US 3147811 A
Abstract available in
Claims available in
Description (OCR text may contain errors)
Sept 8 1964 s. w. KLoNosKl 3,147,811
FAN ASSEMBLY Filed Dec. 24, 1962 ,4Z 35 /f 45 l' 3 FIG 3 a z2 INVENTO. ya 52 l l STEPHEN w. KLoNosKl ATTOR N EYS United States Patent() 3,147,811 FAN ASSEMBLY Stephen W. Klonoski, Torrington, Conn., assigner to The Torrington Manufacturing Company, Torrington, Conn., a corporation of Connecticut Filed Dec. 24, 1962, Ser. No. 246,738 7 Claims. (Cl. 170-173) This invention relates to air moving fans and the like and, more particularly, to an improved central support structure or spider particularly well suited to comparatively large fans in a range including 20 and 24 inch diameters.
It is the general object of the invention to provide a one-piece fan spider `of sheet material which is substantially lighter `and yet more rigid than similar spiders of known construction, and which exhibits vibration characteristics superior to those of spiders heretofore provided.
The drawing shows a preferred embodiment of the invention and such embodiment will =be described, but it will be understood that various changes may be made from the construction disclosed, and that the drawing and description are not to be construed as defining or limiting the scope of the invention, the claims forming a part of this specification being relied upon for that purpose.
Of the drawing:
FIG. 1 is a front view of a fan spider embodying the invention and which has attached thereto fan blades shown in broken line form.
FIG. 2 is a side View of the fan spider of FIG. l with the fan blades removed.
FIG. 3 is a fragmentary sectional View taken generally as indicated at 3--3 in FIG. 1 with background parts omitted.
Referring particularly to FIG. l, it will be observed that a spider shown therein includes a central or hub section formed integrally of sheet material with a plu-` rality of similar generally radially extending and circumf axially spaced arms 12, 12. Preferably, the spider is formed of sheet steel in a series of blanking and forming operations but the construction is equally adaptable to other materials. Similarly, four arms 12, 12 are shown but the number of arms is optional. Fan blades such as 14, 14 shown mounted on the arms 12, 12 in broken line form in FIG. l may Vary widely in configuration.
The central or hub section 10 of the spider is preferably apertured for convenient attachment to a hub rotatable on an -axis 16 and a central opening 18 is shown for this purpose. An inner annular portion 20 of the hub section 10 lies adjacent the central opening 18 and extends generally radially outwardly therefrom to an outer and marginal annular portion 22 of said section. Further, the inner annular portion 20 comprises inner and outer annular zones 24 and 26, the inner zone 24 being offset forwardly with respect to the outer zone 26 as shown. Other configurations may be provided for the inner zone 24 but said zone preferably takes a substantially conical form as best shown in FIG. 3.
Referring now to the outer and marginal annular portion 22 of the hub section 10, it will be observed in FIG. l that parts 28, 28 thereof between the arms 12, 12 are forwardly offset with respect to adjacent parts of the inner annular portion 20. The said parts 28, 28 of the marginal portion 22 may be regarded as comprising narrow elongated forwardly facing flanges 30, 30 and narrow elongated transition sections 32, 32 projecting generally rearwardly from the flanges to the outer zone 26 of the annular portion 20. As best shown in FIG. 3, the forwardly facing flanges 30, 30 extend at least in part in a radial plane as does the outer zone 26 of the annular portion 20. The transition sections 32, 32 extend angularly between the said flanges and said outer zone of the annular portion 20.
Now with regard to the arms 12, 12, it should be observed that provision is made for suitably pitching fan blades such :as the blades 14, 14 shown. That is, each of the arms 12, 12 is disposed in an angularly displaced or twisted relationship about a radial center line such as 34 with respect to the -aforesaid inner annular portion 20 of the hub section 10. As best illustrated in FIG. 2, the angularly twisted or displaced relationship of the arms is provided for in arcuately extending portions of the arms at inner end sections thereof.
Each of the arms 12, 12 may be regarded as comprising a central portion 36 and opposite side marginal portions 38, 38. The central portions 36, 36 of the arms are shown as being substantially flat over a major part of the radial extent of the arms viewed inwardly from their outer ends and the marginal portions 38, 38 are, in accordance with the invention, offset forwardly with respect to said central portions. Further, each forwardly offset marginal portion 38 forms a smoothly blending and continuous junction at its inner end with 4an adjacent forwardly offset part 28 of the marginal portion 22 of the hub section. Still further, it is to be noted that the degree or extent of forward 'offset of the arm portions 33, 38 is substantially equal to the degree or extent of forward offset of the parts 28, 28 of the hub marginal portion 22. Thus, a continuous forwardly offset portion is provided along the side of each arm 12, along an adjacent interarm part 28 of the hub section 10, and along the side of the next adjacent arm 12.
As ybest shown in FIG. 2, each of the forwardly offset arm portions 38, 38 comprises a narrow elongated generally forwardly facing flange 40 and an adjacent narrow elongated transition section 42 projecting generally rearwardly from the flange to the adjacent arm central portion 36. At each of the aforesaid junctions between offset arm portions 38, 38 and offset interarm parts 28, 28, the transition sections 32, 42 and the flanges 30, 40 are continuous and blend gradually with Iall of the transition sections being substantially equal in width. As illustrated in FIG. l, an inner portion 40a of each flange 40 is substantially equal in width to the aforementioned flange 30 of the forwardly `offset interarm parts 28, 28. A longitudinally adjacent outer portion 40b of each flange 40, however, is substantially wider than the portion 40a and is provided with apertures 43, 43 for the convenient attachment of fan blades such as 14, 14. Opposite flange portions 4Gb, 40b on each arm `12 lie substantially in a common plane for attachment of a fan blade with a substantially flat central portion to the front face thereof.
With a fan blade such as 14 mounted on the front face of the flange portions 40b, 4Gb of an arm 12, a generally radially extending channel is provided adjacent the rear surface of the blade and the central portion 36 of the spider arm. As shown, the said central portion 36 extends throughout the length of the arm whereby to provide a channel open radially at inner and outer ends.
' From the foregoing it will be apparent that the fan spider of the present invention is well suited to low cost quantity production. Sheet steel may be supplied in blank form for a bending operation to provide the continuous offset marginal portions comprising the arm and hub section offset portions. Thereafter, the arms may readily be twisted relative to the hub section resulting in a completed spider of lightweight, a high degree of rigidity, and superior vibration characteristics.
Particularly with regard to vibration characteristics, it is to be noted that a spider of the type shown can be employed effectively in a 24 inch diameter fan when formed of sheet steel a mere 83 thousandths in thickness.
By contrast, a similar spider of known design but which lacks the offset marginal and central portions of the present design, may be formed with sheet steel 109 thousandths of an inch thick and yet fall far short of the superior rigidity and vibration characteristics of the present fan. A fan including the spider of known construction may have a first fundamental resonant frequency between 35 and 45 cycles per second whereas a similar fan employing the improved spider can be expected to exhibit a first fundamental resonant frequency between 50 and 55 cycles per second. This substantial increase in resonant frequency is of critical importance in fans of the type under consideration where operating speeds in numerous applications fall in the neighborhood of 1,000 r.p.m, or slightly higher. Serious vibration difficulties are often encountered in such fans at twice the rotational speed or at cycles per second levels ranging in the midthirties. A fan employing the improved spider and exhibiting a fundamental resonant frequency in the 50 to 55 cycles per second range is found to be immune to such dif'lculties whereas the fan employing the spider of known design and exhibiting fundamental resonant frequencies in the A35 to 45 cycle per second range may be subject to excitation and serious detrimental effects.
The aforementioned improvements in frequency characteristics of the present spider are believed attributable in large part to the continuity of the offset marginal portions along the sides of the spider arms and particularly through the aforesaid interarm parts of the hub section. Additionally, the provision of the forwardly offset annular zone 24 in the hub section 10 is found to enhance rigidity and vibration characteristics. Still further, it is to be noted that the provision of the offset zone 24 serves to move the point of hub attachment closer to the center of gravity of the fan. This reduces the moment arm of inertia forces which exist when the fan is subjected to shock forces exerted in a radial direction and further enhances the strength and structural integrity of the fan assembly.
Finally, it is to be observed that the points of attachment of the spider to a fan blade, apertures 43, 43, are spaced substantially across the width of the blade and yet the area of contact between the blade rear surface and the spider arm is minimized. That is, the area of contact extends throughout the surface area of the portions 40h, 401; of the anges 40, 4f) while the central portion 36 of the arm resides in spaced relationship with the blade. Thus, a secure attachment of the blade to the arm is provided for and yet the likelihood of corrosion between contiguous spider arm and blade surfaces is minimized, it being found that moisture is most likely to collect and corrosion most likely to ensue in the contact area between the spider arm and the blade.
The invention claimed is:
l. The combination in a fan assembly of a one-piece fan spider of sheet metal comprising a generally circular apertured hub section and a plurality of similar generally radially extending circumaxially spaced arms formed integrally at inner end portions with the hub section, said hub section being apertured centrally and having an inner annular portion with front and rear surfaces and which extends approximately in a radial plane and also having an outer and marginal annular portion disposed about said inner portion, said inner annular portion of the hub section comprising inner and outer zones` the former of which lies adjacent the hub section aperture and is offset forwardly with respect to the latter, parts of said marginal portion of the hub section between said arms being offset forwardly with respect to adjacent parts of said inner annular portion, each of said arms being in an angularly twisted relationship about a radial center line with respect to said inner portion of said hub section and each of said `arms having a relatively wide central portion substantially flat `throughout a substantial portion of its length and relatively narrow substantially flat opposite side marginal portions, each of said arm marginal portions being offset forwardly with respect to the adjacent arm central portion to an extent equal to the forward offset of the adjacent part of the marginal portion of the hub section between the arms and forming a smoothly blending and continuous junction at its inner end with said adjacent offset marginal part, and a plurality of separate sheet metal fan blades equal in number to the arms of said spider and attached respectively to front surfaces of said marginal portions of said arms each in radially spaced relationship with the hub section of .the spider.
2. A fan assembly as set forth in claim l wherein the central portion of each arm extends through at least onehalf the total width of the arm at least at an inner end portion thereof.
3. A fan assembly as set forth in claim 2 wherein the width of each of said arm central portions is substantially in excess of twice the extent of forward offset of the arm marginal portions.
4. A fan assembly as set forth in claim l wherein said inner annular zone is substantially conical in form.
5. A fan assembly as set forth in claim l wherein each of said offset parts between the arms includes a narrow elongated forwardly facing flange and a narrow elongated transition section projecting generally rearwardly therefrom to said inner annular portion of the hub section, and wherein each of said offset arm portions includes a narrow elongated generally forwardly facing flange and a narrow elongated transition section projecting generally rearwardly therefrom to the adjacent arm central portion, said anges and transition sections each being continuous and blending gradually at each of said junctions between forwardly offset parts between the arms and forwardly offset arm portions and all of said transition sections being substantially equal in width.
6. A fan assembly as set forth in claim 5 wherein each of said narrow elongated flanges of said forwardly offset arm portions has longitudinally adjacent inner and outer parts the latter of which is apertured and substantially wider than the former.
7. A fan assembly as set forth in claim 6 wherein said central portion of each arm extends throughout the length of the arm to provide a radially open channel behind a fan blade when the latter is mounted on the front face of the flanges of said offset arm portions.
Zaiger Feb. l, 1938 Posh July 17, 1962