MEANS OF SEALING LIDS ON CONTAINERS

Abstract: Plastic portions of a container rim and mating lid (17) are fused together by an electrical conductor wire loop (19) positioned therebetween when electromagnetically coupled to an induction heating coil (18). The wire forms a tab (25) extending outside the closed container which may be manually manipulated to remove a lid fused in place to close the container. This container may be hermetically sealed with sanitized foodstuff (16) or the like by concurrently sterilizing with microwave energy (21) while fusing the lid in place.

Description: TECHNICAL FIELD: This invention relates to sealing of containers and more particularly it relates to the fusing of a lid to a container body by induction heating of a wire loop placed adjacent fusible container materials commonly meeting at mating lid and body surfaces. BACKGROUND ART: Sealing lids on containers by melting container material onto a thin metal foil membrane closing the container is known in the art as evidenced by U. S. Patent 4,044,941 issued to D. Knudsen Aug. 30, 1977. Several problems result. Thus, in effect two lids are required, increasing container costs particularly in view of the problems of handling and quality control imposed by the fragile nature of the film and the inefficiencies of induction heating the metal foil in areas other than those being fused. Furthermore with such a fragile sealing cover it would be difficult to 'vacuum' pack foodstuffs. Also the large area foil may interfere or be inconsistent with microwave sterilization of the contents inside the container, which need be passed through only transparent to electromagnetic energy package areas such as plastic sidewalls. Sterilization of food in sealed containers, such as by microwave energy, has associated problems because of generation of steam and handling of pressure, such as treated in the U. S. Patents, as follows: J. Lundy, 3,215,539, Nov. 2, 1965 requires sealing the food in a vapor tight package of constant volume before directing microwave energy thereinto. M. Beauvais et al. 4,406,860, Sept. 27, 1983 encloses a container within an outer pressure control jar with a steam release valve when sterilizing with microwaves and thereafter during cooling, in order to vacuum pack the food by pressure sealing of a lid into place by internal vacuum pressure of the container when the outer jar is opened to the atmosphere. Clearly the prior art does not provide an inexpensive hermetically sealable container in which food can be quickly, reliably and inexpensively sterilized while sealing the lid on the counter. Another problem with prior art sealed plastic containers is the eventual unsealing or removal of the lid, which has led to the awkward and complex molds required for unusual and complex opening means as exemplified, for example, by U.S. Patents 2,998,158 to E. Tupper, Aug. 29, 1961: 3,799,389 to S. Bloeck, Mar. 26, 1974 and 4,474,304 to S. Jacobs, Oct. 2, 1984. Thus, in heat sealed plastic containers, plastic tear strips or inserted tear threads are provided conventionally to remove the plastic lid from the plastic container body to which it is sealed. However, the opening process is tedious and time consuming rather than a simple pop off of the lid. Moreover, US Patent 3.561.982 is showing a container comprising a body portion and a closing lid, the latter being sealed to the body portion by means of a fusible material heated by using a closed electrically conductive loop of a wire placed along said fusible material. For closing the container, said loop of a wire is heated by induction using an external electromagnet induction coil. US Patent 2.941.660 describes certain steps for opening a container by drawing the accessible end of an inserted tear thread. The teaching of both aforementioned patents is improving the known technique, but still not satisfactory particularly concerning both the closing and opening process. Accordingly, it is generally objective of this invention to improve the state of the art by resolving the foregoing problems with a simplified container. DISCLOSURE OF THE INVENTION: Thus, in accordance with this invention, there is provided a container having a body portion for holding a product and a lid for confining the product in the body portion, comprising in combination, lid and body portion having placed at mating surfaces thereof an electrically insulating fusible material, and a closed electrically conductive loop of wire positioned to heat the fusible material when the lid is on the body portion as a secondary coil for electromagnetically inducing enough heat to fuse together the common surfaces by an external electromagnet induction coil when the lid is in place on the body portion, characterized in that said loop of wire has a tab extending outside the container when closed with the lid fused in place, said tab being adapted for manual manipulation to open a closed container with the lid fused in place, wherein the loop is formed of a stiff wire having an end conductively fastened at a closing point on the loop from which the tab extends comprising a continued portion of the stiff wire formed into a plane perpendicular to that of the loop, thereby to use little electromagnetic energy when the loop is heated and further proving a tab that resides alongside the container body, which tab when used for opening the container is moved to a position substantially parallel with the loop thereby to break the conductively fastened loop end away. BRIEF DESCRIPTION OF THE DRAWINGS: In the various views of the drawing similar features are identified with like reference characters to facilitate comparison. Figure 1 shows in section view a novel container configuration loaded with foodstuff, or the like, in the sanitation and lid sealing process, as afforded by this invention; Figure 2 is a fragmental section view of a particular container body to lid seal structure afforded by the invention; Figure 3 is a top plan view of the container of Figure 1 with its pull tab readied for removal of a sealed on lid; and Figure 4 is a top plan view of an alternative container configuration. THE PREFERRED EMBODIMENTS: It may be seen from Figure 1 that a container body 15, containing foodstuff 16, or the like, has a sealed on lid 17, which is electromagnetically heated by means of primary induction heater coil 18 and secondary coil 19 implanted in a position within the closed container so that it may fuse together the thermoplastic lid and body rim portions as in the region of arrow 20 by induction heating. The force F on the lid assures good contact of mating lid and body surfaces while the fusing occurs and preferably is kept until the plastic is cooled enough to hold the lid securely in place. The container may be hermetically sealed in this manner, or if that is not important, less heat can tack together the surfaces to hold the lid in place. If the contents, such as food, are to be sterilized, this is done as indicated by microwave radiation 21 passing through the container. Since steam is released from moisture in the food, the fusing is done after sufficient steam escapes from between the lid and container body. Thus sequentially the microwave sterilization energy is applied and thereafter at least partly concurrently the fusing induction energy is applied. This results in a hermetic vacuum seal without the introduction of contaminating air after sterilization or during the fusing operation. The pull tab 25 extends from the inductive secondary coil 19 to a position outside the container for manual access in removing the lid 17 sealed onto the body portion 15 of the container, as seen from Figures 1 and 3. When the coil is of heavy, stiff wire such as steel, it provides a pop off action breaking the lid free at a rupture point that may be a weakened section of the lid or at a point adjacent the fused areas, for example. Should the coil be of a more ductile wire such as copper strands, then the tab 25 acts as a handle for a tear string of the prior art. For such cases, and where it is desirable to have a progressive rupture around the periphery of the lid, the coil may have one end soldered or tack welded in a break away joint at 26. Then when the tab, which for inductive reasons is perpendicularly disposed from the coil 19, is manually pulled to a parallel position as shown in Figure 3, the weld or solder joint 26 may be broken to permit the rupture to remove the lid to proceed under manual upwardly directed pressure in a clockwise direction about the lid as shown in Figure 3. The coil 19 may be variously positioned to lie next to the desired fusing area or to be embedded between the lid 17 and container body 15 as shown in Figure 2. Clearly the lid, the container body, and the meeting fusible surfaces may take various configurations. As shown in Figure 4, a quadrilateral rataher than conical container may be used in the same manner. Having therefore advanced the state of the art by introduction of novel container structure and closure techniques, those features of novelty believed descriptive of the spirit and nature of the invention are defined with particularity in the following claims.

Claims: A container having a body portion for holding a product and a lid for confining the product in the body portion, comprising in combination, lid (17) and body portion (15) having placed at mating surfaces (20) thereof an electrically insulating fusible material, and a closed electrically conductive loop of wire (19) positioned to heat the fusible material when the lid (17) is on the body portion (15) as a secondary coil for electromagnetically inducing enough heat to fuse together the common surfaces by an external electromagnet induction coil (18) when the lid (17) is in place on the body portion (15), characterized in that said loop of wire (19) has a tab (25) extending outside the container (15) when closed with the lid (17) fused in place, said tab (25) being adapted for manual manipulation to open a closed container (15) with the lid (17) fused in place, wherein the loop (19) is formed of a stiff wire having an end conductively fastened at a closing point (26) on the loop (19) from which the tab (25) extends comprising a continued portion of the stiff wire formed into a plane perpendicular to that of the loop (19), thereby to use little electromagnetic energy when the loop (19) is heated and further proving a tab (25) that resides alongside the container body (15), which tab (25) when used for opening the container (15) is moved to a position substantially parallel with the loop thereby to break the conductively fastened loop end away. A container as defined in Claim 1 wherein the lid (17) is made of readily frangible material such as a foam plastic, and said loop wire (19) is ductile and easily manually bent comprising an extending tab end (25) manually accessible from outside a closed container with the lid (17) fused in place, with the wire positioned to rupture the lid material when the tab (25) is manually manipulated for opening a closed container (15) with the lid (17) fused in place. A container as defined in Claim 1 wherein the loop (19) is resident in the lid (17) before the common surfaces are fused together. A container as defined in Claim 1 with the lid (17) fused in place to close the container (15) by the application of induced electromagnetic energy to the loop (19). A container as defined in Claim 1 with the lid (17) fused in place on the container (15) to produce a hermetically sealed container. A container as defined in Claim 5 having sterilized contents with a liquid content hermetically sealed therein at a pressure below atmospheric. A container as defined in Claim 1 wherein the body of the container has a rim upon which the lid resides, and the loop comprises a single conductor wire positioned about the rim.

Inventors: LAPEYRE, JAMES MARTIAL
Applicants: THE LAITRAM CORPORATION
Application year: 1988
Main classification: B65B7
IPC codes: B29C65, B65D17, B65B7, B65D43, B65B51