The bonding of the flange 1 to a plastic container wall section, such as a pail head as indicated at 14, is accomplished by inserting the neck of the flange up through the container wall opening 15 which just fits over the enlarged neck pilotportion 7. In FIG. 5 the undersurface of the container wall, prior to bonding, rests on top of the bonding element 13 and just above the ribs 11 and 12.
Induction welding of the flange to the surrounding container wall section commences upon theapplication of a vertical force to the assembly and introduction within the magnetic field of a high frequency induction heating generator. As the thermoplastic resin of the element 13 starts to melt, together with the walls of the groove 10, the ribs11 and 12 also melt, causing the upper surface 9 of the collar 8 and the undersurface of the wall 14 to come together. The rib 12 being further removed from the bonding element 13 tends to melt more slowly, thus forming a dam against the outward flow ofbonding material. As seen in FIG. 6, the result is a permanent homogeneous bonding at the flange container wall interface. It should be noted that the groove and cooperating ribs could also be formed on the undersurface of the flange collar to enablebonding of the flange to the exterior surface of a container wall such as would be required on blow-molded containers.
The bonded flange may then be fitted with a closure plug 16 having a threaded side wall 17 terminating at its upper end in a circumferentially enlarged head 18 designed for gasketing engagement with the flange bead 5. Further protection againstleakage and pilfering can be had by crimping a tamperproof capseal (not shown) about the flange bead 5.
Considering the method herein disclosed for applying the bonding element to the flange, attention is directed to FIG. 7 which shows an applying head 20 mounted on a vertically moveable shaft 21. The head 20 consists of an inverted cup-shapedhousing 22 having a base wall 23 and a depending cylindrical wall 24 terminating in a lowermost locating surface 25. A passage 24a, as clearly seen in FIG. 8, extends angularly through the wall 24 so as to communicate with the housing interior.
The base 23 is formed with a large central opening 26 surrounded by three smaller holes 27. A cutter 28 is nested within the housing 22 having a base wall 29 surrounded by a depending cylindrical wall 30 terminating at its lower end in a shearing edge 31. The shaft 21 is slideably received through the center opening 26 in the housing member base 23 and is secured to the cutter base 29 by nut 32. A cylindrical plunger 33 is slideably mounted within the cutter 28 and has an outwardly opening groove 34formed in its exterior surface. Three screws 35 extend through the holes 27 in the housing base 23 and are secured to the plunger 33. A coiled compression spring 36 surrounds each of the screws 35 so as to resiliently urge cutter 30 and plunger 33apart.
In operation a flange 1 is seated on an anvil 37 positioned beneath the applying head 20. An elongated strand of electromagnetic bonding material 13 is fed into the passage 24a in the housing sidewall 24 and, as seen in FIG. 8, is guided by thegroove 34 around the plunger 33 into an annular form. The head 20 is then lowered down over the flange with the locating surface 25 resting against the upper surface 9 of the flange collar, and with the plunger 33 resting on top of the flange bead 5. Continued downward movement of the shaft 21 overcomes the compression of springs 36 and urges the cutter 28 downwardly relative to the housing and plunger. In so doing the shearing edge 31 is lowered over the passage 24a and severs the strand 13 alongthe interior surface of the housing wall.
As the my 28 continues to move downwardly, it pushes the element 13 ahead of it, forcing the element between the annular upstanding ribs 11 on the flange collar. The final downward movement of the cutter 28 firmly seats the element 13 within theflange groove 10 whereupon the head 20 is retracted upwardly and the parts thereof restored to their initial position. It should be noted that during the downward urging of the element 13 by the cutter 28, the leading cut end 13a and the trailing cutend 13b are lined up in a common axially extending plane as seen in FIG. 10. As a result the strand of electromagnetic bonding material is formed into a complete uninterrupted annulus with the angled surfaces 13a and 13b preventing a detrimentalradially extending gap from occurring at the joint due to minor variations in the strand length.
From the foregoing it is seen how a container closure flange molded of synthetic resin can be very simply assembled with an electromagnetic bonding element for thermoplastic induction bonding to a container openings. The assembly operationdisclosed, while lending itself very well to an automatic or semiautomatic production operation, also contributes to the quality and effectiveness of the bond between the flange and the container wall.
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