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Патент USA US2134946

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Nov. 1, 1938.
2,134,946 . I
Filed Nov. 2, 1935
2 Sheets-Sheet vl
Nov. _l, 1938.
Filed Nov. 2, 1935
2 Sheets-Sheet 2.
Patented Nov. 1, 1938
2,134,946 ,
Roy T. Hurley, Dobbs Ferry, N. Y., assignor to
Bendix Aviation Corporation, South Bend,
Ind., a corporation of Delaware .
Application November 2, 1935, Serial No. 47,963
14 Claims.
(01. 241-5)
This invention relates to electrical apparatus.
whereby servicing of the same is rendered easy
and more particularly to means for shielding
and convenient and an effective continuous screen
electric circuits such as, forexample, the ignition
is insured.
circuit of a radial aircraft engine.
One of the objects of the present invention is
to provide a novel ignition harness for an internal
combustion engine whereby electrical radiation
from the ignition circuit thereof is substantially
A still ‘further object is to provide a novel
electrical radiation screen for an electrical con- .5
ductor which‘ is ?exible, moisture proof and heat
resisting and which has a high resistance to
penetration by gasoline, oil and the like and a
high resistance to abrasion, thus rendering the
It is well-known that electrical radiations from
the high tension oscillating circuits employed in
same durable and dependable.
the operation of internal combustion engines in
terfere with radio reception in the vicinity of
said engine, such as in an airplane, and render
the reception of signals, course indicating beams,
and the. like either ‘impossible or inaccurate.
for screening the electrical radiations ofthe ig
nition circuit of an internal combustion engine
Means have accordingly been heretofore provided
for screening the ignition circuits of engines by
enclosing the various live parts thereof in metal
current conducting casings and connecting the
latter to each other and to ground for the purpose
of avoiding any substantial radiations. The as
semblies or harnesses heretofore provided have
Another object is to provide a novel harness
which is simple in construction and of light
weight, yet durable, effective and dependable in 15
The above and further objects and novel fea
tures of the invention will more fully appear
from the following detail description, when taken
in connection with the accompanying drawings. 20
It is to be expressly understood, however, that the -
not, however, been entirely satisfactory, since the
drawings are for the purpose of illustration only
and are not designed as a de?nition of the limits
of the invention, reference for this latter purpose
same have not beenv dependable for long periods
being primarily had to the appended claims.
of service and the servicing of the same has been
In the drawings, wherein like reference char
acters refer to like parts throughout the several
inconvenient and difficult, comparatively slight
repairs requiring the use of a large number of
tools and a considerable amount of time and
Fig. l is a diagrammatic front view of a radial
engine illustrating a portion of the shielding har- , 30
labor by skilled mechanics. Furthermore, the
radio shielding apparatuses heretofore‘ provided
ness comprehended by the present invention;
which are at all practical have been such as to
subject the ‘insulation of the ignition cable to
‘Fig. ,2 is a perspective view showing. the rear
of said engine with the novel harness installed
deterioration by gasolinaheat, oil and moisture,
and in many instances to abrasion, thusreducing
the life and dependability of the circuit as well
as the effectiveness of the screen.
Fig. '3 is a perspective view illustrating one 35
type of magneto shield which “may be employed in
It is accordingly another object of the invention
to provide a novel ignition harness for screening
an internal combustion engine ignition-circuit
which is so constructed that the same may be
readily and easily installed on and removed from
the engine as a unit, said harness being further
adapted for installation so that necessary repairs
to the circuit or harness can be readily and quick
ly made without removing the entire harness and
without removing or disturbing adjustments of
other engine parts.
_ Still another object of the invention is to pro
vide novel means for effectively screening elec
trical radiations emanating from a current carry
ing conductor.
A further object is to provide a novel Joint
for connecting the individual parts of radiation
screening means for an electrical conductor
carrying out the present invention;
Fig. 4 is a detail view, with parts broken away,
of a manifold ring and connections therefor em
ployed in carrying out the invention;
, Fig. 5 is a partial sectional view, with parts
broken away, taken on line 5—5 of Fig. 4;
Fig. 6 is a section taken on line 6-6 of Fig. 4;
vFig. 7 is an enlarged sectional view of a por
tion of the wall of the shielding conduit of Fig. 5; 45
Fig. 8 is an enlarged section taken on line\8—-8
of Fig. 6;
Fig.9 is a sectional view, with parts broken
away, taken on line 9-9 of Fig. 4; v
Fig._ 10 is an end view and transverse section 50
taken on line l0—-|0 of Fig. 9;
Fig. 1-1 is a front elevation of one type of spar
plug shield which‘may be employed in carrying
out the invention; and,
Fig. 12 is a side elevation, partly in section and 55
with parts broken away, of the spark plug shield
of Fig. 11.
The live parts of the oscillating circuit of the
ignition system of aircraft engines, for example,
radiate magnetic lines of force which rise and
fall with current oscillations in the high tension
circuit and which interfere materially with radio
reception in the vicinity of the engine. In order
to prevent such interference it becomes necessary
to provide a metallic shield about all of said live
parts for the purpose of intercepting said lines
of force and dissipating the energy thereof in
the form of electric current which may be con
ducted to ground by the shield. If the shielding
15 means is to be satisfactorily effective, there must
be no substantial break or opening in the shield
ing system, and it is accordingly highly desirable
that all live wires and current carrying parts be
completely surrounded by metal when originally
20 installed and that the same be of such construc
tion and materials as not to be susceptible to too
rapid deterioration and frequent failure by reason
'of the elements and other conditions under}
which the same are required to operate. Acord
25 ingly, the shielding harness of the present in
vention, in the form illustrated, completely en
closes the» two independent ignition circuits of
a dual ignition radio aircraft engine wherein a
set of spark plugs is mounted at the front of the
30 engine cylinders and a second set is mounted at
satisfactory since sparks are apt to occur between
the engine and metallic braid when the latter rubs
against the former, thereby producing a fire
hazard. A fabric covering is not practical be
cause the same wears too rapidly, becomes oil
soaked, and is apt to take fire at engine tempera
tures. Furthermore, oil, gasoline and moisture
penetrate the fabric and seep through the woven
metallic shielding and deteriorate the rubber and
shellac employed on the current carrying con
Novel flexible tubing is accordingly provided
for shielding the conductors between magneto
shield 20 and manifold tube [5 and between the
latter and spark plug shields 24, which tubing is
not subject to the hazard of sparking and has a
high resistance to penetration and deterioration
by gasoline, oil, moisture, heat and abrasion. One
form of the novel tubing is constituted by mani
fold conduit N which is adapted to shield a plu
rality of conductors 22 and comprises a braided
metallic tube 25, such as phosphor bronze fiat
braid, surrounded by a second braided tube 26 of
smaller tinned copper wire. The former assists
the latter in shielding the current carrying con
ductors and gives su?icient rigidity to the conduit
the rear thereof, each set being connected to
to prevent excessive twisting and vibration there
of. Surrounding said metallic tubes and in inti
one of a pair of magnetos secured to the rear of
mate contact therewith is a covering 21 of syn
the engine.
The novel ignition harness provided is so con
35 structed as to facilitate the servicing and insure
.permanence of operation. In addition, the
length of the cable and weight of the entire unit
is minimized, all of which are important con
siderations, particularly in aircraft engines. As
shown, said harness comprises a pair of arcuate
manifold tubes or rings [5 and 16 extending over
an arc of about 120° and adapted to be secured to
the front and rear, respectively, of the engine I‘!
. by means of suitable brackets, not shown.
shielding conduits for conductors, the outer sur
faces of which have been constituted by metallic
braid or fabric. The former type is not wholly
Referring more particularly to the shielding
harness of that part of the ignition system which
includes the front spark plugs, manifold ring I5 is
preferably constituted by a thin, light metal tube,
such as copper or bronze, which offers compara
50 tively small resistance to the flow of electric cur
rent, and may be plated with nickel, chromium,
cadmium or the like, if ‘desired. Said tube, in the
embodiment illustrated, is made in two parts, one
of which is in the form of a T-joint l8 secured to
55 the remainder of the tube by means of an in
ternally threaded coupling nut l8a adapted to co
operate with threads on tube portion l5. One
branch of joint I8 extends rearwardly for con
nection with a novel ?exible manifold conduit I!
which is in turn connected in a novel manner to
hereinafter appear to a two-part metallic shield
20 supported by and covering the high tension
terminals of a magneto 2|. The individual cur
rent carrying conductors 22 extend from a
thetic rubber, which is not materially affected by
gasoline, oils and other solvents of natural rub
ber which is employed for insulation on con
ductors 22. Said covering also has a high resist
ance to heat, moisture and weather elements and
is tough enough to resist abrasion brought about
by movement and vibration of the conduit in con
tact with the engine by reason of wind currents
and other causes.
By way of example, one suitable composition of
synthetic rubber which may be employed in mak
ing covering 21 comprises about 100% of chloro
prene as a base, the chemical ‘formula of which is
10% of zinc oxide, 10% of magnesium oxide, 5%
of wood resin, and 40% of soft carbonblack. The
composition made in accordance with this typical
formula may be extruded onto braided wire tubes
25 and 26, thus causing the same to ?ll the spaces
between the strands of wire forming said tubes.
Additional rigidity and resistance to twisting
movements is thus given to the entire conduit
without impairing the longitudinal ?exibility
thereof, and relative movement of tubes 25 and
26 is obviated.
Another form of the novel shielding conduit
provided by this invention is illustrated in Fig. 8
wherein conduit 23 is shown as comprising a wire
braided tube 28 having a covering 29 of syn
thetic rubber of the character above described
extruded thereon. In order .to give the conduit
terminal of the magneto through manifold con
duit l9, manifoldv tube l5 and thence through rigidity, (to prevent crushing the latter and to
novelly constructed conduits 23, 23a and spark facilitate the insertion of current carrying con
plug shields 24 to the front plugs of the engine. . ductors 22, conduits “23, 23a also include a coil
Conduits 23, 23a are connected to manifold tube
70 l5 and shields 24 in a novel manner to appear
hereafter. Conductors 22 may be constituted by
standard copper wire insulated with natural rub
' ber, fabric and shellac in a well-known manner.
In ignition harness heretofore provided, the
76 most successful units have employed ?exible
spring 30 within braided tube 28, said spring be- ,
ing under torsional compression and exerting
a radial pressure "against the inner walls of said
braided tube.
As noted above, the present invention, com
prehends the use of a plurality of metallic mani
fold tubes 15 and I 6 in lieu of the single tube
heretofore used in devices of this character and
mounted on the rear of the engine, the arcuate
length of said tubes-being materially reduced for
the purpose of reducing the weight of the har
ness and facilitating installation and servicing
thereof. To further facilitate installation and
servicing, novel connecting means are provided
shields. The inner endscf conduits 23a extend
through a triangular-like coupling member or
ferrule 42 (Figs. 9 and 10.) having three passages
therethrough, the inner walls of which are closely
engaged by .the synthetic rubber covering 29 of
conduits 23a. Braided metallic tubes 28 and
springs 30 of said conduits extend beyond the
in combination with the shielding tubes and con ‘ ends of covering 29, are ?ared outwardly over
duits whereby the harness may be readily dis
the inner face of ferrule 42, and are secured
10 assembled after installation without interfering
thereto. The securing means is preferably con 10
with the engine parts and without removing the stituted by soft soldering in order to permit the
entire shielding unit and whereby dust and mois
renewal of one of the conduits 23a without de
ture are excluded therefrom. The ends of the stroying the entire three-way connection. A cir
shielding conduits and novelly constructed to cular ?ange 43 is provided on the inner end of
constitute part of the coupling means and to in
ferrule 42, which is adapted to be held in elec 15
sure good electrical connections between the sev
eral parts of the shielding harness. As shown
in connection with conduit I9, said coupling
means comprise a pair of ?anged metallic fer
20 rules 3i and 32, Fig. 5, the former of‘which
has a tubular portion extending into the con
duit and the latter a tubular portion which ex
tends ‘outside of the conduit in intimate contact
' with
covering 21.
The ?anges on said ferrules
extend radially and outwardly in' overlapping re
lation and the end portions of braided tubes 25
and‘ 26 which extend beyond covering 21 are
?ared outwardlyv between said ?anges. Said
?ared portions and ?anges are secured together
30 by suitable means such as solder, thus forming
a conduit with a clean, as distinguished from a
ragged end, and insuring an effective electrical
connection. A pair of internally threaded cou
pling nuts 33 having inturned ?anges 34 engag
35 ing the ?ange of ferrule 32 are adapted to coop
erate with threads on a branch of Tejoint l8
and an extended portion of magneto shield 2d
to complete the shielding means between the
magneto and the manifold tube. Upon screw
40 ing coupling nuts 33 tightly into position, the
?ange of ferrule 3! will be held in firm contact
with joint'id or shield 20, as the case may be,
thereby forming 'a tight joint and sure electrical
connection between the shielding parts.
' A modified coupling is shown for connecting
conduits 23 to manifold tube l5 wherein the
inner ends of the three conduits which are shown
connected to said tube intermediate the ends of
the latter are provided with a pair of ?anged
ferrules 3i‘: and 36 (Fig. 8) which have tubular
portions that extend inside of spring 30 and out- .
trical engagement with a threaded collar 44
brazed to the end of manifold tube ill by means
of an internally threaded coupling nut 45 having
an inwardly extending lip 46 engaging the outer
face of ?ange 43.
One type of spark plug shieldlwhich may be
employed in carrying out the invention comprises
a cup-shaped body portion 41 adapted to be re
movably secured to a spark plug 48 by means
of a pair of collars 49 and 56 having coacting
?anges, the former of which has threaded en
gagement with an opening in the bottom of body
121 and the latter a like engagement with the
metallic body of spark plug 48. An opening at
the top of body 41 is covered by a metallic plate
ment with the edges of said opening by a ?anged
ring 53, said ring being secured to the body by
peeping the lower edge of the ?ange thereof 35
over an annular head on body M. For the pur
pose of liberating ozone which. will be generated ‘
within body él'l during engine operation and at
the same time avoiding entrance of dirt and
moisture, a channel 5c is formed around said 4.0
body beneath ring 53 and has small alternate
openings 55 and %_into body-4T and to atmos
phere, respectively. Threaded into an opening
in the side of body“ is a short tubular member
58 to which a shielded conduit 23 or 23a is adapt
ed to be connected by coupling nut W in the
manner above described.
The means for establishing an electrical con
nection between conductor 22, which extends
through conduit 23, and spark plug electrode 59, 50
are preferably constituted by a pin til, an en
side of covering 29, respectively. The ?anges on
said ferrules overlap and have'the ?ared end of
tube 28 soldered or otherwise suitably secured
therebetween. An externally threaded coupling
nutv 3T is adapted to threadedly engage a nipple
38 which may be permanently secured, as'by
larged head portion of which is slidably mounted
in a metallic cylinder 6i’, the pin being normally
held in engagement with electrode 59 by a spring
62 within said cylinder. The inner end of the
wire of conductor 22 is ?ared outwardly and soli
means of silver brazing, over an opening in the
insulating spool 64. The inner end ofcylinder
wall of manifold tube l5. Nut 31 is adapted to
56 and a plurality of layers of mica insulation
52, which plate and layers are held in engage
dered to a metallic? Washer 83 molded into an
Si is held in engagement with the ?ared end of
60 engage the ?ange of ferrule 36 and press the ‘ the wire of conductor 22 by an expandible lock 60
?ange of ferrule 35 against the plane surface of
an internal ?ange 39 on nipple 38, thereby form
ing a tight joint and electrical connection. An
interally threaded coupling-nut 40 (Fig. 12) hav--'
ing an internal lip 4| for engaging the ?ange of
ferrule 36 maybe employed for connecting the
outer end of conduits 23 to spark plug shields 24.
In the illustrated embodiment of the inven-'
tion, three of the current carrying conductors 22
spring 65 adapted to coact with an internalgroove
in spool M. The movement of said spool in
body 41 is limited by a shoulder thereon which v -
cooperates with an internal shoulder on tubular 65
member 58. If desired, a rubber washer 65 may
be interposed between the ends of conduit 23 and
the outer ends of members 58 and 64.
The- shielding harness‘ for ‘thatportion of the
70 are led out from each end of manifold tube I5, > ignition circuit including the rear spark plugs is 70
‘l8 through shielding conduits 23a to the indi
vvidual spark plug shields 24.
Conduits 2311 are
substantially the same as the harness above de
scribed except for minor details of desi n neces
similar in construction to conduits 23, and the
sitated by the particular engine construction to
outer ' ends thereof are provided with similar
which it is to beadapted.
75 coupling means for connection to said spark plug
The manifold conduit .
connecting manifold tube IE to the shield on 75
magneto 2la is of course much shorter than con
duit I9, but of the same construction.
There is thus provided a novel radio shielding
harness for the high tension shielding circuit of
an internal combustion engine whereby electrical
radiations and consequent interference with ra
dio reception in the vicinity of the engine are
Novel shielding means for a current
carrying conductor are also provided, which
10 means are so constructed as to offer high resist
ance to deteriorating causes and agencies present
in the operation of an internal combustion engine,
thus increasing the life of the harness and de
creasing the possibility of failure thereof. Said
15 means are also so constructed as to be readily
installed and serviced in the ?eld as well as in
extending between said ?anges in electrical con
tact therewith.
4. An electrical radiation screen for an electric
current carrying conductor comprising a ?exible
metallic tube, a covering of synthetic rubber on
said tube, a metallic ferrule surrounding said
cover adjacent an end of said tube, said ferrule
having an exterior annular ?ange at the outer
end thereof, and means for electrically connect
ing the end of said metallic tube to said ?ange. 10
5. An electrical radiation screen for an electric
current carrying conductor comprising a ?exible
metallic tube, a. covering of synthetic rubber
therefor, a metallic ferrule at an end thereof
surrounding said covering and electrically con 15
nected to said metallic tube, and a coiled me
the shop.
tallic spring under torsional compression within
Additionally, there is provided a novel ignition
harness for the ignition system of a dual igni
tion engine wherein each ignition circuit is in
dependently shielded so that in the event of
damage to the shield of one circuit the other cir
cuit may be employed singly for operating the
said ?exible tube.
engine without any interruption of satisfactory
25 radio reception. The invention also compre
hends a novel harness wherein a single shielding
conduit is passed between the,hot cylinders of
the engine instead of nine conduits, as has been
the practice in similar devices heretofore pro
30 vided, said single conduit being so constructed
as to withstand for long periods of time the in
tense heat, the action of gas, oil and other mois
tures, and the wearing tendencies to which it
is subjected.
Although only- one embodiment of the inven
tion has been illustrated and described, it is to
be expressly understood that the same is not lim
ited thereto but that various changes may be
made. For example, manifold tubes l5 and i8
40 may, if desired, be further divided into pairs on
some types of engines to increase the facility with
which the same may be serviced. Many other
changes may also be made in the design and
arrangement of parts illustrated, as will now be
45 apparent to those skilled in the art, without de
parting from the spirit and scope of the inven
tion. Reference will accordingly be had pri
marily to the appended claims for a de?nition of
the limits of the invention.
What is claimed is:
1. A radio shield for an electric current car
rying conductor comprising a ?exible metallic
tube, a synthetic rubber covering on said tube,
and a metallic ferrule at each'end of said tube
55 surrounding said cover, ‘the ends ofsaid tube
being electrically connected to said ferrules.
2. A radio shielding conduit for an electric
current carrying conductor comprising a ?exible
metallic tube, a synthetic rubber covering on said
60 tube, a metallic ferrule at each end of said tube
surrounding said cover, the ends of said'tube
being electrically connected to said ferrules, and
a metallic spring under torsional compression
within said metallic tube and exerting a radial
‘pressure against the walls thereof.
3. A radio shield for an electrical conductor
comprising ' a ?exible metallic tube having1 a
?ared end portion, a covering of synthetic rub
70 ber for said tube, a metallicferrule surrounding
said covering adjacent anend thereof, ‘a metallic
spmg inside of said tube, and a ferrule extend
ing into_said tube interiorly of said spring, said
ferrules having overlapping exterior ?anges
thereon with the ?ared end of said metallic tube
6. A radio shield for an electrical conductor’
comprising a loosely braided wire tube, a com
paratively closely braided wire tube surrounding
said ?rst tube, and a cover of synthetic rubber
extruded onto said tubes to surround the same
and fill the spaces between the strands thereof.
7. In apparatus of the character described, a 25
metallic tube having a threaded collar on an .
end thereof, a ?anged ferrule having a plurality
of longitudinal passages therethrough, a ?exible
metallic conduit extending into each of said pas
sages and secured to said ferrule, and a coupling
nut adapted to threadedly engage said collar and
having an internal ?ange adapted to engage
the ?ange on said ferrule to hold the latter in
contact with said collar.
8. In apparatus of the class described, a metal
lic tube having a threaded portion at an end
thereof, a coupling member having a plurality
of passages therethrough and a ?ange adjacent
one end thereof, a ?exible metallic conduit ex
tending through each of said passages and se 40
cured to said member, a synthetic rubber cover
ing on each of said conduits engaging the walls
of said passages, and a coupling nut adapted to
cooperate with said ?ange and the threaded
portion of said tube to secure said member and 45
tube together and establish an electrical con
tact therebetween.
9. A radio shield for an electrical conductor
comprising a braided wire tube, a covering 'of
synthetic rubber extruded onto said tube to sur 50
round the same and ?ll the spaces between the
‘strands thereof, and a metallic spring within
said tube engaging the inner walls thereof.
10. In apparatus of the class described, a me
tallic tube having an opening in the wall thereof, 55
a ?anged nipple covering said opening and elec
trically secured to said tube, a ?exible metallic
conduit, 9. covering of synthetic rubber on said
conduit, a ferrule on an end of said conduit hav
ing a ?ange, a ?ared end of said metallic con
duit being in electrical contact with said ?ange,
and a coupling nut threadedly engaging said
nipple and adapted to hold said flange and ?ared
end against said~nipple whereby a tight Joint is
formed and said tube and conduit are held in
electrical contact.
11. In a radio shielding ignition harness for
an internal combustion engine, a substantially
rigid metallic conduit, an internally threaded
nipple extending outwardly from said conduit, 70
an internal ?ange on said nipple having a plane
~ face, a ?exible metallic tube, a ferrule having an
. external ?ange surrounding said tube, and a
coupling nut threadedly engaging said nipple to
press a ?ared end of said ?exible tube between 75
5 ,
said ?anges whereby a tight joint and electrical
contact is established between said conduit and
12. In a radio shielding ignition harness for
an internal combustion engine, a substantially
rigid metallic conduit, an internally threaded
nipple extending outwardly from said conduit,
an internal ?ange on said nipple having a plane
face, a ?exible metallic tube, a covering of syn
thetic rubber on said tube, a coil spring in said
tube, a ?anged ferrule surrounding the cover
ing adjacent an end thereof, a ?anged ferrule
13. An electrical radiation screen for an elec
tric current carrying conductor comprising a
?exible metallic tube, a metallic ferrule sur
rounding said tube adjacent an end thereof, a
metallic spring inside of said tube, and a ferrule 5
‘extending into said tube'interiorly of said spring,
said ferrules having overlapping exterior ?anges
thereon that have electrical contact with the
end of said metallic tube.
14. An electrical radiation screen for an elec
extending interiorly of said spring, the ?ared
tric current carrying conductor comprising a
?exible metallic tube, a coiled metallic spring in
side of said tube, and a metallic ferrule extend
end of said ?exible tube extending between the
?anges on said ferrules, and a coupling nut'
ing into said tube interiorly of said spring, said
ferrule having an external ?ange electrically 15
threadedly engaging said nipple to clamp said
ferrule ?anges and ?ared portion between said
nut and the plane face of said nipple ?ange.
connected to said tube.
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