Patent Application
20080047204
In the following, the invention will be explained in more detail with reference to the drawing, where
Preferred embodiments of the method for manufacturing a flexible abrasive disc as well as such abrasive discs are described in the following with reference to the above-mentioned figures. The solutions thus comprise the structural parts shown in the figures, each of which is denoted with a corresponding reference numeral. These reference numerals correspond to the reference numerals given in the following description.
The present flexible abrasive disc 1 comprises according to
In the manufacture of the present abrasive disc 1, the backing 2 is arranged separately on an embossing piston 7 according to
Depending on the shaping of the backing 2, the embossing piston 7, which is in this embodiment referred to as the upper embossing piston, is provided with a replaceable press head 9 for supporting the backing against the surface of the embossing piston. If the lower surface 4 of the backing is for instance concave, the embossing piston is thus provided with a convex press head. Naturally, it is also feasible to provide a planar embossing piston with a lower mold of a suitable polymer material to support the backing against the surface of the embossing piston.
The backing 2 having been properly arranged on the upper embossing piston 7, an abrasive agent coating 6 is applied to the upper side of the backing. Hereby, the structure of the surface layer of the abrasive agent coating is formed advantageously by bringing an embossing mold 10, which is arranged on the lower embossing piston 8 opposite the backing, against the abrasive agent coating. The surface layer of the abrasive disc is thus embossed with a desired pattern by pressing together the embossing pistons positioned opposite each other.
The abrasive agent coating 6 can thus be applied directly to the upper side 3 of the backing 2, or alternatively it can be applied to the embossing mold 10 to be transferred to the backing in the pressing together of the pistons described above and illustrated in
By carrying out the work with a press having a press chamber with a small volume, it is simple to utilize a vacuum casting technique known as such. A vacuum pump (not shown) is connected to the press via a mouthpiece 11, after which the atmospheric pressure in the press chamber can be significantly decreased. Thanks to this press and embossing technique, the embossing mold can be provided with a particularly fine-grained structure that can be filled during the embossing, and no empty pockets are generated in the pattern.
The embossing mold 10 can be shaped advantageously according to
After the pressing together has been completed, the abrasive agent coating 6 is cured, after which the molds that at least partly surround the finished abrasive disc 1 can be removed.
Applying the abrasive agent coating 6 can take place stepwise with alternating application of at least glue and sand to the upper side of the backing. Alternatively, the abrasive agent coating can be dripped, sprayed, injection-molded or injected to the upper side 3 of the backing 2, whereby for instance a slurry containing at least abrasive agent and binding agent is used. A screen print coating of the slurry is also possible, whereby the upper surface obtains small dots, i.e. glue spots, of the abrasive agent coating.
The outer layer is shaped substantially spherical by coating a spherical upper surface 3 on the backing 2. In this context, it can be noted that the spherical shape can naturally manifest itself as both convex and concave surfaces. If a concave spherical surface is used, it is the inside of the hollowed concave surface that is coated.
In the manufacture the spherical shape of the abrasive disc 1 can be, broadly speaking, adapted to the rounding of any particular surface, irrespective of whether it is a concave or a convex surface. Further, extra bending up 14 of the edge of the abrasive disc can be implemented to obtain discrete positioning.
Distribution of the abrasive agent coating 6, forming the structure of the surface layer, can be of different forms depending on the shaping of the embossing mold 10 brought to the lower embossing piston 8 to emboss the surface layer by the pistons being pressed together. The shaping of the surface structure of this embossing mold can be advantageously provided by manufacturing a special positive original embossing mold and subsequently casting it in simple polymer molds, for example. After this, an embossing mold thus shaped with a negative embossing mold of releasing polymer is brought to the lower embossing piston to carry out the embossing of the abrasive agent coating. Since such an embossing mold is simple and inexpensive to manufacture, it can advantageously be used only once. The releasing polymer may be an ordinary polyolefin, for example polypropylene or polyethylene, but can also be grafted with a polymer with even better releasing properties.
Since the original embossing mold does not come into contact with the abrasive agent coating 6, it is subjected to minimal wearing. The wearing, which is almost non-existent, and the small dimensions of the mold mean that its structure can be made very detailed. Hereby, what is called a micro replica mold is obtained. At the same time, this allows the pattern to be made non-linear and non-interferential. Thus, the composite formations of the abrasive agent coating are prevented from forming straight paths that can generate traces on the surface to be abraded if the abrasive disc has one-dimensional movement.
In a screen print coating, even distribution of the abrasive agent coating is obtained over the upper surface, meaning that before the pressing together of the pistons small dots are dosed over the surface, which then in the compression molding with the micro replica mold easily brings about the desired distribution.
At the same time as the abrasive agent coating 6 is spread onto the backing 2, according to
The lower embossing piston 8 having the embossing mold 10 with an embossing pattern can advantageously be formed of an elastic material and with a convex end surface. In this way, the embossing piston starts the pressing from the middle of the embossing mold according to
The backing 2 and the embossing mold 10 arranged against the upper surface 3 are kept together, after the above-mentioned pressing together, by the surrounding atmospheric pressure and the abrasive agent coating 6 applied between them before the pressing. Therefore, it is simple to subject the abrasive agent coating to curing of some type known as such before the pressing.
By using a UV-cured resin as the binding agent of the abrasive agent coating and forming both the possible support mold of the backing and the embossing mold 10 of a transparent polymer letting UV rays pass, simple and advantageous curing of the abrasive disc 1 is obtained when it is transported through a cone of rays.
The present invention allows also electron beam cured resins to be used because the radiation source may be relatively small when only one abrasive disc 1 may be exposed to radiation at a time.
Above, the coating of the backing 2 of the abrasive disc 1 has been described. In this context, it can also be mentioned that the backing may be manufactured in compression molding in a separate mold, in which case its upper side 3 can be coated when the backing is still in the mold. The backing may also be manufactured in stretch molding to be subsequently arranged in a separate mold in which its upper side is then coated. The stretch-molded backing can be either cut off a stretch-molded material strip, or a planar backing material can be subjected to stretch molding when it is being cut off a material strip.
The backing 2 of the abrasive disc 1 has, in one of its embodiments, a structure with substantially even thickness, whereby its lower side 4 and the upper side 3 are substantially parallel and have substantially equal bending radii. The backing can, however, have a shape where the lower side and the upper side have different bending radii, whereby its lower side may be substantially planar, for example, while the upper side is spherically convex or concave. According to the present method, the upper side of the backing can be provided with a surface layer in the form of an abrasive agent coating 6 which is substantially of the shape of a spherical segment.
Deviating from today's paper-based abrasive discs, it is advantageous to manufacture the backing 2 of the present abrasive disc of a polymer material.
To simplify the use of the abrasive disc 1, the side edge 5 of the backing may be provided with fastening elements. These fastening elements are arranged to keep, like a lid, the finished abrasive disc fastened when the abrasive disc is, in use, arranged on a fastening plate of an abrasive head. The fastening elements may comprise an edge 14 drawn upwards according to
The abrasive disc 1 may also be provided with holes for extraction of dust or for supply of water. Further, it may also be provided with follower pins that cooperate with guide holes in the fastening plate. These follower pins make the fastening simpler and may, in some cases and particularly in combination with above-mentioned integrated fastening elements, eliminate conventional fastening elements, such as self-adhesive glue and Velcro fastening.
Naturally, the abrasive disc 1 may be provided with fastening elements known as such, such as self-adhesive glue and Velcro fastening on the lower side 4 of the backing 2, to fasten the abrasive disc to the fastening plate in the abrasive head of an abrasive tool.
The above description and the related figures are only intended to illustrate the present solution for the structure of an abrasive disc. Thus, the solution is not restricted to the embodiment described above or in the attached claims, but a plurality of variations and alternative embodiments are feasible within the idea described in the attached claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20065490 | Jul 2006 | FI | national |
