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Патент USA US2120492

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June 14,. 1938.
2,120,492
L. GRAF
smmxme PLUG
Filed April 1, 1937 '
Inventor."
[.60 Gr-(lf
P9"
PM.
A?orne Y.
2,120,492
Patented June 14, 1938
UNITED STATES PATENT OFFICE
SPARKING PLUG
Leo Graf, OoIogne-Bickendorf, Germany, as
_ signor to Karl Werth, Berlin, Germany
Application April 1, 1937, Serial No. 134,374
'
In Germany February 17, 1937
5 Claims. (Cl. l23—169)
This invention relates to sparking plugs the nut. Underneath the headpiece 3, provided with
chief object being to provide a more e?icient the screw ‘thread, there is provided a cup-shaped
sparking plug than heretofore.
cap l0’ and between the cap and the upper. end of
A further object is to provide a construction ' the insulator there is located a spring H or a
device having an equivalent action, whilst a 5
washer I! may also be provided. By means of
5 of plug in which particles of oil are substantially
prevented from coming into contact with the
electrodes.
‘
the spring II the co-emcient of heat expansion
A further object is to provide an extension . between the insulator body and the electrode are
chamber for the gases in one or each of the elec
balanced so that the ignition plug remains per-'
trodes, said gas extension chamberbeing at a manently gas-tight. ~ Between the collar 4 and
higher pressure than the cylinder chamber dur
the foot of the insulator there may be ?tted a
ing the compression stroke.
- washer l3, for example of asbestos or the like.
In acordance with the present invention a The purpose of the washer, in addition to eil'ect- ,
sparking plug comprises a plug body, an in ‘ ing packing, is also to prevent breaking open of
15 sulator body, a plurality of electrodes, an ex
the lower end of the insulator root. This would
pansion chamber fora portion of the gases and a be liable to occur easily when, in consequence of
gas extension chamber provided in one or each heating, the radially‘expanding collar 4 acts di
of said electrodes. Said gas extension chamber rectly on the insulator foot, with the result that
radially directed forces may occur in the in
may, therefore, be provided in the central elec
20 trode, in the mass electrode, or electrodes, or in sulator foot. Consequently it is advisable to in
both the central electrode and the‘ mass electrode, sert the packing disc which, by reason of the
‘10
or electrodes.
25
'
of following the radial expansion of .the collar 4,
whilst the‘ internal resistance to deformation of
accompanying drawing which shows’by way of
example preferred embodiments thereof.
the insertion must be so slight that the forces
transmitted to the top ‘side of the insertion are
less than the allowable radial tension of the in
sulator foot. It is advisable to provide the collar
4 with an undercut as shown in Figure 2.
In the drawing:
Figure 1 is a longitudinal section of the ignition
plllg-
30
change of shape on its lower surface, is‘ capable
In order that the invention may be more clearly
understood reference will nowbe made to the
.
Figure 2 shows the central electrodeand the
. In the foot I of the plug body, provided with a
mass electrode, the central electrode being re- _ screw thread, there is a bore for the. reception of
cessed at its lower end.
'
Figure 3 shows a central section of another
form of the mass electrode.
35 Figure 4 shows a vertical longitudinal section
of another form of construction of the lower part
of an ignition plug according to the invention,
and
Figure 5 shows ‘another form of construction of
40 the mass electrode.
In the drawing like references designate the
same or similar parts.
In the insulating body I is located the central
the mass electrode 9.
This mass electrode con
sists of a member 9 which, for example, is mount
ed on ans-rm II which is enlarged conically out-'
wards and then passes into a cylindrical portion I!
which engages with a corresponding hole of the
foot 8. Opposite to the hole provided for the re
ception of the cylindrical part 15 of the mass
electrode there maybe provided a further hole
26 in the foot of the plug body.
‘
Immediately above the mass electrode 9 and
within the lower part of the central electrode 2,
there is provided a recess 2a, this recess forming
electrode 2 which, as shown in Figure, 2, is pro- 1 a chamber which communicates by means of an
45 vided at its lower end with a hollow chamber 2a.
At the upper end ‘the central electrode 2 engages
with the internal screw- thread of a headpiece 3,
provided with cooling 'ribs, on the screwed spindle
3a of which there is applied the cable securing
>50 nut. At the lower end the central electrode 2 is
provided with a collar 4 which presses against
the under surface of the insulator foot. _
By means of a ?anged nut 5 the insulator body
is secured in the plug body, whilst a copper ring
55 1 is ?tted between the insulator and the ?anged
annular. space with the cylinder chamber proper.
It will be understood, therefore, that this recess
2a. forms what may be termed an auxiliary gas
expansion chamber, or a gas extension chamber,
which appears to have the following action in
practice. ' The chamber 20. in addition to the
chamber 9a in the mass electrode will be herein
after referred to as the gas extension chamber.
when, for example, in the case of a four stroke
engine the piston passes downwardly during the
suction stroke, the mixture passes into the cyl
2,120,492
2
inder chamber and into the gas extension cham
ber. When the piston moves upwardly for the
purpose of compression, the mixture is com
pressed in both chambers. In the actual cyl
inder chamber there are located in the vicinity
of the piston the heaviest moist particles of fuel
and above these light combustible products. As
the compression of the mixture involves heating
and the heating is the more intense the less moist
10 cooling mixture particles are present, the heat
ing in the upper part of the cylinder is greater
than in the lower part and particularly high in
the gas extension chamber in which the combus
tion air is entirely free from moist particles by
15 reason of the paths of ?ow. Consequently there
obtains, during the entire combustion stroke,
in the gas extension chamber a higher pressure
than in the actual cylinder chamber, that is to
say, the gas extension chamber, during the com
'20 pression stroke, blows continuously into the ac
tual cylinder chamber with a certain excess pres
sure. When now during the upward movement
of the piston a particle of oil is projected on
the electrodes it is either entirely prevented from
25 coming into contact with the electrodes, and thus
forming a short-circuit, by the gases blown
through the annular gap, or the oil particle
comes into contact with the electrodes but is
blown off directly at the same moment so that
30 the formation of a short-circuit oil ?lm between
the central electrode and the mass electrode is
prevented and ignition can take place during or
after reaching the upper dead-centre position
of the piston. As the gases which flow through
35 the annular gap between the central and mass
‘ electrodes are particularly hot and particularly
easily explodable these are particularly readily
ignited by the passing spark and projected in
the form of an annular cutting flame outwardly
40 over the spherical mass electrode and thus is
nite the other gas mixture located in the actual
cylinder chamber. As. the gap no longer ignites
the actual cylinder mixture but ignites the par
ticularly readily explodable mixture ?owing from
45 the gas extension chamber and this mixture
forms an annular cutting ?ame, the ignition ve
locity in the cylinder itself is also increased as
the annular cutting flame-like ignited mass has
a greater ignition effect than the spark which
50
passes.
'
The circumstances which have been set out
therefore cause, even in the case of cold plugs‘,
that is to say when starting, an intensive igni
tion and a more efficient utilization of the mix
55 ture. When the electrodes, after a predeter
mined time of action, have reached the working
temperature the ignition property of the plug
is still further increased in that the mixture in
the gas extension chamber is from the start
60 hotter, by reason of being heated by the elec
trodes, than the mixture located in the cylinder
chamber so that the pressure excess of the gases
in the gas extension chamber relatively to the
actual cylinder chamber and thus the blowing
65 outwardly from the gas extension chamber are
further ampli?ed.
To the heating of the mixture in the gas ex
tension chamber by the heating action of the
electrodes there must also be added, as above
70 described, the heating as a result of the com
pression so that also in operation, that is to say
when the electrodes have reached the working
temperature, there obtains a constant excess
pressure in the gas extension chamber rela
75 tively to the cylinder mixture and thus any
bridging of the spark gap by oil and soot parti
cles is prevented.
Even in the case of stoppage of the engine for
any reason should oil or carbon particles have
been deposited on the electrodes these will be
blown from the electrode surfaces when start
ing the engine at the latest during the second
compression stroke prior to the ignition period
so that at the latest the second ignition can
take-‘place unhindered.
Thorough researches 10
have shown that the above mentioned results
actually occur in fact and most probably are
caused by the explanations set out above, whilst
it is not impossible that also other factors play
a part. The above explanations only relate to
the explanation of the apparently most impor
tant point of view of the method of operation of
the ignition plug.
In Figures 1 and 2 is shown a plug construction
wherein the mass electrode 9 consists of a solid
ball and only the central electrode 2 is provided
with a recess which forms the gas extension
chamber. The arrangement may, however, also
be such, as shown in Figure 3, namely that the
mass electrode 9 is also provided with a recess
9a so that the gas extension chamber is located
both'in the central electrode and in the __mass
electrode. In certain forms of constructicr’r" the
‘mass electrode may also be so arranged thattn'e '
gas extension chamber is provided therein alone.
The mass electrode may be so arranged op
posite the central electrode that the mass elec
trode lies along the axial extension of the cen
tral electrode. The arrangement may also be‘
such that for example two or four spherical .
mass‘ electrodes l5 are arranged in a radial di
rection relatively to the central electrode I‘! as
shown in Figure 4. The central electrode H
is then provided with suitable bores l8 which to
gether with the right and left parts of the spheri
cal surface of the mass electrode l6 form the
gas extension chamber. Also in this case the gas
extension chamber may be provided either only
in the central electrode or in the central elec
trode and in the mass electrode, for example by’
providing recesses in the balls of the mass elec—
trodes as shown in Figure 3.
Figure 5 shows the lower end of an ignition plug
wherein the oppositely disposed edges of the cen
tral electrode l9 and the mass electrode 20 are .
provided with sharp edges for facilitating the
passage of the spark. In this case the mass elec
trode 20 is provided on an arm 22 pressed from
a ring 2|. The ring 2| is ?tted into a suitable
groove of the foot 8 of the plug body.
As shown in Figure 1 the central electrode 2
is mounted in a hollow space of the insulator
which is larger, by an amount necessitated by tol
erance, than the external diameter of the central
electrode. In the vicinity of its lower edge the (ill
central electrode is centered by a ring 23. This
ring, in order to prevent the transmission of heat
from the insulator foot to the central electrode,
may be constructed from a material which is a
poor conductor of heat.
In the insulator body there are formed by mill
ing, pressing or the like cooling ribs 24 and in the
surrounding part of the plug body 6 there are
provided openings 25 through which cooling air
reaches the insulator. In order to prevent the " O
foot of the plug body from unnecessarily heating
the foot of the insulator there may be ?tted be
tween the foot of the insulator and the foot of
the plug an insertion of poor'heat conducting
75
material, for example asbestos.
'
3
- 2,120,492
What I claim is:—_
I
.
1. A sparking plug comprising a plug body, an
insulator body, a carrier at the lower end of said
'trode, said spherical electrode having a recess.
therein, said recess being located opposite the re
plug body, an ori?ce in said carrier, a rod shaped _ .
central electrode, a spherical mass electrode held
within the ori?ce in said carrier and disposed op
posite to the central electrode, an expansion
. chamber for a portion of the gases and a recess ~
in said spherical mass electrode to form a gas ex
10
tension chamber.
.
'
-
4
2. A sparking plug comprising aplug body, an
insulator: body mounted in said plug body, a rod
shaped central electrode mounted in said insu
cess in thecentral electrode.
~
4. A sparking plug comprising a plug body, an
insulator body mounted in said plug body, a roll-_
shaped central electrode mounted in said insui
5
lator body,a collar on said central electrode, said‘
collar having an undercut recess therein adjacent
the insulator body and bearing against said insu
lator body, said rod having recesses near the end 10
thereof, and a plurality of spherical electrodes
mounted in said plug body,‘ said spherical elec
trodes being located one opposite each recess in
Jator body, a collar on said central electrode, said . the said central electrode.
15 collar having an undercut recess therein adjacent
5. A sparldng‘plug comprising a plug body, an
the insulator body and bearing against said insu~
insulator body mounted in said plug body, a rod
sbap'ed central electrode mounted in ‘said insu
lator body, acollar on said central electrode, said
said plug body, said spherical electrode being 10-‘ collar having an undercut recess therein- adja
cated opposite the recess in said central electrode. cent the insulator body and bearing against said
3. A sparking plug comprising a plug body, an insulator body, ‘said rod having receses near the 2.0
insulator body mounted in said plug body, a rod
end thereof, and a plurality of spherical elec-‘
shaped‘ central electrode mounted in said insu
trodes mounted in said plug body, said spherical
lator body, a collar on said central electrode, said electrodes being located one opposite each recess
collar having an undercut recess therein adjacent in the said central electrode, each of said spher
25
the insulator body and bearing against said in
electrodes having a recess therein, the re
sulatorbody,saidrodhavingarecessintheend ical’
cesses in said spherical electrodes being located
lator body, said rod having a reces in the end
thereof, a spherical earth electrode mounted in
thereof, a spherical earth electrode mounted in
said plug body. said spherical, electrode being
located opposite the recess in said
elec
opposite the recesses in the central electrode-‘ '
mom.
.
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