Abstract:
Described herein is a Coanda-effect air distributor for distributing a flow between a number of ducts set downstream. Provided in the area that separates the initial ends of two ducts set downstream is the inlet of a recirculation duct that creates an air circulation that masks the entrance of a duct set downstream when the flow is deviated into the other duct.

Description:
SUMMARY OF THE INVENTION 
   The present invention relates to air-distribution devices based upon the Coanda effect, of the type comprising a duct set upstream that branches off into a number of ducts set downstream and means designed to deflect the air flow that traverses said duct into one or the other of said ducts, exploiting the Coanda effect. 
   The Coanda effect is the phenomenon whereby a flow of air exiting from a duct tends to “stick” to a wall that is adjacent to it. In a device previously proposed by the present applicant, the aforesaid means of deflection by the Coanda effect comprise a first mobile element provided on a wall of the duct, which is set upstream in the proximity of the inlet of one of the ducts set downstream and can be displaced between a first position, in which it does not interfere with the flow of air through the duct set upstream, and a second position, in which it projects into said flow, so that, in the aforesaid first position of the mobile element, the flow enters a first duct set downstream, remaining adherent to a wall of this by the Coanda effect, whilst in the aforesaid second position of the mobile element, the flow that traverses the duct set upstream tends to adhere to a wall of a second duct set downstream that is opposite to said first wall, so that the flow enters the aforesaid second duct set downstream. 
   The purpose of the present invention is to provide an air-distribution device based upon the Coanda effect of the type indicated above that will be even more efficient than the devices proposed up to now. 
   In order to achieve said purpose, the subject of the invention is an air-distribution device based upon the Coanda effect of the type described above, characterized in that, in the area that separates the initial ends of two ducts set downstream, there is provided the inlet of a recirculation passage giving out into one of the two ducts set downstream and shaped in such a way as to generate a circulation of air to the inlet of one of the two ducts set downstream, which masks the inlet of said duct when the air flow is deviated into the other duct set downstream. 
   Preferably, said solution is used in combination with means for deflecting the air by the Coanda effect that comprise two mobile elements, which are positioned on opposite walls of the duct set upstream and are each displaceable between a first position, in which it does not interfere with the flow of the air, and a second position, in which it projects into said flow, said mobile elements being displaceable in synchronism with one another so that when a first mobile element is in its first position, the second mobile element is in its second position and when, conversely, the first mobile element is in its second position, the second mobile element is in its first position. 
   According to a further preferred characteristic, also one of said mobile elements can be shaped so that, when it is in its second position projecting into a respective duct, it interferes with the possible flow of air not properly oriented so as to impart a circulatory motion upon said flow, which masks one of the ducts set downstream when the air flow is directed into the other duct. 
   A preferred application of the air-distributing device according to the invention consists of the air-distribution systems built into dashboards of motor vehicles. It is evident, however, that the Coanda-effect air-distributing device according to the invention is of general application. 
   In what follows the invention will now be described in detail with reference to the application to the dashboard of a motor vehicle. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the annexed drawings, which are provided purely by way of non-limiting example: 
       FIG. 1  is a diagram illustrating the principle underlying the air-distribution system according to the invention; 
       FIG. 2  is a partial schematic perspective view of an air-distribution system for the dashboard of a motor vehicle according to the invention; 
       FIG. 3  is a view, at an enlarged scale, of a detail of  FIG. 2 ; 
       FIGS. 4 ,  5 , and  6  are cross-sectional views, at an enlarged scale, of a detail of  FIG. 3 , which show the system according to the invention in different conditions of operation; 
       FIG. 7  is a perspective schematic view of a detail of  FIGS. 4–6 ; 
       FIG. 8  is a schematic view of the actuator of the item represented in  FIG. 7 ; and 
       FIG. 9  illustrates a variant of  FIG. 7 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   In  FIG. 1 , the reference number  1  designates as a whole a dashboard, illustrated only schematically, of a motor vehicle, there being provided, inside the dashboard, an air-distribution system  2 . The system  2  comprises a main duct  3  that receives air from an air-conditioning system, including a main fan  4  and a heater/evaporator  5 . The main duct  3  gives out into a manifold or rail  6 , from which there branch off four auxiliary ducts  7 , distributed in parallel along the dashboard, one pair on the driver side, and one pair on the passenger side, each pair comprising a duct adjacent to the central part of the dashboard and a duct closer to a side window of the motor vehicle. Each auxiliary duct  7  branches off into three terminal ducts  8 ,  9 ,  10  (see also  FIG. 2 ), each of which terminates on air-outflow openings in the passenger compartment of the motor vehicle. In particular, the duct  8  supplies air to openings  11  arranged at the base of the windscreen for directing a flow of air onto the internal surface of the latter. The duct  9  terminates in one or more openings  12  arranged at the front, on the dashboard, for directing air towards the passenger compartment of the motor vehicle, and the duct  10  terminates in one or more openings  13 , which direct a flow of air towards the floor of the passenger compartment. 
   In the area in which each auxiliary duct  7  branches off into the three terminal ducts  8 ,  9 ,  10 , there are provided means for distributing the flow of air between the terminal ducts, which will be illustrated in detail in what follows. 
   An important characteristic, which forms the subject of a separate application, lies in the fact that each of the auxiliary ducts  7  is provided with an additional and independent unit for regulating at least one characteristic of the air flow. In particular, associated to each auxiliary duct  7  is, in the example of embodiment illustrated, a unit  14  for regulating the flow rate of the air and a unit  15  for regulating the temperature of the air. In the example illustrated, the unit  14  comprises a fan with corresponding electric controlling motor, whilst the unit  15  comprises a cross section of duct, in which an electrical resistor is inserted. 
   Therefore, the distribution system illustrated enables regulation of the rate and/or the temperature of the air flow exiting from the openings  11 ,  12 ,  13 , separately for each of the auxiliary ducts  7 , i.e., in the case of the example illustrated, separately for the driver area and for the passenger area and, for each of said areas, separately for the central area of the dashboard and for the area adjacent to the window. 
     FIGS. 4–6  illustrate the way in which the distribution of the air coming from each auxiliary duct  7  into the terminal ducts  8 ,  9 ,  10  that branch off therefrom is controlled. 
   With reference to said figures, the first terminal duct  8  has a first curved wall  8   a  set on the prolongation of a corresponding wall  7   a  of the auxiliary duct  7 . In a position corresponding to said wall, associated to the duct is a mobile element  16 , which is mounted oscillating about an axis of articulation  17  on the wall  7   a  and can be displaced between a first position, visible in  FIG. 4 , and a second position, visible in  FIG. 5 . In the first position illustrated in  FIG. 4 , the mobile element  16  does not interfere with the air flow F coming from the auxiliary duct  7 , so that said flow remains “stuck” to the walls  7   a  and  8   a  and consequently enters the first terminal duct  8 . In the second position of the mobile element  16  illustrated in  FIG. 5 , said mobile element projects into the flow F so that it invites said flow to adhere, by the Coanda effect, to a curved wall  8   b  opposite to the wall  8   a  and situated at the inlet of the two terminal ducts  9 ,  10 . 
   To obtain a more efficient distribution of the air flow between the terminal duct  8  and the inlet  8   c  of the two terminal ducts  9 ,  10 , there is provided a further mobile element  18 , which can be displaced between a first position, in which it does not interfere with the flow F (illustrated in  FIG. 5 ), and a second position, in which it projects into the flow F (illustrated in  FIG. 4 ). The two mobile elements  16 ,  18  must be controlled in synchronism so that when the mobile element  16  is in its first position the mobile element  18  is in its second position ( FIG. 4 ), whereas when the first mobile element  16  is in its second position the second mobile element  18  is in its first position ( FIG. 5 ). In the case of the example illustrated, this is obtained very simply in so far as the mobile element  16  and the mobile element  18  form part of a single member  19  mounted articulated on the structure of the duct  7  about the axis  17 . As may be seen in  FIG. 7 , the member  19  comprises a vaned part that defines the element  16 , and a U-shaped part, rigidly connected to the vane  16  and substantially orthogonal thereto, including a bent cross member that constitutes the mobile element  18 . 
   In the condition illustrated in  FIG. 4 , the mobile element  18  encourages “sticking” of the flow F to the wall  8  in so far as it prevents the flow F from remaining adherent to the wall  8   b . In the condition illustrated in  FIG. 5 , since the element  18  does not disturb the flow F it enables said flow to stick to the wall  8   b  by the Coanda effect. 
   As may be seen in  FIGS. 4–6 , a further mobile member  19 , which includes a first mobile element  16  and a second mobile element  18  altogether similar to the ones described above, is moreover provided in a position corresponding to the inlets  8   c  of the two terminal ducts  9 ,  10 . The mode of operation of said second mobile member is altogether similar to what has been described above. In the condition illustrated in  FIG. 5 , the second mobile member favours sticking, by the Coanda effect, of the flow to a first curved wall  9   a  of the terminal duct  9 , so that the flow enters said duct, whilst in the condition illustrated in  FIG. 6  it favours the sticking of the flow to a wall  10   a , which is also curved, of the terminal duct  10 , so that the flow enters this latter duct. Furthermore, the mobile element  18  in this case also performs the function of interfering (in the condition illustrated in  FIG. 4 ) with a possible part of the main flow F that were to enter the inlets  8   c  bestowing thereon a circulatory motion C ( FIG. 4 ) that “obstructs” the inlets  8   c , reducing to a minimum any undesired leakages of air in the ducts  9 ,  10 . 
   For the same purpose, according to the invention, in a position corresponding to the inlets of the terminal duct  8  and of the terminal duct  9  there are provided air-recirculation passages  20  shaped so that, in the conditions illustrated respectively in  FIG. 5  and  FIG. 6 , any possible undesired leakages of air give rise to an air circulation C that obstructs the duct into which the flow is to be directed. 
   The mobile members  19  are controlled by actuators of any type, for example electromagnetic actuators (such as the actuator  40  in  FIG. 8 ), or piezoelectric actuators, or shape-memory actuators. 
     FIG. 8  illustrates a variant of the member  19 , in which the U-shaped portion defining the mobile element  18  also includes vanes  21  having the function of straightening the flow. 
   Of course, without prejudice to the principle of the invention, the details of construction and the embodiments may vary widely with respect to what is described and illustrated herein purely by way of example, without thereby departing from the scope of the present invention.