DK145152B - CONTAINER OF METAL PLATE WITH AN OPENING FIELD AND PROCEDURE AND APPARATUS FOR ITS MANUFACTURING - Google Patents

Description

1 145152

BACKGROUND OF THE INVENTION The present invention relates to a metal plate container portion having an opening field and of the kind specified in the preamble of claim 1.

From the disclosures of U.S. Patents Nos. 3,227,304 and 3,246,791, canned lids with indentable opening fields are defined by a V-shaped weakening line located in a flat portion of the can lid. When pressed, the forces are distributed over essentially the entire extent of the line of weakening, making the start of the tearing difficult. Furthermore, the line of weakening can be plotted by rising overpressure in the can of the same order of magnitude as the finger pressure required by the user for the can opening.

From the specification of US Patent No. 3,334,775, a can lid with a 180 ° edge fold is known which covers a deep cut weakening line defining the opening field. This requires additional sealing material to prevent premature leakage and the tearing is hampered by the folded metal layers.

From the specification of US Patent No. 3,638,825, a can lid with a V-shaped weakening line is known in an elevated portion of the can lid. When opening the can, essentially the entire can lid must be removed, which requires a separate pull tab, and there is also a risk here of an early blowout of the can lid in case of a small overpressure in the can interior.

The invention has for its object to provide a metal casing wall of the type specified without these disadvantages. It is achieved according to the invention by an embodiment of the characterizing part of claim 1. So there is an elevated area around the line of weakness. At a fingertip against this portion, a concentration of force can be produced in a single area which facilitates the onset of tearing. Therefore, the r V-shaped cut can be designed so that substantially greater force effects are required to rupture the can lid when an internal overpressure occurs.

2 1-45152

In the configuration of claim 2, the outer edge portion of the opening field supports the inner edge portion of the breakthrough zone, so that the internal pressure is prevented from pushing the field outwards through the surrounding wall. .

The angle between the push-in zone and the flat wall must not be so small that the arrow height of the push-in zone is too small to produce the necessary stresses for breaking the breakthrough zone, and not so large that the push-in zone will form an angle of resistance opposing the deflection. The angle of 6 ° mentioned in claim 3 has been found to be the optimum.

The design of claim 4 also contributes to securing the opening field against extortion due to the internal pressure.

The invention further relates to a process for making such a container part, which method is suitable. judicious in that it is exercised as set forth in the characterizing part of claim 5, as well as an apparatus for making such a container part, which is peculiar to the design of the characterizing part of claim 6. This results in the use of a single tool set simultaneously forming an outward bulging, easily compressible zone and a permeable zone without damaging the lining on the inside of the container part, the rounded corner edge of the underbody distributing the stresses of the metal and its inner lining during molding and preventing effective breakage of the metal. and the clothing.

The tool objectives set out in claim 7 have been found to give the best results in practice.

The invention will be explained in more detail in the following description of some embodiments, with reference to the drawing, in which: 1 is a top plan view of a can of the invention; FIG. 2 is an enlarged sectional view taken along line II-II of FIG. 1, FIG. 3 shows a corresponding section along a direction perpendicular to line II-II in FIG. 1, showing the initiation of rupture in a rupture zone around an opening field; FIG. Fig. 4 is a section through an embodiment of a tool which can be used in forming a container part according to the invention; 5 shows a portion of the same on a larger scale, showing formation of a V-shaped cut, an embossed line and a foldable part in such a container part; FIG. 6 is an enlargement of a photomicrograph of a section through a portion of an end bottom according to the invention, showing the V-shaped incision and the embossed line along an opening field, while FIG. 7 similarly shows a breakthrough fracture zone.

The terms "inside" and "outside" are hereinafter referred to as directions relative to the interior and exterior, respectively, of a cylindrical container on which the described bottom floor is mounted.

FIG. 1 and 2 show a container portion in the form of a can bottom 10 having a generally planar middle portion 12, a groove 14 along the rim, an upright wall 16 outside the groove, a flange 18 extending outwardly from the upper edge of the raised end wall , as well as a rolled edge 20 at the outer edge of the flange. Such an end bottom is typical of the ordinary end bottom construction adapted to be secured to cans by conventional double seam operations.

The end base 10 may be formed of metal sheet, such as a machining plate of an aluminum alloy, and is preferably formed of such material that is at least three-quarters hard, or an additional hard alloy that has been partially annealed by heating to cure a protective coating. then. The bottom floor 10 may have on the inside a protective covering not shown to protect against liquid content corrosion, such as soda or fruit juice. The garment 4 145152 may be any of a variety of known materials for this purpose and

ISLAND

may be applied in an amount of e.g. about 1.5 - 1.9 mg / cm. Vinyl coatings have been found to work well on container parts of the invention.

The end floor 10 has at least one, preferably two, rigid, within slidable circular aperture panels 22 of the same size, defined by weakening lines 24 in the middle surface 12. The panels 22 are intended to be opened by displacement inwardly in a container to which the end floor is attached. forming a pour opening and an air opening in the end floor. Each of the aperture panels 22 may have a hinge 26 in the form of a weakened portion between the ends of the weakening line to prevent the field from completely separating from the end bottom 10 and falling into the container.

Each weakening line 24 consists of a generally V-shaped cut 28 at the outside of the end floor 10 to form a permeable zone, hereinafter referred to as "breaking zone", of remaining material 38 at the bottom of "V" towards the inside of the end floor. The V-shaped incision preferably forms an angle of about 75 °. However, an angle between about 45 ° and 90 ° or more can also be used with satisfactory results. The bottom of the cut is sharp due to the shape of the tool with which it is formed. The inside 39 under the cut is formed concave inwards, also due to the shape of the tools used. The significance of the V-shaped notch 28 and the concave inside 39 will be apparent from the following description of the method used.

The rupture zone 38 between the bottom of the notch 28 and the inside 31 is preferably relatively thin to facilitate rupture therein to impress an opening field. The breaking zone 38 may e.g. have a thickness between the bottom of the notch 28 and the inside of about 0.05 to 0.1 mm.

The bottom floor 10 further has a bulging compressible zone 32 about each opening field 22 extending from the plate 12 to the weakening line 24. The impressionable zone 32 consists of an annular outer surface 34 and an annular upper surface 36. The outer surface 34 extends at an acute angle from the surface 12 to the upper portion 36 continuing into the fracture zone 38. The upper surface 36 may form a small angle with the plate 12, e.g. an angle of approx. 6 °. However, the upper portion 5 may also be parallel to the plate 12 or may form an angle up to 15 ° therewith. The depressible zone 32, in particular its upper portion 36, is adapted to yield when a finger is applied directly inwardly, thereby causing a relative displacement between the metal parts on both sides of the fracture zone 38, thereby straining the metal therein. a breach is initiated as described later.

Furthermore, the end floor 10 preferably has a further line of weakening in the form of an embossed line 40 on the outside of the retractable zone 32 up to the fracture zone 38 around the opening field 22. The embossed line 40 is substantially parallel to the fracture zone 38 and is spaced apart therebetween. one and three times the thickness of the metal sheet from which the end floor is made. The addition of the embossed line 40 facilitates the formation of the V-shaped notch 28 in metal plates, regardless of possible thickness variations thereof within the manufacturing tolerances that could otherwise cause small cracks in the fracture zone 38.

Each opening field 22 is, as mentioned above, preferably rigid. It is assumed that a rigid orifice 22 promotes the initiation of fractures in the fracture zone 28 of the weakening line 24 around each orifice. For example, the rigid shape of each aperture field 22 may. is provided by concave convex design as shown in FIG. 2 and 5 and will be able to project inwards or outwards, preferably inwards as shown.

The outer edge 42 of the subsequently convex aperture 22 is curved outwardly and upwardly and is connected through the breaking zone 38 to an inner and downwardly curved inner edge or lip 44 of the retractable zone 32. The undersides of these portions form the inner concave surface 39 below the breaking zone. 38. Preferably, the V-shaped notch 28 is formed within or below the highest portion of the flexible portion such that the bottom of the notch is substantially in the same plane as at least a portion of the underside of the indentable zone 32, and thus the outer edge of the opening field is at least partially below the inner edge of the lip of the retractable zone around the opening field, thereby ensuring that the opening field cannot be pressed outwards from the end floor by rising weaker overpressures in the container of the same size as the opening required by the opening. This positioning of the V-shaped incision, projected on a plane perpendicular to the container axis, causes an overlap between the metal in the lip of the indentable zone and the metal at the edge of the opening field, thereby preventing the opening field from being blown out. This overlap also causes the aperture field to be pressed in only because it has a larger diameter than the aperture formed in the end bottom.

Therefore, a loosened opening box cannot be thrown out of the container by negligence.

FIG. 3 shows the initiation of fractures in the fracture zone 38 around an opening field 22. This can be caused by an inwardly directed finger pressure being applied to the end floor in the area around the fracture zone 38, whereby a portion of the compressible zone 32 and the opening field 22 are bent inward. This causes an intersection of the metal on the two sides of the fracture zone, thereby straining it and initiating a fracture and allowing the released opening field to be pressed inward. Finger pressure against the end floor above the fracture zone will cause localized bending of the compressible zone 32 in the region where the pressure is exerted, while other portions of the compressible zone and the opening field will retain their original shape.

Hereby, the fracture zone is used to initiate fractures as shown in FIG. 3. Such a rupture may begin at the point where the pressure is exerted but often appears to occur at a location approximately 90 ° away.

It is believed that the shape of the retractable zone 32 shown in FIG. 2 and 3 will be favorable for relatively easy initiation of fractures in the fracture zone when the end bottom 10 is placed in a container having a relatively high internal overpressure such as 4.2-7 kg / cm. The combination of the outer wall portion 34 and the upper wall portion 36 may allow an inward displacement of a relatively small area of the end floor which will be less offset by a high internal pressure in the container than a large area would be. Finger pressure against the end floor at or near the weakening line 24 will depress a portion of the flexible portion, the upper wall portion 36 being rotated down about the corner between it and the outer wall 34. The area of the upper wall 36 being depressed is relatively small. , so that only a minimum of force is required in the applied finger pressure.

7 145152

FIG. 4 shows an embodiment of a tool for forming a container part according to the invention. The figure shows a first die 50 with an annular rib 52, which is limited by a first working surface 54 and a second working surface 56, whose intersection line forms the corner edge of the rib 58. The two faces 54 and 56 form an angle of approx. 75 °, although another angle between 45 ° and 90 ° may also be used. The corner edge 58 of the rib is formed as a sharp protruding edge which can be formed only by degrading the edge after the surfaces 54 and 56 have been formed, e.g. by grinding. Further, there is an additional embossing rib 60, either contiguous with the punch 50 or as a separate portion, with a vertical surface 62 and an oblique surface 64, which together form a corner edge 66. The corner edge 66 is preferably rounded with a radius of curvature of approx. 0.025 mm. The angle between the faces 62 and 64 can e.g. be approx. 45 °.

Further, there is a lower side 68 with a abutment surface comprising a first rounded corner 70 next to the rib 52 on the abutment 50, a surface 72 which lies at a small angle of about 6 ° with respect to the horizontal and outside this surface another rounded corner 74. Corner 70 has a radius of curvature of about 0.51 mm, while corner 74 has a radius of curvature of about 0.76 mm. These rounded surfaces begin at tangents to the surface 72 and curl downwardly therefrom.

Further, the tool comprises an auxiliary punch 76 with a bottom surface 78 and a rounded corner 80 approximately off the corner 74 of the lower die 68. The rounded surfaces 80 and 74 are intended to cooperate in the formation of an compressible zone on the container portion. They will also be able to emboss or thin the metal at the end bottom 10 when closed. Such embossing may facilitate the formation of an indelible zone in the end floor and may also facilitate inward displacement of such an indelible zone.

The punch 50, the embossing rib 60 and the auxiliary punch 76 are arranged to be displaced linearly against the punch 68 to guide the faces 54 and 56 of the punch against the abutment to engage the abutment surface, in particular the first rounded corner 70 of the punch, to engage a metal plate blank. end bottom 10 therebetween, and laterally displacing portions of the sheet metal as the corner edge 58 of the punch penetrates into the sheet to form a weakening line with a residual metal break zone as shown in FIG. 5th

The work stroke for the punch is interrupted when the corner edge 58 of the rib is pushed into the plate until approx. 0.05-0.1 mm from the abutment surface, leaving a break zone of residual metal of similar thickness. In the closed position of the punches, the apex of the corner 58 of the punch punch 50 is approximately aligned with the surface 72 of the punch punch 68.

The upper die 50 and the lower die 68 are preferably formed and dimensioned such that the annular rib 52 has a diameter measured at the edge 58 smaller than the diameter of the die as measured at the tangent point between the corner arch 70 and the surface 72. Said diameters can be obtained. eg. be 12.75 mm and 13.0 mm respectively to form an aperture field having a diameter of approx. 12.7 mm. Upon displacement of the upper body against the lower body, the edge 58 will form a V-shaped notch 28 in the end base 10 where it rests against the rounded corner 70 of the lower body. This creates an inner concave underside of the end floor under zone 38. It is assumed that the rounded corner 70 distributes the stresses of the metal and the inner lining thereof during the molding process and effectively prevents breakage of the metal and cladding. The sharp V-shaped edge 58 of the rib 52 also helps prevent damage to the lining because the metal is cut by the rib bending edge while only developing a minimum of tension in the metal and the lining below the cutting edge. Reducing the stresses in the metal and cladding reduces the risk of defects in the metal and cladding.

The embossing rib 60 strikes the end base 10 and embosses it with a parallel continuous cut in a zone along the fracture zone 38 to facilitate the formation of the weakening line in sheet metal with the practically varying thicknesses. By moving the auxiliary die 76 against the lower die 68, an compressible zone 32 is formed in the end floor by the combined effect of the auxiliary die 76 and abutment surfaces 72 and 74 on the lower die. The movement of the auxiliary punch 76 is stopped when its lower surface 78 is in a predetermined position lower than the abutment surface 72 of the lower die. 5, to form the bulging compressible zone 32 projecting upwardly from the end floor approx. 0.25-1.02 nun over the surrounding flat.

The opening means thus formed can be opened by applying finger pressure to the bendable portion such that a portion of it is pressed inwardly thereby exerting the fracture zone to initiate fractures therein, allowing an inward displacement of a partially separated opening field.

FIG. 6 shows a photographer! of a section through an end floor according to the invention, whereby the V-shaped cut-in 28 is seen at the outside of the end floor and the concave surface 39 on the inside with an easily pierced zone 38 therebetween. The grain structure shows that the metal is re-cut and laterally displaced by the cutting rib with little deformation of the grain boundaries. As is typical of most container parts according to the invention, the end bottom of the photograph is found to have a backward displacement of metal in the region of the fracture zone, which is assumed to occur when the punches are opened and the slightly breakthrough zone 38 is slightly deformed upon release of the internal stresses. the metal after the molding process. This back offset is seen as a small ledge 41 on the inside and something that appears to be a sliding plane or sliding line between this ledge and the bottom of the V-shaped notch. This backward firing of the metal does not appear to have any adverse effect on the operation or on the protective lining on the inside and may contribute to easy opening at finger pressure without excessive loss of ability to absorb internal pressure. FIG. 6 also shows an embossed line 40 next to the weakening line 28.

FIG. 7 shows a photomicrograph of a section through the end floor after fracture in the fracture zone 38 by exerting pressure in the area around the fracture zone. Although the fracture line appears to take the form of an angle in the left side of the image corresponding to the indentable zone 32, it is believed that this is merely further evidence of the backward displacement of metal partially closing the bottom of the V-shaped notch 28 before the fracture. The actual fracture line appears to extend from the inside of the end floor to the first crack above it in the left side of the image.

Claims (6)

Patent Claims: A metal plate container (10) having a wall (12) having at least one inwardly displaceable, substantially rigid orifice (22), which is bounded along a substantial stretch by a permeable zone (38) defining a line to separating the field from the surrounding part of the wall by pressing the field, and with an outward bulging depressive zone (32) which surrounds and abuts the breakthrough zone (38) and is adapted to give way to this inward finger pressure in such a way as to cause such a large displacement of the metal on the top and bottom of the breakthrough zone (38)} that a local overstretching of the breakthrough zone occurs and a fracture therein is initiated, characterized in that it breakthrough zone (38) is provided by a generally V-shaped cut (28) in the outside of the container portion (10) around the aperture field (22), and that the inside of the container portion (10) below the permeable zone (38) has. e n inward concave shape. Container portion according to Claim 1, characterized in that the opening field (22) protrudes from within the permeable zone (38) with its outer edge portion located below the inner edge portion of the compressible zone (32). Container part according to claim 1 or 2, characterized in that the outward bulging compressive zone (32) forms an angle of approx. 6 with the flat wall (12). Container part according to claims 1-3, characterized in that the indentable zone (32) has a portion of its underside aligned substantially with the tip of the V-shaped cut (28) surrounding the aperture (22), and extends into the underside of the outer edge of the aperture (22) at a distance of 0.05-0.1 mm from the V-shaped notch (28). 11 145152 A method of manufacturing a container part according to claim 1, wherein a metal plate blank is inserted between a first punch member having a rib having a first substantially planar metalworking surface and a second, relative to this inclined, substantially planar a metalworking surface, which ribs define a corner edge at their intersection line, and an underlay with a metal-bearing and metal-forming abutment surface that faces substantially the first punching member and wherein an auxiliary punching member is disposed on the same side of the sheet metal as the first punching member with a metal forming a surface which substantially faces the abutment surface of the abutment, but is positioned to the side thereof, and wherein the first punching member during the punching process is displaced against the abutment in such a way that, when moving against the abutment abutment, the abutment will engage with the metal plate member and transverse displacement parts of the sheet metal as the rib corner edge penetrates in the plate, and where the shear movement of the first die is stopped when its rib bending edge is penetrated into the plate blank to several hundred millimeters from the abutment abutment, the auxiliary abutment member being linearly displaced against the abutment and such a portion past the abutment abutment in the abutment direction that effect of the punching surfaces forms an outward bulging compressive zone (32) which projects 0.25-1 mm above the surrounding plate wall (12), characterized in that a first punching means is used in which the rib edge is formed as a relatively sharp V-shaped edge, and an underpiece formed with a rounded corner edge substantially facing the Vf wormed rib bend edge so as to form a V-shaped cut in the top of the sheet metal and a rounded indentation on the underside of the sheet metal with an intermediate pervious zone (38). Apparatus for forming a container part according to claim 1 and having a first punching means (50) having a rib (52) having a first substantially planar metalworking surface (54) and a second relative to this inclined, a substantially planar metalworking surface (56), said rib surfaces defining a corner edge (58) at their intersection line, a lower edge (68) with metal abutment faces (72, 74) substantially facing said first punching means, and an auxiliary punching means (76) ) with a metal forming