EP1663541B1 - Method for producing a cup-shaped object - Google Patents

Abstract

A method for the production of a cup-shaped article, in particular a blank of a screw cap for glass bottles or the like, from an enameled metal sheet, using two tools in a stepwise manner: 1) the blank is stamped from the metal sheet in a first tool by the relative motion between a cutting bell cooperating with a blank holder and a drawing block, and the blank is drawn around the drawing block, the width of a flange forming between the cutting bell and the blank holder being continuously reduced with a progressive degree of deformation until the flange reaches a defined width (R-r), and 2) the blank is deformed in a second tool such that the radially outwardly directed flange is deflected toward a profiling introduced in a wall of the blank.

Description

1. 1) Ausstanzen des Rohlings aus dem Blech in einem Werkzeug durch die Relativbewegung zwischen einer mit einem Niederhalter zusammenwirkenden Schnittglocke und einem Ziehklotz und Ziehen des Rohlings um den Ziehklotz unter Kraftbeaufschlagung des Niederhalters, wobei die Breite eines sich zwischen der Schnittglocke und dem Niederhalter ausbildenden Bördels mit fortschreitendem Verformungsgrad stetig reduziert wird, bis der Bördel eine definierte Breite errreicht hat,
2. 2) Ausziehen des definierten Bördels in einem Werkzeug durch die Relativbewegung zwischen der Schnittglocke und dem Ziehklotz des Werkzeugs ohne eine Kraftbeaufschlagung in der der Bewegung der Schnittglocke entgegengesetzten Richtung.

The invention relates to a method for deep drawing a cup-shaped article, in particular a blank, a screw cap for glass bottles or the like, from a painted sheet metal with the following steps:

1. 1) punching the blank from the sheet metal in a tool by the relative movement between a cooperating with a blank holder Schnittglocke and a drawing block and pulling the blank around the drawing block under application of force of the blank holder, wherein the width of a forming between the cut bell and the blank holder flare is progressively reduced in the progressive degree of deformation until the flange has reached a defined width,
2. 2) Extracting the defined flange in a tool by the relative movement between the cutting bell and the drawing block of the tool without a force in the direction opposite to the movement of the cutting bell direction.

Such a method is for example from the DD 233 036 A3 known. A similar procedure is in the DE 433 094 A described.

Deep drawing is understood to mean the forming of a sheet metal blank (blank, blank) into a hollow body or a hollow body into a hollow body with a smaller circumference, with or without intended change in the sheet thickness. When forming segments of the blank must be folded up to the cylinder wall and displaced intermediate sections. In this case, radial tensile and tangential compressive stresses occur. When overflowing the cut bell creates a bend. Thus, the radially outwardly projecting flange or flange under the action of the tangential compressive stresses not kinks and folds, the kraftbeaufschlagte hold-down is provided.

The provided for glass bottles lid are drawn from relatively thin sheets. These sheets are, especially if they are intended for the food industry, varnished and often have advertising imprints on. The problem with the lid production is that when forming in the axially outer region of the cup, the coating breaks and form fine color threads. The cracked paint does not affect the appearance of the lid, as the axial end of the blank is subsequently rolled, so that the torn areas, which are otherwise very fine, are invisible on the finished product. The lacquer threads settle not only in the tools, but also on the edge of the blank, in the tools forms a cotton-like consistency, which must be removed regularly. Also, the threads on the cup, especially at its edge must be carefully removed so that they do not come into contact with the bottling (food) at the bottler, which would not be acceptable.

Lids for glass bottles are mass-produced articles, of which large quantities are produced in a mold with high cycle times. The cycle times usually include values of about 300 min ^-1 . To remove the threads, the production plant comprising the tool must be shut down and blown down or cleaned, which prolongs the production time and thus also increases the production costs. The blowing off of the threads must be done very carefully done so that the staff operating the plant is not endangered. The hall in which the systems are installed must also be constantly cleaned of the colored threads.

Various methods have been developed in the prior art with a stepwise deformation. So will in the DD 233 036 A3 discloses a method for deep drawing sheet metal parts, in which a first train is followed by a second train within the same press stroke in the same direction, wherein the pulling force of the first train is used as a hold-down force of the second train and reduced with progressive draw depth. The hold-down force is progressively reduced from the beginning of the second turn and completely canceled before the end of the second turn.

From the DE 692 06 748 T2 Further, a drawing method for a disc-like metal sheet is known, in which an annular holding member and / or the drawing tool, which have a remaining flange area, is moved so that the holding operation is stopped immediately before the completion of the drawing stage. Subsequently, the flange portion is pulled while the rear end of the flange portion is released.

Common to both methods is the implementation in each case a tool, so that the molding remains in the stepwise deformation in this tool. The release of the hold-down force can not be guaranteed in the practical implementation, especially at high cycle times. For example, in a pneumatic The response time for the controller is too slow to maintain the high cycle time. Therefore, even if the hold-down in the second process step should exert no force on the blank to be deformed, a thread or a Zipfelbildung can not be excluded.

Starting from this problem, the method explained in the introduction is intended to be improved so that, especially at high cycle times, threading or earing is significantly reduced or even completely eliminated by reliably ensuring the powerless execution of the pulling out step.

To solve the problem, a generic method is characterized in that the step of punching out and pulling is performed under force in a first tool and the pulling is interrupted when the flange has reached a defined width (R - r), and then the step of Extracting without force in a second tool without holddown is performed.

The invention is based on the finding that the thread formation is not formed when punching out the blank from the sheet due to the high cutting forces, as might be expected, but to the end of deep drawing when the surface pressure on the flange formed between the cut bell and the hold-down is reached very high levels. Due to the defined width (R - r) of the flare, shortly before the surface pressure in this flare reaches values which cause the lacquer layer to crack, the deep drawing or the deformation are interrupted. By tearing the lacquer layer due to the high surface pressure, the lacquer layer would draw threads.

The flange then has a width of, for example, a maximum of 3 mm, which is very small compared to the cup height. The deformation or deflection of the flange is then carried out in a second step in a second tool then without applying force to a hold-down, so that when deflecting no surface pressure acts on the hemming. The necessary forming force can be kept very low due to the only small necessary deformation, whereby the tearing of the paint layer is prevented and can form any threads. If, in the second step, a profiling is introduced into the wall of the blank, it is prepared for further processing, for example curling the wall inwards.

This process eliminates the downtime and associated costs previously required for cleaning, thereby significantly reducing production costs. Since there are also no threads on the blank, the further step previously necessary for removing the threads and corresponding control steps are also eliminated, which further reduces the production costs. In addition, the earing is reduced. In addition to reducing manufacturing costs, the quality of the products is increased.

An advantageous embodiment of the inventive concept provides that the deformation takes place by pulling the flange due to the relative movement between a cutting bell and a drawing block of the second tool.

An alternative embodiment of the method according to the invention provides that the deformation takes place by means of a guide cooperating with the second tool. Finally, a further alternative embodiment of the method according to the invention provides that the deformation takes place by rolling in a second tool. Rolling enables a simple and efficient forming process to prepare the blank for further processing.

Preferably, the wall is pulled radially outward by the profiling. Alternatively, the profile is deformed by the wall facing radially inward. These configurations of the profiling allow for a later curling of the wall that in the Wall no wrinkles or Einknickungen arise, which increases the quality of the finished lid. In addition, the lid must not be tipped or rolled forward later to curl the edge.

The radial width of the flange at the end of the first forming step is less than three millimeters, preferably 0.1-1.5 mm, and more preferably 0.5-1.0 mm. The smaller the width of the flange, the lower forces are necessary for forming in the second step. The width of the flange is of course dependent on the surface pressure occurring, which in turn depends on the material and the material thickness or sheet thickness and their compatible maximum value is in correlation with the thickness of the ink layer. The best width of the flange is determined in each case for different boundary conditions, such as material, material thickness and the color or lacquer layer, iteratively.

Figur 1 -

einen Teilhalbschnitt durch ein erstes Tiefziehwerk- zeug;

Figur 2 -

ein Tiefziehwerkzeug im Teilhalbschnitt nach dem Stand der Technik;

Figur 3 -

ein erstes Tiefziehwerkzeug im Teilhalbschnitt zur Durchführung des erfindungsgemäßen Verfahrens am Ende des ersten Teilschrittes;

Figur 4 -

zweites Tiefziehwerkzeug im Teilhalbschnitt am Ende des zweiten Teilschrittes;

Figur 5 -

ein weiteres zweites Tiefziehwerk zur Ausführung des erfindungsgemäßen Verfahrens am Ende des zweiten Teilschrittes im Teilhalbschnitt;

Figur 6 -

die schematische Darstellung zur Weiterbearbeitung des erfindungsgemäß hergestellten Rohlings;

Figur 7a -

ein alternatives Formwerkzeug zur Ausführung des er- findungsgemäßen Verfahrens am Beginn des zweiten Teilschrittes im Teilhalbschnitt;

Figur 7b -

das Formwerkzeug nach Figur 7a am Ende des zweiten Teilschrittes.

Figur 8 -

eine Draufsicht auf das Formwerkzeug aus Figur 7 zur Ausführung des erfindungsgemäßen Verfahrens für den zweiten Teilschritt im Teilhalbschnitt;

Figur 9 -

eine Draufsicht auf ein alternatives Formwerkzeug zur Ausführung des erfindungsgemäßen Verfahrens für den zweiten Teilschritt im Teilhalbschnitt.

With the aid of the attached drawings, the method according to the invention will be explained in more detail by way of example. It shows:

FIG. 1 -

a partial half section through a first thermoforming tool;

FIG. 2 -

a thermoforming tool in partial half section according to the prior art;

FIG. 3 -

a first deep-drawing tool in the partial half section for carrying out the method according to the invention at the end of the first partial step;

FIG. 4 -

second deep-drawing tool in partial half-section at the end of the second partial step;

FIG. 5 -

a further second thermoforming unit for carrying out the method according to the invention at the end of the second partial step in the partial half section;

FIG. 6 -

the schematic representation for further processing of the blank according to the invention;

FIG. 7a -

an alternative mold for performing the method according to the invention at the beginning of the second partial step in the partial half section;

FIG. 7b -

the mold after Figure 7a at the end of the second step.

FIG. 8 -

a plan view of the mold FIG. 7 for carrying out the method according to the invention for the second partial step in the partial half section;

FIG. 9

a plan view of an alternative mold for performing the method according to the invention for the second sub-step in the partial half section.

In the figures, identical or equivalent components have been given the same reference numerals.

FIG. 1 shows the partial section of the center line M symmetrically constructed first thermoforming tool consisting of the cutting ring 1, the cutting bell 2, cooperating with the cutting bell 2 hold-down 3, the drawing block 6 supporting lower part 4 and the embossing block 7. The embossing block 7 and the drawing block 6 with the cutting bell 2 include the blank 8 a. About regularly distributed on a circumferential circle arranged hold-down pins 5, the force of a spring assembly not shown here is transmitted to the hold-3.

The production of the blank 8 is carried out according to the prior art with the tool according to FIG. 2 in which the lacquered sheet metal or a cut-out (punched out) thereof by means of the cut ring 1 Ronde is placed on the drawing block 6. On the sheet of the embossing block 7 and the cutting bell 2 are lowered, the cutting bell 2 punched out a metal plate from the blank. Between the hold-down 3 and the cutting bell 2, a flange or flange is clamped after transection of the sheet, the width of which is steadily reduced in a further lowering movement of cutting bell 2 and hold-down 3. As a result of the reduction in the width of the flange, the surface pressure in the flange increases due to the force F acting on the hold-down device 3.

FIG. 3 shows the first tool at the end of the first sub-step of the method according to the invention. The cut bell 2 and the hold-down 3 are moved together relative to the drawing block 6 until a defined surface pressure occurs in the flange 8a of the blank 8, ie, the width of the flange 8a formed from the difference between the outside radius R and the inside radius r has a defined dimension has reached. This defined dimension is less than 3 mm and is preferably 0.1-1.5 mm, and more preferably 0.5-1.0 mm. Compared to the inner radius r of the blank 8, this measure is therefore very small.

The two steps of the deep-drawing process according to the invention are carried out in two different tools. Therefore, a conventional first tool can be used, in which the hold-3 is force-loaded, for example via a spring assembly. After completion of the first step, the blank 8 is removed from the first tool and inserted into another, second tool, which either has no hold-down 3, as in FIG. 5 shown, or an existing hold-down 3 is powerless, as in the FIG. 4 is shown.

In the second step, for example FIG. 4 As can be seen, in a second tool, the hold-down device 3 is powerless during the deformation and the cutting bell 2 forms the blank 8 by a further deep-drawing step. In this case, at the axially outer end of the wall 8b, a radially outwardly facing profiling 8c is introduced, which ensures the subsequent curling of the wall 8b that in the wall 8b no wrinkles or Einknickungen. The inside of the cutting bell 2 and the outside of the drawing block 6 have a profiling 8c corresponding shape. The Indian FIG. 4 shown hold-down 3 is used in the illustrated tool only as a lifter, therefore, to eject after completion of the deformation of the molding by a lifting movement upwards from the tool.

An alternative second tool based on the FIG. 5 is illustrated, differs from that in FIG. 4 shown tool in that is completely dispensed with a hold-down. For lifting or loosening of the molded part instead of an integrated into the drawing block 6 shock element 9 is provided as a lifter, which ejects by a lifting movement up the molding after completion of the deformation of the tool. There is also the possibility to provide an air channel in the drawing block 6 to solve the molding by a puff of air from the drawing block 6 and eject from the tool.

The curling of the wall 8b is FIG. 6 removable. By rolling radially inward, the radially outwardly facing profiling 8c is canceled, so that the wall 8b takes a straight course. To increase the stability of the lid of the slightly beaded edge is then further rolled. For a screw cap after completion of the curling at the lower end regularly distributed over the circumference of the cam 8d are pressed, which later interact with the thread attached to the neck of the glass bottle.

The following is with reference to the FIGS. 7a and 7b an alternative deformation of the blank 8 in the second sub-step according to the invention explained. The first step (see FIG. 3 ) shaped blank 8 has in the lower region of the wall 8b on a radially outwardly facing flare 8a and is placed on a mold block 10. On its outer circumference, the mold block 10 has a shoulder 11 such that the diameter in the lower region 10a of the mold block 10 is less than the diameter in the upper region 10b. Furthermore, the shoulder 11 is substantially in the region or the height of the bead 8a of the blank 8, when this is placed on the mold block 10.

In the deformation presented here, an applicator 12 is brought to the crimp 8a of the blank 8 coming from the outside. The arrow 13 indicates the direction of movement of this approach. The applicator 12 rotates about its longitudinal axis 14, which is inclined inwardly in the height of the flange 8a. That is, the lower portion of the Anrollers has a smaller distance to the mold block 10 than the upper area. The rotation about the longitudinal axis 14 is indicated by the bent arrow 15. The applicator 12 is further guided inwardly until the blank 8 is deflected in the lower region with the flange 8a, so that in the wall 8b, a radially inwardly facing profiling 8e is formed, as in FIG. 7b is shown. By a relative movement between the applicator 12 and the mold block 10 with the blank 8 lying thereon, for example a rotation of the mold block 10 about its central axis, the profiling 8e is formed radially inward on the entire outer circumference of the wall 8b of the blank 8.

In order to remove the blank 8 from the mold block 10 or to lift, the wall 8 b must be deflected so far radially outward with the profiling 8e in the removal that the inner edge of the profiling 8 e can be performed on the paragraph 11 over. It makes sense that the dimension of the heel 11 or the profiling 8e is selected such that this deflection remains in the elastic deformation region of the blank 8. For then the wall 8b springs back after the removal back into the shape that was generated by the deformation in the second sub-step.

But it is also conceivable that the deflection is not purely elastic, but in addition is accompanied by a plastic deformation. Then, however, the dimension of the heel 11 and the profiling 8e is to be chosen such that after the reshaping of the elastic portion of the deflection, the profiling 8e still points sufficiently radially inward is trained. That is, in this case, the profiling 8e is further deformed inward by rolling up, as is required for further processing.

In the FIG. 8 is a schematic plan view of a device 16 with the mold from the FIGS. 7a and 7b shown. The apparatus 16 in this example comprises a number of a total of 8 forming stations 17 which are arranged on a circle (indicated by a dashed line) equidistant from one another and rotate about the center of this circle. Of the 8 forming stations 17, only the 3 engaged ones are shown in the figure. Each forming station 17 has a mold block 10 on which a blank 8 can be placed. Furthermore, each forming station 17 has a reel-up 12 which is held by a carrier arm assembly 18.

In the presentation of the FIG. 8 the blank 8 of the device 16 is supplied from the left and placed on the rotating mold block 10. While the device 16 with all associated forming stations 17 rotates counterclockwise, the blank 8 is deformed by the rolling. After a partial rotation of the device 16 by about 180 ° leaves the blank 8 in the illustration of FIG. 8 to the right, the device 16. In the subsequent partial rotation of the mold block 10 is left unused until it is again provided in the illustration on the left with a new blank 8. During the deformation of the occupied with a blank 8 mold block 10 is rotated about its longitudinal axis, which is perpendicular to the plane. As a result, the blank 8 at its entire outer periphery with the profiling invention Mistake. For clarification, a cross section through the blank 8 'is shown in each case before the forming and by the blank 8 "after the deformation in the figure.

The FIG. 9 finally shows a further device 19 for carrying out the deformation according to the invention in the second partial step. The device has a number of a total of 8 circular, equidistantly arranged mold blocks 10, which rotate about their common center axis in the counterclockwise direction. Furthermore, each mold block 10 additionally rotates about its longitudinal axis which is perpendicular to the plane of the drawing. As already in the in FIG. 8 shown device 16 is also supplied in the device 19 of the blank 8 from the right side (based on the representation of the drawing) and it is released after a partial rotation of the device 19 by about 180 ° from this.

During the partial rotation of the blank is placed with the located on the wall 8b flange 8a in contact with an inner surface 20 of a rigid guide 21, which has a substantially semicircular configuration. The figure can not be clearly seen that the radius of the semicircle tapers to deform the blank 8 in contact with the inner surface 20 continuously further, so that when leaving the device 19 has an inwardly facing profiling 8e, as with the in FIG. 8 shown device 16 is generated.

In the deformations presented here in the second sub-step, all alternative approaches have in common that no force or counterforce supplied externally to the blank 8 is opposed to the deforming force. When undressing (see FIGS. 4 and 5 ) is exerted by the cutting bell 2 only a vertically downward force acting on the blank 8. When deformed by a roller 12 or by a guide 21 (see FIGS. 8 and 9 ) acts only a force from radially outside and below on the blank 8. A counter force, as exercised by the hold-down in the first step, does not affect the blank in the second step.

LIST OF REFERENCE NUMBERS

1

cutting ring

2

cutting bell

3

Stripper plate

4

lower part

5

Hold-down pins

6

drawing block

7

embossing Klotz

8th

blank

8a

Flare / flange

8b

wall

8c

profiling

8d

cam

8e

profiling

8th'

Blank before the second process step

8th"

Blank after the second process step

9

impact element

10

forming block

10a

upper area

10b

lower area

11

paragraph

12

Anroller

13

arrow

14

longitudinal axis

15

Arrow (rotation)

16

contraption

17

forming station

18

longitudinal axis

19

contraption

20

palm

21

guide

F

force

M

center line

r

inner radius

R

outer radius

Claims (10)

1. Method for deep drawing a cup-shaped article, in particular a blank (8), a screw closure for glass bottles or the like, from a coated metal sheet, comprising the following steps:

   1) stamping the blank (8) out of the metal sheet in a tool by the relative movement between a cutting bell (2) cooperating with a blank holder (3) and a drawing block (6) and drawing the blank (8) around the drawing block (6) with an impingement of force on the blank holder (3), wherein the width of a flange (8a) forming between the cutting bell (2) and the blank holder (3) is continuously reduced with a progressive degree of deformation, until the flange (8a) has reached a defined width,

   2) drawing out the defined flange (8a) in a tool by the relative movement between the cutting bell (2) and the drawing block (6) of the tool without an impingement of force in the direction opposing the movement of the cutting bell (2),

   characterised in that the step of stamping out and drawing with an impingement of force is carried out in a first tool and the drawing is interrupted when the flange (8a) has reached a defined width (R-r) and then the step of drawing out without an impingement of force is carried out in a second tool without a blank holder.
2. Method according to claim 1, characterised in that the deformation is carried out by drawing out the flange (8a) based on the relative movement between a cutting bell (2) and a drawing block (6) of the second tool.
3. Method according to claim 1, characterised in that the deformation is carried out by means of a guide (21) cooperating with the second tool.
4. Method according to claim 1, characterised in that the deformation takes place by rolling in the second tool.
5. Method according to any one of the preceding claims, characterised in that the wall (8b) of the cup-shaped article is radially outwardly deformed by a profiling (8c).
6. Method according to any one of claims 1 to 4, characterised in that the wall (8b) of the cup-shaped article is deformed pointing radially inwardly by the profiling (8e).
7. Method according to any one of the preceding claims, characterised in that the wall (8b) of the cup-shaped article is rolled in radially inwardly at its axially outer end.
8. Method according to any one of the preceding claims, characterised in that the radial width (R-r) of the flange (8a) is less than substantially three millimetres.
9. Method according to claim 8, characterised in that the radial width (R-r) is 0.1 to 1.5 mm.
10. Method according to claim 9, characterised in that the radial width (R-r) is 0.5 to 1.0 mm.

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