Oil burner nozzle

To improve the oil supply and to prevent retarded dripping of oil from an oil burner nozzle when the burner flame has been extinguished, oil supply members are made of a heat-insulating material and positioned in the interior. The oil supply in the nozzle is provided by a oil filter with one or a plurality of solid porous bodies having narrow oil supply conduits. It has been shown that a porous plastic material, in particular a sintered plastic material, is advantageously suited for this purpose. The nozzle head, which can be screwed directly into the oil pre-heater, may comprise a metal with good heat conducting properties or a ceramic material and, in contrast thereto, the oil supply members submerged into the oil are made of a heat-insulating material. Thus, it is not only possible to manufacture the oil burner nozzle in a cost-effective manner, but it also has a considerably improved dripping effect, particularly if the oil supply members have a resistance control because of appropriate porosity or a sponge-like structural design.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to an oil burner nozzle having a nozzle head with a 
nozzle bore as well as oil supply members, such as a retarding disk and an 
oil filter, particularly for direct screw connection with an oil preheater 
of an oil burner. 
2. Description of Prior Art 
In a home heating system the function of the oil burner nozzle as the 
muzzle piece is not only to spray the oil under pressure into the 
combustion chamber, but because of its structural arrangement and the 
intentional formation of a spraying pattern of the atomized oil it also 
considerably contributes to good combustion of the heating oil. A poor 
spraying pattern regularly reduces the efficiency of the entire heating 
system. For this reason, it has become the custom to check and, if 
required, readjust the oil spray effect of a burner nozzle in the course 
of normal maintenance of a heating system. 
The area of the nozzle bore, in particular of the very narrow tangential 
slits in the retarding disk directly ahead of the nozzle bore, is a 
natural, often occurring trouble area because of the danger of blockage. 
Nozzle filters are presently used, almost without exception, for avoiding 
the danger of blockage and are also intended to catch fine dirt particles 
immediately ahead of the nozzle. Simple screens used in older conventional 
nozzles, which were intended more for retaining larger pieces of dirt, are 
useless with respect to fine particles. Filter inserts are almost 
exclusively used today which can also become blocked, particularly as the 
porosity of the filter material becomes relatively fine. Increased demands 
on the total degree of efficiency of combustion, together with continued 
reduction in the use of oil, make the greatest demands on the function of 
the oil burner nozzle. 
In contrast to a pure water or steam nozzle, the oil burner nozzle is 
subject to at least one very particular requirement. The interior surface 
of the oil burner nozzle guides the preheated liquid oil to the outlet 
nozzle. The exterior of the nozzle extends with its nozzle tip directly 
into the combustion chamber. Thus, the oil burner nozzle is unavoidably 
and considerably heated. So that the nozzle can maintain a satisfactory 
degree of effectiveness together with long service life, in the known oil 
burner nozzles at least the nozzle head and the retarding disk are 
constructed of high quality chromium steel and the nozzle oil filter is 
constructed of a sinter metal. 
Without a doubt, the problem of achieving long service life with continuous 
use of the oil burner nozzle is currently solved with the use of highly 
heat-resistant materials. However, recent complaints have arisen with 
respect to retarded drip as a trouble source. It is known that in many 
uses, the oil burner nozzles continue to drip after the burner flame is 
extinguished. The large the oil burner nozzle, the more often such 
retarded drip occurs which, in the extreme case, can lead to the formation 
of a pool of oil at the bottom of the combustion chamber. It is apparent 
that such retarded drip problem can result in damage. It has been 
attempted to avoid at least heavy afterflow by the interposition of 
special valves, analogously to the problem area of dripping prior to the 
ignition of the burner flame. Each drop of oil which is not correctly 
atomized results in degradation of the combustion, in particular in an 
increase in uncombusted fuel. Thus, retarded dripping always results in an 
increased output of uncombusted hydrocarbon compounds, which constitute a 
considerable portion of air pollution. 
SUMMARY OF THE INVENTION 
Thus it is one object of this invention to develop a cost-efficient oil 
burner nozzle which assures optimum function an in particular which 
prevents retarded drip. 
This object is achieved by having at least a portion of the oil supply 
members comprising of a heat-insulating material, or by having the oil 
supply conduits inside the oil burner nozzle at least partially made of 
heat-insulating materials. 
According to this invention, it is shown that additional problems are 
created by conventional attempts to solve the existing problems by 
concentrating only on maximizing heat resistance of the materials. With 
this invention, it is apparent that highly heat-resistant metals can 
resist the effects of the heat of an oil flame over a long service life. 
As long as the flame is burning, fresh air and preheated oil at 70.degree. 
C. to 80.degree. C. flow, so that sufficient heat is removed from the oil 
burner nozzle. But as soon as the burner flame is extinguished, the flow 
of fresh air and heating oil stops. 
In this case, the oil burner nozzle is subjected to comparatively high heat 
radiation, at least in the area of the outlet nozzle. This is the case 
particularly if ceramic blocks are present in the combustion chamber. 
Regarding the present problems, metals have multiple negative properties 
because they not only quickly absorb heat, but are also good heat 
conductors and have a large heat retention capacity. Thus, the metallic 
parts transmit heat they have received and retained to the oil in the 
nozzle by means of direct heat conduction and thereby heat the oil. Then 
the heated oil droplets can exit in the area of the nozzle because of a 
natural increase in volume and the fact that they are otherwise contained 
on all sides. Furthermore, a heat balance of the entire heated oil burner 
nozzle, including the oil preheater and the oil under pressure contained 
therein has never been performed. Heated oil, even though in relatively 
small amounts, continues to flow out of the prechamber of the nozzle until 
sufficient cooling has been attained and exits in droplets. With the known 
solutions, this lasts until superheated wall elements no longer radiate 
heat into the combustion chamber and is continued after every time the 
burner flame is extinguished. 
This problem can be considerably reduced by this invention since at least a 
portion of the oil supply members are made of a heat-insulating material. 
In contrast to metal, heat-insulating materials have exactly opposite 
properties and since heat is not very well absorbed, very little heat is 
retained and thus heat is poorly transmitted. In this way, the amount of 
heat radiation from the combustion chamber into the oil of the nozzle, 
after the flame is extinguished, is reduced to a minimum. Not only is 
retarded dripping due to heat effectively prevented, but it is also 
possible to design and sheathe the combustion chamber. Ceramic portions of 
the combustion chamber which continue to radiate heat are now no longer a 
nuisance. 
This invention has a considerable number of particularly advantageous 
embodiments. For example, the oil filter and in particular the primary 
filter are preferably made of a heat-insulating material, particularly 
preferred is a porous sintered plastic material. This has the advantage 
that the filter, essentially submerged in the oil, absorbs relatively 
little heat from the nozzle head, and retains relatively little heat and 
only minimally transfers heat to the oil. 
According to one preferred embodiment of this invention, the oil filter is 
essentially made from a solid body, in which one or a plurality of narrow 
conduits are provided so that the oil can flow in the direction of the oil 
flow, to increase the filtering effect. Thus, it is possible to reduce the 
free volume of oil in the nozzle and to increase the filter path without 
any disadvantage with respect to the previously mentioned heat problems. 
The solid body can also be of greater length than that of the conventional 
oil filters. To increase the effectiveness of the filter, the filter body 
preferably has a rough porosity on the outside at the oil inlet end and a 
finer porosity towards the inside, which keeps the dirt particles at 
correspondingly different levels. 
The oil filter ca be constructed of a heat-insulating material, preferably 
having colors in a range from white to yellow, as visual indicator colors 
of contamination. In accordance with another preferred embodiment of this 
invention, it is possible to choose the coloring for indicating the flow 
rate in kg/h, for example, yellow for a low flow rate and white for a high 
flow rate. This color scheme can provide maintenance personnel with a 
simple indication of the types, for example in case the oil burner nozzle 
must be replaced. 
It is also possible to position in the oil filter an insert for reducing 
the interior volume of the filter, which preferably is of a non-metallic 
material. The oil filter and the insert can be made of one piece or 
separate pieces. 
A detailed inspection of a conventional oil burner nozzle shows that a 
number of influencing factors, although known, have not been taken into 
consideration for the design of the components. Super-light heating oil 
has properties very similar to that of creep oil. The oil pre-heater can 
be considered to be a small oil reservoir, having a narrow bore in the 
center. Depending on the particular structural design, it is possible for 
oil to drip out of the continuously open nozzle bore until the median oil 
level has been attained. Another problem arises when a certain amount of 
air or, respectively, gas is contained in the oil, which can collect in 
the form of bubbles in the oil pre-heater. In contrast to the gas, the 
bubbles can be compressed which has the result that corresponding to the 
degree of compression of the bubbles, an amount of oil drips out until the 
air bubble is free of pressure. 
For this reason, according to one preferred embodiment of this invention in 
the heat-insulating material of the oil filter is provided a resistance 
control, or pressure barrier, by means of an appropriate structural design 
in such a way that essentially no oil flows below a certain pressure, for 
example 1.5 bar. By selecting a sponge-like interior part of the filter, 
or a structural design having a capillary function, a particularly 
effective pressure barrier is achieved which at a slight overpressue, and 
particularly in a pressure-free state, prevents free dripping, such as 
that of a leaky faucet. The oil filter which is made of a porous material 
can be directly attached to the nozzle head in the form of a clamped body, 
for which purpose it is possible to provide a thread in the plastic of the 
primary filter for a threaded connection with the nozzle head. 
It is particularly cost-effective and advantageous in operation if the 
nozzle head consists of heat-resistant metal, i.e. its exterior is 
heat-conducting, while the filter connected to its inside is made of 
sintered plastic material and acts in a heat-resistant manner. By directly 
screwing the nozzle head to the oil pre-heater, also made of metal, it is 
possible to transfer the heat from the nozzle head, conducted by the 
metal, to the oil pre-heater housing. However, because of its physical 
properties, the filter which is submerged in the oil transfers almost no 
heat to the oil in spite of its connection with the hot nozzle head, 
corresponding to the example of heat insulation between the handle of a 
pan made of plastic and a pan made of metal, known from household use. 
Furthermore it is also possible to make the nozzle head of a ceramic 
material and the oil supply members of a heat-resistant heat-insulating 
material. The primary filter and/or the secondary filter can be embodied 
so that they can be pressed into a metal nozzle head. 
This invention will be described below in further detail by means of a 
number of preferred embodiments.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to FIGS. 1, 1a and 2, an oil burner nozzle, 1 has the basic 
elements of a nozzle head 2, an oil filter 3 and a retarding disk 4. In 
the lower part, the nozzle head 2 has a screw thread 6 and its center part 
has a hexagonal shape and is provided with a nozzle bore 5. The retarding 
disk 4 is positioned directly in front of the nozzle bore 5 in the 
interior of the nozzle head 2. It is important that the retarding disk 4 
is maintained in an exact position, which is assured by a neck 7 of the 
retarding disk 4 and an upper filter part 8. For this purpose, the oil 
filter 3 has a threaded connection 9, over which the filter is screwed 
into the nozzle head 2. The oil is essentially routed along the following 
path inside the oil filter 3: arrows 10 mark the inlet into the oil filter 
3, the arrow 12 shows the path of flow within narrow conduits 11, which 
are disposed longitudinally in the lower filter part (35) which is 
otherwise embodied as a solid body, and arrow 13 indicates the flow change 
into an overflow conduit 14. In accordance with the arrow 15, the oil is 
further guided through a secondary filter 16. The arrow 17 indicates the 
flow within a flow-off conduit 19 ending directly on the top of the 
retarding disk 4 facing the nozzle bore 5. The volume of the overflow 
conduit 14 is reduced by a filler plug 40, which is also constructed of 
heat-insulating material. 
Another preferred embodiment of a oil burner nozzle according to this 
invention is shown in FIG. 3, partially in a plan view and partially in a 
sectional view. 
Similar to that as shown in FIG. 1, here too the oil filter 3 is directly 
screwed into the nozzle head 2 via a thread 20. An oil supply member 21 
extends above the oil filter 3 in the upper central area. The oil supply 
member 21 at the same time has the function of reducing the volume of the 
hollow chamber. The retarding disk 4 is maintained in place with a fixing 
screw 22, known per se. The appropriate parts are shown somewhat distorted 
in FIG. 3 in order to clarify the interior oil supply members. A spray con 
23 has been schematically illustrated in the area of the nozzle bore 5. 
One preferred embodiment of the oil filter 3 is shown in section in FIG. 
3a, which essentially comprises a main filter body 24 and an inner drip 
stopper body 25, both of which are preferably made of a heat-insulating 
material. For example, the outer main filter body 24 can comprise a porous 
sintered plastic material and essentially has a pure filtering function. 
However, here the drip stopper body 25 not only is of a finer porosity, 
but also has a structural shape similar to that of a sponge with strong 
capillary action. As a result, active suction and retaining effects are 
provided by the material, which may be similar in structure to the known 
writing tips of felt ink pens The penetration path into the drip stopper 
body 25 is very short, for example only 1 to 2 mm or less. In contrast 
thereto the flow-through area is large. This has the result that with 
minimum pressure forces the adhesion is great enough that the oil does not 
flow through. By increasing the pressure, for example, to around 10 bar, 
the desired oil flowrate can be assured and can flow off through the 
narrow bore 11. 
A burner nozzle assembly 30 with an oil burner nozzle 1, filled with oil as 
shown by the broken lines, is illustrated in FIGS. 4, 5 and 5a. An air 
bubble 31 has been drawn in FIG. 4 for clarification. Conventional means 
have been attempted to prevent such bubbles, however, it must be assumed 
that retarded dripping of the oil burner nozzle 1 is aided by their 
presence. It is only intended to indicate in FIG. 4, by the crossed-out 
drop "Dr", that the latter should be prevented. It can be further seen in 
the drawing figure that the upper half of the amount of oil in the burner 
nozzle assembly 30 is higher by the distance D/2 than the nozzle bore 5, 
so that by reason of the natural pressure gradient and the creeping 
ability of the oil, a relatively large amount of oil droplets can be 
discharged, depending on the circumstances, something which is intended to 
be prevented in accordance with this invention. 
FIG. 6 shows the head of an oil burner, together with the burner nozzle 
assembly 30, an ignition electrode 32, a photoelectric cell 33 and an air 
supply grid 34, through which air "L" is introduced into the combustion 
chamber.