Abstract:
The air mixing device, for use in an air conditioning apparatus or a vehicle heater system as a flow control device which consists of at least two flap members, the flap members being mutually independently movable between first and second positions in which they respectively obturate first and second air inlet openings.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a device for selectively obscuring heated and cooled air openings to an air mixing device and to a heating or air conditioning apparatus incorporating such a device. 
     BACKGROUND OF THE INVENTION 
     An air conditioning apparatus for a motor vehicle conventionally includes an air mixing chamber having two inlets, one for cooled air directly received from an evaporator and the other for heated air which has been passed over a heater core. A so-called &#34;blend door&#34; device pivots between a first position in which it substantially closes the first opening and a second position in which it substantially closes the second opening. Controls, such as hand-operated controls, set the position of the blend door either to one of the first or second positions, or to an intermediate position. 
     The air conditioning apparatus also has a number of outlets from the air mixing chamber, the outlets being connected via suitable conduits to different parts of the vehicle cabin, for example to the drivers side and to the passengers side. 
     A disadvantage of the known apparatus is that different temperatures exist within the air mixing chamber and thus that depending upon the location of the outlet within the chamber, different temperatures may be delivered to different parts of the vehicle cabin. The reason for the differing temperatures in the air mixing chamber lies in the different flow properties of the heated and the cooled air. Referring to FIG. 1, it will be seen that the cooled air arrives at a mixing chamber directly from the evaporator, whereas the heated air also emanates from the evaporator, but then passes through the heater core, which restricts air flow. 
     It will therefore be clear to one skilled in the art that with the conventional device the effect of the cooled air will predominate, at least on the left hand side, as shown in FIG. 1. 
     It is an object of the present invention to mitigate the above-mentioned difficulties. 
     SUMMARY OF THE INVENTION 
     According to the present invention there is provided a flow control device for selectively pivoting to obscure a first or second opening into an air mixing chamber wherein said flow control device comprises plural independently pivotal flap members. 
     Preferably each flap member has a surface portion which overlaps the surface portion of an adjacent flap member. 
     Preferably there are provided at least three said flap members, and said flow control device further comprises a coupling member for coupling together two non-adjacent of said flap members, whereby said two flap members move together. 
     According to a second aspect of the present invention there is provided an air mixing device comprising walls, said walls defining an air mixing chamber and further defining first and second openings into said chamber, one of said first and second openings being for heated air, and further comprising a flow control device, said flow control device being moveable with respect to said openings between first and second positions, whereby in said first position said flow control device obscures the first opening and in said second position said flow control device obscures said second opening, wherein said flow control device comprises at least two flap members, said flap members being mutually independently moveable between said first and second positions. 
     Preferably said flap members are pivotal about a common axis. 
     Preferably the air mixing device further comprises setting means for moving one of said flap members independently of another of said flap members. 
     Preferably each flap member has a surface portion which overlaps the surface portion of a respective adjacent flap member. 
     According to a third aspect of the present invention there is provided an air mixing device comprising walls, said walls defining an air mixing chamber and further defining first and second openings into said chamber, one of said first and second openings being for heated air, and further comprising a flow control device, said flow control device being moveable with respect to said openings between the first and second positions whereby in said first position said flow control device obscures the first opening and in said second position said flow control device obscures said second opening, wherein said flow control device comprises at least three flap members, said flap members being mutually independently moveable between said first and second positions, and said flow control device further has a coupling member for coupling together two non-adjacent of said flap members whereby said two flap members move together. 
     Preferably each flap member has a surface portion which overlaps a surface portion of a respective adjacent flap member. 
     Preferably in one of said first or second positions, said flap members cooperate together substantially to seal the respective opening. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will now be described with respect to the preferred embodiment thereof, with respect to the accompanying drawings in which: 
     FIG. 1 shows a partial cross-sectional view through a conventional air conditioning system; 
     FIG. 2 shows the blend door device of the ai: conditioning apparatus of FIG. 1; 
     FIG. 3 shows a perspective view of a blend door device in accordance with the present invention; and 
     FIG. 4 shows a partial perspective view of an air conditioning apparatus in accordance with the second embodiment of present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIG. 1, an air conditioning device has an evaporator (1) which receives an air flow (2) in known fashion, for example from an inlet for ambient air or from a vehicle-cabin inlet if re-circulation is desired. In use the evaporator is supplied with coolant and the outlet air flow (3) from the evaporator is thereby cooled. The outlet air of the evaporator is fed via a first passage (10) to an air mixing chamber (20) defined by the walls (30) of the air conditioning apparatus and via a second passageway (11) through a heater core (15). The heater core (15) heats the air flow to provide a heated air flow (4) to the air mixing chamber (20). 
     The first passage (10) has an opening (21) into the air mixing chamber (20), and the outlet of the heater core (15) passes through a second opening (22), of substantially similar size to the first opening (21) , into the air mixing chamber (20). A blend door (40) is moveable from a first position where it abuts the opening (21) so as to substantially seal the opening (21) and a second position where it abuts the opening (22) so as substantially to seal the opening (22). Setting apparatus (not shown in this figure) allows the blend door to be set to either the first or second positions, or to positions intermediate the first and second positions, for example the intermediate position shown in FIG. 1. 
     It will be clear to one skilled in the art that the air flowing through opening (21) will flow at a higher velocity than that flowing through opening (22) due to the impedance effect of the heater core (15) in the second passage (11). The consequence of this is that a larger volume of cooled air per unit time will enter the mixing chamber (20). The average temperature of the air in the mixing chamber can be controlled by selecting a different position of the blend door and the blend door could thus be moved in an anticlockwise direction so as to rather more obscure the flow of cold air so as to achieve a desired average temperature in the mixing chamber. However, the more rapidly flowing cool air will still tend to predominate on the left hand side (as seen in FIG. 1). As a result, air-outlets such as outlet (51) on the left hand side of the air mixing chamber will tend to have colder air than air mixing outlets such as outlet (52) on the right hand side of the chamber. 
     FIG. 2 shows the blend door device (40) of FIG. 1 in the second position, such that flow of heated air into the mixing chamber is substantially prevented. 
     Referring now to FIG. 3, a blend door device in accordance with the present invention is shown. 
     The blend door device (140) consists of three flap members (141,142,143). Each of the flap members is a substantially similar planar body of plastic material, the three flap members pivotally hinged at one end thereof about a common axis (150). It would alternatively be possible to use other materials, for example metal, which could be stamped or cast for instance. The first and third flap members (141,143) are connected together by a coupling (144) and are pivotally mounted on an axle (151). A first crank member (152) is secured to the third flap member (143) so that rotation of the crank member will cause the first and third flap members to rotate on the axle (151). 
     The second flap member (142) is rigidly secured to the axle (151) , and at one end of the axle a second crank member (153) is secured so that rotation of the flap member (153) causes the second flap member (142) to rotate independently of the first and third flap members (141,143). 
     It would also be possible for the two flap members to be on separate axles disposed close together. 
     Continuing to refer to FIG. 3, it will be seen in the embodiments shown that the first flap member (141) has a surface portion (160) which overlaps an adjacent portion (161) of the second flap member (142) with the flap member (142) lying under the flap member (141) in the position shown. Likewise, at the other end of flap member (142) the third flap member (151) has a portion (162) which overlaps the underlying portion (163) of the second flap member (142). 
     It would alternatively be possible for the flap members to abut along their edges. Sealing together is highly desirable. It would also be possible for the flap members to engage separate openings defined by the housing. 
     It will thus be apparent to one skilled in the art that movement of the second flap member (142) in an anticlockwise member will cause, by virtue of the engagement of the second flap member with the first and third flap members, all three of the flap members to move in an anticlockwise direction. Alternatively, it is possible to move the first crank member (153) in an anticlockwise direction so as to move the first and third flap members (141,143) and then to move the second flap member (142) via the second crank member (153) to a desired position. 
     FIG. 4 shows a second embodiment of the blend door device in accordance with the invention, this time having five flap members (171,172,173,174,175). Referring to FIG. 4 the first, third and fifth flap members are shown in a position which closes portions of the cold air opening (21) whereas the second and fourth flap members (172,174) are closing the hot air opening (22). The effect of this is to open three flow passages for heated air, and two flow passages for cooled air. However, because the second and fourth flap members are fully opened, the cooled air flows across the full width of the air mixing chamber as does the heated air from the outlets caused by the opened flap members (171,173,175). 
     As a result, stratification of the air flow in the air mixing chamber is reduced and improved mixing occurs. 
     It will be understood by one skilled in the art that the flow control device can be used in conventional heater systems, i.e. without an evaporator, or in any situation where two air flows are to be mixed together. 
     Although preferred embodiments of the invention have been described it will be clear that the invention is not to be limited thereto but instead has the full extent defined by the appended claims.