MANUFACTURE OF CAN BODIES

Abstract: A can body (50) with a rigid sheet-metal substrate is shaped by draw-processing with diminishing cross dimensions in proceeding height-wise from open end (61) to closed bottom wall (56). The can body is made entirely by draw-processing pre-coated single- or double-reduced sheet steel (or sheet aluminium). The can body, together with an end closure (92) provides dependable tamper-evident and abuse-resistant packaging for shipment and long shelf-life storage without freezing; and, in addition, provides for direct heating in the can body after opening, including microwave heating, for serving and/or eating directly from such disposable container.

Description: This invention relates to the manufacture of can bodies. The invention includes convenience packaging comprising can bodies with end closures secured thereto and packs comprising contents, such as comestibles, in can bodies sealed by end closures. FR-A-2356563 (Fig. 5) discloses a method of making a one-piece metallic can body of the kind having a bottom wall and a sidewall joined to the bottom wall by a rounded transition zone, in which the sidewall comprises at least three portions of differing cross dimensions, which portions descrease progressively in cross dimension from the open end of the can body to the bottom wall and the sidewall portions are joined to one another by curvilinear transition zones. The method of making of the can body described in FR-A-2356563 is by means of a press. GB-A-2140332 discloses the manufacture of a one-piece metallic can body having two wall portions of differing dimensions by means of a double re-drawing process. Cans for comestibles must be coated on the inside to comply with food hygiene regulations. Traditionally, an organic coating is applied to the interiors of the can bodies after they are forced. Attempts to form one-piece can bodies from pre-coated sheet stock have not generally succeeded because the organic coating came away. In the case of convenience foods, it is necessary to remove them from the can and place them in a suitable electrically non-conductive vessel before micro-wave heating of the foods because electrical discharges occur when metal objects are placed in a micro-wave oven. It has now been found that a sheet-metal substrate, pre-coated on both sides with an organic coating material, can be draw-processed without loss of adhrence of the organic coating material provided that the draw-processing is carried out in such a way that the thickness of the metal substrate is nowhere sustantially increased. On the other hand, the coating will withstand a certain amount of stretching which would accompany slight but not significant or major reduction in metal thickness. A method of making a one-piece metallic can body of the above kind is, in accordance with one aspect of the invention, characterised in that the can body is shaped entirely by draw-processing of flat-rolled sheet-metal substrate pre-coated in the flat-rolled state on both sides with organic coating with the organic coating remaining intact at the interior and exterior of the can body. In accordance with another aspect of the invention, a method of forming a one-piece metallic can body so as to have a bottom wall and a sidewall joined thereto by a curvilinear transition zone, so that the sidewall is formed with at least three portions of cross dimensions which decrease progressively from the open end to the bottom wall and so that the sidewall portions are interconnected by curvilinear transition zones, is characterised in that the can body is formed entirely by draw-processing a sheet-metal substrate pre-coated on both sides with organic coating, and in that the sidewall portion of smallest cross dimension adjoining the bottom wall is formed by a first redraw operation and the sidewall portion of largest cross dimension adjacent the open end is formed during a final redraw operation. It has also now been found that metallic vessels may be used successfully in a micro-wave oven provided that the vessels are substantially completely coated with an electrical insulating material and provided that the vessels are so shaped and placed in the oven that they do not shield the contents from the microwaves. Thus, this invention furthermore includes a package comprising a dependable, disposable can body comprising a rigid sheet-metal substrate and with an end closure, preferably with a convenience feature. Such a package is capable of providing for shipment and long shelf-life storage of comestibles without freezing; in addition, such comestibles can be heated directly in the can body, including being heated safely in a micro-wave oven; and, in addition, such can body is fabricated so as to comprise a dish for serving or consuming heated contents directly in a manner which is readily acceptable to the palate because of the similarity in appearance of the opened package to dining ware. There is no need transfer package contents to a separate plate, bowl, or the like for any purpose. The can body of the invention can provide a sturdy reliable container which is safely "micro-wavable" and free from the warping or distortion customarily experienced with the type of packaging used for frozen comestibles during heating. The container can be included in a packaging which is easier to handle before and after heating. In addition, in a specific embodiment of the invention, such convenience packaging is easily reclaimable for recycling and is bio-degradable if not reclaimed. Thus, a rigid one-piece can body having a metal substrate is formed from a metal substrate blank solely by draw-processing to present a sidewall defining multiple cross dimensions between its open end and its closed end. The closed end of the can body is oriented substantially perpendicularly transverse to a centrally located axis of the can body; and such axis is perpendicular to cross-sectional planes at the open and closed ends of the can body. The can body sidewall is symmetrically disposed in relation to such central axis and the multiple cross-dimensions are measured as areas projected onto planes perpendicularly transverse to such axis. The multiple sidewall portions defining such differing cross dimensions or projected areas are separated by curvilinear cross-sectioned transition zones. The rigid sheet-metal substrate is pre-coated with organic coating and preferably with draw lubricant in the coil stage prior to draw-processing; the latter term refers to shaping the metal substrate and reshaping without "ironing" - that is, without sidewall ironing to produce a decrease in thickness gauge. Describing a can body as shaped entirely by draw-processing is without reference to such steps as trimming of flange metal. An organic coating is presented on both interior and exterior surfaces of the drawn can body. The term "organic coating" is used in the can industry to refer to organic polymeric coatings, such as vinyls, epoxys, polyesters and the like, or combinations thereof, which are applied in a solvent form, or as film, to sheet-metal or sheet-metal substrate. Such organic coatings are approved by the U.S. Food and Drug Administration and typical suppliers are The Valspar Corporation of Pittsburgh, Pennsylvania, Dexter Corporation-Midland Division of Waukegan, Illinois, BASF Corporation-Inmont Division of Clifton, New Jersey and DeSoto, Inc. of Des Plaines, Illinois. The draw processing described herein does not disturb coating adhesion of the organic coating as applied. Adhesion of the organic coating as applied is improved for fabrication and use purposes by first coating the base metal with an intermediate layer, preferably a metallic material, such as chrome-chrome oxide. Flat-rolled steel coated with chrome-chrome oxide is referred to as tin-free steel (TFS). Chrome-chrome oxide, and other selected metallic material coatings or chemical treatments for steel, as described herein, facilitate uniform coating and adhesion of organic coatings for forming a composite-coated, rigid sheet-metal can body of the invention. The one-piece can body of the invention provides for a significantly greater cross dimension and projected area, in a plane perpendicularly transverse to the centrally located axis, at the open end of the can body than at the closed end; and also provides for a plurality of differing projected areas between the open and closed ends which diminish in cross-dimensions or projected area from that of the open end in approaching the closed end. Shaping of the can body as described herein improves open-end access to facilitate serving and/or eating directly from the package in a normal and acceptable manner and also improves access and utilization of micro-waves for heating the contents; preset draw stroke processing is described and achieves desired shaping with optimum efficiency. The invention is further described, by way of example, with reference to the accompanying drawings, in which: Fig.1 is a schematic edge elevational view of a rigid metal-substrate blank as used in the present invention; Fig.2 is an enlarged cross-sectional view of one embodiment of a coated metal substrate for the blank of Fig.1; Fig.3 is a schematic sectional view of a work product drawn from the blank of Fig.1; Fig .4 is a schematic sectional view of the work product redrawn from that of Fig.3; Fig .5 is a schematic sectional view of a work product sequential to that of Fig.4 showing a can body embodiment of the invention shaped solely by draw processing, Fig .6 is a schematic sectional view of a specific embodiment for indicating dimensional and other characteristics of a draw-redraw can body of the invention in which the final redraw and bottom wall profiling are carried out on the redrawn work product of Fig.4; Figs. 7 and 8 are schematic sectional detail views for describing a specific embodiment of juncture means for a can body and end closure of the invention; Fig.9 is a plan view showing a convenience-feature end closure in use on a cylindrical can body embodiment of the invention; Fig.10 is a schematic, sectional detail view of a rigid metal-substrate can body and convenience feature end closure embodiment of the invention; Fig.11 is a larger scale sectional detail showing a portion of the end closure and can body sidewall of Fig.10; Fig.12 is a schematic sectional view of a portion of the sidewall, bottom-wall and interconnecting transition zone of an embodiment of can body having integral insulating material covering a portion thereof, Fig.13 is an enlarged sectional view of a sidewall portion of the embodiment of Fig.12; Fig.14 is a schematic sectional view of a portion of the sidewall, bottom-wall and intermediate transition zone of an embodiment of metal-substrate can body with integral insulating coaster means covering portions of the transition zone and the bottom wall, Fig.15 is a schematic sectional view of an opened can with cover means, and Fig.16 is a sectional detail view of tooling for an embodiment of the invention for setting forth dimensional characteristics. The metal-substrate blank 20 of Fig.1 is cut from coil can stock which has been pre-coated on both its surfaces with organic coating and draw lubricant for fabricating the can bodies with the multi-dimensional sidewall configuration of the invention. An embodiment of blank 20, as shown in Fig.2, includes base metal 22, an intermediate coating 24,25 and an organic coating 26 on that surface which will be exposed on the interior of the work product during draw and redraw in accordance with Figs.3 to 5. An organic coating 27 is provided on the external surface which will be exposed on the exterior of the work product during draw-redraw. "Work product" as used herein includes can bodies of the cylindrical and non-cylindrical classifications as defined in the can-making industry in which non-cylindrical includes, e.g, oblong and oval. The intermediate coating of the base metal shown at 24,25 is preferably a metallic material coating such as chrome-chrome oxide; however, when using flat-rolled steel other coatings can be selected from chrome oxide (bath treatment or electrolytic treatment) tin, tin-iron alloy, or tin and tin-iron alloy. Also, chemical cleaning and treatment of blackplate can provide a suitable foundation for satisfactory adhesion of certain organic coating systems for present purposes. Chrome oxide or tin-iron alloy provides improved adhesion for most of the organic polymeric coatings approved by the U.S. Food and Drug Administration. Such metallic-material coatings are identified in MAKING, SHAPING AND TREATING OF STEEL, 10th Edition, 1985, Association of Iron and Steel Engineers, published by Herbick & Held, Pittsburgh, Pennsylvania, U.S.A., pages 1139, 1140; coating methods and specifications for such base metal treatments or coatings are also available in the art. The organic coating 24,25 can be a single organic polymer or a dual-organic coating system (as described in US-A- 4812365; published after priority date. An organic coating weight of about 15.5 g/sq.m (ten mg/sq inch) is used on each surface of a 1.46 kg/sq.m (65 pounds per base box) tin mill product. Such organic coating in combination with other features of the invention provides protection and enables safe "micro-waving" as described in more detail later herein; and provides erosion and corrosion protection for the metal substrate. The organic coating in combination with other contributions enables draw processing to fabricate the configurations shown in Figs.3 to 5 or other configurations for presenting differing cross-dimensions (projected areas) in a unitary can body. Another feature relates to selection of pigmentation for the organic coating. Pigmentation is important to food-serving; and white pigmentation is preferred for both surfaces but, in particular, for the organic coating on the interior of the container. Blank 20 is drawn so as to form unitary shallow-depth work product 30 (Fig.3) with flange metal 32 outwardly from its open end 33 as defined by sidewall 34. Work product 30 is symmetrical about a centrally located axis 35. The longitudinal sectional views in height of Figs.3 to 5 are taken on planes which include such central axis; and the sectional views are identical for can bodies of either cylindrical or non-cylindrical configuration. Curvilinear or rounded transition zone 36 interconnects sidewall 34 and bottom-wall 38; and transition zone 39 interconnects flange metal 32 and sidewall 34 at open end 33. "Transition zone" refers to that area or surface between a sidewall portion of the can body and a portion which is transverse thereto - for example, parallel to the closed end wall. The term is also used in referring to corresponding areas or surfaces of the draw processing tooling which provide the several different cross-sectional areas (that is to say, cross dimensions or projected areas) between open and closed ends of the can bodies. Compound curvilinear transition zone (as used later herein) refers to such a zone, or one of its surfaces, which is curvilinear as viewed in height-wise section (in a plane which includes the central longitudinal axis of a can body) and is also curvilinear as viewed in cross-section (in a plane which is in perpendicularly transverse relationship to central longitudinal axis). Compound curvilinear transition zones occur in cylindrical or oval can bodies and at rounded corner portions of oblong can bodies. A large surface area for transition zone 36 is selected to facilitate the wrinkle-free draw processing fabrication as well as for the heat and serve convenience feature of the container. While work products of Figs.3, 4 and 5 are shown with "open end" facing upwardly, they are preferably drawn and redrawn open end down. In a specific embodiment, first and second redraw steps are carried out on opposite ends of the drawn cup to efficiently provide a sidewall with three sidewall portions of differing cross-sectional dimensions (in a plane perpendicularly transverse to the centrally located axis 35). During the first redraw, the area or dimension of bottom wall 38 of work product 30 is changed while the original sidewall portion 34 at open end 33 is maintained. End wall 38 is redrawn to form a work product 48 having a new sidewall 40 of differing cross-sectional dimensions (Fig.4). Bottom wall 42 has a smaller lateral cross-sectional dimension than that of bottom wall 38 of Fig.3. The decrease in bottom wall dimension, over that of bottom wall 38 adds to the height of sidewall 40. The objective of the draw processing of the invention is for re-shaping to take place without significant change in thickness gauge or with a slight decrease in thickness gauge. That is, for re-shaping to take place without interfering with adhesion of the organic coating as applied. During fabrication, the portion 44 of the sidewall is redrawn with minimal tolerances of the sheet-metal and tooling, so that the outer periphery of the sheet-metal is clamped tightly by the clamping means, whereby thickness change, if any, is limited to a small percentage decrease which does not adversely affect adhesion of the organic coating. Transition zone 46 is formed about a redraw punch nose (shown later) to provide for desired access to the contents of the container. The shape of the work product 48 (Fig.4) is symmetrical about central axis 49. Referring to Fig.5, can body 50, having a metal substrate, is redrawn from work product 48. The cross-sectional dimension of open end 33 is increased by adding curvilinear transition zone 52 and a new (larger cross section dimension) sidewall portion 54; the latter is oriented parallel to centrally located axis 55; overall sidewall height is increased slightly by such addition. Bottom-wall profiling 56, shown in Fig.6, is formed after the metal clamping for final redraw is released, and decreases the height of sidewall portion 44 slightly. Preferably, in commercial practice, bottom wall profiling is carried out at the final redraw station. The bottom wall profiling shown in Fig.6 facilitates flexing of a central panel portion 57 during the heating-up and cooling stages of a sterilizing process for "sanitary" can packs. Similar profiling can be used on cylindrical and non-cylindrical configurations. Other bottom wall profile configurations are described schematically later herein. In an embodiment of cylindrical or oval can body of the cross-sectional configuration shown in Fig.6, each of the sidewall cylindrical portions is joined to a next adjacent portion of the can body by a compound-curvilinear transition zone 76 or 78,80 about the full periphery. In can bodies for an oblong configuration, a compound curvilinear transition zone exists at rounded corner portions while, on straight wall portions, the transition is curvilinear only in cross-sectional height-wise-oriented planes which include the centrally located axis of the can body. Single or double reduced flat-rolled steel substrate having a thickness gauge of about 1.24 to 2.47 kg/sq.m (fifty-five to one hundred and ten pounds per base box) can be used in flat-rolled steel embodiments of the present invention. Dimensions for a specific embodiment as shown in Fig.6, using a 1.46 kg/sq.m (sixty-five pounds per base box) organically coated TFS are as follows: The cross dimension of the open end is minimal for micro-wave heating; that is about 102mm (four inches) across the width of the open end of an oblong or oval can body which would have a greater length dimension, such as approaching 152mm (six inches). Such minimum cross dimension should be at least twice the depth of the can body; and, preferably, should be around two and one-half times the depth of the can body. Transition zone 82 at the bottom wall occupies at least about 7.6mm (0.3″) of the cross dimension at that location, occupying at least about 20% of the area, laterally projected onto a plane perpendicularly transverse to the central axis, of the lowermost sidewall portion of either cylindrical or non-cylindrical embodiments. The combined projected areas of transition zones 78 and 80 are correspondingly larger. Avoiding sharp corner edges contributes to safe and more efficient micro-wave heating of can bodies having a metal substrate and the extended curvilinear area of the bottom transition zone facilitates access internally for utensils for serving and/or eating directly from the container. Fig.7 illustrates how flange metal 84, 85 of can body 86 and a rigid end closure 88 having a sheet-metal substrate respectively, are aligned prior to formation of chime seam 90 (Fig.8). Chuck wall 91, which, in effect acts as a part of chime seam 90, provides backing for the juncture between can body 86 and end closure 88 at the chime seam 90. A rigid end closure having a metal substrate is utilized for shipment and long shelf-life storage of soups and similar comestibles to provide dependable tamper-proof and abuse-resistant packaging which has not previously been available with containers which could provide for micro-wave heating of contents in the package after opening. Other closures for the can body having a metal-substrate in accordance with the invention can be used for certain items while still taking advantage of the can body; and means other than a chime seam can be utilized for sealing certain packs. In a preferred embodiment of a rigid can having a sheet-metal substrate, an easy-open end closure 92 (of circular configuration as illustrated in the plan view of Fig.9) is joined to a cylindrical can body by chime seam 93. Integral opener 94 is secured to removable full panel 95 by rivet 96; the metal for rivet 96 is unitary with panel 95. An indent 97 is located in recessed profiling panel 98 to improve access to handle end 99 of opener 94. Opening instructions 100 can be embossed in or imprinted on the removable panel 95. In accordance with this preferred embodiment of the invention, safety-edge shielding is provided for residual scoreline metal after removal of an easy-open panel. The peripherally-located scoreline 110 (Fig.11) for a full-panel, easy-open end is located contiguously inboard of the chuck wall of the end closure. In Figs. 10,11, end closure 101 is joined to can body 102 at chime area 103. Bottom wall profiling includes a dome-shaped configuration 104 which can facilitate heating of the contents. Opener 107 is secured to end closure 101 by rivet 108. The "over-the-rim" opening instructions for a full-panel, easy-open, convenience-feature, end closure using the features illustrated by Fig.11 are presented in Fig.9. With the edge shielding features of Fig.11, scoreline 110 is located between two multi-layer folds 112,114 of sheet-metal. When the handle end of opener 107 is raised, its working end comes up against multi-layer fold 112; the latter directs the working end of opener 107 into the recessed panel for rupture of scoreline 110. Upon removal of the full panel defined by scoreline 110, rounded edge portions of multi-layer folds 112,114 shield, respectively, the raw edge of the residual scoreline metal remaining with the can body and that remaining with the separated panel (for further details of such shielding, see US-A- 4804106 or the equivalent WO 89/02853). Other embodiments of convenience-feature full-open sheet metal end closure can be used with the invention. In the embodiment of Figs. 12 and 13 the can body 120 includes an insulating material which extends over the exterior surfaces of sidewall portion 122 and transition zone 124. As seen in Fig.13, metal substrate 125 includes organic coating 126 on the internal surface and organic coating 127 on the external surface. An insulating material 128 covers such exterior portions as shown in Fig.12; such insulating material can comprise laminated or otherwise prepared thickened paper product to increase heat insulating properties. Material 128 also serves as a label. In the embodiment of Fig.14, such heat insulating material is used to form a coaster 140 covering the exterior surfaces of transition zone 142 and bottom wall 144. A standard commercial label 146 can be utilized along the sidewall 148. Because of the facility for micro-wave heating and the characteristics thereof in a specific embodiment of the invention, such conventional paper label can be safely used, and provides the minimal amount of thermal shielding, if any, that may be desired for the sidewall of the can body. In the embodiment of Fig.15 a micro-wave-transparent cover 150, e.g. made from paper or plastic, is provided. Such cover 150 can serve as a dust cover for the end closure of the sealed container, and/or as a cover for heating (vents such as 152 being provided for such purpose); or, for retaining heat in the can body after heating, when it is to be used as a serving dish. The multi-layer fold 112 of sheet metal shown in Fig.15 shields the raw edge of scoreline metal remaining with the container and prevents micro-wave-induced arcing at such raw edges. The remainder of the opened rigid package comprising sheet metal is shielded, for purposes of preventing arcing during micro-wave heating, by organic coating. The organic coating, and also an intermediate coating such as chrome oxide, can contribute to warm-up of the sheet metal by micro-waves because of microwave penetration to and action at the interfaces thereof. Some absorption of magnetic wave energy is believed to occur at or near such interfaces and with the base metal. In addition, steel base metal offers the possibility of some surface warming from the electrical wave energy portion of the micro-waves as arcing is inhibited by the organic coating. In an embodiment involving flat-rolled steel substrate, it has been found that the full volume of the can body, which may be 0.23 to 0.28 kg (eight to ten ounces) of contents by weight depending on the comestible, are heated by micro-waves (in a conventional 500 to 700 watt output micro-wave oven in about three minutes to a temperature between 49°C to 54°C (120°F to 130°F); such temperature can be partially dependent on positioning at or slightly above the bottom heat-resistant glass, such as PYREX (Trade Mark) or clear hardened plastic cover conventionally provided within such ovens. However, with a steel can body, spattering of the contents when heated by micro-waves is avoided. Warm up of the can body and absorption of micro-wave energy by the contents at the open surface are provided. As a result, overheating of the contents significantly above eating temperature (about 46°C, 115°F) is avoided with micro-wave heating so that the cover 150 of Fig.15 is provided largely for holding-in heat and/or moisture. Also, since the can body is not distorted in shape (as with certain plastic, e.g. styrofoam, packages) and remains rigid it is easier to handle both before and after heating, not only because of its shape but also because of its rigid character. The can body is not overheated by micro-wave heating. Also the can body and its contents can safely be heated in a conventional oven. The processed foods in "sanitary can packs" do not require "cooking"; they only require heating or warm-up for eating to about 46°C (115°F) and therefore, a conventional oven heating temperature of about 66°C (150°F) is adequate; but, the organic coatings and paper can safely withstand temperatures above 177°C (350°F) to about 204°C (400°F). The paper labels and coasters are largely for instructions and labelling, but do provide insulation during and after heating and help in handling. Such paper material can safely be heated above 204°C (400°F) (but below 232°C, 450°F) without igniting. Or anic coatings can be heated to about 204°C (400°F) without detriment to their integrity; since most sanitary packs contain a high percentage of water, the can body is not likely to be heated to that temperature in a conventional oven. In another cylindrical embodiment of the invention, a punch nose radius of 7.62 mm (0.30″) is used on a 94.0mm (3.7″) diameter punch working into a draw die cavity formed about multiple radii of 1.27 mm (0.050″), 0.63 mm (0.025″) and 1.27 mm (0.050″) entering a die cavity of 94.49 mm (3.72″). In the second operation, the end wall of the drawn cup held within 94.49 mm (3.72″) diameter tooling is redrawn into a first redraw die cavity of 68.33 mm (2.69″) diameter having an entrance transition zone of 5.08 mm (0.20″) radius, by a 67.94 mm (2.675″) diameter punch having a punch nose of 5.08 mm (0.20″) radius while using a spring-loaded clamping ring of 93.98 mm (3.709″) diameter with an outer periphery transition zone of 3.17 mm (0.125″) radius. The final redraw adds a third diameter portion at the open end of the can body. Dimensions for such tooling, shown in Fig.16, are tabulated herein; as they indicate minimal sheet metal and tooling tolerances are relied upon. 1.46 kg/sq.m (65 pounds per base box) flat-rolled steel has a thickness gauge of 0.18 mm (0.007″) and is also coated with organic coating). Such tolerances provide tight clamping on outer peripheries of the multi-dimensional sidewall portions which contributes to the desirable slight decrease in sidewall gauge during "draw processing". Fig.16 shows tooling for the final redraw (without bottom wall profiling). The shaped work product of the previous preset-stroke draw processing stage is omitted from this "open end" down presentation of redraw tooling. A first redraw punch 160, first redraw clamping ring portion 161 with second redraw punch portion 162, a first redraw die 164, a second redraw die 163 are disposed for relative movement to shape the maximum dimension, second redraw sidewall portion at the open end of the can body. Dimensions for the tooling (omitting bottom wall profiling) are tabulated with reference to Fig.16: Specific dimensions, values and materials have been set forth for purposes of describing the invention and the manner and process of making and using the same; however, such dimensions, values and materials can be varied within the scope of the invention.

Claims: A method of making a one-piece metallic can body having a bottom wall (42) and a sidewall (38) joined to the bottom wall by a rounded transition zone (46), in which the sidewall comprises at least three portions (54,34,44) of differing cross dimenions, which portions decrease progressively in cross dimension from the open end (33) of the can body to the bottom wall (42) and the sidewall portions (54,34,44) are joined to one another by curvilinear transition zones, characterised in that the can body is shaped entirely by draw-processing of flat-rolled sheet-metal substrate (22) pre-coated in the flat-rolled state on both sides with organic coating (26,27), with the organic coating (26,27) remaining intact at the interior and exterior of the can body. A method as claimed in claim 1, in which the area of projection of the rounded transition zone (46) onto a transverse plane perpendicular to the central axis (55) of the can body is at least substantially 20% of the area of projection of the adjoining sidewall portion (44) of smallest dimension (63) and in which the area of projection of the open end (33) of the can body onto the said transverse plane is at least substantially 40% larger than the area of projection of the bottom wall (42) onto said plane, whereby the can body can be used safely for heating its contents in a micro-wave oven. A method as claimed in claim 1 or 2, in which the minimum dimension of the open end (33) of the can body is substantially 101.6 mm (4 inches). A method as claimed in claim 3, in which the overall depth dimension of the can body is in the range of about 1/3 to about 1/2 said cross dimension of the sidewall portion at the open end (33) of the can body, and the minimum cross dimension of the largest sidewall portion (54) is no more than about 1/3 larger than the minimum cross dimension of the smallest cross dimension sidewall portion (44) connected to the bottom wall of the can body. A method as claimed in any of claims 1 to 4, in which the projected area defined by the sidewall portion (54) at the open end (33) of the can body is at least about 25% larger than that defined by the sidewall portion (44) which is interconnected with the bottom wall (42). A can body made by the method claimed in any of claims 1 to 5, in which the can body is for shipping and storing comestibles and can be safely used for heating such comestibles in a micro-wave oven and is suitable for serving and consuming such comestibles directly therefrom. A can body as claimed in any of claims 1 to 6, in which the metal substrate (22) of the can body comprises single-reduced or double-reduced flat-rolled steel, having a gauge substantially in the range of 1.24 to 2.47 kg/sq.m (55 to 110 pounds per base box). A can body as claimed in claim 7, in which a metallic-material coating (24,25) is included on each surface of the flat-rolled steel (22) between the steel surface and the organic coating (26,27) on interior and exterior surfaces of the can body, said intermediate metallic-material coating being chrome oxide, chrome and chrome oxide, tin, tin-iron alloy, or tin and tin-iron alloy. An integral package comprising (A) a one-piece can body (50) made by the method as claimed in any preceding claim, (B) a non-unitary end closure (92) for sealing the open end (33) of the can body, and (C) means joining sheet-metal substrate at the open end of the can body to the end closure to seal the open end of the can body. A package as claimed in claim 9, further including a heat insulating covering on the external surface of at least a major portion of the sidewall portion (44), the bottom wall (42) and the interconnecting transition zone (82). A package as claimed in claim 10, in which the insulating covering comprises a cellulose material having a thickness dimension in the range of about 0.794 mm to 2.38 mm (1/32″ to 3/32″). A package as claimed in claim 9, 10 or 11, in which the end closure (92) is formed from a substrate of rigid sheet metal and the joining means comprises a chime seam (90) which joins the substrate of the end closure (92) to the substrate of the can body to seal the can body. A package as claimed in claim 12, in which the can as assembled after filling the can body (50) with one or more comestibles is opened by removing a full panel portion of the end closure (92). A package as claimed in claim 13, in which the end closure comprises an easy-open end closure having a peripherally-located scoreline (110) of decreased sheet metal thickness for defining a full panel (95) to be removed from the end closure, and an opener (94) is secured to the outer surface of the full panel (95) of the end closure, said scoreline (110) being contiguous to and having a matching configuration to a chuck wall (116) of the end closure. A package as claimed in claim 14, in which residual raw edge metal which remains with the can body after removal of the end closure panel (95) is shielded from direct access by a contiguous multi-layer fold (112) of sheet metal located on the portion of the end wall closure remaining with the can body, such sheet metal fold being disposed contiguous to and intermediate the scoreline (110) and the chuck wall (116). A package as claimed in any of claims 9 to 15, further including an over-cap (150) placed over the end closure (92) at the open end (33) of the can body (50), the over-cap (150) being transparent to micro-waves to enable heating of the contents of the can body by passage of micro-waves through the over-cap as placed on the can body after unsealing and removal of the end closure. A method of manufacturing a tamper-evident, abuse-resistant sanitary pack for comestibles which is self-supporting for shipment or storage, and provides for: long shelf life of processed contents without freezing, heating of the contents, including use of micro-waves, after opening such package, and serving and/or eating of the heated contents directly from the opened package, in which the can body of the package claimed in any of claims 12 to 15, prior to sealing, presents peripheral flange metal (84) about its open end with such flange metal extending with a main component in a direction transverse to the centrally located axis of the can body beyond the sidewall portion (86) defining the largest dimension open end (33) of the can body, and in which the pre-coated end closure prior to sealing presents flange metal (85) about its periphery, and the chime seam (90) is formed using such flange metal at the open end of the can body and at the periphery of the end closure, and in which the end closure also presents a chuck wall (91) which is a unitary part of the end closure and forms a part of and helps to provide backing for such chime seam, the chuck wall (91) being contiguous to the interior surface of the sidewall portion (86) at the open end of the can body and having a matching configuration in cross section therewith. A packcage as claimed in claim 16, in which the over-cap comprises a cellulose material. A method of forming a one-piece metallic can body so as to have a bottom wall and a sidewall joined thereto by a curvilinear transition zone, so that the sidewall is formed with at least three portions of cross dimensions which decrease progressively from the open end to the bottom wall and so that the side-wall portions are interconnected by curvilinear transition zones, characterised in that the can body is formed entirely by draw-processing a sheet-metal substrate pre-coated on both sides with organic coating, and in that the sidewall portion of smallest cross dimension adjoining the bottom wall is formed by a first redraw operation and the sidewall portion of largest cross dimension adjacent the open end is formed during a final redraw operation. Method as claimed in claim 19 for making a rigid can body for a convenience package providing for shipment and storage of comestibles without freezing, heating of such contents by micro-wave after opening, and serving and/or eating of heated comestibles directly from the can body, in which the rigid sheet metal substrate from which the can body is formed comprises flat-rolled steel of about 1.24 to 2.47 kg/sq.m) (55 to 110 pounds per base box) or flat-rolled aluminium of a thickness gauge between about 0.18 and 0.30 mm (0.007″ and 0.012″), the can body being symmetrically disposed about a central longitudinal axis, and having a sidewall defining an open end at one axial end of the can body for introducing or removing comestibles, a closed bottom wall at the other axial end of the can body, and a unitary, curvilinear, transition zone interconnecting the sidewall and the closed bottom wall, the sidewall having at least three portions which define differing projected areas as measured in a plane which is perpendicularly transverse to the central axis, with the portion defining the largest projected area being formed during a final redraw operation and located contiguous to the open end of the can body, with the portion defining the smallest projected area being formed during a first redraw operation and interconnected with the closed bottom wall of the can body, with all the sidewall portions being interconnected at each respective longitudinal end thereof with a next adjacent sidewall portion of the can body by a unitary interconnecting, curvilinear cross-section transition zone of diminishing projected area in approaching the bottom wall, and with the interior sidewall portions of the can body defining progressively smaller projected areas from the open end of the can body to the bottom wall. A method as claimed in claim 19 or 20, in which the can body is formed with flange metal at its open end, such flange metal being disposed in an outward direction in relation to the central axis and being transversely oriented in relation thereto, and in which a rigid, steel-substrate, non-unitary end closure for the open end of the can body, having flange metal extending uniformly about its periphery, is made integral with the can body by forming a chime seam from the flange metal at the open end of the can body sidewall and around the periphery of the end closure; and in which insulating covering is applied to at least a portion of the exterior of such sidewall.

Inventors: SAUNDERS, WILLIAM T.
Applicants: WEIRTON STEEL CORPORATION
Application year: 1989
Main classification: B65D1
IPC codes: B65D81, B21D22, B65D1