Importance

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Abstract

A dose metering device for use with a syringe comprises a fixed screwthreaded member (17) which is either integral with or fixed in use to the cylinder (10) of the syringe and is in threaded engagement with a screwthreaded plunger (13) which can be rotated by a manually-rotatable cap (30) acting through a ratchet and pawl mechanism (32, 34) whose ratchet wheel (26) drives a driving rod (24) which is slidably keyed to the plunger (13). The plunger engages the piston or plug (11) of the syringe. A stop (42) limits rotation of the cap (30) which can be turned away from the stop through a variable angle to a selected angular position shown on a scale (39) of volumetric dose units, the pawl (32) overriding the ratchet teeth (34), to preset a dose to be expressed. The cap (30) can then be turned back to the stop, rotating the plunger (13) via the ratchet and pawl mechanism and causing the plunger to advance the syringe piston or plug (11) through a corresponding axial distance so as to express a metered dose, corresponding to the setting preset on the scale, from the syringe. A succession of preset doses, of the same or different volumes can thus be expressed from the syringe until it is empty. The syringe may employ a prefilled ampoule (50B) of dose liquid which is sealed by a sliding plug (11B) engaged in use by the screw plunger (13B).

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First Claim