Patent Publication Number: US-2023146980-A1

Title: Lightweight Low-Profile Vent Systems for Aircraft Fluid Dispersion Tanks

Description:
FIELD OF THE DISCLOSURE 
     This patent generally pertains to agricultural and firefighting product dispersal systems of aircraft and more specifically to means for venting the tanks that contain the product. 
     BACKGROUND 
     Some aircraft (e.g., airplanes and helicopters) are used as crop dusters or air tankers for agricultural and/or firefighting purposes. Such aircraft typically include a bulk container (e.g., a tank or a hopper) for carrying a flowable bulk product, such as dry fertilizer, liquid fertilizer, pesticide, fire extinguishing liquid, water, etc. 
     To selectively release the product, in some examples, a linkage assembly connects a manually operated lever in the cockpit to a movable gate at an outlet of the bulk container. The pilot operates the lever to open and close the gate, and thereby controls the release of the bulk product. When released, the bulk product is dispersed along the aircraft&#39;s trailing flight path. A vent near the top of the container can facilitate the release of product from the container. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a side view of an example aircraft with an example vent system constructed in accordance with the teachings disclosed herein, wherein the vent system is shown closed. 
         FIG.  2    is a side view similar to  FIG.  1    but showing the aircraft dispersing fluid while the vent system is open. 
         FIG.  3    is a perspective view showing various axes of an aircraft. 
         FIG.  4    is a cross-sectional view taken along line  4 - 4  of  FIG.  1   . 
         FIG.  5    is a perspective view of the example vent system shown in  FIG.  1   , wherein parts of a tank and gate valve assembly are schematically illustrated. 
         FIG.  6    is a perspective view similar to  FIG.  6    but showing the vent system open. 
         FIG.  7    is a cross-sectional side view of an example vent system constructed in accordance with the teachings disclosed herein. 
         FIG.  8    is a cross-sectional side view similar to  FIG.  7    but showing the vent system open while operating in a second mode of operation. 
         FIG.  9    is a cross-sectional side view similar to  FIG.  8    but showing the scoop of an upstream vent directing air into a downstream vent. 
         FIG.  10   . is a cross-sectional side view similar to  FIG.  8    but showing an even lower profile vent system constructed in accordance with the teachings disclosed herein. 
         FIG.  11    is a cross-sectional side view similar to  FIG.  7    but showing another example vent constructed in accordance with the teachings disclosed herein. 
         FIG.  12    is a cross-sectional side view similar to  FIG.  11    but showing the vent in an unsealed position while operating in a second mode of operation. 
         FIG.  13    is a cross-sectional side view similar to  FIG.  11    but showing the vent system operating in a first mode of operation. 
         FIG.  14    is a cross-sectional side view similar to  FIG.  7    but showing the vent system operating in a first mode of operation. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS.  1 - 9    pertain to a vent system  10  for a fluid dispersion tank  12  of an aircraft  14 , wherein aircraft  14  is used for dispersing a fluid  16  or other flowable product while in-flight. A gate valve assembly  18  at the bottom of tank  12  includes at least one gate  20  that opens to release fluid  16  from tank  12 . Gate  20  is movable between a closed position ( FIGS.  1 ,  4 ,  5 ,  7 ,  11  and  12   ) to retain fluid  16  and an open position ( FIGS.  2 ,  6 ,  8 ,  9 , and  10   ) to release fluid  16 . When gate  20  opens, it releases fluid  16  from tank  12  while vent system  10  prevents a detrimental vacuum from developing within tank  12 . The released fluid  16  is dispersed along the aircraft&#39;s trailing flight path. Such a system is particularly suited for agricultural and firefighting purposes. 
     The term, “aircraft” refers to any flying machine. Some examples of aircraft  14  include an aerial crop duster, air tanker, an airplane, a helicopter, an Air Tractor AT402, an Air Tractor AT502, an Air Tractor AT602, an Air Tractor AT802A, an Air Tractor AT802F, a Thrush aircraft, and a Dromodier aircraft. 
     The term, “fluid” refers to any product or material that can flow. Some examples of fluid  16  include a liquid, granules, particles, seed, powder, water, chemical mixtures, fertilizer, pesticide, and fire retardant. 
     The term, “tank” refers to any hollow structure for containing a fluid. Some examples of tank  12  include a vessel, a hopper, a container, a receptacle, etc. In the illustrated examples, tank  12  defines a chamber  22  for containing fluid  16 . In some examples, tank  12  is filled with fluid  16  through a fill valve  112  at a port  24  on either tank  12  or gate assembly  18 . 
     The term, “gate” refers to any member that can be moved relative to an opening to vary the flow of a fluid through the opening or selectively stop (or substantially stop) the flow. Some example gates include plates, plugs, flaps, diaphragms, etc. Some example modes of gate movement include translating, pivoting, expanding, contracting, bending, and various combinations thereof. Some examples of gate assembly  18  include those disclosed in U.S. Pat. No. 11,046,433 and U.S. patent application Ser. Nos. 17/202,577 and 17/386,721; all of which are specifically incorporated herein by reference. In some examples, gate  20  is a 5-inch, 7.5-inch or 10-inch wide gate provided by Transland of Wichita Falls, Tex. In some examples, gate  20  is one of a series of gates in a gate assembly, wherein the gates open and close in unison. Gate  20  and gate assembly  18  are schematically illustrated in  FIGS.  5 - 12   . 
     For describing physical orientations and relative positions, certain components of vent system  10  are described herein with reference to known orthogonal axes of aircraft  14 , as shown in  FIG.  3   .  FIG.  3    shows aircraft  14  comprising a nose  26 , a tail  28 , a cockpit  30 , and a windshield  32 . Aircraft  14  defines a roll axis  34 , a pitch axis  36 , and a yaw axis  38 . Aircraft  14  extends lengthwise along roll axis  34  in a forward direction  40  from tail  28  to nose  26 . Windshield  32  faces generally in forward direction  40 . Aircraft  14  extends laterally widthwise along pitch axis  36 . Aircraft  14  extends along yaw axis  38  in an upward direction  42  from a lower portion  44  of aircraft  14  to an upper portion  46  of aircraft  14 . Cockpit  30  is between tail  28  and nose  26  with respect to roll axis  34 . Roll axis  34 , yaw axis  38 , and pitch axis  36  lie perpendicular to each other. 
     In some examples, vent system  10  comprises a vent  48  defining an aperture  50  through tank  12 , a vent member  52  for selectively opening and blocking aperture  50 , a vent closure spring  54  for urging vent member  52  to a closed sealed position ( FIGS.  1 ,  4 ,  5 , and  7   ), a scoop  56  extending at least partially over aperture  50 , and a slender member  58  coupling vent member  52  to gate valve assembly  18 . The term, “vent member” refers to any structure for selectively blocking and unblocking an aperture. A few examples of vent member  52  include a plate, a disc, a plug, a diaphragm, a ball, a flap, a cone, a partially spherical body, etc. Some example modes of vent member movement include translating, pivoting, expanding, contracting, bending, and various combinations thereof. 
     Some examples of vent  48  comprise an inlet well  60  extending down into the tank&#39;s chamber  22  toward the vent&#39;s aperture  50 . Inlet well  60  has a brim  62  at an upper surface  64  of tank  12 . Brim  62  is the outer periphery of inlet-well  60 . In some examples of vent  48 , a lower end  60 ′ of inlet-well  60  defines aperture  50  between the tank&#39;s chamber  22  and an outside atmosphere  66  surrounding aircraft  14 . In some examples, inlet-well  60  includes an upstream surface  68  and a downstream surface  70 . Aperture  50  and downstream surface  70  are behind upstream surface  68  with respect to the forward direction  40  along roll axis  34 . In some examples, upstream surface  68  extends downward from brim  62  toward aperture  50 , and downstream surface  70  extends upward from aperture  50 . In some examples, inlet well  60  is 3D printed and is comprised of carbon fiber reinforced polypropylene. 
     In some examples, upstream surface  68  is sloped more gradually than downstream surface  70 , as viewed along an imaginary plane  72 , wherein imaginary plane  72  is defined as intersecting a centerpoint  74  of aperture  50  and lying perpendicular to pitch axis  36 . In some examples, the aperture&#39;s centerpoint  74  is laterally centered relative to aircraft  14  and roll axis  34 . In other examples, the aperture&#39;s centerpoint  74  is laterally offset to the left or right of roll axis  34 . Some examples of vent system  10  include two vents  48  or  48 ′ on either side of roll axis  34 . Some examples of vent system  10  include more than two vents  48  or  48 ′. 
     In some examples, the gradual slope of upstream surface  68  promotes a beneficial Coanda effect, whereby upstream surface  68  tends to draw air to itself and thereby effectively direct that air down toward aperture  50 . In some examples, upstream surface  68  curves smoothly along imaginary plane  72  to gradually direct the airflow downward. In some examples, upstream surface  68  is substantially linear along imaginary plane  72  to simplify manufacturing of vent  48 . In some examples, upstream surface  68  lies at an obtuse acute angle  76  of less than 45 degrees to roll axis  34  to promote the Coanda effect. 
     Inlet-well  48  placing aperture  50  at a recessed elevation below the tank&#39;s upper surface  64  in combination with the Coanda effect enables vent  48  to draw an ample amount of air down through aperture  50  and into tank  12  without creating a prominent upward protrusion that could otherwise significantly obstruct a pilot&#39;s view. In some examples, however, a relatively low-profile scoop  56  can be added to increase the airflow through aperture  50  and to help shield windshield  32  from backsplash when vent  48  is open. 
     To minimize obstructing the pilot&#39;s view, some examples of scoop  56  extend only a certain height  78  above brim  62 , wherein certain height  78  is less than a well-depth  80  of inlet-well  60 . In some examples, well-depth  80  is preferably at least one inch lower than brim  62  to realize the benefit of a recessed vent. In some examples, the certain height  78  is less than three inches to avoid creating a significant obstruction to the pilot&#39;s view. In some examples, the scoop&#39;s certain height  78  is less than two inches, and well-depth  80  is greater than two inches to provide a good compromise between vent inlet airflow and minimal obstruction to the pilot&#39;s view. In some examples, the scoop&#39;s height  78  is about 1.5 inches, and well-depth  80  is about three inches for best results. To realize at least a minimal benefit of aperture  50  being recessed, inlet-well  60  at aperture  50  is at least one inch lower than brim  62 . In some examples, as shown in  FIG.  10   , a scoop  56 ′ has a certain height  78  that is substantially equal to zero (i.e., scoop  56 ′ is substantially flush with brim  62 ). 
     To further increase vent airflow while reducing backsplash, some examples of scoops  56  and  56 ′ extend in forward direction  40  out over aperture  50 . With the addition of scoop  56  or  56 ′, some backsplash of fluid  16  might collect in a lower rear area  82  of vent-well  60 . In some examples, a drain tube  84  can be used for draining this collection of fluid  16 . 
     In some examples, drain tube  84  has an inlet  86  and an outlet  88 . Inlet  86 , in some examples, is in fluid communication with inlet-well  60  at a point in lower rear area  82  above aperture  50  and below brim  62 . In some examples, the drain tube&#39;s outlet  88  is below the tube&#39;s inlet  86  and below aperture  50 . In some examples, drainage of fluid  16  through drain tube  84  is directed back into tank  12 , directed down into a separate waste collection tank, or simply released into the surrounding atmosphere  66 . The term, “tube” refers to any fluid passageway. Some examples of a tube include a pipe, a hose, a conduit, a drilled hole, a channel, a gutter, and various combinations thereof. 
     In some examples, to reduce assembly costs and avoid leakage points, inlet-well  60  is integrally formed seamlessly in the tank&#39;s upper surface  64 . In such examples, inlet-well  60  and the tank&#39;s upper surface  64  are both made of the same material. In some examples, the tank&#39;s upper surface  64  is part of a lid that is hinged to the rest of tank  12 , whereby the hinged lid provides access to chamber  22 . 
     In some examples, tank  12  adjoins a cowl  90  of aircraft  14 . In some examples, cowl  90  is comprised of a first material (e.g., aluminum alloy), tank  12  and inlet-well  60  are each comprised of a second material (e.g., a polymer, fiberglass, or some other composite), and the first material is different than the second material. The two materials being different from each other allow the use of optimal materials each being uniquely suitable for an aircraft cowl and a tank&#39;s wall. 
     In some examples, vent closure spring  54  urges vent member  52  to its closed position. Vent closure spring  54  is schematically illustrated to represent any resilient member capable of urging vent member  52  to its closed position. Some examples of vent closure spring  54  include a torsion spring, a compression spring, an extensions spring, a leaf spring, a constant force spring, an elastic cord, an elastic strap, a pneumatic spring, a bellows, etc. In some examples, a certain level of vacuum (e.g., −0.5 psig) in chamber  22  overcomes vent closure spring  54  and thereby forces vent member  52  to its open position. A vacuum of −0.5 psig, however, can delay the release of fluid  16  out from within tank  12 . 
     To overcome this problem, some examples of vent system  10  include slender member  58 . The term, “slender member” refers to any elongate structure having a length that is at least ten times greater than its width. Some examples of slender member  58  are rigid. Other examples of slender member  58  are more flexible or pliable. Some examples of slender member  58  include a cable, a chain, a nylon strap, an elastic strap, an extension spring, a wire, a rope, a cord, a rod, a bar, a linkage, a linkage assembly, a tube, and various combinations thereof. 
     In some examples, slender member  58  couples vent member  52  to gate valve assembly  18  such that gate  20  moving between the closed position and the open position causes vent member  52  to move respectively between its sealed position and the unsealed position. In some examples, vent closure spring  54  holds vent member  52  at the sealed position when gate  20  is in its closed position. In some examples, slender member  58  overpowers vent closure spring  54  to force vent member  52  to its unsealed position when gate  20  is in the open position. 
     In some examples, when gate  20  is in the closed position, slender member  58  is slack ( FIGS.  5  and  7   ), which allows vent closure spring  54  to close vent member  52  without appreciable resistance from slender member  58 . In some examples, when gate  20  is in the open position, slender member  58  is taut ( FIGS.  6 ,  8 , and  9   ) and forces vent member  52  to its unsealed position. 
     It should be appreciated by those of ordinary skill in the art that points  92  and  94  to which slender member  58  respectively connects to vent member  52  and gate valve assembly  18  can be at any suitable locations. In some examples, point  92  is on a lug  96  extending from vent member  52 . In some examples, point  94  is on a lug  98  extending from gate  20 , as shown in  FIGS.  5 ,  6 ,  7 , and  8   . In some examples, as shown in  FIG.  9   , point  94  can be attached to a link  100  connecting gate  20  to a gate actuator  102 . 
     Gate actuator  102  is schematically illustrated to represent any means for powering the movement of gate  20 . Some examples of gate actuator  102  include a motor, a hydraulic cylinder, a gearbox, a linkage assembly, and various combinations thereof. In some examples, a linkage assembly, gears, or some other mechanism couples multiple gates  20  to gate actuator  102 , so the multiple gates  20  open and close in unison. 
     In some examples, vent system  10  includes two or more vents  48 , as shown in  FIG.  9   . In some examples, vent system  10  includes a front vent  48   a  and a rear vent  48   b . In some examples, each vent  48   a  and  48   b  are substantially identical to vent  48 . Vents  48   a  and  48   b  have a strategic tandem arrangement such that an upper surface  104  of the front vent&#39;s scoop  56  utilizes the Coanda effect to direct air  106  into an inlet  50  of the rear vent  48   b . In some examples, rear vent  48   b  can capture backsplash that might escape front vent  48   a , thus minimizing the amount of backsplash that might otherwise reach windshield  32 . 
     In the example shown in  FIGS.  11  and  12    an example vent member  52 ′ in the form of a vertically translating plate and an example vent closure spring  54 ′ is in the form of a compression spring. Vent closure spring  54 ′ urges vent member  52 ′ to its sealed position ( FIG.  11   ). When gate  20  opens, slender member  58  pulls vent member  52 ′ to its unsealed position ( FIG.  12   ). In some examples one or more spokes  110  help position vent member  52 ′ in a radial direction. In some examples, to achieve sufficient ventilating airflow, the vertical travel distance of vent member  52 ′ is at least twenty percent of the vent member&#39;s outer diameter. In some examples, the vertical travel distance of vent member  52 ′ is about 2.5 inches. 
     In addition or alternatively, some examples of vent system  10  have two modes of operation, e.g., a first mode and a second mode. Examples of first mode are shown in  FIGS.  13  and  14   . Examples of second mode are shown in  FIGS.  2 ,  6 ,  8 ,  9  and  10   . 
     In some examples of the first mode, vent member  52  or  52 ′ of vent  48  or  48 ′ moves independent of gate  20  from the sealed position to the unsealed position in response to the chamber pressure (i.e., the air pressure in chamber  22 ) decreasing a predetermined amount below the atmospheric pressure. In some examples, the predetermined amount is 0.8 psig below atmospheric pressure (i.e., −0.8 psig). So, in some examples, if the air pressure differential across vent member  52  or  52 ′ reaches or exceeds 0.8 psig (at least 0.8 psig of vacuum in chamber  22 ), then the pressure differential will open the vent. In some examples, the predetermined amount is between about 1.5 psig to 2 psig below atmospheric pressure. 
     Such a first mode of operation helps avoid collapsing or otherwise damaging tank  12  under certain adverse pressure conditions. For instance, in some cases, fill valve  112  or gate  20  might leak. The lost fluid  16  could create excessive vacuum in chamber  22 . In other cases, changes in elevation of aircraft  14  might create an adverse vacuum in chamber  22 . 
     As a means for preventing damagingly high vacuum from developing within chamber  22 , the first mode of operation allows vent member  52  and  52 ′ to open independent of gate  20 . So, in the first mode, vent members  52  and  52 ′ can move regardless of whether gate  20  is open or closed. 
     In the second mode, vent members  52  and  52 ′ can move independent of the chamber pressure from the sealed position to the unsealed position in response to gate valve assembly  10  applying a predetermined amount of tension  114  to slender member  58 . The predetermined amount of tension  114  is that which is needed to overcome the force of vent closure spring  54  or  54 ′. 
     The second mode allows vent members  52  and  52 ′ to open even when there is no pressure differential between the air pressure in chamber  22  and the outside atmosphere. The second mode of operation allows aircraft  14  to release fluid  16  at a maximum fluid flow rate, as vent system  10  does not require a vacuum or −0.5 psig in chamber  22  in order to function properly. 
     To prevent accidentally damaging vent system  10 , some examples of slender member  58  include a tension-limiting spring  116  (e.g., an extension spring). Tension-limiting spring  116  can be installed anywhere along the length of slender member  58 . If for some reason slender member  58  tries to exert excessive pulling force on vent member  52  or  52 ′, tension-limiting spring  116  will yield (resiliently extend) to limit the slender member&#39;s pulling force (tension  114 ). Tension-limiting spring  116 , for example, prevents an installer or mechanic from adjusting slender member  58  so tightly that it damages vent system  10 . Under normal operation, tension-limiting spring  116  remains unextended regardless of whether vent system  10  is open or closed. 
     Although certain example methods, apparatus and articles of manufacture have been disclosed herein, the scope of coverage of this patent is not limited thereto. On the contrary, this patent covers all methods, apparatus and articles of manufacture fairly falling within the scope of the claims of this patent.