Injection device
The invention concerns an injection device for apportioning set doses of a drug from a reservoir to a subject. The injection device comprises a housing having an interior thread formed as an outwardly pointing thread carried on an upstanding tower centrally located in the pen shaped device. This outwardly pointing thread forms a first thread connection with the interior thread of the rotatable scale drum. The injection device further comprises a driver for moving the piston rod forward when moved axially. The driver operates the piston rod through a second thread connection having a pitch different than the first thread connection.
1. An injection device for apportioning set doses of a drug from a reservoir comprising:
a housing ( 10 , 210 , 310 , 510 , 610 ) adapted to hold the reservoir ( 40 , 240 , 340 , 540 , 640 ),
a dose setting member ( 30 , 50 , 230 , 2150 , 330 , 3150 , 550 , 630 , 660 ) for setting the size of the dose to be expelled,
a scale indication sleeve ( 90 , 290 , 390 , 590 , 690 ) having numbers for indicating the size of the set dose,
a piston rod ( 120 , 2120 , 3120 , 5120 , 6120 ) for activating the reservoir ( 40 , 240 , 340 , 540 , 640 ) to expel the set dose,
a drive sleeve ( 70 , 270 , 370 , 570 , 670 ) associated with the piston rod ( 120 , 2120 , 3120 , 5120 , 6120 ) for driving the piston rod ( 120 , 2120 , 3120 , 5120 , 6120 ) forward,
wherein,
the scale indication sleeve ( 90 , 290 , 390 , 590 , 690 ) is surrounded by an axially slideable non-rotating shield ( 60 , 260 , 360 , 560 , 660 ) through which at least a portion of the numbers on the scale indication sleeve ( 90 , 290 , 390 , 590 , 690 ) are visible, wherein the shield moves relative to the housing during ejection of a dose of medication from the reservoir and wherein the numbers can be seen rotating.