Drive-control system for an injection device
A drive-control system for an injection device for delivering settable doses of a pharmaceutical substance contained in a cartridge, including a tubular housing body having a longitudinal axis, a proximal end and a distal end connectable to the cartridge enclosure, a helical spring contained in the housing body and a piston rod moveable towards the distal end and blocked in translation towards the proximal end. The housing body includes a control sleeve on which the spring is mounted, which rotatable around the axis, and a setting sleeve translatable along the axis. Rotation of the control sleeve in a first direction combined with compression of the spring causes the setting sleeve to be translated towards the proximal end of the housing body, and extension of the spring causes the setting sleeve to be translated towards the distal end of the housing body and the control sleeve to be rotated in a second direction and the piston rod to be pushed towards the outside of the housing body.
1. A drive-control system for an injection device, the system comprising:
a tubular housing body having a longitudinal axis a proximal end and a distal end which is connectable to a cartridge enclosure,
a control sleeve which is rotatable around the longitudinal axis, the control sleeve having an external thread formed at its distal end,
a setting sleeve translatable along the axis towards the proximal end and towards the distal end and unable to rotate in relation to the housing body, the setting sleeve having an internal thread engaged with the external thread of the control sleeve,
a helical spring abutting the setting sleeve,
a piston rod having non-circular cross section and at least one series of the ratchet teeth disposed on its side wall,
wherein the setting sleeve, the control sleeve and the piston rod are arranged coaxially,
wherein a dose is set by rotation of the control sleeve in a first direction which causes translation of the setting sleeve towards the proximal end of the housing body and compression of the spring,
wherein extension of the spring causes translation of the setting sleeve towards the distal end of the housing body, rotation of the control sleeve in a second direction and translation of the piston rod towards the outside of the housing body.
2. A drive-control system of claim 1 wherein the setting sleeve is engaged with an internal wall of the housing body by means of at least pair of complementary longitudinal groove.
3. A drive-control system of claim 1 , wherein the helical spring is disposed between the internal wall of the housing body and the control sleeve.
4. A drive-control system of claim 1 , wherein the helical spring abuts a projection inside the housing body.
5. A drive-control system of claim 1 , wherein the helical spring is a helical compression spring.
6. A drive-control system of claim 1 further comprising a blocking member is provided on the distal end of the housing body the blocking member being engaged with the piston rod by the at least one series of ratchet teeth and at least one resilient pawl on the blocking member engaging the ratchet teeth of the piston rod so as to block the translation of the piston rod in the proximal direction.
7. A drive-control system of claim 6 , wherein the blocking member has a form of a blocking sleeve located inside the housing body and fixed to the housing body, the piston rod extending through the blocking sleeve, and the at least one resilient pawl is integral with the blocking sleeve.
8. A drive-control system of claim 1 , wherein the piston rod is immobilized during setting of a dose.
9. A drive-control system of claim 1 , wherein the control sleeve comprises an enlarged portion located above the helical spring.
10. A drive-control system of claim 9 , wherein the body housing comprises an aperture in its proximal portion and wherein the aperture is disposed such that the enlarged portion of the control sleeve is visible through the aperture.
11. A method of delivering a settable dose of a liquid pharmaceutical substance from an injection device, comprising setting the dose with the drive-control system of claim 1 .