US2291535A

US2291535A - Power failure protective system

Info

Publication number: US2291535A
Application number: US337131A
Authority: US
Inventors: Carl H Dicke
Original assignee: MASTER ELECTRIC CO
Current assignee: MASTER ELECTRIC CO
Priority date: 1940-05-25
Filing date: 1940-05-25
Publication date: 1942-07-28
Anticipated expiration: 1959-07-28

Description

July 28, 1942. c. H. DICKE POWER FAILURE PROTECTIVE SYSTEM Filed May 25, 1940 Wa w l A a Y [B Patented July 28, 1942 POWER FAILURE PROTECTIVE SYSTEM Carl H. Dicke, Dayton, Ohio, assignor to The Master Electric Company, a corporation of Ohio Application May 25, 1940, Serial No. 337,131

Claims.

This invention relates to a power failure protective system, and more particularly to one for use in connection with damper controlling apparatus for a furnace.

An object of this invention is to provide a simple and sure arrangement for protecting electrically controlled apparatus upon the occurrence of a power failure.

Another object of this invention is to prevent the overheating of an electrically controlled heating system upon the occurrence of a power failure.

Still another object of this invention is to provide an arrangement for moving the dampers of a furnace to the combustion-retarding position upon failure of the power source and de-energization of the electrical damper controlling apparatus.

Further objects and advantages of this invention will be apparent from consideration of the specification as illustrated by the accompanying drawing of a possible embodiment of the invention, in which drawing the single figure illustrates partially schematically and partially diagrammatically the novel apparatus and circuit connections thereof, forming a preferred embodiment 'of the present invention as applied to the control of a furnace damper.

As seen in the single figure of the accompanying drawing, the invention is applied to a furnace, generally indicated at It! controlled by a damper motor generall indicated at [2. The damper motor I2 is of generally familiar structure in which the motor proper first drives a pinion l4 and, through a series of reduction gears l6 drives a final wheel l8 with which there is rotatably connected as by a common shaft a slotted control arm 29. Through any suitable arrangement known in the art per se, such as a wire or chain 22 guided by pulley 24, rotation of the arm 29 in the direction of the arrow upon energization of the damper motor 12 is adapted to raise a draft damper 28 of the furnace ill. At the same time, and as is also well known to the art, opening of the draft damper 26 may take place simultaneously with the closing of a suitable check damper (not shown). Closure of the draft damper 26 (and/or opening of the check damper) is effective by suitable means such as a spring 2! which is stretched upon movement of the arm 20 to the position corresponding to the open position of the draft damper (as indicated in dotted lines). The closure operation effected by the spring 2| will be explained in more detail hereinafter.

The control of the furnace dampers is adapted to be initiated by a suitable thermo-responsive switch, generally but not necessarily a room thermostat indicated at 28. Closure of the thermoresponsive switch 28 completes an energizing circuit for the damper motor [2 through a second switch 30, whose function will also be later described, This energizing circuit for the damper motor l2 arises from a source of power indicated at 32 and may be traced from one side of the secondary winding of a transformer 34, connected to the source of power, conductors 35 and 38, the damper motor I 2, conductor 40, normally closed contacts 42 and 44 and the switch arm 46 of the switch 30, conductors 48 and 5B, bimetallic arm 52 and contacts 54 and 56 of the thermo-responsive device 28, and conductor 58 to the other side of the secondary winding of the transformer 34. The motor will now rotate in such a direction as to move the arm 28 in the counter-clockwise direction until the damper 26 has been raised, which corresponds to the dotted position of the arm 20 as shown in the drawing. At the same time, the wheel It will have rotated to such an extent that means such as a pin 69 mounted thereon will contact the arm 62 of the switch 30. The switch 30 is preferably of any well-known snap action type, diagrammatically illustrated here as a toggle switch, so that movement of the arm 62 by the pin 66 will move the contact arm 46 and its contact 44 from the stationary contact 42 to the stationary contact M. This switch movement breaks the circuit to the damper motor l2, but substantially simultaneously establishes a circuit for the solenoid $6. This circuit may be traced from one end of the secondary winding of transformer 34 to conductor 68, solenoid winding 66, conductor 10, contacts 64 and 44 and arm 46 of the switch 36,

conductors

48 and 50, switch arm 52 and still closed contacts 54 and 55 of the thermo-responsive element 28, and conductor 58 to the other side of the secondary winding. Energization of the solenoid 66 effects movement of a double-arm lever 12, one end of which is provided with means such as the teeth 14 for en gaging and locking the pinion M of the gear train connected to the wheel it. Thus, despite the fact that the damper motor is now de-energized, the arm 20 and the damper 26 will not return to their original (closed) position under the action of the spring 2 l, but will be locked in the open position. The furnace damper 26 will accordingly will be held open until either one of two conditions occurs. If the condition within the space to be heated is such that the thermostat 28 becomes satisfied, the contact arm 52 thereof will move to the off position thus breaking the circuit to the solenoid E6. The lever 12 will then act under the force of suitable return means such as the spring 16 to release the pinion l4 and the arm 2t will then, under the return action of the tensioned spring 2| move to its original position to close the damper 26. Simultaneously, the switch 39 which is normally biased by any suitable means to maintain the circuit to the damper motor will return to its original position, so that the system as a whole is now prepared to again raise the damper due to a call of the thermostat 28, Similarly, the furnace damper 26 will be closed upon the occurrence of any power failure, since, the solenoid 66 is connected across the secondary winding of the transformer 34, as was previously traced. This feature of the system is extremely important to prevent overheating of the furnace in case of a power failure, with the consequent waste of fuel and actual danger of conflagration. Upon the return of power, the system is prepared to again open the furnace damper if the thermostat 28 so specifies.

The system above described may be used in connection with a signal and pre-heating lamp T8 for the thermo-responsive element 28, which will only be lighted when the thermostat calls for heat. The circuit for the lamp 23 may be traced from one side of the secondary winding of the transformer 34, conductors 36 and 80, the lamp [8, conductors 82 and switch arm 52 and contacts 54 and 55 of th thermo-responsive element 28, and conductor 58 to the other side of the secondary winding.

It will be at once obvious to those skilled in this art, that many modifications and different applications of the above described system are possible. In the first place, the system can be used to control a furnace other than by control of the damper. Also, the system is applicable to the control of other devices than a furnace, which may produce a variablebut controllable condition. Additionally, I do not intend that the invention be limited to include the precise structural elements shown and described. For example, the snap switch, illustrated as a toggle switch, can be of any standard construction and be actuated by the damper motor in any on of several wel1 known and obvious ways. The thermo-responsive switch may also be of any standard construction and, moreover, if the condition to be controlled is not heat-responsive, the switch could be responsiv to any controllable condition as, for example, pressure. While a motor has been illustrated as supplying the power for raising the furnace damper, it is also to be understood that other electromotive devices might be substituted therefor. The type of return spring and its particular interconnection with the control mechanism is of no importance. While the type illustrated is to be preferred, other types of springs, as for example, a spiral spring could also be used, or a spring Of the character illustrated could be connected to the damper itself or in any other manner to return the system to its original position upon power failure or the opening of the control switch 28. The illustration of the electro magnetic brake is merely diagrammatic, and this, too, could be formed in any manner so long as it performs its locking function upon disconnection of the damper motor.

Accordingly while the form of mechanism here shown and described is admirably adapted to fulfill the object primarily stated, it is to be understood that it is not intended to confine the invention to the one form of embodiment herein disclosed, for it is susceptible of embodiment in various forms all coming within the scope of the claims which follow.

I claim:

1. In a damper controlling system, in combination, a furnace damper movable between first and second control positions, a damper motor including a gear train driven by said motor and a rotatable arm driven by said gear train, means interconnecting said arm with said damper for movement of the latter by the former, a source of power, a thermo-responsive switch, a singlepole, double-throw snapaction switch normally biased to one closed position, conductors connecting said motor to said source of power through the normally closed contacts of said single-pole, double-throw switch and said thermoresponsive switch in such a manner as to energize said motor to drive said gear train in a direction to move said damper from its first to its second position, an electro-magnet, means operated upon energization of said electro-magnet for locking said gear train conductors serially connecting said electro-magnet to said source of power through the normally open contacts of said single-pole, double-throw switch and through said thermo-responsive switch, means carried by said gear train for actuating said single-pole, double-throw switch to close its normally open contacts and open its normally closed contacts, when said gear train has been moved to a position corresponding to the second position of said damper, whereby said braking means will hold the gear train and damper in this position during closure of said thermo-responsive switch and maintenance of said power source, and mechanical means continually urging return of said gear train and damper to the first position, whereby upon opening of said thermo-responsive switch or failure of said power source, said damper will be returned to its first position.

2. The combination according to claim 1, in which said mechanical means comprises a spring.

3. The combination according to claim 1, in which said mechanical means comprises a spring connected to and tensioned by movement of said arm corresponding to movement of said damper from the first to the second controlling position.

4. The combination according to claim 1, in combination with a signal light mounted in juxtaposition to said thermo-responsive switch and connected in parallel to th serially connected motor and normally closed single-pole, doublethrow switch contacts.

5. The combination according to claim 1, in which said single-pole, double-throw switch is mounted in juxtaposition to said damper motor, and the means carried by said gear train comprises a pin projecting from one of the gears and movable into engagement with said switch.

CARL H. DICKE.