The invention relates to arc welding and it concerns a method according to the preamble of the accompanying claim 1 and an apparatus according to the preamble of the accompanying claim 3 for making a weld seam between a body to be welded fast and a base, preferably to attach an anticorrosion anode to an underwater metal structure.

For making an underwater weld seam, especially to attach a body, like a leg of an anticorrosion anode or corresponding, to an underwater base, like an underwater metal structure preferably a metal beam, by means of arc welding according to the method and apparatus of the invention it is used a, preferably rod-like, welding electrode insulated from the surrounding mass of water by a case-like protection mantle. For creating the arc the base is connected to one pole of the current source and the welding electrode correspondingly to the other pole. The apparatus itself include;

- an outer, case-like protection mantle which is meant to be placed onto the base,

- at least one, rod-like, welding electrode, which is supported to an oblique angle in respect to its longitudinal axis and the base inside the protection mantle to a space insulated from the surrounding mass of water, both

- means for moving and guiding each welding electrode inside the protection mantle both and then for producing a weld seam between the base and the protection mantle.

The main object of the invention is to make possible producing of the weld seam in a space insulated from water automatically without presence of a diver and at the same to make possible mounting of the apparatus to an arm of a diving robot. THis object can be achieved by the method

and the apparatus mentioned in the beginning characterizing features of which are presented in the accompanying claims.

According to the basic idea of the invention first the body meant to be fastened, surface of which meant to be placed against the base comprises a preferably lip-like gasket ring, is placed on to the base and is attached thereto, preferably by riveting, by tightening means or by using some other suitable mechanic fastening means. Then water and/or moisture remained between the body and the base inside the gasket ring is removed by heating the body meant to fastened by welding, especially by heating that part of the body which is against the base. After an intermediate space has been dried the welding process is activated, whereby the welding electrode is moved, for making a continuous weld seam between the body and the base, inside the protection mantle by means of hydraulic power means driven by an axial force, preferably a thrust force, of hydrostatic pressure, higher than pressure inside the protection mantle, of the surrounding mass of water, which force is directed to the hydraulic power means.

It is advantageous with the method according to the invention that for drying the intermediate space defined by the gasket ring is used resistance or arc heating which is directed to that part of the bode which remains between the periphery of the gasket ring and the outer periphery of the protection mantle.

The invention is described in the following by means of its few advantageous embodiments for fastening a leg of an anticorrosion anode with reference to the accompanying drawing, wherein figure 1 presents a longitudinal section of an apparatus

in accordance with a first preferred embodiment of the invention, figure 2 presents a longitudinal section of an apparatus in accordance with a second preferred embodiment of the invention, figure 3 illustrates a side view of the first preferred embodiment supplemented with a gasket ring according to the invention for drying the intermediate space.

The apparatuses, for making in accordance with the invention a weld seam under water automatically, illustrated in the drawings include;

- an outer, case-like protection mantle 2, which is a part of a leg of an anode meant to be fastened, and which is meant to be placed onto a steel beam acting as a base 1, which is connected to a negative pole of an current source,

- a, rod-like, welding electrode 3, which is supported to an oblique angle in respect to its longitudinal axis and a facing surface of the steel beam inside the protection mantle, and which is connected to a positive pole of the current source, both

- means 4 and 5 for moving and guiding the welding electrode 3 and hence for making a weld seam which fastens the anode leg onto the steel beam.

In the preferred embodiment according to the figure 1 means for moving and guiding the welding electrode include a power cylinder 4 which is driven according to the invention by utilizing a hydrostatic pressure of the surrounding water mass, which pressure is higher than pressure inside the protection mantle. A mantle of the hydraulic cylinder 4 include an outer mantle 46 of electrically unconductive material an inner mantle 47, which is made of electrically conductive material and connected the positive pole of the current source. A

piston of the hydraulic cylinder include; a piston member 41, which is made of electrically unconductive material and to one side of which influences the hydrostatic pressure of said surrounding water mass via a channel which can be closed and open by a sluice valve, and another piston member 42, which is made of electrically conductive material, both as extension thereof a piston rod 43, whereto is jointed in an electrically conductive way the welding rod. The first and the second piston members 41 and 42 are arranged with distance apart from each other and the space therebetween is filled with fluid electrically conductive medium, as the medium it is advantageous to use mercury. Hence an electrically conductive bath extending from a current cable connected to the pole of the current source is composed of the electrically conductive medium inside the intermediate space between the first and the second piston members, of the second piston member 42 and of the piston rod 43 jointed thereto.

The manner how the attachment of the welding rod to the piston rod is made is not the most essential to the invention. For the attachment it is possible to use for example a suitable intermediate member, whereto the end of the welding is attached by a threaded joint or the free, uncovered end of the welding rod, i.e. the core element, can compose itself the piston rod 43, which is attached preferably by means of a threaded joint to the second piston member 42. ^*

For accomplishing the guided movement of the welding rod 3, in an oblique orientation in relation to the surface of the base, caused by the hydraulic cylinder, and for assuring that by the welding process the end of the shortening welding rod stays adjacent to the welding target the hydraulic cylinder 4 is arranged to extend in

an oblique angle through the wall 22 of the protection mantle 2 in relation to the bottom surface 21 of the protection mantle 2. The size of the oblique angle is considerably dependent on properties and dimensions of the welding rod in use, it is advantageous to choose the size of the oblique angle between 5°-45°.

The second advantageous embodiment of the invention illustrated in figure 2 differs from the first embodiment described above in respect to the construction of the hydraulic cylinder 3, to the support solution of the welding rod 3, and to conduction bath for the electric current.

The hydraulic cylinder according to this embodiment include one-mantled, outward electrically unconductive cylinder part 46, wherein moves one single piston member 40 forced by the hydraulic pressure of the surrounding water mass. The piston rod 43 is mounted to the other side of the piston member, whereby the piston member 40 moves the piston rod 43 ahead towards the interior of the protection mantle. According to this second embodiment the welding rod 3 is attached by a separate el _.ectrically conductive intermediate member 45 to the piston rod 43, which is electrically unconductive.

For accomplishing the guided movement of the welding rod 3, in an oblique orientation in relation to the surface of the base, caused by the hydraulic cylinder, and for assuring that by the welding process the end of the shortening welding rod stays adjacent to the welding target the hydraulic cylinder 4 is in this second embodiment like in the first embodiment arranged to extend in an oblique angle through the wall 22 of the protection mantle 2 in relation to the bottom surface 21 of the protection mantle 2. Further for assuring the right

orientation of the welding rod 3 during its movement the inner surfaces of the side walls 22 of the protection mantl& 2 are provided with two pairs of longitudinal, for example rail-like, slide guides 5 arranged in an oblique angle in relation to the surfaces of bottom wall 21 and the base 1. At least one pair of the slide guides is electrically conductive and connected to the positive pole of the current source, for example by a current cable.

In the preferred embodiment of the figure 2 the welding rod 3 is so connected by the electrically conductive and between the pairs of the slide guides along a certain movement bath moveable joint member 45 to the piston rod 43 of piston member 40 of the hydraulic cylinder 4, whereby the conduction bath for the welding current from the current cable connected to the current source to the welding rod 3 is composed of the joint member 45 moving along the slide guide acting as a guide and a current rail.

As can be seen from figures 1 and 2 the bottom wall of protection mantle of the apparatus according to the invention includes a channel-like recess 23 open at least to interior of the protection mantle 2. It is preferable that for each welding rod 3 to be moved inside the protection mantle 2 a recess exists therefore. In the preferred embodiments of figures 1 and 2 the bottom or the base of each recess, which accordingly is directed towards the base 1, is closed by a material strip 24, which is thinner than the thickness of the bottom wall, and which is preferably a material remnant strip of the bottom wall left when recess 23 was made. Said material strip maintains inside the protection mantle 2 a pressure which is lower than the hydrostatic pressure of the surrounding water mass, whereby function of the hydraulic cylinder is possible without need of additional pressure sources, and

the material strip fuses open due to the arc created between the end of the welding rod 3 moving in the recess 23 and the base 1.

The figure 3 illustrates as already mentioned above a side view of the first embodiment supplemented with a gasket ring 25 and a drying solution in accordance with the invention. In this solution the anode leg is first attached by rivet joints 26 to an underwater metal beam 1, whereby the anode will more certainly stay still and drying of the intermediate space and making of the continuous weld seam is assured. For the rivet joint, for example for so called pop-rivet joint, it is preferred that both the beam and the anode leg are provided in advance with suitable bores, whereby the rivet joint can be carried out rapidly by means of a rivet tool. Instead of rivet joints can well use also other solutions for example a band to be tightened by a block (not presented in the figures) for the duration of work. In the solution in accordance with the figure the water remained inside the gasket ring 25 is removed and po. interior or intermediate space is dried by heating locally even slightly red-hot the anode leg at a zone between the protection mantle and the gasket ring by an arc created by a welding rod 27. Hence water and/or moisture inside the gasket ring 25, between the body 2 and the base 1 will get vaporized and its pressure will exceed the hydrostatic pressure of the surrounding water mass, whereby the intermediate space defined by the gasket ring 25 between the body 2 and the base 1 dries when water and/or moisture discharges outward as a steam under the gasket ring. In tests carried out it has been discovered that one single boring made to anode leg and filling weld thereof by a welding rod 27 causes the above described vaporizing and out bursting of water.

The invention is described above only by means of its few preferred embodiments. Naturally this is not meant to limit invention and as it is evident to any skilled in the art several variations and alternative constructions are possible within the scope of the accompanying claims. So the bottom recess for the welding rod end can protrude the bottom wall, whereby between the base and the protection mantle is advantageous to use a gasket ring. Further it is necessary to extend inside the protection mantle a pipe which is in a connection to an under pressure source or to a suction pump, whereby the interior of the protection mantle can be emptied at least partially, most preferably as completely as possible from water before starting the welding process and at the same to create therein a pressure which is lower than the hydraulic pressure of the surrounding water mass for moving the piston member- of the hydraulic cylinder.