Title of Invention

OPTO- ELECTRONIC SHEEET CENTERING SENSOR FOR PROCESS LINE

Abstract

A sensor based on opto-electronic principle for use in detecting the position of a sheet in a continuous process line and for centering it comprising : (a) an array of photocells (D1 to D19),(b) a light source (8a/8b) matching said array of photocells, (c) one sensor (7a) adapted to be mounted towards/near one edge side of a sheet in the process line and to indicate any lateral shift of the sheet from a central position ,(d) another sensor (7b) adapted to be mounted towards /near the other (opposite) edge side of the sheet in the process line and to indicate any lateral shift of the sheet from a central position while, and (e) the corresponding light sources (8a/8b) are adapted to be mounted above the sheet. There is also disclosed a method for centering shifting sheet using the above centering sensor and there is also disclosed a system therefore.

Full Text

Introduction to the Field of the Invention This Invention in one aspect relates to a opto-electronic sheet centering sensor for use in process tine in steel rolling mills. In a second aspect, this Invention relates to a method for centering shifting steel sheet in a rolling mill operation. In a third aspect, this Invention relates to a system for centering shifting steel sheet in a rolling mill process line. Details of Prior Art and Relevance of Prior Art A prior art, by way of Japanese Patent JP-072314134, discloses a line image sensor. Another prior art, by way of US Patent US-5493221 A, discloses a weld joint locations in a sheet material. The Applicant is not aware of any other prior art. The above referred two prior art Patents, though deal with sensors, these are for entirely different Applications and are not suited for sheet centering operations by opto-electronic principle in well known continuous process lines. Needs for Reliable Control Sensor In the continuous process lines like pickling, continuous annealing, chemical cleaning, and galvanizing of cold rolling complex, the moving sheet often flutters more than 200 mm. Because of the fluttering, the conventional capacitor type sensor now used is damaged. This sensor has the limitations of a minimum distance between the sensor and the sheet and hence the centering device becomes ineffective. This result often in off-centering of the sheet, thereby leading to damage due to strikes with the sides of the process lines. During a process operation, the off-centering of the sheet is required to be identified for taking control actions. 2 Objects of the Invention It is an object of this Invention to propose a highly reliable novel sensor useful for indicating the position of the sheet on the roller table. It is another object to propose such a sensor, which, by using photo diode array of suitable dimensions, can accurately detect the sheet position even when there is lateral shift and fluttering in a moving sheet. It is a further object of this Invention to propose such a sensor, which will provide predetermined/desired electrical characteristics through appropriate circuit configuration. It is yet another object of the Invention to propose an appropriate mechanical housing of the sensor array for the sensor. It is a still further object of this Invention to propose such a sensor, which can be safely and easily installed and operated with accuracy even in hot dip galvanizing line. It is a further object of the Invention to propose suitable method and system for centering shifting sheet by using the novel sensor mentioned above. These and other objects will be apparent from the following paragraphs. Brief Statement of the Invention Thus according to this Invention there is provided a sensor based on opto-electronic principle for use in detecting the position of a sheet in a continuous process line and for centering it comprising a. an array of photocells, b. a light source matching said array of photo-cells, c. one sensor adapted to be mounted towards/near one edge side of a sheet in the process line and to indicate any lateral shift of the sheet from a central position, 3 d. another sensor adapted to be mounted towards/near the other (opposite) edge side of the sheet in the process line and to indicate any lateral shift of the sheet from a central position, while, e. the corresponding light sources are adapted to be mounted above the sheet. The sensor on either lateral side of the sheet are adopted to indicate any shift of the sheet either to the left or to the right of a pre-defined position. The sensor on either side of the sheet are inter-linked through a conventional means for activating an appropriate correction means based upon the indications from the sensors. According to the another aspect of the Invention, there is proposed an improved method for carrying out the centering of a sheet, in the instance of a shift in the position of the sheet from a central line in the direction of movement, in a conventional process line in a rolling mill comprising: providing a sensor system as described herein before in the process line such that in the instance of the sheet remaining centered in the process line, the active area exposed of each optoelectronic sensor is the same and in the instance where the sheet shifts off-centre either to the left or to the right, the active area exposed of each sensor varies automatically with an increase or decrease in the active area as the case may be, thereby enabling mechanical actuation of the sheet to centre the same, through a conventional means for activating such a correction. The lateral shifting of the sheet from the central line automatically reduces the exposed active area of the relevant sensor while simultaneously increasing the exposed active area of the other edge side sensor which results in a difference signal either +ve or -ve as the case may be. The correction of this variation is carried out by mechanical actuation of the sheet to reach the central line. "According to yet another aspect of the Invention, there is provided a system for centering a drifting sheet in a sheet rolling mill comprising sensor based on opto-electronic principle for use in detecting the position of a sheet in a continuous process line and for centering it comprising a. an array of photocells, 4 b. a light source matching said array of photo-cells, c. one sensor adapted to be mounted towards/near one edge side of a sheet in the process line and to indicate any lateral shift of a sheet from a central position, d. another sensor adapted to be mounted towards/near the other (opposite) edge side of the sheet in the process line and to indicate any lateral shift of a sheet from a central position, while, e. the corresponding light sources are adapted to be mounted above the sheet/strip, f. correction actiontag for actuating a sheet from the centre and centuring the based on the signals receied from the above said two sets of sensors. The sensor on either lateral side of the sheet are adopted to indicate any shift of the sheet either to the left or to the right of a pre-defined position. The sensor on either side of the sheet are inter-linked through for activating an appropriate correction means based upon the indications from trier-sensors'. Brief Description of the Drawings The Invention will now be more fully described with reference to the accompanying drawings.In the drawings, Figure 1 shows the conventional arrangement used for centering a shifting sheet. / Figure 2 shows the arrangement of the Invention for centering a shifting sheet. / Figure 3 illustrates the photo-diode array used in each sensor shown in Figure 2. Figures 4 to 7 show the different views viz. front view, top view, side view and isometric view respectively, of the mechanical structure used for the installation of the sets of sensors shown in Figure 2. Figures 8 to 9 illustrate respectively the front and side views of the illumination system shown in Figure 2. 5 Figure 10 illustrates the enclosure used for one sheet centering sensor. Figure 11 shows the view of Figure 10 in the portion marked "W". Figure 12 shows the top view of Figure 10 Figure 13 shows the view in the direction of arrow "B-B" in Figure 12. Figure 14 shows the view in the direction of the arrow "A-A" in Figure 12. / Figure 15 shows the bottom view of Figure 10 and Figure 16 shows the positions of the sheet during the shifting and centering. Detailed Description of the Drawings It will be seen from the conventional arrangement shown in Figure 1, that while the sheet 1 is moving, any lateral shift in its position is identified by capacitor plates 2a and 2b and suitable signal is fed to the summing electronic device 3. This device in turn sends necessary signals to the electronic central circuit unit 4 which provides necessary extent of correction signal to the activator unit 5. The activator unit 5, in turn, operates the mechanical system 6 for centering the laterally shifting sheet. These units 3, 4 and 5 are a collective set up and are used in our Invention also. There being nothing new in this set up, we are not describing the known set up in detail. Referring to Figure 2, it will be noticed that the capacitor, based on old or existing system, is being replaced by a new opto-electronic sensor. When the sheet 1 is properly centered, the two opto-electronic sensors 7a, 7b provide identical or uniform signals to the summing electronic unit 3 which feeds unit 4 which in turn feeds unit 5. There being no fault detected in the position of the sheet, the actuator 5 does not trigger any correction signal. 6 Each longitudinal edge 1a, 1b of the sheet is illuminated from above with respective light source 8a, 8b which feed the opto-electronic sensors 7a, 7b with suitable signals. Fig 16 In Figure 3, we have shown the details of the photo diode array comprising 19 diodes D1 to D19 in each sensor 7a and 7b. Referring to Figures 4 to 7, it will be clear how a channel like structure is used for installing one set of sensors, say 7a. Similarly, another structure is used to install another sensor 7b. These sensors are placed directly below the respective light sources below the sheet level. While the light sources are placed above the sheet level having the sheet edges in between. The two light sources are above the longitudinal ends edges region of the sheet and the two sensors are corresponding below the longitudinal end edges of the sheet. In Figures 8 and 9, we have explained the illumination system for each light source, which in simple language has two arrays of a series of electric bulbs. In Figure 10, we have shown in isometric view the enclosure used for one set of centering sensor, which is duplicated for the other set of sensor. This enclosure, in simple statement, is a rectangular enclosure having fixing brackets. The top is provided with a glass sheet and a cover sheet. In Figures 11 to 15, we have explained the various views of the enclosure. Referring to Figure 16, it will be seen that the sheet moves on the roll table in a horizontal direction. The two light sources 8a and 8b and the two corresponding opto-electronic sensor units 9a and 9b are also accordingly in operating position. Assume the width of the long coil of sheet is "A"-"B". So long the edge A and edge B of the sheet are in right position from the centre, the sheet is centered and both the opto-electronic sensors receive same quantity of light thereby there being no residual signal. These two equal quantity of say + and - light emissions cancel each other and the sheet position is not disturbed. 7 Now let us assume a lateral shift in the sheet. The end A shifts to "A1" to the left and the end "B" shifts accordingly to "B1" also to the left. It can be easily seen that the quantum of light received by the diodes of the sensor on the right side will be more than the quantum of light received by the diodes of the left sensor. Thus there is now difference in the signal output one producing more and the other producing less, which can be called +ve and -ve. These signals are immediately processed in the next correction system and the sheet actuator accordingly shifts the sheet from position "A1" to A and "B1" to B thereby equalizing the signals from the opto-electric sensor. Referring back to Figures 2 and 16, it will be seen that these illustrate the active area of sensor when it is centered or when it is shifting to the left or to the right. The active area of the sensor under the above conditions is variable because the sheet width for coils processed in the line is variable. For a single coil the width is constant along the length but the width may be different for different coils within the range processed through the line. Following may be noted regarding design of sheet centering sensor. The range of strip width is 650 mm to 1250 mm. The width of roll table is 1500 mm. When coils with different widths are processed in the line, the maximum edge shift on each side when any width is rolled is 300 mm. Further, in absence of proper sheet centering, strip deflection on left and right side was found to be up to 75 mm on either side. Considering the above two factors, to make sensing effective, a sensing area with at least 450 mm length is required for each sensor installed on both ends of the sheet to cover all ranges of the sheets rolled and considering maximum deflection in the strip sideways (300+75+75). An additional active area of around 25-30 mm was desired in the sensor to take care of any further unpredictable shifts on either side. The active sensing area of each photo diode used in the system is 25.4 mm (length) * 5.1 mm (width). Therefore, an array of 19 photo diodes mounted one after another length wise and connected in series was used to make the opto-electronic sensor with a total active area of 482.6 mm. 8 Advantages of the Invention 1. Provides electrical signal output as position feed back for taking control action to keep the sheet at centre. 2. The reliability damage of the sensor in the field Application is ensured, even if, there is a fluttering of moving sheet by 500m mm in either direction. 3. Identification of the position of sheet on the process line is not affected by ambient light. 4. It replaced capacitor-based sensor as import substitution. 5. Exhibited excellent performance during prolonged trails at hot dip galvanizing line of Bokaro Steel Plant. It may be noted that we have successfully developed an opto-electronic sensor, which generates electrical signal that has been fed to the existing summing and signal amplifying controller of the capacitor based sensor, which in turn controls the mechanical actuator already installed at site for earlier system. The output of the developed sensor was exactly matched with the input requirement of the existing controller. The final resulting signal after proper summing of the signals from a pair of sensors installed on either side of the strip is fed into the existing power pulse type electro-hydraulic controller which operates the strip shifting mechanism to correct the strip position error. 9 We Claim: 1. A sensor based on opto-electronic principle for use in detecting the position of a sheet (1) in a continuous process line and for centering it comprising: a. an array of photocells (01 to D19); b. a light source (8a/8b) matching said array of photo-cells; c. one sensor (7a) adapted to be mounted towards/near one edge side of a sheet in the process line and to Indicate any lateral shift of the sheet from a central position ; d. another sensor (7b) adapted to be mounted towards/near the other (opposite) edge side of the sheet in the process line and to indicate any lateral shift of the sheet from a central position while, e. the corresponding light sources (8a/8b) are adapted to be mounted above the sheet. 2. A sensor as claimed in claim 1 wherein the sensor on either lateral side of the sheet are adapted to indicate any shift of the sheet either to the left or to the right of a pre-defined position. 3. A sensor as claimed in claims 1 or 2 wherein the sensor on either side of the sheet are inter-linked through correction activating means for activating an appropriate correction means based upon the indications from the sensors. 4. An improved method for carrying out the centering of a sheet, in the instance of a shift in the position of the sheet from a central line in the direction of movement, in a conventional process line in a rolling mill comprising: providing a sensor system as described herein before in the process line such that in the instance of the sheet remaining centered in the process line, the active area exposed of each opto-electronic sensor is the same and in the -10- instance where the sheet shifts off-center either to the left or to the right, the active area exposed of each sensor varies automatically with an increase or decrease in the active area as the case may be ,thereby enabling mechanical actuation of the sheet to center the same, through a conventional means for activating such a correction. 5. A method as claimed in claim 4 wherein the lateral shifting of the sheet from the central line automatically reduces the exposed active area of the relevant sensor while simultaneously increasing the exposed active area of the other edge side sensor which results in a difference signal either +ve or -ve , as the case may be. 6. A method as claimed in daims 4 and 5 wherein the correction of this variation is carried out by mechanical actuation of the sheet to reach the central line. 7. A system for centering a drifting sheet in a sheet rolling mill comprising sensor based on optoelectronic principle for use in detecting the position of a sheet in a continuous process line and for centering it comprising: a. an array of photocells (D1-D19); b. a light source (8a/8b) matching said array of photo-cells; c. one sensor (7a) adapted to be mounted towards /near one edge side of a sheet in the process line and to indicate any lateral shift of a sheet from a central position, d. another sensor (7b) adapted to be mounted towards/near the other (opposite) edge side of the sheet in the process line and to indicate any lateral shift of a sheet from a central position, while, e. the corresponding light sources (8a/8b) are adapted to be mounted above the sheet/strip, and, f. correction activating means (3,4,5) for actuating a sheet drifting from the center and centering the same based on the signals received from the above said two sets of sensors. -11- An improved method for carrying out the centering of a sheet in a conventional process line substantially as herein described. 9. A sensor based on opto-electronic principle for use in detecting the position of a sheet in a continuous process line and for adjusting or centering it substantially as herein described with reference to the accompanying drawings. 10. A system for centering a drifting sheet in a sheet rolling mill substantially as herein described with reference to the accompanying drawings. Dated this 19th day of February 2001 OPTO - ELECTRONIC SHEET CENTERING SENSOR FOR PROCESS LINE IN STEEL ROLLING MILLS, A METHOD FOR CENTERING SHIFTING STEEL SHEET IN A ROLLING MILL USING THE SAID SENSOR AND A SYSTEM THEREFOR A sensor based on opto-electronic principle for use in detecting the position of a sheet in a continuous process line and for centering it comprising : (a) an array of photocells (D1 to D19),(b) a light source (8a/8b) matching said array of photocells, (c) one sensor (7a) adapted to be mounted towards/near one edge side of a sheet in the process line and to indicate any lateral shift of the sheet from a central position ,(d) another sensor (7b) adapted to be mounted towards /near the other (opposite) edge side of the sheet in the process line and to indicate any lateral shift of the sheet from a central position while, and (e) the corresponding light sources (8a/8b) are adapted to be mounted above the sheet. There is also disclosed a method for centering shifting sheet using the above centering sensor and there is also disclosed a system therefore.

Documents:

00091-cal-2001-abstract.pdf

00091-cal-2001-claims.pdf

00091-cal-2001-correspondence.pdf

00091-cal-2001-description(complete).pdf

00091-cal-2001-drawings.pdf

00091-cal-2001-form-1.pdf

00091-cal-2001-form-18.pdf

00091-cal-2001-form-2.pdf

00091-cal-2001-form-3.pdf

00091-cal-2001-form-5.pdf

00091-cal-2001-letters patent.pdf

00091-cal-2001-p.a.pdf

00091-cal-2001-reply f.e.r.pdf