FIELD QF INVEKTION
This invention is directed to a caseless compact transmission differential for a vehicle.
BACKGROUND/PRIOR ART
The Transmission differential is a vital link in a vehicle's drive train that allows unequal speeds on two wheels on a given drive axle for smooth turning.
The location of differential gear arrangement can be as follows:
- Within the transmission, mounted on front axle.
- Within the transmission, mounted on rear axle.
- Transmission is placed on front axle and differential arrangement is located on rear axle for front wheel transmission and rear drive vehicle.
Regarding an existing typical differential assembly, reference may be made to fig 1, wherein a pair of pinion gears (1, 1') and differential gears (2,2') are asserdbled inside differential case (3). Said differential gears are guided in the case differential and said pinion gears are supported in case differential and held in position by means of a pinion shaft (4), which is in turn locked with the case differential with the help of an assembly pin (5).

The case differential is mounted inside transmission case with the help of a pair of differential bearings (6, 6'). Further, a plurality of shims (7,7', 8, 8') are employed so as to control the backlash of pinion and differential gears. Final gear (9) is mounted on the case differential through multitude of bolts (10). Further, a speedometer gear (11) is mounted on case differential for speedometer input..
The speedometer gear comprises a ring structure with multitude of steps (P) along its outer circumference with a gap therebetween as shown is implemented to be mounted on the differential case (3).It is hianufactured by sintering/forging.
When the vehicle is in dynamic condition, power and torque are transferred from engine to wheels (W) via differential assembly (fig lA).
The aforesaid known differential assembly involves the following disadvantages:
- Final gear is not symmetrically placed between differential bearings-resulting in eccentric mounting of the final gear.^ Hence, the bearings requirement on both sides are not similar.
- Bulky in size which leads to more weight and cost with less fuel efficiency.
- Poor performance due to bulky size and asymmetric placement.
Some patents/publications may be discussed hereinunder:
A prior art is known to have been provided regarding a differential gear device comprising a plurality of fitting recessed parts in one side surface of a differential gear, a slide member having a protruded part extended in the lengthwise direction to be opposed to the fitting recessed part, wherein the protruded part of the slide member is engaged with the fitting recessed part. The fitting recessed part engaging the protruded part of the slide member is placed in a naember constituted in a separate unit from the differential ring gear.

According to another prior art, there is differential unit consisting of a backlash adjustment arrangement between the pinion gears and side bevel gears comprises of:
A bull pinion shaft with three decreasingly different diametric annular groove
for accommodating 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. , '
In addition to the above, there is also disclosure 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 through a pair of bearing assemblies in which an adapter plate is placed between the housing and the said bull cage.
There is also a provision between the bull cage and adapter plate to receive plurality of shims according to the requirement for adjusting the backlash adjustment.
Still another prior art provides a gearing embodying a central component, which holds a mounting bolt for at least one bevel gearand circumference of which is secured with a concentric cog ring. There is provision of a side housing component fastened to each side of the central component by fastening means. A particular position of the connecting cross section for transmission of torque to the central component, is arranged to be independent

of the fastening means. It can also be in the same axial region as the rotational plane of the central component, and which contains the axis of the mounting bolt.
According to another. available technology, there is an inter-axle differential, comprising: an input shaft and an output shaft disposed co-axially. A spider is coupled to said input shaft, wherein said spider having a plurality of radially outwardly extending arms.
Multitudes of differential gears are mounted on said spider, in which one of said plurality of differential gears is disposed about one arm of said plurality of arms. Further, a thrust washer is placed about said one arm, radially outwardly of said one gear. A retaining ring is located in a groove in said one arm radially outwardly of said thrust waisher; and first and second side gears in mesh with said differentiaLgears, which are configured to transmit power to first and second axles of a vehicle.
Another embodiment of inter-axle differential, comprising said spider provided with a plurality of radially outwardly extending arms and at least one of said arms is having a radially inner portion; and a radially outer portion. Said inner and outer portions are substantially circular in shape and said outer portion defining flats. One of said plurality of differential gears is disposed about said inner portion of said one arm. There is provision of a thrust washer about said outer portion of said one arm. The thrust washer is having a central bore shaped complementary to said outer portion of said arm.
In accordance with still another known art, a differential device comprises a ring gear, a pinion shaft, pinion gears, side gears/planetpinions, a case, and an engagement holding member. The ring gear has at least one side surface which is opened on an inner diameter side of an outer circumferential tooth

and has an insertion portion in which both end portions of the pinion shaft in a shaft length direction are inserted. The insertion portion has ring gear two surface portion in which two planes intersecting with each other in a circumferential direction of the ring gear are disposed in parallel. The pinion shaft has a shaft two surface portion in which two planes intersecting with each other in the circumferential direction are provided in parallel on the both end portions in the shaft length direction and which is inserted in the ring gear two surface portion/ in the crown portion with two toothed surface. The ring gear two surface portion and the shaft two surface portions are in contact with each other with no gap.
Another existing differential assembly comprising:
A central shaft rotatable about an axis, which is surrounded by a spider hub haying a plurality of spider legs extending radially outwardly at circumferentially spaced locations. Further, there is a pinion gear mounted on each said spider legs, which is rotatable thereabout.
In addition to the above, there is a pair of side gears each having teeth engaged with said pinion gears at opposed sides of said spider hub; and each of said pinion gears and said spider legs are associated with a radially outer cap. Said caps being secured to said spider legs and said cap extending radially outwardly beyond an outer periphery of a hub radially inward of said teeth. The cap is having a radially inwardly facing surface which is curved corresponding to a curve of said hub of said pinion gear.
According to another embodiment of this invention, a differential comprising: an input shaft extending along a rotational axis and a spider hub fixed to rotate with said input shaft. Multitude of pinion gears each associated with one of said spider legs. There is provision of a side gear positioned at each axial

side of said spider, and having teeth engaged with said pinion'gears. Each of said side gears being mounted to drive inputs for a front and rear axle of a vehicle; and a cap is fixed to each of said spider legs. Said cap is not extendable beyond an outer periphery of said pinion gear, such that said cap is associated with only one of said pinion gears.
None of the above can fulfill requirements of the present invention. Therefore the invention proposes a caseless compact transmission differential for a vehicle, which can function efficiently.
IBJECTS OF THE INVENTION
An object of this invention is to proppse a case less compact transmission differential for a vehicle which obviates drawbacks of prior arts.
Another object of this invention is to propose a case less compact transmission differential for a vehicle whichis compact in size with improved performance.
Further object of this invention is to propose a case less compact transmission differential for a vehicle which is low in weight and cost effective with improved performance
SUMMARY OF INVENTION
According to this invention there is provided a caseless compact transmission differential for a vehicle comprising a final gear held by means of a cross shaft, which is mounted with a speedometer gear.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Further objects and advantages of this invention will be more apparent from the ensuing description when read in conjunction with the accompanying drawings of exemplary embodiments of invention and wherein:
Fig. 1 shows: Exploded view of conventional differential assembly.
Fig. lA shows: Conventional differential assembly in assembled condition.
Fig. 2 shows: Exploded view of caseless compact transmission differential in
accordance with present invention.
Fig. 2A shows: Elongated structure of cross shaft holder of present invention.
Fig. 2Bshows: Back surface of base of cross shaft holder according to present
invention.
Fig. 3 shows: Caseless compact transm.ission differential of present invention
in assembled form.
DETAIL DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE
ACCOMPANYING DRAWINGS
The present invention makes a disclosure in respect of a caseless compact transmission differential for a vehicle, which includes a novel final gear, speedomieter gear, cross shaft and cross shaft holder without differential case. The differential assemibly of invention as illustrated in fig. 2 is detailed out hereinbelow.
The final gear (lA) is provided with a pair of innermost slots (S) placed diametrically opposite to each other, profile of which corresponds to respective end portion (E) of longitudinal shaft (L) of cross shaft. Further a hole (H) is drilled, on both sides of each of the slots so as to accommodate bolt (B) therethrough during assembly.

The cross shaft comprises two intersecting shafts [longitudinal shaft (L) and transverse hollow shaft (T)] orthogonal to each other constituting a single piece. The longitudinal solid shaft includes a central part with circular cross section interposed between the two end portions (E) having a cross section to match^ with that of the slot (S) as already mentioned. Further as can be best seen in the figure, there is provision of a slot (S') diametrically opposite to each other at both ends of said transverse shaft for lubrication of the differential gears (D).
A single hole (H') is drilled on the transverse shaft to discharge excess oil accumulated between the axle and inner surface of the transverse shaft unlike prior art.
A speedometer gear (G) is placed adjacent to the final gear, which forms a single piece of ring structure made of sheet metal/plastic with multiple steps (P'j on one side circumference maintaining a distance there between. The outer circumferential surface of the speedometer gear is fixedly secured with a plurality of holding means (M) with a through hole for assembling the speedometer gear onto the final gear by means of a number of bolts (B). The novel speedometer gear of invention is lighter than the existing speedometer gear.
In addition to the above, there is provision of two similar holders to hold the cross shaft (spider shaft) in the course of assembly. Each of the holders, is divided into two parts (Pi, P2) as shown.
One part (Pi) is having a base (Bi), outer profile of which is corresponding to the profile of. the slot (S). The base is provided with a through hole and mounted with an elongated structure (E') as in fig 2A with a hole (Hi) at both ends for bolting. Further, a plurality of protruded parts (P") are placed between said holes maintaining a gap therebetween, wherein the protruded parts are symmetrical with respect to each other.

A slot (Si) formed between the protruded parts mates with the end (E) of the cross shaft from both sides, wherein the slot acts as a rotational stopper to the cross shaft. Back surface (C) of the base as shown in fig 2B is having spherical machining so as to act as resting surface for shim (C)
Another part (P2) of the holder comprises a similar elongated structure as described hereinabove to butt against each other while assembling.
The cross shaft holder is bolted with said speedometer and final gear through the bolts as best seen in fig 3.
Differential gears (D) are supported in transmission case with bearings (B'). The cross shaft is supported in differential gears and acts as a guide for pinion gears (A). Said cross shaft is closely guided iri final gear and connected with cross, shaft holders through bolts to restrict its movement. One of major functions of cross shaft is to hold final gear within close tolerance range with respect to transmission case through differential gears. The shims are used for controlling the backlash of pinion and differential.gears. The speedometer gear is mounted on final gear using the bolts.
The differential assembly of invention can be placed within the transmission to be mounted on front axle/rear axle of vehicle. Alternatively it can be positioned separately on one axle and transmission on another axle of vehicle.

The advantageous features of the invention can be briefly summarized hereinbelow:
Compact in size
- Light weight
- Cost effective-
- Efficient functioning
- Imiproved performiace
It is to be noted that the present invention is susceptible to modifications, adaptations and changes by those skilled in the art. Such variant embodiments employing the concepts and features of this invention are intended to be within the scope of the present inventiori, which is further set forth under the following claims:-

CLAIM:
1. A caseless compact transmission differential for a vehicle comprising a
final gear held by means of a cross shaft, which is mounted with a
speedometer gear.
2. A caseless compact transmission differential for a vehicle as claimed in claim 1 wherein the final gear is provided with a pair of innermost slots placed diametrically opposite to each other, profile of which correspond to respective end portion of longitudinal shaft of cross shaft in which a hole is located on both sides of each of the slots.
3. A caseless compact transmission differential for a vehicle as claimed in claim 1 or 2 wherein the cross shaft comprises two intersecting shafts (longitudinal solid shaft and transverse hollow shaft) orthogonal to each other constituting a single piece.
4. A caseless compact transmission differential for a vehicle as claimed in any of the proceeding claims wherein the longitudinal solid shaft includes a central part with circular cross section interposed between the two end portions having a cross section to match with that of the slot.

5. A caseless compact transmission differential for a vehicle as claimed in any of the proceeding claims wherein a slot diametrically opposite to each other at both ends of said transverse shaft is provided for lubrication of a pair of differential gears.
6. A caseless compact transmission differential for a vehicle as claimed in any of the proceeding claims wherein hole is drilled on the transverse shaft to discharge excess oil accumulated. between the axle and inner surface of the transverse shaft.

7. A caseless compact transmission differential for a vehicle as claimed in any of the proceeding claims wherein the central part of said longitudinal shaft supports a pinion gear on both sides of the transverse shaft with a shim adjacent to the pinion gear wherein the pinion gears are free to rotate around the cross shaft.
8. A caseless compact transmission differential for a vehicle as claimed in any of the proceeding claims wherein the speedometer gear forms a single piece of ring structure made of material such as sheet metal, plastic with multitude of steps on one side circumference maintaining a distance therebetween, in which the speedometer gear is secured with a plurality of holding means having a through hole on outer circumferential surface thereof for assembling with said final gear.
9. A caseless compact transmission differential. for a vehicle as claimed in any of the proceeding claimis wherein the cross shaft holds the final gear with the help of cross shaft holder including two parts, in which one part is having a base, outer profile of which is corresponding to the profile of the final gear slot arid the base is provided with a through hole and mounted with an elongated structure.
10. A caseless compact transmission differential for a vehicle as
claimed in any of the proceeding claims wherein the elongated structure
is having a hole at both ends together with a plurality of protruded parts
placed therebetween maintaining a gap .therebetween forming a slot to
mate with the end of the cross shaft inwhich back surface of the base is
having spherical machining so as to act as resting surface for the shim.

11. A caseless compact transmission differential for a vehicle as claimed in any of the proceeding claims wherein theanother part of the holder comprises a similar elongated structure.
12. A caseless compact transmission differential for a vehicle as claimed in any of the proceeding claims wherein a differential gear on both sides of the final gear are mounted in transmission Case with the help of respective bearing. ■
13. A caseless compact transmission differential for a vehicle as claimed in any of the proceeding claims wherein said speedometer gear is mounted on the holder placed on the final gear by means of multitude of fasteners.
14. A caseless compact transmission differential for a vehicle as claimLed in any of the proceeding claims is associated with the advantageous features such as herein described.