EP0696486B1 - Method and device for bending sheet metal blanks - Google Patents

Description

The invention relates to a method and a device according to the corresponding Claims for rounding sheet metal pieces.

According to the prior art, rectangular or square, planes Pieces of sheet metal, for example, for the manufacture of can bodies are rounded and then welded the two axially and parallel edges, whereby the sheet metal pieces are formed into a cylinder jacket.

For rounding, the piece of sheet metal is turned into a curved shape in a round apparatus brought in that, for example, by a round wedge to an inner Round roller is guided and immediately thereafter runs through a press station the inner round roller and an outer round roller, which two rollers are pressed together. This creates the originally flat piece of sheet metal bent around a constant radius of curvature so that the one emerging from the press point Part of the piece of sheet metal is no longer straight, in the original feed direction moved on, but arched on the through the radius of curvature defined rounding circle runs into a natural rounding position. For the If can frames are manufactured, the bent sheet essentially runs along the entire rounding circle, so that the one lying in the rounding position Sheet presented as an almost closed cylinder jacket. In practice it can Rounding circle or the rounding layer by the weight and the elasticity of the curved sheet can be slightly deformed, which is due to guide means for the rounded Sheet metal section is avoidable.

The radius of the rounding circle is determined by the radius of the inner round roller, by the position of the round wedge and by the elasticity of the sheet material (Sheet thickness and yield strength). It is usually used in the manufacture of can frames set so that it is rather smaller than the radius of the welded Frame so that the rounded plate is a cylinder jacket, whereby the axially running edges slightly overlap each other.

The guide means usually consist of the rounded sheet metal section an essentially cylindrical internal round mandrel and an essentially hollow cylindrical outer guide, the space in between the the round gap lying in the rounding circle. After the rounding is completed the piece of sheet metal is ejected from the round gap in the axial direction and another Sheet piece inserted into the bending device and the round gap.

The cycle time required for rounding a piece of sheet metal is set at the above known methods described together from the time taken for the rounding is necessary and from the time necessary for the expulsion. Here is the Rounding time determined by the feed rate and the rounding Length of the sheet. The ejection time is determined, among other things, by the axial Length of the rounded piece of sheet metal. In other words, that means the sheets the round apparatus with a minimum distance from each other not from the rounding process itself, but from the axial expansion the rounded piece of sheet metal and the ejection mechanism used is dependent

US-2 719 562 shows a round apparatus in which the finished rounded sheets in caught in a collecting tray and removed in batches from the round apparatus. The sheets can be stored temporarily in the catch tray, as widen the curve back a little bit elastically. This leaves between Round roller and intermediate sheet metal some space for the new to be rounded Sheet. The cycle time for rounding is reduced somewhat on average, because it is not Sheet by sheet must be ejected individually and so rounding only is interrupted when the stack is removed.

The object of the invention is now to further increase the cycle time for rounding reduce and in particular to enable the cycle time reduction even then comes into being when the sheets come out of the Round apparatus can be removed. The rounding quality should not be reduced in any way and there should also be no significantly higher expenditure on equipment, e.g. with a view to a faster ejection mechanism. This The problem is solved by the method and the device as described in the corresponding Claims are defined.

The fact that the rear end portion of the rounded sheet in one of if the rounding position is different, there is room for that next sheet, with its front area running into the rounding position, although the former sheet metal has not yet or not completely left the circular apparatus Has. Accordingly, the next sheet must be fed into the round apparatus are no longer waited until the dial is free, which allows the to shorten the minimum distance between the sheets for a given feed, so to reduce the overall cycle time.

In a device for performing this method, means are provided to bring the rear part of the rounded plate into the transport position. This is possible by elastic deformation of the front part of the rounded sheet through the guide means so that the rounded rear part of the sheet is under load and, as soon as released by the pressing point, into the transport position jumps. It is also possible to remove the sheet immediately after finishing Braking the front rounding process so abruptly that the rear area thrown out of the rounded position into the transport position by its inertia becomes.

The method according to the invention and the method according to the invention are intended to be illustrated by the following figures Device will be described.

Fig.1a bis 1c

ein Schema des erfindungsgemässen Rundungsverfahrens in drei aufeinanderfolgenden Phasen;

Fig. 2

ein Schema einer Vorrichtung zum Durchführen des Verfahrens gemäss Figuren 1a bis 1c im Querschnitt;

Fig. 3

eine weitere Ausführungsform einer Vorrichtung zum Durchführen des erfindungsgemässen Verfahrens im Querschnitt;

Fig. 4 bis 9

schematisch eine weitere Variante des erfindungsgemässen Verfahrens in sechs Phasen, durchführbar in der Vorrichtung gemäss Fig. 3.

Show it:

1a to 1c

a diagram of the rounding method according to the invention in three successive phases;

Fig. 2

a schematic of a device for performing the method according to Figures 1a to 1c in cross section;

Fig. 3

a further embodiment of a device for performing the method according to the invention in cross section;

4 to 9

schematically a further variant of the method according to the invention in six phases, which can be carried out in the device according to FIG. 3.

1a, a piece of sheet metal 1 is in a direction designated Z Pressing point P (indicated by a double arrow) is fed to a rounding device The rounding device itself is not shown in FIG. 1a. Rounding devices are known per se; an embodiment of such a rounding device, which are part of a rounding apparatus shown in FIGS. 2 and 3 80 forms is described in more detail below with reference to FIG. 3. In the rounding device the sheet metal piece 1, which has been flat until now, is plastically deformed in an arcuate manner, such that after leaving the press point P there is a desired has a constant radius of curvature. The leading, curved part of the sheet metal piece 1 thus runs into a natural rounding position after leaving the press point P. in; the corresponding rounding circle is dash-dotted in Fig. 1a shown and labeled A. In addition to the rounding circle A is in Fig. 1a and in all other figures an ejection circle B shown in dash-dotted lines. The middle-point B's ejection circle B is opposite the center point A 'of the rounding circle A in Offset towards Z. The intersections of the two circles A and B are designated M, M '. The ejection circle B defines a transport position for the rounded Piece of sheet metal 1; as soon as the sheet metal piece 1 is in this transport position (as this happens, is described below), it can also be done by itself known, not shown in the drawing ejection mechanism in axial, i.e. direction perpendicular to the plane of the drawing from the rounding apparatus ejected and transported, for example, to a welding device are no longer related to the subject of the present invention.

1a shows a phase in which the front part of the sheet metal piece 1 has already passed the press point P and is plastically deformed on the rounding circle A runs into its rounding position.

In the phase shown in Fig. 1b, the sheet metal piece 1 is according to the invention on Intersection M 'from the rounding circle A into the ejection circle B, which does not correspond to the rounding position, in a later described with reference to FIG. 2 Directed way. The rear area of the sheet metal piece 1 is through the press point P still fixed, which has the consequence that the between the press point P and the Intersection M 'lying sheet metal section elastically deformed.

1c shows the position of the sheet metal piece 1 a short time after the rounding process has ended Due to the elastic deformation of the front sheet metal section, which is on the ejection circle B, the rear sheet metal section has since it is no longer held by the press point P in the area of the rounding circle A, also relaxed in the area of the ejection circle B, so that the entire Sheet piece 1 on the ejection circle B, that is located in the transport position. The piece of sheet metal 1 can now be axially ejected from the rounding apparatus become. At the same time, a subsequent piece of sheet metal 2 is already in the rounding process and runs with its front area on the rounding circle A in its rounding position, which has become available in time since the rear part of the Sheet metal piece 1 is now on the ejection circle B. The piece of sheet metal 1 must then be expelled from the rounding apparatus when the front edge of the sheet metal piece 2 reaches the intersection M '.

The geometric relationships shown in FIGS. 1a-1d are only exemplary. For example, can, depending on whether the space for the subsequent sheet is larger or should be smaller, the leading sheet later or earlier from the rounding circle be directed away; Likewise, it is not mandatory (but inexpensive) as an ejection circle B. a circle as such or the same radius of curvature as in the rounding circle A to be provided.

Fig. 2 shows schematically and very simplified a device or a rounding apparatus 80 for performing the method according to FIGS. 1a to 1c. The rounding apparatus 80 has a rounding device 10 with the aforementioned press point P assigned to rounding circle A. The well-known Rounding device 10 itself is not closer to FIG. 2 for the sake of simplicity shown. Furthermore, the rounding apparatus 80 has guide means 70 for guidance of the rounded piece of sheet metal 1.2; an inner round mandrel 20 and an outer guide 30 together form a round gap 40, which is closed by an end stop 31 is. Furthermore, the rounding apparatus 80 is open with the one already mentioned the ejection circuit B aligned ejection mechanism, of which only two ejection cams 50.1 and 50.2 are shown in FIG. The exhaust cams 50.1 and 50.2 act axially, i.e. perpendicular to the drawing plane Direction. For the ejection cam 50.1 and 50.2 are in the guide surfaces of the Internal round mandrel 20 or the outer guide 30 corresponding recesses 22, 37, 36 provided. However, instead of the ejection cams 50.1, 50.2 other means of ejection are used.

The circular gap 40 has two sections 41, 42. The first section 41 allows to run the piece of sheet metal 1 or 2 into its rounding position, so it corresponds the rounding position and contains a section of the rounding circle A; it ends at the intersection M 'of the two circles A and B. The second section 42 begins at the intersection M ', contains a section of the ejection circle B and ends in End stop 31. The sections 41, 42 are through the inner dome 20 and External guide 30 limited. The inner round dome 20 is lemon-shaped in cross section formed, which corresponds to the overlap area of circles A and B. The outside tour 30 is substantially hollow-cylindrical and follows in its Cross section of the ejection circle B.

The shift between rounding circle A and ejection circle B, i.e. the distance between center points A 'and B' can e.g. then be chosen that a piece of sheet metal 1 or 2 entering the rounding circle A is not included the inlet-side discharge cam 50.2 comes into conflict.

The rounding method described in connection with FIGS. 1a to 1c, that can be carried out with a device according to FIG. 2 represents the simplest variant of the method according to the invention and required in the area of the round gap 40 a minimum of guide surfaces (theoretically only the final guide after the Intersection M '). This variant is for sheet metal pieces with sufficient inherent stability and elasticity applicable. The inherent stability essentially depends on the modulus of elasticity the sheet metal used, the sheet thickness and sheet size and from the desired rounding radius. For sheet metal pieces to be rounded with less inherent stability (e.g. made of thin sheet metal), it is advantageous to use additional guide means especially for the first phase of rounding and for the final phase provided. Such an expanded method and a corresponding device are described in connection with Figures 3 to 9.

3 shows a further embodiment of the device according to the invention Rounding of pieces of sheet metal. The already known from previous figures, elements with the same effect are again identified by the same reference numerals.

3 has a round wedge 11, an inner one Round roller 12 and an outer round roller 13. The two round rollers 12, 13 are pressed against each other and affect those carried out between them Sheet metal pieces (not shown in Fig. 3) along a line perpendicular to the plane of the drawing in the press point P in such a way that the originally flat sheet metal pieces around the desired constant radius - according to rounding circle A - be bent.

The outer guide 30 has a central part 34 and an end part 35 which carries the end stop 31. In addition, the outer guide 30 has a retaining element 32 equipped. The retaining element 32 has a guide surface 33, a hook-shaped locking groove 38 and an arcuate support surface 39. The mode of operation of the retaining element 32 is described below with reference to FIG Figures 6 to 9 described. Between the retention element 32 and the middle one Part 34 or between the middle part 34 and the end part 35 are the recesses 36 and 37 are arranged, in which the ejection cams 50.1 and 50.2 move. The recess in the inner round dome opposite the recess 37 20 is again designated with 22. The directed against the round gap 40 Guide surfaces of the outer guide 30 are everywhere outside the ejection circle B, which defines the transport position of the rounded sheet metal piece. According to 3, these guide surfaces are designed polygonal.

In this embodiment, the inner round dome 20 has one over the rounding circle A area 21 projecting into the circular gap 40.

The mode of operation of the device according to FIG. 3 will be explained in the following with the aid of figures 4 to 9, which schematically illustrate another, analogous to FIGS. 1a to 1c, variant of the method according to the invention which can be carried out in this device, but this time in six consecutive phases. The in the Active guide surfaces in each phase are indicated with hatching and in Based on Fig. 3 with the apostrophized reference numerals of the corresponding device parts designated.

4, the leading part of the sheet metal piece 1 already has the press point P. happens and is through the area 21 of the inner dome projecting over the rounding circle A. 20 led. As a result, the rounded sheet metal part is easily deformed and pressed against the guide surface 21 'by its elasticity. It follows from this a precisely defined position of the leading one even with one-sided guidance Piece of sheet metal part. The guide surface 11 'of the is also active in this phase Rounding wedge.

5, the leading part of the sheet metal piece 1 has the second section 42 of the circular gap 40 (Fig. 3) reached and is there mainly by the outer Guide surface 34 'guided on the ejection circle B and thereby from the guide surface 21 'pushed away

Fig. 6 shows the phase of the rounding process immediately after the end edge of the rounded sheet metal piece 1 has left the press point P. The end area of the Sheet metal piece 1 is always through the guide surface 33 'of the retaining element 32 still led on rounding circle A. The sheet metal piece 1 moves thanks its kinetic energy continues in the circular gap 40, on the ejection circle B. through the inner and outer guide surfaces 20 ', 34', 35 'of the inner dome 20 or the outer guide 30. The guide surface 33 of the retaining element 32 is designed so that the end edge of the sheet metal piece 1 has not yet reached its end has when the front edge abuts the end stop 31.

Figures 7 and 8 show how the sheet metal piece 1 by the action of the impact the end stop 31 is compressed (Fig. 7), thereby the end edge of the sheet metal piece 1 slides over the guide surface 33 'and finally leaves it, after which the trailing part of the sheet metal piece 1 against the ejection circle B. relaxed (Fig. 8). It is expected that the trailing part over the discharge circle B springs out and it is advantageous to move this spring through the arc Limit the support surface 39 'of the retaining element 32. Will that Sheet piece 1 strongly compressed by the impact on the end stop 31, is the polygonal Design of the outer guide surfaces 34 'and 35' as in FIG. 3 represented of particular advantage, since the sheet metal piece 1 in the resulting Extensions of the circular gap 40 can dodge and spring back better.

In an embodiment not shown, the sheet runs on the rounding circle A until it is braked abruptly by an end stop or other suitable means is what the rear end only because of its kinetic energy slides over the surface 33 'and reaches the retaining element. An elastic Deformation of the front part of the sheet is not necessary, but it can supportive.

9 shows the last phase, the ejection phase. The rear end of the Sheet metal piece 1, which was caught and springed back by the support surface 39 ', is in a hook-shaped locking groove 38 ', which lies on the ejection circle B. further backward movement prevented and imprisoned in the same. So can already another sheet metal piece 2 unhindered via the guide surface 33 of the Retaining element 32 initially run on rounding circle A. That done rounded sheet metal piece 1, the position of which is now precisely defined, can from the Round gap 40 are ejected. The polygonal design of the exterior guidance 30 advantageously contributes to easy ejection.

As already mentioned, the method according to FIGS. 4 to 9 is due to the additional Guiding in the infeed area and by guiding the trailing edge in the end area advantageous for sheet metal pieces with relatively low inherent rigidity in particular 7 to 9 show that the method according to this variant (in contrast to the variant according to Fig. 1a to 1c) in addition to the resilient tension of the rounded Sheet metal piece also uses its kinetic energy to the trailing Part on the output circle B, i.e. to move to the transport position. For this Basically, this method is also to be preferred for less resilient pieces of sheet metal.

Another possible procedure is based on the idea according to the invention, for elastic deformation of the sheet and the resulting movement of the released end section leaving the press point P into the Transport position only when suddenly stopping the feed speed utilize the kinetic energy obtained from the subsequent sheet metal part without first to deform the front sheet metal section elastically. To do this Variant, which is not shown alone in the drawing, is only a front the end stop arranged at the pressing point P and one assigned to the transport position Retaining element, for example in the form of the retaining element known from FIG. 3 32, necessary.

In addition to the shown displacement of the discharge circle defining the transport position B in the feed direction Z and the corresponding elastic deformation the front sheet metal section to the inside could also have a different transport position to get voted; for example, instead of the outer guide 30 an internal guide, e.g. a correspondingly trained inner round dome, the front Steer the sheet metal section outwards and deform it elastically, whereby then likewise the end section which has run out of the rounding device 10 is spring-loaded follow into the transplant position opposite the rounding position and the Rounding position for the subsequent sheet would clear.

Claims (18)

1. A method for bending sheet metal blanks (1, 2) in a rounding machine (80) to which a plurality of sheet metal blanks (1, 2) to be rounded are fed in immediate succession, each sheet metal blank (1, 2) being plastically deformed in a bending device (10) and then passing into a natural rounding position and being immediately ejected from the rounding machine, characterised in that during rounding a front portion of the sheet metal blank (1, 2) and, immediately after completion of the rounding of a sheet metal blank (1), its rear end portion is brought into a transport position deviating from the rounding position, in such a way that the rounding position is freed for at least the front portion of a following sheet metal blank (2) already being rounded, before the finished rounded sheet metal blank (1) is ejected from the rounding machine (80).
2. A method according to Claim 1, whereby guide means for the sheet metal blank (1) passing out of the rounding device (10) into the rounding position are provided, characterised in that at least a section of the already rounded portion of the sheet metal blank (1) being rounded is so deflected out of the rounding position under elastic deformation by the guide means that the sheet metal section passing directly out of the rounding device (10) is maintained under stress by the deflecting forces and, after the sheet metal blank (1) has passed completely through the rounding device (10), springs into the transport position under this stress.
3. A method according to one of the Claims 1 or 2, characterised in that the section of sheet metal brought into the transport position is prevented from returning to the rounding position by a restraining element (32).
4. A method according to Claim 3, characterised in that, as a result of elastic deformation, the sheet metal section moving into the transport position slides beyond a restraining element (32) obstructing it and then is held captured by said restraining element (32) which preferably has the form of a barb hook.
5. A method according to one of the Claims 1 to 4, whereby means are provided in the rounding machine (80) for arresting the feed velocity of the sheet metal blank (1 or 2), characterised in that the sheet metal blank (1 or 2) passing out of the rounding device (10) at the feed velocity is so braked at its front end by said means for arresting the feed velocity that the sheet metal blank (1 or 2) is elastically deformed as a result of the kinetic energy of the following portion that its rearward edge is carried to a predetermined degree beyond its natural end position through elastic deformation of the sheet metal blank (1 or 2), thereafter springs back into the transport position and is held in that position by a restraining element (32).
6. A method according to Claim 2, characterised in that the rounded portion of a sheet metal blank (1 or 2) being rounded first passes through a first section of travel corresponding to the rounding position and then reaches a second section of travel differing from the rounding position, so that the portion of the sheet metal located in said second section of travel is deflected out of the rounding position.
7. A method according to Claim 6, characterised in that said second section of travel lies between the corresponding section of the natural rounding position and the centre of curvature and in that the rounded sheet metal blank (1), after passing through the rounding device (10), is relaxed in that its rearward portion moves outwardly into the transport position.
8. A device for implementing the method according to Claim 1, with a device for feeding individual sheet metal blanks (1, 2), with the rounding machine (80) including the rounding device (10), and with an ejection mechanism for ejecting the finished rounded sheet metal blanks (1, 2) from the rounding machine (80), characterised in that means (30; 31, 32) are present whereby during the rounding process the front portion of the sheet metal blank and then the rearward end portion of the sheet metal blank (1 or 2) is brought into the transport position as it is released on leaving the rounding device (10).
9. A device according to Claim 8, characterised in that means (30; 31, 32) are provided for elastically deforming the sheet metal blank which is passing or has passed out of the rounding device.
10. A device according to Claim 9, characterised in that the means (30 or 31, 32) for elastically deforming the sheet metal blank (1, 2) comprise an arrangement, preferably an end stop (31), for abruptly braking the feed velocity of the sheet metal blank (1, 2) passing or having passed out of the rounding device (10).
11. A device according to one of the claims 9 or 10, characterised in that the means (30; 31, 32) comprise a restraining element (32) designed to hold at least the rear portion of the sheet metal blank in the transport position.
12. A device according to one of the claims 8 to 10, characterised in that the means (30; 31, 32) for elastically deforming the sheet metal blank (1; 2) include a guide whereby a front portion of the sheet metal blank (1; 2) passing out of the rounding device (10) can be deflected from its natural rounding position.
13. A device according to Claim 12, whereby the rounding machine (80) comprises guide means (70) for the sheet metal blank (1, 2) passing out of the rounding device (10), characterised in that the guide is designed as an external guide (30) acting on the front portion of the sheet metal blank and forms part of the guide means (70).
14. A device according to Claim 13, characterised in that the external guide (30) substantially surrounds an ejection circle (B) defining the transport position, the radius of which ejection circle (B) corresponds to the rounding radius and the centre (B') of which ejection circle (B) is offset, preferably in the feed direction (Z) of the sheet metal blanks (1, 2), with respect to the centre (A') of a rounding circle (A) corresponding to the natural rounding position.
15. A device according to one of the claims 11 or 12, characterised in that the external guide (30) forms together with an internal rounding mandrel (20) a rounding gap (40) which receives the portion of the sheet metal blank passing out of the rounding device (10), a part of the rounding gap (40) being designed as a guide gap (42) for the front portion of sheet metal to be elastically deformed and the cross-section of the internal rounding mandrel (20) preferably corresponding substantially to the area of overlap of the two circles (A, B).
16. A device according to one of the claims 14 or 15, characterised in that the external guide (30) has a polygonal configuration and the internal rounding mandrel (20) preferably has a guide portion (21) projecting beyond the rounding circle (A) and located in front of the rounding gap (42) for guiding the portion of the sheet metal blank passing out of the rounding device (10).
17. A device according to Claims 10 and 11, characterised in that the end stop (31) and the restraining element (32) form part of the external guide (30).
18. A device according to Claim 11, characterised in that the restraining element (32) has an arcuate support face (39) to limit the elastic movement of the released portion of the sheet metal blank beyond the ejection circle (B), caused by the elastic deformation of said portion, and to accelerate its engagement in the locking groove (38).

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