disposed in parallel with respect to one another.  
     [0047] In another embodiment of the present invention, the mechanical filter  120  of FIG. 3 and the particulate filter  125  are part of the working fluid device  6 . The mechanical filter  120  and the particulate filter  125  are disposed in the drain conduit line  70  that couples the cleaning basket assembly  2  to the working tank  45 . The mechanical filter  120  and the particulate filter  125  are disposed in the drain conduit  70  between the cleaning basket assembly  2  and the check valve  40 .  
     [0048] In another embodiment of the present invention, the mechanical filter  120  of FIG. 4 and the particulate filter  125  are disposed in the drain conduit  70  between the check valve  40  and the working tank  45 . In an alternative embodiment of the present invention, the mechanical filter  120  is disposed in the drain conduit  70 , while the particulate filter  125  is disposed in the regeneration cartridge  141 . In another embodiment of the present invention, the mechanical filter  120  is not present and the particulate filter  125  is disposed in the regeneration cartridge filter  141 . In another embodiment of the present invention, the mechanical filter  120  is not present and the particulate filter  125  is disposed in the drain conduit  141 . Both the arrangement of the internals of the regeneration cartridge  141  and the location and application of the mechanical filter  120  and the particulate filter  125  are provided for illustrative purposes and are not intended to imply a restriction on the present invention.  
     [0049] In one embodiment of the present invention, mechanical filter  120  has a mesh size in a range from about 50 microns to about 1000 microns. In one embodiment of the present invention, the particulate filter  125  has a mesh size in a range from about 0.5 microns to about 50 microns.  
     [0050] In one embodiment of the present invention, the particulate filter  125  is a cartridge filter fabricated from materials selected from the group consisting of thermoplastics, polyethylene, polypropylene, polyester, aluminum, stainless steel, metallic mesh, sintered metal, ceramic, membrane diatomaceous earth, and any combination thereof.  
     [0051] After the working fluid  165  passes through the regeneration cartridge  141 , it exits the regeneration cartridge  141  as the solvent based cleaning fluid  30 . An outlet side of the regeneration cartridge  141  is typically coupled to an optical turbidity sensor  140 . The optical turbidity sensor  140  is typically coupled to a storage tank  35  in the clean fluid device  8 . The optical turbidity sensor  140  is tuned to a specific absorbance level that provides information about the cleanliness of the solvent based cleaning fluid  30 . When the solvent based cleaning fluid  30  exiting the optical turbidity sensor  140  reaches a preset specific absorbance level, the controller  5  of FIG. 7 sends a “replace regeneration cartridge” message to the operator on a display panel  200  (FIG. 9).  
     [0052] The storage tank  35  of FIG. 2 in the clean fluid device  8  stores the solvent based cleaning fluid  30  received from the fluid regeneration device  7 . The clean fluid device  8  further comprises a pump  25  that is coupled to the storage tank  35 . The pump  25  is coupled to the cleaning basket assembly  2  via an inlet line  26 . In one embodiment of the present invention, the pump  25  is also typically coupled to the air management mechanism  1  via cooling coil wash down tubing  160 . In another embodiment of the present invention, the clean fluid device  8  further comprises a spray nozzle  67  that is typically disposed in the cooling coil wash down tubing  160  to control the flow of the solvent based cleaning fluid  30  to the air management mechanism  1 . As used herein, the term, “spray nozzle” is defined to be a nozzle, an orifice, a spray valve, a pressure reducing tubing section, and any combination thereof. In one embodiment of the present invention, the spray nozzle  67  is coupled to the controller  5  as is shown in FIG. 7 when the spray nozzle  67  is a spray valve.  
     [0053] The air management mechanism  1  of FIG. 5 comprises a cooling coil  65 , a heater  55 , and a fan  50 . The air management mechanism  1  is coupled to the cleaning basket assembly  2  by suction ventilation ducting  51  and discharge ventilation ducting  52 . The fan  50  is disposed to provide airflow  53  through the cooling coil  65 , the heater  55 , the discharge ventilation ducting  52 , the cleaning basket assembly  2 , and the suction ventilation ducting  51 . A temperature sensor  57  is also typically disposed in the airflow  53 . The temperature sensor  57  is typically disposed in the suction ventilation ducting  51 , the discharge ventilation ducting  52 , the cleaning basket assembly  2 , and any combination thereof.  
     [0054] The cooling coil  65  is configured to have a cooling medium disposed to flow across one side of a heat transfer surface of the cooling coil  65 , while the airflow  53  passes across the opposite side of the heat transfer surface of the cooling coil  65 . The heat transfer surface of the cooling coil  65  separates the cooling medium and the airflow  53 . The inlet temperature of the cooling medium utilized is typically cooler that the temperature of the airflow  53  in order to condense vapors in the airflow  53 . As used herein, the term, “cooling medium” is defined, for illustrative purposes and without limitation, as being selected from water, refrigerants, air, other gasses, ethylene glycol/water mixtures, propylene glycol/water mixtures and any combination thereof. The drain tray  73  is disposed under the cooling coil  65  and is coupled to the working tank  45  as described above.  
     [0055] In one embodiment of the present invention, the air management mechanism  1  typically further comprises an air intake  156  and an air exhaust  157 . The air intake  156  and air exhaust  157  are disposed to provide air exchange between the airflow  53  and the air that is outside of the air management mechanism  1  to promote the drying of articles that have been subjected to the water cleaning process  600  of FIG. 14. The air intake  156  and air exhaust  157  are disposed in a similar configuration to that of a conventional dryer. In one embodiment of the present invention, the air intake  156  of FIG. 5 is disposed in the ventilation path between the heater  55  and the fan  50 , while the air exhaust  157  is disposed between the cooling coil  65  and the cleaning basket assembly  2 . The locations of the air intake  156  and air exhaust  157  are provided for illustration and in no way imply a restriction to the present invention.  
     [0056] A solvent sensor  59  may quantifiably detect the presence of the solvent based cleaning fluid  30  in the airflow  53  that circulates between the cleaning basket assembly  2  and the air management mechanism  1 . For example, the solvent sensor  59  may be used to determine whether a solvent vapor pressure level or a solvent concentration reaches a predetermined level that indicates that the airflow  53  is no longer entraining specified amounts of the solvent based cleaning fluid  30  of FIG. 2. As will be appreciated by those skilled in the art, solvent vapor pressure and solvent vapor concentration are parameters that may be related to one another through the molar mass of the solvent. That is, if one measures one of these parameters, one may calculate the other from the measurement. The solvent sensor  59  of FIG. 6 may be disposed in the discharge ventilation ducting  52 . In another embodiment of the present invention, the solvent sensor  59  may be disposed in the suction ventilation ducting  51 , the discharge ventilation ducting  52 , the cleaning basket assembly  2 , and any combination thereof. As set forth in greater detail below in the context of FIGS. 17 through 24, aspects of the present are specifically directed to various practical exemplary embodiments for the solvent sensor  59 . That is, a chemical-specific sensor. Examples of sensor types that may be used for solvent sensor  59  may include spectroscopic sensors; piezo-based sensors with specific coatings; strain-gauge based sensors including an appropriate coating; and capacitive sensors.  
     [0057] The cooling coil  65  of FIG. 6 further comprises a cooling coil air inlet  66 . In one embodiment of the present invention, one end of the cooling coil wash down tubing  160  is aimed at the cooling coil air inlet  66  of FIG. 6. The spray nozzle  67  and the pump  25  flushes away lint and debris that accumulates on the surface of the cooling coil air inlet  66  of FIG. 6 to maintain airflow  53  (i.e. decrease the pressure drop across the cooling coil  65 ) through the air management mechanism  1  and the cleaning basket assembly  2 . In one embodiment of the present invention, spraying the solvent based cleaning fluid  30  of FIG. 2 at the cooling inlet  66  of FIG. 6 provides additional cooling and condensation of vapor in the airflow  53 .  
     [0058] As shown in FIG. 6, in another embodiment of the present invention, the air management mechanism  1  further comprises a compressor  75 , high-pressure tubing  80 , low-pressure tubing  85  and pressure reducing tubing  90  are disposed in a vapor compression cycle. As used herein, the term, “high-pressure tubing” is used to indicate that the high-pressure tubing is designed to contain a refrigerant  95  at a higher pressure than the “low-pressure tubing”. The use of the terms “high-pressure tubing” and “low-pressure tubing” are used to express a relative pressure differential across the compressor  75 . As used herein, the term, “pressure reducing tubing” is defined to indicate that the “pressure reducing tubing” comprises a flow restriction that is sufficient to provide the relative pressure differential at a junction between the “high-pressure tubing” and the “low-pressure tubing”. The high-pressure tubing  80  of FIG. 6 is disposed from the compressor  75  to the heater  55 . The pressure reducing tubing  90  is disposed between the heater  55  and the cooling coil  65 . The low-pressure tubing  85  is disposed from the compressor  75  to the cooling coil  65 . The refrigerant  95  is disposed to flow between the compressor  75 , heater  55 , and cooling coil  65 .  
     [0059] The vapor compression cycle attains a higher coefficient of performance (COP) for solvent wash/dry process  500  of FIG. 13. The vapor compression cycle operating in a heat pump configuration reduces energy requirements for the solvent cleaning process  375  of FIG. 11. Energy is conserved as the refrigerant  95  of FIG. 6 passing through the cooling coil  65  absorbs heat from the airflow  53  and then the refrigerant  95  rejects the heat back into the airflow  53  by passing through the heater  55 . In one embodiment of the present invention, the refrigerant  95  is fluorocarbon R-22; however, other refrigerants known to one skilled in the refrigerant art would be acceptable. The heater  55  functions as a condenser (warming the air flow  53  through the heater  55 ), while the cooling coil  65  functions as an evaporator (cooling the air flow  53  through the cooling coil  65  and condensing any vapor).  
     [0060] In another embodiment of the present invention, the air management mechanism  1  further comprises an auxiliary heater  158  of FIG. 6. The fan  50  is further disposed to provide airflow  53  through the auxiliary heater  158 . Typically, the auxiliary heater  158 , used in conjunction with the heater  55 , provides a higher temperature in the airflow  53  that enters the cleaning basket assembly  2 . The auxiliary heater  158  is disposed in the discharge ventilation ducting  52 . In another embodiment of present invention, the auxiliary heater  158  is disposed in the suction discharge ventilation ducting  53 . Raising the air temperature of the airflow  53  typically decreases the drying time for the articles in the humidity sensing process  400  of FIG. 12 and the solvent wash/dry process  500  of FIG. 13.  
     [0061] The inputs to the controller  5  of FIG. 7 are typically selected from the group consisting of the door lock sensor  18 , the temperature sensor  57 , the solvent sensor  59 , the optical sensor  140 , the conductivity sensor  151 , the basket conductivity cell  170 , the basket level detector  172 , the basket humidity sensor  173 , the operator interface  190 , the access door lock sensor  248 , and any combination thereof. The outputs of the controller  5  are typically selected from the group consisting of the motor  3 , the door lock  19 , the pump  25 , the fluid heater  28 , the check valve  40 , the fan  50 , the heater  55 , the spray nozzle  67 , the compressor  75 , the regeneration pump  115 , the water separator  152 , the waste water drain valve  155 , the auxiliary heater  158 , the mixing valve  185 , the display panel  200 , the access door lock  246 , the water drain valve  260 , and any combination thereof.  
     [0062] The controller  5  is further configured to perform a solvent based cleaning fluid recirculation process. In the solvent based cleaning fluid recirculation process, the solvent based cleaning fluid  30  passes through the fluid processing mechanism  4  and cleaning basket assembly  2  as discussed above for a predetermined amount of time. The solvent based cleaning fluid recirculation process is performed when the article cleaning apparatus  1000  is not engaged in either the cleaning process  350  of FIG. 11 or the drying process  360 . In the case where the operator selects either the cleaning process  350  or the drying process  360  during the solvent based cleaning fluid recirculation process, the controller  5  recovers the article cleaning apparatus  1000  using a cycle interruption recovery process  800  of FIG. 16, which will be subsequently described in detail. As used herein, the term, “recovers the article cleaning apparatus,” relates to placing the article cleaning apparatus  1000  in a condition to perform either the cleaning process  350  or the drying process  360 .  
     [0063] The cleaning basket assembly  2  of FIG. 8 depicts one embodiment of the present invention where a cleaning basket support structure  12  supports the rotating basket  14  through a door end bearing  22  and a motor end bearing  21 . The motor  3  is disposed to the rotating basket  14  at the opposite end of the rotating basket where a basket door  15  is disposed. The cleaning basket assembly  2  further comprises a gasket  16 , a door lock sensor  18 , and a door lock  19 . The basket support structure  12  further comprises a liquid drain connection to the drain conduit  70  and a solvent based cleaning fluid supply connection to the inlet tubing  26 . The basket support structure  12  further comprises a connection to the discharge ventilation ducting  52  and a connection to the suction ventilation ducting  51 . A lint filter  60  is typically situated in the suction ventilation ducting  51 . The cleaning basket assembly  2  of FIG. 8 further comprises a basket humidity sensor  173  that has the capability to determine the humidity level in the rotating basket  14 . In one embodiment of the present invention, the basket humidity sensor  173  is disposed inside the basket support structure  12  adjacent the rotating basket  14 .  
     [0064] The air management mechanism  1  of FIG. 1, the cleaning basket assembly  2 , fluid processing mechanism  4 , and the controller  5  are disposed inside an enclosure  230  of FIG. 9, where only the cleaning basket assembly  2  is depicted in the cut away view of the enclosure  230 . Additionally, the controller  5  of FIG. 7 is configured to receive input controls from the operator from an operator interface  190  of FIG. 9 and configured to provide a cleaning status at the display panel  200 . The enclosure  230  further comprises an enclosure floor  250  that is substantially perpendicular to an enclosure rear wall  240 . The rotating basket  14  has a longitudinal axis  220  that is about parallel to the enclosure floor  250 . As used herein, the term, “about parallel” is defined to include a range from about −3 degrees to about +3 degrees from parallel. The enclosure  230  further comprises an enclosure front wall  242  that is on the side of the enclosure where the basket door  15  is disposed. In one embodiment of the present invention, the operator interface  190  and the display panel  200  are disposed on the enclosure front wall  242 . The location of the operator interface  190  and the display panel  200  is provided by way of illustration and is not intended to imply a limitation to the present invention. In one embodiment of the present invention, the enclosure floor  250  is configured to act as a containment pan to collect leakage of the solvent based cleaning fluid  30 . In another embodiment of the present invention, the enclosure  230  is configured to act as the containment pan to collect leakage of the solvent based cleaning fluid  30 .  
     [0065] In one embodiment of the present invention, the enclosure  230  has an overall volumetric shape of about 0.7 meters in width, by about 0.9 meters in depth, by about 1.4 meters in height. This volumetric shape represents the typical space available in an in-home laundry setting.  
     [0066] The regeneration cartridge  141  of FIG. 2 is typically the one item in the fluid processing mechanism  4  requiring periodic replacement. In one embodiment of the present invention, the enclosure front wall  242  of FIG. 9 comprises an access door  244 , an access door lock  246 , and an access door lock sensor  248 . The location of the access door  244 , access door lock  246  and the access door lock sensor  248  is provided by way of illustration and is not intended to imply a limitation to the present invention. The access door lock  246  and access door lock sensor  248  are coupled to the controller  5  of FIG. 7. The controller logic in the controller  5  keeps the access door lock  246  locked during the cleaning process  350  of FIG. 11, the drying process  360 , and the solvent based cleaning fluid recirculation process. The controller logic only permits replacing the regeneration cartridge  141  of FIG. 2 when the article cleaning apparatus  1000  is not operating any of the following: the cleaning process  350  of FIG. 11, the drying process  360  and the solvent based cleaning fluid recirculation process. When the controller logic verifies that any of the following: the cleaning process  350  of FIG. 11, the drying process  360 , and the solvent based cleaning fluid recirculation process are not in progress, then the controller  5  of FIG. 7 unlocks the access door lock  246  in response to an operator request via the operator interface  190  to replace the regeneration cartridge  141 . If an operator requests to replace the regeneration cartridge  141  and the article cleaning apparatus  1000  is operating any process, the operator is notified that the replacement of the regeneration cartridge  141  is not permitted via a notification message displayed on the display panel  200 . By not permitting the cleaning process  350  of FIG. 11, the drying process  360 , and the solvent based cleaning fluid recirculation process to be performed by the article cleaning apparatus  1000  of FIG. 2 during the regeneration cartridge  141  replacement, the operator is afforded protection from an inadvertent exposure to the solvent based cleaning fluid  30 . Additionally, the controller logic does not allow the article cleaning apparatus  1000  to initiate any process until the access door lock sensor  248  of FIG. 9 verifies that the access door  244  is shut and the access door lock  246  is locked. The access door lock sensor  248  is additionally configured to detect that the regeneration cartridge  141  of FIG. 2 is properly installed before indicating that the access door  244  of FIG. 9 is properly closed and that the access door lock  246  is properly locked.  
     [0067] Additionally, in one embodiment of the present invention, the regeneration cartridge  141  of FIG. 2 further comprises a leak proof double inlet valves assembly  101  and a leak proof double outlet valves assembly  106  to minimize the operator&#39;s contact with the solvent based cleaning fluid  30 . In another embodiment of the present invention, the regeneration cartridge  141  (not shown in FIG. 2) further comprises a leak proof single inlet valve assembly  100  and a leak proof single outlet valve assembly  105  to minimize the operator&#39;s contact with the solvent based cleaning fluid  30 . As used herein, the term, “leak proof” is defined to mean that there is no leakage of the solvent based cleaning fluid  30  beyond about 1 ml evident at 1) either end of the regeneration cartridge  141  after removal and 2) the connection points where the regeneration cartridge  141  installs into the fluid regeneration device  7 .  
     [0068] The controller logic in the controller  5  of FIG. 7 is designed to keep the basket door lock  19  locked shut while performing any of the following: the cleaning process  350 , the drying process  360 , and the solvent based cleaning fluid recirculation process. This limits the operator&#39;s ability to expose oneself to the solvent based cleaning fluid  30  during any of the following: the cleaning process  350 , the drying process  360 , and the solvent based cleaning fluid recirculation process thereby reducing the number of opportunities that the operator is exposed to the solvent based cleaning fluid  30 .  
     [0069] In one embodiment of the present invention, the clean fluid device  8  of FIG. 2 further comprises a fluid heater  27  disposed between the pump  25  and the cleaning basket assembly  2  in the inlet line  26 . The fluid heater  27  is coupled to the controller  5  of FIG. 7. The fluid heater  27  has the ability to increase the temperature of the solvent based cleaning fluid  30 . The elevated temperature of the solvent based cleaning fluid  30  has the effect of improving the soil removal cleaning performance for some types of article and soiling combinations.  
     [0070] In another embodiment of the present invention the article cleaning apparatus  1000  of FIG. 1 is further configured to add a small quantity of water (in the range from about 1 percent to about 8 percent of the total weight of the solvent based cleaning fluid  30 ) and other cleaning agents to the rotating basket  14  to mix with the solvent based cleaning fluid  30  entering the cleaning basket assembly  2  through the inlet line  26 . In one embodiment of the present invention, the cleaning basket assembly  2  of FIG. 8 further comprises a hot water inlet  175  and a cold-water inlet  180 , both of which are coupled to a mixing valve  185 . A basket conductivity cell  170  and a basket level detector  172  are disposed in the cleaning basket assembly  2 , such that the basket conductivity cell  170  determines the conductivity of the fluid in the rotating basket  14  and the basket level detector  172  determines the level of the water based cleaning fluid  31  or the solvent based cleaning fluid  30  in the rotating basket  14 . In one embodiment of the present invention, a dispenser  300  is disposed off a line that couples the mixing valve  185  to the basket support structure  12 . Additionally, the operator adds the cleaning agents to the dispenser  300  and the subsequent action of the water running through the line coupling the mixing valve  185  to the basket support structure  12  entrains the cleaning agents that are disposed in the dispenser  300  into the water entering the rotating basket  14 .  
     [0071] In one embodiment of the present invention, the article cleaning apparatus  1000  of FIG. 1 is further configured to perform the water cleaning process  600  of FIG. 14 utilizing a water based cleaning fluid  31 . In addition to the above-discussed components associated with monitoring and adding water to the rotating basket  14 , a water drain line  270  connects to the drain conduit  70  upstream of the check valve  40 . The water drain line  270  also connects to the suction side of the regeneration pump  115 . A water drain valve  260  is disposed in the water drain line  270 . The method of adding cleaning agents to the water in the rotating basket  14  is the same as discussed above.  
     [0072] A plot of retained moisture content as a percentage of an article&#39;s weight versus the relative humidity is provided in FIG. 10 for a variety of materials that are commonly used to comprise articles. As the fluid processing mechanism  4  of FIG. 2 contains a finite quantity of water removal capability, the controller  5  of FIG. 7 is configured to reduce the amount of water admitted to the fluid processing mechanism  4  of FIG. 2. The reduction of the retained moisture content is accomplished in a humidity sensing process  400  of FIG. 11 that is part of the solvent cleaning process  375 .  
     [0073] By way of example, a chemical-specific sensor, such as solvent sensor  59 , may be configured to monitor amounts of the volatile solvent fluid, and may be coupled to the controller to control a drying cycle for extracting a desired level of moisture from the articles. A memory device or look-up table may comprise means for relating a fixed or time dependent voltage level in the output signal from the chemical specific sensor to moisture content in the article being cleansed/dried. A comparator module may allow for estimating additional time that may be needed to reach a desired level of moisture based on a present reading from the solvent sensor, or may allow for terminating the drying cycle, once a desired level of dryness has been reached.  
     [0074] In one embodiment of the present invention, a process selection  310  of FIG. 11 occurs at the operator interface  190  and provides inputs to the controller  5  of FIG. 7. The operator selects between the cleaning process  350  of FIG. 11 and a drying process  360 . This drying process  360  refers to the drying of articles after completing the water based cleaning  600  of FIG. 14. When the operator selects the cleaning process  350  of FIG. 11, the operator then further chooses between performing either the solvent cleaning process  375  or the water cleaning process  600 . In the present invention, the solvent cleaning process  375  of FIG. 11 is defined to include performing the humidity sensing process  400  and the subsequent solvent wash/dry process  500 . Conversely, when the operator selects the drying process  360 , a basket drying process  700  is performed. In one embodiment of the present invention, the operator has the option to select an additional solvent wash process as part of the solvent wash/dry process  500 . The additional solvent wash process is typically used in conjunction with utilizing the solvent based cleaning fluid  30  that comprises cleaning agents. The additional solvent wash process typically improves the removal of the cleaning agents from the articles that remain after initially completing step  540  as detailed below. In another embodiment of the present invention, the operator has the option to select an additional rinse process  675  as part of the water cleaning process  600 . In another embodiment of the present invention, when the operator selects the drying process  360  the operator is provided with a further option of selecting from either the basket drying process  700  or a timed basket drying process  705 .  
     [0075] The start of the solvent based cleaning cycle  375  of FIG. 11 starts with the controller  5  of FIG. 7 sensing the humidity in the rotating basket  14  of FIG. 8 by initiating the humidity sensing process  400  of FIG. 12. The start  410  of the humidity sensing process  400  initially begins by verifying that the door lock  19  is locked. A starting humidity in the rotating basket  14  of FIG. 8 is determined in the sensing humidity step  410  of FIG. 12 by the basket humidity sensor  173 . The controller  5  of FIG. 7 then tumbles the rotating basket  14  in step  430  of FIG. 12. The airflow  53  of FIG. 5 is heated and passed through the air management mechanism  1  and the cleaning basket assembly  2  while tumbling the rotating basket  14  for a predetermined pre-drying time in step  440  of FIG. 12. The moisture in the rotating basket  14  becomes vapor. The airflow  53  containing the vapor comes out of the rotating basket  14  through the holes  17  of FIG. 8 and then passes through the lint filter  60 . The airflow  53  of FIG. 5 subsequently passes over the cooling coil  65  where the vapor condenses to form condensate. The rotating basket  14  is tumbled and the airflow  53  entering the cleaning basket assembly  2  is heated for the predetermined amount of time. The controller  5  of FIG. 7 then determines a finishing humidity in the rotating basket  14  of FIG. 8. If the controller  5  of FIG. 7 determines that the finishing humidity is too high, then the controller  5  of FIG. 7 sends a warning in step  470  of FIG. 12 to the operator at the display panel  200  indicating that it may take longer to complete the solvent cleaning process  375  and a longer humidity sensing process  400  is initiated.  
     [0076] After completing the humidity sensing process  400 , the solvent wash/dry process  500  of FIG. 13 is typically executed. The following typical solvent wash/dry process  500  of FIG. 13 is utilized in one embodiment of the present invention. The following steps of the solvent wash/dry process  500  are provided for illustration and in no way implies any restriction to the present invention. The initial conditions at the start step  510  include reverifying that the door lock  19  of FIG. 8 is locked. The solvent based cleaning fluid  30  of FIG. 2 is added to the rotating basket  14  of FIG. 8 as depicted in step  520  of FIG. 13 and as described in detail above. The rotating basket  14  of FIG. 8 is then tumbled as shown in step  530  of FIG. 13. After tumbling for a predetermined amount of time, the controller  5  of FIG. 7 opens the check valve  40 , and the solvent based cleaning fluid  30  of FIG. 2 starts to drain from the rotating basket  14  of FIG. 8. Substantially all of the remaining portion of the solvent based cleaning fluid  30  of FIG. 2 is spin extracted by spinning the rotating basket  14  in step  540  of FIG. 13. The solvent based cleaning fluid  30  is drained to the working tank  45  and subsequently the controller  5  of FIG. 7 shuts the check valve  40  of FIG. 2.  
     [0077] Detection of solvent vapor in the rotating basket  14  of FIG. 8 is determined in step  560  of FIG. 13. The controller  5  of FIG. 7 then tumbles the rotating basket  14  and raises the temperature of the airflow  53  of FIG. 5 in step  570  of FIG. 13. A substantial amount of the remaining portion of the solvent based cleaning fluid  30  and any liquid becomes vapor. The vapor flows from the rotating basket  14  through the lint filter  60  and passes over the cooling coil  65 . The vapor condenses on the cooling coil  65  to form a condensate. The post-drying solvent vapor detection in the rotating basket  14  of FIG. 8 is determined in step  580  of FIG. 13. The process steps of  560  through  580  FIG. 13 as detailed above are performed until the post-drying solvent vapor in the rotating basket  14  of FIG. 8 reaches an acceptable level, at which point the controller  5  of FIG. 7 unlocks the basket door  15  in step  590  of FIG. 13. In another embodiment of the present invention, the operator selects the additional solvent wash process. The additional solvent wash process comprises completing step  520 , step  530 , and step  540  occurs after completing step  540  and before performing step  560 , where the individual steps are as described above. In one embodiment of the present invention, the additional solvent wash process enhances the cleaning performance of especially soiled articles. In another embodiment of the present invention, the additional solvent wash process enhances the removal of cleaning agents. The operator selects the additional solvent wash process at the operator interface  190 .  
     [0078] In one embodiment of the present invention the rotating basket  14  of FIG. 8 has a typical load range between about 0.9 kg and about 6.8 kg. The rotating basket  14  has a rotating basket capacity with a typical range between about 17 liters and about 133 liters, which is generally useful for performing laundering utilizing the solvent based cleaning fluid  30  of FIG. 2. The ratio of liters of solvent based cleaning fluid  30  per kg of articles in the laundry load is generally in a range from about 4.2 liters/kg to about 12.5 liters/kg. The corresponding total capacity of the solvent based cleaning fluid  30  per laundry load is generally in a range from about 3.8 liters (4.2 liters/kg times 0.9 kg) to about 85 liters (12.5 liters/kg times 6.8 kg), respectively. The total amount of solvent based cleaning fluid  30  in the article cleaning apparatus  1000  of FIG. 1 is from about 1.05 to about 2.0 times the amount of solvent based cleaning fluid  30  of FIG. 2 required per load. The total amount of solvent based cleaning fluid  30  equates to a range from about 4 liters (3.8 liters times 1.05) to about 170 liters (85 liters times  2 ), which corresponds to a typical ratio of the capacity of the solvent based cleaning fluid  30  to laundry load ranges from about 4.4 liters/kg (4 liters/0.9 kg) to about 25 liters/kg (170 liters/6.8 kg), respectively.  
     [0079] In another embodiment, the typical amount of articles in a laundry load range from about 2.7 kg to about 5.4 kg. The corresponding total capacity of the solvent based cleaning fluid  30  per laundry load is generally in a range from about 11.3 liters (4.2 liters/kg times 2.7 kg) to about 67.5 liters (12.5 liters/kg times 5.4 kg). The total amount of solvent based cleaning fluid  30  in the article cleaning apparatus  1000  of FIG. 1 is from about 1.05 to about 2.0 times the amount of solvent based cleaning fluid  30  of FIG. 2 required per load. The total amount of solvent based cleaning fluid  30  equates to a range from about 11.9 liters (11.3 liters times 1.05) to about 135 liters (67.5 liters times 2).  
     [0080] In another embodiment, the ratio of liters of solvent based cleaning fluid  30  of FIG. 2 to kg of articles is from about 6.7 liters/kg to about 8.3 liters/kg. When the load capacity is in a range from about 0.9 kg to about 6.8 kg, the corresponding total capacity of the solvent based cleaning fluid  30  per laundry load is generally in a range from about 6.0 liters (6.7 liters/kg times 0.9 kg) to about 56.4 liters (8.3 liters/kg times 6.8 kg), respectively. When the load capacity is in a range from about 2.7 kg to about 5.4 kg, the corresponding total capacity of the solvent based cleaning fluid  30  per laundry load is generally in a range from about 18.1 liters (6.7 liters/kg times 2.7 kg) to about 44.8 liters (8.3 liters/kg times 5.4 kg), respectively. The total amount of solvent based cleaning fluid  30  in the article cleaning apparatus  1000  of FIG. 1 is from about 1.05 to about 2.0 times the amount of solvent based cleaning fluid  30  of FIG. 2 required per load. The total amount of solvent based cleaning fluid  30  equates to a range from about 6.3 liters (6.0 liters times 1.05) to about 112.8 liters (56.4 liters times 2).  
     [0081] In order to reduce the total capacity of the solvent based cleaning fluid  30  in the article cleaning apparatus  1000  of FIG. 1, the cleaning fluid processing is performed on-line and the processing is synchronized with the solvent wash/dry process  500  of FIG. 13. Processing the solvent based cleaning fluid  30  of FIG. 2 on-line typically provides sufficient solvent based cleaning fluid  30  in the storage tank  35  to perform a subsequent solvent cleaning process  350  of FIG. 11 after completing the previous solvent cleaning process  350 . The storage tank  35  of FIG. 2 typically has a sufficient capacity of the solvent based cleaning fluid  30  to make up for any solvent based cleaning fluid  30  that is held up in the fluid regeneration device  7 , in the working fluid device  6 , and retention in the “dried” articles. The regeneration cartridge  141  is capable of replenishing the amount of solvent based cleaning fluid  30  that is retained in the “dried” articles. In one embodiment of the present invention, the typical solvent capacity of the storage tank  35  is from about 10.4 liters/kg to about 12.5 liters/kg when the load capacity ranges from about 2.7 kg to about 5.4 kg. The storage tank  35  has a corresponding typical range from about 28.1 liters to about 67.5 liters. Therefore, the storage tank  35  of the present invention typically needs only about 36% (67.5 liter/190 liter) of the capacity of the about 190 liter storage tank found in typical commercial chemical fluid dry cleaning machines. In one embodiment of the present invention, the typical solvent capacity of the storage tank  35  is from about 10.4 liters/kg to about 12.5 liters/kg when the load capacity ranges from about 0.9 kg to about 6.8 kg. The storage tank  35  has a corresponding typical range from about 9.4 liters to about 85 liters. Therefore, the storage tank  35  of the present invention typically needs only about 45% (85 liter/190 liter) of the capacity of the about 190 liter storage tank found in typical commercial chemical fluid dry cleaning machines. The above comparison of storage tank capacity typical range from about 9.4 liters to about 85 liters for the present invention compares favorably to the range of the storage tank capacity of from about 190 liters to about 1325 liters for typical commercial chemical fluid dry cleaning machines.  
     [0082] In another embodiment of the present invention, the solvent wash/dry process  500  adds water to the solvent based cleaning fluid  30  of FIG. 2 in the rotating basket  14 , where the maximum amount of water added is in the range from about 1 percent to about 8 percent of the total weight of the solvent based cleaning fluid  30  that is in the rotating basket  14 . Adding the water to the solvent based cleaning fluid  30  that is in the rotating basket  14  is performed as described above. In another embodiment of the present invention, the solvent wash/dry process  500  adds water and cleaning agents to the solvent based cleaning fluid  30  of FIG. 2 in the rotating basket  14 , where the maximum amount of water added does not exceed a maximum of about 8 percent of the total weight of the solvent based cleaning fluid  30  that is in the rotating basket  14 . Adding the water and the cleaning agents to the solvent based cleaning fluid  30  that is in the rotating basket  14  is performed as described above.  
     [0083] Steps  560  of FIGS. 13 through 580 in the solvent wash/dry process  500  require a typical range from about 15 minutes to about 60 minutes for the typical laundry load, which ranges from about 0.9 kg of articles to about 6.8 kg of articles. The sensible heat required to dry the clothes, which is the principle source of total electrical power the machine requires, is in a range between about 430 watts to about 6300 watts. As used herein, the term, “sensible heat” is defined to be the total amount of heat added by the combination of the heater  55  and auxiliary heater  158  (if installed). In another embodiment, the drying time is between about 20 and about 60 minutes with the typical laundry load range between about 2.7 kg of articles and about 5.4 kg of articles. In this case, the sensible heat required to dry the clothes is in a range between about 1300 watts and about 5200 watts. In each of these cases, the power is easily handled on a household circuit with a maximum voltage of about 240V and a maximum amp rating of about 30 amps. In some embodiments, the article cleaning apparatus  1000  of FIG. 1 is configured to run on about 220V service in an about 20-amp circuit, about 220V service in an about 30-amp circuit, and about 110V service and in a circuit having a amperage range from about 15 amps to about 20 amps. All of these circuit types are typically available in homes for currently available cooking and drying appliances; therefore, presenting no additional installation difficulties.  
     [0084] The controller  5  of FIG. 7 controls the water cleaning process  600  of FIG. 14. The controller  5  of FIG. 7 is configured to reduce the opportunity for introducing large amounts of water into the working tank  45  of FIG. 2 as discussed herein. In the present invention, a fluid in the rotating basket  14  is defined to contain a “large amount of water” when the fluid comprises greater than about 10% water by weight. The water cleaning process  600  of FIG. 14 is provided to illustrate a series of steps used in one embodiment of the present invention and in no way implies any limitation to the water cleaning process  600  utilized in the present invention.  
     [0085] The water cleaning process  600  begins with the initial conditions of the cleaning agents loaded into the dispenser  300 , and the door lock  19  engaged and the door lock sensor  18  verifying that the basket door  15  in the locked position at the start step  610  of FIG. 14. Water and cleaning agents are added to the rotating basket  14  to produce the water based cleaning fluid  31  of FIG. 9 in step  620 . The water may be hot, cold or a mixture as detailed above. The rotating basket  14  is tumbled in step  630  of FIG. 14. Substantially all of the water based cleaning fluid  31  of FIG. 9 is spin extracted by rotating from the rotating basket  14  of FIG. 2 in step  640  of FIG. 14. The controller  5  of FIG. 7 opens the water drain valve  260  of FIG. 2 and operates the regeneration pump  115  as necessary to drain the rotating basket  14  during the spin step  640 , when the basket conductivity cell  170  of FIG. 8 detects that the water based cleaning fluid  31  of FIG. 9 in the rotating basket  14  comprises greater than about 10% water by weight. The controller  5  of FIG. 7 closes the water drain valve  260  of FIG. 2 after removing the water based cleaning fluid  31  of FIG. 9 from the rotating basket  14  of FIG. 2 after completing the spin basket step  640 .  
     [0086] Rinse water is then added to the rotating basket  14  of FIG. 8 and the rotating basket  14  is tumbled in step  670  of FIG. 14. The temperature of the rinse water is determined by the controller  5  of FIG. 7 in conjunction with the mixing valve  185  of FIG. 8. Substantially all of the remaining amount of rinse water is spin extracted by spinning the rotating basket  14  in step  680  of FIG. 14. The rinse water is removed as described above. The rotating basket  14  is tumbled in step  690  of FIG. 14. The basket door  15  of FIG. 8 is then unlocked in step  695  of FIG. 14.  
     [0087] In another embodiment of the present invention, the operator selects an additional rinse process. The additional rinse process reperforms step  670 , step  680 , and step  690 . The additional rinse process occurs after step  690  and before the basket door  15  is unlocked in step  695 . The additional rinse process assists in removing the entrained cleaning agents that are not removed during steps  670 ,  680 , and  690 . The additional rinse process is especially useful when using soft water. As used herein, the term “soft water” is defined as comprising less than about 10 grains of hardness per about 3.8 liters of water.  
     [0088] In another embodiment of the present invention, the article cleaning apparatus  1000  of FIG. 1 is configured to perform the basket drying process  700  of FIG. 15. The basket drying process  700  of FIG. 15 is provided to illustrate the basket drying process  700  used in one embodiment of the present invention and in no way implies any limitation to the basket drying process  700  of the present invention. The basket drying process  700  begins with the initial conditions of the basket door  15  locked, and the door lock sensor  18  verifying the basket door  15  locked at the start step  710  of FIG. 15. The basket drying process  700  initially begins by performing a sensing humidity step  720  to determine a start humidity, a tumble basket step  730  and heat airflow step  740  similar to that described above in steps  420 ,  430 , and  440 , respectively. After tumbling and heating the airflow  53  for a predetermined post-water wash drying time, the controller  5  of FIG. 7 determines a final humidity in the rotating basket  14  of FIG. 8 in step  760 . When the controller  5  of FIG. 7 determines that the final humidity is too high, then the controller  5  initiates a longer drying sequence in step  760  by re-performing steps  730  through  760 . When the final humidity is acceptable, the controller  5  of FIG. 7 stops the basket drying process  700  of FIG. 15 in step  770 , and unlocks the basket door  15  of FIG. 8 in step  780  of FIG. 15.  
     [0089] In another embodiment of the present invention, a timed basket drying process  705  of FIG. 11 is available to the operator at the operator interface  190 . The timed basket drying process  705  comprises the steps of starting the drying cycle  710  of FIG. 15 by setting the predetermined amount of drying time, tumbling the rotating basket  14  in step  730 , heating the airflow  53  in step  740 , and stopping the timed basket drying process in step  770  when predetermined amount of drying time is accomplished. The controller  5  of FIG. 7 unlocks the basket door  15  of FIG. 8 in step  780  of FIG. 15.  
     [0090] It is important that a large amount of the water is not inadvertently directed to the working tank  45  of FIG. 2 during the solvent wash/dry process  500  of FIG. 13 that adds water, in the range from about 1 percent to about 8 percent, to the solvent based cleaning fluid  30  of FIG. 2 in the rotating basket  14  as discussed above. It is also important to reduce the possibility that the solvent based cleaning fluid  30  is not accidentally pumped out of the article cleaning apparatus  1000  of FIG. 1. If the solvent cleaning process  375  of FIG. 11 or the water cleaning process  600  is interrupted by either the operator or a loss of electrical power, the controller  5  of FIG. 7 utilizes a cycle interruption recovery process  800  of FIG. 16. The cycle interruption recovery process  800  operates a series of logical sequence options to control the subsequent operation of the article cleaning apparatus  1000  of FIG. 1. The logical sequence options include completing the appropriate cleaning cycle, completing a fail-safe process, or informing the operator to call service.  
     [0091] In one embodiment of the present invention, the cycle interruption recovery process  800  starts by verifying the locked status of door lock  19  of FIG. 8 via the door lock sensor  18  in step  810  of FIG. 16. If the door lock sensor  18  of FIG. 8 is determined to be non-operational in the component failure detected step  892  of FIG. 16, then a call service message is generated in step  894 , which is then sent to the display  200 . Conversely, if the controller  5  of FIG. 7 does verify that the door lock  19  of FIG. 8 is locked in step  810  of FIG. 16, then the basket level detector  172  of FIG. 8 determines if there is liquid in the rotating basket  14  in step  820  of FIG. 16. If the controller  5  cannot tell if the basket level detector  172  is operational, then the component failure detected step  892  of FIG. 16 generates the call service message in step  894 . If liquid is detected in step  820  of FIG. 16 then the basket conductivity cell  170  of FIG. 8 determines whether the liquid is the solvent based cleaning fluid  30  or the water based cleaning fluid  31  in step  830  of FIG. 16. Siloxane is non-conductive; therefore, the basket conductivity cell  170  of FIG. 8 typically provides a conductivity measurement of the liquid in the article cleaning apparatus  1000 . If the controller  5  cannot tell if the basket conductivity cell  170  of FIG. 8 is operational, then the component failure detected step  892  of FIG. 16 generates a call service message in step  894 .  
     [0092] If the basket conductivity cell  170  of FIG. 8 detects that the fluid in the rotating basket  14  comprises greater than about 10% water, then the fluid is defined to be the water based cleaning fluid  31 . If the fluid in the rotating basket  14  is defined to be the water based cleaning fluid  31 , then a determination of where the interruption occurred in the water cleaning process  600  is performed in step  840 . In step  840 , if the controller  5  of FIG. 7 has a memory of where the water cleaning process interruption occurred, then the water cleaning process  600  resumes as depicted in step  860 . If the controller  5  in step  840  of FIG. 16 cannot remember where the water cleaning process interruption occurred, then the water based cleaning fluid  31  is pumped out and the cleaning process  350  of FIG. 11 is reset in step  850  of FIG. 16. If the controller  5  in step  850  of FIG. 16 cannot tell if the components required to perform step  850  are available, then the component failure detected step  892  generates the call service message in step  894 .  
     [0093] If the basket conductivity cell  170  of FIG. 8 detects less than about 10% water in the liquid in the rotating basket  14 , then the liquid is defined to be the solvent based cleaning fluid  30 . If the liquid is defined to be the solvent based cleaning fluid  30 , then a determination of where the interruption occurred in the solvent cleaning process  375  is performed in step  845 . In step  845 , if the controller  5  of FIG. 7 has a memory of where the solvent cleaning process interruption occurred, then the solvent cleaning process  375  resumes as depicted in step  870 . If the controller  5  of FIG. 7 in step  845  of FIG. 16 cannot determine where the interruption occurred in the solvent cleaning process  375  of FIG. 11, then a warn operator fail-safe message is generated in step  880 , which is then set to the display  200  of FIG. 9.  
     [0094] After generating the warn operator fail-safe message in step  880  of FIG. 16, the solvent based cleaning fluid  30  of FIG. 2 is pumped out in step  882  of FIG. 16. Subsequently the rotating basket  14  of FIG. 8 is tumbled and rotated to spin extract substantially all of the remaining portion of the solvent based cleaning fluid  30  of FIG. 2 from the rotating basket  14  in step  884  of FIG. 16. The airflow  53  is then heated while tumbling the rotating basket  14  of FIG. 8 in step  886  of FIG. 16. The operator is informed that the fail-safe is completed in step  888 , and the fail-safe completed message is sent to the display  200  of FIG. 9, and the basket door  15  of FIG. 8 is unlocked in step  890  of FIG. 16. If it is determined that the components required to operate each of the steps  882 ,  884 ,  886 , and  888  are non-operational, then the component failure detected step  892  of FIG. 16 generates the call service message in step  894 .  
     [0095] The cycle interruption recovery process  800  of FIG. 16 is provided to illustrate the cycle interruption recovery process  800  used in one embodiment of the present invention and in no way implies that any limitation to the cycle interruption recovery process  800  employed in controlling operation of article cleaning apparatus  1000  of FIG. 1 of the present invention.  
     [0096] The efficiency of operation of an appliance, as described above, for cleansing clothes or any other articles washed with water/detergent, and/or a volatile solvent, such as D5, or mixtures of silicone-based fluids and water/detergent can be improved by utilizing a chemical-specific sensor or sensors, e.g., solvent sensor  59 , configured to, for example, determine the vapor concentration or vapor pressure of solvent in the appliance gas exit stream. Controller  5  may process an output signal from such a sensor indicative of the vapor concentration or vapor pressure of the solvent to control inlet gas temperature and/or gas velocity to maximize vapor removal from the clothes load with minimal waste of energy. Such a sensor can also be used to detect leaks that may develop in the appliance or to detect vapor leaks into the surrounding living space.  
     [0097] There may be several desirable sensor capabilities for a so-called In-Home dry cleaning appliance (HDC). Some of these capabilities may be as follows:  
     [0098] 1) Determination of the state of dryness of a load undergoing a drying cycle, such as may be performed by monitoring an indication of siloxane solvent vapor in the drum exit gas stream.  
     [0099] 2) Monitor siloxane solvent vapor concentration for leak detection and fire safety; and  
     [0100] 3) Potential use as a separate environmental monitor of siloxane solvent for use in the room housing the appliance. An additional use could be as a point source detector of siloxane solvent to be used by service personnel as a trouble-shooting tool.  
     [0101] In all of these applications, the sensor technology used should be selective for siloxane solvent, especially in the presence of water vapor, sufficiently sensitive to detect low levels of siloxane solvent vapor and have a range capable of measuring saturation levels of siloxane solvent in air at temperatures from about 0° F. to about 200° F. or any sub-range therein.  
     [0102] As a result, several types of chemical-specific sensors were evaluated for their potential utility for detection of siloxane solvent. Exemplary sensor types evaluated for specific detection of siloxane solvent include the following:  
     [0103] 1. Spectroscopic sensors. This group includes sensors that utilize unique electro-optical absorbance bands of siloxane to determine concentration in a gas stream.  
     [0104] 2. Piezo-based sensors with specific coatings: This group includes surface acoustic wave sensors, quartz crystal microbalances and arrays of piezo sensors that may viewed as an “electronic sniffing” device.  
     [0105] 3. Strain-gauge based sensors. This group includes micro-machined sensors and strain-gauge bridges with siloxane solvent specific coatings.  
     [0106] 4. Capacitive Sensors. This group includes sensors where changes in a dielectric layer in the sensor affects capacitance properties, such as dielectric strength or a dimension, proportional to the siloxane solvent concentration in the surrounding atmosphere.  
     [0107] Spectroscopic Sensors:  
     [0108] Siloxane in the vapor state exhibits absorption at a relatively short UV wavelength (for example &lt;220 nm) and is then transparent through the visible spectrum out to the near infrared region. There are useful bands in the near- and mid-infrared regions that could be utilized to detect siloxane and discriminate against water vapor. Exemplary spectra of siloxane and water vapor for the near infrared are shown in FIG. 17 and for the mid-infrared in FIG. 18. Note that in the near-IR there are unique spectral bands useful for siloxane detection between approximately 2300 nm and approximately 2500 nm (4347 to 4000 cm−1), which show no interference from the water vapor bands centered around 1900 nm and 1400 nm. In the mid-IR, the most prominent band comprises the so-called Si—O stretch, which is centered at approximately 9216 nm, (1085 cm−1) and which is close to but distinguishable from the nearby water vapor bands. The near IR region may be a more accessible region of the spectrum since, presently, the choices of commercially available detectors, optical filters and window materials may be relatively broader than for the more demanding mid-IR region. Also, the band separation width is presently relatively larger in commercially available near IR bandpass filters.  
     [0109] A respective block diagram of two exemplary near-IR siloxane vapor sensors  601  and  650  is shown in FIGS. 19 and 20. Sensor  601  comprises an infrared source  602 , a bandpass filter  604  centered at a band of interest, a flow-through cell  606  for passing samples of the fluid undergoing monitoring. Cell  606  may include windows, such as may be made up of quartz, silicon or sapphire cell, for allowing a beam of infrared radiation from source  602  to pass therethrough. A detector  608 , e.g., a photocell, thermopile or pyrometer IR radiation detector, measures the amount of absorbance experienced by the beam that passes through cell  606 . Optionally, a piezo-based chopper  609  may be used for allowing intermittent passage to the beam from source  602 . The use of a pulsed radiation source (e.g., comprising thin film resistive elements) can eliminate the need for the piezo-based chopper. Sensor  601  could also be constructed with commercially available duplex pyrometers and appropriately centered filters to provide both water and siloxane detection.  
     [0110] Sensor  650  is similar in operation to sensor  601  and functionally equivalent components are identified in FIG. 20 with the same reference numerals used in FIG. 19. In sensor  650 , in lieu of a bandpass filter, a dispersive spectrograph  652  with slits  654 , a mirror  656  and a grating  658  is used to separate at least two wavelengths of interest. Dispersive spectrograph  652  together with two detector channels  660  and  662  may be configured to provide both siloxane and water vapor detection.  
     [0111] A mid-IR prototype sensor was built using commercially-available lab instrumentation along with a controllably heated transfer line and gas cell. This prototype was based on a Foxboro Miran 1B analyzer coupled to a Miran detector. The analog output level from this prototype was in a range from about 0 to 1 volt and was directly compatible with an exemplary data acquisition and control electronics for the HDC appliance. The prototype was installed to sample the drum exit stream with either a pump or the pressure differential that developed across the heat exchanger providing flow through the cell. It has been shown that this type of sensor will permit monitoring the siloxane concentration in the exit stream as a function of dry time and under variable operating conditions. The radiation source wavelength was set at approximately 9.2 microns, which substantially corresponds with the Si—O stretch band in the mid-IR. This band has no interference from water vapor and the heated cell enclosure and teflon transfer lines were all heated to temperatures above 150° F. to prevent condensation.  
     [0112] A sequential vaporizer was constructed to provide selectively switchable streams of dry air or air saturated with water or siloxane vapor at a desired temperature. The sequential saturator consisted of a series of gas washing bottles or impingers that contained siloxane and, separately, water with control of the gas flow rates from a common source. This saturator was used to test each of the solvent sensor prototypes developed for this invention.  
     [0113] Testing of the mid-IR sensor was carried out with a heated cell and a transfer line temperature at approximately 150° F. (65° C.). The slit width was approximately 1 mm and the full-scale absorbance of 1 AU would be equal to 4 volts. A low-pass filter was used to provide some noise reduction with a 1 second time constant. The typical test procedure was to pass dry air through the sensor followed by saturated siloxane vapor, then back to dry air and then to water vapor and then again to dry air. In the plot of FIG. 21 shows an exemplary response of the mid-IR sensor in the presence of saturated siloxane vapor versus the presence of dry air. For example, after 300 seconds with just dry air passing through the cell, the gas source was switched to provide saturated siloxane vapor at approximately 22° C. (72° F). At 550 seconds the gas stream was switched back to dry air and then again at 1060 seconds to saturated D5.  
     [0114] A useful figure of merit for a selective sensor is the response ratio of the detected species to common interference or background materials. In the case of the HDC appliance the most common background is believed to be water vapor, either from the clothes load, from mixed fluid cleaning or from ambient background. The plot of FIG. 22 shows an exemplary response of the mid-IR detector to both D5 and water vapor under the same conditions.  
     [0115] The saturation vapor pressure of water vapor at 21° C. is approximately 18.65 mm and the saturation vapor pressure of siloxane under the same conditions is approximately 0.097 mm. Accordingly, for a concentration ratio of approximately 5.2×10E-3 the measured signal ratio was approximately 17. Thus, the siloxane/water selectivity value for this example was approximately 3269. Given that the detector response to gas concentrations is substantially linear at least up to 1 absorbance unit, the maximum concentration capability for siloxane under these experimental conditions is 50% saturation at a drum exit temperature of 150° F. If the siloxane saturation level in the drum exit is higher than that, one can easily shorten a path length from approximately 1.8″ to approximately 0.75″ and still retain low concentration level capability.  
     INDUSTRIAL UTILITY  
     [0116] It is felt that the spectroscopic sensing solutions to siloxane sensing in the HDC appliance are sufficiently selective and offer a relatively low risk of interferences (water vapor) being seen as siloxane. Sensor designs that integrate the filters in the detector covers, pulsed IR sources and integral sample cells are contemplated to provide further opportunities for a siloxane-specific spectroscopic sensor, especially in the near-IR range, that may be sufficiently cost effective to be viable for a home appliance.  
     [0117] Piezo-Based Sensors:  
     [0118] Quartz crystal microbalances (QCM) comprised the exemplary sensor elements evaluated in this class of sensors. These are typically AT cut quartz crystals with electrodes applied to the opposite surfaces. When driven with an oscillating electric field, the crystal oscillates at the design resonant frequency. In the case of exemplary crystals tested for verifying aspects of the present invention, this frequency was approximately 10 MHz.  
     [0119] As will be appreciated by those skilled in the art, an uncoated QCM is highly sensitive to changes in material weight on the surface of the sensor. The response of a resonating crystal comprises a decrease in resonant frequency proportional to the increase of the mass on the active surface of the crystal. The active resonant surface of the QCM is largely confined to the electrode region of the crystal. Small increases in surface adsorption can lead to rather large changes in frequency of the QCM and this characteristic is innovatively used to detect siloxane in a dry cleaning appliance.  
     [0120] The inventors of the present invention noted that an uncoated QCM when exposed to siloxane or water vapor near saturation accumulated a thin film, possibly a complete monolayer, of the gas molecules on the resonant surface of the crystal and this increased the weight of the crystal and thus decreased the resonant frequency of the sensor. However, in the uncoated devices, which typically have aluminum, gold or nickel electrodes on the quartz crystal, are relatively unselective regarding condensable vapors.  
     [0121] To increase the selectivity of the sensors, as conceptually shown in FIG. 23, one should coat the active resonant surface of a crystal  701  with a transducer film  702  of material that selectively absorbs the analyte of interest and thus increases the film weight and/or modulus of the crystal. This would affect the resonant frequency of the QCM. Since, in aspects of the present invention, one is primarily concerned with selecting siloxane vapor over water vapor, in one exemplary embodiment, one may choose the transducer film  702  to comprise a non-polar organic reagent or polymer. For applications where water detection is of interest, polar polymers including some ionic materials might be used as the coating material. As used herein, the phrase “transducer film” refers to any substance disposed on a resonator to render that resonator responsive to the presence of a volatile dry cleaning solvent, such as siloxane.  
     [0122] Initial experiments involved the use of 10 MHz QCM devices available from International Crystal Manufacturing in Oklahoma City. These devices are provided with removable contacts and include gold electrodes that were found to provide an excellent substrate for attaching monolayers of thio-organics or overcoating with polymeric films. The —SH group is very effective at binding to a gold surface and when a long hydrocarbon chain thiol is used, the result is an organized film of hydrocarbon chains extending from the surface of the gold electrode. Application as a Langmuir-Blodgett film tends to create dense organized monolayers of hydrocarbons. An exemplary thiol used was octadecylthiol, which has a long hydrocarbon chain attached to the thiol and thus the gold surface.  
     [0123] Experimental results obtained when binding or otherwise disposing a monolayer of octadecylthiol on a gold electrode QCM showed a shift of about 125 Hz indicating siloxane saturation at a temperature of approximately 21° C. The signal response was relatively fast but the absolute change was somewhat low, reflecting the relatively low capacity of a monolayer of hydrocarbon chains to accommodate adsorbed siloxane. The selectivity ratio was quite high with a siloxane/water selectivity value of approximately 2115. Addition of a thin coating of RTV-615 (a platinum cured polysiloxane rubber) followed by a thermal cure achieved a selectivity ratio of 3686.  
     [0124] Exemplary commercially available non-polar polymers that may be useful for detecting volatile siloxane are listed below.  
     [0125] GE RTV-615 2-component unfilled silicone RTV  
     [0126] Polystyrene-polyisoprene-polystyrene block copolymer  
     [0127] Polybutadiene (5K MW)  
     [0128] GE SE-33 silicone gum  
     [0129] Ilfineum Polyisoprene C9925 2.5K MW  
     [0130] Hycar CS8596 reactive liquid rubber  
     [0131] Polypropylene co-ethylene  
     [0132] Trilene 65 (Uniroyal)  
     [0133] Hycar X-162 BF Goodrich (5.2K MW)  
     [0134] Hydrogenated polyisoprene (Aldrich)  
     [0135] Durasyn 180 Amoco Poly-α-olefin  
     [0136] Trilene 77 Ethylene/propylene/ethylene norbornene polymer (Uniroyal)  
     [0137] Poly (propylene-alt-ethylene) multi-arm star polymer (Aldrich)  
     [0138] The RTV-615 polymer was preferred and easiest to use to prepare a robust cured film. It is recommendable to conduct further experiments to evaluate possible structural variations on the silicones, such as the effects of vinyl, phenyl, trifluoropropyl groups or the effects of molecular weight (viscosity), cross-link density and film thickness on the selectivity ratio and sensor response times.  
     [0139] In additional experiments, another sensor device available from Allied Electronics was evaluated. This other device exhibited a generally rougher surface texture on the electrodes. This texture led to thicker coatings and improved the magnitude of the response of the device. These devices were cleaned with an appropriate cleanser, e.g., chloroform, and dried before coatings were applied. A plot of an exemplary response for the Allied device coated with RTV-615 polymer is shown in FIG. 24.  
     [0140] The selectivity ratio for the Allied crystal coated with RTV-615 was approximately 3750. This value is comparable to the upper limit achieved with the gold electrode QCM and is also in the same range as the value obtained with the spectroscopic mid-IR device which showed a selectivity ratio of 3269. The change in frequency for the Allied crystal with RTV-615 was about 1100 Hz, which compares favorably with the response of 125 Hz for the gold QCM devices.  
     [0141] The Allied Electronics QCM was mounted in a customized gas cell comprising a ½″ Swagelock “T” fitting. An RTV-61 coated Allied QCM (active QCM) was placed cross-wise relative to the gas flow and a hermetically sealed package of the same QCM type (reference QCM) was attached to the exterior of the Swagelock fitting. Signals from the two crystals were coupled to an HP53131A frequency counter and the ratio of the two signals was used to generate a ratiometric signal proportional to siloxane concentration. This arrangement permits correction for temperature drift. It will be appreciated, however, that some temperature drift may go uncorrected if, for example, sample stream flow rates are sufficiently high that the gas stream is not at thermal equilibrium within the cell and thus the active QCM would be at a different temperature relative to the reference crystal.  
     [0142] The QCM outputs may be processed with a relatively inexpensive counter/timer or FN converter to provide a signal (e.g., a DC signal) proportional to the siloxane concentration. In further experiments, the temperature controlled gas flow cell will be arranged to hold both a hermetically sealed QCM and an open package with polymer coating as a sensor/reference pair.  
     [0143] Strain Gauge Based Devices:  
     [0144] An exemplary device tested was commercially available from Hygrometrix Inc. and consisted of a micro-machined silicon chip including four strain gauges, a thermistor temperature sensor and signal processing circuitry in a TO-5 package. This sensor used comprised approximately a 2 mm×2 mm sensor chip that combines a sensing element and Wheatstone Bridge piezoresistor circuit to deliver a DC output voltage that is linearly proportional to RH from 0% to 100% FS. The vapor-sensing element may be constructed from a thin polymer film deposited and bonded to the top surface of four cantilever beams that are bulk-micromachined from the surrounding silicon substrate. More specifically, it is contemplated to coat the resonator beams with a non-polar polymer film, such as those listed in the context of the discussion of piezo-based sensors. This should provide a selective siloxane sensor. This type of sensor has the potential to be a relatively low-cost sensor due to the self-compensating structure and the straightforward DC output indicative of vapor concentration.  
     [0145] While the preferred embodiments of the present invention have been shown and described herein, it will be obvious that such embodiments are provided by way of example only. Numerous variations, changes and substitutions will occur to those of skill in the art without departing from the invention herein. Accordingly, it is intended that the invention be limited only by the spirit and scope of the appended claims.