Presently wire having a diameter of 5.5 mm is rolled in blocks of this type at the comparatively high speed of 100 m/sec. The known blocks differ somewhat of course as to design, but they have the common feature that the rolling work is done between the two rolls provided with rolling grooves, said rolls being solidly fixed to a free end of an individual rotationally driven shaft, said free end extending from a housing common to both shafts. The reason for this is that the interior of the block can be maintained intact since all the required replacement of rolls can be done on the outside without any need to open the blocks, which could result in contamination because of the dirty rolling mill environment. Contamination of the interior of such a wire rod block could have catastrophic consequences since we are dealing with a high speed machine.
Developments in the rolling mill industry are however going towards higher and higher rolling speeds in order to achieve lower production costs. This especially applies to wire rolling. Multigroove wire rolling mills have been replaced by single groove mills with increased rolling speed.
In response to these developments, study of the possibilities of further increasing the final wire rolling speed within the scope of known technology has led to the realization that known wire blocks with the common basic features described above have too many rotating parts and bearings to permit a further increase in speed. It has also proved be the case that an optimum rolling process requires a relatively small roll diameter. This means in turn that the roll shaft diameter, i.e. the diameter of the shafts carrying the rolls is also reduced since the maximum conceivable roll shaft diameter is equal to the roll diameter minus the bearing thickness. Taken as a whole, these various circumstances will mean that a substantial increase in the roll speed of these known wire blocks with the common basic characteristics described here will result in such a great load on the bearings that the accompanying temperature rise therein will be unacceptable. The small roll shaft diameters will result in greater deflection of the shafts and thus very large deviations in wire dimensions.
In a known wire rod block with the above common basic features, and in which the two shafts extending from the common housing can be moved as a whole towards or away from each other while retaining a parallel relation to each other, there is the additional disadvantage that elevated rolling speeds will result in unacceptable vibrations as a result of the simultaneously increased rotational speed in the complicated transmission arrangement, which is required in this wire block to achieve the required parallel displaceability of the shafts.
Another problem caused by the parallel displaceability of the shafts is the seal arrangement between the block housing and the roll shafts radially displaceable in relation thereto. This sealing arrangement is already so complicated and expensive for the roll speeds now used that it could hardly be employed for still higher roll speeds in the future.
Our prior Swedish patent application No. 8502010-5 describes the advantages of being able to roll at lower temperatures. This increases the resistance to deformation and thus the roll pressure to such levels that the known wire blocks cannot withstand the loads. Therefore the purpose of the present invention is, starting from known wire rod blocks equipped with a pair of grooved rolls cooperating as rolling means, and solidly fixed to a freely projecting end of an individual rotationally driven shaft, to provide a new and improved block for wire rolling, which obviates the described problems and makes it possible to significantly increase rolling speeds.