Moulding of articles

Plastic and nonmetallic article shaping or treating: processes – Treatment of material by vibrating – jarring – or agitating... – By reciprocating or vibrating mold

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Details

264123, 264333, B28B 126

Patent

active

045227721

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD OF THE INVENTION

This invention relates to the moulding of articles and in particular to the moulding of construction products, such as partition panels, roof decking and pipes, from liquid setting particulate materials.


STATE OF THE ART

It has been customary hitherto to mould such articles as aforesaid by mixing the constituent materials, applying a sufficient quantity of setting liquid to the mix, introducing the moistened mix to the mould and allowing the mix to set before removal of the set article from the mould. This process is time-consuming and for quantity production of such articles, since the setting of the article occurs in the mould, a large number of moulds is required.
It has been proposed for example in British Pat. Nos. 528,657, 1,067,671, 1,346,767, 1,417,001 and 1,466,663 that a dry mixture of constituent materials be introduced into the mould and compacted therein. The mould is then immersed in a setting liquid or the liquid is allowed to permeate the mix by capillary action. Of these Patents, only in the case of 1,346,767 is the liquid applied to a vertical surface which is unsupported by a part of the mould apparatus, and in that case the mould is immersed in the water so that the buoyancy effect thus created offsets the tendency of such unsupported walls to collapse due to the increase in weight of the mix.
It has also been proposed in U.S. Pat. No. 1,427,103 that for producing very small moulded articles, for example buttons, the dry constituent materials be pressed into the mould, removed therefrom and then sprayed with setting liquid. However, this process is restricted to use for the production of very small articles and has not been used for the production of relatively very large articles, such as construction products, since such articles would be expected to collapse under their own weight on demoulding and may also shrink and crack during the spraying operation. In consequence it has been considered that if there is to be any vertical surface of mix which is unsupported by a part of the mould apparatus during the wetting process by seepage rather than by total immersion then it is essential to incorporate into the mixture of constituent materials some reinforcing means from which the moulded article can derive support during the spraying and setting stages of the process. The reinforcing means may be fibres, and examples of processes incorporating the use of such fibrous reinforcing material for the supporting of the moulded article whilst unsupported at least in part by the mould are described in German Patent No. 1,683,829, British Pat. No. 1,346,767 and commonly assigned co-pending U.S. application No. 212,707, filed on Nov. 5, 1980.


DISCLOSURE OF THE INVENTION

The invention provides a method for producing moulded construction products from a liquid setting mixture of fine and coarse particulate materials comprising the steps of mixing the dry constituenet materials, said materials including a proportion of fine particles sufficient to substantially surround all coarse particles but not including fibrous reinforcing materials, introducing said mixture into a mould, compacting said mixture in said mould to an extent that said fine particles substantially fill the interstices between said coarse particles, removing at least a part of the mould from contact with the thus moulded product, spraying the product at a surface unsupported by said mould with a predetermined quantity of a setting liquid, being a quantity sufficient to wet all of the compacted constituents but insufficient completely to saturate the same, and allowing said product to set.
Surprisingly, it has now been found that provided that there is sufficient compaction and a sufficient proportion of fine particles in the mixture of constituents no fibres or other reinforcement are required and a satisfactory moulded article may be obtained which, without collapse, can be demoulded before the onset of chemical curing and which does not shrink or crack during the spraying and setting process.

REFERENCES:
patent: 1427103 (1922-08-01), Haenicke
patent: 2944291 (1960-07-01), Prior et al.
patent: 3914359 (1975-10-01), Bevan
patent: 3927163 (1975-12-01), Gabriel et al.
patent: 3959422 (1976-05-01), Wilhelm
patent: 4239716 (1980-12-01), Ishida et al.

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