FORM 2
The Patent Act 1970
(39 of 1970)
&
The Patent Rules  2005

COMPLETE SPECIFICATION
(SEE MEMBER 10 AND RULE 13)

TITLE OF THE INVENTION

“System and method for locking differential in vehicles”

APPLICANT:

Name : Mahindra & Mahindra Ltd.

Nationality : Indian

Address : Mahindra Research Valley  Mahindra World
City Plot No. 41/1  Anjur P.O. Chengalpattu
Kancheepuram Dist  Tamilnadu.- 603204

The following specification particularly describes and ascertains the nature of this invention and the manner in which it is to be performed:-

FIELD OF INVENTION
[001] The embodiments herein relate to a differential system in vehicle  and more particularly but not exclusively to a system and method for locking the differential system in vehicles.

BACKGROUND OF INVENTION
[002] Motor vehicles have become an integral part of human life. People use motor vehicles for transportation purposes and several other purposes such as trading of goods and services from one place to another. In agricultural sectors  motor vehicles such as tractors are used to plow fields  sow seeds  harvest crops and perform various other operations. With respect to agricultural vehicles  features such as delivering of high torque at low speeds make tractors extremely versatile and well suited for use within the often harsh agricultural farm.
[003] In motor vehicles  power from the engine or motor is transmitted to the left and right drive wheels through a differential system. Typical differential system allows the left and right drive wheels to rotate at different speeds thereby allowing the wheel that is travelling around the outside of the turning curve roll farther and faster than the other wheel.
[004] Conventional differential system includes a differential case  a ring gear connected to the differential case by means of fastener  a pair of differential side gears fixed for rotation with the output axle shafts  two or more sets of meshed differential pinion gears mounted within a differential case via a differential pin. The meshed pinion gears are configured to connect the differential case with the side gears.
[005] The power from motor or engine transfers from ring gear to differential case and then to side gears through a set of differential pinion. In normal running conditions  the differential pinion remains stationary over the differential pins thereby transferring equal amount of power onto both the differential side gears. Thus the output axle shafts secured to the differential side gears receive equal amount of power. Further  when the vehicle is taking a turn  the differential pinions rotate over the pins thereby making one set of differential side gear rotates faster than the other. Thus providing differential action necessary for the vehicle.
[006] However  when a working vehicle travels on an inclined ground or an unleveled ground such as agricultural farm  slipping causes a difference in revolution between the right wheel and the left wheel impairing straight running of the vehicle. For example  when one wheel of the vehicle is on a surface having a low coefficient of friction  most or all of the torque from the engine or motor will be delivered to the slipping wheel. As a result  the vehicle often becomes immobilized. This problem associated with the conventional differential system is partially solved with the invention of differential locking mechanism. It is therefore a conventional practice to equip a working vehicle such as a lawn and garden tractor which needs to run straight in a reliable manner with a differential locking mechanism to forcibly stop differential revolutions of the wheels.
[007] At present  mechanisms such as pneumatic  vacuum or cable systems are used to lock the differential system. However  manufacturing the conventional differential with locking mechanism is a tedious process. Further  the cost associated with the process of manufacturing conventional differential with locking mechanism is more thereby making the conventional locking mechanism partially unfeasible. Further  the maintenance of the conventional locking mechanism  such as assembling the locking mechanism with the differential system demands trained labors. Further  other conventional differential locking system includes engaging the differential case with slots provided in the differential side gears. However  these conventional differential locking systems require differential side gears that are huge in size in order to provide slots for differential locking  thereby making the whole differential locking system complex in structure and heavy in weight.
[008] Therefore  there is a need for a simple locking mechanism that could be easily assembled with differential systems. Further  there is a need for a locking mechanism that does not require expensive manufacturing cost. Further  there is a need for a system and a method that could obviate above mentioned drawbacks with respect to locking the differential system in vehicles.

OBJECT OF INVENTION

[009] The principal object of this invention is to provide a simple locking mechanism that could be easily assembled with differential systems.
[0010] A further object of the invention is to provide a differential locking mechanism that involves reduced manufacturing costs.
[0011] Yet another object of the invention is to provide a differential locking mechanism having simple structure and reduced weight.
[0012] These and other objects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood  however  that the following descriptions  while indicating preferred embodiments and numerous specific details thereof  are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof  and the embodiments herein include all such modifications.

BRIEF DESCRIPTION OF FIGURES
[0013] This invention is illustrated in the accompanying drawings  throughout which like reference letters indicate corresponding parts in the various figures. The embodiments herein will be better understood from the following description with reference to the drawings  in which:;
[0014] Fig. 1 depicts a differential system that is disengaged with the system according to an embodiment of the present invention;
[0015] Fig. 2 depicts a locking plate according to an embodiment of the present invention;
[0016] Fig. 3 depicts a shifter ring according to an embodiment of the present invention;
[0017] Fig. 4 depicts engaged position of system that is configured to lock the differential system in vehicles according to an embodiment of the present invention;
[0018] Fig. 5 depicts a differential side gear according to an embodiment of the present invention;
[0019] Fig. 6 depicts a locking plate according to an embodiment of the present invention;
[0020] Fig. 7 depicts a differential system that is disengaged with a system according to an embodiment of the present invention; and
[0021] Fig. 8 is a flowchart depicting a method for locking the differential system in vehicle.

DETAILED DESCRIPTION OF INVENTION
[0022] The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. For example  it should be noted that while some embodiments are explained with respect to tractors for the ease of describing  other vehicles apart from tractors may also incorporate the subject matter of the invention with little or no modifications. Accordingly  the examples should not be construed as limiting the scope of the embodiments herein.
[0023] The embodiments herein provide a system and method for locking the differential system in vehicles. Further  the embodiments herein provide a simple locking mechanism that could be easily assembled with the differential system. Furthermore  the embodiments herein provide a differential locking mechanism that involves reduced manufacturing costs  simple structure and reduced weight. Referring now to the drawings  and more particularly to FIGS. 1 through 8  where similar reference characters denote corresponding features consistently throughout the figures  there are shown embodiments.
[0024] Fig. 1 depicts a differential system 200 that is disengaged with the system 100 according to an embodiment of the present invention. The differential system 200 includes a ring gear 202  a differential case 204  a differential pinion 206  plurality of differential side gears 208a  208b and a differential pin 210. In an embodiment  the ring gear 202 is configured to drive the differential case 204. Further  the differential case 204 is configured to drive the differential side gears 208a and 208b through a set of differential pinion 206. The differential side gears 208a and 208b are engaged with the right output axle shafts 212a and left output axle shafts 212b.
[0025] The system 100 includes a locking plate 102 and a shifter ring 104. In an embodiment  the locking plate 102 is splined on to at least one of the output axle shafts 212a and 212b. Further  the locking plate 102 includes plurality of slots 102a. Fig. 2 depicts the locking pate 102 according to an embodiment of the present invention. In an embodiment  the locking plate 102 includes a toothed inner surface 102b. The toothed inner surface 102b is configured to attach the locking plate 102 to the output axle shaft 212a. Further  the outer surface of the locking plate 102 includes plurality of slots 102a. In another embodiment  both the differential case 204 and the locking plate 102 include plurality of slots. The shifter ring 104 is provided in communication with the differential case 204 and configured to selectively connect the differential case 204 with the locking plate 102. In an embodiment  the shifter ring 104 includes plurality of tabs 104a that are configured to engage with the slots 102a provided in the locking plate 102. In another embodiment  the shifter ring 104 is suitably secured such that the shifter ring 104 is not relatively rotatable but axially slidable in order to engage the differential case 204 with the locking plate 102. Further  the sliding movement of the shifter ring 104 is enabled by means of any conventional mechanism without otherwise deterring the intended function of the system 100 as can be deduced from this description. Fig. 3 depicts the shifter ring 104 according to an embodiment of the present invention.
[0026] In an embodiment  when the system 100 is not engaged with the differential system 200  the shifter ring 104 is provided in contact with the slots provided in the differential case 204. Further  the ring gear 202 is configured to receive the input torque from engine or motor. Further  the ring gear 202 drives the differential case 204 which in turn drives the differential side gears 208a and 208b through differential pinions 206. The actuation of differential side gears 208a and 208b enables the rotation of output axle shafts 212a and 212b along with the locking plate 102. Therefore  when the vehicle is taking a turn  the differential pinions 206 rotate over the pins 210 thereby making one of side gears 208a or 208b rotates faster than the other.
[0027] Fig. 4 depicts engaged position of system 100 that is configured to lock the differential system 200 in vehicles according to an embodiment of the present invention. In an embodiment  in order to lock the system 100 with the differential system 200  the shifter ring 104 is axially slided  such that the tabs 104a provided in the shifter ring 104 engages with the slots 102a provided in the locking plate 102. In the locked position  the ring gear 202 is configured to receive the input torque from engine or motor. Further  the ring gear 202 drives the differential case 204 which in turn drives the output axle shafts 212a and 212b  thereby making the whole differential assembly as a single unit.
[0028] It should be noted that the aforementioned configuration of system 100 for locking the differential system is provided for the ease of understanding of the embodiments of the invention. However  certain embodiments may have a different configuration of the components of the system 100 and certain other embodiments may exclude certain components of the system 100. For example  in certain embodiment  the shifter ring 104 could include slots and the locking plate 102 could include tabs  such that the shifter ring 104 could be coupled with the locking plate by engaging the tabs inside the slots. Therefore  such embodiments and any modification by addition or exclusion of certain components of the system 100 and without otherwise deterring the intended function of the system 100 as is apparent from this description and drawings are also within the scope of this invention.
[0029] In another embodiment  a system 300 is configured to lock the differential system 200. The system 300 includes a locking plate 302 and a shifter ring 304. The differential side gears 208a and 208b includes a toothed inner surface 208d that is configured to spline the differential side gears 208a and 208b to the output axle shafts 212a and 212b respectively. Further  at least one of the differential side gears 208a and 208b that is configured to drive the output axle shafts 212a and 212b respectively is provided with slots 208c. Fig. 5 depicts a differential side gear 208a according to an embodiment of the present invention. The locking plate 302 includes plurality of tabs 302a. The slots 208c provided in at least one of the differential side gears 208a and 208b is configured to receive the tabs 302a provided in the locking plate 302 in order to engage locking plate 302 with at least one of differential side gears 208a and 208b. In an embodiment  the plurality of tabs 302a is provided on the surface of locking plate 302 that faces at least one of the differential side gears 208a and 208b having slots 208c. However  it is also within the scope of invention that the tabs 302a could be provided anywhere in the locking plate 302 without otherwise deterring intended function of the system 300 as can be deduced from this description. Further  the locking plate 302 includes plurality of slots 302b. Fig. 6 depicts the locking plate 302 according to an embodiment of the present invention. The shifter ring 304 is provided in communication with a differential case 204 and configured to selectively connect the differential case 204 with the differential side gears 208a or 208b via the locking plate 302. The differential case 204 includes plurality of slots that are configured to receive the shifter ring 304. In an embodiment  the shifter ring 304 includes plurality of tabs 304a that are configured to selectively connect the differential case 204 with the differential side gears 208a or 208b via the locking plate 302. The plurality of tabs 304a are configured to engage with the plurality of slots 302b provided in the locking plate 302. Further  the locking plate 302 is secured to at least one of differential side gears by engaging tabs 302a provided in the locking plate with slots 208c provided in at least one of differential side gears.
[0030] In another embodiment  the shifter ring 304 is suitably secured such that the shifter ring 304 is not relatively rotatable but axially slidable in order to engage the differential case 204 with at least one of differential side gears 208 and 208b via locking plate 302. Further  the sliding movement of the shifter ring 304 is enabled by means of any conventional mechanism without otherwise deterring the intended function of the system 300 as can be deduced from this description.
[0031] Fig. 7 depicts a differential system 200 that is disengaged with a system 300 according to an embodiment of the present invention. In an embodiment  in order to lock the differential system 200 using system 300  the locking plate 302 is engaged with at least one of differential side gears 208a and 208b using tabs 302a and slots 208c. The slots 208c provided in at least one of differential side gears 208a and 208b is configured to receive the tabs 302a provided in the locking plate 302. Further  the shifter ring 304 is axially slided  such that the tabs 304a provided in the shifter ring 304 engages with the slots 302b provided in the locking plate 302. In the locked position  the ring gear 202 is configured to receive the input torque from engine or motor. Further  the ring gear 202 drives the differential case 204 which in turn drives the output axle shafts 212a and 212b through system 300  thereby making the whole differential assembly as a single unit.
[0032] It should be noted that the aforementioned configuration of system 300 for locking the differential system is provided for the ease of understanding of the embodiments of the invention. However  certain embodiments may have a different configuration of the components of the system 300 and certain other embodiments may exclude certain components of the system 300. For example  in certain embodiment  the shifter ring 304  the locking plate 302 and side gears 208a or 208b is engaged by any other conventional mechanism other than tabs and slots. Therefore  such embodiments and any modification by addition or exclusion of certain components of the system 300 and without otherwise deterring the intended function of the system 300 as is apparent from this description and drawings are also within the scope of this invention.
[0033] A method 400 for locking the differential system 200 in vehicle is described herein below. Fig. 8 is a flowchart depicting a method for locking the differential system in vehicle. The method includes providing a first member in communication with at least one of the output axle shaft 212a and 212b (step 402). In an embodiment  the first member is a locking plate 102 or 302. Further  a second member is provided in communication with the differential case 204 (step 404). In an embodiment  the second member is a shifter ring 104 or 304. In an embodiment  the locking of differential system 200 is enabled by engaging the second member with the first member by suitable mechanism (step 406) thereby delivering equal power to both the output shaft axle 212a and 212b. In an embodiment  the second member includes plurality of tab and the first member includes plurality of slot. The slots are configured to receive tabs in order to engage the first member with the second member. In another embodiment  the second member is engaged with the first member and at least one of side gears 208a and 208b. In order to activate the differential system 200  the second member is disengaged with the first member thereby enabling differential action (step 408).
[0034] As is evident from the above description  with the system 100 or 300 and the method disclosed herein  the objectives as was set forth initially will be achieved.
[0035] It should be noted that the aforementioned steps for locking the differential system 200 in vehicle are provided for the ease of understanding of the embodiments of the invention. However  various steps provided in the above method may be performed in the order presented  in a different order  or simultaneously. Further  in some embodiments  one or more steps listed in the above method may be omitted. Therefore  such embodiments and any modification that is apparent from this description and drawings are also within the scope of this invention.
[0036] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can  by applying current knowledge  readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept  and  therefore  such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore  while the embodiments herein have been described in terms of preferred embodiments  those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.

CLAIMS
We claim
1. A system for locking differential in a vehicle  said system comprising:
a locking plate provided in communication with at least one of left output axle shaft and right output axle shaft; and
a shifter ring provided in communication with a differential case 
wherein
said shifter ring and said locking plate is configured to engage said differential case with said at least one of left output axle shaft and right output axle shaft.

2. The system as claimed in claim 1  wherein
said shifter ring includes plurality of tabs;
said locking plate includes plurality of slots; and
said shifter ring is configured slide axially for engaging said tabs with said slots.

3. The system as claimed in claim 1  wherein said locking plate includes a toothed inner surface in order to engage said locking plate with at least one of said left output axle shaft and said right output axle shaft.

4. A system for locking differential in a vehicle  said system comprising:
a locking plate provided in communication with at least one of left output axle shaft and right output axle shaft; and
a shifter ring provided in communication with a differential case 
wherein
said differential includes plurality of differential side gears engaged with at least one of left output axle shafts and right output axle shafts; and
said shifter ring  said locking plate and at least one of said side gears are configured to engage said differential case with said at least one of left output axle shaft and right output axle shaft.

5. The system as claimed in claim 4  wherein
said shifter ring includes plurality of tabs;
said locking plate includes plurality of slots and plurality of tabs;
said at least one of side gears includes plurality of slots;
said shifter ring is configured slide axially for engaging said tabs provided in the shifter ring with said slots provided in the locking plate; and
said plurality of slots provided in the side gears is configured to receive said plurality of tabs provided in the locking plate .

6. A method for locking differential in vehicle  said method comprising
providing a first member in communication with at least one of left output axle shaft and right output axle shaft; and
providing a second member in communication with a differential case  wherein
said differential is locked by engaging said second member with said first member.

7. A method for locking differential in vehicle  said method comprising
providing a first member in communication with at least one of differential side gears; and
providing a second member in communication with a differential case  wherein
said differential side gears are engaged with at least one of left output axle shafts and right output axle shafts 
wherein
said differential is locked by engaging said second member with said first member.

Date 10th July  2012 Signature

Dr. Kalyan Chakravarthy
Patent Agent

ABSTRACT
A system for locking differential in a vehicle  the system includes a locking plate provided in communication with at least one of left output axle shaft and right output axle shaft and a shifter ring provided in communication with a differential case. Further  the shifter ring and said locking plate is configured to engage the differential case with at least one of left output axle shaft and right output axle shaft in order to lock the differential.