EP0060213B1 - Marking device for different symbols - Google Patents

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 No. 2555849. However, while this known device requires a pair of embossing wheels, on the peripheral surfaces of which there are raised characters or mirror-image depressions (matrices) around different characters to generate, the present invention is intended to simplify the tax expenditure for embossing character strings.

It has been shown that the need to manufacture and control the two embossing wheels not only with small tolerances to match one another 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 claim 1. Advantageous further developments are specified in the subclaims.

Since several characters provided on the embossing wheel thus fit into one die, the risk of breakage of embossing wheels in the event of incorrect switching is also excluded, as is the case with non-synchronous setting of embossing characters when using two embossing wheels in the known arrangement. Furthermore, the number of different characters to be embossed can be greatly increased, since 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 is assigned only a single fixed die on the circumferential surface, 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. When using only a single fixed die and only a single stamping wheel, the manufacturing and 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 matrix has advantages. This means that a universal matrix is available that - 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 also 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 numbers, 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 die preferably consists of polyether-based polyurethane with a Shore hardness of essentially 95 as a homogeneous element embedded in a cutout.

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, 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 (the cushion) does not withstand the comparatively 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, the final embossing takes place after the outer contours of the letters have been mapped beforehand.

An approximately 2 mm thick polyurethane layer is used for embossing approximately 8 mm high characters in sheet steel (body sheet metal 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 when using a metal die, sharp bending edges with a bevel of about 5 to 10 ° favor the embossing process, when embossing with elastic cushions it is necessary to allow the material, which is initially only bulged or bulged, to flow freely. The outer edges of the to be engraved For this reason, signs should 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 allows 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 height of the embossing marks has been increased by 10 to 20% in relation to the embossing with a metallic matrix, since after the first bulging there must still be enough space within the elastic matrix for the final shaping of the symbols.

The embossing process itself takes place with particularly good results under dynamic loading of the embossing tool, and after the roller plunger has been struck, the force is limited so that the sheet is embossed well without causing cracks. The limit is about 200 kN when embossing approx. 20 characters of 8 mm height in the body panel at the same time.

Depending on how large the number of possible characters in a character position is and which requirements are 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 - die is subject to restrictions, which are then 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.

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

Show it:

• 1 is a single embossing wheel with associated die,
• 2 shows an arrangement for several embossing wheels arranged coaxially,
• 3 is a counterfeit-proof pattern for the matrix and associated characters,
• 4 and 5 patterns for matrices and associated characters,
• 6 shows an embodiment of an elastic matrix for several characters side by side in a top view,
• 7 shows a variant of the embodiment according to FIG. 6 in a perspective view,
• Fig. 8 is an illustration for dimensioning the matrices according to Fig. 6 or 7 and
• 9 and 10 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. During operation, these elevations h press material portions 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 does not need to be moved relative to the embossing wheel because the pattern consisting of the depressions t fits 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 FIG. 2, a plurality of embossing wheels p of the same size can also be arranged alongside one another, to which then only one according to the partial figures a (top view) and b (side view) Matrix m 'with several 8-shaped patterns belongs.

Using a single pattern in a matrix to emboss several different characters can result in 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 character), such broad lines in the pattern result in blurred lines in the embossed character during embossing. It is therefore advisable to choose the shape of the characters and that of the pattern so that the 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 that is only adapted to one character. This ensures that the lines of the pattern are not wider than required for a line of a character. When using the pattern shown in FIGS. 2 and 2 in the form of an 8, these desired ratios result because, in such a seven-segment arrangement, as is also common for the alternating display of decimal digits, individual segments or lines are congruent with segments of several other characters .

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 of adding segments - changing a 0 to an 8 by adding the middle slash.) In accordance with the further development mentioned, a character set is now designed by a corresponding selection or arrangement of the segments, that simply by adding segments or their parts, it is not possible to create another character of the agreed character set.

In FIG. 3, such a character set secured against counterfeiting is shown in sub-figures a and b shown with a mirror image of an associated pattern m "for a die. The characters 1 to 0 to be arranged on an embossing wheel of the partial figure a are designed such that within this first number of characters no complete character corresponds to only one part of another, a complete one A set of digits, possibly supplemented by a number of letters, is used as the basis, and the character set according to FIG.

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 can create a number (which, by agreement, 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.

In general, the principle underlying FIG. 3 can be characterized in that - in the 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. 3a, the mentioned. Character parts of the second number (Fig. 3b) are formed as parallel lines to character parts that also occur in the third number (Fig. 3a).

In Fig. 3b a further distinction has been made 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.

4a shows a further design option for characters, namely numbers 1 to 4, for which the associated pattern of the matrix m ^{III is} shown in FIG. 4b.

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

Finally, FIG. 6 shows yet another exemplary embodiment for three matrices m ^v lying next to one another in an arrangement corresponding to three embossing wheels lying next to one another in the axial direction. The special feature of the matrices m ^v is that these are elastically resilient at least on the surface, so that the characters on the associated embossing wheels may be of any shape; special characters can also be embossed, for example Greek letters or mathematical characters. The elastic material of the matrices m ^V is designed to be 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 defined and clearly delimited Embossed characters appear on the workpiece.

The matrix elements m ^{Y shown} in FIG. 6 are plastic parts which are inserted into depressions 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 and a character height of approximately 7 mm, the elevations forming the symbol are raised on the embossing wheel with a depth of approximately 0.6 mm. In a preferred alternative embodiment, the matrix is designed in one piece for several adjacent characters.

The resilience of the plastic elements is such that when a rounded body that corresponds to the punctiform or linear segment of the character to be embossed penetrates the workpiece - after initial embossing - such resistance that only the one directly with the embossing is opposed The workpiece area coming into contact with the segment can move into the die due to the direct transfer 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 of particular importance that the stamping stroke is carried out to such an extent that - after the raised stamping segment has penetrated the workpiece - the stamping wheel presses the workpiece completely against the surface of the die is so that the workpiece completely adapts to the embossing shape in the areas surrounding the raised areas of the sign 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 cutout in a steel carrier element 2. 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 certain bulging of the material are sufficient to sharpen the inner areas of characters so that the desired embossed sharpness is also achieved where parts of the letter form corners with each other. 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 protrusion of the die elements in relation to the arrangement shown in FIG. 6.

In Fig. 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 approx. 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 .

9 and 10, the embossing tool 10 is shown in two positions with respect to a sheet to be embossed. In Fig. 9 it is located above the sheet 11 resting on the die m ^VI . The die in turn rests on the die carrier 2.

In FIG. 9, an element of an embossing mark 12 is visible in section on the embossing tool 10, the mark being raised by approximately 1.3 mm (dimension t). The top area of the embossing element is rounded almost semicircularly, 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 sheet (during the deformation) is reduced. The flanks of the embossing 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 with constant force in the direction of the die. The sheet metal is preferably deformed by stretching the material in the deformation area, the material beginning 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 building up. The specified dimensioning according to the invention also sharpens the inner surfaces of characters. In the dynamic stamping process, the sheet bulges less overall than in static stamping. (The dynamic embossing principle is realized by hydraulic circuits based on the so-called Dynapark system. When a limit pressure is exceeded, a larger piston area is accelerated so that the roller ram strikes. For precise guidance, the sheet metal can be clamped beforehand using a hold-down frame the indentation of the characters is smaller with dynamic embossing.)

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

Claims (14)

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).

2. A stamping device as claimed in Claim 1, characterised in that the bottom die (m^v, m^VI) is made resiliently flexible at least in regions of its surface adjacent to the characters on the stamping wheel to be stamped.

3. A stamping device as claimed in Claim 1 or 2, characterised in that the bottom die (m to m^w) comprises a sunk pattern which corresponds tothe superimposed images of a least two characters of the stamping wheel (p).

4. A stamping device as claimed in Claim 3, characterised in that the pattern corresponds to a seven-segment or multiple-segment arrangement or a dot matrix such as is known for the alternate display of decimal figures or alphanumeric characters, for example in digital displays.

5. Astamping device as claimed in Claim 3 or 4, characterised in that, on the stamping wheel (p), within a first plurality of characters (Fig. 3) no complete character corresponds to only a portion of another.

6. A stamping device as claimed in Claim 3, characterised in that the bottom die (m^v, mVI) consists of polyurethane on a polyether base with a Shore hardness of substantially 95.

7. A stamping device as claimed in Claim 6, characterised in that the bottom die (mV, m^VI) is made so thin that the flexibility is substantially spent when the edge of the letter is stamped out.

8. A stamping device as claimed in Claim 6 or 7, characterised in that the bottom die (m^V, m^VI) is mouled in a metal bed in such a manner that plastic flow of the resilient material by preswelling is prevented.

9. A stamping device as claimed in Claim 8, characterised in that the bottom die (m^VI) is stuck to the metal bed, in the case of strip-shaped material at least at the ends (3).

10. A stamping device as claimed in Claim 3, characterised in that the raised regions of the characters to be stamped are rounded in substantially semicircular form in cross-section.

11. A stamping device as claimed in Claim 3, characterised in that the summit regions (13) of the web-shaped portions are rounded and the radius of rounding is selected in such a manner that it corresponds substantially to half the difference between the width of the base of the web-shaped portions and their width at the height of that region in which, with a rectilinearconstruc- tion of the flanks, these would be tangent to the radius of rounding.

12. A stamping device as claimed in Claim 10 or 11, characterised in that at least the rounded regions (13) are polished.

13. A stamping device as claimed in Claim 3, characterised in that the raised web-shaped portions of the stamping characters become narrower with a flank taper at an angle of substantially 25° in relation to a vertical on the stamping plane.

14. A stamping device as claimed in Claim 3, characterised in that the stamping operation is effected dynamically with limitation of force.

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