US2801793A - Fan blade - Google Patents

Description

Augvs, 1I957 A. E. KLINE 2,801,793

FAN BLADE Filed July 21, 1955 INVENTOR. "flrt/mr' E. Kline BYWAQW ATTORNEY United States FAN BLADE Arthur E. Kline, Albion, Mic-11., assignor to McGraw- Edison Company, a corporation of Delaware Application July 21, 1955, Serial No. 523,513 Claims. (Cl. 230-259 which not only efliciently performs its primary purpose of propelling air but in addition, coacts with its driving motor in such manner as to exert a motor cooling influence thereon.

Another object is to incorporate motor cooling features in the fan design without sacrifice of mechanical strength,

balance or appearance and without materially increasing-the burden on the fan driving motor.

A further object of this invention is to design a fan whose supporting hub does not extend axially an appreciable distance beyond the margins .of the efiective .air moving surfaces of the blades so that the fan in combination with its driving motor shall require a minimum .of axial space.

A general object is to provide a new and improved fan blade structure and more specific objects will appear from time to time throughout the course of the specification.

Although the fan construction forming the subject of the instant invention is intended for general use, its employment is particularly advantageous in residential, portable, or window mounted room ventilating units where for esthetic and practical reasons it is highly desirable that the fan cabinet occupy a bare minimum of room space. Hence, the illustrative embodiment includes certain figures which suggest the compactness attainable through use of the fan in such an air circulating device.

In general terms, the invention comprises a fan having a deep drawn central portion from which the integral pitched main blades extend radially, and wherein the margins of the blades lie wholly Within parallel planes transverse to the axis of revolution, and spaced not greater than the axial length of the deep drawn cuplike central portion. The cuplike portion is further characterized by its having peripheral blade distinguishing openings communicating from its interior to its exterior. One margin of these openings is preferably inclined and extends radially inward toward the fans axis of revolution to define individual motor skimming vanes which, during rotation of the fan blade, skim the outer periphery of the driving motor in such manner as to impel the normally quiescent air surrounding it into the path of the main fan blades. This motor cooling phenomenon is further augmented by providing the fans central portion with suitable axially impressed fins which serve the purpose of centrifugal fan blades. Air which is drawn through apertures in the end bearing caps of the motor is acted upon by the salient centrifugal fins and forced into the path of the aforesaid vanes. The combined effect of these structural features is to disrupt or agitate the laminar, entrapped, quiescent air surround- 2,801,793 Patented Aug. 6, 1957 ing the motor and remove it for replacement by compartively cooler, air, so that the thermal. rating of the motor will not be exceeded and as an ultimate consequence, a smaller motor may be utilized than would normally be required to impel a given quantity of air with conventional fan designs.

The foregoing objects and advantages will be more evident from the following detailed description of an illustrative embodiment of the invention, particularly when considered in connection with the accompanying drawing in which:

Fig. 1 is a front elevational view taken on what is the normal air discharge side of the fan blade;

Fig. 2 is a rear elevational view taken on the air input side of the fan blade, the driving motor thereof being suggested by a concentric broken line and the supporting cabinet being indicated by broken boundary lines;

Fig. 3 ,is an elevational view taken on the right side of Fig. 1, the driving motor and supporting cabinet being indicated by broken lines; and,

Fig. 4tis a sectional view taken on a line corresponding. with .44 of Fig. 1, the driving motor being indicated in broken transparent phantom lines.

In the interest of brevity, the mechanical steps of progressively forming a fan such as the subject of the instant invention will not be discussed in detail since a more complete description of the final product will enable those versed in the art of sheet metal and plastic fabrication to reproduce the fan blade.

Referring to Fig. 1 it will be seen that the fan is of unitary construction comprising a deep drawn central .cup designated generally by the reference numeral 1 from which the integral blades 2, defined by leading edge 21 and trailing edge 22, extend radially. To those familiar with the art, it is, of course, evident that cup 1 and blades 2 are initially coplanar with each other whenthe outline of the fan is stamped from a flat piece of sheet metal. Concentric with central cup 1 in Fig. 1 there is a circular recess 3 for accommodating a three screw hub 4 which is used for attaching the fan to the shaft of its driving motor. Hub 4 may be of any conventional construction but it is preferred that it embody shock absorbing means such as a rubber bushing (not apparent) in order that noise causing vibrations will be minimized.-

From inspection of the drawing it is obvious that in this instance the individual blades 2 are flat, thereby permitting rotation of the fan in either direction if that is desired. However, insofar as the features of the instant invention are concerned, it is immaterial Whether the blades are planar or of some curvate cross section.

In Figs. 2 and 3 the novel fan is shown mounted in a substantially square sheet metal cabinet. 5 defined by broken lines. It is understood that cabinet 5 forms no part of the invention but merely suggests how the fan may be mounted within the confines of a window frame when it is desired to draw fresh air into a room of a residential dwelling, for example. Adapters for accommodating housing 5 to a particular size of window frame are also omitted. For mounting "a motor 6 with in cabinet 5 any suitable means such as four straps '7 may be used, here shown attached to the motor 6 and extending to the cabinet 5 upon which they are anchored.

While motor 5 may be of any conventional construc tion it is preferable that it have a configuration somewhat similar to that indicated in the drawing. In the illus trated motor each bearim cap 8, i3 is provided with a plurality of radial vent apertures 10, 11 communicating with the interior of the motor. A plurality of axial holes It will appear more fully hereinafter how the air passageways just alluded to cooperate with the central fan cup 1 for effecting cooling of the motor and .thus substantially increasing the air output of the fan Without exceeding the thermal rating of the motor, or in the alternative, permitting reduction of 'motor size. It is to be appreciated that maximum loading of the motor is a prime objective not only for sake of economy but for enhancing the overall esthetic appearance of the fan cabinet by reducing its size with respect to the ventilating units capacity.

Specific features of the fan which impress it with motor cooling and space conserving properties will now be discussed in detail. As indicated hereinabove, one of the motor cooling characteristics of the fan results from providing it with vanes which lie in the margin of the blade separating openings 16 resulting from forming the blade from the body of central cup 1. In the back view, Fig. 2, particularly, and in Fig. 3 it will be noted that the vanes 15 are sharp edged and directed inwardly toward the periphery of motor 6. Thus, it is evident that clockwise rotation of the fan in Fig. 2 will cause the vanes 15 to skim the outer periphery of the motor in such manner as to pick up the entrapped quiescent air normally surrounding it and direct the air into the path of the fans flow. The vanes 15 are particularly signicant features of the invention because, as those familiar with the art are aware, air has a propensity to exhibit a property analogous to viscosity which causes layers of it to adhere more or less dormantly on surfaces defining its path of how and as a result of air having considerable thermal. insulating ability which impedes heat dissipation fron the motor unless it is constantly moved from the periphery thereof by external means such as the novel vanes E5, the motor will be inclined to overheat dangerously.

Further reference to the drawing will reveal how the central cup 1 of the fan is provided with a plurality of circumferentially spaced radially extending fins 17 impressed therein. These fins 17 aside from performing the function of stiffening central cup I, serve an additional purpose. That is, the fins are impressed a little more deeply that is normally required for reinforcement in order that they together constitute what is in effect a centrifugal fan disposed inside the cup 1 in endwise adjacence to motor 6. in Figs. 3 and 4, particularly, it will be noted that fins 17 also extend axially along the inner surface of central cup 1 and that certain of them terminate in the reinforcing rib 18 disposed in the heel 19 of each fan blade 2. From this construction it should be evident that the combined effect of the fins i7 is that of a centrifugal fan acting upon the air surrounding both the outer periphery of motor 6 and its front end 8. When this air is acted upon by the fins 17, it is centrifugally expelled through blade separating opening 16, its only possible outlet, and into the path of trailing vanes 15 which deflect it ahead of blades 2 into the main air flow stream of the fan.

As indicated above there are provided both radial it ill and axial l2, l3 apertures in the motor 6 for facilitating flow of cooling air therethrough. Now, it is well known that the velocity of the principal air stream through the fan is maximum near the outer tips of the blades and approaches a minimum or near zero at or near the axis of revolution. Normally this inherent characteristic of fans would tend to limit the quantity of air flowing through the apertures because that air would not only be of low velocity but would also be entrapped between cup 1 and the motor 6. However, according to the invention, When what would be low velocity air is drawn axially through apertures 11 and 13 and expelled from 10 and 12, it is further accelerated by deeply impressed centrifugal fins 17 which force the air radially into the path of vanes 15. Thus, the motor is effectively cooled by convectional currents on the inside and outside.

It is evident from inspection of the broken away section of Fig. 4 that the clearance space between fins 17 and motor 6 is not particularly critical, it being controlled principally by the amount of freedom required by vibration absorbing hub 4. Obviously, such clearances will always be maintained as to preclude rubbing of the fan on the motor.

It is recognized that in conventional construction of small motors, it is common practice to include within the motor housing, at the shaft end particularly, a centrifugal fan for drawing cooling air through the inside of the motor. However, in a fan construction where the motor is adapted to reside within a cup for saving axial space there is little advantage to employing a motor having a built in centrifugal cooling fan unless the fan embodies elements of the instant invention which effectively removes the heated air when it is expelled from the motor. For this reason, the effectiveness of a motor having a built in fan can be realized most completely by using it in conjunction with a fan such as that herein described.

Although only one form of fan incorporating the inventive features has been described and illustrated, the invention may be variously embodied in fans having a general configuration substantially different from that shown. Accordingly, it is intended that the scope of the invention be limited only by the clear import of the claims which follow.

It is claimed:

1. In combination, a motor and a unitary propeller type fan coaxial therewith, said motor having a rear end and a shaft end provided respectively with cooling air inlet and outlet apetures communicating interiorly of said motor, said fan comprising a central cup-like portion substantially axially coextensive with said motor and including a face transverse to the motor axis and an axially extending surface, a plurality of fan blades having leading and trailing edges lying within parallel planes normal to the axis of said motor and intersecting the axial extremities of said motor and said face, said blades being formed integrally from said axially extending surface and spaced from each other by openings therein, a substantially radially directed vane extending axially intermediate said face and one of said blade edges to define a margin of each opening, said vanes being adapted to skim the periphery of said motor during rotation of said fan, a plurality of radial fins embossed in said face and confluently continuing into said axially extending surface and terminating in proximity with the blades, whereby air flowing from the interior of said motor through said outlet aperture may be engaged by said vanes through said openings and discharged into the main air flow path of said fan.

2. In combination, a motor and a unitary propeller type fan coaxial therewith, said motor having a rear end and a shaft end provided respectively with cooling air inlet and outlet apertures communicating interiorly of said motor, said fan comprising a central cup-like portion substantially axially coextensive with said motor and including a face substantially normal to the motor axis and an axially extending peripheral surface, a plurality of fan blades having leading and trailing edges lying within parallel planes normal to the axis of said motor and intersecting the axial extremities of said face and motor, said blades being formed integrally from said axially extending surface and spaced from each other by openings therein, a plurality of radial fins protruding from said face toward the outlet apertures of said motor for centrifugally expelling air therefrom toward said openings, a substantially radially directed vane extending longitudinally intermediate said face and one of said blade edges to define a margin of each opening, whereby air centrifugally expelled from said radial fins may be received by said vanes through said openings and discharged into the main air flow path of said fan.

3. The invention according to claim 2 wherein the fins impressed in said face extend confluently into said axially extending surface.

4. In combination, a motor and a unitary fan blade mounted thereon, said fan comprising a central cup-like portion substantially axially coextensively surrounding said motor and including a face transverse to the axis of revolution and an axially extending periphery, a plurality of fan blades extending integrally from said axially extending periphery and circumferentially spaced from each other by openings therein, an axially disposed vane defining one margin of each respective opening and extending inwardly of said cup-like portion toward the periphery of said motor, a plurality of radial fins embossed in said face and confluently continuing into said axially extending periphery and terminating in proximity with said blades, whereby during revolution of said fan said vane may skim entrapped gas from the periphery of said motor and discharge it into the main air flow path of the blades.

5. A unitary propeller type fan comprising a cup-like central portion formed concentricallywith the axis of revolution and including a front face normal to said axis and an axially extending surface projecting rearwardly and integrally from the face, a plurality of fan blades each having a heel portion bent from the rearward margin of the axial surface, said blades being pitched to the front with the rear radial edge of each blade substantially in a first transverse plane including the rearmost extremity of said margin and another radial edge of each. blade lying in a parallel plane spaced wholly forward of said first plane, said blades being circumferentially spaced from each other by openings in said axial surface, a substan' tially radial integral vane axially coextensive with said opening and terminating at the rearmost region of the heel portion, said vane defining an edge of said opening, a plurality of radial fins embossed in said front face and continuing into said axially extending surface toward the heel of the blade, said fins and said vane impelling air entrapped within said cup-like portion into the main air stream of said fan.

References Cited in the file of this patent UNITED STATES PATENTS 997,678 Jalonick July 11, 1911 1,383,883 Truitt et a1. July 5, 1921 1,620,875 'Currie Mar. 15, 1927 1,977,072 Lyman Oct. 16, 1934 2,073,868 Fladeland Mar. 16, 1937 2,262,695 Moeller Nov. 11, 1941 2,585,265 Moeller Feb. 12, 1952 2,590,877 Lindberg Apr. 1, 1952 2,622,793 Ganger et a1. Dec. 23, 1952 2,731,193 Lall et al. Jan. 17, 1956 FOREIGN PATENTS 478,417 Great Britain Jan. 18, 1938 509,842 Belgium Mar. 31, 1952

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