GB2331731A

GB2331731A - Ornamenting extruded plastic for use as picture frames using heated embossing roller

Info

Publication number: GB2331731A
Application number: GB9723881A
Authority: GB
Inventors: Robert Detenon
Original assignee: Robobond Ltd
Current assignee: Robobond Ltd
Priority date: 1997-11-13
Filing date: 1997-11-13
Publication date: 1999-06-02
Also published as: GB9723881D0; AU1046699A; WO1999025538A1

Abstract

Extruded plastics strip 2 (eg foamed PVC or polystyrene) is ornamented by feeding the strip through the gap 9 between an embossing roller 7 heated by a gas burner 8 to a temperature of 250-550‹C and a drive roller 6. Pressure is applied to the strip so that the gap 9 is 1-6mm less than the thickness of the strip.

Description

2331731 METHOD OF ORNAMENTING PLASTICS ARTICLES The present invention

relates to the ornamentation of plastics articles and is particularly, but not exclusively, concerned with the ornamentation of lengths of extruded plastics material such as polystyrene and PVC. The invention is particularly but not exclusively concerned with the manufacture of extruded lengths suitable for use in the picture frame manufacturing industry.

There is a continuing demand for picture frames of differing ornamental appeal and also for the provision of means to apply an ornamental finish to other household items such as furniture and to building products. Consequently, with the increasing cost of natural raw materials such as wood, the industries who make such ornamental frames and other mouldings have turned to the use of synthetic materials, Among these, extruded plastics material, in particular extruded foamed polystyrene or PVC has been found to give extrusions of 1.

adequate rigidity for picture frames. Various ornamental techniques have been used for such frames. One example, employing the application of wood pulp paste to a plastics extrusion, is described in UK patent number 2 276 318. A later European patent application EP723845 describes the use of an alternative technique for providing ornamented profiled members, such as picture frames, where the ornamentation is produced, not by external application of a material such as wood pulp, but, instead, by forming an elongate profiled member with a solid skin on a portion of the surface of the member and a decorative enhancement integrally formed on another portion of the surface of the member, This is accomplished by hardening a portion of the surface of a non-hardened foam material formed by extrusion to provide a solid skin on that portion and embossing a remaining portion of the surface to provide decorative enhancement integrally in the foam material and then solidifying the foamed material to form the desired solid elongate member. This integral process where extrusion, hardening of a portion of the extrusion and embossing of the remaining portion are carried out at the same time provides a decorative effect well suited to the picture frame industry.

Nevertheless, the provision of means to harden only a portion of the profiled extrusion so that the remainder can be embossed requires the provision of complex cooling mechanisms for the extruded profile.

The present invention seeks to provide a technique for ornamenting extruded plastics members that does not require the ornamentation step to be carried out at the same time as the extrusion and which is simple and economical and can produce a new and attractive ornamental appearance not readily achievable by other means.

According to the present invention we provide a method of ornamenting a preformed plastics article comprising feeding the article, which is initially at ambient temperature, through an embossing station having an embossing wheel maintained at a temperature of at least 250'C and arranged to provide a pressure gap of from minus I to minus 6mm in relation to the thickness of the article.

The temperature, pressure and speed of feed through the embossing station are selected so that an ornamental embossed pattern is cut into the article with formation of a raised beading around the embossed portions, while being nondestructive of the remaining non-embossed surface of the article.

A preferred surface temperature of operation is from 250'C to 550'C, more preferably 35WC to 450'. A preferred pressure gap is of the order of minus 1 to minus 6mm, more preferably minus 2 to minus 3mm. The speed of feed through the embossing station is preferably 20 to 40 metres per minute.

The embossing station preferably comprises a top embossing roller which is heated to the elevated temperature and a bottom drive roller which is also heated.

Heating of the bottom roller has been found to be useful in preventing bowing of the article being ornamented, The embossing roller is preferably mounted on a water cooled shaft. Heating of the surface of the embossing roller is preferably effected by high pressure gas heating, The embossing roller bears an embossing pattern which may be of many forms but preferably comprises raised portions the cutting edges of which are substantially at right angles with the main surface of the roller. In this way, the edges of the pattern are sharply defined and the formation of the raised beading is enhanced.

Other types of ornamentation such as paint and lacquer may be applied to the article before or after it passes through the embossing station. In this way a variety of effects can be formed in the finished article.

The pre-formed plastics article is preferably of extruded foamed polystyrene or polyvinyl chloride, The formation of such extrusions having a rigid outer skin and of sufficient strength to form members such as picture frames is already known in the art and does not form part of this invention. It will be recognised that the extrusions can be formed at a time and site which differs from that where the embossing operation is carried out. Indeed, the pre-formed extrusions can be prepared months or even years before the ornamentation is applied, provided that the surface prior to embossing is of sufficient hardness.

The invention further includes ornamented plastics articles prepared by the method as described above.

The invention also includes an ornamented article, suitable for use in forming picture frames, of extruded foamed plastics having an ornamental embossed pattern, the embossed portions being bordered by raised beading integral with the extruded plastics.

One form of the invention will now be described with reference to the accompanying drawings wherein:

Figure 1 is a schematic diagram of the method used for ornamenting a plastics article; Figure 2 is a planned view of an ornamented article; and Figure 3 is an enlarged cross-section on line 2-2 of Figure 2.

As shown in Figure 1, a length 2 of pre-formed plastics material, such as extruded foamed PVC or polystyrene is passed through an embossing station generally indicated at 4. The embossing station comprises a support 5 and a lower driving roller 6 which is provided with heating means (not shown) in order to prevent bowing of the plastics article being embossed. The embossing station further comprises an upper heated embossing roller 7 which is heated via a gas burner shown schematically at 8.

The article 2 is drawn through the embossing station at a speed of 30 metres per minute. The upper embossing roller is heated to a temperature of about 40CC. The rollers 6 and 7 operate to provide a pressure gap 9 of minus 1 to 6mrn which pressurises the plastics article as it passes through the embossing station.

The embossing roller 7 bears a raised cutting pattern with the raised portions making substantially a right angle with the main surface of the roller. In this way, an embossed pattern is produced on the article 2 as illustrated in Figure 2. As can be seen from Figures 2 and 3 the pattern has indentations 10 which are bordered by raised beading 11 to give an attractive 3-dimensional ornamental appearance to the plastics article.

As can be seen from Figure 3, the plastics article has been pre-formed to be suitable for use in the formation of picture frames. However, the method described is equally applicable to the formation of articles of other cross-sections, for example to apply decorative finishes to other items of furniture or to building products.

The article 2 can be supplied from a stack of previously prepared articles which have been formed by any suitable and well known technique for the extrusion of plastics foam to provide an article with sufficient rigidity and surface hardness for a purpose such as picture framing. The articles are at ambient temperature when they pass to the embossing station 4.

Paint or lacquer finishes can be applied to the article 2 before or after it passes through the embossing station 4. Furthermore, if desired, a flexible material such as a thin layer of paper may be applied to the article 2 before and during its passage through the embossing station 4. This enables the production of alternative decorative effects on the surface of the article.

It will be noted that the embossing temperature is very high (about 400'C, thus requiring high pressure gas heating to achieve such temperatures. Damage to the machinery is prevented by employing a high through put speed and/or the provision of water cooling for the shaft of the embossing roller 7.

Claims

1 A method of ornamenting a pre-formed plastics article comprising feeding the article, which is initially at ambient temperature, through an embossing station havin. an embossing wheel/roller maintained at a temperature of at c least 2STC and arranged to provide a pressure gap of from minus 1 to minus 6mm in relation to the thickness of the article.

2. A method of ornamenting according to claim 1, in which the temperature of the wheel/roller, the pressure applied by the wheel/roller and the speed of feed of the article through the embossing station are selected so that an ornamental embossed pattern is cut into the article with formation of raised beading around the embossed portions, said embossing being nondestructive of the remaining non-embossed surface of the article.

A method of ornamenting according to claim 1 or claim 2, in which the wheel/roller surface temperature during operation is between 3STC and 450T.

A method of ornamenting according to any one of the preceding claims in which the pressure gap is between minus 2 and minus 3mm.

A method of ornamenting according to any one of claims 2 to 4, in which the speed of feed of the article through the embossing station is between 20 to 40 metres per minute.

A method of ornamenting according to any one of the preceding claims in 1 which a drive wheellroller disposed on the opposite side of the article to the embossing wheel/roller is heated to attenuate the tendency of the article to bow.

IL 7. A method of ornamenting according to any one of the preceding claims in which cutting edges on the embossing portions of the embossing Z= 11-5 wheel/roller are substantially perpendicular to the main surface of the wheel/roller to enhance definition and repeatability of the embossed design and to regulate the quantity of beading formed.

8. A method of ornamenting according to any one of the preceding claims which includes applying a paint or lacquer to the article before embossing to provide a variety of decorative effects.

9. An ornamenting apparatus for ornamenting pre-formed plastics articles comprising an embossing station having an embossin, wheel/roller, means for feeding the plastics article to the wheel/roller, and means for heating the wheel/roller to a temperature of at least 250T so that in use a pattern on the article engaging surface of the wheel/roller is impressed into the article in such a way as to cause molten plastics material to bead creating a decorative ornamentation on the article in addition to the pattern transferred by the wheel/roller.

10. An ornamenting apparatus according to claim 10 in which the embossing station includes a heated drive wheellroller.

An ornamenting apparatus according to claim 9 or claim 10 in which high pressure gas heating is used to heat the embossing wheel/roller and said wheel/roller is mounted on a water cooled shaft.

12.

An ornamenting apparatus according to any one of claims 9 to 11 in which the embossing wheel/roller bears an embossing pattern which comprises cutting edges which are substantially at right angles with the main surface of the roller, so that the edges of the pattern are sharply defined and the formation of raised beading is enhanced.

13.

An ornamented plastics article prepared in accordance with the method as defined in claim 1.

14. An ornamented article according to claim 13 suitable for use in forming picture frames, of extruded foamed plastics material having an ornamental I embossed pattern, the embossed pattern being bordered by raised beading integral with the extruded plastics.

15. A method of ornamenting a pre-formed plastics article substantially as herein described with reference to the accompanying drawings.

16.An ornamenting apparatus for ornamenting a pre-formed plastics article substantially as herein described with reference to and as shown in Figure 1 of the accompanying drawings.

0 17. An ornamented plastics article substantially as herein described with reference to and as shown in Figures 2 and 3 of the accompanying drawings.