Abstract:
An apparatus and method for determining the diameter of a measured object including a frame having a quick disconnect fitting that demountably couples to a sensor selected from a collection of different length sensors so that the measurement range for determining diameters is increased. Each different length sensor includes a sensor probe tip that is biased in an outward direction therefrom so that when a selected sensor is coupled to the quick disconnect fitting, the probe tip contacts the measured object. The sensor includes means to generate a signal indicative of its probe tip position, and a microprocessor is programmed to receive the generated signal and provide an output display that corresponds to the diameter of the measured object.

Description:
FIELD OF THE INVENTION 
     This invention is directed to apparatus for measuring large diameter rolls, and in particular, it is directed to a roll diameter measuring device having an LVDT probe in combination with an internal processor programmed to provide a direct roll diameter display. 
     BACKGROUND OF THE INVENTION 
     The space between the lower and upper working rolls in a rolling mill stand define a roll gap that must be adjusted to transfer a proper rolling force from the working rolls to the incoming metal plate or strip product being manufactured. To more accurately control the thickness of the metal product, it is necessary to monitor the roll gap using any one of a variety of measuring devices known in the art. In accordance with the known state of the art, such roll gap measurement devices calculate and adjust the roll gap, and hence the rolling force, based upon the known diameters of working and backup rolls supported within the mill stand. Therefore, it follows that in order to more accurately control both the roll gap and product quality, it is necessary to be able to determine correct roll diameter to insure product quality. Accurate roll diameter measurements are necessary to set and control roll gap in both hot and cold rolling mills as well as in other industrial applications. For example, similar accuracy is required in continuous caster rolls that contain and control the path of the cast product. Similarly, it is necessary to accurately determine original and refinished roll or shaft diameter in other industrial applications including rolls in paper and plastic manufacturing processes, in large shafts used in electrical generators, and drive shafts used in marine applications. Therefore, although the present invention may be directed to metal rolling mill applications, it should be understood that the scope of the invention extends into other manufacturing processes and industries. 
     In a rolling mill that manufactures steel plate and sheet, large diameter rolls are used to deform, contain, and/or manipulate the product being manufactured. For example, at our rolling mill operations, a new work roll will measure between about 30-37 inches (76.20-93.98 cm) in diameter depending upon the particular mill stand. The backup rolls measure approximately 50-60 inches (127.0-152.4 cm) in diameter when they are new. Similarly, new continuous caster rolls that contain and control the liquids strand moving through the roll segments positioned below the caster mold measure somewhere between 4-12 inches (10.16-30.48 cm) in diameter. Such industrial rolls are systematically refinished throughout their service life to insure that they continue to deliver a product having good surface quality. Refinishing includes surface grinding along the roll diameter to remove any roll defects, for example pits, burrs, gouges, or wear spots that may reduce product quality, and the rolls are periodically refinished until the diameter has been reduced to a size where the roll is no longer suitable for service. Typically, roll service life ends when the roll diameter is reduced to about 90% of its original roll diameter size. For example, at our Steckel Mill, a new work roll should have a 32 inch (81.28 cm) diameter. When refinishing operations have finally reduced the roll diameter to 30 inches (76.20 cm), the roll is considered scrap and is removed from the rolling line. Therefore, in this instance, roll service life ends when the diameter is reduced to about 93.75% of the original roll diameter. Roll service life criterion will vary from mill to mill. 
     As clearly illustrated above, the working diameter of industrial roll and the like continually changes throughout service life. Therefore, in rolling mill applications, when operators manually adjust a roll gap, or when they calibrate a device that automatically adjusts the roll gap, it is critical for operators to have an accurate diameter reading of each roll mounted within a particular mill stand. It is also critical to the manufacturing process to have such accurate roll diameter information available from the time a new roll is installed in the mill stand and throughout its service life. 
     In past roll refinishing operations, both pre-grinding and post-grinding roll diameter measurements were taken with either large diameter micrometers or with Pi (π) tapes. Large diameter micrometers are heavy and awkward to use. They require considerable skill and “feel” on the part of the user in order to take accurate readings, and as a result, measurement readings are often not repeatable, particularly if the measurements are taken by different people. Such error is a constant source of concern because it may result in faulty roll gap adjustments and out-of-spec product. On the other hand, Pi tapes are also problematic because operators need to encircle the large roll circumference with the tape and read the roll diameter measurement directly from the calibrated scale that appears on the face of the tape. Again, user skill is a requirement to take accurate Pi tape measurements. Any tape sag or misalignment along the circumference of the roll will result in measurement error and inaccurate roll gap adjustments. Therefore, there is a long felt need within the art, to develop a simple large diameter measuring device that overcomes the problems and limitations set forth above. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a diameter-measuring device having improved measurement repeatability. 
     It is a further object of the present invention to provide a measuring device that is not dependent upon user skill for accuracy. 
     It is another object of the present invention to provide a measuring device capable of measuring an increased diameter range as compared to measuring devices of the past. 
     It is a further object of the present invention to provide a measuring device having replaceable sensor probes to increase diameter measuring range. 
     It is an additional object of the present invention to provide a measuring device that displays direct readout corresponding to the diameter of a measured object. 
     It is still another object of the present invention to provide a measuring device that includes a sensor probe in combination with a microprocessor that generates an LCD display corresponding to the diameter of a measured object. 
     Other objects and advantages of the present invention will become apparent as a description thereof proceeds. 
     In satisfaction of the foregoing objects and advantages, the present invention provides a measuring apparatus having a frame adapted to receive an interchangeable sensor assemblies and a centering head adapted to engage then object being measured. The interchangeable sensor assemblies include a sensor probe that is biased in an outward direction therefrom so that its tip end contacts the measured object, and the probe includes means to generate a signal indicative of its tip end position. The frame portion of the measuring device also includes a microprocessor capable of receiving the sensor probe signals, and the microprocessor is programmed to provide an output display that corresponds to the diameter of the object. 
     The diameter of the object being measured is determined by storing in the microprocessor a calibrated gap distance in the based upon a first sensor probe signal indicative of probe tip position, calculating a measured gap distance based upon the stored calibrated gap distance and a second first sensor probe signal indicative of probe tip position, and determining diameter of the object based upon the calculated measured gap distance. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects and advantages and novel features of the present invention will become apparent from the following detailed description of the preferred embodiment of the invention illustrated in the accompanying drawings, wherein: 
     FIG. 1 is an elevation view of the preferred diameter measuring system of the present invention. 
     FIG. 1A is an alternate view of the digital display shown in FIG.  1 . 
     FIG. 2 is a view showing the present invention used to measure an increased range of different diameter objects. 
     FIG. 3 is an enlarged portion of FIG. 2 showing a first sensor assembly. 
     FIG. 4 is an enlarged portion of FIG. 2 showing a second sensor assembly. 
     FIG. 5 is an isometric view showing an alternate frame embodiment. 
     FIG. 6 is a cross-section view taken through a set of calibration rings included in the diameter measuring system. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIGS. 1 and 2 of the drawings, the preferred embodiment of the present invention includes a frame  1  having a pair of converging arms or jaws  2   a  and  2   b  that extend outward from a cross member  3  to provide a centering head  2  formed by the opening  4  between jaws  2   a  and  2   b . Preferably, frame  1  is constructed using a lightweight material having a low coefficient of expansion, and the design of the frame is such that its section modulus and torsional properties provide rigidity against bending forces. For example, as shown in FIG. 5, measuring device “M” may comprise a beam shape member  23  having sufficient depth to provide desired section properties. Suitable materials for constructing the frame include, but are not limited to, extruded aluminum or aluminum alloy materials, phenolic plastic materials, and carbon graphite materials, etc. The measuring device may include handles  25  for ease of placement along the circumference of a large diameter object, and similar to the embodiment shown in FIG. 1, includes a cross member  3 , a centering head  2  formed by jaws  2   a  and  2   b , a sensor assembly  5 , a microprocessor (not shown), and a display  16 . 
     Referring to the enlarged FIGS. 3 and 4, cross member  3  is adapted to receive removable sensor assemblies  5  and  5   a , and the cross member includes a quick disconnect coupling  6  to facilitate attaching different removable sensor assemblies to frame  1 . Any suitable locking means known in the art may be used for a quick disconnect fastener without departing from the scope of this invention. For example, a bayonet type coupling may be used to provide a quick disconnect. In the preferred embodiment shown in the drawing figures, coupling  6  includes a plurality of detents  7  shaped to receive and capture corresponding lugs  8  provided in the locking end  9  of the sensor assemblies  5  and  5   a.    
     The sensor assemblies  5  and  5   a  include the above mentioned lock end  9 , an extendable sensor probe  10  such as an LVDT probe or the like, and a biasing mechanism  11  positioned between the lock end  9  and probe  10 . The biasing mechanism  11  continuously urges the extendable sensor probe  10  in an outward direction away from frame  1  and into opening  4  of the centering head  2 . Additionally, as illustrated in FIG. 1, coupling mechanism  6  is arranged so that the sensor assembly is positioned and aligned along axis “X” that bisects an angle  9  formed by an extension of the jaws  2   a  and  2   b . Such axial alignment insures that the extendable sensor probe  10  is radially aligned to the object being measured, for example objects  20 ,  21 , and  22  in FIGS. 1-4, when the inside surfaces  12   a  and  12   b  of the centering head  2  tangentially engage the measured object. 
     Referring again to FIGS. 3 and 4, lock end  6  includes contacts  13  that communicate with corresponding contacts  14  provided in a microprocessor  15  housed within frame  1  of the measuring device portion of the diameter measuring system. The sensor probe of the sensor assembly generates an output signal indicative of the extended position of the probe tip  10   a , and the microprocessor receives the sensor output signal via contacts  13  and  14 . 
     Microprocessor  15  is programmed to process and digitize the output signal from the sensor probe and generate a digital display  16  that provides a readout, in either English units  17  or metric units  18  as illustrated in FIGS. 1 and 1A; the readout corresponding to the diameter of the object being measured. 
     It is well known that micrometers and the like have a limited diameter measuring range, typically one-inch diameter increments. For example, a one-inch micrometer to measure one-inch diameter and smaller round stock. A two-inch micrometer is used to measure rounds between one and two inches in diameter, and so on. Such one-inch measuring increments makes it necessary to purchase a wide range of different micrometers in order to meet various job requirements in a machine shop operation. In instances where a machine shop is manufacturing or refurbishing large diameter products, for example, working rolls and backup rolls used to manufacture metal plate and sheet products collecting a large variety of different micrometers to meet different product sizes is both inconvenient and expensive. 
     The present invention provides removable sensor assemblies that increase the measuring range of device “M”. Referring again to FIG. 3, the extendable sensor probe  10  has a measuring range that falls between D 1  and a maximum extended D 2  probe position. In instances where the diameter of the object being measured falls outside the maximum D 2  position, sensor assembly  5  is disconnected from coupling  6  and a different sensor assembly  5 A is attached to coupling  6  as shown in FIG.  4 . The different sensor assembly  5 A provides an extended measuring range that falls between D 2  and a maximum extended D 3  probe position. Such removable sensor assemblies provide means for using a single measuring device to determine the diameter of a wide range of different diameter objects as illustrated in FIG.  2 . It should be understood, however, that although the preferred embodiment shows using two sensor assemblies  5  and  5   a , any number of different sensor assemblies may be coupled to frame  1  without departing from the scope of this invention. For example, referring again to FIG. 2, centering head  2  of frame  1  is shown placed on a round object  21  so that jaws  2   a  and  2   b  are tangent to the object at  21   a  with the probe of sensor assembly  5  extended to engage the surface of the object  21  being measured. As illustrated by the readout  18   a  on display  16 , the round object has a 70.000 cm (27.559 inch) diameter. Similarly, when sensor assembly  5   a  is coupled to frame  1 , jaws  2   a  and  2   b  are tangent to object  22  at  22   a  and the readout  18   b  of display  16  shows a 100.000 cm (39.370 inch) diameter for the object being measured. Therefore, using only two different sensor assemblies, the measuring device is capable of measuring a range of diameters that would have required using 11-12 different micrometers and anvil combinations as taught in the past. 
     Referring now to FIGS. 1 and 6, a diameter measuring kit or set includes a measuring device “M”, at least one replaceable sensor assembly “S”, and a collection of calibration rings “CC”. Preferably, collection “C” comprises a plurality of ring segments  20 , each ring segment providing a different measurement standard for calibrating the sensor probe  10 . The number of ring segments will correspond to the diameter measuring range of a particular kit or system, and the measuring range is determined by the number of interchangeable or replaceable sensor assemblies “S” in a particular kit. In the preferred embodiment, collection “C” comprises a calibration box having a base  19  adapted to hold the ring segments  20  and a lid or cover  24  to protect the ring segments  20  from damage when they are not being used. 
     In a machining operation for refurbishing mill rolls, an operator will first calibrate the measuring device “M” using an appropriate ring segment  20   a  that is slightly larger in diameter than the work piece. To illustrate, lets assume that a 32 inch (81.280 cm) diameter mill roll has been removed from a mill stand for roll surface refinishing. The 32 inch measurement is representative of the “new roll” diameter when the roll was first placed into service. A machinist will first select an appropriate ring segment to calibrate the measuring device, for example 32 inch (81.280 cm) diameter ring segment  20   a  provided in collection “C”. Referring for a moment to either FIG. 3 or  4 , a lock ring  26  is loosened to adjust the sensor probe  10  until the digital display  16  reads either 32.000 inches or 81.280 cm depending on the units selected. When the sensor probe is calibrated to the proper diameter measurement for the selected calibration ring segment  20   a , lock ring  26  is tightened and the measuring device “M” is ready for use. Referring to FIG. 1, the readout on the digital display is responsive to a calibrated “GAP” distance measured from the vertex of angle to the tip  10   a  of the sensor probe, and the calibrated “GAP” distance is stored in microprocessor  15  (FIG. 3) for later use in determining roll diameter during the machining operation. 
     As the work piece is machined, its diameter may be periodically measured, and its changing machined size affects its position within the centering head  2 . For example, the exemplary different work pieces  21  and  22  (FIG. 2) show that the diameter size determines the position of a work piece within the centering head  2 . During machining, the decreasing diameter of the work piece results in a measured “GAP” distance that is less than the calibrated “GAP” distance. Microprocessor  15  is programmed to calculate the measured “GAP” by comparing the difference between the calibrated “GAP” and different position of the probe tip  10   a , and the calculated “GAP” is multiplied by a constant to determine the diameter of the measured object as shown at the different Roll Measurements 1-4 in the following Table A. 
     
       
         
               
             
               
               
               
               
             
               
               
               
               
             
           
               
                 TABLE A 
               
             
             
               
                   
               
               
                 Machining Operation - 32 Inch Roll 
               
             
          
           
               
                   
                 {square root over (2r 2 − r)} 
                 OD/GAP 
                 Roll OD 
               
               
                 Measured Object 
                 GAP 
                 Constant 
                 Display (inches) 
               
               
                   
               
             
          
           
               
                   Calibration GAP 
                 6.6274 
                 4.8284 
                 32.0000 
               
               
                 Roll Measurement No. 1 
                 6.5239 
                 4.8284 
                 31.5000 
               
               
                 Roll Measurement No. 2 
                 6.4203 
                 4.8284 
                 31.0000 
               
               
                 Roll Measurement No. 3 
                 6.3168 
                 4.8284 
                 30.5000 
               
               
                 Roll Measurement No. 4 
                 6.2132 
                 4.8284 
                 30.0000 
               
               
                   
               
             
          
         
       
     
     Table A shows an exemplary series of roll measurements that may be taken throughout the service life of 32 inch roll. To illustrate, when the example roll is brought into service, mill operators calibrate measuring device “M” using the 32 inch ring segment  20   a  (FIGS.  1  and  6 ). Device “M” is then positioned along the circumference of roll  21  (FIG.  2 ), and a diameter reading is taken to verify roll size. The resulting digitized output on display  16  (FIG. 3) is recorded for future use and for setting roll gap in the manufacturing operation. Throughout its service life, the roll is periodically removed from the mill stand for reconditioning worn or damaged roll surface areas. Each time the exemplary roll  21  is removed from the mill stand for refurbishing, the measuring device “M” is calibrated using the 32 inch calibration ring segment  20   a  before new diameter measurements are taken during the machining operation. As heretofore mentioned above, the change in the “GAP”, herein defined as a distance from the vertex of angle to the sensor probe tip  10   a . In instances where the roll  21  is in use at our operation, when the digitized output on display  16  reads 30 inches or less (81.280 cm), the roll is considered scrap and is removed from service. 
     While this invention has been described as having a preferred design, it is understood that the invention is not limited to the illustrated and described features. To the contrary, the invention is capable of further modifications, uses, and/or adaptations following the general principles of the invention and therefore includes such departures from the present disclosure as come within known or customary practice in the art to which the invention pertains, and as may be applied to the central features set forth above, and which fall within the scope of the appended claims.