Abstract:
Anti-fogging systems for air-cooled, piston powered single engine aircraft which effectively prevent windshields from fogging during cold weather by directing a forceful stream of unheated, ambient air in a direction which intercepts exhaled air from an aircraft occupant to impede the moist exhaled air from directly reaching the windshield and condensing on the windshield. The disclosed systems keep the windshield of a small air-cooled, piston powered single engine aircraft from fogging while permitting a pilot to perform his pre-flight preparation, taxi and takeoff in cold climates.

Description:
[0001]    The present invention is directed to anti-fogging systems for small, air cooled, piston powered, single engine aircraft which temporarily prevents warm, moist exhaled air from directly reaching a cold windshield of an aircraft with an intercepting, forceful stream of ambient air. The disclosed systems prevent fogging by carrying moist exhaled air away from the windshield and aggressively mixing it with cabin air. The present invention is particularly beneficial before the engine has sufficiently heated up e.g. during preflight checks, taxiing, and takeoff in cold climates. 
       BACKGROUND 
       [0002]    Various systems have been suggested for defrosting the windshield of an aircraft, i.e. for removing frost after the frost has formed on the windshield. Large planes, commercial aircraft, jet aircraft and military helicopters are equipped with very extensive heating, defogging and air conditioning systems for the cabin, whether in flight or on the ground. Multi-engine, piston powered airplanes have auxiliary gas powered heaters which are usually ignited immediately after the engines are started. Such heaters include a combustion chamber, a heat exchange system and a battery-powered blower. Soon after being ignited, the auxiliary heater begins delivering heat to the cabin including the windshield&#39;s defrosting system without the need for aircraft motion or ram effect. 
         [0003]    Small piston powered, single engine aircraft, however, are normally equipped with simple systems which, when in flight, take in outside air and the ram speed of the aircraft pushes the ambient air past a portion of the aircraft&#39;s exhaust system where it is heated and then through ducts into the cabin. Unfortunately, when such an aircraft is not in flight, there is virtually no ram air pushing through the heating system. Such systems also require sufficient heat from the engine. Also, some single engine, piston driven aircraft have no defrost provisions. This can create serious visibility problems in cold, wintry conditions, particularly in northern climates such as those found in Canada or the northern United States. During pre-flight preparations, engine start up, warm up, taxiing, and takeoff prior to flight, the cabin is not usually heated or is heated insufficiently by existing heating systems to defrost the windshield. During cold months, this can cause a very serious problem since the pilot&#39;s visibility of the outside can be poor because of fogging windows. During taxi and takeoff, this can lead to serious accidents. 
         [0004]    Systems have been suggested for enhancing the heat supply to the defrosting systems for small aircrafts. For example, the present inventor disclosed a blower assisted heating and defogging system for small aircraft in U.S. Pat. No. 7,017,828 which utilizes heated air from a muffler shroud to heat external air drawn from outside the aircraft with the blower. 
         [0005]    Thus, various systems have addressed the issue of clearing frost from a windshield, but have not addressed the problem of fogging windshields by impeding moist exhaled air from reaching a windshield and thereby preventing frost from forming on the windshield in the first instance. 
       SUMMARY OF THE INVENTION 
       [0006]    Disclosed are anti-fogging systems for small, air-cooled, piston-powered single engine aircrafts which temporarily, effectively prevent windshields from fogging during cold weather by directing a forceful stream of unheated ambient air in a direction which intercepts exhaled air from an aircraft occupant to prevent the exhaled air from directly reaching the windshield. An embodiment of the present invention has been found useful to effectively keep the windshield of a small, air-cooled, piston powered single engine airplane from fogging while permitting a pilot to perform his pre-flight checklist, taxi and takeoff. The present invention significantly enhances the safety of small, air-cooled, piston powered single engine aircraft operation in cold climates commonly found in Canada and northern parts of the United States during cold seasons. Unlike previously disclosed systems which are designed to remove frost which has already formed on a windshield, the disclosed embodiments provide inexpensive systems designed to prevent moist, exhaled air from directly reaching a cold windshield by intercepting the exhaled air with a forceful stream of ambient air before the exhaled air reaches the windshield. 
         [0007]    One preferred embodiment comprises an anti-fogging system in an air-cooled, piston powered single engine airplane, where the airplane comprises a cabin, a dashboard, an instrument panel comprising a rearwardly facing surface, and a windshield. The dashboard is typically positioned below at least most of the windshield. The anti-fogging system comprises at least one electrically powered blower preferably located in the cabin. The blower is connected to at least one air conduit to form a continuous air passage from an inlet end to an outlet end. The inlet end of the air passage is located in the cabin, preferably below the dashboard, to receive ambient cabin air. The outlet end of the air passage is configured to direct a forceful stream of the ambient air received from the inlet end rearwardly of the windshield. The forceful stream is most preferably directed upwardly in the cabin. The system and specifically the air passage do not comprise a heater or other mechanism for altering the temperature or the humidity of the ambient air. This minimizes the cost and weight of the disclosed systems. In operation, the blower creates a forceful stream of ambient air which exits the outlet and directly intercepts exhaled air from the pilot and/or other occupant to prevent warm, moist exhaled air from directly reaching the windshield. By positioning the inlet of the air passage below the dashboard, the inlet draws in relatively dry, ambient air which has a dew point below the temperature of the windshield as compared to air that is exhaled by the pilot/passengers which has a higher moisture content and would otherwise condense on the windshield when the temperature of the windshield is below the dew point for the exhaled air reaching the windshield. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a cross-sectional view of one embodiment of the present invention. 
           [0009]      FIG. 2  is a cross-sectional view of a blower and air conduit connected to a firewall and dashboard. 
           [0010]      FIG. 3  is a close-up view of the embodiment shown in  FIG. 1 . 
           [0011]      FIG. 4  is a top view showing the outlet of the embodiment of  FIG. 1   
           [0012]      FIG. 5  is a partially exploded, perspective view of the blower and air conduit of  FIG. 1 . 
           [0013]      FIG. 6  is a right side view of the blower and air conduit shown in  FIG. 1 . 
           [0014]      FIG. 7  is a top view of the blower and air conduit shown in  FIG. 1 . 
           [0015]      FIG. 8  is a bottom view of the blower and air conduit shown in  FIG. 1 . 
           [0016]      FIG. 9  is a side view of the blower of the embodiment of  FIG. 1 . 
           [0017]      FIG. 10  is a top view of the blower of  FIG. 1 . 
           [0018]      FIG. 11  is a front view of the blower of  FIG. 9 . 
           [0019]      FIG. 12  is a front view of the forward portion of an aircraft cabin showing the instrument panel and part of the anti-fogging system of  FIG. 1 . 
           [0020]      FIG. 13  is a close-up view of the switch shown in  FIG. 12 . 
           [0021]      FIGS. 14 and 15  are cross sectional views of an alternative embodiment of the present invention. 
           [0022]      FIG. 16  is a perspective view of a blower and air conduits of a still further embodiment of the present invention comprising two outlets. 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    The disclosed embodiments provide anti-fogging systems which utilize untreated ambient air to forcefully intercept the warm, moist air exhaled by the occupant(s) to prevent it from directly reaching a cold windshield of the aircraft. As used herein, the term “occupants” includes pilots and passengers. As used herein the term “untreated ambient air” is used to indicate that the air is not heated or dehumidified, such as by a heating coil or compressor. The ambient air is preferably drawn from an area somewhat remote from the occupants exhaled breath, and most preferably from a location lower than the dashboard. One disclosed embodiment comprises a small, air-cooled, piston powered single engine airplane. Another disclosed embodiment comprises a kit for use in an air-cooled, piston powered single engine aircraft. 
         [0024]      FIG. 1  is a cross-sectional view of a forward portion of an exemplary air cooled, piston powered, single engine airplane of the type for which the disclosed anti-fogging systems are particularly useful.  FIG. 1  illustrates the passenger portion of a cabin of a Piper Super Cub which includes two tandem seats  25 , each comprising a control stick  29 . The cabin is generally defined by a firewall  10  and windshield  20  in the forward region, the fuselage roof  21  above, a storage compartment wall  24  in the rear, and the fuselage floor  23 , plus the sidewalls and doors which are not shown in the figures. It will be appreciated that cabins of small piston powered single engine aircraft, come in various shapes and sizes. Some Piper Super Cubs do not have storage compartment walls  24 , in which case the cabin would include a storage area located further aft of the illustrated wall  24 . In this illustrated embodiment, the cabin is only one seat wide, but the present invention is applicable to air-cooled, piston powered, single engine aircraft having larger cabins such as those with side-by-side seating. 
         [0025]    With reference to  FIGS. 1-3 , the illustrated anti-fogging system comprises a blower  50  having an inlet  52  and an air conduit  30 . The air conduit  30  has an outlet  36  which in this illustrated embodiment is secured to dashboard  40 . The blower  50  and air conduit  30  are mounted on the aft side of firewall  10 . The illustrated air conduit  30  is generally S-shaped and extends from the outlet of blower  50  upwardly adjacent to the firewall  10  and through the dashboard  40  with the outlet  36  secured to the dashboard  40 . 
         [0026]      FIG. 2  is a cross-sectional view of the anti-fogging system showing the blower motor  51  and vanes  53  of blower  50 .  FIG. 2  also illustrates electrical leads  54  which connect fan motor  51  to switch  47  on instrument panel  45  as shown in  FIGS. 12 and 13 . Fan  50  draws air into inlet  52  and creates a forceful stream of air which travels up through air duct  30  and exits outlet  36 . Baffles  35  of outlet  36  initially direct the forceful stream of air in the direction of arrow A shown in  FIG. 2 . 
         [0027]    In location A in  FIG. 1 , the dashed lines are extensions of the baffles  35  of outlet  36 . The dashed lines at A better illustrate that the baffles are directed rearwardly of windshield  20  so that the forceful stream of air is directed rearwardly of windshield  20  and not directly at the windshield  20 . As illustrated in  FIG. 1 , the outlet stream of air is most preferably directed rearwardly of windshield  20  and forwardly of pilot P. For example, the air can be directed parallel to the angle of the windshield or at a lesser angle than the angle of the windshield, i.e. angled more rearwardly than the angle of the windshield, as measured by angle W in  FIG. 3 . The purpose of the present invention is to prevent moist exhaled air from directly reaching the windshield in order to avoid the fogging of the windshield by moist exhaled air, rather than trying to remove frost from a windshield by defrosting. Successful defrosting in a very cold climate requires heated air. The various embodiments of the present invention do not rely upon heated air or otherwise modifying the air, for example by dehumidification. Moist, exhaled air from the occupants is intercepted and urged upwardly and rearwardly away from the windshield as indicated by the extension of the dashed lines in  FIGS. 1 and 3 , as well as in  FIGS. 14 and 15  described below. The present invention has been proven to work very effectively in preventing a cold windshield from fogging during pre-flight checks, taxiing and take-off in a cold climate. The baffles  35  shown in  FIG. 2  are relatively long, however it is within the scope of the present invention to use baffles of different sizes, including baffles which are flush with dashboard  40 . The relatively large baffles  35  shown in  FIG. 2  illustrate the angular orientation of the baffles  35 . 
         [0028]      FIG. 3  is a close-up of the anti-fogging system illustrated in  FIG. 1 . The angular orientation of baffles  35  relative to windshield  20  is generally illustrated by the dashed lines at position A. In this illustrated embodiment, the baffles are positioned on angles to direct air rearwardly of windshield  20  and, most preferably, forwardly of the occupants. Ideally, the warm, moist exhaled air from the occupants is pushed toward the rear of the cabin away from windshield  20 . 
         [0029]      FIG. 4  is a top perspective view of the forward pilot area of the cabin showing seat  25 , control stick  29  and outlet baffle plate  37  which passes through dashboard  40  just aft of structural support struts  27  which are aft of windshield support  22  which seals the windshield to the fuselage. 
         [0030]      FIG. 5  is a perspective view of the anti-fogging system shown in  FIG. 1  prior to installation. As illustrated, fan  50  comprises mounting brackets  58  for mounting the fan on the firewall  10 . Electrical leads  54  supply electricity to fan  50 . As illustrated in  FIG. 5 , outlet baffle plate  37  comprising baffles  35  is connected to conduit outlet  36  with screws. The screws pass through outlet baffle plate  37 , dashboard  40  and an upper flange  39  of air conduit  30 . Outlet baffle plate  37  has baffles  35  which direct the out-flowing air in the direction of the dashed lines at location A, as shown in  FIGS. 1-3 . 
         [0031]    One embodiment comprises an anti-fogging system in an air-cooled, piston powered single engine aircraft wherein the outlet of the air conduit comprises baffles angled away from said windshield. 
         [0032]    In another embodiment, the baffles are disposed at an angle no closer to the windshield than parallel to the angle of the windshield. Alternatively, the baffles are angled at least 5° more rearwardly than the angle of the windshield or at least 10° more rearwardly than the angle of the windshield. The term “angle of the windshield” is used to indicate the rearward slope of that portion of the windshield which is on or closest to the centerline of the plane. 
         [0033]    The windshield on the aircraft shown in  FIGS. 1 ,  3 ,  14 , and  15  is inclined at 35° from the dashboard; however, some airplanes have windshields inclined more or less than this angle. In one embodiment, the angle of the baffles is such that it directs the stream of air parallel to the windshield to minimize the losses of flow caused by the fins themselves. So in the case of a windshield angled 35° from the dashboard, baffles also angled at 35° from the dashboard optimize the performance of the blower by moving the air up and away from the windshield. In the alternative embodiments, the baffles on this particular plane would be angled no more than 30° or no more than 25° from the dashboard, respectively. The forwardmost air openings of outlet  36  or outlet baffle plate  37  are preferably spaced at least 3-5 inches from the base of the windshield. 
         [0034]      FIG. 6  is a right side view of the anti-fogging device shown in  FIG. 5  showing the baffles  35  of outlet plate  37  which is connected to upper flange  39  via screws, air conduit  30 , blower  50 , inlet  52 , mounting brackets  58  and electrical leads  54 .  FIG. 7  is a top view of the anti-fogging device shown in  FIG. 6 . As shown in the bottom view of  FIG. 8 , the inlet end  52  of blower  50  comprises a screen  55  which prevents debris and other objects from being drawn into blower  50 . 
         [0035]      FIGS. 9 ,  10 , and  11  are side, top, and front views, respectively, of blower  50  with the internal motor  51 , vanes  53  and electrical connectors  54  shown in phantom in the blower housing. Blower  50  is preferably a light-weight, highly efficient axial vane blower which creates a forceful air flow of about 100 CFM, preferably about 120 CFM, for example, an Attwood Turbo 3000 in-line axial blade blower. 
         [0036]    As noted above, the anti-fogging systems of the present invention do not contain any components which change the temperature or humidity of the ambient air. 
         [0037]      FIGS. 12 and 13  are a front view (looking forwardly from the pilot&#39;s seat) and a partial close-up of the instrument panel  45  and aft side of firewall  10  in the forward section of the cockpit.  FIG. 12  shows blower  50 , the lower portion of air conduit  30 , instrument panel  45  and outlet  36 . As best illustrated in  FIG. 12 , leads  54  from blower  50  are connected to a switch  47  located on the instrument panel  45 . The illustrated leads are illustrated in dashed lines to indicate that they are not exposed to avoid inadvertent damage during operation of the aircraft.  FIG. 13  is a close-up view of anti-fogging system switch  47 . 
         [0038]      FIGS. 14 and 15  illustrate an alternative embodiment of the present invention that has a blower inlet  152  positioned higher than blower inlet  52  shown in  FIG. 1 . In the embodiment of  FIG. 14 , the actual blower can be positioned higher, the blower can be provided with a shorter housing, or a section of conduit  130  can be shorter in order to effectively raise the position of inlet  152  in the cabin. In order to maximize the efficiency of the blower, in this embodiment and all other embodiments of the present invention, it is preferable to make the conduits as short as possible while connecting the outlet with the desired inlet position. Since warm air rises, it is preferable that the inlets of the present invention be positioned below the level of the dashboard. Though not illustrated, a portion of a conduit can be provided below the blower. 
         [0039]    The embodiment shown in  FIGS. 14 and 15  comprises a baffle plate having baffles  135  which are angled more rearwardly than the angle of the windshield in order to direct the forceful stream of ambient air in the direction of the dashed lines at location B shown in  FIGS. 14 and 15 . 
         [0040]    According to an alternative embodiment shown in  FIG. 16 , particularly used for wider planes such as a Cessna 172 or Piper Cherokee, the anti-fogging system comprises a plurality of blowers and/or air conduits and outlets. While a plurality of the blower/conduit arrangements shown in  FIGS. 1-5  can be utilized at different locations along the width of a small aircraft, in order to save weight, it may be preferable to provide a single high volume blower  250  connected to a conduit  230  having a plurality of outlets. As shown in  FIG. 16 , an alternative embodiment of the present invention comprises a single blower  250  comprising leads  254  and mounting brackets  258  connected to a generally Y-pipe type air conduit  230  comprising two sets of outlets  236  and outlet baffle plates  237 . This configuration saves weight and cost when compared to a system having separate blowers and conduits for each outlet. The blower is sufficiently powerful in terms of air output volume and velocity to intercept warm moist exhaled air from the occupants and preferably each outlet has an output of 80 CFM, most preferably at least 100 CFM.