SK16995A3 - Method of vibration-pressing and apparatus for realization of this method - Google Patents

Abstract

A method of compression moulding which comprises providing moulding apparatus including first and second moulding surfaces defining a moulding cavity. At least one moulding surface is movable such that the surfaces are arrangeable at relatively distal and proximal positions with respect to each other. A curable material to be moulded is arranged in the moulding cavity and at least one surface is advanced from the distal to the proximal position. One or more moulding surface is vibrated during closure of the moulding cavity, so as to urge non-cured material into contact with substantially the entire of the moulding surfaces.

Description

Method of vibratory pressing and apparatus for carrying out this method.

Technical field

The invention relates to molding and more particularly relates to a molding technique which promotes the filling of the mold cavity with molded material.

State of the art

The requirement is that during the molding operation, the molded material is fed to all edges of the mold cavity to produce a molded product that accurately copies the shapes and details of the mold cavity. Achieving this requirement is difficult, especially if the viscous thermosetting material begins to cure when it is introduced into the press cavity. We have now developed a molding method and apparatuses for carrying out this method which help to reduce the problem.

SUMMARY OF THE INVENTION

The method of compression formed according to the invention comprises:

a) providing a pressing device comprising at least first and second forming surfaces forming a pressing cavity, at least one pressing surface movable such that said surfaces are positioned in a mutually spaced and approached position;

b) placing the curable material to be molded in said mold cavity; and

c) bringing said at least one movable surface from said distal position to said approached position and simultaneously subjecting the vibrations of one or more of said press surfaces to contact the uncured material with substantially all of said press surfaces.

In addition, in order to improve the filling of the molding cavity with the thermosetting material, it is advantageous to subject the molding surface or surfaces as described above to vibrations, thereby reducing the force required to clamp the molding cavity.

Advantageously, the pressing cavity is formed by a first and opposed second surface and when these surfaces are subjected to vibrations in opposite directions. The vibrations are then preferably those which cause the cavity to be completely filled with the molded material.

These vibrations may include transverse vibrations of the at least one forming surface to substantially fill the press cavity with a thermosetting material. The vibrations may hopefully include vibrations of the opposing surfaces between their spaced and approached locations relative to each other, thereby promoting material compression between these surfaces.

The transverse vibrations of the press surface may include transverse movement in more than one direction. For example, the transverse vibrations may comprise a substantially orthogonal vibration movement of the at least one pressing surface.

It is also preferred that the molded material comprises a thermosetting resin or plastic.

The resin or plastic may optionally be mixed with fillers and fibrous reinforcement. Advantageously, the thermosetting resin or plastic may also be mixed with the initiator or curing catalyst to achieve improved curing of the material.

Preferably, the thermosetting material comprises a polyester resin mixed with slate powder and glass fibers as reinforcement and curing initiator. The material may also contain other additives such as crushed limestone and a lubricant, for example stearate.

The compression method includes, for example, a mixing step wherein the above-mentioned preferred additives are admixed into the thermosetting resin or plastic prior to being placed in the compression cavity.

Said pressing process may be part of a system of a substantially continuous pressing process where a plurality of such processes are carried out in the form of a production line. In a preferred embodiment, one or more pressing cavities suitable for carrying out the method of the present invention are disposed on a conveyor belt or the like such that a plurality of pressing steps can be performed simultaneously.

Furthermore, according to the invention, there is provided an apparatus for carrying out the compression method as described above. This equipment includes:

a) one or more press cavities, each cavity formed by first and second press surfaces;

b) means for moving at least one pressing surface such that said surfaces are positioned in a mutually spaced and approached position; and

c) means for generating vibrations of one or more of said surfaces during the process of said at least one movable surface from said distal position to said approached position, whereby the curable material present in the pressing cavity is brought into contact with substantially all of said pressing surfaces before being completely cured.

The apparatus according to a preferred embodiment of the invention comprises a plurality of press cavities such that it is suitable for use in a substantially continuous press as described above. For example, the press cavities are positioned gracefully on a conveyor belt or similar conveying surface. The vibration means preferably allows the pressing surface to be vibrated in a substantially controlled manner as described above.

In a particularly preferred embodiment of the invention, the molded article comprises a roofing tile. In the case where the thermosetting material comprises slate filler, the molded article may comprise a roofing tile with the appearance of a natural slate, especially if the pressing surface has a relief surface corresponding to the natural slate.

In a preferred embodiment of the invention, the at least one pressing surface of the above described pressing device carries a supplementary impression of the natural slate.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be further elucidated by way of example, shown in the accompanying drawings, which in no way limits the scope of the invention. The drawings represent a schematic view of a device according to the invention which is suitable for pressing and shows various states during the pressing process.

In the drawing there is shown a mold, generally designated 1, which consists of two mold halves 2, 3. The positions A, B, c of the mold 1 during the molding process are shown sequentially.

Examples of a particular embodiment of the invention

The thermosetting material 4 is disposed in the press cavity 5 between the end faces 2a, 3a of the mold halves 2, 3. The press faces 2a, 3a are maintained at a temperature of about 120 ° C at which the material 4 cures.

The thermosetting material 4 is mixed and weighed prior to being placed in the mold cavity 5 as shown by state A. Mold halves 2, 2 are placed in a spaced position for easy insertion of the molded material 4 into the cavity 5.

Surfaces 2a, respectively. 3a include complementary profiled convex and recessed formations. The side walls 3b are provided with a resilient surface 3c which reduces damage to the mold half 2 when joining the pressing surfaces.

As shown in state B, the mold half 2 proceeds towards the mold half 2 to compress the material 4 between said faces 2a and 2a. During the process of this mold half 2, the other half is subjected to vibrations in a substantially horizontal direction, which is an arrow D in the drawing. These vibrations help fill the cavity 5 with material 4. The resilient surface 3c is also advantageous for absorbing the above vibrations of mold half 2.

In the last closing stages of the mold 1, as shown in the drawing, state C, the mold half 2 is also subjected to vibrations in the vertical direction, as shown by the arrow E. These vibrations promote the pressing of the material 4 between surfaces 2a and 3a.

The mold 1 is then clamped and the pressing surfaces 2a and 3a are heated until the curing of the thermosetting material 4 is complete and the molded article is sufficiently rigid to be removed from the pressing cavity 5.

Claims (10)

PATENT CLAIMS 1. A method of compression comprising: a) forming a pressing device comprising at least a first and a second forming surface forming a pressing cavity, at least one pressing surface movable such that said surfaces are positioned in a mutually spaced and approached position; b) placing the curable material to be molded in said mold cavity; and c) approaching said at least one moving surface from said distal position to said approached position; d) subjecting one or more of said press surfaces to vibrations in a first plane so as to contact the uncured material with substantially the entire press surfaces; and e) subjecting one or more of said press surfaces to vibrations in a second plane orthogonal to said first plane. Method according to claim 1, characterized in that said vibrations comprise vibrations of opposing pressing surfaces between their spaced and approached locations so as to promote the pressing of material between the surfaces. The method of claim 1, wherein the curable material comprises a thermoset resin or plastic. Method according to claim 3, characterized in that the resin or plastics comprises a filler and a fiber reinforcement. The method of claim 3 or 4, wherein the thermosetting resin or plastic comprises a curing initiator or catalyst. 6. Apparatus for carrying out a method of compression comprising: a) one or more press cavities, each cavity formed by first and second press surfaces; b) means for moving at least one of said pressing surfaces from a distant position to an approached position relative to another of said pressing surfaces; c) means for causing vibration of at least one of said press surfaces in a first plane during the process of said at least one movable press surface from said distal position to said approached position, thereby bringing the curable material present in the press cavity into substantially all of said pressing surfaces before it is fully cured; and * d) means for causing vibration of at least one of said press surfaces in a second plane orthogonal to said first plane. 7. The apparatus of claim 6 including a plurality of said press cavities. Device according to claim 6 or 7, characterized in that said vibration means allow vibration of opposing pressing surfaces between their spaced and approached locations so as to promote the pressing of material between the surfaces. Apparatus according to any one of claims 6 to 8, characterized in that it comprises a resilient surface of said pressing surfaces for absorbing vibrations caused by said vibration means. Device according to any one of claims 6 to 9, characterized in that at least one pressing surface carries a supplementary impression of the natural slate.