US1161926A

US1161926A - Centrifugal fan.

Info

Publication number: US1161926A
Application number: US86002414A
Authority: US
Inventors: Albert A Criqui
Original assignee: Individual
Current assignee: Individual
Priority date: 1914-09-03
Filing date: 1914-09-03
Publication date: 1915-11-30
Anticipated expiration: 1932-11-30

Description

A. A. CRIQUI.

CENTRIFUGAL FAN.

AT'PLICATION FILED SEPT. 3. 1914.

Patented Nov. 30, 1915 ma. em J Zn A TTO/YNEY z m M w sra'rns ra'rnnr @FFICE.

\ p ALBERT A. CRIQUI, or BUFFALO, NEw'YoRK.

CENTRIFUGAL FAN.

Specification of Letters Patent.

Application filed September 3, 1914. Serial No. 860,024.

To all whom it may concern Be it known that I, ALBERT A. CRIQUI, a citizen of the United, States of America, and a resident of the city of Buflalo, county of Erie, and State of New York, have invented certain new and useful Improvements in Centrifugal Fans, of which the following is a full, clear, and exact description.

My invention relates generally to a multiblade centrifugal fan of the type in which a large number of blades are arranged in annular serles around a central space, open at one side for the entrance of the air which is drawn in through the central opening and forced outwardly through the spaces be tween the blades by centrifugal force. 7

My invention relates particularly to improvements in the formation of the blades,

which form part of the wheel of the centrifugal fan.. As is well known to those skilled in the art, fans of this type are generally constructed to deliver air under pressure at a comparatively slow speed of rotation- In places where direct-connected fans, of this type, are installed and a low pressure of air is desired, it is necessary to run the fan wheel at a slow speed and a large frame motor is therefore required in order that a slow speed of rotation may be obtained. This is because of the fact that in most fan constructions inventors have sought to produce fans in which the velocity of the air leaving the wheel would be greater than the peripheral velocity of thewheel.

The general object of my invention has been, therefore, to provide a fan having a wheel with blades in which the velocity of the air leaving thewheel shall be less than the velocity of the periphery of the wheel, thereby producing'a low velocity-pressure at a comparatively high speed of rotation' snail-shaped casing is used in connection with the wheel, by means of which a portion of the velocity pressure of the air leaving the wheel is converted into static pressure. And my wheel, in connection with its casing,

will produce a lower static pressure than asure of the discharge of the air along the entire length of the same, and/also one which shall pick up the air at a minimum loss by shock or lmpact with the entering air.

Another object has been to provide a blade the surfaces of which are developed from twocones, having their curved surfaces tangent to each other.

Each blade of my fan, as shown herein, has a forward curve at the heel and a backward curve at the tip. By reason of the backward curve at the tip the kinetic energy of the air as it leaves the tip is reduced to a minimum, thereby producing a low velocity pressure which is far less than that produced by the forwardly curved or straight surfaced type of blade.

Throughout this description I use the term air as applied to my fan, but obviously the Same may be used for gases or other fluids and it is not intended to restrict this application to the use of air.

In my application for Letters Patent on improvements in centrifugal fans, filed Feb-- ruary 20, 1914, Serial No. 819,861, I have shown and described a structure similar, in some respects, .to that herein shown and described. i

In the drawings which show an embodiment of my invention like characters of reference indicate like parts throughout the the axis of thewheel and the end of the tip farthest from the inlet precedes the end of the tip nearest to the inlet.

in Fig. 3 exceptthat the end of the tip of the blade farthest from the inlet follows the end of the tip nearest the inlet. Fig. 5 is an end' elevation of blade similar to those shown in Figs. 3 a d 4 and shows in a' diagrammatic manner a neans of ascertaining the pressures and velocities of the air at the heel and tip of the blade. Fig. 6 is an end Fig. f is an end elevation of a blade similar to that shown v elevation of a modified form of blade for a wheel having a diameter substantially equal at each end. Fig. 7 is a side elevation of the blade shown in Fig. 6.

Referring to the drawings, 6 is the Wheel of my fan which is carried by a shaft 7, rotatably mounted in suitable bearings 8. For convenience of illustration I have shown the shaft provided with a pulley 9 for driving the same but obviously an electric motor or any other suitable direct-connected or belted means, may be used to furnish motive power to the fan. The wheel 6 is inclosed within a snail-shaped casing 10, which is provided with an inlet opening or eye 11 opposite to the inlet end of the wheel 6 and provided with an inlet cone 12, which directs the air from the exterior of the casing into the central opening of the wheel. The cas ing 10 is also provided with discharge opening 13.

The blades 14 of the wheel of my fan are secured laterally at one end to a disk 15, carried by hub 16 secured to the shaft 7.

a tangential An annular band or ring 17 is disposed at the. inlet end of the wheel and the outer ends of the blades, are secured thereto by suitable means. In the ordinary type of fan, as is well known, the tendency of the entering air is to rush to the end farthest from the entrance and to be discharged from that part of the wheel, thus making the discharge at the entrance end of the wheel comparatively light. In order to take care of this inequality of the discharge at the tip of the blade,

2 along the tip and thus change the angle at which the air leaves the same.

The blades of my fan are each developed from two cones, having their curved surfaces tangent to each other, and is arranged so that the surface of each blade is presented to the air at the heel of the blade and the convex surface is presented to the air as it leaves the tip of the blade. Each of these blades may have its tip and heel coplanar or non-coplanar with the axis of the wheel and may have the entrance end of its tip and heel precede or follow the disk end thereof, as desired, to suit the different conditions.

The-blades 14 of my fan are each developed from the two truncated cones A and B, which have their surfaces in contact are so arranged with relation to each other that when the blade is wrapped around their surfaces, a smooth forward and backward curve is produced.

In Fig. 3 the blade 18 has its tip 19 noncoplanar with the axis 0 of the wheel and with its end 19, which isfarther from the axis in a radial direction, preceded by the end 19",

I change the curvature of the blade" which is nearer the axis in a radial direction.

'The heel 23 of this blade is non-coplanar which is nearer the axis in a radial direction.

The blade shown in Fig. t has its tip 21 non-coplanar with the axis 0 of the wheel and has its end 21 which is farther from the axis in a radial direction, preceded by the end 21*, which is nearer the axis in a radial direction. The heel 22 of this blade is non-coplanar with the axis of the wheel and has its end 22*, which is farther from the axis in a radial direction, preceded by the end 22", which is nearer the axis in a radial direction.

Referring now to Fig. 5, where the pressures and velocities are shown diagrammatically, 2 1 is the tip of the blade and 25 the heel thereof. The end 24: of the tip, at the disk end of the wheel, is farther from the axis in a radial direction and the end 24 of the tip at the entrance end of the wheel is nearer the axis. The broken line 24 -0 represents the lineal velocity of the tip of the blade at the end 24 The line 2al D represents the tangential line of discharge of the air as it leaves the tip of the blade at the end'2l of the tip of blade. The resultant velocity of the air as it leaves the tip of the blade at the end 24 is indicated by the full line 24' -E. The line 24"C and the line 2t D represent respectively, the lineal velocity of the blade and the tangential discharge of the air as it leaves the tip of the the entrance end of the blade and the end 25 is at the disk end of.the blade. The broken line 25 c represents the lineal velocity of the end 25 at the heel of the blade and the broken line 25(Z represents the radial velocity of the air passing from the blade at the end 25 The resultant velocity of the blade at the end 25 is indicated by the full line 25 e. The lineal velocity of the blade at the end 25 of the heel is indicated by the broken line 25(: and the radial velocity of the air passing through the blade at this end is indicated by the broken line 25"-cZ. The resultant velocity of the air at the end 25 of the blade is represented by the full line 25 e.

As hereinbefore pointed out, I may change the curvature of the blade at the tip so as to equalize the discharge of the air along the same. By reference to Fig. 5 it will be seen that the angle formed between the line 2P-C, representing the lineal velocity of the end 24 of the blade and the line 24"D representing the tangential line of air disend is less than the angle formed'between the lines 2PC and 24*'D. The less the angle between the line representing the lineal velocity of the tip of the blade and the line representing the tangential discharge of the air from the blade the greater will be the resultant velocity of the air as it leaves the tip of the blade. Thus, it will be clearly seen that the resultant velocity represented by the line 24 -E at ,the end of the tip, which is nearer the axis in a radial direction is substantially equal to the resultant velocity represented by the line 24*E at the end of the tip, which is farther from the axisin a radial direction, thereby equalizing the discharge along the tip .of the blade.

The blade 26 shown in Figs. 6 and 7 is for use on wheels where the entrance end' is substantially of the same diameter as the disk end. The blade is developed from the surfaces of two truncatedcones and the tip 27 thereof lies in planes which are parallel and coplanar with the axis of the wheel.

The heel 28 is non-coplanar and has its entrance end 28 preceded by its disk end 28*.

The curvature of the tip of this blade is changed so as to equalize the air discharge along its tip, as hereintofore described with reference to the'blade shown in Fig. 5.

While I have shown and described my invention as applied to a fan having a single wheel and a single inlet opening, it is obvious that it may be applied to fans having a double'opening or to fans where two wheels are provided, each with an inlet opening.

These and other modifications of the details herein shown and described" may be made without departing from the spirit of my invention orthe'scopeof the appended claims.

Having thus described my invention, what I claim 1s:

1. A centrifugal fan having a wheel provided with a plurality of blades, the surface of each of said blades being made from a portion of the surfaces of two cones, having their curved surfaces tangent to each other, and the external diameter'at the disk end of said wheelbeing substantially the same as that at the entrance end thereof.

2. A centrifugalfan having a wheel provided with a plurality of blades, the surface of each of said blades being made from a portion of .the surfaces of two cones, having their curved surfaces tangent to each other, the tip' of each blade being substantially coplanar with the axis of said wheel and the heel of each of said blades being non-cosigned my Witnesses planar with the axis of said wheel, and the disk end of said wheel being substantially the same in external diameter as that at the entrance end thereof.

' 3. A centrifugal fan having a wheel provided with a plurality of blades, the surface of each of said blades being made from a portion of the surfaces of two cones, having their curved surfaces tangent to each other 'the tip of each blade being substantially coplanar with the axis of said wheel, and the disk end of said wheel being substantially the same in external diameter as that at the entrance end thereof.

4. A. centrifugal fan having a wheel provided with a plurality of blades, the surface of "each of said blades being made from a portion of the surfaces of two cones, having their "curved surfaces tangent to each other, the disk end of said wheel being substantially the-same in external diameter as that at the entranceend thereof, and the tipof each" blade being so shaped that the angle formed between the line representing the lineal velocity of the tip of the blade and the line representing the tangential discharge of air from the blade increases from the entrance end of the wheel toward the disk end thereof.

5. A centrifugal fan having a wheel proi vided with a plurality of blades, the surfaces of each f said blades being made from a portion of the surfaces of two cones, and the tip of each blade being so shaped that theangle formed between the line representmg the lineal velocityof the tip ofthe blade Y and the line representing the tangential discharge of air from the blade increases from the entrance end of said wheel toward the disk end thereof.

6. A'centrifugal fan having a wheel provided with a plurality of blades, the surface of each of said blades beingmade from .a portion of the surfaces of two cones, having their curved surfaces tangent to each other, the heel of each of said blades being non-coplanar with the axis of said wheel, and the disk end of said wheel being substantially the same in external diameter as that of the entrance end thereof. 7 In testimony whereof, I have hereunto name in the presence of the two subscribed witnesses.

ALBERT A. CRIQUI.

J. WM. ELLIS WALTER H. KELLEY.