US3581546A - Dedenting containers and the like - Google Patents

Dedenting containers and the like Download PDF

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Publication number
US3581546A
US3581546A US822614A US3581546DA US3581546A US 3581546 A US3581546 A US 3581546A US 822614 A US822614 A US 822614A US 3581546D A US3581546D A US 3581546DA US 3581546 A US3581546 A US 3581546A
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United States
Prior art keywords
cylinder
metal
die
compression
radially
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Expired - Lifetime
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US822614A
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English (en)
Inventor
Christain Ragettli
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Inland Steel Co
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Inland Steel Co
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Publication date
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D1/00—Straightening, restoring form or removing local distortions of sheet metal or specific articles made therefrom; Stretching sheet metal combined with rolling
    • B21D1/06—Removing local distortions
    • B21D1/08—Removing local distortions of hollow bodies made from sheet metal
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D1/00—Straightening, restoring form or removing local distortions of sheet metal or specific articles made therefrom; Stretching sheet metal combined with rolling
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09F—DISPLAYING; ADVERTISING; SIGNS; LABELS OR NAME-PLATES; SEALS
    • G09F5/00—Means for displaying samples
    • G09F5/02—Portable sample cases

Definitions

  • This invention relates to the removal of dents and the reduction of asymmetrical stresses in thin wall metal cylinders, and more particularly concerns an apparatus and method for dedenting cylinders of the type used in thin wall containers and the like.
  • Thin wall metal containers are widely used by reason of the protection they afford to their contents. This protection, however, is frequently achieved at the cost of a dented container, and one that cannot be reused.
  • Methods and apparatus have been proposed for dedenting, or removing dents from, these containers, but in many respects these are unable to restore a badly dented container to its original condition.
  • Local hammering, die forming, expanding, compressing, or rolling the dented area have each been proposed and used, but the restored area has invariably been cold worked. As a result, the restored area has stress concentrations that can and do afford a weakened container and one which is susceptible to stress corrosion cracking. It is accordingly a primary object of the invention to provide a method and apparatus for removing dents from thin wall metal cylinders whereby the adverse affects of local restoration are avoided or minimized.
  • An additional object of the invention is to provide a system for dedenting cylinders wherein the final cylinder exhibits no local areas of reduced wall thickness.
  • the problem of dent removal from thin wall metal cylinders even before the cylinders have been fabricated into containers is an especially troublesome one. While the purchaser or user of a reconditioned container expects and is willing to tolerate an unsightly appearance, the purchaser of a new container can properly object if the container walls look as though they had been straightened. Yet the cylinders, before they are fabricated into containers, are particularly vul' nerable to denting, and the container manufacturer accordingly' requires a dedenting system which produces containers that do not appear as though they had been either dedented or manufactured from dedented cylinders. It is therefore a major object of the invention to provide a method and apparatus for removing dents from thin wall metal cylinders without leaving an unsightly cylinder wall; in other words, a method of dedenting cylinders without having them visibly appear dedented.
  • An overall object is to provide a method and apparatus for removing dents and for reducing asymmetrical stresses from thin wall metal cylinders, either before or after fabrication into containers, which method and apparatus are rapid, effective, and compatible with high quality, mass production, techniques. Yet other and more particular objects, aims, and advantages of the invention will become apparent as the description of the invention proceeds.
  • FIG. 1 depicts an end view of an apparatus according to the invention, showing only the upper half of the inventive apparatus
  • FIG. 2 is a side view, partly in section, of the apparatus of FIG. 1;
  • FIG. 3 is a schematic drawing depicting the operation of the apparatus of FIG. 1 and FIG. 2;
  • FIG. 4 is a partial top view of two expanding (or contracting) sectors as used in the inventive apparatus.
  • the invention is particularly applicable to thin wall metal cylinders, whether the cylinder is employed as such or whether it is previously provided with one or two end walls, chimes, circumferential beads, or the like, as are commonly used in thin wall metal container construction.
  • thin wall as used herein is generally although not exclusively applicable to those containers made of sheet metal, conventionally iron, whose external diameters are at least about 20 times the thickness ofthe wall.
  • the apparatus of the invention essentially includes a set of radially expansible cylindrical internal dies 11 which are disposed within a thin wall metal cylinder 12, and a concentrically disposed, radially compressible, set of cylindrical dies 141 disposed externally of the cylinder 12.
  • Internal die 11 is expanded radially outward by axial movement of the expander plug 15, and similarly the external die 14 is compressed inwardly by an axial relative movement of the'shrink ring 16.
  • the internal die 11 comprises a plurality of truncated sectorlike elements 11a, 11b, respectively connected via the gib, generally shown at 18, to the ex pander plug 15.
  • the gib I8 anend view of which is shown in FIG. I, is a Tshaped tongue and groove extending conically along the intersection of the internal die elements Ila, 11b, etc. and the expander plug 15.
  • a similar gib 19 connects the external die segments 14a, 14b, etc. with the shrink ring 16.
  • a thin wall cylinder 12 is positioned between the expansible internal cylindrical die 11 and the compressible ext'ernal cylindrical die 14, and expanding pressure is applied to the internal die 11.
  • the expansion of the die elements 11a, 11b, etc. uniformly in a radial outward direction causes the effective diameter of the internal die 11 to increase, initially until it equals the internal diameter of the cylinder 12.
  • the internal die 11 As the internal die 11 continues to expand, its outer diameter begins to exceed the original inner diameter of the cylinder 12. When this occurs, the thin metal wall constituting the cylinder 12 is placed under tension in a circumferential direction. (The tensile stress is equal to the product of the radial expansive pressure times the radius, divided by the cylinder 12 wall thickness). Consequently, the cylinder 12 itself begins to expand under the radial pressure of the internal die 11.
  • Expanding the cylinder 12 beyond its yield point or elastic limit causes plastic deformation of the cylinder 12 wall metal. In other words, it stretches the cylinder 12 uniformly in a radial direction, so that dents, deformations, and other nonhomogeneities are removed. Since the stress applied to the cylinder 12 is essentially uniform about all portions of its diameter, the cylinder 12 is consequently stretched uniformly at all points around its circumference, and as a result there are no local stress concentrations in the region of dents or other imperfections.
  • the internal die 11 has expanded sufficiently to exceed the yield point of the cylinder 12 metal in tension and also to plastically deform the metal by a predetermined amount, further expansion of the internal die 11 is terminated, and a radially inward or compressing force is applied to the external die 14 to constrict the cylinder 12. While the internal die 11 is expanding, the external die 14 is advantageously spaced slightly away from the ultimate expansion of the cylinder 12. However, as the external die segments 14a, 14b, etc. are compressed radially and uniformly inward, they begin to engage the outer surface of the cylinder 12.
  • the net compressive force is applied to the cylinder 12 by imposing a higher pressure on the external die 14 than on the internal die 11. This force is continued, first through the elastic deformation region of the stress-strain curve of the metal of the cylinder 12, and then beyond the compressive yield point to where the wall metal constricts in plastic compression.
  • Compression of the cylinder 12 need be continued only until the cylinder 12 walls are compressed to an extent sufficient to exceed the yield point of the metal or, in other words, to deform the metal plastically by compression.
  • Plastic compression quite effectively reduces asymmetric stresses in the cylinder 12 so long as there is at least some measurable plastic deformation beyond the lower yield point.
  • the cylinder 12 is compressed to a diameter smaller than that of the original cylinder diameter, so that when compression is finally released, the cylinder expands slightly by elastic expansion to substantially its original diameter.
  • the necessary extent of elastic compression is best determined by actual trial and is a function of the cylinder 12 dimensions, the metal composition and history, the rate of compressive stress application, temperature, etc., all of which are generally too complex for calculation in advance.
  • the closeness to which the diameter is to be restored to that of the original cylinder diameter depends also on the use to which the cylinder is to be put; that is, if the cylinder is to be part of a container, the volume constancy of the container will dictate the tolerance of the cylinder diameter.
  • the final operation of the apparatus depicted in FIGS. 1 and 2 is the withdrawal or retraction of the outwardly expanding internal die 11 and the inwardly contracting external die 14. These actions separate the die walls from the walls of the cylinder 12, and permit the cylinder to be extracted from the region between the respective dies.
  • FIGS. 1 and 2 an exemplary apparatus or device for performing the previous operations is described.
  • the specific interactions of the components may more clearly be appreciated with reference to FIG. 3, and in the ensuing discussion all three FlGS. will be referred to,
  • the internal die segments 11a, 11b, etc. are urged radially outward by relative axial movement of the conical expander plug 15 with respect to the ramplike inner camming surfaces of the die elements or sectors lla, etc.
  • Axial movement between the two is established by applying pressure from hydraulic cylinder 20 (FIG. 2) to the expander plug 15, which is opposed by an abutment 2] contacting the distal end of each of the inner die elements 11a, 11b, etc.
  • the abutments 21 are advantageously removably secured to the respective elements by connections, not shown, so that opposed hydraulic pressure may be applied to the hydraulic cylinder 20 at the conclusion of the cylinder expansion-compression cycle to thereby retract the inner die elements 11a, 11b, etc.
  • the overall apparatus of the invention includes a set of hydraulic cylinders 22 to apply longitudinal, or axial, pressure on the shrinking ring 16, while a set of abutments 24, one each against each of the external die elements 14a, 14b, etc. (FIG. 1) causes longitudinal motion of the shrink ring 16 to be translated into a radially inward movement of the external die 14 to compress the cylinder 12.
  • the abutments 24 are best connected removably to the external die 14 so that retraction of the hydraulic cylinder 22 and its shrinking ring 16 retracts the external die elements 14a, 14b, etc.
  • FIG. 3 depicts schematically the operation of a pair of opposed internal die elements 11a, 111', and a pair of opposed external die elements 1411, 141', together with the associated expander plug 15 and shrinking ring 16. It will be appreciated that these elements are in a concentrically disposed array, as shown in FIG. 1, but only some of the die elements are included for clarity.
  • Hydraulic pressure is applied to the expander plug 15 via hydraulic cylinder 20, receiving hydraulic fluid from conduit 25 via a reversible continuous volume delivery, or gear, pump 26.
  • hydraulic cylinders 22 operate to move the shrinking ring 16 axially with respect to the external die elements 14a, 14i, and are supplied with hydraulic fluid via conduits 28 and a reversible continuous delivery, or gear, pump 29, having a higher ultimate pressure than that of the pump 26.
  • the apparatus of the invention is suitable for a variety of generally cylindrical configurations, although only a straightsided cylinder has been shown and discussed.
  • the cylinder is beaded, flanged, provided with one or more chimes, or provided with either longitudinal or circumferential seams, these protuberances may be accommodated by providing a corresponding recess in the die face.
  • a longitudinal lap seam 34 is accommodated within a recess 35 in the inner cylinder-contacting surface of external die element Me.
  • the invention is broadly applicable to virtually any thin wall metal container. Not only does it apply to cylinders having diameter-to-thickness ratios under 20:], but cylinders having diameter-to-wall thickness ratio of below 200:] may be dedented and stress relieved. Where the ratio is quite high, it is preferable that the longitudinal edges of the die be sinusoidal lines indicated in the partial top view shown in FIG. 4. This nonlinear contact is even better able to resist buckling forces, particularly at the intersecting edges of adjacent die sectors.
  • the internal die may comprise a pneumatic or hydraulic flexible bag, in which event controlled retraction of the external die 14 governs the elastic expansion of the cylinder 12.
  • the preferred embodiment described earlier employs no opposing pressure on the external die while the internal die is expanding, to reduce the necessary stroke of the internal die it may be desirable, under some instances, to apply an opposing force on the external die while the internal one is in the expansion phase.
  • a method for removing dents and for reducing asymmetrical stresses in a thin wall metal cylinder comprising:
  • a method for removing dents and for reducing asymmetrical stresses in a thin wall metal cylinder while preserving substantially the original diameter of said cylinder comprising:
  • a method for removing dents and for reducing asymmetrical stresses in a thin wall metal cylinder comprising:
  • Method of claim 4 including the subsequent step of collapsing said internal and said external dies to their original positions to permit removal of said cylinder.
  • Apparatus for removing dents and for reducing asymmetrical stresses in a thin wall metal cylinder comprising:
  • Apparatus for removing dents and for reducing asymmetrical stresses in a thin wall metal cylinder while preserving substantially the original diameter of said cylinder comprising:
  • a radially compressible cylinder external die disposable externally of said cylinder
US822614A 1968-05-14 1969-05-07 Dedenting containers and the like Expired - Lifetime US3581546A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB22931/68A GB1204736A (en) 1968-05-14 1968-05-14 Method of and apparatus for reducing asymmetrical stresses in a generally cylindrical sheet metal side wall of a container of such a side wall

Publications (1)

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US3581546A true US3581546A (en) 1971-06-01

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US822614A Expired - Lifetime US3581546A (en) 1968-05-14 1969-05-07 Dedenting containers and the like

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US (1) US3581546A (es)
AT (1) AT298954B (es)
BE (1) BE733079A (es)
BR (1) BR6908825D0 (es)
CH (1) CH490904A (es)
DE (1) DE1924716C3 (es)
ES (2) ES367178A1 (es)
FR (1) FR2008472A1 (es)
GB (1) GB1204736A (es)
IE (1) IE33454B1 (es)
NL (1) NL7305621A (es)
NO (1) NO130754C (es)
SE (1) SE391464B (es)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4262517A (en) * 1978-08-07 1981-04-21 Hitachi, Ltd. Method of correcting distorted pipe end
US5022254A (en) * 1988-08-09 1991-06-11 Kramer Antonio H Method and device for the manufacture of can bodies by extension, including expansion of the diameter and reduction of the thickness of the sheet metal, starting out from a can body with smaller diameter, made of thicker sheet metal
US5595086A (en) * 1994-08-02 1997-01-21 Aluminum Company Of America Apparatus for calibrating hollow nonsymmetrical multiplane extrusions and associated method
US5826457A (en) * 1997-07-11 1998-10-27 Eagles; Allen S. Wheel for mandrel of pipe straightening presses
US6338189B1 (en) 1999-10-07 2002-01-15 Allison Engine Company, Inc. Method and apparatus for expansion forming a workpiece using an external deformable supporting fixture
US20070175260A1 (en) * 2006-02-01 2007-08-02 Honggie Kim Method for repairing metal pipe

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US373743A (en) * 1887-11-22 William kent
US2461839A (en) * 1949-02-15 Device for eestoking to shape the
US2931416A (en) * 1958-05-20 1960-04-05 Krise Otis Milk case straightener

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US373743A (en) * 1887-11-22 William kent
US2461839A (en) * 1949-02-15 Device for eestoking to shape the
US2931416A (en) * 1958-05-20 1960-04-05 Krise Otis Milk case straightener

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4262517A (en) * 1978-08-07 1981-04-21 Hitachi, Ltd. Method of correcting distorted pipe end
US5022254A (en) * 1988-08-09 1991-06-11 Kramer Antonio H Method and device for the manufacture of can bodies by extension, including expansion of the diameter and reduction of the thickness of the sheet metal, starting out from a can body with smaller diameter, made of thicker sheet metal
US5595086A (en) * 1994-08-02 1997-01-21 Aluminum Company Of America Apparatus for calibrating hollow nonsymmetrical multiplane extrusions and associated method
US5826457A (en) * 1997-07-11 1998-10-27 Eagles; Allen S. Wheel for mandrel of pipe straightening presses
US6338189B1 (en) 1999-10-07 2002-01-15 Allison Engine Company, Inc. Method and apparatus for expansion forming a workpiece using an external deformable supporting fixture
US20070175260A1 (en) * 2006-02-01 2007-08-02 Honggie Kim Method for repairing metal pipe
US7475583B2 (en) * 2006-02-01 2009-01-13 State Pipe & Supply, Inc. Method for repairing metal pipe

Also Published As

Publication number Publication date
NO130754C (es) 1975-02-05
AT298954B (de) 1972-05-25
FR2008472A1 (es) 1970-01-23
DE1924716B2 (de) 1978-11-30
BE733079A (es) 1969-11-14
DE1924716C3 (de) 1979-08-09
DE1924716A1 (de) 1969-11-27
SE391464B (sv) 1977-02-21
CH490904A (de) 1970-05-31
ES368571A1 (es) 1971-05-01
NL7305621A (es) 1973-07-25
NO130754B (es) 1974-10-28
BR6908825D0 (pt) 1973-01-02
ES367178A1 (es) 1971-04-01
IE33454B1 (en) 1974-07-10
IE33454L (en) 1969-11-14
GB1204736A (en) 1970-09-09

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