FORM 2
THE PATENTS ACT, 1970
(39 OF 1970)
As amended by the Patents (Amendment) Act, 2005
&
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2006
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION
A mixer grinder
APPLICANTS
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company
INVENTOR
Ganpule Vaibhav Sitaram, Fans & Appliances Division, Crompton Greaves Limited, Plot No 1, Bethora Industrial Estate, Bethora, Ponda, Goa 403 401, India, an Indian National
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the nature of this invention and the manner in which it is to be performed:

FIELD OF THE INVENTION
This invention relates to a mixer grinder.
PRIOR ART DESCRIPTION
A mixer grinder, especially a food mixer grinder, generally comprises a main unit or motor unit and one or more utility jars. The main unit comprises a main body of injection moulded plastics like acrylonitrile butadiene styrene. The main body houses the electric motor driving the mixer grinder and a speed selector switch for the motor connected to the speed tappings of the stator winding of the motor and provided with an operating knob. The main body comprises a utility jar locating collar or cavity at the top thereof. Each of the utility jars is provided with a pair of diametrically opposite locking lugs at the outer surface of the base thereof. The inner surface of the jar locating collar is provided with a pair of diametrically opposite guide grooves along the height thereof corresponding to the locking lugs. The jar locating collar is further provided with a pair of diametrically opposite locking slots at the extreme lower end of the guide grooves in diametrically opposite directions. The utility jar is introduced into the jar locating collar by aligning the locking lugs with the guide grooves and moving the jar down. The utility jar is locked in position by rotating the jar in the collar and engaging the locking lugs in
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the locking slots. The jar is removed from the collar by rotating the jar in the opposite direction and disengaging the locking lugs from the locking slots, aligning the locking lugs with the guide grooves and lifting the jar up. During locking and unlocking of the jar from the collar, it is necessary to hold the jar by one hand and the main body by the other hand so as to prevent relative rotation of the main body. Therefore, fitment and removal of the utility jar from the jar locating collar is inconvenient and cumbersome. Besides, if the locking lugs are not fully engaged in the locking slots, the jar will start vibrating and making noise during the operation of the mixer grinder, especially at higher speeds.
OBJECTS OF THE INVENTION
An object of the invention is to provide a mixer grinder which can be firmly locked in position and unlocked very easily and conveniently.
Another object of the invention is to provide a mixer grinder which is simple in construction and easy and convenient to operate.
Another object of the invention is to provide a mixer grinder which is safe and reliable.
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DETAILED DESCRIPTION OF THE INVENTION
According to the invention there is provided a mixer grinder comprising at least two electromagnetic locks for the utility jar thereof, the locks being located in the utility jar locating collar of the mixer grinder diametrically opposite to each other. The following is a detailed description of the invention with reference to the accompanying drawings, in which;
Fig 1 is a crossectional elevation of the mixer grinder according to an embodiment of the invention;
Fig 2 is an enlarged view at X in Fig 1;
Fig 3 A is crossectional view of an electromagnetic lock of Fig 1 with the plunger at its extreme forward position;
Fig 3B is a crossectional view of the electromagnetic lock of Fig 1 with the plunger thereof at its extreme backward position;
Fig 4A is a partial isometric view of a utility jar of the mixer grinder of Fig 1; Fig 4B is an enlarged view at Y in Fig 4A; and
Fig 5 is an electric layout diagram of the mixer grinder of Fig 1
The mixer grinder 1 as illustrated in the accompanying drawings comprises a main body 2 made of injection moulded plastics such as acrylonitrile butadiene styrene. The main
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body houses the electric motor 3 driving the mixer grinder. The speed selector switch of the motor and its moving contact are marked 4 and 5, respectively. Representative speed tappings from the stator winding (not shown) of the motor are marked 6, 7 and 8. The motor is connected to a Power Supply S through the speed selector switch. Operating knob of the speed selector switch is marked 9. Vacuum feet of the mixer grinder are marked 10. The mixer grinder comprises a utility jar locating collar or cavity marked 11 at the to thereof. 12 is a utility jar and 13 is the handle of the jar. The base of the jar is marked 12a. The mixer grinder comprises a pair of electromagnetic locks 14 for the utility jar thereof. The locks are located in the utility jar locating collar of the mixer grinder diametrically opposite to each other. Each of the locks comprises a plunger 15 made of an electromagnetic material such as stainless steel and reciprocably held in an electromagnetic coil 16 which is located in a closed end tubular housing 17 over a holding sleeve 18 at the inner surface thereof. The sleeve is made of a magnetic flux permeating material such as aluminium. The housing is made of an electric insulating and nonmagnetic material such as injection moulded plastics such as polypropylene or nylon. The housing is provided with a pair of mounting lugs 19 with holes 20. 21 is a rib formed in the main body corresponding to each of the housings. A pair of upright pins 22, 22 are provided on the rib. The housings are mounted on the ribs by engaging the holes in the mounting lugs of the housings over the upright pins on the ribs. The plungers are each provided with a head 23 at the outer end thereof and are biased in the direction of the utility jar by compression springs 24 disposed over the plungers and held between the heads of the plungers and closed front ends 25 of the housings. The plungers are also provided with a stopper flange 26 adapted to slide against the inner surface of the respective holding sleeves and guide the forward and backward movement of the plungers in the tubular housings. The stopper flanges also restrict the forward movement of the plungers by abutting against the respective closed front ends of the housings. The outer
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ends of the plungers are tapered and are marked 15a. The electromagnetic coils are connected to the speed selector switch through a normally open single push single throw type switch 27. The moving contact and fixed contact of the switch 27 are marked 28 and 29. The leads of the electromagnetic coils connected to the switch 27 are marked 30. The operating knob of the normally open switch is marked 31. The outer ends of the plungers are adapted to engage in corresponding notches 32 provided at the outer surface of the base 12a of the utility jar at the extreme forward position thereof. The notches at the outer surface of the base of the utility of the jar is aligned with the handle of the jar. The jar is fitted in the jar locating collar of the mixer grinder by aligning the handle of the jar with the plungers and moving the jar down into the jar locating collar. On coming into contact with the jar, the plungers move in under compression of the springs and allow the jar to slide down in the jar locating collar against the outer ends of the plungers. The taperings at the outer ends of the plungers facilitate sliding down of the utility jar in the jar locating collar past the plungers. When the notches at the outer surface of the base of the utility jar are aligned with the plungers, the plungers move out into the notches under expansion of the springs so as to hold the utility jar in position firmly and lock the jar in position. When the utility jar is fully introduced in the collar, the motor coupler 33 at the top end of the motor shaft 34 is coupled to the blade coupler 35 at the lower end of the shaft 36 of the blades 37 of the mixer grinder. The mixer grinder is operated at different speeds by selecting the speed by turning the selector switch so as to allow the movable contact thereof to make contact with the different tappings of the stator winding of the motor. When the motor is in the switched off position and the mixer grinder is not in the operating mode, the movable contact of the speed selector switch is in contact with the fixed contact of the normally open switch. In order to release and remove the utility jar from the locating collar, the normally open switch 27 is closed momentarily by operating the knob thereof. The electromagnetic coils are energised momentarily and as a result the
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plungers are magnetised and pulled in under compression of the respective springs. The utility jar is now free and can be easily lifted up from the locating collar by holding the handle thereof. The switch 27 opens after a short interval and continues to remain open. As a result, flow of current to the electromagnetic coils is discontinued and the coils are deenergised and the plungers move out to their original position. According to the invention, the utility jar can be introduced into the locating collar and locked in position easily and very conveniently without holding the main body. The mixer grinder of the invention is also simple in construction and easy and convenient to operate. The moving contact of the speed selector switch makes contact with the fixed contact of the normally open switch only in the switched off position of the electric motor. Therefore, the jar does not get unlocked during the operation of the motor and mixer grinder. Therefore the locks of the invention are safe and reliable also.
The tubular housings of the locks can be held in the main body by different arrangements. The tubular housings, the plungers and the holding sleeves can be made of different materials. The electromagnetic locks can be of a different construction. There can be more than two electromagnetic locks. The three speeds are only representative and there can be more number of speed tappings of the stator. Such variations of the invention are obvious to those skilled in the art and are to be construed and understood to be within the scope of the invention.
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We claim
1) A mixer grinder comprising at least two electromagnetic locks for the utility jar thereof, the locks being located in the utility jar locating collar of the mixer grinder diametrically opposite to each other.
2) The mixer grinder as claimed in claim 1, wherein the electromagnetic locks each comprises a plunger made of an electromagnetic material, the plungers being movable forward and backward electromagnetically and spring biased in the forward direction, the outer ends of the plungers being adapted to engage in corresponding notches provided at the outer surface of the base of the utility jar.
3) The mixer grinder as claimed in claim 2, wherein the plungers are made of stainless steel.
4) The mixer grinder as claimed in claim 2 or 3, wherein the notches on the outer surface of the base of the utility jar are aligned with the handle of the jar.
5) The mixer grinder as claimed in anyone of claims 2 to 4, wherein the outer ends of the plungers are tapered.
6) The mixer grinder as claimed in claim 1, wherein the electromagnetic locks each comprises a plunger made of an electromagnetic material and reciprocably held in an electromagnetic coil which is located in a closed end tubular housing over a holding sleeve at the inner side thereof, the sleeve being made of a magnetic flux permeating material, the housing being made of an electric insulating and non-magnetic material and
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fitted in the utility jar locating collar of the mixer grinder, the outer end of the plunger being spring biased in the direction of the utility jar and adapted to engage in a corresponding notch provided at the outer surface of the base of the utility jar, the plunger being provided with a stopper flange adapted to abut against the closed front end of the holding sleeve and restrict the forward movement of the plunger and further adapted to slide against the inner surface of the holding sleeve so as to guide the forward and backward movement of the plunger in the tubular housing, the electromagnetic coil being connected to the speed selector switch of the mixer grinder through a normally open single push single throw type switch.
7) The mixer grinder as claimed in claim 6, wherein the plungers are made of stainless steel, the tubular housings are made of moulded plastics such as polypropylene or nylon and the holding sleeves are made of aluminium.
8) The mixer grinder as claimed in claim 6 or 7, wherein the notches at the outer surface of the base of the utility jar are aligned with the handle of the jar.
9) The mixer grinder as claimed in any one of claims 6 to 8, wherein the outer ends of the plungers are tapered.
Dated this 4th day of March 2008

(Jose M A)
ofKhaitan&Co
Agent for the Applicants
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ABSTRACT A mixer grinder (1) comprising at least two electromagnetic locks (14, 14) for the utility jar (12) thereof. The locks are located in the utility jar locating collar (11) of the mixer grinder diametrically opposite to each other. (Fig 1)