Abstract:
A machine wraps packages such as bales of crumb rubber, or other containers of goods, into a protective synthetic resin film bag or cover. The machine is provided with a set of movable jaws each having a heat-sealing frame assembly having improved heat transfer characteristics. The heat-sealing frame assembly is composed of heat sealing units which have enhanced heat distribution and reduced cold spot or no-seal areas, and also reduced hot spot burn-through. Heat transfer from the heat sealing elements to the remaining portions of the baling assembly is also reduced.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to sealing machines for bales or packages, such as high quality rubber crumbs or chips. 
     2. Description of the Related Art 
     A considerable number of types of packages or cartons are wrapped and then heat sealed into a protective synthetic resin film for shipment. So far as is known, the heat sealing has been done by a set of elongate heat elements formed in the horizontal outline or configuration of the package, usually a rectangle or square. An example of such an elongate heat element or rod is a product known as a Calrod® sold by General Electric Company. The rod received a flow of electrical current through it and generated heat to partially melt edges of the film together to seal the film into a protective film wrap over the box or product. The heat rod was usually enclosed in a non-adhesive protective cover, such as that sold by E. I. duPont de Nemours and Company under the trademark Teflon®, to prevent the film from sticking to heat element. 
     For example, high quality rubber is prepared in a process that forms small chips or clumps, often termed crumbs, of relatively soft, pliable rubber. The resultant rubber is typically referred to as crumb rubber. Examples of such types of crumb rubber are those provided under the trademarks Budene®, Natsyn® and Chemigum® of Goodyear Tire &amp; Rubber Company. It has been typical to form the rubber crumbs into bales for ease of handling, storage and shipment. U.S. patent application Ser. No. 08/873,388, filed Jun. 11, 1997 now U.S. Pat. No. 5,870,951, of which applicant is the inventor, is one type of such a baling machine. 
     After the bale of rubber particles is formed, the bales are then wrapped within a protective synthetic resin film. The protective synthetic resin film prevented the relatively soft bales from sticking together when stacked for storage or shipment. The film wrapping also maintained the integrity of the bale during handling, storage and shipment. It was also desirable that this rubber after being made be kept free from contamination by metal particles, dirt, liquids, or other contaminants. The film wrapping was then heat sealed along seams about the rubber bale to enclose the rubber to prevent sticking, maintain integrity of the bale and also keep out contaminants. Typically, a set of heating element rods or blades in a sealing machine or press of the type described above gripped portions of the film and heated it to form a sealed seam. 
     There have, however, been problems with these heat sealing elements and assemblies. The temperature of the heat sealing assemblies fluctuated along their length, and in a non-uniform manner. Where the temperature was uneven along the heat sealing element, either cold spots or hot spots could result at certain locations. Where there were cold spots, the film edges of the seam often did not seal, or only partially sealed. This left openings along the seam where rubber or other package contents would be exposed and possibly adhere to adjacent bales or other objects or where contaminants might enter. 
     If the temperature of the heating elements was raised to avoid cold spots, the service life of the heating element was reduced because of increased temperature. Further, certain areas along the length of the heating elements could reach too high a temperature and cause hot spots. At hot spots, the heat could become high enough to burn holes through the film, again causing exposure of the contents with sticking problems and also the risk of contamination of the contents of the bale or package. 
     SUMMARY OF THE INVENTION 
     Briefly, the present invention provides a new and improved wrapping machine for wrapping a package into a synthetic resin film. The wrapping machine includes a set of sealing jaw members which receive between them a sleeve of the synthetic resin film. The package to be wrapped is moved or inserted into an open end of the synthetic resin film sleeve. The sealing jaw members are movable with respect to each other to enclose the package within the film sleeve. 
     Each of the movable jaw members of the machine has a heat sealing frame assembly mounted with it. The heat sealing frame assembly is formed of heat sealing units arranged in a shape conforming to the horizontal outline of the package. 
     The heat sealing units form seams in the synthetic resin film wrapping along side wall portions of the wrapping of the package. The heat sealing units include a heating element for heating the synthetic resin film to form the seams in the synthetic resin film wrapping. A heat sealing member is provided in the heat sealing unit for transferring heat from the heating element to portions of the film at the location of forming the seam. The heat sealing member is formed of a heat conductive material of a length corresponding to the seam to be formed. The heat sealing member also has a film contact strip extending along its length for contacting the synthetic resin film and heating it. An internal channel is formed in the heat sealing member for receiving the heating element. The heat sealing member is mounted with the wrapping machine by means of a mounting plate, which is preferably of an insulative material. By mounting the heating element in the heat conductive heat sealing member, the film contact strip is more uniformly heated, therefore eliminating hot or cold spots in the heating element. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevation view, partially exploded, of a sealing machine according to the present invention; 
     FIGS. 2,  3  and  4  schematic views of portions of the sealing machine of FIG. 1 during its operation; 
     FIG. 5 is an isometric view of the sealing machine of FIG. 1 sealing a film wrapper about a rubber bale; 
     FIG. 6 is an isometric view of a bale sealed in a film wrapper by the sealing machine of FIG. 1; 
     FIG. 7 is an exploded isometric view of a sealing jaw assembly for the sealing machine of FIG. 1; and 
     FIG. 8 is a cross-sectional view taken along the line  8 — 8  of FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF INVENTION 
     In the drawings, the letter W (FIGS. 1 and 5) designates generally a wrapping machine according to the present invention for wrapping a package P (FIG. 6) into a synthetic resin film F. The wrapping machine W includes a set of jaw members  10  and  12  which in the preferred embodiment are movable support frames. The jaw or frame members  10  and  12  are movable inwardly and outwardly with respect to each other, as indicated by an arrow  14 , by a suitable movement mechanism. As shown in the drawing, the movement mechanism for each of the jaw members  10  and  12  may be a hydraulic or pneumatic cylinder  18  mounted with such jaw member. It should be understood that other forms of mechanisms conventional in the art may also be used as movement mechanisms as well. 
     The cylinder  18  for each such jaw member receives a flow of driving fluid through suitably positioned fluid supply flow ports  18   a  and  18   b.  The fluid is received into one of the ports  18   a  or  18   b  and pressurized to drive a piston rod  20  to cause movement of the jaw member  10  or  12 , as the case may be, in one direction. Similarly, pressurized fluid received into the other of the ports reverses the direction of movement of the jaw member. The movement mechanisms  18  are anchored or affixed as indicated schematically at  22  to some base, floor, or other immobile frame work or structure. 
     The particular structural arrangement of beams, channels and other structural components of the jaw members  10  and  12  is conventional and may include limit switches or position sensors to control relative amounts of their movement with respect to each other. A suitable source for such jaw or frame members  10  and  12 , for example, is J &amp; J Manufacturing Co. of Beaumont, Tex. It should be understood that movable support frames available from other suppliers may also be used. 
     In the preferred embodiment, the package P is shown as a bale of crumb rubber, typically weighing about eighty pounds and having horizontal cross-sectional dimensions of fourteen inches by twenty-three inches and a height of about ten inches. When produced, the crumb rubber is typically formed into bales, of this type, for ease of handling, storage and shipment. U.S. patent application Ser. No. 08/873,388, filed Jun. 11, 1997 now U.S. Pat. No. 5,870,951, and of which Applicant is the inventor, is a suitable type of machine for forming crumb rubber into such a bale. Such patent is incorporated herein by reference for all purposes. 
     The crumb rubber in such a bale is relatively pliable and adhesive. For this reason, it is desirable to encapsulate the crumb rubber bale or package P to a relatively snugly fitted seamed package (FIG. 4) of the synthetic resin film F. As will be set forth, the relative snugness of the fit can be adjusted to a suitable fit. Further, although the preferred embodiment is in the context of a crumb rubber package or bale, it should be understood that other types of packages could also be wrapped, such as food products, frozen food, or any other suitable type of package which is desirable to be wrapped and heat-sealed into a protective synthetic resin film F for shipment. 
     The package P is transported into position next to the jaw members  10  and  12  on a conveyor belt  24 . Portions of the conveyor belt  24  are not shown in FIG. 1 in order that structure of the wrapping machine W may be more clearly seen. The film F for wrapping the package P is initially contained as two separate sheets  25   a  and  26   a,  stored on spaced upper storage roll  25  and lower storage roll  26 . The film sheets  25   a  and  26   a  from the rolls  25  and  26  are fused together by a front or lead heating element  27  into a lateral seam  28  extending transversely to the direction of movement, indicated at  24   a,  of the package P along conveyor belt  24 . 
     The leading portion of package P contacts the seam  28  (FIG. 2) and moves along with the film sheets  25   a  and  26   a  into position for wrapping in the machine W. A heat resistant, non-adhesive cushion  29  is located between the jaw members  10  and  12  for receipt of the package P. The cushion  29  is preferably fixedly mounted on machine W with respect to the movable jaw members  10  and  12 . The package P to be wrapped moves from the conveyor belt  24  into place on the cushion  29  for sealing. As the package P to be wrapped moves, it engages (FIG. 3) the package P wrapped and sealed during the previous cycle and moves it away for subsequent handling, storage or transport P. Depending on the size of machine W and cushion  29 , one or more previously wrapped packages may be present on cushion  29  in a sequence at this time. 
     The package P to be wrapped moves from the conveyor belt  24  along with the film F into position in the machine W along with the film sheets  24   a  and  26   a  until the package P is in proper position for wrapping (FIG.  4 ). The detection of position of package P is done in the conventional manner by photodetectors or other sensors. The jaw members  10  and  12  are then movable inwardly once the package P to be wrapped is sensed as being in the proper position on the cushion  29 . 
     According to the present invention, each of the jaw members  10  and  12  is provided with a heat sealing frame assembly A for forming seams  30  in the protective cover or wrapping formed from the synthetic resin film. The seams  30  (FIG. 6) are formed along side and rear walls  32  about the package P. When the package P is in proper position for wrapping (FIG.  4 ), the jaw members  10  and  12  move inwardly to enclose (FIG. 5) the package P within the heat sealing frame assembly A. 
     The heat sealing frame assembly A (FIGS. 7 and 8) for each of members  10  and  12  is composed of a number of heat sealing apparatus or units H mounted to such member. When the bale B is in proper position (FIG. 5) the moveable frame members  10  and  12  with their heat frame assemblies H move together to form a seal about the sides of the bale B. Heat frame assemblies are provided for at least the two side walls and rear wall  32  in a general U-shape. If desired, a fourth or front heat frame assembly H may also be provided. The heat sealing units H are connected together to conform an outline to the shape of the package P. Typically, the package P is rectangular or square in horizontal cross-section and the frame assembly A, whether U-shaped or box-shaped with a fourth element as shown, is of a corresponding rectangular or square configuration. 
     Each of the heat sealing apparatus or assemblies H includes a heating element  40  in the form of an elongate electrical heating rod, such as of the type mentioned above sold by General Electric Company under the trademark CALROD®. The length of each of the heating elements  40  is determined by the dimensions of the side walls of the package P to be wrapped in the machine W. The heating element  40  is connected in a conventional manner to a suitable source of electrical current at each end outwardly from the unit and on flow of such current generates heat along its length. If desired, the front or lead heating element  27  may be formed of a similar construction to the heat sealing assembly H. 
     The heat sealing element  40  is mounted in a heat sealing member M according to the present invention for transferring heat to side wall portions  32  of the film F at the locations where the seams  30  are to be formed. The heat sealing member M is an elongate bar or rod  42  mounted along a generally flat rear base surface  44  to a mounting plate  46  by screw, or bolts  48  or other suitable fasteners. The screws  48  are connected into receptor sockets  44   a  formed in the base surface  44 . 
     Each heat sealing bar or element  42  in assembly A is also drilled and tapped as indicated at a number of receptor sockets  44   a  at a number of suitably spaced locations. The receptor sockets  44   a  receive bolts or other suitable connectors for connection of the heat sealing bars  42  of heat sealing frame assembly A to one of the moveable jaw members  10  and  12 . 
     The rear base surface  44  is, for example, one inch or so wide. The mounting plate  46  is preferably of a heat insulative material, such as a fiberglass adapted for high heat conditions. A suitable such material is Green Core Series 500. In this manner, heat transfer from the heat sealing element  40  and the heat sealing rod or bar  42  to the wrapping structure, as well as jaw members  10  and  12 , is substantially reduced and the remaining portions of the machine W are also not recipients of such heat. The mounting plates  46  are mounted to one of the jaw members  10  or  12  by screws, bolts or other suitable fasteners. 
     The heat sealing bar members  42  are preferably formed by any suitable metal forming technique of a single unitary piece of heat conductive material, such as a lightweight metal, preferably aluminum for cost and weight reasons. The use of lightweight aluminum in the bar members  42  also reduces weight of the sealing assembly for ease in handling. The elongate heat sealing bars  42  have side walls  50  and  52  tapering inwardly from lower side walls  51  and  53 , respectively. The lower walls  51  and  53  extend vertically a slight distance, such as one-eighth inch from the base surface  44 . 
     A film contact strip portion  54  is formed between the innermost portions of side walls  50  and  52 . The film contact strip portion  54  is an arcuate or curved surface of about one-quarter inch radius extending between the side wall members  50  and  52  along the length of the heating element bar  42 . The arcuate film contact surface  54  is adapted to engage a corresponding oppositely faced film contact strip portion or the other jaw member. If desired, the film contact strip portion  52  may be provided with a suitable non-adhesive coating by tape, spraying, deposit or other technique. A suitable non-adhesive coating, for example, is a commercially available tape of Teflon® or comparable material containing glass particles such as that sold as 3M5488 by 3M Company. 
     When the jaw members  10  and  12  are brought together, the oppositely facing film contact strip portions  54  engage each other adjacent the side walls of the package P between them. Lateral spacing between the heat sealing elements  42  and the side walls of the package may be adjusted to vary the snugness of the wrap to be formed over the package P. 
     Flow of electrical current through the heat sealing element  40  is transferred through the heat sealing bar  42  to heat portions of the film located between the film contact strip portions  54 . The film contact strip portions  54  fuse the wall portions  30  of the resin film together, forming the seams  32  and causing a snugly fitted synthetic film resin wrapping to be placed onto the package P. Portions of the film F external to the seams  32  and outside the heating elements are separated from the wrapping during the sealing operation. These excess side portions of the film F which are not part of the wrapping separate and fall away from the package P. The arcuate surface of the contact strip portions and their junction with side walls  50  and  52  provides a wider, more uniform seal. The non-adhesive coating on strip  52  reduces any tendency of the film to adhere to the contact strips  54  of heat sealing bar  42 . 
     The heat sealing bar  42  has an internal channel  56  formed extending approximately one-quarter inch inwardly from the base surface  44  along a pair of spaced side walls  58  and  60  to a lower surface  62 . The lower surface  62  is of a shape conforming to the outer surface of the heat sealing element. Where, as shown, the heat sealing element  40  is a cylindrical rod having a curved outer surface  64 , the lower surface  62  of the internal channel  56  is a curved surface. If the heat sealing element  40  were rectangular in configuration, the lower surface  62  of the internal channel  56  could be a correspondingly flat surface, if desired. 
     The sealing bars  42 , whether three in a U-shape, or four in a box shape are assembled into a generally rectangular framework according to the configuration of the package P. Each such frame thus includes a set of longitudinally extending bars  42   a  and either one or two transversely extending end bars  42   b.  The bars  42   a  are located to extend in the direction of movement of the conveyor belt  24 . The end bars  42   b  extend transversely to the conveyor belt  24  between opposite ends of the bars  42   a.  As previously mentioned, the front sealing bar  42   b  adjacent the front lateral seam  28  is optional. End portions  43  (FIG. 7) of the bars  42   a  at each end are mitered to have a surface conforming to the angle of tapered side walls  50  and  52  of end bars  42   b.  The mitered end portions  43  permit the heat sealing members M to form a continuous, uninterrupted heated surface about the package P for contact with the film F, even at corner portions and ends. 
     The base surface  44  of the heat sealing member M and the mounting plate  46  are co-extensive, forming a heat boundary surface above the heat sealing members  42 . The mounting plate  46  thus serves as a closure surface for the internal channel  56  and confines the flow of heat from the heating sealing element  40  effectively into the heat conductive body of heat sealing bars  42 . 
     The heat sealing bars  42  function as heat sinks for heat from the rod  40  due to the presence of the insulative mounting plate  46 . The unitary structure of the heat sealing bar  42  distributes the heat substantially uniformly over its volume, because of its being integrally formed from a single conductive element. With the bar member  42  being solid unitary bodies, compensation is provided for any tendency that might occur of the heating rod  40  to generate hot spots or cold spots along its length. If a hot spot develops in the rod  40 , the mass of the unitary body of bar  42  provides temperature distribution and averaging functions, tending to alleviate any potential hot spots. The unitary structure of the heat sealing bars  42  prevents the harmful effects of such hot or cold spots in formation of seals along the seams of the package. 
     Similarly, portions of the bar member  42  adjacent any areas of the rod  40  that may be cold spots are drawn to a composite higher temperature by the remaining heated mass of other portions the bar member  42 . The presence of the heat sealing bar  42  thus reduces any tendency for cold spots to occur in sealing. This also allows the heating element  40  to be operated at lower operating temperatures and still form proper seals in the film F. The lower operating temperatures for the heating element  40  extend its service life. 
     As is conventional, at least one of the jaw members  10  and  12  is provided with a knife or other suitable cutter assembly  15 . The cutter assembly or assemblies  15  are spaced laterally from each other transverse the path of movement of the package P. The cutter assemblies  15  are used to cut the surplus tail portion  31  of the resin film F at its rearwardly of package P, but forward of lead sealing element  27 . The laterally extending heat sealing element H at the rear seam  30  of the package senses the forward end of the tail portion  31 . At the same time, as previously mentioned, the front or lead heating element  27  forms a new lateral seam  28  between the film sheets from rolls  25  and  26  from the next bale B to be wrapped. 
     The foregoing disclosure and description of the invention are illustrative and explanatory thereof, and various changes in the details of the illustrated apparatus and construction and method of operation may be made without departing from the spirit of the invention.