Abstract:
A combination sealing and cutting device comprising: an elongated anvil having an elongated slot therein; an elongated blade having a longitudinal aperture therein; a heating element in the longitudinal aperture; and an actuator mechanism for driving the blade toward and into the elongated slot to accomplish simultaneous sealing and cutting of overlying polymer films. According to various preferred embodiments, the combination sealing and cutting device further includes a pair of parallel flanges extending along both edges of the blade that serve to retain the blade; and film retaining beads along the longitudinal edges of the parallel flanges that serve to retain the plastic films being cut and sealed against the outer edges of the elongated slot.

Description:
This application is a continuation-in-part of U.S. patent application Ser. No. 10/997,298 Filed Nov. 24, 2004 and copending herewith. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to devices for cutting and sealing polymeric films and more particularly to such a device that simultaneously in a single operation or stroke performs both such operations. 
     BACKGROUND OF THE INVENTION 
     In the packaging industry, it is common practice in the continuous packaging of product to transfer the product to a position between two sheets of polymeric or plastic material and to form a package by sealing about the periphery of the contained product once it is within the confines of the overlying and underlying plastic wrapping material. 
     While it is a relatively simple matter to obtain a seal along the continuous outer edges of the overlying sheets of plastic material, it is a more difficult task to obtain sealing of the individual packages between units thereof, especially in high speed packaging operations since in this processing step, the overlying sheets of plastic material that contain the product must be sealed and cut rapidly and virtually simultaneously to meet the speed demands of such high speed packaging equipment. 
     A variety of systems have been suggested in the prior art for obtaining such cutting and sealing of the intermediate portions of plastic packaging material over and under wrapped about a unit of product. While no such systems are described specifically herein, suffice it to say that they have been largely either quite bulky because of the division of the cutting and sealing operations into two separate steps or relatively slow when compared to the packaging line speed overall attainable without the rather slow cutting and sealing operation. 
     Thus, there remains a need in the art for a short cycle, rapid and accurate cutting and sealing device that can meet the demands of high speed packaging equipment. 
     OBJECT OF THE INVENTION 
     It is therefore and object of the present invention to provide a high speed, simple to operate yet accurate cutting and sealing system for, for example, plastic packaging operations. 
     SUMMARY OF THE INVENTION 
     According to the present invention, there is provided a combination sealing and cutting device comprising: an elongated anvil having an elongated slot therein; an elongated blade having a longitudinal aperture therein; a heating element in the longitudinal aperture; and an actuator mechanism for driving the blade toward and into the elongated slot to accomplish simultaneous sealing and cutting of overlying polymer films. According to various preferred embodiments, the combination sealing and cutting device further includes a pair of parallel flanges extending along both edges of the blade that serve to retain the blade; and film retaining beads along the longitudinal edges of the parallel flanges that serve to retain the plastic films being cut and sealed against the outer edges of the elongated slot. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of the combination sealing and cutting bar of the present invention. 
         FIG. 2  is a side view of the combination sealing and cutting bar of the present invention in its raised position. 
         FIG. 3  is a side view of the combination sealing and cutting bar of the present invention as it approaches its cutting/sealing position. 
         FIG. 4  is a side view of the combination sealing and cutting bar of the present invention in its cutting/sealing position. 
         FIG. 5  is a side view of the combination sealing and cutting bar of the present invention in its retracted post cutting/sealing position. 
         FIG. 6  is an isometric view of an alternate preferred embodiment of the cutter bar of the present invention. 
         FIG. 7  is a detail side view of one element of the cutter bar of  FIG. 6 . 
         FIG. 8  is an end view of a portion of the cutter bar of  FIGS. 6 and 7 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to the accompanying Figures, the combination sealing and cutting bar of the present invention  10  comprises; an elongated cutting and sealing blade  12  having a longitudinal aperture  14  running the length of the interior thereof; a anvil  16  having a longitudinal or elongated slot  18  running the length thereof; an actuator  20  that initiates movement upwards and downwards or reciprocal movement as indicated by double headed arrow  22 ; and a frame  23  that provides support for the entire mechanism. Located within aperture  14  is a heating element  24  best seen in  FIGS. 2–5  that show a side view of the sealing and cutting device of the present invention. Heating element  14  that may be of any suitable material and configuration well known in the art including various resistance type heaters etc. provides the heat necessary to accomplish cutting and sealing of polymeric films, as described below, to blade  12 . Actuator  20  may comprise any of a well known number of actuating mechanisms such as pneumatic, hydraulic and servo based actuators. Support  26 , although not essential to the operation of the device of the present invention is provided as an attachment between actuator  20  and blade  20 . Additionally, support  26 , at its extremities provides mounting points for brackets  28  that contact guide rails  30  as described below. 
     As best seen in  FIGS. 2–5  anvil  16  encompasses a longitudinal slot  18 . While in the accompanying drawings slot  18  is shown as being rectangular in shape it could, of course, be of any suitable shape that does not affect the operation of device  10  as described below. As also shown in  FIGS. 2–5  are auxiliary elements of device  10  that significantly enhance its functioning in the particular application shown. These include brackets  28  that include a recess  29  that rides on guide rails  30  to provide stability and positional accuracy and retaining beads  32  fabricated from a resilient and temperature resistant material such as a silicone polymer that serve to restrain movement of any kind between a pair of films  34  and  36  that are being cut and sealed to each other. Retaining beads  32  are coated or applied along the entire length of flanges  38  and  40  on the edges thereof that are remote from the point of attachment to blade  12 . Flanges  38  and  40  serve the multiple purposes of securing blade  12  and providing attachment points for retaining beads  32 . 
     Operation of sealing and cutting device  10  is best understood by a sequential study of  FIGS. 2–5  that show, in order, the various steps in the operation of device  10 .  FIG. 2  shows device  10  in the raised or non-contacting position above slot  18  with polymer sheets  34  and  36  to be cut and sealed therebelow before initiation of the cutting and sealing operation. Referring now to  FIG. 3 , in this position retaining beads  32  have just contacted films  34  and  36  and have brought them into taut contact with upper surface  42  of anvil  16  along either side of slot  18 . In this condition, movement of polymer films  34  and  36  relative to each other, longitudinally or laterally is inhibited. It should be noted that the lower extremities of retaining beads  32  are approximately parallel to the tip  44  of blade  12  in the retracted position depicted in  FIG. 2 . 
       FIG. 4  shows device  10  in the sealing and cutting position wherein depression of retaining beads  32  allows the tip  44  of elongated blade  12  to extend slightly below the bottom beads of retaining beads  32  in their compressed condition to penetrate very slightly into slot  18 . Heat from heating element  24  that has heated elongated blade  12  to a suitable temperature initiates cutting of polymer sheets  34  and  36  as well as fusion thereof. As will be apparent to the skilled artisan, while it is shown in the accompanying Figures and is preferred in the operation of the device as described herein that retaining beads  32  compress upon contact with anvil surface  42 , some depression of anvil surface  42  or any combination of the depression of retaining beads  32  and anvil surface  42  could also provide the conditions necessary to obtain sealing and cutting as described herein. As best seen in  FIG. 5  that depicts the post sealing/cutting position for device  10 , i.e. the retracted position thereof, polymer material from polymer sheets  34  and  36  that has been fused during the cutting/sealing operation shown in  FIG. 4  forms elongated beads of polymer  46  that serve to seal the opposing and now separated edges of polymer sheets  34  and  36  thereby having accomplished both the cutting and sealing of polymer sheets  34  and  36  in a single very fast operation. 
     Thus, in a single stroke of device  10  both cutting and sealing of the edges of polymer sheets  36  and  38  has been accomplished. Such an operation can be performed extremely quickly thereby allowing for high speed operation of device  10 . 
     Depicted in  FIGS. 6–8  is an alternative preferred embodiment of the device  10  of the present invention. As depicted in these Figures, flange  38  is attached to sealing blade  12  by a pair of attachment assemblies  53  described below. Flange  38  is attached to a slide  52  by bolts  54 . A shaft  56  that is mounted to a bracket  58  at the top  60  and bottom  62  of bracket  58  passes loosely and unimpeded through an aperture  68  in slide  52 . Springs  65  and  66  are mounted about shaft  56 . Bracket  58  is in turn attached to blade  12  with bolts  59  such that flange  38  can move up and down in the direction indicated by arrow  22  as slide  52  moves similarly in aperture  68  in bracket  58 . Spring  65  serves to drive slide  52  downward while spring  66  provides cushioned resistance to such movement. Thus, as the seal assembly comprising sealing blade  12  and flange  38  moves downward, spring  65  remains extended until flange  38  strikes anvil  16 . As this assembly continues downward pressure is applied to tip  32  through flange  38  thereby retaining pressure on film  34  at its inward side while allowing the assembly to continue its downward movement. During the up stroke of the assembly spring loaded flange and associated retaining bead  32  stays down after sealing blade  12  has disengaged from anvil  16  and the material in slot  18  thereby maintaining pressure on the now severed inward bound portion of film  34 . This delayed removal of flange  38  and associated retaining bead  32  from contact with the inward bound portion of film  34 , i.e. that moving from the direction of arrow A shown in  FIG. 8 , allows the outward bound portion of film  34 , i.e. that moving in the direction of arrow B in  FIG. 8  or away from anvil  16  with a package being formed downstream, without pulling additional inward bound film with it in cases where cutting is not entirely complete. Absent such delayed action between removal outward bound film  34  and release of pressure on inward bound film  34  inward bound film  34  might in some instances of incomplete cutting remain attached to outward bound film  34  thereby affecting both the integrity of a package being formed downstream and causing film waste. As seen in  FIG. 6 , slots  70  are provided for access to bolts  59 . 
     Because of the operational efficiency just described, it is highly desirable that only one flange  38 , that flange addressing the inward bound side of the apparatus  10  be fabricated as just described. It would of course be possible to equip both the inward and outward bound sides of apparatus  10 , i.e. both flanges  38  and  40  with the spring loadings just described in connection with the inward bound side, if one desired to do so. Of course, in order to achieve the operational advantage just described, the inward bound flange would still have to release after the outward bound flange released film  34 . 
     While blade  12  and anvil  16  can be fabricated from a wide variety of materials, the use of a high heat conductivity material such as aluminum or copper and alloys thereof has been found most desirable for fabrication of blade  12 , while the use of a heat resistant foam such as one fabricated from a silicone polymer has been found most effective for anvil  16 . Operating temperatures for blade  12  will, of course, vary with the material being sealed as well as the speed of operation, but are readily determinable by those skilled the polymer fusing/sealing arts. 
     There has thus been described a very simple yet highly effective high speed cutting and sealing device for cutting and sealing a pair of overlying polymer sheets. 
     As the invention has been described, it will be apparent to those skilled in the art that the same may be varied in many ways without departing from the spirit and scope of the invention. Any and all such modifications are intended to be included within the scope of the appended claims.