Note: Descriptions are shown in the official language in which they were submitted.
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I'he present invention relates to a heater for
use in thawing frozen plastic water pipes. In this
application the term "water pipe" is intended to include
both supply and return pipes and pipes carrying waste
water such as sewage lines.
It is known to use electric heating to thaw
frozen water pipes. U.S. Patent No. 2,516,950 issued
August 1, 1950 to Bragy shows a heater suitable for use
with metallic water pipes consisting of a sealed heating
unit advanced into the water pipe by means of the metallic
conduit sheathing the power cable. U,S. Patent No.
3,519,023, issued July 7, 1970 to Burns ee al. sliows the
use of an external collar for defrosting pipes. U.S.
Patent No. 3,900,0~7, issued August 19, 1975 to Heppell
deals with the thawing of plastic pipe and teaches the
use of an internal conductor permanently formed on the pipe.
Clearly, the thawing of plastic pipe raises
additional problems in that overheating can cause sub-
stantial damage to the pipe itself. The device of the
present invention provides a specific amount of heat
dissipation for any particular situation which is such that
it will not melt the plastic pipe, even in -the absence
of liquid, or burn out by i-tself. By making the device
of this invention of the immersion type, heat is conveyed
from the heater to the plastic pipe by the melted liquid.
Further, the hot water generated by the heater rises and
can thus operate ahead of or behind the lo_ation of the
heater.
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Specifically, the present invention relates to
a heater for use in thawing a frozen plastic water pipe,
comprising an apertured housing with rounded ends, whereby
liquid in the pipe may enter the apertures. ~n electrical
heating element is carried by an insula-ting plate
suppor-ted within the housing and terminal means are
positioned on the insulating plate adjacent the rear end
of the housing for connecting the heating element to a
source of electrical power. The heat dissipation of the
heating element is less than that necessary to melt the
plastic pipe in the absence of liquid.
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Particular embodiments of the invention will
now be described in conjunction with the accompanying
drawings, in which:
Figures lA, lB and lC are front, side and rear
views, respectively, of a heating device useful to be
manipulated around bends in larger diameter pipes, such
as sewage lines;
Figures lD, lE and lF are corresponding views
with the housing shown in phantom;
Figures 2A, 2B and 2C are front, side and rear
views, respectively, of a heating device using a coiled
tubular element;
Figures 2D, 2E and 2F and Figures 2G, 2H and 2I
are corresponding views with the housing shown in phantom;
Figures 3A, 3B and 3C are front, side and rear
views, respectively, of a heating device useful in low
wattage applications;
Figures 3D, 3E and 3F are corresponding views
with the housing shown in phantom;
Figures 4A, 4B and 4C are front, side and
rear views, respectively, of a heating device useful in
higher wattage applications; and
Figures 4D, 4E and 4F are corresponding views
with the housing shown in phantom.
Figure 1 show~ a heater in which the housing 10,
preferably made of copper is of relatively stub configuration,
the length being less than twice the diameter. This is
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intended for use with relatively large plastic lines such
as are used for sewage. The configuration of the heater
enables it to be manipulated around bends in the line.
Typically, it will be 4" long and 2~" in diameter. The
housing is formed in two sections detachably connected by
screws 11. This enables the heating element to be easily
changed deper.ding on the wattage required or in the event
of failure. Housing 10 is formed with apertures 12 permitting
liquid in the line to be thawed,to enter the housing and
thereby facilitate heat transfer.
The heating element contained in housing 10 consists
of asbestos cards or plates 13 arranged in a cross configuration
with stainless steel resistance wire 14 wound therearound.
A shoulder 15 is formed in the asbestos cards so that they are
held in position between the two portions of the housing.
The wire 1~ forms an inner and outer winding to provide a
relatively high wattage heater. The inner winding passes
through apertures 16 formed in the insulating cards. These
apertures also permit circulation of liquid in the heater
and thus promote heat transfer. Terminals 17 are provided
whereby the heating element can be connected to a source of
electrical power through an insulated conductor, not shown.
Figure 2 shows another embodiment of a heating
device in accordance with the present invention. The housing
20 is of more elongated configuration, typically of copper
and of length 6" and diameter 1". Again, apertures 22 are
formed in the housing to permit liquid in the pipe to be
thawed,to reach the heating element.
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The single insulating plate 23 carries a tubular
coiled heating element 24 passing through apertures 25.
The apertures permit circulation of the liquid inside the
housing to promote heat transfer. Terminals 27 are provided
for connection to an insulated conductor supplying the
necessary electrical power.
Figure 3 shows a different embodiment of a heater
for low wattage applications in accordance with the present
invention. The copper housing 30 again is of elongated
configuration, typically of length 10" and diameter 11". The
apertures 32 are smaller than in the heaters shown in Figures
1 and 2.
The heating element is formed on asbestos cards 33
arranged in a cross configuration and consists of a single
winding 34 of stainless steel wire terminating in terminals
37. It will be noted that no apertures are formed in the
asbestos cards 33 since in -this low wattage application
there is no requirement for enhanced circulation.
Figure 4 shows a heater similar to that of
Figure 3 but adapted for higher wattage applications. Housing
40 is of elongated configuration, typically formed of copper,
with length 9" and diameter 2". Rows of apertures 42 are
formed in the housing. The heating element consists of
stainless steel wire 44 wound on asbestos cards 43 arranged
in a cross configuration. Apertures 46 are provided in the
asbestos cards to promote circulation of the liquid from the
pipe to be thawed and hence increase heat transfer. Terminals
47 are provided for wire 44.
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Thus, there have been disclosed heaters for
thawing frozen plastic water pipes which operate as
immersion type devices. The hot water ~enerated by the
heater rises and, thus, can operate ahead of or behind
the location of the heater. The heaters are advanced
towards the frozen section of the pipe by means of a
rubber covered, insulated power line. Some embodiments
can be manipulated around bends in the line. In all cases,
the heat generated by the heater is selected to be less
than that which would melt the plastic pipe under the
worst conditions, i.e. in the absence of liquid. Clearly,
the invention is not restricted to ~he particular dimensions
and confi~urations shown.
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