Syringe and tip mount mountable to tip part of barrel

Abstract

This syringe comprises: a barrel including a tip part with a base end portion and a discharge portion; a tip mount mountable on the tip part; and a screw part. The tip part includes a mounting portion formed on the circumference of the discharge portion. The tip mount includes a mounted portion that is rotated around the central axis and screwed onto the mounting portion in the central axis direction to be mounted on the mounting portion. A mounting mechanism constituted by the mounting portion and the mounted portion includes: a restriction mechanism that restricts movement of the tip mount in the central axis direction due to the screwing action; and a torque increasing mechanism that increases rotational torque by forming a biting portion in which one of the mounting portion and the mounted portion bites into the other or the mounting portion and the mounted portion bite into each other by further rotation of the mounted portion under the restriction by the restriction mechanism.

Description

Syringe and tip attachment that can be attached to the tip of the barrel Cross-reference to related applications

[0001] This application claims the priority of Japanese Patent Application No. 2024-207272, which is incorporated herein by reference in its entirety.

[0002] The present invention relates to a syringe including a barrel for storing a chemical solution or the like and a tip attachment that can be attached to the tip of the barrel, and the tip attachment.

[0003] Conventionally, as shown in FIG. 13, a syringe outer cylinder 901 for storing a medical liquid is known (Patent Document 1). The syringe outer cylinder 901 includes an outer cylinder 902 and a cap 903 that is detachable from the outer cylinder 902.

[0004] The outer cylinder 902 includes an outer cylinder body 920, a hollow nozzle portion 922 having an opening at the tip, and a lock adapter 904 rotatably attached to the nozzle portion 922. The nozzle portion 922 can be connected to other medical devices (for example, a syringe needle, a connector, a three-way stopcock). The tip opening of the nozzle portion 922 is sealed by an elastic seal member 906. The lock adapter 904 has a lock adapter side screw portion 941a on its inner surface that can be screwed with a medical device connected to the nozzle portion 922. The cap 903 includes a seal member storage portion 931 for storing the elastic seal member 906, a nozzle portion storage portion 933 for storing the nozzle portion 922, and a cap side screw portion 933a formed on the outer surface of the nozzle portion storage portion 933. The cap 903 is attached to the outer cylinder 902 by screwing the cap side screw portion 933a of the cap 903 with the adapter side screw portion 941a of the lock adapter 904.

[0005] WO2023 / 176064 publication

[0006] However, if the cap 903 is inadvertently screwed too much with respect to the outer cylinder 902, the screwing force at the screw portions 933a and 941a of each other increases, and there is a risk that damage such as cracks may occur in the outer cylinder 902.

[0007] The present invention aims to provide a syringe and a tip attachment that can be appropriately attached to a barrel, which is the outer cylinder.

[0008] The syringe of the present invention comprises a cylindrical barrel along a central axis, including a base end having an opening into which a piston can be pushed, and a tip end having a discharge portion for discharging contents; a tip attachment that can be attached to the tip; and a threaded portion, wherein the tip has a mounting portion formed around the discharge portion, and the tip attachment has a mounting portion that is attached to the mounting portion by rotating around the central axis and screwing into the mounting portion in the direction of the central axis, and the mounting portion and the mounting portion form a mounting mechanism, the mounting mechanism comprising a restricting mechanism that restricts the movement of the tip attachment in the direction of the central axis by screwing, and a torque increasing mechanism that increases rotational torque by further rotation of the mounting portion in the state restricted by the restricting mechanism, causing one of the mounting portion and the mounting portion to bite into the other or into each other.

[0009] Furthermore, in the syringe, the threaded portion engages with the mounted portion when the mounted portion is screwed into the mounting portion, and the mounted portion comprises a base end projection provided on the base end side that is radially convex, and a tip projection provided on the tip side that is radially convex, and the base end projection engages with the threaded portion to guide screwing in when the mounted portion is screwed into the mounting portion, and engages with the threaded portion to guide unscrewing when unscrewing, and the tip projection functions as the torque-increasing mechanism, and may bite into the threaded portion and form a biting portion due to the rotation of the mounted portion from a state restricted by the restricting mechanism.

[0010] Furthermore, in the syringe, the threaded portion engages with the mounted portion when the mounted portion is screwed into the mounting portion, and the mounted portion comprises a base end projection provided on the base end side that is radially convex, and a tip projection provided on the tip side that is radially convex, and the base end projection engages with the threaded portion to guide the screwing in when the mounted portion is screwed into the mounting portion and functions as the torque-increasing mechanism, and due to the rotation of the mounted portion from a state restricted by the restricting mechanism, it bites into the threaded portion and forms a biting portion, and the tip projection engages with the threaded portion to guide the unscrewing when the screwing in is released.

[0011] The tip attachment of the present invention is a cylindrical barrel along a central axis, and is attachable to the tip of a barrel having a base end having an opening into which a piston can be pushed, and a tip having a discharge portion capable of discharging contents and a mounting portion formed around the discharge portion, wherein the tip attachment is attached to the mounting portion by rotating around the central axis and screwing into the mounting portion in the direction of the central axis, a restricting portion that restricts the movement of the tip attachment in the direction of the central axis by the screwing, and a biting portion that forms a biting portion that bites into the mounting portion by further rotation of the attached portion while restricted by the restricting portion.

[0012] Furthermore, in the tip attachment, the threaded portion engages with the attached portion when the attached portion is screwed into the attachment portion, and the attached portion comprises a base end projection provided on the base end side that is radially convex, and a tip projection provided on the tip side that is radially convex, and the base end projection engages with the threaded portion to guide screwing in when the attached portion is screwed into the attachment portion, and engages with the threaded portion to guide unscrewing when screwing in, and the tip projection functions as the biting portion, and may bite into the threaded portion and form the biting portion by the rotation of the attached portion from a state restricted by the restricting portion.

[0013] Furthermore, in the tip attachment, the threaded portion engages with the attached portion when the attached portion is screwed into the attachment portion, and the attached portion comprises a base end projection provided on the base end side that is radially convex, and a tip projection provided on the tip side that is radially convex, and the base end projection engages with the threaded portion to guide the screwing in when the attached portion is screwed into the attachment portion and functions as the biting portion, and as the attached portion rotates from a state restricted by the restricting portion, it bites into the threaded portion and forms a biting portion, and the tip projection engages with the threaded portion to guide the unscrewing when the screwing in is released.

[0014] Figure 1 is a front view of the syringe according to this embodiment. Figure 2 is an exploded perspective view of the syringe. Figure 3 is a schematic diagram illustrating the attachment of the tip attachment to the barrel in the syringe. Figure 4 is a cross-sectional view of the tip attachment in Figure 3 along line IV-IV. Figure 5 is a longitudinal cross-sectional view of the tip attachment when screwed in to illustrate the attachment of the tip attachment to the barrel. Figure 6 is a longitudinal cross-sectional view of the tip attachment when screwed in to illustrate the attachment of the tip attachment to the barrel. Figure 7A is an exploded view of the main parts of the attached portion of the tip attachment and the attached portion of the barrel when screwed in. Figure 7B is an exploded view of the main parts of the attached portion and the attached portion when screwed in to complete. Figure 7C is an exploded view of the main parts of the attached portion and the attached portion when screwed out. Figure 8 is a schematic diagram illustrating the attachment of the tip attachment to the barrel in a modified syringe. Figure 9 is a cross-sectional view of the tip attachment in Figure 8 along line IX-IX. Figure 10 is a cross-sectional view of the tip attachment in Figure 8 along line X-X. Figure 11 is a longitudinal cross-sectional view illustrating the attachment of the tip attachment to the barrel. Figure 12A is an exploded view of the main parts of the attachment portion of the tip attachment and the attachment portion of the barrel when screwed in. Figure 12B is an exploded view of the main parts of the attachment portion and the attachment portion when screwing in is complete. Figure 12C is an exploded view of the main parts of the attachment portion and the attachment portion when screwing in is unscrewed. Figure 13 is an enlarged cross-sectional view of the main parts of a syringe with a conventional syringe stopper attached.

[0015] Embodiments of the present invention will be described with reference to Figures 1 to 7C. As shown in Figure 1, syringe 1 is a syringe for discharging contents by pushing in a piston P. Syringe 1 also comprises a barrel 2 which is cylindrical along a central axis CL and includes a base end 20 having an opening into which the piston P can be pushed in, and a tip end 21. Syringe 1 is equipped with a tip attachment 3 which can be attached to barrel 2. As shown in Figure 2, tip attachment 3 includes a mounting portion 30 which is attached to barrel 2.

[0016] In syringe 1, the side where the base end 20 of the barrel 2 is located, i.e., the lower side in Figure 1, is the "base end side," and the side where the tip end 21 of the barrel 2 is located, i.e., the upper side in Figure 1, is the "tip side." The "central axis CL" of syringe 1 is the cylindrical axis of syringe 1. Furthermore, the radial direction of syringe 1 is also simply referred to as the "radial direction."

[0017] The barrel 2 is a component that houses contents such as a liquid medicine inside. As shown in Figure 2, the barrel 2 is a barrel with a threaded portion 213 at its tip 21. The barrel 2 is a so-called Luer lock type barrel. In this embodiment, in addition to the base end portion 20 and the tip portion 21, the barrel 2 is provided with a connecting portion 22 that connects the base end portion 20 and the tip portion 21. Furthermore, the barrel 2 is provided with a flange portion 23 that extends radially outward from the entire outer circumference of the base end edge in the cylindrical axis direction of the base end portion 20.

[0018] Furthermore, barrel 2 is formed from a material that is transparent and can withstand the internal pressure applied when dispensing the contents. Specifically, the material of barrel 2 is a resin containing cyclic olefins such as norbornene as repeating units, or glass. More specifically, the material of barrel 2 is a transparent resin such as COP (cycloolefin polymer), which is a homopolymer of cyclic olefins, or COC (cycloolefin copolymer), which is a copolymer of cyclic olefins and ethylene, or glass.

[0019] The connecting portion 22 is, for example, cylindrical. The outer diameter of the connecting portion 22 is approximately the same at all points along the axial direction of the cylinder. Furthermore, the outer circumferential surface of the connecting portion 22 is continuous with the outer circumferential surface of the tip portion 21 without any step at the tip end. The outer circumferential surface of the connecting portion 22 is continuous with the outer circumferential surface of the base end portion 20 without any step at the base end end.

[0020] The tip portion 21 has a discharge portion 210 capable of dispensing contents and a mounting portion 211 formed around the discharge portion 210. The outer diameter of the tip portion 21 is approximately the same as the outer diameter of the connecting portion 22.

[0021] The discharge portion 210 is a nozzle for dispensing liquid medicine or the like. In this embodiment, the discharge portion 210 protrudes further forward than the tip edge of the mounting portion 211. However, the discharge portion 210 does not necessarily have to protrude further forward than the tip edge of the mounting portion 211. For example, the tip edge of the discharge portion 210 may be positioned at the same location as the tip edge of the mounting portion 211 in the direction of the central axis.

[0022] The discharge section 210 has a discharge hole 210a, and the tip edge of the discharge section 210 is open. As shown in Figure 5, the discharge hole 210a is continuous with the internal space 220 of the connection section 22.

[0023] The outer diameter of the discharge portion 210 has a shape that widens towards the base end, i.e., it has a flared base. The base end of the discharge portion 210 is continuous with the tip end of the connecting portion 22. In addition, the first tip surface 210b, which is the surface of the base end of the discharge portion 210 facing the tip side, is continuous with the inner circumferential surface of the mounting portion 211.

[0024] The mounting portion 211 is a substantially cylindrical part. Furthermore, the mounting portion 211 is provided so as to surround the discharge portion 210 from the outer diameter. The mounting portion 211 is the part into which the mounting portion 30 of the tip attachment 3 is screwed. In this embodiment, the mounting portion 30 is screwed inside the mounting portion 211. Alternatively, the mounting portion 30 may be screwed outside the mounting portion 211.

[0025] Furthermore, the mounting portion 211 includes a cylindrical mounting tube portion 212 (see Figure 2). The mounting portion 211 also includes a threaded portion 213 into which the mounting portion 30 of the tip mounting device 3 engages when the mounting portion 30 is screwed into the mounting portion 211. The threaded portion 213 is formed on the inner circumferential surface of the mounting tube portion 212. In a configuration where the mounting portion 30 is screwed onto the outside of the mounting portion 211, the threaded portion 213 is formed on the outer circumferential surface of the mounting tube portion 212.

[0026] The tip attachment 3 is a component that can be attached to the tip portion 21 of the barrel 2. Specifically, the tip attachment 3 can be attached to the tip portion 21 so as to be engageable with the discharge portion 210 of the barrel 2. In this embodiment, the tip attachment 3 is a cap and is the part that is held by the user when using the assembled syringe 1. Note that the tip attachment 3 may be something other than a cap, and includes, for example, any thing that can be attached to the Luer lock of the barrel 2, such as a needle.

[0027] Furthermore, the tip attachment 3 includes a part to be attached 30 that is mounted on the mounting part 211 by rotating around the central axis CL and screwing into the mounting part 211 in the direction of the central axis. In this embodiment, in addition to the part to be attached 30, the tip attachment 3 includes a functional part 31 that performs the function of the tip attachment 3. The tip attachment 3 also includes a plug 4 that is held by the functional part 31.

[0028] As shown in Figure 3, the mounting portion 30 is substantially cylindrical. In this embodiment, the mounting portion 30 includes a cylindrical portion 300. The mounting portion 30 also includes a base end projection 301 that is radially convex and provided on the base end side, and a tip projection 302 that is radially convex and provided on the tip side. The outer diameter of the mounting portion 30 is smaller than the outer diameter of the functional portion 31. That is, a step is provided at the boundary between the outer circumferential surface of the mounting portion 30 and the outer circumferential surface of the functional portion 31.

[0029] The mounting portion 30 is screwed onto the mounting portion 211 with the mounting portion 30 positioned on the inner side of the diameter and the mounting portion 211 positioned on the outer side of the diameter. Alternatively, the mounting portion 30 may be screwed onto the mounting portion 211 with the mounting portion 30 positioned on the outer side of the diameter and the mounting portion 211 positioned on the inner side of the diameter.

[0030] The base end projection 301 protrudes radially outward from the outer circumferential surface of the cylindrical portion 300. Furthermore, a pair of base end projections 301 are provided, straddling the central axis CL. The number of base end projections 301 may be one or three or more. When there are three or more base end projections 301, it is preferable that the multiple base end projections 301 are arranged at equal intervals in the circumferential direction.

[0031] In this embodiment, the base projection 301 is an elongated rib. The width of this base projection 301, that is, the dimension of the base projection 301 in the direction of the central axis, is uniform. As shown in Figure 3, the base projection 301 extends on the outer circumferential surface of the cylindrical portion 300 at an inclination with respect to the central axis CL, such that one end 301a on the screw-unscrew direction side is located towards the tip side, and the other end 301b on the screw-in direction side is located towards the base end side. In other words, the base projection 301 extends spirally along the outer circumferential surface of the cylindrical portion 300 from one end 301a to the other end 301b, moving from the tip side to the base end side. The base end surface 301c, which is the surface of the base projection 301 facing the base end side, is a flat plane. The tip surface 301d, which is the surface of the base projection 301 facing the tip side, is a flat plane.

[0032] The tip projection 302 protrudes radially outward from the outer circumferential surface of the cylindrical portion 300. Furthermore, a pair of tip projections 302 are provided, straddling the central axis CL. The number of tip projections 302 may be one or three or more. When there are three or more tip projections 302, it is preferable that the multiple tip projections 302 are arranged at equal intervals in the circumferential direction.

[0033] In this embodiment, the tip projection 302 is a rectangular projection. The width of this tip projection 302, that is, the dimension of the tip projection 302 in the direction of the central axis, is narrower in the part located in the screw-in direction. The tip projection 302 extends on the outer circumferential surface of the cylindrical portion 300 such that one end 302a on the screw-out direction side and the other end 302b on the screw-in direction side are positioned at the same location in the direction of the central axis. In other words, when viewed from the front, the tip projection 302 extends along the outer circumferential surface of the cylindrical portion 300 so as to be parallel to the radial direction.

[0034] The base end surface 302c, which faces the base end of the tip projection 302, is a flat surface. When viewed from the front, this base end surface 302c extends along the outer circumferential surface so as to be parallel to the radial direction. The tip surface 302d, which faces the tip end of the tip projection 302, is a flat surface. This tip surface 302d extends at an inclination with respect to the central axis CL such that it is located closer to the base end as it is screwed in. Furthermore, one end 302a of the tip projection 302 on the screw-out direction side is aligned with one end 301a of the base projection 301 on the screw-out direction side in the direction of the central axis.

[0035] As shown in Figure 2, the functional part 31 is substantially cylindrical. The functional part 31 is the part that houses and holds the plug body 4. In this embodiment, the functional part 31 comprises a cylindrical main body portion 310 and a protruding portion 311 that protrudes radially outward from the main body portion 310.

[0036] The protrusions 311 are parts that provide a non-slip grip when holding the tip attachment 3. Furthermore, multiple protrusions 311 extend from the outer circumferential surface of the main cylindrical portion 310. Specifically, there are eight protrusions 311. In this embodiment, the multiple protrusions 311 are arranged at equal intervals in the circumferential direction. The protrusion dimensions of each protrusion 311 are approximately uniform.

[0037] The main cylindrical portion 310 has a thin-walled portion 310a located at the tip end, a thick-walled portion 310c located at the base end, and a connecting portion 310b that connects the thin-walled portion 310a and the thick-walled portion 310c. A protruding portion 311 is arranged on the outer circumferential surface of the thin-walled portion 310a. The thickness of the connecting portion 310b, i.e., its radial dimension, is thicker than the thickness of the thin-walled portion 310a and thinner than the thickness of the thick-walled portion 310c.

[0038] As shown in Figure 4, the inner circumferential surface of the main cylindrical portion 310 has a first inner projection 310d that protrudes inward in diameter, and a second inner projection 310e that is located closer to the base end than the first inner projection 310d and also protrudes inward in diameter. Both the inner projections 310d and 310e are parts that lock the plug body 4 into the mounting portion 30.

[0039] The first inner protruding portion 310d is provided in a pair with the central axis CL interposed therebetween. As shown in FIG. 5, the first inner protruding portion 310d can prevent the plug body 4 from moving to the tip side by pressing the plug flange portion 40 of the plug body 4 from the tip side.

[0040] The second inner protruding portion 310e is provided in a pair with the central axis CL interposed therebetween. Further, the edge on the inner diameter side of the second inner protruding portion 310e extends to the inside of the outer diameter of the closing plate portion 410 of the plug body 4. The second inner protruding portion 310e holds the plug body 4 in the tip attachment tool 3 by biting into the closing plate portion 410 from the outside in the diameter direction.

[0041] As shown in FIG. 2, the plug body 4 is a member that engages with the discharge portion 210 of the barrel 2 to close the discharge hole 210a. Further, the plug body 4 is housed and held in the tip attachment tool 3. When the tip attachment tool 3 is attached to the barrel 2, the plug body 4 is in a state of being externally fitted to the discharge portion 210. The plug body 4 includes a plug flange portion 40 and a plug main body portion 41. Examples of the material of the plug body 4 include an elastic body such as butyl rubber.

[0042] The plug flange portion 40 constitutes the tip portion of the plug body 4. Further, the plug flange portion 40 is placed on the discharge portion 210. The plug flange portion 40 is, for example, disc-shaped.

[0043] The plug main body portion 41 constitutes the portion of the plug body 4 excluding the tip portion. Further, as shown in FIG. 5, the plug main body portion 41 is cylindrical with the tip side closed. In the present embodiment, the plug main body portion 41 has a disc-shaped closing plate portion 410 and a cylindrical leg portion 411 extending from the closing plate portion 410 toward the proximal end side. The outer diameter of the closing plate portion 410 is larger than the outer diameter of the discharge portion 210 and smaller than the outer diameter of the plug flange portion 40. The base end surface 410a facing the base end side of the closing plate portion 410 is in close contact with the second tip surface 210d facing the tip side of the tip portion of the discharge portion 210, and the inner peripheral surface 411a of the leg portion 411 is in close contact with the outer peripheral surface 210e of the discharge portion 210, so that the plug body 4 tightly seals the discharge portion 210.

[0044] In the syringe 1 described above, the mounting mechanism 5 is formed by the mounting portion 211 of the barrel 2 and the mounted portion 30 of the tip attachment tool 3. The mounting mechanism 5 includes a regulating mechanism 50 and a torque increasing mechanism 51.

[0045] The regulating mechanism 50 restricts the movement of the tip fixture 3 in the central axis direction by screwing it into the mounting portion 211 of the mounted portion 30. Also, the regulating mechanism 50 is constituted by both the mounting portion 211 and the mounted portion 30. In the present embodiment, the regulating mechanism 50 is constituted by the regulation receiving portion 210c and the cylindrical base end portion 300a of the cylindrical portion 300 of the mounted portion 30.

[0046] In the tip fixture 3, the mounted portion 30 includes a regulating portion 500 that restricts the movement of the tip fixture 3 in the central axis direction by screwing the mounted portion 30 of the tip fixture 3 into the mounting portion 211. Specifically, the cylindrical base end portion 300a of the cylindrical portion 300 of the mounted portion 30 functions as the regulating portion 500. In the barrel 2, the first front end surface 210b of the discharge portion 210 serves as a regulation receiving portion 210c against which the mounted portion 30 of the tip fixture 3 abuts in the central axis direction when screwing the mounted portion 30 of the tip fixture 3 into the mounting portion 211. That is, the regulating mechanism 50 exhibits its regulating effect when the regulating portion 500, which is the cylindrical base end portion 300a, abuts against the regulation receiving portion 210c, which is the first front end surface 210b, in the central axis direction.

[0047] The torque increasing mechanism 51 forms an engaging portion 510 where one of the mounting portion 211 and the mounted portion 30 bites into the other as shown in FIG. 6 by further rotating the mounted portion 30 in the state regulated by the regulating mechanism 50, thereby increasing the rotational torque. In the present embodiment, by further rotating the mounted portion 30 in the state regulated by the regulating mechanism 50, an engaging portion 510 where the mounted portion 30 bites into the mounting portion 211 is formed to increase the rotational torque.

[0048] Thus, the torque increasing mechanism 51 is constituted by both the mounting portion 211 and the mounted portion 30. In the present embodiment, the torque increasing mechanism 51 is constituted by the screw portion 213 of the mounting portion 211 and the tip convex portion 302 of the mounted portion 30.

[0049] In the tip attachment device 3, the attachment portion 30 is provided with a biting portion 511 that bites into the attachment portion 211 by further rotation while restricted by the restricting portion 500. In the barrel 2, the threaded portion 213 of the attachment portion 211 becomes a biting portion 512 that bites into the biting portion 510 by further rotation of the attachment portion 30 while restricted by the restricting portion 500.

[0050] Furthermore, the torque-increasing mechanism 51 may increase rotational torque by further rotation of the mounted portion 30 while it is restricted by the restricting mechanism 50, thereby forming a biting portion 510 where the mounted portion 211 and the mounted portion 30 bite into each other. For example, a torque projection different from the threaded portion 213, which is radially convex, may be formed on the mounted portion 211, and this torque projection and the tip projection 302 of the mounted portion 30 may bite into each other to form a biting portion 510 and increase rotational torque.

[0051] The syringe 1 of this embodiment is equipped with a mechanism that guides the rotation of the part to be attached 30 when screwing it into the mounting part 211 and when unscrewing the part to be attached 30 into the mounting part 211. Specifically, the base end projection 301 engages with the threaded portion 213 to guide screwing when screwing the part to be attached 30 into the mounting part 211. Also, the base end projection 301 engages with the threaded portion 213 to guide unscrewing when unscrewing.

[0052] Furthermore, the syringe mounting mechanism 5 only needs to include a regulating mechanism 50 and a torque increasing mechanism 51, and does not need to include a guide mechanism for screwing in or unscrewing in.

[0053] In summary, in this embodiment, the tip projection 302 of the mounting portion 30 functions as a torque-increasing mechanism 51, and as the mounting portion 30 rotates from a state restricted by the restricting mechanism 50, it bites into the threaded portion 213 and forms a biting portion 510. That is, the tip projection 302 functions as a biting portion 511, and as the mounting portion 30 rotates from a state restricted by the restricting portion 500, it bites into the threaded portion 213 and forms a biting portion 510.

[0054] Furthermore, the threaded portion 213 functions as a torque-increasing mechanism 51, and as the mounted portion 30 rotates from a state restricted by the restricting mechanism 50 of the tip projection 302, it bites into the tip projection 302, which acts as a biting portion 511, to form a biting portion 512.

[0055] Next, the operation of attaching and detaching the tip attachment 3 to the barrel 2 will be described. When attaching the tip attachment 3 to the barrel 2, as shown in Figure 3, first, the attachment portion 30 of the tip attachment 3 is screwed into the attachment portion 211 of the barrel 2. Specifically, the worker performing the attachment inserts the attachment portion 30 of the tip attachment 3 into the attachment portion 211 of the barrel 2 and rotates the tip attachment 3 in the screwing direction while pushing it toward the base end. During this screwing, as shown in Figure 7A, the base end projection 301 and the tip projection 302 are positioned between a pair of adjacent threads 213a and 213b in the central axis direction of the threaded portion 213. This screwing may be done manually or using a jig. When using a jig for screwing, for example, the jig is inserted into the gap S between the tip attachment 3 and the barrel 2 as shown in Figure 5 and the screwing is performed.

[0056] During this screwing process, the base projection 301 engages with the threaded portion 213, specifically the threads 213b on the base end side, to guide the screwing (see Figure 7A). More specifically, the base end surface 301c of the base projection 301, facing the base end, contacts the surface 213c of the threads 213b on the base end side, guiding the screwing.

[0057] As shown in Figure 5, the screwing of the mounting portion 30 into the mounting portion 211 is completed when the movement of the tip attachment 3 in the direction of the central axis, that is, the movement toward the base end, is restricted by the mounting portion 211 of the barrel 2, which is the regulating mechanism 50, and the mounting portion 30 of the tip attachment 3. In this embodiment, this screwing is completed when the regulating portion 500, which is the cylindrical base end portion 300a of the cylindrical portion 300 of the mounting portion 30, comes into contact with the regulating receiving portion 210c of the mounting portion 211. Specifically, this screwing is completed when the regulating portion 500 comes into contact with the regulating receiving portion 210c, which is the first tip surface 210b. As a result of this screwing, the plug body 4 is pushed toward the base end and becomes elastically deformed. Specifically, the plug body 4 is pressed in the direction of the central axis and elastically deformed between the tip edge of the discharge portion 210 and the first internal projection portion 310d of the functional portion 31. Furthermore, the plug body 4 is made to be airtight by being tightly fitted to the tip edge of the discharge section 210 so as to cover the discharge hole 210a.

[0058] With the movement of the tip attachment 3 toward the base end restricted by the regulating mechanism 50, if the worker further rotates the tip attachment 3, the tip attachment 3 rotates while its position in the central axis direction remains unchanged. That is, the tip attachment 3 rotates horizontally. This rotation causes the part to be attached 30 to come into contact with the attachment part 211 from the horizontal direction. Specifically, the tip projection 302 comes into contact with the threads 213a on the tip side of the attachment part 211.

[0059] Furthermore, as the mounting portion 30 rotates, it forms a biting portion 510 that bites into the mounting portion 211, as shown in Figure 7B, thereby increasing the rotational torque. In this embodiment, the tip projection 302 bites into the thread 213a on the tip side to form the biting portion 510. That is, the tip projection 302 and the thread 213a on the tip side function as a torque-increasing mechanism 51. At this time, the tip projection 302 is in a concave state in the diameter, i.e., a crushed state (see Figure 6). This completes the mounting of the mounting portion 30 to the mounting portion 211. The syringe 1 is sold and stored with the mounting portion 30 mounted to the mounting portion 211. Even in this state, the stopper 4 is pushed towards the base end and deformed. The biting portion 510 also maintains the mounted state of the mounting portion 30 to the mounting portion 211.

[0060] When removing the tip attachment 3 from the barrel 2, the user rotates the tip attachment 3 in the unscrew direction. At this time, a restoring force is generated in the plug body 4 as it attempts to restore its deformation, and a force is generated on the tip attachment 3 itself toward the tip. In this embodiment, the plug flange portion 40 of the plug body 4 pushes the first internal projection portion 310d of the functional portion 31 toward the tip. As a result, the base end projection 301 of the attached portion 30 is pressed against the threads 213a on the tip side, as shown in Figure 7C. Specifically, the tip surface 301d of the base end projection 301 facing toward the tip comes into contact with the base end surface 213d of the threads 213a on the tip side. Therefore, with the base end projection 301 guided by the threads 213a on the tip side, the attached portion 30 rotates in the unscrew direction, the screwing of the attached portion 30 into the mounting portion 211 is released, and the tip attachment 3 can be removed from the barrel 2.

[0061] In the syringe 1 described above, when attaching the tip attachment 3 to the barrel 2, the movement of the tip attachment 3 in the direction of the central axis, i.e., movement toward the base end, is restricted by the regulating mechanism 50, which consists of the mounting portion 211 of the barrel 2 and the attached portion 30 of the tip attachment 3, thereby preventing the tip attachment 3 from being overtightened. Furthermore, further rotation of the attached portion 30 from that state increases the rotational torque by the torque increasing mechanism 51, thereby maintaining the screwed-in state at the engagement portion 510. In this way, the tip attachment 3, such as a cap, can be properly attached to the barrel 2. In addition, by suppressing the load caused by overtightening, damage such as cracks in the mounting portion 211 can be prevented.

[0062] The effect of the tip attachment 3 is that when attaching the tip attachment 3 to the barrel 2, the restricting portion 500 restricts the movement of the tip attachment 3 in the direction of the central axis, that is, the movement toward the base end, thereby suppressing over-screwing of the tip attachment 3. Furthermore, by further rotation of the attached portion 30 from that state, the biting portion 511 can maintain the state in which the tip attachment 3 is screwed into the attachment portion 211. In addition, by suppressing the load caused by over-screwing, damage such as cracks in the attachment portion 211 can be prevented.

[0063] In the syringe 1 of this embodiment, the threaded portion 213 and the base end projection 301 allow for screwing in and unscrewing, and the regulating mechanism 50 and the threaded portion 213 and tip projection 302, which function as a torque increasing mechanism 51, suppress over-screwing of the tip attachment 3, while the tip projection 302 bites into the threaded portion 213 to firmly maintain the screwed-in state.

[0064] The effect of the tip attachment 3 of this embodiment is that the threaded portion 213 and the base end projection 301 allow for screwing in and unscrewing, and the restricting portion 500 and the biting portion 510 formed by the threaded portion 213 and the tip projection 302 allow for increased rotational torque while restricting the movement of the tip attachment 3, thereby preventing over-screwing of the tip attachment 3, and allowing the tip projection 302 to bite into the threaded portion 213 and firmly maintain the screwed-in state.

[0065] It should be noted that the syringe and tip attachment of the present invention are not limited to the embodiments described above, and various modifications can be made without departing from the spirit of the invention. For example, the configuration of one embodiment can be added to the configuration of another embodiment, and a part of the configuration of one embodiment can be replaced with the configuration of another embodiment. Furthermore, a part of the configuration of one embodiment can be deleted.

[0066] In the above embodiment, the tip projection 302 functions as a torque-increasing mechanism 51 to form the engagement portion 510, and the base projection 301 guides screwing in and screwing out, but the embodiment is not limited to this. Hereinafter, using Figures 8 to 12C, a configuration in which the base projection 301 functions as a torque-increasing mechanism 51 and guides screwing in, and the tip projection 302 guides screwing out, will be described. Note that the syringe 1 of this embodiment differs from the syringe 1 of the above embodiment only in the configuration of the mounting portion 30 of the tip attachment 3.

[0067] As shown in Figure 8, the mounting portion 30 comprises a cylindrical portion 300, a base end projection 301 provided on the base end side and convex in the radially outward direction, and a tip projection 302 provided on the tip side and convex in the radially outward direction. The cylindrical portion 300 has a notch 303 formed through it in the thickness direction of the cylindrical portion 300.

[0068] The base end projection 301 protrudes radially outward from the outer circumferential surface of the cylindrical portion 300. Furthermore, a pair of base end projections 301 are provided, straddling the central axis CL. The number of base end projections 301 may be one or more than three.

[0069] In this embodiment, the base projection 301 is an elongated rib. The base projection 301 extends along the outer circumferential surface of the cylindrical portion 300 such that one end 301a on the unscrew direction side and the other end 301b on the screw-in direction side are positioned at the same location in the central axis direction. In other words, when viewed from the front, the base projection 301 extends along the outer circumferential surface of the cylindrical portion 300 so as to be parallel to the radial direction. That is, the base projection 301 extends in a single straight line. The width of this base projection 301, i.e., the dimension of the base projection 301 in the central axis direction, is uniform at all parts in the circumferential direction. Furthermore, the base projection 301 has a shape that tapers toward the radially outward side. In addition, the base end surface 301c, which is the surface of the base projection 301 facing the base end side, is a flat surface. The tip surface 301d, which is the surface of the base projection 301 facing the tip side, is a flat surface. The outer surface 301e, which is the surface facing the radially outward side of the base end projection 301, is a flat surface.

[0070] The tip projection 302 protrudes radially outward from the outer circumferential surface of the cylindrical portion 300. Furthermore, a pair of tip projections 302 are provided, straddling the central axis CL. The number of tip projections 302 may be one or more.

[0071] In this embodiment, the tip projection 302 is a rectangular projection. The width of this tip projection 302, that is, the dimension of the tip projection 302 in the direction of the central axis, is narrower towards the part located in the screw-in direction. The tip projection 302 extends on the outer circumferential surface of the cylindrical portion 300 such that one end 302a on the screw-out direction side and the other end 302b on the screw-in direction side are positioned at the same location in the direction of the central axis. In other words, when viewed from the front, the tip projection 302 extends along the outer circumferential surface of the cylindrical portion 300 so as to be parallel to the radial direction. The base end surface 302c, which is the surface facing the base end side of the tip projection 302, is a flat plane. The base end surface 302c extends along the outer circumferential surface so as to be parallel to the radial direction when viewed from the front. The tip surface 302d, which is the surface facing the tip side of the tip projection 302, is a flat plane. The tip surface 302d extends at an inclination with respect to the central axis CL such that it is located closer to the base end as it is screwed in. Furthermore, one end 302a of the tip projection 302 on the screw-out direction side is aligned with one end 301a of the base projection 301 on the screw-out direction side in the direction of the central axis.

[0072] The notch 303 is positioned to overlap with the end portion 301f of the base projection 301 on the screw-in side. In this embodiment, the notch 303 is an elongated hole extending in the direction of the central axis, but it may also be a square-shaped hole, an elongated hole extending in the circumferential direction, a round hole, an elliptical-shaped hole, etc.

[0073] Thus, in this embodiment, a cavity formed by the notch 303 is located in the diameter inward of the end 301f of the base projection 301. Therefore, when a force is applied to the base projection 301 from the diameter outward, the end 301f of the base projection 301 bends inward, as shown in Figure 10.

[0074] In the syringe 1 of this embodiment, as shown in Figure 11, a mounting mechanism 5 is formed by the mounting portion 211 of the barrel 2 and the mounting portion 30 of the tip attachment 3. The mounting mechanism 5 includes a regulating mechanism 50 and a torque increasing mechanism 51.

[0075] The regulating mechanism 50 is composed of a regulating receiving portion 210c which is the first tip surface 210b and a regulating portion 500 which is the cylindrical base end portion 300a of the cylindrical portion 300 of the mounted portion 30. The torque increasing mechanism 51 is composed of a threaded portion 213 of the mounting portion 211 and a base end projection 301 of the mounted portion 30.

[0076] Furthermore, as shown in Figure 12A, the base projection 301 engages with the threaded portion 213 to guide the screwing process when the mounting portion 30 is screwed into the mounting portion 211. Also, as shown in Figure 12C, the tip projection 302 engages with the threaded portion 213 to guide the unscrewing process when the screwing is released.

[0077] To summarize, in the mounting portion 30 of this embodiment, the base end projection 301 engages with the threaded portion 213 to guide the screwing in when the mounting portion 30 is screwed into the mounting portion 211, and also functions as a torque-increasing mechanism 51. As the mounting portion 30 rotates from a state restricted by the restricting mechanism 50, it bites into the threaded portion 213 and forms a biting portion 510. In other words, at the time of screwing in, the base end projection 301 engages with the threaded portion 213 to guide the screwing in and also functions as a biting portion 511. As the mounting portion 30 rotates from a state restricted by the restricting portion 500, it bites into the threaded portion 213 and forms a biting portion 510.

[0078] Furthermore, the threaded portion 213 functions as a torque-increasing mechanism 51, and as the mounted portion 30 rotates from a state restricted by the regulating mechanism 50 of the base end projection 301, it bites into the base end projection 301, which acts as a biting portion 511, to form a biting portion 512.

[0079] Next, the operation of attaching and detaching the tip attachment 3 to the barrel 2 will be described. When attaching the tip attachment 3 to the barrel 2, when screwing the attachment portion 30 of the tip attachment 3 into the attachment portion 211 of the barrel 2, as shown in Figure 12A, the base end projection 301 and the tip projection 302 are positioned between a pair of adjacent threads 213a and 213b in the central axis direction of the threaded portion 213. During this screwing, the unscrewed portion of the base end surface 301c of the base end projection 301 comes into contact with the surface 213c of the base end thread 213b facing the tip, pushing this surface 213c toward the base end and guiding the screwing. As shown in Figure 11, the screwing of the mounting portion 30 into the mounting portion 211 is completed when the regulating portion 500, which is the cylindrical base end 300a of the cylindrical portion 300 of the mounting portion 30, comes into contact with the regulating receiving portion 210c, which is the first tip surface 210b. This screwing pushes the plug body 4 towards the base end, causing it to be elastically deformed. In this configuration as well, the plug body 4 is pressed in the direction of the central axis between the tip edge of the discharge portion 210 and the first internal projection 310d of the functional portion 31, causing it to be elastically deformed. Furthermore, the plug body 4 adheres tightly to the tip edge of the discharge portion 210, covering the discharge hole 210a, to create an airtight seal.

[0080] With the movement of the tip attachment 3 toward the base end restricted by the regulating mechanism 50, if the operator further rotates the tip attachment 3, the tip attachment 3 rotates while its position in the central axis direction remains unchanged. This rotation causes the part to be attached 30 to come into contact with the attachment part 211 from the horizontal direction. Furthermore, as the part to be attached 30 rotates, it forms a biting portion 510 that bites into the attachment part 211, as shown in Figure 12B, and increases the rotational torque. In this embodiment, the base end projection 301 bites into the tip-side thread 213a of the pair of adjacent threads 213a and 213b, forming a biting portion 510. Specifically, the end portion 301f of the base end projection 301 bends inward in diameter, causing it to penetrate and come into contact with the tip-side thread 213a. In this embodiment, the base end projection 301 has a tapered shape towards the outer diameter, making it easier to bend inward in diameter. In this way, the base projection 301 and the screw thread 213a on the tip side function as a torque-increasing mechanism 51. This completes the attachment of the part to be attached 30 to the mounting part 211. Even in this state, the plug body 4 is pushed in towards the base end and deformed. In addition, the biting portion 510 maintains the attached state of the part to be attached 30 to the mounting part 211.

[0081] When removing the tip attachment 3 from the barrel 2, the user rotates the tip attachment 3 in the unscrew direction. At this time, the restoring force generated in the plug 4 pushes the tip attachment 3 itself toward the tip. As a result, the tip projection 302 is pressed against the threads 213a on the tip side. Specifically, the tip surface 302d of the tip projection 302 facing toward the tip comes into contact with the surface 213d of the threads 213a facing toward the base end, pushing this surface 213d toward the tip. As a result, with the tip projection 302 guided by the threads 213a, the mounted portion 30 rotates in the unscrew direction, releasing the screw-on engagement of the mounted portion 30 with the mounting portion 211, and the tip attachment 3 can be removed from the barrel.

[0082] In this syringe 1, screwing is performed using the threaded portion 213 and the base end projection 301, and unscrewing is performed using the threaded portion 213 and the tip projection 302. Furthermore, the threaded portion 213 and the base end projection 301, which function as a regulating mechanism 50 and a torque increasing mechanism 51, suppress over-screwing of the tip attachment 3, while the base end projection 301 bites into the threaded portion 213 to firmly maintain the screwed state.

[0083] The effect of this tip attachment 3 is that it can be screwed in using the threaded portion 213 and the base end projection 301, and unscrewed using the threaded portion 213 and the tip projection 302. Furthermore, the restricting portion 500 and the biting portion 510 formed by the threaded portion 213 and the base end projection 301 can increase the rotational torque while restricting the movement of the tip attachment 3, thereby preventing over-screwing of the tip attachment 3, and allowing the base end projection 301 to bite into the threaded portion 213 and firmly hold the screwed-in state.

[0084] In the above embodiment, the tip attachment 3 was a cap and included a stopper 4 that engaged with the discharge section 210 of the barrel 2 to close the discharge hole 210a. However, the member that engages with the discharge section 210 may be different from the stopper 4. For example, if the tip attachment 3 is a needle, it may be provided with a member that is in close contact with and communicates with the discharge section 210.

[0085] Based on the above, the present invention provides a syringe and a tip attachment that can be appropriately attached to a barrel, which is an outer cylinder.

[0086] The syringe of the present invention comprises a cylindrical barrel along a central axis, including a base end having an opening into which a piston can be pushed, and a tip end having a discharge portion for discharging contents, and a tip attachment that can be attached to the tip, wherein the tip has a mounting portion formed around the discharge portion and a threaded portion, and the tip attachment comprises a mounting portion that is attached to the mounting portion by rotating around the central axis and screwing into the mounting portion in the direction of the central axis, and the mounting portion and the mounting portion form a mounting mechanism, the mounting mechanism comprising a restricting mechanism that restricts the movement of the tip attachment in the direction of the central axis by the screwing, and a torque increasing mechanism that increases rotational torque by further rotation of the mounting portion in the state restricted by the restricting mechanism, causing one of the mounting portion and the mounting portion to bite into the other or into each other.

[0087] With this configuration, when attaching the tip attachment to the barrel, the regulating mechanism restricts the movement of the tip attachment in the direction of the central axis, thereby preventing over-screwing of the tip attachment. Furthermore, further rotation of the attached part from that state increases the rotational torque due to the torque-increasing mechanism, thereby maintaining the screwed-in state at the engagement point. In this way, by suppressing the load caused by over-screwing, damage such as cracks in the attached part can be prevented.

[0088] Furthermore, in the syringe, the threaded portion engages with the mounted portion when the mounted portion is screwed into the mounting portion, and the mounted portion comprises a base end projection provided on the base end side that is radially convex, and a tip projection provided on the tip side that is radially convex, and the base end projection engages with the threaded portion to guide screwing in when the mounted portion is screwed into the mounting portion, and engages with the threaded portion to guide unscrewing when unscrewing, and the tip projection functions as the torque-increasing mechanism, and may bite into the threaded portion and form a biting portion due to the rotation of the mounted portion from a state restricted by the restricting mechanism.

[0089] With this configuration, the threaded portion and the base projection allow for screwing in and unscrewing, and the regulating mechanism and the threaded portion and tip projection, which function as a torque-increasing mechanism, suppress over-screwing of the tip attachment while the tip projection bites into the threaded portion to firmly maintain the screwed-in state.

[0090] Furthermore, in the syringe, the threaded portion engages with the mounted portion when the mounted portion is screwed into the mounting portion, and the mounted portion comprises a base end projection provided on the base end side that is radially convex, and a tip projection provided on the tip side that is radially convex, and the base end projection engages with the threaded portion to guide the screwing in when the mounted portion is screwed into the mounting portion and functions as the torque-increasing mechanism, and due to the rotation of the mounted portion from a state restricted by the restricting mechanism, it bites into the threaded portion and forms a biting portion, and the tip projection engages with the threaded portion to guide the unscrewing when the screwing in is released.

[0091] With this configuration, screwing can be performed using the threaded portion and the base projection, and unscrewing can be performed using the threaded portion and the tip projection. Furthermore, the threaded portion and base projection, which function as a regulating mechanism and a torque-increasing mechanism, can suppress over-screwing of the tip attachment, while the base projection bites into the threaded portion to firmly maintain the screwed-in state.

[0092] The tip attachment of the present invention is a cylindrical barrel along a central axis, and is attachable to the tip of a barrel having a base end having an opening into which a piston can be pushed, and a tip having a discharge portion capable of discharging contents and a mounting portion formed around the discharge portion, wherein the tip attachment is attached to the mounting portion by rotating around the central axis and screwing into the mounting portion in the direction of the central axis, a restricting portion that restricts the movement of the tip attachment in the direction of the central axis by the screwing, and a biting portion that forms a biting portion that bites into the mounting portion by further rotation of the attached portion while restricted by the restricting portion.

[0093] With this configuration, when attaching the tip attachment to the barrel, the restricting part restricts the movement of the tip attachment in the direction of the central axis, and further rotation of the part to be attached from that state suppresses over-screwing of the tip attachment, while the biting part can maintain the screwed-in state. In this way, by suppressing the load caused by over-screwing, damage such as cracks in the attachment part can be prevented.

[0094] Furthermore, in the tip attachment, the threaded portion engages with the attached portion when the attached portion is screwed into the attachment portion, and the attached portion comprises a base end projection provided on the base end side that is radially convex, and a tip projection provided on the tip side that is radially convex, and the base end projection engages with the threaded portion to guide screwing in when the attached portion is screwed into the attachment portion, and engages with the threaded portion to guide unscrewing when unscrewing, and the tip projection functions as the biting portion, and may bite into the threaded portion and form the biting portion by the rotation of the attached portion from a state restricted by the restricting portion.

[0095] With this configuration, the threaded portion and the base projection allow for screwing in and unscrewing, and the restricting portion and the biting portion formed by the threaded portion and the tip projection allow for increased rotational torque while restricting the movement of the tip attachment, thereby preventing over-screwing of the tip attachment and ensuring that the tip projection bites into the threaded portion to firmly maintain the screwed-in state.

[0096] Furthermore, in the tip attachment, the threaded portion engages with the attached portion when the attached portion is screwed into the attachment portion, and the attached portion comprises a base end projection provided on the base end side that is radially convex, and a tip projection provided on the tip side that is radially convex, and the base end projection engages with the threaded portion to guide the screwing in when the attached portion is screwed into the attachment portion and functions as the biting portion, and as the attached portion rotates from a state restricted by the restricting portion, it bites into the threaded portion and forms a biting portion, and the tip projection engages with the threaded portion to guide the unscrewing when the screwing in is released.

[0097] With this configuration, screwing can be performed using the threaded portion and the base projection, and unscrewing can be performed using the threaded portion and the tip projection. Furthermore, the regulating portion and the biting portion formed by the threaded portion and the base projection can increase the rotational torque while restricting the movement of the tip attachment, thereby preventing over-screwing of the tip attachment and firmly maintaining the screwed state by the base projection biting into the threaded portion.

[0098] 1...Syringe, 2...Barrel, 3...Tip attachment, 4...Plug body, 5...Mounting mechanism, 20...Base end, 21...Tip, 22...Connection part, 23...Flange part, 30...Mounted part, 31...Functional part, 40...Plug flange part, 41...Plug body part, 50...Regulating mechanism, 51...Torque increase mechanism, 210...Discharge part, 210a...Discharge hole, 210b...First tip surface, 210c...Regulating receiving part, 210d...Second tip surface, 210e ...outer surface, 211...mounting part, 212...mounting cylinder part, 213...thread part, 213a, 213b...thread, 213c, 213d...surface, 220...internal space, 300...cylindrical part, 300a...base end of cylinder, 301...base end projection, 301a...one end, 301b...other end, 301c...base end surface, 301d...tip surface, 301e...outer surface, 301f...end, 302...tip projection, 302a...one end, 302b...other end, 30 1c...Proximal end surface, 302d...Distal end surface, 303...Notch part, 310...Main body cylinder part, 310a...Thin wall part, 310b...Connecting part, 310c...Thick wall part, 310d...First inner protrusion part, 310e...Second inner protrusion part, 311... Protrusion part, 410... Closure plate part, 410a... Proximal end surface, 411... Leg part, 411a... Inner peripheral surface, 500... Regulating part, 510... Biting part, 511... Biting part, 512... Biting part, 901... Syringe 902...Outer cylinder, 903...Cap, 904...Lock adapter, 906...Elastic sealing member, 920...Outer cylinder body, 922...Nozzle part, 931...Seal member storage part, 933...Nozzle part storage part, 933a...Threaded part, 933a...Cap side threaded part, 941a...Threaded part, 941a...Lock adapter side threaded part, 941a...Adapter side threaded part, S...Gap, P...Piston, CL...Center axis

Claims

1. A syringe comprising: a cylindrical barrel along a central axis, including a base end having an opening into which a piston can be pushed, and a tip end having a discharge portion for discharging contents; and a tip attachment that can be attached to the tip, wherein the tip has a mounting portion formed around the discharge portion and a threaded portion; the tip attachment comprises a part to be attached to the mounting portion by rotating around the central axis and screwing into the mounting portion in the direction of the central axis; the mounting portion and the part to be attached form a mounting mechanism; the mounting mechanism comprises a restricting mechanism that restricts the movement of the tip attachment in the direction of the central axis by screwing; and a torque increasing mechanism that increases rotational torque by further rotation of the part to be attached in a state restricted by the restricting mechanism, causing one of the mounting portion and the part to be attached to the other or to each other to form a biting portion.

2. The syringe according to claim 1, wherein the threaded portion engages with the mounted portion when the mounted portion is screwed into the mounting portion, the mounted portion comprises a base end projection provided on the base end side and convex in the radial direction, and a tip projection provided on the tip side and convex in the radial direction, the base end projection engages with the threaded portion to guide screwing in when the mounted portion is screwed into the mounting portion and engages with the threaded portion to guide unscrewing when unscrewing, and the tip projection functions as the torque-increasing mechanism and bites into the threaded portion to form a biting portion due to the rotation of the mounted portion from a state restricted by the restricting mechanism.

3. The syringe according to claim 1, wherein the threaded portion engages with the mounted portion when the mounted portion is screwed into the mounting portion, the mounted portion comprises a base end projection provided on the base end side and convex in the radial direction, and a tip projection provided on the tip side and convex in the radial direction, the base end projection engages with the threaded portion to guide screwing in when the mounted portion is screwed into the mounting portion and functions as the torque-increasing mechanism, and bites into the threaded portion to form a biting portion due to the rotation of the mounted portion from a state restricted by the restricting mechanism, and the tip projection engages with the threaded portion to guide unscrewing when screwing in.

4. A tip attachment that can be attached to the tip of a cylindrical barrel along a central axis, the barrel having a base end having an opening into which a piston can be pushed, and a tip end having a discharge portion capable of discharging contents and a mounting portion formed around the discharge portion, the tip attachment comprising: a mounted portion that is attached to the mounting portion by rotating around the central axis and screwing into the mounting portion in the direction of the central axis; a restricting portion that restricts the movement of the tip attachment in the direction of the central axis by the screwing; and a biting portion that forms a biting portion that bites into the mounting portion by further rotation of the mounted portion while restricted by the restricting portion.

5. The tip attachment according to claim 4, wherein the threaded portion engages with the attached portion when the attached portion is screwed into the mounting portion, the attached portion comprises a base end projection provided on the base end side and convex in the radial direction, and a tip projection provided on the tip side and convex in the radial direction, the base end projection engages with the threaded portion to guide screwing in when the attached portion is screwed into the mounting portion, and engages with the threaded portion to guide unscrewing when unscrewing, and the tip projection functions as the biting portion, and by the rotation of the attached portion from a state restricted by the restricting portion, it bites into the threaded portion and forms the biting portion.

6. The tip attachment according to claim 4, wherein the threaded portion engages with the attached portion when the attached portion is screwed into the mounting portion, the attached portion comprises a base end projection provided on the base end side and convex in the radial direction, and a tip projection provided on the tip side and convex in the radial direction, the base end projection engages with the threaded portion to guide screwing in when the attached portion is screwed into the mounting portion and functions as a biting portion, and as the attached portion rotates from a state restricted by the restricting portion, it bites into the threaded portion and forms a biting portion, and the tip projection engages with the threaded portion to guide unscrewing when screwing in.

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