1. Technical Field
The present invention relates to an improved assembly of plunger and needle hub for a safety syringe needle device and, more particularly, to a safety syringe needle device with a retractable needle hub that has integrated combining ring formed as inward-bent hooks for being engaged with a plunger and capable of being retracted back to the syringe accompanying retreat of the plunger.
2. Description of Related Art
A conventional safety syringe needle device is illustrated through FIGS. 8 and 9, which is primarily composed of a tubular syringe barrel 5, a needle hub 6 and a plunger 7, wherein the interior periphery of the syringe barrel 5 is shaped as a straight tube, and inside the syringe barrel 5, a flange 51 is provided adjacent to the front end thereof while two opposite notches 52 are arranged at the front end of the syringe barrel 5.
Said needle hub 6 is inserted into the syringe barrel 5 and has a retaining ring 61, which comprises a plurality of retaining hooks 62, each having a hook portion 621 for being engaged with the notches 52 of the syringe barrel 5 and a snap segment 622 settled at the outer edge thereof. As there is an interval between the retaining hooks 62 and the retaining ring 61, the syringe barrel 5 can hold the needle hood 6 by implementing the flange 51 to retain the retaining ring 61 and press upon the retaining hooks 62. Moreover, the retaining ring 61 further comprises a nozzle 63, which is jutting out of the syringe barrel 5 and comprises a recess 631 positioned corresponding to the retaining hooks 62. In the meantime, each of the retaining hooks 62 has a combining portion 623 positioned corresponding to the recess 631 so that when the combining portions 623 is engaged with the recess 631, the retaining hooks 62 can be squeezed and the hook portions 621 can be withdrawn from engaging the syringe barrel 5. Furthermore, a combining portion 64 is extended from the needle hub 6 and is composed of a plurality of flexible pieces 641 each having a retaining portion 642. Also, a needle 65 and a sheath 66 can be sleeved onto the nozzle 63.
The plunger 7 comprises a plug 71 for being fitly received by the syringe barrel 5. The plug 71 further has a combining portion 72 protruding at the front end thereof wherein the combining portion 72 includes two wings 721 each attached by an extended retaining piece 722 and the combining portion 72 is thereby formed as a diamond-shaped structure. Thus, the combining portion 72 and the combining portion 64 can be assembled by piercing the combining portion 72 through the combining portion 64 to make the retaining pieces 722 retained by the retaining portions 642 of the combining portion 64.
Accordingly, as the plural pieces 641 of the combining portion 64 of the needle hub 6 are quite complicated in the structure, the components need to be made very precisely in order to ensure appropriate combination with the combining portion 72 and the manufacturing cost can be consequently raised.
Hence, a need exists for an improvement on the conventional assembly of plunger and needle hub for a safety syringe needle device.