CAPPING DEVICE

Abstract

 Occurrence of "thread overriding" during attachment of a cap to the resin container, which is a phenomenon in which a lower end of a threaded portion of the cap being lowered overrides the first thread and reaches the second thread of a threaded portion of the container, is suppressed. In a case of attaching a cap 8 to a mouth 5C of a container 5 by a capping head 3 while conveying the container 5 at a predetermined operation speed (850 bpm), rotation of a servomotor 12 is started to rotate the cap 8 in a fastening direction in the middle of lowering the capping head 3 (at a point X1), prior to contact between threaded portions of the cap 8 and the container 5. And then, a lower end 8A' of a threaded portion 8A of the cap 8 being lowered while being rotated is brought into contact and smoothly engaged with the threaded portion 5D of the container 5 while rotating, thus enabling suppression of occurrence of "thread overriding". Consequently, prevention of the contamination of an inner face of the cap 8 and the threaded portions 8A, 5D is enabled through suppression of spill of a filling liquid due to impact of the "thread overriding".

Description

BACKGROUND OF THE INVENTION

Field of the Invention

[0001] The present invention relates to a capping device, in particular to a capping device that screws a cap onto a container made of a resin.

Description of the Related Art

[0002] Conventionally, a capping device has been known that is configured to screw a cap onto a container made of a resin (for example, Japanese Patent Laid-Open No. 2002-308380).

[0003] The capping device disclosed in Japanese Patent Laid-Open No. 2002-308380 is provided with a capping head employing a servomotor, and, more specifically, attaches the cap to a mouth of the container as follows. First, a chuck of the capping head holding the cap is lowered by a necessary distance to cover the mouth of the container with the cap in such a way that a lower end of a threaded portion of the cap comes in contact with a threaded portion of the mouth of the container, and then, in this state, the cap is rotated by the servomotor via the chuck, whereby the cap is screwed onto the mouth of the container.

[0004] Incidentally, the capping device disclosed in Japanese Patent Laid-Open No. 2002-308380 lowers the chuck holding the cap to the position of the mouth of the container to bring the lower end of the threaded portion of the cap into contact with the threaded portion of the container, prior to screwing the cap onto the mouth of the container. During this procedure, "thread overriding", a phenomenon in which the threaded portion of the cap overrides the first thread and falls into the second thread of the threaded portion of the container, may occur. This "thread overriding" phenomenon may result in a problem of contamination of an inner face of the cap, the threaded portion of the cap, and the threaded portion of the container caused by spill of a filling liquid in the container due to impact of the overriding.

[0005] In addition, in recent years, for reduction in weight of the container and the cap, the threaded portion of the cap and the threaded portion of the container may not be sufficiently strong. For this reason, the aforementioned "thread overriding" occurring during attachment of the cap leads to a problem of damage of the threaded portion of the cap and the threaded portion of the container.

SUMMARY OF THE INVENTION

[0006] In view of the aforementioned circumstances, a capping device according to the present invention includes: a conveying mechanism that conveys a container; a capping head that has a chuck for holding a cap and attaches the cap to a mouth of the container being conveyed by the conveying mechanism; a servomotor that rotates the chuck of the capping head; an elevating mechanism that raises and lowers the capping head; and a control device that controls driving of the servomotor and the conveying mechanism, in which the capping head holding the cap at the chuck is lowered by the elevating mechanism while rotation of the chuck is started from a stop state by the servomotor, whereby the cap held by the chuck is rotated to be screwed onto the mouth of the container, characterized in that: the capping device includes a speed detection mechanism that detects conveying speed of the container conveyed by the conveying mechanism; and the control device postpones rotation start timing for rotating the servomotor in a case in which the conveying speed of the conveying mechanism detected by the speed detection mechanism is lower than a predetermined operation speed.

[0007]  Such a configuration enables, when the conveying mechanism is operated at a predetermined operation speed, the cap to be lowered while being rotated to thereby cover the container with the cap, through advancement of the rotation start timing for rotating the servomotor. The impact from engagement between the threaded portion of the cap and the threaded portion of the mouth of the container can thus be alleviated. This enables suppression of occurrence of the aforementioned "thread overriding", and in turn prevention of contamination of the inner face and the threaded portion of the cap by the filling liquid spilled from the mouth of the container.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] 

FIG. 1 is a plan view showing an embodiment of the present invention;

FIG. 2 is a vertical cross-sectional view of a main section of FIG. 1;

FIG. 3 is an enlarged view of the main section of FIG. 1;

FIG. 4 is a lateral view showing lowering of the cap in respective positions shown in FIG. 3 and the rotation start timing for the cap; and

FIG. 5 shows a result of an experiment carried out for comparing weights of the filling liquid contaminating the cap after the completion of attachment of the cap, between a conventional capping device and the capping device of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0009] The embodiment illustrated in the drawings is described hereinafter. In FIGS. 1 and 2, 1 denotes a filling system. The filling system 1 is provided with: a rotary filler 2 with a plurality of filling valves (not illustrated) at regular intervals on an outer periphery; and a rotary capping device 4 with a plurality of capping heads 3 at regular intervals on an outer periphery.

[0010] When the filler 2 and the capping device 4 rotate in respective directions indicated by arrows, a feeding wheel (not illustrated) feeds an empty container 5 below each of the filling valves of the filler 2, and a gripper (not illustrated) provided in the filler 2 grips each container 5 while the filling valve fills the container 5 with a predetermined amount of a filling liquid. And then, each container 5 filled with the filling liquid by the filling valve of the filler 2 is released from the gripped state by the gripper of the filler 2 and handed over from the filler 2 to the capping device 4 via an intermediate wheel 6.

[0011] The capping device 4 is provided with: a capping head 3 that holds a cap 8 by means of a chuck 7 in positions at regular intervals in the outer periphery; and an openable and closable gripper 4A that grips a neck portion 5A of the container 5 below each capping head 3.

[0012] The container 5 handed over from the intermediate wheel 6 is filled with a filling liquid 9, of which liquid surface 9A is positioned slightly below a flange portion 5B of the neck portion 5A. The container 5 is conveyed at a predetermined height in a state in which the gripper 4A grips both sides of the neck portion 5A and supports the flange portion 5B formed on the neck portion 5A (see FIG. 2).

[0013] In addition, a threaded portion 5D is formed on an outer periphery of a mouth 5C of the container 5, while a threaded portion 8A to be screwed onto the threaded portion 5D of the container 5 is formed on an inner periphery of the cap 8 (see FIGS. 2 and 4).

[0014] Furthermore, an inner ring 5E is formed between the flange portion 5B and the threaded portion 5D of the container 5, while a detachment ring 8B is provided on a lower end of the cap 8 (see FIGS. 2 and 4).

[0015] As the capping device 4 is rotated in the direction indicated by the arrow, the capping head 3 is lowered by an elevation mechanism 11 from an ascent end to a descent end, while a servomotor 12 provided for each capping head 3 rotates the chuck 7 in a fastening direction at predetermined timing, whereby the cap 8 held by the chuck 7 is lowered to cover the mouth 5C of the container 5 and screwed onto the mouth 5C.

[0016] As described later in detail, in the present embodiment, when the capping device 4 is operated at a speed no lower than a predetermined operation speed, it is configured to start rotation of the servomotor 12 to rotate the cap 8 in the middle of lowering the capping head 3 by the elevation mechanism 11, whereby occurrence of the aforementioned "thread overriding" is suppressed and a lower end 8A' of the threaded portion 8A of the cap 8 is smoothly engaged with the threaded portion 5D of the container 5.

[0017] The container 5 to which the cap 8 has been attached by each capping head 3 of the capping device 4 is then released from the gripped state of the neck portion 5A by the gripper 4A, ejected from the capping device 4 to an ejection conveyor 14 in a state of being gripped by an ejection wheel 13, and then conveyed by the ejection conveyor 14 toward a processing device (not illustrated) on a downstream side (see FIG. 1).

[0018] The capping device 4 is provided with: a rotary member 16 that is rotated clockwise to convey the container 5; the plurality of capping heads 3 arranged at regular intervals in a peripheral direction on an outer periphery of the rotary member 16; the elevation mechanism 11 that raises and lowers the capping head 3 in a predetermined region in a rotational direction of the rotary member 16; the gripper 4A that is arranged below the capping head 3 and grips the neck portion 5A of the container 5; and a control device 17 that controls driving of a driving source of the rotary member 16 and each servomotor 12.

[0019] A conveying mechanism for conveying the container 5 comprises the rotary member 16 and the plurality of grippers 4A provided thereon. As described above, in a state in which the gripper 4A grips the neck portion 5A of the container 5 and supports the flange portion 5B of the container 5, the container 5 is conveyed at a predetermined speed as the rotary member 16 rotates.

[0020] Driving of a motor (not illustrated) as the driving source of the rotary member 16 is controlled by the control device 17. In addition, a speed detection mechanism 18 (encoder) that detects the operation speed of the rotary member 16 is attached to the motor as the driving source of the rotary member 16. The conveying speed of the rotary member 16, i.e., the operation speed of the capping device 4, detected by the speed detection mechanism 18 is input to the control device 17.

[0021] In the present embodiment, the operation speed at which, when the control device 17 rotates the rotary member 16 by means of a motor (not illustrated), the capping heads 3 conveyed by the rotary member 16 attach the caps 8 to 850 containers 5 in total is referred to as the "predetermined operation speed (850 bpm)".

[0022] The control device 17 is configured to control driving of the motor as the driving source of the rotary member 16, to rotate the rotary member 16 at the operation speed (e.g., 750 to 650 bpm) lower than the predetermined operation speed (850 bpm) as necessary.

[0023] The conveying speed (operation speed) at which the rotary member 16 is rotated is detected by the speed detection mechanism 18 and input to the control device 17. The control device 17 is configured to recognize the operation speed of the capping device 4 on the basis of a detection signal being input from the speed detection mechanism 18.

[0024] As shown in FIG. 2, the capping head 3 is provided with: a cylindrical outer cylinder 21 provided on the outer periphery of the rotary member 16 so as to be vertically movable; a spindle 22 provided inside the outer cylinder 21 so as to be rotatable and vertically movable; the chuck 7 that is attached to a lower end of the spindle 22 and detachably holds the cap 8; an inner cylinder 23 that has a spline groove formed on an inner periphery thereof and is connected to an upper end of the spindle 22; a spline shaft 24 spline-fitted to the spline groove on the inner cylinder 23; and the servomotor 12 connected to an upper end of the spline shaft 24.

[0025] The inner cylinder 23, the spindle 22, and the chuck 7 are vertically movable with respect to the outer cylinder 21 and are supported by a stepped portion 21A of the outer cylinder 21. A spring 26 is elastically mounted between a flange portion 22A of the spindle 22 and the aforementioned stepped portion 21A in the outer cylinder 21 facing the flange portion 22A. The repulsive force of the spring 26 biases the spindle 22 and the chuck 7 provided on a lower end thereof constantly downward with respect to the outer cylinder 21.

[0026] A cam follower 27 is attached to an inner side of an upper portion of the outer cylinder 21, and rollably engaged with a cam groove 28A of an annular cam 28 arranged around the outer periphery of the rotary member 16. The elevation mechanism 11 that raises and lowers the capping head 3 comprises the annular cam 28 and the cam follower 27.

[0027] As the rotary member 16 is rotated in the direction indicated by the arrow in FIG. 1, the chuck 7 of the capping head 3 is raised and lowered between the ascent end and the descent end in accordance with the height of the cam groove 28A of the elevation mechanism 11 in a predetermined region within a rotation range, while the chuck 7 is rotated at predetermined timing by the servomotor 12 in the fastening direction at a predetermined cap-closing torque.

[0028] As shown in FIGS. 3 and 4, in a handover position A where the container 5 is handed over from the intermediate wheel 6 to the capping device 4 and a position on an adjacent downstream side thereof, the annular cam 28 of the elevation mechanism 11 is at the upper end, i.e., the top dead center; and then, the height of the annular cam 28 gradually lowers on an adjacent downstream side of the rotary member 16 in the rotational direction and reaches the descent end B, i.e., the bottom dead center (see FIG. 4). An intermediate region between the ascent end and the descent end of the annular cam 28 is defined as a descending region C in which the capping head 3 is lowered by the annular cam 28. Note that, in a region on an adjacent upstream side (not illustrated) of the handover position A, the annular cam 28 is configured to return from the descent end to the ascent end.

[0029] Driving of the servomotor 12 that rotates the chuck 7 holding the cap 8 is controlled by the control device 17. An encoder 31 that outputs a pulse signal, and an ammeter 32 that detects an output current from the servomotor 12 are connected to a rotating part of the servomotor 12. Once the servomotor 12 is rotationally driven, the pulse signal output from the encoder 31 is input to the control device 17, while the current output from the servomotor 12 is detected by the ammeter 32 and a current value thereof is input to the control device 17.

[0030] The control device 17 is configured to be capable of recognizing a rotational angle and a rotational speed of the servomotor 12 on the basis of the pulse signal detected by the encoder 31. In addition, the control device 17 is configured to detect the cap-closing torque applied to the chuck 7 on the basis of the current value detected by the ammeter 32 since the start of rotational driving of the servomotor 12, and to record the cap-closing torque in chronological order.

[0031] As described above, the present embodiment is characterized in that the rotation start timing of the servomotor 12 is changed between: the case of operating the rotary member 16 of the capping device 4 at a speed no lower than the predetermined operation speed (850 bpm); and the case of operating the rotary member 16 at a speed lower than the predetermined operation speed.

[0032] More specifically, the control device 17 is configured to, when the capping head 3 and the chuck 7 are lowered by the elevation mechanism 11, control the rotation start timing of the servomotor 12 as follows.

[0033] In the case of operating the rotary member 16 at a speed no lower than the predetermined operation speed (850 bpm), the control device 17 recognizes that the rotary member 16 is operated at the predetermined operation speed on the basis of the input signal from the speed detection mechanism 18, and starts rotating the servomotor 12 when the chuck 7 (cap 8) is lowered by the annular cam 28 of the elevation mechanism 11 to a point X1 where the capping head 3 is at a middle position in the descending region C (see FIGS. 3 and 4).

[0034] Consequently, while the capping head 3 is lowered by the elevation mechanism 11 from the point X1 to the descent end B, the cap 8 is rotated in the fastening direction, whereby the lower end 8A' of the threaded portion 8A of the cap 8 being rotated is smoothly brought into contact with the threaded portion 5D of the container 5 from above, such that the threaded portion 8A and the threaded portion 5D are engaged.

[0035] After the threaded portion 8A and the threaded portion 5D are thus smoothly engaged, the cap 8 in a state of being pressed downward by the spring 26 is constantly rotated by the servomotor 12 in the fastening direction, whereby the threaded portion 8A of the cap 8 is screwed onto the threaded portion 5D of the container 5, thus completing attachment of the cap 8.

[0036] In other words, in the present embodiment, in the case of operating the rotary member 16 at a speed no lower than the predetermined operation speed (850 bpm), at the point X1 where the lower end 8A' of the threaded portion 8A of the cap 8 is not yet in contact with the threaded portion 5D of the container 5, rotation of the servomotor 12 is started from a stop state.

[0037] Consequently, the lower end 8A' of the threaded portion 8A of the cap 8 is smoothly engaged with the threaded portion 5D of the container 5, thus enabling effective suppression of occurrence of the aforementioned "thread overriding".

[0038] On the other hand, in the state in which the rotary member 16 is operated at the predetermined operation speed (850 bpm), some sort of trouble may occur in a processing device (not illustrated) installed on a downstream side of the ejection conveyor 14. In such a case, the rotary member 16 is operated at an operation speed (e.g., 600 bpm or 750 bpm) lower than the predetermined operation speed. At that time, the control device 17 recognizes that the operation speed is lower than the predetermined operation speed, from the speed detection mechanism 18.

[0039] The control device 17 keeps the servomotor 12 in the stop state until the capping head 3 is lowered to the descent end B by the annular cam 28 of the elevation mechanism 11, and then, at the point X2 where the capping head 3 has been lowered to the descent end B by the elevation mechanism 11, starts rotating the servomotor 12. In other words, at the point X2 where the cap 8 has been lowered to the descent end B to bring the lower end 8A' of the threaded portion 8A of the cap 8 into contact with the threaded portion 5D of the container 5, the control device 17 starts rotating the servomotor 12 to rotate the cap 8 in the fastening direction, thus attaching the cap 8 onto the mouth 5C of the container 5 (see FIGS. 3 and 4).

[0040] As described above, in the present embodiment, in the case of operating the rotary member 16 of the capping device 4 at the predetermined operation speed (850 bpm), rotation of the servomotor 12 is started at the point X1 where the capping head 3 has been lowered by the elevation mechanism 11 to a middle position in the descending region C in which the capping head 3 is being lowered. As a result, as the chuck 7 is being lowered to the descent end B, the cap 8 is rotated in the fastening direction via the chuck 7, whereby the impact caused by the lower end 8A' of the threaded portion 8A of the cap 8 coming into contact with the threaded portion 5D of the container 5 from above is alleviated, thus enabling smooth engagement between the threaded portion 8A and the threaded portion 5D.

[0041] Eventually, effective suppression of occurrence of the "thread overriding" during attachment of the cap 8 to the container 5 is enabled. And in turn, prevention of the contamination of the inner face of the cap 8 and the threaded portions 8A, 5D caused by spill of the filling liquid 9 in the container 5 due to impact of the "thread overriding" is enabled.

[0042] In addition, during operation of the rotary member 16 at the predetermined operation speed (850 bpm), the operation speed of the rotary member 16 is switched to the operation speed (e.g., 650 bpm or 750 bpm) lower than the predetermined operation speed, the rotation start timing of the servomotor 12 can be changed according to the operation speed by the control device 17.

[0043] Given this, when a trouble occurs in a processing device on the downstream side and the operation speed of the rotary member 16 is switched from the predetermined operation speed to a lower operation speed, the rotation start timing of the servomotor 12 can be controlled accordingly at appropriate timing.

[0044] FIG. 5 shows a result of an experiment of comparing contamination states of the cap 8 after the completion of attachment of the cap 8, between a case of using the conventional capping device and a case of using the capping device 4 of the present embodiment (present invention). Note that, in the experiment, the comparison was made between results obtained after the completion of attachment of the cap 8 according to the prior art and according to the present embodiment, without conveying the container 5, i.e., in a state in which the container 5 is stationary.

[0045] As can be seen from the data in FIG. 5, with the conventional capping device configured to rotate the cap 8 after lowering the cap 8 to the descent end to bring the lower end of the threaded portion of the cap 8 into contact with the threaded portion of the container 5, the maximum amount of the filling liquid (liquid product) contaminating the cap 8 and the like is 51 mg.

[0046] On the contrary, in the case of the present embodiment configured to rotate the cap 8 in the middle of lowering in the descending region C for attaching the cap 8 to the container 5, the amount of the filling liquid (liquid product) contaminating the cap 8 and the like is 1 mg. As is obvious from the result of the experiment shown in FIG. 5, it is possible to presume that the capping device 4 according to the present embodiment enables, through suppression of the "thread overriding" phenomenon, effective suppression of contamination of the cap 8 and the like due to spill caused by the impact of the "thread overriding", in comparison to the conventional capping device.

[0047] Note that, although the predetermined operation speed is defined as 850 bpm in the aforementioned embodiment, the predetermined operation speed is not limited thereto and may also be 900 bpm or higher, for example 1000 bpm. In this case as well, it is configured to rotate the cap 8 in the middle of lowering in the descending region C for attaching the cap 8 to the container 5.

Reference Signs List

[0048] 

3 Capping head

4 Capping device

5 Container

5C Mouth

5D Threaded portion

7 Chuck

8 Cap

8A Threaded portion

8A' Lower end of threaded portion

9 Filling liquid

11 Elevation mechanism

12 Servomotor

16 Control device

18 Speed detection mechanism

Claims

1. A capping device comprising: a conveying mechanism that conveys a container; a capping head that has a chuck for holding a cap and attaches the cap to a mouth of the container being conveyed by the conveying mechanism; a servomotor that rotates the chuck of the capping head; an elevating mechanism that raises and lowers the capping head; and a control device that controls driving of the servomotor and the conveying mechanism,
in which the capping head holding the cap at the chuck is lowered by the elevating mechanism while rotation of the chuck is started from a stop state by the servomotor, whereby the cap held by the chuck is rotated to be screwed onto the mouth of the container,
characterized in that:

the capping device comprises a speed detection mechanism that detects conveying speed of the container conveyed by the conveying mechanism; and

the control device postpones rotation start timing for rotating the servomotor in a case in which the conveying speed of the conveying mechanism detected by the speed detection mechanism is lower than a predetermined operation speed.

2. The capping device according to claim 1, characterized in that, when the conveying mechanism conveys the container at the predetermined operation speed, the control device starts rotating the servomotor at a moment at which the chuck of the capping head is being lowered by the elevating mechanism, and a threaded portion of the cap held by the chuck is not yet in contact with a threaded portion of the container.

3. The capping device according to claim 2, characterized in that, when the conveying mechanism conveys the container at an operation speed lower than the predetermined operation speed, the control device starts rotating the servomotor at a moment at which the chuck of the capping head has been lowered by the elevating mechanism, and the threaded portion of the cap held by the chuck is in contact with the threaded portion of the container.

Drawing