AU632765B2 - Method of filling and sealing a deformable container - Google Patents

Abstract

A method of filling and sealing a container (10) having a deformable bottom (12) with a product (34) having a volume less than the initial volume of the container, but equal to the volume of the final container with its bottom (12) deformed upward. The container is filled and a lid (26) is placed onto the container adjacent to a sealing surface (27). In its initial position enough headspace exists to permit the proper lid placement without squeezing product onto the sealing surface (27). The filled container with its unsealed lid (26) is placed on an anvil (30) in a vacuum chamber (38). The vacuum chamber (38) is vacuumized to a desired pressure and the lid (26) is sealed to the sealing surface (27) by sealing head (40). The container is then removed from the vacuum chamber (38). As a result of atmospheric pressure the bottom (12) is inverted upwardly thereby forcing the product (34) to fill the headspace voids.

Description

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I pages 1/4-4/4. drawings, replaced by new pages bearing the PCT same number, due to late transmittal by the receiving Dffice INTERNATIONAL APPLICATION PU BI HE UN' 1 1 TI P t N'IC OPERATION TREATY (PCT) (51) International Patent Classification 4 V (1l ernational Publication Number: WO 90/02687 31/02, 7/28, 1/04 Al (43) International Publication Date: 22 March 1990 (22.03.90) (21) International Application Number: PCT/US89/03987 (81) Designated States: AT (European patent), AU, BE (European patent), CH (European patent), DE (European pa- (22) International Filing Date: 13 September 1989 (13.09.89) tent), FR (European patent), GB (European patent), IT (European patent), JP, LU (European patent), NL (European patent), SE (European patent).

Priority data: 244,829 14 September 1988 (14.09.88) US Published With international search report.

(71) Applicant: KAL KAN FOODS, INC. [US/US]; 3386 East Before the expiration of the time limit for amending the 44th Street, P.O. Box 58853, Vernon, CA 90058-0853 claims and to be republished in the event of the receipt of amendments.

(72)Inventor: BALCOMBE, Roy 5091 Churchill Avenue, Westminster, CA 92683 (US).

(74) Agent: SANTISI, Leonard, Curtis, Morris Safford, 530 Fifth Avenue, New York, NY 10036 (US).

(54)Title: METHOD OF FILLING AND SEALING A DEFORMABLE CONTAINER (57) Abstract A method of filling and sealing a container (10) having a deformable bottom (12) with a product (34) having a volume less than the initial volume of the container, but equal to the volume of the final container with its bottom (12) deformed upward. The container is filled and a lid (26) is placed onto the container adjacent to a sealing surface In its initial position enough headspace exists to permit the proper lid placement without squeezing product onto the sealing surface The filled container with its unsealed lid (26) is placed on an anvil (30) in a vacuum chamber The vacuum chamber (38) is vacuumized to a desired pressure and the lid (26) is sealed to the sealing surface (27) by sealing head The container is then removed from the vacuum chamber As a result of atmospheric pressure the bottom (12) is inverted upwardly thereby forcing the product (34) to fill the headspace voids.

*(Referred to in PCT Gazette No. 15/1990. Section II) WO 90/02687 PCr/US89/03987 METHOD OF FILLING AND SEALING A DEFORM4ABLE CONTAINER BACKGROUND OF THE INVENTION This invention relates to a method of filling and sealing a container with a product, and more particularly, to a method of producing a package in which the integrity of the seal is preserved and voids within the container are virtually eliminated.

Prior methods for filling and sealing a container have provided a substant-ial 'headspace" within the container in order that the seal area of the container is not contaminated with the product, which will result in incomplete.and leaking seals.

This headspace gas hinders exploitation of sterilizable containers, because of the difficulty 6f accurately controlling the pressure within the containers during temperature changes, to ensure the seals are not ruptured or containers otherwise deformed or damaged. if the headspace gas is air, this will cause spoilage of oxygen-sensitive products.

This headspace also has the appearance of a partially filled container, giving a poor value impression to the consumer.

Additionally, the headspace allows movement of product during shipment, resulting in stressing of the lid mrateria (which may rupture), and also damage to the product.

It is well known to use a diaphragm of stretchable lid material to close a container which is deformed to eliminate headspace. This stretchable lid material, however, typically is not puncture resistant and, hence, requires some secondary protection to maximize quality control of the product.

WO 90/02687 PCT/US89/03987 OBJECTS OF THE INVENTION It is a general object of this invention to provide an improved method of filling and sealing a package with a product.

i It is also an object of this invention to provide a method of producing an extended package in which the integrity of the seal of the lid is preserved and the voids within the container that allow product movement are eliminated.

It is another object of this invention to provide a method for filling and sealing a container which does not require that a diaphragm or flexible lid be used in addition to the seal to close a container body.

It is a further object of this invention to i provide a method for filling and sealing a container which not only reduces seal area contamination but also increases value impression.

SIt is another object of this invention to provide a method for filling and sealing a deformable container which enables the fill volume of the container to be less than the initial container volume to thereby isolate the Sproduct from the seal area and avoid seal area contamination.

A It is still and further object of this invention to provide a retortable container which allows for shorter cooking time.

Other objects and advantages of the invention will become apparent from the detailed description and from the appended drawings in which like numbers have been used to designate like parts in the sevreral views.

SUMMPRY OF THE INVENTION This invention relates to a method of filling and sealing a package with a product, and more particularly to a method of producing a sterilized package in which the integrity of the seal and the lid is preserved and the voids within the container that allow product movement are eliminated. The container of the present invention is r SWO 90/02687 PCr/US89/03987 -3designed with a base having a deformable or drawable insert B and with the correct ratio of wall strength to the radius of curvature so that the bottom is stable in either the up i or down position. The whole container is made of a semi-rigid material, and hence, the bottom is not a stretchable diaphragm. The use of laminations of Sthermoplastic foil, thin aluminum or steel enables the icontainer to be puncture resistant and provides for considerable resistance to damage in handling and transportation.

In opera~ion, the container is filled with the base in its downward position so that the charging product falls below the seal surface. Thus, there is sufficient i headspace to permit the lid placement without squeezing product onto the seal surface. The edge of a top cut lid is then positioned adjacent to a rim section of the container. The filled container and lid are then transferred into a vacuum chamber with the sealing surface Sof the container being supported on an anvil. The gas in the vacuum chamber is then evacuated. In this position, a sealing head above the container is in a raised position.

SThis process lowers the pressure of the headspace gas within the container to that of the chamber. When the desired vacuum level is achieved the sealing head is lowered and the lid is sealed to the container. Subsequent thereto, the chamber is brought back to atmospheric pressure such that the base is inverted thereby forcing the product to move upwardly to fill the headspace or voids within the container.

S As such, this method to fill and seal a container enables the fill volume to be less than the initial container volume to thereby isolate the product from the i seal area to avoid seal area contamination. In addition, this process eliminates the voids within the container which allow product movement.

I I WO 90/02687 PCU/US89/03987 4 BRIEF DESCRIPTION OF THE DRAWINGS The following detailed description, given by way of example, but not intended to limit the invention solely to the specific embodiments described, may best be understood in conjunction with the accompanying drawings in which: SFigure 1 is a front perspective view of a i preferred embodiment of the container of this invention.

Figure 2 is a side cross-sectional view taken along line 2-2 of Fig. 1 with the base of the container in its downward position.

i Figure 3 is a side cross-sectional view taken along line 2-2 of Fig. 1 with the base of the container in its intermediate position.

Figure 4 is a side cross-sectional view taken along line 2-2 of Fig. 1 illustrating the base of the container in its upward position.

Figures 5-9 illustrate a preferred method of filling and sealing a deformable container.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT This invention relates to a method of filling and 1 sealing a package with a product, and more particularly, to Sa method of producing an extended life package in which the A integrity of the seal and the lid is preserved and the U voids within the container that allow product movement are eliminated.. Referring now to Fig. 1, a preferred U embodiment of a container 10 is provided. The body 10 has U a bottom 12 which has a flexible insert 14 substantially deformable in shape. Since the hoop stress provides for tension along the circumference of the container base, in the preferred embodiment, the container can be "bi-stable" in that it is. stationary in either the up or down positions of the container. The base includes a deformable hoop webbing 16 between the insert 14 and the side edges 18 of the container. These rigid side edges 18 support an upper flange 20 which extends outwardly therefrom. The upper r i WO 90/02687 PCT/US89/03987 flange 20 includes a sealing surface 22 which terminates in j a crimped raised rim section 24.

As is best shown in Fig. 2, the container body is capable of receiving and retaining a top cut lid 26 which is sealed to the container in the grooves 27 formed between the sealing surface 22 and the raised rim section 24. This lid is preferably formed of a puncture-resistant plastic i material, but any material, including a nonplastic material, such as reinforced paper, which is substantially Spuncture-resistant may be utilized. As a force A (see Fig.

moves the base 12 upwardly, the outer rim or hoop i member 16 of the base is stretched. As is illustrated in Fig. 3, the bending at the edges of the body induces stress to restore the body 10 to its original shape in the intermediate position of the deformable bottom. After a force A is applied to the container bottom, the bottom is inverted forming an inverted U shape (see Fig. This angle o( is decreased as the hoop stress of the hoop member 16 resists the bending stress around the base.

As a result of this design, the bottom is stable in either the up or down position, and as such, the bottom is bi-stable. Since the whole container is made of a semi-rigid material, the bottom is not a stretchable diaphragm. The base 12 is thus held stable in either position by the hoop stress of the outer diameter 16 of the base 12.

In another preferred embodiment of the deformable container of this invention, the container body may have a deformable bottom which is entirely deformable in shape.

In this configuration, the base does not include a hoop member, such as 16 (see Fig. The body of this preferred embodiment also includes semi-rigid side members which support an upper flange which extends outwardly from the side surfaces. The upper flange includes a sealing surface which terminates in the rim section. A force A applied to the container base, moves the base upwardly thereby stretching the outer rim of the base. In the r SWO 90/02687 PCT/US89/03987 6 intermediate stage, the side walls of the container are pushed outward as the base is inverted. The bending at the i edges induces stress to restore the container to its Soriginal shape. When the base is in its final upward position, the hoop stress along the side edges resists this bending stress and holds the base stable in the up position.

In these or other embodiments, the containers may be manufactured with the base either up or down, provided the hoop stress induced in the outer diameter of the base can resist the restoring- stresses, and can hold the base stable in the position opposite to the manufactured position.

A preferred method for filling and sealing these deformable containers is shown in Figs. 5-9. Referring now to Fig. 5, the sealing surface 22 of the container body is mounted on support arms 28 of an anvil 30. The cavity 32 of container body 10 is charged with a product 34 from a filler 36. This product charge is sufficiently fluid or malleable so that it will not tend to assume any specific natural shape, but however, will fill the void volume of the container with a secured lid. In this configuration, the container is filled with the insert 14 of the base 12 j in its downwardly position. After the product has been initially charged into the container, there is still sufficient headspace, however, to permit lid placement without squeezing the top of the product fill onto the sealing surface (see Fig. 6).

r Referring now to Fig. 7, the filled container supported on anvil 30 and lid are then transferred into a vacuum chamber 38. When the container and lid are initially transferred into the vacuum chamber, a sealing head 40 is disposed in the vacuum chamber immediately above anvil 30 in its raised position. In this position, the gas in the vacuum chamber 38 is evacuated through multiple ports 42a, b and c. Due to the force of the evacuation, an opening 44 is formed between lid 26 and sealing surface 22 r WO 90/02687 PCT/US89/03987 -7of the container body 10, and as a result thereof, the pressure of the headspace air within the container is lowered to that of the vacuum chamber.

When the desired vacuum level is achieved within the chamber 38, and as such, gas has been exhausted through ports 42a, b and c, the seal head 40 is lowered and the lid 26 is sealed to the sealing surface 22 of the container body 10, as is shown in Fig. 8. Even though the preferred embodiment herein discloses that the lid may be heat sealed to the sealing surface 22 of container body 10, other methods of sealing 'may be utilized. These include induction sealing, spin welding, cold seal, ultrasonic sealing or seaming. The edges 46 of the seal head 40 apply pressure to the outward edges 48 of the continuous top lid 26 such that the outward edges 48 are closely confined to the sealing surface 22 of container body 10 (see Fig. 8).

During this sealing process, the vacuum is maintained.

As is illustrated in Fig. 9, the container is removed from the vacuum chamber such that the container is brought back to atmospheric pressure. As a result thereof, the deformable insert 14 of base 12 is inverted upwardly, thereby forcing the product 34 in the direction of arrow B to fill the headspace and voids 50. The wet or dry products within the container must be sufficiently mobile to move into the voids. Since the product is forced into the voids 50 when the container is brought back to atmospheric pressure, the value impression of the product to the consumer is thereby improved. As a result thereof, such a method of filling and sealing a deformable container 1 enables the fill volume to be less than the initial container volume to thereby isolate the product from the 1seal area to avoid seal area contamination. This process, however, also eliminates voids within the container which allow product movement.

While the preferred embodiment of the present invention has been described, it should be understood that various changes, adaptations and modifications may be made WO 90/02687 PCr/US89/03987 -8 therein without departing from the spirit of the invention and the scope of the appended claims. For instance, the i force A, as is shown in Figs. 2, 3, and 8 may be caused by either the return to atmospheric pressure of the container after the vacuum environment is terminated or by a mechanical push. In addition, preferably the container body is bi-stable, the container is stable with the deformable insert being in either the up or down position.

Q If, however, the container is not bi-stable, such that the deformable bottom will remain in the down position unless held up by a vacuum, or partial vacuum, within the container, a worker will then be able to recognize that a loss of sufficient vacuum occurred during filling. As a result thereof, the product should be rejected.

Additionally, this method may be utilized for steam flushing, as is shown in Figs. 10 and 11, which is an important alternative for filling the container with a hot product. Without steam flushing, the vacuum maintained during the process would cause the hot product to boil.

SWith this steam flushing process, the evacuation of the pack may be achieved by flushing out-the headspace gas 52 (see Fig. 10) with steam 54 from a steam duct 56 just prior i to sealing the lid. The steam exits the headspace through an extract duct 58. While the steam flushing is taking place, the lid 60 of container 62 is held above the container 62 by a lid holding device 64. As in the previous preferred embodiment, the sealing surface 66 of the container is mounted on support arms 68 of an anvil Additionally, a sealing head 74 is in its raised position above the sealing surface of the container.

After the headspace gas is steam flushed, the sealing head is lowered and the lid is sealed to the sealing surface of the container body (see Fig. 11). This steam will then condense to water, on cooling, resulting in a vacuum within the container headspace. As in Fig. 9, the container is then subjected to atmospheric pressure to invert the container bottom into its upward position WO 90/02687 PCT/US89/03987 9 thereby forcing the product into close contact with the lid to thereby reduce the headspace between the product and the lid.

With steam flushing, it is possible to utilize a container that has a bottom which is stable only in the up position. This base can be held down with a vacuum suction cup during filling and sealing, then released to invert to its original and stable position aided by the vacuum induced by the steam flush. This container design, with its dome base stable in the up position, could be used with a vacuum chamber, but, in order to deform the bottom of the: container downwardly, a mechanical gripper could engage any suitable attachment member extending from the container bottom.

It is intended that the appended claims be interpreted as including the foregoing as well as various other such changes and modifications.

Claims (14)

1. A method of filling and sealing a bi-stable container, subjected to a gaseous environment, with a product comprising the steps of providing a semi-rigid container having a bi-stable, unribbed bottom having a hoop member surrounding the side edges of the container and movable between a first position, wherein said container bottom is moved into a stable downwardly extended position, and a second position, wherein said i container bottom is moved into a stable inverted domed configuration; placing the container bottom in its stable downwardly extended position; charging the product into the container to a level having a volume less than the container volume but equal to the filled volume with such level defining a headspace opening; placing the container in a vacuum environment chamber; sealing a generally flat lid to said container; removing the vacuum environment from the container so as to return the container to atmospheric pressure wherein hoop stress of said hoop member overcomes the bending stress around said unribbed bottom such that the unribbed bottom of the container is inverted into said stable inverted domed configuration thereby forcing the product into close contact with the lid to reduce the headspace between the product and the lid and wherein the lid f remains in its generally flat configuration. i

2. The method as recited in claim 1 wherein the sealing step is achieved by sealing the lid onto the container body at a seal surface of the container.

3. The method as recited in claim2 wherein the lid is located adjacent to the sealing surface and a rim section of the container body before the headspace is eliminated.

4. A method as in claim 1, wherein the lid is formed of a puncture-resistance l nonplastic material.

The method as recited in claim 1 wherein the lid is formed of a puncture- resistant plastic material.

6. The method as recited in claim 1 wherein the lid is supported by a groove of said container formed by said rim section and sealing surface. N1, :I ii 11 1

7. The method as recited in claim 1 and further including a product charge i that is sufficiently liquid or mobile so as not to tend to assume any specific natural shape.

S8. The method as recited in claim 1 and further including evacuating the gas within the vacuum chamber and container such that the pressure of the headspace ga. within the container is lowered to that of the vacuum chamber.

9. A method as recited in claim 1 and further including positioning the container in the vacuum chamber below a sealing head.

The method as recited in claim 9 and further including lowering the sealing head within the vacuum chamber when the desired vacuum level is achieved such that the sealing head impinges upon said-lid to seal said lid to the sealing surface of the container.

11. The method as recited in claim 1 wherein the unribbed bottom of the container may be inverted inwardly by a mechanical push when the chamber is brought back to atmospheric pressure thus forcing the product to fill the headspace voids.

12. The method as recited in claim 1 and further including mounting said sealing surface of said container within the vacuum environment along a leading edge of an anvil.

13. A method of filling and sealing a bi-stable container, subjected to a gaseous environment, with a product comprising the steps of: providing a semi-rigid container having a bi-stable, unribbed bottom having a hoop member surrounding the side edges of the container and movable between a first position, wherein said container bottom is moved into a stable downwardly extended position, and a second position, wherein said container bottom is moved into a stable inverted domed configuration; placing the container bottom in its stable downwardly extended position; charging the product into the container to a level having a volume less than the container volume but equal to the filled volume with such level defining a headspace ening; I 12 i positioning a generally flat lid adjacent to a sealing surface and rim section of said container; placing the container in a vacuum environment chamber below a sealing head; mounting the sealing surface of said container within said vacuum chamber along a leading edge of an anvil; 4 evacuating the gas within said 'vacuum chamber and container such that said pressure of the headspace air within said container is lowered to that of said vacuum chamber; lowering said sealing head within said vacuum chamber when the desired vacuum level is achieved such tMat the sealing head seals the lid to said sealing surface of said -container; and removing said vacuum environment from said container so as to return the Scontainer to atmospheric pressure wherein hoop stress of said hoop member overcomes the bending stress around said unribbed bottom such that said unribbed bottom of the container is inverted into said stable inverted domed configuration thereby forcing the product into close contact with said lid to reduce the headspace between said product and said lid and wherein said lid remains in its generally flat configuration.

14. A bi-stable container, subjected to a gaseous environment, holding a product, said container being manufactured by the process comprising the steps of: providing a semi-rigid container having a bi-stable, unribbed bottom having a hoop member surrounding the side edges of the container and movable between a first position, wherein said container bottom is moved into a stable downwardly extended position, and a second position, wherein said container is moved into a stable inverted i domed configuration; placing the container bottom in its stable downwardly extended position; charging the product into the container to a level having a volume less than the container volume but equal to the filled volume with such level defining a headspace opening; placing the container in a vacuum environment chamber; sealing a generally flat lid to said container; and removing the vacuum environment from the container so as to return the container to atmospheric pressure wherein hoop stress of said hoop member overcomes ?A L he bending stress around said unribbed bottom such that the unribbed bottom of the S13 i container is inverted Into said stable inverted domed configuration thereby forcing the i product into close contact with the lid to reduce the headspace between the product and said lid and wherein said lid remains in its generally flat configuration. A bi-stable container, subjected to a gaseous environment, holding a product, said container being manufactured according to a method comprising the steps of: providing a semi-rigid container having a bi-stable, unribbed bottom having a hoop member surrounding the side edges of the container and movable between a first position, wherein said container bottom is moved into a stable downwardly extended position, and a second position, wherein said container bottom is moved into a stable inverted domed configuration; placing the container bottom in its stable downwardly extended position; charging the product into the container to a level having a volume less than the container volume but equal to the filled volume with such level defining a headspace opening; positioning a generally flat lid adjacent to a sealing surface and a rim section of said container; placing the container in a vacuum environment chamber below a sealing head; mounting the sealing surface of said container within said vacuum I chamber along a leading edge of an anvil; evacuating the gas within said vacuum chamber and container such that said pressure of the headspace gas within said container is lowered to that of said vacuum chamber; lowering said sealing head within said vacuum chamber when the desired vacuum level is achieved such that the sealing head seals the lid to said sealing surface of said container; and removing said vacuum environment from said container so as to return the container to atmospheric pressure wherein hoop stress of said hoop member overcomes the bending .stress around said unribbed bottom such that said unribbed bottom of the container is inverted into said stable inverted domed configuration thereby forcing the product into close contact with said lid to reduce the headspace between said product and. said lid and wherein said lid remains in its generally flat configuration. *r 1 6. A method of filling and sealing a semi-rigid bi-stable container, subjected to a gaseous environment, with a product and having a mechanically bi-stable bottom movable between a first position, wherein said container bottom is moved into a stable downwardly extended position, and a second position, wherein said container bottom is moved into a stable inverted domed configuration, and further having a hoop member surrounding the side edges of the container, said method comprising the steps of placing the container bottom formed of a semi-rigid material in said stable downwardly extended position, charging the product into the container to a level having a volume less than the container volume but equal to the filled volume with such level defining a headspace opening; flushing out the headspace gas with steam; sealing a generally flat lid to the container; allowing the headspace to cool, and condensing the steam to water resulting in a vacuum within the headspace; returning the container to atmospheric pressure wherein hoop stress of said hoop member overcomes the bending stress around said unribbed bottom such that the unribbed container bottom is inverted into said stable inverted domed configuration thereby forcing the product into close contact with the lid to reduce the headspace between the product and the lid and wherein the lid remains in its generally flat configuration. 1 7. A method of filling and sealing a bi-stable container, subjected to a gaseous environment, with a product and having a bottom deformable between stable upward and downward positions and having a hoop member surrounding the side edges of the container, said method comprising the steps of:. i placing the semi-rigid container having an unribbed bottom upon an anvil; icharging the container with the unribbed bottom in its stable downward position with a product to a level having a volume less than the container volume but equal to the filled volume with such level defining a headspace opening; ii maintaining the unribbed bottom .in its downward position with a vacuum suction cup; positioning a lid adjacent to a sealing surface; placing the container in a position to be steam flushed; flushing out the headspace gas with steam; placing the container below a sealing head; mounting the sealing surface of said container along a leading edge of said lowering said sealing head such that the sealing head seals the lid to said sealing surface of said container; allowing the headspace to cool, and condensing the steam to water resulting in a vacuum within the headspace; maintaining the unribbed bottom of the base in its downward position with a vacuum suction cup; releasing the vacuum suction cup from the base of the container and returning the container to atmospheric pressure wherein hoop stress of said hoop member resists the bending stress around said unribbed bottom such that the unribbed bottom is inverted to its stable upwardly extended position thereby forcing the product into close contact with said lid to reduce the headspace between said product and said lid. 1 8. A container, subjected to a gaseous environment, holding a product and having a bottom deformable in shape between downward and upward stable positions and having a hoop member surrounding the side edges of the container, said container being manufactured by the process comprising the steps of: l placing the semi-rigid container having an unribbed bottom in said stable downward position upon an anvil; charging the container with its unribbed bottom in its downward position with the product having a volume less than the container volume but equal to the filled volume with such level defining a headspace opening; Z flushing out the headspace gas with steam; i sealing said lid to said container; allowing the headspace to cool, and condensing the steam to water resulting in a vacuum within the headspace; maintaining the unribbed bottom of the base in its downward position with a vacuum suction cup; releasing the vacuum suction cup from the base of the container and returning the container to atmospheric pressure wherein hoop stress of said hoop member resists the bending stress around said unribbed bottom such that the bottom of the container is inverted into its stable upwardly extended position thereby forcing the product into close contact with the lid to thereby reduce the headspace between the product and the lid. 1 9. A container comprising: lei 00 16 a semi-rigid container housing for receiving a product filled therein to a volume less than the container volume but equal to the filled volume with such level i defining a headspace opening; a generally flat lid sealed to said container housing for covering the product within said container housing; and said container housing having a bi-stable, unribbed bottom having a hoop member surrounding the side edges of the container housing and movable between a first position, wherein said container bottom is moved into a stable downwardly extended position, and a second position, wherein hoop stress of said hoop member overcomes the bending stress around said unribbed bottom such that said bottom is inverted into a stable inverted domed configuration thereby forcing the product into close contact with the lid to reduce the headspace opening between the product and the lid and wherein the lid remains in its generally flat configuration. A container comprising: a semi-rigid container housing for receiving a product filled therein to a volume less than the container volume but equal to the filled volume with such level defining a headspace opening; a generally flat lid sealed to said container housing for covering the product within said container housing; and pI i J- 17 said container housing having a bi-stable, unribbed bottom movable between a first position, wherein said container bottom is moved into a stable downwardly extended position, and a second position, wherein said unribbed bottom is inverted into a stable inverted domed configuration thereby forcing the product into close contact with the lid to reduce the headspace opening between the product and the lid and wherein the lid remains in its generally flat configuration. DATED this 21st day of October, 1992. KAL KAN FOODS. INC. WATERMARK PATENT TRADEMARK ATTORNEYS THE ATRIUM 290 BURWOOD ROAD HAWTHORN VICTORIA 3122 AUSTRAUA I: i 1: :4 ~ai i i