Apparatus and method for producing resin product

An apparatus produces a resin product which includes a first resin layer partially covered with a second resin layer so that a boundary line between the first and second resin layers is visible from the outside. The apparatus may include a first mold side having a recess, a second mold side configured and dimensioned to enclose the recess of the first mold side ,a slide core movably fitted in the recess of the first mold side, which may be movable toward the second mold side to an extracted position to define a first cavity, and may be movable rearward to a retracted position after a first resin is injected into the first cavity to form the first resin layer, thus defining a second cavity into which a second resin is injected to form the second resin layer, the slide core including a dam dimensioned and configured to form a groove in the first resin layer during the formation of the first resin layer, wherein the dame partially positioned in the groove during the formation of the second resin layer, a first resin supply unit for supplying the first cavity with the first resin, and/or a second resin supply unit for supplying the second cavity with the second resin. The resin product produced by the apparatus is excellent in appearance, and obviates the post-processing formation of a tear line. Methods of forming the resin product are also described.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an apparatus and a method for producing a resin product which includes an inner layer and an outer layer, and, more particularly, to an apparatus and a method for producing a resin product in which part of an inner layer (a first resin layer) is covered with an outer layer (a second resin layer) so that a boundary line between the inner layer and the outer layer is visible from the outside.

2. Description of Related Art

Recently, various attempts are being made to improve the esthetic appearance and tactile impression of a resin product by covering a partial area of a surface of the resin product with an outer layer which is comprised of material different from that of the resin product. In an exemplary automotive crash pad, as shown inFIG. 1, an outer layer, which has a material (in particular, a soft material unlike that of the crash pad) and a color, different from that of the crash pad1, is formed on a door region2of a passenger air bag (“PAB”) so as to give off a feeling of sophistication.

As shown inFIG. 2, such a conventional crash pad has been generally manufactured in a manner in which an outer component, which is separately produced in advance, is attached to the crash pad1. These days, a recent technical development is to realize a PAB door region2which is integrally covered with an outer layer of material different from that of the PAB door at the time of the injection molding process of a crash pad. As compared with the former process which requires two different molds and processes of assembly of the outer component, the latter method is relatively advantageous in that it is excellent in terms of cost and the appearance of a fabricated crash pad, in particular, the boundary line of the PAB door region2is clean-cut and clearly demarcated.

Referring toFIGS. 3A to 3E, a process of producing a crash pad through the latter method will be described below.

An apparatus for producing the crash pad comprises a mold, and a first resin supply unit10and a second resin supply unit20for supplying resin material into an internal space in a mold. The mold comprises a first mold side having a recess30, a second mold side, and a slide core movably fitted in the recess30of the first mold side. In such a crash pad, PPF resin (Polypropylene Filled Resin) such as talc-filled polypropylene resin is used as a first resin material, and flexible TPO resin (Thermoplastic Olefin Resin) is used as a second resin material.

The process of producing the crash pad is conducted in a manner that the slide core is moved to the extracted position to define a first cavity11(FIG. 3A), the first resin is supplied into the first cavity11to form a first resin layer1a(FIG. 3B), the slide core is moved to the retracted position to define a second cavity21(FIG. 3C), and prior to the solidification of the first resin, second resin is supplied into the second cavity21to form a second resin layer2aon the first resin layer1a(FIG. 3D). The resulting crash pad, which is produced in this manner, has a considerably well delimited boundary line B between the first and second resin layers1aand2a(FIG. 3E).

However, the above apparatus and method for producing a crash pad has the following disadvantages.

As shown inFIG. 4, since the second resin (PPF) is injected before the complete solidification of the first resin (TPO), there may be a gap between the first and second mold sides, so that the second resin leaks into the zone of the first resin through the gap, thus hindering the clean-cut appearance at the boundary line.

Furthermore, as shown inFIG. 5, the rear surface of the resulting crash pad is post-processed to produce a tear line L, and is attached to a chute3of an airbag module in a fusion manner. The chute3is assembled with a housing4which accommodates a folded cushion5. Unfortunately, such a post-processing formation of the tear line L increases production costs of the crash pads, and a degree of freedom of the post-process is not so high. Furthermore, when the processing accuracy is lowered, there may be a fear that the breaking strength at the tear line L is excessively increased.

BRIEF SUMMARY OF THE INVENTION

Accordingly, the present invention has been made keeping in mind the above problems occurring in the related art, and the present invention provides an apparatus and a method for producing a resin product in which a first resin layer is partially covered with a second resin layer and which has a very fine appearance at a tear line and obviates post-processing for the formation of the tear line.

Various aspects of the present invention are directed to an apparatus for producing a resin product which includes a first resin layer partially covered with a second resin layer so that a boundary line between the first and second resin layers is visible from the outside. The apparatus may include a first mold side having a recess, a second mold side configured and dimensioned to enclose the recess of the first mold side, a slide core movably fitted in the recess of the first mold side, which may be movable toward the second mold side to an extracted position to define a first cavity, and may be movable rearward to a retracted position after a first resin is injected into the first cavity to form the first resin layer, thus defining a second cavity into which a second resin is injected to form the second resin layer, the slide core including a dam dimensioned and configured to form a groove in the first resin layer during the formation of the first resin layer, wherein the dame partially positioned in the groove during the formation of the second resin layer, a first resin supply unit for supplying the first cavity with the first resin, and/or a second resin supply unit for supplying the second cavity with the second resin.

The recess may be a stepped structure including a first recess section and a second recess section having a greater depth than that of the first recess section, and the slide core may be positioned in the second recess section. The dam may be formed along a circumference of the slide core. The second mold side may include a wedge ridge for forming a tear line in the first resin layer. The slide core may include a pressure sensor for measuring a pressure of resin in a vicinity of the wedge ridge.

Another aspect of the present invention is directed to a method of producing a resin product which may include a first resin layer partially covered with a second resin layer so that a boundary line between the first and second resin layers is visible from the outside. The method may include closing a first mold side having a recess with a second mold side, moving a slide core fitted in the recess of the first mold side toward the second mold side to an extracted position to define a first cavity, the slide core including a dam to form a groove in the first resin layer, filling the first cavity with a first resin to form the first resin layer, moving the slide core to a retracted position, thus defining a second cavity while the dam may be partially disposed in the groove of the first resin layer, and/or filling the second cavity with a second resin to form the second resin layer.

The recess may be a stepped structure including a first recess section and a second recess section having a greater depth than the first recess section, and the slide core may be positioned in the second recess section, the method further comprising filling the first cavity with the first resin such that when the first cavity may be fully filled with the first resin, a region of the first resin layer corresponding to the second recess section has a thickness less than that of a remaining region of the first resin layer. The second mold side may include a wedge ridge forming a tear line in the first resin layer. The method may further include measuring a pressure of the second resin in a vicinity of the wedge ridge while filling the second cavity with the second resin, and controlling an injection pressure of the second resin so as to maintain the pressure of the second resin within a predetermined range.

Another aspect of the present invention is directed to a method of producing a resin product which includes a first resin layer partially covered with a second resin layer so that a boundary line between the first and second resin layers is visible from the outside. The method may include closing a first mold side having a recess with a second mold side, the second mold side including a wedge ridge for forming a tear line in the first resin layer, moving a slide core fitted in the recess of the first mold side toward the second mold side to an extracted position to define a first cavity, filling the first cavity with a first resin to form the first resin layer, moving the slide core to a retracted position to define a second cavity, and/or filling the second cavity with a second resin to form the second resin layer and measuring a pressure of the second resin in a vicinity of the wedge ridge, and controlling pressure of injection of the second resin so as to maintain the pressure of the second resin within a predetermined range.

The groove in the first resin layer has a thickness ranging from about 1 mm to about 2 mm. The groove in the first resin layer have a thickness ranging from about 1 mm to about 1.5 mm. The dam extends toward the second mold side along an outer circumference of the slide core with a predetermined height. The second mold side may include a wedge ridge, extending along on an upper surface thereof within the dam and toward the slide core, for forming a tear line in the first resin layer. The height of the wedge ridge may be smaller than thickness of the first resin layer.

The above-mentioned resin products may be a vehicle dashboard.

DETAILED DESCRIPTION OF THE INVENTION

First, an apparatus for producing a crash pad, according to various aspects of the present invention is described with reference toFIGS. 6A and 6B. As also disclosed in the above description of the related art, the apparatus includes a mold, and a first resin supply unit10and a second resin supply unit20, and the mold includes a first mold part or side100, a second mold part or side200, and a slide core300.

The first mold side100has a recess, which is configured into a stepped structure including a first recess section31and a second recess section32having a depth deeper than the first recess section31. In various embodiments, the first recess section31may be formed only at one side of the second recess section32, as shown inFIGS. 6A to 6D, or may be formed at both right and left sides of the second recess section32. In the latter case, the outer layer, that is the second resin layer, will have a shape isolated from the outside by the inner layer, that is, the first resin layer, like a fried egg.

The second mold side200is coupled with the first mold side100so as to form an enclosed space defined by the first recess section31and the second recess section32. The upper surface of the second mold side200, which faces the second recess section32of the first mold side100, may be provided with a wedge ridge50. The wedge ridge50is intended to form a tear line on the rear surface of the crash pad.

The slide core300is movably fitted in the second recess section32. When the slide core300is moved toward the second mold side200in the extracted position with a predetermined distance, a first cavity11is defined between the first and second mold sides100and200(FIG. 6A). When the slide core300is moved toward the first mold side100to the retracted position after the first cavity11is filled with a first resin supplied by the first resin supply unit10, a second cavity21is defined therebetween (FIG. 6C). The slide core300movably inserted into in the second recess section32of the first mold side100is provided at the front surface thereof (the surface facing the second mold side200) with a dam40and a pressure sensor60. The dam40protrudes along the outer circumference of the front surface of the slide core300, and the pressure sensor60is incorporated at the area corresponding to the wedge ridge50formed on upper surface of the second mold side200.

The first resin supply unit10is configured to supply the first cavity11with a first resin, for example, PPF resin, and the second resin supply unit20is configured to supply the second cavity21with a second resin, for example, TPO resin. As shown inFIG. 6D, the pressure of injection, by which the second resin is supplied from the second resin supply unit20, is positively controlled by a control unit which will be described later.

Referring toFIGS. 6A to 8, the method of producing a crash pad, according to various aspects of the present invention is described.

Formation of the First Resin Layer

The first and second mold sides100and200are coupled together, and the slide core300is moved in the recess section of the first mold side100, thus defining the first cavity11(FIG. 6A) and the second cavity21(FIG. 6C). The first cavity11is a space to form the first resin layer10aand the second cavity21is a space to form the second resin layer20ain which the moving distance of the slide core300is controlled such that the thickness of the second cavity is less than that of the first cavity.

When the first resin is injected into the first cavity11(FIG. 6B), the first cavity11is fully filled with the first resin, thus forming the first resin layer10ain which a resin layer formed in the second cavity section20ahas a thickness less than that of a resin layer formed in the first cavity.

The first resin layer10ais formed with a groove10b(FIG. 6E) made by the dam40of the slide core300. The groove10bmay have a thickness ranging from 1 mm to 2 mm, and preferably a thickness ranging from 1 mm to 1.5 mm. Furthermore, since the second mold side200includes the wedge ridge50protruding upwards therefrom, the first resin layer10ais provided with a valley groove (L) at a region corresponding to the wedge ridge50. In this regard, when the first resin is injected, a pressure of the first resin is locally increased at the region corresponding to the wedge ridge50. When the movable slide core300is retracted toward the first mold side100before the solidification of the first resin, the locally increased pressure of the first resin causes the formation of a protrusion10c(FIG. 6E) at the region corresponding to the wedge ridge50.

Formation of the Second Resin Layer

Prior to the solidification of the first resin, the slide core300is retracted toward the first mold side100to define the second cavity21(FIG. 6C). At this time, the dam40of the slide core300partially remains disposed in the groove10b(FIG. 7). When the second resin is injected into the second cavity21, the second resin is blocked by the dam40and thus cannot leak into the first resin layer10a. Even if a portion of the second resin leaks, the leaked portion of the second resin does not infiltrate between the first mold side100and the first resin layer10abut instead is trapped in the groove10bas shown inFIG. 7. When the thickness of the groove10bis in a range of 1 mm to 2 mm, and preferably a range of 1 mm to 1.5 mm, the second resin in the groove10bis almost invisible. Consequently, the boundary region between the first resin layer10aand the second resin layer20ahas a remarkably clean appearance.

As shown inFIG. 6E, the protrusion10cof the first resin layer10a, which is formed along the tear line, may also cause the formation of a protrusion on the second resin layer20aduring the injection of the second resin. The reason for this has been mentioned above. Accordingly, in order to prevent this formation of a protrusion on the second resin layer20a, it is necessary to control the pressure of the second resin in the vicinity of the protrusion10c. More specifically, as shown inFIGS. 6D to 8, the pressure of the second resin at the protrusion10cis measured using the pressure sensor60, and then the injection pressure control unit controls an injection pressure of the second resin supplied from the second resin supply unit20, depending on the measured pressure value, such that the pressure of the second resin at the protrusion is maintained within a predetermined range. Referring toFIG. 8, when the pressure of the second resin measured by the pressure sensor is represented as curve1, the present injection pressure of the second resin may be maintained as it is. When the pressure of the second resin is represented as curve2, the injection pressure of the second resin needs to be decreased. Meanwhile, when the pressure of the second resin is represented as curve3, the injection pressure of the second resin needs to be increased. The appropriate range of the injection pressure of the second resin may be acquired through repeated experiments. Of course, the height of the protrusion10cmay be properly controlled by controlling the pressure of the first resin at the wedge ridge50during the injection of the first resin.

As described above, the present invention provides an apparatus and a method for producing a resin product having an excellent appearance, and obviates post-processing formation of a tear line.