US2060672A - Control system - Google Patents

Description

H. HEYMANN CONTROL SYSTEM Nov. 10, 1936.

Filed Jan. 28, 1935 Ifivenbor: Hugo Heym b 7% 5.9

y l- 'l i yAttorney O ZOT Patented Nov. 10, 1936 UNITED" STATES- common system Hugo Heymann, Berlin-Friedman, Germany, assignor to General Electric Company, a corporation of New York Application January 28, 1935, Serial No. 3,828 In Germany February 12, 1934 Claims. ,(CI. 80-32) This invention relates to control systems, more particularly to controls for apparatus performing operations on a strip of material and it has for an object the provision of a simple-reliable 5 and improved system of this character.

More specifically the invention relates to control systems for cold-strip rolling mills and the I like in which the strip delivered from the mill rolls is wound on a drum under constant tension; the reels or drums are driven by separate machines which are controlled to render the coiling operation uniform.

Similar conditions prevail in some hot-rolling mills producing wide metal strip, with the difierence, however, that in this case no tension must be put on the material when the latter is wound on the reel or drum, in order to avoid undue variation in the gauge of the hot strip. Likewise, the treated material must not be allowed to become piled up on itself on the take-up reel is a result of being taken up too slowly in relation to the angular speed of the rolls.

A short description of the operation of these rolling mills will be given first. The initial stage consists in reducing the strip in the rolling stand according to the reversing method until the thickness of the strip is sufilciently reduced to render the coiling operation possible. The

30 drums or reels are in separate heating furnaces, disposed on opposite sides of the mill stand. As soon as the rolled strip is thin enough to be coiled, it is fed to the furnaces by operation of a throw-over switching mechanism. for the purpose of reheating the strip and for coiling it on or uncolling it from the reel concerned, in ac cordance with the direction in which the material is being rolled. For the reasons stated in the foregoing, it is necessary that the strip should be wound on the leading or take-up reel and unwound from the trailing or unwinding reel at a linear speed in accordance with that of the rolls. In other words, since the overall in proportion as the strip is coiled thereon, the angular speed of this reel must decrease accordingly while the R. P. M. of the unwinding reel must increase at the same rate. The duty of the reels is therefore to take up and pay out the strip at a linear speed accurately equivalent to that of the rolls. I

A further object of this invention is the provision of means for effecting reliable cooperation between the two reels and the rolling stand by providing that the speed. of the winding reel motor as well as that of the unwinding reel motor shall be accurately controlled in accordance with the speed of the rolls, and by taking into most careful consideration the respective increase and decrease of diameter of the reels diameter of the take-up reel gradually increases or drums. To this end, and according to the said invention, a speed indicator generator is coupled to each drum-driving motor, whereby the R. P. M. of one motor are caused to increase in the same proportion as the R. P. M. 0! the 6 other motor decrease. This is obtained by suitably and alternately influencing the fields of the drum-driving motors with the aid 01' these generators which are high-saturation machines whose voltage, at constant excitation, increases and decreases proportionally to the speed.

In illustrating the invention in one form thereof, it is shown as embodied in a system for controlling the operation of a reversing hot strip mill.

For a better andmore complete understanding of the invention, reference should be had to the following specification and to the accompanying drawing, the single figure of which is a simple diagrammatical illustration of an embodiment of my invention.

Referring now to the drawing, the rolls ill of a reversing rolling mill are driven by a suitable reversible motor I l and reels or drums i2 and i3 disposed in the heating furnaces are driven by means of motors l4 and i5 respectively. Although the motors I 4 and i5 may be of any suitable type, they are illustrated as direct current motors supplied from a common variable voltage motor generator I6. Generator I6 is 39 driven at a speed which is preferably substantially constant by any suitable means represented in the drawing by the alternating current motor i'i, supplied from a suitable source 1%. Suitable control mechanism I9, illustrated conventionally in the drawing, is connected in the field circuit of generator 56 and serves to control the magnitude and polarity of the voltage supplied to motors it, It and I5. While the first reduction passes are in progress the control mechanism i9 is utilized only for starting and regulating the main mill motor H, but at the beginning of the reeling operation, this mechanism serves the purpose of starting and controlling, in common and in Ward-Leonard arrangement, the motors ii and I l or II and i5, according as the reel it or reel i3 is acting as take-up reel. High saturation direct current pilot generators 20 and 2| are coupled to the reel driving motors i4 and i5 and therefore to the reels 5% l2 and I3 respectively. The field windings of the motors H, M and I5, and the generators i6, 20, and 2| are connected to the excitation supply busses 22 which in turn are supplied with a substantially constant direct voltage from the exciter 23 which is coupled to the shaft of the main drive motor H.

In operation, as the work progresses in the direction of the arrow, the switch 24 is closed and the switch 25 is open so that the motor i5 is energized and the motor l4 is-disconnected. The diameter or the reel it increases as the coiling of the strip progresses, while at the same time the diameter 01' the unwinding reel I! de creases. This consequently involves the necessity oi. gradually decreasing the angular velocity the take-up reel I! while increasing that of reel I3 is altered by gradually strengthening the field of the take-up motor IS with the aid or the pilot generator 20 which is coupled to the reel l2 and whose voltage rises proportionally ,to the increasing angular speed or real l2 so that the speed of the take-up motor I is decreased in proportion to the increase in the speed of the unwinding reel II. The switch 24 is opened and the switch 25 is closed when the direction of rotation andtherefore the direction of travel of the strip is reversed so that the pilot generator 2! coupled to the reel i3 strengthens the field or the motor l4 (now driving reel H as take-up reel) which is consequently caused to-slow down. Speed regulation is smooth and uniformly continuous. As regards the total excitation oi the reel driving motors, it is immaterial whether the latter have two field windings/or whether they are excited by a separate machine inwhich one field is excited by the fundamental excitation and the second by the speed indicator generator.

This equipment'is also adaptable for reversing cold strip mills where tension is maintained, either or both, between the mill andthe winding or unwinding reel. Whether there is tension or not depends upon the speed of the strip and the relative field strength of the reel motors, which can be adjusted by hand or automatically with constant current regulators.

Although in accordance with the provisions of the patent statutes this invention is described as embodied in concrete form, it will be understood that the invention is not limited to the specific apparatus and connections which are merely illustrative, since modifications and alterations will readily suggest themselves to persons skilled in the art without departing from the true spirit of this invention or from the scope of the annexed claims.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. In combination with rolling mill apparatus and the like having means for performing an operation on a strip of material, and an unwinding reel for supplying the strip to said means and a winding reel for coiling the strip delivered by said means, a separate motor for driving each of said reels, means for rendering the motor connected to the take-up reel ineffective, and a separate pilot generator driven by each of said reels and connected to the field winding of the motor driving the other of said reels thereby to vary the excitation and the speed of the motor driving the take-up reel inversely with the speed of said unwinding reel.

2. A control system for strip rolling mills and the like having an element operating on a strip of material and winding and unwinding reels therefor arranged on opposite sides or said element comprising, a motor for driving the winding reel and a motor for driving the unwinding reel, each of said motors being provided with a field winding, means for rendering the motor connected to the unwinding reel inactive a generator driven by said winding reel connected to energize the field winding of said unwinding reel motor and a second generator driven by said unwinding reel and connected to the field winding of said winding reel motor, so that the speed of said winding reel motor is varied inversely with the speed of the unwinding reel.

3. A control system for rolling mill apparatus and the like having rolls for reducing the thickness of the strip and winding and unwinding reels therefor comprising a. motor for driving said unwinding reel, a motor for driving said winding reel, a motor for driving said rolls at a substantially constant speed, means for reversing the rotation of said motors, means for rendering the unwinding reel motor inactive and a pair of pilot generators each driven by one of said reels and each connected to a. field winding of the motor driving the other. of said reels thereby to vary the speed of the winding reel motor inversely with the speed of said unwinding reel so that the speed of the strip at the periphery oi! the winding reel is substantially equalized with the strip speed of said rolls.

4. A control system for arolling mill having a winding reel and an unwinding reel disposedunwinding reel influences the field of the motor driving the winding reel so as to produce a peripheral velocity of the winding reel equal to the peripheral velocity of the rolls.

5. A control system for reversing strip rolling mills and the like having thickness reducing rolls and a pair' of reels arranged on opposite sides of the rolls so that during one pass one reel acts as a winding reel and the other acts as an unwinding reel, a motor for driving said rolls, a pair of motors each provided with a field winding, each connected to drive one of said reels, a

variable voltage generator for supplying all of said motors, means for reversing the rotation of all of said motors so that during succeeding passes each of said reels acts alternately as winding and unwinding reel, a pair of pilot generators designed to generate voltages linearly proportional to their speeds, each connected to be driven by one of said reels and having its armature connected to the field winding of the motor connected to the other of said reels whereby the speed or the motor driving the winding reel is varied so that the linear speed of the strip at the periphery of the coil of the winding reel is equalized with the speed of the strip emerging from said rolls.

HUGO HEYMANN.

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