Abstract:
A dual-chamber safety hypodermic syringe. The syringe includes a barrel having a medicine chamber, a needle chamber, and a guide hole connected between the chambers. The needle assembly is moved in and out of the needle chamber between the extended position where an inlet on a neck of the needle assembly is disposed in communication with the guide hole for enabling liquid medicine to be squeezed out from the medicine chamber through the needle cannula of the needle assembly, and the received position where the needle assembly is safely received inside the needle chamber and kept from sight.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a safety hypodermic syringe and, more particularly, to a dual-chamber safety hypodermic syringe, which is suitable for use to inject medicine into the body as well as to draw blood from the body, and enables the needle cannula to be safely received in an independent needle chamber after its service. 
     2. Description of Related Art 
     In regular safety hypodermic syringes, the plunger has catch means at the front side for catching the needle assembly. After the plunger had been pushed to the front side to squeeze medicine out of the barrel, the catch means is forced into engagement with the needle hub of the needle assembly. Therefore, the needle assembly is pulled backwards and received inside the barrel after a backstroke of the plunger. However, when the user pulls the plunger to the rear limit position, the plunger protrudes over the rear side of the barrel at a distance, and the length of the hypodermic syringe is relatively increased. Because the front side of the barrel is kept in an open status, the needle cannula tends to be forced out of the barrel again when hitting the plunger against an object accidentally. In order to eliminate this problem, another prior art may employ much effort forwards to the plunger to curve the metal needle cannula after the needle assembly has been moved backwards with the plunger inside the barrel. However, the needle cannula may be forced to pierce through the peripheral wall of the barrel when employing force forwards to the plunger to curve the needle cannula. There is still one another structure of safety hypodermic syringe, in which the plunger is broken and plugged into the front opening of the barrel again to curve the needle cannula of the needle assembly after the needle assembly had been received inside the barrel. However, it requires much effort to plug the plunger into the front opening of the barrel against the metal needle cannula and to curve the metal needle cannula, and an accident of piercing through the peripheral wall may still occur when curving the metal needle cannula. 
     Further, in order to prevent engagement of the catch means of the plunger with the needle hub of the needle assembly before the use of the safety syringe, a gap must be maintained between the plunger and the needle hub of the needle assembly. However, the presence of the gap causes the safety hypodermic syringe unable to be used to draw blood from the body. This design also causes a high cost of packing material to keep the gap in distance. 
     Therefore, it is desirable to provide an improved hypodermic syringe to mitigate and/or obviate the aforementioned problems. 
     SUMMARY OF THE INVENTION 
     The main object of the present invention is to provide a dual-chamber safety hypodermic syringe, which enabling the needle assembly to be safely received in an independent needle chamber after its service, and preventing the needle cannula from being pushed forwardly or piercing sideways to the outside of the barrel to injure people by an accident. Another object of the present invention is to provide a dual-chamber safety hypodermic syringe, which is practical for use to inject medicine into the body as well as to draw blood from the body. 
     To achieve the object, the dual-chamber safety hypodermic syringe of the present invention includes a needle assembly, the needle assembly comprising a needle hub and a needle cannula mounted in the needle hub, the needle hub comprising a neck on the middle and an inlet on the neck in communication with the needle cannula, and a handle extended sideways from the periphery thereof; and a barrel, the barrel comprising a front side, a rear side, a medicine chamber and a needle chamber respectively extended in axial direction, an outlet in the front side of the barrel, the needle chamber having a front open side connected to the outlet and a rear open side extended through the rear side of the barrel, the medicine chamber having a closed front side and a rear open side extended to through the rear side of the barrel, a guide hole communicated between the medicine chamber and the needle chamber, a longitudinal sliding slot disposed in parallel to and in communication with the needle chamber, and a front retaining hole extended sideways from a front end of the longitudinal sliding slot; wherein the needle assembly is slidably mounted in the needle chamber such that when the handle is moved forwards along the longitudinal sliding slot and engaged into the front retaining hole, the needle assembly is locked in an extended position to hold the needle cannula outside said barrel and to keep the inlet in communication with the guide hole for enabling a liquid medicine or blood to pass through the medicine chamber, the guide hole, the inlet and the needle cannula. After the service of the safety hypodermic syringe, the handle is disengaged from the front retaining hole and then moved along the longitudinal sliding slot needle in the reversed direction to receive the needle assembly safely inside the needle chamber. 
     Other objects, advantages, and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an elevational view of a dual-chamber safety hypodermis syringe according to the preferred embodiment of the present invention. 
     FIG. 2 is an exploded view of the dual-chamber safety hypodermic syringe according to the preferred embodiment of the present invention. 
     FIG. 3 is a longitudinal view in section of the present invention showing the needle assembly received inside the needle chamber of the barrel. 
     FIG. 4 is a longitudinal view in section of the present invention showing the needle cannula extended out of the outlet of the cover of the barrel. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 is an elevational view of the preferred embodiment of the present invention, showing a needle assembly  1  installed in a barrel  2 . 
     FIG. 2 is an exploded view of the preferred embodiment of the present invention. The needle assembly  1  is comprised of a needle cannula  11  and a needle hub  12  holding the needle cannula  11 . The needle hub  12  is a cylindrical member that is attached to a neck  121  and an inlet  122  on the neck  121  is in communication with the inside space of the needle cannula  11 . Two O-rings  123  and  124  are respectively mounted around the periphery in front of an behind the neck  121  and adapted to prevent leakage of liquid medicine or blood, and a handle  125  is perpendicularly extended from a peripheral surface of the needle hub  12 . 
     The barrel  2  comprises a hollow cylindrical body  201 , a cover  202  covered on the front side of the body  201 , and an O-ring  203  sealed between the outside wall of the body  201  and the inside wall of the cover  202 . The cover  202  comprises an axially extended outlet  221  in its front side, a positioning block  205  disposed on the inside, and an inwardly extended bottom coupling flange  207 . The body  201  comprises an axially extended medicine chamber  21 , an axially extended needle chamber  22 , a top positioning notch  204 , and an outside coupling flange  206  disposed around the periphery adjacent to the top positioning notch  204 . By means of forcing the coupling means, i.e. coupling flange  207  of the cover  202  into engagement with the coupling flange  206  of the body  201 , the body  201  and the cover  202  are coupled together. Further, when covering the cover  202  on the front side of body  201 , the positioning block  205  is engaged into the positioning notch  204  to hold the cover  202  in position, keeping the outlet  221  in alignment with the needle chamber  22 . As an alternate form of the present invention, the cover  202  can be fastened to the body  201  by a heat-sealing or bonding procedure. The cover  202  can also be formed integral with the body  201 . 
     The medicine chamber  21  is adapted to hold liquid medicine or to collect blood from the patient. The cover  202  blocks the closed front side of the medicine chamber  21 . The rear open side of the medicine chamber  21  is an open end into which a plunger  3  is inserted. According to the present preferred embodiment, the medicine chamber  21  has a circular cross section. Alternatively, the medicine chamber  21  can be made having an oval, heart-like or polygonal cross section. The needle chamber  22  is adapted to receive the needle assembly  1 , having a front open side axially connected to the outlet  221  of the cover  202  and a rear open side fixedly sealed with a plug  226 . Spring means  225  is connected between the plug  226  and the needle assembly  1 , and adapted to hold the needle assembly  1  normally inside the needle chamber  22 . The spring means  225  can be a tensile spring, a rubber rod, an elastic band, or any equivalent elastic material. The body  201  further comprises a longitudinal sliding slot  222  axially forwardly extended from the rear end and disposed in parallel to and in communication with the needle chamber  22 , and a retaining hole, namely, the first retaining hole  223  extended sideways from the front end of the longitudinal sliding slot  222  and adapted to hold the needle assembly  1  in the extended position. After installation of the needle assembly  1  in the needle chamber  22 , the handle  125  extends through the longitudinal sliding slot  222  to the outside of the body  201 . 
     Referring to FIG. 3, the medicine chamber  21  and the needle chamber  22  are separated chambers that communicate with each other through a guide hole  23 , which is disposed in the border area between the front side of the medicine chamber  21  of the body  201  and the cover  202 . The design of the guide hole  23  enables the body  201  to be easily removed from the injection mold. 
     Referring to FIG. 3 again, when not in use, the spring means  225  imparts a downward pressure to the needle assembly  1 , keeping the needle assembly  1  received inside the needle chamber  22 . The body  201  further comprises a second retaining hole  224  extended sideways from a middle part of the longitudinal sliding slot  222  and adapted to hold the needle assembly  1  positively in the received position inside the needle chamber  22 . By means of moving the handle  125  along the longitudinal sliding slot  222  to the elevation of the second retaining hole  224  and then turning the handle  125  sideways into the second retaining hole  224 , the needle assembly  1  is locked in the received position inside the needle chamber  22 . Alternatively, the handle  125  can be slided sideways into another tight second retaining hole to hold the needle assembly  1  tightly in its received position, the aforesaid spring means  225  and plug  226  can be eliminated. 
     Referring to FIG. 4, when in use, the handle  125  is disengaged from the second retaining hole  224  and moved forwards along the longitudinal sliding slot  222  to extend the needle cannula  11  out of the outlet  221  of the cover  202 , and then the handle  125  is turned sideways and engaged into the first retaining hole  223  at the top end of the longitudinal sliding slot  222  to lock the needle assembly  1  in the extended (operative) position. At this time, the neck  121  of the needle hub  12  is aimed at the guide hole  23 , keeping the inlet  122  in communication with the medicine chamber  21 , and therefore liquid medicine is squeezed out through the medicine chamber  21 ,the guide hole  23 , the neck  121 , the inlet  122  and the needle cannula  11  when pushing the plunger  3  forwards. 
     After the service of the hypodermic syringe, the handle  125  is turned sideways from the first retaining hole  223  into the longitudinal sliding slot  222 , and then moved downwards along the longitudinal sliding slot  222  to receive the needle assembly  1  inside the needle chamber  22 , and then engaged into the second retaining hole  224  to lock the needle assembly  1  safely in the received (non-operative) position as shown in FIG.  3 . 
     Because the plunger  3  is received in the medicine chamber  21 , it can be pushed first to the front limit position in close contact with the inside wall of the cover  202  (no gap is left in front of the plunger inside the barrel). Therefore, the hypodermic syringe can be used to draw blood from the patient when pulling the plunger  3  backwards, and no special packing material is needed to pack the hypodermic syringe, which reduces package cost. 
     Although the present invention has been explained in relation to its preferred embodiment, it is to be understood that many other possible modifications and variations can be made without departing from the spirit and scope of the invention as hereinafter claimed.