Note: Descriptions are shown in the official language in which they were submitted.
~(~47~25
Tllis irlvention relates to an apparatus for limiting
the outgoing air flow in natural ventila-tion systems of
buildings.
In dwellinys and other premises a not insignificant
natural ventilation occurs by the pene~ ation of ou-tdoor air
through cracks especially around windows and doors an~ by the
exhaust of this air as draught -through outgoing air ducts,
usually from kitchens, water-closets and bathrooms. ~ very great
percentage of the e~tant housing, int. al. practically all
1~ detached houses, have natural ventilation systems of this
type.
When the outdoor temperature is low and in particular
if a wind is blowing at the same time, natural ventilation
will be strong and result in grea' heat losses, unless the
outgoing air ducts have draught limiting devices for counter-
acting this increase in natural ventilation, which is unnecessary
and uneconomical from the point of view of ventilation. It is
certainly true that natural ventilation can be limited in win-
ter by manual stepwise or complete shutting of the dampers, if
any, in the individual rooms of the dwellings, but this method
is impractical and too coarse. It results in either too ample
or too meagre a ventilation. The regulation of the dampers can
not become economically efficient unless it is continuously
adapted int. al. to weather variations that may occur in the
course of the day.
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It is ~rue that it has already been suggested to place
in an outgoing air duct a temperature sensing means having a
sensitive element whlch by changing ils dimension or configu-
ration at temperature variations in the ambient air gradually
closes or opens a damper so that the amount of outgoing air
can be controlled to some eY~tent. It has also been suggested
to place the temperature sensing means at the outlet of the
outgoing air duct so that the temperature of the outdoor air
will become a factor which may affect the dimensional or con-
figurational conditions of the sensitive element and its abi]i-
ty to close and open a damper in the outlet.
It has proved, however, that these apparatuses for limiting
the amount of outgoing air do not provide any actually energy-
saving draught in the natural ventilation system. When the out-
door temperature is low and a wind is blowing much more air
will be exchanged than at the same low temperature and in calm
weather. In dwellings ventilated by natural draught the ventila-
tion losses during the cold ~ime of the year are approximately
one third of the total heat losses. It is therefore highly de-
sirable to be able to limit the amount of outgoing air to the
same extent as the wind increases. The prior art temperature
sensing means in ventilation systems are temperature sensitive
but do not simultaneously record outdoor air velocity changes.
In a cold day with a strong wind blowing the ventilation
losses will therefore be unreasonably great in a conventional
natural ventilation system even if some of the prior art tem-
perature sensing and damper closing apparatuses are utilized
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in the outlet of the outgoing air duct.
It is highly desirable to be able to limit the ventilation
in cold weather also for the reason that indoor air humidity
would other,lise fall to unsanitarily low values. Present-day
low air humidity in dwellings during the heating season is
experienced by many people as inconvenient. The unusually
great exchange of warm air by cold air highly contributes
thereto. After being heated to room temperature the originally
cold air will have an uncomfortably low relative humidity. The
IG greater the change of air allowed in cold weather the drier
the air in the house.
A third weather factor of importance apart from outdoor
temperature and wind force, is the intensity of radiation. For
instance at heavy solar radiation the indoor temperature will
increase in spite of the cold outdoor temperature. It would
then be suitable to increase the amount of outgoing air per
unit of time. ~Iowever, a prior art type of sensitive element
in the outlet of the outgoing air duct, which mainly senses
only the cold outdoor air, will not diminish natural draught
limitation in the requisite degree, from which follows an un-
comfortably high indoor temperature and poor ventilation.
At heavy thermal radiation, "cold radiation", for instance
during a cold winter night, increased throttling and reduced
ventilation are desirable.
~ pparatuses capable of maintaining, automatically and by
volume, the amowlts of incoming air and outgoing air constant
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per uni~ of time, are of course conceivable. However, no appa-
ratus of simple design and satisfac-tory function has hitherto
been developed and proved specifically suited for the large
number of ex~ant houses with natural ventilation. The introduc-
tion of, for instance, considerably more expensive mechanical
ventilation systems, possibly combined with heat recovery units,
require much space and the houses into which such systems are
installed, must be extremely well-insulated. The air movements
necessarily produced by the mechanical ventilation imply highly
IG increased risks for heavy leakage and great heat losses.
If the ventilation losses could be better restricted,
particularly in very cold weather, it would be possible to make
considerable gains in installation and energy production costs.
It is a well-known fact that the installation and energy pro-
duction units of a house must be dimensioned for but a few days
per year that require specially great heat quantities. By
restricting the very high ventilation losses during these days
radically the installation and energy production units could be
given small dimensions. This would imply lower installation costs
for both individuals and society.
A general object of the present invention is to provide a
simple mechanical apparatus which senses the temperature, wind
force and possibly thermal radiation, "cold radiation", of out-
door air and which automatically limits the change of air in a
house having natural ventilation to an economically and physio-
logically reasonable level irrespective of variations in these
parameters.
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A special object of the invention is, particularly during
the cold time of the year, to keep the change of air in natural
ventilation at an acceptable level w:Lth regard to both the
temperature variations of the outdoor air and the prevailing
wind conditions, and also at an acceptable level when solar
radiation is intense and the indoor temperature rises, which is
a particularly difficult problem in otherwise cold weather.
More precisely, the object of the invention is automatically
to control the amounts of outgoing air according to both in-
significant and heavy variations of the outdoor climate, whichmeans both outdoor temperature and wind force but also heat and
cold radiation intensity so that a satisfactory as well as
an economical ventilation can automatically be maintained also
under highly varying circumstances.
It has now surprisingly been found that the object of the
invention can be attained with the aid of a simple apparatus in
- the outlet duct of a natural ventilation system. The apparatus
according to the invention controls, as do prior art temperature
- sensitive air flow controlling devices to some extent, the flow
of outgoing air in the outlet duct of the system. The appa-
ratus according to the invention comprises a damper in the
outlet duct, an operating means which is connected to the damper
and can be for instance rotary or displaceable and in the
form of a shaft, by means of which the damper can be gradually
opened and closed, and a temperature sensitive element which is
adapted heavily to expand or contract at small temperature
changes and is stationarily arranged on the operating means of
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the dam~er i.n order by the action of said operating means to
real.ize gradua] closing or opening of the damper by dirnensional
or configurational changes of the sensiti~e element at temperature
variations.
Particularly characteristic of the apparatus according to
the invention is that 1) the sensitive element is located out-
side the outlet duct and exposed to the prevailing ou'cdoor
. temperature and wind conditions, and 2) the outlet duct has
openings which deflect part of the warm outgoing alr towards
1~ the sensitive element. Said part of the warm outgoing air and
the prevailing cold wind thus simultaneously influence the
sensitive element but to a varying extent owing to the wind
force and the temperature and velocity of the outgoing air.
When a strong wind is blowing the temperature effect the wind
exerts on the sensitive element will predominate, and when a
weak wind is hlowing the effect of the warm outgoing air. With
strong, cold winds the damper is closed more than with weak
winds of the same temperature since in the first case the part
flow of warm outgoing air is not given the opportunity of heat-
ing the sensitive element so much as it is capable of doing in
the second case. The result will thus be that the heat effect
exerted by the warm outgoing air on the sensitive element de-
creases at increasing wind force and increases at decreasing
wind force, and that the damper is gradually closed at increas-
ing wind force and gradually opened at decreasing wind force,
or gradually closed at decreasing outgoing air temperature and/or
outdoor temperature and gradually opened at increasing outgo~ng
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air temperatuxe and/or outdoor temperature.
In a pr~ferred cmbodiment of the apparatus accordiny to
the invention the sensitive element is a temperature sensitive
bimetal strip in the shape of a sinyl~ helix. The helix is
arranged at the outer wall of the out1et duct and exposed to
wind and weather. Its one end is fixedly anchored to the wall
of the duct and the other end to a shaft which turns a damper
disposed in the in~erior of the duct for limiting the outgoing
air when the helix is turned by the action of outdoor air and
the part flow of outgoing air exiting from holes in the duct
in the vicinity of the helix.
In another preferred embodiment of the apparatus accord-
ing to the invention the sensitive element is a temperature sen-
sitive bimetal strip in the form of a single helix of small
diameter, which in turn is shaped into a coil of large diameter
so that a double helix sensitive element is obtained. This
bimetal construction is of heavily varying dimensions in the
axial sense. This feature is exploited in this second preferred
embodiment in order, at falling temperature, to displace a shaft
with a damper disposed thereon so that the damper is gradually
closed. The double helix itself can also function as a shaft,
which gives a very simple construction. In that case the sensi-
tive element and the control means are united in one and the
same movable detail. The double helix shoula suitably be placed
in upright position in a housing which is formed with wind
openings and in which the double helix can slide vertically as
its diameter varies while the housing should be placed coaxially
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lV4~825
on the ve~rticall~ directed outlet of the outgoing air duct so
that the double helix can open and close a damper connected
therewith and coaxially arranged in the duct. A part flow of
the warm out~oing air is conducted through the housing of the
bimetal element while the rest of the outyoin~ air flows away
around the housing. At increasing wind force -the part flow of
warm outgoing air will have the opportunity to a diminishing
extent of keeping the double helix at a temperature deviating
from that of the outdoor air, which results in that the double
helix gradually expands or contracts depending upon how the he-
lical shape of the bimetal strip has been realized, and in that
the damper is gradually closed if the outdoor air is cold.
In a further emhodiment of the apparatus according to the
invention the sensitive element comprises a stack of washer-
shaped bimetal elements. At rather insignificant variations of
temperature the stack of bimetal elements will experience heavy
length variations in axial direction and pulls or pushes its
coaxial axis so that a damper fixedly connected thereto in the
outlet duct is gradually closed when the wind increases and/or
the temperature of the outdoor air falls.
- In a specifically preferred embodiment of the invention
the housing of the bimetal element may be combined with a top
wall member for the vertical outlet duct. Said top wall member
covers the outlet of the entire outgoing air duct, is preferably
slightly sloping and protrudes over the edges of the duct out-
let so that the outgoing air will be caused to flow substantially
horizontally out of the outlet duct. Such a further improvement
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of the apparatus according to the inv~ntion results in an i,n-
creased capability of the apparatus to control the amount of
outgoing air. With the aid of the sloping top wall member a
correction can he made for the heat radiation and "cold radiation",
respectively. If the sloping top wal] member moreover is made
from a heavily radiation absorbiny/emitting sheet material or
provided with a surface coat of this type, said capability is
further increased. The pa-^~, of the wind that possibly penetrates
beneath the top wall member and flows together with the part
1~ flows of outgoing air upwardly in the housing, is heated and
therefore does not cool the l~imetal element to the same extent
as ~oes a non-heated air ~luantity, or is coolcd and therefore
cools the bimetal element in a greater degree than wind that
has not been cooled. An improved effect is thus obtained in
cold windy and overcast weather as well as in warm sunny and
windy weather. The "cold radiation" towards the sloping sheet
metal top wall member cools the warm outgoing air flow and
said flow will have a higher temperature effect on the bimetal
element than an outgoing air controlling apparatus without such
a top wall member. The colder the weather, the greater the inten-
sified effect resulting from the reverse radiation ("cold radia-
tion"2 which is obtained by the described top wall member since
natural ventilation has a tendency of growing exponentially as
the outdoor temperature falls and since the combined effect of
outgoing air and incoming air on the bimetal element is advan-
tageous for draught control.
1~47B~5
~ mbodiments of the inven-t:loll will be described in more
detail hereinbelow with reference to -he accompanying drawinys
in which
Fig. 1 is a schematic view illustrating the function of
the apparatus;
Fig. 2 is an axial section of a particularly preferred
embodiment of the apparatus, which includes a temperature
sensitive element in the form of a double helix bimetal strip
in a housing having a slopiny top wall member at the outlet end
1~ of the housing;
Fig. 3 is a fragmentary cross-sectional view taken on the
line III-III in Fig. 2.
Fig. 1 illustrates a natural ventilation system in which
the apparatus according to the invention is installed in the
outgoing air duct 1 of the system, the outlet end of said duct
being designated 2, and in which a damper 3 is provided near
the outlet. A temperature sensitive element 5 is arranged on
the outer side of the duct 1 outside the damper 3, thus at or
in the vicinity of the outlet end 2. The sensitive element 5 is
adapted to operate the damper via a shaft 4 connected thereto
by rotary or possibly shifting movement in dependence on tempera-
ture changes acting upon the element 5. The damper is thus
adjustable in the duct 1 for regulating the flow of outgoing air
into ambient air. The sensitive element 5 shall thus be adapted
to operate the damper 3 for reduction of the cross-sectional area
of the duct 1 when the temperature falls, and vice versa.
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The outgoing air 7 flows towardc the clam~er 3 in the duc
1 but before it reaches the damper 3 one or more part flows 7a
are deflected ~rom the main flow 7 through one or more openings
6 to actuate the sensitive element 5 thermally. Of the main
flow 7 there only rernains the flow 8 which is led into ambient
air at the outlet end 2. The wind factor is represented by the
arrow 9. The stronger the wind, the more rapidly will the out-
going air flow 8 escape as a flow 11 in the wind direction. In
windy weather the warm part flows 7a are also affected. The
1~ sensitive element 5 is thus exposed both to wind and t~eather
and to the part flow 7a. The stronger the wind, the lesser
possibility have the part flows 7a of heating the sensitive
element 5. The part flows (or flow) then do not reach the
sensitive element to the same extent as in calm weather but
are mixed by wind actuation with the outdoor air and are more or
less deflected, from which results a lesser actuation of the
sensitive element. The arrow 10 represents some of the outgoing
part flow. This implies that the stronger the wind in cold
weather, the colder the sensitive element 5, and the more will
the sensitive element 5 turn or push the connecting element 4
and thus the damper 3 to such positions that the outgoing air
will be given a limited possibility of flowing through the
outgoing air duct 1. The tendency of an increase of the out-
going air flow 7, 8, 11 at increasing wind force in cold weatller
ar.d the resulting poor heat economy of the natural ventilation
system aréthus corrected or reduced automatically by the appara-
tus according to the invention.
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~0478Z5i
In a preferred embodiment of the apparatus the sensitive
element 5 is a temperature sensitive bimetal strip shaped into
a single helix. The helix is arranged at the outer wall of the
outlet duct 1 and is exposed to wind and weather. One end there-
of is fixedly anchGred to the wall of the duct while the other
end is rota-tably mounted on a shaft 4. A rotary damper in the
duct 1 is operated in dependence of the twist of the helix via
said shaft 4 by the action of outdoor air 9 and the part flow
7a of outgoing air exiting in the vicinity of the hellx through
the duct openings 6.
Figs. 2 and 3 show a specifically preferred embodiment of
the invention, which can be influenced also by heat radiation
and "cold radiation". This apparatus includes a temperature
sensitive element S in the form of a double helix. The double
helix 5 is made from a bimetal strip which has been formed into
a single helix of small diameter which in turn has been formed
into a single helix of larger diameter, for which reason the
term "double helix" for the element 5 is entirely adequate. To
wind bimetal strips into such double helic2s is previously
known. Depending upon the manner in which the double helix is
wound it will expand or alternatively contract when heated.
The embodiment illustrated in Fig. 2 operates on the lastmentioned
principle which means that the double helix 5 when cooled closes
the damper 3 which in its fully closed position bears against
a sealing edge 15.
With the use of a double helix made according to the
firstmentioned alternative, that is, of opposite movement with
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regard to the case illustrated, the sealing edge 15 shall be
- placed above ~he damper 3 so that the iatter upon closure
approaches said sealing edge.
If desired, the sealing edge 15 can be movable so that
it can be set into such a position that some ventilation is
obtained through the duct also at fully closed damper. The
sealing edge r~ also be arranged in another manner for attain-
ing this result. At severe cold or when a strong cold wind i 9
blowing the ventilation in normally insulated dwelling-houses
is fully satisfactory through existing leaks, for which reason
the damper 3 can be fully closed in these circumstances.
The double hel.ix is placed in a housing 16 formed with
several ventilation openings 16a at the outlet end of the duct 1
and is fixed at its upper end to the roof 16' of the housing 16
and with its lower L-shaped end portion, which forms a motion
transmitting member 4, connected to the damper 3. The double
helix thus in an integral piece forms both the temperature
sensitive element 5 and a damper operating means 4. A guide
sleeve 6a formed with slots or openings 6 is secured to the
damper 3 at. the point of fixation of the damper 3 to the end
portion 4 of the eIement 5. Said guide sleeve is arranged to
slide in a guide 13 in a top wall element 12 which is disposed
over the outlet of the duct 1 and is fixed to the duct, forming
a supporting means for the housing 16 in which the bimetal helix
5 is placed.
Warm outgoing air 7 flows towards the outlet end 2 of the
outgoing air duct 1. The amount of outgoirlg air 7 is determined
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by the gap between the damper 3 and the sealing edge 15. Part
of the warm outgoing air 7 is conducted in the form of part
flows 7a through the openings 6 of the guide sleeve 6a (cf.
Fig. 3) and in an upwar~ direction in the housing 16 and there
forms a heat addition which toyether with the outdoor air in
the housing imparts to the bimetal helix 5 a certain temperature
and resulting ïength expansion and to the damper 3 associated
with the bime:tal helix 5 a definite position in relation to the
sealing edge 15.
I~ A certain temperature condition in the housing 16 results
in a definite gap between the damper 3 and the sealing edge 15.
The major portion of the outgoing air flow 7 escapes as flows
8 through this gap and through the main ventilatlon openinys 17
spaced around the outlet end 2 of the duct 1. The part flows
7a successively escape as part flows 10 through the ventilation
openings 16a of the housing 16.
By wind influence and by the successive increase of the
wind 9 from zero successively changing flow conditions arise,
these conditions being exemplified hereinbelow by three phases
designated A, B and C. Each of said phases gives an increased
and intensified cooling of the bimetal element 5 with resulting
ever more decreasing flow of outgoing air.
A. The ~ore the wind increases from zero the lesser possi-
bility have the part flows 7a of outgoing air to deliver their
heat addition to the bimetal element 5 since said part flows
escape ever more early and rapidly as part flows 10 in the dlrec-
tion of the wind 9.
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1~47~
B. At a ~ind force of cercain s-trength some part flows 9a
of outdoor air besides penetrate through the main ventilation
openings 17 and mix with the part flows 7a of outgoiny air, and
depending upon the wind force, said part flovJs 9a wholly or part-
ly pass upwardly through the housing 16 in the same way as the
earlier part flows 7a of outgoing air alone, in order to acutate
the bimetal element 5 therein. ~y the admixture of the cool part
~lows ga of outdoor air in this manner the heat actuation of
the bimetal element 5 will be even somewhat lower and as a con-
sequence the flow of outgoing air will be reduced as compared
to that prevailing in calm weather and in case A above.
C. According as the wind force increases the majority of the
warm part flows 7a of outgoing air disappear in ever earlier
stages. With very strong winds no warm part flows 7a of outgoing
air at all reach the bimetal element 5 but blow away in the
direction of the wind 9, escaping directly into ambient air like
the flow 11. The result is that the stronger the wind the bi-
metal element 5 is cooled to an ever increasing extent and
that as a consequence the outflow of outgoing air will be
successively reduced, this being the aim contemplated.
The third weather factor, radiation, influences the appa-
ratus according to the invention in the following manner.
The influence of radiation may be considered as an intensi-
fying effect which is superimposed on earlier temperature and
wind influences. The radiation (represented by arrows 18) is
directed respectively towards the top wall member 12 and the
housing 16 upon influence of solar radiation, and from the top
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wall memlber upon influence of "co]d radiation" i.e., heat radia-
tion frorn the top wall member, particularly against a dark sky
The top wall member 1~ above the duct 1 and the housirg 16 are
of such a material and/or so surEace-treated as to be heavily
radiation-absorbing or heavily radiation-emitting.
Upon incidence of solar radiation 18 towards the radiation-
/ absorbing top ~;all member 12 the part flows 7a of outgoing air
and possibly the part flows 9a of outdoor air will receive a
heat addition when they pass beneath the slightly sloping top
l~ wall member 12 on their way up in the housing 16. This implies
a larger heat actuation of the bimetal element 5 with an ensuing
increase of flow of outgoing air. Since the housing 1~ also is
radiation-absorbing this will entail an additional heating of
the bimetal element 5 directly and as a function of the intensity
of solar radiation. That the amount of outgoing air per unit
of time thus increases with the intensity of the solar radiation
18 is desirable from the viewpoint of ventilation and can be
allowed also at a relatively low outdoor temperature, since the
room temperature would otherwise be uncomfortably high because
of the absorbed solar radiation energy of the building, primarily
directly through the windows. The heat amounts absorbed and
stored in the walls etc. of the building, which later, in hours
of unintensive sun, emit a desired heat addition are not affected
by the embodiment of the invention comprising a bimetal element
in the form of a double helix. The night following upon a clear
sunny day is often clear and cool with intensive "cold radiation"
whereby the double helix will be heavily cooled in a correspond-
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ing degree since the top wall member 12 and the housing 16 alsoare heavily radia-tion-emitting.
An excess temperature, if any, which has arisen for various
reasons in the building implies an increase of the outgoing air
flow and temperature as well as higher temperatures of the part
flows 7a of outgoing air, which will thus be capahle of heat-
\ ing the double helix 5 in a higher degvte, entailing adesired increase of ventilation.
In a further embodiment of the apparatus according to the
l~ invention the sensitive element 5 comprises a stack of washer-
shaped bimetal elements (not shown), said stack heavily varying
in axial length at rather insignificant temperature variations
and being adapted to operate a damper or like means in the duct
1 on the same principle as that described with reference to
Figs. 2 and 3.
Some further positive effects and system alternatives
will now be described.
A thorough sealing of such ordinary paths of heat leakage
in buildings as are formed for instance by cracks around windows
and doors, is not a sufficient measure to prevent heat losses
by natural draught. If the most usual paths of heat leakage
are sealed the draught may increase through other leakage paths,
and for an efficient saving of energy a satisfactory sealing
should be supplemented with a positive control of the ventila-
tion systems in conformity with the invention. A well-sealed
building equipped with means for natural ventilation and an
automatically operating control apparatus according to the
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invention will provide an optimum ecoromical result as the con-
trol takes place with due regard to a]l important factors, such
as indoor temperature, outdoor temperature, wind force and radia-
tion conditions and as the apparatus according to the invention
is ine~pensive and can be incorporated without any great costs
in ordinary natural ventilation systems.
The invention is applicable also to such prior art systems
of mechanical ventilation as are designed for intermittent
operation to prevent unnecessary heat losses. In those cases
1~ the mechanical ventilation can be caused to operate only during
the periods when considerable ventilation is required. During
the intervening periods of natural ventilation the apparatus
according to the invention can be utilized also in such a mecha-
nical system. During the forced ventilation periods when the
ventilators of the mechanical system are in operation the heavy
air flow will cause the apparatus according to the invention
to open fully. Said apparatus thus automatically adapts itself
to the operation of the ventilators of the mechanical system ~nd
opens the ventilation duct, and then,that is, during the
standstill periods of the ventilators, it controls the ventila-
tion duct in the manner described.
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