US2805652A

US2805652A - Water level responsive controls for combustion apparatus

Info

Publication number: US2805652A
Application number: US352500A
Authority: US
Inventors: Minor W Stout
Original assignee: Individual
Current assignee: Individual
Priority date: 1953-05-01
Filing date: 1953-05-01
Publication date: 1957-09-10
Anticipated expiration: 1974-09-10

Description

3 Sheets-Sheet l ySept. 10, 1957 M. w. sToUT WATER 4LEVEL. RESPONSIVE CONTROLS FOR COMBUSTION FFRA'IUS Filed May 1, 1953 INVENToR MmqrW Stout BY m4,

his ATTORNEY .Hmmm

Sept. '10, 1957 M. w. srou'r 2,805,652

WATER LEVEL RESPONSIVE CONTROLE RoR ooMBUsTroN APRARA'rus Filed May 1, 1953 `SASheelLS-Sheet 2 iai/l I Fig. 2.

INVENTOR BVE E. his ATTORNEY.

Minor-'W Stout Sept. l0, 1957 M. w. sTOLUVT 'A 172,805,652

WATER LEVEL REsPoNsIvEcoN-TRQLS FORV CQMBUSTIONAPPARATUS j Filed May 1, 1955 v 1 INVENTOR C Minarmsfwt y United States Patentv 2,805,652 Patented Sept. 10, 1957 hfice WATERLEVEL RESPONSIVE CONTROLS FOR COMBUSTION APPARATUS Minor W. Stout, Webster Groves, Mo. ApplicatiorrMay 1, 1953, Serial No. 352,500 V1- Claim. (Cl. 122-448) This invention relates to improvements in controls for combustion apparatus. More particularly this invention relates to improvements in controls that eration of combustion apparatus.

It is therefore an object of the presenti invention lo provide an improved control that assures safe operation of combustion apparatus.

Most boilers have indicators or controls that respond to the level of the water in the boiler. Where the controls are automatic, it is essential that the' controls do not become 'stuck in a position that indicates a full supply of water for the boiler at a time when that supply is insuflicient. If this were to happen, the flame in the` boiler could readily destroy the met-al walls-.of the boiler. Where the operators of the boiler regularly flush out the boiler and keep it free of sludge, the controls usually work.

However, it is known that the operators of' boilers areA not as regular in` their cleaning of the boilers as -they could be and that sludge accumulates in a great number of boilers. That sludge can interferewith the operation of thelow water controls and cause them tofstick in a1 position which indicates a full supply of water in the boiler even though the supply of water is low. This is dangerously objectionable. The present invention obviates this objection by providing a low water control that is strongly resistant to sticking and which will cause the makeup water valve to open if it sticks. This is desirable because the boiler cannot then be injured -because of false indications of the low water control. It isttherefore an object of lthe present invention to provide a low water control that is Astrongly resistant to sticking and which will energize the makeup water valve if it does stick.

The present invention makes this possible by utilizing a light-sensitive cell in the low water control, and by using a float in the water gage .of the boiler to selectively intercept light directed toward that cell. If the level of the water in the boiler becomes low enough for the float to intercept the light to the light-sensitive cell, that cell will energize the makeup water valve and assureV replenishment of the water in thefboiler. The float will be strongly resistant to sticking and will only stick in the water gage if the sludge in the boiler becomes excessive. However, before the sludge in the boiler can become heavy enough `to make the float stick, that sludge will render the water in the water gage opaque andl will cause the makeup water valve to open and introduce freshwater into the boiler. The introduction of. the fresh water will veither dilute the sludge in the boiler to the extent that the water in the water gage become transparent or the water from the makeup water valve will till the boiler and preventI further generation of steam. The consequent cooling of the area being heated will lead to prompt investigation and prompt cleaningV of theA boiler. lnk either event, the boiler will be protected against damage. It is therefore anv object of the` present invention toprovide al low water control which has a*y light-sensitive cell adjacent the water `gage of a boiler and which has a float to selectively interassure safe opcept light directed toward that cell as the level Iof the water in the boiler varies.

The control provided by the present invention has a light-sensitive cell to control the operation of the combustion apparatus, and that cell will shut off that apparatus if the water level in the boiler falls below a predetermined value. The light-sensitive cell that shuts off the combustion apparatus is disposed below the light-sensitive cell that controls the makeup Water valve. With this arrangement, the ylight-sensitive cell that controls the makeup water valve will normally assure the maintenance of an adequate supply of water for the boiler, but if for some reason that cell is not able to do so, the lower lightsensitive cell will shut off the combustion apparatus. The float that can interrupt the light to the light-sensitive cells will be long enough so that when it is in register with the cell which can shut olf the combustion apparatus, it will1 also intercept light to the cell which controls the makeup water valve. This is desirable since it will keepl water flowing into the boiler and may make it possible for the combustion apparatus to cycle again. However, if there is a serious leak in the boiler and the ply is unable to raise the level of the water in the boiler sufficiently to raise the float, the owner of the boiler will be assured that no explosion can occur.

Other and further objects and advantages of the present i invention should 'become apparent fromv an examination of the drawing and accompanying description.

In the drawing and accompanying description, a preferred embodiment ofthe present invention is shown and described but it is to be understood that the drawing and accompanying description are for the purpose of illustration only and do not limit the'v invention and that' the invention will be defined by the appended claim;

In the drawing.

Fig. 1 i-s a schematic diagram of the control circuit provided by the present invention,

Fig. 2 is a view of the basic amplifier circuit and lightsensitive cell used therewith inthe control circuit of the present invention,

Fig. 3 is a front elevational view of a combustion head which can be controlled by the circuit of the present invention,

Fig. 4 is a side elevational View ofy an electrically responsive makeup water valve,

Fig. 5 is a partially sectioned side elevational View of a header and water gage for a boiler and of light sourcesand light-sensitive cells used with that water gage, and

Fig. 6 is a sectional view of the water gage and one light source and light-sensitive cell of Fig. 5.

Referring to the drawing in detail, the numerals 10 and 12 denote the terminals of a preferred form of control circuit provided by the present invention. These terminals can be connected to a suitable source of electricity, as for example, one hundred and fifteen volts alternating current. The terminals are connected toa main switch that has

contacts

14 and 16. This switch will preferably be manually operated and when it is operated', the circuit is completely disconnected from the source' of electricity. Two

fuses

18 and 20 are connected in the lines' extending from the

contacts

14 and 16 of the main switch. A switch 22 is provided which will open whenever the level of the water in the boiler or other heat absorbing device falls rbelow a predetermined value. This switch will preferably be electrically responsive and will automatically operate whenever the level of the falls too far. A fuel pressure switch 24 is provided that' will respond to decreases in the pressure of the fuel supply to open the circuit. This switch will be' a pressureresponsive switch of standard design and willV have the pressure-responsive portion thereof inj communication y with the fuel supplied to the combustion-apparatus under makeupwater sup-v water in the boiler 200'A 3 the control of the circuit provided `by the present `invention. A lead extends from the switch 24- to a scanner 26 which is shown in detail in Fig. 2. rlie lead 27 extends rom the fuse 18 to that scanner. Two leads 29j and 31 extend from the scanner 26, and the lead 29 is directly connected to the lead 25 at the junction 23 within the` scanner 26. A junction 28 is provided in the lead 29 and a junction `30 is provided in the lead 31. These junctions connect the coil 32 of a relay across the leads 29 and 31.` That relay has an armature 34 with spaced

contactors

42 and 44 thereon. The contactor is movable by the'coil 32 into engagement with the spaced contacts 36 of that relay, and the contacter 44 is movable to selectively bridge the spaced contacts 40 and the spaced contacts 3S. The armature 34 will normally be in the i position shown in Fig. l and will hold the contacter 44 in bridging relation tothe spaced contacts 4, but will respond to energization of the coil 32 to move the contactor 44 into bridging relation with the spaced contacts 38 and will move the contacter 42 simultaneously into bridging engagement with the spaced contacts 36. The upper contact 36 `is connected to the fuse 18 `by the junction 35 and the upper contact 38 is connected to the fuse 18 by the junction 37.`

The primary winding 46 of a transformer is connected between the lower contact 40 of the relay and a junction 92 in the conductor 29. The secondary winding 48 of that transformer has one end thereof connected to one of two spaced electrodes 50 and has the other end connected to the other of those spaced electrodes by the coil 52 of a sensitive relay and bythe lead 51. The armature 62 yof the relay carries contactors 58 and `6), andA the contactor 58 selectively bridges spacedcontacts 54 and contactor 60 selectively. bridges `spaced contacts 56. When the coil 52 isenergized the armature 62 will move upwardly and cause the

contactors

58 and 60 to bridge the spaced

contacts

54 and 56 respectively.` The right hand contact 54 is connected to the fuse 18 by way of junctions 55, 53, 35 .and .37; and the right hand contact 56 is connected to the fuse 18 by the junctions 55, 53, 35 and.37.` The lefthand contact 54 is connected to an electrically responsive valve 64 and through that valve to the junction 92 in the lead 29. The valve 64 is the starting pilot valve. The lefthand contact 56 is connected by a junction 67 to a relay 68 for the blower motor of the pilot. The other side of the relay 68 is connected to the junction 92 in the lead 29.` The bottom contact 38 is connected to an electrically responsive valve 66 4which has the other terminal thereof connected to the junction 92 in the lead 29. The valve 66 is the running pilot valve and supplies fuel to the pilot nozzle during running conditions. The Contact 36 of the relay which has the coil 32 is connected through the junction 67 to the relay coil 68.

A manually set main fuel valve, which is commercially available, is denoted by the numeral '70, and one terminal thereof is connected to the lead 31 by way of the

junctions

69 and 30. The other` terminal of that valve is connected to the lead 29 at the` junction 92.` A low lire blower relay for a blower motor is denoted by the numeral 74 and one terminal of that relay is connected to the junction 92 of lead 29. i The other terminal of that relay is selectively connected to the junction 69 of the lead 31 by a normally open steam pressure switch 72. This switch will preferably be a steam pressure-operated switch commercially known and available as a Pressuretrol switch. An electrically responsive low tire main fuel valve 78 is connected to the junction 92 of lead 29 and is; selectively connected to the junction 69 of the lead31 by the switches 72 `and 76. The switch 76 is an air-pressure switch that will respond to air pressure generated by the blower controlled by the relay 74. A high re blower relay 82 which controls the blower of still another nozzle of the combustion apparatus with which the present control is` used is denoted by the numeral 82. One terminal of this relay is connected to the junction 92 lil of lead 29 and the other terminal is connected to the junction 69 of the lead 31 through the

switches

72, 76 and 80. The switch will preferably be a steam pressure-operated switch which is commercially known and available as a Pressuretrol switch. An air pressure switch 84 extends between the switch 80 and the switch 86, and the switch 84 is an air-pressure switch which will be operated by the air-pressure from the blower controlled by the relay 82. The switch 86 is a thermally responsive switch that is controlled by temperatures exteriorly of the building being heated by the combustion apparatus. The switch 86 is normally in the position shown but will automatically shift to its other contact in periods of abnormally cold weather. The numeral 88 denotes an electrically responsive valve for the regularly used fuel of the combustion apparatus, and it is referred to as the regular main fuel valve; and the numeral 90 denotes an electrically responsive valve for the alternatively used fuel of that combustion apparatus, and it is referred to as the alternate main fuel valve.

The scanner includes a primary winding 94 of a transformer, and that winding is connected to the leads 2S and 27. A low voltage secondary winding 96 is provided for the transformer, and that Winding supplies the current for the lament of a triode 100.` A high voltage sec ondary winding 98 is provided for that transformer, and one end of that winding is connected to a condenser 108. The condenser 1081is connected to the grid of the triode 100 through a grid leak 106 and is also connected to the cathode of a light-sensitive cell 110. The anode of the light-sensitive cell is connected to a tap 111 on the high voltage secondary winding 98. The cathode of the triode 100 is connected to a tap 102 on the high voltage secondary winding 98. A lead 104 connects the cathode to oneside of the filament of the triode 100. The plate of the triode 100 is connected to the other end of the high voltage secondary winding 98 through a relay 112 and a resistor 114.` A condenser 11.6 is connected in parallel with the serially-connected relay 112 and resistor 114. The relay 112 has an armature 118 that responds to energization of the relay 112 to connect the lead 31 with the lead 27. The triode 100, the light-sensitive cell and the condensers, resistors and relay associated there with constitute a scanner which can shut off the combustion apparatus whenever the flame of the combustion apparatus is extinguished However, that scanner will permit operation of the combustion apparatus under the control of the steam pressure-operated switches whenever the light-sensitive cell 110 sees a flame.

When the

contacts

14 and 16 of the main switch arc closed, current will ow through the primary winding 94 if the normally-closed switches 22 and 24 are closed. This current will cause the secondary Winding 96 to heat the iilament of triode 100, and will cause the upper end of the secondary winding 98 to become successively` positive and negative with respect to the lower end of that winding. During the positive half cycles, when the upper end of winding 98 is positive relative to the lower end of that winding, the grid of triode 100 will be more positive than the cathode of that triode; and grid current will flow. This grid current will create a voltage drop across the resistor 106 that will bias the` triode to cut ott; and condenser 108 will maintain that bias and prevent the flow of plate current during the negative half cycles when the upper end of winding 98 is negative relative to the lower end of that winding. Grid current will again ow on the succeeding positive half cycles, and if any of the grid bias is lost during the negative half cycles because of leakage through the condenser 108, the ow of grid current on the positive half cycles will restore the grid bias. Accordingly, until the light-sensitive cell 110 sees a flame, the triode `100 will be biased to cut off and no plate current will flow to energize relay 112.

When the lght-sensitive cell 110 sees a arne, that cell will conduct current on the negative half cycles, and

the current flowing through the cell 110 will discharge condenser 10.8 and thus reduce the bias on the grid ofv triode 100 to ,a value that will permit plate current to llow through triode 100; That plate current will energize the relay 112 and pull the armature 11,8'into circuitclosing position. The plate current will also charge condenser 116 to the value of thevoltage drop across relay 112 and resistor 114, and on the positive half cycles that condenser will partially discharge through that relay and resistor and keep the relay 112 energized. The time constant of condenser 116 and resistor 114 will be great enough to maintain an energizing current flow through relay 112 until the plate current again flows in the next negative half cycle. Hence, as long as the light-sensitive cell 110 sees a llame, the relay 112 will be keptv energized and armature 118 will be held in closed circuit position. However, when the cell 110 fails to see a llame it will be unable to conduct current, and a bias will be generated on the next positive half cycle that will bias the triode 100 to cut olf. Thereupon the relay 112 will become de-energized, and armature 1'18 will move to circuit-opening position.

The numeral 120 denotes a cylinder which is' part of a combustion head for combustion apparatus such as is shown in my application for Combustion Apparatus, which was filed May 1, 1953, and which 'bears Serial No. 352,498. That cylinder has an opening in one side thereof and a tube 122 is secured to the cylinder adjacent that opening. The tube 122 may be secured to the cylinder 120 by welding or other suitable means. The scanner 26 is mounted on the outer end of the tube 122 and the light-sensitive cell 110 is in register with the tube 122. Consequently, the llame which is vcreated by the combustion head `of which the cylinder 120 is a part can be seen by the light-sensitive cell 110, The cylinderl 120 cooperates with a cylinder 124 to deine a nozzle for high lire air, and the cylinder'124 coacts with a cylinder 126 to define a nozzle for the pre-mixed gas and air of the high lire. The cylinder 124 has an inwardly directed ilange at the end thereof which coacts with the exterior of the cylinder 126 to define a nozzle of predetermined' cross-section. The tube or cylinder 126 has an inwardly directed ange which coacts with the exterior of a cylinder 128 to define a nozzle for the premixed gas and air of the low fire provided by the combustion' head. The cylinder 128 cooperates with the pilot nozzle 130 to dene a nozzle for low re air. A nozzle for uid fuel, such as `oil or powdered coal, is disposed in the center of the pilot nozzle 130, and it is denoted by the numeral 132. Suitable pipes and ducts, not shown, are provided to supply gas to the low lire, high fire and pilot nozzles and to supply oil or powdered coal to the nozzle 132. The combustion head disclosed in Fig. 3 is an efficient and effective source of heat, but the control provided by the present invention could be used with other combustion heads, andthe combustion head of Fig'. 3 is for illustrative purposes primarily.

A rod 134 of stainless steel or other corrosion resistant metal extends through the wall of the cylinder 12) and extends adjacent the pilot nozzle, the low re nozzle and the high lire nozzle. The rod 134 isv supported by a mounting 136 which is carried by the exterior of the cylinder 120. The rod 134 will act as a` llame rod and will respond to either the pilot, the' low tire or the high re to become hot enough to evolve light. In addition, that llame rod will cause the products' of combustion which are adjacent that rod to assume a characteristic orange color. Where the pilot nozzle alone is operating, the innermost end of the ame rod 134 will become red and the pilot flame will assume the characteristic orange color. When the low fire is burning the rod 134 will have a section of red heat that is as long as the combined length of the rodv in the pilot llame and'in lthe low re llame. Both the pilot and low lire flames willv have the characteristic orange color; When thehigh ltire is` f the pilot nozzle 130 and which can 'cell 170. Moreover,

also operating, the red hotsection of the rod 134 will extend from `the pilot flame through the low lire flame to the high lire flame, and all three ames will assume the characteristic orange color. the combustion head so it is in register with the lightsensitive cell throughout the' portion that will be heated to a red heat by the three llames. Moreover, the portions of those llames which are adjacent the llame rod 134 will also be in visual communication with the light-sensitive cell 110;. As a result, the cell 110 will see a llame of distinctive orange color and will see a red hot llame rod whenever the pilot or the low tire or the high lire is operating. The presence of the llame rod is desirable for two reasons; rst, it makes certain that when a llame is in the combustion head it will provide a visible target for the light-sensitive cell 110 irrespective of the color or composition of the flame, and second it will convert the llame to` a characteristic and distinctive color that will be constant irrespective of variations in pressure and largely irrespective of changes in the composition of the fuel.

The numeral 138 denotes insulators which extend through openings in the wall ofthe cylinder 120. These insulators carry the electrodes 50 which extend toward draw an arc between them to ignite the pilot. The insulators 138 are sealed to the cylinder by mounting seals 140, and leads 49 and 51 are connected to the electrodes Sil.

The numeral 142 denotes a line which extends between a source of water, such as a water main, and the boiler or other heat absorbing device 200. This line will provide' make-up water for the boiler or other heat absorbing device. An electrically responsive valve 144 is provided inthe line 142, and that valve is spring biased to open position. Whenever current flows through the ycoil of the valve 144, that valve will close and halt further introduction of make-up water into the boiler or other heat absorbing device.

The numeral 146 denotes a header for the boiler 200 and that header has an L extending toward the boiler, and it has a nipple the L being denoted by the numeral 148 and the nipple being denoted by the numeral 150. The L 148 is suitably connected to the boiler 200 by piping 202, and the nipple 150 is suitably connected to the boiler 200 by piping 204. A number of drain lcocks are denoted by the numeral 152, and those drain cocks are mounted ron the side of the header 146. The header 146, the L 148, the nipple 150, and the drain cocks 152 are of standard and usual design. A water gage 154 is supported by the header 146 through the medium of shut olf valves 156 and nipples 158. The nipples 158 and the shut olf Valves 156 selectively place the water gage 154 in communication with the water in the boiler. A drain cock 160 is provided at the bottom of the lower shut olf valve 156 to facilitate draining of the water gage 154.

A hood 164 is mounted adjacent the water gage 154 and that hood contains

light sources

166 and 168. These light sources can be luorescent lamps or incandescent lamps or other customary and well known sources of light. and they each direct light through the water gage 154 and the water therein. A light-sensitive cell 170 is disposed on the opposite side of the water gage 154 from the light source 166 and it is in register with that light source. A light-sensitive cell 172 is disposed on the opposite side of the water gage 154 from the light source 168 and it is in register with the light source 168. A hood 174 encases the light-

sensitive cells

170 and 171 is disposed between those cells. A baille 167 is disposed between the

light sources

166 and 168. The

bales

167 and 171 and the two hoods, 164 and 174, keep the light from the source 166 from striking the cell 172 and keep the light from the source 168 from striking the The rod 134 is disposed in The source 166 is disposed above the source 168 172; and a baille,

those hoods keep light from .other sources from striking the

cells

170 and 172. A float 176 of opaque material, such as a hollow metalfloat, is mounted Within the water gage 154. The tloat has axially directed and radially extending projections 178 thereon to minimize the contact between the float 176 and the interior of the water gage 154. Moreover, those projections tend to reduce the effect that surface tension or capillary action could have in restricting movement of the float within the water gage 154. A stop 180, in the form of a section of tubing, is mounted within the water gage 154. The top of the tubing 1&0 is adjacent the bottom of the hood 164, and it will keep the float 176 from moving downwardly below and out of register with the light-sensitive cell 172.

The light-

sensitive cells

170 and 172 will bc similar to the light-sensitive cell 1.10ct Fig. 2. Moreover, those light-sensitive cells will be `.connected in amplifying circuits similar to that disclosed in Fig. 2. However, the transfoirners in those amplifying circuits will be connected directly to a source of electricityV by leads 208 and 206 respectively and will not be connected through the main switch contacts14 and 16. As a result, the light sources 166 and 16S will be on throughout the twenty-four hours of the day. The amplifying circuit which is connected to the light-sensitive cell 170 by leads 210 is indicated by the box 212 in Fig. 4; and it will not have a relay such as the relay 112 but instead will have the coil of the electrically-responsive valve 144 connected between the plate of the triode and the resistor of the resistor-capacitance network. Thus; whenever light reaches the lightsensitive cell 170, the valve 144 will be energized to closed position to halt the introduction of make-up water into the boiler. If the tioat' 176 intercepts the light from the. source 166 or if the sludge in the boiler 200 discolors the water in the water gage 154 sufficiently, light will no longer be able to reach the light-sensitive cell'170 and thereupon the triode will be biased to cutoff and the spring bias of the valve 144 will open that valve and permit make-up water to enter the boiler. rThe amplifying circuit connected to the light-sensitive cell 172 by leads 214 is indicated by the box 216 in Fig. 1; and it will have `a relayicoil similar to the relay coil 112, but that relay coil will be adjacent the switch 22 of Fig. l.` The switchr 22 will be biased to open positionbut `will be pulled into closed position whenever the light from source 168 strikes the light-sensitive cell 172. If the oat 176 ever intercepts the light from the source 16S, or if the sludge in the boiler colors the water in the water gage 154 sufficiently, the bias on the grid of the triode `in the arnplifying circuit for the cell 172 will `be great enough to prevent the ow of current through the relay controlling the switch 22; and thereupon the spring bias on that, switch Willcause it to open and shut olf the control.

It will be noted that the float 176 is long enough that it wiil intercept the light to both of the

cells

170 and 172. This is desirable since it will enable the control of the present invention to continue `to pass make-up water into the boiler when the control shuts off the burner. As a result, there is a possibility that a self-healing break in a water tube or tire tube could permit the control to continue to operate safely after the water level had been raised suiciently. The stop 181i will keep the float 176 from moving below and out of register with the cell 172; and this is desirable since any such movement of the float 176 would restore the light to 172 even though the water level was too low.

in the operation of the control provided by the pres ent invention, the switches 22 and 24 are normally closed; the switch 22 being held closed by the amplifying circuit connected with the light-sensitive cell 172, and the switch 24 being held closed by the pressure of the fuel used in the combustion apparatus withwhich the control is operated. When the

master contacts

14 and 16 are closed, current will flow from the terminal through switch contact .14, through fuse 18, across the bridged contacts 40, through the primary winding 46, through junction 92, through junction 28 and through the lead 29 to the junction 23 and .then through the lead 25' to the switches 24 and 22 and finally throughthe fuse 20, and switch `contact 16 to the terminal 12. In addition, current will flow from the terminal 10 through the switch contact 14 through the fuse 18, past the

junctions

37, 35, and 53, through the` primary winding 94, past the junction 23 and through the switches 24 and 22, through the fuse 2i) and through the switch contact 16 to the terminal 12. The passage of the alternating current through the primary windings 46 and 94 will energize the secondary windings 48 and 98. No current will flow in the triode plate circuit connected to the secondary winding 98 because the triode will be biased to cut off since the light-sensitive cell 11i) sees no llame. The ow of current in the secondary winding 48 will cause an arc to span a gap between the electrodes 50 and the arc will complete the circuit through the relay coil 52. This relay is a very sensitive `relay and will respond to that current flow to move the armature 62 and bridge the spaced

contacts

54 and 56. Thereupon, current will flow from the tert minal 10 past contact 14, past fuse 18,

past junctions

37, 35, and 53 to junction 55; and the current will then ow either past the bridged contacts 54 or past the bridged contacts 56. The current flowing past the bridged contacts 54 will pass through the starting pilot valve 64 to the junction 92 and the current flowing past the bridged contacts 56 will pass through the relay 68 which controls the blower for the pilot. The current will unite at the junction 92 and ow past the junction 28 and past the junction 23 to the lead 25 and then successively past the switches 24 and 22, the fuse 20 and the switch contact 16 Vto the terminal 12. It Will be noted that until the current spanned the gap to establish an arc, that the valve 64 was closed and that the

valves

66, 70, 78 and 38 were also closed. Hence, no fuel could be introduced into the combustion head until after the spark had proved itself, and then the only fuel that could be introduced into the combustion head was the fuel for the starting pilot. The fuel from the valve 64 will mix with the air from the blower controlled by the coil 68 and will be discharged from the pilot nozzle 130. This fuel and air will be ignited by the arc between the electrodes` 50 and the resulting flamewill heat the flame rod 134. The ame rodwill become red hot and will also provide a characteristic orange color for the pilot fiame; and the lightsensitive cell will see both the red hot portion of the rod 134 and the ycharacteristically colored portion oi the flame surrounding that rod. Thereupon, the negative bias on the grid of the triode 100 will be reduced to the point where the triode can conduct current and thereupon the relay 112 will close the switch 118. The closing of the switch 118 will establish a circuit from the terminal 10 through contact 14 through fuse 18,

past junctions

37 and 35 and 53, through the switch 118, past the junction 30,` through the relay coil 32, past the junction 28, past the junction 23 and through the switches 24 and 22, through the fuse 20 and through the contact 16 to the terminal 12. This flow of current energizes the solenoid coil 32 and moves the armature 34 to the right where it causes the contactor 44 to bridge the spaced contacts 3S and causes the contacter 42 to bridge the spaced contacts 36. As the armature 34 moved, it broke the circuit through the primary winding 46 and thus interrupted the spark between the electrodes 50. However, the pilot ame from the nozzle will supply the llame necessary to ignite the fuel from the other nozzles of the combustion head. When the contactor 44 was moved out of engagement with the spaced contacts 40, the relay 52 was deenergized and the circuit to the starting pilot valve 64 and the circuits to the relay for the pilot blower motor were interrupted. However, almost simultaneously, the

.circuit to the running pilot valve 66 was established through the bridging of the spaced contacts 38 and the einem eireuit te the relay 68 whielieemrele the Pilet blauer tor was established through the spacedI contacts 361'. In' the rst instance the current flows from the' terminal 10r through the contact 14, through the fuse 18, past the junction 37, through the contacts 38 and the contactor 44, through the running pilot valve 66. peet the junctions 92.. 28' and 23 to the switches 2 4 and' 2 2' and then through the fuse v and the contact 16 to the terminal 12, In the second case the circuit extends' from the terminal` 10 past the contact 14, past the fuse 18,

past ythe junctions

37 and 35, through the contacts 36 and the contacter 42, past junction 67 and through the relay 68 which controls the pilot blower motor, past the junctions' 92, 2 8, and 2 3 to the switches 24 and 22 and then through the f use 20 and thecontact 16 to the terminal 1 2, Immediately, and without any quenching of the pilot flame the shift from the Starring pilot valve tothe running, alle? valve .is made, and the flame rod 134' will yretain" itfsf redf heat' and the flame will retain its characteristic; orange color.

If the pilot llame were to become extinguished, the ylightsensitive cell 110vwould, no longer see a haine andthe triode 100 would immediately be. biased to cut oif and the switch 118 would open. This would deenergize the relay coil 32 and thereupon the circuit to the running pilot valve and to the relay for the pilot blower motor wouldbe interrupted at the spaced contacts 38`and 3 6 respectively.r

Simultaneously, the circuit to the primary winding 46 would be restored by the contactor 44, and-"the arc would again be proved. The valve 6.4 would again be opened and the relay 68 would again be energized by movement` of the armature 62 o f the sensitive relay 52, and the pilot would again be ignited and the flame vrod 134 heated `to red heat. The scanner 2 6 would then reenergize the running pilot valve 66 and reenergize the relay 6 8 for the pilot blower motor while also deenergizing'the circuit. o f the electrodes 50 and the sensitive relay 52.l Thus, the present invention fully proves the spark before it permits any fuel to enter the combustion. head, andV it monitors the pilot and shuts olf the fuel to the piiotif the pilot becomes extinguished. Moreover, the present invention automatically recycles the igniter for the pilot until the pilot llamey proves on the scanner.v

Once the running pilot flame-has been established and proved, the valve 70 can be operated. This valve, which is commercially known and available, has" a handle which is operated manually but which will remain in moved position only if current hows-throughthe` electromagnetic coil of that 'va-lve. Thus, until the circuit through vthe valve 70 is completedat the switch 118 in the amplifier circuit of the scanner, the valve 70 cannot be kept on Once the pilot ame has beeneestablished and then proved by the scanner, however, the valve 70 can be kept on The valve 70 is connected between the source of fuel and the

fuel valves

78 and 88 and it will automatically close and stop further flow of fuel to

valves

78 and 88 if the scanner 26 does not see a ame in the combustion head; however as long as the pilot flame continues, the valve 70 will permit the ow of fuel to the

valves

78 and 88.

If the boiler or other heat absorbing device requires additional heat, the switch 72 will close and energize the relay 74 which controls the blower for the low fire. After that low lire blower has created a predetermined air pressure in the duct leading to the secondary air nozzle for the low re, the switch 76 will close and energize the valve 78. This valve supplies the fuel for the low lire. If the heat provided by the low tire is suflicient to meet the needs of the boiler or other heat absorbing device, the low tire will continue to supply heat until the needs of the boiler or other heat absorbing device are met and then the switch 72 will open. Thereupon the relay 74 and the valve 78 will be de-energized, and the low tire will be extinguished.

If the low fire was unable to provide the heat required by the boiler or other heat-absorbiug device, the switch 10 would loseand energize the relay 82 which controls thehlowerrnotor'for the-highfhe Asthe blower'motor for the high hre starts to operate, it willA increase the pressure'ny the air duct tothe secondary air nozzle for the high fire and will close the switch 84; and thereupon either the valve'88 or 90 will open, the particular valve being opened being dependent upon the position of the thermally responsive` switch 86; In either event the fuel from the valvev 88 or the valve'9`0` will mix with the air from the blower controlled by the relay 82, and the resulting mixture will ignite from the pilot or from .the low lire. The

resulting llame will be the high lire of the combustion head. If the temperature exteriorly of the area being heated by the boiler or other heat absorbing device is above a predetermined value, the closing of the switch 84 will energize the valve 88, but if that temperature is below that predetermined value, the closing of the switch 84 will energize the valve 90. The secondary air and the fuel ofthe high lire will continue to supply heat to the boiler or' other heat absorbing device until the switch 80 opens. Thereupon the relay 8 2 and the valve 88 or 90 will be deenergized- It'will be noted that the high lire fuel and air can not be supplied to the combustion head until after the low re fuel and air are being supplied to that combustion head, because the

switches

72 and 76 are intermediate the terminals 10 and 12 and the

switches

80 and 84. In one particular embodiment of the present invention the switch 72 was set 'so it closed when the pressure of the steam in the boiler was seventy pounds and so it opened when the steam pressure exceeded eighty pounds, and so the switch 80 closed when the steam pressure fell to sixty eight pounds and opened when that pressure reached seventy ve pounds. The arrangement used in the said embodiment enabled the control provided by the present invention to closely match the needs of the boiler with'- out any overshooting.

The fuel from the

valves

64 and 66 will support the pilot, the fuel from the valve 78 will support the low re, and the fuel from the valves 88 and 90 will selectively support the high lire. In each case the ames will envelope portions of the llame rod and heat those portions to a red heat and also cause that llame rod to give the flames the characteristic orange color. rl`.he light-sensitive cell will continuously monitor the flames in the combustionn head, and the light-sensitive cells and 172 will continuously monitor the level of .the water in the boiler. In this way, full and complete protection is afforded to the boiler and to the personnel working with that boiler; If thelight-sensitive cell 110 fails to see a flame it will open the circuit of the valve 70 at the switch 118 and thereafter the switch 78 will have to be re-closed by hand. This makes certain that the cause of the extinction of the pilot, low iire and high tire flames will be investigated before the low lire and high lire tiames can be reeestablished. The pilot will automatically be re-established if a spark can be drawn between electrodes 5G, and the re-establishment of the pilot is desirable since it will enable that pilot to burn any fuel that might be leaking past any of the

valves

70, 78, 88 or 90. Even the best valves can leak if pipe scale or other foreign material lodges between the seat of the valve and the movable element of the valve.

In some instances it may be desirable to use a glow plug instead of spark plugs, such as the spark plugs 50. In those instances the step-up transformer of Fig. 1 will be replaced with a step-down transformer, and the spark plugs will be replaced by a glow plug. Current flowing through the primary winding of the step-down transformer will cause current to ow through the secondary 'winding of that transformer and thus through the glow plug and the coil S2. As long as the glow plug is in good condition, it will conduct current in sufficient quantities to energize the coil 52; but if that glow plug burns out or otherwise fails to pass its normal current, the coil 52 will be unable fi1 f to hold the armature 62 in position to bridge the spaced

contacts

54 and 56. Whether the glow plug or the sparkv t plugs are used, the coil 52 can not be energized' properly unless the igniter, in the form of the glow plug or the spark plugs, can pass the required current for the said coil.

Whereas a preferred embodiment of the present invention has been shown and described in the` drawing and accompanying description, it should be apparent to those skilled in the art that various changes may be made in the form of the invention without affecting the scope thereof.

What I claim is:

In combustion apparatus that heats liquid `in a boiler, a control that comprises a transparent casing connected to and in communication with said boiler, an opaque float disposed within said casing for vertical movements therein, a water line connected to said boiler to supply make-up water thereto, an electrically responsive valve incorporated in said make-up water `line that is biased to open position but is normally held closed by the energization thereof, a light-sensitive cell that is adjacent said casing and that is positioned to receive light passing through said casing, a fuel line connected to said combustion apparatus to supply fuel thereto, a second electrically responsive valve that is incorporated in said fuel line and that is biased to closed position but can be energized to open and permit the flow of fuel to said combustion apparatus, a second light-sensitive cell that is adjacent said casing and that is positioned to receive light passing through said casing, a source of light that is adjacent said casing and that is aligned with the first said light-sensitive cell, a second source of light that is adjacent said casing and that is aligned withisaid second light-sensitive cell, the iirst said and said second light sensitive cells `normally receiving light that is emitted by the lirst said and said second sources of light respectively and that passes through said casing, the first said light-sensitive cell being positioned above the level of said second light-sensitive cell, a baiiie intermediate said light-sensitive cells to isolate each of said light-sensitive cells from the light intended for` the other of said cells, said opaque float being movable into position intermediate the tirst said light source and the irst said light-sensi tive cell to intercept the ,light that is emitted by the iirst said light source and normally passes through said casing to the first said light-sensitive cell, said opaque `iioat being movable into position intermediate said second source `ot light and said second lightsensitive cell to intercept the light that is emitted bysaid second source of light and normally passes to said second lightsensitive cell, said opaque tloat being longer than the spacing between said light-sensitive cells whereby said float can 12 t simultaneously intercept the light that normally passes to both of said light-sensitive cells, a stop that prevents said oat from moving down to a position where it would be wholly below the level of said second light-sensitive cell, a circuit that responds to interruptions in the light normally received by the first said light-sensitive cell to de-energize, and thus open, the rst said electrically responsive valve and that responds to restoration of the light received by the first said light-sensitive cell to energize, and thus etect the closing of, the first said electrically responsive valve, and a circuit that responds to the light received by said second light-responsive cell to energize, and thereby open, said second electrically responsive valve to permit the ow of fuel to said combustion apparatus and that responds to interruptions of the light received by said second light-responsive cell to de-energize, and permit the closing of, `said second electrically responsive valve, said casing being long enough to permit said tloat to move to an upper position wholly above the level of the first said light-sensitive cell, said lloat responding to the water level in said boiler, and hence in said casing, to move to said upper position to permit both of said lightsensitive cells to receive light and thereby energize the first said electrically responsive valve and to energize said second electrically responsive valve, said iioat responding to a lower Water level to move to an intermediate position to intercept light normally received by the rst said light-sensitive cell and thereby die-energize and open the rst said electrically responsive valve while permitting said second light-sensitive cell to receive light from said second source of light and hold said second electrically responsive valve energized, said float responding to a still lower water level to intercept the light normally received byboth of said light-sensitive cells to de-energize both said electrically responsive valves, thereby supplying make-up water while shutting olf the supply of fuel.

References Cited in the tile of this patent UNITED STATES PATENTS 352,647 Chegan Nov. I6, 1886 1,840,744 Scott Ian. 12, 1932 2,078,479 Briggs Apr. 27, 1937 2,091,303 Brelsford Aug. 3l, 1937 2,127,445 Hardgrove Aug. 16. ,1938, 2,210,852 Falkenberg Aug. 6, 1940 2,335,655 Dickey Nov. 30, 1943 2,362,045 Bliss Nov. 7, 1944 2,418,845 Long Apr. 15, 1947 2,579,883 Thomson Dec. 25, 1951 FOREIGN PATENTS 600,450 Great Britain Apr. 8, 1948