FORM 2
THE PATENTS ACT 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See Section 10; rule 13)
TITLE OF THE INVENTION
Fixture and method for torsion spring assembling and dismantling gear box
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
INVENTORS
Vaij Sanjay Yashawant
Indian nationals of
TATA MOTORS LIMITED,
an Indian company having its registered office
at Bombay House, 24 Homi Mody Street, Hutatma Chowk,
Mumbai 400 001 Maharashtra, India
PREAMBLE TO THE DESCRIPTION
The following specification describes the invention and the manner in which it is to be performed.

TITLE OF INVENTION
Fixture and method for torsion spring assembling and dismantling gear box.
FIELD OF INVENTION
This invention relates to a Fixture and method for torsion spring assembling and dismantling gear box more particularly to G76 gearbox.
BACKGROUND OF THE INVENTION
Earlier the assembly was done by another tool. The use of that tool resulted in certain problems, including assembler's finger injury. Only highly skilled persons could use the tool. A lot of effort was also necessary while assembling the gear box. Also it was not useful for dismantling the assembly. The existing prior arts are not able to provide an adequate device or method for assembling and dismantling of torsion spring in an easy and safe manner.
SUMMARY
The current invention provides a method and fixture for assembling and dismantling of the torsion spring in G76 gear box, which permits the successful assembly and dismantling of torsion spring. Various features of the invention provide safe and easy assembly of the spring without the need of assembler's expertise.
The invention includes means for rotating the spring up to the necessary position and locking it in the compressed condition.
According to the another aspect of the invention, all the parts which are to be fitted in the gearbox along with the torsion spring, are assembled on the separate plate, held together in the fixture. The latch mounted on the handle of the fixture for locking the position of the spring in compressed condition. The whole assembly is placed inside the gearbox housing and the screw is fitted from outside of the gearbox housing. After tightening the screw the latch of the fixture is released and the fixture is taken out. Embodiment
BRIEF DESCRIPTION OF THE DRAWINGS

The above brief description as well as further objects, features and advantages of the present invention will be more fully appreciated by reference to the following detailed description of presently preferred but nonetheless illustrative embodiments in accord with the present invention when taken in conjunction with the accompanying drawing wherein:
FIG. 1 is an isometric view of the fixture in the latched condition
FIG. 2 is an isometric view of the fixture in open latch condition
FIG. 3 is an exploded view of the fixture.
FIG. 4 is the isometric view of the plate which is used fordoing the spring assembly.
FIG. 5 is an exploded view of the torsion spring assembly.
FIG. 6 to FIG. 16 are the isometric views show the assembly sequence.
DETAILED DESCRIPTION
The current invention provides a method and fixture for assembling and dismantling of the torsion spring in a gear box, which permits the successful assembly and dismantling of torsion spring. Various features of the invention provide safe and easy assembly of the spring without the need of assembler's expertise.
The invention includes means for rotating the spring up to the necessary position and locking it in the compressed condition.
According to the another aspect of the invention, all the parts which are to be fitted in the gearbox along with the torsion spring, are assembled on the separate plate, held together in the fixture. The latch mounted on the handle of the fixture for locking the position of the spring in compressed condition. The whole assembly is placed inside the gearbox housing and the screw is fitted from outside of the gearbox housing. After tightening the screw the latch of the fixture is released and the fixture is taken out.
Now referring to the drawings the shaft 14 of the fixture is having the diameter to suit to the bearing block 33. The shaft can easily slide in the bearing block. The lower end of the

shaft is having the splines to suit to the lever 30 hole. At the upper end of the shaft threading is done to fit the nut 20. Two flat surfaces are machined on the threaded portion to suit the rectangular hole made in the fixed arm 10. The flat surface restricts the free rotation of the shaft in the fixed arm. The length of the flat surface is maintained well enough to create proper clearance between the moving arm top and the fixed arm bottom. Below the flat and threaded portion, the shaft has a step portion and the step-diameter is suited to the moving arm hole. A gauge piece 13 is attached to the shaft just below the moving arm. It maintains the orientation of bearing block.
The moving arm is the part of the fixture which rotates around the shaft more than 180°. It has a hole to rotate freely around the shaft. The step is provided inside the hole just to rest on the step on the shaft. The moving arm consists of handle 16, stopper 11 and finger 12. A handle is a sheet metal component attached to the arm using two rivets 17 and 18. The shape of the handle is such that it is gripped by hand properly. Similar handle is used for the fix arm. One of the rivets 18 is extended upward and a rolling bush is inserted in it. The upper end of the rivet is then bulged to prevent the falling of bush. The purpose of bush is to avoid the wear of the rivet in operation of locking and opening of the latch 15 repeatedly. A finger 12 is attached to the lower end of the moving arm. It is a hardened piece of steel having a projection at the lower side. This projection is used to hold the upper end of the torsion spring and twist it. A stopper 11 is provided to the moving arm to establish the proper entry of the fixture in to the gear box housing 35. While entering the fixture in the gearbox housing the stopper rests on the face of the housing.
The fix arm has a rectangular hole which suits to the upper end of the shaft. A handle 16 is attached to the fix arm using two rivets 17 and 22. One of the rivets 22 is extended upward and a rolling bush and the latch 15 inserted in it. A small torsion spring is attached to the latch winding over the rolling bush. The spring retains the latch to its original position. The upper end of the rivet is then bulged to hold the latch.
The moving and fixed arms are inserted in the shaft and the nut is fitted at the upper end of the shaft. Now the fixed arm and the shaft were held together tightly and the moving arm can rotate freely around the shaft. Thus the fixture is ready for use.

In the fixture the shaft and the finger are made up of high carbon steel and are heat treated to harden for making them wear resistant. All other parts are made of mild steel.
In one of the embodiment a Fixture for torsion spring assembling and dismantling gear box comprising a shaft of said fixture having suitable diameter to slide in bearing block, - said shaft having splines at lower end, threading at upper end to fit nut, Two flats are machined on the threaded portion to suit the rectangular hole made in the fixed arm 10. The flat restricts the free rotation of the shaft in the fixed arm. The length of the flat is maintained well enough to create proper clearance between the moving arm top and the fixed arm bottom. Below the flat and threaded portion, the shaft has a step and the step-diameter is suited to the moving arm hole. A gauge piece 13 is attached to the shaft just below the moving arm. It maintains the orientation of bearing block.
The moving arm is the part of the fixture which rotates around the shaft more than 180°. It has a hole to rotate freely around the shaft. The step is provided inside the hole just to rest on the step on the shaft. The moving arm consists of handle 16. stopper 11 and finger 12. A handle is a sheet metal component attached to the arm using two rivets 17 and 18. The shape of the handle is such that it is gripped by hand properly. Similar handle is used for the fix arm. One of the rivets 18 is extended upward and a rolling bush is inserted in it. The upper end of the rivet is then bulged to prevent the falling of bush. The purpose of bush is to avoid the wear of the rivet in operation of locking and opening of the latch 15 repeatedly. A finger 12 is attached to the lower end of the moving arm. It is a hardened piece of steel having a projection at the lower side. This projection is used to hold the upper end of the torsion spring and twist it. A stopper 11 is provided to the moving arm to establish the proper entry of the fixture in to the gear box housing 35. While entering the fixture in the gearbox housing the stopper rests on the face of the housing.
The fix arm has a rectangular hole which suits to the upper end of the shaft. A handle 16 is attached to the fix arm using two rivets 17 and 22. One of the rivets 22 is extended upward and a rolling bush and the latch 15 inserted in it. A small torsion spring

is attached to the latch winding over the rolling bush. The spring retains the latch to its original position. The upper end of the rivet is then bulged to hold the latch.
The moving and fixed arms are inserted in the shaft and the nut is fitted at the upper end of the shaft. Now the fixed arm and the shaft were held together tightly and the moving arm can rotate freely around the shaft. Thus the fixture is ready for use.
In the fixture the shaft and the finger are made up of high carbon steel and are heat treated to harden for making them wear resistant. All other parts are made of mild steel.
DETAILED DESCRIPTION OF THE ASSEMBLY METHOD
The metal plate 21 is used to make the torsion spring assembly. The plate has two holes to locate the lever 30 in it (FIG. 6).
The long end of the torsion spring 31 is inserted to the lever hole and placed on the lever. The barrel piece 32 is inserted in the spring (FIG 7).
The fixture is opened and the bearing block 33 is inserted in the shaft. While inserting the bearing block ensure the step on the bearing block is at the outer side (FIG 8).
The gauge piece 13 on the shaft set the bearing block to fix the proper orientation (FIG 9). The fixture is inserted in the barrel piece (FIG 10).
The splines at the lower end of the shaft are inserted into the lever hole. Since the shaft has the splines, its position in the lever is fixed. Ensure that the bearing block is properly rest on the barrel piece (FIG 11).
The moving arm is rotated along with the upper end of the torsion spring till it gets latched (FIG 12)
The fixture is lifted up along with the assembly. Insert the roller 34 in the lever pin (FIG 13)
The roller is held with the thumb and placed the whole assembly inside the hole in the gearbox housing (FIG 14)
The screw along with the spring washer and plain washer is fitted to hold the whole assembly inside the gearbox housing (FIG 15)

After fitting of the screw the latch of the fixture is opened and the fixture is removed out. Thus the assembly is completed (FIG 16)
For dismantling the assembly same process is reversed,
The foregoing description is a specific embodiment of the present invention. It should be appreciated that this embodiment is described for purpose of illustration only, and that numerous alterations and modifications may be practiced by those skilled in the art without departing from the spirit and scope of the invention. It is intended that all such modifications and alterations be included insofar as they come within the scope of the invention as claimed or the equivalents thereof.

I Claim
1. A fixture for torsion spring assembling and dismantling gear box comprising:
a shaft 14 having diameter suitable to bearing block 33 so as to slide easily in said
bearing block;
lower end of said shaft having splines coherent with lever 30 hole and upper end of
having threading to fit nut 20;
two flat surfaces provided on said threaded portion to engage with rectangular hole made
in fixed arm 10 having a handle;
a moving arm 19 which consists of handle, stopper, finger, being coupled to said fixed
arm, said handles attached to said moving arm and fixed arm using at least one rivet.
2. The system as claimed in claim 1 wherein, a gauge piece 13 is attached to said shaft just below said moving arm to maintain orientation of bearing block.
3. The system as claimed in claim 1 wherein, said finger 12 having a projection at the lower side being provided at lower end of said moving arm is perpendicular to said handle and parallel to said shaft.
4. The system as claimed in claim 1 wherein, said projection in said finger twistably holds upper end of torsion spring.
5. The system as claimed in claim 1 wherein, said rivets 18 is extended upward, a rolling bush being inserted in it and upper end of said rivet is bulged to prevent the falling of bush.
6. The system as claimed in claim 1 wherein, said stopper 11 is provided in said moving arm to establish proper entry of said fixture into the gear box housing 35.
7. The system as claimed in claim 1 wherein, said stopper rests on the face of the housing while entering the fixture in the gearbox housing.

8. The system as claimed in claim 1 wherein, one of said rivets in each arm is extended upward and a rolling bush and the latch 15 inserted in it.
9. The system as claimed in claim 1 wherein, said moving arm is provided with a stepped hole to rotate freely around said shaft in such a way that said moving arm can rotate more than 180°.

10. The system as claimed in claim 1 wherein, said flat surfaces restrict free rotation of said shaft in said fixed arm.
11. The system as claimed in claim 1 wherein, a step portion is provided in said shaft below said flat and threaded portion, and step-diameter is suited to the moving arm hole.
12. The system as claimed in claim 1 wherein, said moving arm and fixed arms are inserted in the shaft and a nut is fitted at the upper end of the shaft in such a way that the fixed arm and the shaft were held together tightly and the moving arm can rotate freely around the shaft.
13. A fixture and method for torsion spring assembling and dismantling gear box substantially as hereinabove described with reference to the accompanying drawings.