Plastic and nonmetallic article shaping or treating: processes – Forming articles by uniting randomly associated particles – Plural – intermittent pressure applying
Patent
1984-11-01
1987-03-10
Czaja, Donald
Plastic and nonmetallic article shaping or treating: processes
Forming articles by uniting randomly associated particles
Plural, intermittent pressure applying
264125, 264126, 264294, 264347, 425330, 425404, D04H 116
Patent
active
046490060
DESCRIPTION:
BRIEF SUMMARY
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a national phase application corresponding to the international application PCT/EP No. 84100040 filed Feb. 20, 1984 and based, in turn, upon a German application No. 33 07 557.3 filed Mar. 3, 1983.
FIELD OF THE INVENTION
The invention relates to a process for the compression molding of sections, bars, molded articles, or the like, consisting of vegetable particles mixed with binding media, particularly wood particles which are cured in their compressed state by heat.
BACKGROUND OF THE INVENTION
A compression molding process of this type is described in the German specification DE-OS No. 30 35 701. According to this, the section or other body is compressed in a compression mold to its ultimate shape, and cured by a heating process. A curing process must be carried out if the binding medium is to bind the individual particles.
The problem of the process referred to hereinabove is the time during which the curing of the compression molded article or section requires that the body remain in the mold, before a new operation can be initiated. In many cases, it is also necessary to cool the mold, before the next run can be executed.
It is, therefore, of paramount importance to keep the molding time for the individual production pieces as short as possible, so as to be able to recoup the high investment costs. Due to this problem, most experiments have failed. Those plants that are in production are uneconomical, as large investment costs only yield a very low production.
For this reason, compression molded articles made of vegetable particles mixed with binding media have so far been unable to find an appreciable share of the market. The greatest progress has obviously been achieved with the production of one-piece pallets made of compression molded vegetable particles which have the disadvantage of the afore-mentioned disproportion in regard to investment and production.
OBJECT OF THE INVENTION
The object of the invention is, therefore, to provide a further developed process by means of which it is possible to considerably increase the productivity of sections, bars, molded articles, or the like, without increasing the investment costs.
SUMMARY OF THE INVENTION
According to the invention, the solution of this problem is based on DE-OS No. 30 35 701 wherein the section, having been molded into its ultimate shape, is shifted with its molding jaws, which enclose the section or other body, along its longitudinal axis into at least one movable clamping device, while maintaining the molding end position, whereupon the clamped section is cured by the effects of heat, and the molding jaws of another set of molding jaws are returned to molding position.
The general concept of this invention is to cure the molded sections or bodies outside the mold. This is not surprising, as it appears to be logical that the molding cycle within a mold should not be prolonged by the curing time.
The difficulty arises in that a compression molded section, which is to possess the desired high degree of strength and rigidity, behaves differently when made of vegetable particles than an object molded with a different material, e.g. plastic. It has been proved that a mixture consisting of vegetable particles and mixed with binding media immediately loses in strength or even crumbles if subject to the effects of expansion, if it remains untreated even over a short period of time. On the basis of these facts, which cannot be deduced from the state of the art, the molded section, according to the invention, is then fed, together with the shape-giving molding jaws to the curing unit, whereby it is essential that the molding jaws located in the curing zone are unable to recede. It has further been proved that the force of expansion inherent in the molded section unexpectedly decreases during the continuance of curing, so that the frictional resistance, which has presented some misgivings, does not take effect during the curing phase of the section to the extent that normally
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Czaja Donald
Dubno Herbert
Pyon Harold Y.
Ross Karl F.
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