A closure flange molded of synthetic plastic resin has an internally threaded cylindrical neck surrounded at one end by a circumferentially enlarged base. An annular groove is formed on the flange base for retention of a thermoplastic bonding element having electromagnetic conducting particles embedded therein. The flange manufacture includes making the bonding element up from an elongated strand into a complete annulus and securely inserting the annular bonding element within the groove in the flange base.
Claims
Having described my invention, what I claim is as follows:
1. A method of manufacturing closure flanges for electromagnetic bonding to containers comprising the steps of molding an annularclosure flange of thermoplastic synthetic resin, supporting said flange in concentric alignment with an applying head, feeding an elongated strand of electromagnetic bonding material into said head to form an annulus displacing said head and flangetoward each other, cutting said strand into a predetermined length and applying said strand as a complete annulus to said flange as said annulus is discharged from said head.
2. A method of manufacturing closure flanges as in claim 1 and said cutting of said strand within said head forming a lap joint at the strand ends.
3. A method of manufacturing closure flanges as in claim 1 and positively locking said strand onto said flange.
Description
In the manufacture of plastic pails and drums it has been proposed to provide a closure receiving neck thereon by permanently bonding an internally threaded closure flange about a flat opening molded within the container wall. One advantageouslyemployed bonding technique consists of interposing an electromagnetic bonding element at the flange container wall interface. The bonding element is energized by placing the closure assembly within a high frequency magnetic field, causing a melt zoneand resultant bonding at the flange container wall interface.
Heretofore a number of difficulties presented themselves in attempts to refine the above described bonding technique into an efficient container fabricating operation. One such difficulty concerns the need for a production oriented applicationof the bonding element to the groove in the flange base as opposed to a strictly manual operation. Another problem concerns the need for effectively forming a strand of electromagnetic bonding material into a complete and continuous annulus. Any spacegap created at the intended juncture of the severed strand ends may introduce the likelihood of failure in bonding. Once the strand is properly applied to the flange base, the problem arises of securely retaining the bonding element within the flangebase groove during subsequent shipping and handling conditions.
SUMMARY
The closure flange assembly and method of manufacture disclosed by the instant invention advantageously overcomes the above mentioned problems through the formation of a novel groove configuration in the flange base which precludes accidentaldislodgment of the bonding element under the severest handling conditions. The method of manufacture herein disclosed includes feeding the bonding element as an elongated strand into a circular die cavity whereupon closing of the die severs the strandand inserts it as a complete annulus into the flange base groove.
It is, accordingly, a principal object of the invention to provide a new plastic closure assembly for thermoplastic bonding to a plastic container wall opening.
Another object is to provide a method of applying an electromagnetic bonding element to a closure flange to facilitate bonding to a container wall opening through the use of electromagnetic induction.
Still another object is to form an electromagnetic bonding element from an elongated strand into a complete annulus and apply the element to a closure flange so as to be securely retained thereon.
Other and more detailed objects will in part be obvious and in part be pointed out as the description of the invention taken in conjunction with the accompanying drawing proceeds.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a part elevational, part sectional view of the closure flange of the invention;
FIG. 2 is an enlarged fragmentary sectional view showing the initial position of the bonding element as it is applied to the flange base;
FIG. 3 is a sectional view similar to FIG. 3 but showing the bonding element fully seated in the flange base;
FIG. 4 is an enlarged fragmentary top plan view of the flange base with the bonding element applied;
FIG. 5 is a fragmentary sectional view showing the flange in position for bonding within a container wall opening;
FIG. 6 is a sectional view similar to FIG. 4 but showing the completed bond and a closure plug in place;
FIG. 7 is an exploded sectional view of the mechanism for applying the bonding element to the flange base in accordance with the method steps of the invention;
FIG. 8 is a view taken on line 8--8 of FIG. 7 and looking in the direction of the arrows;
FIG. 9 is an enlarged fragmentary sectional view similar to FIG. 8 showing an advanced position of the strand of bonding material within the applying mechanism; and
FIG. 10 is a sectional view similar to FIG. 9 showing a further advanced position with the strand severed and formed into a complete annulus.
As seen in FIGS. 1-6, the closure flange 1 is molded of a thermoplastic synthetic resin such aspolyethylene and consists of an upstanding cylindrical neck 2 having an interior screw thread 3. The upper end of the flange neck has a short unthreaded portion 4 and terminates in a circumferentially enlarged bead 5. The exterior surface of the flangeneck 2 has a short section 6 of reduced diameter beneath the bead 5 and is then circumferentially thickened into a lower pilot portion as indicated at 7. An annular collar 8 surrounds the base of the flange neck having an upper surface 9. An annular,upwardly opening, groove 10 is formed in the upper surface 9 spaced radially outwardly from the thickened pilot portion 7 of the flange neck. The mouth of the groove 10 is partially closed off by a pair of annular ribs 11, one at each side of the grooveand extending above the flange upper surface 9. An additional annular rib 12, extending above the upper surface 9, is formed at the outer edge of the collar 8.
The final step in the flange manufacture involves the application of an electromagnetic bonding element 13 to the flange collar for the purpose of forming a thermoplastic bond to a container wall opening. The bonding element here employed ismade up from an elongated strand of thermoplastic material, circular in cross-section and having minute metal electromagnetic conducting particles embedded therein.
The strand is formed into an annulus having overlapping end surfaces 13a and 13b whichform a lap joint and insure against the presence of any radial gap in the bonding zone. As clearly see in FIGS. 2 and 3, the cross-sectional diameter of the bonding element 13 is substantially equal to the width of the groove 10 and slightly greaterthan the closest distance between the ribs 11.
A downwardly directed force applied to the bonding element 13 causes the flexible ribs 11 to open up, allowing the element to enter the groove 10. Subsequent relaxation of the ribs after the element isfully seated within the groove serves to positively retain the element securely in place. The mechanical grip applied by the ribs 11 prevents accidental dislodgment of the element 13 during packing, shipping and handling of the finished flange.
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