Metal founding – Process – With measuring – testing – inspecting – or condition determination
Reexamination Certificate
1998-11-05
2001-04-03
Lin, Kuang Y. (Department: 1722)
Metal founding
Process
With measuring, testing, inspecting, or condition determination
C164S442000, C164S484000, C164S413000
Reexamination Certificate
active
06209619
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a strand guide for a continuous casting plant, in particular for a continuous casting plant for steel, comprising a plurality of strand supporting elements for supporting the strand, in particular support segments carrying supporting rollers, several support segments being fastened adjacent each other on an optionally arcuate supporting framework designed in one piece in its longitudinal extension, wherein each support segment is fastened to the supporting framework by means of a fixed bearing and a movable bearing spaced apart therefrom in the longitudinal extension of the strand guide and each support segment by at least one bearing (fixed and/or movable bearing) is pivotally mounted to the supporting framework so as to be pivotable about an axis, said axis being oriented transversely with respect to the longitudinal extension of the strand guide and horizontally, as well as in a vertical plane passing through the longitudinal extension of the supporting framework and by at least one bearing (fixed and/or movable bearing) is mounted so as to be adjustable with respect to the supporting framework in a direction roughly perpendicular to the longitudinal extension of the supporting framework to enable the pivoting movement of the support segment, and a method of adjusting the position of support segments.
A strand guide of this kind is known e.g. from DE-A - 30 29 991. There, alignment of the support segments is feasible by displacing the support means at the bearings, namely through manipulations which have to be effected manually. However, this involves complications since it requires the plant to be out of operation and moreover can only be carried out in cooled-down condition. Hence, deformation caused by thermal expansion and influences occurring after start-up cannot be taken into account.
From EP-B - 0 222 732 a strand guide is known in which several support segments each carrying a plurality of strand guide rollers are arranged on a continuous longitudinal carrier designed in one piece, with the support segments being mounted on the longitudinal carriers via carrying brackets rigidly fastened to the longitudinal carriers by means of fitting pins, two neighboring support segments each being commonly mounted on the carrying brackets by means of carrying elements arranged on their ends. Each carrying bracket has a recess immovably receiving the carrying element of a support segment and a recess receiving the carrying element of the neighboring support segment with a play, thereby forming movable and fixed bearings. The play extends parallel to the path of the strand guide so that a thermal expansion of the support segments or of the longitudinal carrier will have no adverse effect on the accuracy of the strand guide.
From FR-A - 2 447 764 a strand guide is known in which strand guide the carrying brackets are pivotally fastened to the single-piece longitudinal carrier so that by pivoting the carrying brackets a support segment supported on the carrying bracket is lifted or lowered on the one hand and the neighboring support segment supported on the same carrying bracket is moved in a direction counter to the first one. In this way, the neighboring support segments can be aligned while avoiding a step-like transition in the path of the strand guide. One disadvantage involved here is that at least two neighboring support segments are pivoted in each instance if there is a height step at a site of transition from one support segment to the other support segment. This renders it difficult to keep to the path of the strand guide while maintaining the deviation from the ideal path of the strand guide as slight as possible, i.e. for instance to observe a circular-arc-shaped path of the strand guide, in the case of an arcuate strand guide. Major deviations of several support segments from the ideal position may occur since none of the support segments is fastened to the supporting framework by means of a fixed bearing.
The invention aims at avoiding these disadvantages and difficulties and has as its object to further develop a strand guide of the initially described kind in such a way as to ensure precise adjustment of the support segments during the entire operating time of the strand guide, requiring only short interruptions, if any, for adjusting the strand guide.
SUMMARY OF THE INVENTION
According to the invention, this object is achieved in that a measuring device for detecting the pivoting movement of the support segment, preferably a position sensor or an angle measuring device, is provided which via a controller is coupled with an adjusting device for adjusting the position of the support segment.
A particularly simple and robust construction of a strand guide is characterized in that vertically adjustable shims are provided for adjusting the position of the adjustable bearing.
For adjusting the adjustable bearing, there preferably is provided a threaded spindle, or according to another embodiment an axially displaceable wedge which is movable by means of a hydraulic adjusting cylinder, or according to yet another embodiment a hydraulic adjusting cylinder which acts between the supporting framework and the support segment.
A preferred embodiment is characterized in that for actuating the hydraulic adjusting cylinder there is provided at least one directional control valve which is capable of being switched via a three-level controller or a higher-level controller or a controller with a pulse-width output to which the actual value detected by the position sensor can be fed via a coupling.
The provision of a directional control valve enables a very simple control technique. A particularly high accuracy, which could be achieved e.g. by using the servo valve technology, is renounced here, yet in accordance with the invention there result the advantages of substantially reduced costs and a substantially reduced sensitivity to disturbances such as e.g. contamination of the oil or pressure drops or the like as compared to the servo valve technology. Surprisingly, the directional control valve technology has proved satisfactory for continuous casting operations even in the case of sensitive steel grades.
By employing a controller with a pulse-width output, nearly continuous control as it is typically achieved using servo or proportional valves can be achieved even with directional control valves. In the case of the on-off valve, the variable valve opening which is used with these continuously operating valves is replaced with a sequence of pulsed valve openings. This enables positioning operations to be carried out with high precision.
The servo valve technology enables very sensitive and rapid control of high outputs by means of small control inputs due to the supporting effect of the medium that flows through. The servo valve technology is mainly applied for difficult positioning tasks in machine tool technology. The demands both in terms of material and cost for realizing the servo valve technology are correspondingly high. Maintenance and measures for avoiding disturbing influences are likewise expensive.
Application of the servo valve technology in connection with continuous casting technology is known from U.S. Pat. No. 3,812,900; it allows adjusting the position of the movable strand guide roller with utmost precision. Disadvantages of this method are the great expenditures in terms of materials which are incurred in applying the servo valve technology as well as the great sensitivity to a contamination of the same; difficulties may result in heavy-duty iron- and steelworks operations.
Since according to the invention only minor volume flows are required for adjusting a support segment whereas the total system operates at high pressures (e.g. 160 bar), a throttle or screen suitably is integrated in at least one hydraulic working duct of the hydraulic adjusting cylinder leading from a pressure-medium supply station to the directional control valve or from this latter to the hydraulic adjusting cylinder.
A preferred embod
Brandstetter Reinhard
Engel Kurt
Fitzel Helmut
Fürhofer Horst
Mörwald Karl
Lin Kuang Y.
Ostrolenk Faber Gerb & Soffen, LLP
Voest-Alpine Industriean-lagenbau GmbH
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