Welding method and welding equipment for welding plastic sheets

Abstract

To provide a welding method and apparatus that can judge whether welding is good or bad when welding and sealing contents by using a thermoplastic resin sheet, and can properly judge the cause of welding failure when it occurs.SOLUTION: The welding method uses a thermoplastic sheet having a predetermined pattern on one surface and transparency, and the welding method comprises the steps of: forming a welding area by overlapping two layers with the patterned surfaces inside each other; heating the welding area from only the first layer side to form a welded area; and determining whether the welding of the welded area is successful or not. In the welding success / failure judging step, it judges whether the pattern is lost / identifiable and judges the welding to be complete if the pattern is completely lost, and if the pattern is identifiable, it proceeds to the heating side pattern judging sub-step to judge whether the pattern of the first layer is lost / identifiable, and if the pattern of the first layer is identifiable on the area to be welded, it judges the heating to be insufficient and judges the first layer to be welded to be complete. If the pattern of the first layer is discernible in the area to be welded, it is judged as insufficient heating, and if the pattern of the first layer is lost but the pattern of the second layer is discernible, it is judged as poor adhesion.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a resin sheet welding technology, and in particular to a welding method and a welding device that enables sealing when a thermoplastic resin sheet is used to package contents even if wrinkles or folds occur in the sealing portion of the resin sheet. [Background technology]

[0002] In commercial packaging used in the food and medical fields, contents are often placed in soft packaging containers or molded containers made of resin, and the containers are often sealed by a welding means. However, since it is difficult to determine the melt-joined state of the welding of resin materials from the outside, there has been a demand for a technology that can non-destructively confirm the sealing quality of the welding.

[0003] In response to such demands, for example, Patent Document 1 (JP 2021-66529 A) teaches a container comprising a container body having an opening area formed at one end, the inner surface of the opening area being weldable, and the opening area being provided with a sealing confirmation mechanism that enables confirmation from the outer surface side of the opening area of ​​whether or not the opening area is sealed when the opening area is welded. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-66529 Summary of the Invention [Problem to be solved by the invention]

[0005] According to Patent Document 1, it is possible to easily determine by visual inspection that the opening area has been welded without using destructive means. However, based on the description, it is believed that the technology in Patent Document 1 is intended for containers with a relatively small volume of contents (up to about 2 L at most).

[0006] On the other hand, when sealing contents that may have adverse effects on the environment or human body (e.g., contaminated waste), it is preferable to seal large volumes of contents (at least 20 L pails, preferably 200 L drums) all at once from the viewpoint of work efficiency, transportation efficiency, and storage efficiency. In addition, it is preferable to perform the sealing work of such contents by remote control to avoid adverse effects on workers.

[0007] However, when attempting to package such large-volume contents using a resin sheet and remotely operating it, wrinkles and folds (hereinafter collectively referred to as wrinkles) are likely to occur in the sealed parts of the resin sheet, and there is a concern that the wrinkled parts may cause poor welding.

[0008] In addition, even for large-volume contents, the occurrence of wrinkles in the sealed portion can be suppressed by using a bag-shaped sheet having a volume much larger than the volume of the contents (for example, about twice as large or more), but this causes other problems, such as an increase in wasted space that does not contribute to storage and an increase in the size of the welding device. In other words, when a resin sheet is used to seal a large-volume content with the minimum necessary volume, there is a very high possibility that wrinkles will occur in the sealed portion of the resin sheet.

[0009] The present inventors have conducted extensive research into a welding method that enables sealing even when wrinkles occur in the sealing portion of a resin sheet. In the course of their research, they have found that it is extremely important to be able to appropriately and easily determine whether welding is good or not when welding is performed, and to be able to appropriately determine the cause of welding defects when they occur. This is because the method of dealing with welding defects differs depending on the cause.

[0010] The present invention has been made to solve the problem of poor welding caused by wrinkles in the sealing portion of a resin sheet, and its primary object is to provide a welding method and a welding device that can appropriately and easily determine whether the welding is good or not when a thermoplastic resin sheet is used to seal contents, and can appropriately determine the cause of poor welding if such a defect occurs. Also, its secondary object is to provide a welding method and a welding device that can seal contents even if wrinkles occur in the sealing portion of a thermoplastic resin sheet when the contents are sealed using the thermoplastic resin sheet. [Means for solving the problem]

[0011] (I) One aspect of the present invention is a method for welding resin sheets, comprising the steps of: the resin sheet is a thermoplastic resin sheet, has a predetermined pattern on one surface, and has a transparency that allows the predetermined pattern to be identified when viewed from the other surface; the predetermined pattern is a pattern drawn with ink, and when the resin sheets are laminated in two layers with the surfaces on which the patterns are drawn facing each other, the resin sheets have a form that allows a first layer and a second layer to be distinguished from each other; The welding method comprises: a step of forming a region to be welded by overlapping and contacting the resin sheets with the surfaces on which the predetermined patterns are formed facing each other to form a region to be welded; a welding step of heating the region to be welded only from the side of the first layer by a predetermined heating method to form a welded region; and a welding success / failure determination step for determining whether welding of the welded region has been successful, In the welding success / failure determination step, determining whether the predetermined pattern has disappeared in the welded area; When the predetermined pattern has completely disappeared from the welded area, it is determined that the welding is completed. If the predetermined pattern is identifiable in the welded region, the process proceeds to a heating side pattern determination substep of determining whether or not the predetermined pattern in the first layer has disappeared; When the predetermined pattern of the first layer is discernible in the welded region, the welded region is judged to be “insufficiently heated”; When the predetermined pattern of the first layer has disappeared in the welded area, but the predetermined pattern of the second layer is still identifiable, the welded area is judged to be “poor adhesion.” The present invention provides a method for welding resin sheets, comprising the steps of:

[0012] In the present invention, the following improvements and modifications can be freely combined in the above-mentioned resin sheet welding method (I). (i) If it is determined that "insufficient heating" is present in the heating side pattern determination sub-step, the process proceeds to a welding condition check step, where the welding conditions are changed to increase the amount of heat, and then the process returns to the welding step. (ii) when it is determined that the adhesion is poor in the heating side pattern determination sub-step, a pattern remaining area measurement sub-step is performed to measure the size of an area in which the predetermined pattern is identifiable; After returning to the welding step, the process proceeds to the welding success / failure determination step, In the second or subsequent welding success / failure determination steps, When the predetermined pattern has completely disappeared from the welded area, it is determined that the welding is completed. If it is determined that the predetermined pattern of the second layer is identifiable and therefore "poor adhesion", the method proceeds via the pattern remaining area measurement substep to a pattern remaining area comparison substep of determining whether or not the size of the remaining area of ​​the predetermined pattern measured this time is smaller than the size of the remaining area of ​​the predetermined pattern measured immediately before, In the pattern remaining area comparison sub-step, If the size of the remaining area of ​​the predetermined pattern measured this time is smaller than the size of the remaining area of ​​the predetermined pattern measured immediately before, the process returns to the welding step, If the size of the remaining area of ​​the predetermined pattern measured this time is not smaller than the size of the remaining area of ​​the predetermined pattern measured immediately before, it is determined to be "unweldable." (iii) If the pattern remaining area comparison sub-step determines that welding is not possible, the process returns to the welding step for another area different from the area to be welded, or returns to the area to be welded formation step so as to form an area to be welded that is different from the area to be welded. (iv) In the step of forming the region to be welded, the resin sheets are pressed with at least a pair of pressing tools to bring the resin sheets into contact with each other in an overlapping manner, thereby forming the region to be welded. (v) The at least one pair of pressing tools move in a direction sandwiching the resin sheet while creating a step in the height direction of the bag shape of the resin sheet, thereby forming the region to be fused. (vi) The predetermined heating method is ultrasonic welding or thermal welding. (vii) The predetermined pattern is a pattern drawn in ink, and has a repeating pattern consisting of line drawings that are asymmetrical with respect to an axis parallel to the height direction of the bag shape of the resin sheet. (viii) the ink is a fluorescent ink; The determination of disappearance or discernibility of the predetermined pattern in the welding state determining step and / or the welding state re-determining step is performed by irradiating the substrate with light having a wavelength capable of exciting fluorescence.

[0013] (II) Another aspect of the present invention is a welding apparatus for performing the above-mentioned resin sheet welding method, A resin sheet holding mechanism for holding the resin sheet; At least one pair of pressing tools and a driving mechanism for the pressing tools for forming the regions to be fused in the region to be fused forming step; A heating means and a receiving jig for forming the welded region in the welding step; a camera for checking the welding state of the welded region in the welding success / failure determination step, a control device for the camera, and a monitor connected to the control device; The present invention provides a resin sheet welding device comprising:

[0014] In the present invention, the following improvements and modifications can be freely combined in the above-mentioned resin sheet welding apparatus (II). (ix) The control device has an image processing mechanism for measuring the size of the remaining area of ​​the predetermined pattern in the pattern remaining area measuring sub-step. (x) The at least one pair of pressing tools and their driving mechanisms are configured to move in a direction sandwiching the resin sheet while a step is present in the height direction of the bag shape of the resin sheet. (xi) The welding method further includes an illumination mechanism for illuminating the welded area in the welding success / failure determining step. (xii) The bag-shaped resin sheet further includes a transfer mechanism for storing contents inside the bag-shaped resin sheet. Effect of the Invention

[0015] According to the present invention, it is possible to provide a welding method and a welding device that can appropriately and simply determine whether or not the welding is good when packaging contents using a thermoplastic resin sheet, and can appropriately determine the cause of poor welding if poor welding occurs. As a result, it is possible to provide a welding method and a welding device that can seal contents even if wrinkles occur in the sealing part of the resin sheet when welding and sealing contents using a thermoplastic resin sheet. Problems, configurations, and effects other than those described above will be made clear by the description of the embodiments described below. [Brief description of the drawings]

[0016] [Figure 1] FIG. 2 is a schematic plan view showing an example of a pattern drawn on the surface of a resin sheet used in the present invention. [Diagram 2] 1 is a schematic diagram showing the relationship between the state during welding and the determination of the welding state in the present invention. FIG. [Diagram 3] 1 is a flowchart showing an example of a method for welding resin sheets according to the present invention. [Figure 4] 1A and 1B are a front view and a side view showing an example of a resin sheet welding device according to the present invention. [Diagram 5]4 is another example of a pattern drawn on the resin sheet used in the present invention. [Figure 6] 4 is another example of a pattern drawn on the resin sheet used in the present invention. [Figure 7] 1A to 1C are schematic diagrams showing the state during the welding step and the pattern remaining area measurement sub-step when welding an area where wrinkles have occurred, where (a) is a cross-sectional view during the welding step, (b) is a cross-sectional view after the first welding step, (c) is a cross-sectional view after the second or subsequent welding step, (d) is a plan view during the first pattern remaining area measurement sub-step, and (e) is a plan view during the second or subsequent pattern remaining area measurement sub-step. [Figure 8] FIG. 4 is a schematic side view showing another example of the resin sheet welding device according to the present invention. [Figure 9] FIG. 11 is an enlarged schematic side view showing a welding step in the second embodiment. [Figure 10] FIG. 13 is a schematic perspective view showing a content accommodating step in the third embodiment. [Figure 11A] FIG. 13 is a schematic perspective view showing a welding step in the third embodiment. [Figure 11B] FIG. 13 is a schematic perspective view showing a welding step in the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Each drawing is exaggerated to facilitate understanding of the description. The same symbols are used for parts, structures, and steps that have the same meaning and are similar, and duplicated descriptions are omitted. Furthermore, the present invention is not limited to the specific embodiments described, and can be appropriately combined with known technologies or improved based on known technologies within the scope of the technical idea of ​​the invention.

[0018] (Basic concept of the present invention) In the prior art, when a resin sheet is used to seal the contents, any product with wrinkles in the sealed portion is deemed to be a defective product that cannot be shipped, and it is considered a prerequisite to prevent wrinkles from occurring. In contrast, in the present invention, wrinkles are permitted to occur in the sealed portion. In other words, the present invention is significantly different from the prior art at least in this respect.

[0019] The basic concept of the present invention will be described with reference to Figures 1 and 2. Figure 1 is a plan view schematic diagram showing an example of a pattern drawn on the surface of a resin sheet used in the present invention. Figure 2 is a schematic diagram showing the relationship between the state during welding and the judgment of the welding state in the present invention.

[0020] The resin sheet 1 used in the present invention is a resin sheet for sealing the contents, and is a thermoplastic resin sheet (e.g., a polypropylene sheet) having a predetermined pattern 2 drawn on one surface as shown in Figure 1, and having a transparency that allows the pattern 2 to be visually distinguishable when turned over and viewed from the other surface.

[0021] The resin sheet 1 may have a bag shape from the beginning, or may be a cylindrical resin sheet having the bottom welded to form a bag shape, or a single resin sheet folded in half and the sides welded to form a bag shape.

[0022] Pattern 2 is a pattern drawn with ink, and preferably has a repeating pattern consisting of line drawings that are asymmetrical with respect to an axis parallel to the height direction of the bag-shaped resin sheet 1. When two resin sheets 1 are stacked with the surfaces with such patterns on the inside and viewed from the outside, the pattern of pattern 2 on one resin sheet 1 is inverted, making it easy to distinguish between the first layer 1a and the second layer 1b.

[0023] Pattern 2 does not necessarily have to be drawn over the entire surface of one surface of resin sheet 1, but it is preferable that it is drawn over the entire surface of the area to be fused. In addition, ink for drawing pattern 2 preferably has chemical resistance (including water resistance) equivalent to that of the resin sheet, but is not otherwise limited.

[0024] The welding of resin sheets is basically a process of "softening and flowing of resin molecules → rearrangement and hardening of resin molecules." In the present invention, the ink of the pattern 2 drawn on the surface to be welded flows and diffuses together with the resin molecules as the resin molecules "soften and flow," so the original shape of the pattern 2 cannot be maintained during the "rearrangement and hardening of resin molecules." Therefore, in the present invention, a state in which the pattern 2 cannot maintain its original shape is defined as "disappeared." In other words, the pattern 2 has the property of disappearing when the resin sheet 1 is welded.

[0025] The ink used to draw the pattern 2 may be an ink that fades at a predetermined temperature (for example, the welding temperature). This makes it possible to determine whether the surface to be welded has risen to a desired temperature. Also, fluorescent ink may be used to draw the pattern 2. By irradiating the welded area that has undergone the welding step with light of a wavelength that can excite fluorescence, it becomes easier to determine whether the ink has flowed and diffused (whether welding of the resin sheet has occurred).

[0026] Next, a welding step by heating one side of the two-layered resin sheets 1 (1a, 1b) is assumed. For example, as shown in Fig. 2, the two-layered resin sheets 1 (1a, 1b) are sandwiched between a heating means 14 and a receiving jig 15, and heated only from the side of the first layer 1a by the heating means 14. In other words, in the present invention, the layer on the heated side is referred to as the first layer.

[0027] 2(a) shows a case where two overlapping resin sheets 1 (1a, 1b) are properly adhered to each other and the amount of heat is also proper. In this case, when the first layer 1a and the second layer 1b are well welded, the pattern 2 in the welded area 1d disappears completely. In other words, when the pattern 2 in the welded area 1d disappears completely, it can be easily determined that the welding has been well completed (welding completed).

[0028] 2(b) shows a case where two overlapping resin sheets 1 (1a, 1b) are properly adhered to each other, but the amount of heat is insufficient. In this case, the first layer 1a and the second layer 1b are not welded to each other, so the patterns 2 of each layer remain in the welded area 1d and are identifiable. In other words, if the patterns 2 of each layer remain in the welded area 1d, it can be determined that the heating for welding is insufficient (insufficient heating).

[0029] FIG. 2(c) shows a case where the amount of heat is appropriate, but the adhesion between the two overlapping resin sheets 1 (1a, 1b) is insufficient. If wrinkles are generated in the welded region 1d, this state is likely to occur in the wrinkled portion. In this case, the welded region 1d of the heated resin sheet 1 (here, the first layer 1a) rises to a weldable temperature (softens to a weldable state), so the pattern 2 of the first layer 1a disappears, but the heat conduction to the non-heated resin sheet 1 (here, the second layer 1b) is insufficient and does not rise to a weldable temperature, so the pattern 2 of the welded region 1d of the second layer 1b remains. In other words, if the pattern 2 of the heated resin sheet 1 disappears in the welded region 1d, but the pattern 2 of the non-heated resin sheet 1 remains, it can be determined that the adhesion for welding is poor (poor adhesion).

[0030] As described above, in the present invention, it is possible to easily determine whether the resin sheet 1 is welded, and also to appropriately determine the cause of the poor welding. By clarifying the cause of the poor welding, it becomes possible to take appropriate measures for each cause. As a result, sealing is possible even if wrinkles occur in the sealing portion of the resin sheet 1. Details of the method of dealing with each cause of poor welding will be described later.

[0031] (First embodiment) In the first embodiment, a case where the contents such as contaminated waste are directly put into a bag-shaped resin sheet and sealed will be described as an example. Note that, as described above, the present invention is premised on the premise that the operation is performed by remote control to avoid adverse effects on workers.

[0032] Fig. 3 is a flow chart showing an example of a resin sheet welding method according to the present invention. Fig. 4 is a schematic front view and a schematic side view showing an example of a resin sheet welding device according to the present invention. In Fig. 4, the names of the directions of the bag shape of the resin sheet 1 are defined.

[0033] First, a bag-shaped resin sheet 1 is placed on the base 10 of the welding device 100, and while holding the resin sheet 1 using the resin sheet holding mechanism 11, the contents 5 are placed inside the bag shape using a transfer mechanism (e.g., a robot arm, etc.) not shown (contents containing step S1).

[0034] At this time, it is preferable to check the bulk / volume of the contents 5 while using a camera 12 for checking the amount of storage. The camera 12 is connected to a control device (e.g., a computer) not shown, and it is preferable that the worker can visually check the camera image on the screen of a monitor (not shown) connected to the control device. The camera 12 may be substituted with a camera 16 for checking the welding state described below (it may be shared with the camera 16 for checking the welding state), or it may be installed separately for checking the amount of storage.

[0035] Next, the bag-shaped resin sheet 1 is pressed with at least one pair of pressing tools 13 (13a, 13b) (two pairs of pressing tools in Figure 4) to bring the resin sheets 1 into contact with each other in an overlapping manner, thereby forming a region to be welded 1c (region to be welded forming step S2).

[0036] The position to be pushed by the pusher 13 needs to be set so as not to pinch the contents 5, but is preferably set as close as possible to the contents 5. In other words, it is preferable to adjust the bulk / volume of the contents 5 in the contents accommodation step S1 so as to be as close as possible to the position to be pushed by the pusher 13, but not to pinch the contents 5.

[0037] As shown in Figures 1 and 2, the resin sheet 1 used in the present invention has a predetermined pattern 2 drawn on one surface, and has a transparency that allows the pattern 2 to be visually distinguished from the other surface. Since the pattern 2 has a repeating pattern consisting of line drawings that are asymmetrical with respect to an axis parallel to the height direction of the bag-shaped resin sheet 1, when the resin sheets 1 are stacked in two layers with the surfaces on which the pattern 2 is drawn facing each other, the first layer 1a and the second layer 1b can be distinguished. In other words, the pattern 2 is drawn on the inner surface side of the bag-shaped shape.

[0038] The pattern 2 is not limited to the simple oblique lines as exemplified in Figures 1 and 2, and may be, for example, a geometric pattern as shown in Figures 5 and 6. Figures 5 and 6 each show another example of a pattern drawn on the resin sheet used in the present invention.

[0039] Although not a required step, a sub-step S2a for confirming the regions to be fused may be performed to confirm whether or not both the pattern 2 of the first layer 1a and the pattern 2 of the second layer 1b are distinguishable. If it is confirmed that they are distinguishable, the process proceeds to the next step, and if not, it is preferable to redo the step S2 for forming the regions to be fused.

[0040] Here, in the region to be welded forming step S2, wrinkles may occur in the region to be welded 1c due to the relative relationship between the bulk / volume of the contents 5 and the pressing position of the pressing tool 13, or due to the thickness of the bag shape due to the amount of the contents 5. However, the present invention allows wrinkles to occur in the region to be welded 1c.

[0041] Next, the region to be welded 1c is sandwiched between the heating means 14 and the receiving jig 15, and the resin sheet 1 is welded by heating only from the side of the heating means 14 (welding step S3), thereby forming the welded region 1d.

[0042] There is no particular limitation on the heating means 14, but for example, ultrasonic welding or thermal welding can be suitably used. There is also no particular limitation on the length (length parallel to the width direction of the bag shape) of the heating means 14 and the receiving jig 15. For example, when the length of the heating means 14 and the receiving jig 15 is shorter than the width direction length of the bag shape of the resin sheet 1 (see FIG. 4), welding can be performed while moving the heating means 14 and the receiving jig 15.

[0043] In order to properly weld the resin sheet, it is necessary to heat the welded region 1d to a temperature equal to or higher than the softening point of the resin sheet 1. As an example, when polypropylene is used for the resin sheet 1, since the softening point is 100 to 110°C, it is preferable to heat the welded region 1d to about 110°C or higher.

[0044] Next, the success or failure of welding of the welded region 1d and the welding state are judged using a camera 16 for checking the welding state, etc. (welding success or failure judgment step S4). The camera 16 is connected to a control device (e.g., a computer) not shown, and it is preferable that the worker can visually check the camera image on the screen of a monitor (not shown) connected to the control device.

[0045] The welding success / failure determination step S4 may be performed after the welding step S3 is completed, but if the welding step S3 is performed while the heating means 14 is moving, it may be performed sequentially for the areas that the heating means 14 has passed through.

[0046] Although the lighting 17 is not an essential component, it may be installed as necessary so as to facilitate determination of disappearance / distinguishability of the pattern 2. On the other hand, when the pattern 2 is drawn with fluorescent ink, it is preferable to use the lighting 17 to irradiate light with a wavelength capable of exciting fluorescence.

[0047] The welding success / failure determination step S4 will now be described in more detail.

[0048] First, it is determined whether or not the pattern 2 of the resin sheet 1 has completely disappeared in the welded area 1d. If the pattern 2 of the welded area 1d has completely disappeared, it is determined that the welding has been satisfactorily completed, and the welding operation is finished.

[0049] If the pattern 2 in the welded area 1d has not disappeared even in part (if it is at least partially identifiable), a heating side pattern determination sub-step S4a is performed to determine whether the pattern 2 on the heating side resin sheet 1 (here, the first layer 1a) has disappeared or not. If the pattern 2 on the heating side resin sheet 1 has not disappeared (if it is identifiable), it is determined that insufficient heating has occurred.

[0050] If it is determined in the heating side pattern determination sub-step S4a that the heating is insufficient, the process goes through a welding condition check step S5 in which the welding conditions are checked and changed as necessary (for example, the output of the heating means 14, the heating retention time, or the pressing force between the heating means 14 and the receiving jig 15 is changed to increase the amount of heat), and then returns to the welding step S3, and then proceeds to the welding success / failure determination step S4.

[0051] In the welding step S3 and the welding condition check step S5, since heating to a temperature near or above the melting point of the resin sheet 1 may cause the resin sheet 1 to deform excessively or develop holes, making it impossible to seal, it is necessary to set an upper limit for the welding temperature. The upper limit of the welding temperature is preferably set to a temperature, for example, 20 to 30°C lower than the melting point of the resin sheet 1. As an example, when polypropylene with a melting point of 160 to 170°C is used for the resin sheet 1, it is preferable to set the upper limit of the welding temperature to about 140°C.

[0052] In the second or subsequent welding success / failure determination step S4, if the pattern 2 in the welded area 1d has completely disappeared, it is determined that the welding has been satisfactorily completed, and the welding operation is terminated.

[0053] On the other hand, if it is determined that the heating is insufficient in the second and subsequent welding success / failure determination steps S4, the cycle of the welding condition check step S5, the welding step S3, and the welding success / failure determination step S4 is repeated.

[0054] In contrast, in the first and second or later heated side pattern determination sub-step S4a, if the pattern 2 of the heated side resin sheet 1 (here, the first layer 1a) has disappeared but the pattern 2 of the non-heated side resin sheet 1 (here, the second layer 1b) has not disappeared (remains), it is determined that there is poor adhesion. In that case, a pattern remaining area measurement sub-step S4b is performed to measure the size of the area where the pattern 2 remains.

[0055] There is no particular limitation on the method of measuring the size of the remaining area of ​​pattern 2. For example, the area of ​​the area may be directly measured using the image processing mechanism of the control device for image data captured by camera 16, or the length of the remaining area of ​​pattern 2 (the length parallel to the width direction of the bag shape) may be measured (because the size of heating means 14 is known, the area can be roughly calculated if the length is known).

[0056] Next, a measurement count determination sub-step S4c is performed to determine whether the measurement of the pattern remaining area size is the first time. If the measurement of the pattern remaining area is the first time, the process returns to the welding step S3 via the welding condition check step S5, and proceeds to the welding success / failure determination step S4.

[0057] In this welding condition check step S5, it is not necessary to change any of the welding conditions. This is because it is determined that there is no major problem with the output of the heating means 14 in the welding step S3 because it is confirmed in the heating side pattern determination sub-step S4a that the pattern 2 of the resin sheet 1 on the heating side has disappeared. In other words, the welding condition check step S5 includes not making any changes.

[0058] When the welding conditions are changed in the welding condition check step S5, for example, the heating holding time and the pressing force between the heating means 14 and the receiving jig 15 may be changed. Of course, the output of the heating means 14 may be changed within the range of the allowable welding temperature.

[0059] In the second or subsequent welding success / failure determination step S4, if the pattern 2 in the welded area 1d has completely disappeared, it is determined that the welding has been satisfactorily completed, and the welding operation is terminated.

[0060] On the other hand, if poor adhesion is also determined in the second or subsequent heating side pattern judgment sub-step S4a, proceed to pattern remaining area measurement sub-step S4b to measure the size of the area in which pattern 2 remains, and after it is determined in measurement count judgment sub-step S4c that this is the second or subsequent time (not the first time), a pattern remaining area comparison sub-step S4d is performed to determine whether the size of the remaining area of ​​pattern 2 measured this time is smaller than the measurement result of the previous time (the time immediately preceding it).

[0061] FIG. 7 is a schematic diagram showing the welding step and the pattern remaining area measurement sub-step when welding an area where wrinkles have occurred, where (a) is a cross-sectional view during the welding step, (b) is a cross-sectional view after the first welding step, (c) is a cross-sectional view after the second or subsequent welding steps, (d) is a plan view during the first pattern remaining area measurement sub-step, and (e) is a plan view during the second or subsequent pattern remaining area measurement sub-step.

[0062] As shown in Fig. 7(a), when attempting to weld a wrinkled area, the wrinkled area may be sandwiched between heating means 14 and receiving jig 15 and folded into pleats. When heating is applied from heating means 14 in this state, the resin molecules soften, flow, and infiltrate the area where the resin sheet 1 on the heated side (here, the first layer 1a) and the normal non-pleated area of ​​the resin sheet 1 on the unheated side (here, the second layer 1b) join together, and part of the pleated area of ​​the second layer 1b (for example, near the base), causing welding (i.e., integration).

[0063] However, in the vicinity of the voids 3 in the pleated portions of the second layer 1b, the heat conduction to the portions may be insufficient, and thus the welding may not be completed, leaving the voids 3 (see Figs. 7(a) and 7(b)). As a result, as shown in Fig. 7(d), in the pattern remaining area measurement sub-step S4b, the remaining area of ​​the pattern 2 caused by the voids 3 is confirmed and measured.

[0064] Therefore, if welding step S3 is performed again after welding condition check step S5 (for example, after increasing the pressing force between heating means 14 and receiving jig 15), the portion welded the first time will have sufficient thermal conductivity, and heat will be easily conducted to the pleated portion of second layer 1b as well, causing welding of a part of the pleated portion and reducing the unwelded pleated portion (see FIG. 7(c)). As a result, as shown in FIG. 7(e), in pattern remaining area measurement sub-step S4b from the second time onwards, the size of the remaining area of ​​pattern 2 in second layer 1b will decrease.

[0065] In the pattern remaining area comparison sub-step S4d, if it is determined that the size of the measured remaining area of ​​pattern 2 is smaller than the previous measurement result, it can be determined that welding is progressing although welding is not complete, and therefore by repeating this cycle, welding can be completed.

[0066] On the other hand, if it is determined in the pattern remaining area comparison sub-step S4d that the size of the measured remaining area of ​​the pattern 2 has not become smaller than the previous measurement result, it is determined that welding does not progress in that area 1d to be welded and does not reach completion of welding (welding is not possible). In that case, it is preferable to return to the welding step S3 for another part in the area to be welded 1c, or to the area to be welded formation step S2 and start over.

[0067] Second embodiment In the second embodiment, an example will be described in which the entire container containing contaminated waste etc. is sealed with a bag-shaped resin sheet as the contents. Here, a large-volume container (at least about a 20 L pail can, preferably about a 200 L drum can or more) is assumed.

[0068] In the following, differences from the first embodiment will be mainly described with reference to Fig. 3, Fig. 8, and Fig. 9. Fig. 8 is a schematic side view showing another example of the welding device for resin sheets according to the present invention. Fig. 9 is an enlarged schematic side view showing the welding step in the second embodiment. Note that in order to emphasize the differences from the first embodiment, the parts common to the first embodiment are omitted in the drawings.

[0069] First, a bag-shaped resin sheet 1 is placed on the base 10 of the welding device 200, and while the bag-shaped resin sheet 1 is held using the resin sheet holding mechanism 11, a transfer mechanism (e.g., a crane, etc.) is used to place contents 6 (a container containing contaminated waste, etc.) inside the bag-shaped resin sheet 1 (contents placement step S1).

[0070] Next, the bag-shaped resin sheet 1 is pressed with at least a pair of pressing tools 21 (21a, 21b) (a pair of pressing tools in Figure 8) to bring the resin sheets 1 into contact with each other in an overlapping manner, thereby forming a region to be welded 1c (region to be welded forming step S2).

[0071] Here, when sealing the entire container containing contaminated waste or the like as the contents 6 as in this embodiment, if an attempt is made to pinch the contents as close as possible with a pair of pressers 13 (13a, 13b) as in Fig. 4 of the first embodiment, there is a possibility that the resin sheet 1 will break at the edge of the contents 6 (particularly the edge of the container). This is because the outer shape of the contents 6 is not substantially deformed by the pressing force from the resin sheet 1, and instead a local tension is applied to the resin sheet 1.

[0072] Therefore, in this embodiment, the pair of pressing tools 21 (21a, 21b) are configured to move in a direction sandwiching the resin sheet 1 in a state where there is a step in the height direction of the bag shape of the resin sheet 1. This makes it possible to relieve the local tension applied to the resin sheet 1 by the contents 6, thereby preventing the risk of the resin sheet 1 being torn.

[0073] Although not an essential step, the region-to-be-fused region confirming sub-step S2a may be performed on the region-to-be-fused region 1c in the same manner as in the first embodiment.

[0074] 9, the region to be welded 1c is sandwiched between the heating means 14 and the receiving jig 15, and the resin sheet 1 is welded by heating only from the side of the heating means 14 (welding step S3). As a result, the welded region 1d is formed.

[0075] The rest is the same as in the first embodiment.

[0076] In this embodiment, since the outer shape of the large-volume content 6 is not substantially deformed, wrinkles tend to occur more easily in the resin sheet 1 in the region to be welded forming step S2 than in the first embodiment. However, since the present invention allows wrinkles to occur in the region to be welded 1c, good sealing can be achieved even when the entire large-volume container is sealed with the bag-shaped resin sheet 1.

[0077] Third embodiment In the third embodiment, an example is described in which there is a risk that the bag-shaped resin sheet will tear if the contents to be sealed are directly poured into the bag-shaped resin sheet, or in which the contents to be sealed have a shape that is not suitable for storage in a normal container (e.g., a long rod shape, a large plate shape, etc.).

[0078] In the first and second embodiments, one side of a bag-shaped resin sheet is welded and sealed, but this embodiment differs from the first and second embodiments in that a single resin sheet is folded in half and welded and sealed along three sides.

[0079] In the following, the differences from the first embodiment will be mainly described with reference to Fig. 3, Fig. 10, Fig. 11A, and Fig. 11B. Fig. 10 is a perspective schematic diagram showing the state of the content accommodation step in the third embodiment. Figs. 11A and 11B are perspective schematic diagrams showing the state of the welding step in the third embodiment. Note that in order to emphasize the differences from the first embodiment, the parts common to the first embodiment are omitted in the figures.

[0080] First, as shown in FIG. 10, a resin sheet 1 is placed on the base 10 of the welding device, and contents 7 are placed on the resin sheet 1 using a transfer mechanism (e.g., a robot arm, etc.) not shown. After that, the resin sheet 1 is folded in half using a resin sheet holding mechanism not shown to cover the contents 7 (contents storage step S1).

[0081] Next, as shown in FIG. 11A, at least a pair of pressing tools 31 (31a, 31b) are used to press the resin sheet 1 at a portion corresponding to one side of the folded portion, thereby bringing the resin sheets 1 into contact with each other so as to overlap, thereby forming a region to be welded 1c (region to be welded forming step S2).

[0082] Although not an essential step, the region-to-be-fused region confirming sub-step S2a may be performed on the region-to-be-fused region 1c in the same manner as in the first embodiment.

[0083] Next, the region to be welded 1c is sandwiched between the heating means 14 and the base 10, and the resin sheet 1 is welded by heating only from the side of the heating means 14 (welding step S3). As a result, a first welded region 1e is formed. In this embodiment, the base 10 also serves as a receiving jig for the heating means 14.

[0084] Next, the first welded region 1e is subjected to a welding success / failure determination step S4, and each step is repeated until it is determined that welding of the first welded region 1e is complete by a process similar to that of the first embodiment.

[0085] Next, the welding region forming step S2 and the welding step S3 are performed on the portion corresponding to the other side of the folded portion to form a second welding region 1f (see FIG. 11A).

[0086] Next, the second welded region 1f is subjected to a welding success / failure determination step S4, and each step is repeated until it is determined that welding of the second welded region 1f is complete by a process similar to that of the first embodiment.

[0087] Next, as shown in FIG. 11B, a third region to be welded 1g (not shown) is formed by carrying out a region to be welded forming step S2 and a welding step S3 on a portion corresponding to the mouth of the bag shape.

[0088] Next, the third welded region 1g is subjected to a welding success / failure determination step S4, and each step is repeated until it is determined that welding of the third welded region 1g is complete by a process similar to that of the first embodiment.

[0089] In the above description, the welding and sealing was performed in the order of the first welded area 1e, the second welded area 1f, and the third welded area 1g, but this embodiment is not limited to this order, and any order may be used as long as the final seal is achieved.

[0090] In this embodiment, the contents to be sealed can be sealed well even in cases where there is a risk that the resin sheet will tear if the contents to be sealed are directly poured into the bag-shaped resin sheet, or even in cases where the contents to be sealed have a shape that is not suitable for storage in a container of a normal shape.

[0091] The above-mentioned embodiment has been described to aid in understanding the present invention, and the present invention is not limited to the specific configurations described. For example, it is possible to replace a part of the configuration of the embodiment with a configuration according to the technical common sense of a person skilled in the art, and it is also possible to add a configuration according to the technical common sense of a person skilled in the art to the configuration of the embodiment. In other words, it is possible to delete, replace, or add a part of the configuration of the embodiment of this specification to the extent that does not deviate from the technical idea of ​​the invention. [Explanation of symbols]

[0092] 1: resin sheet, 1a: first layer, 1b: second layer, 1c: region to be welded, 1d: region to be welded, 1e: first welded region, 1f: second welded region, 1g: third welded region, 2...Pattern, 3...Vacuum, 5,6,7...Contents, 10: base; 11: resin sheet holding mechanism; 12: camera; 13: pressing tool; 14...heating means, 15...receiving jig, 16...camera, 17...lighting, 21...pressing tool, 31...pressing tool, 100, 200, 300... welding equipment.

Claims

1. A method for welding a resin sheet, comprising the steps of: the resin sheet is a thermoplastic resin sheet, has a predetermined pattern on one surface, and has a transparency that allows the predetermined pattern to be identified when viewed from the other surface; the predetermined pattern is a pattern drawn with ink, and has a form that allows a first layer and a second layer to be distinguished from each other when the resin sheets are stacked in two layers with the surfaces on which the patterns are drawn facing each other; The welding method comprises: a step of forming an area to be welded by overlapping and contacting the resin sheets with the surfaces on which the predetermined patterns are formed facing each other to form an area to be welded; a welding step of heating the region to be welded only from the side of the first layer by a predetermined heating method to form a welded region; and a welding success / failure determination step for determining whether welding of the welded region has been successful, In the welding success / failure determination step, determining whether the predetermined pattern has disappeared in the welded area; When the predetermined pattern has completely disappeared from the welded area, it is determined that the welding is completed. If the predetermined pattern is identifiable in the welded region, the process proceeds to a heating side pattern determination substep of determining whether or not the predetermined pattern of the first layer has disappeared; When the predetermined pattern of the first layer is discernible in the welded region, the welded region is judged to be “insufficiently heated”; When the predetermined pattern of the first layer has disappeared in the welded area, but the predetermined pattern of the second layer is still identifiable, the welded area is judged to be “poor adhesion.” A method for welding resin sheets comprising the steps of:

2. The method for welding resin sheets according to claim 1, If it is determined that "insufficient heating" in the heating side pattern determination sub-step, the process proceeds to a welding condition check step, where the welding conditions are changed so as to increase the amount of heat, and then the process returns to the welding step. A method for welding resin sheets comprising the steps of:

3. The method for welding resin sheets according to claim 1, When the heating side pattern determination sub-step determines that the adhesion is poor, a pattern remaining area measurement sub-step is performed to measure the size of an area in which the predetermined pattern is identifiable; After returning to the welding step, the process proceeds to the welding success / failure determination step, In the second or subsequent welding success / failure determination steps, When the predetermined pattern has completely disappeared from the welded area, it is determined that the welding is completed. If it is determined that the predetermined pattern of the second layer is identifiable and therefore "poor adhesion", the method proceeds via the pattern remaining area measurement substep to a pattern remaining area comparison substep of determining whether or not the size of the remaining area of ​​the predetermined pattern measured this time is smaller than the size of the remaining area of ​​the predetermined pattern measured immediately before, In the pattern remaining area comparison sub-step, If the size of the remaining area of ​​the predetermined pattern measured this time is smaller than the size of the remaining area of ​​the predetermined pattern measured immediately before, the process returns to the welding step, If the size of the remaining area of ​​the predetermined pattern measured this time is not smaller than the size of the remaining area of ​​the predetermined pattern measured immediately before, it is determined that the pattern is "unweldable." A method for welding resin sheets comprising the steps of:

4. The resin sheet welding method according to claim 3, If it is determined that "welding is not possible" in the pattern remaining area comparison sub-step, the process returns to the welding step for another area different from the area to be welded, or returns to the intended welding area formation step so as to form an intended welding area different from the intended welding area. A method for welding resin sheets comprising the steps of:

5. The method for welding resin sheets according to any one of claims 1 to 4, The method for welding a resin sheet is characterized in that the step of forming the region to be welded comprises pressing the resin sheet with at least a pair of pressing tools to bring the resin sheets into contact with each other in an overlapping manner, thereby forming the region to be welded.

6. The resin sheet welding method according to claim 5, A method for welding a resin sheet, characterized in that the at least one pair of pressing tools move in a direction sandwiching the resin sheet while creating a step in the height direction of the bag shape of the resin sheet, thereby forming the intended welding area.

7. The method for welding resin sheets according to any one of claims 1 to 4, The method for welding resin sheets, wherein the predetermined heating method is ultrasonic welding or thermal welding.

8. The method for welding resin sheets according to any one of claims 1 to 4, A method for welding a resin sheet, characterized in that the predetermined pattern has a repeating pattern consisting of line drawings that are asymmetrical with respect to an axis parallel to the height direction of the bag shape of the resin sheet.

9. The method for welding resin sheets according to any one of claims 1 to 4, the ink is a fluorescent ink, A method for welding resin sheets, characterized in that in the welding success determining step, the determination of whether the predetermined pattern has disappeared or is distinguishable is performed by irradiating light with a wavelength capable of exciting fluorescence.

10. A welding apparatus for carrying out the resin sheet welding method according to any one of claims 1 to 4, A resin sheet holding mechanism for holding the resin sheet; At least one pair of pressing tools and a driving mechanism for the pressing tools for forming the regions to be fused in the region to be fused forming step; A heating means and a receiving jig for forming the welded region in the welding step; a camera for checking the welding state of the welded region in the welding success / failure determination step, a control device for the camera, and a monitor connected to the control device; A resin sheet welding apparatus comprising:

11. The resin sheet welding apparatus according to claim 10, A resin sheet welding apparatus, characterized in that the control device has an image processing mechanism for measuring the size of the remaining area of ​​the predetermined pattern.

12. The resin sheet welding apparatus according to claim 10, A resin sheet welding device characterized in that at least one pair of pressing tools and their driving mechanisms are configured to move in a direction to clamp the resin sheet while creating a step in the height direction of the bag shape of the resin sheet.

13. The resin sheet welding apparatus according to claim 10, The resin sheet welding apparatus further comprises an illumination mechanism for illuminating the welded area in the welding success / failure determining step.

14. The resin sheet welding apparatus according to claim 10, A resin sheet welding apparatus further comprising a transfer mechanism for storing contents inside the bag-shaped resin sheet.

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