METHOD FOR MAKING A V-BELT

Abstract

A method for making a V-ribbed belt is made by inserting a first partial blank in the form of a base tube into a cylindrical vulcanization mold having a negative of a V-ribbed profile. The first partial blank is molded into a surrounding negative and thus provided with the V-ribbed profile without vulcanization. A second partial blank made as a top ply tube with a tension strand is inserted into the virtually completely molded-in base tube and is expanded under heat and pressure so that the top ply tube and the base tube are bonded to one another. Thereafter, the latter is molded into the surrounding negative of the vulcanization mold, and the top ply tube and the base tube are vulcanized to form a V-ribbed blank, whereafter the V-ribbed blank is removed from the vulcanization mold and is fed to the cutting device.

Claims

1. A method for making a V-ribbed belt, wherein the V-ribbed belt is cut in the form of a ring from a tube-like V-ribbed blank on a cutting device, the method comprising the steps of: a) a first partial blank in the form of a base tube is produced or fabricated such that the ends of a plate made of non-vulcanized elastomer material are joined together in overlapping fashion and with a joint formed so as to be preferably inclined over the thickness of the plate; b) the first partial blank in the form of the base tube is inserted into a cylindrical vulcanization mold which is equipped on its inner side with a surrounding negative of a V-ribbed profile, wherein, into the inner cavity of the base tube, there are inserted an expandable tube-like sleeve and corresponding devices for the expansion of the sleeve and for the heating of the base tube, these devices including feed devices and devices for the expansion of the sleeve with compressed air and for the heating of the vulcanization mold with hot steam; c) the sleeve is expanded under the action of heat and pressure to such an extent that the base tube is virtually completely molded into the surrounding negative of the vulcanization mold and is thus virtually completely equipped with the V-ribbed profile; d) after the molding of the V-ribbed profile, cooling is performed by virtue of further heating of the base tube being ended, without vulcanization of the base tube occurring; e) a second partial blank is made, as a top ply tube, on a belt building drum by virtue of a top ply which later forms the belt backing of the V-ribbed belt being applied and a tension strand of one or more strengthening members being wound in one or more plies as a tension strand onto the top ply over the entire width of the belt building drum, wherein the top ply tube together with tension strand has an outer diameter slightly smaller than the inner diameter of the virtually completely molded-in base tube; f) the second partial blank in the form of the top ply tube is removed from the belt building drum and, after removal of the sleeve from the cylindrical vulcanization mold, is inserted into the latter and into the virtually completely molded-in base tube; g) the expandable tube-like sleeve and corresponding feed means and devices for the expansion of the sleeve and of the overall assembly, surrounding the sleeve, composed of top ply tube and base tube are inserted into the inner cavity of the top ply tube again; h) the sleeve is expanded under the action of heat and pressure to such an extent that the top ply tube and the base tube are connected to one another, and the latter is molded completely into the surrounding negative of the vulcanization mold; and, i) the top ply tube and the base tube are completely vulcanized with one another to form a V-ribbed blank by a further supply of heat and pressure and/or a supply of hot steam, following which the V-ribbed blank is removed from the vulcanization mold and is fed to the cutting device.

2. The method of claim 1, wherein the strengthening members of the tension strand are made of fibers or yarns which exhibit small expansion, preferably of glass fibers or aramide fibers.

3. The method of claim 1, wherein, on the outer side of the first partial blank or base tube, there is applied a further layer, preferably a fabric ply for providing special profile characteristics.

4. The method of claim 1, wherein, on the inner side of the first partial blank or base tube, there is applied a further layer, preferably a release foil or a protective foil which is impermeable to release agent.

5. The method of claim 1, wherein the first partial blank is produced in the form of a base tube on a table separate from the belt building drum, wherein the joint is preferably joined together by means of a pressing device.

6. The method of claim 1, wherein the top ply of the second partial blank is produced on a table separate from the belt building drum and is then applied to the belt building drum.

7. The method of claim 1, wherein, during the winding-on of the tension strand, a solution is applied to, preferably sprayed in a flow-regulated manner onto, the strengthening members, which solution effects a connection between top ply and tension strand.

8. The method of claim 1, wherein the circumference of the first partial blank or of the virtually completely molded-in base tube is less than 1400 mm.

9. The method of claim 1, wherein the circumference of the first partial blank or of the virtually completely molded-in base tube is less than 1200 mm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The invention will now be described with reference to the drawings wherein:

[0035] FIGS. 1 to 4 show the basic steps of the inventive two-stage method, in which the molding of the V-ribbed profile on the outer side of the base tube is performed separately during the course of a pre-molding (pre-forming) step.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

[0036] FIG. 1 shows the left half of a cylindrical vulcanization mold 1 as a cross section. Vulcanization mold 1 substantially includes the cylindrical mold parts 1a and 1b, the mold parts 1a and 1b forming an inner cavity 2. The inner cavity 2 is equipped with an expandable tube-like sleeve 3 and is connected to appropriate devices for the expansion of the sleeve and for the heating the inside of cavity and the walls of the mold. The heating is preferably done by hot steam 4 entering into heating channels of the mold part 1b and into the cavity 2. The expansion is done by feeding compressed air and/or compressed hot steam into the cavity 2.

[0037] The production of the V-ribbed blank is carried out as follows:

[0038] A first partial blank in the form of a base tube 5 is produced or fabricated such that the ends of a plate composed of non-vulcanized elastomer material are joined together in overlapping fashion and with a joint formed so as to be preferably inclined over the thickness of the plate.

[0039] This first partial blank in the form of the base tube 5 is inserted into the cylindrical vulcanization mold 1 where the inner side of mold part 1b is equipped with the negative profile 6 of a V-ribbed profile. During insertion there is a temperature t.sub.0 and a pressure p.sub.0 in the cavity.

[0040] The expandable tube-like sleeve 3 is situated inside, i.e. inside the inner cavity of the base tube 5. After expansion and heating of the sleeve 3 and heating of the vulcanization mold 1 with hot steam, the sleeve 3 is expanded under the action of heat and pressure to such an extent that the base tube 5 is virtually completely molded into the surrounding negative profile 6 of the vulcanization mold part 1b and is thus virtually completely equipped with the V-ribbed profile. FIG. 2 shows this step, where increased molding temperature t.sub.1 and a molding pressure p.sub.1 are present in the cavity 2 and also the mold 1 is heated to molding temperature or slightly above.

[0041] After the molding of the V-ribbed profile, cooling is performed by virtue of further heating of the base tube being ended, without vulcanization of the base tube 5 occurring.

[0042] On another belt building drum, not depicted here, a second partial blank is fabricated, as a top ply tube, which later forms the belt backing of the V-ribbed belt being applied and a tension strand composed of one or more strengthening members being wound in one or more plies onto the top ply over the entire width of the belt building drum, wherein the top ply tube 7 (together with tension strand) has an outer diameter slightly smaller than the inner diameter of the virtually completely molded-in base tube 5.

[0043] The second partial blank in the form of the top ply tube 7 is then removed from the belt building drum and, after removal of the sleeve 3 from the cylindrical vulcanization mold 1, is inserted into the latter and into the virtually completely molded-in base tube 5. As shown in FIG. 3, the expandable tube-like sleeve 3 and corresponding feed means and devices for the expansion of the sleeve and of the overall assembly, surrounding said sleeve, now composed of top ply tube 7 and base tube 5 are inserted into the inner cavity of the top ply tube again. During this step of insertion again a temperature of around t.sub.0 and a pressure p.sub.0 is present in the cavity.

[0044] Again the sleeve 3 is expanded under the action of heat and pressure to such an extent that the top ply tube 7 and the base tube 5 are connected to one another, and the latter is molded completely into the surrounding negative of the vulcanization mold part 1b. In this action, shown in FIG. 4, the top ply tube 7 and the base tube 5 are completely vulcanized with one another to form a V-ribbed blank by means of a further supply of heat and pressure/supply of hot steam. During this final vulcanization and connection of the tubes 5 and 7 an increased molding temperature t.sub.2 and a molding pressure p.sub.2 are present in the cavity and also the mold 1 is heated to this molding temperature.

[0045] After this final vulcanization, the completed V-ribbed blank is removed from the vulcanization mold 1 and is fed to a cutting device, not depicted here.

[0046] The two-stage method according to the invention in which the molding process of the base tube, by means of which the V-ribbed profile in the base tube is virtually completely molded, and the vulcanization and remaining molding process, for the overall assembly of top ply tube and base tube, are separated from one another has the effect that, during the molding of the V-ribbed profile on the negative on the inner side of the cylindrical vulcanization mold, the expansions required for this purpose are not transmitted to the tension strand. Specifically, the tension strand is situated on the top ply tube, which is connected to the base tube only later, that is, after the V-ribbed profile has been virtually completely molded in, with minimal expansion being imparted for the remaining molding process, and the overall assembly is supplied for complete molding and vulcanization.

[0047] The considerable relative expansion required for the major part of the molding process, which expansion approximately corresponds in terms of its magnitude to the profile depth, therefore does not need to be accommodated by the tension strand, only by the base tube.

[0048] The tension strand, which is indeed situated on the outer side of the top ply tube which is inserted into the base tube after the molding of the latter, then only has to accommodate a minimal expansion, which is necessary for the connection of the top ply tube to the base tube and for the remaining molding process. The magnitude of this minimal expansion can, during the fabrication process, be easily influenced by virtue of the outer diameter of the top ply tube being brought as close as possible to the inner diameter of the base tube formed after the molding-in of the V-ribbed profile. The outer diameter of the top ply tube is thus selected such that the latter can just be inserted without any difficulties into the base tube in the vulcanization mold.

[0049] The major advantage of this two-stage method consists in that, with corresponding configuration, it is even possible to use tension strands composed of aramide or glass fibers. It is thus possible by means of this method according to the invention to produce V-ribbed blanks of small diameter, that is, ultimately very short V-ribbed belts, which have all the advantages of the molding method, without encountering the problems with the relative expansion of the tension strand. It is thus possible for all advantages of the molding method, such as for example targeted and adapted profile coating by means of fabric plies et cetera, to also be used for short, highly loaded V-ribbed belts.

[0050] An advantageous embodiment consists in that the strengthening members of the tension strand are composed of fibers or yarns which exhibit small expansion, preferably of glass fibers or aramide fibers. As already discussed above, it is thus possible to produce high-strength short V-ribbed belts with a very low modulus of expansion, for example for high loads in an automatic start-stop system of a motor vehicle. In such applications, a low modulus of expansion is imperatively necessary in order to prevent slip phenomena or transmission delays during starting operation.

[0051] A further advantageous embodiment consists in that, on the outer side of the first partial blank or base tube, there is applied a further layer, preferably a fabric ply for providing special profile characteristics. By means of the application of such a layer, the characteristics during the operation of the V-ribbed belt can be influenced. For example, fabric plies are suitable for positively influencing the friction characteristics of a V-ribbed belt of this type and thus also the noise characteristics. For particular usage situations, it is also possible to apply for example polyethylene coatings or other friction-minimizing layers.

[0052] A further advantageous embodiment consists in that, on the inner side of the first partial blank or base tube, there is applied a further layer, preferably a release foil or a protective foil which is impermeable to release agent. Such a layer yields advantages in the further production method according to the invention in that release agents that are possibly applied to the sleeve introduced into the cylindrical vulcanization mold cannot ingress into the material of the base tube. The release foil or the protective foil/coating that is impermeable to release agent is then removed again before the insertion of the top ply tube.

[0053] A further advantageous embodiment consists in that the first partial blank is produced in the form of a base tube on a table separate from the belt building drum, wherein the joint is preferably joined together by means of a pressing device. In this way, it is possible for the base tube and top ply tube to be manufactured in parallel, such that the production process as a whole is accelerated.

[0054] A further advantageous embodiment consists in that the top ply of the second partial blank is produced on a table separate from the belt building drum and is then applied to the belt building drum, where the strengthening members are then wound on. This embodiment, too, serves for the adaptation of the manufacturing flow by means of further splitting-up of the production process into individual shorter manufacturing steps.

[0055] A further advantageous embodiment consists in that, during the winding-on of the tension strand, a solution is applied to, preferably sprayed in a flow-regulated manner onto, the strengthening members, which solution effects a connection between top ply and tension strand. This often involves a so-called dip, by means of which the adhesion and connection of the tension strand to the surrounding material matrix are intensified.

[0056] A further advantageous embodiment consists in that the circumference of the first partial blank or of the virtually completely molded-in base tube is less than 1400 mm, preferably less than 1200 mm. In this way, short V-ribbed belts with high-strength fibers and exhibiting extremely small expansion for use in highly loaded drives are formed after the individual V-ribbed belts are cut off from the V-ribbed blank.

[0057] It is understood that the foregoing description is that of the preferred embodiments of the invention and that various changes and modifications may be made thereto without departing from the spirit and scope of the invention as defined in the appended claims.