METHOD OF AND MACHINE FOR ASSEMBLING CARDBOARD CASES

Abstract: An upper-inner flap (F1U) of a flat preassembled cardboard (12) is folded downward to open the cardboard (12) by a flap-folding member (26), while the cardboard (12) is being lifted from a stock stage to a flap-folding stage, attracted to and held by suction cups (20). Once the upper-­ inner flap (F1U) has been folded downward, it comes into the gap between the outer flaps (F2). The upper-inner flap (F1U), which has been folded downward, pushes the left outer flap (F2L). Thus, as the cardboard (12) is lifted higher and higher, both outer flaps (F2) are opened simultaneously. The preassembled cardboard (12) is therefore gradually opened, forming a hollow cylindrical case.

Description: The present invention relates to a method of assembling cardboard cases, wherein flat preassembled cardboards for cases are opened and shaped into cases, and the case are sequentially placed at a prescribed position, and the flaps of each case are folded and sealed, thereby assembling a case. The invention also relates to a machine for assembling cardboard cases. Most corrugated cardboard cases have four panels, two pairs of top flaps, and two pairs of bottom flaps. When they are stocked, their panels and flaps are folded flat. To shape such a flat corrugated cardboard into a case, the cardboard is first opened and shaped like a hollow cylinder, then the bottom flaps are folded and sealed, thus forming a bottomed case. Goods are packed into this case through the open top, and the top flaps are folded and sealed, so that the packed goods may be shipped. A case-assembling machine is used to open flat preassembled cardboards, shape the cardboards into cases, and seal the bottom flaps of these cases. To pack goods into the cases, and to fold and seal the top flaps of these cases, a packaging machine is employed. Of the bottom flaps of each flat preassembled cardboard, those of the first pair, which are to be folded first, are called "inner flaps", while those of the second pair, which are to be folded next, are called "outer flaps." The same naming applies to the top flaps of the flat preassembled cardboard. Of the four panels of the flat cardboard, the first two opposing panels to which the inner flaps, both top and bottom, are called "end panels", while the second two opposing panels are called "side panels." Generally, a flat preassembled cardboard is shaped and sealed into a bottomed case, in the following steps: 1. First, a compressive force is applied to the flat cardboard as is shown in Fig. 38(a), thereby opening the board into a hollow cylinder as is illustrated in Fig. 38(b). 2. Then, the inner bottom flaps, i.e., upper-inner flap F1U and lower-inner flap F1L, are folded inward, as is shown in Fig. 38(c), and the bottom outer flaps, i.e., left-outer flap F2L and right-outer flaps F2R, are folded inward onto inner bottom flaps F1U and F1L, as is illustrated in Fig. 38(d). As a result, a case, closed at the bottom and open at the top, is made as is shown in Fig. 38(e). 3. Finally, adhesive tape, gummed tape, staples, hot-melt, or other sealing means is applied to the folded outer bottom flaps F2L and F2R, thereby sealing the bottom of the case, as is illustrated in Fig. 38(f). As has been described, a flat preassembled cardboard is opened, shaped and sealed, thus made into a cardboard case. Outer bottom flaps F2L and F2R tend to open by themselves immediately after they have been folded inward as is shown in Fig. 38(d). Unless these outer bottom flaps are strongly holding to the folded position, the case will be deformed. In order to prevent such deformation of the case, both outer bottom flaps F2L and F2R are held together, with their opposing edges abutting on each other, while the sealing means such as adhesive tape is being applied to the abutting edges of flaps F2L and F2R. If the opposing edges of these outer flaps are spaced apart while the sealing means is being applied, the case will not only have a poor appearance, but also be insufficiently strong. According to JIS (Japanese Industrial Standards), flat, corrugated cardboard cases are classified into A type, B type, and C type. The A type is sub-classified into A-1 to A-5 types; the B type is sub-classified into B-1 to B-6 types; the C type is sub-classified into C-1 to C-3 types. Of the cases of these sub-classes, the A-1 type case is the most popular. As is illustrated in Figs. 39 and 40, inner flaps F1 of the A-1 type case have a width f1, and outer flaps F2 thereof have a width f2. Widths f1 and f2 are equal, and are half the width W of the case. Namely, f1 = f2= W/2. Therefore, when outer flaps F2 are folded inward onto inner flaps F1 already folded inwardly, their opposing edges abut on each other, and extend along the center line of the case. When sealing means, such as adhesive tape, is applied to the abutting edges of outer flaps F2, it also extends straight along the center line of the case. Hence, the bottom of the case is sealed strongly, and the sealed bottom looks tidy. This is the reason why the A-1 type case is used more commonly than any other types. As for the other flat A type cases, i.e., the A-2 to A-5 type cases, the inner flaps F1 and outer flaps F2 have the following relationship with the width W and length L of the cases: A-2 Type Case: f1 = f2 > W/2 A-3 Type Case: f1 = L/2, f2= W/2 A-4 Type Case: f1 = f2 = L/2 A-5 Type Case: f1 = f2 > L/2 In the case of the A-3 type case, the abutting edges of the outer flaps extend along the center line of the case, as can be understood from Fig. 40. Therefore, the case-assembling machine designed for the A-1 type case can be employed also to assemble the A-3 type case, though the A-3 type case is used in less numbers than the A-1 type case. The corrugated cardboard cases of the sub-classes of each type are commercially available, which are different in length L, width W, and depth D. The case-assembling machine for the A-1 type case is generally considered to be a standard one, whereas the machines for assembling any other types of cases are regarded as custom-made ones. The A-1 case-assembling machine needs to be versatile enough to make the A-1 cases of various sizes. In addition, the board-guiding mechanism, board-opening mechanism, flap-holding mechanism and case-sealing mechanism of the A-1 case-assembling machine must be adjusted such that they can open, shape, and seal A-1 type cases of different sizes. Here arises a problem with the conventional case-assembling machines, as will be explained below. The conventional case-assembling machines, including those for assembling A-1 type cases, have a belt conveyor for transporting flat preassembled cardboards. While each flat cardboard is being transported, it is first opened, then shaped, and finally sealed. More specifically, as is shown in Fig. 40, the flat cardboard is loaded on the conveyor belt, with its two outer flaps of each pair, facing upward and downward, respectively. Obviously, the flat cardboard for a case of a specific type has a width different from that of the flat cardboard for a case of another type. Hence, to assemble cases of any other type than those which the machine has been assembling, the board-guiding mechanism, the board-opening mechanism, the flap-folding mechanism, and the sealing mechanism must be aligned to the center line of the flat cardboard for the cases of the other type. It usually takes a long time to align these mechanisms with the center line of the cardboards for the other type cases. The operation efficiency of the case-assembling machine is inevitably low. Since the machine requires a device for aligning these mechanisms with the center line of the flat cardboard for any type case which the machine can assemble, the machine is rather complex, large, and heavy. In other words, if the machine is versatile enough to assemble cases of various types and sizes, it cannot be compact or light. The method of assembling corrugated cardboard cases by means of the conventional machine described above can give rise to trouble in the process of holding the flaps of the cases. As can be seen from Figs. 38(b) and 38(c), either inner flap F1 cannot be folded inward should either or both the outer flaps F2 have been closed if only partly. When either inner flap is folded inward, with either or both outer flaps F2 closed, the inner flap F1 abuts on outer flap or flaps F2, and is interposed, as bridge, between outer flaps F2. This trouble, occurring when either or both outer flaps F2 are closed, is known as "bridging." If inner flap F1 is forcedly folded inward in spite of the bridging, both the inner flap and the outer flaps will be deformed or broken, rendering the cardboard case unusable. Therefore, a new type of a case-assembling machine has been invented which has a sensor for detecting a bridging. As soon as the sensor detects a bridging, that is, as soon as the detector detects a stress being applied to either inner flap F1, the flap-folding mechanism of the machine is automatically stopped thereby to prevent the deformation or rupture of the case. The interruption of the flap-folding process inevitably reduces the efficiency of the case-assembling. Another new type of a case-assembling machine has been developed which also has sensor for determining whether or not either outer flap F2 is in a closing position to prevent inner flaps F1 from being folded inward. This machine has a flap-folding mechanism which first opens up the outer flaps from the closing postions and then folds inner flaps F1 inward. The flaps cannot be folded fast, and the case-assembling efficiency is rather low. Further, due to the necessary use of the sensor and the flap-folding mechanism which not only folds flaps but also open them, the machine as a whole is complex in structure. It is therefore an object of the present invention to provide a method of assembling corrugated cardboard cases, wherein no bridgings occur, and the flaps of each case can thus be folded fast and easily, and also to provide a machine for performing this method. It is another object of this invention to provide a method of assembling corrugated cardboard cases, which is versatile enough to assemble corrugated cardboard cases of different sizes, and also to provide a machine for performing this specific method. It is further object of this invention to provide a mechanism for opening flat preassembled cardboards for cases, without causing any bridging. The case-assembling machine according to the present invention is designed for assembling A-1 type and A-3 type corrugated cardboard cases. Nonetheless, the machine can be used to make A-2 type, A-4 type and A-5 type corrugated cardboard cases as well, only if given minor changes in design. According to the invention, in order to achieve the first object, each flat cardboard is opened while the cardboard is being transported upward from a stock stage onto a flap-folding stage. More specifically, the upper-inner flap of each cardboard is folded downward to open the cardboard, while the cardboard is being lifted from the stock stage to the flap-folding stage, attracted to and supported by a suction cup. Once the upper-inner flap has been folded downward, it comes into the gap between the outer flaps. Thus, neither outer flap can no longer be closed. Hence, the upper-inner flap causes no bridgings. The lower-inner flap does not cause a bridging, either. The upper-inner flap, which has been folded downward, pushes the left-outer flap. Thus, as the cardboard is lifted higher and higher, both outer flaps are opened simultaneously. The flat preassembled cardboard is therefore gradually opened, forming a hollow cylindrical case. In the method according to this invention, a lower edge of any flat preassembled cardboard which is mounted on a stock stage is aligned parallel to reference line Y₀, and the center line of one end panel of the cardboard is aligned with reference line X₀ of the stock stage. On a flap-folding stage, the case made by opening the cardboard is positioned such that the center line of the end panel is aligned with reference line Xfc of the flap-folding stage. On a sealing stage, the case is positioned such that the center line of the end panel is aligned with reference line Xsc of a sealing stage. Reference line Yo is parallel to the direction in which the cardboard is transported from the stock stage to the flap-folding stage, and further to the sealing stage. Reference lines Xo, Xfc and Xsc are parallel to one another, intersect the reference line Yo, and are spaced apart from one another for specific distances. The method according to the invention requires no adjustment other than placing each flat cardboard on the stock stage, such that one of the end panels will have its center line aligned with reference line Xo and its lower edge aligned parallel to reference line Yo. Once the flat cardboard has been thus placed on the stock stage, it suffices to transport the cardboard, first from the stock stage to the flap-folding stage for the distance between lines Xo and Xfc, and then from the flap-folding stage to the sealing stage for the distance between lines Xfc and Xsc. Then, the flaps of a cardboard case are folded on the flap-folding stage, and the case is sealed on the sealing stage, regardless of its size. A method of assembling cardboard cases is known, e.g. from GB-A-2 058 706 and US-A-4,163,414, wherein a flat cardboard preform is opened at a stock stage and bottom inner and bottom outer flaps are folded at a flap-folding stage, thus forming an erected case, and a sealing member is applied to the folded outer flaps at a case-sealing stage. A machine for assembling cardboard cases is likewise known, wherein a flat cardboard preform is opened at a stock stage of the machine by a board-opening mechanism, bottom inner and outer flaps of the cardboard preform are folded at a flap-folding stage of the machine to form a cardboard case, by means of a flap-folding mechanism, and a sealing member is applied to the folded outer flaps at a case-sealing stage of the machine by means of a case-sealing mechanism. A method according the to present invention is characterised by the characterising portion of claim 1 appended hereto. A machine according to the present invention is characterised by the characterising portion of claim 8 appended hereto. In the accompanying drawings: Fig. 1 is a perspective view of a case-assembling machine according to the invention, explaining a method performed by the machine to assemble corrugated cardboard cases; Fig. 2 is a top plan view of the machine, also explaining the method of assembling corrugated cardboard cases; Fig. 3 is a perspective view showing a flat preassembled cardboard; Fig. 4 is a front view showing a cardboard case mounted on the flap-folding stage of the case-assembling machine; Fig. 5 is a front view illustrating the cardboard case with its lower-inner flap already folded; Fig. 6 is a front view showing the cardboard case with its both outer flaps already folded; Fig. 7 is a top plan view showing the machine in more details than Fig. 2; Fig. 8 is a perspective view showing the cardboard case assembled by the machine; Fig. 9 is a side view showing the board-opening mechanism incorporated in the machine; Fig. 10 is a top plan view taken along line X-X in Fig. 9; Fig. 11 is a front view schematically showing the case-assembling machine; Fig. 12 is a right-side view schematically illustrating the case-assembling machine; Fig. 13 is a graph showing how the speed changes, at which the rotatable arm of the machine moves up and down; Figs. 14(A) to 14(D) are side views of the machine, explaining how the board-opening mechanism operates, thus opening a flat preassembled cardboard; Figs. 15(A) to 15(E) are perspective views of a stack of flat cardboards, explaining how the board-opening mechanism opens the uppermost cardboard; Fig. 16 is a top plan view showing the suction cups and the vibration-damping mechanism, both mounted on the flap-folding stage of the case-assembling machine; Figs. 17(A) and (B) are a left-side view and a front view, respectively, illustrating the suction cups and the vibration-damping mechanism; Figs. 18 and 19 are a front view and a left-side view, respectively, showing the mechanism incorporated in the machine, for folding the lower-inner flap of each cardboard case; Figs 20(A) to 20(D) are side views of the mechanism for folding the lower-inner flap of each case, explaining how this mechanism folds the lower-inner flap of the case; Figs. 21(A) to 21(D) are front views of the inner flap-folding mechanism, explaining how this mechanism folds the lower-inner flap of the case; Fig. 22 is a perspective view illustrating the mechanism incorporated in the machine, for folding the outer flaps of each case; Figs. 23(A) and 23(B) are front views of the outer flap-folding mechanism, explaining how this mechanism folds the left and right outer flaps of the case; Fig. 24 is a top plan view of the corrugated cardboard case with its left and right outer flaps already folded by means of the outer flap-folding mechanism; Figs. 25 and 26 are a left-side view and a schematic front view, respectively, illustrating the case-holding mechanism for holding each case on the case-sealing stage of the machine; Fig. 27 is a front view of the case-holding mechanism taken along line XXVII-XXVII; Figs. 28(A) to 28(C) are left-side views of the case-holding mechanism, representing how this mechanism holds each case on the case-sealing stage; Figs. 29(A) to 29(C) are perspective views of the case-holding mechanism, explaining how this mechanism holds each case on the case-sealing stage; Fig. 30 is a perspective view showing a unit comprising suction cups and a vibration-damping mechanism; Fig. 31 is a side view of a board-opening mechanism which can rotate through an angle of 180°; Figs. 32(A) and 32(B) are top plan views of a part of the board-opening mechanism shown in Fig. 31, explaining how the mechanism operates; Figs. 33 and 34 are a top plan view and a front view, respectively, showing the stocker used in the case-assembling machine; Figs. 35 and 36 are a top plan view and a front view, respectively, showing a stocker of shuttle type; Fig. 37 is a top plan view schematically illustrating a stocker of rotary type; Figs. 38(a) to 38(f) are perspective views of a flat preassembled cardboard, explaining how the cardboard is assembled into a case by the conventional method; Fig. 39 shows the perspective views of the A-1 to A-5 type cardboard cases; and Fig. 40 shows the bottom views of the A-1 to A-5 type cardboard cases. The embodiments of the present invention will now be described in detail, with reference to the accompanying drawings by way of example. Case-assembling machine 10 according to the invention, which is designed to make A-1 type cardboard cases, will be briefly described, and then a method according to the invention, of assembling cardboard cases will be described. As is shown is Figs. 1 and 2, flat preassembled cardboards 12 are stacked on a stocker 14, one upon another. On the stocker 14, each cardboard 12 is positioned with respect to both an X-axis direction (i.e., its lengthwise direction) and a Y-axis direction (i.e., its widthwise direction), as will be specifically explained below. The stocker 14 has two positioning members 16 and 18. First positioning member 16 can slide in the X-axis direction, whereas second positioning member 18 can slide in the Y-axis direction. Both positioning members 16, 18 are moved to and fixed at desired positions, such that end panel 12A of each cardboard 12, which is turned upward, is centered with respect to reference line X₀. More precisely, as is shown in Fig. 2, first positioning member 16 is moved leftward from line X₀ for distance of W/2, where W is, as can be understood from Fig. 3, the width of the case which is to be assembled from cardboard 12. Second positioning member 18 is moved forward from reference line Y₀ for distance of W/2 which is equal to the width of the inner flaps of cardboard 12. It should be noted that side panel of cardboard 12, which is turned upward, is denoted by "12B" in Fig. 3. In short, member 16 is moved leftward from reference line X₀ through distance W/2, and member 18 is moved forward from the reference line Y₀ for the distance equal to the width of the inner flaps, thus placing cardboard 12 at a desired position. All cardboards 12 stacked on stocker 14 are thus properly positioned by means of postioning members 16 and 18. As will be clear later, the method according to the invention requires no adjustment other than moving members 16 and 18, in order to assemble cardboard cases of different sizes. As is shown in Fig. 1, board-opening mechanism 28 having suction cups 20 is located above stocker 14. The mechanism 28 is lowered until suction cups 20 are pressed onto end panel 12A of flat preassembled cardboard 12. Due to the partial vacuum created in cups 20, cardboard 12 is attracted to cups 20. Then, board-opening mechanism 28 is lifted and moved to a flap-folding stage, thus transporting cardboard 12 from stocker 14 to the flap-folding stage. Suction cups 20 are attached to the lower surface of support block 23 which in turn is secured to the distal end of rotatable arm 22. The proximal end of arm 22 is connected to a slider 74 slidably mounded on post 24. Flap-folding member 26 is rotatably coupled to support block 23. Suction cups 20, support block 23, and flap-folding member 26 constitute board-opening mechanism 28. Rotatable arm 22 is lowered to the position shown by solid lines (Fig. 1), and suction cups 20 hold the uppermost cardboard 12 of the stack mounted on stocker 14. Arm 22 is then lifted to the position shown by one-dot chain line (Fig. 1). Arm 22 is rotated, for example, in the clockwise direction, thereby transporting cardboard 12 to the flap-folding stage. While rotatable arm 22 is being lifted, thus moving flat cardboard 12 upward from stocker 14, cardboard 12 is opened, thus forming a hollow cylindrical case. More specifically, as arm 22 moves up, flap-folding member 26 is rotated downward, thus folding the upper-inner flap Flu downward. As a result, flat cardboard 12 is forcedly opened, as in illustrated in Fig.1. As is evident from Fig. 2, the reference line X₀ of stocker 14 is set apart from the reference line Xfc of the flap-folding stage by distance L1 in the X-axis direction. Arm 22 is rotated until preassembled cardboard 12 moves through distance L1 so that the center line of end panel 12A is aligned with reference line Xfc. When end panel 12A is thus aligned with line Xfc, arm 22 is lowered until the opened cardboard 12 is placed on the flap-folding stage, as is shown in Fig. 2 and Fig. 4. On the flap-folding stage, flap-folding mechanism 30 (described later), which has three folding members 114, 134 and 135, folds lower-inner flap F1L inward, and also both outer flaps, i.e., left flap F2L and right flap F2R, inward. More precisely, after the opened cardboard 12 has been positioned, with its end panel 12A aligned with reference line Xfc, flap-folding member 114 of mechanism 30 is rotated upward thereby folding lower-inner flap F1L, as is shown in Fig. 5. Then, left folding member 134 and the right folding member 135 of mechanism 30 are rotated, thus folding left-outer flap F2L and right-outer flap F2R inward, respectively, as is illustrated in Fig. 6. As soon as folding member 114 folds lower-inner flap F1L, it is rotated downward to its initial position, so as not to prevent folding members 134 and 135 from rotating to fold outer flaps F2L and F2R. As has been described, flat preassembled cardboard 12 is opened as upper-inner flap F1U is folded downward while cardboard 12 is being lifted. When cardboard 12 is opened in this way, flap F1U pushes both outer flaps F2L and F2R aside as is shown in Fig. 4. Once upper-inner flap F1U has folded completely, thus taking a vertical position, both outer flaps F2L and F2R are fully opened and not in such positions as to prevent lower-inner flap F1L from being folded upward. Lower-inner flap F1L is therefore is easily and quickly folded upward by means of flap-folding member 114. As is evident from Fig. 2, the reference line Xfc of the flap-folding stage and the reference line Xsc of the case-sealing stage are spaced apart for predetermined distance L2 in the X-axis direction. Therefore, when cardboard 12 is moved from the flap-folding stage for this distance L2 in the X-axis direction, it will be automatically aligned with the reference line Xsc and placed on the case-sealing stage. While cardboard case 12 is being transported from the flap-folding stage to the case-sealing stage, the folding members 134 and 135 of mechanism 30 remain in their flap-folding positions. Hence, cardboard case 12 is not deformed. Before these members 134 and 135 leave case 12, both outer flaps F2L and F2R are moved onto guide 154, as may be understood from Fig. 7. Thereafter, guide 154 keeps both outer flaps in folded position, whereby cardboard case 12 is not deformed. After cardboard case 12 has been moved for distance L2 from the flap-folding stage, it is sealed by means of case-sealing mechanism 40, which is of the well-known type, such as the one manufactured by SIAT Inc., Italy. As is shown in Fig. 7, for example, case-sealing mechanism 40 comprises tape reel 44 holding a roll of adhesive tape. When cardboard case 12 is aligned with the reference line Xsc of the case-sealing stage, tape reel 44 is moved up until the roll of adhesive tape contacts the bottom of case 12. The adhesive tape is applied to the abutting edges of the outer flaps, thus sealing the bottom of case 12. As a result, the cardboard case 12 shown in Fig. 8 is assembled. As has been described, the reference line X₀ of stocker 14 and the reference line Xfc of the flap-folding stage are set apart for distance L1, and the reference line Xfc and the reference line Xsc of the case-sealing stage are set apart for distance L2. Further, the lower edge 13 of cardboard 12 is aligned with the reference line Y₀ when cardboard 12 is placed on the stocker 14 and also when cardboard 12 is mounted on the flap-folding stage. Therefore, when cardboard 12 is transported from stocker 14 for distance L1, it is automatically aligned with the reference line Xfc. While cardboard 12 remains in alignment with the reference line Xfc, lower-inner flap F1U and both outer flaps F2L and F2R are folded. Hence, flap-folding mechanism 30 need not be adjusted in order to fold the lower-inner flap and two outer flaps of a cardboard case of a different size. Moreover, when cardboard 12 is transported from the flap-folding stage for distance L2, it is automatically aligned with the reference line Xsc of the case-sealing stage. While cardboard 12 remains in alignment with the reference line Xsc, case-sealing mechanism 40 can apply sealing means such as adhesive tape to the abutting edges of outer flaps F2L and F2R. Hence, case-sealing mechanism 40 need not be adjusted in order to seal the bottom of a cardboard case of a different size. As may be understood from the above, case-assembling machine 10 according to the invention can shape and seal cardboard cases of different sizes, provided that positioning members 16 and 18 are moved in the X-axis direction and the Y-axis direction, respectively, thereby to set each flat cardboard 12 to the desired position on stocker 14. Machine 10, therefore, can assemble cases of different sizes, and is thus versatile. In addition, since machine 10 requires no means for adjusting flap-folding mechanism 30 or case-sealing mechanism 40, case-assembling machine 10 is compact and light. Case-assembling machine 10, which comprises board-opening mechanism 28, flap-folding mechanism 30, and case-sealing mechanism 40, will be described in greater detail. As is shown is Figs. 1 and 7, board-opening mechanism 28 comprises suction cups 20 and flap-folding member 26. As has been explained, suction cups 20 and flap-folding member 26 are attached to support block 23, and support block 23 is secured to the distal end of rotatable arm 22. The proximal end of arm 22 is connected to slider 74 slidably mounted on post 24. As is shown in Figs. 9 and 10, support block 23 comprises base plate 50, vertical member 51 having an H-shaped cross section, and pivotal member 52 fastened to the upper end of vertical member 51 by bolts and having a U-shaped cross section. Three suction cups 20-1 to 20-3 are located below base plate 50 and connected to thereto by means of shafts 54. The first cup 20-1 is aligned with reference line X₀ of stocker 14, whereas the remaining cups 20-2 and 20-3 are arranged symmetrically to each other with respect to reference line X₀. Shaft 54 of each suction cup 20 passes through base plate 50 and is pivotally supported by support 56 mounted on base plate 50. The upper end 54A of each shaft 54 has a diameter larger than the other portion, so that shaft 54 does not slip down out of support 56. Washer 58 is mounted on the intermediate portion of each shaft 54, and a compression spring, such as compression coil spring 60 is wound around shaft 54 and located between washer 58 and the lower surface of base plate 50. Conduit 62 is connected, at one end, to each suction cup 20 which is attached to the lower end of shaft 54. Conduit 62 is connected, at the other end to a vacuum pump (not shown). When the vacuum pump is operated, each cup 20 is evacuated, thus creating a partial vacuum within it and attracting flat preassembled cardboard 12 to it. Proximity switch 63, functioning as a sensor for controlling the speed at which suction cups 20-1 to 20-3 are moved vertically, is attached to support 56 and located close to shaft 54 connecting cup 20-2 to support 56. The embodiment has three suction cups 20-1 to 20-3 which are arranged at the vertices of triangle. Nonetheless, one or two suction cups suffice. When only one suction cup is used, it is aligned on the reference line X₀ of stocker 14. When two suction cups are used, they are either juxtaposed on the reference line X₀ or arranged symmetrically with respect to the line X₀. Flap-folding member 26 is a plate. It can be replaced with a claw. As is shown in Fig. 9, flap-folding member 26 is fixed to support block 23. While flat cardboard 12 attracted to suction cups 20 is being lifted, flap-folding member 26 is rotated downward, thus folding upper-inner flap F1U of cardboard 12. Pneumatic 90°-actuator 64 is fastened to vertical member 51 by bracket 66. This actuator 64 has a shaft 65, to which member 26 is attached by a fastener 68 having a slit. Flap-folding member 26 has a notch in its upper end portion, and 90°-actuator 64 is placed in this notch. Pneumatic 90°-actuator 64 is designed such that its shaft 65 is rotated through 90° when compressed air is supplied to actuator 64. When shaft 65 is rotated by 90°, flap-folding member 26, which is connected to shaft 65, is also rotated through 90°. Flap-folding member 26 is attached to shaft 65, inclined downward at a small angle ϑ. Since member 26 is inclined downward, its distal end can easily enter opening preassembled cardboard 12, thereby folding upper-inner flap F1U readily. Angle ϑ may be, for example, 5° to 10°. As is illustrated in Figs, 1, 7, 11 and 12, arm 22 is comprised of only two parallel bars 70 and cylinder mechanism 72, and is relatively simple in structure. Both bars 70 are pivotally connected, at one end, to pivotal member 52 of the support block 23, and at the other end, to slider 74 slidably mounted on post 24. As is shown in Fig. 7, cylinder mechanism 72, which is pneumatic, comprises a cylinder, a piston slidably inserted in the cylinder, and a rod connected, at its proximal end, to the piston. The distal end of the rod is pivotally connected to the first bar 70, and the proximal end of the cylinder is pivotally coupled to the second bar 70. When compressed air is supplied to cylinder mechanism 72, the piston is moved in one direction or the other within the cylinder, whereby the rod moves inwardly or outwardly. As the rod moves in this way, arm 22 rotates around post 24. As is shown in Figs. 11 and 12, endless chain 76 is wrapped around two guide rollers fixed to the upper end of post 24, and a guide roller secured to the lower end of post 24. Hence, endless chain 76 extends vertically and is fastened, at one portion, to slider 74. Endless chain 76 can be driven by motor 78 fastened to the upper end of post 24. Chain 76 in covered and protected by long, trough-shaped cover 80. When motor 78 drives endless chain 76 in one direction or the other, slider 74 slides up or down on post 24, whereby arm 22 is moved up or down. It will now be explained how board-opening mechanism 28 performs its function. In the initial phase of the operation, suction cups 20 are located above end panel 12A of flat preassembled cardboard 12. Motor 78 is turned on, thus driving endless chain 76 in the first direction, whereby slider 74 is moved downward, and arm 22 is also moved downward. Hence, suction cups 20 are lowered, and eventually contact end panel 12A of cardboard 12. As can be understood from Fig. 13, which shows how the speed changes at which arm 22 is lowered and lifted suction cups 20 are moved down at high speed, starting at time TO. Immediately thereafter, at time T1, cups 20 are decelerated. Upon lapse of period T1′ from time T1, cups 20 abut on end panel 12A of cardboard 12 as shown in Fig. 14(A). As suction cups 20 are further lowered as shown Fig. 14(B), the distal end 54A of each shaft 54 projects upward from the top of support 56. Then, at time T2, proximity switch 63 (Fig. 10) detects that shaft 54 has projected upward from support 56, thus determining that cup 20 has contacted cardboard 12. The brakes are at once applied on slider 74 at time T2′. Nonetheless, slider 74 further moves down, along with arm 22, for distance Y1, while compressing springs 60 wound around shafts 54. Springs 60, thus compressed and shortened by about 40 mm, attain a biasing force and push suction cups 20 onto cardboard 12. Hence, cups 20 are strongly pressed onto the end panel 12A of cardboard 12, as is shown in Fig. 14(B). Arm 22 completely stops at time T2. Then, the vacuum pump is turned on, thereby pumping air out of suction cups 20 via conduits 62. A partial vacuum is thereby created within each cup 20, and suction cups 20 attract cardboard 12 readily and reliably. This is because no vacuum leaks from cups 20 since all cups 20 are strongly pressed onto cardboard due to the biasing force of springs 60 which are now compressed. Thereafter at time T3, slider 74 is released from brake, and starts moving upward as it is driven by endless chain 76. Hence, arm 22 is lifted. Suction cups 20 do not moved up at once since compression springs 60, which are compressed, are shorter than their original length by distance Y1. Thus, cups 20 starts moving up at time T3′ when arm 22 has been lifted for distance Y1. As arm 22 is further lifted, suction cups 20 are also lifted. Shortly before suction cups 20 start moving upward, 90°-actuator 64 is operated, thereby rotating flap-folding member 26 downward. Hence, flap-folding member 26 starts folding the upper-inner flap F1U of cardboard 12 at time T3′ when cups 20 begin to move up along with arm 22. With reference to Figs. 15(A) to 15(D), it will be explained how flap-folding member 26 folds upper-inner flap F1U. As is indicated by the one-dot chain line shown in Fig. 15(A), flap-folding member 26 presses against upper-inner flap F1U before cups 20 are lifted. As a result, the left edge F1U-L of flap F1U pushes against left-outer flap F2L. As suction cups 20 move upward, thus lifting cardboard 12, the left edge F1U-L of flap F1U further pushes against left outer flap F2L, whereby cardboard 12 is gradually opened and held up, as is illustrated in Figs 15(B) to 15(D). Along with left outer flap F2L, right outer flap F2R is held up as cardboard 12 is lifted further. Cardboard 12 is eventually opened completely at time T4 as is shown in Fig. 15(E). While cardboard 12 is being opened, rotatable arm 22 is moved up at low speed. When cardboard 12 is fully opened at time T4, the brake on slider 74 is released whereby arm 22 is lifted at high speed. Rotatable arm 22 moves up at high speed until it reaches a prescribed position at time T5. Cardboard case 12, thus fully opened and elevated, is shown by the one-dot chain line in Fig. 1. Then, the piston of cylinder mechanism 72 is pushed outward, whereby arm 22 is rotated in the clockwise direction as is shown in Fig. 1. Cardboard case 12 is therefore transported to a position right above the flap-folding stage. When cardboard case 12 reaches this position slider 74 is lowered to a prescribed position. As a result of this, case 12 is placed on the flap-folding stage, as is illustrated in Figs. 2 and 4. While upper-inner flap F1U is folded downward at the same time as cardboard 12 is lifted, it forthwith pushes left-outer flap F2L aside. Hence, as can be clearly seen from Fig. 4, neither left outer flap F2L nor indeed right outer flap F2R can remain in a closed position to prevent lower-inner flap F1L from being folded upward. Therefore, no sensor is required to detect whether or not either outer flap remains in such a closed position. Nor is a mechanism required which forcedly pushes open both outer flaps to facilitate the folding of lower-inner flap F1L. Case-assembling machine 10 according to this invention is therefore simple, compact, and light. Since compressed springs 60 require some finite time to return to their original states, suction cups 20 start moving upward, not at the moment rotatable arm 22 begins to move up, but at a little later time. After arm 22 has begun to rise, springs 60 gradually expand, thus reducing the force applied on suction cups 20. Springs 60, which have been compressed, therefore expand little by little as arm 22 is moved up. Hence, an upward pulling force is applied to cardboard 12 increasingly, and cardboard 12 is lifted in this way, the gap between it and the next cardboard broadens gradually, allowing air to flow into this gap in an increasing amount. The uppermost cardboard 12 can therefore be smoothly released from the stack of cardboards, and the next cardboard is never lifted together with the uppermost one. As has been explained, because of the use of compression springs 60, a time-lag is provided between the start of the lifting of arm 22 and the lifting of cardboard 12. Owning to this time-lag, flat cardboards 12 are lifted from stocker 14, one by one without fail. Therefore, the stack of cardboard is not distorted, and the case-assembling process is not interrupted, as might happen in the case where two or more flat cardboards 12 are lifted together from stocker 14. This ensures a high case-assembling efficiency. Rotatable arm 22 is rotated from stocker 14 to the flap-folding stage through such a predetermined angle that not only the end panel 12A of any cardboard case 12 placed on the flap-folding stage is aligned with the reference line Xfc of the flap-folding stage, but also the lower edge 13 of end panel 12A is aligned with the reference line Y₀. While arm 22 is rotating from stocker 14 to the flap-folding stage, rotation moment is exerted on suction cups 20 since cups 20 hold cardboard case 12. Since case-assembling machine 10 according to the invention has three suction cups 20, and cardboard 12 is held at three points, cardboard 12 is not rotated at all with respect to arm 22. Hence, cardboard 12 is place at the desired position on the flap-folding stage. One suction cup suffices, provided this cup has a diameter large enough not to rotate cardboard case 12. Flap-folding mechanism 30 is located at the flap-folding stage. As is shown in Figs 7, 16, 18 and 19, this mechanism 30 comprises two suction cups 82, inner-flap folder 84, and outer-flap folder 86. Suction cups 82 are of the same type as suction cups 20 of board-opening mechanism 28, and are designed to hold cardboard case 12 transported from the flap-folding stage to the case-sealing stage. When suction cups 82 contact onto the lower end panel 12A of cardboard case 12, a vacuum pump (not shown) connected to cups 82 are driven, thus creating a partial vacuum within both cups 82. As a result, suction cups 82 attract cardboard case 12 and hold cardboard case 12 in place. Cups 82 continue to hold cardboard case 12 until cardboard case 12 is transported from the flap-folding stage to the case-sealing stage and is sealed by means of case-sealing mechanism 40. As is shown in Fig. 16 and Figs. 17(A) and 17(B), support 88 supporting both suction cups 82 is secured to box-shaped slider 90. Slider 90 is coupled to a rod-less cylinder mechanism 92 and slidably mounted on guide 94. Flap-folding mechanism 30 further comprises stopper mechanism 96 for preventing cardboard case 12 from rotating and for accurately positioning the same on the flap-folding stage. It should be noted that stopper mechanism 96 can be dispensed with. Stopper mechanism 96 comprises right guide 98 and left guide 99. Either guide is made of a thin steel plate, the upper end portion of which is bent outward to guide cardboard case 12 downward, smoothly into contact with suction cups 82. Guides 98 and 99 are connected to sliders 102 and 103, respectively. Sliders 102 and 103 are mounted on a drive shaft 104, two half portions of which are threaded in the opposite directions. Left guide 99 is located in the path in which cardboard case 12 is transported from the flap-folding stage to the case-sealing stage. In order not to hinder the transport of case 12, left guide 99 can rotate, whereas right guide 98 cannot rotate and always extends vertically. More specifically, guide 99 is connected to the shaft of 90°-actuator 106, so that actuator 106 can rotate left guide 99, thus moving guide 99 out of the path of cardboard case 12. Sliders 102 and 103 are coupled drive shafts 104 in such a manner that both guides 98 and 99 are positioned symmetrically with respect to reference line Xfc of the flap-folding stage. As is illustrated in Fig. 16, flap-folding mechanism 30 further comprises guide shaft 108 extending parallel to drive shaft 104, and brackets 110 supporting both drive shaft 104 and guide shaft 108. Brackets 110 are fastened to frame 11 of case-assembling machine 10. Positions of guides 98 and 99 are adjusted, before use, to the width W of cardboard case 12. That is, handle 112 attached to drive shaft 104 is rotated, thereby moving guides 98 and 99 in the opposite directions, either toward each other or away from each other, thus changing the gap between them to a value a few millimeters greater than the width W of cardboard case 12. It is desirable that drive shaft 104 be automatically rotated as the second positioning member 18 of stocker 14 is adjusted in the X-axis direction. If this is the case, the positions of guides 98 and 99 are automatically adjusted, without rotating handle 112. Before cardboard 12 is transported from stocker 14 to flap-folding stage, 90°-actuator 106 for rotating left guide 99 is operated, thus bringing guide 99 into the vertical position. Left guide 99 remains vertical during the flap-folding process. After the flap-folding process, and before the transport of case 12 to the case-sealing stage, 90°-actuator 106 is operated, this time rotating guide 99 into a horizontal position. Hence, case 12 can be transported to the case-sealing stage unobstructedly. As is illustrated in Figs. 18 and 19, the inner-flap folder 84 of flap-folding mechanism 30 comprises flap-folding member 114 which is rotatable, and shaft 116 to which member 114 is welded. Shaft 116 extends horizontally, and can be moved up and down while remaining in the horizontal position. To be more specific, shaft 116 is coupled to slider 123 which is slidably mounted on a pair of shafts 122 spaced apart in the horizontal direction and both extending vertically between two supports 120. These supports 120 are fastened to the upper and lower ends of bracket 118, respectively, which in turn is fixed to the frame 11 of case-assembling machine 10. Bracket 118 has broad notch 119 in its upper end. Cylinder mechanism 124 is coupled to the lower surface of lower support 120. The piston 126 of cylinder mechanism 124 passes through lower support 120 and is connected, at its upper end, to slider 123. Operation plate 129 is welded to shaft 116. The flap-folding member 114 is shaped such that it can abut on the edge 119A of notch 119 cut in bracket 118. A torsion spring 130 is wound around shaft 116, with its right end 130R inserted in a hole 131 made in slider 123 and its left end 130L biased onto the edge 132A of a notch 132 cut in the lower-right portion of operation plate 129. Hence, torsion spring 130 urges operation plate 129 to rotate counterclockwise as represented by the arrow in Fig. 19. Further, the upper end portion of flap-folding member 114 is bent downward such that, in its initial position, flap-folding member 114 abuts on the edge 119A of notch 119, and plate 129 is located below shaft 128. Inner-flap folder 84 operates in the following manner. Holder 84 stays in its initial position shown in Figs. 19 and Fig. 20(A), which can be below the end panel 12A of cardboard case 12 mounted on the flap-folding stage. As can be seen from Fig. 21, the suction cups 20 of board-opening mechanism 28 still keep holding cardboard case 12 which is already transported to the flap-folding stage, and the flap-folding member 26 of mechanism 28 remains in its operation position, thus holding the upper-inner flap F1L of case 12. Since inner flap F1L has been folded downward no sooner than cardboard 12 had been moved upward from stocker 14, both outer flaps F2L and F2R are pushed open by inner flap F1U. Hence, neither outer flap is in such a position as to hinder a smooth upward folding of lower-inner flap F1L. Then, cylinder mechanism 124 is driven, whereby piston 126 extends outward, lifting slider 123. Hence, shaft 116 attached to slider 123 is also lifted. Since the biasing force of torsion spring 130 is applied to shaft 116, both flap-folding member 114 and operation plate 129 are rotated counterclockwise as shaft 116 is moved up, as is illustrated in Fig. 20. Eventually, plate 129 abuts on shaft 128, whereby plate 129 can no longer rotate counterclockwise as is shown in Fig. 20(B), Then, flap-folding member 114 is rotated clockwise as shaft 116 is lifted further, as is illustrated in Figs. 20(B) and 20(C). In the position shown in Figs. 20(A) and 20(B), flap-folding member 114 is located below cardboard case 12 and is thus unable to fold lower-inner flap F1L of cardboard case 12, as may be understood from Figs. 21(A) and 21(B). When member 114 is further rotated clockwise, however, the upper end of member 114 rises above the bottom of case 12, as is illustrated in Figs. 20 (C) and 21(C). Therefore, member 114 starts folding inner flap F1L upward. As inner flap F1L is folded upward, it makes no bridging whatever with either outer flap F2L or F2R since both outer flaps have been fully opened or pushed aside by upper-inner flap F1U which has been already folded downward. As a result, lower-inner flap F1L is easily folded upward as is shown in Fig. 20(D) and Fig. 21(D). A rubber sheet 127 is wrapped around shaft 128, thus reducing the shock which operation plate 129 suffers when abutting on shaft 128. Therefore, lower-inner flap F1L can be folded upward readily even if cardboard case 12 is displaced in the Y-axis direction. After lower-inner flap F1L has been folded, outer-flap folder 86 is operated. As is shown in Fig. 22, folder 86 comprises left flap-folding member 134 and right flap-folding member 135. Both flap-folding members 134 and 135 secured to upper ends of two shafts 136, respectively, which are pivotally supported by supports 138. Either support 138 is attached to frame bracket 140 which in turn is fastened to the frame 11 of case-assembling machine 10, as is illustrated in Fig. 23(A). Bevel gear 142 is mounted on the lower end of either shaft 136. Bevel gear 144, which meshes with bevel gear 142, is mounted on horizontal shaft 146 extending through both brackets 140. Cylinder mechanism 148 having piston 150 is connected at its proximal end 148A to the frame 11 of case-assembling machine 10. The distal end of piston 150 is coupled by coupler 152 with horizontal shaft 146. Coupler 152 is a flexible one, and is rotated when shaft 146 is rotated. As is shown Figs. 22 and 23(A), flap-folding member 134 and 135 are set apart from outer flaps F2L and F2R, respectively, when outer-flap folder 86 is in its initial position. When cylinder mechanism 148 is actuated, thus extending piston 150 outward, shaft 146 is rotated. As a result, both shafts 136 are rotated since bevel gears 144 mounted on shaft 146 are in mesh with bevel gears 140 mounted on the lower ends of shafts 136. Flap-folding members 134 and 135, which are mounted on shafts 136, are therefore rotated, folding outer flaps F2L and F2R inwardly as is illustrated in Fig. 23(B). Both flap-folding members 134 and 135 function not only to fold outer flaps F2L and F2R, but also to guide cardboard case 12 from the flap-folding stage to the case-sealing stage in the following manner. Cylinder mechanism 148 is actuated such that flap-folding member 134 and 135 do not fold outer flaps F2L and F2R up until flaps F2L and F2R are completely aligned with the reference line Y₀; flaps F2L and F2R are not completely folded as is shown is Fig. 24. This is an important feature. Were flaps F2L and F2R completely folded and aligned with line Y₀, the friction between each outer flap and the flap-folding member would increases, rendering it difficult to smoothly transport cardboard case 12 to the case-sealing stage, and the reaction of flaps F2L and F2R would be great enough to topple case 12. As is shown in Fig. 24, left flap-folding member 134 is longer than right flap-folding member 135, extending beyond the reference line Xfc of the flap-folding stage, and its distal end 134A, which is beyond line Xfc, is bent outwardly. Since the distal end 134A of member 134 is thus bent, right outer flap F2R does not abut on distal end 134A of left flap-folding member 134 at all as cardboard case 12 is transported forward. Hence, case 12 is smoothly transported from the flap-folding stage to the case-sealing stage. As a comparison between Fig. 23(A) and Fig. 23(B) may show, flap-folding members 26 and 114, which are designed for folding inner flaps F1U and F1L, respectively, are removed from their flap-folding positions as soon as flap-folding members 134 and 135 start rotating to fold outer flaps F2L and F2R inward. More specifically, the moment flap-folding members 134 and 135 are rotated, thus folding flaps F2L and F2R to some extent, the vacuum is released from all suction cups 20 of board-opening mechanism 28, and rotatable arm 22 is lifted, whereby member 26 attached to arm 22 is smoothly pulled out of cardboard case 12. Thereafter, when 90°-actuator 64 is driven, thus returning flap-folding member 26 to the initial position, and arm 22 is rotated back to its initial position above stocker 14. Hence, board-opening mechanism 28 is now ready to open the uppermost one of the cardboards 12 stacked on stocker 14. Almost at the same time as flap-folding member 26 is pulled from cardboard case 12, cylinder mechanism 124 is actuated, thereby lowering piston 126. As a result, flap-folding member 114 is pulled from cardboard case 12. Although torsion spring 130 urges flap-folding member 114 to rotate, operation plate 129 abuts on shaft 128, whereby flap-folding member 114 cannot rotate, until it is completely pulled out of cardboard case 12. When flap-folding member 114 is completely pulled from case 126, it starts rotating. Then member 114 and piston 126 return to their respective initial positions as shown in Fig. 19. Thus, flap-folding mechanism 30 is now ready to fold the flaps of the next cardboard case 12 which is to be transported to the flap-folding stage. When lower-inner flap F1L and both outer flaps F2L and F2R of cardboard case 12 have been folded, rod-less cylinder mechanism 92 (Fig. 16) is driven, thus sliding slider 90 on guide 94 for distance L2 to the left. Cardboard case 12 attracted to suction cups 82 mounted on slider 90 is therefore positioned in alignment with the reference line Xsc of the case-sealing stage. In other words, when cardboard case 12 is moved to the left from the flap-folding stage for distance L2, it is automatically aligned with reference line Xsc of the case-sealing stage. Guides 154, 156 and 157 secured to frame 11 continuously guide cardboard case 12 before case 12 is released from flap-folding members 134 and 135 which also guide case 12 as is shown in Fig. 7. As has been described above, carboard case 12 is fixed on the case-sealing stage before case-sealing mechanism 40 is operated to seal cardboard case 12. Cardboard case 12 is held on the case-sealing stage by means of case-holding mechanism 160 shown in Figs. 25 and 26. As is shown in these figures, case-holding mechanism 160 comprises first case holder 162 for pushing cardboard case 12 vertically, and second case holder 164 for pushing case 12 horizontally from behind the back of case 12 on guides 156 and 157. As is shown in Figs. 25 and 26, first case holder 162 comprises cylinder mechanism 166 including piston 168, and plate 170. The lower end of piston 168 is coupled to upper slider 172 which is a horizontal flat bar. Slider 172 is connected to lower slider 176 by means of two vertical rods 174. Plate 170 is attached to the lower surface of lower slider 176. First case holder 162 further comprises a pair of guide bars 178 which extend vertically, parallel to cylinder mechanism 166. Guide bars 178 extend upward from upper slider 172, passing through the holes made in frame 11 and slidably supported by support 179. Stopper 178A is connected to the upper end of either guide bar 178, so that guide bar 178 may not fall, slipping from support 178 and 179. Compression coil spring 180 is wound around either guide bar 178 and interposed between frame 11 and upper slider 172. As piston 158 extends downward, plate 170 is lowered to push lower edge 13 of case 12 and also the upper sides of outer flaps F2L and F2R. As is shown in Figs. 25 and 27, second case holder 164 comprises cylinder mechanism 182 and plate 186. Mechanism 182 has piston 184. A pair of guide bars 187 extend horizontally, parallel to each other, passing through holes made in support 188 attached to the lower surface of frame 11. Slider 190 slidably mounted on guide bars 187 is locked thereto by means of lock lever 192. Cylinder mechanism 182 is horizontally attached to slider 190. Coupler 193 is connected to the distal end of piston 184. A pair of steel bars 194 are connected to coupler 193. Plate 186 is secured to these steel bars 194 and extend downward therefrom. As piston 184 extends horizontally to the right (Fig. 25), plate 186 is moved in the same direction, thus contacting the back of case 12 and pushing case 12 to the right. Case-holding mechanism 160 operates in the following way to hold cardboard case 12 on the case-sealing stage. As is shown in Fig. 28(A), case 12 transported from the case-sealing stage and aligned with the reference line Xsc of this stage is set apart from both the plate 170 of first case holder 162 and the plate 186 of second case holder 164. Nonetheless, as is evident from Fig. 29(A), both outer flaps F2L and F2R are lightly pressed onto guides 156 and 157, respectively. In this condition, cylinder mechanism 166 is actuated, thus thrusting piston 168 downward. Hence, plate 170 is lowered and presses end panel 12A of cardboard case 12. The force which plate 170 applies to end panel 12A is the biasing force of compression spring 180, and is not strong. Since plate 170 lightly presses the lower edge 13 of case 12 and the upper sides of outer flaps F2L and F2R, case 12 is not distorted or deformed, and remains upright while lightly clamped between suction cups 82 and plate 170, as is illustrated in Figs. 28(B) and 29(B). While holding case 12 upright between cups 82 and plate 170, cylinder mechanism 182 is actuated, thereby thrusting piston 184 to the right. Plate 186, which is connected to piston 184 by coupler 193 and steel bars 194, is moved to the right, contacting and pushing the back of case 12. Plate 186 is large enough to touch the entire back of case 12. Plate 186 is moved to the right until the front of case 12 goes into contact with guides 156 and 157. Thus, cardboard case 12 is held between plate 186 and guides 156, 157. In this condition, both outer flaps F2L and F2R are completely folded, with their opposing edges F′ abutting on each other and extending vertically along the center line of cardboard case 12. Case-sealing mechanism 40 (e.g., the sealing machine manufactured by SIAT, Inc.) is operated to move up, thus applying sealing member such as the adhesive tape 44 to the abutting edges F′ of flaps F2L and F2R, which extend vertically. The position of mechanism 40 need not be adjusted in order to seal cardboard cases of different sizes. This is because, as has been explained, any cardboard case 12 of whichever size supplied to the case-sealing stage is positioned such that its center line is aligned with the reference line Xsc of the case-sealing stage. In addition, since each cardboard 12 is held immovably during the sealing process, it can be sealed by means of staples. Upon completion of the sealing process, the vacuum is released from suction cups 82. These cups 82 are returned to their initial positions where they can hold the next cardboard case 12. Cardboard case 12, which has been thus sealed, temporarily remains on the case-sealing stage. It is pushed to the left from the case-sealing stage by the next case 12 held by suction cups 82 and being transported to the case-sealing stage. Stopper mechanism 96 and suction cups 82 shown in Figs. 16 and 17 can be assembled into such a single stopper mechanism 296 as is illustrated in Fig. 30. In this stopper mechanism 296, main body 297 is secured to frame 11, and rod-less cylinder mechanism 292 is mounted on main body 297. The stopper mechanism comprises a pair of guides 294 extending between the raised ends of rod-less cylinder mechanism 292, slider 290 slidably mounted on these guides 294, guides 298 and 299 slidably mounted on slider 290, and two suction cups 282 attached to guide 298. The operation of stopper mechanism 296 will be explained. First, drive shaft 304 is rotated, thus moving guides 298 and 299 until the distance between them becomes a little greater than the width W of cardboard case 12. Rotatable arm 22 holding case 12 is lowered until case 12 is placed in the gap between guides 298 and 299. Then, suction cups 282 are moved to the left until they contact one side of case 12. Both cups 282 are evacuated, thus creating a partial vacuum in them. As a result, cardboard case 12 is held between guides 298 and 299. After case 12 has been folded in the same way as has been described, rod-less mechanism 292 is actuated, thus sliding slider 290 along guides 294 to the left. Hence, case 12 held between guides 298 and 299, both mounted on slider 290, is transported from the flap-folding stage to the case-sealing stage. Since suction cups 282 hold one side of cardboard case 12, case 12 is prevented from being deformed while it is mounted on the case-sealing stage. Data is usually printed in the same manner on the top and bottom panels of a cardboard case 12. In some cases, however, printing data is turned upside down. A cardboard case thus printed with data is called "upside down case." To open such a cardboard case, it suffices to rotate cups 20 and flap-folding member 26 together, through 180°. Fig. 31 illustrates board-opening mechanism 228 which is designed to open upside down cardboard cases. Mechanism 228 is different from board-opening mechanism 28 in two aspects. First, 180°-actuator 116 is connected to support block 23 which in turn is connected to the distal end of rotatable arm 22. Second, unit 220, which is a combination of suction cups 20 and flap-folding member 26, is fastened to the shaft 197 of l80°-actuator 116. As is shown in Figs. 32(A) and 32(B), the shaft 197 of 180°-actuator 196 is aligned with the reference X₀ and set apart from the reference Y₀ line for the distance equal to half the depth D of case 12 (i.e., D/2). Unit 220 is fastened to shaft 197 such that flap-folding member 26 can fold upper flap F1U of cardboard 12. As can be clearly seen from Fig. 32(A), flat cardboards 12 are stacked on stocker 14, each having center line of its end panel 12A aligned with the reference line X₀, and its upper edge (not its lower edge 13) aligned with the reference line Y₀. In operation, suction cups 20 are evacuated, thus holding flat cardboard 12. Then, 180°-actuator 196 is operated such that shaft 197 is rotated through 180°. Unit 220, which is fastened to shaft 197, is therefore rotated through 180°. As has been specified, shaft 197 is set apart from the reference line Y₀ for the distance of 2/D, the lower edge 13 of flat cardboard 12 is aligned with the reference line Y₀. As a result, cardboard 12 automatically takes a desired position. Thereafter, cardboard case 12 is opened, shaped, and sealed, in the same way as has been explained. According to the present invention, stocker 14 can by modified such that it may function as a carrier, too. For instance, as is shown in Figs. 33 and 34, casters 408, which can be moved up and down, are attached to the lower surface of stocker 14. When pedal 410 is depressed, casters 408 are lowered, whereby stocker 14 is used as a carrier. Alternatively, casters 408 can be ordinary fixed casters, when the legs 412 of stocker 14 can be of the type which can be extended up or down. In this case, when pedal 412 is depressed, legs 412 are lifted, whereby stocker 14 can be used as a carrier. Preferably, positioning members 16 and 18 are moved such that intersection Z₀ of reference lines X₀ and Y₀ moves in straight line z intersecting with both lines X₀ and Y₀ at 45°. In this case, both positioning members 16 and 18 can be moved by rotating only one handle 411, to the desired positions determined by the width W of flat cardboard 12. Further, it is desirable that positioning members 16 and 18, and the guides 98 and 99 of stopper mechanism 96 be automatically moved in accordance with the input data representing the width W of cardboard 12. In this case, a fully automatic case-assembling machine 10 will be provided. As is shown in Figs. 33 and 34, roller 416 is located such that it contacts the right portion of the side panel 12B of cardboard 12, thus functioning as a weight. Since the right portion of cardboard 12 is held by roller 416, side panel 12B is not raised in its entirety, and is gradually raised from its left portion adjacent to end panel 12A. Hence, no bridgings occur, and cardboard 12 can be smoothly opened. Roller 416 is mounted on rod 417. Rod 417 is slidably supported by slider 420 which is slidably mounted on two vertical, parallel guide bars 418 arranged at the back of stocker 14. Rod 417 can thus be moved up and down. Roller 416, which is mounted on rod 417 can also be moved up and down. Since rod 417 can slide horizontally, back and forth, roller 415 can be moved in the horizontal direction for a disired distance in accordance with the size of flat preassembled cardboard 12. Roller 416 is set at a desired position, merely by operating lock handle 422, thereby fixing rod 417 to slider 420. Whenever a cardboard is lifted from the stack of cardboards, roller 416 lowers, due to its own weight, to contact the uppermost cardboard. Furthermore, stocker 14 can be made to move on the frame 11 of machine 10, back and forth in the Y-axis direction, as is shown in Figs. 35 and 36. In this case, flat cardboards 12-1, 12-2, and so on, can be continuously opened one after another, thus ensuring a high case-assembling efficiency. This type of a stocker is called "shuttle type". As is shown in Fig. 35, shuttle-type stocker 14 comprises two pairs of positioning members 16 and 18, which are used to position two cardboards 12-1 and 12-2 of different sizes. More specifically, the lower edge 13 of the first cardboard 12-1 is aligned with the reference line Y₀, whereas the second cardboard 12-2 is positioned such that its lower edge 13 will be aligned with the reference line Y₀ when the front edge 14A of stocker 14 moves back to the position indicated by the one-dot chain line (Fig. 35). Proximity switch 424 mounted on frame 11, which functions as a sensor, detects the front and rear edges 14A and 14B of stocker 14, thus determining which cardboard, cardboard 12-1 or 12-2, is located at the board-opening position. In the case of shuttle-type stocker 14, roller 416 is provided at such a position above frame 11 that it does not collide with flat cardboard 12-1 while stocker 14 is being moved toward a desired position. Roller 416 is placed on cardboard 12-1 after stocker 14 has reached the desired position. As is shown in Fig. 36, casters 408 of stocker 14 are mounted on rails 423. As has been described above, each flat cardboard 12 is automatically set at a disired position when stocker 14 is positioned appropriately. Therefore, the shuttle-type stocker 14 can be used, whereby cardboard cases of different sizes are open, shaped, and sealed easily and fast, continuously one after another. Still further, such a rotary-type stocker as is shown in Fig. 37 can be used in the present invention. The use of the rotary-type stocker 14 makes it possible to open, shape, and seal cardboard cases of different sizes easily and fast, continuously one after another. The case-assembling machine provided with the shattle-type stocker or the rotary-type stocker can open, shape, and seal cardboard cases of the same size, equally fast one after another, since no delay occurs in positioning each flat cardboard on the stoker. The case-assembling machine 10 according to this invention can erect cardboards 12 of different sizes, thus assembling cardboard cases of different sizes, one after another. Obviously, machine 10 is versatile since it can assemble cases of various types, each type in a small quantity, in accordance with users' requests. The description of the embodiment has been limited to the case where machine 10 assembles only A-1 type cardboard cases 12. Nevertheless, machine 10 can assemble A-3 type cardboard cases exactly in the same manner as A-1 type cases 12. Although machine 10 described above is suitable for assembling A-1 type cases or A-3 type cases, it can assemble A-2 type, A-4 type and A-5 type cases only if modified a little. For example, it can fold the flaps of a A-2 type, A-4 type, or A-5 type case if flap-folding mechanism 30 is modified so as to fold outer flaps F2L and F2R with a time-lag therebetween instead of simultaneously. Further, machine 10 can make a A-2 type, A-4 type, or A-5 type case, wherein the edges of the outer flaps deviate from the center line of the case, merely by changing distance L2 through which the case is transported from the flap-folding stage to the case-sealing stage. As long as distance L2 is changed appropriately, one of the edges of the outer flaps of the A-2 type, A-4 type or A-5 type case is automatically aligned with the reference line Xsc when the case is placed on the case-sealing stage. According to the present invention, it suffices to adjust the positioning members 16 and 18 of stocker 14 only once in accordance with the size of the cardboard cases which are to be opened, shaped, and sealed. Therefore, it is easy to design machine 10 into a fully automatic one, wherein the positioning members are automatically adjusted in accordance with input data items which represent the length L, width W and depth D of the cardboard cases to be opened, shaped, and sealed. The present invention is not limited to the embodiment described above. Various changes and modifications can be made. For example, each cardboard case 12 can be transported in a straight path from stocker 14 to the flap-folding stage, unlike in the above embodiment wherein arm 22 is rotated, thus transporting case 12 to the flap-folding stage, so that machine 10 requires but a smaller floor area than when case 12 is transported in a straight path. To transport case 12 in a straight path is advantageous in that no rotation moment is exerted on case 12, and hence case 12 assures a correct position on the flap-folding stage. According to the present invention, as has been explained in detail, suction cups hold each flat preassembled cardboard, and the cardboard is opened while being transported from the stock stage to the flap-folding stage. To be more precise, the upper-inner flap of the cardboard is first folded downward, pushing left outer flap aside. Since both outer flaps are thus opened, the lower-inner flap is smoothly and quickly folded, causing no bridging at all. No bridging having occurred, the inner flaps or the outer flaps are not distorted, torn, or broken, nor is the flap-folding process interrupted. Further, in the case-assembling method according to the present invention, it suffices to adjust the positioning members 16, 18 to properly position each flat cardboard on the stocker stage. No positional adjustment of the components is required on the flap-folding stage or the case-sealing stage. Therefore, cardboard cases of different sizes can be opened, shaped, and sealed with high efficiency by means of this case-assembling method. Moreover, since the reference lines of the stock stage, the flap-folding stage, and the case-sealing stage are parallel and set apart by predetermined distances, each cardboard case will be automatically positioned correctly on the flap-folding stage and then on the case-sealing stage, only if transported in the X-axis direction for these distances, provided that the case has been correctly positioned on the stock stage. Since the distances need not be much longer than the width of the cardboard case, the case-assembling machine can have a small length as measured in the X-axis direction. In addition, since neither flap-folding mechanism nor the case-sealing mechanism requires any components for positioning the cardboard case, the case-assembling machine is simple, compact and light. Furthermore, the board-opening mechanism, which comprises at least one suction cup and a flap-folding member, can open the flat cardboards reliably. The board-opening mechanism is relatively simple in structure, which also serves to simplify the case-assembling machine further.

Claims: A method of assembling cardboard cases, wherein a flat preassembled cardboard (12) is opened at a stock stage, the bottom inner flaps (F1, F1U, F1L) and the bottom outer flaps (F2, F2L, F2R) of the cardboard (12) are folded at a flap-folding stage, thus forming the cardboard case (12), and a sealing member is applied to the folded outer flaps (F2) at a case-sealing stage, thereby sealing the bottom of the case, characterized in that the method comprises the steps of: lifting an uppermost flat cardboard (12) stacked horizontally on a stocker (14) at the stock stage, with an end panel (12A) of the uppermost flat cardboard (12) being attracted to and held by a suction cup (20) so as to extend opposing edges (F') of the bottom outer flaps (F2) vertically; folding the bottom upper-inner flap (F1U) of the end panel (12A) of the cardboard (12) during lifting of the cardboard (12), while the suction cup continues to hold the end panel (12A); transporting the cardboard (12) from the stock stage to a flap-folding stage for a predetermined distance (L1) after said bottom upper-inner flap (F1U) is folded downward so as to have outer bottom flaps (F2) folded subsequently; folding the bottom lower-inner flap (F1L) and a pair of bottom outer flaps (F2) thereof at the flap-folding stage; transporting the cardboard (12) from the flap-folding stage to a sealing stage for a predetermined distance (L2); and sealing the folded bottom outer flap (F2) of the cardboard (12) at the sealing stage along the vertical opposing edges (F'). The method according to claim 1, wherein said flat cardboard (12) is placed on said stock stage, with its lower edge (13) aligned with a reference line (Y₀) parallel to the transport direction of said cardboard (12), and with the center line of its end panel (12A) aligned with a reference line (X₀) of said stock stage; said flap-folding stage has a reference line (Xfc) parallel to the reference line (X₀) and spaced apart therefrom by a predetermined distance; said case-sealing stage has a reference line (Xsc) parallel to the reference line (X₀) and spaced apart therefrom by a predetermined distance; and the lower-inner flap (F1L) of the cardboard case is folded, and the outer flaps (F2) thereof are then folded, while the cardboard case is placed on the flap-folding stage with its lower edge (13) aligned with the reference line (Y₀) and the center line of its end panel (12A) aligned with the reference line (Xfc). The method according to claim 1 or 2, wherein the suction cup (20) is mounted on a shaft (54) which is slidably supported in a vertical direction on a rotatable arm (22), and a spring means (60) is wound around the shaft (54) to press the suction cup (22) onto the end panel (12A) of the uppermost flat cardboard (12); the step of lifting the uppermost flat cardboard (12) comprises raising said rotatable arm (22) while applying a compression force to the suction cup (20) by means of the spring means (60) such that the compression force applied to the suction cup (20) decreases as the rotatable arm (22) lifts the uppermost flat cardboard (12), and leaving a gap between the uppermost flat cardboard (12) and a following lower case when the uppermost flat cardboard (12) is lifted, thereby allowing air to flow in the gap in an increasing amount as the gap increases during the lifting, to prevent the following flat cardboard (12) from being lifted together with the uppermost cardboard (12). The method according to any one of claims 1 to 3, wherein the cardboard (12) is transported from the stock stage to the flap-folding stage, with its end panel (12A) attracted to and held by the suction cup (20) attached to the rotatable arm (22), by rotating the rotatable arm (22) by a predetermined angle. The method according to any one of claims 1 to 4, wherein; a first plate (170) which is able to move vertically, is made to contact the lower edge (13) of the end panel (12A) of the cardboard case placed on the case-sealing stage, and also the upper sides of the left and right outer flaps (F2L, F2R) of the cardboard (12); a second plate (186), which is able to move horizontally, is moved to contact the upper-inner flap (F1U) and the outer flaps (F2) of the cardboard (12), thereby pushing the cardbord (12) forward until the cardboard (12) abuts on front guides (156, 157), whereby the opposing edges (F') of the left and right outer flaps (F2L, F2R) abut on each other; and the sealing member (42) is applied to the abutting edges (F') of the left and right flaps (F2L, F2R) extending vertically thereby sealing the bottom of the cardboard (12). The method according to any one of claims 1 to 5, wherein the lifting step comprises the step of lifting the uppermost flat cardboard (12) against the weight of a roller (416) which is applied to the side panel (12B) of the flat cardboard (12). The method according to any one of claims 1 to 6, wherein the suction cup (20) and the flap-folding member (26) are combined, thus forming a board-opening unit (228), and this board-opening unit (228) opens each flat cardboard (12) after it has been rotated by 180° around the center of the end panel (12A) of the flat cardboard (12), with the end panel (12A) being attracted to and held by the suction cup (20). A machine for assembling cardboard cases, wherein a flat preassembled cardboard (12) is opened at a stock stage of the machine by means of a board-opening mechanism (28), bottom inner flaps (F1) and bottom outer flaps (F2) of the flat cardboard (12) are folded at a flap-folding stage of the machine to form a cardboard case, by means of a flap-folding mechanism (30), and sealing member (42) is applied to the folded outer flaps (F2) at a case-sealing stage of the machine by means of a case-sealing mechanism (40), thereby sealing the bottom of the cardboard (12), characterized in that the board-opening mechanism (28) comprises: at least one suction cup (20) for holding an end panel (12A) of the uppermost flat cardboard (12) stored horizontally on a stocker (14) while the uppermost flat cardboard (12) is being lifted from the stocker (14); and a flap-folding member (26) which pivots at the time the uppermost flat cardboard (12) is being lifted, thereby folding the upper-inner flap (F1U) downward and opening the outer flaps (F2) above the stocker (14). The machine according to claim 8, wherein the suction cup (20) is mounted on a shaft (54) which is slidably supported in a vertical direction on a rotatable arm (22) and a spring means (60) is wound around the shaft (54) to press the suction cup (20) onto the end panel (12A). The machine according to claim 9, further comprising a stopper mechanism (160) which comprises: a first plate (170) which is able to move vertically, for pressing the lower edge (13) of the end panel (12A) of the cardboard (12) placed on the case-sealing stage, and also the upper sides of the left and right outer flaps (F2L, F2R) of the cardboard (12); and a second plate (186) which is able to move horizontally, for pressing the upper-inner flap (F1U) and the outer flaps (F2) of the cardboard (12) and for pushing the cardboard (12) forward until the flat cardboard (12) abuts on front guides (156, 157), whereby the vertical extending edges (F') of the left and right outer flaps (F2L, F2R) abut on each other. The machine according to claim 9 or 10, further comprising a roller (416) for pressing the side panel (12B) of the uppermost flat cardboard (12) stored horizontally on the stocker (14), and for applying a force on the flat cardboard (12) while the flat cardboard (12) is being lifted from the stocker (14). The machine according to any one of claims 9 to 11, wherein the suction cup (20) and the flap-folding member (26) are combined, thus forming a board-opening unit (228), and this board-opening unit (228) is operable to open each flat cardboard (12) after it has been rotated by 180° around the center of the end panel (12A) of the flat cardboard (12), with the end panel (12A) attracted to and held by the suction cup (20).

Inventors: SAITOH, TAKASHI
Applicants: KABUSHIKI KAISHA FUJI SEISAKUSHO
Application year: 1988
Main classification: B31B5
IPC codes: B31B5