Metal deforming – By deflecting successively-presented portions of work during... – By use of deflected arranged to provide longitudinally...
Patent
1997-04-09
1999-01-05
Crane, Daniel C.
Metal deforming
By deflecting successively-presented portions of work during...
By use of deflected arranged to provide longitudinally...
72205, B21D 105
Patent
active
058551328
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/IT94/00205, filed Dec. 5, 1994.
The invention concerns machines used for unfinished or finished metal products to eliminate the effects of bending and warping generally that occur after application of mechanical processes or heat treatment.
The distorsion that is commonly produced in unfinished products arises during the cooling stage that follows the rolling process and causes bending in the plane perpendicular to that to which the minimum moment of inertia in the unfinished product corresponds.
The internal stresses present in laminated metal bands usually originate in some irregularity in the mechanical characteristics of the rolling operation.
During subsequent processes such as shearing, cutting and others, these internal tensions cause warping and in particular a lack of flatness.
Such defects are chiefly due to differences in length of the metal fibres as well as to internal residual and opposing stresses.
To achieve flatness all the metal fibres must be of the same length, creating new internal stresses which act against and can overcome the existing ones.
For this purpose machines known as levellers are used.
The levellers for metal bands and long sheets operate by means of a continuous process using transversal rollers which make high working speeds possible.
Cold levelling can with advantage be obtained by applying appropriate traction to the material in a process called stretching.
The operation is known as flattening under tension and is done with a leveller called a tensio-flattener.
This machine comprises a tightening device at the entry, a group of rollers for stretching to yield point, a group for straightening, another group for flattening and a tightening device at the exit.
Tension is set up by the tightening devices at entry and exit, and these keep the band at a constant previously set tension while it is passing through the machine.
Function of the first group is to stretch the material evenly to yield point.
Function of the straightener is to straighten the band that leaves the stretching rollers in a very warped condition.
Function of the flattener is to free the material from its residual stresses.
The operative rollers used for stretching,straightening and flattening are drawn along by passage of the band which produces friction and so moves the rollers.
The operative rollers in turn transmit movement to the supporting rollers whose function is to sustain the operative rollers and prevent any excessive bending.
In the flattening group the operative rollers have a constant diameter and their contact with the band is assured by movement of the lower bed that rises up to the desired position; said lower bed can also be inclined in the direction of band movement in relation to the upper bed.
Flatness is achieved by adjusting the length of time when the band is in contact with the flattening roller.
For a certain band speed this time is obviously a function of the position of operative rollers supported by the lower bed in relation to the operative rollers supported by the upper bed.
The more closely the lower bed approaches the upper one the greater will be the fraction of band that is made to surround, one by one, the upper and lower rollers waving in one direction and in the opposite one.
Since the diameter of these rollers is constant, it is impossible to adjust the time variable independently of the length of band that passes round each roller.
In other words, to obtain a longer period of contact between band and roller, the fraction of band round the rollers must be increased while the radius of curvature of the various waves of band obviously remains unchanged.
Further, adjustment of the machine is left to the discretion of the operator and is limited by the time of bending. When flattening speed is high, band stretching times are therefore short and stretching is not uniform.
The above invention greatly improves performance of the machine achieving unprecedented flattening results as will be explained below.
Subject of the invention is a flatte
REFERENCES:
patent: 2386533 (1945-10-01), Yoder
patent: 5097691 (1992-03-01), Slabowski
Crane Daniel C.
Selema, S.R.L.
Striker Michael J.
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