Patent Publication Number: US-2023158755-A1

Title: Heat seal device

Description:
TECHNICAL FIELD 
     This application relates to a heat seal device for use in a bag making apparatus. 
     BACKGROUND 
     For example, a bag making apparatus includes a feed device that superposes two or more continuous sheet panels (webs) on each other and intermittently feeds them in their longitudinal direction. The bag making apparatus further includes at least one heat seal device that heat-seals the sheet panels during every intermittent feed cycle of the sheet panels. The bag making apparatus further includes a cross cut device that is disposed downstream of the heat seal device and cross-cuts the sheet panels in their width direction during every intermittent feed cycle of the sheet panels. Every time the sheet panels are cross-cut, a bag such as a plastic bag is made. 
     As disclosed in Patent documents 1 and 2, the heat seal device generally includes a first heat seal member and a second heat seal member facing each other. At least one of the first or second heat seal member is heated by a heater. The heat seal device further includes a drive mechanism that moves the first heat seal member towards and away from the second heat seal member. 
     The drive mechanism moves the first heat seal member towards the second heat seal member to sandwich the sheet panels between both heat seal members. This causes the sheet panels to be heat-sealed. Then, the drive mechanism moves the first heat seal member away from the second heat seal member to release sandwiching the sheet panels. 
     There are various factors that influence quality of heat-sealing, such as seal pressure. One of the factors is a seal time, that is, a sandwiching time during which the sheet panels are sandwiched by the heat seal members. The sandwiching time should be properly adjusted and controlled. Typically, a user of the heat seal device checks the sandwiching time by visually observing the heat seal operation, and then adjusts the sandwiching time by operating the component(s) of the drive mechanism. However, the visual check may be inaccurate and can lead to improper adjustment. This can result in variability in the quality of heat-sealing. 
     An object of the present application is to provide a heat seal device including a configuration for accurately detecting a sandwiching time during which a web is sandwiched by heat seal members. 
     SUMMARY 
     According to an aspect of the present application, there is provided a heat seal device for use in a bag making apparatus, the heat seal device including: a first heat seal member; a second heat seal member facing the first heat seal member; a heater for heating at least one of the first heat seal member or the second heat seal member; a drive mechanism configured to move the first heat seal member towards and away from the second heat seal member so as to releasably sandwich a web between the first and second heat seal members; a sensor disposed to detect acceleration of the first heat seal member; and a measurement part configured to measure a sandwiching time during which the web is sandwiched by the first and second heat seal members based on data from the sensor. 
     The measurement part may be configured to calculate a time from a first peak of the acceleration to a second peak of the acceleration as the sandwiching time. Here, the first peak is generated due to start of sandwiching the web by the first and second heat seal members, and the second peak is generated due to release of sandwiching the web by the first and second heat seal members. 
     The heat seal device may further include: a determination part configured to determine whether the sandwiching time complies with a predetermined requirement; and a warning device configured to output a warning if the determination part determines that the sandwiching time complies with the predetermined requirement. 
     The predetermined requirement may include a requirement that the sandwiching time is out of a predetermined range. 
     The predetermined requirement may include a requirement that the sandwiching time is greater than or less than a predetermined threshold value. 
     The drive mechanism may include a support for supporting the first heat seal member. The sensor may be attached to the support. 
     The drive mechanism may include a charge spring disposed to bias the first heat seal member towards the second heat seal member while the web is sandwiched by the first and second heat seal members. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    schematically and partially illustrates an example of a heat seal device. 
         FIG.  2    illustrates operation by the heat seal device. 
         FIG.  3    illustrates operation by the heat seal device. 
         FIG.  4    illustrates a profile of heat seal operation in association with feed status of a web. 
         FIG.  5 A  is a schematic plan view of an example of a bag making apparatus,  FIG.  5 B  is a side view of  FIG.  5 A , and  FIG.  5 C  is a schematic view of an inside of a region T in  FIG.  5 A . 
     
    
    
     DETAILED DESCRIPTION 
     A heat seal device according to implementations of the present application will now be described with reference to the accompanying drawings. The heat seal device is incorporated into a bag making apparatus, for example, an example of a bag making apparatus in  FIG.  5 A  and  FIG.  5 B . 
     FIG. 1  schematically illustrates a main section of an example of a heat seal device  1 . As illustrated in  FIG.  1   , the heat seal device  1  includes a first seal unit  2 , a second seal unit  3 , a drive mechanism  4  and a retraction mechanism  5 . 
     At least two webs  60  and  61  are superposed on each other and intermittently fed in their longitudinal direction by a feed device (e.g., a feed device  7  in  FIG.  5 B ) of the bag making apparatus. The first and second seal units  2  and  3  face each other with the webs  60  and  61  interposed therebetween. The webs  60  and  61  are horizontally fed, and the facing direction of the seal units  2  and  3  is the vertical direction. The first seal unit  2  is located above the web  60  and  61 , and the second seal unit  3  is located below the webs  60  and  61 . 
     The first seal unit  2  includes a first heat seal member  20  and a first heater  21  for heating the first heat seal member  20 . The second seal unit  3  includes a second heat seal member  30  and a second heater  31  for heating the second heat seal member  30 . 
     The first and second heat seal members  20  and  30  are used to sandwich at least two or more webs  60  and  61  for heat-sealing them as described below. The first and second heat seal members  20  and  30  are attached to the first and second heaters  21  and  31 , respectively, to face each other in the vertical direction with the webs  60  and  61  interposed therebetween. Each of the first and second heaters  21  and  31  has a heater cartridge inside thereof. Supplying electric power to the heater cartridge makes the heater cartridge generate heat. The heat is transmitted to the heat seal member  20  or  30 . 
     The drive mechanism  4  is configured to move the first heat seal member  20  towards and away from the second heat seal member  30  so as to releasably sandwich the webs  60  and  61  between the first and second heat seal members  20  and  30 . The drive mechanism  4  in the implementation is configured to move the whole of the first seal unit  2  towards and away from the second seal unit  3 . 
     The drive mechanism  4  may include, for example, a support  40 , a pole  41 , an adjustment nut  42 , a charge spring  43  and a pole operation mechanism  44 . 
     The support  40  is configured as an upper beam and supports the first seal unit  2  and thus the first heat seal member  20 . 
     The pole  41  extends in the facing direction of the seal units  2  and  3  (the first and second heat seal members  20  and  30 ), that is, in the vertical direction. The pole  41  is inserted through a through hole  400  of the support  40 . The pole  41  has a flange stopper  410  around its circumference. The stopper  410  is located on one side (lower side) with respect to the through hole  400 . The stopper  410  is configured to be vertically adjustable in position with respect to the pole  41 . For example, a well-known double nut may be used as the stopper  410 . That is, two nuts are mounted on and around the threaded outer circumference of the pole  41 . A bolt portion  411  having a threaded outer circumference is provided on the other side (upper side) with respect to the through hole  400  of the pole  41 . 
     The adjustment nut  42  is mounted on and around the bolt portion  411  of the pole  41  and screwed with it. Therefore, operating (rotating) the adjustment nut  42  allows the adjustment nut  42  to move along the bolt portion  411  with respect to the bolt portion  411 . 
     The charge spring  43  is disposed to bias the first heat seal member  20  towards the second heat seal member  30  as described below while the webs  60  and  61  are sandwiched by the first and second heat seal members  20  and  30 . The charge spring  43  is arranged between the support  40  and the adjustment nut  42  and extends between these  40  and  42  to bias the support  40  towards the stopper  410 . The pole  41  (the bottle portion  411 ) is inserted through the charge spring  43 . Operating the adjustment nut  42  allows for adjusting the biasing force of the charge spring  43 . 
     The pole operation mechanism  44  is operably connected to the pole  41  at the lower end of the pole  41  and configured to move the pole  41  in the facing direction of the seal units  2  and  3 , that is, in the vertical direction. The pole operation mechanism  44  in the implementation is configured to move the pole  41  in conjunction with the intermittent feed of the webs  60  and  61  by the feed device (e.g., the feed device  7  in  FIG.  5 B ) of the bag making apparatus. The pole operation mechanism  44  may employ the well-known configuration as disclosed in Patent documents 1 and 2, etc. 
     Although  FIG.  1    only illustrates the section of the heat seal device  1  including one end of the support  40 , the poles  41  and the components related thereto are located on the opposite ends of the support  40 . 
     The retraction mechanism  5  is configured to move the second seal unit  3  between the position ( FIG.  1   ) where its second heat seal member  30  is retracted to some extent from the feed height  62  of the webs  60  and  61 , and the position ( FIG.  2   ) where the second heat seal member  30  reaches the feed height  62 . The second heat seal member  30  being retracted below from the feed height  62  as illustrated in  FIG.  1    prevents the webs  60  and  61  from being scorched during the stand-by state of the heat seal device  1  due to the heat which is transmitted from the heat seal member  30 . 
     The retraction mechanism  5  may include, for example, a support  50 , an arm  51  and a cylinder  52 . 
     The support  50  is configured as a lower beam and supports the second (lower) seal unit  3  and thus the second heat seal member  30 . A slot  500  is formed in the support  50  to extend horizontally. 
     The arm  51  is supported by a frame (not shown) to be rotatable around a rotation shaft  510  which is located at the center section of the arm  51 . The arm  51  include a slider  511  at the first end thereof. The slider  511  is located in the slot  500  to be slidable along the slot  500 . 
     The cylinder  52  includes a tube  520  and a rod  521 . The tube  520  is attached to the frame (not shown). The tip of the rod  521  is attached to the second end  512  of the arm  51 . 
     With the above configuration, the retraction mechanism  5  can move the second seal unit  3  in the vertical direction by actuating the cylinder  52 . The retraction mechanism  5  can expand the rod  521  to rotate the arm  51  around the rotation shaft  510 , thereby moving the support  50  and the second seal unit  3  upward, that is, positioning the second heat seal member  30  at the feed height  62  (see  FIG.  2   ). Conversely, the retraction mechanism  5  can contract the rod  521 , thereby moving the support  50  and the second seal unit  3  downward, that is, retracting the second heat seal member  30  from the feed height  62 . 
     The drive mechanism  4  and the retraction mechanism  5  are mere examples. Several configurations may be adopted. 
     The heat seal operation will now be described.  FIG.  1    illustrates the heat seal device  1  in the stand-by state. The first and second seal units  2  and  3  are kept retracted from the webs  60  and  61  (thus, the feed height  62 ) by the drive mechanism  4  and the retraction mechanism  5 , respectively. The heat seal device  1  heat-seals the webs  60  and  61  as described below during the pause phase of the intermittent feed cycle of the webs  60  and  61 . 
     As illustrated in  FIG.  1    and  FIG.  2   , the retraction mechanism  5  moves the second seal unit  3  upward towards the webs  60  and  61  to position the second heat seal member  30  at the feed height  62 . Then, the drive mechanism  4  moves the pole  41  downward to move the support  40  and the first seal unit  2  downward towards the webs  60  and  61 , thereby also positioning the first heat seal member  20  at the feed height  62 . As a result, the webs  60  and  61  are sandwiched and heated by the first and second heat seal members  20  and  30  (which are heated by the first and second heaters  21  and  31 , respectively). 
     The drive mechanism  4  keeps moving the pole  41  downward. Since the first heat seal member  20  has already sandwiched the webs  60  and  61  in cooperation with the second heat seal member  30 , the first seal unit  2  and the support  40  fail to move any further downward. Thus, only the pole  41  moves downward while compressing the charge spring  43  as illustrated in  FIG.  2    and  FIG.  3   . 
     Then, the compressed charge spring  43  biases the first heat seal member  20  towards the second heat seal member  30  via the support  40 . That is, the biasing force of the charge spring  43  is applied to the webs  60  and  61 . This causes the webs  60  and  61  to be pressurized. The webs  60  and  61  are heat-sealed by being heated and pressurized. 
     Thereafter, the drive mechanism  4  moves the pole  41  upward to move the first heat seal member  20  away from the webs  60  and  61 . The sandwiching of the webs  60  and  61  by the heat seal members  20  and  30  is released. In other words, heat-sealing is finished. During the continuation of the series of the driving operations, the retraction mechanism  5  maintains the position illustrated in  FIG.  2   , while the first heat seal member  20  repeatedly moves upward and downward in conjunction with the intermittent feed of the webs  60  and  61 . When the apparatus is not supposed to be operated for a while after completion of the series of the driving operations, the retraction mechanism  5  moves the second heat seal member  30  away from the webs  60  and  61 , and the heat seal device  1  returns to the stand-by state illustrated in  FIG.  1   . When the apparatus is operated again, the webs  60  and  61  restart to be fed, so that the above operations are repeated. 
     It is possible to check the time during which the webs  60  and  61  are sandwiched by the first and second heat seal members  20  and  30  (hereinafter, referred to as the sandwiching time), i.e., the heat seal time by visually observing a gap  45  generated between the stopper  410  and the support  40  only when the webs  60  and  61  are being pressurized, as illustrated in  FIG.  3   . As described below, if the gap  45  which is formed in the state that the pole  41  has moved downward to the lower stroke end is larger, the heat seal time is longer; if this gap  45  is smaller, the heat seal time is shorter. In addition to this, the heat seal device  1  in the implementation provides a configuration for accurately detecting the sandwiching time without visual observation, as described below. 
     As illustrated in only  FIG.  1   , the heat seal device  1  further includes a sensor  10 , a measurement part  11 , a determination part  12  and a warning device  13 . 
     The sensor  10  is disposed to detect acceleration of the first heat seal member  20 . The sensor  10  is an accelerometer which outputs signals indicating the acceleration to the measurement part  11 . The sensor  10  in the implementation is attached, specifically affixed to the support  40 . Since the support  40  and the first heat seal member  20  move together, the sensor  10  detects the acceleration of the first heat seal member  20 . Thus, the data (constituted by the output signals) from the sensor  10  indicates the temporal change of the acceleration of the heat seal member  20 . 
     The measurement part  11  is configured to measure the sandwiching time based on the data from the sensor  10 . The principle of the measurement will be described. 
       FIG.  4    shows the temporal changes in height (h), velocity (v) and acceleration (a) of the first heat seal member  20  during the heat seal operation. The abscissa denotes time (t).  FIG.  4    also shows the heat seal operation and the feed status of the webs  60  and  61  in association with each other. The height (h) is referenced to the feed height  62 . The upward velocity (v) and acceleration (a) are positive. 
     As illustrated in  FIG.  4   , the drive mechanism  4  changes the height (h) in a substantial sine curve. When the first heat seal member  20  moves downward to the feed height  62  to start sandwiching the webs  60  and  61  in cooperation with the second heat seal member  30  (see t=t 1 ), the first heat seal member  20  instantly stops (v=0). Therefore, the first peak of the acceleration (a) is generated due to the start of sandwiching the webs  60  and  61  by the first and second heat seal members  20  and  30 , that is, the start of heat-sealing. 
     Then, as described above, the biasing force of the charge spring  43  continues to be applied to the webs  60  and  61  for a certain period by the pole  41  further moving downward. Throughout heat-sealing (t 1 ≤t≤t 2 ), a gap  45  ( FIG.  3   ) is generated. If the relative position of the stopper  410  to the pole  41  is higher, the time (t 1 ) when the first heat seal member  20  reaches the feed height  62  is later; if it is lower, the time (t 1 ) is earlier. 
     Then, the movement of pole  41  reverses from downward to upward, so that the gap  45  becomes smaller. The moment the pole  41  has moved upward by the time the gap  45  disappears (t=t 2 ), the application of the biasing pressure is terminated. The support  40  and the first seal unit  2  start to move together with the pole  41  upward, so that the first heat seal member  20  starts to move away from the webs  60  and  61 . At this moment (t=t 2 ), the velocity (v) increases instantly. Therefore, the second peak of the acceleration (a) is generated due to the release of sandwiching the webs  60  and  61  by the first and second heat seal members  20  and  30 , i.e., the termination of heat-sealing. At this point, if the relative position of the stopper  410  to the pole  41  is higher, the time (t 2 ) when the first heat seal member  20  starts to move away from the feed height  62  is earlier; if it is lower, the time (t 2 ) is later. In other words, moving the stopper  410  upward with respect to the pole  41  shortens the heat seal time (t 2 −t 1 ), whereas moving it downward lengthens the heat seal time (t 2 −t 1 ). 
     The first and second peaks are detected by the sensor  10 . The measurement part  11  then analyses the data received from the sensor  10  to calculate the time from the detected first peak to the detected second peak as the sandwiching time. In this way, the sensor  10  and the measurement part  11  enable accurate measurement of the sandwiching time (i.e., the heat seal time). 
     The determination part  12  is configured to determine whether or not the measured sandwiching time complies with the predetermined requirement(s). For example, the predetermined requirement may include a requirement that the sandwiching time is out of a predetermined range, a requirement that the sandwiching time is less than a first threshold value, or a requirement that the sandwiching time is greater than a second threshold value. The determination part  12  is capable of determining whether the sandwiching time (the heat seal time) is longer or shorter than the desired time. Here, the sandwiching time may be an average of the sandwiching times measured over multiple heat-sealing operations. 
     The functional parts (the measurement part  11  and the determination part  12 ) may be implemented by a processor executing programs stored in a memory medium. 
     The warning device  13  is configured to output a warning if the sandwiching time complies with the predetermined requirement(s). For example, a too short sandwiching time can be regarded as the application of insufficient biasing pressure to the webs  60  and  61 . Therefore, the warning device  13  may output a warning if it is determined that the sandwiching time is less than the lower limit of the predetermined range or the first threshold value. Conversely, a too long sandwiching time can be regarded as the application of excessive biasing pressure to the webs  60  and  61 . Therefore, the warning device  13  may output a warning if the sandwiching time is greater than the upper limit of the predetermined range or the second threshold value. 
     The warning device  13  may include a visual device such as a LED, a lamp, a display, and/or an audio device such as a speaker. Therefore, the output of the warning may be implemented by means of the emission of light and/or the generation of sound. 
     In addition to and/or instead of this, the warning device  13  may include an emergency stop device that stops the heat seal device  1  or the bag making apparatus including it. If the sandwiching time is too long, the webs  60  and  61  may be fed by the feed device of the bag making apparatus while being sandwiched by the first and second heat seal members  20  and  30 . This can result in the failure to feed. Therefore, the output of the warning may be implemented by means of the emergency stop of the heat seal device  1  or the bag making apparatus including it. 
     Alternatively, the heat seal device  1  may further include a display that indicates the measured sandwiching time. The display may indicate the measured sandwiching time together with the designed value of the sandwiching time. 
     Since the above configuration allows the sandwiching time and thus the heat seal time to be detected accurately, a user can appropriately adjust and manage this. When the sandwiching time is unsuitable for heat seal or bag making, the user can adjust the sandwiching time (heat seal time). In the implementation, the sandwiching time can be adjusted by the vertical adjustment of the relative position of the stopper  410  to the pole  41 . Specifically, adjusting stopper  410  upward with respect to pole  41  shortens the sandwiching time, and adjusting it downward lengthens the sandwiching time. As the failure of the adjustment can be corrected immediately in this way, it is possible to stabilize the quality of heat-sealing without variations. 
     The sensor  10  in the implementation is located close to one of the poles  41  located on the opposite ends of the support  40 , but it may be mounted at any position on the support  40 , for example, on the center section of the support  40 . 
     Even a slight difference in the adjusted position of the stopper  410  on the pole  41  between the two poles  41  can lead to differences in the time at which the first and second peaks are detected by the sensor  10  between the position near one pole  41  and the position near the other pole  41 . Thus, one sensor  10  may be mounted on one end of the support  40  to be located near one pole  41 , and the other sensor  10  may be mounted on the other end of the support  40  to be located near the other pole  41 . A user can then adjust the positions of both stoppers  410  referring to the data from these two sensors  10 , thereby eliminating the differences in the above peak detection time between the positions near both poles  41 . This provides a uniform heat seal time over the longitudinal direction of the heat seal member  20 / 30 , and thus provides heat-sealing with high quality. 
     The sensor  10  might detect vibration of at least one mechanical component located in the vicinity of the support  40 . Therefore, the heat seal device  1  may further include a filter circuit (not shown), which removes the natural frequency of the mechanical component, and pass the detection signals of the sensor  10  through this filter circuit to make the detection signals at the first and second peaks more prominent. 
     In the above implementation, the first and second heat seal members  20  and  30  are heated by the first and second heaters  21  and  31 , respectively, during the heat seal operation. During the heat seal operation, only one of the heat seal members  20  and  30  may be heated and the other may not be heated. In other words, the heat seal device  1  may put one of the internal heater cartridges in a non-heating state during the heat seal operation. Alternatively, the heat seal device  1  may include only one of the heaters  21  and  31 . Whether to heat one or both of the heat seal members  20  and  30  is determined depending on the properties of the webs  60  and  61  and the type of bags to be made. 
     An example of the bag making apparatus including the heat seal device  1  will be described with reference to  FIG.  5 A  to  FIG.  5 C . 
     The bag making apparatus includes a feed device  7  ( FIG.  5 B ) which intermittently feeds the webs  60  and  61  as the sheet panels in their longitudinal direction. The reference sign Xi designates the feed direction of the webs  60  and  61 . The feed device  7  may include, for example, a roller  70  for guiding the webs  60  and  61  to superpose them on each other, and a pair of feed rollers  71  which is driven to intermittently feed the webs  60  and  61 . 
     In the implementation, a single wide web is continuously unwound from the roll  6  and slit into the webs  60  and  61 . A dancer device  8  appropriately converts the feed of the webs  60  and  61  from the continuous feed into the intermittent feed. The webs  60  and  61  may be, for example, plastic films. Alternatively, each of the webs  60  and  61  may include a base made of paper, and a film or resin material laminated partially or fully to the base. 
     The bag making apparatus further includes a longitudinal heat seal device  1  a as an example of the heat seal device  1 . The longitudinal heat seal device  1  a is arranged downstream of the dancer device  8  and configured to heat-seal the webs  60  and  61  in their longitudinal direction during the pause phase of the intermittent feed cycle of the webs  60  and  61 . The longitudinal heat seal device  1  a is configured to heat-seal the webs  60  and  61  every intermittent feed cycle. 
     The longitudinal heat seal device  1  a in the implementation includes two pairs of the first and second seal units  2  and  3  for heat-sealing the webs  60  and  61  on the opposite sides of the webs  60  and  61 .  FIG.  5 C  is an enlarged illustration of the region T in  FIG.  5 A . As illustrated in  FIG.  5 C , each of two supports  40  extends in the width direction of the webs  60  and  61  over the webs  60  and  61 , and supports the two first seal units  2  such that these units  2  are movable in the width direction of the webs  60  and  61 . Similarly, the second seal units  3  are also supported by the supports  50  (not shown in  FIG.  5 A  to  FIG.  5 C ) to be movable in the width direction of the webs  60  and  61 . It is, therefore, possible to adjust the positions of the pairs of the first and second seal units  2  and  3  in the width direction of the webs  60  and  61 . The poles  41  and the components related thereto are disposed on the opposite sides of the two support  40 . The two supports  40  and the two supports  50  are disposed to be movable in the longitudinal direction of the webs  60  and  61  via the well-known structure. 
     The bag making apparatus further includes a cross heat seal device  1   b  as an example of the heat seal device  1 . The cross heat seal device  1   b  is arranged downstream of the longitudinal heat seal device  1   a  and configured to heat-seal the webs  60  and  61  in their width direction during the pause phase of the intermittent feed cycle of the webs  60  and  61 . The cross heat seal device  1   b  is configured to heat-seal the webs  60  and  61  every intermittent feed cycle. The cross heat seal device  1   b  in the implementation includes multiple pairs of first and second seal units  2  and  3 . 
     The number and arrangement of the pairs of first and second seal units  2  and  3  of the heat seal devices  1   a  and  1   b  are determined according to such factors as single-line bag making, two-line bag making, the structure of the bag, etc. 
     The bag making apparatus further includes a cross cut device  9 . The cross cut device  9  is configured to cross-cut the webs  60  and  61  in the width direction of the webs  60  and  61  during every intermittent feed cycle of the webs  60  and  61 . The bag is made every cross-cutting. 
     The above bag making apparatus is a mere example. The heat seal device  1  ( 1   a,    1   b ) may be incorporated into several kinds of the bag making apparatuses. For example, the heat seal device  1  may be incorporated into a bag making apparats for making bags each including not only the webs  60  and  61  as the sheet panels but also an additional component(s), such as side gussets, a bottom gusset, and optionally, may heat-seal the additional component(s) in addition to the webs  60  and  61 . 
     As described above, the heat seal device  1  is capable of adjusting the heat seal time, which is one of the factors that greatly affect the quality of heat-sealing, with high precision, thereby reducing variations in the quality of heat-sealing. Therefore, the bag making apparatus including the heat seal device  1  can reduce production loss due to its high quality of heat-sealing.