Abstract:
A device is provided to protect the hypodermic needlepoint of a syringe from being dulled as it penetrates through the stopple of a fluid vial for the purpose of filling the syringe with fluid from the vial. Specifically, the device includes a blunt needle that covers the hypodermic needle and that interacts with the syringe to establish relative friction forces between them. Importantly, this friction force is less than the friction force subsequently established between the dull needle and the stopple. Thus, after the hypodermic syringe has been filled, and is withdrawn from the fluid vial, the stronger friction force between the stopple and the dull needle causes the dull needle to remain with the stopple as the hypodermic syringe is removed from the fluid vial.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention pertains generally to hypodermic syringes. More particularly, the present invention pertains to methods and devices for protecting the distal tip of a hypodermic needle from being dulled when it is used to penetrate the stopple of a fluid vial for the purpose of filling the syringe with fluid from the vial. The present invention is particularly, but not exclusively, useful as a method and device for employing static friction forces that will hold a protective cover (i.e. blunt needle) over the distal end of a hypodermic needle until after the hypodermic syringe has been filled with fluid from a fluid vial. 
       BACKGROUND OF THE INVENTION 
       [0002]    As is well known, fluid transfer systems or devices can be employed in many different procedures and applications, and for many different reasons. Perhaps one of the most well known applications requiring the transfer of a fluid from one container to another involves the filling of a hypodermic syringe with a fluid medicament. Although pre-filled syringes and disposable pre-filled fluid cartridges are often used, they do not satisfy all needs. There are still many applications wherein it is necessary, or desirable, to fill an empty or partially filled syringe with a fluid that is taken directly from a fluid vial. 
         [0003]    Heretofore, the filling of a hypodermic syringe (or other similar device) with fluid medicament from a fluid vial has been done in a rather straightforward manner. Specifically, to perform such a task, the needle of the hypodermic syringe is inserted through the stopple of a medical fluid vial. The plunger of the syringe is then pulled back to transfer a desired amount of fluid from the vial into the fluid chamber of the syringe. Once this has been done, the hypodermic needle is then withdrawn from the stopple of the fluid vial and the hypodermic syringe is ready to be used. 
         [0004]    Although the general procedure set forth above is simple and straightforward, there are still some drawbacks. For instance, it happens that during the insertion of a hypodermic needle into the stopple of a fluid vial, the needlepoint of the hypodermic needle can become significantly dulled. This, obviously, has an adverse effect on any subsequent use of the syringe for injecting fluid medicament into a patient. 
         [0005]    In light of the above, it is an object of the present invention to provide a device for protecting the needlepoint of a needle of a hypodermic syringe from being dulled when it is used during a procedure to fill the syringe with fluid medicament from a fluid vial. Another object of the present invention is to provide a protective device for the needlepoint of a needle of a hypodermic syringe that is easily and automatically removed from the needle without requiring any additional manipulation, during a syringe filling procedure. Yet another object of the present invention is to provide a device for protecting the needlepoint of a hypodermic needle that is easy to use, is simple to manufacture, and is cost effective. 
       SUMMARY OF THE INVENTION 
       [0006]    In accordance with the present invention, a device is provided for protecting the needlepoint of a hypodermic needle as it (i.e. the needlepoint) is inserted through the stopple of a fluid medicament vial. Specifically, the device of the present invention includes a blunt needle that fits over the needlepoint at the distal end of the hypodermic needle. Importantly, the blunt needle is held on the hypodermic needle by only static friction forces until it (i.e. the blunt needle) is no longer needed. 
         [0007]    For one embodiment of the present invention, the device includes a shrink wrap that is used to hold the blunt needle on the hypodermic needle. For this embodiment, the hypodermic needle is formed with an abutment that is located at a proximal distance “d” from the needlepoint. Importantly, relative to the hypodermic needle, the blunt needle has a length “l” that is greater than the distance “d” (l&gt;d). Further, the blunt needle is formed with a lumen that is dimensioned for receiving the distal needlepoint of the hypodermic needle. Thus, the blunt needle can be advanced over the hypodermic needle until its proximal end urges against the abutment on the hypodermic needle. In this combination, the needlepoint of the blunt needle extends distally beyond the distal needlepoint of the hypodermic needle by approximately one eighth of an inch. 
         [0008]    As indicated above, this first embodiment of the present invention also includes a shrink wrap. Specifically, part of the shrink wrap is positioned over the abutment and a portion of the hypodermic needle. The rest of the shrink wrap is then used to extend over the proximal end of the blunt needle. The purpose here is to have the shrink wrap hold the blunt needle on the hypodermic needle until it is to be removed, as described below. Importantly, with this combination, a static friction force “f 2 ” is established between the shrink wrap and the blunt needle. Also, a static friction force “f 3 ” is established between the shrink wrap and the hypodermic needle. An important aspect of the present invention is that “f 3 ” is a predetermined static friction force, and is much less than the static friction force “f 2 ” (f 3 &lt;&lt;f 2 ). 
         [0009]    For an alternate embodiment of the present invention, the hypodermic syringe body is formed with an annular recess that surrounds the proximal end of the hypodermic needle. This recess will be characterized by having an inner diameter (i.d.) while, on the other hand, the blunt needle has an outer diameter (o.d.). For this embodiment, the o.d. of the blunt needle and the i.d. of the recess are relatively dimensioned to establish an interference fit between them when the proximal end of the blunt needle is received into the recess of the syringe. As intended for the present invention this interference fit establishes a predetermined static friction force between the blunt needle and the syringe. 
         [0010]    For the operation of the present invention, it is envisioned that the hypodermic syringe is to be filled with fluid from a fluid vial. To do this, because the fluid vial will typically include a stopple, the stopple needs to be penetrated by a sharp object, such as the needlepoint of the syringe. For the present invention, this penetration is to be accomplished by the blunt needle, while it is in position over the hypodermic needle. The purpose here is two-fold. For one, with this penetration, fluid communication is established between the vial and the syringe for filling the fluid chamber of said syringe. For another, a static friction force “f 1 ” is established between the blunt needle and the stopple. As required for the present invention, this static friction force “f 1 ” needs to be much greater than the predetermined static friction force established between the blunt needle and the syringe. Consequently, after the syringe has been filled, and after the hypodermic needle and syringe have been withdrawn from the fluid vial, the blunt needle will remain held by the stopple. The syringe can then be operationally used. 
         [0011]    In operation, the blunt needle, while it is in place over the hypodermic needle, is inserted through the stopple of a fluid medicament vial. Importantly, this penetration of the stopple establishes a static friction “f 1 ” between the blunt needle and the stopple. For the shrink wrap embodiment of the present invention the static friction force “f 1 ” is comparable to the static friction force “f 2 ” between the shrink wrap and the blunt needle. On the other hand, a predetermined static friction force “f 3 ” is established between the shrink wrap and the hypodermic needle that is much less than either “f 1 ” or “f 2 ” (f 1 ≅f 2 &gt;&gt;f 3 ). On the other hand, for the alternate embodiment of the present invention (i.e. no shrink wrap), it is only important that the static friction force “f 1 ” be greater than the predetermined static friction force that is generated by the interference fit between the blunt needle and the syringe body. In all embodiments, both the hypodermic needle and the blunt needle are preferably made of a stainless steel, the stopple is made of an elastomeric material, and the shrink wrap is made of a polymer well known in the pertinent art. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The novel features of this invention, as well as the invention itself, both as to its structure and its operation, will be best understood from the accompanying drawings, taken in conjunction with the accompanying description, in which similar reference characters refer to similar parts, and in which: 
           [0013]      FIG. 1  is an exploded perspective view of a device in accordance with the present invention; 
           [0014]      FIG. 2  is a perspective view of the combination of a blunt needle engaged with a hypodermic needle in accordance with an embodiment of the present invention; 
           [0015]      FIG. 3  is a cross-section view of the combination as seen along the line  3 - 3  in  FIG. 2 ; 
           [0016]      FIG. 4  is a cross-section view of the combination of a blunt needle engaged with a hypodermic syringe as seen along the line  4 - 4  in  FIG. 1 ; 
           [0017]      FIG. 5  is a perspective view of a hypodermic syringe engaged with a fluid vial during a filling of the hypodermic syringe; and 
           [0018]      FIG. 6  is an elevation cross-sectional view of a fluid vial with a penetrating blunt needle after the blunt needle has been used for filling a hypodermic syringe. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0019]    A device for filling a hypodermic syringe with a fluid medicament is shown in  FIG. 1  and is generally designated  10 . In  FIG. 1  it will be seen that the device  10  includes a hypodermic syringe  12  and a blunt needle  14 . For purposes of the present invention, the hypodermic syringe  12  that is shown is only exemplary. Accordingly, as will be appreciated by the skilled artisan, any device that is functionally similar to the hypodermic syringe  12  can be used. In general, such a device  10  will include a syringe body  16  that is formed with a fluid chamber  18 . Also, there will be a plunger  20  that is mounted on the syringe body  16  for advancement into the fluid chamber  18  to expel fluid from the chamber  18  through a hypodermic needle  22 . As shown, the hypodermic needle  22  will typically have a distal needlepoint  24  and a proximal end  26  that is mounted on the syringe body  16  for fluid communication with the fluid chamber  18 . 
         [0020]    Referring now to  FIG. 2 , the salient aspects of a preferred embodiment for the present invention are shown. In  FIG. 2  it will be seen that this embodiment for the present invention includes a shrink wrap  28  that interconnects with both the blunt needle  14  and the hypodermic needle  22 . In further detail, and as perhaps best seen in  FIG. 3 , the blunt needle  14  is formed with a lumen  30 . Also, the hypodermic needle  22  is formed with an abutment  32  that is located at a distance “d” proximal from the distal needlepoint  24  of the hypodermic needle  22 . As intended for the present invention, with this structure the hypodermic needle  22  is advanced into the lumen  30  of the blunt needle  14  until its abutment  32  comes in contact with the proximal end  34  of the blunt needle  14 . The distal needlepoint  24  of the hypodermic needle  22  will then be located inside the lumen  30  of the blunt needle  14 . It will also be positioned at a distance “d p ” proximal to the distal needlepoint  36  of the blunt needle  14 . For purposes of the present invention, the distance “d p ” will preferably be about one eighth of an inch. The shrink wrap  28  is then used to hold the blunt needle  14  on the hypodermic needle  22 . 
         [0021]    Still referring to  FIG. 3 , it will be seen that approximately two thirds (⅔) of the shrink wrap  28  covers a length “l” along the portion of the blunt needle  14  at its proximal end  34 . The remaining one third (⅓) of the shrink wrap  28  covers the abutment  32 , as well as a portion of the hypodermic needle  22  along a length “l e ” (i.e. l≅2l e ). Further, it is shown that the outer diameter of the blunt needle  14  (o.d.) is greater than the outer diameter of the hypodermic needle  22  (o.d. h ). The consequence of these dimensional distinctions is manifested in the resultant static friction forces that are developed between the various components. Specifically, due to the greater area of contact between the shrink wrap  28  and the blunt needle  14 , a static friction force “f 2 ” is established at their interface  38  that is much greater than the static friction force “f 3 ” that is established at the interface  40  between the shrink wrap  28  and the hypodermic needle  22 . In addition to holding the blunt needle  14  on the hypodermic needle  22 , the present invention envisions that the shrink wrap  28  will also create a fluid seal that will prevent fluid from leaking between the hypodermic needle  22  and the blunt needle  14 . 
         [0022]    Referring now to  FIG. 4 , an alternate preferred embodiment for the device  10  of the present invention is shown that relies on a direct contact between the blunt needle  14  and the syringe body  16 . Specifically, for this embodiment, the syringe body  16  includes a circular wall  42  that creates an annular recess  44  on the syringe body  16  that is characterized by an inner diameter (i.d.). With this structure, the proximal end  26  of hypodermic needle  22  is affixed to the syringe body  16  to extend distally through the annular recess  44 , and beyond. Similar to the preferred embodiment disclosed above, for the alternate preferred embodiment, the hypodermic needle  22  is also inserted into the lumen  30  of the blunt needle  14 . This time, however, the proximal end  34  of the blunt needle  14  becomes inserted into the annular recess  44  that is formed on the syringe body  16 . With this in mind, the inner diameter (i.d.) of the annular recess  44  is dimensioned relative to the o.d. of the blunt needle  14  to allow for this insertion. Moreover, the selected dimensions also establish an interference fit between the recess  44  and the needle  14  that is characterized by a static friction force “f 4 ”. Also, and again similar to the other preferred embodiment disclosed above, when engaged with each other, the distal needlepoint  24  is positioned inside the lumen  30  of the blunt needle  14 , and it is located at a proximal distance “d p ” from the distal needlepoint  36  of the blunt needle  14 . 
         [0023]    As envisioned for the present invention, both the blunt needle  14  and the hypodermic needle  22  can be made of a stainless steel. Alternatively, the blunt needle  14  may be made of a plastic material, if desired. Also, it is envisioned for the present invention that the shrink wrap  28  can be made of any type material well known in the pertinent art that has a shrink ratio of approximately 2:1. 
         [0024]    In operation, the hypodermic syringe  12  is provided, with the blunt needle  14  that is attached thereto as disclosed above. The blunt needle  14  is then inserted into a fluid vial  46 , as shown in  FIG. 5 , for the purpose of filling the fluid chamber  18  of the syringe  12  with a fluid (e.g. a fluid medicament). For this task, it is necessary that the blunt needle  14  penetrate through a stopple  48  on the fluid vial  46  (see  FIG. 6 ). The necessary force to do this is transferred from the syringe body  16  to the proximal end  34  of the blunt needle  14  as it urges against the abutment  32  (preferred embodiment), or against the syringe body  16  itself (alternate preferred embodiment). Importantly, once the blunt needle  14  has penetrated the stopple  48 , a static friction force “f 1 ” is established between the blunt needle  14  and the stopple  48 . 
         [0025]    It is an important operational aspect of the present invention that all of the static friction forces established during the manufacture of the device  10  have a predetermined relationship to each other. Specifically, for the preferred embodiment (i.e. wherein the shrink wrap  28  is employed) it is important that the static friction force “f 1 ” established between the blunt needle  14  and the stopple  48  be much greater than the static friction force “f 3 ” that is established between the shrink wrap  28  and the hypodermic needle  22  (f 1 &gt;&gt;f 3 ). As disclosed above for this embodiment, the static friction force “f 2 ” that is established between the shrink wrap  28  and the blunt needle  14  is also much greater than the friction force “f 3 ”. Further, in their general relationship to each other, “f 1 ” is preferably about equal to “f 2 ” and thus: f 1 ≅f 2 &gt;&gt;f 3 . For the alternate preferred embodiment of the device  10 , it is important that the static friction force “f 1 ” established between the blunt needle  14  and the stopple  48  be much greater than the static friction force “f 4 ” that is established between the proximal end  34  of the blunt needle  14  and the annular recess  44  of the syringe body  16  (f 1 &gt;&gt;f 4 ). 
         [0026]    With the above in mind, after the blunt needle  14  has penetrated the stopple  48  and the hypodermic syringe  12  has been filled with fluid from the fluid vial  46 , the hypodermic syringe  12  is withdrawn from the vial  46 . Due to the significant differences in the respective static friction forces that are involved, the blunt needle  14  will remain stuck in the stopple  48  under the influence of the relatively large static friction force “f 1 ” (see  FIG. 6 ). On the other hand, because “f 3 ” is the smallest friction force involved in the preferred embodiment (i.e. with shrink wrap  28 ) the hypodermic needle  22  of the hypodermic syringe  12  will be removed from the blunt needle  14 . In this case the shrink wrap  28  will remain with the blunt needle  14  (see  FIG. 6 ). Recall, f 2 &gt;&gt;f 3 . Further, the shrink wrap  28  that remains with the blunt needle  14  may help prevent subsequent fluid leakage from the vial  46 . For the alternate preferred embodiment, because the “f 4 ” is less than “f 1 ”, the hypodermic syringe  12  will also be removed from the blunt needle  14 . 
         [0027]    For both embodiments of the present invention, the friction force “f 3 ” (preferred embodiment) and the friction force “f 4 ” (alternate preferred embodiment) are specifically designed and engineered. In detail, they are designed and engineered to establish predetermined static friction forces between the hypodermic syringe  12  and the blunt needle  14  that will be overcome by any static friction force that may result from the penetration of the dull needle  14  into the stopple  48 . 
         [0028]    While the particular Hypodermic Needle Tip Protector, as herein shown and disclosed in detail is fully capable of obtaining the objects and providing the advantages herein before stated, it is to be understood that it is merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended to the details of construction or design herein shown other than as described in the appended claims.