Abstract:
A machine for producing corrugated board which utilizes a dual thermal sensing system to determine the length of the web is disclosed. The corrugating machine includes a frame through which a web material is adapted to be traversed, an applicator adapted to apply a liquid spot, such as water, to the web, and first and second temperature sensors adapted to detect the liquid spot after the liquid spot is applied.

Description:
FIELD OF THE DISCLOSURE  
         [0001]    The present disclosure relates to machines for producing corrugated board, and more specifically, it relates to machines having a mechanism for automatically determining the length of web material in a bridge of the machine.  
         BACKGROUND OF THE DISCLOSURE  
         [0002]    Conventional corrugating machines produce double-faced corrugated board from two continuous webs of flat paper and a third continuous web of corrugated paper. In one prior art corrugating machine, a web of paper is corrugated by a pair of corrugating rollers and glued to a web of flat paper to produce a single-faced corrugated web, which is supplied to the bridge of the corrugating machine.  
           [0003]    Each of the paper webs used to form the single-faced corrugated web is fed from a large roll of paper, which periodically runs out. As one of the paper rolls runs out of paper, a paper web from a new roll is spliced onto the paper web from the old roll via a conventional splicer. To accommodate the splicing of the new roll to the old roll, the portion of the corrugating machine which produces single-faced corrugated board may be slowed somewhat; consequently, the speed at which the single-faced corrugated web is provided to the bridge is variable.  
           [0004]    The single-faced corrugated web is removed from the bridge of the corrugating machine and is bonded to a third web of paper to produce double-faced corrugated web, which is then supplied to a conventional cutter which cuts the double-faced corrugated web into desirable sizes.  
           [0005]    When one of the paper webs from which the single-faced corrugated board is produced is spliced by one of the splicers, the web portion in which the splice is made is twice as thick as usual due to overlap of the original paper web with the new paper web. This extra-thick web portion is undesirable and is automatically cut out by the cutter (which may be the main cutter or an auxiliary cutter) after the double-faced corrugated web is produced.  
           [0006]    The prior art corrugating machine described above may incorporate a method of automatically cutting out the extra-thick web portion based upon a procedure which periodically determines the length of the web that is in the bridge portion of the corrugating machine. Since the single-faced corrugated web is supplied to the bridge at a variable rate and removed from the bridge at a variable rate, the length of the web in the bridge at any time is variable.  
           [0007]    In the prior art method, the length of the web in the bridge is determined, and then the total length of the web from one of the splicers to the cutter is determined based thereon (the length of the web from one of the splicers to the bridge is a known constant, and the length of the web from the bridge to the cutter is a known constant). As soon as a splice is made, the corrugating machine starts measuring the web length from the splicer to the cutter. When the measured web length is slightly less than the total web length, the cutter makes a first cut, waits for a period of time or a distance, and then makes a second cut, so that the extra-thick spliced portion of the web is cut out from the web.  
           [0008]    In a prior art method of determining the length of the web in the bridge, an ink mark is sprayed onto a portion of the single-faced corrugated web just prior to its entry into the bridge. An ink mark detector is positioned at the exit of the bridge, and a measuring wheel that abuts against the single-faced corrugated web generates a plurality of counts in direct proportion to the travel of the single-faced corrugated web. The length of the single-faced web in the bridge is determined based on the number of pulses that are generated by the measuring wheel between the time the ink mark is sprayed and the time the ink mark is later detected by the detector. This manner of determining the length of the single-faced corrugated web in the bridge allows the splice to be cut out, without the need to cut out usable, adjacent portions of the web. While effective, such a method is relatively expensive, can be messy in use, leaves an undesirable ink stain on the corrugated board, and can cause maintenance problems.  
           [0009]    Accordingly, it is also known to use a thermal position sensor system. For example, U.S. Pat. No. 5,676,790, assigned to the present assignee, discloses the use of a water mark instead of an ink spot to determine the length of the web in the bridge. A temperature detector is used to detect the passing water mark. The water is generally cooler than the web itself, and when the temperature detector reads a lower temperature than a preset level, the water mark is detected. Where water or another colorless liquid is used, a corrugating machine in accordance with such a disclosure is advantageous in that the water spots evaporate completely, leaving no objectionable mark on the paper web. However, false signals can be generated under this system as the temperature of the paper itself can vary along its length due to the festooning process or other variables affecting the line. The temperature also may be too hot to register under the preset level.  
           [0010]    Other methods of determining the length of the web in the bridge, such as the use of metal foil pieces which are adhesively applied to the web, are relatively expensive and have other disadvantages including maintenance problems.  
         SUMMARY OF THE DISCLOSURE  
         [0011]    A machine is disclosed which is designed to detect a liquid spot on a web of material. In the first example, a frame is provided through which a web of material traverses. An applicator is positioned proximate the web, adapted to apply a liquid spot to the web material. Two temperature sensors are placed downstream of the applicator and proximate the web. By detecting the temperature of the web, they are able to detect the presence of the liquid spot.  
           [0012]    In a second example, a method to detect the length of a web is disclosed. The moving web is sprayed with a spray nozzle before the web enters a bridge. The length of the web is continuously monitored as it traverses its path. The presence of a liquid spot is detected by comparing two temperatures of the web read by two temperature detectors. When the difference between the two temperatures is greater than a preset level, the liquid spot is detected.  
           [0013]    These and other aspects and features of the present disclosure will be apparent to those of ordinary skill in the art upon reading the following when taken in conjunction with the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    [0014]FIG. 1A is a schematic side view of a first portion of a corrugating machine, constructed in accordance with the teachings of the disclosure;  
         [0015]    [0015] 
         [0016]    [0016]FIG. 1B is a schematic side view of a second portion of a corrugating machine, constructed in accordance with the teachings of the disclosure;  
         [0017]    [0017] 
         [0018]    [0018]FIG. 2 is a flowchart of the method of determining the length of the web in the bridge of the corrugating machine; and  
         [0019]    [0019] 
         [0020]    [0020]FIG. 3 is a flowchart of the method of cutting out a portion of a web which is undesirably thick due to its being spliced.  
         [0021]    [0021]FIG. 4 is a schematic plan view of the web, liquid spot and first and second temperature sensors.  
     
    
     DETAILED DESCRIPTION  
       [0022]    Referring now to the drawings and with specific reference to FIG. 1A, a first portion of a corrugating machine, constructed in accordance with the teachings of the disclosure is generally referred to by reference numeral  10 . The corrugating machine  10  includes a conventional splicer  12  which supplies a paper web  14  from a paper roll (not shown) to a cylindrical idler roller  16  rotatably supported by a support member  18  attached to a frame portion  20 . The paper web  14  passes underneath a pair of cylindrical rollers  22  and over a top portion of a large pre-heating roller  24  supported by a frame portion  26 . The web  14  passes underneath a lower roller  30 , between the roller  30  and an upper roller  32 , and to the underside of a roller  34 .  
         [0023]    The corrugating machine  10  includes a second conventional splicer  42  which supplies a paper web  44  from a paper roll (not shown) to a cylindrical idler roller  46  rotatably supported by a support member  48  attached to the frame portion  20 . The paper web  44  passes underneath a pair of cylindrical rollers  52  and over a top portion of a large pre-conditioner roller  54  supported by a frame portion  56 . The web  44  passes between a pair of corrugating rollers  58 , each of which has a fluted corrugating surface  59 , which corrugate the web  44 . An adhesive is applied to the top portions of the corrugated web  44  via a conventional apparatus in the form of a pair of adhesive applicator rollers  60 ,  62 .  
         [0024]    The paper web  14  is adhesively bonded to the corrugated web  44  when the webs  14 ,  44  come into contact together at the junction of the rollers  34 ,  58  so that a single-faced corrugated web  64  is formed. The web  64  is transported to a bridge  66  via a conveyor mechanism composed of a pair of conveyors  68 , each of which has a pair of rollers  70  which support a respective conveyor belt  72 , with the web  64  passing between the conveyor belts  72  through an aperture  74  formed in the bridge  66 . The conveyor mechanism supplies the web  64  to the bridge  66  at a rate which may be about seven times greater than the speed at which the web  64  is conveyed along the bridge  66  by a number of bridge conveyor belts (not shown). When supplied to the bridge  66 , a portion of the web  64  may automatically fold over itself a number of times as shown in FIG. 1A.  
         [0025]    As it passes between the conveyor belts  72 , the single-faced corrugated web  64  makes non-slip contact with a measuring wheel  76  that rolls along the top surface of the web  64  and generates a number of electrical pulses on a line  78 , each pulse corresponding to a given length of the web  64 . For example, the measuring wheel  76  may generate  10  pulses for each foot or meter of the web  64  that passes underneath it.  
         [0026]    The single-faced corrugated web  64  may be selectively sprayed with liquid at a spot or location on the web  64  via a spraying apparatus  80  with a spray nozzle  82  upon the receipt of an electrical spray signal generated on a line  84 . This creates a liquid spot  65  on the web  64  as can best be seen in FIG. 4.  
         [0027]    A second portion of the corrugating machine  10  is illustrated in FIG. 1B. Referring to FIG. 1B, the single-faced corrugated web  64  passes from the bridge  66  to a curved web support  86  and then beneath a pair of rollers  88  and over the top portion of a large pre-heater roller  90 , from which it passes to a small roller  92  disposed adjacent a larger roller  93  and to a bonding machine  94 . The bonding machine  94  is conventional and may include a pair of adhesive applicator rollers like the rollers  60 ,  62  which apply adhesive to the corrugated portions of the single-faced web  64  and a pair of rollers through which the web  64  passes along with a third web after adhesive is applied.  
         [0028]    The length of the web  64  which leaves the bridge  66  is measured by a second measuring wheel  96  which rolls along the top surface of the web  64  and generates a number of electrical pulses on a line  98 , each pulse corresponding to a given length of the web  64 . The measuring wheel  96  could be provided at different locations within the corrugating machine  10 . The controller  130  is connected to receive the electrical pulses generated on the line  98  by the measuring wheel  96 .  
         [0029]    A third splicer  102  supplies a third paper web  104  from a paper roll (not shown) to a cylindrical roller  106  rotatably supported by a support member  108  attached to a frame portion  110 . The paper web  104  passes underneath a pair of cylindrical rollers  112 , over a top portion of a large roller  114  supported by a frame portion  116 , and to the bonding machine  94  where it is bonded to the single-faced corrugated web  64  to form a double-faced corrugated web  120 . The double-faced corrugated web  120  is provided to a cutter  122 , which selectively cuts the web  120  into pieces of desired size, in accordance with electrical signals generated on a line  124  connected to a controller  130 .  
         [0030]    The controller  130  is connected to receive electrical signals transmitted by a temperature relay system  132 , generated by a temperature detection system  134 . The temperature detection system  134  is disposed directly adjacent the same side of the surface of the web  64  that was previously sprayed with the liquid via the nozzle  82 . As can be best seen in FIG. 4, the temperature detection system  134  may be composed of a first temperature detector  135  and a second temperature detector  137 . In alternative embodiments, it is to be understood that multiple detectors in excess of two may be employed. The temperature relay system  132  is composed of a first relay line  136  and a second relay line  138 . The first temperature detector  135  is disposed directly in the path of travel of the liquid spot  65 . It continuously reads the temperature of the web  64 , including the temperature of the liquid spot  65 . The second temperature detector  137  is disposed laterally from the first temperature detector  135 , perpendicular to the direction of travel of the web  64 . The second temperature detector is disposed such that it is not in line with the path of the liquid spot  65 , and it only reads the temperature of the web  64  that has not been sprayed with liquid.  
         [0031]    The operation of the corrugating machine  10  is described below in connection with FIGS. 2 and 3, which illustrate a portion of the operation of the controller  130 . The controller  130  may be composed of one or more conventional programmable logic controllers or a conventional computer system, such as a personal computer.  
         [0032]    [0032]FIG. 2 illustrates a procedure  200  that may be periodically performed by the controller  130  to determine the length of the web  64  that is in the bridge  66 . This web length may be arbitrarily defined in a number of different ways, such as the length of the web  64  from the measuring wheel  76  (FIG. 1A) to the temperature detector  134  (FIG. 1B), and is not limited to the length of the web  64  that physically lies on top of the bridge  66 . The procedure  200  may be performed every five or ten minutes or so, for example, or a predetermined number of times between each expected splice of one of the paper webs  14 ,  44 .  
         [0033]    Referring to FIG. 2, the first step in the procedure  200  is step  202 , at which liquid is sprayed at a spot or location on the corrugated web  64  via the nozzle  82 . This is initiated by sending a SPRAY command from the controller  130  to the spray apparatus  80  via the line  84 . As soon as SPRAY command is sent, step  204  is initiated and the controller  130  begins counting the number of pulses that are being generated by the measuring wheel  78 . The temperature detectors  135 ,  137  then begin continuously monitoring the temperature of the web at their respective locations at step  205 .  
         [0034]    The controller  130  continues to count the number of pulses, while simultaneously determining at step  206  if the difference in temperatures senses by detectors  135 , 137  is greater than a predetermined threshold as determined. The controller  130  is able to determine when the spot is detected by the detectors  135 ,  137  by comparing the electrical signal generated by the detector  135 , which is representative of the temperature of the web  64  in line with the liquid spot  65 , with the electrical signal generated by the detector  137 , which is representative of the temperature of the web  64 , because the spot at which the liquid was sprayed is generally cooler, due to evaporation of the liquid from the spot, than the remaining portions of the web  64 . When the difference between the temperatures sensed by the detectors  135 ,  137  is greater than a predetermined temperature threshold, the liquid spot  65  is detected. In so doing, the likelihood of a false positive reading, such as those periodically encountered with single temperature sensor systems due to variations in the web temperature, is abated. If the difference is not greater than the preset level, the controller continues counting at step  208 , and the temperature detectors continue monitoring the temperature of the web.  
         [0035]    Once the liquid spot is detected at step  207 , the length of the web  64  in the bridge  66  is determined at step  209  based upon the number of pulses counted by the controller  130  between the spraying of the liquid spot at step  202  and the detection of the liquid spot at step  207 . That number of pulses corresponds to the current length of the web  64  from the measuring wheel  78  to the temperature detection system  134 .  
         [0036]    The length of the web in the bridge  66  periodically calculated via the procedure illustrated in FIG. 2 is used to perform a cutting procedure  220  which controls when the cutter  122  cuts out an extra-thick portion of the double-faced corrugated web  120  which is generated by a splice.  
         [0037]    Referring to FIG. 3, when either one of the splicers  12 ,  42  splices a new web onto the current web, a SPLICE signal is transmitted to the controller  130  via one of a pair of lines  140 ,  142 . As soon as the SPLICE signal is received, the controller  130  starts counting the number of pulses received at step  222  from the measuring wheel  96  via the line  98 .  
         [0038]    It should be understood that the total length of the web from either of the two splicers  12 ,  42  to the cutter  122  is known, since the web length from one of the splicers to the bridge  66  is fixed (and corresponds to a fixed number of pulses), since the variable length of the web  64  within the bridge  66  is known (and corresponds with a given number of pulses), and since the length of the web from the bridge  66  to the cutter  122  is fixed (and corresponds to a fixed number of pulses).  
         [0039]    At step  224 , when the number of pulses being counted at step  222  reaches a predetermined number of pulses corresponding to a length slightly shorter, e.g. four inches, than the total length of the web from one of the splicers  12 ,  42  to the cutter  122 , then at step  226  the controller  130  sends a CUT signal to the cutter  122 . In response to the CUT signal, the cutter  122  makes a first cut in the double-faced corrugated web  120 , waits a predetermined period of time, e.g. corresponding to eight inches of web travel, and then makes a second cut in the double-faced corrugated web  120  a predetermined distance after the first cut, so that the extra-thick spliced portion is cut out of the web  120 .  
         [0040]    It should be understood that if the fixed web length between the splicer  12  and the bridge  66  is different than the fixed web length between the splicer  42  and the bridge  66 , two different pulse thresholds may be used at step  224 , depending upon which of the splicers  12 ,  42  generated the splice. The cutter  122  also cuts out extra-thick portions of the web  120  caused by splices made by the splicer  102 ; however, those portions are easily identified since the splicer  102  is located a fixed web length from the cutter  122 .  
         [0041]    It should also be understood that the procedures illustrated in FIGS. 2 and 3 are only exemplary, and that different procedures could be utilized in the implementation of the invention. A number of conventional components of the corrugating machine  10  illustrated in FIGS. 1A and 1B have been omitted, such as an oven for curing the corrugated board and a stacker for stacking pieces of the corrugated board after it is cut by the cutter  122 . Other conventional components could be included in the corrugating machine  10 .  
         [0042]    It is clear that modifications and alternative embodiments of the disclosure will be apparent to those skilled in the art in view of the foregoing description. In particular, the disclosure could be used to determine the length of any kind web in a machine during processing, not just a corrugated paper web. This could include another kind of paper, fabric, tape, etc. Moreover, the teachings of the disclosure provide a more accurate and reliable temperature sensing system in that false positive readings are reduced through the use of first and second temperature sensors.  
         [0043]    This description is to be construed as illustrative only, and is for the purpose of teaching those skilled in the art the best mode of carrying out the invention. The details of the structure and method may be varied substantially without departing from the spirit of the invention, and the exclusive use of all modifications which come within the scope of the appended claims is reserved.