GB2264252A - Containers - Google Patents

Abstract

An end component 61 is seamed to a tubular body 1 by forming a double seam and applying an inwardly directed pressure to the double seam to tighten the folds RS and RB of the seam and optionally tilting the seam to incline over the centre panel of the end component 61. The internal pressure retention of metal containers having such tightened double seams is improved. <IMAGE>

Description

CONTAINERS This invention relates to containers having a side wall and an end wall attached to the side wall by a double seam, and more particulary but not exclusively to a method and apparatus for making the double seam.

In a conventional apparatus for forming a double seam a can end, having a central panel, a chuck wall upstanding from the central panel, and a peripheral flange or cover hook, is placed on to the body of a can having a peripheral outwardly directed flange. The can body is lifted to engage the can end with a chuck which engages the chuck wall of the can end to centre the can end and body for rotation about a central axis. While the can body is rotated a first operation roll is applied to the periphery of the cover hook to curl the hook under the body flange so that the cover hook and body flange are interlocked. A second operation roll having a flatter work profile is then applied to the interlocked seam created by the first operation to flatten the seam and complete an hermetic seam. Apparatus for roll forming this double seam is shown diagrammatically in Fig.l.

In an alternative apparatus described in British Patent 765753 the can and can end are supported on a turret which rotates to roll the cover hook of the can end along an arcuate rail having a profile to progressively form the first operation seam and then flatten the seam to the second operation form.

Both the roll-forming seamers and the rail seamers create a double seam which is located externally relative to the side wall of the body. Often the double seam is inclined outwardly from the body, reflecting the chuck wall inclination of the can end. Typically, inclined chuck walls have an angle of inclination to the central panel of about 94 or 950.

When a can end seamed to a body is subjected to excessive internal pressure the can end everts initially by localised collapse of the chuck wall (called peaking).

Once the continuous hoop of chuck wall is disturbed, complete eversion develops by reversal of the chuck wall.

Such eversion can occur in cans containing carbonated beverages and aerosol cans, or during thermal processing of foodcans.

French Patent No. 1533260 describes and shows in Figs. 11 and 12 a double seam and the chuck used to tilt the seam to overhang the centre panel of the can end.

We have discovered that the pressure at which eversion of a can end is caused, may be significantly increased if pressure is applied to the double seam in an inwardly directed radical direction to tighten the folds at the top of the seam. Further improvement of the pressure resistance of the seam is achieved if the radial pressure is continued to further deflect the double seam to incline or tilt towards the central panel of the can end.

Accordingly, in a first aspect, this invention provides a container body comprising a tubular side wall and end wall having a central panel and a peripheral chuck wall fixed to the side wall by a double seam which is tilted to extend radially inwards over the centre panel, characterised in that the side wall and chuck wall are bent at a level adjacent the lower extremity of the double seam, and the body hook radius Rb of the double seam is less than half the metal thickness of the side wall.

Preferably the chuck wall is inclined to the plane of the central panel at an angle between Ioand 300.

In a second aspect, this invention provides a method of making a container body according to claim 1 or claim 2, said method comprising the steps of: (a) providing a tubular body with an outwardly directed seaming panel terminating in a peripheral coverhook, (b) entering the flange of the body between the annular wall and cover hook, and (c) supporting the body and end component while progressively interlocking the coverhook and flange to create a double seam.

characterised in that, application of said inwarldly directed radial pressure to the double seam is continued to deflect the double seam radially inwards to tilt about a circular line just below the double seam to an angle to the central axis of the tubular body and reduce the body hook radius of the seam to less than half the thickness of the side wall.

The radial force to deflect the double seam radially inwards may be applied by a roll applied to the exterior of the double seam while the body and end component are rotated. If desired, the radial force is applied to a double seam on a can body having a shoulder and neck of diameter smaller than the side wall until the entire double seam is within the compass of the tubular body.

In a further aspect this invention provides apparatus for carrying out the method comprising means to support a flanged tubular body with a flanged end component fitted to at least one end thereof, and means to form a double seam between the flange of the body and end component, characterised by means to apply an inwardly directed pressure to the double seam against a support means adjacent the chuck wall to tighten the body hook radius and seaming wall radius of the double seam.

The means to tighten the double seam may be a roll movable to apply an inwardly directed radial pressure to the exterior of the double seam.

The support means may be a second roll is mounted eccentrically on a centring means adapted to engage the chuck wall of an end component during rotation.

In a preferred embodiment, the support means is in the form of a chuck having a chuck sleeve (115, 104) to support the chuck wall of the end component during formation of the double seam, and a plurality of collapsible segments (5,97) adapted to support an annulus of the chuck wall during application of the inwardly directed pressure to tilt the double seam.

It is desirable that a rotatable chuck operably connected to driving means, supports the other end of the tubular body.

In an alternative embodiment of the apparatus the means to deflect the double seam to incline includes a rotable chuck; and a support plate mounted on a rotable turret, and a rail surrounding the turret and provided with a groove of continuously changing profile to form a first operation seam, then a second operation seam and then apply said inwardly directed press to crush and tilt the double seam as the turret rotates.

The rotable chuck may include an eccentially mounted support roll and a sleeve movable from a first position in which it acts as a chuck to a second position clear of the support roll which supports the chuck wall during application of said inwardly directed pressure.

Although the method and apparatus are particularly described with reference to round cans, the method and apparatus may be adapted to make cans of other cross section such as rectilinear or oval.

Various embodiments will now be described by way of example and with reference to the accompanying drawings in which: Fig.la is a diagrammatic side view of apparatus for roll forming a conventional double seam; Fig.lb is an enlarged fragmentary section showing a can end fitted on a body flange at commencement of a first operation seam; Fig.lc is a fragmentary section showing a first operation seam; Fig.ld is a fragmentary section showing a first operation seam of Fig.lc at commencement of formation of a second operation seam; Fig.le is a fragmentary section showing a completed second operation seam.

Fig.2 is a diagrammatic plan view of apparatus for rail forming a double seam; Figs.2a, 2b and 2c are fragmentary sections of the seam during formation along the rail showing development of a double seam; Fig.2d is a fragmentary section of the rail shown in Fig.2 after modification to a first embodiment of the invention to form inwardly tilted seam; Fig.2e is a sectional side view on an enlarged scale of a chuck shown in Fig.2d.

Fig.3a is an enlarged sectioned side view of a double seam; Fig.3b is an enlarged sectioned side view of the seam of Fig. 3a after small deformation; and Fig.3c is an enlarged sectioned side view of the seam of Fig.3b after further inward tilting.

Figs.4a, 4b, 4c and 4d are part sectioned side views of apparatus for forming a tilted seam on a cylindrical can body; Fig.4e is a perspective sketch of the can produced by the apparatus of Fig.4; Fig.5a is a fragmentary sectioned side view of a necked in can having a double seam supported on a shoulder; Fig.5b shows the can of Fig.5 during tilting of the seam; Fig.6 is a cut away perspective sketch of a beverage can produced by the apparatus of Fig.5b.

Fig.7 is a sectioned side view of apparatus for tilting a double seam on the cone top of an aerosol can.

Figs.7a and 7b show detail of the cone seam and dome end seam respectivly.

Fig.8 is a sectioned side view of apparatus for tilting the domed end seam of an aerosol can; Fig. 9 is a graph of seam tilt v pressure to eversion; Figs.10a, 10b and 10c are sectioned side views of a chuck which is collapsible to permit removal from the tilted double seam.

Fig.la shows a can body 1 having a bottom end 2 already connected by a double seam 3 to the side wall 4 terminating in an outwardly directed flange 5. A can end 6 having a centre panel 7, chuck wall 8 a seaming panel 9a and a peripheral end hook 9b. A lining compound c is placed in the interior surface of the seaming panel and hook. The can end 6 is centred on the top of the body flange 5 by a chuck 10 engaged with the chuck wall as can be seen in Figs.la and lb. The can body 1 is supported by a lifter pad 11. During formation of the first operation of the double seam, as shown in Figs.la and lb, the chuck 10 is rotated to drive the can body 1 and end 6 to rotate while a first operation roll 12 is moved inwards against the periphery of the can end flange so the peripheral end hook 9b of the can end and flange of the body become interlocked.Figs.ld and le show a second operation of forming the double seam in which a roll 13, having an upwardly convergent annular profile, is moved to compress the interlocked first operation seam to achieve an hermetic seam in which the end hook 9b and body hook 5a overlap and are compressed against the lining compound to form a primary seal S in the lower part of the double seam. These principles are widely used in can seamers to make double seams the bulk of which is located outside the body surface.

Fig.2 shows diagrammatically a turret 14 surrounded by a rail 15. The turret carries a plurality of rotable chucks and support pads 16 similar to those shown in Fig.1. Fig. 2a shows the rail 15 has a groove 17 which is profiled along its length to cooperate with the chucks 18 to first curl the flange of a can body and peripheral hook of a can end into a first operation seam 19 shown in Fig.2b. Continued rolling of the can seam along the rail groove flattens the seam as shown in Fig.2c in known manner to a second operation seam profile 20.

However, Fig.2d shows a modified rail portion 15a having an inclined surface 21 which extends over the seam 20 so that during continued rolling motion along the inclined surface of the rail thrusts the seam to a tilted form 20a. Whilst some thicker can ends may permit tilting of the seam without internal support of the chuck wall of the can end, thinner walled cans may require a modified chuck 18 which is shown in detail in Fig. 2e to have a retractable sleeve and inner roll to permit withdrawal from the tilted seam.

In Fig.2e, the chuck 18 comprises a central stem 110 fixed to the turret (not shown). The stem 110 has a flange plate 111, in which a spindle 112 is rooted eccentric to the stem 110 to support a freely rotating roll 113 having a substantially frustoconical peripheral wall 114. As shown in Fig.2e, an external sleeve 115 surrounds the stem 110 and roll 113. The sleeve 115 is operably connected by splines 116 to a drive tube 117 which is mounted for rotation on the stem 110. In operation, the drive tube 117 is driven to rotate so rotating the external sleeve in the manner of a conventional chuck.

However, when the chuck 18 reaches a rising cam surface 118 on the top of rail 15 (as shown in Fig.2d) an annular flange 119 of the sleeve 115 is lifted to expose the roll surface 114 to the chuck wall of the can end so that the double seam may be urged inwardly by the inclined surface 21 of the rail 15 against the support given by roll surface 114.

Upon leaving the cam 118, the sleeve 115 returns to surround the roll surface 114 in readiness to receive another can and can end for double seaming.

Figs.3a, 3b and 3c are respectively enlarged sections of the double seam, an early stage in compression of the top of the double seam and a final stage in which the seam is tilted inwards to over the centre panel of a domed can end.

In Fig.3a, the double seam extends outwardly at an angle governed by the exterior surface of the chuck used. The body hook radius RB approximates to just over the half of the body metal thickness and the seaming wall radius approximates just over 1+ times the metal thickness.

In Fig.3b, the body hook and seaming wall radius have been reduced and the seam has been brought to nearly upright giving some improvement in pressure retention by the seam.

In Fig.3c, the double seam has been further tilted to about 170 to the can axis giving further improvement in pressure tests.

In Fig.4a a cylindrical can body 24 drawn from a blank has a bottom wall 25 integral with a cylindrical side wall 26 which terminates in an outwardly directed flange 27. The body flange 27 supports the peripheral flange 28 of a can end 29 having a chuck wall 30 and centre panel 31. In Fig.4a, the can end is centred by a rotating chuck 32 engaged with the chuck wall 30 while a lifter pad 33 supports the bottom of the body. A first operation roll 34 having a curved profile 35 is about to be applied to the periphery of the can end.

Fig.4b shows the interlocked engagement or first operation seam 36 of the body flange and periphery of the can end after progressive rolling.

Fig. 4c shows a conventional flattened seam 37 created by a second operation roll 38.

Fig.4d shows a cluster of tapered rolls 39 each having a peripheral work surface 39a inclined to the side wall of the can body 24. As shown, the can body has been rotated and pushed axially into the cluster of rolls 39 so that the double seam 37 of Fig.4c has been tilted inwardly to overhang the periphery of the centre panel 31 of the can end. This extra rolling operation avoids the need for a collapsible chuck.

Fig.4e shows a cylindrical can having an inclined or tilted double seam 40 as maybe made by the apparatus of Fig.4d.

Fig.5a shows a top end of a beverage can 41 which comprises a shoulder 42 neck 43 and double seam 44 which connects the body to a can end 45. The can end comprises a seam portion 46 and a chuck wall 47 depending from the seam portion at an angle of about 50 to the axis of the can. A reinforcing bead 48 joins the chuck wall to an inner annular wall 49 which supports a slightly domed central panel. The central panel may include easy opening features such as an openable portion defined by a scored line 51, and a pull tab 52 as shown in Fig.6. Typically the double seam shown in Fig.5a will tilt outwardly at about 50.

Fig.5b shows the can 41 of Fig.5a after the double seam 44 has been tilted by rotating of the can while an external roll 53 is pressed onto the exterior of the double seam and the chuck wall 47 is supported by a collapsible chuck 54. On completion of the tilting of the double seam to an inwardly directed tilted double seam 55 the wedge plunger P is lowered and the garter spring G causes the segments S of the chuck to retract as the chuck is lifted away from the can end to permit removal of the finished can as shown in Fig.6.

Fig.7 shows apparatus for tilting the double seam 56 of a cone top 57 of an aerosol can 58. The can comprises a cylindrical body 59 having a shoulder portion 60 at both ends. A domed bottom end 61 is attached by a double seam 62, as can be seen in Fig.7b, to one end of the cylindrical body, and to the other end is attached a cone 57 comprising a seam portion 63, a chuck wall 64 and a domed annulus 65 joined to the chuck wall by a reinforcing channel 66. A central aperture in the domed annulus is defined by an outwardly directed curl 67 as can be seen in Fig.7a. Typically the outwardly directed curl defines an aperture 1 inch in diameter.

The apparatus of Fig.7 comprises a spring loaded rotable chuck 68, a rotatable domed end support 69 and a work roll 70. The chuck 68 comprises a plug portion 71 which fits in the aperture in the cone end of the aerosol can. The plug portion 71 is surrounded by a flange 72 which presses on the curl 67 around the aperture of the cone. The flange 72 is connected with a body 73 of the chuck that is mounted for free rotation on a shaft 74 mounted firmly on a frame (not shown).

The rotatable end support 69 comprises a pad 75 having a hollow defined by an annulus 76 in which fits the bottom double seam 62 of the can bottom. The pad 75 is fixed to the flange of a drive shaft 78 which is mounted on the apparatus frame for rotation by driving means not shown.

The work roll 70 is mounted for rotation on a bearing 79 which is fixed to an arm 80 by a bolt. The arm is mounted on the frame and movable in a radial direction towards and away from the rotating can body 59. The work roll 70 has a substantially conical work surface 81 supported on a cylindrical portion 82.

In Fig.7 the double seam 56 of the cone end is shown before tilting (at the left of the drawing) and after tilting at the roll (marked 83 in Fig.7a). The distance of roll travel towards the can is measured during tests to observe the effect of seam inclination on pressure holding ability of the cans.

For experimental purposes the apparatus of Fig.7 was mounted in a lathe. The chuck 68 was fitted in the tailstock of the lathe for free rotation; the rotatable end support 69 was mounted in the headstock to receive drive from the lathe motor; and the work roll 70 was mounted in a tool post so that linear motion of the work roll was read off the calibrated scale of the cross slide in order to make cans having a range of angles of tilted seams 83. The cans were assessed by internal pressure tests to evert the seams as shown in Table 1: CONES Pressure to eversion p.si.

Conventional 225 225 225 225 225 225 225 Performance Roll travel 0.01 0.02 0.03 0.04 0.05 0.06 0.07 (inches) Samples 1 - - 240 250 240 250 270 Samples 2 - - 255 240 250 260 245 Mean - - 247.5 245 245 255 257.5 These results show that movement of the double seam inwards to tighten the body hook and seam panel radii and progressively tilt the seam increases the pressure which the cone end seam may contain.

Fig.8 shows apparatus for tilting the double seam at the dome end of the aerosol can already described with reference to Fig.7.

In Fig.8 the apparatus comprises a rotatable end support 85 mounted in the headstock of the lathe and applied to the cone top end 57 of the aerosol can; a work roll 70 mounted on an arm 80 supported by the tool post of the lathe and a support roll 86 smaller in diameter than the internal diameter of the domed bottom 61 of the aerosol can. The support roll 86 is mounted eccentrically for free rotation on a bearing 87 which surrounds a collar 110, spring-loaded on shaft 88 terminating a centring pad 89 engaged with the domed bottom 61 of the aerosol can. As shown in Fig.8 the external work roll 70 and internal support roll 86 cooperate to tilt the double seam 62 inwardly from the not yet tilted position shown at the right of the domed portion as drawn.On completion of this progressive rolling operation there is no difficulty in removing the tilted seam because the internal support roll is smaller in diameter than the internal diameter of the tilted seam 90.

Samples were made with various angles of tilt of the double seams of domed bottoms and the cans were pressure tested to give results shown in Table 2: DOMES Conventional 247 247 247 247 247 Roll Travel 0.01 0.02 0.03 0.04 0.05 (inches) Samples 1 290 280 295 290 + Samples 2 310 275 300 + + Mean 300 277.7 297.5 290 + These results show that movement of the double seam, at the domed bottom, to a tilted angle combined with a tightening of body hook and seaming panel radii increases the pressure which the dome end seam may contain. Results tabulated + were higher than could be measured on our test apparatus.

The pressure test results tabulated in tables 1 and 2 are shown graphically in Fig.9 which shows the significant improvement achieved.

Whilst the eccentric support roll of Fig.8 has given useful test results it may be preferable to use a chuck having a array of segments which are retractable to permit removal of the chuck from the tilted seam.

In Fig.lOa a can body 91 is supported for rotation by a lifter pad 92. The peripheral flange 93 of a can end is engaged with the outwardly directed flange 94 of the body and a first operation roll 95 is about to make a first operation seam.

Fig.lOa shows a chuck 96 with expandable and retractable segments 97 to support the chuck wall 98 of a can end during the entire double seaming and seam tilting operations.

In Fig.lOa the chuck 96 comprises a plurality of segments 97 arranged around a plunger 99 having a cylindrical portion 100 extending from an outwardly flared portion 101 which is engaged with a complimentary surface 102 of each segment. In Fig.lOa the segments are shown in an expanded position in which they support only the bottom of the chuck wall of the can end. In this position a garter spring 103 around the segments is extended. After double seaming and tilting of the seam the plunger 99 is lifted and the garter spring 103 contracts to urge the segments against the cylindrical portion of the plunger so the chuck can be removed from within the tilted double seam.

The chuck has a retractable chuck sleeve 104 which surrounds the garter spring and is slidably connected to the body 105 of the chuck. The internal diameter of an aperture in this pressure ring serves to limit the outward movement of the segments so that excessive force is not applied to the chuck wall.

As shown in Fig.lOb a modified second operation roll having a sloped work surface 108 may be used to not only flatten the first operation seam but also tilt it into the recess between the upper surface of the segments and the lower surface of the pressure ring.

If further tilt is required a further roll 108a may be applied after the chuck sleeve 104 is raised to permit increase of the tilt as shown in Fig.lOc.

Whilst the invention has been described with reference to the roll forming of tilted double seams it will be understood that a double seam may alternatively be tilted by pushing the double seam into a convergent cone in a die if the side wall on the can is strong enough to deliver the force required to tilt the seam.

If the benefit of enhanced strength of double seam is not needed, benefit may be achieved by use of thinner metal for the can end or body components.

Claims (15)

CLAIMS:

1. A container body comprising a tubular side wall and end wall having a central panel and a peripheral chuck wall fixed to the side wall by a double seam which is tilted to extend radially inwards over the centre panel, characterised in that the side wall and chuck wall are bent at a level adjacent the lower extremity of the double seam, and the body hook radius Rb of the double seam is less than half the metal thickness of the side wall.

2. A container body according to claim 1 characterised in that the chuck wall is inclined to the plane of the central panel at an angle between 10 and 300.

3. A method of making a container body according to claim 1 or claim 2, said method comprising the steps of: (a) providing a tubular body with an outwardly directed flange and an end component having an annular chuck wall surrounded by an outwardly directed seaming panel terminating in a peripheral coverhook, (b) entering the flange of the body between the annular wall and cover hook, and (c) supporting the body and end component while progressively interlocking the coverhook and flange to create a double seam.

characterised in that, application of said inwardly directed radial pressure to the double seam is continued to deflect the double seam radially inwards to tilt about a circular line just below the double seam to an angle to the central axis of the tubular body and reduce the body hook radius of the seam to less that half the thickness of the side wall.

4. A method according to claim 1 or claim 2 wherein the radial force to deflect the double seam radially inwards is applied by a roll applied to the exterior of the double seam while the body and end component are rotated.

5. A method according to any preceding claim wherein the radial force is applied to a double seam on a can body having a shoulder and neck of diameter smaller than the side wall until the entire double seam is within the compass of the tubular body.

6. Apparatus, for carrying out the method of claims 3 or 4, comprising means to support a flanged tubular body with a flanged end component fitted to at least one end thereof, and means to form a double seam between the flange of the body and end component, characterised by means to apply an inwardly directed pressure to the double seam against a support means adjacent the chuck wall to tighten the body hook radius and seaming wall radius of the double seam.

7. Apparatus according to claim 7 characterised in that the means to tighten the double seam is a roll movable to apply an inwardly directed radial pressure to the exterior of the double seam.

8. Apparatus according to claim 6 or claim 7 characterised in that the support means is a second roll is mounted eccentrically on a centring means adapted to engage the chuck wall of an end component during rotation.

9. Apparatus according to claim 6 or claim 7 characterised by a support means in the form of a chuck having a chuck sleeve (115, 104) to support the chuck wall of the end component during formation of the double seam, and a plurality of collapsible segments (5, 97) adapted to support an annulus of the chuck wall during application of the inwardly directed pressure to tilt the double seam.

10. Apparatus according to any one of claims 6 to 9 characterised in that a rotatable chuck operably connected to driving means supports the other end of the tubular body.

11. Apparatus according to claim 6 wherein the means to deflect the double seam to incline includes a rotatable chuck; and a support plate mounted on a rotatable turret, and a rail surrounding the turret and provided with a groove of continuously changing profile to form a first operation seam, then a second operation seam and then apply said inwardly directed pressure to tilt the double seam as the turret rotates.

12. Apparatus according to claim 11 wherein the rotable chuck includes an eccentically mounted support roll and a sleeve movable from a first position in which it acts as a chuck to a second position clear of the support roll which supports the chuck wall during application of said inwardly directed pressure.

13. A container substantially as herein before described with reference to Fig.ld; Fig.3b; Fig.3c; Figs.4d and 4e; Figs.5b and 6; Fig.7a; Fig.7b; or Fig.lOc.

14. A method of seaming an end component to a tubular body, substantially as hereinbefore described with reference to Figs. 2d and 2e; Figs.3a, 3b and 3c; Figs.4a, 4b, 4c, 4d, 4e, Figs.5a, 5b; Fig.7; Fig.8; and Figs.lOa, lOb and lOc of the accompanying drawings.

15. Apparatus for seaming an end component to a tubular body, substantially as herein before described with reference to Figs.2d, 2e; Figs.4d; Figs.5b; Fig.7; Fig.8; and Figs.lOa, lOb and lOc of the accompanying drawings.