This application is based upon and claims the benefit under 35 U.S.C. ยง 119 of Japanese Patent Application No. 2008-097519, filed on Apr. 3, 2008, which is hereby incorporated by reference herein in its entirety.
[Field of the Invention]
The present invention relates to a foam molding mold structure or the like to mold a foam molded product by making a movable mold move in relation to a fixed mold, and more detailedly, relates to a foam molding mold structure or the like to improve a strength of a projecting portion or a recessed portion in the foam molded product.
[Description of the Related Art]
Conventionally, there is used a molding method in which a molten resin is filled into a cavity and a movable mold is made to move by a predetermined distance in a mold opening direction, whereby a foam molded product is obtained (for example, see Patent Document 1).
At a time of performing foam molding in the foam molding mold structure described above, first, as referred to in
[Patent Document 1] Japanese Laid-open Patent Publication No. 2002-120252
As referred to in
However, in a foam molded product of such a kind, there is a problem that since the projecting portion 151 is only held by the thin skin layer A, its strength is quite weak and that the projecting portion 151 is easily folded at a root portion when a large load acts on the projecting portion 151.
Further, though not illustrated specifically, there is also a problem that when a recessed portion to fit a member thereinto is formed in a foam-molded product a holding strength of the member fitted into the recessed portion becomes quite weak.
The present invention is made to solve such problems, and an object of the present invention is to improve a strength of a projecting portion or a recessed portion in a foam molded product.
A foam molding mold structure of the present invention is a foam molding mold structure in which a foam molded product is molded by a molten resin being filled into a cavity formed by a movable mold and a fixed mold and the movable mode being made to move in relation to the fixed mold, the foam molding mold structure including: in at least either one of cavity surfaces of the movable mold and the fixed mold, a cavity surface movable relatively to the cavity surface.
The foam molding mold structure of the present invention includes a recessed portion or a projecting portion formed in a cavity surface facing the cavity surface movable relatively.
The foam molding mold structure of the present invention includes a recessed portion or a projecting portion formed in the cavity surface movable relatively.
Further, in the foam molding mold structure of the present invention, the recessed portion is to form at least one of a rib, a boss, a clip stay, and a tab shape in the foam molded product.
The foam molding mold of the present invention includes a movable nest constituting the cavity surface movable relatively.
A manufacturing method of a foam molded product of the present invention is a manufacturing method of a foam molded product using a foam molding mold structure including, in at least either one of cavity surfaces of a movable mold and a fixed mold, a cavity surface movable relatively to the cavity surface, the method including: filling a molten resin into a cavity formed by the movable mold and the fixed mold; and, when the movable mold is made to move in relation to the fixed mold, making the cavity surface movable relatively move relatively to a cavity surface having the cavity surface movable relatively.
A foam molded product of the present invention is a foam molded product including: a base portion; and a projecting portion or a recessed portion formed in the base portion, wherein in the base portion, a proportion of a foaming layer having a foaming magnification equal to or more than a predetermined foaming magnification in a thickness direction of a predetermined region in which the projecting portion or the recessed portion is formed is lower than a proportion of the foaming layer having the foaming magnification equal to or more than the predetermined foaming magnification in a thickness direction of a region other than the predetermined region.
Further, in the foam molded product of the present invention, in the base portion, all in the thickness direction of the predetermined region is constituted with a low foaming layer having a lower foaming magnification than the predetermined foaming magnification or with a non-foaming layer.
Hereinafter, embodiments of the present invention will be described.
In
A reference numeral 6 indicates a fixed plate to hold the fixed mold 1. A reference numeral 7 indicates an injection device fixed to the fixed plate 6, the injection device 7 injecting and filling the molten resin into the cavity 5 via the sprue 5. A reference numeral 8 indicates a movable plate holding the movable mold 3, the movable plate 8 being constituted movable in a horizontal direction, and thereby the movable mold 3 moves forward and backward in relation to the fixed mold 1. A reference numeral 9 indicates a tie bar supporting the movable plate 8 and making the movable plate 8 movable. The tie bar 9 is constituted with a ball screw and a drive motor, or a hydraulic cylinder or the like.
A reference numeral 10 indicates a nest fitting portion boredly provided in the movable mold 3, the nest fitting portion 10 penetrating through the movable mold 3 and the movable plate 8 and opening in a cavity surface 3a. A reference numeral 11 indicates a movable nest insertedly provided in a manner to be movable in the nest fitting portion 10. Here, the movable nest 11 and the recessed portion 2 formed in the cavity surface 1a of the fixed mold 1 are in a positional relation of facing each other. A reference numeral 12 indicates a plunger which couples with the movable nest 11 and moves forward and backward. A reference numeral 13 indicates a drive mechanism portion driving the plunger 12. The drive mechanism portion 13 is disposed in the movable mold 3, and is constituted with a ball screw and a drive motor, or a hydraulic cylinder or the like. Depending on a disposition position of the projecting portion such as the rib, the boss, the clip stay or the tab shape, the movable nest 11 can be contacted with the fixed mold 1 by a spring, a hydraulic cylinder, a gas cylinder or the like so that a thickness of the cavity is held.
In the foam molding mold structure as above, a front end surface of the movable nest 11 constitutes part of the cavity surface 3a of the movable mold 3, so that the cavity surface 3a has a cavity surface 1a which is movable relatively to the cavity surface 3a.
Next, a foam molding method by the injection molding machine constituted as above according to the present embodiment will be described by using
First, as referred to in
Then, as referred to in
When the foam molding is performed as described above, as referred to in
Here, in this specification, a foaming layer means a layer whose foaming magnification is equal to or more than a predetermined foaming magnification, while a skin layer means a low foaming layer whose foaming magnification is lower than the predetermined foaming magnification or a non-foaming layer.
In such a foam molded product 20, the projecting portion 22 can be held by the thick skin layer A, so that a strength of the projecting portion 22 can be improved. Therefore, even when a large load acts on the projecting portion 22, it is possible to solve a problem that the projecting portion 22 is easily folded at the root portion, and so on.
It should be noted that though in the present embodiment an example is explained in which all in the thickness direction of the predetermined region S is constituted with the skin layer A in the base portion 21 as referred to in
As stated above, in the present embodiment, a movable nest 11 which can move forward and backward in a movable mold 3 is provided, and the movable nest 11 is disposed in a position facing a recessed portion 2 of a fixed mold 1 for molding of a projecting portion such as a rib. Then, at a time of filling of a molten resin, the movable nest 11 is set in a position retired from a mold matching surface 3a in correspondence with a thickness of a foam molded product, the movable nest 11 constituting a cavity surface, and then the molten resin is filled into a cavity 4, and the movable nest 11 is made not to move in relation to the movable mold 3 when the movable mold 3 moves backward at the foam molding time. Thereby, a portion positioned in a thickness direction of a predetermined region S including a root portion of a projecting portion 22 formed by the recessed portion 2 of the fixed mold 1 can be made constituted with a skin layer A, so that the foam molded product in which a strength of the projecting portion 22 is improved can be obtained.
Further, in a constitution in which the movable nest 11 is insertedly provided in the movable mold 3 as in the present embodiment, as a modified example, there can be formed a recessed portion 11b in a cavity surface 11a of a movable nest 11 as referred to in
Further, as referred to in
Next, a second embodiment of the present invention will be described.
In
A foam molding method in the foam molding mold structure constituted as above will be described.
First, as referred to in
Then, as referred to in
As a result that the movable mold 3 is made to move backward and the movable nest 15 is made to move forward as described above, a foam molded product 60 is molded by a pressure of a predetermined portion of the molten resin filled into the cavity 4 being released and the predetermined portion being foamed but the other portion being not foamed.
In the foam molded product 60 as above, the projecting portion 62 can be held by the thick skin layer A, so that a strength of the projecting portion 62 can be improved. Therefore, even when a large load acts on the projecting portion 62, it is possible to solve a problem that the projecting portion 62 is easily folded at the root portion, and so on.
As stated above, in the present embodiment, a movable nest 15 which can move forward and backward in a fixed mold 1 is provided, and a recessed portion 15b to mold a projecting portion such as a rib is provided in the movable nest 15. Then, at a time of filling of a molten resin, the movable nest 15 is set in a position retired from a mold matching surface 1a by a predetermined distance in correspondence with a thickness of a foam molded product, the movable nest 15 constituting a cavity surface, and then the molten resin is filled into a cavity 4, and the movable nest 15 is made to move forward synchronously with the movable mold 3 when a movable mold 3 is made to move backward at a foam molding time. Thereby, a portion positioned in a thickness direction of a predetermined region S including a root portion of a projecting portion 62 formed by the recessed portion 15b of the movable mold 15 can be made constituted with a skin layer A, so that the foam molded product in which a strength of the projecting portion 62 is improved can be obtained.
Further, in a constitution in which the movable nest 15 is insertedly provided in the fixed mold 1 as in the present embodiment, as a modified example there can be formed a recessed portion 3a in a movable mold 3 as referred to in
Further, as referred to in
It should be noted that in the first and the second embodiment, the movable nest 11 or 15 can be constituted attachable/detachable in accordance with a shape of the foam molded product. It is also possible to constitute so that a nest having a predetermined shape can be additionally mounted to the movable nest 11 or 15. It is also possible to constitute so that a nest having a predetermined shape can be additionally mounted in the fixed mold 1 or the movable mold 3. By a constitution in which the nest is attachable/detachable or mountable, it is possible to cope with foam molded products having various shapes.
Further, in the first and the second embodiments, it is described that the drive mechanisms to enable the movable mold 3 and the movable nest 11 or 15 move are each constituted with a ball screw and a drive motor, or a hydraulic cylinder or the like. However, in the present embodiment, since it is preferable to perform an accurate core-back control by accurately recognizing an initial position of the movable nest 11 or 15 or by accurately synchronizing the movable nest 15 with the movable mold 3 in order to improve quality of a foam molded product, it is desired that the movable nest 11 or 15 is made contact with the facing fixed mold 1 or movable mold 3 with a cylinder, a spring or the like so that a thickness of a cavity can be accurately controlled at a time of opening the mold.
Further, the constitution of the first embodiment and the constitution of the second embodiment can be implemented combinedly, and the number of movable nests can be plural. Though in the present embodiments the projecting portion or the recessed portion is formed in the movable nest, the fixed mold or the movable mold to improve the strength of the projecting portion or the like in the foam molded product, the present embodiments are also effective for a foam molded product in which a projecting portion is not formed, and in such a case, a strength of a predetermined portion of the foam molded product can be improved.
As the molten resin used in the present invention, a thermoplastic resin is preferable, and a chemical foaming agent can be used or a physical foaming agent can be used.
According to the present invention, when a projecting portion such as a rib, a boss, a clip stay or a tab shape, or a recessed portion to fit a member thereinto is integrally formed in a foam molded product, it is possible to improve a strength of the projecting portion or the recessed portion.
The present embodiments are to be considered in all respects as illustrative and no restrictive, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof.
Number | Date | Country | Kind |
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2008-097519 | Apr 2008 | JP | national |