JP2016077749A - Gasket for pre-filled syringe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent tilting of a gasket by increasing slide resistance of the gasket in a sterilization process without increasing the slide resistance of the gasket in inserting the gasket into an outer cylinder and in using as an injection syringe.SOLUTION: A gasket 3 for a pre-filled syringe comprises a barrel part 36 and a tail par 37. The barrel part 36 is connected to a distal end of a plunger and forms at least a seal surface 35 brought into contact with an inner peripheral surface 25 of an outer cylinder 2. The tail part 37 protrudes from a rear end surface 33 of the barrel part 36 to the back, is brought into contact with the inner peripheral surface 25 of the outer cylinder 2, is thinner than the barrel part 36, and shows flexibility for bending in a direction separated from the inner peripheral surface 25 of the outer cylinder 2.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a gasket for a syringe used in a medical syringe. More specifically, the present invention relates to a prefilled syringe gasket prefilled with a chemical solution or the like.

  In recent years, syringes (prefilled syringes) pre-filled with chemicals have been used because of the merit of easier drug management, such as reducing the risk of infection, ensuring accurate dosages, and enabling quick administration in emergency situations. It has been. The prefilled syringe is generally a cylindrical tube (also referred to as an outer tube or a syringe; hereinafter referred to as an outer tube), a movable plunger, and a distal end of the plunger as well as being held in the outer tube. It is comprised with the gasket which can slide, keeping airtight. The plunger that pushes in the gasket is used by being screwed into a screw hole of the gasket when used as a syringe.

  For example, as shown in FIG. 6, the prefilled syringe is sterilized by spraying high-pressure steam or hot water in a state where the outer cylinder 2 is filled with a chemical solution and sealed with the top cap 8 and the gasket 103 ( For example, see Patent Documents 1 and 2).

JP 2006-239048 Special Table 2004-532076

  Here, since the prefilled syringe is operated by the hands of a doctor, a nurse, etc., like a general syringe, if the sliding resistance of the gasket 103 is high, the usability as a syringe is poor. Become. For this reason, it is desirable to reduce the sliding resistance by shortening the axial length of the sealing surface 135 of the gasket 103 (the surface constituting the seal with the inner peripheral surface of the outer cylinder: sealing surface).

  However, if the axial length of the seal surface 135 of the gasket 103 is shortened to reduce the sliding resistance, the gasket 103 moves and tilts due to the liquid pressure of the chemical liquid due to the temperature rise of the chemical liquid during the sterilization process. Sometimes. The inclination of the gasket 103 may reduce the sealing performance due to the gasket 103 and may cause leakage of the chemical solution. Further, when the gasket 103 is inclined, there is a problem that it becomes difficult to attach the plunger to the gasket 103. For example, when the gasket 103 and the plunger are connected by a screw, there is a problem that it is difficult to screw the male screw at the tip of the plunger into the screw hole 134 formed in the gasket 103.

  Therefore, in the prefilled syringe, in order to prevent the inclination of the gasket 103 during the sterilization process, the axial length of the seal surface 135 of the gasket is lengthened to increase the contact area with the inner peripheral surface of the outer cylinder, thereby sliding the gasket. It is necessary to increase dynamic resistance. By increasing the length of the sealing surface of the gasket, it is difficult to move the gasket during the final sterilization process. However, when the length of the gasket sealing surface is increased, the sliding resistance between the gasket and the outer cylinder increases, so that it becomes difficult to insert the gasket into the outer cylinder, and sliding when used as a syringe. As described above, since the mobility becomes worse, the usability as a syringe becomes worse.

  In other words, in the gasket of a conventional prefilled syringe, the gasket sliding resistance is lowered when inserting the gasket into the outer cylinder and when used as a syringe, and the gasket sliding resistance is increased during the sterilization process to move the gasket. In addition, preventing tilting is a trade-off and is difficult to achieve.

  The present invention is for a prefilled syringe that can increase the sliding resistance of the gasket during the sterilization process and suppress the inclination of the gasket without increasing the sliding resistance of the gasket when inserting the gasket into the outer cylinder and when used as a syringe. An object is to provide a gasket.

  In order to achieve this object, a gasket for a prefilled syringe according to claim 1 is connected to the tip of a plunger and forms at least one sealing surface that comes into contact with the inner peripheral surface of the outer cylinder. A rear end surface projecting rearwardly, coming into contact with the inner peripheral surface of the outer cylinder, being thinner than the barrel, and having a flexible tail that bends away from the inner peripheral surface of the outer cylinder. ing.

  The invention according to claim 2 is the prefilled syringe gasket according to claim 1, wherein the plunger rod protrudes in a direction away from the inner peripheral surface of the outer cylinder on the inner peripheral surface side of the tail portion and is connected to the trunk portion. Or it has the protrusion pushed toward a trunk | drum by a gasket mounting jig | tool, and when this protrusion falls, a tail part separates or reduces a contact pressure with respect to an outer peripheral surface of an outer cylinder, It is characterized by the above-mentioned.

  According to a third aspect of the present invention, in the prefilled syringe gasket according to the second aspect, the protrusion is inclined toward the side opposite to the rear end surface of the body portion.

  According to the gasket for a prefilled syringe according to claim 1, since the sterilization process by high-pressure steam is performed in a state where the tail portion of the gasket is in contact with the inner peripheral surface of the outer cylinder, the tail portion is placed on the inner peripheral surface of the outer cylinder by vapor pressure or the like. The effect of increasing the contact pressure when pressed is obtained. That is, during the sterilization process, the tail portion can come into contact with the inner peripheral surface of the outer cylinder with high tightening allowance. In other words, during the sterilization process, sliding resistance is obtained not only on the sealing surface of the trunk but also on the entire length of the gasket including the tail, making it difficult for the gasket to move. Even if the gasket moves more than the sliding resistance, the entire length of the gasket is longer than in the case of only the body portion, so that the gasket can be prevented from being inclined in the outer cylinder.

  In addition, when the gasket is inserted into the outer cylinder by the gasket mounting jig, the tail is thinner than the barrel, and the inside is hollow and there is no backup, so the sealing surface of the gasket barrel Sliding resistance is weaker than For this reason, since sliding resistance is low compared with the time of a sterilization process, and the sliding of a gasket becomes easy, the usability as a syringe becomes good. Further, since the gasket can be easily inserted into the outer cylinder, the assembly work of the prefilled syringe is simplified.

  Therefore, it is possible to suppress the inclination of the gasket by increasing the sliding resistance of the gasket during the sterilization process without increasing the sliding resistance of the gasket when inserting the gasket into the outer cylinder and when used as a syringe.

  According to the invention of claim 2, since it protrudes in the direction away from the inner peripheral surface of the outer cylinder on the inner peripheral surface side of the tail portion, and has a protrusion pushed toward the trunk portion by the plunger rod or the gasket mounting jig, When the plunger rod is attached to the gasket and the gasket is pushed, or when the gasket is inserted into the outer cylinder by a gasket mounting jig that inserts the gasket into the outer cylinder, the protrusion is deformed so as to be pushed down to the barrel side of the gasket. Accordingly, the portion contacting the inner peripheral surface of the outer cylinder with the contact pressure of the tail can be deformed so as to warp, and the separation or contact pressure from the inner peripheral surface of the outer cylinder can be reduced. Therefore, during the sterilization process, the presence of the tail increases the sliding resistance of the gasket to prevent the gasket from tilting, but when used as a syringe or when the gasket is incorporated into the outer cylinder, the sliding resistance of the gasket is reduced at the tail. The gasket can be easily slid by reliably reducing the amount of dynamic resistance.

  Further, according to the third aspect of the present invention, since the protrusion is inclined to the atmosphere side, when mounting a plunger or a dedicated jig / gasket mounting jig for inserting the outer cylinder on the gasket, A force that causes the tail to warp away from the inner peripheral surface is easily applied to the protrusion. For this reason, it is possible to reduce the sliding resistance by deforming the tail portion so as to warp inward in the radial direction and pulling it away from the inner peripheral surface of the outer cylinder.

It is a center longitudinal cross-sectional view which shows one Embodiment of the gasket for prefilled syringes concerning this invention. It is a center longitudinal cross-sectional view which shows the state which connected the plunger to the gasket for prefilled syringes. It is an expanded sectional view which shows the relationship between the trunk | drum and tail part of the gasket for refilled syringes of FIG. It is a center longitudinal cross-sectional view which shows other embodiment of the gasket for prefilled syringes concerning this invention. It is a figure which shows other embodiment of the gasket for prefilled syringes concerning this invention, (A) is a center longitudinal cross-sectional view, (B) is a bottom view. It is a center longitudinal cross-sectional view which shows the structure of the conventional prefilled syringe and its gasket.

  Hereinafter, the configuration of the present invention will be described in detail based on embodiments shown in the drawings.

  1 to 3 show an example of an embodiment of the gasket for prefilled syringe of the present invention. The prefilled syringe 1 is a syringe pre-filled with a chemical solution or the like (not shown), and is generally a cylindrical tube (also referred to as an outer tube or a syringe; hereinafter referred to as an outer tube) 2 and a movable plunger ( 6) (also called a pusher) and a gasket 3 which is slidable while maintaining airtightness in the outer cylinder 2 at the tip of the plunger 6.

  The outer cylinder 2 is a bottomed cylindrical cylinder having a bottom portion 21, for example, and a reduced diameter portion 22 is integrally formed at the center of the bottom portion 21. The diameter-reduced portion 22 is used with, for example, a hub of needle tubes, various connectors, tubes, catheters and the like (not shown) for drug solution administration and blood collection. The outer cylinder 2 is formed with a chemical solution storage space 24 surrounded by the gasket 3, and the chemical solution storage space 24 communicates with the inner cavity 23 of the reduced diameter portion 22.

  In the storage space 24, for example, sugar injection solutions such as blood and glucose, electrolyte correction injection solutions such as sodium chloride and potassium lactate, vitamin agents, vaccines, antibiotic injection solutions, contrast agents, steroid agents, and proteolysis Contains various chemical solutions such as enzyme inhibitors, fat emulsions, anticancer agents, anesthetics, or liquids such as distilled water, disinfectant, liquid food, and alcohol (collectively referred to herein as chemical solutions). Is done.

  The gasket 3 includes a barrel portion 36 that forms at least one sealing surface 35 that contacts the inner circumferential surface 25 of the outer cylinder 2, and projects rearward from a rear end surface 33 of the barrel portion 36. 25 and a tail portion 37 having flexibility to bend in a direction away from the inner peripheral surface 25 of the outer cylinder.

  The gasket 3 includes a gasket body 4 made of an elastic material and a resin film 5 that covers the outer surface of the gasket body 4. The gasket main body 4 is usually formed of an elastic material, and the maximum outer diameter portion of the gasket 3 is set slightly larger than the inner diameter of the outer cylinder 2, so that the outer periphery of the gasket is surrounded by the elastic force of the gasket main body 4. 2 is provided so as to maintain liquid tightness by being in contact with the inner peripheral surface 25 of the second.

  The elastic material constituting the gasket body 4 is not limited to a specific elastic material, but examples thereof include natural rubber, butyl rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, halogenated butyl rubber, and silicone rubber. Of these various rubber materials, various thermoplastic elastomers such as polyurethane, polyester, polyamide, olefin, and styrene are preferably used in combination of one or more. Among these, a material that can obtain elasticity by vulcanization is more preferable.

  As shown in FIG. 1, the gasket 3 according to the present embodiment includes at least a portion in contact with the inner peripheral surface 25 of the outer cylinder 2, that is, an outer peripheral surface 31, preferably an outer peripheral surface 31 that is a portion in contact with the inner peripheral surface 25 of the outer cylinder 2 and A surface that comes into contact with and seals the chemical solution filled in the outer cylinder 2, that is, a conical tip end surface (referred to as a liquid sealing surface in the present specification) 32 is covered with a liquid-tight resin film 5 having excellent peristaltic properties. ing. In this embodiment, except for the rear end surface (the rear end surface of the body portion 36, which is referred to as an anti-liquid sealing surface in this specification) 33 to which the plunger (not shown) of the gasket body 4 is connected. The liquid sealing surface 32 and the outer peripheral surface 31 of the gasket body 4 are covered with the resin film 5. Since this resin film 5 requires high liquid-tightness in addition to at least high slidability, it is necessary to be composed of a water-impermeable material having a low coefficient of friction and excellent slidability. However, depending on the liquid to be filled, it is necessary to have chemical resistance for other properties such as drugs. Therefore, the resin film 5 is preferably made of a material excellent in slidability and chemical resistance, such as polytetrafluoroethylene or a copolymer thereof, ETFE (ethylene-tetrafluoroethylene copolymer), or tetrafluoroethylene. , PFA (tetrafluoroethylene-perfluoroalkoxyethylene copolymer (for example, a copolymer of tetrafluoroethylene and perfluoroalkoxyethylene whose alkoxyl group has 1 to 5 carbon atoms)), PVdF (polyvinylidene) Fluoride resins such as fluoride), PCTFE (polychlorotrifluoroethylene), TFE (tetrafluoroethylene), and FEP (fluorinated ethylene propylene) can be used, and one or more of these can be used in combination. it can. Of course, the constituent material of the resin film 5 is not particularly limited to those exemplified above.

  Further, at least one seal surface 35 which is the maximum outer diameter portion of the gasket 3 is formed on the outer peripheral surface 31 of the gasket 3 facing the inner peripheral surface 25 of the outer cylinder 2 so as to protrude outward in the radial direction. Here, when the length of the sealing surface 35 that contacts the inner peripheral surface 25 of the outer cylinder 2 is the same, a plurality of sealing surfaces are formed rather than contacting the inner peripheral surface of the outer cylinder with one sealing surface. It is preferable to use a plurality of seal locations. In this case, even if leaking from one sealing surface, it is easy to ensure sealing performance because the sealing can be performed with the other sealing surface. Moreover, since it becomes easy to slide also by disperse | distributing a sealing surface, what formed two or more sealing surfaces is preferable. Therefore, in the case of the present embodiment, the first seal surface 35a near the liquid sealing surface 32 having a trapezoidal axial cross section and the second seal surface 35b near the rear end surface 33 that becomes the atmosphere side 7 are provided. It has a sealing surface.

  In addition, the barrel portion 36 of the gasket 3 of the present embodiment is thinner than the barrel portion 36, and the diameter increases again from the valley portion of the second seal surface 35b, which is the end of the barrel portion 36, toward the end portion. A tail portion 37 having a paraboloidal surface (a shell-shaped surface) or a conical surface is formed. That is, the tail portion 37 of the present embodiment does not closely contact the inner peripheral surface 25 of the outer cylinder 2 with contact pressure in the entire region, but strongly against the inner peripheral surface 25 of the outer cylinder 2 toward the free end (tip) side. It is provided in a structure that can be pressed. Here, the gasket 3 is in a natural state (a state where no external force is applied), as shown in FIG. 3, if the relationship of “diameter of seal surface (d1) <maximum diameter of tail (d2)” is satisfied. Since the contact pressure of the tail portion 37 is increased, it is preferable for increasing the sliding resistance of the gasket 3 when the tail portion 37 is in contact. The relationship between the diameters of the sealing surface 35 and the tail portion 37 is not particularly limited to this, and any configuration may be used as long as the tail portion 37 contacts the inner peripheral surface 25 of the outer cylinder 2 with a contact pressure.

  Further, the tail portion 37 of the gasket 3 is formed in a structure that is easily bent toward the direction away from the inner peripheral surface 25 of the outer cylinder 2, that is, radially inward. For example, in this embodiment, it is provided so as to be easily bent inward in the radial direction by reducing the wall thickness. Specifically, the tail portion 37 has a form in which the outer peripheral portion of the trunk portion 36 is extended rearward from the rear end surface 33 of the trunk portion 36, and the boundary between the root of the tail portion 37, that is, the trunk rear end surface 33. The portion is formed to be the thickest, and the thickness gradually decreases from the portion toward the protrusion 38, and the tip from the protrusion 38 is formed to have the same thickness. Accordingly, the tail portion 37 is mainly deformed so as to be bent from the protrusion 38, and the entire tail portion 37 is provided so as to be separated from the inner peripheral surface 25 of the outer cylinder 2. Of course, the thickness of the tail portion 37 is not limited to the above-mentioned relationship. For example, by making the thickness of the tail portion 37 uniform from the root to the end portion, the entire portion from the root of the tail portion 37 to the tip of the tail portion 37 is radially inward. You may provide so that it may bend easily toward.

  Further, in order to make the tail portion 37 positively bent easily inward in the radial direction, it is preferable that a projection 38 protruding radially inward is formed on the inner peripheral surface side of the tail portion 37. This protrusion 38 is directed toward the body portion 36 by a plunger rod 61 connected to the body portion 36 or a dedicated jig for inserting the gasket 3 into the outer cylinder 2 (referred to as a gasket mounting jig in the present specification, not shown). The outer cylinder 2 is deformed so as to be pushed down toward the body part 36 by being pushed and deformed so that the part of the tail part 37 that comes into contact with the inner peripheral surface 25 of the outer cylinder mainly warps with a high contact pressure of the tail part 37. The distance from the inner peripheral surface 25 or the contact pressure is reduced. With respect to the shape and dimensions (height h, thickness t) of the protrusion 38, when used as a syringe or when the gasket is incorporated into the outer cylinder, a plunger rod 61 connected to the body portion 36 or a gasket not shown is attached. The embodiment shown in the drawings is particularly suitable if it can be pushed by the jig toward the body portion 36 and the tail portion 37 can be reliably separated from the inner peripheral surface 25 of the outer cylinder 2 or the contact pressure can be reduced. Not limited to. If the length / height does not reach the screw hole 34 of the trunk portion 36 when it is pushed and deformed by the plunger rod 61 connected to the trunk portion 36 or a gasket mounting jig (not shown), There is no particular problem.

  Furthermore, in the present embodiment, the protrusions 38 formed on the inner peripheral surface side of the tail portion 37 are formed in a shape extending straight inward in the radial direction as shown in FIG. 1, but as shown in FIG. It is preferable to incline toward the side opposite to the rear end surface 33 of the body portion 36. In this case, a force that warps the tail portion 37 so as to be separated from the inner peripheral surface 25 of the outer cylinder is easily applied to the protrusion 38.

  As shown in FIG. 2, the plunger 6 includes a plunger rod 61 and a portion for connecting the gasket 3 at the tip thereof, that is, a male screw portion 62, and a protrusion 38 of the tail portion 37 on the tip side of the plunger rod 61. A portion having a diameter larger than the inner diameter of the substrate. The portion having a diameter larger than the inner diameter of the protrusion 38 of the gasket 3 may be the shoulder portion 64 of the plunger rod or the flange 63. Further, at the front end side of the plunger rod 61 (in the vicinity of the back of the screw portion 62), it is sufficient that there is a surface / part that can push at least the protrusion 38 toward the front (the body rear end surface 33). It doesn't have to exist.

  Further, the gasket 3 is detachably or integrally attached to the distal end portion of the plunger 6. For example, in the case of this embodiment, the internal thread 34 is formed inside the gasket 3 and is provided so as to be integrated by screwing the external thread 62 formed at the tip of the plunger 6. Here, the screw thread 62b and the screw tip 62a of the male screw 62 at the tip of the plunger 6 are in contact with the screw thread 34b and the screw bottom 34a of the female screw 34 of the body portion 36, and the plunger is formed by the screw thread 34b and the screw bottom 34a. 6 pressing force is received at the same time. Therefore, the gasket 3 can be pushed out by pushing the plunger 6 without bringing the shoulder portion 64 of the plunger rod 61 into contact with the barrel rear end surface 33 of the gasket 6. Of course, the gasket 3 can be pushed out only by the structure in which the shoulder tip surface 64 of the plunger rod 61 is brought into contact with the gasket rear end surface 33. However, preferably, the thread bottom (top) 34a and the thread 34b of the threaded hole 34 of the gasket body 36 are brought into contact with the thread tip 62a and the thread 62b of the thread 62 at the distal end of the plunger 6, and the gasket rear end face. 33 is configured such that the shoulder 64 of the plunger rod 61 is brought into contact with 33 and the gasket is pushed out. In this case, the gasket 3 can be pushed out by simultaneously receiving the pushing force of the plunger 6 by the screw thread 34b, the screw bottom 34a and the body rear end face 33, so that the gasket 3 can be pushed out without being tapered. . Therefore, when the gasket 3 is pushed in using the plunger 6, the seal surface 35 of the gasket 3 is not separated from the inner peripheral surface 25 of the outer cylinder 2, and the medicine does not leak from the periphery of the gasket 3. The connection relationship between the plunger 6 and the gasket 3 is not limited to the above-described screw fastening. For example, as in the relationship between the plunger and the gasket described in JP-A-2004-24768 and JP-A-5-131029, a hook is used. It is good also as an uneven | corrugated fitting type like. In this case, as in JP-A-2004-24768, the shoulder 64 of the plunger rod 61 does not have to contact the rear end surface of the body of the gasket, or JP-A-5-131029.

  Also in the embodiment in which the protrusion 38 is provided on the inner peripheral surface side of the tail portion 37, when the gasket 3 and the plunger 6 are connected (or when the gasket 3 and the gasket mounting jig are connected), the plunger 6 Or if the structure by which the protrusion 38 is pushed to the trunk | drum 36 side with a gasket mounting jig | tool is satisfy | filled, it will be specifically limited to the thing of the above-mentioned embodiment about the connection structure of the plunger 6 and a plunger and a gasket. is not.

  In the present embodiment, as shown in FIG. 2, the protrusion 38 is sandwiched between the barrel rear end surface 33 of the gasket 3 and the flange 63 of the plunger rod 61. However, the present invention is not limited to this. For example, as shown in FIG. 5, a convex portion 39 longer than the thickness of the protrusion 38 is formed on the gasket rear end surface 33, and the convex portion 39 and the shoulder portion of the plunger rod 61 (the male screw portion 62 and the plunger rod 61 at the tip of the plunger). The projection 38 may be prevented from being sandwiched between the gasket 3 and the plunger 6 by contacting the boundary portion 64). The convex portion 39 is formed between the projections 38 arranged in the circumferential direction, and is arranged between the long projection and the short projection. In the above-described embodiment, one type of protrusion 38 having the same length in the circumferential direction is provided intermittently with a constant interval. However, the present invention is not particularly limited to this, and as shown in FIG. Two types of projections 38 having different sizes may be alternately arranged, and the convex portions 39 may be arranged between them.

  According to the gasket for a prefilled syringe configured as described above, the outer cylinder 2 is sealed with the top cap 8 and the gasket 3 in a state where the outer cylinder 2 is filled with a chemical solution, and then sterilized by spraying high-pressure steam or hot water. Processing is performed. At this time, since the tail portion 37 at the rear portion of the gasket 3 is pressed against the inner peripheral surface 25 of the outer cylinder 2 by vapor pressure or the like, an effect of increasing the contact pressure is obtained. In addition, the inclination can be suppressed.

  When the plunger is attached to the gasket of the prefilled syringe that has been sterilized and used as a syringe (or when the gasket is inserted into the outer cylinder before the sterilization process), the tail 37 is thinner than the barrel 36. In addition, since the inside of the tail portion 37 is hollow and there is no backup, there is no effect of increasing the contact pressure, the sliding resistance is less than that during the sterilization process, and the gasket 3 is easily slid. And In particular, when there is a projection 38 that is pushed by the plunger (or gasket mounting jig) 6 as shown in FIG. 2, the projection 38 is pushed toward the rear end surface 33 of the trunk portion, so that the tail portion 37 is moved inward. By pulling it, it is possible to reduce the separation resistance or contact pressure from the outer peripheral surface 25 of the outer cylinder, and to surely reduce the sliding resistance.

  The above-described embodiment is an example of a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the scope of the present invention. For example, in the gasket of the present embodiment, the gasket body 4 of an elastic member (elastomer such as rubber or thermoplastic resin) is covered with the film 5, but the present invention is not limited to this, and only the gasket body 4 of the elastic member is used. It may be a configured gasket, that is, a gasket without coating of the film 5. Further, even if the gasket 3 is of the type covered with the resin film 5, the resin film 5 of the gasket 3 is not limited to the one shown in the figure, and sufficient slidability with the inner peripheral surface 25 of the outer cylinder 2 and liquid It may be anything as long as it has tightness, and may cover at least the outer peripheral surface of the gasket body 4 and the peripheral portion of the liquid sealing surface 32.

  Moreover, although the tail part 37 of the gasket 3 in the above-mentioned embodiment is comprised in the shape which continued in the circumferential direction of the paraboloid or conical surface shape, it is not specifically limited to this, The tail part 37 is radial direction. Although not shown so as to be easily moved inward, it may be discontinuous on the circumference. For example, the tail may be intermittently formed in the circumferential direction by inserting slits or notches.

  Furthermore, in the above-described embodiment, the example in which the plurality of protrusions 38 protruding to the inner peripheral surface side of the tail portion 37 are mainly formed intermittently in the circumferential direction has been mainly described, but the present invention is particularly limited thereto. Instead of a thing, it is good also as the protrusion of the annular body continued in the circumferential direction. Further, as shown in the figure, the protrusion 38 does not have to be formed as a separate block clearly divided in the circumferential direction, and may be divided by a slit, for example.

DESCRIPTION OF SYMBOLS 1 Prefilled syringe 2 Outer cylinder 21 Bottom part 22 Reduced diameter part 23 Lumen of reduced diameter part 24 Chemical solution storage space 25 Inner peripheral surface 3 Gasket 31 Outer peripheral surface (surface which contacts the inner peripheral surface of an outer cylinder)
32 Liquid-sealing surface (the surface that comes into contact with and seals with chemicals, that is, the end surface of the gasket)
33 Anti-liquid sealing surface (rear end surface on the air side opposite to the liquid sealing surface)
34 Female thread (screw hole)
34a Thread bottom 34b Thread 35 Seal surface 35a First seal surface 35b Second seal surface 36 Body 37 Tail 38 Projection 39 Protrusion 4 Gasket body 5 Resin film 6 Plunger 61 Plunger rod 62 Screw part (Male thread)
62a Screw tip
62b Thread 63 Flange 64 Shoulder 7 Atmosphere side 8 Top cap

Claims (3)

In the gasket for prefilled syringe,
The gasket is connected to the tip of the plunger and forms a barrel that forms at least one sealing surface that contacts the inner peripheral surface of the outer cylinder;
Projecting rearward from the rear end surface of the body portion, contacting the inner peripheral surface of the outer cylinder, being thinner than the body portion, and having flexibility to bend away from the inner peripheral surface of the outer cylinder. A gasket for prefilled syringes, comprising a tail portion. On the inner peripheral surface side of the tail portion, there is a protrusion that protrudes in a direction away from the inner peripheral surface of the outer cylinder and is pushed toward the trunk portion by a plunger rod or a gasket mounting jig connected to the trunk portion. 2. The gasket for a prefilled syringe according to claim 1, wherein the projection is tilted so that the tail portion is separated from the inner peripheral surface of the outer cylinder or the contact pressure is reduced. The gasket for a prefilled syringe according to claim 2, wherein the protrusion is inclined toward a side opposite to a rear end surface of the body portion.

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