Patent ID: 7740618

Claim:
A syringe device comprising: a housing; a first member ( 112 , 212 ) that is axially fixed to the housing; a piston rod ( 106 ; 206 ) having a threaded outer surface, the piston rod ( 106 ; 206 ) being retained in relation to the first member( 112 ; 212 ) in such a way that no relative rotation of the piston rod ( 106 ; 206 ) and the first member ( 112 ; 212 ) is possible and in such a way that the piston rod ( 106 ; 206 ) can slide longitudinally relative to the first member ( 112 ; 212 ); a dose setting member ( 108 ; 208 ) defining a passage for the piston rod ( 106 ; 206 ), the passage having a threaded inner surface for engagement with the threaded outer surface of the piston rod ( 106 ; 206 ), so as to define a connection between the dose setting member ( 108 ; 208 ) and the piston rod ( 106 ; 206 ), the dose setting member ( 108 ; 208 ) being arranged with respect to the piston rod ( 106 ; 206 ) such that rotation of the dose setting member ( 108 ; 208 ) causes the dose setting member ( 108 ; 208 ) to be displaced longitudinally along the piston rod ( 106 ; 206 ), whereby a stroke length of the piston rod ( 106 ; 206 ) is defined by the longitudinal displacement of the dose setting member ( 108 ; 208 ) in a proximal direction ( 104 ) relative to a predetermined position of the dose setting member ( 108 ; 208 ), and such that a translational displacement of the dose setting member ( 108 ; 208 ) relative to the housing is transmittable via said connection into a translational displacement of the piston rod ( 106 ; 206 ) relative to the housing; a second member ( 110 ; 210 ) defining a passage for the piston rod ( 106 ; 206 ) the passage having a threaded inner surface for engagement with the threaded outer surface of the piston rod ( 106 ; 206 ), and; a first locking means ( 126 ; 250 ) for locking the first member ( 112 ; 212 ) and second member ( 110 ; 210 ) against relative rotation, so that no displacement of the piston rod ( 106 ; 206 ) in the proximal direction ( 104 ) is possible, when the first locking means ( 126 ; 250 ) is in its locking position, characterized by a spring ( 118 ; 218 ) which interconnects the second member ( 110 ; 210 ) and the dose setting member ( 108 ; 208 ) and biases them towards each other, such that when the dose setting member ( 108 ; 208 ) is rotated and thereby displaced longitudinally along the piston rod ( 106 ; 206 ), the spring is strained, and such that translational displacement of the dose setting member ( 108 ; 208 ) and the piston rod ( 106 ; 206 ) in the distal direction ( 102 ) to eject the dose unstrains the spring ( 118 ; 218 ), whereby energy accumulated during straining of the spring ( 118 ; 218 ) is released to provide said ejection force.