Advancing material of indeterminate length – By orbitally traveling material-engaging surface – Comprising rotary pinch pair
Reexamination Certificate
2000-06-01
2001-11-20
Mansen, Michael R. (Department: 3653)
Advancing material of indeterminate length
By orbitally traveling material-engaging surface
Comprising rotary pinch pair
C492S030000, C492S053000
Reexamination Certificate
active
06318614
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to welding equipment, and more specifically ceramic wire feeding rollers which possess a longer wear life than metallic wire feed rollers and which prohibit welding wire from slipping in a roller assembly.
A long recognized need in the wire feed roller industry, specifically with robotic MIG welders, is for wire feed rollers that do not wear out and allow the welding wire to slip in the roller assembly. To date, wire feed rollers are fabricated from various metallic materials which are life limited due to active wear mechanisms within the metallic materials. As the wire is fed through the rollers, high tangential shear stresses between the welding wire and the rollers results in material removal from the rollers. When a sufficient amount of material is removed, the clamping, or contact, load is reduced due to the increased clearances and the wire begins to slip in the rollers. Further, as the rollers wear, the contact surface becomes smooth effectively reducing the friction coefficient between the wire and the roller contact surface. If an increase in the clamping load is not made via tensioning adjustments, as found on many assemblies, the wire will fail to feed to the weld tip, thus causing an interrupted weld and entanglement, or balling, of the wire in the wire feed mechanism. This action results in costly equipment downtime and repair to interrupted weldments.
To enhance the functional life of metallic rollers, surface features are sometimes added to the contact surfaces to aid in gripping the wire. These surfaces too, are subject to wear through continuous welder usage which effectively eliminates any functional advantage. Since all metallic materials have active wear mechanisms (i.e., slip plane movement, dislocation movement, grain boundary movement, low relative compressive strength, low relative surface hardness, etc.), a specific high friction surface finish/feature cannot be maintained for extended usage periods.
It can be seen therefore that a need exists for wire feed rollers that possess significantly longer wear life than existing metallic rollers both to eliminate equipment downtime and to maintain continuous weld integrity. Further, reduced drive load requirements for wire feed roller drive motor assemblies and a sustainable clamping load regime that would not require regular tensioning adjustments to ensure welding wire slippage is minimized would be useful to the wire feed and welding equipment industries.
SUMMARY OF THE INVENTION
In view of the deficiencies of the existing conventional metallic wire feed rollers as a direct result of metallic material property limitations as stated herein, it is the objective of this invention to provide a unique wire feed roller design capable of being operated for periods greatly exceeding existing metallic wire feed roller technology thereby virtually eliminating wire feed roller equipment downtime and, in the case of robotic (or other) MIG welding equipment, interrupted weldments and high wire feed roller drive motor torque requirements.
An advantage of the present invention is that it provides a wire feed system of rollers that do not allow the feed wire to substantially slip while clamped together at relatively light contact loads. Further, since material wear mechanisms are not active in the candidate ceramic materials under the conditions typically seen in wire feed roller mechanisms, specially in robotic MIG welders, the ceramic rollers survive many times the life of metallic rollers under identical wire hardness and clamping load/feed scenarios. Another advantage of the present invention is the relatively light clamping, or contact, load requirements imposed on the wire feed rollers to enable continuous wire feed without substantial wire slippage in the contact region. These relatively light clamping loads results in reduced roller drive motor torque requirements which should effectively increase the operational life of the drive motor mechanisms. (i.e., electric drive motors, roller support bearings/bushings, etc.) Another advantage of the present invention is the light weight of the ceramic rollers when compared to state-of-the-art metallic rollers. Still another advantage of the present invention is the oxidation resistance of the ceramic roller material enabling indefinite storage without the need for oxidation resistant coatings or preservatives. Another advantage of the present invention is the ability of the ceramic wire feed roller to operate at elevated temperatures relative to state-of-the-art metallic rollers without adversely compromising roller form, fit, or function. Finally, another advantage exists should harder wire materials be required for some applications which would increase the wear rate of existing metallic materials but would not adversely affect the life or performance of the present invention. Prototype samples of this technology have been successfully fabricated and tested in actual field use equipment.
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Ceramic Engineering Consulting, Inc.
Mansen Michael R.
Wolland & Knight LLP
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