Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
'7
Case 2780
--1--
SHIELDING DEVICE FOR RESTRAINING
.
ULTRAVIOLET RADIATION
The present invention relates to a
mechanical shielding device for restraining
ultraviolet light radiated from an arc of a
metal-inert-gas welding torch.
It is well known that metal-inert-gas ~MIG~
welding of aluminum results in the formation of
ozone. ultraviolet light radiated from the electric
arc reacts with oxygen to produce the ozone. For the
most part, the ozone is generated close to the arc
and atenuates rapidly as the distance from the arc
ncreasesO
Because ozone is a severe respiratory
irritant, and at low levels can promote significant
~ irritation of mucous membranes of the eyes, nose, and
;15 throat, it can be seen that there is a need to reduce
the` hazardous effects due to ozone.
In the past one method of reducing the
amount of ozone generated was to surround the arc with
a glass or acrylic shield. The problem with such a
shield, however,~was that the shield could not
~; withstand the high temperatures generated near the
arc. Thus,~ for this type of shielding to be
successful the~shield would have to be excessively
large and this would result in it being impractical
to use. Glass shields further suffered from
breakage. Thus there is a need for a practical
mechanical shield to be developed which minimizes the '
production of ozone and is not subject to easy
: .
-'
Case 2780
--2--
breakage.
Accordingly it is an object of the present
invention to provide a mechanical shielding device
that reduces the produc~ion of ozone in a MIG welding
process and is not subject -to breakage.
Briefly the present invention provides a
mechanical sheilding device for restraining
ultraviolet light radiated from an arc of a MIG
welding torch. The device includes a support means
which is adapted to be secured to the torch. The
device further includes a flexible shroud which is at
least partially impervious to ultraviolet light. The
shroud is supported from the support means and
surrounds the arc. Further, the shroud will contact
the parent metal when the support means is secured to
the torch and when in use. The shroud when used in
conjunction with the parent metal and the torch
defines a substantially enclosed area beyond which
transmission of ozone is restricted~ Because the
shroud comprises a flexible material it will not be
readily subject to breakage and may be used in most
practical MIG welding applications~ While the
shielding device may be readily used for automatic MIG
welding, it should be understood that this shielding
device also finds application in manual welding.
Additionally, the support means of the
shielding device may comprise a disk shaped member
having a central aperture into which the welding torch
is fitted. The disk will have a downwardly depending
cyclindrical flange on its periphery about which the
shroud is positioned and attached thereto by suitable
means. The material for the shroud may be any
suitable flexible material which can withstand the
high temperatures associated with the arc. One such
suitable material, for example, would be stainless
steel.
Furthermore, the shroud may include a
viewing port through which an operator may monitor
4~;~7
Case 2780
--3--
the arc and weld puddle. This viewing port may
comprise a portion cut away from the shielding
device. Such a viewing por-t in this instance would
not be impervious to ultraviolet light, the size of
the viewing port however, would be chosen such that
the amount of ultraviolet light escaping would be
insufficient to produce a hazardous amount of ozone.
For better understanding of the nature an
objects of the present invention, reference may be had
by way of example to the accompanying diagrammatic
drawings of the preferred embodiment of the present
invention in which:
Figure 1 shows a perspective view of a
manual welding torch including the shielding device
attached to the torch;
Figure 2 is an elevational view illustrating
the shielding device;
Figure 3 is a sectional view of the shroud
taken at section 3-3 of Figure 2.
Referring now to the drawings there is shown
a welding torch 10 of a MIG welder having the wire 12
to be welded entering through a rear portion of the
torch 10. Electricity is provided to the MIG welder
by electrical power lines 14. Shielding gas is
provided to the vicinity of the weId by passing
through the torch and the gas enters the torch through
tubing 16. Secured to the torch is a mechanical
flexible shielding device 18. Shielding device 18
surrounds the arc 20 and, together with the aluminum
parent metal 22 being welded, defines an enclosed area
which restricts the transmission of ozone beyond that
area.
The mechanical shielding device comprises a
support means 24 and a flexible shroud 26. The support
means 24 comprises a metallic disk shaped member 28
which is provided with a downwardly depending
cylindrical flange 30 on its peripheral edge (see
,
~7~
Case 2780
_aS_
figure 1). Surrounding flange 30 is the flexible
shroud 26. The flexible shroud 26 is clamped to
flange 30 by suitable means such as the pipe clamp 32
illustrated in the figures of the preferred embodiment.
The cylindrical flange 30 is provided with a central
aperture 34 which surrounds a portion of torch 10.
Brazed to flange 30 adjacent aperture 34 are a
plurality of nuts 36 through which screws 38 pass to
secure the support member to the torch.
The shroud 26 comprises a plurality of
layers of metallic metal chain link. These layers are
shown to comprise three layers in Figure 3. The more
layers used the more impervious the metallic shroud
will be to the transmission of ultraviolet light~ In
the preferred embodiment illustrated, three layers are
used because this number of layers is sufficient to
effectively reduce the transmission of ozone beyond
the area defined by the shroud, the support means and
parent metal to an accpetable and safe level. As
stated previously, in the preferred embodiment,
stainless steel is employed; however~ it should be
understood that any material which can withstand the
high temperature of the weld, which i5 impervious to
transmission of ultraviolet light and which is
flexible may be used.
As illustrated in Figure 2, a viewing port
is provided at 40. Viewing port 40 is formed by
cutting a knotched aperture out from the shroud.
Accordingly, this portion of the shielding device (the
viewing port) is not impervious to the transmission of
ultraviolet light~ The size of the viewing port
however, is chosen such that the operator may
adequately view the arc and the weld puddle. The size
chosen should not result in significant amounts of
ozone being transmitted.
It should be understood that alternate
embodiments may be readily apparent to a man skilled
Case 2780
in the art in view of the foregoing disclosure.
Accordinly, the scope of the present invention ~hould
only be limited to that which is claimed in the
accompanying claims.
.
