Plastic and nonmetallic article shaping or treating: processes – Direct application of electrical or wave energy to work – Forming articles by uniting randomly associated particles
Reexamination Certificate
2002-08-19
2004-01-13
Lechert, Jr., Stephen J. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Direct application of electrical or wave energy to work
Forming articles by uniting randomly associated particles
C264S122000, C264S127000, C264S463000, C264S489000, C264S159000, C264S237000
Reexamination Certificate
active
06676880
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates generally to polytetraflouroethylene (PTFE) seals for use in dynamic shaft seal applications and the like where a PTFE wafer is used as a seal component and a method of fabrication therefor.
2. Related Art
The art of producing effective seals between a rotating member and a stationary member is under continual development. It is well know that seals acting between a rotating member and a stationary member often comprise a PTFE component in combination with an elastomer component. The manufacture of the PTFE seal component is typically the bottleneck in the process of producing a seal. PTFE is difficult to form to a desired shape due to its inherent heat resistant characteristics, and thus, poor conductivity. This makes PTFE difficult to mold, thus complicating the manufacture process of making components parts from PTFE.
Typically, PTFE is formed to the desired component geometry by exposing PTFE resin powder to melting temperatures, in the desired mold geometry, for an extended period of time. The amount of time required to process the PTFE resin powder from a “green” state to a cured or sintered state can take anywhere between 2 to 10 hours or more, depending on the geometry sought. This amount of time investment to produce a component for a seal is highly cost inefficient from the standpoint of labor, energy consumption, and space consumption in a furnace, among other associated costs. Additionally, the interruption of the manufacture process to produce a seal by having to spend so much time in a single operation, i.e. sintering of the PTFE seal element, prevents manufacturing efficiencies otherwise possible by utilizing a continuous manufacturing process.
Therefore, being as many seals in production today utilize a PTFE component for its lubricious properties, it would be highly advantageous to have a process for construction a PTFE seal component in an efficient manner. A method of constructing a PTFE seal component according to the current invention as described hereafter in a currently preferred embodiment of the invention overcomes or greatly minimizes the limitations of prior methods of forming a seal component manufactured from PTFE.
SUMMARY OF THE INVENTION
A method of constructing a PTFE seal component is provided that enables construction of the component in a quick and relatively cost efficient manner. The seal component construction begins by creating a mixture of PTFE resin powder and a susceptor material. The mixture is then routed to a compacting zone wherein the mixture is compacted to a specific geometry. Upon being compacted, the mixture is then sintered by exciting the susceptor material to generate heat uniformly throughout the mixture. Thereafter, the sintered material is routed to a cutting tool wherein a desired thickness of seal component is cut from the sintered mixture.
Another currently preferred embodiment of the invention employs a continuous method of constructing a seal component comprised of PTFE resin powder and a susceptor material. Upon creating the mixture, the mixture is routed to a compaction zone to a least partially compact the mixture. A continuous flow of the mixture is then routed from the compaction zone to a heating zone wherein the mixture is sintered by exciting the susceptor material within the mixture to create a billet of PTFE seal material. From the heating zone, the billet flows continuously to a cutting zone where a cutting tool is used to cut the seal component of a desired thickness from the billet.
One advantage of the current invention is that a PTFE seal component can be constructed in a relatively short period of time.
Another advantage of the invention is that the costs associated with the production of a PTFE seal component is reduced.
Another advantage of the invention is that a PTFE seal component can be constructed in a continuous process.
Another advantage of the invention is that a PTFE seal component can be constructed such that the material of the seal component is relatively uniform in strength.
Another advantage of the invention is that a PTFE seal component can be cut to a desired thickness in a reliable and repeatable manner.
Another advantage of the invention is that PTFE resin powder may be compacted to a more uniform density, thus producing a more uniform PTFE seal component.
Another advantage of the invention is that a PTFE seal component may be constructed in a relatively easy manner, thereby reducing the amount of time and associated costs in constructing the PTFE seal component.
The above list of advantages for the method of construction of a PTFE seal component embodying the current invention is meant to represent only a partial listing of advantages, and in no way is to be construed and a complete list of advantages of the current invention.
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Federal-Mogul World Wide Inc.
Howard & Howard
Lechert Jr. Stephen J.
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