US3448941A

US3448941A - Lift mechanism initiate control system

Info

Publication number: US3448941A
Application number: US675143A
Authority: US
Inventors: Henry A Dickerson
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1967-10-13
Filing date: 1967-10-13
Publication date: 1969-06-10
Anticipated expiration: 1986-06-10
Also published as: FR1587485A

Description

H. A. nlcKERsoN LIFT-MECHANISM INITIATE CONTROL SYSTEM Filed oct. 15.1967

myENToR Henry A. Dickerson ATTORNEY June l0, 1969 WITNESSES United States Patent O LIFT MECHANISM INITIATE CONTROL SYSTEM Henry A. Dickerson, Snyder, N.Y., assignor to Westinghouse Electric Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed Oct. 13, 1967, Ser. No. 675,143 Int. Cl. B21c 47/00 U.S. Cl. 242--79 8 Claims ABSTRACT F THE DISCLOSURE A control system activates a lift mechanism at the proper time to effect movement of a lift mechanism to receive coils having variable radii being formed from strip being run at variable speeds. A -control signal indicative of the proper time to activate the lift mechanism is generated in response to the speed of the strip and the radius of the coils being wound. A timing cycle is initiated when the end of the coil reaches a predetermined point and, in response to the control signal, times out to activate the lift mechanism at the proper time.

Background of the invention The present invention relates to control systems for activating a mechanism at the proper time in response to variables and, more particularly, to control systems for activating a mechanism at the proper time to effect movement thereof so that a desired function is performed at the desired time in response to various variables in the system.

The downcoilers of a hot strip mill usually are equipped with coil cars which include hydraulic lift mechanisms which have top mounted coil supporting rollers. After a coil has been wound onto a downcoiler mandrel, the hydraulic lift mechanism of the coil car is hydraulically raised so that the coil supporting rollers engage the completed coil so that the coil car may then transport the coil 'from the downcoiler mandrel to other coil handling equipment for removing the coil from the downcoiler area.

At the beginning of each coil winding operation, a coil car is positioned under the downcoiler mandrel with the mechanism in its lowered position. Thus, as the coil is being completed, it is necessary that the coil lift mechanism be activated and raised to bring the coil supporting rollers into contact with the coil. It is highly desirable for efficiency of operation of the mill that the lift mechanism be activated at a time so that the rollers will engage the coils just as they are being finished. Since the lift mechanism typically is raised at a constant velocity, it would be relatively easy to provide a control system to activate the lift mechanism at the proper time if the strip were run at a constant velocity and each of the coils had the same radius. If this were the case the coil lift mechanism could be activated when the tail end of the strip for a given coil reached a predetermined distance from the mandrel, for example. However, in most cases, coils are not wound to the same radius and may have radii varying over relatively wide ranges. Moreover, in many instances, the speed of the strip from which the coils are wound varies from coil to coil. Also the speed of the strip is often changed during a cycle of operation, the speed being reduced leaving the mill for delivery to the coil mandrel, for example. Thus, in such instances of producing coils of diiferent diameters and running strip at different speeds, it is not possible to have the lift mechanism activated at the proper time for the rollers thereof to engage the coil just as the coil is completed if only the position of the tail end of the coil is sensed. lf a highly eicient and non-destructive coil Winding oper- 3,448,941 Patented June 10, 1969 ation is to be provided, it becomes necessary that the control system takes into account variable factors in the system including the radius of the coil being wound and the speed of the strip as being wound in addition to the constant factors of the system.

Summary of the invention Accordingly, the present invention provides a control system for activating a mechanism at the proper time to effect the movement thereof to receive an article of manufacture having variable factors associatedtherewith. In the system the variable factors are sensed and utilized to generate control signals which in turn are employed to activate the mechanism to eifect the movement at the proper time.

Brie]c description of the drawing The single figure is a schematic-block diagram showing the control system of the present invention.

Description of the preferred embodiment Referring now to the figure, the downcoiler arrangement is shown wherein a strip 10, which may comprise a metal such as steel being rolled to a predetermined thickness, is supplied by a hot strip mill, for example. The strip 10 passes through a plurality of mill stands 12 and then over a plurality of runout tables 14 to the downcoiler. The strip 10 is fed through a pair of pinch rolls 16 and Wound about a downcoiler mandrel 18. 'Ihe strip 10 wound about the mandrel forms a coil 20 which has a radius RC as shown on the drawing.

Disposed immediately below the coil 20 is a coil car 22 which includes a hydraulic lift mechanism 24 having coil supporting rollers 26 positioned immediately under the coil 20. The coil supporting rollers 26 are shown in their rest position spaced below the axis of the mandrel 18 by a distance RL. The coil supporting rollers 26 are adapted to receive the coil 20 when raised the necessary distance RL-Rc. As previously explained it is highly desirable to activate the lift mechanism 24 of the coil car 22 at the proper time in order to insurethat the coil supporting rollers 26 are in position to engage the coil 20 just as the coil is being completed as the tail end of the strip 10 is entering the pinch rolls 16. The control system of the present invention effects the activation of the hydraulic lift mechanism 24 at the proper time taking into account that the coil 20 may have differing raddi Rc and also that the strip speed VS may vary.

The equation representing the time interval AT between the strip 10 leaving the mill and the coil car lift initiation may be written as follows:

The time ts is the time required for the end of the strip to travel from the end A of the mill at the rollers 12 to a selected coil car contact point A' as shown in the gure. Time ts may then be defined by: rS=F/VS; where F is the distance from the end of the mill A to the coil car contact point A', and Vs is the average speed of the end of the strip over the distance F. The time t1, is the time required for the coil car lift mechanism 24 to move from its rest position a distance RL from the axis of the mandrel 18 until it contacts the coil 20 having a radius Rc. Time tL may thus be dened by the equation t :RL-RC L VL vwhere VL equals the speed of raising of the lift mechanism 24.

Using the above definitions for the times fs and tL, the time AT may be defined as:

RLRC ALV( VL If this equation is now multiplied at the top and bottom by Vs, we find:

AT: VS

Taking the inverse of the above equation, we obtain:

AT F-(RL- RdVs/VL (l) This equation can be represented by a voltage and resistance analog. The control system of the present invention derives a voltage which is proportional to the above equation which is to be applied to an inverse Voltage timer 28 as shown in the figure. The inverse voltage timer 28 is designed to take the time integral of the voltage applied thereto and to provide an output signal therefrom when the time integral of the input voltage has reached a predetermined level. Thus, the time at which the inverse voltage timer provides an output signal at its output 30 is dependent upon the magnitude of voltage applied across its

inputs

32 and 33. Hence if the magnitude of the 4voltage applied to the inputs 32-33 is doubled the time interval for an output to appear at the output 30 will be halved, or, if the voltage input is halved, the time interval for an output at 30 to appear will be doubled. The output 30 is supplied as an activating signal to the coil car lift mechanism 24 to cause the activation thereof, so that the lift mechanism 24 will begin to rise and will engage the coil at the desired time when the tail of the strip being wound is at point A.

The control system for generating the control function as defined in Equation l is generated in response to the variable speed of the strip VS and the variable radius RC of the coil 20 and in accordance with the fixed parameters of the system. The inverse voltage timer 28 is activated in response to an input 36- applied thereto to initiate the timing out of the timer 28. The initiate signal is supplied to the input 36 from a position sensing device 34 which senses when the tail end of the strip 10 leaves the mill stands 12 at the point A. The control system functions to generate a voltage according to the Equation 1 which is applied to the input 32 of the inverse voltage timer 28. When the input 36 occurs, the timer 28 begins to time out in response to an input 32 supplied thereto which is supplied according to Equation l. Hence, after a time interval defined by the equation AAT=tStL an activating signal is provided by the inverse voltage timer 28 via its output 30 to the coil car lift mechanism 24. The lift mechanism 24 will then raise to be at the desired position to engage the coil 20 as the coil 20 is being completed.

A control voltage EC proportional to Equation 1 is developed in the following manner to be applied as the input of the inverse voltage timer across the

leads

32 and 34. In order to generate a voltage ES proportional to the speed of the strip 10, a speed sensor 38, such as a tachometer, is provided adjacent the strip 10 to sense the speed thereof. The voltage Es is thus generated to satisfy the equation: ES=VS/KV, wherein KV is the constant of proportionality having units of speed over voltage. The voltage ES developed at the speed sensor 38 is supplied across an input line 40 and a common line 42.

A constant voltage EF isV provided which is proportional to the fixed distance F between the points A and A. A constant of proportionality KF is used so that A voltage -l-KFEF is supplied to a terminal 44 and a voltage -KFEF is supplied to a terminal 46 as one input to a servo amplifier 48.

The fixed distance RL is represented in the analog by the total resistance of the series combination of: a resistor R1, a potentiometer P1 and a potentiometer P2, which are respectively connected in series between the ES line 40 and the common line 42. The variable distance RC, indicative of the radius of the coil 20, is represented by the resistance between the top end of the resistor R1 at the line 40 and the slider on the potentiometer P1. The slider on the potentiometer P1 is set in response to the radius RC of the particular coil 20 being wound. This is effected via a radius sensor S2 sensing the radius RC and supplying a mechanical output proportional thereto to the slider on the potentiometer P1 via a mechanical coupling 54. With the slider of the potentiometer P1 at the top end thereof, the mandrel radius is defined, and with the slider at the bottom end, the maximum coil radius is defined:

A scaling circuit 55 including a potentiometer P3 and a resistor R2, with one end of the potentiometer and the slider thereof connected to the slider of the potentiometer P1. The other end of the potentiometer P3 is connected to the servo amplifier 48 at an input 50 and through the resistor R2 to the common line 42. The input to the scaling circuit at the slider of the potentiometer P1 may be stated as:

The scaling circuit is designed to provide the factor RL/ VL so that the input 50 is defined by a voltage EA wherein:

The output of the servo amplier 48 is utilized to drive a servo motor 56. The servo motor 56 provides a rnechanical output 58 which is coupled to the slider on a potentiometer P4 and a mechanical output 60 coupled to the slider on a potentiometer P5. The top end of the potentiometer P4 is connected to the terminal 44 where the -i-KFEF voltage is applied. The bottom end of the potentiometer P4 is connected through a resistor R3 to the common line 42. The top end of the potentiometer P5 is connected to the line 40 and the bottom end thereof is connected through a resistor R4 to the commo-n line 42. The

inputs

32 and 33 to the inverse voltage timer 28 are connected, respectively, to the top and bottom ends of the resistor R4, with the voltage EC being developed across the resistor R4 to be applied to the inverse voltage timer 28. The slider on the potentiometer P4 is electrically connected as an input via an input 62 to the servo amplifier 48.

Assume, for example, that the input EA to the servo amplifier 48 is zero. The only input to the servo amplifier 48 is then -KFEF representing the fixed distance F. With this input only the servo amplifier 48 via the servo moto-r 56 and coupling 58 drives to its upper limit. With the potentiometer P4 set to its upper limit, the feedback appearing on the lead 62 will be -l-KFEF, the voltage appearing at the terminal 44, The servo amplifier 48 will thus be balanced with a -KFEF input at lead 46 and a -i-KFEF input at the feedback input 62. If the EA input 56 to the servo amplifier 48 is made equal to KFEF/Z, the output of the servo amplifier 48 will cause the servo motor 56 to position the slider on the mechanical coupling 58 on the potentiometer P4 downwardly until the total resistance of the potentiometer P4 and resistor R3 is equal to 1/2 of the total resistance P4+R3. Thus a feedback signal equal to -}-KFEF/2 will be applied via the lead 62 to balance the servo amplifier 48. This would represent a condition when the coil car lift raise time tL times the average strip speed VS would be equal to 1/2 of the distance F.

Since the potentiometer 'P5 connected to the ES line 40 is driven in parallel -with the potentiometer P4, the slider thereon assumes .a corresponding physical relationship with respect to the slider on the potentiometer P4. Assume, for example, that the resistor R3 is a resistor equal to a of the total resistance of the potentiometer P4. With such a relationship between R3 and P4 the value of the input EA can range from zero to of the xed -value KFEF for the servo amplifier 48 and servo motor 56 to drive the slider of the potentiometer P4 through its total operating range. The potentiometer P and the resistor R4 are selected to have the same relationship with the resistor R4 having a resistance equal to J; of the total resistance of the potentiometer P5. When the input EA to the servo amplifier 48 is zero, the potentiometer P5 will be at its maximum resistance position with the slider thereon at the top position. The voltage developed across the resistor R4 at leads 32 and 33 will be PAO of the voltage ES across the potentiometer P5 and resistor R4 between the

lines

40 and 42. Accordingly when the voltage EA is equal to KFEF/Z, 1%; of the voltage EF will appear across the resistor R4. The voltage across the resistor R4 -is proportional to:

Multiplying this expression by the speed-voltage scale factor KV, it can be seen that this is the desired equation for driving the inverse voltage timer 28 to obtain the desired timing interval of:

VL AT- VS Thus, for example, if the speed VS of the strip is doubled, the voltage EC appearing across the input to the inverse timer 28 is doubled thereby halving the time at which the inverse voltage timer 28 would time out to supply an activating signal via the lead 30 to the lift mechanism 24. Conversely, if the strip speed VS were halved, the time required for timing out the inverse voltage timer 28 would be doubled before activating the coil car lift mechanism 24.

In setting up the control system as shown on the drawing, the following procedure may be followed: The resistance of the potentiometer P2 is adjusted via the slider thereon to correspond to the distance from the coil car supporting roller 26 rest position to the maximum coil radius to be wound in the system. If the maximum coil radius is dened as Re, the resistance setting of the potentiometer P2 may be defined as:

Next voltage ES representing a strip speed of KVES is supplied to the line 40 and hence to the resistor R1 and the potentiometer P5. The potentiometer P3 is disconnected from the slider on the potentiometer P1 so that servo motor 56 positions the sliders on the potentiometers P4 and P5 to their upper limits. The inverse voltage timer 28 is then adjusted to time out after an interval tS=F/VS.

The time zL for the coil car lift mechanism 24 to raise from its rest position to the maximum coil RC' of the coil it is then calculated or measured. The slider end of the potentiometer P3 of the scaling circuit is disconnected from the slider on the potentiometer P1 and connected to the lower end of the potentiometer P1 at the maximum coil radius end at the junction between the potentiometer P1 and the potentiometer P2 in order to obtain the known time interval tL input corresponding to a maximum coil radius Rc, to the scaling circuit.

The potentiometer P3 of the scaling circuit is now adjusted until a voltage proportional to the distance traveled by the strip 10 during the time interval t1, is obtained CII 6 across the resistor R2 of the scaling circuit. Thus, the potentiometer P3 is adjusted until a voltage is obtained across the resistor R2.

The general procedure is completed by disconnecting the end of the potentiometer P3 from the junction of the potentiometers P1 and P2 reconnecting it to the slider on the potentiometer P1. The control system is thus calibrated for operation as described above with a control signal EC developed and supplied as the proper input voltage to the inverse voltage timer 28 to cause the coil car lift mechanism 24 to be activated at the proper time to rise and engage the coil 24 as each coil is being completed.

Although the presenty 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 and the details of `construction and the combination and arrangements and components can be resorted to without departing from the scope and the spirit of the present invention.

I claim:

1. In a control system for activating a lift mechanism at the proper time to effect the movement thereof to receive articles of manufacture upon being completed having variable sizes and being formed from material being provided at variable speeds, the combination of:

first means for providing speed signals indicative of the speed of said material;

second means for providing an indication of the size of a given article of manufacture;

third means for providing an initiate signal in response to material being used for the given article of manufacture reaching a predetermined point;

generating means for providing a control signal indicative of said proper time in response to said speed signals and said indication of the size of the given article of manufacture; and

timer means responsive to said initiate signal to begin a timing operation and for activating said lift mechanism at said proper time in response to said control signal.

2. The combination of claim 1 wherein:

said control signal comprising a control voltage inversely proportional to said proper time, and

said timer means comprising an inverse voltage timer operative to time out in a time period proportional to said control voltage applied thereto.

3. In a control system for activating a lift mechanism at the proper time to eifect the movement thereof to receive coils upon being completed having variable radii being formed from strip being run at variable speeds, the combination of:

irst means for providing speed signals indicative of the speed of said strip;

second means for providing an indication of the radius of a given coil;

third means for providing an initiate signal in response to the end of said given coil reaching a predetermined point;

generating means for providing a control signal indicative of said proper time in response to said speed signals and said indication of the radius of said given coil; and

4. The ycombination of claim 3 wherein:

5. The combination of claim 3 wherein:

the generating means including,

iirst impedance means having applied thereto said speed signal and including a slider thereon, said slider being driven in response to said indication of the radius of a given coil so that the output of said impedance means is related to said speed signals and the radius of said given coil,

fourth means for providing reference signals indicative of a fixed distance of travel of said strip,

servo means receiving as inputs thereto scaled signals proportional to said output of said first impedance means, said reference signals, and a feedback signal indicative of difference between said scaled signals and said reference signals, said servo means providing a servo output in response thereto,

second impedance means for receiving said reference signals and including a slider thereon responsive to said servo output to provide said feedback signals, and

third impedan-ce means for receiving said speed signals thereto and including a slider thereon being driven by said servo output to develop said control signal across `a portion thereof to be applied to said timer means.

6. The combination of claim 5 wherein:

said control signal comprising a control 'voltage inversely proportional to said proper time, and

7. The combination of claim 6 wherein:

said generating means further including,

a scaling circuit being connected between said slider on said iirst impedance means and said servo means for providing said scaling signals in response to said output of said first impedance means.

3. The combination of claim 7 wherein:

said rst, second and third impedance means comprising respectively first, second and third potentiometers including sliders thereon adapted to be mechanically driven,

said first potentiometer having its slider driven by said indication of the radius of a given coil provided by said second means;

said servo means including a servo amplifier receiving said scaled signals, said reference signals and said feedback signals and a servo motor responsive to the output of said servo amplifier for providing mechanical outputs,

said second and third impedance potentiometers having their sliders respectively driven by said mechanical output of said servo motor.

References Cited UNITED STATES PATENTS 2,911,164 11/1959 Caine i 242-79 3,108,759 10/ 1963 McConegly 242--79 NATHAN L. MINTZ, Primary Examiner.