JP5952804B2 - Can manufacturing - Google Patents

Description

  The present invention relates to the manufacture of metal cups and in particular (but not exclusively) to metal cups suitable for the manufacture of “two-piece” metal containers.

US Pat. No. 4,095,544, registered on June 20, 1978 (NATIONAL STEEL CORPORATION), “Drawing and wall ironing”, which manufactures cup sections for making conventional two-piece metal containers. DWI) and “ draw and redraw” (DRD) processes are detailed. (Note that in the United States, DWI is commonly referred to as D & I). The term “two-piece” refers to i) a cup section and ii) a lid for later closing the opening of the cup section to form a container.

  In the DWI (D & I) process (as shown in FIGS. 6 to 10 of US Pat. No. 4,095,544), flat (generally) circular blanks stamped from rolls of metal sheet are Thus, a shallow first stage cup is formed by drawing through a drawing die. This initial drawing step does not lead to the intentional thinning of the blank. Thereafter, the cup, which is generally attached to the end face of the tightly fitted punch or ram, is pushed into one or more annular wall ironing dies to reduce the thickness of the cup side wall, resulting in a cup The side wall extends. Thus, in this ironing process, the nominal diameter of the first stage cup should not change at all.

FIG. 1 shows the metal distribution of a container body obtained by a conventional DWI (D & I) process. FIG. 1 is exemplary and is not intended for precise scaling. In FIG. 1, three regions are shown.
Region 1 is the base material that has not been ironed. This region remains approximately the same thickness as the incoming standard dimensions of the blank, i.e., this region is not affected by another manufacturing step of the conventional DWI process.
Region 2 is the middle section of the side wall that has been ironed. This thickness (and hence the desired amount of ironing) depends on the performance required of the container body.
Region 3 is the top section of the side wall that has been ironed. In general, in can manufacturing, this ironed top section is about 50-75% of the incoming standard dimension thickness of the blank.

In the DRD process (as shown in FIGS. 1 to 5 of US Pat. No. 4,095,544), the same drawing technique is used to form the first stage cup, however, the ironing process is used. Alternatively, then, the first stage of the cup, and gradually reduced in diameter to result in one act to extend the side walls of the cup or more re-drawing the cup (re-drawing) is Applied. Alone, many conventional redrawing steps are not aimed at changing the thickness of the cup material as a result. However, taking a container body manufactured by a typical DRD process as an example, in practice, it is generally somewhat thickened (on the order of 10% or more) at the upper end of the finished container body. This thickening is an action specific to the redrawing process, and can be explained by a compression action on the material when a large diameter cup is redrawn into a small diameter cup.

It should be noted that there is another known DRD process that reduces the thickness of the cup side wall through thinning the side wall by drawing at the squeezing and redrawing stage using a small or compound diameter drawing die. .

Alternatively, a combination of ironing and redrawing can be used for the first stage cup, which reduces the cup diameter and sidewall thickness. For example, in the field of manufacturing two-piece metal containers (cans), the container body is typically drawn from a blank into a first stage cup and subjected to multiple redraw steps in the cup until the container body of the desired nominal diameter is reached. And then ironing the side walls to the desired side wall thickness and height.

  However, DWI (D & I) and DRD processes used in large scale industries have significant limitations that do not act to reduce the thickness (and hence weight) of the cup base material. In particular, drawing does not lead to a reduction in the thickness of the object to be drawn, and only the ironing acts on the side wall of the cup. In essence, for the known DWI (D & I) and DRD processes for manufacturing cups for two-piece containers, the thickness of the base remains largely unchanged from the incoming standard dimensions of the blank. This may cause the base to be much thicker than required for performance goals.

  The metal packing industry is highly competitive and weight reduction is the main objective because it reduces transportation costs and raw material costs. For example, about 65% of the manufacturing cost of a typical two-piece metal food container is the raw material cost.

US Pat. No. 4,095,544

  Accordingly, there is a need to improve the weight reduction of metal cup sections in a cost effective manner. It should be noted that the terms “cup section” and “cup” are synonymous herein.

In a first aspect of the invention (as defined in claim 1), a method for producing a metal cup from a metal sheet is provided, the method comprising:
i. A drawing process comprising drawing a metal sheet into a cup having a side wall and an integral base;
ii. A stretching process applied to the cup;
Including
The stretching process includes a step of clamping an annular region on the base of the cup to define a surrounding portion, and deforming and stretching at least a portion of the base located in the surrounding portion. The annular clamp is designed to limit or prevent the flow of material from the clamp area to the enclosed part during the stretching process. ,
The drawing process and the drawing process are performed by the same press machine.

In a second aspect of the present invention (as defined in claim 5) there is provided a press for producing a metal cup from a metal sheet,
i. Means for drawing a metal sheet into a cup having a side wall and an integral base;
ii. A clamping element adapted to clamp an annular region of the base of the drawn cup to define a surrounding portion for clamping the drawn cup during the drawing process;
iii. A stretching tool adapted to deform and stretch at least a portion of the base located in a portion surrounded by the periphery during the stretching process, thereby increasing the surface area of the base and reducing the thickness; and
With
The clamping element is further adapted to limit or prevent the flow of material from the clamping area to the surrounding part during the drawing process.

  The method and apparatus of the different aspects of the present invention has the advantage of achieving the manufacture of cups having a base that is thinner than the incoming reference dimensions of the metal sheet without causing loss or wear of the metal (in known processes / apparatuses). for). This is achieved using a single press, thus simplifying the manufacturing process. When applied to the manufacture of two-piece containers, the present invention allows cost savings on the order of several dollars for 1000 containers compared to existing manufacturing techniques.

  The base of the cup that has been drawn during the drawing process is moved from the clamping area to the enclosed part to ensure that the surrounding part (and thus the cup base) is stretched and thinned during the drawing process. It is clamped firmly to limit or prevent the flow of material. If the clamping load is insufficient, the material from the clamping area (or from the outside of the clamping area) is surrounded by the surrounding area (and the cup base) without any thinning. Will simply be drawn into the part. Stretching and thinning restricts the flow of material from the clamping area (from outside the clamping area) to the surrounding part, ie restricts rather than completely prevents metal flow It has been found that the case still occurs.

The method and apparatus of the present invention is best used in the manufacture of metal containers, where the final cup is used for the container body. The final cup can be formed into a closed container by securing a lid to the open end of the cup. For example, the metal can end can be joined to the open end of the final cup. However, in general, the cup obtained by the method of the present invention will suffer one or a combination of the redrawing step and the ironing step. The redrawing process can include one or more stages, each stage having the effect of causing a gradual reduction in cup diameter. The ironing process should have the advantage of increasing the height of the cup sidewall made with the method and apparatus of the present invention. Preferably, the stretching process includes a step of deforming and stretching at least a part of a base located in a portion surrounded by the periphery into a dome shape. In the field of metal containers for carbonated beverages, it is common to make the base of the container body domed inward to withstand the pressure generated by the product. The “dome” provided by the method and apparatus of the present invention functions as an inward dome-shaped region of the beverage container body. However, the cup may later undergo a straightening process to bring the dome-shaped base into the desired final shape to withstand the can internal pressure.

  The method of the present invention is suitable for use on cups with circular or non-circular surfaces. However. Works best with round cups.

  Another way of minimizing the amount of material at the base of the cup section manufactured using conventional DWI and DR processes would be to use a thin standard size raw stock. However, the cost per metric ton of tinplate increases as standard dimensions decrease. This high cost can be explained by the additional costs of rolling, cleaning and tinning thin steel. Also, when considering the amount of material used during the manufacture of the two-piece container, the change in net overall cost for manufacturing the container relative to the incoming standard dimensions of the material is shown in the graph of FIG. This graph shows that, from a cost standpoint, the thinnest standard dimension material does not necessarily reduce costs. In essence, there is the cheapest standard size material for any container of a given sidewall thickness. The graph also shows that the effect of reducing the thickness of the top and middle sections of the container pushes down the cost curve. FIG. 3 shows the same graph based on actual data for tinplate supplied in the UK, commonly used in can manufacturing. For the material shown in FIG. 3, 0.285 mm is the optimum thickness from a cost standpoint, and using thinner standard sized material increases the net overall cost of can manufacturing. The graph of FIG. 3 shows the percentage increase in net overall cost for 1000 cans when deviating from the optimal incoming standard dimension thickness of 0.285 mm.

The final cup of the present invention provides the advantage of a thin (and thus lightweight) base.
“Metal sheet” includes blanks cut from large, expensive metal sheets.
By "annular clamp" or "annular region" clamp is meant that the base of the drawn cup is clamped continuously or spaced apart in an annular manner.
The clamping element can be in the form of a continuous annular sleeve, or it can be a collection of separate clamping elements distributed in an annular manner, acting on the metal sheet.

  The method and apparatus of the present invention is not limited to a particular metal. This is particularly suitable for use with any metal commonly used in DWI (D & I) and DRD processes. Also, the end use of the cup obtained from the method and apparatus of the present invention is not limited. As a non-limiting example, the cup can be used in any type of container for food, beverages, or others.

  Embodiments of the invention are illustrated in the following drawings with reference to the accompanying description.

It is a side view of the conventional container main body by the conventional DWI process. The material distribution of the base part and side wall area | region of a container main body is shown. In general terms, it is a graph showing how the net overall cost for producing a typical two-piece metal container varies with the incoming standard dimensions of the metal sheet. This graph shows how reducing the thickness of the sidewall region affects the reduction in net overall cost. FIG. 3 is a graph corresponding to FIG. 2 but based on the actual price of a tin plate supplied in the UK. It is sectional drawing of the press of the invention which shows the blank of the metal sheet before a drawing and drawing process. FIG. 5 is a cross-sectional view of the press of FIG. 4 after a drawing step for drawing a blank of metal sheet into a cup having a side wall and an integral base. FIG. 6 is a cross-sectional view of the press of FIGS. 4 and 5, but after the drawing process for deforming and stretching the base of the drawn cup.

(Drawing process)
FIG. 4 shows a press 10 that combines drawing and stretching. The blank 5 of metal sheet is “slidably clamped” at an appropriate position between the opposing surface of the aperture pad 11 and the end surface of the aperture die 12. The drawing punch 13 is arranged above the upper surface of the metal sheet blank 5. In the bore defined by the drawing die 12, there is a stretch punch 14 that is surrounded by the clamping element radially inside the annular clamping element 15.

  When the blank 5 is “slidably clamped” between the aperture pad 11 and the aperture die 12, the aperture punch 13 is axially moved until the peripheral annular region 17 of the punch end surface contacts the corresponding region of the blank 5. Move downward (along axis 16) (see FIG. 5). The squeezing punch 13 is biased downwardly through the bore of the squeezing die 12 and initially squeezes the circular blank 5 until it becomes a cup having a side wall 31 and an integral base 32.

  “Slidably clamped” means that the metal sheet 5 can be used with any clamping means (in this case “drawing” depending on the deformation action of the drawing punch 13 / drawing die 12 on the metal sheet). Pad 11 ") means that the clamp load at the time of drawing is selected so that it can slide. The purpose of this slidable clamp is to prevent or limit material wrinkling during drawing.

(Stretching process)
When the drawing punch 13 reaches the stroke end, the annular clamp 33 is clamped until the annular region 33 on the base 32 of the drawn cup is clamped between the annular clamping element and the peripheral annular region 17 on the end face of the drawing punch 13. The element 15 moves axially upward (see FIG. 5). The material of the cup base surrounded by this annular clamp is referred to as the “surrounded portion” 34.

  Next, the extending punch 14 moves upward (along the axis 16) and comes into contact with the portion 34 surrounded by the periphery (see FIG. 6). The stretching punch 14 is urged upward toward the recess 18 formed in the end face of the drawing punch 13, and the material of the portion 34 surrounded by the periphery of the cup 30 is gradually deformed and stretched into a dome shape. (See FIG. 6). The clamping load applied between the annular clamping element 15 and the peripheral annular region 17 at the end face of the drawing punch 13 is transferred from the annular region 33 in which the material is clamped to the surrounded portion 34 during this drawing process. It is large enough to prevent or limit flow. To enhance the holding effect, the end face of the annular clamping element 15 can be textured (not shown), resulting in a reduced clamping load compared to an annular clamping element having a smooth polished end face. be able to.

As shown in FIG. 6, the thickness of the base of the cup obtained from the stretching process by the press machine 10 is reduced with respect to the incoming standard dimension of the metal sheet blank 5. As shown in the summary of the present invention, the cup can be used as a container body, but generally may be subjected to one or both of a redrawing step and an ironing step to optimize the cup diameter and sidewall thickness. it can. Furthermore, as shown in the summary of the invention, the dome-shaped region 35 is particularly useful for containers intended for pressurized products such as carbonated beverages.

Claims (8)

A method of producing a metal cup from a metal sheet, the method comprising:
i. A drawing process comprising drawing a metal sheet into a cup having a side wall and an integral base;
ii. A stretching process applied to the cup;
Including
The drawing process and the drawing process are performed by the same press machine,
The stretching step includes a step of clamping an annular region on the base of the cup to define a surrounding portion, and deforming and stretching at least a portion of the base located in the surrounding portion. And, consequently, increasing the surface area of the base and reducing the thickness thereof, the annular clamp restricts or prevents material flow from the clamp area to the surrounding portion during the stretching process. Is supposed to
Thereafter, one or a combination of said cup redrawing and ironing is performed, leading to a gradual reduction in cup diameter and / or an increase in cup side wall height, respectively .   The drawing step includes placing the metal sheet between a drawing punch and a drawing die, and extending the drawing punch through the drawing die so that the metal sheet is drawn into the cup. Moving one or both of the squeeze punch and the squeeze die toward each other, and the annular clamp during the stretching process includes an annular region on the base of the cup, the squeeze punch, and the cup The method of claim 1, comprising clamping between a clamping element disposed opposite to the drawing punch.   The stretching process includes the step of using a stretching punch disposed on the opposite side of the drawing punch, and moving one or both of the stretching punch and the clamped cup toward each other to surround the periphery. And deforming and stretching at least a portion of the base located within the portion.   The method according to any one of claims 1 to 3, wherein the stretching step includes a step of deforming and stretching a part of the base located in the portion surrounded by the periphery into a dome shape. A press for producing a metal cup from a metal sheet,
i. Means for drawing the metal sheet into a cup having a side wall and an integral base;
ii. A clamping element adapted to clamp an annular region of the base of the drawn cup to define a surrounding portion for clamping a drawn cup during a drawing process;
iii. During the stretching process, at least a part of the base located in a portion surrounded by the periphery is deformed and stretched, and as a result, the surface area of the base is increased to reduce the thickness. A stretching tool;
With
The clamping element is further adapted to limit or prevent the flow of material from the clamping area to the surrounded part during the stretching process ,
iV. Press machine comprising redrawing and / or ironing means to optimize cup diameter and sidewall thickness following engagement of the cup by the stretching tool .   The means for drawing the metal sheet comprises a drawing punch and a drawing die, and one or both of the drawing punch and the drawing die are arranged such that the drawing punch extends through the drawing die and the metal sheet is put into the cup. The clamping elements are movable towards each other so that they can be squeezed, and the clamping elements are arranged on the opposite side of the cup with respect to the squeezing punch, and when used during the stretching process, the clamping elements are 6. Press according to claim 5, adapted to clamp the annular region of the base between a clamping element and a drawing punch.   The drawing tool comprises a drawing punch disposed on the opposite side of the cup with respect to the drawing punch, and one or both of the drawing punch and the combination of the drawing punch and the clamping element are movable toward each other. 6. The press machine according to claim 5, wherein the stretching punch is configured to deform and stretch at least a part of the base portion located in the portion surrounded by the periphery during use in the stretching process. .   8. The drawing punch according to claim 6, wherein the drawing punch includes a recess or a bore, and a stretching tool can extend all or part of the recess or the bore during a stretching process. Press machine.

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