Manually driven transfer pump for liquefied gases
This invention is a manually driven pump used to transfer a liquefied gas such as nitrous oxide or carbon dioxide between containers. The pump is designed to minimize friction, can be directly attached to a mother bottle, and has an automatic piston return on the pumping stroke, all of which optimize operator use for the particular gas which is being pumped. The pump is small, portable, and requires no additional power source in its operation, making it ideal for field use. The pump can be used to fill nursing bottles from a mother bottle or to raise the pressure of a nursing bottle to a desired operating level.
This invention is a manually driven pump used to transfer nitrous oxide, carbon dioxide, or other liquefied gas between storage containers, requiring no other energy source such as electricity or compressed air for its operation. It is small and easily portable, making it ideal for field use for nitrous oxide snowmobile applications or carbon dioxide paintball applications. It can also be used to raise the pressure of a liquefied gas container to a desired level.
BACKGROUNDDescription of Prior Art
Nitrous oxide, sometimes just called nitrous, is an oxidizing agent and when delivered to an engine, results in an increase in engine power output. The nitrous is pressurized and stored in a container as a liquid in equilibrium with its vapor, thereby allowing a relatively high mass storage density. Since the liquid is in equilibrium with its vapor, the pressure of the nitrous in the bottle is determined by its temperature. For instance, at 0 degrees Celsius, the bottle pressure is 31 E06 dynes/cm̂2 (450 pounds per square inch (PSI)); when at 22 degrees Celsius, the bottle pressure is 51E06 dynes/cm̂2 (735 PSI). Carbon dioxide pressure is similar; zero degree Celsius pressure is 36E06 dynes/cm̂2 (520 PSI) and 22 degrees Celsius pressure is 61E06 dynes/cm̂2 (880 PSI). Liquefied nitrous oxide and carbon dioxide have very similar thermodynamic characteristics and transfer pumps presently manufactured can be adapted to pump either nitrous oxide or carbon dioxide.
Nitrous oxide delivery systems used for engine power enhancement typically contain a relatively small nitrous bottle, commonly called a “nursing bottle”, to store a relatively small amount of nitrous on the vehicle, but use a larger bottle, commonly called a “mother bottle”, to store larger amounts of nitrous oxide apart from the vehicle. Mother bottles typically hold between 9000 grams (20 pounds) of nitrous and larger ones hold 30,000 grams (65 pounds). Nursing bottles hold considerably less; 1100 grams (2.5 pounds) is typical for a snowmobile which has a nitrous system installed to increase horsepower for drag racing or mountain climbing. This amount of nitrous only lasts a relatively short time; typically 1100 grams of nitrous is used in 30 to 100 seconds of nitrous system operation.
Presently, two methods are commonly used to replace the nitrous on the vehicle in the field. One method is to have more than one nursing bottle, perhaps two to four, these bottles having previously been filled at a refill station. These are replaced on the vehicle as required. This is relatively expensive because of the purchase of the extra bottles. Also, this puts a practical limit on the amount of nitrous which can be stored at the race site or on the side of a mountain. For instance, if the snowmobile operator has four nursing bottles at 1100 grams each, this only provides 4400 grams total on site, which is less than half what one 9000 gram mother bottle and one 1100 gram nursing bottle holds, and is considerably less than what is contained in a 30,000 gram mother bottle.
The other method is to have a current technology refill station on site. These refill stations use a transfer pump which is relatively expensive, large, heavy, and typically requires a source of compressed air in its operation. These refill stations are difficult to use at a race site or on a mountain because of the above limitations.
Compressed carbon dioxide is used in the game of paintball. Paintball guns are driven by compressed carbon dioxide which is held in a relatively small nursing bottle which, as in the case of nitrous, must be filled from a mother bottle. Similar problems with field filling are also encountered in this industry.
In addition, there are instances where the pressure in a nursing bottle must be kept at a certain level. Applicant holds U.S. Pat. No. 6,938,841 which is a nitrous oxide jet which varies in size according to bottle pressure to maintain a constant nitrous flow rate. Other manufacturers of nitrous systems, however, not having this technology, for proper system operation require the users of their systems to maintain a certain nitrous bottle pressure, 62E06 dynes/cm̂2 (900 PSI) for instance. Presently, users of these systems maintain this bottle pressure by heating, either using bottle heaters or illegally using a torch applied to the bottle.
OBJECTS AND ADVANTAGESIt is an object of this invention to provide a manually driven pump for the transfer of liquid nitrous oxide, liquid carbon dioxide, or other liquefied gas which requires no other energy source for its operation.
It is a further object of this invention to provide a manually driven pump for the transfer of liquid nitrous oxide, liquid carbon dioxide, or other liquefied gas which is relatively small, has relatively low weight, and is relatively inexpensive to produce.
It is a further object of this invention to provide a manually driven pump for transfer of liquid nitrous oxide, carbon dioxide, or other liquefied gas which can easily be attached directly to a mother bottle which is delivering the nitrous oxide, carbon dioxide, or other liquefied gas.
It is a further object of this invention to provide a manually driven pump for transfer of liquid nitrous oxide, carbon dioxide, or other liquefied gas which is specifically designed for efficient operation with the pressure characteristics of the liquefied gas with which it will be used.
It is a further object of this invention to provide a manually driven pump for transfer of liquid nitrous oxide, carbon dioxide, or other liquefied gas which can be used to raise the pressure of a liquefied gas container to a desired operating level.
Still further objects and advantages will become apparent from a consideration of the ensuing description and drawings.
- 1 manually driven transfer pump assembly
- 10 pump body
- 12 threaded body inlet
- 14 inlet sealing washer
- 20 threaded body outlet
- 30 bore
- 31 bore inlet chamber
- 32 bore pump chamber
- 40 outlet connection and one-way valve assembly
- 42 outlet body
- 46 threaded flare connection
- 50 one-way valve sealing ball
- 51 one-way valve seat
- 52 one-way valve spring
- 60 bushing
- 61 bushing retaining ring
- 62 bushing bore o-ring
- 64 bushing rod o-ring
- 70 rod and piston assembly
- 72 rod
- 74 knob
- 76 piston
- 78 piston o-ring
- 80 wave washer
- 82 rod retaining ring
- 100 mother bottle assembly
- 102 mother bottle
- 104 material in liquid state
- 106 material in vapor state
- 110 mother bottle valve assembly
- 111 mother bottle valve body
- 114 mother bottle valve connection threads
- 116 mother bottle valve knob
- 117 mother bottle valve stem
- 118 mother bottle valve seat
- 119 mother bottle siphon tube
- 120 bottle nut
- 122 bottle nut threaded flare connection
- 150 nursing bottle
- 152 nursing bottle threaded flare connection
- 160 connection conduit
The filling procedure for an empty nursing bottle 150 is as follows. Inlet 12 of pump assembly 1 is connected to mother 100 bottle containing a liquefied gas such as nitrous oxide or carbon dioxide and its outlet 40 is connected to nursing bottle 150 which normally contains air at atmospheric pressure. Mother bottle valve 110 is opened first and then the valve of nursing bottle 150 is opened. Mother bottle 100, since it contains a liquefied gas, has a pressure which is high relative to atmospheric. This high pressure is easily able to overcome the “pop-off” or opening pressure of the one-way valve in outlet fitting 40 of pump assembly 1 since the pre-load of spring 52 urging ball 50 toward seat 51 is normally set to give a relatively low pop-off pressure, typically 350,000 dynes/cm̂2 (5 PSI) or less. The effect of pop-off pressure on assembly 1 operation will be ignored in subsequent discussion since it is normally relatively small but can easily be included in any calculations if it is significant for a particular design. Liquefied gas flows from mother bottle 100 to nursing bottle 150 until the pressure in the two bottles is essentially equal (modified slightly by the pop-off pressure of one-way outlet fitting 40) at which point the one-way valve of outlet fitting 40 closes.
Pressurization of pump assembly 1 initially forces rod 72 to its fully extended position out from bushing 60 with a consequent minimum volume in pump chamber 32 and a maximum volume in inlet chamber 31. An operator of pump 1 then applies a sufficient inward force to knob 74 and consequently rod 72 to overcome the outward force on rod 72 due to the pressurization of assembly 1 and any frictional forces present. Rod 72 and piston 76 move to the left, decreasing the volume of bore inlet chamber 31 and increasing the volume of bore pump chamber 32. Piston o-ring 78 has an internal diameter larger than the outside diameter of rod 72 but an outside diameter larger than the diameter of bore 30, and due to its inherent rigidity and consequent friction against bore 30, it moves away from piston 76 and against wave washer 80. O-ring 78 cannot seal in this position due to the waves in washer 80, and therefore liquefied gas moves freely past o-ring 78 from bore inlet chamber 31 into bore pump chamber 32. This stroke wherein pump chamber 32 is filled is called the filling stroke of pump assembly 1.
When the operator has forced rod 72 to its fully inserted position, the inward force is removed and rod 72 will again move outward due to the pressure on rod 72. The pressure in bore pump chamber 32 will rise slightly above the pressure in bore inlet chamber 31 due to the pop-off pressure of the one-way valve contained in outlet fitting 40. This, combined with the rightward movement of piston 76 and the o-ring 78 frictional effects discussed above, moves o-ring 78 away from wave washer 80 and against piston 76 where it consequently seals piston 76 to bore 30. This rightward movement decreases the volume of bore pump chamber 32, thereby increasing its pressure and opening the one-way valve in outlet 40, and liquefied gas exits pump 1 toward nursing bottle 150. When rod 72 is fully extended and becomes stationary, the pressure across ball 50 ceases since there is no further movement of fluid through seat 51. Ball 50 moves against seat 51 thereby trapping upstream a portion of the liquefied gas which has passed through seat 51. This is called the pumping stroke. Pumping and filling strokes are repeated and this is the pumping action of assembly 1.
Nursing bottle 150 is not always empty when the filling process begins as described above but can be partially full. In this case the pumping action is similar to that above except for the initial flow from mother bottle 100 to nursing bottle 150. As above, downstream flow through pump assembly 1 will occur if the pressure in nursing bottle 150 happens to be sufficiently less than the pressure in mother bottle 100 to open the one-way valve in outlet 40, for instance if nursing bottle 150 is sufficiently lower than that of mother bottle 100. This flow, as above, will continue until the two bottle pressures are essentially equal. If the two bottles are at the same temperature and consequently at the same pressure, no initial flow will occur. If mother bottle 100 is colder than nursing bottle 150, a back-pressure will exist across pump 1, but one-way valve outlet connection 40 will prevent reverse flow. Subsequent pumping action is then the same as discussed above for an initially empty nursing bottle 150.
As pumping moves material from mother bottle 100 to nursing bottle 150, the pressure in mother bottle 100 decreases and the pressure in nursing bottle 150 increases. The decrease in mother bottle 100 pressure is normally relatively small due to its larger size, but the increase in nursing bottle 150 pressure can be substantial. For instance, transferring 454 grams (1 pound) from a 23000 gram (50 pound) capacity mother bottle 100 which contains carbon dioxide at room temperature (22 degrees Celsius) results in only a slight decrease in its initial pressure of 61E06 dynes/cm̂2 (880 PSI). However, transferring 454 grams (1 pound) of carbon dioxide to a nursing bottle 150 with an 100 gram (2.5 pound) capacity initially containing 680 grams (1.5 pounds) at room temperature will raise its pressure by about 6.9E06 dynes/cm̂2 (100 PSI) to 68E06 dynes/cm̂2 (980 PSI).
Pump assembly 1 works best when rod and piston assembly 70 automatically extends outward from bushing 60 because an operator of assembly 1 is not required to pull assembly 70 out. Ignoring frictional effects, this automatic extension will occur if there is a net outward force (the outward force less the inward force) on rod and piston assembly 70. The outward force is the pressure in bore inlet chamber 31 times its area which equals the area of bore 30. The inlet force is the pressure in bore pump chamber 32 times its area which is the area of bore 30 less the area of rod 72. Parameters affecting the automatic extension of rod and piston assembly 70 are the pressure characteristics of the specific liquefied gas which is being pumped, the relationship between the areas of inlet chamber 30 and pump chamber 32, and frictional forces. Pump assembly 1 can have what's called a “pressure rating” which is the maximum outlet pressure at which rod and piston assembly 70 automatically extends from pump assembly 1 for a given inlet pressure. The inlet pressure of pump assembly 1 used in establishing its pressure rating would normally be chosen to be the room temperature pressure of the specific liquefied gas for which it is designed, which is 51E06 dynes/cm̂2 (735 PSI) for nitrous and 61E06 dynes/cm̂2 (880 PSI) for carbon dioxide.
Ignoring frictional effects, the relationship between the areas of rod 72 and bore 30 determines the pressure rating of pump assembly 1 for any given mother bottle 100 liquefied gas and temperature. For instance, if pump assembly 1 has a bore 30 diameter of 9.5 mm (0.375 inches) and a rod 72 diameter of 4 mm (0.156 inches) and it is being used with a room temperature mother bottle 100 containing carbon dioxide at 61E06 dynes/cm̂2 (880 PSI), the pressure rating of the pump is determined as follows. The outward force on rod and piston assembly 70 is the area of bore inlet chamber 31 times its pressure, this pressure being the mother bottle 100 pressure since this chamber is directly connected to mother bottle 100. This outward force is 43.2E06 dynes. The inward force is the pressure in bore pump chamber 32 (essentially equal to the pressure in nursing bottle 150) times its area, which is the area of bore 30 reduced by the area of rod 72. The pressure in bore pump chamber 32 at which the inward force equals the outward force can be calculated and is 73E06 dynes/cm̂2 (1060 PSI). Therefore, for this application, the pressure rating of pump assembly 1 is 73E06 dynes/cm̂2 (1060 PSI) at a mother bottle pressure of 61E06 dynes/cm̂2 (880 PSI).
Another design consideration is the diameter of rod 72 and the force required to push rod 72 inward. The pressure rating of assembly 1 is established by the pumping stroke where the pressure in bore inlet chamber 31 is the mother bottle 100 pressure and the pressure in bore pumping chamber 32 essentially equals nursing bottle 150 pressure. But on the inward movement of rod 72 on the filling stroke, the pressures in chambers 31 and 32 are essentially equal due to the fact that piston o-ring 78 is not sealed, and these pressures are essentially equal to mother bottle 100 pressure. The outward force on rod 72 is still determined as above using the inward and outward force calculations, but in this case since the pressures in chambers 31 and 32 are the same, the formula can be simplified. In the case of the filling stroke, the formula for the outward force on rod 72 can be simplified to be just the area of rod 72 times mother bottle 100 pressure. This puts a practical limit on the diameter of rod 72 which will allow relatively easy operator function when on the filling stroke. For the same design discussed above with a mother bottle 100 pressure of 61E06 dynes/cm̂2 (880 PSI) and rod 72 diameter of 4 mm (0.156 inches), this gives an outward force on rod 72 on the filling stroke of 7.5E06 dynes (17 pounds) which is a reasonable force for an operator of pump assembly 1 to apply. Of course the diameter of rod 72 can be chosen as required to provide optimum performance of pump assembly 1 for any combination of liquefied gas and mother bottle 100 temperature, along with a corresponding adjustment if necessary to bore 30 diameter to achieve the desired pump pressure rating.
Frictional effects should be minimized in pump assembly 1 to reduce the operator's pumping effort and to maximize the pressure rating for any given condition. The largest sources of friction in assembly 1 are piston o-ring 78 and bushing rod o-ring 64. A good material for both is a 90 Shore A durometer polyurethane since this material provides low friction, high tensile strength, and good resistance to abrasion. Normally O-rings used as reciprocating seals to seal a piston in a bore use radial compression to provide the seal. In other words, the radial clearance between the surface upon which the o-ring is mounted and the bore is less than the cross-sectional dimension of the o-ring, hence the radial compression. In the case of a relatively hard o-ring material such as this 90 durometer polyurethane material, the compressive force on the o-ring, even for relatively small radial compression, can be considerable. This, coupled with additional compression of the o-ring due to any pressure existing across the o-ring, can create relatively high frictional forces in this conventional o-ring construction.
In assembly 1, however, the radial clearance between rod 72 and bore 30 is greater than the cross-section of o-ring 78. This allows, as discussed above, o-ring 78 to move relative to rod 72 so it can perform its one-way valve function, but this construction also provides inherently low friction as compared to a construction in which there is radial compression of the o-ring. In fact, when rod and piston assembly 70 is moving to the left on the filling stroke and o-ring 78 is pushed against wave washer 80 with consequently no pressure across it, o-ring 78 causes essentially no friction force on this stroke. Even when rod and piston assembly 70 is moving to the right on the pumping stroke with o-ring 78 sealing bore 30 to piston 76, the frictional force of o-ring 78 is higher than on the filling stroke due to the pressure existing across o-ring 78 but this force is still considerably less than that which would be present with a conventional radially compressed o-ring construction.
Pump 1 has a maximum mass transfer per cycle determined by the density of the particular liquefied gas at its temperature multiplied by the maximum volume change in bore pump chamber 32. The maximum volume change of bore pump chamber 32 equals the area of bore pump chamber 32 (the area of bore 30 less the area of rod 72) times the maximum stroke of piston o-ring 78. The actual mass transfer per cycle of pump 1 equals the maximum mass transfer per cycle times the pumping efficiency factor of pump 1. A pump was assembled similar to pump 1 having a bore 30 diameter of 9.5 mm (0.375 inches), a rod 72 diameter of 4 mm (0.156 inches), and a maximum o-ring 78 stroke of 22 mm (0.87 inches) giving a maximum volume change in bore pump chamber 32 equal to 1.3 cm̂3. The density of liquefied carbon dioxide at room temperature is approximately 0.77 grams/cm̂3 giving a maximum mass transfer per cycle of 1 gram. This pump was tested and it actually pumped about 0.92 grams of liquid carbon dioxide per cycle giving a pumping efficiency factor of 0.92.
An operator of pump 1 needs a scale to weigh nursing bottle 150, and knowing the tare weight of bottle 150 and its rated capacity of liquefied gas, the operator knows how much material must be added to bottle 150 to fill it to any desired level. Therefore, knowing the desired quantity of mass to transfer and knowing the mass transfer per cycle of assembly 1, the operator knows approximately how many pump strokes are required to complete the filling. This eliminates much of the trial-and-error which can occur when filling nursing bottle 150 using presently available pumps which use air pressure in their operation.
As discussed above, many conventional nitrous oxide delivery systems which do not have the adjustable nitrous jet discussed in Applicant's U.S. Pat. No. 6,938,841 require a constant nitrous bottle pressure for proper operation. Presently, a typical procedure is to check nitrous pressure just before a race, and if it is low, to apply heat, typically with a torch, to raise the pressure to an acceptable level. This application of heat with a torch weakens the aluminum typically used in these high pressure bottles, and this heating procedure is illegal. Users of these systems, however, being somewhat independent thinkers, do it anyway. Pump assembly 1 of this invention can replace this illegal heating method. As discussed above, transferring material into nursing bottle 150 raises its pressure (the bottle actually is heated internally due to the enthalpy added to the liquid nitrous during the pumping stroke), and this pressure increase is very gradual and easily controlled. A pressure gauge can be connected into conduit 160 (using a “tee” for instance) and pump assembly 1 can simply be operated until the desired pressure level is reached.
Summary, Ramification, and ScopeThis invention is a manually driven pump used to transfer a liquefied gas such as nitrous oxide or carbon dioxide between containers. The pump is designed to minimize friction, can be directly attached to a mother bottle, and has an automatic piston return on the pumping stroke, all of which optimize operator use for the particular gas which is being pumped. The pump is small, portable, and requires no additional power source in its operation, making it ideal for field use. The pump can be used to fill nursing bottles from a mother bottle or to raise the pressure of a nursing bottle to a desired operating level.
Although the description above contains many specificities, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the presently preferred embodiments of this invention. For instance, the assembly is shown with a one-way valve function present in an outlet fitting in the pump. This is preferable in most cases, but this one way valve can also be placed in the pump's inlet or one-way valves can be placed in both the inlet and outlet if desired. The one-way valve shown is a spring loaded ball and seat design, but other one-way valve designs can be used, such as a diaphragm. The pump is shown as having an inlet which is directly attached to a mother bottle, and this is preferable because in some cases the pumping action is easier with this connection, but in some situations a different inlet connection may be beneficial, such as a flare connection commonly used with flexible conduits. It may be desirable in some cases to rigidly fix the pump to a fixture such as a table, perhaps attaching the end opposite the operating rod to the fixture and placing its inlet on the side rather than on its axis. It may even be desirable in some cases to have the operating shaft extend completely through the pump along its axis, thereby eliminating the automatic rod extension function present in the preferred embodiment shown. Thus, the scope of the invention should be determined by the appended claims and their legal equivalents, rather than by the examples given.
Claims
1. In a pump used to transfer a liquefied gas from a first container to a second container,
- wherein said first container contains a liquefied gas in equilibrium with its vapor at a first pressure level,
- and wherein said pump has a piston means,
- the improvement wherein said piston means is moved by application of a manual force by an operator of said pump.
2. The pump of claim 1 wherein said pump is directly attached to said first container.
3. The pump of claim 2 wherein said pump is directly attached to said first container using an inlet fitting of said pump.
4. The pump of claim 1 wherein said second container contains a liquefied gas in equilibrium with its vapor,
- and wherein said second container has an initial second pressure and a higher desired second pressure,
- and wherein said pump is operated to increase the pressure of said second container.
5. The pump of claim 1 wherein said piston means is contained in a bore of said pump,
- and wherein said piston means has a portion which passes through a sealing member,
- and wherein said portion has a radial clearance to said bore,
- and wherein said sealing means when relaxed has a radial thickness,
- the improvement wherein said radial thickness is smaller than said radial clearance.
6. The pump of claim 5 wherein said piston has a movement in a first direction and a movement in a second direction,
- and wherein said sealing member prevents movement of said liquefied gas past said piston means when said movement in said first direction,
- and wherein said sealing member allows movement of said liquefied gas past said piston means when said movement is in said second direction.
7. The pump of claim 1 wherein said liquefied gas is nitrous oxide.
8. The pump of claim 1 wherein said liquefied gas is carbon dioxide.
9. The pump of claim 1 wherein internal pressurization of said pump by said liquefied gas moves said piston means.
10. The pump of claim 9 wherein said piston moves in a first direction by said internal pressurization of said pump and in a second direction by said application of said manual force.
11. The pump of claim 9 wherein said pump has a pumping cycle consisting of a maximum displacement of said piston in a first direction and a subsequent maximum displacement of said piston in a second direction and wherein said maximum displacement of said piston in said first direction occurs due to said internal pressurization only.
12. The pump of claim 1 wherein said pump has a pumping cycle consisting of a maximum displacement of said piston in a first direction and a subsequent maximum displacement of said piston in a second direction, and wherein said pump has an actual mass transfer per cycle,
- and wherein knowledge of said actual mass transfer per cycle of said pump is used to estimate a mass which has been transferred with said pump.
Type: Application
Filed: Aug 24, 2006
Publication Date: Feb 28, 2008
Inventor: Barry Lyn Holtzman (Eagle River, WI)
Application Number: 11/509,887
International Classification: B65B 31/04 (20060101);
