US3587279A - Fast response screwdown system for rolling mills - Google Patents

Abstract

A FAST RESPONSE SCREWDOWN CONTROL SYSTEM ESPECIALLY USEFUL WITH THE SENDZIMIR TYPE CLUSTER MILL A MANUALLY SETTABLE INPUT IS PROVIDED FOR A SERVOCONTROLLER AS WELL AS A FEEDBACK FROM THE SCREWDOWN TRAIN TO THE SERVOCONTROLLER WHEREBY

GAUGE MAY BE ACCURATELY MAINTAINED WITH THE SERVOCONTROLLER OPERATING A HYDRAULIC ROTARY ACTUATOR THROUGH VARIOUS VALVES.

Description

United States Patent Michael G. Seuhinlr; Lewis I. Seelhg, Waterbury, Conn. 747,519

Inventors FAST RESPONSE SCREWDOWN SYSTEM FOR ROLLING MILLS' Primary Examiner-Charles W. Lanham Assistant Examiner-Gene P. Crosby v Attorney-Melville, Strasser, Foster and Hoffman ABS'IRACT: A fast response serewdown control system espe- 3 Cm M ciully useful with the Sendzimir type cluster mill. A manually [1.8. 72/240, settsble input is provided for a servocontroller as well as a 72/21,72/245,72/248 feedback from the screwdown train to the servocontroller Int. 3211: 31/22 whereby gauge may be accurately maintained with the ser- FlelllelSenreh 72/237, vocontroller operating a hydraulic rotary actuator through 248, 240, 241, 242, 243, 21, 245 various valves.

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' sum 2 or 6 l 9 10 F1 fi I /IZ 2 20 I 8 UPPER HALF CLUSTER TYPE. F l RoLLm l G MILL INVENTOR/S MICHAEL G. SENDZ/M/Q LEW/S l2, SEEM/V6 ATTORNkYS PATENTEIIJIIII28I9II 3587.279

" I sum 6 0F 6 .4 I ,v/ 21 J 11 HYDRAULICS ROTARY FRONT AcTUAToR AcTUAToR ANGULAR DISPUXCEMENT H IIIFNON CONTACT-1| TRANSDUCER I GAUGE I INPUT II r W DIFF Y PRESSURE I I 8 TRANsDUcER MANUAL 1 I 9 I 11 DIAL-IN j I I SERVO ROTARY REAR IN PUT v I VALVE ACTUATOR ACTUATOR I I 17 12 I3 I I ANGULAR I DISPLACEMENT H I TRANSDUCER I I/ DIFF.

i ifi gfi m MENTOR/S FIQIQ 11 MICHAELGSENDZIMIR 5 LEWIS RSEELING ATTORNEYS FAST RESPONSE SCREWDOWN SYSTEM FOR ROLLING MILLS BACKGROUND OF THE INVENTION The invention relates to the field of rolling mills and more particularly to the screwdown arrangement for such rolling mills. While the basic system herein disclosed is applicable to rolling mills of various types, it is particularly useful and is described herein in relation to the so-called Sendzimir mill as exemplified in the Sendzimir U.S. Pat. No. 2,776,586.

Various screwdown systems have been provided for rolling mills over a great many years. A particularly accurate and minutely adjustable screwdown system has been made possible by the Sendzimir cluster mill such as is described in U.S. Pat. No. 2, 776,586. In such a mill, the work rolls which are of very small diameter are backed by a pair of backing rolls which in turn are backed by three intermediate backing rolls and these in turn are backed by a series of four backing rolls which are eccentrically mounted so that a screwdown effect may be obtained by rotating the eccentric mountings of one or more of the last backing rolls. According to the above mentioned patent, gear segments are provided on the shafts of two of the last backing rolls and these are engaged by a double faced rack actuated by a hydraulic piston. Thus, if the hydraulic piston moves the double faced rack up or down, the eccentric mountings of these backing rolls are rotated and thus the screwdown is accomplished. The hydraulic cylinder was controlled manually by the operator at a control station. Obviously with such operator control there is a time lag between a departure fromguage and the restoration to correct gauge. The present invention provides for automatic and fast response to sensings of a gauge which may either be a contact type or a noncontact type of guage and the system, because of the high speed response, will provide better control of quality and gauge from end to end of the strip.

SUMMARY According to the present invention, the double faced racks which actuate the gear segments of the backing roll mounted to effect screwdown, are actuated by a rotary actuator rather than by a hydraulic cylinder. It will be course be understood that the mechanism is duplicated in the front and back of the mill, i.e. for each end of the backing roll structure. Thus, there is provided at the front and rear of the machine a rotary actuator which drives a pair of gears counterrotatively and these gears mesh with a double faced rack on the upper end of the screwdown actuating rod.

The rotary actuator, which may be of conventional type and in itself does not constitute a part of this invention, is provided with suitable valves actuated by a servocontroller. The operators station is provided with a manual dial-in input which will divide the full range of the screwdown from top to bottom into 99, 999, 9,999 or more increments of work roll position. By means of this manual dial-in, a desired screwdown position is put into the servocontroller. The servocontroller operates certain valves: to actuate the rotary actuator and actual movement of the screwdown is fed back into the servocontroller in the form of a voltage which is balanced against the manually dialed-in voltage and when these voltages areequal, the rotary actuator stops. Thus, at any time that the actual screwdown position varies so as to feed back av voltage to the'servocontroller, the servovalve is actuated in'the appropriate direction to. return the system to null.

Suitable meters are provided for reading displacement or pressure and the operator station is provided with a mode select switchso'that the system may be controlled on the basis of displacement of the screwdown or on the basis of' the pressure beingexerted during the rollingoperation.

A manualcontrol'switch is also provided to bypass the low volume high pressure pump normally used and to utilize a high volume low-pressure pumpfor fast upor fast'down movement of the screwdown mechanism, and for large movements such as when having to change rolls or thread a new coil'into the mill.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary elevational view with parts in cross section of the upper portion portion of a rolling mill seen in the direction of the strip passage.

FIG. 2 is a fragmentary elevational view showing one embodiment of the location of the feedback transducer.

FIG. 3 is a view similar to FIG. 2 but showing a geared arrangement of the feedback transducer of FIG. 2.

FIG. 4 is a fragmentary elevational view with parts in cross section as seen from the left of FIG. 1.

FIG. 5 is a fragmentary view showing a different disposition of the feedback transducer.

FIG. 6 is an enlarged cross sectional view taken on the line VI-VI of FIG. 7. FIG. 7 is a cross sectional view taken on the line VII-VII of FIG. I on an enlarged scale.

FIG. 8 is a diagram of the control system.

FIG. 9 is a diagram helpful in understanding the operation of the control system.

FIG. I0 is a block diagram of simplified form.

FIG. 11 is a fragmentary elevational view showing the rotary actuator connected directly to the screwdown backing shaft rather than to the actuating rod asin FIG. 1.

FIG. 12 is a view similar to FIG. 11 but showing gearing between the rotary actuator and the screwdown backing shaft.

DESCRIPTION OF THE PREFERRED EMBODIMENT cluster mill such as shown in U.S. Pat. No. 2,776,586. It will be understood that the member 21 will be one of the last set of backing elements with which the screwdown is accomplished and as disclosed in the said patent the shaft is provided at each end with a gear segment which engages with the rack 22, one at the front and one at the back of the mill. It will be clear that the rack 22 is a double faced rack and that the corresponding backing element which would be engaged by the rack 22 in FIG. 1 has been omitted for clarity (see FIG. 4 wherein the gear segments are indicated at 23.). From FIG. 4 it will be apparent that as the screwdown rod 1 is caused to move upward or downward, it produced counterrotation of the shafts carrying the gear segments 23 and by virtue of the eccentric mounting, the backing elements 21 are caused to move up or down.

Referring back to FIG. 1', the rods 1 are provided with double faced racks 2 at their upper ends and these racks 2 are engaged by the gears 3 and 30 (see FIG. 4). Thus, as the gears 3 and 3a are caused to rotate in one direction or another, the rod 1 is caused to move upwardly or downwardly and thus to actuate the backing elements 21 to move up or down.

Rotation of the gears 3 and 3a is accomplished as best seen in FIGS. 1 and 7. A hydraulic actuator is directly connected to the shaft 5a upon which the gear 311 is mounted and this shaft alsocarries a gear 7a which meshes with a gear 7 fixed to the shaft 5. Thus rotation imparted to the shaft 5a is directly transmitted counterrotatively to the shaft 5. The gears 3 and 3a are preferably mounted on the shafts 5 and 5a respectively by means of splines or they may be integral with the shaft. Similarly the gears 7 and 7aare preferably splin'ed as at 6 and 6a to the shafts 5 and 5a. Preferably in order to eliminate backlash, the splines 6 and 611' have a different number of teeth. By way of example, the spline 6 may have teeth and the spline 6a may have I42 teeth. This results in a balanced gear drive pedestal free of backlash.

The rotary actuator 8 is connected directly to the shaft 5a, as for example by means of splines or inany other suitable manner. The rotary actuator 8 does not itself form a part of the present invention and such devices are available on the market. It can be'a fully self-contained unit which is provided with a servovalve 9, a solenoid-valve 16, a rotary feedback displacement'transducer 12, a transducer 11, cross relief valves 10, and is mounted directly on the pedestal 4. It will be understood that the parts just described may be mounted on an existing mill such as is shown in the Sendzimir U.S. Pat. No.

2,776,586 to replace the hydraulic cylinder and piston which actuates the screwdown rods corresponding to the rods 1. Also they can be mounted to rolling mills generally in order to operate the screwdown.

The servovalve 9 is a standard industrial servovalve available on the market and is commonly used in various machine tool, steel mill and automation controls. Such valves have a high level of dirt contamination rated on the order of 200 micron particles or finer.

Similarly, the solenoid valve 16 is a standard industrial fourway dual electrohydraulic solenoid valve.

The displacement feedback transducer 12 may be either a rotary potentiometer with a plastic film resistance element having infinite resolution and long life or it may be a linear transducer of similar characteristics. In FIG. 4 this feedback transducer is shown coupled to the rotary actuator shift. However, it may with equal success be coupled directly to one of the gear segments 23 as shown in FIG. 2, and if desired gearing may be introduced between the transducer 12 and the gear segment 23 as shown in FIG. 3. Depending upon results desired, this may be an up gearing or a down gearing. If it is desired to use a linear transducer as suggested above, it may be connected anywhere on the screwdown rod 1 as shown at 12a in FIG. I. It will be clear also that up or down gearing may be employed as at between the transducer 12 and the rotary actuator 8 as shown in the fragmentary view of FIG. 5. The transducer 12 will of course be housed in a rugged oil and dust tight enclosure and the required low voltage excitation and output signals are provided through a suitable connector and shielded multiconductor cable from the servocontroller 14.

The pressure transducer 11 is preferably an encapsulated diaphragm unit of rugged construction rated in the high pressure range of 300 psi. with rated pressure overloads of 200 percent or more. The necessary alternating current excitation demodulation and amplification are again provided through suitable connector and shielded multiconductor cables from the servocontroller 14. The cross relief valves 10 are simply fast acting adjustable units designed to protect the servovalve and actuator from sudden pressure transients above normal operating pressures.

The servocontroller 14 (see diagram FIG. 9) is also a commercial unit which in itself does not form a part of this invention. All the necessary amplifiers, exciters, demodulators, electronic power supplies, balance and gain controls, relay circuitry, etc. are all mounted on suitable component boards for easy maintenance and checkup. The amplifiers are preferably solid state transistorized circuitry mounted in encapsulated plug-in modules for ease of check out or replacement. All of the foregoing elements are housed in an oiltight enclosure. Such a unit is available on the market from Nashua Servocontrols and others and has long life reliability.

In FIG. 9, a manual dial-in control is shown at 13. This is simply a finitely variable resistance unit permitting the operator to dial in increments of desired position between zero and full stroke of the mill screwdown. With a four dial unit, it is thus possible to dial in 9,999 increments of position between zero and full stroke. On a typical Sendzimir cluster mill this represents an increment per dial-in digit of approximately 0.000025 inch. This dial-in control can be any other form of potentiometer.

The solenoid valve- 16 is a four-way solenoid valve to make possible a manual fast up or fast down screwdown operation such as is desirable when opening or closing the mill when not rolling under load.

Mention has been made of pressure control of screwdown as well as displacement control. In some cases it is advantageous to control the screwdown on the basis of force or pressure rather than displacement of the rolls. As seen in FIG. 9, there is provided a mode select switch 18, which also has an off position, so that the operator may select displacement mode or pressure mode for operation. In the displacement mode, the feedback to the servocontroller 14 comes from the feedback transducer 12 while in the pressure mode the feedback comes from a pressure differential transducer as can be clearly seen in FIG. 10. The displacement transducer circuit is provided with a suitably calibrated displacement meter and the differential pressure transducer is provided with a pressure meter. One of the advantages of operation in the pressure mode is that the mill may be operated as a hydraulically controlled skinpass mill.

Referring to FIG. 9, ti will be clear that a voltage is fed to the servocontroller 14 by the manual dialin 13. The output of the servocontroller actuates the servovalve 9 in the appropriate direction to cause the rotary actuator to effect a screwdown movement in one direction or the other. At the same time, the displacement transducer 12 feeds the signal to the servocontroller and the signal from the element 13 and the transducer 12 are balanced against each other and when they are balanced, the servovalve stops the actuator 8. It will be clear that these circuits are duplicated for the front actuator 8 and the rear actuator 8. The servocontroller 14 also yields a signal which is displayed on suitably calibrated front and rear displacement meters 17.

In the pressure mode of operation, the signal from the differential pressure transducer 11 is balanced against the preset pressure setting and the pressure signal is displayed on suitably calibrated meters at 17a.

The switch 15 is manually operated to achieve fast up or down motion and switching to fast motion deenergizes the servovalve and energizes the solenoid valve 16 so that the low pressure, high volume pump passes through the solenoid valve to the rotary actuator.

It will be understood that for a simplified and less expensive installation, the two rotary actuators 8 may be serviced by one servovalve 9 with one cross relief assembly 10, one pressure transducer 1 l, and one solenoid valve 16. The connections for such an arrangement will be apparent to one skilled in the art on the basis of these teachings.

Summarizing the operation of the system when the manual dial-in device 13 is actuated, it feeds a fixed voltage into an electronic amplifier in the servocontroller. 14. There the voltage signal is amplified to drive the electrohydraulic servovalve 9. The servovalve 9 feeds oil in one direction or the other to the rotary actuator 8 which, therefore, rotates in a direction determined by the polarity of the input voltage.

As the actuator rotates and accomplished a displacement, the displacement transducer 12 measures the actual displacement and converts it into a voltage which is then fed back into the servoamplifier. There is balanced with the input voltage from the dial-in or other input. When the input voltage and feedback voltage balance, the servovalve is nulled and then the actuator and the work roll will be held in a fixed position until a new command is manually dialed in. It will be understood the same manual input voltage is supplied to both front and rear actuators and both will then track as a function of the manual dial-in system. At the same time the meter 17 will indicate the position of the screwdown.

By means of the fast response control system herein disclosed, it is possible to obtain a control voltage signal proportional to the strip thickness by means of a noncontact gauge transducer on the mill. This will make gauge control fully automatic. It will be understood that such an automatic control system must'include a bumpless transfer system" to prevent sudden transient movement of the mill rolls when the mode of operation is changed from automatic to manual or vice versa. In other words, the input voltage must be compatible with the feedback voltage at that particular moment. This type of equipment is well known and available on the market.

From the foregoing description and a study of the diagrams of FIGS. 8, 9 and 10, it is believed that the operation of the system will be clearly understood.

Limitations not specifically set forth in the claims hereinafter are not intended and should not be presumed.

We claim: I

1. In a rolling mill having upper and lower work rolls, each work roll being supported by a pair of backing elements, wherein screwdown is effected by means of rods at the front and back of the mill, said rods being provided with double faced racks engaging pairs of pinions, said pairs of pinions being eccentrically mounted with respect of the pair of backing elements, whereby axial movement of said rods produces counterrotation of said pinions and causes said backing elementsto be moved up or down; a rotary hydraulic actuator for each of said rods, operative connections between said actuators and said rods to move the latteraxially, each of said rods having an additional double faced rack, gears engaging the two faces of said racks, said gears being mounted on shafts which are geared together for counterrotation, and an operative connection between said rotary actuators and one of each set of counterrotating shafts, respectively.

2. A rolling mill according to claim 1, wherein the gears on said counterrotating shafts are secured to their respective shafts by splines, one of the spline connections of each set having a number of teeth differing slightly from the other, whereby the gearing is adjustable to be free of backlash.

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