Abstract:
A hot air popcorn machine including a programmable control system for precisely controlling various operating parameters including air flow and air temperature to enable the machine to consistently produce high quality popcorn in a low maintenance environment, e.g., a free-standing vending machine.

Description:
This application is a 371 of PCT/US98/23,305, filed Nov. 2, 1998 which claims the benefit of U.S. Provisional Application No. 60/064,933, filed Nov. 7, 1997. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention is directed to apparatus for preparing popcorn via a closed-loop hot air cooking process and more particularly to such an apparatus suitable for use as a low maintenance, free-standing vending machine. 
     Popcorn vending machines are well known in the art and are discussed in various prior patents including, for example, U.S. Pat. Nos. 4,307,657 and 5,020,688, as well as the references cited therein. 
     The use of hot air to “cook” or “pop” hard popcorn kernels is well known. The quality of the end product, i.e., the popcorn, is dependent upon several factors including the temperature of the air used for cooking and the cooking time duration. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a hot air popcorn machine including a programmable control system for precisely controlling various operating parameters including air flow and air temperature to enable the machine to consistently produce high quality popcorn in a low maintenance environment, e.g., a free-standing vending machine. 
     A machine in accordance with the invention includes a reservoir for hard kernel inventory; a cooking chamber; a kernel metering device, e.g., an auger, for delivering hard kernels to the cooking chamber; a heater; a blower for delivering heated air to the cooking chamber; an output container for receiving popped kernels, i.e., popcorn, from the cooking chamber; and a programmable control system for controlling operation of the machine. In use, the control system responds to a “start” event, e.g., a user depositing money into a coin/currency reader, to initiate an operational cycle preferably comprised of the following sequential phases: (1) preheat, (2) kernel delivery, (3) cook (including flavoring dispensing), and (4) kernel purge. 
     A preferred control system in accordance with the invention incorporates a programmed controller, e.g., a microprocessor based microcomputer, and a feedback loop for controlling air flow to the cooking chamber. More particularly, the controller responds to an air flow sensor to control the air flow to the cooking chamber to conform to a set point defined by a programmed or calculated air flow profile. Closed loop, i.e., feedback, control of air flow compensates for variations in components (attributable to either manufacture and/or aging) and environment (e.g., voltage and air temperature variations). Various techniques can be used to control air flow such as blower speed control and/or air baffle control. 
     In accordance with a preferred embodiment, the speed of a blower motor is controlled by duty cycle variation; e.g., by use of a pulse density modulation technique with the controller applying fixed duration pulses at a rate appropriate to establish the desired set point air flow. 
     In accordance with a further aspect of a preferred embodiment, the blower functions not only to deliver heated air to the cooking chamber for cooking but additionally functions to propel each popped kernel through an output chute to the output container. Still further, the blower is selectively controlled to purge any kernels from the cooking chamber toward the end of each operational cycle. 
     A control system in accordance with the invention preferably also incorporates a closed loop heater control. That is, a temperature sensor is preferably provided to measure the temperature in a heat chamber to allow the controller to control the heater to maintain air flow temperature at a target set point. 
     In accordance with a further aspect of a preferred embodiment, an optical sensor is provided for counting popped kernels delivered out of the cooking chamber through the output chute. The popped kernel count can be selectively used by the controller to time the actuation of a pump for delivering butter flavoring, e.g., butter, to the output container. 
     When used as a vending machine, apparatus in accordance with the invention is preferably configured with a transparent housing so that a user can readily watch the popcorn preparation process; i.e., the steps of metering the hard kernels into the cooking chamber, the popping of the kernels, the delivery of the popped kernels through the chute to the output container, and the dispensing of butter flavoring into the container. An alphanumeric visual display is preferably carried by the housing for presenting informative (and/or entertaining) messages to the user such as instructions and feedback. Further, the housing is preferably adorned with attractive eye-catching lighting such as multicolor neon lights so that the machine will afford a user an entertaining experience in addition to providing a high quality popcorn product. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a functional block diagram of a preferred system in accordance with the present invention depicting a microprocessor based controller coupled to the primary functional elements of a preferred machine embodiment; 
     FIG. 2 is a timing chart generally depicting the operation of the system of FIG. 1; 
     FIGS. 3A,  3 B is a flow chart generally describing the operation of the system of FIG. 1; 
     FIG. 4 is an isometric view illustrating the external appearance of a preferred structural embodiment of a popcorn machine in accordance with the present invention; and 
     FIG. 5 is a vertical sectional view through the machine of FIG. 4 illustrating the primary structural elements of a preferred embodiment of the invention. 
    
    
     DETAILED DESCRIPTION 
     Attention is now directed to FIG. 1 which depicts a functional block diagram of a hot air popcorn machine  10  in accordance with the present invention. The machine  10  includes a reservoir  12  for storing an inventory of hard popcorn kernels. In a typical application of the invention as a vending machine, the reservoir  12  will accommodate a volume of hard kernels sufficient to produce two-hundred or more large cups (e.g., 46 ounces) of popcorn. The machine  10  also includes a metering device  14 , e.g., an auger, actuatable to deliver a unit volume of hard corn kernels  15  from the reservoir  12  to a cooking chamber  16 . 
     The kernels  15  delivered to the cooking chamber  16  are then cooked, i.e., popped, by a heated air flow  17  supplied thereto from an air blower/motor  18  via a heat chamber  20 . The heat chamber  20  is heated by an electric heater  22  so that ambient air  24  blown through the heat chamber  20  emerges as heated air  17  for application to the hard kernels in the cooking chamber  16 . After the kernels pop in the cooking chamber  16 , they are preferably blown by the air flow  17  through output chute  30  to an output container  34 , e.g., a removable cardboard or plastic cup. 
     The machine  10  further includes a reservoir  36  for storing flavoring  38 , typically butter. The flavoring  38  can be drawn by an actuatable pump  40  from the reservoir  36  for dispensing via tube  42  directly into the output container  34 . 
     The functional elements thus far described are controlled in accordance with the intention by a programmed microprocessor based controller  48 . The controller  48  is capable of being programmed via an operator input/output (I/O) device  50 . The operator I/O device  50  is intended to be available to a machine operator, i.e., a person responsible for installation and/or maintenance of the machine. As used herein, the term “operator” is to be distinguished from the term “user” which will be used to refer to a person who uses the machine  10  to purchase or obtain a cup of popcorn. 
     In accordance with a preferred embodiment of the invention, the controller  48  is programmed with multiple operating parameter values which are used to control sequential phases of an operational cycle of the apparatus. FIG. 2 depicts a typical operational cycle and the sequential phases occurring therein. The cycle is initiated by a “START” event (at time T 0 ) which, in a vending machine environment, will typically be produced by a user depositing the correct amount of money into the coin/currency scanner  52 . The START event initiates a preheat phase  53  and causes the controller  48  to actuate the heater  22  to start warming the heat chamber  20 . At time T 1 , the controller  48  actuates the hard kernel delivery device  14  and the air blower/motor  18 . The delivery device  14 , e.g., an auger, meters a portion of hard kernels to the cooking chamber by time T 2 . During this T 1 -T 2  interval (kernel delivery phase  54 ), the blower/motor speed is ramped up to a Start Air Flow Rate (corresponding to a stored parameter value to be discussed hereinafter) to follow a first portion of stored airflow profile  55 . The slope of the ramp is selected to provide sufficient air flow to slightly agitate the hard kernels  15  arriving in the cooking chamber  16  but low enough to allow the temperature in the chamber to rise toward cooking temperature. 
     With the kernels  15  in the cooking chamber  16  and the heater  22  and blower/motor  18  actuated, cook phase  56  is initiated at time T 2 . The cook phase  56  extends to time T 8 , the duration T 2 -T 8  being determined by the controller  48  in response to a stored or calculated Cook Phase Duration parameter value, to be discussed hereinafter. During the cook phase (i.e., T 2 -T 8 ), the heater is maintained at a temperature corresponding to a stored parameter value and the blower/motor speed is preferably ramped down to an End Air Flow Rate in accordance with a second portion of the stored or calculated air flow profile  55 . At the beginning of the cook phase, the controller  48  preferably causes the alphanumeric message display  58  to instruct the user to “insert cup” and illuminates a butter switch lamp  60  to invite the user to actuate a butter command switch  62 . If switch  62  is actuated, then at some later time, e.g., T 5 , T 6 , T 7 , the controller  48  actuates pump  40  to dispense butter flavoring into the output container  34 . At the end of the cook phase T 8 , the controller  48  preferably pulses the blower/motor  18  to increase air flow to blow any remaining popped kernels from the cooking chamber  16  into the output container  34 . Additionally, via the display  58 , the user at time T 9  is instructed to remove the output cup. At a subsequent time T 10  in the operational cycle, the blower/motor  18  is pulsed again so, in the unlikely event any unpopped kernels remain in the cooking chamber  16 , they will be blown out to a waste receptacle. 
     The controller  48  controls the various functional elements thus far described in accordance with the stored program represented in FIG. 3, stored operating parameter values listed in FIG. 1, and feedback information provided by air flow sensor  64 , temperature sensor  66 , and optical sensor  68 , all schematically shown in FIG.  1 . 
     The air flow sensor  64  produces an air flow signal  65  which indicates the air flow rate produced by blower/motor  18 . This information is used by the controller  48  to either increase or reduce the blower/motor duty cycle to match the measured flow rate to the flow rate setpoint determined by the controller. 
     The temperature sensor  66  produces an air temperature signal  67  which indicates the temperature in the heat chamber  20 . This information is compared by the controller  48  with a target setpoint. If the measured temperature is too high, the controller terminates current to the heater until the temperature falls below the setpoint. If the controller is unable to bring the temperature below a fail-safe level, a fail-safe contactor  69  is opened to remove power to the heater  22  and to cause the display  58  to show an “out of service” message. An over temperature switch  70  with a predetermined temperature preset, and separate from the controller  48 , is mechanically attached to the heat chamber  20 . In case of controller  48  failure, over temperature switch  70  cuts power to the contactor  72  and causes display  58  to show an “out of service” message. 
     The optical sensor  68  produces a popped kernel count signal  71  corresponding to the amount of popped kernels blown through the chute  30  to the output container  34 . The popped kernel count signal  69  is preferably used by the controller  48  to time the actuation of butter pump  40  for delivering butter flavoring, e.g., butter, to the output container  34 . 
     Various operating parameter values are field programmable into the controller  48  via the operator I/O device  50 . Although these values are typically set at the time of manufacture (e.g., in ROM or EPROM within the controller  48 ), the I/O device  50  enables them to be adjusted on site to compensate for component aging and/or environmental variation, e.g., by storing operating parameters within RAM or EEPROM located within or associated with the controller  48  (typically a microcomputer). In accordance with the preferred embodiment, the following operator parameters are field programmable: 
     
       
         
               
               
             
           
               
                   
               
               
                 PARAMETER 
                 NAME/FUNCTION 
               
               
                   
               
             
             
               
                 [0] 
                 Kernel Delivery Duration 
               
               
                 [1] 
                 Butter Pump Duration 
               
               
                 [2] 
                 Cook Phase Duration 
               
               
                 [3] 
                 Cook Temperature Maximum 
               
               
                 [4] 
                 Start Air Flow Rate 
               
               
                 [5] 
                 End Air Flow Rate 
               
               
                   
               
             
          
         
       
     
     The controller  48  typically stores a value V for each parameter. For example, where Parameter [0] defines the Kernel Delivery Duration, if the variable V[0]=16, the kernel delivery device  14  is turned on for sixteen time increments. In a preferred embodiment, each Parameter [0] increment equals 0.25 seconds so that V[0]=16 designates that the kernel delivery device should be turned ON for four seconds. This duration determines the size of a unit volume of kernels  15  delivered to the cooking chamber  16  to produce a single popcorn portion. 
     Parameter [1] defines the Butter Pump Duration. As an example, assuming 0.25 second increments, when V[1]=22, pump  40  will be turned ON for five and one-half seconds. The larger the programmed value, the more butter flavoring  38  will be dispensed into the output container  34 . The butter pump ON time is preferably comprised of two or more noncontiguous subintervals to better distribute the flavoring over kernels delivered to the output container  34 . The butter pump ON time preferably should not exceed one-half of the cook phase duration. 
     Parameter [2] defines the Cook Phase Duration. As an example, assuming one second increments, when V[2]=150, the cook phase duration is set to 150 seconds, i.e., 2.5 minutes, independent of preheat, kernel delivery and purge phases. 
     Parameter [3] defines the Cook Temperature Maximum, the temperature setpoint  72 . As an example, the value V[3]=110 refers to the raw readout from the heat chamber temperature sensor  66 . The larger the number, the higher the temperature that can be developed in the heat chamber. It is parenthetically pointed out that although there is an optimum theoretical temperature at which hard popcorn kernels will pop, each different heat chamber may have slightly different characteristics so that it is desirable to be able to define this parameter value differently for each particular heat chamber. 
     Parameter [4] defines the Start Air Flow Rate (a first air flow setpoint  73 ) at the start of the cook phase, T 2 . As an example, the value V[4]=225 defines the speed which the blower/motor  18  should reach at time T 2 . In a preferred embodiment, the blower/motor speed is controlled by a pulse density modulation technique and the exemplary number 225 defines a 3.33% duty cycle (where duty cycle=(255−X) −1  and a value of 255 defines a 100% duty cycle). 
     Parameter [5] defines the End Air Flow Rate (a second air flow setpoint  74 ) at the end of the cook phase T 8 . As an example, the value V[5]=113 defines a 0.7% duty cycle for the blower/motor  18 . The number is preferably selected to be as low as possible while still providing sufficient flow to blow popped kernels out of the cooking chamber into the output chute  30 . 
     Attention is now called to FIG. 3 which illustrates a flow chart describing an exemplary program executed by controller  48 . When in the READY state awaiting a START event, the system will continue to loop through blocks  200  and  202 . Block  200  causes the alphanumeric display  58  to generate attractive, entertaining and instructive messages, e.g., “insert one dollar”. Block  202  determines whether the coin/currency scanner  52  has accepted a correct deposit from a user. If NO, then operation loops back to block  200 . If YES, the message display electronics producing the message “insert one dollar” is disabled (block  204 ) and operation proceeds to block  206  which executes a preheat test. If the test fails then operation proceeds to point D in the flow chart of FIG. 3, to be discussed hereinafter. If the preheat test succeeds, operation proceeds to block  208  which causes the display  58  to tell the user that air flow is being initiated. Subsequently block  210  is executed which actuates the kernel delivery device  14 . If kernel delivery fails, block  212  is executed which attempts to free the jam in the delivery device  14  by, for example, reversing the auger motor. Block  214  determines whether the jam has cleared. If YES operation returns to block  210  to effect kernel delivery. If the auger has not recovered from the jam, then operation proceeds from block  214  to point D in the flow chart to be discussed hereinafter. 
     Assuming a successful kernel delivery by device  14  to cooking chamber  16 , operation proceeds from block  210  to block  218  which determines whether the temperature in the heat chamber  20  is less than the temperature set point  70 . If YES, then operation proceed to block  220  which turns the heater  22  ON. If NO, operation proceeds to block  222  which queries whether the temperature is equal to or greater than a fail safe temperature. If YES, operation proceeds to point D of the flow chart. If NO, normal operation proceeds from block  222  to block  224 . Block  224  tests the air flow and adjusts the pulse density modulation to bring the air flow to the first desired set point  72 . If the air flow test fails, then operation proceeds to block  226  which executes a test for motor or sensor failure. If motor failure is determined, operation proceeds to point D of the flow chart. If the test in block  226  determines sensor failure, operation proceeds to point D of the flow chart. If no sensor failure was detected, operation proceeds to block  228  which determines whether the butter switch  62  has been pressed. If YES, then operation proceeds to block  230  which resets the butter lamp and perhaps generates an acknowledgment message on the alphanumeric display  58 . If decision block  228  indicates NO, then the operation bypasses block  230 . 
     Block  232  is next executed. If the butter switch  62  had not been pressed, then operation proceeds out of block  232  along the NO path bypassing block  234 . If block  232  indicates YES then operation proceeds to block  234  which actuates butter pump  40 . Block  234  tests for butter pump failure and if failure occurs, operation loops to block  236  which attempts to clear the pump failure by reversing the pump motor. Block  238  tests to determine if the jam has been cleared. If YES, operation loops back to block  234 . If the block  238  test indicates failure, then operation proceeds to point D. It will be recalled that prior failures in the flow chart also lead to point D. Execution from point D will be discussed hereinafter. 
     Proceeding from a successful pump operation in block  234 , block  242  is executed which looks to see if the cook phase is finished by monitoring output  69  of sensor  68 . If NO, operation proceeds to point B in the flow chart leading to block  218 . If YES, operation proceeds to block  244  which turns the heater OFF. Operation then proceeds through block  248  to execute the initial air purge operation at time T 8  and block  250  which enables the currency scanner  52  and displays a new message on display  58 , e.g., a company logo and/or operating information such as “insert one dollar”. Block  252  introduces a WAIT state and block  254  reestablishes new pulse density modulation values. Block  256  then causes the second air purge at time T 10  which completes the operational cycle and returns operation to point A, the READY state. 
     It has been mentioned that in the event of a failed test, operation proceeds to point D. This causes execution of block  260  which opens the fail-safe contactor  69  and disables the scanner  52 . Operation then proceeds to block  262  which generates an “out of service” message on display  58 . 
     Attention is now directed to FIGS. 4 and 5 which depict a preferred structural embodiment of a popcorn machine  300  in accordance with the present invention. The machine  300  includes a housing  302  defined by a rectilinear frame  304 . The frame  304  defines an upper section  306  which, as will be seen, houses most of the aforediscussed functional elements of the invention and a lower section  308  which is primarily used for storage, waste collection, and cooling, as will be discussed. 
     The frame  304  in the upper section  306  defines front and rear open areas,  310  and  312  respectively, and left and right open areas  314  and  316  respectively. 
     The front open area  310  is generally filled by a transparent panel  320  defining an open area  322  through which a user is able to insert a cup  324  for filling. The open area  310  also defines a solid panel portion  326  having openings  328  therein for storing unused cups for use by a user. The solid panel portion  326  also supports the coin/currency scanner  52  which is accessible to the user at  330  and the butter switch  62  accessible to the user at  332 . The front open area  310  also preferably supports the alphanumeric message display device  58  which is visible to the user at  340 . Preferably, the display  58  is capable of displaying dynamic multi color messages. 
     The housing rear open area  312  and right open area  316  are preferably closed by removable opaque panels. The left open area  314  is preferably closed by a transparent panel. Thus a user is able to observe the interior of the housing through the open areas  310  and  314 , and will be able to watch the preparation of a popcorn portion. In addition to the functional elements mounted within the housing  302 , aesthetic elements such as colored neon tubes  348  are preferably mounted within the housing adjacent to the transparent panels of the front and left open areas  310 ,  314  to enhance the entertainment value and eye-catching appeal of the unit. 
     FIG. 5 is a cross section of the housing and depicts the functional elements of FIG. 1 mounted therein. Thus, the housing includes the hard kernel reservoir  12  preferably formed of transparent walls  360  and having a lid  362  removable for filling. An auger  364 , forming the aforediscussed kernel delivery device  14 , is mounted on the shaft of motor  366 . The auger  364  passes through open tube  370  extending from below the tube entrance at  372  to the tube discharge end at  374 . Thus, as the auger  364  rotates, its deep helical thread  365  picks up kernels at its lower end below the tube entrance  372  and carries them upwardly through the tube  370  for discharge at  374  into tube  378 . Tube  378  discharges at  380  into the funnel entrance  382  of the cooking chamber  16  preferably defined by transparent wall  384 . Mounted within the cooking chamber  16  is a pan or skillet  386  having holes. Thus, the hard kernels delivered by the auger  364  to the cooking chamber via tube  378  are deposited onto the skillet  386 . The skillet  386  is mounted above the heat chamber  20  defined by wall  390  and communicates therewith via holes in the heat chamber  20 . A blower/motor  18  is mounted in the air manifold  388  in close proximity to the heater  22 . Thus, the blower and heater generate a heated air flow, as has been discussed, which passes through openings in the heat chamber  20  into the cooking chamber  16 . This causes the deposited hard kernels to pop and to be carried by the air flow into output chute  30  defined by transparent wall  392 . The chute  30  includes an entrance  394  located proximate to the skillet  386  and an exit  396  which empties into a funnel shaped popcorn separation chamber  398 . The separation chamber  398  is preferably formed by a transparent wall  400  and accommodates a removable lid  402  above a discharge opening  404 . The discharge opening  404  is aligned with the aforementioned opening  322  and transparent panel  320  which accommodates the output container or cup  324 . The floor  406  of the housing upper section  306  is preferably formed with a recess  408  below the discharge opening  404  to accommodate the cup  324 . The floor of the recess  408  includes openings which communicate with a drawer  412  for collecting kernels purged from the cooking chamber after removal of the cup  324 . The drawer  412  can be removed via handle  414  to empty its waste content. A butter ring  417  is mechanically connected around opening  404 . Silicone tube  42  is attached to the butter ring  417  by which the pressurized butter flavoring  38  is sprayed into the cup  324 . 
     From the foregoing, it should now be appreciated that an apparatus has been disclosed herein for preparing popcorn in a manner such that it is particularly suited for use as a vending machine in a low maintenance environment. It is contemplated that the machine can function in an essentially unattended mode to dispense one-hundred or more popcorn portions without replenishing the kernel inventory. Although a specific embodiment of the invention has been disclosed herein, it should be understood that innumerable modifications and variations may occur to those skilled in the art falling within the intended scope of the invention as defined by the accompanying claims.