Ventilation unit

A ventilation unit comprising: a first channel for a relatively cold air stream; a second channel for a relatively hot air stream; and an outlet door located at the ends of the first and second channels for dividing air from the first and second channels between a first outlet and a second outlet in such a way that desired proportions of each of the cold and hot air streams are divided to each of the first and second outlets.

BACKGROUND OF THE INVENTION 
This invention relates to ventilation units; for example in heating systems 
and air conditioning systems. 
FIG. 1 shows a typical prior art air conditioning system for a vehicle. Air 
is drawn inwards through inlet 1 by a radial blower 2 running in a scroll 
3. This forces air through evaporator 4. From the evaporator the air meets 
a blend door 5 which can pivot about a hinge 6. The blend door divides the 
airflow from the evaporator into a first (cold) stream which passes 
directly to a mixing chamber 7 and a second (hot) stream which passes 
through a heater core 8 on its way to the mixing chamber. The hot and cold 
air streams recombine and mix together in the mixing chamber. At the 
outlet of the mixing chamber is a movable panel door 9 which divides the 
air from the mixing chamber into a stream directed through outlet 10 
towards the vehicle's panel and a remaining stream directed through 
passage 11 to a movable floor/defrost door 12. The floor/defrost door 
divides that remaining stream between the vehicle's floor and defrost 
outlets. The blend door 5 can be moved to control the temperature of the 
outgoing air by setting the amount of air in the hot and cold streams. The 
doors 9 and 12 are movable by a user to set the desired flow pattern in 
the vehicle. 
For proper operation of the system the hot and cold air streams must be 
properly mixed by the time they reach the panel door. To achieve this the 
mixing chamber must be of a sufficient length. This occupies considerable 
space. 
One aim of this invention is to reduce the space occupied by the system. 
Another aim is to allow a user to have the air flows to the panel vents 
and to the other outlets at different temperatures. 
SUMMARY OF THE INVENTION 
According to the present invention there is provided a ventilation unit 
comprising: a first channel for a relatively cold air stream; a second 
channel for a relatively hot air stream; and an outlet door located at the 
ends of the first and second channels for dividing air from the first and 
second channels between a first outlet and a second outlet in such a way 
that desired proportions of each of the cold and hot air streams are 
divided to each of the first and second outlets. 
Preferably the outlet door has a first edge that is located in the first 
channel for dividing the cold air stream. The first edge may be straight 
or curved to achieve the desired division of the hot and cold air. 
Preferably the outlet door has a second edge that is located in the second 
channel for dividing the hot air stream. The second edge may be straight 
or curved to achieve the desired division of the hot and cold air. The 
outlet door (or at least the part of it that is operative to divide the 
air) may be planar or non-planar, flat or having variable thickness as 
needed to achieve the desired division. One preferred division is for a 
greater proportion of the cold air than of the hot air to be directed to 
the first outlet (to provide a relatively cold output air stream there) 
and for a greater proportion of the hot air than of the cold air to be 
directed to the second outlet (to provide a relatively hot output air 
stream there). Another preferred division is for substantially equal 
proportions of the cold and hot air streams to be directed to each of the 
first and second outlets. 
The outlet door is preferably movable (most preferably rotatable) about a 
hinge or pivot axis. The axis is preferably located at one edge of the 
door. The outlet door preferably pivots about an edge opposite the said 
first edge, although not necessarily parallel to the first edge. The 
outlet door preferably achieves the said division for substantially all 
its positions. The air division achieved by the outlet door preferably 
provides air flows of substantially the same average temperature to each 
of the first and second outlets. Preferably volumes are provided 
downstream of the outlet door for allowing mixing of the air streams to 
each outlet. 
The first and second channels preferably meet at the outlet door. At the 
other ends of the channels is preferably a blend door for dividing an air 
stream from an inlet into the cold and hot air streams. A heater is 
preferably located in the second channel for warming the hot air stream. 
The outlet door is preferably located close to the air heater and/or the 
blend door. 
The first and second channels are preferably directed so that the hot and 
cold air streams meet at the mode door at a considerable angle (greater 
than 50.degree. or 60.degree. for instance, and preferably substantially 
at right angles). Means (such as baffles or other obstructions) may also 
be provided downstream of the mode door (preferably immediately 
downstream) to promote mixing. 
A bypass channel may be provided which allows air to pass from the inlet to 
one of the outlets without passing through the first or second channels. 
The bypass channel is preferably closable to prevent air flow 
therethrough. 
The ventilation system may form part of an air conditioning system. The 
ventilation system may form part of an air-conditioned or 
non-air-conditioned heating and/or ventilation system for a vehicle. In a 
vehicle the first and second outlets preferably provide air to respective 
locations in the vehicle, for instance facia or panel vents, floor vents 
or defrost vents. One of the first and second outlets most preferably 
provides air to facia or panel vents.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIGS. 2 and 3 show a ventilation system which provides the air conditioning 
system for a vehicle. As in the system of FIG. 1, air is drawn inwards 
through inlet 20 by a radial blower 21 running in a scroll 22. This forces 
air through evaporator 23. From the evaporator the air meets a blend door 
24 which can pivot about a hinge 25 as indicated by dashed line 26. The 
blend door divides the airflow from the evaporator into a first (cold) 
stream which passes through a cold air channel 27 and a second (hot) 
stream which passes through a hot air channel 28 where it is warmed by 
passing through a heater core 29. 
The hot and cold air channels meet at mode door 30. The mode door pivots 
about hinge 31 as indicated by dashed line 32 in FIG. 3. The cold air 
stream in the cold air channel meets leading edge 33 of the mode door, 
which splits the cold air stream into two parts: one destined for the 
vehicle's panel vents 34 and the other destined for the vehicle's 
floor/defrost vents 35,36. The hot air stream in the hot air channel meets 
side edge 37 of the mode door, which splits the hot air stream into two 
parts: one destined for the vehicle's panel vents 34 and the other 
destined for the vehicle's floor/defrost vents 35.36. The mode door is 
shaped so that desired proportions of the cold and hot air streams are 
divided to each of the first and second outlets. In the extreme positions 
of the mode door all the air flow is directed to a single one of the 
outlets. 
It is sometimes desired to have colder air at the vehicle's panel vents 
than at the floor/defrost vents. Therefore, one possibility is for the 
mode door to be shaped so as to achieve this temperature split: for 
instance so that in one position of the mode door roughly 60% of the cold 
air stream goes to the panel vents and 40% to the floor/defrost vents and 
roughly 40% of the hot air stream goes to the panel vents and 60% to the 
floor/defrost vents. 
Another possibility is for the mode door to split the hot and cold air 
streams so that roughly equal proportions of them are directed to the 
panel vents and to the floor/defrost vents. The effect of this is that the 
air destined for the vehicle's panel vents will (when fully mixed) be 
roughly the same temperature as the air destined for the floor/defrost 
vents (when fully mixed). For example, in one position of the mode door 
roughly 30% of the cold air stream goes to the panel vents and 70% to the 
floor/defrost vents and roughly 30% of the hot air stream goes to the 
panel vents and 70% to the floor/defrost vents. 
To promote a uniform flow in the hot air channel 28 a longitudinal wall 45 
is provided in the channel, downstream of the heater core 29. 
From the mode door the air flow to the floor/defrost vents passes through 
an intermediate channel 38 to a floor/defrost door 39. This pivots about 
hinge 40 (as shown by dashed line 41) and divides the air flow between the 
floor vents 35 and the defrost vents 36. 
Because the mode door divides the air streams as required, there is no need 
for a mixing chamber (7 in FIG. 1). The air streams recombine and mix 
together in the channels downstream of the mode door as they pass to the 
vents--for example in the intermediate channel 38 on the way to the 
floor/defrost door 39. This saves space. In the embodiment shown, because 
the hot and cold air streams meet at a considerable angle (roughly 
90.degree.) there is turbulent flow downstream of the mode door and 
relatively little space is needed for mixing the air streams. 
Typical dimensions of the channels are as follows: 
cold air channel 27: 160 mm.times.120 mm, 
hot air channel 28: 180 mm.times.80 mm. 
A bypass channel 42 is provided for achieving a temperature split 
independently of the mode door. A bypass channel 42 passes from the 
chamber 43 immediately downstream of the evaporator 23 directly to the 
panel vent channel that leads from the mode door 30 to the panel vents. A 
bypass door 44 at the upstream end of the bypass channel can be opened to 
allow relatively cold air to pass through the bypass channel and towards 
the panel vent channel. In the panel vent channel the air from the bypass 
channel mixes with and cools the air flow from the hot and cold air 
channels via the mode door. 
The doors are movable by a user to set the temperature and flow pattern in 
the vehicle. The doors could be controlled automatically. 
The shape of the mode door, its movement as the controls are altered and 
its location are selected to provide the desired division of air. The 
geometry of the channels and the flow patterns through them must also be 
taken into account. Most preferably the air is divided in the desired 
proportions for all available settings of the blend door and for all 
available flow rates (influenced by the vehicle's speed and the speed of 
the blower 21); alternatively the division could vary with the position of 
the mode door, for instance with relatively cooler air going to the panel 
vents when the mode door is set to provide a relatively large flow to the 
floor/defrost vents. FIGS. 4 and 5 (in which like parts are numbered as 
for FIGS. 2 and 3) illustrate examples of modifications to provide the 
desired divisions. In FIG. 4 the edges 33 and 37 of the mode door 30 are 
curved. In FIG. 5 the mode door 30 is non-planar. A non-planar door with 
one or more curved edges is possible, as is a door that has surface 
projections or depressions or a non-uniform thickness or other types of 
shaping to influence flow in the desired way. 
The present invention may include any feature or combination of features 
disclosed herein either implicitly or explicitly or any generalisation 
thereof irrespective of whether it relates to the presently claimed 
invention. In view of the foregoing description it will be evident to a 
person skilled in the art that various modifications may be made within 
the scope of the invention.