WO2002038301A1

WO2002038301A1 - Process for can manufacture

Info

Publication number: WO2002038301A1
Application number: PCT/AU2001/001471
Authority: WO
Inventors: John Evans
Original assignee: Amcor Packaging (Australia) Pty Ltd
Priority date: 2000-11-13
Filing date: 2001-11-13
Publication date: 2002-05-16
Also published as: AU2002214816A1; AUPR144100A0

Abstract

A process for manufacturing a can body comprising the steps of: (a) cutting a blank from a material and drawing the blank into a cup using a vertical press (3) in a first continuous step; and (b) using a horizontal press and redrawing die (4) to redraw the cup to the desired can diameter and forming a dome in the can bottom using a doming die in a second continuous step and a can body manufactured according to the process.

Description

Process for can manufacture

Field of the invention

The present invention relates to a process for manufacturing can bodies, particularly can bodies for hermetic containment of food. More particularly the invention relates to a novel process for manufacturing two piece cans suitable for hermetic containment of food.

Background of the invention

In this specification, where a document, act or item of knowledge is referred to or discussed, this reference or discussion is not an admission that the document, act or item of knowledge or any combination thereof was at the priority date, publicly available, known to the public, part of the common general knowledge; or known to be relevant to an attempt to solve any problem with which this specification is concerned.

Consumable goods are packaged in a wide range of containers constructed from a range of . materials. One of oldest and most efficient methods for long term containment of consumable goods are metal cans, preferably made of steel or aluminium. Cans are popular because they maintain the condition of goods and resist spoilage.

Cans for beverages usually differ from cans for food both in appearance and method of manufacture, although some beverage cans have in recent times been adapted for containment of food. Any traditional differences between the cans used for beverages and cans used for food can be attributed in part from the tendency of the food industry and the beverage industry to source their cans from different manufacturers who have developed independent manufacturing processes.

Commonly, cans for food are made from three pieces; a first piece comprising a cylinder; and a second piece and third piece forming closures at either end of the cylinder.

The process for manufacturing the body of a three piece food can is depicted schematically as follows;

COIL CUTTING COATING & SLITTING

FEEDING DECORATING |

NECK/FLANGE - — BEADING WELDING ROLLFORMING

FORMING

The process is commenced by feeding a coil of material such as steel or aluminium through a cutter that reduces it to predetermined lengths. Coatings may be applied to the surfaces of the material. For example protective coatings may inhibit reaction between the food stored in the can and the interior can surface. The exterior surface of the can may have a basecoat, decorative ink and lacquer applied both for aesthetics and protection.

The material is then passed through a slitting machine that slits the material into square or rectangular sheets that are fed into a roll former, forming them into cylinders that are welded along a longitudinal seam to form the can body. The body is beaded before the open end of the can body is necked, that is, the can end is slightly reduced in diameter. A spin necker and flanging device then remove ridges left in the can neck by the necker and a small flange is formed to facilitate addition of a closure at a later date. A closure piece is appHed to the bottom end of the cylinder, thus completing formation of the can body. The can bodies are then palletised or otherwise packaged for transport to food manufacturers. The manufacturers fill the can body with their food product and apply a closure to the necked/ flanged end of the can body. The neck/flange on the can body facilitates application of a closure at the top of the can body that is slightly smaller than the closure at the bottom, thus enabling the finished cans to be readily stacked.

The three piece design for food cans (as described above) has existed for at least 50 years, and the process for manufacture has undergone very little change during this time. It is only relatively recently that the two piece can design (as described below) has been used for food containment. One of the disadvantages of the three piece can manufacture process is that decoration has to be applied to the flat material prior to rollforming and welding. The manufacturing process involves relatively harsh handling of the can and application of relatively high temperatures thus limiting the types of decorative ink used. In general, manufacturers of three piece cans apply up to ten basic ink colours and many print styles and fonts. However, because the three piece process a batch process, with every step running separately from the others, the process is relatively slow.

By contrast with food cans, beverage cans have traditionally been manufactured from two pieces; a first piece forming a generally cylindrical can body closed at one end and a second piece applied as a closure to the open end of the can body. Because they have no seams, and fewer pieces to join, two piece cans have less potential for leakage or rupture (as compared with three piece cans) and are thus particularly favoured for carbonated beverages that are contained at a pressure greater than 1 atmosphere.

The process for manufacturing the two piece beverage can is depicted schematically as follows;

COIL CUPMAKING BODYMAKING TRIMMING

FEED PRESS |

NECK/FLANGE INTERNAL - — DECORATING WASHING FORMING SPRAYING

The process is commenced by feeding a coil of material such as steel or aluminium to a cupmaking press. The cupmaking press is essentially a vertical press which first cuts a circular blank and then draws the blank into a cup shape.

The cup is passed to a bodymaker which is a hori2ontal press consisting of a redraw die, two or three ironing dies and a doming die. The cup is thus redrawn to the desired can diameter, ironed out to form the long sides of the can body, and then the bottom of the can body is pressed against a die that forms the domed base. A trimmer then trims the can body to the desired height so that all can bodies produced are of uniform height. The can body is washed to remove any lubricants that may have been appHed during processing.

Coatings may be appHed to the surfaces of the material. For example a decorative coating may be appHed to the outer surface of the can body and/or a protective coating may be sprayed over the inside of the can.

A neck is formed at the open end of the cylinder before the can body passes to a spin necker and flanger. The can bodies are then paUetised or otherwise packaged for transport to food manufacturers for filling with food and appHcation of a closure to the necked/ flanged end of the can body. One of the advantages of the two piece process is that the decorative coating is appHed after the can body has been worked and formed and otherwise subjected to relatively rough processing that would damage the decorative coating. The two piece printing process is limited to a base coat and up to eight separate colours. However, the two piece process is continuous and far more rapid than the three piece can forming process. Given the advantage of the two piece can making process it is not surprising that some manufacturers have used the process to make cans for the food industry. However, two piece cans formed by this process have not managed to replace three piece cans as preferred cans for food containment. One of the principal reasons is that an existing manufacturing line for producing three piece cans cannot be readily adapted to the two piece process. A new production line would have to be assembled for this purpose, thus incurring high capital expenditure. Furthermore, the process reHes upon economy of scale and may be attractive for manufacturers supplying large scale markets such as the US, but the process is considerably less attractive for manufacturers supplying to smaller markets such as AustraHa and New Zealand. Accordingly, attempts have been made to apply the two piece can making process to the manufacture of cans for food containment. The process consists of the foUowing steps;

COIL CUPMAKING REDRAWING TRIMMING

FEED PRESS I

NECK/FLANGE FORMING

The process is again commenced by feeding a coil of material such as steel or aluminium to a cupmaking press which cuts a circular blank that is drawn into a cup shape.

The cup is then passed to a purpose built redraw die so that the cup can be redrawn. Both the cupmaking press and redraw press are vertical presses. The can body thus formed is trimmed, and the open end of the can body is necked and flanged. The products are then paUetised or otherwise packaged for transport to food manufacturers who fill the can body with food and apply a closure to the necked/ flanged end of the can body.

The main disadvantage of this process is that it can only be used to manufacture a can falling within a Hmited range of aspect ratios. In general, the process can only be used to form cans of relatively short sides, and thus low volume.

Object of the invention

It is an object of the present invention to provide a process for the manufacture of can bodies and two piece cans which is not Hmited to manufacture of cans of low aspect ratio. It is a further object to provide a process that can provide good economy of scale and can be configured by modifying existing equipment.

Summary of the invention

The present invention provides a process for manufacturing a can body comprising:

(a) cutting a blank from a material and drawing the blank into a cup using a vertical press in a first continuous step; and

(b) using a horizontal press and redrawing die to redraw the cup to the desired can diameter and forming a dome in the can bottom using a doming die in a second continuous step.

TypicaUy a conventional cup making press is used to cut a circular blank of material and draw the blank into a cup.

TypicaUy the redrawing and dome formation is carried out using a modified bodymaker, the bodymaker having a horizontal pressing action. The bodymaker is modified by removing or bypassing the ironing dies, thus leaving the redraw die and doming die.

The can body thus formed may then be subjected to the steps of: (a) triinming the can body to desired height;

(b) optionaUy applying coatings to the can body;

(c) applying a neck to the open end of the can body; and

(d) spin necking the open end of the can body and applying a flange.

It will be readily apparent to those skilled in the relevant art that the steps of trimming, coating, necking, spin necking and applying a flange may be carried out using any relevant apparatus known in the industry.

The can bodies thus formed may then be paUetised or otherwise packed for transport to food manufacturers for filling and appHcation of a can end.

Embodiments of the invention will now be described with reference to the foUowing non- Hmiting examples of the invention. Example

A coU of aluminium sheet loaded on an uncoiler was fed through a lubricator to apply a thin film of lubricant to the aluminium and into a cupper. The cupper, cut circular blanks of aluminium sheet that were drawn into a cup shape at the rate of 2000 cups/minute. The cups then passed to a bodymaker from which the ironing dies had been removed, leaving the redraw die and doming die. The cups where redrawn to form a can body approximately 12 cms in height, 7 cms in diameter with a domed base. The can bodies thus formed were passed to a trimmer, and trimmed to uniform height.

The cans were then washed with water and deionized water to remove the lubricant appHed earHer. The cans then passed to a basecoater which appHed white basecoat for a good quaHty appearance. The basecoat was dried and cured in an oven. A decorator then appHed decorative ink, foUowed by a thin film of lacquer to protect the can and ink. A bottom rim coater then appHed a coat of lacquer to the base rim of the can. The inks and lacquer were dried and cured in a decorator oven. An internal lacquer spray machine then appHed lacquer to the inside of the can body to protect product integrity. The internal lacquer was then cured in an internal bake oven.

A waxer then appHed a thin coat of lubricant to the outside of the open end of the can to facilitate the necking process. A necker "necked in" the open end of the can body to facilitate later appHcation of a closure. A spin necker removed ridges left in the can neck by the necker and a flanger appHed a smaU flange to the neck. A closure was then appHed to the neck.

The cans thus formed were passed through a Hght tester in order to detect any physical damage that could cause leakage in a finished can fiUed with food. The cans were subjected to testing and satisfied the relevant AustraHan Standards Association guidelines.

Description of the drawings The invention will now be further explained and illustrated by reference to the accompanying drawings in which:

Figure 1 is a schematic view of a can forming process according to one embodiment of the present invention/ The reference numerals included in the drawing of Figure 1 relate to the foUowing apparatus used in the process;

1. uncoUer 10. bottom rim coater

2. lubricator 11. decorator oven

3. cupper 12. internal spray

4. modified bodymaker 13. internal bake oven

5. trimmer 14. waxer

6. washer 15. necker

7. basecoater 16. spin necker/flanger

8. basecoater oven 17. Hght tester

9. decorator 18. paUetiser

19. strapper

The drawing of figure 1 shows a coU of alurniniurn sheet loaded on an uncoUer (1) being fed through a lubricator (2) which appHes a thin film of lubricant to the aluminium. The lubricated aluminium sheet passes into the cupper (3) which cuts circular blanks of alurniniurn from the sheet and then draws the blanks into a cup shapes.

The cups then pass to a modified bodymaker(4) from which the ironing dies had been removed, leaving the redraw die and doming die. The redrawn cups thus formed are passed to a tritnrner (5), and trimmed to uniform height. The cans are then washed in a washer (6) and passed to a basecoater (7) which appHes white basecoat for a good quaHty appearance. The basecoat is dried and cured in a basecoater oven (8). A decorator (9) then appHes decorative ink, foUowed by a thin film of lacquer. A bottom rim coater (10) then appHes a coat of lacquer to the base rim of the can. The inks and lacquer are dried and cured in a decorator oven(l 1). An internal lacquer spray machine (12) then appHes lacquer to the inside of the can body to protect product integrity. The internal lacquer is then cured in an internal bake oven (13).

A waxer (14) then appHes a thin coat of lubricant to the outside of the open end of the can to facilitate the necking process. A necker (15) "necks in" the open end of the can body to facilitate later appHcation of a closure. A spin necker/ flanger (16) removes ridges left in the can neck by the necker and appHes a smaU flange to the neck.

The can bodies thus formed are passed through a Hght tester (17) in order to detect any physical damage that could cause leakage in a finished can filled with food. Cans that pass the Hght test are packed onto a transportation paUet by a paUetiser (18) and strapped into place by a strapper (19).

Whilst the present invention has been described in relation to particularly preferred embodiments, it is to be appreciated that other construction and arrangements faU within the scope of the invention. Various modifications, alterations, variations and/or additions to the constructions and arrangements described herein are also considered as falling within the scope and ambit of the present invention.

Furthermore, the word 'comprising' and forms of the word 'comprising' as used in this description does not limit the invention claimed to exclude any variants or additions.

Claims

The claims defining the invention are as foUows;

1. A process for manufacturing a can body comprising:

(a) cutting a blank from a material and drawing the blank into a cup using a vertical press in a first continuous step; and (b) using a horizontal press and redrawing die to redraw the cup to the desired can diameter and forming a dome in the can bottom using a doming die in a second continuous step.

2. A process according to claim 1 wherein a conventional cup making press is used in step (a) to cut a circular blank of material and draw the blank into a cup.

3. A process according to claim 1 wherein a modified bodymaker having a horizontal pression action is used in step (b) to redraw the cup form the dome.

4. A process according to claim 3 wherein the bodymaker is modified by removing or bypassing ironing dies to leave the redraw die and doming die.

5. A process according to claim 1 wherein the can body thus formed is subjected to the subsequent steps of:

(c) teώiming the can body to desired height;

(d) optionaUy applying coatings to the can body;

(e) applying a neck to the open end of the can body; and

(f) spin necking the open end of the can body and applying a flange.

6. A process according to claim 1 or 5 wherein the can body formed is packed for transport.

7. A process for manufacturing a can body comprising:

(a) feeding a coU of metal sheet from an uncoUer through a lubricator and into a cupper, cutting a blank from the metal sheet and drawing the blank into a cup using a vertical press in a first continuous step; and (b) using a modified bodymaker compπsing a horizontal press and redrawing die to redraw the cup to the desired can diameter and forming a dome in the can bottom using a doming die in a second continuous step.

(c) using a trimmer to trim the can body to desired height; (d) washing the can body then passing the washed can body to a basecoater to apply basecoat then drying and curing the basecoat in an oven,

(e) passing the basecoated can body to a decorator to apply decorative ink, foUowed by a thin film of lacquer,

(f) passing the decorated and lacquered can body to a bottom πm coater to apply a coat of lacquer to the base rim of the can, then drying and curing the inks and lacquer in a decorator oven,

(g) passing the lacquer coated can body to an internal lacquer spray machine to apply lacquer to the inside of the can body, then curing the internal lacquer an internal bake oven. (e) applying a thin coat of lubncant to the outside of the open end of the can before passing the can to a necker to neck in the open end of the can body,

(f) passing the necked can body to a spin necker to removed ndges left in the can neck by the necker,

(g) passing the necked can body to a flanger to apply a smaU flange to the neck and then applying a closure to the neck.

8. A process according to any of the preceding claims wherein the redrawn can bodies are 11 to 13 cms in height and 6 to 8 cms in diameter with a domed base closure.

9. A process according to any of the preceding claims wherein blanks are cut and drawn at a rate of 2000 cups/minute.

10. A can body produced according to the process of any one of the preceding claims.

11. A process according to claim 1 and substantiaUy as herein described with reference to the drawings.