Packaging device for covering and sealing cover film onto tray

A packaging device is provided which prevents trays accommodating packaged items from being broken due to the tension in a film acting from above. The sealing base and the sealer perform a box motion by the combination of the back and forth movement of the general frame, and the upward and downward movement of the sealing base and the sealer, and the film is welded onto the flange of the tray while in movement. In this case, by setting the upper limit of the sealing base to the lower surface of the flange of the tray, it is possible for the deck plate to receive the tension of the film acting on the tray through the packaged item.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a packaging device which stretches and covers a cover film onto a packaged item accommodated in a mounded fashion in a tray, and welds the film onto the flange section of the tray, in the conveyance path of the tray in a conveyor line.

2. Description of the Related Art

The invention disclosed in U.S. Pat. No. 6,834,476B presented by the same applicants as the present case is a packaging device for covering and sealing a cover film onto a tray, in which a sealing frame is moved back and forth reciprocally above the conveyance path of a band-shaped cover film, and a sealing base performs a box motion operation in conjunction with the reciprocal movement of the sealing frame, a tray together with a packaged item being pushed upwards by the upward movement in the box motion operation of the sealing base, the film thus being stretched by the upward pushing of the packaged item, and the film becoming sealed to the flange section of the tray by being pressed against the upper-positioned sealing frame. According to this device, the film is pushed and stretched from below by an upward impact from the packaged item, and the film can be welded to the flange section of the tray.

The chain conveyor conveys respective trays in which packaged items are mounded, at equidistant intervals, in a horizontal direction, and the sealing frame moves back and forth reciprocally above the trays in synchronism with the conveyance pitch of the trays. On the other hand, the sealing base performs a box motion operation in conjunction with the reciprocal movement of the sealing frame.

However, since this device causes the tray to press against an upper-positioned sealing frame, by means of a box motion operation of the lower sealing base only, the amount of vertical movement of the sealing base is large, and the bottom face of the tray becomes separated from the receiving plate which supports it. In this separated state, the tension in the film acts directly downwards on the tray, through the packaged item accommodated in a mounded fashion in the tray, and therefore, depending on the circumstances, the flange of the tray may break, or the flange may be bent backwards due to the load, thus presenting an obstacle to the welding between the flange and the cover film.

SUMMARY OF THE INVENTION

The present invention provides a device which resolves the aforementioned problems, that is a packaging device, comprising: a conveyance mechanism for causing respective trays to slide over the upper surface of a horizontal conveyance path by the pressing action of respective touch bars disposed at equidistant intervals on an endless chain; a mechanism for causing a deck plate disposed in an intermediate region between a preceding path region and a subsequent path region positioned on opposite sides of a cutaway region of the path, to move back and forth reciprocally in the direction of movement of the tray in unison with a general frame, and for successively transferring the trays from the preceding path region to the subsequent path region using the upper surface of the deck plate as a passage thereof; a mechanism for causing the general frame comprising a sealer provided in an upper region and a sealing base provided in a lower region, with the conveyance path therebetween, to move back and forth reciprocally; a mechanism for moving the sealing base upwards and downwards by means of the operation of a first lift mechanism, while moving reciprocally back and forth in unison with the general frame, sealing base having the same outline as the tray and being disposed about the perimeter of the deck plate; and a mechanism for moving a sealing frame set upwards and downwards by means of the operation of a second lift mechanism in unison with the sealer, the sealing frame set comprising a cutting blade surrounding the sealer having the same outline as the tray and a film pressing member, wherein during the movement of the general frame in the same direction as the tray, the first lift mechanism pushes the sealing base upwards until a position where the upper surface thereof makes contact with the lower surface of the flange of the tray mounted on the deck plate, and then lowers the sealing base to its original position in accordance with a withdrawing action of the general frame, and during the movement of the general frame in the same direction as the tray, the second lift mechanism pushes the sealing frame set downwards until a position where the sealing frame set makes contact with the upper surface of the flange of the tray supported on the sealing base, to weld a cover film onto the flange, and then lifts the sealing frame set to its original position in accordance with a withdrawing action of the general frame.

In this device, a sealer and a sealing frame positioned above and below the tray conveyance path perform a box motion, and cover film is welded by the sealer and the sealing frame onto a tray in which a packaged item is accommodated in a mounded fashion. In this, the first lift mechanism pushes the sealing base upwards until a position where the upper surface of the sealing base makes contact with the lower surface of the flange of a tray mounted on the deck plate, and the second lift mechanism pushes the sealer downwards until a position where it makes contact with the upper surface of the flange of the tray supported by the sealing base, thereby welding the cover film to the flange. Therefore, since the tension of the cover film that acts on the packaged item is received by the deck plate carrying the tray, then it is possible to prevent difficulties with sealing of the film due to bending of the flange of the tray as a result of the tension of the cover film, or problems such as breaking of the flange.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 3shows a general side view of the device, in which touch bars2disposed equidistantly on endless chains1cause trays4to advance at equidistant intervals in the direction of the arrow, along the upper surface of a horizontal conveyance path3, by the rotational movement of the chains1. A general frame8comprising four corner pillar members5, a ceiling plate6provided on top of these pillar members5, and a base plate7provided below the pillar members5, is composed in such a manner that a sealing frame set9and a sealing base10are disposed respectively in upper and lower regions of the general frame8, and the seal base10and the sealing frame set9are moved upwards and downwards by means of a first lift mechanism11and a second lift mechanism12, respectively. A band-shaped cover film14wound and held on a first reel13moves at the same speed as the chains1through the lower region of the sealing frame set9, and it is wound up onto a second reel15.

FIG. 1is a partial enlarged diagram ofFIG. 3, in which the aforementioned general frame8travels back and forth reciprocally19,20, in concordance with the conveyance pitch of the trays4, by means of forward and reverse rotation of a screw rod17which is operated by a motor16. When the general frame8performs a reciprocal back and forth movement, the touch bars2cause the trays4to move successively onto the upper face of a deck plate22which is positioned on an intermediate plate18, via leg members21.

FIG. 4is a plan diagram of the horizontal conveyance path3; the aforementioned touch bars2are spanned at equidistant intervals between the pair of endless chains1, which are disposed on opposite sides of the path3and rotate along the path3, and an intermediate region25is formed between the preceding path region23and the subsequent path region24in the conveyance path3. The general frame8, which is depicted in a plate shape in this diagram, moves back and forth reciprocally along rails26disposed on opposite sides in this cutaway region25. In this case, the speed of advance of the side chains1and the speed of advance of the general frame8are the same.

Furthermore, in this diagram, a composition is achieved in which two fixed fingers29project toward the intermediate region25respectively, from front and rear stays28which are spanned between a pair of side plates27provided on opposite sides, and sets of three movable fingers30are disposed respectively facing these fixed fingers29, these fingers30being caused to slide against the individual fingers29by the reciprocal movement of the general frame8and thus creating an expanding and contracting mechanism. The trays10are conveyed by using these fingers29and30, and the deck plate22serving as a transfer area.

As shown inFIG. 1, a sealing base10having the same outline shape as the flange33formed on the perimeter edge of the tray4(seeFIG. 5) is disposed about the periphery of the deck plate22.FIG. 5shows a plan view of this sealing base10, in which a tray4bearing a packaged item32has a continuous flange33on the perimeter of the upper side open section thereof. The sealing base10which surrounds the deck plate22holds the flange33of the tray on a supporting face31thereof, and it is also formed with an endless cutting blade insertion groove34following the outline of the flange33.

InFIG. 1, a first lift mechanism11which moves the sealing base10upwards and downwards is constituted by a first servo motor35and a crank arm36which is caused to rotate by the motor35. As shown inFIG. 2, a crank pin37in the crank arm36is connected to the supporting frame41of the sealing base10, by means of a coupling bar38. The crank arm36is caused to rotate by means of the motive force of the first servo motor35being applied to a gear wheel40fixed to a main shaft39.

The sealing base10and the frame-shaped supporting frame41shown in enlarged form inFIG. 6move upwards and downwards in an integral manner with sleeves42which slide along leg members21erected in a standing fashion on the intermediate plate18. In this case, the amount of lift43of the sealing base10is limited at the point where the upper face of the sealing base10makes contact with the lower face of the flange33of the tray4, as shown inFIG. 7. If the height44of the tray4used is changed, then the amount of lift43must also be changed. Supposing that the amount of lift43is taken to be uniform and unchangeable, then if the height44of the tray is reduced, the tray4will float up above the deck plate22when it is lifted up by the sealing base10. On the other hand, if the height44of the tray4is increased, then the sealing base10will not reach the position of the flange33. As a means of resolving these problems, the rotational diameter of the crank pin37is adjusted, as described below.

More specifically, as shown inFIG. 8, guides45are formed on both sides of the inner part of the crank arm36, and a supporting base body46of the crank pin37is supported slidably by these guides45. Two screw bars48and49which are coupled by the intermeshing of two gear wheels50, are disposed on the crank arm36, and these screw bars48and49engage in a screwing action with a female screw threaded on the inner surface of the supporting base body46. By rotating the screw bars48and49by operating a handle51, it is possible to change the gap between the main shaft39, indicated by the broken line, and the crank pin37. By means of this mechanism, the lower limit position of the sealing base10inFIG. 7can be changed, and hence the amount of lift43of the sealing base10can be adjusted in accordance with the height44of the tray.

On the other hand, the sealing frame set9provided on the general frame8inFIG. 1moves upwards and downwards along guides52by means of the second lift mechanism12, and the second lift mechanism12is constituted by a second servo motor53and a crank arm54which is caused to rotate by this motor53. A crank pin55in the crank arm54inFIG. 2is connected to a supporting frame56of the sealing frame set9, by means of a coupling bar57, and the sealing frame set9can be pushed downwards in concordance with the forward motion of the general frame8.

The first servo motor35is provided as a source of rotational force for the crank arm36of the first lift mechanism11inFIG. 1, and the second servo motor53is provided as a source of rotational force for the crank arm54of the second lift mechanism12, in such a manner that the mutual speed of the crank arms36and54can be changed, or their movement can be halted, by synchronizing the operations of the two servo motors.

As shown in enlarged view inFIG. 9, in the sealing frame set9, an inverted trough-shaped sealer58having the same outline shape as the tray4is supported on a support frame56via springs59. An endless cutting blade61for cutting away the cover film14by penetrating into the lower-positioned insertion groove34described previously is fixed onto a fixing plate60which surrounds the sealer58, on the lower side of the frame56. Furthermore, coil springs63are wound respectively about a plurality of vertically slidable bar members62, which surround the cutting blade61, and furthermore, flexible, continuous or non-continuous film pressing members64which surround the perimeter of the tray4are disposed on the lower ends of the bar members62.

InFIG. 9, when the packaged item32is lifted up together with the tray4, by the lifting of the sealing base10, the film pressing members64press the film14down onto the upper surface of the sealing base10, by the elastic force of the coil springs63. On the other hand, urethane rubber69disposed inside the sealer58expels the air inside the film14by pressing the film14against the packaged item32. In this case, the tension in the cover film14and the pressing force of the urethane rubber69act as a load on the flange33of the tray4, through the packaged item32, but since the tray4is supported from below by the deck plate22, breaking or bending back of the flange33is prevented and perfect welding of the cover film14onto the flange33of the tray4can be achieved. Subsequently, the sealer58pushes the film14against the sealing base10by means of the elastic force of the main springs59, and the cover film14welds onto the upper surface of the flange on the tray4. The cutting blade61is then inserted into the insertion groove34, and the film14is cut about the perimeter of the tray4, in accordance with the outline of the flange provided on the tray4.

Stoppers71on the upper ends of core bars70provided in a standing fashion on the upper face of the sealer58receive the tension of the main springs59on the upper face of cylinders72, thereby holding the main springs59in an appropriate state of compression, and welding the cover film14onto the tray4by means of the sealing frame10and the sealer58.

InFIG. 1, a sealing base10in a lower region and a sealer58in an upper region approach each other mutually during the course of movement in the direction of arrow19of a reciprocally moving general frame8. Thereupon, when the general frame8is withdrawn in the direction of the arrow20, the sealing base10and the upper-positioned sealing frame set9are separated from each other, and this movement of the respective elements is shown inFIG. 10; since the crank arm54which lowers the sealer58rotates in one direction by the second servo motor53, the sealer58moves along a virtually elliptical box motion path68as shown inFIG. 10. However, in this case, since the sealer58abuts against the sealing base10as it rises upwards from below in the region73indicated, and since the main springs59provided between the sealer58and the supporting frame56are compressed, then the downward movement is halted in this region73, whereby both the sealing base10and the sealer58move linearly through the region73, and the cover film is welded onto the flange of the tray by the sealing base10and the sealer58.

The fact of adjusting the rotational diameter of the crank pin37in accordance with the height44of the tray4was previously described with respect toFIG. 7andFIG. 8, and the rotational diameter can be adjusted by adopting the composition shown in the drawings to the crank pin55of the second lift mechanism12inFIG. 2. In other words, since the main shaft gap74between the upper and lower crank arms inFIG. 11is unchangeable, then if the rotational diameter75of the lower crank pin is adjusted in accordance with the height of the tray, it becomes necessary to adjust the rotational diameter76of the upper side crank pin in inverse proportion to the adjustment of the lower crank pin. In this case, the upper crank arm54rotates completely through 360°, but the lower crank arm36rotates forwards and rearwards between the top dead center point P1and a point P2which does not reach the top dead center.

FIG. 12shows an embodiment in which the lower-positioned sealing base10and the upper-position sealing frame set9have different lifting mechanisms, and taking the lower-positioned sealing base10as an example, the lift mechanism is formed by a fluid cylinder77fixed to the intermediate plate18. In order that the upper limit of the lifting movement of the sealing base10is always restricted by the lower face portion of the flange33on the tray4which is mounted on the deck plate22in accordance with the height of the tray4, a stopper79is provided on the lower side of the piston rod78, in a position which can be changed along the rod78, and a variable stopper80is also provided on the rod78in the upper portion of the cylinder. Furthermore, this composition may also be adopted for the upper-positioned sealing frame set9.