Claims:
1. A locking mechanism for differential threaded ring (102) for live rear axle comprising:
at least one locking plate (200) provided with plurality of lugs with their axis offset and/or inclined with the axis of said locking plate configured for covering the total range of one slot movement of the threaded ring (102) in one lock plate by engaging the said lugs alternately in plurality of their combinations in the slot of threaded ring (102) for optimum preloading of the threaded ring (102).

2. The locking mechanism for differential threaded ring (102) for live rear axle as claimed in claim 1, wherein said plurality of lugs of said at least one locking plate (200) is configured with at least one straight lug (202) provided at the offset with axis of said locking plate (200) for engaging the said straight lug (202) alternately in plurality of their combinations in the slot of threaded ring (102) for optimum preloading of the threaded ring (102).

3. The locking mechanism for differential threaded ring (102) for live rear axle as claimed in claim 1, wherein said plurality of lugs of said at least one locking plate (200) is configured with at least one inclined lug (204) provided at angle with axis of said locking plate (200) for engaging the said inclined lug (204) alternately in plurality of their combinations in the slot of threaded ring (102) to cover the remaining angle for locking said threaded ring (102).

4. The locking mechanism for differential threaded ring (102) for live rear axle as claimed in claim 1, wherein the offset of the straight lug (202) to the locking plate (200) is configured to be provided to convert angular movement of the threaded ring (102) to linear movement.

5. The locking mechanism for differential threaded ring (102) for live rear axle as claimed in claim 1, wherein said inclined lug (204) is configured to accommodate the remaining angle for locking to cover the total range of one slot movement in one locking plate (200).

6. The locking mechanism for differential threaded ring (102) for live rear axle as claimed in claim 1, wherein said locking plate (200) is configured to optimally tightening of the threaded ring (102) with over tightening of 3 degree.

7. The locking mechanism for differential threaded ring (102) for live rear axle as claimed in claim 1, wherein said locking plate (200) is offset and/or inclined from the centerline of locking plate mounting bolts (210) configured for providing 4 locking combinations of said locking plate (200) avoiding over tightening of the threaded ring (102).

8. The locking mechanism for differential threaded ring (102) for live rear axle as claimed in claim 1, wherein said locking plate (200) is configured to provide preloading tolerance of 12-14 microns.

9. The locking mechanism for differential threaded ring (102) for live rear axle as claimed in claim 1, wherein said locking plate (200) is configured to reduce the severity by 5.5 times.
, Description:FORM 2

THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENT RULES, 2003

COMPLETE SPECIFICATION
(See Section 10 and Rule 13)

Title of invention:
LOCKING PLATE FOR DIFFERENTIAL THREADED RING FOR LIVE REAR AXLE

Applicant:
Tata Motors Limited
A company Incorporated in India under the Companies Act, 1956
Having address:
Bombay House, 24 Homi Mody Street,
Hutatma Chowk, Mumbai 400001,
Maharashtra, India

The following specification particularly describes the invention and the manner in which it is to be performed.

FIELD OF THE INVENTION
[001] The present subject matter described herein generally relates to a rear live axle, differential assembly, more specifically it relates to a locking plate for differential threaded ring for live rear axle.
BACKGROUND
[002] In rear live axles, differential assembly is mounted on taper roller bearings. Refer Fig (1). These bearings are preloaded in axles for optimum life of bearings and Crown Wheel Pinion. During operation of vehicle, jerks are expected. Hence optimum preload of bearings is desired. These jerks may cause sudden torsional forces on threaded rings and hence its loosening. To prevent loosening of threaded ring typical existing arrangement is as shown in Fig (2). In this arrangement a positive stopper (spring split dowel) is provided to arrest rotation of threaded ring in loosening direction. Currently threaded ring is locked by inserting a split spring dowel in the slots provided in the threaded ring through a hole made in Plummer block to avoid loosening. Preloading of bearings are achieved by tightening of the threaded rings. If threaded rings are tightened excessively, it will cause over-preload of bearings which is detrimental for bearing life. If threaded ring remains loose, it will cause play in bearing and may cause reduced bearing and gear life.
[003] Drawback of this arrangement is that, if the dowel lug is not matching to the slot, it is required to overtighten the threaded ring at times by approximately by 16 degrees for locking threaded rings by inserting a split spring dowel in the slots provided in the threaded ring the arrangement (by approx. 16 deg) or loosen the arrangement. Either of these two actions will lead to reduced bearing life as described above. Excessive tightening will cause excessive preload and hence reduce bearings life. In order to overcome the above drawback a locking plate is to be developed which will enable the locking of the threaded rings on permissible tightening limit. To address the problem of excessive tightening of the threaded ring or chances of loosening of the threaded ring, special kind of locking plate is developed.
OBJECTS OF THE INVENTION
[004] An object of the present subject matter is to provide a locking plate for differential threaded ring for live rear axle to avoid excessive over tightening of the threaded ring and enhance the bearing life and the axle life.
[005] Another object of the present subject matter is to provide a locking plate for differential threaded ring for live rear axle with offset straight lug and an inclined lug.
[006] Yet another object of the present subject matter is to provide a locking plate for differential threaded ring for live rear axle capable of locking at four positions of the threaded ring to provide optimum preloading.
[007] Another object of the present subject matter is to provide a locking plate for differential threaded ring for live rear axle with offset from the centerline of bolts for mounting lug with 4 permutation combinations.

SUMMARY
[008] Before the present system is described, it is to be understood that this application is not limited to the particular machine or device, as there can be multiple possible embodiments that are not expressly illustrated in the present disclosures. It is also to be understood that the terminology used in the description is for the purpose of describing the particular versions or embodiments only and is not intended to limit the scope of the present application. This summary is not intended to identify essential features of the proposed subject matter nor is it intended for use in determining or limiting the scope of the proposed subject matter.
[009] The present subject matter describes a locking mechanism for differential threaded ring for live rear axle comprising at least one locking plate provided with plurality of lugs with their axis offset and/or inclined with the axis of said locking plate configured for covering the total range of one slot movement of the threaded ring in one lock plate by engaging the said lugs alternately in plurality of their combinations in the slot of threaded ring for optimum preloading of the threaded ring.
[0010] The lugs of said at least one locking plate is configured with at least one straight lug provided at the offset with axis of said locking plate for engaging the said straight lug alternately in plurality of their combinations in the slot of threaded ring for optimum preloading of the threaded ring. The lugs of said at least one locking plate is configured with at least one inclined lug provided at angle with axis of said locking plate for engaging the said inclined lug alternately in plurality of their combinations in the slot of threaded ring to cover the angle for locking said threaded ring. The offset of the straight lug to the locking plate is configured to be provided to convert angular movement of the threaded ring to linear movement.

BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The foregoing summary, as well as the following detailed description of embodiments, is better understood when read in conjunction with the appended drawings. For the purpose of illustrating the disclosure, there is shown in the present document example constructions of the disclosure, however, the disclosure is not limited to the specific methods and device disclosed in the document and the drawings. The detailed description is described with reference to the following accompanying figures.
[0012] Figure 1 illustrates a view of a rear live axles, differential assembly with taper roller bearings preloaded by threaded rings (prior art)
[0013] Figure 2 illustrates a view of a rear live axles, differential assembly arrangement with a positive stopper (spring split dowel) to arrest rotation of threaded ring (Prior Art).
[0014] Figure 3 illustrates a view of a locking plate with offset straight lug and an inclined lug.
[0015] Figure 4 illustrates the exploded view of the rear live axles, differential assembly with a locking plate arrangement.
[0016] Figure 5 illustrates a front view of the rear live axles, differential assembly with a locking plate arrangement showing first mounting combination.
[0017] Figure 6 illustrates a front view of the rear live axles, differential assembly with a locking plate arrangement showing second mounting combination
[0018] Figure 7 illustrates a front view of the rear live axles, differential assembly with a locking plate arrangement showing third mounting combination
[0019] Figure 8 illustrates a front view of the rear live axles, differential assembly with a locking plate arrangement showing fourth mounting combination
[0020] The figure depicts various embodiments of the present disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following discussion that alternative embodiments of the structures illustrated herein may be employed without departing from the principles of the disclosure described herein.
REFERRAL NUMERALS:

Element Description Reference Numeral
Rear Live Axle Differential Assembly 100
Threaded Ring 102
Tapered Roller bearing 104
Differential Assembly 106
Locking Plate 200
Straight Lug 202
Inclined Lug 204
Mounting holes 206
Offset of Lug 208
Locking plate mounting bolts 210

DETAILED DESCRIPTION
[0021] Some embodiments of this disclosure, illustrating all its features, will now be discussed in detail. The words "comprising", “having”, and "including," and other forms thereof, are intended to be equivalent in meaning and be open ended in that an item or items following any one of these words is not meant to be an exhaustive listing of such item or items, or meant to be limited to only the listed item or items. It must also be noted that as used herein and in the appended claims, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise. Although any devices and methods similar or equivalent to those described herein can be used in the practice or testing of embodiments of the present disclosure, the exemplary, devices and methods are now described. The disclosed embodiments are merely exemplary of the disclosure, which may be embodied in various forms.
[0022] Various modifications to the embodiment will be readily apparent to those skilled in the art and the generic principles herein may be applied to other embodiments. However, one of ordinary skill in the art will readily recognize that the present disclosure is not intended to be limited to the embodiments illustrated but is to be accorded the widest scope consistent with the principles and features described herein.
[0023] The present subject matter describes the proposed art, to address the problem of excessive tightening of the threaded ring or chances of loosening of the threaded ring, special kind of locking plate is designed as shown in Fig (3). Offset of the straight lug is provided to the plate such that angular movement of the threaded ring is converted to linear movement. The calculation of the offset is provided in the next section. Design of the inclined lug is such that the remaining angle for locking is also equally covered. Hence the total range of one slot movement is covered in one lock plate. Approximately, maximum 3-degree angle remains uncovered with this lock plate design. Hence the overtightening of the threaded ring is reduced from 16 degree to 3 degree. Refer Fig (4) for the exploded view of the arrangement.
[0024] The present subject matter describes a locking plate capable of locking at four positions of the threaded ring to provide optimum preloading. The locking plate is offset from the centerline of bolts. This locking plate gives provision of 4 permutation combinations as shown in Figure 5. These combinations provide 4 options for assembly and avoid excessive over tightening of the threaded ring. Hence the bearing life and the axle life get enhanced.
[0025] Calculations for the design of the Lug: Lug width is 10 mm while slot width is 12 mm i.e. difference =2 mm. Angle between two consecutive lugs is 22.5 degree and diameter is 96 mm. Refer below table for calculated offset in the lock plate.

FORMULA
Minimum threaded ring diameter where the lug will be inserted 96.000 mm D
Theta 22.500 degree ?
linear distance 18.850 mm X = (?/360) * (p * 96)
four assembly combinations 4.712 mm M = X/4
width difference between slot and lug 2.000 mm W
offset of the lug (L) 2.7 mm L = M - W

[0026] This linear movement is further divided into four equal parts. Offset of the lug from differential centerline is provided with this amount (L) to get the four equal combinations. Four such combinations are shown in the Fig (5). These four combinations covers the entire range of the incremental slot movement of threaded ring.
[0027] The tolerance allowed by the threaded ring locking arrangement for preloaded in existing arrangement ranges from 65 to 75 microns. With the above given solution, this tolerance on preloading is reduced to 12-14 microns. i.e. the severity is reduced by 5.5 times.
[0028] Accordingly the present invention discloses a locking mechanism for differential threaded ring (102) for live rear axle comprising at least one locking plate (200) provided with plurality of lugs with their axis offset and/or inclined with the axis of said locking plate configured for covering the total range of one slot movement of the threaded ring (102) in one lock plate by engaging the said lugs alternately in plurality of their combinations in the slot of threaded ring (102) for optimum preloading of the threaded ring (102).
[0029] The lugs of said at least one locking plate (200) is configured with at least one straight lug (202) provided at the offset with axis of said locking plate (200) for engaging the said straight lug (202) alternately in plurality of their combinations in the slot of threaded ring (102) for optimum preloading of the threaded ring (102). The lugs of said at least one locking plate (200) is configured with at least one inclined lug (204) provided at angle with axis of said locking plate (200) for engaging the said inclined lug (204) alternately in plurality of their combinations in the slot of threaded ring (102) to cover the angle for locking said threaded ring (102). The offset of the straight lug (202) to the locking plate (200) is configured to be provided to convert angular movement of the threaded ring (102) to linear movement.
[0030] The inclined lug (204) is configured to accommodate the remaining angle for locking to cover the total range of one slot movement in one locking plate (200). The locking plate (200) is configured to optimally tightening of the threaded ring (102) with over tightening of 3 degree. The locking plate (200) is offset from the centerline of locking plate mounting bolts (210) configured for providing 4 locking combinations of said locking plate (200) avoiding over tightening of the threaded ring (102). The locking plate (200) is configured to provide preloading tolerance of 12-14 microns. The locking plate (200) is configured to reduce the severity by 5.5 times.