US2087040A - Speed control for continuous strip mill - Google Patents

Description

July 13, 1937.

G. s. MICAN 7 SPEED CONTROL FOR CONTINUOUS STRIP MILL Filed Jan. 13, 1956 2 Sheets-Sheep 1 July 13, 1 937. G. s. MICAN SPEED CONTROL FOR CONTINUOUS STRIP MILL Filed Jail. 1a, 1936 2 Sheets-Sheet 2 D1 m 11:31 m H w Fatented July 13, 193? caries SPEED CONTROL FOR CONTDUUOUS MILL STRIP George S. Mican, Chicago, Ill. Application January 13, 1936. Serial No. 58,934

11 Claims.

The invention relates to improvements in apparatus for controlling the speed of continuous rolling mills and has reference particularly to improved apparatus for applying and maintaining a predetermined amount of tension on the material between the roll stands of a continuous hot strip rolling mill.

Heretofore the desired respective speeds of the successive roll motors of the individual stands of a continuous rolling mill have been .obtained approximately by the method of manually setting field rheostats for the roll motors respectively. The speed settings of the successive stands are based on the speed of the initial or entering stand of the-mill, on the respective reduction in each stand and on the intent to maintain a degree of termined amount of tension on the material be tween roll stands.

Another object of the invention is to provide improved means for automatically regulating the speeds of continuous mills by means of predetermined tension between stands and which will incorporate safety means for automatically regulating the speed of the various roll stands as the material enters and leaves said stands respectively.

With these and other objects in view the invention may consist of certain novel features of .con-

struction and operation, as will bemore fully described and particularly pointed out in the specification, drawings and claims appended hereto.

In the drawings which illustrate an embodiment of the invention and wherein like reference characters are used 'to designate like parts Figure 1 is a schematic illustration of two successive roll stands of a continuous rolling mill and which are shown equipped with the speed control apparatus of the present invention;

Figure 2 is a wiring diagram illustrating the electrical connections for the speed control mechanism; and

Figures 3, 4 and 5 are wiring diagrams showing the connections between the speed control mechanism and the motor for number I stand, number 8 stand and number 9 stand, respectively.

In Figure 1 the apparatus of the invention is shown in association with successive mill stands of a continuous rolling mill and which stands may perform the last rolling operation on the material, although it is of course understood that the invention is not limited in this respect. For 5 purposes of description the stand to the left may be considered as number 8 and the stand to the right as number 9, each comprising vertically extending spaced uprights ill which journal the upper and lower backing-up rolls II and the 10 working rolls i2. The material travels from left to right, entering number 8 stand where it is reduced in thickness and correspondingly elon-' gated and thereupon enters number 9 stand which further reduces and elongates the material. In practice the speed of the working rolls of a forward stand is somewhat greater than that of the rolls of the next adjacent rearward stand in order to compensate for the elongation in length of the material andsince it is desirable to maintain a certain amount of tension on the material between successive stands.

The speed control mechanism of the invention automatically regulates the speed of the forward working rolls responsive to the tension of the material between stands. The same consists of a looping roll it carried by the member I4 suitably .pivoted at iii to supporting structure. To the upper end of member i4 is pivotally connected an upright it which actuates a limit switch ll, said switch being closed when the looping roll i3 is positioned even with or below a horizontal plane represented by the material when the same travels between the stands with the proper tension thereon. Said switch is accordingly opened when the looping roll travels upwardly which takes place when the material between the stands becomes slack. Pivoted to the member I4 is a link l8 connecting at its other end with a counterbalancing arm 20 suitably journalled at 2| to the vertical standard 22 and carrJing on one end thereof theweight 23. Said arm to theleft of the pivot point connects with rod 24 joined tothe piston 25 adapted to have vertical reciprocat-' ing movements within the air cylinder 26. To the other side of the pivot II the arm connects with rod 2! which in turn actuates piston 28 having reciprocating movement in the oil cylinder 30.

The air line. it connects the valve housing 32 with the air cylinder 26. The valves of said' housing are in turn actuated by a motor operated thruster 33 and said housing is supplied with air under pressure from the air receiver 34 through pipe line 35. -The air receiver is equipped with a pressure governor 36 and connects with the air compressor 31 through the pipe line 38. With the thruster 33 in the position shown in the drawings the exhaust valve 45 is open and therefore the air cylinder 25 communicates with the atmosphere. With the thruster in its other position of operation the exhaust 40 will be closed and the pressure valve 4| will be opened, admitting air from receiver 34 to the connection 3| and eventually to the air cylinder 25 to produce upward movement of the looping roll t3.

The oil cylinder 30 is joined by pipe line 42 and branch lines 43 and 44 with an oil reservoir 45. Line 43 is provided with a relief valve 45 and line 44 with a shut-off valve 41. The oil cylinder 35 also connects through line 42 and line 48 with a second oil cylinder 50 provided with piston and connecting rod 52 in the form of a rack, whereby said rod can be elevated or lowered by operating an electric motor 53 operatively connecting with the racl; through gearing 54. The rack 52 extends upwardly through a stop plate 55 which supports counterweights 55. Said weights are elevated by the rod 52 when the same is forced upwardly either by actuation of the electric motor 53 or through pneumatic pressure existing within the oil cylinder 55. At its extreme upper end rod 52 provides a rack operatively connecting with a rheostat sweep arm 51 forming part of the rheostat which is electrically connected in the field of the roll motor of number 9 stand and therefore functions to control the speed of the working rolls of said stand. The oil line 48 joins with oil line 42 between the solenoid operated valves 50 and 5|, the former being normally closed and valve 5| being normally open. A by-pass 53 is provided around said valves 55 and 5|, said by-pass containing a third solenoid operated valve 54. During manual actuation of the mechanism described the solenoid valve 54 is open so as to connect the oil cylinder 35 with the reservoir 45, thus allowing actuation of the counter-balance arm 20 without effecting corresponding actuation of the rheostat sweep arm 51. For manual operation speed regulation and adjustment are obtained by means of an independent rheostat, not shown. When valves 5| and 54 are closed and the normally closed valve 50 isopen the oil cylinders 35 and 50 are joined in a closed system and pneumatic pressure induced in cylinder 25 is communicated to cylinder 50.

Referring to Figure 2, the various elements comprising the control apparatus above described are shown as connected in parallel to conductors LI and L2 which are electrically connected by means of a single throw double pole switch 59 with the power lines 55 providing the source of power for operating the apparatus. For manual control the switch 59 is first closed and then the selector switch 'I' is closed on the lower contact 51, energizing coil M which actuates to close the contactors Ml Closing of these contactors energizes the coil of solenoid valve 54 to cause opening of said valve. The circuit to the thruster motor 33 can then be closed by actuation of push button V to result in operation of the motor. Opening and closing the circuit to the thrustmotor will alternately open and close the valves 45 and 4| and therefore air under pressure can be admitted to the air cylinder 25 to raise the looping roll II or air can be exhausted from said air cylinder to lower said looping roll as desired.

For automatic control the switch T is closed and M2.

on the uppercontact 58, breaking the circuit to coil M and energizing coil N which efiects closing of the contactors Ni and N2, as a result of which the coil of solenoid valve 5| will be energized to open the valve since the looping roll l3 will normally assume its lowermost position, thus maintaining the limit switch |1- closed. The coil P of a time relay will also be energized upon closing of the contact NI and N2 which will have the effect of opening the contacts PI.

The above operations take place before the material enters the rolls of stand number 1. Referring to Figure 3, which shows certain electrical connections with the interpole field of the motor of stand number 1, it will be understood that the switch is first closed, which would result in energization-of coil D except for the fact that the contacts Al are normally open. When the material enters stand number 1 a voltage drop occurs across the interpole field 13, energizing coil A, closing the contacts Al, which energizes coil D to eifect closing of the contacts Dl. Referring again to the wiring diagram of Figure 2, it will be observed that contacts D| are in circuit with the coil G and thus closing of these contacts will energize coil G to cause closing of contacts GI and G2. With the closing of contacts Gl the coil of solenoid valve 50 is energized and accordingly said valve is opened.

The preliminary operations above described must take place before the material enters the rolls of stand number 8. When this occurs a voltage drop is likewise produced across the interpole field 14 of its respective roll motor. Coil B, Figure 4, is thereupon energized to close contacts Bl which energizes coil E since it is understood that switch 1| has'been previously closed. Energization of coil E effects a closing of contacts El which as shown in Figure 2 is in circuit with coil H, the same being thus energized, closing the butterfly contacts HL, The material thereupon enters number 9 stand and produces a voltage drop across the interpole field of the motor of said stand, energizing coil C, closing contact Cl, energizing coil F, closing contacts Fl. Fl is in circuit with coil J which is thereupon energized to cause closing of contactor J2 and the butterfly contacts J I. Energization of this coil also effects opening of the butterfly contacts J3. It will be observed that closing of the contacts HI and J I will short-circuit the time relay coil P, which allows the contacts Pl to again close. Closing of the contactor J2 completes the circuit to the thruster motor which is thereupon energized, with the result that the exhaustvalve 40 is closed and valve 4| is opened and air under pressure is admitted to the air cylinder 25. Opening of butterfly contact J3 preventsany possibility of motor 53 actuating the rheostat sweep arm 51 to speed up the motor of number 9 stand.

By admitting air under pressure to the air cylinder 25 the looping .roll l3 will be forced upwardly. If slack exists in the material mtween stands 8 and 9 upward movement of the looping roll II will be sufflcient to open the limit switch |1. As shown in Figure 2 this switch is in circuit with the coil of solenoid valve 5| and as a result said coil is deenergized, closing the valve. The oil cylinder 30 and the oil cylinder 50 are now connected in a closed circuit and any further upward movement of the looping roll will induce pneumatic pressure in oil cylinder 30 which will be communicated to cylinder 50 to eifect actuation of the rack 52 and sweep arm 51. As the looping roll I! travels upwardly, rack 52 likewise has upward. movement, rotating the sweep arm 51 in a direction to speed up the roll motor of number 9 stand to take up the slack in the material. The-mechanism will-now continue to operate automatically to maintain the proper tension on the material between stands.

In the event that the looping roll l3 does not have initial upward movement to open the limit switch I 1, which would indicate that the material is under tension greater than that desired, the following operations take place. As the limit switch I! remains closed and since contacts Pl are closed, the coil K will beenergized, closing the contactors KI and K2, which resultsin operation of motor 53 in a direction to turn rheostat sweep arm 51 to lower the speed of number 9 roll motor. This immediately causes slack in the material which allows the looping roll l3 to rise, thereupon opening limit-switch II which breaks the circuit to coil K and also the coil of the solenoid valve 6i. As aresult the oil cylinders 30 and 50 are placed in the closed circuit and actuation of the mechanism takes place automatically as described.

When the material leaves stand number i the voltage drop across the lnterpole field of its respective motor diminishes, deenergizing coil A, coil D and coil G. The contacts GI and G2 are accordingly opened which opens the circuit to and no other means of oil feed to cylinder 30.

was provided, the possibil ty of air binding would be encountered. In order to avoid this check valve 65 is incorporated in the system.

As the material leaves stand number 8 the drop in voltage across the interpole field of its respective motor also diminishes, deenergizing relay E. coil E, coil H, and thus opening butterfly contact HI. This permits the time relay coil P to reenergize, whereupon contacts Pi are opened, which by deenergizlng coil K, has the effect of preventing the rheostat motor from slowing up the motor of number 3 stand which would take place in the event limit switch l'l closes while the material is still between .number 8 and number 9 stands.

When the material leaves number 9 stand the drop in voltage across the interpole of its respective motor likewise diminishes deenergizing coil 0, coil F and coil J, which effects opening of the butterfly contact J I contactor J2 and closing of butterfly contact J3. The butterfly contact J3 is in.circuit with coil S and a limit switch WI which limits the travel of the rheostat motor in a'direction ofspeeding up the motor of numher 9 stand. In circuit with coil K is another limit switch W which limitstravel of the rheostat motor in the direction of slowing down the motor of number 9 stand. The circuit to the thruster motor 33 was opened as previously explained when the material left stand number I and accordingly air will be exhausted from cylinder 26 to allow the looping roll to descend to its lowermost position, whereupon limit switch ll will be closed. Closing of this switch energizes the coil of solenoid valve 6|, opening the valve to con-' nect oil cylinder 50 with the oil reservoir 45, allowing the counterweights 56 to descend and return the rheostat sweep arm to its normalposition which will slow down the motor of number 9 stand. I

and K2.

Limit switch W isclosed when the rheostat sweep arm is in the normal or mid-position. It opens only to limit the travel of the rheostat motor in the direction of slowing down number 9 roll motor. When coil K is energized, butterfly K3 is opened, the rheostat motor rotates moving rack 52 downward, closing limit switch Wi at the beginning of its downward motion. If rack 52 is still below normal or. mid-position when coil K is de-energized by the opening of'either limit switch W or H, WI will be closed and butterfly K3 will be closed by the opening of contactors Kl If the material is still in number 9 stand, J3 will be open. When the material leaves number 9 stand, J3 will close, coil S will be energized, closing contactors Si and S2 and opening butterfly S3 causing rheostat motor 53 to rotate to return rack 52 tomid-position. At mid-position, limit switch WI is opened and the rheostat motor is stopped. The return of the rheostat arm to normal position may be summarized as follows: If when the material leaves number 9 stand, the rheostat arm is in aposition to speed the material leaves number 9 stand, the rheostat arm is in a position to slow up number 9 roll motor, it is returned to a normal position by the rheostat, motor. i

From the foregoing, it will be understood that the speed control apparatus of the' invention is automatically actuated in response to the slack in the material between stands and therefore maintains a predetermined tension on the material. In the event the material is slack the. &

looping roll is permitted to rise, which results in the actuation of certain instrumentalities to speed up the motor of the forward stand, which takes up the slack and applies proper tension on the material. In case the materialis stretched by the initial speeds of the motors, then other elements are actuated to cause a reduction in the speed of the motor of the forward stand, thereupon producing some slack in the material. The invention further makes provision forproper control of the various ins'trumentalities as the material leaves the several stands having electrical connection with the control apparatus. Thus, as the material leaves stand number i of the apparatus disclosed the circuit to the thruster motor is opened so that the looping roll is permitted to descend and simultaneously therewith solenoid valve 6! is energized to open, breaking the closed oil circuit between cylinders 30 and tall. These operations and others which take place as the material leaves stand number 8 counteract the normal tendency of the motor of number 9 stand to speed up. The invention is not limited to the particular form of looping 9 the motor of stand 8 could be reduced in speed.

What is claimed. is: 1. In a. continuous rolling mill, the combination with successive roll stands, of movable means located between a pair of stands and having motion some component of which is' perpendicular to the plane of travel of the material, pneumatic pressure means operatively connecting with said movable means for maintaining the same in contact with said material, control apparatus including a field rheostat adapted to regulate the speed 01 one roll stand of said pair of stands between which said movable means is located, and a. pneumatic pressure line connecting said movable means and said field rheostat whereby said rheostat is actuated responsive to the motion of said movable means, said pressure line being automatically connected to a reservoir as the end of the material leaves the stand immediately forward of said pair of stands, thereby rendering inoperative the connection between said movable means and field rheostat.

2. In a continuous rolling mill, the combination with successive roll stands, of movable means located between a pair 0! stands and having motion some component 0! which is perpendicular to the plane or travel of the material, pneumatic pressure means operatively connecting with said movable means for maintaining the same in contact with said material, control apparatus including a field rheostat adapted to regulate the speed of one roll stand of said pair 01' stands between which said movable means is located, a pressure cylinder operatively connecting with said movable means, a second pressure cylinder operatively connecting with the field rheostat, and a pressure line connecting said cylinders whereby said field rheostat is ac-- tuated responsive to the motion of said movable means, said pressure line being automatically established by the initial travel of the material between stands provided said movable means is permitted to move ina direction indicating the existence of slack in said material.

3. In a continuous rolling mill, the combination with successive roll stands, of movable means located between a pair 0! stands and adapted to have motion some component 01' which is perpendicular to the plane of travel of the material, means operatively connecting with said movable means for maintaining the same in contact with said material, control apparatus including electrical means adapted to regulate the speed or one roll stand of the-pair oi! stands between which said movable means is located, a pressure cylinder operatively connecting with said movable means, a second pressure cylinder operatively connecting with the electrical means, a pressure line connecting said cylinders and being joined at a mid-point to a reservoir containing a pressure medium, a valve for closing the connection between said pressure line and reservoir rendering said pressure line operative whereby said electrical means is actuated responsive to the motion of said movable means, and means actuated by the movement of said movable means in a. direction indicating the existence of slack in the initial travel of the material between the stands and eiifective to cause said valve to close. 1

4. In a continuous rolling mill, the combination with successive roll stands, or movable means located between a pair of stands and adapted to have motion some component of which is perpendicular to the plane of travel of the material, means operatively connecting with said movable means for maintaining the same in contact with said material, control apparatus including electrical means adapted to regulate the speed of one roll stand of the pair of stands between which said movable means is located,

a pressure cylinder operatively connecting with said movable means, a second pressure cylinder operatively connecting with the electrical means, a premureline connecting said cylinders and being Joined at a mid-point to a reservoir containing a pressure medium, a valve for closing the connection between said pressure line and reservoir rendering said pressure line operative whereby said electrical means is actuated responsive to the motion of said movable meanl. and a limit switch actuated by movement of said movable means in a direction indicating slack in the material between the stands and effective to render said pressure means operative, whereby said field rheostat is actuated responsive to the motion of the movable means.

5. In a continuous rolling mill, the combination with successive roll stands, of movable means located between a pair 0! stands and adapted to have motion some component of which is perpendicular to the plane of travel of the material, pressure means operatively connecting with said movable means for maintaining the same in contact with the material, control apparatus including a field rheostat adapted to regulate the speed of one roll stand of the pair of stands between which said means is located, pressure means connecting said movable means with the field rheostat whereby said field rheostat is actuated responsive ,to the motion oi. the movable means, and an electric motor operatively connecting with said field rheostat, said motor providing auxiliary means for actuating said rheostat.

6. In a continuous rolling mill, the combination with successive roll stands, of movable means located between a pair of stands'and adapted to have motion some component of which is per- I pendicular to the plane of travel of the material, pneumatic pressure means operatively connecting with said movable means for maintaining the same in contact with the material, control apparatus including a field rheostat adapted to regulate the speed or one roll stand of the pair 0! stands between which said means is located, pressure means connecting said movable means with the field rheostat, means actuated by movement of said movable means in a direction indicating slack in the initial travel of the material between said stands and efiective in rendering said pressure means operative, whereby said field rheostat is actuated responsive to the motion of the movable means, an electric motor operatively connecting with the field rheostat, said motor being operative to actuate the rheostat in the event slack does not exist in said material preventing motion of said movable means.

'7. In a continuous rolling mill, the combination with successive roll stands, of movable means located between a pair of stands and adapted to have motion some component 01' which is perpendicular to the plane of travel of the material, pneumatic pressure means operatively connecting with said movable means for maintaining the same in contact with the material, control apparatus including a field rheostat adapted to regulate the speed of one roll stand of the pair of stands between which said means is located, pressure means connecting said movable means with the field rheostat and constructed'and arranged to actuate the field rheostat responsive to the motion of said movable means, an electric motor connected to said field rheostat for actuating the same, and means controlling the operation of said motor,.said means being rendered operative during the initial travel of the material between stands in the event slack does not exist in said material and also being rendered operative as the end of said material leaves the forward roll stand of said pair.

8. In a continuous rolling mill, the combination with successive roll stands, of a motor for driving the rolls of each stand,-a movable member located between a pair of stands and adapted to contact the material, a valve for regulating the; movement of said member to cause the same'to move into contact with the material or recede therefrom,- control apparatus including electrical means adapted to regulate the speed of one roll stand of said pair of stands between which said movable member is located, pressure means connecting the movable member and said electrical means whereby said electrical means is actuated responsive to the motion of said movable member, and an electrical connection between said regulating valve and the motor of the last roll stand of said pair of stands, said electrical connection being constructed and arranged to effect actuation of said valve when the material enters said last r011 stand to produce movement of the movablemember into contact with the material.

9. In a continuous rolling mill, the combination with successive roll stands, of a motor for driving the rolls of each stand, a movable member located between a pair or stands and adapted to contact the material, a valve for regulating the movement of said member ,to cause the same to move into contact with the material or recede therefrom, control apparatus including electrical means adapted to regulate the speed of one roll stand of said pair of stands between which said movable member is located, pressure means conthe material leaves said preceding roll stand to produce movement of the movable member out of contact with the material.

10. Ina continuous rolling mill, the combination with successive roll stands, of a motor for driving the rolls of each stand, a movable member located between a pair of stands and having motion some component of which is perpendicular to the plane of travel of the material, pressure means for producing movement of said movable member, motor actuated regulating valves for regulatingsaid pressure means to cause movement of said member, whereby said member may be caused to move into contact with the material or recede therefrom, control apparatus including electrical means adapted to regulate the speed of one roll stand of said pair of stands between which said movable member is located,

a pressure line connecting the movable member and said electrical means, whereby said electrical means is actuated responsive to the motion of said movable member, and an electrical connection between the motor of said regulating valves and the motor of the last roll stand of said pair of stands, said electrical connection being constructed and arranged to effect actuation of said valves when the material enters said last roll stand to produce movement of the movable member into contact with the material.

11. In a continuous rolling mill, the combina tion with successive roll stands, of a motor for driving the rolls of each stand, a movable member located between a pair of stands and having motion some component of which is perpendicular to the plane of travel of the material, pressure means for producing movement of said movable member, motor actuated regulating valves for regulating said pressure means to cause movement of said member, whereby said member may be caused to move into contact with the material or recede therefrom, control apparatus including electrical means adapted to regulate the speed i of one roll stand of said pair of stands between which said movable member is located, a pressure line connecting the movable member and said' electrical means, whereby said electrical means is actuated responsive to the motion of said movable member, an electrical connection between the motor of the regulating valves and the motor of the roll stand preceding. said pair of stands, said electrical connection being constructed and arranged to effect actuation of said valves when the material leaves said preceding roll stand to 'producelmovement of the movable member out of contact with the material. I GEORGE S. MICAN.

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