Patent Abstract:
A centrifugal humidifier having a rotatable body for propelling water outwardly on to an impingement surface that brake up the propelled water into droplets which are then entrained in a stream of air and discharged to the surroundings, wherein the impingement surface has a multiplicity of sawtooth ridges oriented with the more gradually inclined sides facing toward the direction from which the water is propelled by the rotatable body which promotes breaking up the water into finer droplets.

Full Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates to humidification devices, particularly centrifugal humidifiers.  
         BACKGROUND OF THE INVENTION  
         [0002]    Various types of humidification devices have been developed to add moisture to dry air. In certain industrial and commercial environments, centrifugal humidifiers are often used. In such devices, water is propelled outwardly by a rapidly rotating plate or other body to impinge on a surface where it is broken up into small droplets that are entrained in a stream of air and then discharged to the surroundings.  
           [0003]    Although the discharged air has a higher moisture content, the size of the droplets produced on the impingement surface of known centrifugal humidifiers is generally not sufficiently fine to be readily absorbed by the air. Instead, such humidifiers tend to produce a mist-like discharge. Not only does this result in a less than optimum overall humidity level, it also tends to create water build up on the surfaces of walls, equipment, furniture and so forth in the vicinity of the humidifier. More than merely an inconvenience, this promotes the growth of moulds and other microorganisms that can pose health risks to workers in the area.  
           [0004]    Known centrifugal humidifiers are also limited in their throughput and efficiency. While increased humidification can be obtained by using larger humidifiers, or by using more humidifiers, doing so increases energy consumption and heat generation from the electric motors that are generally used to drive such centrifugal humidifiers.  
           [0005]    Known centrifugal humidifiers also have a tendency to become clogged with dust and other particles when they are used in industrial environments such as textile mills.  
           [0006]    It is a general object of the present invention to obviate or mitigate these and other disadvantages of known centrifugal humidifiers.  
         SUMMARY OF THE INVENTION  
         [0007]    In accordance with the present invention, there is provided a centrifugal humidifier having a dish or other body rotatable on an axis for propelling supplied water outwardly by centrifugal force onto an impingement surface, generally concentric to the axis of the rotatable body, which breaks up the outwardly propelled water into fine droplets. The humidifier of the present invention also has means to intake a stream of air for entraining the fine droplets of water and thereafter to discharge the stream of air to the surroundings.  
           [0008]    The impingement surface of the humidifier of the present invention has a multiplicity of sawtooth ridges. The ridges are each defined by a broader, more gradually inclined first side that faces toward the direction of rotation of the rotatable body, and a narrower, steeper second side that faces away from the direction of rotation of the rotatable body.  
           [0009]    Because of the sawtooth profile, the water tends to hit and bounce repeatedly on the first sides of successive ridges which promotes breaking up the water into finer droplets that are readily absorbed by the stream of air. The centrifugal humidifier of the present invention can therefor produce a fog-like discharge, rather than the mist-like discharge of known centrifugal humidifiers. This greatly reduces the problem of wetting nearby surfaces, and also greatly increases the throughput the efficiency. The invention eliminates or reduces the need for filters or similar moisture eliminators which are commonly used in known centrifugal humidifiers to reduce wetting, but which also tend to reduce efficiency by screening out the finer water droplets as well as the larger ones. The sawtooth ridge impingement surface of the present invention also resists buildup of dust and other particles that can clog other centrifugal humidifiers.  
           [0010]    Preferably, the centrifugal humidifier of the present invention includes a fan to take in and discharge the stream of air, and also includes a motor for driving the fan and for driving the rotatable body. Advantageously, the centrifugal humidifier of the present invention includes as well a water reservoir, and the rotatable body is generally bell shaped, with a broader flared rim and a narrower, cup-like lower portion immersed in the reservoir, such that rapid rotation of the body causes water in the reservoir to rise up the outer surface of the body to its rim from which it is propelled outwardly onto the impingement surface.  
           [0011]    Most preferably, the centrifugal humidifier of the present invention also has a pump and conduit for delivering additional water from the reservoir to the inner surface of the rotating body.  
           [0012]    It has been found that the centrifugal humidifier of the present invention provides an effective solution to obviate or mitigate problems presented by known prior art centrifugal humidifiers, as described above. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    For a better understanding of the present invention and to show more clearly how it may be carried into effect, reference will now be made to the accompanying drawings in which:  
         [0014]    [0014]FIG. 1 is an oblique perspective view, partly exploded, of one embodiment of a centrifugal humidifier according to the present invention;  
         [0015]    [0015]FIG. 2 is a cross-sectional view of the humidifier of FIG. 1;  
         [0016]    [0016]FIG. 3 is a perspective view of a component of the humidifier of FIG. 1 which includes the impingement surface;  
         [0017]    [0017]FIG. 4 is a close up view of the impingement surface on the component of FIG. 3;  
         [0018]    [0018]FIG. 5 is a cross-sectional view of the sawtooth ridges on the impingement surface of FIG. 4;  
         [0019]    [0019]FIG. 6 is a perspective view of the impingement surface component of an alternate embodiment of a humidifier according to the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0020]    Referring first to FIGS. 1 and 2, the humidifier  10  has three main sections, namely a base  11 , a head  12 , and a core assembly  13  positioned between the base  11  and the head  12 .  
         [0021]    The base  11  is generally box-like, and has side panels  14 , end panels  15 , tapered sides  16 , shoulders  17 , and flanges  20 . The material used to construct base  11  must be able to support the core assembly  13  and the head  12 , and should be rustproof since the lower inside portion of base  11  provides a water reservoir  21 . A heavy gauge galvanized sheet metal can be used, wherein seams of adjoining pieces are welded. Alternatively, base  11  may be constructed of plastic using molding techniques as are known in the art.  
         [0022]    The head  12  has a mounting plate  22 , a hood  23 , and an outlet duct  24 . The mounting plate  22  has an opening  25  and mounting holes  26 . Mounting plate  22  is sized to fit over the flanges  20  of the base  11  with a gasket  19  between them.  
         [0023]    The hood  23  is sized to cover the opening  25  and has intake vents  27  around a portion of its periphery near its lower edge, and an outlet duct  28  on one side.  
         [0024]    The head  12  can be made of duct material commonly known in the art, such as sheet metal, plastic or other rustproof material.  
         [0025]    The core assembly  13  includes a cover  30 , and a motor  31  having a shaft  32 , on which are mounted both a composite dish and cup  33 ,  34 , and a fan  35 .  
         [0026]    The cover  30  has a top  36 , a frustoconical sidewall  37 , a lip  40  along the lower perimeter, and mounting tabs  41  which extend outwardly from lip  40 . The cover  30  is sized so that it can be mounted to the shoulders  17  of the base  11  resting on the lip  40  and secured by threaded fasteners through the mounting tabs  41 .  
         [0027]    Preferably risers  42  are provided between the cover  30  and the shoulders  17 . The risers  42  are comprised of threaded rods, one end of which are fastened to the shoulders  17  of the base  11  and the other end of which are fastened to the mounting tabs  41  of the cover  30 . This adds space between the cover  30  and the base  11 , thereby facilitating the evacuation of air and water droplets from underneath the cover  30 .  
         [0028]    The cover  30  is provided with sharp edged ridges  43  along the inner surface of the sidewall  37  which are described in greater detail below.  
         [0029]    The motor  31  is mounted on top of the cover  30 , with a vertical shaft  32  positioned coaxially with the cover  30  and extending both above and below the motor  31 . Motor mounting holes  44  are provided in the top surface  36  of the cover  30 , as is a shaft opening  45 .  
         [0030]    On the portion of the shaft  32  extending above the motor  31 , the fan  35  is mounted. On the portion of the shaft  32  extending below the motor  31 , an optional spool  47  is mounted using a stop collar or set screw or other means known in the art.  
         [0031]    The spool  47  has three flat cylindrical elements with different outer diameters stacked together but separated by spacers of a smaller diameter. The largest cylindrical surface of the spool  47  has a diameter less than the largest diameter of the cup  34 , and is positioned to face the lower end of the shaft  32 .  
         [0032]    Immediately adjacent to the spool  47  and coaxially on the shaft  32  is mounted the rotating dish  33 . The axial position of the dish  33  is such that its rim  38  is aligned toward the ridges  43  of the cover  30 .  
         [0033]    The cup  34  is assembled coaxially on the shaft  32  immediately below the dish  33  and has a tapered profile that merges with the lower portion of the dish  33 .  
         [0034]    A nut  52  is provided on the shaft  32  to secure the cup  34 , dish  33 , and spool  47 .  
         [0035]    Connection to an external water supply is provided through a fitting  53  mounted in an end panel  15 . The fitting  53  leads to a float valve  54  which is controlled by a float  55  in the water reservoir  21 . When the water level in the reservoir  21  falls below a predetermined level, the float  55  causes the valve  54  to open, permitting water to flow into the reservoir  21 .  
         [0036]    In the illustrated embodiment, the water handling system includes an optional pump  56 , which draws water from the reservoir  21  through an inlet  58 , and supplies water through a hose  57 . The hose  57  passes through an opening in the base  11 , to a coupling  60  mounted in the upper surface of the cover  30 . From the coupling  60 , a rigid tube  61  directs the water to against the spool  47 .  
         [0037]    In operation, the motor  31  causes the fan  35  to rotate thereby creating a stream of air entering the intake vents  27  and discharged through the outlet duct  28 , and also causes the dish  33  and cup  34  to spin with the shaft  32 .  
         [0038]    As the cup  34  spins, it draws water upwardly from the reservoir  21 . The water moves upwardly in the form of a thin film along the outer surface  51  of the cup  34  and dish  33 , until it reaches the rim  38  of the dish  33 . At this point the spinning action causes the water to be thrown free of the dish  33  whereupon it strikes the ridges  43  provided on the inner surface of the cover  30 .  
         [0039]    Upon striking the ridges  43 , the water is broken into very fine particles. The very fine droplets are readily entrained and absorbed into the air to provide a humidified air discharge from the head  12  that is fog-like rather than mist-like. In this sense, the discharge is “non-wetting” because objects even very close to the discharge do not become wet. The fog-like discharge becomes invisible within a relatively short distance of the outlet duct  28  in typical operation.  
         [0040]    As the water in the reservoir  21  is depleted, the float valve  54  opens allowing supply water to flow into the reservoir  21  through the valve outlet  59 . This ensures that the water level in the reservoir  21  is sufficient to keep the lower portion of the cup  34  immersed.  
         [0041]    As shown more clearly in FIGS. 3, 4 and  5 , the ridges  43  of the cover  30  provide an impingement surface that is significantly different from those of known centrifugal humidifiers. The ridges  43  present a sawtooth profile with each ridge having a broader, more gradually inclined first side  62  that faces toward the direction of rotation of the spinning dish  33 , and a narrower, steeper second side  63  that faces away from the direction of rotation of the spinning dish  33 .  
         [0042]    This sawtooth profile of the ridges  43  increases the effective impact surface. Water droplets thus impinge repeatedly on successive ridges to be broken into a finer size. Moreover, less water is trapped between successive ridges so throughput and efficiency are enhanced.  
         [0043]    The sawtooth profile is also less prone to entrapment and buildup of dust and other airborne particles.  
         [0044]    Measurement of the droplet size in the discharge during operation of a prototype of this humidifier showed: 95 percent of the droplets between 5 to 21 microns; a minimum size of 2.2 microns; and 50 percent of the droplets under 11 microns. It was also observed that the discharge was non-wetting on human skin at a distance of 20 centimeters.  
         [0045]    In the embodiment illustrated in FIG. 3, the sawtooth ridges are oriented radially. In an alternative embodiment shown in FIG. 6 the sawtooth ridges are spirally inclined.  
         [0046]    The operation of the illustrated embodiment of the present invention is further enhanced by the optional pump  56 . As described earlier, the pump  56  draws water from the reservoir  21  to direct a stream of water toward the spool  47  which then distributes a film of water outwardly onto the inner surface  64  of the dish  33 . This water rises up the inner surface  64  until it reaches the rim  38  of the dish  33 , where it is thrown free to strike the ridges  43  in the same fashion as the water drawn upwards along the outer surface  51  of the dish  33 .  
         [0047]    By using both the inner surface  64  and outer surface  51  of the dish  33  to distribute water against the ridges  43 , the rate at which water is transferred to the surrounding air is increased. Use of an internal circulation pump in a prototype of this humidifier has been measured to double the performance with little effect on discharge droplet size.  
         [0048]    Although only one tube  61  is illustrated, a plurality of tubes may also be provided to direct water at various points.  
         [0049]    It is to be understood that the invention is not limited in its application to the details of an arrangement of components illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced or carried out in various ways within the scope of the claims. It is also to be understood that the terminology employed herein is intended for the purpose of description and not limitation. In its broadest scope, the present invention encompasses many modifications and alternative embodiments, appropriate for different circumstances.

Technology Classification (CPC): 5