US1893184A - Fan - Google Patents

Description

D. G. SMELLIE Jan. 3, 1933.

FAN

Filed Jan. 24, 1929 IXVENTOR. fianale? Smellje A T TORNE Y.

Patented Jan. 3, 1933 UNITED STTES DONALD G. SMELLIE, OF CANTON, OHIO, ASSIGNOR TO THE HOOVER COMPANY, A CORPORATION OF OHIO FAN Application filed January 24, 1929.

This invention relates to fans and more particularly to high speed fans and consists primarily in a new and novel fan structure adapted to be operated at a high rate of 5 speed with efliciency and absence of howling heretofore present in high speed fans.

In the operation of an ordinary high speed fan, such as is found in suction cleaners, air is drawn into the fan chamber at the 10 center of the fan and fan chamber which is the low pressure point and is exhausted at the periphery of the fan blades or high pressure area through an opening in the surrounding housing. With the fan revolving at a constant rate of speed the individual blades pass the point of cutoff, a point in the fan chamber which the fan blade passes just after passing the exhaust outlet, at equal time intervals. The result of the con- 23 tinued high frequency passing of the fan blades past this point of cutoff is a howling noise or siren effect, caused by the vibration set up in the air acted upon within the structure itself. The fan structure forming the subjectmatter of the present invention is adapted to eliminate this high frequency howling at high speeds.

The principal object of thisinvention is a the provision of an eflicient high speed fan which will function with an absence of noise due to howling or siren effect. It is a further object of this invention to provide a fan constructed in a new and novel manner V which is adapted to function at high speed within the ordinary fan chamber with absence of noise.

Referring now to the drawing in which like reference characters refer to the same parts throughout: 7

Figure 1 is a vertical cross section through a fan constructed in accordance with this invention. I

Figure 2 is a bottom view of a fan constructed in accordance with this invention. Figure 3 is a bottomview of a modification of the present invention.

Figure 4 illustrates a fan constructed in accordance with the present invention, positioned in a common type fan casing.

Referring to Figure 1 in particular the Serial No. 334,625.

reference character 1 refers generally to a fan constructed in accordance with this invention in which the body of the fan comprises a rigid back or web 7 and central hub member 8. Positioned centrally of the fan and within the member 8 is the shaft 5 adapted to be connected to a high speed center and so positioned that imaginary extensions thereof are tangent to an imaginary circle described about the fan axis. Referring now to Figure 2 in particular the blades 2 of the fan constructed in accordance with this invention are shown spaced apart by spaces 4 which are varied in :1.

definite manner, the angles between the blades I being varied by a decrement or increment 2A in a fixed sequence. The sequence of the angular arrangement of the blade is (Of A) (a+A), (dA), (a+A) etc.

In the operation of the ordinary fan, the blades pass the point of cutoff of the fan chamber at high speed and are separated by very small time intervals. In Figure 4 of the drawing, a fan constructed as in the present invention, is shown embodied in a fan chamber 10, the point of cutoff being indicated by the reference character 11. The result is a high frequency vibration of the surrounding air and chamber which is equal or proportional to the product of the R. P. M. of the fan times the number of fan blades (=R. P. M. N). The surrounding air is set into vibration at a certain frequency and as each succeeding blade reaches the point of cutoff in synchronism with the period of vibration the resultis cumulative and the accompanying howling or siren efi'ect grows to an unpleasant degree. Withthe -fan constructed in accordance with the present invention the blades do not pass the point of cutofi' at constant frequency or time intervals but'at unequal time intervals, the extent of which are determined by the increment or decrement A to the angle between successive blades. The result of this arrangement of blades is to eliminate the cumulative effect present in fans having blades equi-spaced. Each blade sets up a vibration of the surrounding air as it passes the cutoff point, the frequency of which is determined by the time interval between its passing the cutofi point and the preceding blade passing said point.

the sequence of angular displacement of the blades is (a) (aA), (a-l-A), (or) In such a construction the cancellation of vibrations is accomplished by the proper selection of the angular lncrement delta.

In the present invention a new and novel fan is presented which is designed and adapted for high speed operation such as is found in suction cleaners. The design is such that under high speed conditions high frequency vibrations have been dampened resulting in the elimination of unnecessary, but heretofore ever present, high frequency howling or' siren effect in the operation of the fan. lhis result has been accomplished without the sacrifice of fan efliciency or a radical departure from standard fan construction;

I claim:

1. A fan comprising a body and fan blades carried by said body, characterized by the fact that said blades are tangent at their inner ends to a common circle and by the fact that said blades are spaced unequally in a definite sequence.

2. A rotary fan comprising a body, and blades mounted on said body about the axis of rotation, characterized by the fact that said blades are substantially alike and the included angle separating adjacent blades is varied in the sequence (a), (on-A), (m+A), (01), etc.

'3. A fan adapted for axis comprising blades positioned about that axis, said blades being perpendicular to a common plane and separated by unequal angles differing by a definite angular increment.

4. A fan adapted for rotation about an axis comprising blades positioned about that axis said blades being perpendicular to a common plane and separated by unequal spaces differing by a definite increment, said 7 spaces being arranged in a definite sequence.

5. A rotary fan comprising a web adapted for rotation about an axis perpendicular to rotation about an said web, and fan blades carried by said web positioned about said axis of rotation, said fan being characterized by the fact that said blades are spaced unequally in a definite sequence.

6. A centrifugal fan comprising a body and fan blades carried by said body, characterized by the fact that said blades are tangent at their inner ends to a common circle and by the fact that said blades are spaced unequally in a definite sequence.

Signed at North Canton, in the county of Stark and State of Ohio, this 12th day of January, A. D. 1929.

. DONALD G. SMELLIE.

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