FORM 2
THE PATENTS ACT 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
PROVISIONAL SPECIFICATION
(See Section 10; rule 13)


TITLE OF THE INVENTION A MILLING TOOL
APPLICANTS
TATA MOTORS LIMITED, an Indian company
having its registered office at Bombay House,
24 Homi Mody Street, Hutatma Chowk,
Mumbai 400 001 Maharashtra, India
INVENTOR
Mr. Dattatraya D. Narhe and Mr.Sunil D. Sonawani both Indian nationals of TATA MOTORS LIMITED,
an Indian company having its registered office Bombay House, 24 Homi Mody Street, Hutatma Chow Mumbai 400 001 Maharashtra, India
PREAMBLE TO THE DESCRIPTION
The following specification describes the invention


FIELD OF INVENTION
This invention relates to cutting tools for milling of rubber components and method of milling in rubber.
PRIOR ART
The elastic properties of Rubber make it difficult to be cut with normal cutting tools (milling cutter etc). Rubber elasticity, also known as hyper elasticity, describes the mechanical behavior of many polymers, especially those with cross-linking. Invoking the theory of rubber elasticity, one considers a polymer chain in a cross-linked network as an entropic spring. When the chain is stretched, the entropy is reduced by a large margin because there are fewer conformations available. Therefore there is a restoring force, which causes the polymer chain to return to its equilibrium or unstretched state, once the external force is removed, such as a high entropy random coil configuration. This is the reason why rubber bands return to their original state. There are lots of parts in the automobile industry which are made of rubber and to machine these for prototype applications is another challenge. Conventionally for any modification in the existing geometry of the rubber parts, had to cut the part with saw or some sharp tool. However this process had the following disadvantages:-
1. The geometrical accuracy is not achievable.
2. The surface finish and the quality of the part was not good..
So to counter these problems new cutter is developed. Conventional cutting tools used for milling applications cannot be used, since the tool tend to shear the rubber material and removal of sliced material is also not efficient. This disadvantage has been overcome by new designed cutting tool.
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SUMMARY OF THE INVENTION
The objective of the present invention is to develop a tool which can be used for milling application in rubber like material.
The milling tool comprises of the main shank, the body, and the specially designed cutting tips for that. The one end of the shank (cylindrical) is held in the spindle and on the other end the cutting tips are assembled with the main body with the help of screws.
There are two types of invented cutting tips. The one with 'L' shape is being used for slicing the material form the side wall and the other a straight one is being used for the slicing or cutting of the material from the top surface. These inserts are being mounted on the main shank alternatively to facilitate the cutting action rhythmically. First the material is being cut form the side walls and then it is being removed form the surface.
BRIEF DESCRIPTION OF DRAWINGS
Fig.l & Fig.7 shows the front view of the draft milling tool used for cutting rubber.
Fig.2 shows the top & side view of the main tool body used for cutting rubber.
Fig. 3 shows the plan view of the draft milling tool.
Fig. 4 & Fig.8 shows the front, top & side view of the cutting tips.l
Fig. 5 & Fig.9 shows the front, top & side view of the cutting tips.2
Fig. 6 shows the cross sectional view of the draft milling tool.
DETAILED DESCRIPTION OF INVENTION
Referring now to the drawings wherein the showings are for the purpose of illustrating a preferred embodiment of the invention only, and not for the purpose of limiting the same.
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An embodiment of the present invention will now be explained with reference to the drawings as shown in Fig 1 to Fig. 6, the cutting tool has a main tool body (1) cutting tips (3 & 4) and tool body includes a shank (2) as shown in Fig.l. Fig.l refers to draft milling tool with its different parts. The main tool body has hole along the rotational axis up to some length i.e. S mm at both end. The whole tool body is made out of single block so that material flows freely through the milling body and can be removed through shank. The main tool body has a draft on its flat surface which is the milling face of the tool. The draft angle ranges from 3-6 degree. The body of main tool is larger at one end (milling face) and shorter at other end (body at shank side) in short the diameter varies at both ends.
The main tool body also consists of shank (2) at one end. This shank acts has a holding tool for the milling tool while carrying out the operation and also assembling the tips to the main tool body. The shank has a drilled hole at its open end.. Also the main tool body as a circular slot at its drafted end face. The body below the shank of the main tool body has a taper of certain angle. The cutting tips ( 3&4) located on drafted end face of the main tool body (1) to cut and slice the material in vertical and horizontal direction respectively. The main tool body further has slots along the draft face and these slots has a through drill hole with standard threads. The depth of this slot denoted by 'D' shown if in Fig.7 and the width of the slot is equal to the width of the cutting tip (3) which gets fitted in this slot. The purpose of holes drilled on the main tool body is to engage the tip (3).
The Fig.4 shows the detail description of the cutting tip (3). The tip (3) member is 'L' shaped member having one end flat (3') and other end (3") is bended and has a narrow & sharp elongated tip. There are four tip (3) member and are spaced rectangular to the axis of the main tool body. This tip member is acting as a cutting edge which is being used for slicing the material from the side wall. The tip (3) is screwed to the main tool body member by means of screw (5) engaged with the protrusion in main tool body. The narrowed end performs the cutting action. Tip
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member (3'') cut the material perpendicular to the axis of the hole and cut material flows through the hollow portion of the cutting tool.
After cutting the material along the wall, then the remaining material along the top surface is cutted by means of the tip (4). The detail description of the tip (4) is shown in the Fig.5. The cutting tip (4) performs the cutting of the material along the top surface in the form of slice. Body of tip (4) is same as cutting tip (3), but it is straight through out the length. The cutting tip (4) has a narrowed end with a particular type of profile i.e. it has thickness at one side (4"a) and it gets narrower at other side (4"b) forming the sharp edge at an angle of 6 degree. This sharp edge acts as cutting blade. The cutting tip (4) is provided with a hole drilled on it, by means of which with the help of screw it is assembled to the main tool body.
Method of cutting:
The shank (2) is being held in the collect chuck and then the collect chuck is being held in the milling machine spindle. The rubber work piece to be cut is being clamped firmly on the machine table. The tool rotates in the machine spindle and the cutter starts moving towards the work piece by moving in the cutting depth direction outside of its boundaries. There are two types of cutting actions:
> The tip (3) removes the material from the side wall and the
> The tip (4) removes the material form the bottom face of the work piece.
This way the material is being cut and removed in the slices from the work piece and it gives a smooth surface finish on the job.

7 th
Dated this 17m day of March 2009

TATA MOTORS LIMITED By their Agent & Attorney

CfL CC

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Karuna Goleria of DePENNING & DePENNING