EP2342030B1

EP2342030B1 - Improvements in or relating to a method of forming metal articles

Info

Publication number: EP2342030B1
Application number: EP09784582.0A
Authority: EP
Inventors: Paul Robert Dunwoody
Original assignee: Obrist Closures Switzerland GmbH
Current assignee: Gcl International Sarl
Priority date: 2008-10-01
Filing date: 2009-05-22
Publication date: 2019-11-06
Anticipated expiration: 2029-05-22
Also published as: ES2770645T3; PL2342030T3; GB0817942D0; MY175340A; CN102245327B; CN102245327A; EP2342030A1; WO2010037996A1

Description

Field of the Invention

The present invention relates generally to a method of shaping metal closures and particularly to a method of forming a shaped metal closure from a tubular blank having a closed end an open end.

Background of the Invention

It is known to produce metal closures from easily worked materials such as aluminium. These are typically formed from a flat sheet of relatively thin material which may be initially shaped by means of one, or a series of, die or spin-flanging tools such that a generally cylindrical, tubular blank is formed with one axial end closed and the other end open to give an elongated cup-shape. Typically such blanks are subjected to a number of processing steps before, during and after they are applied to a bottle neck, such as rolling threads into the sides, knurling, slitting and application of surface decoration.
With standard techniques the shape of metal closures is limited to being generally cylindrical. However, it is known, for example, from WO 2006/075132 and WO 99/32242 , to provide shaping of a metal closure sidewall to improve aesthetics and/or physical properties of the resultant closure. However, these methods rely solely on expansion steps and this limits the extent to which the blank can be shaped.
European Patent Publication No. EP 1 640 283 A1 discloses a method of forming an opening structure for a container, the opening structure continuously and integrally forming a cap portion and a pouring portion that are separated during opening due to an easy-to-break portion formed therebetween, the method comprising forming an enlarged-diameter portion of a cylindrical portion, forming an easy-to-break portion on the enlarged-diameter portion, and pressurizing the cylindrical portion in the height direction such than a centre portion thereof is formed as an intermediate wall portion and an upper wall portion is arranged on an outermost side.
The present invention seeks to address the problems with known metal closure production techniques.

Summary of the Invention

According to a first aspect of the present invention there is provided a metal closure forming method for shaping a closure for a container neck finish from a tubular blank having a closed end, an open end and a sidewall, comprising at least one expansion step and at least one reduction step, as claimed in claim 1.
The method may comprise two or more expansion steps. This may be to provide two or more areas of expansion and/or to expand the blank gradually so as to reduce the risk of splitting.
The method may comprise two or more reduction steps. This may be to provide two or more areas of reduction and/or to reduce the blank gradually so as to reduce the risk of splitting.
The expansion step/s may be performed using a male forming tool. The shape of the male forming tool may be fixed. Other tools, such as expandable mandrels, may also be used.
The reduction step/s may be performed using a female die. The die may be a fixed shape. The reduction step/s may also be performed using a male forming tool so that the blank is shaped from the outside towards the inside.
Successive expansion and reduction steps may occur at points successively closer to the open end. In other words, the shaping occurs from the closed end down towards the open end.
The method may further comprise one or more flaring steps at or in the region of the open end. The flaring step/s may occur after the expansion and reduction steps. The flaring may be curved or straight and may lie at an angle which is less than 45 degrees from the longitudinal axis of the blank.
The method may further comprise a knurling step at or in the region of the closed end. The knurling step may be conducted before and/or after the expansion and reduction step/s.
The method may further comprise a trimming step at the open end of the blank. The trimming step is used to achieve a required shell length. Typically this will be done after the expansion and reduction step/s.
The method may further comprise a slitting step. The slitting may be used, for example, to add a frangible line around the blank so that it can be caused to break on first opening of the metal closure after capping, to serve as a tamper-evident feature.
The thickness of the wall of the metal tube (at least at the start of the forming process) may be less than 1 mm and may be less than 0.25mm, for example 0.23mm.

Brief Description of the Accompanying Drawings

The present invention will now be more particularly described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a series of drawings illustrating the progression of a shaping method formed in accordance with a first embodiment of the present invention; and
Figure 2 is a series of drawings and text illustrating the progression of a shaping method formed in accordance with an alternative embodiment of the present invention.

Detailed Description

Referring first to Figure 1 there is shown a tubular blank generally indicated 10. The blank comprises a generally cylindrical sidewall 15 closed at one end by a disc-shape top plate 20. In this embodiment the closed end of the blank is provided with a plurality of axial knurls or ribs 25 extending around its periphery. In addition, a circumferential groove 30 is formed below the knurls 25.
In stage one of the method a male forming tool is inserted into the blank to cause circumferential expansion over the length of the sidewall downstream from the groove 30 over length A.
At stage two the blank undergoes a reduction step in which it is passed through a female die whilst a male forming is inserted. The result is that a circumferential reduction occurs over length B which produces a bulge 35 in the sidewall 15.
At stage three a second expansion step is used to circumferentially expand the sidewall 15 over length C. The expansion step is achieved with a male forming tool.
At stage four a second reduction step is used to circumferentially reduce the sidewall 15 over length D which results in a bulge 40 in the sidewall 15. The reduction step is achieved by passing the blank through a female die whilst inserting a male forming tool.
At stage five the open end of the sidewall 15 is flared outwardly over length E by inserting a male forming tool. The result is a flared closure mouth 45.
Referring now to Figure 2 there is shown a tubular blank generally indicated 110. The blank 110 comprises a generally cylindrical sidewall 115 closed at one end by a disc-shape top plate 120. In this embodiment the closed end of the blank is provided with a plurality of axial knurls or ribs 125 extending around its periphery. In addition, a circumferential groove 130 is formed below the knurls 125.
There follows a sequence of stations involved in the shaping of the blank I 10.
Stations I to 3 prepare the blank I 10 for shaping. Station I loads a blank from a supply into the shaping machinery, station 2 grips the blank ready for shaping and station 3 provides lubrication for the blank to allow the shaping equipment to function.
At station 4 of the method a male forming tool is inserted into the blank to cause circumferential expansion over the length A₁ of the sidewall downstream from the groove 130. At stations 5 and 6 successively greater expansion step are caused over lengths A₂ and A₃. By expanding the sidewall gradually the risk of splitting is decreased.
At stations 7 and 8 the blank undergoes two successively greater reduction steps in which it is passed through a female die whilst a male forming is inserted. The result is that a circumferential reduction occurs first over length B, and then over length B₂, which produces a bulge 135 in the sidewall 115. By reducing the sidewall gradually the risk of splitting is decreased.
At stations 9 and 10 a second series of expansion steps is used to circumferentially expand the sidewall 115 over length C₁, C₂. The expansion steps are both achieved with a male forming tool. By expanding the sidewall gradually the risk of splitting is decreased.
At station 11 the blank is re-lubricated.
At stations 12 and 13 a second series of reduction steps is used to circumferentially reduce the sidewall 15 over length D₁, D₂ which results in a bulge 140 in the sidewall 115. The reduction steps are achieved by passing the blank through a female die whilst inserting a male forming tool. By reducing the sidewall gradually the risk of splitting is decreased.
In this embodiment station 14 is vacant, but is available, for example, for a further reduction step if required.
At station 15 the open end of the blank is trimmed to achieve a desired closure length.
At stations 17 and 18 the open end of the blank 110 is flared outwardly over length E₁, E₂ by inserting male forming tools which penetrate successively deeper into the sidewall. The result is a flared mouth 145.
At station 19 a slitting operation is conducted to introduce a ring of notches which will subsequently be used a tamper-evident feature.
At station 20 the newly formed shaped closure is inspected by a camera to check for imperfections, with any closures which do not meet set criteria being rejected.
At station 21 the closure is loaded onto apparatus ready to be applied to a container neck finish (not shown).

Claims

A metal closure forming method for shaping a metal closure for a container neck finish from a tubular blank (10) having a closed end, an open end and a sidewall (15), comprising successively:
i. at least one expansion step at a first point axially displaced from the open end, to circumferentially expand the sidewall (15) over a first length (A) of the sidewall (15); characterised by:

ii. at least one reduction step at a second point axially displaced from the open end, to circumferentially reduce the sidewall (15) over a second length (B) of the sidewall (15); wherein
the second point is closer to the open end than the first point, and the first length (A) is longer than the second length (B).
A metal closure forming method as claimed in claim 1, wherein the first of the at least one expansion step and the at least one reduction step is an expansion step.
A metal closure forming method as claimed in any preceding claim, comprising two or more expansion steps.
A metal closure forming method as claimed in any preceding claim, comprising two or more reduction steps.
A metal closure forming method as claimed in any preceding claim, in which the expansion step/s is/are performed using a male forming tool.
A metal closure forming method as claimed in claim 5, in which the shape of the male forming tool is fixed.
A metal closure forming method as claimed in any preceding claim, in which the reduction step/s is/are performed using a female die.
A metal closure forming method as claimed in claim 7, in which the die is a fixed shape.
A metal closure forming method as claimed in claim 7 or claim 8, in which the reduction step/s is/are performed using a male forming tool.
A metal closure forming method as claimed in any preceding claim, in which successive expansion and reduction steps occur at points successively closer to the open end.
A metal closure forming method as claimed in any preceding claim, further comprising one or more flaring steps at the open end.
A metal closure forming method as claimed in claim 11, in which the flaring step/s occur after the expansion and reduction steps.
A metal closure forming method as claimed in any preceding claim, further comprising one or more of: a knurling step at the closed end; a trimming step at the open end; a slitting step.
A metal closure forming method as claimed in any preceding claim, wherein the tubular blank (10) comprises aluminium.
A metal closure forming method as claimed in any preceding claim, wherein a thickness of a wall (15) of the tubular blank (10) is less than 1 mm and optionally less than 0.25mm.