DESC:NATURE OF THE INVENTION:-

The present invention relates to a process of producing high compressive strength bearing. More particularly, the present invention relates to subjecting bearing components to cold working process.

BACKGROUND OF THE INVENTION:-

There is a need for enhancing life of bearing FI 357217M without changing bearing model, boundary dimensions, structure and the type. Hence, applicant has developed new way to enhance bearing life, without changing principle dimensions of design. The present invention introduces a new process of subjecting the parts of bearing to cold working process at the last stage of manufacturing for the purposes of increasing compressive residual stress.

High compressive strength bearings can take more compressive load than the conventional one. Removing of other stress from the surface and inducing good compressive residual stress in surface improves the life of the bearings. Life of bearing is comparatively very high over conventional bearing. Applicant has successfully introduced cold working process and developed high compressive strength bearing FI 357217M that has almost 3 times more life than the conventional bearing.

Drawback of prior art that is rectified by present Invention:

• Relatively low life
• High consumption
• More maintenance
• More failure
• Less operating time

OBJECT OF THE PRESENT INVENTION:-

1. It is an object of the present invention to increase the life of bearing by increasing compressive strength of surface.
2. Another object of the present invention is to lower the maintenance and failure frequency by increasing compressive strength of surface of bearing components.
3. It is also an object of invention to reduce fatigue damage by increasing compressive strength of surface of bearing components.
4. Yet another object of invention is to prevents cracks on surfaces by strengthening surface of bearing components by increasing compressive strength of bearing components.

STATEMENT OF THE INVENTION:-

Accordingly, the invention provides a process for producing high compressive strength bearing, with cold working of bearing components viz. outer ring and inner ring, with suction induction nozzle machine so as to form plastic deformation in the surface by displacing materials sideways thereby the atoms below resists said displacing of materials and creates lateral compressive stress which attempts to restore surface to original state resulting hardened surface thereby resisting any deformation or cracks due to increase in bearing compressive strength; the said cold worked components assembled to form high compressive strength bearing.

REFERENCE TO DRAWINGS:-

The invention is described with reference to the figures of accompanying drawings wherein:

Figure 1 shows front view of the high compressive strength bearing according to invention;

Figure 2 shows the effect of cold working on components surface subjected to compressive force results in high compressive strength;

Figures 3A, 3B, 3C and 3D showing the components of bearings and assembly view respectively.

Figure 4 shows the bombarding by round abrasive for cold working for high compressive strength;

Figure 5 shows stretched surface after cold working of metal surface;

Figure 6 shows inner ring surface to be cold worked;

Figure 7 shows blast gun nozzle for bombarding round abrasive with air blast;

Figure 8 shows suction induction nozzle machine for cold working og metal surface;

Figure 9 shows pictorial view of abrasive bombarding machine for cold working of metal surface for imparting high compressive strength;

Figure 10 shows Almen strip for checking intensity of abrasive

Figure 11 shows arc height curve.

BRIEF DESCRIPTION OF THE INVENTION:-

Applicant has introduced one cold working process in prior known manufacturing process of bearing FI 357217, as shown in figure 1 which eliminates tensile and other stresses and creates good compressive residual stress in the top layer by plastic deformation of bearing. It increases its resistance to metal fatigue and some forms of stress corrosion. This residual compressive stress keeps compression on surface molecules which restricts formation of surface cracks and also automatically heals small surface cracks.

Figure 2 shows cold working effect on the component parts, viz. outer ring, inner ring and rolling elements. Figure 3A, 3B, and 3C shows components inner ring 1, outer ring 2 and rolling element 3. Figure 3D shows assembly of the said cold worked components to form high compressive strength bearing.

When the cold working creates plastic deformation in the surface by displacing materials sideways, the atoms below resists this and creates lateral compressive stress which attempts to restore surface to original state. This process hardens the surface and resists any deformation or cracks. By this, bearing compressive strength increases and it increases bearing life by 3-5 times.
The cold working: Cold working process increases the stiffness and hardness of surface. Cold working process used to produce a compressive residual stress layer and modify mechanical properties in metals, by Bombarding round metal/ceramic/glass shots with enough intensity to dent the surface as shown in Fig 4. This process is carried out after the grinding and before super finishing.

It carries on two parts of Cylindrical Roller Bearing FI 357217.
(1) Inner ring raceway
(2) Outer ring raceway

These two parts of bearing are also important to carry the load. So, better strength is required. In Cold working Process, mainly two inputs are required:

(1) Abrasive particles (Glass Beads) and (2) Cycle Time
Glass beads indentation on the raceway increases the compressive strength of it. This process is carried out in three stages as below in the machine as shown below Fig 9.
Stage 1: Glass beads are feed into the strainer container as shown in Fig 9. In which different mesh size strainers are fitted. Recommended mesh size for this process is 50 microns. From them first strainer’s output is disposed because its grade is not suitable for the bearing. The second and third strainer’s output is used.
Stage 2: Then an intensity of glass beads form nozzle has checked by standard Almen Strip before starting the indentation as shown in Fig 10. In this case, intensity must be in range of 0.05-0.15 mm.
If a flat strip of metal is cold worked on one side only, it will slightly curl away from the side which has been treated and produce a convex surface. On the basis of glass bead grade (size), cycle time has to be decided by trial and error method. Abrasive air ratio (intensity) can be adjusted by abrasive regulator valve and determined by plotting the arc height against the time spent in cold working.
Stage 3: Before spraying the bead on the work piece vacuum has been created in the blast chamber. Machine operates with the help of compressed air. Before starting the process, small particles and dust particles must be removed from the chamber, because small particles of beads do not give any positive effect on the surface of raceway. Dust generated in this process is separated and collected in a dust collector. Air pressure is depends on the abrasive used, type of work material, speed of cleaning and type of finishing required. The air pressure in range of 2.5-5 Kg/Sq.cm used for the process.

Stage 4: After closing the door of chamber, workpiece table is rotated manually. So that spray of glass bead is spread equally throughout the work piece surface. At the completion of cycle time spray will be stop automatically.

MACHINE FOR COLD WORKING:

Referring to figure 8, the cold working machine, is a suction induction nozzle machine, having an enclosed cabinet with exhaust ventilator comprising gravity hopper and storage bin. A rotative work table fixed above the said gravity hopper. A shot regulating valve/orifice with air inlet adjustable provided at the bottom of said hopper. A blast gun with air supply connected by pipe mean pipe to said shot regulating valve.

The newly developed bearings have been tested and certified by ARAI (Automotive Research association of India). The results of the comparison test found better than the conventional bearings.

Further, applicant has conducted bearing life test trials for the bench marking and results were compared between conventional bearing and new bearing. Results clearly show that the improved bearing FI357217M has achieved three times more life than the conventional bearing. (The conventional bearing runs for approximately 597 Hours whereas new bearing lasts for approximately 1810 Hours).

LIST OF PARTS AND THEIR CONNECTIVITY:-

1. Inner ring (Raceway Cold Worked).
2. Outer ring (Raceway Cold Worked).
3. Rolling Elements (No change)
4. Assembly

FUNCTION/ PURPOSE OF EACH PART:-

Function of this bearing is same as any conventional bearing. But difference is life of bearing. Load carrying capacity and life is longer when compared to prior known/ conventional bearings. Its fatigue and ultimate strength is increased due to present invention. Also by this cold working process its surface will also resist formation of cracks, fretting, corrosion, and wear.

ADVANTAGES OF THE PRESENT INVENTION:-
High compressive strength bearing exhibits some of the following properties:

? Enhanced fatigue strength
? Improved ultimate strength
? Prevents cracking due to wear
? Prevents corrosion
? Prevents fretting
? Increased lubricity
,CLAIMS:1. A process for producing high compressive strength bearing comprising steps-
i. subjecting components viz. outer ring and inner ring to cold working in a suction induction nozzle machine so as to form plastic deformation in the surface to resist any deformation or cracks due to increase in bearing compressive strength;
ii. said cold worked components assembled to form high compressive strength bearing;

2. A process for producing high compressive strength bearing as claimed in claim 1 wherein, the said cold working of bearing components viz. outer ring, inner ring of bearing carried out in the said machine by bombarding round abrasive particles such as metal/ceramic/glass shots with enough intensity to dent the surface after the grinding and before super finishing;

3. A process for producing high compressive strength bearing as claimed in claims 1 and 2 wherein, the said cold working of bearing components viz. outer ring, inner ring of bearing done in the said machine comprising steps:
i. feeding of glass beads into the strainer container in which different mesh size strainers are fitted preferably 50 microns. Such that first strainer’s output is disposed because its grade is not suitable for the bearing. The second and third strainer’s output is used;
ii. an intensity of glass beads form maintained in range of 0.05-0.15 mm form nozzle has checked by standard Almen Strip before starting the indentation;
iii. on the basis of glass bead grade (size), cycle time decided by trial and error method;
iv. abrasive air ratio (intensity) adjusted by abrasive regulator valve and determined by plotting the arc height against the time spent in cold working;
v. before spraying the bead on the work piece vacuum created in the blast chamber;
vi. after closing the door of chamber, work piece table rotated manually such that spray of glass bead is spread equally throughout the work piece surface and at the completion of cycle time spray stops automatically.

4. A process for producing high compressive strength bearing as claimed in claims 1 to 3 wherein, the said machine operates with the help of compressed air with an air pressure depending on the abrasive used, type of work material, speed of cleaning and type of finishing required;

5. A process for producing high compressive strength bearing as claimed in claims 1 to 4 wherein, the said air pressure of compressor maintained in the range of 2.5-5 Kg/Sq.cm.