Continuous casting plant roller stand

A roller stand to be used in continuous casting plants comprises two strand guide parts arranged opposite each other so as to guide the strand between them, which strand guide parts are held together by drawing anchors. The roller carrying means of one of the strand guide parts are movable relative to the strand by piston driving means. Overload protection means are provided within the area of the piston driving means and spacers maintain the distance between the opposing rollers.

BACKGROUND OF THE INVENTION 
The invention relates to a roller stand for continuous casting plants 
having an inner and outer or upper and lower strand guide part, 
respectively, held together at the corners by drawing anchors. With these 
strands guide parts the rollers are arranged opposite each other on roller 
carriers. A roller carrier on one side of the strand surface is movable 
relative to the strand surface by piston driving means is guided in the 
stand by guiding faces. An overload protection comprised of a laminated 
spring or the like is being provided to guard against an excessive load on 
the rollers, and the distance between opposite rollers is fixable by means 
of spacers. 
In modern continuous casting plants the strand is guided between two roller 
paths consisting of a plurality of rollers arranged closely adjacent one 
another. These rollers which guide and support the strand are arranged in 
roller stands, which have to meet numerous demands. The most important of 
these demands are: 
EASY ADJUSTABILITY OF THE ROLLER DISTANCE, I.E. THE DISTANCE BETWEEN 
OPOSITE ROLLER PATHS; 
RELIABLE MAINTENANCE OF THE ADJUSTED ROLLER DISTANCE; 
PROTECTION OF THE ROLLERS AGAINST DAMAGE BY THE STRAND, E.G. BY AN END OF 
THE STRAND THAT HAS COOLED TOO MUCH; 
AJUSTABILITY OF THE ROLLERS TO THE STARTER BAR AND TO A STRAND OF SHRUNKEN 
THICKNESS; 
EASY AND QUICK INSTALLATION AND REMOVAL OF THE ROLLERS 
EXPOSURE OF THE STRAND TO ONLY THOSE FORCES WHICH ARE ABSOLUTELY NECESSARY, 
SUCH AS EXTRACTION, BENDING AND STRAIGHTENING FORCES; 
SECURING OF THE ROLLERS AGAINST DAMAGE BY A LONGITUDINALLY TWISTED STRAND 
I.E., THE ROLLERS ARE TO BE RESILIENTLY MOUNTED ON ONE SIDE AT ONE END 
ONLY; 
USE OF CONSTRUCTION ELEMENTS ABLE TO ENDURE THE ROUGH OPERATION OF A STEEL 
PLANT, WHICH ELEMENTS REMAIN OPERATIVE IN SPITE OF RUST AND SCALE 
DESPOSITS. 
For a large part of the above mentioned task the construction elements 
which have proved best in practice are known. Thus laminated springs are 
known as overload protection, hydraulic piston driving means are known for 
roller adjustment and spacers are known for fixing the roller at a new 
distance when the thickness of the strand is changed (see Austrian Pat. 
No. 276,656, German Auslegeschrift No. 1,965,115). With these construction 
elements rollers stands have been built which, depend on the demands 
considered to be most important, have met only some of the above listed 
demands, but do not satisfy other requirements. The interaction of the 
individual construction elements is essential and in turn is dependent on 
their special arrangement in the roller stand. 
SUMMARY OF THE INVENTION 
It is the object of the invention to create a roller stand of the 
above-defined kind which meets all the above-listed demands in a 
satisfying manner. In particular, the rollers are also to be adjustable to 
a strand of shrunken thickness under controllable pressure without 
necessitating manipulations at the roller stand so that, when driven 
rollers are used, the transmission of the extraction force in maintained 
automatically. Furthermore, the rollers are to be effectively protected 
against overload and also the excessive forces caused by a longitudinally 
twisted strand are to be effectively reduced. Finally, the rollers of the 
roller stand according to the invention are to be especially easy to 
remove and install, without necessitating a removal from the roller stand 
of the means acting for an adjustment of the rollers to the surface of the 
strand and for an adjustment of a particular roller distance. 
These objects of the invention are achieved in that two rollers are always 
arranged on a movable roller carrier, that the roller carriers are each 
actuated by two piston driving means, provided at their ends, the other 
ends of the piston driving means being secured to the stand at a distance 
exceeding the length of the movable roller carrier. The overload 
protection means are provided in the form of a laminated spring or the 
like within the piston driving means, i.e. between their articulation 
points on the roller carriers, on the one hand, and on the stand, on the 
other hand, and that the spacers are arranged on the drawing anchors 
connecting the inner and outer or upper and lower strand guide part, 
respectively. 
According to a preferred embodiment, the movable roller carriers have a 
bowed guiding shape for those end faces lying perpendicular to the roller 
axis so as to guide the carriers in an approximately vertical direction 
relative to the strand surface. This enables a pivoting of the roller 
carriers perpendicularly to the guiding direction of the strand without 
the danger of jamming; however, a lateral yielding of the roller carriers 
is prevented. 
Advantageously, the two rollers arranged on a movable roller carrier are 
arranged in adjacent pocket-like recesses of supporting brackets secured 
to the roller carrier.

DESCRIPTION OF AN EXEMPLARY EMBODIMENT 
The strand at its upper and lower sides, is supported, guided and 
straightened by the rollers 2 and 3. The rollers 2 allocated to the lower 
or outer side of the strand rest in supporting brackets 4 which are 
inserted in longitudinal carriers 5. Two transverse carriers 6 resting on 
the base 7 support the longitudinal carriers. The transverse carriers 6 
are welded together with carriers 8 to form a frame construction. Four 
drawings anchors 9 arranged parallel to one another are rigidly arrranged 
at the corners of the frame. Two of them, i.e. those arranged at one side 
of the strand, are always rigidly connected to one another by a box-like 
carrrier 10. A frame 11 movable above these rigid box-like carriers along 
the drawing anchors is articulated to the box-like carriers 10 by means of 
four hydraulic cylinders 12 arranged at its corners. As a result the frame 
11 can be lifted or lowered for adjusting a roller distance corresponding 
to the thickness of the strand by actuating the cylinders 12. For fixing 
the movable frame 11 at a certain height, spacers 14 are provided, which 
spacers are inserted, on the one hand, between wedges 13, arranged at the 
upper ends of the drawing anchors, and the movable frame 11, and, on the 
other hand, between consoles 15, welded onto the drawing anchors above the 
box- like carriers, and the frame 11. 
The rollers 3 are allocated to the strand upper or inner side, are always 
arranged in pairs on roller carriers 18 and 18' which extend in the 
longitudinal direction of the rollers. The rollers 3 are arranged in 
adjacent pocket- like recesses 17 of supporting brackets 16 which are 
secured to the roller carriers 18 and 18'. The roller carriers 18 and 
18'are movable relative to one another. Also, they are guided on rail 
guides 19 of the laterally arranged box-like carriers 10 and are thus 
secured against turning. For reasons of space, only the last one of the 
roller carriers arranged in the conveying direction on the roller stand is 
articulated by means of guide rods 23 to the roller carrier arranged in 
front of it. 
The two outermost roller carriers 18 arranged at the two ends of the roller 
stand are secured to the respective transversal bridges of the movable 
frame 11 with two intermediary pre-stressed laminated cup springs 20 each, 
which springs are articulated to the ends of the transversal bridges. 
Hydraulic cylinders 21 articulately engage the two ends of the remaining 
rollers carriers 18' to the movable frame 11 such that the two hydraulic 
cylinders 21 pertaining to one roller carrier 18' are secured on the frame 
11 at a distance that exceeds the length of the roller carriers 18'. 
Within the articulation points of each one of the hydraulic cylinders 21, 
i.e. between their articulation points on the roller carriers 18', on the 
one hand, and on the frame 11, on the other hand, overload protection 
means in the form of laminated cup springs 22 are provided. The springs of 
all the laminated springs 20 and 22 are under such a pre-stress that the 
rollers, when loaded by the ferrostatic pressure and the bending force 
only and at normal temperature, do not yield; yielding only occurs when 
the maximally allowable load acting on the rollers is exceeded. Thus the 
described casting thickness during the normal operation remains 
safeguarded. Only under an extreme load is the pre-stress overcome and the 
rollers 3 yield in the direction of the load. Advantageously, in the 
laminatad cup springs 20 and 22, spring excursion indicators are 
installed, which give an optic or acoustic signal when the laminated cup 
springs respond. 
There is the possibility of using the signals of the spring excursion 
indicators for turning off the continuous casting plant, e.g., when the 
rollers are subjected to an especially high overload and a number of 
spring excursion indicators respond simultaneously. Such an overload may 
occur, e.g., when the extraction of a cooled-off strand from the plant is 
attempted. 
By means of the hydraulic cylinders 21 the rollers, which may optionally be 
driven by a slip-on motor, can be adjusted to the starter bar or also to a 
hot strand that has shrunk in the direction of thickness. Thereby, a 
reliable transmission of the extraction force to the starter bar and to 
the hot strand can be achieved, if driven rollers are used. 
For transporting the starter bar, the rollers are adjusted with only so 
much pressure that the permissible Hertzian pressure between roller and 
starter bar is not exceeded. 
When the hot strand enters the straightening path, the pressure in the 
hydraulic cylinders 21 is reduced, so that the force acting on the strand 
is reliably less than the force caused by the ferrostatic pressure of the 
strand. Thus the rollers press the pistons of the hydraulic cylinders 21 
into the final position due to the ferrostatic pressure, i.e. the rollers 
are hampered in their movement away from the strand surface. Bending 
forces that occur increase this effect. When the slab shrinks, the rollers 
follow the surface of the slab maintain and the contact, thus the 
transmission of the extraction force remains assured. 
The roller carriers 18 and 18' are inserted with play between the box-like 
carriers 10 and have bowed frontal faces 24, whereby jamming on the 
box-like carriers 10 is prevented, when the roller carriers yield, and a 
one- sided yielding of the roller carrier is made possible. Thus it 
becomes possible to extract longitudinally twisted strands without 
damaging the rollers. 
The inclined arrangement of the hydraulic cylinders 21 according to the 
invention, which can be seen in FIG. 2, enables an especially easy removal 
and installation of the adjustable rollers. For roller removal, the 
hydraulic cylinders 21 are detached from the roller carrier 18' carrying 
the roller to be removed by removing the bolt connecting these parts. The 
cylinders are then outwardly pivoted about the opposite articulation point 
on the frame 11, whereby the space necessary for lifting out the roller 
carrier 18' together with the two rollers mounted thereon is created. This 
position is entered in FIG. 2 in dot-and-dash lines. The installation of 
the roller is effected by an opposite sequence. 
The roller stand according to the invention can also be constructed in such 
a manner that all the roller carriers, including the two outer ones, are 
adjustable by hydraulic cylinders. It is also possible to omit the 
articulation of the roller carrier 18 arranged on the roller stand to the 
roller carrier 18' arranged in front of it and also to guide this last 
roller carrier 18 with both of its ends in the box-like carriers 10.