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, 2005
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION
AN IMPROVED STATOR HOUSING
APPLICANTS
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Prabhadevi, Mumbai 400 030, Maharashtra, India, an Indian Company
INVENTORS
Pinto Neil; Mettem Navadeep and Kulkarni Shrihari; all of Crompton Greaves Ltd, Commercial Motors Division, 196-198, Kundaim Industrial Estate, Kundaim, Goa - 403115, India; all Indian Nationals
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 stator housings.
Background of the Invention:
A 'stator housing' includes a body which is cast using a specific casting procedure in relation to defining the exterior and interior of its body.
In the earlier casting process of stator housing, a self cored process, was used. The self cored process is also termed as cope and drag which refers to the upper and lower parts of a two-part casting flask used in sand casting. In this process, metal is poured into a mould. In flaskless molding, the same terms are used; cope for the top or upper piece and drag for the bottom or lower piece.
In the simplest sand casting procedure, the drag is placed on a board, around a pattern of the part to be cast. The pattern is a model of the desired casting. Sand is sifted over the pattern until the model is covered by a few inches of sand. More sand is then dumped into the drag, and rammed with a wooden wedge, or mechanically vibrated to pack the sand down. The sand is then struck level with the top edge of the cope, using a wooden or metal strake. A board is then placed on top of the drag and the drag is flipped over. The pattern is then removed leaving behind its impression on the sand to form the mold. A similar method is adopted for the cope. The cope and the drag are then aligned together to form a complete mold and the molten metal is then poured into it. On solidifying the sand mold is broken out leaving behind the cast component.

In this method since the mold is made up of only 2 parts, to permit removal of pattern from sand the pattern is drawn axially and exactly one half is taken into the cope and the other into the drag. Also a draft has to be given in the direction in which the pattern will be drawn out, so that it facilitates removal of the pattern. As the pattern in this case is drawn axially the draft allowance has to be given all along the length of the body and the fins, making the design bulky. Also the stator stamping used in this motor is in contact with the body only at 4 places, but the bore of the body is cast all along the fall circumference of bore. This further adds to the weight of the body.
There is a need for an improved stator housing.
Prior Art:
United States Patent Application 5821654 describes a bearing support for a cylindrical rotating shaft bearing for preventing partial deformation of the stator housing due to difference in cooling time and shrinkage between thick and thin parts of the housing during formation by injection molding.
However, the prior art reduces weight merely by forming holes in the stator housing.
Objectives of the Invention:
An object of the invention is to provide a stator housing with reduced weight.

Another object of the invention is to provide a stator housing with improved heat dissipation.
Yet another object of the invention is to reduce wastage of material due to conventional casting process.
Still another object of the invention is to provide an economically manufactured stator housing, due to its design.
Summary of Invention:
According to this invention, there is provided an improved stator housing for an electric motor, said stator housing comprises:
a. segmented bore, said segments being defined along the inner circumference
of said housing, by intermittent depression pockets along pre-defined zones
of its inner circumferential curvature;
b. plurality of hollow foots beneath said stator housing for providing support to
said stator housing; and
c. plurality of linear fins protruding out of external circumferential surface of
said stator housing are directional i.e. they are aligned along 4 directions,
each set being in different cores (4 segmented cores total) they are along the
direction in which the pattern will be drawn from the core.
Typically the stator body being cast through self core method, the draft allowances on the body and the fins were required to be given all along the length of the body.

Typically, said linear fins include tapering side walls adapted to provide draft only along said tapered side walls.
Typically, said linear fins include a linear top surface which ensures that there is no draft along said top surface, thereby providing better heat dissipation.
Typically, said segmented bore includes pre-defined zones such that the curved portions (not defined by the pocket zones) complement the rounded ends of the stator stamping.
Typically, said hollow feet include predefined zones such as that the solid feet (not defined by hollow zones) complement the base of the foot.
Brief Description of the Accompanying Drawings:
Figure 1 illustrates an isometric view of the stator housing of the prior art;
Figure 2 illustrates an isometric view, depicting the underside, of the stator housing of the prior art;
Figures 3a, 3b, 4a, and 4b illustrate various views of the fins extending out of the outer side of the stator housing of the prior art of Figures 1 and 2;

Figure 6 illustrates an isometric view of the stator stamping adapted to be co-axially placed inside said stator housing; and
Figure 7 illustrates a front view of the stator stamping adapted to be co-axially placed inside said stator housing.
The invention will now be described in relation to the accompanying
drawings, in which:
Figure 5 illustrates a schematic of the isometric view of the stator housing;
Figure 8 illustrates an isometric view, depicting the underside, of the stator housing of Figure 5; and
Figures 9a, 9b, 10a, and 10b illustrate various views of the fins extending out of the outer side of the stator housing of the prior art of Figures 1 and 2;
Detailed description of the Accompanying Drawings:
Figure 1 illustrates an isometric view of the stator housing of the prior art;
Figure 2 illustrates an isometric view, depicting the underside, of the stator housing of the prior art;
Figures 3a, 3b, 4a, and 4b illustrate various views of the fins extending out of the outer side of the stator housing of the prior art of Figures 1 and 2;

Figure 6 illustrates an isometric view of the stator stamping adapted to be co-axially placed inside said stator housing; and
Figure 7 illustrates a front view of the stator stamping adapted to be co-axially placed inside said stator housing.
In the stator housing (100) of the prior art, the inner circumference i.e. the bore (10) of the stator housing was substantially curved throughout.
The stator stamping (12), as seen in Figures 6 and 7, used in motor body is not round. It contains rounded corners. As depicted, only the curved portion (rounded corners) of the stator stamping is in contact with the bore of the stator body. Hence, there is no need to have a substantially curved inner circumference of the stator housing.
In the conventional stator the pattern was drawn along the length of the stator housing such that draft allowances have to be provided all along the length of the fins (25) of the body. This has made the fins thicker at the centre (47) and reducing the thickness (tapering) towards the edges (49, 51). Hence, the shape of the fins was not uniform throughout the body resulting in inefficient heat dissipation. Further due to requirement of draft allowances in the conventional system the thickness of the fins is more towards the centre resulting in increase in weight and higher consumption of material.
The draft allowances have to be provided along the direction of pull of the pattern to ensure easy removal of the pattern. Thus, as seen, draft is added along the length and height.

In the conventional stator, the fins are radially extending.
In the conventional system, the foot (41, 43, 45, 47) for mounting the stator housing was solid and requires significant amount of material to be filed in.
According to this invention, there is provided an improved stator housing (200).
In accordance with the improved design of said stator housing, significant amount of weight reduction is achieved by maintaining the same quality output parameters.
Figure 5 illustrates a schematic of the stator housing.
In accordance with an embodiment of this invention, there is provided a segmented bore (inner circumference) (11), said segment being defined by intermittent depression pockets (12) along pre-defined zones of its curvature. Typically, said pre-defined zones are defined such that the curved portions (not defined by the pocket zones) complement the rounded ends (14, 16, 18, 20) of the stator stamping (150). The linear portions (22, 24, 26, 28) thus face the depressed pocket zones, and are spaced apart from said pocket zones.
Furthermore, since there is interference fit between the bore of stator body and the stator stamping, to facilitate easy entry and proper locking, the surface finish of the stator bore has to be very good. This is not possible to get directly in a casting process and hence the practice followed is to cast the

bore with a little extra material and then to perform a boring operation (a material removal operation to get required size and surface finish). Thus, in both conventional and the new body, additional material is given on the bore as machining allowance. In case of conventional process this was much more than the new body as material was added all round the bore while in the new body in accordance with this invention, the material will be added only along the area of contact i.e. material will not be added in the pockets provided.
Figure 8 illustrates an isometric view, depicting the underside, of the stator housing of Figure 5.
In accordance with yet another embodiment of this invention, there is provided a plurality of hollow foots (40, 42, 44, 46) beneath said stator housing for providing support. Here, optimum amount of material is used for bearing the load of motor. Rest of the excess material is removed by introducing pockets in the foot,
Figures 9a, 9b, 10a, and 10b illustrate various views of the fins extending out of the outer side of the stator housing of the prior art of Figures 1 and 2;
In accordance with another embodiment of this invention, there is provided a plurality of linear fins (30) protruding out of external circumferential surface of said stator housing. Typically, said linear fins include tapering side walls (32, 34) adapted to provide draft only along said tapered side walls. The linear nature of the top surface (36) ensures that there is no draft along the top edge. This provides better heat dissipation. In the segmented core casting

the draft allowances are to be drawn along the height of the fins of the stator housing. The height being much lesser as compared to length of the fins, the material consumption is very less.
In new body, the method of casting used is segmented core. Here the direction of pull of pattern will be as shown by arrows in Figure 2 of the accompanying drawings. Thus, the draft required on each fin is only along the height of fin as shown in Figure 9b of the accompanying drawings.
The length of fin being much more than the height, the amount of material to be given as draft will be much more in case of conventional body. Thus the weight on account of fins will be lesser in new body.
The fit between the stamping and the stator housing bore (inner diameter of stator body where the stamping is located) is very critical. To maintain the required fit between the stamping and stator housing bore, the stator housing bore has to be machined. In order to get a clean surface, a cut of at least 1.5 mm has to be taken during the machining process. In the convention system excess material was casted along the complete diameter of the stator housing bore, which was later machined to achieve the required size and clean area. In the proposed invention, the contact area between the stamping and stator housing bore has been restricted to some pads i.e. the non-depressed zones, which in this case are 4. As the contact area between the stamping and bore was limited to these pads hence the area to be machined is only along the pads. Thus, the excess material for machining allowance is to be given along the pads only hence reducing the wastage of material.

Using the above process of casting the reduction is consumption of material is about 30%. Thus, the stator housing is made cost-effective.

We claim,
1. An improved stator housing for an electric motor, said stator housing comprising:
a. segmented bore, said segments being defined along the inner circumference
of said housing, by intermittent depression pockets along pre-defined zones
of its inner circumferential curvature;
b. plurality of hollow foots beneath said stator housing for providing support to
said stator housing; and
c. plurality of linear fins protruding out of external circumferential surface of
said stator housing.
2. A stator housing as claimed in claim 1 wherein, said linear fins include tapering side walls adapted to provide draft only along said tapered side walls.
3. A stator housing as claimed in claim 1 wherein, said linear fins include a linear top surface which ensures that there is no draft along said top surface, thereby providing better heat dissipation.
4. A stator housing as claimed in claim 1 wherein, said segmented bore includes pre-defined zones such that the curved portions (not defined by the pocket zones) complement the rounded ends of the stator stamping.