Plunger rod and syringe adapted for compression failure

Abstract

A plunger rod (104) for use in conjunction with a syringe barrel (102) is provided. The plunger rod (104) includes a distal plunger top (105) having a proximal bottom surface (113) and a proximal elongate shaft (106), the proximal elongate shaft (106) including a proximal end (107a) adapted to receive a force applied along an axis (1000) and a distal end plate (107b) adapted to transmit the applied force along the axis (1000). The plunger rod (104) is adapted to be inserted into the barrel (102) of the syringe (100) extending along the axis (1000). The distal plunger top (105) and the proximal elongate shaft (106) are connected to one another by a releasable connection (115). The releasable connection (115) comprises a distal apex breaking means (116) comprising at least one distal apex rib (125a) disposed eccentrically from the axis (1000) on the proximal bottom surface (113), and a proximal shaft breaking means (117) comprising at least one proximal shaft rib (125b) disposed eccentrically from the axis (1000) on the distal end plate (107b). Each of the at least one distal apex rib (125a) is connected to a corresponding at least one proximal shaft rib (125b), the ribs (125a, 125b) being connected at a contact region (118), and the distal apex breaking means (116) is configured to separate from the proximal shaft breaking means (117) by compressive breaking when the distal plunger apex (105) is forced into the distal end (110) of the barrel (102). A syringe is also provided.

Description

[Technical field]

[0001] The present invention relates to a plunger rod for a syringe for preventing the reuse of the syringe, which can be manufactured at the same cost as a conventional syringe.The present invention further relates to a syringe including the plunger rod. [Background technology]

[0002] Injections are one of the most common medical procedures, with at least 16 billion injections administered worldwide each year. Multiple use of the same syringe to inject multiple people can lead to the spread of several infectious diseases. It is estimated that syringe misuse causes more than 2 million patients and users to become infected with serious blood-borne diseases such as HIV, Hepatitis B, and Hepatitis C each year. The majority of these injections are administered using commercially available or pre-filled conventional syringes.

[0003] In 2015, the World Health Organization (WHO) set a deadline that by 2020, all syringes worldwide should be replaced with so-called "smart syringes", such as auto-disable (AD) syringes.

[0004] AD syringes available on the market have several drawbacks. Most smart syringes are based on a locking mechanism between the plunger rod and the syringe barrel. When the plunger rod is inserted and reaches the front of the cylinder barrel of the syringe, the locking mechanism is activated. While trying to retract the plunger rod, a tensile fracture occurs, splitting the plunger rod into two separate parts. Thus, re-use of the syringe is prevented. Such an AD syringe is described, for example, in US Pat. No. 5,399,363.

[0005] However, these types of syringes have a complex design. For example, the inner wall of the barrel may be provided with a flange, and the piston rod is correspondingly designed to engage with the flange. Such a difficult design results in a manufacturing cost substantially higher than that of a conventional syringe.

[0006] Another type of AD syringe is the syringe with sharps protection (SIP) and reuse prevention (RUP). SIP+RUP syringes are available as manual or automatic versions. In the manual version, the user manually activates the safety feature. The automatic retractable model is essentially similar to the manual version, but it includes a device such as a spring that automatically retracts the needle into the plunger when the plunger rod hits the bottom of the barrel. When pressure is applied to the plunger rod, a spring mechanism in the syringe is activated, retracting the needle into the syringe barrel. Thus, after one use, additional injections are not possible. The risk of injury due to contact with the needle, for example in the disposal process, is more or less eliminated. However, this design includes many different components and multiple implementation steps. This, in turn, results in very high manufacturing costs.

[0007] Therefore, there is a need for an auto-defeat syringe that addresses the disadvantages and shortcomings of the prior art and that can be manufactured in a cost-effective manner. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] US Patent Application Publication No. 2013 / 0110044 Summary of the Invention

[0009] Accordingly, the present invention seeks to preferably mitigate, alleviate or eliminate one or more of the above mentioned deficiencies and disadvantages in the art, either singly or in any combination, and solves at least the above mentioned problems by proposing a solution according to the attached independent claims. Advantageous embodiments are defined in the attached dependent claims.

[0010] In a first aspect, a plunger rod for use in connection with a syringe barrel is provided. The plunger rod comprises a distal plunger top having a proximal bottom surface, and a proximal elongated shaft, the proximal elongated shaft comprising a proximal end adapted to receive an applied force along an axis, and a distal end plate adapted to transmit said applied force along said axis. The plunger rod is adapted to be inserted into a barrel of a syringe extending along an axis. The distal plunger top and the proximal elongated shaft are connected to each other by a releasable connection, the releasable connection comprising a distal apex rupture means having at least one distal apex rib disposed eccentrically from the axis on the proximal bottom surface, and a proximal shaft rupture means having at least one proximal shaft rib disposed eccentrically from the axis on the distal end plate. Each at least one distal apex rib is connected to a corresponding at least one proximal shaft rib, the ribs being connected at a contact area. The distal apex fracturing means is configured to separate from the proximal shaft fracturing means by compressive fracturing when the distal plunger apex is forced into the distal end of the barrel.

[0011] In a second aspect, a syringe is provided comprising a barrel having a syringe tip disposed at a distal end of the barrel, the barrel adapted to contain a medicament and having a tubular wall extending proximally from said distal end, the barrel extending along an axis, the barrel including an opening disposed at a proximal end of the barrel, and the syringe further comprising a plunger rod extending along the axis.

[0012] Further advantages will become apparent from the detailed description as well as the appended dependent claims.

[0013] These and other aspects, features and advantages to which the present invention is capable will become apparent and elucidated from the following description of embodiments of the invention, taken in conjunction with the accompanying drawings. [Brief description of the drawings]

[0014] [Figure 1A] FIG. 2 illustrates a longitudinal view of a syringe and an isometric view of a plunger rod according to one example. [Figure 1B] FIG. 1B is a longitudinal view of the syringe and plunger rod according to the example of FIG. 1A. [Diagram 2] 1A-1C are longitudinal and isometric views of a syringe and plunger rod according to a second example; [Diagram 3] 13A-13C are longitudinal and isometric views of a syringe and plunger rod according to a third example; [Figure 4] 4A-4D are longitudinal and isometric views of a syringe and plunger rod according to a fourth example; [Diagram 5] 13A-13C show a cross-sectional view of a syringe and plunger rod according to a fifth example and an isometric view of said plunger rod. [Figure 6] 6 shows an alternative to the syringe and plunger rod shown in FIG. 4 according to a sixth embodiment. [Figure 7] 7 shows yet another alternative to the syringe and plunger rod shown in FIG. 4 according to a seventh example. [Figure 7B] 8 shows a further embodiment of the syringe of FIG. 7. [Figure 8] FIG. 13 shows longitudinal and isometric views of a pre-filled syringe and plunger rod according to an eighth example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, the embodiments of the present invention will be described in more detail with reference to the accompanying drawings so that those skilled in the art can practice the present invention. However, the present invention may be embodied in many different forms and should not be construed as being limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present invention to those skilled in the art. The embodiments do not limit the present invention, but the present invention is limited only by the appended "claims". Furthermore, the terms used in the detailed description of the specific embodiments shown in the accompanying drawings are not intended to limit the present invention.

[0016] Referring to FIG. 1, an example of a syringe 100 and plunger rod 104 according to the teachings herein is shown. The syringe 100 comprises a barrel 102 having a distal end 110 and a proximal end 112. The distal end 110 comprises a distal tip 111 to which a needle may be attached. The barrel 102 of the syringe 100 may be made of any material suitable for containing a medicament, but is preferably made of plastic. The plastic is preferably transparent. The barrel 102 is configured to contain a medicament. The medicament may be in liquid form to be injected into a patient or user. Additionally, the barrel 102 has a tubular wall 101.

[0017] The syringe 100 extends along an axis 1000 that defines the direction in which the barrel 102 extends; for example, the barrel 102 extends along the axis 1000 .

[0018] The syringe 100 of FIG. 1 further comprises a plunger rod 104 disposed within the barrel 102. The plunger rod 104 extends along the tubular wall 101 and the axis 1000. The washer 103 is disposed on a distal plunger top 105 of the plunger rod 104. The distal plunger top 105 comprises a proximal bottom plate 113. The plunger rod 104 further comprises an elongated proximal shaft 106 having a proximal end 107a and a distal end plate 107b.

[0019] The washer 103 is adapted for fluid-tight engagement with the tubular wall 101 of the barrel 102. By fluid-tight engagement with the tubular wall 101 of the barrel 102, a medicament or liquid contained within the barrel 102 is prevented from leaking out of the syringe 100 in any other direction other than through the distal tip 111 (or a needle attached to said distal tip) at the distal end 110 of the barrel 102.

[0020] The distal plunger top 105 and the elongated proximal shaft 106 are connected to each other by a releasable connection 115. The releasable connection 115 of FIG. 1A comprises a distal apex rupture means 116 and a proximal shaft rupture means 117. The distal apex rupture means 116 is disposed on the proximal bottom surface 113 of the distal plunger top 105. The proximal shaft rupture means 117 is disposed on the distal end plate 107 of the elongated proximal shaft 106. The distal apex rupture means 116 on the bottom surface 113 comprises three distal apex ribs 125a. The proximal shaft rupture means 117 on the distal end plate 107b comprises three proximal shaft ribs 125b. The distal apex rib 125a is disposed centrally relative to the proximal shaft rib 125b. Thus, the proximal shaft rib 125b is disposed transversely relative to the distal apex rib 125a. The connection between the distal apex rib 125a and the proximal shaft rib 125b is further described with reference to FIG.

[0021] Each of the examples in Figures 1A-8 shows a different non-limiting embodiment of a releasable connection 115 connecting the distal tip 105 to the proximal elongated shaft 106 of the plunger rod 104. In all embodiments, an axis 1000 defines the longitudinal direction of the syringe and plunger rod, having a distal end and a proximal end. The axis 1000 extends along the center of the syringe. The perimeter of the plunger rod and the syringe barrel define a lateral perimeter.

[0022] The distal apex rib 125a and the proximal shaft rib 125b of the releasable connection 115 disclosed herein are eccentrically disposed with respect to each other and with respect to the axis 1000. Breaking of the releasable connection 115 occurs when the plunger rod 104 is subjected to a force applied along the axis 1000, forcing the distal plunger apex 105 into the distal end 110 of the barrel 102. When the distal plunger apex 105 reaches and is further pressed toward the distal end 110, a compression break occurs between the distal apex breaking means 116 and the proximal shaft breaking means 117, which disengage from each other. Thus, when the user withdraws the plunger rod 104, the distal plunger apex 105 remains in the barrel 102, and only the elongated proximal shaft 106 is withdrawn from the barrel 102. Obviously, the syringe 100 cannot be reused.

[0023] FIG. 1B shows a cross section of the plunger rod 104 disclosed in FIG. 1A in an in-use position AE.

[0024] Position A (mounted position): The plunger rod 104 is positioned within the barrel 102. A releasable connection 115 connects the distal plunger top 105 to the plunger rod 104.

[0025] In this embodiment, the releasable connection 115 is shown in an enlarged view of position A. The distal end plate 107b and the proximal bottom surface 113 each include three separately arranged proximal shafts 125b and three separately arranged distal apices 125a. However, due to the longitudinal cross-sectional view of FIG. 1B, only two distal apices ribs 125a and two proximal shaft ribs 125b are visible. Each distal apices rib 125a located on the bottom surface 113 is paired and connected to a corresponding proximal shaft rib 125b located on the distal end plate 107b. The distal apices ribs 125a are connected to the proximal shaft ribs 125b at the contact area 118. The longitudinal cross-sections of the distal apices ribs 125a and the proximal shaft ribs 125b have a conical or pyramidal shape.

[0026] The distal apex rib 125a of the distal apex breaking means 116 and the proximal shaft rib 125b of the proximal shaft breaking means 117 are connected to each other along the extension of the axis 1000. Each distal apex rib 125a is connected to a corresponding proximal shaft rib 125b. The two connected distal apex ribs 125a and proximal shaft ribs 125b are arranged eccentrically with respect to each other and with respect to the axis 1000. The central facing surface of one proximal shaft rib 125b (facing toward the axis 1000) is connected to the lateral facing surface of the distal apex rib 125a (facing away from the axis 1000) at the contact area 118. Thus, the normal of the surface of the distal apex rib 125a points laterally outward from the center. The normal of the surface of the proximal shaft rib 125b points toward the center toward the central axis 1000. This provides greater stability in the lateral / medial direction (perpendicular to axis 1000). The distal apex disrupting means 116 is more centrally located closer to axis 1000 relative to the proximal shaft disrupting means 117.

[0027] Position B (withdrawn position): The plunger rod 104 is withdrawn, exposing the lumen 108 within the barrel 102. In the close-up of position B, the releasable connection 115 is intact and connects the distal plunger top 105 to the elongated shaft 106. Additionally, the barrel 102 includes a flattened angle 120 that extends from the opening 109 of the barrel 102 to a circumferential flange 119 formed on the inner wall of the barrel 102. This helps the washer 103 establish quicker contact with the inner wall of the barrel 102 during installation. Additionally, this design prevents the build-up of friction as the washer 103 passes over the circumferential flange 119. Additionally, the proximal bottom plate 113 has angled side edges 128 that also reduce friction as the bottom plate 113 passes over the circumferential flange 119.

[0028] The proximal bottom plate 113 has a smaller diameter than that of the circumferential flange 119 to avoid contact therebetween, which could damage the releasable connection 115 during installation. The distal end plate 107b ensures that the piston rod 104 cannot be withdrawn from the barrel 102 after the drug has been withdrawn into the lumen 108.

[0029] Position C (forward position - no pressure load): The plunger rod 104 has been pushed to the distal end 110 of the barrel 102. The applied pressure load was sufficient to force the contents of the lumen 108 out of the syringe 100, but not enough force to allow compressive failure of the releasable connection 115. Thus, the releasable connection 115 is intact. The distal contact surface between the distal apex rib 125a of the distal apex breaking means 116 and the proximal shaft rib 125b of the proximal shaft breaking means 117 comprises a weakened portion in the form of a sharp edge 122. The proximal contact surface between the distal apex breaking means 116 and the proximal shaft breaking means 117 comprises a reinforcement in the form of a bend 121. The sharp edge 122 acts as a weakening of the releasable connection 115, accelerating and facilitating compressive failure when the plunger rod 104 is pushed distally, as described further in connection with position D. Conversely, the bend 121 prevents undesirable tensile failure during withdrawal of the plunger rod 104, as shown in position B.

[0030] Position D (forward position - applied pressure load): The plunger rod 104 is subjected to further force along the axis 1000 and is therefore pushed further towards and into the distal end 110 of the barrel 102. This causes the releasable connection 115 to actuate and break. A compressive break occurs and the distal apex rib 125a and the proximal shaft rib 125b are separated from each other. The cavity 114 allows the proximal shaft rib 125b to be pushed forward and a compressive break occurs, even though the distal plunger apex 105 has reached and is in contact with the distal end 110. As shown in the close-up portion of position D, there is no longer a direct contact between the distal apex rib 125a and the proximal shaft rib 125b. When the break occurs, the distal rib 125a has a distal rib break surface 135 and the proximal shaft rib 125b has a proximal shaft rib break surface 136. The distal rib surface 135 faces toward the center. The proximal shaft rib fracture surface 136 faces laterally.

[0031] Position E (distal plunger top removal): When the user pulls out the plunger rod 104 in the barrel 102, the distal plunger top 105 is detached from the plunger rod 104. Thus, the syringe 100 cannot be reused. Each distal top rib 125a and the proximal shaft rib 125b are angled towards each other (as shown in the enlarged views of positions A and D). The angle between the centrally facing surface of the rib 125b and the distal end plate 107b is less than 90 degrees. The angle between the laterally facing surface of the rib 125a and the proximal bottom surface 113 is greater than 90 degrees. This reduces the risk that the distal top breaking means 116 and the proximal shaft breaking means 117 will engage each other when the distal plunger top 105 is released from the plunger rod 104.

[0032] 2-8, additional embodiments of seven plunger rods 204, 304, 404, 504, 604, 704, 804 are shown. The use of plunger rods in the embodiments shown in FIGS. 2-7 all include positions AE. Since the example in FIG. 8 relates to a pre-filled AD syringe 800, FIG. 8 does not include position A. Position A is the loading position. Position B is the withdrawn position where the lumen 108 of the barrel 102 is filled with drug. Position C is the forward position where the lumen 108 has been emptied of its contents but no excessive force is being applied to the plunger rod 104. Thus, the releasable connections 115, 215, 315, 415, 515, 615, 715, 815 are still intact. Position D is the forward position where a pressure load is applied and compressive failure of the releasable connections occurs. In the disengagement position, position E, the distal plunger tip 105 is released from the plunger rod 104 .

[0033] 2 shows a plunger rod 204 according to a second embodiment, comprising a releasable connection 215. The releasable connection 215 comprises a distal apex breaking means 216 disposed on a proximal bottom surface 213 of the distal apex 205. A proximal shaft breaking means 217 is disposed on the distal end plate 207 of the elongated proximal end shaft 206.

[0034] The distal apex rupturing means 216 and the proximal shaft breaking means 217 each include two eccentrically disposed distal apex ribs 225a and proximal shaft ribs 225b, respectively. The distal apex rupturing means 216 and the proximal shaft breaking means 217 may include three or more eccentrically disposed distal apex ribs 225a and proximal shaft ribs 225b. The distal apex ribs 225a and the proximal shaft ribs 225b are linearly disposed along the diameter of the bottom surface 213 and the distal end plate 207, respectively. The proximal shaft ribs 225b are centrally disposed closer to the axis 2000 relative to the distal apex ribs 225a.

[0035] The distal apex rib 225a includes two distal rib projections 223a, respectively, and the proximal shaft rib 225b includes two proximal rib projections 223b, respectively. The distal apex rib 125a and the proximal shaft rib 125b are connected to each other through the distal rib projections 223a and the proximal shaft projections 223b. The projections are also referred to herein as fracture cones. The distal rib projections 223a and the proximal shaft projections 223b extend radially from the distal apex rib 225a and the proximal shaft rib 225b.

[0036] The distal rib protrusion 223a on the rib 225a faces toward the center. The proximal shaft protrusion 223b points laterally along the same diameter along which the distal apex rib 225a and the proximal shaft rib 225b are linearly disposed. Each distal rib protrusion 223a is connected to a corresponding proximal rib protrusion 223b. The corresponding distal rib protrusions 223a and proximal rib protrusions 223b are disposed at longitudinal heights relative to one another such that they face one another. The connected distal rib protrusions 223a and proximal rib protrusions 223b form an hourglass-shaped connection between the distal apex rib 225a and the proximal shaft rib 225b.

[0037] The hourglass shaped connection formed by the distal rib projection 223a and the proximal rib projection 223b may include weakening grooves 224. In Figure 2, the grooves 224 are located at the nodes of the hourglass shaped connection. The grooves 224 will accelerate failure during compression failure and allow for a sharp / clear failure.

[0038] The distal rib projections 223a and the proximal rib projections 223b may have different diameters and lengths. A smaller distance between the distal apex rib 225a and the proximal shaft rib 225b prevents viscoelastic deformation and / or shear of the distal rib projections 223a and the proximal rib projections 223b before compressive failure occurs, and therefore prevents more effective / obvious compressive failure of the distal rib projections 223a and the proximal rib projections 223b. The distal rib projections 223a and the proximal rib projections 223b are linearly arranged on the distal apex rib 225a and the proximal shaft rib 225b along the axis 2000, allowing the use of three or more distal rib projections 223a and the proximal rib projections 223b.

[0039] When failure occurs as shown at position D, distal rib 225a has a distal rib failure surface 235 and proximal shaft rib 225b has a proximal shaft rib failure surface 236. Distal rib failure surface 235 faces inward. Proximal shaft rib failure surface 236 faces laterally.

[0040] FIG. 3 shows a plunger rod 304 according to a third embodiment. The plunger rod 304 has a distal end apex 305 and an elongated proximal shaft 306. The releasable connection 315 is similar to the embodiment shown in FIG. 2. The releasable connection 315 comprises a distal apex breaking means 316 having two distal apex ribs 325a eccentrically arranged on the proximal bottom plate 313. The two proximal shaft ribs 325b of the proximal shaft breaking means 317 are eccentrically arranged on the distal apex 307b. The proximal shaft ribs 325b are arranged transversely to the distal apex rib 325a. The distal apex rib 325a and the proximal shaft rib 325b extend along the axis 3000.

[0041] The distal apex rib 325a and the proximal shaft rib 325b are linearly disposed along the central diameter of the bottom surface 313 and the distal end plate 307b, respectively. The proximal shaft rib 325b is more centrally disposed closer to the axis 3000 relative to the distal apex rib 325a.

[0042] The distal apex rib 325a includes a distal rib protrusion 323a, and the proximal shaft rib 325b includes a proximal rib protrusion 323b, respectively. The distal apex rib 325a and the proximal shaft rib 325b are connected to each other through the distal rib protrusion 323a and the proximal shaft protrusion 323b. The distal rib protrusion 323a and the proximal shaft protrusion 323b extend radially from the distal apex rib 325a and the proximal shaft rib 325b.

[0043] The distal rib projection 323a on the rib 325a faces toward the center. The proximal shaft projection 323b faces laterally along the same diameter along which the distal apex rib 325a and the proximal shaft rib 325b are linearly disposed. Each distal rib projection 323a is connected to a corresponding proximal rib projection 323b. The corresponding tip rib projection 323a and the proximal rib projection 323b are disposed at a longitudinal height from each other such that they face each other. The connected distal rib projection 323a and the proximal rib projection 323b form an hourglass-shaped connection between the distal apex rib 325a and the proximal shaft rib 325b.

[0044] The hourglass shaped connection formed by the distal rib projection 323a and the proximal rib projection 323b may include weakened grooves 324 (shown in close-up at point D in FIG. 3). The grooves 224 are located at the nodes of the hourglass shaped connection. The grooves 324 facilitate a sharp break between the cones 323.

[0045] The distal apex rib 325a and the proximal shaft rib 325b are hexagonal and asymmetric. An advantage of this embodiment is that it is easier to optimize the compression failure behavior.

[0046] Use positions AD are shown in FIG. 3, and in position C, a close-up view shows the third embodiment with and without optional groove 324. In position D, proximal shaft breaking means 317 is released from distal apex breaking means 316 and proximal shaft rib 325b is forced into cavity 314. Once the compression break is established (position D), plunger rod 304 may be retracted from barrel 302 (position E - not shown in FIG. 3). Once breakage occurs, distal rib 325a has a distal rib break surface 335 and proximal shaft rib 325b has a proximal shaft rib break surface 336. Distal rib break surface 335 faces toward the center. Proximal shaft rib break surface 336 faces laterally.

[0047] A fourth embodiment of a plunger rod 404 is shown in Figure 4. The plunger rod 404 has a distal plunger apex 405 and an elongated proximal shaft 406. The releasable connection 415 is similar to the embodiment shown in Figure 2 and includes a breaking means 416 having two distal apex ribs 425a eccentrically disposed on the proximal bottom plate 413 of the distal end apex 405. Two proximal shaft ribs 425b of the proximal shaft breaking means 417 are eccentrically disposed on the distal end apex 407b.

[0048] The distal apex rib 425a and the proximal shaft rib 425b extend along the axis 4000. Each distal apex rib 425a includes two distal rib projections 423a. Each proximal shaft rib 425b includes two proximal rib projections 423b. The distal rib projections 423a and the proximal rib projections 423b extend substantially perpendicularly from the distal apex rib 425a and the proximal shaft rib 425b and the axis 4000.

[0049] The distal apex rib 425a and the proximal shaft rib 425b are connected to one another through the distal rib protrusions 423a and the proximal shaft protrusions 423b which extend radially from the distal apex rib 425a and the proximal shaft rib 425b.

[0050] The distal rib protrusion 423a on the rib 425a faces toward the center. The proximal shaft protrusion 423b faces laterally along the same diameter along which the distal apex rib 425a and the proximal shaft rib 425b are linearly disposed. Each distal rib protrusion 423a is connected to a corresponding proximal rib protrusion 423b at a contact area 418. The corresponding distal rib protrusions 423a and proximal rib protrusions 423b are disposed at longitudinal heights relative to one another so as to face one another. The connected distal rib protrusions 423a and proximal rib protrusions 423b form an hourglass-shaped connection between the distal apex rib 425a and the proximal shaft rib 425b.

[0051] Upon fracture, distal rib 425a has a distal rib fracture surface 435 and proximal shaft rib 425b has a proximal shaft rib fracture surface 436. Distal rib fracture surface 435 faces inward. Proximal shaft rib fracture surface 436 faces laterally.

[0052] Distal apex rib 425a and proximal shaft rib 425b are linearly disposed along a central diameter of bottom surface 413 and distal end plate 407, respectively. Proximal shaft rib 425b is disposed closer to axis 4000 than distal apex rib 425a.

[0053] In this embodiment, the protrusion 423 is shaped like a triangular prism. As a result, the contact area 418 has an elongated width 426. This embodiment of the releasable connection 415 has good stability due to the elongated width 426. The contact area 418 may further comprise a reinforcement 427 facing the elongated shaft 406. The contact area 418 may further comprise a groove 424 facing the distal end apex 405.

[0054] 5 shows a plunger rod 504 according to a fifth embodiment. The distal end plate 507b and the proximal bottom plate 513 include two eccentrically disposed distal top ribs 525a and proximal shaft ribs 525b, respectively.

[0055] Each distal apex rib 525a includes a distal rib protrusion 523a. Each proximal shaft rib 525b includes a proximal rib protrusion 523b. The distal apex rib 525a and the proximal shaft rib 525b are connected to each other through the distal rib protrusion 523a and the proximal shaft protrusion 523b. The distal rib protrusion 523a and the proximal shaft protrusion 523b extend radially from the distal apex rib 525a and the proximal shaft rib 525b.

[0056] The distal rib projections 523a on the ribs 525a face in a central direction. The proximal shaft projections 523b face laterally. Each distal rib projection 523a connects to a corresponding proximal rib projection 523b at a contact region 518. The corresponding distal and proximal rib projections 523a, 523b are disposed at longitudinal heights opposite one another.

[0057] 1-4, the distal rib projection 523a and the proximal shaft projection 523b in this embodiment are not linearly opposed to one another. Instead, the contact area 518 is formed by the overlap between the side edges of the distal rib projection 523a and the proximal shaft projection 523b. Each centrally opposed side edge of the distal rib projection 523a is connected to a centrally opposed side edge of the proximal rib projection 523b.

[0058] The two distal apex ribs 525a are eccentrically disposed relative to the axis 5000 and relative to the proximal shaft rib 525b. As shown in the close-up view of position C, the distal apex rib 525a is centrally disposed relative to the proximal shaft rib 525b. Furthermore, as seen in the close-up view of the top of the plunger rod 504, the distal rib 525a is also horizontally displaced relative to the proximal shaft rib 525b, the horizontal direction being perpendicular to the longitudinal axis 5000. Thus, the distal apex rib 525a and the proximal shaft rib 525b are not linearly disposed along the diameter of the bottom surface 513 and the distal end plate 507b.

[0059] Preferably, the contact area 518 is small, approximately 0.2 mm 2The overlap at the contact area 518 provides stability during rotation of the plunger rod 504 within the barrel 502.

[0060] When the plunger rod 504 is pushed into a forward position and an overload is applied, the distal rib protrusion 523a and the proximal rib protrusion 523b disengage from each other and the proximal shaft rib 525b is pushed into the cavity 514, as shown in the enlarged view of position D in FIG. 5.

[0061] Upon fracture, distal rib 525a has a distal rib fracture surface 535 and proximal shaft rib 525b has a proximal shaft rib fracture surface 536. Distal rib fracture surface 535 and proximal shaft rib fracture surface 536 face the central axis 5000.

[0062] FIG. 6 shows a plunger rod 604 with a releasable connection 615 according to embodiment number 3 (FIG. 3), where the washer is an O-ring seal 603. Since the distal plunger top 605 is not covered by a washer as shown in FIG. 3, in this embodiment the compressive failure is performed with two solid and hard polymers, such as polypropylene (PP), in direct contact with each other. The distal end 610 of the barrel 602 is in direct contact with the top surface 629 of the distal plunger top 605 at positions C and D. This results in a sharper and more pronounced failure of the failure cone 623. The O-ring seal 603 is made of a damping material, such as an elastomer, e.g., synthetic rubber or silicone. The O-ring seal 603 may be combined with any other of the embodiments disclosed herein.

[0063] 7 shows a plunger rod 704 according to a third embodiment, where the syringe 700 further comprises an additional locking mechanism 730. The plunger top 705 comprises an end projection 731 extending from the upper surface 729 through the washer 703. The distal top 711 of the syringe 700 comprises an internal retaining wall 732 configured to engage with a retaining portion 733 disposed on the end projection 731. The releasable connection 715 is of the same type as shown in FIGS. 3 and 6.

[0064] The addition of locking mechanism 730 creates an auto-defeat syringe 700 with features that allow for both compressive and tensile failure. As seen in position A of FIG. 7, retaining portion 733 is located proximal to the distal end 710 of barrel 702 and distal top 711 of syringe 700. When retaining protrusion 733 on end protrusion 731 is pushed past retaining wall 732, the locking mechanism is actuated. This is shown in a close-up view in position C. In position D, both locking mechanisms 730 are engaged and releasable connection 715 is released. In position E, locking mechanism 730 is actuated but releasable connection 715 is still intact. If releasable connection 715 does not fail during compression, retaining portion 733 will engage retaining wall 732 as shown in a close-up view in position F and plunger top 705 will be released from plunger rod 704 as shown in position G.

[0065] The additional locking mechanism 730 may be combined with any other releasable connections 115, 215, 315, 415, 515, 615, 815 of the embodiments disclosed herein.

[0066] In Figure 7B, a further embodiment of the syringe 700 of Figure 7 is shown. The syringe 700' has a plunger rod 704' of the same type as shown in Figure 7 and an additional locking mechanism 730'. The distal plunger top 705' includes an end projection 731' that extends from the top surface 729' through the washer 703'. The distal tip 711' of the syringe 700' includes an internal retaining wall 732' configured to engage with a retaining portion 733' disposed on the end projection 73. The releasable connection 715' is of the same type as shown in Figures 3, 6 and 7.

[0067] Further, the washer 703' has a central opening 737'. The distal plunger top 705' has a raised socket 738' that extends through said central opening 737' of the washer 703'. The central opening 737' may be formed, for example, by injection molding or by punching. The diameter of the socket 738' is in the same range as the diameter of the central opening 737' or is slightly wider. If the diameter of the socket 738' is larger than the width of the central opening 737', the socket 737' may be press-fit into the opening 738'.

[0068] The distal end face 739' of the socket 738' is at the same longitudinal level as the washer 703', as seen, for example, in the enlarged portion of position CG in FIG. 7B. When the distal plunger top 705' reaches the distal end 710', the distal end face 739' of the socket 738' and the distal end 710' of the barrel 702' come into direct contact with one another. Because the socket 738' and the distal end 710' preferably comprise two solid and hard polymers, such as polypropylene (PP), a sharper and more obvious break between the plunger rod 704' and the distal plunger top 705' occurs in the same manner as described for the embodiment shown in FIG.

[0069] Similar to the embodiment shown in FIG. 3, when a break occurs between the distal plunger top 605, 705, 705' and the plunger rod 604, 704, 704' of FIGS. 6, 7 and 7B, the distal rib 625a, 725a, 725a' has a distal rib break surface 635, 735, 735' and the proximal shaft rib 625b, 725b, 725b' has a proximal shaft rib break surface 636, 736, 736'. The distal rib break surface 635, 735, 735' faces medially. The proximal shaft rib break surface 636, 736, 736' faces laterally.

[0070] Referring to FIG. 8, a plunger rod 804 according to an eighth embodiment is shown. The plunger rod 804 is designed to be placed in a pre-filled syringe 800 and includes an elongated proximal shaft 806 and a distal end apex 805. The distal end apex 805 includes a proximal bottom plate connected to a distal end plate 807 through a releasable connection 815 similar to the fifth embodiment of FIG. 5. The barrel 802 is preferably made of glass. In position A, the lumen 808 of the barrel 802 is filled with a liquid or drug. The syringe 800 includes a needle 840 covered by a needle cap 841. The distal plunger apex 805 includes a threaded protrusion 845 extending from a distal surface of the bottom plate 813.

[0071] When installing the pre-filled syringe 800, preferably the washer 803 is first inserted into the opening 809 of the barrel 802. The plunger rod 804 is then inserted into the opening 809 by threading the threaded protrusion 845 through the washer 803. The releasable connection 815 in this embodiment is adapted to withstand such threading during installation without damage.

[0072] The releasable connection 815 includes a distal apex rib 825a and a proximal shaft rib 825b eccentrically disposed on the bottom surface 813 and the distal end plate 807, respectively. The bottom surface 813 and the distal end plate 807 include two distal apex ribs 825a and two proximal shaft ribs 825b, respectively. The proximal shaft ribs 825b are linearly disposed along a diameter of the distal end plate 807b. The distal apex ribs 825a are centrally disposed closer to the axis 8000 relative to the proximal shaft ribs 825b. The distal apex ribs 825a include a distal rib projection 823a, respectively. The proximal shaft ribs 825b include a proximal rib projection 823b, respectively. The distal rib projections 823a and the proximal rib projections 823b are connected to each other at a contact area 818. The contact area 818 is located in an interface plane that extends along and through the axis 8000. Two distal apex ribs 825a are disposed on either side of the interface plane. Two proximal shaft ribs 825b are disposed on either side of the interface plane. The two formed contact areas 818 are the medial lateral overlaps between the distal rib projections 823a and the proximal rib projections 823b.

[0073] Thus, the structure of the releasable connection 815 in FIG. 8 is an overlapping lateral connection. The central lateral overlap of the contact areas 818 allows the releasable connection 815 to withstand rotation, for example, when assembling and installing a pre-filled syringe. When the plunger rod 804 is rotated in one direction, the distal rib projection 823a presses against the proximal rib projection 823b at the contact area 818. When the plunger rod 804 is rotated in the opposite direction, the proximal rib projection 823b presses against the distal rib projection 823a at the contact area 818. Thus, the structure of the releasable connection 815 is durable during both clockwise and counterclockwise rotation. Preferably, the contact area 818 is minimal and no greater than 0.2 mm. 2 And so on.

[0074] The releasable connection 815' comprises an eccentrically disposed distal apex rib 825a and a proximal shaft rib 825b. The distal apex rib 825a is disposed on the bottom surface 813, and the proximal shaft rib 825b is disposed on the distal end plate 807b. As described for the releasable connection 815, the distal apex rib 825a and the proximal shaft rib 825b are connected to each other in an overlapping manner. The releasable connection 815' is suitable for, for example, a syringe having a small diameter of the barrel 802. As described for the releasable connection 815, the overlap between the distal apex rib 825a and the proximal shaft rib 825b makes the releasable connection 815' resistant to rotation of the plunger rod 804.

[0075] When a break occurs between distal plunger top 805 and plunger rod 804 in FIG. 8, distal rib 825a has a distal rib break surface 835 and proximal shaft rib 825b has a proximal shaft rib break surface 836.

[0076] The embodiment shown in Figures 1-8 minimizes the manufacturing cost of the auto-defeat syringe. Because the structure relies on failure by compression failure and not on interaction between the plunger rod and the syringe barrel, the plunger rod herein can be used with existing syringes (embodiments 1-6) or existing pre-filled syringes (embodiment 8). The seventh embodiment requires the formation of an internal retention recess 732. However, such a feature is easily manufactured during injection molding. The design disclosed herein is simpler than current syringes with features for tensile failure or spring-loaded syringes. Thus, manufacturing costs can be reduced to the same level or below that of conventional syringes or conventional pre-filled syringes.

[0077] In addition, the new design provides good stability that allows for a fast packaging process. Furthermore, the plunger rod disclosed herein may be manufactured from different polymers suitable for medical devices with varying material properties. The brittleness and impact strength of the polymer affect the behavior of the plunger rod. Therefore, there is a wide range of possibilities for optimizing the strength and the compressive failure during the withdrawal of the plunger rod to fill the barrel with the drug.

[0078] All embodiments herein may include fewer or more ribs than described for each example. Additionally, each rib may have fewer or more protrusions extending therefrom. Ribs described as being located proximate the axis may be located on either the distal end plate of the proximal elongate shaft or the proximal bottom surface of the distal plunger top. The ribs may have various dimensions, i.e., different lengths and widths. The protrusions may have varying shapes and dimensions.

[0079] Additionally, the present invention has been described primarily with reference to certain embodiments. However, as will be readily appreciated by those skilled in the art, other embodiments besides those disclosed above are equally possible within the scope of the present invention, as defined by the appended claims.

[0080] In the claims, the term "comprises / comprising" does not exclude the presence of other elements or steps. Furthermore, although individually listed, a plurality of means, elements or method steps may be implemented by, for example, a single unit or processor. Furthermore, although individual features may be included in different claims, these may in some cases be advantageously combined, and the inclusion in different claims does not imply that a combination of features is not feasible and / or advantageous. In addition, the reference of the singular does not exclude a plurality. The use of the terms "a", "an", "first", "second", etc. does not exclude a plurality. Reference signs in the claims are provided merely as a clarifying example and shall not be construed as limiting the scope of the claims in any way.

Claims

1. A plunger rod (104) for use in connection with a syringe barrel (102), said plunger rod (104) comprising a distal plunger top (105) having a proximal bottom surface (113), and a proximal elongated shaft (106), said proximal elongated shaft (106) comprising a proximal end (107a) adapted to receive an applied force along an axis (1000), and a distal end plate (107b) adapted to transmit said applied force along said axis (1000); The plunger rod (104) is adapted to be inserted into the barrel (102) of the syringe (100) extending along the axis (1000); The distal plunger top (105) and the proximal elongate shaft (106) are connected to one another by a releasable connection (115), the releasable connection (115) comprising: a distal apex disrupting means (116) comprising at least one distal apex rib (125a) disposed eccentrically from the axis (1000) on the proximal bottom surface (113); a proximal shaft breaking means (117) comprising at least one proximal shaft rib (125b) disposed eccentrically from the axis (1000) on said distal end plate (107b); Equipped with each of the at least one distal apex rib (125a) is connected to a corresponding at least one proximal shaft rib (125b), the ribs (125a, 125b) being connected at a contact area (118), and the distal apex breaking means (116) is configured to detach from the proximal shaft breaking means (117) by compressive breaking when the distal plunger apex (105) is forced into the distal end (110) of the barrel (102); The plunger rod (104) further comprises a cavity (114), the cavity (114) being formed between the proximal shaft rib (125b) and the proximal bottom surface (113) of the distal end plate (107b) and configured to receive the proximal shaft rib (125b) when the force is transmitted along the axis (1000) to the distal plunger top (105) to release the distal top rib (125a) and the proximal shaft rib (125b) from one another.

2. 2. The plunger rod of claim 1, wherein the ribs (125a, 125b) extend along the axis (1000) from the distal end plate (107b) and from the proximal bottom surface (113), respectively.

3. 3. The plunger rod of claim 1 or 2, wherein the distal apex rib (125a) is radially displaced relative to the proximal shaft rib (125b).

4. A plunger rod as described in any one of claims 1 to 3, wherein when the distal rib (125a) and the proximal shaft rib (125b) are separated from each other, the distal rib (125a) has a distal rib fracture surface (135) and the proximal shaft rib (125b) has a proximal shaft rib fracture surface (136), which are oriented centrally and laterally, respectively, with respect to the axis (1000).

5. 5. A plunger rod as claimed in any one of claims 1 to 4, wherein the distal top rib (125a) and the proximal shaft rib (125b) are aligned linearly along a diameter of the proximal bottom surface (113) and the distal end plate (107b).

6. A plunger rod as described in any one of claims 1 to 5, wherein the ribs (125a, 125b) extend along the axis (1000) and the center-facing side of each distal top rib (125a) is connected to a laterally-facing side of a corresponding proximal shaft rib (125b), or vice versa.

7. 7. The plunger rod of claim 6, wherein the distal apex rib (125a) is angled away from the axis (1000) and the proximal shaft rib (125b) is angled toward the axis (1000), or vice versa.

8. A plunger rod as described in any one of claims 1 to 7, wherein the ribs (125a, 125b) are arranged so that a side edge of the distal apex rib (125a) perpendicular to a side of the distal apex rib (125a) facing outward when viewed from the axis (1000) is connected to a side edge of the approximate shaft rib (125b) perpendicular to a side of the approximate shaft rib (125b) facing outward when viewed from the axis (1000).

9. 9. A plunger rod as claimed in any one of claims 1 to 8, wherein the distal top rib (125a) and the proximal shaft rib (125b) respectively include at least one distal rib protrusion (123a) and a proximal rib protrusion (123b).

10. 10. A plunger rod as described in claim 9, wherein each distal apex protrusion (123a) faces a corresponding proximal shaft protrusion (123b) and is positioned opposite the corresponding proximal shaft protrusion (123b), the protrusions (123a, 123b) forming a connection between the distal apex rib (125a) and the proximal shaft rib (125b).

11. A plunger rod as claimed in any one of claims 1 to 10, wherein the distal plunger top (105) comprises a washer (103), the washer (103) adapted for fluid-tight engagement with a tubular wall (101) of the barrel (102), and the washer (103) is displaceable along the axis (1000) within the barrel (102).

12. 12. A plunger rod as claimed in any one of claims 1 to 11, wherein the distal plunger top (105) further comprises an end projection (731) disposed distally on the plunger top (105) comprising a retaining portion (733) configured to engage with an internal retaining recess (732) of the end projection (731).

13. 13. A plunger rod according to any one of claims 1 to 12, wherein the contact area (118) is provided with a weakened portion (122, 124), the weakened portion (122, 124) being preferably a groove (124) or a sharp edge (122) arranged on a distal side of the contact area (118).

14. A syringe (100) comprising a barrel (102) having a syringe tip (111) disposed at a distal end (110) of the barrel (102), the barrel (102) adapted to contain a medicament, the barrel (102) having a tubular wall (101) extending proximally from the distal end (110), the barrel (102) extending along an axis (1000); the barrel (102) includes an opening (109) disposed at a proximal end (112) of the barrel (102); The syringe (100) further comprises a plunger rod (104) according to any one of claims 1 to 13, the plunger rod (104) extending along the axis (1000).

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