Rib- or fin-shaped element, profile ring segment and method for producing a profile ring segment

Abstract

Rib- or fin-shaped element (1, 10) comprising an anchoring part (1 b.sub.1, 10b.sub.1) and a molding part (1b.sub.2, 10b.sub.2), wherein the anchoring part (1 b.sub.1, 10b.sub.1) can be anchored in a profile ring segment of a profile ring of a vulcanizing mold that molds the tread of a vehicle tire and the molding part (1 b.sub.2, 10b.sub.2) is provided for molding a sipe or a groove in the tread. The element (1, 10) has at least one elongate projection (1a, 11), which forms a bevel at the periphery of the tread and is produced by means of selective laser melting.

Claims

1. A method for forming a fin for producing a tire tread, the method comprising: forming a fin having an anchoring part and a molding part that run in an L-shaped manner and together enclose an obtuse inner angle and have a smooth outer surface; forming the anchoring part to have a substantially constant width; forming a bevel projection on an inner surface of the anchoring part; forming a plurality of holes in the anchoring part; forming the molding part to have varied widths and a constant thickness that correspond to grooves of a tire tread; forming a milling model to have elevations and slits for receiving the fin; inserting the fin into one of the slits of the milling model; producing a plaster core after inserting the fin into the slits of the milling model having the molding part within the plaster core and the anchoring part protrudes from the plaster core; forming a ring segment from the plaster core that has the molding part protrude from inside the segment and the anchoring part located within the segment; and forming a milling model from the ring segment and having the fin.

2. The method of claim 1, the bevel projection is formed as a 0.1 mm to 1.0 mm web on an outer surface of the milling model.

3. The method of claim 1, forming the anchoring part having a height h1 of 4.0 mm to 5.0 mm.

4. The method of claim 1, forming the holes periodically and to firmly anchor the fin in an aluminum alloy.

5. The method of claim 1, forming the L-shape comprising forming a longitudinal portion and a transverse portion.

6. The method of claim 5, the transverse portion is less than half a length of the longitudinal portion.

7. The method of claim 1, inserting a plurality of additional fins into the slits of the milling model.

8. The method of claim 7, forming the tire tread having the grooves that correspond to the varied widths and thicknesses of the molding part.

9. The method of claim 1, forming the fin by laser melting.

Description

(1) Further features, advantages and details of the invention will now be described in more detail on the basis of the schematic drawing, which schematically illustrates exemplary embodiments. In the drawing:

(2) FIG. 1 and FIG. 2 show views of a fin according to the invention,

(3) FIG. 3 and FIG. 4 show views of an associated model fin,

(4) FIG. 5 shows a view of a detail of a milling model segment with inserted model fins,

(5) FIG. 6 shows a detail of a variant of a milling model segment,

(6) FIG. 7 shows a view of a detail of a flexible before the insertion of fins,

(7) FIG. 8 and FIG. 9 show views of a rib,

(8) FIG. 10 and FIG. 11 show views of an associated model rib,

(9) FIG. 12 shows a view of a detail of the milling model segment with inserted model ribs,

(10) FIG. 13 shows a view of a detail of a flexible.

(11) The invention is concerned with specially designed fin- or rib-shaped elements for molding sipes and/or narrow grooves, in particular transverse grooves, having beveled edge regions, in a tread of a pneumatic vehicle tire while it is being vulcanized in a vulcanizing mold. The invention is also concerned with the design and production of profile ring segments of a profile ring of a vulcanizing mold for pneumatic vehicle tires.

(12) Pneumatic vehicle tires are to be understood as meaning radial-type tires, in particular tires for passenger cars, vans, light trucks, trucks or buses. A bevel is known to be a slanted narrow surface formed locally or in a specific place and running along an edge of a groove or an edge of a sipe. Both in the case of narrow grooves and in the case of sipes, the bevels may only run over a portion of an edge. A sipe has—apart from that region where a bevel is formed—a particularly constant thickness of 0.3 mm to 1.5 mm, preferably up to 0.9 mm; a narrow groove has—likewise apart from that region where a bevel is formed—a width of 1.0 mm to 3.0 mm, wherein the width can vary over the longitudinal extent of the groove, for example can become continuously smaller. A transverse groove is a groove that extends over a large part of its extent at an angle greater than 45° to the circumferential direction of the tread.

(13) According to the invention, the sipes provided with beveled edges or edge regions and/or narrow grooves, in particular transverse grooves, are formed in the rubber material of the tread by fins and ribs, which are produced from metal powder by means of SLM (Selective Laser Melting) during the vulcanizing of the pneumatic vehicle tire in a vulcanizing mold.

(14) Vulcanizing molds for pneumatic vehicle tires usually contain profile rings consisting of a number of profile ring segments, formed on the insides of which are webs for forming wide grooves, for example circumferential grooves, and anchored on the insides of which are the fins for forming the sipes and/or the ribs for forming narrow grooves.

(15) The production of the profile ring segments is performed in a number of steps with the creation or production of a milling model, a flexible, a plaster core and finally the profile ring segment consisting of an aluminum alloy.

(16) The milling model is usually a milled plastic model of a mold segment, created in a program-controlled manner with a CNC milling machine, with sipes corresponding to the course of the grooves and sipes intended for the tread concerned, but without bevels. Model fins and/or model ribs are inserted into the milling model, into the sipes in a way corresponding to the design of the tread, and protrude a few millimeters beyond the outer surface.

(17) The flexible is produced using the milling model from a flexible plastics material by casting. The flexible contains slits as “impressions” of the protruding parts of the model fins and/or model ribs. The fins or the ribs are inserted into the slits, the fins and the ribs protruding a few millimeters beyond the outer surface.

(18) The plaster core is created as an impression of the flexible and contains the parts of the fins and ribs protruding from the previous flexible. Therefore, those parts of the fins and the ribs that were within the flexible in the step before protrude from the outer surface of the plaster core.

(19) A ring is formed from a corresponding number of plaster core segments and a ring of an aluminum alloy is cast over the outside thereof. The segments of the plaster core are destroyed and removed. The ring of the aluminum alloy is cut into segments, which are then processed in a manner known per se and finally inserted as profile segment rings into a vulcanizing mold. The parts of the fins and the ribs projecting from the plaster core segments are then firmly anchored in the profile segment rings; the parts of the fins and ribs projecting from the profile segment rings form sipes and narrow grooves in the tread of the tire to be vulcanized.

(20) In the production of the fins and/or ribs by SLM (Selective Laser Melting), the material, a metal powder, is applied in a thin layer to a base plate, completely melted locally by means of laser radiation and, after solidifying, forms a layer of solid material. The base plate is lowered by a layer thickness and powder is once again applied and melted. The individual layers are generated from 3D data, for example using CAD systems. The model fins and model ribs can also be produced by means of SLM.

(21) FIG. 1 and FIG. 2 show views of an example of a fin 1; FIG. 3 and FIG. 4 show views of an associated model fin 2. The fin 1 has two lamellar portions, which run in an L-shaped manner in relation to one another and together enclose an obtuse inner angle, which in the example is of the order of magnitude of approximately 120°. The outer side surfaces of the portions of the fin 1 that cannot be seen in the figures are smooth surfaces. On the inner surfaces of the portions of the fin 1 enclosing the inner angle, a bevel-forming projection 1a runs over the majority of the two portions, and is thus responsible for forming a corresponding bevel along one edge of a sipe in the tread of the tire.

(22) The bevel-forming projection 1a has a cross section which cannot be seen and is approximately triangular, since it is designed as a positive of the bevel to be formed. The dashed line l.sub.1 in FIG. 1 symbolizes the boundary between an anchoring part 1b.sub.1, with which the fin 1 is anchored in the profile ring segment consisting of the aluminum alloy, and a molding part 1b.sub.2, with which the fin 1 penetrates into the tread of the green tire. A narrow, approximately 0.1 mm to 1.0 mm wide, strip-shaped portion 1a.sub.1 of the projection 1a, which extends over the longitudinal extent of the bevel-forming projection 1a, is located in the anchoring part 1b.sub.1 of the fin 1 or belongs to the anchoring part 1b.sub.1. In the anchoring part 1b.sub.1, which has for example a height h.sub.1 of 4.0 mm to 5.0 mm, holes 1c are formed in order to firmly anchor the fin 1 in the aluminum alloy. In the example, the molding part 1b.sub.2 has portions of different widths in order to form a sipe with corresponding portions of different depths.

(23) In a way corresponding to the design of the fin 1, the model fin 2 shown in FIG. 3 and FIG. 4 is provided in plan view with two portions running in an L-shaped manner in relation to one another, over which an anchoring part 2b.sub.1 and a molding part 2b.sub.2 runs, the dashed line l.sub.2 symbolizing the boundary between the anchoring part 2b.sub.1 and the molding part 2b.sub.2. Formed along the line l.sub.2 is a 0.1 mm to 1.0 mm thin web 2a, belonging to the molding part 2b.sub.2, the outer shape of which, viewed in plan view, is designed according to the outer contours, also viewed in plan view, of the portion 1a.sub.1 of the projection 1a of the fin 1. The fin 1 and the model fin 2 have, apart from those regions where the projection 1a or the web 2a is formed, a thickness which corresponds to the width of the sipe to be produced.

(24) FIG. 5 shows a plan view of a small detail of a milling model 3 with model fins 2 inserted in L-shaped slits. The anchoring part 2b.sub.1 of the model fins 2 is located in the L-shaped slits of the milling model 3; the molding part 2b.sub.2 with the web 2a protrudes above the surface of the milling model 3, the web 2a lying on the surface. The milling model 3 also contains further structures that are either not shown or are not described further, for example wide grooves.

(25) FIG. 6 shows a detail of a milling model 3′ with alternative designs in which model fins 2′, 2″ that do not have a web are used. Instead of the web, elevations 4 with a height of 0.1 mm to 1.0 mm and a corresponding outer contour are milled in the milling model 3′ along the corresponding edges of the slits provided for receiving the model fins 2′, 2″.

(26) FIG. 7 shows a plan view of a detail of a flexible 5 corresponding to FIG. 5. What can be seen are the slit 6 formed by the molding part 2b.sub.2 of the model fin 2 or 2′ and the shallow depression 7 in the flexible 5 formed by the web 2a or by projections 4.

(27) In the next step, a fin 1 is inserted with its anchoring part 1b.sub.2 into each slit 6 and, when all of the fins 1 have been inserted, the plaster core, not shown, is produced. In the plaster core, the molding part 1b.sub.2 is located within the material of the plaster core; the anchoring part 1b.sub.1 protrudes. In the profile ring segments subsequently produced, as already described, the molding parts 1b.sub.2 therefore protrude from the insides of the segments; the anchoring parts 1b.sub.1 are located within the segments.

(28) FIG. 8 and FIG. 9 show views of a rib 10, for example for forming a narrow transverse groove in the tread of the pneumatic vehicle tire. The rib 10 has an anchoring part 10b.sub.1 and a molding part 10b.sub.2, one side surface of which, which cannot be seen, is smooth in the example and the second side surface of which is provided with a bevel-forming projection 11. The thickness of the molding part 1b.sub.2 outside the projection 11 is 1.0 mm to 3.0 mm. The dashed line l.sub.3 marks the boundary between the parts 10b.sub.1 and 10b.sub.2. A 0.1 mm to 1.0 mm thin strip-shaped portion 11a of the projection 11 is located outside the line l.sub.3 in the anchoring part 10b.sub.1 and belongs to the anchoring part 10b.sub.1. Apart from the portion 11a, the thickness of the anchoring part 10b.sub.1 is mostly less than the thickness of the molding part 10b.sub.2 and is, for example, of the order of magnitude of 0.5 mm, in particular 0.3 mm to 1.5 mm, preferably 0.5 mm to 0.8 mm. The projection 11, which in the example tapers out toward one end of the rib 10, provides for the formation of a bevel on the molding part 10b.sub.2 along one edge of the transverse groove.

(29) FIG. 10 and FIG. 11 show an associated model rib 12 with an anchoring part 12b.sub.1 and a molding part 12b.sub.2, in each case on one side of a dashed line l.sub.4. Formed on one side surface of the model rib 12 is a bevel-forming projection 12a, which corresponds to a part of the projection 11, to be specific the upper part of the projection 11 in FIG. 8, on the rib 12. The projection 12a extends beyond the line l.sub.4 with a strip-shaped portion having a thickness of 0.1 mm to 1.0 mm. The anchoring part 12b.sub.2 has a thickness which corresponds in particular to that of the anchoring part 10b.sub.1 of the rib 10. The molding part 12b.sub.1 is adapted in its dimensions to the molding part 10b.sub.2 of the rib 10.

(30) FIG. 12 shows a detail of the milling model 14 at the point where a model rib 12 is inserted with its anchoring part 12b.sub.1 in a correspondingly shaped slit. With the model rib 12 inserted, the projection 12a is located within the slit of the milling model 14, apart from a protrusion of approximately 0.1 mm to 0.2 mm.

(31) By analogy with FIG. 6, it can alternatively be envisaged to use model ribs without projections and to form corresponding flat elevations in the milling model.

(32) Once all of the model ribs 12 have been inserted, the flexible 15 is produced from a plastic compound. FIG. 13 shows a plan view of a detail of the produced flexible 15 in that region where the molding parts 12b.sub.2 of two model ribs 12 have corresponding depressions 15a and slits 15b. Alternatively, the depressions 15a may have been formed by flat projections on the milling model.

(33) By analogy with the first exemplary embodiment, in the next step the ribs 10 are correspondingly inserted in the flexible 15 and, by analogy with the description already given of the first exemplary embodiment, a plaster core is created, from which the anchoring parts 10b.sub.1 protrude. The further steps for producing the profile ring segments from an aluminum alloy largely correspond to those already described.

LIST OF REFERENCE SIGNS

(34) 1 . . . Fin 1a . . . Projection 1a.sub.1 . . . Portion 1b.sub.1 . . . Anchoring part 1b.sub.2 . . . Molding part 1c . . . Hole 2, 2′, 2″ . . . Model fin 2a . . . Web 2b.sub.1 . . . Anchoring part 2b.sub.2 . . . Molding part 3, 3′ Milling model 4 . . . Elevation 5 . . . Flexible 6 . . . Slit 7 . . . Depression 10 . . . Rib 10b.sub.1 . . . Anchoring part 10b.sub.2 . . . Molding part 11 . . . Projection 11a . . . Portion 12 . . . Model rib 12a . . . Projection 12b.sub.1 . . . Anchoring part 12b.sub.2 . . . Molding part 14 . . . Milling model 15 . . . Flexible 15a . . . Depression 15b . . . Slit h.sub.1 . . . Height l.sub.1, l.sub.2 . . . Line l.sub.3, l.sub.4 . . . Line