Sparkplug boot and wire protector and assembly

Details Sparkplug boot and wire protector and assembly Sparkplug boot and wire protector and assembly

2000-04-13

2001-10-23

Sircus, Brian (Department: 2839)

Electrical connectors

Having spark or glow plug cover

C439S128000

Reexamination Certificate

active

06305954

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a sparkplug boot and wire protector and assembly. More particularly, the invention relates to a protector that shields a silicone covered sparkplug wire and silicone sparkplug boot from extremely high temperatures derived from spark ignited engines.
2. Discussion of Related Art
Sparkplugs in conventional spark ignited engines are positioned in close proximity to exhaust manifolds. The exhaust manifolds are routed near a secondary ignition system and have been measured at temperatures exceeding approximately 1,240 degrees Fahrenheit for extended periods of time. The ignition system includes ignition wires, a metal clip, boot and a sparkplug.
The boot is typically constructed of silicone while the ignition wire is a conventional conductive wire covered with a silicone wrap (hereinafter referred to as a silicone wire). The silicone boot that attaches the sparkplug high voltage wire to the sparkplug begins offgasing at approximately 350 degrees Fahrenheit, at which time the silicone begins to break down and deteriorate.
To overcome this situation, conventional manufacturers place a shield, typically made of aluminum, over the silicone boot to protect the boot from the high temperatures. However, the shield is not long enough nor does it have enough insulating properties to protect the wire as well as the boot.
Furthermore, if the engine develops an exhaust leak at the exhaust manifold to the cylinder head gasket, hot exhaust gases leak directly onto the sparkplug boot shield, boot, the sparkplug itself and sparkplug wire. Since the sparkplug boot and wire are made of silicone, they begin to deteriorate. As the silicone boot and wire deteriorate, they become brittle and lose their dielectric value, causing a leakage of electricity and/or creates an open circuit.
Because the voltage is very high, ranging between a thousand volts to tens of thousands of volts, a high voltage spark can leak from the insulated area to ground without creating the spark in the gap of the sparkplug necessary to initiate the combustion process. Accordingly, the engine misfires and additional heat is created, thereby worsening the situation. If the embrittled sparkplug wire results in the open circuit condition, cross fire will occur, resulting in potentially catastrophic engine damage.
SUMMARY OF THE INVENTION
An object of this invention is to overcome the drawbacks of the conventional shield discussed above.
Another object of this invention is to provide a ceramic sparkplug boot protector that also extends over the sparkplug wire. The protector insulates the silicone boot and wire from the high temperatures the silicone cannot withstand. Specifically, the protector is designed to withstand temperatures up to approximately 5,000 degrees Fahrenheit. Furthermore, at an internal combustion engine temperature of 1,500 degree Fahrenheit in the region the protector is located, the protector will transfer less than 250 degrees Fahrenheit, well short of the silicone degradation point.
The ceramic protector is designed to extend out over the silicone sparkplug boot from the cylinder head recess beyond the exhaust manifold to protect the silicone sparkplug wire as well. The loose fit of the protector over the boot results in an air gap between the protector and boot. The air gap provides, in addition to the temperature insulation properties of the ceramic protector, further protection of the boot and wire from surface heat damage during extreme operating conditions.


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