US3508425A - Tension limit modification control - Google Patents

Tension limit modification control Download PDF

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Publication number
US3508425A
US3508425A US711290A US3508425DA US3508425A US 3508425 A US3508425 A US 3508425A US 711290 A US711290 A US 711290A US 3508425D A US3508425D A US 3508425DA US 3508425 A US3508425 A US 3508425A
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Prior art keywords
tension
strip
resistor
computer
tension limit
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Expired - Lifetime
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US711290A
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English (en)
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Howard N Cox
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General Electric Co
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General Electric Co
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
    • B21B37/48—Tension control; Compression control
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
    • B21B37/16—Control of thickness, width, diameter or other transverse dimensions

Definitions

  • Apparatus for adjusting the roll force of a metals rolling strip mill including a digital computer having an output signal representative of predetermined values of strip tension derived from computer inputs of strip speed, strip width and strip thickness (disregarding the nature of the strip material), the output signal being fed to a pair of digital/analog converters calibrated respectively according to preselected high and low limits of strip tension, each of the analog outputs being compared in an amplifier with actual (measured) strip tension and each of the amplifiers being arranged via servomechanisms to change the roll force oppositely according to the deviation of actual strip tension above and below the respective high and low limits.
  • tension or roll force, or both, must increase. If the roll force is not changed and the strip thickness is held constant as speed decreases by adjusting speed ratios between adjacent pairs of work rolls, the tension may increase approximately 400% when rolling very thin strip. Consequently, the strip might be torn or pulled apart.
  • the invention provides a means to overcome the excessive roll force resulting from arbitrary substitution of roll force for tension in the use of the automatic tension limit control and avoids the presently used alternative of manual manipulation of substituting roll force for tension through providing an automatic tension limit modification control having a computer which has three input signals applied thereto, representing the width, thickness, and the speed of the strip of material being rolled.
  • the computer provides two outputs derived from three input signals, representing allowable tension limits during predetermined ranges of speed. Of these three signals the width and the predetermined thickness of the strip remain relatively conice stant for each run and are therefore used in the calculation of the total tension prior to the run.
  • the speed provides an input signal to the computer which varies from standstill to top speed.
  • the computer Based on this signal and the two other predetermined signals, the computer produces two digital output signals which adjust a pair of voltage divider bridges so that each produces a voltage representing a maximum and a minimum allowable tension limit respectively which is applied to a pair of amplifiers which also receive a signal from a tensiometer representing the actual total tension developed in the strip of metal being rolled.
  • the resultant signals from these amplifiers are applied to a pair of relays which in turn operate the screwdown controls of the mill and cause a change in roll force when required to offset a change in tension due to a change in speed.
  • the computer is programmed to provide a stepped program for substituting roll force for tension so that both the roll force and the tension are held within allowable limits.
  • FIGURE 1 presents a block diagram of the tension limit modification control showing the relationship between the components.
  • FIGURE 2 shows a typical resistance bridge for providing stepped digital to analog conversion of signals.
  • a signal 11 representing the strip speed derived from a tachometer (not shown) is applied to a first input of a digital computer 15.
  • a second signal 13 representing the strip thickness derived from a thickness gage (not shown) is applied to a second input of computer 15.
  • a third signal 14, representing strip width, is applied to a third input of computer 15.
  • the computer produces two signals and applies them to a high tension limit reference circuit 17 and a low tension limit reference circuit 19.
  • the construction of these tension limit reference circuits is described lat-er.
  • the output of the tension limit reference circuits is in the form of an analog voltage signal having a negative polarity and values which are not equal thereby providing a dead band between them.
  • the output of the high tension limit reference circuit 17 may be 7 volts, and the output of the low tension limit reference circuit 19 may be 5 volts, thereby providing a dead band of 2 volts of negative polarity.
  • These two voltages are applied to a first input terminal of two amplifiers 21 and 23, respectively, each of which has applied to a second input terminal a positive potential signal 25 which is proportional to the total tension developed in the strip.
  • the output from the amplifier 21 is applied to the high tension limit screw adjustment relay coil 29 while the output of the amplifier 23 is applied to the low tension limit screw adjustment relay 27.
  • a normally open contact 31 closes and causes current to be applied to the screwdown motor (not shown) Whereby the screws are run down and roll force in the mill is increased.
  • coil 27 of the low tension screw adjustment relay 27 is energized, a normally open contact 33 closes and current is applied to the screwdown motor which causes the screws to be run up and the roll force to be decreased.
  • the strip speed signal 11 in addition to the predetermined strip thickness and the strip width signals applied to the computer causes an adjustment to be made by the computer in the output of the high and low tension limit reference circuits 17 and 19, respectively.
  • the circuitry involved in these tension limit reference circuits is shown in FIG. 2 where a series of resistors 50-57 are connected in series to form a resistor voltage division bridge between positive and negative power supply busses 59 and 61, respectively. Connected in parallel to this resistor bridge is a series of normally open contacts 63-66 each of which is connected to the junctions between adjacent resistors.
  • normally open contact 63 is at one end connected to the negative bus 61 and at the other end to normally open contact 64 and to the junction between resistors 56 and 57, thereby forming a parallel path to resistor 57.
  • normally open contact 64 is connected in parallel to resistor 56 and normally open contact 6-5 connects in parallel to resistor 55.
  • Resistor 54 is shunted by normally open contact 66.
  • a series of normally closed contacts 71-74 is connected in parallel with resistors 50-53 so that normally closed contact 71 is in parallel with resistor 53, normally closed contact 72 is in parallel with resistor 52, normally closed contact 73 is connected in parallel with resistor 51 and normally closed contact 74 connects in parallel with resistor 50 and to positive bus 59.
  • the value of resistor 54 is the same as the value of resistor 53, similarly the value of resistor 55 is the same as that of resistor 52, and resistor 56 has the same resistance as resistor 51.
  • Resistor 57 is of the same value as resistor 50.
  • the total resistance of the circuit between the positive bus 59 and the negative bus 61 is equal to the sum of the resistances 57-54, since the normally closed contacts 71-74 short out the resistors 50-53.
  • normally open contact 66 operated simultaneously with normally closed contact 71, so that when 71 opens normally open contact 66 closes; hence, resistor 53 is placed in the circuit while resistor 54 is removed by being shorted out, each time the contacts 66 and 71 change state. Since both these resistors have the same value, the total resistance between the positive bus 59 and the negative bus 61 remains constant.
  • This circuit is a voltage divider circuit and allows a convenient voltage adjustment in steps from a digital output.
  • Each set of normally open and normally closed contacts are part of a relay which is energized by the computer in FIGURE 1 indicated by numeral 15. The voltage thus produced is proportional to the total allowable tension in the strip calculated based on the three input signals to the computer.
  • relay coil 27 will become energized and cause normally open contact 33 to close causing the screws to be run up so that roll force is decreased.
  • normally open contact 33 closes, the screwdown control circuit is energized and causes the screws to be run up to increases the tension in the strip being rolled.
  • a digital computer an input to said computer representative of strip speed, inputs respectively to said computer representative of strip width and strip thickness for producing computer output signals representative of predetermined values of strip tension in respect to difierent strip speeds, a pair of circuits arranged to receive said output signals, means biasing each said circuit input representative of assigned high and low values of strip tension, means for measuring the value of the actual strip tension, means for comparing the output of said circuits with said measured value, and
  • each said comparing means controlled oppositely by each said comparing means respectively for changing the roll force upon said strip according to said comparison in response to changes in strip speed.
  • each of said pair of circuits comprises a digital to analog converter, each arranged to receive said output signals, means for biasing said converter input representative of a diiferent preselected value of strip tension, means for measuring the value of the actual strip tension, an amplifier for each said converter output including means for comparing the outputs of said converters with said measured value, and means controlled oppositely by each of said amplifiers respectively for changing the roll force upon said strip according to said comparison in response to changes in strip speed.
  • said comparison means comprises a pair of amplifiers each having an input terminal connected to one of said pair of circuits for receiving a first voltage signal and a second input terminal connected to said tension measuring means for receiving a second voltage signal.
  • said oppositely controlled means comprises a first and second relay connected to said comparing means for receiving one of the output signals and thereby operate to adjust 5 6 the roll force and tension limit in predetermined incre- 3,208,251 9/1965 Hulls et a1.
  • 72-11 mental steps. 3,440,846 4/ 1969 Scott 72--205 X References Cited 3,049,036 8/1962 Wallace et a1.
  • 72 205 3,194,036 7/1965 Canfor et al. 7211

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Control Of Metal Rolling (AREA)
US711290A 1968-03-07 1968-03-07 Tension limit modification control Expired - Lifetime US3508425A (en)

Applications Claiming Priority (1)

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US71129068A 1968-03-07 1968-03-07

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US3508425A true US3508425A (en) 1970-04-28

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US (1) US3508425A (enrdf_load_stackoverflow)
GB (1) GB1257562A (enrdf_load_stackoverflow)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3603124A (en) * 1968-05-09 1971-09-07 Nippon Kokan Kk Computer control system for rolling metal strips using feed-forward and prediction
US3782151A (en) * 1972-02-29 1974-01-01 Westinghouse Electric Corp Automatic gauge control system for tandem rolling mill
FR2403839A1 (fr) * 1977-09-26 1979-04-20 Secim Procede de regulation de l'epaisseur d'un produit plat en cours de laminage et installation correspondante
US20100050727A1 (en) * 2006-10-12 2010-03-04 Berthold Botta Rolling Mill and Method for Controlling a Rolling Mill

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3049036A (en) * 1957-04-08 1962-08-14 Westinghouse Electric Corp Automatic strip thickness control apparatus
US3169421A (en) * 1960-10-24 1965-02-16 Allis Chalmers Mfg Co Automatic gauge control
US3194036A (en) * 1958-01-02 1965-07-13 Westinghouse Canada Ltd Material thickness control apparatus
US3208251A (en) * 1961-05-03 1965-09-28 Westinghouse Canada Ltd Rolling mill control system
US3440846A (en) * 1967-06-06 1969-04-29 United States Steel Corp Apparatus for maintaining the gauge of steel strip

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3049036A (en) * 1957-04-08 1962-08-14 Westinghouse Electric Corp Automatic strip thickness control apparatus
US3194036A (en) * 1958-01-02 1965-07-13 Westinghouse Canada Ltd Material thickness control apparatus
US3169421A (en) * 1960-10-24 1965-02-16 Allis Chalmers Mfg Co Automatic gauge control
US3208251A (en) * 1961-05-03 1965-09-28 Westinghouse Canada Ltd Rolling mill control system
US3440846A (en) * 1967-06-06 1969-04-29 United States Steel Corp Apparatus for maintaining the gauge of steel strip

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3603124A (en) * 1968-05-09 1971-09-07 Nippon Kokan Kk Computer control system for rolling metal strips using feed-forward and prediction
US3782151A (en) * 1972-02-29 1974-01-01 Westinghouse Electric Corp Automatic gauge control system for tandem rolling mill
FR2403839A1 (fr) * 1977-09-26 1979-04-20 Secim Procede de regulation de l'epaisseur d'un produit plat en cours de laminage et installation correspondante
US20100050727A1 (en) * 2006-10-12 2010-03-04 Berthold Botta Rolling Mill and Method for Controlling a Rolling Mill

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GB1257562A (enrdf_load_stackoverflow) 1971-12-22

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