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Патент USA US2105411

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Jan. 11, 1938;
2,105,411 1
K. c. DE WALT
SPARK PLUG‘
Filed Aug. 1, 1936
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Inverwtor:
Kenneth C. DeWal t,
by Hwyafjwlw
Hls Attorneg.
2,105,411
Patented Jan. 11, 1938
UNITED STATES
PATENT OFFICE
2,105,411
.
SPARK PLUG
Kenneth C. De Walt, Schenectady, N. Y., assign
or to General Electric Company, a corporation
of New York
. Application August 1, was, Serial No. 93,855 .
4 Claims. v(c1. 1zs_1e9>
The present invention comprises an improved
spark plug for internal combustion engines.
Heretoi'ore it has been common practice to in
sulate from one another the oppositely charged
5 parts of a spark plug by an elongated insulator
commonly consisting of porcelain. The central
conductor is threaded through the insulator
which is mechanically clamped by a screw‘
threaded member within the casing of the plug.
10 It is well known that some disadvantages ac
company such a construction. For'example, the
end of the insulator is subject to carbon deposi
tion from the combustion mixture and the- in
sulator sometimes is cracked by the compressive
35 forces to which it is subjected, when it consists
oi’ opaque material, such as porcelain, the light
irom the spark cannot be seen from the exterior
and hence the operativeness of the spark plug
cannot be ascertained by observing light emitted
u by the plug.
.
‘
In accordance with the present invention all
an engine‘ cylinder. The attached end 01' the
conductor 4 is grooved at 8 and is ?rmly gripped
by the cap 3, which engages with the groove.
The body portion I terminates at the end 0p
posite the spark tip 6 in a lip 9 of reduced thick— 5
ness which preferably tapers down to an even
smaller rim. The opposite rims of the glass
cylinder 2 are sealed by fusion to‘ the rim of the
lip 9 and the rim of the cap 3. The seals between ‘
the glass and the metal members are maintained 10
strain-free by so choosing the glass and metal
that the thermal expansion characteristics of the
glass and metal are substantially coincident at
temperatures below the zone of transformation
temperatures of the glass, that is, at the zone of 15
temperature at which the thermal expansion
characteristics rapidly increase with temperature.
Such a seal is described in a copending applica
tion, Serial No. 705,250, ?led January 4, 1934 by
E. E. Burger and A. W. Hull (see corresponding 20
French Patent 784,164 issued April 23, 1935).
such di?iculties are absent and a convenient struc
This seal also is described in an article by A. W.
ture is provided by making part or the shell or , Hull and E. E. Burger in Physics, Vol. 5, No. 12,
outer member of a spark plug oi glass which is pages 384-411. As there explained, a suitable
’ integrally united or welded to adjoining metal
parts. No other insulator need be provided be
tween the sparking conductors. An internal
conductor is joined to a metal portion of the shell
at the endof the plug which is remote from the
location 01 the terminals between which the
spark occurs. If partial obscuration of the light
emitted by the spark can be tolerated, a battle is
provided between the sparking terminals and the
glass insulator, thereby preventing deposition of
U carbon or other conductive material upon the
inner surface of the‘insulator.
.
”
-
'
'
strain-free seal may be made by sealing a hard
glass, sold in the open market by the Corning 25
Glass Co. of Corning under the name “Corning
Gill”, to metal members having suitable thermal
expansion characteristics, for example, an’ alloy
consisting oi’ 54 per cent iron, 28 per cent nickel
and 18 per cent cobalt. The above application 30
and article describes various equivalents for this
particular glass and this particular metal alloy.
vIf desired, the member 1 may be constructed
of two parts brazed or otherwise joined to an- 3,
other, the thick walled part in consisting of iron 0
The accompanying drawing shows in Fig. 1 a or other inexpensive metal and the lip 5 consist~
longitudinal section of a preferred form of spark ing of alloy suitable for joining to glass.
plug embodying my invention; Figs. 2 and 3 are‘
In the spark plug shown in Fig. 1, the space
longitudinal sections of modifications; and Fig. 4 between theinner conductor 4 and the outer shell
is a perspective enlarged view of a bailie and sup
is unobscured so that light from the spark be~ 40
port employed in the modi?cation of Fig.
tween-the tips 5 and 6 may be seen‘ through the
Referring to Fig. 1, the spark plug illustrated ‘glass member 2. The condition of the spark thus
consists of an elongated shell or housing made may be observed and the condition of the plug
up of a heavy-walled metal body portion i, a thus may be determined, without the necessity of
glass portion '2, and a relatively thin-walled metal using special testing appliances or removing the
cap portion 3. An interior conductor 4 is at
plug.
tached at one end to the cap portion 8 of the
Inthe modi?cation shown in Fig. 2, the metal
shell. It terminates at the opposite in a spark 'ba?le ii is mounted upon the inner conductor 4,
ing tip I, whichlas illustrated, may have a smaller the walls of the shell i being somewhat cut away 50
cross section than the main portion of the con
as indicated at H. Particles of metal, carbon,
ductor l. The sparking tip I cooperates with a or other conducting material can only reach the
similar sparking tip 8 projecting from the screw
inner surface of the glass\window 2 through a ,
‘threaded portion 1 of the plug which is con
sinuous elongated path. Hence the amount of
structed to engage with an opening in the wall of such deposition will be greatly decreased. The 1,.
2
2,105,411
battle H, as indicated, consists of a cylindrical
portion and an outwardly extending radial ‘por
tion, the former making frictional engagement
with the conductor i.
In the modi?cation shown in Fig. 3, the bailie
l4 consists of an insulating .rnateii'al such as
alumina, magnesia, porcelain or silica. It is
shown somewhat enlarged in Fig. 4 together with
the holder i5 whereby it is mounted upon the
10 conductor E. The support 15 makes a frictional
engagement, both with battle H and the con“
ductor ‘. The segmental members l5a may be
bent outwardly to engage firmly and positively
with the baille H.
r
,
What I claim as new and desire to secure by ‘
Letters Patent of the United States is:
l. A spark plug for internal combustion ap~
paratus comprising the combination of a hollow
casing the wall of which consists of metal and
glass having approximately the same thermal co
e?icient of expansion, said metal and glass mem
bers being fusion-sealed to one another at adjan
cent edges and a cooperating conductor located
within said‘casing and being connected at one
end only with said casing.
2. A spark plug for internal combustion ap
paratus comprising the combination of a hollow
casing consisting of a plurality of metal members
and an intermediate hollow cylindrical glass
member which is sealed at opposite ends to said
respective metal members and a cooperating con
ductor sealed to one of said members and ex
tending in sparking relation to another of said
metal members.
3. A spark plug for internal combustion ap
paratus comprising the combination of a hollow
casing consisting of a metal base, a cap and a 10
glass insulator which is fusion-sealed to said base
and cap, a conductor sealed to said cap and pro
jecting through said casing and a baille mounted
on said conductor.
4. A spark plug comprising the combination of 15
a massive, hollow metal base constructed to en
gage with an engine cylinder well, said base hav
ing a rim of reduced thickness, a hollow glass
cylinder sealed at one rim thereof to said base
rim, 2. cap closing the opposite rim of said glass
cylinder and being fusion-sealed thereto, a con~
ductor extending from said base, and a second
conductor joined to said cap, projecting longi
tudinally through said casing and extending in
sparking relation to said base conductor.
KENNETH C. DE WALT.
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