Abstract: A substantially paper container has a top end closure adapted to be removed for opening the container and repositioned for closing the container. The container includes a tubular body of substantially paper material, a cup-shaped end closure of substantially paper material and a cup-shaped membrane having an outer upwardly-extending rim portion of substantially the same height as an upwardly-extending rim portion of the cup-shaped end closure. The membrane and end closure are positioned in an open upper end portion of the body in superimposed relationship with the membrane below the end closure. An upper area of the upper end portion of the body extends above the superimposed rim portions of the membrane and the end closure and is folded inwardly over and around the upper ends of the superimposed rim portions.

Abstract: An easily-opened can lid includes a cover ring having an outer edge and an inner edge. The inner edge folds inwardly to form an annular flange surrounding a lid opening. A tear-off portion aligned about the annular flange has a lateral area covering the entirety of the lid opening such that the lid opening is smaller than the tear-off portion. An attachment tab is secured at a location on the lateral area of the tear-off portion and an opening ring is secured to that attachment tab. An outside edge of the tear-off portion can be aligned with the inside edge of the cover ring so that the annular flange is entirely covered by the lateral area of the tear-off portion. Heat sealing coatings can be applied to the lateral area of the tear-off portion on a bottom side thereof and to the top side of the annular flange to secure the cover ring to the tear-off portion.

Abstract: The invention relates to a lid for tins, cans and the like, which lid is made of a layer of sheet metal or plastic that is attached to the wall (3) of the container by means of a seam-folded or other type of joint. The lid has a groove (5) in which the tip of a spoon or other suitable utensil can be inserted so that the latter can act as a lever therein and open the lid by tearing the material along a first line of weakness (6) located on the bottom of the groove (5). The lid advantageously has a second line of weakness (7) that is located in the area where the cross section of the groove (5), which is essentially U-shaped, joins the central portion of the lid; this second line of weakness contributes to weakening the lid material locally, in the above mentioned area, thereby enhancing the leverage exerted in order to open the lid.

Abstract: An innovative container lid having an integrally formed tamper evident band that goes through a series of changes or metamorphoses during the manufacturing and application process. The tamper evident band is attached to the lid at weak points on dogs formed around the periphery of the lid. Before use, the tamper evident band has a diameter substantially larger than the outer diameter of the lid. When the lid is installed in a container, and tangential and radial forces are applied to the periphery of the lid, the attachment points of the tamper evident band rupture and the band is displaced in a rippling effect with the dogs locking into sockets formed in the sidewall of the tamper evident band. Continued pressure is applied to the side of the tamper evident band until it is pressed firmly around the entire periphery of the lid against the side of a container with all the dogs engaged in sockets.

Abstract: A closure system for open headed containers utilizing a thermoplastic closure of the type having a disk and skirt depending therefrom the skirt portion including an annular ring adjacent its lower extremity adapted to lie beneath and radially inwardly with respect to an outwardly directed annular protrusion on a complementary container; a weakened stress relieving annular portion on the skirt lying immediately above said annular ring; the annular weakened portion having a wall thickness sized to ensure that stress relief and attendant creep in the thermoplastic material of the closure after affixation of the closure to the container occurs substantially at the annular weakened portion thereby allowing the lower portions of the annular ring to move radially inwardly; the wall thickness of the annular weakened portion at all times being of adequate thickness to resist premature rupture in the event that the closure/container unit is subjected to an impact; seal means between the closure and the container above

Abstract: Various embodiments of a sealing member disposed between a container body and an endpiece attached thereto are disclosed, as well as a method for disposing a sealing member between an endpiece and a container body. In one embodiment, a sealing member is disposed within a space between a container body flange and a corresponding portion of the sidewall of the container body, is disposed between a space between an endpiece flange and a corresponding portion of an endpiece wall, and is further disposed between the endpiece flange and container body flange. As such, the sealing member has a generally S-shaped configuration in cross-section. At least one and preferably two scores are incorporated on the sealing member to facilitate at least a partial removal of the endpiece from the container body so as to be able to access the contents of the container.

Abstract: A pilferproof or tamper resistant cover or lid for a container comprising a skirt having on its inner surface a circumferential nose for engaging a flange at an upper end of the container and a tear-off safety band having an inwardly inclined generally half tear-shaped cross-sectional form adapted to be snugly received in a groove of the container below the flange thereof.

Abstract: An open-ended container body is covered, preferably sealingly, by an endpiece/sealing-member. An annular flange of the endpiece/sealing-member is captured by crimping with a container body flange. The endpiece/sealing-member flange is coupled to the remainder of the endpiece/sealing-member by a tear strip which, upon removal, permits the remainder of the endpiece/sealing-member to be fully or partially removed from the open end of the container. The tearstrip is preferably integrally formed with the remainder of the endcap.

Abstract: A container assembly is provided including a cover and a container. The cover is securely engaged to the container by means of a primary lock to prevent removal of the cover from the container during handling. A secondary lock is also provided between the cover and the container. The secondary lock can be disengaged only after disengagement of the primary lock. The cover is readily removed by an end user of the container assembly.

Abstract: A package comprising a container, a closure assembly which includes a tearing portion. The container includes a sidewall, a closed end and an end with an opening. The closure assembly includes a central panel covering the container opening and a circumferential edge secured to the container. The tearing portion allows the closure to be opened for access to the contents of the package.

Abstract: A closure tear handle which prevents damage to the closure tear skirt under large application forces when the closure is applied to the bottle; this invention also provides a tear skirt which is easier for consumers to remove. A weak region is placed at the base of the intersection of the tear handle and the wall of the tear skirt. This weak region of the closure is designed such that upon contact with the neck finish of a bottle, which puts the tear skirt into tension, it attracts the tensile forces and relieves stress from the adjacent weak point of the closure tear skirt to prevent damage to this area that would be offensive to consumers and result in wasted product.

Abstract: A closure for a beverage bottle includes a plug element having a disk shaped head portion and a hollow cylindrical portion which seals with the inner surface of the opening of the bottle. An annular projection is formed around the circumference of the bottle 12 near its mouth. The closure further includes a cap element which fits over the plug element and which includes with a skirt having an annular recess which locks onto the annular projection of the bottle. A first precut line is provided in the cap, extending around its circumference and a second precut line portion extends from the distal edge of the skirt to the first precut line across the annular recess. The cap may be disengaged from the bottle by cutting through the second precut line and the first precut line.

Abstract: The present invention relates to a device for transporting materials which are potentially hazardous in primary containers, especially biological materials. The device comprises an enclosure having a top that snapably locks into a body to prevent removal of the top after it is placed into the body. The body includes a grasping flange which can be engaged and pulled along a spiralling line of weakness to rip open a top portion of the body section which does not directly house the specimen containers. The inside of the shipping container includes a resilient material to cushion any shock that the shipping container might undergo. The resilient material is preferably highly absorbent and is impregnated with one or more of several visual indicators, so that in the unlikely event a primary specimen container breaks, its contents will be absorbed, held inside the shipping container, and even the casual observer will be aware that a specimen leak has occurred.

Abstract: A container and closure assembly includes a container including a bottom portion and an encircling wall extending therefrom and defining a body portion. The body portion has an open end with a span equal to or different than the span of the body portion. The assembly also includes a removable cap liner including a seal for sealably engaging the container at its open end in a manner which traps fluids in the container and a removable cap which substantially covers the cap liner and thereby the open end of the container. The cap is adapted for reclosing the container after it is removed from the container.

Abstract: A plastic screw cap for the closure of a plastic container is provided for the closure of a container made of plastics. The screw cap has a simple configuration similar to corresponding closures for metal containers, but nevertheless ensures stable and sealed seating of the closure on the container opening. The screw cap is provided with an extension, extending radially over the side of the screw cap, which is made from a material which can be welded to the material from which the container lid is made.

Abstract: Package with safety lid and seal including a cylindrical body with a lid coupled by a thread at the mouth thereof and which includes an outside coaxial skirt having projections on its inside face. It is characterized in that the package body comprises around the body a seal made up with a strap weakly joined to this body, this strap having on the periphery, at least, one recess into which the corresponding projection of the skirt of the lid is fitted, preventing in this way the unscrewing of the lid. One of the ends of the sealing strap includes a handlelike extension facilitating through pulling, the tearing off and separation of the sealing strap with respect to the package body.

Abstract: An easy open end for food and beverage cans having reduced aluminum content is provided in an end having a metal polymer metal laminate construction. An opening panel as defined in the end body by a pair of first and second spaced apart score lines disposed in the first and second major surfaces, respectively. Each of the first and second score lines define an area of reduced thickness for both the metal layer and the adjacent polymer layer. The opening panel can be displaced from the remainder of the end body to provide an easy opening can by perforating the end body at a point along the first and second score lines.

Abstract: The invention provides a glue-on closure for a composite can or the like that affords an original hermetic seal. A tamper-evident tear band allows the closure to be conveniently opened. Separate end wall and sidewall parts of the closure are configured to provide reclosability with a surface-to-surface contact plug fit.

Abstract: An easy-opening closure is provided for hermetically sealing of an open end of a retortable container. The closure includes a metal end ring having a deformable outside peripheral area for being double seamed to the open end of the retortable container and having an inside area defining a large circular central opening to allow access therethrough to the interior of the container. An outside peripheral area of a membrane ring overlaps and is attached to the inside area of the metal end ring by a bond having predetermined shear and tensile force strengths. An inside peripheral area of the membrane ring extends inwardly into the circular central opening. A membrane patch is provided to cover the central opening and has an outer peripheral area overlapping and attached to an upper side of the membrane ring by a bond having predetermined shear and tensile force strengths.

Abstract: A fitment and closure assembly useful with a gable-topped carton having a gable-forming panel with a pouring hole, through which contents are pourable from the carton, is molded from low density polyethylene. A fitment having a tubular spout formed with an external thread and an annular flange extending outwardly from the tubular spout, below the external thread, is attachable to the gable-forming panel so that the annular flange is attached to the gable-forming panel, around the pouring hole, and so that the tubular spout extends upwardly from the pouring hole. A closure having an upper wall, a tubular skirt with an internal thread and an upper shoulder, and a plug seal forming an annular recess between the plug seal and the upper shoulder is threadable onto the fitment so that the external and internal threads are interengaged and so that the upper end of the tubular spout enters the annular recess with an interference fit.

Abstract: A container lid and container body locking mechanism includes a plurality of annular flanges and annular notch rings respectively and spaced apart in a pre-determined configuration so as to provide a tight leak-proof seal when the lid is fitted over the container body. A tamper proof detachable strip is provided in the container lid.

Abstract: A lid 1 for a container body 8 having a side wall 7 portion at one end of which an annular portion 9 extends at an obtuse angle to the side wall to define the mouth of the container. The lid has an elastically deformable central panel 2 and a peripheral annular flange 3 which extends downwardly and outwardly from the central panel to define a seal surface to co-operate with the annular portion 9 of the body. When adhered or fused together the inclined portion of the lid and body receive the stress, arising as a thermal processing increases the volume of product packed, as a load in shear peel force being minimized.

Abstract: A cap and container combination wherein the cap fits about the container in at least two closure positions. Two circumferential bands are provided around the skirt of the cap and there is an internal thread which engages an external thread about the container neck. In the first position, one band of the cap engages a circumferential slot about the container. The internal thread seals with the top of the container. The first band is removed and the container opened by removing the cap. In the second position, the second band engages the slot and the threads engage each other. In the second position, the second band is located about the container. It remains in position when and after the cap is removed. Tampering of the container and cap can be visually detected with this configuration. A bead about the container is formed of a reduced cross-section in portions circumferentially around the cap. This facilitates assembly and disassembly of cap and container.

Abstract: A full panel pull out easy opening end having vent means which includes at least one vent hole adjacent the pull tab and a strip of tape over the vent hole and over the handle end of the tab so the tab cannot be easily lifted without first at least partially removing the tape over the vent hole.

Abstract: A twist-on/twist-off resealable assembly for a can-end, such as a metal can used in the beverage industry includes a first set of knuckles formed on the can body near its top opening. A plurality of cooperating fingers on the inside of the can lid engage the knuckles so that the lid is tightened by its progressive downward motion as the lid is rotated. The lid also includes a weakened or frangible portion for forming a straw opening. A second set of knuckles are located below the top set of knuckles for engagement by fingers extending from a pilfer-proof ring. The twist-off can lid may be made from the same metal as the can body or alternatively from a transparent plastic material or a combination of metal and plastic.

Abstract: The present invention relates to a device for opening a receptacle having a peripheral rim on which a capsule is head sealed. The capsule includes a heat-sealable bottom layer and a metal top layer that adheres to the heat-sealable layer. Above the capsule, there is provided a tongue constituted by a metal sheet suitable for completely covering the metal layer of the capsule. The sheet is bonded to the metal layer in a lateral segment by a layer of adhesive material that adheres to the metal layer and to the metal sheet. The capsule is peeled off the receptacle by pulling the tongue upwards.

Abstract: Rigid container structure for hermetic sealing of particulate solids which emit an off-gas during containment. Provisions are made for enclosing chamber space with a gas-permeable imperforate membrane film so as to selectively separate and retain an off-gas out of contact with container contents. In a specific embodiment, carbon dioxide is selectively separated from coffee contents while the entire container, including such enclosed chamber as established, is hermetically sealed from ambient atmosphere. Provision is also made for venting of a separated off-gas in initiating a rupture of an end closure structure prior to full opening of the container. That arrangement further diminishes the opportunity for inadvertent discharge of particulate solids due to expulsion of gas from inert gas purging and from gas emitted during hermetic sealing.

Abstract: A package comprising a container, a closure assembly which includes a tearing portion. The container includes a sidewall, a closed end and an end with an opening. The closure assembly includes a central panel covering the container opening and a circumferential edge secured to the container. The tearing portion allows the closure to be opened for access to the contents of the package.

Abstract: A rupturable stopper for a pouring spout for a receptacle includes a base having a pouring zone sealed closed by a cover connected to the base by frangible connection. The spout includes a tubular neck having internal screw threads connected to the base so as to surround the frangible connection and terminating at a pouring lip. A cylindrical appendage extending up from the cover lies concentrically within the neck and receives a closure cap thereon that includes screw threads engageable with the neck and a seal that engages a spout pouring lip when the cap is engaged with the spout neck. Interlocking elements between the cap and the appendage prevent reverse rotation of the cap relative to the appendage so that, once the cap is secured in place within the neck by the screw threads, the first attempt to remove the cap drives the appendage in a twisting and axial movement to cause rupture of the frangible connection to open the pouring zone of the base.

Abstract: A container and closure assembly includes a container including a bottom portion and an encircling wall extending therefrom and defining a body portion. The body portion has an open end with a span equal to or different than the span of the body portion. The assembly also includes a removable cap liner including a seal for sealably engaging the container at its open end in a manner which traps fluids in the container and a removable cap which substantially covers the cap liner and thereby the open end of the container. The cap is adapted for reclosing the container after it is removed from the container.

Abstract: Full-aperture easy-open metal can-end for a can of the lift-up type with a tab, having an endless score-line close to its outer circumference of the can-end, wherein the removable part is profiled with a plurality of terraces at different heights, including an outer terrace close to the outer circumference of the can-end, an innermost terrace and at least one intermediate terrace. Adjacent terraces merge into one another with a height transition. To achieve low tear-force and/or other advantages, the intermediate terrace is inclined in a direction opposite to that of the outwardly adjoining transition at an angle .alpha. in the range 3 to 20 degrees to a plane perpendicular to the can axis.

Abstract: A tamper-evident, snap-on, screw-off closure which is used with a specially shaped container neck is provided with a foil liner. Once the closure is applied to the neck, the foil liner is sealed to the neck of the container. The foil liner includes a tab for removal of the seal disc from the neck. The closure is characterized by the absence of a second liner between the top of the cap and the foil liner. The closure, neck and the foil liner are formed to inhibit adherence of the tab to the cap interior and the neck exterior.

Abstract: A process for producing a container and closure assembly includes molding a preliminary container including a closed bottom portion, a body portion and a shoulder and neck portion. The shoulder and neck portion is separated from the body portion. An open ended second container is formed from the body portion, the second container having a rim at its open end and an encircling wall. The open end of the second container is then closed with a closure comprised of a cap and a cap liner. The cap liner has a weakened portion adapted to be broken by the cap. The cap or the cap liner are formed from the shoulder and neck portion of the preliminary container.

Abstract: A protective, low cost removable cover protects from dust, dirt, bacteria and the like a beverage container. This beverage container has a top wall formed with an outer surface, an opening member constituted by a partially stamped portion of the top wall, and an upwardly extending peripheral lip defining a top annular edge surface. The protective removable cover comprises a piece of sheet material covering at least a major portion of the partially stamped portion of the top wall, and is contoured to fit on the outer top wall surface inside the top annular edge surface. An annular strip of glue removably adheres the piece of sheet material to the outer top wall surface inside the top annular edge surface. The sheet material preferably comprises plastic, metal or composite material. Finally, the piece of sheet material may comprise a peripheral tab of any shape to facilitate manual removal thereof from the outer top wall surface.

Abstract: A frangible pour spout construction is improved by the addition of reinforcing webs at the upper plug portion. These webs function to localize the upward pulling force to thereby concentrate the rupture force at the frangible connection between the upper plug and lower pour spout portions. This insures that the pulling force is concentrated so that the frangible connection will rupture prior to the entire fitment being pulled off of the container to which the fitment is secured. The upper plug, later to function as a cap or stopper for the lower spout portion, is provided with a pull ring. The entire construction is die molded, as for example of polyethylene, with the pull ring being molded substantially at 90.degree. from its flat or storage position. A pair of lugs carried by the upper plug holds the pull ring down in its storage position.

Abstract: A container lid is characterized by a tamper-evidencing tear-strip member having a tab that protrudes from a plane formed by adjacent portions of the lid. The tab preferably includes gripping rib members on opposing surfaces of the tab and is surrounded by a sufficient gap to permit the tab to be readily grasped for easier removal of the tear-strip member from the lid, prior to initial removal of the lid from the container. In container and lid embodiments that are substantially rectangular, the lid also preferably includes mating engagement structure between the lid and the container which is interrupted or not present at the corners of the lid. The tear-strip in this rectangular embodiment also preferably includes a widened portion at the corners, whereby the removal of the tear-strip results in a "scalloping" of the corners. These features on rectangular embodiments facilitate easier attachment and removal of the lid to and from the container, after the removal of the tear-strip.

Abstract: A cover for a container is provided with primary and secondary detent means, the primary detent means being mounted on a tamper-evident tear strip and being removable with the tear strip as opening of the cover is desired. Secondary detent means is provided on detent tabs which remain operatively associated with the cover. The limited engagement of the detent tabs with the retaining means of the cover results in facile removal of the cover from operative engagement with the container and the reinstallation and the corresponding and facile reinstallation of the cover upon the container.

Abstract: For tent-type paperboard containers as well as other containers, a spout fitment is attached surrounding a hole in the container. The fitment spout has internal threads and an external flange which seals around the hole and is fixed to the container by thermal means, adhesive or the like. The cap has a top disk from which an externally threaded skirt depends. The exterior of the skirt has gripping ribs to assist in screwing and unscrewing the cap. The lower edge of the skirt seals against a sealing membrane on the spout. Surrounding the skirt is a tamper-evident band attached to the lower edges of the ribs by frangible bridges. The tamper-evident band has locking means engaging complementary locking means on the fitment. Thus, the cap cannot be unscrewed without removing the tamper-evident band. By unique design, the fitment and cap may be molded in one mold cavity.

Abstract: A container having a body and a tamper-evident band and a lid for closing the container. The band has a proximal portion frangibly attached to the container body and a distal portion. The distal portion of the band is deformable to an inward extending orientation with the distal portion shaped and positioned to extend inwardly across the peripheral outer portion of a lid. The deformed distal portion of the band optionally has a curvature of 90.degree. to 360.degree. or more. The lid optionally has an annular groove for concealing the terminus of the band. The lid may also have an outward extending peripheral flange, an upward extending annular rib and a stacking ring for arranging several lids in a nested stack.

Abstract: A snap-on tamper resistant lid having a dual locking system to retain the lid on the container. The lid has a top and a depending skirt. A plurality of beads extend inwardly from the skirt and serve as a primary locking device to retain the lid on a container. A plurality of secondary locking ribs are hinged to the skirt below the level of the beads. The secondary locking ribs have a distal end or edge biased toward the container. Upon initial installation the locking ribs are positioned below the container lip. To remove the lid one must remove the tear strip and the locking ribs. The beads still serve to secure the lid to the container.

Abstract: A container (1) for a lubricant has a cap (31) for sealing of one end (50) of a cylindrical tube (2). The cap shows a bottom (32), from the periphery of which extends in an axial direction a circumferential interior collar (36), which abuts the inside of the tube end and has a double function, namely a sealing function and a second function as a plunger for feeding out the tube contents by the use of a device such as a plunger rod of a pistol-like tool as known per se. To this purpose, the delimitation edge of the interior collar (36) which is turned away from the bottom connects to a bridge (39) located within a radial plane and leading to an exterior collar (40) which is concentric with the interior collar and surrounds the tube end together with the interior collar and the bridge. This cap is provided with a groove-like circumferential weakened part (38) permitting release of the bottom (32) during the transition to a plunger function.

Abstract: A resealable container closure including a cap and a tear band formed therewith for engagement with the external wall of the container. A depending flange formed on the underside of the cap engages the internal wall of the container to form a plug seal therewith. Removal of the tear band permits separation of the cap from the container, but re-sealing therewith upon re-engagement of the plug seal with the internal wall of the container.

Abstract: A wide-mouth, plastic container and lid. A leak-resistant seal is disclosed that withstands the stresses and strains imposed due to rough handling. An easily removable, tamper-evident lid is disclosed.

Abstract: A cap and container combination wherein the cap fits about the container in at least two closure positions. Two circumferential bands are provided around the skirt of the cap and there is an internal thread which engages an external thread about the container neck. In the first position, one band of the cap engages a circumferential slot about the container. The internal thread seals with the top of the container. The first band is removed and the container opened by removing the cap. In the second position, the second band engages the slot and the threads engage each other. In the second position, the second band is located about the container. It remains in position when and after the cap is removed. Tampering of the container and cap can be visually detected with this configuration. A bead about the container is formed of a reduced cross-section in portions circumferentially around the cap. This facilitates assembly and disassembly of cap and container.

Abstract: A container having a zip-top with said top having the contour of a spoon integral with the upper surface of the top. The contour of the spoon being formed by a weakened edge and with the end of the spoon handle being attached to a pull-tab used for removing the spoon.

Abstract: A tray having a peripheral flange with one or more raised ledges to secure a pair of membranes to enclose the tray. A lower membrane may be attached to a first ledge of the flange. An upper membrane may be attached to a second ledge or a recessed lip of the flange without connection to the lower membrane, except through the tray. The two attachment surfaces may be separated by a trough or by being positioned on different levels to facilitate trimming of the upper membrane in a continuous manufacturing process. In one embodiment, each membrane may bear one or more selected labels. The upper membrane may, for example, bear a label intended for a retail operator, while the lower membrane bears a label designed for an ultimate purchaser of the packaged product. In another embodiment, the lower membrane has a higher permeability, and the upper membrane has a lower permeability. In this embodiment, a desired gaseous environment may be maintained within the package.

Abstract: The recloseable clamshell package of the invention includes a container portion and a lid portion. The lid portion has a lip portion which is congruently shaped with the container lip portion for mating engagement therewith in order to form a closed package. The lid portion includes corner portions which are congruently shaped with the container portions for mating engagement therewith.

Abstract: A plastics container (10) for hermetically sealed unrefrigerated storage of perishable food that is capable of retaining the hermetic seal during steam retort cooking and sterilizing at temperatures up to 130.degree. C. The container has a body (12) and cover (16) of a lightweight, disposable nature made from thermoformable plastics barrier sheet capable of prolonged resistance to transmission of oxygen, other gases and water vapor. The container and lid have flange portions (14, 18) that are retained in contact by an injection moulded thermoplastics reinforcing clamp ring in two pieces, a plug half (24) and a socket half (26) that twist-to-lock together in screw thread manner. The clamp ring parts are preferably of polypropylene and moulded with structural cross-sectional thicknesses (t1, t2FIGS. 4, 5) at least twice the thickness of that of the body sheet.

Abstract: A tamper-evident, snap-on, screw-off closure which is used with a specially shaped container neck is provided with a foil liner. Once the closure is applied to the neck, the foil liner is sealed to the neck of the container. The foil liner includes a tab for removal of the seal disc from the neck. The closure is characterized by the absence of a second liner between the top of the cap and the foil liner. The cap and the foil liner are formed to inhibit adherence of the tab to the interior of the cap.

Abstract: A can end is provided for a tubular easy-open can which includes an upper panel having a rim portion and a central portion. The can end includes a pressing seam portion which is formed on the upper panel and defines an open-ended loop, thereby defining a cap sheet which has an open end integrally formed to the upper panel and a closed end. A tab is mounted on the closed end of the cap sheet, whereby, when the tab is pulled upwardly, the cap sheet is synchronously pulled upwardly with the open end thereof still fixed to the upper panel.