Note: Descriptions are shown in the official language in which they were submitted.
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MIG WELDER ATTACHMENT FOR AN ELECTRIC HAND DRILL
FIELD OF THE INVENTION
This invention relates to a MIG arc welding
apparatus and more particularly to a simple attachment
to a variable speed electric hand drill, which may be
readily attached to and detached thPrefrom, to provide
a highly effective professional quality, low cost MIG
arc welding appaxatus with variable speed drill power
source electrically independent from the arc power
source.
BACKGROUND OF THE INVENTION
MIG arc welding apparatus is in high vogue. U.S.
Patent No. 4,079,231 is exemplary of such MIG arc
welding apparatus. A torch supports a consumable wire
electrode, fed to the torch by wire feeder rolls which
sandwich the wire to drive it through a passage within
the torch. That passage is also subjected to a shield-
ing gas with the gas surrounding and shieldiny the
consumable wire electrode as it exits Erom a contact
tube. It ~unctions to shield the arc which is estab-
lished between the consumable wire electrode and a
second electrode constituted by the workpiece. In that
patent, the wire feeder rolls are driven by a motor
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whose speed is controlled by a motor governor via a
con~rol circuit. To effect welding, the operator
touches the end of the consumable wire against the
workpiece and this results in an instantaneous short
circuit across a power supply in a sensing circuit.
The sensing circuit provides a low voltage output
signal which is fed to the control circuit. The
control circuit produces, in turn, an output signal
which energizes the welding contactor and the welding
contactor produces a signal which turns on the power
supply. With the power supply turned on, the arc is
immediately established between the consumable wire
electrode and the workpiece electrode. Also, in
response to the sensing circuit output signal, the
control circuit feeds a signal to the motor governor
which starts the wire feeder motor. Additionally, the
control circuit feeds the signal to the gas supply
which initiates flow of a shielding gas to tne torch.
Upon establishment of the arc between the consumable
wire elect~ode and the workpiece electrode, the output
from the sensing circuit terminates. However, the flow
of welding current through the cable lead to the torch
and thus to the consumable wire electrode is
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immediately sensed by a current detector circuit, which
circuit is connected to a part of the cable lead. The
detector circuit produces in turn an output signal
which is fed to the control circuit, and the control
circuit in response to the output signal, contlnues to
maintain the signal to the welding contactor. This
keeps the power supply in circuit and also maintains
the signal to the motor governor and the signal to the
gas supply so that the motor drive s~stem and the
supply of inert gas continues. Thus, the wire feeder
motor continues to operate and the flow of shielding
gas to the torch is maintained.
Such consumable metal inert gas (MIG) arc welding
is in large use because the MIG welders are faster and
use less heat (amperage) for a given weld than other
common welding methods so that heat distortion of the
workpiece is minimal. Such conventional MIG welders
may utilize storage batteries as the source of the DC
arc current. But in each case, the arc and drive power
is electronically coupled to yield "semi-automatic"
features. MIG welders are not necessarily inexpensive.
Units sold under the trademark CENTUR~ cost about $700
while, a MILL~R SPOOLMATIC MIG welder gun alone may
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cost about $1000 with a further cost of $2,000 for a
power source. The MILLER SPOOLMATIC requires electron-
ic modification to a 240 volt AC (household or three-
phase industrial current) to obtain a 24 volt DC
non-drooping voltage current at the arc. As for the
CENTURY unit, which runs on DC batteries, the unit is
too large for portability. Cost is high because drive
and arc power are electronically coupled. It is
designed for use almost exclusively in welding steel
and the drive speed is too slow for soft metal welds,
particularly aluminum. The long drive train powered by
a 24 volt motor causes the Century unit to be less
energy-efficient and the push drive o the consumable
wire electrode tends to cause "bird-nesting" of the
consumable thin wire electrode.
MIG arc welding is also known as "semi-automatic
~ine wire welding". The term "semi-automatic" refers
to the electrical or electronic coupling of arc and
drive power in an effort to stabilize the arc voltage
independent of human-induced accidental variations in
arc distance. In most systems, the arc powex source
requires expensive electronic components to achieve a
"non-drooping voltage" characteristic. In some systems
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where auto or deep-cycle storage batteries are used as
the power source, as in the CENTURY's portable MIG
welding system, an expensive and wholly unnecessary
electronic couple exists between the drive and the arc.
The applicant has determined, and the present invention
is based on, the recognition of the inherent stability
of arc power when storage batteries are used for the
power source. Thus, when auto or deep-cycle storage
batteries are used for the arc power source, the
resulting arc is so inherently stable that no electric
or electronic couple to the drive power is required or
desired. The applicant has determined that storage
batteries are capable of such power (inherent reserve
power) that any attempt at manual modification of arc
distance, accidental or intentional, has no appreciable
effect on arc stability; specifically on arc voltage.
A fortuitous and inherently stable match in arc and
power source resistances assures an inherently stable
arc gap and stable arc voltage where auto or deep cycle
batteries are employed as arc power source. Applicant
has determined that where one might expect a manual
decrease of welding gun to workpiece distance to
decrease arc distance and to decrease arc voltage and a
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manual increase of welding gun to workpiece distance to
increase_arc distance and to increase arc voltage, this
is in fact not ostensibly the case where, and only
where, storage batteries of common auto or deep-cycle
type are used as the arc power source. In act, if the
fine wire electrode should contact the workpiece
electrode, as it does in initiating -the arc, the
reserve power of the arc is sufficient to instantane-
ously melt the electrode, thus opening the arc to a
stable gap and initiating the weld process.
Attempts have been made to simplify the handling
and feed of the consumable wire to the torch electrode
nozzle assembly in such welding equipment. U.S. Patent
No. 2,909,646 uses a pistol type welding gun which is
provided with a water cooled electrode noæzle assembly
through which a shielding gas is directed to the weld
area. However, the electrode wire is fed from a
separate and isolated box-like structure which encloses
an adjustable speed motor operatively coupled to a
drive roll~ and a pressure roll sandwiching the wire.
This requires push feeding o~ the wire a significant
distance to the gun ~nd through the gun nozzle assem-
bly. A trigger switch carried on the pistol grip of
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the welding gun controls drive motor operation for
feeding the thin wire electrode and for controlling
shield gas and cooling water 10w to the gun.
U.S. Patent No. 2,4gO,593 describes a combined
portable welding and pneumatic tool useful in repairing
cracked parts or castings by welding where it is
usually necessary to first form a channel pocket for
the welding material where the part is cracked or
requires repair, through the use of a chisel~ then to
deposit the welding material in the channel or pocket
which is preferably done by vibrating a rod of welding
material and passing an electric current of lower
voltage and high amperage through the stick of welding
materials. Finally, it is desirable to peen the
deposited welded material to produce a smooth dense
surface over the welded portion. The patent employs a
simple and ef~icient tool which may be interchangeably
used in performing the chisel, welding and peening
operations. The versatile tool includes a maga7ine for
holding a ~eries of rods which can be successively used
for welding, incorporates a pulsating hammer, operable
to impart strokes of variable force such as light
strokes or peening and welding and heavier strokes for
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chiseling. It has a welding rod holder which comprises
a collet for positively holding the welding rod during
welding operations. A pulsating hammer is detachably
connected to the welding rod holder with a removable
shield on the holder for the hammer. A welding rod
holder includes means for delivering air from the
hammer to the weld and varying th~ air flow to provide
cooling of the desired degree. A pneumatic hammer has
the intensity of the hammer pulsations varied by
controlling the air exhausted from the hammer. A
single valve means variably controls the operation of
the pulsating hammer and variably controls the Elow of
air to the electrode controlling means. A pneumatic
hammer has the operated tool insulated to prevent
arcing between the tool and the work while carrying on
peening or chiseling operations via a quick detachable
connection between the body of the pneumatic hammer and
tha welding rod or the electrode holder, to permit
separate use of the hammer for peening or chiseling.
U.S. Patent No. 2,909,646 teaches a welding tool
of gun form using a pistol grip trigger mechanism for
selectively initiating and shutting off of the movemen~
of the drive of the thin wire and the supply of cooling
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liquid and inert gas to a pistol type apparatus. U.S.
Patent No. 2,490,593 suggests the creating of a com-
hined portable welding a pneumatic tool. U.S. Patent
No. 2,909~646 teaches isolation of the wire feed drive
from the gun receiving the same, and U.S. Patent No.
2,490,593 suggests only the decoupling of mechanisms
integrating a portable welding and pneumatic tool.
It is, therefore, a primary object of the present
invention to provide an accessory or attachment to an
ordinary electric hand drill for effecting a low cost
battery powered MIG welder utilizing the variable speed
motor of the electric motor hand drill for controlling
the amperage of the welder by variable speed driving of
the fine wire electrode while maintaining the current
source to the electric hand drill motor electrically
uncoupled to the DC voltage source creating the arc
without materially affecting the stability of the
welding arc.
It is a further object of the present invention to
provide a ~ighly versatile, low cost portable welder as
an attachment or accessory to an ordinary AC or DC
electric hand drill particularly useful in forming a
MIG welder which is easy to use, lightweight, and well
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suited to heavy or light welding. It is noteworthy
that where circumstance dictates the parallel hook-up
of both arc and drive to the same batteries, that no
desta~ilizing relationship between arc and drive is
implied or in act exists. Performance remains unaf-
fected regardless of the existence of said circumstan-
tial parallel circuits because the power reserve of
said batteries is sufficient to maintain a stable power
supply to the drive unit unaffected by the power to the
arc.
SUMMARY OF T~E INVENTION
The invention is directed to a simplified, low
cost arc welder attachment for an electric hand drill
or welding a workpiece acting as a first electrode. A
common, standard hand drill comprises a drill casing
carrying a drill drive motor with the motor shaft
protruding from one end of the casing and operating on
a first AC or DC power source. The MIG attachment
comprises cover means for attachment to the drill
casing, and frictional wire drive means mounted to the
cover at 90 to the drill shaft drive and mechanically
coupled to the drill motor shaft feeding a fine wire,
second electrode. A standard electrode nozzle assembly
2~
connected to the wire drive means and including a metal
contact tube receives said fine wire second electrode
fed by the wire drive means. Second electrical power
source means (i.e., two 12 volt DC auto or deep cycle
batteries in series, or one 24 volt aircraft battery,
or eguivalent) are provided for subjecting the work-
piece first electrode and the fine wire second elec-
trode to a DC potential difference so as to create an
electric arc therebetween capable of melting the wire
to create an inexpensive, highly portable welder with
the electrical power sources for the arc and for the
hand drill motor being independent and electronically
uncoupled, wherein the arc heat, or amperage, is
directly responsive to the wire feed speed and where
both soft and hard consumable wire electrod~s may be
readily employed.
Incorporated within and rotatably mounted on the
cover is a spool of fine wire which functions as the
fin~ wire, first electrode supply~ Pre~erably, the
hand drill~is o~ pistol form with a hand grip at right
angles to the portion of the casing housing the elec-
trical motor, with a~ trigger switch within the hand
grip. The cover supports a right angle drive unit
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within a portion of the cover overlying the protruding
drill motor drive shaft and being directly mechanically
coupled to the drive shaft. The cover supports a wire
guide assembly via metallic blocks integrated to the
right angle drive unit. Wire guide assembly blocks
support a pair of laterally spaced, aligned cylindrical
bushin~s through which the fine wire second electrode
passes, and across the gap therebetween. The aligned
bushings are in juxtaposition to a drive wheel coupled
directly to the right angle drive unit. The wire is
positioned within a peripheral groove on the drive
wheel whose axis is at right angles to the axis of the
bushings and the fine wire electrode passing there-
through. One wire guide block mounts an idler wheel on
a pivotal arm and resilient means are provided for
resiliently pressing the idler wheel, through the arm,
against the drive wheel and pxessing the fine wire
electrode within the groove of the drive wheel to
affect frictional pulling of the wire from the spool.
The blocksA may be formed of conductive metal and may
function as a terminal for a low voltage DC cable from
the DC supply source. Further, the contact tube may be
of metal and be directly supported and fixed to one end
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of one conductive block, in alignment coaxially with
one of the wire guides. A l'TIi coupling may be inte-
grated with the contact tube and the conductive block
and coupled to a source of inert shielding gas for
supplying an inert shielding gas to the contact tube so
as to surround the arc at th~ emergence of the fine
wire second electrode from the contact tube.
One or more VELCRO ~ or buckled straps may
releasably mount the covar to the hand drill casing
portion housing the electric drill motor. The electric
drill motor may be any standard AC or DC rechargeable
unit operating on any convenient and standard power
source at any convenient speed while two 12 volt lead
acid storage batteries may constitute the source of DC
potential for effecting the arc between the first and
second electrodes.
BRIEF DESCRIPTION OF ~HE DR WINGS
Figure 1 is a side elevational view of the MIG
weldex attachment and an electric hand drill to which
it is attached and forming a preferred embodiment of
the present invention.
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Figure 2 is a side elevational view, partially
broken away of the drill and attachment shown in Figure
1, with the cover removed.
Figure 3 is a bottom plan view of the assembly of
Figure 2.
Fi~ure 4 is an electrical schematic diagram o a
MIG welding system utiliæing the attachment shown in
Figures 1 through 3, inclusive.
DESCRIPTION OF THE PRE~ERRED EMBODIMENT
. . _
RPferring to the drawings, and particularly to
Figures 1, 2 and 3, there is shown a MIG arc welder
attachment 10 constituting a preferred embodiment of
the present invention as mounted to a conventional
alternating current electric hand drill indicated
generally at 12. Alternatively, the hand drill may be
DC powered. Th~ MIG arc welder attachment forms a
preferred embodimen~ of the present invention and
constitutes an accessory to the ordinary electric hand
drill 12. while all MIG welding equipment is inherent-
ly versati~e in its ability to achieve good quality
results in a wide variety of materials, the extreme
simplicity of the MIG welder drill attachment 10 is
consistent with and conducive to this versatility. By
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utilizing attachment 10, it is easy to change loads,
tips, gases, polarity, and above all, welding speeds.
The ability to vary speed (or amperage) while welding,
is a eature of the finest and most expensive welders.
In the past, this invariably required the modification
of one circuit in order to vary another circuit render-
ing the control system electronically complex. In
contrast, the proliferation of variable speed electric
motor drive hand drills insures this feature utilizing
the MIG welder attachment of the present invention.
Moreover, the user has the option of selecting from a
variety of drills for speed, balance~ weight, di-
electric quali~ies, etc. For example, the drill 12 may
constitute a drill manufactured and sold by Black and
Decker under trade designation 3/8" VSR (Variable Speed
Reversing). The chuck normally borne by the drill
motor shaft 24 may be eliminated, thereby moving the
bal nce of the tool aft. As seen in Figures 1 and 2,
the drill casing 14 which is preferably formed o~
electrically insulating material has, projecting
downward therefrom, an integral handle 16 or hand grip
bearing a trigger switch 18. The trigger switch
includes solid state circuitry (not shown) for varying
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the current flow through the windings of the electrical
motor 28, Figure 2 so as to vary the output speed of
the drill output shaft 24 which projects outwardly from
casing 14 at the end of the drill gear speed reduction
unit 22. An electric drive motor section 20 of casing
14 carrie~ internally the electric motor 28. Conven-
tionally, an electrical cord 29, which may receive
current from a 110 volt AC electrical source (not
shown), extends from the bottom of the handle 16 or the
drill may be powered by internally contained DC batter-
es ~
In terms of the conventional AC hand-held and
relatively inexpensive drill 12, there is believed to
be no further need of explanation of the drill or its
nature of operation. Pressing the switch 18 inwardly
into the handle 16 energizes the electrical drive motor
28 and drives it at variable speed depanding upon the
amount o~ retraction of the trigger 18.
The present invention is directed to the MIG arc
welder attachment 10 which is constituted principally
by a cover assembly 30 housing all o~ the components
and including flexibl~ upper dielectric concave cover
32, overlying the top, configured to and partially
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surrounding the cylindrical drill casing 14. Cover
center portion 32a extends over the full length of the
drill casing and cover 32 terminates in ends 32b, 32c
which extend beyond the drill casing, at respective
rear and front ends thereof. The cover assembly 30 is
completed by a lower dielectric cover 34 which is
removably or detachably mounted to the upper cover via
90 angle drive reduction gear assembly 38. As may be
appreciatedt since all of the components are either
borne by the upper cover 32, lower cover 34, or the
right angle drive reduction gear assembly 38 and since
these elements are fixed to each other, a simple
mechanical expedient may be employed or detachably
coupling the MIG arc welder attachment 10 to the hand
drill casing 14, specifically via the drill's chuck or,
by removing the chuck, via the drill's spindle. As
illustrated, tha upper cover 32 is of inverted U shape
in transverse section with paired sidewalls of center
section 32a being slotted at vertically aligned posi-
tions through which slots 32 pass a VELCRO ~ strap 37
to frictionally lock the upper cover 32 closely abut
the cylindrical drill casing 14. Additionally, a
mechanical connection is effected between the drill
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output shaft 24 and the drive reduct.ion gear assembly
38 so that the attachment 10 and its components are
firmly mechanically attached to the hand drill 12 for
operation of the MIG arc welder utilizing these compo-
nents. A 90 angle drive gear assembly housing 40 is
composed of laterally spaced, inverted L shape plates
39 screwed to opposite sides of transverse blocks as at
43, 45 and 47. Blocks 43 and 47 include suitably,
horizontal and vertical bores 49 and 51 respectively
within which are positi.oned multiple sleev~ bearings
53. Bearings 53 xotatably support shafts 55 and 57
which terminate in a pair of bevel gears 59 and 61,
respecti~ely, which gears are enmeshed and which are at
right angles to each other. Shaft 55 bears a tapped
hole within its end remote from bevel gear 59 which
receives the drill shaft 24. Drill output 24 shaft is
threaded at its end and preferably threaded into angle
drive thread of shaft 55 for the right angle drive
reduction gear assembly 38. Right angle shaft 57, at
its end opposite bevel gear 61, fixably mounts a single
cylindrical drive wheel 65. Drive wheel 65 terminates
in a threaded end 67 which is threaded into a tapped
bore 69 of shaft 57. A lock nut 71 is threaded to the
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threaded end 67 of the drive wheel to permit an axially
adjustable threaded coupling between drive wheel 65 and
its driving shaft 57. The drive wheel 65 is given a
certain diameter and is provided with a circumferential
groove 69 on its periphery sized to the diameter of a
consumable ~ine wire electrode 900 Wire electrode 90
is driven by being compressed within groove 69 by an
idler wheel 54 whose periphery presses with variable
pressure against the periphery o drive wheel 65 and
sandwiches the wire electrode therebetween~
In order to effect that action, a consumable fine
wire electrode feed block assembly, indicated generally
at 42, is effectively coupled to the right angle drive
reduction gear assembly housing 40, specifically to the
lower end of that housing. Feed block assembly 42 is
composed principally of left and right side block 42a,
42b, respectively, Figure 2, which are spaced rom each
other, and which are of inverted L shape configuration
forming a relatively large rectangular cavity 73
therebetween. The blocks 42a, 42b are provided with
cylindrical bores 46 within which are inserted cylin-
drical wire guides or bushings 44. At right anyles to
bores 46, are tapped holes 75 for side blocks 42a, 42b
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within which are threaded set screws 77. The set
screws may be loosened to permit insertion of the wire
guides or bushings 44 within bores 46, or to adjust
them a~d the set screws are then turned down to lock
the bushings in axially spaced positions. The bushings
may be shifted axially, the purpose of which is to
create a gap G of a certain width between conical ends
44a of the respective bushings 44, supported by the
left and right side blocks 42a, 42b. The bushings
include small diameter axial bores 45, sized slightly
larger than the diameter of the consumable fine wire
electrode 90 which passes therethrough and which is
positioned so as to project within the groove 69 of the
drive wheel 65. In order to insure frictional drive of
the fine wire electrode 90, and the pulling of the wire
electrode 90 from its source, the idler wheel 54 is
mounted for rotation a~out is axis on an axle or pin 56
fixed to idler wheel mounting arm 50. In turn, one end
50a of the idler wheel mounting arm 50 is pivotally
mounted by~way of mounting screw 52 to the bottom of
right side block 42b, Figure 3. Additionally, an
adjustable tension spring 110 has one end affixed to a
left side block 42a on its bottom surface by means of a
.
2~q~
tension spring mounting plate 108 and screw 112.
Spring 110 has a second end coupled to tension adjuster
lever 115 carried by arm 50. Lever 115 pivots in the
direction shown by double headed arrow 114. Thus, the
adjustable tension spring 110 (or a rubber band equiva-
lent thereto) adjusts the idler wheel 54 compression on
drive wheel 65 which compression mu~t be higher for a
hard metal consumable fine wire electrode such as steel
in contrast to one formed of a soft metal such as
aluminum where low compression is exerted. By utiliz-
ing a drive wheel 65 which screws into the tapped hole
69 of the driven gear 61, it may be readily inter-
changed with other drive wheels for different wire
sizes and t~pes with the groove 69 within the periphery
of the driv~ wheel 65 varying in diameter to match the
diameter of the consumable wire electrode. Extending
outwardly of the right side block section 42b and
mounted thereto is an electrode nozzle assembly indi-
cated generally at 72. Assembly 72 is coupled to block
42 via a c~nductor indicated generally at 64, forming a
part thereof. Conductor tube 64 is composed of a pair
of external threaded p~pes 66, 68 coupled together by a
"T" coupling 70. Bore 46 within right side block
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section 42b is tapped so as to receive the threaded end
of pipe 66. The electrode nozzle assembly 72 may
constitute a nozzle assembly such as that sold wnder
the trade name TWECO. It comprises a nozzle 76 having
a small diameter nozzle bore 88 and counter bore 82
leading to an insulator cavity 84 housing insulator 85.
Further, a gas diffuser 86 is carried within counter
bore 82 and bore ~8. To the left, Figure 2, a further
counter bore 87 of nozzle 76 is threaded and sized to
the external thread of pipe 68. "T" coupling 70 is
connected to hose 98 supplying a shield gas to elec-
trode nozzle assembly 72.
Further, bore 46 of left side block 42a carries a
terminal 89, which is connected to one end of a wire
guide hose 48 of plastic material. The wire guide hose
48 is formed of plastic for insulating the consumable
fine wire electrode 90 as it passes to the right angle
drive reductian gear assembly for feed by drive wheel
65. The consumable fine wire electrode 90 is stored in
coil form ~on a spool 92 which mounts for rotation
hori~ontally about its axis on axle 94 within rear end
32b of the upper cover 32. In that respect, oppositely
aligned paired holes 96 within the upper cover
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sidewalls suppor~ the spool 92 for rotation with the
wire being pulled off the spool due to the frictional
drive between the drive wheel 65 and the idler wheel
54.
Turning to Figure 4, the welding system is sche-
matically represented in one form, in which the attach-
ment 10 is mounted to conventional electric motor
dxiven hand drill 12. In that respect, one end of DC
cable 100 has an exposed conductor 101 swaged to
terminal 102 with ~erminal 102 being mounted to the
conductive metal block 42a by way of a mounting screw
104 with a lock washer 106 interposed between the head
o~ the screw 104 and the face of the block against
which the terminal 102 contacts is in flush engagement.
A tapped hole 103 receives the threaded end 104a of
screw 104, Figure 2. The DC cable 100 attaches at i~s
opposite end to the positive terminal 122b, for in-
stance, of one of two lead acid auto or deep cycle
storaqe batteries 122 which are series connected. The
series connectian is made via a short length cable 123
from the negative terminal 122a of one battery to the
positive terminal 122b of the adjacent battery 122. In
turn, a further DC cable 120 connects at one end to
128~
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negative terminal 122a of the secund battery and
terminates in a mechanical clamp 118 which detachably
clamps to the workpiece 116 functioning as the first
electrode for the arc welding system. The consumable
fine wire second electrode 90 when positioned adjacent
to the workpiece 116 create~ arc 124 and the tip of the
fine wire electrode 90 is consumed in the process. The
speed of the weld and the arc power is controlled by
the drive speed of the electrical motor 28 for hand
drill 12 feeding th~ wire electrode to arc 124.
In addition, as shown in Figure 4, an inert or
other shield gas, if used, is fed via hose 98 to
surround the arc 124 by escaping from the small diame-
ter bore 88 of nozzle 76. The shield gas is supplied
form a tank or bottle 126 controlled by regulator 12
and flow may be shut off by either a manual valve or a
solenoid valve such as valve 130 and connected between
attachment 10 and the regulator 28.
With bevel gears 59, 61 sized to provide a 2 to 1
speed red~ction, the fine wire electrode is pulled
through the attachment 10 with ease. Variable speed
drive may be assured and with input provision of a 24
volt arc power source such as two ordinary 12 volt lead
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acid storage batteries, the fine wire consumable
electrode 90 may constitute a .045 inch flux core mild
steel wire which may be used without a shieldiny gas.
An inert/shielding gas may be employed as necessary. A
s~andard TW~CO No. 2 MI~ torch tip may form nozzle
assembly 72 readily mounted via its contact tube 64 to
the end of block 42 remote from the source of the wire
electrode 90.
Attachment 10 makes ready provision for changing
the drive wheels or capstans and adjusting the tension
on the idler wheel to suit dif~erent types of wire
electrodes being fed. Either polarity may be used and
drive wheel speed control is achieved by speed control
incorporated in the drill, sufficiently geared down to
the 2 to 1 by right angle reduction. A one-half inch
drive wheel provide~ a 1.57 linear inch of wire feed
per revolu~ion so that surges and uneven wire feed
speed are avoided when the speed is varied during
welding. The deep-cycle or auto batteries 122 may be
of the 80 amp hour type. As appreciated, it is simple
and quick to change loads, tips, gases, polarity and
speeds. Of course, as the diameter of the fine wire
electrode 90 increases, it may be necessary to us~ a
'llZ~4~
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higher speed 1/4 inch electric drill rather than a 3/8
inch electric drill. The invention has application to
300 and 600 RPM rechargeable drills with or without
speed control particularly for welding 1/8" al~inum by
reversing 90 an~le drive ~rom 2:l reductio~ to 1:2
increase in drive speed. Further, all 6 and 9.5 volt
DC drills can be run on 12 volts for more speed. The
applicant has found that it is both possible and safe
to have the drill running on a power source which is
entirely ind~pendent of the 24 volt arc power source.
The applicant has found that the common car battery has
so little internal resistance and such immense power
that one does not vary the arc voltage significantly by
attempting to vary the arc distance and so, fortuitous-
ly, an ordinary auto batkery happens to be an ideal
source of inherently stable arc voltage. As such, the
applicant derives the versatility of a variable speed
wire drive without expensive electr~nic complications
that are normally required when utilizing a common
electrical~source for both the wire drive and the arc
power. A DC battery such as an ordinary auto battery,
or several DC batteries in series such as batteries
122, Figure 4, may additionally function as the source
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of DC power to the drill motor of the 12 V DC electric
drill 12 in which case, the connection is made via line
29' as shown in dotted form and in which, the two
electrical wires 39 thereof connect to the positive and
negative electr~des 122b, 122a of a ~attery 122. In
such case, the arc source is formed ~y the two batter-
ies 122 in series, while the source of drive power for
the hand drill motor of hand drill 12 is a single one
of the ~atteries with the circuit including the drive
motor 22 being across a single battery and the circuit
including the arc 124 across both batteries.
It should be kept in mind that the ordinary
electric hand drill may be of the conventional 110 volt
AC t~pe. It may be 220 volt AC, it may be 12 volt DC,
rechargeable or any other powered hand drill capable of
feeding the consumable fine wire electrode. Further,
the consumable wire electrode (which is shown as
positive in Figure 4) may be of either polarity (i.e.
positive or negative) without affecting the motor drive
at all al~ since the motor drive is electrically
independent of arc power. Therefore, no changes are
required for the drill to which the welding attachment
is coupled. (In some units changing arc polarity
'IL~8Z~
- 28 -
causes the drive motor to reverse and this must be
adjusted or hy separate means).
While there has been described what is at present
considered to be the preferred embodiments of this
invention, it will be obvious to those skilled in the
art that various changes and modifications can be made
therein without departing from the invention, and it
is, therefore, intended to cover all such changes and
modifications as fall within the true spirit and scope
of the invention.
