US 3830595 A
A centrifugal blower having a cantilever support structure for positioning the fan motor within the interior of the fan wheel. The support includes cantilever arms extending through the housing inlet opening to connections with a motor base plate located between the fan back plate and motor. Special tie rods are provided between the cantilever arms, whereby each arm cooperates with the others to resist tilt or wobble forces.
Description (OCR text may contain errors)
United States Patent [191 Carpenter et a1.
[451 Aug. 20, 1974 Filed:
MOTOR MOUNTING SUPPORT Inventors: Charlie P. Carpenter; Robert A.
Zeller, both of Elyria, Ohio Assignee: The Tappan Company, Mansfield,
Aug. 16, 1972 Appl. No.: 281,130
U.S. C1 417/363, 248/15, 310/91 Int. Cl. F16t 15/00, H02k 5/24 Field of Search 417/360, 363, 355, 353;
References Cited UNITED STATES PATENTS Hess et a1. 417/363 X Coe 417/363 Cole 417/363 X Cann et a1. 417/363 X FOREIGN PATENTS OR APPLICATIONS 729,484 11/1942 Germany 417/363 Primary Examiner-William L. Freeh Assistant Examiner--Richard Saer Attorney, Agent, or Firm-Donnelly, Maky, Renner & Otto [5 7 ABSTRACT A centrifugal blower having a cantilever support structure for positioning the fan motor within the interior of the fan wheel. The support includes cantilever arms extending through the housing inlet opening to connections with a motor base plate located between the fan back plate and motor. Special tie rods are provided between the cantilever arms, whereby each arm cooperates with the others to resist tilt or wobble forces.
3 Claims, 3 Drawing Figures MOTOR MOUNTING SUPPORT THE DRAWINGS FIG. 1 is a fragmentary sectional view through a blower utilizing the invention.
FIG. 2 is a right end view of the FIG. 1 structure with the fan motor removed.
FIG. 3 is a perspective view of a rod-formed strut or arm structure used in the FIG. I assembly.
GENERAL ARRANGEMENT FIG. 1 shows a double inlet centrifugal blower having a scroll housing which includes a housing side sheet 10, said sheet being inwardly curved at 12 to define an inlet opening 14 for air going into the interior space 16 within a centrifugal fan wheel 18.
Fan wheel 18 comprises two end plates or rings, one of which is shown at 20. lnterconnecting the end plates are the usual fan blades 22. The fan wheel is completed by a centerplate 24 and hub 26. In operation, an electric motor 28 is energized to rotate wheel 18 around the axis of motor shaft 30, whereby the blades draw air through inlet opening 14 and another similar inlet opening (not shown) in the non-illustrated housing side sheet. The air is exhausted through an outlet opening in the housing, not shown. The arrangement is generally similar to that shown in U.S. Pat. No. 3,127,092, issued Mar. 31, 1964 to R. E. Schenberger or U.S. Pat. No. 2,936,947, issued May 17, 1960 to J. H. Staak.
M OTOR-BASE ARRANGEMENT Motor 28 includes bearings for shaft 30 contained within end caps 32. The inner of left end of the motor carries four axially spaced mounting screws, two of which are shown at 34 in FIG. I. These mounting screws project through slots 36 in a sheet metal base plate 38. Nuts 40 are threaded onto the ends of the screws to lock the motor onto the base plate.
Base plate 38 is of circular outline as seen in FIG. 2, and is provided with an enlarged central opening 42 to accommodate the left end cap 32. An endless reinforcing flange 44 extends axially from the peripheral edge of the plate; additional reinforcement could be provided by forming the plate with embossed areas, as is common in many sheet metal structures.
As shown in FIG. 2, plate 38 is formed with eight radial slots 36. In the usual situation only four of the slots would accommodate mounting screws 34; the extra slots are provided for adapting the plate to different motors, varying in horsepower, mounting screw location frame size, etc. Preferably slots are used instead of round holes to permit radial adjustment of the fan wheel, as may be necessary for best alignment with inlet opening 14 and the housing cut off (not shown).
CANTILEVER ARM STRUCTURES Motor base plate 38 is supported and positioned within the fan interior by means of three identical cantilever arms or struts 46 evenly spaced around the motor periphery. As shown best in FIG. 3, each arm 46 is formed by a single circular cross section rod bent or curved at 48 into a hairpin shape. The hairpin element is further bent at 50 and 52 to form a central straight section 53, an outwardly radiating end section 54, and an inwardly radiating end section 56. Each of these sections comprises two generally parallel rod elements.
Each arm or strut 46 has its inwardly radiating rod section 56 welded to the left face of plate 38. The outwardly radiating end section 54 of each arm 46 is located adjacent the outer surface of the housing side sheet 10 for connection thereto by means of the semiresilient anchors 60. Each anchor comprises an elastomeric sound-absorbing grommet 62 encircling a metal sleeve 64 that in turn surrounds a screw 66 that threads into a taped opening in the housing side sheet. One or more washers 68 distribute axial thrust forces from screw 66 onto the elastomeric grommet.
Each grommet is provided with an external groove which enables the grommet to fit onto the U-bend area 48 of the rod section 54. After the three grommets have thus been inserted onto the respective rod section 54, the entire assembly can be positioned within the inlet opening 14 of the housing for thread-in of the screws 66.
TIE RODS The three arms 46 are preferably rigidified and interconnected by means of three circular cross-sectioned tie rods 70 oriented as chords with respect to the motor axis. Each tie rod comprises an elongated straight central section 72 and short turned end sections 74. Sections 74 are welded to the rod sections 54 of the arms 46 to provide a stress-transmitting ring structure. As seen in FIG. 2, the endless ring is of generally triangular cross section wherein the central sections 72 of the tie rods form the sides of the triangle and the U-bend portions 48 of the arms 46 form the apex portions of the triangle. The space circumscribed by the triangle is large enough to permit passage of motor 28 therethrough, as when the motor is being affixed to base plate 38.
INSTALLATION PROCEDURE Initially fan motor 28 is connected to base plate 38 while outside the blower housing. With fan wheel 18 plished by reversing the procedure.
OPERATING FEATURES The fan motor 28 is ultimately supported or suspended in the general plane 10a near housing sheet 10; i.e., in the plane of the three anchors 60. The weight of the fan wheel and the centrifugal flywheel-like loading forces are transmitted to the motor in the plane 24a of the fan center plate (or back plate if the blower is of the single inlet type). Thus, the motor support must be of sufficient stiffness and character to adequately counteract the product of the load forces and the moment arm existing between the two planes 10a and.24a.
Radial load forces in plane 24a tend to momentarily or continuously deflect one or more of the arms 46 around their points of connection with anchors 60. The deflecting force is resisted by the other two arms 46 and the three tie rods 70. Assuming the lowermost arm 46 is subjected to a radial (downward) deflecting force, the other two uppermost arms 46 will be put in tension so that their elastomeric grommets will'be compressed to resist the force. The uppermost (horizontal) tie rod 70 interconnectthe two uppermost screws 66 so that each screw-grommet unit is better able to absorb a proportionate share of the load. Circumferential loadforces in plane 24a tend to twist the arms 46 about their anchors 60; the twisting action is generally along directional line 76 (FIG. 2). Tie rods 72 interconnect the various arms 46 so that the arms are not able to independently twist; instead the three arms must twist together more or less as a unit. Each arm reinforces its fellow arms so that each is required to absorb or counteract only a portion of the twisting force. Preferably each tie rod is straight, as opposed to being curved, whereby to prevent bending of the rod in response to load forces.
Each arm 46 includes two parallel rod elements. These elements individually are relatively flexible and hence unstable. However, after the arms have been welded to base plate 38 the parallel rod elements acquire increased flex resistance; they then act somewhat in the nature of solid plates (in which the space be tween the rod elements is filled in). When the respective arms 46 are further interconnected by the tie rods 70 the resultant assembly becomes a fairly rigid, nonflexible unit.
It will be noted that the motor mounting screws 34 are shown near the outer periphery of the motor. This outermost disposition of the screws is preferred since there is then a lessened tendency for the motor to wobble or work loose from plate 38. In structure where the motor is mounted near its axis, as by means of a ring clamped onto end cap 32, there is a possibility for transverse wobble of the motor about its mounting connection. When widely spaced mounting screws are employed there is a lessened tendency for wobble between the motor and its mounting structure.
For utmost rigidity the motor support structure should be of heavy gauge material. Prior art devices have sometimes employed heavy gauge channels and plates. However, such structures act as air obstructions to reduce the effective size of the air inlet opening and thus unduly limit the volumetric flow and/or pressure capability of the blower. The illustrated use of rodformed elements achieves what is believed to be a satisfactory combination of good support structure rigidity and good air flow.
This invention was conceived primarily for use in blowers employed in hot air furnaces. Such blowers have wheel diameters on the order of ten inches, wheel speeds in the vicinity of 1,000 rpm, volumetric deliveries on the order of 1,500 c.f.m., and motor sizes up to about one half horsepower. With such blowers we have constructed motor support structure using steel rods with diameters of about 0.2 inch and steel plate (for plate 38) of about 0.05 inch thickness. We have I found that the motor support structures thus formed comprising a single rod member bent into a generally U-shaped configuration including an interconnecting neck portion and an inner end portion, said neck portion and inner end portion of each said strut being respectively bent generally radially outward and inward, a plurality of circumferentially-spaced resilient anchors secured to the outer surface of said side sheet and having said neck portions extending partially therearound for connecting said struts to said side sheet, said motor being mounted to a base plate at its inserted end within said inlet, said inner end portions of said struts being attached to said base plate, tie means interconnecting all of said rod struts at said neck portions thereof inwardly of said resilient anchors and lying in a plane closely adjacent the plane of said housing side sheet, and said struts extending freely in unconnected relationship to one another between said tie means and said inner end portions thereof.
2. The device of claim 1 wherein said tie means comprises a plurality of individual tie rods spanning adjacent ones of said rod struts.
3. The device of claim 2 wherein each of said tie rods has inwardly bent end portions and is longitudinally straight between said end portions. l