Electric heating – Metal heating – By arc
Reexamination Certificate
2000-08-30
2003-04-29
Dunn, Tom (Department: 1725)
Electric heating
Metal heating
By arc
C219S121840
Reexamination Certificate
active
06555779
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a novel underwater processing apparatus and an underwater processing method, as well as to an automatic underwater processing apparatus, and in particular to a device for and a method of carrying out cutting, grinding, welding and surface-treatment in order to install, repair and process equipments belonging to nuclear facilities, marine vessels, bridges or the like.
2. Related Art
Conventionally, in the case of underwater processing metal or nonmetal, for example, in the case of underwater welding, in a method of carrying out a covered arc welding in an atmosphere in which no water is displaced therefrom, that is, the so-called wet process, a defect such as blow-holes are likely to be formed in a joint part or the like, and accordingly, a problem in view of reliability has been raised. Further, in a dry type process in which a part to be welded is surrounded by a water drainage chamber in its entirety, water in the chamber is displaced with air or shield gas, and then welding which has been carried out on the ground is directly carried out within the chamber, the drainage chamber should have a shape corresponding to that of the part to be welded. Thus, the facility becomes expensive. Accordingly, a local dry process wherein a cave from which water is displaced locally around a part to be processed, is defined, and welding, surface-treatment or the like is carried out within the cave, (which process will be hereinbelow referred as “a local shield method”), has been most prosperously used as an underwater processing method.
It is important for processing in the local shield process to stably displace water from the local shield, and accordingly, various methods have been proposed in order to stably displace water from the local shield. For example, Japanese Patent Laid-Open No. S49-799939 discloses such a method in which triple shield gas nozzles are used, a first jet nozzle jetting shield gas, a second jet nozzle jetting gas in the form of a high velocity jet stream, and a third jet nozzle jetting water in the form of a high velocity jet stream in order to create a stable gas phase zone in the shield.
Further, Japanese Laid-Open Utility Model No. S55-116785 discloses a welding torch having a skirt shape partition member made of carbon fibers or the like, and provided in a skirt portion of a local shield.
Further, Japanese Patent Laid-Open No. S56-141956 proposes a method in which a slidable solid wall is provided in the front end part of a jet stream welding nozzle, being separated from and opposed to a torch so that its front end is made into contact with a mother material by means of a processing mechanism (a spring) while another front end part of the nozzle front end part is opened.
Further, Japanese Laid-Open Patent No. S56-6782 discloses a method in which metal or nonmetal thin wires are bundled so as to be formed into an annular brush-like flexible wall. Heat-resistant stainless steel wires are preferably used as the metal thin wires, and carbon fibers are preferably used as the nonmetal thin wires.
However, in such a technical field that high quality is earnestly desirable for a processed part in a device belonging to, for example, a nuclear installation, affection by a bit of remaining moisture in a local shield would be caused. In a general utility field in which a marine vessel, a bridge or the like is repaired, it is desirable to obtain a highly reliable processed part. Finally, it is most desirable that the above-mentioned welding part is surrounded by the displacement chamber in its entirety, so as to obtain a processing part which is near, as possible as it can, to a processing part obtained by using a dry type process in which water in the displacement chamber is displaced with air or shield gas. However, it can be hardly achieved in the above-mentioned conventional technology. Japanese Laid-Open Patent No. S49-79939 discloses the provision of a third nozzle for jetting water at a high velocity so as to form a water curtain in order to prevent water from entering the local shield. However such a water curtain may not completely prevent water from entering into the local shield if a workpiece is complicated in its shape.
Further, in the method disclosed in the Japanese Laid-Open Utility Mode No. S55-116785, the pressing force of a welder relies upon a force adjusted by a worker himself, and accordingly, high skill is required for preventing water from entering. Further, repairing in a nuclear reactor can not be carried out by this method due to the presence of radio-active rays.
Further, in the Japanese Laid-Open Patent No. S56-141965, the slidable solid wall is not the one which completely shields the outer periphery of the torch in order to make contact with the mother material, and further, if the workpiece has a complicated shape, it would be impossible to completely prevent water from entering.
Further, in the Japanese Laid-Open Patent No. S56-6782, the flexible wall which is formed by bundling thin wires in a brush-like shape may not be completely prevent water from entering if a workpiece has a complicated shape.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an underwater processing apparatus and an underwater processing method, which can effectively prevent water from entering a shield even though a workpiece has recesses and protrusions, and which can reduce variation of gas flow for a part to be processed, and also to provide an automatic underwater processing apparatus, and the application thereof to a nuclear reactor.
To the end according to the present invention, there is provided an underwater processing apparatus including a shield means for locally shielding a part to be processed of a workpiece with gas in an underwater environment in order to prevent water from entering the shield, for underwater processing the workpiece underwater, wherein the shield means is composed of a solid wall formed of a member having a slidable part making contact with the workpiece, and adapted to be made into contact with the workpiece and to be vertically movable by a pressing force, and a water jetting means for creating a water stream curtain around the outer periphery of the solid wall.
If the above-mentioned processing is accompanied with heating within the shield, it is preferable to introduce nonoxidative gas.
In combination of the water steam curtain, the gas shield around the solid wall according to the present invention, can prevent water from entering into a part to be processed, and the supply volume of gas for the gas shield can be reduced while variation in the supply volume of the gas can be decreased, thereby it is possible to stably carry out processing such as welding.
In particular, a stable gas shield is indispensable for welding with low input heat.
Further, according to the present invention, there is provided an underwater processing apparatus including a shield means for locally covering a part to be welded of a workpiece in order to prevent water from entering thereinto, in which nonoxidative gas is introduced into the shield means while a welding bevel of the workpiece is moved along a welding edge during welding, wherein an opening part is formed around the outer periphery of a torch for carrying out buildup welding in the welding bevel of the workpiece, facing the workpiece, a solid wall similar to the above-mentioned solid wall, formed of a slidable member is provided in a skirt part which makes contact with the workpiece so as to cover the entire welding width in a direction orthogonal to the direction of a welding line, and water jet nozzles for creating a water stream curtain around the outer periphery of the solid wall is provided. As a heat source, arc or laser may be used. The arc is more preferable for welding with low heat, using a high frequency pulse current.
Further, the above-mentioned water jet nozzles are provided along the welding bevel of the workpiece so as to be opened in front and rear of the welding beve
Kato Takahiko
Koshiishi Masato
Miyazaki Kunio
Obana Takeshi
Okamura Hisanori
Hitachi , Ltd.
Mattingly Stanger & Malur, P.C.
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