JPH10324311A - Method and device for opening rectangular prismatic case - Google Patents

Abstract

PROBLEM TO BE SOLVED: To automatic the work for forming a paper box in a flat folded and crushed state into a three-dimensional opened shape, and to prevent the paper box in the opened shape from returning to the original folded and crushed shape. SOLUTION: A bottom surface C1 of a paper box C is kept in a fixed state by a loading table provided with upward suction cups, and an upper surface C2 of the paper box C is moved in a circle above the bottom surface C1 while sucked by an elevating/lowering plate provided with the downward suction cups. The paper box C is in an opened shape thereby, and further deformed into a flattened-out shape passing through the opened shape, and then, returned to the opened shape again. The folding habit in the original crushed shape is eliminated thereby.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for opening a rectangular cylindrical case formed of paper, plastic sheet or the like from a flat folded shape to a three-dimensional open shape. .

[0002]

2. Description of the Related Art A rectangular cylindrical case C as shown in FIG. The quadrangular cylindrical case C has four sides forming a main body as a case-shaped body connected endlessly, and flaps F for closing the lid are provided at both ends. Then, as shown in FIG. 10, this type of case C initially has one set of diagonal parts folded in two, and the other set of diagonal parts is flattened out, so that the whole is formed into a flat folded shape. Have been prepared.

[0003] Therefore, in the above box packing line or the like, it is necessary to automate the operation of converting the case C from the folded shape in FIG. 10 to the open shape in FIG. Conventionally,
As an apparatus for automating this work, Japanese Patent Application Laid-Open No. H8-3
The technology described in JP-A-01228 is known. In this technique, a flat spatula is inserted from both ends of a case C in a collapsed shape, and an opening action is generated from the inside of the case as if the spatula is prying open.

[0004] In addition, there is also known an apparatus in which a case C in a collapsed shape is placed flat, and one side facing upward is sucked up by a suction cup and lifted upward, so that an opening action is generated in the case C. ing.

[0005]

Even after the case C is formed into an open shape, the case C has a habit of being folded at the time of initial preparation. Therefore, depending on the material and thickness of the case C, the fold structure, the size of the case C, etc., when the above-described opening action by the spatula or the suction cup is released, the case C is completely turned to the original folded shape. Or, he returned halfway.

Therefore, in order to ensure that the case C is formed in the form of an opening so as not to adversely affect the subsequent boxing line or the like, it is necessary to assist the worker in performing the three-dimensional opening work and to make the structure complicated and large. An opening force assisting mechanism was required. The present invention has been made in view of the above circumstances, and can completely automate the work of converting a rectangular cylindrical case from a flat folded shape to a three-dimensional opening shape,
It is an object of the present invention to provide an opening method and an opening device for a square cylindrical case that can achieve labor saving, high work efficiency, and the like, and can simplify the structure of the device.

[0007]

According to the present invention, the following technical measures have been taken in order to achieve the above object. That is, in the method of opening a rectangular cylindrical case according to the present invention, first, the case in the folded shape is immovably held with one of the predetermined surfaces as a reference side surface. Then, the bent side extending to one side of the reference side surface is moved toward the facing position of the reference side surface. Thereby, the two side surfaces on both sides of the reference side surface are bent.

[0008] Next, the side face opposed to the reference side face is
Instead of stopping at the position facing the reference side face as it is, the sheet is once sent to the other side after passing the position facing the reference side by a predetermined amount. Thereafter, the facing side surface is returned to a position facing the reference side surface again. By doing so, the folding habit and the like when the case is folded at the initial preparation stage is removed. Therefore, even if the function of closing the opening is released from the case after the opening, the opening is securely held.

On the other hand, in the opening device for a rectangular cylindrical case according to the present invention, a case holding portion for holding a predetermined one side of a case of a folded shape as a reference side surface when performing the opening method according to the present invention; And opening operation means for bending two sides on both sides of the reference side while moving the bent side extending to one side of the reference side toward the position facing the reference side. I have.

[0010] As the opening operation means, a suction portion capable of holding the outer surface of a side surface opposite to the reference side surface by suction with respect to the folded case held by the case holding portion; It is possible to adopt a configuration having a moving mechanism for circularly moving around the reference side surface. Further, as another opening operation means, with respect to the case of the folded shape held by the case holding portion, the bent side extending to one side of the reference side face is directed to a position facing the reference side face. It is also possible to adopt a configuration having an extruding portion to be pressed and a stopper portion that can be engaged with the bent side on the other side of the reference side surface.

The structure having the push-out portion and the abutment portion may be provided in an auxiliary position with respect to the structure having the suction cup and the moving mechanism thereof.
In this case, it is preferable that the push-out portion and the abutment stop can be retracted from the corresponding bent sides when the opposite side surface of the case first reaches the position facing the reference side surface of the case. It is.

[0012] The opening operation means having these various configurations, after once sending out the side surface disposed opposite to the reference side surface of the case to the other side which has passed a predetermined distance from the position facing the reference side surface, The operation of returning the facing side surface to the position facing the reference side surface is performed again.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIGS. 1 and 2 show an opening device 1 according to the present invention for opening the flat cylindrical case C shown in FIG. 10 into the three-dimensional opening form shown in FIG. 1 is an explanatory view of the operation from the side (a direction in which both ends of the case C can be seen), and FIG. 2 is a partially crushed front view showing the state in which the case C is omitted from FIG. is there.

The case C has a height of 60 mm and a width of 15 mm.
The length was 0 mm and the length was 330 mm. In FIG.
The opening device 1 includes a case holding portion 3 that receives the case C in a folded shape and holds the case C immovably, and an operation for opening the case C held by the case holding portion 3. And an opening operation means 4 to be added.

The case holding portion 3 is provided above the bottom plate portion 6 of the apparatus main body frame 5 with a receiving table 8 provided substantially horizontally through a support 7 or the like. In this case, a plurality of suction cups 9 are embedded. Each suction cup 9 is provided upward, and the opening edge thereof is aligned along the upper surface of the receiving table 8 so as to be flush or slightly sunk.

All the suction cups 9 are connected to a separately provided air supply / discharge device (not shown) so that the suction state and the stop state can be simultaneously switched as required. . Thereby, the case C can be held immovably with one predetermined surface of the case C as a reference side surface (hereinafter, referred to as a lower side surface C1 in the state shown in FIG. 9).

The receiving table 8 is made of a stainless steel plate in order to improve the sliding of the case C when carrying in and out. The opening operation means 4 will be described separately from a main function part 12 and an auxiliary function part 13 in terms of its function.
The main function section 12 has a suction section 14 provided above the case holding section 3 and a moving mechanism section 15 for moving the suction section 14 in an arc shape in the elevating direction with respect to the receiving table 8.

The suction unit 14 is formed by vertically lowering a plurality of suction cups 17 at predetermined intervals with respect to an elevating substrate 16 substantially parallel to the receiving table 8 of the case holding unit 3. The lower opening edge of each suction cup 17 is flush with the surface. All the suction cups 17 are connected to a separately provided air supply / discharge device (not shown), so that the suction state and the stop state can be switched simultaneously as needed.
In this case, the supply / discharge device is connected to the case holder 3 described above, for example.
When the suction cups 9 and 17 are connected in parallel with each other in a manner common to the suction cups 9 connected to the suction cups 9, when the suction / stop of the suction cups 9 of the case holding section 3 is switched, the suction section 14 is switched. Of the suction cup 17 can be brought into the suction state or the stopped state in synchronization therewith.

The moving mechanism 15 holds the elevating board 16 substantially horizontally between the left and right side plates 18 of the apparatus body frame 5 via two sets of crankshafts 19, crank arms 20, and hanger brackets 21, respectively. And, as shown in FIG. 3, the transmission shaft 2
Rotational drive from the motor 23 is transmitted via the motor 2.

Therefore, when the motor 23 is operated, the crank arm 20 swings about the crankshaft 19, and the elevating board 16 moves in an arc with the swing. At this time, the lifting board 16 is attached to the hanger bracket 21.
Is held so as to be able to swing freely with respect to the crank arm 20, so that the horizontal state is always maintained during the arc movement.

A servomotor is used as the motor 23, and toothed belts or the like are used as transmission means 24, 25 for transmitting the power from the motor 23 to the transmission shaft 22 and the crankshaft 19. Then, as shown in FIG. 2, an angle detector 26 capable of detecting the rotation amount of one of the crankshafts 19 and the like is provided. Therefore, the rotation control by the motor 23 can be performed with high accuracy, and accordingly, the vertical movement range of the suction unit 14 can be controlled with high accuracy.

In the main function unit 12 having such a configuration,
The suction unit 14 is kept up and waiting until the folded case C is carried into the case holding unit 3, and after the case C is held by the case holding unit 3, the side surface opposed to the reference side surface C 1. (The upper side C in the state shown in FIG. 9
2, which is hereinafter referred to as an opposing side surface) is adsorbed and held by the adsorbing portion 14, and then the opposing side surface C2 is circularly moved with the adsorbing portion 14 by the moving mechanism 15 around the reference side surface C1. A series of operations are possible.

Therefore, in the case C, as shown in FIGS. 1A to 1C, the bent side extending to one side (right side in the drawing) of the reference side surface C1 moves to a position facing the reference side surface C1. While moving toward the two sides C on both sides of the reference side C1
3 and C4 (see FIG. 9) are bent and raised. Further, in the main function unit 12, even after reaching the stage of FIG.
As shown in FIG. 1 (d), the opposite side surface C2 is once sent to the other side, which has passed a predetermined distance from the position facing the reference side surface C1, and then the opposite side surface C2 is again shown in FIG.
The position is returned to the position facing the reference side surface C1 as shown in FIG.

Therefore, the habit of the case C that has been folded in the initial preparation stage is removed when the case C is finally opened, and from this state the suction cup 9 and the suction cup 9 of the case holder 3 are removed. Even when the suction cup 17 of the suction section 14 is in the suction stop state, the open form of the case C is securely held. On the other hand, the auxiliary function unit 13 includes the main function unit 12.
And the case holding section 3 to complete the above-mentioned opening operation without being affected by the material and size of the case C or other disturbances, etc. (to ensure that there is no failure). The main function unit 1
2 and an abutment portion 29 provided in the case holding portion 3.

As shown in FIG. 4, the push-out portion 28 has a vertically long bar-shaped upper locking piece 30 provided to the lifting board 16 provided in the main function portion 12. A pair of upper locking pieces 30 are provided on both sides in the longitudinal direction of the lifting board 16. In addition, each of these upper locking pieces 30
When the lifting board 16 is moved to the lower position by the operation of the moving mechanism section 15, the lower end thereof is positioned on one side of the reference side face C1 with respect to the folded case C held by the case holding section 3. And can be engaged with the bent side extending out (see FIG. 1A).

Therefore, the push-out portion 28 is multiplied by the movement mechanism portion 15 raising the elevating substrate 16 from the lowered state by the circular movement, thereby causing the upper locking piece 30 to move together with the circular arc, and the lower end portion thereof. Then, the bent side of the case C engaged by the step S1 is pushed out toward the facing position of the reference side surface C1. As is apparent from the above description, the push-out portion 28 does not use only the upper locking piece 30 as a component, but uses the moving mechanism portion 15 of the main function portion 12 as a part of the configuration. Will be.

Here, the opening operation means 4 includes:
For example, the auxiliary function unit 13 without the main function unit 12
The case C can be opened by itself. Therefore, in this case, it is necessary to provide the pushing mechanism 28 with the moving mechanism section 15 independently.
With respect to such an extruded portion 28,
Has a vertically long rod-shaped lower locking piece 32 provided for the receiving table 3 as shown in FIG.

A pair of the lower locking pieces 32 are provided on both sides in the longitudinal direction of the receiving table 3. The upper end of each of the lower locking pieces 32 protrudes from the upper surface of the receiving table 3, and the other of the reference side surface C 1 and the folded side case C held by the case holding section 3. It can be engaged with the side (the one that does not extend) of the bent side (see FIG. 1A).

Accordingly, the abutment stop portion 29 prevents the case C from escaping when the bent side on the extension side of the case C is pushed out by the pushing portion 28 as described above. By the way, the extruded part 2
8 and the abutment portion 29, when the foldable case C is formed into the open shape shown in FIG. 1C, that is, when the opposing side surface C2 first reaches the position facing the reference side surface C1. After that, when the state is further shifted to the shaved shape shown in FIG. 1D, the upper locking pieces 30 and the lower locking pieces 32
Are retracted from the corresponding bent sides.

The retracting structure provided on the push-out portion 28
It looks like this: That is, as shown in FIG. 4, the upper locking piece 30 swings in the direction approaching and separating from the lifting board 16 by the first pivot 35 rotatably held via the bracket 34 on the lifting board 16. It is freely held. A cam lever 36 extending radially outward of the first pivot 35 is attached to the other end of the first pivot 35. The cam lever 36 has a transmission piece 36a protruding upward at its extended end.

The upper locking piece 30 is normally kept close to the lifting board 16 under the tensile force of the spring 37. On the other hand, as shown in FIG. 3, in the moving mechanism 15, the suspension shaft 38 fixed to the swinging end of the crank arm 20 has penetrated the hanger bracket 21 of the lifting board 16 in a rotatable manner. , And further project inward of the lifting board 16. A kick piece 39 is provided on the protruding end side of the suspension shaft 38 as shown in FIG.

The kick piece 39 is provided with a slide member 40 such as a cam follower. The slide member 40 starts abutting on the transmission piece 36a of the cam lever 36 when the crank arm 20 rotates to position the lift board 16 at the uppermost position in the arc movement range. When the crank arm 20 continues to rotate, the transmission piece 36a is pushed.

From the above, when the case C in the folded shape is shifted from the open shape shown in FIG. 1C to the shaved shape shown in FIG. Through the swing of the cam lever 36 and the rotation of the first pivot 35 by the kick piece 39 (slider member 40), the upper locking piece 30 swings in the direction away from the lifting board 16 against the spring 37. Will do. Therefore, no undesired mutual interference occurs between the upper locking piece 30 and the case C.

The speed at which the upper locking piece 30 swings in the direction away from the lifting board 16 is controlled so as to be synchronized with the swing speed of the cam lever 36 by the kick piece 39.
The upper locking piece 30 avoids interference with the case C,
The action of pushing out the bent side on the extension side of the case C can be continued. The retracting structure provided on the contact stopper 29 is as follows.

That is, as shown in FIG. 2, brackets 42 are fixed to the left and right side plates 18 of the apparatus main body frame 5, and the brackets 42 hold the second pivots 43 rotatably along the bottom plate 6. Have been. And FIG.
As shown in FIG. 3, the lower locking piece 32 is attached to the second pivot 43 via a mounting lever 44 extending outward in the radial direction.
Is held. Therefore, the lower locking piece 32 is swingable in a direction approaching / separating from the receiving table 8.

A swing input lever 45 extending in the same direction as the mounting lever 44 is provided at one end of the second pivot 43.
The swing input lever 45 is vertically swingable by a driving tool 46 such as a fluid pressure cylinder. The driving tool 46 is configured to swing the swing input lever 45 in a direction to push down when the moving mechanism unit 15 positions the lifting board 16 at the uppermost position in the circular movement range.

As described above, when the case C in the folded shape is shifted from the open shape shown in FIG. 1C to the shaver shape shown in FIG. 1D, the driving tool 46 is actuated and shakes. Motion input lever 45, second pivot 43, mounting lever 4
4, the lower locking piece 32 swings in a direction away from the receiving table 8. Therefore, undesired mutual interference does not occur between the lower locking piece 32 and the case C.

The speed at which the lower locking piece 32 swings away from the receiving table 8 can be adjusted by adjusting the operating speed of the driving tool 46. In addition, while preventing interference with the case C, it is possible to continue the action of engaging with the bent side of the case C that does not extend. In the opening device 1 having such a configuration, an opening method according to the present invention will be described based on a series of procedures until the case C in the folded shape is opened to the opening shape.

At first, the suction unit 14 is on standby until the folded case C is carried into the case holding unit 3. Then, when the case C is carried into the case holding unit 3 in a predetermined arrangement, the suction cup 9 provided on the receiving table 8 is brought into a suction state, and the reference side surface C1 of the case C is held immovably. Next, when the moving mechanism section 15 of the opening operation means 4 operates to lower the suction section 14, the suction cup 17 provided on the elevating substrate 16 of the suction section 14 is brought into the suction state. Therefore, the suction side 17 causes the opposite side surface C of the case C to move.
2 is adsorbed (see FIG. 1A).

Next, the moving mechanism 15 raises the suction unit 14. Accordingly, with this, the bent side extending to one side of the reference side surface C1 in the case C corresponds to the reference side surface C1.
Move in an arc toward the confronting position (see FIG. 1).
(B)). Eventually, the opposing side surface C2 reaches the position opposing the reference side surface C1, and the two side surfaces C3, C4 on both sides of the reference side surface C1 are bent and raised, whereby the case C once becomes an open shape (FIG. c)).

However, the moving mechanism section 15 continues to operate, and sends the case C until the opposing side surface C2 passes the position facing the reference side surface C1 by a predetermined amount and reaches the other side.
Therefore, the case C is once in the shape of a whisker (FIG. 1).
(D)). At the same time, the pushing portion 28 of the auxiliary function portion 13 in the opening operation means 4 (the upper locking piece 3
0) and the abutment stop 29 (the lower locking piece 32) respectively perform a retreat operation.

Thereafter, the moving mechanism 15 returns the opposing side surface C2 of the case C to the position opposing the reference side surface C1 again to form a regular opening shape (see FIG. 1C). Then, the case holding unit 3 and the suction unit 14 of the opening operation means 4
However, the suction states of the suction cups 9 and 17 are stopped. Thus, one cycle of the opening operation is completed. Such an opening device 1 is, for example, as shown in FIGS. 6 to 8, a rack device 50 for stocking a case C in a folded shape in a stacked manner, and a case C after the opening shape is directed to a predetermined process. Can be adopted as a part of the line configuration in combination with the conveyor device 51 or the like that transports the paper.

In the illustrated embodiment, the apparatus main body frame 5 is separated into a fixed base 53 and a movable frame 55 which is horizontally movable via a slider 54 above the fixed base 53. There is. The receiving table 8 of the case holder 3 is fixed to the fixed base 53 (that is, the fixed base 53 corresponds to the bottom plate 6 shown in FIG. 2), and the opening operation means is provided. 4 is provided for the moving frame portion 55 (that is, the moving frame portion 5
5 corresponds to the left and right side plates 18 shown in FIG. 2).

The horizontal movement of the moving frame portion 55 is performed by opening operation means between the upper portion of the case holding portion 3 and the upper position of the conveyor device 51 disposed on the downstream side (left side in FIG. 6) in the conveying direction. 4 is made to reciprocate. When the opening operation means 4 is positioned above the case holding portion 3, the movable frame portion 55 protrudes upward from the rack device 50 disposed on the upstream side in the transport direction (right side in FIG. 6). An extension frame portion 57 is provided.

The extension frame portion 57 is provided with a take-out device 6 having a lift plate 59 having a plurality of suction cups 58 directed downward, which can be raised and lowered by a suitable lift mechanism 60 such as a fluid pressure cylinder.
1 is provided. Note that the horizontal movement of the moving frame portion 55 along the slider 54 is performed by a link mechanism 64 using the motor 63 as a drive source.

The conveyor device 51 is provided with individual partitioning pieces 66 at a predetermined pitch for holding the open form of the case C, and has an upper guide rail 67 for shape keeping. The rack device 50 is provided with an appropriate elevator mechanism 68 in order to always keep the highest level of the stacked cases C constant.

With such a configuration, the rack device 5
The case C in a collapsed shape held at a constant level at 0 is moved by a combination of the lifting / lowering of the lifting / lowering plate 59 and the suction / stop switching of the suction cup 58 by the unloading device 61 and the horizontal movement by the moving frame portion 55. 3 will be automatically supplied. At this time, the abutment portion 29 provided in the auxiliary function portion 13 of the opening operation means 4 is useful for physically positioning the case C and is useful.

The case C in the form of being folded into the case holding portion 3
Is automatically supplied, the moving frame portion 55 returns to the original position and ends the one-cycle operation. Then, after the opening device 1 makes the case C on the case holding portion 3 into an opening shape, the moving frame portion 55 performs the horizontal movement again for the automatic supply. While the suction cup 9 provided is stopped in the suction state, the suction section 1 of the opening operation means 4 is stopped.
The suction cups 17 provided in 4 are controlled so as to continue the suction state of the case C having the open shape.

Therefore, the case C after the opening is sent as it is above the carry-in position of the conveyor device 50. Here, the suction cup 17 of the opening operation means 4 is switched to the suction stop state, and the case C is automatically carried out to the conveyor device 50. By the way, the present invention is not limited to the above embodiment. For example, when the size of the reference side surface C1 and the size of the opposite side surface C2 of the case C are different, the size of the receiving table 8 of the case holding unit 3 and the size of the elevating substrate 16 of the suction unit 14 in the opening operation unit 4 are determined. What is necessary is just to make it different according to this. Of course, the number of used suction cups 9, 17 and the arrangement state thereof can be changed as appropriate.

When the sides C3 and C4 adjacent to the reference side C1 are different in size as the case C, the crank arm 20 of the moving mechanism 15 in the opening operation means 4 is set to a corresponding length. You can change it. Case C
(Including hardness and thickness of the material) and size
The shape and the like are not limited at all. Therefore, it is of course possible to use synthetic paper or ramie paper.

However, when the material and the like of the case C are changed in this way, the strength of the fold when folded in the preparatory stage may change in various ways. Therefore, it may be necessary to change the inclination angle (degree of shading) for forming the shaving shape shown in FIG. Therefore, in the moving mechanism unit 15 of the opening operation means 4, the detection set value of the angle detector 26 may be changed, and the operation amount of the motor 23 may be controlled.
Alternatively, it is possible to keep in mind the control that does not require the deformation to the whisker form shown in FIG.

The suction cup 9 used in the case holding section 3 and the suction cup 17 used in the suction section 14 of the opening operation means 4 are provided with a breathable member such as a sponge or the like to provide a suction case capable of generating a spread suction action in a planar manner. It is possible to substitute. Further, when the case material has a smooth glossy surface such as plastic, for example, the suction cups 9 and 17 may not be connected to the air supply / discharge device.

In the above embodiment, the motors, fluid pressure cylinders, various mechanisms, etc., which are shown as examples of the apparatus configuration, can of course be changed among conventionally known various apparatuses, mechanisms, etc.

[0054]

As is apparent from the above description, according to the method and apparatus for opening a square tubular case according to the present invention,
Even if the bent side is long, the material is thick, and the material is hard, even if it is a rectangular cylindrical case, it will be possible to reliably perform the work of changing from a flat folded shape to a three-dimensional open shape, Complete automation can be achieved, and labor saving and work efficiency can be improved. Further, the structure of the device can be simplified.

[Brief description of the drawings]

FIG. 1 is an operation explanatory view showing a side view of an opening device according to the present invention.

FIG. 2 is a partially crushed front view showing a case omitted from FIG. 1 (c).

FIG. 3 is a perspective view showing a moving mechanism section included in a main function section of the opening operation means.

FIG. 4 is a perspective view showing a push-out portion of the auxiliary function portion of the opening operation means.

FIG. 5 is a perspective view showing an abutment portion of the auxiliary function portion of the opening operation means.

FIG. 6 is a schematic side view showing an example in which an opening device is employed as a part of a line configuration.

FIG. 7 is a view taken along line AA of FIG. 6;

FIG. 8 is an operation explanatory diagram from FIG. 6;

FIG. 9 is a perspective view showing a case in the form of an opening.

FIG. 10 is a plan view showing a case in a folded shape.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Opening device 3 Case holding part 4 Opening operation means 12 Main function part 13 Auxiliary function part 14 Suction part 15 Moving mechanism part 28 Extruding part 29 Contact stop part C Square cylindrical case C1 Reference side surface C2 Opposing side surface

Claims (5)

[Claims] 1. An opening method for opening a rectangular cylindrical case (C) from a flat folded shape to a three-dimensional opening shape, wherein a predetermined surface of the folded shape case (C) is set as a reference side surface (C1). While holding and moving the bent side extending to one side of the reference side surface (C1) toward a position facing the reference side surface (C1), the two side surfaces (C3, C3) on both sides of the reference side surface (C1) C4) is bent and raised, and the side surface (C2) arranged opposite to the reference side surface (C1) is temporarily changed to the reference side surface (C1).
After being sent out to the other side, which has passed by a predetermined distance from the position facing the object, the opposite side surface (C2) is renewed to the reference side surface (C
A method of opening a rectangular cylindrical case, wherein the method is to return to a position facing 1). 2. An opening device for opening a rectangular cylindrical case (C) from a flat folded shape to a three-dimensional opening shape, wherein a predetermined surface of the folded shape case (C) is set as a reference side surface (C1). The case holding portion (3) for holding, and the reference while moving the bent side of the case (C) extending to one side of the reference side (C1) toward the position facing the reference side (C1). Opening operation means (4) for bending two side surfaces (C3, C4) on both sides of the side surface (C1). The opening operation means (4) is provided on the reference side surface (C1) of the case (C). After the side surface (C2) that is opposed to the reference side surface (C1) is once sent out to the other side after a predetermined distance from the position facing the reference side surface (C1), the opposed side surface (C2) is again opposed to the reference side surface (C1). The operation to return to the position is possible. An opening device for a rectangular cylindrical case. 3. A side face (C) arranged opposite to a reference side face (C1) of the folded case (C) held by the case holding portion (3).
2) a suction portion (14) capable of holding the outer surface by suction, and a moving mechanism (15) for circularly moving the suction portion (14) around the reference side surface (C1). The opening device for a square tubular case according to claim 2. 4. The opening operation means (4) extends to one side of a reference side surface (C1) of the folded case (C) held by the case holding portion (3). An extruding part (28) for pressing the folded side of the reference side toward the position facing the reference side surface (C1), and a contact stop part (29) capable of engaging with the other side of the reference side surface (C1). The opening device for a square tubular case according to claim 2 or 3, wherein the opening device has: 5. The push-out portion (28) and the abutment portion (29) move when the opposite side surface (C2) of the case (C) first reaches the position facing the reference side surface (C1). 5. The opening device for a square tubular case according to claim 4, wherein the opening device can be retracted from a corresponding bent side.