High efficiency feeder apparatus for pneumatic conveying lines

An apparatus is disclosed for pneumatically conveying dry particulate material from a source to a destination by cyclically loading and unloading a transfer vessel. The loading stage is accomplishing by creating a vacuum pressure within the transfer vessel to pull material into it, and after it is filled to its optimum capacity, switch a number of valves to convert the apparatus to the unloading stage wherein positive pressure is applied to the interior of the vessel to push the material down the output conveying line to its destination. The motive force in the operation of both stages is positive air pressure. The vacuum is generating by a high velocity venturi structure in combination with valving and piping which uses the positive air pressure. The unloading stage of operation utilizes the dense phase conveying, which is high pressure, low volume conveying.

The present invention generally relates to pneumatic conveying of dry 
particulate materials, and more particularly to an improved feeder 
apparatus for cyclically conveying such materials from an inlet line to an 
outlet conveying line by means of a highly efficient feeder apparatus. 
Automatic feeder apparatus have now been used for decades for conveying dry 
particulate material through a conveying line through the use of pneumatic 
techniques. One of the first apparatus that operated effectively was 
disclosed in the Black U.S. Pat. No. 3,372,958. The structure of that 
apparatus generally comprised a substantially closed, generally conically 
shaped transfer vessel with a material inlet at the top and a material 
outlet at the bottom, the latter of which was coupled to an outlet chamber 
where the material exiting the transfer vessel was fluidized and guided to 
a discharge line which led to the intended location Pressure generating 
means utilized pressure at a level of close to but less than 15 lbs per 
square inch and included appropriate valving was provided for continuously 
supplying a positive air pressure to the chamber for fluidizing the 
material, and for alternatively establishing a positive and negative air 
pressure within the interior of the transfer vessel several times a minute 
for unloading and loading the transfer vessel, respectively. The pressure 
generating means contained a venturi assembly which was used to create a 
suction for assisting in filling the transfer vessel. Improvements to the 
Black apparatus were disclosed in the Jacobson U.S. Pat. No. 4,278,367 and 
consisted of regulating the pressure in the transfer vessel and utilizing 
a flap valve to maximize flow without experiencing clogging. The nature of 
the operation of both of these apparatus was to use a high volume of air 
under relatively low pressure to accomplish the conveying operation. While 
such apparatus are extremely effective, one disadvantage is that the 
efficiency of the loading cycle is often less than desired, and the length 
of the output conveying line is also less than desired. The venturi 
assembly operates by applying positive air pressure to a venturi throat 
having an associated throat chamber in which vacuum pressure is induced. 
The positive air pressure must be exhausted and in the above described 
apparatus, it was exhausted to the outlet conveying line to aid in 
clearing the line after the material was unloaded from the vessel into the 
line. 
Another type of technique for pneumatic conveying uses a low volume of air 
under significantly higher pressure, with concomitant high material to air 
ratios, and is generally known in the industry as dense phase conveying. 
This type of conveying generally results in less degradation of the 
conveying lines through wear, requires smaller diameter conveying lines 
with comparable throughput capacities, results in less breakage of the 
product because of lower conveying velocities, less energy consumption and 
longer conveying distance capabilities. In this type of conveying 
operation, the material is typically not cleared from the line, even if it 
is conveyed in a cyclic manner. One of the disadvantages of this type of 
conveying is that such systems have traditionally required a large amount 
of head room because they are gravity loaded. As a consequence, such 
installations have required a large pit beneath the silo or rail car or 
the use of a separate filter vessel and vacuum pump for vacuum loading. 
Such auxiliary equipment or size requirements have significantly increased 
the manufacturing costs or have been impractical for many applications 
because of physical constraints. 
Accordingly, it is an object of the present invention to provide an 
improved feeder apparatus that offers the advantages of both of the above 
types of system, by using both types of operation at different stages of 
the operation of the apparatus. 
It is another object of the present invention to provide an improved feeder 
apparatus which utilizes a low volume of high pressure air to accomplish 
loading of the transfer vessel thereof, and which utilizes a low volume of 
high pressure air to accomplish the unloading of the transfer vessel and 
to convey the dry particulate material down the output line. 
Still another object of the present invention is to provide an improved 
feeder apparatus that utilizes a venturi for inducing a vacuum for loading 
a vessel, wherein the venturi outlet is vented to atmosphere rather than 
the output conveying line, which significantly reduces the back pressure 
on the venturi outlet and thereby permits greater loading efficiencies to 
be achieved. 
It is yet another object of the present invention to provide such an 
improved feeder apparatus which carries out such loading, unloading and 
conveying and which does not require any significant head room in which to 
operate, provides increased inlet conveying line length capabilities, 
provides increased outlet conveying line length capability, and operates 
with lesser energy requirements. 
Still another object of the present invention is to provide such an 
improved feeder apparatus which utilizes in its loading stage a highly 
efficient venturi for developing a low pressure level for a suction force 
for pulling the material into the transfer vessel, and the use of 
relatively high supply pressure for operation in the apparatus during both 
the loading and unloading stages of operation. 
A related object of the present invention lies in the provision of 
increased efficiency and lower energy consumption due to the utilization 
of dense phase conveying from the feeder apparatus to the conveying 
destination, which means that the conveying line to the destination is not 
required to be cleared of material at the completion of each unloading 
stage.

DETAILED DESCRIPTION 
Broadly stated, the present invention comprises an apparatus that is 
adapted to pneumatically convey dry particulate material from a source to 
a destination by cyclically loading and unloading a transfer vessel. The 
loading stage is accomplishing by creating a vacuum pressure within the 
transfer vessel to pull material into it, and after it is filled to its 
optimum capacity, switch a number of valves to convert the apparatus to 
the unloading stage wherein positive pressure is applied to the interior 
of the vessel to push the material down the output conveying line to its 
destination. The motive force in the operation of both stages is positive 
air pressure of at least approximately 60 pounds per square inch 
(hereinafter referred to 60 lbs). Even though positive air pressure is 
used in the operation of the apparatus during both the loading and 
unloading stages of operation, the loading stage is done using vacuum or 
suction pressure applied to the interior of the vessel, and the vacuum is 
generating by a high velocity venturi structure in combination with 
valving and piping which uses the positive air pressure. 
The operation of the apparatus is significantly different from that 
disclosed in the aforementioned patents in at least one critical respect, 
which is markedly different from merely increasing the air pressure 
utilized in the apparatus. Another significant difference is in the design 
of the venturi nozzel which allows supersonic primary air flow thus 
creating a higher operating vacuum and greater suction efficiency. The 
significant difference lies in the combination of two technologies that 
have become known in the industry as dense phase conveying unloading and 
vacuum loading, which is not dense phase conveying. Certainly the venturi 
induced vacuum loading is disclosed in the aforementioned patents, and the 
apparatus of the present invention is conceptually similar, albeit much 
more efficient, because it utilizes an improved venturi that has been 
developed by the assignee of the present invention. By utilizing the 60 lb 
air pressure air supply applied to the venturi, there is air flow through 
the nozzle on the order of twice the speed of sound, which generates a 
vacuum pressure of approximately 23 inches of mercury within the vessel. 
The increased efficiency of the vacuum loading utilizing a 60 lb air 
supply has demonstrated a literally doubling of the length of the inlet 
line compared to vacuum loading inlet line lengths achieved with apparatus 
disclosed in the aforementioned patents. 
In accordance with another important aspect of the present invention, the 
positive air pressure that is applied to the venturi must be exhausted, 
and in prior feeder apparatus the air has been applied to the outlet 
conveying line for the purpose of clearing the line of material 
immediately prior to or while the vessel is being loaded. Because the 
dense phase conveying is being used during the unloading stage, it is 
unnecessary and in fact inefficient to clear the outlet conveying line of 
material. It has also been known that by exhausting the air from the 
venturi into the outlet conveying line, back pressure is developed that 
lowers the efficiency of the venturi itself, with the amount of back 
pressure being proportional to the length of the line. In the present 
invention, this undesirable back pressure is effectively eliminated by 
venting the venturi exhaust directly to atmosphere. Because of the 
extremely high air speeds that are developed, a silencer is usually 
provided to reduce the noise levels that are produced. 
Unlike the aforementioned patents, the unloading stage of operation 
utilizes the dense phase conveying, which utilizes a high pressure, low 
volume air supply. The aforementioned patents utilized high volume, low 
pressure air supply, where the material to air ratio was much lower than 
is present in the present invention and in other dense phase systems. The 
advantages of dense phase conveying are many, and include the advantage 
that the same amount of material can be conveyed using smaller convey line 
sizes, higher capacities, less particle degradation, less convey line wear 
and lower energy requirements. 
The advantages of marrying the venturi induced vacuum loading and dense 
phase unloading technologies results in achieving the advantages of each 
technology, while eliminating the disadvantages of each. This is a 
significant development for the reason that the vacuum loading eliminates 
one of the most problematic obstacles that has usually always been present 
with dense phase conveying. 
Typically, dense phase conveying systems either require gravity loading of 
the vessel, or loading with a vacuum pump having a filter structure. Such 
loading systems in turn requires a substantial amount of head room above 
the vessel to load it. Because of the head room requirements, 
installations typically require a large pit beneath the silo or rail car 
which is to be unloaded, or a separate filter and vacuum pump are 
required. As might be expected, such equipment must be sizeable to operate 
effectively, and for that reason, are often expensive. The present 
invention has a filter that is located within the vessel itself, thereby 
requiring no additional head room, and through the use of the venturi 
structure, eliminates the need for a separate vacuum pump. 
It should also be readily appreciated that constructing pits beneath silos 
is also very expensive, and often totally impractical. Constructing pits 
beneath rail sidings is similarly expensive, and greatly reduces the 
flexibility of use of any system, since each location for unloading must 
have its own pit. 
Turning now to the drawings and particularly FIGS. 1 and 2, the apparatus 
of the present invention is shown diagrammatically during the loading and 
unloading stages of operation, respectively. The apparatus, indicated 
generally at 10, has a closed vessel 12 that is generally cylindrical 
upper side portion 14 and a generally conical lower side portion 16. A 
material inlet conduit 18 terminates at an annular flange 20 that is 
conventionally bolted to a similar flange 22 that is attached to a 
cylindrical portion 24 of the vessel. An interiorly attached conduit 26 
extends from the flange 24 to an elevation near a domed shaped top portion 
28. A flap valve 30 is secured to the upper end of the conduit 26 and 
opens to admit the material being conveyed during the load stage and is 
biased to close when material is not moving through the conduit 26. 
The bottom of the vessel terminates in an outlet conduit portion that has 
an upper vertical section 32 and a lower horizontal section 34 that is 
attached to a discharge valve 36 that is preferably pneumatically and 
optionally electrically controlled so that it is closed during loading and 
open during unloading. An outlet conveying line 38 is attached to the 
valve 36 and extends to the destination where the material is to be 
conveyed. 
The domed top 28 of the vessel 12 has a cylindrical portion 38 which 
communicates the vacuum pressure or positive air pressure to the interior 
of the vessel via conduit 40 which may conveniently be fabricated in 
sections suitably attached to one another by clamps 42 and to an inlet 
port connected to the top of the cylindrical portion 38. A filter 46 is 
provided to minimize dust from the material being communicated to the 
conduit 40 during the loading stage which would eventually be exhausted to 
atmosphere. The exhausting of dust is environmentally undesirable and also 
may have a detrimental effect on the internal surfaces of the venturi over 
time. 
Since the positive air pressure is also introduced through the conduit 40, 
the flow of air in the opposite direction has the effect of cleaning the 
filter elements during each unloading stage of a loading and unloading 
cycle. The conduit extends to a control cabinet 48 that is of sufficient 
size to include conduit sections, electrical and pneumatic controls and 
the previously mentioned venturi structure. The conduit 40 has a "T" 
section that branches the conduit 40 to sections 40a and 40b. Section 40b 
is connected to section 40c which in turn branches via a "T" section to 
sections 40d and 40e. Section 40e is connected to a source 50 of positive 
air pressure having a preferred pressure of 60 lbs per square inch. 
Section 40d is connected to a venturi structure 52, as is the section 40a. 
Each of the sections 40a, 40c and 40d have preferably pneumatic valves that 
are selectively controlled to be open or closed during operation in the 
loading and unloading stages. More particularly, a suction valve 54 is 
located in section 40a, a convey valve 56 is located in section 40c and a 
venturi supply valve 58 is located in conduit section 40d. A silencer 60 
is provided and attached to the upper end of the venturi structure 52. As 
previously mentioned, the air flow through the throat of the venturi is 
supersonic, which creates a substantial noise and therefore a silencer is 
needed in most installations. 
Referring to FIG. 6 which illustrates the venturi structure 52, it has a 
venturi nozzle 62 which is connected to conduit section 40d. The nozzle 
has an opening in its upper end and directs a flow of air into the lower 
end of a venturi throat section 64, the upper end of which is connected to 
the silencer 60. The venturi structure 52 has a chamber 66 which is in 
communication with the conduit section 40a. During operation of the 
venturi structure, air is directed through the nozzle 62 into the throat 
section 64, creating a substantially lower air pressure or vacuum in the 
chamber 66 and conduit section 40a. 
Returning to FIG. 1, and in connection with the loading stage of the 
apparatus during operation, the source of positive air pressure 50 
supplies air in section 40e, 40d and to the venturi nozzle 62. During 
loading, the valves 54 and 58 are open and valve 56 is closed. A vacuum is 
then induced in conduit sections 40a and 50, and in the vessel 12. The 
material discharge valve 36 is also closed so that the material present in 
the inlet is vacuum loaded into the vessel. When it reaches a 
predetermined elevation as determined by one or the other of two level 
switches 68 (see FIGS. 3 and 5), the loading stage is terminated and the 
unloading stage is commenced. 
To unload the vessel and convey the material down the output line 38, and 
referring to FIG. 2, the valves 54 and 58 are closed, valves 56 and 36 are 
opened. This permits positive air pressure to be applied to the interior 
of the vessel via conduit sections 40e, 40c, 40b and 40. 
The operation of the apparatus is essentially as described above, and the 
apparatus shown in FIGS. 3, 4, 5 and 6 illustrate the actual apparatus, 
where like reference numerals refer to the same components as have been 
described in connection with FIGS. 1 and 2. In addition to the operation 
as previously described, the actual apparatus includes other features 
which will be described in connection with FIGS. 3, 4 and 5. 
More particularly, the apparatus includes structure for injecting 
supplemental air into the material during the unloading stage of 
operation, and to this end, air supply lines 70, 72 and 74 are provided to 
inject air into either the vessel or the conduit 32 and output line 38. 
The line 70 is connected to a circular manifold or aeration ring 76 which 
injects air into the upper portion of the conduit 32 to aerate the 
material so that it will flow more easily. Similarly, lines (one of which 
is shown) 78 extend from the aeration ring 76 to aeration pads 80 which 
inject air into the conical portion of the vessel. While the number of 
such pads is not critical, it is preferred that at least six of such pads 
be provided. Line 72 injects air into the lower portion of the conduit 32 
and line 74 injects air into the output line 38 at regular intervals along 
its length. As is conventional, leg assemblies 82 provide structural 
support for the vessel. As shown in FIG. 5, a pressure relief valve 84 is 
provided to protect the apparatus from excessive pressure in the event a 
malfunction occurs which results in a build up of pressure the vessel. 
From the foregoing description, it should be appreciated that an improved 
apparatus for conveying dry particulate material has been set forth which 
provides the advantages of a venturi generated vacuum loading and dense 
phase unloading, which operations result in a highly efficient apparatus 
in terms of energy consumption. The apparatus also provides extreme 
flexibility in that it requires no construction of pits below silos or 
rail sidings, and can be utilized at virtually any realistic location 
without incurring the expense of construction. The advantages of dense 
phase conveying are achieved, as are those of a venturi generated vacuum 
loading. 
While various embodiments of the present invention have been shown and 
described, it should be understood that various alternatives, 
substitutions and equivalents can be used, and the present invention 
should only be limited by the claims and equivalents thereof. 
Various features of the present invention are set forth in the following 
claims.