METHOD OF VIBRATION-MOULDING AND AN APPARATUS FOR CARRYING OUT THE MOULDING

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 VIBRATION-MOULDING AND AN APPARATUS FOR CARRYING OUT THE MOULDING The present invention is concerned with moulding, and in particular a moulding technique which assists filling of a mould cavity with a mould material. It is desirable during moulding processes to urge a mould material into the extremities of a mould cavity, so as to produce a moulded article replicating the contours and detail of the cavity. It is however often difficult to achieve the above, particularly so when a viscous thermosetting material commences curing during introduction into the cavity. We have now developed a moulding process and apparatus which help to alleviate the above problem. According to the present invention there is provided a method of compression moulding which comprises: (a) providing moulding apparatus comprising at least first and second moulding surfaces defining a moulding cavity, at least one surface being movable such that said surfaces are arrangeable at relatively distal and proximal positions with respect to each other; (b) arranging a curable material to be moulded in said cavity; and (c) advancing said at least one movable surface from said distal to said proximal position, and concurrently vibrating one or more of said moulding surfaces so as to urge non-cured material into contact with substantially the entire of said moulding surfaces. In addition to promoting filling of the moulding cavity with the thermosetting material, vibration of the moulding surface or surfaces substantially as hereinbefore described is advantageous for reducing the force required to close the cavity. It is preferred that the moulding cavity is defined by opposed first and second surfaces, and the surfaces may be respectively vibrated in opposed directions. The vibration is preferably such as to effect substantially complete filling of the cavity with the mould material. The vibration may involve transverse vibration of at least one moulding surface, so as to urge the thermosetting material to substantially fill the moulding cavity. The vibration may further comprise vibration of the opposed moulding surfaces between relatively proximal and distal arrangements, so as to assist compacting of the material between the surfaces. The transverse vibration of a moulding surface may involve transverse motion in more than one direction. Typically the transverse vibration may involve substantially orthogonal vibratory motion of at least one surface. It is preferred that the material to be moulded comprises a thermosetting resin or plastics material. The resin or plastics material may be optionally mixed with fillers and fibre reinforcement. The thermosetting resin or plastics material may preferably be mixed with an initiator or catalyst for enhancing curing of the material. A preferred thermosetting material comprises a polyester resin mixed with slate dust and glass fibre reinforcement, together with a curing initiator. The material may further include additional ingredients such as crushed limestone and a lubricant such as stearate. The method may typically comprise a premixing stage, wherein the thermosetting resin or plastics material is admixed with the above preferred ingredients, prior to arrangement within the moulding cavity. The moulding process may be part of a substantially continuous compression moulding system, wherein a plurality of such processes are operated on a production line type method. In a preferred embodiment, moulding apparatus providing one or more cavities suitable for carrying out a process according to the present invention are arranged on a conveyor belt or the like, so that a plurality of moulding processes can be simultaneously operated. There is still further provided by the present invention apparatus suitable for carrying out a moulding process substantially as hereinbefore described, which apparatus comprises: (a) one or more moulding cavities each defined by at least first and second moulding surfaces; (b) means for moving at least one moulding surface, such that said surfaces are arrangeable at relatively distal and proximal positions with respect to each other; and (c) means for vibrating one or more of said surfaces during advancement of said at least one movable surface from said distal position to said proximal position, whereby a curable material to be moulded present in said cavity is urged into contact with substantially the entire of said moulding surfaces before said material is fully cured. In a preferred embodiment, the apparatus comprises a plurality of moulding cavities, such that the apparatus is suitable to be employed in a substantially continuous compression moulding system as hereinbefore described. Typically, the moulding cavities are arranged on a conveyor belt or similar transfer surface as hereinbefore described. The vibrating means are advantageously capable of vibrating the moulding surface in a substantially controlled fashion as described above. There is further provided by the present invention a moulded article obtained by a moulding process substantially as hereinbefore described. In a particularly preferred embodiment of the present invention, the moulded article comprises a roofing tile. In the case where the thermosetting material comprises a slate filler, the moulded article may preferably comprise a roofing tile having the appearance of natural slate, particularly when the moulding surface has a surface relief corresponding to that of natural slate. According to this preferred embodiment of the present invention, at least one moulding surface of the moulding apparatus hereinbefore described bears a complementary impression of natural slate. The present invention will now be further illustrated, by way of example only by reference to the accompanying drawing, which does not limit the scope of the invention in any way. The drawing is a schematic representation of apparatus according to the present invention suitable for use in compression moulding, and illustrates different stages during the moulding process. There is shown a mould generally designated 1 comprising mould halves 2,3. The arrangement of mould 1 at progressive stages A,B,C of a compression moulding method is illustrated. A thermosetting material 4 is located in a mould cavity 5 between facing surfaces 2a, 3a of halves 2,3. Mould surfaces 2a, 3a are maintained at about 120°C, for effecting curing of material 4. Material 4 has been subjected to a pre-mixing stage, and weighed out as a batch of pre-determined weight prior to arrangement in cavity 5 as shown in stage A. In stage A, mould halves 2,3 are disposed in a distal arrangement for ease of insertion of material 4 into cavity 5. Surfaces 2a, 3a respectively comprise complementarily profiled raised and recessed formations. Side walls 3b are provided with a resilient surfacing 3c, such that on coupling of the mould surfaces damage to mould half 3 is reduced. As shown in stage B, mould half 2 is advanced towards mould half 3 so as to compress material 4 between surfaces 2a, 3a. During advance of mould half 2, the latter is vibrated in a substantially horizontal direction as shown by arrow D. This vibration urges filling of cavity 5 with material 4. Resilient surfacing 3c is also advantageous in absorbing the above described vibration of mould half 2. During the latter stages of closure of mould 1, as shown in stage C, mould half 2 is also vibrated in a vertical direction as shown by arrow E, so as to aid compacting of material 4 between surfaces 2a, 3a. Mould 1 is clamped shut and surfaces 2a,3a heated until curing of thermosetting material 4 is complete and the moulded article is sufficiently rigid for removal from cavity 5.

Claims: Claims: 1. A method of compression moulding which comprises: (a) providing moulding apparatus comprising at least first and second moulding surfaces defining a moulding cavity, at least one surface being movable such that said surfaces are arrangeable at relatively distal and proximal positions with respect to each other; (b) arranging a curable material to be moulded in said cavity; and (c) advancing said at least one movable surface from said distal to said proximal position, and concurrently vibrating one or more of said moulding surfaces so as to urge non-cured material into contact with substantially the entire of said moulding surfaces. 2. A method according to claim 1, wherein said surfaces are respectively vibrated in opposed directions. 3. A method according to claim 1 or 2, wherein said vibration involves transverse vibration of at least one moulding surface. 4. A method according to claim 3, wherein said transverse vibration of said at least one moulding surface involves transverse motion in more than one direction. 5. A method according to claim 4, wherein said transverse vibration involves substantially orthogonal vibratory motion of at least one surface. 6. A method according to any of claims 1 to 5, wherein said vibration further comprises vibration of the opposed moulding surfaces between relatively proximal and distal arrangements, so as to assist compacting of the material between the surfaces. 7. A method according to any of claims 1 to 6, wherein the curable material comprises a thermosetting resin or plastics material. 8. A method according to claim 7, wherein the resin or plastics material includes fillers and fibre reinforcement. 9. A method according to claim 7 or 8, wherein the thermosetting resin or plastics material includes a curing initiator or catalyst. 10. Apparatus for carrying out a compression moulding process, which apparatus comprises: (a) one or more moulding cavities each defined by at least first and second moulding surfaces; (b) means for moving at least one moulding surface, such that said surfaces are arrangeable at relatively distal and proximal positions with respect to each other; and (c) means for vibrating one or more of said surfaces during advancement of said at least one movable surface from said distal position whereby a curable material to be moulded present in said cavity is urged into contact with substantially the entire of said moulding surfaces before said material is fully cured. 11. Apparatus according to claim 10, which comprises a plurality of said moulding cavities. 12. Apparatus according to claim 10 or 11, wherein said vibrating means are capable of respectively vibrating said moulding surfaces in opposed directions. 13. Apparatus according to any of claims 10 to 12, wherein said vibrating means are capable of transversely vibrating at least one moulding surface. 14. Apparatus according to claim 13, wherein said transverse vibration of said at least one moulding surface involves transverse motion in more than one direction. 15. Apparatus according to claim 14, wherein the transverse vibration involves substantially orthogonal vibratory motion of at least one surface. 16. Apparatus according to any of claims 10 to 15, wherein said vibrating means are capable of vibrating opposed moulding surfaces between relatively distal and proximal arrangements, so as to assist compacting of the material between the surfaces. 17. Apparatus according to any of claims 10 to 16, wherein at least one moulding surface bears a complementary impression of natural slate.

Inventors: GRIBBLE MEIRION, GRIBBLE, MEIRION
Applicants: GRIBBLE MEIRION, GRIBBLE, MEIRION
Application year: 1993
Main classification: B29C43
IPC codes: B28B1, B29C43, B29K105, B30B11