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Патент USA US2108525

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Patented Feb. 15, 1938
Charles Molyneux Carington and Archibald Ed
ward Postlethwaite, London, England, assign
ors to K. L. G. Sparking Plugs Limited, London,
England, a British company’
Application July 7, 1937, Serial No. 152,294
In Great Britain December 5, 1936
10 Claims. ( Cl. 123-119)
This invention is for improvements in spark
ing-plugs, for internal-combustion engines, of of inserting the wires into the grooves of the
the kind in which the earthed electrode, which is ring, Figure 4 being a sectional elevation to an
carried by the body of the plug, is constituted enlarged scale on the line 4-4 of Figure 3 and
by one or more ?ne wires; a sparking-plug of this
kind is described in British patent speci?cation
No. 448,913.
The attachment of the wires to the body of
the plug has hitherto presented serious manu
10 facturing difficulties. For example, it is com
mercially impracticable to drill holes of, say, .02
inch diameter in the plug-body owing to the fre~
quent breakage of the drill bits. The object of
this invention is to provide an inexpensive mount
15 ing for the ?ne wires.
According to the present invention, the plug
,body comprises two interengaging parts, and each
;wire is located by a groove in one part; prefer
ably each groove is closed by the other part.
20 The said grooves are preferably formed in the
said part prior to the ?tting of the parts together,
and the width of each groove is preferably slight
ly less than the diameter of the wire, so that
the wire‘is gripped in addition to being located,
by the groove.
The part of the body which is formed with the
grooves maybe a small metal ring which, when
the wires have been inserted in the grooves, is
placed on a shoulder in the plug-body which
30 closes the grooves. The ring may be held in
place by any suitable means.
Where the wires are disposed substantially
radially with respect to the plug axis, they are
located against movement radially outwards by
35 their abutment against the inner wall of the plug
body surrounding the ring; in order to locate
them against movement in the other direction
each groove may be formed with a local enlarge
_ ment at a part of its length other than its inner
40 most end so that the diameter of the wire at this
part is uncompressed, or is compressed to a less
extent than the remainder, when the wire is
forced into the groove. For example, the groove
may be discontinued at a point near its outer
' end so that the wire at this
and thus provides a head.
point is undeformed
A speci?c embodiment of the present invention
will now be described by way of example with
reference to the accompanying drawing of
Figure 1 is a plan view of the small metal ring
into which the wires are a?'ixed,
Figure 2 is a sectional elevation on the line
2-2 of Figure 1,
Figure 3 is a diagram illustrating the method
Figure 5 a plan view, to the same enlarged scale,
of the wire and the part of the ring shown in Fig
ure 4, and
Figure 6 is a sectional elevation of the assem
bled sparking-plug body.
As shown ?rst in Figures 1 and 2, a steel ring
IE3 is milled on one face with six radial grooves ‘
H ‘of substantially square cross-section. The
outer‘ edge of the grooved face of the ring is
chamfered as shown at E2 and the inner edge
of the other face is chamfered at IS. The pur
pose of these chamfers is explained below.
When the wires are to be inserted into the
grooves, the ring I I] is placed on an anvil M hav
ing a locating ledge l5 and a central cylindrical
mandrel Hi. The wires H1 are brought in from
six supply spools until their ends abut against
the mandrel E6 and they are then pressed lightly
into the grooves H. A tubular tool E8 is now
brought down on to the wires'whereby they are
pressed tightly into the grooves. An outer tool
l9 slidable on the tube #8 is now pressed down '
so as to shear off the Wires ?ush with the outer
wall of the ring ill.
The diameter of each wire is slightly greater
than the corresponding ‘dimension of the groove
H. For example, the diameter of the wire may
be .02 inch and each groove H may be .018 inch
in breadth and .018 inch in depth. Consequent
ly when the wires are forced into the grooves, the
part of each wire which engages the groove is
deformed into an approximately square shape as
shown in Figure 4.
The friction between this deformed portion
and the groove is su?icient to retain the wire in
position until the ?nal assembly of the spark~
ing-plug. The outer end of the wire, however,
at the region of the chamfered edge I2 of the
ring is unconstrained in a direction laterally of
the groove so that at this region an enlarged head
23 is formed as shown in Figure 5 and in broken
lines in Figure 4. This head is of larger trans
verse dimensions than the groove and therefore
prevents movement of the wire in a direction
towards the centre of the ring H1. ‘ The chamfer
constitutes, in eifect, a local enlargement in the
groove I! at the outer end of the groove. But
such enlargement could be provided at any other
part of the groove except at the innermost end
The pressure applied by the tool l8 may be
such as to leave the wires standing very slight
1y above of the ring In as shown in Figure 4.
As shown in Figure 6, the sparking-plug body
21 is formed near the mouth with an inwardly
directed shoulder 22. The ring with the wires
in position is removed from the anvil l4, turned
upsidedown, and placed with the wires down
wards on the shoulder 22. The ring IE3 and the
shoulder 22 thus constitute the two “interengag
ing parts” referred to above and in the claims.
10 The upstanding wall 23 of the plug-body is now
rolled down on to the ring Ill so as to clamp it
tightly in position. In Figure 6 the wall '23 is
shown on the left-hand side as it appears before
the rolling operation and on the right-hand side
as it appears after the rolling operation. The
protrusion of each wire by a very small distance
beyond the face of the ring ensures that, when
the plug is ?nally assembled as above described,
the wires are ?rmly clamped between the ring
20 l0 and the shoulder 22.
In the assembled plug it will be seen that the
wires II, the inner ends of which have been ac
curately positioned by their abutment against
which is formed with a plurality of grooves which
are closed by the other part, and electrode means
comprising a plurality of ?ne wires located by
said grooves.
3. A sparking-plug comprising a body formed
in two parts, one of which is formed with grooves
prior to assembly of the ‘plug, said grooves be
ing closed by theother part, and electrode means
comprising a plurality of fine wires located by
said grooves.
4. A sparking-plug according to claim 3 where
in the width of each groove is such as to grip
the wire within it.
5. A sparking-plug comprising a body, a metal
ring adapted to engage the body and formed on
one 'face with a plurality of radial grooves, a
shoulder on‘the'body against which the ring abuts
so that the grooves are closed by the shoulder,
and electrode means comprising ?ne wires located
by said grooves.
6. A sparking-plug comprising a body having
a shoulder, a metal ring'adapted to rest against
said shoulder and formed with grooves which are
closed by said shoulder, a rolled-over projection
the mandrel iii, are prevented from moving radi
‘on the-body to locate said ring in position, and 1'
electrode means comprising ?ne wires located by
against the wall of the plug-body. They are pre
said grooves and said shoulder.
vented from moving radially inwards by the en
'7. A sparking~plug accordingto claim 6 where
larged heads described above with reference to ineach said groove is formed with a vlocal en
Figures 4 and 5. Movement in any other direc
largement at a part of its length other than its .30
30 tion is rendered impossible by the walls of the
grooves and by the gripping action of the ring innermost
8. A sparking-plug»according to claim‘6 where
in and the shoulder 22.
in each said groove is=discontinued ‘at a point
The purpose of the inner chamfer I3 is to
near its outer end.
provide with the rolled~over wall 23 of the body,
9. A sparking-plug according to claim 6 where
in the grooved ‘face of the ring is chamfered at
on theright-hand side of Figure 6.
outer edge.
It will be understood that any desired number its 10.
A- sparking-plug comprising a plug-body
of wires may be used and that they need not having a shouldered recess, a ?at ring adapted
be arranged radially. For example, each wire to reston the said-shoulder and formed on the .40
may pass continuously from one groove to an
face which abuts said shoulder with a chamfer
other in either a straight or suitably curved path. at ‘its outer edge and with radial grooves of
The metal for the wire may be platinum, iridium, rectangular cross-section, platinum wires adapt
or platinum-iridium alloy.
ed to engage the grooves in such manner as
We claim—
partially to protrude beyond the grooved face of . ,
1. A sparking-plug comprising a plug-body
45 composed of two inter-engaging parts, one of the ring, andmeans for-pressing the ring towards
the shoulder whereby the said wires are clamped
which is grooved, and an electrode comprising at between the ring and the shoulder.
least one ?ne wire located in said groove.
2. A sparking-plug comprising a plug-body
composed of two interengaging parts, one of
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