WO1997035676A1

WO1997035676A1 - Process and apparatus for shaping containers

Info

Publication number: WO1997035676A1
Application number: PCT/GB1997/000583
Authority: WO
Inventors: Joseph William Daintrey; Timothy Michael Wood; Richard Mark Orlando Golding
Original assignee: Carnaudmetalbox Plc; Carnaudmetalbox S.A.; Carnaudmetalbox N.V.; Carnaudmetalbox (Holdings) Usa Inc.
Priority date: 1996-03-22
Filing date: 1997-03-03
Publication date: 1997-10-02
Also published as: GB9606080D0; AU4190597A

Abstract

An apparatus (1) for shaping containers (10) such as can bodies is described, which is inserted within the container and expanded outwardly so as to produce a stress in the material of the container side wall. When this stress exceeds the yield stress of the material permanent deformation is achieved. Typically, the apparatus uses outward expansion of a circle of ball (2) bearings in order to deform the side wall, these being then rolled along the side wall in order to produce different shapes, flutes, etc.

Description

PROCESS AND APPARATUS FOR SHAPING CONTAINERS

This invention relates to shaping containers and, m particular, to the shaping of a side wall of metal containers such as cylindrical can bodies.

The use of metal containers is well established as a method of packaging a large range of products. As limitations on the reduction in material used for the manufacture of cans is reached, it has become necessary to seek ways of differentiating between products other than lust cost reduction. Typically, such differentiation can be achieved by variation in the graphics, colour and aspect ratio of a can. Alternative methods of product differentiation have also been achieved by shaping, that is by varying the profile of a can side wall from its traditional cylindrical shape.

Known methods of shaping have used pneumatic, hydraulic, electromagnetic or elastomeric forming techniques. GB-B-2257073, for example, describes a method and apparatus for blow-forming a three piece container. In that invention, the container is clamped in a mould and compressed air is supplied to the interior of the container. The compressed air causes the container to expand to the mould shape, whilst end clamping members move inwardly to maintain the orientation of the container within the mould.

Most of the prior art shaping processes are based upon pressure forming which requires the cylindrical container to be loaded into and held within a split die or mould. This is costly, complex, inflexible and generally slow as a production process.

Whilst known techniques are able to produce significant changes m shape on three piece metal containers and on two piece aluminium cans, these techniques are not usable to shape two piece steel cans where the can material is highly work hardened.

This invention seeks to provide a high speed process for shaping containers which is simpler than the prior art methods and more cost effective. It is a further object of the present invention to shape both two and three piece cans {that is either with or without an integral base) made from a variety of materials and in particular two piece cans made from steel.

According to the present invention, there is provided an apparatus for shaping a side wall of a container comprising:

An apparatus for shaping a container having a side wall and a peripheral portion adapted to be connected to a closure, the apparatus comprising: at least one forming member which is rotatable about is own axis; means for moving the or each forming member radially outwards against the inside of the side wall; and means for supporting the or each forming member such that it can rotate longitudinally and/or circumferentially along the inside of the side wall, the or each forming member being mounted for free rotation on the moving means; whereby, in use, pressing and rotating the or each forming member on the side wall generates a stress in the side wall such that, when the stress exceeds the yield stress of the material of the side wall, permanent deformation is created m the side wall.

This combination of expansion of the container side wall and rotation of individual forming members is known as "flow turning" since the metal of the container is caused to flow.

Generally, more than one forming member is used. The container is usually mounted on a holder and either or both of the holder and supporting means are rotatable relative to each other. Preferably, the moving means comprises a pair of discs and each forming member is mounted between the discs. Typically, each forming member may be retained at least partially between the discs by a cage device.

The discs may be mounted on the same or separate shafts and may be moveable towards each other, for example by longitudinal movement of their shafts, thus causing the forming members to move radially outwards. Generally, the discs are adapted for rotation about their respective shafts so that the forming members are caused to rotate around the side wall of the container. The discs may be frustoconical in shape, with the forming members positioned between the conical parts of the discs.

Rotation of the discs about their shafts in combination with outward movement of the forming members creates both a steady rolling action which deforms the container wall outwardly according to amount of movement of the discs towards each other and also rolls this deformation around the container wall.

In an alternative embodiment, the moving means comprises a pivotable shaft, each forming member being typically mounted at the end of the shaft. The extent of pivoting may be variable so as to enable different degrees of deformation to be achieved. Usually, forming members may comprise ball bearings, profiled rollers or a combination of balls and rollers. The rollers may have a profile which is complementary to that desired in the final shape of container. According to a further aspect of the present invention, there is provided a method for shaping a container having a side wall and a peripheral portion adapted to be connected to a closure, the method comprising: holding a container for forming; inserting at least one rotatable forming member into a container; moving the or each forming member radially outwards against the side wall of the container; and moving the or each forming member longitudinally and/or circumferentially along the inside of the side wall such that the or each forming member rotates; whereby, when the stress generated in the side wall by the moving steps exceeds the yield stress of the material of the side wall, the method creates permanent deformation in the side wall.

The step of rotating the or each forming member may comprise moving the or each forming member around, up or down the side wall. Movement of ball bearings up or down the side wall without any movement around the wall results in a fluted profile. A fluted or panelled effect is thus obtainable with the number of flutes/panels being equivalent to the number of forming members provided.

A cylindrical container wall may thus be deformed in three separate movements of the apparatus/method of the present invention giving radial, circumferential and/or longitudinal deformation. Carefully controlled co- ordmation of axial/rotational movement and radial force enables a complex profile to be produced in the container wall, including a combination of shapes and flutes, as αesired. For production purposes, the tool may be installed on a carousel or turret handling system in order to provide a continuous forming process at commercially desirable line speeds.

Preferred embodiments of the invention will now be described, with reference to the drawings, in which: Figure 1 is a partial side section of a first embodiment of shaping apparatus;

Figure 2 is a plan section of the apparatus of figure 1; Figure 3 is a partial side section of the apparatus of figures 1 and 2, showing formation of a circumferential bead shape;

Figure 4 is a partial side section of the apparatus of figures 1 and 2, showing deformation of an enlarged lower cup shape;

Figure 5 is a partial side section of the apparatus of figures 1 and 2, showing formation of a longitudinally curved shape.

Figure 6 is a partial side section of a second emoodiment of shaping apparatus; and

Figure 7 is a partial side section of a third erruDodiment of shaping apparatus.

Fxgure 1 shows a shaping apparatus 1 m which forming members comprising ball bearings 2 are disposed around the periphery of a pair of frustoconical discs 3 and 4. The discs are attached to a common shaft 5, which comprises an inner sleeve 6 and an outer sleeve 7. Lower disc 3 is fixed to the end of inner sleeve 6 and upper disc 4 is fixed to outer sleeve 7. In this manner the two discs are independently rotatable about a common axis by independent rotation of the inner and outer sleeves of the shaft 5.

The discs 3 and 4 are moveable towards/away from each other by longitudinal movement of respective sleeves of the shaft 5. Movement towards each other causes a squeezing action to be applied on the ball bearings by the conical portions 8 of the discs 3 and 4. This squeezing action forces the ball bearings radially outwards from the discs and into contact with a container side wall. By varying the degree of longitudinal movement of the shaft sleeves 6 and 7, the amount of lateral movement of the balls can be adjusted according to the amount of deformation required in the side wall.

It can be seen that the apparatus is compact and can easily be inserted into the container to be formed.

In figure 2, a schematic plan view of the apparatus of figure 1 shows cage components 9 which retain the ball bearings 2 in position around the circumference of the discs 3 and 4 within their working range of lateral movement. As shown in figure 2, the cage components 9 hold the ball bearings m separation from each other but do not restrict their ability to rotate freely.

Typically, the cage itself is similar to that used in conventional roller element bearings and comprises a spoked device, components 9 being ends of the individual spokes. The cage itself is optional in that its prime purpose is to restrain the forming members (that is ball bearings in this example) from becoming detached from the rest of the apparatus. However alternative restraining mechanisms may be used such as choice of a disc size which causes the ball bearings to contact both the inner wall of the container to be shaped and the conical portion of the discs. In that configuration, the shaping apparatus should be withdrawn from the shaped container, as this is removed and an unformed container is positioned, into a hollow retention bore. The bore is of approximately the same size as the shaped container, this preventing loss of ball bearings.

Operation of the apparatus of figures 1 and 2 can be seen in more detail in figures 3 to 5. The apparatus is first inserted into a container such as a metal can 10 until the apparatus is at the desired height from the base of the can for the formation of the relevant shape. The inner sleeve 6 of the shaft 5 is then pulled upwardly and the outer sleeve pushed downwardly so as to force the discs 3 and 4 towards each other. This movement is continued until the required increase in diameter is achieved in the can side wall as this deforms to the shape of the ball bearing. For permanent deformation to take place, that deformation must be sufficient for the stress which arises in the can side wall to exceed the yield stress of the material of the side wall.

At the same time as application of this squeezing action on the ball bearings, the shaft 5 is rotated about its longitudinal axis, thus causing the ball bearings to rotate around the circumference of the can side wall. It is believed that it is only this combination of rotation of the ball bearings and lateral movement of the balls against the side wall which has enabled deformation of up to about 10% of the diameter of 211 (66mm) wall ironed two piece steel and aluminium cans. Significantly more deformation is possible with three piece cans since the material of the can side wall is less work hardened than wall-ironed side wall material .

The shape formed by the rotation of shaft 5 in figure 3 leads to a circumferential bead shape in the container wall. In figure 4, the apparatus 1 has been inserted to the base of the inside of the container and, with the ball bearings 2 pressing outwards against the container wall and the disc 3 and 4 maintained in close position, the shaft is both rotated and retracted upwardly out of the container. In this way the ball bearings are rolled around and up the side wall so that the basic circumferential shape of figure 3 is extended up the side wall to provide a cup shape in the lower portion of the container.

Yet another type of shape is shown in figure 5, in which the method used for the shape of figure 4 is combined with relative disc movement obtaineα by reciprocating motion of the sleeves 6 and 7 of the shaft 5. As the discs 3 and 4 are gradually moved towards each other, the ball bearings are forced radially outwards and the diameter of the container side wall increases as at 11. Gradual movement of the discs away from each other reduces the radial force acting on the ball bearings and thereby expansion of the side wall, allowing the side wall to decrease in diameter again, as at 12. Instead of rotating the shaft 5 so as to roll any shape around the container side wall, the shaft may simply be retracted from the container whilst the discs are held close to each other. In this way, the ball bearings 2 are rolled up the side wall to produce a vertical fluted pattern in the side wall.

It can therefore be seen that a combination of shaft rotation, longitudinal upward or downward movement of the shaft and relative axial movement of the discs 3 and 4 enables a wide variety and combination of shapes/flutes to be provided in the side wall. Such combinations may be used to create highly complex shapes by pre- programming of a drive mechanism for the individual movements.

Although all the examples described herein have used discs to produce a bead at constant height from the base of the container, variations may be made by use of an eccentric shaft or by having the discs mounted with different axes of rotation. For example, elliptical shapes could be produced by eccentric mounting, or the feature could be rolled around the can wall at varying height from the base to produce an inclined bead feature. It will be appreciated that whereas the container is generally held stationary in a chuck or similar clamping device, rotational or longitudinal movement of the shaft 5 may be replaced or enhanced by movement of the container itself to produce the same shaping/fluting effects. Movement of both container and shaft enables combined forming speeds to be increased without the need for either container or shaft independent speeds themselves to be significantly high.

Although not shown in the drawings, the shaft 5 and discs 3 and 4 may incorporate ducts through which cooling fluid may be transmitted around the apparatus and thus enable higher process speeds to be achieved without over- heatmg. Even without the provision of ducts, it is believed that rotation speeds in excess of 2000 rpm are possible which can produce an increase in side wall diameter of around 10% in only a few milliseconds. The apparatus shown in figures 1 to 5 can be used to achieve high speeds and very high flexibility in the production of shapes. However, the apparatus is limited in its use by the time which is required to progress the shape along the side wall of the container. If attempts are made to progress to shaping at too fast a rate, this will become apparent as forming ridges arise m the surface finish. The relationships between axial movement of the ball bearings and rotation of the shaft 5 is also important in establishing the maximum forming speeds possible whilst maintaining surface quality.

An alternative type of forming member which uses the same disc actuation method is shown in figure 6. The apparatus is particularly suitable for obtaining fast rates of shaping albeit with less flexibility of shaping than is possible when using ball bearings. In this embodiment, the ball oeanngs have been replaced by caged or uncaged profiled rollers 20, which have dedicated complementary shapes to that required in the finished container side wall. Such rollers are able to shape an extensive portion of the side wall with no or limited longitudinal movement of the shaft 5 and may have more complex profiles than are shown in figure 6.

The discs used m combination with rollers as the forming members are often complementary in shape to the rollers themselves. As in the methods using ball bearings, rotation and radially outward movement of the rollers must create a stress in the material of the container side wall which exceeds the yield stress of the material, if the deformation is to be permanent.

Where shaping of a greater height of the side wall is required, it is possible to use further sets of rollers 21 with their own disc actuation as shown in figure 7. Upper rollers 21 in figure 7 are forced outwardly in the same manner as lower rollers 20 by relative axial movement of discs 23 and 24. Disc 24 is fixed to the outermost sleeve 28 of shaft 22 and disc 23 is fixed to sleeve 27. Operation of the relative disc movement is achieved in the same manner as is described above. Separate sleeves 26 and 25 of shaft 22 are used for relative movement of the lower discs 4 and 3 respectively. Thus nesting of shaft sleeves 25, 26, 27 and 28 enables independent movement of each disc or disc pair to be achieved, if desired.

An alternative method of actuation of ball bearings and/or profiled rollers (not shown) is to pivot the forming members about a fulcrum point on a central shaft. The forming members may be connected directly to the central shaft or may have independent shafts wnich are connected to tne fulcrum point. Direct or indirect connection to the central shaft eliminates the need for any cage arrangement or hollow bore into which the apparatus might otherwise need to be retracted after forming has taken place.

Typically, the fulcrum point comprises a spherical bearing and radial actuation of the forming members is achieved by means of a cam or other mechanical means. In all the above methods, it is envisaged that greater process control is obtainable by pressurising the container prior to the shaping operation. Typically pressurising by a suitable fluid would be used to assist in supporting and stabilising the can during the shaping process. Generally, air would be used for pressurisation, although water may alternatively be used if some cooling of the container is desirable.

Example 1

Three two piece aluminium beverage cans having an external diameter of 66mm (standard 211 can) were placed in a test rig and a forming apparatus as shown in figure 1 inserted. The forming apparatus used 13 ball bearings, each having a diameter of 12.65mm ( " ) .

Adjustment of the relative disc portion was made to provide corresponding tooling diameter movement as indicated in table 1. Each can was manually rotated to provide a bead-like deformation by rolling the deformation around the can wall. Measurements of can wall thickness were taken both before and after forming, the latter comprising averages of measurements of the bead feature itself and above and below the feature. The results obtained are also shown in table 1.

Table 1

Tooling Original Feature Thickness Thickness diameter thickness thickness above below movement (mm) (mm) (mm) (mm) (mm)

4 0.168 0.095 0.115 0.105

3 0.175 0.111 0.105 0.11

4 + 2 * 0.180 0.105 0.155 0.115

* Two measurements of 4mm and 2mm respectively, giving a total movement of 6mm. Example 2

Six two piece aluminium beverage cans having an external diameter of 66mm (standard 211 can) were shaped with a static bead feature using the method of example 1 and height and diameter readings taken. The results are given in table 2.

Table 2

Tooling Original Height Base Feature Diameter diameter can after outside outside increase movement height forming diameter diameter (%)

(mm) (mm) (mm) (mm) (mm)

3 116.76 116.08 66.2 69.2 4.5

4 116.70 115.75 66.22 69.6 5.1

4 116.70 115.70 66.28 70.1 5.8

6 * 116.62 115.50 66.24 70.32 6.2

+ 1 * 116.70 115.42 66.36 70.0 5.5

5 116.70 115.64 65.9 70.2 6.5

some buckling on forming.

example 3

Three two piece aluminium beverage cans having an external diameter of 66mm (standard 211 can) were shaped with a static bead feature using the apparatus of example 1. A tooling diameter movement of 4mm was used to form the bead which was then extended vertically up the can side wall to give a band shape as shown in figure 4. The cans were rotated on a milling machine chuck at the speeds shown in table 3. Height and diameter readings were taken, these results also being given in table 3. Tabl e 3

Vertical Original Height Base Feature Diameter movement can after outside outside increase

(mm) height forming diameter diameter (%) and rpm (mm) (mm) (mm) (mm)

20 @ 278 116.62 115.90 66.3 68.52 3.3

20 @ 588 116.52 115.36 66.36 69.50 4.7

25 @ 278 116.68 115.18 66.22 68.84 4.0

Example 4

Four two piece steel beverage cans having an external diameter of 66mm (standard 211 can) were shaped with a static bead feature using the apparatus of example 1. In the latter two cans, the bead was extended vertically up the can side wall by 20mm to give a band shape as shown in figure 4. The cans were rotated on a milling machine chuck at 278rpm. Height and diameter readings were taken, these results being given in table 4.

Table 4

Tooling Original Height Base Feature Diameter diameter can after outside outside increase movement height forming diameter diameter %

(mm) (mm) (mm) (mm) (mm)

4 115.0 114.72 65.9 67.76 2.8

5 115.0* 114.42 65.9 68.28 5.8

4 115.0 115.0 65.9 66.28 5.8

5 115.0 Bad buckling - no measurable feature

Slight buckling below the feature. Example 5

Three steel can bodies (ie without base) for three piece food cans having an internal diameter of 65mm were shaped with a static bead feature using the apparatus of example 1. In the third can, the bead was extended vertically by 20mm up to the can side wall to give a band shape as shown in figure 4. The cans were rotated on a milling machine chuck at 278 rpm. Height and diameter readings were taken, these results being given in table 5.

Table 5

riginal Height Base Feature Dia eter diameter can - after outside outside increase movement height forming diameter diameter (%)

(mm) (mm) (mm) (mm) (mm)

4 160.62 160.0 65.70 68.58 4.4 5 160.72 160.1 65.62 69.24 5.5 4 160.82 160.0 65.5 69.78 6.5

Claims

1. An apparatus for shaping a container having a side wall and a peripheral portion adapted to be connected to a closure, the apparatus comprising: at least one forming member which is rotatable about its own axis; means for moving the or each forming member radially outwards against the inside of the side wall; and means for supporting the or each forming member such that it can rotate longitudinally and/or circumferentially along the inside of the side wall, the or each forming member being mounted for free rotation on the moving means; whereby, in use, pressing and rotating the or each forming member on the side wall generates a stress in the side wall such that, when the stress exceeds the yield stress of the material of the side wall, permanent deformation is created in the side wall.

2. An apparatus according to claim 1, in which the container is mounted on a holder and either or both of the holder and supporting means are rotatable relative to each other.

3. An apparatus according to claim 1 or claim 2, in which the moving means comprises a pair of discs and the or each forming member is mounted between the discs.

4. An apparatus according to claim 3, in which the or each forming member is retained at least partially between the discs by a cage device.

5. An apparatus according to claim 1 or claim 2, in which the moving means comprises a pivotable shaft.

6. An apparatus according to any one of claims 1 to 5, in which the or each forming member comprises a ball bearing or profiled roller.

7. A method for shaping a container having a side wall and a peripheral portion adapted to be connected to a closure, the method comprising: holding a container for forming; inserting at least one rotatable forming member into a container; moving the or each forming member radially outwards against the side wall of the container; and moving the or each forming member longitudinally and/or circumferentially along the inside of the side wall such that the or each forming member rotates; whereby, when stress generated in the side wall by the moving steps exceeds the yield stress of the material of the side wall, the method creates permanent deformation in the side wall.

8. A method according to claim 7 in which the step of circumferentially moving forming members comprises rotating the container holder and/or a forming member support relative to each other.

9. A method according to claim 7 or claim 8 in which the step of circumferentially moving forming members comprises rotating the container holder and a forming member support in opposite directions.

10. A method according to any one of claims 7 to 9, further comprising pressurising the container prior to the shaping steps.

11. An apparatus substantially as hereinbefore described, with reference to figures 1 to 5 or to figures 6 and 7 of the drawings.

12. A method substantially as hereinbefore described, with reference to figures 1 to 5 or to figures 6 and 7 of the drawings .