GB2042391A - Underwater arc stud welding gun - Google Patents

Abstract

An underwater arc stud welding gun, for use with a ceramic ferrule 6, comprises a stud welding gun body 1, a shroud 5 (e.g. transparent) having one end thereof fixed watertightly to the leading end of the gun body, an annular ferrule retainer 7 fitted airtightly to the inner wall of the shroud close to the open edge thereof, and means for introducing a gas under pressure into the interior of the shroud. In use, the ferrule and stud dimensions are arranged such that a fine gap is formed in the shape of a cylinder between the ferrule and the stud to permit passage of said gas under pressure to displace water from the stud-adjacent surface of a workpiece 3. As shown, the shroud and ferrule end faces have water and gas egress recesses 23, 24. A porous belt 25 (e.g. of steel wool or sponge) prevents re-entry of water. Disclosed gases are air, CO2 and a mixture of CO2 and A. Gas flow start and stop before and after current flow may be under manual or timer control. <IMAGE>

Description

SPECIFICATION Underwater stud welding gun This invention relates to an underwater stud welding gun.

When an anode block formed of aluminum, zinc or an alloy thereof is to be fastened to an underwater structure for the purpose of protecting the underwater structure against electrolytic corrosion, for example, it has been a customary practice for a diver-welder to fix the anode block to the underwater structure by manually welding a mild steel plate projectingly fixed on the anode block to the underwater structure by the underwater wet welding method using a covered electrode.

For successful practice of this method, the diver-welder is required to be highly skilled in both welding and diving. The work of welding requires much labor and time. On no few occasions, there occurs accidental separation of welded blocks from underwater structures by reason of defective welding work.

With a view to eliminating the need for a diver-welder to engage in the difficult work of underwater arc welding and to allowing the anode block to be fastened readily and safely to the underwater structure, there has been developed a method which accomplishes the desired union by (a) stud welding bolts to the underwater structure, (b) passing the welded bolts through matching holes bored in a mild steel plate projected from the anode block and (c) securing the mild steel plate in position on the underwater structure by tightening the nuts on the protruding bolts.

An object of this invention is to provide an underwater stud welding gun which permits the aforementioned work of stud welding to be readily and safely carried out under water.

To accomplish the object described above according to the present invention, there is provided an underwater stud welding gun, which comprises a stud welding gun proper incorporating therein a ferrule, a shroud having one end thereof fixed watertightly to the leading end of the gun proper, an annular ferrule retainer fitted airtightly to the inner wall close to the open edge of the shroud, and means for introducing a gas under pressure into the interior of the shroud, the ferrule possessing a diameter such that there occurs a fine gap in the shape of a cylinder between the ferrule and the stud when a stud to be welded is chucked therein.

When the aforementioned gun is used under water, therefore, the gas introduced under pressure into the interior of the shroud shoots its way through the cylindrical gap formed between the stud and the ferrule, empties the shroud interior of water and removes water from the surface of a given article subjected to welding, enabling stud welding to be carried out in the absence of surrounding water. Consequently, the welding gun permits the studs to be welded as safely to the substratal article as when the welding is performed on land.

The other objects and characteristics of the present invention will become apparent from the further disclosure of the invention to be given hereinbelow with reference to the accompanying drawing in which: Figure 1 is a sectioned view of an underwater stud welding gun according to the present invention; Figure 2 and Figure 3 are explanatory diagrams illustrating the conditions under which the gas discharged by the stud welding gun is forced out in the form of bubbles; and Figure 4 is an explanatory diagram illustrating the stud welding gun of Fig. 1 being operated as held in its lateral position.

Stud welding provides reliable welded joints in a short period of time (on the order of 0.1 to 2 seconds) and enjoys great ease of handling. The stud welding is practiced in a variety of manners. Where thick bolts are desired to be welded powerfully, for example, there is generally employed the arc stud welding technique which makes use of a ferrule.

The ferrule, as widely known, is made of ceramic, which prevents magnetic blow, casts the molten metal and functions to keep the ambient air away from the molten metal being formed as the stud is slightly lifted away from the substratal metal and the arc is consequently generated across the gap to melt the metal and the stud.

The underwater stud welding gun of the present invention represents an improved version of the aforementioned known arc stud gun utilizing such a ferrule, the improvement being such as to enable desired stud welding to be carried out under water with ease. Now, the gun is described by reference to the accompanying drawing.

The arc stud welding gun proper 1 illustrated in Fig. 1 represents one example of the type adapted so that the stud is lifted by the electromagnetic force generated by the welding current. This gun proper 1 can be put to use as it is when the cover of the gun proper is molded of an insulating material in a watertight construction. If the gun proper 1 is not watertight, it may be made watertight by filling all void spaces with resin so as to isolate the start switch, power line, terminal, etc. from the ambient water.

Now the operation of this gun will be described briefly. When the trigger 17 is drawn, the switch 18 is turned on and the magnet switch 16 of the arc welder 15 is turned and set to its ON state. Consequently, the welding current flows through the substratal article (work being welded) 3, the stud (welding article) 8, the strand wire terminal 8b, the strand wire 12, the connection terminal 11, the power line 13 and the coil 19 back to the welder 15. As the electric current flows through the coil 19, the stationary iron core 20 is excited to attract the movable iron core 21 which is connected to the stud supporting shaft 8a holding the stud 8 in position, with the result that an arc is generated across the gap formed between the stud 8 and the substratal article 3 to melt the portions of the opposed articles exposed to the arc.The arc length is determined by the distance which separates the stationary iron core and the movable iron core from each other. This distance can be adjusted by rotating the adjusting screw 20a to change the vertical position of the stationary iron core 20.

On lapse of a prescribed time, the timer 2 is actuated to turn off the magnet switch 16, discontinue the flow of electric current, demagnetize the stationary iron core 20 and allow the stud 8 to be pressed against the substratal article 3 by means of the spring 22, bringing the welding work to completion.

To the leading edge of the stud welding gun proper 1 of the aforementioned construction, one end of a shroud 5 is watertightly fitted by means of an O-ring 14 and secured in position with a thumbscrew 10. When the thumbscrew 10 is loosened, therefore, the shroud 5 releases its firm hold of the leading end of the gun proper and allows it to be rotated about its axis or slid up or down in its axial direction inside the shroud 5. The shroud 5 is desirably formed of a transparent material so that the stud held therein can be observed from outside. Polycarbonate resin is a typical example of a material satisfying this requirement.

On the inside surface close to the open end of the shroud 5 which comes into contact with the substratal article 3, an annular ferrule retainer 7 is formed airtightly. A ferrule 6 is supported in position on the inner wall of the ferrule retainer 7. A plurality of recesses 23, 24 adapted to release water and gas are disposed respectively on the open ends of the shroud 5 and the ferrule 6 which come into contact with the substratal article 3. The ferrule 6 has an inner diameter 1 mm to 3 mm greater than the diameter of the stud 8 to be fastened by welding. For this reason, there is formed between the ferrule and the stud a cylindrical gap having a width of 0.5 to 1.5 mm.

The ferrule retainer 7 is fitted as in screwed engagement, for example, to the inner wall of the shroud so that the ferrule 6 is allowed to make a fine adjustment of its vertical position relative to the inside of the shroud in accordance with the length of the stud. The shroud 5 is further provided with a flexible gas feed pipe 9 adapted to supply a gas under pressure to the interior of the shroud. Generally air or carbon dioxide is used as the gas supplied under pressure to the shroud interior. When the welding operation is to be performed at a great depth under water, however, a mixed gas consisting of argon and carbon dioxide is used with a view to stabilizing the arc.

A belt 25 of porous material such as steel wool or gas-pervious sponge is wrapped round the outer surface of the open end of the shroud.

Now, the actual work wherein the underwater stud welding gun of the aforementioned construction is used with the gun held in its downward position will be described. After a stud 8 of a prescribed size has been set in position on a stud supporting shaft 8a, the ferrule 6 is fixed on the ferrule retainer 7 and the open edge of the shroud is brought into tight contact with the surface of the substratal article 3 under water and locked in that position. The recesses 24 formed in the open edge of the ferrule 6 may be omitted when the ferrule retainer 7 is so adapted that a proper positional adjustment thereof gives rise to a fine gap between the open edge of the ferrule 6 and the surface of the substratal article 3.

After the open edge of the shroud of the gun 1 has been locked fast against the substratal article 3, the gas from a gas source 4 is introduced under pressure into the shroud interior via the gas feed pipe 9. In consequence of the supply of the gas into the shroud interior, the water entrapped in the shroud interior is discharged in conjunction with the introduced gas through the cylindrical gap formed between the ferrule and the stud, the recesses 24 formed in the lower end of the ferrule, the recesses 23 formed in the lower end of the shroud, and the porous belt 25 into the ambient body of water. Generally when the water is discharged through the recesses, it gives birth to large bubbles which float up the surrounding water as shown in Fig. 2.At the moment that the bubbles depart from these recesses, the ambient water flows back into the shroud interior so much as to deprive the arc of its stability and render the work of welding incomplete. In the present invention, however, the undesired phenomenon of backflow of water is precluded by having the porous belt 24 wrapped round the outer surface at the lower end of the shroud as illustrated in Fig. 3 and thereby permitting the gas to be discharged in the form of finely divided bubbles.

After the introduced gas has thoroughly displaced the water inside the shroud and the forced collision of the introduced gas against the surface of the substratal article has removed the water from the surface, the trigger 17 is drawn to apply the welding current to the gun proper and generate the arc, starting the welding operation. After the generation of this arc has been continued for a prescribed time, the flow of electric current is discontinued and the stud is pressed into union with the substrata article. This completes the work of welding. Then, the supply of gas under pressure to the interior of the shroud is stopped.

The aforementioned supply of gas can be started and stopped manually by the diverwelder. Otherwise, this operation may be performed by signals set in advance in the timer 2. In this arrangement, the diver-welder has only to draw the trigger. Consequently, the timer 2 issues to the gas source 4 the signal to start the supply of gas under pressure to the interior of the shroud 5 and, at the time that the water entrapped in the shroud has been thoroughly displaced by the introduced gas, the timer issues a signal to the contactor of the arc welder commanding it to apply the welding current to the gun proper and, upon completion of the welding work, the timer commands the gas source to discontinue the supply of gas.

The procedure of operating the stud welding gun described above with respect to the work requiring the gun proper to be used in its downward position applies to the work wherein the stud welding gun is used with the gun proper held in its overhead position for the purpose of fastening studs to a substratal article situated overhead.

In the work wherein the stud welding gun is held in its horizontal position for the purpose of fastening studs to a vertical surface of the substratal article, however, the gas supplied under pressure is desired to be introduced through the upper side of the shroud and then discharged through the lower side so as to facilitate the removal of entrapped water by the force of gravity. This is accomplished by loosening the thumbscrew 10, turning the shroud 5 so much that the gas inlet falls on the uppermost level of the shroud, as shown in Fig. 4, when the gun proper is held in its horizontal position and thereafter retightening the thumbscrew to fix the shroud again. Further, a baffleplate 26 is fixed to stopper the upper recesses at the leading end of the shroud and a porous belt (not shown in Fig.

4) is laid over the baffleplate so that the water and the introduced gas are allowed to flow out of only the lower recesses. The attachment of the baffleplate 26 and the detachment thereof for the purpose described above may be accomplished by any of various methods known in the art.

As is clear from the description given above, this invention aims to materialize powerful attachment of studs to an underwater structure by causing the ferrule used in the arc stud welding gun and, at the same time, the function of orifices serving to remove water from the space required for the generation of a welding arc. Thus, the stud welding gun of this invention permits studs to be fastened to the substratal article under water as safely as when the welding work is carried out on land.

This invention has issued from a specific improvement attained in and concerning the known stud welding gun, which improvement comprises giving the welding gun a watertight construction, attaching a shroud to the leading end of the gun proper and incorporating therein an arrangement adapted to introduce a gas under pressure into the interior of the shroud. The stud welding gun of this invention operates so simply that, when welding is carried out at a shallow depth, the diverwelder can carry the gun on his person and manually operate the gun and, when the welding is carried out at a great depth, the gun can be mounted on a robot, lowered to the place of welding and then operated there by remote control to have studs readily attached to the underwater structure.

The underwater stud welding gun according to the present invention can be either of the type having a coil with a small number of turns through which a large welding current is passed or of the type having a coil with a large number of turns through which a small DC current is passed from another electric power source.

Claims (5)

1. An underwater stud welding gun, which comprises a stud welding gun proper incorporating therein a ferrule, a shroud having one end thereof fixed watertightly to the leading end of said gun proper, an annular ferrule retainer fitted airtightly to the inner wall close to the open edge of said shroud, and means for introducing a gas under pressure into the interior of said shroud, said ferrule possessing a inner diameter such that when a stud to be welded is chucked therein, a fine gap in the shape of a cylinder is formed between the ferrule and the stud.

2. The underwater stud welding gun according to claim 1, wherein the shroud is fixed to the leading end of the gun proper in a manner such as to enable the gun proper to be rotated around its axis and slid in its axial direction on the inside of the shroud.

3. The underwater stud welding gun according to either of claims 1 and 2, wherein the shroud is provided along the open end thereof with a plurality of recesses for discharging a gas introduced into the interior of the shroud.

4. The underwater stud welding gun according to any of claims 1, 2 and 3, wherein a porous belt is wrapped round the periphery along the open edge of the shroud.

5. The underwater stud welding gun according to claim 1 and substantially as hereinbefore described with reference to Figs. 1, 3 and 4 of the accompanying drawings.