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Патент USA US3090122

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May 21, 1963
N. L. S M ITH
METHOD OF DETERMIN IN G LEAKS IN LIGHTNING
ARRESTERS AND THE! LÍKE
3,090,1 l2
Filed Jan. 14, 1960
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United States Patent Oiiice
i
Bßd?ilz
Patented May 2i, i953
2
of the vessel in an atmosphere of an inert gas and then
subjecting the sealed vessel to an atmosphere of substan
3,090,112
NETHÜD 0F DETERMHNDIG LLEAKS IN
tially reduced pressure while simultaneously applying a
LIGHïNlNG ARRESTERS ANB THE LIKE
desired to maintain sealed off from communication with y
strong electrostatic lield thereto, the reduced pressure at«
mosphere causing the inert gas sealed within the vessel to
be accelerated in its outward ilow through any non-sealed
openings and so resulting in a material decrease in the
time required to test a particular unit.
Still another object of the invention -is to provide a
novel method of determining the presence of leaks in sup
posedly sealed containers which method does not require
the use of the usually employed and very expensive mass
an external ambient atmosphere. More particularly, this
invention relates to a method of leak-testing lightning ar
tively inexpensive vacuum chamber form of apparatus by
Norman L. Smith, Haddoniield, NJ., assigner to H. K.
Porter Company, Inc., Philadelphia, Pa., a corporation
of Delaware
Filed Jan. 14, 1960, Ser. No. 2,435
6 Claims. (Cl. 29-d07)
This invention relates to a method of testing for leaks
in any vessel having an interior volume which it is
resters, either after the completion of the manufacturing
thereof or at some later time.
spectrometer apparatus, but which rather utilizes a rela
15
The purpose of sealing the interior of a lightning ar
rester from its surrounding environment is ‘to prevent the
entry of moisture or other substances which interfere with
the proper functioning of the spark gap structure or the
reason of which the incremental cost assignable to any
particular tested unit .may be kept very small.
The foregoing and other objects of the invention will
ybecome clear from a reading of the following .specifica
tion in conjunction with an examination of the appended
drawings, wherein:
potential barrier material housed within the lightning 20
FIGURE l is a longitudinal sectional view through a
arrester and by means of which a designed for light-ning
typical lightning arrester such as could be tested according
arrester breakdown potential is established.
to the method of the invention;
it is known that moisture laden lightning arresters are
not only the cause of radio disturbances but also that the
25
FIGURE 2 is an illustration in diagrammatic form of
an empty lightning arrester body positioned within a
chamber whose atmosphere may be controlled by charg
results in the failure thereof, this failure being due to the
ing and iiushing with various gases, and also illustrates in
4fact that the moisture forms upon the spark gap elec
schematic form means for fabricating and sealing the
trodes electrically conductive salts of the metal of which
lightning arrester;
the electrodes are made. Consequently, the gaps between
FIGURE 3 illustrates, also in schematic form, a com
the electrodes are substantially decreased if not entirely
pleted lightning arrester positioned within a vacuum cham
bridged. Moreover, in those types of lightning arrester
-ber and means for testing the same for the presence of
employing crystalline conductive particles, or bonded
leaks; and
conductive materials in the form of rods, plates or blocks,
FIGURE 4 illustrates a combination of the structures of
exhibiting the proper characteristics required for use in 35 FIGURES 2 and 3 for effecting `fabrication and testing of
lightning arresters, the presence of moisture within the
lightning arresters in one chamber.
arrester eventually aliects the characteristics of such ele
In the several figures like elements are denoted by like
ments to such an extent as to interfere with the normal
reference characters.
operation of the lightning arrester, if not 4rendering it
Referring now to the iigures and firstly to FÍGURE
wholly inoperative.
40 l, it will be observed that the illustrated typical lightning
The operating characteristics tof the lightning arrester
arrester comprises a non-conducting substantially cylin
are adversely affected by the establishment of electrically
drical casing or main body portion 10, preferably of
conductive current leakage paths by means of which cur
porcelain, into the lower end of which is lit-ted a ground
rent ñow through the lightning arrester takes place even
ing assembly consisting of the metallic plate r11 and
under circumstances in which >the lightning arrester should 45 terminal stud 12, the entire assembly being held in place
appear as an open circuit. The leakage paths through
by the sealing compound 13 and cement ifi. Filling a sub
the lightning arrester give rise to radio interference sig
stantial portion of the casing 10 and in electrical contact
nals and also render the lightning arrester incapable of
with the metallic plate l1 is a discrete mass of crystalline
performing with maximum efiiciency, in some extreme
conducting granules 15 such as silicon carbide crystals.
cases even causing fused circuits to be open circuited by 50 This granular mass of conducting material is confined
blowing the fuses or opening circuit breakers associated
Within the casing 1t) by an upper metallic plate 16 periph
therewith. The importance of maintaining the interior ' erally sealed to the interior surface of the wall of the
of the lightning arrester effectively isolated from its sur
body portion 10 by means tof the cement ring 17, the
presence of moisture within the arrester sooner or later
rounding external atmosphere is ltherefore readily under
plate 16 Ihaving a centrally located vertically upwardly
standable. Accordingly, it is a primary object of this in 55 extending threaded stud 18 añ‘ixed thereto. The stud 18'
vention to provide a novel method of testing lightning
is threaded into the lower end of an insulator rod 19
upon which is disposed a plurality of vertically spaced
not a complete seal has been effected during manufacture
pairs of dished spark gap electrodes 20, each pair of elec
and to thereby avoid faulty operation and premature fail
trodes being maintained in a predeterminedly spaced rela
ure of the lightning arrester when installed for operation 60 tion by the insulator spacers Z1.
in the field.
The upper end of the casing l@ is closed by a metal
Another object of the invention is to provide a novel
closure cap 22 sealed thereto by an annular llayer 0f
method of determining the presence of leaks in a sup
cement 24 and having centrally secured thereto a down
posedly sealed vessel by first carrying out the sealing
wardly projecting threaded stud 23 which is threaded
process in an inert gas atmosphere and then subjecting the 65 into the upper end of the insulator rod 19. The stud 23
sealed vessel to an electrostatic ñeld of suiñcient strength
is part of a central terminal assembly which extends up
to produce a visible glow discharge in the event that the
Ward through a porcelain insulator fitting 27 and termi
inert gas issues out of the supposedly sealed vessel due
nates in a terminal portion 3d. The arrester is completed
to the existence of an incomplete seal.
by the insulator porcelain cap 25 secured physically in
Yet another object of this invention is to provide a 70 place between the gaskets 28 and 20 by the fitting 27 and
novel method of detecting the presence of leaks in sup
having its interior filled with sealing compound 26 which
posedly sealed vessels by iirst carrying out the sealing
completely fills the space between the inside of the cap
arresters or other sealed vessels to determine whether or
3,090,112
4
3
25and the closure cap 22. together with its associated
central Áterminal assembly, the sealing :compound 26 ex
tending downwardly below the bottom edge of the closure
then, of course, have an internal volume of argon gas
instead or air so that any leaks occasioned by imperfect
cap Z2 lfor some distance along the outer surface of the
argon gas to escape thereoutof, and when subjected to an
main body portion l@ of the lightning arrester. A mount
ing bracket 3 and a pair of opposite end terminal insulat
ing covers 32 complete the lightning arrester assembly.
Barring ñaws or cracks in the casing 1€), it will be ob
served from the showing of FIGURE l that the casing
interior containing the granules 15 and the spark gap 10
electrode structures 2li is completely sealed away from
electrostatic field of proper strength will produce a visible
violet glow in the region of the leak. Of course, should
a perfect seal yhave been effected then there will appear
no characteristic glow since the argon gas will be wholly
contained within the body of the lightning arrester, hav
the lightning arrester ambient atmosphere by the sealing
sealing of the ends of the lightning arrester will allow the
ing no means for egress therefrom.
One form of testing apparatus for applying the requisite
compound 13 and cement 14 at the lower end of the
electrostatic field to the linished lightning arrester is illus
trated in the showing of FIGURE 3, to which attention
lightning arrester, and by the sealing compound 26 and
should be now directed.
cement 24 at the upper end of the lightning arrester.
transparent vacuum chamber 41 closed at the top by a
ycover plate 42 peripherally sealed to the chamber by a
While cracks in the casing Iii are fairly readily detected,
In FIGURE 3 there is seen a
gasket 43. The bottom of the chamber is provided with
voids or ñaws in the closures provided by the sealing com
a fitting 44 by means of which a vacuum pump (not
pound and cement ylayers can easilyl go undetected and
shown) may be connected lto the vacuum chamber 4d.
as a consequence lightning arresters may be placed in
useiwhich are in fact not completely sealed, >and which 20 Secured to the inside surface of the vacuum chamber walls
are a pair of peripherally extending electrical conductor
are, therefore, subject to »faulty operation and premature
bands 45 and 46 electrically connected together by the
failure due to the entry of moisture as already previously
external leads 47 and ‘i3 which pass through the wall of
described. It is the detection ot these normally unnoticed
the vacuum chamber 4l for connection to the conductors
sealing imperfections with which this invention is con
45 and 45 and which are externally connected to one
cerned and which will now be described in coniunction
terminal 49 of a source of electrical potential.
with the showings of FIGURES 2 and 3 of the drawings.
The lightning arrester itself is positoned within the
Considering ñrst the showing of FIGURE 2, there will
chamber 4 as illustrated and electrical connections are
be seen a vessel 33 having a `top closure plate 34 sealingly
made to the arrester terminals l2 and Sii by means of the
engaged with the vessel 33 by means of a gasket 35 and
through which are downwardly extended into the interior 30 supporting electrodes 5'@ and 5l respectively which pass
through the top and bottom of the vacuum chamber and
of the vessel 33 a pair of feeder devices 36 and 37‘ and a
are connected together by the external leads 52 and S3,
means 3S for inserting and positioning >into the body lha
which in turn are connected to the other terminal 54- of
_of the lightning arreste-r the metalli-c .plate il and attached
the electrical potential source. It will be noted that the
terminal stud 12, The lightning arrester, which is dia
grammatically shown in FIGURES 2 and 3, may be of 35 conductor bands 45 and 46 are spaced apart the proper
distance to place them in the immediate regions of the
any type and may or may not be provided with littings
ends of the lightning arrester body portion i0 since these
27a and 30a such as those of the arrester shown in HG
are the points at which the leaks, if any, will occur.
URE 1. The feeder device 36 may be adapted to till
In operation, a high electrostatic potential is applied
the body of the lightning arrester with the silicone carbide
granules, and the feeder device 37 may be adapted to ñow 40 to the terminals 49 and 54 so that an electric lield is
the sealing compound 13 (as .shown in FÈGURE 1) into
the end of the body of the lightning arrester after the
positioning means 38 has inserted the bottom terminal
established between the leads Si) and 51 on the one hand
acting as a common electrode and the conductor bands
¿i5 and d5 on the other hand acting as the opposite elec
assembly thereinto.
trode. The internal atmosphere of the vacuum chamber
.
4l is then exhausted by means of the vacuum pump so
Of course, the feeder devices 36 and 37 and the inser
tion means 38 are >properly sealed where they pass through
the top closure plate 34 (by means not sho-wn) to insure
that the interior of the vessel 33 is maintained in isolation
that the pressure therein drops to an absolute pressure of
approximately twenty millimeters of mercury or less. If
a leak exists due to imperfect sealing of the ends of the
from the outside atmosphere.
lightning arrester, the gas contained within the lightning
arrested vbody at approximately normal atmospheric pres
Similarly, the lightning
arrester is held in proper position within the vessel 33 by
means also not shown and which may constitute any suit
sure will tend to flow outward through such leaks and into
the substantially reduced .pressure zione of the vacuum
chamber interior.
The vessel 33 is provided with a bottom fitting 39 and
As the gas issues from the leak, it emerges into a re
a side fitting 40, one of which may be considered an inlet
and the other an outlet, by means of which the vessel 55 gion between the lightning arrester terminal l2 and con
ducting band 4S or the region between the lightning ar
33 may be placed in a closed gas circuit with apparatus for
' flushing and charging the interior of .the vessel 33 with a
rester terminal Sii and the conductor band 46. Since both
able apparatus such as a clamp or other device.
of these regions are precisely the regions of maximum
desired gas or combination of gases to provide an artiñ
cial atmosphere for the assembling of the 4lightning ar
electric field a glow discharge takes place in the well
rester. In general, it is contemplated that a chemically 60 known fashion due to excitation of the electron shells
inert gas or combination of such gases would be em
of the gas atoms attended by the release of quanta of
ployed, as for example neon, argon, krypton, or xenon.
light of a wave length characteristic of the particular
The foregoing gases are particularly suitable for use be
gas employed. The glow discharge is, of course, immedi
cause being chemically inert they will not combine with or
ately visible, it is known for a certainty that a leak ex
otherwise contaminate the substances lfrom which the
ists, and the location of the leak is ascertained. The
lightning arrester is made, and additionally pprovide the
lightning arrester may then be removed and reprocessed
means for producing characteristically colored glow dis
and again tested until, under test condi-tions, the glow dis
charge when subjected to an electrostatic field of suthcient
charge is found to be absent. It follows, naturally, that
Y
a properly sealed lightning arrester will not even in the
Thus, when a lightning arrester is assembled in the 70 first instance exhibit lthe glow discharge and hence it will
vessel 33 in an atmosphere of argon for example, the
be known to be completely sealed and hence ready for
argon molecules will permeate the interior of the light
use.
ning arrester casing it? and replace the air which would
It should be borne in mind that the illustrated methods
strength.
normally -be there but which has been removed by the
ñushing operation. The Yfinished lightning arrester will
of assembling and testing the lightning arrester are only
exemplary and that alternate systems of so doing may
3,090,112
5
6
be employed with equal success without departing bas
ically from the concept of the invention. For example,
it is possible that the ñlling and testing chambers illus
uum chamber having a pair of spaced apart electrodes,
trated in FIGURES 2 and 3 could be combined into a
chamber electrodes to a source of electric potential to
connecting the arrester metallic terminal to one of the
Vacuum chamber electrodes, connecting the vacuum
single chamber and the entire operation carried out there
in without the need for transferring the lightning ar
thereby establish an electric ñeld therebetween, and re
ducing the pressure in the vacuum chamber below the
rester from one chamber to another. Such an arrange
pressure of the inert gas atmosphere in which the ar
ment is shown in FIGURE 4 which is observed to be the
rester was sealed, whereby if a leak exists in the arrester
physical structure of FIGURE 2 to which has been added
seal the inert gas within the arrester will flow outward
the electrical testing aspects of FIGURE 3, correspond 10 therethrough into the electric iield region of the vacuum
ing parts to those of FIGURES 2 and 3 being similarly
chamber and emit a characteristically colored glow in
numbered and primed, as for example 4S and 4.5’. Also,
the visible spectrum.
although merely a single lightning arrester is illustrated
4. A method of excluding an undesirable atmosphere
in the iigures as being assembled and tested, it is pos
from the interior of a hollow container to be sealed and
sible to lill a plurality of such arresters at the same time,
and, moreover to simultaneously test such a plurality of
lightning arresters. Finally, it will be understood that
the particular structure illustrated as being tested, namely,
a lightning arrester, is merely illustrative of the testing
then testing >the sealed container for leaks consisting of
the steps of placin‘y an open hollow container into a
sealable vessel having means for inserting material into
of any of a nu'de range of sealed Vessels which may be
the vessel interior without breaking the sealed condition
and including a pair of spaced apart electrodes, said con
tainer being so placed within the vessel that the container
completely dissimilar in shape or function but which
neverthless are susceptible to testing by the method of
region to be sealed lies substantially between the spaced
electrodes, sealing the vessel, charging and iiushing the
the invention.
sealed vessel interior with an inert gas until substantially
Accordingly, although the invention has been de
all of the previous atmosphere has been removed, and
scribed in connection with a particularly illustrated em 25 inserting sealing compound into the vessel interior to seal
bodiment thereof, it ís to be understood that variations
and modiñcations may now naturally occur from time to
the hoilow container placed therein so that the hollow
interior of the sealed container contains an inert gas at
time to those persons normally skilled in the art without
mosphere non-communicative with the container ambient
eparting from the essential scope or spirit of the inven
atmosphere, followed by the steps of flushing the sealed
tion, and it is, therefore, intended to claim the same 30 vessel of the inert gas atmosphere, connecting the elec
broadly as well as specifically as indicated by the ap
trodes to a source of electric potential to thereby estab
pended claims.
lish an electric tield therebetween, and reducing the pres
What is claimed as new and useful is:
sure in the sealed vessel below the pressure at which the
1. A method of testing for leaks a hollow container
container was sealed, whereby if a leak exists in the con
35
sealed in an inert gas atmosphere consisting of the steps
tainer seal the inert gas within the container will flow
of, placing the container to be tested into a vacuum cham
outward therethrough into the electric ñeld region of the
ber having a pair of spaced apart electrodes, said con
sealed vessel and emit a characteristically colored glow
tainer being so placed within the chamber that the sealed
in the visible spectrum.
region of the container lies substantially between the 40
5. The method according to claim 4 wherein the step
spaced electrodes, connecting the electrodes to a source
of reducing the pressure in the sealed vessel below the
oí electric potential to -thereby establish an electric field
pressure at which the container was sealed is continued
therebetween, and reducing the pressure in the vacuum
until the vacuum chamber absolute pressure is equal to
chamber below the pressure at which the container was
substantially not more than 2O millimeters of mercury.
sealed, whereby if a leak exists in the container seal the 45
6. The method according to claim 4 wherein prior to
inert gas within the container will ñow outward there
the step of inserting sealing compound into the sealed
through into the electric field region of the Vacuum cham
vessel interior to seal the hollow container placed there
ber and emit a characteristically colored glow in the
in, there is performed the step of depositing within the
visible spectrum.
2. The method according to claim 1 wherein the step 50 hollow container a substance desired to be sealed there
within.
of reducing the pressure in the vacuum chamber below
the pressure at which the container was sealed is con
tinued until the vacuum chamber absolute pressure is
equal to substantially not more than 20 millimeters of
mercury.
55
3. A method of testing a hollow lightning arrester hav
ing a metallic terminal projecting outward through a
layer of material applied in an inert gas atmosphere to
seal the hollow interior of the arrester, including the steps
of placing the lightning arrester to be tested into a vac 60
References Cited in the ñle of this patent
UNITED STATES PATENTS
2,864,998
Lee _________________ _.. Dec. 16, 1958
2,897,437
2,911,709
2,944,324
Briggs et al. __________ _.. July
Boynton ____________ __ Nov.
Moyer ______________ __ July
Elarde ______________ _.. June
2,940,161
28,
10,
12,
14,
1959
1959
1960
1960
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