Compression relief adapter

An improved spark plug and a compression relief adapter are described which are designed to permit a portion of the gases in the cylinder of an internal combustion engine to vent during the starting operation so as to make it easier to manually start the engine.

BACKGROUND OF THE INVENTION 
This invention relates to an improved spark plug and, more particularly, to 
mechanisms for relieving a portion of the normal compression forces during 
the starting operation of an internal combustion engine. 
Because of the normal compression forces obtained in conventional internal 
combustion engines it is often difficult for some persons to manually 
start such engines (e.g. on conventional lawn mowers, snow blowers, etc.) 
using a normal recoil starter. Although pressure relief or bleed valves 
are commercially available which are designed to vent a portion of the 
gases from the cylinder during the starting operation of the engine, it is 
necessary to drill a separate hole or aperture in the cylinder head in 
order to accommodate the pressure relief or bleed valve. This technique, 
of course, does not lend itself to practical retrofitting on engines 
already in the hands of consumers. 
The present invention provides means for relieving the normal compression 
in an internal combustion engine so that the starting operation is much 
easier, for example, for children and elderly persons. The apparatus of 
the invention is designed such that any conventional engine may be easily 
and readily retrofitted with such pressure relief means. 
SUMMARY OF THE INVENTION 
In one embodiment of the invention there is provided a spark plug of the 
type having a lower portion adapted to be threaded into the cylinder head 
of an internal combustion engine, wherein said lower portion surrounds an 
electrode encased in an insulator, wherein the improvement comprises a 
passageway in said lower portion which is adapted to communicate with the 
combustion cylinder of said engine in a manner such that gases in said 
cylinder may exit said cylinder through said passageway. 
In another embodiment of the invention there is provided an article 
comprising an inlet portion and an exit portion, said inlet portion having 
an opening therethrough which is adapted to permit the lower threaded 
portion of a spark plug to extend therethrough, said exit portion being 
laterally offset from said inlet portion and being adapted to receive a 
bleed valve therein, wherein said exit portion communicates with said 
inlet portion by means of a passageway.

In FIGS. 1, 2 and 3 there is shown the upper portion of cylinder 10 of an 
internal combustion engine in which spark plug 12 is threadably received 
in head 14. Compression relief adapter 16 comprises a base or inlet 
portion 18, through which the lower end 15 of spark plug 12 passes, and an 
exit portion 20 which is laterally offset from the inlet portion 18. 
Pressure relief or bleed valve 30 is threadably received in exit portion 
20. Inlet portion 18 communicates with exit portion 20 by means of 
passageway 22. 
The lower portion 15 of spark plug 12 preferably has an aperture or 
passageway therein which enables a portion of the gases in the cylinder 10 
to exit the cylinder. For example, there may be an aperture 24 extending 
transversely through the lower portion of the plug. Alternatively there 
may be one or more elongated grooves or passageways 26 extending 
longitudinally of the plug 13 as shown in FIG. 4. Another alternative 
involves forming a passageway in the head 14 which communicates between 
the cylinder 10 and the inlet portion 18. This latter alternative is less 
preferred, however, because it requires slight modification of the engine 
in the consumer's hands and therefore does not readily permit 
retrofitting. 
The gases which exit the cylinder 10 enter the inlet portion 18 and are 
directed through passageway 22 to exit portion 20. Bleed valve 30 is 
threadably received in exit portion 20 and it is moveable between an open 
position (where plunger 32 is pushed downward to permit gases to exit 
through aperture 34 in the side of the valve) and a closed position (where 
plunger 32 is pushed upward to block the flow of gases through the valve). 
Bleed valves of this type are conventional; a commonly used valve is Model 
No. 11245 which is commercially available from Dapco Industries. 
When it is desired to start the engine the plunger 32 of bleed valve 30 is 
pushed downward by means of button 36 so as to establish an open path from 
cylinder 10 to the atmosphere. During the starting of the engine a portion 
of the gases from the cylinder are thus able to exit to the atmosphere so 
that the compression forces are thereby reduced. This enables children and 
elderly persons to more easily start the engine. As the engine starts the 
sharp increase in compression due to the expansion of combustion gases 
pushes the plunger 32 of bleed valve 30 upward to its closed position. 
The manner in which the present invention relieves a portion of the 
compression forces through the spark plug or through the spark plug hole 
in the engine head also provides another significant advantage in that it 
assures that the airfuel mixture is brought into intimate contact with the 
spark plug during the starting operation. This increases the likelihood 
that the engine will start promptly. This result is contrasted with other 
techniques for relieving compression forces wherein the bleed valve is 
placed in a specially made aperture elsewhere in the head (i.e. away from 
the spark plug).