FORM 2
THE PATENTS ACT 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See Section 10; rule 13)
TITLE OF THE INVENTION
Hollow rear axle shaft with spline and flange and manufacturing
process of the same
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
Mr. Deodatta Shende
Mr. Udayan Balvant Pathak
Mr. Momin Vaseem Ahmad S
Indian National
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.

FIELD OF INVENTION:
The invention relates to hollow rear axle shaft with spline and flange at two ends and manufacturing process of the same more particularly to hollow rear axle shaft through friction welding and spline construction.
BACKGROUND OF INVENTION:
Presently rear axle shaft are manufactured by using conventional upset forging, machining and heat treatment. The torsional load coming on flange is carried through radius to the stem of the axle shaft. Because of the present constructional features and method of manufacturing problems associated with the current designs are that it is very heavy and bulky, the load path for the current design leads to extra material requirements and associated processing, machining and tooling cost is high, costly. Again the present forms of rear axle require energy intensive operations like through hardening and case induction hardening which increases the carbon foot print of the component thus has an adverse impact on the environment. Again control on case depth during induction hardening is a difficult manufacturing process.
OBJECT OF THIS INVENTION:
Main object of the invention is to obviate the above mentioned drawbacks by providing hollow rear axle shaft through friction welding and spline construction . Another object of this invention is to reduce part weight. Yet another object of the invention is to ensure static and dynamic strength.
SUMMARY OF INVENTION:
A hollow rear axle shaft with spline and flange comprising a hollow tube with spline at one end and flange at other end, said spline has stepped like structure near central opening projected opposite to end joined with a flange, projection of said stepped portion of spline is such that part of the stepped portion does not touch the hollow tube, said spline and flange are joined to said hollow tube at two

ends firmly such that they can carry requisite load. The projection of said stepped portion of spline is such that outer part of said stepped portion does not touch the hollow tube. The spline has multiple cylindrical holes symmetrically placed in outer circle of the stepped structure. The flange is a solid flange with teeth like structure on its outer surface.
The hollow tube is uniform in thickness and diameter throughout the length for ease of manufacturing. The spline and/ or flange are joined to said hollow tube by friction welding for better surface contact and better mechanical property. The spline is manufactured by solid bar machining or spline rolling. The joining process is done by laser welding or TIG or MIG welding or C02 welding or Plasma welding or Submerged arc welding or Resistance welding or combination of the above. The spline end is joined by locking arrangements such as Circlip locking or key way locking or fastening or spring pin locking or special locking arrangements provided at flange end with splines.
The flange is manufactured from Medium Carbon steel and said tube is manufactured from Low or Medium Carbon steel. The arrangement is hardened thoroughly by induction hardening or laser hardening or conventional hardening.
A method of manufacturing a hollow rear axle shaft with spline and flange, said method comprising acts of: manufacturing of spline end through solid bar / hollow tube, by machining and spline forming, said spline forming can be roiling or hobbing, welding said spline to said hollow tube at one end, induction hardening carried out for predetermined depth, manufacturing flange end through machining, performing heat treatment such as hardening and tempering on flange for required strength, welding said flange to other end of said hollow tube (without spline).
A method of manufacturing a hollow rear axle shaft with spline and flange, said method comprising acts of: manufacturing of spline end through solid bar / hollow

tube, by machining and spline forming, said spline forming can be rolling or nobbing, welding said spline to both ends of said hollow tube of tube, induction hardening carried out for predetermined depth, manufacturing flange end through machining and spline cutting at center, performing heat treatment such as hardening and tempering on flange for required strength, one of the spline ends of tube is assembled with flange spline.
A method of manufacturing a hollow rear axle shaft with spline and flange, said method comprising acts of: manufacturing of splines on tube / solid bar through rolling or hobbing operation, induction hardening carried out for predetermined depth, manufacturing of flange end through machining and spline cutting at the center, performing heat treatment such as hardening and tempering on flange for required strength, one of the spline ends of tube is assembled with flange spline.
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:
Figure 1 shows cut section of Rear axle shaft with desired features
Figure 2 shows Rear axle shaft with Flange and spline end
Figure 3 shows the flow chart of manufacturing process of one embodiment
Figure 4 shows the flow chart of manufacturing process of another embodiment
Figure 5 shows the flow chart of manufacturing process of yet another
embodiment
DETAILED DESCRIPTION OF INVENTION:
The on going demand of saving fuel is forcing the automotive industry to reduce the weight of the components / parts and simultaneously improve the

performance and reduce cost. The instant application incorporates advanced welding and forming processes to get economical and weight reduction in rear axle shaft.
Axle shaft transmits the torque received from engine through differential case to the wheels causing vehicle to move. The torque is transmitted through the fillet radius to flange. This makes fillet radius critical. Also due to this construction and limitation of manufacturing process solid construction is required. It has been found that the load is transmitted through the cylindrical skin having 25% thickness of the radius of such solid shaft and solid portion near the center does not contribute significantly for transmission of load.
This application incorporates the above findings and method of matching stiffness requirements of the design along with the manufacturing techniques leading to the hollow construction of axle shaft through either of the following routes.
The instant application is provided with a tube to get desired torque and fatigue life. The various combinations of welding processes, spline construction at both end differential and hub assembly end have been found out which have been exemplified in the embodiments. This is possible through different load paths-either through splines or through circular welding.
In the instant application substitute for solid construction of rear axle shaft has been provided. This gives similar performance during operation of the vehicle with reduced part weight i.e. to transmit the torque under operating conditions also to ensure the static and dynamic strength. Again the strength of spline joint is enhanced through friction welding and the extra material processing by which solid construction has been replaced by hollow construction. This is chip less environmental friendly process. The proposed manufacturing process does away with costly and energy intensive operations like through hardening of bulk

mass in conventional design by suitable and easier through hardening of lower mass for environmental sustainability and to ensure performance in motion and vibration characteristics.
The hollow rear axle shaft through friction welding and spline construction comprising combination of joining processes like welding to spline end and flange end, and using hollow shaft to decrease the weight.
The proposed feature in rear axle shaft is combination of joining processes like friction welding / TIG / MIG/ laser/ Resistance / Plasma/ Submerged arc/ CO2 welding to spline end and flange end. Also in another embodiment process of friction welding is being eliminated at both ends by manufacturing of hollow rear axle shaft through suitable forming process.
The spline is a disc typed shape. It has a stepped like structure preferably at one side near the central opening. Said stepped like structure is projected outward i.e. in the opposite direction to the hollow tube. The projection of said stepped portion of spline is such that outer part of the stepped portion does not touch the hollow tube. Hence one end of the hollow tube which is joined to the spline remains inside the opening and does not come out of it. Said spline has multiple cylindrical holes in it symmetrically placed in outer circle of the stepped structure. The other end of said hollow tube is joined to a flange. Said flange is a solid flange. Said flange has teeth like structure in its outer surface. Said flange is manufactured by forging or casting or forming. Said hollow tube is uniform in thickness and diameter throughout the length. The uniform thickness and diameter is easy to achieve in manufacturing process. Hence, manufacturing of such uniform thickness and diameter is less time consuming, is (ess complicated and easy to manufacture and economical as well. Apart from the economic benefits it gives technical benefit of higher efficiency. Said hollow tube is manufactured by rolling or extrusion or hydro forming or centrifugal casting. Moreover the friction welding makes better surface contact between the spline

and hollow tube which increases the strength and stability. Moreover it is less expensive than laser welding and also does not involve any hazard, neither requires controlled environmental condition like laser welding. Similar friction welding is used for joining of flange portion with hollow shaft providing similar technical and economic benefits.
In one embodiment of the instant application Tube (part 2) is friction joined to flange without spline construction. The joining process can be done by process of welding or press fitting or serrating and press fitting or welding to flange (part 3). Spline end (parti), is manufactured by solid bar machining or spline rolling. Said joining is done by welding. The proposed system is formed by welding such as friction / laser/TIG / MIG/ C02 / Plasma/ Submerged arc/ Resistance welding to tube (part 2).
In another embodiment of the instant application Spline end (part 1) is manufactured in solid or hollow construction according to the need. Spline end (part 1) is joined at both ends of the tube (part 2) with required locking arrangements. Said locking arrangement can be like Circlip locking or key way locking or fastening or spring pin locking or special locking arrangements provided at flange end (part 3) with splines. Said joining process can be welding of any kind such as friction welding, laser welding, TIG or MIG welding , C02 welding, Plasma welding, Submerged arc welding or Resistance welding or combination of the above.
In yet another embodiment of the instant application Splines are manufactured on solid shaft or hollow tube at both ends, through forming process such as rolling or forming or without friction welding with required locking arrangements. Said locking arrangement can be like Circlip locking or key way locking or fastening or spring pin locking or special locking arrangements provided at flange end (part 3) with splines.

Manufacturing process of above mentioned embodiments involve many processes as described in figures 3, 4 and 5.
As shown in figure 4 Spline end (part 1- refer fig.1) is manufactured through solid bar / hollow tube, by machining and spline forming (rolling / nobbing) and is welded to tube at one end (part 2). Induction hardening is carried out to required predetermined depth. Flange end (part 3) is manufactured through machining. Heat treatment is done. The heat treatment performed are hardening and tempering carried out on flange for required strength and welded to other end of tube (without spline).
As shown in figure 5 Spline end (part 1- refer fig. 1) is manufactured through solid bar / hollow tube, by machining and spline forming (rolling / hobbing) is welded to both ends of tube (part 2). Induction hardening is carried out to required predetermined depth. Flange end (part 3) is manufactured through machining and spline cutting at the center. Heat treatments carried out are hardening and tempering; carried out on flange for required strength. One of the spline ends of tube assembled with flange spline.
As shown in figure 6 Splines are manufactured on tube / solid bar through rolling or hobbing operation. Induction hardening carried out to required depth. Flange end (part 3) manufactured through machining and spline cutting at the center. Heat treatment - hardening and tempering carried out for flange to get required strength. One of the spline ends of tube assembled with flange spline.
Materials used for flange is Medium Carbon steel and materials used for tube are Low or Medium Carbon steel. Thorough hardening is done using Induction or laser or Conventional hardening method will be provided as per design requirements.

Advantages:
1. Reduced part weight - 30% reduction in weight as compared with solid
construction.
2. Less material processing for solid construction due to hollow construction. This is chip less environmental friendly process.
3. Light weight rear axle shaft is easier for vehicle maintenance, replacement and better serviceability.
4. Deletion of costly and energy intensive operations like through hardening of bulk mass and Induction Hardening of Case in conventional design by suitable and easier through hardening of lower mass for environmental sustainability.
5. Chip (Swarf) less manufacturing process hence no wastage of steel during machining.
6. Load path either through splines or through circular welding, deletion of complex & critical conventional fillet radius leading to lower material requirements and associated processing.
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.

We claim:
1. A hollow rear axle shaft with spline and flange comprising:
- a hollow tube with spline at one end and flange at other end,
- said spline has stepped like structure near central opening projected opposite to end joined with a flange,
- projection of said stepped portion of spline is such that part of the stepped portion does not touch the hollow tube,
- said spline and flange are joined to said hollow tube at two ends firmly such that they can carry requisite load.

2. The hollow rear axle shaft with spline and flange as claimed in claim 1, wherein projection of said stepped portion of spline is such that outer part of said stepped portion does not touch the hollow tube
3. The hollow rear axle shaft with spline and flange as claimed in claim 1, wherein said spline has multiple cylindrical holes symmetrically placed in outer circle of the stepped structure.
4. The hollow rear axle shaft with spline and flange as claimed in claim 1, wherein said flange is a solid flange with teeth like structure on its outer surface.
5. The hollow rear axle shaft with spline and flange as claimed in claim 1, wherein said hollow tube is uniform in thickness and diameter throughout the length for ease of manufacturing.
6. The hollow rear axle shaft with spline and flange as claimed in claim 1, wherein said slines and/ or flange are joined to said hollow tube by friction welding for better surface contact and better mechanical property.
7. The hollow rear axle shaft with spline and flange as claimed in claim 1, wherein said spline is manufactured by solid bar machining or spline rolling.

8. The hollow rear axle shaft with spline and flange as claimed in claim 1, wherein said joining process is done by laser welding or TIG or MIG welding or C02 welding or Plasma welding or Submerged arc welding or Resistance welding or combination of the above.
9. The hollow rear axle shaft with spline and flange as claimed in claim 1, wherein said spline end is joined by locking arrangements such as Circlip locking or key way locking or fastening or spring pin locking or special locking arrangements provided at flange end with splines.

10. The hollow rear axle shaft with spline and flange as claimed in claim 1, wherein said flange is manufactured from Medium Carbon steel and said tube is manufactured from Low or Medium Carbon steel.
11. The hollow rear axle shaft with spline and flange as claimed in claim 1, wherein said arrangement is hardened thoroughly by induction hardening or laser hardening or conventional hardening.
12. A method of manufacturing a hollow rear axle shaft with spline and flange, said method comprising acts of:

- manufacturing of spline end through solid bar / hollow tube, by machining and spline forming,
- said spline forming can be rolling or hobbing,
- welding said spline to said hollow tube at one end,
- induction hardening carried out for predetermined depth,
- manufacturing flange end through machining,
- performing heat treatment such as hardening and tempering on flange for
required strength,
- welding said flange to other end of said hollow tube (without spline).

13. A method of manufacturing a hollow rear axle shaft with spline and flange,
said method comprising acts of:
- manufacturing of spline end through solid bar / hollow tube, by machining and spline forming,
- said spline forming can be rolling or hobbing,
- welding said spline to both ends of said hollow tube of tube,
- induction hardening carried out for predetermined depth,
- manufacturing flange end through machining and spline cutting at center,
- performing heat treatment such as hardening and tempering on flange for
required strength,
- one of the spline ends of tube is assembled with flange spline.
14. A method of manufacturing a hollow rear axle shaft with spline and flange,
said method comprising acts of:
- manufacturing of splines on tube / solid bar through rolling or hobbing
operation,
- induction hardening carried out for predetermined depth,
- manufacturing of flange end through machining and spline cutting at the center,
- performing heat treatment such as hardening and tempering on flange for required strength,
- one of the spline ends of tube is assembled with flange spline.
15. A hollow rear axle shaft with spline and flange and manufacturing process of
the same as hereinabove described with reference to the accompanying
drawings.