Metal deforming – By deflecting successively-presented portions of work during... – To form spiral coil
Reexamination Certificate
2003-07-10
2004-11-02
Tolan, Ed (Department: 3725)
Metal deforming
By deflecting successively-presented portions of work during...
To form spiral coil
C072S010100, C072S010300, C072S014700, C072S205000, C242S534000
Reexamination Certificate
active
06810706
ABSTRACT:
The present invention relates to apparatus for reducing tension variations in a metal strip being coiled and/or uncoiled. In particular it relates to the coiling and/or uncoiling of metal strips in the furnace coiling/uncoiling drums of a Steckel type rolling mill in which the metal strip passes from the uncoiling drum to the coiling drum via a reduction stand. It is also applicable to other mill types, both reversing and non-reversing, for steel and other metals.
In a conventional Steckel mill a major factor in causing tension variations during coiling and uncoiling is the eccentric build up of the coil on a coiling drum. This is a particular problem in Steckel rolling because the design of the Steckel coiling/uncoiling drums tends to produce a bump in the diameter of the coil at the position of the slot in the coiling drum. It is obvious that as the coiler drum rotates the larger coil diameter, at the position of the bump caused by the drum slot, results in an increase in circumferential speed at this point and hence in an increase in rate at which strip is wound onto the drum. If strip is wound onto the drum faster than it is exiting the mill stand then the differential speed causes the strip to be stretched and this increases the tension. This results in undesirable variations in the product.
U.S. Pat. No. 4,905,491 discloses a method for reducing the cyclic tension changes caused by coil eccentricity. This method relies on a tension measuring device and the analysis of the variations in this tension to generate control signals to either the coiler motor torque or the roll gap. However, it is easy to show by calculations that the inertia of the coiler motor plus the coiler drum in a conventional Steckel mill is so large that it is not possible to accelerate and decelerate the coiler fast enough to compensate for eccentricity of the coil at conventional Steckel rolling speeds. Therefore the practical application of this patent on a Steckel mill would require that the roll gap is used to control the tension. It is well known that changing the roll gap during rolling changes the entry speed of the strip in proportion to the change in the exit thickness but it has only a very small effect on the exit speed of the strip. Consequently this method can only be used on the uncoiler and is not suitable for a coiler on the exit side. Another problem is that modifying the roll gap changes the exit thickness of the strip as well as changing the entry-speed. Consequently the use of the roll gap to control the tension will make the thickness variations worse. This is precisely the opposite of the desired effect which is to improve the thickness and width tolerances of the strip by reducing the tension variations.
GB2074138 discloses another method of reducing the tension variations due to eccentricity of the coil. This method uses a sensor to measure the diameter of the coil as it rotates and it applies the signal from this sensor to the motor speed control. It is simple to show by calculation that the inertia of a conventional Steckel mill coiler motor and drum is so large that it would not be possible to accelerate and decelerate the coiler/uncoiler fast enough to follow the signal from the coil diameter sensor.
It is therefore the objective of this invention to reduce the tension variations caused by eccentricity of the coil in order to improve the width and thickness tolerances of the rolled metal strip in a way which overcomes the problems discussed in the prior art. It is a further objective of this invention to improve the mill stability and to reduce risk of strip breakage and equipment damage by minimising the tension variations due to coil eccentricity. The present invention uses anticipatory adjustment to achieve this. Reactive attempts to address the problem, as provided in the prior art, are unsuitable due to to inertia effects.
According to a first aspect of the invention we provide an apparatus for the handling of a metal strip, wherein the apparatus includes a first coiler and second coiler and a moveable roll, a strip path being defined between a first location and a second location, movement of the movable roll changing the length of the strip path, the apparatus further including a measurer of the angular position of at least one of the coilers and an actuator for the moveable roll, the actuator being provided with signals from the measurer, the position of the moveable roll being defined, at least in part, as a function of the angular position of at least one of the coilers.
Preferably both the first coiler and the second coiler are provided with a measurer of the angular position of the coiler. Preferably one or both of the coilers are fitted with angular position transducers to measure the angular position of the coiler or coilers during coiling or uncoiling.
The first and/or second coilers are preferably coiler drums. Preferably the first and/or second coilers are provided with a slot for receiving an end of the metal strip in use. Preferably the slot is defined as a part of a chord to the circular cross section of the coiler. Preferably the angular position of a slot in the first and/or second coilers is measured.
In addition the invention may provide that one or more of the rolls are moveable pinch rolls. The rolls may be fitted with position transducers and/or roll position controllers, such as hydraulic actuators. Preferably a control system which controls the position of the rolls in response to the signals is also provided. The control system may control the position of the rolls in response to information from the measurer or measurers alone. It is preferred, however, that the control system controls the position of the rolls in response to that information in combination with further information. A database may be provided to store the further information. Preferably the information and further information are combined to give an overall control signal to the roll position controllers.
Preferably a moveable roll is provided between a coiler and a rolling mill stand or other processing stage. Preferably a roll is provided between each coiler and a rolling mill stand or other process stage. Preferably the movement of the roll changes the length of the strip path between a coiler and the rolling mill stand or other processing stage. The first location may be a rolling stand or other process stage. The second location may be the coiler, or more particularly the part of the coiler at which the metal strip comes into contact with the coiler, or alternatively the location at which the metal strip comes into contact with a part of the metal strip coiled on the coiler. It is preferred that the second location is a further roll, particularly a deflector roll. Preferably the first and second locations are at fixed positions and/or in a fixed configuration relative to one another. Preferably at least one further roll is provided between a coiler and a roll. Preferably a further roll is provided between each coiler and its respective rolls. Preferably the further roll is a deflector roll. The movement of the roll may change the length of the strip path between the further roll and the rolling mill stand or other process stage. The apparatus may include a rotational speed measurer for one or more of the coilers. Preferably signals from the rotational speed measurer are provided to the control system. The rotational speed measurer may be the same as the angular position measurer. The apparatus may be provided with a tension measurer for the strip. The apparatus may be provided with a load measurer for the moveable roll. Preferably signals from the tension measurer and/or load measurer are provided to the control system. The apparatus may include a strip coil diameter measurer, preferably one for each coiler. Preferably signals from the strip coil diameter measurer are provided to the control system.
Preferably two moveable rolls and their associated controllers are provided on a reversing mill, one reducing the tension variations of the uncoiling product and one reducing
Clark Michael
Marples Anthony
Schein, Esq. Daniel B.
Tolan Ed
VAI Industries (UK) Limited
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