Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02656973 2009-03-10
HEATING APPARATUS FOR INSTALLATION ON ROOFTOP END OF SEWER
VENT PIPE
FIELD OF THE INVENTION
This invention relates generally to heating devices for preventing the
clogging of sewer vent pipes that occurs in cold-whether climates due to ice
and
snow buildup at the rooftop exhaust ends of these pipes.
BACKGROUND OF THE INVENTION
Sewer vent pipes are vertically oriented pipes made of, for example,
acrylonitrile butadiene styrene (ABS) or polyvinyl chloride (PVC), installed
to extend
upwardly through the roof structures of buildings to an open exhaust end,
allowing
sewer gases, fumes or odors from the waste water system of a building to be
vented
outside the building. A well known problem in cold weather climates is that
sub-zero
temperatures in the outside environment will promote freezing of water vapour
as it
exits the sewer vent pipe, causing a build up of ice on the interior wall
surface of the
pipe. Alone or compounded with by snow-fall accumulation, this build up may
eventually close off and completely plug the pipe, thereby preventing the
intended
venting of the waste water system and potentially causing backing up of
undesirable
gases or fumes into the building interior. A number of prior art devices have
been
developed with the intention of solving this problem.
U.S. Patent No. 4,524,262 of Meyer teaches an electric sewer vent line
defroster intended for use on a plastic vent pipe. The defroster is of a multi-
piece
construction requiring a relatively complex rooftop installation, including
modification
of the existing sewer vent pipe to cut away the top end thereof. The defroster
uses
CA 02656973 2009-03-10
2
an electric heater externally mounted to a section of metal pipe that replaces
the
removed top portion of the existing plastic vent pipe.
U.S. Patent No. 5,214,266 of Halone, Jr. teaches an electric heating
attachment for a sewer vent pipe that can be easily installed by lowering the
bottom
end of a vertically depending rod carrying electrical heat tape into the open
top end
of the sewer vent pipe until lateral support arms projecting horizontally from
the rod
rest atop the pipe end. While easy to install, the device blocks a significant
portion
of the pipe's open top end.
U.S. Patent No. 6,097,008 of Mahin teaches another electric device for
preventing ice build up on a sewer vent pipe. The device is produced in a
single
size and the reference teaches the use of a separately acquired coupler to
effect
installation of the device on a sewer vent pipe of a particular size. The
device uses
heat cable coiled in an annular space between inner and outer sleeves to heat
space inside the inner sleeve that communicates end-to-end with the sewer vent
pipe through the coupler.
U.S. Patent Application Publication No. 2006/0057950 of Heise, in one
embodiment, teaches a heat vent cap assembly installed in place of a removed
section of the existing sewer vent pipe at the passage thereof through a
building's
roof structure. This device requires modification of the existing sewer vent
line and
uses an electric heating element coiled around an inner sleeve or cylinder.
The
device may suffer from a higher level of installation difficulty, as it is
installed to pass
through the existing roof structure and is of a greater diameter than the
previously
installed section of pipe that it replaces. Another embodiment uses a hydronic
CA 02656973 2009-03-10
3
heating element placed in communication with the vent pipe interior by
addition of a
cap assembly to the top end of the pipe or modification of the pipe to pass
the cable
thereinto.
SUMMARY OF THE INVENTION
According to a first aspect of the invention there is provided a heating
apparatus for installation on a top end of a sewer vent pipe projecting
upwardly
through a roof structure of a building to prevent frozen build up within said
sewer
vent pipe, the heating apparatus comprising:
a heater body having open top and bottom ends interconnected by an
internal passage extending through the heater body along an axis passing
through
said top and bottom ends, the heater body having a stop defined at a position
along
the axis between the open top and bottom ends to make a cross-sectional area
of
the internal passage in a plane normal to the axis smaller at said position
than at the
open bottom end of the heater body, the open bottom end of the heater body
having
an internal diameter sized for snug receipt of the top end of the sewer vent
pipe into
the internal passage of the heater body through the open bottom end thereof
and the
cross-sectional area of the internal passage, at all positions between the
open top
and bottom ends of the heater body, being no less than a cross sectional area
bound by an inner diameter of the sewer vent pipe; and
an electrical heating device supported by the heater body and being
arranged on a same side of the stop as the open top end of the heater body for
connection to an electrical power source, a heating element of the electrical
device
being positioned in or adjacent the internal passage for heating thereof.
CA 02656973 2009-03-10
4
Preferably the electrical heating element loops around the internal
passage of the heater body on the same side of the stop as the open top end of
the
heater body.
Preferably the electrical heating element loops around the internal
passage of the heater body in an annular cavity between an outer periphery of
the
heater body and an inner periphery of the heater body defining boundaries of
the
internal passage.
Preferably at least a portion of the heating element projects into the
internal passage of the heater body.
Preferably the electrical heating element, from where it loops around
the interior passage of the heater body within the annular cavity, projects
into the
interior space of heater body from the annular cavity.
Preferably the heater body comprises an inner sleeve fitted within and
fixed to an outer sleeve, the stop projecting inward from an inner surface of
the outer
sleeve and the inner sleeve being disposed on the same side of the stop as the
open top end of the heater body, the annular cavity being defined between the
inner
and outer sleeves.
The stop may comprise a ridge formed integrally on the outer sleeve.
Preferably a bottom end of the inner sleeve is seated against the stop.
Preferably a pathway connecting the annular cavity to the internal
passage accommodates passage of the heater element from the annular cavity
into
the internal passage.
CA 02656973 2009-03-10
Preferably the pathway is sized to prevent passage of more than a
single pass only of the heater element therethrough.
Preferably sides of the pathway spaced apart are obliquely sloped
relative to the axis of the internal passage to encourage the heater element
to curve
5 around the axis of the internal passage as it extends thereinto from the
annular
cavity.
The sides of the pathway may converge along a direction parallel to
the axis of the internal passage toward the open top end of the heater body.
According to a second aspect of the invention there is provided a
heating apparatus for installation on a top end of a sewer vent pipe
projecting
upwardly through a roof structure of a building to prevent frozen build up
within said
sewer vent pipe, the heating apparatus comprising:
a heater body having an internal passage that extends therethrough
and is open at top and bottom ends interconnected by an internal passage
extending
through the heater body along an axis passing through said top and bottom
ends,
the heater body being arranged for connection to the sewer vent at the top end
thereof to communicate the interior passage of the heater body with an
interior of the
sewer vent pipe; and
an electrical heating device comprising a heating element that loops
around the interior passage of the heater body proximate the open top end
thereof
and depends downward toward the open bottom end of the heater body within the
interior passage thereof from where the heating element loops around the
interior
CA 02656973 2009-03-10
6
passage for receipt of a bottom end of the heating element inside the sewer
vent
pipe.
Preferably the heating element comprises heat cable.
Preferably the heating element is self-regulating heat cable.
Preferably the heating device comprises a power supply cord
connected to the heating element.
Preferably the power supply cord is connected to the heating element
inside the heater body.
Preferably the heating device is of an elongated structure passing into
the heater body through an aperture in an outer wall thereof and features a
bend
inside the heater body to prevent withdrawal of the heating device therefrom
through
the aperture.
BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings, which illustrate an exemplary
embodiment of the present invention:
Figure 1 is a perspective view of a sewer vent pipe heating apparatus
in accordance with the present invention.
Figure 2 is a schematic sectional view of a building illustrating the
heating apparatus installed at the top end of a sewer vent pipe projecting
vertically
through the building's roof structure.
Figure 3 is a schematic cross sectional view taken along a vertical
plane containing the central longitudinal axis of the sewer vent pipe during
installation of the heating apparatus thereon.
CA 02656973 2009-03-10
7
Figure 4 is a schematic cross sectional view of the heating apparatus
and pipe of Figure 3 taken along line IV - IV thereof.
Figure 5 is an overhead plan view of a spacing ring of a body or
housing of the heating apparatus.
Figure 6 is a bottom plan view of the spacing ring.
Figure 7 is a side elevational view of the spacing ring
Figure 8 is schematic cross-sectional view of an outer sleeve of the
body or housing as taken along line VIII - VIII of Figure 4, but with a
heating element
and inner sleeve of the apparatus removed for illustrative clarity.
Figure 9 is a schematic cross-section view of the housing of Figure 8
as taken along line IX - IX thereof, but with the spacing ring removed.
Figure 10 is schematic cross-sectional view of the housing of the
heating apparatus similar to Figure 8, but with the ring removed.
DETAILED DESCRIPTION
Figure 1 shows a heating apparatus 10 that is configured as a one-
piece unit to easily install atop a sewer vent pipe projecting vertically
upward through
the rooftop of a building without any separate fasteners or couplers and to
provide
ice-preventing heating at both the effective top end of the sewer vent pipe,
as
defined by the installed unit, and within the previously existing length of
sewer vent
pipe directly below the installed unit. The unit features a heater body or
housing 12
having an internal passage 14 extending fully therethrough along a vertical
axis 16
to define an open top end 18 and open bottom end 20 of the housing at opposite
ends of the internal passage 14. An electric heating element 22 coils around
the
CA 02656973 2009-03-10
8
internal passage of the heater body 12 within an upper portion of thereof
before
projecting into the internal passage 14 in order to depend downward through
the
open bottom end 20 of the housing into the sewer vent pipe when the heater
body is
installed thereon. The top end of the heating element 22 from which it coils
downward inside the heater body is conductively coupled to a power supply
cable 24
that extends outward through an outer peripheral wall of the housing 12
proximate
the open top end 18 for connection to a suitable electric power source.
Figure 2 shows the heating apparatus 10 installed on the sewer vent
pipe 200 extending vertically upward through the roof structure 202 of a
building 204
in a conventional manner so as to position a top exhaust end of the pipe 200
at a
distance above the roofline at the pipe's position therealong. Figure 3 shows
a
schematic cross section of the heating apparatus 10 and the building's
existing
sewer vent pipe 200 once the heater body 12 is fitted thereon. The heater body
12
features an outer sleeve 26 that closes around the central vertical axis 16 of
the
heater body and presents cylindrical outer surface 26a over its full length
along this
axis. This length of the outer sleeve 26 defines the full height of the heater
body 12,
extending fully from the open top end 18 to the open bottom end 20. At a
central
position along the length of the outer sleeve 26, an annular ridge is defined
to project
inward from the rest of the outer sleeve 26 a short distance toward, without
reaching,
the heater body's central axis 16. Below this ridge 28, the inside of the
outer sleeve
features a lower cylindrical surface 26b extending concentrically about the
heater
body's central axis 16, giving the internal passage 14 of the heater body 12 a
uniform circular cross-section normal to the body's central axis 16 from the
open
CA 02656973 2009-03-10
9
bottom end 20 to the ridge 28. The round annular ridge 28 acts to reduce the
diameter and thus area of the internal passage's circular cross-section at the
ridge's
position along the body's central axis 16 and presents a flat horizontal
shoulder
projecting inward from the portion of the outer sleeve below it.
As shown in Figures 3 and 4, the uniform diameter of the internal
passage 14 below the ridge 28, as defined by the uniform diameter of the outer
sleeve's lower inside cylindrical surface 26b below the ridge 28, is sized to
fit snugly
around the outside diameter of the existing sewer vent pipe 200. The
horizontal
shoulder defined at the bottom of the ridge 28 by the projection thereof
inward from
the lower inside cylindrical surface 26b of the outer sleeve toward the body's
axis 16
thus defines a stop against which the annular upper end face of the sewer vent
pipe
200 abuts when the open bottom end 20 of the outer sleeve 26 is fitted over
the
pipe's top end and slid down the pipe. The heater body 12 thus sits atop the
sewer
vent pipe at the ridge 28 and is held laterally stationary by the snug
friction fit of the
outer sleeve's inside lower cylindrical surface 26b against the cylindrical
outer
surface of the pipe wall.
Opposite the ridge's flat bottom face that defines the horizontal
shoulder against which the top end face of the vent pipe 200 abuts with the
heater
apparatus installed, the ridge features a flat top face that defines a
horizontal ledge
parallel to the shoulder. An inner assembly 32 fixed to the outer sleeve 26
sits atop
this ledge and is composed of an inner sleeve 34 and a spacing ring 36 fixed
to the
bottom of the inner sleeve 34. The ring 36 and the inner sleeve 34 close about
the
central axis 16 of the body concentric with the outer sleeve 26 and ridge 28
thereon.
CA 02656973 2009-03-10
A flat bottom face of the spacing ring 36 abuts face-to-face against the
horizontal top
face or ledge of the ridge 28 and an opposing flat top face of the spacing
ring 36
abuts face-to-face against the flat annular horizontal bottom face of the
inner sleeve
24. With reference to Figure 4, the outer diameter of the circular ring 36
exceeds the
5 outer diameter of the sleeve's circular bottom end, but the inner diameter
of the ring
36 equals that of the inner sleeve's annular bottom end so that inner
peripheral
surfaces of the inner sleeve and spacing ring are flush. An outer peripheral
surface
of the spacing ring 36 fits against the inner surface of the outer sleeve
where the ring
36 sits atop the ridge 28 over most of the ring's perimeter, the inner surface
of the
10 outer sleeve having the same uniform diameter most of the way around the
body's
central axis 16 at the portion 26c of the inner surface spanning the height or
thickness of the ring immediately above the ridge as it does at the lower
cylindrical
portion 26b of the outer sleeve's inner surface below the ridge 28. From
immediately above the spacing ring 36 to a short distance below the open top
end
18 of the housing, the outer sleeve 26 is cylindrical, but thinner than at all
other
locations therealong. Immediately above this thinner portion 26d, the outer
sleeve
26 returns to the same thickness as immediately above and below the ridge 28,
and
is uniform in this thickness right to the open top end 18 of the housing 12.
With the
outer sleeve's cylindrical outer surface, these sections of different uniform
thicknesses make the inner surface of the outer sleeve recessed from the
remainder
of this inner surface at the thinnest portion 26d of the outer sleeve 26, and
define an
internally flanged upper end 26e of the outer sleeve 26.
CA 02656973 2009-03-10
11
The inner sleeve 34 has a cylindrical portion 34a that is of uniform wall
thickness, uniform inner diameter and uniform outer diameter and extends
upward
from the spacing ring 36 at the inner sleeve's bottom end to the top end of
the
thinnest cylindrical portion 26d of the outer sleeve, where the inner sleeve
then
increases in thickness, keeping the same inner diameter but increasing its
outer
diameter to match the outer diameter of the spacing ring 36, thus forming an
externally flanged upper end 34b of the inner sleeve 34. At this top end 34b
of the
inner sleeve 34, the outer surface thereof therefore fits against the inner
surface 26b
of the outer sleeve at the internally flanged top end 26e thereof. The heater
body 12
defined by the assembly of the inner and outer sleeves and spacing ring
features an
annular cavity 38 defined in the heater body and extending around the internal
passage thereof. The annular cavity features a rectangular cross section in
vertical
planes passing radially through the heater body's central axis 16, the
opposing
vertical sides of this cross section being defined by the thinner portions
26d, 34a of
the inner and outer sleeves 26, 34 aligned along the body's central axis 16,
the
horizontal top of this cross section being defined by the mating flanges of
the top
end portions 34b, 26e of the inner and outer sleeves and the horizontal bottom
of
this cross section being defined by the mating of the spacing ring's outer
surface and
corresponding portion 26c of the outer sleeve's inner surface above the stop
ridge
28.
With reference to Figure 3, the insulated power supply cord 24 extends
from outside the heater body 12 to the annular cavity 38 defined therein
through a
hole or aperture 40 provided in the thin portion of the outer sleeve wall 26
to
CA 02656973 2009-03-10
12
communicate directly with the cavity 38 at or near the top end thereof. The
power
supply cord is connected directly to the heating element 22 inside the annular
cavity
38 after a significant bend in the power supply cord at the entry thereof to
the cavity
to begin following a circular path defined concentrically around the internal
passage
14 of the heater body by the annular cavity 37. From its connection to the
power
supply cable 24, the heating element 22 coils downward around the internal
passage
of the heater body within the annular cavity 37, preferably making at least
the two
complete loops around the internal passage shown in the illustrated
embodiment.
As shown in Figures 3 and 4, the portions of the heater body 12 from the ridge
28
upward to the top end 18 of the heater body at the flanged top ends 34b, 26e
of the
sleeves effectively defines a short of extension of the sewer vent pipe 200
when
fitted thereon. The coiling of the heating element 22 around the internal
passage 14
of the heater body 12 provides ice-preventing heating at this new effective
top end of
the vent pipe 200, but as shown, the heating element then continues downward
within the existing vent pipe itself to provide heating further down the
resulting vent
line, preferably down to levels actually within the building itself below the
roofline
(see Figure 2).
Figures 9 and 10 show the outer sleeve 26, including the ridge 28
formed integrally therewith in the illustrated embodiment, in isolation. A
trapezoidal
cut-away 42 is formed in the outer sleeve 26 at a single position about the
central
axis 16 of the heater body, recessing into the ring-surrounding portion 26c of
the
outer sleeve's inner surface 26 immediately above the ridge 28 and extending
vertically from the ridge 28 to the thin walled portion 26d of the outer
sleeve that
CA 02656973 2009-03-10
13
defines a respective half of the annular cavity 38 in the assembled heater
body 12.
The depth to which the cut-away portion 42 is recessed from the ring
surrounding
portion 26c of the outer sleeve's inner surface is equal to the depth of the
recess
defined at the thinnest portion 26d of the outer sleeve so that the cut-away
portion
42 is flush with the inner surface of the outer sleeve's thinnest portion 26d.
The
sloped sides 42a of the cut-away portion 42 converge upwardly from the ridge
28 to
the outer sleeve's thinnest portion 26d so that the trapezoidal cut-away's
base is
defined by the ledge formed by the ridge 28 at the bottom of the cut-away.
Figures 5 to 7 show the spacing ring 36 in isolation. The ring 36 also
features a trapezoidal cut-away 44 formed at the ring's outer surface 36a. A
top
portion of the ring's cut-away 44 is only recessed into the ring's outer
surface 36a so
as to not extend fully therethrough toward the ring's center in a radial
direction. A
bottom portion of the ring's cut-away 44 however does extend radially through
the
ring 36. This leaves an integral connecting portion 46 at the top end face 36b
of the
ring that completes the ring's circular enclosure around the central axis 16
of the
heater body 12 at the inside surface 36c of the ring, while the outside
surface 36a of
the ring is broken over the full height of the trapezoidal cut-away. The
ring's cut-
away 44, like the outer sleeve's cut-away 42, is trapezoidal as viewed from a
vertical
plane and features upwardly converging sides 44a. The two cut-aways share the
same height and the same width, each vertically spanning a respective one of
the
equally high spacing ring 36 and ring surrounding portion 26c of the outer
sleeve 26.
Figure 8 shows the outer sleeve 26 and spacing ring 36 assembled,
but without the inner sleeve 34, heating element 22 and power supply cable 24.
CA 02656973 2009-03-10
14
Referring additionally to Figures 3 and 4, the trapezoidal cut-aways 42, 44 of
the
outer sleeve 26 and spacing ring 36 are aligned with one another about the
central
axis 16 of the heater body with the spacing ring 36 placed atop the ridge 28.
The
two cut-sways thus communicate directly with one another to define an enclosed
pathway 48 interconnecting the annular cavity 38 with the portion of the
heater
body's internal passage 14 defined beneath the spacing ring 36. As shown in
Figures 3 and 4, this is where the heating element 22 passes from the annular
cavity
38 into the heater body's internal passage 14 so as to depend downward into
the
sewer vent pipe 200 when the heating apparatus 10 is installed. The bottom of
the
annular cavity 38 is closed around the heater body's central axis 16 and
internal
passage 14, except where the two cut-aways 42, 44 cooperate to form this
pathway
48. From where it is coiled within the annular cavity 38, the heating element
22
bends downward and passes through the communicating trapezoidal cut-aways,
downward past the connecting portion 46 of the spacing ring 36 and then inward
into
the internal passage 14, passing beneath the connecting portion 46 of the
spacing
ring 36 where the ring's cut-away 44 extends completely through the ring 36 in
a
radial direction.
As shown in Figure 4, a horizontal cross-section of the pathway formed
by the aligned cut-aways 42, 44 at the top end of the pathway is of an area
sized to
only accommodate a single pass of the heating element 22 therethrough. The
heating element sits against a respective one of the sloped sides of the
mating
trapezoidal cut-aways as it passes downward, giving it a tendency to coil
downward
along the inner periphery of the sewer vent pipe 200 around the pipe's central
CA 02656973 2009-03-10
longitudinal axis, which is coincident with the heater body's central axis 16
when the
heating apparatus 10 is installed. As shown in the figures, the slope of the
sides of
the pathway's trapezoidal vertical cross section is preferably steeper than
the angle
at which the heating element 22 is coiled around the internal passage 14
within the
5 annular cavity 38, giving the heater element 22 a more tightly packed
coiling within
the annular cavity 38 than within the sewer vent pipe 200.
The heating element 22 is preferably a length of self-regulating heat
cable, which is known to those of skill in the art and thus not described in
detail
herein. For ease of illustration, details of the heat cable's construction
have been
10 omitted in the drawings, which instead schematically show a cable of
uniform cross-
section within the cross-sectional view of the heating apparatus. As shown in
Figure
2, the power supply cable 24 may be fitted with a conventional male electrical
plug
50 at an end thereof opposite the heating element 22 outside the heater body
12 for
connection to the female socket end 52 of an extension cord 54 outside the
building.
15 Alternatively, the power supply cord 24 may plug directly into an
electrical outlet
installed outside the building or be hardwired to the building's electrical
system. The
power supply cord 24 may pass through the roof structure 202 of the building
in a
sealed weatherproof manner through the roof flashing for releasable coupling
to an
electrical outlet or hardwiring to the building's electrical system within the
building
interior, for example within the attic space of a home or dwelling.
A prototype of the present invention has been produced for use on a
sewer vent pipe of 3-inch internal diameter and 1/4-inch wall thickness. An
off the
shelf ABS pipe coupling of 3.5-inch inner diameter and 5.25-inch length and
having
CA 02656973 2009-03-10
16
already having a '/4-inch high internal stop ridge 28 integrally formed
centrally
therealong was internally lathed fully around its central axis above the stop
ridge to
define the outer sleeve 26 with the thin-walled section 26d and inwardly
flanged top
end 26e. A cut-away having a parallelogram vertical cross-section, rather than
the
trapezoidal cross-section of the illustrated embodiment, was grinded away from
the
inside surface of the coupler from the ridge 28 to the thin-walled portion 26d
and a
hole was drilled through this thin portion of the coupler's cylindrical wall
to form the
power supply cord aperture 40. The ring of the prototype was cut from an ABS
pipe
of equal inner and outer diameters to the sewer vent pipe to define a ring of
approximately 3/8-inch height, and then grinded at the outside surface to form
a cut-
away of parallelogram vertical cross-section extending part way through the
ring wall
over a top half of its height or thickness and extending fully through the
ring over the
bottom half thereof. The ring was then inserted to sit atop the ridge 28 with
the two
cut-aways aligned about the coupler's central axis to defined the single
heating
element pathway past the ring. The heating element 22 was then passed through
the aperture 40 until the power supply cord extended approximately two inches
into
the outer sleeve, whereafter the power supply cord was bent inside the upper
sleeve
at the aperture 40 to coil the heating element twice around the central axis
of the
coupler against the inside surface thereof before having its lower end being
passed
downwardly through the pathway to below the spacing ring 36. Prior to such
installation, the heating cable was coated with heat shrink tubing from its
free end to
a position along the heating cable a short distance past where the cable would
later
transition from the annular space to the interal passage of the heater body
through
CA 02656973 2009-03-10
17
the pathway defined between the ring and the outer sleeve to better protect
heat
cable.
The inner sleeve 34 was formed from a 1-1/8-inch length of pipe of the
same inner and outer diameters as the vent pipe and ring that was externally
lathed
over most of its length from its bottom end upward 7/8 of an inch, thereby
leaving a
1/4-inch high externally flanged upper end 34b having an outer diameter sized
to fit
against the inwardly directed '/4-inch high flange 26e left above the
internally lathed
portion 26d of the outer sleeve 26. This inner sleeve 34 was then inserted
through
the open top end of the outer sleeve to sit atop the ring 36 to defined the
inner wall
of the annular cavity 38 and close off the heating element 22 inside the
resulting
heater body between the inner and walls thereof defined by the inner and outer
sleeves, which where then adhered together at their flanged upper ends.
The parallel sloped sides of the parallelogram cut-aways of the
prototype were angled at forty-five degrees to vertical, but other oblique
acute
angles may be used. The illustrated embodiment uses trapezoidal cut-aways
having
sloped sides converging at opposite forty-five degree angles to vertical. This
trapezoidal shape allows either side to have the heating element placed
thereagainst
so that the coiling of the heating element around the central axis 16 can be
made the
same above and below the spacing ring 36 regardless of which direction it is
coiled
above the ring during assembly, thereby avoiding a sharp bend in the heating
cable
to change direction. The parallelogram shape of the prototype cut-aways
required
that the heating coil be coiled in the direction dictated by the slope of the
cut-away
sides above the ring in order to avoid such a direction change, but similarly
provided
CA 02656973 2009-03-10
18
the coil-encouraging slope of the heating element as it projects into the
internal
passage of the heater body above the open exhaust end of the sewer vent pipe.
Turning back now to the illustrated embodiment, the equal inner
diameters of the sewer vent pipe 200 and the inner sleeve 24 and the
projecting of
the ridge 28 inward from the cylindrical bottom portion of the outer sleeve by
a
distance less than the pipe wall thickness of the sewer vent pipe provide an
extension of the vent pipe of equal diameter and equal cross-sectional area to
the
projecting portion of the vent pipe extending upward from the roof. The
internal
passage extending through the heater body 12 can be thought of as divided into
three cylindrical sections each having a diameter, and thus cross-sectional
area
perpendicular to the shared axis of the heater body and vent pipe, that are no
less
than the inner diameter and cross-sectional area, respectively, of the vent
pipe. The
cylindrical boundary of the internal passage 14 at these three sections are
defined
by respective ones of the cylindrical bottom portion 26b of the outer sleeve
26, the
annular stop ridge 28 and the cylindrical inner surface of the sleeve assembly
34
formed by the inner sleeve 34 and spacing ring 36.
The installation of the heater body on the top exhaust end of the vent
pipe 200 is thus not only simple, requiring only sliding placement of the
heater body
over this top end of the vent pipe with the lower portion of the heating
element 22
depending down the vent pipe in a coil-like manner, but also does not restrict
the
cross-sectional area or flow at the vent pipe's upper end. The heating
apparatus
also benefits from the combination of both a wrap-around heating element
arrangement adjacent the top of the pipe-extending heater body and a direct
pipe-
CA 02656973 2009-03-10
19
interior heating arrangement depending downward inside the existing vent pipe
below the heater body to maximize prevention of freezing and clogging of the
pipe's
internal sewer gas exhaust passage. It will be appreciated that the seat-in-
place and
non-restrictive structure of a heater body having an inward projecting stop
and an
inner passage equal to or greater than the inside cross-sectional area of the
pipe
may be used with different arrangements of heating elements, and that likewise
a
combinative external wrap-around and internally-depending heating element
arrangement outside and inside the heater body's internal passage may be used
with heater bodies that do not provide direct seat-in-place installation on
the pipe
and restriction-free extension of the pipe .
The heater body is preferably formed of ABS or PVC plastic, materials
commonly used for sewer vent pipes, but may instead feature constructions
using
other materials. The stop within the internal passage through the heater body
need
not necessary be defined by an integral annular ridge. For example, with
reference
to Figure 3, without the integral ridge, the ring-defined bottom flange of the
inner
assembly 32 could instead define a non-integral ridge fixed to the outer
sleeve at its
inners surface to extend inward toward the central axis and define the stop.
In such
an embodiment, the heating element could extend radially inward through the
gap in
the ring above the bottom face thereof toward the central axis and then bend
downward past the bottom of the ring. This would avoid pinching of the heating
element 22 between the ring bottom end the vent pipe top and would allow the
same
flat seating of the housing atop the vent pipe as the illustrated embodiment.
The
downward extending pathway between the ring and outer sleeve could be replaced
CA 02656973 2009-03-10
with a horizontal hole passing through the inner sleeve 34 slightly above the
ring 36
so that the heating element instead projects into the internal passage 14
above the
bottom flange of the inner assembly and then bends downward into the vent pipe
200 below. The heating element need not necessarily depend downward in the
pipe
5 in a coiled fashion up against the pipe's inner walls surface, and may
alternatively
simply hang freely within the vent pipe (see Figure 1 where the heating
element
simply hangs downward through the open bottom of the heating apparatus).
The inner assembly need not necessarily have the two piece ring and
sleeve structure, and may be produced as a single integral part having
externally
10 flanged upper and lower ends around which the heating element can be pre-
wrapped before insertion, provided that the depth of the recess defined at the
exterior of the inner sleeve between the flanges is sufficient to receive the
heating
element wraps fully therein. With reference to Figure 3, this may involve
having the
full width of the annular cavity defined solely by this outer recess in the
inner
15 assembly, in which case no inward extending flange 26e would be included on
the
outer sleeve 26.
The illustrated embodiment provides a high level of tamper resistance
by making the annular cavity or chamber substantially fully closed and
preventing
easy withdrawal of the heating element therefrom through the generally right
angle
20 bend in the power supply cord where it enters the cavity. The sloping of
the
pathway, which may be at angles other than the forty-five degree angle of the
prototype, at a steeper angle than the coiling of the heater element within
the
annular cavity also forms a slight bend at the transition of the heating
element from
CA 02656973 2009-03-10
21
the cavity to the internal passage of the heater body that resists pulling of
the
heating element out of the cavity. However, it will be appreciated that such
relatively
full and complete enclosure of the space housing the heating element around
the
internal passage is not necessarily required. The bottom end of the housing
for
fitting over the vent pipe and the stop defined within the internal passage
need not
necessarily be a full and continuous cylinder and fully-closing ring about the
central
axis 16. The stop for example may be formed of distinct ledges or shoulders
projecting inward from the inside of the outer sleeve at spaced positions
about the
axis 16, just as the bottom of the housing could be distinct flaps or sections
projecting downward below the stop fit snugly against the vent pipe outer
periphery
at spaced locations thereabout, preferably still presenting concave inner
surfaces
with curved dimensions suitable for flush engagement to the pipe's outer
periphery.
As a result, the internal passage need not necessarily be fully surrounded
around
the central axis at each location along the passage, and so the cross-
sectional area
or diameter of the internal passage at any point therealong may instead be
thought
of in terms of a circular cross section normal to the central axis with a
circumference
determined by elements of the housing that are each radially equidistant to
the
central axis, whether integral with or separate from one another at this
location along
the passage.
In the illustrated embodiment, the diameter and cross-sectional area of
the internal passage at the ridge 28 are slightly greater than above the ridge
because the projecting length of the ridge 28 inward toward the central axis
16 is
less than the wall thickness of the pipe 200. It will be appreciated that that
diameter
CA 02656973 2009-03-10
22
and cross-sectional of internal passage of the heater body instead may be
uniform
from the bottom of the stop to the open top end of the passage. Also, the
diameter
and cross-section of the internal passage 14 may be larger than those of the
vent
pipe's interior above the pipe's open top end, so long as the inner diameter
of the
stop ridge is small enough to project the ridge over the vent pipe wall at the
open top
thereof to firmly seat the heater body atop the pipe.
Since various modifications can be made in my invention as herein
above described, and many apparently widely different embodiments of same made
within the spirit and scope of the claims without department from such spirit
and
scope, it is intended that all matter contained in the accompanying
specification shall
be interpreted as illustrative only and not in a limiting sense.
