Abstract:
An airlock assembly for allowing fermentation gasses to escape from a sealed fermentation vessel and preventing ambient gasses from entering the fermentation vessel and including a structure for producing electrical signals that can be used to detect said escape of fermentation gasses.

Description:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable. 
     REFERENCE TO A MICROFICHE APPENDIX 
     Not Applicable. 
     BACKGROUND 
     1. Field of Invention 
     This invention relates to airlocks, specifically to an airlock assembly that provides a means to electronically detect air as it escapes from the airlock. 
     2. Discussion of Prior Art 
     These days, homebrewing has become a popular hobby. Many people produce fermented beverages, primarily beer and wine, in their own home. To produce a fermented beverage, yeast is added to a liquid containing sugar, the liquid being crushed grapes in the case of wine, or mashed barley in the case of beer. The yeast cells employ complicated metabolic reactions to produce, among other things, alcohol and carbon dioxide. It is important that no wild yeast or bacteria contaminate the fermenting beverage - producing undesirable flavors. To accomplish this, homebrewing requires a fermentation vessel that is fitted with an airlock The air lock allows fermentation gasses to escape the vessel, but does not allow surrounding air into the vessel. An economic fermentation vessel is typically fashioned by using a food grade plastic bucket, a tight fitting lid, and a two piece airlock 
     FIG. 1 shows a typical prior art airlock commonly used in homebrewing. Gasses produced by fermentation enter the airlock through intake tube  12 , which extends into the fermentation vessel  14  through a hole in stopper  16 . Stopper  16  forms an airtight seal with fermentation vessel  14 . Therefore, fermentation gasses can only escape through intake manifold  22 , which is formed by intake tube  12 . The airlock also consists of a reservoir  21  for holding a fluid such as water, and an airlock partition  18 . Airlock partition  18  is in the shape of a cup and covers the portion of the intake tube that is inside the reservoir  21 . The interior of the fermentation vessel is isolated from the ambient air by filling the reservoir with a fluid such that the initial fluid level is between the opening of the airlock partition  18  and the top of the intake tube  12 . As the fermentation process causes the pressure within the intake manifold  22  to increase, the airlock partition  18  rises above the top of the intake manifold  12  and the fluid level inside the airlock partition  18  lowers. When a sufficient pressure inside the intake manifold  22  is reached, fermentation gasses escape from under airlock partition  18 . This causes airlock partition  18  to fall back toward intake tube  12 , producing a “bloop” sound The fermentation gasses escape the airlock through airlock lid holes  26  or through the seal between airlock lid  24  and the reservoir container  28 . Various types of similar airlocks can be found in prior art. One example is found in U.S. Pat. No. 5,950,524, issued to C Reitz et al on Sep. 14, 1999. 
     While these devices are suited for their intended usage, none of them provide a means to produce an electrical signal when fermentation gasses escape from the airlock. 
     SUMMARY 
     In order to track fermentation progress, homebrewers observe the air escaping form the airlock Since it is impractical to watch the air lock for the entire fermentation cycle, a device that can monitor the escaping air from the airlock and produce an electrical signal that can be recorded on a device, such as a personal computer, is desirable. This invention is an airlock that produces an electrical signal each time air escapes from the airlock. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an airlock that generates electrical signals that indicate gasses have flowed from the intake manifold to the ambient atmosphere. It is another object of this invention to monitor said electrical signals, and produce a second electrical signal that distinctly indicates the event of gas escaping from said airlock 
     A third object of this invention to detect gasses escaping from the airlock using an induction coil that has a non-critical tolerance. 
     In order to attain above objects, the present invention comprises an airlock with a partition which rises as gas collects in the intake manifold, a solenoid type induction coil wound around a non-conductive hollow tube, a ferrite core disposed inside said induction coil such that movement of the core causes a change in the inductance of the coil, a connecting rod which attaches said core to said airlock partition, an oscillator circuit that produces a square wave output and uses said inductive coil is used as an inductive element, a processor which counts the number of rising or falling edges of said square wave for a period of time, stores a history of such counts, and determines if air has escaped from said airlock by performing statistic analysis on said stored counts. 
     Further objects and advantages of the present invention will become apparent from a consideration of the drawings and ensuing description. 
    
    
     DESCRIPTION OF DRAWINGS 
     FIG. 1 shows a cross section of a known airlock (prior art). 
     FIG. 2 shows a block diagram of the components of this invention. 
     FIG. 3 shows a cross section of the airlock sensor assembly. 
     FIG. 4 shows a schematic of the oscillator. 
     FIG. 5 shows the voltage output of the oscillator circuit 
     FIG. 6 shows a flowchart of the processing used to clearly indicate the event of air escaping the airlock 
    
    
     DETAILED DESCRIPTION 
     The present invention will now be described with reference to the drawings. FIG. 2 shows the four subcomponents of my invention, which are; airlock-sensor assembly  20 , LC oscillator  40 , processor  60 , and interface circuit  80 . First, the airlock sensor assembly  20 , which consists of an airlock assembly  10  and an inductor assembly  30  is responsible for translating movement within the airlock assembly to a change in inductance of said inductor assemble  30 . Inductor assembly  30  forms the inductive component of LC oscillator circuit  40 . LC oscillator circuit  40  produces a square wave output of a frequency that varies with inductor assembly  30 . The square wave output of the LC oscillator is connected to a processor  60 . Processor  60  performs three functions. First, it counts each rising edge of the LC oscillator square wave output for a period of time (T 1 ). The count for each time period is stored in a buffer and statistical analysis is performed to determine if air has escaped from the airlock. Processor  60  also drives interface circuit  80 . Interface circuit  80  provides electrical isolation between the components of this device and any external recording device. A detailed description of each subcomponent is given in the following paragraphs. 
     Airlock Sensor 
     FIG. 3 shows the airlock sensor assembly. Gasses produced by fermentation enter the airlock through intake tube  12 , which extends into the fermentation vessel  14  through a hole in stopper  16 . Stopper  16 , made of cork or rubber, forms an airtight seal with fermentation vessel  14 . Therefore, fermentation gasses can only escape through intake manifold  22 , which is formed by intake tube  12 . The airlock also consists of a reservoir container  28  for holding a fluid such as water, and an airlock partition  18 . Partition  18  separates intake manifold  22  from exit manifold  23  and extends into fluid contained in reservoir  21  such that gasses cannot pass freely from intake manifold  22  to exit manifold  23 . Gasses can freely flow form exit manifold  23  to the ambient air through airlock lid holes  26 . Airlock partition  18  is in the shape of a cup and covers the portion of the intake tube that is inside the reservoir  21 , which is formed by reservoir container  28 . Reservoir container  28  and intake tube  12  are typically one piece and typically made of plastic or synthetic resin. 
     The interior of the fermentation vessel  14  is isolated from the ambient air by filling the reservoir container  28  with a fluid such that the initial fluid level is between the opening at the bottom of airlock partition  18  and the top of the intake tube  12 . 
     Attached to airlock partition  18  is connector rod  34 . Attached to connector rod  34 , is inductor ferrite core  32 . Airlock partition  18 , connector rod  34 , and inductor ferrite core  32  move as one piece. Inductor assembly  30  is comprised of inductive coil  37  and non-conductive hollow tube  31 . Inductor ferrite core  32  is disposed inside said non-conductive hollow tube  31  such that movement of said inductor ferrite core  32  causes a change in the inductance of inductor assembly  30 . Inductor assembly  30  forms the inductive element of an LC oscillator, which is further described in the section titled LC Oscillator. Partition  18 , connector rod  34 , inductor ferrite core  32 , and inductor ferrite core  37  form a ferrite core support means for securing ferrite core  32  such that motion of said partition  18  causes motion of said ferrite core  32  within inductive coil  37 , causing a change in the inductance of the coil. 
     Carbon dioxide gas released by the fermentation process causes the pressure within the intake manifold  22  to increase. This pressure forces airlock partition  18 , connector rod  34 , and inductor ferrite core  32  to rise. Said pressure also and forces fluid level  19  inside airlock partition  18  to decrease. 
     When a sufficient pressure inside the intake manifold  22  is reached, fermentation gasses escape from under airlock partition  18 . This causes airlock partition  18 , connector rod  34 , and inductor ferrite core  37  to rapidly fall back toward intake tube  12 . This rapid fall causes a correspondingly rapid decrease in the inductance of inductor  30 . The fermentation gasses escape the airlock through airlock lid holes  26  or through the seal between airlock lid  24  and the reservoir container  28 . 
     LC Oscillator 
     Explained next with references to FIGS.3 and 4 is the LC Oscillator, which generates a square wave with a frequency that varies with inductor assembly  30 . This provides a means of generating a voltage that varies in frequency with the value of said inductive coil  37  by using the coil as an inductive element in a oscillator. FIG. 4 shows a Colpitts oscillator, which is suitable for producing an AC voltage with frequency that varies with the value of an inductor. The Op Amp, resistors R 1  and R 2 , capacitors C 1  and C 2 , and inductor L form the Colpitts oscillator. Capacitors C 1  and C 2  form the capacitive reactance and inductor L forms the inductive reactance that provides the 180° feedback necessary for oscillation to occur. Resistors R 5  and R 6  form a voltage divider that allows the circuit to operate using a single power supply. Although FIG. 4 shows a Colpitts oscillator, it is possible that the same effect can be realized with any oscillator that uses an inductor as a reactive element. The output of the oscillator V osc  closely resembles a sin wave. 
     Resistors R 3  and R 4 , and transistor Q 1  convert the sinusoidal output voltage V osc  into a square wave voltage V 0 . 
     From the LC oscillator circuit in FIG. 4 the following equation can be obtained for the frequency fof the output voltage V 0 :                  f   0     =     1       C   ,   L           ;                  where                   C   t       =         C   1          C   2           C   1     +     C   2                   Eqn                 1                                
     From Eqn 1, it can be seen that as the value of the inductor increases, the frequency of the output voltage decreases. Likewise, as the value of the inductor decreases, the frequency of the output voltage increases. In reference to FIG. 3, as airlock partition  18  pushes inductor ferrite core  32  further inside inductive coil  37 , the inductance of inductive coil  37  increases—leading to a decrease in frequency of the output voltage V 0  Likewise, as airlock partition  18  falls back towards intake tube  12 , the inductor ferrite core  32  falls, evacuating from inside inductive coil  37 . This reduces the inductance of inductive coil  37 , resulting in an increase in the frequency of output voltage V 0.    
     In reference to FIG. 2, processor  60  monitors the LC Oscillator output voltage V 0  and measures its frequency f 0 . From this measurement, said processor determines if air has escaped from the airlock and produces an output that can be recorded. Said processor is further described in the section titled Processor. 
     Processor 
     As shown in FIG. 2, the output of the LC oscillator  40  is connected to a processor  60 . Said output of the LC oscillator  40  is described as LC Oscillator voltage V 0  in the previous section. Processor  60  performs three functions. First, it measures the frequency of the output of the LC Oscillator by counting the number of voltage transitions in a single direction of the electrical signals generated by the LC oscillator square wave output for a period of time (T 1 ). This is accomplished by either counting the number of positive going edges or the number of negative going edges of voltage V 0  for a period of time. If said period of time is equal to one second, the voltage transition count would equal the frequency of V 0 . A single measurement of the voltage transition count for a period of time is denoted by the letter F. 
     Second, a series of the most recent voltage transition counts (F) are stored in a memory buffer. The maximum number of stored voltage transition counts is designated by N. Once the number of voltage transition counts stored equals N, new voltage transition counts over write the oldest voltage transition count so that the total number of stored voltage transition counts equals N. 
     Net, in order to detect gasses escaping from the airlock using an inductive coil that has a non-critical tolerance, the most recent measurement of the voltage transition count is compared to the average and standard deviation of the stored voltage transition counts. This eliminates critical tolerance in the inductor because each measurement is compared relative to older measurements. 
     Finally, the decision of whether or not air has escaped from the airlock is made by counting the number of times the voltage transition count is less than a threshold. This threshold is calculated by the following formula. 
      Threshold=Avg−K(SDev)  Eqn 2 
     Where: 
     Avg is the average of the stored voltage transition counts, 
     SDev is the standard deviation of the stored voltage transition counts, 
     K is an experimentally determined constant (typically 1). 
     The Processor operation is described in more detail with respect to the flowchart in FIG.  6 . The number of voltage transition counts stored in the buffer, n, is set to zero. Also the number of times the voltage transition count is greater the threshold (DetCnt) is set to zero. Next, series voltage transition counts are stored in a memory buffer. The total size of the memory buffer, and thus, the total maximum number of voltage transition counts stored is designated by N. Once the memory buffer is filled, the Average (Avg) and t the Standard Deviation (SDev) of the data stored in the memory buffer is calculated. 
     At this point, the device is ready to begin to detect air escaping from the airlock The Threshold, Thresh, is calculated using equation 2, and a new measurement of the voltage transition count, F, is made. If F is less than or equal to the threshold, the event of air escaping from the airlock is unlikely. The number of times the voltage transition count is greater than the threshold (DetCnt) is decremented if it is not equal to zero. The oldest voltage transition count is removed from the memory buffer, and the most recent measurement, F, is stored. Finally, a new average and standard deviation is calculated and the process begins again with a new measurement of the voltage transition count. 
     If F is greater that the threshold, the event of air escaping from the airlock is likely. The number of times the voltage transition count is greater than the threshold (DetCnt) is incremented. DetCnt is compared to an experimentally determined value DetThresh. If DetCnt is equal to DetThresh, the device indicates that gasses have escaped from the airlock If DetCnt is less than DetThresh, a new voltage transition count is made.