Insulator assembly for a high voltage power supply wire

An apparatus for electrically insulating and supporting a power supply wire relative to a substantially planar boundary, is disclosed. A translucent insulator is formed from a supercooled, nonporous igneous magma, such as glass, and includes a head and a shank extending from the head, the shank extendable through an opening in the boundary. The head and the shank form an annular passageway for receiving disposition of the wire. A shoulder surface limits the extension of the shank through the boundary opening and a retaining member, such as a nut, engages corresponding features of the shank to secure the insulator relative to the boundary. A seal can be additionally provided to engage the head and the wire to further seal the insulator.

BACKGROUND OF THE INVENTION 
The present invention relates generally to the field of electrically 
insulative devices, and more particularly, but not by way of limitation, 
to an improved insulator for the disposal of high voltage power supply 
wires used in comnmercial electrical signs. 
Electrical signs used commercially to advertise a business or event 
typically require high voltage power supply wires to transfer electrical 
power from a power distribution source to the point of power termination 
within the sign. Neon signs in particular commonly employ step-up 
transformers that generate secondary side voltages in the range of five to 
fifteen thousand volts. With such relatively high secondary side voltages, 
wires have commonly been found to prematurely fail over time, causing a 
short circuiting of the supply power to the sign enclosure. These 
electrical failures can create a dangerous safety hazard to personnel 
working in and around the sign and can initiate an electrical fire 
resulting in the catastrophic loss of property and lives. 
Such failures usually stem from a breakdown of insulation between the 
wire's conductors and a grounded conductive portion of the sign. Although 
the power supply wires typically employ the use of an insulative sheath, 
the sheath alone commonly does not provide reliable protection when 
subjected to the harsh and continuous duty operation conditions 
characteristic of a high voltage sign. 
In a commercial sign the power supply wire is generally passed through an 
opening in a substantially planar boundary, such as through a wall of an 
enclosure (sometimes referred to as a can), which is typically made of a 
conductive material such as aluminum or sheet metal. The boundary may also 
comprise a facia of a sign or a structural member such as plywood, 
sheetrock, concrete and the like. 
Insulators of various types have been employed to electrically insulate the 
wire from the boundary to prevent short circuiting and failure of the 
wire. Such insulators have been fabricated using well known electrically 
insulative materials such as rubber, plastic, and the like. No insulator 
has been found to date, however, that will consistently and reliably 
prevent premature short circuit failures. 
One solution commonly employed by those skilled in the art to minimize 
electrical shorting is to fabricate an insulator for the wires for a glass 
slip stick comprising a hollow, cylindrical member. To do so, an operator 
passes the wire through the slip stick and secures the slip stick in the 
boundary opening using a suitable caulking material, such as silicon. 
Although the use of slip sticks has been found to provide improved 
electrical insulation for wires in a commercial sign application, 
limitations are associated with this approach. First, the process of 
installing the slip sticks is labor and material intensive, especially for 
large signs which may require the fabrication of tens, or even hundreds of 
such hand-crafted insulators. 
Second, there is a risk of injury to the operator through the handling of 
the slip sticks, should one be inadvertently broken during installation. 
Third, the resulting insulator can distract from the cosmetic appearance 
of the sign, especially when the insulators are visible when a passerby 
views the sign. Finally, the process does not completely prevent failure, 
as over time the caulking materials can adsorb moisture or dry out and 
crack, leading to an eventual failure of the sign. 
Accordingly, there is a need for an improved approach to insulating high 
voltage wires in a commercial sign application that is easily installed, 
cosmetically appealing, and reliable in operation. 
SUMMARY OF THE INVENTION 
The present invention provides an improved insulator apparatus for the 
support and electrical insulation of high voltage electrical wires passed 
through an electrically conductive boundary, such as in a commercial 
electrical sign. 
In accordance with the preferred embodiment, an insulator is formed from a 
supercooled, nonporous igneous magma, such as glass. The insulator has a 
longitudinal annular passageway through which the high voltage supply wire 
is disposed and is supportable within an opening in the boundary to 
insulate the wire from the boundary in all radial directions. 
The insulator has a shank that is cross-sectionally smaller than the 
boundary opening and is thereby extendable through the opening. A head 
connected to the shank is cross-sectionally larger than the boundary 
opening and includes a shoulder surface which pressingly abuts the 
boundary to limit the extension of the shank tough the opening. A 
retaining member engages features of the shank and pressingly engages the 
boundary in opposition to the shoulder surface, thereby cooperating with 
the shoulder surface to support the insulator relative to the boundary. 
Preferably, the shank includes an external screw thread and the retaining 
member comprises a backing nut which threadingly advances upon the 
external screw thread. 
A weatherproof seal is additionally provided as desired to form an 
insulator assembly which reduces the ingress of environmental elements 
such as moisture and contaminants. The seal is formed with a ring portion 
at a first end which supportingly engages a mating groove on the head of 
the insulator so that the seal can be installed or removed without 
removing the insulator from the boundary. The seal forms an annular 
passageway at a distal end for receiving the wire and providing a 
weatherproof seal thereagainst. 
These and other features as well as advantages which characterize the 
present invention will be apparent from a reading of the following 
detailed description and a review of the associated drawings.

DETAILED DESCRIPTIONS 
Referring to the drawings in general and in particular to FIG. 1, shown 
therein is a cross-sectional, elevational view of an electrical insulator 
assembly 10 shown in an installed state with respect to an electrically 
conductive, substantially planar boundary, which is contemplated as 
comprising a portion of a enclosure 12 housing an electrical device, such 
as a transformer (not shown). However, it will be recognized that the 
boundary could also readily represent a facia portion of a commercial sign 
or other structural barrier. The insulator assembly 10 generally comprises 
an insulator 14 and a resilient seal 16. An electrical wire 18 passes 
though an annular passageway 20 formed by the seal 16, and also through a 
coextensive annular passageway 22 formed in the insulator 14. 
The enclosure 12 is constructed of a conductive material such as aluminum 
or sheet metal. An opening 24 is provided in the enclosure to allow 
passage of the wire 18 from an external power source (not shown) to the 
device's point of power termination (not shown) contained within the 
enclosure 12. In practice, the opening 24 will usually have a sharp edge 
26. 
Those skilled in the art will recognize the importance of electrically 
insulating the wire 18 from the electrically conductive enclosure 12 to 
prevent electrical discharge, or short circuiting, between the wire 18 and 
the enclosure 12. Typically the wire 18 will include an outer insulative 
sheath (not separately designated) for electrical insulation purposes, but 
it will be recognized that the sheath in and of itself is insufficient to 
prevent a short circuit if the wire 18 contacts the edge 26 of the 
enclosure opening 24. Furthermore, it will be understood that where the 
wire 18 carries high voltage power, additional insulation will be 
necessary to prevent premature breakdown of the sheath where the wire 18 
passes through a conductive support. 
Turning now to the support of the insulator 14 by the enclosure 12, it will 
be noted that the insulator 14 includes a head 28 and a shank 30, with the 
head 30 having a larger cross-sectional diameter than that of the shank 
30. Medially, a shoulder surface 32 is formed which is substantially 
parallel to the enclosure 12 in the area proximate the opening 24. In an 
installed state the shoulder 32 abuttingly engages the enclosure 12, 
limiting the extension of the shank 30 through the opening 24. 
In the preferred embodiment of FIG. 1 it will be noted that a continuous 
external screw thread 34 is formed on the shank 30. A retaining member 
comprising a backing nut 36 has an internal screw thread (not separately 
designated) which matingly engages the thread 34, allowing the nut 36 to 
be threadingly advanced toward the enclosure 12. The backing nut 36 is 
advanced until it engages the enclosure 12, and thereafter further 
advanced to pressingly engage the enclosure 12 in opposition to the 
shoulder 32 on the opposing side of the enclosure 12. In this manner, 
tightening of the nut 36 provides support to the insulator 14 by the 
opposing pressing engagement of the shoulder 32 and the nut 36. 
It will be apparent that methods other than the thread 34 and nut 36 may be 
employed to secure the insulator 14 with in the enclosure 12. For example, 
a smooth or barbed shank may be used in conjunction with a retaining 
member comprising a push-on retaining clip to achieve similar results. One 
advantage of the configuration of FIG. 1, however is that the nut 36 can 
be readily removed and then subsequently replaced. Another advantage is 
the ability to adjust the retaining force by selecting the torque imparted 
to the nut 36. Yet another advantage is that the thread 34 can be sized to 
mate with conduit commonly used to route electrical wires inside 
buildings. Hence, as desired the insulator 14 can be screwed into mating 
conduit hardware and the wire 18 can pass through the insulator 14 and 
into the conduit. 
It will be noted that FIG. 1 shows the insulator 14 to be unitarily formed 
so that no sections exist creating joints therebetween. Such a joint would 
adversely create an uninsulated path for an electrical short circuit 
between the wire 18 and the enclosure 12. 
The insulator 14 is preferably formed from a nonporous, nonconductive, 
noncrystalline material to optimize its insulative characteristics to 
withstand deleterious environmental effects such as sunlight and 
temperature variations, as well as the effects of electrical flux energy 
forces and heat generated by the voltage on the wire 18. More 
particularly, the insulator 14 is formed from a supercooled, nonporous 
igneous magma, such as glass, using a conventional high pressure,injection 
molding process. Glass provides superior electrical insulation 
characteristics as compared to other well known insulation materials, such 
as rubber, plastic, cork and the like. The superiority of glass is due to 
its homogenous, nonporous amorphous constituency and its superior 
resistance to the adverse internal and external decaying effects described 
above. An insulator made of rubber, for instance, will typically become 
brittle with time when subjected to these conditions, resulting in an 
increased likelihood that a pin hole or fault crack will develop, 
providing a short circuit path through the rubber insulator. 
Other rigid, noncrystalline materials like ceramics have also been used in 
the fabrication of various insulator configurations. As will be 
recognized, ceramics are formed by firing nonmetallic earthy materials 
(clay, bauxite, etc.) at a high temperature. Unlike glass, however, 
ceramics are relatively porous and as such have a tendency to adsorb 
moisture and break down over time. To reduce these deleterious effects, 
ceramics typically include a glazing operation to reduce surface porosity. 
However, such glazing tends to degrade when subjected to heat and 
electrical fields established by high voltages on the wires proximate to 
such ceramic insulators; moreover, such glazing is often applied only to 
portions of the surface of these insulators. 
Finally, making the insulator 14 of glass provides the additional benefit 
of a transparent component which is thus substantially invisible from an 
appreciable distance. This feature is advantageous where the insulator is 
used in an electric sign, where the insulator's translucent character will 
assume the color of the sign to which it is attached, thus providing an 
aesthetically pleasing effect. Of course, the glass can also be colored as 
desired through the introduction of appropriate materials (such as cobalt 
to create a blue glass insulator). 
It is often desirable to seal the enclosure opening around the wire 18, 
where moisture or environmental conditions are harmful to the device's 
components within the enclosure 12, To meet this need the insulator 4 can 
be used in combination with the seal 16 shown in FIG. 1. 
Referring now to FIG. 2, to accommodate the seal 16 a peripheral groove 37 
is formed within the head 28 of the insulator 14. FIG. 3 shows that the 
groove 37 does not intersect, and is thereby electrically insulated from, 
the annular passageway 22 through which the electrical wire 18 passes. 
Returning to FIG. 1, the seal 16 includes a ring 38 which matingly engages 
and substantially fills the groove 37 of the insulator 14. A transitioning 
portion 40 depends from the ring 38, which in turn supports a sealing 
portion 42. The sealing portion 42 is marginally smaller than the 
cross-sectional size of the wire 18 so that the sealing portion 42 presses 
against the wire 18, providing a fluid-tight seal therebetween. A 
stiffener ring 44 can further be provided at a distal end of the sealing 
portion 42 to locally increase the pressure against the wire 18 at a 
lading edge 46 of the sealing portion 42. 
It will be noted that the seal 16 can be installed on the insulator 14, or 
removed therefrom, by the engagement or disengagement of the ring portion 
38 from the groove 37. As such, it is possible to install or remove the 
seal 16 with the insulator 14 intact within the enclosure 12. 
From the foregoing discussion it will be recognized that the present 
invention provides an apparatus for supporting and insulating an 
electrical power supply wire (such as 18) relative to a substantially 
planar boundary (such as the enclosure 12). 
More particularly, an insulator (such as 14) is formed as a supercooled, 
nonporous igneous magma having a head (such as 28), a shank (such as 30) 
depending from the head and a shoulder (such as 32) disposed between the 
head and the shank, the shoulder limiting extension of the shank through 
an opening (such as 24) through the boundary. An annular passageway (such 
as 22) is formed through the head and the shank for receiving disposition 
of the wire. 
A retaining member (such as the nut 36) cooperates with features of the 
shank (such as threads 34) to retain the insulator relative to the 
boundary. A seal (such as 16) can additionally be provided to engage the 
isolator and the wire to further seal the isolator. 
For purposes of the appended claims, the phrase "supercooled, nonporous 
igneous magma" will be understood as used by those skilled in the art as 
an amorphous, inorganic substance comprising silicates, borates and/or 
phosphates formed by a fusion of silica or oxides of boron or phosphorus 
with a flux and stabilizer into a mass that cools to a rigid, 
noncrystallized condition, such as glass including quartz glass and silica 
glass. 
It is clear that the present invention is well adapted to attain the ends 
and advantages mentioned as well as those inherent therein. While a 
presently preferred embodiment of the invention has been described for 
purposes of the disclosure, it will be understood that numerous changes 
may be made which will readily suggest themselves to those skilled in the 
art and which are encompassed within the spirit of the invention disclosed 
and as defined in the appended claims.