FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
FIXTURE FOR SUBMARINE GATE SPARKING;
LARSEN & TOUBRO LIMITED, A COMPANY INCORPORATED UNDER THE COMPANIES ACT, 1956, WHOSE ADDRESS IS L&T HOUSE, BALLARD ESTATE, MUMBAI - 400 001, MAHARASHTRA, INDIA
THE FOLLOWING SPECIFICATION
PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.

FIELD OF INVENTION
The present invention relates to submarine gate sparking and more particularly to spark eroding gate profiles that are at an angle along vertical axis.
BACKGROUND OF INVENTION
A submarine gate or a tunnel gate is used in two-plate mold construction. An angled, tapered tunnel is machined from the end of the runner to the cavity, just below the parting line. As the parts and runners are ejected, the gate is sheared at the part. The tunnel can be located either in the moving mould half or in the fixed half. A sub-gate is often located into the side of an ejector pin on the non-visible side of the part when appearance is important. To degate, the tunnel requires a good taper and must be free to bend. Typical gate sizes range from 0.8 mm to 1.5 mm. For glass reinforced materials, the size may be large.
In injection molding of plastic parts, one must not see the gate vestige. It is a clean and efficient way to make a gate, but also requires a bit of expertise.
It is also important that the sub-gate have a smooth finish in order for the gate to eject. Injection molding plastic parts is hard enough without sticking gates. This is sometimes overlooked and as a result flakes are formed on the face of the mold during the molding operation. These flakes can then be removed by polishing with the help of available ceramic stones, or diamond impregnated stones.
There are many ways to locate the tunnel gate, and CNC EDM's have made the process much easier. In the past, when all the gates were machined on a milling machine, it was a common problem to properly locate the gate, as well as to cut it, especially in hardened steel
Problems in the existing solution : A submarine gate sparking requires separate setup since the job has to tilted to the required angle. So the job setup which is used for sparking other electrodes cannot be used here. Further, it has to be done on a non CNC machine since there is no scope for giving a co-ordinate sheet to the machine operator. The setting is difficult and time consuming. Also the positioning is not very accurate since it is done manually by the operator using the electrode itself.

Furthermore, the grinding allowance (G. A.) on the tool item complicates the calculation for positioning. In case of compound angle, the difficulty is further increased.
Also, the gate opening has to be checked manually and has to be gradually increased in order to get the required gate opening.
To eliminate the above mentioned drawbacks a novel fixture for submarine gate sparking is required in the art and the same is disclosed as follows.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a fixture as to spark erode the submarine gates at a required angle in CNC EDM machines.
In accordance with this a fixture for submarine gate sparking is provided that comprises a base fitted into a holder. The base has a slot in which a rotating holder placed and is pivoted through a pivot pin. An index pin is provided for setting the angle of inclination of the rotating holder. Bolt and nut arrangement fasten the rotating holder and the base together. An electrode holding pocket is provided in the rotating holder and is connected to the said base through the said pivot pin, index pin and bolt and nut arrangement. The electrode holding pocket holds an electrode tightly with the help of screws.
In one embodiment herein, the angle of inclination is set by engaging the index pin through the corresponding index pin holes in the rotating holder and the base.
A wide range of angles varying from 5 deg to 45 deg can be set in fixture by corresponding combination of the holes in the base and the rotating holder.
In one embodiment of the invention, operation of the fixture can be automated.
BRIEF DESCRIPTION OF THE DRAWINGS
Reference will be made to embodiments of the invention, examples of which may be illustrated in the accompanying figures. These figures are intended to be

illustrative, not limiting. Although the invention is generally described in the context of these embodiments, it should be understood that it is not intended to limit the scope of the invention to these particular embodiments.
Fig. 1 shows the full assembly for the submarine gate sparking as per the present invention.
Fig. 2 shows the EROWA holder known in the art.
Fig. 3 shows the base.
Fig. 4 shows the index pin.
Fig. 5 shows the pivot pin.
Fig. 6 shows the rotating holder.
Fig. 7 shows the electrode.
Fig. 8 shows the circlip.
Fig. 9 shows the bolt.
Fig. 10 shows the nut.
DESCRIPTION OF THE INVENTION
Disclosed herein is a fixture for submarine gate sparking that can be used to spark erode the submarine gates at a required angle in CNC EDM machines. The fixture for submarine gate sparking comprises a base fitted into a holder. The base has a slot in which a rotating holder placed and is pivoted through a pivot pin. An index pin is provided for setting the angle of inclination of the rotating holder. Bolt and nut fasten the rotating holder and the base together. An electrode holding pocket is provided in the rotating holder for holding an electrode tightly with the help of screws.
Fig. 1 shows the full assembly for the submarine gate sparking as per the present invention.
Fig. 2 to Fig. 10 show different components of the fixture including a holder 1, a base 2, an index pin 3, a pivot pin 4, a rotating holder 5, an electrode 6, a circlip 7, a bolt 8 and a nut 9.

In one embodiment herein and as shown in Fig. 1 the fixture for submarine gate sparking comprises a base 2 that is fitted into a holder 1. The holder is preferably an EROWA HOLDER 1 having a seat 1a on which the base fits. EROWA holder is a universal holder known in the art. The holder 1 has a slot 1b for the electrode holder. The base 2 has a slot 1d in which a rotating holder 5 is placed and is pivoted through a pivot pin 4 and pivot pin hole 1e. An index pin 3 is provided for setting the angle of inclination of the rotating holder 5. Arrangement of bolt 8 and nut 9 fasten the rotating holder 5 and the base 2 together. An electrode holding pocket 5d is provided in the rotating holder for holding an electrode 6 tightly with the help of screws e.g. Allen Screws. Inside the rotating holder the said electrode holding pocket is connected to the said base through the said pivot pin, index pin and bolt and nut arrangement
In one embodiment herein the angle of inclination of the rotating holder 5 may be set by engaging the index pin 3 through the corresponding index pin holes 1c provided in the rotating holder 5 and the base 2. A wide range of angles varying from 5 deg to 45 deg can be set in the fixture by corresponding combinations of the holes 1e in the base 2 and the rotating holder 5.
Thus the fixture as described above, helps to spark erode the submarine gates in CNC EDM machines. The fixture has a suitable attachment which makes it possible to spark erode at the required angle. The job doesn't need to be tilted for the machining. The machining may be carried out in the normal fashion, which is employed for vertical Spark EDM.
While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

We Claim
1. A fixture for submarine gate sparking comprising:
a base having a slot;
a rotating holder placed inside the said slot and pivoted through a pivot pin;
an index pin for setting an angle of inclination of the said rotating holder;
a bolt and nut arrangement for fastening the rotating holder and the base; and
an electrode holding pocket for holding an electrode tightly with the help of screws;
wherein, the said electrode holding pocket is connected to the said base through the said pivot pin, index pin and bolt and nut arrangement.
2. The fixture in claim 1, wherein the angle of inclination is set by engaging the index pin through the corresponding index pin holes in the rotating holder and the base.
3. The fixture in claim 1, wherein spark erosion of submarine gates is carried out in CNC EDM.
4. The fixture in claim 1, wherein a wide range of angles varying from 5 deg to 45 deg can be set in fixture by corresponding combination of the holes in the base and the rotating holder.
5. The fixture in claim 1, wherein operation of the fixture can be automated.