US2562507A

US2562507A - Smoke eliminating apparatus

Info

Publication number: US2562507A
Application number: US755296A
Authority: US
Inventors: Pierce Conway
Original assignee: Individual
Current assignee: Individual
Priority date: 1947-06-18
Filing date: 1947-06-18
Publication date: 1951-07-31
Anticipated expiration: 1968-07-31

Description

SMOKE ELIMINATING APPARATUS Filed June 18, 1947 4 Sheets-Sheet 1 INVENTOR.

Co/vw/r Y /f/PCf 9 /WQZJQQ A TTORNEYS July 31, 1951 c. PIERCE I 5 5 SMOKE ELIMINATING APPARATUS Filed June 18,. 1947 4 Sheets-Sheet 2 INVENTOR. CONWAY IO/ERCE July 31, 1951 c, PIERCE 2,562,507

SMOKE ELIMINATING APPARATUS 4 Sheets-Sheet 3 Filed June 18, 1947 INVENTOR.

CQA/WHV PIERCE July 31, 1951' v c PIERCE 2,562,507

SMOKE ELIMINATING APPARATUS Filed June 18, 1947 4 Sheets-Sheet 4 V A I ,e l as ATTORNEY Patented July 31, 1951 UNITED STATES PATENT F F ICE 2,562,507 SMQKE ELIMINATING APPARATUS Conway Pierce, Detroit, Mich.

Application tune 18, 1947, Serial No. 755,296 16 Claims. (01. 236-15) means in response to the density of the smoke,

discharged from the fuel burning equipment.

Another feature of this invention is to incorporate in the control apparatus a timing device which is rendered operative by the smoke detector means to connect the fluid supply means to the combustion Zone of the fuel burning equipment and maintains this connection for a predetermined period of time, regardless of the condition of the smok detector means. This arrangement assures effective elimination of the,

smoke and minimizes repeated starting and stopping of the apparatus.

Still another feature of this invention is to provide an arrangement wherein the fluid supplied to the combustion zone may be supplied from areas within the combustion chamber or may be supplied from the atmosphere exteriorly of the chamber, or in some instances, may be taken from both places. By supplying air to the combustion zone which is collected from areas within the chamber, a minimum loss ofheat results because the amount of air to the furnace is not thereby increased with a consequent increase of heat losses in the exit flue gases.

A further object of this invention is to provide smoke abatement apparatus having two or more fluid supply devices, and having means for successively operating the devices in response to the production of smoke in the combustion chamber.

A still further object of this invention is to provide apparatus of the type set forth in the preceding paragraph having means for delaying the operation of the second device for a predetermined period of time after the first device is started.

The foregoing as well as other objects will be made more apparent as this description proceeds, especially when considered in connection with the accompanying drawings, wherein:

Figure 1 is a diagrammatic sectional elevational view showing fuel burning equipment embody- .ing smoke abatement apparatus constructed in accordance with this invention;

Figure 2 is a wiring diagram of the arrangement shown in Figure l;

Figure 3 is a diagrammatic sectional elevational view of a modified construction;

Figure 4 is a wiring diagram for the arrangement shown in Figure 3;

Figure 5 is a diagrammatic view of another embodiment of the invention;

Figure 6 is a diagrammatic sectional elevational view of a further embodiment of this invention; and

Figure 7 is a wiring diagram for the arrangement shown in Figure 6.

Each of the several embodiments of this invention about to be described are applicable to practically an type of fuel burning equipment in which improper combustion results in the production of smoke. Also provision is made in each of the several modifications illustrated herein for introducing fluid into the combustion zon of the equipment in response to the density of the smoke generated by the equipment. The introduction of fluid to the combustion zone of the fuel burning equipment creates a turbulence in the combustion chamber and supplies additional air to the region in which combustion originates. This additional air materially aids combustion and is supplied in sufficient quantities to assure substantially complete burning of the smoke or unburned gases in the combustion chamber, so that very little or no perceptible amount of smoke or unburned gases escape from th combustion chamber through the flue usually provided for this purpose.

As will be more fully hereinafter set forth, the fluid or air may be supplied to the combustion zone from the atmosphere exteriorly oi the chamber, or may be supplied to the combustion zone from the remote areas in the chamber proper. In fact the supplemental air may, under certain conditions, be taken both from the atmosphere eXteriorly-of the chamber and from points within the chamber. The advantage of supplying the supplemental air from a region within the chamber is that the quantity of excess air is not increased by the process and th heat losses carried away'to the flue in the form of sensible heat is kept at a minimum. I

With the above in view, reference is now made more in detail to the embodiment shown in Figures 1 and 2 of the drawings. Referring first to Figure l of the drawings, it will be noted that the reference numeral 10 indicates a conventional type of coal burning furnace having a combustion chamber H and having a combustion zone indicated generally by the reference numeral 12. In accordance with orthodox practice, the products of combustion are discharged from the chamber I I through a flue l3 extending from the furnace II) in communication with the chamber H. In the normal operation of a furnace of the above general type, all of. the gases are not thoroughly burned due to the presence of insufiicientair in the combustion zone 42, and these gases are released through the flue IS in the form of smoke, which for the purpose of this description is .considered the gaseous products of combustion made visible by small particles of carflue.

bon suspended therein. The density of the smoke passing upwardly through the flue depends upon the number of particles of carbon suspended therein, which in turn depends on the efficiency at which combustion takes place in the zone l2. The particles of carbon suspended in the smoke or roducts of combustion eventually settle out in the form of soot, and this, of course, is very objectionable.

In order to increase the elficiency of combustion in the zone |2 of the chamber sufficiently to avoid the production of smoke, provision is made herein for introducing air and steam into the zone l2. In the present instance air is introduced into the chamber II from the atmosphere exteriorly of the latter through a tube l4 extending through one side wall of the furnace l and positioned with the delivery end directly opposite the zone |2. Air is induced to flow through the tube I4 into the combustion chamber by discharging a stream of steam through the tube M. The steam is discharged into the entrant end of the tube by a jet l5 spaced axially outwardly from the supply end of the tube a suflicient distance to enable the entrance of air into the tube and connected to a suitable source of supply (not shown) by a conduit IS. The flow of steam from the source of supply to the jet is controlled by a conventional two-way valve suitably supported in the conduit l6 between the jet l5 and the source of supply.

The valve I1 is automatically operated in response to the density of the smoke passing through the flue l3. The means for accomplishing the above result comprises a source of illumination I8 and a light sensitive unit I9, respectively suitably supported at opposite sides of the The source of illumination |8 is electrically connected to a source of electric energy by a circuit 2| having a manually operable switch 22 therein. The light sensitive unit I3 may be any one of a number of orthodox units available to the trade and need not be described in detail herein. It will sufiice to point out that the unit l9 comprises a photoelectric cell 23 and a relay switch 24.

The above arrangement is such that the pho toelectric cell 23 is energized by rays of light projected across the flue [3 by the illuminating device l8, and thereby maintains the relay switch 24 in its open position. On the other hand, when the beam of light emitted by the device It is interrupted or substantially diminished by the density of the smoke passing through the flue, the photoelectric cell is deenergized, and the relay switch 24 is closed. Referring again to Figure 2 of the drawings, it will be noted that the photoelectric cell is connected to the source 20 of electrical energy by an operating circuit 25 having a manually operable switch 26 therein. In

practice the switch 26 is located in close proximity to the switch 22, and both switches are normally closed when the apparatus is in its operative condition.

The operating circuit 25 also includes a solenoid 21 having a coil 28 connected in series in the circuit 25 and having an armature 29 in the coil operatively connected to the valve IT. The valve I1 is normally closed, and is moved to its open position by the armature 29 when the coil 28 of the solenoid is energized by the operating circuit 25.

The operating circuit is controlled by an electrically operated timer 30, which also may be any one of the standard types available to the trade, and therefore, is not described in detail herein. It will suffice to point out that the timer is of the automatic resetting type having an electric motor 3| for operating the timing means 32 and having a relay switch 33 connected in series in the operating circuit 25. In accordance with conventional ractice, the switch 33 is closed by the timer as soon as the motor 3| is operated to start the timing means 32. The means 32 may be previously set in accordance with orthodox practice to correspond to a predetermined time interval. When this time interval expires, operation of the motor 3| is discontinued and the switch 33 is not only opened, but the timing means is automatically reset to its zero or initial starting position.

The timing device briefly described above is energized by a control circuit 34 including the motor 3| oi the timing device, and also including the relay switch 24. It follows, therefore, that when the relay switch 24 is closed by the presence of smoke in the flue I3, the motor 3| in the timer is started, and the switch 33 is closed. Closing of the switch 33 in the timer 30 energizes the coil 28 of the solenoid 21 and operates the armature 29 to open the valve As stated above, opening of the valve introduces steam and air into the combustion zone |2 in the chamber The introduction of this fluid into the chamber produces a turbulence in the chamber, so that air from remote areas in the chamber is also circulated through the combustion zone l2. This turbulence also causes the smoke which has accumulated in the chamber |2 to pass or circulate through other parts of the combustion zone where there is sufficient air for burning. The unburned smoke and gases are thereby quickly burned and pass from the furnace as a smokeless product.

When the density of the smoke passing through the flue between the light source l8 and light sensitive unit l9 diminishes to such an extent as to permit the beam of light from the source to again energize the photoelectric cell 23, the switch 24 is opened. At this 'point it is important to note that the control circuit 34 is so connected with the operating circuit 25 that both the motor 3| and switch 33 are connected in parallel relation with the relay switch 24. Thus the solenoid 21 remains energized or, in other words, the valve remains open until both

switches

24 and 33 are opened. Accordingly,

should the switch 24 open before the timing means 32 on the timer 30 reaches the preselected setting, the motor 3| continues to operate, and the switch 33 remains closed until the timer completes its cycle of operation. Thus the introduction of fluid into the combustion chamber is continued until the timer relay switch 33 is opened. It follows from the above that the operating circuit is maintained closed by the timer 30 for a predetermined length of time, regardless of the condition of the relay 24, and this is highly desirable in that it prevents constant fluctuation or repeat operation of the apparatus.

The embodiment of the invention shown in Figures 3 and 4 of the drawings differs from the above described arrangement in that a blower 35 is provided for supplying air to the combustion chamber The blower 35 is driven by an electric motor 36 of suitable design and the latter is connected to a power circuit 31 including a switch 38. The switch 38 takes the place of the valve shown in Figure 2 of the drawings,

The solenoid 21 is operated in response to the density of the smoke passing through the flue I3 by the same circuit arrangement shown in Figure 1. Accordingly corresponding parts of the two embodiments described above are indicated by the same reference numerals.

The timer as and associated parts are replaced in the embodiment of the invention shown in Figure 5 'of the drawings by a fluid-pressure operated timing system designated generally by the numeral ill. This system comprises a number of parts among which are a displacement pump il, a fluid motor 42, a control valve 43 and a reservoir M. The pump 4| may be operated by any suitable type of prime mover, and has a piston it slidably supported in a cylinder 53 having the end at the pressure side of the piston connected to the reservoir through a check valve 41. The end aforesaid of the pump cylinder also has a fluid connection with the control valve 43 and a check valve E8 is included in the above connection to prevent fiow of fluid from the valve to the pump cylinder.

The fluid motor 32 has a piston 39 slidably mounted in a cylinder 59 connected at its upper end to the reservoir by a fluid return conduit 5! and connected at its lower end to the control valve by a conduit 52. The lower end of the cylinder 58 is also connected to the fluid return conduit 5! by a conduit 53 including a metering valve 5%. The piston 48 has a mechanical connection with one end of a lever 55 by a rod 56 ex" tending downwardly from the piston 49 through an opening in the lower end of the cylinder 5!! and the other end of the lever 55 is pivoted to a suitable fixed support 5?. The lever 55 is connected intermediate the ends to a valve l1 identical in purpose to the correspondingly numbered valve in the first embodiment of the invention. The valve ii? is normally urged to its closed position by a coil spring 58 having the lower end bearing on the lever intermediate the ends of the latter and having the upper end engaging an abutment 59 fixed to the upper end of a vertical rod GB. The rod extends axially through the coil spring and is connected to the valve ii. The general arrangement is such that the coil spring 53 tends to maintain related positions between the lever 55, rod 55 and valve ll, such that when the lever 55 is down, the valve I! is closed by the spring 58.

The valve 43 is normally held in its closed position or in a position wherein the portion of the power cylinder 50 below the piston 59 is closed to the discharge side of the pump cylinder 4!, The valve 43 is operated by a solenoid 2'! identical to the correspondingly numbered solenoid in the operating circuit of the first embodiment of this invention. The same type of operating circuit is provided in Figure 5 of the drawings and is automatically controlled in response to the density of the smoke passing through the flue by the same instrumentali ies described in connection with the arrangement disclosed in Figures 1 and 2 of the drawings.

In operation when the solenoid 2'! is energized the valve 33 is opened permitting. fluid under pressure to how from the discharge side of the pump 1 to the lower end of the power cylinder 56 below the piston 49. As the piston 49 is moved upwardly in the cylinder 50 by the pressure of the fluid acting on the bottom surface of the piston, the free end of the lever 55 is swung upwardly compressing the spring 5'8 and thereby opening the valve I? to admit steam and air into the combustion chamber H through the tubes M.

Assuming now that the smoke condition in the combustion chamber II has been relieved or eliminated, and that the light sensitive cell controlled relay 24 is again opened, it will be noted that the solenoid 27 is deenergized and the valve -"$3 is again closed. However, the valve I1 is prevented from closing by the rod 6e and remains open uhtil the pressure in the cylinder 58 below the piston t3 drops sufiiciently to enable downward movement of the piston by the spring 58. In the present instance the rate at which fiuid escapes from the lower end of the cylinder 50 is regulated by the needle valve 54 and, as a consequence, any desired lag between opening of the relay 24 and closing of the valve I! may be provided. Of course if the relay 2 again closes before the valve l l is closed, the valve 43 opens, and closing of the valve I7 is further delayed. Thus effective elimination of the smoke in the combustion chamber ii is assured, and the objectionable fiuctuating action of the control mechanism is avoided. V

In Figures 6 and '7 of the drawings, I have shown a dual stage smoke abatement system in connection with a power boiler and furnace equipped with an overi'eed coal stoker of the chain grate type. This type of equipment is well known in the art, and need not be described in detail. For the purpose of this description, it will suffice to point out that this furnace is also provided with a combustion zone I? in the chamber 1 l and with a flue i3 through which the products of combustion are discharged.

Referring now more in detail to Figure 7 of the drawings, it will be noted that the reference numeral 538 indicates the first stage of the smoke abatement apparatus, and the numeral Bl designates the second stage. The operation of the two stages is controlled by a common light source I 8 and a common light sensitive unit 19 positioned at opposite sides of the path of the products of combustion flowing from the combustion chamber II through the flue 13. These instrumentalities are the same as those previously described in connection with the above modifications of this invention, and operate in an identical manner.

Actually, the stage 6%! corresponds to the embodiment shown in Figures 3 and 4 of the drawings, and similar parts are indicated by the same reference characters. However, in Figure 6 of the drawings, the intake side of the blower 35 is connected to a conduit 62 which extends into the boiler setting and is positioned to draw gas from the last pass 63 of the boiler. The discharge side of the blower is connected to delivery tubes 65 by a supply conduit 65 and these tubes are positioned to discharge the gases into the combustion zone 1! of the furnace. As pointed out in connection with the modification shown in Figures 3 and 4 of the drawings, the blower 35 is operated by an electric motor. 35 connected in an electric supply circuit 3'! and controlled by a switch 38 in aid circuit. The switch 38 is operated by a solenoid 27 and the latter in turn is operated in response to the density of the smoke passing upwardly through the flue l3. As further pointed out in the description of the first embodiment of this invention, the coil 28 of the solenoid 21 is electrically connected in an op erating circuit 25 including the switch 33 of the timer 3!], and the motor 3! for the timer is electrically connected in both the operating circuit 25 and control circuit 3 3. The arrangement is such that should the relay switch 24 open prior to completion of the operation of the timer, the latter continues to operate under power received from the operating circuit 25.

The second stage of the smoke abatement system comprises a plurality of jets 66 corresponding to the jets l and adapted to inject air and steam into the combustion chamber through one or more sides of the furnace in the same manner described in connection with Figures 1 and 2 of the drawings. The flow of steam to the jets 66 is controlled by a valve [1 and the latter is operated by a solenoid 2T identical to the solenoid 21. The coil 28 of the solenoid 21' is connected in an operating circuit 25 in parallel with the coil 28 of the solenoid 21 and is operated by the relay 24 through a second timer 36' identical to the timer 30. The switch 33 of the timer 38' is electrically connected in the operating circuit 25' in parallel with the timer switch 33, and the motor 3| for the second timer 30' is connected in the operating and control circuits so as to continue operation of the timer until it completes its cycle, regardless of the condition of the relay switch 24.

As shown in Figure '7 of the drawings, a time delay relay switch 61 is connected in series with the timer motor 3|, and a relay switch 68 is connected in series with the timer motor 3 I. The switch 68 is normally closed and the actuating coil of this switch is connected in series with the switch 33' of the timer 30, so that when the switch 33' is closed to energize the solenoid 21', the switch 68 is opened. The time delay switch 81 may be of any suitable design available to the trade, and the actuating coil thereof is shown in Figure 7 as connected in parallel with the timer 30. As a result, the coil for the switch 61 is energized as soon as the operating circuit 25 is closed by the timer switch 33. However, the closing of the switch 6! is delayed for some time, as will be presently described.

In operation of the modified construction shown in Figures 6 and 7 of the drawings, it will be noted that when the density of the smoke passing through the flue l3 exceeds a value sufiicient to interrupt the light beam directed by the source l8 toward the light sensitive unit 19, the relay switch 24 closes and starts the timer 3!]. As a result the switch 33 closes the operating circuit 25, and the switch 38 is closed by the solenoid 21 to operate the blower 35. The blower draws heated gas from the last pass of the boiler and delivers it to the combustion zone l2 of the chamber l l to improve the efficiency of the come bustion taking place in this zone.

In most instances the above procedure will eliminate smoke production with negligible heat loss. However, in some instances, the production of smoke in the furnace may be so severe. that it cannot be eliminated by the above operation. In such cases the time delay switch 61 closes and starts operation of the timer 30', which like the timer 30, has been preset to operate for a preselected period of time. 33, of course, closes the circuit 25' to the solenoid 2'1 and causes the latter to open the valve I1. Thus steam and air from the outside of the furnace are supplied to the combustion zone [2 to supplement the gases supplied by the blower and combustion in the zone I2 is immediately improved. Attention is called to the fact that closing of the switch 33 also energizes the relay coil for the switch 68 and opens the latter to discontinue operation of the motor 3| for the timer The switch,

30, so that the blower will continue to operate during the period the second stage 6| of the system is in operation.

When the timer 30' completes its operation and the timing means is reset to its zero or initial starting position, the switch 33 is operated to open the operating circuit 25'. As a result the solenoid 27' is deenergized and the valve I! is again closed. Opening of the operating circuit 25' by the timer switch 33 also deenergizes the coil of the relay switch 68 and permits the latter to again close. This enables the timer motor 3| to continue its operation until the preselected timing period is expired, whereupon the switch 33 is opened and operation of the blower 35 is discontinued. Opening of the switch 24 also serves to deenergize the coil for the time delay relay switch 61 and permits the latter to open, so that the timer 30 is again disconnected from the control circuit 34 of the system. Thus both stages of the system are again ready to operate on demand from the smoke detector and the cycle repeats for another preselected period Of time when smoke is again detected.

The second stage 6| will not start operating until the first stage 60 is operated for a length of time determined by the time delay switch 61. Therefore, the second stage 6| may be considered as an emergency system which is called upon to afford protection only in severe cases, or in the event of failure of the first stage.

What I claim as my invention is:

1. Apparatus for substantially eliminating the production of smoke resulting from improper combustion of a fuel in a chamber having an outlet through which the products of combustion pass, said apparatus comprising means for supplying a smoke reducing fluid to the combustion zone in the chamber, an electric circuit having a switch connected in series in said circuit, a solenoid for operating the fluid supplying means and having a coil connected in series in said circuit, means for opening and closing the switch including an electrically operated timer of the automatic resetting type having provision for delaying opening of the switch for a predetermined time, a control circuit for the timer, and means controlled by the density of the smoke discharged from the combustion chamber for closing the control circuit upon an increase in the smoke density above a predetermined value and for opening the control circuit upon a decrease in smoke density below said predetermined value.

2. Apparatus for substantially eliminating the production of smoke resulting from improper combustion of a fuel in a chamber having an outlet through which the products of combustion pass, said apparatus comprising means for supplying a fluid to the combustion zone in the chamber, electrically operated means for controlling the operation of the fluid supplying means and including an electric operating circuit having a switch therein, an electric control circuit having means for closing said switch, a switch in the control circuit controlled by the density of the smoke discharged from the chamber for closing the switch in the control circuit upon an increase in the smoke density at the outlet above a predetermined value and for opening the switch in the control circuit at the outlet upon a decrease in the smoke density below said predetermined value, and means for delaying opening of the switch in the operating circuit for a predetermined period of time.

3. Apparatus for substantially eliminating the production of smoke resulting from improper combustion of a fuel in a chamber having an outlet through which the products of combustion pass, said apparatus comprising an electric control circuit having a relay, means also in the control circuit responsive to an increase in smoke density at the outlet above a predetermined value to close the relay and responsive to a decrease in smoke density at the outlet below said predetermined value to open said relay, means for supplying a smoke reducing fluid to the combustion zone in the chamber in response to closing of the relay and a timer renderedoperative by the closing Of the relay and having means for continuing the supply of fluid to the chamber for a preselected period of time independently of the operation of said relay.

4. Apparatusfor substantially eliminating the production of smoke resulting from improper combustion of a fuel in a chamber having an outlet through which the products of combustion pass, said apparatus comprising an electric control circuit having a switch, means also in the control circuit responsive to an increase in smoke density at the outlet above a predetermined value to close the switch and responsive to a decrease in smoke density at the outletbelow said predetermined value to open the switch, means for supplying fluid to the combustion zone of the chamber including an operating electric circuit, a switch in the operating circuit shunting the switch in the control circuit, and a timer for operating the second named switch including electrically operated mechanism connected in the control circuit.

5. Apparatus for substantially eliminating the production of smoke resulting from improper combustion of a fuel in a chamber having an outlet through which the products of combustion pass, said apparatus comprising an electric control circuit having a relay movable to its open and closed positions in response to the density of the products of combustion discharged from the chamber, an electrically operated blower having the discharge side communicating with the chamber and included in an electric supply circuit having a switch, an operating electric circuit including means for operating the switch in the supply circuit, and a timer having a switch shunting the switch in the control circuit and having mechanism for operating the timer switch connected in the control circuit.

6. Apparatus for substantially eliminating the production of smoke resulting from improper combustion of a fuel in a chamber having an outlet through which the products of combustion pass, said apparatus comprising an electric control circuit having a relay movable to its open and closed positions in response to the density of the products of combustion discharged from the chamber, valve controlled means for supplying fluid to the combustion zone in the chamber, means for opening and closing the valve in response to the operation of the relay, and fluid pressure operated means for delaying closing of said valve for a predetermined period of time regardless of the condition of said relay.

'7. Apparatus for substantially eliminating the production of smoke resulting from improper combustion of a fuel in a chamber having an outlet through which the products of combustion pass, said apparatus comprising an electric control circuit having a relay, means also in the control circuit responsive to an increase in the smoke density at the outlet above a predetermined value to close the relay and responsive to a decrease in smoke density at the outlet below said predetermined value to open the relay, means for supplying fluid to the combustion zone of the chamber, means for operating the supply means in response to closing of the relay including an operating circuit having a solenoid, a switch connected in the operating circuit in series with the solenoid and shunting the switch in the control circuit, and an electrically operated timer connected in the control circuit for closing and opening the switch in said operating circuit.

8. Apparatus for substantially eliminating the production of smoke resulting from improper combustion of a fuel in a chamber having an outlet through which the products of combustion pass, said apparatus comprising an electric control circuit having a relay switch movable to its open and closed positions in response to the density of the products of combustion discharged,

from the combustion zone, means for supplying a fluid to the combustion zone in the chamber including an operating circuit having two solenoids connected in parallel in the operating circuit, first and second switches in the operating circuit for respectively controlling the solenoids, means for successively closing the switches in response to closing of the relay switch, and means for delaying closing of the second switch for a predetermined period of time after closing of the first switch.

9.- Apparatus for substantially eliminating the production of smoke resulting from improper combustion of a fuel in a chamber having an outlet through which the products of combustion pass, said apparatus comprising an electric control circuit having a relay switch movable to its open and closed positions in response to the density of the products of combustion discharged from the combustion zone, means for supplying a fluid to the combustion zone in the chamber including an operating circuit having two solenoids connected in parallel in the operating circuit, first and second switches in the operating circuit for respectively controllingthe solenoids, a timer for closing the first switch in response to closing of the relay switch and for maintaining said first switch closed for a predetermined period of time, a second timer for closing the second switch, and time delay means in response to closing of the relay switch for initiating the operating of the second timer.

10. Apparatus for substantially eliminating the production of smoke resulting from improper combustion of a fuel in a chamber having an outletthrough which the products of combustion pass, said apparatus comprising an electric control circuit having a relay switch movable to its open and closed positions in response to the density of the products of combustion discharged from the combustion zone, means for supplying a fluid to the combustion zone in the chamber including an operating circuit having two solenoids connected in parallel in the operating circuit, first and second switches in the operating circuit for respectively controlling the solenoids, a timer for closing the first switch in response to closing of the relay switch and for maintaining said first switch closed for a predetermined period of time, a second timer for closing the second switch in response to closing of the relay switch and for maintaining the secondswitch closed for a predetermined period of time, and means for delaying operation of the second timer to close the second switch for a predetermined period of time after closing of the first switch.

11. Apparatus for substantially eliminating the production of smoke resulting from improper combustion of a fuel in a chamber having an outlet through which the products of combustion pass, said apparatus comprising an electric control circuit having a relay switch movable to its open and closed positions in response to the density of the products of combusiton discharged from the combustion zone, means for supplying a fluid to the combustion zone in the chamber including an operating circuit having two solenoids connected in parallel in the operating circuit, first and second switches in the operating circuit for respectively controlling the solenoids, a timer for closing the first switch in response to closing of the relay switch and for maintain-- ing said first switch closed for a predetermined period of time, a second timer for closing the second switch in response to closing of the relay switch and for maintaining the second switch closed for a predetermined period of time, means for delaying operation of the second timer for a predetermined length of time, and means for interrupting the timing cycle of the first timer in response to operation of the second timer to close the second switch.

12. Apparatus for substantially eliminating the production of smoke resulting from improper combustion of a fuel in a chamber having an outlet through which the products of combustion pass, said apparatus comprising an electric control circuit having a relay switch movable to its open and closed positions in response to the density of the products of combustion discharged from the combustion zone, means for supplying a fluid to the combustion zone in the chamber including an operating circuit having two solenoids connected in parallel in the operating circuit, first and second switches in the operating circuit for respectively controlling the solenoids, a timer for closing the first switch in response to closing of the relay switch and for maintaining said first switch closed for a predetermined period of time, a second timer for closing the second switch in response to closing of the relay switch and for maintaining the second switch closed for a predetermined period of time, means for delaying operation of the second timer to close the second switch for a predetermined period of time after closing of the first switch, and means for interrupting the timing cycle of the first timer in response to operation of the second timer.

13. Apparatus for substantially eliminating the production of smoke resulting from improper combustion of a fuel in a chamber having an outlet through which the products of combustion pass, said apparatus comprising an electric control circuit having a relay switch movable to its open and closed positions in response to the density of the products of combustion discharged from the combustion zone, means for supplying a fluid to the combustion zone in the chamber including an operating circuit having two solenoids connected in parallel in the operating circuit, first and second switches in the operating circuit for respectively controlling the solenoids, a timer for closing the first switch in response to closing of the relay switch and for maintaining said first switch closed for a predetermined period of time, a second timer for closing the second switch in response to closing of the relay switch Number and for maintaining the second switch closed for a predetermined period of time, means for delaying operation of the second timer to close the second switch for a predetermined period of time after closing of the first switch, and a normally closed relay switch for also controlling the operation of the first timer and connected in series with the second switch for successively stopping and starting the first timer upon closing and opening the second switch.

14. Apparatus for substantially eliminating the production of smoke resulting from improper combustion of a fuel in a chamber having an outlet through which the products of combustion pass, said apparatus comprising an electric control circuit having a relay switch movable to its open and closed positions in response to the density of the products of combustion discharged from the combustion zone, first and second devices for independently supplying fluid to the combustion zone, and means responsive to closing of the relay switch for successively operating said devices.

15. Apparatus for substantially eliminating the production of smoke resulting from improper combustion of a fuel in a chamber having an outlet through which the products of combustion pass, said apparatus comprising electric control circuit having a relay switch movable to its open and closed positions in response to the density of the products of combustion discharged from the combustion zone, first and second devices for independently supplying fluid to the combustion zone, and means for delaying the operation of the second device for a predetermined period of time after the operation of the first device.

16. Apparatus for substantially eliminating the production of smoke resulting from improper combustion of a fuel in a chamber having an outlet through which the products of combustion pass, said apparatus comprising means for supplying a smoke reducing fluid to the combustion zone in the chamber, an electric operating circuit having a switch connected in series therein, means in said circuit for operating the fluid supply means and controlled by said switch, a timer for opening and closing said switch, a control circuit having means for operating the timer, a switch in the control circuit for opening and closing the control circuit, and means controlled by the density of the smoke passing through the outlet for closing the switch in the control circuit upon an increase insmoke density above a predetermined value and for opening the switch in the control circuit upon a decrease in the smoke density below said predetermined value.

CONWAY PIERCE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date McDonald Dec. 27, 1898 Holby Apr. 9, 1940 Adams Mar. 10, 1942 FOREIGN PATENTS Country Date Germany Mar. 27, 1907 Great Britain Mar, 11, 1929 Great Britain Dec. 3, 1934 Number