Abstract:
A syringe stopper for use in a syringe having a substantially cylindrical syringe barrel and a piston-like plunger rod for sliding inside the syringe barrel in a fluid-tight engagement. A malleable stopper is located on a distal end of the plunger rod and protrudes outwardly therefrom. The malleable stopper changes shape in response to a pressure applied thereon.

Description:
RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/477,739 filed Apr. 21, 2011, which is incorporated herein by reference in its entirety. 
     
    
     FIELD OF INVENTION 
       [0002]    The present invention relates to syringes and syringe stoppers, and more particularly to a malleable syringe stopper which helps provide for a more complete expulsion of the contents of the syringe at the time of drug delivery. 
       BACKGROUND OF THE INVENTION 
       [0003]    Hypodermic syringes include an elongate barrel having opposed proximal and distal ends and a chamber therebetween for receiving a fluid. A passageway extends through the distal end of the syringe barrel and communicates with the chamber. The distal end of the syringe barrel is connected to a needle cannula for delivering fluid from the chamber and passageway. The proximal end of the syringe barrel slidably receives a plunger rod and stopper assembly, such that force applied to the plunger rod urges the stopper along the barrel to drive liquid from the chamber through the needle cannula. 
         [0004]    A problem with some prior art hypodermic syringes involves the amount of liquid which can remain in the barrel after the stopper is advanced the full length of the barrel during the injection process. There remains in every syringe a certain residual volume, no matter how small, which is trapped between the end of the stopper and the needle tip, including the volume of the needle cannula and the volume of the extreme distal end of the syringe barrel. For very expensive liquid medications and medications which require very precise dose delivery it may be necessary to overfill the barrel for the amount of the dead space so that the dose delivered will be the dose desired and the additional medication will be disposed of with the used syringe. Over many of syringes the amount of unused medication can become substantial. 
         [0005]    One way to minimize dead space is to carefully control the dimensions of the inside of the syringe barrel and to conform the distal end of the stopper as closely as possible to the syringe barrel dimensions. This solution is not a complete answer because, especially in the case of glass syringe barrels, the interior shape of the barrel, as it transitions between the bore of the chamber to the needle holding tip cannot be as precisely controlled as an injection molded plastic barrel. Further, when the angle of the stopper tip is designed to conform with the interior angle of the barrel, variations in dimensions experienced in the manufacturing process can result in angular variations between the surfaces of the stopper and the barrel interior wherein the distal portion of the stopper is capable of occluding the passageway at the distal end of the barrel and trapping fluid in the barrel behind the distal end of the stopper. 
         [0006]    Accordingly, the claimed invention proceeds upon the desirability of providing a syringe stopper, preferably a malleable syringe stopper, which minimizes dead space to assure that liquid medication is not trapped in the barrel when the stopper occludes or blocks off the exit passageway in the barrel. 
       SUMMARY OF THE INVENTION 
       [0007]    Therefore, an object of the claimed invention is to provide a malleable (or shape changing) syringe stopper which minimizes any dead space when the syringe stopper is at the fully advanced position to maximize the expulsion of the liquid medication from the syringe barrel. 
         [0008]    Another object of the claimed invention is to provide aforesaid syringe stopper which extends to the syringe tip. 
         [0009]    The syringe stopper of the claimed invention, for use in a syringe barrel having a substantially cylindrical body, comprises a piston-like stopper body for slidable fluid-tight engagement inside the barrel of the syringe. The body includes a distal end, a proximal end and a longitudinal axis therethrough. A distally directed, generally conically-shaped malleable protrusion is provided on the distal end of the stopper body. The conically-shaped protrusion is malleable to fill-up any dead space in the syringe barrel, including the syringe tip, when the stopper body is at the distal end of the barrel (or at the fully advanced position) to assure that liquid mediation is not trapped in the syringe barrel. 
         [0010]    The stopper can be combined with a syringe barrel having an open proximal end, a distal end and a cylindrical body portion therebetween which defines a chamber for retaining liquid. The stopper, in the combination, is positioned in fluid-tight engagement inside the barrel so the distal end of the stopper faces the distal end of the barrel. The distal end of the barrel includes an aperture therethrough in fluid communication with the chamber. In some applications, the proximal end of the stopper may be connected to the distal end of a rigid elongate plunger rod. 
         [0011]    Various other objects, advantages, and features of the claimed invention will become readily apparent from the ensuing detailed description, and the novel features will be particularly pointed out in the appended claims 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The following detailed description, given by way of example, and not intended to limit the claimed invention solely thereto, will best be understood in conjunction with the accompanying drawings in which: 
           [0013]      FIG. 1  is a side partial cross-sectional view of a syringe assembly utilizing the stopper in accordance with an exemplary embodiment of the claimed invention; and 
           [0014]      FIG. 2  is an enlarged partial cross-sectional view of the syringe of  FIG. 1  showing the stopper in a fully advanced position expelling the last portion of the medication. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    The term “distal end” as used herein is intended to refer to the end of the syringe is closer to the syringe needle and the term “proximal end” is intended to refer to the end of the syringe closer to the holder of the syringe. 
         [0016]    Turning now to  FIGS. 1-2 , the malleable (i.e., shape changing) syringe stopper  100  of the claimed invention for use in a syringe barrel  200  has a substantially cylindrical body. The syringe stopper  100  comprises a piston-like stopper body for slidable fluid-tight engagement inside the syringe barrel  200  of the syringe  1000 . The syringe stopper  100  comprises a distal end  110  close to the syringe tip  210  and a proximal end  120 . The syringe stopper  100  also comprises annular ribs  130  with a recess  140  therebetween. The annular ribs  130  are intended to provide a stable fluid-tight seal between the syringe stopper  100  and the syringe barrel  200 . 
         [0017]    In accordance with an exemplary embodiment of the claimed invention, a distally directed generally conically-shaped malleable protrusion  150  is located on the distal end  110  of the syringe stopper  100 . The syringe stopper  100  of the claimed invention can be used in any syringe assembly, as long as it is the last stopper. That is, the syringe stopper  100  of the claimed invention is the stopper which contacts the distal end  230  of the syringe barrel  200 , as shown in  FIG. 2 . It is appreciated the syringe stopper  100  can be a floating stopper which is not connected to a plunger rod  300 . For simplicity, the claimed malleable or shape changing stopper  100  will be discussed herein in the context of a single stopper syringe as depicted in  FIGS. 1-2 . The syringe assembly comprises a plunger rod  300  having a distal end  310  and a proximal end  320 . In accordance with an exemplary embodiment of the claimed invention, the distal end  310  of the plunger rod  300  is connected to syringe stopper  100  through the action of a threaded tip (not shown) on the distal end  310  of the plunger rod  300  which engages a threaded recess (not shown) in the syringe stopper  100 . It is appreciated that there are many ways to join the plunger rod  300  to the syringe stopper  100  and threaded engagement is one of many possibilities. In accordance with an aspect of the claimed invention, the syringe stopper  100  can include a cavity in the proximal end  120  of the syringe stopper  100  shaped to accept the distal end  310  of the plunger rod  300 . Preferably, the plunger rod  300  has an enlarged distal end  310  so that the syringe stopper  100  and the plunger rod  300  come together in a snap-fit arrangement. Alternatively, the syringe stopper  100  can be adhesively attached to the plunger rod  300 . In accordance with another aspect of the claimed invention, the plunger rod  300  and the syringe stopper  100  can be integrally molded wherein a soft thermoplastic elastomer, which is preferably malleable when cured, is injected into one end to form the syringe stopper  100  and a more rigid plastic is injected on the other end to form the plunger rod  300 . 
         [0018]    The syringe barrel  200  comprises an open proximal end  220 , distal end  230  and a cylindrical body portion  240  therebetween defining a chamber  250  for retaining liquid  400 , preferably liquid medication. The syringe barrel  200  can be made of glass, plastic or the like. As shown in  FIGS. 1-2 , the syringe stopper  100  is positioned in fluid-tight engagement inside the syringe barrel  200  through the action of annular ribs  130  with the distal end  110  of the syringe stopper  100  facing the distal end  230  of the syringe barrel  200 . The distal end  230  of the syringe barrel  200  includes a passageway  260  which is in fluid communication with chamber  250 . An elongate needle cannula  500  comprises a distal end  510 , a proximal end  201  and a bore therethrough. The proximal end  520  of the needle cannula  500  is connected, preferably removeably connected, to the distal end  230  of the syringe barrel  200  so that the bore of the needle cannula  500  is in fluid communication with the chamber  250  through the passageway  260 . It is appreciated that the needle cannula  500  can be permanently attached to the syringe barrel  200 , removably or frictionally attached to the syringe tip  210  of the syringe barrel  200 . 
         [0019]    In mass production, uniformity in the shape of the interior area  270  of the syringe barrel  200  at the distal end  230  may be difficult to control. The syringe stopper  100  of the claimed invention is made of durable and malleable material, e.g. natural rubber, synthetic rubber, high density polyethylene, neoprene, thermoplastic elastomers, silicone, latex and the like, to conform to any shape of the interior area  270  of the syringe barrel  200  to eliminate any dead space to expel the liquid  400  from the syringe barrel  200 , thereby minimizing the potential for liquid  400  being trapped in the syringe barrel  200 . As shown in  FIG. 2 , the claimed malleable stopper  100  changed its shape to occupy the dead space  280  of the syringe barrel  200 . Although the shape of the barrel interior area  270  may not be precisely uniform from syringe barrel  200  to syringe barrel  200 , the claimed malleable syringe stopper  100  can change its shape or contour to conform the non-uniform barrel interior area  270  of the syringes  1000 . In accordance with an aspect of the claimed invention, the claimed malleable stopper  100  expands to occupy any dead space  280  in the syringe barrel  200  including interior area  290  of the syringe tip  210 , thereby minimizing the potential for liquid  400  being trapped in the syringe tip  210  and the syringe barrel  200 . 
         [0020]    Various omissions, modifications, substitutions and changes in the forms and details of the device illustrated and in its operation can be made by those skilled in the art without departing in any way from the spirit of the present invention. Accordingly, the scope of the invention is not limited to the foregoing specification, but instead is given by the appended claims along with their full range of equivalents.