Oscillating Table

Abstract

Oscillating table in which the oscillation drive, comprising a hydraulic actuator, transmits the oscillating motion to the mould via a spring subject to bending stress, for example a fitted rod. The body of the hydraulic actuator is also anchored to the floor by means of a fitted spring subjected to bending stress. Thus thanks to the absence of any mechanical bearings in the drive mechanism, all disadvantageous movements caused as a result of bearing play, which increases at high oscillation frequencies, are eliminated. Moreover, the use of mould guide elements having a much simpler design and consisting of straightforward bars, also ensures greater guidance precision and enables a reduction in the oscillation marks on the cast product, a reduction that is even more noticeable when working at higher oscillation frequencies. Advantageously, the presence of an anti-roll device, consisting of two or more pairs of bars, for example two pairs, ensures good torsional rigidity of the table.

Description

FIELD OF THE INVENTION

This invention relates to an oscillating table, in particular to a table, used for instance in bloom and billet production plants, used to obtain the oscillation of the mould.

PRIOR ART

Conventional oscillating tables are described in various patent documents. One such document, U.S. Pat. No. 4,456,052, describes a continuous casting apparatus in which a casting mould, mounted in a suitable mounting arrangement, is oscillated by means of oscillation levers. These levers are hinged at one end to the mould mounting arrangement and at the other end to a supporting block. The presence of bearings, and other mechanical parts that are subject to wear, means that the use of such devices is disadvantageous, as they require a great deal of maintenance which is expensive in terms of money and time. Moreover, during the production process some disadvantageous movements of the oscillating table occur as a result of bearing backlash, which increases at higher oscillation frequencies. Some of these drawbacks have been overcome by means of new oscillating systems based on the use of leaf springs.

A document, DE2248066, describes a device in which a mould is guided laterally by two leaf spring assemblies arranged parallel to one another and one above the other. Oscillation is brought about by a hydraulic cylinder. The two spring assemblies, which are arranged one on each side of the mould and clamped in place on one side to the bearing structure and on the other side to the mould, must absorb all the guide forces. The springs are, in actual fact, subjected to tensile as well as axial and bending stresses. On account of this the spring assemblies must be much longer and much thicker than is necessary for the maximum tensile forces that occur. Due to the large size of the spring assemblies, higher drive forces are necessary, that is to say the oscillation drive must be correspondingly larger in size. Moreover, the service life of the spring assemblies is reduced because of the high alternating bending stress occurring due to the large thickness. The use of very long spring assemblies means that there is also a more pronounced elastic behaviour, resulting in greater deflections and deviations of the mould from the desired guide path. Thermal influences are also more noticeable.

Another document, WO9912676, describes a device in which a mould is supported on a mould-supporting device by means of at least one pair of leaf springs, extending approximately transversely to the direction of oscillation and absorbing forces in the elastic range. At least one first guide element extends from the mould-supporting device towards the mould in a first direction and at least one second guide element extends from the mould-supporting device towards the mould in a direction opposite to the first direction. The leaf springs are arranged in such a way that they are bend-resistant in the directions transverse to the direction of oscillation and bendable in the direction of oscillation, and are only subjected to tensile forces. Said device is thus certainly more compact that those described previously but still has several drawbacks: the use of leaf springs does not enable high precision guidance or the reduction of oscillation marks on the cast product; the oscillating table has poor torsional rigidity; its operation requires the use of mechanical bearings with the drawbacks described above; finally, the oscillation frequency is not easily increased.

This invention aims to overcome these drawbacks.

SUMMARY OF THE INVENTION

One of the main purposes of this invention is to provide an oscillating table that is of a more straightforward design and more compact and that allows greater precision in the guidance of the mould even if the frequency of oscillation is increased. Another purpose is to produce an oscillating table in which there are no mechanical parts subject to wear, to enable a significant reduction in the amount of maintenance required and thus obtain considerable savings in terms of time and money.

This invention therefore aims to overcome the drawbacks described above with an oscillating table having the characteristics set forth in claim 1.

The total absence of bearings in the oscillating table according to this invention not only means that the table is maintenance-free but also enables the elimination of all disadvantageous movements caused as a result of bearing clearance, which increases at high oscillation frequencies.

The oscillation drive mechanism, comprising a hydraulic actuator, advantageously transmits the motion via a spring subjected to bending stress, for example a fitted rod.

According to one advantageous alternative form of this invention, the body of the hydraulic actuator is also anchored to the floor by means of a fitted spring subjected to bending stress. Thus also the drive mechanism has no mechanical bearings, with the advantages described above.

Furthermore, the use of simpler guide elements, that no longer consist of leaf springs comprising a plurality of elements that are joined to one another, but of straightforward bars, ensures greater guidance precision and enables a reduction in the oscillation marks on the cast product, a reduction that is even more noticeable when working at higher oscillation frequencies.

Said guide elements also have a long service life and automatically compensate thermal expansions thus avoiding guide deviations.

Finally, the presence of an anti-roll device, comprising two or more pairs of bars, for example two pairs, ensures good torsional rigidity of the table. Each bar in each pair has a first end that is fastened to the mobile part of the table and a second end that is fastened to the fixed part, in opposite order in relation to the corresponding ends of the adjacent bar of the same pair. According to the direction of the torsional moment, in the case of two pairs of bars, two bars will be subjected to tensile stress, acting as tension bars, while the other two will be subjected to compressive stress, acting as compression members.

The dependent claims describe preferred embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages of this invention will become clear from the following detailed description of a preferred, but not exclusive, embodiment of an oscillating table that is merely illustrative and not limitative, with the help of the drawings that are attached hereto, in which:

FIG. 1 is a vertical cross-section of the oscillating table according to this invention;

FIG. 1a is a large view of a component of the oscillating table of FIG. 1;

FIG. 2 is a cross-section of the plan view of the oscillating table in FIG. 1.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

With reference to FIG. 1, an oscillating table is illustrated with an external supporting structure 1, that is fixed to the floor.

In one particularly advantageous alternative embodiment, said structure comprises a single beam that supports the structure on the floor and that in turn comprises all the necessary elements in order to support the various parts that make up the table.

A mould 3 comprising a cylindrical crystallizer 2 is mounted in the external supporting structure. The oscillating movement of said mould is controlled by an oscillation drive mechanism, comprising a hydraulic actuator 4, via a spring subjected to bending stress 5, for example a fitted rod. Said spring subjected to bending stress 5, is connected at the other end to an element 8, for example a bar or a monolithic beam, integral with the mould 3.

According to one advantageous alternative embodiment the body of the actuator 4 is also anchored to the floor by means of a spring subjected to bending stress 9, for example a fitted rod. Since there are no mechanical bearings whatsoever in the above-described oscillation drive, all the backlash, characteristic of said components, which are notoriously subject to wear, is eliminated.

There are elastic guide elements 6, 7 to prevent any deviation of the mould 3 from the predetermined path. Said elements 6, 7, which are oblong in shape, are oriented approximately on radial lines of the arc defined by the cavity of the crystallizer 2 if said cavity is curvilinear; on basically parallel lines if the cavity of the crystallizer is rectilinear.

In this embodiment of the invention said elastic guide elements advantageously consist of a first pair of upper bars 6 and a second pair of lower bars 7, both pairs having a flat cross-section. The elastic bars 6, 7 must absorb tensile forces only and are therefore arranged so as to be bend-resistant in the directions transversal to the direction of oscillation and bendable in the direction of oscillation. The four bars 6, 7 are fastened to one end of the mould 3, i.e. to the mobile part of the table, by means of fastening devices 10, for example bolts, and at the other end to the external supporting structure 1 by means of fastening devices 11.

One alternative embodiment provides for the use of leaf springs or springs of a similar type as the elastic elements to guide the mould 3.

To contrast the torsional moment that occurs on a plane that is basically orthogonal to the casting direction, the table according to this invention advantageously incorporates an anti-roll device, comprising two or more pairs of bars 12. Said bars 12, which are horizontal and arranged in directions that are basically transversal to the elastic guide elements 6, 7, ensure a predetermined torsional rigidity of the table. Each bar in each pair has a first end that is fastened to the mobile part of the table and a second end that is fastened to the fixed part, in opposite order in relation to the corresponding ends of the adjacent bar of the same pair. According to the direction of the torsional moment, in the case of two pairs of bars, two bars will be subjected to tension, acting as tie rods, while the other two will be subjected to compression, acting as struts.

In another advantageous alternative embodiment there are elastic means 13, for example compression or air or leaf springs, the function of which is to lighten the mould 3 and the actual table structure ensuring a better distribution of the weight. Thanks to the total absence of mechanical bearings in the oscillating table according to this invention the table requires no special maintenance, resulting in savings in terms of time and money, and all disadvantageous movements due to bearing play, which increases at higher oscillation frequencies, are eliminated. Moreover, the use of much simplified elastic guide elements ensures better precision in mould guidance and results in a reduction in the oscillation marks on the cast product.

Finally, thanks to the improvements described above, the oscillating table according to this invention is more compact and of a simpler design and can be used at oscillation frequencies of above 4.5 Hz, which is higher than the normal frequencies of 3.5 Hz.

The specific embodiments described in this document are not limitative and this patent application covers all the alternative embodiments of the invention as set forth in the claims.

Claims

1. Oscillating table comprising

a mobile structure, mounted in a supporting structure integral with the floor, wherein the mobile structure comprises a mould (3) defining a first casting direction and being guided in an oscillation by first elastic members (6, 7) having an elongated shape and arranged transversely to the direction of casting,

a hydraulic actuator (4) transmitting oscillations to the mould (3), characterized in that there are provided two or more pairs of bars (12), arranged horizontally in a second direction basically transversal to the first elastic members (6, 7) and to the first direction of casting, whereby the table is provided with a predetermined torsional rigidity about an axis substantially parallel to the first elastic means.

2. Oscillating table according to claim 1, wherein each bar (12) of each pair has a first end fastened to the mobile structure and a second end fastened to the supporting structure, in opposite order with respect to the corresponding ends of the other bar in the pair.

3. Oscillating table according to claim 1, wherein there are provided second elastic members (13) connecting the mould (3) to the supporting structure that lighten the mould (3) and distribute its weight in a uniform manner.

4. Oscillating table according to claim 3, wherein there is provided a third elastic member (5) clamped in place and connecting the hydraulic actuator (4) to the mould (3).

5. Oscillating table according to claim 4, wherein there is a fourth elastic member (9) clamped in place and connecting the hydraulic actuator (4) to the floor.

6. Oscillating table according to claim 5, wherein said third and fourth elastic members (5, 9) consist of a spring subjected to bending stress.

7. Oscillating table according to claim 6, wherein said spring subjected to bending stress consists of a fitted rod.

8. Oscillating table according to claim 3, wherein said second elastic members (13) consist of compression or air or leaf springs.

9. Oscillating table according to claim 1, wherein said first elastic members (6, 7) consist of bars or leaf springs.