Abstract:
A retractable safety syringe includes a syringe barrel, a needle mount, a plunger rod and a needle. The needle mount includes a hollow truncated cone extending inward and upward with a completely surrounded lower conical portion. The hollow truncated cone includes a slit cutting from a ridge of the truncated cone. The plunger rod includes a rod and a plunger formed at one end of the rod. The plunger has a plunger crown and a detent connected to the plunger crown. The hollow truncated cone containing a slit allows the plunger rod&#39;s detent to latch on to the needle mount making the plunger rod and needle mount components become jointly retractable. Using the hollow truncated cone design augments the robustness factor of the needle retraction mechanism, using the slit increases its ease of use, while both hollow truncated cone and slit jointly minimize fluid loss.

Description:
BACKGROUND OF INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a disposable safety syringe, and more particularly, to a disposable safety syringe whose needle is retracted after injection to prevent reuse and needle stick injuries.  
         [0003]     2. Description of the Prior Art  
         [0004]     Due to the serious risk of contamination to various diseases by using infected needles, virtually all syringes in use nowadays are disposable. Furthermore, some of these also possess a retractable mechanism, which retracts the needle inside the syringe after use so that the person administering the injection is prevented from impaling himself and others with a potentially infected needle.  
         [0005]     Accordingly, the needle retraction mechanism is considered an especially critical component. Issues such as minimizing the quantity of medicinal fluid being trapped inside the syringe after needle retraction, the amount of pressure required to engage the hooking mechanism and the robustness of the hooking mechanism itself are essential to the creation of an excellent needle retraction mechanism.  
         [0006]     Please refer to  FIG. 1 , where all the essential components of a retractable safety syringe  150  are illustrated. First, a needle  100  comprises of a needle seat  102  that connects to a needle cannula  104 . Secondly, a syringe barrel  110  comprises at a lower end a winged handle  112 , and at an upper end, a socket  108 , containing a cavity  106 . Thirdly, a needle mount  114  comprises at an upper end a needle holder  116  and at a lower end, assembled on the inside walls of the needle mount  114 , a clamp  118  and a clamp  118 ′. The clamps  118  and  118 ′ are positioned symmetrically with respect to each other. Finally, a plunger rod  134  comprises at an upper end a hooking mechanism  120 , which is made up of a stem  124  that terminates in a detent  122 . The hooking mechanism  120  is connected to a crown  126 , which is the terminating upper layer of a plunger  128 . The plunger  128  is further connected to a rod  130 , which terminates at a lower end with a thumb press  132 .  
         [0007]     Please refer to  FIG. 2 .  FIG. 2  is a magnified view of the needle mount  114  shown in  FIG. 1 . In addition to the needle holder  116  and the clamps  118  and  118 ′, the needle mount  114  comprises a plug section  200 , which allows the needle mount to be attached at assembly time air tightly inside the syringe barrel  110 , and a pulling member  202 , which is the lower part of the needle mount  114  containing the clamps  118  and  118 ′.  
         [0008]     Note that the hooking mechanism&#39;s  120  detent  122  and stem  124 , the pulling member  202  and the clamps  118  and  118 ′ constitute the needle retraction mechanism.  
         [0009]     The needle retraction mechanism becomes engaged when the plunger rod is fully inserted inside the syringe barrel by additional pressure on the thumb press, so that the hooking mechanism goes passed the clamps and the detent latches on to them.  
         [0010]     This type of needle retraction mechanism, which uses the two clamps  118  and  118 ′, has two serious shortcomings. First of all, the clamps  118  and  118 ′ are protruding components that are latched on to the wall of pulling member  202 . As such, they are not sufficiently robust and can, henceforth, as protrusions can generally break easily. Secondly, using the hooking mechanism  120 , as suggested by prior art, does not minimize the loss of medicinal fluid. While it is true that the space between the clamps  118  and  118 ′ allows the free passage of fluid, this does not prevent fluid to be caught that between the detent  122  and plunger crown  126  after the detent  122  has latched on to the clamps  118  and  118 ′, as the hooking mechanism  120  does not have the ability expel fluid trapped between itself and the crown  126 .  
         [0011]     Please refer to  FIG. 3  where all the essential components of another retractable safety syringe  350  are illustrated. First, a needle  300  is illustrated. Secondly, a syringe barrel  304  comprises at an upper end a retaining edge  302 , and at a lower end, a winged handle  306 . Thirdly, a needle mount  310  comprises an inner hub  308 , a retaining groove  312  and a ring  314 , which is fastened inside the needle mount  310 . The needle mount  310  is air tightly installed inside the syringe barrel  304 , at its upper end, so that the syringe barrel&#39;s  304  retaining edge  302  retains the needle mount&#39;s  310  retaining groove  312 . Finally, a plunger rod  328  comprises at an upper end a hooking mechanism  320 , which is made up of a stem  318  that terminates in a detent  316 . The hooking mechanism  320  is connected to a crown  322 , which is the terminating upper layer of a plunger  324 . The plunger  324  is further connected to a rod  326 , which terminates at a lower end with a thumb press  340 . Note that the hooking mechanism&#39;s  320  detent  316  and stem  318 , plus the ring  314  constitute the needle retraction mechanism.  
         [0012]     Please refer to  FIG. 4 .  FIG. 4  is a magnified view of the needle mount&#39;s  310  ring  314 , shown in  FIG. 3 . The ring  314  comprises a ring face  402  and a central hollow  400  in the middle of the ring  314 .  
         [0013]     This kind of hooking mechanism has its own drawbacks, which are as follows. First of all, in order for the detent  316  to go through the central hollow  400 , an unreasonable amount of pressure is required to push the plunger. Consequently, it is probable that the individual administering the injection does not have the sufficient strength to generate sufficient pressure on the thumb press in order to get the detent through the central hollow  400  of the ring  314 . Furthermore, the large force applied on the plunger will cause the syringe and the needle to shake while the needle is still in the patient, which is dangerous and uncomfortable for the patient.  
         [0014]     Another disadvantage of the prior art is that this type of hooking mechanism does not minimize fluid loss to the maximum extent possible. As the detent  316  latches on to the ring  314 , some fluid becomes trapped below the face  402  of the ring  314 , between the face  402  and the plunger crown  322 . This occurs due to the fact that the neck  318  acts as an obstacle that prevents the face  402  of the ring  314  from touching the crown  322 , hence creating an area that will be filled with fluid even after the hooking mechanism has been engaged.  
       SUMMARY OF INVENTION  
       [0015]     It is therefore a primary objective of the claimed invention to provide a disposable retractable safety syringe that solves the above-mentioned problems of the prior art.  
         [0016]     According to the claimed invention, a retractable safety syringe comprises a syringe barrel, a needle mount, a plunger rod and a needle. The needle mount is assembled at an upper end of the syringe barrel and formed with an inner hub, and a hollow truncated cone extending inward and upward with a completely surrounded lower conical portion. The hollow truncated cone includes a slit cutting from a ridge of the truncated cone. The plunger rod includes a rod and a plunger formed at one end of the rod. The plunger has a plunger crown and a detent connected to the plunger crown. The needle includes a needle cannula coupled to an upper portion of the inner hub.  
         [0017]     These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
     
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0018]      FIG. 1  is an exploded perspective view of a prior art retractable safety syringe.  
         [0019]      FIG. 2  is a perspective view of the needle mount of the prior art retractable safety syringe in  FIG. 1 .  
         [0020]      FIG. 3  is an exploded perspective view of another prior art retractable safety syringe.  
         [0021]      FIG. 4  is a perspective view of the needle mount&#39;s connection ring of the retractable safety syringe in  FIG. 3 .  
         [0022]      FIG. 5  is an exploded perspective view of a first retractable safety syringe according to the current invention.  
         [0023]      FIG. 6  is a perspective view of the needle mount of the retractable safety syringe in  FIG. 5 .  
         [0024]      FIG. 7  is a perspective view of the plunger rod of the retractable safety syringe in  FIG. 5 .  
         [0025]      FIG. 8  is an exploded perspective view of a second retractable safety syringe according to the current invention.  
         [0026]      FIG. 9  is a perspective view of the plunger rod of the retractable safety syringe in  FIG. 8 .  
         [0027]      FIG. 10  is a schematic operation view of the retractable safety syringe in  FIG. 5  before the hooking mechanism is engaged.  
         [0028]      FIG. 11  is a schematic operation view of the retractable safety syringe in  FIG. 5  after the hooking mechanism is engaged.  
         [0029]      FIG. 12  is a schematic operation view of the retractable safety syringe in  FIG. 5  after the retraction of the needle mount has commenced.  
         [0030]      FIG. 13  is a perspective view of another needle mount of the retractable safety syringe in  FIG. 5 . 
     
    
     DETAILED DESCRIPTION  
       [0031]     Please refer to  FIG. 5  in conjunction with  FIG. 6  and  FIG. 7 , for a first embodiment of a disposable retractable safety syringe  550  according to the present invention. First, the retractable safety syringe  550  comprises a needle  500 , which includes a cannula  501  that is connected to an upper portion of an inner hub  508 . It is possible for the cannula  501  to be coupled to the upper portion of the inner hub  508  via a needle base  503 . Secondly, a syringe barrel  504  comprises at an upper end a retaining edge  502 , and at a lower end, a winged handle  506 . The syringe barrel  504  also comprises on its interior a stopper  505 , which is used to allow a plunger rod  528  to be inserted into the syringe barrel  504  and prevents a needle mount  510  from being removed from the syringe barrel  504 . The stopper  505  could be in the form of a flange or a rim, continuously or discontinuously formed on the inside of the syringe barrel  504 .  
         [0032]     Subsequently, the needle mount  510  comprises the inner hub  508 , an outer hub  509 , a fluid passage  507  and a retaining groove  512 . The needle mount  510  is air tightly installed inside the syringe barrel  504 , at its upper end, so that the syringe barrel&#39;s  504  retaining edge  502  retains the needle mount&#39;s  510  retaining groove  512 , preventing the needle mount  510  from coming out at the upper end of the syringe barrel  504 . It is to be noted that the outer hub  509  is an optional element, meaning that the retractable safety syringe  550  could be manufactured with or without an outer hub.  
         [0033]     As shown in  FIG. 6 , the needle mount  510  further comprises a hollow truncated cone  600 , which has its base attached to the inside of the needle mount  510  and could be made of an elastic material. The hollow truncated cone  600  includes at its upper opening a ridge  602 . Also forming at the hollow truncated cone&#39;s  600  upper opening there is a slit  604 . Although just one slit is disclosed in  FIGS. 5 and 6 , the hollow truncated cone  600  may contain more than one slit in this embodiment. This invention is not limited to only one slit.  
         [0034]     Furthermore, a plunger rod  528  comprises at an upper end a detent  520 , which is made up of a connector  518  that continues with a truncated cone-shaped neck  516 . The truncated cone-shaped neck  516  contains on its upper end a detent lip  515 . The detent  520  is connected to a crown  522 , which is the terminating upper layer of a plunger  524 . The plunger  524  contains on its upper end a color band  532  that serves for identification of the fluid level in the syringe barrel  504 . The plunger  524  is further connected to a rod  526 , which terminates at a lower end with a thumb press  540 . The rod  526  further comprises a V-notch  530  that facilitates the breaking of the rod  526  after use, for the purpose of recycling the rod  526  separately from the rest of the syringe and preventing the needle from being pushed out of the injecting end of the syringe barrel  504  after retraction.  
         [0035]     Note that the detent&#39;s  520  truncated cone-shaped neck  516 , detent lip  515 , connector  518 , plus the needle mount&#39;s  510  hollow truncated cone  600  constitute the needle retraction mechanism.  
         [0036]     Please refer to  FIG. 8  in conjunction with  FIG. 6  and  FIG. 9 , for a second embodiment of a disposable retractable safety syringe  850  according to the present invention. The retractable safety syringe  850  comprises a needle  500 , a syringe barrel  504 , a needle mount  510  and a plunger rod  830 . It is to be noted that the needle  500 , syringe barrel  504  and needle mount  510  are identical to the ones illustrated in  FIGS. 5 and 6 .  
         [0037]     The difference between the retractable safety syringes  850  and  550  is in the structure of the plunger rods  830  and  528 . The plunger rod  830  of the retractable safety syringe  850  comprises at an upper end a detent  820 , which is made up of a connector  816  and a detent lip  815 . The detent  820  is connected to a crown  522 , which is the terminating upper layer of a plunger  524 . The plunger  524  contains on its upper end a color band  532 . The plunger  524  is further connected to a rod  526 , which terminates at a lower end with a thumb press  540 . The rod  526  further comprises a V-notch  530 .  
         [0038]     Please refer to  FIG. 13  which illustrates another embodiment of a needle mount  130  of the retractable safety syringe  550 ,  850 . Please refer to  FIG. 13  in conjunction with  FIG. 5  and  FIG. 6  as an example.  
         [0039]     A needle mount  130  comprises an inner hub  140  and a retaining groove  144 . The inner hub  140  includes a fluid passage  138  and a hollow truncated cone  132 , which has its base attached to the inside of the inner hub  140 . The hollow truncated cone  132  includes at its upper opening a ridge  136 . Also forming at the hollow truncated cone&#39;s  132  upper opening there is one or more slits  134 .  
         [0040]     Please refer to  FIG. 10 ,  FIG. 11  and  FIG. 12  which are schematic operational views of the fully assembled retractable safety syringe at three points in time: before, at the exact time and after the syringe&#39;s hooking mechanism has been engaged. Please refer to these figures in conjunction with  FIGS. 5, 6  and  7 .  
         [0041]     First of all, in  FIG. 10  it can be seen that the rod  526  has not been fully inserted in the syringe barrel  504 , and hence the detent lip  515  have not yet latched onto the hollow truncated cone&#39;s  600  ridge  602 . The gray area of  FIG. 10  represents the area of the syringe that still contains medicinal fluid. Subsequently, in  FIG. 11 , the exact instance when the detent  520  is engaged is displayed. Here, the rod  526  is fully inserted in the syringe barrel  504 , and consequently, the detent lip  515  has penetrated past the ridge  602 , causing the plunger rod  830  and the needle mount  510  to ‘hook’. At this point, the downward movement of the plunger rod  830  would dislodge the needle mount  510 . It is to be noted that in  FIG. 11 , the gray area representing the fluid remaining in the syringe is smaller than in  FIG. 10  as engaging the hooking mechanism has caused almost all of the fluid in the syringe to be expelled. Finally,  FIG. 12  illustrates an instance when the needle mount  510  has been retracted from its original position in the upper end of the syringe barrel  504  and the needle  500  itself is inside the syringe barrel  504 . At this point, since the needle mount  510  is no longer air tightly attached to the syringe barrel  504 , any movement would cause plunger rod  830 , the needle mount  510  and hence the needle  500  to move in unison. Preventing the needle mount  510  to be drawn out of the syringe barrel  504  on its lower end is the stopper  505 , which stops the plunger  524  from going past it, and consequently the needle  500 , needle mount  510  and plunger rod  528  from exiting the syringe barrel  504  at the lower end. Furthermore, the combination of needle  500 , needle mount  510  and plunger rod  830  are prevented from exiting the syringe barrel  504  at its upper end by the retaining edge  502 .  
         [0042]     Minimizing the quantity of medicinal fluid being trapped inside the syringe after needle retraction and reducing the amount of pressure required to engage the hooking mechanism while increasing the robustness of the hooking mechanism are issues not adequately addressed by the prior art. However, the present invention manages to address and to solve many of these problems that were left unsolved in prior art retractable safety syringes.  
         [0043]     First of all, as it has been discussed above, the prior art has not been able to minimize the amount of the fluid trapped in the syringe to the same degree as the present invention. In the present invention, due to the shape of the detent, which hermetically hugs the inside of the hollow truncated cone as the hooking mechanism is engaged, the amount of little fluid being trapped is insignificant, since being only limited to small portions of the inner hub of the needle mount. However, in the prior art, fluid is also being caught between the plunger crown and the detent itself, making this aspect of the prior art inferior to the current invention.  
         [0044]     Also different from the prior art, the present invention is successful in maximizing the robustness of the hooking mechanism, while at the same time minimizing the pressure required to drive the detent lip past the hollow truncated cone&#39;s upper opening ridge.  
         [0045]     Robustness is primarily attained by using the hollow truncated cone, which unlike the prior art&#39;s clamps or ring, is inherently a sturdier shape that is capable to bear more pressure on its upper opening than a mechanism employing either a ring or clamps.  
         [0046]     Moreover, in the present invention, the pressure required to engage the hooking mechanism is not unreasonable, and fortunately, it does not come at the expense of robustness. To ensure that everybody can engage the syringe&#39;s hooking mechanism without undue effort and to prevent excessive movement of the needle while it is still inside the patients body, the present invention has procured the hollow truncated cone with a slit. The slit permits the upper opening of the hollow truncated cone to expand more readily than it would be possible if there was no slit and the detent lip would have had to force its way through a rigid upper opening of the hollow truncated cone.  
         [0047]     Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.