Arrangement for pneumatically regulating the introduction of substances into chambers

An arrangement for regulating the introduction of substances into chambers is disclosed and is particularly well-suited for the feeding of coal into coke ovens. The arrangement includes a chamber which is to be filled to a predetermined level and a feeding device is provided for feeding material into the chamber. The feeding device has a switch which stops the introduction of the material to the chamber when the level of the material reaches the predetermined level. The switch for the feeding device is electrically connected with a differential pressure switch which is actuated upon the generating of a predetermined pressure differential across it. The requisite pressure differential is generated by introducing pressurized gas into the chamber and an air compressor may be provided for this purpose. A sensing conduit, which is connected with one terminal of the differential pressure switch, extends into the chamber and has an end positioned at the predetermined level to which the chamber is to be filled. The pressurized gas admitted into the chamber sets up certain pressure characteristics in the sensing conduit which are changed when the level of material in the chamber reaches the predetermined level so that the gas no longer has free access to the open end of the sensing conduit. The change in the pressure characteristics causes a pressure differential to be established across the differential pressure switch which, in turn, activates the feeding device switch to stop the introduction of material into the chamber. In order to compensate for shock waves which may be generated in the chamber by the feeding of the material and which may cause a false signal to be transmitted to the switch of the feeding device, a compensating conduit is provided which has an end in the chamber and is connected with the terminal of the differential pressure switch opposite that to which the sensing conduit is connected. A supply conduit for the pressurized gas is also provided and introduces the pressurized gas into the chamber in the vicinity of the end of the sensing conduit.

BACKGROUND OF THE INVENTION 
The invention relates generally to an arrangement for regulating the 
introduction of substances into chambers. Of particular interest to the 
invention is the introduction of particulate materials into chambers, and 
especially the feeding of coal into coke ovens. 
A known arrangement for measuring and regulating the level of coal in coke 
ovens includes one or more pressure of sensing tubes which extend into an 
oven chamber or chambers. A predetermined gas pressure is maintained in 
such a pressure tube by passing a gas therethrough. A pressure switch is 
connected with the pressure tube and the pressure switch is, in turn, 
electrically connected with a switch for the transporting device which 
conveys the coal to the coke oven. The arrangement just described operates 
to pneumatically measure and regulate the level of the coal in the coke 
oven. 
The pressure of sensing tube has an end located in the coke oven chamber at 
a predetermined level of the latter and, as indicated above, a certain gas 
pressure is maintained interiorly of this tube. The measuring principle of 
pneumatic devices for determining the filling level in coke ovens is 
generally based on the fact that the moist or preheated coal blocks the 
end of the sensing tube to at least some extent when, during the filling 
operation, the level of the coal reaches the level at which the end of the 
sensing tube is located. As a result, the gas flowing through the sensing 
tube which may, for instance, be air, is prevented from freely entering 
the coke oven chamber, that is, the flow of the gas is restricted at the 
outlet end of the sensing tube. This causes a backpressure to be 
generated, that is, this causes a pressure increase interiorly of the 
sensing tube. 
A certain gas flow quantity is required in order that a pressure increase 
may be associated with the abovementioned blockage of the sensing tube. In 
addition, the end of the sensing tube must be immersed in the coal charge 
to a certain predetermined extent. 
The pressure increase which may be achieved interiorly of the sensing tube 
is limited inasmuch as the charge surrounding the end of the sensing tube 
does not completely seal the sensing tube. Thus, only a certain, limited 
resistance to flow will be achieved for a given depth of penetration of 
the end of the sensing tube into the coal charge and gas will continue 
flowing out of the sensing tube into the coke oven chamber even after the 
end of the sensing tube is immersed in the coal charge. Upon exceeding a 
relatively low backpressure, for instance, a pressure corresponding to a 
water column of 100 millimeters where preheated coal is being charged, the 
gas pressure becomes sufficient to blow the end of the sensing tube free 
of coal and to thereby permit the gas, e.g., air, to freely flow into the 
coal charge. The critical pressure increase is still lower where moist 
coal is being charged. Here, the pressure corresponds to a water column of 
only about 20 millimeters. The low pressure increase achieved in the 
sensing tube, which pressure increase may also be referred to as the 
switching pressure, must suffice, when in the form of an impulse, to 
activate the subsequent switching operations such as, for example, those 
terminating the filling operating. For terminating the filling operation, 
the pressure increase must suffice to activate the abovementioned pressure 
switch which, in turn, operates the switch provided for the transporting 
device which conveys the coal to the coke oven. 
The reason why the critical pressures for moist and preheated coals are 
different resides in that the bulk density of moist coal differs from that 
of preheated coal. The difference in bulk density is associated with the 
fact that the free spaces between the individual coal particles are of 
different size for moist and preheated coals. As a result, different 
pressures will be generated in a sensing tube for a given gas quantity, 
the pressure in the sensing tube corresponding to the bulk density of the 
coal being charged. A high bulk density results in a higher pressure and 
vice versa. 
The measuring devices of the above type, which are intended to provide 
signals for the orderly filling of coke oven chambers via small regulating 
impulses as just described, possess certain disadvantages. A particularly 
severe disadvantage resides in the fact that pressure waves are generated 
in the coke oven chamber during the filling operation, especially at the 
beginning of the filling operation. These pressure waves are caused by the 
coal which is being charged into the coke oven chamber. The pressures 
associated with the pressure waves are of about the same magnitude as the 
switching pressures and, accordingly, the pressure waves do not only 
disturb the measuring procedure but make it impossible to carry this out. 
Another disadvantage is associated with the fact that a certain 
predetermined quantity of gas, e.g., air, must be conveyed through the 
sensing tube in order to guarantee that the requisite pressure increase, 
that is, the switching pressure, is achieved. This requires that the 
supply pressure for the gas be adjusted to a level which approximates the 
magnitude of the switching pressure itself. As a result, the measuring 
procedure is made difficult, if not impossible, to carry out. 
SUMMARY OF THE INVENTION 
One subject of the invention is to provide a device and arrangement for 
regulating the introduction of substances into chambers which enable the 
effects of pressure waves generated in the chambers to be eliminated or at 
least virtually eliminated. 
Another object of the invention is to provide a device and arrangement for 
regulating the introduction of substances into chambers which enable the 
effects of the gas supply pressure on the switching pressure to be 
avoided, at least to a great extent. 
An additional object of the invention is to provide a pneumatic device for 
measuring or sensing the filling level in coke ovens which enables the 
disturbing effect of the pressure waves generated in a coke oven during 
the filling operation to be eliminated, which enables the counteraction of 
the gas supply pressure on the switching pressure to be aovided and which, 
simultaneously, enables a sure functioning of the measuring or sensing 
procedure to be insured. 
These objects, as well as others which will become apparent as the 
description proceeds, are achieved in accordance with the invention. 
According to one aspect of the invention, there is provided an arrangement 
for regulating the introduction of substances into chambers, particularly 
for use in the feeding of particulate materials into chambers, which 
comprises a chamber to be filled with a substance to a predetermined 
level. Means is provided for feeding the substance into the chamber and 
switch means is provided for the feeding means. The switch means is 
operative for interrupting the introduction of the substance into the 
chamber in response to a signal generated when the substance fills the 
chamber to the predetermined level to which the chamber is to be filled. 
The switch means includes a differential pressure switch actuable in 
response to the generation of a predetermined pressure differential 
thereacross. The arrangement further includes means for admitting 
pressurized gas into the chamber so as to permit the generation of a 
pressure differential across the differential pressure switch. Means is 
also provided for transmitting pressure signals to the differential 
pressure switch. The transmitting means includes a sensing conduit 
connected with the differential pressure switch. The sensing conduit has 
an end portion arranged in the chamber at approximately the predetermined 
level to which the chamber is to be filled so as to permit the pressure 
characteristics generated in the sensing conduit due to the flow of the 
pressurized gas into the chamber to be changed and a corresponding signal 
to be transmitted to the differential pressure switch when the level of 
the substance in the chamber reaches the predetermined level. The 
transmitting means further includes a compensating conduit having an end 
portion in the chamber and also connected with the differential pressure 
switch. The compensating conduit is operative, in cooperation with the 
sensing conduit, for preventing unintentional actuation of the 
differential pressure switch due to pressure waves generated in the 
chamber by permitting cancellation of the pressure waves occurring across 
the differential pressure switch. 
According to a particularly advantageous embodiment of the invention, the 
objects of the invention are achieved in that a compensating conduit is 
provided in addition to a measuring or sensing conduit which operates as a 
pressure conduit. The compensating conduit and sensing conduit are 
connected with one another exteriorily of the chamber, e.g., a coke oven 
chamber, via a differential pressure switch. A special or separate supply 
conduit is provided for the pressurized gas and is arranged to admit the 
pressurized gas into the sensing conduit at a location of the latter 
immediately adjacent the end or end portion of the sensing conduit which 
is located in the chamber. In the event that the sensing conduit extends 
downwardly into the chamber, the supply conduit is arranged to admit the 
pressurized gas into the sensing conduit immediately above the lower end 
or opening of the sensing conduit. 
A very favorable embodiment of the invention contemplates for the sensing 
conduit and the compensating conduit to be arranged closely adjacent one 
another interiorly of the chamber, e.g., the oven chamber. 
It is further advantageous within the concept of the invention for the 
compensating conduit, the sensing conduit and the gas supply conduit to be 
arranged concentrically within the chamber, e.g., the oven chamber, in 
such a manner that the compensating conduit surrounds the supply conduit 
which, in turn, surrounds the sensing conduit. 
A further embodiment of the invention contemplates for the sensing conduit 
to be bent adjacent the end thereof which is located in the chamber. 
According to an additional embodiment of the invention, the supply conduit 
surrounds the sensing conduit interiorly of the chamber and the lengths of 
the sensing conduit and the supply conduit interiorly of the chamber are 
about the same. The end of the supply conduit interiorly of the chamber is 
open and both the sensing conduit and the supply conduit are provided with 
a bend adjacent the respective ends thereof which are located in the 
chamber. 
The technical advance achievable with the invention resides particularly in 
that an overall reliable measurement may be insured with a pneumatic 
measuring or sensing device according to the invention. This is achieved 
by virtue of simple and neat groupings and with the use of simple means. 
The novel features which are considered as characteristic for the invention 
are set forth in particular in the appended claims. The invention itself, 
however, both as to its construction and its method of operation, together 
with additional objects and advantages thereof, will be best understood 
from the following description of specific embodiments when read in 
connection with the accompanying drawing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The invention relates, in a preferred aspect, to an arrangement for the 
pneumatic measurement and regulation of the filling level of coal in 
coking ovens. The preferred arrangement according to the invention is of 
the type which includes one or more pressure or sensing conduits and a 
pressure switch which is electrically connected with a switch or circuit 
breaker for the coal transporting device. The sensing conduit or conduits 
extend into an oven chamber and a certain pressure exists in the sensing 
conduit or conduits. 
The description which follows will be with reference to the preferred 
application contemplated by the invention, namely, the charging of coal 
into coking ovens. 
Referring now to FIG. 1 of the drawing, it may be seen that this partially 
and schematically illustrates one embodiment of a device according to the 
invention which may be used for measuring and regulating the introduction 
of a coal into coking ovens. The device includes a sensing conduit 1 
having an open end 4 which, in operation of the device, is located 
interiorly of a coke oven chamber. Usually, the sensing conduit 1 will 
extend downwardly into the oven chamber and, hence, the open end 4 of the 
sensing conduit 1 will also be referred to here as the lower end of the 
sensing conduit 1. The sensing conduit 1 also has another end which is not 
shown in FIG. 1 and which, in operation of the device, is located 
exteriorly of the coke oven chamber and is connected with a differential 
pressure switch which has also not been shown in FIG. 1. 
The sensing conduit 1 is surrounded by a gas supply conduit 3 through which 
a pressurized gas such as, for instance, pressurized air, is conveyed. The 
end of the supply conduit 3 which is located in the oven chamber and faces 
tha charge in the chamber, that is, the end of the supply conduit 3 
nearest the open end 4 of the sensing conduit 1, is circumferentially 
closed. Openings 5 are provided in the common wall between the sensing 
conduit 1 and the supply conduit 3 so that the interior of the sensing 
conduit 1 communicates with the interior of the supply conduit 3. The 
openings 5 are provided in the immediate region of the open end 4 of the 
sensing conduit 1. 
The supply conduit 3 has another end remote from that near which the 
openings 5 are provided in the illustrated embodiment. This other end of 
the supply conduit 3, which has not been shown in FIG. 1, is connected 
with a compressor which has likewise not been illustrated in FIG. 1. 
The supply conduit 3 is surrounded by a compensating conduit 2 interiorly 
of the coke oven chamber. The compensating conduit 2 is here assumed to 
have an annular configuration. The compensating conduit 2 has an end, 
shown in FIG. 1, which is located interiorly of the coke oven chamber and 
another end, not illustrated in FIG. 1, which is located exteriorly of the 
coke oven and is connected with the previously mentioned differential 
pressure guage, namely, the differential pressure guage with which the 
sensing conduit 1 is connected. The sensing conduit 1 and the compensating 
conduit 2 are connected to opposite sides or poles of the differential 
pressure switch. 
The sensing conduit 1, the compensating conduit 2 and the supply conduit 3 
are concentrically arranged in FIG. 1. As is clear from FIG. 1, the 
sensing conduit 1 is centrally positioned within the concentric 
arrangement. 
The course of a measuring procedure is as follows: The pressure waves 
generated by the falling coal during a process of charging or filling a 
coke oven or coke oven chamber are corrected for in that the compensating 
conduit 2 is located in the oven chamber in addition to the sensing 
conduit 1. The pressure waves, which affect the actual measuring or 
sensing operation in the prior art, here simultaneously travel to the two 
sides of the differential pressure switch via the sensing conduit 1 on the 
one hand and the compensating conduit 2 on the other hand. As a result, 
the pressure waves are mutually compensated for. In this manner, it is 
possible to insure that a falsified switching pressure is not transmitted 
to the switching devices beyond the differential pressure switch whereas a 
non-falsified or true switching pressure is transmitted to the switching 
devices beyond the differential pressure switch via the latter. 
On the other hand, the counteraction of the gas supply pressure on the 
switching pressure may be avoided in that the pressurized gas is conveyed 
through a separate conduit 3 to a location immediately adjacent the lower 
end 4 of the sensing conduit 1 and is first admitted into the sensing 
conduit 1 proper at this location. This measure permits any arbitrary flow 
losses and gas supply pressures to exist within the limits of the gas 
quantities which are required without any substantial influence on the 
pressure characteristics interiorly of the sensing conduit 1 arising 
therefrom. It is only when the sensing conduit 1 becomes immersed in the 
coal charge that an increase in pressure occurs at the lower open end 4 of 
the sensing conduit 1. This pressure increase quickly travels to the 
differential pressure switch and signals the presence of the corresponding 
switching pressure. 
Referring once again to the construction of a device according to the 
invention, it is pointed out that another embodiment of the invention 
contemplates for the sensing condiut 1 of FIG. 1 to be connected with the 
compressor and to serve as a gas supply conduit whereas the conduit 3 
which previously served as a gas supply conduit is connected with the 
differential pressure switch. This embodiment of the device possesses the 
advantage that, even if relatively large quantities of pressurized gas are 
supplied, the supply pressure is almost zero. Thus, the gas is accelerated 
by the compressor and flows out of the conduit 1 without having to undergo 
a change in direction as is the case when the gas is supplied via the 
conduit 3 and must change direction upon flowing into the conduit 1 via 
the openings 5. Due to the fact that the gas accelerated by the compressor 
flows out of the conduit 1 without undergoing a change in direction, it is 
only the static pressure at the locations of the openings 5 which is 
measured through the latter via the conduit 3. In the first embodiment 
described, namely, the embodiment where the conduit 1 serves as a sensing 
conduit and the conduit 3 serves as a gas supply conduit, it is the 
dynamic pressure which is measured since, due to the change in direction 
of the gas stream, there is additionally generated in the conduit 1 the 
pressure for accelerating the gas in the new direction. 
A further embodiment which falls within the scope of the invention resides 
in that the conduits, and particularly the sensing conduit 1 and the 
compensating conduit 2, are arranged immediately adjacent, yet separate 
from, one another. 
According to still another embodiment of the invention, the gas supply 
conduit 3 surrounding the sensing conduit 1 has the same length as the 
sensing conduit 1 and is constructed with an open end. In other words, the 
lengths of the sensing conduit 1 and the gas supply conduit 3 interiorly 
of the oven chamber are about the same and the end of the supply conduit 3 
located interiorly of the oven chamber is open. The advantage of this 
embodiment resides in that absolutely no supply pressure, which latter is 
dependent upon the flow quantity of the pressurized gas or air, is 
generated in the sensing conduit 1. This is particularly advantageous 
since, upon the introduction of the device into an oven chamber which is 
heated to 1000.degree. C or so, the conduits and, concomitantly, the gas 
quantities within the conduits, are strongly heated. The heating causes a 
volume change of the gas which is accompanied by a change in the flow 
quantity of the gas. The change in the gas flow quantity in turn affects 
the supply pressure. The present embodiment makes it possible to avoid in 
the sensing conduit 1 the changes in supply pressure occasioned by changes 
in the gas flow quantity inasmuch as the present embodiment makes 
provision for supplying the pressurized gas entirely through the gas 
supply conduit 3. A pressure increase in the sensing conduit 1 first 
occurs when the annular gas stream flowing out of the gas supply conduit 3 
surrounding the sensing conduit 1 impinges the coal charge. The 
backpressure which is generated thereby creates the requisite switching 
pressure in the sensing conduit 1. 
FIG. 2 of the drawing illustrates a device according to the invention in 
use during a filling operation and, in particular, during the feeding of 
coal into a coke oven chamber. The same reference numerals as in FIG. 1 
have been used to designate similar components in FIG. 2 and it is pointed 
out that the device in FIG. 2 comprising the conduits 1, 2 and 3 has a 
construction corresponding to the last-mentioned embodiment of the 
invention but with somewhat of a variation as will be discussed more fully 
below. 
FIG. 2 shows a coke oven chamber 10 having a wall 9 and the wall 9 is 
provided with an opening 13 for the introduction of coal into the chamber 
10. A feeding member 14 is positioned astride the filling opening 13 and 
coal is fed into the feeding member 14 via a charging device 18 which may, 
for instance, be in the form of a transporting device for conveying the 
coal to the chamber 10. The coal passes downwardly through the feeding 
member 14 into the chamber 10 via the filling opening 13. The coal 
admitted into the chamber 10 forms a pile 16 therein. 
The feeding member 14 has an opening provided with a bushing 15 and the 
device according to the invention comprising the conduits 1, 2 and 3 
sealingly extends through the bushing 15 and into the chamber 10 via the 
feeding member 14 and the filling opening 13. The lower end of the device, 
that is, the lower end of the sensing conduit 1, is arranged so as to be 
positioned at approximately that level of the chamber 10 to which it is 
desired to fill the chamber 10. 
The conduits 1, 2 and 3 are connected with a compressor 8 via valves 12 of 
which one is provided in each of the conduits 1, 2 and 3. The compressor 8 
services to convey the pressurized gas used for sensing the level of the 
coal in the chamber 10 into the latter. The pressurized gas is here 
assumed to be compressed air. The valves 12 permit the quantity of air 
admitted into the chamber 10 to be adjusted to the valve required for 
sensing the level of the coal in the chamber 10. An expansion valve 11 is 
provided intermediate the compressor 8 and the valves 12 and the expansion 
valve 11 makes it possible to regulate the pressure of the compressed air 
so that this remains uniform. 
The sensing conduit 1 and the compensating conduit 2 are each provided with 
a branch intermediate the chamber 10 and the respective valves 12. The 
branches of the sensing conduit 1 and the compensating conduit 2 lead to a 
differential pressure switch 6. The branch of the sensing conduit 1 
communicates with what is indicated as the plus side or pole of the 
differential pressure switch 6 whereas the branch of the compensating 
conduit 2 communicates with what is indicated as the minus side or pole of 
the differential pressure switch 6. 
The differential pressure switch 6 is connected with an electrical switch 
17 which cooperates with a pair of contacts 7. The electrical switch 17 
and the contacts 7 are, in turn, located in an electrical circuit which 
leads to the charging device 18. An upward movement of the membrane of the 
differential pressure switch 6 is carried over to the electrical switch 17 
and causes the latter to break the contact of the contacts 7. This results 
in the generation of an electrical signal which interrupts the 
introduction of coal into the chamber 10 by the charging device 18. 
In operation, the compressor 8 conveys compressed air into the chamber 10. 
Coal is charged into the chamber 10 by the charging device 18. As long as 
the level of the coal in the chamber 10 is below that at which the lower 
ends of the sensing conduit 1 and the gas supply conduit 3 are located, no 
backpressure or pressure increase is generated in the supply conduit 3 and 
the sensing conduit 1 since the compressed air flows freely into the 
chamber. Any pressure waves created in the chamber 10 by the falling coal 
are transmitted to the opposite sides of the differential pressure switch 
6 via the sensing conduit 1 and the compensating conduit 2. The pressure 
waves thus are compensated for across the differential pressure switch 6 
so that the latter is not actuated and, hence, does not interrupt the 
introduction of coal into the chamber 10, in response to the pressure 
waves. 
The air flowing through the device first experiences a backpressure or 
pressure increase when, as is illustrated in FIG. 2, the ends of the 
sensing conduit 1 and the supply conduit 3 become immersed in the coal 
pile 16, that is, when the level of the coal in the chamber 10 reaches the 
level at which the ends of the sensing conduit 1 and the supply conduit 3 
are positioned. As soon as the sensing conduit 1 and the supply conduit 3 
extend into the coal pile 16, a pressure increase is generated in the 
sensing conduit 1. The pressure increase is enhanced by the air which 
continues to flow out of the gas supply conduit 3. This pressure increase 
is transmitted to the plus side of the differential pressure switch 6 via 
the branch of the sensing conduit 1 which leads thereto. On the other 
hand, the minus side of the differential pressure switch 6 does not 
experience a pressure increase inasmuch as this is connected with the 
compensating conduit 2 and the end of the latter is not immersed in the 
coal pile 16. 
Due to the fact that a higher pressure now exists at the plus side of the 
differential pressure switch 6 than at the minus side thereof, the 
membrane of the differential pressure switch 6 is displaced upwardly. This 
motion of the membrane is carried over to the electrical switch 17 which, 
in turn, brakes the contact of the contacts 7. An electrical signal 
results and is transmitted to the charging device 18 thereby causing an 
interruption in the introduction of coal into the chamber 10. 
In the embodiment of FIG. 2, the end of the sensing conduit 1 located in 
the chamber 10 is provided with a bend as is the end of the supply conduit 
3 located in the chamber 10. Although the bends have here been shown as 
being in the form of right-angled bends, this need not necessarily be so 
and the sensing conduit 1 and supply conduit 3 may be bent to other than 
right angles. It is also pointed out that a bend could be provided in the 
embodiment of FIG. 1 but that, in this case, it is advantageously only the 
sensing conduit 1 which is provided with a bend. 
The provision of a bend in the sensing conduit 1, or bends in the sensing 
conduit 1 and the supply conduit 3, provides the advantage that the 
switching pressure, that is, the pressure increase necessary to activate 
the differential pressure switch 6 and the electrical switch 17, may be 
achieved with smaller quantities of the pressurized gas than would be 
necessary otherwise. This effect has been observed in practice. The 
explanation therefor is currently based on the assumption that, for the 
embodiments without a bend or bends, the kinetic energy of the gas flowing 
into the chamber 10 causes the formation of a hollow space or cavity in 
the coal pile 16 which is elongated in the direction of flow of the gas 
and which has such a stable arch that no collapse occurs. Accordingly, the 
resistance to flow is lower than that which would be achieved in the 
absence of a hollow space or cavity. On the other hand, it may be assumed 
that no arch is formed when the gas flows out of the sensing conduit 1 or 
the supply conduit 3 at an angle to the direction of elongation of the 
respective conduit so that the coal is positioned directly in front of the 
open end of the respective conduit. As a result, a higher resistance to 
flow is occasioned than would be the case in the presence of a cavity. 
It has been mentioned earlier that the critical pressures for moist and 
preheated coals are different due to the fact that the bulk density of 
moist coal differs from that of preheated coal. The difference in bulk 
density is associated with the fact that the free spaces between the 
individual coal particles are of different size for moist and preheated 
coals. As a result, different pressures will be created in the sensing 
conduit 1 for a given flow quantity of gas through a device according to 
the invention, the pressure in the sensing conduit 1 corresponding to the 
bulk density of the coal being charged. A high bulk density results in a 
higher pressure and vice versa. It is possible to achieve the same 
pressures in the sensing conduit 1 for coal charges of different bulk 
density but, in order to achieve this, the quantity of pressurized gas 
delivered via the supply conduit 3 must normally be changed, that is, 
larger quantities of air will normally be required for lower bulk 
densities. 
It will be understood that each of the elements described above, or two or 
more together, may also find a useful application in other types of 
constructions and operations differing from the types described above. 
While the invention has been illustrated and described as embodied in a 
device and an arrangement for pneumatically regulating the introduction of 
coal into coke ovens, it is noted intended to be limited to the details 
shown, since various modifications and structural changes may be made 
without departing in any way from the spirit of the present invention. 
Without further analysis, the foregoing will so fully reveal the gist of 
the present invention that others can, by applying current knowledge, 
readily adapt it for various applications without omitting features that, 
from the standpoint of prior art, fairly constitute essential 
characteristics of the generic or specific aspects of this invention.