Powder metallurgy processes – Forming articles by uniting randomly associated metal particles – Powder pretreatment
Reexamination Certificate
1999-10-28
2001-09-04
Jenkins, Daniel J. (Department: 1742)
Powder metallurgy processes
Forming articles by uniting randomly associated metal particles
Powder pretreatment
C419S067000, C419S036000
Reexamination Certificate
active
06284192
ABSTRACT:
FIELD OF THE INVENTION
Method and extruder assembly for extruding electrode material.
BACKGROUND OF THE INVENTION
Rechargeable batteries, based on nickel-zinc cells, have drawn attention from time to time since at least the 1930s. These batteries offer potential advantages over other rechargeable, alkaline systems in terms of energy output and/or cost. For example, a nickel-zinc battery potentially equals the performance of a silver-zinc battery, but at an obviously lower, material cost.
The nickel-zinc battery has been plagued with abbreviated life and installation cost. These problems have arisen largely due to difficulties in production, and behavior in use, of the electrodes, particularly the zinc electrode. During normal cycling, the zinc electrode tends to replate in a non-uniform manner during recharging. Also, dendrites, growing out from the zinc electrode, tend to cause short circuiting during discharge of the battery.
Recently, attention has been directed to the potential that the nickel-zinc battery has, as a replacement for the lead-acid battery, in automotive vehicles. This replacement would be particularly desirable since the nickel-zinc battery could provide a substantially greater, driving range before recharging.
Currently, however, except for special applications, there is no commercial production of a nickel-zinc battery. A major factor lies in the problems that arise in production and use of the electrodes.
There is, then, an apparent need for improvements in the manufacture of electrodes for a nickel-zinc battery. This is particularly true of the zinc electrode which appears to be the primary source of problems.
It is a basic purpose of this invention to meet the need for improved, electrode production.
Another purpose is to provide a stronger, more homogeneous material for production of zinc and nickel electrodes.
A further purpose is to provide a rapid, efficient and cost-effective process for extrusion of electrode material.
A still further purpose is to provide a novel, extruder assembly for processing electrode material.
BRIEF SUMMARY OF THE INVENTION
The invention resides, in part, in a method of extruding a zinc or nickel, electrode material which comprises mixing a homogeneous batch of raw materials composed predominantly of a source of zinc or nickel and also containing a small amount of essentially unfibrillated polytetrafluoroethylene (PTFE), feeding the batch to an extruder, conveying the batch material through a first portion of the extruder, then generating a controlled degree of fibrillation, conveying the batch through a second portion of the extruder to a forming member, and extruding the batch material through the forming member.
The invention further resides in an extruder assembly for extruding zinc or nickel, electrode materials which comprises an intermeshing, twin screw extruder, a smooth wall, twin tubular member within which the feeder operates, the twin tubular member having an opening through which batch material is fed to the intermeshing, twin screw extruder, the extruder having an initial, flighted portion that conveys the material forward while generating a degree of pressure to effect a limited fibrillation of polytetrafluoroethylene in the batch, the extruder having a second portion that is unflighted and that extends into a forming section of the twin tubular member, whereby a twin tubular, electrode material is extruded.
REFERENCES:
patent: 3101511 (1963-08-01), Heston
patent: 4547278 (1985-10-01), Hall et al.
patent: 4859383 (1989-08-01), Dillon
patent: 4945125 (1990-07-01), Dillon et al.
patent: 5393213 (1995-02-01), Murata et al.
patent: 5728337 (1998-03-01), Yoshikawa et al.
patent: 0 490 361 B1 (1994-07-01), None
patent: 0 709 176 A2 (1996-05-01), None
Coonan Everett W.
Frayer Paul D.
Monahan Roy J.
Wexell Kathleen A.
Corning Incorporated
Jenkins Daniel J.
Peterson Milton M.
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