Patent Publication Number: US-2013239519-A1

Title: Easily removable selvage device

Description:
BACKGROUND OF THE INVENTION 
     Machines used to wrap and seal articles and packages in thermoplastic film are well known in the art. Two types of machines are commonly referred to as side-sealing and lap-sealing machines. In the typical side-sealing configuration, an article or set of articles travels, typically via a conveyer belt, toward the machine. A sheet of center-folded plastic film, having two layers, is fed from a direction, which is preferably perpendicular to the direction of the conveyer. The two layers of the film are then separated such that the article is placed between the lower layer and the upper layer. On one side of the article is the center-fold, while on the other side, there is an open edge where the two layers are not attached. The machine has several sets of belts to hold and guide the film, and a side sealing mechanism, which typically comprises a heating/sealing element that fuses or welds the two layers together and a cutting element that removes the excess material. In some embodiments, the heating element serves to cut the film as well. These elements, whether a unitary element or separate components, are referred to as the heating/sealing/cutting element throughout this disclosure. Thus, as the article passes by the side sealing mechanism, this open edge is sealed by welding the two layers together, the plastic is cut and the waste is removed. At this point, the plastic film resembles a tube, with openings at both the leading and trailing ends of the article, but sealed along both sides. As the article continues to advance, an end sealing mechanism is then employed to seal the film at the leading end of the article. The article is then advanced and the end sealing mechanism then seals the film at the trailing end of the article. 
     Typically, when the film is cut, the waste, or selvage, is pulled or transported away from the tube and discarded. In some embodiments, the selvage is wound onto a spool to keep the waste contained in a small, easily manageable area. When the spool is filled with selvage, the machine is stopped, the selvage is then removed from the spool and discarded. 
     As the waste is cut by the machine, it is at an elevated temperature. As it is wound on the spool, the selvage shrinks as it cools. In some cases, such as with specific types of film, the selvage shrinks and hardens to a point where it is difficult to remove from the spool. In these instances, typically the selvage must be cut off the spool. This is time consuming and reduces machine efficiency, as the machine is typically turned off while the selvage is being removed. 
     Therefore, it would be beneficial if there were a device which held the selvage as it was being removed by the machine, but allows the selvage to be easily removed without the use of a knife. 
     SUMMARY OF THE INVENTION 
     The problems associated with the prior art have been overcome by the present invention, which describes a device for spooling selvage as it is cut by a side-sealing machine. The device includes a two part core, which is held together by a friction fitting, such as a keyless bushing. The two parts of the core are shaped so that as the selvage is wound onto the core, it exerts both a radial and axial force on the core. This axial force provides the force needed to separate the two parts of the core when the bushing is removed. Various shaped core parts may be used, and various friction fittings are also envisioned. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a representative side-sealing machine of the prior art; 
         FIG. 2  illustrates a view of the side-sealing mechanism in accordance with the present invention; 
         FIG. 3  illustrates a top view of the side-sealing mechanism shown in  FIG. 2 ; 
         FIGS. 4A-B  show a selvage spool of the prior art. 
         FIG. 5  shows a first embodiment of a selvage spool in accordance with the present invention. 
         FIG. 6  shows a second embodiment of a selvage spool in accordance with the present invention. 
         FIG. 7  shows a hydraulic keyless bushing for use with the present invention. 
         FIG. 8  shows a second keyless bushing for use with the present invention. 
         FIG. 9  shows an exploded view of one embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  illustrates a representative side-sealing machine used to encapsulate or wrap an article in thermoplastic film, as described in U.S. Pat. No. 6,526,728. The machine  10  utilizes a conveyer belt  12  operating at a relatively constant speed to deliver articles  8  that are to be encapsulated. The thermoplastic film  1  is center-folded, such that the side with the fold is closed, while the opposite side  6  is open. On this opposite side, there are two layers of film  4 , 5 , which will later be sealed. This center-folded thermoplastic film  1  is fed from a reel (not shown) that is preferably mounted such that the film is fed perpendicular to the direction of travel of the conveyer belt  12 . The film is then inverted and separated by an inverter  13  such that the article is enveloped between the two layers  4 , 5 . At this point, the film  1  on one side of the article is closed, while the opposite side  6  remains open. Also, the film at both the leading and trailing ends of the article are not sealed. Downstream from the inverter is the side-sealing mechanism  20 . After proper relative positioning of the article between the layers of the film  4 , 5 , the enveloped article approaches the side-sealing mechanism  20 . 
     The side-sealing mechanism  20  is located on the open side  6  of the enveloped article. The mechanism holds the two layers of film  4 , 5  together, and guides the layers through the heating and cutting means. It then welds the two layers together, and cuts off the surplus material. The surplus material is pulled away so as not to reattach to the film while it is still at an elevated temperature. 
     As shown in  FIG. 2 , to perform these actions, the mechanism  20  preferably comprises two sets of cooperating pulleys, an upper set  101  and a lower set  102 . These sets work in unison to pull the two layers of film  103  into the mechanism and hold the layers in place. In the preferred embodiment, each of the pulleys has teeth  110  in its channel so as to accept one or more, preferably two, timing belts  120 . The presence of teeth  110  ensures that the timing belt does not slip relative to the pulleys. However, V belts can also be utilized with this invention, as well. The first set of pulleys  101  is located above the layers of film, while the second set  102  is located below the layers. Each set comprises a drive pulley  101   a,    102   a  and a tail pulley  101   b,    102   b.  There may optionally be one or more idler pulleys (not shown). Each of these pulleys also has one or more, preferably two, O-rings mounted in the channel where the belts are located, so as to provide individual channels for each of the timing belts. 
     Each of the timing belts preferably has a special gripping outer surface, that is bonded to a truly endless steel or Kevlar reinforced timing belt. Each corresponding set of belts has upper and lower pressure plates that are preset to insure good contact between the pair of belts. 
     In one embodiment, as shown in  FIG. 3 , one set of O-rings  200  is positioned such that the movement of the outermost belt  210  is made to be parallel to the direction of the film movement. The outer wall of the pulley  240  and this first set of O-rings  200  provide the guides for the outermost belt  210 . As shown in  FIG. 3 , O-ring  200   a  and O-ring  200   b  are equidistant from the outer wall of their respective pulleys. A second set of O-rings  201  is used to guide the innermost belt  220  in a path that diverges away from the direction of the film and the outermost belt. This can be accomplished in a number of ways. For example, a combination of one O-ring and the inner wall of the downstream pulley  250   b  can be used to define the channel for the innermost belt  220 , as shown in  FIG. 3 . Similarly, two O-rings may be inserted on the upstream pulley to define a channel for the innermost belt. Alternatively, a single O-ring  201   a,  as shown in  FIG. 3 , can be used to define the inner wall of the channel for the innermost belt  220 . Because of the divergence angle, there are no forces pushing the innermost belt  220  toward the outermost belt  210 , thus the second O-ring may be eliminated. In other words, in the channel associated with the upstream pulley  240   a,  the O-ring  201   a  provides the inner guide for the belt  220 . In the channel associated with the downstream pulley  240   b,  the O-ring  201   b  provides the outer guide for the belt  220 . As a result, the innermost belt  220  is closest to the outermost belt  210  at the upstream pulley, and farthest away from it at the downstream pulley. The tubular heating element  230  is preferably located between the upstream and downstream pulleys. Thus, as the film passes the upstream pulley, it is still intact; however, it is cut before it reaches the downstream pulley. By introducing this divergence angle, the innermost belt  220  helps guide the unwanted surplus away from the film after it is cut. In the preferred embodiment, the innermost belt  220  is guided in the channel of the downstream pulley a distance further away from the film than on the upstream pulley sufficient to force the surplus plastic away from the film. One such suitable distance is about ¼ inch. This ensures that the surplus material does not reattach itself to the film while still at an elevated temperature. This surplus material is then held under tension and fed onto a reel, which is later discarded. While the use of multiple belts, with a divergence between them is preferred, the use of a single belt, or multiple parallel belts is also within the scope of the present invention. 
     The side-sealing mechanism  20  includes the heating and cutting element  230 . As described above, this element is preferably located between the upstream and downstream pulleys, so that it can seal and cut the film before it is separated by the downstream pulley. The heating and cutting element  230  may be any suitable shape and type. For example, the heating and cutting element  230  may be formed into an open oval, or may be a heated knife. 
     As the film is cut, the waste is removed and pulled away from the side-sealing mechanism. In some embodiments, the waste is routed through one or more loops  185  (see  FIG. 2 ) and onto a spool located distal from the mechanism  20 . 
     In some embodiments, the spool rotates so as to wind the selvage onto the spool. The speed of rotation may be controlled in various ways. In one embodiment, the rotational speed of the spool is coupled to the speed that the film is moving on the mechanism  20 . In another embodiment, the tension on the selvage as it approaches the spool is used to control the rotational speed of the spool. For example, if the tension is too low, the spool rotates more rapidly. If the tension is too high, the rotational speed of the spool slows. Of course, other methods of controlling the rotational speed of the spool, such as a slip clutch, can be used, without departing from the spirit of the invention. 
       FIG. 4   a  shows a side view of a traditional spool  300  and  FIG. 4   b  shows a front view of the spool  300 . The spool  300  is typically made up of two parts  301 ,  302 , which are pressed next to one another, typically on a rod  303 . These two parts  301 ,  302  are held together using a screw  304  fastened to the distal end of the rod  303 . The two core parts  301 ,  302  are typically constructed to have higher outside walls  305 ,  306 , thereby allowing the selvage to amass in the trough  310  between the walls  305 ,  306 . Other shapes for the core parts may also be used. 
     When the selvage is spooled onto parts  301 ,  302 , it may shrink as it cools. In certain embodiments, the selvage forms a hard plastic, which serves to tightly couple parts  301 ,  302  together. As the selvage cools, the majority of the compression force is directed radially on the parts, as the parts  301 ,  302  are relatively flat in the trough  310 . This compression force served to bind the two parts  301 ,  302  together, often requiring an operator to pry the parts apart or cut the selvage off the spool. 
     To overcome this issue, the present device, shown in  FIG. 5 , utilizes two frustoconical parts  401 ,  402 , which are arranged with the narrow ends adjacent to each other. The incline angle θ of each port  401 ,  402  is defined as the angle of incline from the axis  403  passing through the center of the cone. Thus, smaller incline angles create a shallower trough, while larger angles create a steeper trough. The incline angle helps distribute the amount of axial and radial force created by the compression of the selvage. Higher incline angles create increasing amount of axial force, with reduced radial force. This higher axial force tends to force the two core parts  401 ,  402  apart, thereby eliminating the problem of the prior art, where the two parts of the core become stuck together. 
     Therefore, by utilizing two core parts  401 ,  402  which are shaped such that the compression force of the selvage creates an adequate axial force, the core parts  401 ,  402  are inherently being forced apart, thereby eliminating the issue of the core parts being affixed together by the selvage. In some embodiments, an incline angle greater than about 15° is used. In some embodiments, an incline angle of between about 15° and 20° is used, although other angles are also possible. 
     While two identical frustoconical parts  401 ,  402  may be used, the invention is not limited to this embodiment. For example, the two parts do not need to be symmetrical. For example, the incline angles of the two parts may differ. In other embodiments, the cones are not linear, but rather have a curvilinear shape. 
     In another embodiment, shown in  FIG. 6 , one frustoconical part  500  is used with a planar end plate  501 . The incline angle of the part  500  serves to transform the compression force generated by the selvage at least partially into an axial force, thereby pushing the end plate  501  away from the frustoconical part  500 , thereby easing separation of the two parts when the spool is to be emptied. 
     The use of core parts shaped so as to translate the compression force generated by the shrinkage of the selvage into an axial force greatly reduces the difficulty in separating the two core parts. In fact, in some embodiments, the axial force is sufficiently great that the two core parts separate as soon as the fastener used to hold them together is removed. 
     In some embodiments, the faster used to hold the two core parts together may be a threaded bolt, as is traditionally used in the prior art. However, in some embodiments, the axial force generated by the compression force is sufficiently high so as to cause the threaded bolt to seize, making it difficult to remove. 
     In some embodiments, a friction fitting is used to hold the core parts together on the rod. For example, a hydraulic keyless bushing, as shown in  FIG. 7 , may be used. In this embodiment, the bushing  600  has a sleeve  601 , and a flange  602 , having a tightening screw  603 . 
     Hydraulic fluid is contained within the flange  602 . As the screw  603  on the flange  602  is tightened, the hydraulic fluid flows into the sleeve  601 . This fluid causes the sleeve  601  to expand, both inwardly and outwardly. This inward expansion serves to tighten the sleeve  601  onto the rod, thereby forming a friction fitting. 
     In another embodiment, other types of keyless bushings are used. For example,  FIG. 8  shows a keyless bushing  700  which expands due to internal wedges used to deform the sleeve. In this embodiment, tightening the screws  703  around the flange  702  causes wedges within the bushing  700  to extend into the sleeve  701 , causing it to expand, exerting inward and outward forces. Such a keyless bushing can also be used. The invention is not limited to these embodiments, other types of keyless bushing are known in the art and are suitable for this application. An advantage of keyless bushings is that they remain in place by using radial force, pressing the sleeve against the internal rod. Thus, the operation of this type of bushing is not affected by the presence of a large axial force against the bushing, in the way a threaded bolt is affected. 
     In fact, any fastener which uses radial force to fasten to the internal rod may be used. While hydraulic and wedge type keyless bushings are described, any such fastener may be used. 
       FIG. 9  shows an exploded view of the components used in accordance with one embodiment. As described earlier, the selvage spool has a rod  800 , onto which the core is placed. The core may be comprised of two symmetric frustoconical portions  801 ,  802 , arranged such that the narrow ends of the portions  801 ,  802  are adjacent to one another. In some embodiments, vertical plates  803 ,  804  are placed adjacent the wider ends of the portions  801 ,  802 , respectively, to increase the amount of selvage which may be accumulated on the spool. The vertical walls may be any suitable radius, such as 11.5″ or 14″, although other dimensions are also possible. As described above, the assembly, which includes the vertical walls  803 ,  804  and the two core portions  801 ,  802  is held on the rod  800  through the use of a fastener  805  which utilizes radial force to hold itself in place, such as a keyless bushing. Of course, as described above, other configurations are possible. For example, one only of portions  801 ,  802  may be used. The incline angle of the core portion would translate the compression force of the selvage into an axial force, which presses against the vertical wall that is adjacent to the narrower end of the portion. 
     The core portions may be made of any suitable material, such as polyurethane, or a metal, such as aluminum. Thus, the invention includes at least one core portion which has an incline angle which translates the compression force of the selvage at least partially into a axial force, which in turn is used to separate the core portion from its adjacent component. In  FIGS. 5 and 9 , this axial force is used to separate two core portions from one another. In  FIG. 6 , this axial force is used to separate the core portion from the vertical wall adjacent to it. The intentional creation of an axial force to enable separate of the core portion also tends to cause certain types of fasteners, such as threaded bolts, to seize. Thus, in some embodiments, fasteners which utilize radial force to secure themselves in place are used to hold the core portions on the rod. 
     The present disclosure is not to be limited in scope by the specific embodiments described herein. Indeed, other various embodiments of and modifications to the present disclosure, in addition to those described herein, will be apparent to those of ordinary skill in the art from the foregoing description and accompanying drawings. Thus, such other embodiments and modifications are intended to fall within the scope of the present disclosure. Further, although the present disclosure has been described herein in the context of a particular implementation in a particular environment for a particular purpose, those of ordinary skill in the art will recognize that its usefulness is not limited thereto and that the present disclosure may be beneficially implemented in any number of environments for any number of purposes.