GB2229697A - Easy open can end - Google Patents

Abstract

A can end 4 made of a laminate of sheet metal and polymeric material has a central panel 11 with an aperture 12 therein closed by a hinged flap 15. A peripheral margin 16 of the flap overlaps the downturned margin 13 of the aperture and is sealed thereto. A lever 19 moulded from polymeric material is hingedly connected to the central panel by means of a shank passing through an aperture 17 in the central panel, and a flange 26 heat sealed to the polymeric underside of the central panel. Lifting of a grippable portion 21 of the lever causes a pressure plate formed at the other end of the lever to press the flap portion 15 to an open position (Figure 5(d)). Preferably the lever includes a vent plug portion 29 extending through a further aperture in the can end and terminating in a collar sealingly bonded to the underside of the panel. The lever and sealant between the flap and the aperture margin may be formed by enclosing the can end between opposing mould sections and injecting plastics material via a passageway into the mould cavity (Figures 6-8), the moulding of the lever and sealant being carried and simultaneously (Figure 7) or separately (Figure 8). The pressure in the headspace above the carbonated beverage urges the flap into the closed position. <IMAGE>

Description

CAN ENDS This invention relates to can ends having a central panel defining an openable portion which is pushed open by means of a lever hingedly connected to the central panel.

British Patent No. 1540229 describes a container end wall having a tear panel defined by a rupturable score line which is progressively torn by action of a lever in the form of a liftable tab. This metal tab has a hinge plate connected by a flexible portion to the rest of the tab so that upon lifting of the tab the nose of the tab presses upon the tear panel while the hinge plate is held firmly by rivet material of a rivet raised integral with the metal of the container end wall. Manufacture of this can end requires careful control of the press tools that score the rupturable score line and raise the integral rivet that retains the lever on the end can.

US Patent No. 2261117 describes an alternative form of "push-in" can end in which the central panel of a can end defines an aperture which is closed by a flap of panel material hingedly connected to the rest of the central panel. This flap of metal has a marginal edge that overlaps a complementary margin of the underside of the panel around the aperture. The overlapping margins are sealed by a frangible plastics sealant. During manufacture of these can ends a blister of panel material is stretch formed to stand proud of the rest of the panel; a horseshoe shaped cut is made around the blister to define the flap and hinge; the blister is then flattened to spread a peripheral margin of the flap into overlapping relationship with the margin around the aperture.The pressure required to open these can ends by pushing on the flap, can be smaller than the force to break a scored line although the sealing compound may resist opening forces.

A problem with these push-in can ends is that there is a risk that the user's finger passes at risk of injury into the aperture defined by cut metal of the central panel.

British Patent No. 1361784 and US Patent 3981652 describe alternative forms of these push-in can ends and how to seal them.

Obviously one could adapt the can end of US 2261117 by adding the rivet and "push" tab of GB 1540229 but one would still be faced with the problem of rivet raising/staking to fix the tab to the can end and the control of a multistation tab forming tool.

Accordingly, this invention provides in a first aspect, a can end of a kind having a central panel with an aperture therein closed by an openable flap portion hingedly connected to the rest of the central panel; and a lever of plastics material pivotably connected to the rest of the panel by an integral shank passing through the central panel and retained in engagement therewith by a flange, the lever being arranged so that an end of the lever extends over the openable portion, characterised in that, the can end is made of a laminate of sheet metal and a polymeric material; on at least the underside of the sheet metal; the flange of the shank of the lever is fused to the polymeric material; and said openable flap portion has a peripheral margin overlapping the periphery of the aperture, and sealed by a sealant provided therebetween.

Benefits arising from this construction are that the tasks of scoring and rivet raising are eliminated.

In a preferred embodiment the lever comprises a grippable portion at one end, a pressure plate at the other end and a hinge plate therebetween. Preferably a vent plug portion extends from the underside of the grippable portion to pass through the central panel portion to terminate in a collar sealingly bonded to the underside of the central panel. Provision of this vent plug portion permits abatement of the carbonation pressure that would otherwise resist opening of the flap portion.

According to a further aspect of the invention there is provided a method of making a can end, said method comprising the steps of: providing a can end shell, made of a laminate of sheet metal and polymeric material and having a central panel with a first aperture therein obturated by a cut flap hingedly connected to the rest of the central panel with a peripheral margin thereof overlapping the periphery of the aperture and a second aperture adjacent the first aperture; enclosing the can end shell between opposing mould sections which together form mould cavities to define a lever on the metal side of the shell, a shank connected to the lever and passing through the second aperture, and a flanged head of the shank on the polymer-faced side of the can end shell; and injecting plastics material via an injection passageway into said mould cavities to mould in situ the lever held onto the can end shell by a fusion of said flanged head to the polymeric material.

By injection moulding in situ onto the pre-pierced can end shell the heat of injection moulding is able to fuse the flange of the plastics shank into sealing engagement with the polymeric coating on the underside of the can end to achieve an hermetic seal.

One embodiment will now be described by way of example and with reference to the accompanying drawings in which:- Figure 1 is a perspective sketch of an upper part of a can closed by a can end according to the invention; Fig. 2 is an enlarged fragmentary section on line A-A' showing how an operating lever is fixed to the can end; Fig. 3 is an enlarged fragmentary section on line A-A' showing details of a vent plug and vent hole; Fig. 4 is an enlarged fragmentary section on line A-A' showing placement of a sealant; Fig. 5(a) to 5(d) show respectively the closed position, venting, an intermediate opening position, and tab position during dispensing of the contents of a can; Fig. 6 is a sectional side view of an injection mould for moulding of the lever;; Fig. 7 is a sectional side view of an injection mould for simultaneous moulding of the lever and sealing material; and Fig. 8 is a sectional side view of an injection mould for sequential moulding of the lever and sealing material.

Referring to Figs. 1 and 5a it will be seen that a can body 1 has a shoulder 2 and neck 3 closed by a can end 4 which is fixed by a double seam 5 to flange 6 of the can body. The can end 4 comprises a peripheral seam portion 7, an annular chuck wall 8 depending from the seam portion, and an antipeaking bead or channel portion 9 which joins to the chuck wall to a frustoconical annulus 10 that supports a central panel 11 which spans the frustoconical annulus.

An aperture 12 in the central panel is defined by an arcuate cut edge 13 and a fold 14 which acts as a hinge as will be explained later. The aperture 12 is closed by an outwardly convex flap portion 15, a peripheral margin 16 of which extends in overlapping relationship to the cut edge 13 which is preferably turned down as shown in Fig. 4. The flap portion 15 was made by stretch forming a convex blister of panel material, cutting the arcuate cut edge 13 to displace the flap portion out of the plane of the central panel 11 and then spreading the peripheral margin of the flap to the overlap as shown whilst retaining the integral connection of the flap to the fold 14. The can end is made from sheet metal such as aluminium alloy or steel, e.g. steel about 0.25 mm thick laminated to a polymeric film 27 such as polypropylene.

The central panel 11 is also penetrated by a second hole 17 used to connect a lever 19 to the can end, and a third hole 18 which is used for venting, best seen in Fig. 2. Fig. 2 shows that the lever 19 comprises a lifting portion 20 which has gripping ribs 21; a pressure portion 22 and a hinge plate 23 therebetween. The hinge plate is located in an aperture 24 in the lever and is much thinner than the rest of the lever so it is able to be bent along a line where it joins the pressure portion 22. A shank 25 extends from the lower surface of the lever to pass through the aperture 17 to a flange portion 26 that is heat sealed to the polymeric surface 27 of the can end.For example, a polypropylene lever will adequately heat seal to a polypropylene film/steel laminate for use in beverage cans: Other polymers may be used for lever and film to achieve compatibility with a product to be packed, e.g. nylon to nylon in cans to contain some solvent based products.

In Figs. 2, 3 and 5b the lever 19 is shown after the grippable portion 20 has been lifted to break open the vent hole 18 leaving a residual collar 28 of lever material firmly sealed to the polymeric material 27 around the downturned metal/polymer laminate defining the hole 18. A vent plug portion 29, shown closing the hole 18 in Fig. 5a, is seen to have cleared the hole in Figs. 2, 3 and 5b in the manner of a blunt needle valve so that the user is protected from any violent eruption during venting. Fig. 3 is simply provided to show the venting position more clearly.

Fig. 4 shows, on an enlarged scale, how the peripheral margin 16 of the flap 15 overlaps the turned down cut edge 13 and is sealed by a polymeric sealing material 30. The polymeric sealing material may be applied as a plastisol or organosol in the manner described in US Patent 3981652 to which the reader is directed for any further information required. However, there is a risk that this process will only apply sealing material to the underside of the can end leaving the cut edge 13 unprotected from atmospheric corrosion.

In Fig. 4 the sealing material 30 is shown to cover both sides of the overlap of the peripheral margin 16 and cut edge 13. This is achieved by enclosing the can end in a mould having a cavity defining the profile of the sealant required, and injecting a polymeric material. An advantage of this insert moulding process is that it permits moulding of a groove 131 which defines a line of weakness to facilitate opening of the flap 15 from the cut edge 13.

Figure 6 shows an injection mould for moulding the lever 19 onto the cut and pre-prepared can end shell. The can end shell is held in its closed position between mould sections 31 and 32 which together have cavities which define the lever shape, and the polymeric material of the lever is injected via a lever injection passageway 33.

Alternatively, the polymeric material of the lever 19 and sealing material 30 can be injected simultaneously using the mould shown in Figure 7. Mould sections 34 and 35 have cavities defining both the lever shape and the sealing material shape 30, with a lever injection passageway 33 and sealing material injection passageway 36 connected so that the polymeric material is fed simultaneously to form the lever and sealing material.

Additionally, the mould sections can define a cavity 37 for receiving polymeric material to form a lining compound for that portion of the can end which goes to form the closable seam.

Alternatively, as shown in Figure 8, mould sections can employ unconnected passages 38,39 for injection of the sealing material and lever separately.

If desired moulding of the lever and sealant may be carried out simultaneously or alternatively sequentially.

If desired a first material such as polypropylene may be injected to create the lever and a second material such as a more readily frangible polymer, e.g. a filled polymer with low extensibility under stress e.g. filled polypropylene, injected to form the sealant profile.

Referring to Fig. 5a it will be understood that the headspace pressure in a can of carbonated beverage maybe as much as 80 psi. This pressure is received on the flap 15 and passed to the downturned cut edge 13. The flap is being urged to a closed position so the sealant is required only to seal the lap joint, not to provide all the mechanical strength. The flange 26,fixing shank 25, collar 28 and vent plug 29 are also subjected to the carbonation pressure so a heat seal is adequate sealant.

Finger pressure applied to the flap would have to overcome the carbonation pressure to achieve opening which is suddenly abated on initial opening of the flap putting the user at risk of inserting the finger into the cut edge 13. In contrast, Fig. 2 shows that lifting of the lever 19 first opens the vent hole to abate the carbonation pressure. Thereafter, further raising of the lever only has to break the sealant 30 to achieve opening of the flap 15 as shown in Fig. 5(c).

Fig.5(d) shows that the lever 19 is returned to a position flat against the central panel 11 of the can end so that it does not obstruct drinking from the can.

Claims (8)

Claims:

1. A can end (4) of a kind having a central panel (11) with an aperture (12) therein closed by an openable flap portion (15) hingedly connected to the rest of the central panel (11); and a lever (19) of plastics material pivotably connected to the rest of the panel by an integral shank (25) passing through the central panel and retained in engagement therewith by a flange (26), the lever being arranged so that an end of the lever extends over the openable portion, characterised in that, the can end is made of a laminate of sheet metal and a polymeric material provided on at least the underside of the sheet metal; the flange (26) of the shank of the lever is fused to the polymeric material; and said openable flap portion has a peripheral margin overlapping the periphery of the aperture, and sealed by a sealant provided therebetween.

2. A can end according to claim 1, characterised in that the lever comprises a grippable portion (20) at one end, a pressure plate (22) at the other end and a hinge plate (23) therebetween; the shank of the lever extending from the hinge plate.

3. A can end according to claim 2, characterised in that a vent plug portion (29) extends from the underside of the grippable portion (20), through the central panel (11) to terminate in a collar (28) sealingly bonded to the underside of the central panel.

4. A can end substantially as hereinbefore described with reference to the accompanying drawings.

5. A method of making a can end, said method comprising the steps of: providing a can end shell, made of a laminate of sheet metal and polymeric material and having a central panel with a first aperture therein obturated by a cut flap hingedly connected to the rest of the central panel with a peripheral margin thereof overlapping the periphery of the aperture and a second aperture adjacent the first aperture; enclosing the can end shell between opposing mould sections which together form mould cavities to define a lever on the metal side of the shell, a shank connected to the lever and passing through the second aperture, and a flanged head of the shank on the polymer-faced side of the can end shell; and injecting plastics material via an injection passageway into said mould cavities to mould in situ the lever held onto the can end shell by a fusion of said flanged head to the polymeric material.

6. A method of making a can end according to claim 5 wherein the mould sections together also form a further cavity which defines the shape of sealing material for forming a seal between the peripheral margin of the cut flap and the periphery of the aperture, and a sealing material injection passageway is provided in at least one of the mould sections.

7. A method of making a can end according to claim 6 wherein the lever injection passageway and sealing material injection passageway are connected so that the lever material and sealing material can be injected simultaneously.

8. A method of making a can end substantially as described herein with reference to Figures 6-8 of the accompanying drawings.