FORM 2
THE PATENT ACT 1970
(39 of 1970)
&
The Patents Rules, 2003
PROVISIONAL SPECIFICATION
(See section 10 and rule 13)


1. TITLE OF THE INVENTION
PLANETARY CARRIER ASSEMBLY WITH FACE PLATE
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 invention relates to planetary gear systems and, more particularly, relates to compact planetary gear assemblies for final drives of tractor or other slow moving vehicles.
A Planet gear carrier assembly has a spider in which is rotatably mounted a pluraity of planet gears. Each planet gear is mounted on a respective shaft which is disposed in bores formed on the separate spacer and the spider. The planet shaft assembly is constrained both racially and axially with roll pin arrangement and linearly by the spacer arrangement.
Background of the Invention
Planetary carrier assemblies comprises to carry planet gears, planet shafts and bearings and to transmit the power and torque to any external device providing torque conversion of differential drive action. The planetary gears are designed so that several gear teeth are always in mesh at once. This design distributes the mechanical forces over several gear teeth for added strength and prevents any damage associated with gears going in and out of mesh. The torque carrying capacity of the assembly is restricted by bearing capacity and the deflection, stress developed in the planet shaft.
In one application, the construction of assemblies is that planetary carrier as a closed type, i.e., integral spider arrangement, which gives the simply supported configuration to planet shaft thus minimizing the deflection of the shaft, thereby increasing the life, load capacity and performance of the planetary system. This type of construction allows

the use of only needle bearing as the fit required by cage bearing cannot be satisfied and space necessary for cage bearing fitment is not available. Also using needle bearing induces scoring marks of planet shaft, leading to fatigue failure of shaft, thus reducing life of the system.
US Patent 7448980B2 discloses the solution to prevent scoring by providing a sleeve to orevent the damage to the planet shaft. Even as it prevents scoring, there are disadvantages in terms of (necessity of?) usage of high capacity bearing in the closed type construction. Also sleeve adds to the number of components and requires good wear resisting material with proper heat treatment. Lubrication is more critical which will be an additional constraint.
US Patent 7214160 B2 discloses the guide washer assembly for a planet carrier for a planetary transmission having two guide washer interconnected via adequate connecting elements and held parallel at a distance from each other, the connecting elements being integral component parts of at least one of the two guide washer.
The guide washer assembly consists of two round guide washers aligned parallel with each other and firmly interconnected via connecting element. The axial length of the connecting element is defined space requirement of guide washer. The connecting element is made on either on one element or both elements (Guide washer). The connecting elements have a vaulted, tapered or cylindrical geometry. The connecting elements on at least on one guide washer are preferably produced by a sheet deforming process which is a combination of cold hammering, deep drawing and precision blanking

processes. The disadvantage of this design is that cold hammering, deep drawing and precision blanking processes is required which adds cost to the system.
US Patent 5382203 discloses a carrier for an automatic transmission of a motor vehicle comprising a hub, an annular face plate, a plurality of posts, and a plurality of planetary gears. The posts are generally cylindrical, and extended between the hub and the face plate substantially within the respective perimeters of the hub and the face plate. The method of assembly comprises providing a hub, face plate, and a plurality of planetary gears in a gear pocket between the hub and the face plate. A plurality of generally cylindrical posts having ends shaped for controlled weldment are then capacity discharge welded between the hub and the face plate substantially within their respective perimeters to maintain the gear pocket there between. This patent is mainly for automatic transmission for motor vehicle and hub and face plates are connected by plurality of cylindrical post with the assistance of capacity discharge welding process. Moreover plurality of planet gears can be inserted into the space after welding of face plates and the hub restriction the use of needle bearing between the planet gear and shaft putting addition constrain on the torque carrying capacity of planetary system.
In another application, carrier without face plate is used. The carrier is manufactured by forging process with integral planet shaft. This construction allows the use of any type of bearing increasing the torque carrying capacity of the planetary system. The disadvantage of the system is that complicated machining process is required for machining of planet shaft and also machining time and setting time is

also increased, thus overall machining cost is increased. It is further known to produce such a planet carrier as a forging part which involves comparatively heavy parts which are expensive because of the finishing costs that are needed.
The present invention has been developed to resolve the above problems and other short comings of the prior art particularly with the objective of reducing cost of the drive. Another objective of the present inventions is to provide a choice of a wide range of materials for use in the hub and the face plate and also provide ease of manufacture. Yet another object of the present invention is to make the whole planetary assembly compact and light weight.
Object of the Invention
According, it is an object of the present invention to provide a carrier assembly of the type described above which an effective has multiple piece construction which is easy to manufacture at a relatively low cost with high durability.
Another objective of the present invention is to provide a carrier of the type described above which allows the flexibility of design in the choice of number of planet and a choice of a wide range of materials for used in the carrier and the spacer plate.

Summary of the Invention
The invention provides a construction in which the cost of the assembly is reduced to a minimum by making use of elimination of complex manufacturing process, reduction in weight and reducing of separate parts
The invention provides a planetary gear assembly that includes a spider, atleast one planet shaft, atleast one planet gear and atleast roller bearing. The planet gear is rotatable about the planet shaft. Roller bearings may be provided between the planet gear and the planet shaft to facilitate rotation of the planet gear about the planet shaft. The planetary gear assembly further includes the face plate which may be press fitted with the planet shaft and joined with the planet gear thus rotating with the spider.
In one aspect of invention, the planet shaft is made as a separate piece without any vanation in section to take advantage of cheaper manufacturing processes. In another aspect of the present invention, particularly where higher load capacities are required, the shaft may have two diameters with a filet radius between the two diameters, the portion with larger diameter joined to the spider.
For higher bearing load and use of helical bearing, it may be necessary to employ a pair of taper roller bearing in place of needle, CRB or Ball bearing in which case some preloading means needs to be provided. In the form of preloading means threads along with preloading or graded spacer or shims can be provided in the planet shaft along with preloading nut.

It may be possible to construct an embodiment of low cost planetary drive assembly, where in the face plate is not provided but only separate planet shafts are joined to the spider, the planet shaft being of single section or stepped section with fillet radius described above.
The above said joint may be welding, soldering, bolting, riveting, screw connection, roll pin arrangements and any other retaining means. The pressing connection may be made with the aid of temperature difference which may be higher or lower between the planet shaft and the carrier.
Other aspects of the invention will become apparent by construction of the detailed description and accompanying drawings.
It should be understood that while the forms of the invention herein shown and described constitute preferred embodiments of the invention, they are net intended to illustrate all possible forms thereof. It should also be understood that the words used are words of description rather than limitation, and various changes may be made without departing from the spirit ans scope of the invention disclosed.
Brief Description of the Drawings
FIG 1 is an exploded view of a planetary carrier assembly embodying
the present invention FIG 2 is a exploded view of the planetary gear assembly FIG 3 is the section view of planetary gear assembly

FIG 4 is an alternate construction of planet shaft for incorporating
taper roller bearing. FIG 5 an alternate construction of the planet shaft FIG 6 is an alternate construction of the planetary carrier assembly
without face pfate.
Detailed Description of the Preferred Embodiment
Referring to the drawings, wherein like characters represent the same or corresponding parts throughout the several views, there in Fig 1 a planet carrier assembly 1 to which include a spider 1, atleast one planet gear 3, and atleast one planet shaft 4, each supporting a planet gear 3 and face plate 19.It is understood by one of skill in the art, the planetary carrier assembly would typically further include a sun gear and a ring gear.
The spider 2 has a single diameter bore 5. The spiders 2 has a hole 6 perpendicular or at angle to the bore 5 at distance from the face of the carrier 7. The planet shaft 4 have through bore 8 at distance form the face 9 of the planet shaft 4. A Groove 10 is made on the planet shaft 4 at certain length depends on the space required from the bore 8.
The planet shafts 4 are disposed in the single diameter bore 5. The planet shafts 4 are preferably a press fit or in line fit with the bore 5. the planet shaft is made without any step or geometrical variation for taking advantage of cheaper manufacturing processes preferably centre less grinding. Each planet shaft having bore 8 which is made inline with the hole 6 and roil pin 11 is inserted to provide both axial and linear constrain to the planet shaft 4. Length of roll pin 11 is equal

to diameter of planet shaft 4 for easy removal of planet shaft from spider. Welding, bolting, riveting or any other means can be used for constraining planet shaft in axial as well as linear motion.
The Planet Gear 3 and Bearing 12 form an assembly 16. The planet gear 3 have internal bore 13. Grooves 14 spaced apart depending on the span of Bearing 12 on the bore 13. The bearing 12 is inserted in the bore 13. Bearing 12 is constrained axially by a ring 15 which fits in the grooves 14. Planet gear bearing subassembly 16 is press fitted on the planet shaft 4 outer surface 17. Planet gear bearing subassembly 16 is press until bearing face 18 butts with the carrier face 7.
The face plate 19 has bores 20 which are coaxial with the carrier bores 5. The face plate 19 is press fitted until the front face of spacer 21 butts with another end of the planet shaft 4 faces 18. The whole system is packed with the ring 22 to prevent the axial movement of the Bearing 12. The face plate 19 is made as a separate plate to reduce the material of the carrier thus reducing the material cost Weight thereby cost of the system is reduced by separating the integral type carrier into two pieces i.e., spider and face plate with simple construction without loss in reliability and durability.
In all such arrangements it is desirable to either restrain the carrier from rotation or to secure it to a rotating member for simultaneous rotation therewith. The carrier assembly 1 therefore, includes a spline 23 disposed on the outer surface of the side wall 24 which might be connected with a conventional friction clutch brake member or with a

toothed hub which in turn would be secured to another element within the planetary transmission or any output device.
In alternate construction, to increase the load carrying capacity, planet shaft 14 is made as stepped shaft. The bigger diameter 25 and smaller diameter 26 are provided with fillet for reducing stress concentration. The portion with bigger diameter 25 is joined to the spider bore 5 as shown in fig 5
For Taper roller bearing, shim 27 and spacer 28 is provided for
controlling preload.

Dated

this 26th day of March 2009


Mr. Shyam Sunder Iyer (Agent on behalf of the Applicant)