Plastic and nonmetallic article shaping or treating: processes – With severing – removing material from preform mechanically,... – Removing surface portion of composite workpiece to expose...
Reexamination Certificate
1999-10-15
2002-05-14
Silbaugh, Jan H. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
With severing, removing material from preform mechanically,...
Removing surface portion of composite workpiece to expose...
C264S219000, C264S225000, C264S259000, C264S265000, C264S271100, C264S274000, C264S338000
Reexamination Certificate
active
06387309
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a press die mainly composed of concrete.
BACKGROUND OF THE INVENTION
Conventionally, a metallic die having abrasion-resistance and shock-resistance has been widely used as a press die.
When manufacturing a metallic die, a blank of the die taken out of a casting mold is provided with a finishing process such as grinding and the like. Thereafter, precision finishing is performed to the contact surface of the processed blank of the die, so as to complete the press die with which a product may be press-molded. However, the above-mentioned steps of manufacturing a metallic die involve large amount of labor and time, and therefore, are not economical.
A concrete material having high strength is now being used as a die material in forming a press mold for steel plates, since it is economically advantageous and may be manufactured in a short time.
However, when forming a press mold using a die formed of concrete material, the sliding of the steel plate is obstructed by the high frictional resistance of the concrete material. As a result, the steel plate has to stretch or extend more than when compared to molding by a die made of cast material. When the steel plate can not extend sufficiently, a crack may occur in the product (steel plate), or a scratch occur in the surface of the product, caused by hard, sharp particles included in the concrete.
Moreover, it is impossible from the characteristics of the concrete material to fill the necessary space of the die with concrete material to repair and improve the abrasiveness of the die.
Therefore, a press die is being developed in which a surface layer is applied to a pressing surface of the concrete material, in order to compensate for the insufficient abrasiveness of the concrete die (refer for example to Japanese Laid-Open Patent Publication No. 8-47732).
Now, a general method of manufacturing a press die made of concrete with a surface layer is explained with reference to
FIGS. 8-10
.
A. An enclosure
11
is placed around a casting mold
10
which creates the form.
B. A surface material
20
is applied above the casting mold
10
so that is has even thickness.
C. Anchors
21
are placed on the surface material
20
, after the surface material
20
has hardened to a predetermined level (half-hardened).
Since the boundary surface (upper surface) of the surface material
20
is smooth unless roughened artificially, the bond with concrete is weak. Therefore, the anchors
21
, made of materials having sufficient rigidity and to which the concrete material and the surface layer material cling easily, are placed densely in the surface layer
20
, so as to bond the surface material to the concrete to be placed on the surface material, and to prevent exfoliation of the surface material therefrom.
D. Concrete
25
is inpoured to the surface material
20
equipped with anchors
21
.
E. An atmospheric pressure steam-curing is performed.
F. The enclosure
11
is removed, and a press die
27
made of concrete to which the surface material
20
is bonded through anchors
21
is taken out of the casting mold
10
.
The conventional press die
27
made of concrete has the following drawbacks.
After the surface material
20
and the concrete
25
are bonded, the steam-curing is performed in step E. Since the heat resistance temperature of the surface material is 60° C., the curing process is performed under the resistance temperature (60° C.), and so the compression strength of the die just after the curing process is low, and it takes time for the die to reach the intrinsic strength of concrete.
Moreover, since the curing process is performed after bonding the surface material
20
to the concrete
25
, the difference in contraction between the concrete
25
and the surface material
20
leads to exfoliation of the surface material
20
from the concrete
25
.
Even further, when performing a reversing process utilizing a master model, the concrete has to be hardened/cured after reversing the form of the concrete, so the size accuracy of the molding surface due to contraction of the concrete is poor.
SUMMARY OF THE INVENTION
The present invention aims at providing a press die made of concrete with improved size accuracy and improved adhesion characteristics of the surface material to the concrete, and a method of manufacturing the same by primarily hardening the base concrete member through steam-curing, and utilizing the aggregate included in the concrete as an anchor when bonding the surface material layer.
The press die made of concrete with a surface layer formed to a pressing surface of a concrete body according to the present invention includes the surface layer formed of synthetic resin bonded to the concrete body utilizing aggregate included in the concrete as the anchor.
Further, the method of manufacturing a press die made of concrete according to the present invention comprises a retardation means mounting step of placing a retardation means on a casting mold for the press die, a concrete filling step of filling an unhardened concrete above said retardation means, a primary hardening step of naturally hardening said concrete, a washing step of washing the portion of the hardened concrete member contacting said retardation means so as to expose aggregate, a secondary hardening step of steam-curing said hardened concrete member, and a surface layer forming step of forming a surface layer on the aggregate exposed surface of the hardened concrete member.
Moreover, the retardation means mounting step includes a step of mounting a means for retarding the hardening of concrete to the pressing surface.
Even further, the surface layer forming step includes steps such as pressing and adhering a surface material on the surface of said hardened concrete, forming said surface layer by inpouring a surface material to the space between the concrete surface and the casting mold for the press die, forming said surface layer by applying a surface material to the concrete surface, and the like.
According to any of the above processes, the surface material constituting the surface layer is bonded to the concrete member utilizing the aggregate comprised in said concrete member as the anchor.
REFERENCES:
patent: 1691721 (1928-11-01), Johnson
patent: 2724868 (1955-11-01), Kish
patent: 2836530 (1958-05-01), Rees
patent: 3763542 (1973-10-01), Gutnajer
patent: 4205040 (1980-05-01), Aoyama et al.
patent: 5057256 (1991-10-01), Gorin
patent: 0341797 (1989-11-01), None
patent: 2654034 (1991-05-01), None
patent: 63091208 (1988-04-01), None
patent: 1-242205 (1989-09-01), None
patent: 8-47732 (1996-02-01), None
patent: 08047732 (1996-02-01), None
patent: 10-193326 (1998-07-01), None
patent: 11-28710 (1999-02-01), None
patent: 698961 (1979-11-01), None
Kojima Akihiko
Morita Hiroshi
Saito Kiyoshi
Antonelli Terry Stout & Kraus LLP
Isuzu Motors Limited
Poe Michael I.
Silbaugh Jan H.
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