The subject of this invention is an apparatus for under- T water working, especially for heating, welding, torch " 5 cutting, cleaning and electrolytical coating of metal constructions with the aid of electric current. The apparatus consists of an electrically conductive rota¬ table shaft which is arranged on the frame element and conducts electric current to a removable tip element, which is 10 attached to the end of the shaft and is rotating with the shaft, this tip can be heating bush, welding electrode, cutting, cleaning and/or coating disk.

It has been previously known to use in this type of 15 apparatuses different electric terminals and carbon arrangements to conduct necessary electric current to shaft. The problem and great, disadvantage of these solutions is, however, that apparatuses cannot be used in great depths due to insufficient compensation of hydraulicwater pressure. 20

Attempts have been made to solve this problem through massive frame constructions and complicated sealing systems that would stand the high external pressure. Such apparatues are, however, expensive and rather difficult 25 to handle because they are heavy arid big in size. As a ¹ result of non-existing or defective pressure compensation water breaks into the tool preventing its use or the casing of the frame part literally breaks down.

30 An additional disadvantage of existing tools is that they need, without exception, an earth wire connected with

. _≠ the "-" pole of the power source in order to create flame arc. This aspect will essentially limit the applications _•» of the apparatus and makes it nearly impossible to use

35 it as a tool in driving robots or remote controlled equipment. As the work usually requires driver's help it is obvious that to use such equipment is slow and expensive involving safety hazards.

The purpose of the present invention is to eliminate the disadvantages and weak .points found in existing apparatuses, and to produce an apparatus for underwater working which will be lighter, more reliable and eas.ier to use.

This purpose has been achieved with an apparatus in accordance with the invention the characteristics of which have been presented in the enclosed patent - claims

As to the advantages of the invention it should be mentioned that , according to the invention, the solution of electrical conductance serves both conduction of electricity and compensation of hydraulic water pressure. Another advantage is that also earth current may be conducted through-the rotable shaft , which means that flame arc can be created exactly where it is needed without any clumsy separately connected earth wires . Thus the apparatus according to the invention is simple to use also in diving robots and other remote controlled equipment.' It is also characteristic of the present apparatus that the pressure is essentially the same inside and outside the frame element, the hydraulic water pressure may thus be rather high without presenting any significant problem, and it is possible to use relatively simple and cheap solutions for design of the frame element.

In the following the invention is de>scribed by an advan- tageous example of application, reference is made to the enclosed drawing showing the side cross section of the apparatus according to the invention. This apparatus was made to serve as a cutting tool.

In the Figure, index number 1 refers; generally to the frame element consisting of several units joined together, like a pack, by means of a bolt as εhown in Figure, a rotating, two-piece electrically conductive shaft 2 has been mounted in bearings on this she.ft. As is shown in

Figure, in this example the shaft 2 of the apparatus based on the invention is formed of two shaft elements arranged within each other and one rotating shaft element 21 and 22.

->t* ⁵

^• * Shaft elements 21 and 22 have been electrically insulated 5 from each other by arranging an electrically insulating intermediate element 23 between their opposite faces. The intermediate element 23 used in the shown example is an appropriate sleeve made of rubber or plastic-based material. Also the profiles of the opposite faces of the shaft

10 elements 21 and 22 have been designed so as to prevent rotation of the shaft elements in relation to each other. Suitable profiles are any forms except round ones , for instance, the outer shaft element 21 is tubular shaft-with central polygonal cave while the outer circumference

15 of the inner shaft element 22 is formed to correspond the form of the outer tubular shaft 21. Alternative solution to prevent the shaft elements 21 and 22 from rotating in relation to each other is to lock them together with a wedge element, for instance.

20

For conduction of electricity to shaft 2 , there are two chambers 13 and 14- in the frame element 1 containing liquid,electrically conductive medium, advantageously mercury. One of the chambers , in this example chamber 13 , is designed to

25 surround the outer circumference of the outer shaft element 21 while the other chamber, in this example chamber 14*, is designed to surround the outer circumference of the inner shaft element 22.protruding from inside of the outer shaft element 21. Both chambers '13 and 14 are closed

30 in this example with a cover made of electrically conductive _e material such as metal, and connected with electric wire with one of the poles of the power source, whereby electric _* current passes from the wire through the cover element to medium and from there further tp the shaft. In the shown

35 example the outer shaft element 21 is connected, through the medium contained in the surrounding chamber 13 , to the "+" pole of the power source (not shown), and the inner

shaft element 22 , through the medium contained in the surrounding chamber 14, to the "-" pole of the power source. In addition, the chambers 13 and 14 are sealed against the surfaces of outer circumferences of the shaft elements 21 and 22 by means of suitable gaskets which will stand the mechanical wear caused by rotating shaft 2, these prevent leakage of medium; There is a same type of gasket between frame element and shaft 2 to prevent access of water into the frame element 1.

In order to prevent electric conductance from chamber 13 and 1 to frame element 1 and the eventual damages , the chambers are lined with an electrically insulating layer or, as is the case in the example, the frame element walls surrounding the chambers 13 and 14, most advantageously the entire part of the frame element 1, where the chamber is situated, is made of non-conductive material, advanta- ^■ geously of rubber or plastic-based material.

In order to compensate the hydrostatic water pressure, which is an important aspect in underwater working, both chambers 13 and 14 are provided with pressure balancing devices 11 and 12. In the shown example the pressure balancing devices 11 and 12 consist each of cylinder 17,18 and spring-loaded piston 15,16 moving back and forth inside the cylinder according to the hydrostatic pressure of water. Cylinder 15,16 consist of a cavity extending through the frame element 1 and widened out in the middle, its one end opens up to a space outside the frame element 1, and the other end to the chamber 13,14 containing medium, whereby the pressure is essentially the same outside frame part 1 and inside the chamber 13,14. Thanks to this pressure compensation it is possible to reduce the strength and load of the chamber sealings , compared with the situation where no pressure balancing is available.

In the example shown the tip element 3 is formed of two electrically conductive flange-type elements 31 and 32 arranged concentrically apart from each. The element 32 situated nearer the frame element 1 is attached to the outer shaft element 21 in a removable manner, and the element 31 likewise to the inner shaft element 22 in a removable manner. The apparatus made to serve as a cutting tool comprises also devices 4,5,6 and 7 the purpose of which is to feed cutting medium between the flange-type elements 31 and 32 and the material to be cut. It should be pointed out in this connection that the flange-type elements 31 and 32 do not participate in the actual cutting procedure, they only serve as instruments in conductance of electricity to the piece to be cut and in formation of flame arc. The most advanta¬ geous" cutting medium used is paste-type or powder-type thermal material burning in flame arc, such as graphite grease alloyed with aluminium powder, this will melt the material in the required point.

In the shown example the feeding devices fpr cutting ■ medium comprise forced feeding device 7, such as screw ump, which is driven,through power transmission elements 9 and 10, by power shaft 8 of the power unit (not shown) which drives the shaft 2. Gear drive is used in this example, whereby one of the gears, gear 10, is arranged on shaft 8 and the other gear on the shaft of the screw pump 7. From the forced feeding device 7 one flow channel 6 for cutting medium is directed to the ring-type chamber space surrounding the inner shaft element 22. In order to direct cutting medium to the cutting point between the flange-type elements 31 and 32, second flow channel 4 for cutting medium was added to the feeding devices , it starts from chamber space 5 running centrally inside the inner shaft element 22 and ends in radial outlet channels which open in the space between the flange-type elements 31 and 32

Containing aluminium grains the cutting medium is electrically conductive, thatswhy at least one of the flow channels , channel 4 as well as its radial outlet channels are coated with electrically insulating material in order to prevent conduction of electric current, through cutting medium, from shaft 2 to forced feeding device 7 or the power unit driving shaft 2. Current leakage has further been eliminated by means of an inter¬ mediate element made of electrically insulating material and mounted between shaft 2 and power shaft . 8.

In order to create flame arc exactly in the required point, that is, close to the outer circumference of the flange-type elements 31 and 32, and not, for instance, between the flange-type elements 31 and 32, the opposite faces of the flange-type elements 31 and 32 are coated with a layer of electrically insulating material. Naturally, the flange-type elements can be assembled with other method as well , for instance so that fingerlike electric wires built into non-conductive material are running insidethe elements, leading from the conductive centre ring element to the conductive outer circumference.

In order to increase safety at work ₅ the flange-type elements are enclosed inside the casing halves 19,20 attached to the frame element and turning within each other like jaws as the apparatus is pressed against the work piece. The casing halves are most advantagously spring-loaded, whereby they are automatically pressed against each other as the apparatus is pulled off the work piece. Moreover the inner circumferences of the casing halves are designed to correspond essentially the circumference of the flange- type elements 31 and 32, and advantageously they are sealed against the flange-type elements , which prevents excessive inflow of surrounding water ^' nd unnecessary flow of cutting medium into the casing or out of the casing.

To minimize waste of cutting medium, and to direct it accurately to the piece to be cut there is an immovable nozzle device attached inside the casing surrounding the flange-type elements 31 and 32, this nozzle device directs the cutting medium coming out of radial outlet channels to the section in the circumference of the flange-type elements 31 and 32, which at a given time is towards the work piece. Thus flame arc is created only in one point between the flange-type elements 31 and 32. A suitable directing instrument would be a ring bush, for instance, which is immobile and surrounds the part of shaft 2 between the flange-type elements 31 and 32 and has in its wall one outlet for cutting medium. A tubular flow channel for cutting medium, for instance, runs from • the ring bush to the circumference of the flange-type elements 31 and 32.

In accordance with an advantageous application of the invention, radial outflow channels of one flow channel, channel- 4, ^" are arranged in..a removable end piece 24 attached to the end of shaft 2. Thus by changing tip element and end piece, which can be, as a whole, made of electrically conductive material, it is possible to alterate the apparatus based on the invention from a cutting tool into other applications , of which the most important would be: welding with a welding electrode rotating round its longitudinal axis , whereby earthing is arranged by means of a bush rotating against base material and surrounding the welding electrode; cleaning and coating of metal surface by using one of the flange-type elements attached to one of the shaft elements , cleaning agent or coating material is thereby feeded through the flow channel in the inner shaft, most advantageously between the surface to be treated and the flange-type elements.

The invention was described above on the basis of only one advantageous example of application. The purpose was, however, by no means to limit the range of the invention.

As to the details , the invention and its applications may considerably differ from the above description, and significant alterations can be made to it within the framework of the enclosed patent claims.