Electric heating – Metal heating – For bonding with pressure
Reexamination Certificate
2000-01-10
2001-09-11
Dunn, Tom (Department: 1725)
Electric heating
Metal heating
For bonding with pressure
C219S116000
Reexamination Certificate
active
06288356
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for welding, and in particular to a welder adapted to weld components of a material having a relatively sharp melting point, such as cathodic and anodic lead alloy plates in some types of batteries.
Robotic welders are used in a wide variety of applications to facilitate automated welding in assembly lines. These robotic welders typically include a robot, a welder mounted thereon, and a controller in communication with the robot and controlling the location and movements thereof. However, robotic welders are often not able to position welds as accurate as may be desired due to product variations, locational variations due to inconsistent fixturing, and variations caused by conditions inherent in the robot, such as wear and play in joints and members of the robot's moveable arm. In batteries, this can be problematic since anodic plates (or cathodic plates) in adjacent cells of a battery must be welded together through a hole in a cell-separating wall in a battery casing. If the weld tips are not very accurately located at a center of the hole during welding, the welded material to be welded heats non-uniformly. Since the plates are made of a lead or lead alloy having a relatively sharp melting point, uneven heating of a weld causes “hot” spots to occur that spit and splatter liquid material, while “cool” spots do not weld properly for good electrical contact and current flow.
AC welders have been employed to create welds on the anode or cathode components of a battery. However, there are several problems with AC welders, particularly when used on materials having a sharp melting point where close and accurate control of the welding process is required. For example, AC welders typically use a single phase power that can result in an unbalanced line power. AC welders require a large amperage disconnect switch separating them from the main power supply. AC welders operate on a relatively low power factor, thereby increasing the energy costs associated with running these welders. Also, AC welders typically operate at about 60 Hz making the energy input into the associated weld relatively imprecise, which can prove problematic in precision welding applications. AC welders create a high impedance because of the reversing magnetic fields building and collapsing when operating within the 60 Hz range. Exemplary of this is a typical situation in which a source voltage to the AC welder is about 10 VAC (voltage alternating current), it is considered sufficient when only one VAC is actually supplied to the weld point. This example illustrates the significant voltage loss. Another problem associated with the use of an AC welder is that the reversing magnetic fields as produced in an AC weld secondary loop make the loop sensitive to magnetic materials. When an excessive amount of magnetic material accumulates on the associated clamps and tilling within this loop, the loop will become saturated, resulting in failure to obtain the desired weld current, thereby resulting in an imprecise or uneven weld. Yet another drawback associated with AC weld systems is the size and relative weight of the AC weld system transformer. As an example, an AC weld system transformer capable of delivering 22 kA (kilo amps) weighs approximately 200-300 pounds, which is large, bulky, and difficult to deal with around a robot since the robot requires significant open space to operate. Another problem associated with AC welders is the fact that most metals become magnetic when molten. As a result, the oscillating magnetic field of the AC welder tend to create a condition where the molten metal is expelled from the weld joint, thereby resulting in an inadequate weld joint or contamination of components surrounding the weld joint. Finally, the AC wave form of an AC welder cannot be easily controlled, and therefore it does not allow the fine tuning wanted and necessary in precision welding applications.
Specific to welding processes as associated with the manufacture of batteries, it is often difficult to provide for an exact alignment between the precise location of the battery casing and anodic (or cathodic) components at which point the weld is to be located. One reason is because the rigid construction of the weld heads results in a large weld-tip-holding mechanism and frame that is heavy, massive, and difficult to manipulate with accuracy. More specifically, the rigid construction of the weld heads result in spatial and physical limitations that prevent the weld heads from reacting to correct misalignment conditions between the welding tips of the weld head and the battery components being welded. Further, many welding machines are difficult to access during routine maintenance. Along the same lines, precise fixturing of the battery to be welded is highly important due to the precise nature of the welds in the exact locations thereof.
Accordingly, a welding apparatus is desired solving the aforementioned problems and having the aforementioned advantages, especially for the purpose of robot welding materials having relatively sharp melting points such as lead alloy components used in batteries.
SUMMARY OF THE INVENTION
One aspect of the present invention is to provide an apparatus for welding a product including a weldable material having a relatively sharp melting point, such as lead or lead alloy for a battery, that includes a fixture for locating product to be welded. The apparatus further includes a robot positioned adjacent to the fixture and that has a moveable arm and a controller programmable to control movement of the arm, and a welder assembly including a midfrequency DC transformer and a weld mechanism attached to the arm and operably connected to the mid-frequency DC transformer. The weld mechanism includes a pair of opposing weld tips adapted and configured to weld a pair of plates that include the weldable material.
Another aspect of the present invention is to provide an apparatus for welding a product including a pair of plates that include a weldable material for a cathode or anode, such as a lead or lead alloy for a battery, and that has a casing for a battery, wherein the casing includes a top edge. The apparatus includes a conveyor line that conveys product to be welded. The apparatus further includes a robot positioned adjacent to the conveyor line and that has a moveable arm and a controller programmable to control movement of the arm, and a welder assembly including a weld mechanism attached to the arm. The weld mechanism includes a pair of opposing weld tips adapted and configured to weld the pair of plates, and further includes a fixture shaped to mateably engage the top edge of the casing to accurately locate the battery relative to the casing for welding the weldable material.
Yet another aspect of the present invention is to provide an apparatus for welding a product to be welded that includes a weldable material, wherein the apparatus includes a fixture for positioning a product to be welded, and a robot positioned adjacent the fixture and has a moveable arm and a controller programmable to control movement of the arm. The apparatus also includes a welder assembly that includes a weld mechanism attached to the arm. The weld mechanism includes a mounting plate, a pair of opposing weld tips mounted for linear movement on the mounting plate, and scissor arms pivotally mounted to the mounting plate and operably connected to the weld tips to move the weld tips with a linear motion.
Yet still another aspect of the present invention is to provide a welding mechanism for a welding apparatus, that includes a mounting plate having two oval-shaped apertures extending therethrough, and a pair of opposing welding tips operably mounted for linear movement on the mounting plate and operable between an open non-welding position and a closed welding position. The welding mechanism also includes at least one actuator arm moveable between a first position corresponding to the open non-welding position of the welding tips and a se
Goodspeed Grant Stanford
Harder Steven Henry
Scygiel Dennis Walter
Cooke Colleen
Dane Systems, Inc.
Dunn Tom
Price Heneveld Cooper DeWitt & Litton
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