Sealing device of packaging device

Abstract: A total heating calorie to be given to the folded parts is changed within a short period of time in response to a variation of a transferring speed of the box-like items. As the heater moving mechanisms 4 are operated, each of the heater blocks 3 is moved to or away from the inside parts 2a of each of the annular belts 2 in synchronous with the transferring speed of the box-like items A and the number of heater blocks 3 abutting against the inside parts 2a of each of the annular belts 2 is varied in response to the transferring speed of the box-like items A.

Description: BACKGROUND OF THE INVENTION This invention relates to a sealing device of a packaging machine for covering a thermoplastic packaging sheet such as cellophane or polypropylene on box-like items such as cigarettes covered by a packaging sheet, for example, and more particularly a sealing device in which each of annular belts is wound around in opposition to the right and left sides of the box-like items along both right and left sides of a transferring passage for continuously transferring the box-like items, for example, these both annular belts are moved toward a transferring direction of the box-like items in synchronous with their transferring speed, a plurality of heater blocks are disposed within each of the annular belts in the transferring direction, and heat from the heater blocks is transmitted to the folding parts of the folded packaging sheet along the right and left side surfaces of the box-like items through the inner sides of each of the annular belts so as to thermally adhere them. As the prior art sealing device of a packaging machine, there is provided a system disclosed in Japanese Patent Laid-Open No. Hei 1-294406, wherein a plurality of heater blocks are abutted against the inner sides of each of the annular belts and the right and left side surfaces of the box-like items by springs at a specified pressure, the folded box-like items pass between these right and left annular belts, both folded parts are held by the inner side of each of the annular belts, heat from the heater blocks is transmitted to thermally melt both folded parts and at the same time a plurality of heater blocks are separately heated to cause a temperature of each of the annular belts to be controlled in response to a transferring speed of the box-like items and then a specified amount of heating calories is given to each of the folded parts without having any relation with a variation of the transferring speed of the box-like items. In addition, the sealing device for a packaging machine is constructed such that, as disclosed in Japanese Patent Publication No. Sho 61-39251, for example, a winding device for winding the packaging sheet around the box-like items and a folding device for projecting ends of the packaging sheet projected from both right and left side surfaces of the wound box-like items in a rectangular cylinder form along the side surfaces are continuously disposed as its pre-stage and then an item discharging device for discharging the box-like items of poor packaged state and a multi-stage piling and discharging device for piling up the items in a predetermined number of stages and discharging the items into a box packaging stage as a post-stage are continuously disposed and they are cooperated with other device placed thereacross. However, such a prior art sealing device for a packaging machine has some problems that a plurality of heater blocks are always abutted against the annular belts, and even if a temperature of the heater blocks is tried to be lowered or decreased, for example, the temperature is not decreased rapidly due to its surplus heat, resulting in that in particular in the case that an operating speed, i.e. a transferring speed of the box-like items may easily be varied, a total amount of heat to be given to the box-like items in response to the transferring speed may not be changed within a short period of time even though the transferring speed of the box-like items is required to be rapidly accelerated or rapidly decelerated within a short period of time, resulting in that a specified amount of heating calorie may not be given to the folded parts of the packaging sheet to be transferred at a different speed, a finished state of the thermal melting is not made uniform and a poor item may easily be produced. EP-A-0 351 553 discloses a sealing device according to the preamble of claim 1. The device includes a plurality of pairs of opposite heater blocks as well as a heater moving mechanism to move the heater blocks sequentially towards or away from the transfer passage in response to a change in the transfer speed of the box-like items. SUMMARY OF THE INVENTION In view of the foregoing circumstances in the prior art, it is an object of the present invention to vary a total amount of heating calorie given to the folded parts in response to a variation of the transferring speed of the box-like items within a short period of time. In order to solve the aforesaid problems the present invention provides a sealing device of a packaging device in which annular belts are held against the right and left surfaces of box-like items along both the left and right sides of a transfer passage for continuously transferring the box-like items, both the annular belts being moved in the transfer direction of the box-like items at the transfer speed of the items, wherein a plurality of heater blocks are arranged inside of each of the annular belts and heat from said heater blocks is transmitted through each of the annular belts to thermally adhere folded parts of a packaging sheet folded against the right and left side surfaces of the box-like items, the said plurality of heater blocks being acted upon by heater moving mechanisms in such a way that they may be moved sequentially towards or away from the transfer passage in response to a change in the transfer speed of the box-like items characterised in that the heater moving mechanisms comprise biasing means biasing the heaters in a direction perpendicular to the said transfer passage, and cam means disposed parallel to the said transfer passage adapted upon reciprocation to act against the heater blocks in opposition to the biasing means. The cam means preferably reciprocate linearly in a direction parallel to the said transfer passage. In order to achieve the effect of the invention, the cam means are preferably formed with inclined surfaces gradually tapering outwards from the transfer passage in the direction of transfer of the box-like items. Similarly, the heater blocks are preferably provided with rollers which are arranged along the path of movement of the inclined surfaces of the cam means. In a preferred embodiment, the annular belts are supported in such a manner as to be reciprocable in a direction perpendicular to the transfer passage and the annular belts are moved in a direction away from the right and left side surfaces of the box-like items on the transfer passage when the movement of the box-like items is stopped. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a top plan view with a part being broken away for showing the sealing device of a packaging machine of one preferred embodiment of the present invention, wherein a state in which the box-like items are transferred at a minimum speed is indicated by a solid line, an accelerated state is indicated by a two-dotted line and a state in which a transferring of the box-like items is stopped is indicated by a dotted line. Fig. 2 is an enlarged side elevational view in a longitudinal section taken along a line (2)-(2) of Fig. 1. Fig. 3 is a front elevational view in a longitudinal section taken along a line (3)-(3) of Fig. 1. Fig. 4 is a top plan view with a part being broken away for showing a state in which the box-like items are transferred at a maximum speed. Fig. 5 is a reduced front elevational view in a longitudinal section for showing an entire packaging machine. Fig. 6 is a front elevational view in a longitudinal section for showing an item discharging device in which the box-like items are being held. Fig. 7 is an enlarged side elevational view in a longitudinal section taken along a line (7)-(7) of Fig. 6. Fig.8 is a front elevational view in a longitudinal section taken along a line (8)-(8) of Fig. 7. Fig. 9 is a partial enlarged top plan view in a lateral section taken along a line (9)-(9) of Fig. 6. DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in Fig. 5, the preferred embodiment of the present invention is operated such that the cigarettes packaged with a packaging sheet are continuously supplied as box-like items A for predetermined spacings by a horizontal transporting conveyor 11, these box-like items A are picked up by the transferring wheels 12 one by one, each of the items is delivered to the pockets 13a of the winding wheel 13 and further delivered to the pockets 14a of the applying wheel 14 from the pockets 13a of the winding wheel 13, thereby a thermoplastic transparent film such as a cellophane or polypropylene as the packaging sheet B is wound around in a U-shape along a surface of each of the box-like items A, thereafter both ends of the packaging sheet B are folded along the surfaces of the box-like items A while the items are being continuously transferred by the applying wheel 14 so as to thermally adhere them to each other, the items are delivered into the pockets 15a of the folding wheel 15, the box-like items A transferred in an arcuate path are held by holding claws 16a, 16a of the low speed conveyor 16, thereby the box-like items A are pulled out of each of the pockets 15a onto a horizontal transferring passage 1 and the expanding ends projected from the right and left side surfaces A1, A1 of the box-like items A in a rectangular shape are folded and subsequently the box-like items A are continuously transferred along the transferring passage 1 up to the annular belts 2, 2. The transferring passage 1 is comprised of a horizontal mounting surface 1a extending in a transferring direction of the box-like items A and a transporting conveyor 1b, the transporting conveyor 1b winds the belt 1c along the mounting surface 1a toward a transferring direction of the box-like items A, pushing claws 1d for holding the items in opposition against the rear surface A2 and the front surface A3 of each of the box-like items A are projected at the outer circumference of the belt 1c while being opened by the same size as the width size in the transferring direction of the box-like items A and at the same time its driving source is cooperatively related to the driving source for the folding wheel 15 or the low speed conveyor 16 or the like, thereby it is continuously operated in synchronous with an operating speed of the folding wheel 15 or the low speed conveyor 16 or the like. Supporting members 5, 5 are disposed below the mounting surface 1a in a rightward or leftward direction perpendicular to the transferring direction of the box-like items A in such a way as they may be moved in a horizontal direction, each of the inside parts 2a, 2a of the annular belts 2, 2 is disposed in opposition to the folding parts B1, B1 of the packaging sheet B folded along the right and left side surfaces A1, A1 of the box-like items A, emergency driving members 5a, 5a such as air cylinders to be reciprocated in a rightward or leftward direction, for example, are cooperatively related to the supporting members 5, 5. The emergency driving parts 5a, 5a are cooperatively related to the driving source for the transporting conveyor 1b and the supporting members 5, 5 are moved away from the right and left side surfaces A1, A1 of the box-like items A fed onto the mounting surface 1a when the operation of the transporting conveyor 1b is stopped. The annular belts 2, 2 are stainless steel belts, for example, formed into bondable form by superior thermo-conductive metal or the like and they are wound around the driving pulleys 2b, 2b spaced apart in the transferring direction of the box-like items A and the driven pulleys 2c, 2c at the supporting members 5, 5 in the transferring direction of the box-like items A. The inside parts 2a, 2a are disposed in parallel on the substantial same vertical states of the right and left side surfaces A1, A1 of the box-like items A supplied on the mounting surface 1a and at the same time the driving pulleys 2b, 2b are cooperatively related with the driving source for the transporting conveyor 1b, thereby the inside parts 2a, 2a are synchronously and continuously moved in such a way as their speeds become substantially equal to the operating speed of the transporting conveyor 1b. When the movement of the transporting conveyor 1b is stopped, the inside parts 2a, 2a of the annular belts 2, 2 are continuously moved in cooperation with the emergency driving source and a plurality of heater blocks 3 are disposed within the annular belts 2, 2 toward the transferring direction of the box-like items A. The heater blocks 3 are of well-known structures which may generate heat under an electrical energization, wherein the heater blocks except the heater blocks 3c, 3c disposed at the most upstream side in the transferring direction of the box-like items A are supported at the supporting members 5, 5 in such a way as they may be reciprocated horizontally in a rightward or a leftward direction, thereby these inner surfaces 3a are disposed in such a way as they may be moved to or away from the inside parts 2a, 2a of the annular belts 2, 2 and at the same time, they are always biased toward the cams 4a, 4a to be described later apart from the inside parts 2a, 2a of the annular belts 2, 2 with the resilient members 3b such as springs, for example, and the heater blocks 3c, 3c disposed at the most upstream side are always abutted against the inside parts 2a, 2a of the annular belts 2, 2 and fixedly disposed. In addition, the heater blocks 3 are provided with the heater moving mechanisms 4, 4 for moving the blocks to or away from the inside parts 2a, 2a of the annular belts 2, 2 in synchronous with the transferring speed of the box-like items A. These heater moving mechanisms 4, 4 are constructed such that the cams 4a, 4a are laterally disposed along the outer surfaces of the heater blocks 3 in such a way as each of them may be reciprocated horizontally in a transferring direction and a counter transferring direction of the box-like items A. The driven rollers 3d are rotatably projected in a transferring direction of the box-like items A at the outer surfaces of the heater blocks 3 in opposition to these cams 4a, 4a. The cams 4a, 4a have some inclined surfaces 4b, 4b which are gradually expanded in a rightward or a leftward direction as they approach toward the downstream at the surfaces opposing against the driven rollers 3d, each of them is further provided with the driving part 4c cooperatively related to the driving source for the transporting conveyor 1b, thereby the cams are reciprocated in synchronous with a moving speed of the transporting conveyor 1b. In the preferred embodiment of the present invention, the driving part 4c is a power driving shaft which is normally rotated when a moving speed of the transporting conveyor 1b is accelerated and in turn when the transferring speed is decelerated, it is rotated in a reverse direction, and the power driving shaft 4c and the cams 4a, 4a are cooperatively related to each other through the transmitting members 4d, 4d such as a belt or a chain or the like, thereby when a transferring speed of the transporting conveyor 1b is accelerated, the cams 4a, 4a are moved toward the transferring direction of the box-like items A in response to an amount of acceleration and at the same time when the transferring speed of the transporting conveyor 1b is decelerated, the cams 4a, 4a are moved in a counter-transferring direction of the box-like items A in response to the amount of deceleration. Accordingly, as the transferring speed of the box-like items A is accelerated, the cams 4a, 4a are moved toward the transferring direction of the box-like items A, the heater blocks 3 disposed at the upstream side in the transferring direction are abutted in sequence against the inside parts 2a, 2a of the annular belts 2, 2 and when the transferring speed of the box-like items A reaches its maximum speed, all the heater blocks 3 are abutted against the inside parts 2a, 2a of the annular belts 2, 2 and at the same time as the transferring speed of the box-like items A is decelerated, the cams 4a, 4a are moved in a counter-transferring direction of the box-like items A, the heater blocks 3 disposed at the downstream side are moved away from the inside parts 2a, 2a of the annular belts 2, 2 in sequence and when the transferring speed of the box-like items A reaches its minimum speed, all the heater blocks 3 except the heater blocks 3c, 3c disposed at the upstream end side are moved away from the inside parts 2a, 2a of the annular belts 2, 2. At the downstream side pulley 1b₁ disposed at the downstream end of the transporting conveyor 1b, each of the disks 1e, 1e is projected at both rightward and leftward directions on the same vertical sides of the right and left side surfaces A1, A1 of the box-like items A, the outer circumferential upper end positions of these right and left disks 1e, 1e are set on an extended line of the mounting surface 1a, the box-like items A are transferred in sequence from the mounting surface 1a to the outer circumferential upper end positions of the disks 1e, 1e in sequence and at the same time, a plurality of item holding mechanisms 6 of the item discharging device 17 acting as a post-stage are disposed in a circumferential direction of the disks 1e, 1e for the same spacings as that of the width of the box-like items A toward the transferring direction so as to oppose to the right and left side surfaces A1, A1 of the box-like items A to be transferred to the outer circumferential upper end positions of the disk members 1e, 1e. Each of the item holding mechanisms 6 is operated temporarily to hold each of the box-like items A transported to the outer circumferential upper end positions of the disks 1e, 1e or suck it in response to an inputting of a discharging signal. In the preferred embodiment, the holding claws 6a, 6a of substantial L-shape engaged with the right and left side surfaces A3, A3 and the upper surface A4 are disposed against each of the right and left side surfaces A1, A1 of each of the box-like items A in such a way as it may be moved to or away from the side surfaces and in addition, the pressing pieces 6b, 6b biased toward the right and left side surfaces A1, A1 of the box-like items A against each of the holding claws 6a, 6a as required through resilient members 6b₁, 6b₁ such as springs are disposed against the right and left side surfaces A1, A1 of each of the box-like items A in such a way as they may be moved to or away from it, and further each of the base ends 6a₁, 6a₁ of the holding claws 6a, 6a is cooperatively related. The control cam 7 is comprised of cam followers 7a which are cooperatively related to each of the base ends 6a₁, 6a₁ of the holding claws 6a, 6a; a fixed cam plate 7b contacting with these cam followers 7a, fixed and disposed without being related to rotations of the downstream side pulley 1b₁ of the transporting conveyor 1b and the disk places 1e, 1e; a moving cam 7c being in contact with the cam followers 7a disposed in respect to the fixed cam plate 7b in such a way as it may be reciprocated vertically; and a driving part 7d such as an air cylinder, for example, for electrically communicating with a sensor for sensing a poor packaging or a manual switch for quality control disposed at the packaging device of the previous stage or the like, and the driving part 7d is operated to move up the moving cam 7c temporarily only when the box-like items A to be fed out pass through the outer circumferential upper end positions of the disk plates 1e, 1e in response to a discharging signal outputted from the sensor or the manual switch for quality control or the like. In the case that a discharging signal is not outputted from the manual switch for quality control to the driving part 7d of the control cam 7, the cam followers 7a are rotated along the fixed cam plate 7b as the disk places 1e, 1e are rotated, thereby the holding claws 6a, 6a and the pressing pieces 6b, 6b are moved in an arcuate path while they are being moved away from the right and left side surfaces A1, A1 of each of the box-like items A. When a discharging signal is outputted to the driving part 7d, the cam followers 7a are rotated along the moving cam 7c moved upwardly as the disk places 1e, 1e are rotated, thereby when the discharging box-like items A reach to the outer circumferential upper end positions of the disk places 1e, 1e, the opposing holding claws 6a, 6a and the pressing pieces 6b, 6b are oscillated toward a direction approaching the right and left side surfaces A1, A1 of the box-like items A and they are moved in an arcuate path and at the same time they are moved in an arcuate path only for a predetermined spacing and then the holding claws 6a, 6a and the pressing pieces 6b, 6b are oscillated in a direction moving away from the right and left side surfaces A1, A1 of each of the box-like items A and returned to their initial states. In addition, the discharging chute 7a is fixed and disposed along the outer circumferences of the disk plates 1e, 1e near a position where the item holding mechanisms 6 release a holding of the box-like items A and near a position, in the preferred embodiment, where the holding claws 6a, 6a and the pressing pieces 6b, 6b are moved by the control cam 7 toward a direction moving away from the right and left side surfaces A1, A1 of the box-like items A, and further a recovering box 7b is disposed at a terminal end of the discharging chute 7a in such a way as it may be removable. A transporting conveyor 8 is continuously and laterally disposed along the mounting surface 1a from a slight upstream side position of the downstream side pulley 1b₁ toward a discharging conveyor 9 communicated with a device at a post-stage at a downstream end of the transporting conveyor 1b, the box-like items A transported near the upstream end are sucked or held so as to immovably hold the box-like items with a lower item holding force than the item holding force of the item holding mechanisms 6 and further the items are moved at the same speed as that of the transporting conveyor 1b and transported to the feeding-out conveyor 9. In the preferred embodiment, an upstream side pulley 8a is disposed at an upstream side slightly higher than a position opposite the outer circumferential upper end positions of the disk plates 1e, 1e with the box-like items A being held thereat as the transferring conveyor 8, and the downstream side pulley 8b is disposed at a position opposite against the feeding-out conveyor 9 with the box-like items A being held thereat, a suction belt 8c is wound around these pulleys 8a, 8b so as to act as a so-called suction conveyor for transporting the box-like items A fed from the transporting conveyor 1b while they are being sucked, wherein its driving source is cooperatively related to the driving source for the transporting conveyor 1b, the suction belt 8c is continuously moved to be slightly faster than the moving speed of the transporting conveyor 1b, and as required, the holding pieces 8e, 8e biased by resilient members 8d, 8d such as springs toward the right and left side surfaces A1, A1 of the box-like items A are disposed against the box-like items A transferred from the transporting conveyor 1b, respectively, and these holding pieces 8e, 8e are continuously moved in a synchronous manner to have the same speed as the moving speed of the suction belt 8c. Operation of the sealing device of such a packaging machine as described above will be explained as follows. At first, as the folded box-like items A are transferred in sequence for a predetermined spacing onto the mounting surface 1a of the transferring passage 1 from the low speed conveyor 16 in the previous stage as shown in Fig. 5, these box-like items A are continuously moved for every predetermined spacing as shown in Fig. 1 under an operation of the transporting conveyor 1b, advance in sequence between the annular belts 2, 2 positioned at right and left sides, and each of the folded parts B1, B1 of the packaging folded sheet B along the right and left side surfaces A1, A1 of the box-like items A is abutted against the inside parts 2a, 2a of the annular belts 2, 2 held thereat and the items are transferred. In this case, the cams 4a, 4a of the heater moving mechanisms 4 are reciprocated in response to the moving speed of the transporting conveyor 1b in a transferring direction and a counter-transferring direction of the box-like items A, thereby each of the inner surfaces 3a of the heater blocks 3 is abutted against, in number corresponding to the moving speed of the box-like items A, the inside parts 2a, 2a of the annular belts 2, 2 so as to heat the entire annular belts 2, 2. Heat from the inside parts 2a, 2a of these annular belts 2, 2 is transmitted to both folded parts B1, B1 of the right and left side surfaces A1, A1 of the box-like items A, and the folded parts are thermally adhered by the items completely pass between the annular belts 2, 2. As the moving speed of the transporting conveyor 1b is accelerated in response to an operating condition of the device positioned in the previous stage or the post-stage during the operation of the transporting conveyor 1b and the transferring speed of the box-like items A is accelerated, the heater blocks 3 disposed at the upstream side as shown by a two-dotted line in Fig. 1 are abutted against the inside parts 2a, 2a of the annular belts 2, 2 in sequence. Heat is continuously applied to both folded parts B1, B1 of the box-like items A in the midway while passing between the annular belts 2, 2 and when the transferring speed of the box-like items A reaches the maximum speed, as shown in Fig. 4, all the heater blocks 3 are abutted against the inside parts 2a, 2a of the annular belts 2, 2 and thus heat is continuously applied until the items completely pass between the annular belts 2, 2. In turn, as the moving speed of the transporting conveyor 1b is decelerated and the transferring speed of the box-like items A is decelerated, the heater blocks 3 disposed at the downstream side are moved away from the inside parts 2a, 2a of the annular belts 2, 2 in sequence and heat is not applied in the midway of both folded parts B1, B1 of the box-like items A during their passings, resulting in that when the transferring speed of the box-like items A reaches its minimum speed, as shown in a solid line in Fig. 1, all the heater blocks 3 except the heater blocks 3d, 3d disposed at the most upstream side are moved away from the inside parts 2a, 2a of the annular belts 2, 2 and heat of the minimum temperature is given only when the box-like items A pass through the heater blocks 3d, 3d disposed at the most upstream side. In addition, during the operation of the transporting conveyor 1b, its movement is stopped in response to an operating state of the device positioned in the previous stage or the post-stage, the transferring of the box-like items A is stopped, resulting in that the inside parts 2a, 2a of the annular belts 2, 2 are moved away from both folded parts B1, B1 of the box-like items A passing between them as shown by a dotted line in Figs. 1 and 2 under an operation of the emergency driving parts 5a, 5a, heat is not applied more than that to prevent any seizure and at the same time the inside parts 2a, 2a of the annular belts 2, 2 are continuously moved at their minimum speed, the entire annular belts 2, 2 are heated by the heater blocks 3d, 3d disposed at the most upstream side and the blocks are waited there. As shown in Fig. 6, as these box-like items A are continuously transferred to the downstream side pulley 1b₁ while being kept at their predetermined spacings under an operation of the transporting conveyor 1b, the item holding mechanisms 6 are operated as shown in Fig. 7 when each of the box-like items A reaches the outer circumferential upper end positions of the disk plates 1e, 1e and a discharging signal is outputted to the item holding mechanisms 6 of the item discharging device 17, resulting in that the box-like items A held by the item holding mechanisms 6 are moved away from the mounting surface 1a under a rotation of the disk plates 1e, 1e and transferred in an arcuate path. After this operation, as the item holding mechanisms 6 holding the box-like items A reach their predetermined angular positions, the holding of the box-like items A to be discharged is released and the mechanisms are returned to their initial states, resulting in that the box-like items A are transferred to the recovering box 7b through the discharging chute 7a. In addition, when each of the box-like items A reach the outer circumferential upper end positions of the disk places 1e, 1e and the discharging signal is not outputted to the item holding mechanisms 6, the item holding mechanisms 6 are not operated, the box-like items A are delivered to the transferring conveyor 8 and the items are transported to the post-stage by the feeding-out conveyor 9. Therefore, the item discharging device 17 can be instantly guided out of the transferring passage without applying any shock against the items, and as compared with the item discharging device for projecting and discharging the items with the reciprocating pushers, the items may not be collapsed even if the item transferring speed is accelerated in order to make a high processing speed and a confirmation of the poor location can be carried out and at the same time if the items are discharged for their quality control, their re-use can be performed and they may be returned back again to the transferring passage. In addition, since the rear surfaces A2 of the box-like items A to be discharged as the operation of the transporting conveyor 1b is performed are pushed up to the downstream side pulley 1b₁, a position alignment between the item holding mechanisms 6 disposed at the downstream side pulley 1b₁ and the pushed and discharged box-like items A becomes correct and the positive discharging operation is performed. Although in the preferred embodiment described above the cigarettes packaged with a packaging sheet as the box-like items A are used, the present invention is not limited to these items, the box-like items A may be products other than the packaged cigarettes and further the structures of the heater moving mechanisms 4 are not limited to the above-described structures and other structures providing a similar operation may also be applied. Since the present invention is constructed as described above, it has the following advantages. 1. As the heater moving mechanisms are operated, the number of heater blocks abutting against the inside parts of each of the annular belts is varied in response to a transferring speed of the box-like items by moving the blocks to or away from the inside parts of each of the annular belts in synchronous with the transferring speed of the box-like items, a total heating calorie to be given to the folded parts in response to the variation of the transferring speed of the box-like items can be varied within a short period of time. Therefore, as compared with the prior art system in which a plurality of heater blocks are always abutted against the annular belts and temperatures of the heater blocks are not rapidly decreased due to their surplus heat, for example, a specified amount of heating calorie can be applied to the folded parts of the packaging sheet transferred at a speed differing from the transferring speed of the box-like items to enable a finished state of the thermal adhered part to be unified and no poor items may be produced even if the transferring speed of the box-like items is rapidly accelerated or decelerated within a short period of time. 2. The heater moving mechanisms abut against the heater blocks disposed at the upstream side in the transferring direction against the inside parts of the annular belts in sequence as the transferring speed of the box-like items is accelerated and the heater blocks disposed at the downstream side of the transferring direction are moved away from the inside parts of the annular belts in sequence, resulting in that the heater blocks at the upstream side are abutted against the inside parts of the annular belts in sequence even if the transferring speed of the box-like items is accelerated under a state in which the box-like items are advanced between the right and left annular belts, heat is continuously applied to both folded parts of the box-like items being transferred, the heater blocks at the downstream side are moved away from the inside parts of the annular belts in sequence even if the transferring speed of the box-like items is decelerated, no heat is applied to both folded parts of the box-like items being transferred in the midway part and a specified amount of heat can be applied to the box-like items being advanced between the right and left annular belts.

Claims: A sealing device of a packaging device in which annular belts (2) are held against the right and left side surfaces of box-like items (A) along both the right and left sides of a transfer passage (1) for continuously transferring the box-like items, both these annular belts (2) being moved in the transfer direction of the box-like items (A) at the transfer speed of the items, wherein a plurality of heater blocks (3) are arranged inside of each of the annular belts (2) and heat from said heater blocks (3) is transmitted through each of the annular belts (2) to thermally adhere folded parts of a packaging-sheet folded against right and left side surfaces of the box-like items (A), the said plurality of heater blocks (3) being acted upon by heater moving mechanisms in such a way that they may be moved sequentially towards or away from the transfer passage (1) in response to a change in the transfer speed of the box-like items characterised in that the heater moving mechanisms comprise biasing means (3b) biasing the heaters (3) in a direction perpendicular to the said transfer passage (1), and cam means (4a, 4b) disposed parallel to the said transfer direction adapted upon reciprocation to act against the heater blocks (3) in opposition to the biasing means (3b). A sealing device as claimed in claim 2, characterised in that the cam means (4a, 4b) reciprocate linearly in a direction parallel to the said transfer passage (1). A sealing device as set forth in claim 1 or 2 in which the cam means (4a, 4b) are formed with inclined surfaces (4b) gradually tapering outwards from the transfer passage in the direction of transfer of the box-like items (A). A sealing device as set forth in claim 3 in which the heater blocks (3) are provided with rollers (3d) which are arranged along the path of movement of the inclined surfaces (4b) of the cam means (4a, 4b). A sealing device as set forth in any of claims 1 to 4 in which each of the annular belts (2) is supported in such a manner as to be reciprocable in a direction perpendicular to the transfer passage (1) and the annular belts (2) are moved in a direction away from the right and left side surfaces of the box-like items (A) on the transfer passage when the movement of the box-like items is stopped.

Inventors: SHIGETA TOSHIO, SHIGETA, TOSHIO
Applicants: TOKYO AUTOMATIC MACH WORKS, TOKYO AUTOMATIC MACHINERY WORKS LIMITED
Application year: 1993
Main classification: B65B51
IPC codes: B65B51