U.S. patent number 3,769,826 [Application Number 05/250,343] was granted by the patent office on 1973-11-06 for apparatus for rolling metal strip.
This patent grant is currently assigned to W. F. Lauener AG. Invention is credited to Wilhelm Friedrich Lauener.
United States Patent |
3,769,826 |
Lauener |
November 6, 1973 |
APPARATUS FOR ROLLING METAL STRIP
Abstract
The disclosed apparatus for rolling metal strip comprises a
driven rotary roller system on both sides of the strip to be
worked. Each roller system comprises a mainshaft and at least two
rollers rotatably mounted on this mainshaft parallel to the latter
and rotatable from a special drive through the agency of friction
clutches. The rollers in each system are uniformly distributed
around the respective mainshaft and at the same radial distance
from the latter. The mainshafts and roller systems are
synchronously driven in relatively opposite directions, and the
rollers in the two systems are so arranged that they meet the strip
in pairs, one from each system, on the two sides of the strip. The
strip is fed between the two roller systems by two driven feed
rollers having a weight sufficient to absorb vibrations which are
set up in the metal strip by the action of the roller systems.
Inventors: |
Lauener; Wilhelm Friedrich
(Rikon, CH) |
Assignee: |
W. F. Lauener AG (Rikon,
CH)
|
Family
ID: |
4313556 |
Appl.
No.: |
05/250,343 |
Filed: |
May 4, 1972 |
Foreign Application Priority Data
Current U.S.
Class: |
72/191;
72/249 |
Current CPC
Class: |
B21B
35/00 (20130101); B21B 13/20 (20130101); B21B
1/463 (20130101); B21B 31/076 (20130101); B21B
2035/005 (20130101); B21B 2003/001 (20130101) |
Current International
Class: |
B21B
35/00 (20060101); B21B 13/20 (20060101); B21B
13/00 (20060101); B21B 3/00 (20060101); B21B
45/02 (20060101); B21B 1/46 (20060101); B21b
021/00 (); B21b 035/00 () |
Field of
Search: |
;72/191,194,249,190,199,189 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Mehr; Milton S.
Claims
What I claim is:
1. An apparatus for rolling metal strip, having two driven feed
rollers, the weight of which is about 80 to 120 kp per centimetre
strip width, and a rolling assembly, said rolling assembly
comprising a driven rotary roller system on both sides of the strip
to be worked, each such system comprising a mainshaft, bearing
blocks at the two ends of said mainshaft which bearing blocks are
adjustable relatively to one another and in which said mainshaft is
rotatably supported, at least two rollers rotatably mounted on said
mainshaft parallel to the latter and a special drive for rotating
these rollers through the agency of friction clutches, the width of
these rollers being greater than that of the strip which is to be
worked, the rollers being all uniformly distributed around the
mainshaft and at the same radial distance from the latter, and the
mass of the rollers being selected so that the centrifugal force
produced by the rotation thereof around the main axis of the roller
system concerned is approximately equal to one half the maximum
rolling force which is produced; and means being provided for
synchronously driving said mainshafts and roller systems in
relatively opposite directions, said mainshafts and roller systems
being so coupled together that, by virtue of the rotary motion of
the two systems, rollers of these systems meet the strip in pairs,
one from each system, simultaneously at the same angle and from the
two sides of the strip, as the latter is being moved by said feed
rollers between the two systems, the cooperating rollers then
engaging the strip between them and forming it under an appropriate
pressure until the minimum distance between the rollers is
achieved, and all these pairs of rollers making such rolling
engagement at each rotation of the roller systems and forming the
forwardly moving strip successively to the required thickness.
Description
The invention relates to apparatus for rolling metal strips.
There exists a requirement for forming cast blocks or metal strips
in maximum feasible reduction stages into such a thickness,
generally 6 to 8 mm, as to make them suitable for being coiled. In
particular this applies in association with continuously operating
strip casting plants which produce cast strip of more than 12 mm
thickness.
It is common to arrange powerful two- or four-high rolling mills
following strip casting machines of this character to form the cast
strip down to the thickness which is required as a preliminary.
Whereas in the case of relatively narrow strips or soft materials,
such as high grade aluminum, this requirement can be met with one
single roll stand (Schweizer Aluminium Rundschau No. 3/1964), in
the case of strips with a width which may for example exceed 500
mm, and in cases where harder materials or strips have to be dealt
with and which have to be cast in relatively thick gauge for
technical reasons, a plurality of successive roll stands is
necessary (The Engineer, Dec. 25, 1964, Page 1,065). Plants of this
nature are extremely expensive to install and also to maintain.
Moreover their erection demands a large floor-space and expensive
foundations. The economy of these installations for the purpose
stated is greatly impaired by the fact that only a small portion of
the actual operating capacity of these roll stands can be utilised
because of the very small strip speed imposed by the casting
machines.
In order to avoid these defects, it has been proposed to use
so-called planetary rolling mills (Light Metals and Industry,
January 1965, Page 60) or swing roll stands (The Engineer, Nov. 22,
1963, Page 842). These arrangements have the advantages over the
method indicated above of achieving a very high reduction ratio in
one pass, wherefore the entire deformation required can be
performed in one single machine even with harder materials. It has
been found in practice, however, that these apparatus are only
suitable for comparatively small widths of strip because of the
deflection of the operating rollers on account of their relatively
small diameter. Further arrangements for the working of strips and
bars even with utilisation of the heat available from the casting
operation are described in the "Handbuch des Stranggiessens" by Dr.
Hermann on pages 446 to 453.
It is an object of the present invention to devise an apparatus
which is able to cope in the single stage with thickness reductions
hitherto only possible with devices as mentioned above. The
apparatus here proposed for this purpose is however much simpler as
a result of which its installation and operating costs are
considerably smaller, and it also has substantially more favourable
economical features in relation to known plants of this character.
Moreover, strips of any width can be handled, so that the range of
utilisation of the apparatus is correspondingly greater.
The apparatus according to the invention comprises two driven feed
rollers, the weight of which is about 80 to 120 kp per centimetre
strip width, and a rolling assembly, and it is characterised by the
fact that this assembly comprises a driven rotary roller system on
both sides of the strip to be worked, each such system comprising a
mainshaft rotatable in bearing blocks at the two ends which are
adjustable relatively to one another, and at least two rollers
rotatably mounted on this mainshaft parallel to the latter and
rotatable from a special drive through the agency of friction
clutches, the width of these rollers being greater than that of the
strip which is to be worked, the rollers being all uniformly
distributed around the mainshaft and at the same radial distance
from the latter, and the mass of the rollers being selected so that
the centrifugal force produced by the rotation thereof around the
main axis of the roller system concerned is approximately equal to
one half the maximum rolling force which is produced, the
mainshafts and roller systems being synchronously driven in
relatively opposite directions and so coupled together that, by
virtue of the rotary motion of the two systems, rollers of these
systems meet the strip in pairs, one from each system,
simultaneously at the same angle and from the two sides of the
strip, as the latter is being moved by the feed rollers between the
two systems, the cooperating rollers then engage the strip between
them and form it under an appropriate pressure until the minimum
distance between the rollers is achieved, and all these pairs of
rollers making such rolling engagement at each rotation of the
roller systems and forming the forwardly moving strip successively
to the required thickness.
A preferred embodiment of the apparatus according to the invention
is illustrated in the drawing, in which:
FIG. 1 is a side view of the actual rolling assembly of the
apparatus,
FIG. 2 is an end view, partly in section of the rolling assembly of
FIG. 1, and
FIG. 3 illustrates the drive means for the rolling assembly.
Two feed rollers 1 and 2, driven at uniform speed, are provided in
the illustrated apparatus for advancing the strip B which is to be
worked, and which for example arrives from a continuously operating
casting machine. Gripper rollers 1 and 2 advance the strip in the
direction of arrow P.sub.1 towards the rolling mill (FIGS. 1 and 2)
adjoining a casting machine. As is well known in the art,
vibrations set up during the rolling procedure are desirably not
transmitted back into the casting machine. For this reason it is
necessary for the feed rollers 1 and 2 to be dimensioned so that
they are of a sufficient mass for the incident vibrations to be
practically completely absorbed. The feed rollers must therefore
have a mass of approximately 80 to 120 kg per centimetre strip
width depending on the resistance to deformation prevailing in the
area of the strip which is to be deformed and on the reduction
ratio. The roller driving gear is infinitely adjustable to enable
the speed of the strip to be accurately set to the prevailing
conditions.
The strip is deformed between two rotating roller systems of the
rolling assembly which are synchronously driven in opposite
directions and are disposed symmetrically in relation to the strip
to be worked (FIGS. 1 and 2). In principle these systems are
constituted as follows:
The actual working rollers 5, 6, which are somewhat wider than the
strip of maximum width to be worked, are arranged on main shafts 3,
4 so as to be disposed parallel to these latter. The rollers 5, 6
are of like form and are distributed uniformly around the main
shafts with their centres at a distance R from the axes of the
latter, being rotatable in special bearings 42 mounted on these
mainshafts. Aside from these bearings there is no contact between
the rolls and the mainshafts.
FIG. 1 shows that the two roller systems each comprise four rollers
5 and 6 respectively. It will be understood that in principle there
may be two or three rollers only in each system, or more than four
rollers.
The distance D separating the axes of the two main shafts 3 and 4
from one another is so chosen that during the rotation of the two
systems the rollers 5 and 6 approach to within a distance a between
one another corresponding to the required thickness of the reduced
strip. The driving means for the two rolling systems can be coupled
in such a way as to meet the requirements that a pair of rollers,
one from each of the two systems, meet the strip simultaneously and
at the same angles and thence roll the strip down between them and
deform it at an appropriate pressure until the minimum distance
between the rollers is reached. As the systems turn the rollers
subsequently part and meet together again against the strip after
one rotation of the systems.
During the travel of the strip from left to right each roller pair
of the roller systems comes into rolling engagement, whereby
successive elements in the body of the strip are reduced to the
required thickness.
The main shafts 3 and 4 are mounted in bearing blocks 17, 18 which
are adjustable relatively to one another to enable the thickness of
the deformed strip to be set to the required amount a.
The roller systems are rotated by their drive means in the
direction of arrow P.sub.2 before the strip to be worked is
introduced into the rolling mill at the start of the operation. At
the same time the rollers 5 and 6 are set into rotation in the
direction of arrow P.sub.3 by a special driving means to avoid
undesirable stresses arising from an excessive angular acceleration
at the commencement of a rolling operation.
The rate of rotation of the rollers is infinitely variable and is
adjusted so that the component of the velocity on the surface of
the rollers in the direction of the strip, resulting from the
rotation of the individual rollers and the whole roller system,
corresponds to the speed of advance of the strip B.
Since during their rolling on the strip, the rolls undergo a
variation in angular speed, due to the stretching of the strip by
its deformation, it is necessary to incorporate in the drive of
each individual roller a yielding element in the form of a
resilient or slipping clutch to cater for the slight variation of
the angular speed of the roller pair concerned during the
engagement of the rollers, independently of the speed of the
remaining rollers of the set.
As a consequence of the rotation of the roller systems about the
axes of the mainshafts 3 and 4 there is a substantial centrifugal
force acting on rollers 5 and 6 which are arranged eccentrically at
a spacing R from the axes of the mainshafts. This centrifugal force
acts against the rolling pressure during the rolling and this is an
advantage which is here exploited. It caters for a very notable
reduction in the strain on the bearings of the roller spindles and
in the rollers themselves and thereby reduces the deflection
thereof during the actual rolling engagement. The choice of speed
of rotation of the roller systems and the eccentricity R of the
rollers and ultimately the masses thereof, are adapted to the
prevailing conditions.
This situation is of particular attribute to machines for the
treatment of wide strips. The most favourable force conditions
arise when the centrifugal force is about one half the maximum
anticipated rolling pressure. The following data is given to
exemplify the order of dimensions which meet these optimum
conditions of force relationships of the rollers in practical
instances:
Rate of rotation of the roller system n = 200 to 800 per
minute.
Number of rollers per roller system Z = 2 to 8
Eccentricity of the rollers R = 200 to 600 mm
Diameter of the rollers d = 200 to 800 mm
A further advantage of the apparatus here proposed, in relation to
planetary rolling mills, lies in the fact that the flywheel effect
of the individual roller systems is very high because they
represent large rotating masses, so that a uniform and smooth
running of the machine is ensured despite the intermittent
action.
The rate of travel of the strip determines the required number of
rolling engagements per unit time, and this is represented by the
product of the rate of rotation and the number of rollers per
roller system. Optimum deformation conditions are fulfilled when
the mean advance of the deformed strip per roller engagement is
about 0.5 to two times the thickness thereof.
With a rate of rotation of the roller systems of about 500
rotations per minute and with a four roller arrangement, a mean
strip speed of 8 to 32 metres per minute, which corresponds to the
output of a continuously operating strip casting machine, is given
for a final strip thickness of 7 mm.
Since the rolling process takes place intermittently a longitudinal
oscillation, superimposed on the mean speed, is applied to the
worked strip by the roller engagement. This oscillation can be
completely compensated and the uniform speed of travel of the strip
restored by the use of a socalled strip loop.
To facilitate reading of the drawing, the feet of the machine,
except for those at the two sides, are not illustrated in FIG. 2.
As can be seen from FIG. 1 the feed rollers 1 and 2 are driven by
way of intermediate shafts 7 and 8 which have keyed thereon pinions
9 and 10 which engage with toothed rings 11 and 12 screwed to
rollers 1 and 2.
Rollers 1 and 2 are rotatably mounted on fixed shafts 1a and 2a
which are mounted in robust plummer blocks 14 and 15 which are
displaceable on the machine frame 13.
Two double acting hydraulic cylinders 16 are provided at the two
ends of the rollers to produce the gripping force thereof and these
are so dimensioned as to be capable of clamping the strip
sufficiently powerfully to avoid any slip during the rolling in the
ensuing working process. The forces required for this purpose can
actually slightly reduce the strip thickness between the rollers
under certain conditions. The cylinders are also used to vary the
distance between the rollers for the introduction or removal of the
strip.
The two roller systems which actually perform the reduction or
deforming of the strip each comprise, as is apparent from FIGS. 1
and 2, a mainshaft 3 or 4, respectively, the bearing bodies 42
which are rigidly connected thereto, the rollers 5 or 6
respectively which are eccentrically mounted at a distance R from
the axis of the mainshaft concerned, and the driving means
described below. The mainshafts 3 and 4 are rotatably mounted at
the two sides of the machine frame 13 in bearing blocks 17 and 18
which are displaceable in slideways.
The two roller systems are rotated by a main motor 19 through a
reduction gear and pinion stand 20 and cardan shafts 21 and 22.
Rollers 5 and 6 are rotated by separate drive means, these merely
serving to accelerate the rollers while the machine is being
started to compensate for frictional forces in the bearings. The
rollers can be driven from one end or, as shown by FIG. 2, for
symmetrical reasons from both ends. In the present instance use is
made of an oil hydraulic system and it will be observed that there
is a hydraulic pump 23 driven by the main motor and given an
infinitely variable rate of feed and two hydraulic motors 24 and
25, connected in parallel, fed from pump 23. The roller drive means
are interconnected through two gearings 25 and 27 through a shaft
28, to ensure a uniform rate of rotation of the rollers of the two
roller systems even during idle running. The drive is imparted from
gearings 26 and 27 through cardan shafts 29 and 30 to intermediate
shafts 33 and 34 rotating in bearings 31 and 32, and thence through
toothed belts 35 and 36 to toothed collars 37 on mainshafts 3 and
4. Thence the drive is imparted to the toothed pinions 38 on the
roller spindles which engage the toothed collars 37.
Whilst in the embodiment illustrated in the drawings, the strip B
passes through the apparatus in the horizontal direction, it will
be appreciated that the apparatus can be devised for an inclined or
reversing direction of travel, and indeed any desired direction of
travel upwards or downwards can be catered for.
The method of driving the rollers illustrated and described merely
represents one of various possibilities. It is for example possible
to conduct this drive without the use of belts and using only
appropriate toothed gearing.
To allow for variation of the angular speed of individual rollers
which are in rolling engagement during performance of the machine,
and without straining the drive, friction clutches with an
appropriately selected torque (not shown for the sake of
simplicity) may be associated with the toothed pinions 38. The
thickness a of the rolled strip, given specific dimensions of the
roller systems, is determined by the axial spacing D of the
mainshafts.
The rate of deformation of the strip can be varied within desired
limits by adjustment of the length of the threaded spindles 40.
This enables a uniform thickness of strip to be achieved at both
sides of the latter.
The bearing blocks 17 and 18 are urged by hydraulic cylinders 39,
arranged at the two sides thereof and numbering four in all,
against the threaded spindles 40 which are arranged between the
bearing blocks and are of adjustable effective length. The closing
pressure exerted by the cylinders must be larger than the rolling
pressure exerted between the roller pair which are cooperating
during the rolling procedure. This closing pressure can be checked
by known limiting means to ensure against overstraining of the
rolling systems.
The adjustment of the bearing blocks, that is to say the regulation
of the distance between them, can be performed by other means such
as are used in the rolling mill art.
The main bearings 41 of the rolling systems and the roller bearings
42 can be lubricated by pressure oil through oil ducts 44 in the
main bearings. Thence the used oil passes through the run-out
connections 46 into an oil storage plant (not shown) comprising a
cooler filter and tank. The major part of the oil is introduced
into the bearings 42 by ducts present in the main shafts and
bearings. Used lubiricating oil emerging laterally from these is
collected in the shell 46 and thence passed in each case through a
connection 47 and conduits (not shown) likewise to the oil storage
plant. Lubrication of the toothed wheels of the roller driving
means and of bearings, for which purpose roller bearings are used,
is performed by the oil mist which prevails in the cavity
concerned.
Appropriate shaft seals and collars are used to prevent undesirable
escape of oil.
To prevent adhesion of the rolls to the strip B which is operated
on, a rolling oil-emulsion is continuously sprayed on to the
rolling surfaces through nozzles 49 at the two sides of the
strip.
The plant illustrated in FIGS. 1 and 2 is intended for the
treatment of continuously cast aluminium strips of about A = 60 mm
thickness to a = 7 mm at a strip speed of v.sub.o = 0.8 to 3.2
m/minute or v.sub.1 = ca. 7 to 28 m/minute. In order to maintain
the feed conditions set out above a rate of rotation of n = 500
/minutes is used and in each case four rolls per roller system.
This gives z = 4 times 500 = 2000 roller engagements per
minute.
The eccentricity of the rollers amounts to R = 300 mm and the
diameter of the same d = 310 mm.
The totalmass of a roller, including roller spindle, clutch and
driving pinions, amounts to M = 625 kg.
Under the conditions indicated and in the treatment of a strip of
an aluminium alloy with 1 % Mn and 1 % Mg, having a width of 750 mm
and at a temperature of 350.degree. to 400.degree. C, a rolling
force of about 100,000 kp is developed.
The centrifugal force K of a roller which develops during the
rotation of a roller system thus amounts to:
K= m .sup.. r .sup.. .omega..sup.2 = 625 .sup.. 0.3 .sup..
52.36.sup.2 = 51.404.sup.. 10.sup.4 n = 52,400 kp
If the rollers are not in engagement, the load on their bearings is
equal to the centrifugal force, and thus during engagement the load
amounts to:
K'= 100,000 - 52,400 = 47,600 kp or
K'/2 = 23,800 kp per bearing.
The reduction in load on the bearings which results from the
centrifugal force of the rollers also has the additional benefit of
less bending strain on the rollers.
* * * * *