Note: Descriptions are shown in the official language in which they were submitted.
FIELD OF INVENTION
The present invention applies to -the art of stud
welding and more particularly -to methods for welding s-tuds
having two or more ends and to the design of such studs.
BACKGROUND OF INVENTION
The present invention relates to stud welding methods
and, more particularly, to methods for weldiny, by the stud end
welding technique, a stud having a plurali-ty of ends which are
to be simultaneously welded to a workplece.
The stud end welding technique has been known and in
practical commercial use for many years. In this welding -tech-
nique, a single end of a metallic member, such as a threaded
bolt or the like, is welded to a metallic member generally
known as a base member by the application of sufficiently high
current passing through -the stud and across an arc between the
stud and the workpiece to create a molten pool of metal into
which the stud is ul-timately plunged and secured following
solidification of the molten pool.
There are many varia-tions of this technique. ~Iowever,
_ lv ~
the tcchnique is generally divided into two major categories, i.e. drawn arc
stud welding and capacitor discharge stud welding. In drawn arc stud welding
current is passed through the stud to be welded while in contact with the
workpiece and then lifted to create an arc between the stud and workpiece.
After sufficient time passes to permit the arc to create melting of the stud
and workpiece, the stud is returned to the workpiece into the molten pool of
metal. In this mode of welding, an arc shield is placed around the end of the
stud and in contact with the workpiece to contain the molten pool of metal to
form a weld fillet following solidification of the metal. This technique is
used for larger diameter studs or the conven~ional shear connectors in ranges
generally in excess of ~" of diameter.
The drawn arc stud welding technique generally employs a ro-mded,
square or rectangular configuration on the end of the stud to be welded. The
current density passing through the end of the stud being welded is relatively
low compared to capacitor discharge welding as will be discussed hereinafter
and is generally in the area of approximately S,000 amps per square inch.
The weld time for drawn arc stud welding varies depending on the application
and the diameter of the stud but i~ is generally in the area of approximately
.5 seconds for an average application for welding of a ~" stud. Thus, drawn
.~arc stud welding is generally considered to be a longer low current welding
process with essentially arc creation resulting in melting of the stud and
the workpiece with little or no significant instantaneous disintegration of
the end of the stud.
The capacitor discharge stud welding technique differs significant-
ly from the drawn arc stud end welding technique in many ways. In capacitor
discharge stud welding, the power source is not a continuous power source as
in drawn arc stud welding but is a
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3L~ 3
stored energy source 9UCll as -that from a bank of capacitors
which have been charged to a predetermined level before ini~ia-
tion of the welding cycle. Additionally, the studs utilized in
capacitor clischarge stud welding are usually of a small diameter
in the range of ~" or less and also inclucle a small diameter and
length welding tip on the end of the stud. The welding tip
serves to space the end of the stud to be welded from the work-
piece at the beginning of the welding cycle. Upon initiation of
the welding cycle, the readily available energy supply from the
energy source such as the capacitors is dumped throu~h the s-tud
at an extremely high current density r~sulting in complete d.isin-
tegration and vapori~ation of the welding tip. The disintegra
tion of the welding tip momentarily leaves the stud spaced from
the workpiece while ~n arc is established between the stud and
the workpiece substantially along the entire face of the stud
due to the high energy level of the capacitors.
In an average capacitor discharge stud welding envi--
ronment, the current density passing through the tip of the
welding stud is, momentarlly, in the range of appro~imately
10,000,000 amps per square inch. mhis flash of high density
current is substantially instantaneous and the entire weld cyele
for an average capacitor discharge welding cyele is approxi-
mately .003 seconds.
Capacitor discharge welding is used primarily but not
restricted to rather small studs, high production rates and with
thin sheet base material which cannot withstand the longer weld-
r;~'~ ing and heating cycles of a~c stud welding~ Additionally, the
weld strength of a capacitor discharge weld is somewhat less than
that of theJ;arc stud welding technique.
The stuc~ end welding technique, eithe~;,arc stud welding
or capacitor discharge stud welding, has not, heretofore, been
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1~L871~
successfully used in the welding of studs having two or more ends
v .. ,~ (~ 'c~-~
which~E-eq-~l-Ee to be welded simultaneously to the base mernber.
There are numerous stud configurations which have two or more
ends which are required to be welded and thus cannot utilize the
stud end welding techniaue. Examples of such studs are double
ended lifting hooks, handles and hold-down loops all of which
must be welded by electric or gas hand welding.
Another major category o~ stud which includes two or
more ends and which must currently be hand welded is the double
ended shear connector. A double ended shear connector is a
U-shaped metallic me~ber which is welded to an I-beam or the
li~e and is later embedded in concrete lying upon the I-beam to
provide a shear interconnection between the concrete slab lying
upon the beam and the beam itself.
There are basica]ly two or more types of shear connec-
tors in use in the industry today. One kind is the headed shear
connector which is an elongate rod like member having one end
weldable thereon and an enlarged flanged hea~ at the opposite end
This stu~ is generally of round configuration and of approximatel~
5/8 to 7/8 inches in diameter and is capable of being welded by
G~
the conventional~arc stud welding technique. Another design of
shear connector conventionally in use is a generally U-shaped
member of rectangular cross section of approximately eight gage
thickness and 1 inches wide with a height of approximately 3
inches and a separation of the two legs of approximately ~ 5/8
inches. This class of shear connector may be referred to as the
double ended shear connector whereas the single elongate shear
connector is generally known as the headed shear connector.
~ double ended shear connector of less total metal
weight than a headed shear connector can still provide equal or
greater shear resistance when welded in place. Thus, the
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3~87~3
material costs and performance of a double ended shear connector
is superior to that of a headed shear connector. However, -the
double ended shear connec-tor suffers from the disadvantage ln
that it must be manua~ly welded and has not, heretofore, been
ca~able of being welded by the stud end welding technique. The
hand welding technique ls more time consuming than the stud end
welding technique and, additionally, the skill and time required
to manually weld the double ended shear connector is greater than
that required of the operator for the stud end welding technique
with the further consbquent addition of expense in the trade
utilized. According-ly, there is a real industry need for a
method and apparatus to ~Jeld double ended shear connectors by the
stud end welding technique.
Different techniques have,in the past, been attempted
to arrive at apparatus and methods to successfully weld multi-
ended studs. The foremost problem encountered with the welding
operation of double ended studs is the initiation of an arc on
both legs of the studr If the arc initiates on one leg and
nothing is done to enhance initiation on the other leg, the arc
will continue to operate on the first l.eg and the second arc
will not be initiate~. There are two main reasons for this
occurrence. First, the operating arc will cause a large voltage
drop from the open circuit voltage. This will make it increas
ingly difficult to break down the air gap resistance at the
unarcing leg. Secondly, the heating of the arcing leg will lowex
the work function and increase the elec-tron flow at that point,
effectively lowering the resistance. These two effects comhine
to make it extremely difficult to initiate a second axc at the
remaining legs once there has been the estahlishment of a firs-t
arc.
The desired solution to this problem of single arc
.,._
initiation is to initiate arcs on both legs of the stud simul-
taneously. However, with the conventional stud welding apparatus
and method of stud liftoff initiation, it is nearly impossible
to maintain equal initial arc gaps. Even a very small difference
in sap size works to prevent one arc from starting b~cause the
breakdown voltage can be in the order of 1,000 volts/mil. in air.
Both legs must leave the base plate surface at exactly the same
time or only one arc will occur.
Assuming that dual arcs can be initiated, the second
problem encountered is to insure that equal welding takes place
on both legs of the stud. Essentially, this means that equal
welding currents must be maintained in both legs. Dlfferences
in cuxrentreadily result from such conditions as oxides on the
S~ ,Je
work surface or -s~t-t-~e changes in metal trar~sferred through
either arc. ~ccordingly, it is extremely difficult if not
impossible to maintain equal current density in the welding legs
and thus, uneven melting occurs with the consequence of one leg
of the double ended stud ~ ~g not being sufficiently welded.
One attempt made at solving the problem of establishing
and regulating arcing between the two legs of a double ended
stud was to place an insulator between the two lègs and apply
separate current sources to the welding legs. Such a concept
is disclosed in the U. S. Patent No. 2,788,434. This solution
suffers the rather critical disadvantage of the two legs of the
stud being separated by a weak insulator between the -two legs
which seriously reduces the strength of the stud.
Another solution tried was to vary the geometry of the
ends of the double ended stud by u-tilizing su~h configurations
as chisel points as well as other configurations such as pointed
ends, rounded ends and square ends. In some cases, fluxes were
used to help lo~er the ionization potential and provide a
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11~714;3
shielding atmosphere. The use of differing stud end confiyura
tions and Eluxes did not prove successful. In a few cases, two
arcs would occur at the two legs. However, one arc was always
larger than the other. The smaller arc usually produced no
melting of either the stud or the base plate. The lighter arc
generally became nothing more than a brief spark which caused
slight heating of the stud and the base plate. The utilization
of fluxes aided slightly in the process but still did not result
in sound commercially acceptable welds. Even compounds that
exhibit lower ionizatl~on potential and higher electroconductivity
than iron, although aiding in establishing arcs on both stud
legs, did not effectively and consistently initiate the required
dual arcs.
Another approach which has been investigated but found
unsuccessful for doub,le ended stud weldirlg is that based upon
the principles of arc gap effect and arc initiation and thermal
emissivity at elevated temperatures. In this approach, the
hypothesis is that, if the arc could be briefly extinguished on
the operating leg by removal of the welding power, then the
arc could be reignited on the opposite leg by virtue of that
being the shortest a,rc path. It was postulated that, in order
for the shorter path effect to dominate, the time that the arc
was exti.nguished would have to be sufficient to allow a complete
dissipation of the electron cloud and for the arc atmosphere to
cool below levels where thermal igni,tion effects dorninate.
In this approach, the power supply providing the weldin
current to the double ended welding stud was operated through a
controller in a manner such that the welding current was rapidly
turned on and off to -the welding stud in bursts of energy spaced
one from another in the order of 100 milliseconds. In some
instances, dual arcing at bo-th legs of the double ended stud were
~ ~7~
achieved. However, control of positioning the stud with
respect ~o the workpiece was extremely delicate and difficult
and the control of the arcing between the two legs was erratic
and generally unsatisfac-tory welds resulted.
SUMMARY OF INVENTION
The foregoing problems encountered in weldi.ng of studs
having two or more ends by the stud end welding technique are
overcome by the studs, methods and apparatus as hereinafter
described.
1.0 The invention provides the method of simultaneously
stud welding the ends of a multi-ended metallic stud to a
meta].lic base member comprising the steps of: providing on each
of the stud at least one elongate relatively thin metallic
extending projection; applying a controlled pressure upon the
stud in the direction of the base member; applying an electrical
potential to the stud from a continuous current power supply;
bringing the metallic projections into contact with the metallic
base member; and controlling the pressure on and the rate of
advance of the stud toward the workpiece and controlling the
electrical potential upon the stud all in proportion to one
another and to the configuration of -the projections and stud
ends to (1) provide a current density in the projections to
essentially immediately and simultaneously disintegrate the pro-
jections to establish arc initiation at all ends of the metallic
stud and (2) thereafter maintain a continuous arc at all ends
of the metallic stud of duration and current density a-t leas-t
equaling that of drawn arc stud welding to maintai.n molten
metal at each end thereof until the ends of the stud corne into
contact with the base material. In larger s-tudsl two or -more
projections or wires can be employed for each stud end.
The stud welding apparatus described herein includes a
chuck for securing the stud which is of configuration comple-
'~
-8-
mentary to the upper portion of the double ended stud. The
chuck maintains the welding stud in proper orientation with
respect to the weld base in order tha-t the projections will
strike the weld base essentially simultaneously. The welding
apparatus further includes a welding gun footpiece which secures
two arc shields properly in place in alignment with the welding
ends of the double ended stud.
There are four methods that can be employed in double
end welding each of which employs a projection or projections
1/16" in diameter or greater by 1/16" long or longer or conical
in nature.
One method entails holding the stud away from the
work surface, establishing a welding voltage between the stud
and the work then advancing the stud toward the work until the
projection or projections contact the work whereby arcs are
established
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between both stud ends and the work and then continue the forward motion of
the stud until contact between stud end and work occur extinguishing the arcs.
A second method is similar except that when contact occurs and
arcing begins, the resultant current flow in the circuit energizes a current
relay which actuates a circuit to stop the forward motion of the stud for a
time suitable to provide adequate melting of stud and work and then plunging
the stud into the molten pool completing the weld.
A third method is to initially contact the stud projection or
projections with the work under sufficient pressure to insure contact then
connecting them to a source of welding power, creating an arc between both
ends of the stud and the work, and then advancing the stud to the work at a
controlled rate until contact between stud and work is made thus completing
the weld.
A fourth method is similar to the third excep-t that when the arcs
between the stud ends and the work is initiated, the stud is held immobile for
a predetermined time then plunged into the molten pool completing the weld.
I'he welding power supply utilized is a continuous current welding
supply. The welding power supply is operated in a manner to provide welding
current density across the welding tip projections or wires of a density suf-
ficient to disintegrate each projection permitting consequellt arc initiation.The relatively thin projection assures arc initiation at both legs of the
double ended stud. Both arcs are maintained through high current densities
while the stud is lowered into the resulting molten pools whereupon the arc
is extinguished and the current swltched off.
Other features, advantages and variations of the studs, apparatus
and methods of multiended stud welding of the present invention will become
apparent to those skilled in the art form
11871'13
the 1 tailed description thereo~ whicll follows talcen in conjunc- ¦
tion with the drawing.
DETAILED DESCRIPTION OF DRAWING
Figure 1 is a perspective view, partially in section,
of a double ended shear connector in accordance with the present
invehtion welded in place in conjunction with a supporting
member and concrete slabi
Figure 2 is an elevational view of a double ended
shear connector in accordance with the present invention;
Figure 3 is a perspective view of a portion of the
welding apparatus, shear connector and arc shields prior to
welding in accordance with the present invention; and
Figure 4 is a perspective view of a portion of the
welding apparatus and shear connector following welding thereof.
DETAILED DESCRIPTION OF INVENTION
. . ...
The foregoing detailed description of the studs,
methods and apparatus for welding studs by the stud end welding
technique wherein the studs have two or more ends to be simul-
taneously welded will be undertaken in respect to a double
ended stud of the double ended shear connecto`r type essentially
as shown in Figures 1 and 2. However, it is to be understood
that the present method and apparatus applies to and may be
utilized in the welding of other configurations of studs as well
as studs having more than two ends to be welded.
A double ended stud of a configuration suitable for
use as a double ended shear connector is shown in Figures 1 and
2 o~ the drawing. The double ended stud 10 is shown utilized
~? as a shear connector and is shown in Figure~ 1 we]ded in place
upon an I-beam 11.
~~
In use, -the stud 10 is welded to thc I-beam 11 directly upon the
I-beam or, in some instances, through decking 12 which is utili~ed as the
bottom form member and protection for a concrete slab to ultimately be poured
upon and supported by the I-beam 11.
A shear connector 10, welded in place, is shown partially embedded
in a slab of concrete 13 as it would appear in actual use. The shear connec-
tor 10 provides an interconnection between the I-beam 11 and the slab 13 to
resist shearing action of the concrete slab 13 in respect to the supporting
beam 11 in a heretofore known manner.
The details of the shear connector design of double ended stud of
the present invention is shown in Figure 2 of the drawing. The shear comlector
stud 10 includes two welcl ends 14 and 15. The ends 14 and 15 oE the stud are
disposed in a common p]ane.
A pair of stud legs or portions 16 and 17 of the stud adjacent
each end 14 and 15 thereof are formed straight. This straight leg or portion
is disposed generally perpendicular to the weld base UpOII which the stud is to
be welded and is necessary for cooperation with the configuration of the arc
shields which are used in the process and which will be described hereinafter.
The remainder of the stud 10 includes a stud body 18 disposed
between the legs 16 and 17 which may be of differing configurations from flat
to U-shaped. In a preferred embodiment, the stud body is of a parabolic
configuration.
The parabolic configuration of the remaining portion or body 18 of
the stud provides for ready orientation of the stud in a stud welding chuck
due to the noncircular configuration of the parabolic curve. Additionally,
the parabolic configuration is of a shorter profile than a circular configur-
ation and results in a material savings of approximately 17% to 25% over a
circular configuration of -the same height without distracting from the shear
strength capabilities of the stud.
The cross section of the stud 10 may be of any desired configur-
ation, i.e. round,eliptical or rectangular. In a preferred embodiment, the
stud is of rectangular configuration as shown in ~igures 1 and 2 of the
drawing.
The weld ends 14 and 15 of the stud 10 are provided with elongate
relatively thin projections or wires 19 extending parallel to the longitud-
inal axis of the legs and Perpendicularly from the weld face of the weld
ends 14 and 15 and thus, extend perpendicular to the weld base upon which the
stud is to be welded. The projections or wires 19 may be formed of the parent
metal of the stud during manufacture of the stud.
Alternately, the projections or wires may be affixed to the stud
by any suitable means such as staking or welding. The projections or wires
may be formed of a mild steel ma-terial such as the welding stud 10 itself or
medium carbon or stainless steel.
The length of the projections 19 depends upon the configuration and
general weld area of the end ofthe stud tobeweldecl. In smaller cliameter or cross
sectional area studs, a projection of approximately 1/16 inch or greater is
acceptable. In studs of larger cross sectional area, the leng-th of the
projections 19 will range up to approximately 1/2 inch. The cross sectional
configuration of the projection 19 may be of any desired configuration such
as circular or rectangular~ By way of example, the cross sectional configur-
ation of a rectangular projection may be in the area of 3/16 inch square
down to the range of approximately 1/16 inch square or the equivalent cross
sectional area in a round cross sectional configuration.
The welding gun apparatus including the stud chuck
118~143
and the weld gun footpiece utilized in accordance with the
¦ present invention are shown in Figures 3 and 4 of the drawing.
The welding gun 20 utilized may be generally of -the hand held
type utilized for welding of conventional shear connectors.
Such a welding gun includes two legs ~1 extending from the
welding gu~ and which provide the support for a footpiece 22.
The footpiece 22 provides the support for two arc
shields 23. The arc shields 23 have an internal configuration
complementary to the configuration of the stud 10 to be welded.
In the embodiment shown, the arc shields 23 are of a rectangular
configuration.
The arc shields 23 are designed to fit into receptacles
24 in the footpiece 22 in the manner shown in Figure 4 of the
drawing. A relieved.section 25 on the arc shields permits the
upper portion 26 of the arc shield to fit into the receptacles
24 of the footpiece 22 with the lower portion of the arc shields
projecting underneath the footpiece 22. In this manner, when
the footpiece is placed in welding position, the arc shields
are held in place between the footpiece and the workpiece as
essentially shown in Figure 4 of the drawing.
The welding gun chuck 27 of the apparatus of the
present invention inclù~es a backing plate 31 which is secured
at it5 upper central portion to the gun extension rod 28 by means
of a conventional threaded arrangement. The i~side configuration
of the backing plate 31 is of a configuration complementary to
the outside configuration of the upper portion of stud 10 to be
utilized with the chuck.
Two chuc}c jaws 29 are disposed on either side of the
backing plate 31. Either or both of the chuck jaws may be
secured to the backing pla-te 31 by means of yieldable threaded
fastener-spring arrangements 32. The width of the.backing plate
~_ ~ ~_
~1871~3
31 is slightly less than the width of the stud 10 to be utilized
in -the chuck. ~he yieldable spring--threaded fastener arrange-
ments 32 thus provide the yield of the chuck jaws 29 to permit
snug fi-t of the stud 10 within the backing plate and chuck jaws
when placed in welding positlon.
The stud 10 is loadecl into the chuck assembly 27
upwardly thro~lgh the opening in the footpiece and into the chuck
assembly. The complementary configuration of the inner surface
of the bac!cing pla-te 31 will permit proper alignment of the
stud within the chuck and in respeck to the weld base upon which
the stud is to be we~ded in all cases where the s-tud 10 is not
of a complete circular configuration. In the particular embodi-
b,~/y ~r
men-t shown, the~upper portion 18 of the stud 10 is of a
parabolic configuration which provides for ready orientation of
the stud ends 14 and-15 and projections 19 perpendicular to the
weld base and the extremities of the projections 19 being dis-
posed in a plane parallel to the weld base.
An alignment pin 33 may also be used to insure proper
alignment of the stud 10 with respec-t -to the wor]cpiece. The
alignment pin 33 is secured at its one end axlally to the
extension rod 2~. The alignment pin 33 extends downwardly below
the backing plate 31 and is adapted to cooperate with an align-
ment aperature 34 formed into the stud 10 as shown in Figures 2
and 30 The length of the alignment pin 33 is such that the
lower end of the alignment pin 33 will mate with the aperture 34
in the stud as the stud is being inser-ted upwardly through -the
footpiece in-to the chuck 27.
Prior to welding, the stud 10 is inserted through the
footpiece into tne chuck 27. The arc shields 23 are positioned
in place within the footpiece and the entire assembly is then
placed in position for welding as shown in Figure 4 of the drawin ¦.
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In one embodiment, the stud welding gun 20 includes a
lift solenoid which will retract the extension rod 28 to position
the stud projection above the workpiece~ The lif-t mechanism of
the gun is also designed such that the extension rod is biased
toward the wor]cpiece. An extension rod locking mechanism is
also provided which is capable of locking the extension rod at
any position uvon application of a control signal to the locking
mechanism, i.e. when the projections come into contact with the
workpiece.
The stud wel~ing gun may also include an extension rod
damper which is variable in nature and may be adjusted to control
the rate of plunge between 1/4 to 3 inches per second.
The extension rod biasing means may be of different
spring rates. In one embodiment, the spring pressure is
approximately 40 pounds upon the chuck.
The stud welding gun of the present invention,
depending upon the embodiments utilized, permits four different
welding methods.
The first welding method utilizes the lift solenoid and
the biasing spring of 40 pounds pressure. The stud is retracted,
stud energized and stud plunged. Upon the stud tips contacting
the workpiece, arc inltiation occurs. The extension rod biasing
means urges the stud toward the workpiece until contact of the
stud ends and workpiece extinguish the arcs.
In the second method, the extension rod locking
mechanism is included along with the lift solenoid. When the
energized stud tips contact the workpiece, this is sensed and
the locking mechanism energized for a time suitable to provide
adequate melting of the stud and workpiece. Thereafter, the
extension rod biasirlg means plunges the stud in-to the molten
pool completing the weld.
~_ . . ~
In the third method, the gun lift solenoid is not used but the gun
includes the extension rod damper, and extension rod biasing means. The stud
tips are engaged with the workpiece and the stud energized to initiate arcing.
The s-tud is advanced toward the workpiece at a controlled rate under control
of the extension rod damper until contact between the stud and workpiece
extinguishing the arcs.
In the fourth method, the extension rod biasing means and extension
rod locking means are used without the lift solenoid. The stud tips are
engaged with the workpiece and the stud locking mechanism engaged. After the
stud is energized, the locking mechanism holds the stud immobile for a
predetermined time after which the stud is plunged into the molten pool
extinguishing the arcs.
The current density drawn from the welding power supply is selected
for the particular projection configuration and method being utilized to
permit the current density in the projections to be sufficiently high to cause
disintegration or explosion of the projection in 5 - 10 milliseconds. This
current density is significantly higher thanthat experienced in normal drawn
arc stud welding which essentially provides only an arc without particular
disintegration of the end of the stud being welded. ~lowever, the weld current
density is controlled at a level signiEicantly below that of the capacitor
discharge welding whic]l essentially causes almost instantaneous destruction
of the entire smaller welding tip associated with the conventional capacitor
discharge studs.
By way of example, with a stud having an approximate 1/16 by 1/16
inch square projection cross section, the power supply may be set to deliver
approximately 3,500 amps. Under this condition, the current density experi-
enced in the projection on the
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~ 3
stud will be in the order of l,000,000 amps per square inch.
This is approximately l/10 of the current density experienced in
a typical capacitor discharge welding cycle but 200 times the
current densi-ty experienced in a typical arc stud welding cycle.
The control of the pressure upon the stud, the rate
of plunge and the current density must be maintained all in pro-
portion and ratio to one another and to the projection configura-
tion to provide for arc initiation. ~ll of these factors are
matters which can be ascertained for given stud and welding pro-
jection configurations.
The welding controller may be calibrated to time-out
and discontinue the weldiny current slightly before, at or after
the stud ends reach the workpiece. In a preferred embodiment,
the weld current is maintained on after the stud reaches the
workpiece for a slight duration of time, which procedure is known
as a hot plunge.
The welding time between the moment of contact of the
projections o the stud and the discontinuance of welding current
depends upon the length and cross sectional area of the projec-
tions as well as the current setting. By way of example, a pro-
jection of l/~ inch in length and of approximately l/16 inch
square configuration results in a welding c~cle time of between
.2 to .3 seconds. When a l/2 inch length projection is utilized
Wit}l a l/16 inch square cross sectional projection, the welding
cycle is from approximately .4 to .6 of a second. sy way of
comparison, the welding cycle time of conventional~capacitor dis-
charge welding is .002 to .004 seconds while conventional arc
stud welding is .100 seconds or greater.
In a preferred embodiment, a positive ground connection
to the workpiece is preferred. Under these circumstances as
above descrihed, it is found that the base metal contributes to
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11617~L43
.'
a major portion of the weld joint with a lesser portion of the
weld fillet material being formed Erom the stud.
From the foregoing description of a preferred embodi-
ment of the double ended stud welding stud, apparatus and methods
in accordance with the present invention, it will be appreciated
that the apparatus and method as well as the s-tud described
provide an effective and reliable method for effecting simul-
taneous welding of a stud having two or more weld ends by the
stud end welding technique. The description of specific embodi-
ments and parameters has been made by way of illustration and
not by way of limitation and the scope of the invention is to
be interpreted in view of the following claims.
What is claimed is:
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I -18~
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