Note: Descriptions are shown in the official language in which they were submitted.
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VARIABLE CROWN ROLL
sackground of the Invention:
The present invention relates to a variable crown roll
of such construction that the value of crowning of the roll
is controlled by adjusting the pressure of a medium.
The variable crown roll (hereinafter re~erred to merely
as a VC roll) generally comprises an arbor and a sleeve which
is shrinkage-fi ted onto the arbor and includes an annulax
cavity of a predetermined width and depth formed between the
arbor and the sleeve, into which a pressure transmitting
medium such as oil, water, grease or the like (hereinafter
referred to merely as a medium) is forced through a leading-in
passage so as to control the value of the crowning o~ the
roll by adjusting the pressure of the medium. The leading-in
passage comprises an axial passage extending axially from
an end to the other of the arbor and radial passages communi-
cating from the axial passage to opposite ends o the cavity.
Heretofore, the VC~roll was used for light rolling
load mills such as skinpass rolling mills for hot rolled
strip or sheets ~ut not for mills, in which extraordinary
load tends to occur, such as hot or cold tandem mills. If the
VC roll is used in such mills~ there~ is a possibility of
rolling troubles or cracking in the sleeve due to the extra-
ordinary load. ~In the conventional VC rolls, since the
initial depth of the cavity (the depth of the cavity a~ the
time of roll assembly) was relatively large, the inner surface
of the central portion of~the sleeve did not contact the
peripheral surface of the arbor;even when the sleeve was
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deflected radially inwardly by the extraordinary load occurred
during rolling at the normal value of crowning of the roll.
As a result, the stress occurring in the sleeve increased
substantially in proportion to the load applied to the sleeve,
leading eventually to cracking of the sleeve when exceeded the
yield strength of the sleeve material. Accordingly, the old
type VC roll could not be used in mills in which the extra-
ordinary load might occur.
In the old type VC rolls, the initial depth of the
cavity was formed relatively large as mentioned above for
the reasons that the application of the VC roll was limited
to small reduction rolling which eliminated the need for con-
sideration of the sleeve cracking caused by the extraordinary
load and that the forming of the cavity and the pouring of
the medium thereinto were made easy.
Further, there was a problem of evacuation of air from
the cavity of the VC roll when pouring the pressure transmitting
medium into the cavity. Heretofore,~when illiny the VC roll
cavity and passages with the medium, air was forced out of
the cavity of the roll through the steps of suspending the
VC roll by a crane vertically, opening the top end of the
axial passage communicating with the cavity, lntroducing the
medium into the axial passage through the lower end thereof
forcing the air therein out of it, and placing a plug at the
top end of the axial opening when the introduction of the
medium was finished.
ln the old type VC roll, in which the axial opening
extended along the overall length of the roll, sufficient
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evacuation of the air was impossible since the medium reached
the top end of the axial opening before the medium spread
sufficiently over the cavity. Presence of air in the roll
presented a few such problems as a slower response speed of
the medium pressure due to compression of the air by elevating
the pressure of the medium and a more intensive splashing of
the medium due to the increase of the stored ener~y of the
air when the cracking of the sleeve would have occurred.
Accordingly, an object of the present invention is to
provide a variable crown roll which can be used in mills in
which extraordinary loads tend to occur.
Another object of the present invention is to provide
a variable crown roli from which air can be easily evacuated
when the medium is poured thereinto.
Summary of the Invention:
A VC roll according to the present invention is of the
construction in which an annular cavity having a predetermined
depth is formed between an arbor and a sleeve, an end of the
cavity is communicated with a medium leading-in passage, and
the other end of the cavity is communicated with a medium
leadin~-out passage.
The cavity-is formed by caving either only one or both
of the interface of the arbor and the sIeeve. The depth of
the cavity is predetermined to a nalue smaller than the
value of maximum~deflection of the sleeve due to an extra-
ordinary load occurring during rolling with a normal value of
roll crowning. Because of the construction described above,
when the extraordinary load occurs, the inner surface of the
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sleeve defining the radially outer wall of the cavity is
brought in contact ln a portion thereof with the peripheral
surface of the arbor defining the radially inner wall of the
cavity, whereby the extraordinary load is supported by the
sleeve and the arbor, and consequently the stress arising in
the sleeve is considerably suppressed.
For pouring the pressure transmitting medium (for example,
oil, water or grease) into the VC roll according to the present
invention, the roll is placed aslant or upright with the
medium leading-in passage held downward and the medium leading-out
passage upward, the medium is poured into the roll through
the leading-in passage while evacuating air in the cavity
and the passages, and the outlet of the leading-out passage
is plugged after the completion of the pouring of the medium.
Brief Description of the Drawings:
The invention will be better understood from the follow-
ing description taken in connection with the accompanying
drawings, in which:
Fig. 1 is a longitudinal sectional view of a VC roll
showing an em~odiment of the present invention;
Fig. 2 is a longitudinal sectional view of a VC roll
showing another embodiment of the present invention;
Fig. 3 is a partial cross-sectional view taken along
the line III - III of Flg. 2;
Fig. 4 is a longitudinal sectional yiew of a VC roll
showing another emboidment of the present invention;
Fig. 5 is a partial cross-sectional view taken along
the line V - V of Fig. 4;
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Fig. 6 is a longltudinal sectional view of a VC roll
showing a still further embodiment of the present invention;
Fig. 7 is a partial cross-sectional vie~ taken along
the line VII - VII of Fig. 6;
Figs. 8 and 9 are partial longitudinal secti~nal views
of a VC roll showing different stages of the sleeve deforma-
tion;
Fig. 10 is a diagram showing the relationship between
the rolling load and the increase in stress in the sleeve at
the different stages of the sleeve deformation; and
Fig. 11 is a diagram similar to Fig. 10, showing an
embodiment of the present invention.
Description of the Preferred Embodiments:
With reference to the drawings and more particularly
to Pig. 1 thereof, there is illustrated an embodiment of the
VC roll according to the present invention, comprising an
arbor 1 and a sleeve 2 shrinkage-fitted to the arbor 1 with
an annular cavity 3 having a predetermlned depth defined
therebetween. An end of the cavity 3 is communicated with
an axial medium leading-in passage 5 at an end of the arbor 1
through a radial passage 4 in the arbor 1, while the other
end of the cavity 3 is communicated~with a medium leading-out
passage 7 provided axially at the other~end of the arbor 1
through a radial passage 6 in the arbor 1.
A conventional rotary joint 52 is attached at an inlet
51 of the medium leading-Ln passage S. The pressure trans-
mitting medium such as water, oil or grease is forced~through
the rotary joint 52 into the medium leading-in passage 5,
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radial passage 4, cav~ty 3, radial passage 6, and an axial
medium leading-out passage 7. While the medium is forced
into the VC roll, air in the passages and in the cavity is
evacuated through an outlet 71. When the medium has reached
s the outlet 71, the outlet 71 is tightly closed with a conven-
tional plug 72.
Another embodiment of the VC roll according to the
present invention is shown in Figs. 2 and 3, in which a
medium leading-out passage 7a is provided in the sleeve 2
and is communicated directly with an end of the cavity 3 with-
out any radial passage.
A further embodiment of the VC roll according to the
present invention is shown in Figs. ~ and S, in which a
medium leading-out passage 7b is provided in the arbor 1 in
the vicinity of its periphery and is communicated directly
with an end of the cavity 3 without any radial passage.
A still further embodiment of the VC roll according to
the present invention is shown in Figs. 6 and 7, in which a
portion of the medium leading-out passage 7a is provided in
the sleeve 2 while the other portlon of the medium leading-
out passage 7b is provided in the arbor 1 in the vicinity of
its periphery, and the two passages are communicated with
each other and an end of the passage 7b is communicated with
an end of the cavity 3.
In the VC roll according to the present invention
having the construction ln which, as described above, the
axial opening is eliminated and the passages are so formed
that the medium passes from one end of the axbor to the
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opposite end of the sleeve through the cavity, it is madepossible to reduce the quantity of the medium heretofore
existed in the arbor and to evacuate the air easily and surely,
to thereby increase the response speed and to decrease the
stored energy.
Determination of initial depth _ of the ca~ity 3 will
now bè described with reference to Figs. 8 to 11. Generally,
in the VC roll assembled, the opposite surfaces in the cavity
3 are parallel to each other as shown in Fig. 8. In a
modified form, however, the sleeve 2 has the V-shaped inner
surface inclined toward the middle of the sleeve so that the
depth d of the cavity gradually increases or decreases.
Accordingly, the depth d will be considered herein on the
basis of the depth at the middle of the sleeve.
In Fig. 8, solid lines A show the sleeve 2 under the
condition of the medium pressure PM = 0 kg/cm2 (gauge pressure)
and rolling load P = 0 kg. Broken lines B show the sleeve 2
under the condition in which the medium pressure PM is a certain
pressure (0 - 500 kg/cm2) for providing a normal value of
crowning and the rolling pressure P is a certain load PB for
performing normal rolling. Two~dot lines C show the sleeve
2 at the moment when an extraordinary load P~ suddenly occurs
whereby a portion of the inner surface of the sleeve 2 contacts
a portion of the periphery of the arbor 1 in the cavity 3. t
Then, in Fig. 9, solid lines D show the sleeve 2
under the condition in which~the extraordinary load Pc has
increased to PD. In the condition shown by the solid lines
D, the most part 7f the inner surface of the sleeve 2 contacts
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the peripheral surface of the arbor 1 in the cavity 3.
In Fig. 9, two-dot lines D' show the sleeve 2 under
the condition in which the initial depth d of the cavity 3
is so sufficiently large that the sleeve 2 freely deflects,
whereby the inner surface of the sleeve 2 is kept seperate
from the peripheral surface of the arbor 1 in the cavity 3.
In this state, the value of the maximum deflection of the
sleeve 2 (from the initial state A) is denoted by ~.
In the present invention, the initial depth d of the
cavity 3 is determined smaller than the value of the maximum
deflection ~. In practicaI application, the initial depth _
is determined preferably to 0 - 2.0 mm in consideration to
the response property of the medium.
Fig. 10 shows graphically the relationship between the
rolling load and the stress induced thereby at the conditions
of the sleeve 2 mentioned above regarding Figs. 8 and 9. In
the diagram of Fig. 10, the horizontal axis denotes the rolling
load P(kg) and the vertical axis denotes an increase in stress
~(kg/cm2) in the sleeve 2 from the initial state A of the
sleeve,
As shown in Fig. 10, in the condition represented by
a line segment AB, the sleeve 2 is in the normal rolllng range
and deflects within the limits of the expansion. In the
condition represented by a line segment BC, the sleeve 2
defIects freely within the range of the initial depth d of
the cavity 3. Further, in the condition represented by the
line segment CD, the sleeve 2 contacts the arbor 1 and the
deflection of the sleeve is limited thereby. At the condition
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represented by the point D, the maxi~lum increase in stress
~ of the sleeve 2 decreases considerably from D' in the old
type VC roll to D.
Accordingly, in the VC roll according to the present
invention, when extraordinary load, for instance causea by
drawing out, occurs during rolling operation, the stress arising
in the sleeve can be considerably reduced by letting the sleeve
to be supported by the arbor which contacts the sleeve within
the cavity. Accordingly, the VC roll according to the present
invention can be used even in mills in which extraordinary
load tends to occur.
It is difficult to determine~ the value of deflection
~ of the sleeve accurately. However, the value ~ can be
estimated theoretically on the basis of the following conception,
the value of maximum deflection ~ may be a sum of bending
deflection ~YB) due to a rolling load, shearing deflection (Ys)~
and flattening (~X) of the roll sleeve ~ ~ = YB + YS + ~X)
Each term is calculated as follows.
i. Bending deflection ~YB) and shearing deflection (~S)
These two terms are determined by solving an equation
of strength of materials assuming that a typical roll model
is uniformly loaded.
ii. Flattening (~X) of roll sleeve
Assuming that a concentrated load F is applied to the
middle portion of the peripheral surface of a sleeve having
mean radius R, thickness t,~and length L, the flattening ~(X)
is expressed by the following formula:
O. 135FR2
~(X) = 3 e ~X (cos~x + sin~X) ...`11)
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where, E : Young's modulus
~ = 0.3125/R
assuming that a load q per unit length of the sleeve is uniform
over a very small length ~X When the load is not concentrated,
F is replaced by q- ~X in the formula (1). Assuming that a
force q' acts against a depression by the load q from the inside
in the shrinkage-fitted portion of the sleeve, the value ~(X)
is obtained determining the value of q! in such a manner that
each of the integrated values of the formula (1) by q ~X and
q' ~X is zero at the shrinkage-fitted end, C and C'.
Fig. 11 shows graphically an example of the relationship
between the rolling load ~ton) and the increase in the stress
~a (kg/mm ) of the inner surface of the sleeve o the VC roll
which is used as a back up roll in a 4 high mill. Dimension
of the rolls used was as follows:
Work Roll
Diameter 700 mm x Drum length 2032 mm x Average
bearing distance 3124 mm x Overall length 5435
Back Up Roll
Diameter 1382 mm x Drum length 2032 mm x Average
~ bearing distance 3124 mm x Overall length 5435
Width of the rolled material was 1000 mm.
While we have shown and described specific embo~iments
of our invention, it will be understood that these embodiments
are merely for the purpose of 1llustration and explanation
and that various other forms may be devised within the scope
of our invention, as defined in the claims.
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