Gas assisted fluid delivery system

A fluid delivery system includes a pump, a fluid conduit and a regulated gas inlet. The fluid conduit has an upper end connected to the pump and a lower end in communication with a fluid supply. The regulated gas inlet includes a gas supply at a first pressure; a pressure monitoring conduit in fluid communication with the fluid conduit between its upper and lower ends; a gas delivery conduit in communication with the fluid conduit; and a pressure-responsive valve. The valve is connected to the pressure monitoring conduit and moves between a closed position wherein gas flow into the fluid conduit is restricted, and at least one open position wherein gas is delivered to the fluid conduit through the gas supply conduit. The valve is normally biased toward the closed position but moves opens when pressure within the pressure monitoring conduit is below the first pressure by more than a predetermined level.

FIELD OF THE INVENTION 
The present invention provides an improved fluid delivery system which has 
particular utility in delivering a liquid over an extended vertical 
distance. 
BACKGROUND OF THE INVENTION 
A number of applications require the delivery of a liquid or other fluid 
from one height to another, significantly higher height. In some 
applications, one can use a positive displacement pump to urge fluid from 
the lower level to the higher level. So long as the pump has sufficient 
power to overcome the force of gravity and lift the fluid to the desired 
height, this is a very effective way to pump fluids to a higher level. 
It is not always possible or convenient to provide a positive displacement 
pump at the lower end of the height to be traversed. In some situations, 
it may be simply inconvenient to place a pump at the bottom. For example, 
if the fluid delivery system is used to pump a fluid from the bottom of a 
deep tank up to the top of that tank, it may be difficult to gain access 
to the pump at the bottom of the tank for routine maintenance or repair. 
In other circumstances, it may be impossible or highly impractical to try 
to place the pump at the lower end of the fluid travel. For example, when 
one attempts to pump water or other fluids from an underground geologic 
formation up to ground level, it is impractical to place a suitable pump 
down into the bore hole used to gain access to the underground formation. 
Instead, one will typically pump the fluid by drawing a vacuum at ground 
level and drawing the water or other fluid up through a fluid delivery 
conduit of some sort. 
This can be very effective for materials having relatively low vapor 
pressures, such as crude oil. With materials having higher vapor 
pressures, though, it can be difficult to withdraw the material from 
particularly deep geologic formations because the material will tend to 
volatilize at the vacuum levels which would be necessary to draw the 
material up to ground level against the force of gravity. 
For example, if one is attempting to pump water from an underground water 
table which is more than about 20 feet (about 6 meters) below the ground 
surface, one generally cannot use a vacuum pump. In order to overcome the 
"head" of the water, i.e., the weight of the column of water, over such a 
vertical distance, one would need to draw a rather substantial vacuum. 
However, the water will tend to boil at such a low pressure, filling the 
column with relatively low density water vapor. This can lead to a highly 
inefficient pumping operation if one can get any water out of the system 
at all. 
The system can be even more problematic if the fluid delivery system is 
attempting to deliver a liquid which has a higher vapor pressure. For 
example, ground water can be contaminated with hydrocarbons having 
relatively high vapor pressures, e.g., gasoline or fuel oil. These 
contaminants will tend to form a layer of the lighter hydrocarbon material 
on top of the water table. One can try to remove this layer of hydrocarbon 
by pumping the top layer of the underground fluid up through a delivery 
conduit. If the hydrocarbon being extracted has a relatively high vapor 
pressure, though, this can make effective recovery rather difficult. 
SUMMARY OF THE INVENTION 
One embodiment of the present invention provides a fluid delivery system 
which includes a pump, a fluid conduit and a regulated gas inlet. The 
fluid conduit has an upper end operatively connected to the pump and a 
lower end having a fluid inlet in communication with a fluid supply. The 
upper end of the fluid conduit is located higher than the lower end. 
The regulated gas inlet of this embodiment includes a gas supply maintained 
at a predictable pressure, a pressure monitoring conduit, a gas delivery 
conduit and a pressure-responsive valve. The pressure monitoring conduit 
is in fluid communication with the fluid conduit at an intermediate 
location positioned between the upper and lower ends of the fluid conduit. 
The gas delivery conduit is in fluid communication with the fluid conduit 
at a location between the upper end and the intermediate location. The 
pressure-responsive valve is operatively connected to the pressure 
monitoring conduit and moves between a closed position and at least one 
open position. In its closed position, the valve restricts the flow of gas 
from the gas supply into the fluid conduit through the gas delivery 
conduit. In its open position or positions, the valve allows gas to be 
delivered from the gas supply to the fluid conduit through the gas supply 
conduit. The valve is normally biased toward the closed position, but 
moves to one of the open positions when pressure within the pressure 
monitoring conduit is below the pressure of the gas supply by more than a 
predetermined level. 
Another, somewhat more specialized embodiment of the invention provides a 
pump for recovering an underground liquid through a bore hole. This 
embodiment includes a pump positioned above a fluid level of the 
underground liquid, a fluid conduit and a regulated gas inlet. The fluid 
conduit has an upper end which is operatively connected to the pump and a 
lower end which has a fluid inlet in communication with the underground 
liquid. The regulated gas inlet of this embodiment may be generally the 
same as that outlined in connection with the previous embodiment. 
The invention also contemplates a third embodiment which is somewhat more 
specialized than either of the other two embodiments. In particular, this 
embodiment provides a skimmer pump system for recovering an underground 
liquid through a bore hole. This skimmer pump system includes a pump 
positioned above the fluid level of the underground liquid, such as at 
ground level. It also includes a float designed to positioned a fluid 
inlet carried on the float adjacent the underground liquid fluid level. A 
fluid conduit has an upper end operatively connected to the pump, with an 
upper length of the fluid conduit being relatively rigid and a lower 
length being relatively flexible. The lower length is operatively 
connected to the fluid inlet of the float. 
This system also includes a pressure monitoring conduit in fluid 
communication with the fluid conduit at an intermediate location disposed 
between the upper and lower ends of the fluid conduit. A gas delivery 
conduit is in fluid communication with the fluid conduit at a location 
between the upper end of the fluid conduit and the intermediate location 
where the pressure monitoring conduit is connected. 
This embodiment also includes a shuttle slidably received in a shuttle 
tube. The shuttle tube has an opening in fluid communication with the 
pressure monitoring conduit at one location, an opening in fluid 
communication with ambient atmosphere at a second location, an opening in 
fluid communication with the gas delivery conduit at a third location and 
an ambient air inlet port at a fourth location. The shuttle is received in 
the shuttle tube between the first and second locations along the tube. 
The shuttle moves between a closed position and at least one open position 
in response to a pressure differential between the pressure in the 
pressure monitoring tube and ambient atmospheric pressure. The shuffle's 
closed position restricts delivery of air from the ambient air inlet port 
of the shuttle tube to the gas delivery conduit. The shuttle in its open 
position delivers gas from the ambient air inlet port to the gas delivery 
conduit.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 schematically illustrates one embodiment of a fluid delivery system 
in accordance with the present invention. FIG. 1 illustrates this fluid 
delivery system used in connection with delivering an underground liquid 
and much of the following discussion also explains the invention in that 
context. However, it should be understood that the present invention can 
be used in connection with delivering other fluids over relatively high 
vertical distances. For example, the present invention may find use in 
delivering fluids from underground storage tanks or skimming fats from the 
surface of a liquid in food processing applications. 
The fluid delivery system 10 illustrated in FIG. 1 generally includes a 
pump 10, a fluid delivery conduit 30, and a regulated gas inlet 50. The 
fluid conduit 30 has an upper end which is in fluid communication with the 
pump 10 and a lower end which is in fluid communication with a fluid 
supply, such as an underground water reservoir 25. The regulated gas inlet 
50 is in fluid communication with the fluid conduit at a space positioned 
between the upper and lower ends, as explained more fully below. 
The pump 10 may be of any suitable type which is capable of drawing a 
vacuum on the fluid delivery conduit 30. For example, the pump may be a 
standard diaphragm pump with an appropriate rating or a peristaltic pump, 
though peristaltic pumps are less desirable due to increased maintenance 
problems for the hosing used in most such pumps. In at least one intended 
application wherein the invention is used to recover hydrocarbons from a 
water table, a diaphragm pump which is capable of pumping about 1.5 
ft.sup.3 of air per minute (about 0.04 m.sup.3 /min) at a vacuum of up to 
about 26" Hg (about 88 kPa) should achieve suitable flow rates. 
In the embodiment schematically shown in FIG. 1, the pump includes a fluid 
collection reservoir 12 for collecting the fluid withdrawn from the fluid 
supply 25. This reservoir 12 is typified by a simple oil drum or the like, 
with a vacuum line 24 connecting the pump to a first fitting 14 at the top 
of the reservoir. The upper end of the conduit 30 can also be connected to 
the reservoir using a fitting 16. As the vacuum line 24 pulls a vacuum on 
the reservoir 12, this will, in turn, draw a vacuum on the fluid delivery 
conduit 30. In order to avoid inadvertently delivering the fluid collected 
in the reservoir 12 to the pump 10, which may damage the pump, one can 
include a floating check valve 18 which will float on top of the fluid 
level and close the fitting 14 if the fluid level gets too high and risks 
being drawn into the vacuum line 24. If so desired, pressure can be 
monitored with a pressure gauge 20 or the like and temperature within the 
reservoir 12 can be monitored with a temperature gauge 22 or the like. 
The fluid delivery conduit 30 may have any suitable construction. In some 
applications, a simple flexible hose hanging down in the borehole 28 will 
suffice. At higher vacuum levels, a flexible hose may tend to crimp down 
or collapse on itself if the hoop strength of the hose is not high enough. 
Accordingly, care should be taken to ensure that the walls have sufficient 
strength to withstand the anticipated vacuum levels applied to the conduit 
30 by the pump 10. One can ordinarily provide a sufficiently strong 
conduit 30 by simply using a relatively rigid, straight pipe formed of 
metal or a rigid plastic such as polyvinyl-chloride. Sections of such pipe 
may be joined end-to-end with appropriate seals to provide a fluid conduit 
30 of the desired length. 
In one particular preferred embodiment, though, the fluid conduit 30 
includes a relatively rigid upper length 32, a relatively flexible lower 
length 34 and a float 40. (These elements are best seen in FIG. 2.) The 
upper end of the upper length 32 of this conduit is in fluid communication 
with the pump 10 such as through reservoir 12. The lower end of the upper 
length 32 is joined to one end of the lower length. The junction between 
these two lengths is desirably substantially fluid-tight. This can be 
accomplished in any variety of ways. For example, the lower end of the 
upper length 32 and the mating end of the lower length 34 can be provided 
with complimentary fittings designed to provide a fluid-tight seal. 
The lower length 34 can be made of a wide variety of materials. As noted 
above, though, it is important to make sure that the hoop strength is 
sufficient to maintain the conduit in an open condition under the 
anticipated operating vacuum within the conduit 30. For example, a high 
density polypropylene tubing should suffice. If the operating environment 
is fairly harsh and is likely to chemically attack the lower length 34, a 
hose made of Tygon.TM. or the like can be used instead. 
The fluid inlet of the fluid conduit 30 can simply comprise an open end of 
the conduit immersed in the fluid to be drawn through the conduit. In 
accordance with one embodiment of the present invention, though, the fluid 
inlet is carried by a float 40. As best seen in FIG. 2, the float 
comprises a buoyant body with at least one fluid inlet 44 carried thereon. 
In this embodiment, a plurality of such fluid inlets are spaced about the 
periphery of the float and are all in fluid communication with one 
another. The end 36 of the lower length 34 of the conduit is in fluid 
communication with each of the joined-together fluid inlets 44. As a 
vacuum is drawn on the fluid conduit 30, this will aspirate fluid into the 
inlets 44 and to the fluid conduit 30. 
The advantage of this embodiment to the invention is that the float permits 
one to position the fluid inlets 44 adjacent the upper surface of the 
underground liquid 25. This can be used, for example, to recover 
contaminants which float on the water table. The underground liquid 25 may 
comprise water with a thin layer 26 of a hydrocarbon material which is to 
be recovered. For example, a thin layer of oil may float on the top of the 
water table in underground formations. If one wishes to recover that 
hydrocarbon, the float can be optimized to float where the inlets 44 are 
positioned within and, perhaps, extend slightly below the hydrocarbon 
layer 26. This will minimize the amount of water which is collected while 
maximizing the ability to skim the hydrocarbon layer 26 from the surface 
of the water. 
The float can be permitted to simply drift on top of the water within the 
borehole. In the preferred embodiment shown in the drawings, though, the 
float 40 has a guideway 42 passing there through. If the float is 
generally oblong in shape, the guideway 42 may be oriented to pass through 
the center of the float along its major longitudinal axis, as shown in 
FIG. 2. The float should be relatively free to move up and down along the 
upper length 32 of the fluid conduit. The relatively flexible lower length 
34 of this conduit allows the float to move up and down within a fairly 
broad range without restricting the flow of fluid through the conduit. 
If so desired, the float 40 and a lower portion of the fluid conduit 30 can 
be encased within a housing (not shown). This housing may comprise, for 
example, a simple polyvinyl chloride pipe having a suitable diameter. In 
order to permit the free flow of fluid to the fluid inlets 44, and 
particularly to permit the hydrocarbon layer 26 to remain in good fluid 
contact with those inlets, the housing may include a plurality of slots. 
These slots should be wide enough to allow fluid to flow in and out of the 
housing with ease. 
As noted above, the fluid delivery system 10 of the invention also includes 
a regulated gas inlet 50. For reasons explained in more detail below, this 
gas inlet 50 is adapted to introduce a gas into the fluid within the fluid 
conduit 30 when the pressure in the fluid conduit 30 drops below a 
predetermined level. 
One preferred embodiment of a regulated gas inlet 50 is best seen in FIG. 
3. In this embodiment, the inlet 50 includes a shuttle 70 received within 
a shuttle tube 52. As explained in more detail below, the shuttle 70 
slides within the shuffle tube 52 and functions as a pressure-responsive 
valve. 
The shuttle tube 52 has an opening in fluid communication with the fluid 
conduit 30. In the illustrated embodiment, this fluid communication is 
accomplished by extending the shuttle tube 52 off to one side of the fluid 
conduit 30. The length of the shuttle tube between the fluid conduit and 
the shuttle 70 can be considered a pressure monitoring conduit 54 as the 
pressure in this length of the shuttle tube will allow one to actively 
monitor the pressure within the fluid conduit 30 at that location along 
its length. The shuttle tube also includes a gas inlet port 56. As 
explained more fully below, a gas which is to be introduced into the fluid 
conduit 30 is drawn into the shuttle tube 52 through this inlet 56. 
The shuttle tube 52 is also in fluid communication with a gas supply 
maintained at a fairly controlled pressure. In the embodiment shown in 
FIG. 1 this gas supply may comprise a compressor 62 or a pressurized tank 
of gas positioned adjacent to ground level. An elongate hose 64 may be 
used to connect the compressor 62 to the shuttle tube 52. By controlling 
the pressure in the hose 64 delivered by the compressor 62, one can 
regulate and effectively maintain a desired pressure on the side of the 
shuttle 70 opposite the pressure monitoring conduit 54. 
In the preferred embodiment shown in FIG. 3, though, there is no need for a 
separate compressor. Instead, ambient air adjacent the regulated gas inlet 
50 is used as the gas supply. Obviously, the pressure of ambient air will 
vary with changes in atmospheric pressure. However, it is believed that 
these variations are within acceptable limits and the regulated gas inlet 
50 of FIG. 3 will operate as intended despite these fluctuations. As 
typified in FIG. 3, the end 58 of the shuttle tube dispose farthest away 
from the fluid conduit 30 is simply open to ambient atmosphere. 
The regulated gas inlet 50 also includes a gas delivery conduit 65. This 
conduit is in fluid communication with both the shuttle tube 52 and the 
fluid conduit 30. As explained below, the gas delivery conduit 65 is used 
to introduce gas into the fluid conduit to regulate the pressure within 
the conduit. 
The shuffle tube 52 optionally includes a pair of O-rings 60, with one 
O-ring positioned on either side of the ambient air inlet port 56. This 
will help provide a fluid-tight seal between the outer surface of the 
shuttle 70 and both the pressure monitoring conduit 54 and ambient 
atmosphere through the end 58 of the tube. It is possible that such 
O-rings could impede the smooth movement of the shuttle 70 in the shuttle 
tube 52 because the shoulder of the shuttle adjacent the reduced diameter 
segment 74 (discussed below) could catch on the O-ring, particularly when 
moving to the shuffle's closed position shown in FIG. 3. To minimize any 
interference between the O-rings 60 and the shuttle, the O-rings may be 
positioned at an angle within the tube (presenting a less abrupt 
interface), for example. 
The shuttle 70 is adapted to the slide within the shuttle tube 52 between 
an open position wherein it restricts delivery of gas from the inlet port 
56 to the gas delivery conduit 65 and an open position wherein gas is free 
to flow into the gas supply conduit and, hence, into the fluid conduit 30. 
As best seen in FIG. 4, the shuttle 70 desirably includes a body 72 and a 
passageway 76 for delivering gas from the gas inlet port 56 to the gas 
supply conduit 65. (The operation of this passageway 76 will be explained 
more fully below.) In the embodiment shown in FIGS. 3 and 4, the 
passageway 76 is defined by a reduced diameter section 74 of the shuttle. 
The difference in diameter between the body 72 and the reduced diameter 
portion 74 defines an annular space between the reduced diameter portion 
and the inner wall of the shuttle tube 52. Opposite the main body 72, the 
shuttle desirably also includes a second area 78 which has substantially 
the same diameter as that of the main body 72. 
The shuttle may also include one or more O-rings to help seal the shuttle 
against the inner surface of the shuttle tube 52. In the embodiment shown 
in FIG. 4, there are two spaced-apart O-rings 82, 84 carried by the body 
72 of the shuttle adjacent the end positioned next to the pressure 
monitoring conduit 54. This will help provide a fluid-tight seal between 
the pressure monitoring conduit 54 and the rest of the shuttle tube 52 so 
that the fluid within the fluid conduit 30 does not escape. 
Another O-ring 86 may also be positioned adjacent the opposite end of the 
shuttle, as shown in FIG. 4. This will help seal the shuttle from the 
ambient atmosphere entering the open end 58 of the shuttle tube. This will 
prevent the undesired ingress of air into the gas delivery conduit 65 
through the open end 58 of the shuttle tube. If so desired, two or more 
spaced-apart O-rings could be used instead of the single one shown in FIG. 
4. 
The shuttle should be free to move within the shuttle tube 52. However, in 
a particularly preferred embodiment, the shuttle is biased by a spring 
toward the closed position shown in FIG. 3. The spring may take any useful 
shape. In the illustrated embodiment, the spring simply comprises a pair 
of elastic members 90 attached to an eyelet 80 on the second end portion 
78 of the shuttle. These elastic members may be attached to the shuttle 
tube itself to provide a physical reference for the position of the 
shuttle 70 within the tube. For example, each of the elastic members 90 
can be attached to a hook 92 provided on the exterior surface of the 
shuttle tube. 
If one desires to provide the regulated gas inlet 50 with the ability to 
adjust the pressure at which gas is introduced into the fluid conduit 30, 
additional hooks 94, 96 can be positioned at different points along the 
length of the outside of the shuttle tube 52. By moving the elastic 
members 90 to different hooks, one can adjust the biasing force exerted on 
the shuttle by the elastic members 90. 
When the shuttle 70 is in its closed position, the main body 72 of the 
shuttle will substantially fill the lumen of the tube 52 adjacent the air 
inlet port 56. Some air may be permitted to enter the shuttle tube 52 
through the inlet port 56 and travel to the gas delivery conduit 65 
through the small space between the shuttle and the inner surface of the 
tube in that area. However, such leakage into the gas delivery tube 65 
should be negligible and should have no substantial impact on operation of 
the system. The O-rings 60 positioned on the inside of the shuttle tube 52 
will also help prevent the introduction of air from other areas of the 
shuttle tube 52. 
As the pressure within the fluid conduit 30 drops, the pressure of the 
ambient air on the second end of the shuttle 70 will tend to urge the 
shuttle away from the open end of the shuttle tube and toward the fluid 
conduit 30. In FIG. 3, this would mean urging the shuttle toward the 
right.) The pressure of the ambient air entering through the open end 58 
of the tube 52 will be counteracted to some extent by the resilient 
members 90. When the force exerted on the shuttle 70 by the pressure 
differential between ambient air and the pressure in the pressure 
monitoring conduit 54 exceeds the force exerted by the resilient members 
90, the shuttle will move to the right. When the pressure differential is 
great enough, at least a portion of the reduced diameter portion 74 of the 
shuttle will be positioned between the two O-rings 60, 60 carried on the 
inner surface of the shuttle tube 52. This will provide a passageway 76 
for gas, i.e., ambient air, to pass between the ambient air inlet port 56 
and the gas delivery conduit 65. This defines an open position of the 
shuttle 70 within the shuttle tube 52. 
The shuttle and shuttle tube of the embodiment of FIGS. 3, 4 and 6 
essentially operates as a pressure-responsive valve. In particular, the 
relative positions of the shuttle 70 and the shuttle tube 52 define the 
closed position wherein the flow of gas from the gas supply (e.g. ambient 
air) into the fluid conduit through the gas delivery conduit 65 is 
restricted. The relative positions of the shuttle and shuttle tube also 
define a number of open positions wherein gas from the gas supply is 
delivered to the fluid conduit 65. It is difficult to define a single open 
position of the shuttle within the shuttle tube because any location which 
permits gas to enter the passageway 76 through the inlet 56 will introduce 
gas into the gas delivery conduit 65. It should be noted, though, that the 
more the shuttle moves toward the pressure monitoring conduit 54 (i.e., to 
the right in FIG. 3) the more readily that gas will flow through this 
passageway because more of the passageway will be open to the inlet port 
56 and the gas delivery conduit 65. 
In the embodiment shown in FIG. 3, the gas delivery conduit 65 is connected 
to the fluid conduit 30 at a location slightly above the position at which 
the shuttle tube is connected to the fluid conduit. This introduces gas 
into the fluid conduit 30 upstream of the pressure monitoring conduit 54. 
As a result, the compressible gas will not pass by the pressure monitoring 
conduit 54 and this conduit will remain filled with a non-compressible 
fluid, improving control of the pressure in the fluid conduit 30. 
In an alternative embodiment, the gas delivery conduit 65 is connected to 
the fluid delivery conduit at a location below the pressure monitoring 
conduit. Ideally, this connection is positioned well below the pressure 
monitoring conduit 54. For example, if the system is being used to deliver 
an underground liquid, the gas delivery conduit 65 can be connected to the 
fluid delivery conduit 30 below the level of the underground liquid. It is 
believed that this would obviate the need for the O-rings 60 carried by 
the shuttle tube 52--the pressure in the gas delivery conduit would be 
greater than the pressure in the pressure monitoring conduit 54 and the 
O-rings 82, 84 and 86 on the shuttle should suffice to seal the shuttle 
from the pressure monitoring conduit 54 and ambient environment. 
If so desired, an O-ring(not shown) can be provided adjacent the end of the 
gas delivery conduit which is connected to the shuttle tube 52. This will 
minimize any interference with movement of the shuttle within the tube 
while still helping seal the gas delivery conduit against an outer surface 
of the shuttle 70. 
If the gas delivery conduit is positioned below the pressure monitoring 
conduit 54 in this manner, the introduction of the gas through the gas 
delivery conduit 65 would reduce the vacuum level in the fluid conduit 30 
before the fluid passes the pressure monitoring conduit 54. The discrete 
pockets of gas introduced into the conduit 30 would appear to cause the 
pressure in the pressure monitoring conduit 54 to fluctuate more widely, 
causing the shuttle 70 to pulsate somewhat in the shuttle tube 52. This 
will tend to introduce smaller bubbles of gas more frequently, which may 
benefit operation by providing a more consistent output than if there were 
larger, more discrete pockets of gas in the fluid delivery conduit 30. 
FIGS. 5A and 5B illustrate an alternative embodiment of a shuttle 70'. In 
this embodiment, the main body 72' of the shuttle 70' may have a 
substantially constant diameter along its length. For the shuttle in FIG. 
4, the reduced diameter segment 74 was used to define a passageway 76 for 
delivery of gas to the gas conduit 65. In the embodiment of FIG. 5, 
though, there is no reduced diameter portion 74. 
Instead, the body 72' of the shuttle is provided with a passageway 76' 
passing through the body. In the illustrated embodiment, this is typified 
by a generally L-shaped passageway having a port on the side and top of 
the shuttle. When the shuttle 70' is in its open position within the 
shuttle tube 52, at least a portion of the opening on the side of the 
shuttle would be aligned with the air inlet port 56 of the shuttle tube. 
At the same time, at least a portion of the upper opening of the 
passageway 76' would be aligned with the bottom of the gas delivery 
conduit 65. This would permit gas to flow between the inlet 56 and the gas 
conduit 65 through the passageway 76'. 
Delivery gas to the fluid conduit 30 through the gas delivery conduit 65 
will help significantly improve the flow of liquid through the fluid 
conduit 30. If the distance which one needs to lift the liquid is 
relatively short, the vacuum levels necessary to overcome the head of the 
liquid generally will not be very substantial. If one attempts to lift the 
liquid through the fluid delivery conduit a greater distance, though, the 
vacuum pressures necessary to lift the liquid may be more significant. 
For materials having low vapor pressure (e.g., crude oil), high vacuum 
levels, i.e., low pressures, within the fluid delivery conduit 30 will not 
present a problem. For materials that have higher vapor pressures, 
including water, the effects of the vacuum in the fluid delivery conduit 
30 can be more problematic. In particular, the liquid within the conduit 
may be caused to boil when the pressure drops below a specific level. When 
the fluid begins to boil, the pump will be extracting primarily vapors 
rather than the liquid intended to be extracted. This will substantially 
adversely impact the flow rate of liquid through the conduit 30 and may 
effectively preclude one from pumping the liquid through the fluid 
delivery conduit. 
For this reason, many pumps intended to pump water from an underground 
formation provide the pump at the bottom of the fluid conduit rather than 
at the top. Since one is, therefore, lifting the water by increasing the 
pressure at the bottom rather than reducing the pressure at the top, the 
vapor pressure of water does not present a problem. If one attempts to 
raise water more than about 20 feet (about 6 meters) using a vacuum at the 
upper end of that length, though, the vacuum levels necessary to overcome 
the head of that length water will typically cause the water to boil. This 
effectively precludes one from using a vacuum pump to lift underground 
water more than about 20 feet (about 6 meters). 
The present invention allows one to pump fluids using a vacuum line across 
a much greater height. This is accomplished by introducing gas into the 
fluid delivery conduit 30 when the pressure within that conduit gets too 
low. The introduced gas will typically form a pocket within the fluid 
delivery conduit. The introduction of gas into the conduit above the 
pressure monitoring conduit 54 will help reduce the pressure sensed in 
that conduit 54. This will, in turn, allow the shuttle 70 to move to its 
closed position and terminate the introduction of gas into the fluid 
conduit 30. In this manner, one will typically introduce a series of 
spaced-apart pockets of gas into the fluid delivery conduit. 
Introducing spaced-apart gas pockets into the fluid delivery conduit 30 
helps reduce the weight of the fluid within the conduit by reducing the 
net density of that fluid. Reducing the weight, in turn, reduces the 
vacuum level necessary to lift the fluid within the conduit 30 up to the 
reservoir 12. Obviously, introducing the gas into the fluid delivery 
conduit will reduce the pumping efficiency somewhat as compared to having 
the entire fluid delivery conduit 30 filled with the liquid at the same 
flow rate. However, introducing gas in this manner will allow one to lift 
a liquid a much greater distance without causing the liquid to volatilize 
and effectively terminate pumping all together. 
The amount of gas introduced into the fluid conduit can be controlled by 
controlling the pressure differential between the gas supply and the fluid 
delivery conduit 30 necessary to move the pressure-sensitive valve of the 
system to its open position. In the embodiment shown in FIGS. 3-6, this 
can be accomplished by adjusting the tension on the elastic members 90. If 
the elastic members are attached to the first pair of hooks 92, the 
biasing force exerted by the elastic members will be incrementally lower 
than if the same elastic members were attached to the second pair of hooks 
94 or the third pair of hooks 96. 
Lowering the biasing force exerted on the shuttle 70 will allow the shuttle 
to move to its open position when the pressure differential between 
ambient air and the pressure monitoring conduit 54 is relatively low. 
Increasing the biasing force of the elastic members 90 will increase the 
pressure differential necessary to move the shuttle to its open position 
and introduce gas into the fluid conduit 30. By adjusting the necessary 
pressure differential in this manner, one can ensure that gas will be 
introduced into the fluid delivery conduit 30 before the pressure in the 
conduit drops below the level necessary to volatilize the liquid being 
recovered. At the same time, one need not set the shuttle to open at 
unnecessarily low pressure differentials, which would more readily 
introduce gas and yield a corresponding reduction in pumping efficiency. 
While a preferred embodiment of the present invention has been described, 
it should be understood that various changes, adaptations and 
modifications may be made therein without departing from the spirit of the 
invention and the scope of the appended claims.