The invention relates to an apparatus for starting the casting of a continuous casting system according to the preamble to claim 1.

It is known for starting the casting of a continuous casting system to tightly close off the lower mould opening before and during the casting start-up process with a dummy bar in order to prevent steel poured into the mould from flowing out. The dummy bar is introduced into the mould via the strand guide provided for the casting strand and which comprises the drive and guide rollers. The steel poured into the mould is partially solidified so that a strand with a solidified edge zone and a liquid core is produced. As soon as this edge zone is of a sufficient thickness, the dummy bar (and after the latter the hot strand, additional steel then being poured into the mould) is drawn out of the mould, once again by means of the strand guide.

The movement of the dummy bar is determined by the drive torque generated by the drive rollers and by the contact force and friction coefficients between the drive and guide rollers and the dummy bar. Interruptions, such as for example with a power failure, can lead to an uncontrollable movement of the dummy bar. This can lead to damage to the system, both when running in and when starting the casting.

The object forming the basis of the present invention is to provide an apparatus of the type specified at the start wherein the risk of the dummy bar sliding through is largely eliminated.

This object is achieved according to the invention by an apparatus with the features of claim 1.

Further preferred embodiments of the apparatus according to the invention form the subject matter of the dependent claims.

Since according to the invention a safety device is provided for the dummy bar which has an element which can be engaged, with form fit, with the dummy bar and limiting the speed of the dummy bar, it is guaranteed that a predetermined maximum strand speed can not be exceeded and the dummy bar will not slide through.

The element that can be engaged with the dummy bar is preferably in the form of a toothed wheel that is operatively connected to the dummy bar in the manner of a rack and pinion or toothed wheel drive. Upon exceeding the predetermined speed generated by the drive rollers for the dummy bar the toothed wheel element applies a braking force or a rotary resistance to the dummy bar.

Here the safety device advantageously comprises an autonomous, hydraulic circuit system with a pump, for example a toothed wheel pump (which is operatively connected to the toothed wheel element) and to a throttle. The practically resistance-free rotary resistance of the toothed wheel element during normal operation can be increased over the circuit system and over a transmission gearing when the dummy bar exceeds the speed due to sliding.

The safety device advantageously constitutes an autonomous system, for example independent of the roller drive, with which it is ensured that e.g. during a power failure and the loss of drive torque or contact force caused by the latter, no sliding through of the dummy bar takes place.

In the following the invention is described in greater detail by means of the drawings.

These show as follows:

FIG. 1 shows a continuous casting system in diagrammatic form;

FIG. 2 is a perspective illustration of an exemplary embodiment of an apparatus according to the invention for starting the casting of a continuous casting system;

FIG. 3 shows the apparatus according to FIG. 2 as a vertical cross-section; and

FIG. 4 is the top view of an apparatus according to FIG. 2.

FIG. 1 shows diagrammatically the structure of a continuous casting system 1 comprising a mould 2 cooled with water which is filled with liquid metal, in particular steel. A casting strand 3 is taken out of the mould 2 such as to form a shell which is a pre-profile. The casting strand 3 is conveyed away by means of rollers 11, 12 of a curved guide 10 and bent into the horizontal. As indicated by dashes in FIG. 1, the casting strand 3â€² could also be led away vertically by means of a vertical strand guide 10â€².

Whereas the rollers 11 disposed on the outside of the curved strand guide 10 and of the pre-profile strand produced in a pouring radius are fixed guide rollers, the rollers 12 located on the inside form the drive rollers and can be adjusted radially to the casting curve.

To one side the vertical strand guide 10â€² also has guide rollers 11â€² positioned securely, and to the other side perpendicular to the vertical casting direction adjustable drive rollers 12â€².

As is known, a dummy bar is also moved and held over the strand guides 10, 10â€², and this is used for starting the casting of the corresponding continuous casting system 1, 1â€² and is used to tightly close off the lower mould opening 15 before and during the casting start-up process in order to prevent steel poured into the mould 2 from flowing out. After the steel poured into the mould 2 has partially solidified so that a strand with a sufficiently thick solidified edge zone and liquid core has been producedâ€”the dummy bar introduced into the mould 2 by means of the strand guide 10 and 10â€² is also drawn out again by means of the strand guide 10 and 10â€² Here the movement of the dummy bar while introducing and while drawing out is determined by the drive torque generated by the drive rollers 12, 12â€² and by the contact force and friction coefficients between the drive and guide rollers 11, 11â€²; 12, 12â€² and the dummy bar.

Both for the continuous casting system 1 with the curved strand guide 10 and for the vertical strand guide 10â€² a rigid dummy bar or a chain dummy bar can be used in a conventional manner.

According to the invention, both for the chain dummy bar conveyed through the curved strand guide 10 and for the rigid dummy bar conveyed through the vertical strand guide 10â€² a safety device 20 and 20â€² is provided which ensures that with a decline or loss of the contact force or the friction coefficient and with a decline or loss of the drive torque the dummy bar does not slide through, as this would inevitably lead to the continuous casting system 1 or 1â€² being damaged.

The safety devices 20, 20â€² indicated in FIG. 1 are designed on the same principle. With the continuous casting system 1 provided with the curved strand guide 10 the safety device 20 is disposed on the inside of the strand guide 10, in the same way as the drive rollers 12. With the continuous casting system 1â€² provided with the vertical strand guide 10â€² the safety device 20â€² is preferably disposed on the same side as the postionable rollers 12â€².

In FIGS. 2 to 4 the safety device 20â€² provided for the vertical continuous casting system 1â€² and co-operating with the rigid dummy bar 22 is shown, and is described in greater detail in the following:

The safety device 20â€² according to the invention disposed on the same side as the drive rollers 12â€² has an element 25 in the form of a toothed wheel which can be engaged, with form fit, with teeth 26 of the dummy bar 22 in the manner of a rack and pinion or toothed wheel drive. With the exemplary embodiment shown the teeth 26 are formed by a plurality of transverse pins. (When using the chain dummy bar moved within the curved strand guide 10 the element can be engaged, with form fit, with the individual links of the chain dummy bar). The toothed wheel element 25 is coupled into the teeth perpendicularly to the direction of casting (with the curved strand guide 10 radial to the casting curve) and when drawn out must be uncoupled again in good time from the upper end of the dummy bar 22 or from the dummy bar head so that the subsequent hot strand is not damaged. This takes place automatically, for example with the aid of controllable a knee lever system, not shown in the drawings.

The safety device 20â€² further comprises an autonomous, hydraulic circuit system having a hydraulic pump (which is operatively connected to the toothed wheel element 25) and a throttle (the circuit system can not be seen in the drawings). If a speed generated by the drive rollers 12â€² for the dummy bar 22 is exceeded due to sliding, the rotary resistance of the toothed wheel element 25 is increased by means of the hydraulic circuit system and by means of transmission gearing comprising further toothed wheels 27, 28, 29, 30 or rack and pinion teeth 31, and so applies a braking effect to the dummy bar 22 in quadratic speed/rotary resistance dependency.

Since the safety apparatus constitutes an autonomous system, for example independent of the roller drive, it is ensured that the dummy bar 22 does not slide through for example with a power failure and loss of the drive torque or the contact force caused by the latter.

As already mentioned, the toothed wheel element 25 (and also the transmission gearing 27, 28, 29, 30, 31) can be positioned for the purpose of coupling and uncoupling perpendicularly to the casting direction (or radially to the casting arch). Independently of this, the whole safety device 20â€² and 20 can be positioned in this directionâ€”depending on the format of the casting strand 3 to be produced and of the corresponding blank bar, preferably together with the drive rollers 12â€² and 12 positionable in relation to the securely positioned guide rollers 11â€² and 11.

Furthermore, in FIG. 3 two pivotable protective caps 41, 42 are indicated which are illustrated in the open position in the engaged state of the toothed wheel element 25. If this toothed wheel element 25 is drawn back with the safety device 20â€², these protective caps 41, 42 are pivoted against the strand by a mechanism (not shown), and they then serve as a closed heat shield for the gear mechanism in this safety apparatus.