CA1087461A - Flue damper crank arrangement - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
An arrangement for coupling flue damper shaft means to actuator means in which the shaft means includes a crank-shaped end at the side of the flue pipe adjacent the actuator means, with the crank-shaped end including a lever arm portion and a pin portion offset from the axis of the shaft means, and a coupling means on the shaft of the actuator means for receiving the pin portion, the pin receiving portion preferably being in the form of a radi-ally extending slot. The lever arm is aligned with the plane of the damper plate and the actuator means is cor-respondingly constructed so that the slot is in the same plane.

Description

This application is one of several relating to a total damper assembly which in its totality is considered - the preferred ~orm.
The thus related applications include:
Nagel-Dietsche Canadian Patent Application Serial No~ 315,301, filed October 31~ 1978, relating to an arrange-ment for biasing the damper to an open position in the absence of actuator means. _ Dietsche-Schuster Canadian Patent Application Serial No. 315,283, filed October 31, 1978, relating to a preferred damper sha~t arrangement in which opposite stub shafts of a particular configuration are applicable to a range of damper sizes.
Nagel Canadian Patent Application Serial No. 315,164 filed October 31, 1978, relating to a control ' .

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~ ~7 ~ 47,878 arrangement for electrically stopping the damper plate in its open position and reducing any chance that the particu-lar arrangement used to accomplish the stopping does not result in a damper hangup in an incorrect positlon under infrequently encountered, but possible, conditions.
BAC~GROUND OF THE INVENTION
The invention pertains to the art of flue or vent dampers useful for saving energy in furnaces such as those typically used domestically.
In the design of power operated flue dampers, it is customary to provide for the replacement of the actuating means without the necessity of replacing the flue damper itself. This is done because the expected li~e of the ;~
actuating means is short compared to that of the flue and its damper, and easy separation of the parts greatly facili-tates normal repair operations. It is noted that in some of ~
the current arrangements that, when replacing the actuating ~ -means, reliance is placed upon the installer to reestablish the proper angular relationship between the operating means and the flue damper.
; It is believed desirable to provide a mechanical configuration for the interconnection of the actuating means and the flue damper which eliminates any possibility of estab-lishing an improper angular relationship between these parts.
The configuration should also provide a visual indication o~ the ~lue damper position at all times, be inexpensive to manu~acture, relax the manufacturing tolerances for the assembly by accommodating a reasonable amount Or misalignment, be easily put together in the field, have no loose parts, require no adjustments, and have other practical advantages ~ ~ 7 ~ ~ 47,878 obvious to those skilled in the art.
SUMMARY 0~ THE INVENTION
. _ In accordance with the invention, it is proposed to terminate the operating shaft of the flue damper in the form of a crank. The plane of the crank is made to coin-cide with that of the damper plate, so that the exposed crank will serve as a visual indication of the position of ~ -the concealed flue damper. It is further proposed to terminate the operating shaft of the actuating means in a disc whose radius is substantially greater than the throw of the flue damper crank, the disc having cut in it a radial slot somewhat wider than the diameter of the crank handle and extending from a radius less than that of the crank arm to a radius greater than that of the crank arm. To facili-tate the reenagement of this slot with the crank in the field, it is preferable to extend the slot to the rim of -the actuating disc and to flare the mouth oftheslot. ~ -DRAWING DESCRIPTION
Figure 1 is a plan view of the damper assembly;
Fig. 2 is a partly broken side view of the damper assembly;
Fig. 3 is a partly fragmentary and exploded view of the coupling, shaft and damper arrangement;
Fig. Ll iS a schematic view of the circuit arrangement;
Fig. 5 is a fragmentary circuit useful as an addi-tion to the circuit of Fig. 4; and Fig. 6 is a cross-section corresponding to one taken along the line VI-VI of Fig. 2.
DESGRIPTION OF THE PREFERRED EMBODIMENT
, 30 The damper assembly as a whole, including the actuator : _3_ - ' '.'.
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~ ~ 7 ~ 47~878 means, is described in some detail in this application to insure compliance ~ith the statutory requirement o~ best mode currently contemplated by the inventor, as well as to provide a thorough understanding Or how the particular features o~ the subject invention are advantageous in con-nection with the structure of the assembly as a whole and the operating characteristics o~ the particular type of actu-ator considered preferable. However, it is to be understood that as generally delineated in the section titled "Cross Reference to Related Applications", other inventive entities have also contributed significantly to the assembly as a whal~ , and what is desired to be claimed in this application ls only that which falls within the scope of the appended claims.
; Referring to ~igures 1 and 2, the assembled flue ; or ~ent pipe damper includes a pipe body 10 formed from ; a sheet of metal~ such as 18 gauge aluminized steel,into a generally cylindrical shape and secured in that shape by a line of rivets 12 along the lap. Circumferentially extending beads 14 and 16 separate the cen~ral part 18 of the length from the inlet and outlet margins 20, 22, respectlvely. While not readily perceptible from the drawing, the pipe body is in fact slightly truncated so that the cross-sectional open area in the plane of the axis of the damper exceeds the cross-sectional area at the discharge end 22 by a sufficient amount such that, upon subtracting the obstruction of all parts in the damper axis plane (with the damper open~, from the gross area in that plane, the unobstructed area equals or exceeds the area at the dis-charge end. By virtue of khe pipe body being rolle~
into shape ~rom relatively inexpensive material, the pipe -~4- -, ', ~ 47,878 body may be made sufficiently long or high that upon in-sertion of sheet metal screws through the lapping inlet and outlet pipes at the marginal ends, the space through which the damper plate moves is sufficiently spaced from the sheet metal screws that accidential obstruction of damper plate ~-movement is avoided.
The damper plate 24 is a flat circular disc of a material such as aluminized steel and has a total area sufficiently less than the cross-sectional area of the plane at the damper axis as to meet the regulatory standards regarding percentage of obstruction with the damper in a closed position. The damper plate is shown in its open position in both Figs. 1 and 2 and is rotatable toward a closed position in a direction which, as viewed in Fig. 2, would have the top edge of the damper moving away from the viewer. To support the damper plate for its pivotal move-ment, two discrete stub shafts are secured to one face of the plate ad~acent diametrically opposite edges of the plate and are journaled in openings at opposite sides o~ the pipe body. Referring to Fig. 3 as well as Figs. 1 and 2, the slla~t means includes the right-hand stub shaft 26 which has a flattened portion 28 and a straight round shaft portion 30 provided with a longitudinally extending slot 32 which lies at 9Q relative to the plane ~f the flat. The left-hand stub shaft 34 also has a flattened portion 36 and a round shaft ~ -end portion 38 formed into a crank shape including a lever ~ -arm portion 40 and a pin portion 42 whose axis is offset from the axis of the shaft means. Each round portion of each stub shaft also carries a washer 44 slipped on and located closely adjacent the transition or beginning part of the flats.

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47,878 ~ coiled torsion spring 46 (Figs. 1-3) cooperates with the right-hand stub shaft 26 in the final assembly to bias the damper plate 24 to an open position in the absense of the actuator means 48 (Figs. 1 and 2) which normally controls damper positioning. The spring has one end tine 50 which ls received into slot 32, and an opposite end hook 52 which is ` received into a hole 54 in the pipe body at a location spaced from the axis of the shaft means. The spring is designed so that the opening ~orce it exerts is relatively light as compared to the force imposed by the actuator means 48 in both its damper closing and opening modes. The opening force of the torsion spring need only be sufficient to overcome any ~rictional resistance in the damper assembly with the actuator removed.
While the torsion spring ~orce aids the force of the actuator in the damper opening mode, it opposes it in the damper closing mode which, in the currently preferred assembly, is accomplished ~; by an electric motor drive. To limit the movement of the damper blade to the full open posltion when the actuator -~
means is removed, a rivet pin 56 (Fig. 2) is fixed below the shaft means at the one side Or the pipe body.
The way in which the parts of the damper assembly thus far described are assembled is as follows, The damper plate 24 is first spot welded or otherwise secured as at 58 tQ the flat 28 of the stub shaft 26, the washer 44 is slipped onto the shaft and the round straight part 30 of the sha~t is inserted through the journaling hole of the pipe with the washer on the inside of the pipe. The torsion spring 46, which has been located with its hooked end 52 in place when the shaft was pushed through the pipe hole, is manipula~ed by ~-winding it up slightly to locate the tine 50 in the slot 32.

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~ 7,878 Then the opposite stub shaft 38 with its washer 44 in place has its crank end portion snaked through the opposite ~ournaling opening in the pipe body from the inside of the pipe. The plate 24 is turned down against the torsion spring and a fixture (not shown) abuts the bottom face of the plate and positions the plate for the second spot weld or other securement at the location 60. The stub shaft 38 is of course angularly disposed so that the flat 36 is aligned with the flat 28 of the other stub shaft, and the crank- `
shaped end is properly directed for the ultimate coupling with the actuator means. Before the welding occurs the stub shafts are moved in opposite outward directions to almost snug up the transition parts of the flats against the washers 44, allowing about 1/16 to 1/8 inch (1.6 to 3.2xlO 3m) slop in the total assembly to avoid any binding problem. The washers 44 facilitate the positioning of the parts and prevent lateral shifting of the damper plate assembly to a ~ -point that binding would occur since the holes in the washers -each lie in a plane whereas the journaling holes ln the pipe body are not each in a plane.
To mount the actuator means 48 (Figs, l and 2)~ a generally U-shaped bracket 62 is secured by riveting as at 64 along the marginal edge portions of the legs of the brac~
' ket to the intermediate section 18 of the pipe body at that ;
side of the pipe body through which the crank-shaped end of the sha~t means pro~ects. It is noted that three openings 66 are provided in each of the opposite legs (only those in the far leg being shown in Fig. 2) to promote ventilation through the bracket regardless of the horizontal or vertical disposition of the pipe body 10 to reduce any likelihood ,, 7~

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~ 6 ~ 47,878 of overheating of the actuator means Li8 from the hot pipe body. The bight 68 of the bracket 62 includes a centered hole (not shown) which is large enough to readily pass the rotatable disc 70 which is fixed on the output shaft 72 of the reduction gear train of the actuator, and which in turn is driven by a synchronous clockwork motorO
The actuator frame supports, in cantilever fashion, a flue temperature responsive element 73 which includes a helical bimetal of the type commonly used for overheat limit purposes in conventional furnace control systems.
As will be explained in connection with Figures 4-6, this element is effective to cause opening of` a normally closed switch if the flue temperature rises above a given tempera-ture which would indicate a stoppage of adequate flow of the hot flue gases.
In accordance with this invention, the coupling of the actuator means to the plate and pipe assembly is accom-plished by the pin portion 42 (Fig. 3) of the crank end of the stub shaft 34 being received in the radial slot 74 of the disc 70. The width of the slot is slightly greater than the diameter of the pin 42 to facilitate the assembly and it is considered preferable that the slot extend to the periphery of the disc and may also be flared thereat to further facilitate assembly. The axis of the output shaft 72 and the damper plate shaft means are of course aligned in the assembly.
The actuator means 48 is of the type in which an electric motor, when energized, rotates the damper plate from open to closed and holds the damper closed so long as energization continues. Upon deenergization of the motor, , '.

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47,878 ~ 6 biasing means built in the actuator means mechanically drives the motor reversely and causes the damper plate to - be moved to an open position.
The schematic circuit of Fig. 4 for controlling - the movement o~ the damper includes transformer 76 to obtain the usual 24 volts AC in the secondary, a room thermostat 78 which operates from open to closed in response to a demand for heat, a fuel controlling device such as a sole- .
noid controlled gas valve 80 as shown (or an oil pump motor .for an oil burner, for example), the damper motor 82 which drives the damper plate shaft means through a gear train, a damper position responsive switch 84, and relay means including actuating means such as coil 86 and controlled switch means 88. The parts of the circuit thus far described .
are conventional with the switch 88 in.the conventional cir- .
- . cuit being a single-pole, single-throw switch which is either open or closed under the control of the coil 86. However in the currently preferred circuit, which is .the subject of .
Nagel Canadian Patent Application Serial NoO 315"164, :. 20 filed October 31~ 197~ the switch - . a single-poIe, double-throw switch which ~unctions, when ;~
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~ the.switch closes to terminal 90 (which in the conventional,- ~.
circuit would be the swltch-open position), to connect a . motor braking circuit including a ~ecti~ier such as diode ~2, and a resistor 94 connected in se~iesO The ~ommon terminal of switch 88 is connected through the normally closed switch 95, controlled by the flue temperature responsive element 73, to the one side of the damper motor 82. Whenever`the switch 95 is open for any reason the damper motor is dls-connected from across full AC, and the biasing means urges ` , ` ` ` , : -9- . ~ : .
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~ ~7 ~6~ 47,878 the damper toward a full open position.
As shown in Fig. 4, the circuit is in a condition in which the furnace is off, the thermostat 78 is open, the ,,, r~olDR
i~; switch 88 is closed to energize ~e~e~ 82 (whlch holds the damper plate closed) and of course the gas valve 80 is shut. Upon a demand for heat sensed by the thermostat~ it -closes and energizes relay coil 86 which opens switch 88 in the conventional circuit ~nd closes the switch to terminal 90 in the preferred circuit). In either case, the motor 82 is deenergized and the biasing means will drive the motor in the reverse direction and mo~e the damper plate to the open position. As the damper plate closely approaches the full open position, the switch 84 closes and this results in energization of the solenoid controlling the gas valve 80 to permit flow of gas to the burners. In the conventional - ~`
arrangement the reverse direction of the motor is stopped mechanically, while in the preferred Nagel arrangement the operation of switch 84 results in the application of DC to the motor through terminal 90 and switch 88. The application o~ DC dynamically brakes the motor so that the gearing is not subject to strain as is more fully set forth in the noted Nagel application. The resistor 94 is pro~ided to limit motor heating and reduce stress on the diode 92~ -; since the rectifier or braking circuit of course remains connected so long as the switch 84 is closed and the switch 88 is in the terminal 90 position corresponding to the damper being open and the furnace operating~ A resistance value in the range of 20 to 50 ohms will perform quite satisfactorlly with a 2LI volt typical clock motor.
When the thermostat 78 opens in response to the -10~
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satisfaction of the demand for heat~ the relay coil 86 is deenergized so that switch 88 operates to a position ener-gizing the damper motor 82 directly across AC to drive the damper against the biasing means to a closed position.
It will be appreciated that the damper position responsive switch 84 opens almost immediately as the damper begins to move from its full open position, and of course the braking circuit is disconnected as soon as the thermostat opens.
An additional circuit herein characterized as an AC trickle circuit is also believed to be preferable to add to the basic circuit of Fig. 4, which is herein characterized -~as the DC dynamic braking circuit. As shown in Fig. 5, the AC trickle circuit comprises a resistor 96 which is connected between one side o~ the motor 82 and one side of the AC
line, and in parallel with the flue temperature responsive switch 95 3 to provide a trickle or reduced AC current to the motor to prevent a residual magnetic locking torque from ~ ~`
hanging-up the damper in an intermediate positlon under highly infrequent, but possible, conditions occurring in the operation of the furnace and controlling circuit, all as explained more fully in the noted Nagél patent application.
For a typical 24-volt clock motor the resistor is preferably in the range of about 200 to 1,000 ohms.
Fig. 6 illustrates the general arrangement o~ and ` relation between the gearing, the drive from the motor 82, the biasing ~eans, and the damper position responsive switch ~, means 84. The overall design of the actuator means shown is --in large part contributed by others The output shaft 72 of the actuator means is journaled in the plate 98 and plvotally mounts the sector gear 100 which has gear teeth along the ~-~ .

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~7~ 47,878 arc 102. These teeth ~i~h mesh with the teeth of spur gear 104 driven by the output shaft 106 of the clockwork motor 82 (not shown in Fig. 6). The arrangement as shown is in the condition corresponding to the damper being full open~ switch 84 in a closed position, and the dynamic brake being on through the application of DC to the motor.
Flue temperature responsive switch 95 is also closed since the flue temperature is assunled to be within the normal limits in which the cam 97 driven by the helical bimetal has not opened the switch. The closure of' the switch 84 occurs when the cam 108 fixed to the sector gear rocks the lever 110 in a counterclockwise direction about the pivot pin 112 to move the remote end 114 away from the switch button 116 and against the pull of the spring 118 biasing the lever in a switch-open direction. The main biasing means for the arrangement shown comprises two tension springs 120 and 122 which urge the sector gear laO in a clockwise direction ~ -which dri~es the clockwork motor in a reverse direction.
While the ~ear 100 carries a backup stop 124 positioned 20 to engage the pin 112 if for any reason the dynamic braking ` should fail, in the intended operation the dynamic braking stops the motor rotor rotation within a fraction of a second of closure of switch 84 and stop 124 does not function by ~ ~
mechanically abutting the pin. ~ ;
When the room thermostat 78 (Fig. 4) is satis~ied and openæ, the motor 82 will be energized as explained here-tofore and drive the sector gear 100 in a counterclockwise direction against the biasing springs until the damper closes with the motor stopping when the abutement 126 on the sector gear has swung through the dashline arc 128 and . ' :' ; . ::,; :

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~ 47,878 engages the lever 110. The motor remains energized to hold the damper in a closed position. It will be understood that the arrangement of a mechanical bias in the damper open direction provides one aspect Or fail-safe operation in the event of an electrical failure in the damper circuit.
It also results in the actuator means automatically being in a damper open position during the assembly o~ the actuator means to the rest of the damper assembly, and this fortuitously corresponds to the position that the damper plate takes be-cause of the torsion spring Ll6 so that the correct assemblyis facilitated. That is~ there is no chance that the coupling between the discs 70 and pin 42 can be at other than the correct angular relationship.

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Claims (5)

CLAIMS:

1. An automatic flue damper assembly comprising:
a flue pipe, a damper plate in said pipe;
shaft means attached to said damper plate and rotatably journaled at opposite sides of said plate from said pipe;
electrically operated damper plate actuator means including a shaft rotatable through a limited arc corresponding to movement of said plate between open and closed positions;
means for securing said actuator means to said pipe;
means for coupling said actuator means to said shaft means including, a crank-shaped end of said shaft means at the side of said pipe adjacent said actuator means, said crank-shaped end including a lever arm portion, and a pin portion having an axis offset from the axis of said shaft means, and means fixed to the end of said actu-ator means shaft to receive said pin portion, said receiving means comprising means defining an opening correspond-lngly offset from the axis of said actuator means shaft at a given angular position.

2. An assembly according to claim 1 wherein:
said means fixed to the end of said actuator means shaft comprises a plate, and said receiving means comprising means defining a generally radially extending slot in said plate.

3. An assembly according to claim 1 wherein:
said crank-shaped end has said lever arm portion generally aligned with the plane of said damper plate.

4. An assembly according to claim 2 wherein:
said slot is open at the edge of said plate.

5. An assembly according to claim 4 wherein:
said plate is generally circular in outline.