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
[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.
[0006] JP 2000 168892 A discloses a capping device in accordance with the preamble of claim 1 and further
a plurality of container grips and capping heads respectively above them provided
at equal intervals in a circumferential direction on a rotating body rotated and driven
by means of a motor. Spindles provided with the capping heads are respectively connected
with servo motors working independently from the above-described motor and are rotated.
Cam followers are respectively fitted on each of the spindles and elevation and lowering
is performed by hooking these cam followers in cam channels of fixed cylindrical cams
and moving them. A speed detecting means and an angle detecting means are provided
on the rotating body and by these detected signals, a control means controls rotation
of each servo motor. Rotation can be started before the capping head reaches the lowest
position and it can cope with speeding-up.
SUMMARY OF THE INVENTION
[0007] According to the present invention, there is provided a capping device as specified
in claim 1.
[0008] 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
[0009]
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
[0010] 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.
[0011] 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.
[0012] 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.
[0013] 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).
[0014] 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).
[0015] 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).
[0016] 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.
[0017] 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.
[0018] 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).
[0019] 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.
[0020] 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.
[0021] 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.
[0022] 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)".
[0023] 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.
[0024] 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.
[0025] 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.
[0026] 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.
[0027] 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.
[0028] 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.
[0029] 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.
[0030] 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.
[0031] 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.
[0032] 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.
[0033] 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.
[0034] 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).
[0035] 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.
[0036] 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.
[0037] 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.
[0038] 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".
[0039] 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.
[0040] 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).
[0041] 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.
[0042] 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.
[0043] 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.
[0044] 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.
[0045] 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.
[0046] 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.
[0047] 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.
[0048] 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
[0049]
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