GB1600319A

GB1600319A - Apparatus and method for making electrical resistance welds

Info

Publication number: GB1600319A
Application number: GB2409778A
Authority: GB
Original assignee: General Battery Corp
Current assignee: General Battery Corp
Priority date: 1977-06-27
Filing date: 1978-05-30
Publication date: 1981-10-14
Also published as: CA1111508A

Description

(54) APPARATUS AND METHOD FOR MAKING ELECTRICAL RESISTANCE WELDS (71) We, GENERAL BATTERY CORPORATION, a Corporation organized and existing under the laws of the State of Delaware, United States of America, of Post Office Box 1262, Reading, State of Pennsylvania, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method bv which it is to be performed, to be particularly described in and by the following statement: Conventional electrical resistance welders for use with lead storage batteries can be thought of as comprising 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 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 resistance of the combination of welding jaws, electrode tips and the contacts that the tips make with the lugs is unknown. Also, surface oxidation, lug composition, and the pressure of the jaws on the parts are all important 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, the constant repeatable 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 No. 3,313,658; 3,388,005; 3,589,948; 3,687,734; 3,723,699; 3,793,086; 3,798,071; and 3,869,316.

Methods for making battery terminals are described in U. S. Patent Nos. 3,303,056; 3,457,118; 3,849,203; and 3,874,933. None of these references disclose provisions or methods for measuring the resistance between the welding means and the lugs for each weld which is to take place, and using this measurement to control the amount of current which is to be delivered to the lug contact surfaces where the weld will take place.

Applicant's invention is based on the following equation: H = (I2) (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 which are undecided once the heat H and the factor K are either analytically or empirically determined are the factors I-. R, 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.

According to the present invention there is provided an apparatus for making welds in lead storage batteries between terminal lugs disposed on either side of an insulating partition having an aperture therethrough, said apparatus including electrodes for engaging said lugs and exerting a force thereon whereby said lugs are extruded into said aperture causing said lugs to come into contact, and means for measuring the electrical resistance across a series combination of said electrodes and said contacting lugs, said measuring means being associated with a control for applying an electrical current through said contacting lugs whereby in operation the magnitude and duration of said current is related to the electrical resistance measured across said series combination.

According to a further aspect of the invention there is provided a method of making welds in lead storage batteries between battery lugs disposed on opposite sides of partitions and pressed together to make contact therethrough, including the steps of applying electrodes to said lugs, measuring the electrical resistance across a series combination of said electrodes and said lugs, determining the magnitude and duration of current required to form said welds in response to said resistance measurement, controlling the magnitude and duration of current delivered by said electrodes to said lugs in response to said determination, and withdrawing said electrodes from said lugs.

The invention will become apparent in the following description with reference to the accompanying drawing, in which Figure I is a schematic view of the electrical resistance welder of applicant's invention: Figure 2 is a cross-sectional view of the electrodes pressing together the lugs to be welded through a plastic partition. the lines contacting the electrodes representing the electrical connection of an electrical resistance measuring means to the electrode means.

Referring to the figures, in Figure 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 Figure 1.

the plastic partition 24 is an internal partition separating the cells of a battery; the lugs 14 and 16 are lead lugs attached to the lead strap 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 through 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 designated 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 Figure 1, and a power control means such as transformer controller 31 in Figure 1 for controlling the amount of current supplied to the electrode means. The schematic representation of the transformer in Figure 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. The 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 resistance measuring means 46 in Figure 1 measures the electrical resistance of the lugs through a portion of the electrode means in contact with the lugs. In Figure 1, the resistance measuring means 46 is shown receiving inputs from line and arrow 48, and line and arrow 50 connected to point 52 and 54 on lines 42 and 44 respectively. Still with respect to Figure 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 portions 18 and 20; the connection between the welding tips 18 and 20 to the lugs 14 and 16; and the contact between the lugs. 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 Figure 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 Figure 1 are shown as 48' and 50' in Figure 2 and they are shown contacting the welding jaws at the electrode tip portions 18 and 20.

Figure 2 shows more clearly how the lugs are extruded 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 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.

Referrring now to Figure 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 interface 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 current 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 equation 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 transformer controller 31 transmits the information back to the interface controller on line and arrow 68 so that it can be compared for accuracy.

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 Figure 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 resistance 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 the current is to flow, and sends this information to the transformer controller; the transformer controller controls the amount of current output 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 the battery. The current delivered to the lugs can be either direct or alternating.

In order to insure that the weld is a proper one, 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 Figure 1, marking means marks those batteries where weld resistance 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 link 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 the battery from 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.

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 measurement. This is indicated by the line and arrow 72.

Hence, 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 Figure 1 measures the current flowing through the lugs during the welding process.

It is shown electrically connected in series with welding jaw 10 at points 54 and 78 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 the 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 if the current, as measured by the current analyzer 76, does not match the current as determined by the interface controller 60. This leads to an even finer control of the process of making the weld.

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 operation 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 delivered 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 ultimately 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 interface 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, the process can be repeated. 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 either signal the transformer controller 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 stop and repeat the process. Finally, the interface controller is capable of providing a signal to the resistance measuring means via line 72 that the final resistance measurement 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 be 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 function 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.

WHAT WE CLAIM IS: 1. An apparatus for making welds in lead storage batteries between terminal lugs disposed on either side of an insulating partition having an aperture therethrough, said apparatus including electrodes for engaging said lugs and exerting a force thereon whereby said lugs are extruded into said aperture causing said lugs to come into contact, and means for measuring the electrical resistance across a series combination of said electrodes and said contacting lugs, said measuring means being associated with a control for applying an electrical current through said contacting lugs whereby in operation the magnitude and duration of said current is related to the electrical resistance measured across said series combination.

2. Apparatus as claimed in Claim 1, wherein said electrodes comprise at least two welding jaws, each jaw having an electrode tip portion for engaging a corresponding lug.

3. Apparatus as claimed in Claim 2, wherein said electrical resistance measuring means is electrically connected to said electrode tip portions.

4. Apparatus as claimed in Claim 1 or Claim 2, wherein said electrical resistance measuring means outputs a resistance information signal which is representative of the resistance across said series combination.

5. Apparatus as claimed in Claim 4.

wherein an interface controller responsive to said resistance information signal is arranged to output a power control signal based upon information contained in said resistance information signal.

6. Apparatus as claimed in Claim 5, including a transformer and a power control electrically connected thereto for controlling the magnitude and duration of current through said contacting lugs in response to said power control signal.

7. Apparatus as claimed in Claim 6, wherein the transformer supplies alternating current.

8. Apparatus as claimed in Claim 6, wherein the transformer has a rectified secondary output for supplying direct current.

9. Apparatus as claimed in any preceding claim wherein a marker responsive to a command signal from said resistance measuring means is provided for marking batteries having defective welds.

10. Apparatus as claimed in Claim 9, wherein said marker is an ink dispenser for depositing ink on said batteries having defective welds.

11. Apparatus as claimed in Claim 9, wherein a reject mechanism, responsive to a signal from the resistance measuring means, is provided for sensing a marked battery and discarding said marked battery with defective welds from further processing in response to said sensing.

12. A method of making welds in lead storage batteries between battery lugs disposed on opposite sides of partitions and pressed together to make contact therethrough, including the steps of applying electrodes to said lugs, measuring the electrical resistance across a series combination of said electrodes and said lugs, determining the magnitude and duration of current required to form said welds in response to said resistance measurement, controlling the magnitude and duration of current delivered by said electrodes to said lugs in response to said determination, and withdrawing said electrodes from said lugs.

13. A method as claimed in Claim 12, wherein the electrical resistance measurement is accomplished using alternating current.

14. A method as claimed in Claim 12, wherein the electrical resistance measuring step is repeated prior to withdrawal of the electrodes from the lugs.

15. A method as claimed in Claim 14, including the additional subsequent steps of marking a battery for rejection when the electrical resistance is greater than a preselected value, and rejecting such a marked battery.

16. An apparatus for making welds in lead storage batteries subsequently as hereinbefore described with reference to the accompanying drawing.

17. A method of making welds in lead storage batteries as hereinbefore described.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. 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 function 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. WHAT WE CLAIM IS:

1. An apparatus for making welds in lead storage batteries between terminal lugs disposed on either side of an insulating partition having an aperture therethrough, said apparatus including electrodes for engaging said lugs and exerting a force thereon whereby said lugs are extruded into said aperture causing said lugs to come into contact, and means for measuring the electrical resistance across a series combination of said electrodes and said contacting lugs, said measuring means being associated with a control for applying an electrical current through said contacting lugs whereby in operation the magnitude and duration of said current is related to the electrical resistance measured across said series combination.

5. Apparatus as claimed in Claim 4.