Abstract:
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.

Description:
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. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side view of a general frame in the device according to the present invention; 
       FIG. 2  is a front view of  FIG. 1 ; 
       FIG. 3  is a general side view of the device according to the present invention; 
       FIG. 4  is a plan view of a tray conveyance path; 
       FIG. 5  is a partially cutaway plan view of a sealing base; 
       FIG. 6  is an enlarged side view of a sealing base; 
       FIG. 7  is an illustrative diagram of the action of a sealing base and a lift mechanism; 
       FIG. 8  is a front view of a crank arm; 
       FIG. 9  is an illustrative diagram of the action of a sealing base and a sealing frame set; 
       FIG. 10  is a diagram of a box motion performed by the sealing base and sealing frame set; 
       FIG. 11  is an illustrative diagram of a crank arm; and 
       FIG. 12  is a diagram of an embodiment of a lift mechanism. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Embodiment 1 
     FIG. 3  shows a general side view of the device, in which touch bars  2  disposed equidistantly on endless chains  1  cause trays  4  to advance at equidistant intervals in the direction of the arrow, along the upper surface of a horizontal conveyance path  3 , by the rotational movement of the chains  1 . A general frame  8  comprising four corner pillar members  5 , a ceiling plate  6  provided on top of these pillar members  5 , and a base plate  7  provided below the pillar members  5 , is composed in such a manner that a sealing frame set  9  and a sealing base  10  are disposed respectively in upper and lower regions of the general frame  8 , and the seal base  10  and the sealing frame set  9  are moved upwards and downwards by means of a first lift mechanism  11  and a second lift mechanism  12 , respectively. A band-shaped cover film  14  wound and held on a first reel  13  moves at the same speed as the chains  1  through the lower region of the sealing frame set  9 , and it is wound up onto a second reel  15 . 
     FIG. 1  is a partial enlarged diagram of  FIG. 3 , in which the aforementioned general frame  8  travels back and forth reciprocally  19 ,  20 , in concordance with the conveyance pitch of the trays  4 , by means of forward and reverse rotation of a screw rod  17  which is operated by a motor  16 . When the general frame  8  performs a reciprocal back and forth movement, the touch bars  2  cause the trays  4  to move successively onto the upper face of a deck plate  22  which is positioned on an intermediate plate  18 , via leg members  21 . 
     FIG. 4  is a plan diagram of the horizontal conveyance path  3 ; the aforementioned touch bars  2  are spanned at equidistant intervals between the pair of endless chains  1 , which are disposed on opposite sides of the path  3  and rotate along the path  3 , and an intermediate region  25  is formed between the preceding path region  23  and the subsequent path region  24  in the conveyance path  3 . The general frame  8 , which is depicted in a plate shape in this diagram, moves back and forth reciprocally along rails  26  disposed on opposite sides in this cutaway region  25 . In this case, the speed of advance of the side chains  1  and the speed of advance of the general frame  8  are the same. 
   Furthermore, in this diagram, a composition is achieved in which two fixed fingers  29  project toward the intermediate region  25  respectively, from front and rear stays  28  which are spanned between a pair of side plates  27  provided on opposite sides, and sets of three movable fingers  30  are disposed respectively facing these fixed fingers  29 , these fingers  30  being caused to slide against the individual fingers  29  by the reciprocal movement of the general frame  8  and thus creating an expanding and contracting mechanism. The trays  10  are conveyed by using these fingers  29  and  30 , and the deck plate  22  serving as a transfer area. 
   As shown in  FIG. 1 , a sealing base  10  having the same outline shape as the flange  33  formed on the perimeter edge of the tray  4  (see  FIG. 5 ) is disposed about the periphery of the deck plate  22 .  FIG. 5  shows a plan view of this sealing base  10 , in which a tray  4  bearing a packaged item  32  has a continuous flange  33  on the perimeter of the upper side open section thereof. The sealing base  10  which surrounds the deck plate  22  holds the flange  33  of the tray on a supporting face  31  thereof, and it is also formed with an endless cutting blade insertion groove  34  following the outline of the flange  33 . 
   In  FIG. 1 , a first lift mechanism  11  which moves the sealing base  10  upwards and downwards is constituted by a first servo motor  35  and a crank arm  36  which is caused to rotate by the motor  35 . As shown in  FIG. 2 , a crank pin  37  in the crank arm  36  is connected to the supporting frame  41  of the sealing base  10 , by means of a coupling bar  38 . The crank arm  36  is caused to rotate by means of the motive force of the first servo motor  35  being applied to a gear wheel  40  fixed to a main shaft  39 . 
   The sealing base  10  and the frame-shaped supporting frame  41  shown in enlarged form in  FIG. 6  move upwards and downwards in an integral manner with sleeves  42  which slide along leg members  21  erected in a standing fashion on the intermediate plate  18 . In this case, the amount of lift  43  of the sealing base  10  is limited at the point where the upper face of the sealing base  10  makes contact with the lower face of the flange  33  of the tray  4 , as shown in  FIG. 7 . If the height  44  of the tray  4  used is changed, then the amount of lift  43  must also be changed. Supposing that the amount of lift  43  is taken to be uniform and unchangeable, then if the height  44  of the tray is reduced, the tray  4  will float up above the deck plate  22  when it is lifted up by the sealing base  10 . On the other hand, if the height  44  of the tray  4  is increased, then the sealing base  10  will not reach the position of the flange  33 . As a means of resolving these problems, the rotational diameter of the crank pin  37  is adjusted, as described below. 
   More specifically, as shown in  FIG. 8 , guides  45  are formed on both sides of the inner part of the crank arm  36 , and a supporting base body  46  of the crank pin  37  is supported slidably by these guides  45 . Two screw bars  48  and  49  which are coupled by the intermeshing of two gear wheels  50 , are disposed on the crank arm  36 , and these screw bars  48  and  49  engage in a screwing action with a female screw threaded on the inner surface of the supporting base body  46 . By rotating the screw bars  48  and  49  by operating a handle  51 , it is possible to change the gap between the main shaft  39 , indicated by the broken line, and the crank pin  37 . By means of this mechanism, the lower limit position of the sealing base  10  in  FIG. 7  can be changed, and hence the amount of lift  43  of the sealing base  10  can be adjusted in accordance with the height  44  of the tray. 
   On the other hand, the sealing frame set  9  provided on the general frame  8  in  FIG. 1  moves upwards and downwards along guides  52  by means of the second lift mechanism  12 , and the second lift mechanism  12  is constituted by a second servo motor  53  and a crank arm  54  which is caused to rotate by this motor  53 . A crank pin  55  in the crank arm  54  in  FIG. 2  is connected to a supporting frame  56  of the sealing frame set  9 , by means of a coupling bar  57 , and the sealing frame set  9  can be pushed downwards in concordance with the forward motion of the general frame  8 . 
   The first servo motor  35  is provided as a source of rotational force for the crank arm  36  of the first lift mechanism  11  in  FIG. 1 , and the second servo motor  53  is provided as a source of rotational force for the crank arm  54  of the second lift mechanism  12 , in such a manner that the mutual speed of the crank arms  36  and  54  can be changed, or their movement can be halted, by synchronizing the operations of the two servo motors. 
   As shown in enlarged view in  FIG. 9 , in the sealing frame set  9 , an inverted trough-shaped sealer  58  having the same outline shape as the tray  4  is supported on a support frame  56  via springs  59 . An endless cutting blade  61  for cutting away the cover film  14  by penetrating into the lower-positioned insertion groove  34  described previously is fixed onto a fixing plate  60  which surrounds the sealer  58 , on the lower side of the frame  56 . Furthermore, coil springs  63  are wound respectively about a plurality of vertically slidable bar members  62 , which surround the cutting blade  61 , and furthermore, flexible, continuous or non-continuous film pressing members  64  which surround the perimeter of the tray  4  are disposed on the lower ends of the bar members  62 . 
   In  FIG. 9 , when the packaged item  32  is lifted up together with the tray  4 , by the lifting of the sealing base  10 , the film pressing members  64  press the film  14  down onto the upper surface of the sealing base  10 , by the elastic force of the coil springs  63 . On the other hand, urethane rubber  69  disposed inside the sealer  58  expels the air inside the film  14  by pressing the film  14  against the packaged item  32 . In this case, the tension in the cover film  14  and the pressing force of the urethane rubber  69  act as a load on the flange  33  of the tray  4 , through the packaged item  32 , but since the tray  4  is supported from below by the deck plate  22 , breaking or bending back of the flange  33  is prevented and perfect welding of the cover film  14  onto the flange  33  of the tray  4  can be achieved. Subsequently, the sealer  58  pushes the film  14  against the sealing base  10  by means of the elastic force of the main springs  59 , and the cover film  14  welds onto the upper surface of the flange on the tray  4 . The cutting blade  61  is then inserted into the insertion groove  34 , and the film  14  is cut about the perimeter of the tray  4 , in accordance with the outline of the flange provided on the tray  4 . 
   Stoppers  71  on the upper ends of core bars  70  provided in a standing fashion on the upper face of the sealer  58  receive the tension of the main springs  59  on the upper face of cylinders  72 , thereby holding the main springs  59  in an appropriate state of compression, and welding the cover film  14  onto the tray  4  by means of the sealing frame  10  and the sealer  58 . 
   In  FIG. 1 , a sealing base  10  in a lower region and a sealer  58  in an upper region approach each other mutually during the course of movement in the direction of arrow  19  of a reciprocally moving general frame  8 . Thereupon, when the general frame  8  is withdrawn in the direction of the arrow  20 , the sealing base  10  and the upper-positioned sealing frame set  9  are separated from each other, and this movement of the respective elements is shown in  FIG. 10 ; since the crank arm  54  which lowers the sealer  58  rotates in one direction by the second servo motor  53 , the sealer  58  moves along a virtually elliptical box motion path  68  as shown in  FIG. 10 . However, in this case, since the sealer  58  abuts against the sealing base  10  as it rises upwards from below in the region  73  indicated, and since the main springs  59  provided between the sealer  58  and the supporting frame  56  are compressed, then the downward movement is halted in this region  73 , whereby both the sealing base  10  and the sealer  58  move linearly through the region  73 , and the cover film is welded onto the flange of the tray by the sealing base  10  and the sealer  58 . 
   The fact of adjusting the rotational diameter of the crank pin  37  in accordance with the height  44  of the tray  4  was previously described with respect to  FIG. 7  and  FIG. 8 , and the rotational diameter can be adjusted by adopting the composition shown in the drawings to the crank pin  55  of the second lift mechanism  12  in  FIG. 2 . In other words, since the main shaft gap  74  between the upper and lower crank arms in  FIG. 11  is unchangeable, then if the rotational diameter  75  of the lower crank pin is adjusted in accordance with the height of the tray, it becomes necessary to adjust the rotational diameter  76  of the upper side crank pin in inverse proportion to the adjustment of the lower crank pin. In this case, the upper crank arm  54  rotates completely through 360°, but the lower crank arm  36  rotates forwards and rearwards between the top dead center point P 1  and a point P 2  which does not reach the top dead center. 
   Embodiment 2 
     FIG. 12  shows an embodiment in which the lower-positioned sealing base  10  and the upper-position sealing frame set  9  have different lifting mechanisms, and taking the lower-positioned sealing base  10  as an example, the lift mechanism is formed by a fluid cylinder  77  fixed to the intermediate plate  18 . In order that the upper limit of the lifting movement of the sealing base  10  is always restricted by the lower face portion of the flange  33  on the tray  4  which is mounted on the deck plate  22  in accordance with the height of the tray  4 , a stopper  79  is provided on the lower side of the piston rod  78 , in a position which can be changed along the rod  78 , and a variable stopper  80  is also provided on the rod  78  in the upper portion of the cylinder. Furthermore, this composition may also be adopted for the upper-positioned sealing frame set  9 . 
   What has been described above are preferred aspects of the present invention. It is of course not possible to describe every conceivable combination of components or methodologies for purposes of describing the present invention, but one of ordinary skill in the art will recognize that many further combinations and permutations of the present invention are possible. Accordingly, the present invention is intended to embrace all such alterations, combinations, modifications, and variations that fall within the spirit and scope of the appended claims.