Medication delivery device

Abstract

A medication delivery device is provided which is switchable between an operational state and a resetting state and which comprises a housing having a proximal end and a distal end, a piston rod being moveable in a distal direction with respect to the housing for medication delivery, a conversion element adapted to at least partially convert a rotational movement of the piston rod into an axial movement of the piston rod, coupling means prevented from rotational movement with respect to the housing and adapted to engage with the conversion element in the operational state, a drive assembly comprising at least two drive assembly members and adapted for moving the piston rod in the distal direction, and a resilient member adapted to provide a force on the drive assembly for engagement of the drive assembly members. In the operational state of the device the coupling means is engaged with the conversion element, the conversion element thereby being prevented from rotation with respect to the housing. In the resetting state of the device the coupling means is disengaged from the conversion element under force of the resilient member, the conversion element thereby being allowed to rotate with respect to the housing and thereby allowing a resetting of the device.

We claim: 
     
       1. A medication delivery device being switchable between an operational state and a resetting state, comprising:
 a housing having a proximal end and a distal end, 
 a piston rod being moveable in a distal direction with respect to the housing for medication delivery, 
 a conversion element adapted to at least partially convert a rotational movement of the piston rod into an axial movement of the piston rod, 
 coupling means prevented from rotational movement with respect to the housing and adapted to engage with the conversion element in the operational state, 
 a drive assembly comprising at least two drive assembly members and adapted for moving the piston rod in the distal direction, 
 a resilient member adapted to provide a force on the drive assembly for engagement of the drive assembly members, 
 wherein in the operational state of the device the coupling means is engaged with the conversion element, the conversion element thereby being prevented from rotation with respect to the housing, and 
 in the resetting state of the device the coupling means is disengaged from the conversion element under force of the resilient member, the conversion element thereby being allowed to rotate with respect to the housing and thereby allowing a resetting of the device. 
 
     
     
       2. The medication delivery device according to  claim 1 , wherein the conversion element is permanently prevented from axial movement with respect to the housing, and during switching of the device between the operational state and the resetting state the coupling means is axially moved with respect to the housing between a first axial position according to the operational state of the device and a second axial position according to the resetting state of the device. 
     
     
       3. The medication delivery device according to  claim 2 , comprising retaining means prevented from axial movement relative to the housing, the conversion element being restrained by the retaining means from moving axially and being allowed to revolve with respect to the housing. 
     
     
       4. The medication delivery device according to  claim 2 , wherein
 in the operational state of the device the coupling means is held in the first axial position, and 
 during switching of the device between the operational state and the resetting state the coupling means is axially moved and brought into the second axial position under force of the resilient member. 
 
     
     
       5. The medication delivery device according to  claim 1 , wherein
 the coupling means is permanently prevented from axial movement with respect to the housing, and 
 during switching of the device between the operational state and the resetting state the conversion element is axially moved with respect to the housing between a first axial position according to the operational state of the device and a second axial position according to the resetting state of the device. 
 
     
     
       6. The medication delivery device according to  claim 5 , wherein
 in the operational state of the device the conversion element is held in the first axial position, and 
 during switching of the device between the operational state and the resetting state the conversion element is moved in distal direction and brought into the second axial position under force of the resilient member. 
 
     
     
       7. The medication delivery device according to  claim 1 , comprising a medication receptacle adapted to be secured to the housing
 wherein in the operational state of the device the medication receptacle is secured to the housing thereby holding the coupling means in engagement with the conversion element, and 
 in the resetting state of the device the medication receptacle is removed from the housing thereby allowing disengagement of the coupling means from the conversion element. 
 
     
     
       8. The medication delivery device according to  claim 1 , wherein the conversion element comprises first locking means and the coupling means comprises second locking means, the first and second locking means being adapted to interlock with each other. 
     
     
       9. The medication delivery device according to  claim 8 , wherein the first and second locking means are formed by at least one of teeth, splines, protrusions, and castellations. 
     
     
       10. The medication delivery device according to  claim 1 , wherein the piston rod is threadedly engaged with the conversion element. 
     
     
       11. The medication delivery device according to  claim 1 , comprising where one of the two drive assembly members comprises a rotation member which is adapted to be rotated in a first direction with respect to the housing during setting of a dose of a medication and to be rotated in a second direction with respect to the housing during delivery of the dose, the second direction being opposite to the first direction. 
     
     
       12. The medication delivery device according to claim  1  11, comprising where one of the two drive assembly members comprises a drive member which is adapted to be rotated with respect to the housing, wherein rotational movement of the drive member with respect to the housing is converted into movement of the piston rod in the distal direction with respect to the housing. 
     
     
       13. The medication delivery device according to claim  11  12, wherein in the operational state the drive member is adapted to follow rotational movement of the rotation member in the second direction with respect to the housing during delivery of the dose. 
     
     
       14. The medication delivery device according to  claim 13 , wherein the drive member and the rotation member are coupled to one another by a first uni-directional friction clutch mechanism which is configured to permit relative rotational movement between the drive member and the rotation member during rotation of the rotation member in the first direction for setting of the dose and to prevent relative rotational movement of drive member and rotation member during rotation of the rotation member in the second direction for delivery of the dose. 
     
     
       15. The medication delivery device according to  claim 12 , wherein the drive member is engaged with a stop member which is adapted to prevent rotational movement of the drive member in the first direction with respect to the housing and to permit rotational movement of the drive member in the second direction with respect to the housing. 
     
     
       16. The medication delivery device according to  claim 15 , wherein the drive member and the stop member are coupled to one another by a second uni-directional friction clutch mechanism, which is configured to prevent relative rotational movement between the drive member and the stop member in the first direction with respect to the housing and to permit relative rotational movement between the drive member and the stop member in the second direction with respect to the housing. 
     
     
       17. A medication delivery device being switchable between an operational state and a resetting state, comprising:
 a housing having a proximal end and a distal end,   a piston rod being moveable in a distal direction with respect to the housing for medication delivery,   a nut configured to cause an axial movement of the piston rod when the device is in the operational state,   a coupling prevented from rotational movement with respect to the housing and configured to engage with the nut in the operational state,   a drive assembly comprising at least two drive assembly members and adapted for moving the piston rod in the distal direction,   a resilient member configured to provide an axial biasing force on the coupling in the operational state,   wherein in the operational state the coupling is engaged with the nut, the nut thereby being prevented from rotation with respect to the housing, and   in the resetting state the coupling is disengaged from the nut under the biasing force of the resilient member, the nut thereby being allowed to rotate with respect to the housing and thereby allowing a resetting of the device.   
     
     
       18. A medication delivery device being switchable between an operational state and a resetting state, comprising:
 a housing having a proximal end and a distal end,   a piston rod being moveable in a distal direction with respect to the housing for medication delivery,   a guide component configured to cause an axial movement of the piston rod when the device is in the operational state,   a coupling prevented from rotational movement with respect to the housing and configured to engage with the guide component in the operational state,   a drive assembly comprising at least two drive assembly members and adapted for moving the piston rod in the distal direction,   a resilient member configured to provide an axial biasing force on the coupling in the operational state,   wherein in the operational state the coupling is engaged with the guide component, the guide component thereby being prevented from rotation with respect to the housing, and   in the resetting state the coupling is disengaged from the guide component under the biasing force of the resilient member, the guide component thereby being allowed to rotate with respect to the housing and thereby allowing a resetting of the device.