US3151508A

US3151508A - Apparatus for controlling a continuous rolling mill to maintain constant gage in theleading and trailing ends of strip lengths

Info

Publication number: US3151508A
Application number: US517504A
Authority: US
Inventors: Robert W Holman; James E Mcnamara
Original assignee: United States Steel Corp
Current assignee: United States Steel Corp
Priority date: 1955-06-23
Filing date: 1955-06-23
Publication date: 1964-10-06
Anticipated expiration: 1981-10-06
Also published as: FR1154539A; DE1116308B; NL104993C; US3029373A; BE548912A; GB813130A; LU34447A1

Description

1964 R. w. HOLMAN ETAL 3,151,503

APPARATUS FOR CONTROLLING A CONTINUOUS ROLLING MILL T0 MAINTAIN CONSTANT GAGE IN THE LEADING AND TRAILING ENDS 0F STRIP LENGTHS Filed June 23, 1955 2 Sheets-Sheet 1 INVENTORS.

ROBERT W HOLMAN and JAMES E. Mc NAMARA,

AmuA/ozem their Attorney.

3,151508 CGNTROLLING A CONTINUOUS ROLLING MAINTAIN CONSTANT GAGE Gci. '5, 1964 R. w. HOLMAN ETAL APPARATUS FOR MILL TO IN THE LEADING AND TRAILING ENDS OF STRIP LENGTHS 2 Sheets-Sheet 2 Filed June 23, 1955 Y INVENTORS ROBERT m HOLMANand -JAME$ E. Mc NAMARA,

their Attorney.

United States Patent APE'ARATUS rota cor irrihrrnto a courmooos ROLLTNG M'EL hlAlNTAIN CSNSTANT GAGE ZN TEE AND TRAELYING 9? STAR? LENGTHS Robert W. Holman, Pittsburgh, and ames E. McNamara,

Bridgeville, Pa, assignors to United States Steel iorporation, a corporation or" New .l'erse Filed dune 23, 1955, Ser. No. 5117,5134- 17 (Ql. till-) This invention relates to the cont nuous hot-rolling of metal and, more particularly, to the con rol of the several stands of a rolling mill in order to maintain a constant gage in the leading and trailing ends of strip length Specifi ally the invention relates to a control system for the motors of a continuous mill for rolling breakdowns into strip, whereby the ed of the second and each subsequent mill stand of the finishing train is reduced temporarily as the leading end or" a breakdown approaches it and again as the trailing end of the breakdown leaves the preceding stand. The effect of such control is to reduce the abnormally heavy tension to which the leading end is subjected on entering successive stands, thereby preventing an excessive reduction of the leading. end as a result or" the added tension otherwise existing. A further effect is to prevent an increase in thickness at the trailing end of the breakdown as a result of the loss of tension which would otherwise occur, by increasing the tension on that portion thereor between the second and third stands, after the trailing end leaves the first stand, and so on.

When a breakdown rolled from a hot slab in the roughing train of a continuous mill is put through the finishing train of the mill to reduce it to a strip or" predetermined gage, there is usually a gradual increase in the strip thickness above that which should be maintained at any stage of the rolling, because the breakdown is being rolled at continuously decreasing temperatures. Usually, furthermore, there is an appreciable amount or tension on the strip as it passes through the finishing train, and there will also be rapid changes in thickness as the head end of the breakdown enters the finishing train andas the trailing end leaves The increase in finished thickness at the trailing end is more serious. This invention relates to means for eliminating the chan s of thickness of the finished strip resulting from vary ng tension.

The motors driving the finishing stands of a hot-strip mill are usually designed with drooping speed characteristics, i.e., the motor speed will decrease with increasing load, to the extent of two percent or more, from no load to full load. The finishin train is thus stable and easily controlled since the overall system tends to be self-regulating. if, at any instant, the mill stand speeds are not exactly proportional relative to the desired percentages of strip reduction at each stand, the stand which is running too fast will increase tension at the input side and relax tension at the output side, thus increasing its motor load which will cause the speed to decrease, thereby tending to correct the unbalanced tension conditions. This stand which is running too fast will also affect the preceding and succeeding stands in a manner which will stabilize the system, since an overhauling load will be transmitted by tension to the preceding stand, thus causing it to speed up and relax tension, and the load on the succeeding stand will decrease because its back tension has been relaxed and it will therefore speed up to again establish tension. Thus the system is stable and does not require exact presetting of motor speeds and roll positions and continual adjustments to meet strip conditions, as would be required if the drive motors were designed with flat speed characteristics.

Patented Get. 6, 1964 ice Usually the operator will adjust each motor to operate on no-load at a speed slightly higher than anticipated rolling speed so that under normal rolling conditions, a motor will not cause the strip to form a loop on the entry side of a mill. trip tension will be established when the strip is in the mill, furthermore, after motor speeds have decreased in accordance with their speed characteristics described above. As the breakdown enters each stand, however, the motor is initially running faster than its full-load speed. Because of the large inertia of each mill stand and drive motor, the slow-down from initial or no-load speed to full-load or normal rolling speed cannot be instantaneous and the head end of the breakdown, in causing this slow-down, is subjected to excessive tension as it enters each stand, depending on the amount or" speed differential, motor speed regulation and the time constants of the system. When the initial se -up of the mill is such that tms over-tension condition will exist, the finished thickness at the head end will be less than desired and there will be variations in the finished thickness over a length of finished strip which is equivalent to the volume of strip between the first and last stand. Stable rolling conditions thus established continue until the trailing end of the strip starts to leave he finishing mill stands.

When the trailing end of the breakdown leaves the first stand there is a loss of tension on the portion thereof between the first and second stands, and the strip enters the second stand at a thickness greater than during normal rolling. Because of the elasticity of the mill housings, the thickness of the strip at the delivery side of the second stand will immediately increase. As the trailing end leaves the second stand, there is loss of tension on the portion of the breakdown between the second and third stands. Consequently, the thickness of the strip at the output side of the third stand will increase immediately. This increase in thickness is progressive as the strip leaves each mill stand. These individual losses of tension will result in a progressive increase in finished thickness over a length of finished strip equivalent to the volume of metal in the portion of the breakdown between the first two stands. There is an additional efiect of loss of tension reflected through the mill as discussed below.

When the trailing end of the strip leaves the first stand and tension is lost on the breakdown portion between the first and second stands, the load on the second stand decreases somewhat, depending on the amount of tension previously maintained between the first two stands and the second stand will speed up slightly because of the speed characteristic of its motor. This results in an 'mrnediate decrease in tension between the second and third stands, which decreases the load on the third stand, thus decreasing tension between the third and fourth stands. In this same manner, tension decreases between the fourth and fifth stands and between the fifth and sixth stands. Thus, loss of tension between the first and second stands results in an immediate decrease in tension between the fifth and sixth stands and the thickness of the finished strip will increase. This reflected loss of tension and resulting increase in thickness occurs as the trailing end of the strip leaves each stand. Therefore, if strip tension is established through the finishing train and the main drive motors have drooping speed characteristics, the th ckness of the finished strip will start to increase as soon as the trailing end leaves the first stand and will increase progressively as the trailing end leaves each stand. The amount of increase in thickness depends on the amount of tension previously established.

There are thus two effects of tension on the thickness of the finished strip at the trailing end; one, the individual loss of tension between adjacent stands, and the other,

' illustrating the present preferred embodiment.

3 the reflected decrease in tension between the last two stands. This increase in thickness at the trailing end has been observed to be as much as 10%, which can result in considerable waste product and increase the manufacturing difiiculties encountered in processes subsequent to the hot-rolling operation. This invention relates to a system of control to alleviate these efiects of tension on finished thickness. The control will operate in such a manner as to decrease temporarily the speed of the main drive motors of the second through the fifth stands as the breakdown enters each immediately preceding stand and again as the breakdown leaves the preced ing stand. 7

We accomplish this object by providing means responsive to the passage of the leading end of a breakdown through the first stand of a finishing train for example, efiective to superimpose a temporary supplemental control on the speed of'the motor driving the second stand, to slow it down temporarily so it will not exert excessive tension in being slowed by the work to normal running speed. The control is removed as normal rolling conditions are achieved. Similarly, the temporary speed reduction is applied to the second stand when the trailing end leaves the first stand. The resulting increased tension causes the trailing end to be reduced more than it otherwise would be, thereby compensating for the thickening effect which would normally occur as above described. The temporary supplemental speed control applied first to the motor of the second stand is later applied to the motor of the third stand when the leading end enters the second stand and again when the trailing end leaves it and so on.

A complete understanding of the invention may be obtained from the following detailed description and explanation which refer to the accompanying drawings In the drawings:

FIGURE 1 is a diagrammatic showing of the first two stands in the finishing train of a continuous hot-strip mill, the motors driving them and some of the auxiliary control devices;

FIGURE 2 is a circuit diagram showing the speed control means provided for each of the motors of the second and succeeding stands; and

FIGURE 3 is a schematic circuit showing the control relays for bringing the control means of FIGURE 2 into operation at the proper times.

Referring now in detail to the drawings, and for the present to FIGURE 1, mill stands 1 and 2 are driven by

motors

3 and 4 respectively. These stands are the first two of, for example, a six-stand finishing train following a roughing train of four stands (not shown). A tachometer generator 5 is driven by motor 4. The speeds of

motors

3 and 4 are manually controlled by motordriven main field rheostats 6 and Vernier rheostatsida, only 'those for motor 4 being shown in FIGURE 1. Supplemental control of the excitation of .motor 4 is effected by a regulator 7. The motor 4 normally operates at a speed somewhat greater than that of motor 3 because of the elongation of the breakdown 8 effected in stand 1, and the need to maintain the portion thereof between the stands under tension to aid the reduction. This tension is abnormally high when the leading end of the breakdown enters stand 2 running at no-load speed. The tension on this trailing end is relieved, however, the instant it leaves the stand 1, so far as the portion of the breakdown between stands 1 and 2 is concerned.

Motor-field regulator 7 is controlled by a speed-follower potentiometer 10 and tachometer generator 5. A speed-follower regulator 9 controls a motor 11 which drives potentiometer 10. Regulators 7 and 9 are Arnplidyne generators driven by a motor 12. The circuits of the various control devices, as shown in detail in FIGURE 2, are completed through a control panel 13. A manual rheostat 14 is also connected thereto for adon the entry side of each stand, by

load cells

17 and 13 mounted on the stands so as to be afiected by the stretch thereof under load, or by shunts 19 and 2t) responsive to the current drawn by motors?) and 4. Whatever the.

source of the signal, it is' amplified and supplied to a control relay associated with each stand, those for stands 1 and 2 being designated 21 and 22, after a suitable time delay introduced by any convenient means indicated at 21' and 22'. 7

FIGURE 2 shows the circuits of the speed-control system for motor 4 indicated schematically in FIGURE 1. The motor of each succeeding stand is provided with the same speed-control system. Control of the speed'of motor 4 is efiected by varying the excitation of its field' the winding of which, indicated at 23, is connected across an

excitation bus

24, 24 in series with rhcostat 6 and regulator 7. Regulator 7 has a dilterential field 25 which normally tends to reduceits terminal voltage, and acts to stabilize this voltage when excitation is maintained by a main or control field winding 27 adapted to be connected across generator 5 in series with potentiometer 10. Regulator 7 has a third field winding 26 adapted to be connected across regulator 9 in order to anticipate the speed levels to be controlled. Regulator 3 has a difierential stabilizing field winding 28 and a speed-anticipating field winding 29 connected across the secondary of a transformer 39 the primary of which is connected across generator 5. Regulator 9 has a main or control field winding 31 connected across an

excitation bus

32, 32 in series with potentiometer 1t and rheostat 14. Currentlimiting resistors are indicated in FIGURE 2 by blocks labeled R. The resistance elements of the rheostats are similarly shown.

The speed-control system of FIGURE 2 is brought into play through the operation of

relays

21 and 22 and auxiliary relays shown in FIGURE 3 which will be desig-.

nated specifically during the following explanation of the operation. Before a breakdown, reduced from a starting slab by the roughing stands, enters stand 1, the speeds of all the motors driving the finishing stands are adjusted to the proper values by operating rheostats 6, 6a and others similar thereto for each main drive motor such as 3 and 4. Rheostat 14 is also adjusted to effect a predetermined reduction in the speed of motor 4 as the breakdown enters stand 1. This reduction is brought about in a manner now to be explained.

When the mill is idling,

motors

3 and 4 turn at their no-load speeds determined by the setting of rheostats 6.

on the setting of rheostat 14. Any difference between.

the voltage drop from 1411 to 5b and the drop from contact finger ltla of potentiometer 10 to 51;, will appear across winding 31, contact 33a of a relay 33 being normally closed. This voltage will cause regulator 9 to apply a voltage to motor 11, contact 33b of relay 33 being normally closed, in a direction such as to restore the balance between

voltages

10a, 5b and 14a, 5b. Thus these voltages are kept balanced until the speed control is initiated.

As the breakdown enters-stand 1, relay 21 is energized after the lapse of a definite time, completing a circuit for relay 33 at contact 21a (see FIGURE 3). thereupon opens contacts 33a, 33b and 330 and closes This relay 7 3,151, sea

contacts 33d, 33:: and a contact 33; in the circuit of the secondary of transformer 3t initiating operation of the speed-control system to reduce the speed of motor 4. This results from the fact that the difference between voltages 5a, 5b and i sa, 5b appears across winding 27 whereupon regulator 7 adds an incremental voltage to increase the current through motor-field winding 23, decelerating the motor 4. The slowing down of motor 4- continues until voltage 5a, 5b is equal to the voltage 190, 517.

While the speed of motor 4 is changing, the voltage applied to the primary Winding of transformer 3% by generator 5 also changes and this induces a voltage in the secondary winding which is applied to winding 29 The effect of the energization of winding 25? is applied by regulator 9 to winding 26 of regulator 7 in such direction as to prevent overshooting in the control of the speed or" motor 4 by winding 27 of regulator 7 when relay 33 is energized.

Reduction of the speed of motor 4- is effected as explained above while the leading end of the breakdown is advancing from stand 1 to stand 2. On entering the latter the breakdown causes energization of relay 22 which closes a contact 22a, energizing a relay 34 (see FIGURE 3). Relay 34 opens a contact 34:: in the circuit of relay 33, deenergizing the latter, whereupon it closes contacts 33a, 33b and 330 and opens

contacts

33a, 33a and 33 This takes the supplemental speed-control means for motor 4 out of operation. Relay 34 also closes a contact 34!) energizing a relay 35. Relay 22 also closes a contact 22b and brings into operation a similar speed-control means for the motor driving the third stand by energizing a relay as and so on up to the sixth and last stand. Timers 21' and 22, shown in FIGURE 2, are used to incorporate proper timing between the initiating signal and energization of relays 21 md 22 so that the controls can be initiated at the proper instant with respect to position of the leading or trailing end of a breakdown.

As already pointed out, the system of our invention not only decelerates the motors driving the several stands successively as the leading end of a breakdown approaches them but also effects a similar speed adiustmerit as the trailing end leaves the preceding stand. After the initial speed adjustment, the motors return to their normal rolling speeds as determined by the settings of their rheostats 6 and 60. When the trailing end of the breakdown leaves stand 1, relay 21 is deenergized, closing a contact 2117. A contact 35a having previously been closed by relay 35, relay 33 is again energized and closes its own sealing circuit at contact 33g.

The second energization of relay 33 again brings into operation the supplemental speed control means to reduce the speed of motor 4 slightly, increasing the tension etween the second and third stands to compensate for the loss of tension between the first and second. When the trailing end of the breakdown leaves stand 2, relay 22 is deenergized, opening the circuit of relay 34 at contact 22a. Deenergization of relay 34 opens the circuit of relay 35 at contact 3419 and deenergization of relay 35 opens contact 351: deenergizing relay 33. This restores all the control elements for motor 4 to starting conditions. Contacts 39a and 395 are those of a relay similar to

relays

21 and 22, controlled by the entrance of the breakdown into the third stand. By this and other similar relays for the several stands, similar reductions of the speeds of the motors of stands three through five occur successively as the trailing end of the breakdown proceeds through the stands. No reduction of the speed or" the sixth stand is necessary because no tension is possible after the strip leaves the fifth stand. The overall result, however, is that the system provides compensation for the loss of tension at each stand individually as the trailing end leaves it, plus the reflected loss of tension between the fifth and sixth stands.

it will be apparent from the foregoing that our invention provides means effective to prevent excessive tension on the leading end of a breakdown as it enters successive stands of a continuous mill and to compensate for loss of tension on the trailing end as it leaves successive stands. As a result, variations from desired gage in the portions of the finished strip adjacent the ends are greatly reduced and a more nearly uniform gage is maintained throughout the entire length or" the strip. The system is fully automatic and requires no attention when it has once been installed and adjusted.

Although we have disclosed herein the preferred embodiment of our invention, we intend to cover as well any change or modification therein which may be made without departing from the spirit or" the invention or the scope of the appended claims.

We claim:

1. t continuous rolling mill comprising several mill stands arranged in tandem, a motor for driving the rolls of each stand, a control for each motor for normally maintaining the rotation of the rolls of its associated stand at a predetermined substantially constant speed, a supplemental control for the motor or" the second stand to cause a predetermined reduction in the speed thereof, means associated with the ihst stand and operable by the entrance of the leading end of a breakdown thereinto to operate the said supplemental control to decrease the speed of the second stand only, and means operable after entrance of the leading end of the breakdown into the second stand to operate the supplemental control to bring the motor of the second stand back to its original speed.

2. A continuous rolling mill comprising several mill stands arranged in tandem, a motor for driving the rolls of each stand, a control for each motor for normally maintaining the rotation of the rolls of its associated stand at a predetermined substantially constant speed, a supplemental control for the motor of the second stand to cause a predetermined reduction in the speed thereof, means associated with the first stand and operable by the passage of the trailing end of a breakdown therebeyond to operate the said supplementm control to decrease the speed of the econd stand only, and means operable by the passage of the trailing end of a breakdown from the second stand to operate said supplemental control to bring the motor of the second stand back to its original speed.

3. A continuous rolling mill comprising several mill stands arranged in tandem, a motor for driving the rolls of each stand, a control for each motor for maintaining the rotation of the rolls of its associated stand at a predetermined substantially constant speed, a supplemental control for the motor of each stand after the first to cause a predetermined reduction in the speed of the associated motor, means associated with each stand except the last and operable by the entrance of the leading end of a breakdown thereinto to operate only the supplemental control of the next succeeding stand to decrease the speed thereof, and means operable after entrance of the leading end of the breakdown into the said next succeeding stand to operate the supplemental control associated therewith to bring the motor of the said next succeeding stand back to its original speed.

4. A continuous rolling mill comprising several mill stands arranged in tandem, a motor for driving the rolls of each stand, a control for each motor for maintaining the rotation of the rolls of its associated stand at a predetermined substantially constant speed, a supplemental control for the motor of each stand after the first to cause a predetermined reduction in the speed of the associated motor, means associated with each stand except the last and operable by the entrance of the leading end of a breakdown thereinto to operate only the supplemental control of the next succeeding stand to decrease the speed thereof, means operable after entrance of the leading end of the breakdown into the next succeeding stand to operate the supplemental control associated therewith to bring the motor of the said next succeeding stand back to its original speed, means associated with each stand except the last two and operable by the passage of the trailing end ofthe breakdown therebeyond to operate only the supplemental control of the next succeeeding stand to decrease the speed thereof, and means operable by the passage of the trailing end of the breakdown from the last mentioned next succeeding stand to operate the supplemental control associated therewith to bring the motor of the last mentioned next succeeding stand back to its original speed. 7

5. The continuous method of hot rolling a breakdown into strip comprising passing the breakdown through a series of roll stands while driving each of the rolls at a predetermined normal speed and as the trailing end of the breakdown reaches the rolls of a stand, temporarily decreasing the speed or the ,rolls of the next succeeding stand a predetermined amount while maintaining each of the other stands at its normal speed to progressively reduce said trailing end to substantially the same gage asithe length of the breakdown preceding the trailing end, and returning the said next succeeding stand to its normal speed as soon as the trailing end of the breakdown passes from the said, next succeeding stand.

6. The continuous method of hot rolling a breakdown into strip comprising passing the breakdown through a series of roll stands while driving each of the rolls at a predetermined normal speed and as the leading end of the breakdown reaches the rolls of a stand, temporarily decreasing the speed of the rolls of the next succeeding stand a predetermined amount while maintaining each of the other stands at its normal speed to prog'ressily reduce said leading end to substantially the same gage as the length of the-breakdown following the leading end is reduced, and returning the said next suc-. ceeding stand to its normal speed when the said leading end reaches the said next succeeding stand.

7. The continuous method of hot rolling a breakdown into strip comprisingpassing thebreakdown through a series of roll stands while driving each of the rolls at a predetermined normal speed and as the leading end of the breakdown reaches the rolls of a stand, temporarily decreasing the speed of the rolls of the next succeeding stand a predetermined amount while maintaining'each of the other stands at its normal speed to progressively reduce said leading end to substantially the same gage as the length of the breakdown following the leading end is reduced, returning the said next succeeding stand to its normal speed when the said leading end reaches the said next succeeding stand and as the trailing end of the breakdown reaches the rolls of a stand, temporarily decreasing the speed of the rolls of the next succeeding stand a predetermined amount while maintaining each of the otherstands at its normal speed to progressively reduce said trailing end to substantially the same gage as the length of the breakdown preceding the trailing end, and returning the said next succeeding stand to its normal speed as soon as the trailing end of the breakdown passes from the said next succeeding stand.

8. In apparatus for controlling the operation of a first device having a motor and being operative with a strip of material and a second device operative with said strip forpulling on the strip relative to said first device, the combination of strip detector means operative with said strip at a predetermined location relative to one of said first and second devices for providing a first control signal when the strip is not'present at said location,'motor op eration sensing means operative with said motor for providing a second control signal that varies in accordance with a predetermined operation of said motor, and a motor control device operative with said motor and responsive to said first control signal for controlling the operation of said motor in accordance with a predetermined value of said second control signal when the strip is not present at said predetermined location.

9. In apparatus for controlling the operation of a first device having a motor and a second device, with each of said devices being operative with a strip of material for pulling on the strip to provide tension in said strip between said first device and second device, the combination of strip detector means operative with said strip at a predetermined location relative to said first device for providing a .first control signal when the strip is not present at said location, operation sensing means operative with said second device for providing a second control signal that varies in accordance with a predetermined operation of said second device, and a control member operative with said second device and responsive to said first control signal for controlling the operation of said second device in accordance with said second control signal when the strip is not. present at said predetermined location.

. 10. In apparatus for controlling theoperation of at least alfirst device and a second device operative with a strip of material for performing a predetermined operation relative to said strip, with each of said devices being operative with said strip forpulling on the strip.

to provide tension in said strip between said devices, the combination of strip detector means operative with said strip at a predetermined location relative to one of said first and second devices for providing a first control signal when the strip is not present at said location, operation sensing means responsive to said first control signal and operative with the other of said devices for providing a second control signal having a value that follows a predetermined operation of said other device when said first control signal is not provided, and a control member operative withsaid other device and responsive to said first control signal for controlling the operation of said other device in accordance with a predetermined value of said second control signal when the strip is not present at said predetermined location.

11. In apparatus for controlling the operation of a first device and a second device operative with a strip of material for pulling on the strip to provide tension in the strip between said first and second devices, the combination of a temperature responsive strip detector device operative with said strip at a predetermined loca tion relativeto one of said firstand second devices for providing a first control signal in accordance with the temperature or" any strip present at said location, operation sensing means responsive to said first control signal and being operative with the other of said first and second devices for providing a second control signal having a value that varies in accordance with a predetermined operation of. said other device and as long as said first control signal is not provided, and acontrol device operative with said other device and responsive to said.

first control signal for controlling the operation of said other device in accordance with a predetermined value of said secondcontrol signal that is present when the strip detector device does not respond to the temperature of any strip at said predetermined location.

12. In apparatus for controlling the operation of a first device and a second device, with said first device.

strip present at said location, motor operation sensing means operative with said motor for providing a second control signalthatvaries in accordance with a predetermined operation of said motor, anda motor control device operative with said motor and responsive to said first control signal for controlling the operation of said motor in accordance with a predetermined value of said second control signal when the strip detector means does not respond to the temperature of any strip present at said predetermined location.

13. In control apparatus for a rolling mill including at least a first device having a motor operative with a pair of roller members between which a strip of material may be positioned for performing a predetermined operation relative to said strip, and with said rolling mill including a tension controlling second device for pulling on the strip relative to said first device, the combination with a strip sensing device for providing a first control signal when the strip is not present at a predetermined location relative to said mill, a motor operation sensing device operative with said motor for providing a second control signal that varies in accordance with the operation of said motor, and a control device operative with one of said first and second devices and responsive to said first control signal for controlling the operation of said one device in accordance with a predetermined function of said second control signal.

14. In control apparatus for a rolling mill including at least a first device having a motor operative with a pair of roller members between which a strip of material may be positioned for performing a predetermined operation relative to said strip, and with said rolling mill including a tension controlling second device for pulling on the strip relative to said first device, the combination with a strip sensing device for providing a first control signal when the strip i not present at a predetermined location relative to said second device, a motor operation sensing device operative with said motor for providing a second control signal that varies in accordance with the operation of said motor, and a control device operative with said first device and responsive to said first control signal for controlling the operation of said first device in accordance with a predetermined function of said second signal.

15. In control apparatus for a rolling mill including at least first and second devices having a pair of roller members between which a strip of material may be positioned for performing a predetermined operation relative to said strip, with said first device including a motor member, the combination with a strip sensing device for providing a first control signal when the strip is not present at a predetermined location relative to said second device, a motor operation sensing device operative with said motor for providing a second control signal that varies in accordance with the operation of said motor, and a control device operative with said second device and responsive to said first control signal for controlling the operation of said second device in accordance with a predetermined function of said second control signal.

16. in control apparatus for a rolling mill including at least first and second devices, with each of said devices having a pair of roller members between which a strip of material may be positioned for performing a predetermined operation relative to said strip, and with each of said first and second devices being operative for pulling on the strip to provide tension in said strip between said first and second devices, the combination with a strip sensing device for providing a first control signal when the strip is not present at a predetermined location relative to one of said first and second devices, an operation sensing device operative with the other of said first and second devices for providing a second control signal that varies in accordance with the operation of said other device, and a control element operative with said second control device and responsive to said first control signal for controlling the operation of said second device in accordance with a predetermined function of said second control signal.

17. In control apparatus for a rolling mill including at least a first device having a motor operative with a pair of roller members between which a strip of material may be positioned for performing a predetermined operation relative to said strip, and with said rolling mill including a tension controlling second device for pulling on the strip relative to said first device, the combination with a strip sensing device for providing a first control signal when the strip is not present at a predetermined location relative to said one of said first and second devices, a motor operation sensing device operative with said motor for providing a second control signal that varies in accordance with the operation of said motor, and a control device operative with the other of said first and second devices and responsive to said first control signal for controlling the operation of said other of the first and second devices in accordance with a predetermined function of said second control signal.

References Cited in the file of this patent UNITED STATES PATENTS 1,871,437 Winne Aug. 16, 1932 2,153,429 Millan Apr. 4, 1939 2,264,277 Cook Dec. 2, 1941 2,287,851 Zeitlin June 30, 1942 2,342,767 Stoltz Sept. 29, 1944 2,468,557 Huston Apr. 26, 1949 2,544,467 Michel Mar. 6, 1951 2,626,376 Harder Jan. 20, 1953

Claims

8. IN APPARATUS FOR CONTROLLING THE OPERATION OF A FIRST DEVICE HAVING A MOTOR AND BEING OPERATIVE WITH A STRIP OF MATERIAL AND A SECOND DEVICE OPERATIVE WITH SAID STRIP FOR PULLING ON THE STRIP RELATIVE TO SAID FIRST DEVICE, THE COMBINATION OF STRIP DETECTOR MEANS OPERATIVE WITH SAID STRIP AT A PREDETERMINED LOCATION RELATIVE TO ONE OF SAID FIRST AND SECOND DEVICES FOR PROVIDING A FIRST CONTROL SIGNAL WHEN THE STRIP IS NOT PRESENT AT SAID LOCATION, MOTOR OPERATION SENSING MEANS OPERATIVE WITH SAID MOTOR FOR PROVIDING A SECOND CONTROL SIGNAL THAT VARIES IN ACCORDANCE WITH A PREDETERMINED OPERATION OF SAID MOTOR, AND A MOTOR CONTROL DEVICE OPERATIVE WITH SAID MOTOR AND RESPONSIVE TO SAID FIRST CONTROL SIGNAL FOR CONTROLLING THE OPERATION OF SAID MOTOR IN ACCORDANCE WITH A PREDETERMINED VALUE OF SAID SECOND CONTROL SIGNAL WHEN THE STRIP IS NOT PRESENT AT SAID PREDETERMINED LOCATION.