Metal deforming – By use of roller or roller-like tool-element – Included in roller-cluster
Reexamination Certificate
2000-09-15
2001-08-21
Tolan, Ed (Department: 3725)
Metal deforming
By use of roller or roller-like tool-element
Included in roller-cluster
C072S235000, C072S237000
Reexamination Certificate
active
06276182
ABSTRACT:
The present invention relates to the rolling of metal pipes and, in particular, of seamless pipes; it may, however also be used in the rolling of rod-shaped bodies in general, such as flat blooms, bars, wire rods, and the like.
Before proceeding further, it should therefore be pointed out that in this description and in the following claims, for sake of brevity, reference will be made mainly to the rolling of pipes; however, what will be stated is to be considered valid also for the above-mentioned rod-shaped bodies, unless specified otherwise.
Relevant improvements have been made in this field during recent years, concerning rolling mills with stands or rolling units with three or more driven rolls; rolling mills produced in accordance with this concept, in fact allow a better quality of work to be achieved than conventional mills with stands having two opposed rolls.
They are therefore preferable from this point of view, but their practical construction involves some considerable difficulties, amongst which there is the adjustment under load. As explained fully in Italian patents Nos. 1254864 and 1264032, to which reference is made for this purpose, this kind of adjustment consists in checking the distance of the axes of rotation of the rolls from the rolling axis along which the pipe to be processed advances, and it has a series of considerable technical difficulties when it must be performed in rolling mills with rolling stands having three or more driven rolls.
In short, these difficulties can be said to have been overcome by mounting the working rolls on respective lever arms swinging in planes transverse to the rolling axis and hinged on a supporting holder or frame which can be extracted from the outer structure of the rolling mill; this structure may advantageously be substantially tubular or open along a side.
In the first case it is particularly suitable for processing pipes on a mandrel because its closed configuration around the rolling axis, compensates best for the considerable radial stresses which arise during this type of working. In the second case, on the other hand, changes and maintenance of the rolls are facilitated, given that each holder on which the respective swinging arms are hinged can be extracted and inserted independently from the others, by simply moving it radially relative to the rolling axis in the region of the open side of the structure.
An important aspect concerning the maintenance of the rolling mills herein considered, consists in periodic re-turning of their rolls; indeed the working surfaces of the latter, which are shaped with a characteristic grooved profile, inevitably wear or are damaged over time so that in order to maintain a good quality of working, the rolls are re-turned after a certain period and are thus brought back to the required operative conditions.
This turning operation is carried out for removing a layer of material from the working surfaces of the rolls, however having care of keeping their profiles unchanged since they have to correspond to the external profile of the pipes to be rolled; upon completion of the returning, the rolls thus have a nominal dimension along their grooved profile which is reduced by a value equal to twice the thickness of material removed along their diameters. In order to roll pipes of predetermined diameter, it is possible to compensate for small values of this machining reduction by the adjustment of the trin of the rolling mill which is permitted by the swinging arms; beyond certain limits, however, this is no longer possible and it is precisely the situation which occurs when the rolls undergo several returning operations.
FIG. 1
of the appended drawings shows this situation and it can be seen therein that, when a large thickness has been removed from the surface of the roll, the swinging of the respective lever arm necessary to bring the grooved profile of the roll in a suitable position for rolling a pipe of predetermined outside diameter, leads to a displacement of the roll from its original plane of symmetry (that is, its median plane passing through the rolling axis of the pipe before the re-turning operation/s) which is unacceptable for correct rolling. To overcome this problem, it is known from the Italian patents indicated above to hinge the lever arms about pins mounted in an adjustable manner on the supporting frame or holder already mentioned; that is to say, according to this solution for compensating the effect just described due to the re-turning of the rolls, the position of the pin about which the lever arms pivot is adjusted. This operation is performed manually by operators attending the maintenance of the mill.
It is however clear that this adjustment, which is not always easy to do since various encrustations and deposits resulting from the rolling process may arise in the regions concerned, has to be repeated for each pin of a holder; since there are three or more lever arms for each holder and there may also be six or more holders in a rolling mill, it is easy to understand that the time and procedures required to adjust all of the pins may become quite lengthy and onerous.
The object of the present invention is therefore to remedy such a situation. In other words, the invention aims at providing a rolling mill of the type with lever arms swinging transversely to the rolling axis, and where these arms are disposed on holders extractable from an outer load-bearing structure, which permits an adjustment of the positions of the pivot points of the arms such as to overcome the problems of the prior art considered above.
This object is achieved by a rolling mill the features thereof are set forth in the claims appended to this description.
REFERENCES:
patent: 5331835 (1994-07-01), Palma et al.
patent: 5765423 (1998-06-01), Cattaneo et al.
patent: 917 963 (1950-01-01), None
patent: 0 565 772 (1993-10-01), None
patent: 1254864 (1995-10-01), None
patent: 1264032 (1996-09-01), None
Bandini Stefano
Brignoli Maurizio
Cernuschi Ettore
Griffin & Szipl, P.C.
SMS Demag Innse SpA
Tolan Ed
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