A retractable needle safety syringe manufacturers is provided having mitigated retraction. The syringe comprises a syringe body, a syringe cavity, a plunger, a variable vacuum compartment, a shaft brake, and a ram member. The plunger assembly includes a plunger shaft and a piston slidably engaged within the syringe body. The variable vacuum compartment is disposed within the syringe cavity and provides a vacuum force on the plunger shaft directed from a bottom syringe body end toward a top syringe body end. The shaft brake, being attached to the top syringe body end, may frictionally engage the plunger shaft to provide first and second frictional forces in opposition to the vacuum force, the first frictional force being exerted prior to the piston reaching the bottom syringe body end, the second frictional force being exerted in response to the engagement of the ram member with the shaft brake.
1. A retractable needle safety syringe with mitigated retraction, the syringe comprising: a syringe body defining opposing top and bottom syringe body ends and including a syringe cavity; an attachment seal defining a shaft orifice and being attached to the top syringe body end; a plunger assembly including a plunger shaft and a piston, the plunger shaft defining opposing top and bottom shaft ends, the plunger shaft being disposed through the shaft orifice in the syringe cavity, the piston being disposed at the bottom shaft end, the plunger being slidably engaged with the syringe body within the syringe cavity; a variable vacuum compartment being disposed within the syringe cavity between the piston and the attachment seal, the variable vacuum compartment being operative to provide a vacuum force on the plunger shaft directed from the bottom syringe body end toward the top syringe body end with the vacuum force increasing upon movement of the piston toward the bottom syringe body end; a shaft brake being attached to the top syringe body end and being operative to frictionally engage the plunger shaft to provide first and second frictional forces in opposition to the vacuum force, the first frictional force being exerted upon the plunger shaft prior to the piston reaching the bottom syringe body end; and a ram member being attached to the top shaft end and being formed to engage the shaft brake upon the piston reaching the bottom syringe body end, the shaft brake exerting the second frictional force upon the plunger shaft in response to the engagement of the ram member with the shaft brake, the second frictional force being less than the first frictional force.

2. The syringe of claim 1 wherein the first frictional force has an associated first normal force.

3. The syringe of claim 1 wherein the second frictional force has an associated second normal force.

4. Thesyringe manufacturersof claim 1 wherein the shaft brake substantially disengages from the plunger shaft upon engagement of the ram member with the shaft brake.

5. The syringe of claim 1 wherein the shaft brake defines a body perimeter and includes an aperture and a bridge, the aperture being disposed within the shaft brake and frictionally engaging the plunger shaft, the bridge defining a bridge width and extending radially from the aperture toward the body perimeter, the shaft brake being operative to exert the second frictional force upon the plunger shaft in response to an increase in bridge width, the bridge width increasing in response to the engagement of the ram member with the shaft brake.

6. The syringe of claim 5 wherein the ram member at least partially severs the bridge to increase the bridge width.

7. The syringe of claim 5 wherein the shaft brake further includes a release member being disposed upon the shaft brake, the bridge width increasing in response to the engagement of the ram member with the release member.

8. The syringe of claim 7 wherein the release member is a shoulder protruding upwardly from the shaft brake opposite the syringe body, and the ram member includes a shoulder press being sized and configured to engage the shoulder upon the piston approaching the bottom syringe body end, the bridge width increasing in response to the engagement of the shoulder press with the shoulder.

9. The syringe of claim 8 wherein the bridge width increases upon deformation of the bridge in response to engagement of the shoulder press with the shoulder and continued movement of the piston toward the bottom syringe body end.

10. The syringe manufacturers of claim 8 wherein the brake body defines a body thickness and the bridge defines a bridge thickness, the bridge thickness being less than the body thickness, the bridge being operative to deform in response to the engagement of the shoulder press with the shoulder.

11. The syringe of claim 7 wherein the bridge comprises a non-continuous slit including a hinge element, and the bridge width increases upon deformation of the hinge element in response to engagement of the shoulder press with the shoulder and continued movement of the piston toward the bottom syringe body end.

12. The syringe of claim 1 wherein the shaft brake is formed to include an anchor member being disposed upon the shaft brake, the anchor member being operative to mechanically couple the shaft brake to the attachment seal.

13. The syringe of claim 1 further including a needle being removably mounted to the bottom syringe body end and extending therefrom opposite the top syringe body end, the piston including a punch to engage the needle upon the piston reaching the bottom syringe body end, the piston being operative to remove the needle into the syringe cavity upon exertion of the vacuum force upon the plunger shaft.

14. A method of mitigating retraction of a retractable needle safetysyringe manufacturers, the syringe comprising a syringe body, an attachment seal, a plunger assembly, a variable vacuum compartment, a shaft brake, and a ram member, the syringe body defining opposing top and bottom syringe body ends and including a syringe cavity, the attachment seal defining a shaft orifice and being attached to the top syringe body end, the plunger assembly including a plunger shaft and a piston, the plunger shaft defining opposing top and bottom shaft ends, the plunger shaft being disposed through the shaft orifice in the syringe cavity, the piston being disposed at the bottom shaft end, the plunger being slidably engaged with the syringe body within the syringe cavity, the variable vacuum compartment being disposed within the syringe cavity between the piston and the attachment seal, the variable vacuum compartment being operative to provide a vacuum force on the plunger shaft directed from the bottom syringe body end toward the top syringe body end with the vacuum force increasing upon movement of the piston toward the bottom syringe body end, the shaft brake being attached to the top syringe body end and being operative to frictionally engage the plunger shaft to provide first and second frictional forces in opposition to the vacuum force, the first frictional force being exerted upon the plunger shaft prior to the piston reaching the bottom syringe body end, the ram member being attached to the top shaft end and being formed to engage the shaft brake upon the piston reaching the bottom syringe body end, the shaft brake exerting the second frictional force upon the plunger shaft in response to the engagement of the ram member with the shaft brake, the second frictional force being less than the first frictional force, the method comprising: a. exerting the first frictional force upon the plunger shaft in opposition to the vacuum force prior to the piston reaching the bottom syringe body end; b. engaging the ram member with the shaft brake; and c. exerting the second frictional force upon the plunger shaft in opposition to the vacuum force in response to the engagement of the ram member with the shaft brake.

15. The method of claim 14 wherein the shaft brake defines a body perimeter and includes an aperture and a bridge, the aperture being disposed within the shaft brake and being operative to frictionally engage the plunger shaft, the bridge defining a bridge width and extending radially from the aperture toward the body perimeter, the shaft brake being operative to exert the second frictional force upon the plunger shaft in response to an increase in bridge width, the bridge width increasing in response to the engagement of the ram member with the shaft brake, and step (b) of the method further includes: a. increasing the bridge width in response to the engagement of the ram member with the shaft brake.

16. The method of claim 14 wherein step (b) further includes: a. severing the bridge in response to the engagement of the ram member with the shaft brake.

17. The method of claim 14 wherein the shaft brake further includes a shoulder being disposed upon the shaft brake and protruding upwardly from the shaft brake opposite the syringe body, and the ram member includes a shoulder press being sized and configured to engage the shoulder upon the piston approaching the bottom syringe body end, the bridge width increasing in response to the engagement of the shoulder press with the shoulder, and step (b) of the method further includes: a. engaging the shoulder press with the shoulder; and b. deforming the bridge to increase the bridge width.

18. The method of claim 14 wherein the syringe manufacturers further includes a needle being removably mounted to the bottom syringe body end and extending therefrom opposite the top syringe body end, the piston including a punch to engage the needle upon the piston reaching the bottom syringe body end, the piston being operative to remove the needle into the syringe cavity upon exertion of the vacuum force upon the plunger shaft, the method further including the steps of: a. engaging the needle with the punch; and b. automatically removing the needle into the syringe cavity.