Syringe having a reverse-taper barrel

A disposable syringe particularly suited to be used for obtaining a blood sample from a patient because of the low force requirement for operation thereof, said syringe comprising:

• a barrel having a generally cylindrical inner wall comprising a working section thereof extending from a forward end of said barrel to a predetermined point, the inner diameter of said working section of said barrel being tapered radially inwardly from the forward end of said barrel to said predetermined point;
• and
• a plunger comprising a plunger stem and a compressible, elastomeric, generally cylindrical plunger tip of lesser diameter than the inner wall of said barrel, said plunger tip having an integral, annular, elastically deformable wiper extending peripherally radially outwardly and axially forwardly from said plunger tip at a forward portion thereof at an acute angle to the longitudinal center axis of said plunger tip and terminating at the outer edge thereof in a wiping edge having a minimal diameter slightly in excess of the diameter of the inner wall of said barrel, thereby forming a sealing engagement with the inner wall of said barrel, said annular wiper being the sole sealing element between said plunger tip and said wall;
• wherein said syringe assembly comprises means for preventing further inward movement of said plunger to define a chamber having a predetermined volume for retaining a desired quantity of anticoagulant.

A disposable syringe particularly suited to be used for obtaining a blood sample from a patient because of the low force requirement for operation thereof, said syringe comprising:

• a barrel having a generally cylindrical innner wall comprising a working section thereof extending from a forward end of said barrel to a predetermined point, the inner diameter of said working section of said barrel being tapered raially inwardly from the forward end of said barrel to said predetermined point;
• and
• a plunger comprising a plunger stem and a compressible, elastomeric, generally cylindrical plunger tip of lesser diameter than the inner wall of said barrel, said plunger tip having an integral, annular, elastically deformable wiper extending peripherally radially outwardly and axially forwardly from said plunger tip at a forward portion thereof at an acute angle to the longitudinal center axis of said plunger tip and terminating at the outer edge thereof in a wiping edge having a minimal diameter slightly in excess of the diameter of the inner wall of said barrel, thereby forming a sealing engagement with the inner wall of said barrel, said annular wiper being the sole sealing element between said plunger tip and said wall;
• wherein said plunger tip has a plurality of raised portions spaced circumferentially around said plunger tip and located at the rearward portion of said plunger tip, said raised portions engaging said inner wall of said barrel with a minimum of frictional contact to prevent canting of said plunger tip in said barrel.

A disposable syringe particularly suited to be used for obtaining a blood sample from a patient because of the low force requirement for operation thereof, said syringe comprising:

• a barrel having a generally cylindrical inner wall comprising a working section thereof extending from a forward end of said barrel to a predetermined point, the inner diameter of said working section of said barrel being tapered radially inwardly from the forward end of said barrel to said predetermined point;
• a plunger comprising a plunger stem and a compressible, elastomeric, generally cylindrical plunger tip of lesser diameter than the inner wall of said barrel, said plunger tip having an integral, annular, elastically deformable wiper extending peripherally radially outwardly and axially forwardly from said plunger tip at a forward portion thereof at an acute angle to the longitudinal center axis of said plunger tip and terminating at the outer edge thereof in a wiping edge having a minimal diameter slightly in excess of the diameter of the inner wall of said barrel, thereby forming a sealing engagement with the inner wall of said barrel, said annular wiper being the sole sealing element between said plunger tip and said wall;
• means for preventing further inward movement of said plunger to define a chamber having a predetermined volume for retaining a desired quantity of anticoagulant;
• and
• means for stopping outward movement of said plunger at said predetermined point when drawing said blood sample;
• said plunger tip having a plurality of raised portions spaced circumferentially around said plunger tip and located at the rearward portion of said plunger tip, said raised portions engaging said inner wall of said barrel with a minimum of frictional contact to prevent canting of said plunger tip in said barrel.