Spark plug for internal combustion engines

A spark plug for internal combustion engines, especially a spark plug deeply arranged in a spark plug recess of the engine. The spark plug includes a mounting portion, a center electrode, and an insulating body. An extension arrangement is adapted to be attached to the spark plug for facilitating access thereto. The extension arrangement includes a center electrode, an insulating body, and a tubular jacket. The tubular jacket is provided at a first end with an inner cross section corresponding to a cross section of the mounting portion of the spark plug, with the inner cross section being adapted to be mounted over the mounting portion of the spark plug. A second end of the tubular jacket is provided with a further mounting portion.

The present invention relates to a spark plug for internal combustion 
engines and, more particularly, to a spark plug adapted to be arranged 
deeply in a spark plug recess, with the spark plug having a polygonal 
mounting means, a center electrode, and an insulating body. 
Accessibility to spark plugs is often quite problematic, especially in 
cases of internal combustion engines wherein the spark plugs are deeply 
housed or accommodated in spark plug niches or openings provided in the 
cylinder head. Moreover, additional difficulties may be encountered in 
electrically insulating and protecting the spark plugs against moisture 
and contamination. 
The aim underlying the present invention essentially resides in providing a 
spark plug arrangement having an extension portion for facilitating 
insertion and removal thereof from an internal combustion engine. 
In accordance with advantageous features of the present invention, the 
spark plug arrangement includes an extension which is adapted to be placed 
on the spark plug, with the extension including a center electrode, an 
insulating body, and a tubular jacket. The tubular jacket is provided at 
one end with an inner polygonal cross section corresponding to the 
polygonal cross section of the mounting means of the tubular jacket, with 
the other end of the spark plug being provided with a further polygonal 
mounting means. Advantageously, the mounting means on the spark plug and 
the mounting at the other end of the tubular jacket are of a hexagonal 
configuration. 
By virtue of the above-noted features of the present invention, a spark 
plug is provided with an extension and has the characteristics of an 
externally-located spark plug with respect to the spark plug terminal and 
mounting means in spite of the deep location within a niche or opening 
accommodating the spark plug at the internal combustion engine. 
Additionally, by virtue of the extension of the spark plug of the present 
invention, a threading of the spark plug into the hole accommodating the 
spark plug is possible manually at least for the initial threads and it is 
not necessary to utilize a special wrench such as a deep socket plug 
wrench. Moreover, when replacing the spark plug, it is normally necessary 
to exchange or replace the spark plug proper which is accommodated in the 
spark plug whole provided in the engine. 
Advantageously, in accordance with further features of the present 
invention, the insulating body and the center electrode of the extension 
may be attached to the spark plug by a threaded connection between the 
center electrode of the extension and the center electrode of the spark 
plug proper. The tubular jacket is adapted to transmit tightening and 
releasing moments to the spark plug accommodated in the spark plug hole. 
Additionally, the tubular jacket may be attached to the insulating body of 
the extension by means of a mounting ring. 
Preferably, the tubular jacket may be sealed in proximity of its two ends 
by sealing rings with respect to the insulating body of the spark plug and 
the insulating body of the extension. 
Advantageously, a sealing ring, especially a lip-type sealing ring may be 
placed on the tubular jacket to seal the spark plug recess proper. 
Accordingly, it is an object of the present invention to provide a spark 
plug for internal combustion engines which avoids, by simple means, 
shortcomings and disadvantages encountered in the prior art. 
Another object of the present invention resides in providing a spark plug 
for internal combustion engines by which the insertion and removal of the 
spark plug is greatly facilitated. 
A further object of the present invention resides in providing a spark plug 
for internal combustion engines which insures the existence of adequate 
electrical insulation as well as protection against moisture and other 
contamination. 
Yet another object of the present invention resides in providing a spark 
plug for internal combustion engines which is simple in construction and 
therefore relatively inexpensive to manufacture. 
A further object of the present invention resides in providing a spark plug 
for internal combustion engines which minimizes, if not avoids, the 
possibility of cross threading of the spark plug in the spark plug 
accommodating hole in the internal combustion engine. 
Yet another object of the present invention resides in providing a spark 
plug for internal combustion engines which facilitates the alignment of 
the spark plug with respect to the spark plug accommodating hole in the 
engine.

Referring now to the drawings, wherein like reference numerals are used in 
both views to designate like parts, and, more particularly, to FIG. 1, 
according to this figure, a cylinder head 1 of an internal combustion 
engine is provided with a spark plug bore 2 disposed at the end of a deep 
spark plug recess 4 with the bore 2 and recess 4 enabling an insertion of 
a spark plug 3 in the cylinder head 1. An extension generally designated 
by the reference numeral 5 is provided so as to render the spark plug 3 
more accessible from outside of the spark plug recess 4. 
As shown in FIG. 1, the extension 5 includes a centrally-disposed electrode 
6, an insulating body 7, and a tubular jacket 8. The insulating body 7 is 
firmly connected with the center electrode 6, and the center electrode 6 
is adapted to be connected to the center electrode 9 of the spark plug 3 
by, for example, a threaded connection. The insulating body 7 includes a 
cylindrical extension 10 which extends over an insulating body 11 of the 
spark plug 3. A silicon seal 12 is attached to the lower end of the 
insulating body 7, with the seal contacting, on the one hand, the 
insulating body 11 of the spark plug 3, and, on the other hand, the 
tubular jacket 8 which is pushed over the insulating body 7 when the 
center electrode 6 has been connected to the center electrode 9. 
A lower end of the tubular jacket is provided with an internal polygonal 
cross-sectional portion 13 which is adapted to extend over a corresponding 
polygonal mounting portion 14 of the spark plug 3. Advantageously, the 
mounting portions 13, 14 have a hexagonal configuration; however, as can 
readily be appreciated, the cross-sectional configuration of the mounting 
portion 13 would be determined by the configuration of the mounting 
portion 14 of the particular spark plug 3 being used in the engine. 
A securing ring 15 fixedly secures the tubular jacket 8 to the insulating 
body 7. A mounting portion 16 is provided at the upper end of the tubular 
jacket 8 for enabling engagement with a suitable wrench such as, for 
example, a spark plug wrench. However, as can readily be appreciated, due 
to the free access to the spark plug provided by the extension portion, a 
suitable open end or a box-type wrench may also be utilized to insert and 
remove the spark plug 3. The mounting portion 16 advantageously has a 
hexagonal configuration. A lip-type sealing ring 17 is placed or mounted 
on the tubular jacket 8 in order to enable a sealing of the spark plug 
recess 4. 
In order to replace the spark plug 3, the spark plug 3 and 
threadably-attached extension 5 are removed from the cylinder head 1 
through the spark plug recess 4. The tubular jacket 8 is then detached 
from the spark plug 3 and from the insulating body 7 with the aid of the 
mounting or securing ring 15 so that the spark plug 3 may then be 
manually, for example, threadedly disconnected from the center electrode 
6. 
The spark plug of FIG. 2 differs with respect to the spark plug of FIG. 1 
in that the tubular jacket 8 is sealed with respect to the insulating body 
11 of the spark plug 3 by a sealing ring 18. Additionally, a further 
sealing ring 19 is provided in a zone of the mounting portion 16 for 
sealing the insulating body 7 of the extension 5 with respect to the 
mounting portion 16. 
In the spark plug of FIG. 2, when mounting the extension 5, the spark plug 
3 is placed into the tubular jacket 8 and thereupon the insulating body 
and center electrode 6 of the extension 5 is connected, for example, by a 
threaded connection, with the center electrode 9 of the spark plug 3. 
While I have shown and described only two embodiments in accordance with 
the present invention, it is understood that the same is not limited 
thereto but is susceptible of numerous changes and modifications as known 
to one of ordinary skill in the art, and I therefore do not wish to be 
limited to the details shown and described herein but intend to cover all 
such changes and modifications obvious to one of ordinary skill in the 
art.