Patent ID: 7303550
Filing Date: 2007-12-04
Classification: A61M

Abstract:
1. A disposable syringe comprising: a barrel having a surrounding barrel wall which surrounds an axis in a longitudinal direction and which defines a passage therein that has front and rear open ends opposite to each other, said surrounding barrel wall having an inner wall surface which includes front and rear surface segments proximate to said front and rear open ends, respectively, and an intermediate surface segment disposed therebetween, said intermediate surface segment having a retaining region which is axially distal from said front surface segment, and first and second friction diminishing regions which are respectively interposed between said retaining region and said front surface segment, and between said retaining region and said rear surface segment; a needle cannula; a tubular needle seat configured to be insertable into said passage from said rear open end, and surrounding the axis, said needle seat including a plunger disposed to be movable in said passage along said rear surface segment, and having a front end wall, an engaging head which is opposite to said front end wall in the longitudinal direction, a neck which is interposed between said engaging head and said front end wall, and which is of a dimension such that a rearwardly facing shoulder wall is formed between said engaging head and said neck, and such that the kinetic frictional force is generated as a result of axial movement of said engaging head relative to said radially yieldable catch towards said ceiling wall, and a deformable sealing member which is sleeved on said engaging head and said neck, which is in frictional engagement with said engaging head with a second frictional force, and which is sealingly slidable relative to said rear surface segment such that, in the position of use, said deformable sealing member is moved forward by virtue of forward movement of said plunger to abut against said rearwardly facing wall, while said engaging head is extended into said cavity, and such that, when said plunger is to be placed in a disposal position, said engaging head is kept moving towards said ceiling wall by a pushing force which is applied to said plunger, and which, when said deformable sealing member is blocked by said rearwardly facing wall from moving with said engaging head, overcomes the second frictional force, thereby exposing said neck so as to permit said rearwardly facing shoulder wall to be forced to slip over said radially yieldable catch and to be retained by said radially yieldable catch such that said rearwardly facing shoulder wall is prevented from moving rearwardly, said engaging head and said inner tubular wall surface being configured such that, after said rearwardly facing shoulder wall has slipped over said radially yieldable catch, continued movement of said engaging head towards said ceiling wall, against the first frictional force, forces said retaining portion and said surrounding sealing flange to move into said first and second friction diminishing regions, respectively, so as to facilitate a subsequent pulling action of said plunger whereby said needle seat is brought towards said rear open end by virtue of the retention of said rearwardly facing shoulder wall by said radially yieldable catch, thereby retracting said needle cannula into said passage.