Plastic and nonmetallic article shaping or treating: processes – Direct application of fluid pressure differential to... – Including use of vacuum
Patent
1992-12-02
1994-07-12
Silbaugh, Jan H.
Plastic and nonmetallic article shaping or treating: processes
Direct application of fluid pressure differential to...
Including use of vacuum
264102, 264240, 264241, 264259, 2643288, 26432811, 26432812, 26433111, B29C 3900, B28B 500
Patent
active
053286561
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a method for vacuum molding of large objects of synthetic resin in a dismountable mold with reinforcing materials placed in the same mold. Monomer with hardening agent and possible accelerator are supplied to the cavity of the mold from below and upwards for filling the cavity held under a vacuum.
BACKGROUND OF THE INVENTION
In vacuum molding of objects of synthetic resin, a dismountable mold is used with reinforcing materials placed in the mold. The vacuum molding is effected in such a way that a vacuum is applied to the cavity through one or several connections arranged at the upper portion of the mold. Ready-mixed synthetic resin in the form of monomer and hardening agent are fed into the lower portion of the mold. The synthetic resin rises in the mold by way of the applied vacuum.
The first synthetic resin supplied rises until it reaches the uppermost part of the mold. When large objects are manufactured, the rising of the resin takes a long time. During this time the synthetic resin will become viscous, producing lumps and plugs of synthetic resin in the cavity, preventing the continued rising of the synthetic resin in the cavity. Thus, it is difficult to manufacture large, particularly shell-like objects, with little thickness relative to the surface area, such as domes, boat hulls, or car bodies, with vacuum molding.
Known methods for vacuum molding avoid the above-mentioned problems by using only small amounts of hardening agent in the monomer and subsequent heating of the mold after the mold has been filled with synthetic resin for hardening. However, this method is circumstantial and difficult to carry out when large objects of synthetic resin shall be vacuum molded.
One of the great advantages of vacuum molding is that it is not harmful to the environment, since no emission of monomer to the atmosphere takes place. An other advantage is that the molding is effected in one single working step, whereby the manufactured object becomes totally homogeneous and free from voids due to the vacuum applied.
SUMMARY OF THE INVENTION
The object of the invention is to provide a method for vacuum molding, which makes it possible to manufacture large objects of synthetic resin without the above-mentioned disadvantages. This is achieved according to the invention mainly in that the synthetic resin is supplied at least at one position in the cavity initially in the lower portion of the cavity and is then successively moved upwards at such a speed that the position is located just below the surface of the synthetic resin as it is supplied and rises in the mold.
In a preferred embodiment according to the invention, the synthetic resin is supplied through at least one hose, which is sealingly inserted through a wall in the upper portion of the mold sufficiently deep into the cavity so that its free end is positioned in the lower portion of the cavity. The hose or hoses are the progressively pulled upwards at such a speed that the free end or ends of the hose or hoses are positioned just below the surface of the synthetic resin as it is supplied and rises in the mold.
With the method according to the invention, domes, boat hulls, flagstaffs, and special types of pipes with a smooth surface, for instance may be manufactured.
BRIEF DESCRIPTION OF THE DRAWINGS
A non-limiting example of the invention will now be described with reference to the accompanying drawing, in which a sectional view of a mold for effecting the method for vacuum molding according to the invention is shown for manufacturing a half-spherical dome. The left side of the drawing illustrates the position of the hose in an initial stage and its right side illustrates the hose partly pulled up and the mold partly filled with synthetic resin.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The method according to the invention is applicable to different types of known apparatuses for vacuum molding, and will be described below in connection with a mold 1 chosen as an example. The mold
REFERENCES:
patent: 3579738 (1971-05-01), Beattie
Fiorilla Christopher A.
Silbaugh Jan H.
LandOfFree
Method for vacuum molding of large objects of synthetic resin does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for vacuum molding of large objects of synthetic resin, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for vacuum molding of large objects of synthetic resin will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-394357