WO2012089597A1

WO2012089597A1 - Bending process of a resin panel

Info

Publication number: WO2012089597A1
Application number: PCT/EP2011/073679
Authority: WO
Inventors: Massimo Mazza
Original assignee: Individual
Current assignee: Individual
Priority date: 2010-12-31
Filing date: 2011-12-21
Publication date: 2012-07-05
Anticipated expiration: 2013-06-30
Also published as: ITAN20100222A1; IT1404114B1

Abstract

The present invention relates to a bending process of a resin-molded panel (6), according to which resin is molded to obtain a flat panel (2) that undergoes one or more finishing works, thus obtaining a finished flat panel (4) adapted to be heated to the tempering temperature of the molding resin and bent by means of a bending mold (7) from which a finished bent panel (6) is extracted.

Description

Bending process of a resin panel

The present patent application for industrial invention relates to a bending process of a flat resin panel that has undergone one or more finishing works.

A curved resin panel is currently obtained with an ordinary mold in which resin is injected and from which a raw panel with desired curved profile is extracted.

The raw panel then undergoes various finishing processes, such as squaring, sizing, painting, smoothing and brushing or polishing.

Said finishing processes are very laborious and complicated, given the fact that they have to be performed with craftsmanlike technique on a curved panel.

Moreover, it must be noted that it is impossible to perform said processes simultaneously on several panels using continuously working machinery, as it normally occurs when machining raw panels with planar configuration.

In view of the above, said finishing processes must be performed on one curved panel at a time, with time waste and high labor costs.

Additionally, in case of realization of a resin-molded curved panel with sides decorated with frames, ashlars or engravings, said engravings must be carried out either manually or using sophisticated expensive milling machines, since the curved configuration of the panel makes it impossible to use the ordinary numeric control machines that are normally used for pantograph milling of planar panels.

WO2006/002020 discloses a method used to make a vehicle component, such as a door. The method provides for injection molding of a panel comprising an extension in the form of a flange. However, such molded panel is already curved, as clearly shown in Figs. 2 and 2a of WO2006/002020. Then, finishing works, such as removal of excessive material, are performed. Evidently, said finishing works performed on a curved panel are impaired by all the foregoing inconveniences.

WO2006/002020 also discloses a curving method wherein a resin substrate undergoes localized heating (for instance, by means of infrared radiation). So the panel is only curved in the heated areas due to melting of substrate in said heated areas. Evidently, melting of the resin substrate is performed at very high temperature and would undoubtedly damage any surface finishing works performed in the heated areas. Hence, said localized curving method is not suitable for complete bending of the panel and cannot be applied to panels with valuable surface finishes.

The purpose of the present invention is to eliminate the inconveniences of the prior art by disclosing a process for bending a flat resin panel that is practical, versatile, efficient, inexpensive and simple to make.

These purposes have been achieved according to the invention, with characteristics claimed in the attached independent claim 1 .

Advantageous embodiments appear from the dependent claims.

The bending process of a resin panel according to the present invention comprises the following steps:

- injection molding of resin to obtain a flat panel,

- finishing works of the flat resin panel in such a way to obtain a finished flat panel,

- heating of the finished flat panel until the panel reaches the tempering temperature of resin,

- bending of the finished heated flat panel by means of a mold in such a way to obtain a bent resin panel.

The advantages of the invention appear evident, given the fact that it allows for performing all finishing works on the flat panel and then bend the finished flat panel without damaging the finished surface of the panel.

Further characteristics of the invention will appear clearer from the detailed description below, which refers to a merely illustrative, not limitative, embodiment, illustrated in the attached drawings, wherein: Fig. 1 is a diagrammatic block diagram of the bending process of a resin panel according to the invention;

Fig. 2 is a diagrammatic cross-sectional view showing heating and bending of the resin panel of the invention.

Referring to Fig. 1 the bending process of a resin panel according to the invention provides for a first molding step (1 ) from which a flat panel (2), which has no bending, is obtained.

The molding step (1 ) provides for injection molding of resins in a mold for flat panels, i.e. panels in the form of a rectangular plate. Advantageously, epoxy resins, especially unsaturated polyester resins, are used.

Advantageously, resins are loaded with colored pigments, in such manner to directly obtain a flat panel (2) with the desired color.

The panel (2) may comprise an insert (20) drowned in a resin coating (21 ) that completely surrounds the insert.

If the resin is colored and non-transparent, the insert (20) is not visible.

The insert (20) can have a filling and lightening function for the panel and in such a case the insert (20) is made of a lighter material than the polyester resin used for coating (21 ) For example, the insert (20) can be a Polyvinyl Chloride (PVC) or expanded polyurethane sheet.

The insert (20) can also have a stiffening function for the panel and in such a case the insert (20) is made of a heavier material than the coating (21 ) For example, the insert (20) can be an aluminum sheet.

In any case, the insert (20) must be a flexible sheet that can be bent together with the flat resin panel (2).

The flat panel (2) with the desired color undergoes a set of finishing works (3) comprising, for example, one or more of the following operations, respecting or not the following sequence:

- thickness sizing of panel (2);

- pantograph milling of panel (2);

- squaring of panel (2);

- finer thickness sizing of panel (2);

- polishing of panel (2) until it is given a specular polished surface. The aforementioned finishing works may be performed according to known technologies by using the machinery of known type used to machine flat wooden panels automatically and continuously. Evidently, such operations cannot be performed on curved panels.

Given the fact that the known installations for the aforementioned finishing works are designed for flat panels, said finishing works are practical and easy and can be performed for several panels simultaneously or continuously.

A finished flat panel (4) is obtained from the finishing step (3) and subjected to final heating and bending (5).

During heating the finished flat panel (4) is heated to the resin tempering temperature. In such a step it is extremely important not to reach the resin melting temperature in order to avoid damaging the finishing works that were previously performed. Generally, the resin tempering temperature is comprised between 80-120 °C, for this reason the finished panel (4) is heated until a temperature comprised between 80 - 120 °C is reached.

The finished panel (4) can be heated either with a hot fluid in gaseous or liquid status or with a suitably heated bending mold. For instance, the panel can be heated with a traditional furnace with rigorous control of the heating temperature.

Preferably, heating can be obtained with hot water.

Advantageously, a polyester resin with tempering temperature of approximately 1 00 °C is used. In such a way, hot water can be used as heat source; the panel (4) is totally immersed in a hot water bath at 1 00 °C, where it is left until the tempering temperature of the molding resin is reached uniformly; the choice of the water bath ensures rapid heating of the flat panel (4) without risk of damaging the finished surface.

Once the panel (4) has reached the resin tempering temperature, it is bent by means of a suitable bending mold, in such manner to obtained a curved panel (6). Referring to Fig. 2 a preferred embodiment of the heating and bending step (5) is disclosed. A tub (50) contains hot water (51 ) at 100 °C temperature. The panel (4) is immersed in hot water (51 ).

The panel (4) is disposed according to a substantially vertical plane and is held by means of suitable holders (52, 53) on the lower and upper edges.

The tub (50) contains a bending mold (7) comprising a die (70) with convex surface (71 ) and a lid (72) with concave surface (73). When the panel (4) reaches the resin tempering temperature, the mold (7) is closed so that the panel (4) is compressed between die (70) and lid (72), assuming a curved configuration such as the concave (71 ) and convex (73) surfaces of die and lid, respectively.

In such way, a curved panel (6) with finished surface and desired color is obtained.

When bending is completed, the panel (6) is cooled with cold water introduced in the tub (50) after draining the hot water (51 ).

After being extracted from the mold (7), the curved panel (6) perfectly maintains its curved shape.

Generally, the external surface of the curved panel (6) (i.e. the surface adapted to remain visible) is the rounded one. For this reason, the concave surface (73) of the lid (72) can be advantageously made of glass in order not to damage the panel visible surface. Evidently, also the convex surface (71 ) of the die can be made of glass.

Although for the sake of simplicity Fig. 2 illustrates a tub (50) with only one mold (7) for bending one panel at a time, said tub can be evidently dimensioned in such manner to contain several molds (7), either in side-by- side or stacked configuration, in such a way to bend several panels simultaneously, thus reducing process time and cost.

Moreover, although the panel (4) is arranged vertically and the mold (7) is illustrated with die and lid, the panel (4) can be disposed in horizontal position on a convex die, without lid, and bent by means of vacuum or air extraction. In other words, bending of the panel is performed by positioning the panel on the die and extracting air or creating a vacuum between panel and die, in such a way that the panel takes the convex profile of the die.

Numerous variations and modifications can be made to the present embodiments of the invention, within the reach of an expert of the field, while still falling within the scope of the invention described in the attached claims.

Claims

1 ) Bending process of a resin panel comprising the following steps:

- injection molding of resin to obtain a flat panel (2) which has no bending,

- finishing works on surface and edges of the flat resin panel (2), in such a way to obtain a finished flat panel (4),

- heating of all finished flat panel (4) until the overall panel reaches the tempering temperature of resin, and it does not reach the melting temperature of resin, in order not to damage said finishing works of the panel, and

- bending of the heated flat panel (4) by means of a bending mold (7) comprising at least one die (70) with convex surface (71 ), in such a way to obtain a bent resin panel (6).

2) Process as claimed in claim 1 , characterized in that during said heating step, the finished flat panel (4) is heated until the panel reaches a temperature comprised between 80 ° C and 120° C.

3) Process as claimed in claim 1 or 2, characterized in that said heating of the panel (4) is obtained by using a hot fluid in gaseous or liquid status or a heated bending mold.

4) Process as claimed in claim 3, characterized in that the heating of the flat panel (4) is obtained by means of a furnace.

5) Process as claimed in claim 3, characterized in that the heating of the flat panel (4) is obtained with immersion in hot water (51 ).

6) Process as claimed in claim 5, characterized in that said bending mold (7) is immersed in said hot water (51 ) in which the panel (4) is.

7) Process as claimed in any one of the preceding claims, characterized in that said mold also comprises a lid (72) with concave surface (73) and bending of heated panel (4) is obtained by compressing the heated panel (4) between die and lid.

8) Process as claimed in any one of the claims 1 to 6, characterized in that bending of panel is obtained by positioning the heated panel (4) on the die and extracting air or creating vacuum between panel (4) and die (70), in such a way that the panel takes the profile of the die.