Plastic and nonmetallic article shaping or treating: processes – Direct application of fluid pressure differential to... – With internal application of fluid pressure
Reexamination Certificate
1998-08-04
2001-03-06
Tentoni, Leo B. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Direct application of fluid pressure differential to...
With internal application of fluid pressure
C249S082000
Reexamination Certificate
active
06197245
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for producing a resin molded article having a hollow space inside, the resin molded article, hereinafter, being referred to as a “hollow molded article”.
2. Description of the Related Art
Japanese unexamined patent publication Nos. Hei 4-212822 and Hei 7-144336 disclose a process for producing a hollow molded article utilizing an injection molding method having a core retracting system. In this process, a molten resin is injected with a high pressure into a cavity which is completely closed with a predetermined clearance. After filling the cavity with the resin, a movable core is retracted to expand the cavity while injecting a high-pressured gas into the molten resin. Consequently, a hollow space is formed in a resin substrate. However, such a method has been problematic in that a sink mark and a blister have been caused in a part of the hollow molded article in the vicinity of the hollow space and the appearance of the hollow molded article has been deteriorated because of the difference in a cooling speed of the resin and in a pressure applied to the resin between a part near to the hollow space and apart far from the hollow space. Additionally, there has been another problem that when molding of the hollow molded article and laminating of a skin material, such as one having a cushion layer and one having hair such as a carpet, onto a surface of the hollow molded article are carried out simultaneously, the cushion layer is crushed and the hair is laid in different degrees between the part near to the hollow space and the part far from the hollow space and the appearance of the hollow molded article is deteriorated.
SUMMARY OF THE INVENTION
The object of the present invention is to solve the problems of the conventional processes. Namely, one object of the present invention is to provide a process for producing a hollow molded article which has a hollow space extending throughout its inside and in which neither the sink mark nor blister is caused in the part near to the hollow space. Another object of the present invention is to provide a process for producing a hollow molded article having good appearance without causing differences both in a residual degree of the cushion layer and in a degree of hair-lying between the part near to the hollow space and the part far from the hollow space, even when a hollow molded article on which the skin material having the cushion layer and the hair is laminated is produced.
According to the present invention, there is provided a process for producing a hollow molded article comprising the following steps of:
Step (A) providing a molding machine comprising a mold including a first mold half and a second mold half, wherein the first mold half has a first mold surface, the second mold half has a second mold surface, the mold surfaces together define a cavity, at least one of the mold halves can move so that the mold surfaces approach and go away from each other, at least one of the mold halves comprises a body and a slidable block, the mold surface of the mold half comprising the body and the slidable block comprises a surface of the body and a surface of the slidable block, the slidable block can move from a first position to a second position, the movement of the slidable block from the first position to the second position expands the cavity;
Step (B) supplying resin in an unsolidified state between the first mold surface and the second mold surface to fill the cavity with the resin, wherein the cavity has a first clearance;
Step (C) supplying pressurized fluid into the resin lying between the mold surfaces;
Step (D) moving the slidable block from the first position to the second position;
Step (E) opening the mold until a cavity clearance becomes a second clearance which is larger than the first clearance; and
Step (F) opening the mold to take out the hollow molded article.
In one embodiment of the present invention, in Step (B), the resin in the unsolidified state may be supplied between the first mold half and the second mold half facing with each other with a clearance larger than the first clearance, and at least one mold half may be moved to press and spread the resin to fill the cavity with the same. In another embodiment of the present invention, Step (E) may be commenced at the same time when or after Step (D) is commenced. In still another embodiment of the present invention, Step (D) may be commenced after Step (E) is commenced. In yet another embodiment of the present invention, Step (D) may be commenced at the same time when or after Step (C) is commenced. In yet another embodiment of the present invention, Step (E) may be commenced at the same time when Step (C) is commenced. In yet another embodiment of the present invention, Step (C) may be commenced after Step (B) is commenced. In yet another embodiment of the present invention, Step (D) may be commenced after Step (B) is completed. In yet another embodiment of the present invention, Step (E) may be commenced after Step (B) is completed. In yet another embodiment, a further step of changing a pressure applied to the resin may be carried out after Step (B) is completed and before Step (E) is commenced. In yet another embodiment of the present invention, Step (C) may be commenced at the same time when or after the step of changing the pressure is commenced. In yet another embodiment, the step of changing the pressure is carried out after Step (B) is completed and after Step (E) is commenced, and Step (D) is commenced at the same time when or after the step of changing the pressure is commenced. In yet another embodiment of the present invention, in Step (B), supplying the resin is commenced at a time when the slidable block is located at the first position, and the mold surface of the slidable block existing at the first position is depressed below the surface of the body adjacent to the slidable block. In yet another embodiment of the present invention, a further step of supplying a skin material between the first mold surface and the second mold surface is carried out before Step (B) is commenced.
Other objects, features, and advantages of this invention will be apparent from a consideration of the following detailed description thereof in conjunction with the accompanying drawings.
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922 Modern Plastics International 23(1993) Mar., No. 3, Lausanne, CH, “Mold automation saves more material than standard gas-assist”.
Furuta Akihiro
Inoue Toru
Usui Nobuhiro
McDowell Suzanne E.
Pillsbury Madison & Sutro LLP
Sumitomo Chemical Company Ltd.
Tentoni Leo B.
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