« AnteriorContinuar »
United States Patent m
Grooms et al.
[li] Patent Number:  Date of Patent:
 METHOD FOR INDUCTION SEALING AN INNER BAG TO AN OUTER CONTAINER
 Inventors: John P. Grooms, Cincinnati, Ohio;
Larry J. Mattson, Charlotte, N.C.
 Assignee: The Proctor & Gamble Company, Cincinnati, Ohio
 Appl. No.: 271,806
 Filed: Jul. 7,1994
 Int. Cl.« H05B 6/10
 U.S. Q 219/633; 219/634;
 Field of Search 219/633, 634, 618, 604,
219/632; 156/69, 273.9, 274.2
 References Cited
U.S. PATENT DOCUMENTS
2,743,038 4/1956 Ferries 222/95
3,461,014 8/1969 James 156/272
3,738,892 6/1973 Curcio 156/380
3,788,928 1/1974 Wise 156/294
3,808,074 4/1974 Smith et al 156/69
3,945,539 3/1976 Sossong 222/386.5
3,981,418 9/1976 Williamson et al 222/386.5
3,988,185 10/1976 Johnson et al 156/69
4,057,444 11/1977 Prot 156/69
4,109,815 8/1978 Collins, III 215/232
4,152,566 5/1979 Magerle 219/633
4,154,366 5/1979 Acres 222/95
4,169,004 9/1979 Kock et al 156/227
4,180,961 1/1980 Collins, III 53/421
4,658,989 4/1987 Bonerb 222/105
4,704,509 11/1987 Hilmersson et al 219/10.53
4,754,113 6/1988 Mohr et al 219/10.79
4,783,233 11/1988 Yasumuro et al 156/69
4,842,165 6/1989 Van Coney 222/95
4,865,224 9/1989 Streck 222/95
4,892,230 1/1990 Lynn, Jr 222/105
4,994,637 2/1991 Fang et al 219/10.53
5,013,878 5/1991 Fries, Jr 219/633
5,047,605 9/1991 Ogden 219/633
5,145,083 9/1992 Takahashi 220/206
5,158,370 10/1992 Jacobi 383/48
5,191,181 3/1993 Regenscheid 219/10.41
5,198,053 3/1993 Duncan 156/64
5,200,587 4/1993 Fang 219/10.53
Primary Examiner—Philip H. Leung
Attorney, Agent, or Firm—Ronald W. Kock; Michael E.
A process for forming, handling, circumferentially sealing, and inverting a thin plastic half bag to an inwardly tapered, continuous inner side wall of an outer plastic container. A non-metallic mandrel is used as a tool for thermoforming a half bag over the top of the mandrel. The top of the mandrel with bag attached is inserted into an open end of the outer plastic container. A continuous metal ring connected at the circumference of the mandrel, positioned near the open end of the half bag, wedges the bag against the tapered inner side wall of the container near the midpoint of the container to form a sealing interface therebetween. A magnetic induction field generated near the container heats the metal ring on the mandrel. Heat is conducted to the sealing interface to weld the bag to the container. After the field is removed and the metal ring cools, the mandrel with metal ring is withdrawn from the thin plastic bag. Vacuum applied to the closed end of the bag from the top of the mandrel causes the bag to be inverted to the open end of the container as the mandrel is withdrawn.
20 Claims, 2 Drawing Sheets
U.S. Patent May 16, 1995 Sheet 1 of 2 5,416,303
U.S. Patent May 16,1995 Sheet 2 of 2 5,416,303
METHOD FOR INDUCTION SEALING AN INNER
BAG TO AN OUTER CONTAINER
FIELD OF THE INVENTION 5
The present invention relates to processes for induction sealing plastic parts to each other, and more particularly to such processes wherein a metal component contacting the plastic parts is heated by a magnetic induction field to conduct heat through one part to the 10 sealable interface between the plastic parts. Even more particularly, the present invention relates to processes for sealing an inner bag to an inner side wall of an outer container.
BACKGROUND OF THE INVENTION
Induction sealing plastic parts together by heating metal embedded in one of the plastic parts, or by heating metal components clamping the parts together, is old in the art. Heat is developed by generating a high 20 frequency oscillating magnetic field in the presence of the metal. Depending on the metal, either eddy current losses or magnetic hysteresis losses are believed responsible for heating the metal. Heat from the metal is then conducted through the plastic parts to their sealable 25 interface. Plastic melting occurs from the conducted heat. If the plastic materials are compatible and sufficient pressure is applied, the plastic parts can be fusion welded together. Once the magnetic induction field is removed, the heat may be dissipated from the sealable 30 interface through the metal contacting the plastic parts. Cooling the sealable interface under pressure is generally required to produce a strong seal. The great benefit of the induction heating process is that heat can be quickly generated in low mass metal dies so that high 35 production rates can be achieved.
Squeezebottle dispensers having fluid-containing, flexible inner bags sealed within them are also common in the art. When such a dispenser is squeezed, fluid is forced from the bag through a discharge opening at the 40 top of the dispenser. Valving in the dispenser enables air to be compressed within the squeezebottle during squeezing, but valving then allows air to vent into the bottle to replace the dispensed fluid after the squeezebottle is released. Repeated squeezing cycles cause the 45 bag to collapse around the fluid within the squeezebottle as the bag empties.
A problem with such dispensers is that a bag tends to collapse most quickly near its discharge opening. This is believed due to higher velocity fluid flow at the dis- 50 charge opening causing lower static pressure there. Fluid flow may be choked off from the rest of the bag if the bag collapses prematurely at the discharge opening. To correct this problem, the manner in which the inner bag can collapse is generally controlled. For ex- 55 ample, bags may be designed to collapse radially about a perforated diptube connected to the discharge opening. When the fluid is highly viscous like toothpaste, however, diptubes provide too much resistance to fluid flow through them. For fluids having viscosities great 60 enough that the fluid cannot flow under gravity, another collapse control approach is often used. That is, a bag is sealed to the midline circumference of the squeezebottle so that the bag can collapse by inverting axially toward the discharge opening. Bag inversion 65 offers minimum flow resistance.
For squeezebottle dispensers having inner bags which invert toward the discharge opening, there is a
construction problem of inserting and sealing a bag inside a squeezebottle. The discharge opening of the squeezebottle is usually smaller in circumference than the inner side wall of the squeezebottle, so that the discharge opening may later be capped with a reasonably sized closure. If the bag is inserted into the squeezebottle from a small diameter discharge opening, it is difficult to insert a sealing tool into the bag to seal the bag to the midline circumference of the squeezebottle. The sealing tool must expand to press the bag against the inner side wall of the squeezebottle. A reliable, high speed method for midline bag sealing, using such an expanding tool, is not currently known.
Alternatively, if the bag is inserted from the opposite end of the squeezebottle, which is usually the bottom of the squeezebottle, the bag must later be filled and sealed closed from the bottom end, and a bottom piece must be added to close the open bottom of the squeezebottle. For example, twisting the open end of the bag after filling and then heat sealing the twisted portion is one approach to closing a filled bag. Closing the bag after filling has been found to be a slow and difficult process.
One solution to the bottom end bag insertion and filling problem for highly viscous fluids is a construction that seals a half bag to the midline circumference of a squeezebottle. A half bag may be inserted from the open bottom of the squeezebottle with its closed end at the discharge opening of the squeezebottle. After sealing the open end of the half bag to the midline circumference of the squeezebottle, the half bag may then be inverted so that its closed end is positioned at the bottom of the squeezebottle. Filling may then be accomplished from the discharge opening of the dispenser. Such a construction requires a complete seal around the midline circumference of the squeezebottle.
The half bag approach enables conventional high speed filling without subsequent bag closing and sealing. However, the half bag approach also requires the formation and handling of a half bag and the inversion of the half bag after sealing it to the squeezebottle. Bag forming and internal sealing operations are complex and difficult even when performed manually.
SUMMARY OF THE INVENTION
One preferred embodiment of the present invention is a method for sealing a thin plastic bag to an inwardly tapered, continuous inner side wall of an outer plastic container. The outer plastic container has an open bottom end, a discharge opening, and a midpoint. The method comprises steps which include placing the plastic bag over a non-metallic mandrel. The mandrel has a top end and a metal member positioned inside the thin plastic bag. The plastic bag has a closed end at the top end of the mandrel. Another step inserts the top end of the mandrel with the plastic bag placed over it into the open bottom end of the outer plastic container. The metal member of the mandrel is adapted to wedge the plastic bag against the inwardly tapered, continuous inner side wall of the outer plastic container, in order to create a sealable interface between the thin plastic bag and the continuous inner side wall of the outer plastic container near the midpoint. Still another step generates a magnetic induction field near and preferably outside of the metal member. The field has a strength that generates sufficient heat in the metal member so that the heat from the metal member may be conducted through the thin plastic bag to the continuous inner side wall of