US2277515A

US2277515A - Thermostatic draft control

Info

Publication number: US2277515A
Application number: US346827A
Authority: US
Inventors: Clennie B Harrell
Original assignee: Individual
Current assignee: Individual
Priority date: 1940-07-22
Filing date: 1940-07-22
Publication date: 1942-03-24
Anticipated expiration: 1959-03-24

Description

March 24, 1942.

c. B. HARRELL T HERMOSTATIC DRAFT CONTROL Filed July 22, 1940 2 Sheets-Sheet 1- f -i tt l- L, If

March 24, 1942. c, B, HARRELL THERMOSTATIG DRAFT CONTROL 2 Sheets-Sheet 2 Filed July 22, 1940 6 ,5. Ha rreZZ Patente 24, E942- para o earners I gusts fer as "at 2 Clas.

The invention relates to means for controlling the draft to space heaters, and particularly to the control of the draft in stoves for heating liv'- ing rooms and the like, or other places, and which will be responsive in'a novel wayto the require- 5 ments of a given space for heat, in order to maintain it' at or near a predetermined temperature, as distinct from devices that operate in response to the temperature within the heater itself to control a damper orvthe like, as a safetyappliance or to maintain the unit at a predetermined heat production condition.

An important aim of the invention is to present an improvement in construction of such devices,

to the end that the functioning of the device will be more dependable for controlling room temperatures, and which will enable the production of the article so as to occupy an extremely small place in an inconspicuous and safe position, where it will be liable in a minimum degree to damage or derangement by being struck by articles, implements or particles of fuel, as well as obviating the need for projecting parts which might represent liability of accidental operation of the device, or engagement in clothing or objects, with resultant damage or impairment of function of the device.

It is also an aim of the invention to presen such construction in which a very simple control and regulating means may be provided of the 3:)

most extreme simplicity, whereby any ordinary person may be able to adjust the device to secure its best function. Another important aim of the invention is to present a construction which will be extremely simple, so-that its parts may be 5 materials and at a low cost for production and 40 assembly.

A further important aim of the invention is to present such an article which is adapted, without material change, to use upon various types of stoves, furnaces, and other equipment and heaters, adaptable to wood-burning stoves, coal stoves, and burners of other fuel, as will appear hereinafter.

It is a further advantage of the invention that it will respond'to cooling of rooms'incident to ventilation, and generally operate as a part of a room unit, as distinct from ,a mere burner or combustion device. It is an important aim of the invention to present a novel means for controlling or regulating and changing the function (or, gre se) of the device in operating a damper or draft shutter, so that the automatic function of the device may be definitely established at will, withp in any desired range of operation in relation to an arbitrary room temperature desired by the operator.

Additional objects, advantages and features of invention reside in the arrangement, construction and combination of parts involved in the embodiment of the invention, as will be more readily understood from the following description and accompanying drawings, wherein Figure 1 is a front view of a simple wood-burning stove, in which the invention is incorporated, although the invention is also applicable to coal burning and other forms of stoves and furnaces, as well as being adapted to control liquid fuel valves andbther elements, these variations not being illustrated, since they will be readily understood and apparent from the present disclosure and knowledge of construction of various types of heaters in the art.

Figure 2 is a side elevation of the stove shown in Figure 1;

Figure 3 is a fragmentary cross section on .the

line 33 of Figurez. 4

Figure 4 is a vertical longitudinal sectional view of the draft flue taken in the major plane Figure 8 is an'elevatio'n at right angles to Figure 7.-

There is illustrated in Figures 1 and 2 a com-- mon form of wood-burning stove, often called King Heaters," having a stoking door H in the 4 top thereof, and a smoke pipe l2 leading out of the 'top at the rear, while at the forward end of the stove means for admitting air by a ,downdraft flue i3 is provided, the flue i3 opening into the lower part of the combustion chamber of the stove by means of a. usual fitting Hl'secured to the front end of the stove, and upon which the flue I3 is erected, the latter being formed of common rolled iron sheeting, after the common practice in the production of stove-pipe. In the present instance the flue I3 is enlarged gradually toward its upper end, where it is of circular form,

closed by a manually operable draft shutterl5 of any usual construction by which an arbitrary limitation of draft through the tube may be ef# fected', as required, or, the draft may be entirely cut off thereby, these functions being well understood in such appliances.

The flue I3 is located very close to the front of the stove at its lower end, but is inclined outwardly therefrom at its upper part, affording a space at l8, within which my automatic control device is mounted,'-so that the flue It serves as a guard for the more or less delicate thermostat device,,its mounting, and connections between the same and the draft shutter in the flue, as will be described.

Set across the flue it near its upper end there is a stationary, circular port plate l'l comprising three sector-shaped portions l8 joined at the center by a small circular integral disc portion l9, and connected at their 'outer parts by a continuous annular portion 20, the intervals between these sector portions constituting ports 2| coextensive with the sector portions l8 in the same annular zone. The port plate generally is in the form of a segment of a sphere, the spherical portion extending into the rim 20 a distance, but stopping shortof the outer edge or periphery of the rim 20, being bounded by an upwardly pressed portion of the plate, as at 22, extending entirely around the plate, the peripheral edge of the plate terminating in a downwardly turned approximately cylindrical flange 23. This plate is made with a diameter which is slightly less than the interior diameter of the flue at its upper extremity, and is secured in place byv being pressed into the flue end, which is tapered downwardly, until the metal of the flue is slightly expanded or pushed outwardly, this forming a sufficiently perthe flue, although it may be welded or otherwise secured in accordance with familiar prac-' pressed portions of the flange, as indicated in notched to receive the ear therein, so that the shutter may lie in registration with the sectors and ports of the plate ll, when in open position,

and so that the ports in the plate I! may be completely closed when the shutter is at the opposite limit of its movement. It will be noted from Figure 3, that one of the sectors of the .,U'-shaped in cross section, the body web portion I manent attachment of theplate H in place in Figm'e 3, at24. A shutter is provided, correspending generally in form to that part of the plate I! whichlies inwardly of the upwardly pressed boundary wall 22 of the plate, having however, a rim portion 26 of slightly less diameter than the inner surfaces of the boundary flange 22, so that the shutter may be free to rotate within the flange 22 without interfering or friction. This shutter is also in the form of a segment of a sphere, approximately, but preferably formed on a slightly longer radius, so that while its center may rest upon the disc l9 at the center of the plate I], its outer edge portion will clear the plate I! so that the shutter may rotate freely thereon without requiring a spacer. It is pivoted upon the plate I! by means of a usual rivet 21 or other'pivot element, as may be found desirable. The shutter is formed with three vanes 28, and corresponding ports 29 all of which areadapted to register respectively with the sector parts and V portsof the-port plate IT, as may be seen. Set

rigidly in one of the vanes there is a wrist pin 29 or stud, upstanding from the vane. One of the vanes '28 has an ear extended from one edge, and bent downwardly so as to lie within one of the ports of the platev l1, serving as a stop to limit movement of the shutter in respective directions by engaging the edges of the ports. In the present instance, the edges of the ports through which the ear is projected may be being secured against the rear face of the flue l3 by welding or otherwise. foramin'ate as at 33, to permit free circulation of air laterally therethrough, for a purpose to be made clear. A resilient bi-metallic bar or strip 34 is mounted at the lower end portion of the guard piece, and in practice, a strip approximately six inches in length has been used, the upper end of which extends slightly above the shutter level, and the lower end is'secured fixedly in relation to the flue, and in'spaced relation to the guard piece 3| and the flue l3, by. any approved fastening, at 35. :In .the present instance, washers are inserted between the strip inner end of thebolt within the flue. The upper end of the strip is the oscillating portion, and in the present instance, it is considered material to have that part of strip 34 with the highest coefllcient of expansion presented toward the stove, the arrangement being such that direct radiation of heat from the surface of the stove will be incident upon the strip 34 without impeding material other than air. The upper end of the strip is apertured, and has pivotally connected thereto a link 36, which in the present instance, may be formed of heavy wire stock with an eye portion engaged around the wrist pin 29. This link extends radially from the strip 34 inwardly, through a suitable aperture in the guard piece 3| and flue for a distance, and is then offset and extended in a parallel direction to the eye portion thereon, so that in inward slidingmovement of the link, it will clear the pivot pin 21 of the shutter.

The bi-metallic strip 34 normally is curved away from the flue II at the upper end of the strip, and it will be seen that when heated, the expansion of the outer element of higher coeflicient of expansion will cause the. upper end of the strip to move inward toward the flue, pushing the wristpin of the shutter. so as to rotate'the shutter clockwise and toward closed position, in a degree corresponding to the effect of heat on the bi-metallic strip, and proportional to the temperature at which the end of the strip is positioned by the heat acting thereon, counteracte i by the draft of air which will pass upwardly beoutward again, drawing the shutter counter- Its flanges 32 are earners clockwise and opening the ports of the plate ii, thereby supplying more oxygen to the stove, the fuel in which will burn with greater intensity and tend to raise the temperature of the room correspondingly.

In order to adjust the function of the damper to suit the requirements of suchjindividuals or special climatic conditions, size of the room, and other factors, I have providedmeans for varying the function of the bi-metaliic strip. consists of a shaft 38, mounted revolubly across the flue it, extending from front to rear, the rear end extending also through the web body of the channel-shaped guard piece at, slightly to one side of the bi-metallic strip 3 3, and having l5 fixed thereon a concentric worm grooved cam 39, the periphery of this cam extending beyond the adjacent edge of the strip 35, a distance, so that the edge portion of the strip sets in the worm groove of the cam, and whereby rotation'go of the cam will press the engaged edge portion of the strip rearwardly from the direction of the flue, or will allow it to move forwardly toward its normal initial psition. The forward end of the shaft 38 is provided with a hand lever 40, the hub of which is formed with a pointer 4i,

arranged in indicating relation to a dial or other indicia 42 formed on a semi-circularbearing fitting 43 attached to the front side of the flue exteriorly thereof. The cam groove is of such lead that movement of the lever til over an angle of '180 degrees will efiect the full range of adjustment of the bi-metallic strip, and the indicia 42 is corelated to the effect produced on the bimetallic strip by the cam, in its result in moving as the shutter.

The device being installed as illustrated, it will be understood that with a fire maintained in the stove, the heat radiated to the thermostatic strip 36 will tend to cause the upper end thereof to move forwardly toward the flue and operate the shutter to close the ports through the plate l1, and that, initially, when a fire is started, the

, cool thermostatic strip will hold the shutter in open position so that a maximum draft is afford- 45 fire when the temperature of the room has risen 5 sufiiciently to minimize'the counteracting effect of air circulation opposed to the heating of the stripby radiation from the stove.

In Figure 5, the application of the invention to use upon a down-draft pipe for one type of 5 coal-stove, commonly used, as illustrated, in which a central flue $5 is mounted in the top of the stove and normally open at its upper end, but closed by a shutter operating upon a port plate of the same construction as the port plate and shutter previously described. The stove has a smoke pipe 46 leading upwardly therefrom at the rear, and upon the side of this there issuitably fixed the face of a bimetallic strip 41 extending forwardly beside the opening at the upper end of the flue, $5, and having a link connection 48 from its forward extremity to the shutter, the strip being properly disposed and arranged to effect closing of the shutter at high temperatures and opening thereof at low temperatures, as desired. The cam adjustment in this instance, for controlling action of the thermostatic strip comprises a shaft 49, suitably mounted on the top of the stove and extended This 10 H mounted upon the side of the pipe, and having sectors and ports therethrough corresponding in of the stove, where it is provided with an operating handle 50, in accordance with the previous disclosure. At its inner end a cam as corresponding to that before described, is'fixed on the shaft and engaged with the edge of the strip or for the operation previously described. 7

In Figures 7 and 8, the manner of embodying this invention upon a smoke pipe as a check draft is illustrated, in this instance, a specially formed port plate M is suitably shaped to be front elevation to those shown in Figures 1 to d. is secured upon the smoke pipe t2. A shutter 53 is mounted pivotally over the plates 58 by means of a shaft 56 exten diametrically across the smoke pipe and mounted revolubly therein conventionally. This shaft is formed with a crank 55 centrally of the pipe, and suitably fixed on the exterior of the pipe in accordance with the prior disclosure, there a a bimetallic strip 56, its point of attachment being located a distance vertically irom'the" level of the shaft 56, and its swinging end being located closely adjacent the same level of the shaft 58, and connected to the crank E5 by means of a link 51 extended slidably through a small aperture in the side of the pipe. A can adjustment for the bi-metallic strip 56 is providedin a shaft 58, mounted revolubly in the pipe t2, one end extending through the. pipe beside the strip 56 and having a cam 39" thereon engaged with the strip as before described, the opposite end of the shaft being provided with the operating hand lever sex which may be coordinated with an index device as described in connection with Figures 1 to 4. If desired, a guard piece 59 may be incorporated with the bi-metallic strip 56, constructed in a form similar to thatofthe guard piece 3| before ment, size, and construction of parts, as well as substitution of equivalents may be carried out without departing from the spirit of the invention,'as more particularly set forth in the appended claims.

I claim:

I. An automatic draft control for stoves and the like consisting of a flue member, a thermostatic bi-metallic strip fixed at one end in relation thereto and having its opposite end free to swing under variations of temperature, a port plate in the flue, a shutter movable thereon to close the port plate and to open the same, op-

erative connections between the swinging end 5 of said bi-metallic strip and said shutter, said strip extending beside said flue in spaced-relation, a shaft revolubly mounted across the flue, adjacent an intermediate .portion of the strip, substantially at right angles to the strip, and having a spiral groove cam thereon, the groove receiving an edge portion of the lei-metallic strip, a pointer lever on the opposite end of the shaft, and a channel guard device mounted between the flue and said bi-metallic strip, open at the top and bottom and having side flanges provided with vertically spaced apertures.

2. In a stove, an automatic draft control therefor, consisting of a stove body having a combustion chamber and a bottom air inlet thereto, a

'flue fixed in relation to the stove communicating at right angles from the strip 41, beyond the side 7 at its one endwith said draft inlet and extending upwardly therefrom, aport plate fixed across the flue, a shutter movable thereon toclose the port plate and open the same, a bi-metallic strip arranged longitudinally of the fine, and secured in fixed spaced relation thereto at a distance from the shutterand having an end portion ar-' ranged to swing adjacent the shutter under-action of heat variations, a link connection between the swinging end of the bi-metailic strip and said shutter, for operation of the latter by variations of temperatures, said flue being mounted in close spaced relation to the stove body, said strip being at the side of the flue next adjacent the stove, a channel-shaped guard device on the flue artly closing the space between the flue and stove, whereby an air draft is formed adjacent the bi-metallic strip, a shaft revolubly mounted across the hue substantially at right-angles to said strip and with one end extended through the flue beside the strip and spaced therefrom, a spiral cam screw device fixed on the shaft b'eside the strip and receiving a strip edge in said groove, and the opposite end 01 the shaft havingv an operating handle thereon outwardly of the CLENNIE B HARREIL.