Invention relates to the underwater welding rod according to the preamble of the claim 1.

Traditionally welding rod for underwater wet welding is either coated impervious to water or its covering is saturated sc that water can not be absorbed into the covering in water.

By means of this kind of welding rods it is possible to prevent damping of the welding rod useless but by means of them can not eliminate the possibly most remarkable problem of the underwater weldings: fast cooling of the weld, as the result of which it will form slag closings, boarder cracks and weld become fragile. As a result of this the Classification Institute, det Norske Veritas, has forbidden the use of wet welding methods on off¬ shore plants, ships etc.

In the previously known Finnish patent application no. 852877 is known welding additive for wet welding, in said additive exists as mixed into carrier material plenty of organic materials By feeding this kind of additive during the welding process to the welding object it will form a slack layer with high thermal capasity onto the weld, said slack layer will remarkably slow down the cooling rate of the weld and hense essentially reduce the forming of the slack closings, boarder cracks etc. which may weaken the quality of the weld. Feeding of the additive is how¬ ever process of it's own and hense very difficult to facilitate in practise.

The main object of the present invention is to eliminate the problems related to the previously known wet welding methods and to accomplish a welding rod of a new type for underwater welding.

These goals have achieved with the welding rod according to the invention, the characterizing features are presented in the accompanying claims. The invention is based on a genious insight that the welding rod is provided with an additive chamber and an additive flow channel which connects the additive chamber with the end of the welding rod, and on that fact that the wall of the additive chamber is made at least partially elastic, whereby with the growing depth of water mass the hydralic pressure will grow around the additive chamber which will cause the additive flow via the channel to the end of the welding rod.

About advantages of the invention can be mentioned; that the remaining part of the welding rod is continiously isolated from water whereby the dampness do not effect to the function of the welding rod; that the flowing additive will form onto the weld, a slack material layer with high thermal capasity, said slack layer prevents too fast cooling of the weld; and that the structure of the welding rod is very simple and reliable, because there are needed no kind of means or equipments to feed the additive.

The invention is described in the following in an example way by means of one advantageous embodyment with reference to the accompanying drawing which presents a partial longitudinal sectio of the welding rod according to the invention for the underwater welding.

As presented in the drawing the welding rod includes: central advantageously metal core element 1, one end of which that is the end away from the welding object, is ment to be connected to one pole of a current source, a covering 2 surrounding a core element, the material of said covering can be chosen from the traditional materials well suitable for the wet welding,

an outer coating material layer 3 which can be for example a thin rubber- and/or plastic based material layer which is formed, for example by spraying or dipping, at least over the covering 2, and means 4, for feeding the additive via the central channel 12 of the core element 1 to the end of the welding rod and further to the arc area.

As mentioned above the additive consist plenty of organic, botanic- and/or animal based conpounds mixed with liquid carrier material and forms mass which is fluid in such a rate that a continious flow of the additive to the welding object is pos¬ sible. To improve the influence of the additive it can be further mixed with resin.

In the advantageous embodyment of the welding rod presented in the drawing the means for feeding additive 7 include layered elastic hollow equipment 4, 5 which limits between the core element 1 of the welding rod and the inner elastic layer part 4 of the elastic hollow equipment in the direction of the welding rod a longitudinal ring space 14 closed at it's both ends which operates as a tank of the additive 7, said tank is referred in the following by definition additive chamber, and said chamber will collapse when the outer pressure increases.

According to the advantageous embodyment of the invention both layer parts 4 and 5 of the two-layered elastic hollow equipment are made of elastic material referably of rubber- and/or plastic film which are vulcanized both to each other and to the central core element so that between the inner layer part 4 and the outer layer part 5 is formed a second longitudinal ring space 5 closed at it's both ends, said ring space according to this advantageous invention is filled with gas most advantageously to a pressure higher than an atmospheric pressure, whereby due to the gas pressure in the second ring space and due to the hydraulic pressure of the surrounding water to the additive is

directed continiously higher pressure than the hydraulic pressure of the surrounding water which will cause the additive discharge to the welding object.

In order to facilitate the additive flow from the additive chamber 14 to the central flow channel 12 existing in the core element the part of the core element facing to the additive chamber is provided with several radial borings 11 which con¬ nect the central flow channel 12 with the additive chamber 14 and make the continious additive flow possible.

As further presented in the drawing in the welding rod according to the advantageous embodyment the central flow channel of the core element is totally filled with additive 7 and the out flow opening of the additive is closed. This closing of the out flow opening can facilitate for example by extending the coating material layer of the welding rod also arround the end of the welding rod alternatively it is possible to use also other materials preferably resin layer 6 covering the end of the welding rod as presented in the drawing.

The invention is described only by means of it's one advantageous embodyment so many variations and combinations are possible within the limits of the accompanying claims. The central flow channel can be ring channel, which surrounds the core element, the covering or both. Further the central flow channel can be replaced by several flow channels arranged symmetrically into the core element specially when the diameter of the core element is large.