Abstract: A safety injection device, such as a hypodermic needle, for dispensing liquid from a cartridge in quantities determined by the length of a plunger which may be selectively adjusted in one position only of the plunger. The plunger comprises first and second threadedly connected sections cooperating with a connector which may be selectively activated when the plunger is moved into the one position to permit rotation of one plunger section relative to the other. Preferably, the adjustment position of the plunger coincides with its positions assumed in preparation of an injection stroke, with the connector preferably providing for undirectional rotation of the one plunger section.

Abstract: An injection device (10) is adapted to receive a cartridge (11) holding injection fluid (12). This cartridge (11) is displaceable in the proximal direction in the injection device counter to the force of a resetting spring (157). An adjustable-length tappet (80) is biased in the proximal direction by a spring (53), is displaceable in the injection device between a proximal end position and a distal end position, and has a threaded spindle (19) which is guided in the thread (17) of an adjusting member (15), serves to act upon a plunger (23) provided in the cartridge (11), and has a guide member (67) associated with it; the guide member is connected to it in a manner fixed against relative rotation but axially freely displaceably. This guide member (67) is rotatable relative to the housing (100) of the injection device (10) in the distal end position of the tappet (80), but not in the proximal end position thereof.