FORM 2
THE PATENTS ACT 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See Section 10; rule 13)
TITLE OF THE INVENTION
Twin Shifter Rail Gear Shifting System For an Automotive Transmission
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
Srinivasa Rao Muvvala
an 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 particularly describes the invention and the manner in
which it is to be performed.

Twin Shifter Rail Gear Shifting System For an Automotive Transmission
Field of invention
The present invention is related to gear shifting system for an automotive transmission and more particularly it is related to twin shifter rail gear shifting system for a twin lay shaft transmission of a front wheel drive automobile
Background of invention
A typical transmission of front wheel driven (FWD) automobile consists of layout with one input shaft and one or two lay shafts with free wheeling gears distributed on either shafts. A particular gear ratio is selected by either sliding the gears axially until they mesh with each other, or by engaging synchroniser coneor ring. The sliding gears or synchroniser cone or rings are usually actuated by shifter forks mounted on their respective shift rail or shaft. Each fork usually selects one or two ratios by sliding in desired direction.
The said forks are actuated by specially configured dogs which in turn are controlled by gear shifting and selection unit like toggle finger or shifter tower mounted on housing or casing. A typical shift tower consists of minimal features like shift finger , interlock, gate guide , stopper, central detent mechanism etc. All of the above mentioned parts, when integrated make shifter tower complex. With more components, fixed and moving parts tolerance gets accumulated resulting in deterioration of overall shift quality due to design as well as manufacturing. Further it adds to complexity in manufacturing, assembling, serviceability or maintainability. With increased vehicle load requirements and torques, gear shift quality and durability get affected. Also demand for better shift feel, durability of gear shift quality and overall Noise Vibration and Harness (NVH) is on rise. All these needs call for transmission with higher centre distances of main shafts, yet lesser inertias, better synchronizers , minimum friction losses, less no. of shift components with

closer clearances and tolerances, use of standardised parts like linear bearings, detents etc.
Nonetheless synchronizer is one major contributor for gear shift quality; this invention addresses the limitations in conventional gear shifting system.
Object of invention
The main object of the present invention is to provide a twin shifter rail gear shifting system for an automotive transmission.
Another object of the present invention is to provide a twin shifter rail gear shifting system for an automotive transmission which reduces number of components and hence variability, tolerance stack up and facilitates improved quality of gear shifting.
Another object of the present invention is to provide a twin shifter rail gear shifting system for an automotive transmission which eliminates externa! shifter tower and is simple in construction, more durable with better overall shift performance for an automotive transmission.
Yet another object of this invention is to provide twin shifter rail gear shifting system for an automotive transmission which gives flexibility for packaging critical parts like power train mount.
Yet another object of the present invention is to provide a twin shifter rail gear shifting system for an automotive transmission which is easy to manufacture , assemble, eliminating errors while assembling and easy to service or maintenance.

Still another object of the present invention is to provide a twin shifter rail gear shifting system for an automotive transmission which caters to any size of transmissions irrespective of centre distances of main shaft.
Statement of invention
Twin shifter rail gear shifting system for an automotive transmission comprises; first shift rail and second shift rail each fixedly mounted on housing axially parallel to each other and inline with gear box axis or main shaft and free to rotate against respective axis; first set of forks slidably mounted on said first shift rail; second set of forks slidably mounted on said second shift rail ; first shift sleeve slidably mounted on said first shift rail ; second shift sleeve slidably mounted on said second shift rail ; first interlock cum stopper fixedly mounted on said first shift rail; second interlock cum stopper fixedly mounted on said second shift rail ; a gate selection lever for connecting said first and second interlock cum stoppers ; a shift lever for actuating said first and second shift sleeves ; and a cam detent fixedly mounted on housing such that said cam detent is radial to axis of said first and second shift rails.
Gear shifting system, in accordance with present invention, wherein said first shift sleeve comprises first set of fingers for actuating said first set of forks through recesses provided on first set of fork dogs of said first set of forks.
Gear shifting system, in accordance with present invention, wherein said first shift sleeve having two projections forming a recess to accommodate first spherical end of said shift lever for actuating said first set of forks depending on selected forks.
Gear shifting system, in accordance with present invention, wherein said second shift sleeve comprises second set of fingers for actuating said second set of forks through recesses provided on second set of fork dogs of said second set of forks.

Gear shifting system, in accordance with present invention , wherein said second shift sleeve having two projections forming a recess to accommodate second spherical end of said shift lever for actuating said second set of forks depending on selected forks.
Gear shifting system, in accordance with present invention, wherein said second shift sleeve comprises a cam profile to engage with said cam detent for smooth gear shifting, gate centralisation and gear neutralisation and prevent gear jump out or slippage of gears.
Gear shifting system, in accordance with present invention, wherein said first and second interlock cum stoppers are having slots for accomodating said first and second set of fork dogs respectively.
Gear shifting system, in accordance with present invention, wherein said slots on said first and second interlock cum stoppers, recesses on said first and second set of fork dogs, and said first and second set of fingers, are configured in such a way that at a time only one fork is free to slide keeping other forks locked by said first and second interlock cum stoppers.
Gear shifting system, in accordance with present invention, wherein said slots on said first and second interlock cum stoppers are configured to guide said fingers for precise gear shifting and avoiding mis shifts.
Gear shifting system, in accordance with present invention, wherein said first and second interlocks cum stoppers are connected to each other with the help of a gate selection lever through a ball or cylindrical joints.
Gear shifting system, in accordance with present invention, wherein length of said first and second interlock cum stoppers, said gate selection lever and said shift

lever is varied for various size of transmission system with different centre distance of main shafts of gear box.
Gear shifting system, in accordance with present invention, wherein said shift lever having first and second spherical ends engaged with recesses on said first and second shift sleeves respectively during gear shifting.
Gear shifting system, in accordance with present invention, wherein said shift lever is mounted on housing axially fixed and free to rotate against its own axis while gear shifting.
Gear shifting system, in accordance with present invention, wherein said shift lever is perpedicular or parallel to said first and second shift rails.
Brief description of invention
In accordance with this invention, gear shifting system comprises; first shift rail 1 and second shift rail 2 each mounted on housing parallel to each other axially fixed but free to rotate against respective axis, first set of forks 3,4 slidably mounted on said first shift rail 1 and second set of forks 5,6 slidably mounted on said second shift rail 2, first shift sleeve 7 slidably mounted on said first shift rail 1 , second shift sleeve 8 slidably mounted on said first shift rail 2 , first interlock cum stopper 9 fixedly mounted on said first shift rail 1 , second interlock cum stopper 10 fixedly mounted on said second shift rail 2, wherein said interlock cum stoppers 9,10 connected positively by selection lever 11 via ball or cylindrical joints , wherein said shift sleeves 7,8 are actuated by shift lever 12 mounted on housing axially fixed but free to rotate against its own axis while gear shifting, cam detent 13 fixedly mounted on main housing 14 such that detent axis is radial to axis of said first shift rail 1 and second shift rail 2 . The cam profile 8'" is fixedly provided on either said first shift sleeve 7 or said second shift sleeve 8.

Detailed description of the 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,
Figure - 01 shows an isometric view in accordance with the present invention.
Figure - 02 shows exploded isometric view in accordance with the present
invention.
Figure - 03 shows top view in accordance with the present invention.
Figure - 04 shows side view in accordance with the present invention.
Figures - 05 and 07 shows the isometric view of shift rail assembly.
Figures - 06 and 08 show an exploded isometric view of shift rail assembly.
Figures - 9 to 12 show views of present invention with perpedicular or parallel
orientation of shift lever with other shafts.
Now referring figure-1 to 8, In accordance with this invention, gear shifting system comprises; first shift rail 1 and second shift rail 2 each mounted on housing axially fixed but free to rotate against respective axis,Said first shift rail 1 and second shift rail 2 are parallel to the axis of main shaft or axis of the gear box, first set of forks 3,4 are slidably mounted on said first shift rail 1 .second set of forks 5,6 are slidably mounted on said second shift rail 2 .first shift sleeve 7 slidably mounted on said first shift rail 1, second shift sleeve 8 slidably mounted on said second shift rail 2, first interlock cum stopper 9 fixedly mounted on said first shift rail 1 , second interlock cum stopper 10 fixedly mounted on said second shift rail 2, a gate selection lever 11 for connecting said first and second interlock cum stoppers 9,10, a shift lever 12 for actuating said first and second shift sleeves 7,8; and cam detent 13 fixedly mounted on main housing 14 such that said cam detent is radially towards axis of said shift rails 1,2.
Said first interlock cum stopper 9 and second interlock cum stoppers 10 are connected by said gate selection lever 11 via ball or cylindrical joints.

Said first shift sleeve 7 and second shift sleeve 8 are actuated by said shift lever
12 mounted on said housing 14. Said shift lever 12 is axially fixed on said housing
14 but is free to rotate against its own axis while gear shifting.
Said cam detent 13 fixedly mounted on main housing 14 such that detent is radial
to the axis of said first shift rail 1 or said second shift rail 2.
The cam profile 8'" is fixedly provided on either said first shift sleeve 7 or said
second shift sleeve 8.
Said cam detent 13 is fixedly mounted on main housing 14 accordingly depending
on the position of said cam profile on either said first shift sleeve 7 or said second
shift sleeve 8.
Said first shift rail 1 comprises first shift sleeve 7 having two projections forming a
recess to accommodate first spherical end 12' of said shift lever 12 for actuating
said first set of forks 3, 4 depending on the selected said forks. Said first shift
sleeve 7 is slidably mounted on said first shift rail 1.
The said first shift sleeve 7 and said interlock cum stopper 9 rotate for selecting either fork 3 or fork 4 or none of said first set of forks 3,4 depending on the relative angular position of the slots provided on said interlock cum stopper 9 with respect to the said first set of fork dogs 3',4' and and said first shift sleeve 7 slides axially and actuates either fork 3 or fork 4 or none of said first set of forks 3,4 for gear shifting.
The said second shift sleeve 8 and said interlock cum stopper 10 rotate for selecting either fork 5 or fork 6 or none of said second set of forks 5,6 depending on the relative angular position of the slots provided on said interlock cum stopper 10 with respect to the said second set of fork dogs 5',6' and and said second shift sleeve 8 slides axially and actuates either fork 5 or fork 6 or none of said second set of forks 5,6 for gear shifting.

The said first shift sleeve 7 comprises first set of fingers 7', 7" for actuating said first set of forks 3, 4 through recesses provided on said first set of fork dogs 3', 4' of the said first set of forks 3, 4.
Said second shifter rail 2 comprises second shift sleeve 8 having two projections forming a recess to accommodate second spherical end 12" of said shift lever 12 for actuating said second set of forks 5, 6 depending on the selected forks. Said second shift sleeve 8 is slidably mounted on said first shifter rail 2.
The said second shift sleeve 8 selects either fork 5 or fork 6 or none of the forks of said second set of forks 5,6 depending on the relative angular position of the recesses on the said interlock cum stopper 10 with respect to the said second set of said fork dogs 5', 6'.
The said second shift sleeve 8 comprises second set of fingers 8', 8" for actuating said second set of forks 5, 6 through recesses provided on said second set of fork dogs 5',6' of the said second set of forks 5,6.
The said second shift sleeve 8 also comprises cam profile 8'" to engage with said cam detent 13 fixedly mounted on main housing 14 of gear box.
Alternatively the said cam profile 8'" can be fixed to said first shift sleeve 7 and the mounting location of said detent 13 is changed accordingly.
The said first interlock cum stopper 9 and second interlock cum stopper 10 are connected with each other with the help of said gate selection lever 11 with ball or cylindrical joints.
Said first shift sleeve 7 and second shift sleeve 8 are actuated simultaneously with the help of said shift lever 12.

The gate selection is done by rotating either said first shift rail 1 or second shift rail 2 on its own axis. The gate selection is done with help of an external lever provided on gear box,
Said fork dog 3' having recess for accomodating said finger 7' of said first shift sleeve 7 during actuation of said first shift sleeve 7.
Said fork dog 4' having recesses for accomodating said finger 7" of said first shift sleeve 7 during actuation of said first shift sleeve 7.
Said fork dog 5' having recess for accomodating said finger 8'of said second shift sleeve 8 during actuation of said second shift sleeve 8.
Said fork dogs 6' having recess for accomodating said finger 8" of said second shift sleeve 8 during actuation of said second shift sleeve 8.
The said first interlock cum stoppers 9 is mounted on said first shift rail 1 and said second interlock cum stoppers 10 is mounted on said second shift rail 2.
It can be appreciated that by rotating either of said shifter rail 1, or said shifter rail 2, the said first interlock cum stopper 9 and second interlock cum stopper 10 rotate simultaneously for the cross gate selection. After gate selection, required gear is engaged by rotating said shift lever 12 on its own axis. The said gate selection and gear shifting is done with help of a lever provided external to gear box. Said first interlock cum stopper 9 and second interlock cum stoppers 10 are having slots for accomodating said first set of fingers 7',7" of said first shift sleeve 7 and said second set of fingers 8',8" of said second shift sleeve 8 respectively.
Said slots provided on said first interlock cum stopper 9 and second interlock cum stopper 10, recesses provided on said first set of fork dogs 3',4' and second set of

fork dogs 5',6' , said first set of fingers 7',7" and second set of finger 8',8" , are configured in such a way that at any point of time only one fork is free to slide keeping other forks locked by said first interlock cum stopper 9 and second interlock cum stopper 10 .
Said slots provided on said first interlock cum stopper 9 and second interlock cum stopper 10 are configured to act as guides to said first set of fingers 7',7", and said second set of fingers 8,'8" respectively ensuring precise gear shifting and avoiding mis shifts.
Said gate selection lever 11 is connected to said first and second shift rails 1, 2 with the help of said first interlock cum stopper 9 and second interlock cum stopper 10. Said gear shift lever 12 having first spherical end 12', and second spherical end 12" engaged with recess provided on said first shift sleeve 7 and second shift sleeve 8 respectively. Said cam detent 13 is provided for gate neutralisation which avoids jump outs of gears or gear slippage. The arrangement of present invention is configured in such a way that, it eliminates the conventional shifter tower which provides flexibility in packaging of power train mount on periphery of the transmission housing.
The first shift rail 1 and second shift rail 2 are inline with the main shaft of gear box. The present invention is configured in such a way that only said first interlock cum stopper 9 and second interlock cum stopper 10 needs to be fixed while assembling gearbox. The said first interlock cum stopper 9 and second interlock cum stopper 10 are fixed to said said first shift rail 1 and second shift rail 2 respectively, hence while assembling gearbox, it is easier to assemble the shifting system on gears and transmission housing.
The said shifting lever 12 having first spherical ends 12' and second spherical ends 12" simultaneously engaged with recess of said first shift sleeve 7 and second shift sleeve 8 during gear shifting. The said cam profile 8'" and detent 13

are provided to assists in smooth gear shifting, gate centralisation and gear neutralisation, prevent gear jump out or slippage of gears.
By varying the length of said first interlock cum stopper 9 and second interlock cum stopper 10, said gate selection lever 11 and said shift lever 12, the various size of transmission system with different centre distance of main shaft can be used.
The said shift lever 12 can be perpedicular or parallel to said first shift rail 1 and second shift rail 2.
Present invention provides flexibility in packaging of power train mount on periphery of the transmission housing.The present system is configured in such a way that only said first interlock cum stopper 9 and second interlock cum stopper 10 needs to be fixedly mounted on said first shift rail 1 and second shift rail 2 respectively while assembling gearbox, hence it is easier to assemble the shifting system on gears and transmission housing. By varying the length of said first interlock cum stopper 9 and second interlock cum stopper 10, said gate selection lever 11 and said shift lever 12, various size of transmission system with different centre distance of main shaft can be used. The said shift lever 12 can be perpedicular or parallel to said first shift rail 1 and second shift rail 2.
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. Twin shifter rail gear shifting system for an automotive transmission comprises; first shift rail and second shift rail each fixedly mounted on housing axially parallel to each other and inline with gear box axis or main shaft and free to rotate against respective axis; first set of forks slidably mounted on said first shift rail ; second set of forks slidably mounted on said second shift rail ; first shift sleeve slidably mounted on said first shift rail ; second shift sleeve slidably mounted on said second shift rail ; first interlock cum stopper fixedly mounted on said first shift rail; second interlock cum stopper fixedly mounted on said second shift rail ; a gate selection lever for connecting said first and second interlock cum stoppers ; a shift lever for actuating said first and second shift sleeves ; and a cam detent fixedly mounted on housing such that said cam detent is radial to axis of said first and second shift rails.
2. Gear shifting system as claimed in claim 1, wherein Said first shift sleeve comprises first set of fingers for actuating said first set of forks through recesses provided on first set of fork dogs of said first set of forks.
3. Gear shifting system as claimed in claim 1, wherein said first shift sleeve having two projections forming a recess to accommodate first spherical end of said shift lever for actuating said first set of forks depending on selected forks.
4. Gear shifting system as claimed in claim 1, wherein said second shift sleeve comprises second set of fingers for actuating said second set of forks through recesses provided on second set of fork dogs of said second set of forks.
5. Gear shifting system as claimed in claim 1, wherein said second shift sleeve having two projections forming a recess to accommodate second spherical end of said shift lever for actuating said second set of forks depending on selected forks.

6. Gear shifting system as claimed in claim 1, wherein said second shift sleeve comprises a cam profile to engage with said cam detent for smooth gear shifting, gate centralisation and gear neutralisation and prevent gear jump out or slippage of gears.
7. Gear shifting system as claimed in claim 1, wherein said first and second interlock cum stoppers are having slots for accomodating said first and second set of fork dogs respectively.
8. Gear shifting system as claimed in claim 1, wherein said slots on said first and second interlock cum stoppers, recesses on said first and second set of fork dogs, and said first and second set of fingers, are configured in such a way that at a time only one fork is free to slide keeping other forks locked by said first and second interlock cum stoppers.
9. Gear shifting system as claimed in claim 1, 7 and 8, wherein said slots on said first and second interlock cum stoppers are configured to guide said fingers for precise gear shifting and avoiding mis shifts.
10. Gear shifting system as claimed in claim 1, wherein said first and second interlocks cum stoppers are connected to each other with the help of a gate selection lever through a ball or cylindrical joints.
11. Gear shifting system as claimed in claim 1, wherein length of said first and second interlock cum stoppers, said gate selection lever and said shift lever is varied for various size of transmission system with different centre distance of main shafts of gear box.

12. Gear shifting system as claimed in claim 1, wherein said shift lever having first and second spherical ends engaged with recesses on said first and second shift sleeves respectively during gear shifting.
13. Gear shifting system as claimed in claim 1, wherein said shift lever is mounted on housing axially fixed and free to rotate against its own axis while gear shifting.
14. Gear shifting system as claimed in claim 1, wherein said shift lever is perpedicular or parallel to said first and second shift rails.
15.Twin shifter rail gear shifting system for an automotive transmission as herein described with reference to accompanying drawings.