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
PROVISIONAL SPECIFICATION
(See section 10 and rule 13)


TITLE OF THE INVENTION
A process to develop new die for rotors
APPLICANTS
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400030, Maharashtra, India, an Indian Company
INVENTOR
Samant Ravindra, Crompton Greaves Ltd, FHP Unit, Kundaiyam, Goa, India, an Indian national
PREAMBLE TO THE DESCRIPTION
The following specification describes the invention


The invention relates to the field of making molding die for the rotor to manufacture the rotor.
Small electric motors are used for various office automation equipment, domestic electrical equipment or an automobile. For example, a fully equipped domestic flour mill includes individual motors for powering such devices, said motors having a rotor die casted with aluminum. Until recently, die cast motor rotors were universally produced using aluminum because rotor fabrication by aluminum pressure die-casting was an established practice. The process of die- casting includes drawbacks such as high imbalance to the tune of20 gm resulting additional process of balancing, high porosity in the filled aluminum affecting motor performance and life, and many more.
The proposed invention disclosed herein tries to overcome the above mentioned disadvantages and to improve the over all quality of rotors.
An object of the invention is to reduce imbalance of rotors, which further results in reduction of rejections of rotors.
Another object of the invention is to increase the overall productivity in less cycle time due to low imbalance of rotors.
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Yet another object of the invention is to reduce the test bed rejection by proper filling of aluminum inside rotor lamination.
Yet another object of the invention is to improve the overall performance of the motor.
Another object of the invention is to reduce rework along the assembly lines.
Yet another object of the invention is to significantly reduce scrap generation.
In accordance with the invention, the process of die casting comprises injecting molten metal under high pressure into a steel mold called a die. Typically die casting machines are rated in clamping tones, which is equivalent to the pressure exerted on the die. Irrespective of the size, the fundamental difference in die casting machines is the method used to inject molten metal into a die i.e. the hot chamber or cold chamber. A complete die casting cycle can vary from less than one second for small components weighing less than an ounce, to two-to-three minutes for a casting of several pounds, making die casting the fastest technique available for producing precise non-ferrous metal parts.
Further dies are made of alloy tool steels in at least two sections, the fixed die half, or cover half, and the ejector die half, to permit removal of castings. The ejectors half usually contain the runners (passageways) and gates (inlets) that route molten metal to the cavity. Dies also include locking pins to secure the two halves, ejector pins to help remove the cast part, and openings for coolant and lubricant. When the die casting machine closes, the two die halves are locked and held together by the machine's
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hydraulic pressure. The surface where the ejector and fixed halves of the die meet and lock is referred to as the "die parting line." The total projected surface area of the part being cast, measured at the die parting line, and the pressure required of the machine to inject metal into the die cavity governs the clamping force of the machine.
In an embodiment of the invention, each mold cavity is generally circular or disc shaped and includes a first side wall, a second wall, an outer wall, and an inner wall. First sidewall, outer wall, and inner wall of mold cavity are formed in first mold portion. Second side wall of mold cavity is formed in generally flat surface of second mold portion. Preferably, outer wall is tapered outwardly and inner wall is tapered inwardly to aid in the insertion of fin core. First side wall and second side wall respectively define a first pad contact surface for a plate and a second pad contact surface for a plate of rotor.
A fin core as disclosed in the invention is generally circular or disc shaped and includes an inner or hub portion, an intermediate or spoke portion and an outer or flange portion. Hub portion is generally ring shaped and includes an inner tapered surface adapted to closely conform to tapered inner wall of mold cavity. Inner tapered surface and outer tapered outer wall of mold cavity. Inner tapered surface and outer tapered surface of fin core serve as draft angles to enable fin core to be easily conveniently inserted into first mold portion before casting. Spoke portion is generally disc- shaped ad interconnects hub portion and flange portion. Spoke portion further includes a plurality of generally radially extending slots for forming a plurality of cooling fins in brake rotor. In accordance to the
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present invention the accurate shape of extending slots produces a rotor having cooling fins that are more capable of heat dissipating heat during the operation.
Dated this 19th day of March 2009
(Ivan Bernard Fuller)
of Khaitan&Co
Agent for the Applicants

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