Accurate dose control mechanisms and drug delivery syringes
A dose control mechanism for a syringe includes an engaging screw thread arrangement between an exterior surface of a plunger and a longitudinally extending channel of a housing. The engaging screw thread arrangement includes at least one thread segment and a pitch guide including a variable pitch thread. At least a portion of the longitudinally extending channel of the housing including one of the pitch guide and the at least one thread segment, and the plunger includes the other of the pitch guide and the at least one thread segment. The plunger resides at least partially within the housing with the at least one thread segment engaged with the pitch guide. An accurate dose drug delivery syringe includes such a dose control mechanism, a barrel, a plunger seal, and a barrel adapter assembly having a barrel tip and a needle. The syringe may be a fill-at-time-of-use syringe, a pre-filled syringe, or a safety syringe having integrated needle retraction or needle sheathing safety features, or a combination thereof. Methods of assembly, manufacturing, and operation are similarly disclosed.
1. A dose control mechanism for a syringe comprising:
a housing having a longitudinally extending channel having an interior surface;
an adapter including a channel having a fine pitch thread,
a plunger having an exterior surface and an axially extending channel, the axially extending channel including a first key aspect;
a screw having a screw exterior surface, a proximal end of the screw disposed at least partially within the axially extending channel of the plunger, the screw exterior surface including a second key aspect along a proximal portion of the screw exterior surface, at least a portion of the second key aspect disposed within the axially extending channel of the plunger and engaging the first key aspect for sliding movement such that rotational movement of the plunger causes rotational movement of the screw, a distal portion of the screw exterior surface including a fine pitch thread at least partially disposed within and interfacing with the fine pitch thread of the adapter; and
an engaging screw thread arrangement including at least one thread segment and a variable pitch thread, at least a portion of the longitudinally extending channel of the housing including one of the variable pitch thread and the at least one thread segment, the plunger including the other of the variable pitch thread and the at least one thread segment, the plunger residing at least partially within the housing with the at least one thread segment engaged with the variable pitch thread.
2. The dose control mechanism of claim 1 , wherein the variable pitch thread includes a thread of at least two different pitches.
3. The dose control mechanism of claim 1 , wherein the variable pitch thread includes at least one length of thread of a constant pitch.
4. The dose control mechanism of claim 1 , wherein the housing includes the variable pitch thread and the variable pitch thread includes a distally-disposed coarse pitch thread and a proximally-disposed fine pitch thread.
5. The dose control mechanism of claim 4 , wherein a pitch of the fine pitch thread of the variable pitch thread is substantially equal to a pitch of the fine pitch thread of the adapter.
6. The dose control mechanism of claim 5 , wherein the housing includes at least a first housing section and a second housing section.
7. The dose control mechanism of claim 6 , wherein the first housing section is an upper housing and the second housing section is a lower housing, the upper and lower housings being coupled together.
8. The dose control mechanism of claim 6 , wherein the first housing section includes one of the coarse pitch thread and the fine pitch thread of the variable pitch thread and the second housing section includes the other of the coarse pitch thread and the fine pitch thread of the variable pitch thread.
9. The dose control mechanism of claim 1 , whereby the engaging screw thread arrangement causes rotation of the plunger within the housing when the plunger is translated relative to at least a portion of the housing, rotation of the plunger within the housing provides rotation of the screw within the adapter channel, and rotation of the screw within the adapter channel and engagement of the first and second key aspects provides a relative axial sliding between the screw and the plunger and movement of the screw in a distal direction relative to the adapter when the plunger is depressed and in a proximal direction when the plunger is moved proximally relative to at least a portion of the housing.
10. The dose control mechanism of claim 1 , wherein at least a portion of the variable pitch thread is of a coarser pitch than the fine pitch thread of the adapter.
11. The dose control mechanism of claim 1 , further comprising one or more volume based detents.
12. The dose control mechanism of claim 11 , wherein the one or more volume based detents comprise a protrusion configured to engage a recess of the plunger.
13. The dose control mechanism of claim 1 , wherein the adapter is adapted to be coupled to a barrel of a syringe, and a distal end of the plunger is adapted to be coupled to a plunger rod disposed within the barrel.
14. A dose control mechanism for a syringe comprising:
a housing having a longitudinally extending channel having an interior surface, the housing including at least a first housing section and a second housing section disposed for telescoping movement relative to one another between a retracted position and an extended position;
an adapter including a channel having a fine pitch thread,
a plunger having an exterior surface and an axially extending channel, the axially extending channel including a first key aspect;
a screw having a screw exterior surface, a proximal end of the screw disposed at least partially within the axially extending channel of the plunger, the screw exterior surface including a second key aspect along a proximal portion of the screw exterior surface, at least a portion of the second key aspect disposed within the axially extending channel of the plunger and engaging the first key aspect for sliding movement such that rotational movement of the plunger causes rotational movement of the screw, a distal portion of the screw exterior surface including a fine pitch thread at least partially disposed within and interfacing with the fine pitch thread of the adapter; and
an engaging screw thread arrangement including at least one thread segment and a a thread, at least a portion of the longitudinally extending channel of the housing including one of the thread and the at least one thread segment, the plunger including the other of the thread and the at least one thread segment, the plunger residing at least partially within the housing with the at least one thread segment engaged with the thread.
15. The dose control mechanism of claim 14 , wherein the first housing section and the second housing section are disposed for movement between the extended position and a primed position.
16. The dose control mechanism of claim 14 , wherein the plunger and the first housing section are coupled to prevent rotational movement relative to one another during telescoping movement from the extended position.
17. The dose control mechanism of claim 14 , wherein the first and second housing sections are disposed for controlled rotational movement relative to one another.
18. The dose control mechanism of claim 14 , wherein the first and second housing sections are adapted to be coupled together in the primed position to prevent relative motion therebetween.
19. The dose control mechanism of claim 14 , wherein the relative movement of the first and second housing sections between the retracted and extended positions is governed by at least one of the first and second housing sections including at least one guide aspect, and the other of the first and second housing sections including at least one track.
20. An accurate dose drug delivery syringe comprising a dose control mechanism of claim 1 , a barrel, a plunger rod, a plunger seal coupled to the plunger rod and disposed within the barrel, and a needle, a proximal end of the plunger rod being coupled to a distal end of the screw and a distal end of the plunger rod being coupled to the plunger seal.