Note: Descriptions are shown in the official language in which they were submitted.
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Background of the Invention
Conventional electrical resistance welders for use
with lead storage batteries can be thought of as com-
prising an electrode means for contacting the lugs as
parts to be welded together and for conducting current
thereto, and power means for supplying a fixed amount
of current to the electrode means. The electrode means
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comprises at least two welding jaws, each having an electrode
tip portion. The welding jaws move together to press the lugs
together with the electrode tip portions making contact with the
lugs. These conventional electrical resistance welders ignore
some of the variables present during the welding process that
effect the making of constant and repeatable welds. For example,
when the electrode tips move with the welding jaws to contact
the lugs, the exact electrical res;stance of the combination of
welding jaws, electrode tips and the contacts that the tips make
with the lugs is unknown. Also, surface oxidation, lug composi-
tion, and the pressure of the jaws on the parts are all impor-
tant factors in determining the resistance. In addition, a
certain amount of heat is dissipated into the atmosphere from
the lugs and parts of the welding apparatus. Hence, if current
is applied to the electrode tips without factoring in the
variation of resistance from weld to weld, then constant repeat-
able welds become more difficult if not impossible to attain.
Apparatuses and methods for making intercell connections
within batteries through the use of electrical resistance
welding are disclosed in U. S. Patent Nos. 3,313!658; 3,388,005;
3,589,948; 3,687,734; 3,723,699; 3,793,086; 3,798,Q71; and
3,869,316. Methods for making battery terminals are described
in U. S. Patent Nos. 3,303,056i 3,457,118; 3,849,203; and
3,874,933. None of these references disclose provisions or
methods for measuring the resistance between the weldi~ng means
and the lugs for each weld which is to take place, and usin~
this measurement to control the amount of current which is to
be delivered to the lug contact surfaces where the weld will
take place.
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508
Summary of the Invention
According to one aspect of the invention there is
provided an electrical resistance welding apparatus
for making repeatable welds in lead storage batteries
between battery lugs disposed on opposite sides of plastic
partitions and pressed together to contact one another
therethrough, comprising: (a) welding means for welding
together a plurality of battery lugs, comprising: (i~
electrode means for contacting said lugs and conducting
current thereto; and (ii) power means electrically con-
nected to said electrode means for supplying a fixed
amount of current to said electrode means for conduction
to said lugs; (b) electrical resistance measuring means
electrically connected across said power means for meas-
uring the electrical resistance of said electrode means
in contact with said lugs; and (c) an interface controller
electrically connected to said resistance measuring means
and to said welding means for determining said fixed amount
of current and the time over which said current is to flow
in response to said measurement of electrical resistance,
and for communicating the same to said welding means,
According to another aspect of the invention there
is provided a method of making repeatable welds in lead
storage batteries between battery lugs disposed on oppo-
site sides of plastic partitions and pressed together to
make contact therethrough, comprising the steps of: (a)
providing welding means for applying current to said lugs;
~b) moving said welding means to contact said lugs; (c)
measuring the electrical resistance of the lugs through
a portion of said welding means in contact with said
lugs; (d) determining the amount and time of current flow
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required to form said welds in response to said resist-
ance measurement (e) controlling the amount and time of
current flow delivered by said welding means to said lugs
in response to said determination; and (f) withdrawing
said welding means from said lugs.
Applicant's invention is based on the following
equation:
H = (I ) (R) (T) (K)
where H equals the heat needed for a weld; I2 equals the
current squared; R equals the resistance of the parts
involved in making the weld; T equals the time needed
over which the current is applied to make the weld; and K
equals a proportionality factor relating H to the other
factors, K relating to the heat dissipated into the
atmosphere from the parts involved in making the weld.
A good weld can not be made without the proper amount
of current being delivered within the right amount of
time. If a certain amount of power is not present, then
the heat can not be generated to melt the lead and create
a fusion zone at the point where contact is made between
the lugs. In order to be sure that the proper amount of
current is delivered, the resistance of the electrode
means in contact with the parts or lugs to be welded
together must be known. This resistance can be made
of several factors, for example, the resistance of the
welding jaws to the electrodes tips; the resistance of
the electrode tips to the welding surface on the lugs;
surface oxidation of the lead lugs; the composition of
the various parts; the amount of antimony present; the
pressure exerted on the lugs to squeeze them together, etc.
The only factors whlch are undecided once the heat H
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and the factor K are either analytically or empirically
determined are the factors I2, ~, and T. Applicant's
system measures R and leaves only I2,T to be determined.
I ,T can be regulated by controlling the transformer
output over a period of time. R is determined by the
proper measurement of the resistance of the electrode
means in contact with the lugs or parts to be welded
together.
In the preferred embodiment, the measured resistance
values are sent to an interface controller which uses this
information to determine the correct amount of current and
the time over which the current is to flow. This infor-
mation is sent to the transformer controller which then
applies a voltage to a transformer primary and a current
begins to flow through the parts to be welded together.
In one embodiment of the invention, as the current is
flowing during the making of the weld, it is measured
by a current analyzer and the current value compared with
the current value predicted by the interface controller.
If the measured current is different from the current
determined by the interface controller, the control of
the transformer through the transformer controller is
adjusted by a command by the interface controller.
In the preferred embodiment, after the weld is com-
plete, the resistance is remeasured if it is too high, the
entire process is repeated. If after the second attempt
at welding, the resistance is still too high, an indica-
tion is made on the battery by a marking means, such as
an inking system. This marking is sensed by a reject
mechanism which~ in turn, rejects the battery from further
processing.
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It is an advantage of the present invention, at least
in preferred forms, that it can provide an electrical
resistance welding apparatus for making repeatable welds
in lead storage batteries between battery lugs disposed
on opposite sides of plastic partitions by measuring the
electrical resistance between the lugs that are to be
welded together and by controlling the current which
flows to make the weld in accordance with the resistance
measurement.
It is another advantage of the present invention, at
least in preferred forms, that it can provide an electrical
resistance welding apparatus which marks those batteries
with defective welds determined by the electrical resist-
ance measurement.
It is another advantage of the present invention, at
least in preferred forms, that it can provide an electrical
resistance welding apparatus which automatically rejects
batteries with defective welds.
Another advantage of the present invention, at least
in preferred forms, is that it can provide an electrical
resistance welding apparatus which measures the current
flowing between the lugs to be welded together and which
has a means of controlling the current delivered to the
lugs to ~e welded together in accordance with the current
measurement.
It is another advantage of the present invention, at
least in preferred forms, that it can provide a method of
making repeatable welds in lead storage battery lugs dis-
posed on spposite sides of plastic partitions.
It is another advantage of the present invention, at
least in preferred forms, that it can provide a method of
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locating batteries with defective welds and rejecting said
batteries.
This and other advantages of my invention will become
apparent in the following description with reference to
the accompanying drawings.
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Brief Description of the Drawings
Fig. 1 is a schematic view of the electrical resistance
welder of applicant's invention;
Fig. 2 is a cross-sectional view of the electrodes
pressing together the lugc to be welded through a plastic
partition, the lines contacting the electrodes representing the
electrical connection of an electrical resistance measur ng
means to the electrode means.
Detailed Description of the Drawings
Although specific forms of the invention have been
selected for illustration in the drawings, and the following
description is drawn in specific terms for the purpose of
describing these forms of the invention, this description is
not intended to limit the scope of the invention which is
defined in the appended claims.
Referring to the figures, in Fig. 1 a pair of welding
jaws 10 and 12, shown in the standby position, are ready to move
in the directions of arrows A and A' respectively to engage the
battery lugs 14 and 16. The actual portions of the jaws 10
and 12 which engage the lugs are specially-designed protrusions
or welding tips 18 and 20. When the welding tips 18 and 20
contact the lugs 14 and 16 and press them together, portions
of the lugs are extruded into the opening 22 in the battery
partition 24 which is shown disposed between the lugs 14 and
16. In the preferred embodiment shown in Fig. 1, the plastic
partition 24 is an internal partition separating the cells o~
a battery; the lugs 14 and 16 are lead lugs
y
attached to the lead straps 26 and 28 which connect the
individual terminal lugs of each of the battery plates
within the adjacent cells. As in most modern batteries,
the battery case and the partitions are made of a plastic
material such as polypropylene. It will be noted that
even though the preferred embodiment shows the weld being
made between two internal battery lugs disposed on either
side of a plastic cell partition, the same apparatus and
method could be used to weld an external terminal throush
a battery case wall to an internal lug within the battery.
Together, the welding jaws 10 and 12 with the electrode
tip portions 18 and 20 comprise the electrode means desig-
nated generally 13 which contact the lugs to be welded
together and conduct current to the lugs to create the
weld. The current is supplied to the electrode means
from a power means designated generally 29 and together
with the electrode means 13 they form the welding means
portion of applicant's welder.
The preferred embodiment power means 29 comprises a
current source for providing current to the electrode
means such as the transformer designated generally 30
in Fig. 1, and a power control means such as transformer
controller 31 in Fig. 1 for controlling the amount of
current supplied to the electrode means. The schematic
representation of the transformer in Fig. 1 shows that
the preferred embodiment transformer is a magnetic core
transformer with a primary 32 and secondary 34 shown
with a rectified output by the diodes 36 and 38 connected
to the ends of the secondary winding 34 and connected
together at point 40. Point 40 is shown connected to
welding jaw 12 by line 42, and line 44 is connected to
welding jaw 10 and center tapped to secondary winding 34.
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This circuit provides a DC current source to the electrode
means.
After the jaws 10 and 12 have contacted the lugs 14
and 16 respectively and extruded portions of the lugs into
the aperture 22 to contact one another, but before power
is delivered to the lugs for welding, an electrical resist-
ance measuring means 46 in Fig. l measures the electrical
resistance of the lugs through a portion of the electrode
means in contact with the lugs. In Fig. 1, the resistance
measuring means 46 is shown receiving inputs from line and
arrow 48, and line and arrow 50 connected to points 52 and
54 on lines 42 and 44 respectively. This connection of the
resistance measuring means at these points is schematic in
nature since the choice of where the resistance is to be
measured is critical in determining the actual resistance
of the parts to be fused. For example, in Fig. 2, the
welding jaws 10 and 12 are shown pressing against the lugs
14 and 16 to cause an extrusion in the aperture 22 and a
contact between the lug extruded portions. The line and
arrow 48 and the line and arrow 50 of Fig. l are shown as
48' and 50' in Fig. 2 and they are shown contacting the
welding jaws at the electrode tip portions 18 and 20.
Hence, in Fig 1, the resistance to be measured will be
made up of the following factors: the connection of the
welding jaw bodies 10 and 12 to the electrode tip por-
tions 18 and 20; the connection between the welding tips
18 and 20 to the lugs 14 and 16; and the contact between
the lugs. Fig. 2 shows more clearly how the lugs are ex-
truded into aperture 22 where the extruded portions 56
and 58 are shown contacting one another. In an alternate
embodiment of applicant's invention where the secondary
output of the transformer is
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not rectified, an alternating current is delivered to the lugs
and the resistance of the electrode means in contact with
the lugs can be made through the transformer.
Referring now to Fig. 1, once the resistance has
been measured, it is transmitted by the measuring means to the
interface controller 60 by the line and arrow 62. The inter-
face controller takes this resistance information and from it
determines the amount of current and time over which the
current is to flow as determined by the aforementioned equation
H = (I2) ~R) (T) (K). This can be accomplished, for example,
by having the interface controller 60 obtain the proper current
and time from a look-up table which is a memory or storage of
different relationships between the resistance that is measured
and the proper c.urrent and time that is required to provide a
given heat as pre-determined and stored in the interface
controller 60. Alternatively, the interface controller could
be a microprocessor which is capable of analytically determining
the current from the measured resistance and use of the heat
e~uation above. The interface controller 60 then sends this
information by way of a signal in line and arrow 64 to the
welding means such as the transformer controller 31 of the
power means which in turn activates the transformer of the
power means to deliver a fixed amount of current during a
fixed time period to said electrode means. The information
sent from the transformer controller 31 to the transformer 30
is sent by line and arrow 66. At the same time, the trans-
former controller 31 transmits the information back to the
interface controller on line and arrow 68 so th~t it can be
compared for accuracy.
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Hence, applicant's preferred embodiment measures the
resistance of the contact between the lugs contacting one
another through the plastic partition wall and, from this
information, determines the proper amount of current and
duration over which this current should flow in order to
provide a thorough and repeatable weld. The method by
which this is accomplished is as follows: the battery
with the lug surrounding the plastic partition is brought
into place between the welding jaws; the welding jaws are
then moved in the direction shown by arrow A and A' in
Fig. 1 until they contact the lug surfaces upon which
pressure is applied and portions of the lug surfaces are
extruded into the aperture 22 to contact one another; the
resistance of the lugs is then measured through a portion
of the welding means in contact with said lugs by the re-
sistance measuring means and that information is then sent
to the interface controller; the interface controller uses
the resistance measurement to determine the proper amount
of current and the time which that current is to flow, and
sends this information to the transformer controller; the
transformer controller controls the amount of current out-
put from the transformer and the period of time of the
output; the transformer receives the command from the
transformer controller and outputs the proper amount of
current over a given amount of time; and this current then
flows through the electrode means, that is, through the
welding jaws, electrode tips and the lug contacts heating
the lugs and fusing the lead in the aperture 22. The
welding means or welding jaws are then withdrawn to free
3~ the battery. The current delivered to the lugs can ~e
either direct or alternating.
In order to insure that the weld is a proper one,
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applicant's invention provides for a second measurement of
the resistance after the welding process is complete. If
a good fusion has taken place, the resistance of the lug
connection will be much lower than that of the pre-weld
contact, e.g., less than 5 micro-ohms. If the resistance
is not within a desirable range, the new value of the
resistance can be used to begin the process over again.
If for some reason a good weld cannot be attained as
determined by the resistance measurement, then applicant
has provided a means in the apparatus for marking and
rejecting defective weld batteries. Referring to Fig. 1,
marking means 7~ marks those batteries where weld resist-
ance values are too high. For example, when the resistance
measuring means is told by the interface controller 60 via
line and arrow 72 that the final resistance measurement of
the attempted weld is too high, then the marking means
such as ink system 70 in response to command from the
measuring means 46 via line and arrow 75 deposits a few
drops of ink in the defective battery in a prominent
location on the battery. Of course, any marking means
which could designate a battery with a bad weld could
be used and the applicant is showing here the preferred
embodiment ink system 70. The battery then proceeds
down the assembly line where the reject mechanism 77
having been notified in advance of the faulty weld by
the resistance measuring means 46 via line and arrow 74
rejects the battery ~rom the conveying system or assembly
line so that further processing on that battery would not
take place. In this way, batteries that had welds which
were not repeatable and up to a certain quality level, for
example, less than 5 micro-ohms, would not proceed further
and find their way into the marketplace.
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Should the interface controller receive a resistance
measurement at any time which did not fall within the
look-up table or other means for determining the amount
of current and time required to create a proper weld,
the interface controller 60 is equipped to signal the
resistance measuring means 46 to make another measure-
ment. This is indicated by the line and arrow 72.
~ ence, a method is disclosed by applicant whereby
batteries with defective welds are detected through
resistance measurements, marked as defective and thereby
rejected upon detecting the marking.
It may be desirable in the apparatus and method to have a
means of correcting the current flowing to the lugs during
the actual welding process. Current analyzer 76 in Fig. 1
measures the current flowing through the lugs during the
welding process. It is shown electrically connected in
series with welding jaw lO at points 54 and 78 connected
by a shunt 44 and the information is received via line and
arrow 80 and line and arrow 82. When the current has been
measured by the current analyzer 76, the information is sent
via line and arrow 100 to the interface controller 60 where
the measured value of the current is compared with the value
of the current determined by the interface controller 60 to
be the optimum for creating the weld from 'he value of the
resistance as measured by the resistance measuring means
46. The interface controller 60 has the ability to control
the transformer controller 31 so that a real time change
in the current flowing through the weld can be made by the
interface controller 60 of the current, as measured by the
current analyzer 76, does not match the current as deter-
mined by the interface controller 60. This leads to an
even finer control of the process of making the weld.
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The interface controller receives information from
various sources such as the resistance measuring means 46, the
transformer controller 31 and the current analyzer 76. It uses
the information that it receives to control the welding opera-
tion of the entire welding apparatus. For example, upon receipt
of information from the resistance measuring instrument 46 as
to the resistance of the preweld lug contact, the interface
controller selects the appropriate current that must be deliver-
ed in a given period of time in order to create enough heat to
fuse the lead together in the aperture 22. This information is
sent to the transformer controller in such a way as to allow the
transformer controller to energize the transformer which ulti-
mately provides the current to the lug region. If there is
something wrong with the initial or subsequent resistance
measurements such that they are not within an acceptable range
of resistance measurements, the interface controller can through
line and arrow 72, signify the resistance measurement to recycle
or to reject. Similarly, after the transformer controller has
signaled the transformer to energize, it can tell the inter-
face controller via line and arrow 68, what information it
provided to the transformer which the interface controller
then compares with its own information to determine whether
or not the transformer controller is acting correctly. If it
is not, it can recycle the process. Also, should the current
analyzer 76 provide current information to the interface
controller which does not agree with the information determined
by the interface controller based on a resistance measurement,
the interface controller can e;ther signal the transformer to
increase or decrease the power from the transformer in order
to bring it in agreement with the value being measured by the
current analyzer, or it can
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stop and recycle the process. Finally, the interface con-
troller is capable of providing a signal to the resistance
measuring means via line 72 that the final resistance mea-
surement in the process was inadequate and that a battery
with a defective weld existed. The interface controller
signals the resistance measuring means 46 to trigger the
ink system 70 to so mark the battery and at the same time
it would tell the resistance measuring means to signal
the reject mechanism to ~e ready to sense a battery with
a defective weld marking so as to reject that battery from
further processing. Hence, the interface controller acts
as a control for the entire welding apparatus in its func-
tion of interfacing with the various instruments and control
mechanisms in the apparatus. This fine control of the
welding operation provides a means of insuring repeatable
welds and high quality control.
It will be understood that various changes in the
details, materials and arrangement of parts which have been
herein described and illustrated in order to explain the
nature of this invention, may be made by those skilled in
the art within the principle and scope of the invention as
expressed in the following claims.
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