Abstract:
An inductive cap sealer for sealing an inner seal over an opening in a container includes a vented sealing head. The sealing head contains an induction coil for producing an electromagnetic field when energized by a power supply. Field focusing elements contain the coil and direct the electromagnetic field to a sealing region beneath the sealing head. The housing has openings and the field focusing elements are spaced to allow cooling air to flow around the field focusing elements and past the coil.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     Not applicable. 
     STATEMENT OF FEDERALLY SPONSORED RESEARCH/DEVELOPMENT 
     Not applicable. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to the field of heat sealing caps to containers. In particular, the invention relates to air cooled sealing heads. 
     2. Discussion of the Prior Art 
     It is known to seal the mouths of bottles and other containers using an inductive sealing process. Inductive sealing requires an electromagnetic-field-producing apparatus and a foil-polymer seal. Typically, the apparatus has at least one coil of wire wound to produce an electromagnetic field when electric current is supplied to the coil. It is well known in the art that electromagnetic fields induce eddy currents within metal which in turn heat the metal. The seal comprises a thin layer of aluminum foil onto which is laminated a polymer layer that is molecularly compatible with the container to be sealed. When the seal is placed onto the container and the container is placed within the electromagnetic field, the foil is heated which melts the layer of polymer. Removing the seal from the electromagnetic field allows the polymer to cool and molecularly fuse with the container to create an air-tight seal. 
     The electromagnetic field strength primarily depends upon the number of turns in the wire coils and the amount of current supplied to the coils. To produce an electromagnetic field adequate for commercial inductive sealing, typically the power supply must output power in the order of a few kilowatts, which produces a great deal of heat. Thus, the power supply must be cooled in order to function properly. Similarly, the sealing head having the induction coil must be cooled. 
     Many methods of cooling the power supply and sealing head are known in the art. In particular, it is known to circulate cool water through the power supply enclosure and the sealing head. Such water cooled cap sealers, however, require complicated piping configurations that increase size and cost. It is also known to vent the power supply and force air past the outside of the sealing head. However, such air cooled cap sealers sometimes provide inadequate cooling of the sealing head which degrades the operating efficiency of the cap sealer. 
     SUMMARY OF THE INVENTION 
     The invention provides a ventilated sealing head for an inductive cap sealer. Specifically, the sealing head includes an induction coil for producing an electromagnetic field. One or more field focusing elements are disposed adjacent the coil to direct the electromagnetic field of the coil toward a sealing region beneath the sealing head. The coil and the field focusing elements are contained in a housing having openings allowing air to flow past the coil. 
     In a preferred form, the field focusing elements are a ferromagnetic compound and there are a plurality of field focusing elements spaced apart along at least a portion of the periphery of the coil allowing air to flow between the spaced field focusing elements and past the coil. 
     In other forms, the housing forms a tunnel extending lengthwise from side to side of the sealing head and opening downward at the sealing region. The coil is wound around the tunnel and within a number of electromagnetic field focusing elements. The sealing head further includes a pair of plug-in shielded connectors for coupling the coil to power. 
     Another aspect of the invention is a cap sealer having an AC power supply and an external vented sealing head as described above. The cap sealer can further include an external fan disposed between the sealing head and the power supply for forcing cooling air through the sealing head. 
     The invention thus provides a vented sealing head for an inductive cap sealer. Venting the sealing head allows cooling air to be blown passed the coil and field focusing elements to carry away heat from these components and convectively cool the sealing head. The sealing head can thus be cooled without a separate cooling circuit and without the costly and difficult to assemble tubing arrangements associated with liquid cooling. 
     The foregoing and other advantages of the invention will appear from the following description. In that description reference is made to the accompanying drawings, which form a part hereof, and in which there is shown by way of illustration a preferred embodiment of the invention. This embodiment does not represent the full scope of the invention. Thus, the claims should be looked to in order to judge the full scope of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is top perspective view of a ventilated sealing head according to the present invention; 
     FIG. 2 is a bottom perspective view of the ventilated sealing head; 
     FIG. 3 is a bottom plan view of the ventilated sealing head with the bottom cover removed to show the wire coil and field focusing assembly; 
     FIG. 4 is a cross-sectional view taken along line  4 — 4  of FIG. 3 with a set of field focusing elements shown in cross-section; 
     FIG. 5 is a cross-sectional view taken along line  5 — 5  of FIG. 3 at an opening between the spaced field focusing elements; 
     FIG. 6 is a partial enlarged view of FIG. 5 with the housing shown in phantom; 
     FIG. 7 is a bottom view taken along lien  7 — 7  of FIG. 6 showing the field focusing assembly with the electromagnetic coil wound therein and with a center panel of the housing shown cut-away to reveal the coil; 
     FIG. 7 a  is a cross-sectional view similar to FIG. 7 albeit taken along line  7   a — 7   a  of FIG. 6; 
     FIG. 8 is a cross-sectional view similar to FIG. 7 albeit taken along line  8 — 8  of FIG. 6; 
     FIG. 9 is a cross-sectional view similar to FIG. 7 albeit taken along line  9 — 9  of FIG. 6; 
     FIG. 10 is a top view of the field focusing assembly and coil taken along line  10 — 10  of FIG. 6; 
     FIG. 11 is a side cross-sectional view taken along line  11 — 11  of FIG.  6  and in partial cut-away to show a coil spacing element; and 
     FIG. 12 is a front perspective view of an induction air cooled cap sealer having a vented sealing head. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     An air cooled cap sealer  10  is shown in FIG.  12 . The cap sealer  10  is preferably of the type described in U.S. Pat. No. 6,153,864 assigned to the assignee of this application and hereby incorporated by reference as through fully set forth herein. Generally, the cap sealer  10  has a sealing head  12  powered by and mounted to a power supply cabinet  14  supported on an adjustable mounting assembly  16 . The sealing head  12  is electrically connected to the power supply cabinet  14  via a pair of bus wires (not shown) coupled to shielded, plug-in type socket connectors mateable with connectors  17  (see FIG. 1) on the sealing head  12 . Preferably, two cooling fans  18  (one shown in FIGS. 4 and 5) are mounted between the sealing head  12  and the power supply cabinet  14 , one cooling the sealing head  12  and the other the power supply cabinet  14 . The sealing head  12  is vented to improve cooling by allowing cooling air to pass through the sealing head  12 . 
     Referring to FIGS. 1,  2  and  3 , the sealing head  12  has a housing  20  containing an electromagnetic coil  22  wound about a field focusing coil housing  24  formed by one or more electromagnetic field focusing elements joined together by a suitable epoxy resin. The housing  20  is preferably made of an ABS plastic material and comprises an inverted tray  26  and a bottom cover  28 . The tray  26  has a rectangular top with downwardly extending walls along its periphery. The bottom cover has front  30 , back  32  and center  34  panels defining a recessed tunnel  36  extending from side to side across the width of the bottom of the sealing head  12 . The top of the inverted tray  26  has a generally circular grille  38  with a plurality of openings allowing air into the housing  20 . The front  30  and back  32  panels of the bottom cover  28  each has two rows of lateral slots  40 , respectively. One of the rows of each panel is located in short legs  41  and  43  forming the sides of the tunnel  36 . The center panel  34  has four rows of five slots  40  aligned in parallel. The bottom cover  28  is fastened to the tray  26  by a suitable adhesive applied to their edges or as disclosed in the &#39;864 patent. When assembled, air can pass into the top of the sealing head  12  through openings in the grille  38  and exit through the slots  40  in the bottom of the sealing head  12 . 
     Referring to FIGS. 4-6, the coil housing  24  and coil  22  are disposed around the tunnel  36  to surround it along its length from the top and sides. The coil  22  is formed of bundled wire, such as Litz wire, known to those skilled in the art. The number of windings and the gauge of the wire are selected according to the sealing requirements of the application, as known in the art. The coil  22  is wound within the coil housing  24  around the tunnel  36  and windings are spaced apart by four sets of four spacers  42  adhered to the center panel  34  of the bottom cover  28  and extending upwardly into the housing  20  (see FIGS. 6,  7   a  and  11 ). 
     Referring still to FIGS. 4-6 as well as FIGS. 7-11, the coil housing  24  is comprised of a number of rectangular blocks made of a ferromagnetic compound having ferric oxide, so that, rather than radiating omni-directionally, the electromagnetic field produced by the coil  22  is directed downward to a sealing region  44  within and/or below the tunnel  36 . In the embodiment shown in the figures, the blocks are arranged in ten inverted U-shaped segments  45  having four blocks  46  each, two aligned end to end in the front-back direction of the sealing head  12  and two bookends extending vertically. Each segment  45  is spaced apart in the side to side direction of the sealing head  12 , approximately the width of a block. Two rows of four blocks  47  are disposed on each side of the tunnel  36  spaced laterally between the coil  22  in the side to side direction. Two rows of seven blocks  48  are disposed end to end with their bottom faces against the front  30  and back  32  panels of the bottom cover  28  on each side of the tunnel  36  beneath the two rows of four blocks  47 . These seven blocks  48  are not spaced in the side to side direction so as to provide a rigid corner along much of the tunnel  36 . Finally, a row of five blocks  49  are disposed end to end on their side edges along the center of the center panel  34  extending in the side to side direction of the sealing head  12  between the coil  22 . 
     The arrangement of the field focusing blocks forming the coil housing  24  has been empirically shown to direct the electromagnetic field toward the sealing region  44  while allowing air entering the housing  20  to pass by the blocks. Air is blown by the fans above the sealing head  12  into the grille openings in the top of the tray  26  and some air will exit the sealing head housing  20  through the centermost slots  40  in the bottom cover  28 . A portion of the air flow, however, is interrupted by the blocks and/or the coil  22  such that it will circulate through the sealing head  12  from front to back and side to side allowing most, if not all, of the coil  22  and coil housing  24  to be cooled convectively. Moreover, warmer portions of the coil  22  will pass heat to cooler portions of the coil  22  so that the coil  22  will be conductively cooled as well. 
     The invention thus provides a vented sealing head for an inductive cap sealer and a cap sealer having such a sealing head. Venting the sealing heat allows cooling air to be blown passed the coil and field focusing elements to carry away heat from these components and convectively cool the sealing head. The sealing head can thus be cooled without a separate cooling circuit and without the costly and difficult to assemble tubing arrangements associated with liquid cooling. 
     With reference to FIGS. 3 and 12, the cap sealer  10  is operated by first adjusting it vertically if needed according to the height of a container  50  to be sealed. The mouth of the container  50  is then covered with an inner seal  52  having a polymer layer laminated to an aluminum foil layer. A cap  54  is snapped, screwed or otherwise fit onto the mouth of the container  50 , which places a downward force on the inner seal  52 . The container  50  is then placed upright with the cap  54  under the sealing head  12  in the sealing region  46 . Applying power to the coil  22  produces an electromagnetic field directed downwardly from the sealing head  12  to the sealing region  46  for a prescribed period of time which heats the foil layer and melts the polymer layer. The container  50  is removed from beneath the sealing head  12  which allows the polymer layer to cool and fuse to the mouth of the container  50 . The cap sealer  10  may be operated manually, placing one container  50  at a time beneath the sealing head  12 , or it may be used to seal a number of containers  50  continuously or intermittently passing through the electromagnetic field under the sealing head  12  on a conveyor belt or similar assembly line. 
     Illustrative embodiments of the invention have been described in considerable detail for the purpose of disclosing practical, operative structures whereby the invention may be practiced advantageously. The designs described are intended to be illustrative only. The novel characteristics of the invention may be incorporated in other structural forms without departing from the scope of the invention. For example, the sealing head can be interchangeably mounted to the power supply cabinet so that sealing heads of other configurations may be used for various sealing applications, such as a vented flat sealing head particularly suitable for wide necked containers. Moreover, the sealing head may have more than one induction coil mounted in various orientations and the coil housing could be monolithic with openings made therein for air to flow through the coil housing and past the coil. 
     It can thus be appreciated that many variations are possible from the preferred embodiment described above without departing from the spirit of the invention. Reference should therefore be made to the claims for interpreting the entire scope of the invention.