Abstract:
A novel check valve for an exhaust device is formed from a thin flexible plate. A plurality of flaps is formed in the thin flexible plate. The flaps are arranged in a vertical manner to form at least one column of flaps. A stopper is coupled to a back side of the thin flexible plate. The stopper prevents the plurality of flaps from moving towards the stopper.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates generally to a device for preventing backflow in a cooling system, and more particularly, to a fan check valve having a plurality of flaps, wherein the flaps control airflow in a single direction.  
         [0003]     2. Background Information  
         [0004]     Enclosed electronic systems, which run on continuous operation, generally employ a system for cooling the enclosure. Most cooling systems typically employ some type of fan or blower. Many cooling systems employ redundant fans that are arranged in parallel. This arrangement is used to guard against catastrophic loss of cooling flow in the event of a single fan device failure. One problem with this type fan configuration is that when one fan fails, the pressure difference across the surviving fan pushes air backwards through the failed fan. This reduces the delivered flow rate that would otherwise be available from the surviving fan(s), a significant fraction of the overall fan output.  
         [0005]     To prevent back flow, the normal practice is to add a flap-type device on the exhaust side of the fans. Prior flapper designs include swinging door flaps, multiple slat vanes, and helical vanes for tubeaxial fans. However, prior art designs consume valuable packaging space and may fail to operate properly in situations where the exhaust flow must turn at any angle to the axially discharging flow, as would be encountered for example in the tightly confined chassis space within a server rack drawer. Under these conditions, transverse flow from surviving fan(s) can prevent the flaps from properly sealing a failed fan if the flow traversing the failed fan re-opens the flaps in shear.  
         [0006]     Therefore, it would be desirable to provide a device that prevents backflow in a cooling system. The device must overcome problems associated with prior art designs.  
       SUMMARY OF THE INVENTION  
       [0007]     It is, therefore, a principle object of this invention to provide a device for preventing backflow in a cooling system.  
         [0008]     It is another object of the invention to provide a device for preventing backflow in a cooling system that solves the above mentioned problems.  
         [0009]     These and other objects of the present invention are accomplished by the device for preventing backflow in a cooling system disclosed herein.  
         [0010]     In an exemplary aspect of this invention, a check valve for an exhaust device is formed from a thin flexible plate. A plurality of flaps is formed in the thin flexible plate. The flaps are arranged in a vertical manner to form at least one column of flaps. One or more stoppers are coupled to a back side of the thin flexible plate. The stopper prevents the plurality of flaps from moving towards the stopper when the pressure reverses in fan fail mode. The backstop function of the stopper may be provided by a bar member, a separate metal or plastic grid attached to the fan, or integral to the chassis, either of which additionally serves as a safety finger guard.  
         [0011]     The foregoing and other objectives, features, and advantages of the invention will be apparent from the following, more particular, description of the preferred embodiment of the invention, as illustrated in the accompanying drawings.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]     The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself, however, as well as a preferred mode of use, further objectives, and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein like reference numerals indicate like components, and:  
         [0013]      FIG. 1A  is a back view of an exhaust fan valve of the present invention.  
         [0014]      FIG. 1B  is a front view of the exhaust fan valve of  FIG. 1A  installed on a cooling fan.  
         [0015]      FIG. 2  is an exploded view of  FIG. 1B .  
         [0016]      FIG. 3  is an elevated perspective view of the exhaust fan valve of  FIG. 1A  installed on a cooling system with the flaps aligning their opening angle with the preferred flow turning direction.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0017]     The invention will now be described in more detail by way of example with reference to the embodiments shown in the accompanying figures. It should be kept in mind that the following described embodiments are only presented by way of example and should not be construed as limiting the inventive concept to any particular physical configuration.  
         [0018]     Further, if used and unless otherwise stated, the terms “upper,” “lower,” “front,” “back,” “over,” “under,” and similar such terms are not to be construed as limiting the invention to a particular orientation. Instead, these terms are used only on a relative basis.  
         [0019]     With reference now to the figures, and in particular with reference to  FIG. 1A , there is depicted a rear view of the fan valve  10  of the present invention. The fan valve  10  is formed of a thin flat flexible plate  12 . The plate  12  is generally some type of plastic or film material. A plurality of flaps  14  are formed in the plate  12 . The flaps  14  are formed so as to allow air flow to move freely out of the fan  26  ( FIG. 1B ) and turn at an angle, normal to the axis of discharging flow. The flaps  14  are cut in a “U” shaped fashion such that each flap  14  will have a pair of side edges  16  and a bottom edge  18 . The flaps  14  are generally slightly tapered. Thus, the side edges  16  on a bottom section  17  are closer together than the side edges  16  on a top section  19  of the flaps  14 .  
         [0020]     The flaps  14  may be formed in a plurality of different configurations. In accordance with one embodiment, the flaps  14  are formed in a column  20 . The fan valve  10  may have one or more columns  20 . In the embodiment depicted in  FIG. 1A , three columns  20  are shown. However, this should not be seen as to limit the scope of the present invention. The flaps  14  are formed in a vertical manner. In this embodiment, the bottom section  17  of a flap  14  will contact a top section  19  of a flap  14  immediately below. The above embodiment allows one to make a cost effective design formed out of a single piece of material.  
         [0021]     The flaps  14  are designed to align their opening angle with the preferred flow turning direction. In normal operation, each flap  14  independently self-aligns with the flow direction to minimize aerodynamic drag. Minimization of aerodynamic drag is a critical performance consideration, because excess drag requires higher fan speeds, higher acoustic levels, and generally reduces the overall availability of cooling flow. This self alignment is made possible by the tapered cut in each flap  14  wherein each flap&#39;s construction allows the connection to behave as a low-bending-force hinge. If the hinge is not thin enough, the flap will not properly align and the resulting angle of incidence with respect to oncoming flow will lead to high drag force and pressure losses which diminish the output of the fan. A higher degree of self-alignment is possible with the flexible material, as compared to fixed solid vane designs.  
         [0022]     However, due to curvature of flowstreams over the span of the flap chord, a finite degree of non-alignment is present, which will induce a turning moment of the airstream in the direction of the flapper opening angle. The overall orientation of the flapper assembly thus also functions to turn the airflow in a preferential direction with respect to the initial discharge axis, similar to a set of airflow turning vanes formed by a cascade of flat plates.  
         [0023]     The embodiment of the flaps  14  does not rely on the action of gravity for flap  14  closure and therefore may be operated in any direction with respect to gravity. This is a significant advantage over heavy pivoted solid flap designs which rely on gravity to assist closure.  
         [0024]     One or more stoppers  22  will be coupled to the plate  12 . The stoppers  22  are used to prevent each flap  14  from moving in a direction towards the fan  26 . The backstop function of the stopper  22  may be provided by a bar member  22   a , a separate metal or plastic grid attached to the fan, or integral to the chassis, either of which additionally serves as a safety finger guard, tab members, or any other mechanism designed to prevent the flaps  14  from moving in a direction towards the stopper  22 .  
         [0025]     In accordance with one embodiment of the present invention, the stopper  22  is a bar member  22   a . Each column  20  of flaps  14  will have a bar member  22   a  which will run the length of the column  20 . The bar  22   a  is used to prevent the flaps  14  from moving in a direction towards the bar member  22   a . Thus, the flaps  14  can only move in a direction away from the bar  22   a . Since the flaps  14  can only move away from the bar  22   a , backflow through the fan valve  10  is prevented.  
         [0026]     A plurality of holes  24  are formed on the plate  12 . The holes  24  are used for mounting the fan valve  10  on a fan  26  ( FIG. 1B ). The holes  24  are generally formed around the outer perimeter of the plate  12 . In the embodiment depicted in  FIG. 1A , the holes  24  are formed in each corner of the plate  12 . However, this should not be seen as to limit the scope of the present invention. It should also be noted that other means may be used to mount the fan valve  10  on a fan  26  ( FIG. 1B ). For example, an adhesive may be placed around the outer perimeter of the back side of the fan valve  10 .  
         [0027]     Referring now to  FIG. 1B , the fan valve  10  is shown mounted on an exhaust device  26 . The fan valve  10  may be coupled to any type of exhaust device  26  such as a fan or blower. The preferred embodiment exhaust device  26  has a low exhaust swirl component, which would encompass centrifugal blowers, radial blowers, or tubeaxial fans with flow-straightening discharge stators.  
         [0028]     The fan valve  10  is mounted to the exhaust side  28  of the exhaust device  26 . The exhaust device  26  is typically used in parallel with other exhaust devices  26  to circulate air and cool electrical components inside an enclosure  40  ( FIG. 3 ).  
         [0029]     Referring now to  FIG. 2 , one embodiment of the exhaust device  26  is shown. In this embodiment, the exhaust device  26  is a fan  26 A. The fan  26 A comprises a fan motor  30  with an impeller  32 , a grill or cover  34 , a back plate  36 , and an optional foam seal  38  between the fan motor  30  and back plate  36 . As stated above, the fan valve  10  is mounted to the exhaust side  28  of the fan  26 A.  
         [0030]     As shown in  FIG. 3 , fans  26 A are used to draw air through the enclosure  40 . Since the enclosure  40  has a partition  42 , fans  26 A are placed on both sides of the partition  42 . As stated above, the fan valve  10  is mounted to the exhaust side  28  of the fans  26 A. The flaps  14  of the fan valve  10  will only move a direction away from the bar  22  and thus away from the fan  26 A. Thus, in case any of the fans  26 A fail, the fan valve  10  will prevent any back flow into the enclosure  40 .  
         [0031]     It should be understood, however, that the invention is not necessarily limited to the specific process, arrangement, materials and components shown and described above, but may be susceptible to numerous variations within the scope of the invention.  
         [0032]     It will be apparent to one skilled in the art that the manner of making and using the claimed invention has been adequately disclosed in the above-written description of the preferred embodiments taken together with the drawings.  
         [0033]     It will be understood that the above description of the preferred embodiments of the present invention are susceptible to various modifications, changes and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.