Fluid cylinder pressure check valve device

The present invention relates to a fluid cylinder pressure check valve device, for use during the recharging of cylinders with fluid(s). In use, the invention is attached to a valve assembly of the cylinder so that when the valve assembly is opened, residual pressure within the cylinder may be determined to enable more efficient recharging. The invention also allows cylinders containing gas mixtures to be recharged to attain enhanced composition uniformity.

FIELD OF THE INVENTION 
The present invention relates to fluid cylinder pressure check valve 
devices, and more particularly to fluid cylinder pressure check valve 
devices for use during the recharging of cylinders with fluid(s). In use, 
the fluid cylinder pressure check valve devices of the present invention 
are attached to a valve assembly of a used fluid cylinder returned for 
recharging so that when the valve assembly is opened, the amount, if any, 
of residual pressure contained within the cylinder may be determined. If 
the residual pressure is equal to or greater than a certain preset 
pressure, the cylinder may be "topped off" with product fluid. If the 
residual pressure is less than the preset pressure or has been exhausted 
to atmospheric pressure, the cylinder may be vented ("blown down"), 
evacuated and then recharged (or evacuated and then recharged) with 
product fluid. The present invention also allows cylinders containing gas 
mixtures to be recharged so as to attain enhanced composition uniformity. 
BACKGROUND OF THE INVENTION 
High pressure cylinders are used widely to transport and dispense large 
quantities of various industrial gases. Such cylinders can be used 
individually or manifolded to supply the user's gas requirements. Often 
when the gas use requirements have ceased and particularly when the gas 
supply is exhausted, the cylinders are sent for refilling or recharging. 
When high pressure gas cylinders are returned for recharging, they may be 
returned empty or they may be returned containing gas under a residual 
pressure. The residual pressure is ordinarily greater than the use 
pressure and may range up to nearly full cylinder pressure, e.g. about 
2200 psig, depending on the gas. 
Presently, when such cylinders are returned for recharging, they are 
connected through a manifold to a filling rack, the cylinder valves on all 
of the cylinders are opened and the contents of the cylinders are vented 
to atmospheric pressure (or "blown down"). Those vented cylinders are then 
evacuated under reduced pressure. Once evacuated, the cylinders may be 
recharged. This practice, though common, is inherently inefficient as 
product gas is wasted when cylinders having high residual pressure are 
vented. In addition, processing time for recharging returned cylinders is 
lengthy since all returned cylinders are vented and evacuated. Such 
cylinder evacuation is necessary using this common practice to minimize 
the opportunity for product gas contamination. 
Attempts have been made during the recharging operation to identify 
cylinders which contain residual pressure. When identified, such cylinders 
are indicated for recharging separately. By so doing, the loss of product 
gas is minimized because only those cylinders having low residual pressure 
are vented; however, this identification practice is labor intensive and 
requires operator or handler judgment when evaluating whether used 
cylinders contain residual pressure. 
Cylinders containing gas mixtures are recharged to varying degrees of 
composition uniformity if topped off from varying residual pressure 
levels. 
High pressure cylinders have valve assemblies which often include pressure 
check systems. These pressure check systems are designed to ensure that a 
residual pressure at a specified pressure always exists in the cylinders 
returned for recharging. The pressure check system containing valve 
assemblies are mechanically complex and add expense to the gas cylinder 
package. Moreover, these valve assemblies require adapters for use with 
the cylinder recharging lead during the recharging operation. 
Certain known cylinder valve assemblies with pressure check systems include 
a pressure retention back check valve having a check valve spool. The 
check valve spool is designed to retain within a cylinder a residual 
pressure using a tension-loaded spring which is gauged to a preset 
pressure. When the residual pressure within the cylinder is higher than 
the preset pressure, a force unbalance exists on the opposing faces of the 
check valve spool. The force unbalance causes the check valve spool to be 
maintained in an open position. In the open position, fluid delivery 
around the spool is permitted when a source of fluid is introduced through 
the valve assembly at a pressure higher than the preset pressure. 
When the check valve spool is in a closed position, residual pressure 
within the cylinder is retained. A bleed channel, which connects the 
opposite faces of the check valve spool, prevents the introduction of gas 
into the cylinder from a higher pressure source. By applying the external 
pressure on the unequal faces of the check valve spool the bleed channel 
prevents the check valve spool from assuming the open position and thereby 
creates an unbalanced closing force. However, in order to charge the 
cylinder, an adapter is required for holding the check valve spool in the 
open position. This adapter also prevents back flow into the cylinder. 
Since valve assemblies of the type described above are designed to prevent 
back flow into the cylinder, they would require a mechanical adaptor for 
maintaining the check valve spool in the open position to have utility in 
a recharging operation. Otherwise, the valve assemblies could not be 
implemented in such an operation. 
Also, in the event the check valve spool malfunctions, e.g. leaks within 
such valve assemblies resulting in a cylinder being returned for 
recharging with no residual pressure, the cylinder contents would not be 
recognized as being at atmospheric pressure unless an operator had 
specifically performed a vent test on that cylinder prior to its 
connection to the refilling rack or manifold. Thus, in a conventional 
recharging operation all returned cylinders are tested for residual 
pressure to avoid topping off an empty cylinder which could result in 
product fluid contamination. 
Incorporation of the check valve spool into many conventional valve 
assemblies would also require a different, larger and complex valve body 
than that which is ordinarily used. Larger and more complex valves 
generally, as noted above, add cost to the cylinder package and also add 
operational steps during cylinder processing which increase cylinder 
handling time. 
Another known device used as an excess flow check valve can also be used to 
check for residual pressure in a cylinder which is greater than a preset 
pressure. In the event the residual pressure is above that preset 
pressure, the cylinder may be recharged by topping off with an 
externally-supplied fluid. However, this device, shown in cross-sectional 
view in FIG. 4B, cannot be used to equalize the residual pressure of all 
cylinders connected to the same charging manifold and charging source. 
U.S. Pat. No. 5,305,794 describes a device for controlling the rate of gas 
flow depending on whether the gas is flowing from the cylinder or to the 
cylinder. This is accomplished by the size of the orifices in the valve 
through which the gas flows. Gas flow is limited or restricted when it is 
being withdrawn from the cylinder and the check valve is opened during the 
filling operation to allow gas flow into the cylinder at a faster rate. 
Similarly, U.S. Pat. No. 5,373,873 discloses a device which includes ports 
of different sizes for the evacuation and filling stages of a cylinder 
recharging operation. A larger port is used during the evacuation stage 
and a smaller port is used during the refilling stage. The difference in 
port size allows the rate of filling to be varied depending again on 
whether the gas is flowing from the cylinder or to the cylinder. The 
devices of these two patents do not include or contemplate a residual 
pressure check device for sealing the flow through the cylinder valve and 
determining whether the residual pressure in the cylinder is above a 
preset pressure so that cylinder evacuation prior to refilling may be 
omitted. Nor do these devices include or contemplate an override feature 
to allow fluid passage irrespective of residual pressure. 
In view of the state of the art, it would be desirable to provide a 
pressure check valve device for recharging fluid cylinders, which would 
allow a seal to be established when the fluid cylinders have a residual 
pressure at or above a preset pressure and also would allow passage to be 
maintained when the cylinders have residual pressure below the preset 
pressure. In addition, it would be desirable for such a device to include 
a mechanism for manually and conveniently overriding the seal established 
within the device. 
OBJECTS OF THE INVENTION 
It is therefore an object of the present invention to provide a pressure 
check valve device for recharging a fluid cylinder in which a 
tension-biased displaceable element seals the device when a fluid is 
supplied from the cylinder at a pressure equal to or greater than a preset 
pressure, maintains passage through the device when the fluid is supplied 
from the cylinder at a pressure less than the preset pressure, or seals 
the device when the fluid is supplied at a pressure equal to or greater 
than the residual pressure within the cylinder unless the fluid is 
supplied through the device from a source whose pressure is greater than 
the residual pressure within the cylinder. It is also an object of this 
aspect of the present invention to include a feature which allows the seal 
to be overridden when the fluid from within the cylinder is at a residual 
pressure equal to or greater than the preset pressure, and which allows 
the residual pressure to pass to a surrounding environment when that 
pressure is less than the preset pressure. 
It is another object of the present invention to provide a system for 
recharging fluid cylinders, which includes cylinders to be recharged; a 
source of product fluid(s) for recharging the cylinders; pressure check 
valve devices for respective connection to the cylinders to be recharged; 
and a manifold to which is connected at its inlet position the source of 
product fluid(s) and to which are connected at its outlet positions each 
of the pressure check valve devices to which are respectively connected 
the cylinders to be recharged. 
SUMMARY OF THE INVENTION 
The present invention meets the desires and objects addressed above, and 
other objects which will become apparent to one skilled in the art upon a 
reading of this disclosure, by providing a pressure check valve device for 
recharging cylinders which includes a valve body adapted for fluid 
communication with the cylinder. The valve body itself includes a joining 
portion for providing fluid communication with the cylinder; a cylinder 
recharging portion; a valve portion disposed between the joining portion 
and the cylinder recharging portion; and a fluid passage control means. 
The valve portion includes a channel extending through the valve body and a 
tension-biased displaceable element which is capable of (a) sealing the 
channel when a fluid at a pressure equal to or greater than the preset 
pressure is supplied from the cylinder to the channel, unless a fluid at a 
pressure greater than the residual pressure within the cylinder is 
supplied to the channel in the cylinder recharging portion, in which event 
an open fluid passage is maintained through the channel, and (b) maintain 
an open fluid passage through the channel when a fluid at a pressure less 
than the preset pressure is supplied from the cylinder to the channel in 
the joining portion. 
The fluid passage control means may include a first position which allows 
fluid communication to be established between the joining portion and the 
cylinder recharging portion when fluid at a residual pressure equal to or 
greater than the preset pressure is supplied from the cylinder, and a 
second position which allows passage to a surrounding environment of fluid 
from the cylinder whose residual pressure is less than the preset 
pressure. 
The tension-biased displaceable element may include a piston, a portion of 
which is capable of sealing the channel. The fluid passage control means 
includes means for allowing or preventing sealing movement of the 
tension-biased displaceable element when a fluid is supplied through the 
channel in the cylinder recharging portion at a pressure greater than the 
residual pressure within the cylinder thereby operating to permit fluid 
flow through the channel. 
The present invention also provides a system for recharging cylinders with 
fluid, which includes a plurality of cylinders to be recharged; a source 
of product fluid(s) for recharging the plurality of cylinders; a plurality 
of pressure check valve devices for respective connection to the plurality 
of cylinders to be recharged; and a manifold to which is connected in 
fluid communication at its inlet position the source of product fluid(s) 
and to which are connected in fluid communication at its outlet positions 
each of the plurality of pressure check valve devices to which are 
respectively connected the plurality of cylinders to be recharged with 
fluid. 
In addition, this invention provides a method of using a pressure check 
valve device in a cylinder recharging operation. This method includes the 
steps of connecting at least one pressure check valve device to at least 
one cylinder; determining a residual pressure within the cylinder(s); and 
using that determination in deciding whether to first vent and/or evacuate 
the cylinder(s) prior to recharging or to directly recharge the 
cylinder(s).

DETAILED DESCRIPTION OF THE INVENTION 
The present invention provides a fluid cylinder check valve assembly which 
will be described in detail hereinafter with reference to the Figures. In 
the Figures common elements have the same numerals. Though the present 
invention may be practiced with a variety of fluids, the invention is 
preferably practiced with industrial gases, such as nitrogen, helium, 
oxygen, argon and the like, and gas mixtures, such as air and welding 
mixtures. 
FIGS. 1A-1C, 2 and 6 illustrate a pressure check valve device according to 
the present invention. The pressure check valve device 1 includes a valve 
body 2 adapted for fluid communication with a cylinder (not shown) to 
which it is attached. The valve body 2 itself includes a joining portion 3 
for providing fluid communication with the cylinder; a cylinder recharging 
portion 4; a valve portion 5 disposed between the joining portion 3 and 
the cylinder recharging portion 4, and a fluid passage control means 6. 
The valve body 2 includes a cylindrical channel 8 bored therethrough. 
Within the channel 8 of the valve portion 5 is a tension-biased 
displaceable element 7 which is capable of sealing the channel 8. The 
tension-biased displaceable element 7 is adapted to seal the channel 8 
when a fluid at a pressure greater than a preset pressure is supplied 
through the channel 8 from a cylinder attached to the joining portion 3. 
The tension-biased displaceable element 7 is also capable of maintaining 
an open fluid passage through the channel 8 when a fluid at a pressure 
less than the preset pressure is supplied through the channel 8 from a 
cylinder attached to the joining portion 3. In addition, the 
tension-biased displaceable element 7 is capable of sealing the channel 8 
when a fluid at a pressure equal to or greater than the preset pressure is 
supplied through the channel 8 from a cylinder attached to the joining 
portion 3, unless a fluid at a pressure greater than the residual pressure 
within the cylinder is supplied through the channel 8 from the cylinder 
recharging portion 4, in which event the channel is maintained in an open 
position. 
The tension-biased displaceable element 7 includes a piston 9, an end 
portion 10 of which is tapered or has a diameter or lateral dimension 
smaller than that of the piston 9, and is capable of sealing the channel 8 
("the sealing end of the piston"). At the other end of the piston 9 is a 
base 11 which has a diameter or lateral dimension slightly greater than 
the diameter of the piston 9. The diameter of the piston 9, and of the 
base 11, is smaller than that of the channel 8 to allow displaceable 
movement therewithin. 
When biased by a residual pressure from within the cylinder equal to or 
greater than a preset pressure, the tension-biased displaceable element 7, 
more particularly the tapered or smaller diameter sealing end of the 
piston 10, seals the channel 8 within the valve portion 5 of the valve 
body 2 to prevent the escape of product gas from the cylinder. 
A sealing washer 12 is provided at the sealing end of the piston 10. The 
sealing washer 12 allows for a tight seal to be formed within the channel 
8 and prevents the flow of gas therethrough. Other sealing arrangements 
which may be employed in connection with the tension-biased displaceable 
element 7 besides the sealing washer 12 include an O-ring seal, a conical 
soft tip and the like. 
The piston 9 is housed within the channel 8 which passes through the valve 
body 2. Disposed around the diameter of the piston 9 is a means for 
providing tension, such as a spring 13. One end of the spring 13 abuts 
against the end of the base 11 of the piston 9, which as noted above, has 
a diameter larger than that of piston 9 (though still smaller than the 
diameter of the channel 8). The other end of the spring 13 abuts against a 
landing at the distal end of channel 8, just before the tapered or reduced 
diameter portion of the channel 8 against which the sealing end of the 
piston 10 may rest. 
The preset pressure is determined by the tension-loaded force exerted by 
the spring 13. The particular choice of a spring 13 or like tension-loaded 
force device will permit selection of an appropriate preset pressure. A 
desirable setting for this preset pressure is within the range of about 5 
to about 4500 pounds per square inch gauge (psig), with about 30 to about 
50 psig being preferred. 
FIGS. 1A-1B, 3A-3E and 6 illustrate the fluid passage control means 6. As 
shown, it includes a stem body 14b having a stem 14 which extends through 
an opening 15 in the valve body 2 and into a slot 17 provided in the base 
11 of the piston 9. The stem body 14b may be an integral part of the valve 
body 2, or may be connected to the opening 15 in the valve body 2 through 
a variety of connection means, such as threading. A primary gasket seal 
12a may be placed about the stem body 14b at the point of joining the 
valve body 2. In addition, grommets 12b are placed around the stem 14 to 
seal against fluid leakage along the stem 14. The stem 14 is dimensioned 
such that it engages slot 17 provided in the base 11 of the piston 9. Such 
engagement allows for the prevention of movement of the tension-biased 
displaceable element 7 within the valve body 2. 
The stem 14 of the fluid passage control means 6 may engage a slot 17 
provided in the base 11 of the piston 9 to prevent sealing of the channel 
8. Alternatively, the stem 14 may engage the slot 17 provided in the base 
11 of the piston 9 to seal the channel 8 unless a fluid is supplied 
through the channel 8 in the cylinder recharging portion 4 at a pressure 
greater than the preset pressure. 
More specifically, the end of the stem 14 may be cut away so that a 
portion, e.g. about half, of the diameter of the stem 14 remains. This 
cut-away portion of the stem end 14a allows the stem 14 to engage the slot 
17 provided in the base 11 of the piston 9 when it is inserted through the 
opening 15 in the valve body 2 and into the slot 17. 
The fluid passage control means 6 should include a handle or lever 19 which 
may be actuated to a first position 18 or a second position 20. The first 
position 18 or "closed check" position allows fluid communication to be 
established between the joining portion 3 and the cylinder recharging 
portion 4 when fluid at a residual pressure greater than the preset 
pressure is supplied from the cylinder. The second position 20 or "open 
bypass" position allows passage to a surrounding environment of fluid from 
within the cylinder. The handle 19 of the fluid passage control means 6 
allows the stem end 14a to engage the slot 17 provided in the base 11 of 
the piston 9 to allow the fluid passage control means 6 to be in the 
closed check position or the open bypass position depending on which 
position, i.e. first position or second position, the handle 19 is placed. 
The valve body 2 may be constructed from a variety of materials, including 
bronze, monel, stainless steel and the like, and may be joined to the 
cylinder valve 21 (a portion of which being shown in FIG. 2) at the 
joining portion 3 through conventional connection mechanisms, such as 
complementary threading, or alternative connection means, such as those 
known in the art, which are well-suited to establishing the connection. 
The cylinder recharging portion 4 may be joined to the cylinder recharging 
lead 22, such as is shown in FIG. 2, by those connection mechanisms as 
well. 
The pressure check valve device 5 determines whether any residual pressure 
exists in the cylinder, i.e. a pressure which is equal to or greater than 
the preset pressure, when the manifold or cylinder recharging lead is 
connected to the cylinder and the cylinder valve is opened. FIG. 5 shows a 
cylinder 50 to which is inserted via threaded connection a cylinder valve 
assembly 51. In FIG. 5, a prior art excess flow check valve 52 is 
connected to the cylinder valve assembly 51 through appropriate connection 
means 53. A cylinder recharging lead 22 provides fluid communication with 
a source of product fluid (not shown) through its connection to the excess 
flow check valve 52 at a location thereon distal to the cylinder 50. 
With reference to FIGS. 1A-1C and 3A-3E, when the pressure in the cylinder 
is equal to or greater than the preset pressure, the force exerted by the 
residual pressure from within the cylinder on the tension-loaded 
displaceable element 7 overcomes the force exerted by the tension-loaded 
spring 13. In this situation, the tension-loaded displaceable element 7 
seals the channel 8 within the valve portion 5. When the pressure exerted 
within the manifold exceeds the pressure exerted from the cylinder 
contents, the resulting pressure exerted on the tension-loaded 
displaceable element 7 maintains an open fluid passage through the channel 
8. 
Alternatively, after evacuating the empty cylinders and manifold under 
reduced pressure, the handle 19 of the fluid passage control means 6 may 
be switched to the open bypass position before recharging the cylinders. 
By so doing, the pressure in all of the cylinders connected to the 
manifold may be partially vented or equalized. When thus 
pressure-equalized, the temperature of the cylinders is maintained 
substantially uniform during recharging. This allows the fluid content of 
the recharging cylinders to be controlled by pressure, volume and 
temperature measurement. Pressure equalization of the cylinders allows for 
a more consistent fill of the cylinders during the recharging operation 
because of the more accurate control of the pressure, volume and 
temperature measurements. In addition, use of the pressure check valve 
devices of the present invention is particularly advantageous in 
connection with the recharging of mixed gas cylinders. There, pressure 
equalization allows cylinders having high residual pressure to be topped 
off with a greater degree of uniformity of the mixed gas product 
composition. 
If the residual pressure in the cylinders is less than the preset pressure, 
the pressure check valve device allows the cylinders to be blown down into 
the manifold and then evacuated under reduced pressure up to full vacuum, 
e.g. 30 inches of mercury, though preferably within the range of from 
about 25 to about 29 inches of mercury. The cylinders may then be 
recharged. Any pressure in the manifold which is higher than the preset 
pressure of the pressure check valve device will force fluid flow through 
the pressure check valve device and into the cylinder thereby recharging 
the cylinders or topping off their contents. With the fluid passage 
control means 6 of the pressure check value devices, irrespective of the 
residual pressure within the cylinder the override mechanism allows a 
passage of gas from the manifold to flow through the pressure check valve 
device and into the cylinder for recharging purposes. 
Accordingly, installation of a pressure valve check device according to the 
present invention allows the following sequence of operation events to 
occur without operator intervention when cylinders to be recharged are 
connected to the manifold: 
Cylinders are checked and those with a residual pressure higher than a 
certain preset pressure are selected for topping off. 
Cylinders which are checked and determined to have a residual pressure less 
than a certain preset pressure are vented into the manifold and then to a 
surrounding environment, such as the ambient atmosphere. 
Only the manifold and vented cylinders are evacuated. 
All cylinders are then recharged (if checked, vented and evacuated) or 
topped off (if checked and indicated). 
Unlike prior art check valves, such as that illustrated in FIG. 4A, the 
pressure check valve devices of this invention are implemented in the 
cylinder recharging system without the necessity and expense of adding 
adapters to the check valve in order to recharge the cylinder. 
Pressure check valve devices in accordance with this invention, unlike the 
prior art excess flow check valve depicted in FIG. 4B, also have a 
lock-out or override feature, through implementation of the fluid passage 
control means 6, an open or unchecked flow path is created between the 
manifold to which the cylinders are connected and the cylinders. Thus, by 
simply setting the fluid passage control means 6 of the pressure check 
valve device to the second position (which is the "open bypass" position), 
a through flow or an unchecked path is created by overriding the 
tension-based displaceable element 7 within the valve portion 5. This 
passage so created permits cylinders to be recharged or topped off with 
pure product gas. The open bypass position path may also be used when 
recharging cylinders in the same rack or manifold with mixtures of two or 
more gases. 
During an ordinary recharging operation of the pressure check valve 
devices, the handle 19 of the fluid passage control means 6 may be placed 
in the closed check position. In this position, the cylinders connected to 
the recharging manifold have been identified as containing a product 
residual pressure equal to or greater than the preset pressure of the 
pressure check valve device. Therefore, the residual pressure within the 
cylinder seals the pressure check valve device so that product fluid does 
not escape through the manifold. This results in minimizing the loss of 
useful product and improves the operating efficiency of the filling plant 
by decreasing the amount of fluid product required to recharge the 
cylinders. 
The time involved in evacuating all cylinders on the manifold is obviated. 
Thus, the recharging operation should be completed in less time as fewer 
cylinders are likely to require a complete recharging. This reduces the 
total time necessary to process all the cylinders on the manifold, and 
increases cylinder filling output which translates into improved filling 
plant efficiency. 
In FIG. 2, a pressure check valve device according to this invention is 
shown installed to the cylinder recharging lead 22 at the cylinder 
recharging portion 4. This installation minimizes the dead-ended volume 
between the cylinder valve assembly 51 (the distribution/charging end of 
which being shown in FIG. 2) and the pressure check valve device. The 
dead-ended volume is not evacuated during manifold and cylinder evacuation 
and must be minimized in order to preserve cylinder product fluid purity 
within the cylinders. 
Data collected during the filling of fifty-two oxygen cylinders with a 
pressure check valve device in accordance with this invention connected 
between the recharging lead and the cylinder valves of the oxygen 
cylinders is summarized as follows. The residual pressure in the cylinders 
returned for recharging varied over a wide range. For example, twenty-four 
of the fifty-two cylinders returned for recharging contained a residual 
pressure within the range of from 50 to 2000 psig, which averages to a 
residual pressure of 155 psig. These cylinders, when filled to 2200 psig, 
correspond to a gas product savings of 7%. Since nearly 50% of the 
cylinders have residual pressure and do not need to be evacuated, the 
manifold evacuation time is correspondingly reduced by 50%. 
Using the pressure check valve devices according to the present invention, 
gas product fluid purity is maintained irrespective of cylinder residual 
pressure. The oxygen purity for these cylinders was determined to be 
greater than 99.6%, which is comparable to the purity of the oxygen 
supplied to the cylinders. 
The pressure check valve devices of this invention may be installed first 
on the cylinder valve 51 or on the cylinder recharging lead 22, which are 
ultimately connected to one another (such as by conventional connections 
22) during a cylinder recharging operation. 
The pressure check valve devices are advantageously used in connection with 
cylinders to be recharged which are placed on a plant rack or manifold, 
blown down (if required), evacuated (if required) and/or recharged. Of 
course, the pressure check valve devices of the present invention may also 
be used during the charging operation of cylinders, which have not 
previously been charged. 
Specific features of the invention are shown in one or more of the Figures 
for convenience only, as each feature may be combined with other features 
in accordance with the invention. Alternative embodiments will be 
recognized by those skilled in the art and are intended to be included 
within the scope of the claims.