Abstract:
A control and actuation system is provided for a molding machine for producing expanded-grain cakes. The system includes a control unit, a temperature-regulated heating system, multiple motors operated by the control unit for separately actuating mechanical functions, multiple sensors for providing grain level and mechanism positional data to the control unit, control inputs for programming and otherwise providing input to the control unit, and a display device allowing the control unit to provide operational status information. The control unit regulates the thermal energy input to the mold, the molding cycle frequency, and the size of the grain charge. Several interrupts are used to ensure conformance to the control parameters and to enhance operator safety.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is related to patent application Ser. No. 13/014,257 which was filed on Jan. 26, 2011 and is incorporated herein by reference in its entirety. The related application claims priority of Republic of Korea Patent Application No. 10-2010-0051387, which was filed on May 31, 2010, and is incorporated herein by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates generally to a control and actuation system for a baking-in-a-mold apparatus for producing molded preforms which, upon release from the mold, become expanded-grain cakes. More particularly, the invention relates to an improving of the control system by incorporating multiple parameter sensors and multiple actuators. 
         [0004]    2. Description of the Prior Art 
         [0005]    Generally, an apparatus for producing expanded-grain cakes is a molding machine in which a predetermined charge of admixed cereal grains is inserted into a hermetically sealed mold cavity thereof and subjected to pressure baking by a predetermined cycle of temperature. The product of the molding machine is a preform or molded cake. During baking the moisture content of the cereal is converted into entrapped steam and, upon rejection from the mold cavity, the entrapped steam from the treated charge of grain expands the molded cake to an expanded grain cake of the desired size. 
         [0006]    As will be seen from the following, the machine control and actuation subsystems enhanced hereby include, but are not limited to, the grain feed and controls therefor, the preheating of the mold cavity, the monitoring and maintenance of mold temperature and pressure, and the control system interrupts of the molding process when an error or component malfunction occurs. 
         [0007]    In detail, when an appropriate charge of cereal grain is sealed in a mold and heat is applied thereto, the grain expands to a preform constrained by the walls of the mold and entrains therewithin the moisture content of the grain in a gaseous, high-pressure state. Thereafter, when the mold which had been sealed opens, the high-pressure gas in the preform suddenly expands until it reaches ambient pressure and, acting as a blowing agent rapidly expands several fold to produce the expanded grain-cakes of the desired size. 
         [0008]    In the past, the machines that were introduced for producing expanded-grain cakes experienced numerous problems that were seemingly inherent to the accepted design at the time Of prominence among the problems was that the shapes of produced expanded-grain cakes were not uniform. Particularly this problem seemed to arise in those machines wherein the supply of cereal grains and the clamping of the mold were provided by the single-drive unit machine. After such a machine was used over an extended period of time, the amount of the charge of cereal grain tended to become non-uniform as errors accumulated. Also and concomitantly, the charge of cereal grain was not spread evenly in the mold cavity resulting in misshapen preforms and lopsided expanded-grain cakes. The early prior art machines did not program the delivery of thermal energy and, once the heat was delivered, were unable to maintain the pressure in the closed-mold unit. Both of these factors contributed to non-uniformity. 
         [0009]    Furthermore, with such errors accumulating due to insufficient parameter monitoring and control, and an insufficient amount of cereal grain being supplied to the mold, the clamping operation during the closed-mold phase frequently occurred when the grain transfer unit was not completely removed from the mold. If not stopped in time, this potentially could result in damage to the grain-transfer unit. 
         [0010]    Moreover, the prior art machines had no means for preheating the mold. Hence, when thermal energy was underdelivered the process in the mold did not sufficiently heat the contents and resulted in insufficient generation of blowing gases. Under such conditions, some of the cereal grains supplied to the mold would remain therein as there was an insufficient volume of gas to clear the cavity. 
         [0011]    The remnant cereal grains in the mold cavity frequently became scorched, burned, and discolored resulting in a contaminated mold. Until all the burned grain was removed from the mold the expanded-grain cakes produced by the contaminated machine was not of marketable quality. 
         [0012]    In the prior art machines, to solve these problems, an operator, upon opening the mold unit, would clear the mold cavity of debris using a tool such as a brush or the like. However, as such cleaning was conducted with the mold at a high temperature, the cleaning was performed under unsafe, hazardous conditions. 
         [0013]    Furthermore, in most prior art machines, the hopper was integrated with the machine and the operator had no visual cue as to the amount of cereal grain remaining. Because the hopper was typically made of stainless steel the user could not observe the amount of cereal grain in the hopper. Without sensors to set off interrupts, such a machine may be operated through one or more molding operations without sufficient cereal grain in the mold and thereby expose the machine to unnecessary downtime. 
         [0014]    While the above recitation of problems inherent in the prior art machines is remarkable, it clearly is not an exhaustive collection hereof. However, these and other problems resulted in certain technological re-evaluations being made prior to the present invention. During re-evaluation, the state-of-the-art was examined and the following discussion is of the patent literature which has become known to the inventor and the assignee hereof. 
         [0015]    In the prior art a number of machines of this type have been developed that include heated mold components which during operation are moved away from one another for loading of a predetermined charge of cereal grain and for unloading a baked product. Such machines were commonly developed in the Pacific Rim countries such as South Korea and Japan where rice cakes play an important role in the diet. 
         [0016]    U.S. Pat. No. 7,444,928 to Kim (Kim &#39;928), entitled “Apparatus for Producing Crackers”, discloses an apparatus capable of mechanically producing expanded-grain cakes. The patent is a non-priority filing of Korean Patent 10-571883, filed Mar. 9, 2004. The Kim &#39;928 apparatus has a single drive motor and, through transmitting the rotary power thereof using power takeoffs and cams, was able to replace the air cylinders and air compressors which sequenced the operations of earlier machines. The controls are simply disclosed as “a control box” with no functional detail taught, and no mention is made of any sensors in the apparatus. The resultant machine did not have sufficient fail/safe features as is apparent when the invention described below is understood. 
         [0017]    The patent to Yoshikazu, U.S. Pat. No. 4,328,741, issued May 11, 1982, is an air cylinder operated molding machine which is distinguished from prior devices as the machine did not require bonding agents in the charge of cereal grains. Yoshikazu describes twice molding the grain cakes by first pressure baking and expansion and, then compressing the expanding cake to achieve the desired form. Yoshikazu teaches the use of control means including multiple timers and limit switches, but no use of programmable controls or sensors with functions other than on/off. 
         [0018]    During the 1970&#39;s and 1980&#39;s, Gevaert obtained several patents on expanded cereal-based food product machines. Typical of the Gevaert patents is U.S. Pat. No. 4,281,593 which describes a molding machine with a hydraulic jack that raises and lowers a lower mold portion to close and open the mold, respectively. The precooked cereal grain is further cooked in the closed mold and gains its final shape by, after releasing the steam from this process, moving the upper mold downward to release the compressed and treated material. Nothing in the way of electronic controls or sensors is disclosed, and neither is any electric motor disclosed. 
         [0019]    A patent to Van den Berghe, U.S. Pat. No. 5,102,677 describes making a pressure baked, cereal grain cake in a heated mold and, afterwards, upon release from the mold, expands. Van den Berghe discloses two different molding units—a two-part mold in which hydraulic cylinders drive mold components to selected positions, and a three-part with a fixed upper, a positionable peripheral or ring mold, and a heatable removable lower mold. In the three-part mold, the downward positioning of the ring mold and the lower mold permits the removal of the expanded grain cake. The use of a programmable control unit is taught, which in combination with limit switches serves to control the sequence and range of motion of the actuators in the molding units. However, the control unit is not shown in the Figures and although there is disclosed control means for monitoring and adjusting the mold temperature, operation of the ingredient feeder, and the operation of the actuators, no specifics are taught and no electric motors or sensors other than on/off are used. 
         [0020]    The above prior art developments are exemplary and provide a background against which the advances presented by the below-described invention may be viewed. 
       SUMMARY 
       [0021]    In the present invention, a control and actuation system of a machine for producing expanded-grain cakes is provided and is constructed with a control unit, temperature-regulated heating system, multiple motors for separately actuating mechanical functions, multiple sensors for providing level and positional data to the control unit, control inputs for programming and otherwise providing input to the control unit, and a display device allowing the control unit to provide operational status information. The grain hopper and metering device supplies a precisely metered charge of cereal grain from a hopper provided on the upper end of the frame to a grain transfer unit. Separate drive units synchronously operate the grain transfer unit and the mold so as to deliver and evenly distribute the charge of cereal grain during the mold open portion of the cycle and to open the mold at the end of each cycle. The heating unit functions to preheat and to heat the mold and provide repetitively the same quantity of thermal energy during each cycle. 
         [0022]    A grain presence sensor monitors grain level and if input to the control unit indicates a lack of grain for molding cakes, the control unit will shut down the machine and activate an alarm. Multiple sensors monitor the positions of actuating portions of the grain dispensing unit and the grain transfer unit, and if any of the actuating portions fail to be in correct position, the control unit will shut down the machine and activate an alarm. 
         [0023]    The electronic controller of this invention besides monitoring the numerous interrupts built into the system, presented in greater detail hereinbelow, also provides advanced programmable heater controls, preferably using Proportional Integral Derivative (PID) control means. The temperature is regulated to compensate for lower power supply variation and for thermal losses while the mold is in the open condition. The upper and lower mold halves each contain temperature-regulated heating elements, where an elevated preheating temperature during mold open conditions compensates for the increased heat dissipation of an open mold and serves to maintain a much more uniform mold temperature throughout the molding cycle. 
         [0024]    The use of a separate motors for actuating different machine functions allows each motor to be tailored to a specific purpose, reduces mechanical complexity within the molding machine, and allows more precise sensing and control of actuation functions. A drive motor is provided for rotating the cam that actuates the pressure arm opening and closing the mold, a dispensing motor is provided to actuate the grain dispensing mechanism, and two pulse (stepping) motors are provided for actuating portions of the grain transfer unit. 
         [0025]    From the grain supply unit, the delivery of a charge of cereal grain proceeds by grain proceeds by gravity feed from a cereal grain hopper to a cup-like rotary housing, serving as a grain dispensing unit. Cereal grain from the hopper falls through an open inlet and fills a rotary housing, which. in synchronicity with a grain transfer unit, accurately meters the amount of grain required for a single preform. During the baking cycle, the rotary housing rotates to align with an outlet and to feed the metered charge of grain to a waiting grain transfer unit. The grain transfer unit shuttles each charge of grain from the grain supply unit to the lower mold while in the mold-open condition. 
         [0026]    The grain transfer unit is operated by two pulse (stepping) motors—one driving the unit into and out of the open mold and the other driving the underlying plate away from the open mold so as to deliver the cereal charge. After delivery, the grain carrier and the underlying plate are re-united and positioned under the outlet of the grain supply unit to receive the next charge of cereal grain. The grain transfer unit is closely monitored by several sensors, which sensors ensure that the sequencing is adhered to and, upon deviation therefrom, halts operations. 
         [0027]    Input to the control unit includes the option of numerically entering a quantity of grain cakes to produce. When the control unit is used in this mode, the machine will sequentially mold the specified number of grain cakes and then cease operation. 
         [0028]    The control unit communicates with a display unit, providing information to the user which may include the numerical quantity of grain cakes to produce, the grain level present, the amount of grain being used to produce a cake and the outputs of positional sensors. Further, an alarm activated if any sensor readings deviate from specified values may have auditory and visual components. 
         [0029]    The expanded grain cake machine of this invention provides numerous advantages over prior art machines largely attributable to the added control features and actuation described herein. In this machine, the trajectory of the molded preform is reproducible from one preform ejection to another by ensuring that the grain charge delivered to the lower cavity of the mold is: (1) accurately metered; (2) distributed evenly in the lower cavity; (3) placed into a preheated mold to compensate for thermal loss during mold-open phase; (4) subjected to a temperature controlled environment which factors in variations in local power supplied; and, (5) exposed during processing to the same amount of thermal energy. 
       OBJECTS AND FEATURES OF THE INVENTION 
       [0030]    It is an object of the present invention to provide a control and actuation system for a machine for producing expanded-grain cakes, that enables accurate control over multiple operating parameters and is equipped with interrupts for operator safety. 
         [0031]    It is another object of the present invention to monitor the availability of cereal grain for use in grain cake molding. 
         [0032]    It is yet another object of the present invention to monitor and control aspects of the cake molding process in order to produce consistently higher quality grain cakes. 
         [0033]    It is a yet further object of the present invention to provide separate motors for grain supply functions and for mold unit operation to simplify construction and enhance reliability. 
         [0034]    It is a feature of the present invention to control preheating and operational temperatures to form the correct size and shape of the expanded product. 
         [0035]    It is yet another feature of the present invention to check all functions with a digital controller and automatically stop upon the occurrence of any abnormal operation. 
         [0036]    Other objects and features of the invention will become apparent upon reading the detailed description which follows. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0037]    The above and other objects, features and advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
           [0038]      FIG. 1  is a perspective view showing the machine for producing expanded-grain cakes of the present invention; 
           [0039]      FIG. 2  is an exploded perspective view of the machine of  FIG. 1 ; 
           [0040]      FIG. 3  is a perspective view of the mold unit of the machine of  FIG. 1 ; 
           [0041]      FIG. 4  is an exploded perspective of the grain supply unit of the machine of  FIG. 1 ; 
           [0042]      FIG. 5  is an exploded perspective view of the blocking unit of the grain supply unit of 
           [0043]      FIG. 6  is an exploded perspective view of the grain transfer unit shown in  FIG. 2 ; 
           [0044]      FIG. 7  is a schematic view of the ferrous impurity removal of the grain transfer unit shown in  FIG. 6 ; 
           [0045]      FIG. 8  is an exploded perspective view showing the cam-operated, mold pressure unit of the machine of  FIG. 2 ; 
           [0046]      FIG. 9  is a perspective view showing the drive unit of the machine of  FIG. 2 ; 
           [0047]      FIG. 10  are progressive schematic views of the grain supply operation of the grain supply unit of  FIG. 4 ; 
           [0048]      FIG. 11  are progressive schematic views of the grain transfer operation of the grain transfer unit of  FIG. 6 ; 
           [0049]      FIG. 12  are schematic views of the opening and closing of the mold unit of  FIG. 1  in accord with the operation of the cam of  FIG. 8 ; 
           [0050]      FIG. 13  is a flowchart of a process of producing expanded-grain cakes using the machine of the present invention; 
           [0051]      FIG. 14  is a further flowchart of the process of transferring a charge of cereal grains according to the present invention; and, 
           [0052]      FIG. 15  is a flowchart of a process of producing expanded-grain cakes according to the present invention. 
           [0053]      FIG. 16  is a process sheet showing which sections of the molding machine are operating at each step of the molding process. 
           [0054]      FIG. 17  is a first flowchart realization of a control system for a grain cracker molding machine. 
           [0055]      FIG. 18  is a second flowchart realization of a control system for a grain cracker molding machine. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0056]    Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the attached drawings. 
         [0057]    The preferred embodiment is only one illustrative example and rather than limiting the bounds of the present invention, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the present invention. An initial general description provides a broad outline of the machine. 
         [0058]    Referring now to  FIGS. 1 and 2 , the expanded-grain cake machine  10  of the present invention is shown and the major subassemblies thereof are first described. The specific embodiment shown is constructed on a main frame or chassis  100 . Mounted thereon is a mold unit  200  into which grain is fed from the grain supply unit  300  and the grain transfer unit  400 . In processing the expanded-grain cake, a mold pressure arm  500  is cycled to and from the mold unit  200  by drive unit  600  and an open cam  700 . The processing is controlled by a control unit  800  described in more detail hereinbelow. The control unit  800  as well as the sensors, actuators, inputs and outputs with which the control unit  800  communicates are best understood in the context of the expanded-grain cake molding machine&#39;s construction and operation. The machine  10  is protected by cover components  900 . 
         [0059]    The base frame or chassis  100  forms the general framework of the machine  10  and is constructed to house the components and subcomponents of the device hereof. 
         [0060]    The mold unit  200  shown in detail in  FIG. 3 , is disposed in the front portion of the installation space of the frame  100 . The mold unit  200  includes upper and lower molds  210  and  220 , respectively. The mold unit  200  is constructed to receive a charge of cereal grains therewithin and, as described in greater detail below, during the mold closed portion of the processing cycle, to apply heat and pressure thereto, and during the open portion of the processing cycle to eject the molded cereal grain cake. The application of heat converts the moisture content of the cereal grains to entrapped steam, expands to a predetermined size as the admixture reaches ambient pressure. 
         [0061]    The grain supply or hopper unit  300  is mounted on the upper portion of the base frame  100  and feeds by gravity a predetermined amount of cereal grain to the mold unit  200  for each molding portion. 
         [0062]    The grain transfer unit  400  transfers cereal grains from the hopper  300  to the mold unit  200 . 
         [0063]    After placing a charge of grains in the mold, the mold pressure unit  500  vertically compresses the mold unit  200 , and, at the conclusion of the baking phase of the cycle, separates the upper mold  210  and the lower mold  220  from one another. Preferably, the mold pressure unit  500  moves the upper mold  210  reciprocally along a substantially vertical pathway with respect to the lower mold  220 . 
         [0064]    The drive unit  600  transmits rotational force to the mold pressure unit  500 . During a single rotation of the drive unit  600 , the working end of the mold pressure unit  500  is moved reciprocally along a substantially vertical path and sequentially provides a clamping force to and removes the same from the mold unit  200 . 
         [0065]    The cam  510  is rotated by the drive unit  600 . The cam  510  is configured so that a portion of the circumference thereof radically protrudes from the rotating shaft. The configuration thereby defines two time periods or phases, namely, (1) a baking phase during which heat and pressure are applied to the cereal grain admixture, and (2) a mold open phase during which a preform or molded cake is ejected, the mold is recharged with cereal grain, and the mold is returned to the closed state. The configuration of the cam  510  and the speed of the drive unit  600  determine the time apportioned to each phase. 
         [0066]    After the supplied cereal grains are molded into a preform, the cam  510  is positioned so that the pressure exerted upon the mold unit  200  by the mold pressure unit  500  is released. 
         [0067]    The control unit  800  measures the temperature of the mold unit  200 , monitors the position of the grain receptor well  332  to ensure grain delivery, monitors the position of the grain transfer unit  400 , monitors the position of the mold pressure arm  520  and the upper mold  210 , and measures the required preset conditions for the operation of the machine for producing expanding grain cakes of this invention. 
         [0068]    If any one of the monitored measurements and/or the preset conditions does not meet the requirements, the control unit  800  interrupts the operation of the drive unit  600 , the grain supply unit  300 , and the grain transfer unit  400  and issues a warning signal. 
         [0069]    Because the control interrupts operations when the machine  10  is not within preset conditions, malfunctioning is prevented. This control unit  800  intervention prevents components from being damaged, cereal grains from being burned, and cakes failing to expand because of insufficient entrapped steam, etc. 
         [0070]    The cover unit or housing  900  encloses the base frame  100  and protects the components installed in the base frame  100 . Besides the cover unit  900  improving the aesthetic appearance of the machine  10 , operating personnel are protected from moving parts, the housing protects the mold unit  200 , the grain supply unit  300 , the grain transfer unit  400 , the mold pressure arm  500 , the drive unit  600 , the open cam  700  and the control unit  800  which are installed in the base frame  100 . 
         [0071]    Besides the interrupts provided by control unit  800 , the control unit  800  upon measuring the required conditions continuously displays the temperature of the mold unit  200  and the level of the cereal grains present in the grain supply unit  300 . A visual display of the selected amount of cereal grains supplied by the grain supply unit  300  is provided as is a position indicator of the grain transfer unit  400  relative to the mold unit  200 . Some of these parameters may be adjusted by the operator during the course of processing. 
         [0072]    The temperature regulation of the mold unit  200  is preferably accomplished via use of Proportional Integral Derivative (PID) controls, which are well known to those skilled in the art. The PID control calculates an “error” value as the difference between a measured process variable and a programmed setpoint. The controller attempts to minimize the error by adjusting the process control inputs. 
         [0073]    The PID controller algorithm involves three separate constant parameters, which are the proportional, the integral and the derivative values, denoted P, I, and D. In simplest form, these values can be interpreted in terms of time P depends on the present error, I on the accumulation of past errors, and D is a prediction of future errors, based on current rate of change. The weighted sum of these three actions is used to adjust the process via the heating elements  230 . 
         [0074]    The construction of the machine  10  is now explained in greater detail. 
         [0075]    Referring now to  FIG. 3 , the mold unit  200  includes the upper mold  210 , the lower mold  220  and heating elements  230 . 
         [0076]    While the lower mold  220  is rigidly mounted to the base  100 , the upper mold  210  is flexibly coupled through coupling shaft  214  to the mold pressure arm  500 . The mounting arrangement includes spring tensioner  216 , which, when the mold pressure arm  500  is clamping the mold closed, is compressed thereby. Upon clamping release, the stored energy in the compressed spring throws the arm upwards. 
         [0077]    The mold cavity is defined by the upper open portion  212  in the underside of upper mold  210  and the mating lower open portion  222  in the lower mold  220 . With the mold unit  200  in an open condition, cereal grains are supplied to the lower open portion or grain receptor. Thereafter the mold is closed and, upon the application of heat, the cereal grains expand to fill the mold cavity and, in turn, entrap steam from the evaporating moisture content thereof Thus, the mold cavity limits the initial grain expansion and defines the size and shape of a preformed grain cake. The preform further expands upon opening of the mold unit during the ejection therefrom. The further expansion results from the entrapped steam returning to ambient pressure. 
         [0078]    The two heating elements  230  are respectively provided in the upper mold  210  and the lower mold  220 . The heating elements  230  heat the upper and lower molds  210  and  220  and maintain the predetermined process temperature. 
         [0079]    To compensate for heat losses during the mold open phase, the upper and lower molds  210  and  220  are heated by the heating elements  230  to an initial temperature higher than the temperature required during the normal baking process. This compensation for the heat loss experienced while the cavity is being refilled enables the system to return quickly to operating temperatures. 
         [0080]    Referring now to  FIG. 4 , the grain supply unit  300  is shown with blocking unit  380  and the grain storage hopper  310  of the grain supply unit  300 . The grain supply unit  300  has a cover or lid  312  and functions as a storage vessel for cereal grains, from which vessel grain is gravity fed to the mold unit  200 . The cereal grains move downwards from the grain storage hopper  310  through an opening which is formed in the lower end of the grain storage hopper  310 . 
         [0081]    A hopper connection tube  370  extends between the grain storage, hopper  310  and the rotor housing  320  and is a conduit for the cereal grain supply from the grain storage hopper  310  to the rotor housing  320 . The hopper connection tube  370  is tapered at the lower end thereof so that the outlet is equal to or smaller than inlet  324  of rotor housing  320 . 
         [0082]    A second supply pipe or funnel  375  provides a conduit for the charge of cereal grain supplied from the rotor housing  320  to the grain transfer unit  400 . The supply funnel  375  is configured such that the inner surface of the upper end thereof is inclined from the bottom to the top in a direction away from the center axis thereof. 
         [0083]    The supply funnel  375  communicates with outlet  326  of the rotor housing  320  and supplies cereal grains from the rotor housing  320  to the grain transfer unit  400 . The blocking unit  380  is disposed between the grain storage hopper  310  and the hopper connection tube  370  and is constructed to selectively interrupt the flow of cereal grain from the grain storage hopper  310  to the hopper connection tube  370 . 
         [0084]    When the lid  312  of the grain storage hopper  310  is opened to load cereal grain into the hopper  310  or remove cereal grain from the hopper  310 , the blocking unit  380  closes the conduit and halts the transfer of cereal grain from the grain storage hopper  310  to the hopper connection tube  370 . The sensor unit  390  has three sensors—a first sensor  392 , a second sensor  394  and a third sensor  396 . The first sensor  392  is mounted adjacent motor  350  and measures the angular position of the rotor driving motor  350  shaft. 
         [0085]    The second sensor  394  is mounted adjacent rotor  330  and measures the angular position of supply rotor  330 . The third sensor  396  monitors the hopper connection tube  370  to determine whether it is filled with cereal grains. 
         [0086]    The angular position data from the first sensor  392  and the second sensor  394  and grain supply available/unavailable data from the third sensor  396  are transferred to the control unit  800 . The control unit  800  compares the transferred values to the reference values and controls the grain supply unit  300 . 
         [0087]    In the present invention, the grain storage hopper  310  is made of transparent material. This allows the user to observe the remaining amount of cereal grain in the hopper  310  and to determine when cereal grain should be added. 
         [0088]    Referring now to  FIG. 5 , the blocking or shutoff unit  380  includes a first supply pipe or hopper outlet pipe  382 , a bracket  384  and a blocking plate  386 . 
         [0089]    The hopper outlet pipe  382  is fitted to the upper end of the hopper connection tube  370  to transfer cereal grain from the grain storage hopper  310  into the hopper connection tube  370 . The bracket  384  is disposed between the upper end of the hopper outlet pipe  382  and the grain storage hopper  310 . 
         [0090]    A supply opening  384   a  extending through the central portion of the blocking bracket  384  transfer cereal grain from the grain storage hopper  310  into the hopper connection tube  370 . The bracket  384  is dimensioned to house the blocking or shutoff plate  386  therewithin. The shutoff plate  386  is movably inserted into the guide slot  384   b  to selectively open or close opening  384   a . A handle  386   c  shown at the outer end of the shutoff plate  386  allows the user to slide the shutoff plate  386  back and forth along guide slot  384   b.    
         [0091]    The shutoff plate  386  is configured with nonremoval tabs to prevent the removal thereof from the blocking bracket  384 . Similarly, the shutoff plate  386  is configured with limit tabs which, when the plate  386  completely closes the supply opening  384   a,  the limit tabs stop the shutoff plate  386  travel at the blocking bracket  384  and reach the insertion endpoint. Because of this configuration, this structure of the blocking unit  380 , the shutoff plate  386  is selectively positionable to open and close the supply opening  384   a  without being removed from the blocking bracket  384 . 
         [0092]    In the present invention, the blocking unit  380  is removably coupled to the hopper connection tube  370 , and with the shutoff plate  386  closed, the grain storage hopper  310  along with the blocking unit  380  are removable from the hopper connection tube  370 . Such configuration simplifies loading cereal grain into the grain storage hopper  310 . 
         [0093]    As shown in  FIG. 6 , a grain transfer unit  400  is housed in a mounting bracket  410 . The grain transfer unit  400  is constructed to include a grain carrier  420  and a grain distributor  430 . The grain carrier  420  and the grain distributor  430  are driven together by a first pulse motor or drive unit  460 . The grain transfer unit  400  has a separately driven plate or support  440  which is driven by a second pulse motor or drive unit  450 . 
         [0094]    The mounting bracket  410  is housed in chassis  100 . The grain carrier  420  and distributor  430  are rotatably coupled at a first end thereof to the inner surface of a top plate of the mounting bracket  410 . An inlet  422  is formed through a second end of the grain carrier  420  enabling the carrier to receive metered amounts of grain from the grain supply unit  300 . 
         [0095]    The grain distributor  430  is coupled to the second end of the grain carrier  420  and has an outlet  432  permitting the gravity flow of grain therethrough. The grain distributor  430  has mounted therewithin a guide and guide blade assembly  434  for evenly distributing the grain on plate  440  at outlet  432 . 
         [0096]    Furthermore when the grain transfer unit  400  is rotated into position over lower mold  220  of mold unit  200 , an actuator  436  of the grain distributor  430  causes the plate  440  to rotate and release the distributed and metered grain through outlet  432  to lower mold  220 . 
         [0097]    After transfer, the actuator  436  reunites with plate  440  and the empty grain carrier  420  along with grain distributor  430 . Then and places the unit is positioned to receive another metered charge of grain from the grain receptor well  332  of grain supply unit  300 . 
         [0098]    The plate or support  440  is provided under the grain distributor  430  and has the same rotational track as that of the grain distributor  430 . In addition, the plate  440  is rotatably coupled at the first end thereof to the inner surface of a bottom plate of the mounting bracket  410  such that the first end of the plate  440  is coaxial with the first end of the grain distributor  430 . A second end of the plate or support  440  selectively opens or closes the outlet  432 . 
         [0099]    The first drive unit  450  includes a first motor  456 , a first drive gear  454  and a first driven gear  452 . The first motor  456  generates rotational force and is housed in mounting bracket  410 . 
         [0100]    The first driven gear  452  is provided under the first end of the plate  440 . The drive train in this embodiment is comprised two gears—drive gear  454  and driven gear  452 —having different diameters. This gear arrangement transmits the rotational force from the drive gear  454  of the first pulse motor  456  to the first driven gear  452  and, in turn, to the plate  440 . 
         [0101]    The second drive unit  460  includes a second pulse motor  466 , a second drive gear  464 —fitted over the output shaft—and a second driven gear  462 . The second motor  466  is fastened to the mounting bracket  410  and generates rotational force to grain carrier  420 . 
         [0102]    The second driven gear  462  is provided on the first end of the grain carrier  420 . The second drive gear  464  is mounted on the output shaft of second pulse motor  466  and transmits the rotational force from the drive gear of the second pulse motor  466  to the second driven gear  462 . 
         [0103]    The drive units  450  and  460  are controlled by the control unit  800 . The plate  440  is rotated by the first drive unit  450 . The grain carrier  420  is rotated by the second drive unit  460 . 
         [0104]    The grain carrier sensor unit  470  includes a first sensor  472  and a second sensor  474  which are respectively disposed on the bottom and top plates of the mounting bracket  410 . In detail, the first sensor  472  is provided under the bottom plate of the mounting bracket  410 . The first sensor  472  measures a rotation angle of the first drive unit  450  and a position of the plate  440  and transmits the measured values to the control unit  800 . 
         [0105]    The second sensor  474  is provided on the top plate of the mounting bracket  410 . The second sensor  474  measures a rotation angle of the second drive unit  460  and a position of the grain carrier  420  and transmits the measured values to the control unit  800 . 
         [0106]    The operation of the grain transfer unit  400  is now explained. The grain carrier  420  and the plate  440  are initially united the one with the other to form a vessel for receiving a metered charge of grain and are disposed below the grain supply unit  300 . In this state, cereal grains supplied from the grain supply unit  300  are held by the grain transfer unit  400  for the next cycle. 
         [0107]    After the cereal grains are deposited in the grain transfer unit  420  the plate or support  440  is rotated by the first drive unit  450  away from the cereal grain supply unit  300  to the mold unit  200 . When the plate or support  440  rotates, the actuator  436  of the grain distributor  430  is carried thereby and the entire grain transfer unit  400  is rotated. 
         [0108]    Subsequently, the plate or support  440  along with the grain carrier  420  is positioned above the cavity  222  of the lower mold  220 . The first drive unit  450  thereafter rotates the plate or support  440  towards the grain supply unit  300 . Then, the outlet  432  becomes open, so that the cereal grains which have been evenly distributed in the grain carrier  420  are gravity fed to mold cavity  222 . Subsequently, the grain carrier  420  is rotated towards the grain supply unit  300  by the second drive unit  460  and thus positioned onto the plate or support  440 , thus completing a single grain transferring process of the grain transfer unit  400 . 
         [0109]    During the grain transfer process, the first sensor  472  and the second sensor  474  respectively detect the positions of the plate or support  440  and the grain carrier  420 . If an error occurs, the control unit  800  stops the operation of the expanded grain cake machine. 
         [0110]    Referring now to  FIG. 7 , a ferrous impurity removal unit  480  is mounted adjacent actuator  436  in the grain distributor  430 . The ferrous impurity removal unit  480  has a magnet  482  to attract and retain ferrous impurities and an impurity collection site  484  therebelow. 
         [0111]    Ferrous impurities may from time-to-time be imparted to the grain supply and enter the mold cavity  222  of the lower mold  220 . In the present invention, the ferrous impurity removal unit  480 , which rotates along with the grain transfer unit, can collect such ferrous impurities and remove the ferrous impurities from the grain supplied prior to the grain cake formation. 
         [0112]    Referring now to  FIG. 8 , the mold pressure unit  500  is shown and cam unit  510 , a pressing arm  520 , a rotary block  530  and a pressure adjustment unit  540 . During the closed-mold phase of operation, heat is applied to the mold contents and evaporates and entraps the moisture content of the charge of grain. The maintenance of pressure in the mold cavity utilizes the gases formed during this phase as propelling means for the ejection of the preform and as an expansion or blowing means to expand the preform to a cake of the desired final size. 
         [0113]    The cam unit  510  includes a cam shaft  512  and a cam  514 . The cam shaft  512  is rotatably supported by the frame  100  and is rotated by the main machine drive unit  600 . 
         [0114]    The cam  514  is fixedly mounted on the cam shaft  512  and rotates with the cam shaft  512 . The cam  514  is configured such that a distance travelled by the circumference thereof and by the cam shaft  512  varies along the circumferential direction. The cam  514  rotates the pressure arm  520 . 
         [0115]    The pressure arm  520  is rotatably supported at a medial portion thereof by the frame  100 . A cam follower  522  is provided on a first end of the pressure arm  520 , and at a second end of the pressure arm  520 , a pivot or mounting arrangement  525  is provided for the pressure adjustment unit  540 . 
         [0116]    As the cam follower  522  provided at the first end of the pressure arm  520  traces the circumference of the cam  514 , the pressure arm  520  rotates around the pivot  525  thereof Thereby, the second end of the pressure arm  520  moves along a predetermined path which alternates between maintaining pressure within the mold and releasing the pressure therewithin. 
         [0117]    The rotary block of coupling  530  is rotatably mounted below the second end of the pressure arm  520 . The rotary block  530  moves concurrently with the second end of the pressure arm  520 . As described in further detail hereinbelow, the second end of the pressure arm is flexibly coupled to the rotary block  530  through pressure adjustment unit  540 . 
         [0118]    In other words, when contact between the cam follower  522  is released at the first end of the pressure arm  520 , the first end of pressure arm  520  falls downwardly and the second end of the pressure arm  520  is raised upwardly. The upward movement, which carries with it rotary block  530  and the upper mold  210 , is aided by the pressure build up in the cavity. The rotary block  530  on the second end of the pressure arm  520  is structured to move upwardly and downwardly without being removed from pressure arm  520 . 
         [0119]    Furthermore, a hemispherical pressing depression  532  is formed in the upper surface of the rotary block  530 . A lower end of the rotary block  530  is rotatably coupled to the upper mold  210 . As such, the rotary block  530  couples the pressure arm  520  to the upper mold  210 , permitting the upper mold  210  to move reciprocally along a substantially vertical pathway resulting from pressure arm  520  rotation being translated into linear movement. 
         [0120]    The pressure adjustment unit  540  is provided in the second end of the pressure arm  520  and functions to control the end play of the rotary block  530  As the end play of the rotary block  530  is minimized, the pressure which the upper mold  210  and the lower mold  220  retain in the mold cavity is maximized. 
         [0121]    The pressure adjustment unit  540  includes a stationary nut  542 , and adjustment rod  544 , a ball  546  and an adjustment knob  548 . The pressure adjustment unit  540  is disposed in aperture  524  of the pressure arm  520  and an internal thread on the inner surface of the stationary nut  542  provides for a fine adjustment of the endplay. 
         [0122]    An external thread corresponding to the internal thread of the stationary nut  542  is formed on the circumferential outer surface of the adjustment rod  544 . Thus, the adjustment rod  544  is threadedly mounted to the stationary nut  542  and the pressure adjustment unit is movable towards and away from the rotary block  530 . 
         [0123]    Furthermore, a hemispherical seat  545  is formed in the surface of the lower end of the adjustment rod  544 . The upper portion of ball  546  is seated into the hemispherical seat  545  and the lower portion of the ball  546  is seated in the hemispherical seat  532  of the rotary block  530 . Therefore, the rotary block  530  coupling of the pressure arm  520  to the upper mold  210  is maintained through the adjustment rod  544  in a manner similar to that of a ball and socket joint. 
         [0124]    Upon rotation of the adjustment knob  548  on the upper end of the adjustment rod  544 , the adjustment rod  544  rotates along the internal thread of the stationary nut  542  and moves in the longitudinal direction. Thereby, the end play between adjustment rod  544  and the rotary block  530  is adjusted. 
         [0125]    The longitudinal direction of the adjustment rod  544  means a direction parallel to an extension line passing both through the center of the upper and lower ends of the adjustment rod  544 . Thus, the position of the adjustment rod  544  is adjusted by rotating the adjustment know  548 . Thereby, the adjustment in position of the rotary block  530  varies the end play of the pressure arm and determines the pressure build up in mold  200 . The pressure adjustment unit  540  precisely adjusts the pressure retained in the mold  200 . 
         [0126]    In the present embodiment, an additional hemispherical pressure arm seat  534  is formed in the lower surface of the rotary block  530 . A ball  547  is seated into the hemispherical pressure arm seat  534  and then the movement of the block  530  with respect to the upper mold  210  is similar to that of a ball and socket joint. A hemispherical seat is formed in the upper surface of the upper mold  210  for accommodating ball  547 . 
         [0127]    Because of the manner in which balls  546  and  547  are mounted on the upper and lower surfaces of the rotary block  530 , the rotary block  530  mimics movement of a ball and socket joint. The rotation of the pressure arm  520  is converted into linear movement above the upper mold  210  and, simultaneously, the required pressure is retained in the mold cavity by the positioning of the pressure arm  520 . The pressure meets that required for reliably ejecting the molded preform from the mold  200  and having the preform follow a substantially predictable trajectory. 
         [0128]    Referring now to  FIG. 9 , the drive unit  600  is constructed with a drive motor  610 , a drive sprocket  620 , a first driven sprocket  630 , a chain  640 , a tension sprocket  650  and a second driven sprocket  660 . 
         [0129]    The drive motor  610  is supported by the frame  100 . The drive sprocket  620  is rotated by the drive motor  610  and includes at least two gears having different diameters. The first driven sprocket  630  is mounted on the mold pressure unit  500  and transmits rotational force to the mold pressure unit  500  which operates during the mold-closed phase of the machine processing cycle. The chain  640  connects the first driven sprocket  630  to the drive sprocket  620  and transmits rotational force from the drive sprocket  620  to the first driven sprocket  630  thereby operating the mold pressure unit  500 . 
         [0130]    The chain  640  connects one of the gears of the drive sprocket  620  to the first driven sprocket  630  to transmit rotational force therebetween. 
         [0131]    The tensioning sprocket  650  presses a portion of the chain  640  towards a line extending from the center of the drive sprocket  620  to the center of the first driven sprocket  630 , and maintains the tension of the chain  640 . Thereby, the rotational force of the drive motor  610  is uniformly transmitted to the first driven sprocket  630 . 
         [0132]    The second driven sprocket  660  connects to the open cam  700 , engages with another gear of the drive sprocket  620 , and transmits the rotational force from the drive sprocket  620 . The open cam  700  imitates operations during the mold-open phase of the machine operating cycle. 
         [0133]    The open cam  700  is rotated by the same rotational force as the rotational force which is transmitted to the mold pressure unit  500 . Thus, after the molded preform is ejected from the mold  200 , the upper mold  210  moves upwards to facilitate the recharging of the mold cavity, the cam follower  522  disengages from cam  514  allowing the mold pressure unit  500  to rotate counterclockwise and to move the upper mold  210  upwards. 
         [0134]    Referring now to  FIGS. 1 and 2 , the cover unit  900  is constructed with a front cover  910 , a rear cover  920  and side covers  930 . 
         [0135]    The cover unit  900  shields the machine operators from access to the major moving parts of the machine  10  and thereby creates a safer work environment. The front cover  910  is assembled to the front portion of the frame  100  and protects the mold unit  200 . The front cover  910  comprises upper and lower portions which protect the upper mold  210  and the lower mold  200 , respectively. 
         [0136]    The rear cover  920  is disposed on the rear portion of the frame  100  and protects the machine from impurities, such as dust and water. 
         [0137]    The side covers  930  on opposite sides of the frame  100  house the control unit  800  and protect the grain transfer unit  400 . 
         [0138]    The side covers  930  are made of acrylonitrile butadiene styrene (ABS) material which absorbs external shocks and reduces the weight of the machine  10 . 
         [0139]    The control unit  800  has operating controls  810  for automatic (programmed) or manual control of machine  10 . The control unit  800  provides for programmatic changes for the drive unit  600 , the grain supply unit  300  and the grain transfer unit  400 . 
         [0140]    The control unit  800  further includes a screen  820  which displays the current operating conditions, reports malfunctions, or indicates a shortage in the supply of cereal grains. To maintain the productivity of the machine  10 , the indicators may be either visual or audible signals. 
         [0141]    The control unit  800  has an emergency button  830  which, when necessary, stops the operation of the drive unit  600 , the grain supply unit  300  and the grain transfer unit  400  and provides additional safety provisions. 
         [0142]    In the present invention, the heaters  230  are programmed and the initial temperature of the mold unit  200  is set by the control unit  800  at a level higher than that required during the mold closed phase. This compensates for heat loss when the mold is open. Thereafter, with the mold  200  closed the temperature is adjusted so that the total thermal energy required for the full cycle develops the entrained gases to eject the preform and, upon release, to expand the cake to the desired size. Thus, the present invention reliably prevents defective preform formation even for the first charge of grain processed. 
         [0143]    The control unit  800  is provided on at least one of the opposite sides of the frame  100 . Preferably, two control units  800  are respectively provided on the opposite sides of the frame  100  to facilitate access by the operator. The two control units  800  are duplicates of one another and any setting on one of the control units is reflected at the control unit on the opposite side. 
         [0144]    Referring now to  FIGS. 10 ,  11  and  12 , the operation of the machine  10  for producing expanded-grain cakes according to the present invention is described below. Cereal grains are loaded into the grain storage hopper  310 . The conditions at startup are (1) the grain storage unit  300  is positioned above the grain transfer unit  400 ; (2) the cam follower  522  of mold pressure unit  500  is released from cam  514  and mold  200  is open; and, the upper and lower molds  210  and  220 , respectively, are at elevated temperatures sufficient to compensate for ambient conditions. Optionally, the batch size is set by the control unit  800 . When these conditions are met, the control unit  800  operates the grain supply unit  300  and the grain supply unit  300  meters a precise amount of cereal grains required for a single mold charge to the grain transfer unit  400 . 
         [0145]    The operation of the grain supply unit  300  is now explained in more detail. As shown in  FIG. 10 , a precise amount of cereal grains required for a single mold charge is metered by the grain receptor well  332  of the supply rotor  330 . The cereal grain is gravity fed through the blocking unit  380  and the hopper duct  370  to the inlet  324  of supply rotor  330 . 
         [0146]    Subsequently, rotational force of the rotor driving motor  350  is transmitted to the supply rotor  330  through the power transmission unit  360 ,—comprised of motor  350 , pulleys  362  and belt  364 —and rotates the supply rotor  330  by 180° to align with outlet  326 . Then the single charge of the cereal grains which has been limited by the interior wall  322  of rotor housing  360  and by the grain receptor well  332  capacity is supplied to the grain transfer unit  400  through the outlet  326  and the supply funnel  375 . 
         [0147]    The grain transfer unit  400  containing the cereal grains is moved into the space above the lower mold  220 . Thereafter, the single charge of cereal grain is supplied from the grain transfer unit  400  into the lower open portion  222  of the lower mold  220 . The grain transfer unit  400  is subsequently returned to its initial position below the grain supply unit  300 . 
         [0148]    With regard to the operation of the grain transfer unit  400 , as shown in  FIG. 11 , the grain carrier  420 , the grain distributor  430 , and the plate  440  thereunder are driven together by the first drive unit  450  from the grain supply unit  300  to the space above the lower mold  220 . When the plate  440  rotates away from the grain supply unit  300 , the grain distributor  430  operates to evenly distribute the grain over the surface of the lower mold  220 . 
         [0149]    Thereafter the plate  440 , as seen most clearly in  FIG. 11 , is driven in a clockwise direction and releases and evenly spreads the charge of cereal grain over the lower open portion  222  of lower mold  220 . When the first drive unit  450  is operated to rotate the plate  440 , the second drive unit  460  simultaneously operates to rotate the grain carrier  420 . In addition, the first drive unit  450  and the second drive unit  460  are controlled by the control unit  800 . During this phase of processing, when an error occurs, the first and second drive units  450  and  460  are stopped by control signals from the control unit  800 . While the charge of grain is being transferred the cam  514  continues counterclockwise until the cam follower  522  again engages cam  514 . 
         [0150]    As seen in  FIG. 12 , from the above state, the control unit  800  operates the drive unit  600  to rotate the mold pressure unit  500  downwards, thereby closing the preheated mold. Then, the upper mold  210  and the lower mold  220  are tightly clamped together as the moisture content of the cereal grains contained in the closed mold  200  is heated and transformed into a gaseous phase. During this phase, the pressure within the closed cavity rises, cereal grain expansion occurs limited by the mold cavity walls, and a preform with entrapped high pressure steam therewithin results. 
         [0151]    The closed-mold phase occurs over a predetermined time. The term “a predetermined time” means the time during which the cam follower  522  travels along the protruding portion of the cam  514 . 
         [0152]    The operation of the mold pressure unit  500 , the mold unit  200  and the open cam  700  by the drive unit  600  is explained in more detail. As shown in  FIG. 12 , the cam unit  510  is rotated by the drive unit  600 . The first end of the pressure arm  520  is moved by the rotation of the cam unit  510 . 
         [0153]    Here, the pressure arm  520  which is rotatably supported at the medial portion thereof by the frame  100  is moved along the circumference of the cam  514  of the cam unit  510 . In detail, the cam follower  522 , mounted on the first end of the pressure arm  520 , traces the protruding portion of cam  514  and rotatably moves along that portion of the cam  514 . 
         [0154]    When the first end of the pressure arm  520  is moved by the cam unit  510 , the second end of the pressure arm  520  rotates downwards around the medial portion thereof The rotary block  530  which is coupled both to the second end of the pressure arm  520  and to the upper end of the upper mold  210  is moved downwards by the rotation of the pressure arm  520 . 
         [0155]    Here, because the upper end of the rotary block  540  is rotatably coupled to the second end of the pressure arm  520  and the lower end thereof is rotatably coupled to the upper end of the upper mold  210 , the rotation of the pressure arm  520  is smoothly converted into the linear motion of the upper mold  210 . 
         [0156]    As such, the upper mold  210  and the lower mold  220  are in a closed mold condition. Because of the mold structure maintains the condition during increasing pressure within the mold cavity. Upon release by the cam reaching the end of the portion thereof, the preform is forcibly ejected from the mold  200 . 
         [0157]    When the cam follower  522  of the pressure arm  520  completely passes through the protruding portion of the cam  514 , the first end of the pressure arm  520  falls downwardly thereby releasing the clamping force and releasing the stored energy in spring tensioner  216 . The upper mold  210  then moves upwardly aided additionally by the pressure build up in the cavity and, simultaneously, the mold pressure arm  520  is rotated. 
         [0158]    The pressure arm  520  is rotated such that the first end of the pressure arm  520  falls downwardly, that is, towards the circumference of the cam  514 , and the second end thereof is rotated upwardly. 
         [0159]    When the preform is ejected from the mold unit  200 , the entrapped gases therewithin cause the preform to expand and form a cake of the desired size. The protruding portion of the cam unit  510  which rotates in the direction opposite to the direction in which the cam unit  510  is rotated by the drive unit  600  pushes the cam follower  522  of the pressure arm  520  downwards, and assists the upper mold  210  to move upwards. 
         [0160]    The process of the operation of the machine  10  according to the present invention is explained below. As shown in  FIGS. 13 through 16 , when power is turned on, the control unit  800  initializes the components to conduct the first operating cycle.  FIG. 13  illustrates the basic operation of the molding machine, including the grain level sensing and control looping if grain is still present. 
         [0161]    The term “initialization” means checking that the grain supply unit  300  is filled with cereal grain; that the grain transfer unit  400 , the mold pressure unit  500 , and mold unit  200  are at the correct starting positions and that the drive unit  600  is operative. Optionally, the operator may set the control unit  800  for the number of processing cycles in the initial batch. 
         [0162]    Thereafter, the mold unit  200  is heated to a preset temperature which initiates the program delivery of thermal energy by the heater  230 . The program compensates for thermal energy losses when the upper and lower molds  210  and  220  are in the mold open state. The program supplies a uniform amount of thermal energy to the mold unit  200  to produce sufficient gaseous content for preform expansion and preform flight on a substantially reproducible trajectory. Under the control of control unit  800 , after the upper and lower molds  210  and  220 , respectively, are closed, the initial temperature is reduced as the closed system no longer requires compensation for heat losses. 
         [0163]    Upon the initiation of the drive unit  600 , the cam unit  510  and during the mold-open phase, the cam follower  522  of the pressure arm  520  is not yet in contact with the protruding portion of the cam  514 . In addition, as the pressure adjustment unit  540  is in a fully raised condition the upper mold  210  is spaced apart from the upper surface of the lower mold  220 . 
         [0164]    The initial charge of cereal grain is delivered to mold cavity  222  of the lower mold  200 . The supply of cereal grains into the mold cavity  222  is conducted by the grain supply unit  300  and the grain transfer unit  400 . This operation is explained in more detail hereinbelow with reference to  FIG. 14 . 
         [0165]    After a charge of the cereal grain is supplied from the grain storage hopper  310  to the grain receptor well  332  of supply rotor  330 , the rotor driving motor  350  rotates the supply rotor  330  and, in doing so, precisely meters the charge of cereal grain. Then the charge of cereal grain is gravity fed from supply rotor  330  to the grain transfer unit  400 . 
         [0166]    The charge of cereal grain enters the grain transfer unit  400 , which is positioned below the grain supply unit  300 , through inlet  422  of the grain carrier  420  and is disposed on the lower end of which is closed by the plate or support  440 . 
         [0167]    Thereafter, the grain carrier  420  and the support  440  are moved over the lower mold  220  by the operation of the first and second drive units  450  and  460 , respectively. During transit the cereal grain is evenly distributed over the support  440  and, upon further movement of the support  440 , deposits the charge on the lower open portion  222  of the lower mold  220  through outlet  326 . Subsequently, the support  440  and the grain carrier  420  are returned to their original positions, that is, below the grain supply unit  300 . It is noted that the support  440  is the first to return to the original position and grain carrier  420  and grain distributor  430  follow thereafter. 
         [0168]    The sensor unit  470  detects the positions of the grain carrier  420  and the support  440  and transmits the detected signals to the control unit  800 . The control unit  800  checks the positions of the grain carrier  420  and the support  440 . If it is determined that the grain carrier  420  and the support  440  are correctly positioned at the original positions, the control unit  800  maintains such positions for a predetermined, dwell time and upon the elapse of the time period, repeats the above-mentioned process. If it is determined that either the grain carrier  420  or the support  440  is not positioned at the correct original positions, the control unit  800  interrupts the operation of all the components. 
         [0169]    The closed-mold phase of operations is next described. This entails the closing of the mold unit  200  and thereafter continuously increasing pressure in the mold unit  200  by applying heat. The closed-mold phase ends with the release of the preform, and, upon release, the expansion thereof to the desired expanded cereal grain cake size. The process requires operating the mold pressure unit  500  in conjunction with operating the drive unit  600 . This process is explained in more detail with reference to  FIG. 15 . 
         [0170]    The first end of the pressure arm  520  is pushed by the protruding portion of the cam  514  which is rotated by the drive unit  600  resulting in the second end of pressure arm  520  rotating downward. The upper mold  210  which is coupled to the second end of the pressure arm  520  through the coupling  530  is moved onto the lower mold  220 , thus closing the mold unit  200 . 
         [0171]    At this time, the open portion  222  of the lower mold  220  has evenly distributed thereover a charge of cereal grain. In the closed-mold phase, the thermal energy received by the closed-mold unit  200  causes the cereal grain to expand, which expansion is limited by the walls of the mold thereby forming a rudimentary preform with ever-increasing entrained gases therewithin. 
         [0172]    After a predetermined period of time, the pressure builds and, upon opening of the mold unit  200 , the expanding preform is forcibly ejected from the mold by the gases entrained at high pressure, causing further expansion until the gases reach ambient pressure. 
         [0173]    The term “a predetermined period of time” is the time taken to move the cam follower  522  at the first end of the pressure arm  520  along the protruding portion of the cam  514 . When the first end of the pressure arm  520  completely passes through the protruding portion of the cam  514 , the clamping force on the mold unit  200  is released and, simultaneously, the preform is ejected as previously described. 
         [0174]    Preferably, after the limited expansion of the charge of cereal grains, the upper mold  210  is moved slightly upwards to control the release of pressure from the mold unit  200  and the direction of the preform trajectory. 
         [0175]    During the opening of the mold unit  200 , the upper mold  210  is moved upwards by the internal pressure and, simultaneously, the open cam  700  rotated by the drive unit  600  pushes the cam follower  522  of the pressure arm  520  downwards, further accelerating the upwards movement of the upper mold  210 . 
         [0176]    Thereafter, the control unit  800  monitors the positions of the mold unit  200  and the pressure arm  520  by sensing the position of the cam unit  510 . When it is determined that the mold unit  200  and the pressure arm  520  are at the correct positions for recharging the mold cavity, the cycle is repeated. If it is determined that the mold unit  200  and the pressure arm  520  are not at the correct positions, the control unit  800  interrupts operations of all the components. 
         [0177]    After the completion of the above-described cycle, the cereal grain hopper  310  of the grain supply unit  300  is checked. When the sensor  390  indicates that there is no cereal grain in hopper connection tube  370 , the control unit  800  interrupts the operations of all the components. Further, an alarm signal is generated and malfunction of the machine  10  is prevented. 
         [0178]      FIG. 16  illustrates the stepwise operation of major functional sections of the molding machine, these being the heater, the main cam, the main lever, the ingredient transferor, the ingredient deliverer, and the mold. For each step, the active functional sections are highlighted for actions performed. 
         [0179]      FIG. 17  and  FIG. 18  show two realizations of a control system for the molding machine. Of particular importance is the use of a PID control means for setting and regulating the temperature in the mold. The use of a standard, cost-effective yet sophisticated temperature control allows the production of much more uniformly baked grain crackers than previous grain cracker molding machines were capable of producing. 
         [0180]    As described above, in a machine for producing expanded-grain cakes according to the present invention, a control unit checks the temperature of a mold unit, the amount of cereal grains and a position of the grain transfer unit and compares the checked values to preset conditions required for producing expanded grain cakes. When the checked values meet the preset conditions, the operation is allowed to continue. Therefore, cereal grains are prevented from being burned in the mold unit, thus preventing defective formation of the expanded-grain cakes and reducing the waste of cereal grains. Furthermore, when the control unit detects a malfunction in the drive unit, the grain supply unit or the grain transfer unit, the operation of the components is immediately interrupted, thus preventing accidents, enhancing the operational reliability of the machine, and extending the lifetime of the machine. 
         [0181]    Although the preferred embodiment of the present invention has been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.