Improving Planing Performance Through Trim Rib Dimensions

Abstract

Disclosed herein is a stopper (10) adapted to be attached to a plunger rod for use in a syringe barrel with improved sliding performance. The stopper (10) includes a body (12) defining an open proximal end (14), a closed distal end (16), and a cylindrical sidewall (20) extending between the open proximal end (14) and the closed distal end (16). At least one rib (22) extends radially outwardly around the periphery of the body (12) and is configured to form an active seal with the syringe barrel. A trim member (30) extends radially outwardly along the periphery of the body (12) at the interface between the closed distal end (16) and the open proximal end (14). The shape, size, and / or diameter of the trim member (30) are controlled to reduce the sliding force of the stopper (10) within the barrel.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to EP application 22305067.5, entitled "IMPROVING SLIDE PERFORMANCE VIA TRIM RIBS DIMENSIONS", filed January 24, 2022, the entire disclosure of which is incorporated by reference herein in its entirety.

[0002] The present invention relates to a stopper or series of stoppers for use in injection devices, such as syringes, cartridges, and / or auto-injectors, which exhibit improved gliding performance by controlling the size and / or shape of the trim member of the stopper. [Background technology]

[0003] Automatic injection devices of products, also called auto-injectors, are widely used in the medical field, where daily injections are necessary to treat pathologies, such as diabetes or arthritis treatment, and where patients often inject themselves. As the patient is not a specialized medical professional, the entire process is designed to be as automated as possible so that the patient does not have to make decisions during the injection. An auto-injector usually comprises, on the one hand, a container (e.g. a prefilled syringe or a cartridge) that has the injection needle and is filled with the product to be injected, and, on the other hand, a motor part, i.e. a part that contains the various systems that trigger the insertion of the needle, realize the injection and potentially activate a protection system at the end of the injection.

[0004] Prefilled or prefillable syringes, auto-injectors, and other types of injection devices often require the slow and controlled initiation and maintenance of a sliding motion from one surface to the other. Two stationary surfaces in a sliding relationship often offer sufficient resistance to the initiation of motion that a gradually increasing force applied to one of the surfaces will not cause motion until a threshold force is reached, at which point sudden sliding or shear separation of the surfaces occurs. The sudden separation of stationary surfaces into a sliding relationship is referred to herein as a "breakout" or "break-loose". This breakout or break-loose is often caused in part by a concentration of stress between the inner surface of the syringe barrel and the trim member of the stopper in contact (i.e., where the individual stopper is trimmed from the molded sheet, typically having its largest diameter). The "breakout force" refers to the force required to overcome the static friction between the surfaces of the syringe assembly that were previously moving in a sliding relationship but that have been stationary ("at rest" or not moving) for a short period of time (e.g., from a few milliseconds to a few hours). A lesser known but important frictional force is the "break-loose force," which refers to the force required to overcome static friction between surfaces of a syringe assembly that have not previously been moved in a sliding relationship or that has been stationary for an extended period of time, often involving chemical or physical bonding or deformation of the surfaces due to aging, sterilization, temperature cycling, or other processing.

[0005] Another important feature of the injection device is that the stopper must have good gliding properties (e.g. low "slide force" to move the stopper within the container). The gliding force of the stopper in a filled or empty syringe is directly related to the main key product parameter of the syringe, namely the injection time of the drug contained in the syringe. This key product parameter is particularly important for syringes used in autoinjectors, as they must comply with a defined injection time. Some stopper designs exhibit a high degree of variability in terms of break-loose and gliding performance, related to the diameter, shape and eccentricity of the cut surface.

[0006] The traditional approach to overcoming breakout, break-loose, and sliding forces is to apply a lubricant to the surface interface. The use of a lubricant increases or decreases the sliding force required to move the stopper within the syringe barrel. Commonly used lubricants are silicone or hydrocarbon oils. The use of some lubricants can have deleterious effects on high value biotechnology pharmaceuticals, especially when used in conjunction with these pharmaceuticals. Thus, there is a need in the art to consistently control and / or reduce the sliding forces required to move stoppers in auto-injectors, syringes, and the like, as well as to consistently control and / or reduce the amount of lubricant required to achieve these reduced sliding forces. Summary of the Invention [Problem to be solved by the invention]

[0007] It is an object of the present invention to provide a tip cover that exhibits reduced pull-out forces when separated from a syringe compared to conventional tip covers, the reduced pull-out forces being achieved without altering the biocompatibility or other properties of the tip cover.

[0008] Additionally, the tip cover sealingly engages the syringe on which it is disposed. Such engagement can prevent contamination of the medicinal fluid disposed in the syringe from the external environment, thereby ensuring the hermeticity of the container. The tip cover can further prevent leakage of the medicinal fluid from the syringe. To that end, a tip cover with reduced pull-out force is required to prevent unintentional removal and to maintain the hermeticity of the container over extended periods of time, such as after extended storage periods. [Means for solving the problem]

[0009] To this end, the present invention relates to a stopper adapted to be attached to a plunger rod for use in a syringe barrel. The stopper comprises a body defining an open rear (proximal) end, a closed front (distal) end, and a cylindrical sidewall extending between the open proximal end and the closed distal end. The open proximal end is adapted to receive a distal front end attachment of a plunger rod. At least one rib extends radially outwardly around said body. The at least one rib is configured to form an active seal with the syringe barrel. The stopper further includes a trim member extending radially outwardly around said body at the interface between the closed distal end and the open proximal end. The trim member is where the individual stoppers are trimmed from the molded sheet. The trim member typically has the largest diameter of the stopper and therefore also contacts the inner surface of the syringe barrel. The trim member is formed by controlling the shape, size, and diameter of the trim member relative to the diameter of the stopper itself to reduce the sliding force of the stopper within the barrel.

[0010] The closed distal end of the stopper has a first diameter and the trim member has a distal extension having a second diameter, the second diameter being equal to or greater than the first diameter. According to one embodiment, the second diameter is about 0-2.8% greater than the first diameter. According to another embodiment, the second diameter is about 2.3-2.8% greater than the first diameter.

[0011] According to one embodiment, a trim member can be disposed between the closed distal end and the at least one rib. Typically, the stopper is molded in two parts and the trim member is disposed at the interface of the closed distal end and the open proximal end. A barrier film may be disposed on and / or adjacent to the closed front end.

[0012] To control the shape, geometry, and / or diameter of the trim members, the trim members are formed with a cutting tool as opposed to a molding tool for forming the stopper body. The cutting tool may be a pre-stretch cutting die. Alternatively, the cutting tool may be a progressive cutting blade die that uses wavy cutting blades that gradually engage the rubber instead of a one-cut stroke die that is prone to rubber displacement due to compressive stresses and Poisson coupling effects. It is understood that other types of cutting tools, such as laser cutting or water jet cutting, can be used to separate the stopper from the molded sheet.

[0013] According to another aspect, the invention relates to a method of forming a consistent sliding force in a series of stoppers. The method includes providing a series of stoppers, each stopper having a body defining an open proximal end, a closed distal end, and a cylindrical sidewall extending between the open proximal end and the closed distal end. The open proximal end is adapted to receive a distal front end attachment of a plunger rod. At least one rib extends radially outwardly around the body. The at least one rib is configured to form an active seal with the syringe barrel, and a trim member extends radially outwardly around the body. The trim member preferably has a diameter configured to reduce the sliding force of the stopper within the barrel, and the shape, geometry, and / or width of the trim member of each of the series of stoppers is controlled by forming the stopper body using a cutting tool rather than a forming tool. The cutting tool can be a pre-stretch cutting die, a progressive cutting die, or any other known cutting tool.

[0014] Each stopper is designed to have a first diameter and the trim member of each stopper is designed to have a distal extension having a second diameter, the second diameter being greater than the first diameter. In one embodiment, the second diameter can be about 0-2.8% greater than the first diameter. In another embodiment, the second diameter can be about 2.3-2.8% greater than the first diameter. The method can optionally include applying a barrier film on the closed leading end of each stopper and / or adjacent the closed leading end, whereby the barrier film extends to the trim member and removing excess barrier material from the stoppers.

[0015] Further embodiments of the present disclosure are described in the following numbered clauses.

[0016] Clause 1: A stopper adapted for attachment to a plunger rod for use in a syringe barrel, the stopper comprising a body defining an open proximal end, a closed distal end, and a cylindrical sidewall extending between the open proximal end, the open proximal end adapted to receive a distal front end attachment portion of the plunger rod, at least one rib extending radially outwardly around the body, the at least one rib configured to form an active seal with the syringe barrel, the stopper characterized by a trim member extending radially outwardly around the body at an interface between the closed distal end and the open proximal end, the trim member having a shape and size configured to reduce sliding forces of the stopper within the barrel.

[0017] Clause 2: The stopper of clause 1, wherein the stopper has a first diameter and the trim member has a distal extension having a second diameter.

[0018] Clause 3: The stopper of clause 2, wherein the second diameter is equal to or greater than the first diameter.

[0019] Clause 4: The stopper according to any one of clauses 2-3, wherein the second diameter is approximately 0-2.8% larger than the first diameter.

[0020] Clause 5: The stopper according to any one of clauses 2 to 4, wherein the second diameter is approximately 2.3 to 2.8% larger than the first diameter.

[0021] Clause 6: The stopper according to any of clauses 1-5, wherein the stopper is molded in two parts, and the trim member is disposed between the closed distal end and the at least one rib.

[0022] Clause 7: The stopper of any of clauses 1-6, comprising a barrier film disposed on and / or adjacent to the closed front end.

[0023] Clause 8: A method of creating a consistent sliding force in a series of stoppers attached to a series of plunger rods for use in a series of syringe barrels, comprising: providing a series of stoppers, each of the stoppers comprising a body defining an open proximal end, a closed distal end, and a cylindrical sidewall extending between the open proximal end and the closed distal end, the open proximal end adapted to receive a distal front end attachment of a plunger rod, at least one rib extending radially outwardly around the body, and a trim member extending radially outwardly around the body, the trim member having a shape, size, and / or diameter configured to reduce the sliding force of the stoppers within the barrel, the shape, size, and / or diameter of the trim member for each of the series of stoppers being controlled using a cutting tool.

[0024] Clause 9: The method of clause 8, wherein each stopper has a first diameter and the trim member of each stopper has a distal extension having a second diameter.

[0025] Clause 10: The method according to clause 9, wherein the second diameter is equal to or greater than the first diameter.

[0026] Clause 11: The method of clause 9 or 10, wherein the second diameter is about 0-2.8% greater than the first diameter.

[0027] Clause 12: The method according to any one of clauses 9 to 11, wherein the second diameter is about 2.3 to 2.8% larger than the first diameter.

[0028] Clause 13: The method of any one of clauses 8 to 12, comprising applying a barrier film to and / or adjacent the closed distal end of each stopper, whereby the barrier film extends to the trim member, and removing excess barrier material from each stopper.

[0029] Clause 14: The method according to any one of clauses 8 to 13, wherein the cutting tool comprises a prestress cutting die or a progressive cutting blade die. [Brief description of the drawings]

[0030] The above and other features and advantages of the present disclosure, as well as the manner in which they are accomplished, will become more apparent, and the disclosure itself will be better understood, by reference to the following description of embodiments of the disclosure taken in conjunction with the accompanying drawings. [Figure 1] FIG. 1 is a side view of a stopper adapted to be attached to a plunger rod for use in a syringe barrel, in accordance with an embodiment of the present invention; [Diagram 2] FIG. 2 is a top perspective view of the stopper of FIG. 1 according to one embodiment of the present invention. [Diagram 3] 2 is a cross-sectional side view of the stopper of FIG. 1 according to one embodiment of the present invention. [Figure 4] 1 is a graph showing the gliding performance of batches "a", "b" and "c" of various stoppers having a trim member according to an embodiment of the present invention. [Figure 5A] 2 is a side view of a portion of the stopper of FIG. 1 with the distal closed front end of the stopper removed in accordance with one embodiment of the present invention. [Figure 5B]2 is a side view of a portion of the stopper of FIG. 1 with the distal closed front end and trim member of the stopper removed in accordance with one embodiment of the present invention. [Figure 5C] FIG. 2 is a side view of a comparative stopper similar to that of FIG. 1, but without the trim member. [Figure 5D1] 5 is a graph similar to FIG. 4 showing the gliding performance of batches a, b, c of stoppers having a trim member according to an embodiment of the invention. [Figure 5D2] 5B is a graph showing the gliding performance of stopper batches a, b, c in which the distal closed front ends of the stoppers have been removed according to the configuration of FIG. 5A. [Figure 5D3] 5C is a graph showing the gliding performance of batches a, b, c of stoppers in which the distal closed front ends and trim members of the stoppers have been removed according to the configuration of FIG. 5B. [Figure 5D4] 5C , showing the gliding performance of batches a, b, c of stoppers without trim members according to the configuration of FIG. 5C . [Figure 6A] 1 is a graph showing the free-gliding performance and trim-up diameter of several batches of stoppers according to one embodiment of the present invention. [Figure 6B] 1 is a graph showing the free-gliding performance and trim-up diameter of several batches of stoppers according to one embodiment of the present invention. [Figure 6C] 1 is a graph illustrating the correlation between free run and trim-up diameter according to one embodiment of the present invention. [Figure 7] 4 is a graph showing the relative ratio of the diameter of the head of the stopper to the diameter of the trim-up member according to one embodiment of the present invention. [Figure 8A] FIG. 2 is a graph showing the distribution of silicone on the barrel before AGF (Activation and Glide Force) testing of batches a, b, and c according to one embodiment of the present invention. [Figure 8B] 1 is a graph showing silicone distribution on the barrel after AGF for batches a, b, and c according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] Corresponding reference characters indicate corresponding parts throughout the several views. The illustrations set forth herein illustrate exemplary embodiments of the present disclosure, and such illustrations are not to be construed as limiting the scope of the present disclosure in any way.

[0032] The following description is provided to enable one of ordinary skill in the art to make and use the described embodiments contemplated for practicing the invention. However, various modifications, equivalents, variations, and alternatives will be readily apparent to those skilled in the art. All such modifications, variations, equivalents, and alternatives are intended to be within the spirit and scope of the invention.

[0033] In the following description, the terms "top", "bottom", "right", "left", "vertical", "horizontal", "upper", "lower", "transverse", "vertical", and their derivatives shall refer to the concepts illustrated in the drawings. However, it shall be understood that the concepts may assume various alternative variations unless expressly specified to the contrary. It shall also be understood that the specific devices illustrated in the accompanying drawings and described in the following specification are merely exemplary embodiments of the concepts. Hence, specific dimensions and other physical characteristics relating to the embodiments disclosed herein are not to be considered as limiting.

[0034] Also, for purposes of describing this invention, the term "distal end" shall refer to the end of the syringe from which the needle protrudes and the end of the stopper nearest the needle, while the term "proximal end" shall refer to the end of the syringe nearest the syringe holder and the end of the stopper furthest from the needle tip.

[0035] Attention is directed to Figures 1-3, which show a stopper, labeled "10," adapted to be attached to a plunger rod (not shown) for use in a syringe barrel (not shown), in accordance with one embodiment of the present invention. As shown in Figure 3, the open proximal end 14 is adapted to receive a front or distal forward end attachment (not shown) of a plunger rod via threads 16. The stopper 10 further includes at least one rib 22, such as two or three ribs, preferably three ribs, extending radially outwardly around the body 12. The at least one rib 22 is configured to form an active seal with the syringe barrel. The at least one rib 22, together with additional ribs of the stopper 10, are configured to ensure a seal between the stopper 10 and the barrel. The presence of multiple ribs ensures container closure integrity. The stopper 10 further includes a trim member 30 extending radially outwardly around the periphery of the body 12. The trim member 30 is where individual stoppers 10 are trimmed from a molded sheet (not shown) during a trimming process. According to one embodiment, the stopper 10 can be molded in two parts, with the trim member 30 located at the interface of the closed distal end 16 and the open proximal end 14. The trim member 30 typically has the largest diameter of the stopper 10 and contacts the inner surface of the syringe barrel, so that the diameter of the trim member 30 is larger than the diameter of the inner surface of the syringe barrel. According to the present invention, the trim member 30 is formed by controlling the shape, size, and / or diameter relative to the diameter of the stopper 10 itself to reduce the sliding force of the stopper within the barrel. It is understood that while the stopper and barrel can have different diameters depending on the size of the syringe and / or injection device, at least the diameter rib 22 of the stopper, and preferably the trim member 30, can form an active seal against the inner surface of the barrel, thereby preventing liquid from escaping and leaking beyond the rear or proximal end 14 of the stopper 10 and ensuring container closure integrity.

[0036] According to one embodiment, a trim member can be disposed between the closed distal end and the at least one rib, as shown in Figures 1-3. A barrier film can be disposed over or adjacent to the closed distal end 16. The barrier film can extend to the distal extension 32 of the trim member 30 and provide a barrier between the contents of the syringe and the stopper material. The material used for the barrier film can be ethylene tetrafluoroethylene (ETFE), although it can be understood that other known types of materials that exhibit barrier properties can be used.

[0037] As mentioned above, the present invention is directed to an optimized stopper design with additional dimensional and geometric control to produce a stopper 10 with lower sliding force and avoid the adverse effects of stress concentrations typically generated by the trimming process. The sliding force (whether for a filled or empty syringe) is directly related to a primary critical product parameter of the syringe, namely, the injection time of the drug contained in the syringe. This critical product parameter is particularly important for syringes used in auto-injectors, since these devices must adhere to prescribed injection times. However, prior to the present invention, some stopper designs with trim members 30 have shown a high degree of variability in terms of sliding performance, as shown in FIG. 4, which shows the sliding performance of three different batches "a", "b", and "c" ranging from 2N to 6N. The three different batches "a", "b", and "c" differ from each other in the dimensions of the diameter of the distal extension 32 of the trim member. In this case, batches "a", "b" and "c" have diameters of the distal extension 32 of the trim member 30 of approximately 6.84 mm, 6.86 mm and 6.92 mm, respectively.

[0038] Prior to the present invention, certain stoppers such as those shown in Figures 1-3 are manufactured in a single molding process that produces a laminated head with a barrier layer applied and a number of unlaminated ribs (three in number). The molding process is completed by trimming the individual stoppers from the molded sheet. In most cases, the trimming occurs between the laminated head and the rear three ribs. An undesirable effect of this process is that the end of the trim width becomes the first place where the syringe contents come into contact with the stopper material without the barrier protection of the film head. This trim width is often irregular and not controlled with respect to a specific size, diameter, or shape.

[0039] In the present invention, tests are performed on three different batches of stoppers (batches "a", "b", and "c") to prove that the trim member 30 contributes significantly to the gliding performance of the stopper 10. Figure 5A shows a stopper 10A comprised of both the trim member 30 and ribs 22, but with the closed distal end 12 removed. Figure 5B shows a stopper 10B comprised only of the ribs 22, with the closed distal end 16 and trim member 30 removed. Figure 5C is a comparative stopper 10C having a closed distal end 16 and ribs 22, but without a trim member in place.

[0040] FIG. 5D shows a series of graphs comparing the stoppers of batches "a", "b" and "c", respectively. The sliding force of the complete stopper configuration (including the trim member) of batches "a", "b" and "c" is shown in graph 5D1. As can be seen in this graph, the stoppers have a sliding force similar to that shown in FIG. 4. The sliding force of the stoppers of batches "a", "b" and "c" having a stopper configuration with three ribs 22 and a trim member 30 as shown in FIG. 5A is shown in graph 5D2. The sliding force of the stoppers of batches "a", "b" and "c" having a stopper configuration with only ribs 22 as shown in FIG. 5B is shown in graph 5D3. The sliding force of the comparative stoppers of batches "a", "b" and "c" configured as shown in FIG. 5C and without the trim member present is shown in graph 5D4. As shown in Figures 5D1 and 5D2, the complete stopper with rib members (Figure 5D1) and the rib and trim configuration of Figure 5B (Figure 5D2) have essentially the same sliding force. However, as shown in Figures 5D3 and 5D4, for batches "a", "b", and "c" where the trim members have been removed, there is no significant difference in sliding force between the batches. This test data proves that the trim members 30 are the main contributor to the difference in sliding performance.

[0041] Thus, the present invention identifies a heretofore unestablished or controlled relationship between the top or distal extension 32 of the trim member 30 and its functional performance (gliding). This dimension is referred to as the "trim-up diameter" or D2, as described below.

[0042] FIG. 6A and the figures show the empty glide performance (measurement of glide force on an empty syringe) and the "trim-up" dimensions of several stopper batches (a)-(k). Correlations can be formed from these performances, as detailed in FIG. 6C. In conclusion, to obtain lower and less variable glide forces, the suggested specifications for the "trim-up" dimensions can be an average maximum of 6.67-6.88 mm, with a maximum of 6.91 mm. The head or distal end 16 of the stopper 10 can have a diameter of 6.75 + / - 0.08 mm, with a maximum diameter of about 6.83 mm. The inner diameter of the syringe barrel can be 6.35 + / - 0.1 mm. For other similar stopper designs, specifications can be applied to the gap between the "trim-up" and "head" diameters.

[0043] 1 and 3, the stopper 10 has a first diameter D1 and the trim member 30 has a distal extension 32 having a second diameter D2, the second diameter D2 being greater than the first diameter D1. In one embodiment, the difference between the second diameter D2 and the first diameter D1 is 0.19 mm or less, for example, D2-D1 is shown as reference numeral 34 in FIG. 2. The second diameter of the distal extension 32 of the trim member 30 can be approximately 6.67-6.91 mm.

[0044] Now referring to the graph of FIG. 7, it is shown that the second diameter D2 may be approximately 2.8% larger than the first diameter.

[0045] According to one embodiment, the second diameter D2 can be approximately 0-2.8% larger than the first diameter D1. According to a further embodiment, the second diameter D2 can be approximately 2.3-2.8% larger than the first diameter D1.

[0046] To control the shape and / or form and / or diameter of the trim member 30, the trim member 30 is formed with a cutting tool as opposed to a molding process to form the stopper body. The cutting tool may be a prestressed cutting die. Alternatively, the cutting tool may be a progressive cutting blade die that uses wavy cutting blades that gradually engage the rubber instead of a one-cut stroke die that is prone to rubber displacement due to compressive stresses and Poisson coupling effects. It will be appreciated that other types of cutting tools can be used to separate the stopper from the molded sheet.

[0047] In accordance with another aspect, and with reference to Figures 1-3 and 6A-7, the present invention relates to a method of forming a consistent sliding force on a series of stoppers 10 adapted to be attached to a series of plunger rods for use with a series of syringe barrels. The method includes providing a series of stoppers 10, each stopper including a body 12 defining an open rear or proximal end 14, a closed front or distal end 16, and a cylindrical sidewall 20 extending between the open rear end 14 and the closed front end 16. The open proximal end 14 is adapted to receive a distal front end attachment (not shown) of a plunger rod. At least one rib 22 is provided extending radially outwardly around the body 12. The at least one rib 22 may include three ribs and may be configured to form an active seal with the syringe barrel. A trim member 30 extends radially outwardly around the body 12. The trim members 30 include distal extensions 32 having relative diameters configured to reduce the sliding force of the stopper within the barrel, and the width of the trim members 30 of each of the series of stoppers is controlled by using a cutting tool. The cutting tool can be either a pre-stretch cutting die or a progressive cutting blade die. Other known cutting dies can also be used to cut the trim members, where the shape, size, and / or diameter of the trim member is controlled. The use of a cutting tool allows for closer control and tolerance of the size and shape of the trim ribs, resulting in a controlled and consistent trim member 30.

[0048] Each stopper 10 is designed to have a first diameter D1 and the trim member 30 of each stopper 10 is designed to have a distal extension 32 having a second diameter D2, the second diameter D2 being greater than the first diameter D1. According to one embodiment, as shown in FIG. 7, the second diameter D2 can be about 0-2.8% greater than the first diameter D1. According to a further embodiment, the second diameter D2 can be about 2.3-2.8% greater than the first diameter D1. The method can further include applying a barrier film on and / or adjacent the closed distal end 12 of each stopper 10, such that the barrier film extends to the trim member 30. The method can further include removing excess barrier material from the stopper 10.

[0049] With reference to Figures 8A and 8B, the present invention has found that one physical phenomenon that explains the correlation between the "trim-up" dimensions and the sliding force is the wiping of the silicone layer from the barrel. This is due to the stress concentration caused by the "trim-up" geometry. The larger the gap between the trim member 30 and the head or front end 12 of the stopper 10, as shown at 34 in Figure 2, the more lubricant, i.e., silicone, is scraped off from the barrel. This is because the compression ratio and corresponding contact pressure at the "trim-up" is greater. Up to a certain threshold, the less silicone in the barrel, the higher the sliding force. This phenomenon is also related to the viscosity of the silicone oil and the rate at which it is extruded from the "trim-up" contact area. The higher the viscosity of the silicone oil, the less it is extruded. However, higher viscosity has a negative effect on the sliding due to Reynolds lubrication. The decrease in sliding force due to increased viscosity is expected to be small compared to the extrusion effect of high contact pressure. This is shown in Figures 9A and 9B. Here, the silicon distribution is analyzed before and after the sliding test of stoppers of batches "a", "b" and "c". In this test, the empty AGF (activation and sliding force) of 15 stoppers (5 from 3 different batches) is tested. Measurements of the thickness of the silicon layer are also performed. Before the AGF test, the silicon distribution of the 15 barrels used was uniform. The results are shown in Figure 9A. As shown in Figure 9B, in the test after AGF, the barrel of batch "c", which corresponds to the stopper with a higher sliding force (about 5.7 N) as shown in Figure 4, has a lower silicon distribution than the other barrels, indicating that the stoppers of batch "c" removed more silicon from the barrel than the other stopper batches.

[0050] While the present disclosure has been described as having an exemplary design, the disclosure can be further modified within the spirit and scope of the disclosure. Accordingly, this application is intended to cover any variations, uses, or adaptations using the general principles of the disclosure. Further, this application is intended to cover such departures from the disclosure as come within known or customary practice in the art to which the disclosure pertains and fall within the scope of the appended claims.

Claims

1. 1. A stopper configured to be attached to a plunger rod for use in a syringe barrel, comprising: a body defining an open proximal end, a closed distal end, and a cylindrical sidewall extending between the open proximal end and the closed distal end, the open proximal end configured to receive a distal front end attachment portion of the plunger rod; at least one rib extending radially outwardly around the body, the at least one rib configured to form an active seal with the syringe barrel; a trim member extending radially outwardly around the body at an interface between the closed distal end and the open proximal end, the trim member having a shape, size, and / or diameter configured to reduce sliding forces of the stopper within the syringe barrel; The stopper, wherein the closed distal end of the stopper has a first diameter and the trim member has a second diameter, the second diameter being approximately 2.3-2.8% larger than the first diameter.

2. The stopper of claim 1 , wherein the trim member has a distal extension having the second diameter.

3. The stopper of claim 1 , wherein the stopper is molded in two parts, and the trim member is disposed between the closed distal end of the stopper and the at least one rib.

4. The stopper of claim 1 , further comprising a barrier film disposed at and / or adjacent the closed distal end.

5. 5. The stopper of claim 4, wherein the barrier film is ethylene tetrafluoroethylene (ETFE).

6. 1. A method of creating a consistent sliding force in a series of stoppers adapted for attachment to a series of plunger rods for use in a series of syringe barrels, said method comprising: providing a series of stoppers; Each of the stoppers is a body defining an open proximal end, a closed distal end, and a cylindrical sidewall extending between the open proximal end and the closed distal end, the open proximal end configured to receive a distal front end attachment portion of the plunger rod; at least one rib extending radially outwardly around the body, the at least one rib configured to form an active seal with the syringe barrel; a trim member extending radially outwardly around the body and having a shape, size, and / or diameter configured to reduce sliding forces of the stopper within the syringe barrel; Equipped with The method wherein the shape, size, and / or diameter of the trim member of each of a series of the stops is controlled using a cutting tool.

7. 7. The method of claim 6, wherein the closed distal end of each of the stoppers has a first diameter and the trim member of each of the stoppers has a second diameter, the second diameter being approximately 2.3-2.8% larger than the first diameter.

8. The method of claim 7 , wherein the trim member of each of the stops has a distal extension having the second diameter.

9. 7. The method of claim 6, further comprising disposing a barrier film on and / or adjacent to the closed leading end of each of the stoppers, whereby the barrier film extends to the trim member and removes excess barrier material from each of the stoppers.

10. 10. The method of claim 9, wherein the barrier film is ethylene tetrafluoroethylene (ETFE).

11. The method of claim 6 , wherein the cutting tool comprises a pre-stretch cutting die or a progressive cutting blade die.

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