1. A pressure vessel for holding CO2, comprising:
a magnetic float assembly disposed within the pressure vessel and adapted to float on liquid-phase CO2 contained within the pressure vessel, over a range of operating vessel temperatures; and
a magnetically sensitive indicator located on an outer surface of the pressure vessel and adapted to detect and to display the location of the magnetic float assembly, thereby to indicate the level of the liquid phase CO2 within the pressure vessel.
2. The pressure vessel of claim 1, wherein the magnetic float assembly comprises:
an elongate member having first and second ends; and
first and second permanent magnets mounted at the first and second ends, respectively, the first and second magnets aligned so that their respective poles are oriented in opposing relation.
3. The pressure vessel of claim 1, wherein the magnetically sensitive indicator comprises:
a coating applied to a label attached to the pressure vessel, the coating including a plurality of magnetically sensitive particles suspended in a cured colloidal dispersion.
4. The pressure vessel of claim 3, wherein the label is attached to the pressure vessel by adhesive.
5. The pressure vessel of claim 1, wherein the range of operating temperatures comprises any temperature up to about 85 degrees Fahrenheit.
6. The pressure vessel of claim 1, wherein the elongate member comprises a composite foam material.
7. The pressure vessel of claim 6, wherein the composite foam material comprises a syntactic foam having a rectangular transverse cross-sectional shape, the syntactic foam including a plurality of hollow glass microspheres embedded in resin.
8. The pressure vessel of claim 1, wherein the elongate member comprises a tube.
9. The pressure vessel of claim 1, wherein the pressure vessel includes a cylindrical body having an inner body diameter, and the magnetic float assembly has a length shorter than the inner body diameter so that the magnetic float assembly can rotate freely within the cylindrical body.
10. A paintball marker comprising:
a body including a handle, a firing chamber, a barrel operatively coupled to the firing chamber, and a hopper operatively coupled to the body and adapted to deliver at least one paintball round to the firing chamber;
a pressure vessel attachable to the body and adapted to supply pressurized CO2 to the firing chamber to expel the at least one paintball round through the barrel; and
a CO2 level indicator comprising:
(a) a magnetic float assembly disposed within the pressure vessel and adapted to float on liquid-phase CO2 contained within the pressure vessel, over a range of operating vessel temperatures; and
(b) a magnetically sensitive indicator located on an outer surface of the pressure vessel and adapted to detect and display the location of the magnetic float assembly, thereby to indicate the level of liquid phase CO2 within the pressure vessel.
11. The paintball marker of claim 10, wherein the magnetically sensitive indicator is adapted to provide an accurate indication of the level of liquid phase CO2 in the pressure vessel when the pressure vessel is in a generally vertical orientation.
12. The pressure vessel of claim 10, wherein the magnetic float assembly comprises:
an elongate member having first and second ends; and
first and second permanent magnets mounted at the first and second ends, respectively, the first and second magnets aligned so that their respective poles are oriented in opposing relation.
13. The pressure vessel of claim 10, wherein the magnetically sensitive indicator comprises:
a coating applied to a label attached to the pressure vessel, the coating including a plurality of magnetically sensitive particles suspended in a cured colloidal dispersion.
14. The pressure vessel of claim 13, wherein the label is attached to the pressure vessel by adhesive.
15. The pressure vessel of claim 10, wherein the range of operating temperatures comprises any temperature that is up to about 85 degrees Fahrenheit and suitable for operation of the paintball marker.
16. The pressure vessel of claim 10, wherein the elongate member comprises a composite foam material.
17. The pressure vessel of claim 16, wherein the composite foam material comprises a syntactic foam having a rectangular transverse cross-sectional shape, the syntactic foam including a plurality of hollow glass microspheres embedded in resin.
18. The pressure vessel of claim 10, wherein the elongate member comprises a tube.
19. The pressure vessel of claim 10, wherein the pressure vessel includes a cylindrical body having an inner body diameter, and the magnetic float assembly has a length shorter than the inner body diameter so that the magnetic float assembly can rotate freely within the cylindrical body.
20. A method of determining the approximate number of remaining paintball rounds that can be shot by a paintball marker, the method comprising:
orienting a pressure vessel to a substantially vertical orientation, the pressure vessel containing therein liquid phase CO2, the pressure vessel also having a magnetic float assembly adapted to float on the liquid phase CO2 contained therein, the pressure vessel also having a magnetically sensitive indicator located on an outer surface thereof and
rotating the pressure vessel to rotatably move the magnetic float assembly contained therein, so as to orient the magnetic float assembly into alignment with the magnetically sensitive indicator, thereby causing the vertical position of the magnetic float assembly to be magnetically indicated on the magnetically sensitive indicator.
21. The method of claim 20, further comprising:
correlating the magnetically indicated position of the magnetic float assembly with an estimated number of remaining paintball rounds.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A method for preparing a compound of formula (II) or a salt thereof:
the method comprising:
(a) reacting aniline with a compound of formula (IV)
and
(b) adding a complex of formula D\u2192A to produce the compound of formula (II), wherein D is a group of atoms having an electron donor atom, and A has formula (III):
wherein R1, R2, and R3 are independently selected from hydrogen, substituted or unsubstituted C1-C10 alkyl, substituted or unsubstituted C1-C10 alkoxy, aryloxy, and wherein at least one of R1, R2, and R3 is hydrogen.
2. The method of claim 1 wherein:
D is heterocyclic.
3. The method of claim 2 wherein:
the electron donor atom is selected from nitrogen, oxygen, or sulfur.
4. The method of claim 2 wherein:
the electron donor atom is nitrogen.
5. The method of claim 1 wherein R1, R2, and R3 are hydrogen.
6. The method of claim 1 wherein:
D is selected from substituted or unsubstituted pyridine, substituted or unsubstituted aniline, or substituted or unsubstituted amine.
7. The method of claim 1 wherein:
D is 5-ethyl-2-methylpyridine, and
R1, R2, and R3 are hydrogen.
8. The method of claim 1 further comprising:
adding a C1-C4 alcoholic solvent in step (b).
9. The method of claim 1 further comprising:
adding an organic acid in step (b).
10. The method of claim 8 wherein:
the organic acid is an alkanoic acid of C1-C8.
11. The method of claim 8 wherein:
the organic acid is acetic acid.
12. The method of claim 1 further comprising:
(c) adding a mineral acid at completion of reaction thereby crystallizing out a salt of the compound of formula (II).
13. The method of claim 12 wherein:
the mineral acid is a hydrohalic acid.
14. The method of claim 12 wherein:
the mineral acid is hydrochloric acid.
15. A method for preparing a compound of formula (I):
the method comprising:
(a) reacting aniline with a compound of formula (IV)
and
(b) adding a complex of formula D\u2192A, wherein D is a group of atoms having an electron donor atom, and A has formula (III):
wherein R1, R2, and R3 are independently selected from hydrogen, substituted or unsubstituted C1-C10 alkyl, substituted or unsubstituted C1-C10 alkoxy, aryloxy, and wherein at least one of R1, R2, and R3 is hydrogen; and
(c) adding a propionyl halide or propionic anhydride to produce the compound of formula (I).
16. The method of claim 15 wherein:
step (b) further comprises adding a mineral acid thereby crystallizing out a salt of a compound of formula (II):
17. The method of claim 16 wherein the mineral acid is a hydrohalic acid.
18. The method of claim 15 wherein:
the propionyl halide is propionyl chloride.
19. The method of claim 15 wherein:
D is heterocyclic, and the electron donor atom is nitrogen.
20. The method of claim 15 wherein:
D is selected from substituted or unsubstituted pyridine, substituted or unsubstituted aniline, substituted or unsubstituted amine.
21. The method of claim 15 wherein:
D is 5-ethyl-2-methylpyridine, and
R1, R2, and R3 are hydrogen.