|Title:||Large dose pen|
|Abstract:||A pen shaped syringe for repetitive injection of individually set doses of a medicine from a cylinder ampoule reservoir comprises a dose setting member which may be rotated to cause a rotative movement of a dosing member and a combined rotative and axial movement of an indicator member indicating the set dose, and a piston drive member which when rotated in one direction moves the piston into the cylinder ampoule. A unidirectional coupling is established between the dosing member and the piston drive member by each member carrying a disc having surfaces with sector shaped saw teeth riding over each other when the dosing member is rotated in the dose setting direction and engaging each other when the dosing member is rotated in the opposite direction corresponding to the direction of rotation by which the piston is moved into the cylinder ampoule. A nut/screw connection is established between a syringe housing and the dose setting member, and means are provided to release the unidirectional coupling between the piston drive member and the dosing member by drawing the coupling discs away from each other.|
|Inventor(s):||Petersen; Lars P. K. (Gentofte, DK), Hansen; Niels-Aage B. (Havdrup, DK)|
|Assignee:||Novo Nordisk A/S (Bagsvaerd, DK)|
1. An apparatus for use with a pen shaped syringe for repetitive injection of individually set doses of a medicine from a cylinder ampoule reservoir, comprising:
a nut member with an internal thread fixed in the housing,
a dose setting member rotatable in a fist direction to set a dose and in a second direction to inject a set dose, and comprising a spindle with an external thread engaging the internal thread of said nut member,
a dosing member coupled to the dose setting member to be rotated with this dose setting member,
an indicator member, rigidly connected to the dose setting member to follow axial and rotational movement of this dose setting member,
a piston drive member which when rotated in said second direction moves a piston into the cylinder ampoule,
a unidirectional coupling provided between the dosing member and the piston drive member, by a first coupling part on the dosing member engaging a second coupling part on the piston drive member and so directed that the rotation of dosing member induced by dose setting rotation of the dose setting member is not transmitted to the piston drive member whereas rotation in the opposite dosing direction is; wherein a nut/screw connection is established between the housing and the dose setting member and means are provided to optionally release the unidirectional coupling between the dosing member and the piston drive member.
2. An apparatus according to claim 1, wherein the dose setting member is tubular with a bore fitting over the spindle of the dose setting member, which spindle has axial recesses engaged by corresponding axial beams on the inner side of the bore of the dosing member.
3. An apparatus according to claim 2, wherein the unidirectional coupling between the dosing member and the piston drive member is provided by said first and second coupling parts having circular surfaces provided with sector shaped teeth having an abrupt and a ramp shaped edge, the surfaces being forced against each other by a first spring with the ramp shaped edges of the teeth on one surface abutting the ramp shaped edges of the teeth on the other surface; said first spring surrounding a part of the dosing member and having a first and a second end, the first end abutting a shoulder in the housing and the second end abutting an outward flange on a first bushing which is fitted on an end of the dose member and further has an inward flange resting on said end of the dose member.
4. An apparatus according to claim 3, wherein the means to optionally release the coupling between the dosing member and the piston drive member comprises a tubular basic element having a first end with an enlarged diameter carrying a cartridge holder accommodating an ampoule, and a second end coaxially surrounded by a tubular element having a first end with an enlarged diameter fitting into an end of the housing and fixed to said housing, and a second end with a reduced diameter forming the nut member, the tubular element being axially displaceable from a fixed position relative to the basic element against the force of a second spring inside said basic element and having a first end abutting an internal projection in said basic element and a second end abutting a second bushing resting on lifting forks which are carried in the wall of the tubular element in openings perpendicular to the axis; an outer projection on the dosing member projects into a space between the arms of the forks so that the forks lift the first coupling part, on the dosing member, out of engagement with the second coupling part of the piston drive, when the tubular member is displaced on the basic element.
5. An apparatus according to claim 1, wherein the internal thread of the nut member and the external thread of the spindle of the dose setting member have a pitch allowing transformation of an axial pressure to a rotation.
6. An apparatus syringe according to claim 5, wherein an outer end of the dose setting member is terminated by a knob wherein a press button is journaled, the button and the knob having mutually abutting surfaces made of materials ensuring low friction.
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