Patent Publication Number: US-6339935-B1

Title: Evaporator scroll for blower wheel

Description:
FIELD OF THE INVENTION 
     This invention relates generally to apparatus for uniformly distributing conditioned air across the full width of an indoor coil of an air conditioner unit. 
     BACKGROUND OF THE INVENTION 
     In U.S. Pat. No. 4,951,737 there is disclosed a packaged terminal air conditioner (PTAC) unit that has an indoor section and an outdoor section that are separated by a dividing wall. Each section contains a heat exchanger or coil and a fan for moving air over the coil surfaces. The fan utilized in the indoor section is a cross flow blower wheel fan that extends laterally across the width of the indoor coil. The cross flow blower contains a series of elongated curved blades that are spaced apart to form a cylindrical unit. The fan is driven by a motor at one end and draws return air through the indoor coil and circulates the conditioned air leaving the coil back into the comfort region. The outdoor fan servicing the outdoor coil is a centrifugal fan that requires the use of a second motor. 
     A similar type PTAC unit is disclosed in a later U.S. Pat. No. 4,944,654, in which the cross flow blower used in the indoor section of the unit is replaced with a centrifugal fan that is driven along with the outdoor fan by a single fan motor. The indoor fan, in this case, is equipped with forward curved blades and is mounted within a split scroll arrangement. The scroll increases in diameter to either side of a cut off point which is located at about the horizontal center line of the blower. Each section of the split scroll is a curved wall defining a logarithmic scroll, both scrolls arranged to discharge air into a plenum that extends horizontally to either side of the wheel above the indoor coil. It has been found, however, that a rather large area of reduced flow is created within the plenum that is generally located directly over the blower. A noise reducing baffle is mounted in the area of reduced flow that further impedes flow in this critical region. 
     It should be further noted that the size and positioning of the scrolls employed in the split scroll arrangement is limited by the available space in this part of the air conditioning unit. This, in turn, limits the amount of air that can be handled by the split scroll system. In addition, the forwarded curved blades of the blower tend to be relatively noisy. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to improve air conditioning units and, in particular, packaged terminal air conditioner (PTAC) units. 
     It is a further object of the present invention to improve the air handling capabilities of the indoor section of a PTAC unit. 
     It is a still further object of the present invention to improve the air handling capabilities of the indoor section of an air conditioning unit that employs a centrifugal blower. 
     Another object of the present invention is to improve the uniformity of air distribution in the indoor section of an air conditioning unit. 
     Yet a further object of the present invention is to reduce the amount of noise produced by a PTAC type unit. 
     These and other objects of the present invention are attained by air handling apparatus suitable for use in an air conditioning unit having an indoor section that is separated from an outdoor section by a divider wherein each section has a fan and a heat exchanger coil. A housing is mounted behind the indoor coil that has a blind opening passing inwardly through the front wall of the housing which faces the indoor coil. The opening has a rectangular shaped upper section that extends laterally above the top of the coil and a volute shaped lower section that houses a centrifugal blower wheel having rearwardly curved blades and which opens upwardly through the bottom wall of the upper section. The lower section contains a scroll shaped wall that is generally centered about on the axis of the blower wheel whose radius of curvature increases from a cut off region at about the 2 o&#39;clock blower location through an arc of about 200°. A second linear wall is positioned tangent with the distal end of the scroll wall and extends upwardly to intersect the bottom wall of the upper section of the opening to establish an exit region through which conditioned air that is drawn into the housing by the blower wheel is uniformly distributed across the upper section of the opening and is discharged back into the comfort region. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     For a better understanding of these and objects of the invention, reference will be made to the following detailed description of the invention which is to be read in connection with the accompanying drawing, wherein: 
     FIG. 1 is a front perspective view of a packaged terminal air conditioning unit embodying the teachings of the present invention; 
     FIG. 2 is a rear perspective view of the air conditioning unit illustrated in FIG. 1 with the shell removed further to display the outdoor section of the unit; 
     FIG. 3 is a front perspective view illustrating the indoor section of the unit; 
     FIG. 4 is a front elevation illustrating the indoor blower and the housing in which the blower is contained; 
     FIG. 5 is a schematic front view of the blower illustrating a generally radial blade suitable for use in one form of the invention; and 
     FIG. 6 is a schematic front view of the blower illustrating a rearwardly curved blade suitable for use in the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Turning now to FIGS. 1-3, there is illustrated a packaged terminal air conditioner (PTAC) unit generally referenced  10 , that embodies the teachings of the present invention. The unit is housed within a shell  12  that typically is mounted within an outside wall of a structure containing the comfort region that is serviced by the unit. The unit contains an indoor section and an outdoor section that are separated by a divider. Each section, in turn, includes a heat exchanger coil and a fan or blower wheel for moving air over the coil surfaces. A removable cover  13  is mounted at the front of the unit that closes against the shell which generally enclosed the indoor section of the unit. The cover includes a lower opening  15  through which return air from the comfort region is drawn into the unit and an upper opening  16  through which conditioned air is delivered back into the comfort region. 
     The unit controls are located in a recessed well beneath the front cover. Access to the controls is provided by a hinged door  17  mounted in the front cover. 
     FIG. 2 illustrates the outdoor section of the unit with parts removed for the sake of clarity. The component parts of the unit are mounted upon a base pan  20 , and include the outdoor coil  21 , a portion of which is shown in phantom outline. An outdoor fan  23  is mounted upon the rear shaft  24  of a drive motor  25  which, in turn, is supported in a mounting bracket  27 . As will be explained in further detail below, the motor also includes a front shaft that is arranged to drive an indoor blower wheel that services the indoor coil. A vertical wall member  28  separates the outdoor section of the unit from the indoor section. A housing, generally referenced  30 , is located on the indoor side of the wall and is secured to the pan adjacent to the wall. 
     The indoor centrifugal blower wheel  31  and the indoor coil  32  are shown in greater detail in FIGS. 3 and 4. The blower wheel is, as explained above, mounted for rotation upon the horizontally disposed front shaft  34  of motor  25 . The blower wheel is contained within the previously noted housing within a blind opening  35  that passes inwardly through the front wall of the housing. The housing  30 , along with the indoor coil  32  are both mounted upon an auxiliary pan  38  which, in assembly, is seated upon the floor of the main base pan  20 . The blind opening in the front wall of the housing is closed off by a vertically disposed rear wall  39  and contains a rectangular shaped upper section  40  that extends substantially across the width of the housing and a volute shaped lower section  41  that opens upwardly into the upper section through the bottom wall  42  of the upper section. The opposed ends of the upper section of the opening are closed by end walls  43 — 43 . 
     The main portion of the blower wheel is contained within the lower volute shaped section of the blind opening so that the tips of the blades  45  pass even with or slightly into the upper section of the opening as they move past the vertical axis  44  of the wheel. The volute shaped lower section of the opening is formed by a first spiral shaped wall  46  that is joined at its distal end by a linear inclined wall  47 . The proximal end of the spiral wall intersects the bottom wall  42  of the upper opening at about the 45° wheel position. A cut off region  50  is established between the proximal end of the spiral wall and the blower wheel which prevents air from passing therethrough as the wheel turns in a clockwise direction. The center of the spiral is located at about the center of the wheel and increases in a clockwise direction. The spiral wall increases through an arc of about 200° from its proximal end to its distal end. The linear wall  47  is placed tangent to the distal end of the spiral wall and extends in an upward direction to intersect the bottom wall of the upper section of the opening to establish a wide discharge region. 
     A logarithmic spiral is described by the spiral wall of the lower opening. In order to accommodate the wall without disturbing the spiral, a portion of the wall passes downwardly into a well  53  formed in the auxiliary pan. 
     The blower wheel contains a series of spaced apart blades  54  that are radially or rearwardly curved as shown in FIGS. 5 and 6 so that the blades angle at the tip diameter  56  is between 80° and 100°. This, in turn, permits the blower wheel to operate at a higher speed when compared to prior art blower wheels that employ forwardly curved blades. The blower wheel is thus able to run at higher speeds to produce a high static pressure while, at the same time, producing less noise when compared to blowers found in the prior art. 
     The wheel in combination with the above described volute shaped lower section of the opening serves to uniformly distribute the flow leaving the wheel across the upper section of the opening. The upper section of the opening is situated at a height that is above the top of the indoor heat exchanger. The flow generated by the blower wheel is turned within the upper section of the opening and directed outwardly over the heat exchanger into the comfort region through the upper opening  16  located in the front cover of the unit. The back wall of the upper section is preferably arcuate in form and arranged to turn the flow toward the opening in the front cover. 
     Both the housing  30  and the auxiliary pan  36  are preferably cast from styrene to the desired shape. 
     While the present invention has been particularly shown and described with reference to the preferred mode as illustrated in the drawing, it will be understood by one skilled in the art that various changes in detail may be effected therein without departing from the spirit and scope of the invention as defined by the claims.