Abstract:
A bonded sheet material manufacturing system capable of setting a moisture content of various types of sheet members to be bonded to each other to an optimum value for stably producing a bonded sheet material with less bonding failure and less warp at all times, where the sheet members are heated by individual sheet member heating means and then bonded to each other to produce the bonded sheet material. The system comprises a moisture content detecting means provided for at least one of the sheet members for detecting a moisture content of the sheet member or a parameter correlating with the moisture content and a control unit for controlling the sheet member heating means on the basis of detection information from the moisture content detecting means so that the moisture content approaches a predetermined optimum moisture content.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1) Field of the Invention  
           [0002]    The present invention relates to a system for manufacturing a bonded sheet material.  
           [0003]    2) Description of the Related Art  
           [0004]    A system for manufacturing a bonded sheet material (corrugated fiberboard material) is made up of a single facer for forming a single faced bonded sheet material by sticking a back linerboard and a wave-shaped corrugated medium together, and a double facer for forming a double faced bonded sheet material by sticking the single faced bonded sheet material and a front linerboard together.  
           [0005]    Each of the back linerboard, the corrugated medium, the single faced bonded sheet material and the front linerboard is preheated by a heating means before the bonding in order to adjust moisture (water) content.  
           [0006]    So far, the heating quantity of the aforesaid preheating has been set by the perception and experience of an operator on the basis of a feed speed, kind and others of an object to be heated. However, the setting of the heating quantity based on the perception and the experience is unreliable; therefore, difficulty is encountered in stably manufacturing a bonded sheet material with less bonding failure and less warp at all times.  
         SUMMARY OF THE INVENTION  
         [0007]    The present invention has been developed in consideration of such a problem, and it is therefore an object of the present invention to provide a bonded sheet material manufacturing system capable of setting optimum moisture content of sheet members to be bonded to each other to stably manufacture a bonded sheet material with less bonding failure and less warp at all times.  
           [0008]    For this purpose, in accordance with the present invention, there is provided a system for manufacturing a bonded sheet material by sticking various types of sheet members together after separately heating the sheet members through the use of individual sheet member heating means, the system comprising moisture content detecting means provided for at least one of the sheet members for detecting moisture content of the sheet member or a parameter correlating with the moisture content, and control means for controlling the sheet member heating means on the basis of detection information from the moisture content detecting means so that the moisture content approaches a predetermined optimum moisture content.  
           [0009]    In this case, preferably, the sheet member is any one of a back linerboard, a corrugated medium and a single faced bonded sheet material.  
           [0010]    In addition, preferably, the sheet member heating means includes a heating roll for heating the sheet member in a state where the sheet member is wound around its circumferential surface and winding angle adjusting means for adjusting a winding angle of the sheet member with respect to the heating roll, and the control means controls the winding angle adjusting means. In this case, it is also appropriate that the winding angle adjusting means includes a guide roll for bringing the sheet member into contact with the heating roll and guide roll moving means for moving the guide roll on the circumferential surface of the heating roll.  
           [0011]    Still additionally, preferably, the sheet member heating means includes a heating roll for heating the sheet member in a state where the sheet member is wound around its circumferential surface and valve means for adjusting a quantity of supply of heating steam to the interior of the heating roll, and the control means controls the valve means.  
           [0012]    Moreover, preferably, the control means comprises a first control element for feedback-controlling the sheet member heating means when a deviation between desired moisture content and the moisture content detected by the moisture content detecting means is equal to or below a predetermined value and a second control element for feedforward-controlling the sheet member heating means when the deviation therebetween is more than the predetermined value.  
           [0013]    Still moreover, the control means further includes a third control element for controlling the sheet member heating means to heat the sheet member to a preset temperature agreeing with an order change during the order change.  
           [0014]    Yet moreover, the control means further includes a fourth control element for, when a feed speed of the sheet member is lower than a predetermined speed, controlling the sheet member heating means to heat the sheet member to a preset temperature agreeing with the lower feed speed than the predetermined speed.  
           [0015]    In addition, preferably, a plurality of heating means each equivalent to the sheet member heating means are provided, and when a total heating quantity of the plurality of heating means reaches an excessive value, the control means decreases the heating quantities of the plurality of heating means successively starting from the upstream side heating means.  
           [0016]    Still additionally, preferably, a plurality of heating means each equivalent to the sheet member heating means are provided, and when a total heating quantity of the plurality of heating means does not reach a required value, the control means increases the heating quantity of the plurality of heating means successively starting from the downstream side heating means.  
           [0017]    Yet additionally, it is also appropriate that a temperature sensor is used as the moisture content detecting means, or that a moisture sensor is used as the moisture content detecting means.  
           [0018]    Furthermore, it is also appropriate that the bonded sheet material manufacturing system further comprises scanning means for shifting the moisture content detecting means to scan the sheet member in a width direction of the sheet member and time-averaging means for time-averaging the outputs of the moisture content detecting means scanning-shifted by scanning means.  
           [0019]    Still furthermore, it is also appropriate that a plurality of moisture content detecting means each equivalent to the aforesaid moisture content detecting means are located at a predetermined interval in a width direction of the sheet member, and width direction averaging means is further provided to average the outputs of the plurality of moisture content detecting means.  
           [0020]    According to this bonded sheet material manufacturing system, the sheet members to be bonded heated by a heating means to optimize their moisture content, thus stably manufacturing a high-quality bonded sheet material with less bonding failure and less warp at all times.  
           [0021]    In addition, the optimum moisture content based on a feed speed, a type of sheet member, a basic weight and others can be optimized through the heating by the heating means, which contributes to improvement of operability and manpower-saving. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]    [0022]FIG. 1 schematically shows a construction of a heating element in a single facer section of a bonded sheet material manufacturing system according to a first embodiment of the present invention;  
         [0023]    [0023]FIG. 2 is a flowchart showing one example of a heating temperature control procedure in the bonded sheet material manufacturing system according to the first embodiment of the invention;  
         [0024]    [0024]FIG. 3 is a graphic illustration of the relationship between a sheet member feed speed and a temperature variation of a sheet member per winding angle of 1° in the bonded sheet material manufacturing system according to the first embodiment of the invention;  
         [0025]    [0025]FIG. 4 schematically shows a construction of a heating element of a single facer section of a bonded sheet material manufacturing system according to a second embodiment of the invention;  
         [0026]    [0026]FIG. 5 schematically shows a construction of a heating element before a double facer section of a bonded sheet material manufacturing system according to the first embodiment of the invention; and  
         [0027]    [0027]FIG. 6 is an illustration of a construction of the bonded sheet material manufacturing system according to the second embodiment of the invention, and schematically shows a construction of a heating element whereby a heating quantity of a heating roll is varied in accordance with control of steam pressure. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0028]    Referring to the drawings, a description will be given hereinbelow of a bonded sheet material manufacturing system according to a first embodiment of the present invention. FIG. 1 is a schematic partial illustration of a construction of only a single facer and peripherals thereof, that is, of only a construction for forming a single faced bonded sheet material (single faced corrugated fiberboard material)  10 .  
         [0029]    This bonded sheet manufacturing system is made up of a heating roll  20  for preheating a back linerboard  11 , heating rolls  30  and  40  for preheating a corrugated medium  12 , and a belt type single facer  50  for sticking the back linerboard  11  and the corrugated medium  12  together. The back linerboard  11  and the corrugated medium  12  are sheet members to be bonded to each other. Each of the heating rolls  20 ,  30  and  40  is heated up to a predetermined temperature in a manner that steam is supplied to its interior.  
         [0030]    A pair of guide rollers  21  and  22  are brought into contact with a circumferential surface of the heating roll  20 . Of these guide rollers  21  and  22 , the guide roller  21  positioned on the upstream side is supported by a tip portion of an arm  23  attached to the shaft of the heating roll  20  to be able to rock and is shifted within an angular range, indicated by arrows in the illustration, in accordance with the rocking motion of the arm  23  made by an operation of a motor  24 . That is, in connection with the guide roller  21 , a guide roller moving means, comprising the arm  23  and the motor  24 , is provided for shifting the guide roller  21  on a circumferential surface of the heating roll  20 . On the other hand, the guide roller  22  positioned on the downstream side is in a fixed condition.  
         [0031]    In connection with the heating roll  30 , guide rollers  31  and  32  are provided which correspond to the guide rollers  21  and  22 , respectively, and an arm  33  is provided which corresponds to the arm  23 , and even a motor  34  is placed which corresponds to the motor  24 . Accordingly, the guide roller  31  is shifted within an angular range, indicated by arrows in the illustration, by the rocking motion of the arm  33  caused by an operation of the motor  34 . That is, in connection with the guide roller  31 , a guide roller moving means, comprising the arm  33  and the motor  34 , is provided for shifting the guide roller  31  on a circumferential surface of the heating roll  30 .  
         [0032]    One guide roller  41  is brought into contact with the heating roll  40 . This guide roller  41  is supported by a tip portion of an arm  43  attached to a shaft of the heating roll  40  to be able to rock, and is shifted within an angular range, indicated by arrows in the illustration, by the rocking motion of the arm  43  made in accordance with an operation of a motor  44 . That is, as with the case of the guide rollers  21  and  31 , a guide roller moving means, comprising the arm  43  and the motor  44 , is provided in connection with the guide roller  41 .  
         [0033]    The single facer  50  is made up of an endless belt  53  stretched between a pair of rolls  51  and  52 , an upper roll  54  brought into pressing contact with the belt  53 , a lower roll  55  brought into contact with the upper roll  54 , and a gluing device  56  placed in the vicinity of the upper roll  54 .  
         [0034]    In this bonded sheet material manufacturing system, since the back linerboard  11  is moved while being wound around the circumferential surface of the heating roll  20 , it is heated by the heating roll  20  during the movement.  
         [0035]    Since the back linerboard  11  is wound around the heating roll  20  between the guide rollers  21  and  22 , the winding angle of the back linerboard  11  with respect to the heating roll  20  is adjustable in a manner that the motor  24  is operated to change the rocking position of the arm  23 . That is, the winding angle is at a maximum when the arm  23  is at a position indicated by a solid line, while it is at a minimum when coming to a position indicated by a dotted line. In addition, since the period of time for which the back linerboard  11  comes into contact with the heating roll  20  is prolonged as the winding angle with respect to the heating roll  20  increases, the heating energy given from the heating roll  20  increases. That is, a winding angle adjusting means comprising the guide rollers  21  and  22  and the guide roller moving means including the arm  23  and the motor  24  is provided for the heating roll  20 , and the heating roll  20  and the winding angle adjusting means constitute a heating means for the back linerboard  11 .  
         [0036]    On the other hand, since the corrugated medium  12  is moved while being wound around the circumferential surfaces of the heating rolls  30  and  40  sequentially, it is heated by these rolls  30  and  40  during the movement. In addition, as the winding angles of the corrugated medium  12  with respect to the heating rolls  30  and  40  become larger, the heating energy given thereto by the heating rolls  30  and  40  increases. That is, a winding angle adjusting means comprising the guide rollers  31  and  32  and the guide roller moving means (the arm  33  and the motor  34 ) is provided for the heating roll  30 , and the heating roll  30  and the winding angle adjusting means constitute a heating means for the corrugated medium  12 . Likewise, a winding angle adjusting means comprising the guide roller  41  and the guide roller moving means (the arm  43  and the motor  44 ) is provided for the heating roll  40 , and the heating roll  40  and the winding angle adjusting means organize a heating means for the corrugated medium  12 .  
         [0037]    The back linerboard  11  heated by the heating roll  20  and the corrugated medium  12  heated by the heating rolls  30  and  40  are conveyed into the single facer  50 . At this time, although the corrugated medium  12  arrives at the belt  53  by way of the upper roll  54  and the lower roll  55 , a glue is applied to the corrugated medium  12  by the gluing device  56  immediately before the arrival thereat.  
         [0038]    The back linerboard  11  and the corrugated medium  12  are pressed by the belt  53  and the upper roll  54 , and at this time, they are bonded to each other by means of the glue applied onto the corrugated medium  12 . The back linerboard  11  and the corrugated medium  12  bonded to each other is carried as a single faced bonded sheet material  10  to the next process.  
         [0039]    Meanwhile, in order to prevent warp or bonding failure of the single faced bonded sheet material  10  manufactured as mentioned above, there is a need to appropriately maintain the moisture contents of the linerboard  11  and/or the corrugated medium  12  before being bonded to each other.  
         [0040]    The moisture content of the back linerboard  11  depends upon its temperature, and decreases as the temperature increases. In addition, the correspondence between the moisture content and the temperature can be proved previously through experiments, simulations or the like. This is also valid for the corrugated medium  12 .  
         [0041]    The temperature (moisture content) of the back linerboard  11  varies in accordance with the winding angle thereof with respect to the heating roll  20 , and likewise, the temperature (moisture content) of the corrugated medium  12  varies with the winding angle thereof with respect to the heating rolls  30  and  40 .  
         [0042]    Therefore, according to this embodiment, the temperature of the heated back linerboard  11  carried from the heating roll  20  is used as a parameter correlating with the moisture content, and is detected by a temperature sensor (moisture content detecting means)  60  placed at a position immediately before the single facer  50 , while the winding angle adjusting means is controlled on the basis of the detection temperature in a controller (control means)  61  to control the winding angle of the back linerboard  11  with respect to the heating roll  20  so that the temperature of the back linerboard  11  becomes an optimum temperature corresponding to optimum moisture content.  
         [0043]    The controller  61  is for controlling an operation of the winding angle adjusting means (heating means) on the basis of the detection result of the temperature sensor  60 , and includes a control element for performing feedback control, a control element for executing feed forward control and a control element for implementing preset control.  
         [0044]    [0044]FIG. 2 is an illustration of an example of such a winding angle control procedure to be implemented in the controller  61 . A description will be given hereinbelow of this procedure.  
         [0045]    [Step  200 ] 
         [0046]    This procedure starts at a step  200  to input, from a host managing unit (not shown), information representative of a feed speed, back linerboard type and basic weight (weight of fiberboard per square meter) of the back linerboard  11  and a flute of the corrugated medium  12 .  
         [0047]    [Step  201 ] 
         [0048]    At a step  201 , an optimum temperature of the back linerboard  11  is set on the basis of the information inputted in the step  200 . This optimum temperature is a temperature which does not cause the bonding failure of the back linerboard  11  or the warp of the single faced bonded sheet material  10 , and is establishable in advance through experiments, simulations or the like.  
         [0049]    The controller  61  previously puts an optimum temperature, corresponding to each of the foregoing information, as a desired temperature in a memory (not shown), and sets a corresponding desired temperature on the basis of the information inputted and the contents stored in the memory.  
         [0050]    [Step  202 ] 
         [0051]    At a step  202 , an actually measured temperature of the back linerboard  11  is detected by the temperature sensor  60  and taken. In this embodiment, a plurality of the temperature sensors  60  are placed in a width direction (direction perpendicular to the paper surface of FIG. 1) of the back linerboard  11  so that the average value of the temperatures detected by these temperature sensors  60  is used as the actually measured temperature value of the back linerboard  11 .  
         [0052]    It goes without saying that it is also appropriate that one temperature sensor  61  is shifted to scan the back linerboard  11  in its width direction so that a time average value of the temperatures detected in this way is used as the actually measured temperature value of the back linerboard  11 .  
         [0053]    [Step  203 ] 
         [0054]    At a step  203 , a decision is made as to whether or not an order change signal is outputted from the managing unit. This order change signal is issued in the case of formation of a double faced bonded sheet material according to a different specification, and at this time the alteration of the feed speed, back linerboard type and others takes place.  
         [0055]    [Step  204 ] 
         [0056]    In the case of no issue of the order change signal, at a step  204 , a decision is made as to whether or not the feed speed of the back linerboard  11  exceeds a predetermined speed.  
         [0057]    [Step  205 ] 
         [0058]    When the back linerboard  11  runs at a speed higher than the predetermined speed, at a step  205 , a decision is made as to whether or not the deviation between the aforesaid desired temperature and the actually measured temperature is below AT.  
         [0059]    [Steps  206  and  207 ] 
         [0060]    When the deviation therebetween is equal to or below AT, at steps  206  and  207 , the motor  24  is feedback-controlled so that the actually measured temperature equals the desired temperature. That is, the winding angle of the back linerboard  11  with respect to the heating roll  20  is feedback-controlled with the PID compensation. Thereafter, the operational flow returns to the step  203 .  
         [0061]    [Steps  208  and  209 ] 
         [0062]    When the deviation therebetween exceeds ΔT, at steps  208  and  209 , the feedforward control is implemented in order to eliminate this temperature deviation.  
         [0063]    The relationship between the feed speed of the back linerboard  11  and the temperature variation per winding angle of 1° in the back linerboard  11  is obtainable through simulations or actual measurements, and is exemplified in FIG. 3. In this illustration, a characteristic plotted with black circles shows a case in which the basic weight M is equal to or below 245 g/square meter (M≦245 g/square meter), while a characteristic plotted with black squares indicates a case in which the basic weight M exceeds 245 g/square meter (M&gt;245 g/square meter).  
         [0064]    A required alteration quantity of the winding angle for decreasing the aforesaid temperature deviation promptly is found from the relationship shown in FIG. 3, and the motor  24  is controlled so that the winding angle varies by that alteration quantity. The aforesaid feedforward control signifies this control.  
         [0065]    The aforesaid relationship is valid for one back linerboard type and one flute. Accordingly, in the case of employment of a different back linerboard type and a different flute, the relationship between feed speed and the winding angle in this case is also set previously through actual measurements or the like, and is also stored previously in the memory (not shown).  
         [0066]    After the implementation of this feedforward control, the operational flow returns to the step  203 .  
         [0067]    [Steps  210  and  211 ] 
         [0068]    When the feed speed of the back linerboard  11  is lower than a predetermined speed (for example, 200 feet/min), the time of heating to the back linerboard  11  by the heating roll  20  becomes longer. In this case, in the aforesaid feedback control or feedforward control, there is a possibility that the temperature control accuracy of the back linerboard  1  lowers because of excessive control or the like.  
         [0069]    For this reason, at steps  210  and  211 , preset control is implemented on the temperature (winding angle) of the back linerboard  11 . In this case, a desired winding angle is preset on the basis of the simulation results, experiments or the like, and the motor  24  is controlled to realize this desired winding angle. To increase the control speed, this desired winding angle is set so that a controlled variable becomes higher than that in the feedforward control. The desired winding angle is naturally preset in consideration of back linerboard type, basic weight and flute.  
         [0070]    After the implementation of the preset control, the operational flow returns to the step  203 .  
         [0071]    [Step  212 ] 
         [0072]    The order change requires alteration of some or all of the feed speed, back linerboard type, basic weight and flute of the back linerboard  11 . Accordingly, at a step  212 , the aforesaid information is again inputted at an input of an order change signal.  
         [0073]    [Steps  213  and  214 ] 
         [0074]    At steps  213  and  214 , the temperature (winding angle) of the back linerboard  11  is preset-controlled. In this case, a plurality of desired winding angles corresponding to feed speeds, back linerboard types, basic weights and flutes are preset on the basis of simulations, experiments. In addition, a desired winding angle agreeing with the speed, back linerboard type, basic weight and flute inputted in the step  212  is selected from these desired winding angles, and the motor  24  is controlled to realize this desired winding angle.  
         [0075]    Incidentally, the temperature of the back linerboard  11  is largely varied at an order change. Accordingly, the aforesaid desired winding angle is properly preset to a value whereby the temperature of the back linerboard  11  rises quickly up to an appropriate temperature.  
         [0076]    [Step  215 ] 
         [0077]    At a step  215 , on the basis of the aforesaid order change signal, a decision is made as to whether or not the order change comes to an end. If the order change does not terminates yet, the aforesaid preset control continues, and if coming to an end, the operational flow returns to the step  200 .  
         [0078]    With the above-described procedure, when the aforesaid temperature deviation is more than AT, the feedforward control is implemented so that the temperature of the back linerboard  11  approaches a desired temperature promptly, and when the aforesaid temperature deviation is equal to or below ΔT, the feedback control is executed so that the temperature of the back linerboard  11  develops to the desired temperature with high accuracy.  
         [0079]    In addition, when the feed speed of the back linerboard  11  is lower than a predetermined speed, the preset control is implemented to provide a stable temperature control result with no hunting, and at an order change, the preset control is executed to change (increase/decrease) the temperature of the back linerboard  11  up to an appropriate temperature promptly; therefore, after the order change, the temperature of the back linerboard  11  can be feedback-controlled or feedforward-controlled smoothly.  
         [0080]    In this way, the temperature of the back linerboard  11  before bonding is maintained appropriately at all times, in other words, the moisture content thereof before the bonding is always kept in an appropriate condition, thus preventing the bonding failure stemming from deterioration of the impregnating ability of a glue or the like in the bonding section to the corrugated medium  12 , and further preventing the warp of the single faced bonded sheet material  10 .  
         [0081]    [0081]FIG. 4 is an illustration of a second embodiment of the present invention in which a heating roll  20 ′ is additionally provided on the upstream side of the aforesaid heating roll  20 . In this illustration, guide rollers  21 ′,  22 ′, an arm  23 ′ and a motor  24 ′ placed in connection with this heating roll  20 ′ are equivalent to the guide rollers  21 ,  22 , the arm  23  and the motor  24  for the heating roll  20 , respectively. That is, for the heating roll  20 ′, there is provided a winding angle adjusting means comprising the guide rollers  21 ′ and  22 ′ and a guide roller moving means (the arm  23 ′ and the motor  24 ′). As compared with the construction shown in FIG. 1, a heating means comprising the heating roll  20 ′ and the winding angle adjusting means is provided additionally.  
         [0082]    In this embodiment, for example, when both the winding angles of the back linerboard  11  with respect to the heating rolls  20  and  20 ′ assume a minimum, the controller  61  first increases the winding angle with respect to the heating roll  20 . In a case in which, although that winding angle reaches a maximum, the back linerboard  11  does not reach an optimum temperature, then the controller  61  increases the winding angle with respect to the heating roll  20 ′.  
         [0083]    In addition, for example, when both the winding angles of the back linerboard  11  with respect to the heating rolls  20  and  20 ′ assume a maximum, the controller  61  first decreases the winding angle with respect to the heating roll  20 ′. In a case in which, although that winding angle reaches a minimum, the back linerboard  11  does not show an optimum temperature, then the controller  61  decreases the winding angle with respect to the heating roll  20 .  
         [0084]    As a matter of course, it is also possible that, when both the winding angles of the back linerboard  11  with respect to the heating rolls  20  and  20 ′ are at a minimum, the controller  61  first increases the winding angle with respect to the heating roll  20 ′, and in a case in which, although this winding angle with respect to the heating roll  20 ′ reaches a maximum, the back linerboard  11  does not show an optimum temperature, then the controller  61  increases the winding angle with respect to the heating roll  20 . In addition, it is also possible that, when both the winding angles of the back linerboard  11  with respect to the heating rolls  20  and  20 ′ are at a maximum, the controller  61  first decreases the winding angle with respect to the heating roll  20 , and in a case in which, although this winding angle with respect to the heating roll  20  reaches a minimum, the back linerboard  11  does not show an optimum temperature, then the controller  61  decreases the winding angle with respect to the heating roll  20 ′.  
         [0085]    This embodiment can provide an advantage of enlarging the temperature controlled range on the back linerboard  11 .  
         [0086]    Secondly, a description will be given hereinbelow of temperature control for the corrugated medium  12 . The corrugated medium  12  are heated by the heating rolls  30  and  40  and the temperature of the corrugated medium  12  after heated is detected as a parameter, correlating with the moisture content of the corrugated medium  12 , by the temperature sensor (moisture content detecting means) placed at a position immediately before the single facer  50 .  
         [0087]    A controller (control means)  63 , as with the controller  61 , is for controlling an operation of the winding angle adjusting means for the heating rolls  30  and  40  on the basis of the detection result of the temperature sensor  62 , and includes a control element for performing feedback control, a control element for performing feedforward control and a control element for executing preset control. This controller  63  fetches the temperature detected by the temperature sensor  62  and maintains the temperature of the corrugated medium  12  before bonding at an appropriate temperature by implementing a temperature control procedure based on the procedure shown in FIG. 2.  
         [0088]    The corrugated medium  12  temperature-adjusted in this way can excellently be bonded to the back linerboard  11  because of improvement of the adhesive property of the glue applied by the gluing device  56 , and the occurrence of warp of the single faced bonded sheet material  10  is preventable.  
         [0089]    Incidentally, the heating rolls  30  and  40  are made to alter the winding angles sequentially, as in the case of the heating rolls  20  and  20 ′.  
         [0090]    That is, for example, when both the winding angles of the corrugated medium  12  to the heating rolls  30  and  40  are at a minimum, the winding angle to the heating roll  40  is first increased. Subsequently, if this winding angle reaches a maximum but the corrugated medium  12  does not show an optimum temperature, the winding angle to the heating roll  30  is also increased.  
         [0091]    Moreover, for example, when both the winding angles of the corrugated medium  12  to the heating rolls  30  and  40  are at a maximum, the winding angle to the heating roll  30  is first decreased, and if this winding angle reaches a minimum but the corrugated medium  12  does not reach an optimum temperature, the winding angle to the heating roll  40  is then decreased.  
         [0092]    Naturally, it is also possible that, when both the winding angles of the corrugated medium  12  to the heating rolls  30  and  40  are at a minimum, the winding angle to the heating roll  30  is first increased, and if, although the winding angle to the heating roll  30  reaches a maximum, the corrugated medium  12  does not show an optimum temperature, the winding angle to the heating roll  40  is then increased. In addition, it is also acceptable that, when both the winding angles of the corrugated medium  12  to the heating rolls  30  and  40  are at a maximum, the winding angle to the heating roll  40  is first decreased, and if, although the winding angle to the heating roll  40  reaches a minimum, the corrugated medium  12  does not have an optimum temperature, the winding angle to the heating roll  30  is then decreased.  
         [0093]    In the meantime, the single faced bonded sheet material  10  formed in the single facer  50  shown in FIG. 1 or  2  is heated by a heating roll  70  shown in FIG. 5 and then fed, as a sheet member to be bonded, to a double facer (not shown). In addition, a front linerboard  13  to be supplied as a sheet member to be bonded to the double facer is heated by heating rolls  80  and  90 .  
         [0094]    Guide rollers  71 ,  72 , an arm  73  and a motor  74  provided in connection with the heating roll  70  correspond to the guide rollers  21 ,  22 , the arm  23  and the motor  24  for the heating roll  20 , respectively. In addition, guide rollers  81  ( 91 ),  82  ( 92 ), an arm  83  ( 93 ) and amotor 84  ( 94 ) provided in connected with the heating roll  80  ( 90 ) also correspond to the guide rollers  21 ,  22 , the arm  23  and the motor  24  for the heating roll  20 .  
         [0095]    That is, for the heating roll  70 , there is provided a winding angle adjusting means comprising the guide rollers  71  and  72  and a guide roller moving means (the arm  73  and the motor  74 ). These heating roll  70  and winding angle adjusting means organize a heating means for the single faced bonded sheet material  10 . Likewise, for the heating roll  80  ( 90 ), there is provided a winding angle adjusting means comprising the guide roller  81  ( 91 ), the guide roller  82  ( 92 ), the arm  83  ( 93 ) and the motor  84  ( 94 ). These heating roll  80  ( 90 ) and the winding angle adjusting means organize a heating means for the front linerboard  13 .  
         [0096]    The temperature of the single faced bonded sheet material  10  heated by the aforesaid heating roll  70  is detected as a parameter correlating with a moisture content of the single faced bonded sheet material  10  by a temperature sensor (moisture content detecting means)  64  located at a downstream position near the heating roll  70 .  
         [0097]    A controller  65  is for controlling an operation of the winding angle adjusting means (heating means) for the heating roll  70  on the basis of the detection result of the temperature sensor  64 , and includes a control element for performing feedback control, a control element for implementing feedforward control and a control element for executing preset control. The controller  65  fetches the temperature detected by the temperature sensor  64 , and implements a temperature control procedure based on the procedure shown in FIG. 2. As a result, the single faced bonded sheet material  10  before bonding is heated up to an appropriate temperature whereby bonding failure or the like in the double facer is preventable. The single faced bonded sheet material  10  temperature-adjusted in this way is conveyed through guide rollers  100  and  101  to the double facer.  
         [0098]    On the other hand, the temperature of the front linerboard  13  heated by the aforesaid heating rolls  80  and  90  is detected as a parameter correlating with a moisture content of the front linerboard  13  by a temperature sensor (moisture content detecting means)  66  placed at a downstream position near the heating roll  90 .  
         [0099]    A controller  67  is for controlling an operation of the winding angle adjusting means (heating means) for each of the heating rolls  80  and  90 , and includes a control element for performing feedback control, a control element for implementing feedforward control and a control element for executing preset control. This controller  67  takes in the temperature detected by the aforesaid temperature sensor  66 , and implements a temperature control procedure based on the procedure shown in FIG. 2. In consequence, the front linerboard  13  before bonding is heated up to an appropriate temperature which can prevent bonding failure or the like in the double facer. The front linerboard  13  temperature-adjusted in this way is fed through a guide roller  102  to the double facer.  
         [0100]    The aforesaid double facer conveys the aforesaid single faced bonded sheet material  10  and the front linerboard  13  in a laminated condition, and heats and presses the single faced bonded sheet material  10  and the front linerboard  13  to stick to each other during the conveyance. Each of the temperatures of the single faced bonded sheet material  10  and the front linerboard  13  is set appropriately under the aforesaid temperature control; therefore, the double faced bonded sheet material (double faced corrugated fiberboard) (not shown) formed by this bonding is released from bonding failure or warp and shows a high quality.  
         [0101]    As with the procedure for the heating rolls  20  and  20 ′ shown in FIG. 2, the aforesaid heating rolls  80  and  90  are made to alter the winding angle sequentially.  
         [0102]    That is, for example, when both the winding angles of the front linerboard  13  to the heating rolls  80  and  90  are at a minimum, the winding angle to the heating roll  90  is first increased, and if this winding angle reaches a maximum but the front linerboard  13  does not reach an optimum temperature, the winding angle to the other heating roll  80  is then increased.  
         [0103]    On the other hand, for example, when both the winding angles of the front linerboard  13  to the heating rolls  80  and  90  are at a maximum, the winding angle to the heating roll  80  is first decreased, and if this winding angle reaches a minimum but the front linerboard  13  does not reach an optimum temperature, the winding angle to the heating roll  90  is then decreased.  
         [0104]    Naturally, it is also possible that, when both the winding angles of the front linerboard  13  to the heating rolls  80  and  90  are at a minimum, the winding angle to the heating roll  80  is first increased, and in a case in which, although this winding angle to the heating roll  80  reaches a maximum, the front linerboard  13  does not reach an optimum temperature, the winding angle to the heating roll  90  is then increased. In addition, it is also acceptable that, when both the winding angles of the front linerboard  13  to the heating rolls  80  and  90  are at a maximum, the winding angle to the heating roll  90  is first decreased, and in a case in which, although this winding angle to the heating roll  90  reaches a minimum, the front linerboard  13  does not reach an optimum temperature, the winding angle to the heating roll  80  is then decreased.  
         [0105]    In this embodiment, a plurality of temperature sensors each equivalent to the aforesaid temperature sensor  64  ( 66 ) are located in a width direction (direction perpendicular to the paper surface of FIG. 5) of the single faced bonded sheet material  10 , and the average value of the temperatures detected by these temperature sensors  64  ( 66 ) is used as an actually measured value of the sheet material  10  (front linerboard  13 ). As a matter of course, it is also acceptable that one sensor is shifted to scan it in the width direction for employing the time average value of the temperatures detected at this time as the aforesaid actually measured value.  
         [0106]    Meanwhile, in a case in which the double facer situated on the downstream side of the guide rollers  100 ,  101  and  102  of FIG. 5 is of a type forming a triple-face bonded sheet material, in addition to the aforesaid single faced bonded sheet material  10  and front linerboard  13 , a single faced bonded sheet material  10 ′ (which is formed in a sheet material forming part similar to the single faced bonded sheet material forming part shown in FIG. 1) indicated by a chain line is fed to the double facer.  
         [0107]    In such a system, a temperature control means similar to the temperature control means for the single faced sheet material  10  is employed, thereby adjusting the temperature of the single faced bonded sheet material  10 ′ to an optimum temperature.  
         [0108]    In each of the above-described embodiments, although a temperature sensor is used as the moisture content detecting means for detecting a parameter correlating with a moisture content of a sheet member such as the back linerboard  11  or the corrugated medium  12 , it is also possible that a moisture sensor is employed as this moisture content detecting means to detect the moisture content directly. In this case, the aforesaid controllers  61 ,  63 ,  65  and  67  are designed to comparatively make a decision on a deviation in moisture in the step  205  of FIG. 2.  
         [0109]    In addition, in each of the above-described embodiments, the winding angles of a sheet member to the heating rolls  23 ,  23 ′,  30 ,  40 ,  70 ,  80  and  90  are changed to vary the heating quantity to the sheet member, it is also acceptable to employ another means for controlling the heating quantity.  
         [0110]    That is, for example, as FIG. 6 shows, if a heating roll  110  equipped with guide rollers  111  and  112  which cannot be shifted in position, i.e., a heating roll  110  which cannot change the winding angle of a sheet member  120 , and a steam pressure adjusting valve (valve means)  130  placed in the middle of a passage for supplying heating steam to the heating roll  110  are provided to produce a heating means for the sheet member  120  and the steam pressure adjusting valve  130  is controlled in valve opening degree by a controller (control means)  140 , then it is possible to vary the heating quantity to the sheet member  120  without altering the aforesaid winding angle. That is, a steam pressure (steam flow rate) to be supplied to the heating roll  110  is adjusted by a valve opening degree to adjust the steam supply quantity to the heating roll  110  for controlling the heating quantity.  
         [0111]    Incidentally, naturally, the control in the embodiments described above with reference to FIGS.  1  to  5  are also applicable to the control in the embodiment shown in FIG. 6.