Electric heating – Capacitive dielectric heating – Bonding
Reexamination Certificate
2000-06-30
2002-03-19
Leung, Philip H. (Department: 3742)
Electric heating
Capacitive dielectric heating
Bonding
C219S773000, C219S777000, C156S274400, C156S275500, C156S380200, C156S380600
Reexamination Certificate
active
06359273
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for preheating a laminate structure in which a plurality of polymer plates and conductive metal plates are laminated alternately, and a method and apparatus for manufacturing a laminated body.
PRIOR ART
Such laminated bodies include, for instance, a laminated rubber body and are variously used for antiseismic or quake-absorbing apparatus and the like.
The laminated rubber body is manufactured by alternately laminating steel plates and raw rubber plates within a mold, and, during heating the mold, pressure is applied by a press machine.
However, since a raw rubber plate as a constituent of the laminated rubber body has a small thermal conductivity, there is a big difference in rising speed of temperature between a portion of the plate close to a heat source and another portion remote therefrom. This causes an uneven cure of raw rubber plates and thereby results in uniformless adherence between raw rubber plates and steel plates and unevenness in substantial characteristics of the resultant laminated rubber body. While it is possible to secure a certain degree of substantial characteristics by gently raising the temperature of the sold, the molding time would be greatly prolonged. In this respect, in order to reduce the time for pressure molding and stabilize substantial characteristics, there have been recently employed the following methods (1) (2) wherein raw rubber plates and steel plates are heated in advance up to a temperature not to cause any trouble in their substantial characteristics and workability before cure-adhesion thereof. However, each still has drawbacks.
(1) Method 1
In this method, layers made of a raw rubber plate and a steel plate to be laminated are respectively preheated.
Referring to
FIG. 4
, in this method, each layer made of a raw rubber plate
1
and a steel plate
2
′ is placed on each of a plurality of shelves t within a drying oven K′, and heated up respectively by hot blast (shown by rightward arrows).
In this method, after preheating, the layers of the raw rubber and steel plates
1
,
2
′ need to be laid and combined together in the mold for subsequent pressure molding. However, since a rise in temperature makes the raw rubber plates
1
soft and this makes laying work difficult, the practical preheating temperature will be limited. As a result, an initial curing temperature cannot be high, and reducing the curing time will not be effectively achieved.
(2) Method 2
In this method, a plurality of raw rubber plates and steel plates are alternately disposed and then preheated as one combined body.
Referring to
FIG. 5
, in this method, using a center core A
1
′ and an outer frame A
2
′ arranged within a drying oven K′, a plurality of raw rubber plates
1
and steel plates
2
′ are disposed alternately and then heated as one body by hot blast (shown by rightward arrows).
In this method, since superposing layers after preheating can be eliminated, the preheating temperature can be raised relatively high. However, this method employs a heating system from outside by hot blast, rise in temperature of an inner layer is delayed compared with that of an outer layer. This is apparent from
FIG. 2
, after 120 minutes from the start of heating, the outside rubber reaches a preheating limit temperature of 80° C., but the temperature of the inside rubber only rises up to approximately 60° C. Therefore, in order to obtain a substantially uniform temperature distribution of the laminate structure, heating must be performed gently, not rapidly, and this prolongs the preheating time. As a result, the time for pressure molding will not be effectively reduced.
The data of
FIG. 2
were obtained under the following conditions.
Raw Rubber Plate
1
diameter: 520 ma, thickness: 6 mm, hole diameter: 90 mm Steel plate
2
′
diameter: 500 mm, thickness: 3 mm, hole diameter: 90 mm Flange
diameter 500 mm, thickness: 25 mm, hole diameter: 90 mm Temperature of hot blast
80° C.
Instead of raw rubber plates, polymer plates may be used in laminated bodies utilized for various purposes other than for antiseismic or quake-absorbing apparatus. Such polymer plates may also be required in some instances to be heated up to a desired temperature with a uniform temperature distribution and in a short time.
Next, the combined rubber body is further processed by (1) heating it up to a rubber fluidizing temperature (80-95° C.) and pressing it to form an integrated laminated rubber body, and (2) securing its desired product dimensions by suppressing thermal vertical expansion of the laminated rubber body and, under a constant pressed condition, curing the rubber and cure-adhering the steel and rubber plates (a cure-adhesion temperature 110-125° C.). However, since the raw rubber plates as constituent of the laminated rubber body have a small thermal conductivity, there is a large difference in temperature rising speed between a portion of the rubber close to a heat source and another portion remote therefrom. This causes uneven curing and thereby results in unevenness in substantial characteristics of the laminated rubber body (vertical elastic modulus, shear modulus, adhesion between raw rubber plates and steel plates, etc.).
Various methods have been tried to overcome these problems but temperature difference between inside and outside portions could not be eliminated. As a result, in order to avoid bad influence to products, the molding time must be prolonged. Further, measures for improvement requires a number of processes and an innovative method has not been found yet.
In case of adhesion of other type of laminated structures such as with synthetic resin plates or ceramics plates and conductive metal plates, there may be also a problem due to the temperature difference between inside and outside portions.
SUMMARY OF THE INVENTION
In is an object of the present invention to provide a method for preheating a laminate structure in which polymer plates incorporated in the structure are heated up to a desired temperature with a substantially uniform temperature distribution and in a short time. It is another object of the present invention to provide a method and apparatus for manufacturing a laminated body with which a laminate structure is heated up to a specific temperature range with few temperature difference between an inner and an outer portion thereof and in a short time.
In order to achieve the above objects, the present invention includes the following means.
According to a first embodiment of the present invention, there is provided a method for preheating a laminate structure which includes applying through electrodes a high-frequency voltage in a lamination direction of the laminate structure having alternate lamination with a plurality of polymer plates and conductive metal plates, so as to dielectrically heat said polymer plates.
According to a preferred embodiment of the present invention, in the above method for preheating a laminate structure, the plurality of conductive metal plates are parallel with each other.
According a preferred embodiment of the present invention, in the above method for preheating a laminate structure, intervals between any adjacent conductive metal plates are substantially the same.
According a preferred embodiment of the present invention, in the above method for preheating a laminate structure, the high-frequency voltage is applied between the electrodes disposed on opposite ends of the laminate structure in the lamination direction.
According a preferred embodiment of the present invention, in the above method for preheating a laminate structure, the outermost opposite conductive metal plates of the laminate structure function as the electrodes.
According a preferred embodiment of the present invention, in the above method for preheating a laminate structure, flanges made of conductive metal plate are provided on outer faces of the outermost opposite plates of the laminate structure and function as the electrodes.
According a prefe
Inui Michiaki
Nagata Tsuneo
Ogawa Kiyoshi
Shimizu Mikiya
Sugizaki Yuichi
Leung Philip H.
Morrison Law Firm
Nitta Corporation
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