US2482597A

US2482597A - Axial flow fan

Info

Publication number: US2482597A
Application number: US712271A
Authority: US
Inventors: Irving S Ritter
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1946-11-26
Filing date: 1946-11-26
Publication date: 1949-09-20
Anticipated expiration: 1966-09-20

Description

Sept. 2o, 1949.

l. s. RITTER 2,432,597

AXIAL FLOW FAN Filed NOV. 26, 1946 @r 5 i i e PRE SSI/2E VUL UME IN VENTOR.

.[P w/v 5. /Q/r TEE Patented Sept. 20, 1949 Irving S. Ritter, Sharon. Mass.. assignor, by

f mesne assignments, to Westinghouse Electric Corporation, a corporation of Pennsylvania Application November 26, 1946, Serial No.l 712,271-

1 This invention relates tolfan systems and relates more particularly to systems yusing axial iiow fans for pressure ventilation.

By forcing large volumes of outdoor air through the passenger space of trolley cars, subway cars and other passenger vehicles, it has been found feasible to cool such vehicles during hot weather without the use of refrigeration.

Several, spaced, axial flow fans mounted in the ceilings of the vehicles along their longitudinal center lines, and arranged to blow the air downwardly into the vehicles, are generally used for such pressure ventilation.

Axial flow fans have pressure-volume characteristics such that there are dips in the characteristic curves in which the 'fans are unstable and in which the direction of air moved by them l may be reversed by a change in fan load.

Due to changes in the number of passengers in a vehicle, the opening of doors, etc., the load on one of the fans may be such that it may become unstable and act to move air in the reverse direction to that desired. This invention provides a control which, when a fan becomes unstable, causes it to speed up so as to operate at a stable 1 Claim. (ci. 230-115) 2 a dip l in the curve. the center of which is variously termed the burble point, the "stalling point or the "pulsatlon point" of the fan. When the volume handled by the fan is shifted for any reason back into the center of the dip, it becomes unstable and tends to operate on either side of the\center of the dip thus drawing or blowing air depending upon which side of the center of the dip it operates.

In passenger cars having fan systems such as illustrated by Fig. 1, the fans act to build up static pressures in the passenger spaces. Due to changes in the number of passengers in the cars, the assembly of a large number of passengers under one fan, or the opening of one or more of the doors of a car, it has been found that a fan which has been operating satisfactorily to blow air into the pointand to deliver the air it handles, in the right direction.

An object of the invention is to reverse the direction of fluid moved by a fan when due to the fan becoming unstable, it moves the fluid in the wrong direction.

A more definite object of the invention is to speed up a fan for shifting its operating point on its pressure-volume characteristic curve when due to a change in loperating condition, it moves the nuid handled by it in the wrong direction.

The invention will now be described with reference to the drawing, of which: c

Fig. 1 is a diagrammatic view illustrating a fan system to which this invention applies;

Fig. 2 is a pressure-volume characteristic curve of an axial flow fan used in the system of F18. 1, and

Fig. 3 is a diagrammatic view illustrating a pressure responsive control for speeding up'one of the fans of the system for causing it to shift from an unstable operating point to a stable one.v

' Fig. 1 illustrates a trolley car having the three axial iiow fans 5 spaced along the longitudinal center of the car and arranged to draw outdoor air into the space above the ceiling 6 of the car, and to blow the air downwardly through apertures in the ceiling, into the car.

Fig. 2 illustrates a pressure-volume charac passenger space, suddenly reverses its direction oi' flow and takes air from the other fans and passes the ail upwardly instead'of downwardly.

Accordingto this invention, one or more of the fans of the systems .would be equipped with the control of Fig. 3 which includes the pivoted vane 8 in the airstream at the normal suction side of the fan, and which operates when the fan blows air backwardly, to move against the contact i to close the electric energizing circuit of the relay l0, causing the relay to pull in its armature Il. The armature Il and the contact I2 are normally in contact, forming a short circuit across the resistor I3 which is in series with the field winding I4 of the fan motor II. When the armature l I is pulled in by the relay I0 as described, the armature Il moves away from the contact l2, thus opening the short circuit across the resistor I3 and placing same in series with .the field winding Il. This causes the speed of the motor I5 to be increased, and causes the fan to shift its operating point to the right, facing Fig. 2 of the drawing, of the dip 'l in the characteristic curve.

The relay l0 would be of the time delay type such as a relay having a yilux decayI solenoid,

' which would keep its armature pulled in for some time after thevane 8 has moved away from the contact 9 as a result of the fan again moving air l istic curve typical o! the fans of Fig. 1. Thereis so While one embodiment of the invention has 4 been described for the purpose of illustration. it increasing its speed when the air ow through it should be understood that the invention is not is rearward, and timing means for causing said limited to the exact apparatus and system illus-L.4 nrst mentioned means to maintain the increased trated, as modications thereof may be suggested speed for a. predetermined time after the air ow by those skilled in the art, without departure from 5 is again forward.

the essence of the invention. IRV'ING S. RITTER.

What is claimed is: l A pressure ventilation system having a plurality REFERENCES CITED of fans for directing air forwardly in Parallel The following references are of record in the streams and building up an air pressure in the 10 me of this patent; space supplied with air, in which due to a change in load on one of the fans, it may become unstable UNITED STATES PATENTS land move air rearwardly, means responsive to Number Name Date the direction of air flow through said one of said 1,085,286 Moss Jan. 27, 1914 fansl for maintaining same at its normal speed 15 1,210,030 Baumann Dec. 26, 1916 when the air ow through it is forward, and 4for 2,395,657 Dinsmore et al. Feb. 26, 1946