EP0060213A1 - Marking device for different symbols - Google Patents

Abstract

1. A stamping device for various characters having at least one stamping wheel on the circumferential face of which the characters to be stamped are provided in relief and associated with which is a bottom die, stamping wheel and bottom die being adapted to be pressed against the workpiece at both sides, from opposite sides of a workpiece to be distinguished by characters and capable of being cupped, and with the force necessary for carrying out the stamping operation, preferably for use in stamping characters in steel sheets which are used as body plates or chassis plates of motor vehicles, characterised in that the bottom die (m to m**VI ) is constructed in such a manner that regions of the workpiece corresponding to the superimposed images of at least two characters of the same stamping wheel (p) can be deformed into the surface plane of the bottom die against a resistance ensuring the deformation of the workpiece, by means of the stamping wheel (p).

Description

The invention relates to an embossing device with the features of the preamble of claim 1, preferably for embossing character strings in chassis made of sheet steel of motor vehicles.

A corresponding device for embossing plastic films is known from DE-A-25 55 849. However, while this known device requires a pair of embossing wheels, on the circumferential surfaces of which there are raised characters or mirror-image depressions (matrices) around different ones To generate characters, the present invention is intended to simplify the control effort for embossing character strings.

It has been shown that the need to manufacture and control the two embossing wheels precisely to one another, not only with small tolerances, requires considerable mechanical and / or electronic effort.

Accordingly, the invention has for its object to reduce the manufacturing and control effort for such an embossing device.

This object is achieved according to the invention by the embossing device with the features of patent claim 1. Advantageous further developments are specified in the subclaims.

Since several characters provided on the embossing wheel fit into one die, the risk of breakage of embossing wheels in the event of incorrect switching is also excluded, as is the case when the embossing characters are not synchronized when using two 'embossing wheels in the known arrangement. Furthermore, the number of different Significantly increase the number of characters to be embossed, as the size of the die remains constant with the increasing number of characters. The arrangement is also more space-saving overall.

The embossing wheel with raised characters on the circumferential surface is assigned only a single fixed die, which either has an overlay of the images of all the characters of the embossing wheel as a recessed pattern or is resilient on its surface. If only a single fixed die and only a single _P n embossing wheel are used, the manufacturing and also the control effort are the least.

Various measures are conceivable for generating counterfeit-proof characters, as specified in the subclaims and in the description. If the number of characters to be embossed is very large and the characters are to be designed as freely as possible, the provision of an elastic die has advantages. A universal matrix is then available, which - in addition to the seven- or multi-segment font - also enables the embossing of numbers, letters and characters that do not adhere to lines that can be superimposed.

An advantageous further development of the invention is further based on the object of improving the deformation in such an embossing device in such a way that, in addition to a sharp representation of the digits, the die made of the elastic material has a long service life. In particular, the inner shape of the characters (for example the inner surface of the number "zero") should also be sharply defined.

Such an elastic universal matrix preferably consists of polyurethane based on polyether with a Shore hardness of essentially 95 as a homogeneous element embedded in a milling.

It is of particular importance that the die is so thin that the flexibility is essentially exhausted when the letter edge is pronounced, the die preferably being molded into a metal bed in such a way that the elastic material is prevented from swelling by swelling .

In contrast to this, for example, a sandwich-like layering of soft types of plastic or rubber as a spring body with a covering wear layer of greater hardness does not withstand the cushion from the relatively large embossing forces.

The thin dimension of the die is in contrast to the dimensioning of rubber matrices for cutting work, where the layer thickness - when using polyurethane with a Shore hardness of approximately 80 - is more than five times the cutting template and the wear layer to be replaced alone is 15 to 20 mm thick having.

With the very thin pillow height, the stresses in the material layers rise steeply during embossing after an exponential function. With this increase in pressure, "finish embossing" takes place after the outer contours of the letters have been mapped.

An approximately 2 mm thick polyurethane layer is used for embossing approximately 8 mm high characters in sheet steel (body sheet St 14.03 according to DIN 1623) with a thickness of 0.8 mm, whereby the cushion width only increases the letter dimensions by approx. 1 to 2.5 mm.

A longitudinally milled metal groove, into which the strip-shaped polyurethane material is glued, is preferably used for embossing rows of characters. A synthetic resin adhesive (Macroplast UK 8202 with hardener UK 5400) is preferably used for this. By gluing, the possibility of the material to evade is further reduced. It is sufficient if the material is glued in the area of the ends.

The embossing tool must have a significantly different design when embossing with an elastic cushion than with hollow embossing with a metallic counter-shape. While sharp bending edges with a bevel of approximately 5 to 10 ° favor the embossing process when using a die made of metal, when embossing with an elastic cushion, good reflow of the material, which at first is only bulged or bulged, must be made possible. The outer edges of the characters to be engraved should therefore be rounded in the cross-section in the summit area - preferably semicircular or almost semicircular. The embossing process around the drawing area to be embossed can thus cause material to slip towards the embossing point, which is favored by a low coefficient of friction of the elastic material.

The full letter depth is thus determined from the material thickness of the sheet. The high of The embossing mark is 10 to 20% larger, based on the embossing with a metallic matrix, since after the first bulging there must still be a sufficient path within the elastic matrix for the final shaping of the symbols.

The embossing process itself takes place with a particularly good result under "dynamic" loading of the embossing tool, with a force limitation being carried out after the roller punch has been "struck", so that the sheet is embossed well without causing cracks. When embossing approx. 20 characters of 8 mm height in body panels at the same time, the limit is approx. 200 kN.

_Depending on the number of possible characters in a character position and the requirements placed on counterfeit protection, matrices can be combined in one line of characters according to the different design variants, whereby only the assignment of the embossing wheel to the die is subject to restrictions, but then are irrelevant if there is a separate embossing wheel for each character position in a character set to be embossed.

With reference to the drawings, the invention and its preferred exemplary embodiments are discussed in more detail.

• Figur 1 ein einzelnes Prägerad mit zugehöriger Matrize,
• Figur 2 eine Anordnung für mehrere gleichachsig angeordnete Prägeräder,
• Figur 3 ein fälschungssicheres Muster für die Matrize und zugehörige Zeichen,
• Figuren 4 und 5 Muster für Matrizen und zugehörige Zeichen,
• Figur 6 eine Ausführung einer elastischen Matrize.für mehrere Zeichen nebeneinander in der Draufsicht,
• Figur 7 eine Variante der Ausführung gemäß Figur 6 in perspektivischer Darstellung,
• Figur 8 eine Darstellung zur Bemessung der Matrizen gemäß Figuren 6 oder 7 sowie
• Figuren 9 und 10 eine Schnittdarstellung von Prägewerkzeug und Matrize gemäß Figuren 6 bis 8 in zwei verschiedenen Arbeitspostionen.

Show it:

• FIG. 1 shows a single stamping wheel with associated die,
• FIG. 2 shows an arrangement for several embossing wheels arranged coaxially,
• FIG. 3 shows a counterfeit-proof pattern for the die and associated characters,
• FIGS. 4 and 5 patterns for matrices and associated characters,
• FIG. 6 shows an embodiment of an elastic matrix for several characters side by side in a top view,
• FIG. 7 shows a variant of the embodiment according to FIG. 6 in a perspective view,
• Figure 8 is an illustration for dimensioning the matrices according to Figures 6 or 7 and
• FIGS. 9 and 10 show a sectional view of the embossing tool and die according to FIGS. 6 to 8 in two different working positions.

In FIG. 1, the partial figures a and b represent a side view or top view of a die m which, in the form of depressions t, has a pattern which corresponds to an "8" of a known seven-segment display.

The partial figures c and d show a top view or side view of an associated stamping wheel p with characters in the form of numbers 0 to 9, which consist of segments in the form of elevations h. These surveys h During operation, press material parts of the workpiece, which is located between the embossing wheel and the die, into the "8" -shaped pattern of the die m. This fixed die need not be moved with respect to the embossing wheel because the pattern consisting of the depressions t matches all characters 0 to 9, since it corresponds to the superimposition of the mirror images of all characters from 0 to 9.

'' As shown in the partial figures c and d (side view or top view) of Figure 2, several embossing wheels p of the same size can be arranged alongside each other on the same axis, to which then only one after the partial figures a (top view) and b (side view) Matrix m 'with several "8" shaped patterns.

The use of a single pattern in a matrix to emboss several different characters can lead to the following difficulty: if the mirror image overlay of several characters results in a pattern of the matrix, the lines contained in the pattern become wider due to the overlay of several non-adjacent lines, than the indentations are otherwise (when adapting to only one sign), such broad lines in the pattern result in blurred lines in the embossed sign during embossing. It is therefore expedient to choose the shape of the characters and that of the pattern in such a way that lines contained in the pattern, which correspond to the superimposition of lines of several characters, are not significantly wider than in the case of a pattern which is only adapted to one character. This ensures that the lines of the pattern are not wider than for a line of one Required. When using the pattern shown in Figures 1 and 2 in the form of an "8", these desired ratios result, because with such a seven-segment arrangement, as is also common for the alternating display of decimal digits, individual segments or lines with segments of several other signs are congruent.

According to a preferred development of the invention, measures are provided to increase the security against forgery when using multi-segment arrangements. In order to secure chassis numbers against subsequent falsifications, for example, efforts are made to make such changes recognizable. (Such a subsequent change of an embossed number could consist in adding segments - changing a "0" to an "8" by adding the middle slash.) In accordance with the further development mentioned, the segments are then selected or arranged accordingly designed a character set in such a way that simply by adding segments or their parts, it is not possible to create another character of the agreed character set.

3 shows a character set of this type, which is secured against counterfeiting, with an associated pattern m "for a die, which is shown in a pictorial manner. The characters" 1 "to" 0 "of the partial figure a to be arranged on an embossing wheel are of this type designed that within this first number of characters no complete character corresponds to only part of another, based on a complete set of digits, possibly supplemented by a number of letters. The character set according to FIG. 3a represents the complete number set.

When identifying, for example, chassis of automobiles, there may be a need to provide an even more extended character set for additional information signs, but the additional signs need not be tamper-proof in the aforementioned sense. However, it should not be possible to convert these characters, which expand the usual character set, into characters of the original, forgery-proof ("protected") character set by adding segments or partial segments. For this purpose, it is proposed in a further embodiment of the invention to use a segment for the extension characters which is not used in the protected character set.

In the exemplary embodiment according to FIG. 3, the protected characters are the digits shown in sub-figure a and the additional characters are letters from sub-figure b, the letters being designed, for example, by doubling the left vertical bar in such a way that segments are never added again by adding segments Digit (which, by convention, must not have double lines). In this way, impermissible attempts to convert digits from the character set b into digits from the character set a can also be made recognizable to those to whom the details of the complete character set are not known. Generalized, the principle underlying FIG. 3 can be characterized in that - in embossed position - character parts of the embossing wheel of a second number of characters corresponding to FIG. 3b cannot be made to coincide with character parts of a third number corresponding to FIG second number (Figure 3b) are formed as parallel lines to parts of characters that also occur in the third number (Figure 3a).

A further distinction has been made in FIG. 3b between upper and lower case letters, in that the full left bar is represented by two parallel lines in the case of large letters, whereas in lower case letters this is only intended for the lower part of the bar. This type of embossing also increases the legibility of the font, since confusion between numbers and letters, as is possible with simple segment arrangements, can be avoided.

FIG. 4a shows a further design option for characters, namely numbers 1 to 4, to which FIG. 4b shows the m ^III pattern associated with the matrix.

Further character forms are shown in FIG. 5a, the associated pattern of the die ^{IV being shown} in FIG. 5b. Here the symbols consist of individual raised cones and the matrix accordingly contains the overlay of all domes, which are adapted to the pyramid shape, for embossing the symbols of an embossing wheel required are. The overlay takes the form of a dot matrix.

In figure 6, finally, another embodiment is also shown for three adjacent matrices ^V m in an array corresponding to three juxtaposed in the axial direction of embossing wheels. The particularity of the matrices m ^V is that they are resilient, at least on the surface, so that the characters on the associated embossing wheels can have any shape; special characters can also be embossed, for example Greek letters or mathematical characters. The elastic material of the matrices m ^V is indeed resilient but nevertheless so hard that the workpiece to be embossed is sufficiently pressed against the raised characters and their surroundings on the embossing wheel ", so that the embossing process is sufficiently sharply formed and clear limited embossed characters appear on the workpiece.

The matrix elements m ^{V shown} in FIG. 6 are plastic parts which are inserted into recesses in a metal frame made of steel. They consist of a polyurethane based on polyether, as it is manufactured under the name Fibroflex rot by Fibro GmbH, D-6954 Haßmersheim.

The Shore hardness of the plastic material is preferably 95 and the thickness is approximately 2 mm if, with an embossing pressure of 20 tons and a character height of approximately 7 mm, the elevations forming the character on the embossing wheel have a Depth of about 0.6 mm are raised. In a preferred alternative embodiment, the matrix is designed in one piece for several adjacent characters.

The plastic elements are dimensioned with regard to their resilience in such a way that when a rounded body, which corresponds to the punctiform or linear segment of the character to be embossed, penetrates the workpiece - after an initial "stamping", such resistance is opposed that only the one directly with the defining segment in contact workpiece area can move into the die due to the direct transmission of the contact pressure.

The die offers such great resistance that the entire workpiece deflects only to a small extent in the area surrounding the embossing segment. It is also particularly important that the embossing stroke is carried out so far that - after the raised embossing segment has penetrated the workpiece - the workpiece is pressed completely against the surface of the die by the embossing wheel, so that the workpiece is in the raised areas of the mark surrounding areas completely adapts to the embossing shape and the raised and flat areas are created in the relation given by the embossed sign on the wheel.

FIG. 7 shows an elastic die designed as an embossing strip 1, the strip being inserted flush into a corresponding cut-out in a support element 2 made of steel. The matrix is made of polyurethane The matrix is glued in an area 3. The gluing reduces the flexing work of the material and thus reduces the risk of fibers shearing off the material at the edge of characters to be embossed. The die has a very small thickness, so that the compression forces that arise after a green bulging of the material are sufficient to sharpen the inner areas of characters, so that the desired embossed sharpness is achieved even where parts of the letter form corners with one another. The matrix serves as a counterpart for sequences of characters arranged side by side (or one above the other). A corresponding dimensioning also applies to the lateral projection of the die elements in relation to the arrangement shown in FIG. 6.

In Figure 8, the height h of a character is related to the width b. of the embossing strip, the strip being only slightly wider than the character high. The overhang is a total of approximately 10% to 15%, the dimensioning being selected such that, on the one hand, the necessary pressure build-up in the material is maintained, but on the other hand the flexing work is not unnecessarily increased in the direction of premature wear of the die m ^VI .

FIGS. 9 and 10 show the embossing tool 10 in two positions with respect to a sheet to be embossed. In FIG. 9 is located above the sheet 11 resting on the matrix m ^VI . The matrix in turn lies on the matrix support 2.

In FIG. 9, an element of an embossed sign 12 is visible in section on the embossing tool 10, the sign around 1.3 mm (dimension t) is raised. The top area of the embossing element is rounded almost semicircular, the flank parts forming an angle of approximately 25 ^* to the vertical. The rounded summit area 13 is polished so that the friction of the embossing plate (during the deformation) is reduced. The flanks of the embossed webs form an angle of essentially 25 ° to the vertical. The sheet thickness d is 0.8 mm and the thickness D of the plastic die is 2 mm.

When the tool is first placed abruptly on the sheet metal surface, there is a slight deflection, the edges of the characters beginning to show. The tool is then moved towards the die with constant force. The sheet metal is preferably deformed by stretching the material in the deformation area, the material starting to slide into the bulge that forms.

A sharp embossing of the edges of the embossing areas of the characters is due to the counter pressure that builds up. Due to the dimensioning specified according to the invention, the inner surfaces of characters are also sharply embossed. In the "dynamic" stamping process, the sheet bulges less overall than in the "static" stamping. (The dynamic embossing principle is implemented by hydraulic circuits based on the so-called DYNAPAK system. When a limit pressure is exceeded, a larger piston area is accelerated so that the roller stamp hits down. For precise guidance, the sheet metal can be fixed beforehand using a hold-down frame be clamped. In addition to a smaller bulge, the indentation of the characters is also smaller during dynamic embossing.)

The embossing device according to the invention can equally well be used both for embossing individual characters one after the other with an embossing wheel and for simultaneously embossing a complete row of characters by means of a set of embossing wheels. Electronic control is preferably used so that a high embossing frequency can be achieved.

Claims (14)

1. Embossing device for various characters with at least one embossing wheel, on the peripheral surface of which the characters to be embossed are raised and to which a die is assigned, the embossing wheel and die from opposite sides of a deep-drawable workpiece to be identified with characters and with that for carrying out the embossing process required force are arranged on both sides pressable against the workpiece, preferably for use in embossing characters in steel sheets, which are used as body or chassis sheets of motor vehicles, characterized in that the die (m to m ^VI ) is designed such that by means of the embossing wheel (p) workpiece areas can be deformed into the surface plane of the die in accordance with the superimposed images of at least two characters of the same embossing wheel (p) against a resistance ensuring the deformation of the workpiece. 2. Embossing device according to claim 1, characterized because the die _{ß (m} V, m ^VI) is made resiliently flexible at least in their areas which faces to be embossed characters on the stamping wheel surface. 3. Embossing device according to claim 1 or 2, characterized in that the die (m to m ^IV ) has a recessed pattern which corresponds to the superimposed images of at least two characters of the embossing wheel (p). 4. Embossing device according to claim 3, characterized in that the pattern corresponds to a seven- or multi-segment arrangement or a dot matrix, as used for the alternating display of decimal numbers or alphanumeric characters, e.g. in digital displays, is known. 5. Embossing device according to claim 3 or 4, characterized in that on the _P rägerad (p) within a first number of characters (Figure 3) does not correspond to a complete character only a part of another. 6. Embossing device according to claim 3, characterized in that the die ( _m V, m ^VI ) consists of polyurethane based on polyether with a Shore hardness of essentially 95. 7. Embossing device according to claim 6, characterized in that the die (m ^V , m ^V I) is so thin that the flexibility in is essentially exhausted when the letter margin is pronounced. 8. _P embossing device according to one of claims 6 or 7, characterized in that the die (m ^V , m ^VI ) is formed in such a way in a metal bed that evasion of the elastic material is prevented by pre-swelling. 9. Embossing device according to claim 8, characterized in that the die (m ^VI ) is glued to the metal bed, at least at the ends (3) in the case of strip-shaped material. 10. Embossing device according to claim 3, characterized in that the raised areas of the characters to be embossed are substantially semicircularly rounded in cross section. 11. Embossing device according to claim 3, characterized in that the top regions (13) of the web-shaped parts are rounded and the rounding radius is selected such that it is essentially half the difference between the foot width of the web-shaped parts and their width at the level of that area corresponds in which, if the flanks were formed in a straight line, they would affect the rounding radius. 12. Embossing device according to one of claims 10 or 11, characterized in that at least the rounded areas (13) are polished. 13. Embossing device according to claim 3, characterized in that the raised web-shaped parts of the embossing characters taper with an edge slope of an angle of substantially 25 °, based on a vertical to the embossing plane. 14. Embossing device according to claim 3, characterized in that the embossing process takes place dynamically with force limitation.

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