Note: Descriptions are shown in the official language in which they were submitted.
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R EC IPR O~TING A IR LOCK VALVE
The subject invention relates generally to valves useci in transferring
gran~llar and powdered stock and more particularly, but not by way of
limitation, to an airlock valve which provides for transferring of the
stock between two aperations and maintaining a pressure clieferential
therebetween.
Heretofore, two common types of airlock valves have been used in
the transferring of granular and powdered stock which maintain a seal
between two operations having different pressures. The most common
type of airlock valve used in material handling of this type is a rotary vane
10 airlock valve. This type of valve is satisfactory in most cases except for
the handling of abrasive materialsr
When handling abrasive materials (such as sand, powdered clay,
and various types of crushed ore), a flap valve or gate-lock valve is used.
These types of valves involve a greater initial expense because of their
inherent complexlty and greater malntenance cost because of worn and
broken replacement parts caused by the jamming of the valve. The flap-
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type valve requires two trap doors, one below the other. These doors are
synchronized to alternately open and close allowing material to drop through
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from one chamber to the next. The drivlng mechanism of these type valves
20 ls mounted outside the stock chambers and require shafts to pass throughthe enclosed walls of the chambers with bearings to support the shaft and
ro~ary seals to seal the shafts. The shafts are connected to a drlve linkage
f~ with counter weights or springs and a driver. This construction with its
moving parts is subject to wear, especially the seals and bearings which
are in contact with ~he abrasive dust from the stock. Also, the upper door
must try to seal agalnst a continuous flow of material since there is no pro-
vision for shutting of~ the flow into the upper chamber.
Another limitation inherent to the design of the flap-type valves is
caused by the large door area compared to the area of flow. This area
30 rnust be large to allow su~ficient material flow. However, this limits ~he
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practical press~lre di~ferellticlls that tile vcllves can work since the doors
have to open against the force create(l by the pressure rnultiplied by the
area of the opening. To open against high pressure differentials wowld
req~lire e~tremely heavy clrive components. This lirnitation has been
vvercome by s~age opening or having two cloors on one gate. The smaller
oE the two doors open first to relieve the pressure or vacuum on one side
of the door prior to allowing the larger door to open. However, increases
in initial expense and maintenance of extra moving parts are involved
when a staged opening device is used at highèr differentials.
The subject invention elimina~es several problems related to the
use of the above described flap val~e or gate-lock valves.
The subject invention reduces the initial cost and maintenance cost
of prior art valves used in conveying granular and powdered stock while
maintaining a pressure differential therebetween.
The invention is simple in design, rugged in construction, and
eliminates the use of complex two stage ~oors such as a gate-lock valve
and will handle both abrasive and nonabrasive stocks. The reciprocating
airlock valve provides an improved flow rate through a smaller outlet
caused by the motion oE first and second plugs through the stock, thus
20 activating the stock.
The valve has fewer moving parts, wear points, and sealing pro-
blems as opposed to the prior art stock valves. The reciprocating airlock
valve insures a positive seal with less tendency to jarn while in operation
and cluring system start up. The valve automatically relieves excess
pressure in the system and is totally enclosed eliminating failure due to
abrasives working on moving parts. Because of the direct application of
forces, less power is required to operate the airlock valve.
The reciprocating airlock valve used in the transfer of stock between
two operations and the maintenance of a pressure differential therebetween
30 includes an upper hopper having a first inlet port for receiving stock therein
ancl a second outlet port for discharging the stock therethrough. A lower
hopper is attached to the bottom o~ the upper hopper ancl Lnclucles a seconcl
inlet port inclexecl with the first outlet port of the upper hopper. The lower
hopper further inclucles a second outlet port in the bottom thereof for
clischarging lhe stock tllerefrom. ~ tirst pl~lg is clisposecl insicle the
upper hopper. The lower portion of the firs~ plug is received in the first
outlet por~ and acts to hold in the stock and seal out pressure. A second
plug is disposed inside the lower hopper. The lower portion ol the second
plug is received in the second outlet port of the lower hopper and acts to
10 hold in the stock and seal out pressure. ~n air motor is disposed in the
first plug and includes an air cylinder and an air cylinder rod extending
downwardly therefrom and connected to the top of the second plug. When
the air motor is activated, it reciprocates the first plug and second plug
continuously, thereby raising and lowering the first plug and second plug
in the hoppers and thus transferring stock from the upper hopper to the
lower hopper and then out of the valve. A stopper is attached to the top of
the first plug and is dimensioned to be received in the first inlet port of
the upper hopper. This stopper provides a means for momentarily
shutting off the flow of stock to the upper hopper, thus allowing the upper
20 plug to seat without interference from the stock.
Figure 1 illustrates a cross section of the upper hopper attached to
the top of the lower hopper with a cross section of the first plug and the
air motor mounted t herein.
Figures 2 through 6 illustrate the cycle of the airlock valve as the
first plug and second plug are raised and lowered in the upper and lower
hopper for discharging granular or powdered stock ~etween two operations
located at opposite ends of the hoppers.
In Figure 1, the reciprocating airlock valve is designated by general
reference numeral 10. The purpose of the valve 10 is to maintain a
3~ pressure di~ferential between two operations located at the opposite ends
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or between an operation and atmosphere while allowing flow of granular
or powdered stock through the valve 10. For example, this type valve
would be used in the emptying of large bins in graln elevators, processlng
plants, mining and milling operations, and road construction. The valve
10 includes an upper hopper 12 attached to the top of a lower hopper 14.
Disposed inside the upper hopper 12 is a first plug 16 shown in cross section.
A second plug 18 is disposed inside the lower hopper 14. A continuously
reciprocating air motor 20 is mounted inside the first plug 16 and includes
an air cylinder 21 and cylinder rod 22 vertically disposed. The rod 22
extends downwardly into the lower hopper 14 and is attached to the top of
the second plug 18. Attached to the bottom of the cylinder 21 and disposed
around the rod 22 is a rod wiper 23 for wiping abrasive dust and the like
from the rod 22 as it reciprocates in the valve 10. The motor 20 further
includes an air pressure hose 25 and exhaust hose 27 which are attached to
the top of the motor 20 and extend outwardly through the side of ~he hopper
12 and are connected to a compressed air source which is not shown. A
stopper rod 24 having a stopper 26 mounted on top thereof is attached to
the top of the first plug 16.
The upper hopper 12 includes a first inlet port 28 disposed in the
top thereof. A first outlet port 30 is disposed in the bottom of the upper
hopper 12. The first inlet port 28 receives stock therein while the first
outlet port discharges the stock into the lower hopper 14.
The lower llopper 14 includes a second inlet port 32 which is indexed
with the first outlet port 30 for receiving the stock from the upper hopper
12. A second outlet port 34 is clisposed in the bottom of the lower hopper
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14. Disposed around the lower portion of the upper hopper 12 is a first
plug seat 36 for receiving the lower portion of the first plug 16 therearound.
The lower portion of the lower hopper 14 includes a second plug seat 38
for receiving the lower portion of the second plug 18 therearound.
In Figures 2 through 6, the reciprocating airlock valve 10 operating
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cycle is illustrated. In operation, compressed air is fed through the
pressure hose 25 to the air motor ~0 with the air exhausted through exhaust
hose 27. The air motor 20 inclucles a ~our-way valve mounted on the top
ot` the cylinder 21 with poppet valves mounted at each end of the cylincler 21
to signal ~he four-way valve to change directions. Therefore, the air
pressure goes to one end or the other of the cylinder 21 at all times while
the opposite end is being exhausted causing continuous reciprocation of the
air motor 20. The four-way valves are mounted on top of the cylinder 21
and the poppet valves are disposed inside the air motor 20 and are not
10 shown in the drawings.
The air cylinder rod 22 is partially extended in Figure 7 and the
- upper hopper 12 is shown receiving stock through the first inlet port 28.
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The stock is represented by a plurality of fine dots 44. The first plug 16
; and second plug l8 are both shown seated in the first plug sea~ 36 and
second plug seat 38 and sealing the first outlet port 30 and second outlet
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port 34.
As the cylinder rod 22 continues extending, the first plug 16 is
raised above the first plug seat 36. At this poin~, the entire weight of
the first plug 16 including ~he weight of the air motor 20 is transferred to
the second plug 18 thus creating a gravitational force to aid in maintaining
a seal around the second outlet port 34. As the first plug 16 continues to
raise, the stock 44 Ls discharged through the first outlet port 30 and the
second inlet port 32 into the lower hopper 14. ~igure 3 shows the air
cylinder rod 22 completely extended and the stock 44 discharged from the
upper hopper 12 into the lower hopper 14. The firs~ plug 16 is in its
raised position with the stopper 26 extended through the firs~ inlet port 28.
~t should be noted that the timing of the raising and lowering of the first
plug 16 and second plug 18 are controlled by adjusting the air flow rate to
the air motor 20,
In Figure 4, ~he purpose of the stopper 26 is illustrated. The
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stopper 26 has the same dimensioll as the Eirst inlet port 28 so that the
stopper 26 provicles a seal when it is received in the first inlet port 28.
~9 the rod 22 begins to retract ancl the first plug 16 ls being lowerecl into
the first plug seat 36, the stopper 26 will temporarily block the contLnuous
flow of the stock 44 into the upper hopper 1~. This momerltary flow stop-
page will allow s~ficient time Eor the first plug 16 tc> seat itself securely
in the first plug seat 36 without interference. As the first plug 16 is lowered,the stopper 26 continues downward through the first inlet port 28 into its
lowered position shown in Figure 5. The upper hopper 12 now begins to
receive the stock 44 through the first inlet port 28.
In Figure 5, the air cylinder rod 22 is partially extencled. However,
the rod 22 is being retracted rather than extended, thus ralsing the second
plug 18 and allowing the stock 44 to be discharged from the lower hopper 14
as shown in Figure 6. As the cyllnder rod 22 continues to be retracted,
the weight of the second plug 18 is transferred to the cylinder rod 22 and
the first plug 16, thereby providing a gravitational force on the first plug 16
and helping maintain a seal around the first outlet port 30
In Figure 6, the lower hopper 14 is emptying and the upper hopper 12
is being filled with the stock 44. As the cylinder rod 22 is completely
retracted and reverses its direction into an extended position, the second
plug 18 will again be lowered in the empty lower hopper 14 and the second
plug 18 will again be seated above the second outlet port 34, as shown in
Fi~ure 2. The operating cycle oi the airlock valve 10 is now repeated.
From reviewing the above described figures, it can be seen that
there is always a seal at either the first discharge port 30 or the seconcl
discharge port 34, thereby maLntaining a pressure diffexential between the
stock received through the first intake port 28 and the operation receiving
the stock from the second discharge port 34 while accommodating stock
flow through the first hopper 12 ancl second hopper 14.
While the air motor 20 ls shown mounted in the first plug 16, it
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should be appreciatecl that the air motor 20 could also be mounted in the
second plug 18 and the operating cycle of the valve :10 could be accomplished
equally as well as discussed uQcler Figures 2 througtl 6.
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