US2364663A - Outfire control - Google Patents

Description

Dec. 12, 1944. A. v. SAMPSEL OUTFIRE CONTROL 115d April 9, 1940 4 Sheets-Sheet 1 Dec.- 12, 1944. A. v. SAMFfSEL OUTFIRE CONTROL Filed April 9, 1940 4 Sheets-Sheet 2 fuj74M Dec.- 12, 1944.

A. v. SAMPS EL OUTFIRE CONTROL Filed April 9, 1940 4 Sheets-Sheet 3 9 1944 A. v. SAMPSEL 2,364,663

OUTFIRE CONTROL Filed April 9, 1940 4 Sheets-Sheet 4 Patented Dec. 12,-1944 OUTFIRE CONTROL Arthur V. Sampsel, Mendota, Ill., assignor to Sears, Roebuck and 00., Chicago, 11]., a corporation of New York Application April 9, 1940; Serial No. 328,740

9 Claims.

, nience of cleaning out the excess fuel, and even injury or destruction of the furnace wall or other structure.

It is accordingly an object of my invention to provide against such a contingency.

It is a further object to provide an improved means for preventing undesired feed of fuel;

whether solid or fluid, when the fire is out.

.It is also an object to provide a stoker-fired furnace equipped with a hold-fire control, 1. e., a device periodically operating the stoker for preventing a' fire from going out, and with an outfire control, i.-e., a device preventing operation of the stoker when for anyreason the fire goes out.

Another object is to provide for temperaturecontrolled periodic operation of a stoker to prevent a fire'from dying and to circumvent such operation when for any reason something in or associated with the heating system is out of order.

A further object is to provide a temperaturecontrolled device for preventing undesired feed of fuel to a heating apparatus.

It is still another object to provide a common temperature control for both a hold-fire control and an out-firecontrol.

It is a still further object to provide a fluid operated heating apparatus with an out-fire switch located where the heat is not of a destructive nature.

It is also an obiect to provide a signal giving notice that something in or associated with the heating system is amiss.

Another object is to mostat construction.

Further objects and advantages of the invention will appear as the description proceeds.

The invention will be better understood upon reference to the. accompanying drawings, in which:

Fig.- 1 is a diagrammatic view of a stolger circuit employing mercury tube hold-fire and outfire controls.

Fig. 2 is afragmentary sectional view showing a wind-box installation of the hold-fire and outflre' control switches of Fig. 1.

Fig. 3 is a plan view of the detent mechanism appearing in Fig. 2.

Fig. 4 is a view similar to Fig. 1 but with the out-fire control omitted.

provide an improved therfor he t. i.e., does not cause operation of the Fig. 5 is a view similar to Fig. 1 but with the hold-fire control omitted.

Fig. 6 is a diagrammatic view similar to Fig. 1 but employing gas to control the hold-fire and out-fire switches.

Fig. 7 is a view similar to Fig. 6 but shows the hold-fire switch clock-controlled.

Fig. 8 is a view similar to Fig. 7 but omits the hold-fire switch and shows a gas-controlled outfire snap switch.

Fig. 9 is similar to Fig. 5 but shows a thermometer type out-fire control switch.

Fig. 10 is a view similar to Fig. 1, but of a modified circuit including an out-fire alarm.

Fig. 11 is similar to Fig. 10, but relates to an out-fire alarm for a gas, oil or other fluid fuel burner.

Fig. 12 is a. front elevation of a double blade. thermostat embodying features of my invention.

Fi 13 is a side elevation of the same.

Fig. 14 is a. partially schematic view taken as indicated by the line u-u m Fig. 12.

Fig. 15 is a front elevation taken as indicated by the line l5-l5 in Fig. 13, the mounting plate being omitted.

Fig. 16 is a top plan viewof Fig. 15.

Fig. 1'7 is a. fragmentary sectional view taken as indicated by the line l'l-|l in Fig. 13.

Fig. 18 is a fragmentarysectional view taken as indicated by the line lB-l8 in Fig. 1'7.

19 is a rear elevation taken as indicated by the line I 9l9 in Fig. 13.

Fig. 20 is a sectional view taken as indicated by the line 20-20 in Fig. 15. V

Referring now more particularly to the drawings, there is shown in Fig. 1 a stoker circuit in which energy from the feed line at passes from the hot side 25 of the line through a hand switch 21, which is normally ciosed. and a transformer primary 29 to the ground 32. The transformer secondary 34, a hold-fire control switch 35, an

out-fire control switch 38 and a relay coil 11 are all in series. A room'ther'mostat switch 38 is in parallel with the hold-fire control switch 35.

' Also in series with the line and the hand switch 21 is a. limit switch 40, which remains closed as long as the furnace temperature is not excessive. a spring-opened relay switch II and a stoker 42. The hold-fire control switch is provided to keep the fire from going out, as it is likely to do particularly in mild weather when for relatively long periods the room thermostat does not call .stoker. The switch 35' is accordingly adjusted to close when the fire is at or Just above the dying ture is about 85 F., for example, and to open when the fire is at a somewhat higher temperature, i. e., when the wind-box temperature is about 100 F., for example.

The out-fire control switch 36 is provided to open and thereby stop. the stoker when the fire is out. It is accordingly adjusted to be closed as long as the fire is alive. The switches and 36 may be mounted to turn in unison, as will appear.

When the furnace is cold, the hold-fire switch 35 is closed and the out-fire switch 36 is open, so that the relay coil is not energized and'accordingly the stoker-controlling relay switch 4| is open. To start the stoker, the out-fire switch 36 is manually moved until it is closed, thereby completing the relay circuit which closes the stoker switch 4|. A fire is thereupon kindled in the furnace, the switch 36 being held in closed position manually or by a suitable retainer for a suitable length of time, say, fifteen or twenty minutes, more or less, while the furnace warms up. Then the switch 36 may be released, and at such time the furnace will be sufficiently warm to maintain the switch 36 automatically in closed position, where the switch will remain until the fire goes out or is dying.

Since while the fire is alive the out-fire switch 36 remains closed, it follows that unless the room thermostat 33 calls for heat, the operation of the stoker while the fire is alive will be controlled by the hold-fire control switch 35. When either or both of the switches 36 and 36 call for heat, the stoker will operate because the relay switch 4| will beclosed, and when both of the switches 35 and '36 are open the stoker will not operate because the relay switch 4i will be open. When the fire dies, the out-fire switch 36 opens, thereby opening the relay switch 41 regardless whether the hold-fire switch 35 or the thermostat switch 33 or both call for heat, and a detent 44 (Figs. 1 and 2) serves to retain the switch 36 in open position until the switch is manually moved past the detent and held in closed position as set forth above.

Should the wind-box temperature upon death of the fire exceed that at which the out-fire switch 36 opens, and should the hold-fire switch 35 or the thermostat switch 38 at such time be closed, the stoker may operate even though the fire is out, but in that event the period will be short, say about a minute, more or less, because the cool air blown into the fire-box will bring the temperature of the wind-box rapidly to the point,

say 70 F., at which the out-fire switch 36 opens.

When the fire is rekindled, the switch 36 must be manually reset, as explained above.

The switches 35 and 36 may be mounted on a common shaft 45 connected to a thermo-sensitive coil 46 protected by a metal or other suitable housing or shell 41 secured in the interior 43 of a wind-box 43 about a burner 50. A rise in wind- .box temperature affects the coil in such manner as to urge the out-fire switch 36 and initially the hold-fire switch toward closed positions- As the wind-box temperature rises above say, 100 F.. the out-fire switch 36 continues to be closed but the hold-fire switch moves to open position.

The hold-fire control switch may be operated otherwise, as by a clock, and the out-fire control switch may be operated otherwise, as by a gas bellows, as will appear more fully hereinafter.

The out-fire control switch 36 of Figs. 1 and 2 may be eliminated simply by omitting the same and/or joining the contacts of said switch, as

temperature, i. e., when the wind-box tempera-' shown in Fig. 4. Then the stoker operates whenever the hold-fire switch 35 or the thermostat switch 33 or both call for heat, and does not operate when neither of these switches calls for heat.

The hold-fire control switch 36 of Fig. 1 may be eliminated simply by omitting the same so that its contacts remain apart, as shown in Fig. 5.

Th thermo-sensitive coil 46 (Fig. 2) has an end 52 secured to an end of the shaft 45. The shaft is journaled in the shell 41 and extends outwardly therefrom. Mounted on the outer end of the shaft 46 is a bracket 55 in which the mercury tube switches 35 and 36 are attached together as a unit, the bracket being iournaled in a suitable bearing 61 in axial alinement with the shell bearing. The bracket 55 carries an arm 63 which is disposed in such relation to the detent 44 that, so long as the fire in the burner 63 is above the dying temperature, and accordingly so long as the wind-box temperature at the coil is above that corresponding to the dying temperature of the fire, the switches 35 and 36 are free to turn without interference from the detent. The detent has a cam face 63 which is engaged by the arm 53 which is turned toward the detent by the cooling coil when the fire is dying, and the detent is thus cammed against the action of its spring until the arm 56 snaps by to the dotted position shown at 66a in Figs. 1 and 3. Now the detent snaps to its outermost or detaining position where it maintains the out-fire switch 36 open, preventing operation of the stoker.

To restart the stoker, it is necessary to reset the out-fire switch 36. This is done by manually pressing back the detent 44 and moving the arm 56 past the same to a position on the other side of the detent so as to close the switch 36, and then allowing the detent to return to its outermost position, the arm being detained in such switch-closing position, as explained above, until the furnace is warm enough to heat the coil 46 sufficiently to hold the switch 36 in closed position without assistance. This may be accomplished by hand in any other desired manner. This may occur when the iumace temperature is ,only slightly above the dying temperature of the fire. The hold-fire switch 36 will be closed at such time to cause the stoker to operate even if the room thermostat 36 may not be calling for heat, thereby raising the furnace temperature. In the regular operation of the apparatus the fire will keep going, the out-fire control switch 36 opening to stop the stoker only in case the fire dies, whether through accident or'intent, as has been explained.

Fig. 6 shows a circuit like that of Fig. 1 but with the hold-fire switch 35 and the out-fire switch 36 actuated by gas'instead of by a thermosensitive coil.

A bellows 60 communicates by means of a tube 6| with a cylinder 62 mounted in a casing 64 secured in the wind-box 43 about a burner 66. The bellows, tube and cylinder form a closed unit containing gas 63. The bellows carries a shaft or rod 10 having a pin and slot or other suitable connection H with the arm 53 to swing it about the staff 45a for controlling the hold-fire and outfire switches 35 and 36 as will be understood from the description of Figs. 1 to 3.

Fig. '7 illustrates still another system having hold-fire and out-fire controls. The operation of this arrangement is like that of Fig. 6, except that the hold-fire switch 36a is clock-controlled and therefore calls for heat atregular intervals 8I opens, stopping the stoker 82.

Fig. but operating through a snap switch 18 and a gas-actuated bellows 88. In this form the rod 18a extending from the bellows 88 carries a contact 18 insulated as at 15 and electrically connected in the relay control circuit as at 11. A blade 18 is urged by a spring 18 toward the contact. 18 and is limited in its movement inthat direction as by asuitable stop 8|. The stop may be arranged to open the switch 18 at a wind-box temperature of, say, 60 F., or may be adjusted to open the switch at any other desired temperature.

Fig. 9 shows diagrammatically an out-fire control switch 88 comprising a mercury thermometer 85 having a graduated column 86 from which, at suitable. out-fire control wind-box temperature graduations, extend metallic contacts 88 and 88 in such manner as to have electrical contact with the mercury and provide a switch which closes when the mercury reaches the upper contact 88 and opens when the mercury leaves the upper contact 88. The operation is evident from the foregoing. If desired, two or more upper contacts may be employed or a single contact 88 made adjustable longitudinally of th column 88 as shown to obtain any desired temperature lag between the room thermostat 88 and the out-fire switch 88.

Fig. 10 shows an installation in which is incor porated' hold-fire and low limit controls, and a device for giving an alarm when the low limit switch is open. In this arrangement, I provide a double blade snap action room temperature responsive switch instrument generally indicated at 85 and comprising the operating room thermostat switch 88 and low limit and signal alarm switches 88 and-81 and a movable blade 88 common to the switches 88 and 81. In parallel with the operating thermostat switch 88 is a hold-fire switch 38a. The devices 88a and 88 may be held in a compact housing or panel I88 in the room or other space to be heated. The low limit switch 88 is in a circuit containing the relay coil 81, the transformer secondary coil 88, the operating thermostat switch 88 and the hold-fire device 88a, and the alarm switch 81 is in a circuit containing an interrupter I82, a bell I88 or other suitable alarm, a battery I88 and a hand switch I88. The interrupter is optional. A telltale lamp I81 may be provided on the panel I88.

Let it b assumed that the normal maximum room temperature is 75 and that the operating room thermostat 88 operates on a temperature differential of, say 1 /z F. The thermostat 88 accordingly will be adjusted or set to open at a room temperature of F. and close at a room temperature of 73 /2" F'. The device 88 maybe adjustedor set so that the low limit switch 88 will remain closed until the air in the room drops to any desired temperature, say, 71 F., for example. When the air in the room drops to the selected temperature, 1. e., 71 F'., whether due to shearing of th stoker shear pin, an empty coal bin, electricity failure, clinker and ashes obstructing further fuel feed, transmission failure,

the death of the fire, an open window in the room, or any other cause, the low limit switch 88 opens and'the blade 88 snaps over, closing the alarm switch 81. When the switch 88 opens, the

and causes the lamp I81 to light, which calls attention to the fact that something is amiss so that an attendant may take care of the matter without delay. If desired, the bell I88 and lamp I81 could be connected to the feed lin instead of being energized by a battery as shown. The

ringing ofthe bell may be stopped as by opening the hand switch I88. The temperature levels and differentials governing the operation of the switches 88, 88 and 81, and the temperature lag between the closing of the switch 88 and the opening of the low limit switch 88 may be varied as desired, as will appear.

When the apparatus has been repaired or otherwise properly attended to, the fire is rekindled, if necessary, and the blade .88 is manually moved to close the low limit switch 88 so that if the room thermostat 88 or fire pilot 3801s calling for heat the stoker will again be operated. When the blade 88 is so moved, the attendant closes the hand switch I88. The blade 88 is held by hand or by a hand switch device I88 in the last temperature lag of 2t? F. between the opening and closing of the switch 88, or whatever the selected temperature and lag might'be, whereupon it will be unnecessary to hold the blade since the instrument is so adjusted that at or above that temperature'the blade will automatically close the switch 88. If desired, a catch 88a may be employed to hold the blade 88 in position to close the switch 88 while the attendant is rekindling the fire or making such repair or adjustment as may be necessary for the continued operation of the apparatus, and until the selected temperature at and above which the switch 88 is automatically closed is reached, whereupon the attendant may secure the catch 88a in inoperative position. I

The arrangement appearng in Fig. 11 is identi cal with that in Fig. 10 except that it relates to a gas oroil burner and thus has no hold-fire device. The operation of the apparatus of Fig. 11 is identical with that just explained, except of course that a gas valve or pump switch and an igniting device are operated instead of a stoker. This low l mit and alarm device could operate for any reason, including failure of fuel supply. drop in the fluid pressure, etc. A gas burner installation is'shown, and comprises a solenoid I I8 controlling a valve III (or pump switch if liquid is used) in a fuel conduit N2, the valve being relay coil 81 is de-energized and the relay switch The closing of. the switch 81: starts ringing of the bell I88 the burnerfan II8 will cool the furnace and urged to close by a spring H8. The conduit 2 leads to a torch nozzle II! from which the fuel II8 discharges, air being supplied as at II8 by a fan H8 or other suitable means. The discharged fuel is ignited by a sparking device I28 -or other suitable means. This device may comprise points I22 urged apart by a. spring I28 and brought together intermittently as by a rotating cam I28.

When the switches 88 and 88 are closed, the

relay switch 8| is closed, energizing the solenoid to open the valve III, and also energizing the sparking device I28 through a transformer I 28, igniting the fuel from the nozzle I 25. The burner fan I I8 and circulating fan or blower I28 are also dependent on the switch 8,I. A time delay relay I 88 may be placed in series with the blower I28 in order to prevent operation of the blower until after the furnace has become warm (usually about three or four minutes). Should the fire go out by accident,the cold air I I8 delivered by position, so that he could give or adjustment.

Another feature of my invention concerns an improved tell-tale thermostat mechanism aiio rd- .same time, the alarm switch 61 closes. Aiter suit-.

able repair or other needed attention, the attend- .ant holds the outflre switch 66 closed as explained above {or a suitable length of time until the furnace is again suiiiciently warm to cause the room temperature to automatically close the low limit switch 66, whereupon the attendant need not further hold the switch 66 closed.

Had the fuel failed to ignite upon 'startinm' the attendant would immediately have noticed this and have released the out-fire switch to open ing accurate instead of hit-or-miss adjustments o'f-on'f and "off" temperatures and temperature differentials and adapted for three-wire or twowire use as desired. For the purpose of illustration the three-wire adaptation is here shown and described. This thermostat instrument, illustrated in Figs. 12, 13 and 14 and designated generally by the numeral v65, is of the double blade type and comprises a base or body I65 on which is rotatably mounted a dial I66 bearing graduations I31 which may designate degrees Fahrenheit. A fixed mark or indicator on the casing or cover, described below, or on the base or other stationary part indicates the reading of the-dial. The dial I36 has an arcuate cam or ramp I62, slidable relative to and engaging a screw I adiustably carried by a strap I65, which may'have graduations I46 calibrated in degrees Fahrenheit ii desired. A pointer I66 rotatable wlththe screw is adapted to overlie the graduations I46.

Thermo-responsive elements II and I52 are connected as at I56 with the arms I56 and I51, respectively, of a strap I56 ,to lea: springs I66 anchored to bosses I6I on the base as at I62. Car-- ri'ed and insulated as at I66 from the thermo-responsive elements are blades I65 and I65, respec- 'tively-. The blade I65 is cooperative with a magnet I66 and has a contact I66 cooperative with an adjustable contact Illl to provide the low limit control switch 66 and with a relatively fixed contact "I to provide the signal switch 61. The

blade I66 is cooperative with a magnet I12 and has a contact I14 cooperative with an adjustable contact I15 to providetheoperating roomthermostat switch 66. -The contact I15 may be formed on a screw for'the purpose of adjustment and may carry a pointer I16 movable relative to graduations I11 to increase or decrease the temperature differential in the operating room'thermostat 66. A spring I16 holds the contact I15 in the desired adjustment.

It will be'dbserved that the arms I55 and I51 of the strap or bracket I56 may be so relatively inclined or ofiset that there is an initial predetermined lag between the engagement of the contact blade I66 with the contact I15 and the engagement oi the blade I65 with thecontact I16.

screw I66 having its head engaged with the lower arm of the element I5I and itsshank threaded in the strap I56, said element being formed of spring metal. It is evident that, once the con- I10, thereby increasing the temperature lag between the closing of the operating room thermoattention to repair s,se4,ees hence the' 'room rapidly, as that the low limit stat switch 66 and I control switch 66, the alarm switch 61 closing upontheopeningoi the switch 66. Oieoursethe instrument is set so that'b'oth oi the contacts I16 and Ill can never be engaged simultaneously,

- and preferably is set at a temperature lag of abuit 2% F. between the closing 0! the op rating switch 66 and the opening of the low limit control switch 66, although the lag may be varied as is apparent from the foregoing.

Although the blades are independently controlled by theirrespective theme-responsive elements, they are movable together simultaneously when the strap I56 is adjusted by the-dial I66.

when the dial is turned in one direction, the ramp I62 .of the dial raises the strap, thereby lowering the blades, and when the dialv is turned inthe opposite direction, the springs I66. force the strap down the receding ramp, raising the blades. This simultaneous adjustment 0! the blades determines the temperature at which the operating room thermostat switch 66 will close, so that, if the temperature lag is, say, 2 /z l"., and the operating switch 66 is set to close at 13 /2 I"., it is known that the low limit switch 66 will open at 71 F., whereupon the bell switch 61 will close.

The hand switch in for turning oi! the signal and rendering the mechanism operative for heating or other air conditioning purposes, as when dle I66 and an operating arm I66 engageable with a spring strip III or other suitable part carried as by the blade I65. 'By moving the bandie I66 in the'Ofl" direction the arm I66 rides against the strip I6I and shiits'or springs the bottom or the strip to a higher position as shown in dotted lines in Fig. 13, thereby maintaining the blade I65 out of engagement with the contact Ill and holding the alarm switch 61 open and the low limit switch 66 closed. The tight mounting of the lever I65 and/or the spring pressure 01' the shifted strip prevents accidental movement of the lever.

It the bell I66 rings, the telltale lamp I61 lights. By swinging the handle I66 in the 0!! direction, the bell is stopped and the lamp turned oil. and the low limit switch 66 closes. After the trouble has been adjusted and the room temperature israised to normal, the lever handle may be returned to On" position,. which is normal for signal operation. 0! course, by leaving the handle at all times in 05" position, the device operates as an operating thermostat without the This lag can 'be varied 'by the adjustment of a tacts I16 and I15 are set, a raising of the blade' I will prolong its engagement with the contact signal control.

In the event thatthe dial I66 is set at. say, '15 F., the temperature at which the operating room thermostat switch 66 is-desired to open, but the user is under the impression that the switch 66 actually opens at 74 R, for example, then by turning the pointer I66. (which rotates with the the opening, 01' the low limit the dial and protection for the .'shelf adjacent the dial may datum point 222 for indicating the reading of slot being toadvance the opening of the switch 30. These calibrations do not affect the lag between the opening of the switch 30 out-fire switch 33. This sible an immediate to the satisfaction of the user, and is a distinct improvement over previous types. which require a cut-and-try method of correction.

The base may be attached in any suitable manner to a wall plate I which itself may be suitably mounted on. a wa1l,.the plate carrying the tell-tale lamp I01, if desired. Said plate may have pins I95a engageable in diagonally opposite recesses in'the base I35 to maintain them in proper relation.

' The dial I35 has a central hole 200 (Fig. 18) alined with a threaded hole 20I in the base I35, and a screw 202 is threaded in said hole and has an enlargement 203 resting on the base and extending through thehole 200, said enlargement journaling the dial. The head 205 of the screw overlies the bored portion 205 of the dial and lies within the cam I42 but does not interfere with the rotation of the dial by the hand, which can conveniently engage the milled edge 201 of the dial. The spring pressure of the foland the opening of the onstruction makes poscorrection of error or change 232 of a thermometer 233, and the depression being of such depth that the thermometer is readily accommodated and slidable therein to engage behind said front wall above and below said depression so as to beprotected by the cover from injury. The front entrance to the depression is preferably flared forward, providing one or moretemperature graduatedsurfaces 235 with the graduations 235 located adjacent the thermometer for easy reading thereof. One of the graduations may be emphasized, as at 231, adjacent which a mark or scratch 231a on the thermometer known by test to be "reached by the liquid therein at the temperature designated by the reading at 231 is placed when the thermometer is adjusted in the depression. Upon such adjustment of the thermometer, cement 230 is applied to the stem of the thermometer and the inner portions of the ends of the depression, so as to securely fasten the thermometer in proper position, the cement being concealed from the outside.

Air holes 233 may be provided at various parts.

of the cover to insure free access of the atmoslower I44 on the gently sloping portion 200 of I the cam I42 prevents accidental turning of the dial while permitting hand adjustment of the dial. The dial may be locked in the desired position of. adjustment as by a plate 2I0 anchored by a screw 2 threaded to the base I35, the plate having an end 2I2 fulcruming on the base and a clamp portion 2I3 adapted to be frictionally clamped against the dial by the screw so tightly as to securely lock the dial. The screw 2 is so arranged as to be inaccessible when the cover 2I5, hereinafter more fully described, is in place. The plate 2I0 is prevented from shifting off the dial by'abutments 2I5 and 2" straddling the same.

The base I35 has a ledge or shelf 220 of curved outline conforming to the curvature of the dial I35 and spaced'from the back 22I of the base, the shelf being substantially flush with or projecting slightly beyond the edge 201 of the dial to afford a support for the projecting part of edge of the dial without interfering with free access of the finger to the edge of the dial to adjust the latter. The have a mark or the dial. The cam is cooperative throughout the entire 360 with the follower I44, the dial being rotatable continuously in each direction.

The relatively steep portion223 of the cam subtends the ungraduated part of the dial so that when the follower I44 is thereon it will not affcct desired adjustments.

The cover 2I5 is shaped to enclose the base I35 and the thermostat mechanism mounted thereon (Figs. 12 and 13), and has a slot 225 the shelf 220'and superposed portron of the dial I33 are adapted to project, the sufficiently wide to provide clearance to enable the slotted portion of the cover to be readily assembled with and disassembled from the shelf and dial notwithstanding tilting of the cover as shown in dotted lines in Fig. 13 to accomplish these results.

The cover has a longitudinal depression 221 in the front wall 228 thereof, said depression being open at its upper and lower ends as shown at 223 and 230, the bottom opening being flared as at 23I to facilitate insertion of the small end phere to the responsive instrumentalities. The hole indicated at 240 is alined with the depression 221 and is of a width to Permit the bulb 240a of the thermometer to pass therethrough so that the thermometer may be inserted and adiusted, or, the hole or than the bulb, in which event the material at the sides of the hole will yield elastically, as when made of plastic molding, to enlarge the hole to enable the bulb to pass therethrough.

The cover may have a slot 24I in the end 242 thereof opposite the slot 225, to slip over the shank 243 of a screw 244 at the corresponding end of the base I35, the screw being adapted to gages the cover when the dial I35 and shelf 220 project through the slot 225, to securely and releasably hold the cover in proper assembly with the base (Fig. 13).

The cover may be suitably reinforced as by one or more preferably integral ribs 240.

.It will be seen from the foregoing that I have provided by simple means a control mechanism whereby in the event any part of the heating or conditioning system goes out of order, as, for example, if the stoker shear pin becomes broken,

or the hopper is empty, or the motor overload is cut out or the electric current is interrupted,

or the flre is dirty, or a fuse is blown, or for any reason whatever the fire becomes cool or dies, the feed of fuel will be stopped and, in accordance with an additional feature of the invention, a signal will be given in such manner as to call immediate attention to the fact that something is out of order, in order that repairs may be made without serious delay. I

It will further be noted'that I have provided an improved dial and cam and mounting therefor, together with arcover ofsimple construction which is readily mounted and removed, said cover protectively carrying a thermometer and being so constructed as to enable the thermostat to be readily positioned and secured in the desired relation to the temperature graduations on the cover. The base, mounting as well as other plastic or other Various modifications may suggest themselves to those skilled in the art without departing from the spirit of my invention, and, hence, I do not wish to be restricted to the specific form shown 240 mat be made'narrow or uses mentioned, except to the extent indicated in the appended claims, which are to be interpreted as broadly as the state of the art will permit I claim:- 1. A space conditioning system, comprising a I conditioner, means for supplying said conditioner with fuel to enable said conditioner to" supply a conditioning medium to said space, means operative in response to a preselected supply-de-.'

ass-gees manding condition of said space to operate the first mentioned means and to a preselected satisfied condition of said space to render said first mentioned means inoperative, and means operative in response to a preselected supply-demanding condition of said space beyond the range defined by'tbe first two conditions aforesaid to render the first mentioned means inoperative.

2. A space conditioning SystemQcomprising a response to a preselectedsupply-demanding condition of said space beyond the range defined by the first two conditions aforesaid to render the first mentioned means inoperative; and a signal device automatically operated upon operation of the last mentioned means. 3. A space conditioning system, comprisinga conditioner, means enabling said conditioner to supply a. conditioning medium to said space, means operative in response to a preselected condition of said space to operate the first men- 'tioned means and in response to another preselected condition of said space to render said first mentioned means inoperative, means operat'ive in response to a preselected condition of said space beyond the range defined by the first two conditions-aforesaid to render said first mentioned means inoperative, a signal device automaticallyoperative upon operation of the last mentioned. means, manually releasable means for preventing reoperation of said last mentioned means, and means'for rendering saidzsignal device inoperative without rendering said last men- 1 tioned means operative.

4. A space heating system comprising a furnace', means for feeding fuel to said furnace,

fuel feed control means responsive to predetermined upper and lower temperatures of said space for respectively stopping and causing operation manually releasable means for retaining said safety means in said second position, whereby control of said fuel feeding means by said control means may be resumed after correction of said cause and while said abnormal temperature still exists, a signal device rendered operative when said safety means is in the first mentioned position, and means for rendering said signal device inoperative without changing the-position of said safety means.

5. A space heating system comprising a furnace, means for feeding fuel to said furnace, fuel feed control means responsive to predetermined *upper and lower temperatures of said space for respectively stopping and causing operation of said fuel feeding means, temperature responsive safety means disposed, whenan abnormally low space temperature obtains, in a position rendering said fuel feeding means inoperative irrespective of said control means, whereby the attendant may have an opportunity to correct the cause of the abnormal temperature without danger resulting from fuel feed if the fire were out, said safety means being disposed, when a space temperature intermediate said lower and abnormal temperatures obtains, in'a second position enabling'said control means to resume control of'said fuel feeding means, said safety means being manually movable to its second position while said abnormal space temperature obtains and in opposition to the influence of said abnormal space temperature on said safety means, manually releasable means for retaining said safety means in said second position whereby control of said fuel feeding means by said control means may be resumed after correction of said cause and while said abnormal temperature still exists, and a signal device rendered operative when said safety means is .in the first mentioned position.

6. .A space heating system comprising a furnace, means for feeding fuel to said furnace, fuel feed control means responsive to predetermined upper and lower temperatures of said space for respectively stopping and causing operation of aid fuel feeding means, temperature responsive safety means disposed, when an abnormally low space temperature obtains, in a position preventing said control means from controlling said fuel feeding means, whereby the attendant may have an opportunity to correct the cause of the abnormal temperatur without danger resulting from fuel feed if the fire were out, said safety means being disposed, when a space temperature intermediate said lower and abnormaltemperatures obtains, in a second position enabling said con- .trol means to resume control of said fuel feedof said fuel feeding means,\temperatur e responsive safety means disposed, when an abnormally low space temperature obtains, in a position rendering said fuel feeding means inoperative irrespective of said control means, whereby. the attendant may have an opportunity to, correct the cause of the abnormal temperature without danger resulting from fuel feed it the fire were out,.

said safety means being disposed, when a space temperature intermediate said lower and abnorimaltemperatures obtains, in a second position enabling said control means to resume control of said f-uel feeding means, said safety means being manually movable to its secondposition while ,said abnormal space temperature obtains and in opposition to the influence of said abnormal space temperature on said safety means,

ing means, means manually operable to resume and maintain operation of said fuel feeding means while abnormal space temperatures obtain, said manually operable means being releasable so as not to interfere with operation of said safety means when normal temperatures are again followed by an abnormally low temperature a signal device rendered operative when said safety means is in its first position, and manually operable means for rendering said signal means operative and inoperative without-chang- :ing the. position of said safety-means.

. 7. A space heating system comprising a furnace, means for feeding fuel to said furnace, fuel feed control means responsive to predetermined upper. and lower temperatures of said space for respectively stopping and causing operation of. said fuel feeding means, temperature responsive safety means disposed, when an abnormally low space temperature obtains, in a position preventing said control means from controlling said fuel feeding means, whereby the attendant may have an opportunity to correct the cause of the abnor. mal temperature without danger resulting from fuel feed if the fire were out, said safety means being disposed, when a space temperature intermediate said lower and abnormal temperatures obtains, in a second position enabling said control means to resume control of said fuel feed ing means, means manually operable to resume and maintain operation of said fuel feeding means while abnormal space temperatures obtain, said manually operable means being releasable so as not to interfere with operation of said safety means when normal temperatures are again followed by an abnormally low temperature, and a signal device rendered operative when said safety means is in its first position.

8. A space heating system, comprising a heater,

to enable said heater to supply a heating medium to the space, means operative in response to preselected heat-demanding space temperature to operate said fuel feeding means and to a pretive, and means for averting the hazards of per- 30 sonal and property damage due to fuel feed to said heater under dead fire conditions, said averting means being operative in response to a preselected heat-demanding space temperature below the aforesaid heat-demanding space temperature to render said fuel feeding means inoperative.

. means for feeding combustible fuel to said heater 9. A space heating system comprising a furnace, means for feeding fuel to said furnace, fuel feed control means responsive to predetermined upper and lower temperatures of said space for respectively stopping and causing operation of said fuel feeding means, temperature responsive safety means disposed, when an abnormally low space temperature obtains, in a position preventing said control means from controlling said fuel feeding means, whereby the attendant may have an opportunity to correct the cause of the abnormally low space temperature without danger resulting from fuel feed if the flre were out, said safety means being disposed, when a space temperature intermediate said lower and abnormally low temperatures obtains, inv a second position enabling said control means to resume control of said fuel feeding means, said safety means being manually movable to said second position after the cause has been corrected and while abnormally low space temperatures still obtain, means manually movable to a position in which it retains said safety means in aid second posi-' tion, whereby to resume and maintain operation of said fuel feeding means under the control of said control means while abnormally low space temperatures obtain, said manually movable means being releasable so as not to interfere with operation of said safety means when normal space temperatures are-again followed by an abnormally low space temperature, and a signal device controlled by said safty means and rendered operative when said safety means moves to 1 its first position.

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