Patent ID: 7066906
Filing Date: 2006-06-27
Classification: A61M

Abstract:
1. A disposable syringe adapted to be used with a needle unit which includes a needle hub and a needle securely affixed to the needle hub, said syringe comprising: a barrel having an inner surrounding barrel wall surface which surrounds an axis and which confines a passage, said passage having lower and upper open ends 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 are disposed proximate to said lower and upper open ends, respectively, and which cooperatively form a first surrounding shoulder portion therebetween, the smaller-diameter segment including a retaining groove defined therein; a tubular needle seat disposed to be insertable into said passage from said lower open end toward said upper open end, said needle seat including a protruding lower surrounding edge portion which is disposed to abut against said first surrounding shoulder portion, an upper surrounding edge portion disposed opposite to said lower surrounding edge portion in the longitudinal direction, and a surrounding seat wall interposed between said lower and upper surrounding edge portions, and having an inner tubular wall surface which surrounds the axis to confine a duct and which has a grip segment, and an outer tubular wall surface which includes a lower segment including a retaining protrusion defined thereon and proximate to said lower surrounding edge portion, lower segment being configured such that, when said upper surrounding edge portion is forced to extend outwardly of said upper open end after said tubular needle seat is inserted into said passage, said lower segment will be brought to a position of use, where said lower segment engages and is retained at said smaller-diameter segment by virtue of a first friction force generated by retaining engagement of the retaining protrusion in the retaining groove while said protruding lower surrounding edge portion abuts against said first surrounding shoulder portion, the lower segment being further configured such that, when said upper surrounding edge portion is forced against the first friction force so as to be retracted into said passage via said upper open end, said upper surrounding edge portion will be brought to a retracted position, where said lower segment and said protruding lower surrounding edge portion are remote from said smaller-diameter segment and said first surrounding shoulder portion, respectively, and an upper segment disposed opposite to said lower segment and proximate to said upper surrounding edge portion, said upper segment being adapted to be sleeved over by the needle hub so as to communicate said duct with the needle hub; and a plunger including a stem portion which is disposed to be movable in said passage of said barrel and which has inner and outer segments opposite to each other in the longitudinal direction, said outer segment extending outwardly of said lower open end, an actuated end extending from said outer segment so as to be actuated to move said stem portion along said passage, a surrounding engaging portion which is disposed to be retainingly sleeved on said inner segment by virtue of a second friction force, and which in sealing contact with and which is slidable relative to said larger-diameter segment so as to be moved with said stem portion in the position of use, and a head disposed to extend from said inner segment toward said grip segment, and configured such that, when said surrounding engaging portion is brought by said inner segment to engage said lower surrounding edge portion and is depressed by said lower surrounding edge portion by virtue of a third force generated as a consequence of continuing movement of said inner segment towards said smaller-diameter segment, the third force being greater than the second friction force such that said surrounding engaging portion is blocked by said lower surrounding edge portion to thereby permit said head to move towards said grip segment of said tubular needle seat and to be held by virtue of a fourth friction force that is greater than the first friction force while said lower segment remains engaged and unmoved relative to said smaller-diameter segment.