Abstract:
A food processor incorporates an electronic motor control and display. Times relevant to the operation of the food processor are displayed for reference by the user. A user can select a food processing cycle duration, in which case the display is operated in a count-down mode. If no duration is selected, the display is operated in a count-up mode. Measured motor speed is used by a microprocessor based motor control circuit to regulate power delivered to the drive motor. A programmed auto pulse function delivers power to the drive motor in an on off pattern, freeing the user&#39;s hands. A safety switch is arranged to sense the presence or absence of the food pusher in the chute. Operation of the food processor drive motor is paused until the food pusher is replaced in the chute. The food processor is provided with a high-speed function.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a household food processor and more particularly to a microprocessor-based control circuit for controlling energization of the food processor drive motor. 
     2. Description of the Related Art 
     It has been traditional for food processors to have mechanical switches which permit two basic operational functions. In the first function, the switch is placed in an “on” position where the drive motor runs constantly until the switch is removed from the “on” position. A second switch (or function of the first switch) is a “momentary” or “pulse” operation where the drive motor is energized as long as the switch is held in the “pulse” position. This arrangement for controlling the drive motor of a food processor requires the user to closely attend the unit and manually control the “pulse” pattern to achieve the desired performance. Since food processors typically do not include any indication of the duration of a manually controlled cycle, the user may have difficulty reproducing a successful cycle. 
     The typical food processor does not include a safety mechanism related to the feeding chute. Therefore, the motor remains running even when the feeding chute has been removed, for example, to add ingredients. 
     Further, the typical food processor is a single speed device. The user has no option for altering the rotational speed of the drive motor. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a new and improved electronic food processor that permits a user to accurately reproduce a successful food processing cycle. 
     Another object of the present invention is to provide a new and improved electronic food processor with enhanced convenience and safety features. 
     An electronic food processor in accordance with the present invention incorporates a microprocessor-based electronic control system which acts as an intelligent interface between the user and the food processor drive motor. The user interacts with the microprocessor-based control system by means of a control panel. The control panel includes a liquid crystal display (LCD), light emitting diode (LED) indicators and contact switches. The LCD and LED indicators provide feedback from the electronic control circuit to the user. The user can select among the various functions using the contact switches located on the control panel. 
     One of the functions selectable by the user through the keypad is the duration of a given food processing cycle. Restated, the control system permits the user to pre-determine a desired end time for the food processing cycle. When the user has selected a pre-established end time, the microprocessor control circuit causes a time remaining to be displayed on the LCD screen in a count down format. Alternatively, the user may simply start the food processor. In which case, an elapse time is displayed on the LCD in a count up format. 
     In accordance with another aspect of the invention, the microprocessor based control system is provided with programmed instructions for responding to inputs from the user and sensors on the food processor. The user can select an “auto-pulse” function in which the food processor drive motor is automatically cycled on and off for predetermined periods in accordance with the programmed instructions. 
     Safety of the electronic food processor is enhanced by including a “pause” feature that removes energy from the drive motor whenever the feed chute is removed. When the feed chute is replaced, the food processing cycle resumes. A food processing cycle can also be paused by pressing the appropriate key on the control panel. 
     The food processing capability of the electronic food processor is improved by providing an optional high speed for the drive motor. The high speed function can be activated at any time during food processor operation. Motor control is accomplished electronically by the microprocessor based control system in accordance with the programmed instructions and in response to user and sensor inputs. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exterior view of an electronic food processor in accordance with the present invention; 
     FIG. 2 is an expanded view of a control panel for use in conjunction with the electronic food processor of FIG. 1; 
     FIG. 3 is a functional block diagram of the electronic food processor of FIG. 1; 
     FIG. 4 is a schematic diagram illustrating the circuitry of the electronic food processor of FIG. 1; 
     FIG. 5 is a flow chart illustrating one portion of the programmed instructions for the electronic food processor of FIG. 1; 
     FIG. 6 is a graphical illustration of the auto-pulse function; and 
     FIGS. 7-11 are flow charts illustrating additional portions of the programmed instructions for the electronic food processor of FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring more particularly to FIGS. 1-9, wherein like numbers refer to similar parts, a preferred embodiment of an electronic food processor  100  comprises a bowl  300  mated to a base  200  containing a drive motor  130 , a motor control unit  140  and an exteriorly mounted control panel  120 . Food bowl  300  surrounds food processing means (not illustrated) comprising exchangeable blades of different configurations as are known in the art. Cover  350  tightly encloses the top of the bowl  300 . The cover  350  defines a feed chute  310  which is in turn filled by a complimentary food pusher  320 . Safety switch S 1  detects the presence or absence of the food pusher  320 . 
     FIG. 2 illustrates a preferred embodiment of a control panel  120  in accordance with the present invention. The control panel  120  is roughly divided into a display portion  115  and a keypad  7 . The keypad  7  includes six switches  7 A through  7 F, the function of which will be discussed below. Display portion  115  includes an LCD  110  for display of times relevant to food processor operation, preferably in digital format. The LCD  110  also includes icons for visual indication of various conditions related to the food processor. Display portion  115  also includes three LEDs  111 - 113 , the function of which will also be discussed below. Some conditions, such as the auto pulse and high speed functions, are indicated by both an icon on the LCD and an LED. 
     The functions and components of the electronic food processor are best introduced with reference to the functional block (FIG. 3) and schematic (FIG. 4) diagrams. Household alternating current (AC) enters FIGS. 3 and 4 in the upper left corner on lines labeled AC IN which correspond to an AC power cord. Plugging in the electronic food processor provides alternating current to an AC/DC converter circuit  1  and regulator  2  which together supply direct current to the microprocessor unit  8  and other electronic components of the food processor  100 . At power-up, reset circuit  5  generates a reset signal to the microprocessor unit  8 , initializing the microprocessor unit and setting it to a standby mode. 
     AC is also provided to an isolated zero cross detection circuit  4 . One leg of the AC is connected to an photo-coupler IC 2  by a current limiting resister R 3  and shunt diode D 3 . This arrangement causes one-half of each AC cycle to pass through an LED in photo-coupler IC 2 . The photo-coupler IC 2  produces a signal 50/60 Hz corresponding to each zero cross of the AC current and provides this signal to the microprocessor unit  8  where it is used for motor control. With particular reference to FIG. 4, it can be seen that safety switch S 1  is arranged to, in one position complete the AC circuit through zero cross detection circuit  4 , and in another position disconnect zero cross detection circuit  4  from the AC. When the AC circuit through zero cross detection circuit is complete, photo-coupler IC 2  will provide the 50/60 Hz signal to the microprocessor unit  8 . When the AC circuit is not complete through zero cross detection circuit  4 , no 50/60 Hz signal will be provided to microprocessor unit  8 . The significance of the presence or absence of the 50/60 Hz signal at the microprocessor unit  8  will be further discussed below. 
     With continuing reference to FIG. 4, safety switch S 1  also provides one leg of alternating current to motor coil drivers  12  and  15  through relay K 1 . It will be understood by those of skill in the art from FIG. 4 that the other leg of AC is provided directly to the motor. Relay K 1  is energized by relay driving circuit  9 , which is in turn controlled by signal RYO from the microprocessor unit  8 . When signal RYO is a logic level “0”, relay K 1  is energized and connects motor coil drivers  12  and  15  to one leg of the alternating current. If relay K 1  is not energized by the microprocessor unit  8 , the motor coil drivers  12  and  15  do not have access to AC. Restated, when signal RYO is logic level “1”, drive motor  130  cannot run. 
     An oscillator circuit  6  provides a clock signal to the microprocessor unit  8 . This clock signal is used by the microprocessor unit  8  to organize its internal functions. 
     A sensor board  3  includes a hall effect sensor integrated circuit IC 3  whose function is to detect the speed of motor  130  and produce a signal Fin corresponding to that speed. Signal Fin is provided to microprocessor unit  8  for use in regulating the speed of motor  130 . 
     Buzzer circuit  16  responds to signals from the microprocessor unit  8  to provide an audible indication of a pause condition as will be discussed below. 
     Activation of relay K 1  by microprocessor unit  8  applies AC to the low speed triac driving circuit  13  to generate a trigger signal through trigger diode D 5 . The trigger signal is received by motor running coil driver  15 . This trigger signal causes pulses of alternating current to be applied to drive motor  130  through triac TA 2 . The energy provided by motor running coil driver  15  through triac TA 2  using the signal from low speed triac driving circuit  13  is sufficient to maintain the drive motor  130  at a predetermined normal running speed. 
     However, in a food processor it is important that the drive motor  130  attain this normal running speed as quickly as possible. To facilitate a rapid increase in motor speed, the drive motor  130  is equipped with a start coil (not illustrated) as is known in the art. A logic level “0” on line P 1  generated by microprocessor unit  8  is used by start up triac driving circuit  11  to trigger motor start coil driver  12 . The motor start coil driver  12  provides additional AC power to the start coil of drive motor  130 , bringing the motor up to speed rapidly. By monitoring signal Fin from the sensor board  3 , the microprocessor can detect when the motor has achieved the desired running speed. When the motor has achieved the desired running speed, microprocessor unit  8  terminates power to the start coil of the motor  130  by making line P 1  a logic level “1”. 
     During drive motor  130  operation, closing switch  7 C on the keyboard can activate an optional high speed. Actuation of switch  7 C causes microprocessor unit  8  to place a logic level “0” on line P 2 . This turns on high speed triac driving circuit  14  which augments the trigger signal generated by low speed triac driving circuit  13 . This augmented, or high speed trigger signal causes TA 2  to supply additional AC current to the running coil of the drive motor  130 . Sensor board  3  detects the increase speed of the motor  130  and relays this signal to the microprocessor unit  8 . The signal P 2  is regulated by microprocessor unit  8  to maintain the motor  130  at the desired high speed as will be discussed below. 
     It should be understood that the microprocessor unit  8  requires the 50/60 Hz signal generated by the 0 cross detection circuit  4  to generate signals RYO, P 1  and P 2  related to motor operation. Removal of the safety chute alters the position of the safety switch S 1  making the AC circuit through zero cross detection circuit  4  incomplete which terminates the 50/60 Hz signal. It can be seen from FIG. 4 that changing the state of switch S 1  also removes the leg of AC power passing through relay K 1  to motor run coil driver and motor start coil driver  15  and  12  respectively. Thus, in a redundant manner, a change of state of switch S 1  removes power from the drive motor  130 . 
     The various functions of the circuit illustrated in FIG. 4 discussed above are coordinated by the microprocessor unit  8  in response to signals generated by the zero cross detection circuit  4  (50/60 Hz), reset circuit  5 , oscillator circuit  6 , sensor board  3  (Fin), and keyboard  7  as will be discussed below with reference to FIGS. 5-10. As a preliminary matter, it should be understood with reference to FIG. 4 that placing signal line RYO at a logic level “0” will turn on Q 1  in relay driving circuit  9 , energizing relay K 1  and activating low-speed triac driving circuit  13 . Placing signals P 1  and P 2  at logic level “0” causes current to flow through photo-couplers IC 5  and IC 4  in start up triac driving circuit  11  and high speed triac driving circuit  14 , respectively. It should be apparent that microprocessor unit  8  can control the trigger signals generated in triac driving circuits  11 ,  13  and  14  by its control of signals RYO, P 1  and P 2 . 
     FIG. 5 illustrates an overall flowchart of the program stored in memory in microprocessor unit  8 . The program is activated by closure of the start button  7 E. With reference to FIG. 2 switch  7 E is a multifunction switch labeled start/stop/clear. For clarity, switch  7 E will be referred to as the start switch  7 E. First closure of the start switch  7 E initiates the program illustrated in FIG.  5 . The first decision made by the program is to decide whether a countdown mode has been selected. The countdown mode is activated by a user selecting a desired end time using the up and down switches  7 A,  7 B. If a pre-established end time has been selected, the right-hand branch of FIG. 5 will be used. If no desired end time has been selected, the left-hand branch of FIG. 5 will be used. 
     The difference between the left and right-hand branches of FIG. 5 is essentially that the right branch displays a countdown or time remaining on the LCD and operates in the selected function until the user selected time has elapsed. The left branch displays a count-up time corresponding to a time elapsed from activation of the drive motor and continues to count-up until the unit is stopped by the user or a pre-established maximum run time Tmax is achieved. 
     Within the left and right branches the function of the program is very similar. A timer is set either to A (the pre-selected time) or 0. The program illustrated in FIG. 5 is a program that manipulates signals RYO, P 1  and P 2  to regulate the rotational speed of drive motor  130 . The program compares motor speed signal Fin from the sensor board  3  to two pre-established standard Fson and Fsoff. If the measured motor speed Fin is less than Fson, the program holds RYO, P 1  and P 2  low. If the measured motor speed Fin is greater than Fson, it is then compared to Fsoff. 
     When the measured motor speed Fin exceeds or is equal to Fsoff, the program looks to see if the “high-speed” function is activated, in which case RYO, P 1  and P 2  are held low delivering max power to the coils of the driver motor.  130 . If the “high-speed” function is not activated, the program sets both P 1  and P 2  to logic level “1”, turning off the start triac driver  11  and the high speed triac driver  14 . This leaves the drive motor  130  with power delivered through motor running coil driver  15  as triggered by low speed triac driver  13 . 
     The first step after timer setting is to look at the motor speed Fin as detected by the sensor board  3 . If the motor speed detected Fin is less than Fson then signals P 1 , P 2  and RYO are set to logic level 0. Setting RYO, P 1 , and P 2  to logic level 0 causes all of the triac driving circuits  11 ,  13 , and  14  to become active simultaneously. This causes the drive motor  130  to rapidly increase speed. A start flag is then enabled. Start flag enable causes LED  111  to be lit indicating that the motor is operating. The respective timer is incremented or decremented depending on which branch of FIG. 5 is operational. If the maximum time Tmax or pre-elected time A has not elapsed and the stop key is not pressed, the program returns to detecting motor speed. If the motor speed has not achieved the desired run speed Fson, program remains in the previously described loop. 
     At some point the motor speed will exceed Fson, at which point the program moves to the next step and compares the motor speed Fin to a predetermined “start off” speed Fsoff. If the motor speed is not greater than or equal to Fsoff, P 1 , P 2  and RYO are maintained at logic level 0. If the motor speed Fin is greater than or equal to Fsoff, the program asks whether high-speed function is enabled. If yes, only P 1  is set to a logic level 1 (meaning that P 2  and RYO remain at logic level 0 supplying an augmented trigger signal to motor running coil driver  15  triac TA 2 ). If high speed is not enabled, P 1  and P 2  are both set to logic level 1 (meaning signal RYO is maintained at logic level 0 which, supplies an unaugmented trigger signal through low speed triac driver  13  to motor running coil driver  15  triac TA 2 . The appropriate timer is incremented or decremented, and if the time (A or Tmax) has not expired and the stop key has not been pressed, the process begins again. 
     This loop program continuously compares detected motor speed Fin to pre-established motor start speed Fson and start off speed Foff, respectively. The motor speed is brought quickly to speed Fsoff and maintained there (unless the “high speed” function is activated) by manipulating P 1 , P 2  and RYO as described above. The high-speed function is available any time the motor is running. 
     The electronic blender is provided with an auto pulse function in which the microprocessor unit operates a drive motor  130  in on-off cycles corresponding to arbitrary predetermined on-off cycle times Ton and Toff respectively. FIGS. 6 and 7 illustrate the condition of drive motor  130  and the program producing the auto pulse function in the electronic blender  100 , respectively. FIG. 7 has left and right branches corresponding to count-up and count-down portions of the program. The count-down mode is selected by the user using the up- down keys to establish a desired food processing cycle duration. A food processing duration timer t 3  is used to regulate the overall food processing cycle duration. If a predetermined food processing cycle duration A has been selected by a user, the right branch of FIG. 7 sets timer t 3  equal to the user selected duration A. If there is no user selected duration, the left branch of FIG. 7 sets timer t 3  equal to 0. In either branch, while the food processor is operating in auto pulse mode, the program steps utilize timers t 1  and t 2  to cycle the drive motor on and off (as best illustrated in FIG. 6) until the pre-selected duration A or Tmax has been achieved. The time values of t 1  and t 2  are arbitrary times and may be different for the “high-speed” function. 
     FIG. 8 illustrates a program loop related to activation of the high-speed function. During food processor operation, the microprocessor unit  8  is programmed to detect closure of the high speed switch  7 C. If the high speed switch  7 C is not closed, operation of the food processor continues undisturbed. A first closure of the high speed switch  7 C causes the microprocessor unit  8  to ask whether the high speed mode is already enabled. If the high speed mode is not enabled, the microprocessor unit enables the high speed flag, turns on LED  112  and the high speed icon on the LCD  110 . The high speed flag is utilized to answer the question HS enable in FIG. 5 left and right branches. 
     If the high speed mode is already enabled (meaning this is a second closure of the high speed switch  7 C) the microprocessor unit  8  disables the high speed flag and turns off LED  112  and the high speed icon on the LCD  110 . Thus, it can be seen that a first closure of the high speed switch  7 C during food processor operation enables the high speed mode, whereas a second closure of the high speed switch  7 C during food processor operation disables the high speed mode. The program of FIG. 5 responds to enablement of the high speed mode as previously described. 
     FIG. 9 illustrates how the microprocessor unit is programmed to operate the digital display when the user has selected a food processing cycle duration, i.e., in the countdown mode. The microprocessor unit  8  sets the display to an initial value A corresponding to the user defined food processing cycle duration. The program then asks if pause is enabled. Pause can be enabled in two ways in accordance with the present invention. First, if the position of safety switch S 1  is changed during food processor operation (indicating removal of the food pusher  320 ) or, alternatively, if start switch  7 E is closed during food processor operation. If pause is enabled, the drive motor is stopped. When the pause mode is enabled, the microprocessor is programmed to stop the unit by removing power from the drive motor  130  and flash the timer digits. If the pause mode is not enabled, the unit runs according to its mode setting (FIG.  5 ). The timer is decremented until t equals 0, at which time the drive motor  130  is stopped and the timer is cleared. 
     FIG. 10 illustrates program loop corresponding to the count-up mode. The only difference between FIG.  9  and FIG. 10 is that the initial timer is set to 0 and incremented in FIG.  10 . In this program loop of FIG. 10, the food processor drive motor will run in accordance with the mode setting and pause condition until the stop key is pressed, the pulse key is released, or the predetermined maximum time Tmax is achieved. 
     FIG. 11 illustrates the program loop related to the pause mode. If the 50/60 Hz signal disappears (switch S 1  changes position) and the unit is operating, the microprocessor unit shifts the operating mode to pause mode (see FIGS.  9  and  10 ). Pause mode causes the displayed time digits to flash and activates the pause icon on the LCD. While the unit is in pause mode an audible signal is generated by the buzzer circuit  16 . When switch S 1  is returned to its safe position, 50/60 Hz returns, the pause flag is cleared and the food processor returns to its previous operation at the moment the pause flag was enabled. Restated, whatever time is displayed when the pause flag is enabled freezes and flashed until the pause flag is disabled. When the pause flag is disabled, the program resumes at the time displayed. 
     While a preferred embodiment of the foregoing invention has been set forth for purposes of illustration, the foregoing description should not be deemed a limitation of the invention herein. Accordingly, various modifications, adaptations, and alternatives may occur to one skilled in the art without departing from the spirit and the scope of the present invention.