US 3846040 A
Disclosed is scroll type blower housing having a non-uniform expansion rate. The periphery is generally curved to form a scroll of linear expansion angle from the cut-off but has at least one flat wall segment within the first 200 DEG which reduces the radius of the scroll in that area to less than the radius required for a linear expansion angle.
Description (OCR text may contain errors)
Umted States Patent 1191 1111 3,846,040 Dennis Nov. 5, 1974 [5 BLOWER HOUSING 2,994,348 8/1961 Cape 415 219 c Wanton Donald L Dennis, Rt- 3,561,906 2/l97l Fermer 4l5/2l9 C Ja ks vill T 75766 FOREIGN PATENTS OR APPLICATIONS June France 1 4 l 5/206  Appl. No.: 263,714 Primary Examiner-Henry F. Raduazo Attorney, Agent, or Firm-Jack A. Kanz  U.S. Cl. 415/219 C, 415/206  1m. (:1. F0411 29/42  ABSTRACT 58] Field of Search 415/204, 206, 205, 203, Disclosed is Scroll yp blower housing having a 415 219 C, 4 uniform expansion rate. The periphery is generally curved to form a scroll of linear expansion angle from 5 R f n Cited the cut-off but has at least one flat wall segment within UNITED STATES PATENTS the first 200 which reduces the radius of the scroll in l 014 321 1/1912 Minor 19 that area to less than the radius required for a linear 214571142 12/1948 French 1:11:11: expansm angle 2,659,294 11/1953 Hersperger 1. 415/204 4 Claims, 2 Drawing Figures La- 45 H BLOWER HOUSING This invention relates to blower housings. More particularly it relates to scroll-type housings having nonlinear rates of expansion.
Conventional blower apparatus using a forwardcurved blade impeller generally employ a scroll housing wherein the impeller is axially mounted and the radial cross-section of the housing increases linearly around the impeller from the cut-off to the housing discharge. Air is drawn axially into the housing through the impeller. The resulting kinetic energy is transformed into pressure by the housing which collects and slows the air.
In many applications it is desirable that the space occupied by the blower housing be reduced as much as possible without substantially adversely affecting the performance of the system. A typical example is the use of such blower systems in connection with automobile air conditioning equipment which is adapted for underdash installation. In such cases usable space in the passenger compartment of the vehicle is somewhat limited, particularly by the usually large floor-board hump provided to allow clearance for the transmission and power-train assembly.
It has been discovered, in contrast to generally recognized principles, that conventional blower wheels may be used in scroll housings having relatively nonuniform expansion rates without adversely affecting the efficiency of the blower system. Furthermore, it has been discovered that by reducing the cross-sectional diameter of the scroll at certain locations and forming a flat wall segment which follows the chord rather than the circumference of the scroll, extremely compact housings may be produced which yield an unexpected increase in blower efflciency.
Accordingly, using the principles of this invention compact scroll-type blower housings may be designed which permit more flexibility in fitting blower housings into small inconvenient compact spaces. Furthermore, increased efficiency of the blower system can be achieved using conventional blower wheels. Other features and advantages of the invention will become more readily understood when taken in connection with the appended claims and attached drawings wherein FIG. 1 is a diagrammatical illustration of the blower housing illustrating the principles of the invention, and
FIG. 2 is a pictorial view of an air conditioner housing employing the blower housing of the invention.
In conventional scroll-type blower housings, the
housing perimeter is in the form of a scroll expanding radially from the impeller in the direction of rotation of the impeller. The point closest to the impeller, known as the cut-off, is positioned at a distance from the perimeter of the impeller which is determined by the diameter and rotational speed of the impeller, In conventional housings the radial cross-section of the scroll perimeter increases linearly from the cut-off to the dis charge. Once the desired expansion rate is determined, the dimensions of the housing may be readily computed.
Dimensions for conventional blower housings are set forth in Table 1 for housings having linear expansion angles of 6,- 8, 10 and l2.
TABLE 1 Housing Expansion Angle 6 8 l0 I 2 GA 0.83 1D 0.942D l.062D l.l68D OB 0.790D 0.886D 0.9920 l.()X4D OC 0.74XD. ().832D ().922D l.00D OD 0.707D 0.776D 0.8530 0.9l7D OE 0.665D 0.72lD ().748D ().843D ()F 0.624I) 0.666D 0.7l5l) 07500 CO 0.583D 0.6] lD 0.64M) 0.667D ()H 0.559D 0.5790 0.012!) (Hill-ID In the table D is the diameter of the impeller wheel and the points A through H indicate the points on the scroll as shown in FIG. I. In the conventional housing contemplated in Table l, the housing is an arcuate scroll expanding linearly from H to A.
It will thus be observed that once the desired expansion angle is determined, the radius of the scroll of any of the points H through A may be readily determined by referring to Table 1. Since the dimensions given in Table l are in terms of impeller diameter, linear expansion angle housings may be easily designed for any impeller.
It has been discovered, however. that unexpectedly improved blower efficiency can be realized when the housing circumference is altered to provide a nonuniform rate of expansion.
In accordance with the present invention at least one outer wall segment of the housing within about 200 of the cut-off follows the chord defined by an angle of about 45 rather than the arcuate circumference. It will be readily observed that when the housing follows the chord defined by the angle at the same radii rather than the arcuate circumference, the expansion angle of the housing is non-linear. Furthermore, it would appear that a partial recompression of the expanding air should occur within the housing in the area of the flat wall segment. Consequently a loss in efficiency of the blower will be expected.
It has been discovered, however, that by forming the wall segment to follow a chord defined by an angle of about 45 within the first approximately 200 of the scroll an increased system efficiency is observed. Furthermore, the increase is accentuated by forming a plurality of adjacent flat wall segments as shown in FIG. 1 and even further increased by reducing the radius of the scroll required for a linear expansion angle in the regions affected.
Referring now to FIG. 1 it will be observed that in a conventional housing radii OH, OG, OF, OE and OD may be defined in terms of the diameter of the wheel as set forth in Table l for any desired linear expansion angle. In accordance with the preferred embodiment of the invention radius OF, which is approximately 71 from the cut-off, is reduced to 95 percent of that required for a linear expansion angle. Radius OE, which is approximately I 16 from the cut-off, is reduced to percent of that required for a linear expansion angle. Radius OD is reduced to 96 percent of the radius which would be required for a linear expansion angle. Furthermore, the wall segments defined by the angles EOF and EOD are flat and follow the chord defined by the specified radii rather than the arcuate circumference of the scroll. In all other respects the scroll housings may conform to conventional dimensions.
Test comparisons have been made using the same impeller and motor in two housings of identical shape and configuration. Both housings were originally formed as conventional linear expansion angles housings. The first housing was not modified. The second housing, however, was modified asdescribed above wherein radius OF was reduced to 95 percent of the original radius OF. Radius OE was reduced to 80 percent of the original radius OE. Radius OD was reduced to 96 percent of the original radius OD. The wall segments DE and EF were fiat rather than curved. in all other respects the second housing was identical to the first housing. When operated under identical conditions,
the system using the second housing delivered percent to l8 percent more air at zero static pressure.
The reason for the demonstrated increase in efficiency is not fully understood. It is believed, however, that reduction of the expansion angle within the first 200 of the scroll, either by reducing radius OE or by forming a flat wall segment over about 45 percent of the scroll perimeter, causes a slight recompression and subsequent rapid expansion at a rate greater than the linear rate. This recompression and expansion appears to permit more volume of air to be moved through the system than may be moved through a system employing a linear expansion angle housing.
It should be recognized that forming any flat rather than curved segment on the periphery of the scroll will result in a reduced radius. Accordingly, the amount of reduction will be determined by the angle defined by the radii at the ends of the flat segment. increased efficiency, however, is achieved when the flat segments span about 45 of the perimeter. Further increase is observed when two flat segments are formed adjacent each other, each segment spanning about 45 of the perimeter, and the radius ofthe scroll at the adjacent ends of the flat segments is about 80 percent of the radius required for a linear expansion angle.
Best results are obtained when the flat segments are within about the first 200 of the scroll perimeter from the cut-off. Advantageously, this permits significant reduction of vertical dimensions of the housing and thus permits the installation of such housings in confined spaces which would not accommodate conventional housings.
An air conditioner housing employing the preferred embodiment of the blower housing of the invention is illustrated in FIG. 2. The housing includes a rectangular housing for containing the expansion coils. A pair of blower housings 21, 22 are attached to the back side of the housing 20 for directing air through the expansion coils. A drive motor 23 is mounted betweenthe blower housings and support impeller 24 within the housings 21, 22.
it will be observed that the housings 21, 22 are generally of the conventional scroll type with the discharge 25 connected directly to the housing 20 containing the expansion coils. The scroll housings 21, 22, however, each have flat segments 26, 27 each spanning about 45 of the housing perimeter within the first 200 of the housing from the cut-off. It will be observed that since the flat segments 26, 27 are within the first 200 of the cut-off the flat segments are generally on the lower and lower back portions of the housings 21, 22 when mounted as used in the air conditioner. Accordingly, the air conditioner housing may be readily used in under-dash installations in which conventional housing would not fit because of the curvature and larger volume of conventional housings.
While the invention has been defined with particular reference to blower housings used for automobile air conditioners, it will be readily apparent to those skilled in the art that the blower housings may be likewise advantageously used in other systems wherein mounting space is limited or increased efficiency is desired.
It is to be understood that although the invention has been described with particular reference to specific embodiments thereof, the forms of the invention shown and described in detail are to be taken as preferred embodiments of same, and that various changes and modifications may be resorted to without departing from the spirit and scope of the invention as defined by the appended claims.
What is claimed is:
l. Housing apparatus for a blower wheel having a radial periphery generally defining a curved scroll expanding at a linear expansion angle from the cut-off and having a first flat wall segment within the first 200 from the cut-off and a second flat wall segment adjacent said first flat wall segment.
2. Apparatus as defined in claim 1 wherein the radii at the ends of said second flat wall segments define an angle of about 45.
3. Apparatus as defined in claim 2 wherein said radius nearest the cut-off is about 95 percent of the length required to define a scroll having a linear expansion angle, the radius at the adjacent ends of said first and second flat segments is about percent of the length required to define a scroll having a linear expansion angle, and the radius of the scroll at the end of said flat segment furthermost from the cut-off is about 96 percent of the length required to define a scroll having a linear expansion angle.
4. Apparatus as defined in claim 3 wherein said radius nearest the cut-off is about 71 from the cut-off.