Note: Descriptions are shown in the official language in which they were submitted.
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BALANCED FLUE SEALED VENT TERMINAL ASSEMBLY
The present invention is directed to a balanced flue
sealed vent terminal assembly and system for use with fuel
fired combustion furnaces and heating appliances.
The venting assembly and system of the present invention
is intended for use in association with a high-efficiency oil
fired furnace or boiler. Such furnaces are now designed for
installation and use without a chimney and to vent directly to
the exterior of a building in which the furnace or boiler is
installed.
BACKGROUND OF THE INVENTION
United States Patent No. 5,282,456 (equivalent to
Canadian Patent No. 2,077,126) describes a high efficiency
induced draft condensing furnace with a horizontal plastic
vent termination assembly. The termination vent assembly
comprises a coaxial arrangement of a combustion gas vent pipe
means for ejecting combustion gas discharged from the furnace
and a combustion air inlet pipe means for drawing air in to
assist with combustion. The combustion air inlet pipe means
is concentrically disposed outwardly around the combustion gas
vent pipe means. The discharge end of the combustion gas vent
pipe means extends beyond the end of the combustion air inlet
pipe means. It provides no means for baffling combustion gas
or inlet air and does not take into account the effects of
wind on the termination assembly.
Such coaxial arrangements of vent pipes and air inlet
pipes are well-known in the trade.
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SUMMARY OF THE INVENTION
The balanced flue sealed venting system of the present
invention is a zero clearance, one piece terminal which mounts
through an exterior wall. It is designed to exhaust flue
gases away from the exterior wall and will also provide pre-
heated combustion air for the operation of the furnace burner.
The terminal is designed to operate in a balanced flue
mode which substantially maintains the pressure difference
between combustion gases and combustion air thus allowing
stable operation of the furnace even in extreme wind
conditions.
The system is independent of the building air and
isolates the heating system from the other building mechanical
systems.
The present invention is directed to a horizontal vent
terminal assembly for simultaneously flowing outside
combustion air to a combustion device located within a
dwelling having an exterior wall and ejecting combustion gases
discharged from the combustion device to the outside of the
dwelling, said horizontal vent termination assembly
comprising:
(a) a combustion gas vent pipe for receiving and axially
ejecting the combustion gases discharged from the
combustion device, said combustion gas vent pipe having
an open discharge end extending horizontally outwardly
beyond an outside surface of the exterior wall;
(b) a head chamber positioned over the open discharge end
of the combustion gas vent pipe, said head chamber
including a plurality of outlet ports and means for
splitting and deflecting the combustion gas travelling
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axially along the combustion gas vent pipe to the
plurality of outlet ports;
(c) a combustion air inlet pipe colinearly disposed
outwardly around the combustion gas vent pipe and
defining therewith an annular flow space operative to
receive a flow of the combustion air; and
(d) a baffle disposed between the outlet ports of the
head chamber and annular flow space of the combustion air
inlet pipe to inhibit the combustion gas from being mixed
with the flow of the combustion air.
The terminal assembly of the present invention will now
be described in detail with reference to the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a perspective view of the terminal assembly;
Figure 2 is a top view of the terminal assembly and also
shows the connection of the terminal assembly as it connects
to the combustion gas vent connector pipe and the combustion
air duct work of the furnace;
Figure 3 is a top view showing the baffles, etc.;
Figure 4 is a side outline view showing the baffles,
etc.;
Figure 5 is a side view of the terminal assembly;
Figure 6a is a top view outline diagram showing the
effects of no wind on the terminal assembly of the present
invention;
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Figure 6b is a side view outline diagram showing the
effects of no wind on the terminal assembly of the present
invention;
Figure 7a is a top view outline diagram showing the
effects of a strong wind normal to the wall;
Figure 7b is a side view outline diagram showing the
effects of a strong wind normal to the wall;
Figure 8a is a top view outline diagram showing the
effects of a strong wind at an angle of about 45° to the
terminal assembly;
Figure 8b is a side view outline diagram showing the
effects of a strong wind at an angle of about 45° to the
terminal assembly;
Figure 9a is a top view outline diagram showing the
effects of a strong wind along the wall;
Figure 9b is a side view outline diagram showing the
effects of a strong wind
along the wall;
Figure 10 shows a typical installation of the sealed vent
terminal assembly of the present invention with a combustion
furnace;
Figure lla shows a mechanical seal clamp;
Figure llb shows a ring seal or 0-ring suitable for use
with the mechanical seal clamp;
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Figure llc shows the manner in which the mechanical seal
and ring seal or 0-ring are used to connect two pipes;
Figure 11d shows the fully assembled unit; and
Figure lle shows a close-up enlarged view of the fully
5 assembled unit.
Whenever possible like numerals have been used to
designate like parts throughout the drawings.
DETAILED DESCRIPTION OF THE INVENTION
As shown in Figures 1 and 2 the present invention
provides a balanced flue sealed vent terminal assembly AA for
use with a heating appliance, for example, an oil fired
combustion furnace, boiler, water heater or similar appliance
(not shown). The heating appliance is located in a building
area near to an outside wall 14.
The terminal assembly AA comprises a terminal assembly
outer head chamber CC that is located on the outside of wall
14 and an inner duct portion DD located through a hole 11 in
the wall 14 and inside the building. The terminal assembly
outer head chamber CC can be considered to comprise two
sections. An outer combustion gas section EE located towards
the front of the outer head chamber CC and an inner air inlet
section FF located towards the rear of the outer head chamber
CC. The inner section FF is located closest to the wall 14.
The outer section EE and the inner section FF are separated
from each other by a divider
plate 5.
The inner duct portion DD comprises a vent pipe 1, a heat
shield and pre-heat pipe 2 and an outer duct 3. The vent pipe
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1 extends through the wall 14 to deliver combustion products
from the furnace along an enclosed passage K to a point beyond
air intake openings D (air inlet). The vent pipe 1 extends
just beyond divider plate 5.
The vent pipe 1 is preferably round in cross section for
uniform flow of the combustion gases and uniform heat loss
characteristics. When the vent pipe 1 is round it easily fits
and connects with the usually round flexible duct conveying
the combustion gases from the furnace or other heating
appliance. The vent pipe 1 is preferably constructed of
stainless steel of low emissivity for corrosion resistance,
for minimizing deposits and for reducing radiant heat transfer
to the wall 14.
The heat shield and pre-heat pipe 2 surrounds the vent
pipe 1 but does not extend beyond the end of vent pipe 1. The
heat shield and pre-heat pipe 2 ends at divider plate 5 and
sits flush against divider plate 5 such that the divider plate
5 closes the end of heat shield and pre-heat pipe 2 and
separates the outer section EE from the inner section FF of
the terminal assembly AA. Divider plate 5 further serves to
separate the outer head chamber CC from the inner duct portion
DD.
The heat shield and pre-heat pipe 2 prevents the heat
from the vent pipe 1 from radiating to its surroundings. It
does this by creating a cavity B around the vent pipe 1. The
primary purpose of this heat shield and pre-heat pipe 2 is to
shield the outer duct 3 from the radiant heat from the vent
pipe 1 thus allowing the terminal assembly AA to be placed in
direct contact with the combustible materials of the wall 14.
The heat shield and pre-heat pipe 2 is provided with air
openings J and a partial baffle 10 positioned so that a
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proportion of the combustion air being drawn in along outer
duct 3 through openings D, passes through cavity B and is
diverted past the surface of vent pipe 1. The incoming
combustion air is warmed as the vent pipe 1 is cooled by a
connective heat transfer process. This raises the temperature
of the combustion air in the outer duct 3.
The heat shield and pre-heat pipe 2 is generally round in
cross section so as to provide uniform shielding and
conveyance of the air inside it. The end of the heat shield
and pre-heat pipe 2 is visible through the air inlet openings
D where it meets divider plate 5. This allows the heat shield
and pre-heat pipe 2 to act as an air inlet baffle when the
wind is travelling along the plane of the wall 14. This will
be described in more detail below. The diameter of the heat
shield and pre-heat pipe 2 is such that under wind conditions
it will provide a baffling effect to produce pressure
variations at the entry to outer duct 3 to counter balance the
pressure effects induced in the combustion gas flow by the
combustion gas heat shields 6, 7, 8, 9 and 13.
The heat shield and pre-heat pipe 2 is also preferably
made of stainless steel of low emissivity for corrosion
resistance and radiant heat transfer reduction.
The outer duct 3 surrounds both the vent pipe 1 and the
heat shield and pre-heat pipe 2 and extends through the wall
14. It is shaped and bent to fit through the hole 11 in the
wall 14 and extends around the hole 11 in all directions. The
outer duct 3 is generally square in cross section and fits
inside the square hole 11 through the wall 14. The outer duct
3 is made square to ensure that the terminal assembly AA is
installed in and is maintained in its upright position. The
outer duct 3 extends through and is attached to terminal head
casing 4 at a slight angle to the exterior of the building so
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that any rainwater or melted snow accumulating in the outer
head chamber CC will drain outwards.
The terminal assembly outer head chamber CC comprises a
terminal head casing 4, a casing face 8, top and bottom covers
13, a plurality of heat shields 6 and 7, a splitter 9, and a
wire screen mesh covering 12. Stainless steel L-shaped
supports (not shown) extend from the terminal head casing 4 to
the casing face 8 to provide the terminal assembly outer head
chamber CC with stability. The wire screen mesh covering 12
surrounds the top, bottom and sides of the head chamber CC and
is secured to the terminal head casing 4 and the casing face 8
with screws or other suitable fastening means.
The terminal head casing 4 is square and has a centrally
located square hole to match with the hole 11 cut into the
wall 14 and also to fit with the square outer duct 3. The
terminal head casing 4 can be recessed up to 1 inch into any
wall covering without blocking the air inlet openings D. The
air inlet openings D are formed between the terminal head
casing 4 and the divider plate 5.
The terminal head casing 4 is easily secured to the wall
14 with screws or other suitable fasteners. The terminal head
casing 4 also serves to support the stainless steel wire mesh
screen 12.
A divider plate 5 serves to divide the combustion gas
section EE of the terminal head CC from the air inlet section
FF. The divider plate 5 is generally square so as to match
with the terminal head chamber CC. The divider plate 5 covers
the end of heat shield and pre-heat pipe 2 to prevent the
combustion gases from being drawn into the outer duct 3 and
defines air inlet openings D on both sides, top and bottom of
the terminal assembly outer head chamber CC.
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Attached to divider plate 5 and located within the outer
section EE of the terminal assembly outer head chamber CC are
side shields 6 angled and positioned so that they shield the
combustion gas outlet opening K' from the wind. The side
shields 6 are angled away from the end of vent pipe 1 so that
they do not constrict the flow of combustion gases as the
gases spread over flow splitter 9. The side shields 6 extend
vertically from the top cover 13 to the bottom cover 13 and
are fixed to the covers 13. The splitter 9 extends to the
same height as the side shields 6.
The side shields 7 serve a similar function as the side
shields 6 but are offset at a slight angle from side shields 6
to form gap E. Under wind conditions gap E acts as a pressure
release slot. If gap E is too small there is insufficient
pressure relief. If gap E is too large there is too much
pressure relief. The ends of side shields 6 and the ends of
side shields 7 overlap slightly at gap E. The amount of
overlap is not particularly important. Side shields 7 are
secured to the top cover 13 and the bottom cover 13 and are
positioned to provide back pressure relief through gap E from
wind blowing normal to the terminal front casing face 8 and
being forced through slot A. The side shields 7 are the same
height as side shields 6 and splitter 9.
The passage between K' and slot A is partially covered
over the top and bottom of splitter 9 by covers 13 to guide
the combustion gases towards the slot A, leaving openings F
and G to provide fresh air entrainment or pressure relief from
the wind, depending on the wind conditions.
The terminal front casing face 8 is also square and
provides two slots A. The terminal front casing 8 protects
the inner head assembly from wind blowing directly at the wall
14. It deflects the wind and combustion gases flowing from
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slots A parallel to the wall 14 so that the combustion gases
stay away from the air inlet openings D at the wall end of the
terminal assembly AA. Terminal front casing face 8 also
covers and prevents access to side shields 7 and the splitter
5 9 which are hot to the touch. The terminal front casing face
8 stays cool to the touch.
The combustion gas splitter 9 is V-shaped and has two
inclined faces that split and spread the combustion gases
expelled from opening K' of the vent pipe 1. The gases are
10 spread both horizontally apart and vertically along the
inclined faces of the splitter 9. They are baffled by the
combined effect of the splitter 9, top and bottom covers 13
and shields 6 and 7 so that they usually flow through slots A.
Some outside air is entrained through openings F and G to cool
the effluent combustion gases. Splitter 9 is cooled by air
which is free to flow through the triangular openings 15
located in top cover 13 and bottom cover 13. The splitter 9
is fixed to the top cover 13 and the bottom cover 13 and is of
about the same size and shape as the triangular openings 15 in
the top cover 13 and the bottom cover 13. Terminal front
casing face 8 is set forward of the sputter 9 to prevent
external contact with splitter 9.
A ring shaped partial baffle 10 surrounds the heat shield
and pre-heat pipe 2 part way along its length. It is
considered a partial baffle because it is round but is located
inside the square outer duct 3. The corner space between the
baffle 10 and the outer duct 3 allows some combustion air to
be drawn in towards the burner. The presence of the baffle 10
encourages some air to travel inside the heat shield and pre-
heat pipe 2 through the openings J at either end of it.
The sides, top and bottom of the terminal assembly head
are covered with a stainless steel wire mesh screen 12. It
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does not cover the front of the casing or the two slots A.
The front of the terminal assembly head is covered with front
casing face 8. The screen prevents insects and other animals
or birds from entering the combustion air inlet openings D and
also prevents contact with the hot parts of the shields 6 and
7 and the splitter 9.
The top and bottom of the shields 6 and 7 and the
splitter 9 are covered by top and bottom covers 13 to direct
the combustion gases towards the slots A. The covers 13 have
triangular openings 15 cut in the top and the bottom through
which heat from the inside of the combustion gas splitter 9
can disperse.
The arrangement of the heat shields 6 and 7 and the
splitter 9 is designed to minimize pressure variations on
combustion gas outlet K' associated with wind and wind
direction. The wall 14 will redirect wind along its face.
The wind flow that is parallel to the face of the wall 14
strikes the heat shields 6 and 7 and the covers 13 in such a
manner that the pressure variations due to the wind on the
combustion gas flow and the pressure variations due to the
wind on the combustion air inlet flow are substantially
balanced against each other. The component of wind flow that
is normal to the wall 14 is turned to flow parallel to the
wall 14. The consequent increase in static pressure
experienced by the combustion air inlet openings D at the wall
counterbalances the velocity pressure experienced through the
slots A by the combustion gas outlet K'. The pressure effect
of the component of the wind flow through slots A which is
normal to the casing face 8 is relieved by top and bottom
slots F and G in cover 13 and gaps E between side shields 6
and 7.
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In a low wind or no wind situation the combustion gases
leave the terminal through slots A. If the component of the
wind velocity normal to the casing face 8 increases, the flow
through these slots reverses, the combustion gases disperse
through the steel mesh screen 12, and the slots A relieve the
pressure due to head-on wind.
The gap M is a conduction break that prevents the heat
from the shield assembly 7, 9 and 13 from being conducted to
the face of casing 8.
The vertical side slot or gap E situated between side
shields 6 and 7 is positioned to relieve pressure from wind
normal to the terminal casing face 8 on the exit point K' of
the vent pipe 1.
The combustion air inlet openings D are present on the
top, bottom and sides near to the rear part DD of the terminal
assembly AA. They permit combustion air to be drawn into the
terminal assembly AA prior to its travelling through the wall
14 and along the outer duct 3 to the furnace burner (not
shown). The air inlet openings D are covered by the wire mesh
screen 12 to prevent insects and other animals or birds from
entering.
For calm wind conditions a passage F is located at the
top of the terminal assembly AA to entrain air for the
combustion gases leaving the vent pipe 1 at exit K'. Under
head-on wind conditions it acts as a pressure relief for the
shield assembly preventing the build up of static pressure at
K' .
A shield assembly bottom opening G similar to F is
provided but entrains more outside air than F because the hot
combustion gases tend to rise away from it due to buoyancy.
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The openings J provide entry for some combustion air to
travel through heat shield and pre-heat pipe 2 to reduce the
temperature of the passage between vent pipe 1 and heat shield
and pre-heat pipe 2.
Referring to Figures 7a, 7b, 8a, 8b, 9a, 9b, l0a and lOb
we will now describe the effect of wind on the terminal
assembly of the present invention.
In a no wind situation the flow of combustion gases
leaves the vent pipe 1 at K' and is split by the splitter 9.
Cool outside dilution air which reduces the combustion gas
temperature is entrained through openings E, F and G and the
air/gas mixture is guided by shields 6 and 7 out through slots
A. The combustion air is drawn in through all four of
openings D, that is, from the top, the bottom and the sides of
section FF of the terminal assembly AA. Some of this air
travels into the space between the vent pipe 1 and the heat
shield and pre-heat pipe 2. The pressure difference between D
and K is maintained at a substantially constant balance.
In a situation where a strong wind blows horizontally or
normal to the wall, i.e. head-on to the wall, wind will blow
through front slots A and will force the combustion gas being
blown out of K' back through slots M, E, F and G. The back
pressure on K' is increased. The wind strikes the wall 14 and
pressurizes the combustion air inlet openings D. The pressure
difference is maintained substantially in balance by the
pressure at D from the stalled wind and the pressure at K',
which is relieved by the slots M, E, F and G.
The horizontal component of a strong wind blowing
parallel to the wall strikes shields 6 and 7 creating a slight
vacuum behind them. Some combustion gas leaves at slots A and
some gas is drawn away by the presence of shields 6 and 7 out
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of slots M and E and the top and bottom openings F and G.
Wind enters through the windward air inlet opening D and
leaves through the leeward air inlet opening D. It strikes
the outer surface of heat shield and pre-heat pipe 2 and some
combustion air is diverted into the passages between pipes 1
and 2 and between pipe 2 and duct 3. The pressure difference
is maintained substantially in balance because the change in
pressure due to the flow around the shields 6 and 7 is
substantially matched by the change in pressure due to the air
flow due to the wind through the side air inlet openings D.
The latter pressure is modified by the baffling effect of the
heat shield and pre-heat pipe 2. Thus the pressure difference
is substantially balanced.
Installation of the balanced flue sealed vent terminal
assembly will now be described briefly. The sealed vent
terminal assembly of the present invention has been designed
specifically for, but not restricted to, use in association
with oil fired warm air furnaces and in association with oil
fired hot water boiler appliances.
Combustion air is drawn through air intake openings D
along cavity B into air take-off box 16 of Figure 2 along duct
AB of Figure 10 into the burner 17. The air take-off box 16
can be installed on either side of the terminal assembly AA or
on the bottom. This allows the installer to match the
installation to the conditions encountered at the installation
site. The burner 17 consists of an electrically powered
combustion air blower which draws the combustion air through
the terminal assembly AA as described above and mixes it with
an oil spray inside the combustion chamber of the furnace GG,
produced by an electrically powered oil pump which pumps oil
into the combustion chamber through a spray nozzle. The spray
nozzle changes the oil into a fine particulate spray. An
electric igniter starts the fire. The burner also includes an
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integral internal electronic safety control that stops the
burner if there is no fire in the combustion chamber 18. The
oil spray burns inside the combustion chamber 18 and the hot
gaseous combustion products move through the heat exchanger 19
5 to breech 20.
A blockage sensor 22 shuts off the burner if the air
inlet or the combustion gas outlet duct is partially or
totally blocked. The blockage sensor 22 senses the difference
in pressure between the combustion air being drawn through the
10 air duct AB into the burner at 17 and the combustion gas in
the vent pipe 21 at the breech 20. Much testing has been
conducted to establish an average maximum differential
pressure at which satisfactory operation of the burner ceases.
A single differential pressure setting has been established
15 which works for vent and air duct lengths up to 7.5 metres (25
feet) and for the specified vent pipe diameters of 4, 5 and 6
inch used for burner oil input rates from 1.9 to 5.7
litres/hour (0.5 to 1.5 USGPH (United States gallons per
hour)). When the differential pressure rises above a
predetermined value the blockage sensor 22 will stop the
burner. The burner will not restart until the blockage is
cleared.
The hot combustion gases pass through the heat exchanger
19 on their way from the combustion chamber 18 to breech 20.
The heat exchanger 19 transfers the heat to a distribution
medium, commonly air in the case of a furnace, or water in the
case of a boiler or water heater.
The furnace includes a circulating blower assembly and
functions in the same manner as any forced warm air heating
furnace drawing cold air from living areas and distributing it
warmed throughout the distribution duct work. Similarly, the
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boiler includes a circulatory system which functions to
distribute the heated water to a heat distribution system.
The terminal assembly AA can also be used with a
conventional hot water boiler appliance and installation is
similar to that described with respect to the furnace.
The vent pipe 21 as seen in Figure 10 is a double walled
insulated flexible vent pipe that runs from the breech 20 to
the terminal adaptor 23. The vent pipe 21 conveys the cooled
combustion gases from the appliance breech 20 to the sealed
vent terminal assembly AA and is attached to the appliance
breech 20 by an improved clamping system comprising a
mechanical screw clamp 24 with a re-usable ring seal or O-ring
25. A similar smaller seal clamp and ring seal are used to
secure the terminal adaptor 23 to the terminal vent pipe 1.
This requires that the pipe coming from the breech and the
vent pipe be fashioned in such a manner to accept the clamp
and the seal. The combined mechanical screw clamp and re-
usable seal allow easy and quick access to the vent system for
cleaning and inspection thus avoiding the use of caulking or
sealant.
When a furnace or hot water boiler is vented through a
conventional chimney the connection between the breech and the
chimney is typically made by means of an unsealed slip-on pipe
that is secured with a single screw or multiple screws through
both the breech and the vent or chimney pipe. Other direct
vent systems which are pressurized have a similar joint which
is caulked by the installer with a high temperature sealant.
When the vent pipe joint must be opened for cleaning and
inspection the seal must be broken, cleaned off and then re-
caulked to restore it to its original condition.
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As mentioned above, the clamping system of the present
invention is an improvement over that known in the art. It
will now be described in more detail with reference to Figures
lla, llb, llc, 11d and lle.
The clamping system of the present invention comprises a
mechanical seal clamp 24, an inner rolled channel 31 and a
ring seal or 0-ring 25. The mechanical seal clamp 24 is a
flat, flexible strap that wraps around the outside of the
pipes to be held together. A separate inner rolled channel 31
fits between the pipe and the mechanical seal clamp 24. The
mechanical seal clamp 24 and inner rolled channel 31 are sized
to fit pipes of various diameters. The mechanical seal clamp
24 is secured and tightened by a standard worm screw 26.
The pipes to be held together, for example, vent pipe 21
to breech 20 or vent pipe 1 to terminal adaptor 23, are
generally of seamless construction. One must be slightly
smaller in diameter than the other so that one will slide
inside the other. Rolled beads 27 and 28 are formed in the
pipes. The rolled bead on one is formed as close to the end
of the pipe as possible while the other is formed at a
specified distance from the end of the pipe. This distance is
determined such that sufficient length of one pipe slides
beyond the bead of the other. As shown in Figure llc, pipe 29
has the bead formed near to the end of the pipe while pipe 30
has the bead formed a predetermined distance in from the end
of the pipe. The pipe 30 with the bead spaced beyond the end
of the pipe slides into the pipe 29 with the bead near the end
of the pipe. The ring seal or 0-ring 25 is placed on the end
of pipe 30, close to the rolled beads.
The mechanical seal clamp 24 is tightened by tightening
worm screw 26 so that the inner rolled channel 31 is forced
into contact with the sloping surfaces of beads 27 and 28 on
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the two mated pipes 29 and 30. The gripping action of the
inner rolled channel 31 slides the mated pipes towards one
another along the same axis and brings the beads 27 and 28
axially closer together. At this same time the inner surface
of the inner rolled channel 31 moves in a radial direction
closer to the axis of the pipes. The ring seal or O-ring 25
is compressed in the space between the two beads 27 and 28 and
the inner rolled channel 31. When all the parts are
appropriately dimensioned the ring seal or 0-ring 25 is wedged
between the three surfaces around the entirety of the mated
pipes and seals the rolled beads 27 and 28 against the escape
of gas. The pipe joint is simultaneously sealed and clamped.
As described above the joint can be easily taken apart
for inspection and cleaning. No sealing or caulking compounds
are needed and the clamping system including the ring seal or
O-ring is re-usable.
The sealed vent terminal assembly of the present
invention operates efficiently and without problems in all
wind conditions. It is designed to overcome the problems
associated with known coaxial sealed vent systems.
The clamping system of the present invention provides
operable joints for easy access to the vent pipes and duct
work of the sealed vent system. It is re-usable and cost
effective.
