CN115666810A

CN115666810A - Method and apparatus for producing two-piece can bodies from laminated metal sheets and two-piece can bodies produced thereby

Info

Publication number: CN115666810A
Application number: CN202180037302.4A
Authority: CN
Inventors: A·吉明克; J·琼克; L·J·比尔斯
Original assignee: Tata Steel Ijmuiden BV
Current assignee: Tata Steel Ijmuiden BV
Priority date: 2020-04-23
Filing date: 2021-04-23
Publication date: 2023-01-31
Also published as: WO2021214317A1; JP2023522449A; BR112022021052A2; KR20230002779A; MX2022013235A; ZA202211537B; US20230150009A1; CA3175814A1; EP4139066A1

Abstract

The present invention relates to a method and apparatus for producing a two-piece can body by drawing and ironing a laminated metal sheet, and more particularly to a method of manufacture which prevents friction from damaging or scratching the laminated layer on the can body during the ironing process of the can body, and to a drawn and ironed two-piece can body produced thereby.

Description

Method and apparatus for producing two-piece can bodies from laminated metal sheets and two-piece can bodies produced thereby

Technical Field

The present invention relates to a method and apparatus for producing a two-piece can body by drawing and ironing (ironing) a laminated metal sheet, and more particularly to a treatment method for preventing galling damage or scratches to a laminate layer on a can body during can body ironing, and a drawn and ironed two-piece can body produced thereby.

Background

Laminated metal sheets for packaging comprise a metal sheet and a laminate layer covering one or both sides of the metal sheet, wherein the laminate layer is produced by laminating the laminate layer onto the metal sheet by thermal bonding or by direct extrusion onto the metal sheet. The laminate layer comprises one or more thermoplastic polymer layers.

Laminated metal sheets are used to produce two-piece cans. Such cans consist of a can body comprising a base and a tubular body made of sheet metal coated on at least one side with a laminate layer, and a lid connected to the can body.

To produce can bodies, a disc (usually circular) is produced from a laminated metal sheet, the disc is then deep-drawn into a cup with the laminated layers at least on the outside, after which the cup is formed into a can body by a wall-reducing extrusion process which is carried out in a single stroke by successively punching the cup through a redraw ring and one or more wall-reducing extrusion rings (see fig. 1) using a punch in a stretch-and-reducing extrusion machine. The outer shape of the punch is generally cylindrical and therefore rotationally symmetrical and may have the same diameter on the operating portion, or the punch may have different diameters on the operating portion, for example in JP2000042644, EP0402006, WO2019154743, GB 2547016.

A separate punch is typically removably secured to the front end of a reciprocating ram in a deep drawing machine. The punch provides an inner mandrel on which the can is formed, drawn and reduced-diameter extruded as it passes through the one or more wall-reducing extrusion rings. The temperature of the punch is increased by the heat generated by the repeated frictional contact between the punch, the interior of the can body and the one or more wall reducing extrusion rings through which the punch moves. During the wall reducing extrusion process, the shear forces may become too high in the laminate layer itself. Such excessive shearing leads to an increased risk of damaging the laminate layer. One type of damage is so-called scuffing or fraying, which damages the laminate layer and can lead to direct contact between the metal substrate and the wall reducing extrusion tool and/or a visually unacceptable laminate layer finish, or in very severe cases, cracking of the can wall. Sufficient lubrication between the wall reducing extrusion tool and the laminate layer is important to prevent scratching or scuffing damage, and such lubrication may be provided by the polymer layer itself (dry process). However, due to the deformation process, the temperature of the metal sheet, the laminate layer, the redraw and reducing extrusion tooling ring, and the punch are increased. If the temperature of the laminate layer increases, the risk of damaging the laminate layer increases. Therefore, the temperature of the wall reducing extrusion tool must be kept below a critical value at which the risk of damaging the laminate layer starts to occur, which means that the productivity of the stretching and wall reducing extrusion process is thereby limited. The critical value depends on the composition of the laminate layer. In conventional can forming, an externally applied cooling fluid maintains operating temperature conditions. However, in dry DWI processes, no externally applied cooling fluid is used, as the externally applied cooling fluid may contaminate the container surfaces, thereby requiring post-forming cleaning processes that are costly and may be environmentally hazardous.

US2030084699 discloses a punch assembly that includes means for providing coolant to a circumferential channel so that the inner surface of the punch disposed at the end of a reciprocating ram in a stretch and reducing extrusion machine can be cooled. However, it has still been found that the use of the punch assembly results in galling damage and scuffing of the can body, particularly when the height of the can body is reduced and high speed production is performed.

Object of the Invention

It is an object of the present invention to provide a method of producing can bodies for two-piece cans produced from laminated metal sheets without abrasion or scratching of the laminate.

It is another object of the present invention to provide a method for producing can bodies of two-piece cans from laminated sheet metal at higher speed/reduced cost without abrasion or scratching of the laminate.

It is another object of the present invention to provide a method of producing two-piece can bodies at increased production speeds without scratching the laminate layers.

The object of the present invention is also to provide an apparatus for producing a can body according to the invention.

Description of the invention

The method according to claim 1 achieves one or more of the objects: a method for producing a can body from a laminated metal sheet by deep drawing and wall reducing extrusion, the can body comprising a base and a tubular body, for a two-piece can, wherein a disc is produced from the laminated metal sheet, the disc being deep drawn into a cup, the cup then being redrawn and the redrawn cup then being formed into a can body by wall reducing extrusion, wherein wall reducing extrusion occurs in a single stroke by punching the redrawn cup through one or more wall reducing extrusion rings by means of an internally cooled punch assembly, wherein the punch assembly comprises:

a ram (14),

a punch (1), preferably removably connected to the punch stem, said punch assembly comprising an internal annular cavity (15) below the surface of the punch between a position (15 a) near the distal end of the punch and a position (15 b) near the proximal end of the punch,

a plurality of cooling fluid inlets (16) for supplying cooling fluid into the inner annular cavity and a plurality of cooling fluid outlets (17) for removing cooling fluid from the inner annular cavity, wherein the inner annular cavity is provided with means for increasing the internal cooling efficiency of the ram,

wherein the means for increasing the internal cooling efficiency of the ram comprises an obstruction (18) in the internal annular cavity to increase turbulence in the cooling fluid during its travel from the cooling fluid inlet to the cooling fluid outlet and to provide a larger cooling surface for extracting heat from the ram, wherein the obstruction comprises

-non-continuous obstacles (18), such as chevrons, cylinders, continuous walls or discontinuous zigzag walls, or

-a plurality of continuous obstacles (18) in the form of adjacent spiral walls defining a plurality of spiral cooling channels in the inner annular cavity to guide the cooling fluid from the cooling fluid inlet to the cooling fluid outlet,

the ram comprising means for supplying cooling fluid to the cooling fluid inlet and removing cooling fluid from the cooling fluid outlet,

in order to effectively cool the punch internally during the production of the can body in order to prevent galling damage or scratching of the laminate layer on the tubular body of the can body, wherein

a. The cooling fluid inlet is disposed closer to the distal end of the punch and wherein the cooling fluid outlet is disposed closer to the proximal end of the punch, preferably wherein the cooling fluid inlet and the cooling fluid outlet are disposed in a regular pattern around the circumference of the punch, or wherein

b. The cooling fluid inlet is disposed closer to the proximal end of the punch and wherein the cooling fluid outlet is disposed closer to the distal end of the punch, preferably wherein the cooling fluid inlet and the cooling fluid outlet are disposed in a regular pattern around the circumference of the punch, or wherein

c. Cooling fluid inlets of some of the spiral cooling channels are disposed closer to the distal end of the punch, and wherein corresponding cooling fluid outlets are disposed closer to the proximal end of the punch, and wherein cooling fluid inlets of other spiral cooling channels are disposed closer to the proximal end of the punch, and wherein corresponding cooling fluid outlets are disposed closer to the distal end of the punch, such that some spiral cooling channels direct cooling fluid from the distal end to the proximal end of the punch, and other cooling channels direct cooling fluid from the proximal end to the distal end of the punch, preferably wherein the direction of the cooling fluid alternates from one spiral cooling channel to its adjacent spiral cooling channel, preferably wherein the cooling fluid inlets and cooling fluid outlets are arranged in a regular pattern around the circumference of the punch.

Thus, the invention is implemented in three different variants: a. b and c. Variants a and b differ in the position of the coolant inlet and outlet in the internal annular chamber with a discontinuous obstacle or a continuous obstacle (spiral cooling channel).

Variant c relates only to an embodiment in which the inner annular chamber is provided with a continuous obstacle in the form of a helical cooling channel.

Preferred embodiments are provided in the dependent claims.

The punch is attached to the end of the ram. Preferably, the punch is removably attached to the ram. This means that the punch, the outer surface of which directly contacts the can body, can be replaced without the need to replace the punch stem, for example if the punch is worn or damaged. However, the invention is also embodied in that the punch and the punch form one integral part, i.e. wherein the punch is non-removably attached to the punch, and wherein the internal annular cavity forms a cavity in the integral punch and punch assembly. If the punch portion is welded to the ram, the punch is considered to form an integral part of the ram and punch assembly because the punch is no longer easily removed from the ram. In such a configuration, if the punch portion wears or breaks, the punch stem and punch combination must be replaced.

Where the ram is removably attached, the obstruction in the inner annular cavity is preferably part of the ram, and therefore is removed with the ram when the ram is removed. Less preferably, the obstruction is formed directly on the punch and therefore remains behind the punch if the punch is removed from the punch. The two embodiments are identical in form when the punch is mounted on the ram.

The method according to the invention is based on improving the internal cooling of the punch assembly by increasing the cooling efficiency. This is achieved by increasing the degree of turbulence in the cooling fluid passing through the punch and by increasing the contact surface between the cooling fluid and the punch. The invention achieves an increase in turbulence in the cooling fluid and an increase in the contact surface between the cooling fluid and the punch by providing discrete or continuous obstacles in the inner annular cavity. The punch includes an internal annular cavity that extends the length of the punch just below the surface of the punch that is in contact with the side wall of the can body during the wall reducing extrusion step. The distance between the surface of the punch and the internal annular cavity, i.e., the wall thickness, must be thick enough to withstand the mechanical stresses of the deep drawing and wall reducing extrusion processes and maintain its dimensions, but thin enough to maximize heat transfer from the surface of the internal annular cavity to the cooling fluid flowing through the cavity. Through the inner annular cavity, cooling fluid may be directed from a cooling fluid inlet at one end of the inner annular cavity to a cooling fluid outlet at the other end of the inner annular cavity. In this manner, heat may be drawn from the punch by the cooling fluid, and the surface temperature of the punch may be maintained below a critical value to prevent scratching or wear damage. Without any obstacle in the inner annular chamber, as is the case in the prior art, the cooling fluid flows directly and laminar between the cooling fluid inlet and outlet. This means that the cooling fluid has little time to absorb heat and, due to the laminar flow, the cooling capacity of the cooling fluid is not used efficiently. Note that typically the redraw ring and the reducing extrusion ring also have internal cooling channels that cool the outer laminate layer of the can. However, most of the heat will be dissipated by the cooled punch because of its longer contact time and larger contact area with the laminate layer.

The cooling fluid is not particularly limited. Water, preferably demineralized water, has proven to be very suitable. Preservatives may be added to the cooling fluid.

The obstruction disrupts the flow of the cooling fluid and also increases the cooling surface of the ram, so the ability to transfer heat from the ram into the cooling fluid increases due to the increase in cooling surface and the increase in turbulence, as turbulence is able to absorb more heat than laminar flow.

In embodiments of the invention, the discontinuous obstacles in the inner annular cavity may for example comprise posts (cylindrical or other shape), chevrons, discontinuous short walls (which are perpendicular to or angled to the flow of cooling fluid through the cavity), or discontinuous zig-zag walls. The outer shape of the punch is preferably rotationally symmetrical with respect to the centre line of the punch.

The continuous obstruction extends the contact time between the cooling fluid and the ram because the obstruction forces the cooling fluid to take a longer path between the cooling fluid inlet and the cooling fluid outlet, and the contact surface of the inner annular cavity becomes larger due to the presence of the discontinuous obstruction in the inner annular cavity. Moreover, the path is longer due to the presence of the continuous obstacles, the area through which the cooling fluid has to flow becomes smaller, and this in turn increases the turbulence in the fluid.

The method according to the invention thus results in a more efficient cooling of the punch compared to the punches of the prior art, and thus in a lower surface temperature of the punch. The cooler pressing temperature results in a lower laminate layer temperature during the wall reducing extrusion process and thus prevents such damage in the laminate layer that is prone to scuffing or fraying damage, and the production speed of the can body can be increased, since the risk of scuffing or fraying damage in the laminate layer becomes significant at higher production speeds than is the case in the prior art.

In one embodiment of the invention (variant a), the cooling fluid inlet is arranged closer to the distal end of the punch and the cooling fluid outlet is arranged closer to the proximal end of the punch. Preferably, the inlet and outlet ports are arranged in a regular pattern around the periphery of the punch. In another embodiment of the invention (variant b), the cooling fluid inlet is arranged closer to the proximal end of the punch and wherein the cooling fluid outlet is arranged closer to the distal end of the punch, preferably wherein the inlet and outlet are arranged in a regular pattern around the circumference of the punch. In variants a and b, the means for increasing the internal cooling efficiency of the punch consist of a continuous obstacle in the form of a discontinuity or a plurality of adjacent spiral walls delimiting a plurality of spiral cooling channels in the internal annular cavity.

In another embodiment of the invention (variant c), the continuous obstacle is a spiral wall in the internal annular cavity, forming a spiral cooling channel in the internal annular cavity. In this embodiment, a portion of the cooling fluid inlets are disposed closer to the distal end of the punch and wherein the other cooling fluid inlets are disposed closer to the proximal end of the punch such that some of the helical cooling channels conduct cooling fluid from the distal end to the proximal end of the punch and the other cooling channels conduct cooling fluid from the proximal end to the distal end of the punch, preferably wherein the direction of the cooling fluid alternates from one helical cooling channel to its adjacent helical cooling channel.

It should be noted that the spiral is shaped like a spiral staircase. It is a smooth spatial curve with a tangent at a constant angle to the fixed axis. The circular helix of radius a and slope b/a (or pitch 2 nb) is described by the following parameterization:

x(t)＝a·cos(t) y(t)＝a·sin(t) z(t)＝b·t

according to the invention, the number of helically continuous obstacles must be such as to form a plurality of and preferably at least three helically cooling channels. Each spiral cooling channel is preferably provided with its own cooling fluid inlet and its own cooling fluid outlet. The inventors have found that three or more spiral cooling channels result in very efficient cooling, as the length of the channels enables the cooling fluid to effectively and efficiently cool the working surface of the punch. In the case of one or two cooling channels, the cooling efficiency is significantly reduced and the risk of scratching or scuffing damage of the laminate layer is increased. Preferably, the punch comprises at least four adjacent helical cooling channels, more preferably at least five adjacent helical cooling channels, even more preferably at least six adjacent helical cooling channels. The inventors have found that six channels result in the best combination of cooling capabilities without unduly complicating the design of the punch. Preferably, the inlets and outlets for the cooling fluid are arranged in a regular pattern around the periphery of the punch, i.e. 60 ° between each inlet or outlet around the periphery for a six-channel embodiment, or 72 ° for a five-channel embodiment. Although one inlet may be used for more than one spiral channel or one outlet for more than one spiral channel, it is preferred that each channel has its own cooling fluid inlet and has its own cooling fluid outlet. Separate inlets and outlets for cooling fluid also allow alternating flow directions between adjacent spiral cooling channels, thereby potentially achieving more uniform cooling of the ram.

The advantage of having the inlet arranged at the distal or proximal end of the punch and the corresponding outlet arranged at the proximal or distal end of the punch means that the cooling liquid only travels directly from the inlet at one end of the punch to the other end, so that a maximum cooling effect can be achieved. In the prior art, such as JP2006055860, JP2006-055860, and JP2005-288483, the cooling fluid must travel up and down the ram because both the inlet and outlet of the cooling fluid are located at the proximal end of the ram. JP2006055860 discloses a punch with continuous zigzag channels, while JP2006-055860 and JP2005-288483 show embodiments with a single spiral channel and embodiments with multiple continuous zigzag channels through which a cooling liquid is guided.

In the prior art, such as JP2006055860, JP2006-055860, and JP2005-288483, the returning heated coolant encounters cooler coolant, thereby heating the incoming coolant. This reduces the cooling capacity of the incoming cooling liquid, thereby reducing the cooling efficiency of the cooled punch as a whole. These prior art constructions therefore have a very low cooling capacity compared to the construction according to the invention.

The exterior temperature of the punch may be continuously monitored, for example by directly contacting or non-contacting measurement of the punch temperature or by monitoring the temperature of the cooling fluid entering and exiting the punch. In an embodiment of the invention, the temperature of the punch assembly is controlled by means of a temperature control unit, wherein the temperature control unit is capable of controlling the temperature of the punch by adjusting the production speed of the can body and/or by adjusting the flow rate of the cooling fluid into the inner annular cavity and/or by adjusting the temperature of the cooling fluid into the inner annular cavity.

In an embodiment, the redraw ring and the one or more reducing extrusion rings also have internal cooling channels that enable cooling of the outer laminate layer of the can during the deep draw and wall reducing extrusion processes.

The invention is also embodied in a punch assembly according to claim 6. Preferred embodiments are provided in the dependent claims.

The punch according to the invention can be provided with obstacles in two ways. Since the internal annular cavity provided with discontinuous or continuous obstacles is very complex in structure, it is preferred to produce the punch by additive manufacturing, such as 3D printing. By means of additive manufacturing, the punch, the outer surface of which (in use) contacts the laminate layer of the can body and which comprises a complex internal structure in the internal annular cavity, can be produced as one integral part in one production step. For example, the punch as shown in fig. 4 may be produced in one production step by additive manufacturing, so that the punch sleeve 19 and the insert 20 may be made in one piece, wherein the sleeve and the insert are combined into one piece, i.e. one integral piece, and thus are not separable. When the punch is produced by additive manufacturing, the channels or obstacles in the inner annular cavity are produced simultaneously with the rest of the punch. The production of such punches of complex shape with discontinuous obstacles in the internal annular cavity cannot be produced in one piece (i.e. one integral piece) by conventional machining.

Alternatively, the punch may be made of at least two parts: the punch sleeve and the insert, when joined together, form an internal annular cavity with discrete or continuous obstructions (e.g., adjacent helical channels). Inserts with obstructions may be produced by Additive Manufacturing (AM), where the insert contains a cooling fluid inlet and a cooling fluid outlet, the insert being made of a material suitable for AM, such as tool steel, cemented carbide (such as WC), or copper alloy. Alternatively, the insert may be produced by machining the insert, for example from tool steel or another suitable material, such as stainless steel, copper or a copper alloy.

The material of the punch with integral internal structure in the internal annular cavity or the material of the insert with discrete or continuous obstructions in the internal annular cavity (after assembly with the punch sleeve) is preferably a material suitable for AM, such as cemented carbide, such as WC, or copper alloys.

The invention is also embodied in a can body produced in a method or apparatus according to the invention.

A laminated metal sheet for packaging comprises a metal sheet and a laminate layer covering at least one side of the metal sheet. Such a laminated metal sheet is produced by laminating a laminate layer onto the metal sheet. The laminate layer may be applied to the metal sheet by thermally bonding the laminate layer to the metal sheet, or by using an adhesion promoter between the laminate layer and the metal sheet, or by using a laminate layer comprising an adhesive layer. The laminate layer may be produced in-line and laminated to the metal sheet in an integrated lamination step, or a pre-produced laminate layer may be laminated to the metal sheet in a separate lamination process step. An alternative lamination method is to extrude the laminate layer through a flat die and laminate the laminate layer directly to the metal sheet.

The reducing extrusion method of the present invention is particularly effective for reducing extrusion of a metal sheet selected from the group consisting of cold rolled steel, black plate, tin plate, ECCS,

A group of metal sheets of galvanized steel or aluminium alloys. The metal sheet is preferably supplied in the form of a roll.

The metal sheet is preferably coated on one or both sides with an organic resin selected from the group consisting of polyesters, polyolefins, polyamides and other thermoplastic resins. The resin film to which the present invention is applied may be a film formed of a single layer or two or more layers, and is preferably a film of a thermoplastic resin, particularly a polyester resin.

The polyester resin preferably has an ester unit such as ethylene terephthalate, ethylene isophthalate, butylene terephthalate, or butylene isophthalate, and is preferably a polyester mainly composed of at least one ester unit selected therefrom. Each ester unit may be a copolymer, or the polyester may be a blend of homopolymers or copolymers of two or more ester units. Other ester units containing, for example, naphthalenedicarboxylic, adipic, sebacic or trimellitic acid as their acid component or, for example, propylene glycol, diethylene glycol, neopentyl glycol, cyclohexanedimethanol or pentaerythritol as their alcohol component can also be used.

The polyester may be a laminate of two or more polyester layers consisting of homopolyesters or copolyesters, or a mixture of two or more thereof. For example, the polyester film may have a copolyester layer of high thermal adhesion as a lower layer, and a polyester or modified polyester layer of high strength, heat resistance and barrier properties against corrosive substances as an upper layer.

When the resin film is a single-layer film, the thickness of the resin film is preferably 5 to 100. Mu.m, more preferably 10 to 40 μm. Any film having a thickness of less than 5 μm is very difficult to laminate on a surface-treated steel sheet, may produce a defective resin layer upon drawing or drawing and reducing press processing, and is unsatisfactory in impermeability to corrosive substances when a can is formed and filled with its contents. An increase in thickness provides satisfactory impermeability, but any thickness in excess of 100 μm is economically a disadvantage. The thickness ratio of the layers of the multilayer film depends on formability, impermeability, and the like, and the thickness of the layers is controlled to obtain a total thickness of 5 to 60 μm.

The resin film may be formed of a resin to which a coloring pigment, a stabilizer, an oxidation inhibitor, a lubricant, and the like have been added to the extent that their necessary characteristics are not impaired. A metal sheet having a pigment-free polyester resin film laminated on the side to define the inner surface of the can and a polyester resin film containing a pigment such as titanium oxide laminated on the side to define the outer surface of the can may be used.

Drawings

The invention is further described with the aid of the following non-limiting figures and figures.

Figure 1 shows how the preformed deep drawn cup 3 forms the final reduced diameter extruded wall can body 9. The cup 3 is placed between the redraw sleeve 2 and the redraw die 4. As the punch 1 moves to the right, the cup 3 is brought to the inner diameter of the final finished can 9 by a redraw step. The punch 1 then continuously forces the product through (in this example) two wall reducing extrusion rings 6 and 7. Ring 8 is an optional stripper ring. The wall reducing extrusion process provides the can body 9 to be formed with its final wall thickness and wall length. Finally, the base of the can body 9 is formed by moving the punch 1 towards the optional base tool 10. Retracting the punch 1 allows the can 9 to be detached from the punch 1 so that it can be ejected in a lateral direction. An optional stripper ring may assist in this. The can 9 is then trimmed, optionally necked down, flanged and provided with a lid after filling.

Fig. 2 provides a detailed illustration of a portion of a can wall to be formed through, for example, a wall reducing extrusion ring 6. The punch 1 is schematically shown. The entry plane of the wall-reducing extrusion ring 6 forms an entry angle α with the axial direction of the wall-reducing extrusion ring. The thickness of the material of the wall to be formed is reduced between the punch 1 and the wall reducing extrusion ring 6. The material comprises the actual metal can wall 11 with

laminate layers

12 and 13 on each side. The laminate layer 12 becomes the exterior of the can body and the laminate layer 13 becomes the interior of the can body, eventually coming into contact with the contents of the can. The figure shows how the thickness of all three

layers

11, 12 and 13 is reduced.

Fig. 3 shows a punch 1 which is typically removably secured to the front end of a reciprocating ram (ram) 14 in a stretch and reducing press. Figure 3 shows in detail the punch on top of the ram in one embodiment of the invention. The inner annular cavity extends between 15a and 15b and is shown more prominently in figure 4 by the dashed box in the cross-section of the punch.

FIG. 4 shows a cross-section of a punch in which successive obstructions form adjacent spiral cooling channels. In this figure, the punch comprises a punch sleeve 19 and an insert 20. The inner annular cavity formed by the joined punch sleeve and insert is filled with a continuous barrier.

Fig. 5a shows the outer surface of the insert 20 with the helically continuous barrier 18. It shows six adjacent spiral cooling channels (channels a-f), each with their own separate inlet and outlet for cooling fluid. Fig. 5b shows a cross section of the same insert as used in fig. 4.

Figure 6 shows six different examples of internal annular cavities: no obstacles (A: prior art); with discontinuous obstacles (B: short walls perpendicular to the cooling fluid flow; C: cylinder; D: V; E: zigzag channel); and with continuous obstacles (F: six adjacent spiral cooling channels formed by continuous obstacles forming the channel walls). The distance between the cooling fluid and the working surface of the punch is the same for all embodiments.

Fig. 7 illustrates surface temperatures for various embodiments. It is clear that all embodiments according to the present invention provide a very uniform temperature profile along the length of the punch (from about 40 to about 110 mm). The prior art shows significantly higher surface temperatures of the punches, illustrating the improvements that the present invention can provide with respect to the surface temperature of the punches. The lowest surface temperature is achieved by the continuous barrier forming the helical channel, regardless of the direction of flow of the cooling fluid in the channel (distal to proximal, proximal to distal, or mixed). All embodiments of the present invention show significant improvements over the prior art.

The effect of this lower surface temperature is shown in figure 8. The closed loop shows the temperature during production of the can body at 165 cans/minute using the prior art annular cavity without obstructions. The triangles show the punch temperatures for the embodiment with six adjacent spiral cooling channels at the same production rate and the same boundary conditions, and a steady state temperature of about 65 ℃ was reached compared to 95 ℃ for the prior art punch. This means that productivity can be increased. In this example, the production rate is increased by 70% to 280 cans/min and this results in a maximum temperature of the ram slightly below 90 ℃, which is still lower than in the prior art case at very low production rates. Cans produced with increased productivity by the process according to the invention were not scratched and no galling damage was observed.

The results of discontinuous obstacles are only slightly less favorable than continuous obstacles, and also allow a significant improvement in surface temperature control and an associated productivity increase of about 60-65%.

Claims

1. A method for producing a can body from a laminated metal sheet by deep drawing and wall reducing extrusion, the can body comprising a base and a tubular body, for a two-piece can, wherein a disc is produced from the laminated metal sheet, the disc being deep drawn into a cup, the cup then being redrawn and the redrawn cup then being cup-shaped into a can body by wall reducing extrusion, wherein wall reducing extrusion occurs in a single stroke by punching the redrawn cup through one or more wall reducing extrusion rings by means of an internally cooled punch assembly, wherein the punch assembly comprises:

a ram (14),

in order to effectively cool the punch internally during the production of can bodies to prevent abrasion damage or scratching of the laminate layer on the tubular body of the can body, wherein

2. The method of claim 1, wherein the punch comprises at least three adjacent spiral cooling channels, preferably at least four adjacent spiral cooling channels, more preferably at least five adjacent spiral cooling channels, even more preferably at least six adjacent spiral cooling channels.

3. A method according to any one of claims 1 or 2, wherein each spiral cooling channel is provided with its own cooling fluid inlet and its own cooling fluid outlet.

4. A method according to any one of claims 1 to 3, wherein the redraw ring and the one or more wall reducing extrusion rings also have internal cooling channels that cool the outer laminated layer of the can during the deep drawing and wall reducing extrusion processes.

5. A method according to any one of claims 1 to 4, wherein the temperature of the punch assembly is controlled by means of a temperature control unit, and wherein the temperature control unit is capable of controlling the temperature of the punches by adjusting the production rate of the can body and/or by adjusting the flow rate of the cooling fluid into the inner annular cavity and/or by adjusting the temperature of the cooling fluid into the inner annular cavity.

6. An internally cooled punch assembly for use in a method according to any of claims 1 to 4, wherein the punch assembly comprises

A ram (14),

a punch (1), preferably removably connected to a ram, said punch assembly comprising an internal annular cavity (15) below the surface of said punch between a position (15 a) near the distal end of the punch and a position (15 b) near the proximal end of the punch,

-non-continuous obstacles (18), such as chevrons, columns, continuous walls or discontinuous zig-zag walls, or

c. The cooling fluid inlets of some of the helical cooling channels are disposed closer to the distal end of the punch, and wherein the respective cooling fluid outlets are disposed closer to the proximal end of the punch, and wherein the cooling fluid inlets of other helical cooling channels are disposed closer to the proximal end of the punch, and wherein the respective cooling fluid outlets are disposed closer to the distal end of the punch, such that some of the helical cooling channels direct cooling fluid from the distal end to the proximal end of the punch, and other cooling channels direct cooling fluid from the proximal end to the distal end of the punch, preferably wherein the direction of the cooling fluid alternates from one helical cooling channel to its adjacent helical cooling channel, preferably wherein the cooling fluid inlets and cooling fluid outlets are arranged in a regular pattern around the periphery of the punch.

7. The punch assembly according to claim 6, wherein the punch (1) comprising an inner annular cavity (15) with an obstruction or a plurality of adjacent helical cooling channels is an additive manufactured product.

8. The punch assembly of claim 7, wherein the punch (1) comprises a punch sleeve (19) and an insert (20), the punch sleeve (19) and insert (20) forming, when assembled, the punch (1) having an inner annular cavity (15) with an obstruction (18).

9. The punch assembly according to claim 8, wherein the insert with the obstruction (18) is an additive manufactured product, wherein the insert (20) preferably further comprises a cooling fluid inlet (16) and a cooling fluid outlet (17).

10. The punch assembly according to claim 9, wherein the material of the insert (20) is a machined tool steel, wherein the barrier (18) is machined in the insert, and wherein the insert preferably further comprises a cooling fluid inlet (16) and a cooling fluid outlet (17).

11. A punch as claimed in any one of claims 6 to 10, wherein a plurality of successive obstacles forming the helical cooling channels extend between a position (15 a) near the distal end of the punch and a position (15 b) near the proximal end of the punch, and wherein the helical cooling channels extend below the surface of the punch, wherein preferably each helical cooling channel is provided with its own cooling fluid inlet (16) and its own cooling fluid outlet (17), and wherein the punch comprises at least three adjacent helical cooling channels, preferably at least four, more preferably at least five, even more preferably at least six adjacent helical cooling channels.

12. A punch as claimed in any one of claims 6 to 10, wherein a plurality of successive obstacles forming the helical cooling channels extend between a position (15 a) near the proximal end of the punch and a position (15 b) near the distal end of the punch, and wherein the helical cooling channels extend below the surface of the punch, wherein preferably each helical cooling channel is provided with its own cooling fluid inlet (16) and its own cooling fluid outlet (17), and wherein the punch comprises at least three adjacent helical cooling channels, preferably at least four, more preferably at least five, even more preferably at least six adjacent helical cooling channels.

13. The punch assembly according to any one of claims 6 to 12, wherein the temperature of the punch assembly is controlled by means of a temperature control unit capable of controlling the temperature of the punch by adjusting the production speed of the can body and/or by adjusting the flow rate of the cooling fluid into the inner annular cavity and/or by adjusting the temperature of the cooling fluid into the inner annular cavity.

14. A can body produced by the method according to any one of claims 1 to 5.