Press die made of concrete and method of manufacturing the same

Abstract: A concrete member (60A) is hardened through steam-curing. Thereafter, a surface material layer (70) is formed to a pressing surface of the concrete member (60A) utilizing the aggregate (65) comprised in the concrete member (60A) as the anchor. Thereby, a press die made of concrete having a surface layer bonded to the concrete member (60A) is manufactured.

Description: FIELD OF THE INVENTION The present invention relates to a press die mainly composed of concrete, and a method of manufacturing a press die, as indicated in the pre-characterising portion of claims 1 and 2. Such a die and method is known from JP-A-08047732. DESCRIPTION OF THE PRIOR ART Conventionally, a metallic die having abrasion-resistance and shock-resistance was popularly used as a press die . When manufacturing a metallic die, a blank of 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 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 involved large amount of labor and time, and therefore, was not economical. A concrete material having high strength is now being noticed 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 carrying out the press mold using the die formed of concrete material, the sliding of the steel plate was obstructed by the high frictional resistance of the concrete material. As a result, the steel plate had to stretch or extend more than when compared to molding by a die made of cast material. When the steel plate could not extend sufficiently, a crack occurred to the product (steel plate), or a scratch occurred to the surface of the product caused by hard, sharp particles included in the concrete. Moreover, it was 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 it 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 may be clung easily, are placed densely to 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 took 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 occurred, which lead to exfoliation of the surface material 20 from the concrete 25. Even further, when performing a reversing process utilizing a master model, the concrete had to be hardened/cured after reversing the form of the concrete, so the size accuracy of the molding surface was deteriorated due to contraction of the concrete. SUMMARY OF THE INVENTION Therefore, 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 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 the 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 bonding the surface layer formed of synthetic resin 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. BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is an explanatory view of the retardation means mounting step; FIG. 2 is an explanatory view of the concrete filling step; FIG. 3 is an explanatory view of the concrete in the state where the aggregate is exposed; FIG. 4 is an explanatory view of the surface layer forming step; FIG. 5 is an explanatory view of another embodiment of the surface layer forming step; FIG. 6 is an explanatory view of yet another embodiment of the surface layer forming step; FIG. 7 is an explanatory view showing the surface layer repairing method; FIG. 8 is an explanatory view showing the method of manufacturing the press die made of concrete according to the prior art; FIG. 9 is an explanatory view showing the method of manufacturing the press die made of concrete according to the prior art; and FIG. 10 is an explanatory view showing the method of manufacturing the press die made of concrete according to the prior art. PREFERRED EMBODIMENT OF THE INVENTION The embodiment of the press die made of concrete and method of manufacturing the same will now be explained with reference to the drawings. The method of manufacturing the press die made of concrete will be explained step by step. (1) Spacer mounting step (refer to FIG. 1) A spacer 61 made of expanded polystyrene and the like having a thickness corresponding to the thickness of a surface material is placed and adhered to a concave surface 53 of a casting mold 50 having a concaved shape. (2) Retardation means mounting step (refer to FIG. 1) A sheet 63 impregnated with a retarder is mounted on the upper surface of the spacer 61.The retarder has a function to delay the hardening of concrete.Either an organic retarder such as oxycarboxylate or ketocarboxylate, or an inorganic retarder such as silicofluoride, is used as the retarder.Further, instead of mounting the sheet 63, the retarder may be applied to the surface of the spacer 61. (3) An enclosure 51 is placed around the casting mold 50. (4) Concrete filling step (refer to FIG. 2) An unhardened concrete 60 is filled inside the enclosure 51.The concrete 60 is a mixture of cement paste and aggregate. Normally, crushed stone and the like are used as the aggregate, and the mixture rate of the aggregate is 65 - 80 % to the concrete volume. Various sizes of crushed stone are combined, and the aggregate utilizing crushed stone and the like normally has a strength exceeding that of the cement paste, and therefore, determines the strength of the concrete. (5) Primary hardening step The concrete is naturally hardened.When the concrete is hardened, the hardened concrete member 60A is taken out of the mold form.At this stage, the portion of the concrete contacting the retarder impregnated sheet or the retarder applied to the spacer surface is not yet hardened. (6) Press die washing step (refer to FIG. 3) The retarder contacting surface of the concrete member 60A is washed, and aggregate (crushed stone) 65 comprised in the concrete member 60A is exposed.The concrete which had been contacting the retarder and therefore has not yet hardened at this stage is removed through washing.The unhardened cement has been removed through washing, and thereby, a hardened concrete member 60A exposing the aggregate 65 which is the component of the cement is formed. (7) Secondary hardening step The concrete member 60A having the aggregate 65 exposed is steam-cured.The steam-curing is performed under a temperature of 80 °C for 12 hours. (8) The spacer 61 mounted to the concave surface 53 of the casting mold 50 is removed. (9) Surface layer forming step (refer to FIG. 4) A surface material layer 70 is formed to the surface of the concrete member 60A where the aggregate 65 is exposed. The surface material is made of synthetic resin, and the surface layer 70 is fixed to the hardened concrete member 60A with the exposed aggregate 65 functioning as the anchor. The method of forming the surface layer 70 will now be explained. Press-fix method (refer to FIG. 5) The surface material 70A for forming the surface layer is mounted to the die surface of the casting mold model 50 of the cast. The aggregate exposed surface is pressed and adhered to the surface material 70A. The surface material 70A fills the gap between the concrete member 60A and the casting mold 50, thereby forming a surface layer formed in the shape of the spacer with the aggregate 65 functioning as the anchor. Inpouring method (refer to FIG. 6) The hardened concrete member 60A is placed inside the casting mold model 50 of the cast, and the surface material 70B is inpoured to the gap formed between the concrete member 60A and the casting mold 50. The surface material 70B forms a surface material layer utilizing the aggregate 65 as the anchor. As explained above, a press die made of concrete is created. Further, according to the above embodiment, the aggregate functioning as the anchor is exposed to the surface of the concrete member using a retarder. However, in a simplified method, the contact surface of the surface layer may be made to have a rough surface by use of a grinder, or bolts and the like may be embedded to the concrete member as the anchor, and the base concrete may be hardened in advance, but according to the simplified methods, the bonding strength is reduced. Next, the characteristics of the press die 100 made of concrete is explained. (a) There is no special technique concerned in mounting the retarder, since a sheet evenly impregnating the retarder is simply placed on the spacer mounted to the press forming concave surface 53 of the casting mold model 50. Further, even in an example where the retarder must be applied to the surface of the spacer, the retarder may be applied uniformly to the surface easily. (b) The anchor may be placed easily and economically. The aggregate 65 functioning as the anchor may be placed uniformly to the whole surface to which the surface layer 70 is to be fixed. Therefore, the bonding of the surface layer 70 to the concrete member 60A becomes firm.Moreover, since the aggregate 65 which is the component of the concrete member 60A is utilized as the anchor, the manufacturing cost may be cut down.Even further, the step of placing the anchor during hardening of the concrete, which was necessary in the conventional method, is unnecessary according to the present method. Therefore, the present invention is free from limitations concerning time such as the adjustment of the degree of hardening, and also free from individual differences of the worker involved in placing the anchor. (c) Since the surface layer 70 is formed on the secondary hardened concrete member 60A, sufficient strength may be obtained even at the initial time of manufacturing the die. The secondary hardening of the concrete member 60A is performed under a sufficient temperature (80 °C), so a concrete having high compression strength and a sufficient intensity may be gained in a short period of time.Moreover, since the contraction of the concrete member 60A has already ended through the secondary hardening process before applying the surface layer 70, the shape of the surface layer may be reversed with high accuracy. Moreover, since the surface layer 70 is formed after the contraction of the concrete member 60A through the secondary hardening has ended, the contraction difference between the concrete member 60A and the surface layer 70 is very small, and therefore, the surface layer 70 will not exfoliate from the concrete member 60A. (d) The present press die may be repaired easily. As shown in FIG. 7, when there is a need to repair a portion 71 of the surface layer 70C, the surface layer may be repaired easily by filling the area 71 with a repairing surface material 75. Since the aggregate 65 is exposed evenly, the aggregate 65 functioning as the anchor will exist in even small areas to be repaired, and therefore, a firm bond may be achieved between the repaired surface layer and the concrete member. The press die made of concrete according to the present invention utilizes aggregate which is the component of concrete as the anchor in bonding the surface material to the concrete, so a press die having -a uniform strength may be provided economically. Further, a solid press die may easily be manufactured by the method of manufacturing a press die made of concrete according to the present invention. Moreover, since a secondary hardening step is carried out before forming a surface layer, no difference in shape of the concrete member and the surface layer due to the difference in contraction will occur. Therefore, a press die with a highly accurate size and having a firm bond between the concrete member and the surface layer may be provided. Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included just for the sole purpose of increasing intelligibility of the claims and accordingly, such reference signs do not have any limiting effect on the scope of each element identified by way of example by such reference signs.

Claims: A press die made of concrete comprising a concrete body (60A), and a surface layer (70) bonded to a pressing surface of said concrete body; wherein said surface layer is made of synthetic resin, characterised in that the surface layer (70) is bonded to said concrete body utilizing aggregate (65) comprised in said concrete body as the anchor. A method of manufacturing a press die made of concrete comprising a concrete body (60A), and a surface layer (70) bonded to a pressing surface of said concrete body; characterised in said method comprising: a retardation means mounting step of placing a retardation means on a casting mold (50) for the press die; a concrete filling step of filling an unhardened concrete (60) above said retardation means; a primary hardening step of naturally hardening said concrete; a washing step of washing a portion of the hardened concrete member contacting said retardation means, and thereby exposing aggregate (65); a secondary hardening step of steam-curing said hardened concrete member; and a surface layer forming step of forming a surface layer to the aggregate exposed surface of said hardened concrete member. A method of manufacturing a press die according to claim 2, wherein said retardation means mounting step includes a step of mounting a means (63) for retarding the hardening of concrete to the pressing surface. A method of manufacturing a press die according to claim 2, wherein said surface layer forming step includes pressing and adhering a surface material constituting said surface layer on the surface of said hardened concrete where said aggregate is exposed. A method of manufacturing a press die according to claim 2, wherein said surface layer forming step includes forming said surface layer by inpouring a surface material constituting said surface layer to the space between the surface of said concrete where said aggregate is exposed and said casting mold for the press die. A method of manufacturing a press die according to claim 2, wherein said surface layer forming step includes forming said surface layer by applying a surface material constituting said surface layer to the surface of said concrete where said aggregate is exposed. A method of manufacturing a press die according to claim 2, wherein said surface material constituting said surface layer is bonded to said concrete member utilizing said aggregate comprised in said concrete member as the anchor. A method of manufacturing a press die according to claim 2, wherein said surface layer forming step includes pressing and adhering a surface material constituting said surface layer on the surface of said hardened concrete where said aggregate is exposed, and said surface material is bonded to said concrete member utilizing said aggregate comprised in said concrete member as the anchor. A method of manufacturing a press die according to claim 2, wherein said surface layer forming step includes forming said surface layer by inpouring a surface material constituting said surface layer to the space between the surface of said concrete where said aggregate is exposed and said casting mold for the press die, and said surface material is bonded to said concrete member utilizing said aggregate comprised in said concrete member as the anchor. A method of manufacturing a press die according to claim 2, wherein said surface layer forming step includes forming said surface layer by applying a surface material constituting said surface layer to the surface of said concrete where said aggregate is exposed, and said surface material is bonded to said concrete member utilizing said aggregate comprised in said concrete member as the anchor.

Inventors: KOJIMA AKIHIKO, MORITA HIROSHI, SAITO KIYOSHI, KOJIMA, AKIHIKO, MORITA, HIROSHI, SAITO, KIYOSHI
Applicants: ISUZU MOTORS LTD, ISUZU MOTORS LIMITED
Application year: 1999
Main classification: B21D37
IPC codes: B21D37, B32B13, B23P15, B28B11