Disposable syringe

Abstract

A disposable syringe includes a barrel, a needle assembly in fluid communication with the barrel, and a plunger movable in an accommodation chamber of the barrel. The needle assembly includes a needle seat sleeved on a small-diameter wall portion of the barrel, and a tubular insert extending axially into a duct of the needle seat and defining a fluid channel, and a needle cannula in fluid communication with the fluid channel. A space minimizing member is disposed to be in a fluid-tight engagement with an inner surface of the small-diameter wall portion, and has a tubular grip surface which defines a passageway fluidly communicated with the duct such that the insert is in a fluid-tight engagement with the grip surface to thereby communicate the channel with the chamber. Thus, the amount of residual medication fluid in the barrel after completion of an injection operation can be minimized.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiments of the invention, with reference to the accompanying drawings, in which:

FIG. 1 is a sectional view of a conventional disposable syringe in an injection-completed state;

FIG. 2 is an exploded sectional view of the first preferred embodiment of a disposable syringe according to this invention;

FIG. 3 is a fragmentary sectional view of the first preferred embodiment in an injection-completed state;

FIG. 4 is an exploded sectional view of the second preferred embodiment of a disposable syringe according to this invention;

FIG. 5 is a fragmentary sectional view of the third preferred embodiment in an injection-completed state;

FIG. 6 is a fragmentary sectional view of the third preferred embodiment of a disposable syringe according to this invention;

FIG. 7 is a fragmentary sectional view of the fourth preferred embodiment of a disposable syringe according to this invention;

FIG. 8 is a fragmentary sectional view of the fourth preferred embodiment in a plunger-withdrawn state;

FIG. 9 is a fragmentary sectional view of the fifth preferred embodiment of a disposable syringe according to this invention in a plunger-withdrawn state;

FIG. 10 is an exploded sectional view of the sixth preferred embodiment of a disposable syringe according to this invention;

FIG. 11 is a fragmentary sectional view of the sixth preferred embodiment;

FIG. 12 is a sectional view of the seventh preferred embodiment of a disposable syringe according to this invention;

FIGS. 13-15 are, respectively, fragmentary sectional views of the eighth, ninth and tenth preferred embodiments of a disposable syringe according to this invention in a plunger-withdrawn state; and

FIG. 16 is a fragmentary sectional view of the eleventh preferred embodiment of a disposable syringe according to this invention.

Claims

1. A disposable syringe comprising: a barrel including front and rear barrel ends opposite to each other along an axis in an axial direction, and a surrounding barrel wall which interconnects said front and rear barrel ends, and which includes small-diameter and large-diameter wall portions that are disposed proximate to said front and rear barrel ends, respectively, and that respectively have front and rear inner wall surfaces defining a passage and an accommodation chamber which are in fluid communication with each other, anda shoulder that is interposed between said small-diameter and large-diameter wall portions;a needle cannula having a rear secured end and a front tip end opposite to each other along the axis;a tubular needle seat having a front retaining wall portion which retains said rear secured end of said needle cannula to permit forward extension of said front tip end from said front retaining wall portion, and a rear sleeve wall portion which is opposite to said front retaining wall portion along the axis to define a duct that is fluidly communicated with said needle cannula, and which is detachably sleeved on said small-diameter wall portion to fluidly communicate said duct with said passage;a tubular insert disposed to extend from said front retaining wall portion along the axis and into said duct, and having an inner tubular surface which defines a fluid channel that is disposed to be fluidly communicated with said rear secured end of said needle cannula, and an outer tubular surface which is opposite to said inner tubular surface in radial directions relative to the axis;a space minimizing member including a tubular abutment surface which surrounds the axis, and which is disposed to be in a fluid-tight engagement with said front inner wall surface, anda tubular grip surface which is surrounded by said tubular abutment surface, and which defines a passageway that fluidly communicates said duct with said accommodation chamber such that when said rear sleeve wall portion is sleeved on said small-diameter wall portion, said tubular insert is inserted into said passage and is in a fluid-tight engagement with said tubular grip surface to thereby communicate said fluid channel with said accommodation chamber; anda plunger which is disposed to be movable in said accommodation chamber of said large-diameter wall portion along the axis so as to force a medication fluid in said accommodation chamber to flow into said needle cannula through said passageway and said fluid channel.

2. The disposable syringe of claim 1, wherein said barrel further has a tubular guard portion which extends rearwardly from said rear barrel end and which defines a receiving space communicated with said accommodation chamber, said plunger having a thumb rest which extends rearwardly and outwardly of said tubular guard portion for manual operation, and which is received in said receiving space when said plunger reaches said shoulder.

3. The disposable syringe of claim 1, wherein said tubular abutment surface of said space minimizing member is integrally formed with said front inner wall surface of said small-diameter wall portion.

4. The disposable syringe of claim 3, wherein said plunger has a front end wall which confronts said passage, a carrier portion which extends from said front end wall forwardly along the axis, and a hollow deformable sealing member which is detachably disposed on said carrier portion and which is in fluid-tight and sliding engagement with said rear inner wall surface, and an interrupting portion which is engaged with said sealing member and which is configured to be forced by said carrier portion to plug said passage, thereby interrupting fluid communication between said accommodation chamber and said passageway and rendering said syringe unreusable.

5. The disposable syringe of claim 4, wherein said small-diameter wall portion has an annular retaining ledge disposed on said front inner wall surface to ensure retention of said interrupting portion in said passage.

6. The disposable syringe of claim 1, wherein said tubular insert is integrally formed with and extends rearwardly from said rear secured end of said needle cannula along the axis.

7. The disposable syringe of claim 6, wherein said tubular insert is configured such that when said rear sleeve wall portion is sleeved on said small-diameter wall portion, said tubular insert is press-fitted into said passageway by virtue of a fluid-tight engagement between said outer tubular surface and said tubular grip surface.

8. The disposable syringe of claim 1, wherein said tubular insert is integrally formed with said front retaining wall portion.

9. The disposable syringe of claim 8, wherein said tubular insert is configured such that when said rear sleeve wall portion is sleeved on said small-diameter wall portion, said tubular insert is press-fitted into said passage by virtue of a fluid-tight engagement between said front inner wall surface and said outer tubular surface.

10. The disposable syringe of claim 1, wherein said space minimizing member is disposed to be inserted into said passage from said rear barrel end to bring said tubular abutment surface into abutment against said front inner wall surface.

11. The disposable syringe of claim 10, wherein said space minimizing member has a tubular rear barrier flange which is disposed to abut against said shoulder so as to prevent forward movement of said space minimizing member, and which extends radially and outwardly to terminate at an outer flange surface, said outer flange surface being in a fluid-tight engagement with said rear inner wall surface.

12. The disposable syringe of claim 1, wherein said small-diameter wall portion is in form of a plurality of ribs which are angularly displaced from one another about the axis.