US2242039A - Furnace control - Google Patents

Description

n; A. MULcEY ErAL 22%2939 May 13,3941.

FURNACE commox,

Filed Feb. 14, 1940 2 sheets-sheet 1 will 6 m fllemfzfohms' Martians,-

,Psrub EB Y A. MULCEY ETAL FURNACE CONTROL Filed Feb. 14, 1940 2 Sheets-Sheet 2 minimum; and to provide will hereinafter appear.

sents a fragmentary sectional Patented May 13. 1941 'UNITEVDASVTATES PATENT OFFICE mmififiiim Drexel Hill Plaza,

and Allen J. Johnson, Pa., assignors to Anthracite Industries, Inc., New York, N. Y., a corporation of Delaware Application February 14, 1940, SerialNo. 318,8 2}

4 Claims. (01. 236-93) The present invention relates to the control of ases from furnaces fired with solid fuel'and more particularly to a control conditions pertaining to a banked fire.

It has heretofore been'the practice in banking and controlling such furnaces to provide a operable under check damper in the smoke pipe arranged to open andadmit cool air to the stack when the ash pit damper is closed. These two dampers are usuallyso interconnected thatthe opening of one closes the other. The result of having a check damper open for any length of time,.as for example when the fire is banked at night, is to so reduce the temperature of the stack as to not only require the burning of a considerable amount of fuel to reheat the stack for proper draft but there is also the loss of time in restoring room temperature. This reheating of the stack may mean a loss of ten to twenty pounds of coal according to the particular furnace installation. In addition to the ash-pit damper and the check damper it is quite customary to locate an-apertured damper in the smoke pipe and this is generally set'in one position and so remains.

Some of the objects of the present invention are to provide an improved damper control for furnaces burning solid fuel; toprovide a control wherein provision is made for the elimination of a check damper or other device for admitting cool .air to the stack of a furnace; to'provide means for retaining heat in the stack of a furnace when the fire is either banked or operating at minimum capacity; to provide means responsive to stack or smoke pipe gas temperatures for maintaining an eificient draft temperature in the stack; to provide a furnace control wherein fuel waste due to cold stacks is reduced to a minimum; to provide an automatic control responsive to flue gas temperature for maintaining a substantially constant predetermined temperature in the stack from a furnace when the fire in the latter is two diametrically opposite locations with tubuiar trunnions II which eirtend respectively banked or operating at minimum capacit'y;to

provide a furnace control whereby the room temperature lag during the change from banked fire conditions to draftnconditions is reduced to .a

Fig. 2 represents a section on line-22 of Fig. 1; Fig. 3 represents a section on line 3-4 of Fig. {2;

other improvements as t Fig. 4 represents a section similar to Fig. 2 but illustrating a modified form of the invention; Fig. 5 represents a detail plan showing one means for changing the position of the main damper; and Fig. 6 represents a section on line H of Fig. 4'.

Referring to the drawings the form of the present invention of Figs. lvto 3 is shown located in the smoke pipe ll leading from the combustion chamber .l I, or associated passages, to achimney l2, forming the usual stack II which leads upwardly to the atmosphere and includes as a part the passage through the pipe ll. The. fire bed It is illustrated as in banked condition for overnight conservation of fuel and the control of the present invention is shown in full lines as'iust set to produce banking and in dotted lines as follows from complete banking conditions;

In the present instance this control consists of a main damper ll having a shape to conform to the contour of the inner wall 'of'the smoke pipe III and of a size to prevent productsof 'com-' bustion passing between this inner wall and the main damper .II where the latter is disposed transversely of the pipe i0. Preferablycoaxially arranged in the main damper II there is a port it which allowsproducts from the escape to the chimney flue ll.

For moving. the main damper II from open to closed position or vice versa, it is provided at through the pipe It for convenient outside manipulation. Each t on I! is transversely slotted to straddle the margin of the damper. for attachment thereto by screws II or other suitable fastening means. Collars II are attached to the proiecting end of the respective trunnions II to support and properly register the damper II with respect, to the pipe l0. 'As shown one of the trunnion ends mounts a lever jll by which the main damper II can be swung to either open or closed position through manual or automatic means. Also the position of the lever 2| relating to the smoke pipe ll indicates the set position of the damper at any time.

For the purpose of automatically controlling the port I, an auxiliary damper 2-2 is arranged to fit within the port I I with suiilcient clearance for a minute gas flow and for proper relative movement between the parts. Thus when'the damper 22 substantially closes the port ll it will E lie in the plane of the damper II. As shownthis auxiliary damper 2-2 is carried by a thermostatic .strip "none end of which is riveted or otherfurnace to curve, and riveted to the main damper [5.

the form of a spiral of wise made fast to the auxiliary damper 22, while its opposite end is reversely. bent, on a smooth Thus in side elevation the strip 23 is of loop shape with its short leg fixed and its long leg supporting the auxiliary damper 22. It is to be understood that the shape of the thermostatic strip is not limited to that shown as obviously a straight bimetallic strip could be used equally well. The strip assembly is such that it operates to open the auxiliary damper 22 as the temperature rises in .the pipe I and to gradually close the auxiliary damper 22 as that temperature'falls. An adjusting screw 24 is threaded through the main damper l at a convenient point to contact with the short leg of the strip loop and thereby make it possible to adjust the strip so that the auxil iary damper 22 responds .to a predetermined temperature range. This setting is generally such that the auxiliary damper 2-2 reaches its closed position when the temperature of the flue gas drops to a predetermined value and this should be such that the stack gases are maintained sufllciently healted during fire banked condition as to ensure prompt main damper I5 is opened at the end of the banking period. In other words the normal fuel waste required to restore heating conditions, be-

cause of a cold stack, is now materially reduced.

In the form of the invention shown in Fig. 4

to 6 a main damper generally similar to that heretofore described is mounted in the pipe ill for swinging movement from an open position parallel to the longitudinal axis of the pipe in to a closed position transversely of the pipe I0. This swinging or pivotal action is made possible by a slotted trunnion 3| straddling the margin of the damper 3D and fastened thereto by a screw 32 or the like, while a portion of the trunnion projects throught/he pipe Hi as a journal. A collar 33 is fixed to this projecting end by a set screw 34, the

collar 33 being located to support the damper 30 properly registered or centered with respect to the interior of the smoke pipe. A second trunnion 35 projects through the pipe 10 at a point diametrically opposite to the trunnion 3| to complete the pivotal mounting, In the present instance the trunnion 35 is in the form of a tubular sleeve fastened to the damper 30 by transverse clamps 36 which are er 30 by screws 31 or other fastening means. Located in the damper 30 is a port 40 corresponding to the port l6 heretofore described. An auxiliary damper 4| is supported within the port 40 and is of a diameter such as 40 when it is in the plane of the damper 30, though still allows some gas to flow to ensure removal of products of combustion.

In ,order to support the auxiliary damper 4| and automatically control its operation by the temperature of the flue gases a thermostat 42 in bimetallic metal has its outer end attached to the auxiliary damper 4| and its inner end welded or otherwise fixed to an end of a shaft 43 which passes through the sleeve 36 as a bearing to project from the outer end thereof. As shown the shaft 43 has a split end straddling the thermostat end and clamped thereto by a bolt 39. A boss 44, formed as a part of a quadrant lever 45, is fixed to the extended end of the shaft 43 by a set screw 46 or the like, so that rotary movement of the lever istransmitted to the shaft 43 for placing the thermostat 42 under a tension directly related to a selected temperature range. A slot 41, develdraft response when the anchored to the dampto practically close the port adjust the oped on a radius with the shaft 43 as a center, is provided in the quadrant lever 45 as a guide for a thumb screw lock 48, which is mounted on a bracket 50 attached to the pipe l0. Thus by releasing the lock 48, the lever 45 can be moved to thermostat 42, after which the lock 48 is again set to retain the parts in adjusted relation. The main damper 30 is manually operated by a hand lever 5| fixed to one or the other of the trunnions I1 or 35 but is here shown as attached to the latter.

In both forms of the invention it is desirable to provide means for limiting the swing of the main damper so that its proper closed position is assured and to that end two arcuate stop flanges 52 and 53 are attached to opposite sides of'the inner wall of the pipe ll by means of integral laterally bent tabs 54 which are spot welded or otherwise made fast to the pipe in; These flanges 52 and 53 are spaced apart axially of the pipe ID a distance to receive the thickness of the damper be explained as follows: Assuming as an arbitrary minimum temperature of 225 F. for the stack the thermostat controlling the auxiliary damper is so set that when the stack temperature falls to that selected temperature the auxiliary damper will be coincident with the plane. of the main damper and the port will be closed. With this in mind the main damper is swung to closed position to bank the fire and therefore the volume of gas flow is reduced to that passing through the port, because at this time the auxiliary damper is open by reason of the working temperature of the stack being above 225 F. With the fire banked the temperature of the stack gases lowers to thereby cause the thermostat to progressively move the auxiliary damper towards closed position in accordance with the falling temperature. When the selected low temperature value isreached the auxiliary damper is substantially in closed position since the flow perature value the thermostat will bontinue its movement of the auxiliary damper and swing it beyond the dead center position to thereby open the port sufficiently to increase the draft and cause the fire to pick-up to restore the stack temperature to that selected, namely 225 F. in the above example, when the auxiliary damper will again return to its" substantially closed position. At the end of the banked flre condition the main damper can be manually or automatically swung to full open position and the flre will respond promptly because the time lag and fuel waste caused by a cold stack temperature has been eliminated.

From the foregoing it will be seen that the present invention embodies a broadly new meth- 0d of control for banked fires in furnaces and which have been here illustrated by two forms of apparatus by way of example. Thus broadly considered the method consists in reducing the area of a stack passage to permit a safely reduced volume of gas to flow and thereafter regulating this minimum volume fiow as a function of the decrease in temperature of such gas flow.

Having thus described our invention, we claim:

1. A control for a banked fire in a furnace, consisting of a smoke pipe leading from a furnace, a main damper for controlling gas flow through said pipe, said damper having a port 'therethrough for discharge of gases when said damper is closed, an auxiliary damper arranged to control said port, and means responsive to the temperature in said pipe for closing said auxiliary damper when said temperature drops to a predetermined valve and for opening said auxiliary damper when said temperature falls below said valve.

2. A control for a banked fire in a furnace comprising a smoke pipe leading from a furnace, a main damper in said pipe of a size, when closed, to reduce the volume of gaseous products to a banked fire volume, said damper having a port therethrough, an auxiliary damper of a size and shape to fit within said port to substantially close the same, and a support for locating said auxiliary damper in operative association with said port, said support including a thermostat so responsive to flue gas temperature as to close said auidliary damper when said temperature falls to a. predetermined value, to opensaid auxiliary damper when said temperature falls below said predetermined value, and to again close said auxiliary damper as said temperature rises to said predetermined value.

3. A control for a banked fire in a furnace comprising a smoke pipe leading from a furnace, a main damper in said pipe of a size, when closed, to reduce the volume of gaseous products to a predetermined value, and means supplemental to said main damper and responsive to a falling flue gas temperature for reducing said predeter-- mined value to a secondary value comprising a banked fire minimum at a predetermined flue gas temperature, said means also operating to increase said last mentioned value at a temperature below said predetermined flue gas temperature.

4. The method of banking and controlling a banked fire in a furnace, which consists in reducing to a predetermined value the volume of gaseous products travelling from a furnace to a stack under operative combustion conditions of the furnace, gradually reducing the volume below said predetermined value as the temperature in the stack falls to a selected temperature, and increasing the volume of the gaseous products when the stack temperature falls below the selected temperature.

ALLEN J. JOHNSON.

PAUL A. Monster.

CERTIFICATE OF CORRECTION. Patent No. 2,2h2,039. May 15 1911.1.

PAUL A. MULCEY, ET AL. It-1 hereby certified that error appears in the printeci specifi cation 9f the above numbered patent requiring correction as follows! Page 5, first olmnn, linee 1 8 and 20, claim'l,'for the word "valve" read --value--; and

that the said Letters Patent should be'read with this correction therein that thesime may conform to the fecord of the case in the Patent Office.

Signed and sealed true-17th day or mm, A. D. 19m.-

Henry VanlArsdale, (Seal) v Acting Commiasionei' of Patents.

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