Abstract:
A blender for home food preparation is improved by the incorporation of electronic motor control circuitry responsive to a microcontroller. The microcontroller includes memory for storage of data and programmed instructions. The programmed instructions permit a user to select from a plurality of blending speeds and define a pre-determined end time. Use of a pre-determined end time produces a two-speed blending cycle. The programmed instructions determine the length and energy level associated with each portion of the two-speed blending cycle. A user can stop the blending cycle at any time, with or without a pre-determined end time. Safety features include a pre-determined maximum motor run time, top jar load detector and auto shut down after a period of inactivity. The pre-determined end time from a previous blending cycle is stored in memory, allowing the microcontroller to reproduce the duration of the previous blending cycle.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to a household blender of the type used for altering the consistency of and/or blending liquid and solid food and more particularly to a microprocessor-based control circuit for controlling energization of the blender drive motor. 
     2. Description of the Related Art 
     Traditional household blenders have an array of mechanical switches for speed selection. A selected speed switch is engaged and the blender operates at the selected speed until the operator pushes an off switch that mechanically disengages the speed switch. Some prior art blenders (such as those used in bars and restaurants for mixing frozen drinks) are equipped with a rotary timer which permits unattended operation for a limited period of time. In either case the user of a traditional blender, and in particular the home user, has difficulty obtaining consistent and repeatable results. The traditional blender retains no record of the previous blending cycle. Nor does the traditional blender display the duration of the blending cycle. The operator must rely on his or her memory and/or visual observation of the results to reproduce a successful blending operation. 
     Some aspects of traditional blender design also present a safety hazard. A traditional blender (not equipped with a timer) will continue to run if left unattended and therefore constitutes an obvious safety hazard. Blenders are not typically equipped with safety mechanisms that detect the proper installation of the blender jar. Operation of the blender motor at high speeds when unloaded, i.e., not connected to the blender jar, can present a hazard to the operator as well as damage to the blender motor. 
     SUMMARY OF THE INVENTION 
     A preferred embodiment of a programmable electronic blender is provided with a microprocessor-based circuit for control of the blender motor drive. The microprocessor may be incorporated into a micro-controller that includes programmable memory (PROM or EPROM) for retention of programmed instructions as well as random access memory (RAM) for recording previous blending cycles. The instructions and memory improve the user-friendliness and utility of the programmable electronic blender. For example, the instructions allow a particular blending cycle to incorporate more than one blending speed. Additionally, the programmable electronic blender will repeat a previous user-selected blending cycle recorded in memory. Programmed instructions provide elapsed and countdown timers that allow a user to monitor the elapsed time of the blending program or the time remaining to completion of the blending program, depending on the blending program selected. A display portion includes a liquid crystal display for indication of the blending cycle selected as well as the relevant elapsed or remaining times. The display and memory capabilities of the programmable electronic blender permit the user to achieve more consistent and reproducible results. 
     In accordance with an additional aspect of the present invention, the programmable electronic blender is provided with safety features that will not permit the blender motor drive to be activated unless the blender jar is properly installed to the blender base. The energy efficiency and safety of the programmable blender are improved by incorporation of instructions to stop blending upon expiration of a user-selected time and shut down completely after a pre-determined period of inactivity. 
     An object of the present invention is to provide a new and improved programmable electronic blender that permits the home user to produce consistent and repeatable blending results. 
     Another object of the present invention is to provide a new and improved programmable electronic blender that provides the user with enhanced safety and convenience. 
     These and other objects, features, and advantages of the invention will become readily apparent to those skilled in the art upon reading the description of the preferred embodiments, in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exterior view, partly in phantom, of a programmable electronic blender in accordance with the present invention; 
     FIG. 2 is a plan view of a control panel appropriate for use in conjunction with the programmable electronic blender of FIG. 1; 
     FIG. 3 is a functional block diagram of the programmable electronic blender of FIG. 1; 
     FIG. 4 is a schematic diagram of the programmable electronic blender of FIG. 1; and 
     FIGS. 5-9 are flowcharts illustrating portions of a program for control of the programmable electronic blender of FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring more particularly to FIGS. 1 through 9, wherein like numbers refer to similar parts, a preferred embodiment of a programmable electronic blender  100  comprises a blending container  300  mated to a base  200  containing a drive motor  130 , a motor control unit  140  and an exteriorly mounted control panel  120 , including a liquid crystal display (LCD)  110 . 
     The various capabilities and functional components of the programmable electronic blender are best introduced with reference to the functional block (FIG. 3) and schematic (FIG. 4) diagrams. Closure of a “Power On” switch  6 C applies household current to the circuitry of the programmable electronic blender. Incoming alternating current (AC) is converted to direct current (DC) in a converter circuit  2  and applied to the electronic portions of the programmable electronic blender. A regulator circuit  4  conditions and regulates the DC provided to the micro-controller  9 . On power up, one of the first tasks of the micro-controller  9  is to provide a latching signal to relay driving circuit  11 , which in turn applies AC current to the coil of latching relay Kl. Together, the micro-controller  9 , relay driving circuit  11  and latching relay K 1  maintain power to the circuitry of the programmable electronic blender. 
     A zero-cross detection circuit  3  and filtering circuit  8  provide a shaped signal to the micro-controller  9  corresponding to each zero-cross of the household AC current. This shaped signal is used by the micro-controller  9  to synchronize the triac driving circuit  13  with the household AC for the purpose of motor control. The micro-controller  9  sends trigger signals to the triac driving circuit  13  to advance or retard the triggering (turn on) point of the triac in the motor driver  14 . An advanced triggering point provides increased power to the motor  130 , while a retarded triggering point decreases power to the motor  130 . The motor  130  is driven at higher speeds when fed higher power levels and lower speeds when lower power is provided. This enables the micro-controller to alter motor speed electronically. 
     An oscillation circuit  7  provides high frequency clock pulses which the micro-controller  9  uses to synchronize its internal functions. A buzzer circuit  15  permits the audible indication of functional conditions to the user. A load sensor  10  provides an indication to the micro-controller unit  9  that the blending jar  300  is properly attached to the base  200 . A reset circuit  5  provides a reset signal to the micro-controller  9  at system power up to initialize the micro-controller  9  and place the micro-controller in stand-by mode. 
     The micro-controller  9  preferably incorporates a microprocessor, programmable read-only memory (PROM) or erasable programmable read-only memory (EPROM) and random access memory (RAM) as well as buffers and circuitry for the reception and manipulation of various inputs and outputs. The RAM memory is volatile, or as is known in the art, temporary storage for data. Resetting the micro-controller or removing power from the programmable blender will erase the contents of the RAM. The microprocessor, memory, buffers and circuitry are typically incorporated into a single integrated circuit or chip package that is then referred to as a micro-controller. In the preferred embodiment, sets of instructions or programs are installed in the programmable memory. These instructions will be discussed below with reference to FIGS. 5-9. The RAM is preferably used to store the power level and duration characteristics of a user-selected previous blending cycle as will be further discussed below. 
     The “Power On” switch  6 C, keyboard  6  and display portion  110  are incorporated into a control panel  120  to provide a user interface for the programmable electronic blender  100 . The control panel  120 , illustrated in FIG. 2, preferably includes an LCD display portion  110 . The LCD shows, preferably in digital format, the results of the elapsed or countdown timers included in the micro-controller programs, depending on the circumstances. The LCD  110  also indicates several functional conditions, such as the selected power level, the load status (from load sensor  10 ) and pause condition. The illustrated embodiment of programmable electronic blender  100  includes six user-selectable blending speeds/power levels: stir, chop, mix, puree, liquefy and ice crusher. 
     The remainder of the control panel is dedicated to a plurality of contact-type switches. These switches are normally open and are closed by pressure applied to the face of the control panel  120 . The functions of these switches are best discussed with reference to FIGS. 2 and 4. The function of Power On switch  6 C has already been discussed. Off switch  6 D provides a signal to micro-controller  9 , causing the micro-controller to interrupt current to latching relay K 1  and remove power from the programmable electronic blender. Start/Stop switch  6 E initiates or interrupts a selected blending cycle. Timer reset switch  6 F resets the time displayed on the LCD and in a corresponding internal count-down timer to zero. This internal count 10  down timer is stored in RAM. When the internal count-down timer is cleared by closure of the timer reset switch  6 F or the off switch  6 D, the programmable blender operates in a count-up mode as will be discussed below. Pulse switch  6 A initiates a momentary blending cycle that lasts as long as the pulse switch  6 A is held. This function is similar to the mechanical momentary switches for pulsing conventional blenders. Select switch  6 B permits the user to select from among the six available power levels corresponding to blending speeds. Of course, greater or fewer numbers of power levels are possible. Up switch  6 H and Down switch  6 G permit the user to select a desired duration for the blending cycle. When the user pre-selects a time for the blending cycle, the LCD displays a remainder of the pre-selected time in a count down format as will be further discussed below. 
     Closure of the various switches on the control panel  120 , with the exception of Power On switch  6 C provide inputs to the micro-controller  9 . The micro-controller  9  contains programmed instructions for responding to these inputs. FIGS. 5-9 are flow charts illustrating portions of the programmed instructions. 
     In accordance with a particular aspect of the invention, the ease of use and overall utility of the programmable electronic blender are enhanced by the particular programmed instructions installed in micro-controller  9 . Upon initialization, the micro-controller  9  enters an idle mode. FIG. 5 illustrates the micro-controller response to closure of the start/stop switch  6 E. If the start/stop switch is not pressed, the micro-controller remains in the idle mode program loop. If the start/stop switch  6 E is pressed, micro-controller proceeds to program section A illustrated in FIG.  9 . 
     The idle mode program is illustrated in FIG.  8 . The micro-controller is programmed with a predetermined idle time T Idle . If no switches are closed before the predetermined idle time T Idle  expires, the micro-controller will remove power from latching relay K 1  by signaling relay driving circuit  11 . This removes power from the circuitry of the programmable electronic blender. If any switch is closed, the idle timer is reset to the maximum idle time T Idle  permitted and the program proceeds to program section G in FIG.  5 . FIGS. 5 and 8 together illustrate the functioning of the micro-controller in the idle mode. 
     When the start/stop switch  6 E is closed for the first time, micro-controller  9  proceeds to program section A illustrated in FIG.  9 . The micro-controller  9  is programmed to look at the output of the load sensor  10  to see if the top jar  300  is properly loaded to the base  200 . If load sensor  10  indicates that the top jar is not properly loaded, the start function is disabled and the motor  130  will not be permitted to start. If the top jar  300  is properly loaded, the micro-controller is programmed to initiate a blending cycle by proceeding to program section E illustrated in FIG. 7. A preferred load sensor  10  is a reed switch responsive to a magnet. The magnet (not shown) is preferably mounted to the top jar  300  and actuates the reed switch load sensor when correctly installed to the base  200 . 
     The initial step in any blending cycle is to look and see if the user pre-selected a blending cycle time for the previous blending cycle. The blending cycle program section E (FIG. 7) has two alternative sets or branches of program steps. One set of program steps (the right branch, to program section C) will take place if the user has pre-selected a desired cycle time or if a user-selected blending cycle time remains from a previous blending cycle. The previous blending cycle will be repeated only if the user pre-selected a desired cycle time in the previous blending cycle. LCD display  110  will show a count down timer when the micro-controller  9  is executing the right branch (program section C, FIG. 6) of the blending cycle instructions (FIG.  7 ). 
     The left branch of FIG. 7 illustrates the program steps taken by the micro controller when no desired cycle time has been selected. The micro-controller  9  loads the selected speed parameter Si, initiates power to the motor and increments a count-up timer which is displayed on the LCD screen. This branch of the program section E asks whether the start/stop switch  6 E has been closed a second time. If not, the micro-controller  9  will continue to apply power to the motor  130  and increment the count-up timer until a pre-established maximum motor run time T max  is achieved. T max  is pre-established according to the capabilities of the particular embodiment of the blender and reasonable safety concerns. An appropriate T max  may be, for example, five minutes. When the count up timer reaches T max , the micro-controller  9  will reset the count-up timer and display to zero and stop the motor. At any time during the blending cycle, if the start/stop switch  6 E is closed, the motor is stopped and the count-up timer and display are reset. 
     If, upon initiation of a blending cycle (first start/stop switch  6 E closure) the micro-controller  9  finds that a user-selected cycle time T total  is stored in memory, the micro-controller proceeds to program section C illustrated in FIG.  6 . The user-selected cycle time T total  may be a user-selected cycle time from the previous blending cycle as described above. The first two decision blocks of program section E (FIG. 7) graphically represent the program steps of looking for a newly input speed parameter Si and cycle time T total  or a user selected cycle time T total  and speed parameter Si stored in memory from a previous cycle before proceeding to program section C. It will be understood by those of skill in the art that the memory used to store T total  and Si is volatile, meaning that a newly entered T total  or newly selected Si replaces the previously selected T total  or Si, respectively. Pressing the T. Reset switch  6 F clears a previously selected or stored T total . 
     The micro-controller is programmed to retain a user-selected cycle time T total  even if the motor speed parameter Si is changed. This permits the user to select a new blending speed for a blending cycle of the same duration as the previous blending cycle. The micro-controller  9  utilizes the most recently selected motor speed parameter Si until that parameter is changed. 
     In accordance with another aspect of the invention, user-selection of a desired cycle time T total  produces a two-stage blending cycle as illustrated in program section C (FIG.  6 ). Each blending speed has a motor speed S l  associated with it. A speed reduction parameter (a), representing a percentage is programmed into the instructions for each selected blending speed. The step of “Generate 1 st  speed parameter” multiplies the motor speed S l  by 1 minus the speed reduction parameter (a) for that blending speed. Thus, the first speed in any two stage blending cycle produced by program section C is determined by the formula (1−a)×S l . The resulting reduced motor speed is applied for a time period equal to T 1 . 
     T 1  is calculated by multiplying T total  by (b), where b is an arbitrary programmed percentage of T total . Since total blending time T Total  is the sum of time portions T 1  and T 2 , T 2  is calculated by the formula (1−b)×T total . Hence, 1 st  motor speed (1−a)×S i  is applied for T 1  and 2 nd  motor speed S i  is applied for T 2  to produce a two speed blending cycle. The values of (a) and (b) vary depending on the T total  and blending speed selected by the user. 
     Internal timer t is loaded first with the calculated T 1  and subsequently with the calculated T 2 . Program section C causes the remainder of T total  to be displayed on the LCD  110  in a count-down format. Up switch  6 H and down switch  6 G are used to set T total  for a given blending cycle. Select switch  6 B is used to indicate the desired blending speed. When these steps have been taken, closing the start/stop switch  6 E will initiate program sections A and E (FIGS. 9 and 7, respectively). Program section E (right branch) will utilize program section C to execute the two-stage blending cycle as discussed above (FIGS. 7 and 6, respectively). 
     Alternatively, the user may simply select a blending speed using the select switch  6 B and press the start/stop switch  6 E. As illustrated in program section E, if the user has not pre-selected a cycle time the left-hand branch of program section E will be utilized. A count-up timer internally tracks the run time for the blending cycle and compares this time to T max . The value of the count up timer is displayed on the LCD  110 . The motor is run at the selected speed S i  until the start/stop switch  6 E is closed a second time or a pre-determined time T max  is elapsed. Pressing the start/stop switch  6 E stops the motor and resets the timer, clearing the value shown in the LCD  110 . 
     The micro-controller  9  is programmed to display either a count-up (increment) timer, or a count-down (decrement) timer depending on the circumstances. Program section C (FIG. 6) causes the remainder of T total  to appear in count-down format on the LCD  110 . Times T 1  and T 2  are used internally by the microcontroller to adjust motor speed via the triac driving circuit  13  and the motor driver  14 . The micro-controller  9  will stop the motor  130  automatically when the count down timer reaches zero. If no time has been entered by the user or remains from a previous cycle (program section E, left branch), a count-up timer is displayed. This permits the user to see the elapsed time. The user can effectively select when to stop the blending cycle by referring to the elapsed time. 
     Together, the components and programming of the programmable electronic blender provide an unprecedented ease of use, safety, energy efficiency and improved utility. 
     While a preferred embodiment of the foregoing invention has been set forth for the 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.