US2158359A

US2158359A - Viscosity regulated fluid fuel control means

Info

Publication number: US2158359A
Application number: US664306A
Authority: US
Inventors: Lawrence L Finnlgan
Original assignee: Individual
Current assignee: Individual
Priority date: 1933-04-04
Filing date: 1933-04-04
Publication date: 1939-05-16
Anticipated expiration: 1956-05-16

Description

May 16, 1939- L. L. FINNIGAN 2,158,359

VISCOSITY REGULATED FLUID FUEL CONTROL MEANS 'Fi-led April 4, 1935 3 Sheets-Sheet l .mm um E om ww ...i f

- INVENTOR ,4 12W/'ence L. lzmyn h BY y ATTOR EY May 16, 1939. L. L. FINNIGAN 2,158,359

VISCOSITY REGULATED FLUID FUEL CONTROL MEANS 3 Sheets-Sheet 2 Filed April 4, 1953 IJYVENTOR .ip/17x ya ATTOR bnl/agence Caa/ May 16, 1939. 1.. L. FINNIGAN 2,158,359

VISCOSITY REGULATED FLUID F/UEL CONTROL MEANS Filed April 4, 1953 3 Sheets-Sheet 3 INVQNTOR mg/fence 4 .F1/mgm? Patented May 16, 1939 PATENT OFFICE vlscosrrr REGULATED FLUTD'FUEL ooN- 1 TRoLMEANs Lawrence L. Finnigan, Seattle, Wash.

Application April 4, 1933, Serial No. 664,306

14 Claims.

My invention relates to the art of controlling the discharge of oil from the atomizer nozzle of an oil burner and the general object of my invention is lto provide fully automatic means for'preventing the discharge of oilfrom an atomizer 'nozzle of an oil burner when said oil is too thick and is not of proper viscosity and permitting the discharge of such oil when the oil is thin enough to be of the correct viscosity to atomize properly '19 'and burn efliciently.

In the burning oi oil in oil burners of the atomizing type it is essential to have the oil thin enough so thatit will atomize properly before eilcient`combustion can be secured. For this 15 reason it is common practice to thin the oil by heating the same before the oil is fed to the oil burner.

to the temperature and the generally accepted method of changing the viscosity is to change the v temperature.

Knowing the viscosity of the oil as determined by a viscosimeter at a given temperature then the most eicient atomizing viscosity can be determined lay/temperature alone- I find that the eirlciency' with which the oil is atomizedv and burned depends primarily on the viscosity and that the effect of temperature on the atomization is due chieflyto vviscosity changes produced by changes of temperature. In one form of my invention I utilize the temperature of the oil for controlling the discharge of said oil from an atomizer nozzle and in this way I obtain a control which is responsive to variations in the viscosity of the oil while in another. form of the invention I utilize the viscosity of the oil directly for controlling the discharge of said oil. In both of these types of control I attain the much desired result of controlling the discharge of the oil in response to a change in the viscosity 'of said oil.

40 In this application I use the term high viscosiity to describe oil which 4is relatively thick and sluggish, and low viscosity to describe oil which is relatively thin and of high fluidity. Oil having a high viscosity is relatively thic and sluggish and hard to atomize properly and' .consequently it can not be burned efhciently when it is discharged from an oil burner atomizer nozzle. Oil of lower viscosity is thinner and more easily atomized and will produce a more nely divided spray and consequently burns more easily and more efliciently. 'For these reasons it is desirable to provide automatic means which operates proportional to changes in the viscosity of the oil for preventing the discharge from a burner nozzle of thicker oil of higher viscosity and per- The viscosity of oil varies in proportion f (Cl. 15S- 36) mitting the discharge from the burner nozzle of said oil only after the viscosity is low enough and the oil thin enough to bef properly atomized for eiiicient combustion as it is discharged from an atomizer nozzle of a burner.

. Another object of my invention is to provide a new and eicient circulating head for an oil burner said head having means for maintaining a' continuous circulation of oilY to a point lirrimediately adjacent the atomizer nozzle without permitting the oil to discharge if the viscosity of the oil is high and further having means for permitting the oil to discharge if the viscosity is reduced to a predetermined iluility at which the oil is thin enough to permit eicient atomization and burn- 15 lng.

Another object is to provide electric circuit opening and closing means in connection with my viscosity responsive control so that this control can be used with oil burner systems Without alter- 20 ation of thepresent safety circuits 'of the same.

Other andmore specific objects will be apparent from the following-description taken in connection with the accompanying drawings.

In the drawings v Fig. 1 is a plan view with parts removed and other parts broken away, of oil burner control means constructed in accordance with my invention.

Fig. 2 is a sectional view of the same substan- 30 ltially on breken line 2--2 of Fig. 1.

Fig. 3 is a diagrammatic viewshowing Ione manner of connecting parts of my control mechanism with the electric circuits of an oil burner system. 35

Fig. 4 is a fragmentary sectional view on a larger scale of an oil atomizer nozzle and control valve means embodied in this invention.

Fig. 5 is a vertical sectional View of electromagnetically operated control-means constructed 40 in accordance with my invention. J

Fig. 6 is a diagrammatic viewshowing electrical controls and oil ow means.

Figs.l 7, 8 and 9 are sectional viewsrespectively of another form of my invention in which the 45 control depends directly on the viscosity of the fuel.

Referring to Figs. 1, 2, 3 and 4, the numeral I0 designates a housing having a plurality of cornpartments or chambers II, I2, I2', I3-andv I4 pro- 50 vided ther/ein and having a cover member I5 removably secured thereon. The compartment I2' is cylindrical and intersects the compartment I2.

A burner pipe I6 is secured to the housing I0 and extends outwardly from one side' thereof. A t- 55 thermostatic liquid. The space 88 communiting I1 is provided on the end of the pipe I6 and an atomizer nozzle I8 having a delivery orifice is supported at the end of the burner pipe by a cap 20. An atomizer nozzle control valve 2| is positioned adjacent the atomizer I8 and is arranged to seat on a valve seat 22 in the fitting I1. A return tube 23 of smaller diameter than the burner pipe I6 is disposed substantially coaxially Within said burner pipe |6 in such a manner as to leave an annular passageway 24 between the outer wall of the tube 23 and the inner wall of the pipe I6. The pipe I6 communicates with the chamber II while the tube 23 extends through the chamber I I and communicates with the chamber I 2 and is threaded into a wall 25 which forms a partition between .the chamber Il and the chamber I2.

A valve Voperating rod 26 is secured to the atomizer nozzle control valve 2| and extends `lengthwise through the tube 23 and is secured to a piston valve 21 which is longitudinally movable in the cylindrical chamber I2". A compression spring 28 engages the piston valve 21 and exerts pressure tending to keep the nozzle valve 2I- closed. The spring28 is adjustably supported by a Washer 30 which is engaged by a set screw 3| threaded through a 'fitting 32 and having a lock nut3 thereon.

The chamber I3 is positioned below the chambers I2 and I2 and is connected with the chamber I2 by a by-pass port 34 andv a` relief port 35. A by-pass valve 36 controls the opening and closing of the by-pass port 34 and has a stem`39 which is suitably guided and extends upwardly into the chamber I4. The relief port 35 is opened and closed by the piston valve 21, An opening 34' is provided between chamber I3 and the portion of chamberl2 in which the spring 28 is disposed to'prevent back pressure on piston 21.

A jacket member 31 surrounds the pipe I6 and affords a space 38 which is iilled with a cates through an opening 40 with a chamber 4I within which is disposed a pressure responsive belloWs-like-device 42 which is arranged to be compressed upwardly by the fluid from the space 38. A stem 43 is connected with the bot` tom of the pressure responsive device 42 and extends upwardly through the upper end wall 44 of the chamber 4I. 'I'he upper end of this stem `43 is connected with suitable quick throw mechanism which controls the opening and closing of the by-pass valve 36. A compression spring 45 opposes the` pressure of the fluid against the' bottom side of the pressure responsive mem--4 thereto. 'I'he end of the crank arm 54 is forked and engages with a collar 56 on the stem 39 of the by-pass valve 36 whereby the by-pass valve 36 may be moved into open or closed position by oscillation of the crank arm 54. The crank arm extends in one direction'from the shaft 52 While the toggle member 5| extends in the opposite direction. 'I'he non-pivoted ends of the crank arm 55 and toggle member 5| are connected with each other by a tension spring 51; the arrangement being such that the line of pull of the 'spring 51 may cross from one side to the other of the center of the shaft 52 due to movement of the toggle member 5I and may thus cause the crank arm 65 to be snapped up or down thus snapping the crank arm 54 up or down at the same time and opening or closing the by-pass valve 36 by a quick movement.

An electric switch 58, which may be of conventional mercury contact type may be secured to the lever arm 46 and connected in an oil burner circuit in such a manner as to prevent a safety circuit which forms part of the usual oil burner control from completely stopping the operation of the burner mechanism when the oil is circulating through the burner head but is not discharging from the nozzle. One typi- -cal oil burner control system of this nature is shown in Fig. 3, in which |05 is a motor which may furnishpower to drive the pump and blower which supply oil and air -to the burner. |06fis a switch vcontrolling the supply of current from a source |01 to this motor. |08 is an electromagnetic operating means for this switch. |09 is a control circuit controlling the electromagnetic operating means |08. I|0 and III are automatic or thermostatic control switches of .any conventional type provided in circuit |09. ||2 is a switch in circuit |09 which may be operated either by'hand or preferably by an electromagnet H3, which electromagnet H3 is usually time delayed in its operation. ||4 is a safety circuit for the burner, which safetycircuit II4 is connected with the electromagnet ||3 and usually includes a stack switch ||5 or like circuit control device which, in the usual oil burner system is capable of functioning to energize the electromagnet II3 and to stop the operation of the burner in case of flame failure. When my viscosity control is used the burner will not light off promptly after it is put into operation but should continue to circulate oil until said oil has been reduced to proper viscosity before my oil is sprayed from the atomizer nozzle I8.1 Also if the viscosity of the oil becomes too high during the operation ofthe burner the nozzle control valve 2| will be closed and the burner name extinguished but the oil circulating mechanism should continue to operate and the burner should light oi! again as soon as the viscosity of the oil has been reduced enough to open the nozzle control valve 2|. 'I'he stack switch ||5 in the usual oil burner safety circuit, if used in connection with my viscosity control and without alteration of the safety circuit. would stop the burner motor I05 before the circulating oil had become thin enough to cause the nozzle valve; 2| to open. To avoid this I interpose the switch 58 in the safety circuit |I4 and arrange this switch so that it will open or break the safety circuit ||4 at all times` when'the nozzle valve 2| is closed thus neutralizing any operation of the stack switch I|5 which might otherwise tend to stop the burner motor |05. When the nozzle control valve 2| is ppen then the switch 58 will be closed and the safety circuit of the burner will be effective in the usual manner. 'I'he neutralizing of the safety circuit when the nozzle valve 2| is closed does not lessen the safety of the burner as no oil can be discharged when the nozzle control valve is closed. Y

'Ihe chamber has an oil inlet port 60 which may be connected by a pipe 6| with any sultable source of supply of oll under pressure. The chamber I3 has an oil outlet port 62 which may be connected with an oil circulation pipe 63. The oil inlet and outlet pipes may connect with any suitable source of supply of oil, not shown, and may further have pump means and heating means associated therewith whereby the oil may be circulated and heated and placed under pressure as more fully hereinafter explained in connection with Fig. 6.

In the operation of the device disclosed in Figs. 1, 2, 3 and 4 the control of the nozzle valve 2| is accomplished by variations in the temperature of the oil. As the viscosity of the oil varies with the temperature this constitutes one practical way of controlling the discharge of oil from the burner may be re-circulated through suitable heating means. It will be understood that the by-pass valve 36 will always be open when the liquid in the chamber 38 surrounding the pipe I6l is cold. As the temperature of the circulating oil increases the viscosity thereof will be lessened and this Warmer oil will'heat up the liquid in the chamber 38 thereby producing expansion of said liquid, which expansion will be exerted under the bellows-like member 42. This will lift the stem 43 and swing the outer end of the lever 46 downwardly and depress the outer end of `the toggle member 5I until the line of pull of the spring 51 passes below the center of the bolt 52 whereupon the

cranks

55 and 54 will both be snapped downwardly and the by-pass valve 36 will close the port 34. This closing of the by-pass valve 36 will not occur until the oil has been heated up sufliciently to be of proper viscosity for efcient atomizing and burning. As soon as the by-pass valve 36 closes oil pressure will build up in the chamber I2 and move the piston valve 21 to the right from the position shown in Fig. 2, thus opening the nozzle valve 2| and allowing oil to be sprayed from the atomizing nozzle I8. While the by-pass valve 36 remains closed the piston 21 will hold the nozzle valve 2| open and said piston may uncover or partially uncover the relief port 35 thus keeping the oil pressure at the nozzle constant and permitting excess oil to escape through the relief port 35 and re-circulate. As long as oil above a predetermined temperature is flowing through the annular passageway 24 it will keep the thermostatic liquid in the chamber 38 heated and expanded, the stem 43 will be held in lan elevated position and the by-pass valve 36 will remain closed and the burner will continue'to operate normally. If the temperature of the oil drops below the predetermined minimum temperature the liquid in the chamber 38 will contract thus permitting the spring 45 to move the stem 43 downward and actuate the quick opening and closing mechanism which will open the by-pass valve, whereupon the pressure against the piston 21 will be relieved and the nozzle valve 2| closed. This stops the discharge of oil from the burner until the oil is again heated up enough to close the by-pass valve 36 and re-open the nozzle valve 2 I. The switch 58 will be in an open circuit position when by-pass valve 36 is open and nozzle valve 2| closed and in a closed circuit position when the by-pass valve 36 is closed and nozzle valve 2| open as hereinbefore explained,v to prevent operation` of -the safety circuit of the burner when the nozzle valve 2| is closed and the oil circulating but not discharging from the nozzle.

In Figs. v5 and 6 I have shown an alternative construction in which an electromagnet is employed as a quick opening and quick closing means for the by-pass valve. In this disclosure is shown a

housing having chambers

66, 61, 68 and 69 which correspond with the chambers II, I2, I2' and I3 respectively of the type ofl control first described, Fig. 5 also discloses a burner pipe 10, burner tube`1I, by-pass port 12, relief port 13, and spring loaded piston 14 all similar to the previously described corresponding parts. A by-pass valve 15 arranged to close the by-pass port 12 is connectedwith the core 16 ofan electromagnet 11. The circuit to the electromagnet 11 is controlled by the temperature of the oil which circulates through the pipe 10 and tube 1I. When the temperature of this oil is below a predetermined minimum then the circuit to the electromagnet 11 will b e closed and the by-pass valve 15 snapped open and held open until the oil is again heated up suiliciently to open the circuit to the electromagnet 11 whereupon the by-pass valve 15 will be permitted to close by gravity. The chamber 66 has an oil inlet port 18 and the chamber 69 has an oil discharge port I I8` The control of the circuit to the electromagnet 11, see Fig. 6, will preferably be by Ymeans of a thermostatically operated switch II9 which is located so that it will be controlled by oil returning through pipe I 20 to a tank |22. The oil may be drawn from tank |22 through pipe |23 to pump |24 and may then pass through pipe |25, oil heater |26 and pipe |21 to the intake port 18, thereby completing an oil circulation circuit. Circuit `wires |28 may extend between the switch I I9 and the electromagnet 11.

In Figs. 7, 8 and 9 I have disclosed control means which is operated by the viscosity of the uid fuel. In this disclosure I provide a housing 60 having chambers 8|, 82, 83 and 84. An oil inlet 86 connects with the chambe`8| A tapered viscosity control valve 81 is adjustably supported within a tapered passageway 88 in the wall which separates the chambers 8| and 62. An oil burner pipe 89 communicates with the chamber 82. A return tube 90 coaxial within the oil burner pipe 89 extends back through the chamber 82 and communicates with the chamber 84. An axial nozzle valve control rod 9| disposed within the return tube 90 is connected with a spring pressed piston valve 92 in a cylinder 93 which opens into the chamber 84. 'I'he cylinder 93 has a relief port 94 communicating with the oil outlet charnber 83. A cylindrical opening 95 is provided between the chamber 8| and the chamber 84 and a piston valve 96 is movably disposed within said opening 95. A spring 91 exerts a downward pressure on the piston 'valve 96. A relief port 98 con-- nects the cylindrical opening 95 with the chamber 82. A by-pass port |00 connects the chamber 84 with the outlet chamber 83 and a by-pass valve IIII is provided for opening and closing the by-pass `port |00. IThe by-passvalve IUI is connected with the piston valve 96 by a yoke |02 whereby said by-pass valve is opened and closed by move- A ment of the piston valve. A compression spring |03 is interposed between the top side of the yoke |02 and ahead |04 on the top of the by-pass valve I0| whereby lost motion in an upward direction is aiorded the yoke |02 relative to the by-pass valve IUI as the piston valve 96 moves upwardly. Assuming that the valve |0| is closed, as shown in Fig. 9, and held closed by oil pressure in chamber 84. Then if the piston 96 is moved slowly upwardly the spring |03 will rst be compressed until the coils are substantially closed at which time the valve 8| will begin to open, pressure in chamber 84 will be relieved andthe spring |03 will snap the valve wide open irrespective of further upward movement of the piston. In closing, the spring |93 holds the valve |0| in the uppermost position as respects the yoke |82 until the end oft-the valve IUI begins to substantially restrict the outlet of oil through by-pass port |80 and increase the pressure in chamber 84 whereupon the spring allows the valve |0| to snap entirely closed irrespective of downward movement of the piston 96.

In the operation of this viscosity controlled means, when fuel of relatively high viscosity is introduced into the chamber 8| it will be of too thick and sluggish a consistency to iiow readily through the restricted port 88- and past the tapered valve 81 and a pressure will be built up in the chamber 8| which will raise the piston valve 96 and open the by-pass valve |0| and port 98. This will permit the oilto ow through port 98 into chamber 82 thence out through burner pipe 89 and back through tube 90 to chamber 84 thence downthrough by-pass port |88 into outlet chamber 83 from which it may pass outwardly through outlet, pipe 83' and be re-circulated. When this occurs the oil will be in contact with the piston 92 but will not exert pressure enough to move said piston 92 against the pressure of a spring 92' because the by-pass valve is open. As long as the high pressure is maintained in chamber 8|, the oil will thus continue to circulate without opening the nozzle control valve 2|, which may be identical with the valve 2| shown in Fig. 4.

As the viscosity of the oil becomes less and when the desired viscosity is attained the thinner oil will flow more freely past the tapered valve 81, pressure within the chamber 8| will be lessened and the piston valve 96 will close and `will close the by-pass valve IM, at the same time. As soon as the by-pass valve |0| is closed the pressure in the chamber 84 will increase and move the piston 92 rearwardly thus opening the nozzle 2| and permitting atomized oil to be discharged from the nozzle. 'Ihe port 94 will also be partially opened by rearward movement of the piston 92 and will maintain an even pressure and allow excess oil to re-circulate. As long as the fuel remains thin and of low' viscosity it will ow past the tapered valve 81 and maintain an approximately equal pressure in` the chambers 8|, 82 and 84 and the by-pass valve |8I will remain closed. If however the viscosity -of the fuel increases and produces a suiliciently yhigh pressure in chamber 8| the piston valve 96 will be raised andthe by-pass valve |0| opened thus lowering the pressure against the piston valve 92 and permitting the spring behind said piston 1 valve 92 to vmove this piston valve and shut oi I claim:

1. In an oil burner, a burner head including a housing, an oil burner pipe extending outwardly from said housing, an oil atomizing nozzle connected with the outer endA of said burner pipe, a return pipe within said oil burner pipe, an oil inlet chamber in said housing communieating with the inner end of said oil 4burner pipe, a by-pass chamber in said housing separate from said oil inlet chamber and communicating with said return pipe, by-pass valve means controlling the pressure of oil within said bypass chamber by-pass valve opening and closing means connected with said by-pass valve means and controlled by the physical condition of the oil passing through the burner, a nozzle valve positioned between said oil atomizing nozzle and the outer end of said return pipe, a .cylindrical chamber communicating with said by-pass chamber, a piston in said cylindrical chamber having one end subject to the pressure within said by-pass chamber, spring means yieldingly engaging the other end of said piston, and stem means connecting said piston with said nozzle valve whereby said nozzle valve is opened by movement of said piston in response to pressure within said by-pass `chamber.

2. In an oil burner, a burner head including a housing, a burner pipe extending outwardly from said housing, a return pipe within said burner pipe, an oil inlet4 chamber within said housing communicating with the inner end of said burnerI pipe, a by-pass chamber in said housing separatel from said oil inlet chamber and communicating with said return pipe, bypass valve means controlling the discharge of oil from said by-pass chamber, a nozzle valve positioned between said oil atomizing nozzle and the outer end of said return pipe, opening and closing means connected with said bly-pass valve means, means responsive to the physical condition of the oil which is being supplied to the burner controlling said opening and closing means, a cylindrical .chamber communicating with said by-pass chamber, said cylindrical chamber having a relief port in the wall thereof, a piston in`said cylindrical chamber movable to cover or uncover said relief port and having one end subject to the pressure within said bypass chamber, spring means supporting said piston against the pressure in said by-pass cham.

ber, and stem means connecting said piston with said nozzle valve whereby said nozzle valve and said relief port may both be opened by movement `of said piston due to pressure within said by-pass chamber.

3. In an oil burner, a burner head including a housing, an oil burner pipe connected with said housing, an atomizing nozzle connected with the outer end portion -of said burner pipe, a return pipe within said burner pipe, an oil inlet chamber in said housing, a second chamber in said housing, communicating with the inner end of said oil burner pipe and having an -opening of restricted area communicating with said oil inlet chamber through which oil under.pressure will pass from said oil inlet chamber to said second chamber at a rate varying with the viscosity of the oil, a by-pass chamber in said housing communicating with said return conduit and separate from the chamber which communicates with said burner pipe, by-pass valve means controlling the discharge of oil from said'bypass chamber, a nozzle Valve positioned between said oil atomizing nozzle and the outer end of said return pipe, a cylindrical chamber communicating with said inlet chamberand having a port connecting said second chamber and said cylindrical chamber, a piston valve in said cylindrical chamber responsive to the pressure in'said oil inlet chamber and `connected with said by-pass valve means for opening and closing said by-pass valve means, said port being arranged to be opened and closed by movement of said by-pass valve control piston, a second cylindrical chamber communicating with said by-pass chamber, said second cylindrical chamber having a relief port in the wall thereof, a nozzle valve control piston in said second cylindrical chamber movable to close said relief port or open said relief port as respects said by-pass chamber and said return pipe and having one end subject to the pressure within said by-pass chamber, spring means supporting said nozzle valve control piston against the pressure in said by-pass chamber,

and stem means connecting said nozzle valve.

control piston with said nozzle valve.

4. In an -oil burner, an oil` atomizing nozzle, pressure oil supply means communicatively connected with said oil atomizing nozzle, oil return conduit means connected with said pres-` sure oil supply means, a nozzle valve in said pressure oil supply means between said oil atomizing nozzle and said oil return conduit means, a bypass chamber communicating with said oil return conduit means, a by-pass valve controlling the discharge of oil from and thereby the pressure in 'said by-pass chamber, by-pass valve operating means connected with said by-pass valve, control devices lfor said by-pass valve operating means governed by the physical condition of the oil which is being supplied at said oil burner, and pressure actuated nozzle valve opening and closing means controlled by pressure in said by-pass chamber.

5. In an oil burner, an oil atomizing nozzle, pressure oil supply means communicatively connected with said oil atomizing nozzle, oil return conduit means "connected with said pressure oil supply means, a nozzle valve in said pressure oil supply means between said oil return conduit` pressure on the two sides'of said passageway` higher on` the inlet and lower on the discharge side 'of said passageway said diilerence increasing as the viscosity of the oil increases and decreasing as the viscosity of the oil decreases,v

and by-pass'valve operating means controlled by difference in pressure on the two sides of said restricted orifice -opening said by-pass' valve as said difference in pressure increases and closing said by-pass valve as said difference in pressure decreases.

6. In an oil burner, an o il circulating burner headembodyinga housing, an oil conduit extending outwardly from saidv housing, a return conduit within said oil conduit," said return conduit leaving a space between its exterior and the interiorof said oil conduit, said housing having an oil inlet communicating vwith the inner end of said oil conduit and a by-pass chamber communicating with the inner end of said return conduit, a by-pass valve controlling the discharge of oilfrom and thereby the pressure insaid b'ypass chamber, thermostatic means operatively connected with said oil conduit responsive to variations in the temperature of the oil which is being circulated through said oil conduit; bypass valve `opening and closing means connected with said by-pass valve and controlled by said thermostatic means; an oil atomizing nozzle on the outer end of said oil conduit adjacent an end of said return conduit, a nozzle valve controlling the flow of oil through said nozzle positioned between said oil atomizing nozzle and the outer end of said return conduit, and pressure operated opening and closing devices connected with said nozzle valve and in communication with said by-pass chamber whereby said nozzle valve is controlled by said by-pass valve.

'7. In an oil burner, an oil circulating burner head embodying a housing, an oil conduit extending outwardly from said housing, a return' conduit within said oil conduit, said return 'conduit leaving a space between its exterior and the interior of said oil conduit, said housing having an oil inlet communicating with the inner end of said oil conduit and a by-pass chamber communicating with the inner end of said return conduit, a by-pass valve controlling the discharge of oil from and thereby the pressure in said bypass chamber, electromagnetic valve opening and closing means connected with said by-pass valve, thermostatic switch means responsive to the temperature of oil which is being supplied to the burner controlling said electromagnetic means, an oil atomizing noz'zle on the outer end of said oil conduit adjacent an end of saidfreturn vconduit, a nozzle valve controlling the ow of oil through said nozzle positioned between said oil atomizing nozzle and the outer end of said return conduit, and pressure operated opening and closing devices connected with said nozzle valve and in communication with said by-'pass chamber whereby said nozzle valve is controlled by said by-pass valve. Y

8. In an oil burner, an oil circulating burner head embodying a housing, an oil conduit extending outwardly from said housing, a return conduit within said oilconduit. said return conduit leaving a space between its' exterior and the interior of said oil conduit, said housing having an oil inlet communicating with the inner end of said oil conduit and a chamber communicating with the inner end of said return conduit, said chamber lhaving a by-pass port, a

by-pass valve controllingV the discharge of oil through said port and thereby the pressure in said chamber, an oil atomizing nozzle on the outer end of said oil conduit adjacent an end of said return conduit, a valve controlling the flow of oil through said nozzle positioned between said `oil atomizing nozzle and the outer end ot said return conduit, opening and closing means con- ,nected with said by-pass valve, operating Jmeans for said opening and closing means, said operatingmeans being responsive to variations in the viscosity oi the oil which is being. supplied to the burner, and pressure operated opening and l closing devices connectedwith said nozzle valve and in communication with said chamber whereby said nozzle valve is controlled by said by-pass valve.

9. In an oil burner, a burner head including-a housing, an oil burner pipe extending outwardly from said housing, an oil atomizing nozzle connected with the outer end of said burner pipe, a return pipe within said .oil burner pipe, an oli inlet chamber within said housing and communieating with said oil burner pipe, a by-pass chamber in said housing, separate from said oil inlet chamber, and communicating with said return pipe, a by-pass valve controlling the discharge of oil from and thereby the pressure in said-by-pass chamber, a nozzle valve positioned between said oil atomizing nozzle and the outer end ofv said return pipe, by-pass valve opening and closing means connected with said by-pass valve, means responsive to the physical condition of the oil which is being 1supplied at the burner for controlling said by-pass valve opening and closing means, a pressure operated opening and closing device connected with said nozzle Valve and operated by the pressure in said by-pass chamber, and said by-pass chamber having a pressure relief port controlled by said opening and closing device so as to permit a circulation of oil through said by-pass chamber when said by-pass valve is closed.

10. In an oil burner: an atomizing nozzle having a delivery orifice, a conduit for conducting oil to a point adjacent said orifice, a conduit for conducting oil from said point, a valve between4 said point and said orifice for controlling the flow of oil from said point to said orifice, and

means for operating said valve in response to a 11. A liquid fuel burning apparatus including a burner tube supplied with liquid fuel by means of a pump, an oil heater for said fuel, a valve provided in said burner tube and adapted to open automatically to discharge the liquid for ignition when said fuel reaches a predetermined pressure, a discharge pipe extending from said burner tube, and automatically acting retardation means associated with said discharge pipe and adapted t delay the rise of liquid fuel pressure in the burner tube after the pump' has been started and Ythereby delay the opening of the aforesaid valve.

12. A liquid fuelburning apparatus as claimed in claim 11 in which the automatically acting retardation means include a thermostatically-controlled valve provided in the discharge pipe from the burner tube.

13. A liquid fuel burning apparatus as claimed in claim 11 in which the automatically acting retardation means include a valve adapted to control the flow of the liquid fuel through the discharge pipe from the burner tube, and means adapted to maintain said valve open-after the pump has started and subsequently to close said valve and thereby permit the burner valve tube to open.

14. A liquid fuel burning apparatus, comprising: a burner, means for supplying fuel under pressure to said burner, a Valve provided in said burner and adapted to open to discharge fuel for ignition upon a predetermined pressure in said fuel, a discharge pipe extending from said valve, retardation means in said discharge pipe for changing the pressure in said fuel, a heater for said fuel, and means for controlling said retarde.

tion means in response to a change in the temperature of said fuel.

LAWRENCE L. FINNIGAN.