Road snow melting system using a surface heating element

The object of the present invention is to avoid the difficulty of recruiting snow removal personnel by automatically melting snow that has accumulated on roads in areas having cold climates, and protect human life and secure the safety of vehicles and aircraft traveling on such roads and runways. The present invention is comprised of a heating unit wherein a surface heating element, in which an electrically conductive coating is applied onto a cloth, is positioned between metal plates such as aluminum plates above and below and wrapped in a tar-based moisture-proof sheet. Said heating unit is then embedded beneath the surface of road paving. After particularly carefully steam rolling the asphalt and concrete base layer in this case so that it is free of irregularities, the upper surface of said base layer is coated with a primer. After installing and wiring the above-mentioned heating unit on top of said primer-coated base layer, an additional coating of primer is applied followed by paving with a material having a high degree of thermal conductivity, such as an asphalt layer or concrete layer containing fine granules of blast furnace slag, to function as the surface material.

BACKGROUND OF THE INVENTION 
The present invention relates to an ice and snow melting structure which 
prevents accidents involving vehicles and aircraft traveling on roads or 
runways due to slipping caused by snow by removing said snow as a result 
of embedding a surface heating element beneath the surface of the ground 
to melt said snow. 
Although there are numerous problems due to freezing and accumulation of 
snow on road surfaces in areas having cold climates, an example of one of 
those problems is the removal of snow from railroad crossings. The number 
of railroad crossings may be unexpectedly high, numbering as many as 60 
within a single territorial jurisdiction in cities. Although more than 100 
snow removal personnel are deployed for the removal of snow from these 
railroad crossings each time there is a significant snowfall, difficulties 
have recently been encountered in assembling enough personnel to perform 
this work. 
At present, railroad crossings equipped with ice and snow melting equipment 
using heating systems powered by electric power have not come into common 
use. The reason for this is primarily based on apprehensions concerning 
problems with electrical connection systems caused by vibrations and so on 
when a train passes over the crossing, as well as the detrimental effects 
on the heating unit due to load pressure at the time heavily loaded 
freight cars or roadway vehicles pass over the crossing. 
In addition, the use of these types of heating systems has also not 
proliferated in the case of removal of snow from runways at airports and 
removal of snow from ordinary roads due to problems similar to those 
described above being encountered. 
Furthermore, although the shortcoming in terms of the strength of surface 
heating elements of the prior art was in the joint between the surface 
portion and the electrodes, Yoshinori Nagai, one of the inventors of the 
present invention, succeeded in improving on this shortcoming and applied 
for patent of such in the form of UM Application 1-146306 (Laid open No. 
3-84584) dated Dec. 29, 1989. 
SUMMARY OF THE INVENTION 
The object of the present invention is to provide an ice and snow melting 
system, wherein the heating element is not damaged by the loads of 
vehicles traveling on roads or aircraft taking off and landing on runways, 
and which does not affect the service life of the road, etc. 
In the present invention, a heating unit comprising a surface heating 
element is embedded beneath the surface of the ground. 
The constitution of the heating unit which composes the surface heating 
element involves the surface heating element positioned between aluminum 
plates above and below, with the top and bottom of said heating element 
wrapped in a tar-based moisture-proof sheet that is adhered around it. 
Metal plates such as those of copper or iron may be used in place of 
aluminum, and different metal plates may be used for the upper and lower 
surfaces to prevent electrolytic corrosion. 
The foundation for embedding the above-mentioned heating heating beneath 
the surface of the ground is first sufficiently steam rolled so that there 
are no irregularities in the asphalt beneath the ground as well as in the 
concrete base layer. Then, primer is applied, the heating unit is 
installed at the prescribed location and wiring connections are made. 
When wiring work is completed, an additional coating of primer is applied 
to the upper surface of the heating unit. This is then covered with fine 
granular asphalt and concrete having a high degree of thermal conductivity 
as the surface material. A blend of fine granules of blast furnace slag 
used in iron manufacturing and asphalt is optimum for the asphalt used in 
the present invention. 
As the surface heating element is comprised of cloth and coating, those 
factors which are cause for the greatest apprehension when embedding the 
heating element beneath the surface of the ground are whether or not said 
heating element will be able to withstand load pressure, as well as the 
risk of the crushed stones blended into the asphalt and concrete eating 
into the surface heating element. As such, in order to protect the surface 
heating element as well as to attach a ground wire, aluminum plates are 
installed above and below the surface heating element. Moreover, with 
respect to the action of the aluminum plates, the upper aluminum plate 
gradually transfers the heat radiated from the heating element to the 
tar-based moisture-proof sheet by temporarily accumulating said heat, and 
then transferring said heat to the highly thermal conductive fine granular 
asphalt that comprises the surface material in order to raise the 
temperature of the ground surface. On the other hand, the lower aluminum 
plate demonstrates effects which suppress the transfer of heat radiated 
from the heating element. 
Thus, thermal efficiency is extremely favorable allowing a savings of 
roughly 40% less electrical power to maintain the surface temperature at a 
constant level than in the case of a heating element in which electric 
heating cords simply run through said heating element in zig-zag fashion. 
In addition, in contrast to the surface temperature one and a half hours 
after starting operation being -3.0 degrees Celsius in the case of a 
cord-type heating element, the surface temperature in the case of 
implementing the heating element of the present invention in the manner 
described above demonstrated a temperature of +0.6 degrees Celsius. In 
addition, in contrast to the surface temperature after 7 hours being +0.3 
degrees Celsius in the case of a cord-type heating element, a temperature 
of +8.0 degrees Celsius was attained in the case of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The following provides an explanation of a preferred embodiment of the 
present invention using an example wherein the present invention is 
applied at a railroad crossing. 
FIG. 1 is a schematic drawing which indicates a portion of the 
cross-section of heating unit 4. The actual heating unit is a thin object 
free of any lamellar space. A surface heating element 1 of the heating 
unit 4 is comprised of an electrically conductive coating applied on both 
sides of cloth followed by lamination of a vinyl sheet. The surface 
heating element 1 is positioned between aluminum plates 2 which are 
adhered above and below the surface heating element. Moreover, tar-based 
moisture-proof sheet 3 is adhered around the outside of the plates 2 thus 
resulting in said heating unit 4 being sealed from the outside between 
cabtyre cables of the electrode wires. 
FIG. 2 is a cross-sectional side view of the foundation in which heating 
unit 4 is embedded. Although cobblestone layer 7 is covered over the 
bottom using a procedure similar to routine construction procedures, the 
asphalt base 6 on top of said cobblestone layer 7 is steam rolled more 
carefully than in the case of routine construction procedures because it 
is critically important that the surface be flat and completely free of 
irregularities in comparison to routine construction procedures. Moreover, 
primer is coated onto said asphalt base 6 after which the heating unit 4 
is installed at the prescribed location followed by wiring. Wiring work is 
performed in accordance with routine electrical wiring procedures, with 
wiring performed from said heating unit 4 to a control box using cabtyre 
cables and conduit. The control box is equipped with devices including an 
automatic operating unit activated by a snowfall sensor, and safety 
devices including a thermostat. The ground wire is taken off from aluminum 
plates 2. Following wiring work, an additional coating of primer is 
applied on the upper surface of heating unit 4 followed by the spreading 
of fine granular asphalt having a high degree of thermal conductivity to a 
thickness of 50-60 mm on top of said primer coating to function as surface 
material 5. Steam rolling, pressing and so on using a compactor or roller, 
etc. are then performed in accordance with conventional construction 
procedures. 
With respect to the installation of the present invention, as the roadway 
portion is of a structure nearly identical to that of ordinary road 
paving, being comprised of asphalt and concrete without using foam heat 
insulating materials having a low level of strength, there is no reduction 
in the strength of the road paving. Consequently, although aluminum plates 
are used as heat insulating materials beneath the heating unit, the action 
of those plates as heat insulating materials is minimal. Instead, it was 
possible to obtain a higher degree of thermal efficiency in comparison to 
using foam heat insulating materials by using a material having a higher 
degree of thermal conductivity than ordinary paving material for the 
surface material. In addition, the present invention also offers the 
advantage of suffering fewer malfunctions as a result of the surface 
heating element being positioned between metal plates on both sides. 
Thus, roadways and runways embedded with the surface heating element of the 
present invention are continuously kept free of snow and ice, thus nearly 
completely eliminating accidents caused by snow, including slipping and 
leaving of the roadway of vehicles crossing said roadways, thereby 
allowing the securing of safety and accuracy of drivers. 
Moreover, it goes without saying that the present invention is not limited 
to use in only roadways and runways, but is also a system that can be 
widely applied in building roofs, athletic grounds and other locations at 
which removal of snow is required.