GB2297074A

GB2297074A - Sealing apparatus for packaging machine

Info

Publication number: GB2297074A
Application number: GB9500871A
Authority: GB
Inventors: Yasutaka Suga
Original assignee: Ibaraki Seiki Machinery Co Ltd
Current assignee: Ibaraki Seiki Co Ltd
Priority date: 1995-01-17
Filing date: 1995-01-17
Publication date: 1996-07-24
Anticipated expiration: 2015-01-17
Also published as: GB9500871D0; GB2297074B

Abstract

In a packaging machine, a frame 21 which carries seal bars 52, 53 is reciprocated in direction 23 by a servo motor 54 via a crank mechanism 22. A servo motor 47 drives the upper and lower seal bars 52, 53 to cross-seal an advancing tubular film 15 accommodating a number of package articles 16 equidistantly in line. When a photo-electric sensor 64 attached to the seal bar or frame detects an irregular spacing between the package articles accommodated in the tubular film (by detecting an article 16 in zone 68 after the seal bars commence closing) and outputs a detection signal to a computer 58, the computer instructs the servo motor 47 to reverse or stop the rotation thereof. At this time, though the operation of the seal bars is interrupted, the reciprocal motion of the frame supporting the seal bars is continued. The position of the frame 21 is monitored by means 57, 59 sensing the rotary position of servo motor 54.

Description

SEALING APPARATUS FOR PACKAGING MACHINE FIELD OF THE INVENTION The present invention relates to a sealing apparatus for a packaging machine. More particularly, the present invention relates to a sealing apparatus for use in a packaging machine adapted to package articles by longitudinally rolling a continuously supplied elongated film into a tubular form simultaneously with supplying package articles equidistantly in line in the tubular film, and fusion-bonding both sides of the tubular film, said sealing apparatus having a pair of upper and lower seal bars which travel along a traveling direction of the tubular film in a box-motion to cross-seal the tubular film on a pitch-by-pitch basis.

BACKGROUND OF THE INVENTION When relatively thick films and films requiring limited fusion-bonding conditions are to be used for packaging, a sufficiently long fusion time is required for heat sealing performed by means of a sealing apparatus of box-motion type.

This type of sealing apparatus is constructed such that a heavy frame supporting a pair of seal bars is reciprocated along the traveling direction of a film. In general, the frame is reciprocated by means of a crank mechanism. When a photo-electric sensor, for example, provided in an article transportation track detects an irregular spacing between package articles in a tubular film, the operation of the crank mechanism is immediately stopped to prevent the package article from being bitten by the pair of seal bars. After the dislocated article passes through, the operation of the crank mechanism is resumed in harmonization with the movement of the tubular film.

When the operation of the crank mechanism once interrupted is restarted, the crank mechanism should be accelerated simultaneously with the restart. At this time, the weight of the frame suddenly loaded onto the crank mechanism causes a shock and vibration. Further, the traveling speed of the frame should be essentially the same as that of the film. However, when the movement of the frame once stopped is to be brought into harmonization with the movement of the film, a control gap in the relative movement between the film and frame is caused, whereby the seal bars holding the film therebetween interfere with the movement of the film.

DISCLOSURE OF THE INVENTION It is an object of the present invention to provide a sealing apparatus which can prevent a package article from being bitten by a pair of seal bars without stopping a frame reciprocated in harmonization with the movement of the film when the dislocation of the package article in the tubular film is detected, thereby eliminating the shock and vibration resulting from the stoppage of a crank mechanism and the interference with the movement of the film by the seal bars.

In accordance with the present invention, to achieve this object, there is provided a sealing apparatus of box-motion type including a crank mechanism for reciprocating a frame along the transportation direction of a tubular film for a distance equivalent to a spacing between package articles, said frame being disposed across the tubular film traveling in a longitudinal direction with the package articles being accommodated equidistantly in line in the tubular film, and a sealing mechanism having a pair of seal bars supported by the frame so as to be located below and above the tubular film, said seal bars being adapted to press against and away from the tubular film through the forward and backward rotations of a servo motor, said sealing apparatus comprising: a position detecting means for detecting the position of the frame, based on the rotational angle of a main motor for driving the crank mechanism; a photo-electric sensor disposed on or around the seal bars for monitoring the tubular film between upper and lower positions or between right and left positions of the film; a sensor operation range setting means for setting the operation range of the photo-electric sensor around a position where the frame once retracted restarts moving in the same direction as the traveling direction of the tubular film, based on information from the position detecting means; a continuation instruction means for continuously rotating the servo motor in accordance with predetermined data if the photo-electric sensor does not detect a package article in the operation range set by the sensor operation range setting means; and a return instruction means for rotating the servo motor so as to move the seal bars away from each other to the most distant positions if the photo-electric sensor detects a package article.

With the aforesaid construction, the frame disposed across the tubular film traveling in the longitudinal direction with the package articles being accommodated therein is reciprocated along the traveling direction of the tubular film by means of the crank mechanism. The position detecting means for reading the rotational angle of the main motor for driving the crank mechanism detects the continuously changing position of the frame based on the rotational angle of the main motor.

The operation range setting means sets the operation range of the photo-electric sensor only in a particular position in the path of the continuously moving frame, based on the information output from the position detecting means.

The particular position is a position where the reciprocated frame is fully retracted. Only when the frame is in that particular position, the photo-electric sensors mounted on the seal bars are actuated.

If the shadow of the package article is not detected by the actuated photo-electric sensor, the continuation instruction means instructs the servo motor for driving seal bars to continue the operation thereof, and if the shadow of the package article is detected and the package article is expected to be bitten by the seal bars, the return instruction means allows the pair of seal bars to move away from each other by rotating the servo motor in a reverse direction.

As can be understood from the foregoing, the sealing apparatus for a packaging machine in accordance with the present invention has a construction characterized in that the photo-electric sensor for detecting package article mounted on the pair of seal bars detects the irregular spacing between the package articles within a range where the pair of seal bars moving in a box-motion approach from the upper and lower positions, and if the dislocation of a package article is detected, the approaching movement of the seal bars is interrupted by controlling the servo motor without stopping the reciprocal movement of the frame supporting the seal bars. Therefore, it is not necessary to slow down or stop the frame supporting the seal bars, thereby eliminating the mechanical shock and the gap in the transportation speed between the frame and package article.

Further, the sealing apparatus of the present invention employs the servo motor as a driving power source to move the seal bars away from each other. The spacing between the seal bars can be adjusted to the possible minimum distance in accordance with the size of the package articles by controlling the rotational angle of the servo motor.

Therefore, unnecessary movement of the seal bars can be avoided.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a side view of the entire sealing apparatus accompanying a block diagram of an electronic circuit.

Fig. 2 is a front view illustrating a frame portion of the sealing apparatus shown in Fig. 1.

Fig. 3 is a block diagram of a control system.

Fig. 4 is an enlarged side view illustrating seal bars.

Fig. 5 is a diagram for explaining the block-motion paths of seal bars.

Figs. 6 and 7 are diagrams for explaining a switch operation range.

Fig. 8 is a sectional view taken along the line VIII-VIII in Fig. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the field of packaging technology, a tube forming and filling machine is known to be adapted to continuously feed an elongated film and form the film into a tube, while supplying a number of package articles of regular shape equidistantly in the tubular film thus formed.

In Fig. 1, a tubular film 15 formed by a tube forming and filling machine is continuously supplied along with a number of package articles in a direction indicated by an arrow 18 on a belt conveyor 17. A frame 21 is slidably supported by a pair of guide bars 20 fixed to a platform 19 at the both ends thereof, and reciprocated in a direction indicated by an arrow 23 along the guide bars 20 by the motion of a crank mechanism 22. The traveling speed of the frame 21 in the direction of the arrow 18 is substantially the same as the speed of the tubular film traveling in the same direction as that of the frame. The forward and backward traveling distance corresponds to a spacing between the package articles accommodated in the tubular film. In this case, belt conveyors 17 and 29 supported by the frame 21 via wheel shafts 17A and 29A move together with the frame 21.

In general, a crank mechanism is characterized in that a crank pin revolves eccentrically with respect to the center of a main shaft and the revolving motion is converted into a linear motion. The crank mechanism 22 shown in Fig. 1 is constructed such that a lever 27 having a pin 26 engaged with an endless groove 25 formed on a cam plate 24 is pivoted by the clockwise rotational motion of the cam plate 24, and the pivotal movement of the lever 27 is transmitted to the frame 21 via a connection rod 28. In accordance with the present invention, the crank mechanism is defined as the entire mechanism for transmitting driving power by converting the rotational motion of the main shaft to the linear motion.

As shown in Fig. 2, the aforesaid frame 21 is of a square arch shape. That is, a pair of guide posts 31 are fixed upright on the upper surfaces of a pair of blocks 30 supported by the pair of horizontal guide bars 20. Upper and lower cross bars 32 and 33 are slidably mounted to the guide posts 30 via sleeves 34 and 35. A pair of side plates 37 fixed to the side walls of the respective blocks 30 by tapping screws 36 are vertically provided parallel to the guide posts 31. A top plate 38 is connected with the pair of guide posts 31 and the pair of side plates 37 at their upper end portions to form the frame 21 of square-arch shape.

As shown in Fig. 2, a shaft 41 is rotatably supported via a bearing 40 by lateral openings 39 respectively formed in the blocks 30 on the both sides. Bell cranks 42 are fixed to the opposite ends of the shaft 41, and the opposite ends of each of the bell cranks 42 are respectively interlocked with the upper and lower cross bars 32 and 33 via links 43 and 44 (this construction is also shown in Fig. 1). Accordingly, as the bell cranks 42 are rotated alternately in forward and backward directions together with the shaft 41, the upper and lower cross bars 32 and 33 move toward and away from each other. At this time, the cross bars 32 and 33 relatively tightly engaging in elongated slits 45 formed in the respective side plates 37 move up and down along these slits 45.

Further, a servo motor 47 having a decelerator is mounted on a base 46 supported between the pair of blocks 30. A pinion 48 provided to the shaft of the servo motor 47 is engaged with a gear 49 fixed to the shaft 41 which is rotated forward and backward by means of the servo motor 47 to reverse the rotation of the bell cranks 42. Air cylinders 50 are fixed onto the upper face of the upper cross bar 32, and an upper seal bar 52 is fixed to piston rods 51 of the air cylinders 50. Whenever the upper seal bar 52 is brought into contact with a lower seal bar 53 fixed onto the upper face of the lower cross bar 33, the tubular film 15 is tightly pressed between the upper and lower seal bars 52 and 53 while being buffered with pressurized air supplied from the air cylinders 50.

In Fig. 1, a main shaft 55 of a main motor 54 serves as a rotational power source for the cam plate 24, and an encoder 57 linked with the main shaft 55 via a belt converts the rotation of the main shaft 55 into a pulse signal which is fed into a computer 58. A position detecting means 59 in the computer 58 detects the position of the continuously moving frame 21 every moment, based on the rotational angle of the main motor 54 input as the pulse signal. (Reference will also be made to Fig. 3 for the following explanation.) A smallsized motor 60 mounted on the lever 27 rotates a threaded rod 61 to move up and down one end portion 62 of the connection rod 28, so that the traveling distance of the frame 21 can be changed in accordance with the length of the package articles 16.Therefore, the position detecting means 59 can detect the position of the frame 21 even if the traveling distance of the frame 21 is changed.

As shown in Fig. 4, a photo-electric tube 63 is attached to the rear face of the lower seal bar 53, and a photoreceptor tube 64 is attached to the rear face of the upper seal bar 52. The photo-electric tube 63 and photo-receptor tube 64 constitutes a photo-electric sensor 65. The light from the photo-electric tube 63 usually passes through the transparent tubular film 15. However, when the package article 16 blocks the light, the photo-electric sensor 64 is actuated. As shown in Fig. 8 illustrating a transverse sectional view of the frame 21 shown in Fig. 4, the photoelectric tubes 63 and photo-receptor tubes 64 may be attached inside the pair of side plates, so that the photo-electric sensors monitor the film from a lateral direction.

As shown in Fig. 5, the seal bars 52 and 53 moving along block-motion paths 66 and 67 advance at the same speed as the traveling speed of the package articles in harmonization therewith. However, when the seal bars 52 and 53 start retracting in the reverse direction with respect to the traveling direction of the package articles, the light from the photo-electric tube mounted on the seal bar is blocked by the package article. Therefore, the operation range 68 of the photo-electric sensor is set around a position where the retracted seal bars 52 and 53 turn the traveling direction to restart moving ! > the same direction as the traveling direction of the package articles. Since the position of the moving seal bar 52 is detected by decoding the aforesaid information sent from the frame position detecting means 59 by means of the computer, the photo-electric sensor 65 can be actuated only when the frame is located in the aforesaid sensor operation range 68 shown in Fig. 5. Therefore, if the package article 16 is forwardly dislocated within the sensor operation range 68 as shown in Fig. 6, or if the package article 16 is backwardly dislocated as shown in Fig. 7, a package article detecting means 71 shown in Fig. 3 outputs a warning signal to a return instruction means 69. In response to the warning signal, the rotation of the servo motor 47 is reversed or stopped. Therefore, the upper and lower seal bars 52 and 53 travel in an opened state as shown in Fig. 1 to prevent the package article from being bitten between the seal bars.While the package article 16 is dislocated, the seal bars 52 and 53 remain opened, and the film containing the package article passes through without being sealed. When the light 70 can pass through the film in the sensor operation range, a signal is output to a continuation instruction means 72 from the package article detecting means 71 shown in Fig. 3 to allow the servo motor 47 to be operated in accordance with a program for the sealing of the package article 16, and then the operation is continued.

A rotational angle setting means 73 shown in Fig. 3 can set the forward or backward rotational angle of the servo motor 47 to any desired angle through the feedback by an encoder 74 to adjust the spacing between the upper and lower seal bars 52 and 53, so that the upper and lower seal bars 52 and 53 are not spaced more apart from each other than required for the height 75 of the package article 16, as shown in Fig.

4. Further, this allows the seal bars to travel in the box motion with sufficient clearance.

Claims

What is claimed is:

1. A sealing apparatus of box-motion type for a packaging apparatus, which includes a crank mechanism for reciprocating a frame along a transportation direction of a tubular film for a distance equivalent to a spacing between package articles, said frame being disposed across the tubular film traveling in a longitudinal direction with the package articles being accommodated equidistantly in line in the tubular film, and a sealing mechanism having a pair of seal bars supported by the frame so as to be located below and above the tubular film, said seal bars being adapted to press against and away from the tubular film through forward and backward rotations of a servo motor, said sealing apparatus comprising:: a position detecting means for detecting a position of the frame, based on a rotational angle of a main motor for driving the crank mechanism; a photo-electric sensor mounted on the seal bars or on the frame for monitoring the tubular film to check for the presence of a package article; a sensor operation range setting means for setting an operation range of said photo-electric sensor around a position where the frame once retracted restarts moving in the same direction as the traveling direction of the tubular film, based on information from said position detecting means; a continuation instruction means for continuously rotating the servo motor in accordance with predetermined data if said photo-electric sensor does not detect a package article in the operation range set by said sensor operation range setting means; and a return instruction means for rotating the servo motor so as to move the seal bars away from each other to the most distant positions if said photo-electric sensor detects a package article.

2. A sealing apparatus as set forth in claim 1, further comprising means for setting the rotational angle of the servo motor to any desired angle to alter the spacing between the pair of seal bars.

3. A sealing apparatus of box motion type for a packaging apparatus substantially as hereindescribed with reference to the accompanying drawings.