Fluid fuel burner with automatic fuel shut-off valve

An oil burner having an atomizing nozzle receptive of a supply of oil through an oil tube therein and receptive of a supply of air under pressure through an air tube therein for atomizing the oil, includes an oil shut-off valve device which is responsive to the pressure of the air in the air tube for normally preventing the passage of oil from the oil tube to the nozzle until the air pressure rises above a given value and for shutting off the passage of oil from the oil tube to the nozzle when the air pressure falls below a given value.

BACKGROUND OF THE INVENTION 
The present invention relates to fluid fuel burners and in particular oil 
burners having atomizing nozzles which are supplied with oil and 
pressurized air for atomizing the oil. Such burners are typically used in 
glass melting furnaces and applied vertically downwards through the crown 
of the furnace ports. 
With oil burners of this type, when in normal use, they are fired for a 
20-minute period and then shut off for a similar time. During the shut-off 
period, cooling air is passed through the burner to keep the nozzle cool 
and clean. 
A problem that has developed with this type of burner during the shut-off 
period, is that when the fuel is shut off, a slight amount of oil remains 
in the burner and consequently travels to the nozzle. After-burning occurs 
at the fuel nozzle when the burner is left in the furnace. This 
after-burning acts to damage the nozzle and shorten its useful life. 
In a known prior art device, a burner has an oil shut-off valve which is 
operated by the oil pressure therein. This burner has the disadvantage 
that the position of the oil shut-off valve is dependent on the oil 
pressure and the oil pressure is dependent in turn on the flow to the 
burner. This means that a highly complex control system is required on 
each burner to control the oil flow and a reliable shutting off of the oil 
flow without leaving oil in the nozzle is not obtained. 
SUMMARY OF THE INVENTION 
The present invention eliminates the disadvantages of the prior art oil 
burners and provides an oil burner with an automatic oil shut-off valve 
which is responsive to the pressure of the atomizing air to prevent oil 
from remaining in the nozzle when the burner is shut off. 
The present invention also provides a visual indication that the oil 
shut-off valve is either in the open or closed position and a pilot valve 
in addition to the oil shut-off valve for providing a more positive action 
by the oil shut-off valve in response to the turning on and off of the 
atomizing air supply. 
These are achieved according to the present invention in a fluid fuel 
burner having an atomizing nozzle receptive of a supply of fuel through a 
fuel tube therein and receptive of a supply of air under pressure through 
an air tube therein for atomizing the fuel, the fuel burner comprising 
fuel valving means responsive to the pressure of the air in the air tube 
for normally preventing the passage of fuel from the fuel tube to the 
nozzle until the air pressure rises above a given value and for shutting 
off the passage of fuel from the fuel tube to the nozzle when the air 
pressure falls below a given value. 
The fuel valving means comprises a fuel feed passage in the nozzle having a 
diameter smaller than that of the fuel tube and disposed concentrically 
with respect thereto and a fuel shut-off rod disposed in the fuel tube and 
having a diameter less than that of the fuel tube to enable fuel to flow 
therearound and through the fuel tube and having a valve head at one end 
thereof nearest the nozzle and configured to close the fuel feed passage 
when disposed therein. Means are provided for mounting the rod for sliding 
movement in the fuel tube, in response to changes in air pressure, for 
movement between a first position wherein the valve head extends into the 
fuel feed passage closing same to the supply of fuel at the second 
position wherein the valve head is retracted into the fuel tube enabling 
fuel to flow therearound and into the fuel feed passage. 
The mounting means comprises a piston connected to the other end of the rod 
and having a bearing surface thereon which defines a portion of a piston 
air chamber which receives air from the air tube. Spring means biases the 
piston against the force of the air in the piston air chamber to normally 
maintain the rod in the first position until the air pressure rises above 
a given value. 
The fuel shut-off valve also includes means movable in response to the 
movement of the fuel shut-off rod and having a portion thereof extending 
outside of the burner for visually indicating whether the rod is in the 
first position or in the second position. In one embodiment the indicating 
means includes an indicator rod connected at one end to the piston and 
movable therewith and having the other end extending outwardly of the 
burner. 
In order to provide for a more positive action by the fuel shut-off valve, 
air is communicated from the air tube to the piston air chamber via a 
passage having a second valving means therein responsive to the air 
pressure in the air passage for normally preventing passage of air from 
the air tube to the piston air chamber until the pressure rises above a 
given value and for shutting off the passage of air from the air tube to 
the piston chamber when the air pressure falls below a given value. In 
this way, the air pressure which acts on the piston is not communicated 
thereto until it reaches a given value thus ensuring a faster action 
thereon. Moreover, the fuel shut-off valve will close faster when the 
atomizing air pressure is reduced, since the pilot valve will sense the 
decrease in pressure and immediately create a zero pressure condition on 
the piston enabling it to shut off the fuel shut-off valve immediately. 
The second valving means also has means for adjusting the spring tension on 
the valve by means of an adjusting screw, this giving the facility of 
altering the effective air pressure that will open or close the fuel 
shut-off valve.

DETAILED DESCRIPTION OF THE INVENTION 
Referring now to FIGS. 1 and 2, the oil burner of the present invention has 
been broken down into four sections for the sake of explanation. Firstly, 
there is the nozzle section 1, an elongated main body section 2, a 
mid-body section 3 and an end section 4. Aside from the portions of the 
oil burner constituting the oil shut-off valve mechanism and the 
conventional oil burner components which have been modified to interrelate 
with the oil shut-off valve, the oil burner displayed in FIG. 1 is 
conventional in construction and, therefore, only those portions which 
interrelate with the improvement of the present invention are discussed 
herein. 
The nozzle section 1 includes a nozzle block 10 having a conventional 
atomizer therein including swirler 11, choke 12 and pressure plate 13. The 
atomizing nozzle is fed with atomizing air under pressure through air 
inlet tube 22 which runs the length of the main body section and which 
receives air through air inlet 30. 
The nozzle also receives the fuel input, which is preferably oil but which 
may be any fluid fuel which is atomizable, from oil inlet 34 which is 
connected to a supply of oil and which thereafter passes through oil tube 
23 which extends the length of the main body section and which terminates 
at the nozzle and feeds passages 15 and 16. Passage 15 is disposed 
concentrically with oil tube 23 and has a diameter which is smaller than 
that of the oil tube 23. 
Also illustrated is water jacket 20 and water inlet tube 21 which are fed 
from a water inlet 26 and which passes outwardly of the burner through 
water outlet 27. 
The oil shut-off valving means includes oil shut-off rod 24 which is 
disposed in the oil tube 23 and has a diameter smaller than that of the 
oil tube so as to enable oil to flow around the oil shut-off rod 24 and 
through the oil tube 23. Oil shut-off rod 24 has a valve head 24a at the 
end thereof closest to the nozzle. The valve head 24a includes an O-ring 
25 which is configured to be received in the oil passage 15 to seal same 
off when disposed therein. 
The oil shut-off rod 24 is mounted for sliding movement in the oil tube 23 
from a first position shown in FIG. 1 wherein the valve head 24a is in oil 
passage 15 and preventing the flow of oil from the oil tube to the nozzle 
and the position shown in FIG. 2 wherein the valve head 24a is retracted 
into the oil tube 23 enabling oil to flow from the oil tube 23 through 
passages 15 and 16 and into the atomizing nozzle. 
The movement of the oil shut-off rod 24 between these two positions is 
effected by the structure shown in the mid-body section 3 and the end 
section 4 of the oil burner and which is responsive to the pressure of the 
atomizing air received through air inlet 30. This structure includes 
piston 40 which is slidably mounted in the end section 4 of the burner and 
limited in its movement on the one hand by shoulder 46 and on the other 
hand by cap plate 43 attached to the end section 4 by screws 44. 
The piston 40 is connected to the other end of the oil shut-off rod 24 via 
locking pin 38. In order to make the movement of the piston 40 responsive 
to the air pressure in air tube 22, a piston air chamber 33 is provided 
which includes as one of its boundries bearing surface 46 of the piston 
40. In order to make the piston air chamber 33 airtight, seal 35 is 
provided on the piston 40 along with seal 36 held in place by a washer 39 
and circlip 37 around oil shut-off rod 24. Air is communicated from the 
air inlet 30 by providing an air inlet chamber 31 in communication with 
the air inlet tube 22 and a piston air feed passage 32 which connects air 
inlet chamber 31 to piston air chamber 33. 
In order to maintain the oil shut-off valve in the closed position until 
the air pressure of the atomizing air reaches a given value, spring 42 is 
provided between seat 41 and cap plate 43 for biasing the piston towards 
the left in FIG. 1 and therefore, the valve head 24a in the closed 
position. 
Furthermore, in order to provide a visual indication of the state of the 
oil shut-off valve, an indicator rod 45 is provided connected to the 
piston by a piston seat 41 and movable therewith. The indicator rod 45 has 
the other end portion thereof passing through aperture 47 in the cap plate 
43 so as to be exposed to observation by a user of the oil burner. 
In operation, when the burner is shut-off, air is provided at the air inlet 
30 of such reduced pressure so as only to act as a coolant for the nozzle 
but has virtually no effect on the piston 40 due to the action of the 
spring 42. As the full air is turned on and the pressure is increased, air 
is bled off from the air inlet chamber 31 through the piston air feed 
passage 32 to the piston air chamber 33 wherein it acts on the bearing 
surface 46 of the piston 40. The piston 40 is moved to the right as the 
pressure is increased, however, oil does not flow into passage 15 until 
the O-ring 25 is retracted into the oil tube 23. 
When the air pressure reaches a given value which is predetermined by 
spring 42 and the distance that the rod 24 must travel to the right before 
the oil passage 15 is opened, oil will then pass into the atomizing 
nozzle. The piston moves to the right in response to further increasing of 
the air pressure until the rear end thereof contacts the cap plate 43 as 
is shown in FIG. 2. In this position the oil shut-off valve is completely 
open so that oil can freely flow into the nozzle and be atomized by the 
atomizing air. 
As can be clearly seen, the indicator rod 45 unmistakably indicates that 
the oil shut-off valve is open when it protrudes extensively as shown in 
FIG. 2 as opposed to it being slightly protruding in FIG. 1 and provides a 
clear indication that the shut-off valve is either open or closed. 
When the burner is to be shut off, the air pressure from the air inlet 30 
is reduced thus enabling the piston 40 under the action of spring 42 to 
move to the left and effect closing of the fuel passage 15. When the fuel 
passage 15 is closed and no more oil can pass into the nozzle, the 
atomizing air which is steadily reducing in pressure acts to atomize all 
of the remaining oil in the nozzle so that no after burning will occur. 
It will be recognized by those skilled in the art that the air pressure 
value at which the piston closes and at which the piston will open may be 
different due to the hysteresis effects of the spring and any 
non-linearities in the spring characteristic thereof. 
By selecting the spring and setting the distance of movement of the oil 
shut-off rod 24, the system can be set up so that when the air pressure 
reaches a certain preset level, oil will flow into the nozzle. This means 
that when the air is at the normal pressure for operating the burner, the 
oil valve is open and when the air pressure is reduced to the non-firing 
condition, the oil valve closes. 
Because of the size of the piston and spring required for the operation 
above, it may be desirable to obtain a more positive action by the oil 
shut-off valve without changing the basic principle of operation. This is 
carried out by the structure shown in FIGS. 3 and 4 wherein piston air 
feed passage 32 is replaced by air passages 32a, 32b, 32c, 32d and 32e 
with a pilot valve arrangement disposed therebetween including piston 50 
and spring 51 in housing 57. 
The pilot valve arrangement is mounted to the side of the burner body by 
means of fixing elements such as screws. A seal is obtained between 
passages 32a, and 32c and air chamber 33 by means of O-ring seals 56. The 
piston 50 in the pilot valve is in two sections 50a and 50b. Section 50b 
is larger in diameter and has an O-ring seal 50c fitted therearound. 
Section 50a has a reduced diameter portion 50e and passes through a seal 
and spacer assembly 50d to ensure that no air passes between passages 32b 
and 32c when piston 50 is in the closed position. 
Passages 32a, 32b, 32d and 32e are in communication with air inlet chamber 
31 while passage 32c is in communication with piston air chamber 33. When 
piston 50 is in the position shown in FIG. 3, there is no communication 
between passages 32a and 32c and any air in piston air chamber 33 can be 
exhausted via passage 32c, reduced piston portion 50e and exhaust hole 53 
in housing 57. 
Spring 51 maintains the piston 50 in the closed position and there includes 
a set screw 54 which is threadably engaged in bore 55 to enable one to 
preset the pressure level at which air passing through passage 32a, 32e 
and 32b will push piston section 50b rightwardly so that passage 32a will 
be in communication with passage 32c. 
In normal use, the full atomizing air pressure is approximately 40 pounds 
per square inch and thus the pilot valve is set to operate at 
approximately 35 pounds per square inch while the piston 40 and spring 42 
can be set to operate at a far lower pressure as long as it is greater 
than zero pounds per square inch. A preferable value for the pressure is 
25 lbs/iq.sup.2. This is particularly useful in actual systems where 
cooling air is passed through the burner during shut-off at a pressure of 
10-15 lbs/in.sup.2. 
In operation (in the ideal case where hysteresis is ignored) as the air 
pressure increases and reaches the value of 35 pounds per square inch, 
piston 50 will open, enabling the air to act upon the piston 40 by sealing 
off hole 53 and providing the path 32a, 32e, 32d, 50e, 32c, where upon it 
will open immediately due to its threshold value of less than 35 pounds 
per square inch. When it is desired to shut off the burner, when the air 
pressure is reduced to below 35 pounds per square inch, but above the 
threshold value of the piston 40, the piston 50 will close the passage 32d 
and open the passage 32c via 50e to exhaust hole 53 whereupon the pressure 
acting on the piston 40 will be zero and the valve will immediately close 
due to the action of spring 42.