[0001] The invention relates to a method for manufacturing a tool, liquid nozzle or corresponding product, in which method one or more holes or openings of a desired shape are made into the product during manufacture, and when using said product, said hole or opening is required to have at least one of the following characteristics: interchangeability, serviceability, processability or mechanical wear-resistance, and to achieve this, the inner surface of said hole or opening is accessible in an appropriate manner.

[0002] Tools and products according to the above introduction are previously known, in which the inner diameter of the holes and openings is so large that the product can be depth-hardened in such a manner that the inner surface of the hole also hardens. The size of the holes has also permitted the hard chromium plating, hard-coating or plasma-coating of their inner surfaces, when a required wear-resistance is obtained for the inner surface.

[0003] If the tool comprises holes that are small in diameter, such as less than 5 mm, and over 20 mm, for instance, in length, it has been possible earlier to make them of hardened preforms by making the holes by spark machining instead of drilling, for example, but processing their inner surfaces by hard- coating and plasma-coating, such as DVD-, CVD-, PACVD-coating, is afterwards impossible. The method of the present invention is directed to tools and products, which have holes of this type having small diameters but requiring wear- resistance and with no means to do the coating afterward.

[0004] A new method has now been developed to remove this drawback and to solve the problem. The method of the invention is characterised in that the product is divided into at least two parts with the dividing line arranged to run through said hole or opening in such a manner that in the product parts, the hole or opening is open, such as an open groove, in which case it is freely accessible in each part.

[0005] The invention provides the advantage that even holes and openings that are small in diameter can be processed on their inner surface like other open surfaces, when they are made accessible to a required extent according to the invention. Thanks to the invention, even small holes of tools and nozzles, such as holes with a diameter of 0.2 to 5.0 mm, requiring wear-resistance can be hard-coated in all known manners.

[0006] Splitting the tool into two or more parts by means of a dividing line running through the holes provides on the inner surface of the holes joints that may affect the function of the holes in some applications. In the method of the invention, the joint lines of the parts are on the sides of the holes, which are susceptible to minor wear, when steel wires are led through the holes and the holes are used as guides for the steel wires to adjust mainly the relative sideways distance between the wires.

[0007] In the following, the invention will be described in greater detail with reference to the attached drawing, in which

Figure 1 shows a steel wire guide unit as seen from the direction of the holes,

Figure 2 shows a guide unit, in which the holes are side-by-side in a direct line,

Figure 3 shows the unit of Figure 1 with the parts detached, Figure 4 shows the unit of Figure 2 with the parts detached, Figure 5 is an oblique view of the unit of Figure 3 with the parts detached, and

Figure 6 is an oblique view of the unit of Figure 4 with the parts detached.

[0008] The method of the invention is described using the example of Figure 1, which relates to the manufacture of vehicle tyres, where a guide tool is required to feed thin steel wires forming a steel web in a tyre. Figure 1 shows the left side of a symmetrical tool la. The tool la comprises a row of holes evenly distributed in a zigzag form, in which the diameters of the holes 6 are less than 1 mm. Thin steel wires are led through the holes 6 in the tool la inside a rubber mixture to form a metal web of the tyre. The tool la is divided into two parts 2 and 3 through a dividing plane L that is horizontal in Figure 1. The dividing line 5, instead, runs in a waveform comprising vertical portions, where the dividing line 5 runs through the holes 6. The dividing line 5 extends from one edge of the tool la to another and forms the dividing plane L, the parts 2 and 3 of which are detachable from each other.

[0009] The dividing line 5 runs through the holes 6 preferably symmetrically in the middle, whereby the grooves forming the holes 6 in the parts 2 and 3 are semi-circular profiles that are needed to guide a round wire.

[0010] Direct detachment of the parts 2, 3 from each other is prevented by sideways deviations 4 added at some points of the waveform. The start and end parts of the dividing line 5 also contain corresponding deviations 4 that prevent the direct detachment of the parts 2, 3 from each other. The deviation may also be a rectangular profile. The parts 2 and 3 can be separated from each other by sliding the parts 2, 3 in relation to each other in the direction of the holes 6 until they detach.

[0011] In the example of Figure 2, all adjacent holes 6 are on the same line. In spite of this, the dividing line 5 still has a waveform. In this case, too, the dividing line 5 runs vertically at the holes 6, even though the dividing plane L is substantially horizontal.

[0012] Figures 3 to 6 show the parts 2, 3 of the examples of Figures 1 and 2 separate. The parts 2, 3 are made by precision work using wire spark machining. The parts 2, 3 can be hardened preforms, into which the waveforms and holes, or as in this case hole halves, are made using wire spark machining. Hard- coatings can be made in different ways to the inner surfaces of the hole 6 halves in the separate parts 2 and 3.

[0013] It is previously known to make small holes that are less than 2 mm, for instance, by drilling them into a uniform preform before hardening. It is also possible to make small holes in a uniform hardened preform by spark machining. The small holes made into a uniform preform in the above-mentioned ways cannot, however, be hard-coated afterward. The splitting of the tool according to the invention and providing small holes as hole halves makes it possible to coat the inner surfaces of the holes afterward. A damaged part can also be replaced with a new one.

[0014] The method of the invention can be applied to all industrial products, in which the guidance of wires and fibres or liquid flows, such as liquids used in nozzle units with a small diameter or high-pressure liquids, is needed. In a nozzle split according to the method, the wear surfaces can be easily accessed and coated or replaced.

[0015] In an embodiment, other cross-sectional profiles than a round hole are also needed. These profiles may include a rectangle, square, oval and, especially in liquid nozzles, a slotted cross-sectional profile having a length considerably bigger, for instance 10 times bigger, than the width.

[0016] In an embodiment, the parts are not only as top and bottom parts, but also side by side in the lateral direction, whereby replacement parts become smaller units.