JP5911324B2 - Apparatus and method for thermal welding of thermoplastic resin - Google Patents

Description

  The present invention relates to a thermoplastic resin thermal welding apparatus and method, and is used, for example, when a container and a lid are joined. The present invention is particularly useful when a joining method such as ultrasonic welding cannot be used for precision parts.

  Conventionally, since a high speed is required for a general apparatus for joining packaging materials, various joining methods such as thermal welding, ultrasonic welding, and vibration welding are used. Especially for precision parts that dislike vibration, thermal welding is mainly used. Thermal welding is a technique in which a heating body having a heating means is pressed and bonded by crushing the container and lid of the packaging material.

  The role of the packaging material is to ensure hermeticity that can withstand pressure fluctuations and temperature changes during transportation. In addition, as an incompatible requirement, an easy opening property that is a welding strength that is easily peeled off manually is also important. Thus, as a role of the packaging material, it is necessary to achieve both airtightness and easy opening. As a sealing quality evaluation method, a pressurization test in which pressurization and decompression are repeated, and a heat cycle test in which the test is alternately performed in a high temperature environment and a normal temperature environment are generally performed. In addition, as an easy-opening quality evaluation method, there is an example in which a peel test of a welded part is performed. In order to satisfy both the requirements of hermeticity and easy opening, it is necessary to manage the welding strength. The welding strength is determined based on the bonding area. In general, in order to effectively squeeze the container and the lid, the surface to be welded to the lid of the welding rib on the container side, which is an object to be welded, is provided around the opening as shown in FIG. Convex-shaped welding ribs are formed. FIGS. 7B and 7C show examples of cross sections of convex weld ribs. When this convex shape is not a certain width, it is important to manage the amount of displacement corresponding to the crushing margin of the container and the lid. When the width of the convex shape of the welding rib is uniform as shown in FIG. 7B, the welding length is constant because the joining lengths 1 and 2 are constant without managing the crushing allowance. Although the amount of welding burrs generated varies depending on the crushing allowance, it does not affect the welding strength. However, as shown in FIG. 7C, in order to form the container with a mold, the width of the convex shape may vary depending on the height. In that case, since the joining length varies depending on the crushing margin, it is necessary to manage the crushing margin in order to maintain a predetermined welding strength.

  Patent Document 1 below discloses a general method and apparatus for thermally welding a packaging material. The target packaging material is composed of a thermoplastic resin container and a film-like lid. This thermal welding apparatus includes a mechanism for supplying a container and a lid, a conveyance path for intermittently moving the container, a mechanism for storing an object to be packaged in the container, and a mechanism for thermally welding the lid to the container by pressing a heating body. It is configured. The object to be packaged is stored in the supplied container, a lid is supplied thereon, and the lid and the container are pressed by a heating body having a heating means to perform heat welding.

Japanese Patent Laid-Open No. 10-81304

  In the conventional heat welding method, the welding strength is managed by time management. However, in this method, the welding ends uniformly in a certain time regardless of variations in the height and width of the welding ribs of the lid and the container, so that the variation in the welding strength of the bonded packaging material becomes large. There was a problem.

  Therefore, in order to solve such a problem, it is necessary to perform penetration amount control capable of canceling the influence of variations in height and width of the convex ribs for welding the lid and the container.

  However, when the thermoplastic resins are welded to each other, they are thermally deformed, so that it is difficult to detect a contact load that can be easily detected between rigid bodies. In order to accurately detect the contact load, it is necessary to set the load low or to set the temperature of the heating body low. However, in order to perform heat welding with a high-speed tact within 1.0 seconds, it is necessary to set the welding load high or set the temperature of the heating body high. When the welding load is increased, the welding is completed before the heat is properly transmitted, resulting in a problem that the welding strength is lowered. Similarly, when the heating body is heated to a high temperature, when the heating body approaches the lid, the thermoplastic resin starts to melt and softens, and the welding strength is not stable. Therefore, in high-speed tact, it is difficult to detect the load when the heating body contacts the lid, so that it is difficult to manage the welding strength.

  Accordingly, it is an object of the thermal welding apparatus and method according to the present invention to stabilize the welding strength with a simple configuration and to achieve high speed.

  In order to achieve the above object, the present invention is a thermal welding apparatus for joining a container of a packaging material made of a thermoplastic resin and a lid by thermal welding, and includes a heating body having a heating means and a displacement detection means. It has a pressing means and a load detection means, the load applied to the heating body is detected by the load detection means, and the welding strength can be managed without being affected by individual differences of the welded material and the welded material. It is a thing.

  Further, the second problem solving means is the above-mentioned heat welding apparatus, for displacement amount management that enables management of the displacement amount from the position where the contact load immediately after the heating body and the lid are in contact is detected. The actuator includes an actuator having position detecting means such as an encoder and an eddy current sensor.

  The operation of the first problem solving means is as follows. That is, since the contact point between the lid and the container is detected every time, it is possible to manage the welding strength without being affected by the individual difference between the welded material such as the lid and the container and the material to be welded.

  Moreover, the effect | action by a 2nd problem-solving means exhibits the effect that penetration amount control can be easily performed by using the actuator which has a position detection means.

  According to the heat welding apparatus and method of the present invention, it is possible to suppress a variation in welding strength even at a high speed tact, and it is possible to prevent the occurrence of defective products due to poor sealing performance and easy opening performance.

Schematic which showed the structure of the heat welding apparatus of embodiment of this invention. The figure which showed the operation | movement flow in 1st Embodiment The figure which showed the time change of the load and displacement in 1st Embodiment The figure which showed the operation | movement flow in the comparative example 1. The figure which showed the change of the press load and displacement in the comparative example 1. The figure which showed the operation | movement flow in 2nd Embodiment. Top view of general container and cross-sectional view of welding rib

Hereinafter, embodiments of the present invention will be described with reference to FIGS.
(First embodiment)
FIG. 1 is a schematic view showing a configuration of a heat welding apparatus according to a preferred embodiment of the present invention. The lid 11 is thermally welded (joined) to the container 12 by the heat welding apparatus of FIG. The lid 11 is supported while being placed on the container 12, and the container 12 is supported by a backup 33.
In FIG. 1, reference numeral 21 denotes a heating body that directly heats the lid 11. Heating means 22 such as a cartridge heater or a pulse heater is provided inside the heating body 21. The heating means 22 is controlled by a temperature adjusting controller 23.

  Further, as an actuator for driving the heating body 21 in the vertical direction, a pressing means 31 such as a servo motor, an electric cylinder, an electric actuator of a single-axis robot using a stepping motor or a linear motor is provided. The pressing means 31 may have both a displacement amount management function and a load switching function described later. The pressing means 31 includes a displacement detecting means 32 such as an encoder of a servo motor or an external eddy current sensor. Moreover, in order to detect the load at the time of pressing the heating body 21 and the lid | cover 11, it has the load detection means 41, such as a load cell.

Next, a heat welding method using the heat welding apparatus shown in FIG. 1 will be described using the operation flow of FIG. In step 1 (S 1), the lid 11 and the container 12 are set on the backup 33, and the heating body 21 stands by at a position away from the lid 11. The heating body 21 is heated by the heating means 22 and is in a heated state. Next, in step 2 (S2), the entire heating body 21 is moved by the pressing means 31 and moved to a predetermined moving speed switching point at a high speed. In the case of this embodiment, the moving speed switching point is 0.5 mm or more before the position where the heating body 21 and the lid 11 are in contact. Thereafter, the moving speed of the pressing means 31 is switched at step 3 (S3), and the entire heating element 21 starts moving at a low speed of 10 mm / sec or less at step 4 (S4). In step 5 (S5), the heating body 21 and the lid 11 are kept in contact with each other at a low speed, and the thermoplastic resin begins to melt, whereby the load is gradually increased. Next, in step 6 (S6), the pressing means 31 continues to move until a predetermined contact load is detected, and it is determined that the heating body 21 and the lid 11 are in contact. Thereafter, in step 7 (S7), the movement is continued so that the load is switched in a predetermined time from the contact load to the welding load, and the predetermined welding load is reached in step 8 (S8). Next, in step 9 (S9), the current position at the time of step 7 is set as a zero point, and the movement is continued so that the load becomes constant until a predetermined penetration amount is reached. At that time, Steps 7 and 8 and Step 9 are performed simultaneously. After the penetration amount reaches a predetermined value in step 9, the welding is completed in step 10 (S10). After that, in step 11 (S11), high-speed movement is started so that the entire heating element 21 returns to the position in step 1. At the time of step 12 (S12) when returning to the same position as step 1, the one-cycle operation ends .

In this way, by performing the heat welding method of the operation flow shown in FIG. 2, it is possible to manage so that a stable welding strength can be always achieved without being affected by individual differences in the welded material and the welded material.
In the above-mentioned heat welding apparatus, an encoder or an eddy current sensor is used for displacement amount management that makes it possible to manage the displacement amount (movement amount) from the position at which the contact load is detected immediately after the heating body contacts the lid. An actuator having various position detecting means may be provided.

  Next, the thermal welding apparatus and the thermal welding method of Example 1 of the 1st Embodiment of this invention are demonstrated with reference to FIGS. 1-3. As a comparative example 1, a conventional thermal welding method for managing the welding strength by time management will be described with reference to FIGS. 4 and 5. FIG. From a comparison between Example 1 and Comparative Example 1, a specific example of a difference in welding strength variation depending on whether or not the load is switched will be shown. However, the present invention is not limited to the following examples.

(Example 1)
The apparatus configuration of the thermal welding apparatus in Example 1 of the first embodiment is as schematically shown in FIG. Since the lid 11 is welded to the upper end of the container 12, a welding rib having a convex shape in the longitudinal section is formed in a ring shape, similar to the shape of the container 12 shown in FIG. Yes. Further, the width of the convex shape (ring width) varies depending on the height, and as shown in FIG. 7C, the cross section has a shape in which the bowl is turned upside down. That is, as the height of the convex shape increases, the width of the convex shape decreases. Specifically, the following apparatus configuration was used.

  The apparatus has a heating body 21 made of brass, and two 150 W sheath type cartridge heaters as heating means 22 therein. A controller 23 with a sampling period of 100 mS was used as a temperature regulator for controlling the heating means 22.

  Further, a servo motor is provided as the pressing means 31, and a load cell having a maximum capacity of 2000N and a resolution of 0.1% is provided as the load detecting means 41. The servo motor as the pressing unit 31 can perform feedback control on the detection value of the load detection unit 41. The lid 11 used in this example has a total thickness composed of a plurality of layers such as an unstretched polypropylene layer which is a thermoplastic resin as a heat-welding layer, a gas barrier layer which prevents ink evaporation, and a heat protective layer having a melting point higher than that of polypropylene. It was a 120 μm thermoplastic resin film. The container 12 is made of polypropylene, and has a welding rib having a reverse bowl-shaped cross section having a height of 200 μm and a width of 1.2 mm on the outer periphery for thermal welding.

  Next, the heat welding method in Example 1 is demonstrated with reference to FIG. 2 and FIG.

  In FIG. 3, the horizontal axis represents time (Sec), and the vertical axis represents the load (N) detected by the load detector 41 and the displacement (mm) detected by the displacement detector 32. In addition, the solid line in the graph represents the transition of the load, and the chain line represents the transition of the displacement. Further, S1, S3, S5, S6, S8, and S10 shown on the horizontal time axis correspond to the steps of the operation flow shown in FIG.

  The lid 11 and the container 12 were thermally welded under the setting conditions described below. The heating means 22 was controlled by the controller 23 so that the welding temperature of the heating body 21 became a constant temperature state of 200 ° C.

  Further, as the load switching condition, the contact load in step 6 was set to 200 N and the welding load in step 8 was set to 500 N in the operation flow shown in FIG. 2, and the load was continuously switched. Further, by performing feedback control so as to continue to maintain a predetermined pressing load after reaching the welding load in Step 8, it is possible to reduce the overrun of the pressing means 31 and manage the welding strength.

  Furthermore, in FIG. 2, the set value of the penetration amount for stepping from Step 6 to Step 10 was set to 130 μm.

(Comparative Example 1)
As Comparative Example 1 using the prior art, a thermal welding apparatus and a thermal welding method that perform only time management without switching loads will be described.

First, the thermal welding apparatus in Comparative Example 1 is configured without some of the components of the apparatus shown in FIG. Specifically, the experiment was performed with the following apparatus configuration.
The difference between the apparatus configuration of this comparative example and the apparatus configuration of the first embodiment is that the apparatus of this comparative example uses an air cylinder as the pressing means 31 and does not have the displacement detection means 32. Further, the device of this comparative example does not have the load detection means 41.

  Next, the heat welding method using the heat welding apparatus of the comparative example 1 is demonstrated with reference to the operation | movement flow of FIG. In step 1 (S 1), the lid 11 and the container 12 are set on the backup 33, and the heating body 21 stands by at a position away from the lid 11. The heating body 21 is heated by the heating means 22 and is in a heated state. Next, in step 2 (S2), the whole heating body 21 starts moving by the pressing means 31, and at the same time, time management is started in step 3 (S3). In step 4 (S4), the heating body 21 and the lid 11 come into contact with each other, and when a predetermined time is reached, welding is completed in step 5 (S5). Thereafter, in step 6 (S6), the entire heating element 21 starts high-speed movement so as to return to the position at the time of step 1 (S1). The one-cycle operation ends at the time of step 7 (S7) when the position returns to the same position as at the time of step 1.

  Next, the heat welding method in the comparative example 1 is demonstrated with reference to FIG. 4 and FIG.

  Each axis of the graph of FIG. 5 represents the same time, load, and displacement values as in FIG. 3, but since the displacement detection means 32 and the load detection means 41 are not provided, the values assumed for the load and displacement are as follows. Is shown in a simulated manner. Specifically, the thrust of the air cylinder is assumed to be a load.

  The lid 11 and the container 12 were thermally welded under the setting conditions described below. The heating means 22 was controlled by the controller 23 so that the welding temperature of the heating body 21 became a constant temperature state of 210 ° C.

  Further, as the thrust of the air cylinder, about 500 N was applied at an air pressure of 0.4 MPa. Furthermore, the timer time for completing the welding in step 5 was set to 1.2 sec.

  However, since the pressing means 31 is an air cylinder, there is no means for detecting Step 4 (S4) in which the heating body 21 and the lid 11 are in contact with each other, and the pressure means 31 is not uniquely determined by the variation in the welding ribs of the lid 11 and the container 12. In addition, the thrust of the air cylinder may vary at the time of Step 2 (S2) when the operation of the piston of the air cylinder is started or Step 4 (S4) when it contacts the lid 11.

  From the above, as shown by displacement 1 and displacement 2 in FIG. 5, it is estimated that the welding completion position after each cycle is not stable.

  In order to evaluate the welding strength of the packaging material heat-welded in Example 1 and Comparative Example 1, a peel test was performed by the following method. Specifically, the corner of the lid 11 was peeled while being held with a gripper, and a peel test was performed to measure the load applied at the time of peeling with a push-pull gauge, and the welding strength variation was measured and compared.

  The variation in welding strength was shown by a value three times the standard deviation, and Example 1 and Comparative Example 1 were compared. As a result, the variation in welding strength in the case of Comparative Example 1 was ± 10.2 N, whereas in the case of Example 1, it was ± 4.5 N, and the variation was halved.

  Further, when the time required for welding was compared, the welding time in the comparative example was 1.0 sec, whereas in Example 1, it was 0.8 sec, and the welding strength could be further stabilized. Furthermore, the operating time of the heating element 21 is more advantageous in terms of tact, as compared with the first embodiment using a servo motor capable of speed control instead of an air cylinder.

  In this way, by switching the load, even if the welding load is set high and the speed is increased, the variation in welding strength is reduced, and it is possible to prevent the occurrence of defective products due to poor sealing performance and easy opening performance. I understand.

(Second Embodiment)
2nd Embodiment is an example at the time of using a pulse heater as the heating means 22 of the heating body 21 in the heat welding apparatus shown in FIG. Other apparatus configurations are the same as those of the heat welding apparatus shown in FIG.

  A thermal welding method according to the second embodiment will be described with reference to an operation flow of FIG.

  In step 1 (S 1), the lid 11 and the container 12 are set on the backup 33, and the heating body 21 stands by at a position away from the lid 11. Further, the heating means 22 is in an unheated state, and the heating body 21 is in a normal temperature state. Next, in step 2 (S2), the entire heating body 21 is moved at a constant speed by the pressing means 31. In step 3 (S3), the heating body 21 and the lid 11 come into contact with each other while maintaining a constant speed, and the welding rib of the container 12 is elastically deformed, whereby the load is gradually increased, and the contact load is reached in step 4 (S4). Thereafter, in step 5 (S5), the movement is continued so that the load is switched from the contact load to the welding load in a predetermined time. In step 8 (S8), the predetermined welding load is reached. In the meantime, the process proceeds to step 5 (S5) and at the same time, the impulse heater as the heating means 22 is energized in step 6 (S6), and the welding temperature is instantaneously reached in step 7 (S7). Next, the resin begins to melt gradually as the heater enters a heated state. Meanwhile, in step 9 (S9), the position at the time of step 4 (S4) is set as the zero point, and the movement is continued until a predetermined penetration amount is reached. At that time, Step 5 to Step 9 are performed in parallel. When the amount of penetration reaches a predetermined value in step 10 (S10), the welding is completed. Thereafter, in step 11 (S11), high-speed movement is started so that the entire heating element 21 returns to the position at the time of step 1. The one-cycle operation ends at the time of step 12 when the position returns to the same position as at the time of step 1.

  As described above, by performing the heat welding method of the operation flow shown in FIG. 6, it is possible to omit the operations of Steps 2 to 4 in FIG. 2, and it is possible to manage stable welding strength at a higher speed.

  The second embodiment can be preferably applied when the heat capacity of the heating element 21 is small, that is, when the object to be welded is small. However, when the lid 11 to be welded is made of a plurality of layers of thermoplastic resin, it is necessary to set a temperature that does not exceed the deflection temperature under load of the surface heat protection layer or the heat resistance temperature of the adhesive layer as the welding temperature of the heating element 21. There is.

11 lid 12 container 21 heating body 22 heating means 23 controller 31 pressing means 32 displacement detection means 33 backup 41 load detection means

Claims (10)

A heat welding apparatus for melting and joining a packaging material made of thermoplastic resin by heat,
A heating element having a heating means;
A pressing means for moving the heating body;
Load detecting means for detecting a load applied to the heating body;
Displacement detecting means for detecting a moving amount of the heating body after the load detecting means detects a predetermined value, and moving the pressing means until the moving amount reaches a predetermined value. A heat welding apparatus characterized by   The thermal welding apparatus according to claim 1, wherein the displacement detection means is an encoder or an eddy current sensor.   The heat welding apparatus according to claim 1, wherein the pressing unit is an electric actuator.   The heat welding apparatus according to claim 1, wherein the heating unit is a heater. A thermal welding method in which a packaging material made of a thermoplastic resin is melted and joined by heat,
Move the heating element to contact the packaging material,
The heating body is further moved until a predetermined load is reached from the contact load at the time of the contact,
The thermal welding method characterized by joining the packaging material by further moving the heating body until reaching a predetermined penetration amount after reaching the predetermined load.   6. The heat welding method according to claim 5, wherein the heating body is moved so that the load becomes constant until the predetermined penetration amount is reached after reaching the predetermined load.   The heat welding method according to claim 5 or 6, wherein a rib of a container of the packaging material is melted and joined.   The heat welding method according to claim 7, wherein a width of the rib is narrowed as a height is increased. The manufacturing method of the packaging material characterized by joining with the heat welding apparatus as described in any one of Claims 1-4. The manufacturing method of the packaging material characterized by using the heat welding method as described in any one of Claims 5-8 .