US Patent 9022991 Injection device

An injection device for injection of set doses of medicine from a cartridge, in which syringe a dose is set by screwing a nut up along a threaded piston rod, whereby a dose setting drum, which carries on its cylindrical surface along a helix a scale of which a number corresponding to the set dose is shown in a window in the housing of the syringe, and an injection button, which is elevated over the end of the syringe, are moved axially a distance which is larger than the axial movement of the nut. A gear wheel gear transmission is established between the nut and the injection button.