Disposable syringe

A disposable syringe, comprising:

• a needle cannula;
• a barrel having an inner surrounding barrel wall surface which surrounds an axis and which confines a passage, said passage having rearward and forward openings which are disposed opposite to each other in a longitudinal direction parallel to the axis, said inner surrounding barrel wall surface including a larger-diameter segment and a smaller-diameter segment which confine rear and front passageways, respectively, and which are disposed proximate to said rearward and forward openings, respectively, to form a surrounding shoulder portion therebetween, said smaller-diameter segment including a front surrounding region and a rear surrounding region which is proximate to said surrounding shoulder portion and which is of a larger dimension than that of said front surrounding region so as to form a surrounding abutment wall therebetween, said larger-diameter segment including proximate and distal surrounding regions opposite to each other in the longitudinal direction and respectively proximate to and distal from said surrounding shoulder portion, said proximate surrounding region having a retaining area which is spaced apart from said surrounding shoulder portion in the longitudinal direction;
• a tubular barrier member which includes front and rear surrounding edge portions opposite to each other in the longitudinal direction and which includes inner and outer barrier wall surfaces opposite to each other and surrounding the axis, said outer barrier wall surface, in a position of use, being retained at said retaining area by virtue of a first frictional force generated therebetween while in water-tight engagement with said proximate surrounding region, thereby partitioning said rear passageway into a compressible chamber which confronts said surrounding shoulder portion, and an accommodation chamber which confronts said rear surrounding edge portion, said inner barrier wall surface having a grip segment, said compressible chamber being filled with a fluid;
• a tubular needle seat including
• a hub portion which is disposed to fix said needle cannula therein, and which has a surrounding front end wall extending radially relative to the axis, said surrounding front end wall including a sealing member which is in air-tight engagement with said rear surrounding region, said inner barrier wall surface of said tubular barrier member being formed with a deformable sealing portion which is in air-tight engagement with said hub portion of said tubular needle seat so as to maintain air-tightness of said compressible chamber, said hub portion further having a plurality of through holes which extend from said surrounding front end wall in the longitudinal direction and which are formed therethrough to be in fluid communication with said compressible chamber;
• a surrounding gripped portion which extends from said hub portion in the longitudinal direction and away from said surrounding front end wall, and which is retained at said grip segment by virtue of a second frictional force generated between said surrounding gripped portion and said grip segment when said sealing member abuts against said surrounding abutment wall and when said needle cannula is disposed outwardly of said forward opening, and
• an anchoring portion extending from said surrounding gripped portion in the longitudinal direction and away from said hub portion;
• and
• a plunger which, in the use position, is disposed to be movable in said accommodation chamber, said plunger including
• a plunger body which includes a top end wall disposed movably to abut against said rear surrounding edge portion of said tubular barrier member, and a bottom end wall disposed opposite to said top end wall in the longitudinal direction and extending outwardly of said rearward opening so as to be manually operable, said top end wall having an inner peripheral edge portion which surrounds the axis and which defines a cavity therein, said cavity extending along the axis and towards said bottom end wall, and
• a seal member attached to said inner peripheral edge portion along a line, said sealing line being configured such that when a pushing force greater than the first and second frictional forces, is manually applied to said bottom end wall to move said top end wall to abut against said rear surrounding edge portion of said tubular barrier member, said tubular barrier member is pushed to move towards said surrounding shoulder portion to compress said fluid in said compressible chamber into said through holes, thereby generating a pressure force in the longitudinal direction on said surrounding gripped portion and forcing said grip segment to disengage from said surrounding gripped portion, so that said anchoring portion, which remains fixedly in place due to abutment of said sealing member against said surrounding abutment wall, is exposed to and is impacted by an impact force from said seal member along the axis such that said line is ruptured, thereby releasing said seal member from said plunger body, and thereby permitting said tubular needle seat to be forced by the pressure force into engagement with said seal member to be subsequently moved into said cavity.