Expanding plunger rods for syringes

1. An expanding plunger rod for a syringe, the expanding plunger rod configured to transition from a packaged configuration for packaging to an expanded configuration for operation, the expanding plunger rod comprising:

a substantially cylindrical outer sleeve having a closed-off bottom end and an open upper end;

an inner sleeve having a lower end and an upper end, the inner sleeve being slidably disposed coaxially within the outer sleeve;

an inner rod having a lower end and an upper end, the inner rod being slidably disposed coaxially within the inner sleeve and including a top piece extending axially above the open upper end of the outer sleeve; and

a biasing member disposed axially within a cavity defined by the inner rod between the top piece of the inner rod and the closed-off bottom end of the outer sleeve, the biasing member biasing the top piece and the closed-off bottom end axially away from one another;

wherein, in the packaged configuration, the inner rod is nested within the outer sleeve, and in the expanded configuration, the inner rod is disposed substantially axially above the outer sleeve, and the inner rod is configured to lock axially in place so as to prevent transition from the expanded configuration to the packaged configuration;

wherein, in the expanded configuration, the upper end of the inner sleeve and the lower end of the inner rod are both disposed axially above the open upper end of the outer sleeve; and

wherein the biasing member is configured to automatically transition the expanding plunger rod from the packaged configuration to the expanded configuration.

2. The expanding plunger rod of claim 1 , wherein the closed-off bottom end of the outer sleeve is configured to connect to a plunger seal, the outer sleeve and the plunger seal being slidable within a fluid compartment of the syringe.

3. The expanding plunger rod of claim 1 , wherein the biasing member is configured to automatically transition the expanding plunger rod from the packaged configuration to the expanded configuration upon being triggered.

4. The expanding plunger rod of claim 1 , wherein the outer sleeve includes a first locking mechanism, the inner sleeve includes a second locking mechanism and a third locking mechanism, and the inner rod includes a fourth locking mechanism, and wherein, in the expanded configuration, the first locking mechanism is engaged with the second locking mechanism and the third locking mechanism is engaged with the fourth locking mechanism so as to prevent transition from the expanded configuration to the packaged configuration.

5. The expanding plunger rod of claim 4 , wherein the first locking mechanism is an outer lock orifice formed into a side of the outer sleeve and the second locking mechanism is an inner sleeve lock disposed on a side of the inner sleeve, wherein, in the expanded configuration, the inner sleeve lock extends radially outward into the outer lock orifice.

6. The expanding plunger rod of claim 4 , wherein the third locking mechanism is an inner lock orifice formed into a side of the inner sleeve, and the fourth locking mechanism is an inner rod lock disposed on a side of the inner rod, wherein, in the expanded configuration the inner rod lock extends radially outward into the inner lock orifice.

7. The expanding plunger rod of claim 1 , wherein the biasing member comprises at least two biasing members.

8. A syringe assembly, comprising:

a substantially cylindrical barrel having a plunger end and a connection end;

a plunger seal disposed within the plunger end of the barrel;

a needle seal disposed within the connection end of the barrel;

a fluid compartment defined within the barrel between the plunger seal and the needle seal; and

an expanding plunger rod comprising:

a substantially cylindrical outer sleeve having a closed-off bottom end and an open upper end;

an inner sleeve having a lower end and an upper end, the inner sleeve being slidably disposed coaxially within the outer sleeve;

an inner rod having a lower end and an upper end, the inner rod being slidably disposed coaxially within the inner sleeve and including a top piece extending axially above the open upper end of the outer sleeve; and

a biasing member disposed axially within a cavity defined by the inner rod between the top piece of the inner rod and the closed-off bottom end of the outer sleeve, the biasing member biasing the top piece and the closed-off bottom end axially away from one another;

wherein, in the packaged configuration, the inner rod is nested within the outer sleeve, and in the expanded configuration, the inner rod is disposed substantially axially above the outer sleeve, and the inner rod is configured to lock axially in place so as to prevent transition from the expanded configuration to the packaged configuration;

wherein, in the expanded configuration, the upper end of the inner sleeve and the lower end of the inner rod are both disposed axially above the open upper end of the outer sleeve; and

wherein the biasing member is configured to automatically transition the expanding plunger rod from the packaged configuration to the expanded configuration.

9. The syringe assembly of claim 8 , wherein the closed-off bottom end of the outer sleeve is configured to connect to the plunger seal, the outer sleeve and the plunger seal being slidable within the fluid compartment of the syringe assembly.

10. The syringe assembly of claim 8 , wherein the biasing member is configured to automatically transition the expanding plunger rod from the packaged configuration to the expanded configuration upon being triggered.

11. The syringe assembly of claim 8 , wherein the outer sleeve includes a first locking mechanism, the inner sleeve includes a second locking mechanism and a third locking mechanism, and the inner rod includes a fourth locking mechanism, and wherein, in the expanded configuration, the first locking mechanism is engaged with the second locking mechanism and the third locking mechanism is engaged with the fourth locking mechanism so as to prevent transition from the expanded configuration to the packaged configuration.

12. The syringe assembly of claim 11 , wherein the first locking mechanism is an outer lock orifice formed into a side of the outer sleeve and the second locking mechanism is an inner sleeve lock disposed on a side of the inner sleeve, wherein, in the expanded configuration, the inner sleeve lock extends radially outward into the outer lock orifice.

13. The syringe assembly of claim 11 , wherein the third locking mechanism is an inner lock orifice formed into a side of the inner sleeve, and the fourth locking mechanism is an inner rod lock disposed on a side of the inner rod, wherein, in the expanded configuration the inner rod lock extends radially outward into the inner lock orifice.

14. The syringe assembly of claim 8 , wherein the biasing member comprises at least two biasing members.

15. The syringe assembly of claim 8 , wherein the outer sleeve and the plunger seal are slidable within the fluid compartment of the syringe assembly to expel fluid out of the fluid compartment.

16. The syringe assembly of claim 8 , wherein the outer sleeve further comprises a stop mechanism configured to engage with the barrel so as to prevent the expanding plunger rod from being removed from the barrel.

17. The syringe assembly of claim 16 , wherein the barrel further comprises a collar disposed at the plunger end of the barrel, the stop mechanism of the outer sleeve being configured to engage with the collar to so as to prevent the expanding plunger rod from being removed from the barrel.