Patent Publication Number: US-6705833-B2

Title: Airflow flapper valve

Description:
FIELD OF THE INVENTION 
     This invention relates to the field of blowers for equipment enclosures. In particular, this invention is directed to the elimination of reverse airflow through blowers. 
     BACKGROUND OF THE INVENTION 
     Cabinetry or enclosures for heat generating equipment may contain one or more blowers for active or forced air cooling. The blower displaces the air within the enclosure volume with cooler air external from the enclosure volume. The blower acts as a pump to transfer air between the two environments. Air pumped from the interior by the blower is replaced with air external to the enclosure through the vents or ports of the cabinet or enclosure. Alternatively, air pumped from the exterior of the enclosure into the enclosure displaces the air in the enclosure through the vents. Heat generating components requiring forced air cooling may overheat resulting in erratic, unpredictable behavior or a shortened lifespan among other maladies if there is no active cooling. 
     Blower systems may incorporate multiple blowers for redundancy or to achieve a specific airflow pattern in order to ensure adequate cooling. The failure of a single blower, however, creates a new source for air via its exhaust or intake vent. As a result, the airflow patterns within the enclosure may be sufficiently disrupted which prevents adequate cooling or which significantly decreases the efficiency of redundant blower systems. 
     Baffles may be used to prevent reverse airflow. Baffles have a number of members that pivot to enable opening and closing the baffle. Passive baffles typically rely on gravity or springs to keep the baffles closed when the blower is off. During normal operation, passive baffles rely upon the pressure developed by the blower to open. Active baffles require power and airflow detecting control circuitry at least to open the baffles. These passive or active baffle designs tend to introduce complexity into the manufacturing and assembly of the equipment enclosures. The active baffles undesirably require additional electrical connections and introduce additional points of failure due to the electrical components. The passive baffles additionally tend to significantly impede the flow of air through the blower exhaust thus imposing greater performance requirements on the blowers. 
     SUMMARY OF THE INVENTION 
     In view of limitations of known systems and methods, methods and apparatus for assembling a blower having a one-way valve are provided. 
     A method of assembling a blower includes the step of providing a blower housing having at least one channel. A flexible sheet having at least one flap is attached to the blower housing such that the flap overlaps the channel to form a one-way valve. The flexible sheet may include mounting features such as holes to facilitate assembly. For example, in one embodiment, the flexible sheet is pressed onto a plurality of pegs residing on the blower housing such that the holes receive the pegs. In another embodiment, the flexible sheet is pressed onto a plurality of pegs residing on an exhaust cover that is subsequently attached to the blower housing. 
     A blower apparatus includes a blower housing having a plurality of channels at an exhaust port. A flexible sheet having a plurality of flaps is coupled to the blower housing such that each flap overlaps at least one channel to form a one-way valve. 
     Other features and advantages of the present invention will be apparent from the accompanying drawings and from the detailed description that follows below. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention is illustrated by way of example and not limitation in the figures of the accompanying drawings, in which like references indicate similar elements and in which: 
     FIG. 1 illustrates one embodiment of airflow patterns in an enclosure utilizing a plurality of blowers for forced air cooling. 
     FIG. 2 illustrates disruption of airflow patterns due to reverse airflow through a failed blower. 
     FIG. 3 illustrates one embodiment of a flapper valve. 
     FIG. 4 illustrates one embodiment of the flapper valve and a blower housing. 
     FIG. 5 illustrates one embodiment of a method of assembling a blower having a one way valve. 
     FIG. 6 illustrates an alternative embodiment of a method of assembling a blower having a one way valve. 
    
    
     DETAILED DESCRIPTION 
     In a typical redundant air mover or blower system, the system must be designed to adequately accommodate both the loss of pumping ability and the reduction in efficiency due to changed airflow patterns. In a system having multiple air movers specifically to achieve a particular airflow pattern without regard to redundancy, the introduction of a new source (or sink) of air may disrupt the airflow patterns sufficiently to prevent adequate cooling. 
     Air movers are effectively air pumps formed by a motor having an impeller for a rotor. The impellers comprise a plurality of air moving surfaces such as blades. Air mover impellers may be classified as axial flow, centrifugal (i.e., radial) flow, or mixed flow with respect to how the air is moved relative to the axis of rotation of the impeller. The motor and blade designs are driven by the efficiency and power requirements of the application. The term “blower” will be used interchangeably with “air mover”. 
     FIG. 1 illustrates one embodiment of an equipment enclosure  100  having a plurality of blowers  110 ,  120 ,  130  and vents  140 . In this embodiment, airflow pattern indicators  150  show that forced air cooling is achieved when air external to the enclosure passes through vents  140  when replacing the air being pumped out of the enclosure by the blowers. 
     The number and placement of the blowers may have been chosen for the purpose of redundancy or to achieve a specific airflow pattern without regard to the possibility of failure. FIG. 2 illustrates an enclosure  200  with operating blowers  210  and  230  and failed blower  220 . The blowers reside at interfaces between the inside and the outside of the enclosure  200  and thus serve as unintended sources for external air compared to any other vents  240  in the event of failure. Reverse airflow through failed blower  220  undesirably disrupts the airflow  250  through the enclosure  200 . 
     FIG. 3 illustrates one embodiment of a passive baffle blower flapper valve  300 . The flapper valve  310  is made of a thin, resilient, flexible material. The valve preferably includes a plurality of valves variously referred to as doors, flaps, flappers, valves, or louvers  312 - 314 . Positive airflow from the blower causes the flaps or louvers  312 - 314  to flex open such that exhaust air may exit. When positive airflow ceases, the flaps return to the closed position. Due to the use of a thin, flexible material, this valve design does not significantly impede exhaust airflow. The valve of the illustrated embodiment introduces negligible resistance to airflow. Airflow resistance is a function of the number and design of the door cut outs, enclosure design, flapper valve thickness, and flapper valve material among other factors. 
     Any number of materials may be selected for the valve  300  including a variety of plastics, rubber, silicon rubber, elastomers, or even coated fabrics. A coated fabric such as COHRlastic® may be used to ensure meeting certain thermal ratings. The flapper material is sufficiently resilient to retain the louver substantially closed when its associated blower is not active. 
     The flapper valve may formed by die cutting the selected material. In one embodiment, the flapper valve incorporates a plurality of mounting holes  302 ,  304  or other mounting features to facilitate mounting on the blower housing. 
     FIG. 4 illustrates one embodiment of a blower housing  410 , flapper valve  420 , and exhaust cover  430 . Blower housing  410  incorporates a motorized blower (not indicated). The motorized blower has an impeller with a plurality of blades. Common blade configurations include airfoil, backward inclined, backward curved, radial, paddle and forward curved configurations. 
     The housing  410  is designed with a plurality of channels  412  for the flaps  422 . When the flapper valve  420  is attached to the blower housing, the flaps  422  overlap the channel  412  boundaries  440  to prevent the flaps from opening inwards, thus eliminating reverse airflow through the blower. 
     In one embodiment, the flapper valve includes a plurality of mounting features  454  to facilitate attachment to the exhaust cover and/or the blower. The cover and the blower housing may also have features that cooperate with the mounting features of the flapper valve. 
     In the illustrated embodiment, the cover  430  includes a plurality of pegs  452  which pass through corresponding holes  454 ,  456  in the flapper valve and in the blower housing, respectively. The cover is designed to permit the flaps  422  to flex outwards when the blower is active. The channel boundaries, however, prevent the flaps from opening inwards. 
     In an alternative embodiment, pegs may be located on the blower housing. The flapper valve is pressed onto the blower housing so that the plurality of mounting holes receive the pegs. An exhaust cover may be provided to ensure that the valve is retained on the pegs. 
     FIG. 5 illustrates one embodiment of a method of assembling the blower apparatus incorporating the one-way valve. In step  510 , a blower housing having a plurality of channels is provided. A flexible sheet having a plurality of flaps is provided in step  520 . In step  530 , the flexible sheet is attached to the blower housing such that each flap overlaps at least one channel to form a one-way valve. 
     FIG. 6 illustrates an alternative embodiment of a method of assembling a blower apparatus incorporating a one-way valve. In step  610 , a blower housing having a plurality of channels is provided. A flexible sheet having a plurality of flaps is provided in step  620 . The flexible sheet is attached to an exhaust cover in step  630 . The cover is then placed on the blower housing such that each flap overlaps a channel to form a one-way valve. 
     In the preceding detailed description, the invention is described with reference to specific exemplary embodiments thereof. Various modifications and changes may be made thereto without departing from the broader spirit and scope of the invention as set forth in the claims. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.