FIELD OF THE INVENTION
The present invention relates to shaft mounted deflector roll for tandem cold rolling
mill for feeding sheet to the first stand by changing direction of sheet. More
particularly, the present invention is directed to providing a shaft mounted deflector
roll system wherein bearing is mounted inside roll barrel, favouring increased load
bearing capacity and reduced damage due to misalignment and deflection of stand
and consequent bearing failure or damage of the housing, reducing downtime and
improving productivity in cold rolling mill ensuring desired shape/edge of rolled sheet
product.
BACKGROUND ART
In the new millennium, the steel section manufacturers have the objective to retain
customers by supplying quality product and adhering to delivery schedules along
with high production level. Increasingly stringent requirements for shape and
thickness of strip can only be met through fine-tuning of mechanical and electrical
equipments.
The applicants' steel plant is engaged in producing flat products from the range of
0.2mm to 16mm.Bokaro Steel Plant is poised to augment its production from 4.0
Million MT to 7.0 Million MT without capacity addition.
The Tandem Cold Mill #1 of Cold Rolling Mill receives the material from Hot strip Mill
after undergoing pickling operation to remove scales in Pickling Line-1.Thickness of
the strip is reduced in Tandem Mill#1. The Mill is 4 high 4 stand.(It has 4 stands and
each stand has 2 work rolls and 2 back up rolls). Force is applied from the top on the
rolls by setting the screw down mechanism. Inter stand tension is also provided.
With the help of load and strip tension thickness is reduced. Cooling is through
lubrication & emulsion system for the rolls emulsion (mixture of dispersible oil &
water) applied to the roll bite. Sheet is fed to the first stand by changing direction of
sheet through Deflector Roll- Apart from inter stand tension, back tension exist
between Uncoiler & stand # 1 and between stand # 4 & Coiler.
It is well known in the field of cold rolling of strips that deflector roll help to feed the
strip in the first stand in the same line. Skewing of the roll results in damage of one
side of the strip. It helps to open the strip from uncoiler and straighten it partially. It
is critical for Mill running and very important due to impact on shape and edge of the
strip.
There was frequent occurring problem of deflector Roll in guiding the sheet. The back
Tension of the Uncoiler is high. The back tension result in massive load on the
Deflector Roll. Wrap angle is also very high. The deflector Roll was bearing mounted.
The stand is cantilever and hence deflection of the stand on load becomes
substantial. Due to deflection of stands bearing alignment was a major problem. The
bearing housing was also damaged in due course of time due to several bearing
failures. Bearing failure (bearing no SKF 22235) rate was very high (as high as up to
eight to ten per month). Sometimes Roll neck also broke down. After every bearing
failure or roll damage, roll assembly needed to be changed which took about two
hours causing interruption of cold rolling operation.
Due to this failure consumption of bearing was very high (around 10 per month).
Production downtime of around 12-15 hours per month and bearing consumption of
around 10/month affected productivity and cost adversely/ apart from mental stress
of the personnel working there and poor reliability of the system. Neck failure was a
safety hazard for persons inspecting surrounding equipments. It also used to cause
damage to other hydraulic hoses and electrical cables in the vicinity. Due to hose
damage hydraulic fluid loss was a major environmental concern.
There has been therefore a need in the art to developing a deflector roll system for
cold rolling mill stand which would be capable to withstand higher rolling load free of
bearing failure and effectively guide the strip without causing damage of edge/shape
of sheet. The present invention attempts to solve the problems relating to
conventional bearing mounted deflector roll in cold rolling mill stand to ensure
enhanced product quality, enhanced mill availability and productivity in a cost
effective manner.
OBJECTS OF THE INVENTION
The basic object of the present invention is directed to providing a modified and
improved shaft mounted Defector roll in tandem cold rolling mill for effective feeding
of strip in first roll free of bearing damage due to excess load avoiding deflection and
misalignment of stand in tandem mill of the cold rolling mill in a reliable and cost
effective manner.
A further object of the present invention is directed to shaft mounted deflector roll
for cold rolling mill stand which would ensure improved product quality by
maintaining desired shape/edge of finished rolled sheet.
A still further object of the present invention is directed to shaft mounted deflector
roll for cold rolling mill stand wherein the bearing is mounted inside the roll barrel,
thus reducing the rate of failure of bearing.
A still further object of the present invention is directed to shaft mounted deflector
roll for tandem cold rolling mill stand wherein the bearing is mounted inside the roll
barrel, to favour reducing bearing housing damage or roll neck damage due to
factors like deflection, misalignment, impact or high wrap angle.
A still further object of the present invention is directed to shaft mounted deflector
roll with bearing mounted inside the roll barrel for cold rolling mill stand wherein
modification of the deflector roll would increase the load bearing capacity of the
bearing.
A still further object of the present invention is directed to shaft mounted deflector
roll system with bearing mounted inside the roll barrel for cold rolling mill stand
wherein the impact load which the shaft can bear would be increased by increasing
the cross section.
A still further object of the present invention is directed to shaft mounted deflector
roll for cold rolling mill stand wherein the bearing is mounted inside the roll barrel
and thus by putting the bearing inside the barrel, the chances of contaminant
entering into the bearing is minimized.
A still further object of the present invention is directed to shaft mounted deflector
roll with bearing mounted inside the roll barrel for cold rolling mill stand wherein
safety hazard for persons inspecting surrounding equipments and resultant damage
to other hydraulic hoses and electrical cables or hydraulic fluid loss is avoided by
eliminating neck failure, ensuring safe and environment friendly operation.
SUMMARY OF THE INVENTION
The basic aspect of the present invention is thus directed to a deflector roll for
tandem cold rolling mill adapted to withstand increased load and impact comprising:
shaft mounted defector roll with bearings mounted inside deflector roll barrel
for contaminant free bearing housing.
A further aspect of the present invention is directed to a deflector roll for tandem
cold rolling mill comprising:
said shaft comprising of a stepped shaft ;
said roll barrel comprising of a hollow roll barrel;
said shaft housed co-axially inside said roll barrel with end of shaft extending
outward equally at two ends of the roll barrel for mounting on stand;
bearings mounted on shaft inside the roll barrel at each end to support the
barrel rotatably on said shaft and retained in position by means of end cover
plates detachably fixed at the ends of said barrel.
A still further aspect of the present invention is directed to a deflector roll for tandem
cold rolling mill wherein Shaft diameter is increased to 130mm against trunion
diameter 120mm to minimize the effect of misalignment on the bearing.
A still further aspect of the present invention is directed to said deflector roll for
tandem cold rolling mill wherein said bearing having size 130 mm inner dia and
280mm outer dia having load capacity of 1270KN(static) to be accommodated inside
the roll barrel.
Yet another aspect of the present invention is directed to said deflector roll for
tandem cold rolling mill which is adapted for mounting free of any welding.
The objects and advantages of the present invention are described in greater details
with reference to the following accompanying non limiting drawings.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1: is the schematic view of the conventional deflector roll in cold rolling mill
with bearing mounting at ends.
Figure 2: is the schematic view of the modified deflector roll which is shaft mounted
having bearing installed inside the roll barrel according to the present invention
adapted to with stand higher impact load without bearing failure.
DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE
ACCOMPANYING DRAWINGS
The present invention relates to providing a deflector roll system for cold rolling mill
stand which would be capable to withstand higher impact load free of bearing failure
or roller neck failure and effectively guide the strip without causing damage of
edge/shape of sheet.
Accompanying Figure 1 shows the schematic view of the conventional Deflector Roll
which was bearing mounted. The head end of the coil is fed to the stand #1 of the
Tandem Mill#l holding the coil in Uncoiler. The sheet is guided through Deflector
Roll. The back Tension of the Uncoiler is high. The back tension result in massive
load on the Deflector Roll. Wrap angle is also very high. The stand is cantilever and
hence deflection of the stand on load becomes substantial. Due to deflection of
stands bearing alignment was a major problem. The bearing housing was also
damaged in due course of time due to several bearing failures. Bearing failure
(bearing no SKF 22224) rate was very high (as high as up to eight per month).
Sometimes Roll neck also broke down. After every bearing failure or roll damage roll
assembly needed to be changed. It used to take two hours. Due to space constrain
larger bearing could not be provided in the existing design. Due to cantilever support
and impact, chances of misalignment could not be ruled out.
To overcome the problems of the existing deflector roll, a modification in design of
deflector roll assembly has been proposed by way of the present invention and
successfully implemented resulting in elimination of bearing failure or rolls neck
damage and associated problems with production interruption.
Accompanying Figure 2 shows the schematic view of the modified deflector roll
which is shaft mounted having bearing installed inside the roll barrel according to the
present invention adapted to with stand higher impact load without bearing failure.
The present design attempts to resolve misalignment caused due to stand and
housing. The possibility of increasing the neck diameter has been adopted. The
bearing size is increased.
In this design three things improved. Larger bearing no SKF 22236 could be installed
which has more load bearing capacity. Shaft dia was increased to dia 130 mm
against trunion dia of 120 mm. Effect of misalignment could be minimized on the
bearing. As already described that bearing failure was the result of many adverse
conditions.The impact is unavoidable. The wrap angle could also not be changed
because that would require major design change of the feeding system itself and
heavy investment.
To overcome all the above problems design of the Roll has been changed from
bearing mounted to shaft mounted. Bearing is now mounted inside the Roll barrel.
This option is implemented for the first time in deflector roll design to overcome
impact and misalignment. The shaft is placed coaxially inside the roll barrel with
bearing installed inside the barrel as illustrated in the accompanying Figure 2. In
earlier design trunion needed welding. In this design no welding is needed to
assemble the Roll. To retain the relative position of the shaft and bearings in relation
to roll barrel, end covers are fixed detachably at both ends of the roll barrel. By
putting the bearing inside the barrel we also minimized the scope of contaminant
entering into the bearing. The modification is also applicable to the areas where wrap
angle is high, chances of impact load and misalignment is there. It can also take care
of the space constrains.
It is thus possible by way of the present invention to providing a modified deflector
roil assembly adapted to increased load bearing capacity of the bearing. The impact
load which the shaft can bear also increased due to increase of the cross section to
1.2 times. These resulted in Zero failure in tandem cold rolling mill. The same roll
onfiguration can be applied to other areas where impact load is high , wrap angle is
high and chances of misalignment is there.
We Claim:
1. A deflector roll for tandem cold rolling mill adapted to withstand increased load
and impact comprising:
shaft mounted defector roll with bearings mounted inside deflector roll barrel
for contaminant free bearing housing.
2. A deflector roll for tandem cold rolling mill as claimed in claim lcomprising:
said shaft comprising of a stepped shaft ;
said roll barrel comprising of a hollow roll barrel;
said shaft housed co-axially inside said roll barrel with end of shaft extending
outward equally at two ends of the roll barrel for mounting on stand;
bearings mounted on shaft inside the roll barrel at each end to support the
barrel rotatably on said shaft and retained in position by means of end cover
plates detachably fixed at the ends of said barrel.
3. A deflector roll for tandem cold rolling mill as claimed in anyone of claims 1 or 2
wherein Shaft diameter is increased to 130 mm against trunion diameter of 120
mm to minimize the effect of misalignment on the bearing.
4. A deflector roll for tandem cold rolling mill as claimed in anyone of claims 1 to 3
wherein said bearing having size 130 mm inner dia and 280mm outer dia having
load capacity of 1270KN is adapted to be accommodated inside the roll barrel.
5. A deflector roll for tandem cold rolling mill as claimed in anyone of claims 1 to 4
which is adapted for mounting free of any welding.

ABSTRACT

The present invention relates to a shaft mounted deflector roll for tandem cold rolling
mill for feeding sheet to the first stand wherein a stepped shaft is placed coaxially
inside a hollow roll barrel and bearings are mounted inside said roll barrel at two
ends between shaft and barrel, favouring increased load bearing capacity and
reduced damage due to misalignment and deflection of stand and consequent
bearing failure or damage of the bearing housing or roll neck, reducing downtime
and improving productivity in cold rolling mill ensuring desired shape/edge of rolled
sheet product.