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Dose metering plunger devices for use with syringes

  • US 4,498,904 A
  • Filed: 10/12/1982
  • Issued: 02/12/1985
  • Est. Priority Date: 02/12/1981
  • Status: Expired due to Term
First Claim
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1. A dose metering device for a syringe having a cylinder in which a piston moves to express liquid therefrom, which device comprises an axially-movable plunger which is adapted in use to drive the piston axially in the cylinder for dose expression therefrom, a manually-rotatable operating member, a rotary screw mechanism operatively associated with the plunger, a unidirectional coupling by which the operating member is operatively coupled to the rotary screw mechanism, angular rotation of the operating member in one direction (referred to as the forward direction) being transmitted by the unidirectional coupling to the rotary screw mechanism which is arranged to convert said transmitted rotation into corresponding axial movement of the plunger, whereby in use successive rotary operating strokes of the operating member in the said forward direction are converted into successive axial movement steps of the plunger to express successive doses from the syringe whose volumes correspond to the angular extents of the respective operating strokes of the operating member, and stop means arranged to limit each of the said operating strokes of the operating member at the same predetermined angular finishing point, the unidirectional coupling permitting the manual angular retraction of the operating member independently of the plunger after each said operating stroke from its finishing point predetermined by the stop means to a selected angular position constituting a variable starting point for the next operating stroke, and scale means arranged to indicate selectable angular positions of a plurality of said starting points, whereby the volume of each dose to be expressed is variably preset in use by selection of the angular position, as indicated by the scale means, of the starting point of the respective operating stroke of the operating member.

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