Liquid dispensing syringe and method for reducing piston bounce

1. A dispensing syringe for use with a pressurized gas, comprising:

a barrel having a first end and a second end, and defining an interior reservoir having an inner surface;

a piston slidably disposed within the interior reservoir, the piston having a distal end, a proximal end, a generally rigid portion, and an elastic portion, the proximal end configured to receive the pressurized gas and move the piston toward the first end in order to decrease a volume of the interior reservoir proximate to the first end of the barrel and discharge a liquid contained therein, the elastic portion configured to expand under the influence of the pressurized gas;

a first circumferentially extending wiper seal positioned on the generally rigid portion of the piston between the distal and proximal ends, the first wiper seal engaging the inner surface such that the first wiper seal liquidly seals against the inner surface and inhibits the liquid within the interior reservoir from flowing proximally beyond the first wiper seal; and

a second circumferentially extending wiper seal positioned on the elastic portion of the piston proximally from the first wiper seal, the elastic portion being more flexible than the generally rigid portion such that the elastic portion forces the second wiper seal to contact the inner surface with an increased pressure and an increased surface area to fluidly seal against the inner surface for inhibiting pressurized gas from flowing distally beyond the second wiper seal in order to reduce piston bounce.

2. The dispensing syringe of claim 1 wherein the interior reservoir has an inner diameter and the first and second wiper seals have a first diameter and a second diameter in a relaxed state, respectively, the first diameter and the second diameter are larger than the inner diameter, and the second diameter of the second wiper seal is at least the same size as the first diameter of the first wiper seal.

3. The dispensing syringe of claim 1 wherein the elastic portion further comprises a wall, and the wall is generally thinner than the generally rigid portion such that the wall is more elastic than the generally rigid portion.

4. The dispensing syringe of claim 3 wherein the elastic and generally rigid portions of the piston are formed from a same material.

5. The dispensing syringe of claim 3 wherein the wall tapers toward the proximal end of the piston.

6. The dispensing syringe of claim 1 wherein the elastic portion is formed from an elastic material and the generally rigid portion is formed from a different, generally rigid material.

7. The dispensing syringe of claim 1 further comprising:

said first wiper seal having a radially outwardly flared skirt with a first lip defining an open end facing toward the first end of the piston; and

said second wiper seal having a radially outwardly flared skirt with a second lip defining an open end facing toward the second end of the piston.

8. A piston for use with a dispensing syringe and a pressurized gas, the dispensing syringe having a barrel with a first end and a second end, and defining an interior reservoir having an inner surface, the piston comprising:

a body configured to be slidably positioned within the interior reservoir of the barrel, the body having a distal end, a proximal end, a generally rigid portion, and an elastic portion, the proximal end configured to receive the pressurized gas such that the body moves toward the first end in order to decrease a volume of the interior reservoir proximate to the first end of the barrel and discharge a liquid contained therein, the elastic portion configured to expand under the influence of the pressurized gas;

a first circumferentially extending wiper seal positioned on the generally rigid portion of the body between the distal and proximal ends, the first wiper seal configured to liquidly seal against the inner surface and inhibit the liquid within the interior reservoir from flowing proximally beyond the first wiper seal; and

a second circumferentially extending wiper seal positioned on the elastic portion of the body proximally from the first wiper seal, the elastic portion being more flexible than the generally rigid portion and configured to force the second wiper seal to contact the inner surface with an increased pressure and an increased surface area to fluidly seal against the inner surface for inhibiting pressurized gas from flowing distally beyond the second wiper seal in order to reduce piston bounce.

9. The piston of claim 8 wherein the interior reservoir has an inner diameter and the first and second wiper seals have a first diameter and a second diameter in a relaxed state, respectively, the first and second diameters are configured for an interference fit with the inner diameter, and the second diameter of the second wiper seal is at least the same size as the first diameter of the first wiper seal.

10. The piston of claim 8 wherein the elastic portion further comprises a wall, and the wall is generally thinner than the generally rigid portion such that the wall is more elastic than the generally rigid portion.

11. The piston of claim 10 wherein the elastic and generally rigid portions of the body are formed from a same material.

12. The piston of claim 10 wherein the wall tapers toward the proximal end of the body.

13. The piston of claim 8 wherein the elastic portion is formed from an elastic material and the generally rigid portion is formed from a different, generally rigid material.

14. The piston of claim 8 further comprising:

said first wiper seal having a radially outwardly flared skirt with a first lip defining an open end facing toward the first end of the body; and

said second wiper seal having a radially outwardly flared skirt with a second lip defining an open end facing toward the second end of the body.