US2753119A

US2753119A - Fan control system

Info

Publication number: US2753119A
Application number: US312144A
Authority: US
Inventors: Norman W Stunkard
Original assignee: Iron Fireman Manufacturing Co
Current assignee: Iron Fireman Manufacturing Co
Priority date: 1952-09-29
Filing date: 1952-09-29
Publication date: 1956-07-03
Anticipated expiration: 1973-07-03

Description

y 3 1956 N. w. STUNKARD FAN CONTROL SYSTEM Filed Sept. 29, 1952 //\/L//\/7-UR Norman W Jfunkara FAN CONTROL SYSTEM Norman W. Stunkard, Portland, Oreg., assignor to Iron Fireman Manufacturing Company, Portland, Greg.

Application September 29, 1952, Serial No. 312,144

4 Claims. (Cl. 236-49) This invention relates generally to air flow systems and more particularly to an air flow system which is required to supply air for a needed use at two different rates of fiow in response to the attainment of two different values of a condition of the systems.

To illustrate a use of one form of my system this disclosure is directed to a forced warm air heating system for a residence. It is assumed that in this system there is a warm air furnace heated by an automatic fuel burner which operates to heat the furnace when a thermostat in the living space of the house indicates that heat is required. It is further assumed that a Warm air duct system is provided to conduct cool air from the living space to the interior of a casing surrounding the warm air furnace and back to the living space and that in the duct system is a motor driven fan adapted to impel the air through the duct system.

It should be understood that in such a heating system it is desirable to keep the air circulating through the duct system at all times to prevent stratification of the air but that if the air is not warmed to a comfort temperature the air circulating fan should be stopped to prevent the feeling of cold drafts. It should further be understood that it has been found highly desirable to cause the fan to circulate air through the duct system at a lower rate when the air temperature at the furnace is below a preset temperature and to cause the fan to circulate air at a higher rate when the air temperature at the furnace is above said preset temperature. In the past various schemes have been used to change the rate of air flow through the duct system but the most common way has been to provide a two speed motor for the fan.

I have found that where a fan, having a housing of generally logarithmic spiral shape and having a fan wheel of either the paddle wheel or multiblade type, has a usual high capacity direction of rotation, it will also deliver air but at a greatly reduced rate when rotated in the opposite direction at normal speed. Also by experiment 1 have found that I can greatly vary the discharge of the fan when rotated in the reverse direction by varying the blade design of the fan. Practically I have found that it is a relatively simple matter of varying the angle of the fan blades at their outlet ends or tips with respect to a radial line through each blade tip to give the desired relation of fan discharge at reverse rotation to fan discharge at forward rotation. In practice I like to hold this relation at about one third for the duty described.

In the air flow control system of this invention I have discovered that a reversible fan of the above type driven by a reversible motor of the type shown in U. S. Patent 2,382,827 issued August 14, 1945, to Chester E. Sprague is convenient to use and economical to apply. However for my purpose I usually replace the separate controller shown in the Sprague patent with a magnetic switch secured to the motor frame and a two valued condition responsive switch remotely mounted at the bonnet of the furnace. In this case the condition responsive switch '"nited States Patent comprises a single temperature responsive actuator adapted to operate two single pole, single throw, nor mally open, switches one of the switches being set to close at a lower temperature of, say, F. and the other being set to close at a higher temperature of, say, 140 F.

It will be seen that in the above arrangement I have provided means for controlling the air flow means of a forced warm air furnace installation so that when the furnace bonnet temperature is below, say, F. a minimum of air will flow through the system, but when the air temperature at the furnace bonnet reaches 110 F. the lower setting bonnet switch closes to start the motor and fan in the reverse direction thus circulating air at a rate of about one-third of the full fan capacity. Then if the furnace temperature at the bonnet increases to F., say, the higher setting bonnet switch closes, thus reversing the motor to cause it to rotate in the normal or high capacity direction of fan rotation. These sequential control changes are reversed when sufiicient heat has been supplied to the living space of the residence so that the room thermostat stops the burner and the furnace temperature gradually is reduced.

It is a principal object of this invention to provide a simple, safe, and economical means for limiting the flow of air in a warm air heating system to a small amount when the air at the heat supply is below a first preset temperature, to increase the flow of air through the system to a first preset rate when the air at the heat supply is above said first preset temperature and below a second, but higher, preset temperature, and to increase the flow of air through the system to a second preset rate when the air at the heat supply is above said second preset temperature.

It is a second object to provide a fan for such as system which fan at normal speed in one direction will cause the air in the system to fiow at said first preset rate and at normal speed in the other direction will cause the air in the system to flow at said second preset rate.

It is a third object to provide such a fan adaptable for use with the reversing motor of the above noted U. S. patent.

It is a fourth object to provide a condition responsive control means adapted to run said motor operated fan in one direction of rotation at normal speed on the attainment of one preset value of a condition and to run said motor operated fan in the other direction of rotation at normal speed on the attainment of a second preset value of said condition.

How these and other objects are attained will be understood from the following description referring to the attached drawing in which- Figure 1 is a schematic drawing showing the electrical circuits and devices of this invention when the motor is at rest or in an unenergized condition.

Figure 2 is a schematic drawing showing the electrical circuits and devices of this invention when the motor is operating at normal speed in one direction of rotation.

Figure 3 is a schematic drawing showing the electrical circuits and devices of this invention when the motor is operating at normal speed in the other direction of its rotation.

Like numerals of reference denote like parts in the several figures of the drawing.

Referring now to the drawing, shown schematically at M is a reversing single phase motor of the type shown in the above noted Sprague Patent No. 2,382,827 but equipped with a reversing starting switch mechanism of the type shown in Sprague, et al., Patent No. 2,586,734 issued February 19, 1952. As above described for my system and as indicated in Figure 3 this motor would be drivably connected to a fan wheel adapted with its casing 49 to deliver about one-third the amount of air when running at normal speed in one direction that it would deliver when running at normal speed in the other direction. The fan casing 40 would be part of a force warm air heating system furnace installation as previously referred to.

Shown schematically at R is reversing magnetic switch or relay which 1 would preferably mount on the motor frame to simplify the wiring of the relay to the motor.

Shown schematically at C is a control instrument which wcuid mount on the bonnet of the furnace and would replace the usual fan switch there mounted in a forced warm air heating system.

Motor M is shown to have a running winding 11, a starting winding 2, and a pair of

starting switches

13 and 14.

Relay R is shown to have two normally closed switches, 15 and 16, two normally open switches, 17 and 18, and an operating coil 19.

Control instrument C is shown to comprise two condition

responsive switches

24 and 21, switch 2% having a stationary contact 22 and a movable contact 23 carried on a bimetallic blade operator 24, while switch 21 has a stationary contact 25 and a movable contact 26 carried on a bimetallic blade operator 27. Switch 29 would be set to close at a low air temperature of, say, 110 F., while switch 21 would be set to close at a higher air temperature of, say, 140 F., although both settings would be adjustable and settings would be selected to give best operation on a particular job.

It is seen that power line L1 is connected to one side of each of the

switches

29 and 21. Power line L2 is connected to one side of motor running winding 11 to one side of operating coil 19, to one side of normally closed switch 16, and to one side of normally open swi'ch 17. Contact 25 or" switch 21 is connected to the other side of operating coil 19. Contact 22 of switch 26 is connected to the other side of motor running winding 11 and to one side each of normally closed switch 15 and normally open switch 18. Gne end of starting winding 12 is connected to the other sides of

switches

17 and 15. The other end of starting winding 12 is connected to both switch blades 23 and 2? of

starting switches

13 and 14 respectively. Stationary contacts 36 and 31 respectively of switches 13 and 1d are connected respectively to the other sides of switches 18 and 16.

With this circuit arrangement if the air temperature is beiow the setting of switch 21), the system is as shown in Figure l with no circuits complete from L1 to L2.

When the air temperature rises so that switch 20 closes, motor running winding 11 is energized from L1, L2 through switch 29, and starting winding 12 is energized from L1, L2, through

switches

20, 14, 15, and 16. The motor starts up and before it gets up to normal speed the directional centrifugal operator of

switches

13 and 14 open switch 14 and leaves switch 13 closed. See the above noted patents. The condition of the system is now as shown in Figure 2, with the motor running in the direction of low fan output.

As the air temperature continues to rise and finally reaches the setting of switch 21, switch 21 closes and energizes relay operating coil 19 from L1, L2. Relay R operates to open normally closed

switches

15 and 16 and close normally open switches 17 and 18, thus energizing starting winding 12 from L1, L2 through switches 21 13, 1? and 18. Starting winding 12 being thus energized in opposite phase to its previous energization it will have the effect of slowing down the motor to zero speed and then bringing it up to speed in the opposite direction of rotation. As the motor stops switch 14 will close and as it starts in the opposite direction switch 13 will open, thus leaving the motor in the condition of full speed operation on the running winding only in the direction of rotation of maximum air delivery by the fan 49. This condition is shown in Figure 3.

It is apparent from the above description and the drawing that the fan will be stopped when the air temperature is below the setting of switch 21 the fan will be running at normal speed in the direction of rotation of reduced air flow when the air temperature is between the settings of

switches

20 and 21, and the fan will be running at normal speed in the direction of rotation of maximum air flow when the air temperature is above the setting of switch 21.

Having thus explained some of the objects of my invention, described the construction of one form of my invention and explained its operation, I claim:

1. in an air flow control system adapted to supply air at one rat in response to the attainment of one value or" a condition and to supply air at another rate in response to the attainment of another value of said condition, said system comprising a fan adapted at normal speed to supply air at said one rate in one direction of rotation and at said other rate in the other direction of rotation, said fan being adapted to deliver air in the same direction irrespective of the direction of its rotation, a reversible electric motor adapted to drive said fan, a source of electric power, and a condition responsive control means adapted at one value of said condition to energize said motor from said power source to rotate in one direction of rotation and at another value of said condition to energize said motor from said power source to rotate in the other direction of rotation.

2. Means for selectively driving a fan in either direction of its rotation in selective response to two selected values of a condition, said fan being adapted to deliver air in the same direction irrespective of the direction of its rotation, said means comprising a source of electric power, a reversible electric motor adapted to drive said fan in the selected direction of its rotation, a first normally open condition responsive switch, a second normally open condition responsive switch, and circuit means adapted on the closure of said first switch to energize said motor from said power source for one direction of rotation and on the closure of said second switch to energize said motor from said power source for the other direction of rotation.

3. Means for selectively driving a fan in either direction of its rotation in selective response to two selected values of a condition, said fan being adapted to deliver air in the same direction irrespective of the direction of its rotation, said means comprising a source of electric power, a reversible electric motor adapted to drive said fan in the selected direction of its rotation, a first normally open condition responsive switch, a second normally open condition responsive switch, and circuit means adapted on the closure of said first switch to energize said motor from said power source for one direction of rotation and on the additional closure of said second switch to energize said motor from said power source for the other direction of rotation.

4. Means for selectively driving a fan in either direction of its rotation in selective response to two selected values of a condition: said means comprising a source of electric power, a reversible electric motor adapted to drive said fan, a first normally open condition responsive switch, a second normally open condition responsive switch, and a relay means; said motor comprising a running winding, a starting winding, :1 first starting switch, a second starting switch, resilient means biasing said starting switches towards their closed positions and means responsive to the direction of rotation of said motor selectively to open one or the other of said switches when said motor is operating in one or the other of its directions of rotation; said relay means comprising a first normally closed switch, a second normally closed switch, a first normally open switch, a second normally open switch, electrical operating means for said four last mentioned switches adapted when energized to open said normally closed switches and close said normally open switches; together with circuit means adapted when said first condition responsive switch is closed to energize said running winding of said motor from said source of power and to energize said starting winding of said motor from said source of power in one phase relation to said running Winding through said first starting switch, said two normally closed switches and said first condition responsive switch, and when both said condition responsive switches are closed to energize said electrical operating means from said source of power and energize said starting winding of said motor in an opposite phase relation to said running winding through said first condition responsive switch, said second starting switch and said two normally open switches.

References Cited in the file of this patent UNITED STATES PATENTS