US3338079A

US3338079A - Motor speed control apparatus for runout tables

Info

Publication number: US3338079A
Application number: US279511A
Authority: US
Inventors: John W Cook
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1963-05-10
Filing date: 1963-05-10
Publication date: 1967-08-29
Anticipated expiration: 1984-08-29
Also published as: JPS4319375B1; GB1012392A; FR1402162A

Description

4 Sheets-Sheet l Aug. 29, 1967 J. w. cooK MOTOR SPEED CONTROL APPARATUS FOR HUNOUI TABLES Filed May 10, 1963 mobEmzmw w M256 A H mv mam 2:1 55E 2462mm z? m mw 5o L W Tmm k H A. y mom 05E; H mm v 3 7 mozfizmw ww So V 6 5E Ev q 05$; t. 85 F Om I, V mam :28 7 l.. 6528 m W mm mm l 353% 7 iii "62 moZmmm "62 581 (E moEomm K Swim 35% Swim w aw W 230a ism-mom J- W. COOK Aug. 29, 1967 MOTOR SPEED CONTROL APPARATUS FOR RUNOUT: TABLES Filed May 10, 1963 4 Sheets-$heet 2 zzoo mmom Aug. 29, 1967 J. W.'COOK 3,338,079

I MOTOR SPEED CONTROL APPARATUS FOR RUNOUT TABLES Filed May 10, 1983 4 Sheets-Sheet 3 us I SOURCE VOLTAGE Fug 3.

LOAD

SENSING DEVICE TENSION REGULATOR COMMON BUS THREAD BUS RUN BUS Aug. 29, 1967 3,338,079

MOTOR SPEED CONTROL APPARATUS FOR RUNOUT TABLES J. w. COOK 4 Sheets-Sheet Filed May 10. 1963 V w H A 2 5 E ow H 1Ili1l1+ .31: i+ I: I i V M255 M255 M255 W 9252mm 9262mm 0262mm I wozmmmnza 555KB MT mozmmwta W ww 5o v uo 5o M959 K 4 B l I I l I I II m\. ms \L\ mam 20:2 3 V $2 5m? .6528 $0230? $238. 2062M; Ro 56% Km 3 853mm Swim 29.6mm 3m: 02,5 53

M Ai United States Patent 3,338,079 MOTOR SPEED CONTROL APPARATUS FOR RUNOUT TABLES John W. Cook, Monroeville, Pa., assignor to Westinghouse Electric Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed May 10, 1963, Ser. No. 279,511 6 Claims. (Cl. 72-15) The present invention relates in general to motor speed control apparatus and more particularly to motor speed control apparatus for varying the operative speed of one or more drive motors operative with particularly a workpiece rolling mill runout table of a strip mill for metal rolling.

In the well known operation of a hot rolling mill, up to the present time all of the stands of the rolling mill'have been threaded at a running speed up to two thousand feet per minute. The workpiece slabs have in the past been of such size that delivered strips about two thousand feet in length have resulted to necessitate up to approximately sixty seconds of elapsed rolling time.

It has recently been contemplated to increase the incoming slab weights to obtain larger and larger coils of rolled strip without the necessity of providing welds between delivered strip portions. If a four thousand foot long strip is delivered from a rolling mill operating in the order of two thousand feet ,per minute, this would require about two minutes of time to complete the rolling operation. Such an elapsed time results in undesired temperature losses in particularly the tail-end of the strip as compared to the. leading end of the strip, A higher rolling mill speed is desired to reduce this elapsed rolling time but this presents threading problems for both the rolling mill and the subsequent coil winding equipment for winding the rolled strip into a coil.

The strip runout table following the rolling mill stands are provided to carry the rolled strip to a strip winding or coiling device. In accordance with known prior art teachings, the runout table motors are controlled as a speed reference by the operating speed of the last mill stand. Thusly, the voltage level of the respective generators operative with each motor of the runout table is established in accordance with a pilot generator or the like connected to the last stand of the rolling mill. This practice presents a problem when a mill is threaded at one lower speed to permit entering the strip coiling device and then accelerated to a second higher running speed. To increase the rolling capacity of the mill with regard to the passage of a succeeding strip through the rolling mill, each stand is rapidly reset to the thread speed when the tail end of a given stri leaves that stand to facilitate accepting the next succeeding bar. It requires in the order of fifteen seconds for the tail end of a given strip to reach the strip coiling device after leaving the last mill stand. The strip coiler and runout table motors cannot be slowed down in operation during the desired speed reset of the last mill stand since this will have an adverse eifect upon the wrapping of the strip coil. In actual practice the head end of the succeeding bar can be only five seconds or even less behind the tail end of the previous bar, so the mill stands must each be reset to thread speed very rapidly after the tail end of the previous bar or strip leaves the respective stands.

It becomes desirable that each section of the runout table should continue to operate at run speed and not be reset to thread speed until after the tail end of a bar or strip leaves that particular section. For this reason, a pilot generator operative with the last mill stand will not provide a suitable speed reference signal to control the operation of all the runout table motors or the drive motor for the strip coiling device.

3,338,079 Patented Aug. 29, 1967 Accordingly, it is an object of this invention to provide an improved motor speed control apparatus for particular drive motors of a rolling mill, for example the runout table motors, such that a more suitable performance is provided for both threading speed and desired running speed to result in a better operation of the rolling mill and to increase the productivity of the rolling mill.

It is a different object to provide an improved motor speed control apparatus for the runout table motors op erative with a strip rolling mill such that undesired effects are minimized relative to the rolling of any particular workpiece strip and permitting the better coiling of strips than was previously practical.

In accordance with the teachings of the present invention a speed control apparatus for hot strip mill drive motors is provided to be operative at a first threading speed and then accelerated to a second and higher running speed. Two speed reference buses are provided for this purpose. One is the thread speed bus and the other is the run speed bus. The thread speed bus is supplied by a separate thread exciter generator which controls the voltage of the thread speed bus. The run speed bus is energized by a combination of the thread exciter generator plus a run exciter generator, which are connected together such that the run speed bus voltage is the sum of the output voltages of the two exciter generators. The thread bus voltage is set by an adjustable reference working in the thread exciter generator voltage regulator and the run bus voltage is controlled at a maximum value by a voltage limiting device operative with a ramp function generator connected to control the output voltage of the run exciter generator. The runout table motor speed reference is additionally determined by the passage of the strip between the last mill stand and the strip coiling device.

The invention described and claimed in the present patent application is related to a copending patent application by the same inventor, now issued as US. Patent No. 3,213,656, entitled Rolling Mill Motor Speed Control Apparatus, and assigned to the same assignee.

These and other objects and advantages of the present invention will become apparent in view of the following description taken in conjunction with the drawings, wherein:

FIGURE 1 is adiagrammatic showing of the motor speed control apparatus in accordance with the present invention;

FIGURE 2 is a schematic showing of the present control apparatus operative with the runout table motors of a strip rolling mill;

FIGURE 3 is a schematic showing of the speed control apparatus for the strip winding apparatus in accordance with the present invention; and

FIGURE 4 illustrates the operation of the runout table motors regarding the last stand of the rolling mill.

In FIGURE 1 there are shown six stands of the finishing train for a hot strip mill, with the strip entering successively a first stand 10, a second stand 12, a third stand 14, a fourth stand 16, a fifth stand 18 and a sixth stand 20 from which it passes across a roll table 22 to a strip winding device 24.

Each of the stands is provided with a screwdown mechanism, such as the screwdown mechanism 26 operative with the first stand 10. Similarly, each of these stands includes a drive motor, such as the drive motor 28 operative with the first stand 10. Each of the drive motors is controlled in speed by the output voltage from a generator operative with the armature of the drive motor. For the first stand 10 this voltage is provided by a stand generator 30 shown operative with the drive motor 28. A speed regulator for each stand is provided to energize the field of the generator, such as the speed regulator 32 provided for the first stand and operative with the field winding 34 of the generator 30.

There is provided a thread voltage bus 40 and a run voltage bus 42 operative with each of the rolling mill stands. The thread bus 40 is energized by a thread voltage exciter generator 44 connected between a common return bus or conductor 46 and the thread voltage bus 40. A run voltage exciter generator 48 is connected between the common bus 46 and the run voltage bus 42 in series with the thread voltage exciter generator 44, such that the output voltage from the run exciter 48 is added to the output voltage from the thread exciter generator 44 and provided between the run voltage bus 42 and the common conductor 46.

The speed regulator for each stand includes a voltage sensing impedance member operative with a first contactor connected between the common conductor 46 and the thread bus 40 and a second contactor to connect this impedance member between the common conductor 46 and the run bus 42. More specifically, the first stand speed regulator 32 operative with the first stand 10 includes a voltage sensing impedance member 50 operative with a first contactor 52, which when closed connects the impedance member 50 between the thread bus 40 and the common conductor 46 such that the motor operated movable tap 54 provided with the impedance member 50 is adjustableto provide a predetermined and desired speed range for the motor 28 of the first stand 10 and is connected to energize the speed regulator 32 through a vernier resistor 56. A second contactor 58 is operative to energize the resistor 50 between the run bus 42 and the common conductor 46.

A roll force sensing device 62 is operative with the first stand for providing an output signal to indicate the roll force loading of the first stand or when the workpiece strip 60 is passing through the first stand 10. A similar roll force loading sensing device. is provided for each of the stands'of the rolling mill, with each of the respective roll force sensing devices being connected to a sequence control apparatus 64 operative to open and close as desired the respective contactors for each of the stands, such as the contactors 52 and 58 operative with the first stand 10 as will be later described.

The strip winding device 24 is provided with a drive motor 70 and a motor load sensing device 72 operative to sense the loading of the strip winding device 24 through the armature current of the motor 70. If desired a different load sensing member may be provided such as a tension member operative directly with the strip entering the winding device to indicate when the winding device :24 is applying tension to the workpiece strip 60.

A first ramp signal providing generator 80 is operative with a field winding 82 of the thread 'exciter generator 44 for providing the desired ramp function pattern to the energization of the thread bus 40 relative to the common conductor 46. A run ramp signal providing generator 84, is operative with a field winding 86 of the run exciter generator 48 for causing the voltage of the run bus 42 to increase above the thread voltage of the thread bus 40 in a ramp function pattern. This is done after closing the run contactors, such as the contact 58 for the first stand 10 is closed, and after opening the thread contactors, such as the contactor 52 for the first stand 10, by the sequence control apparatus 64.

The runout table 22 can include 400 motors, with each being in the order of 4 horsepower and connected to a different one of the table rolls as shown in FIGURE 1. These table motors can be arranged in several sections, for example five sections, with each section including eighty commonly operated table motors. A speed regulator is provided for each section of table motors. The speed regulator 23 is operative to commonly control the table motors in section 25, While the speed regulator 27 is operative 4 to commonly control the table motors in section 29 of the strip runout table 22.

In FIG. 2 there is shown a portion of the control apparatus of the present invention operative to sequence the opening and closing of the respective contactors to switch the operation of the stand drive motors and the runout table motors from the thread bus 40 to energization by the run bus 42. The sixth stand 20 is shown including a roll force sensing device providing an output signal through a minimum signal responsive amplifier 112 to energize a control winding 114 operative with a contactor 116 which controls the energization from a suitable voltage source 118 of a control winding 120 through a time delay device 121, which control winding 120 is operative with a contactor 122 connected between the speed regulator 124 for the drive motor 126 of the sixth stand 20 and the thread bus 40. The contactor 116 also controls the energization of a control winding 128 operative with a contactor 130 connected between the run bus 42 and the speed regulator 124 for the drive motor 126. It should be understood in this regard that the stands 10, 12, 14, 16, and 18 are similarly provided with control circuitry such as shown for stand 20.

The strip winding device 24 is provided with a motor load sensing device 72 which energizes through the sequence control 64 a control winding operative with a contactor 142 connected between the voltage source 118 and the respective control windings for each ofthe contactors connected between the thread bus 40 and the run bus 42 and the respective speed regulators for all of the stands 10, 12, 14, 16, 18 and 20.

Three of the runout table motors in section 29 are shown for illustration as energized by a common generator 31. The speed regulator 27 is controlled by a motor operated rheostat 33 operative with a contactor 35, which when closed contacts the rheostat 33 between the thread bus 40 and the common bus 46. The motor operated tap 37 is adjustable to provide a predetermined and desired speed for the table motors of the section 29. In practice, all of the table motor speed regulators, such as the speed regulator 27 are caused to operate at substantially the same speed as does the last stand 20 of the rolling mill.

A pulse source 39 is connected to the pinch rolls 43 to measurethe passage or movement of the strip 60 from the last stand 20 to the strip coiling device 24. The signals from the pulse source 39 are counted by a counter 41. The distance between the last stand 20 and the strip coiling device 24 is known. For example, if the latter distance is 500 feet, each of the five provided table sections could extend in the order of 100 feet along the strip travel path. If the pulse source 39 provides one output signal for each foot of strip passage, then after 100 such signals are counted by the counter 41 a first control signal is supplied to the sequence control 64 to disconnect from the run bus 42 the speed regulator for the first section of table motors and to connect the same to the thread bus 40. After the pulse source 39 supplies 200 signals to the counter 41, it supplies a control signal to the sequence control 64 to disconnect from the run bus 42 the speed regulator for the second section of table motors and to connect the same to the thread bus 40. In this same manner the speed regulator 27 for the table motor section 29 is controlled. For example, if section 29 is the third section, after 300 signals are supplied to counter 41, it provides a control signal to sequence control 64 to deenergize the relay winding 65 to open contact 67 and allow contact 35 to close and contact 69 to open to disconnect speed regulator 27 from run bus 42 and connect it to thread bus 40 after the tail end of. strip 60 has passed this third section 29 of table motors.

After the strip 60 has passed the last section of table motors, a suitable reset signal is supplied to the counter 41 by the sequence control 64. A photocell or the like can be utilized for this reset signal if desired.

in FIG. 3 there is shown the control apparatus for controlling the operative speed of the motor 70 of the strip coiling device 24 through energization first by the thread bus 40 and subsequently by the run bus 42. As the workpiece strip 60 enters the strip coiling device 24, it is desired to sense the resultant additional loading of the motor 70 to energize the control winding 140 and close the contactor 142, such that the regulator 150 operative to energize a field winding 152 of the generator 154 operative with the strip winding device motor 70 will change the operative speed of the strip winding device 24 from a threading speed as determined by the voltage of the thread bus 40 to a run speed as determined by the voltage of the run bus 42. It should be understood that a current or tension regulator can be operative with the generator 154 and a counter EMF regulator with the field winding of the motor 70, such that the counter EMF regulator reference is held proportional to strip speed to provide a substantially constant strip tension. The closing of contactor 142 energizes a control winding 156 to open contactor 157 through a time delay device 158 and energizes a control winding 160 to close a contact member 162. Thusly, when the load sensing device 72 indicates that a strip has entered the strip coiling device 24, the contactor 142 is closed resulting in closing of the contactor 162 and subsequently as determined by the time delay 158 the opening of the contactor 157 to change the energization of the regulator 150 from across the thread bus 40 relative to the common conductor 46 and instead to be energized by the run bus 42 relative to the common conductor 46. Thusly, as the voltage of the run bus 42 is increased in a ramp or linear function by the ramp generator 84, the operative speed of the motor 70 is in this manner caused to increase from the predetermined thread speed to the desired and predetermined run speed. The respective predetermined speeds are set by the maximum output voltages provided by the thread and the run exciter generators when the top of the ramp control signals are supplied to the respective generator field windings for those generators.

In FIGURE 4 there is illustrated the apparatus utilized to control the operation of the run out table motor sections and the strip coiling device in accordance with the operation of the last mill stand 20. The human operator dials or sets a rheostat 71 to establish the desired speed of the last stand 20. A voltage difference sensing device 73, which can be a relay device, is operative with a motor 75 to adjust a stand speed controlling rheostat 77 to correspond to the manual setting of the rheostat 71. The motor 75 also adjusts a reference rheostat 79 to correspond to the positional setting of the rheostat 77.

A motor operated rheostat is provided to set the operating speed for each section of the table motors and for the coiling device 24. Such a rheostat 81 is provided for the table motor section 29 and is operative with the speed regulator 27 for this purpose. A voltage difference sensing device 83 is responsive to the difference in voltage drops across the respective rheostats 79 and 81 to operate motor 85 to adjust rheostat 81 to correspond to the setting of reference rheostat 79.

Similarly, a speed setting rheostat 87 is provided for the coiling device regulator 150. A voltage difference sensing device 89 is operative with motor 91 to adjust rheostat 87 to correspond to the setting of reference rheostat 7 9.

Contact 93 is shown operative with motor 85 and contact 95 is shown operative with motor 91 to prevent the functioning of the latter motors to follow speed setting adjustments of the rheostat 71 whenever the strip has not as yet passed the respective table section controlled by the motor 85 and whenever the strip is not coiled on the coiling device 24. The contact 93 is opened after a given strip is threaded through the rolling mill and has entered the coiling device 24 to prevent changes in the speed setting .of rheostat 81 until after the strip is properly coiled.

6 Any interim changes made in the setting of the reference rheostat 79 will be followed by the motor 85 after the strip has passed the table motor section controlled :by speed regulator 27, at which time the contact 93 is closed.

The contact 95 is closed after a given strip is coiled by the strip coiling device 24, as can be sensed by a photocell or suitable load sensing device as may be desired, and is again opened when a succeeding strip is threaded through the rolling mill and has entered the strip coiling device 24.

In the operation of the control apparatus shown in FIG. 1 the thread speed contactor for each of the stands 10, 12, 14, 16, 18 and 20, and corresponding to the contact member 52 shown for stand 10, is normally closed to energize the speed regulators and thereby the stand generators to control the operation of the stand drive motors such that the first stand 10 and the other stands operate at a thread speed determined by the voltage of the thread bus from the excitation generator 44. In this regard, it should be understood that the thread ramp generator 80 initially controlled the operation of the exciter generator 44 through the generator field 82 such that the voltage of the thread bus 40 was caused to increase initially in a ramp function or linear manner to a predetermined maximum or thread run excitation voltage. When the workpiece strip 60 has passed through each of the stands 10, 12, 14, 16, 18 and 20 and passes the run- -out table rollers 22 and enters the strip coiling device 24, this changes the loading of the drive motor 70 operative with the strip coiling device 24 such that the motor load sensing device 72 can provide an output signal to a sequence control apparatus 64. This causes the contactors, such as contactor 58, connected between the run bus 42 and the respective speed regulators for the stand drive motors and the run out table motor sections to close, and subsequently this opens after a provided time delay the normally closed contactors connected between the thread bus 40 and the same speed regulators.

It should be noted that a voltage sensing device 45 is operative with the run bus ex'citer generator 48 and provides an output control signal to the sequence control apparatus 64 such that only when the output voltage of the run exciter generator 48 is zero can the normally open contactors operative with run bus 42, such as the contactor 58, be closed. When the control signal from the load sensing device 72 is provided to the sequence control apparatus 64 to indicate that the workpiece strip 60 has entered the strip coiling device 24, it is now desired to increase the operating speed of each of the stands 10, 12, 14, 16, 18 and 20 as Well as to increase the operating speed of the run out table motor sections and the strip coiling device 24 from the thread speed to the higher desired run speed. To do this, the sequence control apparatus 64 closes the contactors connected between the run bus 42 and each of the speed regulators. After a suitable time delay, the contactors open which are connected between the thread bus 40 and the speed regulators. Now the run ramp generator 84 begins to increase the output voltage from the excitation generator 48 such that the operating speed of the drive motors is increased to a predetermined maximum running speed established by the respective speed setting rheostats.

Thusly, a typical run out table motor section will initially accelerate from a zero speed to a desired thread speed. When the workpiece strip 60 enters the strip coiling device 24, the speed of the table motor sections will increase in a ramp function .or linear manner to a desired run speed as determined by the maximum voltage energization of the run bus 42 and the speed setting of the last stand 20. After the workpiece 60 passes through each particular run out table motor section, the operative speed of that section will then decrease in a predetermined manner by dynamic braking or the like back to the thread speed of the last stand and it will remain at this thread speed until a second workpiece strip has been 1 the rolling mill, that stand is reset threaded through all of the stands of the rolling mill and enters the strip coiling device at which time the operative speed of that sect-ion will again increase in a ramp func-' tion manner to the desired run speed of the last stand 20.

Each stand includes a roll force sensing device, such as the roll force sensing device 62 provided for the first stand 10. This provides an output signal to the sequence control apparatus 64 which causes the operating speed of that particular stand to decrease from the run speed back to the thread speed when the workpiece strip 60 has passed through that particular stand. In other words, when the workpiece strip 60 leaves, the operating speed of the first stand will change from the run speed back to the thread speed. Subsequently, as the tail end of the workpiece strip passes through the second stand 12, it will in turn then change from run speed to thread speed. This speed changing operation will successively move through the plurality of stands and the run out table motor sections in conjunction with the tail-end of the workpiece strip 60 passing through the respective stands and table motor sections. This allows a succeeding workpiece strip to enter stand 10, for example, before the tail-end of the preceding workpiece strip 60 has left some of the other stands. In theory, depending upon the time period required to decelerate the first stand 10 from its run speed to its thread speed, the leading end of the succeeding workpiece strip could enter stand 10 before the tail-end of the preceding workpiece strip traveling at run speed had left the second stand 12 or perhaps the third stand 14.

As shown in FIG. 2, the strip winding device 24 is provided with a motor load sensing device 72 to close the contactor 142 through the sequence control 64 when the workpiece strip enters the strip winding device 24 which energizes the control winding 128 for the normally open contactor 130 for the last stand 20 of the rolling mill, from the voltage source 118 whenever the workpiece strip 60 enters the strip winding device 24. This simultaneously changes the operating speed of each of the stand drive motors and the table motor section and the strip coiling device from the thread speed to the run speed in accordance with the ramp function or linear increase in the voltage energization of the run bus 42. On the other hand, the roll force sensing device operative with the first stand individually causes the speed regulator 32 to change the operative speed of the drive motor 28 v for the first stand 10 from its run speed to its thread speed,

as shown in FIG. 1. As the trailing end of the workpiece strip passes through the rolling mill and eventually passes through the sixth stand 20, the roll force sensing device 110 similarly opens the contactor 116 to result in opening of the contactor member 130 and closing the contactor 122 to cause the speed regulator 124 for the drive motor 126 of the sixth stand 20 to change its operating speed from the run speed to the thread speed.

The load sensing device 72 shown in FIG. 3 is operative to sense the increased load taken by the motor 70 when the workpiece strip 60 enters the strip coiling or winding device 24. This closes the contactor 142 to result in closing the contact-or 162 and to open the contactor 157. The tension regulator 150 now energizes the drive motor 70 through the generator 154 in accordance with the increased voltage of the run bus 42 as compared to the previous thread bus 40 energization of the tension regulator 150.

Thusly, it will be seen that when the tail-end of the workpiece strip 60 drops out of the last stand 20 of to its thread speed to be ready to accept the head-end of the next workpiece strip or bar to enter the rolling mill. The runout table motor sections are cooperative with the last stand 20 regarding thread speed operation and run speed operation with the strip passing through the entire rolling mill and being coiled by the strip coiling device 24. However, when the tail-end of a strip leaves the last stand 20, the successive table motor section .is not concurrently reset to thread speed operation. Instead, it is only after the tail end of the strip leaves a particular table motor section that this section will change from the run speed operation to the thread speed operation in accordance with the passage of the strip 60 as sensed bythe pulse source 39 operative with the pinch rolls 43. This assures 'a desirable coiling operation by the strip coiling device 24. In accordance with the teachings of the present invention, the successive workpiece strips are permitted thereby to enter the rolling mill on a more frequent time schedule and are closer together such that only a few seconds is required between the tail-end of a previous workpiece strip to leave a particular stand of the rolling mill and the entry of the head-end of the next and succeeding workpiece strip, while the desired strip coiling operation is maintained.

The two reference exciter generators 44 and 48 as shown in FIG. 1 are provided to supply the desired speed reference signals to the stand speed regulators and the erator 48. The voltage output of the generator 48'is adjusted by the speed operator to allow setting the running speed of the rolling mill in accordance with any desired work schedule. This in theory could vary over a range from the thread speed operation to a value corresponding to the top speed of the rolling mill. The indi- V vidual speed setting motor operated rheostats, such as the rheostat 50 for the stand 10 and the 'vernier rheostat 56, are used to set the individual stand and table motor section speeds for the various rolling schedules substantially in accordance with the conventional practice at the present time. The speed regulator, such as the speed regulator 32 operative with the first stand 10, is operative with either the field winding of the drive motor or could be operative with the power supply connected to energize the motor armature.

In a typical operation, the mill operator will set the thread speed for the mill to a value which he knows to be correct by setting the thread excite-r output voltage from the exciter generator 44. In addition, the motor operate-d rheostat 77 of the last stand 20 is set to provide the desired speed operation for the last stand 20 and the table motor sections and strip coiling device 24. The

other stands Will be set to their correct speed by operation of the individual stand motor operated rheostat. The operator will then set the top run speed by adjusting a potentiometer 83 operative with the run ramp generator 84 to determine the maximum output voltage of the run exciter generator 48. However, the run exciter generator 48 will have a zero output voltage until it is properly sequenced to go to the increased output voltage value, and which zero output voltage is provided when the sequence control apparatus 64 operates to close the run bus contactors corresponding to the contactor 58 operative with the first stand 10. A workpiece strip 60 is then threaded into the rolling mill at the set thread speed. As soon as the head-end of the workpiece strip 60 enters the coiler or strip winding device 24, the mill acceleration will be initiated by the motor load sensing device 72. The run exciter generator 48 will then increase its output voltage in a ramp function buildup manner to a predetermined top speed value. The desired ramp function pattern can be controlled by any of the well known ramp function generator devices, such as a motor operated rheostat or the like. The whole of the rolling mill will then accelerate from the threading speed toward the running speed in conjunction with the voltage increase of the run bus 42.

When the tail-end of the workpiece strip leaves stand 10, the roll force sensing device 62, which could if desired be a well known load relay or some other sensing device, will cause the contactor 58 to open and the contactor 52 to close. Stand 1 will then be decelerated back to thread speed. In a similar manner, when the tail end of the workpiece strip leaves stand 12, the control apparatus will cause stand 12 to be reset to thread speed. All other stands follow this pattern of operation in a similar manner as do the successive table motor sections. When the tail end of the strip enters the coiling device 24, the run reference exciter generator 48 will be returned to a zero output voltage ,value and all the contacts operative with the thread bus 40 will then be closed and the contacts corresponding to contact 58 operative with the run bus 42 will be open. The mill control apparatus will then be ready to accelerate the rolling mill from the thread speed to the run speed when a new workpiece strip has been threaded through the six stands of the rolling mill and has entered the strip coiling device 24.

The operation of the present control apparatus is such that the head-end of a succeeding workpiece strip may actually have entered the first stand or first few stands of the rolling mill before the tail-end of the preceding work-piece strip has passed through the final table motor section. The practical limitation controlling the spacing between the successive workpieces is how long it will take before the individual stand motors and table section motors can be reset from their run speed to the lower thread speed.

The contactor for each stand and table motor section corresponding to contactor 52 should remain closed for a short time after the contactor corresponding to contactor 58 is closed. Further the latter contactor 58 can close only at zero voltage output from the run exciter generator 48. Similarly it is mandatory when changing from the run speed operation for a given stand to the thread speed operation, that the contactor 58 open before the contactor 52 is closed. The roll force sensing device 62 for a particular stand such as stand will initiate the opening of the contactor 58 when the workpiece leaves that stand. When the head-end of the workpiece strip enters the strip coiling device 24, this will initiate the closing of the contactor 58 when it is desired to change to the higher run speed.

It should be further noted that the last stand motor operated rheostat 77 will be calibrated in feet per minute at top desired mill speed. In other words, if the speed range of the last stand 20 is between 1,300 feet per minute and 3,750 feet per minute at rated output voltage from the run exciter generator 48, the preset rheostat 77 will be calibrated from 1,300 to 3,750 feet per minute. In addition, the energization of the run bus 42 will be such that regardless of the actual operating speed of the rolling mill, the run bus 42 will always go to the same voltage level during the normal run condition and different settings of the speed controlling rheostats will be made. The run excitation provided by the run bus 42 is the sum of the output voltages provided by the thread exciter generator 44 and the run exciter generator 48. It should be further understood that further adjustment of the thread speed may be provided by an additional control field winding for the thread exciter generator 44 to determine the actual output voltage supplied by the thread exciter generator 44 to the thread bus 40. The voltage sensing device 45 only allows the sequence control apparatus 64 to close the run bus contactors when the output voltage supplied by the run exciter generator 48 per se, in zero. The voltage limit circuit 47 is operative to limit the reference voltage of the run bus 42 to its correct desired maximum value. The operation of the voltage limit circuit 47 is such that the correct run reference voltage is provided by the run bus 42, and this is not necessarily determined by the run exciter generator 48 voltage, depending upon the thread speed selected, which in turn determines the thread exciter voltage provided by the generator 44. The voltage supplied by the run exciter generator 48 will have to cover a wide range of voltages to provide the desired run reference as a correct steady state value. g

If the mill operator wants to deliver the next workpiece schedule at 3,200 feet per minute and he wants to thread at 1,600 feet per minute, he first sets his preset rheostat 77 for the last stand 20 at 3,200 feet :per minute, and this also sets the speed for the table motor sections and the coiler device. He can set the other stands at the correct run speed inaccordance with the well known speed cone relationship for a rolling mill. As soon as the tailend of the last bar of the present schedule leaves the last stand of the rolling mill, the operator can cause all of the motor operated rheostats of the respective stands to change to their new desired positions for the succeeding schedule. However, the individual mill stands will have decelerated to thread speed when the previous workpiece strip or bar left the succeeding stands. This means that the stands are all at the predetermined thread speed but are running at approximately the correct speed ratios for the schedule selected. The table motor sections continue to operate at the previous run speed setting of the last stand until the tail end of the strip successively leaves each individual table motor section and it changes to the thread speed setting of the last stand when the pulse source 39 senses the departure of the strip tail end from that particular table motor section. The operator adjusts the rheostat 81 operative with the thread ramp generator 80 to obtain the correct thread speed out of the last stand 20 by observing the speed indicator for that stand. The adjustment of rheostat 81 will cause all stands to change thread speed by the same percentage. If desired, the rheostat 81 can also have a preset feature such as do the mill stands. As soon as the thread speed of the last stand is correct the mill can then be threaded. It will also be possible to change thread speed of the mill after a bar has started through the mill provided the rate of change of speed is slow.

The mill will then run at the 1,600 feet per minute until the strip enters the down coiler or strip winding device 24, which will cause the mill to be accelerated to the run speed by the contactors corresponding to the contactor 58 being closed for each of the stands and the contactors connected to the thread bus 40 corresponding to the contactor 52 being opened. The run exciter voltage is then raised until the desired reference value is provided for the run bus 42. This reference voltage will have been determined in advance and the mill will have been set up for this value such that the speed range of each individual stand is correct for the involved particular motor design. When the run bus voltage reaches this value, the limit circuit :47 will function to prevent the run bus voltage from being raised further.

In the same manner, any delivery run speed Within the speed cone of the mill can be set and also any thread speed within the range the mill was originally designed for can be set. The thread control is set so that the thread voltage can be lowered to a predetermined minimum value and the run reference can be raised to a predetermined maximum value. This allows the necessary flexibility for the mill operator and at the same time offers a maximum of protection preventing the operator from attempting to overspeed the stand and table motors.

In the operation of the apparatus shown in FIG. 3 the strip coiling device 24 is controlled from the same thread bus 40 and run bus 42 as are the stands and table motor sections of the rolling mill. The previous practice was to control the strip coiling device 24 speed from a pilot generator operative with the last stand 20 of the rolling mill. This was suitable for rolling mills run at a substantially constant speed for a given schedule-The 1 1 thread speed of the strip coiilng device 24 is'limited by the top speed at which the workpiece strip can enter the strip coiling device 24 or down coiler. When the tail-end of a given workpiece strip leaves the individual stands of the rolling mill, those stands are individually reset to thread speed to accept the next succeeding bar. However, it might take in the order of fifteen seconds for the tailend of a preceding strip to travel past the table sections and to reach the strip coiling device 24 after leaving the last stand 20. It will not be desirable to attempt to slow down the strip coiling device 24 during the resetting of the mill stand as this may adversely affect the wrapping of the coil. Since the head end of a given succeeding workpiece strip may be only a few seconds behind the tail-end of the previous workpiece strip, the stands must be reset to thread speed immediately after the tail-end leaves. Therefore, it is not practical to use a pilot generator on the last mill stand 24 as a speed reference to the down coilers. A load relay can be used to maintain the operative speed of the motor 70 until the coil is completed, and when the strip coiling device is not under load it can change its operative speed to a predetermined thread speed provided by the thread bus 40. If a plurality of alternative strip coiling devices or down coilers are provided, the one which is actually winding strip should be maintained at run speed and the other down coilers may change to thread speed as provided by the thread bus 40. In this same manner only the strip coiling device which is operative with a work strip should follow the mill as it increases speed from the thread speed to the run speed. Suitable interlocking of the provided selector switch can be provided to accomplish this function.

Although the present invention has been described with a certain degree of particularity, it should be understood that the present disclosure has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the scope and spirit of the present invention.

I claim as my invention:

1. In apparatus for controlling the operating speed of at least one motor of a strip rolling mill operative with a strip coil coiling device, the combination of first voltage means connected to energize at least said one motor to operate at a first predetermined speed, second voltage means for energizing at least said one motor to operate at a second predetermined speed greater than said first speed, strip movement sensing means operativewith said strip for providing control signals in accordance with the passage of discrete units of said strip relative to the position of said one motor, and circuit connection means including a signal counter cooperative with strip position sensing means provided between the second voltage means and at least said one motor for controlling the energization of said one motor by a predetermined one of said first voltage means and said second voltage means in response to said control signals.

2. In apparatus for controlling the operating speed of a plurality of runout table motor sections for a workpiece strip rolling mill operative with a workpiece strip coil winding device, the combination of first voltage means, connected to energize each of said motor sections to operate at a predetermined threading speed, second voltage means for energizing each of said motor sections to operate at a predetermined running speed greater than said threading speed, strip movement sensing means operative with the workpiece strip for providing control signals in accordance with the passage of the workpiece relative to said table motor sections, and circuit connection means provided between one of the first voltage means, and the second voltage means and said plurality of motor sections for controlling the energization of said motor sections in response to said control signals such that each motor section changes its speed of operation in accordance with the passage of the workpiece strip.

3. In apparatus for controlling the operating speed of a plurality of table motor sections of a strip rolling mill including a workpiece strip coil winding device, the combination of first voltage means for energizing each of said plurality of motor sections to operate at a first predetermined threading speed, second voltage means for energizing each of said plurality of motor sections to operate at a second predetermined running speed greater than said first speed, workpiece strip position sensing means operative with the workpiece strip for providing a control signal in accordance with the position of the workpiece strip, and circuit connection means provided between the first and second voltage means and said motor sections for changing successively the operation of said motor sections from one of said threading and running speeds to the other of said speeds in response to said control signal.

4. In apparatus for controlling the operating speed-of a plurality of motors of a workpiece strip rolling mill operative with a strip coil winding device, 'the combination of first voltage supply means for energizing said motors to operate at a first predetermined threading speed, second voltage supply means for energizing said motors to operate at a second predetermined running speed greater than said first speed, strip movement sensing means operative with said workpiece strip for providing first control signals when there occurs a predetermined movement of the workpiece strip, load sensing means operative with said rolling mill for providing a second control signal when the workpiece strip leaves the rolling mill, circuit connection means provided between said motors and the first voltage supply means and the second voltage supply means for changing the connection of said motors from the second voltage supply means to the first voltage supply means in response to said second control signal, with said circuit connection means being further responsive to said first control signals for disconnecting the second voltage supply means from said motors successively in accordance with the movement of the workpiece strip.

5. In speed control apparatus for a plurality of motors operative with a workpiece strip rolling mill including a strip coiling device, the combination of first voltage supply means operative with said motors to provide a first predetermined speed of operation, second voltage supply means operative with said motors to provide a second predetermined speed of operation ditferentthan said first speed, load sensing means operative with said strip coiling device for providing a first control signal when a workpiece strip is being coiled by said strip coiling device, strip position sensing means operative with said strip for providing second control signals in accordance with the positional changes of said strip, first circuit means connected between the first voltage supply means and said motors for initially energizing said motors to operate at said first speed, and second circuit means connected between the second voltage supply means and said motors and being responsive to said first control signal for energizing said motors to operate at said second speed when a workpiece strip is being coiled by said strip coiling device, with said second circuit means being responsive to said second control signals to disconnect the second voltage supply means relative to at least one of said motors for each of the second control signals provided.

6. In speed control apparatus for a plurality of motors respectively operative with a workpiece strip rolling mill including a strip coiling device, the combination of first voltage supply means operative with said motors to provide a first predetermined speed of operation, second voltage supply means operative with said motors to provide a second predetermined speed of operation greater than said first speed, load sensing means operative with said strip coiling device for providing a first output control signal when the leading end of the workpiece strip is being coiled by said strip coiling device, position sensing means operative with the workpiece strip to sense the passage of the tail-end of the workpiece strip relative to the position of each of said motors and provide second control signals as a function of such passage, first circuit means connected between the first voltage supply means and said motors for initially energizing all of said motors to operate at said first speed, second circuit means connected between the second voltage supply means and said motors and being responsive to said first output control signal for energizing said motors to operate at said second speed when a workpiece strip is being coiled by said strip coiling device, and third circuit means responsive to said second control signals from the position sensing means and operative with the second voltage supply means for sequentially returning each of said motors to operation at said first speed as the tail-end of the workpiece strip respectively leaves the position of each of said motors.

References Cited UNITED STATES PATENTS 2,254,886 9/ 1941 Cook 7229 2,342,767 2/ 1944 'Stoltz 728 3,109,330 11/1963 Barnitz et a1 72-19 3,213,656 10/1965 Cook 72--15 CHARLES W. LANHAM, Primary Examiner.

A. RUDERMAN, C. H. HITT SON, Assistant Examiners.

Claims

1. IN APPARATUS FOR CONTROLLING THE OPERATING SPEED OF AT LEAST ONE MOTOR OF A STRIP ROLLING MILL OPERATIVE WITH A STRIP COIL COILING DEVICE, THE COMBINATION OF FIRST VOLTAGE MEANS CONNECTED TO ENERGIZE AT LEAST SAID ONE MOTOR TO OPERATE AT A FIRST PREDETERMINED SPEED, SECOND VOLTAGE MEANS FOR ENERGIZING AT LEAST SAID ONE MOTOR TO OPERATE AT A SECOND PREDETERMINED SPEED GREATER THAN SAID FIRST SPEED, STRIP MOVEMENT SENSING MEANS OPERATIVE WITH SAID STRIP FOR PROVIDING CONTROL SIGNALS IN ACCORDANCE WITH THE PASSAGE OF DISCRETE UNITS OF SAID STRIP RELATIVE TO THE POSITION OF SAID ONE MOTOR, AND CIRCUIT CONNECTION MEANS INCLUDING A SIGNAL COUNTER COOPERATIVE WITH STRIP POSITION SENSING MEANS PROVIDED BETWEEN THE SECOND VOLTAGE MEANS AND AT LEAST SAID ONE MOTOR FOR CONTROLLING THE ENERIZATION OF SAID ONE MOTOR BY A PREDETERMINED ONE OF SAID FIRST VOLTAGE MEANS AND SAID SECOND VOLTAGE MEANS IN RESPONSE TO SAID CONTROL SIGNALS.