Importance

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Abstract

A prefilled syringe (3) with plunger (5) is arranged in the lower housing member (2) of the injection device, and a drive stem (39) for the advancement of the plunger is supported in the upper housing member (1), this drive stem being advanceable by a specific stroke (1.sub.1) by means of a knob (11) and being retractable by the same stroke (1.sub.1) by means of a spring (49). The two housing members (1, 2) can be telescoped by means of a helical gear mechanism (9, 50) approximately by the entire advancement path (1.sub.3) of the plunger (5) within the ampoule (3). The amount of fluid to be injected in each case is determined by the respective extent of telescoping of the two housing members (1, 2). The length of the injection device is a measure for the content of the ampoule (3) so that the user, without giving special attention, will recognize when the liquid reservoir is running low by the feature that the device becomes increasingly shorter with progressive injections.

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First Claim