Mixing hypodermic syringe

• US 6,817,987 B2
• Filed: 08/16/2002
• Issued: 11/16/2004
• Est. Priority Date: 08/18/2001
• Status: Expired due to Term

• Current Assignee: Arzneimittel GmbH Apotheker Vetter & Co. Ravensburg
• Original Assignee: Arzneimittel GmbH Apotheker Vetter & Co. Ravensburg
• Inventors: Otto, Thomas, Vetter, Udo J.
• Primary Examiner(s): Casler, Brian L.
• Assistant Examiner(s): Thompson, Michael M.
• Application Number:
  US10/222,677
• Publication Number:
  US 20030036724A1
• Time in Patent Office: 823 Days
• Field of Search: 604/19, 604/27, 604/28, 604/500, 604/506, 604/507, 604/82, 604/85, 604/89-92, 604/145, 604/181, 604/182, 604/187, 604/191-192, 604/207-208, 604/210-211, 604/218, 604/220-224
• US Class Current: 604/85
• CPC Class Codes: A61M 2005/31508 provided on the piston-rod
• CPC Class Codes: A61M 5/284 comprising means for injection of two or more media, e.g. by mixing

Abstract

A syringe holding a solvent and a soluble component has a tubular body formed its front and rear ends with a bypass, a plunger axially slidable in the body, and a stem projecting axially rearward out of the body from the plunger. A cover fits over the front end of the body and is so tight that the front compartment can be pressurized to a superatmospheric pressure without leakage out the front end. A free piston slidable in the body forward of the plunger subdivides the body forward of the plunger into a front compartment at the front body end holding the soluble component and a rear compartment between the plunger and the piston and holding the solvent. Stops are provided for arresting the free piston when it is level with the bypass in a position permitting flow through the bypass between the compartments.

Claims

1. A syringe comprising:

a tubular body extending along an axis and having a front end and a rear end and formed therebetween with a bypass;

a plunger axially slidable in the body;

a stem projecting axially rearward out of the body from the plunger

a cover over the front end of the body and sufficiently tight to allow superatmospheric pressurization of the front compartment;

a free piston slidable in the body forward of the plunger and subdividing the body forward of the plunger into a front compartment at the front body end holding the soluble medicament and a rear compartment between the plunger and the piston and holding the solvent, whereby when the plunger and stem are pressed axially forward from a rearmost end position into an intermediate position to pressurize the rear compartment and force the piston forward until the piston is at the bypass and the solvent can flow through the bypass into the front compartment to mix with the soluble medicament with build up of gas pressure in the front compartment; and

stop means for arresting the piston when it is at the bypass for permitting fluid flow in two directions through the bypass past the piston while still permitting free axial movement of the plunger, whereby gas pressure in the front compartment can force the plunger rearward and pump the solvent and any of the medicament mixed therewith back past the arrested piston and through the bypass into the rear compartment.

2. The syringe defined in claim 1 wherein the stop means is interengageable radially extending formations on the body and piston.

3. The syringe defined in claim 2 wherein the formations include a radially inwardly projecting bump on the body and a complementary radially outwardly open recess on the piston.

4. The syringe defined in claim 1, further comprising

means including stops on the stem and body for inhibiting forward movement of the plunger past the intermediate position.

5. The syringe defined in claim 4 wherein the stops include screwthread formations on the stem and body, whereby the stem has to be rotated about the axis for movement forward past the intermediate position.

6. The syringe defined in claim 5 wherein the screwthread on the stem is of limited axial extent.

7. The syringe defined in claim 4 wherein the stops include screwthread formations on the stem and body, whereby the stem has to be rotated about the axis for movement forward past the rear end position.

8. The syringe defined in claim 7 wherein the screwthread on the stem is of limited axial extent.

9. The syringe defined in claim 4 wherein the stops include at least one radially projecting bump on the stem and at least one radially inwardly open notch through which the bump can pass axially on the body, whereby the stem has to be rotated about the axis and angularly position for movement forward past the intermediate position.

10. The syringe defined in claim 4 wherein the stops include at least one radially projecting bump on the stem and at least one radially inwardly open notch through which the bump can pass axially on the body, whereby the stem has to be rotated about the axis and angularly position for movement forward past the rear end position.

11. A method of operating a syringe having:

a tubular body extending along an axis and having a front end and a rear end and formed therebetween with a bypass,

a plunger axially slidable in the body;

a stem projecting axially rearward out of the body from the plunger

a cover over the front end of the body; and

a free piston slidable in the body forward of the plunger and subdividing the body forward of the plunger into a front compartment at the front body end and a rear compartment between the plunger and the piston the method comprising the steps, after having provided the front compartment with a charge of compressible gas and a dose of a dry soluble medicament and the rear compartment with a liquid solvent for the medicament and starting with the plunger and stem in a rearmost end position and the piston at least partially axially rearward of the bypass and separating the solvent from the soluble medicament, of;

a) pressing the plunger and stem axially forward from the rearmost end position into an intermediate position with the plunger rearward of the bypass and thereby pressurizing the rear compartment and forcing the piston forward until the piston is at the bypass and the solvent can flow through the bypass and into the front compartment to mix with the soluble medicament while maintaining the front end closed such that gas pressure builds up in the front compartment;

b) when the piston is at the bypass, arresting the piston at the bypass and permitting fluid flow in two directions through the bypass past the piston; and

c) releasing the plunger and stem such that gas pressure built up in the front compartment forces the plunger rearward and pumps the solvent and any of the medicament mixed there-with back past the arrested piston and through the bypass into the rear compartment.

12. The syringe-operating method defined in claim 11, further comprising:

stopping forward movement of the plunger and stem in the intermediate position by engagement between formations on the plunger and body.

13. The syringe-operating method defined in claim 11, further comprising the step of

d) repeating steps a) and c) while continuing to arrest the piston at the bypass to pump the solvent back and forth between the compartments and thereby thoroughly mix the solvent and medicament.

14. The syringe-operating method defined in claim 11, further comprising the steps after step c) of sequentially:

e) uncovering the front body end;

f) pushing the plunger and stem forward from the intermediate position and thereby pressing generally all of the solvent/medicament mixture in the rear compartment into the front compartment until the plunger rearwardly engages the piston; and

g) pushing the plunger, stem, and piston forward to express the solvent/medicament mixture out the front end of the syringe body.