FI91836B - Method for producing a layer of release agent on a mould - Google Patents

Description

91836

A method of providing a release agent layer in a mold 5

The invention relates to a method for providing a release agent layer in a mold as set out in the preamble of appended claim 1.

10 In casting technology, it is particularly difficult to remove large pieces from the mold due to the large adhesion area. As a result, several types of release agents are used to facilitate removal. Prior to casting, the release liner is applied to the surfaces that come into contact with the body to be cast.

For example, release agents have been sprayed onto the surface of the mold. Such a technique is known, for example, from U.S. Pat. No. 3,931,381, in which a mixture of wax and solvent is used as the release agent 20, which is first injected into the mold and then dried.

Other application methods in which the release agent is applied, e.g., by spraying into a mold, are disclosed in U.S. Patent 4,491,607, GB Patent 1,572,403, GB Patent. 25 1,213,940, GB Patent 1,370,023 and GB Patent Application Publication 2,081,637.

These methods do not provide a uniform layer of release agent, especially in the case of a mold 30 with a plurality of alternating recesses and protrusions transverse to the main plane of the mold.

This results in the casting sticking in places to the mold or to the poor quality of the casting surface.

35 Finnish patent application 894830 discloses a method in which a thin release agent layer is present on the surface of a liquid, and the mold is immersed in this liquid from above. In this case, the recesses and protrusions in the surface of the mold 91836 2 facing the casting are evenly covered with a thin layer of release agent. The release agent can then be, for example, a fatty acid lighter in the molten state on the surface of the liquid, which solidifies on the surface of the mold when the mold is lifted up. A mold is a rigid structure that is lowered into a liquid so that its main plane is parallel to the liquid surface. In this case, the problem has become that, due to the diversity of the mold surface, air pockets tend to remain there despite the fact that air can escape e.g. from the edges of the mold as the recesses extend there, e.g. in the case of a mold for making honeycomb-shaped pieces. Air trapped inside the mold, in turn, impairs the spread of the release agent layer on the mold surface and degrades the quality of the casting.

It is an object of the invention to provide an improvement e.m. technology and eliminate e.m. ills. To achieve this object, the method according to the invention is mainly characterized by what is set forth in the characterizing part of the appended claim 1. When the mold is immersed in the liquid in a curved manner so that its various points gradually come into successive contact with the release agent, there is time in the air to leave the various points of the mold.

In addition, the implementation of the method has several alternatives, which are described in the appended claims 30 2-5 and in the description below.

The invention will now be described in more detail with reference to the accompanying drawings, in which Figure 1 shows an alternative embodiment of the method according to the invention,

II

3 91836 Fig. 2 shows a second embodiment of the method according to the invention, Fig. 3 shows a third embodiment of the method according to the invention, Fig. 4 shows a mold treated by the method on a larger scale during the casting step, Fig. 5 illustrates detachment of a casting from a mold according to the invention; is an example of a product that can be made by a mold treated by the method of the invention.

Figure 1 below shows the principle of the method according to the invention in its main features. The container has a liquid 3, the surface of which has a layer 1 of a lower-density release agent in a liquid state.

A mold having a dimension mainly in the direction of the two dimensions 25, i.e. a mold with a relatively large surface area, is immersed in the liquid so that the release agent moves from the layer 1 to the mold surface, uniformly covering the recesses and protrusions in the mold, i.e. perpendicular to the plane.

.. During immersion, the main plane of the mold is curved, whereby the immersion is carried out in such a way that, in the direction of curvature (arrow A), successive points of the mold come into contact with the liquid 3 in succession. In Fig. 1 35 the immersion is performed so that the mold is initially in contact with the liquid at one of its edges 2a,. after which the remainder is gradually lowered into the liquid, as illustrated by the broken lines.

4,91836

Figure 2 shows another alternative in which the mold is initially in contact with the liquid from the central part 2b, after which both parts between the central part and the edges 2a and 2c 5 are gradually lowered into the liquid, whereby successive areas from the central part to the edge come into contact with the liquid.

In the previous examples, the mold is in the final stage 10 straight parallel to the plane of the liquid surface. According to the alternative of Figure 3, the release agent can also be introduced into the mold in such a way that, in the direction of curvature, successive parts of the mold are in alternate contact with the liquid, i.e. only one area at a time is in the liquid. The curved mold is then turned so that the release agent always moves from the release agent layer 1 to the part which is in the liquid. In Fig. 3, this is realized in practice so that the upper surface of the liquid has a rotating drum 5, on the circumference of which the mold is attached. As the drum rotates, the areas at successive points on its circumference come into alternate contact with the liquid 3. The drum 5 may move forward (arrow B) as it rotates, bringing the mold into contact with different areas of the liquid surface at all times, or rotate 25 in place, with sufficient release agent and low surface tension relative to the rotational speed of the drum to move to where the mold is. in contact with the liquid surface.

30 ·. Figure 4 shows a part of the mold as a cross-leak after immersion in a liquid. The release agent 1 has remained in a thin layer on the surface of the mold 2 (the thickness of the layer is greatly exaggerated for the sake of clarity 35). As shown in Figure 4, the mold has a relatively thin wall, with its walls following the shapes of the protrusions and recesses of the mold. Such a mold, which can be made of, for example, a material with sufficient heat stability and a flexible material, is easy to bend even with very small radii of curvature. On the surface of the mold with the release agent layer, a casting material in a fluid state is poured, which solidifies into the mold. Thereafter, by heating the mold 2, the release agent layer between the casting and the mold is melted, whereby the casting 4 can be easily removed from the mold (Fig. 5). It can also be mentioned that the flexibility of the mold 2 is also useful here, since the mold can be bent off the casting 4 so that its successive parts are successively detached from the casting.

Figure 6 shows a casting 4 made by a mold 15 according to the invention. This is a honeycomb structure with hexagonal openings passing through the plane of the cell. The corresponding mold 2 is implemented in such a way that the recesses against its main plane form a network of 20 interconnected hexagons, which forms a mold cavity into which the casting material is applied as shown in Fig. 4.

The invention can also be used to make castings of other shapes. In addition, the invention can: use all molds that can be bent from a straight shape to a curved shape and back straight. Likewise, the invention is not limited to the use of a particular release agent, but the release agent 30 can be any release agent that can be applied to the surface of the mold by immersing the mold in a liquid. The release agent may then be a melting agent at a suitable temperature, such as stearic acid (melting point about 70 ° C), which is on the surface of a liquid with a density 35 heavier than the melting point, such as water. The release agent can also cause release due to its other physical properties.

Claims (6)

A method for obtaining a release agent layer of a mold in which there are transverse recesses, alternating recesses and elevations against the main plane of the mold, wherein in the method the mold (2) is lowered into a liquid (3) on the surface of the mold. in liquid state a layer (1) of lower density release agent, characterized in that during the lowering the main plane of the mold is curved, the lowering being carried out so that the successive places of the mold come into contact with the liquid (3). one after another. 15 Method according to claim 1, characterized in that the curved mold (2) is first in contact with the liquid (3), after which its other part is deposited in the liquid so that the mold is ultimately in the direction of the liquid ( 3) surface. Method according to Claim 2, characterized in that the mold is first in contact with the liquid (3a) at its edge (3), after which the other part is imperviously deposited in the liquid (3). 4. A method according to claim 2, characterized in that the mold is first in contact with the liquid at the center (2b), after which both parts between the center (2b) and the edges (2a, 2c) are imperviously deposited in the liquid (3). 5. A method according to claim 1, characterized in that the curved mold (2) is inverted in the liquid (3) so that the locations of the mold (2) lying in contact in the direction of curvature are alternately in contact with the liquid (3). t · li 91836 6. A method according to claim 5, characterized in that the mold (2) is fixed to a curved surface, such as the surface of a drum (5), and the piece where the said surface is present is rotated while the mold 5 (2) is present. in contact with the liquid (3).