Abstract:
A air curtain adapted for use in a car wash. The air curtain includes a rotating diffuser allowing for multiple airflow trajectories, including airflow trajectories having vector components both into and out of the car wash tunnel. The air curtain utilizes a variable cross-section duct connected to the rotating diffuser to provide a constant velocity airflow from the numerous air outlets in the rotating diffuser with only a single motor and blower acting as a source of airflow.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to an air curtain for preventing ambient air from entering an enclosure through a door thereof, and, more particularly, to an air curtain particularly adapted for use in a car wash.  
           [0003]    2. Description of the Related Art  
           [0004]    Air curtains can be utilized to provide airflow across a doorway or other opening, to, e.g., reduce airflow in or out of an enclosed space accessed by the doorway, and prevent insects from entering the enclosed space. Reducing airflow out of the enclosed space works to retain conditioned air therein. To achieve the aforementioned goals, known air curtains are adapted to provide an airflow having a vector component perpendicular to the frame of the relevant doorway and directed out of the doorway. A number of air ducts or nozzles are progressively positioned along the width of the doorway to provide the desired airflow. Each duct or nozzle is secured to the door frame in an orientation providing the desired airflow trajectory, i.e., a trajectory having a vector component perpendicular to the frame of the relevant doorway and directed out of the doorway. To provide a constant velocity airflow across the width of a door, each duct has an associated motor and blower for accelerating air through the duct. Each motor/blower combination is positioned directly above the associated duct.  
           [0005]    Many car washes are arranged as tunnels, with cars entering an entrance to the tunnel, being directed through the tunnel on a conveyor track, and thereafter exiting the tunnel. The car wash tunnel includes progressively positioned pre-soak, wash, and rinse stations for washing the car as it is guided through the tunnel. In cold climates, car washes typically include devices designed to prevent ambient air from entering the car wash tunnel to facilitate heat retention and prevent freezing of car wash components including, e.g., soft cloths and sprayer nozzles. Typically, the entrance and exit of the car wash is equipped with a door which is opened to allow a car to enter or exit the car wash and is thereafter closed. Conventional “garage doors” can be utilized, or doors formed from a number of plastic panels hung in a vertical orientation on a track. Garage doors associated with car washes are opened and closed in a conventional manner, and plastic panel doors are opened and closed by moving the panels in a horizontal direction. Doors positioned at the entrance and exit of a car wash cannot entirely prevent ambient air from entering the car wash because the doors must be opened to allow a car to enter or exit the car wash.  
           [0006]    Due to the orientation of the entrance and exit of a car wash tunnel, i.e., at opposite ends of the tunnel, a conventional air curtain cannot easily be utilized to prevent ambient air from entering the car wash because the nozzles or ducts of conventional air curtains have a fixed position with respect to the door frame. For example, if the car wash tunnel has an east/west orientation, with the entrance positioned east of the exit, then ambient airflow traveling west to east, i.e., a westerly wind will not be retarded by a conventional air curtain positioned at the entrance of the car wash. To the contrary, such a westerly wind will be facilitated by a conventional air curtain positioned at the entrance of the example car wash. Moreover, the multiple motor/blower combinations of a conventional air curtain cannot be positioned at the entrance or exit of a car wash because of the size of this structure and the relatively small overhead space provided in a car wash.  
           [0007]    What is needed in the art is an air curtain adapted for use in a car wash to prevent ambient air from entering the car wash.  
           [0008]    What is further needed in the art is an air curtain designed to provide consistent velocity airflow from a number of air outlets utilizing a single motor and blower to accelerate the air.  
         SUMMARY OF THE INVENTION  
         [0009]    The present invention provides an air curtain adapted for use in a car wash. The air curtain of the present invention includes a rotating diffuser allowing for multiple airflow trajectories, including airflow trajectories having vector components both into and out of the car wash tunnel. Moreover, the air curtain of the present invention utilizes a variable cross section duct connected to the rotating diffuser to provide a consistent velocity airflow from the numerous air outlets in the rotating diffuser with only a single motor and blower acting as a source of airflow.  
           [0010]    With the car wash environment in mind, the air curtain of the present invention is, in one embodiment thereof, constructed from a non-corrosive material such as aluminum or stainless steel. The rotating diffuser and variable cross section duct of the air curtain of the present invention are generally positioned along the top of the relevant door frame. Various additional parts of the air curtain are located below and offset from the variable cross section duct and rotating diffuser, including an air inlet, a conditioning section (e.g., heating coils), and a blower (including the associated motor) with various transition sections located therebetween. Generally the air inlet, conditioning section, and blower are vertically oriented, i.e., the airflow through the air curtain is generally vertical as it traverses these sections of the air curtain. With this in mind, an elbow is utilized to connect the aforementioned portions of the air curtain of the present invention to the variable cross section duct and rotating diffuser, with the airflow being generally horizontal through the variable cross section duct until being directed out from the rotating diffuser with a vertical component of direction, and, typically, a horizontal component of direction as well.  
           [0011]    A handle is operably connected to the rotating diffuser to allow for manual adjustment thereof into multiple positions, including positions in which the airflow from the rotating diffuser has a directional component into the car wash tunnel, or out of the car wash tunnel. In all cases, the airflow from the rotating diffuser has a vertical component. The rotating diffuser may also be repositioned by a motor. In embodiments in which the rotating diffuser is motorized, a control unit will be connected to the rotating diffuser motor to control energization of the motor to reposition the diffuser. The present invention further contemplates the provision of a wind detector, e.g., a weather vane communicatively connected to the control unit to automatically control the control unit and, therefore, the position of the rotating diffuser. Additionally, the heating coils may be provided with temperature controls allowing for variable fluid temperature  
           [0012]    In one embodiment of the present invention, rotating diffusers are associated with both the entrance and the exit of the car wash. The two diffusers of this embodiment of the present invention may be adjusted to account for ambient airflows tending to enter the car wash from either the entrance or the exit. If an ambient airflow is tending to enter the car wash through the entrance to the car wash, the rotating diffusers may be positioned so that the airflow exiting the entrance diffuser exits the car wash, while the airflow exiting the exit diffuser enters the car wash. Stated another way, the rotating diffusers of this embodiment of the present invention can be adjusted, so that the air exiting each diffuser has a directional component into the wind, whether the wind is tending to enter the entrance to the car wash or is tending to enter the exit of the car wash.  
           [0013]    As described above, the duct supplying air to the rotating diffuser comprises a variable cross section duct. Specifically, the cross section of a diffuser in accordance with the present invention varies along its length, with the cross sectional area adjacent the elbow connecting the duct to the blower comprising the largest cross section of the duct, and the cross section of the end of the duct furthest from the elbow being the smallest, with the cross section of the duct progressively decreasing in size from the largest to the smallest cross section. The variable cross section duct of the present invention provides a consistent air pressure across the entire length of the duct to allow the numerous ducts of the rotating diffuser to provide a consistent velocity airflow across the entire length of the rotating diffuser, with only a single source of air being utilized.  
           [0014]    The invention, in one form thereof, comprises a method of preventing ambient air from entering a building through at least one of a pair of doors allowing access to the building. The method of this form of the present invention includes the steps of: providing a first air curtain positioned adjacent a first one of the pair of doors, the first air curtain having a first rotatable diffuser through which a first air curtain airflow can pass, the first rotatable diffuser rotatable relative to the building; and rotating the first air curtain diffuser to a position wherein the first air curtain airflow is directed out of the building through one of the pair of doors.  
           [0015]    The invention, in another form thereof, comprises a building and an air curtain combination. The combination of this form of the present invention includes a building having a pair of doors allowing access to the building and an air curtain including: an intake duct; a blower in fluid communication with the air intake duct, the blower operable to provide an airflow into the air intake duct and through the blower; a distribution duct in fluid communication with the blower, the distribution duct receiving the airflow from the blower; and a rotatable diffuser rotatably connected to the building, the rotatable diffuser having a plurality of air outlets, the rotatable diffuser in fluid communication with the distribution duct, whereby the airflow exits the air curtain through the air outlets, the rotatable diffuser rotatable between a first position in which the airflow is directed through the air outlets and out of a first of the pair of doors and a second position in which the airflow is directed through the air outlets and out a second of the pair of doors.  
           [0016]    The invention, in another form thereof, comprises an air curtain including an air intake duct; a blower in fluid communication with the air intake duct, the blower operable to provide an airflow into the air intake duct and through the blower; a variable cross-section distribution duct in fluid communication with the blower, the variable cross-section distribution duct receiving the airflow from the blower, the variable cross-section duct having a variable cross-section along its length, whereby the airflow creates a substantially constant air pressure in the variable cross-section duct; and a diffuser having a plurality of air outlets, the diffuser in fluid communication with the distribution duct, whereby the airflow exits the air curtain through the air outlets.  
           [0017]    The invention, in yet another form thereof, comprises an air curtain including an air intake duct; a blower in fluid communication with the air intake duct, the blower operable to provide an airflow into the air intake duct and through the blower; a distribution duct in fluid communication with the blower, the distribution duct receiving the airflow, the distribution duct including air pressure means for creating a substantially constant air pressure in the air distribution duct; and a diffuser having a plurality of air outlets, the diffuser in fluid communication with the distribution duct, whereby the airflow exits the air curtain through the air outlets.  
           [0018]    The variable cross section duct of the present invention advantageously permits a single motor and blower to provide a consistent air pressure across the entire length of the variable cross section duct whereby the numerous nozzles or ducts of the rotating diffuser provide a consistent airflow velocity.  
           [0019]    The rotating diffuser of the present invention advantageously allows a pair of air curtains in accordance with the present invention positioned at the entrance and exit of, e.g., a car wash tunnel to be positioned whereby the airflow from both diffusers has a directional component into the wind.  
           [0020]    The variable cross section duct of the present invention advantageously allows the air curtain of the present invention to be powered by a single blower/motor combination. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]    The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:  
         [0022]    [0022]FIG. 1 is a top, sectional view illustrating a car wash tunnel equipped with a pair of air curtains in accordance with the present invention;  
         [0023]    [0023]FIG. 2 is a front plan view illustrating an air curtain of the present invention;  
         [0024]    [0024]FIG. 3 is a partial plan view of an air curtain of the present invention taken along line  3 - 3  of FIG. 2;  
         [0025]    [0025]FIG. 4 is a sectional view of the air curtain illustrated in FIG. 2 taken along line  4 - 4  of FIG. 2 and illustrating a handle operable to manually actuate the rotating diffuser of the present invention; and  
         [0026]    [0026]FIG. 5 is a sectional view illustrating a variable cross section duct and rotating diffuser combination in accordance with the present invention. 
     
    
       [0027]    Corresponding reference characters indicate corresponding parts throughout the several views. Although the drawings represent embodiments of the present invention, the drawings are not necessarily to scale and certain features may be exaggerated to better illustrate and explain the present invention. The exemplifications set out herein illustrate embodiments of the invention, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0028]    As illustrated in FIG. 2, air curtain  26  includes air inlet  44  supported by leg  46  and upright  34 . Air inlet  44  allows for airflow into air curtain  26  and, in one embodiment of the present invention includes an air filter positioned to prevent debris from entering air curtain  26 . Air inlet  44  is connected via hot water coil  43 , and transition  42  to blower  40 . Blower  40  is connected to a motor and creates an airflow into air inlet  44 . Air is drawn by blower  40  into air inlet  44 , past hot water coil  43 , and through transition  42 . Blower  40  thereafter pushes air into transition  38 , elbow  36 , and variable cross section duct  30 . As described above, the cross section of variable cross section duct  30  varies along its length to provide constant air pressure therein. Variable cross section duct  30  is in fluid communication with rotating diffuser  28  and provides consistent velocity airflow through a number of air outlets in rotating diffuser  28 .  
         [0029]    [0029]FIG. 1 illustrates car wash  10  equipped with a pair of air curtains in accordance with the present invention. As illustrated in FIG. 1, car wash  10  includes car wash tunnel  11  having entrance  22  and exit  24  as well as conveyor track  12 . In use, a vehicle enters car wash tunnel  11  through entrance  22  and is pulled or pushed through car wash tunnel  11  by conveyor track  12 . FIG. 1 schematically depicts a typical car wash tunnel including presoak nozzles  16 , scrubbers  18 , soap nozzles  19 , and rinse nozzles  20 . As illustrated, car  14  is moved through car wash tunnel  11  on conveyor track  12  and progressively passes presoak, wash, and rinse stations in the car wash. As illustrated in FIG. 1, an air curtain of the present invention is positioned at entrance  22  as well as exit  24 . Each of these air curtains is designed to provide a constant velocity airflow across the width of the associated doorway. Moreover, as will be further described hereinbelow, each air curtain is operable to provide an airflow having a vector component generally parallel to conveyor track  12  and directed either into car wash tunnel  11  or out from one of entrance  22  and exit  24 .  
         [0030]    Car wash  10  illustrated in FIG. 1 is shown as having an east-west configuration, with exit  24  located on a west end of car wash  10  and entrance  22  located on an east end of car wash  10 . In the case of a westerly wind W as illustrated in FIG. 1, both the entrance and the exit air curtains will be adjusted to provide an airflow having a vector component into the wind, i.e., directed toward exit  24 . In the case of an easterly wind E as schematically depicted in FIG. 1, both air curtains will be configured to provide airflow having a vector component into the wind, i.e., toward entrance  22 .  
         [0031]    [0031]FIG. 3 illustrates rotating diffuser  28  and variable cross section duct  30  of an air curtain of the present invention. Variable cross section duct  30  and rotating diffuser  28  are further depicted, e.g., in FIG. 5. As illustrated in FIG. 5, variable cross section duct  30  has height H. Height H is consistent across the length of variable cross section duct  30  as depicted in FIG. 2. The cross section of variable cross section duct  30  is varied, e.g., by varying the distance between front wall  70  and rear wall  72  of variable cross section duct  30 . Furthermore, internal baffle  31  (FIG. 5) is utilized to vary the internal height of variable cross section duct  30 . Internal baffle  31  is arc shaped with the distance of internal baffle  31  to the bottom of variable cross section duct  30  being substantially equal to H at the end of variable cross section duct  30  adjacent elbow  36  and being zero at the distal end of variable cross section duct  30 . Internal baffle  31  is arc shaped as opposed to linear to provide optimum ratios of h/w along the length of variable cross section duct  30  to decrease frictional losses through variable cross section duct  30 , with h and w denoting the height and width of a cross section of variable cross section duct  30 . In alternative embodiments of the present invention, the height of variable cross section duct  30  will vary along the length. For example, the height of variable cross section duct  30  may be varied to lessen friction losses through the length of the duct.  
         [0032]    [0032]FIG. 3 illustrates an embodiment of the present invention in which rear wall  72  tapers from a point adjacent elbow  36 , i.e., an air inlet for variable cross section duct  30  to the distal end of variable cross section duct  30 , i.e., the end of variable cross section duct  30  furthest from elbow  36 . FIG. 3 illustrates an arrangement in which rear wall  72  tapers linearly. This depiction is schematic in nature, and rear wall  72  may, in practice, taper along an arc.  
         [0033]    As illustrated in FIG. 5, rotating diffuser  28  is operatively associated with variable cross section duct  30  so that airflow exits variable cross section duct  30  at air outlet  74  and travels through rotating diffuser  28 . As illustrated in FIG. 5, lateral diaphragms  66  are positioned between rotating diffuser  28  and variable cross section duct  30  and provide a seal therebetween. Referring to FIG. 3, end diaphragms  76  are provided on either end of rotating diffuser  28  to complete sealing between rotating diffuser  28  and variable cross section duct  30 . Lateral diaphragms  66  and end diaphragms  76  are constructed of a flexible, heat resistant, and air impermeable material. The flexibility of lateral diaphragms  66  and end diaphragms  76  allow for relative rotation of rotating diffuser  28  relative to variable cross section duct  30 , while maintaining a seal therebetween. In one exemplary embodiment, lateral diaphragm  66  and end diaphragm  76  are formed of DUROLON available from Duro Dyne Corp. The DUROLON material is woven fiberglass coated with hypalon.  
         [0034]    Referring to FIGS. 3 and 4, rotating diffuser  28  is pivotally connected to support plates  52  positioned on either end thereof via pivot pins  48 ,  50 . Support plates  52  are rigidly secured to variable cross section duct  30  or are otherwise stationary with respect to variable cross section duct  30 . Pivot pins  48 ,  50  are rigidly secured to end walls  78  of rotating diffuser  28 , and traverse appertures in support plates  52  to provide for rotation of rotating diffuser  28  relative to support plates  52 . Proximal pivot pin  48  is further rigidly connected to handle  32 . In this way, handle  32  can be manipulated to rotate rotating diffuser  28  relative to variable cross section duct  30  into alternate positions as illustrated, e.g., in FIG. 5. Various mechanisms, including, e.g., washers  51  may be utilized to control the resistance to rotation of rotating diffuser  28 . As illustrated in FIG. 4, handle  32  is connected to handle locking plate  54  via bolt  58  and wing nut  56 . Once rotating diffuser  28  is positioned as desired, wing nut  56  may be tightened to secure handle  32  to handle locking plate  54  and retain the position of rotating diffuser  28 .  
         [0035]    In alternative embodiments, pivot pins  48 ,  50  can be connected to one or more motors whereby energization of these motor(s) will actuate rotating diffuser  28 . In one alternative embodiment, a motor connected to one of pivot pins  48 ,  50  is further connected to a controller for controlling energization of the motor. In this embodiment, the controller is further connected to a wind sensor designed to detect wind direction, e.g., a weather vane. The controller receives data related to wind direction and, based thereon, automatically repositions rotating diffuser  28  as necessary to prevent ambient winds from entering car wash  10 . Both the entrance and the exit air curtains can be motorized as described above.  
         [0036]    As illustrated in FIG. 3, a plurality of vanes  68  are positioned along the length of rotating diffuser  28  to redirect duct airflow D into diffuser airflow E as schematically depicted in FIG. 2. This redirection requires a 90 degree turning of the air stream. With this in mind, vanes  68  are positioned perpendicular to duct airflow D. Each vane extends across the entire width of the outlet and, in one exemplary embodiment of the present invention, the ratio of the height of the vane, i.e., the distance the vane extends into the diffuser (Hv in FIG. 5) to the distance between the next adjacent vane equals 1.5.  
         [0037]    It is contemplated that copper tubing can be used for hot water coil  43  and a corrosion resistant material such as aluminum or stainless steel can be used to construct the duct work, framing and rotating diffuser of the present invention. Moreover, hot water coil  43  can be connected to controls for regulating the fluid temperature therein to advantageously provide operating efficiency and cost savings to the user. Hot water coil  43  provides the further advantage of heating the car wash. For example, if the entrance and exit air curtains are positioned to provide an airflow to combat a westerly wind W in the example depicted in FIG. 1, then the warmed air from the entrance air curtain will be directed into car wash  10  and heat the same. Generally, a car wash is only heated to a temperature above freezing to avoid freezing of, e.g., the scrubbers and nozzles. With this in mind, the aforementioned temperature control can be used to lower the temperature of air exiting air curtains  26  when ambient temperatures are not excessively cold.  
       EXAMPLE  
       [0038]    In one exemplary installation, an air curtain of the present invention was designed to provide a 6,000 cubic feet per minute (CFM) airflow using a 5 horsepower motor. In this embodiment, the air curtain utilizes hot water coils providing 230,00 BTU using a water temperature of 200° F. and a flow rate of 20 fluid gallons per minute. The hot water coil of this embodiment was constructed using an aluminum fin and copper tubing. With a 6,000 CFM airflow entering the variable cross section duct, the following equations were utilized to determine the cross sectional areas of the variable cross section duct along its length.  
           v=Q/A   [1] 
           A=wh   [2] 
           Q   L =( Q   I   /L   T ) L   [3] 
           W   L =0.1 L+ 10  [4] 
           h   L =(1.836 L )/(0.1 L +10)  [5] 
         [0039]    where  
         [0040]    v airflow velocity in the variable cross section duct  
         [0041]    Q=volumetric airflow  
         [0042]    A=cross sectional area of the variable cross section duct  
         [0043]    w=width of a cross sectional area of the variable cross section duct  
         [0044]    h=height of a cross sectional area of the variable cross section duct  
         [0045]    Q L  volumetric airflow as a function of L (defined below)  
         [0046]    Q I =initial volumetric airflow into the variable cross section duct  
         [0047]    L T  the total length of the variable cross section duct  
         [0048]    L=the location of a particular cross section measured from the distal end of the variable cross section duct  
         [0049]    A L  the area of a cross section of the variable cross section duct as a function of L  
         [0050]    w L =the width of a cross section of the variable cross section duct as a function of L  
         [0051]    h L =the width of a cross section of the variable cross section duct as a function of L  
         [0052]    This exemplary air curtain includes a variable cross section duct having a ten foot length (“L” in FIG. 3), a cross section adjacent the elbow measuring 10″×22″, and a distal cross section having a width of 10″. Initially, equations 1 and 2 above were utilized to determine the velocity of airflow at the cross section adjacent the elbow as indicated below.  
         
       v=Q/A  
     
         
       A=wh  
     
         
       v=Q/wh  
     
           v= 6,000 CFM/22 in×10 in=3,922 ft/min=47,064 in/min  
         [0053]    Next, calculations were made to determine the cross sections required along the 10 foot long variable cross section duct to maintain an airflow velocity (v) of 3,922 ft/min along the length of the duct. To make this determination, the initial determination was made that volumetric airflow will constantly decrease along the length of the variable cross section duct. Based on this determination, equation 3 above was derived. To determine a value of w as a function of L, the slope of the back wall of the diffuser was determined (note that the back wall of the diffuser will converge from the end adjacent the elbow to the distal end thereof, with the front wall position being constant) and an equation for the line of the back wall was determined (i.e., equation 4 above), taking the front wall as the positive x-axis, the intersection of the front wall and the distal end of the variable cross section duct as the origin, with the distal end wall being the positive y-axis. Finally, equation 3 was utilized to determine h as a function of L (i.e., equation 5 above) as follows.  
           Q =(6,000  CFM/ 120″) L =(50  ft   3   /min·in ) L= 86,400  in   3   /min·in    
           Q=vA,  therefore,  
           A=Q/v =(86,400  in   3   /min·in )/(47,064  in/min )=(1.836  in ) L    
           A   L   =W   L   h   L , therefore,  
         h L   =A   L   /W   L   =[( 1.836  in ) L ]/(0.1 L+ 10)  
         [0054]    Utilizing equations 4 and 5 above, the height and width of cross sections along the length were determined. The width was altered along the length of the variable cross section duct according to equation 4, with the back wall of the variable cross section duct converging from the proximal end to the distal end of the variable cross section duct to adjust the width as necessary. The height of the variable cross section duct was varied by supplying an internal baffle generally parallel to the bottom wall of the variable cross section duct at any cross section thereof and spanning the length of the variable cross section duct. The baffle travels along an arc from the proximal end of the variable cross section duct to the distal end thereof. While the height of the baffle will go to zero at the distal end of the variable cross section duct according to equation 5 above, a minimal height, e.g., 0.5″ is maintained.  
         [0055]    While this invention has been described as having a preferred design, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from their present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.