US1735911A - Automatic oil burner - Google Patents

Description

Nov. 19, '1929.

ZZZ

OIL.

G. D. SUNDSTRAND AUTOMATIC OIL BURNER Original Filed Dec. 2, 1925 8 Sheets-Sheet 1 171116171751 v5' d d, 6, ,3 an 5 ran Nov. 19, 1929. e. D. SUNDSTRAND AUTOMATIC OIL BURNER Original Filed Dec. 2, 1925 8 Sheets-Sheet 2 New Nov. 19, 1929. G. D. SUNDSTRAND AUTOMATIC OIL BURNER 8 Sheets-Sheet 5 Original Filed Dec. 2, 1925 QR Nu Q NNN kw N 1929. G. D. SUNDSTRAND 1,735,911

V AUTOMATIC OIL BURNER 7 Original Filed Dec. 2, 1925 8 Sheets-Shet 4 Nov. 19, '1929. cs. D. SUNDSTRAND AUTOMATIC OIL BURNER Original Filed Dec. 2, 192's 8 Sheets-Sheet 5 hand, M

Nov. 19, 1929. G. D. SUNDSTRAND 1,735,911

AUTOMATIC OIL BURNER Original Filed Dec. 2, 1925 8 Sheets-Sheet 6 j I @'5 /260 FRONT 265 v/Ew. a, r.

PHI/V.

Nov. 19, 1929. G. D. SUNDSTRAND 1.735,-911

AUTOMATIC OIL BURNER Original Filed Dec. 1925 8 SIieQtS -Sheet 7 Patented Nov. 19, 1929 UNITED STATES GUSTAF DAVID SUNDSTRAND, OF ROCKFORD, ILLINOIS, ASSIGNOR TO SO'NDSTBAND ENGINEERING COMPANY, OF ROCKFORD,

PATENT orrlcs ILLINOIS, A CORPORATION OF- ILLINOIS AUTOMATIC OIL BURNER Application filed December 2, 1925,8er1 a1 No. 72,634. Renewed May 24, 1928.

The present invention relates generally to oil burners and especially to the type of burner which is usually associated with automatic controlling mechanism. The invention re- I 5 lates more specially to that type of self-con trolled burner which is adapted to mamta-m' a predetermined degree of heat within a very narrow range of temperature wlthout the mtervention of an attendant, unless some emer- 1 gency defect arises, in which instance the burner is adapted to become inoperative and non-responsive to the startm control.

The general object of the inventlon is to provide a noiseless and efficient combustion, and a suitable mechanism for furnishing oil and air for combustion, together with an automatic controlling system providing perfect control over the burner in normal and in emergency conditions. t

Another object is to provide an 01l:bllIIllng apparatus which is capable of burnlngrelatively heavy fuel oil, as, for example, 011 of 18 to 24 Baum gravlty.

Still another object of the invention is the provision of a fuel control and. delivery system which ensures that no oil remains 1n the nozzle on shutting off the supply thereto, thereby preventing the. nozzle from accumulating residues therein by the actlon of heat upon oil which otherwise would be reta ned within the nozzle. A further object is the provlsion ofa mechanical control device operated directly from the moving burner parts and disengagetrolled clutch mechanism. 0

It is another object of the invention to pro- 'vide a device which will recycle the burner through stopping and starting actionswhen its normal operation dllIlIlg'COlTlbllStlOIt 1s prevented by an interruption 1n the hue power.

A further ob ect 1s to provide a control device responsive to a type of thermostat WhlCll requires a small current through the thermostat during burner operation, the control device being arranged so that a defect 1n the thermostat circuit is effective to shut off the burner.

Still another object of the lnvention 15 to able therefrom by a thermostatically conprovide, in combination with a normally con tinuousl acting ignition means, a device capable 0 cutting out the ignition at will at a time onl when it is not absolutely necessary, which evice is operative automatically to place the ignition means' again into operation when its function is required. Various other objects and advantages of the invention will be appa'rentafter an understandin of the invention as hereinafter explained ully and in detail, with reference to a preferred embodiment of the invention shown in the accompanying drawings primarily for thepurpose of explanation.

The preferred embodiment of the invention comprises a nozzle, a burner bowl, an ignition means, a motor, a blower, an air pump, means for supplying oil under pressure, a control mecha ism, and a controlled clutch connection beween the control mechanism and the dri ing power, a thermostat for starting and stopping the 'burner through the control mechanism, and certain safety devices and constructions which avoid the usual and the emergency hazards ,of burneropera tion. The various safety units include a shut-off mechanism operated by an accumulation of unconsumed oil, a heater control which stops operation of the burner when excessive heat is produced regardless of the temperature ofthe normal controlling thermostat, a recycling device which causes the burner to pass through the igniting and starting actions incase there is an interruption in the line power during the operation of the burner, and a cut-out device which operates to stop the burner when there is a defective circuit to the controlling thermostat or in any other circuits essential to the proper control of the burner. 3

Alt ough the foregoing enumeration of the parts of the burner refers to certain devices, mechanisms or constructions having different functions, it is to be understood that these parts are not independent parts assembled togetherinto an operative unit, but they are rather individually active constructions having many parts in common which have overlapping and dual functions. This results from the provision of simple structural scribed. One familiar with the art will rea'dused, itis to electrically operated devices.

Although the various functionalunits may overlap in construction inthe combinations lbe understoodjthat'the following description of an'exmplary or preferred embodiment of the accompanying drawings-is not to be construed as a limitation of the inventlonto the form herein dislosed and hereinafter deily conceive of other arrangements and alternative constructions of the functional units Therefore the following description is to be taken merely as explanatory of the invention, the scope of which is determined by the appended claims. f 1

In the accompanying drawings,"F1gure 1 1s a front elevation of an apparatus embodying the features of my invention.

Fig. 1 illustrates an alternative arrangement for forcing oil to the nozzle.

Fig. 2 is a plan view of the form of apparatus shown in Fig. 1, parts being broken away to shorten the view.

Fig.- 2* is a fragmental view illustrating an adjustable air intake for the blower.

Fig. 3 is a side elevation of the apparatus shown in Fig. 2, parts being broken away to shorten .the view.

Fig. 3 is a detail view of a safety device.

operated by the weight of unconsumed oil. Fig. 3 is a section on line b-b of Fig. 3

- Figs. 4 and 5 are sectional views illustrating the air pump and related parts.

Fig. 6 is a vertical sectional view of a valve mechanism for controlling the flow of oil and air to the nozzle.

Fig. 7 is a'sectional view illustrating the nozzle and the igniter. v, Fig. 7 is a horizontal sectional view of the igniter. v Fig. 8 is a front view of the control mechanism, the view being taken approximately in the plane of line 88 of Fig. 9 and line 88 of Fig. 10. The parts are in position shown in'Fig. 11.

Fig. 9 is a plan view of the control mechanism.

Fig. 10 is a vertical sectional view of the control mechanism taken approximately in the plane of line 10!10 of Fig. 9.

' Flg. 10 is a detail view of a certain detent. Fig. 10" is a fragmental detail view of the ignition switch and the lever on which it is mounted. A

Fig. 11 is a vertical sectional view of the control mechanism takenv approximately in the plane of line 11-11 of Figs. 8 and 9.

Fig. 11 is a detail view of one of the elements of the clutch through which the control mechanism is driven.

Fig. 11 is a detail view of a certain bell the invention as illustrated in F stat circuits. 1

R f rr ng t g 2 d 3 t ere is crank member comprised in the control mechanism a Fig. 12 is a diagram ofthe motor circuit and the ignition circuit, showing also the transformers that supply current to the room thermostat circuitsu Fig, 13 illustrates diagrammatically. three different positionsof the room thermostat.

Fig. 14is a diagram shown a burner unit mounted on a base 10 and adapted to be placed before a boiler or other heater shown in part and designated 11. The-upper or combustion chamber door 12 of the heater has an opening therethrough which is covered by a plate 13 on which cerof the room thermotain of 'the burner parts are mounted. The

general arrangement of the burner parts in the heater is such as to spray a mixture of oil and air from a nozzle14 located high in the combustion chamber down into a bowl 15 herein shown as circular, into which a tangential stream of air'is forced by a blower 16, the arrangement being such that the oil spra' follows generally the path indicated by t e dotted line 17 (shown offset in Fig.

3), in order that the oil spray may impinge on the entering stream of air in the bowl in -the vicinity of the point 18 (Fig. 2). Of-

course, it'is to be understood that the spray spreads outwardly from the nozzle and-is carried or dragged away from a true conical path by the whirling air and gases.

The blower 16 comprises, in the present instance, a casing 20 enclosing a fan 21 (Fig. 2) carried on a shaft 22. A coupling 23 is provided for connectingthe shaft 22 to a motor shaft 24. Any typeof motor such as that indicated at 25 may thus be used. As.

shown in Fig. 1, a suitable adjustable motormounting-platform is provided. This comprises a vertically adjustable leg'26 fitting in a socket 27 on the base 10 and held by a set screw 28. The leg 26 carries a platform or shelf 30 upon which the motor 25 is bolted. The fan casing has a tangential outlet 31 (Fig. 3) leading into a suitable conduit 32 which enters at the bottom of the heater 11 for connection to the bowl 15. The inlet to the fan is through a central opening 33 (.Fig.

2) about the motor shaft 24, and it is partially closed by an adjustable crescent shaped damper 35 movable about its pivotal clamping screw 36. The casing 20 is supported for limited rotary adjustment on the axis of the fan shaft. This facilitates locating the burner with reference to any heater by permitting the outlet 31 to be moved circumferentially of the fan and to permit its being telescoped, if desired, into the conduit 32. Adjacent the blower casing 20 and on the base 10 is a' framework comprised of various housings or casings and generally designated by the numeral 40. The main shaft 22 extends through the framework and serves to provide power for operating pumping means.

for air and oil,-or for air alone, and for driving acontrol mechanism associated with the electrical control features or safety devices above alluded to. On the extreme .end of the main shaft 22 outside of the framework there is shown a centrifugal oil pump 41 which may be used for supplying oil to the burner, the

' details of the pump, however, forming no part of this invention. This position makes the oil pump readily removable and it can thus easily be attached or dispensed with .when not desired without mechanical difficulty. p

The air pump involves parts moving relatively slowl compared to the speed of the motor 25; Tie first speed reduction is obtainedfrom a worm 42 (Fig. 4) on the main shaft 22 meshing with a worm wheel 43 on a transverse countershaft 44 within the housing. The other end of the shaft 44 carries a disk 45 carrying a crank-pin 46 operatively connected to anair pump 47.

Because of the extensive useof oil burnersof this general type for domestic purposes, it is desirable to use an air pump construction which minimizes the danger of break-down or' of failure of the pump. Such failures would leave the housewithout heat awaiting the return of the householder or the arrival of a service man to remedy the defect. terruption of the burner should be minimized. The reciprocatory oscillating air pump of the type herein described is preferred because of its simplicity of construction, its durability, and its minimum number of moving or wearing parts, and also because of its slower action compared to the usual rotary pump. Heretofore rotary air pumps which have been used employ sliding vanes and the vanes are subject to great piston, these parts are eliminated and by the provision of an oscillatory pump valve mechanism is also eliminated whereby to simplify the construction.

Within the housing 40 there is a depending web or supporting wall in which there are two vertical passages formed which extend throu h the top 61 of the housing. The

I passage 62 (Fig. 5) is closed by a plug 62 screwed into the top 61 and has a laterally communicating hole or port 63 opening into the space 64 within the hous ing beneath the top 61. Port 63 is an air inlet port for the pump. The left hand passage 65 (Fig. 5) opens through the top 61 and is screw-threaded as shown at 66. This opening is the outlet for the air pump 47 Both passages 62 and 65 are closed at the Hence, the likelihood .of such in end of the wall'serves as a bearing for a trunnion 68 having at one end a pump cylinder 69 and at the other a nut 70. The cylinder and the lower right face (Fig. 4) of the web 60 have finishedsuperimposed plane bearing surfaces indicated at 71. Inlet and outlet ports connect the interior of the cylinder and the passages 62 and 65, there being in .thecylinder a shifting port to register alternately vwith the inlet and outlet ports in the wall 60. The inlet ports in the web 60 are designated as 72 and 73 and are connected to the inlet passage 62 by suitable passages 7 4 in the interior of said web. The outlet ports 75 and 76 are connected by passages 77 to the outlet passage 65. The inlet port 72 and the outlet port 75 are arranged to communicate alternatively with a port 78 in the cylinder. v Similarly the inlet port 73 and the discharge port 76 communicate alternatively witha port 79 in the pump cylinder. A piston rod 80 slides in, long bearings 81 at each end of the cylinder. The upper end of the piston rod is connected to the crank pin 46.

Situated on the rear part of the oil burner framework is an adjustable standard 86 (Fig. 3) held in a socket 87 by a screw 88. The upper end of the standard carries a nozzle structure and ignition means which project through the door 12 of the heater. In the plate 13 on the door 12 is an observation hole providedwith a hinged closure 89 (Fig.

1). On the plate 13 is a nozzle-carrying plate 90 which is so mounted as to swing angularly for the purpose of adjusting the angular direction of the spray to cause it to impinge at the proper point in the bowl 15. The plate 90 swings about the axis of a sleeve 91 and is provided with arcuate slots 92 and clamping screws-93. The sleeve 91 is integral with the plate 13 and a bracket 94 (Figs. 3 and 7 secured to the standard 86.

The nozzle structure comprises a suitable means arranged to receive a supply of air and a supply of oil, the air being used to spray theoil. by aspiration, t hat is, the differential pressure between the atmosphere and the oil is in efiect increased by the aspirating effect of the escaping air. In the present nozzle, however, the reverse is true, the pressure of the air serving to repress the flow of oil under its own applied pressure.

The nozzle construction in the present instance comprises a cast head 101 (Fig. 7) having an axial threaded bore 102 enlarged at its lower end to form a chamber 103 and there screw threaded to receive a nozzle tip 104. The latter has a conical recess 105 formed fromthe inner face thereof and a short narrow cylindrical delivery hole 106. A threaded plug 107 screws into the upper portionof the bore 102' and is provided with Ordinarily nozzles of this type spray a tapered or rearwardly conical end 108 narrower than the taper 1051;} The-plug 107 i's-provide'd with an ,annularicliannel 109 "and passages .1110 which extend from the chafniel to the axial bore 111 ofthe "plu g,- t he passage 111 opening atithe 'tapered" 'end 108.- The head 101 has an oil inlet 112 andangair inlet 1'13 communi'cat; ing're'spectively with the oil channel-109 and the air chamber 103'. Both'conical parts are provided 'wi h right f'rustal bases which are in the present instance of the'same'v diameter as indicated at 114 and 114 Thus, the plug 107 may be screwed'tightly against the nozzle cap andwhen withdrawn therefrom it terminates' at successively greater cross section'- al areas of the conical recess: 105 and .may therefore be Subjected to different pressures according to itsposition. There will',a of course, be one pointw ere the annular. space 115.at thebase 114-bet" een the two tapered surfaces willbe equal in areato the opening 106. This is referred to position. By movingthe plug forward from this position this annular space becomes the issuing orifice for the air and by movingit the opening 106 becomes the issuing orifice. InI'the latter case'the tipof the plug will be subject to the air pressure within the space 115 and this air .pressure will repress the oil. 'When the opening 106 is the air orifice adjustment of the plug 107 will not vary thepressure on the oil exerted by the air. However, when the plug is in a position forwardof the transitional position the annular space 115 becomes the issuing orifice, and the pressure willbe less than the applied air pressure, thus permitting more oil to flow as the plug 1S II1OVQ(1 forwardly. It should be remembered, however, that the exact conditions above dcscribedare in practice varied, because a' portion of the orifice 106 is occupied by the stream of oil thus reducing its cross sectional area available for air delivery. The construction therefore provides for an adjustment of the positionof the plug 107 to vary the air pressure bucking the oil pressure and yet the differential pressure under which oil is emitted Wlll be small. This enables the maintenance of a high oil pressure in the system without the necessity ofemitting oil under a high pressure into the fire box. It further permits adjustment of the differential oil pressure at the nozzle without adjusting the pressure-producin g mechanism. The nozzle 14 is mounted on an extension 118 of the plate 90. Oil and air pipes 119 and 120 coupled to conduits 121 and 122, respectively, extend through the portion 118.

The flow of air and oil to the nozzle is controlled by a valve structure which has a'novel arrangement particularly related to the nozzle just described. The whole oil burning system herein described is of a type adapted to be frequently shut 011 and turned on to maintain an even temperature. Upon shutting as the transitional off the supply of-oil to the nozzle as is ordinari'ly one in other. burners, there will ree main-in the'nozzleLaJcertain quantit of oil. Although the combustion, in the fire ox will cease at the {same time, "there is ahiglrdegree of heat in the firev box which soon heatsup the nozzle. Ordinarily the flow;- of oil and'air I through the, nozzle keeps it relatively cool, but when the oiland air are shut 011 it is immediately subjected to heating action without a; cooling action and-will become hotter than when it is in use with combustion in the fire box. The-efiect of increased heat'on the nozzle would ordinarily serve to evaporate the fuelremaining therein leaving tar or residues in the nozzle which may carbonize therein. This would soon choke the nozzle, 7

making it ineffective and requiring. that: itbe cleaned frequently. To avoid this I provide a means for blowing out the residual oil in the nozzle upon shutting off the oil supply.

This is preferably'done by blowing out also theoil l1ne leadin tothe nozzle so that there 1s no creeping of oil therefrom into the nozzle. In Fig. 6 a construction is disclosed which 18 in eflecta two-wa ."valve connecting the nozzle 011 llne 121 eit er'with theroil supply or wlth an air supply. The valve structure comprises a casting 125 into which the oil and air conduits 121 and 122 are connected. 011 and air entry ports 126 and 127 are also prov1ded,there beingin the present instance two opposing posts 126 for oil and one port 127 for air on-(gye sides of the valve. structure. Butone used according to the desired connections made in the apparatus. The ports open respectively into an oil passage 128 and an air passage 129. In Figs. 1 and 2 it will be observed that one oil port is closed by a plug 130, while the other oil. portis connected to an oil conduit 131 extending from the oil pump ,41. An air supply pipe 132 '(Fig. 3) 1s connected into the air port 127. The valve casing 125 has a tubular stem 133 by which it is mounted in the part 1351 on the housing 10. The valve casing125 is bored at 137 in continuation of the bore of the stem 133. In the lower portion of thebore 137 is fixed a bush ng 137. The upper end of the bore 137 15 enlarged at 138, andscrew-threaded plugs139 and 140 are provided for the ends of the .two portions of different diameters. The plug 139 closes the passage at the outside of the casing, while the plug 140 serves as-a valve sea being provided'with an opening liil therethrough so that oil may pass. The 011 passage 128 leads into the chamber 138, and a port 142 leads from the bore 137 to the 011 conduit 121. A constantly open duct 143 connects the passage 129 to the air conduit 122. A valve means is provided which is operable to shut off the oil to the oil conduit and to permit the entry of air thereto to blow l the opposing ports need be i out the oil. A valve stem 144 slides in the The oil port 142 leading to the nozzle is be-' tween the oil supply port 141 and the air supply port-146. On said valve stem is a valve head 147 which is slightly smaller than the bore in order to leave an air space 148 about the head from end to end. The head 147 has a tapered seat-and-plug end 149 which closes the oil passage 141 in the uppermost position of the valve stem; and it has a similar end 150 which closes the air port 146 in the lowermost position of the valve stem.

To operate the valve a movable plunger 4 151 acts on the valve stem 144 through an impositive connection including spring means. A socket member 152 is fixed on the end of the valve stem 144, and in its socket an .expansible spring 153 is placed. Plunger 151 operates to move the stem by compression through the spring 153. The valve stem 144 is suitably packed and guided in the bottom of the extension 133 as indicated at 154 Be tween the stufiing box 154 and the socket member 152-is a second and lighter spring 156 which normally tends to compel the socket member 152 to follow the plunger 151 when the latter is withdrawn, whereby to open the oil valve.

To regulate the supply of oil and air to the nozzle 101, needle valves are dispensed with and an adjustable valve member is provided for each of the oil and air passages 128 and 129. Each comprises a plug 158 longitudinallyadjustable in the passages by means of their screw-threaded relation at 159 with the casing. The plug extends through a stufling box 160 and has an outer slotted end 162 for engagement by a screw-driver. The inner end of the plug terminates adjacent to the entry port and is notched as shown at 163. Varyingthe longitudinal position of the notch in front of the port 126 or 127 will vary the inlet opening. This construction is very advantageous, because as the plug is turned the edge of the notch serves to scrape the interior of the passage and to free it from collected dirt of any kind. Likewise, a half 1 turn on the screw plug will reverse the notch,

compelling the oil or air to clean out any obstruction which may have lodged in the notch.

Referring to the air supply leading to the nozzle 101, it has been set forth that the oil line and the nozzle are cleared of oil on shutting off the oil, by letting airblow therethrough. For this reason there is provided in the system a sufficient reservoir of air under compression to supply thev necessary air for clearing out the oil line after the air pump has stopped. The reservoir for air is also provided for the purpose of eliminating pulsations of the reciprocatory pump above described, which might otherwise be undesirably effective at the nozzle. Referring now to Figs..3, 4 and 5, an air reservoir 165 is preferably mounted on the top plate 61 of the housing 40 directly over the air pump 47. Thusthe pump outlet 66 discharges directly into the. chamber 165 to which the pipe 132 is connected as shown at 166 (Figs. 2 and 3).

The housing 40 contains suflicient lubricating oil to submerge the pump 47, gears 42 and 43, etc. This arrangement and the pump construction makes it likely that the air pump will suck a slight amount of'oil and deliver it with the air to the chamber 165.1 A constant air pressure is desired in the air chamber in order to prevent a change in the differential oil regulating pressure at the nozzle. For this reason a relief valve is arranged to permit the escape of excess air, thereby keeping the pressure constant. Because of the likelihood of oil gathering in the bottom of the reservoir the air relief valve is arranged to blow from the bottom of the chamber to carry off the accumulated oil. The valve is so arranged as to'blow ofi' into the housing 40 to return the oil thereto.

Any desired structure may be used for the relief valve, but the following is preferred. A hole 167 (Fig. 4) is tapped in the top 61 into which a valve casing 168 is threaded, the valve being contained within the reservoir 165. A chamber 169 having a seat 170 is formed upwardly into the valve casing.

Passages 171 communicate from the air reservoir 165 to the chamber 169. The passages 171 are arranged close to the level of the top 61 so that the liquid gathering in the chamber may flow into the valve. A valve head 172 and stem 173 are provided, the latter extend ing through the valve casing and having a nut 174 and spring 175 for yieldably holding the valve seated. The position of nut 174 of course determines the blow-oft pressure of the valve; Since it is desirable that this be fixed for proper operation of the burner, the adjusting nut is located inside of the air reservoir. This insures that it will not be tampered with during operation of the burner, and further because of its inaccessibility it in effect compels competent service to make an adjustment. This is an important feature in domestic oil burners.

The ignition means is shown in Figs. 7 and 7 Within the sleeve 91 is insulating material 176 which supports two conductors 177 and 178 having sparking points 179. The sparking points are located in the path of the oil spray issuing from the nozzle 101.

A safety device is provided for assuring that the burner will be rendered inoperative to supply oil to the combustion chamber when there is a failure of combustion. Such means is operative through an accumulation of unconsumed oil collected in a basin or covered chamber 180 (Fig. 3) in the bottom of the bowl 15, the oil entering through a hole 180*. Into the basin 180 there is tapped a pipe 181 leading to an axially tiltablc drum 182 (F gs. 1, 2, 3 and 3). The drum has a partition 183 therein so that oil may collect in but one side of the drum behind the partition in order to overbalance the same to tilt it. An elongated slot 184 at the top of the drum into which the pipe 181- projects both permits and limits the tilting of the drum. A mercury switch 185 carried by the drum is suitably connected into a circuit, later to be described. for the purpose of stopping the operation of the burner.

'Other well known safety devices and appliances may be used in connection with the foregoing as will appear more fully hereinafter in the diagrammatic representation of the controlling circuits and mechanisms.

Control mechanism The control mechanism is herein shown as arranged to be driven by-the burner motor, and preferably under the control of the main motor switch. An intermediate controlling nism, the latter being driven by the motor,

and being made responsive to a thermostatically controlled current.

The mechanical control is preferably made as a unit having a frame comprising the two opposing plates 195 and 196 (Figs. 8 to 11) connected by a web-plate 197 at the forward side. At the rear of the unit there is a shaft 1 198 carrying a worm wheel 199. The gear 199 meshes with a worm 200 (Fig. 3) on a shaft 201. Said shaft is connected by miter gears 202 to a shaft 203 (Fig. 4) The latter is driven from the shaft 44through a worm wheel 204 meshing with a worm 205 formed on" the periphery of the crank disk 45.

The shaft 198 drives the controlling'cam I shaft 206 which makes a half-revolution .to

. the control unit.

initiate combustion and a half-revolution to stop combustion. The shaft 206 is preferably made tubular and surrounds the shaft 198,

being rotatably supported thereon. The

210 which is provided with a tooth-engaging 'part 211 designed to be caught by the ratchet wheel to turn the disk. A tension spring 212 tends to swinw the dog into engagement with spring 212 is connected to both the dog 210' and the plate 213 and tends to hold the plate 213 in a position which may be described as advanced in the direction of normal rotation of the disk. The plate 213 carries a lug 216 projecting beyond the periphery of the disk 208 so that during rotation of the disk a stop means, later to be described, may move the plate 213 from its advanced position (Fig. 10) to its rear position (Fig. 11) relative to its carrying disk 208, this motion being efl'ecv tive to move the dog 210 out of engagement with the ratchet wheel, whereby to stop the rotation of disk 208. moving the dog includes a cam projection 217 on the plate 213, which cam is moved into a position wherein it operates to raise the dog against the tension of its spring 212 into a position free from engagement with the teeth of the ratchet wheel.

The present means for On the shaft 206 adjacent the disk 208 there is fixed a cam 218 (Fig. 8) having a circular periphery containing a recess 219 (Fig. 11) which is positioned on the periphery ata point opposite to the stopping lug 216. 'An

electric switch is incorporated into the device and so arranged as to be closed in all positions of the cam 218-except one, at which position a movable part enters into the recess 219 to permit opening of the switch. Thus, when said movable 'part' is permitted by the remainder of the mechanism to enter the recess, the switch is opened and the motor stopped.

Various constructions for mounting the i switch may be employed but thepreferable form comprises a plate 220 (Fig. 9) swinging on a fixed .pin 221 carried by the side plate 196. The plate 220 carries a mercury switch which is arranged in such a manner that it effects stopping of the main control shaft 198, in the present instance, it being connected into the motor circuit. The plate 220 carries a counterweight 222 tending normally to swing the plate to open the motor switch 222 as shown in Fig. 10.' A linkage is connected to the plate to tilt it mechanically against the counterweight, said linkage being arranged to be operated by the cam 218. The.

- bell crank 223224 also has a projecting heel 228 upon which pressure may be placed to raise the cam roller 227 out of the recess 219 thereby to close the switch 222, closing the motor circuit and turning the cam disk 218 through the dog and ratchet device (which is thrown in as indicated in Fig. 10). The cam 218 therefore revolves and moves its recess 219 out from under the roller 227. The motor switch. cannot be opened until the cam disk has made at least a complete revolution to return the recess 219 into a position to receive the roller 227.

The shaft 225 is a rock shaft held between the cone bearings 230 and 231, (Fig. 9) located respectively in the side plates 195 and 196. To the rock shaft is fixed a plurality of arms including an arm 232 (Fig. 9) having an adjustable counterweight 233, a downwardly projecting heel 234 arranged to press on the heel 228 of the bell crank lever 223224, a forwardly projecting arm 235 which carries an armature 236, and a rearwardly extending stop arm 237. The tilting of the rock shaft 2251's limited in one direction by the armature strikinga screw 236 adjustably fixed in the frame.

The stop means heretofore alluded to and employed as an obstruction in the path of the advancedly positioned lug 216 of the pawl and ratchet mechanism isa detent 238 (Fig. 10) depending loosely from the pivot pin 221 (Fig. 11) and drawn rearwardly by a light spring 239 secured to a pin 240 (Fig. 11)

on the side plate 196, the pin being right angular to provide a rear stop for the detent. The detent has a forwardly projecting lug 241 which terminates near. the end of the stop arm 237 on the rock shaft 225. \Vhen the rock shaft 225 isnormally tilted I by its counterweight 233 the arm 237 is lowered from its position in Fig. 11 to its position in Fig. 10. and it is then out of the path through which the lug 241 may swing about pivot 221. lock the detent 238 in fixed position. In its locked position (full lines Fig. 11) it is a fixed stop means to cause throwing out of the dog 210, whereas in its unlocked position (dotted lines Fig. 10) it yields to permit the lug 216 to pass without throwing out the dog 210, the detent 238'swinging into the position as shown in dotted lines 238 and 241 in Fig. 11.

Also upon release of the detent 238 through Thus the arm 237 may serve to the lowering of the stop arm 237, the dog 210 is automatically swung into engagement with the ratchet wheel through the efl'ect of.' its spring 212, the lug 216 and the plate 213 advance rotatively relatively to the plate 208 through the action of tlie'spring 212, and the plate 208 again rotates with the. main control shaft 198. In the initial advance of the lug,

216 to its dotted line position 216 in Fig. 11, the detent 238 is swung ahead of it into the dotted-line position indicated in Fig. 11 at position (dotted lines Fig. 11) while the arm 237 is raised even though the lug 216 has passed and thus. permits its return.

From the foregoing it will be. seen thatthere are certain positions of the arm 237 requisite for proper operation of the device. For a variety of reasons this is preferably controlled by an electromagnet 242 (Figs. 9, 10 and 11) acting on the armature 236 carried by the rock shaft 225. Current to the magnet is in part controlled by a switch device carried on the'cam shaft 206 and in part by thermostatic means to which the burner is made responsive.

Assuming the motor 25 to be stopped and the burner idle, the counter-weight 222 holdsthe parts in the'position shown in Fig. 10 with the cam roller 227 in the cam recess 219. Energizing the magnet 242 will cause the heel 234 to act on the heel 228'and thereby to 7 close the motor switch 222 and thus start the shaft 198as heretofore described. The dog being located at the lower side of its orbit,

the cam shaft 216 will rotate half a revolution until the lug 216 meets. its detent 238. During this period any program of operations requisite to initiate combustion is carried out, the several operations being performed in proper sequence through the action of the rotating cam shaft 206. In order to stop the cam shaft the arm 237 must be in locking position as regards the detent 238 at the time when the lug 216 meets said detent; and said arm 237 must be maintained in its raised locking position during the time in which the clutch is to be kept thrownout, that is while the burner is operating. The mere dropping of the arm 237 out of locking position allows the clutch to be thrown in automatically and the cam shaft again rotates half arevolution, during which suitable stopping operations of the burner parts may be effected in proper sequence by the rotation of the cam shaft. lVhen the recess 219 of the motor switch cam 218 comes around to the cam roller 227, the switch will open by the dropping of the roller 256 (Fig.

ma net being so arranged that it is energized.

whgn heat is demanded and deenergized when no heat is demanded. In the present instance there is employed a room thermostat of the well known type wherein one circuitis closed when the room becomes too' cold and another circuit is opened when the room hecomes too hot. Thus, above a maximum temperature no circuit is closed in the thermostat; between the desired upper and lower limitsof temperature control one circuit is closed in the thermostat; and below the minimum desired temperature, both circuits are closed in the thermostat. Such a thermostat is indicateddiagrammatically in Fig. 13 in which L and H represent adjustably fixed contact .points corresponding to the lower and higher temperature limits desired, and to which independent circuits are connected indent-ified respectively as cold and hot. A common wire J is connected to a thermal expansive element 245 which is electrically common to both circuits. The element is in efiect split at the movable end forming two branches which make successive contact with the contact points L and H as the temperature varies. The three conditions are .respectively indicated in (a), (b) and (c) in Fig. 13 corresponding to the room being (a) too cold, (1)) properly tempered between the desired limits, and (a) too hot.

In the diagram Fig. 14, the thermostat is generally designated 245, it being understood that it partakes of the character of the thermostat described with reference to Fig. 13

and having three possible internal conditions.

There is provided a low voltage electrical source indicated at 246, which in the present instance is'a six volt source, connected from one terminal by wire 247 to one side of the electromagnet 242. Wire 248 leads from the magnet to the J or common wire of the thermostat. On the cam shaft 206 (Figs. 8 and 9) there is an insulating drum 249 around which is a continuous metallic band 250. The band has alternate and diametrically opposite lateral projections 251 and 252 arranged so that one of them, 251, is on top when the recess 219 of the motor switch cam is on top. In the diagram (Fig. 14) the dotted line position of the ring lugs indicates the position of the ring after a half revolution of the drum. Three spring contacts 253, 254, and 255 respectively engage with the ring 250 and the lugs 251 and 252, these being securely fastened to an insulating strip 9) on the front connecting frame plate 197. Screws 257, 258 and 259 are used contact bar 254 t'o the cold circuit L of the thermostat; a wire 261 connects the hot circuit H of the thermostat and the contact bar 255; and a wire 262 connects the source 246 and the middle contact bar 253."

Diagram Fig. 14 represents in full lines the control device in the running position of the burner (Fig. 11) the electromagnet 242 being energized because contact H in the thermostat is closed and the circuit therethrough is completed by wire 262, contact bar 253,-ring 250, lug 252, bar 255, wire 261, thermostat contact H, common wire 248, electromagnet 242, wire 247, source 246. \Vhen the room temperature goes over the upper temperature limit, contact I-I opens whereupon the magnet. 242 is deenergized, the arm 237 drops through the dropping of the counter-weight 233, and the clutch automatically throws itself into engaging position to turn the cam shaft 206 including the drum 249 which carries the contacts 251 and 252. The ring and lugs on drum 249 move to the dotted line position of Fig. 14. Just prior to the recess 219 arriving at the cam roller 227 the contact bar 254 wipes the lug contact 251 but no circuit is completed through the magnet because contact L in the thermostat is open. Therefore the arm 237 remains down and the cam roller drops into the recess 219 to open the motor switch 222 and thus stop the entire apparatus. This condition continues until the lower limit of room temperature is reached. Thereupon closure'of the contact L energizes the magnet 242 and rocks the shaft 225, to close the motor switch, raising the roller 227 out of its recess 219 as an incident to the operation. This starts the motor and thus sets the cam shaft 206 in rotation, said cam shaft again causing the required starting operations to be performed according to the mechanisms associated with the cam shaft. After a slight rotation from the starting position the lug 251 recedes from the bar 254 and the magnet 242 is de-energized, but this does not take place until the recess in cam 218 has moved away from the raised roller so that the cam periphery holds the roller up and maintains the switch in closed position. As rotation continues the clutch lug 216 approaches the detent 238. The magnet being de-energized, the arm 237 is not in a position to lock the detent. However,'the lug 252 is arranged to make contact with the bar 255 prior to the arm 266 pivoted in the frame of the control device at 267. The arm 266- carries at its outer end a cam roller 268 which rides on a cam 269 rigid with the cam shaft 206. One

portion 270 of the cam surface is substantially radial, which permits the cam roller 268 to drop and the oil valve to open suddenly. The cam surface 270 is placed so that the oil valve opens just prior to the disengagement of the clutch. The cam 269 has an inner concentric cam surfaceor dwell 271 which permits the cam shaft to turn approximately one-eighth of a revolution in its burner-stopping operation without affecting the valve, after which a rise in the cam surface at 272 raises the roller to close the valve. The closing action of the valve is completed in about one-eighth of a revolution, after which the cam turns for approximately one-fourth of a revolution before the power is shut off through the motor switch 222. Thus the air pump continues in operation after the oil has been shut off and assures the blowing out of the oil line and nozzle, as heretofore described.

The supply of current to the sparking points 179 is primarily controlled by the motor switch 222, as indicated in Fig. 12, the supply of current to the igniter being cut of]? when the motor switch is opened. However, since the character of spark ordinarily employed is such as to interfere with the use of a radio receiver, means is provided for cutting out the spark when it is not necessary and. for automatically connecting it when it is required for proper operation of the burner.

The ignition circuit includes a mercury switch 280 (Fig. 9) which is carried by a lever 281 (Figs. 8, 9, 10 and 11) pivotally mounted on a boss 282 secured to the side wall 195. A screw 284 forms the pivot, and a spring 285 acting on a washer 286 places frictional pressure on the lever 281. The lever 281 extends forwardly and projects through the casing so that one may raise said end of the lever to open the switch. Friction holds the lever in raised position to maintain the switch open. On the rear end of the lever 281 is a downwardly extending arm 287 carrying a cam roller 288 arranged to be moved by a cam 289 on the cam shaft,

206. The cam 289 is similar to the cam 218 having one cam recess 290 (Fig. 11) arranged to lie at the top in the operat ng osition of the burner, and hence diametrical y opposite the recess 219 of the motor switch cam 218, which lies at the top in the idle position of the burner. Thus while the burner is in operation the notch 290 is so positioned that the ignition switch 280 may be manually opened, that is, roller 288 may enter the recess 290 of cam 289. Subsequent rotation of the cam 289 when the burner is being stopped will close the switch so that the ignition system will be effective in a subsequent starting operation.

A spring pressed plunger 291 (Fig. 3) on the housing 40 is arranged for manual depression of the armature 236 when the magnet is not energized. This enables one to start the burner independently of the thermostat circuit which, of course, will control the further action of the burner after being so started.

The remaining electrical devices and circuits of the oil burner are indicated in Fig. 12. The boiler or heater with which the burner is used is preferably provided with a well known safety control device indicated generally at 301 which is effective upon exccssive steam pressure or excessive rater temperature to shut off the burner independently of the room thermostat. This device is represented as containing a mercury tube switch 302 adapted to open on excessive heat. The mercury tube switch 185 is also arranged to open on accumulation of oil in the drum 182. Both these switches, together with the motor 25 and the cam operated switch 222, are connected in series in the order named to a power source 303 which in the present instance is 110 volt alternating current. The spark ignition is obtained through an induction coil having the primary coil 304 and secondary coil 305 from which the wires 306 lead to the spark terminals 179. One side of the primary coil is connected by wire 307 to one side of the motor 25 and the other side is connected by wire 308 to the other side of the motor through the optionally cut-out and automatically cam-closed ignition switch 280. The low voltage source 246 of Fig. 14 of the thermostat circuit as above mentioned is a six volt circuit obtained from a transformer connected to the main AC line. In the present instance two similar transformers 309 are used and are connected parallel, this arrangement being chosen so that when a 220 volt source is available the two transformers may be connected in series. The transformers are connected by wire 310 to one side of the power source 303, and by the wire 311 to the other side at a point between the boiler control switch 302 and the oil control switch 185. This point is chosen for connection of the transformer circuits because in the instance when the heater becomes excessively hot while the room thermostat is still demanding heat, the boiler control switch 302 cuts outthe motor and also the control current.

Assuming the parts to be in the position shown in Fig. 11, opening of the switch 302 cuts out the transformers, and thus deenergizes the magnet 242, so that the clutch lug 216 is released and the clutch thrown in.

However, the cam shaft 206 remains at rest,

motor begins running and turns the cam shaft 206 through a half-revolution, thus bringing the recess 219' into register with the roller 227. If'the room is still cold, there is a circuit through the magnet 242 as follows Source 246 (the transformers), line 262, bar 253, ring 250, lug 251, bar 254, wire 260, contact L, wire 248', magnet 242, source 246. Hence the magnet will prevent the roller 227 from dropping into the recess 219, and the motor will continue running. The cam shaft 206 will therefore make another half-revolih tion to complete a cycle 'during which the starting operations are initiated. This is called recycling. In the initial stage of the recycling, after'the lug 216 has passed its unlocked detent 238, the electromagnet circuit is broken so that arm 238 may return to normal obstructing position. Just prior to the completion of the cycle of cam revolution a circuit is established through lug 252 and contact H in the thermostat to energize the magnet, to lock the detent, and thus to throw out the clutch.

The above operation has been described with reference to the operation of the boiler safety switch 302, but it is obvious that the same operation will also take place when the source of power 303 fails. The whole arrangement is thus sufficient to protect the burner from a hazardous condition on failure of power, because on return of power the burner,

although stopped in the operative osition by the failure, will be recycled throug its starting stage to ensure that combustion is initiated.

The function of the control mechanism to cut off the burner when there is a break in the thermostat circuit should be clear from the foregoing description. Under such conditions the magnet cannot be energized, the clutch cannot be thrown" out and the cam shaft will always rotate until the motor switch cam roller 227 drops into its cam recess 219 whereupon the motor will stop. Nothing can operate to start the motor except the energization of the magnet, or the manual depression of the plunger 291. In the latter instance the cam shaft will turn for one cycle and then stop automatically.

Although the motor control mechanism has been shown specifically as moved directly by the motor 25, it is to be understood that the arrangement is not limited to such a driving means. The motor is under control of the motor switch, hence the motive power for the control mechanism may be regarded as under the control of said switch. For this reason the driving shaft 198 is to be considered broadly as a secondary source of power, or

rather as a source of motive power for the control mechanism, and the clutch mechanism is to-be considered broadly as a power cut-01f between said source and the control mechanism, said power cut-off having a power-onand a power-01f position corresponding respectively to throwing in and out the dog of the clutch.

The burner is adapted for 'two types of installation, one wherein the oil is pumped,

and the other wherein air pressure is utilized to force oil from a tank. The oil-pumping system has been describe'd'only generally as including the oil pump 41, but it involves further an intake pi e 315 (Figs. 1 and 3),

an outlet pipe 316 igs. 1,2 and 3), and a constant pressure relie or by-pass valve 317 of well known construction, which delivers the excess oil supplied by the pump through a return flow ipe 318 back to the initial source. Oil under the pressure at which the valve 317 is set flows through the pipe 131 as heretofore described. The contlnuous flow of oil obtained by this arrangement prior to the opening of the oil line to the nozzle allows all air bubbles to be removed from the oil stream so that the nozzle line upon opening of the valve 125 can be tapped into a completely fille'd air-free oil-flow. This prevents delivery of a mixture of oil and air to the nozzle which causes an undesirable sputtering. and frequently an extinguishment of the flame within the heater.

When the oil pump is not to be used, the air chamber 165 on top of the burner housing may be dispensed with, if desired. Such a modified use of the apparatus is shown in Fig. 1

wherein 61 represents the top of the housing, heretofore described with re erence to Figs. 4 and 5. The air delivered from the pump outlet 66 is carried directly by a conduit 320 to an air chamber 321 on a fuel pressure tank 322. An oil line 323 runs from the bottom of the tank to the oil valve casing 125. An air line 324 runs from the chamber 321 to the valve structure 125. This construction prevents pulsations of the air pump from being felt at the nozzle and also allows any oil which may be pumped with the air to be discharged into the tank and mixed with the fuel oil. A relief valve 325 is also placed on the air reservoir 321 to maintain the air pressure therein constant in the same manner as desired when the air chamber 165 is employed.

The operation of the apparatus shown in all of the views except Fig. 1 maybe briefly summarized as follows, assuming that the burner is idle, the control mechanism being in the position shown in Fi 10, and the ignition switch 280 being he (1 closed by the cam 289: When the temperature in the room in which the thermostat 245 is located falls below a predetermined minimum, the electrorelief or byzpassvalve 317; the air pump begins to'buil up air pressure in the reservoir 165 (air flowing through the air line 122, and

'a negligible quantity of air escaping through the oil line); and the cam shaft 206 begins to turn. By the time the cam shaft has nearly completed a half revolution, the air pump has built u suflicient pressure in the reservoir 165, an the roller 268 (Fig. 10) drops onto the dwell 271 of the oil valve cam 269, thereby opening the oil supply port 141, whereupon oil flows to the nozzle, where it is ignited by the are between the points 179. As the cam shaft 206 completes a half revolution the clutch is thrown out, thus leaving the control mechanism in the position shown in Fig. 11. By reference to Fig. 11, it will be seen that the dog 210 lies on the projection 217 and that the tension of the spring 212 (which is stretched between the dog 210 and the plate 213) holds the lug 216 on said plate pressed against the detent 238. l Vhen the temperature in the room containing the thermostat 245 rises to the predetermined maximum, the electromagnet 242 is deener gized, whereupon the counterweight 233 lifts the armature 236 and swings the stop arm 237 down below the arm 241 of the detent 238, whereupon the spring 212 is permitted to turn the plate 213 clockwise (as viewed in Fig. 11) to withdraw the lug 217 from beneath the dog 210, the detent 238 yielding tothe right to allow of such movement of the plate 213. Shortly after the cam shaft 206 has commenced to turn by reason of the throwing in of the dog 210, the cam surface 272 of the cam 269 closes the oil supply port 141 and allows air to flow through the port 146, the air passage 148 and the air port 142 to the oil line until the pressure in the reservoir 165 is reduced to atmospheric pressure, thus blowing out all the oil in the oil line 121 and the nozzle. As the cam shaft 206 completes a half revolution the recess 219 arrives under the roller 227, whereupon the weight 222 places said roller in said recess and tilts the motor switch 222 into the open-circuit position, whereu on the motor stops, leaving parts in the position shown in Fig. 10.

With the form of oil supply means shown in Fig. 1, the operation is substantially the same as that just described. \Vhether one or the other form of oil supply means is used, the opening of the oil valve 149 (Fig. 6) is timed to occur when suflicient air pressure has been built up in the reservoir 165 or 321, as the case may be.

It will be seen that the control mechanism herein disclosed is of such character that the necessary program of operations required in through in proper order and time relation.

The arrangement herein shown of the fuel discharge means, the combustion bowl and the air supply means is claimed in a divisional application Serial No. 90,452, filed February 25, 1926.

I .claim as my invention:

1. A control device adapted for operation by a motor operated oil burner for the purpose of controlling said burner comprising, inv combination, a power shaft arranged to be operated directly by the burner motor, a control shaft, a clutch connecting said two shafts, means under electrical control and positioned to throw out said clutch, mean's positioned on said control shaft to cause said first means to disengage the clutch at a predetermined position of said control shaft, a switch to control the motor of the burner, means on said control shaft permitting free operation of said switch in one position of the shaft and compelling closing of said switch in other positions of the shaft, said opened position of the switch occurring while the control shaft is opcratively connected to the burner through said clutch, means tending normally to open said switch whereby it opens automatically when permitted for the purpose of stopping the motor and the control shaft, a room thermostat, and means operatively arranged to close the switch from said thermostat when heat is required, whereby the control shaft rotates to a position to throw out the clutch, the switch meanwhile being held in closed position, said electric clutch-coutrolling means being operatively associated with the thermostat to permit engagement of said clutch when heat is not required whereby the control shaft rotates to permit opening of the switch by the means tending normally to open. the switch. I

2. In combination, a motor operated oil burner, a thermostat, a mechanical motive device arranged to move for starting the burner into operation, said device being also arranged to move for stopping the burner, said device including self-stopping mechanism, a clutch connection from the burner to the motive device, said self-stopping mechanism being operative upon the clutch to disengage the same, said mechanism being affected by the thermostat to throw in said clutch to start the device on its burner stopping motive action, an electric switch controlling the burner motor and arranged to be operated by the motive device to stop the burner motor, said switch being arranged also to be closed-by the thermostat to start the motor.

3. In combination, an oil burner motor, a thermostat to control the starting and stopping of the motor, a control mechanism operable to apredetermined extent in starting the motor and in stopping the motor, said mechastarting or stopping the apparatus is carried rect control of the electrically nism including a. motor switch, the position of which is in part controlled by said mechanism, a power connection between the motor and the control mechanism, said thern'iostat being arranged to close the switch to start the motor and the control mechanism, and being further arranged to control the power connection for stopping and starting the control mechanism during operation of the motor.

4. In combination, an oil burner motor, a

thermostat to control the starting and stopping of the motor; a control mechanism operable to a predetern'iined extent in starting the motor and in stopping the motor, said mechanism including a switch to control the motor, the position of said switch being controlled by the position of the control mechanism, a power connection between the motor and the mechanism, said thermostat being arranged to start the motor initially to move the control mechanism through said power connec-, tion, and being further arranged to control the power connection for stopping and starting the control mechanism during operation of the motor.

5. An automatically controlled oil burner comprising, in combination, an electrically operated burner, a mechanical controlling motive device for the burner, and a motive power source for said device. under the dioperated burner so as to be on and olt' with said burner. said device including a control means for said source operative to cut in and out said source during operation of the burner. a thermostat responsive to the burner. and means responsive to said thermostat for controlling said power controlling means and also the electrically operated burner.

(i. In combination, an oil burner motor. a switch to control said motor. a thermostat, a control mechanism operative upon the switch to control the motor and to institute starting and stopping operations of the burnor said motor being responsive to the thermostat for starting the motor. and a source of power for the control device. said source being dependent upon the power controlled by the main motor switch. and means actuated by the control mechanism responsive to said thern'iostat to control the transmission of power from said source to the mechanism.

7. A thern'iostatic control for a rotary control device movable in a cycle between two positions for starting and stopping an oil burner comprising, in combination. a three wire two circuit thermostat arranged to have both circuits closed below a minimum temperature, both circuits opened above. a maximum temperature, and a certain circuit closed at the intervening temperatures, an electromagnet and an electrical source connected in' Serise with the common wire of the thermostat circuits, a switch device ope 'ated by the rotary device to shift the connection of the free terminal of the source to one or to the other of the thermostat circuits, the arrangement being such that upon the temperature decreasing to the minimum the magnet is energized, whereupon movement of the rotary device to its second position operates upon the switch means to shift the electromagnet to the other circuit, whereupon the magnet is again energized while the device occupies its second position and until the temperature reaches a maximum, whereupon de-energization of the magnet causes the parts to assume the initially described position.

8. In combination, a thermostat, an electromagnet energized by current passing through said thermostat when heat is required to raise the temperature of the thermostat to a predetermined degree, an oil burner motor arranged to be controlled by I the thermostat, an electric switch for the motor, said switch being arranged to be closed on energization of the magnet, a control mechanism to institute starting and stopping operations of the burner including the opening of said motor switch during the period of de-energization of the magnet, said mechanism having means therein to hold.- said switch closed and to open it automatically at a predetermined position of the mechanism, a power transmitting clutch between the motor and said mechanism, and means operable during energization of said magnet to effect disengagement of the clutch at a second predetermined position of the control mechanism.

t). In combination, a thermostat, an electromagnet energized by current passing through said thermostat when heat is required to raise the temperature of the thermostat to a predetern'iined degree, an oil burner motor arranged to be controlled by the thermostat, an electric switch for the motor, said switch being arranged to be closed on energization of the magnet, a control mechanism to iustil ute starting and stopping operations of the burner including the opening of said motor switch during the period otdeenergization oi the magnet, said mechanism having means therein to hold said switch closed and to open it automatically at a predetermined position of the mechanism. a power transmitting clutch between the motor and said mechanism. and means operable during energizatipn of said magnet to ellect disengagement ot the clutch at a second predetermined position of the control mechanism, and means in the control device to break the circuit to the magnet for an interval durin the movement of the mechanism from the set ond to the tirst predetermined position. I it). In combination, a thermostat, an electromagnet energized by current 1' assing through said thermostat when heat is required to raise the temperature of the ther loo

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