Injection device with holding means to prevent unintentional movements of piston rod

Abstract

The invention relates to a injection device, comprising a housing being adapted to receive in its proximal housing portion a container with an injection fluid and to receive in its distal housing portion a dose setting and injection mechanism, wherein the mechanism includes a piston rod being axially displaceable with respect to the housing for dispensing injection fluid from the container, wherein the piston rod has an outer thread and is arranged torque proof with respect to the housing, dose setting means comprising a threaded element, which threaded element has an inner thread being in engagement with the outer thread of the piston rod, is designed so that its axial position relative to the housing is changeable and is rotatable relative to the piston rod and relative to the housing during setting of an injection dose, wherein the dose setting means are designed such that the threaded element is held in torque proof manner relative to the piston rod and to the housing during the injection of the beforehand set injection dose in such a manner that the threaded element and the piston rod are axially displaceable together with respect to the housing, wherein the mechanism further comprises holding means being in contact with the piston rod and being designed such that the axial displacement of the piston rod can be substantially immobilized during use of the device except for the dispensing of the injection dose. It is proposed according to the invention that the holding means are axially fixed with respect to the housing.

1 . Injection device, comprising a housing being adapted to receive in its proximal housing portion a container with an injection fluid and to receive in its distal housing portion a dose setting and injection mechanism, wherein the mechanism includes a piston rod being axially displaceable with respect to the housing for dispensing injection fluid from the container, wherein the piston rod has an outer thread and is arranged torque proof with respect to the housing,
 dose setting means comprising a threaded element, which threaded element   has an inner thread being in engagement with the outer thread of the piston rod,   is designed so that its axial position relative to the housing is changeable and   is rotatable relative to the piston rod and relative to the housing during setting of an injection dose,   wherein the dose setting means are designed such that the threaded element is held in torque proof manner relative to the piston rod and to the housing during the injection of the beforehand set injection dose in such a manner that the threaded element and the piston rod are axially displaceable together with respect to the housing,   wherein the mechanism further comprises holding means being in contact with the piston rod and being designed such that the axial displacement of the piston rod can be substantially immobilized during use of the device except for the dispensing of the injection dose,   characterized in that the holding means are axially fixed with respect to the housing.