Static molds – Container-type molding device – Plural article forming mold – or molds with community feature
Reexamination Certificate
1999-07-06
2001-09-11
Nguyen, Nam (Department: 1722)
Static molds
Container-type molding device
Plural article forming mold, or molds with community feature
C249S129000, C249S130000
Reexamination Certificate
active
06286807
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to molds for foam casting expanded moldings such as polyurethane foams, and in particular relates to a mold suitable for foam casting small-sized expanded moldings.
DESCRIPTION OF THE RELATED ART
Polyurethane foams have various uses such as thermal insulators, shock absorbers, cushioning materials, moisture absorbers, and sound-absorbing materials, and are formed by spray forming in place, foam casting, lamination, etc., according to applications.
Among these methods, the foam casting is suitable for producing comparative small-sized products of miscellaneous shapes such as pads, automobile interior parts, and sundries, utilizing a mold having cavities of predetermined shapes. In this method, the component of polyisocyanates is blended in a mixing head with a liquid mixture of the component of polyol, a blowing agent, a catalyst, a foam regulating agent, and other auxiliary agents to obtain a raw liquid material for foaming (liquid for pouring) which is poured into cavities of a mold to be foam cast in the mold.
Generally, a mold for use in foam casting is vessel-shaped and has one cavity per mold. When small-sized moldings are formed, a plurality of molds are arranged on a pallet to perform foam casting by sequentially pouring the liquid for pouring from the mixing head into each cavity.
When small-sized moldings are formed by this method, there have been the following problems.
i) The weight of the molding is limited to the minimum delivery amount of the mixing head and a smaller-sized molding than the minimum delivery amount cannot be formed.
ii) As the size of the molding decreases, variations in the weight of the moldings increase due to errors in pouring amount of liquid for pouring in each mold, resulting in a reduced manufacturing yield.
iii) Although a large number of the molds for a smaller-sized molding can be arranged on a pallet to increase the number of moldings per pallet, as the time for pouring from the mixing head is limited, the number of molds arrangeable on a pallet is also limited, so that a large number of the molds cannot be produced at a time.
iv) Since the same number of molds as that of moldings is arranged on a pallet, dead air spaces (walls of molds and spaces between molds) are large.
Accordingly, in a conventional mold for expanded moldings, miniaturization of the product is limited and small-sized expanded products cannot be efficiently produced in high-yield.
OBJECT AND SUMMARY OF THE INVENTION
It is an object of the present invention to provide a mold for expanded moldings capable of efficiently producing smaller-sized products in high-yield by solving the above-mentioned problems.
A mold for expanded moldings according to the present invention comprises a vessel-shaped lower mold; an upper mold covering the lower mold; and a partition wall disposed protrusively from the bottom surface of the upper mold, wherein the inside of the mold is divided into a plurality of small cavities by the partition wall.
Since in the mold for expanded moldings according to the present invention, the inside space of the vessel-shaped lower mold is divided into a plurality of small cavities by the partition wall of the upper mold, a plurality of moldings can be formed by one casting in one mold, and the following effects will come into play.
A. The possible minimum weight of the product is to be (the minimum delivery amount of the mixing head)/(the number of divisions), thus a smaller size product than the minimum delivery amount can be produced.
B. The moldings formed in at least one mold are hardly subject to variations in weight, etc., and can be produced in high-yield.
C. When the number of molds corresponding to the maximum number of pouring by the mixing head are disposed, moldings as a multiple of both the number of divisions of each mold and the number of molds on a pallet can be produced on one pallet.
D. Since the number of molds disposed on a pallet relative to the number of moldings produced is extremely reduced, efficiency of space utilization is increased and the dead air spaces are reduced so that a large number of moldings can be produced on one pallet.
The following features of the present invention permit an equalized level of poured liquid in each small cavity by smooth feeding of the liquid to each small cavity of the lower mold without being divided by any portion other than the partition wall.
(i) In order to feed the poured liquid along the cavity base, the cavity base may be a smooth surface.
(ii) When a protrusion or a raised line is formed on the base of the cavity of the lower mold, the height of the protrusion or the raised line may be lower than a level of poured liquid so that the poured liquid can readily flow across the protrusion or the raised line. The raised line may be preferably disposed in a portion of the base of the cavity of the lower mold facing the bottom end of the partition wall.
(iii) The base of the cavity of the lower mold may be an inclined surface so that a portion of the base facing the bottom end of the partition wall is to be the deepest portion of the lower mold, preferably with a falling gradient of below 60° toward the deepest portion.
In the mold according to the present invention, although it is preferable that the casting be performed by spraying liquid for pouring toward the cavity base facing the bottom end of the partition wall so as to uniformly distribute the liquid to each cavity, there are some cases, in effect, that the spraying misses the target, or the poured liquid is splashed onto other places. However, the above-described features enable the poured liquid in the cavity to smoothly flow toward the bottom end of the partition wall to produce equalized products within target specifications.
Foaming pressure in each of the small cavities divided by the partition wall is equalized by a clearance of approximately 1 to 10 mm defined between the bottom end of the partition wall and the portion of the base of the cavity of the lower mold facing the bottom end of the partition wall, so that variations in weight and dimensions of the product due to foaming pressure deviation can be suppressed.
REFERENCES:
patent: 1889481 (1932-11-01), Kennedy, Jr.
patent: 2804755 (1957-09-01), Ansel
patent: 4372526 (1983-02-01), Daenen et al.
patent: 29 14 042 (1980-10-01), None
patent: 4-371812 (1992-12-01), None
Horimatsu Toshiyuki
Nabeshima Yoichi
Yata Tatsuo
Bridgestone Corporation
Del Sole Joseph S.
Kanesaka & Takeuchi
Nguyen Nam
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