SYRINGE ASSEMBLY

Abstract: The syringe assembly (10) includes a syringe barrel (12) having an interior surface (22) and a substantially closed discharge end (24) defining a discharge opening (26). A stop (34) is mounted on the interior surface (22) of the syringe barrel (12). A piston (14) is slidably disposed within the syringe barrel (12). The piston has a forward-most sealing surface and the rearward-most sealing surface. The forward-most sealing surface (39) and the rearward-most sealing surface (45) are spaced a first distance from one another. The piston (14) is movable between a first position and a second position. The plunger rod (18) has at least one finger (76) extending therefrom, the at least one finger (76) having a distal end portion constructed to engage the stop (34) when the piston (14) is in its second position. The distal end portion of the at least one finger (76) is positioned no more than the first distance from the stop (34) when the piston (14) is in its first position.

Description: - 1 - SYRINGE ASSEMBLY Field Of The Invention The present invention relates generally to syringe assemblies that include a syringe barrel in which a slidable piston can be moved forwardly to administer a fluid contained in the syringe barrel. More particularly, the invention relates to a syringe assembly constructed to provide an indication when the slidable piston has been withdrawn to a predetermined limit. Background Of The Invention Syringe assemblies typically include a plunger assembly and a hollow, generally cylindrical syringe barrel. The plunger assembly typically includes a slidable piston and a plunger rod. The syringe barrel includes a substantially closed discharge end which defines a discharge opening and an opposite, substantially open end for receiving the forward end of the plunger assembly. The piston typically is cylindrical and is slidable within the cylinder. The peripheral edge of the piston sealingly engages the interior surface of the syringe barrel. Movement of the piston toward the discharge end forces fluids out of the syringe barrel through the discharge opening. Movement of the piston toward the open end draws fluids into the syringe barrel. Some syringe assemblies are pre-filled, that is, they are filled during manufacture rather than being filled at the time of use. In these syringe assemblies, fluid is placed in a fill chamber defined by the area between the discharge opening and the position of the forward-most seal effected between the piston and the interior surface of the syringe barrel. The discharge opening is then sealed. The plunger rod may be attached to the piston during manufacture of the syringe assembly or may remain separate from the piston until the syringe assembly is to be used. Filling of the syringe can be _: performed aseptically. Alternatively, the syringe assembly can be terminally sterilized after it is filled using a variety of known sterilization techniques. The fill chamber and the fluid contents therein are intended to be sterile. However, the exterior of the syringe barrel and those portions of the piston, plunger rod, and interior of the syringe barrel located rearward of the rearward-most seal effected between the piston and the interior surface of the barrel are exposed to the syringe's external environment, thereby making it difficult to maintain sterility for these portions of the syringe. Thus, retracting the piston beyond a certain limit, i.e., the original position of the rearward-most seal between the piston and the syringe barrel when the syringe assembly and its contents are sterile, will cause the fluid contents of the barrel to contact an area which may have been exposed to a non-sterile environment prior to retraction of the piston, thereby compromising the sterility of the fluid in the barrel. The sterile portion of the syringe assembly is defined as the area between the discharge opening and the position of the rearward-most seal effected between the piston and the interior surface of the syringe barrel after sterilization of the syringe, if terminal sterilization is used, or after the syringe has been filled, if aseptic filling techniques are used. To maintain sterility of the fluid contents of the syringe, it is important that the piston not be retracted such that the forward-most seal effected between the piston and the interior of the syringe barrel is moved outwardly to a point outside the sterile portion of the syringe assembly. To ensure that the forward- most seal is not moved to a point outside the sterile chamber, retraction of the piston should be limited to a distance less than or equal to the distance between the forward-most and rearward-most seals, this position being defined as the sterile-withdrawal-limit. It is desirable to have an indicator or stop positioned on the interior of the syringe barrel or on the plunger assembly to indicate that the sterile-withdrawal-limit has been reached. Syringe assemblies are used to deliver a wide range of fluid volumes to patients. For economy in manufacture, it is desirable to standardize the - 3 - components used in producing syringe assemblies so that a single syringe assembly model can be used to deliver a range of volumes. The range of volumes can be split into a number of families. The various volumes included within a family are those that can be accommodated by using a volume-specific plunger rod in combination with standardized syringe barrel, piston, and discharge end cap components. Thus, standardized equipment can be used to fabricate standardized components, and assembly, filling and sterilization can be performed using standardized equipment. Summary Of The Invention The present invention is directed to a syringe assembly. The syringe assembly includes a syringe barrel having an interior surface. The syringe barrel further includes a substantially closed discharge end defining a discharge opening providing fluid communication between an interior of the syringe barrel and an external environment of the syringe barrel. The syringe barrel also includes a substantially open end positioned opposite the substantially closed discharge end. A stop is mounted on the interior surface of the syringe barrel. A piston is slidably disposed within the syringe barrel between the substantially closed discharge end and the stop. The piston has a forward- most sealing surface and a rearward-most sealing surface, the forward-most and rearward-most sealing surfaces being constructed to provide respective fluid-tight seals between the piston and the interior surface of the syringe barrel. The forward-most sealing surface and the rearward-most sealing surface are spaced a first distance from one another. The piston is movable within the syringe barrel between a first position and a second position, the second position being positioned between the first position and the substantially open end of the syringe barrel. The syringe assembly further includes a plunger rod having a forward end portion constructed to engage the piston. The plunger rod has at least - 4 - one finger extending therefrom. The at least one finger includes a distal end portion constructed to engage the stop mounted on the interior surface when the piston is in the second position. The distal end portion of the at least one finger is positioned no more than the first distance from the stop mounted on the interior surface of the syringe barrel when the piston is in the first position. Numerous other advantages and features of the present invention will become readily apparent from the following detailed description of the invention, from the appended claims, and from the accompanying drawings in which the details of the invention are fully and completely disclosed as part of this specification. Brief Description Of The Drawings FIGURE 1 is a perspective view of components of a syringe assembly constructed in accordance with the present invention; FIGURE 2 is a cross-sectional view of the syringe assembly of the present invention in which the plunger rod is in an initial position; FIGURE 3 is a cross-sectional view of the syringe assembly of the present invention in which the plunger rod is in a sterile-withdrawal-limit position; FIGURE 4 is a cross-sectional view of a portion of the syringe assembly of the present invention prior to full insertion of the plunger rod into the syringe barrel; FIGURE 5 is a cross-sectional view of a portion of the syringe assembly of the present invention in which the plunger rod is partially inserted into the syringe barrel; and FIGURE 6 is a cross-section view of a portion of the syringe assembly of the present invention in which the plunger rod is positioned at the sterile-withdrawal-limit. - 5 - Detailed Description While this invention is susceptible of embodiment in many different forms, there is shown in the accompanying figures, and will be described herein in detail, specific embodiments thereof with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the specific embodiments illustrated. Referring now to the embodiment of the present invention shown in the accompanying figures, syringe assembly 10 includes a syringe barrel 12, a slidable piston 14, a discharge end cap 16, and a plunger rod 18. The plunger rod 18 includes a sterile-withdrawal-limit indicator 20. The syringe barrel 12, piston 14, and discharge end cap 16 can be manufactured as standardized components for use in delivering a wide range of volumes of fluids to patients. However, plunger rod 18 preferably is constructed such that it is volume-specific, i.e., such that a single plunger rod 18 configuration can be used to deliver a specific volume of fluid to a patient. Plunger rod 18 can have a standardized length. However, the position of sterile-withdrawal-limit indicator 20 will vary dependent upon the volume of fluid to be delivered. Alternatively, the location of sterile-withdrawal-limit indicator 20 can be standardized at a fixed distance from the rearward-most end of plunger rod 18 so that only the overall length of plunger rod 18 differs between volume -specific sizes. Syringe barrel 12 is hollow and defines an interior surface 22 and a substantially closed discharge end 24. Discharge opening 26 is defined through discharge end 24 of syringe barrel 12. In the embodiment of the present invention depicted in the accompanying figures, discharge opening 26 is configured for connection to a device having a locking luer configuration. However, it will be appreciated that discharge opening can be configured for connection to a variety of other devices. For example, discharge opening 26 can be configured for connection to a hypodermic syringe needle or to a no ' n- - 6 - locking luer. Syringe barrel 12 is substantially open at open end 28. Open end 28 is constructed such that piston 14 and plunger rod 18 can be slidably positioned within syringe barrel 12. Flanges 32 extend radially outwardly from syringe barrel 12 proximate open end 28. Flanges 32 serve as finger grips to facilitate usage of syringe assembly 10 of the present invention. Piston stop 34 extends radially inwardly from interior surface 22 of syringe barrel 12 at a preselected position. The position will be selected based upon the volume of fluid to be delivered to a patient and/or the configuration of the plunger rod 18, as above-discussed. Piston stop 34 can have a variety of configurations, including, but not necessarily limited to, an internally projecting annular ring 34a, one or more protrusions projecting inwardly from interior surface 22, or one or more indentations along an otherwise smooth interior surface 22 of syringe barrel 18. Piston stop 34 is constructed to interact with sterile- withdrawal-limit-indicator 20 to provide an indication that the sterile withdrawal limit of the syringe assembly 10 has been reached, as discussed in greater detail herein. Syringe barrel 12 and piston stop 34 can be unitarily molded, or can be molded as separate parts and subsequently bonded to one another using known molding and bonding techniques. Syringe barrel 12 and piston stop 34 can be formed from a variety of materials that do not chemically interact with pharmaceutical products during prolonged periods of contact. Piston 14 includes a forward portion 36 having a forward face 37 and an annular forward-most edge 38. Piston 12 also includes a rearward portion 42 having a rearward face 43 and an annular rearward-most edge 44. Forward-most edge 38 and rearward-most edge 44 both slidably seal against the interior surface 22 of syringe barrel 12, thus defining a forward-most seal 39 and a rearward-most seal 45, respectively. It will be appreciated that piston 14 of the present invention can have a variety of configurations without departing from the intended spirit of the invention set forth in the appended claims. That is, piston 14 can have a substantially cylindrical configuration - 7 - such that it sealingly contacts interior surface 22 along its entire length. Piston 14 also can be constructed such that it provides two or more edges that sealing contact interior surface 22 of syringe barrel 12. Piston 14 also is preferably constructed from a material that does not chemically interact with pharmaceutical products during prolonged periods of contact. Rearward face 43 is constructed to engage plunger rod 18 such that plunger rod 18 can impart sliding motion to piston 14. Rearward face 43 can be constructed so as to include a threaded socket 45 constructed to threadingly receive threaded member 48 on plunger rod 18. Alternatively, rearward face 43 can be constructed such that it receives and frictionally retains a portion of plunger rod 18 therein. In each of these embodiments, reciprocating movement of piston 14 can be imparted by plunger rod 18 due to the resulting mechanical connection therebetween. Discharge end cap 16 is also preferably constructed of material that does not interact with a pharmaceutical product during a prolonged period of contact therebetween. Discharge end cap 16 is constructed such that it fluidly seals dischage opening 26, thereby preventing inadvertent discharge of the contents of syringe barrel 12. Discharge end cap 16 also preferably is constructed such that it prevents the ingress of contaminants into syringe barrel 12, thereby maintaining the sterility of the contents of syringe barrel 12. Discharge end cap 16 can have a variety of configurations, such configurations being dependent upon the configuration of discharge opening 26 as well as the configuration of the fluid transfer device to which syringe assembly 10 is to be fluidly connected. Plunger rod 18 can have a variety of configurations, including a substantially cylindrical configuration. However, in the embodiment of the present invention depicted in the accompanying figures, plunger rod 18 is defined by four vanes 80 disposed substantially perpendicularly to one another. Plunger rod 18 further includes a forward end portion 54 constructed to engage piston 14. as above-discussed. Plunger rod rearward end portion 55 includes push surface 56 constructed to be engaged by a user's hand or by a syringe pumping device. As above-indicated, plunger rod 18 further includes a sterile-withdrawal-limit indicator 20. The location of indicator 20 on plunger rod 18 is determined by the preselected fill volume of syringe assembly 10 as well as the position of stop 34. Indicator 20 can be constructed to engage stop 34 so that stop 34 prevents further withdrawal of piston 14 and plunger rod 18 from syringe barrel 12. In an alternative embodiment depicted in the accompanying figures, indicator 20 and stop 34 are constructed such that a tactile indication is given to a user of syringe assembly 10 when contact occurs therebetween. That is, indicator 20 and stop 34 are constructed such that withdrawal of indicator 20 beyond stop 34 is more difficult that withdrawal of indicator 20 from its original position to stop 34. The resulting tactile signal will indicate to the user that further withdrawal of the piston 14 and plunger rod 18 may compromise the sterility of the contents of syringe assembly 10. However, it is possible for a user to withdraw further piston 14 and plunger rod 18 from syringe barrel 12 by applying an outwardly directed force of sufficient magnitude to overcome the interaction between indicator 20 and stop 34. In the embodiment of the invention depicted in the accompanying figures, indicator 20 includes one or more flexible, cantilevered fingers 76 extending radially outwardly and rearwardly on the plunger rod. Each finger 76 extends radially outwardly slightly beyond the perimeter of vanes 80 such that the fingers 76 will engage stop 34. The outer radial dimension of fingers 76 can be less than, equal to, or greater than the diameter of the interior surface 22 of the syringe barrel. The flexible fingers preferably are constructed to deflect readily so plunger rod 18 can be inserted into syringe barrel 12 and past stop 34 when syringe assembly 10 is assembled. Vanes 80 preferably are constructed such that they do not engage stop 34 as plunger rod 18 is moved through syringe barrel 12. The angular orientation of the fingers 76 relative to vanes 80 preferably is selected such that the angle facilitates insertion of the rod without excessive force. It will be appreciated that the preferable angle of fingers 76 will be determined by a number of factors including the material used to construct fingers 76, the thickness of fingers 76, and the amount of radial overlap between stop 34 and fingers 76. The angular orientation of fingers 76 preferably is selected such that the force required to insert plunger rod 18 into syringe barrel 12 past stop 34 is less than the force to withdraw plunger rod 18 from syringe barrel 12 past stop 34. Where "x" is the longitudinal distance between forward-most seal 39 and rearward-most seal 45 effected between the piston 14 and interior surface 22, syringe assembly 10 is constructed such that stop 34 is positioned no more than a distance "x" behind the position of indicator 20 when syringe 10 is in a filled and sterilized condition. It will be appreciated that a maximum fill volume for syringe assembly 10 will be achieved if indicator 20 is positioned proximate to rearward-most seal 45. However, indicator 20 can be positioned at any desired location on plunger rod 18, so long as the above-referenced relative positions of indicator 20 and stop 34 are provided. The piston 14 of the syringe assembly 10 of the present invention can be retracted a total longitudinal distance "x" equal to the distance between the forward-most and rearward-most seals between piston 14 and interior surface 22. Withdrawal of plunger rod 18 and piston 14 a distance less than or equal to "x" ensures that the pharmaceutical product contained in syringe barrel 12 will not come into physical contact with a portion of syringe assembly 10 that may have been exposed to non-sterile conditions. Withdrawal of plunger rod 18 and piston 14 a distance greater than "x" may compromise the sterility of the pharmaceutical product. A process for assembling a pre-filled svringe assembly 10 in accordance with the present invention will now be described. As previously described, for a family of fill volumes, the syringe barrel 12, piston 14, and discharge end cap 16 can each have a single size and configuration. The plunger rod 18 preferably is manufactured in a size and configuration that is specific to the preselected fill volume for the syringe assembly 10. - 10 - In a first step of the assembly process, a syringe barrel 12 constructed as above-described is provided and fed into an assembly machine. A piston 14 as above-described is provided and is placed in the open end 28 of syringe barrel 12. The piston 14 is moved forwardly through syringe barrel 12 until piston 14 is positioned proximate to, or in contact with, discharge end 24 of syringe barrel 12. Next, a preselected volume of a pharmaceutical fluid is provided and is introduced into the syringe barrel 12 through the discharge opening 26, thereby causing piston 14 to move a volume-related distance towards the substantially open end 28 of the syringe barrel 12. The discharge opening 26 of the syringe barrel 12 is then capped with a provided discharge end cap 16. The above-recited process can be conducted using an aseptic fill technique in which all of the portions of the syringe assembly 10 and the pharmaceutical product are sterilized prior to assembly and filling and in which the filling and capping is conducted under aseptic conditions. Alternatively, the pharmaceutical product and the syringe assembly 10 can be terminally sterilized after it has been filled using known sterilization methods including, but not necessarily limited to, heat and UV sterilization techniques. Attachment of plunger rod 18 to piston 14 can be performed at any point in the above-referenced process. That is, plunger rod 18 can be attached to piston 14 (a) prior to insertion of piston 14 into syringe barrel 12; (b) prior to filling syringe barrel 12 with the pharmaceutical product; (c) prior to terminal sterilization of the syringe assembly 10; or (d) at the time of use of the syringe assembly 10. In the preferred embodiment of the present invention, a particular configuration of plunger rod 18 is selected at the time the pharmaceutical product is to be administered from the syringe assembly 10 to the patient, the configuration of plunger rod 18 being determined by the volume of pharmaceutical product contained in syringe assembly 10 that is to be delivered to the patient. - 11 - In order to administer the pharmaceutical product contained in syringe assembly 10 to a patient, the discharge end cap 16 is removed from discharge opening 26. At this juncture, the slidable piston 14 and plunger rod 18 can be withdrawn to the sterile-withdrawal-limit without risking contamination of the fluid contents of the syringe assembly. A user of syringe assembly 10 will know when this point has been reached due to the tactile signal given when one or more fingers 76, i.e., indicator 20, engage stop 34. From the foregoing, it will be observed that numerous modifications and variations can be effected without departing from the true spirit and scope of the novel concept of the present invention. It will be appreciated that the present disclosure is intended as an exemplification of the invention, and is not intended to limit the invention to the specific embodiment illustrated. The disclosure is intended to cover by the appended claims all such modifications as fall within the scope of the claims.

Claims: - 12 - What is claimed is: 1. A syringe assembly comprising: a syringe barrel having an interior surface, a substantially closed discharge end defining a discharge opening providing fluid communication between an interior of said syringe barrel and an external environment of said syringe barrel, and a substantially open end positioned opposite said substantially closed discharge end; a stop mounted on said interior surface of said syringe barrel; a piston slidably disposed within said syringe barrel between said substantially closed discharge end and said stop, said piston having a forward-most sealing surface and a rearward-most sealing surface, said forward-most and rearward-most sealing surfaces constructed to provide respective fluid-tight seals between said piston and said interior surface of said syringe barrel, said forward-most sealing surface and said rearward-most sealing surface being spaced a first distance from one another, said piston movable between a first position and a second position, said second position being positioned between said first position and said substantially open end of said syringe barrel; a plunger rod having a forward end portion constructed to engage said piston, said plunger rod having at least one finger extending therefrom, said at least one finger having a distal end portion constructed to engage said stop mounted on said interior surface when said piston is in said second position, said distal end portion of said at least one finger being positioned no more than said first distance from said stop mounted on said interior surface of said syringe barrel when said piston is in said first position. 2. A syringe assembly in accordance with Claim 1, wherein said plunger rod comprises four vanes disposed at substantially right angles with respect to one another, and wherein said at least one finger is defined by at least one of said vanes. - 13 - 3. A syringe assembly in accordance with Claim 1, wherein said at least one finger extends radially outwardly from said plunger rod and wherein said at least one finger extends away from said forward end portion of said plunger rod. 4. A syringe assembly in accordance with Claim 1, wherein said syringe assembly further comprises a cap constructed to seal fluidly said discharge opening, said cap further constructed to be releasably mounted on said syringe barrel. 5. A syringe assembly in accordance with Claim 1, wherein said syringe assembly further comprises a pharmaceutical product disposed in said syringe barrel between said piston and said substantially closed discharge end. 6. A method for delivering a pharmaceutical product to a patient, said method comprising: providing a syringe assembly comprising: a syringe barrel having an interior surface, a substantially closed discharge end defining a discharge opening providing fluid communication between an interior of said syringe barrel and an external environment of said syringe barrel, and a substantially open end positioned opposite said substantially closed discharge end; a stop mounted on said interior surface of said syringe barrel; a piston slidably disposed within said syringe barrel between said substantially closed discharge end and said stop, said piston having a forward-most sealing surface and a rearward-most sealing surface, said forward-most and rearward-most sealing surfaces constructed to provide respective fluid-tight seals between said piston and said interior surface of said syringe barrel, said forward-most - 14 - sealing surface and said rearward- most sealing surface being spaced a first distance from one another, said piston movable between a first position and a second position, said second position being positioned between said first position and said substantially open end of said syringe barrel; a pharmaceutical product disposed in said syringe barrel between said piston and said substantially closed discharge end; a plunger rod having a forward end portion constructed to engage said piston, said plunger rod having at least one finger extending therefrom, said at least one finger having a distal end portion constructed to engage said stop mounted on said interior surface when said piston is in said second position, said distal end portion of said at least one finger being positioned no more than said first distance from said stop mounted on said interior surface of said syringe barrel when said piston is in said first position; and applying an inwardly directed force to said plunger rod, thereby forcing said pharmaceutical product through said discharge opening defined by said substantially closed discharge end. 7. A method for delivering a pharmaceutical product to a patient in accordance with Claim 6, wherein said method further comprises applying an outwardly directed force to said plunger rod, thereby moving said piston from said first position to said second position, prior to said step of applying an inwardly directed force to the plunger rod.

Inventors: ZIEGLER JOHN S, ZIEGLER, JOHN, S.
Applicants: ABBOTT LAB, ABBOTT LABORATORIES
Application year: 1999
Main classification: A61M5
IPC codes: A61M5