Abstract:
A process for creating a stop surface on a plunger rod of a syringe is disclosed. The process includes the step of providing a preformed or molded plunger rod, and the step of forming a radially-extending deformation on the molded plunger rod. The presently disclosed in-line process allows for the use of a single molding rod to form plunger rods having one or more selectively located stop positions.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application claims priority from U.S. provisional application Ser. No. 60/877,757, filed Dec. 29, 2006, the entirety of which is incorporated herein by reference. 

   BACKGROUND 
   1. Technical Field 
   The present disclosure relates to a process for creating a stop surface on a syringe. More specifically, the present disclosure relates to an in-line process for creating a stop surface on the plunger rod of a syringe. 
   2. Background of Related Art 
   Referring to  FIGS. 1 and 2 , standard syringes  10  typically include a syringe barrel  12 , a plunger rod  14  and a plunger tip  16  ( FIG. 2 ). A proximal end  12   a  of syringe barrel  12  defines a circular opening dimensioned to slidably receive plunger tip  16  and plunger rod  14 . Typically, the distal end  12   b  of barrel  12  defines a small diameter opening and a connector  20 , e.g., a luer type connector, for securing syringe barrel  12  to a medical device, e.g., a needle  21 , a catheter, a blood collection device, etc. 
   It is known in the syringe arts to provide limiting structure within a syringe barrel  12  and/or on a plunger rod  14  to limit or restrict the extent of movement of the plunger in relation to the barrel of the syringe. Generally, the limiting structure is integrally formed on the syringe barrel and/or plunger rod during the molding operation of the syringe barrel and/or plunger rod. As such, changing the location of the position of the limiting structure requires a different molding tool for each stop position. This can be costly and time consuming. 
   The present disclosure is directed to a new process for creating limiting structure, i.e., a stop member, on a syringe plunger rod. As will be described in detail below, the presently disclosed process allows the design of the plunger rod to be modified in an inline process, after the initial molding process has been completed, such that limiting structure can be provided on the plunger rod to selectively define one or more stop positions at selective locations along the plunger rod. By providing such an inline process, a single molding tool can be used to form plunger rods with one or more selectively located stop positions. Further, a single plunger rod design can be molded and inventoried and later subjected to the in-line process to make plunger rods having stop positions at a variety of different positions. 

   
     BRIEF DESCRIPTION OF EMBODIMENTS 
     Embodiments of the presently disclosed process for creating a stop on a syringe plunger rod are disclosed herein with reference to the drawings, wherein: 
       FIG. 1  is a side perspective view from the distal end of a “Prior Art” syringe; 
       FIG. 2  is a side perspective exploded view from the distal end of the syringe shown in  FIG. 1 ; 
       FIG. 3  is a front cross-sectional view of a distorting tool in the process of deforming portions of the plunger rod of the syringe shown in  FIG. 2  during one embodiment of the presently disclosed process for creating a stop on a syringe plunger rod; 
       FIG. 4  is a side view of the distorting tool and plunger rod shown in  FIG. 3 ; 
       FIG. 5  is a side view of the plunger rod having stops created using the presently disclosed process; 
       FIG. 6  is a side cross-sectional view of a syringe with the plunger rod shown in  FIG. 5  with parts separated; 
       FIG. 7  is a side cross-sectional view of the syringe shown in  FIG. 6  with the plunger rod positioned within the syringe barrel; 
       FIG. 8  is an enlarged view of the indicated area of detail shown in  FIG. 7 ; 
       FIG. 9  is a side cross-sectional view of a distorting tool in the process of deforming portions of the plunger rod of the syringe shown in  FIG. 2  during another embodiment of the presently disclosed process for creating a stop on a syringe plunger rod; 
       FIG. 10  is a front cross-sectional view of the distorting tool and plunger rod shown in  FIG. 9 ; 
       FIG. 11  is a side view of the plunger rod having stops created using the presently disclosed process; 
       FIG. 12  is a side view of the plunger rod shown in  FIG. 11  and a shaping tool during an additional stop of the presently disclosed process; 
       FIG. 13  is a front cross-sectional view of the plunger rod and shaping tool shown in  FIG. 12 ; 
       FIG. 14  is a side view of the plunger rod created using the presently disclosed process; 
       FIG. 15  is a side cross-sectional view of a syringe having a plunger rod having stops created using one of the presently disclosed processes with parts separated; and 
       FIG. 16  is a side cross-sectional view of the syringe shown in  FIG. 15  with the plunger rod positioned within the syringe barrel. 
   

   DETAILED DESCRIPTION 
   Embodiments of the presently disclosed Process For Creating A Stop On a Syringe Plunger Rod will now be described in detail with reference to the drawings wherein like reference numerals designate identical or corresponding elements in each of the several views. 
   Referring to  FIGS. 1 ,  2  and  6 , syringes  10  includes a syringe barrel  12  defining a reservoir  22  and having an inner diameter “i”. A stop  24  or limiting structure is formed on an internal surface of reservoir  22 . Stop  24  may include an annular or semi-annular protrusion or one or more spaced protrusions. Stop  24  defines an inner diameter “y” which is less than “i”. A plunger rod  14  having a plunger tip  16  supported on the distal end of the plunger rod  14  is slidably positioned within reservoir  22 . 
   As illustrated, in one embodiment, plunger rod  14  includes a body having a plurality of orthogonal ribs  26  which define a “+”-shaped cross-section. During one embodiment of the presently disclosed in-line process shown in  FIGS. 3-5 , one or more of the ribs  26  can be positioned within a slot  30   a  in a fixture  30 . Preferably, slot  30   a  confines ribs  26 . Next, a distorting or swedging tool  32  is pressed in the direction of arrow “a” into the slot or slots  30   a  to engage and deform a side edge  26   a  of one or more of ribs  26  of plunger rod  14  to form an indentation  33  and a radial deformation  34  on rib  26 . Distorting tool  32  can be in the form of a heated member or having an angled face  32   a  which creates a radial deformation that has a steeper slope on a proximal side  34   a  of deformation  34  than on its distal side  34   b . Alternately, blade or member  32  can be energized with RF or ultrasonic energy or strictly a mechanical operator. The configuration of radial deformation  34  facilitates easy insertion of plunger rod  14  into reservoir  22  past stop  24  of barrel  12  ( FIG. 6 ), while providing a secure stop to preclude withdrawal of plunger rod  14  beyond stop  24  (See  FIG. 8 ). 
   The width C of plunger rod  14  added to the outward radial deformation β of radial deformation  34  should be less than the internal diameter i of barrel  12 , i.e., i&gt;C+β. This prevents interference between radial deformation  34  and the internal surface of plunger rod  14  during normal operation of syringe  10 . 
     FIGS. 9-11  illustrate an alternate embodiment of the presently disclosed inline process for creating a stop on a plunger rod of a syringe. As illustrated in  FIG. 9 , plunger rod  14  is identical to the above-described plunger rod. In this process, a pair of dies  38  are moved inwardly in the direction indicated by arrows “b”,  FIG. 10 , on opposite sides of one or more of ribs  26  to deform one or more of ribs  26  to create a radial deformation  40  and resulting indentation  41  shown in phantom. Dies  38  can include angled distal surfaces  38   a  which are configured to create a radial deformation  40  which has a steeper proximal slope  40   a  and a less steep distal slope  40   b . The less steep distal slope  40   b  facilitates easy plunger rod insertion into reservoir  22  of barrel  12  while the steeper proximal slope  40   a  provides a secure stop to prevent plunger withdrawal beyond the predefined stop surface of barrel  12 . 
   Referring to  FIGS. 12-14 , additional machining steps can be performed to provide a more effective stop surface. For example, the proximal side of radial deformation  40  (or radial deformation  34 ) can be machined further to provide a steeper proximal edge, e.g., ninety degree. This can be accomplished using any known machining process including grinding, cutting, melting, etc. In one embodiment, a shaping tool, e.g., heated blocks or cutters  52 , can be used to provide a steeper, e.g., 90 degrees, proximal edge  52   a  of radial deformation  40  (or radial deformation  34 ). Alternately, proximal edge  52   a  can be selectively sloped to provide an effective stop surface, preferably, 60-90 degrees. 
   Limiting structure or stop surfaces on the barrel and the plunger rod may be provided to achieve a number of objectives. Such objectives include simply to prevent disengagement of the barrel and plunger rod or to limit the amount of fluid the syringe can withdraw or expel. Another objective which will be discussed in detail below is to prevent a sterilized region of the syringe barrel to become exposed to an unsterilized region of the syringe. 
   When a syringe  110  (See  FIGS. 15 and 16 ) is packaged, plunger rod  114  is positioned within reservoir  22  of barrel  112  ( FIG. 16 ). Although not shown, a cap is provided on connector  120 . Plunger tip  116  includes a distal sealing surface  116   a  and a proximal sealing surface  116   b . A distance “x” is defined between distal sealing surface  116   a  and proximal sealing surface  116   b . Although syringe  110  is sterilized prior to packaging, typically, the packaging does not maintain sterility. Thus, only the sterile region  122   a  of reservoir  122  between proximal sealing surface  116   b  and the cap (not shown) remains sterile. 
   Because the proximal portion of reservoir  122  is not sterile, for obvious reasons, it is not desirable to expose sterile portion  122   a  of reservoir  122  to the unsterilized portion of reservoir  122  positioned proximally of sterile portion  122   a . To prevent this from occurring, a stop surface  134  is formed on plunger rod  114 . Stop surface  134  is positioned on plunger rod  114  to engage stop surface  124  on the inner surface of barrel  112  to prevent distal sealing surface  116   a  from being retracted within reservoir  122  proximally beyond the original location of proximal sealing surface  116   b  (which defines the proximal end of sterile region  122   a  of reservoir  122 ). More specifically, stop surface  134  and stop surface  124  are positioned apart a distance of x− wherein is a small incremental distance. By limiting retraction of plunger rod  114  to a distance of x−, movement of distal sealing surface  116   a  beyond the original location of proximal sealing surface  116   b  is prevented. 
   When syringe  110  is operated by medical personnel, plunger rod  114  is initially advanced slightly to remove air bubbles that may be present within reservoir  122  of barrel  112 . When this step is performed, syringe  110  should be positioned with the distal end of barrel  112  at a higher elevation than the proximal end of barrel  112 . Next, plunger rod  114  is retracted to draw blood into the medical device, e.g., needle or catheter (not shown), to which the syringe is attached. By drawing blood into the medical device, medical personnel can confirm that an open flow path exists between the patient&#39;s vasculature and syringe barrel. During this step, stop surface or surfaces  134  engage stop surface or surfaces  124  to prevent over retraction of plunger rod  114  which would result in contamination of sterile portion  122   a  of syringe  110 . Thereafter, plunger rod  114  is advanced distally within barrel  112  to dispense fluid from within sterile portion  122   a  of reservoir  122  into the patient. 
   It will be understood that various modifications may be made to the embodiments disclosed herein. For example, the shape of the stop surface created and the instruments used to create the stop surface can be selectively chosen and need not be as disclosed herein. Further, it is envisioned that the above disclosed processes can be used to create one or more stop surfaces, e.g., one to four, on the plunger rod. Therefore, the above description should not be construed as limiting, but merely as exemplifications of preferred embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto.