Packaging container, packaging method and packing apparatus using same

Abstract

For providing a packaging container which permits easy separation of a film from the container, as well as a packaging method and a packing apparatus using the packaging container, the packaging container is constituted by a container for accommodating an article to be packaged, the container having a peripheral fitting edge and an upper opening, and a cover member formed by a film for covering the opening of the container, end portions of the film being converged to form a solid edge portion for fitting with the fitting edge of the container.

Description

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a packaging container having an upper opening such as a tray or a cup for receiving therein an article to be packaged and covering the upper opening with film, as well as a packaging method and packing apparatus using the container.

[0003] 2. Description of the Prior Art

[0004] Heretofore, as one of packaging methods of this type used most frequently there has been known a stretch packaging method. According to this known method, a container having an upper opening is charged with an article to be packaged and is then covered from above with a synthetic resin film such as a soft polyvinyl chloride film or a polyethylene film while stretching the film up to the bottom of the container until the stretched film portions overlap each other, then the overlapped portions are united by utilizing the tackiness of the film itself or both tackiness and heat-fusibility of the film.

[0005] This packaging method is highly versatile for the difference in size and shape of containers and permits packaging even when an article to be packaged projects upward from the container used. Besides, since the whole of the container charged with an article to be packaged is wrapped in a single film, this packaging method does not depend on the material of the container used. However, since the film must be folded back up to the container bottom and overlapped, the amount of the film used is large, thus leading to the discharge of a large amount of wastes. There also arise such problems as the film is apt to tear and the package is difficult to be opened.

[0006] For eliminating such drawbacks involved in the stretch packaging method there has been invented such a method as is disclosed in Japanese Published Examined Patent Application No. Sho 57-29335. FIG. 19 is a sectional view showing a container about to be sealed by the method and FIG. 20 is a sectional view of the container after sealed. According to the method, a container 1 having an upper opening is formed with an edge portion 2 which projects laterally outwards, and in a charged state of the container 1 with an article 3 to be packaged, the container 1 is covered with film 4 which has been cut to an area larger than the area of the upper opening, as shown in FIG. 19, then the whole of the film 4 is heated by subjecting the film to infrared heating or by blowing hot air to the film, while pressing the overhanging portions of the film overhanging from the edge portion 2 against side faces of the container 1, allowing the film 4 to shrink thermally, and at the same time the film is heat-fused to the underside of the edge portion 2 to seal the to-be-packaged article 3 as in FIG. 20.

[0007] Problem involved in such conventional technique will now be described. The packaging method disclosed in the foregoing Japanese Published Examined Patent Application No. Sho 57-29335 involves a problem that it is difficult to strip off the film 4 alone at the time of opening the package. More particularly, the heat-fused portion between the film 4 and the container 1 is so strong that the container often tears at the time of stripping off the film. Therefore, for retaining the container 1 in its original state it is necessary to remove the heat-fused portion of the film 4 with use of an edged tool such as a knife. A further difficulty is encountered in the case where the to-be-packaged article 3 projects higher than the height of the container 1.

SUMMARY OF THE INVENTION

[0008] It is an object of the invention to provide a packaging container, a packaging method and a packing apparatus using the container, which permit film to be separated easily from the container.

[0009] For solving the above-mentioned problems, according to the present invention, in one aspect thereof, there is provided a packaging container comprising a container for accommodating an article to be packaged, the container having a peripheral fitting edge and an upper opening and a cover member formed by a film for covering the opening of the container, end portions of the film being converged to form a solid edge portion for fitting with the fitting edge of the container.

[0010] Another aspect of the present invention there is provided a packaging method wherein an opening of a container for accommodating an article to be packaged is covered with a film of a size which permits the film to overhang sideways from the opening of the container, and overhanging portions of the film overhanging sideways from the container opening are converged to form a solid edge portion of a high rigidity for fitting with a fitting edge formed on the container side.

[0011] Another aspect of the present invention there is provided a packaging method wherein a central portion of a film for covering an opening of a container which accommodates an article to be packaged is stretched outwards of the film so as to afford a film size overhanging sideways from the container opening, then the container opening is covered with the thus-stretched film, and overhanging portions of the film overhanging from the container opening are converged to form a solid edge portion for fitting with a fitting edge formed on the container side, the solid edge portion having a higher rigidity than the rigidity of the film.

[0012] Further aspect of the present invention there is provided a packaging apparatus comprising a controller for controlling each portion so as to allow execution of certain operation, a film grippers, controlled by the controller, for grasping a film afforded a film size overhanging sideways from the opening of the container which accommodates an article to be packaged, the film grippers positioning the film above the container opening, a mechanism, controlled by the controller, for moving the film grasped by the film grippers to the container opening relatively so as to cover the container opening with the film, and a mechanism, controlled by the controller, for converging the overhanging portions of the film overhanging sideways from the container opening to form a solid edge portion of a high rigidity for fitting with a fitting edge formed on the container side.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] A more complete appreciation of the present invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, in which:

[0014] FIG. 1 is a perspective view of a packaging apparatus according to the first embodiment of the present invention;

[0015] FIG. 2 is a front view of a container with film drawn out above the container;

[0016] FIG. 3 is a front view of the container with film positioned on the container;

[0017] FIG. 4 is a front view of the container with film portions overhanging from the container pulled down sideways of the container;

[0018] FIG. 5 is a perspective view of the container with film positioned on the container;

[0019] FIG. 6 is a perspective view of the container with film positioned on the container and spread;

[0020] FIG. 7 is a front view of the container with film started to converge under the jet of hot air;

[0021] FIG. 8 is a front view of the container with a solid edge portion formed by film;

[0022] FIG. 9 is a perspective view of a packaging apparatus according to the second embodiment of the present invention;

[0023] FIG. 10 is a perspective view showing an inner structure of the packing apparatus;

[0024] FIG. 11 is a perspective view showing another example of an inner structure of the packing apparatus;

[0025] FIG. 12 is a perspective view of a packaging apparatus according to the third embodiment of the present invention.

[0026] FIG. 13 is a perspective of an inner structure of a packaging unit with film being subjected to pre-stretching in the third embodiment;

[0027] FIG. 14 is a perspective view of the inner structure of the packaging unit showing a film stretching mechanism in descent position for film stretching;

[0028] FIG. 15 is a perspective view of the inner structure of the packaging unit showing a state in which the film stretching mechanism stretches the film in the third embodiment;

[0029] FIG. 16 is a perspective view of the inner structure of the packaging unit showing a state in which hot air is blown against film ends by means of blowers in the third embodiment;

[0030] FIG. 17 is a block diagram showing an operating mechanism;

[0031] FIG. 18 is a flow chart showing an operating process;

[0032] FIG. 19 is a partially cut-away front view of a container with film applied over the container, showing a conventional example; and

[0033] FIG. 20 is a partially cut-away front view in a fused state of film.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0034] The present invention relates to a packaging container having an upper opening such as a tray or a cup for receiving therein an article to be packaged and covering the upper opening with film, as well as a packaging method and packing apparatus using the container. Thus, some preferred embodiments are of the packing container, the packing method and the packing apparatus is introduced hereinafter.

[0035] Since one embodiment of the present invention resides in a packaging container comprising a container for accommodating an article to be packaged, the container having a peripheral fitting edge and an upper opening, and a cover member formed by a film for covering the opening of the container, end portions of the film being converged to form a solid edge portion for fitting with the fitting edge of the container. Therefore, when the packaged article is to be taken out, by merely putting a finger on the solid edge portion and removing the solid edge portion from the fitting edge of the container, the film can be separated easily from the container and thus the upper surface of the container in a packaged state can be opened easily without damaging the container.

[0036] Another embodiment of the present invention resides in a packaging container wherein the fitting edge of the container is formed so as to project laterally outwards. Therefore, the solid edge portion of the film can be positively fitted with the container and it is possible to enhance the sealing performance.

[0037] Another embodiment of the present invention resides in a packaging container wherein the opening of the container is formed in a shape which expands upwards of the container, and the edge of the container opening is formed as the fitting edge. Therefore, even without forming an outwardly projecting edge-like portion on the container side, the solid edge portion of the film can be fitted with the container positively.

[0038] Another embodiment of the present invention resides in a packaging container wherein the film is a stretch film. Therefore, even an article to be packaged which projects upwards of the container can be packaged positively.

[0039] One embodiment of the present invention resides in a packaging method wherein an opening of a container for accommodating an article to be packaged is covered with a film of a size which permits the film to overhang sideways from the opening of the container, and overhanging portions of the film overhanging sideways from the container opening are converged to form a solid edge portion of a high rigidity for fitting with a fitting edge formed on the container side. Therefore, the container can be packaged with the film in an extremely simple working process.

[0040] Other embodiment of the present invention resides in a packaging method wherein a central portion of a film for covering an opening of a container which accommodates an article to be packaged is stretched outwards of the film so as to afford a film size overhanging sideways from the container opening, then the container opening is covered with the thus-stretched film, and overhanging portions of the film overhanging from the container opening are converged to form a solid edge portion for fitting with a fitting edge formed on the container side, the solid edge portion having a higher rigidity than the rigidity of the film. Therefore, the container can be packaged with the film in an extremely simple working process. There also is attained an effect that the formation of the solid edge portion is ensured because the film is stretched uniformly along the container edge. That the film is stretched uniformly brings about a further effect that not only wrinkling of the film caused by a returning force in the container opening at the time of formation of a packaged container is suppressed but also the deformation of the container is prevented.

[0041] Another embodiment of the present invention resides in a packaging method wherein the central portion of the film is stretched outwards of the film and in directions perpendicular to sides of the container. Therefore, the film can be stretched in conformity with the shape of the container used. Also, there is attained an effect that the formation of the solid edge portion is ensured because the film is stretched uniformly along the container edge. That the film is stretched uniformly brings about a further effect that not only wrinkling of the film caused by a returning force in the container opening at the time of formation of a packaged container is suppressed but also the deformation of the container is prevented.

[0042] Another embodiment of the present invention resides in a packaging method wherein a central portion of the film is allowed to stretch outwards of the film by straight movement of film grippers that grasps the film. Therefore, it is possible to reduce the necessary operating steps and necessary parts for apparatus because the film can be stretched by use of the film grippers that is required instinctively for grasping the film.

[0043] Another embodiment of the present invention resides in a packaging method wherein a central portion of the film is allowed to stretch outwards of the film by rotating movement of film grippers that grasps the film. Therefore, it is possible to reduce the necessary operating steps and necessary parts for apparatus because the film can be stretched by use of the film grippers that is required instinctively for grasping the film.

[0044] Another embodiment of the present invention resides in a packaging method wherein a central portion of the film is allowed to stretch outwards of the film by the steps including grasping the film by a film gripper, sinking a plurality of fingers that is capable of spreading, and spreading the fingers so as to stretch outwards of the film. Therefore, there is attained an effect that the formation of the solid edge portion is ensured. There is attained a further effect that not only wrinkling of the film caused by a returning force in the container opening at the time of formation of a packaged container is suppressed but also the deformation of the container is prevented.

[0045] Another embodiment of the present invention resides in a packaging method wherein end portions of the film are allowed to converge by heating to form the solid edge portion. Therefore, the solid edge portion can be formed easily.

[0046] One embodiment of the present invention resides in a packaging apparatus comprising a controller for controlling each portion so as to allow execution of certain operation, a film grippers, controlled by the controller, for grasping a film afforded a film size overhanging sideways from the opening of the container which accommodates an article to be packaged, the film grippers positioning the film above the container opening, a mechanism, controlled by the controller, for moving the film grasped by the film grippers to the container opening relatively so as to cover the container opening with the film, and a mechanism, controlled by the controller, for converging the overhanging portions of the film overhanging sideways from the container opening to form a solid edge portion of a high rigidity for fitting with a fitting edge formed on the container side. Therefore, the container can be packaged with the film in an extremely simple working process.

[0047] Another embodiment of the present invention resides in a packaging apparatus wherein the film grippers grasp four corners of the film and stretch the film outwards of the film. Therefore, the container can be packaged with the film in an extremely simple working process. There also is attained an effect that the formation of the solid edge portion is ensured because the film is stretched uniformly along the container edge. That the film is stretched uniformly brings about a further effect that not only wrinkling of the film caused by a returning force in the container opening at the time of formation of a packaged container is suppressed but also the deformation of the container is prevented.

[0048] Another embodiment of the present invention resides in a packaging apparatus further comprising a film pulling mechanism, controlled by the controller, that grasps each sides between the corners of the film and stretch the film outwards of the film. Therefore, the film can be stretched in conformity with the shape of the container used. Also, there is attained an effect that the formation of the solid edge portion is ensured because the film is stretched uniformly along the container edge. That the film is stretched uniformly brings about a further effect that not only wrinkling of the film caused by a returning force in the container opening at the time of formation of a packaged container is suppressed but also the deformation of the container is prevented. Further, it is possible to reduce the necessary operating steps and necessary parts for apparatus because the film can be stretched by use of the film grippers that is required instinctively for grasping the film.

[0049] Another embodiment of the present invention resides in a packaging apparatus further comprising a plurality of fingers, controlled by the controller, that is capable of spreading and spread so as to stretch outwards of the film. Therefore, there is attained an effect that the formation of the solid edge portion is ensured. There is attained a further effect that not only wrinkling of the film caused by a returning force in the container opening at the time of formation of a packaged container is suppressed but also the deformation of the container is prevented.

[0050] Another embodiment of the present invention resides in a packaging apparatus wherein the mechanism for converging the film converges by heating the edge of the film to form the solid edge portion. Therefore, the solid edge portion can be formed easily.

[0051] Another embodiment of the present invention resides in a packaging apparatus further comprising a film unit for cutting the film so as to afford a film size overhanging sideways from the opening of the container. Therefore, appropriate size film for the container can be supplied automatically, so that operation is improved.

First Embodiment

[0052] An embodiment of the present invention will be described below with reference to FIGS. 1 to 8. What is illustrated in FIG. 1 is a packaging apparatus 5. The packaging apparatus 5 comprises a packaging unit 6, a container feed unit 7 and a container discharge unit 8 disposed on the left and right sides, respectively, of the packaging unit 6, and a film loading unit 9 disposed behind the packaging unit 6. With this arrangement, the packaging apparatus 5 can package continuously a large number of articles to be packaged. The container feed unit 7 feeds a container 10 to the packaging unit 6 in a continuous manner, the container discharge unit 8 discharges the container 10 after packaged, and the film loading unit 9 feeds a film 11 to the packaging unit 6 in a successive manner. As to detailed structures of the container feed unit 7, container discharge unit 8 and film loading unit 9, explanations thereof are here omitted.

[0053] The packaging unit 6 is provided with a container carrier 12 on which the container 10 is placed. Four blowers 13 are arranged so as to surround four sides of the container 10 put on the container carrier 12. Also mounted are four film grippers 14 (only two are shown in FIG. 1) for gripping four corners of the film 11 pulled out from the film loading unit 9.

[0054] The container 10 is formed with an upper opening 16 having a peripheral fitting edge 15 and is in the shape of an upwardly expanded tray as a whole.

[0055] In such a construction, as shown in FIG. 2, the container 10 charged with an article (not shown) to be packaged is fed from the container feed unit 7 onto the container carrier 12 in the packaging unit 6 and at the same time the film 11 is fed from the film loading unit 9. The film 11 has been cut and is gripped at four corners thereof by the film grippers 14. In this state, the film grippers 14 move down into contact with the container 10 while pulling the film so as not to wrinkle the film, to cover the opening 16 of the container 10, as shown in FIGS. 3, 5 and 6. Further, as shown in FIG. 4, the film grippers 14 turn and move down, causing overhanging portions of the film 11 overhanging from the container 10 to approach the side faces of the container. At this time it is desirable that the gripping direction of the film grippers 14 is an upward direction toward the fitting edge 15.

[0056] When end portions of the film 11 have reached a position lower than the opening 16 of the container 10 in a fully pulled state of the film 11, the blowers 13 positioned around the container 10 are driven to blow hot air against the four sides of the container. Taking the influence on the article to be packaged into account, a jet of hot air at 120° C. for about 3 seconds is desirable. With this hot air, end portions of the film 11 become hot and shrink. As a result of this thermal shrinkage the overhanging portions of the film 11 overhanging from the container 10 converge to enhance their rigidity and extend inside along the fitting edge 15 to form a solid edge portion 17 below the fitting edge 15. In this case, an appropriate timing for ungripping the film 11 from the gripped state by the film grippers 14 is set in synchronism with shrinkage of the film positioned at the side portions of the container 10. The solid edge portion 17 is formed also by the four corners of the film 11. As a result of formation of the solid edge portion 17 there is formed a cover member 18 by the film 11. The solid edge portion 17 is fitted with the fitting edge 15 of the container 10 and is not heat-fused to the container. Of course, the solid edge portion 17 may be heat-fused to the container 10 to such an extent that it can be stripped off easily. Therefore, when the article thus packaged is to be taken out from the container 10, a finger is put on the solid edge portion 17 and is moved in a direction to come off the fitting edge 15, whereby the film 11 is separated easily from the container and the upper surface of the container can be opened without damaging the container.

[0057] One concrete example is as follows. As the container 10 there is used, for example, a tray 200 mm by 100 mm and 25 mm high and having a fitting edge 15, or a tray having an upwardly expanded opening, or a cup or the like having an upwardly expanded opening 16 and having a diameter of 100 mm and a height of 70 mm. For example, in the case of a tray 200 mm by 100 mm and 25 mm high and having a fitting edge 15, there is used, as the film 11 to be applied over the container 10, a film of a soft polyvinyl chloride having a melting temperature of 120° C., a stretch ratio of 3.0, a thickness of 30 &mgr;m, which film has been cut to a size large enough for the film to overhang from the container 10, for example, a size of 220 mm×120 mm for a tray of 200 mm by 100 mm and 25 mm high and having a fitting edge 15. For a cup having an upwardly expanded opening 16 and having a diameter of 100 mm and a height of 70 mm there is used a film of a soft polyvinyl chloride which has been cut to a diameter of 120 mm.

[0058] Although in the above embodiment the shape of the container opening is upwardly expanded as a whole, for another embodiment, when the present invention is applied to such a container as shown in FIGS. 19 and 20 wherein an opening of the container, denoted as 1 in FIGS. 19 and 20, is formed with an edge portion, denoted as 2 in FIGS. 19 and 20, projecting laterally outwards, film is sure to be fitted with the projecting edge portion denoted as 2 in FIGS. 19 and 20, so that a solid edge portion of the film can be formed more positively and it is possible to enhance the sealing performance.

[0059] For another embodiment of the present invention, as the film 11 there also may be used a polyethylene stretch film having a melt temperature of 100° to 150° C., a stretch ratio of 3 to 10, and a thickness of 11 &mgr;m to 40 &mgr;m, or a biaxially stretchable, multi-layer stretch film formed of an ethylene/vinyl acetate copolymer and a soft polyolefin resin.

[0060] For another embodiment of the present invention, as means for heating end portions of the film 11, the hot air blowers 13 may be replaced by electric heaters or heating rollers.

[0061] Although in the above embodiment end portions of the film are allowed to converge by heating to form the solid edge portion, means for shrinking end of the film 11 is not limited merely heating means. For another embodiment of the present invention, as means for shrinking end portions of the film 11, acid or the like may be applied to end of the film 11 for shrinking and converging end of the film 11. This is useful in case heating means gives harmful influence to the film 11. Applied acid should be eliminated by cleaning or the like if necessary.

Second Embodiment

[0062] Another method for pulling a film which covers a container according to the present invention will now be described with reference to FIGS. 9 to 11. What is illustrated in FIG. 9 is a packaging apparatus 103 provided with a packaging unit 102 for stretching a film 101. The packaging apparatus 103 comprises a container feed unit 104 and a container discharge unit 105 disposed on the left and right sides, respectively, of the packaging unit 102 and a film loading unit 106 disposed behind the packaging unit 102. According to this arrangement, a large number of articles to be packaged can be packaged in a continuous manner. The container feed unit 104 feeds containers 107 to the packaging unit 102 continuously one by one, the container discharge unit 105 discharges a packaged container 108, and the film loading unit 106 feeds the film 101 to the packaging unit 102 in a successive manner. As to detailed structures of the container feed unit 104 and the container discharge unit 105, explanations thereof are here omitted.

[0063] The packaging unit 102 comprises a container carrier 109 which includes a container raising/lowering mechanism (not shown) for moving the container 107 up and down while carrying it thereon, film drawers 110, as a film grippers, for drawing out the film 101 to the packaging unit 102 and gripping four corners of the film, the film drawers 110 being also used for stretching, film pulling mechanisms 111, as the film gripper, and linear-acting actuators 112. The film pulling mechanisms 111 themselves, which are provided four, can move back and forth and turn vertically and the film pulling mechanisms 111 located on the linear-acting actuators 112 which are disposed two at right and left positions can also move in the longitudinal direction of the packaging apparatus 103, whereby a cut film 101 can be gripped, stretched and ungripped.

[0064] On the other hand, the film 101, typical of which is a roll stretch film for food packaging, is inserted into the film loading unit 106 at a predetermined position. A front end portion of the film 101 is fed to a film delivery section 113. In this case, a control is made so that the front end portion of the film is set at an initial position at which it slightly overhangs to the packaging unit 102 side with respect to the film delivery section 113.

[0065] In such a configuration, when the container 107 charged with an article (not shown) has been fed onto the container carrier 109 in the packaging unit 102, the linear-acting actuator 112 operates and two film drawers 110 located on the linear-acting actuators 112 and on the front side of the apparatus grip the film 101 overhanging from the film delivery section 113, then the film 101 is drawn out to above the container 107. Thereafter, two film drawers 110 located at rear positions grip the film 101. The amount of the film 101 to be drawn out differs depending on the size of the container 107 and a control unit 201 described below controls the film drawing-out operation (refer FIG. 17). At this time, the film pulling mechanisms 111 not concerned in drawing out the film 101 are located at positions not obstructing the drawing-out operation.

[0066] After the film 101 has been drawn out to above the container 107, the film pulling mechanisms 111 grasp the centers in each side of the film 101, both film pulling mechanisms 111 and film drawers 110 stretches the cut film 101. More specifically, the film 101 is cut with a cutter (not shown) while both film pulling mechanisms 111 and film drawers 110 grasp the film 101. As a result, as shown in FIG. 9, the four corners of the cut film 101, which is rectangular, are grasped by the film drawers 110 and a central portion of the film is grasped at four points by the film pulling mechanisms 111. For stretching the cut film 101 from the central portion of the film, as shown in FIG. 10, the film pulling mechanisms 111 move outwards crosswise from the central portion of the cut film 101, while the film drawers 110 move in diagonal directions. As a result, the cut film 101 whose central portion and four corners are thus grasped at eight points can be stretched by being pulled from its central portion. The pulling operation is performed by actuators provided in the film pulling mechanisms 111 and the film drawers 110, but conditions such as pulling speed and pulling quantity differ depending on the properties of the film 101 and the specification of actuators.

[0067] It is also possible to provide rotating mechanisms in the cut film grasping portions of both film pulling mechanisms 111 and film drawers 110 and effect film stretching through the rotating mechanisms. To be more specific, by grasping the cut film 101 at eight points through the film pulling mechanisms 111 and the film drawers 110 and causing the film grasping portions of the actuators to turn downward as showing in FIG. 11, a frictional force developed between the cut film 101 and the film grasping portions becomes larger, so that the cut film 101 can be grasped more firmly. Then, the film pulling mechanisms 111 applies an outward pulling force to the film crosswise from the central portion of the film, whereby the film is pulled from its central portion and is stretched thereby.

[0068] After the film 101 grasped at its four corners has thus been stretched by being pulled from its central portion through the film pulling mechanisms 111, the stretched film 101 is applied over the container 107 and is made integral with the container, whereby there is formed a packaged container 108, in which the stretched film 101 constitutes a cover portion as is the case with the description of the first embodiment. The process for forming the cover portion of the packaged container 108 is as follows.

[0069] First, when such a state as shown in FIG. 10 has been attained, the container raising/lowering mechanism of the container carrier 109 causes the container 107 charged with the to-be-packaged article to rise toward the stretched film 101. It is preferable that the rising speed be 50 mm or so per second.

[0070] Upon contact of the to-be-packaged article or a container opening 121 with the stretched film 101, the rising speed is decreased to 20 mm or so per second to cover the container opening 121 little by little. The container opening 121 is a fitting edge. Further, as shown in FIG. 10, the stretched film 101 is pushed upward with the pressure of the container 107 of the to-be-packaged article and the film drawers 110 and the film pulling mechanisms 111 turn slightly, causing the overhanging portions of the film 101 overhanging from the container opening 121 to approach the side faces of the container 107. At this time it is preferable that the film grasping direction of the film drawers 110 and film pulling mechanisms 111 is upward toward the container opening 121 (refer FIG. 4 for First Embodiment).

[0071] When end portions of the stretched film 101 have arrived at a position lower than the container opening 121, as shown in FIG. 10, blowers 999 positioned within the packaging unit 102 are driven to blow hot air to the four sides of the container 107, thereby allowing the stretched film 101 to be fitted with the container opening 121, whereby a solid edge portion is formed and it is possible to form a packaged container 108.

[0072] Also in the case where the grasping portions for the cut film 101 by the film pulling mechanisms 111 and the film drawers 110 shown in FIG. 11 are each provided with a rotating mechanism, it is possible to form such a solid edge portion.

[0073] Although in the above embodiment end portions of the film are allowed to converge by heating to form the solid edge portion, means for shrinking end of the film 101 is not limited merely heating means. For another embodiment of the present invention, as means for shrinking end portions of the film 101, acid or the like may be applied to end of the film 101 for shrinking and converging end of the film 101. This is useful in case heating means gives harmful influence to the film 101. Applied acid should be eliminated by cleaning or the like if necessary.

Third Embodiment

[0074] A further pulling method will now be described with reference to FIGS. 12 to 16. The same parts as those in the second embodiment are designated by the same reference numerals, and are not again explained herein.

[0075] In the pulling method of the second embodiment the cut film 101 was stretched by pulling with the film drawers 110 as well as the film pulling mechanisms 111. On the other hand, in the pulling method about to be described below, there is used such a film stretching mechanism 115 as shown in FIGS. 12 to 16 as a mechanism which applies an outward push-out force to the cut film 101 from the central portion of the film to stretch the film.

[0076] The film stretching mechanism 115 is composed of a base 116 that is capable of rising and lowering, and four arms 117 provided on the base 116 and is positioned above the container carrier 109. The arms 117 are each composed of an upper arm 118, a lower arm 119, and fingers 120. The film stretching mechanism 115 is a multi-joint robot adapted to perform a straight movement according to the rising and lowering of the base 116 and rotation in the vertical direction and impart a swing motion to the upper and lower arms 118, 119.

[0077] In such a configuration there are performed a pre-stretching step using film drawers 110 and a stretching step of expanding the cut film 101 outwards from a central portion of the film with use of the film stretching mechanism 115.

[0078] In the same manner as in the preceding pulling method the film 101 which has been cut with a cutter (not shown) is grasped by film drawers 110. In this case, as shown in FIG. 13, after the four corners of the cut film 101 have been grasped, the film is subjected to the pre-stretching step. In the pre-stretching step, the film 101, which is thus grasped at its four corners, is stretched in its diagonal directions. More specifically, the film 101 gasped at its four corners is stretched until the area thereof becomes 1.1 to 1.2 times the initial area thereof. At this time the film 101 is wrinkle-free and is deformed elastically. If the film 101 is stretched to a greater extent at the stage of pre-stretching, a large pulling force is exerted in only diagonal directions, so that only the grasped four corners of the film are stretched rapidly, which causes tear of the film.

[0079] After completion of the pre-stretching step there is performed the stretching step in which the four-corner grasped film 101, which has been stretched to 1.1 to 1.2 times, is expanded from its central portion outwards in directions perpendicular to the four sides of the container opening 121. First, as shown in FIG. 14, the film stretching mechanism 115 moves down from above the four-corner grasped film 101 in such a manner that the four sides of the container opening 121 are in a one-to-one relation to the fingers 120 of the film stretching mechanism 115. Since in this embodiment a tray having a generally rectangular container opening 121 is used as the container 107, four fingers 120 are needed in the film stretching mechanism 115. As the film stretching mechanism 115 moves down, the fingers 120 apply pressure perpendicularly to the four-corner grasped film 101, with the result that the fingers 120 sink to the film. At this time, a perpendicular pressure exerted on the film is about 90 to 170 kPa.

[0080] Next, the stretching step is carried out, in which the four-corner grasped film 101 is expanded from its central portion outwards in directions perpendicular to the four sides of the container opening 121. This is attained by operation of the arms 117.

[0081] The upper and lower arms 118, 119 of the four arms 117 in the film stretching mechanism 115 are turned in directions perpendicular to the four sides of the container 107, causing a frictional force and an adhesive force to be developed in an interface between the fingers 120 of the film stretching mechanism 115 and the four-corner grasped film 101 and thereby expanding the film 101. At this time the film 101 can be stretched horizontally by controlling the upper and lower arms 118, 119 of the arms 117. If the amount of turn of the arms 117 is further increased, the film 101 undergoes a plastic deformation. For stretching the film 101 in conformity with the size of the container opening 121 it is necessary that the amount of turn of the upper and lower arms 118, 119 in the film stretching mechanism 115 be controlled in conformity with the size of the container 107, as shown in FIG. 15. In this stage, fingers 120 provided in the film stretching mechanism 115 are caught at side portions of the film 101 without slipping off. This is because film 101 winds in the fingers 120 according to the stretching of the film 101.

[0082] While the film is stretched by the film stretching mechanism 115, the film 101 is held at the four corners thereof by the film drawers 110 and its central portion is in a stretched state outwards under the action of the arms 117. The amount of stretch of the film 101 stretched by the film stretching mechanism 115 is such that the area of the stretched film is about 1.8 times the original area of the film, in which condition there is obtained a wrinkle-free, lustrous condition. If the area is made larger, the film becomes easier to tear, so it is preferable that the film be stretched to an area of 1.5 to 2 times the original area.

[0083] Concrete conditions are as follows. Supposed that it is used a plastic tray having a container opening 121 of 150 mm×230 mm and 30 mm high. In this case, a roll stretch film constituted by a biaxially stretchable, multi-layer polyethylene film having a commercial size of 250 mm wide by 10˜20 &mgr;m thick is used as film 101. The film 101 is cut to a 250 mm square with a cutter, which cut film is then subjected to pre-stretching up to a size of about 260 mm×260 mm. In this case, care must be exercised so that the film is not brought into contact with the container 107 and the upper and lower arms 118, 119 and fingers 120 as constituents of the film stretching mechanism 115 at least in the pre-stretching stage because the stretch film itself becomes very sticky and would adhere to them due to its adherence.

[0084] After the end of pre-stretching, the fingers 120 of the film stretching mechanism 115 move down toward the four-corner grasped film 101 and sink to the film. At the end of the fingers 120 there are provided a material having characteristics in which causes friction more than certain value to the film 101. It is preferable used fiber structured material having Netting formation mingled with innumerable fibers for the material, e.g., leathers (including both genuine leathers and artificial leathers like vinyl leathers, synthesis leathers, or the like), non-woven fabric, and cellular urethane sponge rubber having closed cell or continuous cell. These materials have moisture-absorbed characteristics, so that friction power thereof does not decrease under high damp atmosphere. Thus, film 101 can be used easily by using above material in the fingers 120.

[0085] After pre-stretching by the film drawers 110 and after stretching of the four-corner grasped film 101 from inside to the outside by the film stretching mechanism 115, the stretched film is united with the container 107 charged with an article to be packaged to form a packaged container 108, in which the stretched film 101 constitutes a cover portion as is the case with the description of the first embodiment. The process for forming the cover portion of the packaged container 108 is as follows.

[0086] First, a container raising/lowering mechanism of a container carrier 109 causes the container 107 to rise toward the stretched film 101 at a speed of 50 mm or so per second. After a portion of the container 107 comes into contact with the stretched film 101, the film is pushed upward at a rate of 20 mm or so per second by the pressure of the container 107 or of the to-be-packaged article, so that the film drawers 110 turn slightly. The film drawers 110 cause overhanging portions of the stretched film 101 overhanging from the container opening 121 to approach the side faces of the container 107. At this time the film grasping direction of each film drawer 110 is preferably upward toward the container opening 121. By so doing, front ends of the film drawers 110 are positioned below the container opening 121.

[0087] On the other hand, the fingers 120 of the film stretching mechanism 115 are at this time positioned outside the four sides of the container 107 as in FIG. 15. In this state, blowers 999 positioned within a packaging unit 102 as in FIG. 16 are driven to blow hot air against the four sides of the container 107 to form a solid edge portion, allowing the stretched film 101 to be fitted with the container opening 121, whereby a packaged container 108 can be formed.

[0088] By stretching the film 101 outward from its central portion in accordance with the above pulling method it becomes possible to stretch the entire film 101 uniformly along the container edge and the formation of a solid edge portion can be done positively. Besides, since the central portion of the film 101 is stretched or expanded outwards and the film 101 is thereby stretched uniformly, wrinkling of the film 101 caused by a returning force in the container opening 121 at the time of formation of the packaged container 108 is suppressed and the container 107 is prevented from being deformed. Further, since the film expanding directions are perpendicular to the sides of the container 107, it is possible to stretch the film 101 in conformity with the shape of the container 107 used.

[0089] Although in the above embodiment end portions of the film are allowed to converge by heating to form the solid edge portion, means for shrinking end of the film 101 is not limited merely heating means. For another embodiment of the present invention, as means for shrinking end portions of the film 101, acid or the like may be applied to end of the film 101 for shrinking and converging end of the film 101. This is useful in case heating means gives harmful influence to the film 101. Applied acid should be eliminated by cleaning or the like if necessary.

[0090] FIGS. 17 is a block diagram of an operating mechanism used in this packaging apparatus 103 introduced in the second embodiment and third embodiment. Although same structured-operating mechanism illustrated in FIG. 17 also controls the packaging apparatus 5 introduced in the first embodiment, details thereof are eliminated.

[0091] A control unit 201 as a controller is microcomputer consist of CPU, RAM and ROM. The control unit 201 controls peripheral portions or units by calculating operation of the CPU according to operating systems and operating program stored in a data storage apparatus. It is used, for instance, ROM, Hard disk, or optical information recorded media like MO, DVD-ROM, DVD-RAM, as the data storage apparatus. The recorded data in the hard disk, MO, DVD-ROM and DVD-RAM can be read by a data readable apparatus, such as HDD, MO driver, DVD driver or the like, connected with CPU. The peripheral portions or units are controlled so as to operate preferable by control of the control unit 201 according to the operating program stored in the data storage unit, thereby operation of the controller is executed.

[0092] Under control of the control unit 201, initial conditions are set from an operating conditions input device 202, and upon detection of a container 107 by a container sensor 203 there is started a packaging operation. The sensing operation of the container sensor 203 and that of a counter circuit 204 cover a container feed mechanism 205 and a container discharge mechanism 206, and a comparison is made between a preset number of packaged containers 108, which is inputted by the operating conditions input device 202, and the present packaging state. Processing (packaging operation) is continued until the preset number of packaged containers 108 is reached. Further, in the same figure, there appears a film actuator 207 as a generic term for film grasping, drawing-out and stretching actuators, and a film feed mechanism 208 controls the amount of film 101 to be drawn out with operation of the film actuator 207. A container raising/lowering mechanism 209 causes to elevate the container carrier 109. The actuator of the container raising/lowering mechanism 209 that is controlled by the control unit 201 attains the rising and lowering of the container carrier 109. The blower 999 (blower heater 999) is also connected with the control unit 201 and is controlled by the control unit 201.

[0093] FIG. 18 is a flow chart showing an outline of a packaging procedure used in the packaging apparatus 103. The packaging operation will now be described on the basis of this flow chart.

[0094] First, the control unit 201 executes initializing process according to an initial values input by the operating conditions input device 202 (step S1). As initial values, an operator inputs the size (type) of the container 107 and a preset number of packaged containers 108. The film 101 inserted in the film loading unit 106 differs in its cut area depending on the size of the container opening 121, so once the size (type) of the container 107 is inputted, the area of the film 101 to be cut is determined unconditionally.

[0095] After the input of initial values the operator puts the container 107 on the container carrier 109 disposed in the container feed unit 104. In this stage, the control unit 201 detects whether the container 107 is present or not on the container carrier 109 in the container feed unit 104 by the container sensor 203 (step S2). That is, whether the container is present or not is checked by the container sensor 203 as a limit switch, an image sensor, or a pressure sensor.

[0096] When the feed of the container 107 onto the container carrier 109 has been detected, the control unit 201 controls the container feed mechanism 205, so that the container 107 is fed into the packing unit 102 by the container feed mechanism 205 (step S3). After this process, packing operation of the container 107 is performed by a container raising/lowering mechanism 209 and the film actuator 207. In the first half of the packaging operation the film 101 is subjected to a series of such operations as drawing-out, grasping (step S4), cutting and pulling and is stretched thereby (step S5). In the latter half of the packaging operation, which operation is for forming a solid edge portion, the container opening 121 is covered with film 101, hot air is blown against end portions of the film 101, and the grippers of the film drawers 110 and the film pulling mechanism 111 are deactuated. In this case, the film 101 is drawn near the container opening 121 and hot air is jetted by the blowers 999. The film 101 shrinks during the lapse of a hot air jet time of about 3 seconds and the film 101 is ungrasped in synchronism therewith (step S6). As a result of this operation, film 101 is converged around the edge of the container 107, so that the film 101 covers the container opening 121.

[0097] The packaged container 108 thus obtained is fed from the packaging unit 102 to the container discharge unit 105 by the container discharge mechanism 206 (step S7) and is counted by a counter circuit 204 (step S8). The above flow is repeated until the initially set number of packaged containers is reached (step S9). Immediately after the discharge of one packaged container 108 the next container 107 is detected.

[0098] Although the packaging apparatus 5 introduced in the first embodiment of the present invention is also controlled by same process described in the flow chart showing in FIG. 18, the details thereof is eliminated.

[0099] The present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered in all respects as illustrative and not restrictive, the scope of the present invention being indicated by the appended claims rather than by the foregoing description and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

[0100] The present application is based on Japanese Priority Document Hei 11-18503 filed on Jan. 27, 1999 and Hei 11-369376 filed on Dec. 27, 1999 the content of which are incorporated herein by reference.

Claims

1. A packaging container, comprising:

a container for accommodating an article to be packaged, the container having a peripheral fitting edge and an upper opening; and

a cover member formed by a film for covering the opening of the container, end portions of the film being converged to form a solid edge portion for fitting with the fitting edge of the container.

2. A packaging container according to claim 1, wherein the fitting edge of the container is formed so as to project laterally outwards.

3. A packaging container according to claim 1, wherein the opening of the container is formed in a shape which expands upwards of the container, and the edge of the container opening is formed as the fitting edge.

4. A packaging container according to claim 1, wherein the film is a stretch film.

5. A packaging method, comprising the steps of:

covering an opening of a container for accommodating an article to be packaged is covered with a film of a size which permits the film to overhang sideways from the opening of the container; and

converging the overhanging portions of the film overhanging sideways from the container opening to form a solid edge portion of a high rigidity for fitting with a fitting edge formed on the container side.

6. A packaging method, comprising the steps of:

stretching a central portion of a film for covering an opening of a container which accommodates an article to be packaged outwards of the film so as to afford a film size overhanging sideways from the opening of the container;

covering the opening of the container with the stretched film; and

converging overhanging portions of the film overhanging from the container opening to form a solid edge portion for fitting with a fitting edge formed on the container side, the solid edge portion having a higher rigidity than the rigidity of the film.

7. A packaging method according to claim 6, wherein the central portion of the film is stretched outwards of the film and in directions perpendicular to sides of the container.

8. A packaging method according to claim 6 or 7, wherein a central portion of the film is allowed to stretch outwards of the film by straight movement of film grippers that grasps the film.

9. A packaging method according to claim 6 or 7, wherein a central portion of the film is allowed to stretch outwards of the film by rotating movement of film grippers that grasps the film.

10. A packaging method according to claim 6 or 7, wherein a central portion of the film is allowed to stretch outwards of the film by the steps including:

grasping the film by film grippers;

sinking a plurality of fingers that is capable of spreading; and

spreading the fingers so as to stretch outwards of the film.

11. A packaging method according to claims 5, 6, 7, 8, 9 or 10, wherein end portions of the film are allowed to converge by heating to form the solid edge portion.

12. A packing apparatus, comprising:

a controller for controlling each portion so as to allow execution of certain operation;

a film grippers, controlled by the controller, for grasping a film afforded a film size overhanging sideways from the opening of the container which accommodates an article to be packaged, the film grippers positioning the film above the container opening;

a mechanism, controlled by the controller, for moving the film grasped by the film grippers to the container opening relatively so as to cover the container opening with the film; and

a mechanism, controlled by the controller, for converging the overhanging portions of the film overhanging sideways from the container opening to form a solid edge portion of a high rigidity for fitting with a fitting edge formed on the container side.

13. A packaging apparatus according to claims 12, wherein the film grippers grasp four corners of the film and stretch the film outwards of the film.

14. A packaging apparatus according to claims 13, further comprising a film pulling mechanism, controlled by the controller, that grasps each sides between the corners of the film and stretch the film outwards of the film.

15. A packaging apparatus according to claims 12, further comprising a plurality of fingers, controlled by the controller, that is capable of spreading and spread so as to stretch outwards of the film.

16. A packaging apparatus according to claims 12, 13, 14 or 15, wherein the mechanism for converging the film converges by heating the edge of the film to form the solid edge portion.

17. A packaging apparatus according to claims 12, 13, 14, 15 or 16, further comprising a film unit for cutting the film so as to afford a film size overhanging sideways from the opening of the container.