FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
Patent Rules 2003
PROVISIONAL SPECIFICATION
(See section 10; rule 13)

1. Title -

A DIFFERENTIAL ARRANGEMENT WITHOUT CASE


2. Applicant - MAHINDRA & MAHINDRA LTD.
1, GATEWAY BUILDING, APOLLO BUNDER, MUMBAI - 400001, AN INDIAN COMPANY
The following specification describes the invention,


FIELD OF THE INVENTION:
The present invention relates to differential mechanism for agricultural vehicles such as tractor and alike, and particularly to a differential arrangement without case with a means of adjusting backlash among the gears therein.
BACKGROUND OF THE INVENTION:
Generally, various constructions of differential (gear) arrangements exist / are designed with principle objective of transmitting equal amount of torque to a pair of aligned wheel axle shafts and also compensating the differences occurring in the speed of the drive wheels on each side of the vehicle while turning / cornering. In most of the typical agricultural vehicles, differential arrangement, to transfer the driving force from engine to the wheels, is accommodated within a differential case. Even as such arrangements provide satisfactory performance and utility, the differential gear arrangement of this invention does away with differential case offering the same performance. In accordance with the aforementioned intention the present invention is to achieve the said principle objective with reduced complexity in parts, arrangement and with lower cost of development and manufacture.
US Patent 6840881 discloses a transmission with a differential arrangement of an automotive vehicle. It provides a transmission with a case-less differential arrangement for an automotive vehicle to drive

four wheels instead of two differential unit. Also the invention speaks about a compact; low cost structure and provides increased ground clearance. US Patent 6935975 discloses a transmission mechanism with a differential mechanism of automotive vehicle. It comprises a core shaft and a caseless differential mechanism including a side bevel gears. However, as these inventions are related to automotive vehicle, it does not talk about the bull gear arrangement for braking mechanism which is generally associated with the differential mechanism in agricultural vehicle, and also backlash adjustment among the gears which is one of the main aspects for the efficient performance of the mechanism.
Eventhough the aforementioned prior arts give satisfactory performance in the field of the invention, following are the shortcomings in the said prior arts:
The backlash adjustment arrangements are not provided in the
system which is one of the main parameter determines the
performance of the differential mechanism.
Making separate provision for receiving the pinion gears within
the ring gear leads to complex manufacturing process.
Loose supporting of pinion gears with corresponding plurality of
pinion shafts makes variation in backlash further due to wear &
tear further leads to deterioration in performance.

SUMMARY OF THE INVENTION:
The main object of the present invention is to provide a differential mechanism with caseless differential gear arrangement by disposing a core shaft through the ring gear adapted to receive the pinion gears in the same plane of the said ring gear.
Another object of the present invention is to provide a robust support to the differential assembly with the help of bull pinion shaft rather than core shaft in the housing via bearing assemblies.
Further object of the invention is to provide a more feasible backlash adjustment system between the pinion gears and bevel gears by providing stud & nut arrangements from both sides of the housing coaxial with the core shaft.
Yet another object of the invention is to provide a provision for backlash adjustment between the ring gear and the bevel pinion gear by putting the required plurality of shims in the said provision.
Yet another object of the invention is to by supporting the differential assembly via deep groove ball bearing assemblies in the housing, preloading arrangement which would needed for taper roller bearing assemblies, otherwise, is avoided.
Yet another object of the invention is to provide a robust structure of bull gear arrangement by integrating the gear, which engaged with the bull gear, with the bull pinion shaft.

Yet another object of the present invention is to provide lubrication to outer bearing assemblies by forming a helical groove around the axis of the core shaft.
Yet another object of the invention is to achieve the conventional position of the brake arrangements without affecting its performance.
Yet another object of the invention is to reduce the complexity of the parts used in the differential mechanism compare with existing system.
Yet another object of the invention is to obtain a cost effective differential mechanism with less involvement of manufacturing processes.
Thus in accordance with the present invention one aspect of the
differential unit consists of a backlash adjustment arrangement
between the pinion gears and side bevel gears comprises of:
a bull pinion shaft having three decreasingly different diametric
annular grove for holding a core shaft, a back lash adjusting
means/spacer and a stud respectively,
wherein
the said stud is threadingly engaged with the annular groove also
threadingly engaged with a nut so as to make the rotation of nut into
reciprocate motion of the stud in the said groove to push the core
shaft forward for proper engagement of a pair of pinion gear with a
pair of bevel gears.

The further aspect of the present invention consists of a backlash
adjusting arrangement between the bevel pinion gear and the ring
gears comprising of:
a pair of bull cage mounted in either side of the housing to rotatably
support the differential gear arrangement unit via a pair of bearing
assemblies and an adapter plate kept inbetween the housing and the
said bull cage
wherein
a provision is made inbetween the bull cage and adapter plate to
receive plurality of shims as per the requirement for adjusting the
backlash adjustment.
BRIEF DESCRIPTION OF THE DRAWINGS:
The aforementioned objectives and other features of the present invention will become apparent from the preferred embodiment with reference to the accompanying drawings:
Figure 1 illustrates the differential gear arrangements.
Figure 2 exploded perspective view in accordance with the present
invention. Figure 3 illustrates the backlash adjustment arrangements among the
gears. Figure 4 shows the isometric view for the differential unit in
accordance with the present invention.
Referring to fig.land fig.2, illustrates a differential unit in accordance with the present invention, comprising a ring gear 2 and a core shaft 3

which transversely positioned in the housing 9 and mounting means provided in the said core shaft 3 to mount the said ring gear 2 so as to restricts the rotary and radial misalignment of the said ring gear 2 relative to the said core shaft 3. The said ring gear 2 is positioned at an offset distance from the longitudinal central axis of the housing 9 to mesh with bevel pinion gear 1. The said core shaft 3 is adapted to receive a differential pinion shaft 5 to rotatably carry a pair of differential pinions 4 and also provided with helical grooves circumferentially around the central axis for providing lubrication even at the outer bearing assemblies 21. A locating diameter means (not shown) as same as differential pinion shaft 5 diameter is provided in the ring gear 2 to arrest the axial movement of the said differential shaft 5. The said differential pinions 4 are supported on the differential pinion shaft 5 in such a way to mesh wfth a pair of bevel gears/side gears means 6 which provided at the ends of the bull pinion shafts 7, 11. The said bull pinion shafts 7, 11 are integrated with bull pinion gears 10, 8 respectively to mesh with the bull gears 24 shown in fig. 2.
The aforementioned differential assembly, with reference to fig. 1 & 2, is rotatably supported in a pair of bull cage 16 via a pair of bearing assemblies 21. The said core shaft 3 is inserted into the annular grooves provided in the bull pinion shafts 7, 11 via four bearing surface area means 25 for avoiding wear therein at the time of cornering and more specifically outer bearing surface areas are provided exactly below the bearing assemblies 21 to strengthen the support of ring gear 2 and to avoid the deflection of core shaft 3. The inner surface of the said bull gages 16 is provided with oil seal 20 to avoid the oil leakage. The said bull pinion shafts 7, 11 are having

three decreasingly different diametric annular groove portion from end of bevel gear/side gear means 6 to hold the core shaft 3, backlash adjuster 13 coaxial with the said core shaft 3 and a stud 14 coaxial with the said core shaft 3 and the said backlash adjuster 13, respectively. The said stud 14 is threadingly engaged with the said respective annular groove means and also engaged with a nut 15. The said backlash adjuster 13 is provided with O-ring 12 to restrict the oil coming out from the housing via the clearance between the inner surface of the bull pinion shafts 7, 11 and the core shaft 3. An adapter plate 18 is provided axially over the bull gage 16 thereby to provide a provision for putting plurality of shims 17 to adjust the backlash between the bevel pinion gear 1 and ring gear 2.
The operation of the present invention will now be described as follows. The power drive coming from the transmission main output shaft is transmitted to the ring gear 2 via the bevel pinion gear 1. Since, the central axis of the said bevel pinion gear 1 and ring gear 2 is perpendicular to each other; the direction of power drive is changing from straight line to 90°. When the vehicle is running in a straight line path, the ring gear 3 and the mounted core shaft 3 rotate around its axis at same speed thereupon the pinion gear 4 rotates in an orbit which in turn rotates a pair of bevel gear means 6 around its axis to rotate the bull pinion gears 10 and 8, which integrated with bull pinion shaft 7 and 11, respectively, thereby to rotate the bull gears 24 and then to rotate the axle shafts (not shown). Thus, in accordance with the present invention, principle functionality of the conventional differential gear arrangement is achieved by not having a differential case and reducing the complexity of the parts.

Another embodiment of the present invention illustrates the backlash adjustment, shown in fig. 2, between the said pair of pinion gears 4 and the said pair of bevel gear/side gear means 6. The said bull pinion shafts 7 and 11 are provided with stud 14 threadingly engaged with nut 15 so as to make the stud 14 to reciprocate axially within the annular groove by rotating the nut 15 thereupon to move the said adjuster 13 forward to push the core shaft 3 thereby to adjust the backlash between the pinion gears 4 and bevel gear means 6. Further embodiment of the present invention with reference to fig.2 illustrates backlash adjustment between the bevel pinion gear 1 and the ring gear 2. Here a plurality of shims 17 is disposed between the bull cage 16 and the said adapter plate 18 axially to achieve the required backlash.
While the foregoing invention has been shown and described with reference to the preferred embodiments, it will be understood by those possessing skill in the art may change and modify the present invention without departing from the spirit and scope of the invention.