US2371512A

US2371512A - Draft control

Info

Publication number: US2371512A
Application number: US453400A
Authority: US
Inventors: Jr Edward A Field
Original assignee: Individual
Current assignee: Individual
Priority date: 1942-08-03
Filing date: 1942-08-03
Publication date: 1945-03-13
Anticipated expiration: 1962-03-13

Description

March 13, 1945. E. I JR 2,371,512

DRAFT CONTROL Filed Ahg. s, 1942 .3 Sheets-Sheet l March 13, 1945.

E. A. FIELD, JR

DRAFT CONTROL Filed Aug. 3', 1942 3 Sheets-Sheet 3 4 H; A55 44 56 I I r Y t I v I W 17/10/40 if fla M.

INVENTOR.

Patented Mar. '13,

UNITED STATES, PATENT OFFICE "DRAFT coN'moL Edward A. Field, In, Mendota, Ill. Application August 3, 1942, SerialNo. 453,400

22 Claims.

This invention relates to improvements in draft controls.

The main objects of' this invention are:

First, to provide an improved automatic draft control device for combustion heaters. stoves and the like which are entirely dependent 'upon natural draft for their air supply.

.Second, to provide an automatic thermally responsive draft control which is responsive to the temperature of the flue gases of the heater to effect regulation of the draft in accordance with said temperature, appropriately increasing thedraft when the flue temperature rises and decreasing the draft when the temperature falls.

Third, to provide a draft control of the type described, preferably for oil burning space heaters, which is effective to closely regulate the draft of said heaters in accordance with the flue temperature, thereby preventing wasteful combustion on the one hand due to excessive draft and accumulation of soot on theother due to too low draft, and at the same time affording requisite increased drafts for high burning rates which result in high fuel temperatures.

Fourth, to provide a device of the'type described which is highly sensitive in its operation, having provision for counteracting or neutralizing factors normally tending to affect the accuracy of its operation, and which is simple and inexpensive in its parts notwithstanding its sensitivity.

Fifth, to provide an automatic temperature controlleddraft regulator of the'type described which has provision for maintaining the draft gate, in which the regulating action is exerted on the gate in a manner to be consistent with the action of the counterweight on the gate, with resultant improved and more accurate operation. Further objects relating todetails and economies of the inventionwill definitely appear from the description to follow. The invention is defor minimum flue gas temperature and the draft control gatebeing shown in partially closed position. I

' Fig. 2 is a viewsimilar to Fig. 1, illustrating the parts in position for maximum or increased temperature control, the draft'control gate in this case being shown in fully opened position under the influence of air pressure thereon.

Fig. 3 is an enlarged fragmentary detail view in section on a line corresponding to line 3-3 of Fig. 1 illustrating the thermally responsive actuating element of the control and details of mounting thereon the smoke flue.

Fig. 4 is an enlarged fragmentary view in section on a line corresponding to line |4 of Figs.

. 1 and 5, illustrating the structural details and the relationship ofthe parts of the control with the at values proportionate to the flue temperature,

regardless of differences in the 'rate of increase thereof at differing temperature ranges, for a givenfuel consumption.

Sixth, to provide an'automatic, thermally controlled device of the type described including a bimetallic temperature responsive element positioned relative to the flue so as to lie-subject to the temperature of the flue gases and likewise in such manner as to withstand destructive action thereon of the sometimes exceedingly hot flue gases. Y Seventh, to provide an automatic control of the type described which positively limits the draft at a predetermined desired minimum value, regulating the draft proportionally to the increasingflue gas temperaturesuptoa maximum, at. V which the drattislikewise positively limited.

Eighth, to provide a regulator of the W9 described including a thermally responsive element and actuated thereby to vary the to movement of a counterweighted s; m. 9 is a tummy latter automatically positioned for minimum temperature operation.-

-Fig. 5 is a view partially broken away and in horizontal section further illustrating structural details and relationships, with the control parts in the position illustrated in Figs. 1 and 4. 5

Fig. 6 is an enlarged fragmentary. view in section on a line corresponding to line 6-6 of Fig. 2 illustrating further structural details and indicating the operation of the-thermal element and parts \zonnccted thereto in solid and dotted 1 5 lines respectively.

Fig. '7 is an enlarged frag'meiitary detail view in section on a line corresponding to line 1-1 of Fig. 5 illustrating provisions for-preserving accuracy and maximum sensitivity in the movements of the control mechanism. Fig. 8 is a fragmentary perspective view partially broken away and in section illustrating a detail of the gate mounting and stop means of.-

the control.

view in section on a linewhen the temperature rises and increase the draft when the temperature falls. In the present rearwardlytherefrom parallel to said wines which act as end abutments preventing excessive lustrating a modified structure incorporating the s invention The present invention relates to an automatic thermally controlled draft regulator well adapted for the regulation of oil burning space heaters of the type dependent. entirely upon natural draft for their air supply. Most such heaters can be operated at burning rates which vary from a maximum down to a minimum of only or of the maximum rate. It is desirable that at the lower burning rates only a comparatively 5 small amount ofair shall be supplied to the burner; however, it is a very rare occurrence when the operator takes the trouble to alter the setting of the draft control of the heater for each change in the position of the fuel control valve. 20

a of a type which is dependent entirely upon nat- Manufacturers have heretofore provided draft 4 ontrols with adjustments appropriately marked nd settable to correspond to similar fuel consumption markings on an oil dial, but the results neglects tochange the draft setting and simply manipulates the oil control dial up or down to regulate the fuel supply. This is objectionable,

for excessively high-drafts wastefuel and excessively low drafts cause accumulation of soot.

An attempt has been made to overcome this difficulty by permanently setting the draft control for a rather highdraft; for example, a draft which is about right for a burning rate of 80% 'asvasia plied to the gate in a manner such that it counteracts to a maximum extent the torque of the gate counterweight and thereby renders the gate least resistant to oppose the flow of air there through into the flue. It will be appreciated that a temperature sensitive mechanism of this comq pensating type is applicable to various types of draft control to automatically regulate the set- No. 2,358,390, Sept. 19, 1944, 1 illustrate the mechanism associatedwith a well-known blocking Y type control. Further details of the operation of the structure chosen for illustration herein and of the principle embodied in the invention, generally considered, will become apparent as the description of the structure proceeds. V I Referring to the drawings, the reference nu metal I designates an 011" burning space heater ural draft. The reference numeral 2 in general designates the draft control employed in the present embodiment of this invention, which is are still not satisfactory. The operator usually 25 housed in and supported by a pipe T, arm 3 of which is applied directlyto the smoke outlet of the heater i and serves in the manner of a smoke flue; hence it will-be referred to as such. This control device will also operam correctly if the tee is located so as to constitute the second or third length of the flue from the stove, with appropriate calibration of the device for such a mounting.

The outwardly projecting leg 8 of the 1 con-- or 90% of maximum, but the fact remains that as stitutes-a cylindrical draft control housing, being this draft is still a trifle too low for the maximum combustion rate and a great deal too high for medium or low burner settings. Most oil burning heaters are operated at a medium or low oil setdeal of fuel is needlessly. wasted by excessive draft when the latter is set in the manner referred to.

The device of the present invention consists of a draft control'having applied thereto a thermally controlled apparatus which issensitive or responsive to fine ass temperature to automatically regulate the draft settings according to the temperature of the gases in the fine as dis- ;charged from the heater. with this invention I- increase the draft when the temperature in the fine rises and decrease the draft when the temperature in the fiue falls. This is a markeddeparture from the operation of most thermally controlled regulators, which reduce the draft invention I take advantage of the fact that fuel temperatures increase with higher burning rates so as to provide increased drafts for such higher" is operative in response to fuel temperaturesin direct relation thereto. 7

Generally stated. the device'eifects the foregoing operation by an adjustable compensating I weight appropriately connected to the draft control gate, which in the illustrated embodiment isa counter-weighted one, and swingable to vary the resulting torque stresses on the gate as theprovided at .its outer end with an annular stamped, sheet-metal gate frame 5 disposed in and abutting said outer end. The framefhas a gate opening 5 therein, preferably straight sided,

' ting the majority of time, which means a great 40 provi w laterally inwardly extending formed on the sides thereof adjacent wings 8,- and a pintle rod 12 secured eccentrically to the gate and extending through apertures in said sate flanges ll serves to provide pivot trunnions ll for the gate. The said housingwings 8 adjacent the forward end of the latter are provided with elongated recesses II on the lower edge of which gate pivoting trunnions' II are rollingly received to effect a very free frictionless journaling of the gate; while the radially extending side shoulder I! of, the gate frame immediately to either outer side of-wings 8 has-lips'or lugs l6 struck,

longitudinal or endwise movement of the gate burning rates, inasmuch as the present. device-ootrunnions.

As illustrated in Fig. 8, the gate'flange ii on one side of the gate is slit and conformed to provide a spring stop finger I? which projects laterally outwardly through an arcuate opening as m provided in the housing flange or wing a.

the oppositeangular limits of said opening Ill the spring stop i1 limits the swinging oftlie gate at its closed and maximum open; positions. This is performed effectively and n silently, due to the resilient character of stop H.

The smoke flue 3 intermediate the heater I horizontally elongated opening It by the expe dient of slitting the side wall horizontally is located in a position and has its torque ap- 1| and offsetting outwardly to provide a -peir of .latter (see Figs, 2 and 5).

2371.512 parallel flanges 20 from the material thereof.

Within this opening I mount a blade-like bimetallic thermal element 2|, see Figs. 1, 2, 3 and ,6. This thermal element is fixedly secured at one end to the side of the fluethrough its engagement by lugs l9 and 22 on the latter. .At its other end the thermal element is securedas by the rivets 22| to the laterally disposed end 23 of an angled actuating arm 24, this arm being angled as shown in Fig. so that its outer end is positioned below the housing 4 as is clearly shown in the drawings. The portion 23 of the arm is'provided with ears 23| receiving the pivot 25 carried by the flanges 20-, see Figs. 1 and 3.

The thermal element 2| is disposed with its high-expansive side on the outer side of the flue and exposed to the air in the room being heated.v This is advantageous because of the fact that the thermal element thus does not become undesirably heated as is likely to be the case where it is entirely surrounded by the hot gases in the flue. A slight amount of air leaks in around the cracks at theedges of the thermal element and tends to further cool the same. Thus an ordinary comparatively inexpensive bimetallic bladelike member will serve my purpose, whereas, if the latter were disposed entirely within the flue and surrounded by gases, the temperature of which reaches 900 or 1000 degrees F., a very special grade or design of thermal element would be called for. It is evident that' as the temperature in the flue increases the thermal element 2| warps or bows outwardly from the position indicated in solid to dotted line position,

, correspondingly swinging the actuating arm 23,

] tion for the control, to be hereinafter referred to more fully, inwhich a predetermined pressure is exerted on the actuating arm and the thermal element-2|, and likewise a predetermined posiunder maximum flue gas temperature to which the control is responsive. This is desirable be-- cause, if an excessive temperature should prevail in the flue for some reason, the movement of the actuating arm 24 might be so great as to damage: the parts of the device to .be described.

At its, outer end the arm; 24 has adjustably mounted thereon an extension-arm 28, .a rivet 29 serving as a-pivotal connection. Arm 24 and its extension}! are fixedly secured to one another in appropriately adjusted position by :ineans of a screw 30 threadedlyreceived bythe ,arm .24 and'extending through a slot 3| in ex-.

tension 28 with'its head bearing against the This permits relative adjustment of j the actuating arm and its extension'for minimum draft positioning o'f-th'e gate 10. Assuming that a minimum draft of .02 inch is desired, the extension 28 is appropriately set so that the parts actuated by said arm (to be Zdescribed) are positioned and exert appropriate action on the gate. Instruments are employed Referrlng-nowtoFigs. 1, 4'and 5, the control tion of maximum movement of the actuating arm housing 4 has depending therefrom a sheet metal supporting frame or bracket 32 provided with an' opening to receive arm 24 for free swinging movement. Bracket 32 has V notch, openings 33 in its opposite side walls receiving knife edge pivots 34 which are turned outwardly from a stirrup-like U shaped rocker member-35. This U shaped rocker member 35 hasrigidly secured to one of theparallel arms thereof a forwardly projecting gate compensating control arm 36 andsaid arm has as an integral part thereof a pair of out-tumed upper and lower ears 31, 38 located rearwardiy of the knife edge pivots 33, said ears serving to' receive a vertical pivot pin 39. The

lower end of this pin rounded to minimize friction in its turning and restson the cross member 40 of the rocking member 35 (see Fig. 7). Pin 39 has secured thereto a laterally 'osciliatable compensating weight swing arm 4|. has a free, frictionless pivotal movement in the journaling ears 31, 38therefor and the swing arm 4| is secured flxedly to said pin for movement therewith. At its outer end the lever is oifset upwardly at 42, bringing the upwardly offset portion into a plane which includes the pivot point of knife edges 34!. Appropriate, preferably equal-sized, compensating

weights

43, 44 are mounted on the upper and lower sides of arm portion 42 so that their center of gravity lies in this plane.

By referenceto Fig. 5 it will be noted that compensating weight swing arm 4|, which is of sheet metal material, has its pivot pin 39 secured thereto at one inner corner thereof. Adjacent the opposite inner corner, or at least in substantially spaced relation to pin 39; arm 4| is provided with an upwardly and forwardly turned 'ear 45 for eflecting a pivotally actuating -connection between the swing arm and a link 48 by which the same is actuated from the actuating arm extension 28. Link 48 is pivoted at its op posite end to said extension.

In effecting the aforesaid pivotal connections of link 46 to the arm 4| and actuating arm exarm extension 28. The bearings are provided with openings 48 for the reception of the pivot, pins 50, 5|. Pin 50 extends downwardly through alined openings in swing arm 4| and the ear 43 thereon, while pin 50 is received in an opening in the arm extension 28. The purpose'of the convex bearings 41. 48 is. to reduce the friction between the parts when the actuating extension 23 is rocked horizontally, also permitting vertical rocking or tilting mpyement of the arm without binding of the parts such as would detract Y armjt :and the actuating arm extension, re-

spectively, lie in a plane ing through the pivot point of the'kni'fe edges Thepurpose of this arrangement willbe hereinafter referred to.

At its outer endthe forwardly projecting gate compensating control-,arm38, which as stated is rigidly secured to. the rocking support 35 for vertical rocking movement therewith, has at-- tached thereto a-connector linkl2 which extends upwardly through an opening 43 in the lower part of control housing 4 and is connected at its This pin to the gate In on the rear side thereof. The point of pivotal connection of th link 52 to bracket I53 lies in a plane extending through the gate pivot I! at an angle of approximately 70 degrees to the gate; The gate itself is provided beneath its'pivot point with a pair of counterweights 8t, 85 on theouter and inner sides thereof. respectively, the weight 5 being fixed and the weight a -'torque ofcounterweights 54, 65 on the gate in accordance with the temperature of the hue gases, and thereby render the gate more resistant to opening under the external pressure of air.

thereon as the temperature increases and less resistant to opening as the temperature decreases. It will be understood that t combined

weights

54, 55 in combination with the weight of the gate 60 itself will, when properly adjusted, produce a predetermined closing torque effective on the gate.

In actual manufacture, after the factory balancing operation is completed, the center of gravity of all of the gate carried parts will be located in a plane passing through the gate pivot point outwardly and downwardly at an angle of .10 degrees to the plane of the gate, and it is essentially important, in accordance with the present invention, that the efiect of the compensatlng provisions carried by the rockablesupport and connected to the gate shall be applied on the latter in the same manner as the fixed

counterweights

54, 55. Consequently I have made assists upper end to a relatively short bracket I88 secured be .02. ds'the bimetallic strip as warps and bows outwardly under increasing flue gas temperature due to an increase in the fuel consumed,

actuating arm 26 is rotated counterclockwise about pin 25, as viewed in Figs. 5 and 6, from solid towarddotted line position in th latter, being thereby effective through extension 28, link 46 and arm II to swing the weights at, 46 rear- ;vlsrdgy or in clockwise direction as viewed in As weights #3, is approach the vertical lane passing through the knife edge pivots of the rockabie support so the torque exerted through wire link 8 becomes less, due to decrease in moment arm of the weights; hence the counteracting compensation of the fixed gate counterweights M, It is diminished and the closing torque effective on the gate increased, requiring a greater draft to swing the same. In this connection it is pointed out that the link 52 may be attached to the front of the gate instead of the back if the action of the compensating weight swing arm 4|:

is reversed, and the same results accomplished. However. attaching the link to the front side of the gate would require offsetting or bending of the same to avoid being struck by the gate as v the latter is opened. Hence, it is found more the link to the rear side to the heater, likewise to stabilize the bimetallic strip 2|, I provide an internal strut 58 extending particular provision that the links: shall .con-

nect to the gate or bracket I53 thereon in degree plane referred to.

In actual practice the gate is permitted by the stop I] and limit opening I81 to'open' about 80 degrees from its closed position and although the. center of gravity is located in a plane extending downwardly a slight degree when the gate is closed or in vertical position, nevertheless throughout the greater part of the swing or movement of the gate the center of gravity of the combined gate parts moves upwardly and over toward the vertical plane of the gate, there being the 70- only about 20 degrees of gate movement (at the time the latter starts to open) when the center of gravity movesaway from the vertical plane of the gate. This is consistent with principles which 'Ihave found to be sound.

position for minimum draft and temperature control, as illustrated in Figs. 1, 4 and 5, a torque will be exerted on the rocking support 35 in a clockwise direction as viewed in Fig. 5, which is of sumcient magnitude to oflsetor neutralize most of the aforesaid counterweight closing torque on the gate, leaving a net difference of only the amount necessary to close the gate across between the two sides of the T. Also, in order to prevent the bimetallic strip from bein unduly influenced by cool air entering and passing through the draft control housing 1, which air sometimes tends to eddy back into the flue toward the heater l, I provide deflecting louvers it at the inner corner of housing 4 adjacent its union with the flue portion of the T. In the illustrated example these louvers consist of curved bands of metal arranged overlapping in such a manner as to tend to direct the air flow towards the chimney instead of striking the back side of the 1' and swirling in all directions; These louvers also assist in preventing disposition of soot in the draft control, but the primary purpose thereof as regards the present invention is to prevent the cold air from contacting or influencing or affecting the inner side of the thermal element. If this occurs, then on a day when the gate IQ has to be opened quite wide, as on a clear cold day, much more air will be passed into the pipe than would be the case on" a warmer day, and consequently the most desirable actionof the control device will not be had. 7

Referring to Figs. 4 and 5, it will be noted that the link actuating compensating arm 33 on the rocker support "has an added piece 51' affixed thereto constituting a counterbalance or counterweight for the rocking assembly. This weight is positioned on the arm 86 to counterbalance the weight of the other parts of the rocking assembly, so that when the compensating weights", .44 are removed and swing arm 4| is in the forwardminimum draft position of Fig. 5 thecombinedparts are substantially 'in'balance, with their combined center of gravity coincident with theaxis of the rocker assembly, 1. e., on a line passing through the knife edges 3 by which said asscmblyispivoted.

While the rocking assembly does not swing' more than five or six degrees to either side of the horizontal position of arm 30 as shown in against the desired minimum draft, assumed to 1 Pig. 4, yet if the combinedcenter of. gravity were .6, so that link 46 is thrust under bearings 41,

n ider ly above or below the pivotal axis of the assembly, then, as the rocking support 35 rocked and the center of ravity was shifted over close to the vertical plane of the axis, the torque developed would vary considerably. To avoid this I have provided that the compensating

weights

43, 44 are of the same size and weight and are disposed one above and one below the vertical offset end 42 of lever arm 4|. This assures that the plane in which the outer portion of the arm swings. and the center of mass of the two weights will pass through the pivotal axis of has been pointed disposes the'end the rocker assembly, since, as out, the ofiset in swing arm 4| thereof in a plane passing through the pivot point of knife edges 34. The combined center of gravity of

weights

43, 44 and arm It always rocks through the same part of a vertical arc, regardless of the lateral position of the compensating weight swing arm 4|.

If the temperature of the flue gas increases, indicating the need for a greater draft for perfect combustion, the bimetallic strip 2| bows outwardly from solid lineposition of Fig. 6 toward the dotted line position, rocking the actuatin arm 24 which is rigidly secured thereto in counterclockwise direction as viewed in Figs. 5 and compression to the left in Fig. 5 and thereby pivoting swing arm 4| in clockwise direction as viewed in Fig. 5. This thermally derived force is transmiitted accurate-- ly and proportionately regardless of the position of the gate l0, and hence of therocking assembly on which the force transmission link 46 is carried, due to the provision'of the rounded pivotal connection to actuating arm extension 23 and the swing-arm 4|. The holes in said link receiving the pivot pins large so that the rocker assembly can swing up or down 8 or 10 degrees without any appreciable detract from thebinding action suchas would accuracy or sensitivity of the device.

I have pointed out above the aforesaid link pivotal points or bearings are in a plane passing through the pivotal axis of the rocking assembly at knife edges 34 (see Fig. '7). It will be further noted by reference to this; last figure that the point where the link is pivoted to the actuating arm extension 28 is very close to said rocker assembly axis at knife edges 34, hence, as. arm 24 and extension 28 swing to the rear in compensating to provide increased draft, the link pivot to extension 28 passes by a short movementthrough the rocker assembly axis and beyond the same a slight distance on the other side thereof. By making the distance traversed by the pivot link connection on either side of the rocker assembly axis comparatively small, the accuracy 'vice is considerably contributed to. If link 48 of the deing arm 24 and extension 28 thereof. The latter should, and in the arrangement as described does, only function to position the compensating weights temperature so that said compensating weight may accurately exert its proportional compensating effect on the counterweighted gate.

As compensating

weights

43, 44 are swung to the rear in clockwise direction under the. influence of increasing flue temperature, they become, as stated, decreasingly effective in their ability to offset the action of the

main gate counterweights

54, 55, with resultant increase in the resistance of gate iii to swinging and production of a higher draft for the heater I. This swinging movement continues to a maximum draft position so far as the control is concerned, in which actuating arm 24 strikes the stop 21-. Further excessive increase in the temperature due to an abnormal combustion condition is thereafter ineffective in moving the compensating weights, with attendant possible-damage to the more delicate parts of the device.

It is a well-known fact that operating characteristics of different stoves are not the same. with some stoves or heaters the rise in flue gas temperatures as the fuel consumption is increased, is approximately a straight line, while with others it is in the form of a curve. This may be allowed for in the present device by changing the point of attachment ofthe link 48 to the swing arm 4 I, also by changing the position of the said swin 48 on the link at the points of its and the number of so, an are sufficiently were attached to extension 28 at a relatively great the link pivot to arm extension 28 is closely adjacent the rocker assembly pivot axis in any position of said extension there is substantially no horizontal swinging of the arm 4| due to the vertical rock of the rocking assembly.'- In otherwords, said assembly is rocked'only in response to -preponderating pressure of air on gate rather than the possibility of rocking the same accidentally due to the movement of the'actuatarm at its initial starting position for low draft, using the adjustment described above. Thus the swing arm can be made to rotate through different parts of the are for different stoves or heaters,

be varied. Also, if the

size ofjthe weights

43, 44 is changed the torque developed can be made to conform approximately to-the requirements of practically anyv stove.

,As will be apparent from an inspection of Fig. 5, the change in torque exerted by

weights

48, 44 is relatively small as the arm 4| first starts to swing away from its position in that figure,

there being little movement toward the rocking assembly axis, but as the arm 4| approaches its other extreme position the change in torque is quite rapid for each degree of swing. This onsets the fact that flue gas temperatures rise more as the fuel feed is increased from alow than is true after the stove is already operating at a fairly high burning rate. To illustrate this, in a given type heater, if the oil feed is increased from '1 cc. per minute to 14 cc. per minute, the flue gas temperature may increase asmuch as 200 degrees F., but when the oil feed is changed a similar amount from 21 cc. to 28 cc. per minute the flue gas temperature may increase 'only degrees F; Therefore, it will be appreciated that my control is sensitive to this nonlinear relation fuel feed to flue temperature to in-' sure the supply of adequate yet not excessive air to. the heater, in proportion with the air requirements for most eiilcient combustion. Under the conditions stated the draft at the lower rate of fuel consumption is maintained proportionately low and at the high rate of consumption is maintained proportionately high, notwithstanding the fact that the ultimate adjustment of the-mechanism itself, i. e., the angular swing of arm 4|, is linearly responsive .in proportion to the changes in flue gas temperatures.

mm. 10 Ihave illustrated a modified'adaw' tation of the invention, similar tothe foregoing- 43, .44 in accordance with the flue gas degrees of rotation may also in all respects, save that the actuating arm 2Q (or appropriate adjustable extension thereon, not shown) is effective on the compensating weight swing arm 4| by a camming action instead of the linkage arrangement illustrated in the preceding figures. In this embodiment arm 24 is provided with 9. lug or pin 60 engaging the cam slot 6| which is provided in the swing arm ii in spaced' relation to its pivot 39. The arms N and 6! are swing from solid to dotted line position in the manner illustrated, as the bimetallic strip 2! bows under increasing flue gas temperature and reversely under decreasing'temperature. by cam engagement of lug Bil with opposite sides of the cam slot 8| as will be readily appreciated.

Further modifications incorporating the principles discussed at length above will readily sug- -gest themselves to those skilled in the art. Thus different forms of thermally responsive element connected to the rocking support 35 in appropriate fashion will procure a similar result, if the broad concepts explained above are adhered to. Similarly various alternative methods of. applyassume control member resisting movement thereof, a

compensating swing arm pivoted, on said rocker member for lateral swinging movement at right angles to the plane of rocking movement of the a member, a compensating weight carried by said swing arm, the center of gravity of the swing arm and weight traveling laterally in. a plane including the pivotal axisof said rocker member to alter the moment arm of said compensating weight and thereby vary the torque of said rocker memher, and means forvariably positioning said swing arm and compensating weight in accord ance with the temperature in said flue to thereby regulate the bias on said draft control member, comprising a thermally responsive bimetallic element positioned adjacent said fine and subject to the flue. gas temperature therein, an actuating arm pivoted adjacent said flue, said element being secured at one end thereof to the flue and at thermally controlled devices which operate inversely to reduce draft upon increase in the flue gas temperatures, my device maintains a direct proportion therebetween, within certain definite predetermined chosen maximum and minimum draft conditionswhich may be selected as dethe other end thereof to said actuating arm, whereby movement of said element in response to changes in the flue temperature results in swinging of the actuating arm around its pivot, and a link eccentrically pivoted to said swing arm and pivoted to the free end of said actuating arm for actuation of the swing arm and compensating weight in response to thermal changes in the fine, said link pivot points lying in-a plane in cluding the pivotal axis of the rocker member. 2. An automatic, thermally responsive draft control device, comprising in combination with a heater flue, a draft control housing communicating with said flue provided with a pivoted draft control member subject to air pressure externally of the housing and normally biased to resist movement under said pressure, a rocker member pivotally supported for vertical rocking movement and operativeiy connected .to said draft control member whereby rocking torque of said so rocker member is effective-to modify the bias on sired upon installation. 0! course, high buming rates produce high fuel temperatures and my device takes advantage of this fact to provide increased drafts for the higher burning rates, with the resultant improved emciency, since it is responsive to the fiue temperature. Use shows that a very close correspondence exists in the proportion between fuel consumption and the flue gas temperature on the one hand and the draft as regulated by my device on the other hand, with highly desirable combustion indeed under all operating conditions as reflected by C02 analysis. I have illustrated and described my invention in embodiments which have been found to be very satisfactory in operation. I have not attempted to illustrate or describe other embodiments or adaptations which I contemplate as it is believed this disclosure will enable those skilled in the art to embody the invention as may be desired. v i

- Having thus described the invention what I claimvas new and desire to secure-by Letters Patout is: I

1. An automatic responsive draft said control member resisting movement thereof.

a compensating swing arm pivoted on said rocker member for lateral swinging movement at right angles to the plane of rocking movement of the member, a compensating weight carried by said swing arm for lateral movement to alter the moment arm. of said compensating weight and thereby vary the torque of saidrocker member.

and-means'for variably positioning said swing arm and compensating weight in accordance with the temperature in said flue to thereby regulate the bias on said draft control member comprising a thermally responsive element positioned adjacent said flue and subject to the flue gas temperature therein,, an actuating arm pivoted adjacent said flue, said element being secured to said actuating arm whereby movement of said element in response to changes in the flue tem-;

perature results in swinging of the actuating arm around its pivot, and a link eccentrically pivoted to said swing armm'nd pivoted to the free end '01 said actuating arm foiactuation of the swing control device comprising incombination with a heater flue, a draftcontrol housing communicat ing'with said flue provided with-a pivoted draft controlmember subject to air pressureextemally of the housing and normally biased to resist movement under said pressure, a rocker member subject to torque tending to resist ment of the gate in response to external air prespivotally supported for vertical rocking movement and operatively connected to said draft control member whereby rocking torque of said rocker member is effective to modify the bias on said arm andcompensating'weight in response to thermal changes in the flue.

3. In combination with a heater smoke flue dischar combustion gases, a draft control housing cornmunicating'therewith at one end and at its other end provided with an air admission opening and a counter-weighted gateeccentrically pivoted in the opening. said gate being normaly opening movesure thereonra thermally responsive element located adjacent and subject to the temperature in the flue, a pivoted actuating arm connected earner: I 7

to said element and pivotally mama thereby in resopnse to thermally induced movement of the latter, a rocker member mounted for vertical swinging movement and operatively connectrocking torque of said ed to said gate whereby member is transmitted to the gate to alter the torque normally effective thereoma swing arm pivoted on said rocker member having a compensating weight thereon, a link pivotally connected eccentrically to said swing and actuating arms respectively to transmit thermally induced movement of the latter to the former and thereby vary the moment arm of the compensating weight relative to the pivotal axis the rocker member, said compensating weight,'depending on its moment arm relative to theepivotal axis of said rocker member beingeffective through said rocker member and connection thereof to the gate to exert greater or less compensating e!- iect on the torque on the gate tending to resist movement-of the latter, andmeans to-limit the movement-of said actuating arm at opposite extriemes thereof.

4. In combination with-a heater smoke flue discharging combustion gases, of a draft control housing communicating therewith atone end and at its other end provided with an air admission opening and a counterweighted gate eccentrically pivoted in the opening, said gate being nor mally subject to torque tending to resist opening movement of the gate in response-to external air pressure thereon, a thermally responsive element located adjacent and subject to the temperature in the flue, a ivoted actuating arm connected to said element and pivotally actuated thereby in response to thermally inducedmovement of the latter, a rocker member ,mounted for vertical swinging movement and operatively connected to said gate whereby rocking torque of said mom-.-

her is transmitted to the gate to alter the torque normally efi'ective thereon, a swing arm pivoted on said rocker member having a compensating weight thereon, means operatively connecting said swing and actuating arms respectively to transmit thermally induced movement of the latter to the former and thereby vary the moment arm of the compensating weight relative to the pivotal axis of the rocker member, said com'-. pensating weight, depending on its moment arm relative to the pivotal axis of said rocker ,mem-

ber', being effective through said rocker member and connection thereof to the gate to exert greater or less compensating effect on the torque of the gate tending to resist movement of the latter.

' 5. In an automatic thermally responsive draft control device, inv combination with a heater smoke flue adapted to be traversed by combus-e tion gases, a draft control housing communicating therewith at one end and at its other end provided with an air admission opening and a counterweighted gate eccentrioally pivoted'inthe opening, said gate being normally subject to torque tending to resist opening movement of the gate in response to external air. pressure thereon, a thermally responsive element subject to the temperature in the flue between said control housing and the heater to which the flue is saidmembe'r is transmitted the gate to alter the torque normally eflective thereon, a swing arm pivoted on said rocker member having a axis of the rocker member,- and' a link pivotally connected eccentrically to said swing and actuating arms respectively to transmit thermally induced movement of the latter to the former and thereby vary the moment arm oi the compensating weight relative to the pivotal axis of the rocker member, the pivotal points of connection of said link to said arms lying in a, plane passing through the ivotal axis of the rockable member, said compensating weight, depending on its moment arm relative to the pivotal axis of said rocker member, being effective through said rocker member and connection thereof to the gate to exert greater or less compensating effect on the torque onthe gate tending to resist movement. of the latter, and means to limit the movement of said actuating arm at opposite extremes thereof. l r

6. In combination -with afheater smoke flue discharging combustion gases, a draft control housing communicating therewith 1 at one end and at its other'end provided with an air admission opening and a counterweighted gate eccentrically pivoted in the opening, said gate being. normally subject to torque tending to resist opening, movement of the gate in response to external air pressure thereon, a thermally respon'sive element located adjacent and subject to the temperature in the flue, an actuating member connected to said element and actuated thereby in response to thermally induced, movement of the latter, a rocker member mounted for vertical swinging movement and operativelyconnected to said gate whereby rocking torque of said member is transmitted to the gate to alter the torque normally efiective thereon, a compensating weight shiftably mounted eccentrically a pivotal axis of the rocker member, said compensating weight, depending on its moment arm relative to the pivotal axis of said rocker member, being effective through said rocker member and connection thereof to exert greater or less compensating effect on the torque on the' gate tending to resist movement of the latter.

7. In combination with a heater smoke flue I discharging combustion gases, a draft control connected, apivoted actuating arm connectedto said element and pivotally actuated thereby in response to thermally induced movement of the latter, a rocker member mounted for vertical swinging movement and operatively connected to said gate at a point in a plane including the gatepivotal axis and the center of gravity of the counterweighted gate, whereby rocking torque of housing communicating therewith at one end and at its other end provided with an air admission opening and a counterweighted gate eccentrically pivoted in the opening, said gate being normally subject to torque tending to'resist opening movement of the gate in response to external air pressure thereon, a thermally responsive element located adjacent and subject to the temperature in the flue, an actuating member connected to' said element and" actuated thereby in response to' thermally induced movement of the latter, a rocker member operatively connected to said gate whereby rocking torque of said member is transmitted to the gate to alter the torque normally efiective thereon, a compensating weight shiftably'mounted on said rocking member, and means operatively connecting ,said weight to said actuating element to transmit thermallyinduced movement of the latter to the former and thereby vary-the moment arm of the compensating weight relative to the pivotal axis ofthe rocker member, said compensating weight, depending on its moment arm relative to the pivotal axis of said rocker. member, being eiiective through said rocker member and connection thereof to exert greater or less compensating efiect on the torque on-the gate tending to resist movement of the latter.

8, An automatic thermally responsive draft control device comprising, in combination with a heater flue, a draft control housing communicatheater flue, a draft control housing communicating with-said flue provided with a swingable draft control member subjectto air pressure externally ing with said flue provided with a rotatable draft control member subject'to air pressure externally of the housing and normally biased to resist rotative movement under said pressure, a rocker' member mounted for vertical rocking movement and operatively connected to said draft control member so that vertical movement of said rocker member is efiective to modify the bias on said control member resisting movement thereof,' a

compensating weight swing arm pivoted on said rocker member for lateral swinging movement of'the member, a compensating weight carried by said swing arm, the swing arm and weight swinging laterallyto alter the moment arm of said.

compensating weight on the rocker member and thereby vary the torque exerted by said rocker "member, and means for variably positioning said swing arm and compensating weight in accordance with the temperature in said flue to thereby regulate the biason said draft control member, comprising a thermally responsive element subjectv to the temperature of gases which are discharged to the flue, actuating means connected to said element for operation thereby in mponse to changes in t e flue gas tempera-)- ture, means operatively connecting said actuating means to said swing arm for swinging movement of the compensating weight in response to thermal changes in the flue gas, therebyaltering the torque applicable through said rocker membeer on said draft control member.

' .9. An automatic thermally responsive. draft control device comprising, in combination with a heater flue, a draft control housing communie eating with said flue provided with a rotatable draft control member subject to air pressure exresist rotative movement under said pressure; a

' rocker member operatively. connected-to said draft control member so thatvertical movement of said rocker member is efiective to modify the bias onsaid control member resisting movement thereof, a compensating weight shiftablymounted on .said rocker member to alter the I moment of said compensating weight on the rocker member and therebyvarythe torque exthe closing bias on the control member in accordance with the temperature in said flue, comprising a thermally responsive element subject to the temperature of the gases which are discharged to "the flue, an actuating member mounted adjacent said flue and connected to said element for actuation thereby upon operation of the element in response to changes in the flue gas temperature, and means operatively connecting said actuating member to said weight for shifting of the compensating weight in response to thermal changes in the flue gas.

11. An automatic thermally responsive draft control device comprising in combination with a smoke flue, a draft control housing communicating with the flue, means to prevent swirling of ternally of the housing and normally biased to 50 erted by said rocker member, and means for variably positioning said compensating weight in accordance with the temperature in said flue to thereby regulate the bias. on said draft control member, comprising a thermallyresponsive element subject to the temperature of the gases which are discharged to the flue, actuating means connected to said element for operation thereby in response to changes in the flue-gas temperatuating means to said compensating weight inf response to thermal chang'esin the flue gas, thereby altering the torque applicable through said rocker member on said draft control mam ber.

10. automatic thermally. responsive draft air entering said housing into said flue in the direction'of the heater attached thereto, a draft control member pivoted in said housing subject to external air pressure, a thermally responsive bimetailic element disposed in an opening in said flue between the heater and housing and fixedly secured at one end to the flue, a pivoted actuating arm operatively connected to the other end of said element for swinging movement in response to thermal changes in the latter, asupport so cured to said housing, a compensating assembly comprising a rocker member pivoted on said support for vertical rocking movement having a compensating arm connected by a link to said draft control member, said rocker member being pro-- vided with a compensating weight positioiiable variably relative to the axis ofsthe rocker member, and means connecting said weig'htto said actuating arm for shifting of the weight-relative to the axis of rotation of the rocker member in response to changes in temperature in said flue.

12. In an automatic thermally responsive draft regulatonin' combination with a flue member dis-' charging products of combustion, a draft control device having adraft passageway communicating with the member, said device being provided with a draft control element having opening and closing movements in said passageway for regulating the flow of air therethrough to the member, said ture', andmeans operatively connecting said acdraft control element being mounted to be opened by excess of outside atmospheric pressure over inside flue pressure, means for resisting openingmovement of said control element, said member havingan opening therein inadyance of the draft rol connection thereto, af**"blade-like thermany responsive element located in said opening and secured at tone end to the member so as to be subject onone Side thereof :to the temperature internally of the member and on the other side to the temperature externally of the member, and

control device, comprising in combination with a 78 for' resisting means operatively connecting the other end of.

said thermally responsiveelement-tosaid means opening movement of said draft tiv to increase the resistance of said control element draft control element toopeningmovement in accordance with increase in the temperature in mounted end of said thermal responsive element whereby Y the arm is swung on its pivot withthe flexing ofv said member eflective on said thermallyresponsive element,

7 1a. In an automatic thermally responsive draft regulator for a combustion heater, a smoke flue having an opening in the wall thereof, a draft control device provided with a draft control member regulating the heater draft, a thermally responsive element located in said opening in the wall of the smoke flue of the heater, said thermally responsive lement being a blade-like structure disposed to constitute a closure means for said opening, saidelement being subject directly on one side thereof to the temperature of the flue gases internally or the flue and on the other side to the temperature of the atmosphere externallyof the flue, and means operativelyconnecting said thermally responsive element to said draft control memberto regulate said member in accordance with the temperature in said flue eflecon said element. 4. An automatic thermally responsive draft control device comprising, incombustion with a ing with the flue, means to prevent swirling of air entering said housing into trol member pivoted in said housing, said draft control member to be' opened by excess of outside said flue and comprising a gate sociated with over inside flue pressure and provided with normal closing torque means, said smoke-flue havingan opening in the wall thereof in advance of the inlet from said gate, a blade-like thermal responsive element disposed in said opening and subject on its inner side to the temperature. within the flue and on its outer side to the temperature without the flue, there being air inlet spaces at the longitudinal edges of said thermal responsive element, said at one end thereof, an arm said-thermal responsive element is swung on its pivot other end 'of mounted counterweight operatively assaid gate, and operating connections for said arm to said shiftable weight.

16. In combination with charging combustion gases, a drart control assoelated with said device and comprising a gate shifts-151$ mounted to be opened by excess of outside atmospheric pressure over inside flue pressure andprovided with closing torque means, said device having an opening therein in advance of the inlet said gate, a thermal responsive element dis osed in said opening and subject on one side to the temperature within the device and on its other side A to the temperature without.- said thermal res ve element being secured to said device at one end thereof, an arm pivotally said flue in the direction of the heater attached thereto, a draft conthermal responsive element being secured tothe said flue Y pivotaily mounted on said flue and secured to the a heater device dis smoke flue, a draft control housing cofnmunicatmeans to increase the closing on said device and secured to theother' said thermal responsive connections for said arm torque means whereby the closing torque'is varied as the temperature within and without the device is varied. i I i 1'7. In combination with the smoke flue of an oil burning apparatus, a draft control associated with said flue and comprising a gate mounted to be opened by excess of outside atmospheric pressure over inside flue pressure and provided with closing torque means, said smoke flue having an opening in the wall thereof, a thermal responsive element disposed in said opening. and subject on on -side to the temperature within'the flue and onits other side to the temperature without the flue, and operating connections for said thermal responsive element to said gate closing torque torque on the gate as .the flue temperature rises, whereby differences between outside atmospheric pressure and inside flue pressure, on sa'd gate, may effect automatic opening andiclosing temperatures of the flue gases as well as at rela- 1 tively' low temperatures of said'gases.

, disposed'in said opening to be subject on its inner Z.

, outerside to the 18. In combination with'the flue of a combustion apparatus, a draft control associated therewith and comprising a housing opening tothe flue, a gate swingably be opened by excess sure over inside flue press e-and provided with variable closing torque the said flue having an opening therein, athermal responsive element side to the temperaturewithin the flueand on its temperature without the flue,

delivery and of said houslouvers disposed at the therethrough rearing to .deflect air passing jwardly in" the flue and away from the said ther mal responsive element, and operating connectionsfor said thermal; responsive element to :said

variable-closing torque means for said gate, 7 19. In combination [with the flue of a'combustion apparatus, a draft control associated ther I with and comprising a. gate mounted to be opened vfltlrthe flexing of 'said' thermal responsive element, a

' outer side to the 'inside' flue pressure posed in said openin side to the temperature outer side to the temperature-without the flue, a movably mounted weight operatively connected:

by excess of outside ing therein, a thermal responsive element disto within the flue and on its to the gate, and operating connections for said thermal responsive element-to'saidweight toincrease the closing torque on the gate as the flue temperature rises, whereby differences between outside atmospheric pressure and inside flue pressure, on said gate, may effect automatic opening and closing of the-same at relatively high temperatures of the flue gases as well as at relatively low temperatures of said gases. 4 20. In combination with the flue of a-combustion apparatus, a draftcontrol associated therewith and comprising by excess of outside atmospheric pressure over inside flue pressure and, torque means including a weight, said flue having an opening therein, a disposed in said opening to be subject on its inner side to the'temperature within the-flue and on its and operating connections for said thermal reelement, and operating to said gate-closingof the same at relatively high mounted inysaid housing to v of outside atmospheric presatmospheric pressure over and provided with normal. closing torque means, said fluehaving anopenbe subject on itsinner a gate mounted to be. opened provided with closing thermal responsive element temperature without the flue,

sponsive element to said weight to increase the closing torque on the gate as the flue temperature rises, whereby diflerences between outside atmospheric pressure and insid flue pressure, on said gate, may effect automatic opening and closing of the same at relatively high temperatures of the flue gases as well as at relatively low temperatures of said gases.

21.. In combination with a combustion apparatus discharging Products of combustion, a draft control associated therewith and comprising a gate mounted to be opened by excess of outside atmospheric pressure over inside flue pressure and atmospheric pressure and inside flue pressure, on

said gate, may effect automatic'opening and closing of the same at relatively high temperatures of the flue gases as-well as at relatively low temperatures of said gases.

22. In an automatic thermally responsive draft control, in combination with a smoke flue, a draft control device having a passageway to said flue,

, a gate pivotally mounted in said passageway to be increasing and decreasing the closing torque on said gate, thermally controlled means disposed to be subject to the temperature ofthe gases passing through the smoke flue, said thermally controlled means being conneeted to said compensating weight to move the same towards and-from said pivotal axis, whereby differences between outside atmospheric pressure and inside flue pressure, on said gate, may effect automatic opening and closing of the same at relatively high temperatures of the flue gases as well as at relatively low temperatures of said gases.

- EDWARD A. FIELD, JR. 1