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Патент USA US2128817

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Aug. 30,938.
Filed March 5, 1933
2 Sheets-Sheet l
Patented Aug. 30, 1938
I Kent A. Hawley, Baltimore, Md., assignor to
Locke Insulator Corporation, Baltimore, Md.,
a corporation of Maryland
Application March 3, 1933, Serial No. 659,576 _
3 Claims.
(Cl. 173-318)
The invention relates to insulators, particu
larly, but not necessarily, those intended. and
adapted for use in connection with high fre
other though the voltage applied does endeavor
quency- currents, for instance in association with
the supporting legs of “radio towers whether they
be of the self-supporting or guyedtype.
to cause current to flow.
‘ It is known that for some time it has been.
proposed to make use of all-porcelain insulators
for example for use in connection with discon
ering insulators, there is of course no actual
current flow, as such, from one terminal to the
This, electrically con
sidered, is divided along the way in accordance
with certain rules. Considering current flow it
is relatively easy to visualize the idea that a
certain current starting at one point will ?ow
directly to the opposite point along certain chan
necting switches, bus bars and other equipment
at sub-stations. _By an all-porcelain insulator is
nels or flow lines, and that currents starting 10
from two points 'side by side will not cross their
meant one which is provided simply at its ends
with metallic ?ttings for mounting purposes, such
?ttings being of a type totally dissimilar to me
tallic pins or posts entering the insulator.v In
paths but will ?ow side by side in separate chan
otherwords insulators of this variety were con
structed on the theory that the absence‘of me
the travel of the stress or electrical pressure from
tallic parts within the interior would increase the
insulating value. However, it has been found in
'sequently merely necessary to visualize a condi
tion corresponding to that which is physically dis
cernible ‘as described above. It is therefore
proper toconsider porcelain of an insulator and
20 actual practice that insulators of this variety pos
sess marked objections or drawbackswhen con
nels. Mathematically these flow lines Where ac
tual moving electricity is involved- are the same
as the electro-static stress lines which determine
a live terminal to the other terminal. ~ It is con
sidered from the electrical viewpoint. When '. the surrounding air not as insulators but as con- I
efforts have been made to use, insulators of this ductors. It is known that air has seven times
general type in connection with even normal the resistance to the flow of electro-static ?ux
frequency currents and particularly with high
that the porcelain has.
frequency currents, for instance those at radio
frequencies, there is a concentration of the flux
density at the high potential end and likewise
excessive leakage to earth. This condition causes
there are two electrical terminals with air and
porcelain between them, roughly considered the
air takes seven times the electrical pressure that
30 not only a loss of power but results in very
objectionable heating effects within the porcelain.
Brie?y, insulators of the elongated hollow type
provided simply at their ends with exteriorly lo
catedmetallic ?ttings are not satisfactory on
35 account of the low e?iciency.
To explain what is meant by a-concentration
of the flux density, it might be well to consider
some of the theoretical aspects of the situation
especially as in some respects some of the condi
40 tions discovered are largely a new development.
To those skilled in the art there is no di?iculty
in picturing what occurs where a current of
electricity actually ?ows, for such current will
follow almost exactly thesame laws that a flow
45 ing stream of’ water would follow, assuming that
the water is not travelling at a very great speed.‘
It is known that if there are two paths by which
electrical current can flow from one‘place to
another, it will ?ow by both paths, the current
dividing indirectly accordingto the respective re
sistances of the two paths. The division of volt- ‘
age along the way to create the ?ow will be in
proportion to‘ the resistance to ?ow-along the
way, inch .by inch. This is of course an ele
55 mentary proposition. When it comes to consid
In other words, where ' N.6
the porcelain takes. Consequently, where there
is a column of air and a column of porcelain side 30
by side with a ?ux in each, there will be seven
times the amount of flux in the porcelain as
there is in the air. This conception is a material
aid in picturing the ?eld about insulators-and
the changing of the relative positions of the air 5
and porcelain about the parts of the insulators
where the air 'is over-stressed by the velectrical
pressure, resulting in the formation of corona
which causes heating as well as lowered arc-over
Considering. an elementary porcelain post such
as a tube or rod set on end with the ends capped
and the upper end electrically alive and the lower
end grounded, it is known that from the upper
end the ?ux ?ow will pass in all directions. A 45
very, considerable amount of the ?ux will pass
directly through- the porcelain to the earth but
some of it will pass outward from the live cap in
all directions to the earth, even upwards through
in?nite distances.
Now, that portion of - the ?ux
which starts downward through the porcelain to
ward the‘ earth will ?nd part way .down that the
surrounding air is not ?lled electrically, and con
‘sequently this electrical ?ux- will wander away
from the porcelain with the result that the ?ux
density in the porcelainat the lower or grounded
end of the insulator is less than above. Conse
quently, the electrical pressure per inch of length
is not as great at the lower end as at the upper
will naturally break down appreciably before the
bus bars, switches and other equipment at power
stations where the frequencies are normal, the
principle of grading or flux density control being
the same in any instance‘
An additional object is to provide an insulator
having the above pointed out electrical charac
teristics and which will at the same time be
simple and inexpensive to make and therefore
practical from a commercial viewpoint in addi
space near the lower end has approached the
tion to being unusually strong, mechanically, and
end. The air in the immediate vicinity of the
porcelain naturally assumes the same rate of
voltage drop as exists within the porcelain.
There has therefore been pictured a condition
under which the space between the live cap or
10 terminal and the earth is not being used in the
most efficient way as the space at the upper end
critical point.
association with radio towers or in connection
with high frequencies but which may be used in
stacks or superposed series for the support of
Considering now not an elementary cylindrical
bolster as an insulator but in contradistinction
thereto taking one shaped like the frustum of a
cone such as is used for instance for the insula- '
tion of the legs of radio towers, the same elec
20 trical disadvantages are present. In many in
stances it has been proposed to use radio towers
themselves as antennae for radio broadcasting
and under such circumstances the tower itself
must of course be well insulated from the ground.
For mechanical reasons conical insulators vused
in such a connection are logically placed with
their large ends down and with their upper or
smaller ends supporting the tower. From an
electrical viewpoint this is absolutely incorrect
30 but it is manifestly not feasible to mount the
insulators in the reverse relation which would
insure proper electrical performance.
a general improvement in the art.
To the attainment of the foregoing and other 15
objects and advantages, the invention preferably
consists in the details of construction and the
arrangement and combination or" parts to be here
inafter more fully described and claimed, and
illustrated in the accompanying drawings in 20
cylindrical type insulator,
Figure 2 is a diagrammatic view showing the 25
flux lines in and about an inverted conical in
Figure 3 is a vertical sectional view through
one half of a cone type insulator constructed in
accordance with my invention,
that the truncated cone insulator is placer‘: in its
normal position with its large end grounded and
35 its smaller end electrically “live” I have found
that the distribution of ?ux density is incorrect
40 ness of the dielectric material at the small or
live end the flux density may be properly con
trolled or distributed or the insulator graded
within itself so as to overcome the heating ef
fects and likewise to eliminate danger of corona
45 which occurs as the result of overstressing a part
of the ?eld. The last mentioned characteristic
is of great importance as the formation of corona
is a serious disturbing feature in radio reception
as well as objectionable on account of heating
50 and the lowering of arc-over values.
It is with the above facts and discussion in
view that I have devised the present invention
which has for its general or primary object the
provision of an insulator, particularly but not
65 necessarily of porcelain, in which the flux den
sity will be controlled and distributed.
An important object of the invention is to pro
vide an insulator in which the thickness at the
live end is the maximum and .decreasing to a
Figure 5 is a similar view of yet another varia
igure 6 is a half sectional View through an 35
insulator of the post type having internally lo‘
cated adjunctive flux density distribution means,
Figure '7 is a similar view through the‘sarne type
of insulator but disclosing an additional m0di~
Figure 8 is a vertical sectional view showing
half of a stack oi‘ insulators constructed along
the lines disclosed in Figures 6 and 7,
Figure 9 is a longitudinal section showing the
invention embodied in a tubular type of in
have pictured the electro—static ?eld in and about
the insulator l0 which is represented as of the
plain cylindrical type equipped at its top with
a cap H which is electrically live. It is assumed
that the lower end is grounded. From the upper
end the flux flow will pass in all directions as in
may be brought about in any one of numerous
electrically and as a consequence this electrical
?ux will wander away from the porcelain or other
est at the stressed end or ends and decreases to- -
added thickness for eifecting flux density control
ways for instance by thickening the material of
the insulator wall or placing within the interior
70 auxiliary or adjunctive means more or less in the
nature of bushings of appropriate shape and di
mensions which will bring about the same highly
desirable result.
Still another object of the invention is to pro
75 vide an insulator which need not be used in
Rereiring more particularly to the drawings
and especially Figure 1, it will be noted that I
ward the unstressed end or intermediate portion.
Another object is to provide an. insulator pref
65 erably of the truncated cone type in which the
grounded end, or in which the thickness is great
Figure 10 is a similar View showing another
dicated by the radiating lines. A very consider
able amount will pass directly through the porce
lain to the earth as indicated by the lines 52.
Moreover some of this flow will pass outward from
the cap H in all directions not only to the earth
but even upward through in?nite distances. The
flux which starts downward through the porce
lain toward the earth will ?nd, part way down,
that the outside or surrounding air is not ?lled
60 minimum at or near or at least toward the
Figure 4 is a similar view showing a modifica
and causes objectionable heating in the porcelain.
From a series of tests and also from computation
I have found that by increasing the bulk or thick
Figure 1 is a preliminary diagrammatic view
showing the ?ux lines in and about a simple
dielectric material as indicated by the lines l3.
The result of this is that the flux density in the
porcelain at the lower end is not as great as above 70
and the electrical pressure per inch of length is
not as great at the lower end as at the upper
end. The air in the immediate vicinity of the
porcelain naturally assumes the same rate of
voltage drop as exists within the porcelain. The
space between the cap and the earth is conse
quently not being used in the most efficient way
as the spaceat the upper end will naturally break‘
down appreciably before the space near‘ the lower
end has approached the critical point.
Referring to Figure 2 it will be abserved that
I have diagrammed an insulator I4 which embodies
the principle of my invention in that the capped
upper end i5 which is electrically live is of greater ,
10 thickness than the lower end which is grounded.
' In this way it is possible to carry the greater
amount of ?ux that exists at the upper end with
insulator 21 equipped with the ring or base 28
and cap 29 is partly ?lled with some appropriate
insulating compound 30 which is plunged or
otherwise treated so as to have the maximum
thickness at the upper end and the minimum at 5
the lower end. This likewise brings about the
same effect as the one-piece construction shown
in Figure '3.
Figures 6 and 7 are capable of being construed
to refer to insulators of the same general type 10
as above described or to those of that variety
adapted to be used either singly or in superposed
out danger of over-stressing. Accordingly ‘it is series or in stacks for the support of , station
feasible to keep the voltage‘ drop per inch of equipment. This may be considered as a de
15 length approximately uniform and thereby most velopment or enlargement of the basic idea.‘ Re 16
eiiectively grade the voltage through the air from ' ferring to Figure 6 in detail the insulator is dis
closed as comprising a body 3| having a baseor
top to bottom. Of course, commercially consid
ered, this can be done only within certain limits
-as it is obviously impossible to ?re porcelain of
20 excessive differences in thickness at diiierent
points in the length owing to the setting up of
extraordinary strains in the material during the
?ring process, which strains will cause distortion
and probable eventual fracture or at least other
25 defects which are present even though latent.
ring 32 and a cap 33 and within which is located
a series of nested shells 34 which may be secured
in place and to each other in any desired manner. 20
These shells are represented as having their walls
of uniform thickness except at their lower edges
where they are tapered off as indicated at 35 so
as to vary the thickness of the insulator wall as
a whole throughout the major portion of its .25
A practical embodiment, within reasonable
‘limits, -of .the basic idea_disclosed in Figure 2 is
shown in Figure 3 wherein there is represented
length, the maximum thickness being at the upper
an insulator‘ 16 of truncated cone shaped equipped
at its lower or grounded end with a, metallic ring
The structure in Figure '7 distinguishes from
that in Figure 6_ in'the single respect that the
inner .shells 36 may be more accurately described
or base I? cemented or otherwise secured in place
as at I8, and provided at its upper or live end
with a metal cap I9. It will be observed that the
dielectric materiaLpreferably porcelain, is of much
35 greater thickness at the upper end 20 than-at any
other point in the length of the insulator. The
insulator body is hollow or formed with a cavity
2| the wall of which is tapered inwardly and up
or live end and the minimum being toward the
lower or grounded end._
as bushings in that the upper ends ‘thereof are
open instead of closed as [in Figure 6. These
nested bushingsv are represented as of uniform
thickness except for their beveled or tapered low
er ends 31. These bushings may be secured'to
each other and within the outer insulator body
30' by any appropriate means or method. In this
wardly at aygreaterinclinationor pitch than the ‘form as in Figure 6 the maximum thickness o1’\
40 exterior‘suriace.
By virtue of this formation it
is clear that the maximum-bulk ‘or thickness of
material is at the upper end of the insulator,
notwithstanding the fact that the_upper end is
. oi the smallest» diameter, that the walls taper
45 gradually in thickness toward the bottom. In
accordance with the previously given discussion
this provides for an even ?ux distribution so
that the upper end will be easily capable of carry
iiig the (burden imposed upon it without being
Owing to manufacturing di?icultiescinvolved in
making an insulator having portions of, greatly
varying’ thickness,‘I may prefer to resort to the
material is ‘at-the upper capped end 39, the min- 40
imum being toward the grounded end where the
ring or base 40 is provided.
In Figure 8 I have disclosed a stack of insula—
tors constituting a development or enlargement '
of the idea shown in Figures 6 and 7 and dis-_ 45
cussed in connection therewith. A stack such as.‘
this is often employed at stations and sub-sta
tions for various purposeswhere currents at nor
mal frequencies are handled, though naturally
there is no limitation as tothe exact use.
Re- 50 .
ferring to this ?gure in detail it will be-observed
that I have shown a plurality of "units 41,‘ 42 h
and 43 each formed as ‘a porcelain body or shell I
44 equipped at its top- and bottom with metallic
?ttings 45 and 46, the ?ttings 46 at the bottom 55
equipped at its lower end.with a metallic ring' of each unit being customarily bolted to" the ?t
23 and at its upper or liye-end with a cap 24. tings 45 at the top- of the units next below. In
The insulator is hollow or formed with a cavity vembodying the principle of the invention in such .
25. _In this instance the requisite added thickness a stack,.in which the top is ‘naturally the line'
60 of material at the upper end is-shown as obtained end, I increase the thickness ofthe stressed top 50 .
by the use of a shell 26 which ?ts telescopically unit 4| by securing within the'body thereof, a
within the cavity 25 and which maybe'secured bushing 41 of dielectric material, preferably but I
inplace by any. suitable ‘or preferred means, such not necessarily porcelain, this~ bushing extend‘- v
for instance as by bituminous material or other ing the full length or height of the unit. Then,
within the intermediate unit 42, there is provided 65
non-conducting adhesive 265/ While the thick
atsirnilar bushing 48 which, however, willprob
ness of the insulator body 22 is uniform, through
out, the thickness of the shell 26 varies from its 1 ably terminate short of the bottom, the lower
closed upper end to its open lower end,. thereby end of this bushing being tapered off, beveled or
bringing about, from, the electrical viewpoint,‘the otherwise reduced in thickness as shown at 49. I
same conditions which exist {in the- one-piece It is the assumptionthat the increased thicknessv 16
expedient disclosed in Figure 4 wherein I have
illustrated a truncated .cone shaped insulator 22
type shown in Figure 3.
The shell 26 need not be of porcelain even ‘if
in the intermediate unit a?orded by‘ the bushing
48 will reléive it of any overstressing and will
the’ body 22 .is as it is conceivable that it might _ act to effect grading or ?ux density control.
be of some other appropriate dielectric material, However, as the maximum stress exists in the
75 for instance as shown in Figure 5 wherein the - uppermost unit 4|, I take care of this by pro-,7“
viding the uppermost unit with an additional
bushing 50 located and appropriately secured
within thebushing 41 and tapering oiT at its
lower end as shown at 5 I. By following this con
struction it will be apparent that the greatest
mass of dielectric material is at the upper end
of the topmost unit, this mass being gradually
reduced toward the lower end. It is also clear
that the thickness of the dielectric at the upper
portion of
the intermediate unit, while
than the thickness at the top of the uppermost
whether the increase be brought about by the
use of interior bushings or external sleeves, the
effect being the same in any case. There is how
ever, a point of possible advantage in the use of
external sleeves, namely an increase in the area
or radiating surface which would tend to effect
dissipation of any heat as well as reducing con
centration of stress.
In all of the various forms disclosed it is clear
' that the same underlying principle is involved,
namely the employment or provision of the
maximum thickness of material at the electri
cally stressed'end or ends of the insulator with
a progressive decrease toward the grounded end,
unit, ‘is nevertheless materially greater than that
of the lowermost unit. I have found that by car
rying out this scheme as indicated a very ef
15 fective grading and flux density control may be
had so that the objectionable stressing and co
rona formation will be entirely avoided and the
or the intermediate and unstressed portion, as 15
the case may be. As mentioned in the forepart
of this speci?cation this causes a more nearly
are-over value increased, thus rendering the as- ' uniform ?ux density distribution and enables
sembly eminently suitable, regardless of the fre
the upper or live end of the insulator to carry
20 quencies handled.
its electrical load without being overstressed and
For antenna insulation and for other more or - consequently without danger of corona which
less similar purposes, use may be made of elon
results from breaking down of the electro~static
gated tubular insulators provided at their ends
?eld in and about the insulator.
While I have shown and described various
alternative forms‘ it should be understood that 26
the right is reserved to make any changes in the
construction, arrangement, mode of manufac
ture and the like provided such constitute no de~
.parture from the spirit of the invention or the
scope of the claims hereunto appended.
Having thus described the invention, I claim:
with metal ?ttings, one of which is of course at
26 the live end and the other at the grounded one.
As another variation of the fundamental idea in
volved, I contemplate constructing insulators of
this type in such manner as to control the flux
density properly. To accomplish this I may re~
80 sort to the simple expedient disclosed in Figure 9
wherein I provide a dielectric bushing 52 within
the live end portion of the tubular insulator 53
having terminal ?ttings 54 and 55. The bush
, 1. A
ing 52 need extend only part way of the length
dielectric body having a live end and a grounded
end each equipped with a metallic ?tting, said
body being hollow, and a dielectric shell located
‘The added thickness afforded by the bushing 52
within the hollow body and having portions of
its wall ofvvarying thickness and cooperating
with the walls of the dielectric body for provid
35 of the insulator and it is preferably tapered off
as shown at 56 toward the intermediate portion.
will take care of the flux density and provide
grading. In the use of insulators of this type
ing the maximum dielectric thickness of mate~
rial at the live end of the insulator, the thick 40
ness gradually decreasing toward the grounded
for the purpose mentioned it frequently occurs
that there is also a flux concentration at the
grounded end though of less magnitude than at
the live end. In view of this condition I may,
if found desirable provide a tapered bushing 51'
45 within the grounded end. The extent of the
bushings 52 and 51 compared with the length of
the tube 53 is dependent upon various condi~
2. A high
body tension
having a insulator
live end and
a grounded
end each equipped with a metallic ?tting, the 45
body having‘a cavity therein, and a series of
nested shell members secured in telescoped rela
tions or circumstances but the point is that the
tion within the cavity, said shell members hav
ing their walls tapered in thickness toward the
grounded end of the insulator, whereby the 50
cross section of the porcelain or dielectric ma
terial should be proportioned as closely as pos
sible _to the total amount of ?ux within it. In
other words the thickness at any given point is
dependent upon the flux density and may be
varied to meet conditions which may be found
In the various ?gures above discussed it will
be noted that the increase in the thickness of
the dielectric material has been brought about
by the use of interiorly located auxiliary means
such as the bushings. However, there is no par
ticular limitation as to the location inasmuch as
it is easily conceivable that I may resort to the
expedient disclosed in Figure 10 wherein I pro
vide a sleeve 58 telescoped exteriorly upon and
appropriately secured to the live end of an elon
gated tubular insulator 59. In other words in
accordance with my conception it makes no dif
ference whether the increase in thickness be
brought about by increasing the material of the
10 insulator itself during manufacture thereof or
maximum thickness of dielectric material will
be at the live end of the insulator.
3. A high tension insulator comprising a di
electric body equipped at its ends with metallic
?ttings and having one end of greater diameter 55
than the other, said body having a cavity
therein, and a dielectric member of hollow con~~
ical shape with its wall tapered in thickness
secured within said cavity in contacting rela
tion to the wall thereof with its thinnest wall
‘portion disposed adjacent the larger diameter
portion of the body and with its thickest portion
adjacent the smaller diameter portion of the
body, the combined thickness of the walls of the
body and the dielectric member at the‘smaller
diameter portion of the former exceeding the
combined thickness of the walls of the body and
the dielectric member at the larger diameter
portion of the former“
Patent Non 2,128,817.
August 50, 1958.,
KENT A. Emma’.
It is hereby certified that error appears in theprinted. specification;
of the above numbered patent requiring correction as follows: Page 5, second
column, line 59, for the word "line" read live; and'1ine72, for "releive"
read relieve; and that the said Letters Patent should be read with this
__ correction therein that the same may conform to the record of the case in
Signed and sealed this 11th” day of October, A. D. 1958'.
Henry Van Arsdale
Acting Commissioner of Patents.
Patent No. 2,128,817.
August 50, 1958.
It is hereby certified that error appearsv in the‘ printed specification;
of the above numbered patent requiring correction as follows: Page 3’, second
column, line 59, for the word "line" read live; arid'1ii1e72, for “re1eive"
read relieve; and that the said. Letters Patent‘ should be read with this
_. correction therein that'the same Inlay conform to therecord of the case in
the Patent Office.
Signed and sealed'this 11th’ day oi‘ October, A. D, 1958.,
Henry ‘Jan Arsdale I
Acting Commissioner of Patents.
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