FORM 2
THE PATENTS ACT, 1970 (39 of 1970)
As amended by the Patents (Amendment) Act, 2005
&
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2006
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION
Floor mounted mechanical gear shifting mechanism for automotive vehicle
APPLICANTS
Mahindra & Mahindra Ltd., Gateway Building, Apollo Bunder, Mumbai 400 001, Maharashtra, India, an Indian company
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be performed:

FIELD OF THE INVENTION
This invention relates to a floor mounted mechanical gear shifting mechanism for automotive vehicle.
BACKGROUND OF THE INVENTION
In automotive vehicles or automobiles including on road and off road vehicles, especially tractors and earth movers, multi-speed change gear transmissions are generally controlled with floor mounted mechanical gear shifting mechanisms to drive the vehicle at different forward and reverse speeds. One version or design of a floor mounted mechanical gear shifting mechanism (horizontal configuration) comprises a plurality of shift rails arranged horizontally spaced apart from one another at the same level and up and down movably supported in the speed forward-reverse gear unit housing of the vehicle. Another version or design of a floor mounted mechanical gear shifting mechanism (vertical configuration) comprises a plurality of shift rails arranged vertically one directly below another spaced apart from one another and up and down movably supported in the forward-reverse gear unit housing of the vehicle.
In both the versions, one ends of the shifting rails are connected to a gear shifting lever disposed vertically close to the driver seat in the vehicle through a shift finger and shift blocks and the other ends of the shift rails are connected to the speed forward-reverse gear unit housed in the speed forward-reverse gear unit housing through shift forks and dog clutches. In the vertical configuration, the shift blocks are arranged horizontally spaced apart from one another at the same level and each of the shift blocks is provided with a slot at the upper end thereof open at a pair of opposite

sides. The slots are disposed aligned with their open sides end to end and the shift blocks are connected to the gear shifting lever through the shift finger engaged in the slots at the upper ends of the shift blocks.
In one construction of shift rail and shift block assembly of the .vertical configuration of the gear shifting mechanism, the shift blocks are welded to the one ends of the shift rails and in another construction of the shift rail and shift block assembly of the vertical configuration of the gear shifting mechanism, the shift blocks are fixed to the one end of the shift rails with roll pins tightened in fixing holes in the rails and in the shift blocks. In both the cases, the shift blocks are first welded or fixed to the shift rails and then the shift rail and shift block assemblies are mounted in the speed forward-reverse gear unit housing through mounting holes provided in the mounting walls of the housing. The mounting holes are large enough to provide up and down movements to the shift rail and shift block assemblies.
In both the above constructions of the shift rail and shift block assemblies, if there is any misalignment of the mounting holes, there will be uneven gap or level difference between the slots at the upper ends of the shifting blocks. As a result, during gear change and speed change by operating the gear shifting lever, the shift finger will not make proper contact with the respective shift block and speed change will not be achieved effectively and smoothly. Further the driver will have to make extra effort with the gear shifting lever to ensure proper contact between the shift finger and the respective shift block. This will be unpleasant to the driver and will give a bad or inadequate shift feel and lead to driver fatigue. Because of the uneven gap or level difference between the slots in the shift blocks and rough handling of the gear shifting

lever by the driver, the gear shifting mechanism will develop problems like double gear engagement or no engagement at all and will become ineffective over a period of time and will have to be replaced thereby reducing the life of the gear shifting mechanism and increasing the maintenance cost of the vehicle.
Also in the case of both the above constructions of the shift rail and shift block assemblies, if there is any misalignment between the shift rails and shift blocks during assembly, mounting of the rail and block assemblies in the respective mounting holes in the mounting walls in the speed forward-reverse gear unit housing will become difficult and may even become impossible. Mounting of misaligned rail and block assemblies in the speed forward-reverse gear unit housing will also cause uneven gap between the blocks and level difference between the slots and problems as discussed above. Therefore, in order to avoid misalignment between the rail and block assemblies, it is absolutely essential to exercise very precise control and accuracy in the fitment between the rails and blocks. As a result, assembly cost and time for assembling the shift rails and shift blocks are increased.
Further in the case of the roll pin assembly between the rails and blocks, wear and tear will occur to the roll pins and sidewalls of the fixing holes in the shift rails and shift blocks. This will give rise to play between the roll pins and fixing holes in the shift rails and shift blocks and uneven gap between the blocks and problems as discussed above. In case of misaligned fitment between the shift blocks and shift rails, the assemblies may become unusable, especially in the case of weld fitted assemblies and may have to the rejected resulting in wastage of material and losses. Also in case of

damage to one of the components, either rails or blocks, the entire assemblies will have to be rejected thereby causing material wastage and losses.
SUMMARY OF THE INVENTION
According to the invention there is provided a floor mounted mechanical gear shifting mechanism for automotive vehicle comprising a plurality of shift rail and shift block assemblies disposed in the speed forward-reverse gear unit housing of the vehicle, each of the shift rail and shift block assemblies comprising a shift block mounted to one end of a shift rail, the shift rails being arranged vertically one directly below another spaced apart from one another and up and down movably mounted in the speed forward-reverse gear unit housing and the shift blocks being arranged horizontally spaced apart from one another at the same level in the speed forward-reverse gear unit housing and being provided with a slot at the upper ends thereof open at a pair of opposite sides thereof, the slots being aligned with one another with the open sides thereof end to the end the shift blocks being connected to the gear shifting lever of the vehicle disposed vertically close to the driver seat in the vehicle through a shift finger engaged in the slots in the upper ends of the shift blocks, the other ends of the shift rails being connected to the speed forward-reverse gear unit of the vehicle through shift forks and dog clutches, wherein one of the shift rail and shift block assemblies is of fixed construction comprising a shift block rigidly fixed to one end of a shift rail to act as a reference and each remaining shift rail and shift block assembly is of detachable construction comprising a shift block detachably and circumferentially adjustably engaged over the one end of a shift rail and locked in position on the one end of the shift rail with a clamping means.

The automotive vehicle is, preferably, a tractor.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
In the accompanying schematic drawings:
Fig 1 is a schematic lay out of a multi speed change gear transmission of an automotive vehicle such as tractor including a floor mounted mechanical gear shifting mechanism according to an embodiment of the invention;
Fig 2 is an isometric view of the speed forward reverse gear unit housing of the multispeed change gear transmission of Fig 1 including the gear shifting mechanism;
Fig 3 is a crosssectional view of the gear shifting mechanism of Fig 2;
Fig 4 is an isometric view of the gear shifting mechanism of Fig 2 without the housing;
Fig 5 is an isometric view of a shift rail and shift block assembly of fixed construction of the gear shifting mechanism of Fig 4;
Fig 6 is an isometric view of a shift rail and shift block assembly of detachable construction of the gear shifting mechanism of Fig 4;
Fig 7 is a sectional view at line AA in Fig 6; and '

Fig 8 is an exploded view of the shift rail and shift block assembly of Fig 6.
DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS
The multispeed change gear transmission 1 of an automotive vehicle such as tractor (not shown) as illustrated in Fig 1 of the accompanying drawings comprises an IC engine 2 housed in an engine housing 3, a clutch 4 housed in a clutch housing 5, a speed forward-reverse gear unit 6 housed in a speed forward-reverse gear unit housing 7, a speed change gear unit 8 housed in a speed change gear unit housing 9 and a differential gear 10 mounted on shaft 11 of the rear wheels (not shown) of the vehicle and housed in a differential gear housing 12. 13 and 14 are the main shaft and counter shaft, respectively of the vehicle. Main shaft is connected to shaft 11 and counter shaft is connected to clutch shaft 15. 16 is a coupling device provided in the counter shaft 14.17 is a power take off shaft connected to the main shaft. Power take off shaft is optional and is required only if additional drive is to be taken from the main shaft to drive auxiliary machine or apparatus like water pump, rotavator or generator (not shown) with the same engine.
Multispeed change gear transmission 1 includes a floor mounted mechanical gear shifting mechanism 18 comprising three shift rail and shift block assemblies 19, 20 and 21 housed in the speed forward-reverse gear unit housing 7. As illustrated in detail in Figs 2 to 8 of the accompanying drawings, shift rail and shift block assembly 19 is of fixed construction comprising a shift block 23 welded to one end of a shift rail 24 (Fig 5). Shift rail and shift block assembly 20 is of detachable construction comprising a shift block 25 detachably and circumferentially adjustably fixed to one

end of a shift rail 26 (Fig 6). Shift rail and shift block assembly 21 comprising shift block 27 and shift rail 28 is also of detachable construction similar to shift rail and shift block assembly 20. Shift rails 24, 26 and 28 are arranged vertically one directly below another spaced apart from one another and up and down movably mounted in mounting holes (not shown) in the mounting walls 29 and 30 in the housing 7 (Fig 2).
Shift blocks 23, 25 and 27 are arranged horizontally spaced apart from one another at the same level and are provided with a slot 31 at the upper end of each of them. The slots 31 are open at a pair of opposite sides thereof and are aligned with one another with the open sides thereof end to end. 32 is a shift finger engaged in the slots at the upper ends of the shift blocks and connected to the gear shifting lever 33 disposed vertically close to the driver seat (not shown) in the vehicle through connecting rod 34 (Fig 2 and 3). The other ends of the shift rails are connected to the speed forward-reverse gear unit 6 of the vehicle through shift forks 35 and dog clutches 36.
Shift block 25 of shift block and shift rail assembly 20 comprises a lateral sleeve 37 at the lower end thereof and spaced apart projections 38 at the outer end thereof. Shift rail 26 of the shift block and shift rail assembly 20 comprises a collar 39 at the one end thereof. The collar has as many notches 40 at the circumference thereof as there are projections 38 at the outer end of the sleeve 37. The notches are as equally spaced apart as the projections and are wider than the projections. The shift block is circumferentially adjustably and detachably engaged over the one end of the shift rail through the sleeve with the projections engaged in the notches. Because of the notches being wider than the projections, the shift block can be adjusted on the one

end of the shift rail circumferentially to the extent of movements allowed for the projections in the notches.
A clamping means 41 comprising a tapped axial hole 41a is provided at the one end of the shift rail and a slot 42 is provided in the sidewall of the axial hole at the one end of the shift rail. A depression 43 is formed across the inner end of the sleeve and a straight primary lock plate 44 matching with the depression is located in the depression at the inner end of the sleeve. Primary lock plate has a hole 45 aligned with the sleeve and a protrusion 46 at one side of the hole 45 corresponding to the slot 42 in the sidewall of the axial hole 41 adapted to be engaged in the slot 42. 47 is a L-shaped secondary lock plate with one limb 48 thereof located against the primary lock plate and the other limb 49 thereof extending over the other end of the primary lock plate and the inner end of the sleeve. The one limb 48 of the secondary lock plate has a hole 50 aligned with the hole 45 in the primary lock plate and preferably formed with teeth 51 around the circumference thereof.
52 is washer with a recess 53 across the inner surface of the washer corresponding to the one limb 48 of the secondary lock plate and located against the one limb aligned with the recess. Washer has a hole 54 aligned with the hole 50 in the one limb 48. 55 is a collar bolt (collar marked 56) tightened in the tapped axial hole 41 in the one end of the shift rail through the holes in the washer, one limb of the secondary lock plate and primary lock plate against the washer. The shift rail and shift block of shift block and shift rail assembly 21 and assembly thereof are identical to that of shift rail and shift block assembly 20 except for the difference that the shift block 27 will be extending laterally more to take position at the outer side of the shift block 25.

In the above construction of the shift block and rail assembly 20 or shift block and shift rail assembly 21, rotational movements of the primary lock plate is prevented by the sidewalls at the bottom and top of the depression 43 at the inner end of the sleeve 37, protrusion 46 of the primary lock plate 44 engaged in the slot 42 at the one end of the respective rail and the other limb 49 of the secondary lock plate abutting against the other end of the primary lock plate and extending over the inner end of the sleeve. Rotational movement of the secondary lock plate is prevented by the sidewalls at the top and bottom of the recess 53 in the washer 52 and also by the bolt 55 engaged against the teeth 51 at the circumference of the hole 50 in the one limb 48 of the secondary lock plate 47. The collar 56 of the bolt also ensures enlarged surface area of contact between the bolt and washer to ensure a tight fit and positive lock of the shift block on the one end of the shift rail. However, a positive locking of the shift block on the shift rail will take place even without the teeth 51 in the hole 50 in the one limb of the secondary lock and without the lock plate 49 and collar of the bolt. Therefore, hole 50 without teeth and bolt without collar 56 and clamping means without the lock plate 49 are also within the scope of the invention.
According to the invention, the shift rail 24 with the shift block 23 of assembly 19 of fixed construction is mounted at the top as a reference and the shift rail 26 with shift block 25 of assembly 20 of detachable construction and shift rail 28 with block 27 of assembly 21 of detachable construction are mounted below the shift rail and shift block assembly 19 of fixed construction. Misalignment, if any, in the mounting holes 29 and 30 in the housing 7 or in the mounting of the shift blocks to the respective rails of detachable constructions can be taken care by adjusting the shift blocks on the shift

rails circumferentially after disengaging the bolts 55 from the tapped hole 41a at the one end of the rails 26 and 28 and then locking the shift blocks to the rails with the bolts.
In the case of the shift block and shift rail of fixed construction, instead of welding, the shift block 23 also can be fixed to the one end of the shift rail 24 in any other known manner for instance clamping with thread engagement and check nut fixing or with key fixing. In the case of shift blocks and shift rails of detachable construction, adjustability of the shift block over the one end of the shift rail circumferentially and positive locking can be achieved with a different configuration and construction. The clamping means also can be of different configuration and construction. Instead of mounting rail 24 and block 23 of fixed construction at the top as reference, the combination also can be mounted below as reference. Then can be two or more than three shift block and shift rail assemblies. Such variations of the invention are obvious to a person skilled in the art and are to be construed and understood to be within the scope of the invention
According to the invention it is possible to detach the shift rail and shift block of the shift rail and shift block assemblies of detachable construction and adjust the position of the shift blocks on the shaft rails circumferentially during assembly and after assembly. If there is any misalignment between the mounting holes in the mounting walls in the housing 7 or any misalignment between the shift blocks and shift rails at the time of assembly thereof, such can be adjusted and set right with respect to the shift rail and shift block assembly of fixed construction as reference and the gaps between the shift blocks can be maintained. This ensures proper contact between the

shift finger and respective shift block during gear change and speed change by operating the gear shifting lever and very effective and smooth speed control of the vehicle. As a result, the gear shift mechanism will have a long life and will give trouble free service for a long period of time. Driving will be a pleasant experience and driver fatigue will also be reduced.
Because of the flexibility of adjustment of the shift blocks on the shift rails and the detachability of the shift blocks from the shift rails, rejection, wastage and production loss are eliminated. In case of damage to any one of the components namely shift blocks, shift rails or clamping means, such can be easily replaced without having to reject and throw away the entire assembly and suffer the resultant losses.
It is easy and convenient to assemble the shift blocks on the shift rails and also to adjust the shift blocks on the shift rails. According to the invention, assembly of the shift blocks to the shift rails has been simplified and provides flexibility of adjustment and detachability. Therefore, control over the assembly of the shift blocks on the shift rails need not be as precise and rigorous as in the conventional cases. As a result, assembly cost and time for the assembly of the shift blocks and shift rails are also reduced.

We claim:
1. A floor mounted mechanical gear shifting mechanism for automotive vehicle comprising a plurality of shift rail and shift block assemblies disposed in the speed forward-reverse gear unit housing of the vehicle, each of the shift rail and shift block assemblies comprising a shift block mounted to one end of a shift rail, the shift rails being arranged vertically one directly below another spaced apart from one another and up and down movably mounted in the speed forward-reverse gear unit housing and the shift blocks being arranged horizontally spaced apart from one another at the same level in the speed forward-reverse gear unit housing and being provided with a slot at the upper ends thereof open at a pair of opposite sides thereof, the slots being aligned with one another with the open sides thereof end to the end the shift blocks being connected to the gear shifting lever of the vehicle disposed vertically close to the driver seat in the vehicle through a shift finger engaged in the slots in the upper ends of the shift blocks, the other ends of the shift rails being connected to the speed forward-reverse gear unit of the vehicle through shift forks and dog clutches, wherein one of the shift rail and shift block assemblies is of fixed construction comprising a shift block rigidly fixed to one end of a shift rail to act as a reference and each remaining shift rail and shift block assembly is of detachable construction comprising a shift block detachably and circumferentially adjustably engaged over the one end of a shift rail and locked in position on the one end of the shift rail with a clamping means.
2. The gear shifting mechanism as claimed in claim 1, which comprises three shift rail and shift block assemblies, wherein one of the shift rail and shift block

assemblies is of fixed construction to act as a reference and the remaining two shift rail and shift block assemblies are of detachable construction.
3. The gear shifting mechanism as claimed in claim 1 or 2, wherein the shift rail of said one shift rail and shift block assembly of fixed construction is disposed at the top to act as a reference.
4. The gear shifting mechanism as claimed in claim 1, 2 or 3, wherein the shift rail and shift block assembly of fixed construction comprises a shift block welded to the one end of the shift rail.
5. The gear shifting mechanism as claimed in claim 1, 2 or 3, wherein each of the detachable shift rail and shift block assembly comprises a shift block having a lateral sleeve at the lower end thereof and spaced apart projections at the outer end thereof and a shift rail having a collar at the one end thereof, the collar having as many notches at the circumference thereof as there are projections at the outer end of the sleeve, the notches being as equally spaced apart as the projections and being wider than the projections, the shift block being circumferentially adjustably engaged over the one end of the shift rail through the sleeve with the projections engaged in the notches and locked in position on the one end of the shift rail with the clamping means.
6. The gear shifting mechanism as claimed in claim 5, wherein the clamping means comprises a tapped axial hole at the one end of the shift rail and a slot in the sidewall of the axial hole at the one end of the shift rail, a depression across the inner

end of the sleeve, a straight primary lock plate matching with the depression at the inner end of the sleeve and located in the depression and having a hole aligned with the sleeve and a protrusion at one side of the hole in the primary lock plate corresponding to the slot in the sidewall of the axial hole and engaged in the slot, a L-shaped secondary lock plate with one limb thereof located against the primary lock plate and the other limb thereof extending over the other end of the primary lock plate and the inner end of the sleeve, the one limb having a hole aligned with the hole in the primary lock plate, a washer with a recess across the washer at the inner surface thereof corresponding to the one limb of the secondary lock plate and located against the one limb and having a hole aligned with the hole in the one limb and a bolt tightened in the axial hole in the one end of the shift rail through the holes in the washer, one limb of the secondary lock plate and primary lock plate against the washer.
7. The gear shifting mechanism as claimed in claim 6, wherein the hole in the one limb of the secondary lock plate is formed with teeth around the circumference thereof.
8. The gear shifting mechanism as claimed in claim 6, wherein the bolt is a collar bolt.

9. The gear shifting mechanism as claimed in claim 1, 2, 3, 4, 5, 6, 7 or 8 which
is for a tractor.