A plug

Abstract

A stopper adapted for attachment with a plunger rod for use within a syringe barrel, comprising: a body portion defining an open rear end, a closed front end, and an internal cavity defined between the open rear end and the closed front end, the internal cavity defining an interior profile, the interior profile including a recess extending outwardly from an interior surface of the internal cavity, the recess separating a first contact surface of the interior profile from a second contact surface of the interior profile; a first rib extending from an exterior surface of the body portion and extending around an outer circumference of the body portion; and a second rib spaced apart from the first rib, the second rib extending from an exterior surface of the body portion and extending around an outer circumference of the body portion, wherein a width of the first contact surface is substantially equal to a width of the first rib, and a width of the second contact surface is substantially equal to a width of the second rib.

Description

[0001] This application is a continuation-in-part of Chinese Patent Application No. 201980020147.8, filed in the Chinese National Phase of International Application PCT / US2019 / 022300 entitled “Syringe Stopper and Plunger Rod Apparatus for Syringe Assembly” having an international filing date of March 14, 2019.

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This application claims priority to U.S. Provisional Application Serial No. 62 / 645,353, filed March 20, 2018, entitled “Syringe Stopper and Plunger Rod Apparatus for Syringe Assembly,” the entirety of which is incorporated herein by reference. TECHNICAL FIELD

[0004] The present invention relates generally to stopper assemblies for use with syringes, and more particularly to a stopper and plunger rod apparatus for use with syringes. BACKGROUND

[0005] Current syringe designs can typically be classified as either a two-piece syringe or a three-piece syringe. A typical three-piece syringe includes a tubular barrel formed with an entry opening at one end and a smaller exit opening at the opposite end. A leading end of an elongated plunger rod is received within the entry opening of the barrel so as to be slidable within the barrel. Attached to the leading end of the plunger rod is a flexible sealing member or stopper that seals against the inner surface of the barrel. A needle, threaded member, or unthreaded member is typically attached to the exit opening of the barrel. The needle can be used to penetrate a surface, while the threaded member can be used to attach the syringe to another medical device, such as a catheter. The flexible stopper is typically manufactured from an elastomeric material, such as rubber, or a cross-linked elastomer or thermoplastic elastomer.

[0006] On the other hand, a two-piece syringe includes a “stopper” in the form of a rigid sealing disc. It is typically made of the same rigid plastic as the rest of the plunger rod. The sealing force in a two-piece syringe comes from a thin elastomeric barrel that deforms around the rigid plunger rod head.

[0007] During use, the exit end of the syringe is initially placed in contact with a fluid. For example, a needle on the syringe can be inserted into a liquid medication. As the plunger is retracted within the barrel (a process known as priming), a negative pressure is created within the end of the barrel to draw fluid into the barrel. The syringe can then be moved to a second location, at which time advancing the plunger within the barrel will cause the fluid to be pushed out or expelled from the exit end of the barrel.

[0008] Current two-piece and three-piece syringe designs suffer from various deficiencies. In some cases, the syringes can be used during an autoclave sterilization process. Autoclaves are typically used to sterilize surgical equipment, laboratory instruments, pharmaceuticals, and other materials. They can sterilize solids, liquids, hollow bodies, and instruments of various shapes and sizes. Autoclave chambers sterilize medical or laboratory instruments by heating them above the boiling point. Steam is the sterilizing agent for autoclaves, which is typically generated at higher temperatures and pressures.

[0009] Typically, syringe designs that are subjected to high temperatures and pressures during an autoclave sterilization cycle use vulcanized rubber as the stopper base material. However, there are several significant disadvantages to using vulcanized rubber in syringe stopper applications that use an autoclave sterilization process. The bulk material cost of vulcanized rubber is significantly higher than alternative materials such as thermoplastic elastomers. Additionally, vulcanized rubber is more expensive to manufacture, both in capital equipment costs and in production labor, as compared to injection moldable thermoplastic elastomers. Vulcanized rubber also has a relatively high chemical leach characteristic as compared to thermoplastic elastomers, which can negatively impact the pharmaceuticals stored in the syringe.

[0010] Due to these unfavorable characteristics, medical device manufacturers have begun to use thermoplastic elastomers in pre-filled autoclave syringes. However, thermoplastic elastomer materials have significantly less resistance to high temperature compression set characteristics as compared to vulcanized rubber syringes. Therefore, syringe stoppers made of thermoplastic elastomer materials are designed to have a relatively low contact stress concentration in order to have a lower yield strength at the high temperatures of the autoclave, which translates to acceptable fluid seal robustness.

[0011] Some manufacturers have also partially used thermoplastic elastomer materials in the stopper by using more complex multi-part plunger rod designs in order to reduce the lateral load transfer of the plunger rod to the stopper. This effectively reduces the stopper stress induced yielding and leakage. However, multi-part syringe designs tend to increase manufacturing and assembly costs. Additionally, multi-part plunger rod designs have a relatively large amount of mechanical backlash or play in both the axial and tilt directions. This play has less than ideal infusion site control (feel) for the end user (clinician). SUMMARY

[0012] It is an object of the present invention to provide an improved syringe stopper and plunger rod device for use with thermoplastic elastomers. The improved device is configured to better withstand the high temperatures experienced by the device during autoclave sterilization processes in order to improve the robustness of syringe seal performance. The new device enables the use of lower compression set performance materials, such as thermoplastic elastomer resins, for syringe stoppers while still meeting the sterility, leakage, and other performance requirements needed for syringes. The use of thermoplastic elastomer resins for syringe stoppers will significantly reduce bulk material costs, manufacturing costs, and leachable toxicants from syringe drugs compared to traditional vulcanized rubber syringe stoppers.

[0013] The incorporation of thermoplastic elastomers into syringe stoppers for use with autoclave syringes can reduce stopper stress concentrations in order to reduce material yielding and increase seal pressure. Additionally, lateral loading of the plunger rod can be directly transferred from the plunger rod to the syringe barrel, reducing load / leakage caused by asymmetric stopper deflection.

[0014] During autoclave sterilization processes, stopper seal stress concentrations in the stopper ribs can be reduced to minimize local yielding of the stopper ribs. This reduction in stress concentration can be achieved by balancing the contact area of the stopper ribs with the internal structural features of the stopper and the interference fit of the entire barrel. The robustness of the fluid seal can be improved by using fluid pressure during infusion with stopper conic internal support features. These support features allow the stopper conic to slightly collapse or flex slightly when the syringe fluid is under pressure. The conic flex causes the stopper conic base to exert a radial load on the stopper ribs, which increases the seal contact pressure in proportion to the syringe fluid pressure.

[0015] By incorporating design features to limit angular misalignment between the plunger rod and the barrel, angular misalignment of the stopper when the plunger rod is subjected to lateral loading can also be reduced. Angular misalignment of the plunger rod can be further reduced by incorporating an angularly flexed plunger rod design feature between the plunger rod and the stopper. The angularly flexed feature allows the angular misalignment load of the plunger rod and barrel to be decoupled or significantly reduced at the interface of the plunger rod and stopper.

[0016] According to one aspect of the application, a syringe assembly includes a substantially cylindrical syringe barrel including a fluid dispensing end, an open end, and at least one protrusion adjacent the open end, the at least one protrusion protruding inwardly from an inner surface of the syringe barrel; a stopper configured to be received within the open end of the syringe barrel; and a plunger rod having a plunger rod body extending along a longitudinal axis from a proximal end to a distal end and at least one support disc disposed on the distal end thereof. The support disc on the plunger rod is configured to bear against the protrusion of the syringe barrel when the plunger rod is misaligned in the syringe barrel. The at least one protrusion of the syringe barrel is a continuous rib extending around an inner peripheral surface of the syringe barrel. The at least one support disc includes two support discs spaced apart from each other on the plunger rod such that, when the plunger rod is misaligned in the syringe barrel, a first support disc bears against a proximal side of the protrusion at a first bearing point and a second support disc bears against a distal side of the protrusion at a second bearing point. The plunger rod further includes a groove defined in the plunger rod body adjacent the support discs, the groove defined by two protruding members extending from an outer surface of the plunger rod body. When the plunger rod is misaligned in the syringe barrel, a first protruding member bears against the proximal side of the protrusion at the first bearing point, a second protruding member bears against the distal side of the protrusion at the second bearing point, and the support disc bears against the inner surface of the syringe barrel at a third bearing point. The plunger rod further includes an attachment member disposed on the distal end and configured for connection to the stopper. The support disc is spaced apart from the attachment member proximally. The plunger rod body further includes a rigid outer body member and a flexible inner body member disposed within the rigid outer body member. The flexible inner body member is configured to flex when the plunger rod is misaligned in the syringe barrel. The plunger rod body further includes an attachment member configured for connection with the stopper. The attachment member is disposed on a distal end of the flexible inner body member. The at least one support disc includes two support discs spaced apart from each other on the plunger rod. The plunger rod further includes a flexible region disposed between the support discs, the flexible region configured to flex when the plunger rod is misaligned in the syringe barrel. The stopper includes a body portion defining an open rear end, a closed front end, and an internal cavity for receiving the distal end of the plunger rod. An inner surface of the internal cavity defines a groove configured to act as a bearing point for the plunger rod when the plunger rod is misaligned within the syringe barrel. The stopper includes a body portion defining an open rear end, a closed front end, and an internal cavity for receiving the distal end of the plunger rod. A portion of an inner surface of the internal cavity defines a plurality of recesses configured to receive a plurality of protrusions extending from the distal end of the plunger rod body. At least one protrusion on the plunger rod body bears against a corresponding recess in the internal cavity of the stopper at a bearing point when the plunger rod is misaligned in the syringe barrel. The stopper is made of a thermoplastic elastomer.

[0017] In another aspect of the application, a plunger rod attached stopper for use within a syringe barrel comprises a body portion defining an open rear end, a closed front end, and an internal cavity defined between the rear end and the front end, the internal cavity defining an interior profile, the interior profile including a recess extending outwardly from an interior surface of the internal cavity, the recess separating a first contact surface of the interior profile from a second contact surface of the interior profile; a first rib extending from an outer surface of the body portion and extending around an outer circumference of the body portion; and a second rib spaced apart from the first rib, the second rib extending from an outer surface of the body portion and extending around an outer circumference of the body portion. The first contact surface has a width substantially equal to a width of the first rib, and the second contact surface has a width substantially equal to a width of the second rib. The recess defined in the interior profile provides a reduced thickness of the body portion from the interior profile to an outer surface of the body portion. The closed front end of the body portion has a conical shape with a pointed tip. A groove is formed on the outer surface of the body portion between the first rib and the second rib. The groove has a width substantially equal to a width of the recess. At least one collapsible cutout is defined in the interior profile of the internal cavity. The collapsible cutout permits the stopper to collapse or flex under pressure. The stopper is made of a thermoplastic elastomer.

[0018] In another aspect of the application, a plunger rod for a syringe assembly comprises a plunger rod body extending along a longitudinal axis from a proximal end to a distal end and at least two support disks provided on the distal end thereof. The support disks on the plunger rod are configured to bear against a protrusion on a syringe barrel when the plunger rod is misaligned in the syringe barrel. An attachment member is provided on the distal end and is configured for attachment to a stopper. The support disks are spaced apart proximally from the attachment member. The plunger rod further comprises a groove defined in the plunger rod body adjacent to the support disks. The groove is defined by two protruding members extending from an outer surface of the plunger rod body. The plunger rod body further comprises a rigid outer body member and a flexible inner body member provided within the rigid outer body member. The flexible inner body member is configured to flex when the plunger rod is misaligned in the syringe barrel. The plunger rod body further comprises an attachment member configured for connection with the stopper. The attachment member is provided on a distal end of the flexible inner body member. The plunger rod further comprises a flexible region provided between the support disks, the flexible region configured to flex when the plunger rod is misaligned in the syringe barrel.

[0019] These and other features and characteristics of the present application, as well as the methods of operation and functions of the related elements of structure and the combination of parts and economies of manufacture, will become more apparent upon consideration of the following description and appended claims with reference to the accompanying drawings, all of which form a part of this specification, wherein like reference numerals designate corresponding parts in the various figures. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended as a definition of the limits of the application. As used in the specification and in the claims, the singular form of "a", "an", and "the" include plural referents unless the context clearly dictates otherwise. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is a side view of a stopper according to one aspect of the present application;

[0021] Figure 2 is a side view of a stopper according to one aspect of the present application; Figure 1 is a side view cross-section of a stopper of

[0022] Figure 3 is a side view cross-section of a stopper of Figure 1 is a side view cross-section of a stopper of

[0023] Figure 4 is a side view cross-section of a stopper of

[0024] Figure 5 is a side view cross-section of a stopper of Figure 4 is a side view cross-section of a stopper of DETAILED DESCRIPTION

[0025] For purposes of the description hereinafter, the terms "upper", "lower", "right", "left", "vertical", "horizontal", "upward", "downward", "lateral", "longitudinal", and derivatives thereof shall relate to the application as it is oriented in the drawing figures. However, it is to be understood that the application can assume various alternative orientations and, accordingly, such specific embodiments are not to be taken in a limiting sense as the scope of the present application is to be limited solely by the appended claims.

[0026] Referring now to the drawings Figure 1 and Figure 2, the first aspect of the stopper 2 includes a body portion 4 defining an open rear end 6 configured to receive a plunger rod and a closed front end 8 forming a flexible tip. In one aspect, the stopper 2 is made of a thermoplastic elastomer. It is also contemplated that the stopper 2 is made of any alternative hard or soft plastic. The closed front end 8 of the body portion 4 includes a substantially cylindrical portion 9, a first angled portion 10 and a second angled portion 12, both of which are part of a single conical surface and extend toward a tip 14, providing the closed front end 8 with a substantially conical appearance. However, this shape of the flexible tip is not considered limiting to the present invention as the tip can also be flat. Such a tip would not provide a flex tip action in which the flexible tip of the stopper flexes inward and expands laterally in a radial direction. As Figure 1 shown, at least dimples 16, 18 extend from the outer surfaces of the first and second angled portions 10, 12 of the closed front end 8. The dimples 16, 18 are designed to prevent the stopper 2 from contacting the front portion of the syringe barrel to prevent backflow at the end of the injection process. Although only one dimple 16, 18 is shown extending from the first and second angled portions 10, 12, it is contemplated that additional features can be provided on these surfaces or no dimples can be provided on these surfaces.

[0027] As Figure 2 shown, the body portion 4 of the stopper 2 is substantially hollow and designed to receive an attachment portion of a plunger rod, as described below. The body portion 4 of the stopper 2 defines an internal cavity 20 that receives the attachment portion of the plunger rod. The internal cavity 20 is defined between the rear end 6 and the closed front end 8 of the body portion 4. The internal cavity 20 defines an internal profile 22 in the body portion 4. The internal profile 22 defines a recess 24 configured to receive a portion of the attachment portion of the plunger rod to retain the attachment portion within the internal cavity 20. The recess 24 is defined in the cylindrical portion 9 of the body portion 4 and extends outwardly from an inner surface of the internal cavity 20 and around a circumferential surface of the internal cavity 20. The recess 24 defined in the internal profile 22 defines a reduced thickness of the body portion 4 from the internal profile 22 to an outer surface of the body portion 4 compared to the thickness of the rest of the body portion 4. The recess 24 is defined between a first contact surface 25a and a second contact surface 25b of the internal profile 22. The reduced thickness of the cylindrical portion 9 helps to reduce plunger rod misalignment load forces transmitted to the stopper rib contact surfaces.

[0028] The inner profile 22 of the lumen 20 also defines a first angled portion 26 and a second angled portion 28 in the front end 8 of the stopper 2, which correspond to the first angled portion 10 and the second angled portion 12 of the outer surface of the front end 8. The first angled portion 26 and the second angled portion 28 are both part of a single conical surface, which provides a substantially conical appearance to the inner surface of the closed front end 8. Adjacent to the first angled portion 26 and the second angled portion 28, a pair of collapsible notches 30, 32 are defined in the inner profile 22. The collapsible notches 30, 32 are recesses or grooves defined in the inner profile 22 of the body portion 4. The collapsible notches 30, 32 are configured to allow adjacent portions of the body portion 4 to flex radially outward when the stopper is under fluid pressure, which causes the flexible top portion of the front end 8 to flex axially inward in a rearward direction. The radially outward flexing of the body portion 4 helps maintain the outer surface of the body portion 4 in contact with the inner surface of the syringe barrel in which the stopper 2 is moving to improve the interference fit between the stopper 2 and the syringe barrel such that the sealing contact pressure between the stopper 2 and the syringe barrel is proportional to the syringe fluid pressure acting on the stopper 2.

[0029] Referring to Figure 1 and Figure 2 The outer surface of the cylindrical portion 9 of the body portion 4 includes a first rib 34 disposed adjacent to the rear end 6 and a second rib 36 disposed adjacent to the front end 8 of the body portion 4. In one aspect, the ribs 34, 36 extend around the entire circumferential outer surface of the cylindrical portion 9. In another aspect, the ribs 34, 36 are disposed segmentally around the circumferential outer surface of the cylindrical portion 9. The ribs 34, 36 extend outward from the outer surface of the cylindrical portion 9 to act as bearing points against the inner surface of the syringe barrel. The first rib 34 is spaced apart from the second rib 36 on the cylindrical portion 9. As shown in Figure 2 , the width of the first rib 34 is substantially equal to the width of the first contact surface 25a of the inner profile 22. The width of the second rib 36 is substantially equal to the width of the second contact surface 25b of the inner profile 22. Because the width of the ribs 34, 36 is substantially equal to the width of the contact surfaces 25a, 25b of the inner profile 22, balanced support of the ribs 34, 36 on the inner surface of the syringe barrel is achieved. This feature helps to reduce stopper seal stress concentration within the stopper 2. The reduction in this stress concentration in turn reduces localized yielding of the stopper ribs during an autoclave sterilization process. The reduction in material yielding translates into increased passive seal robustness of the stopper 2. The first rib 34 and the second rib 36 of the cylindrical portion 9 form a groove 38 on the outer surface of the body portion 4. The width of the groove 38 is substantially equal to the width of the recess 24 defined in the inner profile 22. The surface of the groove 38 does not contact the inner surface of the syringe barrel.

[0030] Referring to Figure 3FIG. 1 shows a syringe assembly 44 in which the stopper 2 is used with a plunger rod 40 and a syringe barrel 42 to form the syringe assembly 44. The stopper 2 and the plunger rod 40 are adapted for use with the syringe barrel 42. The syringe barrel 42 is made of medical grade plastic or glass. The plunger rod 40 is made of medical grade plastic. The syringe barrel 42 is substantially cylindrical and extends from an open proximal end 46 to a dispensing distal end (not shown) from which fluid is expelled during use of the syringe assembly 44. The dispensing distal end includes an outlet and / or a mechanism (e.g., a luer fitting) for connecting to a separate medical device (e.g., a catheter). The open proximal end 46 is configured to receive the stopper 2 and the plunger rod 40. A flange 48 is disposed about the circumferential surface of the open proximal end 46. At least one protrusion 50 protrudes inwardly from an inner surface 52 of the syringe barrel 42. In one aspect, the protrusion 50 extends about the entire circumferential surface of the inner surface 52 of the syringe barrel 42. In another aspect, the protrusion 50 is disposed as a plurality of segments extending about the circumferential surface of the inner surface 52. The protrusion 50 is disposed adjacent to the open proximal end 46 of the syringe barrel 42. It is also contemplated that additional protrusions can be disposed on the syringe barrel 42 at a distal location from the protrusion 50.

[0031] The plunger rod 40 is operably connected to the stopper 2 such that when the plunger rod 40 is depressed in a distal direction, the stopper 2 moves in a distal direction within the syringe barrel 42 to draw fluid out of the dispensing distal end of the syringe barrel 42. The plunger rod 40 includes a body portion 54, at least one support disk 56, 58, and an attachment member 60. The body portion 54 includes a proximal end having an actuator button or tab for moving the plunger rod 40 in a distal or proximal direction, and a distal end on which the support disks 56, 58 are formed. The support disks 56, 58 extend outwardly from the distal end of the body portion 54 and are substantially circular in shape to correspond to the shape of the syringe barrel 42. However, it is contemplated that the support disks 56, 58 can have an alternative shape that is accommodated within the syringe barrel 42. The first support disk 56 is spaced proximally from the second support disk 58 on the distal end of the body portion 54. The support disks 56, 58 have substantially the same diameter.

[0032] An attachment member 60 is disposed on the distal end of the plunger rod 40 and is distally spaced from the support discs 56, 58 on the plunger rod 40. The diameter of the attachment member 60 is smaller than the diameter of the support discs 56, 58. The attachment member 60 also includes at least one gripping protrusion 62 extending distally from the attachment member 60. The gripping protrusion 62 is configured to assist in gripping the plug 2 when the attachment member 60 is inserted into the inner cavity 20 of the plug 2. During use, the plunger rod 40 is pushed distally into the open rear end 6 of the plug 2, thereby inserting the attachment member 60 into the inner cavity 20 of the plug 2. As the plunger rod 40 moves distally, the attachment member 60 moves into a recess 24 defined in the inner contour 22 of the plug 2. Using this interlocking connection between the attachment member 60 and the recess 24, the plunger rod 40 is held in the plug 2, allowing the plug 2 and the plunger rod 40 to move together within the syringe barrel 42. It is also conceivable that the plunger rod 40 and the plug 2 are integrally molded to form this configuration. Since the diameter of the recess 24 is larger than the diameter of the attachment member 60, rotation of the plunger rod 40 relative to the plug 2 is permitted.

[0033] like Figure 3 As shown, during use of the syringe assembly 44, the plunger rod 40 may become misaligned relative to the longitudinal axis A of the syringe assembly 44, which extends through the syringe barrel 42, the stopper 2, and the plunger rod 40. This misalignment of the plunger rod 40 may occur due to a clinician's thumb load on the plunger rod 40 being misaligned relative to the longitudinal axis A of the syringe assembly. Due to a lateral load force B on the plunger rod 40, the plunger rod 40 may rotate by an angle α relative to the longitudinal axis A of the syringe assembly 44. Based on this lateral load force B, the attachment member 60 of the plunger rod 40 rotates within the stopper 2, causing stress concentration in a portion of the stopper 2. Due to these stress concentrations, the seal between the stopper 2 and the syringe barrel 42 may deteriorate, or the material of the stopper 2 may wear at high temperatures. To mitigate the effects of the plunger rod 40 misalignment, support discs 56, 58 are configured to support a protrusion 50 extending from the inner surface 52 of the syringe barrel 42. As the plunger rod 40 rotates relative to the longitudinal axis A, the proximal support disc 56 is configured to support the proximal side of the protrusion 50, while the distal support disc 58 is configured to support the distal side of the protrusion 50. The protrusion 50 serves as a support point for the support discs 56 and 58 to limit the rotation of the plunger rod 40 and reduce the support force applied by the attachment member 60 within the plug 2. Using the protrusion 50 as a support point causes most of the lateral load force B to be transmitted directly from the plunger rod 40 to the syringe barrel 42 as a barrel reaction load force C, resulting in a reduction in the load force transmitted from the plunger rod 40 to the plug 2. This reduction in the load force acting on the side of the plug 2 reduces the load / leakage caused by asymmetrical plug deflection in the seal between the plug 2 and the syringe barrel 42.

[0034] Referring to Figure 4 , another aspect of the syringe assembly 64 is shown. In this aspect, the syringe barrel 42 is the same as the syringe barrel described in the syringe assembly 44 of Figure 3 . However, the stopper 66 and plunger rod 68 of this aspect are slightly different from the stopper 2 and plunger rod 40 of the syringe assembly 44 shown in Figure 3 . The stopper 66 has all of the same features as the stopper 2 of Figure 3 , except that the stopper 66 does not include a recess similar to the recess 24 in the stopper 2. Instead, the stopper 66 defines a plurality of recesses 70 in an inner profile 72 of the stopper 66.

[0035] The plunger rod 68 includes a body portion 74, at least one support disk 76, 78, and an attachment member 80 configured to connect with the stopper 66. The attachment member 80 is disposed on a distal end of the plunger rod 68 and is spaced apart distally from the support disks 76, 78. The diameter of the attachment member 80 is less than the diameter of the support disks 76, 78 and the diameter of the inner lumen of the stopper 66. A plurality of protrusions 82 are disposed on a circumferential outer surface of the attachment member 80 that are configured to connect the attachment member 80 within the stopper 66. The protrusions 82 are substantially triangular in shape and correspond in shape to the recesses 70 defined in the stopper 66. Thus, as the plunger rod 68 is moved distally toward the stopper 80, the attachment member is inserted into the inner lumen of the stopper 66. As the attachment member 80 is moved in the distal direction within the inner lumen of the stopper 66, the protrusions 82 move from a first recess 70 to a second recess 70 within the stopper 66. The recesses 70 allow the attachment member 80 to move distally within the stopper 66, but prevent the attachment member 80 from moving proximally out of the stopper 66.

[0036] With continued reference to Figure 4A recess 84 is defined in the body portion 74 of the plunger rod 68. The recess 84 is defined proximally of the first support disk 76. The recess 84 is formed between the first support disk 76 and a protrusion 86 extending from the body portion 74. The recess 84 helps to reduce the bearing load imparted to the stopper 66 when the plunger rod 68 is misaligned within the syringe barrel 42. In assembling the plunger rod 68 in the syringe barrel 42, the plunger rod 68 is moved distally within the syringe barrel 42 until the protrusion 50 on the syringe barrel 42 is positioned within the recess 84 of the plunger rod 68. When the plunger rod 68 is misaligned within the syringe barrel 42 due to a lateral load acting on the plunger rod 68, the plunger rod 68 is rotated an angle a from the longitudinal axis A of the syringe assembly 64. Once the plunger rod 68 has rotated, the distal end of the protrusion 86 bears against the proximal side of the protrusion 50 of the syringe barrel 42 and the proximal side of the first support disk 76 bears against the distal side of the protrusion 50. In addition, the second support disk 78 can bear against the inner surface of the syringe barrel 42. The protrusion 82 of the attachment member 80 also bears against the recess 70 defined in the stopper 66.

[0037] The plunger rod 68 also includes a flexible region 88 between the first support disk 76 and the second support disk 78. In one aspect, the flexible region 88 is more flexible than the rest of the plunger rod 68. Due to the flexibility of the flexible region 88, the misalignment angle of the attachment member 80 within the stopper 66 is reduced when the plunger rod 68 is misaligned. In particular, because the flexible region 88 is allowed to flex and rotate with the misalignment of the plunger rod 68, the lateral bearing load is not fully imparted to the attachment member 80, which rotates through an angle less than the angle through which the body portion 74 of the plunger rod 68 rotates. In particular, the angle of rotation β of the attachment member 80 is less than the angle of rotation a of the body portion 74. Due to the smaller rotation of the attachment member 80 within the stopper 66, the lateral load force imparted to the stopper 66 from the attachment member 80 is reduced. This reduction in lateral load force on the stopper 66 reduces the deflection-induced leakage on the sealing surface between the stopper 66 and the inner surface of the syringe barrel 42.

[0038] Referring to Figure 5 , another aspect of a syringe assembly 90 is shown. The syringe assembly 90 includes a stopper 66, a syringe barrel 42, and a plunger rod 92. The stopper 66 is the same as the stopper 66 disclosed in Figure 4 . The syringe barrel 42 is the same as the syringe barrel 42 disclosed in Figure 3 and Figure 4 . However, the plunger rod 92 includes Figure 3 the plunger rod 40 of Figure 4a few features not provided in the plunger rod 68. The plunger rod 92 includes at least one outer body member 94, an inner body member 96, at least one support disk 98, 100, and an attachment member 102 for connecting the plunger rod 92 to the stopper 66. In one aspect, a plurality of outer body members 94 surround the inner body member 96. The outer body members 94 are made of a rigid plastic material and the inner body member 96 is made of a flexible plastic material. The inner body member 96 extends within the outer body members 94. When the plunger rod 92 is misaligned due to a lateral load on the plunger rod 92, the inner body member 96 is configured to flex to reduce the angle of rotation a of the plunger rod 92 within the syringe barrel 42. During rotation of the plunger rod 92, the outer body members 94 remain rigid. In one aspect, the attachment member 102 is formed on a distal end of the inner body member 96 such that the amount of lateral bearing load transmitted to the stopper 66 from the attachment member 102 is reduced due to the flexing of the inner body member 96 during misalignment of the plunger rod 92. During misalignment of the plunger rod 92, the inner body member 96 experiences a significant deflection while the outer body members 94 remain rigid. As described above, the rigid outer body members 94 are designed to transmit a majority of the lateral bearing load from the plunger rod 92 to the syringe barrel 42 through the support disks 98, 100 which bear against the protrusions 50 on the syringe barrel body 42 as described above.

[0039] While particular aspects of the application have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details can be developed in light of the overall teachings of the disclosure. Accordingly, the particular configuration disclosed is meant to be illustrative only and not limiting as to the scope of the application, which is to be given the full breadth of the appended claims and any and all equivalents thereof.

Claims

1. A stopper adapted for attachment with a plunger rod for use within a syringe barrel, the stopper comprising: a body portion defining an open rear end, a closed front end, and an internal cavity defined between the open rear end and the closed front end, the internal cavity defining an interior profile, the interior profile including a recess extending outwardly from an interior surface of the internal cavity, the recess separating a first contact surface of the interior profile from a second contact surface of the interior profile; a first rib extending from an outer surface of the body portion and extending around an outer circumference of the body portion; and a second rib spaced apart from the first rib, the second rib extending from an outer surface of the body portion and extending around an outer circumference of the body portion, wherein a width of the first contact surface is substantially equal to a width of the first rib, a width of the second contact surface is substantially equal to a width of the second rib, and wherein a groove is formed on an outer surface of the body portion between the first rib and the second rib, a width of the groove is substantially equal to a width of the recess. The recess defined in the interior profile provides a reduced thickness of the body portion from the interior profile to an outer surface of the body portion.

2. The plug of claim 1, wherein, The closed front end of the body portion has a conical shape with a tip.

3. The plug of claim 1, wherein, 4. The stopper of claim 1, wherein at least one collapsible cutout is defined in the interior profile of the internal cavity, wherein the collapsible cutout allows the stopper to collapse or flex when subjected to pressure. The stopper is made of a thermoplastic elastomer.

5. The plug of claim 1, wherein, ​

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