Improvements in Electric Insulators.
Year: 1892

page_text: ate of Application, 5th July, 1892-Accepted, 6th Aug., 1892
COMPLETE SPECIFICATION.
[Communicated from abroad by LOUIS MCCARTHY, of 605, Fifth Street, Boston,
Massachusetts, United States of America, Mechanical Engineer.]
Improvements in Electric Insulators.
I, HENRY HARRIS LAKE of the firm of Haseltine Lake & Co., Patent Agents,
45 Southampton Buildings in the County of Middlesex, do hereby declare the
nature of this invention and in what manner the same is to be performed, to be
particularly described and ascertained in and by the following statement :-
My invention has for its object an insulator for electric purposes which shall be
cheap, durable and efficient. In an insulator embodying my invention, the metallic
or conductive parts are separated by layers or sheets of mica laid and pressed
together, as hereinafter set forth. The exterior of the joint thus formed between
the conductive parts may be provided with a covering formed from insulating
composition or similar material and this may in turn be covered with metal, when
for any reason that is deemed desirable.
In the accompanying drawings in which I have shown my invention in the best
forms now known to me,
.
Fig. 1 is a vertical section showing a line insulator for over head conductors such
as are employed in some forms of electric railways.
Fig. 2 is a similar section showing another form of line insulator for electric
railways and the like.
Fig. 3 is a similar view of a "pull-off" or strain insulator also designed to be
employed in the over head construction of electric railways.
Fig. 4 is a similar view of another form of strain insulators.
Figs. 5, 6, 7 and 8 are vertical sectional views showing my invention as embodied
in insulators for gasaliers or combined gasaliers and electroliers.
Figs. 9, 10, 11 and 12 are plan views of the insulators shown Figs. 5, 6, 7 and 8
respectively.
My device is simple and easily constructed and will be readily understood from
the following description.
Referring to Fig. 1 A is a bell-shaped piece of metal or other suitable material
and is similar in form to that cominonly employed in line insulators. The upper
portion or cap a of the bell is adapted to be screwed into the lower portion as
shown. To the cap a or at any convenient point on the exterior of the bell is
secured suitable projections 6 provided with holes by means of which the insulator
may be secured in place by wires or other convenient supports. The interior of the
The bolt d forms
bell is provided with an inwardly projecting annular flange c.
one of the metallic portions of the insulator and the lower end of this bolt is con-
nected with the trolley wire or over head conductor, said bolt serving as a support
therefor. The object of the device is to insulate this metallic support d from the
other portions of the construction. To this end the bolt d is provided with a
number of layers or sheets of mica shown at e.
Each of said sheets of mica is
perforated to receive the shank of the bolt and a sufficient number of sheets is
employed to fully insulate the head and the upper portion of the shank of the bolt
from adjacent portions of the bell A. In constructing the insulator, the cap a is
removed, and the bolt with a sufficient number of sheets of mica strung thereon and
placed immediately under the head thereof, is inserted in the bell, the sheets of
mica being cut to the proper size to fit closely the interior of the bell. Additional
sheets of mica, each of which is provided with a central aperture or hole sufficient
to accommodate the head of the bolt, are then placed within the bell surrounding the
bolt head, and above the bolt head, the space within the bell is filled with sheets of
mica which are not perforated and which serve to fully insulate the head of the bolt

page_text: from the cap a.
The cap a is then screwed tightly into place. The lower
outwardly curved portion or shirt fis for the purpose of shedding moisture and
protecting the insulation and is similar in form to the corresponding portions of the
bells or insulator cases now in use in insulators for overhead conductors.
Another form of my device designed to be used in the same manner as the form
shown Fig. 1, is shown Fig. 2. This consists of a bell A in the top of which is
secured a metallic part g, the upper end of which is provided with a screw-threaded
socket or recess by means of which the device is secured to the over-head cou-
struction which serves to support it. The lower end of the part g is flanged as
shown, the flange being perforated or provided with a number of holes to receive
securing bolts h by means of which another metallic part j corresponding in shape
to the part g is secured to said part g. The part jis provided with a flange in the
same manner as is the part 9 through which the securing bolts pass. The
proximate faces of the flanges of the parts gj are separated by a series of sheets of
mica which are laid and pressed together between said parts, forming a solid mass
of great strength and durability and of high insulative quality. These mica sheets
are shown at e, Fig. 2. The lower end of the part j is also provided with a screw-
threaded recess or socket to receive a rod or connection which serves to support the
trolley wire or overhead conductor. In order to completely insulate the bolts h
from the parts g, the holes in the flanges of said parts, through which the said
bolts pass are made considerably larger in diameter than the said bolts and the
bolts are insulated from the adjacent metallic portions of the flanges by means of
washers or rings cut from sheets of mica which are strung on said bolts and which
fill the spaces around the same. Under the heads of the bolts at either end thereof
are placed metallic rings or washers and between these rings k and the adjacent
parts of the flanges through which the bolts pass are placed a series of sheets of
mica which serve to insulate the rings k and the heads of the bolts from said
flanges. The metallic rings k serve to give the bolts a firm bearing and to prevent
the rings of mica / from being cracked or impaired when the bolts are being secured
in place. By insulating the entire body or shank portion of the bolts from both
the upper and lower metallic parts g; double insulation is effected and a very
efficient and durable insulating device is obtained. As will be obvious in con-
structing the insulator the parts gj are first secured together as described and are
then placed and secured within the bell or case A. After this is done the space
within the bell surrounding the parts gj is preferably filled with an insulating
composition m which while in a plastic condition is pressed into the space completely
filling the same, and is then allowed to set and harden. To assist in retaining the
composition m securely in place within the bell, an annular recess such as is shown
at n may be formed in the interior of the bell. Any well-known insulating
.composition which may be used in a plastic condition and will then harden may be
employed. By thus completely insulating the essential metallic parts gj and then
embedding the insulation thus formed in a non-conducting composition and placing
the whole in a case or bell of metal, a very strong and durable insulator is obtained
which is impervious to moisture and not affected by atmospheric changes.
The pull off or strain insulator shown Fig. 3 is substantially the same in
construction as the device shown Fig. 1. As the strain insulator is usually placed
in a horizontal position the skirt of Fig. 1 is changed to an annular inwardly
projecting flange p in Fig. 3 to more effectually shed moisture. The arched or
hooked portion q carries at its outer extremity the overhead conductor or trolley
wire and is arched to allow the flanged trolley or wheel which makes contact with
the conductor and which is connected with the car to pass the support.
r
The device shown Fig. 4 is especially designed for a transverse or strain insulator
and is of substantially the same construction as the device shown Fig. 2, but is not
provided with an exterior covering or case corresponding to the bell A. In Fig. 4,
the joint is entirely embedded in a covering of plastic composition m which is
moulded around it and then allowed to harden. It will also be noted that in Fig. 4
only one end of the securing bolts is insulated from the flanged metallic parts

page_text: through which said bolts pass, but as will be obvious, both ends of said bolts may
be so insulated in case double insulation is desired. The precise number of bolts
employed in the construction of these insulators is not material and will depend
upon the strength desired and the use to which the insulator is to be put.
ordinary purposes three or four bolts are sufficient.
For
Insulators embodying my invention may be Feadily made in other forms and for
other purposes than those above mentioned. Some of the other forms are shown
in the drawings and will now be described.
At Figs. 5 and 6 I have shown an insulator for gasaliers which may be used to
insulate the gasalier from the gas supply pipe in cases where the gasalier is also
provided with electric lights or insulation for any purpose is desired. In this case
the bell A of Fig. 1 is replaced by two caps or frames g' h¹ which serve to hold
the layers of mica together. These caps or frames are either adapted as shown
Fig. 5 to be screwed together or they may be secured together by the aid of bolts,
as shown at Fig. 6, said bolts passing through the caps or frames y¹ h¹ and
through the interposed sheets of mica. The metallic pieces which are to be
insulated are shown at and they are provided with a central aperture or passage
so that the gas may pass from the supply pipe to the gasalier, said passage being
also continued through the interposed sheets of mica. Said pieces may be
described as flanged tubes. The precise form of the metallic parts which are
insulated will depend upon the purposes for which the insulator is to be used.
It
In constructing an insulator for gasaliers as shown Figs. 5 and 6 it is desirable
that the sheets of mica be laid together firmly by strong pressure and the bolts k¹
inserted and secured while the mica is under pressure, in order that the mass of
mica may be made as solid as possible thus preventing the leakage of the gas.
will also be found desirable to use varnish or a similar substance between the
sheets of mica and around the gas passage as also around the embedded portions
of the pieces to assist in preventing any leakage of gas. When varnish is
employed in this way, less pressure is necessary in firmly setting the sheets of mica
together.
In the gasalier or pipe insulator shown Fig. 7, leakage is further checked by
forming a slight annular projection on one face of the metallic portion to be
insulated as shown at a² and a corresponding recess as shown at 62 on the proximate
face of the other metallic portion. By this means when the parts are bolted
together under heavy pressure the sheets of mica are bent slightly as shown thus
forcing them closely together forming a tight joint and greatly lessening the
liability of leakage from the gas passage.
In the form of pipe insulator shown Fig. 8, the flanged metallic portions which
are to be insulated are secured by means of bolts which pass through the insulating
material one end of the bolt being secured in one of the flanged portions while the
head of the bolt is in an aperture or recess in the other flanged portion. The
adjacent bolt is reversed in position, its head being in a recess in the flange opposite
that in which the head of the preceding bolt is received, that is the bolts alternate
in position or are what are termed "staggered." As will be clear the precise
method of bolting the parts together is not material. The alternating arrange-
ment of the bolts enables a large number of bolts to be used and a tight joint to
be obtained without unduly weakening either of the flanges. At Fig. 8 I have
shown the joint as covered exteriorly with a covering m which is preferably a non-
conductive composition as previously described which is moulded while in a plastic
state around the joint. This covering I consider of great importance in insulators
which are to be used for gasaliers, and the like as it greatly improves the insulation
and protects the proximate parts or edges of the metallic portions of the insulator
and prevents them from becoming connected electrically in consequence of the
deposition of moisture or from other causes. It also prevents the parts from
becoming accidentally connected electrically by wires which pass over them and
which are frequently used in connection with these insulators. The wires employed
are usually provided with an insulating covering, but the covering is sometimes

page_text: impaired and the parts become electrically connected. The precise thickness or
extent of the covering m is not important so long as it is sufficient to thoroughly
cover the joint and be strong and durable. It is further to be noted that a joint
covered in this way may be easily cleaned and does not readily retain dust and dirt
as would a coupling having holes or depressions in its surface or having projecting
bolts or nuts. The metallic portions around which the covering m is placed or
moulded may be recessed or provided with depressions so as to more securely hold
the moulded covering m in place. The covering m may be employed as will be
clear on many forms of insulators or insulating couplings and may be applied
irrespective of the precise form of insulator and irrespective of the means employed
for securing the parts of the insulator together.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, as communicated to me by
my foreign correspondent I declare that what I claim is :-
1. An insulator comprising a bell or case adapted to hold a series of sheets of
mica, a metallic supporting piece placed therein, and a series of sheets of mica
surrounding said piece and adapted to insulate the same from said bell or case,
substantially as and for the purposes set forth.
2. An insulator having the metallic or conductive portions thereof separated by
an interposed layer of insulating material, devices whereby the whole is secured
together, and an exterior layer or covering of insulating material whereby the
joint is covered and whereby also the space between the outer proximate parts of
the conductive portions is prevented from becoming electrically bridged, or
connected, substantially as and for the purposes set forth.
3. An insulator comprising metallic portions separated by an interposed series
of sheets of mica compressed together, securing devices by which said metallic
portions and said mica are secured together, a mass of insulating material in which
Baid metallic portions and said sheets of mica and their securing devices are
embedded and an outer metallic covering or case, substantially as shown and
described.
.
4. An insulator for pipes comprising two.flanged tubes or metallic portions, a
layer of insulating material placed between the flanges thereof, and a series of
securing bolts alternately set with reference to the said flanges and having their
heads alternately engaging with the opposite sides of the said insulating layer,
substantially as set forth.
Dated this 6th day of Iul 1000
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, Agents for the Applicant.