Apparatus for cleaning the heads of welding robots

Apparatus for cleaning the heads of electrical welding robots, the heads including a gas casing and an electrical contact nozzle. The apparatus includes an open vessel which has connected thereto one or more ultrasonic generators which function to generate ultrasonic waves in a liquid contained in the vessel. The vessel has mounted therein a rotary device which is located beneath the upper surface of the liquid. The rotary device operates as a mode stirrer to help loosen rings of weld material that have been deposited at the gas casing outlet. Additionally, wire brushes and cutting tools can be provided on the rotary device and rotationally driven to assist in weld material removal from the casing outlet.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an apparatus for cleaning the heads of 
welding robots. 
2. Description of the Related Art 
Welding robots are used generally within the workshop industry. This 
applies primarily to MIG-welding and MAG-welding A welding robot is 
programed to follow a certain pattern of movements, i.e. the robot head is 
arranged to follow a given pattern of movements. A workpiece to be welded 
by the robot is positioned accurately in relation to the robot, such that 
the workpiece will be located in a predetermined position in relation to 
the robot. As the robot head moves through the predetermined movement 
pattern, it will move in a predetermined manner in relation to the 
workpiece. 
In welding operations, the robot head carries a welding head. The robot is 
thus able to move the welding head to those locations and along those 
edges or corresponding surfaces where welding is to be performed. 
A welding head includes a gas casing which includes a central passageway 
for the delivery of welding gas. The gas is an inert gas and is ejected 
onto the weld location to prevent oxidation of the melt and also oxidation 
of those parts of the workpieces that are heated to high temperatures in 
the welding process. 
The gas casing passageway has a funnel-shaped orifice. An electrical 
contact nozzle is provided in the gas-casing passageway and has a central 
channel through which welding rod is advanced to the welding location. The 
forward end of the nozzle terminates short of the orifice of the gas 
casing opening and is concentric therewith. The nozzle is connected to one 
terminal of the welding unit voltage source and the workpiece is connected 
to the other terminal of said source. 
Splashes of weld material and slag, so-called weld spray, occur during a 
welding operation, these splashes landing on the weld head and therewith 
to a great extent on the edge surfaces defining the gas-casing opening, 
because the edge surfaces are located close to the workpieces during a 
welding operation. These splashes result in the build-up of rings of 
material around and in the opening on the weld head. The weld head and the 
nozzle also include soot from the fumes generated in the welding process. 
The rings of weld-spray that build-up on the welding head and said edge 
surfaces are electrically conductive and result in spark-over between the 
rings and the workpieces, whereas the intention is for spark-over to take 
place between the weld electrode and the workpieces. This results in 
welding interruptions. The weldspray buildup may also prevent sufficient 
gas from being delivered to the weld location through the gas casing, 
resulting in a poor quality weld. 
The above-identified weld-spray ring is built-up to an unacceptable size 
typically in from five to tan minutes, meaning that the gas casing must be 
cleaned relatively often. 
At present, the gas casing is cleaned by placing the gas-casing opening on 
a milling tool and milling away the weldspray ring mechanically. The ring 
is often seated very firmly on the gas casing and removal of the ring 
results in the removal of material from the gas casing by virtue of the 
ring loosening from the casing and being whirled around in contact with 
the casing by the milling tool, therewith causing wear to the casing. The 
task of removing the ring with the aid of other hand-operated tools, such 
as cutting nippers, for instance, is also time-consuming. The interior of 
the gas casing and the electrical contact nozzle are cleaned with the aid 
of compressed air, although the result is not always satisfactory. 
The welding equipment may also include watercooled gas casings, which are 
provided with internal cooling channels. Repeated cleaning of the gas 
casings with subsequent removal of material therefrom may result in the 
removal of so such material as to open the cooling channels so that the 
water conducted therethrough will spray out. This results in interruptions 
in the welding operation. 
In view of the fact that gas casings are relatively expensive and that the 
casings must be cleaned very often, it is highly desirable for the casings 
to be cleaned in a manner which is lass harsh on the casings and which 
will enable the casings to be cleaned much more quickly. It is also 
desirable to be able to clean the inside of the gas casing and the 
electrical contract nozzle quickly and simply. 
The present invention satisfies these desiderata and provides an apparatus 
for cleaning the gas casing and the electrical contact nozzle quickly and 
with such less wear on the casing in the proximity of its opening than 
that experienced with conventional cleaning processes. 
SUMMARY OF THE INVENTION 
The present invention thus relates to an apparatus for cleaning the heads 
of electrical welding robots, said heads including a gas casing and an 
electrical contact nozzle, wherein the apparatus includes an open vessel 
having connected thereto one or more ultrasonic generators which function 
to generate ultrasonic waves in a liquid contained in the vessel; and in 
that a rotary device in mounted in the vessel with said device located 
beneath the upper surface level of the liquid.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIGS. 1, 2 and 4 illustrate an apparatus for cleaning the heads of 
electrical welding robots, said heads including a gas casing and an 
electrical contact nozzle. 
In accordance with the invention, the apparatus includes an open vessel 1 
which has connected thereto one or more ultrasonic generators 2, 3 for 
generating ultrasonic waves in a liquid 4 present in the vessel 1. The 
ultrasonic generators are of a conventional kind and of the type used to 
generate ultrasonic waves it a liquid for cleaning purposes, in a known 
manner. The vessel 1 is preferably made of stainless steel. According to 
the invention, there is mounted in the vessel a rotary device which is 
located beneath the upper surface level of the liquid. This surface level 
is shown by the undulating line 5 in FIG. 4. 
The rotary device functions to stir the modes, i.e. standing waves are 
disturbed in the liquid. This has been found to provide a markedly 
improved cleaning affect. 
According to one preferred embodiment of the invention, the vessel 1 is 
conical in shape with the cone apex 6 facing downwards. The outer mantle 
surface or the cone is provided with a plurality of flat sidepieces 7-12. 
An ultrasound generator 2, 3 is mounted on each of three or more of the 
flat sidepieces 7-12, to generate ultrasonic waves in the liquid. 
According to one preferred embodiment, the vessel 1 includes six sidepieces 
with an ultrasonic generator placed on each alternate sidepiece, i.e. an 
embodiment which includes a total or three generators. 
The side surfaces define an angle v (see FIG. 4) with a plane which extends 
perpendicular to the longitudinal axis 13 of the vessel and the ultrasonic 
generators are so positioned on respective side surfaces that respective 
normals 14, 15 (see FIG. 1) of said side surfaces extending from 
respective ultrasonic generators will coincide with a point 16 on the 
longitudinal axis of the vessel 1 beneath the surface 5 of the liquid. As 
a result, strong interference taken place between the ultrasonic waves at 
the point 16. 
A shaft 17 extends through a penetrating hole 16' in the bottom of the 
vessel 1 and carries a tool attachment device 18 on the end thereof 
located in the vessel. An electric motor 48 which drives the shaft 17 is 
coupled to the other end of the shaft. 
According to one preferred embodiment, the shaft 17 is rotated at a speed 
of 50 to 500 r.p.m., preferably about 180 r.p.m. 
According to one preferred embodiment, the tool attachment device 18 has 
the form of a plate 19 which is positioned at right angles to the shaft 17 
and the upper side 20 of which is provided with tool-mounting means. 
The tool attachment device 18 is preferably fitted detachably to the shaft 
17. According to one embodiment, the upper part 21 of the shaft 17 has a 
square cross-sectional shape, for instance. In this case, the attachment 
device 18 will include a sleeve 22 which projects down from the plate 19 
and which has an internal hole of corresponding cross-section. When the 
sleeve 22 is fitted onto the upper part 21 of the shaft, the two parts 
will be in engagement for rotation of the tool. 
The tool is comprised of one or more brushes and/or a milling tool. 
Examples of such tools are shown in FIGS. 5a-5c. 
FIG. 5a shows a steel-wire brush 23 fitted on a base plate 24. 
FIG. 5b shows a milling tool 25 having upstanding cutting edges 26. The 
outer side of the cutting edges is intended to abut the inside of a ring 
of weld spray adjacent the opening of a gas casing. The milling tool is 
mounted on a base plate 27. The milling tool may have a form which 
corresponds to the form typically used to clean-off rings of weld spray. 
FIG. 5c shows another cutting tool 28 having an upwardly rounded cutting 
edge 29 which is intended to abut the ring of weld spray in the same way 
as the milling tool. This cutting tool is mounted on a base plate 30. 
The tool base plates 24, 27, 30 are fitted to the plate 20 of the tool 
attachment device in a manner which will prevent rotation of the base 
plates on the plate 20. For instance, the plate 20 may be provided with a 
number of upstanding pegs 31-33 which are received in corresponding holes 
34-36 in the base plates 24, 27, 30. Thus, when a tool in fitted to the 
attachment device 18, the tool will rotate as the shaft 17 rotates. 
FIG. 3 illustrates schematically a conventional gas casing 37 fitted to a 
robot head. The casing includes a sleeve 38 and an electrical contact 
nozzle 39. The nozzle 39 is screwed onto a pipe (not shown) and when 
fitted takes the position shown in FIG. 3 relative to the sleeve 38. As 
mentioned before, the nozzle 34 has provided therein a channel 40 in which 
welding rod 41 in advanced. As the welding rod 41 is consumed, the rod is 
advanced down in the direction of the arrow 42. Inert gas flown down 
between the sleeve 38 and the nozzle 39 when welding is in process, as 
indicated by the arrows 43. 
As mentioned in the introduction, welding spray will build-up a ring of 
material around the edges defining the gas casing opening 44. The lower 
part of the casing 37 in the vicinity of the casing opening 44 in shown at 
the bottom of FIG. 3 in broken lines. A ring 45 of material of the 
aforesaid kind is shown in full lines in a normally occurring size. 
Obviously, the presence of such a ring 45 of materials will disturb the 
flow of gas from the gas casing 37, furthermore, such a ring will 
influence the location at which an electric spark-over takes place on the 
workpiece. It is, therefore, necessary to remove such rings. 
The speed at which such a ring builds up will depend on how well the 
welding parameters, such as voltage, current strength, welding speed, 
etc., have been set. It may take from a few minutes to an hour for such a 
ring to build up. Each time a ring builds up, it in necessary to clean-off 
the ring in order not to impair the quality or the weld. 
The present invention works in the following manner. When a gas casing 37 
is to be cleaned, the robot is programmed to move the casing to a position 
corresponding to the position shown in broken lines, in FIG. 4, such that 
the forward part of the casing will be in contact with a tool 24, 27, 30 
mounted for rotation with the plate 19. 
The level 5 or the liquid 4 in the vessel in sufficiently high to allow at 
least the forward part of the casing 37 and the electrical contact nozzle 
39 to be submersed in the liquid. 
According to one preferred embodiment, the liquid is a washing detergent. 
The washing detergent may be any suitable detergent used for industrial 
purposes. One example of a suitable washing detergent is that sold by 
Leverindus, Nykoping, Sweden, under the trade designation ST 104. The 
washing effect can be enhanced with the aid of vessel-mounted immersion 
heaters (not shown), so as to maintain the liquid at an elevated 
temperature, for instance at a temperature of 60.degree. C. 
The ultrasonic generators are started up in conjunction with lowering the 
gas casing 39 into the vessel 1 of the inventive device. It has 
surprisingly been found that the ultrasonic waves cause the ring 45 to 
loosen from the casing 37 such that the ring will either fall off or can 
be easily removed from the casing. The ring is seated initially very 
firmly to the casing, which is one of the main problems encountered when 
cleaning gas casings with the aid of conventional methods. At times, the 
ring will simply fall from the casing when the casing is lowered down into 
the inventive apparatus, without needing to use a tool to this end. In 
this regard, it has been found that the provision of a rotary device in 
the vessel has a significant effect on the tendency of the ring to loosen, 
despite the rotary device not being in contact with the ring. It is 
assumed that the mode stirring affect of a rotary device is highly 
influential in this regard. 
One such rotary device is shown by way of example in FIG. 6, in the form of 
a U-shaped device 46 mounted on a base plate 47. The base plate 47 
corresponds to the base plates 24, 27, 30. The device 46 is designed so as 
not to come into contact with the gas casing 37 when the casing is lowered 
into the vessel 1. Such a rotary device can be referred to as a mode 
stirrer. 
It has been observed that the tendency of the ring 45 to loosen in 
particularly manifest when the ring passes the region of the point 16 (see 
FIG. 1), and consequently a construction which includes such a point is 
highly essential. 
A rotary milling tool is used to split rings which are relatively large, 
wherewith after having been loosened from the gas casing 37, the ring 45 
will split and fall therefrom. Naturally, the milling tool can also be 
used to cut away ring residues from around the gas-casing opening. The 
cutting tool shown in FIG. 5c is used in a corresponding manner. 
A brush can be used to clean the forward part of the casing 37 in a gentler 
manner. The use of a brush will assume that the ring 45 has been loosened 
from the casing by the ultrasonic vibrations, so that when brushed the 
ring will fall from the casing without requiring the use of a milling or 
cutting tool. 
It has been found that when applying the present invention, the ring 45 of 
weld spray material is easily removed and that both the gas casing and the 
electrical contact nozzle 39 are cleaned very effectively. Furthermore, 
the time taken to clean the casing and the nozzle is only about ten 
seconds. The problems mentioned in the introduction are, therefore, 
eliminated by means of the present invention. Because of the short 
cleaning time afforded by the invention, the robot can be programed to 
perform gas casing cleaning operations at very short intervals, so am to 
prevent the build-up of thick rings. This enables welding to be performed 
with gas casings which are practically always clean, therewith 
considerably improving the average weld quality. 
Although the invention has been described with reference to a number of 
exemplifying embodiments thereof, it will be understood that both the 
construction of the vessel and the number of ultrasonic generators used 
and the design of the tools can be varied and modified by those skilled in 
this art. 
The present invention shall not, therefore, be considered to be limited to 
the aforedescribed embodiments, since variations and modifications can be 
made within the scope of the following claims.