Injection device

Abstract

This injection device comprises: an engagement release mechanism for releasing engagement between a plunger and an engagement member 6 when the plunger and the engagement member 6 rotate relative to each other around a center axis line in a state in which an injection needle protrudes from one side of a housing and a barrel is accommodated in a barrel accommodation part, and in which the plunger is positioned at an end point by the urging force of a plunger urging part; and a rotation suppression mechanism for suppressing the rotation speed of relative rotation between the plunger and the engagement member 6.

Description

injection device CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority from Japanese Patent Application No. 2023-130064, the entire disclosure of which is incorporated herein by reference.

[0002] The present invention relates to an injection device in which the injection needle can be pulled out of the housing when in use and can be returned to the housing after use.

[0003] An example of such an injection device is disclosed in Patent Document 1. This injection device includes a syringe, an engaging member, a plunger biasing portion, a barrel biasing portion, a housing that accommodates these, and a trigger portion.

[0004] The syringe includes a barrel filled with a drug solution and having an injection needle at its tip, and a plunger configured to be movable from the base end to the tip end of the barrel and inserted into the barrel. The base end of the barrel is provided with a spirally inclined portion. The plunger includes a rod body extending in the central axis direction and a first branch portion and a second branch portion protruding from the outer circumferential surface of the rod body. The second branch portion is provided closer to the tip end in the central axis direction than the first branch portion.

[0005] The engaging member includes a cylindrical engaging body into which the rod body can be inserted and an outer flange-shaped biasing engaging portion that protrudes radially from the outer circumferential surface of the engaging body. The biasing engaging portion has a release hole in the central axial direction through which the first branch portion can be inserted. The plunger and the engaging member are engaged by the second branch portion engaging with the biasing engaging portion.

[0006] Furthermore, the plunger biasing portion biases the engaging member toward the tip end side in the central axis direction, and the barrel biasing portion biases the barrel toward the base end side in the central axis direction. The biasing force of the barrel biasing portion is set to be weaker than the biasing force of the plunger biasing portion.

[0007] The housing includes a barrel accommodating portion and a plunger accommodating portion. The barrel accommodating portion accommodates the barrel and the barrel biasing portion in this order from the base end to the tip end in the central axis direction. Additionally, the plunger accommodating portion accommodates the plunger biasing portion, the engaging member, and the plunger in this order from the base end to the tip end in the central axis direction. The engaging member is accommodated in the plunger accommodating portion while resisting the bias of the plunger biasing portion. Furthermore, the trigger portion engages with the engaging member accommodated in the plunger accommodating portion, thereby preventing the bias of the plunger biasing portion from being released. When the trigger portion is operated, it disengages from the engaging member, thereby releasing the bias of the plunger biasing portion.

[0008] According to this injection device, the trigger is operated to disengage from the engaging member, thereby releasing the bias of the plunger biasing portion. The bias of the plunger biasing portion then pushes the engaging member and the syringe toward the distal end in the central axis direction. As a result, the barrel moves toward the distal end within the barrel housing portion while compressing the barrel biasing portion, causing the injection needle to protrude from the barrel housing portion. This allows the injection needle to puncture, for example, the skin.

[0009] Furthermore, when the barrel moving toward the distal end abuts against a part inside the barrel housing, the movement of the barrel is restricted. In response to this, the plunger biasing portion biases the engaging member and the plunger further toward the distal end in the central axis direction. Then, when the plunger moves toward the distal end inside the barrel, the medicinal liquid is ejected from the injection needle. Therefore, the medicinal liquid can be administered, for example, into the skin.

[0010] In the injection device described in Patent Document 1, when the plunger reaches just before the tip of the barrel, the second branch abuts and slides against the inclined portion, causing the plunger to rotate relative to the engaging member. As a result, the first branch and the release hole are positioned circumferentially in the same position, disengaging the plunger from the engaging member. Therefore, the syringe is released from the biasing force of the plunger biasing portion and is pushed toward the base end by the biasing force of the barrel biasing portion. Therefore, the injection needle returns into the housing.

[0011] International Publication No. 2021 / 162086

[0012] However, in order to deal with problems such as leakage of the medicinal solution from the puncture site, it may be desirable to keep the injection needle punctured in the skin for a while after administration is completed. However, the injection device described in Patent Document 1 does not have a function for keeping the injection needle punctured in the skin for a while after administration is completed.

[0013] Therefore, an object of the present invention is to provide an injection device that can reliably complete administration by keeping the injection needle protruding from the housing for a while after injection is complete.

[0014] The present invention provides a syringe including a barrel having an injection needle at its tip, and a plunger inserted into the barrel so as to be reciprocally movable between the base end of the barrel as a starting point and the tip end where the injection needle is provided as an end point, and a cylindrical housing for accommodating the syringe, the housing including a barrel accommodating section on one side in the direction of the central axis for accommodating the barrel so that the barrel can move between a state in which the injection needle is accommodated and a state in which the barrel moves a predetermined distance from the accommodated state to one side and the injection needle protrudes from one side of the housing, and a plunger accommodating section on the other side of the barrel accommodating section for accommodating the plunger; and a plunger attached to the barrel accommodating section for attaching the barrel from one side of the housing to the other side. an engaging member that is disposed in the plunger accommodating section and engages with the plunger; a plunger accommodating section that engages with the engaging member and urges the plunger from the starting point toward the end point; and an engagement release mechanism that releases the engagement between the plunger and the engaging member by rotating the plunger and the engaging member relative to each other about a central axis when the barrel is accommodated in the barrel accommodating section with the injection needle protruding from one side of the housing and the plunger is positioned at the end point by the urging force of the plunger accommodating section, and further comprising a rotation suppression mechanism that suppresses the rotational speed of the relative rotation between the plunger and the engaging member in the engagement release mechanism.

[0015] In addition, in the present invention, the disengagement mechanism may be configured to disengage the plunger and the engaging member by rotating the engaging member around a central axis relative to the plunger, and the rotation suppression mechanism may suppress the rotational speed of the engaging member.

[0016] In addition, in the present invention, the engaging member includes an engaging rotating portion that engages with the plunger and rotates about a central axis relative to the plunger to release the engagement with the plunger, and the disengagement mechanism is configured to release the engagement between the plunger and the engaging member by causing the engaging rotating portion to rotate relative to the plunger to release the engagement between the plunger and the engaging rotating portion, and the rotation suppression mechanism includes an engaging non-rotating portion that does not rotate about the central axis relative to the engaging rotating portion, and a rotation suppression portion that is arranged between the engaging rotating portion and the engaging non-rotating portion and suppresses the rotational speed of the engaging rotating portion relative to the engaging non-rotating portion, and may suppress the rotational speed of the engaging rotating portion relative to the engaging non-rotating portion.

[0017] In addition, in the present invention, the rotation suppressing portion may be an elastic body that is disposed in an elastically deformed state between the engaging rotating portion and the engaging non-rotating portion.

[0018] In addition, in the present invention, the disengagement mechanism may be configured to disengage the plunger from the engaging member by rotating the plunger around a central axis relative to the engaging member, and the rotation suppression mechanism may suppress the rotational speed of the plunger.

[0019] Further, in the present invention, the plunger includes a plunger rotating portion that engages with the engaging member and rotates about the central axis relative to the engaging member to release the engagement, a plunger non-rotating portion that does not rotate about the central axis relative to the plunger rotating portion, and a rotation suppressing portion that is disposed between the plunger rotating portion and the plunger non-rotating portion and suppresses the rotational speed of the plunger rotating portion relative to the plunger non-rotating portion, and the disengagement mechanism is configured to release the engagement between the plunger and the engaging member by causing the plunger rotating portion to rotate relative to the engaging member to release the engagement between the engaging member and the plunger rotating portion, and the rotation suppressing mechanism may include the plunger non-rotating portion and the rotation suppressing portion and suppress the rotational speed of the plunger rotating portion relative to the plunger non-rotating portion.

[0020] In the present invention, the rotation suppressing portion may be an elastic body that is disposed in an elastically deformed state between the plunger rotating portion and the plunger non-rotating portion.

[0021] FIG. 1 is a cross-sectional view of an injection device according to a first embodiment of the present invention, showing the initial state and illustrating the plunger in an outline view. FIG. 2 is a cross-sectional view of a housing according to the same embodiment, as viewed in a first radial direction. FIG. 3 is an exploded perspective view of a syringe according to the same embodiment. FIG. 4 is a view showing a plunger main body according to the same embodiment, and is a partially enlarged view of the plunger base. FIG. 5 is a cross-sectional view taken along the V-V cross-sectional line in FIG. 4. FIG. 6 is a perspective view of an engaging member according to the same embodiment. FIG. 7 is a cross-sectional view of an engaging member according to the same embodiment, as viewed in a second radial direction. FIG. 8 is a cross-sectional view taken along the VIII-VIII cross-sectional line in FIG. 1. FIG. 9 is a cross-sectional view taken along the IX-IX cross-sectional line in FIG. 1. FIG. 10 is a detailed view showing the state in which the plunger accommodating engaging portion and the main body engaging portion are engaged in FIG. 1. FIG. 11 is a cross-sectional view of an injection device according to the same embodiment, showing a state in which an injection needle protrudes from a housing, and illustrating the plunger in an outline view. FIG. 12 is a cross-sectional view of the injection device according to the same embodiment, showing a state in which administration of the medicinal liquid is completed and also showing an outline view of the plunger and the engaging member. FIG. 13 is a detailed view showing a state in which the plunger accommodating engagement portion and the main body engagement portion are disengaged from each other in FIG. 12. FIG. 14 is a cross-sectional view of the injection device according to the same embodiment, showing a state in which the engaging member has rotated around the central axis relative to the plunger, and also showing an outline view of the plunger and the engaging member. FIG. 15 is a detailed view showing a state in which the engaging main body of FIG. 14 has rotated around the central axis. FIG. 16 is a cross-sectional view taken along the XVI-XVI cross-sectional line in FIG. 14. FIG. 17 is a cross-sectional view of the injection device according to the same embodiment, showing a state in which the injection needle has returned into the housing, and also showing an outline view of the plunger and the engaging member. FIG. 18 is a cross-sectional view of the plunger accommodating portion according to the second embodiment, as viewed in the second radial direction. FIG. 19 is a front view of the plunger main body according to the same embodiment. FIG. 20 is a cross-sectional view taken along the XX-XX cross-sectional line in FIG. 19. Fig. 21 is a cross-sectional view of the rod body, plunger ring, and elastic body of the plunger. Fig. 22 is a perspective view of the engaging member according to the same embodiment. Fig. 23 is a cross-sectional view of the engaging member according to the same embodiment as viewed in a second radial direction. Fig. 24 is a front view of the injection device according to the same embodiment, showing the housing in cross section and illustrating the initial state.Fig. 25 is a cross-sectional view taken along the XXV-XXV cross-sectional line in Fig. 24. Fig. 26 is a front view of the injection device according to the same embodiment, showing the housing in cross-section and a state in which administration of the medicinal solution has been completed. Fig. 27 is a cross-sectional view taken along the XXVII-XXVII cross-sectional line in Fig. 26. Fig. 28 is a front view of the injection device according to the same embodiment, showing the housing in cross-section and a state in which the plunger has rotated around the central axis relative to the engaging member. Fig. 29 is a cross-sectional view taken along the XXIX-XXIX cross-sectional line in Fig. 28. Fig. 30 is a front view of the injection device according to the same embodiment, showing the housing in cross-section and a state in which the injection needle has returned into the housing.

[0022] Hereinafter, embodiments of the injection device of the present invention will be described. First, the configuration of an injection device 1 according to a first embodiment will be described.

[0023] In the following description, the direction in which the central axis O of the injection device 1 extends will be referred to as the central axis direction X. The lower side of FIG. 1 will be referred to as one side of the central axis direction X, and the upper side of FIG. 1 will be referred to as the other side of the central axis direction X. Furthermore, the direction perpendicular to the central axis direction X will be referred to as the radial direction. As shown in FIGS. 3 and 5, the radial direction includes a first radial direction Y1 and a second radial direction Y2 that are perpendicular to each other. Furthermore, the direction around the central axis O will be referred to as the circumferential direction.

[0024] The injection device 1 is used, for example, when a patient self-administers a liquid medicinal agent such as insulin or a rheumatism treatment drug. As shown in Figures 11 and 17, the injection device 1 has an injection needle 503 that protrudes from the housing 2 during use and returns the injection needle 503 to the housing 2 after use. As shown in Figure 1, the injection device 1 includes a housing 2, a plunger biasing unit 3, a barrel biasing unit 4, a syringe 5, and an engaging member 6.

[0025] The housing 2 accommodates the plunger biasing portion 3, the barrel biasing portion 4, the syringe 5, and the engaging member 6. As shown in Fig. 2, the housing 2 is formed in a tubular (specifically, cylindrical) shape with one side open in the central axial direction X and the other side closed by a trigger portion 23 (described later). The housing 2 includes a barrel accommodating portion 20, a partition portion 21, and a plunger accommodating portion 22.

[0026] As shown in Fig. 1 , the barrel housing portion 20 houses the barrel 50. The barrel housing portion 20 is cylindrical and open on both sides in the central axis direction X. As shown in Fig. 2 , the barrel housing portion 20 includes a cylindrical other-side barrel housing portion 200 disposed on the other side in the central axis direction X, and a cylindrical one-side barrel housing portion 201 disposed on one side in the central axis direction X.

[0027] In this embodiment, a barrel protrusion 20A that protrudes radially inward is provided on the inner circumferential surface of the barrel other-side accommodating portion 200. This barrel protrusion 20A is provided over the entire area in the central axial direction X of the barrel other-side accommodating portion 200. In this embodiment, the barrel protrusion 20A is provided along the central axial direction X. In this embodiment, a pair of barrel protrusions 20A are provided on the inner circumferential surface of the barrel other-side accommodating portion 200 so as to face each other in the first radial direction Y1.

[0028] An inner flange-shaped biasing base 20B having a through hole (not numbered) in the central axial direction X is provided on the inner peripheral surface of the barrel one-side accommodating portion 201. Note that the biasing base 20B in this embodiment is disposed on one side of the other end of the barrel one-side accommodating portion 201 in the central axial direction X.

[0029] In this embodiment, the barrel one accommodating portion 201 is provided with a through-hole 20C that penetrates in the radial direction. This through-hole 20C is a through-hole that penetrates the barrel one accommodating portion 201 in the second radial direction Y2. In this embodiment, the through-hole 20C is configured in a rectangular shape that follows the circumferential surface of the barrel one accommodating portion 201. In addition, in this embodiment, the through-hole 20C is provided on one side and the other side in the central axial direction X with respect to the biasing base portion 20B. Note that a pair of through-holes 20C are provided in the barrel one accommodating portion 201 so as to face each other in the second radial direction Y2.

[0030] The first barrel accommodating portion 201 is connected to one side of the second barrel accommodating portion 200 in the central axial direction X. The inner diameter of the first barrel accommodating portion 201 is smaller than the inner diameter of the second barrel accommodating portion 200. Therefore, a barrel step 20D, which is a step continuous with the second barrel accommodating portion 200, is formed at the other end of the first barrel accommodating portion 201 in the central axial direction X. The barrel step 20D is a flat surface that extends radially and circumferentially.

[0031] The partition 21 is made of an annular member that forms a through hole that penetrates in the central axial direction X. The partition 21 has flat surfaces whose one and other ends in the central axial direction X extend radially and circumferentially. The inner diameter of the partition 21 is smaller than the inner diameter of the other-barrel-accommodating portion 200. On the other hand, the outer diameter of the partition 21 is approximately the same as the outer diameter of the other-barrel-accommodating portion 200. The partition 21 is arranged with one end in the central axial direction X abutting against the other end in the central axial direction X of the barrel accommodating portion 20.

[0032] The plunger accommodating portion 22 is cylindrical and extends in the central axial direction X. As shown in Fig. 2, the plunger accommodating portion 22 includes a cylindrical first plunger accommodating portion 220 arranged on one side in the central axial direction X, and a cylindrical second plunger accommodating portion 221 arranged on the other side in the central axial direction X.

[0033] The plunger first accommodating portion 220 is cylindrical and has an inner diameter larger than the outer diameters of the barrel second accommodating portion 200 and the partition portion 21. Therefore, as shown in Fig. 2 , the plunger first accommodating portion 220 is fitted onto the barrel second accommodating portion 200 and the partition portion 21 from the other side in the central axis direction X, thereby connecting the plunger accommodating portion 22 to the barrel accommodating portion 20 and the partition portion 21. In this way, the housing 2 is formed.

[0034] A plunger accommodating engagement portion (not numbered) is provided on the inner peripheral surface of the plunger other-side accommodating portion 221. The plunger accommodating engagement portion of this embodiment includes a plunger accommodating protrusion 22A that protrudes radially inward from the plunger other-side accommodating portion 221, and a plunger accommodating recess 22B recessed into the plunger other-side accommodating portion 221.

[0035] The plunger accommodating protrusion 22A is formed continuously from the other end of the plunger other-side accommodating portion 221 in the central axial direction X toward one side. Furthermore, one end of the plunger accommodating protrusion 22A in the central axial direction X is located on the other side of the one end of the plunger other-side accommodating portion 221 in the central axial direction X. Therefore, the plunger accommodating protrusion 22A is not formed over the entire area of ​​the plunger other-side accommodating portion 221 in the central axial direction X, and is shorter than the plunger other-side accommodating portion 221 in the central axial direction X. Furthermore, the plunger accommodating protrusion 22A is formed along the central axial direction X. In this embodiment, the plunger accommodating protrusions 22A are provided in pairs on the inner circumferential surface of the plunger other-side accommodating portion 221 so as to face each other in the first radial direction Y1 and the second radial direction Y2. In contrast, the plunger accommodating recesses 22B are provided over the entire area of ​​the plunger other-side accommodating portion 221 in the central axial direction X. The plunger accommodating recess 22B is formed along the central axis direction X. The plunger accommodating recess 22B is disposed between the plunger accommodating protrusions 22A and 21A that are adjacent to each other in the circumferential direction.

[0036] The plunger other accommodating portion 221 is connected to the other side of the plunger first accommodating portion 220 in the central axial direction X, thereby forming the plunger accommodating portion 22. The inner diameter of the plunger other accommodating portion 221 is smaller than the inner diameter of the plunger first accommodating portion 220. Therefore, a plunger step (not numbered) that is a step continuous with the plunger first accommodating portion 220 is formed at one end of the plunger other accommodating portion 221 in the central axial direction X. The plunger step is a flat surface that extends radially and circumferentially.

[0037] Here, the inner diameter of the plunger other-side accommodating portion 221 is smaller than the outer diameter of the partition portion 21. Therefore, as shown in Fig. 2, in the housing 2, the plunger step portion abuts against the other end of the partition portion 21 in the central axis direction X. Note that in this embodiment, the inner diameter of the plunger other-side accommodating portion 221 is larger than the inner diameter of the partition portion 21.

[0038] 1 and 2, the trigger portion 23 is provided on the other side of the plunger other accommodating portion 221 in the central axial direction X. The trigger portion 23 includes a trigger mounting portion 230, a trigger main body portion 23A, and a trigger lock operating portion 23a.

[0039] As shown in Figure 2, the trigger mounting portion 230 includes a trigger mounting base portion 231 that protrudes radially inward from the plunger other side accommodating portion 221, and a cylindrical trigger tube portion 232 that protrudes from the trigger mounting base portion 231 to the other side in the central axial direction X.

[0040] The trigger mount 231 has an inner flange shape that forms an insertion hole in the central axial direction X. The trigger mount 231 is disposed at the other end of the plunger other accommodating portion 221 in the central axial direction X. An insertion hole (not shown) is provided at one end of the trigger mount 231 in the central axial direction.

[0041] The trigger tube portion 232 is disposed so as to surround the insertion hole. A locking step 233 is formed on the inner peripheral surface of the trigger tube portion 232. The locking step 233 extends in the central axial direction X from the trigger mount portion 231 along the trigger tube portion 232. A pair of locking steps 233 are provided circumferentially, spaced approximately 180 degrees apart. In addition, a plurality of protrusions 234 that protrude radially outward are formed on the outer peripheral surface of the trigger tube portion 232.

[0042] The trigger body 23A comprises a disk-shaped top plate 23B that is pressed down by the user to operate it, an outer skirt 23C that hangs down from the outer peripheral edge of the top plate 23B to one side in the central axis direction X, an inner skirt 23F that hangs down from the top plate 23B to one side in the central axis direction X radially inward of the outer skirt 23C, and a flat plate 23G.

[0043] The outer skirt portion 23C is cylindrical. As shown in FIG. 1 , a release groove 23D is formed by cutting out a portion of the outer skirt portion 23C in the circumferential direction from one end in the central axis direction X to the other side in the central axis direction X. This release groove 23D is configured so that the locking step portion 233 can be inserted into it. Furthermore, in this embodiment, the outer skirt portion 23C is formed with a pair of release grooves 23D that face each other in the radial direction. As shown in FIG. 2 , a recessed interlocking groove 23E is formed in the outer peripheral surface of the outer skirt portion 23C. This interlocking groove 23E is formed on one side of the other end in the central axis direction X of the outer skirt portion 23C. Note that multiple interlocking grooves 23E are formed on the outer peripheral surface of the outer skirt portion 23C.

[0044] The outer diameter of the outer skirt portion 23C is smaller than the inner diameter of the trigger tube portion 232. Therefore, the trigger main body 23A is configured to be insertable into the trigger tube portion 232. The length of the outer skirt portion 23C in the central axial direction X is the same as the length of the trigger tube portion 232 in the central axial direction X. In FIG. 2 , the trigger main body 23A is inserted into the trigger tube portion 232 with one end of the outer skirt portion 23C in the central axial direction X abutting against the locking step 233. Furthermore, the outer skirt portion 23C is configured to be rotatable about the central axis O while inserted into the trigger tube portion 232. Therefore, when the outer skirt portion 23C inserted into the trigger tube portion 232 is rotated about the central axis O, the locking step 233 and the release groove 23D circumferentially align, allowing the locking step 233 to be inserted into the release groove 23D. Therefore, when the release groove 23D and the locking step 233 are aligned in the circumferential direction, the trigger body 23A can be pushed to one side in the central axis direction X.

[0045] The inner skirt portion 23F is cylindrical. The outer diameter of the inner skirt portion 23F is smaller than the inner diameter of the outer skirt portion 23C. Therefore, the inner skirt portion 23F is positioned more inward than the outer skirt portion 23C. The inner skirt portion 23F has approximately the same length as the outer skirt portion 23C in the central axis direction X.

[0046] The flat plate portion 23G is a plate-like member having a length in the central axis direction X and a width and thickness in the radial direction. In Figures 1 and 2, the flat plate portion 23G has a width in the first radial direction Y1 and a thickness in the second radial direction Y2. The flat plate portion 23G hangs down from the top plate portion 23B radially inward of the inner skirt portion 23F. The flat plate portion 23G is also longer in the central axis direction X than the inner skirt portion 23F and the outer skirt portion 23C. The flat plate portion 23G is configured to be insertable into the through-hole of the trigger mount portion 231.

[0047] 2, the trigger lock operating portion 23a includes a cylindrical tube portion 23b and a protruding portion 23c that protrudes radially inward from the other end of the tube portion 23b in the central axis direction X. A rotation groove 23d that extends in the circumferential direction is formed in the tube portion 23b by cutting out a portion of the circumferential surface. The rotation groove 23d is configured so that the protrusion 234 can be inserted into it.

[0048] The inner diameter of the tubular portion 23b is larger than the outer diameter of the trigger tubular portion 232. Therefore, in FIG. 2 , the tubular portion 23b fits around the trigger tubular portion 232 with the convex portion 234 inserted into the rotation groove 23d. The protrusion 23c is configured to be insertable into the interlocking groove 23E. Inserting the protrusion 23c into the interlocking groove 23E prevents the trigger main body 23A from slipping out of the trigger tubular portion 232. Note that in this embodiment, multiple protrusions 23c are provided in the circumferential direction. Here, the trigger lock operating portion 23a is configured to be rotatable about the central axis O. Therefore, by rotating the trigger lock operating portion 23a about the central axis O, the trigger main body 23A can be rotated about the central axis O.

[0049] The plunger biasing portion 3 biases the syringe 5 and the engaging member 6 from the other side in the central axial direction X to one side. The plunger biasing portion 3 of this embodiment biases the engaging member 6 to rotate about the central axis O. The plunger biasing portion 3 of this embodiment is a compression coil torsion spring wound around the central axis O. The outer diameter of the plunger biasing portion 3 is smaller than the inner diameter of the plunger accommodating portion 22. Therefore, the plunger biasing portion 3 is configured to be able to be accommodated in the plunger accommodating portion 22. As shown in FIG. 1 , the plunger biasing portion 3 is accommodated in the plunger one accommodating portion 220 with the other end in the central axial direction X inserted into an insertion hole provided in the trigger mount portion 231 from one side in the central axial direction X.

[0050] The barrel biasing portion 4 biases the barrel 50 from one side to the other side in the central axis direction X. As shown in FIG. 1 , the barrel biasing portion 4 in this embodiment is a compression coil spring wound around the central axis O. The barrel biasing portion 4 is configured to be accommodated in the barrel accommodating portion 20. Specifically, the barrel biasing portion 4 has a diameter larger than the through hole formed by the biasing base 20B and smaller than the inner diameter of the barrel one accommodating portion 201. Therefore, as shown in FIG. 1 , the barrel biasing portion 4 is accommodated in the barrel accommodating portion 20 while abutting against the biasing base 20B from the other side in the central axis direction X. Therefore, the barrel biasing portion 4 is prevented from moving toward one side in the central axis direction X by the biasing base 20B. Note that the biasing force of the barrel biasing portion 4 is set to be weaker than the biasing force of the plunger biasing portion 3.

[0051] 3, the syringe 5 includes a barrel 50 having an injection needle 503 at its tip, and a plunger 51. The barrel 50 also includes a barrel main body 500 filled with a medicinal solution, and a cover 50A attached to the barrel main body 500.

[0052] The barrel main body 500 is made of transparent resin, glass, etc. The barrel main body 500 includes a cylindrical barrel portion 501 filled with a chemical solution, and an outer flange portion 502 (see FIG. 1 ) that protrudes radially outward from the other end of the cylindrical barrel portion 501 in the central axial direction X.

[0053] The barrel cylindrical portion 501 is cylindrical. As shown in FIG. 3 , an injection needle 503 protrudes from one end of the barrel cylindrical portion 501 in the central axis direction X. Therefore, the injection needle 503 is provided at one end in the central axis direction X, which is the tip of the barrel 50. In this embodiment, the outer diameter of the barrel cylindrical portion 501 is smaller than the inner diameter of the barrel biasing portion 4, which is a compression coil spring. Therefore, as shown in FIG. 1 , the barrel cylindrical portion 501 is inserted into the barrel biasing portion 4. Furthermore, the outer diameter of the barrel cylindrical portion 501 is smaller than the through-hole formed by the biasing base portion 20B. Therefore, the barrel main body 500 is disposed in the barrel housing 20 with the barrel cylindrical portion 501 inserted into the through-hole.

[0054] As shown in FIG. 3 , the cover portion 50A is cylindrical, with a portion of its outer circumferential surface cut away and a substantially C-shaped bottom. The cover portion 50A has flat surfaces at one end and the other end in the central axial direction X that extend radially and circumferentially. A circular through-hole 50B is formed in the cover portion 50A in the central axial direction X. As shown in FIG. 9 , a shaft movement groove 50C is formed in the through-hole 50B by cutting out a portion of the inner circumferential surface of the cover portion 50A. In this embodiment, two shaft movement grooves 50C, 50C are formed in the second radial direction Y2. Furthermore, as shown in FIGS. 3 and 9 , the outer circumferential surface of the cover portion 50A is provided with a cover recess 50D recessed radially inward. The cover recess 50D is formed along the central axial direction X. The cover recess 50D is formed from one end to the other end of the cover portion 50A in the central axial direction X. In this embodiment, a pair of cover recesses 50D, 50D are provided in the cover portion 50A so as to face each other in the first radial direction Y1.

[0055] The cover part 50A is configured to be attachable to the barrel main body part 500. The cover part 50A of this embodiment is attached to the barrel main body part 500 by sliding the outer flange part 502 radially from a part of the cut outer peripheral surface. Note that when the cover part 50A is attached to the barrel main body part 500, the through-hole 50B of the cover part 50A and the inside of the barrel cylindrical part 501 are in communication.

[0056] The outer diameter of the cover part 50A is substantially the same as the inner diameter of the other-barrel-part accommodating part 200. Therefore, the cover part 50A is configured to be able to be accommodated in the other-barrel-part accommodating part 200. Here, as shown in FIG. 9 , the cover part 50A is accommodated in the other-barrel-part accommodating part 200 with the cover recess 50D of the cover part 50A engaged with the barrel protrusion 20A of the other-barrel-part accommodating part 200.

[0057] 1 , the length of the cover part 50A in the central axis direction X is shorter than the length of the other barrel accommodating part 200 in the central axis direction X. Therefore, the cover part 50A is movable in the other barrel accommodating part 200 in the central axis direction X.

[0058] Here, the outer diameter of the cover portion 50A is larger than the outer diameter of the barrel biasing portion 4, which is a compression coil spring. Therefore, when the barrel 50 is disposed in the barrel housing portion 20, the barrel biasing portion 4 abuts against one end of the cover portion 50A in the central axial direction X. Therefore, the cover portion 50A stops the biasing force of the barrel biasing portion 4 from the other side in the central axial direction X. Therefore, as shown in FIGS. 11 and 17 , the cover portion 50A moves to one side in the central axial direction X by resisting the biasing force of the barrel biasing portion 4, and moves to the other side in the central axial direction X by the biasing force of the barrel biasing portion 4.

[0059] The outer diameter of the cover part 50A is larger than the inner diameter of the first barrel accommodating part 201 and the inner diameter of the partition part 21. Therefore, the cover part 50A is configured to abut against the barrel step part 20D when it moves to one side in the central axial direction X in the second barrel accommodating part 200, and to abut against one end of the partition part 21 in the central axial direction X when it moves to the other side in the central axial direction X.

[0060] The length of the barrel 50 in the central axis direction X is shorter than the length of the barrel housing portion 20 in the central axis direction X. Therefore, in the state shown in FIG. 1 , the barrel 50 (specifically, the cover portion 50A) is biased toward the other side in the central axis direction X by the biasing force of the barrel biasing portion 4, and the injection needle 503 is housed in the housing 2. This state is referred to as a first state. On the other hand, in the state shown in FIG. 11 , the barrel 50 (specifically, the cover portion 50A) resists the biasing force of the barrel biasing portion 4, causing the injection needle 503 to protrude from one side in the central axis direction X of the housing 2. This state is referred to as a second state. That is, the barrel 50 is movable between the first state and the second state.

[0061] The plunger 51 is inserted into the barrel 50. As shown in Fig. 3, the plunger 51 includes a piston 51A and a plunger body 510 that is engaged with the piston 51A.

[0062] The piston 51A prevents the liquid medicine in the barrel 50 from leaking out of the barrel 50 and also pushes the liquid medicine out of the barrel 50 from the injection needle 503. The piston 51A is disposed inside the cylindrical barrel portion 501 and is in close contact with the entire inner circumferential surface of the cylindrical barrel portion 501.

[0063] The plunger body 510 includes a rod 511 and a plunger base 513 disposed on the other side of the rod 511 in the central axis direction X.

[0064] The rod 511 is a member extending along the central axis direction X. The diameter of the rod 511 is smaller than the inner diameter of the barrel tubular portion 501 and the through-hole 50B of the cover portion 50A. Therefore, the rod 511 is configured to be insertable into the barrel 50. Therefore, as shown in FIG. 1 , the plunger 51 is inserted into the barrel 50 in a state in which it can reciprocate on one side and the other side of the central axis direction X of the barrel 50.

[0065] An axial movement protrusion 512 that protrudes outward is formed on the outer peripheral surface of the rod 511. The axial movement protrusion 512 extends from one end of the rod 511 in the central axial direction X toward the other end. The axial movement protrusion 512 is configured to be able to fit into the axial movement groove 50C. In this embodiment, a pair of axial movement protrusions 512, 512 is formed in the second radial direction Y2.

[0066] 9, with the axial movement protrusion 512 fitted in the axial movement groove 50C, the rod 511 is inserted into the through-hole 50B, whereby the plunger body 510 is inserted into the barrel 50 in a state where it cannot rotate around the central axis O. Note that, as shown in FIG. 1, one end of the rod 511 in the central axis direction X abuts against the other end of the piston 51A in the central axis direction X.

[0067] 3, the plunger base 513 is disposed on the other side of the rod 511 in the central axis direction X. In this embodiment, the plunger base 513 has a larger diameter than the rod 511. The plunger base 513 includes a plunger engagement portion 514 and a trigger engagement portion 515.

[0068] 4, the plunger engagement portion 514 is connected to the other end of the rod 511 in the central axis direction X. In this embodiment, the plunger engagement portion 514 is a member having a larger diameter than the rod 511.

[0069] A groove 51a recessed radially inward is formed on the outer peripheral surface of the plunger engagement portion 514. As shown in FIGS. 4 and 5 , the groove 51a in this embodiment includes an axial groove 51b extending in the central axial direction X and a circumferential groove 51c extending in the circumferential direction. The axial groove 51b is provided in the plunger engagement portion 514 so as to extend from one end of the plunger engagement portion 514 in the central axial direction X to the other end. The axial groove 51b extends along the central axial direction X. As shown in FIGS. 4 and 5 , the circumferential groove 51c is provided in the plunger engagement portion 514 so as to extend along the circumferential direction. The circumferential groove 51c includes a circumferential one end 51d that is one end in the circumferential direction and a circumferential other end 51e that is the other end in the circumferential direction. The circumferential groove 51c is located on the other side in the central axial direction X of the axial groove 51b and is continuous with the axial groove 51b in the central axial direction X. Specifically, one circumferential end 51d of the circumferential groove portion 51c is continuous with the shaft groove portion 51b.

[0070] As shown in Figures 3 and 4, the trigger engagement portion 515 is a member configured so that the other side in the central axis direction X is bifurcated. The trigger engagement portion 515 is configured to be able to bend so that the bifurcated portions approach each other. Furthermore, the bent trigger engagement portion 515 is configured to return to its original state. Thus, the trigger engagement portion 515 is configured to be elastically deformable. A rib 516 that protrudes radially outward is formed on the other end of the trigger engagement portion 515 in the central axis direction X. This rib 516 is configured in a tapered shape such that the amount of radial outward protrusion increases as it progresses from the other side in the central axis direction X to one side. Note that one end of the rib 516 in the central axis direction X is a flat surface along the radial direction.

[0071] The trigger engaging portion 515 is configured to be insertable into a through-hole formed by the trigger mount 231. Specifically, the rib 516 abuts against the inner circumferential surface of the trigger mount 231, and the bifurcated portions of the trigger engaging portion 515 bend toward each other, thereby allowing the trigger engaging portion 515 to be inserted into the through-hole formed by the trigger mount 231, as shown in Fig. 1 . The trigger engaging portion 515 then returns to its original state due to its elastic force, and one end of the rib 516 in the central axis direction X abuts against the trigger mount 231 from the other side in the central axis direction X.

[0072] The distance between the bifurcated portions of the trigger engagement portion 515 is longer than the width of the flat portion 23G. Therefore, the flat portion 23G can be inserted between the bifurcated portions of the trigger engagement portion 515. In FIG. 1 , the flat portion 23G is disposed between the bifurcated portions of the trigger engagement portion 515.

[0073] 6, the engaging member 6 is configured in an annular shape. The engaging member 6 includes a cylindrical engaging body 60, an engaging ring 61, and an elastic body 62. The engaging body 60 of this embodiment includes an engaging annular portion 600 and an engaging cylindrical portion 601.

[0074] The engaging annular portion 600 is an annular member. As shown in Fig. 7 , one end and the other end of the engaging annular portion 600 in the central axis direction X are flat surfaces. The inner diameter of the engaging annular portion 600 is larger than the plunger body 510. On the other hand, the outer diameter of the engaging annular portion 600 is smaller than the inner diameter of the plunger other-side accommodating portion 221.

[0075] The engaging annular portion 600 is formed with a radially inward protruding portion 60a. This radially inward protruding portion 60a is configured to be insertable into the groove portion 51a of the plunger engaging portion 514. As shown in FIG. 6 , the engaging annular portion 600 of this embodiment is provided with multiple (specifically, two) radially inward protruding portions 60a in the circumferential direction. Furthermore, the other end of the engaging annular portion 600 in the central axial direction X is provided with a fixing portion for fixing one end of the plunger biasing portion 3 in the central axial direction X. In this embodiment, the fixing portion is an insertion hole 60b into which one end of the plunger biasing portion 3 in the central axial direction X can be inserted. Furthermore, the outer peripheral surface of the engaging annular portion 600 is formed with annular recesses 60A that can be fitted into the plunger accommodating protrusion 22A. A pair of annular recesses 60A is provided in each of the first radial direction Y1 and the second radial direction Y2.

[0076] The engaging cylindrical portion 601 is cylindrical. As shown in Fig. 7 , the engaging cylindrical portion 601 is connected to the engaging annular portion 600 from one side in the central axis direction X. The inner diameter of the engaging cylindrical portion 601 is substantially the same as the inner diameter of the engaging annular portion 600. Therefore, the plunger main body 510 can be inserted into the engaging main body 60. The outer diameter of the engaging cylindrical portion 601 is smaller than the outer diameter of the engaging annular portion 600.

[0077] A flange 602 protruding radially outward is provided on the outer peripheral surface of the engagement cylindrical portion 601. In this embodiment, the flange 602 is disposed on one side of the engagement cylindrical portion 601 in the central axial direction X. This flange 602 is configured in a stepped shape with one side in the central axial direction X positioned radially outward relative to the other side. Therefore, in this embodiment, the flange 602 has the largest outer diameter at one end in the central axial direction X. Furthermore, the other end and one end of the flange 602 in the central axial direction X are flat surfaces that extend radially and circumferentially. Furthermore, the outer diameter of one end of the flange 602 in the central axial direction X is approximately the same as the outer diameter of the engagement annular portion 600. Therefore, the engagement main body 60 can be accommodated in the plunger other-side accommodating portion 221.

[0078] The outer peripheral surface of the flange 602 is provided with a flange recess 60B that can be fitted into the plunger accommodating protrusion 22A. This flange recess 60B is provided at one end of the flange 602 in the central axis direction X, where the outer diameter is largest. The flange recess 60B is also disposed at approximately the same position in the circumferential direction as the annular recess 60A. Therefore, a pair of flange recesses 60B is provided in each of the first radial direction Y1 and the second radial direction Y2. In this embodiment, the flange recess 60B and the annular recess 60A constitute a main body engaging portion 60C that can engage with the plunger accommodating engaging portion.

[0079] The engaging ring 61 is an annular member. One end and the other end of the engaging ring 61 in the central axial direction X are flat surfaces. The inner diameter of the engaging ring 61 is larger than the outer diameter of the engaging cylindrical portion 601. Therefore, as shown in FIG. 7 , the engaging ring 61 is disposed on the outer peripheral surface of the engaging main body 60 while being fitted onto the engaging cylindrical portion 601. Specifically, the engaging ring 61 is disposed between the engaging annular portion 600 and the flange portion 602 in the central axial direction X. Therefore, the length of the engaging ring 61 in the central axial direction X is shorter than the length of the engaging cylindrical portion 601 in the central axial direction X. The outer diameter of the engaging ring 61 is substantially the same as the outer diameter of the engaging annular portion 600 of the engaging main body 60 and the outer diameter of one end of the flange portion 602 in the central axial direction X.

[0080] The outer peripheral surface of the engagement ring 61 is provided with a ring protrusion 61A configured to be able to fit into the plunger accommodating recess 22B, and a ring recess 61B configured to be able to fit into the plunger accommodating recess 22A. As shown in Fig. 6, the ring recess 61B is disposed at approximately the same position as the main body engagement portion 60C in the circumferential direction. Therefore, a pair of ring recesses 61B is provided in each of the first radial direction Y1 and the second radial direction Y2.

[0081] The elastic body 62 is configured to be elastically deformable in the circumferential direction. The elastic body 62 in this embodiment is an O-ring configured in an annular shape. Specifically, the elastic body 62 in this embodiment is configured from oil-bleed silicone rubber, which is silicone rubber mixed with oil. Note that the elastic body 62 may also be configured from a material other than oil-bleed silicone rubber, such as fluororubber, nitrile rubber, or silicone rubber.

[0082] The elastic body 62 is disposed between the engagement main body 60 and the engagement ring 61. In this embodiment, the elastic body 62 is disposed between the engagement main body 60 and the engagement ring 61 in the central axial direction X. Specifically, the elastic body 62 is disposed between one end of the engagement annular portion 600 in the central axial direction X and the other end of the engagement ring 61 in the central axial direction X, and between one end of the engagement ring 61 in the central axial direction X and the other end of the flange portion 602 in the central axial direction X. Thus, in this embodiment, two elastic bodies 62, 62 are disposed between the engagement main body 60 and the engagement ring 61 on one and the other sides in the central axial direction X. Furthermore, the elastic body 62 abuts against the engagement main body 60 and the engagement ring 61.

[0083] The length of the engaging member 6 in the central axis direction X is shorter than the distance between the partition portion 21 and the plunger accommodating protrusion 22A in the central axis direction X. The radial length of the engaging member 6 is larger than the inner diameter of the partition portion 21.

[0084] The engaging member 6 engages with the plunger engaging portion 514. Specifically, when the plunger base 513 is inserted into the engaging member 6, the radially inner protrusion 60a is inserted into the groove 51a, thereby engaging the engaging member 6 with the plunger engaging portion 514. In this embodiment, the radially inner protrusion 60a inserted into the shaft groove 51b is moved to the circumferential groove 51c, and then the engaging member 6 and the plunger main body 510 are rotated relative to each other around the central axis O. Specifically, the engaging main body 60 is rotated around the central axis O relative to the plunger 51. As a result, as shown in FIG. 8 , the radially inner protrusion 60a is positioned on the other circumferential end 51e side of the circumferential groove 51c. Therefore, the engaging member 6 engages with the plunger 51.

[0085] As shown in FIG. 1 , the engagement member 6 engaged with the plunger 51 is accommodated in the plunger accommodating portion 22. This engagement member 6 compresses the plunger biasing portion 3 in the central axial direction X without releasing the twist. Here, the plunger biasing portion 3 is twisted around the central axis O, with the other end in the central axial direction X inserted into an insertion hole provided in the trigger mount portion 231 and one end in the central axial direction X inserted into the insertion hole 60b of the engagement annular portion 600. Meanwhile, the engagement member 6 is accommodated in the plunger other accommodating portion 221 with the main body engaging portion 60C of the engagement main body 60 and the ring recessed portion 61B of the engagement ring 61 fitted into the plunger accommodating protrusion 22A of the plunger other accommodating portion 221, and with the ring protrusion 61A of the engagement ring 61 fitted into the plunger accommodating recessed portion 22B of the plunger other accommodating portion 221. Therefore, the engaging member 6 is unable to rotate around the central axis O, thereby preventing the torsion of the plunger biasing portion 3 from being released. Furthermore, as the engaging member 6 moves to the other side in the central axis direction X within the plunger other-side accommodating portion 221, the engaging member 6 and the trigger mount 231 compress the plunger biasing portion 3 in the central axial direction X. Furthermore, as the trigger engaging portion 515 is inserted into the through-hole formed by the trigger mount 231, the rib 516 abuts against the trigger mount 231 from the other side in the central axial direction X, as shown in FIG. 1 . Therefore, the engaging member 6 holds the plunger biasing portion 3 in a state twisted around the central axis O and compressed in the central axial direction X.

[0086] Furthermore, when the engaging member 6 is accommodated in the plunger other-side accommodating portion 221 , the elastic body 62 is disposed in a state spaced apart from the inner circumferential surface of the plunger other-side accommodating portion 221 in the radial direction.

[0087] The above is a description of the configuration of the injection device 1 according to the first embodiment. Next, a method of using this injection device 1 will be described.

[0088] As shown in Figure 1, the injection device 1 of this embodiment is in an initial state before use. In this initial state, the injection needle 503 is housed in the housing 2. Therefore, the barrel 50 is in a first state. In the initial state, a cap (not shown) is attached to one side of the housing 2 in the central axis direction X, so that the injection needle 503 does not protrude outside the housing 2. Therefore, when using the injection device 1, the cap is first removed from the housing 2.

[0089] Next, the injection needle 503 is protruded from one side of the housing 2 in the central axial direction X, moving the barrel 50 from the first state to the second state. This unlocks the trigger portion 23, and the trigger main body 23A is pushed toward one side in the central axial direction X. Specifically, the trigger lock operating portion 23a and the trigger main body 23A are rotated about the central axial direction X relative to the trigger mounting portion 230, so that the release groove 23D and the lock step portion 233 are aligned in the circumferential direction. As the trigger main body 23A rotates about the central axial direction X, the thickness of the flat portion 23G is oriented in a direction that matches the direction in which the bifurcated portions of the trigger engaging portion 515 face each other. This allows the trigger engaging portion 515 to bend so that the bifurcated portions approach each other. The trigger main body 23A is then pushed toward one side in the central axial direction X. As a result, the locking step 233 is inserted into the release groove 23D, and the inner skirt 23F comes into contact with the rib 516. This causes the bifurcated portions of the trigger engagement portion 515 to bend toward each other, disengaging the plunger 51 from the trigger portion 23. This releases the biasing force of the plunger biasing portion 3, which had been held in a compressed state.

[0090] As shown in FIG. 11 , the biasing force of the released plunger biasing portion 3 moves the engaging member 6 and the syringe 5, which includes the plunger 51 engaged with the engaging member 6, toward one side in the central axial direction X. Here, the biasing force of the barrel biasing portion 4 is set to be weaker than the biasing force of the plunger biasing portion 3. Therefore, due to the biasing force of the plunger biasing portion 3, the syringe 5 first moves toward one side in the central axial direction X while compressing the barrel biasing portion 4 via the engaging member 6. Specifically, the barrel 50 moves toward one side in the central axial direction X until the cover portion 50A abuts against the barrel step portion 20D while compressing the barrel biasing portion 4. That is, the barrel biasing portion 4 is compressed by the plunger biasing portion 3 via the syringe 5. Note that the cover recess 50D and the barrel protrusion 20A are engaged. This prevents the barrel 50 from rotating around the central axial direction X. Then, as the syringe 5 moves to one side in the central axis direction X, the injection needle 503 protrudes outward from one side in the central axis direction X of the housing 2. Thus, the barrel 50 moves from the first state to the second state. Then, when the cover portion 50A abuts against the barrel step portion 20D, the movement of the barrel 50 to one side in the central axis direction X is restricted.

[0091] The biasing force of the plunger biasing portion 3 causes the engaging member 6 and the plunger 51 to move further toward one side in the central axial direction X. Specifically, as shown in Figures 11 and 12, the plunger 51 moves within the barrel 50, starting from the other side in the central axial direction X, which is the base end side of the barrel 50, and ending at one side in the central axial direction X, which is the tip end side where the injection needle 503 is provided. Therefore, as the plunger 51 moves within the barrel 50, the piston 51A pushes the liquid medicine from the injection needle 503 to the outside of the barrel 50. This allows the liquid medicine within the barrel 50 to be discharged. The piston 51A moves to the tip end, which is one end of the barrel 50 in the central axial direction X.

[0092] Here, the plunger biasing portion 3 of this embodiment not only biases the syringe 5 and the engaging member 6 from the other side in the central axial direction X to one side, but also biases them to rotate about the central axis O. The other end of the plunger biasing portion 3 in the central axial direction X is inserted from one side in the central axial direction X into an insertion hole provided in the trigger mount portion 231. Furthermore, as shown in FIGS. 8 and 10 , one end of the plunger biasing portion 3 in the central axial direction X is inserted into the insertion hole 60b. Meanwhile, the annular recess 60A and the flange recess 60B are engaged with the plunger accommodating protrusion 22A. Therefore, the engaging body 60 cannot rotate about the central axis O. Therefore, when the body engaging portion 60C and the plunger accommodating engaging portion are engaged, the torsion of the plunger biasing portion 3 is not released, and the engaging member 6 moves within the plunger other accommodating portion 221 toward one side in the central axial direction X without rotating about the central axis O. As shown in FIGS. 8 and 10, the ring recess 61B and the plunger accommodating protrusion 22A, and the ring protrusion 61A and the plunger accommodating recess 22B also fit together.

[0093] 9, the axial movement protrusion 512 is fitted into the axial movement groove 50C. Therefore, the plunger 51 is configured to be unable to rotate around the central axis O. Therefore, the plunger body 510 also moves to one side in the central axis direction X within the plunger accommodating portion 22 without rotating around the central axis O. Therefore, as shown in FIG. 8, the engaging member 6 and the plunger body 510 move to one side in the central axis direction X while the radially inner protrusion 60a and the groove 51a remain engaged with each other.

[0094] As described above, the length of the engaging member 6 in the central axis direction X is shorter than the distance between the partition portion 21 and the plunger accommodating protrusion 22A in the central axis direction X. As shown in Figures 12 and 13, when the engaging member 6 and the plunger main body 510 move to one side in the central axis direction X until the piston 51A moves to one end in the central axis direction X, which is the end point of the barrel 50, the engaging member 6 is positioned between the partition portion 21 and the plunger accommodating protrusion 22A. Furthermore, the engagement between the annular recess 60A, the flange recess 60B, and the ring recess 61B and the plunger accommodating protrusion 22A is released. That is, the engagement between the main body engaging portion 60C and the plunger accommodating portion 22 is released. Therefore, the engaging main body 60 becomes rotatable about the central axis O, allowing the torsion of the plunger biasing portion 3 to be released.

[0095] On the other hand, even after the plunger body 510 moves to one side in the central axis direction X, the axial movement protrusion 512 remains fitted within the axial movement groove 50C. Also, as shown in Figure 13, the ring convex portion 61A remains fitted into the plunger accommodating recess 22B. Therefore, while the engaging body 60 becomes rotatable around the central axis O, the engaging ring 61 and the plunger body 510 remain unable to rotate around the central axis O.

[0096] 13 and 15, one end of the plunger biasing portion 3 in the central axis direction X is fixed to a fixing portion of the engaging annular portion 600. Specifically, one end of the plunger biasing portion 3 in the central axis direction X is inserted into the insertion hole 60b. Therefore, when the engagement between the main body engaging portion 60C and the plunger accommodating portion is released, the engaging main body 60 is biased to rotate about the central axis O by the torsion of the released plunger biasing portion 3. Therefore, the engaging main body 60 transitions from the pre-rotation state shown in FIGS. 12 and 13 to the post-rotation state shown in FIGS. 14 and 15.

[0097] On the other hand, as described above, the engagement ring 61 and the plunger body 510 remain non-rotatable about the central axis O. Therefore, the engagement body 60 rotates about the central axis O relative to the non-rotatable engagement ring 61 and plunger body 510. Therefore, in this embodiment, the engagement body 60 is configured as an engagement rotation part that rotates about the central axis O relative to the plunger 51, and the engagement ring 61 is configured as an engagement non-rotation part that does not rotate about the central axis O relative to the engagement rotation part.

[0098] 12 , the elastic body 62 is disposed between the engagement main body 60 and the engagement ring 61 in a state in which it abuts against the engagement main body 60 and the engagement ring 61. Therefore, the engagement main body 60 rotates around the central axis O while elastically deforming the elastic body 62 in the circumferential direction. Furthermore, the elastic force of the elastic body 62 acts on the engagement main body 60 and the engagement ring 61, and the engagement main body 60 rotates around the central axis O while receiving the elastic force of the elastic body 62 in its elastically deformed state. Therefore, the elastic force of the elastic body 62 acts as a rotational resistance, which is a resistance force in the opposite direction to the rotational direction of the engagement main body 60, and this rotational resistance suppresses the rotational speed of the engagement main body 60. Therefore, the elastic body 62 is disposed between the engagement rotating portion and the engagement non-rotating portion, and is configured as a rotation suppressing portion that suppresses the rotational speed of the engagement rotating portion relative to the engagement non-rotating portion.

[0099] In this embodiment, two elastic bodies 62, 62 are disposed between the engagement body 60 and the engagement ring 61 on one side and the other side in the central axial direction X. Therefore, the engagement body 60 in this embodiment rotates around the central axis O while receiving rotational resistance from the elastic bodies 62 on one side and the other side in the central axial direction X.

[0100] Furthermore, by suppressing the rotational speed of the engaging body 60, the movement of the radially inner protruding portion 60a from the other circumferential end 51e side to the one circumferential end 51d side in the circumferential groove portion 51c is slowed. Therefore, while the radially inner protruding portion 60a continues to move in the circumferential groove portion 51c, the state in which the engaging member 6 and the plunger 51 are engaged is maintained. Therefore, the state in which the injection needle 503 protrudes from the housing 2 is maintained. In this embodiment, the state in which the injection needle 503 protrudes from the housing 2 is maintained for 3 to 5 seconds.

[0101] Therefore, a rotation suppression mechanism is configured that suppresses the rotation speed of the engagement member 6 about the central axis O relative to the plunger 51. In this embodiment, the rotation suppression mechanism includes the engagement ring 61, which is the non-rotating engagement portion, and the elastic body 62, which is the rotation suppression portion, and suppresses the rotation speed of the engagement main body 60 relative to the engagement ring 61.

[0102] 16, when the radially inner protrusion 60a moves toward one circumferential end 51d of the circumferential groove 51c, the shaft groove 51b and the radially inner protrusion 60a are positioned in the same circumferential position, thereby disengaging the engaging member 6 from the plunger body 510.

[0103] When the engagement between the engaging member 6 and the plunger body 510 is released, the biasing force of the plunger biasing portion 3 on the syringe 5 is released. Therefore, the barrel biasing portion 4, which had been compressed by the plunger biasing portion 3 via the syringe 5, is released. Therefore, as shown in FIG. 17 , the biasing force of the barrel biasing portion 4 moves the syringe 5 to the other side in the central axial direction X. Here, as shown in FIG. 16 , when the engagement between the engaging member 6 and the plunger 51 is released, the radially inner protruding portion 60a and the axial groove portion 51b are aligned in the circumferential direction. Therefore, the syringe 5 moves to the other side in the central axial direction X while the axial groove portion 51b moves to the other side in the central axial direction X relative to the radially inner protruding portion 60a. Therefore, as shown in FIG. 17 , the barrel 50 can be moved from the second state to the first state, and the injection needle 503 can be housed in the housing 2. When the cover portion 50A comes into contact with the partition portion 21 from one side in the central axis direction X, the syringe 5 stops.

[0104] 14, 15, and 16, when the barrel 50 is accommodated in the barrel accommodating portion 20 with the injection needle 503 protruding from one side in the central axis direction X of the housing 2 and the plunger 51 is positioned at the end point due to the biasing force of the plunger biasing portion 3, the plunger 51 and the engaging member 6 rotate relatively around the central axis O. This constitutes a disengagement mechanism that disengages the plunger 51 from the engaging member 6. In this embodiment, twisting of the plunger biasing portion 3 causes the engaging body 60 to rotate relative to the plunger body 510, and the radially inner protrusion 60a and the axial groove 51b are positioned so as to coincide circumferentially. This disengages the plunger body 510 from the engaging member 6. In this embodiment, the plunger biasing portion 3 that biases the engaging body 60 to rotate around the central axis O and the axial groove 51b constitute the disengagement mechanism.

[0105] As described above, according to this embodiment, when the engaging body 60 rotates around the central axis O relative to the plunger body 510, the elastic force of the elastic body 62 acts as a rotational resistance to suppress the rotational speed of the engaging body 60, thereby lengthening the time until the engagement between the engaging member 6 and the plunger 51 is released. Therefore, the injection needle 503 that has discharged the drug solution can be maintained in a state protruding from the housing 2. In this embodiment, the injection needle 503 can be maintained in a state protruding from the housing 2 for 3 to 5 seconds. Therefore, it is possible to prevent, for example, the injection needle 503 that has punctured the patient's skin from coming out of the skin and causing the drug solution to leak from the puncture site.

[0106] Furthermore, in this embodiment, the plunger 51 is configured to be unable to rotate about the central axis O, the engagement body 60 is configured to be rotatable about the central axis O, and the plunger biasing unit 3 applies a biasing force to the engagement body 60 to rotate about the central axis O. Furthermore, the disengagement mechanism causes the engagement body 60 to rotate relative to the plunger 51 due to the biasing force of the plunger biasing unit 3, thereby releasing the engagement between the engagement body 60 and the plunger 51, and the rotation suppression mechanism suppresses the rotational speed of the engagement body 60 due to the biasing force of the plunger biasing unit 3 to rotate about the central axis O. Therefore, by the rotation suppression mechanism suppressing the rotational speed of the engagement body 60 relative to the engagement ring 61, the time until the engagement between the engagement body 60 and the plunger 51 is released by the disengagement mechanism can be extended.

[0107] In this embodiment, the plunger accommodating recess 22B is provided over the entire area of ​​the plunger other-side accommodating portion 221 in the central axis direction X, and the ring protrusion 61A of the engaging ring 61 is engaged with the plunger accommodating recess 22B. Therefore, the engaging ring 61 is unable to rotate around the central axis O. In addition, an elastic body 62 is disposed between the engaging main body 60 and the engaging ring 61. Therefore, the engaging ring 61 and the elastic body 62 can be prevented from rotating together with the rotation of the engaging main body 60, and the mechanism for suppressing the rotational speed of the engaging main body 60 can be reliably activated.

[0108] In addition, the elastic body 62 in this embodiment is made of oil-bleed silicone rubber. Therefore, the oil kneaded into the silicone seeps onto the surface of the elastic body 62, which allows the rotation speed of the engaging body 60 to be adjusted. As a result, the rotation speed of the engaging body 60 can be appropriately suppressed by the elastic body 62.

[0109] Furthermore, in this embodiment, the elastic body 62 is disposed between the engagement main body 60 and the engagement ring 61 in the central axial direction X. Therefore, the elastic body 62 does not affect the movement of the syringe 5 or the engagement member 6 to one side in the central axial direction X due to the biasing force of the plunger biasing portion 3. Furthermore, when the engagement member 6 is housed in the plunger other side accommodating portion 221, the elastic body 62 is disposed in a state spaced apart from the inner circumferential surface of the plunger other side accommodating portion 221 in the radial direction. Therefore, when the engagement member 6 moves to one side in the central axial direction X, the elastic body 62 comes into contact with the plunger other side accommodating portion 221, preventing the engagement member 6 from impeding its movement to one side in the central axial direction X.

[0110] Furthermore, in this embodiment, the engagement ring 61 is disposed between the engagement annular portion 600 and the flange portion 602 in the central axis direction X, and the elastic body 62 is disposed between the engagement main body 60 and the engagement ring 61 in the central axis direction X. Therefore, when the engagement main body 60 rotates around the central axis O, it is possible to prevent the elastic body 62 from separating from the engagement main body 60, which would prevent the rotational speed of the engagement main body 60 from being suppressed.

[0111] Furthermore, in this embodiment, two elastic bodies 62, 62 are disposed between the engagement body 60 and the engagement ring 61 on one side and the other side of the central axis direction X. Therefore, the engagement body 60 in this embodiment rotates around the central axis O while receiving rotational resistance from the elastic bodies 62 on one side and the other side of the central axis direction X. This makes it possible to further suppress the rotational speed of the engagement body 60.

[0112] In this embodiment, one barrel housing portion 201 is provided with a through-hole 20C that penetrates in the radial direction, so that the remaining amount of the liquid medicine in barrel 50 housed in housing 2 can be checked.

[0113] Next, an injection device 1 according to a second embodiment will be described with reference to Figures 18 to 30. In describing the second embodiment, descriptions of the same configuration, method of use, and action as those of the first embodiment will be omitted.

[0114] 18, the plunger accommodating engagement portion of the second embodiment includes only a plunger accommodating protrusion 22A. Therefore, the plunger accommodating engagement portion of the second embodiment does not include a plunger accommodating recess 22B. The plunger accommodating protrusion 22A of the second embodiment is formed over the entire area of ​​the plunger other accommodating portion 221 in the central axial direction X. A pair of plunger accommodating protrusions 22A is provided in each of the first radial direction Y1 and the second radial direction Y2.

[0115] The plunger biasing portion 3 of the second embodiment is a compression coil spring wound around the central axis O. Therefore, unlike the first embodiment, the plunger biasing portion 3 of the second embodiment only biases the syringe 5 and the engaging member 6 from the other side to one side in the central axis direction X.

[0116] 19 , the plunger body 510 of the second embodiment includes a plunger body portion 510 a, a plunger ring 510 b configured in an annular shape, and an elastic body 510 c. The plunger body portion 510 a includes a rod 511 and a plunger base portion 513.

[0117] As shown in FIG. 21 , the rod 511 has a central axial portion 511a with a smaller diameter than the other portions. Therefore, radially extending rod steps 511b, 511c are formed between the central axial portion 511a and portions disposed on one side and the other side of the central axial portion 511a in the central axial direction X. The rod steps 511b, 511c are flat surfaces extending radially and circumferentially. As shown in FIG. 19 , the axial movement protrusion 512 of the second embodiment is formed on the rod 511 on one side of the central axial portion 511a in the central axial direction X.

[0118] A ring-shaped plunger ring 510b and an elastic body 510c are disposed in a middle portion 511a of the rod 511 in the central axis direction X. Therefore, as shown in Fig. 21 , the inner diameter of the plunger ring 510b is larger than the outer diameter of the middle portion 511a of the rod 511 in the central axis direction X. On the other hand, the outer diameter of the plunger ring 510b is substantially the same as the outer diameter of the portion of the rod 511 in the central axis direction X other than the middle portion 511a. In this embodiment, one end of the plunger ring 510b in the central axis direction X abuts against the rod step portion 511c.

[0119] 19, a radially outer protrusion 510d that protrudes radially outward is formed on the outer peripheral surface of the plunger ring 510b. This radially outer protrusion 510d is configured identically to the axial movement protrusion 512 formed on the rod 511. Therefore, the radially outer protrusion 510d is configured to be able to fit into the axial movement groove 50C. The radially outer protrusion 510d is disposed at approximately the same position in the circumferential direction as the axial movement protrusion 512. Therefore, the radially outer protrusion 510d is continuous with the axial movement protrusion 512 in the central axis direction X.

[0120] The elastic body 510c is an O-ring that is elastically deformable in the circumferential direction. The elastic body 510c in this embodiment is made of oil-bleed silicone rubber. As in the first embodiment, the elastic body 510c may be made of a material similar to oil-bleed silicone rubber, such as fluororubber, nitrile rubber, or silicone rubber.

[0121] 19 and 21, the elastic body 510c is disposed between the plunger main body 510a and the plunger ring 510b. In this embodiment, the elastic body 510c is disposed between the rod 511 and the plunger ring 510b in the central axial direction X. Specifically, the elastic body 510c abuts against the rod step portion 511b and the other end of the plunger ring 510b in the central axial direction X.

[0122] As shown in Fig. 19, a groove 51a recessed radially inward is formed on the outer peripheral surface of the plunger engagement portion 514 of the second embodiment, similar to the first embodiment. Here, the groove 51a of the second embodiment is configured as a spiral groove 51a extending in the circumferential direction from one end of the plunger engagement portion 514 in the central axial direction X to the other end. Also, as shown in Fig. 20, the spiral groove 51a has a first circumferential end 51d, which is one end in the circumferential direction, and a second circumferential end 51e, which is the other end in the circumferential direction. The first circumferential end 51d is located on the other side in the central axial direction X, and the second circumferential end 51e is located on one side in the central axial direction X.

[0123] 22 and 23 , the engaging member 6 of the second embodiment includes only an engaging body 60. Therefore, unlike the first embodiment, the engaging member 6 of the second embodiment does not include an engaging ring 61 or an elastic body 62. Furthermore, the flange portion 602 of the second embodiment has the same protrusion amount on one side and the other side in the central axis direction X. Furthermore, the inner radial protrusion portion 60a of the second embodiment is configured to be insertable into the spiral groove portion 51a.

[0124] As shown in Fig. 24, the engaging member 6 engages with the plunger engaging portion 514. In this embodiment, the engaging member 6 and the plunger body 510 rotate relatively about the central axis O so that the inner radial protrusion 60a inserted into the spiral groove portion 51a from one side in the central axis direction X moves from the other circumferential end 51e side to the one circumferential end 51d side. As a result, as shown in Fig. 25, the inner radial protrusion 60a is positioned on the one circumferential end 51d side of the spiral groove portion 51a.

[0125] As described above, the plunger biasing portion 3 of the second embodiment simply biases the syringe 5 and the engaging member 6 from the other side to one side in the central axial direction X. Therefore, as shown in Fig. 24 , the engaging member 6 housed in the plunger other housing portion 221 compresses the plunger biasing portion 3 in the central axial direction X. Furthermore, as shown in Fig. 25 , the engaging member 6 is housed in the plunger other housing portion 221 with the main body engaging portion 60C of the engaging main body 60 and the plunger housing convex portion 22A of the plunger other housing portion 221 fitted together.

[0126] Next, a method of using the injection device 1 of the second embodiment will be described. In describing the method of using the injection device 1 of the second embodiment, the process from the initial state until the injection needle 503 protrudes is the same as that of the first embodiment. Therefore, a description of this process will be omitted.

[0127] 26 and 27 , when the piston 51A has moved to the tip, which is one end of the barrel 50 in the central axis direction X, the radially outer protrusion 510d is fitted into the axial movement groove 50C. Therefore, the plunger ring 510b is configured to be unable to rotate around the central axis O.

[0128] Meanwhile, the biasing force of the plunger biasing portion 3 causes the engaging member 6 to move further toward one side in the central axial direction X. In the second embodiment, the plunger accommodating protrusion 22A is formed over the entire area of ​​the plunger other-side accommodating portion 221 in the central axial direction X, and the main body engaging portion 60C of the engaging body 60 and the plunger accommodating protrusion 22A of the plunger other-side accommodating portion 221 are engaged with each other. Therefore, the engaging member 6 is unable to rotate around the central axis O. Therefore, as the radially inner protrusion 60a moves from the one circumferential end 51d of the spiral groove portion 51a to the other circumferential end 51e, the engaging member 6, which is unable to rotate around the central axis O, moves toward one side in the central axial direction X. Therefore, as the engaging member 6 moves toward one side in the central axial direction X, the plunger main body 510 rotates around the central axis O. In this embodiment, the plunger main body 510 rotates counterclockwise around the central axis O.

[0129] When the plunger main body 510 rotates, the rod 511 rotates around the central axis O relative to the plunger ring 510b, which is configured to be non-rotatable. Therefore, in this embodiment, the plunger main body 510a is configured as a plunger rotating part that rotates around the central axis O relative to the engaging member 6, and the plunger ring 510b is configured as a plunger non-rotating part that does not rotate around the central axis relative to the plunger rotating part.

[0130] As shown in FIG. 26 , the elastic body 510c is disposed between the plunger main body 510a and the plunger ring 510b. The elastic body 510c abuts against the rod step 511b and the other end of the plunger ring 510b in the central axis direction X. Therefore, as shown in FIG. 28 , the plunger main body 510a rotates around the central axis O while elastically deforming the elastic body 510c in the circumferential direction. The elastic force of the elastic body 510c acts on the plunger main body 510a and the plunger ring 510b, and the plunger main body 510a rotates around the central axis O while receiving the elastic force of the elastic body 510c in its elastically deformed state. Therefore, the elastic force of the elastic body 510c acts as a rotational resistance, which is a resisting force acting in the opposite direction to the rotation of the plunger main body 510a. This rotational resistance suppresses the rotational speed of the plunger main body 510a. Therefore, the elastic body 510c is disposed between the plunger rotating portion and the plunger non-rotating portion, and is configured as a rotation suppressing portion that suppresses the rotation speed of the plunger rotating portion relative to the plunger non-rotating portion.

[0131] By suppressing the rotational speed of the plunger body 510a, the movement of the radially inner protruding portion 60a from the one circumferential end 51d side to the other circumferential end 51e side of the spiral groove portion 51a becomes slow. Therefore, while the radially inner protruding portion 60a continues to move along the spiral groove portion 51a, the engagement between the engaging member 6 and the plunger 51 is maintained. Therefore, the injection needle 503 is maintained in a state of protruding from the housing 2.

[0132] Therefore, a rotation suppression mechanism is configured that suppresses the rotation speed of the plunger 51 about the central axis O relative to the engaging member 6. In this embodiment, the rotation suppression mechanism includes the plunger ring 510b, which is the plunger non-rotating portion, and the elastic body 510c, which is the rotation suppression portion, and suppresses the rotation speed of the rod 511 relative to the plunger ring 510b. Therefore, the rotation suppression mechanism suppresses the rotation speed of the plunger 51.

[0133] When the inner radial protrusion 60a moves to the other circumferential end 51e of the spiral groove portion 51a, the inner radial protrusion 60a is positioned at one end of the plunger engagement portion 514 in the central axial direction X. Therefore, the engagement between the inner radial protrusion 60a and the spiral groove portion 51a is released. Therefore, the disengagement mechanism of the second embodiment is configured to disengage the plunger 51 from the engagement member 6 by rotating the plunger 51 (specifically, the plunger main body portion 510a which is the plunger rotating portion) about the central axis O relative to the engagement member 6 and releasing the engagement between the engagement member 6 and the plunger main body portion 510a.

[0134] By releasing the engagement between the plunger 51 and the engaging member 6, the barrel biasing portion 4, which had been compressed by the plunger biasing portion 3, is released. Therefore, as shown in Figure 30, the syringe 5 moves to the other side in the central axis direction X due to the biasing force of the barrel biasing portion 4. Therefore, the injection needle 503 is housed in the housing 2.

[0135] As described above, according to this embodiment, the rotational speed of the plunger 51 can be suppressed, thereby lengthening the time until the engagement between the plunger 51 and the engaging member 6 is released. Therefore, the injection needle 503 that has ejected the medicinal solution can be maintained in a state protruding from the housing 2.

[0136] In addition, in this embodiment, the radially outer protruding portion 510d is inserted into the axial movement groove portion 50C, causing the plunger main body 510a to rotate relative to the plunger ring 510b around the central axis O. At that time, the rotation speed of the rod 511 can be suppressed by the elastic force of the elastic body 510c disposed between the plunger main body 510a and the plunger ring 510b.

[0137] In this embodiment, the engaging member 6 moves to one side in the central axial direction X due to the biasing force of the plunger biasing portion 3, and the radially inner protruding portion 60a moves to one side in the central axial direction X along the spiral groove portion 51a, thereby rotating the plunger body 510 around the central axis O. Therefore, the biasing force of the plunger biasing portion 3 to one side in the central axial direction X is converted into a rotational force that rotates the plunger 51, thereby allowing the plunger 51 to rotate.

[0138] The present invention is not limited to the above-described embodiment, and can be modified as appropriate within the scope of the invention.

[0139] In the second embodiment, the rotation of the engagement body 60 about the central axis O is restricted by the recessed and projecting engagement between the annular recess 60A of the engagement body 60 and the plunger accommodating protrusion 22A of the plunger other accommodating portion 221. However, this is not limiting, and for example, the engagement body 60 may be provided with an annular recess 60A that protrudes radially outward from the engagement body 60, and the recessed and projecting engagement with the plunger accommodating recess 22B of the plunger other accommodating portion 221 may restrict the rotation of the engagement body 60 about the central axis O.

[0140] In the above embodiment, the engaging member 6 includes a rotating engagement portion and a non-rotating engagement portion. However, this is not limiting, and the engaging member 6 may include only a rotating engagement portion. For example, the engaging member 6 may not include the engaging ring 61 and the elastic body 62, and the partition portion 21 may include an elastic body on the other side in the central axial direction X, so that the engaging body 60 abuts against the elastic body of the partition portion 21 when the engagement between the annular recess 60A of the engaging body 60 and the plunger accommodating protrusion 22A of the plunger other accommodating portion 221 is released. In this case, the engaging body 60 abuts against the elastic body in the central axial direction X.

[0141] In the above embodiment, the elastic body 62 is disposed between the engagement main body 60 and the engagement ring 61 in the central axis direction X. However, this is not limiting, and for example, the elastic body 62 may be disposed between the engagement main body 60 and the engagement ring 61 in the radial direction. The same applies to the elastic body 510c of the second embodiment.

[0142] For example, the length of time that the injection needle 503 can be maintained in a state where it protrudes from the housing 2 may be changed by changing the circumferential length of the circumferential groove portion 51c formed in the plunger engagement portion 514.

[0143] In the above embodiment, the barrel biasing portion 4 and the plunger biasing portion 3 are described as being compression coil springs. However, the present invention is not limited to this, and the barrel biasing portion 4 and the plunger biasing portion 3 may be made of, for example, rubber that is elastically deformable so as to stretch in the central axis direction X.

[0144] In the above embodiment, one of the engaging member 6 and the plunger 51 is fixed so as not to rotate about its axis, and the other is configured to be rotatable about its axis and to rotate relative to the other. However, this is not limiting, and for example, both the engaging member 6 and the plunger 51 may be configured to rotate about the central axis O.

[0145] In the above embodiment, the case has been described where the starting point is at a position on one side of the other end in the central axial direction X of the barrel 50, and the ending point is at one end in the central axial direction X of the barrel 50. However, this is not limiting, and for example, the starting point may be at the other end in the central axial direction X of the barrel 50. Also, the ending point may be at the other side of the one end in the central axial direction X of the barrel 50. In other words, as long as the starting point is at the other side in the central axial direction X of the barrel 50 and the ending point is at one side in the central axial direction X of the barrel 50, the starting point may be set at a position other than the other end in the central axial direction X of the barrel 50.

[0146] As described above, according to the present invention, the time until the engagement between the plunger and the engaging member can be extended, and therefore the injection needle can be kept protruding from the housing for a while after injection is complete, thereby ensuring the completion of administration.

[0147] The present invention provides a syringe including a barrel having an injection needle at its tip, and a plunger inserted into the barrel so as to be reciprocally movable between the base end of the barrel as a starting point and the tip end where the injection needle is provided as an end point, and a cylindrical housing for accommodating the syringe, the housing including a barrel accommodating section on one side in the direction of the central axis for accommodating the barrel so that the barrel can move between a state in which the injection needle is accommodated and a state in which the barrel moves a predetermined distance from the accommodated state to one side and the injection needle protrudes from one side of the housing, and a plunger accommodating section on the other side of the barrel accommodating section for accommodating the plunger; and a plunger attached to the barrel accommodating section for attaching the barrel from one side of the housing to the other side. an engaging member that is disposed in the plunger accommodating section and engages with the plunger; a plunger accommodating section that engages with the engaging member and urges the plunger from the starting point toward the end point; and an engagement release mechanism that releases the engagement between the plunger and the engaging member by rotating the plunger and the engaging member relative to each other about a central axis when the barrel is accommodated in the barrel accommodating section with the injection needle protruding from one side of the housing and the plunger is positioned at the end point by the urging force of the plunger accommodating section, and further comprising a rotation suppression mechanism that suppresses the rotational speed of the relative rotation between the plunger and the engaging member in the engagement release mechanism.

[0148] According to the above configuration, when the plunger is positioned at the end point with the injection needle protruding from one side of the housing, dispensing of the medicinal solution is completed. Then, with the plunger positioned at the end point, the disengagement mechanism causes the plunger and the engaging member to rotate relative to each other, thereby disengaging the plunger from the engaging member. Here, since the injection device of the present invention includes the rotation suppression mechanism, when the plunger and the engaging member rotate relative to each other, the rotation speed of the relative rotation is suppressed, thereby lengthening the time until the engagement between the plunger and the engaging member is disengaged.

[0149] In addition, in the present invention, the disengagement mechanism may be configured to disengage the plunger and the engaging member by rotating the engaging member around a central axis relative to the plunger, and the rotation suppression mechanism may suppress the rotational speed of the engaging member.

[0150] According to the above configuration, the rotation suppression mechanism suppresses the rotation speed of the engaging member, thereby lengthening the time until the engagement between the plunger and the engaging member is released.

[0151] In addition, in the present invention, the engaging member includes an engaging rotating portion that engages with the plunger and rotates about a central axis relative to the plunger to release the engagement with the plunger, and the disengagement mechanism is configured to release the engagement between the plunger and the engaging member by causing the engaging rotating portion to rotate relative to the plunger to release the engagement between the plunger and the engaging rotating portion, and the rotation suppression mechanism includes an engaging non-rotating portion that does not rotate about the central axis relative to the engaging rotating portion, and a rotation suppression portion that is arranged between the engaging rotating portion and the engaging non-rotating portion and suppresses the rotational speed of the engaging rotating portion relative to the engaging non-rotating portion, and may suppress the rotational speed of the engaging rotating portion relative to the engaging non-rotating portion.

[0152] According to the above configuration, the rotation suppression mechanism suppresses the rotational speed of the engaging rotating part relative to the engaging non-rotating part, thereby suppressing the rotational speed of the engaging rotating part relative to the plunger, thereby lengthening the time until the engagement between the plunger and the engaging rotating part is released, and lengthening the time until the engagement between the plunger and the engaging member is released.

[0153] In addition, in the present invention, the rotation suppressing portion may be an elastic body that is disposed in an elastically deformed state between the engaging rotating portion and the engaging non-rotating portion.

[0154] According to the above configuration, the rotational speed of the engaging rotating portion relative to the engaging non-rotating portion can be suppressed by the elastic force of the rotation suppression portion, thereby lengthening the time until the engagement between the plunger and the engaging member is released.

[0155] In addition, in the present invention, the disengagement mechanism may be configured to disengage the plunger from the engaging member by rotating the plunger around a central axis relative to the engaging member, and the rotation suppression mechanism may suppress the rotational speed of the plunger.

[0156] According to the above configuration, the rotation suppression mechanism suppresses the rotation speed of the plunger, thereby lengthening the time until the engagement between the plunger and the engaging member is released.

[0157] Further, in the present invention, the plunger includes a plunger rotating portion that engages with the engaging member and rotates about the central axis relative to the engaging member to release the engagement, a plunger non-rotating portion that does not rotate about the central axis relative to the plunger rotating portion, and a rotation suppressing portion that is disposed between the plunger rotating portion and the plunger non-rotating portion and suppresses the rotational speed of the plunger rotating portion relative to the plunger non-rotating portion, and the disengagement mechanism is configured to release the engagement between the plunger and the engaging member by causing the plunger rotating portion to rotate relative to the engaging member to release the engagement between the engaging member and the plunger rotating portion, and the rotation suppressing mechanism may include the plunger non-rotating portion and the rotation suppressing portion and suppress the rotational speed of the plunger rotating portion relative to the plunger non-rotating portion.

[0158] According to the above configuration, the rotation suppression mechanism suppresses the rotational speed of the plunger rotating part relative to the plunger non-rotating part, thereby suppressing the rotational speed of the plunger rotating part relative to the engaging member, thereby lengthening the time until the engagement between the engaging member and the plunger rotating part is released, and lengthening the time until the engagement between the plunger and the engaging member is released.

[0159] In the present invention, the rotation suppressing portion may be an elastic body that is disposed in an elastically deformed state between the plunger rotating portion and the plunger non-rotating portion.

[0160] According to the above configuration, the rotation speed of the plunger rotating portion relative to the plunger non-rotating portion can be suppressed by the elastic force of the rotation suppression portion, thereby lengthening the time until the engagement between the plunger and the engaging member is released.

[0161] 1: injection device, 2: housing, 20: barrel housing, 200: other barrel housing, 201: one barrel housing, 20A: barrel protrusion, 20B: biasing base, 20C: through portion, 20D: barrel step, 21: partition, 22: plunger housing, 220: one plunger housing, 221: other plunger housing, 22A: plunger housing protrusion, 22B: plunger housing recess, 23: trigger, 230: trigger mounting, 231: trigger mounting base, 232: trigger Guard cylinder portion, 233: lock step portion, 234: convex portion, 23A: trigger main body portion, 23B: top plate portion, 23C: outer skirt portion, 23D: release groove, 23E: interlocking groove, 23F: inner skirt portion, 23G: flat plate portion, 23a: trigger lock operation portion, 23b: cylinder portion, 23c: protrusion portion, 23d: rotation groove, 3: plunger biasing portion, 4: barrel biasing portion, 5: syringe, 50: barrel, 500: barrel main body portion, 501: barrel cylinder portion, 502: outer flange portion, 503: injection needle, 50A: cover portion

Claims

1. A syringe comprising: a barrel with an injection needle at its tip; and a plunger inserted into the barrel so as to be movable back and forth between the base end of the barrel and the tip end where the injection needle is provided; a cylindrical housing for accommodating the syringe, the housing comprising: a barrel accommodating section for accommodating the barrel on one side in the direction of the central axis, the barrel accommodating section being adapted to move between a state in which the injection needle is accommodated and a state in which the injection needle protrudes from one side of the housing by moving a predetermined distance from the accommodated state to one side; and a plunger accommodating section for accommodating the plunger on the other side of the barrel accommodating section; a barrel biasing section provided in the barrel accommodating section for biasing the barrel from one side to the other side of the housing; an engaging member disposed in the plunger accommodating section for engaging with the plunger; and a plunger biasing section for engaging with the engaging member for biasing the plunger from the starting point to the end point. an engagement release mechanism that releases the engagement between the plunger and the engaging member by rotating relatively around a central axis between the plunger and the engaging member while the barrel is accommodated in the barrel accommodating section with the injection needle protruding from one side of the housing and the plunger is positioned at the end point by the biasing force of the plunger biasing section; and a rotation suppression mechanism that suppresses the rotational speed of the relative rotation between the plunger and the engaging member in the engagement release mechanism.

2. The injection device of claim 1, wherein the disengagement mechanism is configured to disengage the plunger from the engagement member by rotating the engagement member about a central axis relative to the plunger, and the rotation suppression mechanism suppresses the rotational speed of the engagement member.

3. The injection device of claim 2, wherein the engaging member includes an engaging rotation portion that engages with the plunger and rotates about a central axis relative to the plunger to disengage from the plunger, the disengagement mechanism is configured to disengage the plunger from the engaging member by causing the engaging rotation portion to rotate relative to the plunger to disengage the plunger from the engaging rotation portion, and the rotation suppression mechanism includes an engaging non-rotating portion that does not rotate about the central axis relative to the engaging rotation portion, and a rotation suppression portion that is disposed between the engaging rotation portion and the engaging non-rotating portion and suppresses the rotation speed of the engaging rotation portion relative to the engaging non-rotating portion, suppressing the rotation speed of the engaging rotation portion relative to the engaging non-rotating portion.

4. An injection device as described in claim 3, wherein the rotation suppressing portion is an elastic body arranged in an elastically deformed state between the engaging rotating portion and the engaging non-rotating portion.

5. The injection device of claim 1, wherein the disengagement mechanism is configured to disengage the plunger from the engaging member by rotating the plunger about a central axis relative to the engaging member, and the rotation suppression mechanism suppresses the rotational speed of the plunger.

6. The injection device according to claim 5, wherein the plunger comprises: a plunger rotating portion that engages with the engaging member and rotates about a central axis relative to the engaging member to release the engagement; a plunger non-rotating portion that does not rotate about the central axis relative to the plunger rotating portion; and a rotation suppressing portion that is disposed between the plunger rotating portion and the plunger non-rotating portion and suppresses the rotational speed of the plunger rotating portion relative to the plunger non-rotating portion; the disengagement mechanism is configured to release the engagement between the plunger and the engaging member by causing the plunger rotating portion to rotate relative to the engaging member to release the engagement between the engaging member and the plunger rotating portion; and the rotation suppressing mechanism includes the plunger non-rotating portion and the rotation suppressing portion and suppresses the rotational speed of the plunger rotating portion relative to the plunger non-rotating portion.

7. The injection device according to claim 6, wherein the rotation suppressing portion is an elastic body arranged in an elastically deformed state between the plunger rotating portion and the plunger non-rotating portion.

Images