U.S. patent number 3,904,850 [Application Number 05/449,772] was granted by the patent office on 1975-09-09 for flexible heater panel.
This patent grant is currently assigned to Thermon Manufacturing Company. Invention is credited to Ben C. Johnson.
United States Patent |
3,904,850 |
Johnson |
September 9, 1975 |
Flexible heater panel
Abstract
A flexible heating panel and method for making such a heating
panel, the panel having an insulated flexible heating element
bonded to an overlying insulated flexible electrical ground and
having the electrical connections mounted on the top surface
therewith. The method further including the steps of securing the
connections thereto, and protectively sealing the electrical
connections from the surrounding influences.
Inventors: |
Johnson; Ben C. (San Marcos,
TX) |
Assignee: |
Thermon Manufacturing Company
(N/A)
|
Family
ID: |
23785432 |
Appl.
No.: |
05/449,772 |
Filed: |
March 11, 1974 |
Current U.S.
Class: |
219/528; 174/51;
219/541; 392/468; 171/51; 219/535; 219/549; 392/480 |
Current CPC
Class: |
F24H
9/18 (20130101) |
Current International
Class: |
F24H
9/18 (20060101); H05B 003/34 () |
Field of
Search: |
;219/212,345,528,529,530,535,536,541,549 ;174/51,75.2,7-8 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Mayewsky; Volodymyr Y.
Attorney, Agent or Firm: Pravel & Wilson
Claims
I claim:
1. A flexible heating panel comprising:
a first electrical insulating layer serving as the base of the
panel;
a flexible heating tape for heating, overlying said first
layer;
a second electrical insulating layer, overlying said flexible
heating tape;
a flexible, electrically grounding material for electrically
grounding the heating tape in case of accidental penetration of the
panel, said grounding material overlying said second layer;
a third electrical insulating layer overlying said grounding
material and having a bottom face and an upper face, said upper
face serving as the top of the panel;
said second electrical insulating layer includes:
a heater element insulating layer mounted with said flexible
heating tape, said heater element insulating layer being formed
with said first electrical insulating layer into a heater element
layer; and
a ground insulating layer mounted with said grounding material,
said ground insulating layer being formed with said third
electrical insulating layer into a ground layer, said heater
element insulating layer and said ground insulating layer being
laminated together;
said first electrical insulating layer includes overlapping,
protective portions folded about and adjacent to the end portions
of the panel to protect and enclose all of said layers, said
overlapping, protective portions being attached to said upper face
of said third electrical insulating layer;
electrical leads of an electrical power line and means connecting
said leads to said heating element and said grounding material;
and
clamp means mounted with the panel to fasten said electrical power
line to said upper face of said third electrical insulating layer
to prevent said electrical connection means and said electrical
leads from becoming inadvertently detached from said heating tape
and said grounding material.
2. The structure of claim 1, wherein: said first, second, and third
electrical insulating layers are made of glass reinforced silicon
rubber.
Description
BACKGROUND OF INVENTION
1. Field of Invention
This invention relates to flexible heating panels.
2. Description of the Prior Art
Prior art heater panels disclose the value of having protective
grounding features to prevent inadvertent electrical shocks. Some
of the prior art heater panels utilize a ground layer such as those
devices disclosed in U.S. Pat. Nos. 3,454,746; 2,971,073; and
3,627,981.
However, numerous practical problems are incumbent with the use of
such a heater panel. For example, it is desirable to protect the
edges of the various layers from the effects of environmental
deterioration. Furthermore, it is desirable to secure the
electrical connections located at different layers within the
heater panel firmly to the panel to avoid inadventent electrical
disconnection which would render the panel inoperative. The ground
layer must further be effectively insulated from both the heater
elements and any electrical connections thereto to prevent internal
shorts under normal operating conditions.
SUMMARY OF THE INVENTION
The present invention provides a new and improved flexible heater
panel assembly having a flexible, fully-insulated heater element
bonded to a flexible, fully-insulated electrical ground overlying
the heater element such that, if the panel assembly is
inadvertently pierced by an electrical conductive object, the
ground layer is pierced in such a manner that a subsequent
contacting of the heater element will ground out the heater element
circuit through the ground layer thus preventing electrical shocks.
The heater panel assembly includes electrical lead-in wires
securely mounted on this fully-insulated assembly and all
electrical elements therewith are protectively sealed to prevent
environmental deterioration.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an oblique view of the apparatus in the preferred
embodiment of this invention as used for heating a pipe;
FIG. 2 is a plan view of the present invention, showing the
multiple layer construction; and
FIG. 3 is a sectional view taken along the lines 3--3 of FIG.
2.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to the drawings the letter H designates the flexible
heater panel assembly of the preferred embodiment of this invention
mounted onto a pipe P for heating the same, the heater panel
assembly H having a heater element layer E and a flexible ground
layer G.
The heater panel assembly H includes a heater element layer E
having a base insulation layer 10 having a bottom face 10b and an
upper face 10u of a suitable electrical insulation material, such
as silicon rubber. For strength, glass fibers (not shown) can be
embedded within the insulation materials to reinforce the
insulation layer 10. Alternatively, other electrical insulation
materials such as Teflon, butyl rubber or polyamides can be
used.
Overlying the base insulation layer 10 on face 10u is a series of
electrically resistive heating elements or strips 12 which are
symmetrically arranged in a known manner about the face 10u of the
base insulation layer 10. The elements 12 in the preferred
embodiment of this invention are formed of an electrically
resistive flat foil tape made of a nickel-steel alloy. The heating
elements 12 have appropriate electrical connection points 12a and
12b for making electrical connections, to electric line 22, which
is powered by a suitable power source (not shown). Overlying the
heater element 12 is an electrical insulation layer 14 having a
bottom face 14b and an upper face 14u formed of insulating material
such as silicon rubber as discussed above. The base insulation
layer 10 and the electrical insulation layer 14 are of reinforced
silicon rubber with the opposite faces 10u and 14b of the layers
10, 14 bonded about the heating element 12 by an appropriate
vulcanizing process utilizing proper heat and pressure to form the
heater element layer E. A void 11 (FIG. 3) may be formed between
the faces 10u and 14b or it may be filled by vulcanizing in such a
fashion that faces 10u and 14b are bonded together leaving no
voids.
The flexible ground layer G includes an electrical insulation layer
16 having a bottom face 16b and an upper face 16u of suitable
insulation material. The upper face 16u provides a mounting surface
for a finely woven wire screen 18 of aluminum, copper, or steel, or
any other suitably electrically conductive material that will serve
a grounding function. Such electrically conductive material is also
flexible and of minimal thickness. Overlying the wire screen 18 is
a top insulation layer 20 having a bottom face 20b and an upper
face 20u. The electrical insulation layer 16 and the top insulation
layer 20 are formed of preferably a reinforced silicon rubber
vulcanized about the wire screen 18 to produce the ground material
layer G.
The flexible heater panel H may be defined as including protected
side portions 30, 31, 32 and 33. Each side portion is formed by the
bottom insulation layer 10, which is formed slightly larger in
length L and width W so as to include overlapping, protective
portions 10s. The overlapping portions 10s of the bottom insulation
layer 10 are folded over each of the sides 30, 31, 32, 33 of the
entire panel H and include portions 10t which are vulcanized to the
top insulation layer face 20u. These overlapping, protective
portions 10s of the bottom insulation layer 10 serve to insulate
and protect the otherwise exposed edges of the heater element 12,
insulation layers 14, 16 and 20 and the ground screen 18.
Furthermore, the overlapping portions 10s help to prevent any
portion of the heating element 12 from being exposed thus
preventing inadvertent electrical shock.
A lead-in cable 22 carrying heater wires 24, 25 and a ground wire
26 connected to a suitable electrical ground 34 is securely mounted
with the upper face 20u of the top insulation layer 20 by a clamp
28. The clamp 28 is mounted to the heater panel assembly H by a pin
35 having a backing plate 36 mounted beneath the base insulation
layer 10, to distribute thereon the load exerted on the pin 35, and
prevent the pin 35 from inadvertently being torn therefrom. In
order to connect the wires 24, 25, 26 to their appropriate
connections, a portion (not shown) of the heater panel assembly H
must be removed to expose the connection points 12a and 12b of the
heater element 12 and a ground connection point 27 of the wire
screen 18. This removal operation may be accomplished by etching
with a suitable acidic or basic solution, or by cutting with a
knife, or the like. Thus, a small portion (not shown) of the top
insulation layer 20, the wire screen 18, and layers 14, 16 must be
removed by the above operations to allow electrical connections to
be made. With this portion (not shown) removed, the wires 24, 25
are connected to the heater element 12 at connection points 12a and
12b, respectively, to provide power from a suitable source (not
shown) for the heater element 12. Furthermore, the ground wire 26
is connected to the screen 18 at the connection point 27. The wires
24, 25 and 26 can be secured to the connection points 12a, 12b and
27 by any suitable means such as bradding or riveting.
A sealing block 37 of silicon rubber is formed about the wires 24,
25, 26 and a portion of the lead-in cable 22 as well as any
evacuated portion laid bare during the removal operation to enclose
and secure the wires 24, 25 and 26. The sealing block 37 is molded
under heat and pressure and vulcanized to the heater panel assembly
H by using an appropriate mold (not shown) such that the evacuated
portion is filled with silicon rubber and the wires 24, 25, 26 are
separated and suspended within the sealing block 37 in a locked,
non-touching positon. The sealing block 37 helps to insure a
water-tight connection, electrically insulate the wires 24, 25, 26
as well as help to protect and prevent inadvertent disconnection of
the wires 24, 25, 26.
In the operation and use of the form of the invention illustrated
in FIGS. 1-3, the heater panel assembly H can be used on a flat
surface, or as shown in FIG. 1, on a curved surface of pipe P, or
the like. If wrapped about the pipe P, it is preferred that the
bottom face 10b of the base insulation layer 10 be adhesively
mounted to the pipe P to prevent relative motion therebetween and
insure proper surface area contact with the pipe P to maximize
heating efficiency. Due to the particular laminated configuration
of the elements of the heater panel assembly H, if the panel
assembly H is pierced by an electrically conductive object (not
shown) such as a nail or screwdriver, the direction of the puncture
is such that the object will first pierce the top insulation layer
20, contact the wire screen 18, and then pierce the electrical
insulation layers 16, 14 and finally contact the heating element
12. As such, any electrical surge resultant to contacting the
heating element 12 by the conductive object will ground through the
conductive object contacting the wire screen 18, which is connected
to the wire 26 and the ground 33, thus preventing inadvertent
electrical shocks to one so piercing the heating element 12. Of
course, if the piercing object 13 is not of a conductive material,
no risk is encountered by one who accidentally pierces the heating
element 12.
The foregoing disclosure and description of the invention are
illustrative and explanatory thereof, and various changes in the
size, shape, materials, components, circuit elements, wiring
connections and contacts as well as in the details of the
illustrated circuitry and construction may be made without
departing from the spirit of the invention.
* * * * *