Patent ID: 7074207
Filing Date: 2006-07-11
Classification: A61M

Abstract:
1. A safety syringe comprising: a syringe barrel having a front end wall with a front opening, and a rear end wall with a rear opening; a plunger disposed movably within said barrel and having a front end and a rear end that extends from said rear opening in said syringe barrel; and a needle unit extending through said front opening in said syringe barrel and including a central bore formed therethrough, a needle holder that is formed with a rear opening, and a needle that is connected fixedly to said needle holder at a rear end and that is exposed outwardly from said front opening in said syringe barrel; wherein said syringe barrel includes an annular flexible holder-supporting seat disposed movably within said syringe barrel and sleeved around said needle holder, said holder-supporting seat having a central hole formed therethrough, an outer periphery that is in frictional contact with an inner surface of said syringe barrel in such a manner that a liquid-tight seal is established therebetween, and an inner periphery that is in frictional contact with an outer surface of said needle holder in such a manner that a liquid-tight seal is established therebetween; wherein said plunger has an open front end that is formed with a front opening, a rear end wall, and a front end portion that is formed with an inward flange extending integrally, radially, and inwardly therefrom; wherein said safety syringe further comprises a flexible sealing member disposed movably within said front end portion of said plunger so as to define a vacuum chamber in said plunger between said sealing member and said rear end wall of said plunger, said inward flange being sleeved around and clamping said sealing member in said plunger so as to prevent movement of said sealing member relative to said plunger, thereby permitting synchronous rearward movement of said sealing member and said plunger when said plunger is pulled rearward relative to said syringe barrel, said sealing member having a holder-retaining front portion that is disposed behind and that is spaced apart from said needle holder, and a sealing rear portion for closing said front opening in said plunger; wherein said needle unit has a spacer portion that is formed integrally between said needle holder and said needle and that is sized to prevent movement of said spacer portion into said front opening in said syringe barrel such that said needle holder is clamped within said holder-supporting seat at a position that is spaced apart from said front end wall by a predetermined distance; wherein said holder-retaining front portion of said sealing member moves forward to retain said needle holder thereon, when said plunger is moved forward within said syringe barrel to push said holder-supporting seat forward, such that said holder-supporting seat separates from said needle holder so as to permit automatic rearward movement of an assembly of said sealing member and said needle unit within said syringe barrel due to negative pressure produced within said plunger, thereby retracting said needle into said syringe barrel.