US2326734A - Thermostatic fuel control for heaters - Google Patents

Description

H. C. LiTTLE THERMOSTATIC FUEL CONTROLv FOR HEATERS Aug. 10, 1943.

Filed April 2, 1940 INVENTOR Patented Aug. 10, 1,943 l uruTao STATES PATENT ol-Flca muy c. Lime, stemmi, cam. Application April 2, 1940, serial No. 321,454

2 claims (ci. 12e-11e) The invention relates to air circulating heaters and more particularly to a thermostatic fuel control for Such heaters.

An object of the present invention isto provide a thermostatic control ofthe character described which will operate as a safety device in an air circulating heater to limit the maximum temperature and which is responsive to the temperature in the warm air passage of the heater and may be incorporated into Ythe heater as a unitary part thereof.

Another object of the invention is to provide a thermostatically controlled safety device of the character described which will be simple and positive and foolproof in its operation and which will be constructed of a minimum number of simply formed rugged and inexpensive parts.v

A further object of the invention is to provide a control of the character above which will subject the thermostatic element to a minimum stress when heated and which will provide for the closing off of the fuel supply to the burner should the thermostatic element become broken.

Yet another object of the invention is to provide a thermostatic control of the character. described which may be readily dismantled for inspection, cleaning, repair or replacement of any of the operating parts of the control.

Still a further object of the invention is to provide a control of the character described which may be particularly designed for use in the oil line of an oil burner and which will have the final control of the oil flow to the burner and which may nevertheless be used in conjunction with and without interfering with the operation of an automatic oat control oil valve in the oil flow line to the burner.

The invention possesses other objects and features of advantage, some of which, with the foregoing, will be set forth in the following description of the preferred form of the invention which is illustrated in the drawing accompanying and forming part of the specification. It is to be understood, however, that variations in the showing made by the said drawing and description may Vbe adopted within the scope of the invention as portion of the view being turned from the top part ofthe view. e

Figure 3 is a plan view of the control means illustrated inFigure 2.

Figure 4 is a vertical sectional view of a p0rtion of the upper end of the control means taken substantially at right angles tothe plane of line 4-4 of Figure 3.

I'he thermostatic fuel control of the present invention is particularly adapted for use with an air circulating heater such as for example, the oor furnace illustrated in the accompanying drawing. In this type of heater there is provided a vertical warm air passage extending alongside of the combustion casing of the heater and which is vented into the room or other space -to be heated. 'I'he combustion casing is customarily provided with al burner at its lower end for heating the casing and a fuel conduit leading to the burner. In accordance with the present invention a valve means is provided in this conduit and a thermostat means is mounted in the warm air passage and is operatively connected to the valve and is so designed as to be responsive to an abnormally high operating temperature in said passage to close the valve. Under ordinary circumstances ofoperation with the air vpassages of the happens that a rug or other Objectis placed'over the air discharge passage into the room in such a manner as to partially or fully obstructl the air flow and in the case of the ordinary space heater it is not infrequent that a garmentor other object be placed on the heater for warming or drying. In either of these instances the air is confined in the passages of the heater anda dangerous rise in temperature o'f the heater is likely to take place. Even where the air passagesare not obstructed a dangerous overloading of the unit may occur by reason of an abnormally great flow of fuel to the burner. as maybe caused by a failure of the fuel meter valve usually used in the line or by reason of causes external to the heater itself. In any of these cases the thermostatic control of the present invention operates to reduce,

or entirely close ofi.' the ow of fuel to the burner imtil the cause of the overloading is removed. i With reference more specifically to the accompanylng drawing, the thermostatic control has been illustrated in conjunction with a. floor furnace I I of more or less standard design including a combustion casing I2, an outer casing I3 and intermediately positioned wallsA I4 which divide the space between the combustion casing I2 and the outer casing I3 into vertical air passages I6 and I1 adapted to convey the air into and out of thel heater. A top grill I8 is mounted across the upper end of the casing I3 so as to permit entry and discharge of air into and from passages I6 and I1. As here shown, the wall I Il extends downwardly from an intermediate portion of the grill I8 to adjacent the lower end of the heater casing I2 and cool air is drawn downwardly into the passage I8 defined between the wall I d and the casing I3 to displace air which is heated and which rises in the passage I 1 located between wall Id and the heater casing I2. The passage i1 extends upwardly alongslde of the .heater casing and registers with the mid portion of the grill I8. In the case of a iioor furnace as is here shown, the outer casing I3 is set in an opening formed in the iioor I9 of a room so that the several parts above described depend from the oor level. A uel burner 2i is mounted at the bottom of the casing I2 and discharges its products of combustion into the casing for heating the latter, and a iiue 22 is here connected adjacent the bottom of the casing I2 for discharging the spent products into a stack. Fuel is conducted to the burner from a metering valve 23 by way of connected conduits 24 and 26 and is conducted to the metering valve 23 from a source by way of a conduit 21.

As above described, a fuel regulating valve 28 is mounted in the fuel passage leading to the burner and a thermostatic means 29 is mounted in the warm air passage I1 and the same is operatively connected to the valve and is responsive to increasing temperatures in the passage to throttle down the valve 28. In the present instance the valve 28 is contained within a valve body 3I connected to the conduits 24 and 26. A valve seat 32 is provided in the form of a removable plug threaded into the lower end of the body 3I and the valve 28 is a needle type valve which moves downwardly into an opening 33 provided in the member 32 for sealing off the fuel flow. A tube 34 is threaded into the upper end 36 of the valve body and extends vertically therefrom into the air passage I1 and is arranged in longitudinal alignment with the movement of the valve 28. A bracket 31 is secured to the upper end 38 of the tube and is in turn provided with a skirt portion 39 adapted for connection to the side wall I4 of the heater. Preferably, the tube 34 is of a length sufticient to extend from adjacent the bottom of the burner to adjacent the top of the passage I1. A valve stem or rod 4I is secured to or formed integrally with the valve 28 and extends upwardly through the interior of the tube and out of the upper end of the tube, whereby the upper end 42 of the stem projects upwardly from the upper end 38 of the tube within the confines of the bracket 31. The bracket in its present form is of generally U-shaped construction secured adjacent its center to the upper end 38 of the tube as by means of nuts 43 and 44 and includes a pair of transversely spaced sides 46 and 41. The thermostatic element of the preferred form of the invention consists of an elongated strip 48 of bi-metal which is here supported in the bracket by extension of opposite ends 49 and I of the strip through slots 52 and 53 in the sides 46 and 41 of the bracket. Preferably,

some means such as the cotter keys 54 and 56 here shown, are 'provided for preventing a transverse movement of the strip relative to the bracket out of asupported position.

' As will be best seen in Figures 2, 3 and 4, the strip 48 is mounted across the longitudinal axis of the rodin oifest relation thereto and is here connected to the rod by means of a yoke 51 embracing the strip and extending laterally across the axis of the rod 4I and formed with threaded openings 58 and 59 secured on the threaded upper end 42 of the rod. A cap nut 5I is preferably provided over the upper end of the rod. In accordance with the present arrangement, the strip 48 in cool condition extends substantially straight across the bracket and the length of the stein il is such that in the cool position of the strip, the rod and valve is supported in an elevated open position Aof the valve, as illustrated in Figure 2. The bi-metal characteristics of this strip are such that upon being heated the strip will bow downwardlyso as to permit a gravitation and lowering of the rod and stern towards a seated position of `the valve and at an abnormally high temperature the valve will be fully closed. By reason of the vertical positioning and alignment of the several parts, the valve and rod will normally tend to gravitate to a closed position of the valve and hence the thermostatic strip is not called upon for any substantial actuating force when heated to close the valve, Also, should the strip fail in its operation as by reason of breakage or failure to return to a straight position after being overheated, the valve will close and remain closed until the defect is corrected.

It will be clear that one of the functions of the tube 34 is to act as a vertical guide for the valve stem and in addition, where oil fuel is used, the upper end of the tube is left open to the atmosphere so as to provide a vent for any oil vapor formed in the oil line at or adjacent to the valve body 3 I.

The apparatus depicted in the accompanying d'awing has been particularly designed for use with a burner using oil as its fuel. In such case it is preferable that the metering valve 23 be one that is float controlled, that is a valve which is constantly lled to a predetermined level with oil by means Aof a float controlled valve. In such a case it is desirable as here shown, to locate the safety valve 28 in the line between the oat control valve 23 and the oil burner 2|, so that upon closing of the safety valve 28, a minimum amount of oil will be available for flowing to the cil burner.

One of the advantages of the construction illustrated in the preferred form of the invention, is that the fuel flow is gradually throttled down with increasing temperatures so as to maintain the operation of the heaterA at a safe temperature. The location of the safety valve between the float control valve 23 and the oil burner gives the safety valve 28 the last and final control of the oil input into the burner, and regardless of the setting of the rate of ilow of oil cut of the iioat valve 23, the oil flow can be reduced or entirely shut off by the safety valve 28.

In accordance with the present invention it is extremely desirable that the thermostatic element be responsive to the temperature of the air in the hot air discharge passage of the heater and so near as possible be responsive'only to the temperature of `such air and not to the temperature ofthe heated walls of the heater. I have found that the most effective control is obtained by depending upon the increasing temperature of the air in the hot air discharge passage rather than the increasing temperature of any of the metal parts of the heater. For this reason I prefer to mount the thermostatic element 29 adjacent the top of the hot air discharge passage in furtherest removed position from the heater casing I2 so that the heat received by the thermostatic element by radiation from the heater casing I2, will be reduced to a minimum. Thus the mounting of the thermostatic element directly in the air passage and more particularly at the upper discharge end of the air passage forms an important feature of the present invention.

As will be understood, other forms of thermostatic devices diilerent from the specic bi-metal strip herein illustrated, may be used.,

I claim:

1. In combination with a. floor furnace, an air circulating heater including a combustion casing and exteriorly spaced walls defining a vertical warm air passage alongside of said casing and a iiuid fuel burner mounted at the bottom of said casing to heat the same and having a fuel inlet conduit underlying said passage, a thermostatically operated valve unit comprising a valve body adapted for connection to said conduit at a position under said passage, a valve mounted for vertical reciprocation in said body and closing the passage. through said body in its lower` position, a tube `connected to said valve body and extending upwardly therefrom in alignment with the movement of said valve, a valve stem ex tending vertically through said tube, a bimetal strip supported by the upper end of said tube and connected to said sternv for normally supporting the latter in an elevated open position of said valve and/being responsive to increasing temperature in said passage to permit a gravitation of` said stem and valve towards closed position of said valve, said tube being open at its upper end to permit discharge of oil vapor.

2. In combination with a. floor furnace, an air circulating heater including a combustion casing and exteriorly spaced walls defining a vertical warm air passage alongside and above said casing and communicating with a delivery opening at the top of the heater, said heater also having a fuel burner and a fuel inlet conduit located at the bottom of the casing. a valve comprising a body operatively connected to said conduit and positioned adjacent said burner, a. tube-connected to and extending upwardly from said body to adjacent said delivery opening and being open to permit discharge of oil vapor therefrom, a valve member mounted in said tube and body for closing the passage through the valve body, a thermostat at the upper end of said heater passage positioned in the normal and direct vertical path of the heated air discharging through such' passage to said delivery opening, and means connecting said valve member and thermostat sol that said valve member will move to close said valve passage in response to an increase in temperature in said heater passage.

HARRY C. LITI'LE.

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