US2948276A

US2948276A - Coal-fired space heater

Info

Publication number: US2948276A
Authority: US
Publication date: 1960-08-09
Anticipated expiration: 1977-08-09

Description

e. w. HARDING COAL-FIRED SPACE HEATER Aug. 9

Filed Jan. 24, 1956 2 Sheets-s 1 INVE lWlli Q d y wi ATTOR Aug. 9, 1960 e. w. HARDING COAL-FIRED SPACE HEATER 2 Sheets-Sheet 2 Filed Jan. 24, 1956 INVENTOR ATTORNEYS United States Patent 2,948,276 COAL-FIRED SPACE HEATER- George W. Harding, Lynchburg, Va., assiguor to Automatic Draft and Stove Co., Inc., Lynchbu'rg, Va., a corporation of Virginia Filed Jan. 24, 1956, Ser- No. 560,996

7 Claims. (Cl. 12"667) This invention relates to automatically controlled coalfired space heaters, and more particularly to that type of space heater in which the heat-actuated regulator is carried thereon for regulating the draft entering below the grate bars by opening and closing a damper positioned across the draft access.

Generally speaking, heaters of this type are provided for heating non-insulated, non-weatherstripped, drafty houses. It would be most uneconomical, if not impossible, to adequately heat such houses with a space heater responsive solely to room temperature. A more practical method of operation is to provide a heating unit which responds to the temperature of the stove rather than temperature of the room, and will create a zone of comfort in close proximity to the heater, so that the occupants of the room may position themselves in the room according to their requirements for comfort.

However, it has been found that where the thermostat on the draft regulator responds solely to the temperature of the stove there are times during low combustion within the combustion chamber when the residual heat in the metallic parts of the stove lulls the thermostat into remaining closed at a time when it should begin to open so as to stimulate the wanning fire before combustion becomes so feeble that the fire goesout. Since the room temperature is lower than the temperature of the stove, even during low combustion periods, it follows that if the thermostat could be influenced to an extent by room temperature it would open sooner than if stimulated solely by stove temperature, thus reviving a low' fire which might otherwise diminish to the point of going out.

One of the objects of the present invention is to provide a coal-burning space heater of the type in which draft for combustion is supplied from beneath the grate regulated by a thermostatically controlled damper responsive primarily to the temperature of the stove and secondarily by room temperature, derived from the cooler strata of the room air entering the casing of the heater in a zone below the combustion chamber.

Another object of the invention is to provide a heater of the type described, in which the temperature responsive draft unit is mounted on the ash door of the heater, and includes a conduit communicating through said door with the ash pit, the fuel door, which is above the draft unit being hinged at the bottom so as to overlie said conduit when said door is open shielding said conduit from the entrance of spilled fuel. e

Other objects of the invention will become apparent from the following description of a practical form when considered drawings.

In the drawings:

Figure 1 is a front perspective view of a warm air circulating type of coal fired space heater made in accordance with the present invention;

Figure 2 is a sectional view of a partial side elevation of the lower front portion of the space heater shown in in conjunction with the accompanying "ice heater in accordance with the present invention is shown generally at 1, having a body 2. supported on a base 3 and having a grate 4 transversely disposed therein at an intermediate level dividing the said body into a combustion chamber 5 and an ashpit6. The fuel door 7 which provides access to the combustion chamber is hinged at the bottom permitting the door to swing downward when opened. The ashpit door 8 is hinged at one side permitting the door to swing open laterally as shown in Figure 1. 7

The cabinet '9 completely surrounds the body and is spaced from it on all sides. The cold air louvres 10, 10' near the bottom of the cabinet give access for the cold air from the room, which passes upward by convection between the cabinet and the body. The upper inlet air louvres 11-11' are provided to admit air from a warmer level of the room. to enter the heater. This air is quickly heated to a high temperature and induces rapid circulation of air through the heater. The grill 12 at the top of the heater is the outlet for the warm air. The front of the cabinet is formed with the door 13 to give access to the doors of the combustion chamber and ashpit.

As shown in Figure 2, the ashpit door is provided with the draft access opening 15 and the draft conduit 16 is secured to the outer facing thereof. The effective draft access is at the mouth 17 of the draft conduit 16, since the draft conduit'is extended upward a short distance above the opening 15 to a point just below the bottom of the fuel door 7. This creates a slight upward convection pressure in the conduit 16 which is easily overcome by the draft of the chimney, even under minimum combustion conditions;

The damper 18 is fixed to the shaft 19 within the draft conduit 16 which is pivotally journaled in the opposite walls of said conduit for movement through an arc of The peripheral frame 20 is secured within the conduit 16 having the flange 21 with its halves offset so that the damper engages opposite faces of the flange when closed. p

The end 22 of the damper shaft 19'is extended beyond the draft conduit 16. The thermostatic element 23 con sists of a bimetallic coil having its inner end 24 attached to the end 22 of the damper shaft 19 and being formed with a loop 25 at its opposite end constituting part of a pin and slot connection, as will appear.

The dial shaft 26 is journaled in the walls of the con- I duit 16 beneath the damper shaft 19 in the same vertical plane and at such distance beneath it as to be in the path of movement of the damper, thereby acting as a stop for the damper when it is in full open position." The dial 27 is mounted as shown, on one end of the dial shaft 26 on the outside of the conduit 16 and the other end 28 of the dial shaft-26 has an upturned portion formed with a crank pin 29 which plays within the loop 25 of the thermostatic element 23. The dial shaft 27 is spring loaded (not shown) to produce frictional resistance to rotation of the shaft sufficient to dominate the pull of the thermostatic element, so that the crank pin becomes an anchor against which the thermostatic element thrusts in operating the damper; When the knob is turned, the position of the crank pin is changed, varying the point at which the 3 thermostatic element begins to be effective in controlling the damper.

Incoming air passes into the cabinet through louvres 10, in the lower zone of the cabinet, and before. it comes in contact with the walls of the body whichv surround the combustion chamber, the air in the lower part of the cabinet approximates the temperature of the lower strata of air in the room, and the thermostatic element is located'in this zone of cool air.

It will be noted that when fuel door 7 is in lowered position, it overlies the mouth of the draft conduit 16 and shields it from the entrance of fuel particles spilled when stoking the combustion chamber.

In the present invention the relatively cold room air which enters the louvres l0 and occupies the lower part of the cabinet chamber and which is the source of draft of the conduit 16 passes over the thermostatic element 23, so as to an extent to modify the influence of stove temperature upon said thermostatic element. When the combustion is relatively high, the ratio which the room temperature affecting the thermostatic element bears to the heater temperature is low, so that the etfect of the room temperature is negligible. However, when combustion in the heater is low, the ratio of the room temperature affecting the thermostat becomes relatively high, so that the room temperature becomes a material factor in inducing the thermostatic element to open the damper sooner than would be the case if it remained subject only to: stove temperature. This provides increased draft and stimulates combustion when the fire may be so low that otherwise it could not be revived.

In the modification shown in Figures 3 through 5, the access passage 31 is formed in one side of the wall of the ashpit 6. The draft conduit 16 is mounted at the passage 31, extends upwardly and terminates at a point substantially at the level of the lower edge of the fuel door 7. The damper shaft 19 extends transversely of the conduit perpendicular to the outer wall thereof and extends beyond said outer wall. The thermostatic element 23 is mounted on the extended end of the shaft 19.

The dial 2-7 is mounted on the outside of the cabinet 9 above the location of the thermostatic element. The dial shaft 32 is journaled in the wall of the cabinet 9 and the dial 27 is mounted on the outer end of this shaft. The rotation of the dial 27 is frictionally retarded for the'same purpose as described in connection with dial 27 in the first described modification. A rod 33 is fixedly attached to dial shaft 32 at a right angle thereto. A rod 34 is journaled in the cabinet and has an arm 34 bent at right angle thereto. The rod 34 is in axial alignment with the damper shaft 19, so that the arm 34' and loop 25 will traverse concentric arcs. A link 35 has angularly disposed ends 36 and 37 by means of which it is pivotally connected, respectively, to the rods '33 and 34. The end 3-6 is extended to pass through the loop 25 of thermostatic element 23 and forms the pin which engages the loop 25 for rotating thermostatic element 23. This construction being the same as that disclosed in the first described modification.

While in the above description there has been disclosed practical embodiments of the invention, it will be understood that the invention may include other structural forms.

What is claimed is:

1. In a coal burning circulating space heater of the type having a body with a grate intermediately positioned therein defining therewith a combustion chamber above and an ash pi below the grate and having a cabinet surrounding the body in spaced relation thereto with an air inlet opening in its lower part and a relatively high outlet opening therethrough providing for circulation of room air between said body and said cabinet, the improvement comprising, a down draft conduit within the space between said body and cabinet positioned in heat receiving proximity to said combustion chamber to conduct primary air for combustion downwardly into said ashpit and having its intake end opening within the space between said body and cabinet adjacent said combustion chamber and its outlet end communicating with said ash pit, a damper within said conduit and a bimetallic thermostat controlling said damper mounted on said conduit to be heated thereby, and so positioned as to be bathed by the relatively cool circulating air in transit from said air inlet opening to said air outlet opening.

2. In a coal burning circulating space heater of the type having a body with an intermediate grate therein defining therewith a combustion chamber above and an ash pit below the grate, and having a cabinet surrounding the body in spaced relation thereto with an air inlet opening through the lower part of said cabinet and a relatively high outlet opening therethrough providing for circulation of air between said cabinet and said body, the improvement comprising a laterally swinging door giving access to said ash pit and a door hinged at the bottom, above said ash pit door, giving access to said combustion chamber, a down draft conduit extending upwardly from said ashpit and within the space between said body and said cabinet to conduct primary air for combustion downwardly into said ashpit, said down draft conduit being mounted on said ash pit door, having its discharge end communicating with said ash pit through an aperture in said ash pit door, and being so extended as to be in heat exchanging relation to said combustion chamber, said conduit having its intake end opening within said space between said body and said cabinet and terminating beneath said combustion chamber door, said combustion chamber door having a range of movement causing it when fully open to overlie the said inlet end of said draft conduit whereby said combustion chamber door shields said intake end of said draft conduit from spillage when fuel is being placed in said combustion chamber, a damper mounted in said conduit and a thermostat controlling said damper mounted in heat exchanging relation to said combustion chamber and positioned to be bathed by the relatively cool room air entering the space between said body and. cabinet.

3. A coal burning circulating heater comprising, a body having a grate intermediately positioned therein defining therewith a combustion chamber above and an ashpit below said grate, said ashpit having an access opening, said body having a fuel access opening above said ashpit opening, a laterally swinging door for said ashpit opening, a conduit for downwardly directing draft carried by said ashpit door and opening therethrough, having its inlet end terminating below the level of said fuel access opening, a door for said fuel access opening hinged in a horizontal axis at the bottom of said fuel access opening, said fuel access door being swingable to a position overlying said conduit and functioning as a shield for the inlet end thereof.

4. Coal burning circulating heater comprising, a body having a grate intermediately positioned therein defining a combustion chamber above and an ashpit below said grate, an air supply conduit exterior to said body communicating with said ashpit adjacent said grate and having an upright limb close to said body in the Zone of said combustion chamber, a damper shaft for said conduit journaled in the upper end of said upright limb, a damper mounted on said damper shaft, a thermostat exterior to said conduit at the upper end of said upright limb and operatively connected to the shaft of said damper, a fuel access door for said combustion chamber hinged at its bottom to said body on a horizontal axis and positioned to open out in shielding relation to the upper end of said conduit.

5. Coal burning circulating heater comprising, a body having a grate intermediately positioned therein defining a combustion chamber above and an ashpit below said grate, an access door for said ashpit, an air supply conduit exterior to said body carried by said ashpit door,

communicating with said ashpit adjacent said grate and having an upright limb normally close to said body in the Zone of said combustion chamber, a damper shaft for said conduit journaled in the upper end of said upright limb, a damper mounted on said damper shaft, a thermostat exterior to said conduit at the upper end of said upright limb and operatively connected to the shaft of said damper, a fuel access door for said combustion chamber above said ashpit door, hinged at its bottom to said body on a horizontal axis and positioned to open out in shielding relation to the upper end of said conduit.

6. In a coal burning circulating space heater of the type having a body with a grate intermediately positioned therein defining therewith a combustion chamber above and an ashpit below the grate and having a cabinet surrounding the body in spaced relation thereto with an air inlet opening in its lower part and a relatively high outlet opening therethrough providing for circulation of room air between said cabinet and said body, the improvement comprising, a draft conduit to conduct primary air for combustion downwardly into said ashpit and having an upwardly directed inlet and an outlet, said draft conduit inlet being in said space between said body and said cabinet and adjacent said combustion chamber substantially medially of the horizontally projected plane of said grate and the horizontally projected plane of the top of said body, said draft conduit outlet being in communication with said ashpit, a damper for controlling the draft in said draft conduit, a bimetallic thermostat for operating said damper mounted within the space between said combustion chamber and cabinet in heat exchanging relation to said combustion chamber and in the path of convective flow of room air through said space, and said thermostat being operatively connected to said damper.

7. Coal burning circulating heater comprising, a base, an ashpit extending to a vertical height above said base, a combustion chamber extending to a vertical height above said ashpit, a grate transversely mounted at the intersection of said ashpit and said combustion chamber, a top surmounting said combustion chamber, a primary air supply conduit having a lateral limb and an upright limb, said lateral limb being in communication with said ashpit, said upright limb being spaced outwardly from said ashpit and having a free end extending upwardly and terminating substantially below the medial height of said combustion chamber, a damped shaft journaled in the free end of said upright limb of said primary air supply conduit, a damper fixedly mounted on said damper shaft, a bimetallic thermostat mounted exteriorly of said conduit adjacent said free end of said upright limb, said thermostat being operatively coupled to said damper shaft, and a louvered cabinet surrounding said ashpit and combustion chamber in spaced relation thereto and enclosing said primary air conduit and said thermostat in said space.

References Cited in the file of this patent UNITED STATES PATENTS 1,225,280 Skinner May 8, 1917 2,031,652 Hopping Feb. 25, 1936 2,227,689 Agricola Ian. 7, 1941 2,394,441 Griswold Feb. 5, 1946 2,554,370 Martin May 22, 1951 2,797,874 Harding July 2, 1957 FOREIGN PATENTS 725,059 Great Britain Mar. 2, 1955