FORM 2THE PATENT ACT 1970 (39 OF 1970) &The Patent Rules, 2003 COMPLETE SPECIFICATION (See Section 10 and Rule 13)
1 TITLE OF THE INVENTION :
A SYSTEM FOR REMOVAL AND FITMENT OF FINAL DRIVE SHAFT OF DOZER AND METHOD FOR ITS USE.
2 APPLICANT (S)
Name : STEEL AUTHORITY OF INDIA LIMITED
Nationality : A Govt. of India Enterprise
Address : Bhilai Steel Plant, Bhilai, State of Chattisgarh, India
3 PREAMBLE TO THE DESCRIPTION
COMPLETE
The following specification particularly descibes the invention and the manner in be performed. which it is to

FIELD OF INVENTION:
The present invention is directed to a system for removal and fitment of final drive/sprocket shaft and drive gear assembly of bull dozers and a method for using such system advantageously and cost-effectively which can be applied and used extensively for variety of dozers which are an essential earth moving equipment in various steel plants. Dozers are known to be useful in various departments/sections in industry for purposes like removal/cleaning and or loading /shifting of heavy materials, in either hot or cold
conditions. This is a very costly equipment used for important functions and as such the
breakdown of such vital equipment due to failure of final drive shaft and gear assembly leads to serious bottle neck in production process either due to stock pile of in-process goods/waste or due to shortage in supply of essential input materials to stages of production. The present invention is directed to a simple and cost-effective system of removal and fitment of the drive shaft and drive gear assembly without involving complex machinery and equipments.
BACKGROUND AND PRIOR ART:
The final drive/sprocket shaft and drive gear assembly of bulldozers or similar other heavy earth moving equipments are subjected to heavy load and impact during operation in large industries such as in different sections of Steel plants. Due to this continuous use under heavy load, the final drive shafts/gears of the equipments are subjected to wear and tear and need to be repaired/rebuild as and when necessary. The final drive consists of two step reduction by the use of appropriate diameter/teeth ratio of meshing gears/pinions arranged in specific order/sequence in the gear box, commensurate with the speed/torque
requirements of the equipment. Power from axle and steering system is transmitted through the clutch outer drum (break drum) to final drive flange which drives the primary gear by means of rotating primary pinion which is in turn operatively connected to the secondary gear through secondary pinion. Final drive shaft is press fit in the dozer chassis with a force of 100 tons by means of horizontal press machines deployed from both sides. The particular kind of fit is an interference fit where the amount of interference between the mating surfaces is in the range of 0.085~ 0.145mm.
The bull dozers are heavy type of earth moving equipments which are widely used in steel plants essentially for functions like material handling/recovery in the departments of steel
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melting shop, metal recovery department, ore handling plant, coke ovens, blast furnaces etc. The main subsidiary function of the equipment is to clean up material collection/accumulation at different sections or intermediate stages. Due to the failure of final drive shaft on prolonged harsh use at site conditions, this vital equipment cost of which is around rupees one and a half crore, causes immense loss of production due to either short supply of inputs or bottleneck due to inadequate cleaning. Both of which is having direct impact on consequent financial losses.
The conventional method of removal of the final drive/sprocket shaft for repair/rebuilding
involve heavy machineries like heavy duty presses and EOT cranes for handling of the elements/machines etc, which is not only a costly affair but takes lot of time and space for the complete overhauling and maintenance till the dozer is again put in operation. No simple cost effective and faster method of repair/rebuild/replacement of the final drive shaft of the dozers of any makes to save down time costs. There was therefore a persistent need to develop a device to simplify the method of removal, repair and assembly of the final drive shaft and the drive gear assembly for the earth moving equipments, particularly the bull dozers used for material handling in steel plants, to reduce down time and related costs.
OBJECTS OF THE INVENTION:
The basic object of the present invention is directed to a system and method of removal/dismantling of the final drive/sprocket shaft and drive gears of dozers in a simple and faster way, without the requirement of heavy machineries/cranes, in order to minimize repair/maintenance time and down time costs.
A further object of the present invention is directed to the use of simple system including pulling device comprising simple telescopic hydraulic jacks and tie bars/ hollow pipes, plates means etc. to facilitate the process of dismantling the said drive shaft from the dozer chassis for subsequent repair/rebuild of components as necessary.
A further object of the present invention is directed to a simplified and faster system and method of removal and fitment of final drive shaft and the drive gear so as to enhance the working life of the dozer equipment.
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A further object of the present invention is directed to a system and method of removal and fitment of final drive shaft and drive gear assembly of dozer by advantageous use of liquid nitrogen cooling, preferably in a properly heat insulated container of adequate size, for said interference fit, that help eliminate the necessity of heavy press or cranes etc for the purpose of removing the drive shaft.
A further object of the present invention is directed to a simple and faster system and method of removing and fitment of final drive shaft and drive gears involving three steps-(i) dismantling the drive shaft from said assembly of drive gear box assembly, (ii) repair/rebuilding the shaft or gears/pinions for wear or other damages caused due to prolonged harsh use at shop/sites, (iii) fitment of the drive shaft and drive gears/pinions assembly of dozer.
A further object of the present invention is directed to a system and method of removal and fitment of drive shaft and gear assembly, to make adaptive use of a 5 ton lifting crane while the shaft is cooled by dipping into the liquid nitrogen bath for fitment, after necessary repair has been carried out, to shrink in dimension/diameter to enable said interference fit.
SUMMARY OF INVENTION:
Thus according to the basic aspect of the present invention there is provided a system for removal and fitment of final drive shaft and drive gear assembly of dozer comprising:
shaft dismantling assembly comprising:
cylindrical tube means adapted to insert on the shaft;
a pair of plate means with holes in the centers thereof adapted to insert into said shaft and maintained space depart from one another; and
hydraulic jack means preferably telescopic type adapted for disposition there between said plates on the shaft such that on operation of the jacks the shaft is driven out;
shaft repairing means comprising means to repair and maintain an interference of 0.085 to 0.145mm;
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shaft fitment assembly comprising:
a container means having means to avoid heat dissipation and adapted to contain liquid nitrogen ;
over head crane means to hang the shaft into said container for liquid nitrogen cooling and lifting for desired fitment and assembling with or without any hitting arrangement.
In the above system for removal and fitment of final drive shaft and drive gear assembly of dozer the said shaft repairing means comprises means to deposit metal on damaged shaft and means to machine the shaft for maintaining interference of 0.085 to 0.145mm.
The said shaft dismantling assembly comprises four numbers of said cylindrical tubes and two numbers of thick plates preferably of 25mm size having central hole to insert into the shaft and two numbers of hydraulic jacks telescopic type placed in between said plates.
The said container means used in the system comprises double walled container obtained preferably of 10mm thick plate with wooden pulp provided there between the double walls for avoiding heat dissipation.
In accordance with another aspect of the present invention there is provided a method of removing and fitment of final drive/sprocket shaft and drive gear assembly of dozer using the system as disclosed above comprising:
removal of the final drive shaft using the said shaft dismantling assembly repairing the damaged shaft using the said shaft repairing means; and fitment of the shaft using the said shaft fitment assembly.

In accordance with an aspect the said method of removing and fitment of final
drive/sprocket shaft and drive gear assembly of dozer comprises operating two numbers 25

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ton telescopic hydraulic jacks simultaneously, being adaptively supported by four numbers hollow tubes and two numbers 25mm thick square plates having the central opening and inserted on to the shaft, to facilitate said removal of the drive shaft from the assembly;
repair/rebuilding and machining of the shaft to desired accuracy for further interference fitment of the order of 0.085~0.145mm;
cooling of the said drive shaft by dipping into liquid nitrogen at -190°C for about one hour to one and a half hours such that it shrinks in diameter to favor said interference fit of the drive shaft with drive gear/sprocket hub.
In the above method the cooling of the repaired shaft is carried out by dipping the shaft into the liquid nitrogen filled in said double walled container made of 10mm thick plate, and of size large enough to accommodate the shaft.
Preferably, the said nitrogen cooling of the drive shaft by dipping it into liquid nitrogen comprise covering the entire container with asbestos cloth to prevent heat loss and maintain steady bath temperature.
In accordance with an aspect in the above method the final fitment is carried out by hanging the cooled and shrinked shaft from a 5 ton crane in favored position and lowered to fit in to desired location of drive gear/sprocket hub, such that the interference results upon arriving at the ambient temperature.
A double walled plate fabricated box of suitable size for selective nitrogen cooling by filling the box with liquid nitrogen and dipping the dismantled final drive shaft in it, covering with proper heat insulation of the system to prevent heat loss, to favor desired shrinkage in
diameter of shaft required for subsequent interference fit with the drive gears of dozer.
A further aspect of the present invention is directed to the method of removal and fitment of drive shaft and drive gear assembly of dozer, said interference fit is achieved by said selective nitrogen cooling of the drive shaft wherein said nitrogen bath is maintained at about -190°C for about 1 to 1 ½ hours.
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A further aspect of the present invention is directed to the method of removal and fitment of drive shaft and drive gear assembly of dozer, said fabricated double walled box made from 10mm thick plates, which was insulated by filling wooden pulp in between the walls and the box containing liquid nitrogen was covered with wooden planks and asbestos cloth to prevent heat loss during cooling of the drive shaft.
A further aspect of the present invention is directed to the method of removal and fitment of drive shaft and drive gear assembly of dozer, wherein said drive shaft after cooling at around -190°C, is suspended vertically by means of a 5 ton crane for gradual lowering maintaining alignment to favor desired fitment with drive gears/pinions and to provide said selective interference.
The details of the invention, its objects and advantages are described hereunder in greater detail with particular reference to the accompanying figures.
BRIEF DESCRIPTION OF THE FIGURES:
Figure 1: Illustrates the final drive arrangement comprising the drive shaft and the drive gears as conventionally used in earth moving equipments, particularly the bulldozers.
Figure 2: Illustrates the nitrogen cooling of the drive shaft by providing liquid nitrogen in a double walled fabricated box with proper heat insulation, according to the present invention.
DETAILED DESCRIPTION OF THE ACCOMPANYING FIGURES:
Reference is first invited to the accompanying figure 1 wherein a particular embodiment of the final drive of bull dozer comprising the final drive/sprocket shaft and the drive gears assembly has been illustrated forming part of the Dozer. The final drive consists of two step reduction method using spur gears by engaging the primary and the secondary pinion and gear combinations, provided with splash lubrication.
Power from the axle and steering is transmitted through the clutch outer drum(brake drum) to final drive flange(l) to rotating primary pinion(2) on the flange; the primary pinion in turn engages with and rotates the primary gear(26) which is further engaged with the secondary pinion (25) on the gear shaft. Power is further transferred to the secondary gear
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(20) engaging with the secondary pinion effecting the simultaneous speed reduction in the ratio of diameter/teeth of the meshing gear/pinion. The construction of the said shaft and gear assembly shows that the secondary gear is bolted on the final drive hub/sprocket hub (23) within which the sprocket boss (8) is pressed in, by the taper serration, the rotation of secondary gear operatively turns also the sprocket boss. Sprocket teeth (6) are tightened with nuts and bolts on to the sprocket boss. Final drive shaft is press fit into the dozer chassis with a force of 100 tons and interference is 0.085~0.145mm during manufacturing of the equipment by engaging hydraulic presses from either side of the dozer simultaneously.
Due to continuous use of the dozer, the gear/pinion teeth and the drive shaft mating surfaces are subjected to wear. Also the bearings used in the assembly may need to be
replaced. This require the final shaft to be removed from the final drive assembly, worn out parts/portions repaired and again assembled to be fitted in position in the dozer.
The method of removal and fitment of the drive shaft and gear assembly according to the present invention use simple kits comprising hollow pipes, plates and telescopic hydraulic jacks, avoiding involvement of heavy duty hydraulic press/dual press or the heavy cranes for handling and also the space required for such conventional consuming much of down time of the equipment. The present method of removal and fitment of the drive shaft and the gears assembly are carried out in following three stages:
(a) Removal of final drive/sprocket shaft;
(b) Repair/rebuilding of worn out portions of shaft; and
(c) Fitment of the shaft with drive gears/hub/chassis;
(a) Removal of the drive shaft: The first step of the method according to the present invention involving removal of the final drive shaft from the assembly with drive gears/hub by the adaptive use of a simple pulling device/kit. Said pulling device consist of four numbers of hollow cylindrical tubes to be inserted on to the shaft at preferred locations and two numbers of square shaped plates of thickness 25mm with central holes cut at central position so as to facilitate insertion on to the shaft and provide support for the two numbers of 25 ton telescopic hydraulic jacks placed in between the plates and operated at a time in synchronization effecting driving out the sprocket/drive shaft from the final drive arrangement/assembly for subsequent repair/rebuilding and machining as necessary.
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(b) Repair of the final drive shaft become necessary when the final drive failure take place due to either damage of bearing and/or gear/pinion teeth after running on heavy load for prolonged period, or there may be damage/wear on the shaft surface needing repair/replacement for enhancement of life of the dozer. Usually metal is deposited on the worn out shaft surface up to required uniform thickness by adopting welding or other standard process and then machined accurately with enough precision so as to maintain interference of 0.085~0.145mm.
(c) Fitment of the shaft with drive gears/sprocket hub/ dozer chassis is carried out by preferred cooling of shaft by dipping in liquid nitrogen filled in to a double walled container (CT) fabricated with 10mm thick plates. The size of the container is large enough to facilitate putting into and taking out of the final drive shaft(FDS) for said nitrogen cooling. The empty space between the walls of the container is filled with wooden pulps(WP) to control heat dissipation through the walls in to the atmosphere in natural convection mode. After the container has been filled with liquid nitrogen(LN), the shaft is suspended with the help of a 5 ton overhead crane and lowered gradually to fully immerse in the liquid nitrogen(LN) bath and the entire container is promptly covered with asbestos cloth to prevent heat loss. The persons working/handling the job used fire proof asbestos gloves as precaution to protect from liquid nitrogen. The shaft was allowed to cool for over one hour up to at a temperature of -190°C. The drop in temperature causes the dimension/diameter of the drive shaft to shrink to favor the desired interference fit with the drive gear/sprocket hub/chassis maintaining alignment and concentricity, when the system reach the steady state at ambient temperature. The said procedure did not require any repetition of lifting and lowering of the shaft but achieved the preferred interference fitment successfully in single attempt.
It is thus possible by way of the present invention to provide a simple and cost-effective manner of removal and fitment of final drive shaft and drive gear assembly of dozers and the like. The invention would favour increasing the availability of equipments and can be applied in all types of axles and shafts. Importantly, the invention provides for substantial reduction in repair time and would favour effective use of dozers and like equipments.
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WE CLAIM:
1. A system for removal and fitment of final drive shaft and drive gear assembly of
dozer comprising:
shaft dismantling assembly comprising:
cylindrical tube means adapted to insert on the shaft;
a pair of plate means with holes in the centers thereof adapted to insert into said shaft and maintained space depart from one another; and
hydraulic jack means preferably telescopic type adapted for disposition there between said plates on the shaft such that on operation of the jacks the shaft is driven out;
shaft repairing means comprising means to repair and maintain an interference of 0.085 to 0.145mm;
shaft fitment assembly comprising:
a container means having means to avoid heat dissipation and adapted to contain
liquid nitrogen ;
over head crane means to hang the shaft into said container for liquid nitrogen
cooling and lifting for desired fitment and assembling with or without any hitting
arrangement.
2. A system for removal and fitment of final drive shaft and drive gear assembly of dozer as claimed in claim 1 wherein said shaft repairing means comprises means to deposit metal ores on damaged shaft and means to machine the shaft for maintaining interference of 0.085 to 0.145mm.
3. A system for removal and fitment of final drive shaft and drive gear assembly of dozer as claimed in anyone of claims 1 or 2 wherein said shaft dismantling assembly comprises four numbers of said cylindrical tubes and two numbers of thick plates preferably of 25mm size having central hole to insert into the shaft and two numbers of hydraulic jacks telescopic type placed in between said plates.
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4. A system for removal and fitment of final drive shaft and drive gear assembly of dozer as claimed in anyone of claims 1 to 3 wherein said container means comprises double walled container obtained preferably of 10mm thick plate with wooden pulp provided there between the double walls for avoiding heat dissipation.
5. A method of removing and fitment of final drive/sprocket shaft and drive gear assembly of dozer using the system as claimed in anyone of claims 1 to 4 comprising:
removal of the final drive shaft using the said shaft dismantling assembly ; repairing the damaged shaft using the said shaft repairing means; and fitment of the shaft using the said shaft fitment assembly.
6. A method of removing and fitment of final drive/sprocket shaft and drive gear
assembly of dozer as claimed in claim 5 comprising operating two numbers 25 ton
telescopic hydraulic jacks simultaneously, being adaptively supported by four
numbers hollow tubes and two numbers 25mm thick square plates having the central
opening and inserted on to the shaft, to facilitate said removal of the drive shaft
from the assembly;
repair/rebuilding and machining of the shaft to desired accuracy for further interference fitment of the order of 0.085~0.145mm;
cooling of the said drive shaft by dipping into liquid nitrogen at -190°C for about for 1 to 1 and 1/2 hours such that it shrinks in diameter to favor said interference fit of the drive shaft with drive gear/sprocket hub.
7. A method of removing and fitment of final drive/sprocket shaft and drive gear
assembly of dozer, as claimed in anyone of claims 5 or 6 comprising
cooling of the repaired shaft by dipping the shaft into the liquid nitrogen filled in said double walled container made of 10mm thick plate, and of size large enough to accommodate the shaft.
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8. A method of removing and fitment of final drive/sprocket shaft and drive gear assembly of dozer, as claimed in any one of claims 5 to 7, wherein said nitrogen cooling of the drive shaft by dipping it into liquid nitrogen comprise covering the entire container with asbestos cloth to prevent heat loss and maintain steady bath temperature.
9. A method of removing and fitment of final drive/sprocket shaft and drive gear assembly of dozer, as claimed in claims 5 to 8, the final fitment was carried out by hanging the cooled and shrinked shaft from a 5 ton crane in favoured position and lowered to fit in to desired location of drive gear/sprocket hub, such that the interference results upon arriving at the ambient temperature.
10. A system for removing and fitment of final drive/sprocket shaft and drive
gear/sprocket hub assembly of dozer and a method for using such system
substantially as herein described and illustrated.
Date this 8th day of March, 2007. Anjan Sen
Of Anjan Sen & Associates (Applicants Agent)
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ABSTRACT
A SYSTEM FOR REMOVAL AND FITMENT OF FINAL DRIVE SHAFT OF DOZER AND METHOD FOR ITS USE.
A system of removal and fitment of the final drive shaft(FDS) and drive gear assembly in a simple and cost effective way without involving any heavy duty hydraulic press machines or cranes to dismantle and reassemble said final drive shaft and drive gear assembly and method for its use for dozers. The system basically involves provision for removal, repairing and fitment of the shaft in a very simple and cost-effective manner and providing means for preferred controlled liquid nitrogen(LN) cooling of the said shaft to achieve desired interference fitment with drive gear/sprocket hub. The system is directed to favour increasing the availability of equipments and can be applied in all types of axles and shafts. Importantly, the invention provides for substantial reduction in repair time and would favour effective use of dozers and like equipments.
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