Tubular pneumatic conveyor pipeline

A pneumatic tubular conveyor pipeline is provided for conveying solid products, for example, in granular or chunk form. The conveyor pipeline comprises an outer impervious pipe and a smaller-diameter inner porous pipe. The inner pipe has longitudinally-spaced, uni-directional pressure responsive vents dividing the inner pipe into chambers. A gas pressure source is connected to the upstream portion of the inner pipe. A feed apparatus is connected to the feed end of the outer pipe for injecting the product into and propelling same through the outer pipe. The chambers vent consecutively through the vents in the downstream direction at a rate determined by the product flow through the outer pipe, as the surrounding portions of the outer pipe become filled with the product.

BACKGROUND OF THE INVENTION 
(a) Field of the Invention 
This invention relates to a pneumatic conveyor system for conveying 
substantially dry materials over very long distances, such as is described 
in my U.S. Pat. No. 4,116,491. 
(b) Description of the Prior Art 
Conventional pneumatic pipe conveyor systems transport materials in 
suspension by means of a high-velocity air stream. The principal uses for 
such pipe conveyor systems are the the transport of materials such as 
granular cork, bran, carbon black, copra, grain, wood chips, and saw dust. 
One such known system for transporting pulverized materials consists of a 
motor-driven pump and of a source of compressed air for fluidizing the 
material. The material itself is fed from a bin or hopper into a pump 
mechanism which is of the screw type. Compressed air is admitted from a 
cylindrical manifold into the discharge end of the screw, thus changing 
the material into a semi-fluid substance before allowing it to enter the 
transport line. The greatest present use of such a system is believed to 
be for transporting bulk cement. 
Such a system is obviously restricted as to the types of materials that can 
be transported, especially over long distances. Since this system depends 
upon suspension of the materials in a high-velocity air stream, serious 
limitations are imposed due to pressure drop, especially over long 
distances. Heavier materials fall out of the air stream and gradually 
cause pressure surges and clogging of the transport duct. As would be 
expected, the known systems operate more efficiently through straight runs 
and do not easily tolerate sharp bends and vertical sections. 
Due to the required high-velocity air stream, the conventional systems also 
create severe dust problems at the discharge end of the conduit, thus 
requiring dust collectors which add to the expense of the system. Even the 
suction type of pneumatic conveyor also requires a dust collector at its 
discharge end. 
Various other types of conveyor systems have been proposed in the patent 
literature, such as a pipeline having an impervious outer pipe and a 
porous inner pipe. The products are transported by the inner pipe. 
However, the initial leakage of air pressure downstream of the conveyed 
product from the porous pipe places a severe limitation on the length of 
the pipeline that can be used. For this reason such proposed systems have 
not been commercially acceptable. 
A very practical system, however, is described in my said U.S. Pat. No. 
4,116,491. Other systems have been made of record in my said patent. All 
these systems can be characterized by an inner porous pipe carrying the 
products to be transported. 
SUMMARY OF THE INVENTION 
The present invention utilizes a conveyor pipeline comprising a porous 
inner pipe, which is the fluidizing pipe, and an outer impervious pipe 
which is the product-carrying pipe and which forms a housing about the 
inner pipe. An air pressure source is connected to the upstream portion of 
the inner pipe. One-way pressure relief valves are longitudinally 
spaced-apart in the inner pipe thus dividing the inner pipe into chambers. 
The chambers vent consecutively through the valves, in the direction of 
product flow, only when the surrounding portions of the outer pipe become 
filled with sufficient product to create enough back pressure to operate 
the pressure relief valves. Thus the chambers become consecutively 
pressurized. The air pressure from each pressurized chamber flows through 
its porous wall into the outer pipe, whereby an air cushion is formed 
around the porous wall on which the conveyed product can float with 
reduced resistance. The air stream flowing from the porous wall also 
produces a fluidizing effect which tends to reduce the load on the source 
of compressed air used in propelling the product. The combined effects 
tend to prevent clogging of the product-carrying line due to drag and 
gravitational settling of the product along its downstream path in the 
outer pipe. 
In a preferred embodiment, the outlet of a feed hopper is connected to the 
outer pipe. One end of an air jet pipe is coupled to the inner pipe. The 
other end of the jet pipe is suitably connected to a compressed air or gas 
source. As more and more product is being forced into the outer pipe, the 
product gradually forms a mass against which the air pressure from the 
inner pipe can push. The air entering from the porous wall of the inner 
pipe into the outer pipe tends to form an air cushion under the product, 
and also tends to create a fluidizing effect which greatly reduces 
friction and allows the air pressure from the inner pipe to assist in 
propelling the product through the outer pipe. 
The chambers' valves consecutively open in the direction of product flow, 
as the porous walls of the chambers become progressively covered by the 
product, thus creating the required back pressures on the valves. The 
one-way pressure relief valves prevent unnecessary loss of air pressure 
downstream of the porous pipe except when needed. 
Preferably, the porous pipe is positioned at the bottom of the impervious 
outer pipe, thereby tending to overcome the gravitational pull on the 
products being transported.

DESCRIPTION OF PREFERRED EMBODIMENTS 
In FIG. 1 is shown a prior art system 10 which comprises a conveyor 
pipeline 18 having an impervious pipe 32 which is coupled through a 
suitable valve 13 to a feed hopper 12 containing a granular product 16. 
When the granular product 16 is to be conveyed by pipeline 10 from hopper 
12 to a remote location, a valve 15 is opened and a propelling air stream 
is made to flow from a pipe 14 connected to an air pressure source (not 
shown). The air jet draws the product 16 from hopper 12 and jets the 
aerated product into bore 19 of pipe 32. After a sufficient volume of the 
product is injected into pipe 18, the product will begin to mass at a 
location, generally designated as 22. The product 16 becomes progressively 
dense and forms mounts which are designated by dotted lines 20, 21. 
Eventually, at distance D from hopper 12 depending on the nature of 
product 16, the product will fall out of the air stream and gradually 
cause clogging at pipe 18. The product will then stop moving downstream of 
mount 21. The distance D may be several hundred feet or more. Hence 
conveyor system 10 is definitely limited as to the distance to at which 
the product can be conveyed. 
In FIGS. 2-7 is shown a preferred conveyor system 10' of this invention 
which is not so limited as to distance. In system 10' the same numerals 
will designate the same parts and similar parts will be designated with 
the same reference characters followed by a prime ('). 
The pneumatic conveyor pipeline 18' of this invention is coupled through a 
short pipe 37 and valve 13 to the lower end of feed hopper 12 containing, 
for example, a granular product 16. Pipe 37 is welded to the bell 36 of 
pipeline 18'. The pipeline 18' consists of an impervious outer pipe 32 
having a bore 19, and of a porous, relatively-small diameter, hollow pipe 
41 which is preferably mounted on the bottom of bore 19, as viewed in FIG. 
2. The porous inner pipe 41 contains a plurality of longitudinally-spaced, 
uni-directional, pressure-responsive control vents, generally designated 
as 42, forming chambers C-1 to C-n therebetween. An air conduit 34 is 
coupled through a valve 35 to the first chamber C-1. 
Each vent 42 can comprise a spring-biased, one-way, pressure-relief valve 
42' (FIG. 5) which is coupled to a pair of adjacent chambers in pipe 41 by 
suitable clamps 43. The most remote chamber C-n is sealed off by a plug 
44. All the valves 42' are normally-closed and biased to open in the same 
direction. 
In operation, when the product 16 is to be conveyed by pipeline 10 from 
hopper 12 to a remote location, valve 15 is opened and an air jet produced 
by pipe 14 will draw out the product from hopper 12 and jet it into the 
bore 19 of the impervious pipe 32. Simultaneously, valve 35 is opened and 
the air pressure from conduit 34 will continuously fill the first chamber 
C-1 whose valve 42' is closed. When a sufficient volume of the product 16 
is injected into bore 19 of pipe 32, the product will form a mass against 
which the air pressure, leaking through the porous wall of the first 
chamber C-1, can be exerted (FIG. 3). 
As the product moves downstream, i.e., to the right (as viewed in FIG. 2), 
the pressure in the first chamber C-1 builds up and reaches a back 
pressure which is sufficient to overcome the spring resistance of the 
first valve 42', thereby causing it to open (FIGS. 4, 5). 
This open valve now allows the second chamber C-2 to become gradually 
pressurized, as the product 16 moves downstream, until its valve 42' will 
open. This process will be repeated until all the chambers C-n become 
progressively pressurized. After the last chamber C-n is pressurized, 
product 16 will be discharging through the pipeline's discharge end 18", 
as shown in FIG. 2. 
It will be apparent that a particular chamber C-x will start to pressurize 
only after its immediately preceeding chamber C-(x-l) is fully 
pressurized. 
FIG. 3 schematically illustrates with the aid of arrows that the air stream 
passing through the porous wall of any chamber in pipe 41 forms a 
continuous air cushion 46 underneath the mass of product 16 and also 
aerates and fluidizes the product. As the product moves downstream through 
the impervious pipe 32, it is supported by and rides on the air cushion 
46. Since an air stream is being continuously lost through the porous pipe 
41, air pressure must be continuously supplied thereto through pipe 34. 
By suitably designing the pore sizes in the inner pipe 41, large granular 
or chunk products such as ore, coal, etc., may be transported by the 
pipeline 10'. The pipeline can also be adapted for the transportation of 
products at elevated temperatures. 
Pipeline 18' can be made up from conveyor pipe sections 50 each having a 
bell 36 (FIGS. 6, 7) at one end, and a pin 37 at the other end thereof. A 
plurality of angularly-spaced guides 38 on the outer periphery of pin 37 
fit inside a plurality of corresponding grooves 39 inside bell 36. The 
porous pipe sections 51 of inner pipe 41 in the pipe sections 50 can be 
interconnected by hollow couplings 47 of conventional design. In this 
manner air pressure can freely flow between the interconnected sections 51 
when pipeline 18' of this invention is fully assembled. The last porous 
pipe section 51 is terminated by the plug 44 of conventional design. 
As will be readily appreciated from the above description, when taken in 
conjunction with the drawings the present invention lends itself to 
modifications and all such are intended to be covered by the claims 
attached hereto.