Classifications

• • 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
  • B21D51/00—Making hollow objects
  • B21D51/16—Making hollow objects characterised by the use of the objects
  • B21D51/38—Making inlet or outlet arrangements of cans, tins, baths, bottles, or other vessels; Making can ends; Making closures
  • B21D51/383—Making inlet or outlet arrangements of cans, tins, baths, bottles, or other vessels; Making can ends; Making closures scoring lines, tear strips or pulling tabs
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
  • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
  • B65D17/00—Rigid or semi-rigid containers specially constructed to be opened by cutting or piercing, or by tearing of frangible members or portions
  • B65D17/28—Rigid or semi-rigid containers specially constructed to be opened by cutting or piercing, or by tearing of frangible members or portions at lines or points of weakness
  • B65D17/404—Details of the lines of weakness

Definitions

• This invention relates to easy open can ends and to score dies for manufacturing such easy open ends.
• Easy open ends have a score track defining an operable portion or panel, which can be operated by a tab or other opening mechanism. This principle is the same whether the can end is a full aperture easy open end (normally used for foodstuffs), a pull tab beverage end, or the more modern stay-on tab commonly used for drinks cans.
• a method of producing an operable portion in an easy open can end formed of a metallic substrate coated with a polymer film material comprising the steps of contacting the can end with a score die and an anvil die, the score die comprising a truncated "V" shaped projection having a planar inner sidewall adapted to produce a planar score sidewall adjacent the operable portion, a planar outer sidewall adapted to produce a planar score sidewall adjacent the remainder of the can end, and a generally horizontal flat land portion adapted to form the base of the score, characterised in that each of the inner and outer sidewalls is at an angle of between 15° and 60° to the longitudinal axis of the projection, there being a difference of at least 15° between the angles of the inner and outer sidewalls.
• an easy open can end formed of a metallic substrate coated with a polymer film material, and including a panel portion having an operable portion defined by a score line, the score line comprising a planar inner score sidewall adjacent the operable portion, a planar outer score sidewall adjacent the remainder of the panel portion, and a generally horizontal flat land portion therebetween forming the base of the score, characterised in that each of the inner and outer sidewalls is at an angle of between 15° and 60° to an axis perpendicular to the can end, there being a difference of at least 15° between the angles of inner and outer sidewalls.
• the metallic substrate is an aluminium alloy.
• Figs. 2 and 3 are schematic sectional views of score dies according to the present invention.
• Fig.4 is a graph showing the incidence of angel hairs obtained from the score dies of Figs. 1 to 3.
• a can end 1 comprises a metallic substrate 4, typically of aluminium, with a film 5, typically of polyester, laminated to the upper surface 6 thereof.
• a similar film 7 is laminated to the lower surface 8 of the can end.
• the can end is typically as described in our PCT application No. W093/17864.
• the score die comprises a "V" shaped projection 9 having a first sidewall 10, a second sidewall 11, and a horizontal land portion 12 therebetween.
• the first and second sidewalls are each inclined at an angle of approximately 25° to the longitunal axis of the projection 9.
• the "included angle" of the score die is therefore approximately 50°.
• Score dies such as these are frequently given a surface coating (not shown) in order to increase the wear resistance of the score die.
• the can end 1 is pressed between the score die 2 and an anvil 13 to form the score 3, defining a tear panel 14 within the remainder of the central panel 15 of the can end.
• Table 1 below shows how a range of score dies, with different angles A and B, have been tested.
• the samples were all subjected to a corner treatment, such as a tumbling process which rounds the sharp edges of the score dies prior to use.
• Samples A to C were prior art designs in accordance with Fig.l, samples D to G and J to M were similar to that of Fig.2, whilst sample H was generally in accordance with Fig.3.
• the graph of Fig. shows how these samples behaved in producing angel hairs, with the number of angel hairs observed being shown as a percentage.
• the asymmetric score tracks of samples D, E, F, G, J, K, L and M showed a marked reduction in angel hairs over the conventional score track of samples A to C.
• Sample H showed an actual increase in angel hair percentage, but this is believed to be because the natural inclination of the easy open ends being tested was to fracture around the edge of the panel 15 rather than the tear panel 14. It is believed that other easy open ends of a different diameter or design, or manufactured with different equipment, may have a natural predisposition to fracture adjacent the panel 15 and hence the design of Fig.3 may offer improvements in such cases. Simple tests will be able to demonstrate whether, for any particular type of can end, the design of Fig.2 or that of Fig.3 will give better results.
• Can ends produced from a prior art score die such as sample A were compared with those from a score die in accordance with the invention, such as sample K, in respect of break and tear force, and coating integrity.
• Score break and score tear performance is shown in Table 2 below with the figures being shown in lbf (kgf) .
• the break and tear force figures for the ends made in accordance with the invention were well within the accepted specification of 2.5 to 4.5 lbf (1.14 to 2.05 kgf) for score break, and 3 to 5 lbf (1.36 to 2.27 kgf) for score tear force.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Containers Opened By Tearing Frangible Portions (AREA)

Applications Claiming Priority (3)

Publications (1)

Family

ID=10817482

Family Applications (1)

Country Status (6)

Family Cites Families (5)

• 1997
  • 1997-08-15 GB GBGB9717241.5A patent/GB9717241D0/en not_active Ceased
• 1998
  • 1998-08-10 EP EP98938784A patent/EP1003618A1/de not_active Ceased
  • 1998-08-10 AU AU87388/98A patent/AU8738898A/en not_active Abandoned
  • 1998-08-10 JP JP2000509545A patent/JP2001514975A/ja active Pending
  • 1998-08-10 WO PCT/GB1998/002409 patent/WO1999008819A1/en not_active Ceased
  • 1998-08-10 CA CA002300163A patent/CA2300163A1/en not_active Abandoned

Non-Patent Citations (1)

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