This invention relates to the art of engraving foamed plastic extrusions.
More particularly, the invention relates to providing foamed plastic extrusions such as blind slats or the like which are only partially engraved to uniquely present decorative designs or patterns which occupy only a portion of their width.
While foamed plastic extrusions such as blind slats louvers, frames, trim strips and the like have heretofore been engraved with decorative designs, it has been a requirement that the full surface of the extrusions be engraved to preclude their distortion and impairment of their surfaces and density where they have not been engraved. These problems have precluded the highly desirable decorative effect which it has been found can be obtained by only partially engraving these extrusions in such a way as to provide designs occupying only a portion of their width while leaving their surfaces and density where they have not been engraved unimpaired.
It is therefore the object of the present invention to solve the problems of only partially engraving foamed plastic extrusions.
It is a further object of the invention to enable the designs or patterns created by the partial engraving of the extrusions to be located at any position or positions between their width and to enable such partial engravings to be effected on the upper side or the lower side or on both the upper and lower sides of the extrusion whereby an infinite number of novel designs by partial extrusion can be obtained.
The invention resides in providing an engraving roller having the desired design embossed on a portion of its width, penetrating a foamed plastic extrusion formulated to have residual activatable foaming agents with the roller embossment which has been heated to a temperature of the order of 230 degrees F. to 300 degrees F. sufficient to activate the residual foaming agents.
Penetration of the roller embossment is arranged to be limited so that only the outer portions thereof penetrate the foamed plastic of the extrusion. With this arrangement, the outer portions of the roller embossment cause the residual foaming agents to foam the plastic to precisely conform to the penetrating outer portions of the roller embossment leaving the remainder, that is, the non-engraved portions of the extrusion unaltered.
According to one aspect of the invention the heating of the roller embossment is effected by a hot air gun or guns. Alternatively, the roller itself may be heated by circulating hot oil to bring the embossment up to the required foaming agents activating temperature. In both cases, of course, only the outer portions of the roller embossment penetrate the foamed plastic of the extrusion.
It will be understood that since only the outer portions of the embossment of the roller penetrate the foamed plastic of the extrusion a space will be left in the valleys of the roller embossment for the escape of heat.
If the embossment on the roller is adjacent one side as opposed to being centrally located there may be a tendency to effect the straightness of the extrusion during the engraving operation and accordingly to correct this potential problem following the engraving the extrusion is preferably heated to a temperature of the order of about 150 degrees F. to 200 degrees F. This heating temperature is below any blowing agent activation temperature but softens the extrusion so that an operator can readily correct any distortion thereof as the extrusion is pulled to a cutting table where it can be cut off at the proper lengths.
These and other objects and features will be apparent from the following detailed description taken in conjunction with the accompanying drawings.
With reference to
The strip 2 is formed from foamed plastic material formulated with sufficient blowing agents to leave some residual unactivated or not fully activated blowing agents in the foamed plastic after the extrusion process. A PVC containing between 0.2 p.p.h. to 0.5 p.p.h. of organic type blowing agents and between 0.5 p.p.h. to 1.2 p.p.h. of inorganic blowing agents has been found very satisfactory.
After passing through the water cooling station 6 as shown in
The engraving station 8, illustrated in
The engraving roller 11 has the desired design, indicated generally at 15, embossed thereon and is heated by a hot air gun 16 to bring the temperature of the roller embossment up to between about 230 degrees F. and 300 degrees F.
As illustrated in
As can be seen from
Thus, it will be seen that the depth of penetration of the embossment projections is substantially less than the distance “d” leaving a space 21 between the surface of the extrusion 2 and the body portion 20 of the roller 11.
Since the temperature of these projections 17 and 18 is between about 230 degrees F. and 330 degrees F., their heat is sufficient to activate the residual unactivated or activatable blowing agent or agents causing the plastic in these penetrated areas to foam and flow around the penetrating portions of the projections to precisely conform the grooves 22 engraved in the extrusion to the shape of the embossed roller design 15 as shown in
As shown in
Also as shown in
Upon being pulled clear of the engraving roller 11 and under roller 12, the extrusion appears as in
It is important to note that where the extrusion 2 is to be used to produce self supporting products which require rigidity such as blind slats or louvers that in addition to ensuring that the activatable blowing agents are only activated by the penetrating portions 17 and 18 of the engraving roller but that the extrusions have adequate thickness and density for its purpose. If any of the residual blowing agents are activated in the non-engraved portions of the extrusion, their density would be reduced. The density of a self supporting slat extrusion is very critical as reduction in the density will drastically reduce the horizontal rigidity or vertical hanging characteristics of the slat. If the density of such a slat extrusion, for example, is reduced below a density between about 45 percent to 55 percent of that of a solid slat extrusion having the same thickness, the slat will show bowing characteristics when exposed to a heat source such as heat build up from the sunlight between the blind and the window or any other type of heat source such as interior baseboard heaters or other sources of heat.
However, engraved products that do not require any form of rigidity because they are secured to rigid surfaces may have much lower densities as well as being thinner. Such products include door moldings or window moldings that are secured in position and serve purely decorative purposes.
In the application of the invention illustrated in
It will be understood that the engraving roller 11 may have the desired design embossed thereon at any position across its width or even having more that one design engraved thereon. As shown in
The embossed design on the engraving roller or rollers may be brought up to the blowing agent activating temperature in other ways than with a hot air gun as illustrated in
In this case, the engraving rollers 27 and 28 are heated by circulating hot oil therethrough by means of piping 30 and 31 respectively. As before, only the hot outer most portions of the embossed designs 29 penetrate into the foamed plastic of the extrusion 3.
It will be understood that the width and thickness of the foamed plastic strip 2 can be selected as desired and, using the principles of the invention as described above, multiple designs can be engraved on the extrusion spaced across its width.
While PVC foamed material has been found to be particularly useful, other materials with similar characteristics or properties, more specifically with “absorbing” type characteristics, such as polystyrene, that can retain the engraving can be used. These or other type materials with similar properties or characteristics can be used with a cap stock or as a cap stock. In this connection, the invention is applicable to engrave an extrusion of a non-foamed materials such as ABS, partially or totally encased in a foamed plastic material to produce a partially engraved product having a reinforcing core.
Although various preferred embodiments of the present invention have been described in detail, it will be appreciated by those skilled in the art that variations may be made utilizing the principles of the invention and without departing from the scope of the appended claims.
Number | Date | Country | Kind |
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2,482,500 | Sep 2004 | CA | national |