This invention relates to the discharge of air in air conditioning systems with two ducts by means of units comprising inlet openings controlled by baffles for hot and cold air resp., an exhaust opening from the unit to the space to be conditioned and operating means for the ^' control of the baffles.

In air conditioning systems with two ducts the hot and cold air in the two ducts is admitted to an air control unit adapted to mix the air streams before entering the room or area to be conditioned. This is, however, disadvanta¬ geous since the system must be designed for maximum air . volume during the hottest or coldest days of the year. During the remaining time of the year an excess volume of air must be admitted which means a waste of energy partly in terms of an excess volume of hot air during certain periods of the year, partly in view of the fact that the fans etc. must be sized according to the greatest volume of air. An attempt to compensate for the different operating conditions during diffe¬ rent seasons is to arrange for a specific control of the volume control device present in the air control unit, such as shown in the Swedish Patent Specification No. 7303715-2. The control unit shown in said Patent Specification greatly eliminates the disadvantages of the system with two ducts and is relatively simple in its design and structure but it still contains an fairly great amount of parts.

A main object of this invention is to further simplify the air control unit in systems with two ducts and at the same time compensate for the different operating conditions prevailing during different seasons of the year.

This object is achieved by means of a method and apparatus as characterized in the appended claims. Further objects and advantages will be apparent from the following description in connection with the drawings showing preferred embodiments of the invention. Figure 1 is a horizontal section view through the air control unit according to the invention. Figure 2 is a section view taken along lines II-II of Fig. 1.

Figure 3 is a section view taken along lines III-III of Fig. 1.

Figure 4 is a horizontal section view similar to Fig. 1 of another embodiment.

Figure 5 is a section view taken along lines V-V in Fig. 4.

Figure 6 is a partial section view taken along lines VI-VI in Fig. 4.

The air control unit 10 shown in Figures 1-3 comprises a box-shaped housing 12 which is provided with inlet connec¬ tions 14,16 for hot and cold air respectively from the sys with two ducts (not shown) and an exhaust 18 connected to the room or area to be conditioned. The inlets 14 _» 16 to the housing or box 12 can be closed by means of 'baffles or covers 20 which are pivotally connected at 22 between L-rods 24 on the inside of the box 12. The covers 20 are, thus, swingable between the position shown in the left part of Fig. 1 where the cover closes the inlet 14 to another end position where the cover 20, as shown in the rigjt part of Fig. 1, opens the inlet 16. The actuation of the covers 20 is according to the invention accomplished in a very simple way. An arm 28 pivotally mounted on a partition wall 26 arranged between the walls of the box is actuated by means of a turning motor 30 provided underneath the partition wall 26. The turning motor 30 turns the arm 28 around the pivot 32 in one direction or the other depending on the demand for hot or cold air. This demand is in the usual way controlled e.g. by means of a thermo- static mechanism which in a manner well known in the art is connected to the controls of the motor 30.

On each end of the arm 28 is connected a transmitting

^■ means such as a biasing means, in the embodiment shown a plate spring 34, with such shape e.g. bent outwardly that it with a predetermined biasing force keeps the covers or baffles 20 closed when the arm 28 is in the neutral position, i.e. in parallell with the end sur¬ face of the box 12. When the motor 30 turns the arm 28 in one direction, e.g. such as shown in Fig. 1, the biasing force of the spring 34 against one baffle 20 will be relieved and the baffle will be opened due to the pressure prevailing in .the duct in the two-duct system which is connected to the inlet 16. At the same time the other spring 34 is biased harder against the other baffle 20 and keeps said baffle closed. In this way the motor 30 will turn the arm 28, corresponding to the heating or cooling demand, in one direction or the other and alternately open the baffles 20 in order to admit air of the respective condition to the exhaust connection 18. In order to stop the turning of the motor in the two end positions and prevent excess force on the springs 34 and baffles 20 micro switches 36 are arranged (see also Fig. 3) the actuating arms 38 of the switches being engaged by the arm 28 in the desired end positions to thereby stop the motor 30. Other possibilities are of course appa¬ rent such as a motor with a friction coupling and fixed stops stopping the arm 28 so that the friction coupling will be engaged.

As seen from the above a very simple control of the air admitted is accomplished by means of the control unit shown. During most operating conditions only one of the baffles 20 will be open in order to admit hot or cold air. Only in case the room has the temperature set it may happen that both baffles open slightly so that air of both conditions are mixed. This is also the case if a minimum air stream is to be admitted as described more fully hereinafter. As soon as the tempe¬ rature in the room is altered a cooling or heating demand

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is established and one baffle 20 opens while the other remains closed as described above. Since the mixing of hot and cold air is essentially eliminated a consider¬ able saving of energy is obtained due to the fact that the air streams are not being unnecessarily mixed but normally only air of the required condition is admitted. In the late years when modern buildings are more insulated it has shown that usually only a cooling demand will pre¬ vail during the main part of the year. In only admitting cold air and that with a baffle which only opens to the extent necessary the least possible energy will be re¬ quired for the conditioning demand and the whole system with cooling battery, heating battery, fans etc. will get the smallest dimensions poosible. Another advantage with the air control unit according to the invention is that the pressure in the ducts of the two-duct system may be decreased as the baffles or covers 20 open also at very low pressures. In known systems with air control units of the type mixing the two air streams and provided with volume regulator a considerably higher pressure must be kept in order for the volume regulator to functicn in the way intended. *

If it is desired always to keep a minimum air stream to the room in order to change the air e.g. depending on certain regulations any of the baffles 20 or both may, in the "closed" position, admit the corresponding amount of air. This may be accomplished in that the springs 34 do not close the baffles 20 entirely or in that the baffles engages a stop providing a. gap through which the said amount of air may pass.

Of course the transmitting means between the actuator and the covers or baffles can be embodied in other forms than those illustrated. Instead of a turning motor a motor with linear motion may be used and the transmitting means may have the form of a link system coupled to the baffles 20 and controlling their opening angle. These and other embodiments are within the scope of the inven¬ tion according to the following claims.

In the embodiment shown in Fig. 4 the actuating arm 28 of Fig. 1 is replaced by a cam 40 and the springs 34 are provided on the baffles 20 instead of being on the actuator 40. The drive motor 30 which actuates the cam 40 is mounted on a plate 46. Moreover the parts which are common to the embodiment in Fig. 1 have the same references. In order to adjust the position in which the baffles 20 open the springs 34 are adjustably mounted on the baffles by means of a slit 42 and ad¬ justing screw 44 such as shown in Fig. 6. This embodiment which functions in the same way as the embodiment shown in Fig. 1, i.e. usually only one of the baffles opens so that air of one condition flows into the unit without essentially mixing the air streams, offers a further possibility. In extreme cases, e.g. in case of very strong heat, it is, thus, possible to turn the actuating cam 40 to a backward position away from the baffles 20 in which position the cam 40 overlies the plate 46, whereby the baffles 20 are free to open at the same time. This gives the possibility to admit air streams of the same condition, preferably cold air, through both inlets 14 and 16. The sys.tem can, thus, be used for forced cooling of the spaces or rooms to be conditioned without having to make the admitting ducts extremely big. In this case the usual operation where only one baffle is to be opened is abandoned. In order to accomplish the said operating condition all drive motors 30 in the air control units present in the air conditioning system are preferably connected to a central control from which the air control units may be regulated in a way known per se. Of course the units may also be used for the forced admittance of hot air if desired.