US2193189A - Control means for rolling mills - Google Patents

Description

March 2, 940. E. B. BROOKE Em 2 193 189.

CONTROL MEANS FOR ROLLING MILLS Filed Oct. 21, 1938 1 I INVENTORS .rpWARD .B. BR DUPWA RD MORGAN BYWYM Paiwntcd Mar. 12, 1940 PATENT OFFICE CONTROL MEANS FOR ROLLING IVIILLS Edward B. Brooke, Birmingham, and Durward Morgan, Fairfield, Ala.; said Morgan assignor to said Brooke Application October, 21,

6 Claims.

This invention relates to control means for a continuous strip steel rolling mill, and has for an object the provision of means for controlling the relative speeds of adjacent pairs of rolls in such a mill whereby to avoid tension on the strip as it is being rolled.

A further object of our invention is to provide a means for controlling the speed of adjacent pairs of rolls in a continuous strip rolling mill;

q whereby a predetermined sag in the material between the pairs of rolls may be maintained.

A still further object of our invention is to provide a system of control for the driving means for adjacent pairs of rolls in a continuous strip rolling mill, which shall include electro-magnetic means positioned beneath the strip between the pairs of rolls, and speed control means responsive to entrance into and departure from the magnetic field of said electro-magnetic means, to vary I the relative speeds of the adjacent pairs of rolls.

A still further object of our invention is to providean improved electro-magnetic relay for controlling the speed of the driving means for rolls in a continuous strip rolling mill.

As is well known in the art to which our invention relates, it is essential that the strip in a continuous strip mill be rolled substantially without tension between adjacent pairs of rolls, and also that it be prevented from sagging too much between adjacent pairs of rolls. Too great tension on the strip tends to distort and weaken it, while too great a sag between pairs of rolls will bring about buckling and crumpling of the sheet. Intin plate mills, also, it is highly important that the strip shall not touch or rub against anything other than the rolls in its course through the mill, or else the plating is marked and its value impaired. This last mentioned requirement renders objectionable the use of ordinary limit switches actuated by mechanical contact with the strip. It is accordingly a principal. feature of our invention that our improved control operates by entrance of the strip into or departure from the magnetic field of an electro-magnetic relay, and there is avoided actual physical contact of the strip with anything other than the rolls.

Briefly, our invention comprises a suitable motor drive for adjacent pairs of'rolls through which the steel strip passes, which strip is permitted a predetermined amount of sag between the rolls in order to avoid tension therein. Positioned'beneath the sag of the strip are a pair of electromagnetio'relays having elements movable upon entrance into or departure from the magmas, Serial No. 236,174

netic field thereof by the strip being rolled. The electro-magnetic relays serve to vary the relative speeds of the driving motors for the rolls, as by varying the resistance in the exciter field of one of the motors, though it will be apparent from a further description of our invention, that the relays may be employed to vary the speed of the driving means in any suitable manner known to the art.

Our improved relay embodies a coil having a fixed core and is mounted upon one end of a tilting bar carrying contacts on its opposite end and adapted to open and close a suitable control circuit. The relay is so located with respect to the moving strip that when the strip enters the magnetic field of the coil, the coil moves toward the strip and closes its associated circuit. When the strip leaves the magnetic field of the coil, the Weight of the coil and its core causes that end of the bar to move downwardly and open the control circuit. By placing one such relay farther from the strip than the other, and so operating the mill that the circuit of one relay is normally closed while the other is open, the relative speeds of the driving motors may be so controlled as to maintain a predetermined sag in the strip between the pairs of rolls.

Apparatus embodying features of our invention is illustrated in the accompanying drawing forming a part of this application, in which:

Fig. 1 is a diagrammatic view of the control means;

Fig. 2 is a diagrammatic view illustrating adjacent pairs of rolls and the location of the relays with respect to the sag in the strip between the pairs of rolls;

Fig. 3 is a side elevation of one of the electromagnetic relays; and

Fig. 4 is an end elevation thereof.

Referring to the drawing for a better understanding of our invention, I show adjacent pairs oi rolls Ill and H between which a continuous steel strip I2 passes. -The rolls Ill and II are driven by motors l3 and M respectively, at such, relative speeds that there is a sag in the strip l2, as shown in Fig. 2, to prevent tension of the strip and also to prevent the strip buckling between adjacent pairs of rolls. For the purpose of illustration, the motor l4 may be a constant speed motor and the motor I3 have its speed controlled so as to maintain the proper sa'g in the strip 12. It will be understood, however, that either or both of the motors may be controlled so as to maintain the proper relative speeds between adjacent pairs of rolls.

two electro-magnetic relays RI and R2.

Referring particularly to Fig. 1 for a specific embodiment of the speed control meansr the motor I3 is shown as having a series field winding I6 and a separately excited field winding I1, the winding I1 being included in an exciter circuit consisting of wires I6 and I9. A manually controlled rheostat 2| is included in the exciter circuit and serves to provide as close a manual control of the speed of the motor I3 as is possible. Additional adjustable rheostats 22 and 23 are adapted to be included in the exciter circuit or be short circuited to further vary the speed in response to the position of the strip I2, as hereinafter explained.

Positioned beneath the sag of the strip I2 are Each of the relays RI and R2 comprises a coil 24 constantly energized by a circuit I5. Each coil 24 has a steel core 26 and is mounted upon one end of a tilting bar 21, made of non-magnetic material and pivotally mounted at 28 to a support 29. The support 26 is in turn mounted upon a base 3| of non-magnetic material which carries corner supports 32, and 33 having a plate 34 mounted on the upper ends thereof. The plate 34 is also made of non-magnetic material, such as brass. The weight of the coil 24 and its associated parts is counter-balanced by a spring 36 positioned between adjusting nuts 39 on a threaded stem 31 extending downwardly into the spring 36 from the core 26, and a lower set screw 38 carried by the base 3|. The position of the coil may be adjusted by adjusting the position of the nuts 39 on the stem 31, and thus raise or lower the coil with respect to the spring 36. At the opposite end of the tilting bar 21 is yieldingly mounted a cross bar 4| by means of a screw 42 extending upwardly into the tilting bar 21 and a spring 43 surrounding the screw. On the ends of the cross bar 4| are contacts designated 44 and 46 with respect to relay RI, and as 41 and 48 with respect to relay R2.

The contacts 44 and 46 are adapted to coact with contacts 5| and 52, the contact 5| leading tothe rheostat 2| through wire 26, and the con tact 52 leading through wire 56 to the rheostat 22, which latter rheostat is connected on the other side to the wire 26 by a lead 53.

The contacts 41 and 46 are adapted to coact with contacts 54 and 56. The contact 54 is connected to the rheostat 23 and to wire I6, while the contact 56 is connected to a wire 51 which is connected to the wire 56 and to the other side of the rheostat 23 through wire 55. A resistance 56 and a condenser 56 are interposed across each of the circuits controlled by the relaysRI and R2 to prevent arcing upon breaking of the circuit and'to discharge induced current occurring upon breaking of the circuit. 1

In practice, the relay R2 is located nearer the strip I2 than is the relay RI, and is so located that the strip I2 is normally within the magnetic field of the coil 24. The coil is thus attracted toward the strip and is held in its upward position and the contacts 41 and 46 are held down against the contacts 54 and 56. The relay RI being positioned lower than the relay R2, the strip I2 is above the magnetic field of its coil 24 and the contacts 44 and 46 are accordingly normally separated from the contacts 5| and 52 so that the circuit controlled thereby is open. The exciting current, under such conditions, passes through the field I1, the wire I6, through closed contacts 54, 41, 46 and 56, wires 51 and 56, rheostat 22, wires 53 and 26, through rheostat 2|, and

and 23 would thus be short circuited, reducing the resistance in the exciter field I1 and decreasing the speed of the driving motor I3. As soon as the sag in the strip I2 has reached the full line position of Fig. 1, it is outside the magnetic field of the relay RI and the parts again assume the positions shown in Fig. 1, with the motor I3 runningat normal speed.

Should the sag in the strip I2 become shorter so that it is raised to the upper dotted positions of Figs. 1 and 2, it would leave the magnetic field of relay R2, and its coil 24 would then move down, raising the contacts 41 and 46 off of the contacts 54 and 56, thus opening the circuit. The exciting current would then flow through the field I1, wire I6, rheostat 23, wires 51 and 56, rheostat 22, wires 53 and 26, and thence through rheostat 2| to wire I9. The resistance of the rheostats 22 and 23 would thus be added to the exciter field current, causing the speed of the motor I3 to increase and thus cause the strip I2 to sag lower until it again comes to the full line position of Figs. 1 and 2, and causes the speed of the driving motor I3 to be restored to normal.

It will thus be seen that the relays RI and R2 act as upper and lower limits for controlling the speed of the driving motor I3 and to maintain it at a normal speed whereby to maintain a predetermined looseness or sag in the strip I2 between the adjacent pairs of rolls I6 and II. It will also be apparent that the limits may be varied by varying the positions of the relays RI and R2 with respect to the strip and to each other or by varying the energizing current in the relays by any suitable means, not shown.

While we have shown our invention in but one form, it will be obvious to those skilled in the art that it is not so limited,'but is susceptible of various. changes and modifications, without departing from the spirit thereof, and we desire, therefore, that only such limitations shall be placed thereupon as are imposed by the prior art or as are specifically set forth in the appended claims.

What we claim is:

1. A control means for continuous strip steel rolling mills in which the strip is allowed to sag between adjacent pairs of rolls, comprising a motor for driving one pair of the rolls, an electromagnetic means containing movable elements adapted to be attracted by the strip disposed adjacent the strip between the pairs oi rolls in position for the strip to enter its magneticfield and effect movement of said elements when the sag in the strip is abnormal, and means responsive to movement of the movable elements of said electro-magnetic means to vary the speed of the motor.

2. A control means for continuous strip steel rolling mills in which the strip is caused to sag between adjacent pairs of rolls, comprising a motor for driving one pair of rolls. electro-magnetic means between the pairs of rolls beneath the sag in the strip and containing elementsadapted to be attracted by the strip and movable upon en- 1| trance into and departure from the magnetic iield thereof by said strip, andmeans responsive to movement of said elements for varying the speed'of said motor.-

3. A control meansior continuous strip steel rolling mills comprising a pair of eiectro-magnets disposed beneath the strip between 'adja-' cent pairs of rolls and containing elements adapted to be attracted by the strip andmovable responsive to entrance into and departure from the magnetic fleldthereoi by said strip, means for driving the rolls, and means responsive to movement of said elements to vary the speed of the driving means.

4. In a continuous stripsteel-rolling miil,- adjacent pairs of rolls between which thestrip is allowed to sag, a pair of electro-magnets each having elements movable upon entrance into and departure irom the magnetic field thereof by said strip, one of said-'electro-magnets being positioned nearer said strip than the other, driving means for the rolls, and means responsive to movement of said elements for varying the speed means responsive to movement of said elements for varying the relative speeds of said drivingmeans.

6. In a control means for a continuous strip steel rolling mill, motor driven adjacent pairs of rolls through which the strip passes, a pair of electro-magnetic relays disposed intermediate adjacent pairs of rolls so that the strip is free to enter into and leave the magnetic fields thereof without physically engaging the relays, each of said, relays comprising a movable .coil having a fixed core, a pivoted bar upon which the coil is mounted. speed control circuits for said motor driven rolls associated with each of the relays, and means carried by the pivoted bar for opening and closing the said control circuits upon movement of the coil responsive to entrance of the strip into and departure from the magnetic field of said electro-magnetic relays.

' DURWARD MORGAN.

EDWARD B. BROOKE.

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