FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
As amended by the Patents (Amendment) Act, 2005
AND
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 drill jig
APPLICANTS :
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company
INVENTOR (S):
Bhujbal Eknath Ramdas, of Crompton Greaves Ltd, Motors Division (M3), A-6/2 MIDC Ahmednagar 414111, Maharastra, 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 the field of mechanical engineering.
Particularly, this invention relates to an improved drill jig.
Background of the Invention:
In switchgear equipment or any equipment or any component where holes are to be drilled in a preset configuration, the use of drill jigs is mandated. A drill jig is located to sit atop the component. Locating pins may be used for accurate positioning. These locating pins are dowel pins. Dowel pins are often used as precise locating devices in machinery.
According to one of the embodiments of a drill jig, a round plate is used as a drill jig to sit on a component with a round top view. The continuous use of the drill jig, by screwing or by locating atop a plurality of components, results in wear and tear of the underside of the drill jig as well as that of the locating holes and / or dowel pins. The locating pins are dowel pins which fit itself with the component for locating holes of the jig through which the holes are to be screwed into the component.
A jig bush is provided with pre-positioned holes for the purpose of hole drilling.
In order to reduce wear and tear, a hardened spigot plate was fitted co-centric to said drill jig, on the underside of said jig. This made the drill jig a dual assembly drill jig. Hence, more screws and pins were needed.

Prior Art:
US2005073116 discloses a Jig plate for fixing a work thereto and which is gripped by a main spindle. It is related to a jig plate for fixing a work thereto and which is gripped by a main spindle, and more specifically to a jig plate suitable for application to a system for automatically processing all six surfaces of the work in a lathe -type machine tool or a machining center.
US4013281 discloses a Jig driving apparatus used to move a workpiece mounted on a jig about during the performance of work on the workpiece. It is related to a jig driving means and more specifically to a jig driving means used to move a workpiece mounted on ajig about during the performance of work on the workpiece.
Both the above prior art documents relate to automatic co-location. None of the prior art document relate to reducing the cost of the drill jig or providing a simple jig for location of holes on a component.
Objects of the Invention:
An object of the invention is to provide an improved drill jig.
Another object of the invention is to eliminate a dual assembly drill jig.
Yet another object of the invention is to save material cost by eliminating a dual assembly drill jig.
Still another object of the invention is to provide modularity of providing dowel pins for location even if one set of dowel pin Is damaged.

Summary of the Invention:
According to this invention, there is provided an improved drill jig adapted to be placed on a component for accurately locating hole positions on the component for drilling holes in the component with the use of said drill jig, said drill jig comprises:
a. stepped plate, said step being located annularly on the underside of said plate;
b. four hardened pins dispersed radially about said stepped plate at an angular
spacing of 90 degrees with respect to each other; and
c. plurality of jig bushes dispersed radially about the plate in order to provide
locations for providing holes in the component once the jig is placed on the
component.
Typically, wherein said stepped plate is an annular stepped plate with a central hole.
According to a preferred embodiment of this invention, there is provided an improved drill jig adapted to be placed on a component for accurately locating hole positions on the component for drilling holes in the component with the use of said drill jig, said drill jig comprises:
a. stepped plate, said step being located annularly on the underside of said plate;
b. four hardened pins dispersed radially about a locus of points about the centre of
said stepped plate at an angular spacing of 90 degrees with respect to each other;
and
c. plurality of jig bushes dispersed radially about the plate in order to provide
locations for providing holes in the component once the jig is placed on the
component.

Brief Description of the Accompanying Drawings:
Figure la illustrates a top view of the drill jig with hardened spigot plate;
Figure lb illustrates a front cross-sectional view of the drill jig of Figure la; and
Figure 2 illustrates an exploded view of the drill jig of Figures la and lb.
The invention will now be described in relation to the accompanying drawings, in
which:
Figure 3a illustrates a top view of the drill jig;
Figure 3b illustrates a front cross-sectional view of the drill jig of Figure 3a; Figure 4 illustrates an exploded view of the drill jig of Figures 3a and 3b; and Figure 5 illustrates a bottom isometric view of the drill jig.
Detailed Description of the Accompanying Drawings:
Figure la illustrates a top view of the drill jig with hardened spigot plate. Figure lb illustrates a front cross-sectional view of the drill jig of Figure la. Figure 2 illustrates an exploded view of the drill jig of Figures la and lb.
In the drill jig (10) of the prior art, a first circular plate (12) is provided. This is termed as the jig plate. From its bottom side, the jig plate is a stepped plate. A second co-centric circular plate (14) with a relatively smaller diameter is fitted on the underside of said first circular plate. The second plate is a complementary stepped plate which matched the step of the first circular plate to form a stepped co-operating fit (as seen in Figure lb

of the accompanying drawings). The second plate is a hardened spigot plate. Preferably, it is a hardened MS plate.
The fit is obtained by means of four alien screws (16) and two dowel pins (18). The dowel pins (18) locate the two plates (12 and 14) together. A jig bush (19) provides the holes for guiding holes to be screwed into the component located below. Due to the need to use the given screws and pins, the lead time for manufacturing is more as the locating time increases. The increased material cost of metal components causes the cost of the jig to be relatively higher. Subsequently, the weight of the jig is relatively higher, too. In the event that the spigot wears out or gets damaged, the rework of spigot is relatively expensive. Eventually, the number of processes relating to the use of this drill jig is more; the processes including the steps of hardening of spigot plate, drilling and tapping in spigot plate , drilling and counterboring in jig plate.
According to this invention, there is provided an improved drill jig (20). This invention is related to harden spigot of jig plate which is used for locating the jig plate on the job which is to be drilled with the help of this jig.
Figure 3a illustrates a top view of the drill jig;
Figure 3b illustrates a front cross-sectional view of the drill jig of Figure 3a; Figure 4 illustrates an exploded view of the drill jig of Figures 3a and 3b; and Figure 5 illustrates a bottom isometric view of the drill jig.
In accordance with an embodiment of this invention, there is provided a stepped plate (22), said plate being an annular plate with a central hole, and said step being located annularly on the underside of said plate.

In accordance with another embodiment of this invention, there are provided four hardened pins (24) dispersed radially about the plate (22) at an angular spacing of 90 degrees with respect to each other. These hardened pins eliminate the need to have a hardened spigot plate, thereby eliminating additional material involvement and also avoids the task of locating a second plate.
In accordance with yet another embodiment of this invention, there is provided a plurality of jig bushes (26) dispersed radially about the plate in order to provide locations for providing holes in the component once the jig is placed on the component.
In the drill jig of this invention, there is no hardening process; hence lead time for manufacturing is relatively less. Subsequently, the jig cost and weight is relatively less. Elimination of screws results in a single component drill jig.
Once the hardened pins wears out after use, other positions around the same locus defined by the earlier pins may be used for another four dowel pins located in the same manner as described above. By fixing of harden pins at another position, same jig plate can used for rework of spigot. The steps of hardening, drilling, tapping, and alien screw fixing process are not required.
While this detailed description has disclosed certain specific embodiments of the present invention for illustrative purposes, various modifications will be apparent to those skilled in the art which do not constitute departures from the spirit and scope of the invention as defined in the following claims, and it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.

We claim,
1. An improved drill jig adapted to be placed on a component for accurately locating hole positions on the component for drilling holes in the component with the use of said drill jig, said drill jig comprising:
a. stepped plate, said step being located annularly on the underside of said plate;
b. four hardened pins dispersed radially about said stepped plate at an angular
spacing of 90 degrees with respect to each other; and
c. plurality of jig bushes dispersed radially about the plate in order to provide
locations for providing holes in the component once the jig is placed on the
component.
2. An improved drill jig as claimed in claim 1, wherein said stepped plate is an annular stepped plate with a central hole.
3. An improved drill jig adapted to be placed on a component for accurately locating hole positions on the component for drilling holes in the component with the use of said drill jig, said drill jig comprising:
a. stepped plate, said step being located annularly on the underside of said plate;
b. four hardened pins dispersed radially about a locus of points about the centre
of said stepped plate at an angular spacing of 90 degrees with respect to each
other; and
c. plurality of jig bushes dispersed radially about the plate in order to provide
locations for providing holes in the component once the jig is placed on the
component.