Claims:1. A mixer grinder having a housing adapted to receive a food processing bowl with detachable blades disposed therewith in and the bottom of the housing enclosing a motor for driving the said blades, a switch mechanism to actuate or permit actuation of the said motor, a control button to operate the switch mechanism on a portion of the housing, an actuation means operable by switch mechanism moveable between a first, a second and a third position such that
a) in the first position the actuation means being spaced apart from the switch mechanism to maintain the switch mechanism in an open disengaged position and prevent actuation of the motor,
b) in the second position the actuation means moving selectively and repeatedly towards and away from the switch mechanism at a predetermined first interval, for selectively, engaging and disengaging the switch mechanism and thereby actuating/deactuating the motor correspondingly in a first operating mode for a certain duration and then the actuation means moving selectively and repeatedly towards and away from the switch mechanism at a predetermined second interval, for selectively engaging and disengaging the switch mechanism and thereby actuating/deactuating the motor correspondingly in a second operating mode,
c) in the third position the actuation means moving selectively and repeatedly towards and away from the switch mechanism at a predetermined second interval, for selectively engaging and disengaging the switch mechanism and thereby actuating/deactuating the motor correspondingly in a second operating mode, and
d) the said arrangement characterized in the singular switch mechanism with an unitary button and the actuation means associated with the motor.

2. The mixer grinder as claimed in claim 1 wherein the first interval of first operating mode of the motor is different from second interval of the second operating mode of the motor.

3. The mixer grinder as claimed in claim 1 wherein the control button is adapted for simple press operation required for first operation mode which is whipping and grinding mode of the mixer grinder.

4. The mixer grinder as claimed in claim 1 wherein the control button is adapted for simple press operation required for first operation mode which is whipping and subsequent grinding mode of the mixer grinder.

5. The mixer grinder as claimed in claim 1 wherein the control button is further adapted for simple press and hold operation required for the second operation mode which is whipping mode of the mixer grinder.

6. The mixer grinder as claimed in claim 1 wherein the control button is adapted for simple press operation required for changing from second position/third position to first position which is deactuation state of the motor.

7. The mixer grinder as claimed in claim 1 wherein the actuator means is adapted such that disengaging period/duration of the motor in the first operating mode is different from the disengaging period/duration of the motor in second operating mode.

8. The mixer grinder as claimed in claim 1 wherein the motor is adapted for constant speed in second operating mode during whipping.

9. The mixer grinder as claimed in claim 1 wherein the motor is adapted for constant speed in first operating mode during whipping.

10. The mixer grinder as claimed in claim 1 wherein the motor is adapted for gradual rate of change of speed in the first operation mode during whipping.

11. The mixer grinder as claimed in claim 1 wherein the said arrangement may include a timer for adjusting the first time intervals of the first operation mode.

12. The mixer grinder as claimed in claim 1 wherein the said arrangement may include a timer for adjusting the second time interval of the second operation mode.

13. The mixer grinder as claimed in claim 11 wherein the timer is adjustable conditionally within the prescribed allowed time intervals of the first operation mode.

14. The mixer grinder as claimed in claim 11 wherein the timer is adjustable conditionally within the prescribed allowed time intervals of the second operation mode.

15. The mixer grinder as claimed in claim 1 wherein the said arrangement may include an overload protection means.

16. The mixer grinder as claimed in claim 15 wherein the overload protection means is adapted to disconnect the motor instantly in overload condition.

17. The mixer grinder as claimed in claim 15 wherein the overload protection means is adapted to reset the motor instantly after motor disconnect in overload condition.

18. The mixer grinder as claimed in claim 1 wherein the arrangement shall include display means for displaying the two operating modes, overload condition and standby condition of the mixer grinder.

19. The mixer grinder as claimed in claim 1 wherein the motor shall be adapted for operating in plurality of speeds.

20. The mixer grinder as claimed in claim 1 wherein the arrangement includes DC power supply means for converting the power from AC to DC to power the motor.
, Description:FIELD OF THE INVENTION :

The invention relates to a domestic mixer grinder generally used at home and industrial units for cooking preparations.

PRIOR ART :

The present Mixer Grinder available in the market or either with a Rotary Switch or a Piano switch for operation. Also there are few models with Electronic control by which user can select the required Speeds.

Proper Method for using the Mixer Grinder is as follows:

• The user should do Pulse / whip for few times to set right the uneven load.
• Then gradually increase the speed 1st, 2nd and 3rd.
• Stop in-between to add water / mixing up and follow the same procedure like Pulse / whip, 1st , 2nd& 3rd Speed.

In general most of the user will either directly shift to the 3rd speed or keep the knob always at 3rd Speed and operate from the main switch.

This will result in Heavy load on Mixer Grinder Motor and this will result in frequent failure of components.

The present Mixer Grinder available in the market or either with a Rotary Switch or a Piano switch for operation. Also there are few models with Electronic control by which user can select the required Speeds.

DESCRIPTION OF THE INVENTION :

The control panel of the Mixer Grinder as per invention will be having 3 buttons like, “AUTO”, “TIMER”, “CANCEL / PAUSE” and a 2 digit 7 segment display (digital display).

As per the invention, single touch is sufficient for all the required functions such as grinding including Whip/pulse (for setting right the uneven load) and also increasing the speed gradually(for proper grinding) in the mixer grinder.

Operation:
• When switch is “on”, the Mixer grinder from the mains the display will show as “- - “.
• Press the “AUTO” button the Mixer grinder will start with the Pulse / Whip for few times and gradually increase the speed up to 3rd speed. The display will show “On”.
• The unit can be switched off any time by pressing the “CANCEL / PAUSE” button. Also in any case the Mixer grinder will work continuously only for 5 minutes in line with the rating / specification.
• If we have to do only Pulse / Whip function press &hold the “AUTO” button the motor will work for 2 seconds and off for 1 second with the display showing “PU”. This sequence will continue as long as we press & hold the “AUTO” button.
• Timer setting: The timer can be set in the “AUTO” mode by pressing the “TIMER” button, each press will increase the time by 1 minute with range of 1 to 4 minutes (Max.). Also the unique programme will allow setting the timer after deducting the already elapsed time.
Example:- If the Mixer Grinder already running for 1 minute then it will allow user to set only 3 Minutes.
Also a long press of the “TIMER” button in the middle / at the end of the operation in idle mode will give the user the time taken for the grinding.
• Unique Digital Over load Protection: This One Touch Automatic Mixer grinder is built in with a unique Electronically controlled over load protection, which will not allow the Mixer grinder to run above the rated Power of 750 Watts. In case of over load the Mixer grinder will stop with the display showing “OL”.
• To reset the over load long press the “CANCEL / PAUSE” button after reducing the load or by adding water.

The advantage of this unique function is it will not allow the Mixer grinder motor in over loaded condition. It will switch off immediately if it is over loaded.

Whereas the existing Mixer grinders will allow the motor to run for some time (thus the motor will get heated up) before the Over load switch trips. Also once it is over load switch trips the customer should wait for 2-3 minutes to reset after reducing the load / adding water.

The Unique Electronically Protected over load system will effectively protect the Motor from over load.

Human Machine Interface(HMI)

3 Button Micro Switch and 2 Digit 7 segment Display forms the part of Human Machine Interface for the Product. All the three Buttons are pulled up with 3.3K resistor and switch press is detected by a logic low value on the Input/output Lines of the Microcontroller.

Display is a common cathode multiplexed 7 segment display. Refresh rate is 20 ms.

Following Mnemonics are outputted from the display and their meanings are tabulated down below
Sl No Display Meaning
1 -- Stand By
2 On Mixer Running in AUotmatic Mode
3 Pu Mixer Running in Pulse Mode
4 OL Over load condition

Motor Drive Circuit with one touch auto speed selection:

Motor used in the product is Field Tapped 3 speed universal motor, the three speeds in the Motor are:
1. Low Speed 10,000 RPM (+/- 2000 rpm)
2. Medium Speed 15,000 RPM(+/- 2000RPM)
3. High Speed 18,000 RPM(+/- 2000 RPM)

Different Impedances are derived by tapping’s of the Motor filed(Stator) winding. The highest Impedance winding causes the slowest speed and the lowest impedance winding on the stator/field causes highest speed and the impedance of the stator tapping in between high and low causes the middle speed.

Three relays are employed to select the above speed by powering the corresponding stator/field tapping’s to select the speed as desired. The relays are driven by open drain transistors and are controlled by the Microcontroller.

Automatic sequence of Pulsing the motor and switching to Low Speed, to medium speed and to high speed is done by the firmware in the Microcontroller, transistor driver and the relay.

Digital Over Load Protection:

Over current, that is current above the desired level in our case 3.5 amps RMS current generates an error signal to the microcontroller and the firmware in the microcontroller switches off the power to the motor and there by protects the product from thermal runway. The current is sensed by a shunt resistor and the voltage drop across the shunt resistor is measured by the Firmware of the Microcontroller and on breaching normal values will switch off the motor by cutting of the power supply with the aid of Relays. A “OL” mnemonic is flashed on the two digit display and by a long press (holding for about 2 secs) on the clear button will reset Over Load Condition.

DC Power Supply to the Motor:

A full wave Bridge Rectifier is used to convert AC to DC to power the universal motor to reduce hysteresis of the stator and rotor lamination, further reducing the overall temperature of the motor. Unidirectional current further reduces the sparking between brush and commutator. By operating the Universal Motor with DC supply will reduce the Hysteresis Stator and Rotor lamination will reduce the overall temperature rise of the motor.

Power Supply to Microcontroller, Display and Relays:

12V and 5 Volts is derived using SMPS IC VIPER 12 A for powering Microcontroller, Display and Relay.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 Exploded view of the mixer grinder is illustrated in figure 1.

Fig. 2 Block diagram is illustrated in figure 2.

As detailed above, the mixer grinder in one aspect discloses a mixer grinder. It has a housing adapted to receive a food processing bowl with detachable blades disposed therewith in and the bottom of the housing enclosing a motor for driving the said blades, a switch mechanism to actuate or permit actuation of the said motor, a control button to operate the switch mechanism on a portion of the housing, an actuation means operable by switch mechanism moveable between a first, a second and a third position such that in the first position the actuation means being spaced apart from the switch mechanism to maintain the switch mechanism in an open disengaged position and prevent actuation of the motor. In the second position the actuation means moving selectively and repeatedly towards and away from the switch mechanism at a predetermined first interval, for selectively, engaging and disengaging the switch mechanism and thereby actuating/deactuating the motor correspondingly in a first operating mode for a certain duration and operating in second mode thereby doing whipping prior to grinding process. In the third position the actuation means moving selectively and repeatedly towards and away from the switch mechanism at a predetermined second interval, for selectively engaging and disengaging the switch mechanism and thereby actuating/deactuating the motor correspondingly in a second operating mode. This mode is whipping mode. The said arrangement characterized in the singular switch mechanism with an unitary button.

In another aspect of the invention, the first interval of first operating mode of the motor of the mixer grinder is different from second interval of the second operating mode of the motor.

In another aspect of the invention, a control button is incorporated which is adapted for simple press operation required for first operation mode which is the whipping and grinding mode of the mixer grinder and further adapted for simple press and hold operation required for the second operation mode which is whipping mode of the mixer grinder.

In another aspect of the invention, the control button is adapted for simple press operation required for first operation mode which is whipping and subsequent grinding mode of the mixer grinder.

In another aspect of the invention, the control button is adapted for simple press operation required for changing from second position/third position to first position which is deactuation state of the motor.

In another aspect of the invention, the actuator means is adapted such that engaging period/duration of the motor in the first operating mode is higher than the engaging period/duration of the motor in the second operating mode.

In another aspect of the invention, the actuator means is adapted such that disengaging period/duration of the motor in the first operating mode is different from the disengaging period/duration of the motor in second operating mode.

In another aspect of the invention, the motor is adapted for gradual rate of change of speed during grinding and at constant speed during whipping.

In another aspect of the invention, the said arrangement may include a timer for adjusting the time interval of the operation modes and the timer is adjustable conditionally within the prescribed allowed intervals of the operation modes.

In another aspect of the invention, the said arrangement may include an overload protection means and the said overload protection means is adapted to disconnect and reset the motor instantly during an overload condition and subsequent reset condition correspondingly. This is an Electronically controlled Over load protection which will never allow the Motor to run in the over load (running above the rated power) condition by cut off the motor supply immediately. In all other known available mixer grinder in the prior art with overload protection with an overload switch will allow the motor to run in the overloaded condition and thus will weaken the motor insulation.

In another aspect of the invention, the arrangement shall include display means for displaying the two operating modes, overload condition and standby condition of the mixer grinder.

In another aspect of the invention, the motor shall be adapted for operating in plurality of speeds.

In another aspect of the invention, the arrangement includes DC power supply means for converting the power from AC to DC to power the motor.

All the illustrations and embodiments and examples are for the purpose of understanding the invention. None of them limit the scope of the invention. All the variations and modification as known to skilled person is well within the scope of the invention.